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Sample records for acetylene reduction assays

  1. Problems of the acetylene reduction technique applied to water-saturated paddy soils.

    PubMed

    Lee, K K; Watanabe, I

    1977-12-01

    The acetylene reduction assay for the measurement of N(2) fixation in a water-saturated paddy soil is limited by the slow diffusion of acetylene and ethylene. In laboratory incubation tests, vigorous shaking after the assay period is needed to release ethylene into the gas within the assay vials. Shaking prior to the incubation is also effective for dissolving acetylene in the water-saturated soil. However, a water-saturated soil depth of less than 10 mm during incubation is recommended. In field assays, some amounts of ethylene remain in the water-saturated soil phase of the acetylene reduction assay chamber, but stirring the water-saturated soil before sampling reduces the amount of ethylene remaining in soil. Evidence of a downward movement of acetylene and an upward movement of ethylene through rice plants was obtained. Because of the rapid transfer of acetylene to rice plant roots, an in situ acetylene reduction assay covering a rice hill is likely to detect nitrogen fixation in the proximity of roots where acetylene is easily accessible. Acetylene introduction to the water-saturated soil phase prior to assay did not greatly increase the acetylene reduction rate. Carbon dioxide enrichment in the assay chamber did not enhance nitrogen fixation in a paddy including rice and algae during a 1-day cycle. PMID:16345257

  2. Acetylene inhibition of N2O reduction in laboratory soil and groundwater denitrification assays: evaluation by 15N tracer and 15N site preference of N2O

    NASA Astrophysics Data System (ADS)

    Weymann, Daniel; Well, Reinhard; Lewicka-Szczebak, Dominika; Lena, Rohe

    2013-04-01

    The measurement of denitrification in soils and aquifers is still challenging and often enough associated with considerable experimental effort and high costs. Against this background, the acetylene inhibition technique (AIT) applied in laboratory soil and groundwater denitrification assays is by far the most effective approach. However, this method has been largely criticized, as it is susceptible to underestimate denitrification rates and adds an additional carbon source to the substrates to be investigated. Here we provide evidence that the AIT is not necessarily an inappropriate approach to measure denitrification, that its reliability depends on the drivers governing the process, and that the 15N site preference of N2O (SP) may serve as a tool to assess this reliability. Two laboratory batch experiments were conducted, where sandy aquifer material and a peat soil were incubated as slurries. We established (i) a standard anaerobic treatment by adding KNO3 (10 mg N L-1), (ii) an oxygen treatment by adding KNO3 and O2 (5 mg L-1), and (iii) a glucose treatment by adding KNO3 supplemented with glucose (200 mg C L-1). Both experiments were run under 10 % (v/v) acetylene atmosphere and as 15N tracer treatments using labeled K15NO3 (60 atom % 15N). In the case of the standard anaerobic treatments, we found a very good agreement of denitrification potential obtained by the AIT and 15N tracer methods. SP of N2O of the AIT samples from this treatment ranged between -4.8 and 2.6 which is indicative for N2O production during bacterial denitrification but not for N2O reduction to N2. In contrast, we observed substantial underestimation of denitrification by AIT for the glucose treatments compared to the 15N method, i.e. denitrification was underestimated by 36 % (sandy aquifer material) and 47 % (peat soil). SP of N2O of the AIT samples from this treatment ranged between 4.5 and 9.6 , which suggests occurrence of bacterial N2O reduction. In the case of the oxygen treatments, we observed a very good agreement of denitrification potential obtained by the AIT and 15N tracer methods for the aquifer material, but a significant underestimation of 20 % in the AIT samples of the peat soil. The 15N site preference of N2O again mirrored this and ranged between -1.2 and -3.5 (aquifer material) and 5.5 and 11.0 (peat soil), respectively. We conclude that the AIT can act as a reliable method in laboratory soil and groundwater bacterial denitrification assays, but our results suggest that this relies on substrate types and incubation conditions. Additional measurements of SP have potential to assess AIT efficacy and can help to reduce parallel time-consuming and expensive 15N tracer experiments.

  3. Aquatic acetylene-reduction techniques: solutions to several problems.

    PubMed

    Flett, R J; Hamilton, R D; Campbell, N E

    1976-01-01

    Previous methods of performing aquatic acetylene-reduction assays are described and several problems associated with them are discussed. A refinement of these older techniques is introduced and problems that it overcomes are also discussed. A depth profile of nitrogen fixation (C2H4 production), obtained by the refined technique, is shown for a fertilized Canadian Shield lake in the Experimental Lakes Area of northwestern Ontario. PMID:814983

  4. Effect of polynuclear hydrocarbons on algal nitrogen fixation (acetylene reduction)

    SciTech Connect

    Bastian, M.V.; Toetz, D.W.

    1985-08-01

    The objective of this research was to determine the effects of polynuclear aromatic hydrocarbons (PAH) on N/sub 2/ fixation by the alga, Anabaena flos-aquea. The reduction of acetylene (C/sub 2/H/sub 2/) to ethylene (C/sub 2/H/sub 4/) was measured as a measure of the capacity of an organism to fix atmospheric N/sub 2/ and reduce it to an assimilable form. The primary advantage of this assay is its speed since chemical exposure and quantitative chromatographic analysis can be completed in a few hours.

  5. Biological dinitrogen fixation (acetylene reduction) associated with Florida mangroves.

    PubMed

    Zuberer, D A; Silver, W S

    1978-03-01

    Biological dinitrogen fixation in mangrove communities of the Tampa Bay region of South Florida was investigated using the acetylene reduction technique. Low rates of acetylene reduction (0.01 to 1.84 nmol of C(2)H(4)/g [wet weight] per h) were associated with plant-free sediments, while plant-associated sediments gave rise to slightly higher rates. Activity in sediments increased greatly upon the addition of various carbon sources, indicating an energy limitation for nitrogenase (C(2)H(2)) activity. In situ determinations of dinitrogen fixation in sediments also indicated low rates and exhibited a similar response to glucose amendment. Litter from the green macroalga, Ulva spp., mangrove leaves, and sea grass also gave rise to significant rates of acetylene reduction. Higher rates of nitrogenase activity (15 to 53 nmol of C(2)H(4)/g [wet weight] per h were associated with washed excised roots of three Florida mangrove species [Rhizophora mangle L., Avicennia germinans (L) Stern, and Laguncularia racemosa Gaertn.] as well as with isolated root systems of intact plants (11 to 58 mug of N/g [dry weight] per h). Following a short lag period, root-associated activity was linear and did not exhibit a marked response to glucose amendment. It appears that dinitrogen-fixing bacteria in the mangrove rhizoplane are able to use root exudates and/or sloughed cell debris as energy sources for dinitrogen fixation. PMID:637550

  6. Biological Dinitrogen Fixation (Acetylene Reduction) Associated with Florida Mangroves

    PubMed Central

    Zuberer, D. A.; Silver, W. S.

    1978-01-01

    Biological dinitrogen fixation in mangrove communities of the Tampa Bay region of South Florida was investigated using the acetylene reduction technique. Low rates of acetylene reduction (0.01 to 1.84 nmol of C2H4/g [wet weight] per h) were associated with plant-free sediments, while plant-associated sediments gave rise to slightly higher rates. Activity in sediments increased greatly upon the addition of various carbon sources, indicating an energy limitation for nitrogenase (C2H2) activity. In situ determinations of dinitrogen fixation in sediments also indicated low rates and exhibited a similar response to glucose amendment. Litter from the green macroalga, Ulva spp., mangrove leaves, and sea grass also gave rise to significant rates of acetylene reduction. Higher rates of nitrogenase activity (15 to 53 nmol of C2H4/g [wet weight] per h were associated with washed excised roots of three Florida mangrove species [Rhizophora mangle L., Avicennia germinans (L) Stern, and Laguncularia racemosa Gaertn.] as well as with isolated root systems of intact plants (11 to 58 ?g of N/g [dry weight] per h). Following a short lag period, root-associated activity was linear and did not exhibit a marked response to glucose amendment. It appears that dinitrogen-fixing bacteria in the mangrove rhizoplane are able to use root exudates and/or sloughed cell debris as energy sources for dinitrogen fixation. PMID:637550

  7. Simultaneous Measurement of Acetylene Reduction and Respiratory Gas Exchange of Attached Root Nodules 1

    PubMed Central

    Winship, Lawrence J.; Tjepkema, John D.

    1982-01-01

    A method was developed for the simultaneous measurement of acetylene reduction, carbon dioxide evolution and oxygen uptake by individual root nodules of intact nitrogen-fixing plants (Alnus rubra Bong.). The nodules were enclosed in a temperature-controlled leak-tight cuvette. Assay gas mixtures were passed through the cuvette at a constant, known flow rate and gas exchange was measured by the difference between inlet and outlet gas compositions. Gas concentrations were assayed by a combination of an automated gas chromatograph and a programmable electronic integrator. Carbon dioxide and ethylene evolution were determined with a coefficient of variation which was less than 2%, whereas the coefficient of variation for oxygen uptake measurements was less than 5%. Nodules subjected to repeated removal from and reinsertion into the cuvette and to long exposures of 10% v/v acetylene showed no irreversible decline in respiration or acetylene reduction. This system offers long-term stability and freedom from disturbance artifacts plus the ability to monitor continuously, rapidly and specifically the changes in root nodule activity caused by environmental perturbation. PMID:16662496

  8. Carbon dioxide reduction to methane and coupling with acetylene to form propylene catalyzed by remodeled nitrogenase

    PubMed Central

    Yang, Zhi-Yong; Moure, Vivian R.; Dean, Dennis R.; Seefeldt, Lance C.

    2012-01-01

    A doubly substituted form of the nitrogenase MoFe protein (α-70Val→Ala, α-195His→Gln) has the capacity to catalyze the reduction of carbon dioxide (CO2) to yield methane (CH4). Under optimized conditions, 1 nmol of the substituted MoFe protein catalyzes the formation of 21 nmol of CH4 within 20 min. The catalytic rate depends on the partial pressure of CO2 (or concentration of HCO3−) and the electron flux through nitrogenase. The doubly substituted MoFe protein also has the capacity to catalyze the unprecedented formation of propylene (H2C = CH-CH3) through the reductive coupling of CO2 and acetylene (HC≡CH). In light of these observations, we suggest that an emerging understanding of the mechanistic features of nitrogenase could be relevant to the design of synthetic catalysts for CO2 sequestration and formation of olefins. PMID:23150564

  9. Root and Nodule Respiration in Relation to Acetylene Reduction in Intact Nodulated Peas 1

    PubMed Central

    Mahon, John D.

    1977-01-01

    Inoculated pea plants (Pisum sativum L.) were grown with N-free nutrients in a controlled environment room and rates of respiratory CO2 evolution and C2H2 reduction by the intact nodulated roots were determined. Experiments followed changes related to diurnal cycles, light and dark treatments, partial defoliation, aging of plants and NH4NO3 addition. In all experiments, changes in C2H2 reduction were associated with parallel changes in the respiration rate, although in all but the defoliation experiment there was a basal level of respiration which was independent of the rate of C2H2 reduction. In conditions which affected growth or plant size as well as C2H2 reduction, respiration changed by an average of 0.42 mg CO2 (μmol C2H2 reduced)−1. However, some treatments decreased C2H2 reduction without greatly changing the growth and in these conditions respiration was decreased by an average of 0.27 mg CO2 (μmol C2H2 reduced)−1. While this value may also include some respiration associated with other processes, it is proposed that it more closely estimates respiration directly associated with energy utilization for acetylene reduction; whereas the higher value includes respiration related to maintenance and growth processes as well. PMID:16660191

  10. The Acetylene-Ethylene Assay for N2 Fixation: Laboratory and Field Evaluation 1

    PubMed Central

    Hardy, R. W. F.; Holsten, R. D.; Jackson, E. K.; Burns, R. C.

    1968-01-01

    The methodology, characteristics and application of the sensitive C2H2-C2H4 assay for N2 fixation by nitrogenase preparations and bacterial cultures in the laboratory and by legumes and free-living bacteria in situ is presented in this comprehensive report. This assay is based on the N2ase-catalyzed reduction of C2H2 to C2H4, gas chromatographic isolation of C2H2 and C2H4, and quantitative measurement with a H2-flame analyzer. As little as 1 ??mole C2H4 can be detected, providing a sensitivity 103-fold greater than is possible with 15N analysis. A simple, rapid and effective procedure utilizing syringe-type assay chambers is described for the analysis of C2H2-reducing activity in the field. Applications to field samples included an evaluation of N2 fixation by commercially grown soybeans based on over 2000 analyses made during the course of the growing season. Assay values reflected the degree of nodulation of soybean plants and indicated a calculated seasonal N2 fixation rate of 30 to 33 kg N2 fixed per acre, in good agreement with literature estimates based on Kjeldahl analyses. The assay was successfully applied to measurements of N2 fixation by other symbionts and by free living soil microorganisms, and was also used to assess the effects of light and temperature on the N2 fixing activity of soybeans. The validity of measuring N2 fixation in terms of C2H2 reduction was established through extensive comparisons of these activities using defined systems, including purified N2ase preparations and pure cultures of N2-fixing bacteria. With this assay it now becomes possible and practicable to conduct comprehensive surveys of N2 fixation, to make detailed comparisons among different N2-fixing symbionts, and to rapidly evaluate the effects of cultural practices and environmental factors on N2 fixation. The knowledge obtained through extensive application of this assay should provide the basis for efforts leading to the maximum agricultural exploitation of the N2 fixation reaction. PMID:16656902

  11. Comparison of N{sub 2}-fixation measured with acetylene reduction and {sup 15}N dilution techniques in Gliricidia sepium seedlings grown under varying CO{sub 2} temperature and soil nitrogen

    SciTech Connect

    Bashkin, M.A.; Thomas, R.B.; Richter, D.D.

    1995-06-01

    The acetylene reduction assay is commonly used to quantify N{sub 2}-fixation and the response of N{sub 2}-fixing organisms to environmental factors. However, the technique is often criticized and conclusions based on the assay may be incorrect. In this study we compared the acetylene reduction assay to a {sup 15}N dilution method for estimating N{sub 2}-fixation in Gliricidia sepium. Seedlings were grown for 100 days under two levels of CO{sub 2} (35 and 70 Pa), air temperature (28/24 and 32/28 C day/night) and three levels of soil nitrogen (0, 1 and 10 mM). Nodule activity on a plant basis correlated well between the two methods (r{sup 2}=0.71). CO{sub 2} enrichment enhanced whole plant nodule activity by 77% and 48% as measured with the {sup 15}N dilution and acetylene methods, respectively, and 10 mM N inhibited fixation 52% and 71%. Specific nodule activity weakly correlated between the two methods (r{sup 2}=0.06). The {sup 15}N dilution method estimated a 24% increase in specific nodule activity due to increased CO{sub 2}. Acetylene assay detected a 44% suppression of specific nodule activity at l0mM N, but no effect of CO{sub 2}or temperature. Results indicate that instantaneous acetylene rate may be inaccurate when extrapolated over time. However, the integrative {sup 15}N dilution rate may miss treatment effects when interpolated to shorter time-scales. Ultimately, the choice of method depends on the hypotheses being tested. The time-scale of the phenomenon under study should approximate the time-scale of measurement.

  12. Quantification and Removal of Some Contaminating Gases from Acetylene Used to Study Gas-Utilizing Enzymes and Microorganisms

    PubMed Central

    Hyman, Michael R.; Arp, Daniel J.

    1987-01-01

    Acetylene generated from various grades of calcium carbide and obtained from commercial- and purified-grade acetylene cylinders was shown to contain high concentrations of various contaminants. Dependent on the source of acetylene, these included, at maximal values, H2 (0.023%), O2 (0.779%), N2 (3.78%), PH3 (0.06%), CH4 (0.073%), and acetone (1 to 10%). The concentration of the contaminants in cylinder acetylene was highly dependent on the extent of cylinder discharge. Several conventional methods used to partially purify cylinder acetylene were compared. A small-scale method for extensively purifying acetylene is described. An effect of acetylene quality on acetylene reduction assays conducted with purified nitrogenase from Azotobacter vinelandii was demonstrated. PMID:16347278

  13. Comparing Time Course Profiles of Immediate Acetylene Reduction by Grasses and Legumes

    PubMed Central

    van Berkum, Peter; Sloger, Charles

    1981-01-01

    The time course profiles of C2H2 reduction by intact Scirpus olneyi (bulrush), Oryza sativa (rice) and Spartina alterniflora (cordgrass) with roots in atmospheres of N2 and 30-day-old Glycine max (soybean) in air were all immediately linear. This is the first report of immediately linear rates of C2H2 reduction by grass roots removed from soil. The immediately linear profile of C2H2 reduction by soil-free grass roots was achieved by preventing contact between the roots and air. Roots of soybeans and S. olneyi receiving pretreatments of O2 above normal environmental levels for 15 min before assay exhibited a short delay in C2H2 reduction. These initially nonlinear rates of C2H2 reduction are attributable to transient O2 inhibition of nitrogenase. Initial nonlinear rates of C2H2 reduction were also observed with immature soybean plants and with intact plant assays of O. sativa and S. olneyi in which C2H2 was injected into cylinders surrounding the plant tops. These results indicate that, apart from O2 inhibition of nitrogenase, the diffusion of C2H2 and C2H4 between the nitrogen-fixing sites and the sampling ports may cause initial nonlinear rates of C2H2 reduction. We conclude that in situ plant-associated nitrogenase activity should result in immediate reduction of C2H2 and that linear rates are observed when the proper assay conditions are used. Our data suggest that nitrogen fixation is closely associated with the roots of S. olneyi, O. sativa, and S. alterniflora growing in salt marsh sediment. PMID:16345684

  14. Root-Associated N2 Fixation (Acetylene Reduction) by Enterobacteriaceae and Azospirillum Strains in Cold-Climate Spodosols

    PubMed Central

    Haahtela, Kielo; Wartiovaara, Tuula; Sundman, Veronica; Skuji?, J.

    1981-01-01

    N2 fixation by bacteria in associative symbiosis with washed roots of 13 Poaceae and 8 other noncultivated plant species in Finland was demonstrated by the acetylene reduction method. The roots most active in C2H2 reduction were those of Agrostis stolonifera, Calamagrostis lanceolata, Elytrigia repens, and Phalaris arundinacea, which produced 538 to 1,510 nmol of C2H4g?1 (dry weight) h?1 when incubated at pO2 0.04 with sucrose (pH 6.5), and 70 to 269 nmol of C2H4 g?1 (dry weight)h?1 without an added energy source and unbuffered. Azospirillum lipferum, Enterobacter agglomerans, Klebsiella pneumoniae, and a Pseudomonas sp. were the acetylene-reducing organisms isolated. The results demonstrate the presence of N2-fixing organisms in associative symbiosis with plant roots found in a northern climatic region in acidic soils ranging down to pH 4.0. PMID:16345687

  15. Nitrogen fixation (Acetylene Reduction) by annual winter legumes on a coal surface mine

    SciTech Connect

    Gabrielson, F.C.

    1982-01-01

    The winter annuals, crimson clover, rose clover, subterranean clover and hairy vetch, were evaluated for nitrogen fixing capacity on coal surface mine substrates by measuring their ability to reduce acetylene to ethylene. The effects of fertilizer, Abruzzi rye, Kentucky 31 fescue grass and a phytotoxic plant Chenopodium album on nitrogen fixation were also assessed. Crimson clover was recommended as the best legume to use on topsoil and shale in the south. Hairy vetch gave good results on shale and subterranean clover did well on topsoil. The use of these species for revegetation is discussed. Overall, no correlation between substrate pH and ethylene levels was found and effects of substrate depended upon the legume species. Super phosphate fertilizer supported less nitrogen fixation than 13-13-13. Abruzzi rye in some unknown way inhibited plant density and nitrogen fixation by legumes but not by free living substrate micro-organisms. Shale from under dead Chenopodium plants in both field and greehouse experiments did not inhibit nitrogen fixation. 7 tables.

  16. Nitrogen fixation (acetylene reduction) by annual winter legumes on a coal surface mine

    SciTech Connect

    Gabrielson, F.C.

    1982-01-01

    The winter annuals, crimson clover, rose clover, subterranean clover and hairy vetch, were evaluated for their ability to fix nitrogen on coal surface mine substrates by measuring their ability to reduce acetylene to ethylene. The effects of fertilizer, Abruzzi ryegrass, Kentucky 31 fescue grass and a phytotoxic plant Chenopodium album on nitrogen fixation was also assessed. Crimson clover was recommended as the best legume to use on topsoil and shale in the South. Hairy vetch gave good results on shale and subterranean clover did well on topsoil. The use of these species for revegetation is discussed. Overall, no correlation between substrate pH and ethylene levels was found and effects of substrate depended upon the legume species. Super phosphate fertilizer supported less nitrogen fixation than 13-13-13. Abruzzi ryegrass in some unknown way inhibited plant density and nitrogen fixation by legumes but not by free living substrate micro-organisms. Shale from under dead Chenopodium plants in both field and greenhouse experiments did not inhibit nitrogen fixation. 11 references, 7 tables.

  17. The Effect of NaCl on growth, N2 fixation (acetylene reduction), and percentage total nitrogen in Leucaena leucocephala (Leguminosae) var. K-8.

    PubMed

    Anthraper, Annie; Dubois, John D

    2003-05-01

    Leucaena leucocephala var. K-8 is a fast-growing, tropical leguminous tree that has multiple economic uses. This study was conducted to evaluate the effect(s) of varying NaCl concentrations on growth, N(2) fixation, and percentage of total tissue nitrogen in different organs in L. leucocephala. Seeds were germinated and grown for 10 wk with a nitrogen-free fertilizer applied every 2 wk. At 10 wk, plants were treated for either 0, 7, 14, 21, or 28 wk with either deionized water (control), 0.00625 mol/L, 0.0125 mol/L, 0.025 mol/L, 0.05 mol/L, or 0.1 mol/L NaCl in addition to the fertilizer every 2 wk. Growth was measured as plant height, nodule number and mass, and dry tissue mass. N(2) fixation was measured by the acetylene reduction assay. Percentage of tissue nitrogen was determined using Kjeldahl analysis. In younger plants (7-wk treatment), major fluctuations in NaCl tolerance were observed in the different plant organs. As plants matured (14- and 21-wk treatment) NaCl concentrations of 0.025 mol/L and higher caused the greatest reduction in growth and tissue nitrogen. We conclude that NaCl concentrations of 0.025 mol/L and greater caused a major decrease in growth, N(2) fixation, and percentage of tissue nitrogen in L. leucocephala plants that were less than 1 yr old. PMID:21659163

  18. Simultaneous Measurement of Nitrogen Fixation Estimated by Acetylene-Ethylene Assay and Nitrate Absorption by Soybeans 1

    PubMed Central

    Wych, Robert D.; Rains, D. William

    1978-01-01

    An apparatus was designed for simultaneous measurement of rates of N2 fixation estimated by C2H2-C2H4 assay (N2[C2H2] fixation) and NO3? absorption by roots of intact, nodulated soybeans (Glycine max [L.] Merr.). The principal design features include: (a) a gas-tight mist chamber in which nodulated roots can be exposed simultaneously to C2H2 in the gas phase and to a liquid phase containing NO3? sprayed in a fine mist; and (b) provision for sampling the gas phase for C2H4 determination, and the liquid phase for NO3? determination. We studied NO3? absorption by soybeans as affected by nodulation, NO3? concentration during assay, and previous N nutrition during growth in nutrient solution culture in controlled environment chambers. It was established that 0.5 mm NO3? nearly saturated the NO3? absorption system of both nodulated and unnodulated soybeans when the concentration dependence of NO3? absorption rate was measured just after flowering began. Nitrate absorption rates were measured after development of N stress in unnodulated plants, and during recovery from N stress in nodulated plants. The results suggested that the lower capacity for NO3? absorption of nodulated plants was a consequence of N stress during the period of nodule growth and development. Nitrogen [C2H2] fixation rates were compared in intact plants assayed in the mist chamber and in excised roots assayed in both the mist chamber and in glass jars. Excised roots had a lower N2[C2H2] fixation rate than intact plants. The decline observed during the first hour after shoot removal was more pronounced for glass jar-assayed excised roots than for mist chamber-assayed excised roots. We discuss the advantages of our method for assessing the capability of a nodulated legume to acquire nitrogen through both N2 fixation and absorption and assimilation of NO3?. PMID:16660534

  19. Data-reduction methods for immunoradiometric assays of thyrotropin compared

    SciTech Connect

    Haven, M.C.; Orsulak, P.J.; Arnold, L.L.; Crowley, G.

    1987-07-01

    In an attempt to optimize curve fitting for immunoradiometric assays, we investigated eight data-reduction methods with two commercially available assays of thyrotropin. In four of these methods linear data-reduction models are used: logit-log programs of Iso-Data, Micromedic, and Hewlitt-Packard, and probit-log of Hewlitt-Packard. The other four were nonlinear data-reduction models: Iso-Data's French curve (modified spline), four-parameter logistic function, and point-to-point methods, as well as a nonlinear least squares method. In using the eight data-reduction methods on data from analyses of 78 patients' samples, we found clinically relevant differences between models. In fact, differences found by changing data-reduction models were greater than the difference between the two commercial kits.

  20. Nitrogen Fixation (Acetylene Reduction) Associated with Decaying Leaves of Pond Cypress (Taxodium distichum var. nutans) in a Natural and a Sewage-Enriched Cypress Dome

    PubMed Central

    Dierberg, Forrest E.; Brezonik, Patrick L.

    1981-01-01

    Surface litter from a natural and a sewage-enriched cypress dome in north-central Florida showed a pronounced seasonal pattern of nitrogenase (acetylene reduction) activity associated with seasonal leaf fall from deciduous trees in the domes. Samples of peat from cores indicated negligible nitrogenase activity below the surface layer. Integrating the monthly rates of nitrogen fixation (based on the theoretical molar ratio of 3:2 for C2H4/NH3) yielded 0.39 and 0.12 g of N/m2 per year fixed in the litter of the natural and sewage-enriched domes, respectively. The nitrogen fixed in the first 3 months after leaf fall in the natural dome represented about 14% of the nitrogen increment in the decomposing cypress leaves, but fixation contributed a negligible amount of nitrogen (<1%) to decomposing litter in the sewage-enriched dome. PMID:16345796

  1. Acetylene Reduction by Symbiosomes and Free Bacteroids from Broad Bean (Vicia faba L.) Nodules (Role of Oxalate).

    PubMed Central

    Trinchant, J. C.; Guerin, V.; Rigaud, J.

    1994-01-01

    We report the presence of oxalate in the organic acid fraction of broad bean (Vicia faba L.) nodule cytosol. Using both high-performance liquid chromatography and enzymic assays, high levels of oxalate were detected (70.4 [plus or minus] 2.4 mM). To study the potential role of oxalate as an energy-yielding substrate for nitrogenase activity, free bacteroids were isolated from nodules and found to oxidize oxalate in support of C2H2 reduction under O2 tensions that were lower than those required to oxidize succinate, another dicarboxylate commonly detected in legume nodules. Symbiosomes of broad bean, isolated for the first time from amide-producing nodules, were provided with [14C]oxalate and found to have uptake kinetics with a lower affinity [Km(oxalate) = 330 [mu]M] than that for free bacteroids [Km(oxalate) = 130 [mu]M]. In anaerobic preparations of symbiosomes supplied with purified oxyleghemoglobin, O2 consumption was stimulated by oxalate from 20.2 [plus or minus] 0.8 nmol O2 min-1mg-1 protein to 24.5 [plus or minus] 1.1 nmol O2 min-1 mg-1 protein but always remained lower than the rate of O2 consumption in free bacteroids (32.2 [plus or minus] 1.4 nmol O2 min-1 mg-1 protein). Under these conditions, C2H2 reduction activity was 9.7 [plus or minus] 0.8 and 15.1 [plus or minus] 0.9 nmol C2H4 min-1 mg-1 protein for symbiosomes and bacteroids, respectively. These data support the suggestion that oxalate may play a role as a carbon substrate in support of N2 fixation in broad bean nodules. PMID:12232223

  2. Molecule-assisted nanoparticle clustering effect in immunomagnetic reduction assay

    NASA Astrophysics Data System (ADS)

    Yang, S. Y.; Chieh, J. J.; Huang, K. W.; Yang, C. C.; Chen, T. C.; Ho, C. S.; Chang, S. F.; Chen, H. H.; Horng, H. E.; Hong, C. Y.; Yang, H. C.

    2013-04-01

    Immunomagnetic reduction assay is used to quantitatively detect bio-molecules. Many reports show that the to-be-detected bio-molecular concentration dependent reduction in the alternative-current (ac) magnetic susceptibility of a reagent is governed by the logistic function, which is a four-parameter function. One of the parameters relates to the increase in the rate of the magnetic reduction signal when the concentration of to-be-detected bio-molecules is increased. Theoretically, this parameter is attributed to the clustering associations between to-be-detected bio-molecules and labeling particles in the reagent. In an immunomagnetic reduction assay, the bioactive labeling particles are anti-body-functionalized magnetic nanoparticles. However, there is no detailed information about the effect of the clustering associations on this parameter. In this work, the clustering association is manipulated by controlling the concentrations of anti-body-functionalized magnetic nanoparticles in the reagent. The experimental results show that higher values for this parameter are obtained with concentrated anti-body-functionalized magnetic nanoparticles in the reagent. This implies that particle clustering is enhanced by an increase in the concentration of the bio-functionalized magnetic particles. It is also demonstrated that the particle clustering effect dominates the increased rate of the magnetic reduction signal.

  3. Examining the impact of acetylene on N-fixation and the active sediment microbial community

    PubMed Central

    Fulweiler, Robinson W.; Heiss, Elise M.; Rogener, Mary Kate; Newell, Silvia E.; LeCleir, Gary R.; Kortebein, Sarah M.; Wilhelm, Steven W.

    2015-01-01

    Here we examined the impact of a commonly employed method used to measure nitrogen fixation, the acetylene reduction assay (ARA), on a marine sediment community. Historically, the ARA technique has been broadly employed for its ease of use, in spite of numerous known artifacts. To gauge the severity of these effects in a natural environment, we employed high-throughput 16S rRNA gene sequencing to detect differences in acetylene-treated sediments vs. non-treated control sediments after a 7 h incubation. Within this short time period, significant differences were seen across all activity of microbes identified in the sediment, implying that the changes induced by acetylene occur quickly. The results have important implications for our understanding of marine nitrogen budgets. Moreover, because the ARA technique has been widely used in terrestrial and freshwater habitats, these results may be applicable to other ecosystems. PMID:26029177

  4. Immunomagnetic reduction assay for nervous necrosis virus extracted from groupers.

    PubMed

    Lu, M W; Yang, S Y; Horng, H E; Yang, C C; Chieh, J J; Hong, Y W; Hong, C Y; Yang, H C; Wu, J L

    2012-04-01

    Nervous necrosis virus (NNV) is the cause of viral nervous disease, which is a serious constraint on production for grouper aquaculture. Real-time PCR is commonly used to detect and quantify NNV, has the disadvantages of being expensive and technically demanding. In this study, an immunomagnetic reduction (IMR) assay was developed as a rapid and cost-effective alternative to real-time PCR. This method used magnetic nanoparticles conjugated with antibodies specific for viral surface antigens to detect NNV in grouper tissue samples. The association of NNV with the antibody-conjugated magnetic particles resulted in a reduction in magnetic signal, which was strongly correlated with the concentration of NNV, as determined by real-time PCR. Grouper larvae were prepared for testing using a viral extraction buffer which provided a rapid, 15-min method of extracting viral antigens and had an extraction efficiency of higher than 80%. In addition, this study proposes using magnetic nanoparticles as labeling markers and as an assaying reagent for NNV. The magnetic nanoparticles are functionalized with antibodies against the viral surface of NNV and are able to associate specifically with NNV. The reduction of the magnetic signals comes from the association between magnetic particles and NNV, and relates to the concentration of NNV. The results show that the detected concentrations of NNV are highly correlated to those detected by real-time PCR. PMID:22335935

  5. Properties of acetylene

    SciTech Connect

    Pavlovcak, J.T.

    1994-12-31

    Acetylene continues to be the most widely used fuel in the oxyfuel cutting and welding industry. It displays properties that enhance its benefits to the industry, but at the same time, present potential hazards that have to be addressed. The presentation explores the main properties or characteristics of acetylene -- odor, toxicity, flammability, composition, and manufacture. it expands on those properties that are unique to acetylene and which account for its main value to the user or which constitute the chief concern for safe use of acetylene. The presentation explains characteristics such as anosmia, flammable or explosive range, ignition energy, autoignition temperature, and flame temperature, comparing these values for acetylene to other common gaseous fuels. it explains the unique property of acetylene to decompose explosively in the absence of air or oxygen. The toxicological aspects of acetylene is discussed, including anesthetic effect and simple asphyxiant, showing the increasing severity of symptoms to increasing levels of oxygen deficiency. The main value of this basic review of the properties of acetylene is to remind people of the benefits of acetylene due to its unique properties, and to realert them to the potential hazards that also have to be addressed to control the properties of acetylene.

  6. Plasma Thermal Conversion of Methane to Acetylene

    SciTech Connect

    Fincke, James Russell; Anderson, Raymond Paul; Hyde, Timothy Allen; Detering, Brent Alan; Wright, Randy Ben; Bewley, Randy Lee; Haggard, Delon C; Swank, William David

    2002-03-01

    This paper describes a re-examination of a known process for the direct plasma thermal conversion of methane to acetylene. Conversion efficiencies (% methane converted) approached 100% and acetylene yields in the 90–95% range with 2–4% solid carbon production were demonstrated. Specificity for acetylene was higher than in prior work. Improvements in conversion efficiency, yield, and specificity were due primarily to improved injector design and reactant mixing, and minimization of temperature gradients and cold boundary layers. At the 60-kilowatt scale cooling by wall heat transfer appears to be sufficient to quench the product stream and prevent further reaction of acetylene resulting in the formation of heavier hydrocarbon products or solid carbon. Significantly increasing the quenching rate by aerodynamic expansion of the products through a converging–diverging nozzle led to a reduction in the yield of ethylene but had little effect on the yield of other hydrocarbon products. While greater product selectivity for acetylene has been demonstrated, the specific energy consumption per unit mass of acetylene produced was not improved upon. A kinetic model that includes the reaction mechanisms resulting in the formation of acetylene and heavier hydrocarbons, through benzene, is described.

  7. Acetylenic carbon allotrope

    DOEpatents

    Lagow, Richard J. (6204 Shadow Mountain Dr., Austin, TX 78731)

    1999-01-01

    A fourth allotrope of carbon, an acetylenic carbon allotrope, is described. The acetylenic carbon allotropes of the present invention are more soluble than the other known carbon allotropes in many common organic solvents and possesses other desirable characteristics, e.g. high electron density, ability to burn cleanly, and electrical conductive properties. Many uses for this fourth allotrope are described herein.

  8. Acetylenic carbon allotrope

    DOEpatents

    Lagow, Richard J. (6204 Shadow Mountain Dr., Austin, TX 78731)

    1998-01-01

    A fourth allotrope of carbon, an acetylenic carbon allotrope, is described. The acetylenic carbon allotropes of the present invention are more soluble than the other known carbon allotropes in many common organic solvents and possesses other desirable characteristics, e.g. high electron density, ability to burn cleanly, and electrical conductive properties. Many uses for this fourth allotrope are described herein.

  9. Acetylenic carbon allotrope

    DOEpatents

    Lagow, R.J.

    1998-02-10

    A fourth allotrope of carbon, an acetylenic carbon allotrope, is described. The acetylenic carbon allotropes of the present invention are more soluble than the other known carbon allotropes in many common organic solvents and possesses other desirable characteristics, e.g. high electron density, ability to burn cleanly, and electrical conductive properties. Many uses for this fourth allotrope are described herein. 17 figs.

  10. Proton exchange membrane fuel cell cathode contamination - Acetylene

    NASA Astrophysics Data System (ADS)

    Zhai, Y.; St-Pierre, Jean

    2015-04-01

    Acetylene adsorption on PEMFC electrodes and contamination in single cells are investigated with 300 ppm acetylene at a cathode held at 80 C. The results of adsorption experiments suggest that acetylene adsorbs readily on electrodes and is reduced to ethylene and ethane under an open circuit potential of H2/N2, as the adsorbates can be electro-oxidized at high potentials. The cell voltage response shows that 300 ppm acetylene results in a cell performance loss of approximately 88%. The voltage degradation curve is divided into two stages by an inflection point, which suggests that potential-dependent processes are involved in acetylene poisoning. These potential-dependent processes may include acetylene oxidation and reduction as well as accumulation of intermediates on the electrode surface. Electrochemical impedance spectroscopy analysis suggests that acetylene affects the oxygen reduction reaction and may also affect mass transport processes. Acetylene also may be reduced in the steady poisoning state of the operating cell. After neat air operation, the cyclic voltammetry results imply that the cathode catalyst surface is almost completely restored, with no contaminant residues remaining in the MEA. Linear scanning voltammetry measurements show no change in hydrogen crossover caused by contamination, and polarization curves confirm complete recovery of cell performance.

  11. Anaerobic oxidation of acetylene by estuarine sediments and enrichment cultures

    USGS Publications Warehouse

    Culbertson, Charles W.; Zehnder, Alexander J. B.; Oremland, Ronald S.

    1981-01-01

    Acetylene disappeared from the gas phase of anaerobically incubated estuarine sediment slurries, and loss was accompanied by increased levels of carbon dioxide. Acetylene loss was inhibited by chloramphenicol, air, and autoclaving. Addition of 14C2H2 to slurries resulted in the formation of 14CO2 and the transient appearance of 14C-soluble intermediates, of which acetate was a major component. Acetylene oxidation stimulated sulfate reduction; however, sulfate reduction was not required for the loss of C2H2 to occur. Enrichment cultures were obtained which grew anaerobically at the expense of C2H2.

  12. Acylamidation of acetylenes

    SciTech Connect

    Gridnev, I.D.; Balenkova, E.S.

    1989-01-10

    The reactions of phenylacetylene, 1-heptyne, and diphenylacetylene with the complexes of acetylfluoroborate with acetonitrile and with chloroacetonitrile take place regiospecifically and stereospecifically as syn-addition of the acetyl group and nitrile at the triple bond of the acetylene and lead to previously unknown Z-N-acyl-/beta/-amino, /alpha/,/beta/-unsaturated ketones.

  13. Acetylene terminated matrix resins

    NASA Technical Reports Server (NTRS)

    Goldfarb, I. J.; Lee, Y. C.; Arnold, F. E.; Helminiak, T. E.

    1985-01-01

    The synthesis of resins with terminal acetylene groups has provided a promising technology to yield high performance structural materials. Because these resins cure through an addition reaction, no volatile by-products are produced during the processing. The cured products have high thermal stability and good properties retention after exposure to humidity. Resins with a wide variety of different chemical structures between the terminal acetylene groups are synthesized and their mechanical properties studied. The ability of the acetylene cured polymers to give good mechanical properties is demonstrated by the resins with quinoxaline structures. Processibility of these resins can be manipulated by varying the chain length between the acetylene groups or by blending in different amounts of reactive deluents. Processing conditions similar to the state-of-the-art epoxy can be attained by using backbone structures like ether-sulfone or bis-phenol-A. The wide range of mechanical properties and processing conditions attainable by this class of resins should allow them to be used in a wide variety of applications.

  14. Evaluation of colorimetric assays for analyzing reductively methylated proteins: Biases and mechanistic insights.

    PubMed

    Brady, Pamlea N; Macnaughtan, Megan A

    2015-12-15

    Colorimetric protein assays, such as the Coomassie blue G-250 dye-binding (Bradford) and bicinchoninic acid (BCA) assays, are commonly used to quantify protein concentration. The accuracy of these assays depends on the amino acid composition. Because of the extensive use of reductive methylation in the study of proteins and the importance of biological methylation, it is necessary to evaluate the impact of lysyl methylation on the Bradford and BCA assays. Unmodified and reductively methylated proteins were analyzed using the absorbance at 280nm to standardize the concentrations. Using model compounds, we demonstrate that the dimethylation of lysyl ?-amines does not affect the proteins' molar extinction coefficients at 280nm. For the Bradford assay, the responses (absorbance per unit concentration) of the unmodified and reductively methylated proteins were similar, with a slight decrease in the response upon methylation. For the BCA assay, the responses of the reductively methylated proteins were consistently higher, overestimating the concentrations of the methylated proteins. The enhanced color formation in the BCA assay may be due to the lower acid dissociation constants of the lysyl ?-dimethylamines compared with the unmodified ?-amine, favoring Cu(II) binding in biuret-like complexes. The implications for the analysis of biologically methylated samples are discussed. PMID:26342307

  15. Spectrophotometric total reducing sugars assay based on cupric reduction.

    PubMed

    Başkan, Kevser Sözgen; Tütem, Esma; Akyüz, Esin; Özen, Seda; Apak, Reşat

    2016-01-15

    As the concentration of reducing sugars (RS) is controlled by European legislation for certain specific food and beverages, a simple and sensitive spectrophotometric method for the determination of RS in various food products is proposed. The method is based on the reduction of Cu(II) to Cu(I) with reducing sugars in alkaline medium in the presence of 2,9-dimethyl-1,10-phenanthroline (neocuproine: Nc), followed by the formation of a colored Cu(I)-Nc charge-transfer complex. All simple sugars tested had the linear regression equations with almost equal slope values. The proposed method was successfully applied to fresh apple juice, commercial fruit juices, milk, honey and onion juice. Interference effect of phenolic compounds in plant samples was eliminated by a solid phase extraction (SPE) clean-up process. The method was proven to have higher sensitivity and precision than the widely used dinitrosalicylic acid (DNS) colorimetric method. PMID:26592591

  16. Acetylene-Terminated Polyimide Siloxanes

    NASA Technical Reports Server (NTRS)

    St. Clair, Terry L.; Maudgal, Shubba

    1987-01-01

    Siloxane-containing addition polyimides yield toughened high-temperature adhesives and matrix resins. Addition polyimide made by reaction of aromatic tetracarboxylic acid dianhydride with aromatic diamine in presence of ethynyl-substituted aromatic monoamine. Acetylene-terminated siloxane imide cured by heating to yield acetylene-terminated polyimide siloxane.

  17. Measurement of rotavirus-neutralizing coproantibody in children by fluorescent focus reduction assay.

    PubMed Central

    Coulson, B S; Masendycz, P J

    1990-01-01

    A fluorescent focus reduction assay suitable for the measurement of rotavirus-neutralizing antibodies in the feces of children was developed. Of 408 stools tested, 7% showed false-positive neutralization, and the number of rotavirus serotypes neutralized by a fecal extract was proportional to the levels of antirotaviral immunoglobulin A in the extract. PMID:2166091

  18. 29 CFR 1910.102 - Acetylene.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...). (b) Piped systems. (1) Employers must comply with Chapter 9 (Acetylene Piping) of NFPA 51A-2006... may comply with the provisions of Chapter 7 (Acetylene Piping) of NFPA 51A-2001 (Standard for... acetylene piping systems, see CGA G-1.2-2006, part 3 (Acetylene piping) (Compressed Gas Association,...

  19. 29 CFR 1910.102 - Acetylene.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...). (b) Piped systems. (1) Employers must comply with Chapter 9 (Acetylene Piping) of NFPA 51A-2006... may comply with the provisions of Chapter 7 (Acetylene Piping) of NFPA 51A-2001 (Standard for... acetylene piping systems, see CGA G-1.2-2006, part 3 (Acetylene piping) (Compressed Gas Association,...

  20. 29 CFR 1910.102 - Acetylene.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...., 2003). (b) Piped systems. (1) Employers must comply with Chapter 9 (Acetylene Piping) of NFPA 51A..., 2006, these employers may comply with the provisions of Chapter 7 (Acetylene Piping) of NFPA 51A-2001... additional information on acetylene piping systems, see CGA G-1.2-2006, part 3 (Acetylene...

  1. Infrared Spectra of ACETYLENE-D2 Clusters

    NASA Astrophysics Data System (ADS)

    Mivehvar, F.; Oliaee, J. Norooz; Dehghany, M.; Moazzen-Ahmadi, N.; McKellar, A. R. W.

    2010-06-01

    In an effort to observe the spectra of acetylene clusters (C2H2)% n with ngeq 4 and the very weakly bound He-C2H2 complex, spectra of acetylene-d2 clusters in the region of the C2D2 % ? 3 fundamental ( 2439 cm-1) were recorded using a tunable diode laser to probe a pulsed supersonic slit jet expansion. So far, several bands below 2439 cm-1 have been recorded. Two can be attributed to a parallel ? 3|| and perpendicular ? 3perp band for the T-shaped C2D2 dimer. The interconvesion splittings are clearly seen in these bands. There are other mystery bands whose origins are being investigated both experimentally and theoretically. In this talk I will discuss possible assignments of these bands to C2D2 clusters.

  2. Research in acetylene containing monomers

    NASA Technical Reports Server (NTRS)

    Ogliaruso, M. A.

    1976-01-01

    The preparation of precursor bisbenzils with pendant acetylene linkages for use in the synthesis of new aromatic poly (phenyl quinoxalines) was investigated. Attempts to condense para, para prime-dibromo benzil and potassium acetylide in liquid ammonia and in toluene, to prepare 4-phenyl acetyl phenyl ether, 4-(paraacetylphenyl) acetyl phenyl ether, 4-phenyl acetyl-4 primeacetyl phenyl acetyl phenyl ether, the reaction of 4-phenyl acetyl phenyl ether with Villsmeier reagent to prepare 4-(beta-chloro cinnamaldehyde) phenyl ether, the reaction of 4-(para-acetyl phenyl) acetyl phenyl ether with Villsmeier reagent, and the oxidation of bibenzil to prepare benzil are described. The reactions of phenyl acetylene with oxidizing agent, of phenyl acetylene with bromine, of 1,1,2,2-tetrabromo ethyl benzene with zinc and with oxidizing agent are described.

  3. 46 CFR 147.70 - Acetylene.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 5 2010-10-01 2010-10-01 false Acetylene. 147.70 Section 147.70 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) DANGEROUS CARGOES HAZARDOUS SHIPS' STORES Stowage and Other Special Requirements for Particular Materials § 147.70 Acetylene. (a) Seventeen cubic meters (600 standard cubic feet) or less of acetylene may...

  4. The adaptive control system of acetylene generator

    NASA Astrophysics Data System (ADS)

    Kovaliuk, D. O.; Kovaliuk, Oleg; Burlibay, Aron; Gromaszek, Konrad

    2015-12-01

    The method of acetylene production in acetylene generator was analyzed. It was found that impossible to provide the desired process characteristics by the PID-controller. The adaptive control system of acetylene generator was developed. The proposed system combines the classic controller and fuzzy subsystem for controller parameters tuning.

  5. 41 CFR 50-204.66 - Acetylene.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 41 Public Contracts and Property Management 1 2010-07-01 2010-07-01 true Acetylene. 50-204.66..., Vapors, Fumes, Dusts, and Mists 50-204.66 Acetylene. (a) The in-plant transfer, handling, storage, and utilization of acetylene in cylinders shall be in accordance with Compressed Gas Association Pamphlet...

  6. Thermal Conversion of Methane to Acetylene

    SciTech Connect

    Fincke, James Russell; Anderson, Raymond Paul; Hyde, Timothy Allen; Wright, Randy Ben; Bewley, Randy Lee; Haggard, Delon C; Swank, William David

    2000-01-01

    This report describes the experimental demonstration of a process for the direct thermal conversion of methane to acetylene. The process utilizes a thermal plasma heat source to dissociation products react to form a mixture of acetylene and hydrogen. The use of a supersonic expansion of the hot gas is investigated as a method of rapidly cooling (quenching) the product stream to prevent further reaction or thermal decomposition of the acetylene which can lower the overall efficiency of the process.

  7. Acetylene terminated aspartimides and resins therefrom

    NASA Technical Reports Server (NTRS)

    Hergenrother, Paul M. (inventor); Connell, John W. (inventor); Havens, Stephen J. (inventor)

    1989-01-01

    Acetylene terminated aspartimides are prepared using two methods. In the first, an amino-substituted aromatic acetylene is reacted with an aromatic bismaleimide in a solvent of glacial acetic acid and/or m-cresol. In the second method, an aromatic diamine is reacted with an ethynyl containing maleimide, such an N-(3-ethynyl phenyl) maleimide, in a solvent of glacial acetic acid and/or m-cresol. In addition, acetylene terminated aspartimides are blended with various acetylene terminated oligomers and polymers to yield composite materials exhibiting improved mechanical properties.

  8. Reduction of misleading ("false") positive results in mammalian cell genotoxicity assays. I. Choice of cell type.

    PubMed

    Fowler, Paul; Smith, Katie; Young, Jamie; Jeffrey, Laura; Kirkland, David; Pfuhler, Stefan; Carmichael, Paul

    2012-02-18

    Current in vitro mammalian cell genotoxicity assays show a high rate of positive results, many of which are misleading when compared with in vivo genotoxicity or rodent carcinogenicity data. P53-deficiency in many of the rodent cell lines may be a key factor in this poor predictivity. As part of an European Cosmetics Industry Association initiative for improvement of in vitro mammalian cell assays, we have compared several rodent cell lines (V79, CHL, CHO) with p53-competent human peripheral blood lymphocytes (HuLy), TK6 human lymphoblastoid cells, and the human liver cell line, HepG2. We have compared in vitro micronucleus (MN) induction following treatment with 19 compounds that were accepted as producing misleading or "false" positive results in in vitro mammalian cell assays [6]. Of these, six chemicals (2-ethyl-1,3-hexandiol, benzyl alcohol, urea, sodium saccharin, sulfisoxazole and isobutyraldehyde) were not toxic and did not induce any MN at concentrations up to 10mM. d,l-Menthol and ethionamide induced cytotoxicity, but did not induce MN. o-Anthranilic acid was not toxic and did not induce MN in V79, CHL, CHO, HuLy and HepG2 cells up to 10mM. Toxicity was induced in TK6 cells, although there were no increases in MN frequency up to and above the 55% toxicity level. The other 10 chemicals (1,3-dihydroxybenzene, curcumin, propyl gallate, p-nitrophenol, ethyl acrylate, eugenol, tert-butylhydroquinone, 2,4-dichlorophenol, sodium xylene sulfonate and phthalic anhydride) produced cytotoxicity in at least one cell type, and were evaluated further for MN induction in most or all of the cell types listed above. All these chemicals induced MN at concentrations <10mM, with levels of cytotoxicity below 60% (measured as the replication index) in at least one cell type. The rodent cell lines (V79, CHO and CHL) were consistently more susceptible to cytotoxicity and MN induction than p53-competent cells, and are therefore more susceptible to giving misleading positive results. These data suggest that a reduction in the frequency of misleading positive results can be achieved by careful selection of the mammalian cell type for genotoxicity testing. PMID:22138618

  9. Evaluation of Sorbents for Acetylene Separation in Atmosphere Revitalization Loop Closure

    NASA Technical Reports Server (NTRS)

    Abney, Morgan B.; Miller, Lee A.; Barton, Katherine

    2012-01-01

    State-of-the-art carbon dioxide reduction technology uses a Sabatier reactor to recover water from metabolic carbon dioxide. In order to maximize oxygen loop closure, a byproduct of the system, methane, must be reduced to recover hydrogen. NASA is currently exploring a microwave plasma methane pyrolysis system for this purpose. The resulting product stream of this technology includes unreacted methane, product hydrogen, and acetylene. The hydrogen and the small amount of unreacted methane resulting from the pyrolysis process can be returned to the Sabatier reactor thereby substantially improving the overall efficiency of the system. However, the acetylene is a waste product that must be removed from the pyrolysis product. Two materials have been identified as potential sorbents for acetylene removal: zeolite 4A, a commonly available commercial sorbent, and HKUST-1, a newly developed microporous metal. This paper provides an explanation of the rationale behind acetylene removal and the results of separation testing with both materials

  10. Evaluation of Sorbents for Acetylene Separation in Atmosphere Revitalization Loop Closure

    NASA Technical Reports Server (NTRS)

    Abney, Morgan B.; Miller, Lee A.; Barton, Katherine

    2011-01-01

    State-of-the-art carbon dioxide reduction technology uses a Sabatier reactor to recover water from metabolic carbon dioxide. In order to maximize oxygen loop closure, a byproduct of the system, methane, must be reduced to recover hydrogen. NASA is currently exploring a microwave plasma methane pyrolysis system for this purpose. The resulting product stream of this technology includes unreacted methane, product hydrogen, and acetylene. The hydrogen and the small amount of unreacted methane resulting from the pyrolysis process can be returned to the Sabatier reactor thereby substantially improving the overall efficiency of the system. However, the acetylene is a waste product that must be removed from the pyrolysis product. Two materials have been identified as potential sorbents for acetylene removal: zeolite 4A, a commonly available commercial sorbent, and HKUST-1, a newly developed microporous metal. This paper provides an explanation of the rationale behind acetylene removal and the results of separation testing with both materials.

  11. PERKINSUS-"CIDAL" ACTIVITY OF OYSTER HEMOCYTES USING A TETRAZOLIUM DYE REDUCTION ASSAY: OPTIMIZATION AND APPLICATIONS

    EPA Science Inventory

    A bactericidal assay developed to assess the ability of oyster (Crassostrea virginica) hemocytes to kill the human pathogen Vibrio parahaemolyticus was optimized to estimate killing of the oyster parasite Perkinsus marinus. Assay variables, temperature, hemocyte:parasite ratio, i...

  12. 46 CFR 147.70 - Acetylene.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 5 2011-10-01 2011-10-01 false Acetylene. 147.70 Section 147.70 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) DANGEROUS CARGOES HAZARDOUS SHIPS' STORES Stowage and Other Special Requirements for Particular Materials § 147.70 Acetylene. (a) Seventeen cubic meters (600...

  13. 46 CFR 147.70 - Acetylene.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 5 2014-10-01 2014-10-01 false Acetylene. 147.70 Section 147.70 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) DANGEROUS CARGOES HAZARDOUS SHIPS' STORES Stowage and Other Special Requirements for Particular Materials § 147.70 Acetylene. (a) Seventeen cubic meters (600...

  14. 46 CFR 147.70 - Acetylene.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 5 2013-10-01 2013-10-01 false Acetylene. 147.70 Section 147.70 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) DANGEROUS CARGOES HAZARDOUS SHIPS' STORES Stowage and Other Special Requirements for Particular Materials § 147.70 Acetylene. (a) Seventeen cubic meters (600...

  15. 46 CFR 147.70 - Acetylene.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 5 2012-10-01 2012-10-01 false Acetylene. 147.70 Section 147.70 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) DANGEROUS CARGOES HAZARDOUS SHIPS' STORES Stowage and Other Special Requirements for Particular Materials § 147.70 Acetylene. (a) Seventeen cubic meters (600...

  16. 29 CFR 1910.102 - Acetylene.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...-2006 (“Standard for Acetylene Charging Plants”) (National Fire Protection Association, 2006 ed., 2006... (“Standard for Acetylene Charging Plants”) (National Fire Protection Association, 2001 ed., 2001). (3) The... Plants”) (National Fire Protection Association, 2006 ed., 2006). (2) When employers can demonstrate...

  17. RAPID TETRAZOLIUM DYE REDUCTION ASSAY TO ASSESS THE BACTERICIDAL ACTIVITY OF OYSTER (CRASSOSTREA VIRGINICA) HEMOCYTES AGAINST VIBRIO PARAHAEMOLYTICUS

    EPA Science Inventory

    An assay was developed to assess the ability of oyster, Crassostrea virginica, hemocytes to kill the human pathogenic bacterium, Vibrio parahaemolyticus (ATCC 17802). Bacterial killing was estimated colorimetrically by the enzymatic reduction of a tetrazolium dye, 3-(4,5-dimethyl...

  18. A Novel Detection Platform for Shrimp White Spot Syndrome Virus Using an ICP11-Dependent Immunomagnetic Reduction (IMR) Assay

    PubMed Central

    Liu, Bing-Hsien; Lin, Yu-Chen; Ho, Chia-Shin; Yang, Che-Chuan; Chang, Yun-Tsui; Chang, Jui-Feng; Li, Chun-Yuan; Cheng, Cheng-Shun; Huang, Jiun-Yan; Lee, Yen-Fu; Hsu, Ming-Hung; Lin, Feng-Chun; Wang, Hao-Ching; Lo, Chu-Fang; Yang, Shieh-Yueh; Wang, Han-Ching

    2015-01-01

    Shrimp white spot disease (WSD), which is caused by white spot syndrome virus (WSSV), is one of the world’s most serious shrimp diseases. Our objective in this study was to use an immunomagnetic reduction (IMR) assay to develop a highly sensitive, automatic WSSV detection platform targeted against ICP11 (the most highly expressed WSSV protein). After characterizing the magnetic reagents (Fe3O4 magnetic nanoparticles coated with anti ICP11), the detection limit for ICP11 protein using IMR was approximately 2 x 10−3 ng/ml, and the linear dynamic range of the assay was 0.1~1 x 106 ng/ml. In assays of ICP11 protein in pleopod protein lysates from healthy and WSSV-infected shrimp, IMR signals were successfully detected from shrimp with low WSSV genome copy numbers. We concluded that this IMR assay targeting ICP11 has potential for detecting the WSSV. PMID:26380977

  19. Vibrational relaxation of acetylene and acetylene--rare-gas mixtures

    SciTech Connect

    Haeger, J.; Krieger, W.; Rueegg, T.; Walther, H.

    1980-04-15

    Vibrational relaxation of acetylene (C/sub 2/H/sub 2/) and acetylene--rare-gas mixtures has been investigated using laser-induced fluorescence. Time-dependent fluorescence signals from the vibrational modes ..nu../sub 2/ and ..nu../sub 5/ have been recorded, following excitation of ..nu../sub 3/ and (..nu../sub 2/+..nu../sub 4/+..nu../sub 5/) at 3300 cm/sup -1/ with pulses of a tunable optical parametric oscillator. The activation rate of ..nu../sub 2/ and ..nu../sub 5/ were estimated to be >880 ms/sup -1/ Torr/sup -1/ and >330 ms/sup -1/ Torr/sup -1/, respectively. The following V-T/R relaxation rates have been obtained from the decay of the ..nu../sub 5/ fluorescence signal: (12.7 +- 1.1) ms/sup -1/ Torr/sup -1/ for C/sub 2/H/sub 2/ as collision partner, (0.46 +- 0.05) ms/sup -1/ Torr/sup -1/ for Ne, (0.66 +- 0.06) ms/sup -1/ Torr/sup -1/ for Ar, (0.67 +- 0.04) ms/sup -1/ Torr/sup -1/ for Kr, and (0.57 +- 0.04) ms/sup -1/ Torr/sup -1/ for Xe. Surprisingly small V--V deactivation rates of the CC stretching vibration ..nu../sub 2/ have been measured. These are (21.3 +- 1.0) ms/sup -1/ Torr/sup -1/ for C/sub 2/H/sub 2/ collisions, (0.63 +- 0.06) ms/sup -1/ Torr/sup -1/ for Ne, (0.78 +- 0.08) ms/sup -1/ Torr/sup -1/ for Ar, (0.93 +- 0.09) ms/sup -1/ Torr/sup -1/ for Kr, and (0.77 +- 0.09) ms/sup -1/ Torr/sup -1/ for Xe. Acetylene relaxation mechanisms compatible with these rates are considered.

  20. Application of the rat liver lysosome assay to determining the reduction of toxic gliadin content during breadmaking.

    PubMed

    Cornell, Hugh J; Stelmasiak, Teodor; Small, Darryl M; Buddrick, Oliver

    2016-02-01

    Enriched caricain was able to detoxify a major proportion of the gliadin in wholemeal wheat dough by allowing it to react for 5h at 37 C during the fermentation stage. A reduction of 82% in toxicity, as determined by the rat-liver lysosome assay, was achieved using 0.03% enzyme on weight of dough. Without enzyme, only 26% reduction occurred. The difference in reduction of toxicity achieved is statistically significant (p < 0.01). The results are very similar to those obtained in our previous work using an immuno assay and the same enzyme preparation. They confirm the value of caricain as a means of reducing the toxicity of gliadin and open the way for enzyme therapy as an adjunct to the gluten free diet. This approach should lead to better control over the elimination of dietary gluten intake in conditions such as coeliac disease and dermatitis herpetiformis. PMID:26304430

  1. Infrared Spectra of Complexes Containing ACETYLENE-d2

    NASA Astrophysics Data System (ADS)

    Lauzin, Clément; Oliaee, J. Norooz; Moazzen-Ahmadi, N.; McKellar, A. R. W.

    2011-06-01

    Infrared spectra of the C_2D_2 dimer in the monomer νb{3} region (˜2439 wn) are observed by direct absorption using a rapid-scan tuneable diode laser spectrometer to probe a pulsed supersonic slit-jet expansion. We analyze the perpendicular K = 1-0 and 0-1 subbands of the vibrational mode involving the C_2D_2 monomer located at the top of the T-shaped dimer, but miss the parallel band involving the stem monomer vibration due to limited laser coverage. The results are consistent with previous work on acetylene dimers, but perturbations are much less evident than in the analogous infrared spectrum of C_2H_2. As expected, the tunneling splitting in the excited state (8 MHz) is much smaller than in the ground state (424 MHz). In the same region, we observe the H-bonded isomer of the C_2D_2-C_2H_2 dimer. This has not previously been observed, even though microwave spectra of almost every other conceivable deuterated isotopologue are known.B In addition to these acetylene dimers, our spectra also contain bands arising from impurities in the gas mixture which we assign to the C_2D_2-nitrogen and C_2D_2-water complexes [1] G.T. Fraser, R.D. Suenram, F.J. Lovas, A.S. Pine, J.T. Hougen, W.J. Lafferty, and J.S. Muenter, J. Chem. Phys. 89, 6028 (1988). [2] K. Matsumura, F.J. Lovas, and R.D. Suenram, J. Mol. Spectrosc. 150, 576 (1991)

  2. Ultrafast dynamics of photoionized acetylene.

    PubMed

    Madjet, Mohamed El-Amine; Vendrell, Oriol; Santra, Robin

    2011-12-23

    Acetylene cations [HCCH](+) produced in the A(2)Σ(g)(+) state by extreme ultraviolet (XUV) photoionization are investigated theoretically, based on a mixed quantum-classical approach. We show that the decay of the A(2)Σ(g)(+) state occurs via both ultrafast isomerization and nonradiative electronic relaxation. We find a time scale for hydrogen migration and electronic decay of about 60 fs, in good agreement with recent XUV-pump/XUV-probe time-resolved experiments on the same system [Phys. Rev. Lett. 105, 263002 (2010)]. Moreover, we predict an efficient vibrational energy redistribution mechanism that quickly transfers excess energy from the isomerization coordinates to slower modes in a few hundred femtoseconds, leading to a partial regeneration of acetylenelike conformations. PMID:22243154

  3. Crystallization and preliminary X-ray analysis of the tungsten-dependent acetylene hydratase from Pelobacter acetylenicus.

    PubMed

    Einsle, Oliver; Niessen, Holger; Abt, Dietmar J; Seiffert, Grazyna; Schink, Bernhard; Huber, Robert; Messerschmidt, Albrecht; Kroneck, Peter M H

    2005-03-01

    Acetylene hydratase is a tungsten-containing hydroxylase that converts acetylene to acetaldehyde in a unique reaction that requires a strong reductant. The subsequent disproportionation of acetaldehyde yields acetate and ethanol. Crystals of the tungsten/iron-sulfur protein acetylene hydratase from Pelobacter acetylenicus strain WoAcy 1 (DSM 3246) were grown by the vapour-diffusion method in an N2/H2 atmosphere using polyethylene glycol as precipitant. Growth of crystals suitable for X-ray analysis strictly depended on the presence of Ti(III) citrate or dithionite as reducing agents. PMID:16511024

  4. Oligomers Terminated By Maleimide And Acetylene

    NASA Technical Reports Server (NTRS)

    St. Clair, Terry L.; Pater, Ruth H.; Gerber, Margaret K.

    1994-01-01

    Oligomeric molecules terminated with maleimide and acetylene groups synthesized and thermally treated to form cross-linked polymers exhibiting high or undetectable glass-transition temperatures and high thermo-oxidative stabilities. Compounds used to make thermally stable, glassy polymers.

  5. Reduction of bias in neutron multiplicity assay using a weighted point model

    SciTech Connect

    Geist, W. H.; Krick, M. S.; Mayo, D. R.

    2004-01-01

    Accurate assay of most common plutonium samples was the development goal for the nondestructive assay technique of neutron multiplicity counting. Over the past 20 years the technique has been proven for relatively pure oxides and small metal items. Unfortunately, the technique results in large biases when assaying large metal items. Limiting assumptions, such as unifoh multiplication, in the point model used to derive the multiplicity equations causes these biases for large dense items. A weighted point model has been developed to overcome some of the limitations in the standard point model. Weighting factors are detemiined from Monte Carlo calculations using the MCNPX code. Monte Carlo calculations give the dependence of the weighting factors on sample mass and geometry, and simulated assays using Monte Carlo give the theoretical accuracy of the weighted-point-model assay. Measured multiplicity data evaluated with both the standard and weighted point models are compared to reference values to give the experimental accuracy of the assay. Initial results show significant promise for the weighted point model in reducing or eliminating biases in the neutron multiplicity assay of metal items. The negative biases observed in the assay of plutonium metal samples are caused by variations in the neutron multiplication for neutrons originating in various locations in the sample. The bias depends on the mass and shape of the sample and depends on the amount and energy distribution of the ({alpha},n) neutrons in the sample. When the standard point model is used, this variable-multiplication bias overestimates the multiplication and alpha values of the sample, and underestimates the plutonium mass. The weighted point model potentially can provide assay accuracy of {approx}2% (1 {sigma}) for cylindrical plutonium metal samples < 4 kg with {alpha} < 1 without knowing the exact shape of the samples, provided that the ({alpha},n) source is uniformly distributed throughout the sample and has an average neutron energy close to the O({alpha},n) average neutron energy. Better assay results can be obtained if there is some knowledge of the plutonium geometry, because weighting factor curves can be calculated for any specified geometry.

  6. Acetylene-Terminated Aspartimides And Derived Resins

    NASA Technical Reports Server (NTRS)

    Hergenrother, Paul M.; Connell, John W.; Havens, Stephen J.

    1989-01-01

    New polymers and derived blends exhibit improved processability and properties. New toughened epoxies exhibit excellent properties, but use temperatures limited. Bismaleimide resins are some base materials formulated to develop materials having moderate use temperatures. Work conducted on use of acetylenic (ethynyl) group to cross-link and extend chains of oligomers and polymers to obtain materials to perform at higher temperatures. Extended to include acetylene-terminated aspartimides (ATA's).

  7. Method of producing acetylene from coal

    SciTech Connect

    Kim, C.S.

    1982-11-09

    This invention relates to the conversion by way of decomposing a solid carbonaceous matter to acetylene. Specifically, the invention teaches selecting the operating conditions which will produce high yield at low cost. Specific values of heat and enthalpy for the carbonaceous matter and the gas are proposed in combination with specific particle sizes and reaction time. All of the foregoing contribute to producing acetylene at a commercially competitive cost.

  8. Acetylene fermentation: An Earth-based analog of biological carbon cycling on Titan

    NASA Astrophysics Data System (ADS)

    Miller, L. G.; Baesman, S. M.; Hoeft, S. E.; Kirshtein, J.; Wolf, K.; Voytek, M. A.; Oremland, R. S.

    2009-12-01

    Acetylene (C2H2) is present in part per million quantities in the atmosphere of Titan; conceivably as an intermediate product of methane photolysis. Currently, Earths atmosphere contains only trace amounts of C2H2 (~40 pptv), however higher concentrations likely prevailed during the Hadean and early Archean eons (4.5 - 3.5 Ga). We isolated C2H2-fermenting microbes from various aquatic and sedimentary environments. Acetylene fermentation proceeds via acetylene hydratase (AH) through acetaldehyde, which dismutates to ethanol and acetate, and if oxidants are present (e.g., sulfate) eventually to CO2. Thus, the remnants of a C2H2 cycle exists today on Earth but may also occur on Titan and/or Enceladus, both being planetary bodies hypothesized to have liquid water underlying their frozen surfaces. We developed a molecular method for AH by designing PCR primers to target the functional gene in Pelobacter acetylenicus. We used this method to scan new environments for the presence of AH and we employed DNA sequencing of the 16S rRNA gene in order to positively identify pelobacters in environmental samples. Acetylene fermentation was documented in five diverse salt-, fresh-, and ground-water sites. Pelobacter was identified as the genus responsible for acetylene fermentation in some, but not all, of these sites. Successful probing for AH preceded the discovery of acetylene consumption in a contaminated groundwater site, demonstrating the utility of functional gene probing. A pure culture of a C2H2-fermenting pelobacter was obtained from an intertidal mudflat. We also obtained an enrichment culture (co-cultured with a sulfate reducer) from freshwater lake sediments, but neither was pelobacter nor AH detected in this sample, suggesting that an alternative pathway may be involved here. Slurry experiments using these lake sediments either with or without added C2H2 or sulfate showed that sulfate reduction and acetylene fermentation were independent processes. In general, the ubiquity of acetylene fermentation as well as the presence of AH (an enzyme specific to acetylene) begs the questions; 1) why has this ability persisted on Earth for so long in the absence of significant atmospheric acetylene? 2) does C2H2-fermentation represent a possible means of sustaining growth in the anoxic, aqueous subsurface regions of Titan (and Enceladus)?

  9. A quantitative assay for reductive metabolism of a pesticide in fish using electrochemistry coupled with liquid chromatography tandem mass spectrometry.

    PubMed

    Bussy, Ugo; Chung-Davidson, Yu-Wen; Li, Ke; Li, Weiming

    2015-04-01

    This is the first study to use electrochemistry to generate a nitro reduction metabolite as a standard for a liquid chromatography-mass spectrometry-based quantitative assay. This approach is further used to quantify 3-trifluoromethyl-4-nitrophenol (TFM) reductive metabolism. TFM is a widely used pesticide for the population control of sea lamprey (Petromyzon marinus), an invasive species of the Laurentian Great Lakes. Three animal models, sea lamprey, lake sturgeon (Acipenser fulvescens), and rainbow trout (Oncorhynchus mykiss), were selected to evaluate TFM reductive metabolism because they have been known to show differential susceptibilities to TFM toxicity. Amino-TFM (aTFM; 3-trifluoromethyl-4-aminophenol) was the only reductive metabolite identified through liquid chromatography-high-resolution mass spectrometry screening of liver extracts incubated with TFM and was targeted for electrochemical synthesis. After synthesis and purification, aTFM was used to develop a quantitative assay of the reductive metabolism of TFM through liquid chromatography and tandem mass spectrometry. The concentrations of aTFM were measured from TFM-treated cellular fractions, including cytosolic, nuclear, membrane, and mitochondrial protein extracts. Sea lamprey extracts produced the highest concentrations (500 ng/mL) of aTFM. In addition, sea lamprey and sturgeon cytosolic extracts showed concentrations of aTFM substantially higher than those of rainbow trout. However, other fractions of lake sturgeon extracts tend to show aTFM concentrations similar to those of rainbow trout but not with sea lamprey. These data suggest that the level of reductive metabolism of TFM may be associated with the sensitivities of the animals to this particular pesticide. PMID:25730707

  10. Hydroponic Growth and the Nondestructive Assay for Dinitrogen Fixation 1

    PubMed Central

    Imsande, John; Ralston, Edward J.

    1981-01-01

    Hydroponic growth medium must be well buffered if it is to support sustained plant growth. Although 1.0 millimolar phosphate is commonly used as a buffer for hydroponic growth media, at that concentration it is generally toxic to a soybean plant that derives its nitrogen solely from dinitrogen fixation. On the other hand, we show that 1.0 to 2.0 millimolar 2-(N-morpholino)ethanesulfonic acid, pKa 6.1, has excellent buffering capacity, and it neither interferes with nor contributes nutritionally to soybean plant growth. Furthermore, it neither impedes nodulation nor the assay of dinitrogen fixation. Hence, soybean plants grown hydroponically on a medium supplemented with 1.0 to 2.0 millimolar 2-(N-morpholino)ethanesulfonic acid and 0.1 millimolar phosphate achieve an excellent rate of growth and, in the absence of added fixed nitrogen, attain a very high rate of dinitrogen fixation. Combining the concept of hydroponic growth and the sensitive acetylene reduction technique, we have devised a simple, rapid, reproducible assay procedure whereby the rate of dinitrogen fixation by individual plants can be measured throughout the lifetime of those plants. The rate of dinitrogen fixation as measured by the nondestructive acetylene reduction procedure is shown to be approximately equal to the rate of total plant nitrogen accumulation as measured by Kjeldahl analysis. Because of the simplicity of the procedure, one investigator can readily assay 50 plants individually per day. PMID:16662112

  11. Enhancement of acetylene hydrogenation activity over Ni-Zn bimetallic catalyst by doping with Au.

    PubMed

    Xu, Jinghua; Huang, Yanqiang; Yang, Xiaofeng; He, Lei; Zhou, Huiran; Lin, Qingquan; Zhang, Tao; Geng, Haoran

    2014-09-01

    A series of modified Ni-Zn bimetallic catalysts were prepared by depositing different kinds of 4 wt% metals (Ir, Pt, Au, Cu, Ag) on the Ni-Zn-Al hydrotalcite (NZAH) and tested in the selective hydrogenation of acetylene. The activity was enhanced by 3-fold over the 4 wt% Au/NZAH, meanwhile, the yield of C2H4 was also increased more than 4 times compared with the NZAH. Characterization by means of H2-TPR, XRD, SEM, and TEM revealed that Au was highly dispersed on the catalyst, and the ternary Au-Ni-Zn alloy was formed during the H2 reduction at 500 degrees C. Doping Au in Ni-Zn bimetallic catalyst weakens the adsorption of acetylene and also hinders the coke deposition on the catalyst, which leads to the enhanced activity in acetylene hydrogenation. PMID:25924346

  12. A high-performance liquid chromatography-based assay of glutathione transferase omega 1 supported by glutathione or non-physiological reductants.

    PubMed

    Nmeti, Balzs; Por, Mikls; Gregus, Zoltn

    2015-01-15

    The unusual glutathione S-transferase GSTO1 reduces, rather than conjugates, endo- and xenobiotics, and its role in diverse cellular processes has been proposed. GSTO1 has been assayed spectrophotometrically by measuring the disappearance of its substrate, S-(4-nitrophenacyl)glutathione (4-NPG), in the presence of 2-mercaptoethanol that regenerates GSTO1 from its mixed disulfide. To assay GSTO1 in rat liver cytosol, we have developed a high-performance liquid chromatography (HPLC)-based procedure with two main advantages: (i) it measures the formation of the 4-NPG reduction product 4-nitroacetophenone, thereby offering improved sensitivity and accuracy, and (ii) it can use glutathione, the physiological reductant of GSTO1, which is impossible to do with the spectrophotometric procedure. Using the new assay, we show that (i) the GSTO1-catalyzed reduction of 4-NPG in rat liver cytosol also yields 1-(4-nitrophenyl)ethanol, whose formation from 4-nitroacetophenone requires NAD(P)H; (ii) the two assays measure comparable activities with 2-mercaptoethanol or tris(2-carboxyethyl)phosphine used as reductant; (iii) the cytosolic reduction of 4-NPG is inhibited by GSTO1 inhibitors (KT53, 5-chloromethylfluorescein diacetate, and zinc), although the inhibitory effect is strikingly influenced by the type of reductant in the assay and by the sequence of reductant and inhibitor addition. Characterization of GSTO1 inhibitors with the improved assay provides better understanding of interaction of these chemicals with the enzyme. PMID:25283130

  13. Acetylene Fermentation: Relevance to Primordial Biogeochemistry and the Search for Life in the Outer Solar System

    NASA Astrophysics Data System (ADS)

    Oremland, R. S.; Baesman, S. M.; Miller, L. G.

    2013-12-01

    Acetylene is a highly reactive component of planet(oid)s with anoxic, methane-rich atmospheres, such as Jupiter, Saturn, Titan, and perhaps the primordial Earth. Included in this group is Enceladus, although it is not clear if the acetylene detected within its jets by Cassini was formed by photolysis of methane, from thermo-catalysis of organic matter in the orb's interior, or a fragmentation artifact of the mass spectrum of a larger hydrocarbon. Acetylene inhibits many microbial processes (e.g., methanogenesis, methane oxidation, hydrogen metabolism, denitrification) yet a number of anaerobes can use it as a carbon and energy source to support growth. The best studied is Pelobacter acetylenicus, which carries out a two-step reaction involving the enzymes acetylene hydratase and acetaldehyde dismutase. The former, a low potential W-containing enzyme, forms acetaldehyde while the latter produces ethanol and acetate. Metabolism of acetylene by mixed microbial communities (sediments and/or enrichment cultures) produces these intermediates, and when coupled with sulfate-reduction or methanogenesis respectively forms CO2 or an equal mixtures of CO2 plus CH4. It is not inconceivable that such an anaerobic, microbial food chain could exist in the waters beneath the ice cap of Enceladus, Titan, or even in the mesothermal atmospheric regions of the gas giants. Detection of the identified intermediate products of acetylene fermentation, namely acetaldehyde, ethanol, acetate and formate in the atmospheres of these planet(oid)s would constitute evidence for a microbial life signature. This evidence would be strongly reinforced if a stable carbon isotope fractionation was identified as well, whereby the products of acetylene fermentation were enriched in 12C relative to 13C (i.e., had a lighter δ13C signal) when compared to that of the starting acetylene. The most practical target to test this hypothesis would be Enceladus (if the detected acetylene is shown to be a real presence in the jet vapors) owing to the relative ease of sample collection and analysis either in future flybys or lander/collector missions.

  14. Vapor pressures of acetylene at low temperatures

    NASA Technical Reports Server (NTRS)

    Masterson, C. M.; Allen, John E., Jr.; Kraus, G. F.; Khanna, R. K.

    1990-01-01

    The atmospheres of many of the outer planets and their satellites contain a large number of hydrocarbon species. In particular, acetylene (C2H2) has been identified at Jupiter, Saturn and its satellite Titan, Uranus and Neptune. In the lower atmospheres of these planets, where colder temperatures prevail, the condensation and/or freezing of acetylene is probable. In order to obtain accurate models of the acetylene in these atmospheres, it is necessary to have a complete understanding of its vapor pressures at low temperatures. Vapor pressures at low temperatures for acetylene are being determined. The vapor pressures are measured with two different techniques in order to cover a wide range of temperatures and pressures. In the first, the acetylene is placed in a sample tube which is immersed in a low temperature solvent/liquid nitrogen slush bath whose temperature is measured with a thermocouple. The vapor pressure is then measured directly with a capacitance manometer. For lower pressures, a second technique which was called the thin-film infrared method (TFIR) was developed. It involves measuring the disappearance rate of a thin film of acetylene at a particular temperature. The spectra are then analyzed using previously determined extinction coefficient values, to determine the disappearance rate R (where R = delta n/delta t, the number of molecules that disappear per unit time). This can be related to the vapor pressure directly. This technique facilitates measurement of the lower temperatures and pressures. Both techniques have been calibrated using CO2, and have shown good agreement with the existing literature data.

  15. Detection of measles, mumps and rubella viruses by immuno-colorimetric assay and its application in focus reduction neutralization tests.

    PubMed

    Vaidya, Sunil R; Kumbhar, Neelakshi S; Bhide, Vandana S

    2014-12-01

    Measles, mumps and rubella are vaccine-preventable diseases; however limited epidemiological data are available from low-income or developing countries. Thus, it is important to investigate the transmission of these viruses in different geographical regions. In this context, a cell culture-based rapid and reliable immuno-colorimetric assay (ICA) was established and its utility studied. Twenty-three measles, six mumps and six rubella virus isolates and three vaccine strains were studied. Detection by ICA was compared with plaque and RT-PCR assays. In addition, ICA was used to detect viruses in throat swabs (n?=?24) collected from patients with suspected measles or mumps. Similarly, ICA was used in a focus reduction neutralization test (FRNT) and the results compared with those obtained by a commercial IgG enzyme immuno assay. Measles and mumps virus were detected 2 days post-infection in Vero or Vero-human signaling lymphocytic activation molecule cells, whereas rubella virus was detected 3 days post-infection in Vero cells. The blue stained viral foci were visible by the naked eye or through a magnifying glass. In conclusion, ICA was successfully used on 35 virus isolates, three vaccine strains and clinical specimens collected from suspected cases of measles and mumps. Furthermore, an application of ICA in a neutralization test (i.e., FRNT) was documented; this may be useful for sero-epidemiological, cross-neutralization and pre/post-vaccine studies. PMID:25244651

  16. Thermodynamics of acetylene van der Waals dimerization

    NASA Technical Reports Server (NTRS)

    Colussi, A. J.; Sander, S. P.; Friedl, R. R.

    1991-01-01

    Integrated band intensities of the 620/cm absorption in (C2H2)2 are measured by FTIR spectroscopy at constant acetylene pressure between 198 and 273 K. These data, in conjunction with ab initio results for (C2H2)2, are used for the statistical evaluation of the equilibrium constant Kp(T) for acetylene-cluster dimerization. The present results are used to clarify the role of molecular clusters in chemical systems at or near equilibrium, in particular in Titan's stratosphere.

  17. Solubility of acetylene in certain haloethanes

    SciTech Connect

    Makitra, R.G.; Moin, F.B.; Pirig, Ya.N.; Politanskaya, T.I.

    1987-09-10

    Acetylene is one of the most important raw materials for petrochemical synthesis; it is generally isolated from pyrolysis gases by selective absorption. In this communication the authors present data on the solubility of acetylene in 1,1,2,2-tetrachloroethane, 1,1,2-trichloroethane, and 1,1,1-trichloroethane (methylchloroform) at pressures of 100-725 mm ((160-185) x 10/sup 3/ Pa) and temperatures of 0-80/sup 0/. The solubility was determined under static conditions. The gas and the solvents were chromatographically pure (purity not below 99%). The experimental results are given.

  18. TTC-based screening assay for ω-transaminases: a rapid method to detect reduction of 2-hydroxy ketones.

    PubMed

    Sehl, Torsten; Simon, Robert C; Hailes, Helen C; Ward, John M; Schell, Ursula; Pohl, Martina; Rother, Dörte

    2012-06-15

    A rapid TTC-based screening assay for ω-transaminases was developed to determine the conversion of substrates with a 2-hydroxy ketone motif. Oxidation of the compounds in the presence of 2,3,5-triphenyltetrazolium chloride (TTC) results in a reduction of the colourless TTC to a red-coloured 1,3,5-triphenylformazan. The enzymatic reductive amination of a wide range of various aliphatic, aliphatic-aromatic and aromatic-aromatic 2-hydroxy ketones can be determined by the decrease of the red colouration due to substrate consumption. The conversion can be quantified spectrophotometrically at 510 nm based on reactions, e.g. with crude cell extracts in 96-well plates. Since the assay is independent of the choice of diverse amine donors a panel of ω-transaminases was screened to detect conversion of 2-hydroxy ketones with three different amine donors: l-alanine, (S)-α-methylbenzylamine and benzylamine. The results could be validated using HPLC and GC analyses, showing a deviation of only 5-10%. Using this approach enzymes were identified demonstrating high conversions of acetoin and phenylacetylcarbinol to the corresponding amines. Among these enzymes three novel wild-type ω-transaminases have been identified. PMID:22226934

  19. Microporous metal-organic framework with dual functionalities for highly efficient removal of acetylene from ethylene/acetylene mixtures.

    PubMed

    Hu, Tong-Liang; Wang, Hailong; Li, Bin; Krishna, Rajamani; Wu, Hui; Zhou, Wei; Zhao, Yunfeng; Han, Yu; Wang, Xue; Zhu, Weidong; Yao, Zizhu; Xiang, Shengchang; Chen, Banglin

    2015-01-01

    The removal of acetylene from ethylene/acetylene mixtures containing 1% acetylene is a technologically very important, but highly challenging task. Current removal approaches include the partial hydrogenation over a noble metal catalyst and the solvent extraction of cracked olefins, both of which are cost and energy consumptive. Here we report a microporous metal-organic framework in which the suitable pore/cage spaces preferentially take up much more acetylene than ethylene while the functional amine groups on the pore/cage surfaces further enforce their interactions with acetylene molecules, leading to its superior performance for this separation. The single X-ray diffraction studies, temperature dependent gas sorption isotherms, simulated and experimental column breakthrough curves and molecular simulation studies collaboratively support the claim, underlying the potential of this material for the industrial usage of the removal of acetylene from ethylene/acetylene mixtures containing 1% acetylene at room temperature through the cost- and energy-efficient adsorption separation process. PMID:26041691

  20. Microporous metal–organic framework with dual functionalities for highly efficient removal of acetylene from ethylene/acetylene mixtures

    PubMed Central

    Hu, Tong-Liang; Wang, Hailong; Li, Bin; Krishna, Rajamani; Wu, Hui; Zhou, Wei; Zhao, Yunfeng; Han, Yu; Wang, Xue; Zhu, Weidong; Yao, Zizhu; Xiang, Shengchang; Chen, Banglin

    2015-01-01

    The removal of acetylene from ethylene/acetylene mixtures containing 1% acetylene is a technologically very important, but highly challenging task. Current removal approaches include the partial hydrogenation over a noble metal catalyst and the solvent extraction of cracked olefins, both of which are cost and energy consumptive. Here we report a microporous metal–organic framework in which the suitable pore/cage spaces preferentially take up much more acetylene than ethylene while the functional amine groups on the pore/cage surfaces further enforce their interactions with acetylene molecules, leading to its superior performance for this separation. The single X-ray diffraction studies, temperature dependent gas sorption isotherms, simulated and experimental column breakthrough curves and molecular simulation studies collaboratively support the claim, underlying the potential of this material for the industrial usage of the removal of acetylene from ethylene/acetylene mixtures containing 1% acetylene at room temperature through the cost- and energy-efficient adsorption separation process. PMID:26041691

  1. Microporous metal-organic framework with dual functionalities for highly efficient removal of acetylene from ethylene/acetylene mixtures

    NASA Astrophysics Data System (ADS)

    Hu, Tong-Liang; Wang, Hailong; Li, Bin; Krishna, Rajamani; Wu, Hui; Zhou, Wei; Zhao, Yunfeng; Han, Yu; Wang, Xue; Zhu, Weidong; Yao, Zizhu; Xiang, Shengchang; Chen, Banglin

    2015-06-01

    The removal of acetylene from ethylene/acetylene mixtures containing 1% acetylene is a technologically very important, but highly challenging task. Current removal approaches include the partial hydrogenation over a noble metal catalyst and the solvent extraction of cracked olefins, both of which are cost and energy consumptive. Here we report a microporous metal-organic framework in which the suitable pore/cage spaces preferentially take up much more acetylene than ethylene while the functional amine groups on the pore/cage surfaces further enforce their interactions with acetylene molecules, leading to its superior performance for this separation. The single X-ray diffraction studies, temperature dependent gas sorption isotherms, simulated and experimental column breakthrough curves and molecular simulation studies collaboratively support the claim, underlying the potential of this material for the industrial usage of the removal of acetylene from ethylene/acetylene mixtures containing 1% acetylene at room temperature through the cost- and energy-efficient adsorption separation process.

  2. Oxygen transport through polyethylene terephthalate (PET) coated with plasma-polymerized acetylene at atmospheric pressure

    NASA Astrophysics Data System (ADS)

    Wemlinger, Erik; Pedrow, Patrick; Garcia-Pérez, Manuel; Sablani, Shyam

    2011-10-01

    Moser et al. have shown that oxygen transport through polyethyleneterephthalate (PET) is reduced by a factor of up to 120 when, at reduced pressure, hydrogenated amorphous carbon film with thickness less than 100 nm is applied to the PET substrate. Our work includes using atmospheric pressure cold plasma to grow a plasma-polymerized acetylene film on PET substrate and measuring reductions in oxygen transport. The reactor utilizes corona discharges and is operated at 60 Hz with a maximum voltage of 10 kV RMS. Corona streamers emanate from an array of needles with an average radius of curvature of 50 μm. The reactor utilizes a cylindrical reaction chamber with a vertical orientation such that argon carrier gas and acetylene precursor gas are introduced at the top then pass through the cold plasma activation zone and then through a grounded stainless steel mesh. Acetylene radicals are incident on the PET substrate and form plasma-polymerized acetylene film. Moser et al. have shown that oxygen transport through polyethyleneterephthalate (PET) is reduced by a factor of up to 120 when, at reduced pressure, hydrogenated amorphous carbon film with thickness less than 100 nm is applied to the PET substrate. Our work includes using atmospheric pressure cold plasma to grow a plasma-polymerized acetylene film on PET substrate and measuring reductions in oxygen transport. The reactor utilizes corona discharges and is operated at 60 Hz with a maximum voltage of 10 kV RMS. Corona streamers emanate from an array of needles with an average radius of curvature of 50 μm. The reactor utilizes a cylindrical reaction chamber with a vertical orientation such that argon carrier gas and acetylene precursor gas are introduced at the top then pass through the cold plasma activation zone and then through a grounded stainless steel mesh. Acetylene radicals are incident on the PET substrate and form plasma-polymerized acetylene film. E.M. Moser, R. Urech, E. Hack, H. Künzli, E. Müller, Thin Solid Films, 317, 1998, pp. 388-392.

  3. The relationship between faecal egg count reduction and the lethal dose 50% in the egg hatch assay and larval development assay.

    PubMed

    Maingi, N; Bjørn, H; Dangolla, A

    1998-06-15

    The relationship between resistance detected in the faecal egg count reduction test (FECRT) and the lethal dose 50% (LD50) in the egg hatch assay (EHA) for benzimidazoles (BZs) and a larval development assay (LDA) for BZs, levamisole (LEV) and ivermectin (IVM) was examined on 13 sheep farms and 12 goat farms in Denmark. Out of 10 farms where resistance to BZs was detected according to the FECRT, nine (90%) had LD50 values above 0.5 microM thiabendazole (TBZ) (0.1 microg TBZ/ml) in the EHA, indicating resistance to BZs. However, four out of the 12 isolates susceptible to BZs in the FECRT had LD50 values higher than 0.5 microM TBZ in the EHA. For all isolates examined, LD50 values for TBZ in the LDA were lower than in the EHA. Four out of 11 and five out of 12 farms with worm populations resistant to BZs according to the FECRT and EHA respectively, had LD50 values lower than 0.5 microM TBZ in the LDA. Using the same cut-off point for resistant isolates in the LDA as in the EHA (0.5 microM TBZ), these isolates would be considered susceptible to BZs. All 10 isolates susceptible to BZs according to the FECRT and EHA and two isolates with suspect BZ resistance had LD50 values lower than 0.5 microM TBZ in the LDA. The above results indicated fairly good agreement in the detection of BZ resistance between the FECRT, EHA and the LDA. Groups of farms where resistance to LEV was detected according to the FECRT had higher mean LD50 values compared to those with LEV-susceptible or suspected resistant isolates. However, only four out of 12 farms having isolates resistant to LEV had LD50 values higher than 1.2 microM LEV (0.28 microg LEV/ml) recorded previously for a LEV-susceptible strain of Ostertagia circumcincta. This indicated discrepancies in declaring resistance to LEV between the FECRT and the LDA. Isolates from four farms where resistance to IVM was detected in the FECRT had LD50 values higher than the susceptible isolates. These were 2.5 to 7.5 times higher than those recorded previously for IVM-susceptible strains. PMID:9746283

  4. Hydration of Acetylene: A 125th Anniversary

    ERIC Educational Resources Information Center

    Ponomarev, Dmitry A.; Shevchenko, Sergey M.

    2007-01-01

    The year 2006 is the 125th anniversary of a chemical reaction, the discovery of which by Mikhail Kucherov had a profound effect on the development of industrial chemistry in the 19-20th centuries. This was the hydration of alkynes catalyzed by mercury ions that made possible industrial production of acetaldehyde from acetylene. Historical…

  5. Hydration of Acetylene: A 125th Anniversary

    ERIC Educational Resources Information Center

    Ponomarev, Dmitry A.; Shevchenko, Sergey M.

    2007-01-01

    The year 2006 is the 125th anniversary of a chemical reaction, the discovery of which by Mikhail Kucherov had a profound effect on the development of industrial chemistry in the 19-20th centuries. This was the hydration of alkynes catalyzed by mercury ions that made possible industrial production of acetaldehyde from acetylene. Historical

  6. Living on acetylene. A primordial energy source.

    PubMed

    Ten Brink, Felix

    2014-01-01

    The tungsten iron-sulfur enzyme acetylene hydratase catalyzes the conversion of acetylene to acetaldehyde by addition of one water molecule to the C-C triple bond. For a member of the dimethylsulfoxide (DMSO) reductase family this is a rather unique reaction, since it does not involve a net electron transfer. The acetylene hydratase from the strictly anaerobic bacterium Pelobacter acetylenicus is so far the only known and characterized acetylene hydratase. With a crystal structure solved at 1.26 resolution and several amino acids around the active site exchanged by site-directed mutagenesis, many key features have been explored to understand the function of this novel tungsten enzyme. However, the exact reaction mechanism remains unsolved. Trapped in the reduced W(IV) state, the active site consists of an octahedrally coordinated tungsten ion with a tightly bound water molecule. An aspartate residue in close proximity, forming a short hydrogen bond to the water molecule, was shown to be essential for enzyme activity. The arrangement is completed by a small hydrophobic pocket at the end of an access funnel that is distinct from all other enzymes of the DMSO reductase family. PMID:25416389

  7. Acetylenic scaffolding with derivatives of tetrathiafulvalene

    NASA Astrophysics Data System (ADS)

    Nielsen, M. B.; Gisselbrecht, J.-P.; Nielsen, S. B.; Thorup, N.; Boudon, C.; Gross, M.

    2004-04-01

    A selection of tetrathiafulvalene (TTF) derivatives containing acetylenic moieties have been synthesized and studied by cyclic voltammetry and UV-Vis absorption spectroscopy. Ionization energy calculations on some extended TTFs were carried out employing the DFT method. Key words. Alkynes ? -donors tetrathiafulvalene.

  8. Gold nanoparticle-catalyzed uranine reduction for signal amplification in fluorescent assays for melamine and aflatoxin B1.

    PubMed

    Wang, Xu; Pauli, Jutta; Niessner, Reinhard; Resch-Genger, Ute; Knopp, Dietmar

    2015-11-01

    A multifunctional fluorescence platform has been constructed based on gold nanoparticle (AuNP)-catalyzed uranine reduction. The catalytic reduction of uranine was conducted in aqueous solution using AuNPs as nanocatalyst and sodium borohydride as reducing reagent, which was monitored by fluorescence and UV-vis spectroscopy. The reaction rate was highly dependent on the concentration, size and dispersion state of AuNPs. When AuNPs aggregated, their catalytic ability decreased, and thereby a label-free fluorescent assay was developed for the detection of melamine, which can be used for melamine determination in milk. In addition, a fluorescent immunoassay for aflatoxin B1 (AFB1) was established using the catalytic reaction for signal amplification based on target-induced concentration change of AuNPs, where AFB1-BSA-coated magnetic beads and anti-AFB1 antibody-conjugated AuNPs were employed as capture and signal probe, respectively. The detection can be accomplished in 1 h and acceptable recoveries in spiked maize samples were achieved. The developed fluorescence system is simple, sensitive and specific, which could be used for the detection of a wide range of analytes. PMID:26359515

  9. Purification and characterization of acetylene hydratase of Pelobacter acetylenicus, a tungsten iron-sulfur protein.

    PubMed

    Rosner, B M; Schink, B

    1995-10-01

    Acetylene hydratase of the mesophilic fermenting bacterium Pelobacter acetylenicus catalyzes the hydration of acetylene to acetaldehyde. Growth of P. acetylenicus with acetylene and specific acetylene hydratase activity depended on tungstate or, to a lower degree, molybdate supply in the medium. The specific enzyme activity in cell extract was highest after growth in the presence of tungstate. Enzyme activity was stable even after prolonged storage of the cell extract or of the purified protein under air. However, enzyme activity could be measured only in the presence of a strong reducing agent such as titanium(III) citrate or dithionite. The enzyme was purified 240-fold by ammonium sulfate precipitation, anion-exchange chromatography, size exclusion chromatography, and a second anion-exchange chromatography step, with a yield of 36%. The protein was a monomer with an apparent molecular mass of 73 kDa, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The isoelectric point was at pH 4.2. Per mol of enzyme, 4.8 mol of iron, 3.9 mol of acid-labile sulfur, and 0.4 mol of tungsten, but no molybdenum, were detected. The Km for acetylene as assayed in a coupled photometric test with yeast alcohol dehydrogenase and NADH was 14 microM, and the Vmax was 69 mumol.min-1.mg of protein-1. The optimum temperature for activity was 50 degrees C, and the apparent pH optimum was 6.0 to 6.5. The N-terminal amino acid sequence gave no indication of resemblance to any enzyme protein described so far. PMID:7592321

  10. Selective acetylenic 'suicide' and reversible inhibitors of monoamine oxidase types A and B.

    PubMed Central

    Kalir, A.; Sabbagh, A.; Youdim, M. B.

    1981-01-01

    1 A number of aromatic-N-propargyl (acetylenic) compounds and indoleamines were tested for their inhibitory action on monoamine oxidase (MAO) type A and type B using the substrates 5-hydroxytryptamine (5-HT), beta-phenylethylamine (PEA) and dopamine. 2 Structure activity studies with aromatic-N-propragyl (acetylenic) derivatives have shown that MAO inhibitory potency is least dependent on the aromatic portion of the compounds. N-methylated propargyl derivatives are the most active and replacement of the methyl group with a higher alkyl or aromatic group results in significant reduction of activity. The triple bond in the N-propargyl portion is absolutely essential for activity and must be beta-to the nitrogen. It is the acetylenic group that gives these compounds their irreversible MAO inhibitory property. 3 The present study has indicated that since the acetylenic compounds resemble the enzyme substrates the distance between the aromatic ring and the N-propargyl terminal is crucial in designating the type A or type B MAO inhibitory property. For MAO type A inhibition, a distance equivalent to at least three carbon units is required, while for the inhibition of the B type enzyme this distance can be 1 or 2 carbon units. 4 The compounds AGN-1133 and AGN-1135 show most promise in Parkinson's disease or as anti-depressants because of their irreversible selective type B MAO inhibition in vitro and in vivo. 5 A number of indoleamine derivatives were found to be reversible selective type A inhibitors. PMID:7284698

  11. Acetylenes and fatty acids from Codonopsis pilosula

    PubMed Central

    Jiang, Yueping; Liu, Yufeng; Guo, Qinglan; Jiang, Zhibo; Xu, Chengbo; Zhu, Chenggen; Yang, Yongchun; Lin, Sheng; Shi, Jiangong

    2015-01-01

    Four new acetylenes (14) and one new unsaturated ?-hydroxy fatty acid (5), together with 5 known analogues, were isolated from an aqueous extract of Codonopsis pilosula roots. Their structures were determined by spectroscopic and chemical methods. The new acetylenes are categorized as an unusual cyclotetradecatrienynone (1), tetradecenynetriol (2), and rare octenynoic acids (3 and 4), respectively, and 3 and 4 are possibly derived from oxidative metabolic degradation of 1 and/or 2. The absolute configuration of 1 was assigned by comparison of the experimental circular dichroism (CD) spectrum with the calculated electronic circular dichroism (ECD) spectra of stereoisomers based on the quantum-mechanical time-dependent density functional theory, while the configuration of 2 was assigned by using modified Mosher?s method based on the MPA determination rule of ??RS values for diols. PMID:26579449

  12. Susceptibilities of zidovudine-susceptible and -resistant human immunodeficiency virus isolates to antiviral agents determined by using a quantitative plaque reduction assay.

    PubMed Central

    Larder, B A; Chesebro, B; Richman, D D

    1990-01-01

    Conventional assays based on infection of T-cell lymphoblastoid lines with tissue culture-adapted strains of human immunodeficiency virus (HIV) are well established and have been used successfully to discover potent inhibitors of HIV replication. In this report we show that such assays are not easily applied to testing the susceptibilities of clinical HIV isolates to inhibitors because of differences in replication rates and cytotoxicity, thus demonstrating that conventional HIV assays should be used with caution when the zidovudine susceptibility of clinical isolates is assessed. An assay based on plaque reduction in CD4+ HeLa cell monolayers was validated by determining susceptibilities of HIV to a large number of inhibitors in this system. In general, 50% inhibitory doses for HIV type 1 and 2 strains derived from plaque reduction data were in good agreement with susceptibility data obtained by using conventional assays with T-cell lines. The susceptibilities of previously identified zidovudine-resistant HIV isolates to a large group of inhibitors, including nonucleosides, such as interferons and soluble CD4, were tested by using a plaque reduction assay in CD4+ HeLa cells. Surprisingly, an extremely narrow range of cross resistance was observed; cross resistance was limited to nucleoside analogs containing a 3'-azido group. These data point the way to the use of combinations of inhibitors to delay the appearance of drug resistance. PMID:2334156

  13. Opposite influence of haloalkanes on combustion and pyrolysis of acetylene

    NASA Astrophysics Data System (ADS)

    Drakon, A. V.; Emelianov, A. V.; Eremin, A. V.; Mikheyeva, E. Yu

    2015-11-01

    An influence of haloalkanes CF3H and CCl4 (known as inflammation and explosion suppressors) on combustion and pyrolysis of acetylene behind shock waves was experimentally studied. While ignition delay times in stoihiometric acetylene-oxygen mixtures were expectedly increased by halogenoalkanes admixtures, the induction times of carbon particle formation at acetylene pyrolysis were dramatically reduced in presence of CCl4. A simplified kinetic model was suggested and characteristic rates of diacetylene C4H2 formation were estimated as a limiting stage of acetylene polymerization. An analysis of obtained data has indicated that promoting species is atomic chlorine forming in CCl4 pyrolysis, which interacts with acetylene and produces C2H radical, initiating a chain mechanism of acetylene decomposition. The results of kinetic modeling agree well with experimental data.

  14. Diamond films from combustion of methyl acetylene and propadiene

    NASA Astrophysics Data System (ADS)

    Harris, Stephen J.; Shin, Ho Seon; Goodwin, David G.

    1995-02-01

    To date diamond films grown with the combustion technique have used either acetylene or, rarely, ethylene as the fuel. However, there are barriers to large scale commercialization of the combustion technique using either fuel. For example, acetylene is relatively expensive and difficult to handle, while the use of ethylene gives relatively low growth rates. In this letter we propose replacing acetylene with MAPPTM gas, a commercial mixture of methyl acetylene and propadiene in liquefied petroleum gas (primarily propylene). MAPP gas is considerably cheaper, safer, and easier to handle than acetylene. Furthermore, the experiments described here suggest that MAPP gas flames are only slightly less efficient than acetylene flames at converting fuel carbon atoms into diamond.

  15. High temperature polymer from maleimide-acetylene terminated monomers

    NASA Technical Reports Server (NTRS)

    Gerber, Margaret K. (inventor); St.clair, Terry L. (inventor)

    1993-01-01

    Thermally stable, glassy polymeric materials were prepared from maleimide-acetylene terminated monomeric materials by several methods. The monomers were heated to self-polymerize. The A-B structure of the monomer allowed it to polymerize with either bismaleimide monomers/oligomers or bis-acetylene monomers/oligomers. Copolymerization can also take place by mixing bismaleimide and bisacetylene monomers/oligomers with the maleimide-acetylene terminated monomers to yield homogenous glassy polymers.

  16. Spectroscopic study of acetylene and hydrogen cyanide

    NASA Astrophysics Data System (ADS)

    Rozario, Hoimonti Immaculata

    High-resolution molecular spectroscopy has been used to study acetylene line parameters and emission spectra of hydrogen cyanide. All acetylene spectra were recorded in our laboratory at the University of Lethbridge using a 3-channel tuneable diode laser spectrometer. N2-broadened line widths and N2-pressure induced line shifts have been measured for transitions in the v1+v3 band of acetylene at seven temperatures in the range 213-333K to obtain the temperature dependences of broadening and shift coefficients. The Voigt and hard-collision line profile models were used to retrieve the line parameters. The line-broadening and line-shift coefficients as well as their temperature-dependent parameters have been also evaluated theoretically, in the frame work of a semi-classical approach based on an exponential representation of the scattering operator, an intermolecular potential composed of electrostatic quadrupole--quadrupole and pairwise atom--atom interactions as well as on exact trajectories driven by an effective isotropic potential. The experimental results for both N2-broadening and shifting show good agreement with the theoretical results. We have studied the line intensities of the 1vl 20?0v120 band system from the HCN emission spectrum. The infrared emission spectrum of H12C 14N was measured at the Justus-Liebig University, Giessen, Germany. The emission spectrum was analyzed with the spectrum analysis software Symath running using Mathematica as a platform. This approach allowed us to retrieve information on band intensity parameters.

  17. Effect of phytate reduction of sorghum, through genetic modification, on iron and zinc availability as assessed by an in vitro dialysability bioaccessibility assay, Caco-2 cell uptake assay, and suckling rat pup absorption model.

    PubMed

    Kruger, Johanita; Taylor, John R N; Du, Xiaogu; De Moura, Fabiana F; Lönnerdal, Bo; Oelofse, André

    2013-11-15

    Improved iron and zinc availability from sorghum, a commonly consumed staple, will benefit many malnourished communities in rural Africa burdened with high prevalence of iron and zinc deficiency. This research compared the effect of genetic phytate reduction in sorghum on iron and zinc bioaccessibility and uptake measured by in vitro dialysability and Caco-2 cell uptake assays to that of iron and zinc absorption measured by a suckling rat pup model. The phytate reduction (80-86%) in these sorghums significantly increased zinc availability. The Caco-2 cell method, but not the dialysability assay, proved useful in estimating zinc absorption. The measured increase in iron availability differed between the methods, possibly due to the effect of varying mineral (Ca, Fe, Zn, P) contents of the sorghums. This effect was most prominent in the iron uptake results. More research is needed to determine the effect of naturally occurring variations in mineral contents of sorghum on the iron uptake by Caco-2 cells. PMID:23790881

  18. RECRYSTALLIZATION OF PMDA AND SYNTHESIS OF AN ACETYLENIC DIAMINE

    SciTech Connect

    Sanner, R; Cook, R C

    2004-09-21

    This memo provides documentation for the method of recrystallization of pyromeletic dianhydride (PMDA), the dianhydride used in the vapor deposition of Kapton-like polyimide for ICF shell ablators and for the synthesis of bis(3-aminophenyl) acetylene, a unique acetylenic diamine developed for vapor deposition testing.

  19. 76 FR 75782 - Revising Standards Referenced in the Acetylene Standard

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-12-05

    ... organizations (``SDO standards'') (69 FR 68283). A SDO standard referenced in OSHA's Acetylene Standard (29 CFR... of the Compressed Gas Association standard, CGA G-1-2003, in the Acetylene Standard. See 74 FR 40442 and 74 FR 40450, respectively. OSHA received no adverse comments on the DFR, and it became...

  20. Acetylenic/cyanoacetylenic complexes: simulation of the Titan's atmosphere chemistry

    NASA Astrophysics Data System (ADS)

    Guennoun, Z.; Coupeaud, A.; Couturier-Tamburelli, I.; Piétri, N.; Coussan, S.; Aycard, J.-P.

    2004-05-01

    The structures and energies of the 1:1 acetylene/cyanoacetylene, acetylene/dicyanoacetylene and cyanoacetylene/dicyanoacetylene complexes in solid argon matrices have been investigated using FT-IR spectroscopy and ab initio calculations, at the B3LYP/6-31G** level of theory. For the three complexes, predicted frequency shifts for the L shaped structures, characterized by a hydrogen bond between the nitrogen of the cyano group and the acetylenic proton, were found to be in good agreement with those experimental. Only in the case of acetylene/cyanoacetylene complex, we obtained a second minimum with a T shaped structure characterized by an interaction between the proton of cyanoacetylene and the Π system of acetylene. It appears clearly that HC 3N acts as an electrophile or as a nucleophile in these complexes.

  1. Pressure-induced polymerization in substituted acetylenes

    SciTech Connect

    Chellappa, Raja S.; Dattelbaum, Dana M.; Sheffield, Stephen; Robbins, David

    2012-04-10

    A fundamental understanding of shock-induced chemical reactions in organics is still lacking and there are limited studies devoted to determining reaction mechanisms, evolution of bonding, and effect of functional group substitutions. The fast timescale of reactions occurring during shock compression create significant experimental challenges (diagnostics) to fully quantify the mechanisms involved. Static compression combined with temperature provides a complementary route to investigate the equilibrium phase space and metastable intermediates under extreme P-T conditions. In this study, we present our results from our ongoing high pressure in situ synchrotron x-ray diffraction experiments on substituted acetylenes: tert-butyl acetylene [TBA: (CH{sub 3}){sub 3}-C=CH] and ethynyl trimethylsilane [ETMS: (CH{sub 3}){sub 3}-SiC=CH]. We observed that the onset pressure of chemical reactions (at room temperature) in these compounds is higher under static compression (TBA: 12 GPa and ETMS: 17.6 GPa) when compared to shock input pressures (TBA: 6.1 GPa and ETMS: 6.6 GPa). At elevated temperatures, reactivity was observed to occur at pressures comparable to shock conditions. The products were polymeric in nature, recovered to ambient conditions with little degradation.

  2. Acetylene-Based Materials in Organic Photovoltaics

    PubMed Central

    Silvestri, Fabio; Marrocchi, Assunta

    2010-01-01

    Fossil fuel alternatives, such as solar energy, are moving to the forefront in a variety of research fields. Organic photovoltaic systems hold the promise of a lightweight, flexible, cost-effective solar energy conversion platform, which could benefit from simple solution-processing of the active layer. The discovery of semiconductive polyacetylene by Heeger et al. in the late 1970s was a milestone towards the use of organic materials in electronics; the development of efficient protocols for the palladium catalyzed alkynylation reactions and the new conception of steric and conformational advantages of acetylenes have been recently focused the attention on conjugated triple-bond containing systems as a promising class of semiconductors for OPVs applications. We review here the most important and representative (poly)arylacetylenes that have been used in the field. A general introduction to (poly)arylacetylenes, and the most common synthetic approaches directed toward making these materials will be firstly given. After a brief discussion on working principles and critical parameters of OPVs, we will focus on molecular arylacetylenes, (co)polymers containing triple bonds, and metallopolyyne polymers as p-type semiconductor materials. The last section will deal with hybrids in which oligomeric/polymeric structures incorporating acetylenic linkages such as phenylene ethynylenes have been attached onto C60, and their use as the active materials in photovoltaic devices. PMID:20480031

  3. Photoelectron Angular Distribution in ACETYLENE/VINYLIDENE*.

    NASA Astrophysics Data System (ADS)

    Osipov, Timur; Cocke, Lewis; Prior, Mike; Doerner, Reinhard; Weber, Thorsten; Lothar, Schmidt; Schmidt-Bcking, Horst; Landers, Allen; Cassimi, Amine

    2002-05-01

    The molecular dissociation of acetylene (C_2H_2) following the photoionization of one carbon K-shell, and subsequent Auger decay, has been analyzed using a momentum imaging technique. Momenta of the photoelectron and all charged molecular fragments measured in coincidence reveal two important break up channels: CH^+ + CH^+ and C^+ + CH_2^+. The latter is the result of the dissociation of the dication of vinylidene (C-CH_2)^2+, the isomer of the acetylene dication. The photoelectron angular distribution, measured in the body-fixed frame, appears to be different for the two channels. The difference can be explained by the change of the vinylidene molecular orientation with respect to the initial photoelectron direction due to the C=C bond rotation before the dissociation process occurs. The data indicates that this bond rotates by approximately 30^o prior to the dissociation. This result can be interpreted as due primarily to the rearrangement of the hydrogen atoms during isomerization and places an upper limit on the isomerization time.

  4. Acetylene-based materials in organic photovoltaics.

    PubMed

    Silvestri, Fabio; Marrocchi, Assunta

    2010-01-01

    Fossil fuel alternatives, such as solar energy, are moving to the forefront in a variety of research fields. Organic photovoltaic systems hold the promise of a lightweight, flexible, cost-effective solar energy conversion platform, which could benefit from simple solution-processing of the active layer. The discovery of semiconductive polyacetylene by Heeger et al. in the late 1970s was a milestone towards the use of organic materials in electronics; the development of efficient protocols for the palladium catalyzed alkynylation reactions and the new conception of steric and conformational advantages of acetylenes have been recently focused the attention on conjugated triple-bond containing systems as a promising class of semiconductors for OPVs applications. We review here the most important and representative (poly)arylacetylenes that have been used in the field. A general introduction to (poly)arylacetylenes, and the most common synthetic approaches directed toward making these materials will be firstly given. After a brief discussion on working principles and critical parameters of OPVs, we will focus on molecular arylacetylenes, (co)polymers containing triple bonds, and metallopolyyne polymers as p-type semiconductor materials. The last section will deal with hybrids in which oligomeric/polymeric structures incorporating acetylenic linkages such as phenylene ethynylenes have been attached onto C(60), and their use as the active materials in photovoltaic devices. PMID:20480031

  5. High pressure chemistry of substituted acetylenes

    SciTech Connect

    Chellappa, Raja; Dattelbaum, Dana; Sheffield, Stephen; Robbins, David

    2011-01-25

    High pressure in situ synchrotron x-ray diffraction experiments were performed on substituted polyacetylenes: tert-butyl acetylene [TBA: (CH{sub 3}){sub 3}-C{triple_bond}CH] and ethynyl trimethylsilane [ETMS: (CH{sub 3}){sub 3}-Si{triple_bond}CH] to investigate pressure-induced chemical reactions. The starting samples were the low temperature crystalline phases which persisted metastably at room temperature and polymerized beyond 11 GPa and 26 GPa for TBA and ETMS respectively. These reaction onset pressures are considerably higher than what we observed in the shockwave studies (6.1 GPa for TBA and 6.6 GPa for ETMS). Interestingly, in the case of ETMS, it was observed with fluid ETMS as starting sample, reacts to form a semi-crystalline polymer (crystalline domains corresponding to the low-T phase) at pressures less than {approx}2 GPa. Further characterization using vibrational spectroscopy is in progress.

  6. Interpenetrating polymer networks from acetylene terminated materials

    NASA Technical Reports Server (NTRS)

    Connell, J. W.; Hergenrother, P. M.

    1989-01-01

    As part of a program to develop high temperature/high performance structural resins for aerospace applications, the chemistry and properties of a novel class of interpenetrating polymer networks (IPNs) were investigated. These IPNs consist of a simple diacetylenic compound (aspartimide) blended with an acetylene terminated arylene ether oligomer. Various compositional blends were prepared and thermally cured to evaluate the effect of crosslink density on resin properties. The cured IPNs exhibited glass transition temperatures ranging from 197 to 254 C depending upon the composition and cure temperature. The solvent resistance, fracture toughness and coefficient of thermal expansion of the cured blends were related to the crosslink density. Isothermal aging of neat resin moldings, adhesive and composite specimens showed a postcure effect which resulted in improved elevated temperature properties. The chemistry, physical and mechanical properties of these materials will be discussed.

  7. The experimental equilibrium structure of acetylene.

    PubMed

    Tamassia, Filippo; Can, Elisabetta; Fusina, Luciano; Di Lonardo, Gianfranco

    2016-01-21

    The empirical equilibrium structure of acetylene has been derived by exploiting the very precise experimental rotational constants available in the literature for the 10 isotopologues relative to all the possible combinations of H, D, (12)C and (13)C atoms. The geometry obtained when data for all species are fitted together is: re(CH) = 106.167(14) pm and re(CC) = 120.2866(72) pm. This determination shows some systematic residuals due to the singly D-substituted isotopologues. If we exclude such species from the fit, we obtain our most precise evaluation: re(CH) = 106.1689(23) pm and re(CC) = 120.2817(12) pm. The possibility of a breakdown of the Born-Oppenheimer approximation has also been tested. PMID:26687993

  8. Cooperative Gold Nanoparticle Stabilization by Acetylenic Phosphaalkenes

    PubMed Central

    Orthaber, Andreas; Lfs, Henrik; berg, Elisabet; Grigoriev, Anton; Wallner, Andreas; Jafri, S Hassan M; Santoni, Marie-Pierre; Ahuja, Rajeev; Leifer, Klaus; Ottosson, Henrik; Ott, Sascha

    2015-01-01

    Acetylenic phosphaalkenes (APAs) are used as a novel type of ligands for the stabilization of gold nanoparticles (AuNP). As demonstrated by a variety of experimental and analytical methods, both structural features of the APA, that is, the P=C as well as the C?C units are essential for NP stabilization. The presence of intact APAs on the AuNP is demonstrated by surface-enhanced Raman spectroscopy (SERS), and first principle calculations indicate that bonding occurs most likely at defect sites on the Au surface. AuNP-bound APAs are in chemical equilibrium with free APAs in solution, leading to a dynamic behavior that can be explored for facile place-exchange reactions with other types of anchor groups such as thiols or more weakly binding phosphine ligands. PMID:26211907

  9. A molecular level study of the aqueous microsolvation of acetylene

    NASA Astrophysics Data System (ADS)

    Tzeli, Demeter; Mavridis, Aristides; Xantheas, Sotiris S.

    2001-06-01

    We present an analysis of the structural, energetic and spectral features associated with the different hydrogen bonded networks found in the first few acetylene-water clusters AW n ( n=1-4) from first principles calculations. Contrary to the predictions of an empirical interaction potential, acetylene is incorporated into a hydrogen bonded ring when it clusters with two or three water molecules. This structural pattern changes for n=4 with the formation of a water tetramer interacting with acetylene. This structural transition from n=3 to 4 is spectroscopically manifested by a qualitative change in the appearance of the infrared spectra of the corresponding global minima.

  10. A biogeochemical and genetic survey of acetylene fermentation by environmental samples and bacterial isolates

    USGS Publications Warehouse

    Miller, Laurence G.; Baesman, Shaun M.; Kirshtein, Julie; Voytek, Mary A.; Oremland, Ronald S.

    2013-01-01

    Anoxic samples (sediment and groundwater) from 13 chemically diverse field sites were assayed for their ability to consume acetylene (C2H2). Over incubation periods ranging from ˜ 10 to 80 days, selected samples from 7 of the 13 tested sites displayed significant C2H2 removal. No significant formation of ethylene was noted in these incubations; therefore, C2H2 consumption could be attributed to acetylene hydratase (AH) rather than nitrogenase activity. This putative AH (PAH) activity was observed in only 21% of the total of assayed samples, while amplification of AH genes from extracted DNA using degenerate primers derived from Pelobacter acetylenicus occurred in even fewer (9.8%) samples. Acetylene-fermenting bacteria were isolated as a pure culture from the sediments of a tidal mudflat in San Francisco Bay (SFB93) and as an enrichment culture from freshwater Searsville Lake (SV7). Comparison of 16S rDNA clone libraries revealed that SFB93 was closely related to P. carbolinicus, while SV7 consisted of several unrelated bacteria. AH gene was amplified from SFB93 but not SV7. The inability of the primers to generate amplicons in the SV7 enrichment, as well as from several of the environmental samples that displayed PAH activity, implied that either the primers were too highly constrained in their specificity or that there was a different type of AH gene in these environmental samples than occurs in P. acetylenicus. The significance of this work with regard to the search for life in the outer Solar System, where C2HL2 is abundant, is discussed.

  11. Inhibiting the combustion of air-acetylene mixtures

    NASA Astrophysics Data System (ADS)

    Kopylov, S. N.; Gubina, T. V.

    2016-01-01

    The effect propane, methane, and a mixture of 18 vol % C3H6-40 vol % C3H8-42 vol % C4H10 have on the combustion of air-acetylene mixtures is investigated experimentally. The upper concentration limit of flame propagation, maximum explosion pressure, and maximum rate of rise of explosion pressure are determined. It is found that propane and a mixture of 18 vol % C3H6-40 vol % C3H8-42 vol % C4H10 are strong inhibitors of combustion of acetylene in its concentration ranges of 2-8 vol %. The inhibition effect becomes weaker as the acetylene content in the mixture increases. It disappears completely at C2H2 concentrations exceeding 15 vol %. The above experimental findings are explained using the proposed scheme of acetylene oxidation.

  12. The photolysis of acetylene halides reaction with oxygen

    SciTech Connect

    Hwang, Mei-Lee; Kuo, Yu-Ping

    1996-12-31

    The photolysis of chloro- and bromo-acetylene reactions at low temperature with Hg lamp are carried out. There is no new absorption band observed after in-situ photolysis of acetylene halides in Ar matrix. With the presence of oxygen, several new bands appeared. The new peaks at 2138 and 2342 cm{sup -1} were assigned as CO and CO{sub 2}, respectively. Further work is essential for the assignment of the other new bands.

  13. Insights on Antioxidant Assays for Biological Samples Based on the Reduction of Copper ComplexesThe Importance of Analytical Conditions

    PubMed Central

    Marques, Sara S.; Magalhes, Lus M.; Tth, Ildik V.; Segundo, Marcela A.

    2014-01-01

    Total antioxidant capacity assays are recognized as instrumental to establish antioxidant status of biological samples, however the varying experimental conditions result in conclusions that may not be transposable to other settings. After selection of the complexing agent, reagent addition order, buffer type and concentration, copper reducing assays were adapted to a high-throughput scheme and validated using model biological antioxidant compounds of ascorbic acid, Trolox (a soluble analogue of vitamin E), uric acid and glutathione. A critical comparison was made based on real samples including NIST-909c human serum certified sample, and five study samples. The validated method provided linear range up to 100 M Trolox, (limit of detection 2.3 M; limit of quantification 7.7 M) with recovery results above 85% and precision <5%. The validated developed method with an increased sensitivity is a sound choice for assessment of TAC in serum samples. PMID:24968275

  14. Electron impact induced anion production in acetylene.

    PubMed

    Szyma?ska, Ewelina; ?ade, Iztok; Krishnakumar, E; Mason, Nigel J

    2014-02-28

    A detailed experimental investigation of electron induced anion production in acetylene, C2H2, in the energy range between 1 and 90 eV is presented. The anions are formed by two processes in this energy range: dissociative electron attachment (DEA) and dipolar dissociation (DD). DEA in C2H2 is found to lead to the formation of H(-) and C2(-)/C2H(-) through excitation of resonances in the electron energy range 1-15 eV. These anionic fragments are formed with super thermal kinetic energy and reveal no anisotropy in the angular distributions. DD in C2H2 leads to the formation of H(-), C(-)/CH(-) and C2(-)/C2H(-) with threshold energies of 15.7, 20.0 and 16.5 eV respectively. The measured anion yields have been used to calculate anion production rates for H(-), C(-)/CH(-) and C2(-)/C2H(-) in Titan's ionosphere. PMID:24343432

  15. Mortality of workers at acetylene production plants.

    PubMed Central

    Newhouse, M L; Matthews, G; Sheikh, K; Knight, K L; Oakes, D; Sullivan, K R

    1988-01-01

    To reduce the risk of explosion oxyacetylene cylinders are filled with a spongy mass, acetone is added to saturate the mass, and acetylene is pumped into the cylinder. The first cylinders manufactured before 1936 used a kapok filling topped off with about 16 oz of crocidolite asbestos, with a metal gauze thimble inserted to reduce risk of flash back. Cylinders must be examined annually. The use of crocidolite ceased in 1972 and other fillings have been adopted since 1970; kapok cylinders now constitute less than 5% of the total stock. To assess possible hazards, a mortality study of workers first employed between 1935 and 1975 and followed up to December 1984 was undertaken. Simulation tests showed low concentrations of asbestos in the air even in the earliest period. The population studied consisted of 370 workers at the Bilston plant in the West Midlands, 611 at the 14 other plants in England and Wales, and 120 in Scotland. No deaths occurred from mesothelial tumours but there was an excess of deaths from cancer, particularly lung cancer, cancer of the stomach, and cancer of the pancreas, the latter accounting for eight deaths. Risks appeared to be concentrated at the Bilston plant. The importance of these findings is discussed. PMID:3342189

  16. Ion-induced dissociation dynamics of acetylene

    SciTech Connect

    De, Sankar; Rajput, Jyoti; Roy, A.; Safvan, C. P.; Ghosh, P. N.

    2008-02-15

    We report on the results of dissociation dynamics of multiple charged acetylene molecules formed in collision with 1.2 MeV Ar{sup 8+} projectiles. Using the coincidence map, we can separate out the different dissociation pathways between carbon and hydrogen ionic fragments as well as complete two-body breakup events. From the measured slopes of the coincidence islands for carbon atomic fragments and theoretical values determined from the charge and momentum distribution of the correlated particles, we observe a diatom like behavior of the C-C charged complex during dissociation of multiply charged C{sub 2}H{sub 2}. We conclude that this behavior in breakup dynamics is a signature of sequentiality in dissociation of this multiply charged molecular species. The shape and orientation of the islands give further information about the momentum balance in the fragmentation process of two- or many-body dissociation pathways. Kinetic energy release of different breakup channels are reported here and compared with values calculated from the pure Coulomb explosion model.

  17. The geometry and forcefield of acetylene

    NASA Astrophysics Data System (ADS)

    Carter, Stuart; Handy, Nicholas C.

    The variational method has been used to determine the geometry and ground state potential surface of acetylene. All the parameters were refined through a least-squares fit to J = 0, 1 levels for C2H2 and C2D2. A new program was written to evaluate the rovibrational energy levels; in particular, primitive basis sets were developed for all values of J taking into account the singularity for linear geometries. Thus ?, ?, ?states can be refined. The full theory for tetraatomic linear molecules is presented. In this refinement 150 observed levels were used as data, below 10 000 cm-1. The geometry was refined and gives Re (CC) = 1.2028 , Re (CH) = 1.0618 , to be compared with the best experimentally derived values of 1.2027 0.0005 , 1.062 0.001 , respectively. The zero point energies are 5771.1 cm-1 for C2H2and 4571.1 cm-1 for C2D2.

  18. Comparing an in vivo egg reduction test and in vitro egg hatching assay for different anthelmintics against Fasciola species, in cattle.

    PubMed

    Arafa, Waleed M; Shokeir, Khalid M; Khateib, Abdelrahman M

    2015-11-30

    This study aimed to compare between the efficiency of in vivo fecal egg reduction test (FERT) and in vitro egg hatching assay (EHA) in evaluating of the anti-Fasciola activity of albendazole, triclabendazole, oxyclozanide and praziquantel. A field trial was carried out on fifty naturally Fasciola infected cattle that were divided equally into 5 groups (A-E). On day zero; groups A-D were drenched with albendazole, triclabendazole, oxyclozanide or praziquantel, respectively, while the remaining one, group E, was kept as untreated control. Fecal egg counts of the different groups were conducted weekly over a period of one month post-treatment. In vitro, commercial albendazole and oxyclozanide were diluted to 0.0002, 0.002, 0.02, 0.2 and 2.0 ?g/ml, while commercial triclabendazole and praziquantel were diluted to concentrations of 25, 50, 75 and 100 ?g/ml with dimethyl sulfoxide (DMSO). In vivo, at the 2nd week post-treatment, triclabendazole and oxyclozanide showed 100% fecal egg reduction (FER), and albendazole had a maximum of 73.7% reduction (P < 0.0001), however, praziquantel did not record any reduction of Fasciola egg counts. In vitro, triclabendazole treated Fasciola gigantica eggs showed early embryonic lysis with zero% hatching at the different concentrations (P < 0.01). In albendazole, the hatching varied according to the drug concentration. At the highest two concentrations; 0.2 and 2.0 ?g/ml, the hatching percentages were 7.4 1.6 and 5.6 1.5 (P < 0.01) respectively. On the contrary, there were no significant differences in egg development and hatching percentage of oxyclozanide or praziquantel treated groups. In conclusion, the efficacy of triclabendazole and albendazole as fasciolicdes could be predicted by Egg Hatching Assay (EHA). Meanwhile fasciolicide activity of oxyclozanide could not be assessed with EHA. Based on in vivo and in vitro findings, paraziquantel did not show any fasciolicide effect. PMID:26455573

  19. Chemistry and properties of blends of acetylene terminated materials

    NASA Technical Reports Server (NTRS)

    Connell, John W.; Hergenrother, Paul M.

    1991-01-01

    As part of a NASA program to develop new high temperature/high performance structural materials, the chemistry and properties of acetylene-containing materials and their cured resins are under investigation. The objective of this work is to develop materials that are readily processable (i.e., 200-300 C and about 1.4 MPa or less) and possess usable mechanical properties at temperatures as high as 177 C. An acetylene-terminated aspartimide (ATA) was blended with an equal weight of an acetylene-terminated arylene ether (ATAE) oligomer. The blend was subsequently thermally cured to yield a resin which was evaluated in the form of neat resin moldings, adhesive specimens, and laminates. Adhesive specimens and laminates gave good mechanical properties to temperatures as high as 177 C. In addition, preliminary laminate work is presented on the resin from a blend of a new N-methyl substituted ATA and an ATAE.

  20. Precision spectroscopy of acetylene transitions using an optical frequency synthesizer.

    PubMed

    Ahtee, V; Merimaa, M; Nyholm, K

    2009-09-01

    An optical frequency synthesizer is used for saturation spectroscopy of acetylene near 1540 nm. In the synthesizer, a user-specified frequency is generated from an atomic time base by phase locking the second harmonic of a cw near-IR external-cavity diode laser (ECDL) to a Ti:sapphire frequency comb. By stepping the repetition rate of the frequency comb, the ECDL frequency is swept over an acetylene transition in a saturated absorption spectroscopy setup. Hence, a spectral lineshape is measured with an absolute frequency scale. Line-center frequencies determined by fitting theoretical line profiles to the measured data are in good agreement with values measured with the ECDL stabilized to acetylene by third-harmonic locking and with the values recommended by the International Committee for Weights and Measures (CIPM). PMID:19724510

  1. Structure and Function of the Unusual Tungsten Enzymes Acetylene Hydratase and Class II Benzoyl-Coenzyme A Reductase.

    PubMed

    Boll, Matthias; Einsle, Oliver; Ermler, Ulrich; Kroneck, Peter M H; Ullmann, G Matthias

    2016-01-01

    In biology, tungsten (W) is exclusively found in microbial enzymes bound to a bis-pyranopterin cofactor (bis-WPT). Previously known W enzymes catalyze redox oxo/hydroxyl transfer reactions by directly coordinating their substrates or products to the metal. They comprise the W-containing formate/formylmethanofuran dehydrogenases belonging to the dimethyl sulfoxide reductase (DMSOR) family and the aldehyde:ferredoxin oxidoreductase (AOR) families, which form a separate enzyme family within the Mo/W enzymes. In the last decade, initial insights into the structure and function of two unprecedented W enzymes were obtained: the acetaldehyde forming acetylene hydratase (ACH) belongs to the DMSOR and the class II benzoyl-coenzyme A (CoA) reductase (BCR) to the AOR family. The latter catalyzes the reductive dearomatization of benzoyl-CoA to a cyclic diene. Both are key enzymes in the degradation of acetylene (ACH) or aromatic compounds (BCR) in strictly anaerobic bacteria. They are unusual in either catalyzing a nonredox reaction (ACH) or a redox reaction without coordinating the substrate or product to the metal (BCR). In organic chemical synthesis, analogous reactions require totally nonphysiological conditions depending on Hg2+ (acetylene hydration) or alkali metals (benzene ring reduction). The structural insights obtained pave the way for biological or biomimetic approaches to basic reactions in organic chemistry. PMID:26959374

  2. Asymmetric Kinugasa reaction of cyclic nitrones and nonracemic acetylenes.

    PubMed

    Stecko, Sebastian; Mames, Adam; Furman, Bartlomiej; Chmielewski, Marek

    2009-04-17

    Kinugasa reactions between chiral acetylenes and five-membered nitrones, achiral and bearing a stereogenic center in both enantiomeric forms, proceed in moderate to good yield with high diastereoselectivity affording mostly one dominant product. The first step of the reaction is controlled by the configuration of the nitrone, whereas the protonation of intermediate enolate in the second step depends mainly on the configuration of the bridgehead carbon atom formed in the first step. In the case of the mismatched pair, the configuration at the C-6 center of the carbapenam skeleton may also be affected by the configuration of the stereogenic center in the acetylene portion. PMID:19323546

  3. Microgravity Superagglomerates Produced By Silane And Acetylene

    NASA Technical Reports Server (NTRS)

    Gokoglu, Suleyman (Technical Monitor); Bundy, Matthew; Mulholland, George W.; Manzello, Samuel; Yang, Jiann; Scott, John Henry; Sivathanu, Yudaya

    2003-01-01

    The size of the agglomerates produced in the upper portion of a flame is important for a variety of applications. Soot particle size and density effect the amount of radiative heat transfer from a fire to its surroundings. Particle size determines the lifetime of smoke in a building or in the atmosphere, and exposure hazard for smoke inhaled and deposited in the lungs. The visibility through a smoke layer and dectectability of the smoke are also greatly affected by agglomerate size. Currently there is limited understanding of soot growth with an overall dimension of 10 m and larger. In the case of polystyrene, smoke agglomerates in excess of 1 mm have been observed raining out from large fires. Unlike hydrocarbon fuels, silane has the advantage that silica particles are the major combustion product resulting in a particle volume fraction a factor of ten greater than that for a carbonaceous smoke. There are two very desirable properties of silica aero-gels that are important for both space and earth based applications. The first important property is its inertness to most oxidizing and reducing atmospheres. Therefore, silica aero-gels make excellent fire ablatives and can be used in very demanding applications. The second important property is that silica aero-gels are expected to have very high porosity (greater than 0.999), making them lightweight and ideal for aerospace applications. The added benefit of the high porosity is that they can be used as extremely efficient filters for many earth based applications as well. Evidence of the formation of superagglomerates in a laminar acetylene/air diffusion flame was found by Sorensen et al. [1]. An interconnecting web of super-agglomerates was observed to span the width of the soot plume in the region just above the flame tip and described as a gel state. It was observed that this gel state immediately breaks up into agglomerates as larges as 100 m due to buoyancy induced turbulence. Large soot agglomerates were observed in microgravity butane jet diffusion flames by Ito et al.[2]. Several other works to date have studied the effect of flame structure on soot volume fraction and agglomeration size in a microgravity environment.[3-4]. In microgravity the absence of buoyant convective flows increases the residence time in the flame and causes a broadening of the high temperature region in the flame. Both of these factors play a significant role in gas phase radiation and soot formation

  4. 46 CFR 56.50-103 - Fixed oxygen-acetylene distribution piping.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 2 2010-10-01 2010-10-01 false Fixed oxygen-acetylene distribution piping. 56.50-103... oxygen-acetylene distribution piping. (a) This section applies to fixed piping installed for the distribution of oxygen and acetylene carried in cylinders as vessels stores. (b) The distribution piping...

  5. 46 CFR 56.50-103 - Fixed oxygen-acetylene distribution piping.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 2 2011-10-01 2011-10-01 false Fixed oxygen-acetylene distribution piping. 56.50-103... oxygen-acetylene distribution piping. (a) This section applies to fixed piping installed for the distribution of oxygen and acetylene carried in cylinders as vessels stores. (b) The distribution piping...

  6. 46 CFR 56.50-103 - Fixed oxygen-acetylene distribution piping.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 2 2012-10-01 2012-10-01 false Fixed oxygen-acetylene distribution piping. 56.50-103... oxygen-acetylene distribution piping. (a) This section applies to fixed piping installed for the distribution of oxygen and acetylene carried in cylinders as vessels stores. (b) The distribution piping...

  7. 46 CFR 56.50-103 - Fixed oxygen-acetylene distribution piping.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 2 2014-10-01 2014-10-01 false Fixed oxygen-acetylene distribution piping. 56.50-103... oxygen-acetylene distribution piping. (a) This section applies to fixed piping installed for the distribution of oxygen and acetylene carried in cylinders as vessels stores. (b) The distribution piping...

  8. 46 CFR 56.50-103 - Fixed oxygen-acetylene distribution piping.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 2 2013-10-01 2013-10-01 false Fixed oxygen-acetylene distribution piping. 56.50-103... oxygen-acetylene distribution piping. (a) This section applies to fixed piping installed for the distribution of oxygen and acetylene carried in cylinders as vessels stores. (b) The distribution piping...

  9. Identification of proteins capable of metal reduction from the proteome of the Gram-positive bacterium Desulfotomaculum reducens MI-1 using an NADH-based activity assay

    SciTech Connect

    Otwell, Annie E.; Sherwood, Roberts; Zhang, Sheng; Nelson, Ornella D.; Li, Zhi; Lin, Hening; Callister, Stephen J.; Richardson, Ruth E.

    2015-01-01

    Metal reduction capability has been found in numerous species of environmentally abundant Gram-positive bacteria. However, understanding of microbial metal reduction is based almost solely on studies of Gram-negative organisms. In this study, we focus on Desulfotomaculum reducens MI-1, a Gram-positive metal reducer whose genome lacks genes with similarity to any characterized metal reductase. D. reducens has been shown to reduce not only Fe(III), but also the environmentally important contaminants U(VI) and Cr(VI). By extracting, separating, and analyzing the functional proteome of D. reducens, using a ferrozine-based assay in order to screen for chelated Fe(III)-NTA reduction with NADH as electron donor, we have identified proteins not previously characterized as iron reductases. Their function was confirmed by heterologous expression in E. coli. These are the protein NADH:flavin oxidoreductase (Dred_2421) and a protein complex composed of oxidoreductase FAD/NAD(P)-binding subunit (Dred_1685) and dihydroorotate dehydrogenase 1B (Dred_1686). Dred_2421 was identified in the soluble proteome and is predicted to be a cytoplasmic protein. Dred_1685 and Dred_1686 were identified in both the soluble as well as the insoluble (presumably membrane) protein fraction, suggesting a type of membrane-association, although PSORTb predicts both proteins are cytoplasmic. Furthermore, we show that these proteins have the capability to reduce soluble Cr(VI) and U(VI) with NADH as electron donor. This study is the first functional proteomic analysis of D. reducens, and one of the first analyses of metal and radionuclide reduction in an environmentally relevant Gram-positive bacterium.

  10. Rapid susceptibility testing for slowly growing nontuberculous mycobacteria using a colorimetric microbial viability assay based on the reduction of water-soluble tetrazolium WST-1.

    PubMed

    Tsukatani, T; Suenaga, H; Shiga, M; Ikegami, T; Ishiyama, M; Ezoe, T; Matsumoto, K

    2015-10-01

    Rapid susceptibility testing for slowly growing nontuberculous mycobacteria (NTM) using a colorimetric microbial viability assay based on the reduction of the water-soluble tetrazolium salt {2-(4-iodophenyl)-3-(4-nitrophenyl)-5-(2,4-disulfophenyl)-2H-tetrazolium, monosodium salt (WST-1)} using 2,3,5,6-tetramethyl-1,4-benzoquinone as an electron mediator was developed. Using the Clinical and Laboratory Standards Institute (CLSI) method, a long-term incubation time (7-14 days) was required to determine the minimum inhibitory concentrations (MICs) of the slowly growing NTM. The MICs for a variety of different antibiotics against the slowly growing NTM were determined by the WST-1 colorimetric method and compared with those obtained using the broth microdilution methods approved by the CLSI. Good agreement was found between the MICs determined after 3-4 days using the WST-1 colorimetric method and those obtained after 10-14 days using the broth microdilution method. The results suggest that the WST-1 colorimetric assay is a useful method for the rapid determination of the MICs for the slowly growing NTM. PMID:26173690

  11. Nongenotoxic effects and a reduction of the DXR-induced genotoxic effects of Helianthus annuus Linné (sunflower) seeds revealed by micronucleus assays in mouse bone marrow

    PubMed Central

    2014-01-01

    Background This research evaluated the genotoxicity of oil and tincture of H. annuus L. seeds using the micronucleus assay in bone marrow of mice. The interaction between these preparations and the genotoxic effects of doxorubicin (DXR) was also analysed (antigenotoxicity test). Methods Experimental groups were evaluated at 24-48 h post treatment with N-Nitroso-N-ethylurea (positive control – NEU), DXR (chemotherapeutic), NaCl (negative control), a sunflower tincture (THALS) and two sources of sunflower oils (POHALS and FOHALS). Antigenotoxic assays were carried out using the sunflower tincture and oils separately and in combination with NUE or DXR. Results For THALS, analysis of the MNPCEs showed no significant differences between treatment doses (250–2,000 mg.Kg-1) and NaCl. A significant reduction in MNPCE was observed when THALS (2,000 mg.Kg-1) was administered in combination with DXR (5 mg.Kg-1). For POHALS or FOHALS, analysis of the MNPCEs also showed no significant differences between treatment doses (250–2,000 mg.Kg-1) and NaCl. However, the combination DXR + POHALS (2,000 mg.Kg-1) or DXR + FOHALS (2,000 mg.Kg-1) not contributed to the MNPCEs reduction. Conclusions This research suggests absence of genotoxicity of THALS, dose-, time- and sex-independent, and its combination with DXR can reduce the genotoxic effects of DXR. POHALS and FOHALS also showed absence of genotoxicity, but their association with DXR showed no antigenotoxic effects. PMID:24694203

  12. Bacteriological analysis of water by potentiometric measurement of lipoic acid reduction: preliminary assays for selective detection of indicator organisms.

    PubMed

    Charriere, G; Jouenne, T; Lemeland, J F; Selegny, E; Junter, G A

    1984-01-01

    The practical task of adapting an original potentiometric technique to the bacteriological analysis of water is discussed. Various laboratory strains of organisms belonging to the usual aquatic flora were inoculated one by one in a minimal lactose broth supplied with lipoic (thioctic) acid. The time evolution of the redox potential of the cultures was followed during incubation by combined gold versus reference electrodes. When the incubation temperature was regulated at 36 degrees C, most organisms were able to grow and to reduce the coenzyme, generating changes in the redox potential of the culture. However, very few organisms developed significant reductive activity when the temperature was increased to 41 degrees C and when the broth was provided with sodium deoxycholate. Among the fecal coliform organisms, only Escherichia coli and Klebsiella pneumoniae exhibited early but reproducible potential-time responses. Positive potentiometric responses were also recorded with Acinetobacter calcoaceticus. E. coli showed rapid potentiometric signals as compared with K. pneumoniae. The time required for 100-mV shift of potential to be detected was related to the logarithm of the initial concentration of E. coli or K. pneumoniae in the culture broth. Experiments on natural surface water samples showed the the potentiometric method, associated with the selective incubation conditions, mainly detected E. coli among the bacterial flora of the tested environmental water. The calibration curve relating the time required for a 100-mV shift of potential to be detected to the number of fecal coliforms, as determined by control fecal coliform-selective plate counts, was consistent with the composite standard curve of detection times obtained with six different laboratory strains of E. coli.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:6421230

  13. Denitrification in a Petroleum-Contaminated Aquifer: In-Situ Assessment Using Push-Pull Tests Combined With Acetylene Inhibition and 15N-Techniques

    NASA Astrophysics Data System (ADS)

    Schroth, M. H.; Schrmann, A.; Zeyer, J.

    2001-12-01

    Microbial denitrification is an important process during in-situ bioremediation in many petroleum hydrocarbon (PHC)-contaminated aquifers. Field-scale quantification of denitrification is commonly based on measured consumption of nitrate, e.g., using geochemical data obtained from monitoring wells or data obtained from single-well, push-pull tests (PPTs). The objective of this study was to investigate in more detail the fate of nitrate in-situ during denitrification. We performed three PPTs in a monitoring well of a PHC-contaminated aquifer in Erlen, Switzerland. Injected anoxic test solutions contained bromide as conservative tracer, and nitrate in PPT1, 15N-nitrate in PPT2, and 15N-nitrate/acetylene in PPT3. During PPT extraction phases, we measured concentrations of bromide, nitrate, nitrite, nitrous oxide, dinitrogen and ammonium, and determined stable nitrogen isotope ratios in nitrous oxide, dinitrogen, and ammonium. We computed first order rate coefficients of nitrate consumption for PPT1-3, 15N-dinitrogen production (PPT2-3), and 15N-nitrous oxide production (PPT3). Similar rate coefficients for nitrate consumption (0.39 +/- 0.06 1/d to 0.43 +/- 0.07 1/d) were obtained in all PPTs. However, 15N-dinitrogen production in PPT2 and the sum of 15N-dinitrogen and 15N-nitrous oxide production in PPT3 accounted for only ~50% of the observed nitrate consumption in those tests. Moreover, while we detected traces of 15N-ammonium during PPT2, dissimilatory nitrate reduction to ammonium did not appear to be a relevant process at this site. As a consequence, we were unable to close the mass balance on nitrate based on the measured parameters, which may indicate that nitrate consumption by reductive assimilation (not directly assayed in our study) played an important role during our tests. Furthermore, production of 15N-dinitrogen in the presence of acetylene during PPT3 provided evidence that some nitrate (or nitrite) was chemically reduced. Our results suggest that denitrification rates determined from nitrate consumption alone may overestimate the contribution of this process to PHC-degradation in contaminated aquifers.

  14. Fatal carbon monoxide intoxication after acetylene gas welding of pipes.

    PubMed

    Antonsson, Ann-Beth; Christensson, Bengt; Berge, Johan; Sjgren, Bengt

    2013-06-01

    Acetylene gas welding of district heating pipes can result in exposure to high concentrations of carbon monoxide. A fatal case due to intoxication is described. Measurements of carbon monoxide revealed high levels when gas welding a pipe with closed ends. This fatality and these measurements highlight a new hazard, which must be promptly prevented. PMID:23307861

  15. 46 CFR 154.1735 - Methyl acetylene-propadiene mixture.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 1; (ii) Maximum combined concentration of methyl acetylene and propadiene of 65 mole percent; (iii) Minimum combined concentration of propane, butane, and isobutane of 24 mole percent, of which at least one... of propylene and butadiene of 10 mole percent. (2) A second composition is: (i) Maximum...

  16. 46 CFR 154.1735 - Methyl acetylene-propadiene mixture.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 1; (ii) Maximum combined concentration of methyl acetylene and propadiene of 65 mole percent; (iii) Minimum combined concentration of propane, butane, and isobutane of 24 mole percent, of which at least one... of propylene and butadiene of 10 mole percent. (2) A second composition is: (i) Maximum...

  17. 46 CFR 154.1735 - Methyl acetylene-propadiene mixture.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 1; (ii) Maximum combined concentration of methyl acetylene and propadiene of 65 mole percent; (iii) Minimum combined concentration of propane, butane, and isobutane of 24 mole percent, of which at least one... of propylene and butadiene of 10 mole percent. (2) A second composition is: (i) Maximum...

  18. 46 CFR 154.1735 - Methyl acetylene-propadiene mixture.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 1; (ii) Maximum combined concentration of methyl acetylene and propadiene of 65 mole percent; (iii) Minimum combined concentration of propane, butane, and isobutane of 24 mole percent, of which at least one... of propylene and butadiene of 10 mole percent. (2) A second composition is: (i) Maximum...

  19. 46 CFR 154.1735 - Methyl acetylene-propadiene mixture.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 1; (ii) Maximum combined concentration of methyl acetylene and propadiene of 65 mole percent; (iii) Minimum combined concentration of propane, butane, and isobutane of 24 mole percent, of which at least one... of propylene and butadiene of 10 mole percent. (2) A second composition is: (i) Maximum...

  20. Interstitial pneumonitis after acetylene welding: a case report.

    PubMed

    Brvar, Miran

    2014-01-01

    Acetylene is a colorless gas commonly used for welding. It acts mainly as a simple asphyxiant. In this paper, however, we present a patient who developed a severe interstitial pneumonitis after acetylene exposure during aluminum welding. A 44-year old man was welding with acetylene, argon and aluminum electrode sticks in a non-ventilated aluminum tank for 2 h. Four hours after welding dyspnea appeared and 22 h later he was admitted at the Emergency Department due to severe respiratory insufficiency with pO2 = 6.7 kPa. Chest X-ray showed diffuse interstitial infiltration. Pulmonary function and gas diffusion tests revealed a severe restriction (55% of predictive volume) and impaired diffusion capacity (47% of predicted capacity). Toxic interstitial pneumonitis was diagnosed and high-dose systemic corticosteroid methylprednisolone and inhalatory corticosteroid fluticasone therapy was started. Computed Tomography (CT) of the lungs showed a diffuse patchy ground-glass opacity with no signs of small airway disease associated with interstitial pneumonitis. Corticosteroid therapy was continued for the next 8 weeks gradually reducing the doses. The patient's follow-up did not show any deterioration of respiratory function. In conclusion, acetylene welding might result in severe toxic interstitial pneumonitis that improves after an early systemic and inhalatory corticosteroid therapy. PMID:24658888

  1. 77 FR 13969 - Revising Standards Referenced in the Acetylene Standard

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-03-08

    ... Association (GGA) acetylene standard (see 76 FR 75782). In the DFR, OSHA deleted reference to CGA G-1-2003 and... final rule published on December 5, 2011 (76 FR 75782), is effective on March 5, 2012. For the purposes....C. 553, Secretary of Labor's Order 1-2012 (77 FR 3912), and 29 CFR part 1911. Signed at...

  2. 76 FR 75840 - Revising Standards Referenced in the Acetylene Standard

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-12-05

    ... Association standard, CGA G-1-2003, in the Acetylene Standard. See 74 FR 40442 and 74 FR 40450, respectively. OSHA received no adverse comments on the DFR, and it became effective on November 9, 2009. See 74 FR... language from outdated standards published by standards developing organizations (``SDO standards'') (69...

  3. Thermally induced self-locking of an optical cavity by overtone absorption in acetylene gas

    SciTech Connect

    Dube, P.; Ma, L.; Ye, J.; Jungner, P.; Hall, J.L.

    1996-09-01

    Strong self-locking phenomena are observed when laser power is converted into heat by a weakly absorbing medium within a high-finesse cavity. Deposited heat leads to increased temperature and, for the case of weakly absorbing intracavity gases studied here, to an associated reduction of density and refractive index. This thermal change in refractive index provides self-acting cavity tuning near resonant conditions. In the experiments reported here a Fabry{endash}Perot cavity of finesse 274 was filled with acetylene gas and illuminated with a titanium:sapphire laser tuned to the {ital P}(11) line of the {nu}{sub 1}+3{nu}{sub 3} overtone band near 790 nm. The dependencies of maximum frequency-locking range on gas pressure, laser power, and laser frequency sweep rate and direction were measured and could be well unified by analysis based on the thermal model. In the domain of strong self-tuning an interesting self-sustained oscillation was observed, with its several sharp frequencies directly and quantitatively linked to the acoustic boundary conditions in our cylindrical cell geometry. The differences between the behavior of acetylene near 790 nm and molecular oxygen with electronic transition near 763 nm are instructive; whereas the absorbed powers were similar, they differed strongly in their rates for internal to translational energy conversion by collisional relaxation. {copyright} {ital 1996 Optical Society of America.}

  4. Infrared and ab initio study of acetylene acetone complex in solid argon and nitrogen matrices

    NASA Astrophysics Data System (ADS)

    Sundararajan, K.; Ramanathan, N.

    2007-05-01

    The infrared absorption spectrum of the hydrogen-bonded acetylene-acetone complex has been investigated in solid argon and nitrogen matrices. Formation of the 1:1 acetylene-acetone complex was evidenced by the shifts in the vibrational frequencies of the modes involving the acetylene and acetone submolecules. The structure of the adduct, energies and the vibrational frequencies were computed at the B3LYP and MP2 level using 6-31++G ∗∗ basis sets. The computed vibrational frequencies of 1:1 acetylene-acetone complex agree well with the experimental frequencies. The computed vibrational frequencies indicated a primary C-H⋯O hydrogen-bonded interaction between the hydrogen of acetylene and carbonyl oxygen in acetone. Structures, interaction energies, and vibrational frequencies have also been computed for 2:1 acetylene-acetone and acetylene-acetone-water complexes. AIM analysis was also performed to understand the nature of the interactions in these complexes.

  5. Towards Structural-Functional Mimics of Acetylene Hydratase: Reversible Activation of Acetylene using a Biomimetic Tungsten Complex.

    PubMed

    Peschel, Lydia M; Belaj, Ferdinand; Msch-Zanetti, Nadia C

    2015-10-26

    The synthesis and characterization of a biomimetic system that can reversibly bind acetylene (ethyne) is reported. The system has been designed to mimic catalytic intermediates of the tungstoenzyme acetylene hydratase. The thiophenyloxazoline ligand S-Phoz (2-(4',4'-dimethyloxazolin-2'-yl)thiophenolate) is used to generate a bioinspired donor environment around the W?center, facilitating the stabilization of W-acetylene adducts. The featured complexes [W(C2 H2 )(CO)(S-Phoz)2 ] (2) and [WO(C2 H2 )(S-Phoz)2 ] (3) are extremely rare from a synthetic and structural point of view as very little is known about W-C2 H2 adducts. Upon exposure to visible light, 3 can release C2 H2 from its coordination sphere to yield the 14-electron species [WO(S-Phoz)2 ] (4). Under light-exclusion 4 re-activates C2 H2 making this the first fully characterized system for the reversible activation of acetylene. PMID:26480335

  6. Study of acetylene poisoning of Pt cathode on proton exchange membrane fuel cell spatial performance using a segmented cell system

    NASA Astrophysics Data System (ADS)

    Reshetenko, Tatyana V.; St-Pierre, Jean

    2015-08-01

    Acetylene is a welding fuel and precursor for organic synthesis, which requires considering it to be a possible air pollutant. In this work, the spatial performance of a proton exchange membrane fuel cell exposed to 300 ppm C2H2 and different operating currents was studied with a segmented cell system. The injection of C2H2 resulted in a cell performance decrease and redistribution of segments' currents depending on the operating conditions. Performance loss was 20-50 mV at 0.1-0.2 A cm-2 and was accompanied by a rapid redistribution of localized currents. Acetylene exposure at 0.4-1.0 A cm-2 led to a sharp voltage decrease to 0.07-0.13 V and significant changes in current distribution during a transition period, when the cell reached a voltage of 0.55-0.6 V. A recovery of the cell voltage was observed after stopping the C2H2 injection. Spatial electrochemical impedance spectroscopy (EIS) data showed different segments' behavior at low and high currents. It was assumed that acetylene oxidation occurs at high cell voltage, while it reduces at low cell potential. A detailed analysis of the current density distribution, its correlation with EIS data and possible C2H2 oxidation/reduction mechanisms are presented and discussed.

  7. Importance of gas solubility coefficients as a function of temperature and salinity for use in nitrogen fixation assays

    NASA Astrophysics Data System (ADS)

    Breitbarth, E.; Mills, M. M.; Laroche, J.

    2003-04-01

    The Acetylene Reduction Assay (ARA) is widely established in nitrogen fixation research. Due to its low cost and ease of use it has been the method of choice in numerous marine studies for the past 30 years. Generally this method involves analyzing a gaseous phase that is in equilibrium with the liquid phase of interest. As a substrate, acetylene blocks the reduction of dinitrogen by the nitrogen fixing enzyme nitrogenase, and is instead reduced to ethylene. Ethylene is detected easily and with high sensitivity using gas chromatography. As with any analysis of gases in liquids, it is crucial to use the correct gas solubility (bunsen) coefficients when determining the concentration of a gas in solution. Reviewing all literature available to us describing the use of ARA for marine nitrogen fixation studies concerning the cyanobacterium Trichodesmium we found no information on the bunsen coefficients used, whereas anecdotal information exists that a value of 0.1 is widely applied. This information is insufficient for correct utilization of the ARA since the solubility a gas in water is temperature and salinity dependent. Here we present recalculated bunsen coefficients for ethylene in seawater (ranging from 0.07 to 0.14) based on empirical data for a range of temperatures and salinities that are of concern for marine science. We further demonstrate the possible error in ARA dependent nitrogen fixation rates caused by application of incorrect bunsen coefficients.

  8. Enhanced acetylene emission near the north pole of Jupiter

    NASA Technical Reports Server (NTRS)

    Drossart, Pierre; Bezard, Bruno; Encrenaz, Therese; Atreya, Sushil; Lacy, John; Serabyn, Eugene; Tokunaga, Alan

    1986-01-01

    The present paper is concerned with observations of acetylene fundamental and hot band vibrational emission lines from the planet Jupiter. It is pointed out that the observation of a polar bright spot in the atmosphere of Jupiter is characterized by an enhancement in the individual lines of C2H2 which can be interpreted as an enhancement in the acetylene abundance. However, a purely thermal effect, on non-LTE phenomena cannot be excluded. The intensity of the observed hot band lines is also consistent with either hypothesis. The reported observations were performed with a cooled Fabry-Perot Grating Spectrometer (FPGS). Observations and instrumentation are considered in detail along with the calculation of synthetic spectra on the basis of a line-by-line computation, and the interpretation of the obtained data.

  9. Enhanced acetylene emission near the north pole of Jupiter

    NASA Technical Reports Server (NTRS)

    Drossart, P.; Bezard, B.; Atreya, S.; Lacy, J.; Serabyn, E.

    1986-01-01

    The present paper is concerned with observations of acetylene fundamental and hot band vibrational emission lines from the planet Jupiter. It is pointed out that the observation of a polar bright spot in the atmosphere of Jupiter is characterized by an enhancement in the individual lines of C2H2 which can be interpreted as an enhancement in the acetylene abundance. However, a purely thermal effect, or non-LTE phenomena cannot be excluded. The intensity of the observed hot band lines is also consistent with either hypothesis. The reported observations were performed with a cooled Fabry-Perot Grating Spectrometer (FPGS). Observations and instrumentation are considered in detail along with the calculation of synthetic spectra on the basis of a line-by-line computation, and the interpretation of the obtained data.

  10. Communication: Observation of local-bender eigenstates in acetylene

    NASA Astrophysics Data System (ADS)

    Steeves, Adam H.; Park, G. Barratt; Bechtel, Hans A.; Baraban, Joshua H.; Field, Robert W.

    2015-08-01

    We report the observation of eigenstates that embody large-amplitude, local-bending vibrational motion in acetylene by stimulated emission pumping spectroscopy via vibrational levels of the S1 state involving excitation in the non-totally symmetric bending modes. The Nb = 14 level, lying at 8971.69 cm-1 (J = 0), is assigned on the basis of degeneracy due to dynamical symmetry breaking in the local-mode limit. The level pattern for the Nb = 16 level, lying at 10 218.9 cm-1, is consistent with expectations for increased separation of ℓ = 0 and 2 vibrational angular momentum components. Increasingly poor agreement between our observations and the predicted positions of these levels highlights the failure of currently available normal mode effective Hamiltonian models to extrapolate to regions of the potential energy surface involving large-amplitude displacement along the acetylene ⇌ vinylidene isomerization coordinate.

  11. Communication: Observation of local-bender eigenstates in acetylene.

    PubMed

    Steeves, Adam H; Park, G Barratt; Bechtel, Hans A; Baraban, Joshua H; Field, Robert W

    2015-08-21

    We report the observation of eigenstates that embody large-amplitude, local-bending vibrational motion in acetylene by stimulated emission pumping spectroscopy via vibrational levels of the S1 state involving excitation in the non-totally symmetric bending modes. The N(b) = 14 level, lying at 8971.69 cm(-1) (J = 0), is assigned on the basis of degeneracy due to dynamical symmetry breaking in the local-mode limit. The level pattern for the N(b) = 16 level, lying at 10 218.9 cm(-1), is consistent with expectations for increased separation of ℓ = 0 and 2 vibrational angular momentum components. Increasingly poor agreement between our observations and the predicted positions of these levels highlights the failure of currently available normal mode effective Hamiltonian models to extrapolate to regions of the potential energy surface involving large-amplitude displacement along the acetylene ⇌ vinylidene isomerization coordinate. PMID:26298106

  12. Detonation engine fed by acetylene-oxygen mixture

    NASA Astrophysics Data System (ADS)

    Smirnov, N. N.; Betelin, V. B.; Nikitin, V. F.; Phylippov, Yu. G.; Koo, Jaye

    2014-11-01

    The advantages of a constant volume combustion cycle as compared to constant pressure combustion in terms of thermodynamic efficiency has focused the search for advanced propulsion on detonation engines. Detonation of acetylene mixed with oxygen in various proportions is studied using mathematical modeling. Simplified kinetics of acetylene burning includes 11 reactions with 9 components. Deflagration to detonation transition (DDT) is obtained in a cylindrical tube with a section of obstacles modeling a Shchelkin spiral; the DDT takes place in this section for a wide range of initial mixture compositions. A modified ka-omega turbulence model is used to simulate flame acceleration in the Shchelkin spiral section of the system. The results of numerical simulations were compared with experiments, which had been performed in the same size detonation chamber and turbulent spiral ring section, and with theoretical data on the Chapman-Jouguet detonation parameters.

  13. Acetylene bubble-powered autonomous capsules: towards in situ fuel.

    PubMed

    Moo, James Guo Sheng; Wang, Hong; Pumera, Martin

    2014-12-28

    A fuel-free autonomous self-propelled motor is illustrated. The motor is powered by the chemistry of calcium carbide and utilising water as a co-reactant, through a polymer encapsulation strategy. Expulsion of acetylene bubbles powers the capsule motor. This is an important step, going beyond the toxic hydrogen peroxide fuel used normally, to find alternative propellants for self-propelled machines. PMID:25347401

  14. Propargyl from the reaction of singlet methylene with acetylene

    SciTech Connect

    Adamson, J.D.; Morter, C.L.; DeSain, J.D.; Glass, G.P.; Curl, R.F.

    1996-02-08

    The technique of infrared kinetic spectroscopy has been used to study the production of propargyl radical from the reaction of singlet methylene with acetylene. The rate constant for this product channel was determined to be (3.5{+-}0.7) x 10{sup -10} cm{sup 3} molecule{sup -1} s{sup -1} at 295 K, measured relative to the known rate for {sup 1}CH{sub 2} with H{sub 2} or CH{sub 4}. Methylene was produced in the singlet state by excimer laser photolysis of ketene at 308 nm in the presence of acetylene and either H{sub 2} or CH{sub 4}. Reaction of {sup 1}CH{sub 2} with acetylene produces propargyl, and reaction of {sup 1}CH{sub 2} with either H{sub 2} or CH{sub 4} produces CH{sub 3}. The intensity of a propargyl infrared absorption line was compared with that of a methyl infrared absorption line, and the rate of formation of propargyl was determined from the ratio of these two intensities and the known rate of reaction of singlet methylene with H{sub 2} (or CH{sub 4}) to produce CH{sub 3}. The relative peak infrared absorption cross sections of methyl and propargyl were calibrated under the conditions of the experiment by photolyzing crotyl bromide at 193 nm to produce methyl and propargyl in equal concentrations. 22 refs., 2 figs., 2 tabs.

  15. Tuning the Electronic Properties of Acetylenic Fluorenes by Phosphaalkene Incorporation.

    PubMed

    Svyaschenko, Yurii V; Orthaber, Andreas; Ott, Sascha

    2016-03-14

    Versatile synthetic protocols for 2,7- and 3,6-diacetylenic fluorene-9-ylidene phosphanes (F9Ps) were developed. Protodesilylation of trimethylsilyl-protected acetylenic F9Ps affords terminal acetylenes that can be employed in Sonogashira and Glaser-type C-C coupling reactions to give thienyl-decorated and butadiyne-bridged fluorene-9-ylidene phosphanes, respectively. As evidenced by UV/Vis spectroscopy and cyclic voltammetry and corroborated by ab initio calculations, the presence of the P center in the F9Ps induces a significantly reduced HOMO-LUMO splitting that originates from stabilization of the LUMO levels. Variation of the acetylene substitution pattern is an additional tool to influence the optical and electronic properties. Whereas 3,6-disubstituted F9Ps have strong absorptions around 400 nm, mainly due to π-π* transitions, 2,7-diacetylenic F9Ps exhibit longest-wavelength absorptions that have significant charge-transfer character with an onset around 520 nm. PMID:26833389

  16. Initial stages of soot formation in thermal pyrolysis of acetylene. I. Mechanism for homogeneous pyrolysis of acetylene

    SciTech Connect

    Merkulov, A.A.; Ovsyannikov, A.A.; Polak, L.S.; Popov, V.T.; Pustilnikov, V.Yu. )

    1989-03-01

    A probable mechanism for the homogeneous pyrolysis of acetylene, using carbene reactions, is considered. Analysis of the energetics for the probable mechanism of the initiation reactions shows the rearrangement C{sub 2}H{sub 2} {yields}:CCH{sub 2} to be the most probable. Using the energetic barriers for simple carbene reactions and formation enthalpies for more complicated carbenes, the authors evaluated the activation energies for the reactions mechanism. The vibrational excitation of the products of carbene reactions is taken into account. Calculations of the acetylene conversion kinetics and yields of the main gas-phase pyrolysis products, based on the carbene molecular mechanism, show significantly better agreement with available experimental data as compared to those based on traditional radical mechanisms. The calculated time for the appearance of aromatic products is close to the measured induction times for the appearance of soot particles.

  17. Thermodynamic study on the formation of acetylene during coal pyrolysis in the arc plasma jet

    SciTech Connect

    Bao, W.; Li, F.; Cai, G.; Lu, Y.; Chang, L.

    2009-07-01

    Based on the principle of minimizing the Gibbs free energy, the composition of C-H-O-N-S equilibrium system about acetylene formation during the pyrolysis in arc plasma jet for four kinds of different rank-ordered coals such as Datong, Xianfeng, Yangcheng, and Luan was analyzed and calculated. The results indicated that hydrogen, as the reactive atmosphere, was beneficial to the acetylene formation. The coal ranks and the hydrogen, oxygen, nitrogen, and sulfur in coal all could obviously affect the acetylene yield. The mole fraction of acetylene is the maximum when the ratio value of atom H/C was 2. The content of oxygen was related to the acetylene yield, but it does not compete with CO formation. These agreed with the experimental results, and they could help to select the coal type for the production of acetylene through plasma pyrolysis process.

  18. Effect of Au nano-particle aggregation on the deactivation of the AuCl3/AC catalyst for acetylene hydrochlorination

    NASA Astrophysics Data System (ADS)

    Dai, Bin; Wang, Qinqin; Yu, Feng; Zhu, Mingyuan

    2015-05-01

    A detailed study of the valence state and distribution of the AuCl3/AC catalyst during the acetylene hydrochlorination deactivation process is described and discussed. Temperature-programmed reduction and X-ray photoelectron spectral analysis indicate that the active Au3+ reduction to metallic Au0 is one reason for the deactivation of AuCl3/AC catalyst. Transmission electron microscopy characterization demonstrated that the particle size of Au nano-particles increases with increasing reaction time. The results indicated that metallic Au0 exhibits considerable catalytic activity and that Au nano-particle aggregation may be another reason for the AuCl3/AC catalytic activity in acetylene hydrochlorination.

  19. Effect of Au nano-particle aggregation on the deactivation of the AuCl3/AC catalyst for acetylene hydrochlorination.

    PubMed

    Dai, Bin; Wang, Qinqin; Yu, Feng; Zhu, Mingyuan

    2015-01-01

    A detailed study of the valence state and distribution of the AuCl3/AC catalyst during the acetylene hydrochlorination deactivation process is described and discussed. Temperature-programmed reduction and X-ray photoelectron spectral analysis indicate that the active Au(3+) reduction to metallic Au(0) is one reason for the deactivation of AuCl3/AC catalyst. Transmission electron microscopy characterization demonstrated that the particle size of Au nano-particles increases with increasing reaction time. The results indicated that metallic Au(0) exhibits considerable catalytic activity and that Au nano-particle aggregation may be another reason for the AuCl3/AC catalytic activity in acetylene hydrochlorination. PMID:25994222

  20. Effect of Au nano-particle aggregation on the deactivation of the AuCl3/AC catalyst for acetylene hydrochlorination

    PubMed Central

    Dai, Bin; Wang, Qinqin; Yu, Feng; Zhu, Mingyuan

    2015-01-01

    A detailed study of the valence state and distribution of the AuCl3/AC catalyst during the acetylene hydrochlorination deactivation process is described and discussed. Temperature-programmed reduction and X-ray photoelectron spectral analysis indicate that the active Au3+ reduction to metallic Au0 is one reason for the deactivation of AuCl3/AC catalyst. Transmission electron microscopy characterization demonstrated that the particle size of Au nano-particles increases with increasing reaction time. The results indicated that metallic Au0 exhibits considerable catalytic activity and that Au nano-particle aggregation may be another reason for the AuCl3/AC catalytic activity in acetylene hydrochlorination. PMID:25994222

  1. Mechanism-based inactivation of cytochrome P-450 dependent benzo(a)pyrene hydroxylase activity by acetylenic and olefinic polycyclic arylhydrocarbons

    SciTech Connect

    Gan, L.S.

    1986-01-01

    A series of aryl acetylenes and aryl olefins have been examined as substrates and inhibitors of cytochrome P-450 dependent monooxygenases in liver microsomes from 5,6-benzoflavone or phenobarbital pretreated rats. 1-Ethynylpyrene (EP), 3-ethynylperylene (EPL), cis- and trans-1-(2-bromo-vinyl)pyrene (c-BVP and t-BVP), and 1-allylpyrene (AP) serve as mechanism-based irreversible inactivators (suicide inhibitors) of benzo(a)pyrene (BP) hydroxylase, while 1-vinyl-pyrene (VP) and phenyl 1-pyrenyl acetylene (PPA) do not cause a detectable suicide inhibition of the BP hydroxylase. The mechanism-based loss of BP hydroxylase activity caused by the aryl acetylenes is not accompanied by a corresponding loss of the P-450 content of the microsomes. In the presence of NADPH, /sup 3/H-labeled EP covalently attached to P-450 isozymes with a measured stoichiometry of one mole of EP per mole of the P-450 heme. The results of the effects of these aryl derivatives in the mammalian cell-mediated mutagenesis assay and toxicity assay show that none of the compounds examined nor any of the their metabolites produced in the incubation system are cytotoxic to V79 cells.

  2. Models for reactions of acetylene on platinum(111): a vinyl(acetylene)triplatinum complex and evidence for an ethylidyne intermediate

    SciTech Connect

    Rashidi, M.; Puddephatt, R.J.

    1988-07-01

    Reaction of (Pt/sub 3/(..mu../sub 3/-H)(..mu..-dppm)/sub 3/)/sup +/ (1) with excess acetylene gives (Pt/sub 3/(CH=CH/sub 2/)(..mu../sub 3/-eta/sup 2/(parallel)-HCCH)(..mu..-dppm)/sub 3/)/sup +/, where dppm = Ph/sub 2/PCH/sub 2/PPh/sub 2/. Deuterium-labeling studies indicate that H-D scrambling occurs within the vinyl group but not in the acetylene ligand. For example, (Pt/sub 3/(..mu../sub 3/-D)(..mu..-dppm)/sub 3/)/sup +/ with HCCH gave (Pt/sub 3/(CH==CH/sub 7/-d/sub 1/)(..mu../sub 3/-eta/sup 2/(parallel)-HCCH)(..mu..-dppm)/sub 3/)/sup +/, in which the deuterium label was distributed randomly in all three possible positions in the vinyl group. It is possible that this scrambling occurs by way of a short-lived ethylidyne intermediate. The complex is fluxional, due to rotation of the acetylene ligand, at room temperature. Similar reaction of 1 with excess propyne gives (Pt/sub 3/(CH=CHMe)(..mu../sub 3/-eta/sup 2/(**)-MeCCH)(..mu..-dppm)/sub 3/)/sup +/, but this complex is not fluxional at room temperature and is formed selectively by cis insertion of propyne into the Pt-H groups. There is a strong resemblance to the chemistry resulting from chemisorption of acetylene on a Pt(111) surface, thus providing a clear example of the value of coordinatively unsaturated clusters as mimics of metal surfaces.

  3. Kinetics and Structure of Superagglomerates Produced by Silane and Acetylene

    NASA Technical Reports Server (NTRS)

    Mulholland, G. W.; Hamins, A.; Sivathanu, Y.

    1999-01-01

    The evolution of smoke in a laminar diffusion flame involves several steps. The first step is particle inception/nucleation in the high-temperature fuel-rich region of the flame followed by surface growth and coagulation/coalescence of the small particles. As the primary spheres grow in size and lose hydrogen, the colliding particles no longer coalesce but retain their identity as a cluster of primary spheres, termed an agglomerate. Finally, in the upper portion of the flame, the particles enter an oxidizing environment which may lead to partial or complete burnout of the agglomerates. Currently there is no quantitative model for describing the growth of smoke agglomerates up to superagglomerates with an overall dimension of 10 microns and greater. Such particles are produced during the burning of acetylene and fuels containing benzene rings such as toluene and polystyrene. In the case of polystyrene, smoke agglomerates in excess of 1 mm have been observed "raining" out from large fires. Evidence of the formation of superagglomerates in a laminar acetylene/air diffusion flame has been recently reported. Acetylene was chosen as the fuel since the particulate loading in acetylene/air diffusion flames is very high. Photographs were obtained by Sorensen using a microsecond xenon lamp of the "stream" of soot just above the flame. For low flow rates of acetylene, only submicrometer soot clusters are produced and they give rise to the homogeneous appearance of the soot stream. When the flow rate is increased to 1.7 cu cm/s, soot clusters up to 10 microns are formed and they are responsible for the graininess and at a flow rate of 3.4 cu cm/s, a web of interconnected clusters as large as the width of the flame is seen. This interconnecting web of superagglomerates is described as a gel state by Sorensen et al (1998). This is the first observation of a gel for a gas phase system. It was observed that this gel state immediately breaks up into agglomerates due to buoyancy induced turbulence and gravitational sedimentation.

  4. Acetylene as a substrate in the development of primordial bacterial communities

    NASA Astrophysics Data System (ADS)

    Culbertson, Charles W.; Strohmaier, Francis E.; Oremland, Ronald S.

    1988-12-01

    The fermentation of atmospheric acetylene by anaerobic bacteria is proposed as the basis of a primordial heterotrophic food chain. The accumulation of fermentation products (acetaldehyde, ethanol, acetate and hydrogen) would create niches for sulfate-respiring bacteria as well as methanogens. Formation of acetylene-free environments in soils and sediments would also alter the function of nitrogenase from detoxification to nitrogen-fixation. The possibility of an acetylene-based anaerobic food chain in Jovian-type atmospheres is discussed.

  5. Acetylene-derived polymers and their applications in hair and skin care.

    PubMed

    Petter, P J

    1989-02-01

    Synopsis Since the introduction over 30 years ago of polyvinylpyrrolidone (PVP) as the first synthetic hairspray resin, acetylene-derived polymers have found wide and increasing applications in the cosmetics and toiletries industry. This review covers the two main classes of acetylenic polymers. In the first class, in which the chemistry may be traced back to reaction of acetylene with formaldehyde, are included PVP homopolymers and copolymers of VP with vinyl acetate, dimethylaminoethyl methacrylate, vinylcaprolactam and styrene. In the second class, stemming from reaction of acetylene with methanol, are the poly (vinyl methyl ether/maleic acid) monoester resins. PMID:19456933

  6. Acetylene hydratase: a non-redox enzyme with tungsten and iron-sulfur centers at the active site.

    PubMed

    Kroneck, Peter M H

    2016-03-01

    In living systems, tungsten is exclusively found in microbial enzymes coordinated by the pyranopterin cofactor, with additional metal coordination provided by oxygen and/or sulfur, and/or selenium atoms in diverse arrangements. Prominent examples are formate dehydrogenase, formylmethanofuran dehydrogenase, and aldehyde oxidoreductase all of which catalyze redox reactions. The bacterial enzyme acetylene hydratase (AH) stands out of its class as it catalyzes the conversion of acetylene to acetaldehyde, clearly a non-redox reaction and a reaction distinct from the reduction of acetylene to ethylene by nitrogenase. AH harbors two pyranopterins bound to W, and a [4Fe-4S] cluster. W is coordinated by four dithiolene sulfur atoms, one cysteine sulfur, and one oxygen ligand. AH activity requires a strong reductant suggesting W(IV) as the active oxidation state. Two different types of reaction pathways have been proposed. The 1.26 Å structure reveals a water molecule coordinated to W which could gain a partially positive net charge by the adjacent protonated Asp-13, enabling a direct attack of C2H2. To access the W-Asp site, a substrate channel was evolved distant from where it is found in other members of the DMSOR family. Computational studies of this second shell mechanism led to unrealistically high energy barriers, and alternative pathways were proposed where C2H2 binds directly to W. The architecture of the catalytic cavity, the specificity for C2H2 and the results from site-directed mutagenesis do not support this first shell mechanism. More investigations including structural information on the binding of C2H2 are needed to present a conclusive answer. PMID:26790879

  7. Pathways of chlorinated ethylene and chlorinated acetylene reaction with Zn(0)

    SciTech Connect

    Arnold, W.A.; Roberts, A.L.

    1998-10-01

    The use of zero-valent metals as reductants of chloroalkanes and chloroethylenes represents a promising new approach for treating groundwater contaminated with such solvents. To successfully design treatment systems relying on reactions of chlorocarbons with zero-valent metals, information is needed concerning the kinetics and pathways through which transformations occur. In this study, pathways of chlorinated ethylene reaction with Zn(0) have been elucidated through batch experiments. Data for parent compound disappearance and product appearance were fit to pseudo-first-order rate expressions in order to develop a complete kinetic model. Results indicate that reductive {beta}-elimination plays an important role, accounting for 15% of tetrachloroethylene (PCE), 30% of trichloroethylene (TCE), 85% of cis-dichloroethylene (cis-DCE), and 95% of trans-dichloroethylene (trans-DCE) reaction. The fraction of PCE, TCE, trans-DCE, and cis-DCE transformation that occurs via reductive elimination increases as the two-electron reduction potential (E{sub 2}) for this reaction becomes more favorable relative to hydrogenolysis. IN the case of PCE and TCE, reductive elimination gives rise to chlorinated acetylenes. Chloroacetylene and dichloroacetylene were synthesized and found to react rapidly with zinc, displaying products consistent with both hydrogenolysis and reduction of the triple bond. Surface area-normalized rate constants (k{sub SA}) for chlorinated ethylene disappearance correlate well with both one-electron (E{sub 1}) and two-electron (E{sub 2}) reduction potentials for the appropriate reactions. Correlation with E{sub 2} allows prediction of the distribution of reaction products as well as the rate of disappearance of the parent compound.

  8. Autoxidation and acetylene-accelerated oxidation of NO in a 2-phase system; implications for the expression of denitrification in ex situ experiments

    NASA Astrophysics Data System (ADS)

    Nadeem, Shahid; Drsch, Peter; Bakken, Lars

    2013-04-01

    Denitrification allows microorganisms to sustain respiration under anoxic conditions. The typical niche for denitrification is an environment with fluctuating oxygen concentrations such as soils and borders between anoxic and oxic zones of biofilms and sediments. In such environments, the organisms need adequate regulation of denitrification in response to changing oxygen availability to tackle both oxic and anoxic spells. The regulation of denitrification in soils has environmental implications, since it affects the proportions of N2, N2O and NO emitted to the atmosphere. The expression of denitrification enzymes is regulated by a complex regulatory network involving one or several positive feedback loops via the intermediate nitrogen oxides. Nitric oxide (NO) is known to induce denitrification in model organisms, but the quantitative effect of NO and its concentration dependency has not been assessed for denitrification in soils. NO is chemically unstable in the presence of oxygen due to autoxidation, and the oxidation of NO is accelerated by acetylene (C2H2) which is commonly used as an inhibitor of N2O reductase in denitrification studies. As a first step to a better understanding of NO's role in soil denitrification, we investigated NO oxidation kinetics for a closed "two phase" system (i.e. liquid phase + headspace) typically used for denitrification experiments with soil slurries, with and without acetylene present. Models were developed to adequately predict autoxidation and acetylene-accelerated oxidation. The minimum oxygen concentration in the headspace ([O2]min, mL L-1) for acetylene-accelerated NO oxidation was found to increase linearly with the NO concentration ([NO], mL L-1); [O2]min= 0.192 + [NO]*0.1 (r2=0.978). The models for NO oxidation were then used to assess NO-oxidation rates in denitrification experiments with batches of bacterial cells extracted from soil. The batches were exposed to low initial oxygen concentrations in gas tight serum flasks (with and without C2H2), and monitored for O2, NO, N2O and N2 production while depleting the oxygen and switching to anoxic respiration. Acetylene effectively scavenged NO from the cultures until oxygen concentration reached below ~0.19 mL L-1, and the estimated rate of acetylene-accelerated NO oxidation was more than sufficient to explain an observed reduction of the N2O production induced by acetylene. When [O2] reached below 0.19 mL L-1, the NO concentrations increased and stabilized at the same level as in the treatments without acetylene, but the rate of denitrification was much lower than without acetylene. The results indicate that the early accumulation of 10-20 nM NO during oxygen depletion has a significant effect on the expression of denitrification in soil communities. This warrants a greater interest in NO as a regulator of denitrification in soils and shows that the acetylene inhibition method may be problematic even for intentionally anoxic incubations, unless precautions are taken to secure initial O2-concentrations below 0.19 mL O2 L-1.

  9. Encapsulating Inorganic Acetylene, HBNH, Using Flanking Coordinative Interactions.

    PubMed

    Swarnakar, Anindya K; Hering-Junghans, Christian; Nagata, Koichi; Ferguson, Michael J; McDonald, Robert; Tokitoh, Norihiro; Rivard, Eric

    2015-09-01

    A stable donor-acceptor coordination complex of the elusive parent inorganic iminoborane HBNH (a structural analogue of acetylene) is reported. This species was generated via thermally induced N2 elimination/1,2-H migration from a hydrido(azido)borane adduct NHC?BH2N3 (NHC=N-heterocyclic carbene) in the presence of a fluorinated triarylborane. The mechanism of this process was also investigated by computational and isotopic labeling studies. This transformation represents a new and potentially modular route to unsaturated inorganic building blocks for advanced material synthesis. PMID:26214271

  10. Protonated acetylene - An important circumstellar and interstellar ion

    NASA Technical Reports Server (NTRS)

    Glassgold, A. E.; Omont, A.; Guelin, M.

    1992-01-01

    In a circumstellar envelope, a substantial amount of acetylene is transported in a wind to the outer envelope, where it can be photoionized by interstellar radiation and then converted into C2H3(+) by a low-temperature reaction with H2. New chemical modeling calculations indicate that sufficient C2H3(+) may be produced in the outer envelope of IRC + 10216 to be observable. Similar considerations suggest that C2H3(+) should also be detectable in interstellar clouds, provided its rotational spectrum has been measured accurately in the laboratory.

  11. Enumeration and Relative Importance of Acetylene-Reducing (Nitrogen-Fixing) Bacteria in a Delaware Salt Marsh

    PubMed Central

    Dicker, Howard J.; Smith, David W.

    1980-01-01

    Three groups of N2-fixing bacteria were enumerated from the top 1 cm of the surface in four vegetational areas in a Delaware salt marsh. The results over the 9-month sampling period showed that there were no discernible seasonal patterns for any of the groups enumerated (Azotobacter sp., Clostridium sp., and Desulfovibrio sp.). Azotobacter sp. was present in numbers of 107 per g of dry mud, whereas the two anaerobic fixers were present in much lower numbers (103 to 104 per g of dry mud). There were no differences in the numbers of each group among the different vegetational areas, indicating that there was a heterogeneous population of N2 fixers present. Additional studies indicate that the activity of sulfate reducers (Desulfovibrio sp.) may account for as much as 50% of the total observed acetylene reduction activity. Oxygen was found to exert little effect on the observed acetylene reduction activity, indicating that stable aerobic and anaerobic microenvironments exist in the surface layer of marsh sediments. PMID:16345564

  12. Acetylene Fermentation: Relevance to Primordial Biogeochemistry and the Search for Life in the Outer Solar System

    NASA Astrophysics Data System (ADS)

    Oremland, R. S.; Baesman, S. M.; Miller, L. G.

    2014-02-01

    Acetylene supports the growth of some terrestrial anaerobes. The reaction is highly exothermic. The abundance of acetylene in the methane-rich planet(oid)s of the outer solar system could represent a means of nourishment for resident alien microbes.

  13. Ultrafast hydrogen migration in acetylene cation driven by non-adiabatic effects

    NASA Astrophysics Data System (ADS)

    Madjet, Mohamed El-Amine; Li, Zheng; Vendrell, Oriol

    2013-03-01

    Non-adiabatic dynamics of the acetylene cation is investigated using mixed quantum-classical dynamics based on trajectory surface hopping. To describe the non-adiabatic effects, two surface hopping methods are used, namely, Tully's fewest switches and Landau-Zener surface hopping. Similarities and differences between the results based on those two methods are discussed. We find that the photoionization of acetylene into the first excited state A2? g+ drives the molecule from the linear structure to a trans-bent structure. Through a conical intersection the acetylene cation can relax back to either the ground state of acetylene or vinylidene. We conclude that hydrogen migration always takes place after non-radiative electronic relaxation to the ground state of the monocation. Based on the analysis of correlation functions we identify coherent oscillations between acetylene and vinylidene with a period of about 70 fs after the electronic relaxation.

  14. Mechanism of action of butyryl-CoA dehydrogenase: reactions with acetylenic, olefinic, and fluorinated substrate analogues.

    PubMed

    Fendrich, G; Abeles, R H

    1982-12-21

    The acetylenic thio ester (3-pentynoyl)pantetheine irreversibly inactivates butyryl-CoA dehydrogenase from Megasphaera elsdenii. The inactivator becomes covalently attached to the protein (0.61 +/- 0.1 mol of 14C-labeled inactivator/mol of enzyme flavin). No modification of the flavin cofactor is seen. The covalent enzyme-inactivator adduct is labile toward base and neutral hydroxylamine. These treatments release 85 +/- 5% of the incorporated 14C label from the protein. Base-catalyzed hydrolysis of the adduct releases 3-oxopentanoic acid (0.6 mol/mol of incorporated inactivator). Treatment with hydroxylamine leads to formation of a hydroxamic acid on the protein (0.64 +/- 0.09 mol/mol of incorporated inactivator). The covalent adduct can be reduced with sodium borohydride with release of 1,3-pentanediol. Hydrolysis of the protein with 6 N HCl after sodium borohydride reduction yields 2-amino-5-hydroxyvaleric acid and proline. We conclude that the inactivator has reacted with the gamma-carboxyl group of a glutamate residue at the enzyme active site. The inactivation proceeds through enzyme-catalyzed rearrangement of the acetylene to an allene, followed by nucleophilic addition of the carboxyl group to the allene. (3-Chloro-3-butenoyl)pantetheine irreversibly inactivates the enzyme in a fashion similar to the acetylenic thio ester and also modifies a glutamate residue. Butyryl-CoA dehydrogenase catalyzes the isomerization of (3-butenoyl)pantetheine to (2-butenoyl)pantetheine. The enzyme catalyzes the elimination of HF from 3-fluoropropionyl-CoA and (3,3-difluorobutyryl)pantetheine. We suggest, that these results together support an oxidation mechanism for butyryl-CoA dehydrogenase which is initiated by alpha-proton abstraction. PMID:7159554

  15. Identification of glutathione conjugates of acetylene-containing positive allosteric modulators of metabotropic glutamate receptor subtype 5.

    PubMed

    Zhuo, Xiaoliang; Huang, Xiaohua Stella; Degnan, Andrew P; Snyder, Lawrence B; Yang, Fukang; Huang, Hong; Shu, Yue-Zhong; Johnson, Benjamin M

    2015-04-01

    A recent medicinal chemistry campaign to identify positive allosteric modulators (PAMs) of metabotropic glutamate receptor subtype 5 (mGluR5) led to the discovery of potent compounds featuring an oxazolidinone structural core flanked by biaryl acetylene and haloaryl moieties. However, biotransformation studies of some of these mGluR5 PAMs demonstrated the formation of glutathione (GSH) conjugates. The conjugates in question were formed independently of NADPH as the main products in liver microsomes and liver cytosol (rat and human) and exhibited masses that were 307 u greater than their respective substrates, indicating the involvement of a reductive step in the formation of these metabolites. To further characterize the relevant metabolic sequences, GSH conjugates of (4R,5R)-5-(3-fluorophenyl)-4-(5-(pyrazin-2-ylethynyl)pyridin-3-yl)oxazolidin-2-one and (4R,5R)-5-(4-fluorophenyl)-4-(6-((3-fluoropyridin-2-yl)ethynyl)pyridin-2-yl)oxazolidin-2-one were biosynthesized and isolated. Subsequent analysis by NMR showed that GSH had reacted with the acetylene carbon atoms of these mGluR5 PAMs, suggesting a conjugate addition mechanism and implicating cytosolic and microsomal GSH S-transferases (GSTs) in catalysis. Interestingly, five closely related mGluR5 PAMs were not similarly prone to the formation of GSH conjugates in vitro. These compounds also featured acetylenes, but were flanked by either phenyl or cyclohexyl rings, which indicated that the formation of GSH conjugates was influenced by proximal functional groups that modulated the electron density of the triple bond and/or differences in enzyme-substrate specificity. These results informed an ongoing drug-discovery effort to identify mGluR5 PAMs with drug-like properties and a low risk of reactivity with endogenous thiols. PMID:25633841

  16. Void dynamics in low-pressure acetylene RF plasmas

    NASA Astrophysics Data System (ADS)

    van de Wetering, Ferdinandus Martinus Jozef Henricus; Nijdam, Sander; Beckers, Job; Kroesen, Gerardus Maria Wilhelmus

    2013-09-01

    In low-pressure acetylene plasmas, dust particles spontaneously form under certain conditions. This process occurs in a matter of seconds to minutes after igniting the plasma and results in a cloud of particulates up to micrometer sizes levitated in the plasma. We studied a capacitively coupled radio-frequency plasma under normal gravity conditions and constant flow of feed gas (argon and acetylene). After the dust cloud has been formed, an ellipsoid-shaped dust-free zone - called a void - develops and grows as a function of time. Concurrently, the dust particles grow in size. Peculiar dynamics of the void have been observed, where during its expansions it suddenly stops growing and even shrinks, to shortly thereafter resume its expansion. We infer this is induced by coagulation of a new batch of dust particles inside the void. The whole dust growth and void expansion/contraction is periodical and highly reproducible. Several techniques are used to gain information about the plasma dynamics. Microwave cavity resonance spectroscopy is used to determine the global electron density. Scattering of a vertical laser sheet is used to visualize the dust particle density. The electrical characteristics of the plasma are determined using a commercially available plasma impedance monitor. This work is supported by NanoNextNL, a micro and nanotechnology programme of the Dutch Government and 130 partners.

  17. Lewis acid catalyzed trans-hydrostannation of acetylenes

    SciTech Connect

    Asao, Naoki; Liu, Jian-Xiu; Sudoh, Tomoko; Yamamoto, Yoshinori

    1995-12-31

    A Lewis acid such as ZrCl{sub 4} or HfCl{sub 4} catalyzed the hydrostannation of acetylenes 1 to produce the trans-hydrostannation products 2 regio- and stereoselectively. The use of non-polar solvents such as toluene or hexane was essential for obtaining high stereoselectivity and chemical yield. Since ZrCl{sub 4} or HfCl{sub 4} is not soluble in such solvents, this hydrostannation process was carried out in heterogeneous system. The reactions of internal acetylenes proceeded smoothly, although the use of stoichiometric amounts of ZrCl{sub 4} gave better results. The ZrCl{sub 4} catalyzed hydrostannation of 1-octyne with Bu{sub 3}SnH was monitored by {sup 1}H and {sup 119}Sn NMR spectroscopy, and it was found that an equilibrium process was involved in ZrCl{sub 4}-Bu{sub 3}SnH system and that a complex formed from Bu{sub 3}SnH and ZrCl{sub 4} would be a reactive species.

  18. Numerical study of ethylene and acetylene laminar flame speeds

    SciTech Connect

    Marinov, N.M.; Pitz, W.J.; Westbrook, C.K.

    1995-03-01

    Detailed chemical kinetic computations for ethylene-air and acetylene-air mixtures have been performed to simulate laminar flame speeds. Sensitivity analysis was applied to determine those reactions which strongly influence flame propagation. In ethylene-air mixtures, the C{sub 2}H{sub 3} + O{sub 2} = CH{sub 2}CHO + O reaction was one of the most sensitive reactions in the C{sub 2}H{sub 4}/C{sub 2}H{sub 3} submechanism and therefore this reaction was very important to ethylene flame propagation. This reaction was not considered in previously reported mechanisms used to model ethylene-air flame propagation. In acetylene-air mixtures, the C{sub 2}H{sub 2}+O {yields} Products, HCCO+H=CH{sub 2}(s)+CO, HCCO+O{sub 2}=CO{sub 2}+CO+H, H+C{sub 2}H{sub 2}(+M) = C{sub 2}H{sub 3}(+M) and CH{sub 2}(s)+C{sub 2}H{sub 2} = H{sub 2}CCCH+H were the most sensitive reactions in the C{sub 2}H{sub 2}/HCCO / CH{sub 2}(s) reaction set.

  19. The art of acetylenic scaffolding: rings, rods, and switches.

    PubMed

    Nielsen, Mogens Brøndsted; Diederich, François

    2002-01-01

    Acetylenic scaffolding with derivatives of tetraethynylethene (TEE, 3,4-diethynylhex-3-ene-1,5-diyne) and (E)-1,2-diethynylethene (DEE, (E)-hex-3-ene-1,5-diyne) provides carbon-rich compounds with interesting physicochemical properties. Thus, these modules are building blocks for monodisperse, linearly pi-conjugated oligomers [polytri(acetylene)s, PTAs] extending in length beyond 10nm, and for large, macrocyclic, all-carbon cores (dehydroannulenes and expanded radialenes) exhibiting strong chromophoric properties. The advanced materials' properties were strongly influenced by the presence of electron-donating substituents at the lateral positions, decreasing the decreasing the (HOMO-LUMO) gap in both PTAs and expanded radialenes. Arylated TEEs were found to undergo photochemically induced cis-trans isomerization, paving the way for applications as light-driven molecular switches in optoelectronic devices. Derivatives of 1,3-diethynylallene are new modules that offer the prospect of scaffolding in an orthogonal manner; that is, they represent precursors for helical oligomers. PMID:12112870

  20. Photo-double-ionization of ethylene and acetylene near threshold

    NASA Astrophysics Data System (ADS)

    Gaire, B.; Lee, S. Y.; Haxton, D. J.; Pelz, P. M.; Bocharova, I.; Sturm, F. P.; Gehrken, N.; Honig, M.; Pitzer, M.; Metz, D.; Kim, H.-K.; Schffler, M.; Drner, R.; Gassert, H.; Zeller, S.; Voigtsberger, J.; Cao, W.; Zohrabi, M.; Williams, J.; Gatton, A.; Reedy, D.; Nook, C.; Mller, Thomas; Landers, A. L.; Cocke, C. L.; Ben-Itzhak, I.; Jahnke, T.; Belkacem, A.; Weber, Th.

    2014-01-01

    We present kinematically complete measurements of the photo-double-ionization of ethylene (double CC bond) and acetylene (triple CC bond) hydrocarbons just above the double-ionization threshold. We discuss the results in terms of the coincident kinetic energy of the photoelectrons and the nuclear kinetic-energy release of the recoiling ions. We have incorporated quantum chemistry calculations to interpret which of the electronic states of the dication have been populated and trace the various subsequent fragmentation channels. We suggest pathways that involve the electronic ground and excited states of the precursor ethylene dication and explore the strong influence of the conical intersections between the different electronic states. The nondissociative ionization yield is small in ethylene and high in acetylene when compared with the dissociative ionization channels. The reason for such a striking difference is explained in part on the basis of a propensity rule that influences the population of states in the photo-double-ionization of a centrosymmetric closed-shell molecule by favoring singlet ungerade and triplet gerade final states. This propensity rule and the calculated potential-energy surfaces clarify a picture of the dynamics leading to the observed dication dissociation products.

  1. Nanosecond discharge ignition in acetylene-containing mixtures

    NASA Astrophysics Data System (ADS)

    Kosarev, I. N.; Pakhomov, A. I.; Kindysheva, S. V.; Anokhin, E. M.; Aleksandrov, N. L.

    2013-08-01

    We study experimentally and numerically the kinetics of ignition in lean and stoichiometric C2H2?:?O2?:?Ar mixtures after a high-voltage nanosecond discharge. The ignition delay time is measured behind a reflected shock wave with and without the discharge using detection of CH radiation. Generation of the discharge plasma is shown to lead to a decrease in ignition delay time. Discharge processes followed by chain chemical reactions with energy release are simulated during ignition in the C2H2?:?O2?:?Ar mixtures. The generation of atoms, radicals and excited and charged particles in the discharge phase is numerically simulated. The calculations are based on the measured time-resolved discharge current and electric field. The calculated densities of the active particles produced in the discharge on a nanosecond time scale are employed as input data to simulate plasma-assisted ignition on a microsecond scale. The calculated ignition delay times are compared with the experimental data. It is shown that the effect of the discharge plasma on ignition of the acetylene-containing mixtures is associated with active species production in the discharge phase rather than with gas heating during the discharge and in its afterglow. A sensitivity analysis is made to determine limiting reactions in acetylene autoignition and ignition after the discharge under the conditions studied.

  2. Reduction of misleading ("false") positive results in mammalian cell genotoxicity assays. III: sensitivity of human cell types to known genotoxic agents.

    PubMed

    Fowler, Paul; Smith, Robert; Smith, Katie; Young, Jamie; Jeffrey, Laura; Carmichael, Paul; Kirkland, David; Pfuhler, Stefan

    2014-06-01

    We have demonstrated previously that the seemingly high rate of "false" or "misleading" positive results from in vitro micronucleus assays (MNvit) was greater when rodent derived cell lines and certain toxicity measures, such as relative cell count or replication index, were used. These studies suggested that the use of a human cell type with functional p53 and a toxicity measure that included a function of cell proliferation could dramatically reduce the detection of misleading positive results. A reduced "false positive rate" should not be at the expense of a loss of sensitivity of the assay. Therefore, we have investigated the sensitivity of the MNvit assay to known genotoxic agents using three cell types shown previously to be less prone to misleading positives, namely human lymphocytes (HuLy), TK6 and HepG2 cells. The 17 chemicals are well characterised and are from a list of chemicals known to produce positive results in in vitro mammalian cell assays. These data demonstrated a high sensitivity of the assay in which TK6 and HuLy cells were employed, such that 15 out of the 17 chemicals were correctly identified. By contrast, the use of HepG2 cells resulted in far fewer than expected positive responses. In conclusion, using TK6 and HuLy cells in preference to long established rodent cell lines in order to improve specificity does not compromise the sensitivity of the MNvit to detect known genotoxic agents. PMID:24632063

  3. Designing supported palladium-on-gold bimetallic nano-catalysts for controlled hydrogenation of acetylene in large excess of ethylene

    NASA Astrophysics Data System (ADS)

    Malla, Pavani

    Ethylene is used as a starting point for many chemical intermediates in the petrochemical industry. It is predominantly produced through steam cracking of higher hydrocarbons (ethane, propane, butane, naphtha, and gas oil). During the cracking process, a small amount of acetylene is produced as a side product. However, acetylene must be removed since it acts as a poison for ethylene polymerization catalysts at even ppm concentrations (>5 ppm). Thus, the selective hydrogenation of acetylene to ethylene is an important process for the purification of ethylene. Conventional, low weight loading Pd catalysts are used for this selective reaction in high concentration ethylene streams. Gold was initially considered to be catalytically inactive for a long time. This changed when gold was seen in the context of the nanometric scale, which has indeed shown it to have excellent catalytic activity as a homogeneous or a heterogeneous catalyst. Gold is proved to have high selectivity to ethylene but poor at conversion. Bimetallic Au and Pd catalysts have exhibited superior activity as compared to Pd particles in semi-hydrogenation. Hydrogenation of acetylene was tested using this bimetallic combination. The Pd-on-Au bimetallic catalyst structure provides a new synthesis approach in improving the catalytic properties of monometallic Pd materials. TiO 2 as a support material and 0.05%Pd loading on 1%Au on titania support and used different treatment methods like washing plasma and reduction between the two metal loadings and was observed under 2:1 ratio. In my study there were two set of catalysts which were prepared by a modified incipient wetness impregnation technique. Out of all the reaction condition the catalyst which was reduced after impregnating gold and then impregnating palladium which was further treated in non-thermal hydrogen plasma and then pretreated in hydrogen till 250C for 1 hour produced the best activity of 76% yield at 225C. Stability tests were conducted on the catalysts which were followed by TGA analysis to analyze the coke formation on the catalyst in a period of time at a particular temperature. The catalysts were characterized by the hydrogen chemisorption and atomic absorption spectroscopy.

  4. The reconstructed skin micronucleus assay in EpiDerm: reduction of false-positive results - a mechanistic study with epigallocatechin gallate.

    PubMed

    Yuki, Katsuyuki; Ikeda, Naohiro; Nishiyama, Naohiro; Kasamatsu, Toshio

    2013-10-01

    The high rate of false-positive or misleading results in in vitro mammalian genotoxicity testing is a hurdle in the development of valuable chemicals, especially those used in cosmetics, for which in vivo testing is banned in the European Union. The reconstructed skin micronucleus (RSMN) assay in EpiDerm (MatTek Corporation, USA) has shown promise as a follow-up for positive in vitro mammalian genotoxicity tests. However, few studies have explored its better predictive performance compared with existing in vitro assays. In the present study, we followed the protocol of the RSMN assay and used eight chemicals to compare micronucleus (MN) induction with EpiDerm with that in normal human epidermal keratinocytes (NHEKs), both derived from human skin. The assessments of EpiDerm conformed to those of in vivo MN assay, whereas those of NHEKs did not. The effect of cell differentiation status on MN induction was further addressed using a model compound, epigallocatechin gallate (EGCG), which is a major component of green tea extract that shows positive results in in vitro mammalian genotoxicity assays via oxidative stress and negative results in in vivo MN studies. RSMN assay in an underdeveloped epidermal model, EpiDerm-201 (MatTek Corporation), showed a negative result identical to that in EpiDerm, indicating that the barrier function of keratinocytes has limited impact. Analysis of the gene expression profile of both EpiDerm and NHEKs after EGCG treatment for 12h revealed that the expression of genes related to genotoxic response was significantly induced only in NHEKs. Conversely, antioxidative enzyme activities (catalase and glutathione peroxidase) in EpiDerm were higher than those in NHEKs. These results indicate that EpiDerm has antioxidant properties similar to those of a living body and is capable of eliminating oxidative stress that may be caused by EGCG under in vitro experimental conditions. PMID:23988588

  5. A first principles study of the acetylene-water interaction

    SciTech Connect

    Tzeli, Demeter; Mavridis, Aristides; Xantheas, Sotiris S.

    2000-04-08

    We present an extensive study of the stationary points on the acetylene-water (AW) ground-state potential energy surface (PES) aimed in establishing accurate energetics for the two different bonding scenarios that are considered. Those include arrangements in which water acts either as a proton acceptor from one of the acetylene hydrogen atoms or a proton donor to the triple bond. We used a hierarchy of theoretical methods to account for electron correlation [MP2 (second-order Moller-Plesset), MP4 (fourth-order Moller-Plesset), and CCSD(T) (coupled-cluster single double triple)] coupled with a series of increasing size augmented correlation consistent basis sets (aug-cc-pVnZ, n=2,3,4). We furthermore examined the effect of corrections due to basis set superposition error (BSSE). We found that those have a large effect in altering the qualitative features of the PES of the complex. They are responsible for producing a structure of higher (C{sub 2v}) symmetry for the global minimum. Zero-point energy (ZPE) corrections were found to increase the stability of the C{sub 2v} arrangement. For the global (water acceptor) minimum of C{sub 2v} symmetry our best estimates are {delta}E{sub e}=-2.87 kcal/mol ({delta}E{sub 0}=-2.04 kcal/mol) and a van der Waals distance of R{sub e}=2.190 Aa. The water donor arrangement lies 0.3 kcal/mol (0.5 kcal/mol including ZPE corrections) above the global minimum. The barrier for its isomerization to the global minimum is E{sub e}=0.18 kcal/mol; however, inclusion of BSSE- and ZPE-corrections destabilize the water donor arrangement suggesting that it can readily convert to the global minimum. We therefore conclude that there exists only one minimum on the PES in accordance with previous experimental observations. To this end, vibrational averaging and to a lesser extend proper description of intermolecular interactions (BSSE) were found to have a large effect in altering the qualitative features of the ground-state PES of the acetylene-water complex. (c) 2000 American Institute of Physics.

  6. Extended permutation-inversion groups for simultaneous treatment of the rovibronic states of trans-acetylene, cis-acetylene, and vinylidene

    NASA Astrophysics Data System (ADS)

    Hougen, Jon T.; Merer, Anthony J.

    2011-05-01

    The electronic ground state potential surface of acetylene (H sbnd C tbnd C sbnd H) has a minimum at the linear conformation, but the excited electronic states may have potential minima at a variety of nonlinear equilibrium shapes. This work is concerned with the group theoretical ideas necessary to treat simultaneously the symmetry properties of rovibronic states associated with three different planar acetylene equilibrium configurations, namely trans bent acetylene, cis bent acetylene, and vinylidene (H 2C dbnd C). We make use of three different kinds of groups: (i) point groups, (ii) permutation-inversion (PI) groups, and (iii) extended PI groups. The PI group is G 4 or G8, depending on whether C sbnd H bond breaking is impossible (no bent acetylene ↔ vinylidene interconversion) or possible. The extended PI groups are G4(2) and G8(2), respectively, when the only large amplitude motions are the CCH bends at each end of the molecule, and G4(8) and G8(8), respectively, when internal rotation is added as a third large amplitude motion. Applied to acetylene, the results indicate that there will be no splittings of the rovibronic levels unless CH bond breaking occurs. Even without bond breaking, however, states of the cis and trans isomers just below their interconversion barrier will show "staggerings" in their K-structures, i.e., a given vibrational level will have three tunneling components at slightly different energies: one component will have levels with K = 4 n only (where n is an integer), a second component will have levels with K = 4 n + 2 only, and the third will have only odd- K levels. New experimental results for the S 1-cis electronic state of acetylene [21] are reviewed, and are found to be consistent with the group theory in so far as comparison is possible.

  7. Extended Permutation-Inversion Groups for Simultaneous Treatment of the Rovibronic States of Trans-Acetylene Cis-Acetylene and Vinylidene

    NASA Astrophysics Data System (ADS)

    Hougen, Jon T.; Merer, Anthony J.

    2011-06-01

    The electronic ground state potential surface of acetylene (HCCH) has a minimum at the linear conformation, but the excited electronic states may have potential minima at a variety of nonlinear equilibrium shapes. This work is concerned with the group theoretical ideas necessary to treat simultaneously the symmetry properties of rovibronic states associated with three different planar acetylene equilibrium configurations, namely trans bent acetylene, cis bent acetylene, and vinylidene (H2C=C). We make use of three different kinds of groups: (i) point groups, (ii) permutation-inversion (PI) groups, and (iii) extended PI groups. The PI group is G4 or G8, depending on whether C-H bond breaking is impossible (no bent acetylene leftrightarrow vinylidene interconversion), or possible. The extended PI groups are G4(2) and G8(2), respectively, when the only large amplitude motions are the CCH bends at each end of the molecule, and G4(8) and G8(8), respectively, when internal rotation is added as a third large amplitude motion. Applied to acetylene, the results indicate that there will be no splittings of the rovibronic levels unless CH bond breaking occurs. Even without bond breaking, however, states of the cis and trans isomers just below their interconversion barrier will show "staggerings" in their K-structures, i.e., a given vibrational level will have three tunneling components at slightly different energies: one component will have levels with K=4n only (where n is an integer), a second component will have levels with K=4n+2 only, and the third will have only odd-K levels. New experimental results for the S1-cis electronic state of acetylene are reviewed, and are found to be consistent with the group theory in so far as comparison is possible.

  8. Hydrogen bonded complexes of acetylene and boric acid: A matrix isolation infrared and ab initio study

    NASA Astrophysics Data System (ADS)

    Sundararajan, K.; Ramanathan, N.; Kar, Bishnu Prasad; Viswanathan, K. S.

    2011-04-01

    The infrared spectra of the hydrogen bonded complexes of acetylene-boric acid have been investigated in solid nitrogen matrix. We have observed the 1:1 acetylene-boric acid complex in the nitrogen matrix. Formation of the complex was evidenced from the shifts in the vibrational frequencies corresponding to the modes involving the acetylene and boric acid submolecules in the complex. The structure of the complexes and the energies were computed at HF, B3LYP and MP2 levels of theory using 6-31++G ** basis sets. Only one minimum was obtained, which corresponded to a complex with both O sbnd H⋯π and C sbnd H⋯O interactions. In this complex boric acid acts as a proton donor to the acetylene π-cloud and proton acceptor to the acidic hydrogen in acetylene. The computed vibrational frequencies of acetylene-boric acid complexes at B3LYP/6-31++G ** level corroborated well with the experimental frequencies. Calculations were also performed for the higher 2:1 and 3:1 acetylene-boric acid complexes.

  9. Acetylene as Fast Food: Implications for Development of Life on Anoxic Primordial Earth and in the Outer Solar System

    NASA Astrophysics Data System (ADS)

    Oremland, Ronald S.; Voytek, Mary A.

    2008-02-01

    Acetylene occurs, by photolysis of methane, in the atmospheres of jovian planets and Titan. In contrast, acetylene is only a trace component of Earth's current atmosphere. Nonetheless, a methane-rich atmosphere has been hypothesized for early Earth; this atmosphere would also have been rich in acetylene. This poses a paradox, because acetylene is a potent inhibitor of many key anaerobic microbial processes, including methanogenesis, anaerobic methane oxidation, nitrogen fixation, and hydrogen oxidation. Fermentation of acetylene was discovered 25 years ago, and Pelobacter acetylenicus was shown to grow on acetylene by virtue of acetylene hydratase, which results in the formation of acetaldehyde. Acetaldehyde subsequently dismutates to ethanol and acetate (plus some hydrogen). However, acetylene hydratase is specific for acetylene and does not react with any analogous compounds. We hypothesize that microbes with acetylene hydratase played a key role in the evolution of Earth's early biosphere by exploiting an available source of carbon from the atmosphere and in so doing formed protective niches that allowed for other microbial processes to flourish. Furthermore, the presence of acetylene in the atmosphere of a planet or planetoid could possibly represent evidence for an extraterrestrial anaerobic ecosystem.

  10. Acetylene as fast food: implications for development of life on anoxic primordial Earth and in the outer solar system.

    PubMed

    Oremland, Ronald S; Voytek, Mary A

    2008-02-01

    Acetylene occurs, by photolysis of methane, in the atmospheres of jovian planets and Titan. In contrast, acetylene is only a trace component of Earth's current atmosphere. Nonetheless, a methane-rich atmosphere has been hypothesized for early Earth; this atmosphere would also have been rich in acetylene. This poses a paradox, because acetylene is a potent inhibitor of many key anaerobic microbial processes, including methanogenesis, anaerobic methane oxidation, nitrogen fixation, and hydrogen oxidation. Fermentation of acetylene was discovered approximately 25 years ago, and Pelobacter acetylenicus was shown to grow on acetylene by virtue of acetylene hydratase, which results in the formation of acetaldehyde. Acetaldehyde subsequently dismutates to ethanol and acetate (plus some hydrogen). However, acetylene hydratase is specific for acetylene and does not react with any analogous compounds. We hypothesize that microbes with acetylene hydratase played a key role in the evolution of Earth's early biosphere by exploiting an available source of carbon from the atmosphere and in so doing formed protective niches that allowed for other microbial processes to flourish. Furthermore, the presence of acetylene in the atmosphere of a planet or planetoid could possibly represent evidence for an extraterrestrial anaerobic ecosystem. PMID:18199006

  11. Acetylene as fast food: Implications for development of life on anoxic primordial earth and in the outer solar system

    USGS Publications Warehouse

    Oremland, R.S.; Voytek, M.A.

    2008-01-01

    Acetylene occurs, by photolysis of methane, in the atmospheres of jovian planets and Titan. In contrast, acetylene is only a trace component of Earth's current atmosphere. Nonetheless, a methane-rich atmosphere has been hypothesized for early Earth; this atmosphere would also have been rich in acetylene. This poses a paradox, because acetylene is a potent inhibitor of many key anaerobic microbial processes, including methanogenesis, anaerobic methane oxidation, nitrogen fixation, and hydrogen oxidation. Fermentation of acetylene was discovered 25 years ago, and Pelobacter acetylenicus was shown to grow on acetylene by virtue of acetylene hydratase, which results in the formation of acetaldehyde. Acetaldehyde subsequently dismutates to ethanol and acetate (plus some hydrogen). However, acetylene hydratase is specific for acetylene and does not react with any analogous compounds. We hypothesize that microbes with acetylene hydratase played a key role in the evolution of Earth's early biosphere by exploiting an available source of carbon from the atmosphere and in so doing formed protective niches that allowed for other microbial processes to flourish. Furthermore, the presence of acetylene in the atmosphere of a planet or planetoid could possibly represent evidence for an extraterrestrial anaerobic ecosystem. ?? Mary Ann Liebert, Inc.

  12. Organogermanium Chemistry: Germacyclobutanes and digermane Additions to Acetylenes

    SciTech Connect

    Andrew Michael Chubb

    2003-12-12

    This dissertation comprises two main research projects. The first project, presented in Chapter 1, involves the synthesis and thermochemistry of germacyclobutanes (germetanes). Four new germetanes (spirodigermetane, diallylgermetane, dichlorogermetane, and germacyclobutane) have been synthesized using a modified di-Grignard synthesis. Diallylgermetane is shown to be a useful starting material for obtaining other germetanes, particularly the parent germetane, germacyclobutane. The gas-phase thermochemistries of spirodigermetane, diallylgermetane and germacyclobutane have been explored via pulsed stirred-flow reactor (SFR) studies, showing remarkable differences in decomposition, depending on the substitution at the germanium atom. The second project investigates the thermochemical, photochemical, and catalytic additions of several digermanes to acetylenes. The first examples of thermo- and photochemical additions of Ge-Ge bonds to C{triple_bond}C are demonstrated. Mechanistic investigations are described and comparisons are made to analogous disilane addition reactions, previously studied in their group.

  13. Decoupling in the line mixing of acetylene infrared Q branches

    NASA Technical Reports Server (NTRS)

    Pine, A. S.; Looney, J. P.

    1990-01-01

    A difference-frequency laser spectrometer was used to record the Q-branch profiles of the nu1 + nu5, nu3 + nu4, and nu2 + 2nu4 + nu5 Pi(u)-Sigma(g) combination bands in the 2.5 micron C-H stretch-bend region of acetylene. The experiment was carried out at pressures in the range of 1 to 500 Torr. It is shown that line mixing causes substantial deviation of collisionally overlapped Q-branch profiles from the independently additive superposition of Lorentzian line shapes. It is also found that the degree of line mixing is greatly reduced from that assuming all the broadening arises from rotationally inelastic collisions coupling Q-branch lines only to one another.

  14. Detection of acetylene in the infrared spectrum of comet Hyakutake

    NASA Technical Reports Server (NTRS)

    Brooke, T. Y.; Tokunaga, A. T.; Weaver, H. A.; Crovisier, J.; Bockelee-Morvan, D.; Crisp, D.

    1996-01-01

    Comets are rich in volatile materials, of which roughly 80% (by number) are water molecules. Considerable progress is being made in identifying the other volatile species, the abundances of which should enable us to determine whether comets formed primarily from ice-covered interstellar grains, or from material that was chemically processed in the early solar nebula. Here we report the detection of acetylene (C2H2) in the infrared spectrum of comet C/1996 B2 (Hyakutake). The estimated abundance is 0.3-0.9%, relative to water, which is comparable to the predicted solid-phase abundance in cold interstellar clouds. This suggests that the volatiles in comet Hyakotake may have come from ice-covered interstellar grains, rather than material processed in the accretion disk out of which the Solar System formed.

  15. Acetylene fuel from atmospheric CO2 on Mars

    NASA Technical Reports Server (NTRS)

    Landis, Geoffrey A.; Linne, Diane L.

    1992-01-01

    The Mars mission scenario proposed by Baker and Zubrin (1990) intended for an unmanned preliminary mission is extended to maximize the total impulse of fuel produced with a minimum mass of hydrogen from Earth. The hydrogen along with atmospheric carbon dioxide is processed into methane and oxygen by the exothermic reaction in an atmospheric processing module. Use of simple chemical reactions to produce acetylene/oxygen rocket fuel on Mars from hydrogen makes it possible to produce an amount of fuel that is nearly 100 times the mass of hydrogen brought from earth. If such a process produces the return propellant for a manned Mars mission, the required mission mass in LEO is significantly reduced over a system using all earth-derived propellants.

  16. Acetylene decomposition to helical carbon nanofibers over supported copper catalysts

    SciTech Connect

    Ren Xue; Zhang Hui; Cui Zuolin

    2007-12-04

    The helical carbon nanofibers (CNFs), synthesized at relatively low temperatures (lower than 250 deg. C) by using Cu as a catalyst, SiO{sub 2}, TiO{sub 2}, Al{sub 2}O{sub 3}, MgO as supports and acetylene as gas source, has been investigated. The products were characterized by field emission scanning electron microscope (FE-SEM), transmission electron microscope (TEM) and X-ray diffraction (XRD). The morphologies of obtained products influenced by the types of supports and weight ratios (Cu/support = 1:1, 1:5, and 1:10) were discussed. The average diameter of the helical CNFs was about 80 nm, and these CNFs had the same coil pitch, and coil diameter.

  17. Ultrafast Extreme Ultraviolet Induced Isomerization of Acetylene Cations

    SciTech Connect

    Jiang, Y.; Rudenko, Artem; Herrwerth, O.; Foucar, L.; Kurka, M.; Kuhnel, K.; Lezius, M.; Kling, Matthias; van Tilborg, Jeroen; Belkacem, Ali; Ueda, K.; Dusterer, S.; Treusch, R.; Schroter, Claus-Dieter; Moshammer, Robbert; Ullrich, Joachim

    2011-06-17

    Ultrafast isomerization of acetylene cations ([HC = CH]{sup +}) in the low-lying excited A{sup 2}{Sigma}{sub g}{sup +} state, populated by the absorption of extreme ultraviolet (XUV) photons (38 eV), has been observed at the Free Electron Laser in Hamburg, (FLASH). Recording coincident fragments C{sup +} + CH{sub 2}{sup +} as a function of time between XUV-pump and -probe pulses, generated by a split-mirror device, we find an isomerization time of 52 {+-} 15 fs in a kinetic energy release (KER) window of 5.8 < KER < 8 eV, providing clear evidence for the existence of a fast, nonradiative decay channel.

  18. Ignition of acetylene by high-voltage nanosecond discharge

    NASA Astrophysics Data System (ADS)

    Kosarev, I. N.; Pakhomov, A. I.; Kindysheva, S. V.; Aleksandrov, N. L.

    2013-07-01

    The ignition of acetylene by low-temperature nonequilibrium plasma of a high-voltage nanosecond discharge is experimentally and theoretically studied. The ignition delay time for C2H2: O2 mixtures behind the reflected shock-wave front is measured. It is experimentally shown that discharge initiation leads to a considerable shortening of the ignition delay time. For lean mixtures, this effect is more pronounced. Numerical modeling of discharge and ignition processes under the experimental conditions is carried out. A good agreement between the calculation and experimental results for the ignition delay time is obtained. Analysis of the calculation results shows that the dominant mechanism of the effect of nonequilibrium plasma on ignition is related to the accumulation of atoms and radicals in discharge plasma.

  19. Adhesive and composite evaluation of acetylene-terminated phenylquinoxaline resins

    NASA Technical Reports Server (NTRS)

    Hergenrother, P. M.

    1981-01-01

    A series of acetylene-terminated phenylquinoxaline (ATPQ) oligomers of various molecular weights were prepared and subsequently chain extended by the thermally induced reaction of the ethynyl groups. The processability and thermal properties of these oligomers and their cured resins were compared with that of a relatively high molecular weight linear polyphenylquinoxaline (PPQ) with the same chemical backbone. The ATPQ oligomers exhibited significantly better processability than the linear PPQ but the PPQ displayed substantially better thermooxidative stability. Adhesive (Ti/Ti) and composite (graphite filament reinforcement) work was performed to evaluate the potential of these materials for structural applications. The PPQ exhibited better retention of adhesive and laminate properties than the ATPQ resins at 260 C after aging for 500 hr at 260 C in circulating air.

  20. Theoretical study of unimolecular rearrangements of vinylidenes to acetylenes

    NASA Astrophysics Data System (ADS)

    Kakkar, Rita; Pathak, Mallika; Chadha, Preeti

    The rearrangement of vinylidene to acetylene has been studied in detail by the density functional method, using Becke's three-parameter exchange functional and the gradient-corrected functional of Lee, Yang, and Parr. The rearrangement of the anion, as well as that of fluoro-substituted systems, has also been investigated, in order to determine the effect of fluorine substitution on the activation barrier to the 1,2-hydrogen shift, as well as the relative migratory aptitudes of hydrogen and fluorine. Natural bond orbital analysis is invoked to gain insight into the mechanisms of the rearrangements. Basis size effects are also discussed, particularly in relation to anionic systems. The need to include diffuse functions in geometry optimizations of anionic systems is reinforced by the present calculations.

  1. Acetylene as a substrate in the development of primordial bacterial communities

    USGS Publications Warehouse

    Culbertson, C.W.; Strohmaier, F.E.; Oremland, R.S.

    1988-01-01

    The fermentation of atmospheric acetylene by anaerobic bacteria is proposed as the basis of a primordial heterotrophic food chain. The accumulation of fermentation products (acetaldehyde, ethanol, acetate and hydrogen) would create niches for sulfate-respiring bacteria as well as methanogens. Formation of acetylene-free environments in soils and sediments would also alter the function of nitrogenase from detoxification to nitrogen-fixation. The possibility of an acetylene-based anaerobic food chain in Jovian-type atmospheres is discussed. ?? 1988 Kluwer Academic Publishers.

  2. Can substitution accomplish intact polycationic stability in polyatomic molecules? Illustration with acetylene molecule

    NASA Astrophysics Data System (ADS)

    Sairam, T.; Kumar, Ajit; Safvan, C. P.

    2015-11-01

    In this article, substitution is viewed as a parameter to stabilize intact polycationic species. Acetylene has been chosen for the study and ab-initio structure calculations for acetylene and di-halogen substituted acetylene have been performed using 6-311G** at UHF and DFT (B3LYP) and using 3-21G* at UHF level of theory. In substituted polycationic species the C-X bond length contracts and lead to quadruply charged cationic stability in C2X2 (where X=F, Cl, Br and I) molecule. Transition state calculations for C2I2 dication are also presented.

  3. The abundances of ethane and acetylene in the atmospheres of Jupiter and Saturn

    NASA Technical Reports Server (NTRS)

    Noll, K. S.; Knacke, R. F.; Tokunaga, A. T.; Lacy, J. H.; Beck, S.

    1986-01-01

    The present determination of the stratospheric abundances of ethane and acetylene on Jupiter and Saturn on the basis of IR spectra near 780/cm uses atmospheric models whose thermal and density profiles have constant mixing ratios. The ratio of ethane to acetylene is noted to be insensitive to model atmosphere assumptions; it is 55 + or - 31 for Jupiter and 23 + or - 12 where model mixing ratios are uniform. Atmospheric model density profiles adapted from theoretical photochemical models are noted to also yield a higher ethane/acetylene ratios for Jupiter.

  4. The abundances of ethane to acetylene in the atmospheres of Jupiter and Saturn

    NASA Technical Reports Server (NTRS)

    Noll, K. S.; Knacke, R. F.; Tokunaga, A. T.; Lacy, J. H.; Beck, S.; Serabyn, E.

    1986-01-01

    The present determination of the stratospheric abundances of ethane and acetylene on Jupiter and Saturn on the basis of IR spectra near 780/cm uses atmospheric models whose thermal and density profiles have constant mixing ratios. The ratio of ethane to acetylene is noted to be insensitive to model atmosphere assumptions; it is 55 + or - 31 for Jupiter and 23 + or - 12 where model mixing ratios are uniform. Atmospheric model density profiles adapted from theoretical photochemical models are noted to also yield a higher ethane/acetylene ratios for Jupiter.

  5. Absolute frequency measurement of an acetylene-stabilized laser at 1542 nm

    NASA Astrophysics Data System (ADS)

    Hong, Feng-Lei; Onae, Atsushi; Jiang, Jie; Guo, Ruixiang; Inaba, Hajime; Minoshima, Kaoru; Schibli, Thomas R.; Matsumoto, Hirokazu; Nakagawa, Ken'ichi

    2003-12-01

    The absolute frequency of an acetylene-stabilized laser at 1542 nm is measured at its second harmonic (771 nm) by use of a femtosecond optical comb based on a mode-locked Ti:sapphire laser. Frequency stability and reproducibility of the acetylene-stabilized laser are evaluated by the femtosecond comb with a H maser as a frequency reference. The absolute frequency of a laser diode stabilized on the P(16) transition of 13C2H2 is determined to be 194 369 569 383.6(1.3) kHz. The acetylene-stabilized laser serves as an important optical frequency standard for telecommunication applications.

  6. Denitrification in Low pH Spodosols and Peats Determined with the Acetylene Inhibition Method

    PubMed Central

    Mller, Michael M.; Sundman, Veronica; Skujin, J.

    1980-01-01

    Potential denitrification rates were determined for predominantly acid (pH ? 3.6) horizons of forestal, miry, and agricultural soils from 22 locations in southern Finland. The acetylene inhibition method was used with nitrate-amended water-logged soils incubated in an N2 atmosphere containing 2.5 or 5% C2H2. Complete inhibition of the reduction of N2O to N2 was observed in 99.3% of the samples. The denitrification rates varied from 0.12 to 53.8 ?g of Ncm-3day-1. Correlation between denitrification rate and soil pH was highly significant: r = 0.84 on a volume basis, and r = 0.44 on a weight basis. Vegetation type and amount of soil organic matter had a minor or no effect, respectively. In spodosolized soils the rates were significantly higher for B horizons than for A horizons. These results show that denitrification can occur in acid soils. PMID:16345603

  7. Diameter control of carbon nanotubes using argon-acetylene mixture and their application as IR sensor

    NASA Astrophysics Data System (ADS)

    Afzal, Rana Arslan; Afrin, Rahat; Manzoor, Umair; Bhatti, Arshad Saleem; Islam, Mohammad; Amin, Muhammad T.; Alazba, Abdulrahman A.

    2015-08-01

    Multi-walled carbon nanotubes (CNTs) were grown via pyrolytic chemical vapor deposition technique and explored for their infrared sensing behavior. CNT synthesis was carried out over cobalt zinc ferrite (Co0.5Zn0.5Fe2O4) catalyst nanoparticles under different gas flow conditions to control outside diameter of the nanotubes. It was found that a progressive decrease in the carbon precursor gas (acetylene in this case) from 5:1 to 9:1 (v/v) causes reduction of average CNT diameter from 85 nm to 635 nm. Growth conditions involving higher temperatures yield nanotubes/nanofibers with outer diameter of >500 nm, presumably due to surface aggregation of nanoparticles or increased flux of carbonaceous species at the catalyst surface or both. Current-voltage characteristics of the nanotubes depending on the CNT diameter, revealed linear or nonlinear behavior. When incorporated as sensing layer, the sensitivity of 5.3 was noticed with response time of 4.1 s. It is believed that IR sensing characteristics of such CNT-based detectors can be further enhanced through post-synthesis purification and chemical functionalization treatments.

  8. Characterization of the Minimum Energy Paths and Energetics for the Reaction of Vinylidene with Acetylene

    NASA Technical Reports Server (NTRS)

    Walch, Stephen P.; Taylor, Peter R.

    1995-01-01

    The reaction of vinylidene (CH2C) with acetylene may be an initiating reaction in soot formation. We report minimum energy paths and accurate energetics for a pathway leading to vinyl-acetylene and for a number of isomers of C4H4. The calculations use complete active space self-consistent field (CASSCF) derivative methods to characterize the stationary points and internally contacted configuration interaction (ICCI) and/or coupled cluster singles and doubles with a perturbational estimate of triple excitations (CCSD(T)) to determine the energetics. We find an entrance channel barrier of about 5 kcal/mol for the addition of vinylidene to acetylene, but no barriers above reactants for the reaction pathway leading to vinyl-acetylene.

  9. Silyl-acetylene polymers for use as precursors to silicon carbide fibers

    SciTech Connect

    Meyer, M.K.

    1991-12-20

    The steps involved in production of silicon carbide fiber using silyl acetylene polymer precursors can be separated into four processing steps: polymer synthesis, fiber spinning, fiber crosslinking, and pyrolysis. Practical experimental considerations in each step are discussed.

  10. INHIBITION OF ALKYLBENZENE BIODEGRADATION UNDER DENITRIFYING CONDITIONS BY USING THE ACETYLENE BLOCK TECHNIQUE

    EPA Science Inventory

    Addition of acetylene to microcosms simultaneously amended with nitrate and alkylbenzenes resulted in inhibition of the rate of alkylbenzene biodegradation under denitrifying conditions. Toluene, xylenes, and 1,2,4-trimethylbenzene were recalcitrant, whereas ethylbenzene was degr...

  11. INHIBITION OF ALKYLBENZENE BIODEGRADATION UNDER DENITRIFYING CONDITIONS BY USING THE ACETYLENE BLOCK TECHNIQUE

    EPA Science Inventory

    Addition of acetylene to microcosms simultaneously amended with nitrate and alkylbenzenes resulted in inhibition of the rate of alkylbenzene biodegradation under denitrifying conditions. oluene, xylenes, and 1,2,4-trimethylbenzene were recalcitrant, whereas ethylbenzene was degra...

  12. KISS: Kinetics and Structure of Superagglomerates Produced by Silane and Acetylene

    NASA Technical Reports Server (NTRS)

    Mulholland, G. W.; Yang, J. C.; Scott, J. H.; Sivithanu, Y.

    2001-01-01

    The objective of this study is to understand the process of gas phase agglomeration leading to superagglomerates and a gel-like structure for microgravity (0-g) silane and acetylene flames. Ultimately one would apply this understanding to predicting flame conditions that could lead to the gas phase production of an aero-gel. The approach is to burn acetylene and silane and to analyze the evolution of the soot and silica agglomerates. Acetylene is chosen because it has one of the highest soot volume fractions and there is evidence of super agglomerates being formed in laminar acetylene flames. Silane has the advantage that silica particles are the major combustion product resulting in a particle volume fraction a factor of ten greater than that for a carbonaceous smoke.

  13. Furans Conjugated with Bulky Aromatic Systems: One-Pot Synthesis from Ketones and Acetylene.

    PubMed

    Schmidt, Elena Yu; Bidusenko, Ivan A; Cherimichkina, Natalia A; Ushakov, Igor A; Borodina, Tatyana N; Smirnov, Vladimir I; Trofimov, Boris A

    2015-11-01

    Ketones with bulky aromatic, heteroaromatic and ferrocene substituents react with acetylene in the presence of a KOH/DMSO super-base suspension (90?C, 15?min) to give polysubstituted furans in up to 86?% isolated yields in a one-pot fashion. This assembly of the furan scaffold involves a domino sequence in which one molecule of ketone reacts with two molecules of acetylene. PMID:26387495

  14. Adsorptive Separation of Acetylene from Light Hydrocarbons by Mesoporous Iron Trimesate MIL-100(Fe).

    PubMed

    Yoon, Ji Woong; Lee, Ji Sun; Lee, Sukyung; Cho, Kyoung Ho; Hwang, Young Kyu; Daturi, Marco; Jun, Chul-Ho; Krishna, Rajamani; Chang, Jong-San

    2015-12-01

    A reducible metal-organic framework (MOF), iron(III) trimesate, denoted as MIL-100(Fe), was investigated for the separation and purification of methane/ethane/ethylene/acetylene and an acetylene/CO2 mixtures by using sorption isotherms, breakthrough experiments, ideal adsorbed solution theory (IAST) calculations, and IR spectroscopic analysis. The MIL-100(Fe) showed high adsorption selectivity not only for acetylene and ethylene over methane and ethane, but also for acetylene over CO2 . The separation and purification of acetylene over ethylene was also possible for MIL-100(Fe) activated at 423?K. According to the data obtained from operando IR spectroscopy, the unsaturated Fe(III) sites and surface OH groups are mainly responsible for the successful separation of the acetylene/ethylene mixture, whereas the unsaturated Fe(II) sites have a detrimental effect on both separation and purification. The potential of MIL-100(Fe) for the separation of a mixture of C2 H2 /CO2 was also examined by using the IAST calculations and transient breakthrough simulations. Comparing the IAST selectivity calculations of C2 H2 /CO2 for four MOFs selected from the literature, the selectivity with MIL-100(Fe) was higher than those of CuBTC, ZJU-60a, and PCP-33, but lower than that of HOF-3. PMID:26515022

  15. Mechanism-based inactivation of benzo(a)pyrene hydroxylase by aryl acetylenes and aryl olefins

    SciTech Connect

    Gan, L.S.; Lu, J.Y.L.; Alworth, W.L.

    1986-05-01

    A series of aryl acetylenes and aryl olefins have been examined as substrates and inhibitors of cytochrome P-450 dependent monooxgenases in liver microsomes from 5,6-benzoflavone or phenobarbital pretreated rats. 1-Ethynylpyrene, 3-ethynylperylene, 2-ethynylfluorene, methyl 1-pyrenyl acetylene, cis- and trans-1-(2-bromovinyl)pyrene, and 1-allylpyrene serve as mechanism-based irreversible inactivators (suicide inhibitors) of benzo(a)pyrene hydroxylase, while 1-vinylpyrene and phenyl 1-pyrenyl acetylene do not cause a detectable suicide inhibition of benzo(a)pyrene hydroxylase. The mechanism-based loss of benzo(a)pyrene hydroxylase caused by the aryl acetylenes is not accompanied by a corresponding loss of the P-450 content of the microsomes (suicide destruction). The suicide inhibition by these aryl acetylenes therefore does not involve covalent binding to the heme moiety of the monooxygenase. Nevertheless, in the presence of NADPH, /sup 3/H-labeled 1-ethynylpyrene becomes covalently attached to the cytochrome P-450 protein; the measured stoichiometry of binding is one 1-ethynylpyrene per P-450 heme unit. The authors conclude that the inhibition of benzo(a)pyrene hydroxylase produced by 1-ethynylpyrene may be related to the mechanism of suicide inhibition of P-450 activity by chloramphenicol rather than the mechanism of suicide destruction of P-450 previously described for acetylene and propyne.

  16. Tunable thermal conductivity in carbon allotrope sheets: Role of acetylenic linkages

    NASA Astrophysics Data System (ADS)

    Wang, Jian; Zhang, Ai-Juan; Tang, Yuansheng

    2015-11-01

    The versatility of carbon in forming the hybridization states allows one to design more carbon allotropes with various fascinating properties by replacing some aromatic bonds with acetylenic linkages. We investigate thermal conductivities of carbon allotrope sheets with different configurations by nonequilibrium molecular dynamic simulations. It is found that the acetylenic linkages not only considerably reduce thermal conductivity but also can effectively tune thermal conductivity through the various bonding methods. We suggest that the structure of stripes of benzene rings transversely bonded with the acetylenic linkages can potentially be one of high thermoelectric materials. We find that the reason for the manipulation of thermal conductivity by the acetylenic linkage can be attributed to the strong localizations of phonon modes that result in the reduced phonon group velocity and the shortened lifetime of phonons. It is also observed that thermal conductivity of graphyne sheet shows a power-law divergence with respect to the length. We propose a new approach to manipulating thermal conductivities in the carbon allotropes through the assembling of acetylenic linkages. Our findings conclusively clarify the role of acetylenic linkages in thermal transport and offer some valuable insights into the exploration of new thermoelectric materials as well as the experimental control of heat flux.

  17. Trimethyl phosphate-acetylene interaction: a matrix-isolation infrared and ab initio study

    NASA Astrophysics Data System (ADS)

    Sundararajan, K.; Vidya, V.; Sankaran, K.; Viswanathan, K. S.

    2000-09-01

    Trimethyl phosphate (TMP) and acetylene were codeposited in nitrogen and argon matrices and adducts of these species were identified using infrared spectroscopy. Formation of the adducts was evidenced by shifts in the vibrational frequencies of the modes involving the TMP and acetylene submolecules. The structures of these adducts, energies and the vibrational frequencies were computed at the HF/6-31G** level. Both the experimental and computational studies indicated that two types of TMP-acetylene complexes were formed; one in which the hydrogen in acetylene was bonded to the phosphoryl oxygen and another in which the bonding was at the alkoxy oxygen of the phosphate. In addition to the primary hydrogen bonded interaction at the phosphoryl oxygen, this complex, also appeared to be stablilized by a secondary and weaker interaction involving a methyl hydrogen in TMP and the π cloud in acetylene — a case of a H…π interaction. The computed vibrational frequencies in the adducts agreed well with the observed frequencies for the modes involving the TMP submolecule, while the agreement was relatively poor for the modes involving the acetylene submolecule. The stabilization energies of these adducts, corrected for both zero-point energies and basis set superposition errors, were ≈3 kcal/mol for the phosphoryl complex and ≈1 kcal/mol for the alkoxy complex.

  18. Formation of polycyclic aromatic hydrocarbons from acetylene over nanosized olivine-type silicates

    NASA Astrophysics Data System (ADS)

    Tian, M.; Liu, B. S.; Hammonds, M.; Wang, N.; Sarre, P. J.; Cheung, A. S.-C.

    2012-03-01

    The formation mechanism of polycyclic aromatic hydrocarbon (PAH) molecules in interstellar and circumstellar environments is not well understood although the presence of these molecules is widely accepted. In this paper, addition and aromatization reactions of acetylene over astrophysically relevant nesosilicate particles are reported. Gas-phase PAHs produced from exposure of acetylene gas to crystalline silicates using pulsed supersonic jet expansion (SJE) conditions were detected by time-of-flight mass spectrometry (TOF-MS). The PAHs produced were further confirmed in a separate experiment using a continuous flow fixed-bed reactor in which acetylene was introduced at atmospheric pressure. The gas-phase effluent and solutions of the carbonaceous compounds deposited on the nesosilicate particles were analyzed using gas chromatography-mass spectrometry (GC-MS). A mechanism for PAH formation is proposed in which the Mg2+ ions in the nesosilicate particles act as Lewis acid sites for the acetylene reactions. Our studies indicate that the formation of PAHs in mixed-chemistry astrophysical environments could arise from acetylene interacting with olivine nano-particles. These nesosilicate particles are capable of providing catalytic centres for adsorption and activation of acetylene molecules that are present in the circumstellar environments of mass-losing carbon stars. The structure and physical properties of the particles were characterized by means of X-ray diffraction (XRD), Fourier transform infrared (FT-IR) and high-resolution transmission electron microscopy (HRTEM) techniques.

  19. A porous metal-organic framework with ultrahigh acetylene uptake capacity under ambient conditions

    PubMed Central

    Pang, Jiandong; Jiang, Feilong; Wu, Mingyan; Liu, Caiping; Su, Kongzhao; Lu, Weigang; Yuan, Daqiang; Hong, Maochun

    2015-01-01

    Acetylene, an important petrochemical raw material, is very difficult to store safely under compression because of its highly explosive nature. Here we present a porous metal-organic framework named FJI-H8, with both suitable pore space and rich open metal sites, for efficient storage of acetylene under ambient conditions. Compared with existing reports, FJI-H8 shows a record-high gravimetric acetylene uptake of 224 cm3 (STP) g−1 and the second-highest volumetric uptake of 196 cm3 (STP) cm−3 at 295 K and 1 atm. Increasing the storage temperature to 308 K has only a small effect on its acetylene storage capacity (∼200 cm3 (STP) g−1). Furthermore, FJI-H8 exhibits an excellent repeatability with only 3.8% loss of its acetylene storage capacity after five cycles of adsorption–desorption tests. Grand canonical Monte Carlo simulation reveals that not only open metal sites but also the suitable pore space and geometry play key roles in its remarkable acetylene uptake. PMID:26123775

  20. Synthesis of gem-disubstituted ethylene and acetylene derivatives of the cyclopropane series based on 1,1-diacylcyclopropanes

    SciTech Connect

    Zefirov, N.S.; Kozhushkov, S.I.; Kuznetsova, T.S.; Gleiter, R.; Eckert-Maksic, M.

    1986-06-10

    Methods for the conversion of 1,1-diacylcyclopropanes into gem-disubstituted dienes and acetylenes of the cyclopropene series were investigated: (a) reduction followed by dehydration of the diols; (b) conversion of the diketones into bistosylhydrazones and treatment of the latter with methyllithium; (c) dehydrohalogenation of gem-di(1-halogenoalkyl)cyclopropanes by the action of bases. Dehydration leads to intramolecular nucleophilic opening of the three-membered ring. 1,1-Divinylcyclopropanes and stereoisomeric 1,1-di(1-propenyl)cyclopropanes were obtained by two different methods, and the corresponding diynes and enynes were synthesized from them by bromination followed by dehydrobromination. 1,1-Di(1-propynyl)cyclopropane can be obtained by alkylation of 1,1-diethynyl-cyclopropane and also directly from 1,1-divinylcyclopropane without isolation of the intermediate 1,1-diethynylcyclopropane.

  1. Comparison of an Assay for Dehalococcoides DNA and a Microcosm Study in Predicting Reductive Dechlorination of Chlorinated Ethenes in the field

    EPA Science Inventory

    The study aims to compare the detection of 16S rRNA gene of Dehalococcoides species and the microcosm study for biotransformation in predicting reductive dechlorination of chlorinated ethylenes in ground water at hazardous waste sites. A total of 72 ground water samples were coll...

  2. Topoisomerase Assays

    PubMed Central

    Nitiss, John L.; Soans, Eroica; Rogojina, Anna; Seth, Aman; Mishina, Margarita

    2012-01-01

    Topoisomerases are nuclear enzymes that play essential roles in DNA replication, transcription, chromosome segregation, and recombination. All cells have two major forms of topoisomerases: type I, which makes single-stranded cuts in DNA, and type II enzymes, which cut and pass double-stranded DNA. DNA topoisomerases are important targets of approved and experimental anti-cancer agents. The protocols described in this unit are of assays used to assess new chemical entities for their ability to inhibit both forms of DNA topoisomerase. Included are an in vitro assay for topoisomerase I activity based on relaxation of supercoiled DNA and an assay for topoisomerase II based on the decatenation of double-stranded DNA. The preparation of mammalian cell extracts for assaying topoisomerase activity is described, along with a protocol for an ICE assay for examining topoisomerase covalent complexes in vivo and an assay for measuring DNA cleavage in vitro. PMID:22684721

  3. Kinetic tetrazolium microtiter assay

    NASA Technical Reports Server (NTRS)

    Pierson, Duane L. (Inventor); Stowe, Raymond P. (Inventor); Koeing, David W. (Inventor)

    1992-01-01

    A method for conducting an in vitro cell assay using a tetrazolium indicator is disclosed. The indicator includes a nonionic detergent which solubilizes a tetrazolium reduction product in vitro and has low toxicity for the cells. The incubation of test cells in the presence of zolium bromide and octoxynol (TRITON X-100) permits kinetics of the cell metabolism to be determined.

  4. Fatality due to methyl acetylene-propadiene (MAPP) inhalation.

    PubMed

    Avella, Joseph; Lehrer, Michael

    2004-11-01

    A 33-year-old man died after intentionally inhaling a gaseous mix of methyl acetylene (propyne) and propadiene (allene) commonly known as MAPP, which is used for soldering and welding. He was found with a plastic bag securely placed over his head and a cylinder of MAPP alongside his head. The cylinder had been vented into the bag using a flexible hose. A comprehensive toxicological analysis revealed only a trace of diphenhydramine in the liver and 0.02 mg/L of morphine in the urine. Analysis of blood by headspace gas chromatography (HS-GC) detected two unknown peaks. These were determined to be the components of MAPP gas. MAPP was quantitated in femoral blood (59.6 mg/L) and brain (43.6 mg/kg) using a HS-GC method. The cause of death was attributed to acute MAPP intoxication, and the manner was determined to be suicide. A discussion on the analytical and interpretive considerations commonly encountered when analyzing volatile compounds is also presented. PMID:15568715

  5. Acetylene-chromene terminated resins as high temperature thermosets

    NASA Technical Reports Server (NTRS)

    Godschalx, J. P.; Inbasekaran, M. N.; Bartos, B. R.; Scheck, D. M.; Laman, S. A.

    1990-01-01

    A novel phase transfer catalyzed process for the preparation of propargyl ethers has been developed. The propargyl ethers serve as precursors to a new class of thermosetting resins called acetylene-chromene terminated (ACT) resins. Heat treatment of a solution of propargyl ethers with various catalysts, followed by removal of solvent leads to the ACT resins via partial conversion of the propargyl ether groups to chromenes. This process reduces the energy content of the resin systems and reduces the amount of shrinkage found during cure. Due to the presence of the solvent the process is safe and gives rise to low viscosity products suitable for resin transfer molding and filament winding type applications. Due to the high glass transition temperature, high modulus, and low moisture uptake the cured resins display better than 232 C/wet performance. The thermal stability of the ACT resins in air at 204 C is superior to that of conventional bismaleimide resins. The resins also display excellent electrical properties.

  6. An improved processible acetylene-terminated polyimide for composites

    NASA Technical Reports Server (NTRS)

    Landis, A. L.; Naselow, A. B.

    1985-01-01

    The newest member of a family of thermosetting acetylene-substituted polyimide oligomers is HR600P. This oligomer is the isoimide version of the oligomer known as HR600P and Thermid 600. Although both types of material yield the same heat resistant end products after cure, HR600P has much superior processing characteristics. This attributed to its lower melting temperature (160 + or - 10 C, 320 + or - 20 F) in contrast to 202 C (396 F) for Thermid MC-600, its longer gel time at its processing temperature (16 to 30 minutes bvs 3 minutes), and its excellent solubility in low boiling solvents such as tetrahydrofuran, glymes, or 4:1 methyl ethyl ketone/toluene mixtures. These advantages provide more acceptable coating and impregnation procedures, allow for more complete removal at lower temperatures, provide a longer pot life or working time, and allow composite structure fabrication in conventional autoclaves used for epoxy composite curing. The excellent processing characteristics of HR600P allow its use in large area laminated structures, structural composites, and molding compositions.

  7. Status on the Global Vibration-Rotation Model in Acetylene

    NASA Astrophysics Data System (ADS)

    Amyay, B.; Herman, M.; Fayt, A.

    2009-06-01

    We have developed a global model to deal with all vibration-rotation levels in acetylene up to high vibrational excitation energy, typically up to 9000 wavenumbers. It has been applied to a number of isotopologues, considering all known vibration-rotation lines published in the literature, for various purposes such as line assignment and astrophysical applications. Coriolis interaction is now systematically being introduced in the model. Recent results concerning the analysis of hot emission FTIR spectra recorded around 3 microns by R. Georges et al. at the University of Rennes (France) and of CW-CRDS spectra recorded around 1.5 microns by A. Campargue et al. at the University of Grenoble (France) will help illustrate the role of this vibration-rotation coupling in the global polyad scheme. S. Robert, M. Herman, A. Fayt, A. Campargue, S. Kassi, A. Liu, L. Wang, G. Di Lonardo, and L. Fusina, Mol. Phys., 106, 2581 (2008). A. Jolly, Y. Benilan, E. Can, L. Fusina, F. Tamassia, A. Fayt, S. Robert, and M. Herman, J.Q.S.R.T., 109, 2846 (2008).

  8. Discovery, Development, and Commercialization of Gold Catalysts for Acetylene Hydrochlorination.

    PubMed

    Johnston, Peter; Carthey, Nicholas; Hutchings, Graham J

    2015-11-25

    Vinyl chloride monomer (VCM) is a major chemical intermediate for the manufacture of polyvinyl chloride (PVC), which is the third most important polymer in use today. Hydrochlorination of acetylene is a major route for the production of vinyl chloride, since production of the monomer is based in regions of the world where coal is abundant. Until now, mercuric chloride supported on carbon is used as the catalyst in the commercial process, and this exhibits severe problems associated with catalyst lifetime and mercury loss. It has been known for over 30 years that gold is a superior catalyst, but it is only now that it is being commercialized. In this Perspective we discuss the use and disadvantages of the mercury catalyst and the advent of the gold catalysts for this important reaction. The nature of the active site and the possible reaction mechanism are discussed. Recent advances in the design and preparation of active gold catalysts containing ultralow levels of gold are described. In the final part, a view to the future of this chemistry will be discussed as well as the possible avenues for the commercial potential of gold catalysis. PMID:26529366

  9. Microwave Spectrum, Structure, and Internal Dynamics of the Pyridine - Acetylene Weakly Bound Complex

    NASA Astrophysics Data System (ADS)

    Mackenzie, Becca; Dewberry, Chris; Jarrett, Emma; Legon, Anthony; Leopold, Ken

    2014-06-01

    A-type rotational spectra of the weakly bound complex formed from pyridine and acetylene are reported. Contrary to expectation based on the symmetric structure of HCCH\\cdot \\cdot \\cdotNH3, the acetylene moiety in HCCH\\cdot\\cdot \\cdotNC5H5 does not lie along the symmetry axis of the pyridine. Rotational and 14N hyperfine constants instead indicate that, while the complex is indeed planar with an acetylenic hydrogen directed toward the nitrogen, the HCCH axis forms an angle of {˜}23° with the C2 axis of the pyridine. Spectra of HCCH\\cdot \\cdot \\cdotNC5H5, HCCD\\cdot \\cdot \\cdotNC5H5, DCCH\\cdot \\cdot \\cdotNC5H5, and DCCD\\cdot \\cdot \\cdotNC5H5 are all doubled, revealing the existence of a pair of low energy states. In light of the bent structure, this suggests a tunneling motion through a barrier at the C2v configuration. Because the splitting persists in the singly deuterated species, we conclude that the motion does not involve interchange of the acetylenic hydrogens. Single 13C substitution in either the ortho or meta positions of the pyridine eliminates the doubling and gives rise to separate sets of spectra for which the rotational constants are well predicted by a bent geometry. In this case, the two sets correspond to distinct species in which the 13C is either on the same or the opposite side as the acetylene. This further suggests that the doubling observed with unsubstituted pyridine arises from wagging of the acetylene, as such a tunneling motion is expected to be quenched when the pyridine is rendered asymmetric. The bent structure of the system may arise due to a secondary hydrogen bonding interaction between the ortho hydrogens of the pyridine and the π system of the acetylene.

  10. Acetylene-phenol complexes: A matrix isolation infrared and ab initio study

    NASA Astrophysics Data System (ADS)

    Sundararajan, K.; Ramanathan, N.

    2009-02-01

    The infrared spectra of the hydrogen-bonded complexes of acetylene-phenol have been investigated in solid argon and nitrogen matrices. Two types of acetylene-phenol complexes, O sbnd H⋯π and C sbnd H⋯O, are seen in the infrared spectra. Formation of these complexes was evidenced from the shifts in the vibrational frequencies of the modes involving the acetylene and phenol submolecules. The structure of the complexes and the energies were computed at HF and B3LYP levels of theory using 6-31++G ∗∗ basis sets. The geometries optimized at HF level were used to calculate the single point MP2/6-31++G ∗∗ energies for the complexes. The global minimum corresponded to the O sbnd H⋯π complex, where phenol acts as a proton donor to the acetylene π-cloud. The second minimum corresponded to the C sbnd H⋯O complex where acetylene acts as a proton donor to the oxygen of phenol and the third minimum corresponded to the C sbnd H⋯π complex where acetylene attacks the π-cloud of phenol. The computed vibrational frequencies of acetylene-phenol complexes at B3LYP/6-31++G ∗∗ level corroborated well with the experimental frequencies. No experimental evidence for the formation of C sbnd H⋯π complex in Ar/N 2 matrix was observed. AIM analysis was also performed to understand the nature of the interactions in these complexes.

  11. Ionization of large homogeneous and heterogeneous clusters generated in acetylene-Ar expansions: Cluster ion polymerization

    SciTech Connect

    Kocisek, J.; Lengyel, J.; Farnik, M.

    2013-03-28

    Pure acetylene and mixed Ar-acetylene clusters are formed in supersonic expansions of acetylene/argon mixtures and analysed using reflectron time-of-flight mass spectrometer with variable electron energy ionization source. Acetylene clusters composed of more than a hundred acetylene molecules are generated at the acetylene concentration of Almost-Equal-To 8%, while mixed species are produced at low concentrations ( Almost-Equal-To 0.7%). The electron energy dependence of the mass spectra revealed the ionization process mechanisms in clusters. The ionization above the threshold for acetylene molecule of 11.5 eV results in the main ionic fragment progression (C{sub 2}H{sub 2}){sub n}{sup +}. At the electron energies Greater-Than-Or-Slanted-Equal-To 21.5 eV above the CH+CH{sup +} dissociative ionization limit of acetylene the fragment ions nominally labelled as (C{sub 2}H{sub 2}){sub n}CH{sup +}, n Greater-Than-Or-Slanted-Equal-To 2, are observed. For n Less-Than-Or-Slanted-Equal-To 7 these fragments correspond to covalently bound ionic structures as suggested by the observed strong dehydrogenation [(C{sub 2}H{sub 2}){sub n}-k Multiplication-Sign H]{sup +} and [(C{sub 2}H{sub 2}){sub n}CH -k Multiplication-Sign H]{sup +}. The dehydrogenation is significantly reduced in the mixed clusters where evaporation of Ar instead of hydrogen can stabilize the nascent molecular ion. The C{sub 3}H{sub 3}{sup +} ion was previously assigned to originate from the benzene molecular ion; however, the low appearance energy of Almost-Equal-To 13.7 eV indicates that a less rigid covalently bound structure of C{sub 6}H{sub 6}{sup +} ion must also be formed upon the acetylene cluster electron ionization. The appearance energy of Ar{sub n}(C{sub 2}H{sub 2}){sup +} fragments above Almost-Equal-To 15.1 eV indicates that the argon ionization is the first step in the fragment ion production, and the appearance energy of Ar{sub n{>=}2}(C{sub 2}H{sub 2}){sub m{>=}2}{sup +} at Almost-Equal-To 13.7 eV is discussed in terms of an exciton transfer mechanism.

  12. Infrared Spectra and Optical Constants of Acetylene and Ethane Ices

    NASA Astrophysics Data System (ADS)

    Moore, Marla H.; Ferrante, R. F.; Hudson, R. L.; Moore, W. J.

    2012-10-01

    Hydrocarbon-containing ices have characteristic absorption bands in both the mid- and near-infrared spectral regions, yet accurate optical constants are not available for most of these molecules. Ices with a hydrocarbon component have been identified on several TNOs (1) and the presence of volatiles, such as hydrocarbons, is inferred for intermediate or large TNOs based on sublimation models (2, 3). In our laboratory we recently have undertaken low-temperature spectroscopic studies of C2 hydrocarbons. We report IR spectra for acetylene (C2H2) and ethane (C2H6) ice in both the amorphous and crystalline phases at multiple temperatures. We include measurements of the refractive index at 670 nm for both the amorphous and crystalline phases of each ice. The optical constants, the real (n) and imaginary (k) components of the complex index of refraction, were determined from 7000 - 400 cm-1 (1.4 - 25 microns) at multiple temperatures using a Kramers-Kronig analysis. A goal of the present work is to provide a data base of optical constants of C2 molecules similar to that of Hudgins et al. (4) and Moore et al. (5). These values, as well as our calculated individual band strengths, will have great practical importance for the ongoing analysis of TNO spectra. (1) Brown, M.E. et al., Astron J., 133, 284, 2007. (2) Delsanti, A. et al., A&A, 52, A40, 2010. (3) Schaller, E. L. & Brown, M. E., ApJ, 659, L61, 2007. (4) Hudgins, D. M. et al., ApJS, 86, 713, 1993. (5) Moore, M. H. et al., ApJS, 191, 96, 2010. This work is supported by NASAs Planetary Atmospheres, Outer Planets, and Cassini Data Analysis programs, and The Goddard Center for Astrobiology.

  13. [Photodissociation of Acetylene and Acetone using Step-Scan Time-Resolved FTIR Emission Spectroscopy

    NASA Technical Reports Server (NTRS)

    McLaren, Ian A.; Wrobel, Jacek D.

    1997-01-01

    The photodissociation of acetylene and acetone was investigated as a function of added quenching gas pressures using step-scan time-resolved FTIR emission spectroscopy. Its main components consist of Bruker IFS88, step-scan Fourier Transform Infrared (FTIR) spectrometer coupled to a flow cell equipped with Welsh collection optics. Vibrationally excited C2H radicals were produced from the photodissociation of acetylene in the unfocused experiments. The infrared (IR) emission from these excited C2H radicals was investigated as a function of added argon pressure. Argon quenching rate constants for all C2H emission bands are of the order of 10(exp -13)cc/molecule.sec. Quenching of these radicals by acetylene is efficient, with a rate constant in the range of 10(exp -11) cc/molecule.sec. The relative intensity of the different C2H emission bands did not change with the increasing argon or acetylene pressure. However, the overall IR emission intensity decreased, for example, by more than 50% when the argon partial pressure was raised from 0.2 to 2 Torr at fixed precursor pressure of 160mTorr. These observations provide evidence for the formation of a metastable C2H2 species, which are collisionally quenched by argon or acetylene. Problems encountered in the course of the experimental work are also described.

  14. [Smog chamber simulation of atmospheric photochemical reactions of acetylene and NO(x)].

    PubMed

    Du, Lin; Xu, Yong-Fu; Ge, Mao-Fa; Jia, Long; Wang, Geng-Chen; Wang, Dian-Xun

    2007-03-01

    A series of characteristic experiments were conducted in a self-made photochemical smog chamber, which was used to simulate atmospheric photochemical reactions of acetylene and NO(x) under room temperature of (20 +/- 1) degrees C. The effect of acetylene and NO(x) on ozone production by photochemical reactions was discussed. The wall decay of O3 and NO2 were determined, which were 5.80 x 10(-6) s(-1) and 2.41 x 10(-6) s(-1), respectively. Such decay should be omitted relative to O3 and NO2 in simulative experiments. The effective light intensity for a single black lamp of 40 W was determined to be 0.64 x 10(-3) s(-1), which was expressed by the photolysis rate of NO2. The effect of different light intensity, initial concentrations of acetylene and NO(x) on O3 production was discussed after correction of background O3 from purified air. The incremental reactivity (IR) of acetylene were calculated. For four different experiments, the maximum values of IR are 1.76 x 10(-2), 2.68 x 10(-2), 2.04 x 10(-2) and 2.84 x 10(-2), respectively. It is found that there are close relationships between IR and initial acetylene concentrations, and between IR and irradiation intensity, and that there is no significant relation between IR and initial NO(x) concentrations. PMID:17633620

  15. RAS Assays

    Cancer.gov

    The proportion of oncogenic mutants of KRAS proteins that are in the "active" (GTP-bound) form is far higher than that of wild-type RAS proteins. Scientists at the National Lab are developing high-throughput in vitro assays to measure interactions of GTP-loaded KRAS and effectors, such as CRAF and calmodulin, as well as imaging assays that can detect oncogenic KRAS interactions inside cells.

  16. Nonluminous diffusion flame of diluted acetylene in oxygen-enriched air

    SciTech Connect

    Sugiyama, G.

    1994-12-31

    A soot-reducing mechanism of fuel dilution and oxygen enrichment in laminar diffusion flames is suggested. Analysis using the Burke-Schumann theory for the shape of over ventilated diffusion flames has shown that there is a critical ratio of stoichiometric coefficients of the fuel and the oxidizer under which the gas flows from the fuel side to the oxidizer side throughout the flame. When this condition is satisfied, the soot growth region vanishes. A similar result is also found in a numerical simulation for diffusion flames that do not satisfy the Burke-Schumann assumption of uniform flow field. KIVA code is used for that purpose. The theoretically predicted direction of gas-flow across the flame sheet is verified in an experiment in a coaxial-flow diffusion flame. Soot cloud and velocity fields are visualized through a laser sheet method in the experiment. The fuel is a mixture of acetylene and nitrogen. The oxidizer is a mixture of oxygen and nitrogen. The compositions of the reactants are controlled so that the adiabatic flame temperature is kept constant to avoid the effect of temperature change. Experimental results show substantial reduction of scattered light intensity by fuel dilution and oxygen enrichment. When a sufficient amount of nitrogen is added to the fuel, nonluminous blue flames are obtained. At higher oxygen concentrations, blue flames are obtained at higher flame temperature region. When oxygen concentration in the oxidizer is 70 vol.%, blue flames are obtained up to 2,250 K. The critical condition of the reactants for nonluminous flames agrees with the theoretical prediction when the oxidizer is ordinary air. In oxygen-enriched conditions, the fuel must be diluted more, than theoretically predicted.

  17. ACETYLENE INHIBITION OF TRICHLOROETHENE AND VINYL CHLORIDE REDUCTIVE DECHLORINATION. (R828772)

    EPA Science Inventory

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  18. Use of HPLC/UPLC-spectrophotometry for detection of formazan in in vitro Reconstructed human Tissue (RhT)-based test methods employing the MTT-reduction assay to expand their applicability to strongly coloured test chemicals.

    PubMed

    Alépée, N; Barroso, J; De Smedt, A; De Wever, B; Hibatallah, J; Klaric, M; Mewes, K R; Millet, M; Pfannenbecker, U; Tailhardat, M; Templier, M; McNamee, P

    2015-06-01

    A number of in vitro test methods using Reconstructed human Tissues (RhT) are regulatory accepted for evaluation of skin corrosion/irritation. In such methods, test chemical corrosion/irritation potential is determined by measuring tissue viability using the photometric MTT-reduction assay. A known limitation of this assay is possible interference of strongly coloured test chemicals with measurement of formazan by absorbance (OD). To address this, Cosmetics Europe evaluated use of HPLC/UPLC-spectrophotometry as an alternative formazan measurement system. Using the approach recommended by the FDA guidance for validation of bio-analytical methods, three independent laboratories established and qualified their HPLC/UPLC-spectrophotometry systems to reproducibly measure formazan from tissue extracts. Up to 26 chemicals were then tested in RhT test systems for eye/skin irritation and skin corrosion. Results support that: (1) HPLC/UPLC-spectrophotometry formazan measurement is highly reproducible; (2) formazan measurement by HPLC/UPLC-spectrophotometry and OD gave almost identical tissue viabilities for test chemicals not exhibiting colour interference nor direct MTT reduction; (3) independent of the test system used, HPLC/UPLC-spectrophotometry can measure formazan for strongly coloured test chemicals when this is not possible by absorbance only. It is therefore recommended that HPLC/UPLC-spectrophotometry to measure formazan be included in the procedures of in vitro RhT-based test methods, irrespective of the test system used and the toxicity endpoint evaluated to extend the applicability of these test methods to strongly coloured chemicals. PMID:25701760

  19. Electronic properties and strain sensitivity of CVD-grown graphene with acetylene

    NASA Astrophysics Data System (ADS)

    Yang, Meng; Sasaki, Shinichirou; Ohnishi, Masato; Suzuki, Ken; Miura, Hideo

    2016-04-01

    Although many studies have shown that large-area monolayer graphene can be formed by chemical vapor deposition (CVD) using methane gas, the growth of monolayer graphene using highly reactive acetylene gas remains a big challenge. In this study, we synthesized a uniform monolayer graphene film by low-pressure CVD (LPCVD) with acetylene gas. On the base of Raman spectroscopy measurements, it was found that up to 95% of the as-grown graphene is monolayer. The electronic properties and strain sensitivity of the LPCVD-grown graphene with acetylene were also evaluated by testing the fabricated field-effect transistors (FETs) and strain sensors. The derived carrier mobility and gauge factor are 862–1150 cm2/(V·s) and 3.4, respectively, revealing the potential for high-speed FETs and strain sensor applications. We also investigated the relationship between the electronic properties and the graphene domain size.

  20. Deactivation mechanisms for Pd/Al{sub 2}O{sub 3} acetylene hydrogenation catalysts

    SciTech Connect

    Hall, J.B.; Huggins, B.J.; Meyers, B.L.; Kaminsky, M.P.

    1994-12-31

    The selective hydrogenation of acetylenic impurities to ethylene is a crucial purification step in the production of olefins by steam cracking. This hydrogenation is done catalytically using a Pd/Al{sub 2}O{sub 3} catalyst in a fixed bed reactor. The designed lifetime of the catalyst in a front end acetylene converter is about 4 years. Accelerated catalyst deactivation and thermal runaways caused by loss in catalyst selectivity are common problems which plague acetylene converters. Such problems result in unscheduled shutdowns and increased costs to replace deactivated catalyst. This presentation outlines several deactivation mechanisms of the catalyst and discusses how they affect catalyst lifetime and performance. Catalyst characterization using electron microscopy and CO chemisorption provides information on how poisons deteriorate the catalyst and Pd particle size changes produced by use and regeneration. Thermal gravimetric analysis was also used to determine the extent of coke burn-off using less severe regeneration procedures.

  1. Estimation of nitrogenase activity in the presence of ethylene biosynthesis by use of deuterated acetylene as a substrate

    SciTech Connect

    Lin-Vien, D.; Fateley, W.G.; Davis, L.C. )

    1989-02-01

    Nitrogenase reduces deuterated acetylene primarily to cis dideuterated ethylene. This can be distinguished from undeuterated ethylene by the use of Fourier transform infrared spectroscopy. Characteristic bands in the region from 800 to 3,500 cm-1 can be used to identify and quantitate levels of these products. This technique is applicable to field studies of nitrogen fixation where ethylene biosynthesis by plants or bacteria is occurring. We have verified the reaction stoichiometry by using Klebsiella pneumoniae and Bradyrhizobium japonicum in soybeans. The most useful bands for quantitation of substrate purity and product distribution are as follows: acetylene-d0, 3,374 cm-1; acetylene-d1, 2,584 cm-1; acetylene-d2, 2,439 cm-1; cis-ethylene-d2, 843 cm-1; trans-ethylene-d2, 988 cm-1; ethylene-d1, 943 cm-1; ethylene-d0, 949 cm-1. (The various deuterated ethylenes and acetylenes are designated by a lowercase d and subscript to indicate the number, but not the position, of deuterium atoms in the molecule.) Mass spectrometry coupled to a gas chromatograph system has been used to assist in quantitation of the substrate and product distributions. Significant amounts of trans-ethylene-d2 were produced by both wild-type and nifV mutant K. pneumoniae. Less of this product was observed with the soybean system.

  2. Acetylene- and Phenylacetylene-Terminated Poly(Arylene Ether Benzimidazole)s (PAEBI's)

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

    Polymers prepared by first synthesizing polymers terminated with hydroxy groups, then reacting them with either 4-ethynylbenzoyl chloride or 4-fluoro-4'-phenylethynylbenzophenone. Endcapped polymers thermally cured to yield materials with attractive combination of properties. Cured acetylene-and phenylacetylene-terminated PAEBI's exhibit higher glass-transition temperatures and better retention of mechanical properties at high temperatures. Cured acetylene- and phenylacetylene-terminated polymers exhibit excellent adhesion to copper foil and polyimide film. Potentially useful as adhesives, coatings, composite matrices, fibers, films, membranes, and moldings.

  3. Identification of non-precious metal alloy catalysts for selective hydrogenation of acetylene.

    PubMed

    Studt, Felix; Abild-Pedersen, Frank; Bligaard, Thomas; Srensen, Rasmus Z; Christensen, Claus H; Nrskov, Jens K

    2008-06-01

    The removal of trace acetylene from ethylene is performed industrially by palladium hydrogenation catalysts (often modified with silver) that avoid the hydrogenation of ethylene to ethane. In an effort to identify catalysts based on less expensive and more available metals, density functional calculations were performed that identified relations in heats of adsorption of hydrocarbon molecules and fragments on metal surfaces. This analysis not only verified the facility of known catalysts but identified nickel-zinc alloys as alternatives. Experimental studies demonstrated that these alloys dispersed on an oxide support were selective for acetylene hydrogenation at low pressures. PMID:18535238

  4. Heats of Formation of Triplet Ethylene, Ethylidene, and Acetylene

    SciTech Connect

    Nguyen, M.T.; Matus, M.H.; Lester Jr, W.A.; Dixon, David A.

    2007-06-28

    Heats of formation of the lowest triplet state of ethylene and the ground triplet state of ethylidene have been predicted by high level electronic structure calculations. Total atomization energies obtained from coupled-cluster CCSD(T) energies extrapolated to the complete basis set limit using correlation consistent basis sets (CBS), plus additional corrections predict the following heats of formation in kcal/mol: Delta H0f(C2H4,3A1) = 80.1 at 0 K and 78.5 at 298 K, and Delta H0f(CH3CH,3A") = 86.8 at 0 K and 85.1 at 298 K, with an error of less than +-1.0 kcal/mol. The vertical and adiabatic singlet-triplet separation energies of ethylene were calculated as Delta ES-T,vert = 104.1 and Delta ES-T,adia = 65.8 kcal/mol. These results are in excellent agreement with recent quantum Monte Carlo (DMC) values of 103.5 +- 0.3 and 66.4 +- 0.3 kcal/mol. Both sets of computational values differ from the experimental estimate of 58 +- 3 kcal/mol for the adiabatic splitting. The computed singlet-triplet gap at 0 K for acetylene is Delta ES-T,adia(C2H2) = 90.5 kcal/mol, which is in notable disagreement with the experimental value of 82.6 kcal/mol. The heat of formation of the triplet is Delta H0f(C2H2,3B2) = 145.3 kcal/mol. There is a systematic underestimation of the singlet-triplet gaps in recent photodecomposition experiments by ~;;7 to 8 kcal/mol. For vinylidene, we predict Delta H0f(H2CC,1A1) = 98.8 kcal/mol at 298 K (exptl. 100.3 +- 4.0), Delta H0f(H2CC,3B2) = 146.2 at 298 K, and an energy gap Delta ES-T-adia(H2CC) = 47.7 kcal/mol.

  5. Computational study on C-H...? interactions of acetylene with benzene, 1,3,5-trifluorobenzene and coronene.

    PubMed

    Dinadayalane, Tandabany C; Paytakov, Guvanchmyrat; Leszczynski, Jerzy

    2013-07-01

    Meta-hybrid density functional theory calculations using M06-2X/6-31+G(d,p) and M06-2X/6-311+G(d,p) levels of theory have been performed to understand the strength of C-H()? interactions of two possible types for benzene-acetylene, 1,3,5-trifluorobenzene-acetylene and coronene-acetylene complexes. Our study reveals that the C-H(...)? interaction complex where acetylene located above to the center of benzene ring (classical T-shaped) is the lowest energy structure. This structure is twice more stable than the configuration characterized by H atom of benzene interacting with the ?-cloud of acetylene. The binding energy of 2.91 kcal/mol calculated at the M06-2X/6-311+G(d,p) level for the lowest energy configuration (1A) is in very good agreement with the experimental binding energy of 2.7 0.2 kcal/mol for benzene-acetylene complex. Interestingly, the C-H(...)? interaction of acetylene above to the center of the aromatic ring is not the lowest energy configuration for 1,3,5-trifluorobenzene-acetylene and coronene-acetylene complexes. The lowest energy configuration (2A) for the former complex possesses both C-H(...)? interaction and C-H(...)F hydrogen bond, while the lowest energy structure for the coronene-acetylene complex involves both ?-? and C-H(...)? interactions. C-H stretching vibrational frequencies and the frequency shifts are reported and analyzed for all of the configurations. We observed red-shift of the vibrational frequency for the stretching mode of the C-H bond that interacts with the ?-cloud. Acetylene in the lowest-energy structures of the complexes exhibits significant red-shift of the C-H stretching frequency and change in intensity of the corresponding vibrational frequency, compared to bare acetylene. We have examined the molecular electrostatic potential on the surfaces of benzene, 1,3,5-trifluorobenzene, coronene and acetylene to explain the binding strengths of various complexes studied here. PMID:23247410

  6. Association Mechanisms of Unsaturated C2 Hydrocarbons with Their Cations: Acetylene and Ethylene

    NASA Technical Reports Server (NTRS)

    Bera, Partha P.; Head-Gordon, Martin; Lee, Timothy J.

    2013-01-01

    The ion-molecule association mechanism of acetylene and ethylene with their cations is investigated by ab initio quantum chemical methods to understand the structures, association energies, and the vibrational and electronic spectra of the products. Stable puckered cyclic isomers are found as the result of first forming less stable linear and bridge isomers. The puckered cyclic complexes are calculated to be strongly bound, by 87, 35 and 56 kcal/mol for acetylene-acetylene cation, ethylene-ethylene cation and acetylene-ethylene cation, respectively. These stable complexes may be intermediates that participate in further association reactions. There are no association barriers, and no significant inter-conversion barriers, so the initial linear and bridge encounter complexes are unlikely to be observable. However, the energy gap between the bridged and cyclic puckered isomers greatly differs from complex to complex: it is 44 kcal/mol in C4H4 +, but only 6 kcal/mol in C4H8 +. The accurate CCSD(T) calculations summarized above are also compared against less computationally expensive MP2 and density functional theory (DFT) calculations for structures, relative energies, and vibrational spectra. Calculated vibrational spectra are compared against available experiments for cyclobutadiene cation. Electronic spectra are also calculated using time-dependent DFT.

  7. A Safe and Easy Classroom Demonstration of the Generation of Acetylene Gas.

    ERIC Educational Resources Information Center

    Cox, Marilyn Blagg; Krause, Paul

    1994-01-01

    In this demonstration of the generation and combustion of acetylene, calcium carbide and water are allowed to react in a latex examination glove. Two student volunteers perform the demonstration with instructor guidance. This safe, popular demonstration, originally intended to illustrate the alkyne family of compounds, can be used with a variety

  8. Mechanism of tungsten-dependent acetylene hydratase from quantum chemical calculations.

    PubMed

    Liao, Rong-Zhen; Yu, Jian-Guo; Himo, Fahmi

    2010-12-28

    Acetylene hydratase is a tungsten-dependent enzyme that catalyzes the nonredox hydration of acetylene to acetaldehyde. Density functional theory calculations are used to elucidate the reaction mechanism of this enzyme with a large model of the active site devised on the basis of the native X-ray crystal structure. Based on the calculations, we propose a new mechanism in which the acetylene substrate first displaces the W-coordinated water molecule, and then undergoes a nucleophilic attack by the water molecule assisted by an ionized Asp13 residue at the active site. This is followed by proton transfer from Asp13 to the newly formed vinyl anion intermediate. In the subsequent isomerization, Asp13 shuttles a proton from the hydroxyl group of the vinyl alcohol to the ?-carbon. Asp13 is thus a key player in the mechanism, but also W is directly involved in the reaction by binding and activating acetylene and providing electrostatic stabilization to the transition states and intermediates. Several other mechanisms are also considered but the energetic barriers are found to be very high, ruling out these possibilities. PMID:21149684

  9. OZONE PRODUCTION FROM IRRADIATION OF ACETYLENE/CHLORINE MIXTURES IN AIR

    EPA Science Inventory

    The reaction of chlorine radicals with acetylene in air in the absence of oxides of nitrogen result In the formation of ozone. o ozone is observed when chlorine radicals react with methylacetylene or ethylacetylene under similar conditions. ormyl chloride is observed in all syste...

  10. Free standing acetylene black mesh to capture dissolved polysulfide in lithium sulfur batteries.

    PubMed

    Jeong, Tae-Gyung; Moon, Young Hoon; Chun, Ho-Hwan; Kim, Hyung Sun; Cho, Byung Won; Kim, Yong-Tae

    2013-12-01

    Herein, we report a cheap and simple approach to solve the polysulfide dissolution problem in lithium sulfur batteries. It was interestingly revealed that a simple insertion of acetylene black mesh enabled us to obtain the capacity of 1491 mA h g(-1) at initial discharge and 1062 mA h g(-1) after 50 cycles. PMID:24145813

  11. Measurement of acetylene in breath by ultraviolet absorption spectroscopy: Potential for noninvasive cardiac output monitoring

    NASA Astrophysics Data System (ADS)

    Baum, Marc M.; Kumar, Sasi; Lappas, Anastasios M.; Wagner, Peter D.

    2003-06-01

    A new, miniaturized, noninvasive instrument for rapid acetylene analysis in breath gas is described. Acetylene is a blood-soluble gas and for many years its uptake rate during rebreathing and/or nonrebreathing tests has been used to calculate the volume of lung tissue as well as the flow rate of blood through the lungs. The instrument relies on dispersive UV absorption spectroscopy as its measurement principle and is employed in an extractive (side-stream) configuration. The analyzer afforded fast (276±43 ms, 0%-90%, at 2 L min-1 flow rates), interference-free detection of acetylene, with signal-to-noise ratios in excess of 50. Comparison tests with a mass spectrometer using calibration gas samples gave an excellent correlation {[C2H2]MS=0.999. [C2H2]UV, R2=1.000}, which validated the linearity and accuracy of the UV system. A similar level of correlation between these devices also was observed during human subject C2H2 uptake tests, with both instruments sampling a common extracted gas stream {[C2H2]UV=0.940. [C2H2]MS, R2=0.998}. These results indicate that a miniature, low-cost, rugged, ultraviolet spectrometer system measuring acetylene holds promise for human breath analysis in a clinical setting.

  12. An upper limit to the acetylene abundance toward BN in the orion molecular cloud

    NASA Technical Reports Server (NTRS)

    Knacke, R. F.; Kim, Y. H.; Irvine, W. M.

    1989-01-01

    A search for the acetylene (C2H2) nu3 infrared vibration-rotation absorption near 3 microns toward the Becklin-Neugebauer source in the Orion molecular cloud is reported. The relative abundance of C2H2/CO in the quiescent gas is less than 0.003.

  13. Palladium-Catalyzed Alkynylation of Morita-Baylis-Hillman Carbonates with (Triisopropylsilyl)acetylene on Water.

    PubMed

    Li, Yangxiong; Liu, Li; Kong, Delong; Wang, Dong; Feng, Weichun; Yue, Tao; Li, Chaojun

    2015-06-19

    Direct alkynylation of Morita-Baylis-Hillman carbonates with (triisopropylsilyl)acetylene catalyzed by a Pd(OAc)2-NHC complex was developed "on water" to give the corresponding 1,4-enynes. The significant effects of water amount in the solvent on further transformations of 1,4-enynes were investigated. PMID:25989102

  14. Laboratory astrochemistry: catalytic conversion of acetylene to polycyclic aromatic hydrocarbons over SiC grains.

    PubMed

    Zhao, T Q; Li, Q; Liu, B S; Gover, R K E; Sarre, P J; Cheung, A S-C

    2016-02-01

    Catalytic conversion reactions of acetylene on a solid SiC grain surface lead to the formation of polycyclic aromatic hydrocarbons (PAHs) and are expected to mimic chemical processes in certain astrophysical environments. Gas-phase PAHs and intermediates were detected in situ using time-of-flight mass spectrometry, and their formation was confirmed using GC-MS in a separate experiment by flowing acetylene gas through a fixed-bed reactor. Activation of acetylene correlated closely with the dangling bonds on the SiC surface which interact with and break the C-C ? bond. The addition of acetylene to the resulting radical site forms a surface ring structure which desorbs from the surface. The results of HRTEM and TG indicate that soot and graphene formation on the SiC surface depends strongly on reaction temperature. We propose that PAHs as seen through the 'UIR' emission bands can be formed through decomposition of a graphene-like material, formed on the surface of SiC grains in carbon-rich circumstellar envelopes. PMID:26752613

  15. Methane emissions measured at two California landfills by OTM-10 and an acetylene tracer method

    EPA Science Inventory

    Methane emissions were measured at two municipal solid waste landfills in California using static flux chambers, an optical remote sensing approach known as vertical radial plume mapping (VRPM) using a tunable diode laser (TDL) and a novel acetylene tracer method. The tracer meth...

  16. Mechanism of tungsten-dependent acetylene hydratase from quantum chemical calculations

    PubMed Central

    Liao, Rong-Zhen; Yu, Jian-Guo; Himo, Fahmi

    2010-01-01

    Acetylene hydratase is a tungsten-dependent enzyme that catalyzes the nonredox hydration of acetylene to acetaldehyde. Density functional theory calculations are used to elucidate the reaction mechanism of this enzyme with a large model of the active site devised on the basis of the native X-ray crystal structure. Based on the calculations, we propose a new mechanism in which the acetylene substrate first displaces the W-coordinated water molecule, and then undergoes a nucleophilic attack by the water molecule assisted by an ionized Asp13 residue at the active site. This is followed by proton transfer from Asp13 to the newly formed vinyl anion intermediate. In the subsequent isomerization, Asp13 shuttles a proton from the hydroxyl group of the vinyl alcohol to the ?-carbon. Asp13 is thus a key player in the mechanism, but also W is directly involved in the reaction by binding and activating acetylene and providing electrostatic stabilization to the transition states and intermediates. Several other mechanisms are also considered but the energetic barriers are found to be very high, ruling out these possibilities. PMID:21149684

  17. TOXICITY OF ACETYLENIC ALCOHOLS TO THE FATHEAD MINNOW, PIMEPHALES PROMELAS: NARCOSIS AND PROELECTROPHILE ACTIVATION

    EPA Science Inventory

    The 96-h LC50 values for 16 acetylenic alcohols in the fathead minnow (Pimephales promelas) were determined using continuous-flow diluters. The measured LC50 values for seven tertiary propargylic alcohols agreed closely with the QSAR predictions based upon data for other organic ...

  18. 49 CFR 178.60 - Specification 8AL steel cylinders with porous fillings for acetylene.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 3 2014-10-01 2014-10-01 false Specification 8AL steel cylinders with porous...) SPECIFICATIONS FOR PACKAGINGS Specifications for Cylinders § 178.60 Specification 8AL steel cylinders with porous fillings for acetylene. (a) Type and service pressure. A DOT 8AL cylinder is a seamless steel cylinder...

  19. 49 CFR 178.60 - Specification 8AL steel cylinders with porous fillings for acetylene.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 3 2013-10-01 2013-10-01 false Specification 8AL steel cylinders with porous...) SPECIFICATIONS FOR PACKAGINGS Specifications for Cylinders § 178.60 Specification 8AL steel cylinders with porous fillings for acetylene. (a) Type and service pressure. A DOT 8AL cylinder is a seamless steel cylinder...

  20. 49 CFR 178.60 - Specification 8AL steel cylinders with porous fillings for acetylene.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 3 2011-10-01 2011-10-01 false Specification 8AL steel cylinders with porous...) SPECIFICATIONS FOR PACKAGINGS Specifications for Cylinders § 178.60 Specification 8AL steel cylinders with porous fillings for acetylene. (a) Type and service pressure. A DOT 8AL cylinder is a seamless steel cylinder...

  1. 49 CFR 178.60 - Specification 8AL steel cylinders with porous fillings for acetylene.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 49 Transportation 3 2012-10-01 2012-10-01 false Specification 8AL steel cylinders with porous...) SPECIFICATIONS FOR PACKAGINGS Specifications for Cylinders § 178.60 Specification 8AL steel cylinders with porous fillings for acetylene. (a) Type and service pressure. A DOT 8AL cylinder is a seamless steel cylinder...

  2. [1 0 0] versus [1 1 1] diamond growth from methyl radicals and/or acetylene

    NASA Astrophysics Data System (ADS)

    D'Evelyn, Mark P.; Graham, James D.; Martin, L. Robbin

    2001-11-01

    The goal of this study was to investigate the roles of methyl radicals and acetylene, either individually or together, during diamond growth by chemical vapor deposition. We have nucleated and grown micron-sized diamond particles at 800°C in a flow-tube apparatus that permits growth from only methyl radicals or acetylene in atomic hydrogen, in contrast to the complex mixture of species found in a normal reactor. Growth from methyl radicals only produced cubo-octahedral crystals with an α value ( 3×the ratio of growth rates in the [1 0 0] and [1 1 1] directions) near 1.8, indicating that the absence of acetylene is not a significant impediment in nucleating new (1 1 1) planes, in contradiction to recent modeling work. Diamond growth from pure acetylene produced octahedra ( α=3), indicating that (1 0 0) growth is much more facile than (1 1 1) growth in the absence of methyl radicals, and the (1 1 1) facets had a high concentration of contact twins. Diamond growth from acetylene plus methane produced cubo-octahedra crystals but the highly defective [1 1 1] growth persisted. We propose that at steady state the (1 1 1) growth surface has a high coverage of adsorbed hydrocarbons, rather than resembling the simple hydrogen-terminated (1 1 1)-1×1 : H structure; that steric repulsion and rearrangements play a critical role in the growth mechanism; and that desorption and etching of adsorbed hydrocarbons by atomic hydrogen is less facile than has been commonly supposed. The ratio of C 2 and C 1 gas-phase precursors should be minimized for high quality [1 1 1] epitaxy.

  3. Assaying mechanosensation*

    PubMed Central

    Chalfie, Martin; Hart, Anne C.; Rankin, Catharine H.; Goodman, Miriam B.

    2015-01-01

    C. elegans detect and respond to diverse mechanical stimuli using neuronal circuitry that has been defined by decades of work by C. elegans researchers. In this WormMethods chapter, we review and comment on the techniques currently used to assess mechanosensory response. This methods review is intended both as an introduction for those new to the field and a convenient compendium for the expert. A brief discussion of commonly used mechanosensory assays is provided, along with a discussion of the neural circuits involved, consideration of critical protocol details, and references to the primary literature. PMID:25093996

  4. In situ spectroscopic characterization of Ni1-xZnx/ZnO catalysts and their selectivity for acetylene semihydrogenation in excess ethylene

    SciTech Connect

    Spanjers, Charles S.; Sim, Richard S.; Sturgis, Nicholas P.; Kabius, Bernd; Rioux, Robert M.

    2015-10-30

    The structures of ZnO-supported Ni catalysts were explored with in situ X-ray absorption spectroscopy, temperature-programmed reduction, X-ray diffraction, high-resolution transmission electron microscopy (HRTEM), scanning transmission electron microscopy, and electron energy loss spectroscopy. Calcination of nickel nitrate on a nanoparticulate ZnO support at 450 °C results in the formation of Zn-doped NiO (ca. N₀̣̣₈₅ Zn₀̣̣₁₅O) nanoparticles with the rock salt crystal structure. Subsequent in situ reduction monitored by X-ray absorption near-edge structure (XANES) at the Ni K edge reveals a direct transformation of the Zn-doped NiO nanoparticles to a face-centered cubic alloy, Ni1-xZnx, at ~400 °C with x increasing with increasing temperature. Both in situ XANES and ex situ HRTEM provide evidence for intermetallic β₁-NiZn formation at ~550 °C. In comparison to a Ni/SiO₂ catalyst, Ni/ZnO necessitates a higher temperature for the reduction of NiII to Ni⁰, which highlights the strong interaction between Ni and the ZnO support. The catalytic activity for acetylene removal from an ethylene feed stream is decreased by a factor of 20 on Ni/ZnO in comparison to Ni/SiO₂. The decrease in catalytic activity of Ni/ZnO is accompanied by a reduced absolute selectivity to ethylene. H–D exchange measurements demonstrate a reduced ability of Ni/ZnO to dissociate hydrogen in comparison to Ni/SiO₂.These results of the catalytic experiments suggest that the catalytic properties are controlled, in part, by the zinc oxide support and stress the importance of reporting absolute ethylene selectivity for the catalytic semihydrogenation of acetylene in excess ethylene.

  5. Angiogenesis Assays.

    PubMed

    Nambiar, Dhanya K; Kujur, Praveen K; Singh, Rana P

    2016-01-01

    Neoangiogenesis constitutes one of the first steps of tumor progression beyond a critical size of tumor growth, which supplies a dormant mass of cancerous cells with the required nutrient supply and gaseous exchange through blood vessels essentially needed for their sustained and aggressive growth. In order to understand any biological process, it becomes imperative that we use models, which could mimic the actual biological system as closely as possible. Hence, finding the most appropriate model is always a vital part of any experimental design. Angiogenesis research has also been much affected due to lack of simple, reliable, and relevant models which could be easily quantitated. The angiogenesis models have been used extensively for studying the action of various molecules for agonist or antagonistic behaviour and associated mechanisms. Here, we have described two protocols or models which have been popularly utilized for studying angiogenic parameters. Rat aortic ring assay tends to bridge the gap between in vitro and in vivo models. The chorioallantoic membrane (CAM) assay is one of the most utilized in vivo model system for angiogenesis-related studies. The CAM is highly vascularized tissue of the avian embryo and serves as a good model to study the effects of various test compounds on neoangiogenesis. PMID:26608294

  6. Infrared spectra of acetylene dimers and acetylene-nitrogen: (DCCD) 2, H-bonded DCCD-HCCH, and DCCD-NN in the 4.1 μm region

    NASA Astrophysics Data System (ADS)

    Lauzin, Clément; Moazzen-Ahmadi, N.; McKellar, A. R. W.

    2011-09-01

    Infrared spectra of the weakly-bound T-shaped acetylene dimers DCCD-DCCD and DCCD-HCCH are studied in the region of the DCCD ν3 fundamental (˜2440 cm -1) using a pulsed supersonic slit-jet expansion and a tunable diode laser probe. The K a = 0 ← 1 and 1 ← 0 subbands, corresponding to the vibration of the DCCD monomer at the "top" of the T, are analyzed. Compared to the analogous spectrum of HCCH-HCCH, the present results are much less perturbed. The tunneling splitting for (DCCD) 2 in the excited state is determined to be 141 MHz, a big reduction from the previously determined ground state value of 424 MHz. The dimer A rotational constants show a large apparent increase upon vibrational excitation, and we discuss whether this increase is real. The linear DCCD-NN complex is also observed as an impurity in the spectrum, and it too is found to be unperturbed, in contrast with HCCH-NN.

  7. ESI-MS, DFT, and synthetic studies on the H(2)-mediated coupling of acetylene: insertion of C=X bonds into rhodacyclopentadienes and Brnsted acid cocatalyzed hydrogenolysis of organorhodium intermediates.

    PubMed

    Williams, Vanessa M; Kong, Jong Rock; Ko, Byoung Joon; Mantri, Yogita; Brodbelt, Jennifer S; Baik, Mu-Hyun; Krische, Michael J

    2009-11-11

    The catalytic mechanism of the hydrogen-mediated coupling of acetylene to carbonyl compounds and imines has been examined using three techniques: (a) ESI-MS and ESI-CAD-MS analyses, (b) computational modeling, and (c) experiments wherein putative reactive intermediates are diverted to alternate reaction products. ESI-MS analysis of reaction mixtures from the hydrogen-mediated reductive coupling of acetylene to alpha-ketoesters or N-benzenesulfonyl aldimines corroborate a catalytic mechanism involving C horizontal lineX (X = O, NSO(2)Ph) insertion into a cationic rhodacyclopentadiene obtained by way of acetylene oxidative dimerization with subsequent Brnsted acid cocatalyzed hydrogenolysis of the resulting oxa- or azarhodacycloheptadiene. Hydrogenation of 1,6-diynes in the presence of alpha-ketoesters provides analogous coupling products. ESI mass spectrometric analysis again corroborates a catalytic mechanism involving carbonyl insertion into a cationic rhodacyclopentadiene. For all ESI-MS experiments, the structural assignments of ions are supported by multistage collisional activated dissociation (CAD) analyses. Further support for the proposed catalytic mechanism derives from experiments aimed at the interception of putative reactive intermediates and their diversion to alternate reaction products. For example, rhodium-catalyzed coupling of acetylene to an aldehyde in the absence of hydrogen or Brnsted acid cocatalyst provides the corresponding (Z)-butadienyl ketone, which arises from beta-hydride elimination of the proposed oxarhodacycloheptadiene intermediate, as corroborated by isotopic labeling. Additionally, the putative rhodacyclopentadiene intermediate obtained from the oxidative coupling of acetylene is diverted to the product of reductive [2 + 2 + 2] cycloaddition when N-p-toluenesulfonyl-dehydroalanine ethyl ester is used as the coupling partner. The mechanism of this transformation also is corroborated by isotopic labeling. Computer model studies based on density functional theory (DFT) support the proposed mechanism and identify Brnsted acid cocatalyst assisted hydrogenolysis to be the most difficult step. The collective studies provide new insight into the reactivity of cationic rhodacyclopentadienes, which should facilitate the design of related rhodium-catalyzed C-C couplings. PMID:19845357

  8. Nitrogen-Fixing (Acetylene Redution) Activity and Population of Aerobic Heterotrophic Nitrogen-Fixing Bacteria Associated with Wetland Rice

    PubMed Central

    Watanabe, Iwao; Barraquio, Wilfredo L.; De Guzman, Marcelino R.; Cabrera, Delfin A.

    1979-01-01

    Nitrogen-fixing activity associated with different wetland rice varieties was measured at various growth stages by an in situ acetylene reduction method after the activities of blue-green algae (cyanobacteria) in the flood water and on the lower portion of the rice stem were eliminated. Nitrogen-fixing activities associated with rice varieties differed with plant growth stages. The activities increased with plant age, and the maximum was about at heading stage. The nitrogen fixed during the whole cropping period was estimated at 5.9 kg of N per ha for variety IR26 (7 days) and 4.8 kg of N per ha for variety IR36 (95 days). The population of aerobic heterotrophic N2-fixing bacteria associated with rice roots and stems was determined by the most-probable-number method, using semisolid glucose-yeast extract and semisolid malate-yeast extract media. The addition of yeast extract to the glucose medium increased the number and activity of aerobic heterotrophic N2-fixing bacteria. The glucose-yeast extract medium gave higher counts of aerobic N2-fixing bacteria associated with rice roots than did the malate-yeast extract medium, on which Spirillum-like bacteria were usually observed. The lower portion of the rice stem was also inhabited by N2-fixing bacteria and was an active site of N2 fixation. PMID:16345379

  9. Nonstationary coherent optical effects caused by pulse propagation through acetylene-filled hollow-core photonic-crystal fibers

    NASA Astrophysics Data System (ADS)

    Ocegueda, M.; Hernandez, E.; Stepanov, S.; Agruzov, P.; Shamray, A.

    2014-06-01

    Experimental observations of nonstationary coherent optical phenomena, i.e., optical nutation, free induction, and photon echo, in the acetylene (12C2H2) filled hollow-core photonic-crystal fiber (PCF) are reported. The presented results were obtained for the acetylene vibration-rotational transition P9 at wavelength 1530.37 nm at room temperature under a gas pressure of <0.5 Torr. An all-fiber pumped-through cell based on the commercial 2.6-m-long PCF with a 10-?m hollow-core diameter was used. The characteristic relaxation time T2 during which the optical coherent effects were typically observed in our experiments was estimated to be ?8 ns. This time is governed by the limited time of the acetylene molecules' presence inside the effective PCF modal area and by intermolecule collisions. An accelerated attenuation of the optical nutation oscillations is explained by a random orientation of acetylene molecules.

  10. A potential plant-derived antifungal acetylenic acid mediates its activity by interfering with fatty acid homeostasis

    Technology Transfer Automated Retrieval System (TEKTRAN)

    6-Nonadecynoic acid (6-NDA), a plant-derived acetylenic acid, exhibits strong inhibitory activity against the human fungal pathogens Candida albicans, Aspergillus fumigatus, and Trichophyton mentagrophytes. In the present study, transcriptional profiling coupled with mutant and biochemical analyses...

  11. The photolysis of NH3 in the presence of substituted acetylenes - A possible source of oligomers and HCN on Jupiter

    NASA Technical Reports Server (NTRS)

    Ferris, James P.; Jacobson, Richard R.; Guillemin, Jean C.

    1992-01-01

    An NMR spectral study is presently conducted of NH3 photolysis in the presence of substituted acetylenes with NMR spectra and gas chromatography. Quantum yields and percentage conversions to products are reported. It is shown that acetylenic hydrocarbons generated during methane photolysis in Jupiter's stratosphere can react with radicals formed by NH3 photolysis to yield nonvolatile, yellow-brown polymers, alkylnitriles, and in due course, HCN, as observed on Jupiter.

  12. Control of the nucleation and quality of graphene grown by low-pressure chemical vapor deposition with acetylene

    NASA Astrophysics Data System (ADS)

    Yang, Meng; Sasaki, Shinichirou; Suzuki, Ken; Miura, Hideo

    2016-03-01

    Although many studies have reported the chemical vapor deposition (CVD) growth of large-area monolayer graphene from methane, synthesis of graphene using acetylene as the source gas has not been fully explored. In this study, the low-pressure CVD (LPCVD) growth of graphene from acetylene was systematically investigated. We succeeded in regulating the domain size, defects density, layer number and the sheet resistance of graphene by changing the acetylene flow rates. Scanning electron microscopy and Raman spectroscopy were employed to confirm the layer number, uniformity and quality of the graphene films. It is found that a low flow rate of acetylene (0.28 sccm) is required to form high-quality monolayer graphene in our system. On the other hand, the high acetylene flow rate (7 sccm) will induce the growth of the bilayer graphene domains with high defects density. On the basis of selected area electron diffraction (SAED) pattern, the as-grown monolayer graphene domains were analyzed to be polycrystal. We also discussed the relation between the sheet resistacne and defects density in graphene. Our results provide great insights into the understanding of the CVD growth of monolayer and bilayer graphene from acetylene.

  13. Characterization of the Minimum Energy Paths and Energetics for the reaction of Vinylidene with Acetylene

    NASA Technical Reports Server (NTRS)

    Walch, Stephen P.; Taylor, Peter R.

    1995-01-01

    The reaction of vinylidene (CH2C) with acetylene may be an initiating reaction in soot formation. We report minimum energy paths and accurate energetics for a pathway leading to vinylacetylene and for a number of isomers Of C4H4. The calculations use complete active space self-consistent field (CASSCF) derivative methods to characterize the stationary points and internally contacted configuration interaction (ICCI) and/or coupled cluster singles and doubles with a perturbational estimate of triple excitations (CCSD(T)) to determine the energetics. We find an entrance channel barrier of about 5 kcal/mol for the addition of vinylidene to acetylene, but no barriers above reactants for the reaction pathway leading to vinylacetylene.

  14. Modeling of acetylene pyrolysis under steel vacuum carburizing conditions in a tubular flow reactor.

    PubMed

    Khan, Rafi Ullah; Bajohr, Siegfried; Graf, Frank; Reimert, Rainer

    2007-01-01

    In the present work, the pyrolysis of acetylene was studied under steel vacuum carburizing conditions in a tubular flow reactor. The pyrolysis temperature ranged from 650 degrees C to 1050 degrees C. The partial pressure of acetylene in the feed mixture was 10 and 20 mbar, respectively, while the rest of the mixture consisted of nitrogen. The total pressure of the mixture was 1.6 bar. A kinetic mechanism which consists of seven species and nine reactions has been used in the commercial computational fluid dynamics (CFD) software Fluent. The species transport and reaction model of Fluent was used in the simulations. A comparison of simulated and experimental results is presented in this paper. PMID:17851387

  15. A detailed kinetic modeling study of aromatics formation in laminar premixed acetylene and ethylene flames

    SciTech Connect

    Wang, H.; Frenklach, M.

    1997-07-01

    A computational study was performed for the formation and growth of polycyclic aromatic hydrocarbons (PAHs) in laminar premixed acetylene and ethylene flames. A new detailed reaction mechanism describing fuel pyrolysis and oxidation, benzene formation, and PAH mass growth and oxidation is presented and critically tested. It is shown that the reaction model predicts reasonably well the concentration profiles of major and intermediate species and aromatic molecules in a number of acetylene and ethylene flames reported in the literature. It is demonstrated that reactions of n-C{sub 4}H{sub x} + C{sub 2}H{sub 2} leading to the formation of one-ring aromatics are as important as the propargyl recombination, and hence must be included in kinetic modeling of PAH formation in hydrocarbon flames. It is further demonstrated that the mass growth of PAHs can be accounted for by the previously proposed H-abstraction-C{sub 2}H{sub 2}-addiction mechanism.

  16. Isotope effect in normal-to-local transition of acetylene bending modes

    SciTech Connect

    Ma, Jianyi; Xu, Dingguo; Guo, Hua; Tyng, Vivian; Kellman, Michael E.

    2012-01-01

    The normal-to-local transition for the bending modes of acetylene is considered a prelude to its isomerization to vinylidene. Here, such a transition in fully deuterated acetylene is investigated using a full-dimensional quantum model. It is found that the local benders emerge at much lower energies and bending quantum numbers than in the hydrogen isotopomer HCCH. This is accompanied by a transition to a second kind of bending mode called counter-rotator, again at lower energies and quantum numbers than in HCCH. These transitions are also investigated using bifurcation analysis of two empirical spectroscopic fitting Hamiltonians for pure bending modes, which helps to understand the origin of the transitions semiclassically as branchings or bifurcations out of the trans and normal bend modes when the latter become dynamically unstable. The results of the quantum model and the empirical bifurcation analysis are in very good agreement.

  17. The abundances of ethane and acetylene in the atmospheres of Jupiter and Saturn

    NASA Astrophysics Data System (ADS)

    Noll, K. S.; Knacke, R. F.; Tokunaga, A. T.; Lacy, J. H.; Beck, S.; Serabyn, E.

    1986-03-01

    Infrared spectra near 780 cm-1 of Jupiter and Saturn have been obtained to determine the stratospheric abundances of ethane (C2H6) and acetylene (C2H2). Atmospheric models using Voyager thermal profiles and density profiles with constant mixing ratios result in the mixing ratios, X(C2H2) = 1.0(0.3)10-7 and X(C2H6) = 5.5(1.5)10-6 for Jupiter. The results for Saturn are X(C2H2) = 3.0(1.0)10-7 and X(C2H6) = 7.0(1.5)10-6. The ratio of ethane to acetylene, n[C2H6]/n[C2H2], is found to be insensitive to model atmosphere assumptions. The ratio is 5531 for Jupiter and 2312 for Saturn from models with uniform mixing ratios.

  18. Burn due to misuse of an acetylene gas burner: a case report.

    PubMed

    Shimada, K; Aoki, Y; Ide, Y; Ishikura, N; Kawakami, S

    1999-11-01

    A rare case of deep penetrating burn injury caused by misuse of a high-pressure acetylene burner is reported. A 35 year old man was admitted with second and third degree burns involving the right arm cubital area and a subcutaneous burn on his right arm caused by a high-pressure acetylene gas flame. Early surgical debridement and secondary skin grafting using a preserved subcutaneous vascular network skin graft (PSVNSG) proved effective in this patient. Skin contracture was prevented and function was recovered. The basis of PSVNSG is that the vascular system existing in the graft is used as a permanent vascular system without degeneration. This case shows that, in this kind of burn injury, subcutaneous tissue damage should be suspected and that it is important to perform surgical debridement early after admission. PMID:10563697

  19. Isotope effect in normal-to-local transition of acetylene bending modes

    DOE PAGESBeta

    Ma, Jianyi; Xu, Dingguo; Guo, Hua; Tyng, Vivian; Kellman, Michael E.

    2012-01-01

    The normal-to-local transition for the bending modes of acetylene is considered a prelude to its isomerization to vinylidene. Here, such a transition in fully deuterated acetylene is investigated using a full-dimensional quantum model. It is found that the local benders emerge at much lower energies and bending quantum numbers than in the hydrogen isotopomer HCCH. This is accompanied by a transition to a second kind of bending mode called counter-rotator, again at lower energies and quantum numbers than in HCCH. These transitions are also investigated using bifurcation analysis of two empirical spectroscopic fitting Hamiltonians for pure bending modes, which helpsmore » to understand the origin of the transitions semiclassically as branchings or bifurcations out of the trans and normal bend modes when the latter become dynamically unstable. The results of the quantum model and the empirical bifurcation analysis are in very good agreement.« less

  20. A matrix isolation and ab initio study of the hydrogen bonded complexes of acetylene with pyridine

    NASA Astrophysics Data System (ADS)

    Sundararajan, K.; Sankaran, K.; Viswanathan, K. S.

    2005-01-01

    Hydrogen bonded complexes of acetylene and pyridine were studied using matrix isolation spectroscopy and ab initio computations. The adduct was formed by depositing acetylene and pyridine in an argon matrix and a 1:1 C 2H 2-NC 5H 5 complex was identified using infrared spectroscopy. Formation of the adduct was evidenced from the shifts in the vibrational frequencies of C 2H 2 in the complex compared with that of free C 2H 2. The molecular structure, vibrational frequencies and stabilization energies of the complex were computed at the HF/6-31++G** and B3LYP/6-31++G** levels. We located one minimum on the potential surface, corresponding to a strongly bound C 2H 2-NC 5H 5 n-σ complex. Both experimental and computational data indicated that C 2H 2 acts as a proton donor and C 5H 5N as a proton acceptor.

  1. Unexpected chemistry from the reaction of naphthyl and acetylene at combustion-like temperatures.

    PubMed

    Parker, Dorian S N; Kaiser, Ralf I; Bandyopadhyay, Biswajit; Kostko, Oleg; Troy, Tyler P; Ahmed, Musahid

    2015-04-27

    The hydrogen abstraction/acetylene addition (HACA) mechanism has long been viewed as a key route to aromatic ring growth of polycyclic aromatic hydrocarbons (PAHs) in combustion systems. However, doubt has been drawn on the ubiquity of the mechanism by recent electronic structure calculations which predict that the HACA mechanism starting from the naphthyl radical preferentially forms acenaphthylene, thereby blocking cyclization to a third six-membered ring. Here, by probing the products formed in the reaction of 1- and 2-naphthyl radicals in excess acetylene under combustion-like conditions with the help of photoionization mass spectrometry, we provide experimental evidence that this reaction produces 1- and 2-ethynylnaphthalenes (C12 H8 ), acenaphthylene (C12 H8 ) and diethynylnaphthalenes (C14 H8 ). Importantly, neither phenanthrene nor anthracene (C14 H10 ) was found, which indicates that the HACA mechanism does not lead to cyclization of the third aromatic ring as expected but rather undergoes ethynyl substitution reactions instead. PMID:25752687

  2. Growth of few-wall carbon nanotubes with narrow diameter distribution over Fe-Mo-MgO catalyst by methane/acetylene catalytic decomposition.

    PubMed

    Labunov, Vladimir A; Basaev, Alexander S; Shulitski, Boris G; Shaman, Yuriy P; Komissarov, Ivan; Prudnikava, Alena L; Tay, Beng Kang; Shakerzadeh, Maziar

    2012-01-01

    Few-wall carbon nanotubes were synthesized by methane/acetylene decomposition over bimetallic Fe-Mo catalyst with MgO (1:8:40) support at the temperature of 900°C. No calcinations and reduction pretreatments were applied to the catalytic powder. The transmission electron microscopy investigation showed that the synthesized carbon nanotubes [CNTs] have high purity and narrow diameter distribution. Raman spectrum showed that the ratio of G to D band line intensities of IG/ID is approximately 10, and the peaks in the low frequency range were attributed to the radial breathing mode corresponding to the nanotubes of small diameters. Thermogravimetric analysis data indicated no amorphous carbon phases. Experiments conducted at higher gas pressures showed the increase of CNT yield up to 83%. Mössbauer spectroscopy, magnetization measurements, X-ray diffraction, high-resolution transmission electron microscopy, and electron diffraction were employed to evaluate the nature of catalyst particles. PMID:22300375

  3. IUPAC-NIST Solubility Data Series. 97. Solubility of Higher Acetylenes and Triple Bonded Derivatives

    NASA Astrophysics Data System (ADS)

    Skrzecz, Adam

    2013-03-01

    Solubility of Ethyne in Liquids was published in 2001 as Vol. 76 of the IUPAC-NIST Solubility Data Series. The current work extends the coverage to the solubility in liquids of higher gaseous and liquid acetylenes and to derivatives that contain a triple carbon-carbon bond. Predictive methods for estimating solubilities in water are summarised and usually give values to within an order of magnitude. The literature has been surveyed to the end of 2010.

  4. Theoretical study of the C-H bond dissociation energy of acetylene

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

    The authors present a theoretical study of the convergence of the C-H bond dissociation energy (D sub o) of acetylene with respect to both the one- and n-particle spaces. Their best estimate for D sub o of 130.1 plus or minus 1.0 kcal/mole is slightly below previous theoretical estimates, but substantially above the value determined using Stark anticrossing spectroscopy that is asserted to be an upper bound.

  5. Effect of acetylene and ammonia as reburn fuel additions to methane in nitric oxide reburning

    SciTech Connect

    Kumpaty, S.K.; Nokku, V.P.; Subramanian, K.

    1996-12-31

    Presented in this paper are the computational results of NO reburning with (a) a combination of methane and acetylene and (b) a combination of methane and ammonia. An updated reaction mechanism that was more comprehensive in terms of predicting the ammonia and isocyanic acid oxidation chemistry was employed to run the CKINTERP program. Using the binary file created by executing the above program and the input stoichiometric ratio conditions, the CHEMKIN package predicted the exit concentrations of various species involved in NO reburning.

  6. Pulsed erbium fiber laser with an acetylene-filled photonic crystal fiber for saturable absorption.

    PubMed

    Marty, Patrick Thomas; Morel, Jacques; Feurer, Thomas

    2011-09-15

    We investigate the dynamics of an erbium-doped fiber ring laser that is equipped with an intracavity hollow core photonic crystal fiber gas cell. The cell is filled with acetylene as a saturable absorber. We observe cw operation at low pressures, Q switching at intermediate pressure levels, and mode locking at high pressures applied. Moreover, we show that the transition from the cw to the pulsed mode may be exploited for sensitive gas detection. PMID:21931393

  7. anti-Diradical Formation in 1,3-Dipolar Cycloadditions of Nitrile Oxides to Acetylenes.

    PubMed

    Haberhauer, Gebhard; Gleiter, Rolf; Woitschetzki, Sascha

    2015-12-18

    By means of high level quantum chemical calculations (B2PLYPD and CCSD(T)), the mechanisms of the reaction of nitrile oxides with alkenes and alkynes were investigated. We were able to show that in the case of alkenes, regardless of the chosen substituents, the concerted mechanism is always energetically favored as compared to a two-step process, which runs through an anti-diradical species. In the case of alkynes, the concerted mechanism is favored only for the reaction of alkyl-substituted acetylenes. For aryl-substituted acetylenes, the activation barrier toward the anti-diradical is equal to or lower than the activation barrier of the concerted reaction. This reversal of the reaction paths is not only limited to nitrile oxides as dipolarophiles. Conditions favoring the anti-diradical path are the presence of a triple bond in both the 1,3-dipole and the dipolarophile and additionally an aryl substituent attached to the alkyne. The featured energy relationships between the reaction paths are able to explain the experimentally observed byproducts of the reaction of nitrile oxides with arylacetylenes. The discovered differences for the preferred reaction path of 1,3-dipolar cycloadditions to acetylenes should be of considerable interest to a broader field of chemists. PMID:26560849

  8. Functionalized acetylenic compounds via 1-bromo- 1,2-dienes and organocopper reagents

    SciTech Connect

    Caporusso, A.M.; Iodice, A.; Lardicci, L.; Salvadori, P.

    1995-12-31

    The acetylenic unity provides a convenient handle which may be converted into a variety of functionalities. In this frame, the authors developed a general and efficient method for the synthesis of chiral 1-alkynes, with a tertiary or a quaternary asymmetric carbon atom in the {alpha} position to the triple bond, by stereoselective cross-coupling of bromocuprates [(RCuBr)MaBr LiBr R=Alkyl, aryl] with optically active 1-bromo-1,2-dienes. This method provides terminal acetylenes which can easily converted into biologically active compounds, such as the antiphlogistic (+)-Ibuprofen. The authors report here that this procedure can be extended to the preparation of a large variety of functionalized acetylenic systems. In fact, bromocuprates, obtained from protected functionalized Grignard reagents and LiCuBr{sub 2}, react with bromoallenes affording the 1-alkynes with high yields, regio- and stereoselectivity. Compounds are also conveniently obtained from cyanocuprates, prepared by reaction of functionalized zinc reagents with the cuprous cyanide/lithium chloride complex; the organozinc derivatives are directly obtained from organic halides and highly activated zinc powder, prepared by metal vapour technique.

  9. New insights into the anion formation mechanisms in dusty acetylene discharges

    NASA Astrophysics Data System (ADS)

    Mao, Ming; Benedikt, Jan; Consoli, Angelo; Bogaerts, Annemie

    2008-10-01

    Dust (or nanoparticle) formation is a well-known phenomenon occurring in reactive gas plasmas, such as silane or acetylene. Under some conditions, the dust formation is considered to be harmful, whereas for other applications, it turns out to be beneficial. In this presentation, the initial mechanisms of nanoparticle formation and growth in radiofrequency (RF) acetylene (C2H2) plasmas are investigated by means of a comprehensive self-consistent one-dimensional (1D) fluid model. Based on the comparison of our calculation results with available experimental data for acetylene plasmas in the literature, some new mechanisms for negative ion formation and growth are proposed. Possible routes are considered for the formation of larger (linear and branched) hydrocarbons C2nH2 (n=3-5), which contribute to the generation of C2nH^-anions (n=3-5) due to dissociative electron attachment. Moreover, beside the C2nH^- ions, also the vinylidene anion (H2CC^-) and higher C2nH2^- anions (n=2-4) are found to be important plasma species. This project was supported financially by the Fund for Scientific Research (FWO) Flanders (Project G. 0068.07), the Interuniversity Attraction Poles Programme of the Belgian State (Belgian Science Policy; Project P6/42) and the CALCUA computing facilities of the University of Antwerp.

  10. Soot formation in pyrolysis of acetylene, allene and 1,3-butadiene

    NASA Technical Reports Server (NTRS)

    Frenklach, M.; Durgaprasad, M. B.; Matula, R. A.; Taki, S.

    1983-01-01

    The formation of soot behind reflected shock waves in argon-diluted mixtures of acetylene, allene, and 1,3-butadiene was investigated by monitoring the attenuation of a laser beam in both the visible (632.8 nm) and the infrared (3.39 microns) regions of the spectrum. The experiments utilized temperatures ranging from 1500-3100 K, reflected shock pressures of 0.3-7.0 bar, and total carbon atom concentrations of 2-20 x 10 to the 17th atoms/cu cm. A bell-shaped dependence of soot yield on temperature was observed during the pyrolysis of all three compounds, which was similar to that previously found for toluene. For acetylene, the decrese in total pressure was found to shift the soot bell to higher temperatures with a significant increase in the maximum soot yield. A computer simulation for acetylene pyrolysis suggested that the reactions between C2H3, C4H3, and C4H4 may be those which lead to the formation of aromatic structures. In addition, it was found that soot is formed much faster and in much larger quantities from allene than from 1,3-butadiene.

  11. Exploring the Active Site of the Tungsten, Iron-Sulfur Enzyme Acetylene Hydratase?

    PubMed Central

    tenBrink, Felix; Schink, Bernhard; Kroneck, Peter M. H.

    2011-01-01

    The soluble tungsten, iron-sulfur enzyme acetylene hydratase (AH) from mesophilic Pelobacter acetylenicus is a member of the dimethyl sulfoxide (DMSO) reductase family. It stands out from its class as it catalyzes a nonredox reaction, the addition of H2O to acetylene (HC?CH) to form acetaldehyde (CH3CHO). Caught in its active W(IV) state, the high-resolution three-dimensional structure of AH offers an excellent starting point to tackle its unique chemistry and to identify catalytic amino acid residues within the active site cavity: Asp13 close to W(IV) coordinated to two molybdopterin-guanosine-dinucleotide ligands, Lys48 which couples the [4Fe-4S] cluster to the W site, and Ile142 as part of a hydrophobic ring at the end of the substrate access channel designed to accommodate the substrate acetylene. A protocol was developed to express AH in Escherichia coli and to produce active-site variants which were characterized with regard to activity and occupancy of the tungsten and iron-sulfur centers. By this means, fusion of the N-terminal chaperone binding site of the E. coli nitrate reductase NarG to the AH gene improved the yield and activity of AH and its variants significantly. Results from site-directed mutagenesis of three key residues, Asp13, Lys48, and Ile142, document their important role in catalysis of this unusual tungsten enzyme. PMID:21193613

  12. Toward spectroscopically accurate global ab initio potential energy surface for the acetylene-vinylidene isomerization

    SciTech Connect

    Han, Huixian; Li, Anyang; Guo, Hua

    2014-12-28

    A new full-dimensional global potential energy surface (PES) for the acetylene-vinylidene isomerization on the ground (S{sub 0}) electronic state has been constructed by fitting ∼37 000 high-level ab initio points using the permutation invariant polynomial-neural network method with a root mean square error of 9.54 cm{sup −1}. The geometries and harmonic vibrational frequencies of acetylene, vinylidene, and all other stationary points (two distinct transition states and one secondary minimum in between) have been determined on this PES. Furthermore, acetylene vibrational energy levels have been calculated using the Lanczos algorithm with an exact (J = 0) Hamiltonian. The vibrational energies up to 12 700 cm{sup −1} above the zero-point energy are in excellent agreement with the experimentally derived effective Hamiltonians, suggesting that the PES is approaching spectroscopic accuracy. In addition, analyses of the wavefunctions confirm the experimentally observed emergence of the local bending and counter-rotational modes in the highly excited bending vibrational states. The reproduction of the experimentally derived effective Hamiltonians for highly excited bending states signals the coming of age for the ab initio based PES, which can now be trusted for studying the isomerization reaction.

  13. Acetylene from the co-pyrolysis of biomass and waste tires or coal in the H{sub 2}/Ar plasma

    SciTech Connect

    Bao, W.; Cao, Q.; Lv, Y.; Chang, L.

    2008-07-01

    Acetylene from carbon-containing materials via plasma pyrolysis is not only simple but also environmentally friendly. In this article, the acetylene produced from co-pyrolyzing biomass with waste tire or coal under the conditions of H{sub 2}/Ar DC arc plasma jet was investigated. The experimental results showed that the co-pyrolysis of mixture with biomass and waste tire or coal can improve largely the acetylene relative volume fraction (RVF) in gaseous products and the corresponding yield of acetylene. The change trends for the acetylene yield of plasma pyrolysis from mixture with raw sample properties were the same as relevant RVF. But the yield change trend with feeding rate is different from its RVF. The effects of the feeding rate of raw materials and the electric current of plasmatron on acetylene formation are also discussed.

  14. Kinetics of tetrachloroethylene-reductive dechlorination catalyzed by vitamin B{sub 12}

    SciTech Connect

    Burris, D.R.; Deng, B.; Buck, L.E.; Hatfield, K.

    1998-09-01

    Reductive dechlorination kinetics of tetrachloroethylene (PCE) to ethylene catalyzed by vitamin B{sub 12} using Ti[III] citrate as the bulk reductant was examined in a vapor-water batch system. A kinetic model incorporating substrate-B{sub 12} electron-transfer complex formation and subsequent product release was developed. The model also accounted for the primary reductive dechlorination pathways (hydrogenolysis and reductive {beta} elimination) and vapor/water-phase partitioning. Reaction rate constants were sequentially determined by fitting the model to experimental kinetic data while moving upward through consecutive reaction pathways. The release of product from the complex was found to be second order with respect to substrate concentration for both PCE and acetylene; all other substrates appeared to release by first order. Reductive {beta} elimination was found to be a significant reaction pathway for trichloroethylene (TCE), and chloroacetylene was observed as a reactive intermediate. Acetylene production appears to be primarily due to the reduction of chloroacetylene derived from TCE. The reduction of cis-dichloroethylene (cis-DCE), the primary DCE isomer formed, was extremely slow, leading to a significant buildup of cis-DCE. The kinetics of acetylene and vinyl chloride reduction appeared to be limited by the formation of relatively stable substrate-B{sub 12} complexes. The relatively simple model examined appears to adequately represent the main features of the experimental data.

  15. Hydrogen-Bonded Complexes of Phenylacetylene-Acetylene: Who is the Proton Donor?

    PubMed

    Verma, Kanupriya; Dave, Kapil; Viswanathan, K S

    2015-12-24

    Hydrogen-bonded complexes of C2H2 and phenylacetylene (PhAc) were studied using matrix isolation infrared spectroscopy and quantum chemical computations. Both C2H2 and PhAc, being potential proton donors, the question arises as to which of the two species would be the proton donor in the PhAc-C2H2 complex; a question that this work primarily addresses. The molecular structures, vibrational frequencies, and interaction energies of the PhAc-C2H2 complexes were calculated at the M06-2X and MP2 levels of theory, employing both 6-311++G(d,p) and aug-cc-pVDZ basis sets. At the M06-2X/aug-cc-pVDZ level, two nearly isoenergetic complexes (BSSE corrected) were indicated to be the global minima; one a C-H? complex, where C2H2 served as a proton donor to the phenyl ?-system in PhAc, and the other a C-H? complex, where C2H2 served as a proton donor to the acetylene ?-system in PhAc. Of the two, only the second complex was identified in the matrix, evidenced by a characteristic large shift in the ?C-H stretch of C2H2. Experiments were also performed using PhAc deuterated at the acetylene hydrogen (PhAcD) to study the isotopic effects on the vibrational spectra of complexes. The isotopic studies further confirmed the structure of the complex trapped in the matrix, thereby presenting unambiguous evidence that C2H2 served as the proton donor to the acetylene ?-system of PhAc. The theory of atoms-in-molecules (AIM), energy decomposition (EDA), and natural bond orbital (NBO) analysis were performed to understand the nature of the interactions involved in the complexes. PMID:26643730

  16. Soot Formation in Laminar Acetylene/Air Diffusion Flames at Atmospheric Pressure. Appendix H

    NASA Technical Reports Server (NTRS)

    Xu, F.; Faeth, G. M.; Yuan, Z.-G. (Technical Monitor); Urban, D. L. (Technical Monitor); Yuan, Z.-G. (Technical Monitor)

    2001-01-01

    The flame structure and soot-formation (soot nucleation and growth) properties of axisymmetric laminar coflowing jet diffusion flames were studied experimentally. Test conditions involved acetylene-nitrogen jets burning in coflowing air at atmospheric pressure. Measurements were limited to the axes of the flames and included soot concentrations, soot temperatures, soot structure, major gas species concentrations, radical species (H, OH, and O) concentrations, and gas velocities. The results show that as distance increases along the axes of the flames, detectable soot formation begins when significant H concentrations are present, and ends when acetylene concentrations become small. Species potentially associated with soot oxidation-O2, CO2, H2O, O, and OH-are present throughout the soot-formation region so that soot formation and oxidation proceed at the same time. Strong rates of soot growth compared to soot nucleation early in the soot-formation process, combined with increased rates of soot nucleation and oxidation as soot formation proceeds, causes primary soot particle diameters to reach a maximum relatively early in the soot-formation process. Aggregation of primary soot particles proceeds, however, until the final stages of soot oxidation. Present measurements of soot growth (corrected for soot oxidation) in laminar diffusion flames were consistent with earlier measurements of soot growth in laminar premixed flames and exhibited encouraging agreement with existing hydrogen-abstraction/carbon-addition (HACA) soot growth mechanisms in the literature that were developed based on measurements within laminar premixed flames. Measured primary soot particle nucleation rates in the present laminar diffusion flames also were consistent with corresponding rates measured in laminar premixed flames and yielded a crude correlation in terms of acetylene and H concentrations and the temperature.

  17. Soot Formation in Laminar Acetylene/Air Diffusion Flames at Atmospheric Pressure. Appendix C

    NASA Technical Reports Server (NTRS)

    Xu, F.; Faeth, G. M.; Urban, D. L. (Technical Monitor); Yuan, Z.-G. (Technical Monitor)

    2000-01-01

    The flame structure and soot-formation (soot nucleation and growth) properties of axisymmetric laminar coflowing jet diffusion flames were studied experimentally. Test conditions involved acetylene-nitrogen jets burning in coflowing air at atmospheric pressure. Measurements were limited to the axes of the flames and included soot concentrations, soot temperatures, soot structure, major gas species concentrations, radical species (H, OH, and O) concentrations, and gas velocities. The results show that as distance increases along the axes of the flames, detectable soot formation begins when significant H concentrations are present, and ends when acetylene concentrations become small. Species potentially associated with soot oxidation-O2, CO2, H2O, O, and OH-are present throughout the soot-formation region so that soot formation and oxidation proceed at the same time. Strong rates of soot growth compared to soot nucleation early in the soot-formation process, combined with increased rates of soot nucleation and oxidation as soot formation proceeds, causes primary soot particle diameters to reach a maximum relatively early in the soot-formation process. Aggregation of primary soot particles proceeds, however, until the final stages of soot oxidation. Present measurements of soot growth (corrected for soot oxidation) in laminar diffusion flames were consistent with earlier measurements of soot growth in laminar premixed flames and exhibited encouraging agreement with existing hydrogen-abstraction/carbon-addition (HACA) soot growth mechanisms in the literature that were developed based on measurements within laminar premixed flames. Measured primary soot particle nucleation rates in the present laminar diffusion flames also were consistent with corresponding rates measured in laminar premixed flames and yielded a crude correlation in terms of acetylene and H concentrations and the temperature.

  18. Soot Formation in Laminar Acetylene/Air Diffusion Flames at Atmospheric Pressure. Appendix J

    NASA Technical Reports Server (NTRS)

    Xu, F.; Faeth, G. M.; Urban, D. L. (Technical Monitor); Yuan, Z.-G. (Technical Monitor)

    2001-01-01

    The flame structure and soot-formation (soot nucleation and growth) properties of axisymmetric laminar coflowing jet diffusion flames were studied experimentally. Test conditions involved acetylene-nitrogen jets burning in coflowing air at atmospheric pressure. Measurements were limited to the axes of the flames and included soot concentrations, soot temperatures, soot structure, major gas species concentrations, radical species (H, OH, and O) concentrations, and gas velocities. The results show that as distance increases along the axes of the flames, detectable soot formation begins when significant H concentrations are present, and ends when acetylene concentrations become small. Species potentially associated with soot oxidation--O2, CO2, H2O, O, and OH-are present throughout the soot-formation region so that soot formation and oxidation proceed at the same time. Strong rates of soot growth compared to soot nucleation early in the soot-formation process, combined with increased rates of soot nucleation and oxidation as soot formation proceeds, causes primary soot particle diameters to reach a maximum relatively early in the soot-formation process. Aggregation of primary soot particles proceeds, however, until the final stages of soot oxidation. Present measurements of soot growth (corrected for soot oxidation) in laminar diffusion flames were consistent with earlier measurements of soot growth in laminar premixed flames and exhibited encouraging agreement with existing hydrogen-abstraction/carbon-addition (HACA) soot growth mechanisms in the literature that were developed based on measurements within laminar premixed flames. Measured primary soot particle nucleation rates in the present laminar diffusion flames also were consistent with corresponding rates measured in laminar premixed flames and yielded a crude correlation in terms of acetylene and H concentrations and the temperature.

  19. Wavelength-modulation detection of acetylene with a near-infrared external-cavity diode laser

    NASA Astrophysics Data System (ADS)

    Oh, Daniel B.; Hovde, David Christian

    1995-10-01

    An external-cavity diode laser operating at 1500 nm was used to record the combination band of acetylene (C2H2). By combination of wavelength-modulation spectroscopy with a noise-canceler detection circuit, a minimum detectable absorbance of 4.8 \\times 10 -4 with a 300-ms time constant was achieved, although this result was limited by etalon fringes. When combined with this detection technique, continuous, widely tunable output from an external-cavity laser is ideally suited for high-resolution absorption spectroscopy with excellent sensitivity.

  20. Ion-momentum imaging of dissociative-electron-attachment dynamics in acetylene

    NASA Astrophysics Data System (ADS)

    Fogle, M.; Haxton, D. J.; Landers, A. L.; Orel, A. E.; Rescigno, T. N.

    2014-10-01

    We present experimental results for dissociative electron attachment to acetylene near the 3 eV 2?g resonance. In particular, we use an ion-momentum imaging technique to investigate the dissociation channel leading to C2H- fragments. From our measured ion-momentum results we extract fragment kinetic energy and angular distributions. We directly observe a significant dissociation bending dynamic associated with the formation of the transitory negative ion. In modeling this bending dynamic with ab initio electronic structure and fixed-nuclei scattering calculations we obtain good agreement with the experiment.

  1. Valence band spectra of acetylenic moieties on zinc oxide: Acetylide versus propargyl formation

    SciTech Connect

    Vohs, J.M.; Barteau, M.A. )

    1990-01-25

    Acetylene adsorbs dissociatively on the ZnO(0001) surface, as on other metal oxides, to form acetylide intermediates, CCH. Propyne also dissociates via surface acid-base reactions; however, potential adsorbates include methylacetylide (CH{sub 3}CC) and propargyl (CH{sub 2}CCH) species. Ultraviolet photoelectron spectra (UPS) of the adsorbed intermediates formed from propyne and allene on the ZnO(0001) surface demonstrate that both react to form propargyl intermediates. UPS also provide useful fingerprints of {sigma}-bonded acetylides on both metal and metal oxide surfaces.

  2. Second hyperpolarizability of delta shaped disubstituted acetylene complexes of beryllium, magnesium, and calcium.

    PubMed

    Hatua, Kaushik; Nandi, Prasanta K

    2015-10-01

    Present theoretical study involves the delta shape complexes of beryllium, magnesium, and calcium where the metal atom interacts perpendicularly with disubstituted acetylene. Most of the complexes are found to be fairly stable. The dependence of second-hyperpolarizability on the basis set with increasing polarization and diffuse functions has been examined which showed the importance of 'f-type' type polarization function for heavy metal (Mg, Ca) and 'd-type' polarization function for beryllium. Larger second hyperpolarizability has been predicted for complexes having significant ground state polarization and low lying excited states favoring strong electronic coupling. Transition energy plays the most significant role in modulating the second hyperpolarizability. PMID:26361770

  3. Heat of Combustion of the Product Formed by the Reaction of Acetylene, Ethylene, and Diborane

    NASA Technical Reports Server (NTRS)

    Tannenbaum, Stanley

    1957-01-01

    The net heat of combustion of the product formed by the reaction of diborane with a mixture of acetylene and ethylene was found to be 20,440 +/- 150 Btu per pound for the reaction of liquid fuel to gaseous carbon dioxide, gaseous water, and solid boric oxide. The measurements were made in a Parr oxygen-bomb calorimeter, and the combustion was believed to be 98 percent complete. The estimated net-heat of combustion for complete combustion would therefore be 20,850 +/- 150 Btu per pound.

  4. Mechanisms of. pi. -bond oxidation by cytochrome p-450: acetylenes as probes

    SciTech Connect

    Komives, E.A.

    1987-01-01

    Phenylacetylene and biphenylacetylene are oxidized by microsomal and purified P-450 to the corresponding arylacetic acids. During this transformation, the acetylenic hydrogen undergoes a 1,2 shift which causes a kinetic isotope effect of 1.8 on the overall enzymatic rate. The same products and kinetic isotope effects are observed when the arylacetylenes are oxidized by m-chloroperbenzoic acid. Suicide inactivation of P-450 by the arylacetylenes, which occurs simultaneously with metabolite formation, is insensitive to isotopic substitution so the partition ratio changes from 26 for phenylacetylene of 14 for (1-/sup 2/H) phenylacetylene.

  5. Polymerization of ionized acetylene clusters into covalent bonded ions: evidence for the formation of benzene radical cation.

    PubMed

    Momoh, Paul O; Abrash, Samuel A; Mabrouki, Ridha; El-Shall, M Samy

    2006-09-27

    Since the discovery of acetylene and benzene in protoplanetary nebulae under powerful ultraviolet ionizing radiation, efforts have been made to investigate the polymerization of ionized acetylene. Here we report the efficient formation of benzene ions within gas-phase ionized acetylene clusters (C2H2)n+ with n = 3-60. The results from experiments, which use mass-selected ion mobility techniques, indicate that the (C2H2)3+ ion has unusual stability similar to that of the benzene cation; its primary fragment ions are similar to those reported from the benzene cation, and it has a collision cross section of 47.4 A2 in helium at 300 K, similar to the value of 47.9 A2 reported for the benzene cation. In other words, (C2H2)3+ structurally looks like benzene, it has stability similar to that of benzene, it fragments such as benzene, therefore, it must be benzene! PMID:16984178

  6. Single-molecule phenyl-acetylene-macrocycle-based optoelectronic switch functioning as a quantum-interference-effect transistor.

    PubMed

    Hsu, Liang-Yan; Rabitz, Herschel

    2012-11-01

    This work proposes a new type of optoelectronic switch, the phenyl-acetylene-macrocycle-based single-molecule transistor, which utilizes photon-assisted tunneling and destructive quantum interference. The analysis uses single-particle Green's functions along with Floquet theory. Without the optical field, phenyl-acetylene-macrocycle exhibits a wide range of strong antiresonance between its frontier orbitals. The simulations show large on-off ratios (over 10(4)) and measurable currents (~10(-11) A) enabled by photon-assisted tunneling in a weak optical field (~2 10(5) V/cm) and at a small source-drain voltage (~0.05 V). Field amplitude power scaling laws and a range of field intensities are given for operating one- and two-photon assisted tunneling in phenyl-acetylene-macrocycle-based single-molecule transistors. This development opens up a new direction for creating molecular switches. PMID:23215309

  7. Silicon carbide-derived carbon nanocomposite as a substitute for mercury in the catalytic hydrochlorination of acetylene

    NASA Astrophysics Data System (ADS)

    Li, Xingyun; Pan, Xiulian; Yu, Liang; Ren, Pengju; Wu, Xing; Sun, Litao; Jiao, Feng; Bao, Xinhe

    2014-04-01

    Acetylene hydrochlorination is an important coal-based technology for the industrial production of vinyl chloride, however it is plagued by the toxicity of the mercury chloride catalyst. Therefore extensive efforts have been made to explore alternative catalysts with various metals. Here we report that a nanocomposite of nitrogen-doped carbon derived from silicon carbide activates acetylene directly for hydrochlorination in the absence of additional metal species. The catalyst delivers stable performance during a 150?hour test with acetylene conversion reaching 80% and vinyl chloride selectivity over 98% at 200?C. Experimental studies and theoretical simulations reveal that the carbon atoms bonded with pyrrolic nitrogen atoms are the active sites. This proof-of-concept study demonstrates that such a nanocomposite is a potential substitute for mercury while further work is still necessary to bring this to the industrial stage. Furthermore, the finding also provides guidance for design of carbon-based catalysts for activation of other alkynes.

  8. Silicon carbide-derived carbon nanocomposite as a substitute for mercury in the catalytic hydrochlorination of acetylene.

    PubMed

    Li, Xingyun; Pan, Xiulian; Yu, Liang; Ren, Pengju; Wu, Xing; Sun, Litao; Jiao, Feng; Bao, Xinhe

    2014-01-01

    Acetylene hydrochlorination is an important coal-based technology for the industrial production of vinyl chloride, however it is plagued by the toxicity of the mercury chloride catalyst. Therefore extensive efforts have been made to explore alternative catalysts with various metals. Here we report that a nanocomposite of nitrogen-doped carbon derived from silicon carbide activates acetylene directly for hydrochlorination in the absence of additional metal species. The catalyst delivers stable performance during a 150 hour test with acetylene conversion reaching 80% and vinyl chloride selectivity over 98% at 200 C. Experimental studies and theoretical simulations reveal that the carbon atoms bonded with pyrrolic nitrogen atoms are the active sites. This proof-of-concept study demonstrates that such a nanocomposite is a potential substitute for mercury while further work is still necessary to bring this to the industrial stage. Furthermore, the finding also provides guidance for design of carbon-based catalysts for activation of other alkynes. PMID:24751500

  9. The analysis of the hot bands of acetylene in the 2.5 - 3{mu}m region

    SciTech Connect

    Sarma, Y.A.; D`Cunha, R.; Guelachvili, G.

    1995-12-31

    Renewed interest in acetylene as a calibration standard in the mid-IR region and as a model for IVR (intra vibrational relaxation) studies, has prompted a systematic reinvestigation of its FTIR spectra in the 2.5 - 3{mu}m region. The effect of 1 type resonances has been included in the analysis and molecular parameters that fit the data within the limits of the experimental accuracy have been obtained for several overtone and combination levels of acetylene. The details of the analysis will be presented.

  10. Isolation of cyanobacterial heterocysts with high and sustained dinitrogen-fixation capacity supported by endogenous reductants.

    PubMed

    Jensen, B B; Cox, R P; Burris, R H

    1986-08-01

    A method is described for the preparation of cyanobacterial heterocysts with high nitrogen-fixation (acetylene-reduction) activity supported by endogenous reductants. The starting material was Anabaena variabilis ATCC 29413 grown in the light in the presence of fructose. Heterocysts produced from such cyanobacteria were more active than those from photoautotrophically-grown A. variabilis, presumably because higher reserves of carbohydrate were stored within the heterocysts. It proved important to avoid subjecting the cyanobacteria to low temperatures under aerobic conditions, as inhibition of respiration appeared to lead to inactivation of nitrogenase. Low temperatures were not harmful in the absence of O2. A number of potential osmoregulators at various concentrations were tested for use in heterocyst isolation. The optimal concentration (0.2 M sucrose) proved to be a compromise between adequate osmotic protection for isolated heterocysts and avoidance of inhibition of nitrogenase by high osmotic strength. Isolated heterocysts without added reductants such as H2 had about half the nitrogen-fixation activity expected on the basis of intact filaments. H2 did not increase the rate of acetylene reduction, suggesting that the supply of reductant from heterocyst metabolism did not limit nitrogen fixation under these conditions. Such heterocysts had linear rates of acetylene reduction for at least 2 h, and retained their full potential for at least 12 h when stored at 0 degree C under N2. PMID:3094473

  11. Unconventional ionic hydrogen bonds: CH +⋯π (C tbnd C) binding energies and structures of benzene + rad (acetylene) 1-4 clusters

    NASA Astrophysics Data System (ADS)

    Soliman, Abdel-Rahman; Hamid, Ahmed M.; Abrash, Samuel A.; El-Shall, M. Samy

    2012-01-01

    Rapid condensation of acetylene onto the benzene cation with the addition of up to eight acetylene molecules is observed in the gas phase at 120-140 K forming the C6D6rad +(C2H2)n clusters. The binding energies and entropy changes of the stepwise condensation of the first four acetylene molecules onto the benzene cation have been measured and correlated with the calculated lowest energy isomers. The measured binding energies (3-4 kcal/mol) reflect weak charge-induced dipole and (benzene) Csbnd Hδ+⋯π Ctbnd C (acetylene) hydrogen bonding interactions. Associative charge transfer is suggested to activate the cyclization of three acetylene molecules to form a benzene molecule (C6H6).

  12. The methane-acetylene cycle Aerospace Plane - A promising candidate for earth to orbit transportation

    SciTech Connect

    Zubrin, R.M. )

    1992-01-01

    The methane-acetylene cycle Aerosapce Plane (MACASP) concept is proposed and its theoretical feasibility is shown. In this concept, methane fuel stored on-board the aircraft is run out within the wing leading edge in pipes at temperatures up to 1400 K. In the presence of catalyst, the heat provided by wing drag is used to drive the highly endothermic chemical reaction 2CH4 yields 3H2 + C2H2. The products of this reaction, hydrogen and acetylene, are then fed into a combustion chamber and burned in air. On the NASP, terminal acceleration to orbit beyond the critical Mach number of the scramjet can be enabled by rocket operation using a small on-board supply of LOx. The advantages of this concept are that the two highly energetic but difficult-to-store fuels can be used without on-board storage. It is shown that the MACASP concept offers significant promise for economical earth-to-orbit transportation. 5 refs.

  13. Taple-top imaging of the non-adiabatically driven isomerization in the acetylene cation

    NASA Astrophysics Data System (ADS)

    Beaulieu, Samuel; Ibrahim, Heide; Wales, Benji; Schmidt, Bruno E.; Thir, Nicolas; Bisson, ric; Hebeisen, Christoph T.; Wanie, Vincent; Giguere, Mathieu; Kieffer, Jean-Claude; Sanderson, Joe; Schuurman, Michael S.; Lgar, Franois

    2014-05-01

    One of the primary goals of modern ultrafast science is to follow nuclear and electronic evolution of molecules as they undergo a photo-chemical reaction. Most of the interesting dynamics phenomena in molecules occur when an electronically excited state is populated. When the energy difference between electronic ground and excited states is large, Free Electron Laser (FEL) and HHG-based VUV sources were, up to date, the only light sources able to efficiently initiate those non-adiabatic dynamics. We have developed a simple table-top approach to initiate those rich dynamics via multiphoton absorption. As a proof of principle, we studied the ultrafast isomerization of the acetylene cation. We have chosen this model system for isomerization since the internal conversion mechanism which leads to proton migration is still under debate since decades. Using 266 nm multiphoton absorption as a pump and 800 nm induced Coulomb Explosion as a probe, we have shoot the first high-resolution molecular movie of the non-adiabatically driven proton migration in the acetylene cation. The experimental results are in excellent agreement with high level ab initio trajectory simulations.

  14. Transient Responses of Nitrogenase to Acetylene and Oxygen in Actinorhizal Nodules and Cultured Frankia1

    PubMed Central

    Silvester, Warwick B.; Winship, Lawrence J.

    1990-01-01

    Nitrogenase activity in root nodules of four species of actinorhizal plants showed varying declines in response to exposure to acetylene (10% v/v). Gymnostoma papuanum (S. Moore) L. Johnson. and Casuarina equisetifolia L. nodules showed a small decline (5-15%) with little or no recovery over 15 minutes. Myrica gale L. nodules showed a sharp decline followed by a rapid return to peak activity. Alnus incana ssp. rugosa (Du Roi) Clausen. nodules usually showed varying degrees of decline followed by a slower return to peak or near-peak activity. We call these effects acetylene-induced transients. Rapid increases in oxygen tension also caused dramatic transient decreases in nitrogenase activity in all species. The magnitude of the transient decrease was related to the size of the O2 partial pressure (pO2) rise, to the proximity of the starting and ending oxygen tensions to the pO2 optimum, and to the time for which the plant was exposed to the lower pO2. Oxygen-induced transients, induced both by step jumps in pO2 and by O2 pulses, were also observed in cultures of Frankia. The effects seen in nodules are purely a response by the bacterium and not a nodule effect per se. Oxygen-induced nitrogenase transients in actinorhizal nodules from the plant genera tested here do not appear to be a result of changes in nodule diffusion resistance. PMID:16667301

  15. The Structure of the 1-CHLORO-1-FLUOROETHYLENE--ACETYLENE Complex

    NASA Astrophysics Data System (ADS)

    Leung, Helen O.; Marshall, Mark D.; Grimes, David D.

    2010-06-01

    The insensitivity of the moments of inertia to certain geometric parameters for the limited set of isotopologues studied led to unexpected results for a preliminary structure of the complex formed between 1-chloro-1-fluoroethylene and acetylene presented three years ago. The availability of this chlorofluoroethylene with a single deuterium substitution in both (E) and (Z) isomeric forms allows us to supplement the original data set with microwave spectra of (E)-CHDC35ClF--HCCH and (Z)-CHDC35ClF--HCCH. Supported by the results of ab initio calculations, a planar, chemically reasonable structure is obtained for this complex, in which the acetylene forms a hydrogen bond with the fluorine atom of 1-chloro-1-fluoroethylene. The hydrogen bond bends to allow a secondary interaction with the hydrogen atom cis to this fluorine atom. Comparisons with the structure of the analogous complexes formed with vinyl fluoride and 1,1-difluoroethylene reveal the effects of chlorine substitution geminal to the acceptor atom of the hydrogen bond. H.O. Leung and M.D. Marshall, The 62nd OSU International Symposium on Molecular Spectroscopy, Talk RG10 (2007) Kindly provided by Prof. Norman Craig, Oberlin College

  16. Accurate partition function for acetylene, 12C2H2, and related thermodynamical quantities.

    PubMed

    Amyay, B; Fayt, A; Herman, M

    2011-12-21

    The internal partition function (Q(int)) of ethyne (acetylene), (12)C(2)H(2), is calculated by explicit summation of the contribution of all individual vibration-rotation energy levels up to 15,000 cm(-1). The corresponding energies are predicted from a global model and constants reproducing within 3σ all 18,415 published vibration-rotation lines in the literature involving vibrational states up to 8900 cm(-1), as produced by Amyay et al. [J. Mol. Spectrosc. 267, 80 (2011)]. Values of Q(int), with distinct calculations for para and ortho species are provided from 1 to 2000 K, in step of 1 K. The total internal partition function at 298.15 K is 104.224387(47) or 416.89755(19), with the nuclear degeneracy spin factors taken as 1/4:3/4 (astronomer convention) or 1:3 (atmospheric convention), respectively, for para:ortho species. The Helmholtz function, Gibbs enthalpy function, entropy, and specific heat at constant pressure are also calculated over the same temperature range. Accuracies as well as the missing contribution of the vinylidene isomer of acetylene in the calculations are discussed. PMID:22191873

  17. Selective Hydrogenation of Acetylene over Pd, Au, and PdAu Supported Nanoparticles

    NASA Astrophysics Data System (ADS)

    Walker, Michael P.

    The removal of trace amounts of acetylene in ethylene streams is a high-volume industrial process that must possess high selectivity of alkyne hydrogenation over hydrogenation of alkenes. Current technology uses metallic nanoparticles, typically palladium or platinum, for acetylene removal. However, problems arise due to the deactivation of the catalysts at high temperatures as well as low selectivities at high conversions. Pore expanded MCM-41 is synthesized via a two-step strategy in which MCM-41 was prepared via cetyltrimethylammonium bromide (CTMABr) followed by the hydrothermal treatment with N,N-dimethyldecylamine (DMDA). This material was washed with ethanol to remove DMDA, or calcined to remove both surfactants. PE-MCM-41 based materials were impregnated with palladium, gold, and palladium-gold nanoparticles. The removal of DMDA had an effect on both the conversion and selectivity, in which they were found to drop significantly. However, by using the bimetallic PdAu catalysts, higher selectivity could be achieved due to increased electron density.

  18. Soot volume fraction maps for normal and reduced gravity laminar acetylene jet diffusion flames

    SciTech Connect

    Greenberg, P.S.; Ku, J.C.

    1997-01-01

    The study of soot particulate distribution inside gas jet diffusion flames is important to the understanding of fundamental soot particle and thermal radiative transport processes, as well as providing findings relevant to spacecraft fire safety, soot emissions, and radiant heat loads for combustors used in air-breathing propulsion systems. Compared to those under normal gravity (1-g) conditions, the elimination of buoyancy-induced flows is expected to significantly change the flow field in microgravity (0 g) flames, resulting in taller and wider flames with longer particle residence times. Work by Bahadori and Edelman demonstrate many previously unreported qualitative and semi-quantitative results, including flame shape and radiation, for sooting laminar gas jet diffusion flames. Work by Ku et al. report soot aggregate size and morphology analyses, and data and model predictions of soot volume fraction maps for various gas jet diffusion flames. In this study, the authors present the first 1-g and 0-g comparisons of soot volume fraction maps for laminar acetylene and nitrogen-diluted acetylene jet diffusion flames.

  19. CH⋯B interactions in acetylene containing solutions: experimental and theoretical DFT studies

    NASA Astrophysics Data System (ADS)

    Melikova, S. M.; Rutkowski, K. S.; Rodziewicz, P.; Koll, A.

    2003-01-01

    Weak to medium H-bonded interactions of the CH⋯B type (B=CS 2 and N(CD) 5) have been studied in C 2H 2/B mixtures. The spectral characteristics (frequency, width, and absolute integral intensity) of the CH asymmetric stretching band of acetylene were determined. Analogously to C 2H 2/CO 2 system studied earlier, in the case of CS 2 solutions, the combination bands ascribed to simultaneous excitations of vibrations of interacted CS 2 and C 2H 2 molecular partners have been found. The observed spectroscopic features have been compared with the results of theoretical DFT/B3LYP calculations utilizing the 6-311++G(3df, 3pd) basis set. They predict 1:1 and 1:2 complex formations with the linear H-bonded structure in the case of N(CD) 5 and nonlinear weakly bounded structures in the case of CS 2. The results obtained suggest predomination of 1:1 complexes of acetylene with pyridine in Xe and CS 2 solutions at conditions studied.

  20. An improved choline monooxygenase assay

    SciTech Connect

    Lafontaine, P.J.; Hanson, A.D. )

    1991-05-01

    Glycine betaine accumulates in leaves of plants from several angiosperm families in response to drought or salinization. Its synthesis, from the oxidation of choline, is mediated by a two step pathway. In spinach the first enzyme of this pathway is a ferredoxin-dependent choline monooxygenase (CMO). In order to purify this enzyme a sensitive and reliable assay is necessary. Two types of modifications were explored to improve the existing assay. (1) Ferredoxin reduction - one way of providing reduced Fd to CMO is by the addition of isolated spinach thylakoids in the assay mixture. In order to optimize the reduction of Fd two different systems were compared: (a) where only PS is active, by adding DCMU to inhibit electron transport from PS II and DAD as electron donor for PS I; (b) where both PS II and PS I are active. (2) Betaine aldehyde estimation - to simplify this, it is possible to couple the CMO reaction with betaine aldehyde dehydrogenase (BADH) from E. coli. BADH converts betaine aldehyde to betaine as it is formed in the assay, eliminating the need for a chemical oxidation step.

  1. Ruthenium(0)-Catalyzed [4+2] Cycloaddition of Acetylenic Aldehydes with ?-Ketols: Convergent Construction of Angucycline Ring Systems.

    PubMed

    Saxena, Aakarsh; Perez, Felix; Krische, Michael J

    2016-01-01

    Ruthenium(0) complexes modified by CyJohnPhos or RuPhos catalyze the successive C-C coupling of acetylenic aldehydes with ?-ketols to form [4+2] cycloadducts as single diastereomers. This method enables convergent construction of type?II polyketide ring systems of the angucycline class. PMID:26663806

  2. Theoretical study of the bonding of the first- and second-row transition-metal positive ions to acetylene

    NASA Technical Reports Server (NTRS)

    Sodupe, M.; Bauschlicher, Charles W., Jr.

    1991-01-01

    The bonding of transition-metal ions to acetylene is studied by using a theoretical treatment that includes electron correlation. The ions on the left side of the first and second transition rows insert into the pi bond to form a three-membered ring. On the right side of the row the bonding is electrostatic. The trends in bonding are discussed.

  3. Indirect method for the determination of aluminium by atomic-absorption spectrometry using an air-acetylene flame.

    PubMed

    Ottaway, J M; Coker, D T; Singleton, B

    1972-06-01

    The enhancement of the atomic-absorption signals of iron, cobalt, nickel and chromium in a fuel-rich air-acetylene flame by small amounts of aluminium makes possible the indirect determination of aluminium in the concentration range 0.01-10 ppm. The optimization of working conditions and the occurrence of interferences are reported. PMID:18961114

  4. Effect of the detonation nanodiamond surface on the catalytic activity of deposited nickel catalysts in the hydrogenation of acetylene

    NASA Astrophysics Data System (ADS)

    Tveritinova, E. A.; Kulakova, I. I.; Zhitnev, Yu. N.; Kharlanov, A. N.; Fionov, A. V.; Chen, W.; Buyanova, I.; Lunin, V. V.

    2013-07-01

    A comparative study is performed of the catalytic activity of nanosized nickel deposited on detonation synthesis nanodiamond (DND) and coal (CSUG) produced by burning sugar and crystalline quartz in the hydrogenation of acetylene. Nanosized nickel is obtained through the thermal decomposition of nickel formate under a dynamic vacuum. The catalysts are studied by means of scanning electron and transmission electron microscopy, X-ray fluorescence, IR-spectroscopy, X-ray diffraction, and pulse microcatalytic method. It is shown that Ni/DND is an active catalyst of acetylene hydrogenation, considerably surpassing Ni/quartz and Ni/CSUG. The apparent activation energy of the hydrogenation of acetylene is calculated, and the region of the reaction are determined for all catalysts. It is found that the influence of the structure and nature of a functional coating of nanodiamond on the catalytic activity of Ni/DND deposited catalyst in the hydrogenation of acetylene. The ability of Ni/DND to hold active hydrogen is detected.

  5. Characterization of the Minimum Energy Paths for the Ring Closure Reactions of C4H3 with Acetylene

    NASA Technical Reports Server (NTRS)

    Walch, Stephen P.

    1995-01-01

    The ring closure reaction of C4H3 with acetylene to give phenyl radical is one proposed mechanism for the formation of the first aromatic ring in hydrocarbon combustion. There are two low-lying isomers of C4H3; 1-dehydro-buta-l-ene-3-yne (n-C4H3) and 2-dehydro-buta-l-ene-3-yne (iso-C4H3). It has been proposed that only n-C4H3 reacts with acetylene to give phenyl radical, and since iso-C4H3 is more stable than n-C4H3, formation of phenyl radical by this mechanism is unlikely. We report restricted Hartree-Fock (RHF) plus singles and doubles configuration interaction calculations with a Davidson's correction (RHF+1+2+Q) using the Dunning correlation consistent polarized valence double zeta basis set (cc-pVDZ) for stationary point structures along the reaction pathway for the reactions of n-C4H3 and iso-C4H3 with acetylene. n-C4H3 plus acetylene (9.4) has a small entrance channel barrier (17.7) (all energetics in parentheses are in kcal/mol with respect to iso-C4H3 plus acetylene) and the subsequent closure steps leading to phenyl radical (-91.9) are downhill with respect to the entrance channel barrier. Iso-C4H3 Plus acetylene also has an entrance channel barrier (14.9) and there is a downhill pathway to 1-dehydro-fulvene (-55.0). 1-dehydro-fulvene can rearrange to 6-dehydro-fulvene (-60.3) by a 1,3-hydrogen shift over a barrier (4.0), which is still below the entrance channel barrier, from which rearrangement to phenyl radical can occur by a downhill pathway. Thus, both n-C4H3 and iso-C4H3 can react with acetylene to give phenyl radical with small barriers.

  6. Inactivation of delta 5-3-oxo steroid isomerase with active-site-directed acetylenic steroids.

    PubMed Central

    Penning, T M; Covey, D F; Talalay, P

    1981-01-01

    Several steroid analogues containing conjugated acetylenic ketone groups as part of a seco-ring structure or as substituents on the intact steroid system are irreversible inhibitors of delta 5-3-oxo steroid isomerase (EC 5.3.3.1) from Pseudomonas testosteroni. Thus 10 beta-(1-oxoprop-2-ynyl)oestr-4-ene-3,17-dione (I), 5,10-seco-oestr-4-yne-3,10,17-trione (II), 17 beta-hydroxy-5,10-seco-oestr-4-yne-3,10-dione (III) and 17 beta-(1-oxoprop-2-ynyl)androst-4-en-3-one (IV) irreversibly inactivate isomerase in a time-dependent manner. In all cases saturation kinetics are observed. Protection against inactivation is afforded by the powerful competitive inhibitor 19-nortestosterone. The inhibition constants (Ki) for 19-nortestosterone obtained from such experiments are in good agreement with those determined from conventional competitive-inhibition studies of enzyme activity. These compounds thus appear to be active-site directed. In every case the inactivated enzyme could be dialysed without return of activity, indicating that a stable covalent bond probably had formed between the steroid and enzyme. Compound (I) is a very potent inhibitor of isomerase [Ki = 66.0 microM and k+2 = 12.5 x 10(-3) s-1 (where Ki is the dissociation constant of the reversible enzyme-inhibitor complex and k+2 is the rate constant for the inactivation reaction of the enzyme-inhibitor complex)] giving half-lives of inactivation of 30-45 s at saturation. It is argued that the basic-amino-acid residue that abstracts the intramolecularly transferred 4 beta-proton in the reaction mechanism could form a Michael-addition product with compound (I). In contrast, although compound (IV) has a lower inhibition constant (Ki = 14.5 microM), it is a relatively poor alkylating agent (k+2 = 0.13 x 10(-3) s-1). If the conjugated acetylenic ketone groups are replaced by alpha-hydroxyacetylene groups, the resultant analogues of steroids (I)-(IV) are reversible competitive inhibitors with Ki values in the range 27-350 microM. The enzyme binds steroids in the C19 series with functionalized acetylenic substituents at C-17 in preference to steroids in the C18 series bearing similar groups in the ring structure or as C-10 substituents. In the 5,10-seco-steroid series the presence of hydroxy groups at both C-3 and C-17 is deleterious to binding by the enzyme. PMID:7305923

  7. Hydrothermal Synthesis and Acetylene Sensing Properties of Variety Low Dimensional Zinc Oxide Nanostructures

    PubMed Central

    Chen, Weigen; Peng, Shudi; Zeng, Wen

    2014-01-01

    Various morphologies of low dimensional ZnO nanostructures, including spheres, rods, sheets, and wires, were successfully synthesized using a simple and facile hydrothermal method assisted with different surfactants. Zinc acetate dihydrate was chosen as the precursors of ZnO nanostructures. We found that polyethylene glycol (PEG), polyvinylpyrrolidone (PVP), glycine, and ethylene glycol (EG) play critical roles in the morphologies and microstructures of the synthesized nanostructures, and a series of possible growth processes were discussed in detail. Gas sensors were fabricated using screen-printing technology, and their sensing properties towards acetylene gas (C2H2), one of the most important arc discharge characteristic gases dissolved in oil-filled power equipments, were systematically measured. The ZnO nanowires based sensor exhibits excellent C2H2 sensing behaviors than those of ZnO nanosheets, nanorods, and nanospheres, indicating a feasible way to develop high-performance C2H2 gas sensor for practical application. PMID:24672324

  8. Infrared Spectra and Optical Constants of Astronomical Ices: I. Amorphous and Crystalline Acetylene

    NASA Technical Reports Server (NTRS)

    Hudson, R. L.; Ferrante, R. F.; Moore, M. H.

    2013-01-01

    Here we report recent measurements on acetylene (C2H2) ices at temperatures applicable to the outer Solar System and the interstellar medium. New near- and mid-infrared data, including optical constants (n, k), absorption coefficients (alpha), and absolute band strengths (A), are presented for both amorphous and crystalline phases of C2H2 that exist below 70 K. Comparisons are made to earlier work. Electronic versions of the data are made available, as is a computer routine to use our reported n and k values to simulate the observed IR spectra. Suggestions are given for the use of the data and a comparison to a spectrum of Makemake is made.

  9. Hydrothermal synthesis and acetylene sensing properties of variety low dimensional zinc oxide nanostructures.

    PubMed

    Zhou, Qu; Chen, Weigen; Peng, Shudi; Zeng, Wen

    2014-01-01

    Various morphologies of low dimensional ZnO nanostructures, including spheres, rods, sheets, and wires, were successfully synthesized using a simple and facile hydrothermal method assisted with different surfactants. Zinc acetate dihydrate was chosen as the precursors of ZnO nanostructures. We found that polyethylene glycol (PEG), polyvinylpyrrolidone (PVP), glycine, and ethylene glycol (EG) play critical roles in the morphologies and microstructures of the synthesized nanostructures, and a series of possible growth processes were discussed in detail. Gas sensors were fabricated using screen-printing technology, and their sensing properties towards acetylene gas (C2H2), one of the most important arc discharge characteristic gases dissolved in oil-filled power equipments, were systematically measured. The ZnO nanowires based sensor exhibits excellent C2H2 sensing behaviors than those of ZnO nanosheets, nanorods, and nanospheres, indicating a feasible way to develop high-performance C2H2 gas sensor for practical application. PMID:24672324

  10. Doppler broadening thermometry of acetylene and accurate measurement of the Boltzmann constant.

    PubMed

    Hashemi, R; Povey, C; Derksen, M; Naseri, H; Garber, J; Predoi-Cross, A

    2014-12-01

    In this paper, we present accurate measurements of the fundamental Boltzmann constant based on a line-shape analysis of acetylene spectra in the ?1 + ?3 band recorded using a tunable diode laser. Experimental spectra recorded at low pressures (0.25 - 9 Torr), have been analyzed using a Speed Dependent Voigt model that takes into account the molecular speed dependence effects. This line-shape model reproduces the experimental data with good accuracy and allows us to determine precise line-shape parameters for the P(25) transition of the ?1 + ?3 band. From the recorded spectra we obtained the Doppler-width and then determined the Boltzmann constant, k(B). PMID:25481135

  11. Graphenes in the absence of metals as carbocatalysts for selective acetylene hydrogenation and alkene hydrogenation.

    PubMed

    Primo, Ana; Neatu, Florentina; Florea, Mihaela; Parvulescu, Vasile; Garcia, Hermenegildo

    2014-01-01

    Catalysis makes possible a chemical reaction by increasing the transformation rate. Hydrogenation of carbon-carbon multiple bonds is one of the most important examples of catalytic reactions. Currently, this type of reaction is carried out in petrochemistry at very large scale, using noble metals such as platinum and palladium or first row transition metals such as nickel. Catalysis is dominated by metals and in many cases by precious ones. Here we report that graphene (a single layer of one-atom-thick carbon atoms) can replace metals for hydrogenation of carbon-carbon multiple bonds. Besides alkene hydrogenation, we have shown that graphenes also exhibit high selectivity for the hydrogenation of acetylene in the presence of a large excess of ethylene. PMID:25342228

  12. Graphenes in the absence of metals as carbocatalysts for selective acetylene hydrogenation and alkene hydrogenation

    NASA Astrophysics Data System (ADS)

    Primo, Ana; Neatu, Florentina; Florea, Mihaela; Parvulescu, Vasile; Garcia, Hermenegildo

    2014-10-01

    Catalysis makes possible a chemical reaction by increasing the transformation rate. Hydrogenation of carbon-carbon multiple bonds is one of the most important examples of catalytic reactions. Currently, this type of reaction is carried out in petrochemistry at very large scale, using noble metals such as platinum and palladium or first row transition metals such as nickel. Catalysis is dominated by metals and in many cases by precious ones. Here we report that graphene (a single layer of one-atom-thick carbon atoms) can replace metals for hydrogenation of carbon-carbon multiple bonds. Besides alkene hydrogenation, we have shown that graphenes also exhibit high selectivity for the hydrogenation of acetylene in the presence of a large excess of ethylene.

  13. Tabletop imaging of structural evolutions in chemical reactions demonstrated for the acetylene cation.

    PubMed

    Ibrahim, Heide; Wales, Benji; Beaulieu, Samuel; Schmidt, Bruno E; Thir, Nicolas; Fowe, Emmanuel P; Bisson, ric; Hebeisen, Christoph T; Wanie, Vincent; Gigure, Mathieu; Kieffer, Jean-Claude; Spanner, Michael; Bandrauk, Andr D; Sanderson, Joseph; Schuurman, Michael S; Lgar, Franois

    2014-01-01

    The introduction of femto-chemistry has made it a primary goal to follow the nuclear and electronic evolution of a molecule in time and space as it undergoes a chemical reaction. Using Coulomb Explosion Imaging, we have shot the first high-resolution molecular movie of a to and fro isomerization process in the acetylene cation. So far, this kind of phenomenon could only be observed using vacuum ultraviolet light from a free-electron laser. Here we show that 266 nm ultrashort laser pulses are capable of initiating rich dynamics through multiphoton ionization. With our generally applicable tabletop approach that can be used for other small organic molecules, we have investigated two basic chemical reactions simultaneously: proton migration and C=C bond breaking, triggered by multiphoton ionization. The experimental results are in excellent agreement with the timescales and relaxation pathways predicted by new and quantitative ab initio trajectory simulations. PMID:25034613

  14. Infrared Spectra of Acetylene Diluted in Solid Nitrogen upon Irradiation with Vacuum Ultraviolet Light and Electrons

    NASA Astrophysics Data System (ADS)

    Wu, Yu-Jong; Chuang, Shiang-Jiun; Chen, Sian-Cong; Huang, Tzu-Ping

    2014-05-01

    Infrared spectra and chemical reactions of acetylene diluted in solid nitrogen at 10 K upon irradiation with vacuum ultraviolet (VUV) light and energetic electrons were investigated in separate experiments. Irradiation of the matrix sample with VUV light peaking at 160 and 121.6 nm yielded simple products, including C2H, CN, and isomers of C2N2. In contrast, electron irradiation of a similar sample generated N3, C2H, and various nitriles. The reaction mechanisms for photolysis and radiolysis of the matrix samples are discussed. Our results may help explain the distribution of trace species detected in the atmosphere of Titan. In addition, the UV absorption spectrum of the electron-bombarded icy sample was obtained and might be useful for future spectral investigations of Pluto by New Horizons.

  15. Tabletop imaging of structural evolutions in chemical reactions demonstrated for the acetylene cation

    NASA Astrophysics Data System (ADS)

    Ibrahim, Heide; Wales, Benji; Beaulieu, Samuel; Schmidt, Bruno E.; Thir, Nicolas; Fowe, Emmanuel P.; Bisson, ric; Hebeisen, Christoph T.; Wanie, Vincent; Gigure, Mathieu; Kieffer, Jean-Claude; Spanner, Michael; Bandrauk, Andr D.; Sanderson, Joseph; Schuurman, Michael S.; Lgar, Franois

    2014-07-01

    The introduction of femto-chemistry has made it a primary goal to follow the nuclear and electronic evolution of a molecule in time and space as it undergoes a chemical reaction. Using Coulomb Explosion Imaging, we have shot the first high-resolution molecular movie of a to and fro isomerization process in the acetylene cation. So far, this kind of phenomenon could only be observed using vacuum ultraviolet light from a free-electron laser. Here we show that 266?nm ultrashort laser pulses are capable of initiating rich dynamics through multiphoton ionization. With our generally applicable tabletop approach that can be used for other small organic molecules, we have investigated two basic chemical reactions simultaneously: proton migration and C=C bond breaking, triggered by multiphoton ionization. The experimental results are in excellent agreement with the timescales and relaxation pathways predicted by new and quantitative ab initio trajectory simulations.

  16. Analysis for Mar Vel Black and acetylene soot low reflectivity surfaces for star tracker sunshade applications

    NASA Technical Reports Server (NTRS)

    Yung, E.

    1974-01-01

    Mar Vel Black is a revolutionary new extremely low reflectivity anodized coating developed by Martin Marietta of Denver. It is of great interest in optics in general, and in star trackers specifically because it can reduce extraneous light reflections. A sample of Mar Vel Black was evaluated. Mar Vel Black looks much like a super black surface with many small peaks and very steep sides so that any light incident upon the surface will tend to reflect many times before exiting that surface. Even a high reflectivity surface would thus appear to have a very low reflectivity under such conditions. Conversely, acetylene soot does not have the magnified surface appearance of a super black surface. Its performance is, however, predictable from the surface structure, considering the known configuration of virtually pure carbon.

  17. Interference in acetylene intersystem crossing acts as the molecular analog of Young's double-slit experiment

    PubMed Central

    de Groot, Mattijs; Field, Robert W.; Buma, Wybren J.

    2009-01-01

    We report on an experimental approach that reveals crucial details of the composition of singlet-triplet mixed eigenstates in acetylene. Intersystem crossing in this prototypical polyatomic molecule embodies the mixing of the lowest excited singlet state (S1) with 3 triplet states (T1, T2, and T3). Using high-energy (157-nm) photons from an F2 laser to record excited-state photoelectron spectra, we have decomposed the mixed eigenstates into their S1, T3, T2, and T1 constituent parts. One example of the interpretive power that ensues from the selective sensitivity of the experiment to the individual electronic state characters is the discovery and examination of destructive interference between two doorway-mediated intersystem crossing pathways. This observation of an interference effect in nonradiative decay opens up possibilities for rational coherent control over molecular excited state dynamics. PMID:19179288

  18. Microstructure and performance of titanium oxide coatings sprayed by oxygen-acetylene flame.

    PubMed

    Ctibor, Pavel; Stengl, Vaclav; Zahalka, Frantisek; Murafa, Nataliya

    2011-03-01

    TiO(2) nano-powders were agglomerated by a spray drying process for application to thermal spraying. A conventional oxygen-acetylene flame torch was used to deposit porous partially nanostructured TiO(2) coatings. Steel substrates were used as a support for tested samples. Scanning electron microscopy, X-ray microanalysis and X-ray diffraction were performed to study the morphology and the crystalline phases of the titania coatings. Optical bandgap and kinetics of the acetone decomposition were also studied. The best results were obtained for the powder which is available as a commercial spray feedstock. This powder seems to be most resistant against the reducing atmosphere in the jet of combustive gases. PMID:20938550

  19. Analysis of Effluent Gases During the CCVD Growth of Multi Wall Carbon Nanotubes from Acetylene

    NASA Technical Reports Server (NTRS)

    Schmitt, T. C.; Biris, A. S.; Miller, D. W.; Biris, A. R.; Lupu, D.; Trigwell, S.; Rahman, Z. U.

    2005-01-01

    Catalytic chemical vapor deposition was used to grow multi-walled carbon nanotubes on a Fe:Co:CaCO3 catalyst from acetylene. The influent and effluent gases were analyzed by gas chromatography and mass spectrometry at different time intervals during the nanotubes growth process in order to better understand and optimize the overall reaction. A large number of byproducts were identified and it was found that the number and the level for some of the carbon byproducts significantly increased over time. The CaCO3 catalytic support thermally decomposed into CaO and CO2 resulting in a mixture of two catalysts for growing the nanotubes, which were found to have outer diameters belonging to two main groups 8 to 35 nm and 40 to 60 nm, respectively.

  20. Shock-tube pyrolysis of acetylene - Sensitivity analysis of the reaction mechanism for soot formation

    NASA Technical Reports Server (NTRS)

    Frenklach, M.; Clary, D. W.; Gardiner, W. C., Jr.; Stein, S. E.

    1986-01-01

    The impact of thermodynamic parameters on the sensitivity of model predictions of soot formation by shock-tube pyrolysis of acetylene were assessed analytically. The pyrolysis process was treated as having three components: initiation, the initial pyrolysis stages; cyclization, formation of larger molecules and radicals and small aromatic molecules; and polymerization, further growth of aromatic rings. Rate equations are reviewed for each component. Thermodynamic effects were assessed by varying the C2H-H and C2H3-H bond energies and the Ct-(Ct) group additivity value. Any change in the C2H-H bond energy had a significant impact on the temperature and the maximum amount of the soot yield. The findings underscore the necessity of using accurate thermodynamic data for modeling high-temperature chemical kinetics.

  1. The - CO_2--ACETYLENE Complex: Fundamental and Torsional Combination Band in the CO_2 ?_3 Region

    NASA Astrophysics Data System (ADS)

    Lauzin, C.; Oliaee, J. Norooz; Rezaei, M.; Moazzen-Ahmadi, N.

    2011-06-01

    Infrared spectrum of the weakly-bound CO_2-C_2H_2 complex in the region of the CO_2 ?_3 fundamental band ( 2349 Cm-1) is observed in a pulsed supersonic slit jet expansion using a tunable diode laser probe. Two bands are observed and analyzed: the fundamental (C-O asymmetric stretch) and a combination involving the intermolecular torsional (out-of-plane bend) vibration. The resulting torsional frequency is 44.385(10) Cm-1. This represents the first observation of an intermolecular frequency for carbon dioxide-acetylene complex. A comparison between the results obtained here and those previously reported for N_2O-C_2H_2 complex is discussed. M. Dehghany, Mahin Afshari, J. Norooz Oliaee, N. Moazzen-Ahmadi, A. R. W. McKellar, Chem. Phys. Lett. 473 (2009), 26-29.

  2. Synthesis, structure and cytotoxic activity of acetylenic derivatives of betulonic and betulinic acids

    NASA Astrophysics Data System (ADS)

    Bębenek, Ewa; Chrobak, Elwira; Wietrzyk, Joanna; Kadela, Monika; Chrobak, Artur; Kusz, Joachim; Książek, Maria; Jastrzębska, Maria; Boryczka, Stanisław

    2016-02-01

    A series of acetylenic derivatives of betulonic and betulinic acids has been synthesized and characterized by 1H and 13C NMR, IR and MS spectroscopy. The structure of propargyl betulonate 4 and propargyl betulinate-DMF solvate 8A was solved by X-ray diffraction. Thermal properties were examined using a DSC technique. The resulting alkynyl derivatives, as well as betulin 1 and betulinic acid 3, were evaluated in vitro for their cytotoxic activity against human T47D breast cancer, CCRF/CEM leukemia, SW707 colorectal, murine P388 leukemia and BALB3T3 normal fibroblasts cell lines. Several of the obtained compounds have a favorable cytotoxic profile than betulin 1. Propargyl betulinate 8 was the most active derivative, being up to 3-fold more potent than betulin 1 against the human leukemia (CCRF/CEM) cell line, with an IC50 value of 3.9 μg/mL.

  3. Urea-acetylene dicarboxylic acid reaction: A likely pathway for prebiotic uracil formation

    NASA Astrophysics Data System (ADS)

    Subbaraman, A. S.; Kazi, Z. A.; Choughuley, A. S. U.; Chadha, M. S.

    1980-12-01

    A number of routes have been suggested for the prebiotic synthesis of uracil involving the reaction of urea with malic acid, propiolic acid, cyanoacetylene and others. Cyanoacetylene has been detected in the interstellar medium as well as simulated prebiotic experiments. It is therefore plausible that dicyanoacetylene and its hydrolytic product acetylene dicarboxylic acid, (ADCA) may have played a role in chemical evolution. This aspect has been examined in the present work for the synthesis of uracil from ADCA and urea reaction. It was found that when ADCA reacted with urea, uracil was formed only in the presence of phosphoric acid and phosphates. Ammonium phosphates gave higher yields of uracil than other phosphates. In the absence of phosphoric acid or phosphates no uracil formation took place. This type of synthesis could have taken place in prebiotic oceans which contained ammonium phosphates and other salts.

  4. Efficient diode-pumped mid-infrared emission from acetylene-filled hollow-core fiber.

    PubMed

    Wang, Zefeng; Belardi, Walter; Yu, Fei; Wadsworth, William J; Knight, Jonathan C

    2014-09-01

    We report 3.1-3.2 ?m mid-infrared emission from acetylene-filled low loss antiresonant hollow-core fiber pumped with an amplified, modulated, narrowband, tunable 1.5 ?m diode laser. The maximum power conversion efficiency of ~30%, with respect to the absorbed pump power, is obtained with a 10.5 m length of fiber at 0.7 mbar. The maximum efficiency with respect to the total incident pump power (~20%) and the minimum pump laser energy required (<50 nJ) are both improved compared to similar work reported previously using an optical parametric oscillator as a pump source. This paper provides an effective route to obtain compact mid-infrared fiber lasers. PMID:25321562

  5. Shape and optical properties of aerosols formed by photolysis of acetylene, ethylene, and hydrogen cyanide

    SciTech Connect

    Bar-Nun, A.; Kleinfeld, I.; Ganor, E.

    1988-07-20

    The shapes and sizes of photochemically produced aerosol particles of polyacetylene, polyethylene, and polyhydrogen cyanide were studied experimentally. All of the single particles were found to be perfectly spherical and semiliquid. However, they aggregate readily, with a sticking coefficient near unity, to form nonspherical particles, which could give rise to the observed polarization from Titan's and Jupiter's upper haze layers. The absorbance of polyacetylene was remeasured and corrected, and it is now much closer to that of polyethylene. The measured real and imaginary indices of refraction of the two materials make them both suitable material for Titan's and Jupiter's upper haze layers. However, the larger abundance and higher rate of polymerization of acetylene would make it the dominant aerosol-forming material in both atmospheres. copyright American Geophysical Union 1988

  6. Visualizing Recurrently Migrating Hydrogen in Acetylene Dication by Intense Ultrashort Laser Pulses

    SciTech Connect

    Hishikawa, Akiyoshi; Matsuda, Akitaka; Fushitani, Mizuho; Takahashi, Eiji J.

    2007-12-21

    We demonstrate the visualization of ultrafast hydrogen migration in deuterated acetylene dication (C{sub 2}D{sub 2}{sup 2+}) by employing the pump-probe Coulomb explosion imaging with sub-10-fs intense laser pulses (9 fs, 0.13 PW/cm{sup 2}, 800 nm). It is shown, from the temporal evolution of the momenta of the fragment ions produced by the three-body explosion, C{sub 2}D{sub 2}{sup 3+}{yields}D{sup +}+C{sup +}+CD{sup +}, that the migration proceeds in a recurrent manner: The deuterium atom first shifts from one carbon site to the other in a short time scale ({approx}90 fs) and then migrates back to the original carbon site by 280 fs, in competition with the molecular dissociation.

  7. Soot Volume Fraction Maps for Normal and Reduced Gravity Laminar Acetylene Jet Diffusion Flames

    NASA Technical Reports Server (NTRS)

    Greenberg, Paul S.; Ku, Jerry C.

    1997-01-01

    The study of soot particulate distribution inside gas jet diffusion flames is important to the understanding of fundamental soot particle and thermal radiative transport processes, as well as providing findings relevant to spacecraft fire safety, soot emissions, and radiant heat loads for combustors used in air-breathing propulsion systems. Compared to those under normal gravity (1-g) conditions, the elimination of buoyancy-induced flows is expected to significantly change the flow field in microgravity (O g) flames, resulting in taller and wider flames with longer particle residence times. Work by Bahadori and Edelman demonstrate many previously unreported qualitative and semi-quantitative results, including flame shape and radiation, for sooting laminar zas jet diffusion flames. Work by Ku et al. report soot aggregate size and morphology analyses and data and model predictions of soot volume fraction maps for various gas jet diffusion flames. In this study, we present the first 1-g and 0-g comparisons of soot volume fraction maps for laminar acetylene and nitrogen-diluted acetylene jet diffusion flames. Volume fraction is one of the most useful properties in the study of sooting diffusion flames. The amount of radiation heat transfer depends directly on the volume fraction and this parameter can be measured from line-of-sight extinction measurements. Although most Soot aggregates are submicron in size, the primary particles (20 to 50 nm in diameter) are in the Rayleigh limit, so the extinction absorption) cross section of aggregates can be accurately approximated by the Rayleigh solution as a function of incident wavelength, particles' complex refractive index, and particles' volume fraction.

  8. Complete basis set extrapolations for low-lying triplet electronic states of acetylene and vinylidene

    NASA Astrophysics Data System (ADS)

    Sherrill, C. David; Byrd, Edward F. C.; Head-Gordon, Martin

    2000-07-01

    A recent study by Ahmed, Peterka, and Suits [J. Chem. Phys. 110, 4248 (1999)] has presented the first experimentally derived estimate of the singlet-triplet gap in the simplest alkyne, acetylene. Their value, T0(3B2)=28 900 cm-1, does not agree with previous theoretical predictions using the coupled-cluster singles, doubles, and perturbative triples [CCSD(T)] method and a triple-? plus double polarization plus f-function basis set (TZ2P f ), which yields 30 5001000 cm-1. This discrepancy has prompted us to investigate possible deficiencies in this usually-accurate theoretical approach. Employing extrapolations to the complete basis set limit along with corrections for full connected triple excitations, core correlation, and even relativistic effects, we obtain a value of 30 900 cm-1 (estimated uncertainty 230 cm-1), demonstrating that the experimental value is underestimated. To assist in the interpretation of anticipated future experiments, we also present highly accurate excitation energies for the other three low-lying triplet states of acetylene, 3Bu(33 570230 cm-1), b 3Au(36 040260 cm-1), and b 3A2(38 380260 cm-1), and the three lowest-lying states of vinylidene, X 1A1(15 150230 cm-1), 3B2(31 870230 cm-1), and b 3A2(36 840350 cm-1). Finally, we assess the ability of density functional theory (DFT) and the Gaussian-3 method to match our benchmark results for adiabatic excitation energies of C2H2.

  9. Classical characters of highly excited bend dynamics of acetylene in two coupled SU(2) coset spaces

    NASA Astrophysics Data System (ADS)

    Yu, Jin; Wu, Guozhen

    2000-07-01

    The classical characters of the highly excited bend dynamics of acetylene are analyzed in terms of two coupled SU(2)/U(1) coset spaces corresponding to the right and left circular motion of the two C-H bends. The vibrational modes show a wide variety of behaviors that are not observed in the simple SU(2)/U(1) coset case which deals with, e.g., two coupled stretches, in which case the vibrational modes can be characterized as (low-lying) local and (high-lying) normal modes with a so-called local-normal transition in between. For the two coupled SU(2)/U(1) cosets of acetylene, the general trend is that most modes are perturbed local or normal modes, with distinct characters that are not found in the SU(2) dynamics. Details of their classical characters and the dynamical action flow between the two C-H bends were deduced. When the total action number Nb is small (less than 14), normal mode motions dominate, i.e., trans bend modes at the bottom of each polyad and cis bend at the top. At higher Nb, the vibrational modes are more or less of local character though they, individually, do possess very unique characters. Specifically, as Nb ranges from 12 to 22, the characters of the low-lying levels change from the trans character with action asymmetrically distributed in the two C-H bonds to one hydrogen bending, while those of the high-lying levels change from well concerted cis to local counter rotation. These results are consistent with recent quantal and semiclassical results. [M. P. Jacobson, R. J. Silbey, and R. W. Field, J. Chem. Phys. 110, 845 (1999); M. P. Jacobson, C. Jung, H. S. Taylor, and R. W. Field, ibid. 111, 600 (1999)].

  10. Can Analysis of Acetylene and Its Biodegradation Products in Enceladus Plumes be Used to Detect the Presence of Sub-Surface Life?

    NASA Astrophysics Data System (ADS)

    Miller, L. G.; Baesman, S. M.; Oremland, R. S.

    2014-12-01

    The search for biosignatures of life on Earth includes measurement of the stable isotope fractionation of reactants and products attributed to enzymatic processes and comparison with the often smaller chemical (abiotic) fractionation. We propose that this approach might be applied to study the origin and fate of organic compounds contained in water vapor plumes emanating from Enceladus or other icy bodies, perhaps revealing information about the potential for biology occurring within a sub-surface "habitable" zone. Methanol and C2-hydrocarbons including ethylene, ethane and acetylene (C2H2) have been identified in the plumes of Enceladus. Biological degradation of acetylene proceeds by anaerobic fermentation via acetylene hydratase through acetaldehyde, with a second enzyme (acetaldehyde dismutase) forming acetate and ethanol. We found that incubation of cultures of acetylene-fermenting bacteria exhibit a kinetic isotope effect (KIE) associated with the net removal of C2H2. Consumption of acetylene by both growing and washed-cell cultures of bacteria closely related to Pelobacter acetylenicus (e.g, strain SFB93) was accompanied by a carbon isotopic fractionation of about 2 per mil (KIE = 1.8-2.7 ), a result we are examining with other cultures of acetylene fermenters. In addition, we are measuring the carbon isotopic composition of acetaldehyde, ethanol and acetate during fermentation to learn whether these products are fractionated sufficiently, relative to their substrate, to warrant measurement of their isotopic composition in Enceladus (or Europa) plumes to indicate enzymatic activity in liquid environments below the crust of these moons.

  11. Ferrimagnetism in 2D networks of porphyrin-X and -XO (X=Sc,...,Zn) with acetylene bridges

    NASA Astrophysics Data System (ADS)

    Wierzbowska, Małgorzata; Sobolewski, Andrzej L.

    2016-03-01

    Magnetism in 2D networks of the acetylene-bridged transition metal porphyrins M(P)-2(C-C)-2 (denoted P-TM), and oxo-TM-porphyrins OM(P)-2(C-C)-2 (denoted P-TMO), is studied with the density functional theory (DFT) and the self-interaction corrected pseudopotential scheme (pSIC). Addition of oxygen lowers magnetism of P-TMO with respect to the corresponding P-TM for most of the first-half 3d-row TMs. In contrast, binding O with the second-half 3d-row TMs or Sc increases the magnetic moments. Ferrimagnetism is found for the porphyrin networks with the TMs from V to Co and also for these cases with oxygen. This is a long-range effect of the delocalized spin-polarization, extended even to the acetylene bridges.

  12. Development of a spectrofluorimetry-based device for determining the acetylene content in the oils of power transformers.

    PubMed

    Quintella, Cristina M; Meira, Marilena; Silva, Weidson Leal; Filho, Rogrio G D; Arajo, Andr L C; Jnior, Elias T S; Sales, Lindolfo J O

    2013-12-15

    Power transformers are essential for a functioning electrical system and therefore require special attention by maintenance programs because a fault can harm both the company and society. The temperature inside a power transformer and the dissolved gases, which are primarily composed of acetylene, are the two main parameters monitored when detecting faults. This paper describes the development of a device for analyzing the acetylene content in insulating oil using spectrofluorimetry. Using this device introduces a new methodology for the maintaining and operating power transformers. The prototype is currently operating in a substation. The results presented by this system were satisfactory; when compared to chromatographic data, the errors did not exceed 15%. This prototype may be used to confirm the quality of an insulating oil sample to detect faults in power transformers. PMID:24209339

  13. Detection of acetylene impurities in ethylene and polyethylene manufacturing processes using tunable diode laser spectroscopy in the 3-?m range

    NASA Astrophysics Data System (ADS)

    Kluczynski, P.; Jahjah, M.; Nhle, L.; Axner, O.; Belahsene, S.; Fischer, M.; Koeth, J.; Rouillard, Y.; Westberg, J.; Vicet, A.; Lundqvist, S.

    2011-11-01

    Using recently developed GaInAsSb/AlGaInAsSb DFB lasers, tunable diode laser spectroscopy (TDLS) has been extended into the 3-?m wavelength region for the detection of acetylene impurities in hydrocarbon compounds encountered in ethylene manufacturing. Measurements of acetylene in pure polymer grade ethylene and in a gas mixture of ethylene and ethane typical of the process stream around a hydrogenation reactor have been performed. Using a procedure incorporating subtraction of a hydrocarbon background spectrum a detection limit of 5 ppb m was achieved under ordinary laboratory conditions. Under forced temperature cycling conditions, the detection limit deteriorated to 180 ppb m, due to temperature drift caused by optical interferences generated by reflections in the laser TO8 can.

  14. Homochiral [2]Catenane and Bis[2]catenane from Alleno-Acetylenic Helicates - A Highly Selective Narcissistic Self-Sorting Process.

    PubMed

    Gidron, Ori; Jirásek, Michael; Trapp, Nils; Ebert, Marc-Olivier; Zhang, Xiangyang; Diederich, François

    2015-10-01

    Homochiral strands of alternating alleno-acetylenes and phenanthroline ligands (P)-1 and (P2)-2, as well as their corresponding enantiomers, selectively assemble with the addition of silver(I) salt to yield dinuclear and trinuclear double helicates, respectively. Upon increasing the solvent polarity, the dinuclear and trinuclear helicates interlock to form a [2]catenane and bis[2]catenane, bearing 14 chirality elements, respectively. The solid-state structure of the [2]catenane reveals a nearly perfect fit of the interlocked strands, and the ECD spectra show a significant amplification of the chiroptical properties upon catenation, indicating stabilization of the helical secondary structure. Highly selective narcissistic self-sorting was demonstrated for a racemic mixture consisting of both short and long alleno-acetylenic strands, highlighting their potential for the preparation of linear catenanes of higher order. PMID:26380872

  15. High-Rate Diamond Deposition by Combustion Flame Method Using Twin Acetylene/Oxygen Gas Welding Torch

    NASA Astrophysics Data System (ADS)

    Ando, Yasutaka; Tobe, Shogo; Tahara, Hirokazu

    2009-12-01

    To develop a high-rate diamond deposition process using combustion flame method, diamond deposition equipment with twin acetylene/oxygen welding torch was manufactured, and diamond deposition by using this equipment was carried out. 304 Stainless steel plates and molybdenum plates were used as substrates. The diamond deposition was conducted under the following conditions: oxygen flow rate: 1.25 SLM, acetylene/oxygen flow ratio: 1.15, and diamond deposition temperature: around 1473 K. Consequently, diamonds could be deposited even on the stainless steel substrate, and diamond deposition rate was promoted by using twin torch equipment. Besides, the diamond/molybdenum hybrid coating using diamonds deposited by twin torch equipment have the same wear-resistant property as that using diamonds by the single torch equipment. From these results, this technique was thought to have high potential for high-rate diamond deposition in combustion flame method.

  16. Quantum Chemical Evaluation of the Astrochemical Significance of Reactions between S Atom and Acetylene or Ethylene

    NASA Technical Reports Server (NTRS)

    Woon, David E.

    2007-01-01

    Addition-elimination reactions of S atom in its P-3 ground state with acetylene (C2H2) and ethylene (C2H4) were characterized with both molecular orbital and density functional theory calculations employing correlation consistent basis sets in order to assess the likelihood either reaction might play a general role in astrochemistry or a specific role in the formation of S2 (X (sup 3 SIGMA (sub g) (sup -)) via a mechanism proposed by Saxena and Misra (Mon. Not. R. Astron. Soc. 1995, 272, 89). The acetylene and ethylene reactions proceed through C2H2S ((sup 3)A")) and C2H4S ((sup 3)A")) intermediates, respectively, to yield HCCS ((sup 2)II)) and C2H3S ((sup 2)A')). Substantial barriers were found in the exit channels for every combination of method and basis set considered in this work, which effectively precludes hydrogen elimination pathways for both S + C2H2 and S + C2H4 in the ultracold interstellar medium where only very modest barriers can be surmounted and processes without barriers tend to predominate. However, if one or both intermediates is formed and stabilized efficiently under cometary or dense interstellar cloud conditions, they could serve as temporary reservoirs for S atom and participate in reactions such as S + C2H2S (right arrow) S2 = C2H2 or S + C2H4S (right arrow) S2 + C2H4. For formation and stabilization to be efficient, the reaction must possess a barrier height small enough to be surmountable at low temperatures yet large enough to prevent redissociation to reactants. Barrier heights computed with B3LYP and large basis sets are very low, but more rigorous QCISD(T) and RCCSD(T) results indicate that the barrier heights are closer to 3-4 kcal/mol. The calculations therefore indicate that S + C2H2 or S + C2H4 could contribute to the formation of S2 in comets and may serve as a means to gauge coma temperature. The energetics of the ethylene reaction are more favorable.

  17. Complexes of acetylene-fluoroform: A matrix isolation and computational study

    NASA Astrophysics Data System (ADS)

    Sundararajan, K.; Ramanathan, N.; Viswanathan, K. S.; Vidya, K.; Jemmis, Eluvathingal D.

    2013-10-01

    Hydrogen-bonded complexes of C2H2 and CHF3 have been investigated using matrix isolation infrared spectroscopy and ab initio computations. The complexes were trapped in both solid argon and nitrogen matrices at 12 K. The structure of the complexes and the energies were computed at the B3LYP and MP2 levels of theory using a 6-311++G(d,p) basis set and at the MP2/aug-cc-pvdz level. Our computations indicated two minima for the 1:1 C2H2-CHF3 complex, with the C-H…π complex being the global minimum, where CHF3 is the proton donor. The second minimum corresponded to a relatively less exothermic C-H…F complex, in which C2H2 is the proton donor. Experimentally, we observed only the C-H…π complex in our matrix, which was evidenced by the shifts in the vibrational frequencies of the modes involving the C2H2 and CHF3 sub-molecules. The increase in the blue shift of the C-H stretching frequency in going from CHCl3-acetylene complex to CHF3-acetylene complex with corresponding increase in the interaction energy helps to place these two complexes on the left hand end of the qualitative diagram (Fig. 1). We also performed computations to study the higher complexes of C2H2 and CHF3. One minimum was found for the 1:2 C2H2-CHF3 complexes and two minima for the 2:1 C2H2-CHF3 complexes, at all levels of theory. Experimentally we observed the features corresponding to the 1:2 and 2:1 C2H2-CHF3 complexes in the N2 matrix. The computed vibrational frequencies of C2H2-CHF3 complexes at B3LYP and MP2/6-311++G(d,p) level corroborated well with the experimental frequencies. Interestingly, no experimental evidence for the formation of higher complexes was observed in the Ar matrix.

  18. Absolute nuclear material assay

    DOEpatents

    Prasad, Manoj K.; Snyderman, Neal J.; Rowland, Mark S.

    2010-07-13

    A method of absolute nuclear material assay of an unknown source comprising counting neutrons from the unknown source and providing an absolute nuclear material assay utilizing a model to optimally compare to the measured count distributions. In one embodiment, the step of providing an absolute nuclear material assay comprises utilizing a random sampling of analytically computed fission chain distributions to generate a continuous time-evolving sequence of event-counts by spreading the fission chain distribution in time.

  19. Absolute nuclear material assay

    DOEpatents

    Prasad, Manoj K.; Snyderman, Neal J.; Rowland, Mark S.

    2012-05-15

    A method of absolute nuclear material assay of an unknown source comprising counting neutrons from the unknown source and providing an absolute nuclear material assay utilizing a model to optimally compare to the measured count distributions. In one embodiment, the step of providing an absolute nuclear material assay comprises utilizing a random sampling of analytically computed fission chain distributions to generate a continuous time-evolving sequence of event-counts by spreading the fission chain distribution in time.

  20. Quantum Mechanical Study of Large Amplitude Motion in Small Polyatomic Molecules: Applications to Hydrogen Cyanide and Acetylene

    NASA Astrophysics Data System (ADS)

    Bentley, Joseph Allen

    This dissertation consists of a quantum mechanical investigation of HCN and acetylene via "local" basis set methodology. Specifically, the calculations on the HCN/HNC system include the following: (a) the calculation of converged energy levels as high as 30,000 cm^{ -1} above the zero point energy (zpe), (b) a discussion of the energy level structure including the calculation of vibrational anharmonicity constants, (c) a study of the vibrational wavefunctions near the top of the isomerization barrier and higher, (d) the calculation of both Franck-Condon SEP spectra as well as SEP spectra with an electronic transition dipole operator from several initial excited vibrational states, (e) a Fourier transform of the theoretical spectrum to investigate through the survival probability how the initial wave packet of the excited surface explores the accessible phase space on the ground surface, (f) the calculation of short time ( <200 fs) time-dependent expectation values of the Jacobi coordinates so as to achieve a physical picture of the dynamics of the wave packet while accessing the high energy regime. Finally, a preliminary study of the vibrational eigenvalue spectrum of acetylene is detailed. In this calculation, full use is made of the permutation/reflection symmetry of the acetylene molecule. Energy levels converged to nearly 4,500 cm^{-1} are reported.

  1. Importance of surface carbide formation on the activity and selectivity of Pd surfaces in the selective hydrogenation of acetylene

    NASA Astrophysics Data System (ADS)

    Yang, Bo; Burch, Robbie; Hardacre, Christopher; Hu, P.; Hughes, Philip

    2016-04-01

    A recent experimental investigation (Kim et al. J. Catal. 306 (2013) 146-154) on the selective hydrogenation of acetylene over Pd nanoparticles with different shapes concluded that Pd(100) showed higher activity and selectivity than Pd(111) for acetylene hydrogenation. However, our recent density functional calculations (Yang et al. J. Catal. 305 (2013) 264-276) observed that the clean Pd(111) surface should result in higher activity and ethylene selectivity compared with the clean Pd(100) surface for acetylene hydrogenation. In the current work, using density functional theory calculations, we find that Pd(100) in the carbide form gives rise to higher activity and selectivity than Pd(111) carbide. These results indicate that the catalyst surface is most likely in the carbide form under the experimental reaction conditions. Furthermore, the adsorption energies of hydrogen atoms as a function of the hydrogen coverage at the surface and subsurface sites over Pd(100) are compared with those over Pd(111), and it is found that the adsorption of hydrogen atoms is always less favoured on Pd(100) over the whole coverage range. This suggests that the Pd(100) hydride surface will be less stable than the Pd(111) hydride surface, which is also in accordance with the experimental results reported.

  2. Chemical characterization of plasma-polymerized films from acetylene and nitrogen-containing mixtures and their ethanol vapor sensitivity

    NASA Astrophysics Data System (ADS)

    Chen, Ko-Shao; Wei, Ta-Chin; Li, Ming-Shu; Wu, Hsin-Ming; Tang, Tzu-Piao; Wang, Chieh-Ying; Tu, Yu-Chieh

    2007-06-01

    In this study, plasma-polymerized thin films were prepared from plasma enhanced chemical vapor deposition (PECVD) of acetylene (C 2H 2), acetylene/nitrogen (C 2H 2/N 2), or acetylene/ammonia (C 2H 2/NH 3). When N 2 or NH 3 was mixed with C 2H 2 in the feed, the films were identified to contain all elements of the mixture and the properties of the films were implied by the C-H bonds and nitrogen functionalities. As shown by X-ray photoelectron spectroscopy (XPS) the [N]/[C] atomic ratio varies by changing the mixture composition and reaches a maximum of 0.12 for mixing C 2H 2 with NH 3. It is found that the resistance of the thin film sensors prepared from C 2H 2, C 2H 2/N 2, and C 2H 2/NH 3 is distinctly decreased by over 2 orders of magnitude by the adsorption of ethanol vapor.

  3. Angular and energy distribution of fragment ions in dissociative double photoionization of acetylene molecules at 39 eV

    SciTech Connect

    Alagia, M.; Callegari, C.; Richter, R.; Candori, P.; Falcinelli, S.; Vecchiocattivi, F.; Pirani, F.; Stranges, S.

    2012-05-28

    The two-body dissociation reactions of the dication, C{sub 2}H{sub 2}{sup 2+}, produced by 39.0 eV double photoionization of acetylene molecules, have been studied by coupling photoelectron-photoion-photoion coincidence and ion imaging techniques. The results provide the kinetic energy and angular distributions of product ions. The analysis of the results indicates that the dissociation leading to C{sub 2}H{sup +}+H{sup +} products occurs through a metastable dication with a lifetime of 108 {+-} 22 ns, and a kinetic energy release (KER) distribution exhibiting a maximum at {approx}4.3 eV with a full width at half maximum (FWHM) of about 60%. The reaction leading to CH{sub 2}{sup +}+C{sup +} occurs in a time shorter than the typical rotational period of the acetylene molecules (of the order of 10{sup -12} s). The KER distribution of product ions for this reaction, exhibits a maximum at {approx}4.5 eV with a FWHM of about 28%. The symmetric dissociation, leading to CH{sup +} + CH{sup +}, exhibits a KER distribution with a maximum at {approx}5.2 eV with a FWHM of 44%. For the first two reactions the angular distributions of ion products also indicate that the double photoionization of acetylene occurs when the neutral molecule is mainly oriented perpendicularly to the light polarization vector.

  4. Surface characterization of the interfaces from plasma-polymerized acetylene films deposited onto cold-rolled steel for rubber-to-metal bonding

    NASA Astrophysics Data System (ADS)

    Rosales Lombardi, Pablo I.

    The molecular structure of the interface between plasma-polymerized acetylene films and steel was determined using in-situ reflection-absorption infrared spectroscopy (RAIR) and X-ray photoelectron spectroscopy (XPS). Plasma-polymerized acetylene films were deposited onto polished steel substrates in microwave (MW) and radio frequency (RF)-powered reactors. The films deposited in RF-powered reactors were characterized in-situ using XPS and FTIR spectrometers that were interfaced directly to the reactors. RAIR showed that the plasma polymerized films contained large numbers of methyl and methylene groups but only a small number of monosubstituted acetylene groups, indicating that there was substantial rearrangement of the monomer molecules during plasma polymerization. The rearrangement of the monomer molecules during plasma was also determined by optical emission spectroscopy (OES), where CH and C2 species predominated in the optical emission spectra. Bands were observed near 1020 and 885 cm-1 in the RAIR spectra that were attributed to skeletal stretching vibrations in C-C-O-Fe groups, indicating that the plasma-polymerized films interacted with the substrate through formation of alkoxide bonds. Another band was observed near 1565 cm-1 and attributed to carboxylate groups in the interface between films and the oxidized surface of the substrate. Results from XPS also confirmed the formation of alkoxide and carboxylate groups in the interface during plasma polymerization of acetylene. Results from XPS showed that the surface of steel substrates consisted mostly of a mixture of Fe2O3 and FeOOH and that iron was mostly present in the Fe(III) oxidation state. However, during plasma-polymerization of acetylene, there was a tendency for the concentration of Fe(II) to increase, due to the reducing nature of argon/acetylene plasmas. Natural rubber reacted with plasma-polymerized acetylene primers through unsaturated functional groups present in the film. The RAIR and XPS results showed the presence of amino groups at the early steps of the vulcanization process. Activator products such as sulfenamide groups were found at the rubber/plasma-polymerized acetylene interface, the absorption bands near 1560 cm-1 in the RAIR spectra was due to the C=N stretching mode of the sulfenamide fragments of the accelerator. The band found in the RAIR spectra near 1143 cm -1 is characteristic from aliphatic secondary amines. Similarly, the presence of zinc was also found in the early stages of the vulcanization of natural rubber onto acetylene films. Zinc stearate reacted with accelerator and sulfur to form an accelerator complex. The zinc complex eventually reacted with natural rubber, sulfur, and the plasma-polymerized acetylene film to form rubber-bound intermediates.

  5. Theoretical and practical limitations of the acetylene inhibition technique to determine total denitrification losses

    NASA Astrophysics Data System (ADS)

    Felber, R.; Conen, F.; Flechard, C. R.; Neftel, A.

    2012-10-01

    The loss of N2 from intensively managed agro-ecosystems is an important part of the N budget. Flux monitoring of N2 emissions at the field scale, e.g., by eddy correlation or aerodynamic gradient method, is impossible due to the large atmospheric N2 background (78%). The acetylene (C2H2) inhibition technique (AIT) is a rather simple and frequently used, albeit imperfect, method to determine N2 losses from intact soil cores. In principle, AIT allows an estimation of total denitrification at high temporal resolution and on small spatial scales, with limited workload and costs involved. To investigate its potential and limitations, a laboratory system with two different detection systems (photoacoustic IR spectroscopy and gas chromatography) is presented, which allowed simultaneous measurements of up to 7 intact soil cores in air-tight glass tubes in a temperature controlled cabinet (adjusted to field conditions) with automated C2H2 injection. A survey of total denitrification losses (N2 + N2O) over 1.5 yr in soil cores from an intensively managed, cut grassland system in central Switzerland supports previous reports on severe limitations of the AIT, which precluded reliable estimates of total denitrification losses. Further, the unavoidable sampling and transfer of soil samples to the laboratory causes unpredictable deviations from the denitrification activity in the field.

  6. Anion dynamics in the first 10 milliseconds of an argon-acetylene radio-frequency plasma

    NASA Astrophysics Data System (ADS)

    van de Wetering, F. M. J. H.; Beckers, J.; Kroesen, G. M. W.

    2012-12-01

    The time evolution of the smallest anions (C2H- and H2CC-), just after plasma ignition, is studied by means of microwave cavity resonance spectroscopy (MCRS) in concert with laser-induced photodetachment under varying gas pressure and temperature in an argon-acetylene radio-frequency (13.56 MHz) plasma. These anions act as an initiator for spontaneous dust particle formation in these plasmas. With an intense 355 nm Nd : YAG laser pulse directed through the discharge, electrons are detached only from these anions present in the laser path. This results in a sudden increase in the electron density in the plasma, which can accurately and with sub-microsecond time resolution be measured with MCRS. By adjusting the time after plasma ignition at which the laser is fired through the discharge, the time evolution of the anion density can be studied. We have operated in the linear regime: the photodetachment signal is proportional to the laser intensity. This allowed us to study the trends of the photodetachment signal as a function of the operational parameters of the plasma. The density of the smallest anions steadily increases in the first few milliseconds after plasma ignition, after which it reaches a steady state. While keeping the gas density constant, increasing the gas temperature in the range 30-120 °C limits the number of smallest anions and saturates at a temperature of about 90 °C. A reaction pathway is proposed to explain the observed trends.

  7. Stereoselective inhibition of muscarinic receptor subtypes by the enantiomers of hexahydro-difenidol and acetylenic analogues.

    PubMed Central

    Feifel, R.; Wagner-Röder, M.; Strohmann, C.; Tacke, R.; Waelbroeck, M.; Christophe, J.; Mutschler, E.; Lambrecht, G.

    1990-01-01

    1. The affinities of the (R)- and (S)-enantiomers of hexahydro-difenidol (1) and its acetylenic analogues hexbutinol (2), hexbutinol methiodide (3) and p-fluoro-hexbutinol (4) (stereochemical purity greater than 99.8%) for muscarinic receptors in rabbit vas deferens (M1), guinea-pig atria (M2) and guinea-pig ileum (M3) were measured by dose-ratio experiments. 2. The (R)-enantiomers consistently showed higher affinities than the (S)-isomers. The stereoselectivity ratios [(R)/(S)] were greatest with the enantiomers of 1 (vas deferens: 550; ileum: 191; atria: 17) and least with those of the p-Fluoro-analogue 4 (vas deferens: 34; ileum: 8.5; atria: 1.7). 3. The enantiomeric potency ratios for compounds 1-4 were highest in rabbit vas deferens, intermediate in guinea-pig ileum and much less in guinea-pig atria. Thus, these ratios may serve as a predictor of muscarinic receptor subtype identity. 4. (S)-p-Fluoro-hexbutinol [(S)-4] showed a novel receptor selectivity profile with preference for M3 receptors: M3 greater than M2 greater than or equal to M1. 5. These results do not conform to Pfeiffer's rule that activity differences between enantiomers are greater with more potent compounds. PMID:2331578

  8. Infrared spectroscopy and Mie scattering of acetylene aerosols formed in a low temperature diffusion cell

    NASA Technical Reports Server (NTRS)

    Dunder, T.; Miller, R. E.

    1990-01-01

    A method is described for forming and spectroscopically characterizing cryogenic aerosols formed in a low temperature gas cell. By adjusting the cell pressure, gas composition and flow rate, the size distribution of aerosol particles can be varied over a wide range. The combination of pressure and flow rate determine the residence time of the aerosols in the cell and hence the time available for the particles to grow. FTIR spectroscopy, over the range from 600/cm to 6000/cm, is used to characterize the aerosols. The particle size distribution can be varied so that, at one extreme, the spectra show only absorption features associated with the infrared active vibrational bands and, at the other, they display both absorption and Mie scattering. In the latter case, Mie scattering theory is used to obtain semiquantitative aerosol size distributions, which can be understood in terms of the interplay between nucleation and condensation. In the case of acetylene aerosols, the infrared spectra suggest that the particles exist in the high temperature cubic phase of the solid.

  9. The Methane-Acetylene Cycle Aerospace Plane: A potential option for inexpensive Earth to orbit transportation

    NASA Astrophysics Data System (ADS)

    Zubrin, Robert M.

    1994-06-01

    Methane, a cheap, soft cryogen with six times the density of hydrogen could be an ideal fuel for use in a hypersonic aerospace plane. However, it does not burn fast enough for efficient scramjet operation and it possesses an inadequate thermal heat sink to cool the aircraft effectively. This paper proposes a concept, termed the Methane-Acetylene Cycle Aerospace Plane (MACASP), that may overcome these difficulties. In the MACASP concept, methane fuel is run out within the wing leading edge in pipes which are allowed to rise in temperature to about 1800 K. Drag heating is used to drive the highly endothermic chemical reaction; 2CH4 = 3H2 + C2H2. The reaction occurs on a millisecond time scale and endows the methane with a heat sink per unit mass comparable to that possessed by liquid hydrogen. The reaction products are fed into a combustion chamber and burned in air, releasing as much energy per unit mass at as rapid a combustion rate as hydrogen. This paper explores the thermodynamics of the MACASP concept and theoretical feasibility is demonstrated. Potential problems and areas of concern are identified. A conceptual point design for a MACASP vehicle is advanced and mission analysis performed comparing the MACASP to a conventional hydrogen aerospace plane. It is shown that the MACASP concept offers significant promise for economical Earth to orbit transportation.

  10. Cycloheximide prevents the de novo polypeptide synthesis required to recover from acetylene inhibition in Nitrosopumilus maritimus.

    PubMed

    Vajrala, Neeraja; Bottomley, Peter J; Stahl, David A; Arp, Daniel J; Sayavedra-Soto, Luis A

    2014-06-01

    Developing methods to differentiate the relative contributions of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) to ammonia (NH3) oxidation has been challenging due to the lack of compounds that selectively inhibit AOA. In this study, we investigated the effects of specific bacteria- and eukaryote-selective protein synthesis inhibitors on the recovery of acetylene (C2H2)-inactivated NH3 oxidation in the marine AOA Nitrosopumilus maritimus and compared the results with recovery of the AOB Nitrosomonas europaea. C2 H2 irreversibly inhibited N. maritimus NH3 oxidation in a similar manner to what was observed previously with N. europaea. However, cycloheximide (CHX), a widely used eukaryotic protein synthesis inhibitor, but not bacteria-specific protein synthesis inhibitors (kanamycin and gentamycin), inhibited the recovery of NH3-oxidizing activity in N. maritimus. CHX prevented the incorporation of (14)CO2 -labeling into cellular proteins, providing further evidence that CHX acts as a protein synthesis inhibitor in N. maritimus. If the effect of CHX on protein synthesis can be confirmed among other isolates of AOA, the combination of C2H2 inactivation followed by recovery of NH3 oxidation either in the presence of bacteria-selective protein synthesis inhibitors or CHX might be used to estimate the relative contributions of AOB and AOA to NH3 oxidation in natural environments. PMID:24606542

  11. Intramolecular vibrational relaxation and forbidden transitions in the SEP spectrum of acetylene

    SciTech Connect

    Jonas, D.M.; Solina, S.A.B.; Rajaram, B.; Silbey, R.J.; Field, R.W. ); Yamanouchi, K.; Tsuchiya, S. )

    1992-08-15

    {ital {tilde A}} {sup 1}{ital A}{sub {ital u}}{r arrow}{ital {tilde X}} {sup 1{Sigma}}{sub {ital g}}{sup +} SEP spectra of acetylene near {ital E}{sub VIB}=7000 cm{sup {minus}1} show that Darling--Dennison resonance between the {ital cis}- and {ital trans}-bending vibrations is the {ital first} {ital step} in a series of anharmonic resonances which can transfer nearly all the vibrational energy out of the Franck--Condon bright states at higher energy. In addition to allowed {vert bar}{Delta}{ital K}{vert bar}{equivalent to}{vert bar}{ital K}{prime}{minus}l{double prime}{vert bar}=1 rotational transitions, nominally forbidden {vert bar}{Delta}{ital K}{vert bar}=0,2,3 rotational transitions have also been observed due to axis-switching and rotational-l-resonance. Although the range of detectable fluorescence dips is only about 30, the range of detectable SEP intensities in these spectra is probably about 500.

  12. HCN formation on Jupiter - The coupled photochemistry of ammonia and Acetylene

    NASA Astrophysics Data System (ADS)

    Kaye, J. A.; Strobel, D. F.

    1983-06-01

    A model is presented for the formation of HCN in the upper troposphere and lower stratosphere of Jupiter by ultraviolet photolysis of the C2H5N isomer aziridine, a product of the recombination of NH2 and C2H3 radicals, which originate, respectively, from ammonia photolysis and addition of H atoms to acetylene. An HCN column density of ?21017 cm-2 in the tropopause region is predicted. Sensitivity of the HCN column density to the individual rate constants and the eddy diffusion coefficient profile is discussed, as is the possibility of the existence of additional HCN-yielding pathways. Ammonia, which is saturated in the upper troposphere, is strongly depleted by photolysis in the lower stratosphere. Phosphine is also strongly depleted by photolysis and its abundance in the upper troposphere is shown to depend strongly on vertical mixing in the tropopause region. The possibility of the formation of phosphirane is considered but found to be substantially less probable than aziridine.

  13. A novel surface modification scheme for ITO nanocrystals by acetylene: a combined experimental and DFT study.

    PubMed

    Chen, Z X; Xi, Y J; Huang, L; Li, W C; Li, R; Xu, G Q; Cheng, H S

    2015-10-28

    Many applications of Sn-doped indium oxide (ITO) films in organic electronics require appropriate surface modifications of ITO nanocrystals with small organic molecules, such as silanes, phosophonic acids and carboxylic acids, to improve interfacial contacts and charge transfer. Here, we propose a new surface modification strategy via adsorption of acetylene molecules on an oxygen-terminated ITO(100) surface using a slab crystalline model to represent the nanocrystal surface. The adsorption was first studied using density functional theory. It was found that the chemisorption of C2H2 on two types of surface oxygen dimers is highly exothermic with the calculated adsorption energies of 3.80 eV and 5.19 eV, respectively. Electron population analysis reveals the origin of the strong interaction between the adsorbate and the ITO(100) surface. Experimental studies on the synthesized ITO nanocrystals using X-ray photoelectron spectroscopy and diffuse reflectance infrared Fourier transform spectroscopy confirm the predicted strong adsorption of C2H2 on ITO surfaces. PMID:26395227

  14. Time- and Isomer-Resolved Measurements of Sequential Addition of Acetylene to the Propargyl Radical.

    PubMed

    Savee, John D; Selby, Talitha M; Welz, Oliver; Taatjes, Craig A; Osborn, David L

    2015-10-15

    Soot formation in combustion is a complex process in which polycyclic aromatic hydrocarbons (PAHs) are believed to play a critical role. Recent works concluded that three consecutive additions of acetylene (C2H2) to propargyl (C3H3) create a facile route to the PAH indene (C9H8). However, the isomeric forms of C5H5 and C7H7 intermediates in this reaction sequence are not known. We directly investigate these intermediates using time- and isomer-resolved experiments. Both the resonance stabilized vinylpropargyl (vp-C5H5) and 2,4-cyclopentadienyl (c-C5H5) radical isomers of C5H5 are produced, with substantially different intensities at 800 K vs 1000 K. In agreement with literature master equation calculations, we find that c-C5H5 + C2H2 produces only the tropyl isomer of C7H7 (tp-C7H7) below 1000 K, and that tp-C7H7 + C2H2 terminates the reaction sequence yielding C9H8 (indene) + H. This work demonstrates a pathway for PAH formation that does not proceed through benzene. PMID:26722791

  15. Surface modification of ?-TiAl alloys by acetylene plasma deposition

    NASA Astrophysics Data System (ADS)

    Narksitipan, Suparut; Thongtem, Titipun; McNallan, Michael; Thongtem, Somchai

    2006-10-01

    Surfaces of two ?-TiAl alloys, Ti-47 at% Al-2at% Nb-2 at% Cr (MJ12) and Ti-47 at% Al-2 at% Nb-2 at% Mn + 0.8 at% TiB 2 (MJ47), have been modified by acetylene plasma deposition at bias voltages of -4, -5 and -6 kV for 3.6 10 3 s (1 h) and 1.44 10 4 s (4 h). Knoop hardness (HK) of the alloys is increased with the increase of bias voltage and prolonged time for the deposition. HK of MJ12 and MJ47 deposited at -6 kV for 1.44 10 4 s is, respectively, 3.36 and 3.32 times as hard as the untreated alloys. SEM and AFM analyses show that the deposited alloys compose of a number of nano-dots which reflect their surface properties. The phases analyzed by XRD are in accord with the elements analyzed by EDX.

  16. Synthesis and characterization of graphenated carbon nanotubes on IONPs using acetylene by chemical vapor deposition method

    NASA Astrophysics Data System (ADS)

    Atchudan, Raji; Perumal, Suguna; Edison, Thomas Nesakumar Jebakumar Immanuel; Pandurangan, Arumugam; Lee, Yong Rok

    2015-11-01

    The graphenated carbon nanotubes (G-CNTs) were synthesized on monodisperse spherical iron oxide nanoparticles (IONPs) using acetylene as carbon precursor by simple chemical vapor deposition method. The reaction parameters such as temperature and flow of carbon source were optimized in order to achieve G-CNTs with excellent quality and quantity. Transmission electron microscopy (TEM) clearly illustrated that the graphene flakes are forming along the whole length on CNTs. The degree of graphitization was revealed by X-ray diffraction (XRD) analysis and Raman spectroscopic techniques. The intensity of D to G value was less than one which confirms the obtained G-CNTs have high degree of graphitization. The optimum reaction temperature for the IONPs to form metallic clusters which in turn lead to the formation of G-CNTs with high carbon deposition yield is at 900 °C. The TEM shows the CNTs diameter is 50 nm with foiled graphene flakes of diameter around 70 nm. Our results advocate for IONPs as a promising catalytic template for quantitative and qualitative productivity of nanohybrid G-CNTs. The produced G-CNTs with high degree of graphitization might be an ideal candidate for nanoelectronic application like super capacitors and so on.

  17. The Fourier transform absorption spectrum of acetylene between 7000 and 7500 cm-1

    NASA Astrophysics Data System (ADS)

    Lyulin, O. M.; Vander Auwera, J.; Campargue, A.

    2015-07-01

    High resolution (0.011 cm-1) room temperature (295 K) Fourier transform absorption spectra (FTS) of acetylene have been recorded between 7000 and 7500 cm-1. Line parameters (positions, intensities and self broadening coefficients) have been measured using a multispectrum treatment of three FTS spectra, recorded at 3.84, 8.04 and 56.6 hPa. As a result, a list of 3788 lines was constructed with intensities ranging between about 10-26 and 10-22 cm/molecule. Comparison with accurate predictions provided by a global effective operator model (Lyulin OM, Perevalov VI, Teffo JL, Proc. SPIE 2004;5311:134-43) led to the assignment of 2471 of these lines to 12C2H2. The assigned lines belong to 29 12C2H2 bands, 12 of them being newly reported. Spectroscopic parameters of the upper vibrational levels were derived from band-by-band fits of the line positions (typical rms values are on the order of 0.001 cm-1). About half of the analyzed bands were found to be affected by rovibrational perturbations. Line parameters obtained in this work were compared with those available for about 350 transitions in the HITRAN 2012 database. The large set of new data will be valuable to refine the parameters of the global effective Hamiltonian and dipole moments of 12C2H2.

  18. Global Assays of Hemostasis

    PubMed Central

    Brummel-Ziedins, Kathleen E.; Wolberg, Alisa S.

    2014-01-01

    Purpose of review There exists an imbalance between our understanding of the physiology of the blood coagulation process and the translation of this understanding into useful assays for clinical application. As technology advances, the capabilities for merging the two areas have become more attainable. Global assays have advanced our understanding of the dynamics of the blood coagulation process beyond end point assays and are at the forefront of implementation in the clinic. Recent findings We will review recent advances in the main global assays with a focus on thrombin generation that have potential for clinical utility. These assays include direct (thrombogram, whole blood, purified systems) and indirect empirical measures of thrombin generation (thromboelastography) and mechanism-based computational models that use plasma composition data from individuals to generate thrombin generation profiles. Summary Empirical thrombin generation assays (direct and indirect) and computational modeling of thrombin generation have greatly advanced our understanding of the hemostatic balance. Implementation of these types of assays and visualization approaches in the clinic potentially will provide a basis for the development of individualized patient care. Advances in both empirical and computational global assays have made the goal of predicting pre-crisis changes in an individuals hemostatic state one step closer. PMID:25054908

  19. Rapid mercury assays

    SciTech Connect

    Szurdoki, S.; Kido, H.; Hammock, B.D.

    1996-10-01

    We have developed rapid assays with the potential of detecting mercury in environmental samples. our methods combine the simple ELISA-format with the selective, high affinity complexation of mercuric ions by sulfur-containing ligands. The first assay is based on a sandwich chelate formed by a protein-bound ligand immobilized on the wells of a microliter plate, mercuric ion of the analyzed sample, and another ligand conjugated to a reporter enzyme. The second assay involves competition between mercuric ions and an organomercury-conjugate to bind to a chelating conjugate. Several sulfur containing chelators (e.g., dithiocarbamates) and organomercurials linked to macromolecular carriers have been investigated in these assay formats. The assays detect mercuric ions in ppb/high ppt concentrations with high selectivity.

  20. Single-cell assays

    PubMed Central

    Ryan, Declan; Ren, Kangning; Wu, Hongkai

    2011-01-01

    This review presents an overview of literature that describes the applications of microfluidics to assay individual cells. We quantify the content of an individual mammalian cell, so that we can understand what criteria a single-cell assay must satisfy to be successful. We put in context the justification for single-cell assays and identify the characteristics that are relevant to single-cell assays. We review the literature from the past 24 months that describe the methods that use microfabricationconventional or otherwiseand microfluidics in particular to study individual cells, and we present our views on how an increasing emphasis on three-dimensional cell culture and the demonstration of the first chemically defined cell might impact single-cell assays. PMID:21559238

  1. Properties and reactivity of chlorovinylcobalamin and vinylcobalamin and their implications for vitamin B12-catalyzed reductive dechlorination of chlorinated alkenes.

    PubMed

    McCauley, Kevin M; Pratt, Derek A; Wilson, Scott R; Shey, Justin; Burkey, Theodore J; van der Donk, Wilfred A

    2005-02-01

    Vitamin B12-catalyzed reductive dechlorination of perchloroethylene (PCE) and trichloroethylene (TCE) is a potential strategy for cleanup of polluted environments. Presented are crystal structures of vinylcobalamin 2 and cis-chlorovinylcobalamin 1. They show a strong resistance toward photolysis. Reduction of 2 is difficult, but reduction of 1 occurs readily and produces 2. The mechanism of this latter reaction involves acetylene as an intermediate. These and other findings are discussed in the context of environmental studies on B12-catalyzed dechlorination of PCE and TCE and investigations of the haloalkene reductive dehalogenases that catalyze similar reactions. PMID:15669852

  2. Intramolecular competition between n-pair and π-pair hydrogen bonding: Microwave spectrum and internal dynamics of the pyridine-acetylene hydrogen-bonded complex.

    PubMed

    Mackenzie, Rebecca B; Dewberry, Christopher T; Coulston, Emma; Cole, George C; Legon, Anthony C; Tew, David P; Leopold, Kenneth R

    2015-09-14

    a-type rotational spectra of the hydrogen-bonded complex formed from pyridine and acetylene are reported. Rotational and (14)N hyperfine constants indicate that the complex is planar with an acetylenic hydrogen directed toward the nitrogen. However, unlike the complexes of pyridine with HCl and HBr, the acetylene moiety in HCCH-NC5H5 does not lie along the symmetry axis of the nitrogen lone pair, but rather, forms an average angle of 46° with the C2 axis of the pyridine. The a-type spectra of HCCH-NC5H5 and DCCD-NC5H5 are doubled, suggesting the existence of a low lying pair of tunneling states. This doubling persists in the spectra of HCCD-NC5H5, DCCH-NC5H5, indicating that the underlying motion does not involve interchange of the two hydrogens of the acetylene. Single (13)C substitution in either the ortho- or meta-position of the pyridine eliminates the doubling and gives rise to separate sets of spectra that are well predicted by a bent geometry with the (13)C on either the same side ("inner") or the opposite side ("outer") as the acetylene. High level ab initio calculations are presented which indicate a binding energy of 1.2 kcal/mol and a potential energy barrier of 44 cm(-1) in the C2v configuration. Taken together, these results reveal a complex with a bent hydrogen bond and large amplitude rocking of the acetylene moiety. It is likely that the bent equilibrium structure arises from a competition between a weak hydrogen bond to the nitrogen (an n-pair hydrogen bond) and a secondary interaction between the ortho-hydrogens of the pyridine and the π electron density of the acetylene. PMID:26374037

  3. Intramolecular competition between n-pair and π-pair hydrogen bonding: Microwave spectrum and internal dynamics of the pyridine-acetylene hydrogen-bonded complex

    NASA Astrophysics Data System (ADS)

    Mackenzie, Rebecca B.; Dewberry, Christopher T.; Coulston, Emma; Cole, George C.; Legon, Anthony C.; Tew, David P.; Leopold, Kenneth R.

    2015-09-01

    a-type rotational spectra of the hydrogen-bonded complex formed from pyridine and acetylene are reported. Rotational and 14N hyperfine constants indicate that the complex is planar with an acetylenic hydrogen directed toward the nitrogen. However, unlike the complexes of pyridine with HCl and HBr, the acetylene moiety in HCCH—NC5H5 does not lie along the symmetry axis of the nitrogen lone pair, but rather, forms an average angle of 46° with the C2 axis of the pyridine. The a-type spectra of HCCH—NC5H5 and DCCD—NC5H5 are doubled, suggesting the existence of a low lying pair of tunneling states. This doubling persists in the spectra of HCCD—NC5H5, DCCH—NC5H5, indicating that the underlying motion does not involve interchange of the two hydrogens of the acetylene. Single 13C substitution in either the ortho- or meta-position of the pyridine eliminates the doubling and gives rise to separate sets of spectra that are well predicted by a bent geometry with the 13C on either the same side ("inner") or the opposite side ("outer") as the acetylene. High level ab initio calculations are presented which indicate a binding energy of 1.2 kcal/mol and a potential energy barrier of 44 cm-1 in the C2v configuration. Taken together, these results reveal a complex with a bent hydrogen bond and large amplitude rocking of the acetylene moiety. It is likely that the bent equilibrium structure arises from a competition between a weak hydrogen bond to the nitrogen (an n-pair hydrogen bond) and a secondary interaction between the ortho-hydrogens of the pyridine and the π electron density of the acetylene.

  4. CPTAC Assay Portal: a repository of targeted proteomic assays

    SciTech Connect

    Whiteaker, Jeffrey R.; Halusa, Goran; Hoofnagle, Andrew N.; Sharma, Vagisha; MacLean, Brendan; Yan, Ping; Wrobel, John; Kennedy, Jacob; Mani, DR; Zimmerman, Lisa J.; Meyer, Matthew R.; Mesri, Mehdi; Rodriguez, Henry; Abbateillo, Susan E.; Boja, Emily; Carr, Steven A.; Chan, Daniel W.; Chen, Xian; Chen, Jing; Davies, Sherri; Ellis, Matthew; Fenyo, David; Hiltket, Tara; Ketchum, Karen; Kinsinger, Christopher; Kuhn, Eric; Liebler, Daniel; Lin, De; Liu, Tao; Loss, Michael; MacCoss, Michael; Qian, Weijun; Rivers, Robert; Rodland, Karin D.; Ruggles, Kelly; Scott, Mitchell; Smith, Richard D.; Thomas, Stefani N.; Townsend, Reid; Whiteley, Gordon; Wu, Chaochao; Zhang, Hui; Zhang, Zhen; Paulovich, Amanda G.

    2014-06-27

    To address these issues, the Clinical Proteomic Tumor Analysis Consortium (CPTAC) of the National Cancer Institute (NCI) has launched an Assay Portal (http://assays.cancer.gov) to serve as a public repository of well-characterized quantitative, MS-based, targeted proteomic assays. The purpose of the CPTAC Assay Portal is to facilitate widespread adoption of targeted MS assays by disseminating SOPs, reagents, and assay characterization data for highly characterized assays. A primary aim of the NCI-supported portal is to bring together clinicians or biologists and analytical chemists to answer hypothesis-driven questions using targeted, MS-based assays. Assay content is easily accessed through queries and filters, enabling investigators to find assays to proteins relevant to their areas of interest. Detailed characterization data are available for each assay, enabling researchers to evaluate assay performance prior to launching the assay in their own laboratory.

  5. Diagnostic assays used to control small ruminant lentiviruses

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The serological diagnostic tests such as the agar gel immunodiffusion (AGID) assay and various types of enzyme linked immunosorbent assays (ELISAs) have contributed to the reduction of small ruminant lentivirus infections worldwide. Since there are no treatments or efficacious vaccines, the serolog...

  6. Acetylene-derived strong organic acceptors for planar and nonplanar push-pull chromophores.

    PubMed

    Kivala, Milan; Diederich, Franois

    2009-02-17

    Though investigated for decades, interest in push-pull chromophores (D-pi-A), strong electron donors (D) connected by pi-conjugating spacers to strong electron acceptors (A), continues to grow. Such chromophores are of substantial interest for optoelectronic devices such as waveguides. Also, strong donors and acceptors form bimolecular charge-transfer (CT) complexes and salts, some of which exhibit electrical conductivity and magnetic behavior. Furthermore, strong organic acceptors are increasingly explored as dopants in the fabrication of organic light-emitting diodes (OLEDs) and solar cells. This Account describes systematic efforts pursued over the past decade in our laboratory to generate new families of organic electron acceptors (A) and conjugate them via pi-spacers to electron donors (D) under formation of push-pull systems with intense intramolecular CT interactions and high third-order optical nonlinearities. First, we describe donor-acceptor-substituted tetraethynylethenes (TEEs). In these chromophores, the peripherally attached p-nitrophenyl acceptors and N,N-dimethylanilino donors behave as nearly independent redox centers. Acetylenic scaffolding using TEE building blocks produces large all-carbon sheets, such as perethynylated dehydroannulenes, expanded radialenes, and radiaannulenes with potent electron-acceptor properties. Arylated TEEs act as molecular switches allowing two-way photochemical interconversion that is not perturbed by thermal isomerization pathways. Upon sequential substitution of the acetylene moieties in TEEs, we formed another family of potent acceptors, the cyanoethynylethenes (CEEs). Donor-substituted CEEs are planar CT chromophores with very high third-order optical nonlinearities. Their high environmental stability allows for the formation of thin films by vapor-phase deposition. Through careful analysis of the physicochemical properties of CEEs, we established useful guidelines for evaluating and tuning the optical gap in strong push-pull chromophores: increasing the length of the pi-spacer in D-pi-A systems reduces ground-state D-A conjugation and lowers the HOMO-LUMO gap. By taking advantage of "click-chemistry"-type [2 + 2] cycloadditions of tetracyanoethene (TCNE) and 7,7,8,8-tetracyanoquinodimethane (TCNQ) with appropriately activated alkynes, followed by retro-electrocyclization, the formation of donor-substituted 1,1,4,4-tetracyanobuta-1,3-dienes (TCBDs), 1,1,2,4,4-pentacyanobuta-1,3-dienes (PCBDs), and novel TCNQ adducts is possible. Some of these stable, nonplanar CT chromophores form high optical quality amorphous thin films by vapor-phase deposition. Despite donor substitution, the new acceptors (TCBDs, PCBDs, and the TCNQ adducts) rival TCNE and TCNQ in their ease for reversible electron uptake. High-yielding cycloaddition/retro-electrocyclization cascades provide access to multivalent, dendritic chromophores acting as "molecular batteries" with a remarkable capacity for multiple electron uptake in a narrow potential range. Finally, we used a one-pot protocol for electronically controlled consecutive TCNE and tetrathiafulvalene (TTF) additions to end-capped polyynes to form [AB]-type oligomers with a dendralene-type backbone. PMID:19061332

  7. Acetylene ^1^2C_2H_2 Laboratory Measurements for Astrophysical Applications

    NASA Astrophysics Data System (ADS)

    Jacquemart, D.; Gomez, L.; Lacome, N.; Mandin, J.-Y.; Pirali, O.; Roy, P.

    2010-06-01

    The acetylene molecule is important for atmospheric, planetary, and astrophysical applications. This organic molecule, known as a precursor of amino acids, shows numerous vibration-rotation bands in the IR. Two recent works on line intensities measurements will be presented. A study around 7.7 ?m was motivated by SPITZER observations of C_2H_2 in this spectral region that cannot be modeled using the current line list of HITRAN/GEISA due to the lack of data. High resolution spectra have been recorded with the Bruker HR IFS 120 of the LADIR and analyzed to deduce absolute line intensities of several bands included the one present in HITRAN, the (?_4+?_5)^0_+ strong band. On the whole, line intensities of 2 cold bands and 15 hot bands have been studied, and a complete line list has been generated. Another study using SOLEIL synchrotron will be presented in the spectral region around 100 cm^-^1 of interest for astrophysical applications (SPITZER, ALMA, HERSCHEL...). High resolution spectra have been recorded with the Bruker HR IFS 125 of SOLEIL. For accurate line intensities measurement based on the FIR beam of the synchrotron, the strong wavenumber dependence of the beam radius had to be modeled in the apparatus function calculation. Absolute line intensities of the intense ?_5-?_4 band have been measured, and those of the 4 weaker hot bands are in progress. M. Matzuura et al. Non. Not. R. Astron. Soc. 371, 415-420, 2006. J. Vander Auwera. J. Mol. Spectrosc. 242, 25-30, 2007. L. Gomez, D. Jacquemart, N. Lacome and J.-Y. Mandin. JQSRT 110, 2102-2114, 2009. D. Jacquemart, L. Gomez, N. Lacome, J.-Y. Mandin, O. Pirali and P. Roy. JQSRT in press.

  8. Chromophores from Photolyzed Ammonia Reacting with Acetylene: Application to Jupiters Great Red Spot

    NASA Astrophysics Data System (ADS)

    Carlson, Robert W.; Baines, K. H.; Anderson, M. S.; Filacchione, G.

    2012-10-01

    The production mechanisms of chromophores at Jupiter, and notably at the Great Red Spot (GRS), have been long-standing puzzles. A clue to the formation of the GRS coloring agent may be the great height of this storm, which can upwell ammonia to pressure levels of a few hundred mbar where solar photons capable of dissociating NH3 penetrate. Acetylene formed at higher altitudes can diffuse down and react with the NH3 photodissociation products, forming a deposit that absorbs in the ultraviolet and visible region (Ferris and Ishikawa, J. Amer. Chem. Soc. 110, 4306-4312, 1988). We have investigated the system NH3 + C2H2 + CH4 using a Zn lamp emitting at 214 nm to produce NH2 + H and subsequent reaction products. The deposits produced in these reactions were analyzed by optical and infrared spectroscopy and soft-ionization (He*) time-of-flight mass spectroscopy. The combination of NH3 + CH4 produced no visibly absorbing material, but NH3 + C2H2 and NH3 + C2H2 + CH4 mixtures both produced a yellow-orange film whose transmission spectra are similar to that of the GRS obtained by Cassini VIMS. Infrared spectra show a strong band at 2056 wavenumbers which may arise from nitrile (-CN), isonitrile (-NC), or diazide (-CNN) functional groups. The high-resolution mass spectra are consistent with compounds of the form CnH2n+1Nm, similar to the products formed in NH3 + CH4 spark discharges (Molton and Ponnamperuma, Icarus 21, 166-174, 1974). We thank NASA's Planetary Atmospheres Program for support.

  9. Oxy-acetylene driven laboratory scale shock tubes for studying blast wave effects

    NASA Astrophysics Data System (ADS)

    Courtney, Amy C.; Andrusiv, Lubov P.; Courtney, Michael W.

    2012-04-01

    This paper describes the development and characterization of modular, oxy-acetylene driven laboratory scale shock tubes. Such tools are needed to produce realistic blast waves in a laboratory setting. The pressure-time profiles measured at 1 MHz using high-speed piezoelectric pressure sensors have relevant durations and show a true shock front and exponential decay characteristic of free-field blast waves. Descriptions are included for shock tube diameters of 27-79 mm. A range of peak pressures from 204 kPa to 1187 kPa (with 0.5-5.6% standard error of the mean) were produced by selection of the driver section diameter and distance from the shock tube opening. The peak pressures varied predictably with distance from the shock tube opening while maintaining both a true blast wave profile and relevant pulse duration for distances up to about one diameter from the shock tube opening. This shock tube design provides a more realistic blast profile than current compression-driven shock tubes, and it does not have a large jet effect. In addition, operation does not require specialized personnel or facilities like most blast-driven shock tubes, which reduces operating costs and effort and permits greater throughput and accessibility. It is expected to be useful in assessing the response of various sensors to shock wave loading; assessing the reflection, transmission, and absorption properties of candidate armor materials; assessing material properties at high rates of loading; assessing the response of biological materials to shock wave exposure; and providing a means to validate numerical models of the interaction of shock waves with structures. All of these activities have been difficult to pursue in a laboratory setting due in part to lack of appropriate means to produce a realistic blast loading profile.

  10. Inactivation of the particulate methane monooxygenase (pMMO) in Methylococcus capsulatus (Bath) by acetylene.

    PubMed

    Pham, Minh D; Lin, Ya-Ping; Van Vuong, Quan; Nagababu, Penumaka; Chang, Brian T-A; Ng, Kok Yaoh; Chen, Chein-Hung; Han, Chau-Chung; Chen, Chung-Hsuan; Li, Mai Suan; Yu, Steve S-F; Chan, Sunney I

    2015-12-01

    Acetylene (HCCH) has a long history as a mechanism-based enzyme inhibitor and is considered an active-site probe of the particulate methane monooxygenase (pMMO). Here, we report how HCCH inactivates pMMO in Methylococcus capsulatus (Bath) by using high-resolution mass spectrometry and computational simulation. High-resolution MALDI-TOF MS of intact pMMO complexes has allowed us to confirm that the enzyme oxidizes HCCH to the ketene (C2H2O) intermediate, which then forms an acetylation adduct with the transmembrane PmoC subunit. LC-MS/MS analysis of the peptides derived from in-gel proteolytic digestion of the protein subunit identifies K196 of PmoC as the site of acetylation. No evidence is obtained for chemical modification of the PmoA or PmoB subunit. The inactivation of pMMO by a single adduct in the transmembrane PmoC domain is intriguing given the complexity of the structural fold of this large membrane-protein complex as well as the complicated roles played by the various metal cofactors in the enzyme catalysis. Computational studies suggest that the entry of hydrophobic substrates to, and migration of products from, the catalytic site of pMMO are controlled tightly within the transmembrane domain. Support of these conclusions is provided by parallel experiments with two related alkynes: propyne (CH3CCH) and trifluoropropyne (CF3CCH). Finally, we discuss the implication of these findings to the location of the catalytic site in pMMO. PMID:26275807

  11. Measurement of cardiac output during exercise by open-circuit acetylene uptake.

    PubMed

    Barker, R C; Hopkins, S R; Kellogg, N; Olfert, I M; Brutsaert, T D; Gavin, T P; Entin, P L; Rice, A J; Wagner, P D

    1999-10-01

    Noninvasive measurement of cardiac output (QT) is problematic during heavy exercise. We report a new approach that avoids unpleasant rebreathing and resultant changes in alveolar PO(2) or PCO(2) by measuring short-term acetylene (C(2)H(2)) uptake by an open-circuit technique, with application of mass balance for the calculation of QT. The method assumes that alveolar and arterial C(2)H(2) pressures are the same, and we account for C(2)H(2) recirculation by extrapolating end-tidal C(2)H(2) back to breath 1 of the maneuver. We correct for incomplete gas mixing by using He in the inspired mixture. The maneuver involves switching the subject to air containing trace amounts of C(2)H(2) and He; ventilation and pressures of He, C(2)H(2), and CO(2) are measured continuously (the latter by mass spectrometer) for 20-25 breaths. Data from three subjects for whom multiple Fick O(2) measurements of QT were available showed that measurement of QT by the Fick method and by the C(2)H(2) technique was statistically similar from rest to 90% of maximal O(2) consumption (VO(2 max)). Data from 12 active women and 12 elite male athletes at rest and 90% of VO(2 max) fell on a single linear relationship, with O(2) consumption (VO(2)) predicting QT values of 9.13, 15.9, 22.6, and 29.4 l/min at VO(2) of 1, 2, 3, and 4 l/min. Mixed venous PO(2) predicted from C(2)H(2)-determined QT, measured VO(2), and arterial O(2) concentration was approximately 20-25 Torr at 90% of VO(2 max) during air breathing and 10-15 Torr during 13% O(2) breathing. This modification of previous gas uptake methods, to avoid rebreathing, produces reasonable data from rest to heavy exercise in normal subjects. PMID:10517785

  12. An Experimental and Theoretical Study of Nitrogen-Broadened Acetylene Lines

    NASA Technical Reports Server (NTRS)

    Thibault, Franck; Martinez, Raul Z.; Bermejo, Dionisio; Ivanov, Sergey V.; Buzykin, Oleg G.; Ma, Qiancheng

    2014-01-01

    We present experimental nitrogen-broadening coefficients derived from Voigt profiles of isotropic Raman Q-lines measured in the 2 band of acetylene (C2H2) at 150 K and 298 K, and compare them to theoretical values obtained through calculations that were carried out specifically for this work. Namely, full classical calculations based on Gordon's approach, two kinds of semi-classical calculations based on Robert Bonamy method as well as full quantum dynamical calculations were performed. All the computations employed exactly the same ab initio potential energy surface for the C2H2N2 system which is, to our knowledge, the most realistic, accurate and up-to-date one. The resulting calculated collisional half-widths are in good agreement with the experimental ones only for the full classical and quantum dynamical methods. In addition, we have performed similar calculations for IR absorption lines and compared the results to bibliographic values. Results obtained with the full classical method are again in good agreement with the available room temperature experimental data. The quantum dynamical close-coupling calculations are too time consuming to provide a complete set of values and therefore have been performed only for the R(0) line of C2H2. The broadening coefficient obtained for this line at 173 K and 297 K also compares quite well with the available experimental data. The traditional Robert Bonamy semi-classical formalism, however, strongly overestimates the values of half-width for both Qand R-lines. The refined semi-classical Robert Bonamy method, first proposed for the calculations of pressure broadening coefficients of isotropic Raman lines, is also used for IR lines. By using this improved model that takes into account effects from line coupling, the calculated semi-classical widths are significantly reduced and closer to the measured ones.

  13. Hydrogen-bonded complexes of acetylene and acetonitrile: A matrix isolation infrared and computational study

    NASA Astrophysics Data System (ADS)

    Gopi, R.; Ramanathan, N.; Sundararajan, K.

    2015-03-01

    Hydrogen-bonded complexes of acetylene (C2H2) and acetonitrile (CH3CN) have been investigated using matrix isolation infrared spectroscopy and ab initio computations. The complexes were trapped in both solid argon and N2 matrices. The structure of the complexes and the energies were computed at the B3LYP and MP2 levels of theory using a 6-311++G(d,p) basis set and also at B3LYP/aug-cc-pVDZ level. Our computations indicated one minimum corresponding to the 1:1 C2H2sbnd CH3CN complex, with Csbnd H⋯N interaction, where C2H2 is the proton donor. Experimentally, we observed the 1:1 C2H2sbnd CH3CN complex in Ar and N2 matrices, which was evidenced by the shifts in the vibrational wavenumbers of the modes involving the C2H2 and CH3CN sub-molecules. Computations were also performed to study the higher complexes of C2H2 and CH3CN. One minimum was found for the 1:2 C2H2sbnd CH3CN complex and two minima for the 2:1 C2H2sbnd CH3CN complexes, at all levels of theory. Experimentally we observed features corresponding to the 1:2 C2H2sbnd CH3CN complexes in an Ar and N2 matrices. The computed vibrational wavenumbers of C2H2sbnd CH3CN complexes at B3LYP/6-311++G(d,p) level correlate well with the experimental wavenumbers. Atoms in Molecules (AIM) analysis was performed to understand the nature of interaction in the complexes. Natural Bond Orbital (NBO) analysis was performed to understand the effect of charge-transfer hyperconjugative interactions towards the stability of different C2H2sbnd CH3CN complexes.

  14. Oxy-acetylene driven laboratory scale shock tubes for studying blast wave effects.

    PubMed

    Courtney, Amy C; Andrusiv, Lubov P; Courtney, Michael W

    2012-04-01

    This paper describes the development and characterization of modular, oxy-acetylene driven laboratory scale shock tubes. Such tools are needed to produce realistic blast waves in a laboratory setting. The pressure-time profiles measured at 1 MHz using high-speed piezoelectric pressure sensors have relevant durations and show a true shock front and exponential decay characteristic of free-field blast waves. Descriptions are included for shock tube diameters of 27-79 mm. A range of peak pressures from 204 kPa to 1187 kPa (with 0.5-5.6% standard error of the mean) were produced by selection of the driver section diameter and distance from the shock tube opening. The peak pressures varied predictably with distance from the shock tube opening while maintaining both a true blast wave profile and relevant pulse duration for distances up to about one diameter from the shock tube opening. This shock tube design provides a more realistic blast profile than current compression-driven shock tubes, and it does not have a large jet effect. In addition, operation does not require specialized personnel or facilities like most blast-driven shock tubes, which reduces operating costs and effort and permits greater throughput and accessibility. It is expected to be useful in assessing the response of various sensors to shock wave loading; assessing the reflection, transmission, and absorption properties of candidate armor materials; assessing material properties at high rates of loading; assessing the response of biological materials to shock wave exposure; and providing a means to validate numerical models of the interaction of shock waves with structures. All of these activities have been difficult to pursue in a laboratory setting due in part to lack of appropriate means to produce a realistic blast loading profile. PMID:22559580

  15. Acetylene as an essential building block for prebiotic formation of pyrimidine bases on Titan.

    PubMed

    Jeilani, Yassin A; Fearce, Chelesa; Nguyen, Minh Tho

    2015-10-01

    Prebiotic building blocks for the formation of biomolecules are important in understanding the abiotic origin of biomolecules. However, there is a limited choice of the building blocks as precursors for the biomolecules. Acetylene (HCCH) is found in Titan's atmosphere and is an abiotic-precursor of pyrimidine bases. HCCH reacts with urea to form both cytosine and uracil. The mechanisms for the formation of both cytosine and uracil were studied by density functional theory at B3LYP/6-311G(d,p) level. Ethynyl radicals (?CCH) are relevant for the chemistry of Titan's atmosphere therefore both HCCH and ?CCH were evaluated as carbon sources. The pathways, for both HCCH and ?CCH, lead to intermediates with an unsaturated-group that facilitate the formation of the six-membered ring of the pyrimidine bases. The predicted structures for cytosine and uracil were compared with labeled cytosine and uracil that were formed from the reaction of DCCD with urea. The results suggest that cytosine is formed from HCCH while uracil is formed from ?CCH. The mechanisms are energetically feasible and there is no conclusive evidence for the preferred pathway (HCCH or ?CCH). The pathways were further extended for the formation of both uric acid and 8-oxoguanine from HCCH and urea, and demonstrate the utility of HCCH as a carbon source for diverse biomolecules. Biuret is identified as a precursor for the pyridimine bases, and it unifies the free radical pathways for the pyrimidine bases with those of triazines. The pathways are appropriate for the reducing atmosphere that creates both radicals and electrons due to ionizing radiation on Titan. The mechanisms are feasible for the extraterrestrial formation of the pyrimidine bases. PMID:26325173

  16. Factor VII assay

    MedlinePLUS

    The factor VII assay is a blood test to measure the activity of factor VII. This is one of the proteins in ... the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick ...

  17. Factor V assay

    MedlinePLUS

    The factor V assay is a blood test to measure the activity of factor V. This is one of the proteins in ... the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick ...

  18. Doped colorimetric assay liposomes

    DOEpatents

    Charych, Deborah; Stevens, Raymond C.

    2001-01-01

    The present invention provides compositions comprising colorimetric assay liposomes. The present invention also provides methods for producing colorimetric liposomes and calorimetric liposome assay systems. In preferred embodiments, these calorimetric liposome systems provide high levels of sensitivity through the use of dopant molecules. As these dopants allow the controlled destabilization of the liposome structure, upon exposure of the doped liposomes to analyte(s) of interest, the indicator color change is facilitated and more easily recognized.

  19. Simplified Cartesian basis model for intrapolyad emission intensities in the bent-to-linear electronic transition of acetylene.

    PubMed

    Park, G Barratt; Steeves, Adam H; Baraban, Joshua H; Field, Robert W

    2015-02-01

    The acetylene emission spectrum from the trans-bent electronically excited state to the linear ground electronic X? state has attracted considerable attention because it grants FranckCondon access to local bending vibrational levels of the X? state with large-amplitude motion along the acetylene ? vinylidene isomerization coordinate. For emission from the ground vibrational level of the state, there is a simplifying set of FranckCondon propensity rules that gives rise to only one zero-order bright state per conserved vibrational polyad of the X? state. Unfortunately, when the upper level involves excitation in the highly admixed ungerade bending modes, ?4? and ?6?, the simplifying FranckCondon propensity rule breaks down--as long as the usual polar basis (with v and l quantum numbers) is used to describe the degenerate bending vibrations of the X? state--and the intrapolyad intensities result from complicated interference patterns between many zero-order bright states. In this article, we show that, when the degenerate bending levels are instead treated in the Cartesian two-dimensional harmonic oscillator basis (with vx and vy quantum numbers), the propensity for only one zero-order bright state (in the Cartesian basis) is restored, and the intrapolyad intensities are simple to model, as long as corrections are made for anharmonic interactions. As a result of trans ? cis isomerization in the state, intrapolyad emission patterns from overtones of ?4? and ?6? evolve as quanta of trans bend (?3?) are added, so the emission intensities are not only relevant to the ground-state acetylene ? vinylidene isomerization, they are also a direct reporter of isomerization in the electronically excited state. PMID:25625552

  20. Laser double-resonance studies of electronic spectroscopy and state-resolved collisional relaxation in highly vibrationally excited acetylene

    SciTech Connect

    Tobiason, J.D.

    1992-01-01

    Vibrational overtone excitation combined with laser-induced fluorescence detection of acetylene molecules permits rotation-selected spectroscopy of the ([tilde A][sup 1]A[sub u]) electronic state and direct, state-resolved measurements of collisional energy transfer in the highly vibrationally excited ground electronic state. The author assigns energies of 1,045 transitions to previously unobserved ungerade vibrational states 2800-4500 cm[sup [minus]1] above the [tilde A] state origin. An analysis yields frequencies of 2856.4 and 3894.3 cm[sup [minus]1] for [nu][sub v][prime] and [nu][sub 3][prime] + [nu][sub 5][prime]. The author performs the first normal coordinate analysis of [tilde A] state acetylene based only on directly observed fundamentals. The spectroscopy measurements enable double-resonance experiments on the collisional dynamics of highly vibrationally excited acetylene. The quenching rate for single rotational states is twice the Lennard-Jones gas kinetic rate and fairly independent of vibrational energy level. Collision-induced detection of vibrational overtone excitation under single collision conditions allows direct measurements of state-of-state rotational and vibrational energy transfer. A collision-induced spectrum obtained by this new technique immediately identifies transfer channels and the [Delta]J and [Delta]E dependence of the transfer rates. The author observes changes of [vert bar][Delta]J[vert bar] and [Delta]E [approx] 3kT in a single collision. Directly measured rates for one set of vibrational relaxation pathways account for [approximately]3% of the total relaxation rate. The author also observes other vibrational relaxation pathways. The available pathways suggest that vibrational relaxation accounts for the rest of the total relaxation. Changes of [vert bar]J[vert bar] = 18 and [vert bar][Delta]E[vert bar] [approximately] 500 cm[sup [minus]1] in a single collision are observed.

  1. Differential inhibition of thromboxane B2 and leukotriene B4 biosynthesis by two naturally occurring acetylenic fatty acids.

    PubMed

    Croft, K D; Beilin, L J; Ford, G L

    1987-10-17

    The seed oil of the plant Ixiolaena brevicompta is a rich source of crepenynic acid (octadec-cis-9-en-12-ynoic acid), which has been linked with extensive sheep mortalities in Western New South Wales and Queensland, Australia. A number of acetylenic fatty acids have been found to interfere with lipid and fatty acid metabolism and inhibit cyclooxygenase and lipoxygenase enzymes in a variety of tissues. We have investigated the effects of crepenynic acid and ximenynic acid (octadec-trans-11-en-9-ynoic acid) on leukotriene B4 and thromboxane B2 production in rat peritoneal leukocytes and compare them with non-acetylenic compounds linoleic and ricinoleic acids. In concentrations ranging from 10 to 100 microM linoleic acid and ricinoleic acid had only minimal effects on leukotriene B4 and thromboxane B2 production in ionophore-stimulated cells. Ximenynic acid gave dose-dependent inhibition of leukotriene B4, thromboxane B2 and 6-ketoprostaglandin F1 alpha production. Ximenynic acid appears to be a more effective inhibitor of leukotriene B4 than crepenynic acid with an IC50 of 60 microM compared to 85 microM. On the other hand, crepenynic acid is a much more effective inhibitor of the cyclooxygenase products, having an IC50 for thromboxane B2 of less than 10 microM. Both acetylenic fatty acids inhibited phospholipase activity in these cells by 40-50% at a concentration of 100 microM but had no inhibitory effect at 10 microM. These results indicate that crepenynic acid and ximenynic acid differentially inhibit the cyclooxygenase and lipoxygenase products of stimulated leukocytes, and that at high doses of these fatty acids the effect on these products may be partially due to inhibition of phospholipase A2. PMID:2822134

  2. Recovery of acetylene absorption line profile basing on tunable diode laser spectroscopy with intensity modulation and photoacoustic spectroscopy

    NASA Astrophysics Data System (ADS)

    Li, Li; Thursby, Graham; Stewart, George; Arsad, Norhana; Uttamchandani, Deepak; Culshaw, Brian; Wang, Yiding

    2010-04-01

    A novel and direct absorption line recovery technique based on tunable diode laser spectroscopy with intensity modulation is presented. Photoacoustic spectroscopy is applied for high sensitivity, zero background and efficient acoustic enhancement at a low modulation frequency. A micro-electromechanical systems (MEMS) mirror driven by an electrothermal actuator is used for generating laser intensity modulation (without wavelength modulation) through the external reflection. The MEMS mirror with 10μm thick structure material layer and 100nm thick gold coating is formed as a circular mirror of 2mm diameter attached to an electrothermal actuator and is fabricated on a chip that is wire-bonded and placed on a PCB holder. Low modulation frequency is adopted (since the resonant frequencies of the photoacoustic gas cell and the electrothermal actuator are different) and intrinsic high signal amplitude characteristics in low frequency region achieved from measured frequency responses for the MEMS mirror and the gas cell. Based on the property of photoacoustic spectroscopy and Beer's law that detectable sensitivity is a function of input laser intensity in the case of constant gas concentration and laser path length, a Keopsys erbium doped fibre amplifier (EDFA) with opto-communication C band and high output power up to 1W is chosen to increase the laser power. High modulation depth is achieved through adjusting the MEMS mirror's reflection position and driving voltage. In order to scan through the target gas absorption line, the temperature swept method is adopted for the tunable distributed feed-back (DFB) diode laser working at 1535nm that accesses the near-infrared vibration-rotation spectrum of acetylene. The profile of acetylene P17 absorption line at 1535.39nm is recovered ideally for ~100 parts-per-million (ppm) acetylene balanced by nitrogen. The experimental signal to noise ratio (SNR) of absorption line recovery for 500mW laser power was ~80 and hence the detectable sensitivity is of the order of 1ppm.

  3. Reactions of Cg10062, a cis-3-Chloroacrylic Acid Dehalogenase Homologue, with Acetylene and Allene Substrates: Evidence for a Hydration-Dependent Decarboxylation.

    PubMed

    Huddleston, Jamison P; Johnson, William H; Schroeder, Gottfried K; Whitman, Christian P

    2015-05-19

    Cg10062 is a cis-3-chloroacrylic acid dehalogenase (cis-CaaD) homologue from Corynebacterium glutamicum with an unknown function and an uninformative genomic context. It shares 53% pairwise sequence similarity with cis-CaaD including the six active site amino acids (Pro-1, His-28, Arg-70, Arg-73, Tyr-103, and Glu-114) that are critical for cis-CaaD activity. However, Cg10062 is a poor cis-CaaD: it lacks catalytic efficiency and isomer specificity. Two acetylene compounds (propiolate and 2-butynoate) and an allene compound, 2,3-butadienoate, were investigated as potential substrates. Cg10062 functions as a hydratase/decarboxylase using propiolate as well as the cis-3-chloro- and 3-bromoacrylates, generating mixtures of malonate semialdehyde and acetaldehyde. The two activities occur sequentially at the active site using the initial substrate. With 2,3-butadienoate and 2-butynoate, Cg10062 functions as a hydratase and converts both to acetoacetate. Mutations of the proposed water-activating residues (E114Q, E114D, and Y103F) have a range of consequences from a reduction in wild type activity to a switch of activities (i.e., hydratase into a hydratase/decarboxylase or vice versa). The intermediates for the hydration and decarboxylation products can be trapped as covalent adducts to Pro-1 when NaCNBH3 is incubated with the E114D mutant and 2,3-butadienoate or 2-butynoate, and the Y103F mutant and 2-butynoate. Three mechanisms are presented to explain these findings. One mechanism involves the direct attack of water on the substrate, whereas the other two mechanisms use covalent catalysis in which a covalent bond forms between Pro-1 and the hydration product or the substrate. The strengths and weaknesses of the mechanisms and the implications for Cg10062 function are discussed. PMID:25894805

  4. Is the homogeneous thermal dimerization of acetylene a free-radical chain reaction. Kinetic and thermochemical analysis

    SciTech Connect

    Duran, R.P.; Amorebieta, V.T.; Colussi, A.J.

    1988-02-11

    Basic kinetic and thermochemical arguments incorporated into calculations modeling the initial stages of the homogeneous pyrolysis of acetylene reveal that the usual assumption of a free-radical mechanism is flawed. The key findings are that updated thermochemistry for ethynyl, vinyl, and propargyl radicals and the inclusion of falloff corrections in radical reactions lead to (1) exceedingly slow decomposition rates below 1300 K, (2) kinetic inert gas effects, and (3) the formation of benzene rather than vinylacetylene or diacetylene, all predictions at variance with experimental observations. On this basis the involvement of vinylidene is proposed.

  5. Heat of Combustion of the Product Formed by the Reaction of Acetylene and Diborane (LFPL-CZ-3)

    NASA Technical Reports Server (NTRS)

    Allen, Harrison, Jr.; Tannenbaum, Stanley

    1957-01-01

    The heat of combustion of the product formed by the reaction acetylene and diborane was found to be 20,100 +/- 100 Btu per pound for the reaction of liquid fuel to gaseous carbon dioxide, gaseous water, and solid boric oxide. The measurements were made in a Parr oxygen-bomb calorimeter, and chemical analyses both of the sample and of the combustion products indicated combustion in the bomb calorimeter to have been 97 percent complete. The estimated net heat of combustion for complete combustion would therefore be 20,700 +/- 100 Btu per pound.

  6. Regioselective Transition-Metal-Free Synthesis of 2-(Trimethylsilylmethylene)pyrrol-3-ones by Thermal Cyclization of Acetylenic Enamines.

    PubMed

    Golubev, Pavel R; Pankova, Alena S; Kuznetsov, Mikhail A

    2015-05-01

    Acetylenic enamines generated in situ from readily available enynones and primary amines undergo thermal cyclization in diphenyl ether providing easy access to 4-aryl-2-(trimethylsilylmethylene)-1,2-dihydro-3H-pyrrol-3-ones. This reaction is inherently versatile, allowing for variations of substituents in both enynone and amine. Full regioselectivity along with short reaction time (1-2 h) and simple workup afford single products in good to excellent isolated yields. Fluorescent properties of the obtained compounds were studied. PMID:25893669

  7. State dynamics of acetylene excited to individual rotational level of the V1(2)K1(0,1,2) subbands.

    PubMed

    Makarov, Vladimir I; Kochubei, Sergei A; Khmelinskii, Igor V

    2007-03-01

    The dynamics of the IR emission induced by excitation of the acetylene molecule at the 3(2) Ka2, A1Au<--4(1) la1, X1Sigmag+ transition was investigated. Vibrationally resolved IR emission spectra were recorded at different delay times after the laser excitation pulse. The observed IR emission was assigned to transitions between vibrational levels of the acetylene molecule in the ground state. Values of the relaxation parameters of different vibrational levels of the ground state were obtained. The Ti-->Tj transition was detected by cavity ring-down spectroscopy in the 455 nm spectral range after excitation of the acetylene molecule at the same transition. Rotationally resolved spectra of the respective transition were obtained and analyzed at different delay times after the laser excitation pulse. The dynamics of the S1-->Tx-->T1-->S0 transitions was investigated, and the relaxation parameter values were estimated for the T1 state. PMID:17362104

  8. The electronic structure and second-order nonlinear optical properties of donor-acceptor acetylenes - A detailed investigation of structure-property relationships

    NASA Technical Reports Server (NTRS)

    Stiegman, A. E.; Graham, Eva; Khundkar, Lutfur R.; Perry, Joseph W.; Cheng, L.-T.; Perry, Kelly J.

    1991-01-01

    A series of donor-acceptor acetylene compounds was synthesized in which systematic changes in both the conjugation length and the donor-acceptor strength were made. The effect of these structural changes on the spectroscopic and electronic properties of the molecules and, ultimately, on the measured second-order molecular hyperpolarizabilities (beta) was investigated. It was found that increases in the donor-acceptor strength resulted in increases in the magnitude of beta. For this class of molecules, the increase is dominated by the energy of the intramolecular charge-transfer transition, while factors such as the ground to excited-state dipole moment change and the transition-moment integral are much less important. Increasing the conjugation length from one to two acetylene linkers did not result in an increase in the value of beta; however, beta increased sharply in going from two acetylenes to three. This increase is attributed to the superposition of several nearly isoenergetic excited states.

  9. NO A{sup 2}{Sigma}{sup +}-X{sup 2}II chemiluminescence produced from the reaction of excited NO{sub 2} with acetylene and its derivatives in their triplet states

    SciTech Connect

    Sisk, Wade; Endo; Hiromu; Shibuya, Kazuhiko; Obi, Kinichi

    1992-08-06

    This paper discusses how reacting excited NO{sub 2} with acetylene and its derivatives produced NO(A{sup 2}{Sigma}{sup +}) by a NO A{sup 2}{sigma}{sup +}-X{sup 2}II chemiluminescence produced by a triplet-state mechanism, with acetylene > methylacetylene > ethylacetylene > phenylacetylene > benzene in terms of efficiency. 22 refs., 8 figs., 2 tabs.

  10. Harm reduction

    PubMed Central

    Normand, Jacques; Li, Jih-Heng; Thomson, Nicholas; Jarlais, Don Des

    2014-01-01

    The Harm Reduction session was chaired by Dr. Jacques Normand, Director of the AIDS Research Program of the U.S. National Institute on Drug Abuse. The three presenters (and their presentation topics) were: Dr. Don Des Jarlais (High Coverage Needle/Syringe Programs for People Who Inject Drugs in Low and Middle Income Countries: A Systematic Review), Dr. Nicholas Thomson (Harm Reduction History, Response, and Current Trends in Asia), and Dr. Jih-Heng Li (Harm Reduction Strategies in Taiwan). PMID:25278732

  11. Assaying Hematopoiesis Using Zebrafish

    PubMed Central

    Boatman, Sonja; Barrett, Francesca; Satishchandran, Sruthi; Jing, Lili; Shestopalov, Ilya; Zon, Leonard I.

    2013-01-01

    The zebrafish has become a commonly used model for studying hematopoiesis as a result of its unique attributes. Zebrafish are highly suitable for large-scale genetic and chemical screens compared to other vertebrate systems. It is now possible to analyze hematopoietic lineages in zebrafish and validate cell function via transplantation assays. Here, we review advancements over the past decade in forward genetic screens, chemical screens, fluorescence-activated cell sorting analysis, and transplantation assays. Integrating these approaches enables new chemical and genetic screens that assay cell function within the hematopoietic system. Studies in zebrafish will continue to contribute and expand our knowledge about hematopoiesis, and develop novel treatments for clinical applications. PMID:23916372

  12. Against vaccine assay secrecy

    PubMed Central

    Herder, Matthew; Hatchette, Todd F; Halperin, Scott A; Langley, Joanne M

    2015-01-01

    Increasing the transparency of the evidence base behind health interventions such as pharmaceuticals, biologics, and medical devices, has become a major point of critique, conflict, and policy focus in recent years. Yet the lack of publicly available information regarding the immunogenicity assays upon which many important, widely used vaccines are based has received no attention to date. In this paper we draw attention to this critical public health problem by reporting on our efforts to secure vaccine assay information in respect of 10 vaccines through Canada's access to information law. We argue, under Canadian law, that the public health interest in having access to the methods for these laboratory procedures should override claims by vaccine manufacturers and regulators that this information is proprietary; and, we call upon several actors to take steps to ensure greater transparency with respect to vaccine assays, including regulators, private firms, researchers, research institutions, research funders, and journal editors. PMID:25826194

  13. Miniaturization of hydrolase assays in thermocyclers.

    PubMed

    Lucena, Severino A; Moraes, Caroline S; Costa, Samara G; de Souza, Wanderley; Azambuja, Patrícia; Garcia, Eloi S; Genta, Fernando A

    2013-03-01

    We adapted the protocols of reducing sugar measurements with dinitrosalicylic acid and bicinchoninic acid for thermocyclers and their use in enzymatic assays for hydrolases such as amylase and β-1,3-glucanase. The use of thermocyclers for these enzymatic assays resulted in a 10 times reduction in the amount of reagent and volume of the sample needed when compared with conventional microplate protocols. We standardized absorbance readings from the polymerase chain reaction plates, which allowed us to make direct readings of the techniques above, and a β-glycosidase assay was also established under the same conditions. Standardization of the enzymatic reaction in thermocyclers resulted in less time-consuming temperature calibrations and without loss of volume through leakage or evaporation from the microplate. Kinetic parameters were successfully obtained, and the use of the thermocycler allowed the measurement of enzymatic activities in biological samples from the field with a limited amount of protein. PMID:23123426

  14. RNA encapsidation assay.

    PubMed

    Annamalai, Padmanaban; Rao, A L N

    2008-01-01

    Analysis of viral RNA encapsidation assay provides a rapid means of assaying which of the progeny RNA are competent for packaging into stable mature virions. Generally, a parallel analysis of total RNA and RNA obtained from purified virions is advisable for accurate interpretation of the results. In this, we describe a series of in vivo assays in which viral RNA encapsidation can be verified. These include whole plants inoculated either mechanically or by Agroinfiltration and protoplasts. The encapsidation assay described here is for an extensively studied plant RNA virus, brome mosaic virus, and can be reliably applied to other viral systems as well as with appropriate buffers. In principle, the encapsidation assay requires purification of virions from either symptomatic leaves or transfected plant protoplasts followed by RNA isolation. The procedure involves grinding the infected tissue in an appropriate buffer followed by a low speed centrifugation step to remove the cell debris. The supernatant is then emulsified with an organic solvent such as chloroform to remove chlorophyll and cellular material. After a low seed centrifugation, the supernatant is subjected to high speed centrifugation to concentrate the virus as a pellet. Depending on the purity required, the partially purified virus preparation is further subjected to sucrose density gradient centrifugation. Following purification of virions, encapsidated RNA is isolated using standard phenol-chloroform extraction procedure. An important step in the encapsidation assay is the comparative analysis of total and virion RNA preparations by Northern hybridization. This would allow the investigator to compare the number of progeny RNA components synthesized during replication vs. encapsidation. Northern blots are normally hybridized with radioactively labeled RNA probes (riboprobes) for specific and sensitive detection of desired RNA species. PMID:18370261

  15. Titan haze: structure and properties of cyanoacetylene and cyanoacetylene-acetylene photopolymers

    NASA Technical Reports Server (NTRS)

    Clarke, D. W.; Ferris, J. P.

    1997-01-01

    The structure and morphological properties of polymers produced photochemically from the UV irradiation of cyanoacetylene and cyanoacetylene mixtures have been examined to evaluate their possible contribution to the haze layers found on Titan. A structural analysis of these polymers may contribute to our understanding of the data returned from the Huygens probe of the Cassini mission that will pass through the atmosphere of Titan in the year 2004. Infrared analysis, elemental analysis, and thermal methods (thermogravimetric analysis, thermolysis, pyrolysis) were used to examine structures of polycyanoacetylenes produced by irradiation of the gas phase HC3N at 185 and 254 nm. The resulting brown to black polymer, which exists as small particles, is believed to be a branched chain of conjugated carbon-carbon double bonds, which, on exposure to heat, cyclizes to form a graphitic structure. Similar methods of analysis were used to show that when HC3N is photolyzed in the presence of Titan's other atmospheric constituents (CH4, C2H6, C2H2, and CO), a copolymer is formed in which the added gases are incorporated as substituents on the polymer chain. Of special significance is the copolymer of HC3N and acetylene (C2H2). Even in experiments where C2H2 was absorbing nearly all of the incident photons, the ratio of C2H2 to HC3N found in the resulting polymer was only 2:1. Scanning electron microscopy was used to visually examine the polymer particles. While pure polyacetylene particles are amorphous spheres roughly 1 micrometer in diameter, polycyanoacetylenes appear to be strands of rough, solid particles slightly smaller in size. The copolymer of HC3N and C2H2 exhibits characteristics of both pure polymers. This is particularly important as pure polyacetylenes do not match the optical constants measured for Titan's atmospheric hazes. The copolymers produced by the incorporation of other minor atmospheric constituents, like HC3N, into the polyacetylenes are expected to have optical constants more comparable to those of the Titan haze.

  16. DREAM Assay for Studying Microbial Electron Transfer.

    PubMed

    Vishwanathan, A S; Devkota, Ranjan; Siva Sankara Sai, S; Rao, Govind

    2015-12-01

    Methylene blue undergoes reduction with an accompanying colour change reaction, from blue to colourless, enabling its use as a metric for estimating reducing power. A dye reduction-based electron-transfer activity monitoring (DREAM) assay is demonstrated as a tool to study and understand the process of microbes sourcing electrons from organic substrates and transferring them to an electron acceptor. The rate at which electrons can be transferred to the thermodynamically most feasible electron acceptor directly depends on the activity of microbes. Nature of available substrate determines the quantum of electrons available. Dissolved oxygen intercepts electrons from the microbes before they can be taken up by the dye. Sodium sulfite can be used to offset the detrimental effects of the presence of dissolved oxygen. This easy-to-perform assay has been demonstrated as a proof-of-concept having potential to be extended to other practical applications. PMID:26386586

  17. Fluorometric assay for aflatoxins

    SciTech Connect

    Chakrabarti, A.G.

    1984-11-01

    The method that is now widely adopted by the government laboratories for the assay of individual aflatoxin components (B/sub 1/, B/sub 2/, G/sub 1/, and G/sub 2/) utilizes a TLC technique. The extraction and clean-up steps of this technique were further researched but the method is still time consuming. It is, therefore, very important to develop a rapid and accurate assay technique for aflatoxins. The current research proposes a technique which utilizes a Turner Fluorometer.

  18. Assays for calcitonin receptors

    SciTech Connect

    Teitelbaum, A.P.; Nissenson, R.A.; Arnaud, C.D.

    1985-01-01

    The assays for calcitonin receptors described focus on their use in the study of the well-established target organs for calcitonin, bone and kidney. The radioligand used in virtually all calcitonin binding studies is /sup 125/I-labelled salmon calcitonin. The lack of methionine residues in this peptide permits the use of chloramine-T for the iodination reaction. Binding assays are described for intact bone, skeletal plasma membranes, renal plasma membranes, and primary kidney cell cultures of rats. Studies on calcitonin metabolism in laboratory animals and regulation of calcitonin receptors are reviewed.

  19. Lateral flow strip assay

    DOEpatents

    Miles, Robin R.; Benett, William J.; Coleman, Matthew A.; Pearson, Francesca S.; Nasarabadi, Shanavaz L.

    2011-03-08

    A lateral flow strip assay apparatus comprising a housing; a lateral flow strip in the housing, the lateral flow strip having a receiving portion; a sample collection unit; and a reagent reservoir. Saliva and/or buccal cells are collected from an individual using the sample collection unit. The sample collection unit is immersed in the reagent reservoir. The tip of the lateral flow strip is immersed in the reservoir and the reagent/sample mixture wicks up into the lateral flow strip to perform the assay.

  20. The Effect of Surface Finish on Low-Temperature Acetylene-Based Carburization of 316L Austenitic Stainless Steel

    NASA Astrophysics Data System (ADS)

    Ge, Yindong; Ernst, Frank; Kahn, Harold; Heuer, Arthur H.

    2014-12-01

    We observed a strong influence of surface finish on the efficacy of low-temperature acetylene-based carburization of AISI 316L austenitic stainless steel. Steel coupons were prepared with different surface finishes prior to carburization, from P400 SiC grit paper to 1- m-diameter-diamond-paste. The samples with the finer surface finish developed a thicker "case" (a carbon-rich hardened surface layer) and a larger surface carbon concentration. Transmission electron microscopy revealed that the differences arose mainly from the nature of the deformation-induced disturbed layer on the steel surface. A thick (>400 nm) disturbed layer consisting of nano-crystalline grains (?10 nm diameter) inhibits acetylene-based carburization. The experimental observations can be explained by assuming that during machining or coarse polishing, the surface oxide layer is broken up and becomes incorporated into the deformation-induced disturbed layer. The incorporated oxide-rich films retard or completely prevent the ingress of carbon into the stainless steel.

  1. Quantum Chemical Simulations Reveal Acetylene-Based Growth Mechanisms in the Chemical Vapor Deposition Synthesis of Carbon Nanotubes

    SciTech Connect

    Eres, Gyula; Wang, Ying; Gao, Xingfa; Qian, Hu-Jun; Ohta, Yasuhito; Wu, Xiaona; Morokuma, Keiji; Irle, Stephan

    2014-01-01

    Nonequilibrium quantum chemical molecular dynamics (QM/MD) simulation of early stages in the nucleation process of carbon nanotubes from acetylene feedstock on an Fe38 cluster was performed based on the density-functional tight-binding (DFTB) potential. Representative chemical reactions were studied by complimentary static DFTB and density functional theory (DFT) calculations. Oligomerization and cross-linking reactions between carbon chains were found as the main reaction pathways similar to that suggested in previous experimental work. The calculations highlight the inhibiting effect of hydrogen for the condensation of carbon ring networks, and a propensity for hydrogen disproportionation, thus enriching the hydrogen content in already hydrogen-rich species and abstracting hydrogen content in already hydrogen-deficient clusters. The ethynyl radical C2H was found as a reactive, yet continually regenerated species, facilitating hydrogen transfer reactions across the hydrocarbon clusters. The nonequilibrium QM/MD simulations show the prevalence of a pentagon-first nucleation mechanism where hydrogen may take the role of one arm of an sp2 carbon Y-junction. The results challenge the importance of the metal carbide formation for SWCNT cap nucleation in the VLS model and suggest possible alternative routes following hydrogen-abstraction acetylene addition (HACA)-like mechanisms commonly discussed in combustion synthesis.

  2. Laboratory studies, analysis, and interpretation of the spectra of hydrocarbons present in planetary atmospheres including cyanoacetylene, acetylene, propane, and ethane

    NASA Technical Reports Server (NTRS)

    Blass, William E.; Daunt, Stephen J.; Peters, Antoni V.; Weber, Mark C.

    1990-01-01

    Combining broadband Fourier transform spectrometers (FTS) from the McMath facility at NSO and from NRC in Ottawa and narrow band TDL data from the laboratories with computational physics techniques has produced a broad range of results for the study of planetary atmospheres. Motivation for the effort flows from the Voyager/IRIS observations and the needs of Voyager analysis for laboratory results. In addition, anticipation of the Cassini mission adds incentive to pursue studies of observed and potentially observable constituents of planetary atmospheres. Current studies include cyanoacetylene, acetylene, propane, and ethane. Particular attention is devoted to cyanoacetylen (H3CN) which is observed in the atmosphere of Titan. The results of a high resolution infrared laboratory study of the line positions of the 663, 449, and 22.5/cm fundamental bands are presented. Line position, reproducible to better than 5 MHz for the first two bands, are available for infrared astrophysical searches. Intensity and broadening studies are in progress. Acetylene is a nearly ubiquitous atmospheric constituent of the outer planets and Titan due to the nature of methane photochemistry. Results of ambient temperature absolute intensity measurements are presented for the fundamental and two two-quantum hotband in the 730/cm region. Low temperature hotband intensity and linewidth measurements are planned.

  3. Infrared spectra reveal box-like structures for a pentamer and hexamer of mixed carbon dioxide-acetylene clusters.

    PubMed

    Rezaei, Mojtaba; Norooz Oliaee, J; Moazzen-Ahmadi, N; McKellar, A R W

    2016-01-21

    Except for a few cases like water and carbon dioxide, identification and structural characterization of clusters with more than four monomers is rare. Here, we provide experimental and theoretical evidence for existence of box-like structures for a pentamer and a hexamer of mixed carbon dioxide-acetylene clusters. Two mid-infrared cluster absorption bands are observed in the CO2?3 band region using a tunable diode laser to probe a pulsed supersonic jet. Each requires the presence of both carbon dioxide and acetylene in the jet, and (from observed rotational spacings) involves clusters containing about 4 to 7 molecules. Structures are predicted for mixed CO2 + C2H2 clusters using a distributed multipole model, and the bands are assigned to a specific pentamer, (CO2)3-(C2H2)2, and hexamer, (CO2)4-(C2H2)2. The hexamer has a box-like structure whose D2d symmetry is supported by observed intensity alternation in the spectrum. The pentamer has a closely related structure which is obtained by removing one CO2 molecule from the hexamer. These are among the largest mixed molecular clusters to be assigned by high-resolution spectroscopy. PMID:26315679

  4. A new class of linear tetrapyrroles: acetylenic 10,10a-didehydro-10a-homobilirubins.

    PubMed

    Tu, Bin; Ghosh, Brahmananda; Lightner, David A

    2003-11-14

    Novel bilirubin analogues with dipyrrinones conjoined to an acetylene rather than a methylene group were synthesized and examined spectroscopically. Despite the increased separation of the dipyrrinones forced by replacing a -CH(2)- by a -C(triple bond)C- unit, molecular dynamics calculations show that, like bilirubin, they may still engage in intramolecular hydrogen bonding to carboxylic acid groups when the propionic acid chains are slightly lengthened, e.g., butanoic acids. Unlike bilirubin, however, which is bent in the middle and has a ridge-tile shape, the acetylene orients the attached dipyrrinones along a linear path, and intramolecular hydrogen bonding preserves a twisted linear molecular shape. The extended planes of the dipyrrinones intersect along the -C(triple bond)C- axis at an angle of 136 degrees for the conformation stabilized by intramolecular hydrogen bonding in the bis-butyric acid rubin (1b). With shorter acid chains (propionic), only one CO(2)H can engage an opposing dipyrrinone in intramolecular hydrogen bonding, and in this energy-minimum conformation of the linear pigment 1a, the intersection of the extended planes of the dipyrrinones has an angle of 171 degrees. Spectroscopic evidence for such linearized and twisted structures was found in the pigments' NMR spectral data and their exciton UV-vis and induced circular dichroism spectra. PMID:14604367

  5. X-H⋯π and X-H⋯N hydrogen bonds - Acetylene and hydrogen cyanide as proton acceptors

    NASA Astrophysics Data System (ADS)

    Domagała, Małgorzata; Grabowski, Sławomir J.

    2009-09-01

    The hydrogen-bonded systems were considered where acetylene or hydrogen cyanide acts as a proton acceptor and different proton donating molecules are taken into account. The B3LYP/6-311++G(d,p) and MP2/6-311++G(d,p) calculations were performed for the systems considered; for HCN⋯HF and C 2H 2⋯HF complexes various levels of approximation were applied up to CCSD(T)/6-311++G(3df,3pd)//CCSD/6-311++G(3df,3pd). The Quantum Theory of "Atoms in Molecules" (QTAIM) was also applied. It was found that π-electrons of acetylene might act as the proton accepting centers and the found complex conformations are T-shaped ones. For hydrogen cyanide molecule the nitrogen atom acts as the proton acceptor center but not π-electrons. The characteristics of the bond critical points were also considered for the analyzed interactions and numerous correlations were found between geometrical, energetic and QTAIM parameters. The decomposition of the interaction energy for the systems analyzed was also applied.

  6. In situ TDLAS measurement of absolute acetylene concentration profiles in a non-premixed laminar counter-flow flame

    NASA Astrophysics Data System (ADS)

    Wagner, S.; Klein, M.; Kathrotia, T.; Riedel, U.; Kissel, T.; Dreizler, A.; Ebert, V.

    2012-06-01

    Acetylene (C2H2), as an important precursor for chemiluminescence species, is a key to understand, simulate and model the chemiluminescence and the related reaction paths. Hence we developed a high resolution spectrometer based on direct Tunable Diode Laser Absorption Spectroscopy (TDLAS) allowing the first quantitative, calibration-free and spatially resolved in situ C2H2 measurement in an atmospheric non-premixed counter-flow flame supported on a Tsuji burner. A fiber-coupled distributed feedback diode laser near 1535 nm was used to measure several absolute C2H2 concentration profiles (peak concentrations up to 9700 ppm) in a laminar non-premixed CH4/air flame ( T up to 1950 K) supported on a modified Tsuji counter-flow burner with N2 purge slots to minimize end flames. We achieve a fractional optical resolution of up to 5×10-5 OD (1 σ) in the flame, resulting in temperature-dependent acetylene detection limits for the P17e line at 6513 cm-1 of up to 2.1 ppmṡm. Absolute C2H2 concentration profiles were obtained by translating the burner through the laser beam using a DC motor with 100 μm step widths. Intercomparisons of the experimental C2H2 profiles with simulations using our new hydrocarbon oxidation mechanisms show excellent agreement in position, shape and in the absolute C2H2 values.

  7. Structure and hydration of the C4H4●+ ion formed by electron impact ionization of acetylene clusters.

    PubMed

    Momoh, Paul O; Hamid, Ahmed M; Abrash, Samuel A; El-Shall, M Samy

    2011-05-28

    Here we report ion mobility experiments and theoretical studies aimed at elucidating the identity of the acetylene dimer cation and its hydrated structures. The mobility measurement indicates the presence of more than one isomer for the C(4)H(4)(●+) ion in the cluster beam. The measured average collision cross section of the C(4)H(4)(●+) isomers in helium (38.9 ± 1 Å(2)) is consistent with the calculated cross sections of the four most stable covalent structures calculated for the C(4)H(4)(●+) ion [methylenecyclopropene (39.9 Å(2)), 1,2,3-butatriene (41.1 Å(2)), cyclobutadiene (38.6 Å(2)), and vinyl acetylene (41.1 Å(2))]. However, none of the single isomers is able to reproduce the experimental arrival time distribution of the C(4)H(4)(●+) ion. Combinations of cyclobutadiene and vinyl acetylene isomers show excellent agreement with the experimental mobility profile and the measured collision cross section. The fragment ions obtained by the dissociation of the C(4)H(4)(●+) ion are consistent with the cyclobutadiene structure in agreement with the vibrational predissociation spectrum of the acetylene dimer cation (C(2)H(2))(2)(●+) [R. A. Relph, J. C. Bopp, J. R. Roscioli, and M. A. Johnson, J. Chem. Phys. 131, 114305 (2009)]. The stepwise hydration experiments show that dissociative proton transfer reactions occur within the C(4)H(4)(●+)(H(2)O)(n) clusters with n ≥ 3 resulting in the formation of protonated water clusters. The measured binding energy of the C(4)H(4)(●+)H(2)O cluster, 38.7 ± 4 kJ/mol, is in excellent agreement with the G3(MP2) calculated binding energy of cyclobutadiene(●+)·H(2)O cluster (41 kJ/mol). The binding energies of the C(4)H(4)(●+)(H(2)O)(n) clusters change little from n = 1 to 5 (39-48 kJ/mol) suggesting the presence of multiple binding sites with comparable energies for the water-C(4)H(4)(●+) and water-water interactions. A significant entropy loss is measured for the addition of the fifth water molecule suggesting a structure with restrained water molecules, probably a cyclic water pentamer within the C(4)H(4)(●+)(H(2)O)(5) cluster. Consequently, a drop in the binding energy of the sixth water molecule is observed suggesting a structure in which the sixth water molecule interacts weakly with the C(4)H(4)(●+)(H(2)O)(5) cluster presumably consisting of a cyclobutadiene(●+) cation hydrogen bonded to a cyclic water pentamer. The combination of ion mobility, dissociation, and hydration experiments in conjunction with the theoretical calculations provides strong evidence that the (C(2)H(2))(2)(●+) ions are predominantly present as the cyclobutadiene cation with some contribution from the vinyl acetylene cation. PMID:21639448

  8. Structure and hydration of the C4H4•+ ion formed by electron impact ionization of acetylene clusters

    NASA Astrophysics Data System (ADS)

    Momoh, Paul O.; Hamid, Ahmed M.; Abrash, Samuel A.; Samy El-Shall, M.

    2011-05-01

    Here we report ion mobility experiments and theoretical studies aimed at elucidating the identity of the acetylene dimer cation and its hydrated structures. The mobility measurement indicates the presence of more than one isomer for the C4H4•+ ion in the cluster beam. The measured average collision cross section of the C4H4•+ isomers in helium (38.9 ± 1 Å2) is consistent with the calculated cross sections of the four most stable covalent structures calculated for the C4H4•+ ion [methylenecyclopropene (39.9 Å2), 1,2,3-butatriene (41.1 Å2), cyclobutadiene (38.6 Å2), and vinyl acetylene (41.1 Å2)]. However, none of the single isomers is able to reproduce the experimental arrival time distribution of the C4H4•+ ion. Combinations of cyclobutadiene and vinyl acetylene isomers show excellent agreement with the experimental mobility profile and the measured collision cross section. The fragment ions obtained by the dissociation of the C4H4•+ ion are consistent with the cyclobutadiene structure in agreement with the vibrational predissociation spectrum of the acetylene dimer cation (C2H2)2•+ [R. A. Relph, J. C. Bopp, J. R. Roscioli, and M. A. Johnson, J. Chem. Phys. 131, 114305 (2009)], 10.1063/1.3212595. The stepwise hydration experiments show that dissociative proton transfer reactions occur within the C4H4•+(H2O)n clusters with n ≥ 3 resulting in the formation of protonated water clusters. The measured binding energy of the C4H4•+H2O cluster, 38.7 ± 4 kJ/mol, is in excellent agreement with the G3(MP2) calculated binding energy of cyclobutadiene•+.H2O cluster (41 kJ/mol). The binding energies of the C4H4•+(H2O)n clusters change little from n = 1 to 5 (39-48 kJ/mol) suggesting the presence of multiple binding sites with comparable energies for the water-C4H4•+ and water-water interactions. A significant entropy loss is measured for the addition of the fifth water molecule suggesting a structure with restrained water molecules, probably a cyclic water pentamer within the C4H4•+(H2O)5 cluster. Consequently, a drop in the binding energy of the sixth water molecule is observed suggesting a structure in which the sixth water molecule interacts weakly with the C4H4•+(H2O)5 cluster presumably consisting of a cyclobutadiene•+ cation hydrogen bonded to a cyclic water pentamer. The combination of ion mobility, dissociation, and hydration experiments in conjunction with the theoretical calculations provides strong evidence that the (C2H2)2•+ ions are predominantly present as the cyclobutadiene cation with some contribution from the vinyl acetylene cation.

  9. Sigma Receptor Binding Assays.

    PubMed

    Chu, Uyen B; Ruoho, Arnold E

    2015-01-01

    Sigma receptors, both Sigma-1(S1R) and Sigma-2 (S2R), are small molecule-regulated, primarily endoplasmic reticulum (ER) membrane-associated sites. A number of drugs bind to sigma receptors, including the antipsychotic haloperidol and (+)-pentazocine, an opioid analgesic. Sigma receptors are implicated in many central nervous system disorders, in particular Alzheimer's disease and conditions associated with motor control, such as Amyotrophic Lateral Sclerosis (ALS). Described in this unit are radioligand binding assays used for the pharmacological characterization of S1R and S2R. Methods detailed include a radioligand saturation binding assay for defining receptor densities and a competitive inhibition binding assay employing [(3) H]-(+)-pentazocine for identifying and characterizing novel ligands that interact with S1R. Procedures using [(3) H]-1,3-di(2-tolyl)guanidine ([(3) H]-DTG), a nonselective sigma receptor ligand, are described for conducting a saturation binding and competitive inhibition assays for the S2R site. These protocols are of value in drug discovery in identifying new sigma ligands and in the characterization of these receptors. 2015 by John Wiley & Sons, Inc. PMID:26646191

  10. Factor II assay

    MedlinePLUS

    The factor II assay is a blood test to measure the activity of factor II. Factor II is also known as prothrombin. This is ... the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick ...

  11. Reductive capacity of natural reductants.

    PubMed

    Lee, Woojin; Batchelor, Bill

    2003-02-01

    Reductive capacities of soil minerals and soil for Cr(VI) and chlorinated ethylenes were measured and characterized to provide basic knowledge for in-situ and ex-situ treatment using these natural reductants. The reductive capacities of iron-bearing sulfide (pyrite), hydroxide (green rust; GR(SO4)), and oxide (magnetite) minerals for Cr(VI) and tetrachloroethylene (PCE) were 1-3 orders of magnitude greater than those of iron-bearing phyllosilicates (biotite, vermiculite, and montmorillonite). The reductive capacities of surface soil collected from the plains of central Texas were similar and slightly greater than those of iron-bearing phyllosilicates. The reductive capacity of iron-bearing soil minerals for Cr(VI) was roughly 3-16 times greater than that for PCE, implying that Cr(VI) is more susceptible to being reduced by soil minerals than is PCE. GR(SO4) has the greatest reductive capacity for both Cr(VI) and PCE followed by magnetite, pyrite, biotite, montmorillonite, and vermiculite. This order was the same for both target compounds, which indicates that the relative reductive capacities of soil minerals are consistent. The reductive capacities of pyrite and GR(SO4) for chlorinated ethylenes decreased in the order: trichloroethylene (TCE) > PCE > cis-dichloroethylene (c-DCE) > vinyl chloride (VC). Fe(II) content in soil minerals was directly proportional to the reductive capacity of soil minerals for Cr(VI) and PCE, suggesting that Fe(II) content is an important factor that significantly affects reductive transformations of target contaminants in natural systems. PMID:12630469

  12. Just Click It: Undergraduate Procedures for the Copper(I)-Catalyzed Formation of 1,2,3-Triazoles from Azides and Terminal Acetylenes

    ERIC Educational Resources Information Center

    Sharpless, William D.; Peng Wu; Hansen, Trond Vidar; Lindberg, James G.

    2005-01-01

    The click chemistry uses only the most reliable reactions to build complex molecules from olefins, electrophiles and heteroatom linkers. A variation on Huisgen's azide-alkyne 1,2,3-triazole synthesis, the addition of the copper (I), the premium example of the click reaction, catalyst strongly activates terminal acetylenes towards the 1,3-dipole in

  13. A Model for Self-Assembly of Carbon Nanotubes from Acetylene Based on Real-Time Studies of Vertically Aligned Growth Kinetics

    SciTech Connect

    Eres, Gyula

    2009-01-01

    Time-resolved optical reflectivity was used to study the kinetics in the early stages of vertically aligned carbon nanotube array growth from a molecular beam of acetylene. The molecular beam environment was used to suppress gas phase reaction pathways and limit the growth to surface reactions specific to the molecular structure of acetylene. The observed acetylene flux dependent induction delay and the threshold for vertically aligned growth are characteristic features of heterogeneous chain reactions. Propagation of chain reactions requires regeneration of the active sites that can occur only if catalytic activity is transferred from the metal catalyst film to surface carbon species. After the active site transformation, acetylene self-assembles into carbon structures of progressively increasing size such as chains, graphene fragments, and nanotubes. In this paper we show that a conceptual framework supported by ab initio density functional theory calculations in which active carbon species facilitate incorporation of new carbon readily explains recent results in vertically aligned nanotube growth that are puzzling in the context of the diffusion/precipitation model.

  14. Just Click It: Undergraduate Procedures for the Copper(I)-Catalyzed Formation of 1,2,3-Triazoles from Azides and Terminal Acetylenes

    ERIC Educational Resources Information Center

    Sharpless, William D.; Peng Wu; Hansen, Trond Vidar; Lindberg, James G.

    2005-01-01

    The click chemistry uses only the most reliable reactions to build complex molecules from olefins, electrophiles and heteroatom linkers. A variation on Huisgen's azide-alkyne 1,2,3-triazole synthesis, the addition of the copper (I), the premium example of the click reaction, catalyst strongly activates terminal acetylenes towards the 1,3-dipole in…

  15. Methane Post-Processor Development to Increase Oxygen Recovery beyond State-of-the-Art Carbon Dioxide Reduction Technology

    NASA Technical Reports Server (NTRS)

    Abney, Morgan; Miller, Lee; Greenwood, Zach; Iannantuono, Michelle; Jones, Kenny

    2013-01-01

    State-of-the-art life support carbon dioxide (CO2) reduction technology, based on the Sabatier reaction, is theoretically capable of 50% recovery of oxygen from metabolic CO2. This recovery is constrained by the limited availability of reactant hydrogen. Post-processing of the methane byproduct from the Sabatier reactor results in hydrogen recycle and a subsequent increase in oxygen recovery. For this purpose, a Methane Post-Processor Assembly containing three sub-systems has been developed and tested. The assembly includes a Methane Purification Assembly (MePA) to remove residual CO2 and water vapor from the Sabatier product stream, a Plasma Pyrolysis Assembly (PPA) to partially pyrolyze methane into hydrogen and acetylene, and an Acetylene Separation Assembly (ASepA) to purify the hydrogen product for recycle. The results of partially integrated testing of the sub-systems are reported.

  16. Methane Post-Processor Development to Increase Oxygen Recovery beyond State-of-the-Art Carbon Dioxide Reduction Technology

    NASA Technical Reports Server (NTRS)

    Abney, Morgan B.; Greenwood, Zachary; Miller, Lee A.; Alvarez, Giraldo; Iannantuono, Michelle; Jones, Kenny

    2013-01-01

    State-of-the-art life support carbon dioxide (CO2) reduction technology, based on the Sabatier reaction, is theoretically capable of 50% recovery of oxygen from metabolic CO2. This recovery is constrained by the limited availability of reactant hydrogen. Post-processing of the methane byproduct from the Sabatier reactor results in hydrogen recycle and a subsequent increase in oxygen recovery. For this purpose, a Methane Post-Processor Assembly containing three sub-systems has been developed and tested. The assembly includes a Methane Purification Assembly (MePA) to remove residual CO2 and water vapor from the Sabatier product stream, a Plasma Pyrolysis Assembly (PPA) to partially pyrolyze methane into hydrogen and acetylene, and an Acetylene Separation Assembly (ASepA) to purify the hydrogen product for recycle. The results of partially integrated testing of the sub-systems are reported

  17. Rat mesentery angiogenesis assay.

    PubMed

    Norrby, Klas C

    2011-01-01

    The adult rat mesentery window angiogenesis assay is biologically appropriate and is exceptionally well suited to the study of sprouting angiogenesis in vivo [see review papers], which is the dominating form of angiogenesis in human tumors and non-tumor tissues, as discussed in invited review papers(1,2). Angiogenesis induced in the membranous mesenteric parts by intraperitoneal (i.p.) injection of a pro-angiogenic factor can be modulated by subcutaneous (s.c.), intravenous (i.v.) or oral (p.o.) treatment with modifying agents of choice. Each membranous part of the mesentery is translucent and framed by fatty tissue, giving it a window-like appearance. The assay has the following advantageous features: (i) the test tissue is natively vascularized, albeit sparsely, and since it is extremely thin, the microvessel network is virtually two-dimensional, which allows the entire network to be assessed microscopically in situ; (ii) in adult rats the test tissue lacks significant physiologic angiogenesis, which characterizes most normal adult mammalian tissues; the degree of native vascularization is, however, correlated with age, as discussed in(1); (iii) the negligible level of trauma-induced angiogenesis ensures high sensitivity; (iv) the assay replicates the clinical situation, as the angiogenesis-modulating test drugs are administered systemically and the responses observed reflect the net effect of all the metabolic, cellular, and molecular alterations induced by the treatment; (v) the assay allows assessments of objective, quantitative, unbiased variables of microvascular spatial extension, density, and network pattern formation, as well as of capillary sprouting, thereby enabling robust statistical analyses of the dose-effect and molecular structure-activity relationships; and (vi) the assay reveals with high sensitivity the toxic or harmful effects of treatments in terms of decreased rate of physiologic body-weight gain, as adult rats grow robustly. Mast-cell-mediated angiogenesis was first demonstrated using this assay(3,4). The model demonstrates a high level of discrimination regarding dosage-effect relationships and the measured effects of systemically administered chemically or functionally closely related drugs and proteins, including: (i) low-dosage, metronomically administered standard chemotherapeutics that yield diverse, drug-specific effects (i.e., angiogenesis-suppressive, neutral or angiogenesis-stimulating activities(5)); (ii) natural iron-unsaturated human lactoferrin, which stimulates VEGF-A-mediated angiogenesis(6), and natural iron-unsaturated bovine lactoferrin, which inhibits VEGF-A-mediated angiogenesis(7); and (iii) low-molecular-weight heparin fractions produced by various means(8,9). Moreover, the assay is highly suited to studies of the combined effects on angiogenesis of agents that are administered systemically in a concurrent or sequential fashion. The idea of making this video originated from the late Dr. Judah Folkman when he visited our laboratory and witnessed the methodology being demonstrated. Review papers (invited) discussing and appraising the assay Norrby, K. In vivo models of angiogenesis. J. Cell. Mol. Med. 10, 588-612 (2006). Norrby, K. Drug testing with angiogenesis models. Expert Opin. Drug. Discov. 3, 533-549 (2008). PMID:21712799

  18. The corneal pocket assay.

    PubMed

    Ziche, Marina; Morbidelli, Lucia

    2015-01-01

    The cornea in most species is physiologically avascular, and thus this assay allows the measurement of newly formed vessels. The continuous monitoring of neovascular growth in the same animal allows the evaluation of drugs acting as suppressors or stimulators of angiogenesis. Under anesthesia a micropocket is produced in the cornea thickness and the angiogenesis stimulus (tumor tissue, cell suspension, growth factor) is placed into the pocket in order to induce vascular outgrowth from the limbal capillaries. Neovascular development and progression can be modified by the presence of locally released or applied inhibitory factors or by systemic treatments. In this chapter the experimental details of the avascular cornea assay, the technical challenges, and advantages and disadvantages in different species are discussed. Protocols for local drug treatment and tissue sampling for histology and pharmacokinetic profile are reported. PMID:25468596

  19. Arabidopsis assay for mutagenicity.

    PubMed

    Gichner, T; Badayev, S A; Demchenko, S I; Relichov, J; Sandhu, S S; Usmanov, P D; Usmanova, O; Velemnsk, J

    1994-10-16

    Four laboratories, two in the Czech Republic (Brno and Prague) and two in the CIS (Moscow and Duschanbe), participated in the International Programme on Chemical Safety's (IPCS) collaborative study to evaluate the utility of the most commonly used plant test systems, including the Arabidopsis thaliana assay, for assessing the mutagenic potential of environmental agents. Out of the five compounds evaluated in the Arabidopsis assay, three compounds, i.e., ethyl methanesulfonate, N-methyl-N-nitrosourea, and azidoglycerol, were reported to be mutagenic by all four participating laboratories. Sodium azide (NaN3) demonstrated a negative response in all four laboratories, whereas maleic hydrazide was reported to be weakly mutagenic by one laboratory and nonmutagenic by the other three laboratories. PMID:7523895

  20. Kinetic Tetrazolium Microtiter Assay

    NASA Technical Reports Server (NTRS)

    Pierson, Duane L.; Stowe, Raymond; Koenig, David

    1993-01-01

    Kinetic tetrazolium microtiter assay (KTMA) involves use of tetrazolium salts and Triton X-100 (or equivalent), nontoxic, in vitro color developer solubilizing colored metabolite formazan without injuring or killing metabolizing cells. Provides for continuous measurement of metabolism and makes possible to determine rate of action of antimicrobial agent in real time as well as determines effective inhibitory concentrations. Used to monitor growth after addition of stimulatory compounds. Provides for kinetic determination of efficacy of biocide, greatly increasing reliability and precision of results. Also used to determine relative effectiveness of antimicrobial agent as function of time. Capability of generating results on day of test extremely important in treatment of water and waste, disinfection of hospital rooms, and in pharmaceutical, agricultural, and food-processing industries. Assay also used in many aspects of cell biology.

  1. Electrophoretic Mobility Shift Assays.

    PubMed

    Rowe, Sarah E; O'Gara, James P

    2016-01-01

    Experimental demonstration of regulatory protein interactions with the sequences upstream of potential target genes is an important element in gene expression studies. These experiments termed electrophoretic mobility shift assays (EMSAs) provide valuable insight into the mechanism of action of transcription factors. EMSAs combined with downstream applications such as transcriptional analysis help uncover precisely how regulatory proteins control target gene expression. This chapter comprises a guideline for expression and purification of recombinant transcription factor proteins followed by a detailed protocol for EMSAs. PMID:26194709

  2. Carbon Dioxide Reduction Post-Processing Sub-System Development

    NASA Technical Reports Server (NTRS)

    Abney, Morgan B.; Miller, Lee A.; Greenwood, Zachary; Barton, Katherine

    2012-01-01

    The state-of-the-art Carbon Dioxide (CO2) Reduction Assembly (CRA) on the International Space Station (ISS) facilitates the recovery of oxygen from metabolic CO2. The CRA utilizes the Sabatier process to produce water with methane as a byproduct. The methane is currently vented overboard as a waste product. Because the CRA relies on hydrogen for oxygen recovery, the loss of methane ultimately results in a loss of oxygen. For missions beyond low earth orbit, it will prove essential to maximize oxygen recovery. For this purpose, NASA is exploring an integrated post-processor system to recover hydrogen from CRA methane. The post-processor, called a Plasma Pyrolysis Assembly (PPA) partially pyrolyzes methane to recover hydrogen with acetylene as a byproduct. In-flight operation of post-processor will require a Methane Purification Assembly (MePA) and an Acetylene Separation Assembly (ASepA). Recent efforts have focused on the design, fabrication, and testing of these components. The results and conclusions of these efforts will be discussed as well as future plans.

  3. Rapid Diamond Deposition on Ni and Co Coatings by Using Twin Acetylene/Oxygen Gas Welding Torches

    NASA Astrophysics Data System (ADS)

    Ando, Yasutaka; Noda, Yoshimasa; Adachi, Shin-ichiro

    2015-10-01

    Cermet coatings have been widely used because of their high hardness and excellent wear resistance even under high-temperature conditions. However, since cermet coatings include expensive materials such as WC, TiC, TiN and so on, low-cost hard particles as a dispersing agent need to be developed. In this study, in order to develop a low-cost diamond dispersion system for the creation of diamond/thermal sprayed metal hybrid coatings, diamond deposition on thermal sprayed Ni and Co coatings and Mo and Ni metal substrates by the combustion flame method using twin acetylene/oxygen gas welding torches was carried out. Consequently, even in cases of thermal sprayed Ni and Co coatings, diamond particles could be deposited within only 5 min. From these results, this technique is proved to have a high potential for rapid diamond deposition in order to create diamond/thermal sprayed metal hybrid coatings.

  4. Rapid Diamond Deposition on Ni and Co Coatings by Using Twin Acetylene/Oxygen Gas Welding Torches

    NASA Astrophysics Data System (ADS)

    Ando, Yasutaka; Noda, Yoshimasa; Adachi, Shin-ichiro

    2015-12-01

    Cermet coatings have been widely used because of their high hardness and excellent wear resistance even under high-temperature conditions. However, since cermet coatings include expensive materials such as WC, TiC, TiN and so on, low-cost hard particles as a dispersing agent need to be developed. In this study, in order to develop a low-cost diamond dispersion system for the creation of diamond/thermal sprayed metal hybrid coatings, diamond deposition on thermal sprayed Ni and Co coatings and Mo and Ni metal substrates by the combustion flame method using twin acetylene/oxygen gas welding torches was carried out. Consequently, even in cases of thermal sprayed Ni and Co coatings, diamond particles could be deposited within only 5 min. From these results, this technique is proved to have a high potential for rapid diamond deposition in order to create diamond/thermal sprayed metal hybrid coatings.

  5. The Breathing Orbital Valence Bond Method in Diffusion Monte Carlo: C-H Bond Dissociation ofAcetylene

    SciTech Connect

    Domin, D.; Braida, Benoit; Lester Jr., William A.

    2008-05-30

    This study explores the use of breathing orbital valence bond (BOVB) trial wave functions for diffusion Monte Carlo (DMC). The approach is applied to the computation of the carbon-hydrogen (C-H) bond dissociation energy (BDE) of acetylene. DMC with BOVB trial wave functions yields a C-H BDE of 132.4 {+-} 0.9 kcal/mol, which is in excellent accord with the recommended experimental value of 132.8 {+-} 0.7 kcal/mol. These values are to be compared with DMC results obtained with single determinant trial wave functions, using Hartree-Fock orbitals (137.5 {+-} 0.5 kcal/mol) and local spin density (LDA) Kohn-Sham orbitals (135.6 {+-} 0.5 kcal/mol).

  6. Direct measurements of collisional Raman line broadening in the S-branch transitions of acetylene (C2H2)

    NASA Astrophysics Data System (ADS)

    Hsu, Paul S.; Stauffer, Hans U.; Jiang, Naibo; Gord, James R.; Roy, Sukesh

    2013-10-01

    We report direct measurements of the self- and N2-broadened Raman S-branch linewidths of acetylene (C2H2), obtained by employing time-resolved picosecond rotational coherent anti-Stokes Raman scattering spectroscopy. Using broadband 115-ps pump and Stokes pulses (135 cm-1 bandwidth) and a spectrally narrowed 90-ps probe pulse (0.2 cm-1 bandwidth), Raman-coherence lifetimes are measured at room temperature for the S-branch (?J = +2) transitions associated with rotational quantum number J = 3-25. These directly measured Raman-coherence lifetimes, when converted to collisional linewidth broadening coefficients, differ from the previously reported broadening coefficients extracted from theoretical calculations by 6%-35% for self-broadening for C2H2 and by up to 60% for N2-broadened C2H2.

  7. A Study on the Photoreaction of 2(5H)-Furanones with Substituted Acetylenes: Evidence for a Mechanistic Reformulation.

    PubMed

    Flores, Ramon; Font, Josep; Alibs, Ramon; Figueredo, Marta

    2016-03-01

    The photoreaction of 2(5H)-furanones with alkynes has been investigated. The complexity of this process is evidenced by the variety of isolated products, which have allowed disclosing interesting mechanistic aspects. When the reaction is performed in acetonitrile under direct excitation, in addition to the primary [2+2] cycloadducts, products derived from an 1,3-acyl shift rearrangement are also formed. For unsymmetrical alkynes, the rearrangement of the head-to-tail primary adducts produces new regioisomers and, when the starting furanone is chiral, this rearrangement inverts the relative anti/syn geometry of the primary cycloadducts. In the reactions performed in acetone under photosensitized conditions, rearranged products were never detected, supporting that the 1,3-acyl shift takes place from the singlet excited state S1 of the ?,?-unsaturated lactone. When bis(trimethylsilyl)acetylene is used as the alkyne partner, the major photoproducts are monocyclic bis(trimethylsilyl)lactones. PMID:26749319

  8. ABSORPTION CROSS SECTION OF GASEOUS ACETYLENE AT 85 K IN THE WAVELENGTH RANGE 110-155 nm

    SciTech Connect

    Cheng, Bing-Ming; Chen, Hui-Fen; Lu, Hsiao-Chi; Chen, Hong-Kai; Alam, M. S.; Chou, Sheng-Lung; Lin, Meng-Yeh

    2011-09-01

    Absorption spectra and absorption cross sections of gaseous acetylene, C{sub 2}H{sub 2}, at 298 and 85 K were measured in the wavelength range 110-155 nm with a slit-jet system coupled to a synchrotron as a source of vacuum ultraviolet light. Using published spectral parameters of C{sub 2}H{sub 2}, we simulated the absorption profile for the Rydberg transition to state 4R{sub 0} in the range 124.6-125.1 nm, according to which the temperature of the jet-expanded sample at stagnation pressure 200 Torr is 85 {+-} 5 K. Our cross sections of C{sub 2}H{sub 2} are applicable for determining properties sensitive to temperature for diagnostic work on Saturn and Titan.

  9. The discovery of the [2{sub s}+2{sub a}] reaction of dislanes and acetylenes and their applications

    SciTech Connect

    Za, Zhongxin; Barton, T.J.; Lin, Jibing; Gordon, M.

    1997-12-31

    A concerted [2{sub s}+2{sub a}] intramolecular addition reaction was discovered between disilanes and acetylenes in unimolecular process. The reaction was performed with the 5,5,6,6-tetramethyl-3,3,8,8-tetraphenyl-4,7-dioxa-5,6-disilyl-cyclooctyne (1) under an argon flow at 600{degrees}C to give product 1,1,4,4-tetramethyl-3,3,6,6-tetraphenyl-2,5-dioxa-1,4-disilyl-dicyclo[3,3,0]octa-7-ene (2). Ab initio calculations were performed at the MP4/6-31G** level. The transition state structure was found and the activation energy was calculated to be 34 kcal/mol. The first example of a 3,3{prime}-disilyl-indeno[2,1-a]indene (4) was synthesized from dibenzo-5,6-disilylcyclooctyne (3) in the same manner.

  10. Uranium reduction.

    PubMed

    Wall, Judy D; Krumholz, Lee R

    2006-01-01

    The dramatic decrease in solubility accompanying the reduction of U(VI) to U(IV), producing the insoluble mineral uraninite, has been viewed as a potential mechanism for sequestration of environmental uranium contamination. In the past 15 years, it has been firmly established that a variety of bacteria exhibit this reductive capacity. To obtain an understanding of the microbial metal metabolism, to develop a practical approach for the acceleration of in situ bioreduction, and to predict the long-term fate of environmental uranium, several aspects of the microbial process have been experimentally explored. This review briefly addresses the research to identify specific uranium reductases and their cellular location, competition between uranium and other electron acceptors, attempts to stimulate in situ reduction, and mechanisms of reoxidation of reduced uranium minerals. PMID:16704344

  11. Enhanced reductive dechlorination of tetrachloroethene during reduction of cobalamin (III) by nano-mackinawite.

    PubMed

    Amir, Amnorzahira; Lee, Woojin

    2012-10-15

    We demonstrated adsorption and reduction of cobalamin(III) (Co(III)) on nano-mackinawite (nFeS) surface and their impact on reductive dechlorination of tetrachloroethene (PCE). The adsorption of Co(III) on the nFeS surface followed Langmuir isotherm and the reduction of Co(III) provided different reactive surface chemical species on nFeS surface. Content of Fe(2+)S on nFeS surface decreased (45.9-14.5%) as Fe(2+)S was oxidized to Fe(3+)S and Fe(3+)O coupled with the surface reduction of Co(III) to cobalamin(II) (Co(II)). S(2-) and S(n)(2-) contents on the nFeS surface also decreased by 48.5% and 82.3%, respectively during the formation of sulfidecobalamin(II) (?S(2-)Co(II)) by the reactive surface sulfur. PCE was fully degraded in nFeSCo(III) suspension at pH 8.3 in 120 h. The dechlorination kinetic rate constant of PCE in the nFeSCo(III) suspension (k(FeSCo(III))=0.1880.003 h(-1)) was 145 times greater than that in nFeS suspension, showing a potential role of ?S(2-)Co(II) as an electron transfer mediator to shuttle electrons for the enhanced reductive dechlorination. PCE was transformed to acetylene and 1,3-butadiene as major products via reductive ?-elimination and isomerization reactions, respectively. The experimental findings can provide basic knowledge to identify a reaction mechanism for the enhanced reductive dechlorination of chlorinated organic by biogeochemical reactions possibly observed in natural reducing environments. PMID:22939091

  12. The simultaneous comparison of acetylene or carbon dioxide flux as a measure of effective pulmonary blood flow in children.

    PubMed

    Rosenthal, M; Bush, A

    1997-11-01

    Both acetylene (Ac) and carbon dioxide can be used to measure effective pulmonary blood flow (Q'eff) noninvasively. They are safe and reasonably accurate in adults during rest and exercise, but there have been no simultaneous comparisons in children. One hundred and six healthy children (55 males and 51 females, aged 8-17 yrs) were studied using an Innovision quadrupole mass spectrometer. They all underwent five rebreathing manoeuvres at rest, and then single measurements were again taken after 9 min of bicycle exercise. Mixed venous CO2 levels were calculated either by a linear (L) or curvilinear (C) extrapolation method. At rest, the coefficients of variation for Q'eff were Ac 8%, L 20%, and C 16% (p<0.001). The median resting values were: Ac 3.2 (95% confidence interval (95% CI) 3.1-3.4) L 5.1 (95 % CI 4.6-5.4) and C 4.7 (95 % CI 4.3-5.1) L x min(-1) x m(-2), (p<0.001). Compared to Ac, only 14 and 17% of L and C values, respectively, were +/-0.5 L x min(-1) x m(-2), whilst 41 and 29%, respectively were more than +/-2 L x min(-1) x m(-2). During exercise, median values were: Ac 6.7 (95% CI 6.3-7.0); L 8.0 (95% CI 7.3-8.4); and C 7.2 (95% CI 6.5-7.9) L x min(-1) x m(-2). L was significantly greater than C (p<0.001), but C was similar to Ac (p=0.06). More than 50% of L and C values could not be calculated for various reasons, whereas all 106 Ac values could be calculated. Neither carbon dioxide method is sufficiently reliable to be used in children in a clinical setting. Acetylene was safe, reliable, accurate and preferred. PMID:9426100

  13. Biosensors: Viruses for ultrasensitive assays

    NASA Astrophysics Data System (ADS)

    Donath, Edwin

    2009-04-01

    A three-dimensional assay based on genetically engineered viral nanoparticles and nickel nanohairs can detect much lower levels of protein markers associated with heart attacks than conventional assays.

  14. C. elegans Chemotaxis Assay

    PubMed Central

    Margie, Olivia; Palmer, Chris; Chin-Sang, Ian

    2013-01-01

    Many organisms use chemotaxis to seek out food sources, avoid noxious substances, and find mates. Caenorhabditis elegans has impressive chemotaxis behavior. The premise behind testing the response of the worms to an odorant is to place them in an area and observe the movement evoked in response to an odorant. Even with the many available assays, optimizing worm starting location relative to both the control and test areas, while minimizing the interaction of worms with each other, while maintaining a significant sample size remains a work in progress 1-10. The method described here aims to address these issues by modifying the assay developed by Bargmann et al.1. A Petri dish is divided into four quadrants, two opposite quadrants marked "Test" and two are designated "Control". Anesthetic is placed in all test and control sites. The worms are placed in the center of the plate with a circle marked around the origin to ensure that non-motile worms will be ignored. Utilizing a four-quadrant system rather than one 2 or two 1 eliminates bias in the movement of the worms, as they are equidistant from test and control samples, regardless of which side of the origin they began. This circumvents the problem of worms being forced to travel through a cluster of other worms to respond to an odorant, which can delay worms or force them to take a more circuitous route, yielding an incorrect interpretation of their intended path. This method also shows practical advantages by having a larger sample size and allowing the researcher to run the assay unattended and score the worms once the allotted time has expired. PMID:23644543

  15. Growth cone collapse assay.

    PubMed

    Cook, Geoffrey M W; Jareonsettasin, Prem; Keynes, Roger J

    2014-01-01

    The growth cone collapse assay has proved invaluable in detecting and purifying axonal repellents. Glycoproteins/proteins present in detergent extracts of biological tissues are incorporated into liposomes, added to growth cones in culture and changes in morphology are then assessed. Alternatively purified or recombinant molecules in aqueous solution may be added directly to the cultures. In both cases after a defined period of time (up to 1 h), the cultures are fixed and then assessed by inverted phase contrast microscopy for the percentage of growth cones showing a collapsed profile with loss of flattened morphology, filopodia, and lamellipodia. PMID:24838959

  16. Colony survival assay.

    PubMed

    Simpson, Laura J; Sale, Julian E

    2006-01-01

    For studies of DNA repair networks the sensitivity of mutants and combinations of mutants to varying forms of DNA damaging agents has formed a mainstay of genetic analysis in bacteria and yeast. Likewise, this form of epistasis analysis has proved immensely informative in DT40. Because DT40 is non-adherent, it is necessary to restrict the movement of cells by growing them in a viscous medium containing methylcellulose. Here we present methods for carrying out DNA damage survival assays in DT40 with chemical mutagens, ionising radiation and ultraviolet irradiation. PMID:17623926

  17. Radon assay for SNO+

    NASA Astrophysics Data System (ADS)

    Rumleskie, Janet

    2015-12-01

    The SNO+ experiment will study neutrinos while located 6,800 feet below the surface of the earth at SNOLAB. Though shielded from surface backgrounds, emanation of radon radioisotopes from the surrounding rock leads to back-grounds. The characteristic decay of radon and its daughters allows for an alpha detection technique to count the amount of Rn-222 atoms collected. Traps can collect Rn-222 from various positions and materials, including an assay skid that will collect Rn-222 from the organic liquid scintillator used to detect interactions within SNO+.

  18. Waste Reduction.

    ERIC Educational Resources Information Center

    Bray, Marilyn; And Others

    1996-01-01

    Presents activities that focus on waste reduction in the school and community. The ideas are divided into grade level categories. Sample activities include Techno-Trash, where children use tools to take apart broken appliances or car parts, then reassemble them or build new creations. Activities are suggested for areas including language arts and

  19. TOTAL CULTURABLE VIRUS QUANTAL ASSAY

    EPA Science Inventory

    This chapter describes a quantal method for assaying culturable human enteric viruses from water matrices. The assay differs from the plaque assay described in Chapter 10 (December 1987 Revision) in that it is based upon the direct microscopic viewing of cells for virus-induced ...

  20. Experimental metastasis assay.

    PubMed

    Mohanty, Sonali; Xu, Lei

    2010-01-01

    Metastasis is the leading cause of death in cancer patients. To understand the mechanism of metastasis, an experimental metastasis assay was established using immunodeficient mice. This article delineates the procedures involved in this assay, including sample preparation, intravenous injection, and culturing cells from lung metastases. Briefly, a pre-determined number of human cancer cells were prepared in vitro and directly injected into the circulation of immunodeficient mice through their tail veins. A small number of cells survive the turbulence in the circulation and grow as metastases in internal organs, such as lung. The injected mice are dissected after a certain period. The tissue distribution of metastases is determined under a dissecting microscope. The number of metastases in a specific tissue is counted and it directly correlates with the metastatic ability of the injected cancer cells. The arisen metastases are isolated and cultured in vitro as cell lines, which often show enhanced metastatic abilities than the parental line when injected again into immunodeficient mice. These highly metastatic derivatives become useful tools for identifying genes or molecular pathways that regulate metastatic progression. PMID:20811329

  1. Optimized Diagnostic Assays Based on Redox Tagged Bioreceptive Interfaces.

    PubMed

    Bedatty Fernandes, Flavio C; Patil, Amol V; Bueno, Paulo R; Davis, Jason J

    2015-12-15

    Among the numerous label free electronic biomarker assay methodologies now available, impedance based electrochemical capacitance spectroscopy (ECS), based upon mapping the perturbations in interfacial charging of redox elements incorporated into a biologically receptive interface, has recently been shown to be a convenient and highly sensitive mode of transduction and one which, additionally, requires no predoping of analytical solution. We present, herein, a data acquisition and analysis methodology based on frequency resolved immittance function analysis. Ultimately, this enables both a maximization of assay sensitivity and a reduction in assay acquisition time by an order of magnitude. PMID:26583592

  2. Uranium Reduction

    SciTech Connect

    Wall, J.D.; Krumholz, L.R.

    2007-04-02

    The dramatic decrease in solubility accompanying thereduction of U(VI) to U(IV), producing the insoluble mineral uraninite,has been viewed as a potential mechanism for sequestration of environmentaluranium contamination. In the past 15 years, it has been firmlyestablished that a variety of bacteria exhibit this reductive capacity.To obtain an understanding of the microbial metal metabolism, to developa practical approach for the acceleration of in situ bioreduction, and topredict the long-term fate of environmental uranium, several aspects ofthe microbial process have been experimentally explored. This reviewbriefly addresses the research to identify specific uranium reductasesand their cellular location, competition between uranium and otherelectron acceptors, attempts to stimulate in situ reduction, andmechanisms of reoxidation of reduced uranium minerals.

  3. Cholesterol Efflux Assay

    PubMed Central

    Low, Hann; Hoang, Anh; Sviridov, Dmitri

    2012-01-01

    Cholesterol content of cells must be maintained within the very tight limits, too much or too little cholesterol in a cell results in disruption of cellular membranes, apoptosis and necrosis 1. Cells can source cholesterol from intracellular synthesis and from plasma lipoproteins, both sources are sufficient to fully satisfy cells' requirements for cholesterol. The processes of cholesterol synthesis and uptake are tightly regulated and deficiencies of cholesterol are rare 2. Excessive cholesterol is more common problem 3. With the exception of hepatocytes and to some degree adrenocortical cells, cells are unable to degrade cholesterol. Cells have two options to reduce their cholesterol content: to convert cholesterol into cholesteryl esters, an option with limited capacity as overloading cells with cholesteryl esters is also toxic, and cholesterol efflux, an option with potentially unlimited capacity. Cholesterol efflux is a specific process that is regulated by a number of intracellular transporters, such as ATP binding cassette transporter proteins A1 (ABCA1) and G1 (ABCG1) and scavenger receptor type B1. The natural acceptor of cholesterol in plasma is high density lipoprotein (HDL) and apolipoprotein A-I. The cholesterol efflux assay is designed to quantitate the rate of cholesterol efflux from cultured cells. It measures the capacity of cells to maintain cholesterol efflux and/or the capacity of plasma acceptors to accept cholesterol released from cells. The assay consists of the following steps. Step 1: labelling cellular cholesterol by adding labelled cholesterol to serum-containing medium and incubating with cells for 24-48 h. This step may be combined with loading of cells with cholesterol. Step 2: incubation of cells in serum-free medium to equilibrate labelled cholesterol among all intracellular cholesterol pools. This stage may be combined with activation of cellular cholesterol transporters. Step 3: incubation of cells with extracellular acceptor and quantitation of movement of labelled cholesterol from cells to the acceptor. If cholesterol precursors were used to label newly synthesized cholesterol, a fourth step, purification of cholesterol, may be required. The assay delivers the following information: (i) how a particular treatment (a mutation, a knock-down, an overexpression or a treatment) affects the capacity of cell to efflux cholesterol and (ii) how the capacity of plasma acceptors to accept cholesterol is affected by a disease or a treatment. This method is often used in context of cardiovascular research, metabolic and neurodegenerative disorders, infectious and reproductive diseases. PMID:22414908

  4. Nitrate reduction

    DOEpatents

    Dziewinski, Jacek J. (Los Alamos, NM); Marczak, Stanislaw (Los Alamos, NM)

    2000-01-01

    Nitrates are reduced to nitrogen gas by contacting the nitrates with a metal to reduce the nitrates to nitrites which are then contacted with an amide to produce nitrogen and carbon dioxide or acid anions which can be released to the atmosphere. Minor amounts of metal catalysts can be useful in the reduction of the nitrates to nitrites. Metal salts which are formed can be treated electrochemically to recover the metals.

  5. Chemotaxis: Under Agarose Assay.

    PubMed

    Brazill, Derrick

    2016-01-01

    The unicellular eukaryote Dictyostelium discoideum represents a superb model for examining chemotaxis. Under vegetative conditions, the amoebae are chemotactically responsive to pterins, such as folate. Under starved conditions, they lose their sensitivity to pterins, and become chemotactically responsive to cAMP. As an NIH model system, Dictyostelium offers a variety of advantages in studying chemotaxis, including its conservation of mammalian signaling pathways, its ease of growth, and its genetic tractability. In this chapter, we describe the use of the under agarose chemotaxis assay to identify proteins involved in controlling motility and directional sensing in Dictyostelium discoideum. Given the similarities between Dictyostelium and mammalian cells, this allows us to dissect the conserved pathways involved in eukaryotic chemotaxis. PMID:26498795

  6. Nitrous oxide reduction in nodules: denitrification or N/sub 2/ fixation

    SciTech Connect

    Coyne, M.S.; Focht, D.D.

    1987-05-01

    Detached cowpea nodules that contained a nitrous oxide reductase-positive (Nor/sup +/) rhizobium strain (8A55) and a nitrous oxide reductase-negative (Nor/sup -/) rhizobium strain (32H1) were incubated with 1% /sup 15/N/sub 2/O (95 atom% /sup 15/N) in the following three atmospheres: aerobic with C/sub 2/H/sub 2/ (10%), aerobic without C/sub 2/H/sub 2/, and anaerobic (argon atmosphere) without C/sub 2/H/sub 2/. The greatest production of /sup 15/N/sub 2/ occurred anaerobically with 8A55, yet very little was formed with 32H1. Although acetylene reduction activity was slightly higher with 32H1, about 10 times more /sup 15/N/sub 2/ was produced aerobically by 8A55 than by 32H1 in the absence of acetylene. The major reductive pathway of N/sub 2/O reduction by denitrifying rhizobium strain 8A55 is by nitrous oxide reductase rather than nitrogenase.

  7. Test procedure for boxed waste assay system

    SciTech Connect

    Wachter, J.

    1994-12-07

    This document, prepared by Los Alamos National Laboratory`s NMT-4 group, details the test methodology and requirements for Acceptance/Qualification testing of a Boxed Waste Assay System (BWAS) designed and constructed by Pajarito Scientific Corporation. Testing of the BWAS at the Plutonium Facility (TA55) at Los Alamos National Laboratory will be performed to ascertain system adherence to procurement specification requirements. The test program shall include demonstration of conveyor handling capabilities, gamma ray energy analysis, and imaging passive/active neutron accuracy and sensitivity. Integral to these functions is the system`s embedded operating and data reduction software.

  8. Synthesis of indoles, benzofurans, and related heterocycles via an acetylene-activated SNAr/intramolecular cyclization cascade sequence in water or DMSO.

    PubMed

    Hudson, R; Bizier, N P; Esdale, K N; Katz, J L

    2015-02-28

    The synthesis of 2-substituted indoles and benzofurans was achieved by nucleophilic aromatic substitution, followed by subsequent 5-endo-dig cyclization between the nucleophile and an ortho acetylene. The acetylene serves the dual role of the electron withdrawing group to activate the substrate for SNAr, and the C1-C2 carbon scaffold for the newly formed 5-membered heteroaromatic ring. This method allows for the bond forming sequence of Ar-X-N/O-C1 to proceed in a single synthetic step, furnishing indoles and benzofurans in moderate to high yields. Since the method is not transition metal mediated, brominated and chlorinated substrates are tolerated, and benzofuran formation can be conducted using water or water-DMSO mixtures as solvent. PMID:25608594

  9. Xe-bearing hydrocarbon ions: Observation of Xe.acetylene+rad and Xe.benzene+rad radical cations and calculations of their ground state structures

    NASA Astrophysics Data System (ADS)

    Cui, Zhong-hua; Attah, Isaac K.; Platt, Sean P.; Aziz, Saadullah G.; Kertesz, Miklos; El-Shall, M. S.

    2016-04-01

    This work reports evidence for novel types of Xe-bearing hydrocarbon radical cations. The Xe.acetylene+rad radical cation adduct is observed at nearly room temperature using the mass-selected drift cell technique. The irreversible addition of the Xe atom and the lack of back dissociation to HCCH+rad + Xe is consistent with the calculated binding energy of 0.85 eV to be contrasted with the metastable nature of the neutral Xe.acetylene adduct. The observed Xe.benzene+rad radical cation appears to be a weakly bound complex stabilized mainly by ion-induced dipole interaction consistent with a calculated binding energy in the range of 0.14-0.17 eV.

  10. Effect of Calcination Temperature on La-Modified Al2O3 Catalysts for Vapor Phase Hydrofluorination of Acetylene to Vinyl Fluoride

    NASA Astrophysics Data System (ADS)

    Bi, Qing-yuan; Lu, Ji-qing; Xing, Li-qiong; Guo, Ming; Luo, Meng-fei

    2010-02-01

    A La-modified Al2O3 catalyst was prepared with deposition-precipitation method. The effect of calcination temperature on the reactivity for vapor phase hydrofluorination of acetylene to vinyl fluoride. The catalysts calcined at different temperatures were characterized using NH3-TPD, pyridine-FTIR, X-ray diffraction, and Raman techniques. It was found that the calcination process could not only change the structure of these catalysts but also modify the amount of surface acidity on the catalysts. The catalyst calcined at 400 C exhibited the highest conversion of acetylene (94.6%) and highest selectivity to vinyl fluoride (83.4%) and lower coke deposition selectivity (0.72%). The highest activity was related to the largest amount of surface acidity on the catalyst, and the coke deposition was also related to the total amount of surface acidic sites.

  11. Synthesis of 3-iodoindoles by the Pd/Cu-catalyzed coupling of N,N-dialkyl-2-iodoanilines and terminal acetylenes, followed by electrophilic cyclization.

    PubMed

    Yue, Dawei; Yao, Tuanli; Larock, Richard C

    2006-01-01

    [reaction: see text] 3-Iodoindoles have been prepared in excellent yields by coupling terminal acetylenes with N,N-dialkyl-o-iodoanilines in the presence of a Pd/Cu catalyst, followed by an electrophilic cyclization of the resulting N,N-dialkyl-o-(1-alkynyl)anilines using I2 in CH2Cl2. Aryl-, vinylic-, alkyl-, and silyl-substituted terminal acetylenes undergo this process to produce excellent yields of 3-iodoindoles. The reactivity of the carbon-nitrogen bond cleavage during cyclization follows the following order: Me > n-Bu, Me > Ph, and cyclohexyl > Me. Subsequent palladium-catalyzed Sonogashira, Suzuki, and Heck reactions of the resulting 3-iodoindoles proceed smoothly in good yields. PMID:16388618

  12. Synthesis of 3-Iodoindoles by the Pd/Cu-Catalyzed Coupling of N,N-Dialkyl-2-iodoanilines and Terminal Acetylenes, Followed by Electrophilic Cyclization

    PubMed Central

    Yue, Dawei; Yao, Tuanli

    2008-01-01

    3-Iodoindoles have been prepared in excellent yields by coupling terminal acetylenes with N,N-dialkyl-o-iodoanilines in the presence of a Pd/Cu catalyst and subsequent electrophilic cyclization of the resulting N,N-dialkyl-o-(1-alkynyl)anilines using I2 in CH2Cl2. Aryl-, vinylic-, alkyl- and silyl-substituted terminal acetylenes undergo this process to produce excellent yields of 3-iodoindoles. The reactivity of the carbon-nitrogen bond cleavage during cyclization follows the order: Me > n-Bu, Me > Ph, and cyclohexyl > Me. Subsequent palladium-catalyzed Sonogashira, Suzuki and Heck reactions of the resulting 3-iodoindoles proceed smoothly in good yields. PMID:16388618

  13. Nitrate reduction

    SciTech Connect

    Dziewinski, J.J.; Marczak, S.

    2000-02-29

    Nitrates are reduced to nitrogen gas by contacting the nitrates with a metal to reduce the nitrates to nitrites which are then contacted with an amide to produce nitrogen and carbon dioxide or acid anions which can be released to the atmosphere. Minor amounts of metal catalysts can be useful in the reduction of the nitrates to nitrites. Metal salts which are formed can be treated electrochemically to recover the metals. Many industrial and agricultural processes result in nitrate wastes which would be harmful to the environment if released.

  14. Numerical analysis of the effect of acetylene and benzene addition to low-pressure benzene-rich flat flames on polycyclic aromatic hydrocarbon formation

    SciTech Connect

    Kunioshi, Nilson; Komori, Seisaku; Fukutani, Seishiro

    2006-10-15

    A modification of the CHEMKIN II package has been proposed for modeling addition of an arbitrary species at an arbitrary temperature to an arbitrary distance from the burner along a flat flame. The modified program was applied to the problem of addition of acetylene or benzene to different positions of a 40-Torr, {phi}=2.4 benzene/O{sub 2}/40%-N{sub 2} premixed flame to reach final equivalence ratios of {phi}=2.5 and 2.681. The results obtained showed that acetylene addition to early positions of the flame led to significant increase in pyrene production rates, but pyrene concentrations were lower in the flames with acetylene addition in both the {phi}=2.5 and 2.681 cases. Addition of benzene to the flame did not alter pyrene production rates in either the {phi}=2.5 or 2.681 cases; however, for {phi}=2.5, pyrene concentrations increased with benzene addition, while for {phi}=2.681, pyrene contents decreased in comparison to the correspondent flames with no addition. Acetylene addition led to a significant increase in pyrene production rates, but the pyrene levels dropped due to increase in the flow velocity. Pyrene production rates were not sensitive to benzene addition, but pyrene contents increased with benzene addition when the flow velocity decreased. These results show that PAH concentration changes accompanying species addition to flames should be interpreted carefully, because an increase or decrease in the content of a PAH species does not necessarily reflect an effect on its formation rate or mechanism. (author)

  15. Stereocontrolled synthesis of 1-acetylen-2,3-di-o-benzyl-tetrahydrofurans, 1,4-anhydro-arabinitol, and alpha,beta-dihydroxy-gamma-alkyl-butyrolactones.

    PubMed

    Daz, David D; Ramrez, Miguel A; Ceal, J Pedro; Saad, J Roberto; Tonn, Carlos E; Martn, Victor S

    2003-02-01

    This article describes a concise and efficient synthesis of 1-acetylen-2,3-di-O-benzyl-tetrahydrofurans from tartaric acid esters using as the key step the stereocontrolled cyclization of Co(2)(CO)(6)-complexed propargylic diols. This molecule led to enantiomerically pure 1,4-anhydro-arabinitol and alpha,beta-dihydroxy-gamma-alkyl-butyrolactones. In the latter case, the critical methylene oxidation at the oxygen vicinal position was performed by RuO(4). PMID:12520507

  16. Addition of in situ reduced amidinato-methylaluminium chloride to acetylenes.

    PubMed

    Chlupat, T; Turek, J; De Proft, F; R?i?kov, Z; R?i?ka, A

    2015-10-28

    Two ethylene-bridged methylaluminium amidinates and one aluminium amidinate containing three terminal trimethylstannyl-ethynyl groups interconnected by ?-coordinated potassium ions were prepared in situ. The re-oxidation of the ethylene-bridged compound by iodine followed by further reduction using the same activation procedure demonstrated the versatility of the approach. The reactivity of an ethylene-bridged methylaluminum amidinate towards HCl was examined to demonstrate the building block concept. DFT calculations were performed to gain insight into the mechanism of the in situ activation of diphenylacetylene. PMID:26399401

  17. CATION-π and CH-π Interactions in the Coordination and Solvation of Cu+ (ACETYLENE)n (n=1-6) Complexes Investigated via Infrared Photodissociation Spectroscopy

    NASA Astrophysics Data System (ADS)

    Brathwaite, Antonio David; Walters, Richard S.; Ward, Timothy B.; Duncan, Michael A.

    2015-06-01

    Mass-selected copper-acetylene cation complexes of the form Cu(C2H2)n+ are produced by laser ablation and studied via infrared laser photodissociation spectroscopy in the C-H stretching region (3000-3500 wn). Spectra for larger species are measured via ligand elimination, whereas argon tagging is employed to enhance dissociation yields in smaller complexes. The number of infrared active bands, their frequency positions and their relative intensities provide insight into the structure and bonding of these ions. Density functional theory calculations are carried out in support of this work. The combined data show that cation-π bonds are formed for the n=1-3 species, resulting in red-shifted C-H stretches on the acetylene ligands. Three acetylene ligands complete the coordination of the copper cation. Additional ligands (n=4-6) solvate the n=3 core by forming CH-pi bonds. Distinctive vibrational patterns are exhibited for coordinated vs. solvent ligands. Theory reproduces these results.

  18. Bioassay-directed isolation and identification of phytotoxic and fungitoxic acetylenes from Conyza canadensis.

    PubMed

    Queiroz, Sonia C N; Cantrell, Charles L; Duke, Stephen O; Wedge, David E; Nandula, Vijay K; Moraes, Rita M; Cerdeira, Antonio L

    2012-06-13

    Conyza canadensis (L.) Cronquist syn. (horseweed) is a problematic and invasive weed with reported allelopathic properties. To identify the phytotoxic constituents of the aerial parts, a systematic bioactivity-guided fractionation of the dichloromethane extract was performed. Three active enyne derivatives, (2Z,8Z)-matricaria acid methyl ester, (4Z,8Z)-matricaria lactone, and (4Z)-lachnophyllum lactone, were identified. The lactones inhibited growth of the monocot Agrostis stolonifera (bentgrass) and the dicot Lactuca sativa (lettuce) at 1 mg mL(-1), while the (2Z,8Z)-matricaria acid methyl ester was less active. In a dose-response screening of the lactones for growth inhibitory activity against Lemna paucicostata , (4Z)-lachnophyllum lactone was the most active with an IC50 of 104 ?M, while the (4Z,8Z)-matricaria lactone was less active (IC50 of 220 ?M). In a fungal direct bioautography assay, the two lactones at 10 and 100 ?g/spot inhibited growth of the plant pathogenic fungi Colletotrichum acutatum , Colletotrichum fragariae , and Colletotrichum gloeosporioides . In a dose-response screening of the lactones against six different plant pathogenic fungi, (4Z,8Z)-matricaria lactone was more active than the commercial fungicide azoxystrobin on Col. acutatum , Col. fragariae , and Col. gloeosporioides at 30 ?M and about as active as the commercial fungicide captan against Col. gloeosporioides , while (4Z)-lachnophyllum lactone was less active. PMID:22612410

  19. Assessment of plaque assay methods for alphaviruses.

    PubMed

    Juarez, Diana; Long, Kanya C; Aguilar, Patricia; Kochel, Tadeusz J; Halsey, Eric S

    2013-01-01

    Viruses from the Alphavirus genus are responsible for numerous arboviral diseases impacting human health throughout the world. Confirmation of acute alphavirus infection is based on viral isolation, identification of viral RNA, or a fourfold or greater increase in antibody titers between acute and convalescent samples. In convalescence, the specificity of antibodies to an alphavirus may be confirmed by plaque reduction neutralization test. To identify the best method for alphavirus and neutralizing antibody recognition, the standard solid method using a cell monolayer overlay with 0.4% agarose and the semisolid method using a cell suspension overlay with 0.6% carboxymethyl cellulose (CMC) overlay were evaluated. Mayaro virus, Una virus, Venezuelan equine encephalitis virus (VEEV), and Western equine encephalitis virus (WEEV) were selected to be tested by both methods. The results indicate that the solid method showed consistently greater sensitivity than the semisolid method. Also, a "semisolid-variant method" using a 0.6% CMC overlay on a cell monolayer was assayed for virus titration. This method provided the same sensitivity as the solid method for VEEV and also had greater sensitivity for WEEV titration. Modifications in plaque assay conditions affect significantly results and therefore evaluation of the performance of each new assay is needed. PMID:23085307

  20. The acetylene inhibition technique to determine total denitrification (N2 + N2O) losses from soil samples: potentials and limitations

    NASA Astrophysics Data System (ADS)

    Felber, R.; Conen, F.; Flechard, C. R.; Neftel, A.

    2012-03-01

    The loss of N2 from intensively managed agro-ecosystems is an important part of the N budget. The monitoring of N2 emissions at the field scale is impossible due to the high atmospheric background of 78%, which precludes the measurement of fluxes. The acetylene (C2H2) inhibition technique is a rather simple, albeit imperfect, method to determine N2 losses from entire soil cores. Despites serious limitations it is one among very few methodological options to estimate total denitrification at high temporal resolution and on small spatial scale, with limited workload and costs involved. A laboratory system with two different detection systems (photoacoustic IR spectroscopy and gas chromatography) is presented, which allowed parallel measurements of up to 7 intact soil cores in air-tight glass tubes in a temperature controlled cabinet (adjusted to field conditions) with an automated C2H2 injection. A survey of total denitrification losses (N2 + N2O) over 1.5 yr in soil from an intensively managed, cut grassland system in central Switzerland showed a lower bound loss in the range of 6 to 25 kg N ha-1 yr-1 (3-13% of added N), roughly 3.4 times higher than the N2O loss. However, several drawbacks of the C2H2 inhibition technique preclude a more precise determination of the total denitrification loss.

  1. In vitro platelet adhesion and activation of polyethylene terephthalate modified by acetylene plasma immersion ion implantation and deposition

    NASA Astrophysics Data System (ADS)

    Wang, J.; Chen, J. Y.; Yang, P.; Leng, Y. X.; Wan, G. J.; Sun, H.; Zhao, A. S.; Huang, N.; Chu, P. K.

    2006-01-01

    Acetylene (C2H2) plasma immersion ion implantation-deposition (PIII-D) was conducted on polyethylene terephthalate (PET) to improve its blood compatibility. The platelet adhesion and activation behavior of PET treated by C2H2 PIII-D at different working pressures was investigated. Raman spectroscopy results show that amorphous carbon films were successfully deposited on the PET surfaces. X-ray photoelectron spectroscopy (XPS) analysis indicates that carbon films of various sp2/sp3 composition are formed at different working pressures and the sp3 hybridized C content in the films increases as a function of pressure. Platelet adhesion experiments were conducted to examine the blood compatibility in vitro. Optical microscopy reveals that the amounts of adherent platelets on all modified PET films are less than that on the untreated surface. The adhered platelets on carbon films deposited at 0.5 Pa and 1.0 Pa working pressure are about 32% and 55%, respectively, of that for the untreated PET surface. The platelets are observed to be isolated and round on carbon films deposited at 0.5 Pa, indicating that fewer platelets are activated on the amorphous carbon films. These results thus shows that amorphous carbon films deposited on PET by C2H2 PIII-D suppress platelet adhesion and activation, and the extent of the improvement is related to the structure of the carbon films.

  2. Double-slit experiment with a polyatomic molecule: vibrationally resolved C 1s photoelectron spectra of acetylene

    NASA Astrophysics Data System (ADS)

    Argenti, L.; Thomas, T. D.; Plsiat, E.; Liu, X.-J.; Miron, C.; Lischke, T.; Prmper, G.; Sakai, K.; Ouchi, T.; Pttner, R.; Sekushin, V.; Tanaka, T.; Hoshino, M.; Tanaka, H.; Decleva, P.; Ueda, K.; Martn, F.

    2012-03-01

    We report the first evidence for double-slit interferences in a polyatomic molecule, which we have observed in the experimental carbon 1s photoelectron spectra of acetylene (or ethyne). The spectra have been measured over the photon energy range of 310-930 eV and show prominent oscillations in the intensity ratios ?g(?)/?u(?) for the vibrational quantum numbers ? = 0,1 and for the ratios ?s(? = 1)/?s(? = 0) for the symmetry s = g,u. The experimental findings are in very good agreement with ab initio density functional theory (DFT) calculations and are compatible with the Cohen-Fano mechanism of coherent emission from two equivalent atomic centers. This interpretation is supported by the qualitative predictions of a simple model in which the effect of nuclear recoil is taken into account to the lowest order. Our results confirm the delocalized character of the core hole created in the primary photoionization event and demonstrate that intramolecular core-hole coherence can survive the decoherent influence associated with the asymmetric nuclear degrees of freedom which are characteristic of polyatomic molecules.

  3. Time-Resolved Rotational Energy Transfer and Spectral Line Broadening in Acetylene. a High Resolution Raman Study.

    NASA Astrophysics Data System (ADS)

    Domenech, J. L.; Martinez, R. Z.; Bermejo, D.

    2010-06-01

    The quasi-cw stimulated Raman technique is a powerful tool for the determination of collisional broadening and line-mixing parameters, which bear a very direct relationship with the rotational energy transfer rate constants matrix at the state-to-state level. Indeed, the broadening coefficients and the analysis of line-mixing profiles, frequently combined with a rate-law analysis, have provided a wealth of information on collision physics for many gas systems throughout the years. We report on new high resolution measurements of the broadening coefficients on the Q-branch of the ?_2 band of acetylene. Furthermore, last year at this meeting, we reported on a new technique for the determination of state-to-state rotational energy transfer rate constants. based on a time-resolved double-resonance Raman-Raman scheme. It uses the quasi-continuous stimulated Raman-loss technique for the probe stage. Through a systematic recording of the time evolution of rotational populations from a single initially pupulated J level, it allows the direct determination of most elements of the rate-constant matrix without resorting to fitting or scaling laws. The comparison of the results obtained from from the high resolution spectroscopic approach with those from the time-resolved dynamics experiment provides insight into the collision mechanisms and some of the assumptions or simplifications usually made in rate-law analysis.

  4. A new cytotoxic brominated acetylenic hydrocarbon from the marine sponge Haliclona sp. with a selective effect against human breast cancer.

    PubMed

    Alarif, Walied M; Abdel-Lateff, Ahmed; Al-Lihaibi, Sultan S; Ayyad, Seif-Eldin N; Badria, Farid A

    2013-01-01

    Three acetylenic brominated derivatives were isolated from a Red Sea sponge, Haliclona sp. One of them, 18-bromooctadeca-9(E),17(E)-dien-7,15-diynoic acid (3), is a known metabolite, and the other two are new compounds, (1E,5E,12E,19E)-1,22-dibromodocosa-1,5,12,19-tetraen-3,14,21-triyne (1) and methyl 18-bromooctadeca-9(E),17(E)-dien-7,15-diynoate (2) which was isolated for the first time as a natural metabolite. Structures of all compounds were determined based on extensive spectroscopic measurements [1D (1H, 13C and DEPT) and 2D (HSQC, HMBC and NOESY) NMR, MS, UV, and IR]. All compounds, except 3, were evaluated for their cytotoxicity employing four cancer cell lines, i.e. MCF-7 (human breast cancer), HepG2 (human hepatocellular carcinoma), WI-38 (skin carcinoma), and Vero (African green monkey kidney). Compounds 1 and 2 had potent selective antitumour activity towards MCF-7 cells with IC50 values of 32.5 and 50.8 microM, respectively. PMID:23659175

  5. Optimization of Acetylene Black Conductive Additive andPolyvinylidene Difluoride Composition for High Power RechargeableLithium-Ion Cells

    SciTech Connect

    Liu, G.; Zheng, H.; Battaglia, V.S.; Simens, A.S.; Minor, A.M.; Song, X.

    2007-07-01

    Fundamental electrochemical methods were applied to study the effect of the acetylene black (AB) and the polyvinylidene difluoride (PVDF) polymer binder on the performance of high-power designed rechargeable lithium ion cells. A systematic study of the AB/PVDF long-range electronic conductivity at different weight ratios is performed using four-probe direct current tests and the results reported. There is a wide range of AB/PVDF ratios that satisfy the long-range electronic conductivity requirement of the lithium-ion cathode electrode; however, a significant cell power performance improvement is observed at small AB/PVDF composition ratios that are far from the long-range conductivity optimum of 1 to 1.25. Electrochemical impedance spectroscopy (EIS) tests indicate that the interfacial impedance decreases significantly with increase in binder content. The hybrid power pulse characterization results agree with the EIS tests and also show improvement for cells with a high PVDF content. The AB to PVDF composition plays a significant role in the interfacial resistance. We believe the higher binder contents lead to a more cohesive conductive carbon particle network that results in better overall all local electronic conductivity on the active material surface and hence reduced charge transfer impedance.

  6. Temperature and pressure dependence of the absolute rate constant for the reactions of NH2 radicals with acetylene and ethylene

    NASA Technical Reports Server (NTRS)

    Bosco, S. R.; Nava, D. F.; Brobst, W. D.; Stief, L. J.

    1984-01-01

    The absolute rate constants for the reaction between the NH2 free radical and acetylene and ethylene is measured experimentally using a flash photolysis technique. The constant is considered to be a function of temperature and pressure. At each temperature level of the experiment, the observed pseudo-first-order rate constants were assumed to be independent of flash intensity. The results of the experiment indicate that the bimolecular rate constant for the NH2 + C2H2 reaction increases with pressure at 373 K and 459 K but not at lower temperatures. Results near the pressure limit conform to an Arrhenius expression of 1.11 (+ or -) 0.36 x 10 to the -13th over the temperature range from 241 to 459 K. For the reaction NH2 + C2H4, a smaller rate of increase in the bimolecular rate constant was observed over the temperature range 250-465 K. The implications of these results for current theoretical models of NH2 + C2H2 (or H4) reactions in the atmospheres of Jupiter and Saturn are discussed.

  7. A gas phase complex of acetylene and bromine: geometry, binding strength and charge transfer from rotational spectroscopy

    NASA Astrophysics Data System (ADS)

    Davey, J. B.; Legon, A. C.

    2001-12-01

    Ground-state rotational spectra of a 1:1 complex of acetylene and bromine were observed with a Fourier-transform microwave spectrometer. Rotational, centrifugal distortion and Br nuclear hyperfine coupling constants were determined for the isotopomers C2H2⋯ 79Br79Br, C2H2⋯ 79Br81Br, C2H2⋯ 81Br79Br and C2H2⋯ 81Br81Br. The complex possesses a T-shaped, C2v geometry at equilibrium with a zero-point distance 3.144 Å between the centre (∗) of the CC bond and the inner bromine atom. The inter- and intra-molecular electron transfers on complex formation are δ(∗→ Bri)e=0.010e and δ(Br i→Br o) e=0.037 e, respectively, where i = inner and o = outer. The inter-molecular stretching force constant is k σ=7.80(6) N m -1.

  8. Evidence of Perturbations on the S_1 Surface of Acetylene from Patterns in Stimulated Emission Pumping Spectra

    NASA Astrophysics Data System (ADS)

    Park, G. Barratt; Baraban, Joshua H.; Steeves, Adamh.; Field, Robert W.

    2011-06-01

    Stimulated Emission Pumping (SEP) spectra from the 3^4 level of S_1 acetylene to the N_B=10 polyad of S_0 contain evidence of an unexpected interference effect. S_0 intrapolyad intensity distributions are as a rule governed solely by the fractionation of the (single) bright state. However, the intensity distribution in the SEP spectrum observed from 3^4 deviates from the expected pattern. Reduced dimension DVR calculations on the S_1 surface predict a three-state interaction involving one of the S_1 interloper bands. According to the calculation, this cis interloper state engenders an indirect coupling between the trans 2^13^16^2 and 3^4 zero order states, causing the eigenstates to lie substantially farther apart than one might expect, and lending intensity to the cis 3^16^1 interloper band that appears between them. These predictions agree quite well with the experimental observations. The intensity distribution in the SEP spectrum observed from 3^4 seems to contain an interfering combination of the bright state patterns seen in the 2^13^2 and the 3^2B^2 spectra. This type of indirect effect can yield much information about state mixing, and is particularly interesting in this case since its effects on the level structure cannot reasonably be accounted for by effective Hamiltonian models that rely solely on polyads.

  9. Analysis of the seed oil of Heisteria silvanii (Olacaceae)--a rich source of a novel C18 acetylenic fatty acid.

    PubMed

    Spitzer, V; Tomberg, W; Hartmann, R; Aichholz, R

    1997-11-01

    Besides some usual fatty acids (FA), two conjugated ene-yne acetylenic FA [trans-10-heptadecen-8-ynoic acid (pyrulic acid) (7.4%), and trans-11-octadecen-9-ynoic acid (ximenynic acid) (3.5%)], a novel ene-yne-ene acetylenic FA [cis-7, trans-11-octadecadiene-9-ynoic acid (heisteric acid) (22.6%)], and 9,10-epoxystearic acid (0.6%) could be identified in the seed oil of Heisteria silvanii (Olacaceae). Two further conjugated acetylenic FA [9,11-octadecadiynoic acid (0.1%) and 13-octadecene-9,11-diynoic acid (0.4%)] were identified tentatively by their mass spectra. The FA mixture has been analyzed by gas chromatography/mass spectrometry (GC/MS) of their methyl ester and 4,4-dimethyloxazoline derivatives. The structure of heisteric acid was elucidated after isolation via preparative silver ion thin-layer chromatography and by various spectroscopic methods [ultraviolet; infrared; 1H, 13C nuclear magnetic resonance (NMR); 1H-1H and 1H-13C correlation spectroscopy]. To determine the position of the conjugated ene-yne-ene system, the NMR spectra were also measured after addition of the lanthanide shift reagent Resolve-Al EuFOD. Furthermore, the triyglyceride mixture was analyzed by high-temperature GC and high-temperature GC coupled with negative chemical ionization MS. A glass capillary column coated with a methoxy-terminated 50%-diphenyl-50%-dimethylpolysiloxane was used for the separation of the triacylglycerol (TAG) species. No evidence of decomposition of the TAG species containing conjugated ene-yne-ene FA was observed. Twenty-six species of the separated TAG were identified by means of their abundant quasi molecular ion [M - H]- and their corresponding carboxylate anions [RCOO]- of the fatty acids, respectively. The major molecular species of the TAG were found to be 16:0/18:1/18:1, 16:0/18:1/18:3 (heisteric acid), 17:2 (pyrulic acid)/18:1/18:1, 18:1/18:1/18:3 (heisteric acid). The TAG containing acetylenic FA showed an unexpected increase of the retention time in comparison to the TAG containing usual FA, thus making the prediction of the elution order of lipid samples containing acetylenic FA difficult. PMID:9397405

  10. The comet assay: topical issues.

    PubMed

    Collins, Andrew R; Oscoz, Amaia Azqueta; Brunborg, Gunnar; Gaivo, Isabel; Giovannelli, Lisa; Kruszewski, Marcin; Smith, Catherine C; Stetina, Rudolf

    2008-05-01

    The comet assay is a versatile and sensitive method for measuring single- and double-strand breaks in DNA. The mechanism of formation of comets (under neutral or alkaline conditions) is best understood by analogy with nucleoids, in which relaxation of DNA supercoiling in a structural loop of DNA by a single DNA break releases that loop to extend into a halo-or, in the case of the comet assay, to be pulled towards the anode under the electrophoretic field. A consideration of the simple physics underlying electrophoresis leads to a better understanding of the assay. The sensitivity of the assay is only fully appreciated when it is calibrated: between one hundred and several thousand breaks per cell can be determined. By including lesion-specific enzymes in the assay, its range and sensitivity are greatly increased, but it is important to bear in mind that their specificity is not absolute. Different approaches to quantitation of the comet assay are discussed. Arguments are presented against trying to apply the comet assay to the study of apoptosis. Finally, some of the advantages and disadvantages of using the comet assay on lymphocyte samples collected in human studies are rehearsed. PMID:18283046

  11. COMPUTATIONAL MODELING AND EXPERIMENTAL STUDIES ON NOx REDUCTION UNDER PULVERIZED COAL COMBUSTION CONDITIONS

    SciTech Connect

    Subha K. Kumpaty; Kannikeswaran Subramanian; Victor P. Nokku; Tyrus L. Hodges; Adel Hassouneh; Ansumana Darboe; Sravan K. Kumpati

    1998-06-01

    In this work, both computer simulation and experimental studies were conducted to investigate several strategies for NO{sub x} reduction under pulverized coal combustion conditions with an aim to meet the stringent environmental standards for NO{sub x} control. Both computer predictions and reburning experiments yielded favorable results in terms of NO{sub x} control by reburning with a combination of methane and acetylene as well as non-selective catalytic reduction of NO{sub x} with ammonia following reburning with methane. The greatest reduction was achieved at the reburning stoichiometric ratio of 0.9; the reduction was very significant, as clearly shown in Chapters III and V. Both the experimental and computational results favored mixing gases: methane and acetylene (90% and 10% respectively) and methane and ammonia (98% and 2%) in order to get optimum reduction levels which can not be achieved by individual gases at any amounts. Also, the above gaseous compositions as reburning fuels seemed to have a larger window of stoichiometric ratio (SR2 < 0.9) as opposed to just methane (SR2=0.9) so as to reduce and keep NO{sub x} at low ppm levels. From the various computational runs, it has been observed that although there are several pathways that contribute to NO{sub x} reduction, the key pathway is NO {r_arrow} HCN {r_arrow} NH{sub 3} {r_arrow} N{sub 2} + H{sub 2}. With the trends established in this work, it is possible to scale the experimental results to real time industrial applications using computational calculations.

  12. REDUCTIVE TRANSFORMATION OF TRICHLOROETHENE CATALYZED BY COBALAMIN: REACTIVITIES OF THE INTERMEDIATES, ACETYLENE, CHLOROACETYLENE, AND THE DCE ISOMERS. (R825689C073)

    EPA Science Inventory

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  13. A Simple High-Content Cell Cycle Assay Reveals Frequent Discrepancies between Cell Number and ATP and MTS Proliferation Assays

    PubMed Central

    Chan, Grace Ka Yan; Kleinheinz, Tracy L.; Peterson, David; Moffat, John G.

    2013-01-01

    In order to efficiently characterize both antiproliferative potency and mechanism of action of small molecules targeting the cell cycle, we developed a high-throughput image-based assay to determine cell number and cell cycle phase distribution. Using this we profiled the effects of experimental and approved anti-cancer agents with a range mechanisms of action on a set of cell lines, comparing direct cell counting versus two metabolism-based cell viability/proliferation assay formats, ATP-dependent bioluminescence, MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) reduction, and a whole-well DNA-binding dye fluorescence assay. We show that, depending on compound mechanisms of action, the metabolism-based proxy assays are frequently prone to 1) significant underestimation of compound potency and efficacy, and 2) non-monotonic dose-response curves due to concentration-dependent phenotypic ‘switching’. In particular, potency and efficacy of DNA synthesis-targeting agents such as gemcitabine and etoposide could be profoundly underestimated by ATP and MTS-reduction assays. In the same image-based assay we showed that drug-induced increases in ATP content were associated with increased cell size and proportionate increases in mitochondrial content and respiratory flux concomitant with cell cycle arrest. Therefore, differences in compound mechanism of action and cell line-specific responses can yield significantly misleading results when using ATP or tetrazolium-reduction assays as a proxy for cell number when screening compounds for antiproliferative activity or profiling panels of cell lines for drug sensitivity. PMID:23691072

  14. New low-viscosity overlay medium for viral plaque assays

    PubMed Central

    Matrosovich, Mikhail; Matrosovich, Tatyana; Garten, Wolfgang; Klenk, Hans-Dieter

    2006-01-01

    Background Plaque assays in cell culture monolayers under solid or semisolid overlay media are commonly used for quantification of viruses and antiviral substances. To overcome the pitfalls of known overlays, we tested suspensions of microcrystalline cellulose Avicel RC/CL™ as overlay media in the plaque and plaque-inhibition assay of influenza viruses. Results Significantly larger plaques were formed under Avicel-containing media, as compared to agar and methylcellulose (MC) overlay media. The plaque size increased with decreasing Avicel concentration, but even very diluted Avicel overlays (0.3%) ensured formation of localized plaques. Due to their low viscosity, Avicel overlays were easier to use than methylcellulose overlays, especially in the 96-well culture plates. Furthermore, Avicel overlay could be applied without prior removal of the virus inoculum thus facilitating the assay and reducing chances of cross-contamination. Using neuraminidase inhibitor oseltamivir carboxylate, we demonstrated applicability of the Avicel-based plaque reduction assay for testing of antiviral substances. Conclusion Plaque assay under Avicel-containing overlay media is easier, faster and more sensitive than assays under agar- and methylcellulose overlays. The assay can be readily performed in a 96-well plate format and seems particularly suitable for high-throughput virus titrations, serological studies and experiments on viral drug sensitivity. It may also facilitate work with highly pathogenic agents performed under hampered conditions of bio-safety labs. PMID:16945126

  15. Multiplexing cell viability assays.

    PubMed

    Gerets, Helga H J; Dhalluin, Stéphane; Atienzar, Franck A

    2011-01-01

    Today, obtaining mechanistic insights into biological, toxicological, and pathological processes is of upmost importance. Researchers aim to obtain as many as possible data from one cell sample to understand the biological processes under study. Multiplexing, which is the ability to gather more than one set of data from the same sample, fulfills completely this objective. Obviously, multiplexing has several advantages compared to single plex experiments and probably the most important one is that data on various parameters at exactly the same time point on the same cells or group of cells can be obtained and consequently this may contribute to saving time and effort and a reduction of the costs.In this chapter, different endpoints were measured starting from two-seeded multiwell plates, namely, cell viability, caspase-3/7 activity, lactate dehydrogenase (LDH), adenosine triphosphate (ATP), aspartate aminotransferase (AST), and glutamate dehydrogenase (GLDH) measurements. These -different endpoints were analyzed together to determine the cytotoxic properties of pharmaceutical compounds and/or reference compounds. A 96-well plate was designed to allow appropriate measurement of five doses of a compound in triplicate to determine the effect of the compound on the six different endpoints. The first four endpoints (cell viability, caspase-3/7 activity, LDH, and ATP) are discussed in detail in this chapter. AST and GLDH measurements are not discussed in detail as these are fully automatic measurements and thus behind the scope of this chapter.As an illustrating example, the reference compound tamoxifen was used to evaluate its cytotoxic properties using the hepatocellular carcinoma cell line HepG2 cells. PMID:21468971

  16. Aldehyde reduction by cytochrome P450.

    PubMed

    Amunom, Immaculate; Srivastava, Sanjay; Prough, Russell A

    2011-05-01

    This protocol describes the procedure for measuring the relative rates of metabolism of the α,β-unsaturated aldehydes 9-anthracene aldehyde (9-AA) and 4-hydroxy-trans-2-nonenal (4-HNE). More specifically, these assays measure the aldehyde reduction reactions of cytochrome P450s (CYPs). They can be performed using liver microsomal or other tissue fractions, spherosome preparations of recombinant CYPs, or recombinant CYPs from other sources. The method for reduction of 9-AA (a model α,β-unsaturated aldehyde) by CYPs was adapted from an assay for 9-anthracene oxidation published by Marini et al. (2003). For reduction of the endogenous aldehyde 4-HNE, the substrate was incubated with CYP in the presence of oxygen and NADPH, and the metabolites were separated by HPLC, using an adaptation of the method by Srivastava et al. (2010). For both 9-AA and 4-HNE, the first step involves incubation of the substrate with the CYP in an appropriate medium. This is followed by quantification of metabolites through by spectrofluorometry (9-AA) or HPLC coupled with a radiometric assay (4-HNE). Metabolite identification can be achieved by HPLC GC/MS analysis. Inhibitors of cytochrome P450 can be utilized to show the role of the hemoprotein or other enzymes in these reduction reactions. The reduction of CYPs is not inhibited by either anaerobiosis or inclusion of CO in the gaseous phase of the reaction mixture. These characteristics are similar to those reported for some cytochrome P450-catalyzed azo reduction reactions. PMID:21553396

  17. The assay of diphtheria toxin

    PubMed Central

    Gerwing, Julia; Long, D. A.; Mussett, Marjorie V.

    1957-01-01

    A precise assay of diphtheria toxin is described, based on the linear relationship between the diameter of the skin reaction to, and logarithm of the dose of, toxin. It eliminates the need for preliminary titrations, is economical, provides information about the slope of the log-dose response lines and, therefore, of the validity of the assay, and yields limits of error of potency from the internal evidence of the assay. A study has been made of the effects of avidity, combining power, toxicity and buffering on the assay of diphtheria toxins against the International Standards for both Diphtheria Antitoxin and Schick-Test Toxin. All the toxins assayed against the standard toxin, whatever their other properties might be, gave log-dose response lines of similar slope provided that they were diluted in buffered physiological saline. The assays were therefore valid. These experiments were repeated concurrently in non-immune and in actively immunized guinea-pigs, and comparable figures for potency obtained in both groups. The result was not significantly affected by the avidity or combining power of the toxin. However, non-avid toxins gave low values in Schick units when assayed, by the Rmer & Sames technique, in terms of the International Standard for Diphtheria Antitoxin. The problem of the ultimate standard and the implications of these findings are discussed. PMID:13511133

  18. Comet Assay measurements: a perspective.

    PubMed

    Kumaravel, T S; Vilhar, Barbara; Faux, Stephen P; Jha, Awadhesh N

    2009-02-01

    The Comet Assay or single cell gel electrophoresis assay is one of the very widely used assays to microscopically detect DNA damage at the level of a single cell. The determination of damage is carried out either through visual scoring of cells (after classification into different categories on the basis of tail length and shape) or by using different commercially available or public domain software (which automatically recognise the extent of damage). In this assay, the shape, size and amount of DNA within the 'comet' play important roles in the determination of the level of damage. The use of a software in particular also provides a range of different parameters, many of which might not be relevant in determining the extent of DNA damage. As a large number of factors could influence the shape, size, identification and determination of induced damage, which includes the scoring criteria, staining techniques, selection of parameters (whilst using the software packages) and appearance of 'hedgehog' or 'clouds', this article aims (a) to provide an overview of evolution of measurements of DNA damage using the Comet Assay and (b) to summarise and critically analyse the advantages and disadvantages of different approaches currently being adopted whilst using this assay. It is suggested that judicious selection of different parameters, staining methods along with inter-laboratory validation and harmonisation of methodologies will further help in making this assay more robust and widely acceptable for scientific as well as regulatory studies. PMID:18040874

  19. Transporter assays and assay ontologies: useful tools for drug discovery.

    PubMed

    Zdrazil, Barbara; Chichester, Christine; Zander Balderud, Linda; Engkvist, Ola; Gaulton, Anna; Overington, John P

    2014-06-01

    Transport proteins represent an eminent class of drug targets and ADMET (absorption, distribution, metabolism, excretion, toxicity) associated genes. There exists a large number of distinct activity assays for transport proteins, depending on not only the measurement needed (e.g. transport activity, strength of ligandprotein interaction), but also due to heterogeneous assay setups used by different research groups. Efforts to systematically organize this (divergent) bioassay data have large potential impact in Public-Private partnership and conventional commercial drug discovery. In this short review, we highlight some of the frequently used high-throughput assays for transport proteins, and we discuss emerging assay ontologies and their application to this field. Focusing on human P-glycoprotein (Multidrug resistance protein 1; gene name: ABCB1, MDR1), we exemplify how annotation of bioassay data per target class could improve and add to existing ontologies, and we propose to include an additional layer of metadata supporting data fusion across different bioassays. PMID:25027375

  20. From Antenna to Assay

    PubMed Central

    Moore, Evan G.; Samuel, Amanda P. S.; Raymond, Kenneth N.

    2009-01-01

    Conspectus Ligand-sensitized, luminescent lanthanide(III) complexes are of considerable importance because their unique photophysical properties (microsecond to millisecond lifetimes, characteristic and narrow emission bands, and large Stokes shifts) make them well suited as labels in fluorescence-based bioassays. The long-lived emission of lanthanide(III) cations can be temporally resolved from scattered light and background fluorescence to vastly enhance measurement sensitivity. One challenge in this field is the design of sensitizing ligands that provide highly emissive complexes with sufficient stability and aqueous solubility for practical applications. In this Account, we give an overview of some of the general properties of the trivalent lanthanides and follow with a summary of advances made in our laboratory in the development of highly luminescent Tb(III) and Eu(III) complexes for applications in biotechnology. A focus of our research has been the optimization of these compounds as potential commercial agents for use in Homogeneous Time-Resolved Fluorescence (HTRF) technology. Our approach involves developing high-stability octadentate Tb(III) and Eu(III) complexes that rely on all-oxygen donor atoms and using multi-chromophore chelates to increase molar absorptivity; earlier examples utilized a single pendant chromophore (that is, a single antenna). Ligands based on 2-hydroxyisophthalamide (IAM) provide exceptionally emissive Tb(III) complexes with quantum yield values up to ?60% that are stable at the nanomolar concentrations required for commercial assays. Through synthetic modification of the IAM chromophore and time-dependent density functional theory (TD-DFT) calculations, we have developed a method to predict absorption and emission properties of these chromophores as a tool to guide ligand design. Additionally, we have investigated chiral IAM ligands that yield Tb(III) complexes possessing both high quantum yield values and strong circularly polarized luminescence (CPL) activity. To efficiently sensitize Eu(III) emission, we have used the 1-hydroxypyridin-2-one (1,2-HOPO) chelate to create remarkable ligands that combine excellent photophysical properties and exceptional aqueous stabilities. A more complete understanding of this chromophore has been achieved by combining low-temperature phosphorescence measurements with the same TD-DFT approach used with the IAM system. Eu(III) complexes with strong CPL activity have also been obtained with chiral 1,2-HOPO ligands. We have also undertaken the kinetic analysis of radiative and non-radiative decay pathways for a series of Eu(III) complexes; the importance of the metal ion symmetry on the ensuing photophysical properties is clear. Lastly, we describe a Tb(III)-IAM compoundnow carried through to commercial availabilitythat offers improved performance in the common HTRF platform and has the potential to vastly improve sensitivity. PMID:19323456