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1

Continuous, Automated Acetylene Reduction Assays Using Intact Plants 1  

PubMed Central

An automated method was developed for continuous, in situ determination of acetylene reduction (N2 fixation) by intact soybean plants (Glycine max [L.]). The culture vessel containing the roots of intact plants grown in sand culture is sealed at the surface and an air-acetylene mixture continuously injected into the root chamber. The effluent gas is automatically sampled and injected into a gas chromatograph. Continuous acetylene assay at intervals as short as 3.5 min may be made over a period of several days, without attention, except for plant watering. Adverse effects of prolonged exposure of the root system to acetylene were mitigated by pulse injection of acetylene for 20 min followed by 40 min of acetylene-free air. Bare root systems can be suspended in a reaction chamber and sprayed with water or nutrient solution; this permits periodic removal of the root system for sampling nodules. In studies lasting several diurnal cycles, acetylene reduction did not decline more than 50% of the maximum rate in light, thus nitrogenase activity depends on concomitant photosynthesis and on carbohydrate from storage pools.

Mederski, Henry J.; Streeter, John G.

1977-01-01

2

Acetylene Reduction Assays for Nitrogen Fixation Freshwaters: a Note of Caution  

PubMed Central

Lake water samples were observed to transform [14C]ethylene into water-soluble compounds that were undetectable by conventional acetylene reduction assay procedures. Methane oxidizing bacteria, which are known to be common in freshwaters, appeared to be responsible for this activity. As much as 28% of added ethylene has been observed to be transformed and this figure is probably an underestimate. It is suggested that acetylene reduction assays may not be accurately applied to samples containing methane oxidizing bacteria. Images

Flett, R. J.; Rudd, J. W. M.; Hamilton, R. D.

1975-01-01

3

The Azolla, Anabaena azollae Relationship: II. Localization of Nitrogenase Activity as Assayed by Acetylene Reduction.  

PubMed

Anaerobic (microaerophilic) acetylene reduction by Azolla caroliniana Willd. was dependent on light and saturated at approximately 450 foot candles. Maximum rates of acetylene reduction were 60 nmoles/mg chlorophyll minute. However, rates of 25 to 30 nmoles/mg chlorophyll minute were more common.The growth of Azolla for 35 days with nitrate or urea as a nitrogen source decreased the rate of acetylene reduction approximately 30% compared to controls grown on nitrogen. Prolonged growth on nitrate or urea (6-7 months) resulted in a 90% decrease in the rate of acetylene reduction.The inhibition of acetylene reduction by 3 (3,4-dichlorophenol) 1,1-dimethylurea (12 muM) was not pronounced until the Azolla became depleted of the reserves formed during photosynthesis. The interval required for this depletion was dependent upon pretreatment and varied from 2 to more than 12 hours. Oxygen evolution was inhibited 75% in 10 minutes by the same concentration of 3 (3,4-dichlorophenol) 1,1-dimethylurea.The addition of oxygen, 20% volume per volume, resulted in a 30 to 40% decrease in the rate of acetylene reduction and the onsetof 3(3,4-dichlorophenol) 1,1-dimethylurea inhibition was more rapid then under microaerophilic conditions. The aerobic dark reduction of acetylene was from 10 to 30% of the rate of aerobic reduction in the light.Acetylene reduction activity was absent in fronds freed ofthe symbiotic algae and present in isolated Anabaena azollae. This study shows that the alga is the agent of acetylene reduction and suggests that there is considerable transport of metabolites between the fern and the blue-green alga. PMID:16658797

Peters, G A; Mayne, B C

1974-06-01

4

Effects of nodular extracts of Alnus glutinosa (L.) Gaertn. on nitrogen fixation (Acetylene reduction assay) and denitrification in different soils  

Microsoft Academic Search

European alder (Alnus glutinosa (L.) Gaertn) nodules were maintained under conditions that allow their exudation (water stress). The effect of this nodular extracts colected on free nitrogen fixation (acetylene reduction assay (ARA)) and denitrification, was evaluated in three soils of significatively different physico-chemical characteristics. The comparisons with controls having different concentrations of glucose as carbon source suggest that, in the

F. J. Gutiérrez Mañero; J. M. Pozuelo González; J. A. Lucas; A. Probanza

5

Nitrogen fixation (acetylene reduction) associated with duckweed (lemnaceae) mats.  

PubMed

Duckweed (Lemnaceae) mats in Texas and Florida were investigated, using the acetylene reduction assay, to determine whether nitrogen fixation occurred in these floating aquatic macrophyte communities. N(2)-fixing microorganisms were enumerated by plating or most-probable-number techniques, using appropriate N-free media. Results of the investigations indicated that substantial N(2)-fixation (C(2)H(2)) was associated with duckweed mats in Texas and Florida. Acetylene reduction values ranged from 1 to 18 mumol of C(2)H(4) g (dry weight) day for samples incubated aerobically in light. Dark N(2) fixation was always two- to fivefold lower. 3-(3,4-Dichlorophenyl)-1,1-dimethylurea (7 to 10 muM) reduced acetylene reduction to levels intermediate between light and dark incubation. Acetylene reduction was generally greatest for samples incubated anaerobically in the light. It was estimated that 15 to 20% of the N requirement of the duckweed could be supplied through biological nitrogen fixation. N(2)-fixing heterotrophic bacteria (10 cells g [wet weight] and cyanobacteria (10 propagules g [wet weight] were associated with the duckweed mats. Azotobacter sp. was not detected in these investigations. One diazotrophic isolate was classified as Klebsiella. PMID:16345992

Zuberer, D A

1982-04-01

6

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)

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.

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

2013-04-01

7

Nitrogen fixation (acetylene reduction) on a coral reef  

Microsoft Academic Search

Nitrogen fixation rates associated with various substrates on a fringing reef at Eilat, Red Sea, were estimated by in situ acetylene reduction. High rates of acctylene reduction were associated with bare substrates, such as sand and dead coral skeletons. Low rates of acetylene reduction were associated with substrates covered by macroalgae or living coral tissue. Estimates of nitrogen fixation in

N. Shashar; T. Feldstein; Y. Cohen; Y. Loya

1994-01-01

8

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

SciTech Connect

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.

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

1985-08-01

9

Blockage by acetylene of nitrous oxide reduction in Pseudomonas perfectomarinus.  

PubMed Central

Suspensions of denitrifying cells of Pseudomonas perfectomarinus reduced nitrate and nitrate as expected to dinitrogen; but, in the presence of acetylene, nitrous oxide accumulated when nitrate or nitrate was reduced. When supplied at the outset in place of nitrate and nitrate, nitrous oxide was rapidly reduced to dinitrogen by cells incubated in anaerobic vessels in the absence of acetylene. In the presence of 0.01 atmospheres of acetylene, however, nitrous oxide was not reduced. Ethylene was not produced, nor did it influence the rate of nitrous oxide reduction when provided instead of acetylene. Cells exposed to 0.01 atmospheres of acetylene for as long as 400 min were able to reduce nitrous oxide after removal of acetylene at a rate comparable to that of cells not exposed to acetylene. Acetylene did not affect the production or functioning of assimilatory nitrate or nitrite reductase in axenic cultures of Enterobacter aerogenes or Trichoderma uride. While exposed to acetylene, bacteria in marine sediment slurries produced measurable quantities of nitrous oxide from glucose- or acetate-dependent reduction of added nitrate. Possible use of acetylene blockage for measurement of denitrification in unamended marine sediments is discussed.

Balderston, W L; Sherr, B; Payne, W J

1976-01-01

10

Aerobic nitrogenase activity measured as acetylene reduction in the marine non-heterocystous cyanobacterium Trichodesmium spp. grown under artificial conditions  

Microsoft Academic Search

Aerobic nitrogenase activity in the marine non-heterocystous cyanobacterium Trichodesmium spp. NIBB 1067, isolated off the Izu Peninsula, Japan in 1983 and grown under artificial conditions, was assayed by the acetylene reduction method. This strain exhibited acetylene reduction activity under aerobic conditions when cells had been grown in the medium free of combined nitrogen. Activity was markedly enhanced by light, and

K. Ohki; Y. Fujita

1988-01-01

11

Comparison of N2 Fixation and Yields in Cajanus cajan between Hydrogenase-Positive and Hydrogenase-Negative Rhizobia by In Situ Acetylene Reduction Assays and Direct 15N Partitioning 1  

PubMed Central

Pigeon peas [Cajanus cajan (L.) Millsp.] were grown in soil columns containing 15N-enriched organic matter. Seasonal N2 fixation activity was determined by periodically assaying plants for reduction of C2H2. N2 fixation rose sharply from the first assay period at 51 days after planting to a peak of activity between floral initiation and fruit set. N2 fixation (acetylene reduction) activity dropped concomitantly with pod maturation but recovered after pod harvests. Analysis of 15N content of plant shoots revealed that approximately 91 to 94% of plant N was derived from N2 fixation. The effect of inoculation with hydrogenase-positive and hydrogenase-negative rhizobia was examined. Pigeon peas inoculated with strain P132 (hydrogenase-positive) yielded significantly more total shoot N than other inoculated or uninoculated treatments. However, two other hydrogenase-positive strains did not yield significantly more total shoot N than a hydrogenase-negative strain. The extent of nodulation by inoculum strains compared to indigenous rhizobia was determined by typing nodules according to intrinsic antibiotic resistance of the inoculum strains. The inoculum strains were detected in almost all typed nodules of inoculated plants. Gas samples were taken from soil columns several times during the growth cycle of the plants. H2 was never detected, even in columns containing pigeon peas inoculated with hydrogenase-negative rhizobia. This was attributed to H2 consumption by soil bacteria. Estimation of N2 fixation by acetylene reduction activity was closest to the direct 15N method when ethylene concentrations in the gas headspace (between the column lid and soil surface) were extrapolated to include the soil pore space as opposed solely to measurement in the headspace. There was an 8-fold difference between the two acetylene reduction assay methods of estimation. Based on a planting density of 15,000 plants per hectare, the direct 15N fixation rates ranged from 67 (noninoculated) to 134 kilograms per hectare, while grain yields ranged from 540 to 825 kilograms per hectare. Grain yields were not increased with N fertilizer.

La Favre, Jeffrey S.; Focht, Dennis D.

1983-01-01

12

Acetylene Reduction Activity in Free-Living Cultures of Rhizobia  

Microsoft Academic Search

A survey of 272 free-living rhizobia strains showed that a majority of the Rhizobium japonicum and unclassified Rhizobium isolates are capable of both growth and acetylene reduction on a Casamino Acids-minimal medium. Two other taxonomic categories of Rhizobium were discernible: R. meliloti and R. trifolii, which grow but do not reduce acetylene; and R. leguminosarum, which fails to grow on

T. KANESHIRO; C. D. CROWELL; R. F. HANRAHAN

13

Acetylene reduction (dinitrogen fixation) by clinical isolates of Klebsiella pneumoniae.  

PubMed Central

Freshly isolated clinical strains of Klebsiella were tested for the ability to fix dinitrogen by the acetylene reduction assay. Ability to detect this trait was markedly affected by cultural conditions. When the test was run at 37 degrees C in the presence of yeast extract (50 mg/liter), only 1.6% of the organisms were diazotrophs, whereas this temperature without yeast extract yielded 12.9% positive cultures. The optimum condition found was 28 degrees C without yeast extract (21.9% positive); therefore, search for diazotrophy in clinical strains should not be conducted at the usual incubation temperature. There was a high incidence of indole-positive strains among diazotrophs. No such correlation was noted with any other biochemical trait or antibiotic susceptibility tested. The significance of this correlation is not apparent.

Chambers, C A; Silver, W S

1977-01-01

14

Effects of endomycorrhizas and phosphorus fertiliser on nodulation and acetylene reduction activity of white clover seedlings  

Microsoft Academic Search

Inoculation of white clover (Trifolium repens L.) with the mycorrhizal fungus Glomus tenuis (in the presence of Rhizobium trifolii) had no effect on nodule initiation over a wide range of soil phosphate levels. Acetylene reduction assays of seedlings 21–60-days-old showed that nitrogenase activity per unit plant phosphorus was the same in mycorrhizal and non-mycorrhizal seedlings. The results show that endomycorrhizal

J. R. Crush

1982-01-01

15

Acetylene reduction (nitrogen fixation) associated with corn inoculated with Spirillum.  

PubMed Central

Sorghum and corn breeding lines were grown in soil in field and greenhouse experiments with and without an inoculum of N2-fixing in Spirillum strains from Brazil. Estimated rates of N2 fixation associated with field-grown corn and sorghum plants were less than 4 g of N2/ha per day. The mean estimated N2-fixation rates determined on segments of roots from corn inoculated with Spirillum and grown in the greenhouse at 24 to 27 degrees C were 15 g of N2/ha per day (16 inbreds), 25 g of N2/ha per day (six hybrids), and 165 g of N2/ha per day for one hybird which was heavily inoculated. The corresponding mean rates determined from measurements of in situ cultures of the same series of corn plants (i.e., 16 inbreds, six hybrids, and one heavily inoculated hybrid) were 0.4, 2.3, and 1.1 g of N2/ha per day, respectively. Lower rates of C2H2 reduction were associated with control corn cultures which had been treated with autoclaved Spirillum than with cultures inoculated with live Spirillum. No C2H2 reduction was detected in plant cultures treated with ammonium nitrate. Numbers of nitrogen-fixing bacteria on excised roots of corn plants increased an average of about 30-fold during an overnight preincubation period, and as a result acetylene reduction assays of root samples after preincubation failed to serve as a valid basis for estimating N2 fixation by corn in pot cultures. Plants grown without added nitrogen either with or without inoculum exhibited severe symptoms of nitrogen deficiency and in most cases produced significantly less dry weight than those supplied with fixed nitrogen. Although substantial rates of C2H2 reduction by excised corn roots were observed after preincubation under limited oxygen, the yield and nitrogen content of inoculated plants and the C2H2-reduction rates by inoculated pot cultures of corn, in situ, provided no evidence of appreciable N2 fixation.

Barber, L E; Tjepkema, J D; Russell, S A; Evans, H J

1976-01-01

16

Physiological Ecology of Acetylene Reduction (Nitrogen Fixation) in a Delaware Salt Marsh.  

National Technical Information Service (NTIS)

The effects of several fixed nitrogen compounds on acetylene reduction activity (nitrogen fixation) of surface sediments from a Delaware salt marsh were studied. Ammonia addition caused little decrease in activity early in the summer but resulted in a con...

H. J. Dicker D. W. Smith

1980-01-01

17

Nitrogen-fixation associated with the marine blue-green alga, Trichodesmium , as measured by the acetylene-reduction technique  

Microsoft Academic Search

The marine blue-green alga, Trichodesmium, was collected from the Gulf Stream, near Miami, and occurred in two distinct colonial forms both of which reduced acetylene to ethylene. Trichodesmium was more abundant during the summer but its acetylene-reducing potential showed no obvious seasonal variation. Illuminated Trichodesmium reduced acetylene to ethylene equally well either anaerobically or aerobically (20% oxygen). Acetylene-reduction in the

Barrie F. Taylor; Chun C. Lee; John S. Bunt

1973-01-01

18

Effect of moisture on acetylene reduction (symbiotic nitrogen fixation) by Rhizobium japonicum and soybean root nodules in silica sand  

Microsoft Academic Search

The effect of water stress on acetylene reduction (symbiotic nitrogen fixation) by Rhizobium japonicum and soybean plants grown in silica sand was evaluated. Optimum water contents for acetylene reduction (nitrogen fixation) by the nitrogenase of the soybean root nodules were 60 to 80% of the moisture holding capacity of the sand.

C. M. Tu; G. Hietkamp

1977-01-01

19

A simple method for measuring acetylene reduction of intact, nodulated black locust seedlings.  

PubMed

A simple method is described for measuring acetylene (C(2)H(2)) reduction of nodulated black locust (Robinia pseudoacacia L.) seedlings. The C(2)H(2) reduction chamber consists of a standard plant pot sealed at one end with a stopper having holes for the seedling and a gas inlet port, and sealed at the other end with a stoppered collar with a gas port. The chamber temperature is regulated by circulating water at a controlled temperature through a copper coil surrounding the plant pot. A pump recirculates an approximately ten percent C(2)H(2) atmosphere through the system. Nine-week-old black locust seedlings, grown in sand culture and inoculated with Rhizobium, were used to obtain ethylene (C(2)H(4)) production curves. Ethylene production was linear for up to 60 minutes indicating that, for this particular symbiosis, (1) a simple closed system is adequate and (2) a short duration assay (10 minutes) will reliably estimate C(2)H(2) reduction over a longer period (up to at least 60 minutes). The water content of the soil medium had no influence on the C(2)H(2)/(C(2)H(2) + C(2)H(4)) ratio, which supports the suitability of C(2)H(2) as an internal standard for calculating C(2)H(2) reduction. This system has several desirable features. First, plant disturbance is minimized. Second, plants can be grown in inexpensive pots and no transplanting is necessary. Third, gas exchange and mixing are facilitated by a recirculating pump. Finally, root and nodule temperature can be controlled. PMID:14972842

Johnsen, K H; Apsley, D K

1991-12-01

20

The vanadium nitrogenase of Azotobacter chroococcum. Reduction of acetylene and ethylene to ethane.  

PubMed Central

1. The vanadium (V-) nitrogenase of Azobacter chroococcum transfers up to 7.4% of the electrons used in acetylene (C2H2) reduction for the formation of ethane (C2H6). The apparent Km for C2H2 (6 kPa) is the same for either ethylene (C2H4) or ethane (C2H6) formation and much higher than the reported Km values for C2H2 reduction to C2H4 by molybdenum (Mo-) nitrogenases. Reduction of C2H2 in 2H2O yields predominantly [cis-2H2]ethylene. 2. The ratio of electron flux yielding C2H6 to that yielding C2H4 (the C2H6/C2H4 ratio) is increased by raising the ratio of Fe protein to VFe protein and by increasing the assay temperature up to at least 40 degrees C. pH values above 7.5 decrease the C2H6/C2H4 ratio. 3. C2H4 and C2H6 formation from C2H2 by V-nitrogenase are not inhibited by H2. CO inhibits both processes much less strongly than it inhibits C2H4 formation from C2H2 with Mo-nitrogenase. 4. Although V-nitrogenase also catalyses the slow CO-sensitive reduction of C2H4 to C2H6, free C2H4 is not an intermediate in C2H6 formation from C2H2. 5. Propyne (CH3C identical to CH) is not reduced by the V-nitrogenase. 6. Some implications of these results for the mechanism of C2H6 formation by the V-nitrogenase are discussed.

Dilworth, M J; Eady, R R; Eldridge, M E

1988-01-01

21

Nitrogen fixation (acetylene reduction) in the phyllosphere of Thalassia testudinum  

Microsoft Academic Search

N2 fixation (C2H2 reduction) associated with the leaves of the sea grass Thalassia testudinum was investigated at 5 sites in South Florida (Biscayne Bay) and one site in the Bahamas (Bimini Harbor). Significant activities were correlated with the occurrence of a heterocystous blue-green alga (Calothrix sp.) on the leaves. C2H2 reduction was not stimulated by organic compounds, either aerobically or

D. G. Capone; B. F. Taylor

1977-01-01

22

High rates of nitrogen fixation (acetylene reduction) on coral skeletons following bleaching mortality  

NASA Astrophysics Data System (ADS)

Nubbins of the coral Acropora aspera were artificially bleached and nitrogen fixation (acetylene reduction) rates were measured on the developing epilithic communities. Seasonal comparisons were made between corals that died in summer of heat stress and corals that died in winter from natural cold stress. Rates of acetylene reduction from artificially bleached corals peaked at 26.66 nmol cm-2 h-1 2 weeks after summer mortality, while rates from natural winter mortality peaked at 18.07 nmol cm-2 h-1 12 days after coral death. Comparative rates of acetylene reduction taken from live corals and coral rubble ranged between 0.56 and 1.16 nmol cm-2 h-1, and 0.15 and 12.77 nmol cm-2 h-1, respectively. N2-fixation rates from dead corals were up to 30 times greater than those measured on live corals. The observed increase in N2-fixation from dead corals may increase the availability of nitrogen for use in trophic processes within the reef for an extended period following the initial mortality event. If the spatial scale over which coral mortality has occurred in past thermal bleaching events is considered the ramifications of such an increase may be substantial.

Davey, M.; Holmes, G.; Johnstone, R.

2008-03-01

23

High rate of N2 fixation by East Siberian cryophilic soil bacteria as determined by measuring acetylene reduction in nitrogen-poor medium solidified with gellan gum.  

PubMed

For evaluating N(2) fixation of diazotrophic bacteria, nitrogen-poor liquid media supplemented with at least 0.5% sugar and 0.2% agar are widely used for acetylene reduction assays. In such a soft gel medium, however, many N(2)-fixing soil bacteria generally show only trace acetylene reduction activity. Here, we report that use of a N(2) fixation medium solidified with gellan gum instead of agar promoted growth of some gellan-preferring soil bacteria. In a soft gel medium solidified with 0.3% gellan gum under appropriate culture conditions, bacterial microbiota from boreal forest bed soils and some free-living N(2)-fixing soil bacteria isolated from the microbiota exhibited 10- to 200-fold-higher acetylene reduction than those cultured in 0.2% agar medium. To determine the N(2) fixation-activating mechanism of gellan gum medium, qualitative differences in the colony-forming bacterial components from tested soil microbiota were investigated in plate cultures solidified with either agar or gellan gum for use with modified Winogradsky's medium. On 1.5% agar plates, apparently cryophilic bacterial microbiota showed strictly distinguishable microbiota according to the depth of soil in samples from an eastern Siberian Taiga forest bed. Some pure cultures of proteobacteria, such as Pseudomonas fluorescens and Burkholderia xenovorans, showed remarkable acetylene reduction. On plates solidified with 1.0% gellan gum, some soil bacteria, including Luteibacter sp., Janthinobacterium sp., Paenibacillus sp., and Arthrobacter sp., uniquely grew that had not grown in the presence of the same inoculants on agar plates. In contrast, Pseudomonas spp. and Burkholderia spp. were apparent only as minor colonies on the gellan gum plates. Moreover, only gellan gum plates allowed some bacteria, particularly those isolated from the shallow organic soil layer, to actively swarm. In consequence, gellan gum is a useful gel matrix to bring out growth potential capabilities of many soil diazotrophs and their consortia in communities of soil bacteria. PMID:19286791

Hara, Shintaro; Hashidoko, Yasuyuki; Desyatkin, Roman V; Hatano, Ryusuke; Tahara, Satoshi

2009-05-01

24

The Relationship between H2 Evolution and Acetylene Reduction in Pisum sativum-Rhizobium leguminosarum Symbioses Differing in Uptake Hydrogenase Activity 1  

PubMed Central

Peas (Pisum sativum L.) were inoculated with strains of Rhizobium leguminosarum having different levels of uptake hydrogenase (Hup) activity and were grown in sterile Leonard jars under controlled conditions. Rates of H2 evolution and acetylene reduction were determined for intact nodulated roots at intervals after the onset of darkness or after removal of the shoots. Hup activity was estimated using treatment plants or equivalent plants from the growth chamber, by measuring the uptake of H2 or 3H2 in the presence of acetylene. In all cases, the rate of H2 evolution was a continuous function of the rate of acetylene reduction. In symbioses with no demonstrable Hup activity, H2 evolution increased in direct proportion to acetylene reduction and the slopes were similar with the Hup? strains NA502 and 128C79. Hup activity was similar in strains 128C30 and 128C52 but significantly lower in strain 128C54. With these strains, the slopes of the H2 evolution versus acetylene reduction curves initially increased with acetylene reduction, but became constant and similar to those for the Hup? strains at high rates of acetylene reduction. On these parallel portions of the curves, the decreases in H2 evolution by Hup+ strains were similar in magnitude to their H2-saturated rates of Hup activity. The curvilinear relationship between H2 evolution and acetylene reduction for a representative Hup+ strain (128C52) was the same, regardless of the experimental conditions used to vary the nitrogenase activity.

Mahon, John D.; Nelson, Louise M.

1986-01-01

25

Effect of ammonium nitrate on nodulation and nitrogen fixation (acetylene reduction) of the tropical legume Sesbania rostrata  

Microsoft Academic Search

The effect of ammonium nitrate on nodulation and nitrogen fixation (acetylene reduction activity) was investigated usingSesbania rostrata, a tropical legume with the ability to nodulate both roots and stems. Plants were grown in plastic pots on silica sand and gravel, inoculated one month after sowing and then continuously irrigated with an automatic irrigation system. Four nitrogen treatments were applied: 0,

A. Moudiongui; G. Rinaudo

1987-01-01

26

Nitrogen fixation (acetylene reduction) associated with communities of heterocystous and non-heterocystous blue-green algae in mangrove forests of Sinai  

Microsoft Academic Search

High rates of nitrogen fixation (acetylene reduction) are associated with communities of heterocystous and non-heterocystous blue-green algae, which are widespread and abundant in the coastal mangrove forests of the Sinai Peninsula.

M. Potts; Heinz Steinitz

1979-01-01

27

Reduction of nitric oxide by acetylene on Ir surfaces with different morphologies: comparison with reduction of NO by CO.  

PubMed

Reduction of nitric oxide (NO) by acetylene (C(2)H(2)) has been investigated by temperature-programmed desorption (TPD) on planar Ir(210) and faceted Ir(210) with tunable sizes of three-sided nanopyramids exposing (311), (311[overline]), and (110) faces. Upon adsorption, C(2)H(2) dissociates to form acetylide (CCH) and H species on the Ir surfaces at low C(2)H(2) precoverage. For adsorption of NO on C(2)H(2)-covered Ir, both planar and faceted Ir(210) exhibit high reactivity for reduction of NO with high selectivity to N(2) at low C(2)H(2) precoverage, although the reaction is completely inhibited at high C(2)H(2) precoverage. Coadsorbed C(2)H(2) significantly influences dissociation of NO. The N-, H-, and C-containing TPD products are dominated by N(2), H(2), CO, and CO(2) together with small amounts of H(2)O. For adsorption of NO on C-covered Ir(210) at fractional C precoverage, formation of CO(2) is promoted while production of CO is reduced. Reduction of NO by C(2)H(2) is structure sensitive on faceted Ir(210) versus planar Ir(210), but no evidence is found for size effects in the reduction of NO by C(2)H(2) on faceted Ir(210) for average facet sizes of 5 nm and 14 nm. The results are compared with reduction of NO by CO on the same Ir surfaces. As for NO+C(2)H(2), the Ir surfaces are very active for reduction of NO by CO with high selectivity to N(2) and the reaction is structure sensitive, but clear evidence is found for size effects in the reduction of NO by CO on the nanometer scale. Furthermore, coadsorbed CO does not affect dissociation of NO at low CO precoverage whereas coadsorbed CO considerably influences dissociation of NO at high CO precoverage. The adsorption sites of CCH+H on Ir are characterized by density functional theory. PMID:23273167

Chen, Wenhua; Shen, Quantong; Bartynski, Robert A; Kaghazchi, Payam; Jacob, Timo

2013-01-29

28

Relationship between Ureide N and N2 Fixation, Aboveground N Accumulation, Acetylene Reduction, and Nodule Mass in Greenhouse and Field Studies with Glycine max L. (Merr) 1  

PubMed Central

The relationship between ureide N and N2 fixation was evaluated in greenhouse-grown soybean (Glycine max L. Merr.) and lima bean (Phaseolus lunatus L.) and in field studies with soybean. In the greenhouse, plant N accumulation from N2 fixation in soybean and lima bean correlated with ureide N. In soybean, N2 fixation, ureide N, acetylene reduction, and nodule mass were correlated when N2 fixation was inhibited by applying KNO3 solutions to the plants. The ureide-N concentrations of different plant tissues and of total plant ureide N varied according to the effectiveness of the strain of Bradyrhizobium japonicum used to inoculate plants. The ureide-N concentrations in the different plant tissues correlated with N2 fixation. Ureide N determinations in field studies with soybean correlated with N2 fixation, aboveground N accumulation, nodule weight, and acetylene reduction. N2 fixation was estimated by 15N isotope dilution with nine and ten soybean genotypes in 1979 and 1980, respectively, at the V9, R2, and R5 growth stages. In 1981, we investigated the relationship between ureide N, aboveground N accumulation, acetylene reduction, and nodule mass using four soybean genotypes harvested at the V4, V6, R2, R4, R5, and R6 growth stages. Ureide N concentrations of young stem tissues or plants or aboveground ureide N content of the four soybean genotypes varied throughout growth correlating with acetylene reduction, nodule mass, and aboveground N accumulation. The ureide-N concentrations of young stem tissues or plants or aboveground ureide-N content in three soybean genotypes varied across inoculation treatments of 14 and 13 strains of Bradyrhizobium japonicum in 1981 and 1982, respectively, and correlated with nodule mass and acetylene reduction. In the greenhouse, results correlating nodule mass with N2 fixation and ureide N across strains were variable. Acetylene reduction in soybean across host-strain combinations did not correlate with N2 fixation and ureide N. N2 fixation, ureide N, acetylene reduction, and nodule mass correlated across inoculation treatments with strains of Bradyrhizobium spp. varying in effectiveness on lima beans. Our data indicate that ureide-N determinations may be used as an additional method to acetylene reduction in studies of the physiology of N2 fixation in soybean. Ureide-N measurements also may be useful to rank strains of B. japonicum for effectiveness of N2 fixation.

van Berkum, Peter; Sloger, Charles; Weber, Deane F.; Cregan, Perry B.; Keyser, Harold H.

1985-01-01

29

Acetylene Reduction (Nitrogen Fixation) by Pulp and Paper Mill Effluents and by Klebsiella Isolated from Effluents and Environmental Situations  

PubMed Central

High rates of acetylene (C2H2) reduction (nitrogenase activity) were observed in woodroom effluent from a neutral sulfite semi-chemical mill under aerobic (up to 644 nmol of C2H4 produced per ml per h) and under anaerobic (up to 135 nmol of C2H4 produced per ml per h) conditions. Pasteurized effluent developed C2H2 reduction activity when incubated under anaerobic but not under aerobic conditions. Activities were increased by addition of 0.5 to 3.0% glucose or xylose. Enrichment and enumeration studies showed that N2-fixing Azotobacter and Klebsiella were abundant, and N2-fixing Bacillus was present. Of 129 isolates of Klebsiella from pulp mills, lakes, rivers, and drainage and sewage systems, 32% possessed nitrogen-fixing ability.

Knowles, R.; Neufeld, R.; Simpson, S.

1974-01-01

30

Short-term influence of nitrate on acetylene reduction, photosynthesis and nodule respiration of black alder seedlings  

SciTech Connect

Black alder (Alnus glutinosa L. Gaernt.) has shown significant benefits in several silvicultural applications such as nurse-trees. However, little is known concerning the nitrate/N-fixing interactions. Our objections were to examine the effects of three nitrate levels on acetylene reduction (AR), net photosynthesis (Ps) and nodule respiration (NR). Fifteen month-old black alder rooted cuttings were inoculated with one strain of Frankia inoculum (ARgN22D) at six months, maintained under 16h photoperiod at ambient greenhouse conditions, and fertilized for two months prior to study with a modified Crone's N-free solution. At study initiation seedlings were fertilized for six days with 0, 7.5 or 15 mM NO{sub 3}{sup {minus}}. Measurements of AR, Ps and NR were collected on the second, fourth and sixth day of NO{sub 3}{sup {minus}} application. By day four AR was significantly lowered by 75% for the 15 mM NO{sub 3}{sup {minus}} treatment when compared with the controls. On day six, Ps and NR were lowered significantly by 29% and 59%, respectively, for the 15 mM NO{sub 3}{sup {minus}} treatments when compared to control values. Results suggest any benefit from black alder N-fixation might be negated by nitrate fertilization.

Cazell, B.H.; Samuelson, L.J.; Seiler, J.R. (Virginia Polytechnic Institute State Univ., Blacksburg (USA))

1990-05-01

31

Synthesis of Carbon Fiber by Acetylene Polymerization on Nanostructured Cuprous Oxide Prepared by Hydrothermal-Reductions  

Microsoft Academic Search

Carbon nanofibers (CNFs) were prepared by chemical vapor deposition with Cu2O nanoparticles as a catalyst and were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and infrared absorption spectrum (IR). Effects of hydrogen reduction, acid treatment and growth temperature on component and structures of CNFs were studied. According to the IR analysis, both ?C?C? conjugated bonds and ?CH3, ?CH2?

Cong Zhang; Fanglin Du; Feng Xie

2012-01-01

32

Azolla-Anabaena azollae Relationship: V. N(2) Fixation, Acetylene Reduction, and H(2) Production.  

PubMed

In order to characterize the reactions catalyzed by nitrogenase in the Azolla-Anabaena association, (15)N(2) fixation, C(2)H(2) reduction, and ATP-dependent H(2) production were measured in both the Azolla-Anabaena complex and in the alga isolated from the complex.The rate of reduction of substrates and of ATP-dependent H(2) evolution was determined at various partial pressures of C(2)H(2) and N(2). A pC(2)H(2) of 0.1 atm was nearly optimal for C(2)H(4) production and inhibited H(2) production by 95%. The ratio of C(2)H(2) reduced to N(2) fixed was determined as a function of constant pC(2)H(2) (0.1 atm) and variable pN(2). This ratio decreased with increasing pN(2) and the decrease was correlated with less H(2) production. Ratios obtained at N(2) partial pressures of approximately 0.3, 0.6, and 0.8 atm, respectively, were 3.2, 2.0, and 1.7 for the association and 4.4, 3.0, and 2.5 for the isolated symbiont. Rates obtained for C(2)H(2) reduction, N(2) fixation, and H(2) production were used to obtain an expression of the electron balance in vivo. PMID:16659984

Peters, G A; Toia, R E; Lough, S M

1977-06-01

33

Independency of Fe ions in hemoglobin on immunomagnetic reduction assay  

NASA Astrophysics Data System (ADS)

Immunomagnetic reduction (IMR), which involves measuring the reduction in the ac magnetic susceptibility of magnetic reagents, is due to the association between bio-functionalized magnetic nanoparticles and target bio-molecules. This has been demonstrated for assaying proteins in solutions free of Fe ions, such as serum. In this work, the validity of IMR assay for samples rich in Fe ions like hemoglobin (Hb) is investigated. According to the results, there is no magnetic signal contributed by Fe-ion-rich Hb. Furthermore, the results show a high sensitivity in assaying hemoglobin A1c (HbA1c) by using IMR.

Yang, S. Y.; Lan, C. B.; Chen, C. H.; Horng, H. E.; Hong, Chin-Yih; Yang, H. C.; Lai, Y. K.; Lin, Y. H.; Teng, K. S.

2009-10-01

34

Nitrogenase activity (acetylene reduction) of an iron-oxidizing leptospirillum strain cultured as a pioneer microbe from a recent volcanic deposit on miyake-jima, Japan.  

PubMed

The genus Leptospirillum is known to dominate acid mine drainage and bioleaching systems. In this paper, we describe the isolation of iron-oxidizing bacteria closely related to Leptospirillum ferrooxidans from an acidic volcanic ash deposit on the island of Miyake (Miyake-jima), Japan. We further show the nitrogenase activity (acetylene reduction) for one (strain C2-1) of the isolates. The deposit harbored 1.2×10(8) total direct count (g dry weight)(-1) and 7.1×10(5) (most-probable-number, MPN) (g dry weight)(-1) of iron-oxidizer. A ferrous iron-limited, aerobic chemostat culture using Leptospirillum HH medium (pH 1.8) was performed to select and isolate the Leptospirillum group. Nine isolates were regarded as pure cultures based on uniform colony morphology on Fe(2+)-containing silica gel plates and absence of growth on 100-fold diluted nutrient broth plates. Six strains examined further shared 99.9-100% identity in 16S rRNA gene sequence with each other. Homology-based searches showed that all of the strains belonged to the Leptospirillum ferrooxidans clade. Strain C2-1 grown in ammonium sulfate-free Leptospirillum HH medium (pH 1.8) showed an initial rate of acetylene reduction of 58 ?mol h(-1) (g cell carbon)(-1). PMID:21566388

Sato, Yoshinori; Hosokawa, Ken; Fujimura, Reiko; Nishizawa, Tomoyasu; Kamijo, Takashi; Ohta, Hiroyuki

2009-01-01

35

Molecule-assisted nanoparticle clustering effect in immunomagnetic reduction assay  

NASA Astrophysics Data System (ADS)

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.

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

36

Definition of human rotavirus serotypes by plaque reduction assay.  

PubMed Central

Twenty different human rotavirus reassortants were characterized serologically by a plaque reduction assay as belonging to one of three distinct serotypes. Fourteen were similar if not identical to our prototype Wa strain; two were like the prototype DS-1 strain, and four belonged to a third serotype for which a prototype has not yet been selected. Hyperimmune sera raised against the three serotypes were required to distinguish among them, since postinfection sera had lower titers and were more cross-reactive than hyperimmune sera. These results confirmed the ability of a qualitative cytopathic neutralization test to predict correctly the Wa or DS-1 serotype. A strain of rhesus rotavirus (MMU 18006) was identified as belonging to the newly defined third serotype. Finally, an attempt was made to correlate previously published serotype analysis by neutralization of fluorescent cell-forming units with the results determined by the plaque reduction neutralization assay.

Wyatt, R G; Greenberg, H B; James, W D; Pittman, A L; Kalica, A R; Flores, J; Chanock, R M; Kapikian, A Z

1982-01-01

37

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

PubMed Central

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.

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

1994-01-01

38

Immunomagnetic reduction assay for nervous necrosis virus extracted from groupers.  

PubMed

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

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

39

Acetylene Hydrogenation on Au-Based Catalysts  

Microsoft Academic Search

Hydrogenation of acetylene has been investigated on Au\\/TiO2, Pd\\/TiO2 and Au-Pd\\/TiO2 catalysts at high acetylene conversion levels. The Au\\/TiO2 catalyst (avg. particle size: 4.6 nm) synthesized by the temperature-programmed reduction-oxidation of an Au-phosphine complex on TiO2 showed a remarkably high selectivity to ethylene formation even at 100% acetylene conversion. Au\\/TiO2 prepared by the conventional incipient wet impregnation method (avg. particle

T. V. Choudhary; C. Sivadinarayana; A. K. Datye; D. Kumar; D. W. Goodman

2003-01-01

40

A novel quantitative immunomagnetic reduction assay for Nervous necrosis virus.  

PubMed

Rapid, sensitive, and automatic detection platforms are among the major approaches of controlling viral diseases in aquaculture. An efficient detection platform permits the monitoring of pathogen spread and helps to enhance the economic benefits of commercial aquaculture. Nervous necrosis virus (NNV), the cause of viral encephalopathy and retinopathy, is among the most devastating aquaculture viruses that infect marine fish species worldwide. In the present study, a highly sensitive magnetoreduction assay was developed for detecting target biomolecules with a primary focus on NNV antigens. A standard curve of the different NNV concentrations that were isolated from infected Malabar grouper (Epinephelus malabaricus) was established before experiments were conducted. The test solution was prepared by homogeneous dispersion of magnetic nanoparticles coated with rabbit anti-NNV antibody. The magnetic nanoparticles in the solution were oscillated by magnetic interaction with multiple externally applied, alternating current magnetic fields. The assay's limit of detection was approximately 2 × 10(1) TCID(50)/ml for NNV. Moreover, the immunomagnetic reduction readings for other aquatic viruses (i.e., 1 × 10(7) TCID(50)/ml for Infectious pancreatic necrosis virus and 1 × 10(6.5) TCID(50)/ml for grouper iridovirus) were below the background noise in the NNV solution, demonstrating the specificity of the new detection platform. PMID:22855375

Yang, Shieh Yueh; Wu, Jen Leih; Tso, Chun Hsi; Ngou, Fang Huar; Chou, Hsin Yiu; Nan, Fan Hua; Horng, Herng Er; Lu, Ming Wei

2012-09-01

41

Plasma Thermal Conversion of Methane to Acetylene  

SciTech Connect

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.

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

42

The Azolla-Anabaena azollae Relationship : XI. PHYCOBILIPROTEINS IN THE ACTION SPECTRUM FOR NITROGENASE-CATALYZED ACETYLENE REDUCTION.  

PubMed

Visible absorption spectra are presented for the Azolla caroliniana Willd.-Anabaena azollae Strass. association and the individual partners. Although absorption by the phycobiliproteins of the endophytic cyanobacterium clearly complements the absorption by the fern pigments, their contribution to the absorption spectrum of the association is effectively concealed by the preponderance of the Azolla pigments. Action spectra for nitrogenase-catalyzed C(2)H(2) reduction in both the Azolla-Anabaena association and the endophytic Anabaena demonstrate that quanta absorbed by the phycobiliproteins is as effective as that absorbed by chlorophyll a in driving this photosystem I-linked process. Under anaerobic conditions, the inhibition of photosystem II activity by 3-(3,4-dichlorophenyl)-1,1-dimethylurea, diuron did not selectively decrease the relative quantum yields in the region of phycobiliprotein absorption. At the well-below saturating light intensities used for the action spectra studies, the absolute rates of C(2)H(2) reduction were increased uniformly via respiratory-linked processes under aerobic conditions. The occurrence of phycobiliproteins in heterocysts of the endophytic Anabaena was demonstrated using fluorescence microscopy of intact filaments. Fluorescence micrographs of Anabaena cylindrica filaments are presented for comparison. PMID:16662130

Tyagi, V V; Ray, T B; Mayne, B C; Peters, G A

1981-12-01

43

Acetylenic carbon allotrope  

DOEpatents

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.

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

1998-01-01

44

Acetylenic carbon allotrope  

DOEpatents

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.

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

1999-01-01

45

Acetylenic derivatives of heterocycles  

Microsoft Academic Search

1.The reaction for the catalytic replacement of halogen in the aromatic ring by the acetylenic moiety was extended to imidazole derivatives.2.In this reaction iodine in the 2 position of the imidazole ring is substantially more active than iodine in the 4 position.3.The mono- and diacetylenic derivatives of imidazole with a free acetylenic hydrogen were obtained.

M. S. Shvartsberg; L. N. Bizhan; I. L. Kotlyarevskii

1971-01-01

46

Acetylenic carbon allotrope  

DOEpatents

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.

Lagow, R.J.

1998-02-10

47

Production of acetylene  

SciTech Connect

This patent describes the process for converting essentially pure acetylene from the gaseous out-put stream from a coal to acetylene conversion process, comprising the steps of: (a) processing the gaseous out-put stream in an acid gas removal first stage by absorbing HCN and H/sub 2/S in an organic solvent, and scrubbing with a caustic agent to remove CO/sub 2/; (b) scrubbing the gaseous out-put stream with organic solvent in a sweet gas treatment second stage and removing essentially pure acetylene as a product; and (c) in a third stage, first hydrogenating, then desulfurizing and then methanating the remaining gases from the second stage.

Katz, M.; Carluccio, F.; Mallari, G.; Fitz Patrick, K.; Desai, A.; Casciano, R.; Tsai, J.

1988-11-29

48

Development of a Novel Efficient Fluorescence-Based Plaque Reduction Microneutralization Assay for Measles Virus Immunity  

Microsoft Academic Search

The measurement of functional measles virus-specific neutralizing antibodies is of considerable interest for vaccine-related research. In this study, we developed and standardized a simple, rapid, highly sensitive, and reproducible fluorescence-based plaque reduction microneutralization (PRMN) assay with visual and auto- mated readout, using a recombinant measles virus engineered to express enhanced green fluorescent protein. The assay is performed in micro format,

Iana H. Haralambieva; Inna G. Ovsyannikova; Robert A. Vierkant; Gregory A. Poland

2008-01-01

49

29 CFR 1910.102 - Acetylene.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 2010-07-01 false Acetylene. 1910.102 Section 1910.102... Hazardous Materials § 1910.102 Acetylene. (a) Cylinders. Employers...transfer, handling, storage, and use of acetylene in cylinders comply with the...

2010-07-01

50

Acetylene-Terminated Polyimide Siloxanes  

NASA Technical Reports Server (NTRS)

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.

St. Clair, Terry L.; Maudgal, Shubba

1987-01-01

51

Microtiter plate assay for superoxide dismutase using MTT reduction by superoxide.  

PubMed

A simple microtiter plate based colorimetric assay for superoxide dismutase is described. The method, involves generation of superoxide by pyrogallol autoxidation and the inhibition of superoxide dependent reduction of the tetrazolium dye MTT [3-(4,5-dimethyl-thiazol-2-yl) 2,5-diphenyl tetrazolium bromide] to its formazan, measured at 570 nm. The reaction was terminated by the addition of dimethyl sulfoxide (DMSO) which also helps to solubilize the formazan formed and the colour evolved was stable for many hours. The method was compared with other known methods to measure the activity of purified erythrocyte Cu,ZnSOD and superoxide dismutase activity from various rat tissues. This procedure involves inexpensive reagents, allows a rapid and sensitive measurement of SOD activity and the microtiter plate assay is suitable for use with large number of samples. PMID:9803669

Madesh, M; Balasubramanian, K A

1998-06-01

52

Research in Acetylene Containing Monomers.  

National Technical Information Service (NTIS)

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 an...

M. A. Ogliaruso

1976-01-01

53

29 CFR 1910.102 - Acetylene.  

Code of Federal Regulations, 2013 CFR

...acetylene piping systems, see CGA G-1.2-2006, part 3 (âAcetylene pipingâ) (Compressed Gas Association, Inc., 3rd ed., 2006). (c) Generators and filling cylinders. (1) Employers must ensure that facilities, equipment,...

2013-07-01

54

Electron ionization of acetylene  

NASA Astrophysics Data System (ADS)

Relative partial ionization cross sections and precursor specific relative partial ionization cross sections for fragment ions formed by electron ionization of C2H2 have been measured using time-of-flight mass spectrometry coupled with a 2D ion-ion coincidence technique. We report data for the formation of H+, H2+, C2+, C+/C22+, CH+/C2H22+, CH2+, C2+, and C2H+ relative to the formation of C2H2+, as a function of ionizing electron energy from 30-200 eV. While excellent agreement is found between our data and one set of previously published absolute partial ionization cross sections, some discrepancies exist between the results presented here and two other recent determinations of these absolute partial ionization cross sections. We attribute these differences to the loss of some translationally energetic fragment ions in these earlier studies. Our relative precursor-specific partial ionization cross sections enable us, for the first time, to quantify the contribution to the yield of each fragment ion from single, double, and triple ionization. Analysis shows that at 50 eV double ionization contributes 2% to the total ion yield, increasing to over 10% at an ionizing energy of 100 eV. From our ion-ion coincidence data, we have derived branching ratios for charge separating dissociations of the acetylene dication. Comparison of our data to recent ab initio/RRKM calculations suggest that close to the double ionization potential C2H22+ dissociates predominantly on the ground triplet potential energy surface (3?g-) with a much smaller contribution from dissociation via the lowest singlet potential energy surface (1?g). Measurements of the kinetic energy released in the fragmentation reactions of C2H22+ have been used to obtain precursor state energies for the formation of product ion pairs, and are shown to be in good agreement with available experimental data and with theory.

King, Simon J.; Price, Stephen D.

2007-11-01

55

Research in acetylene containing monomers  

NASA Technical Reports Server (NTRS)

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.

Ogliaruso, M. A.

1976-01-01

56

41 CFR 50-204.66 - Acetylene.  

Code of Federal Regulations, 2010 CFR

...2009-07-01 2009-07-01 false Acetylene. 50-204.66 Section 50-204...and Mists § 50-204.66 Acetylene. (a) The in-plant transfer...handling, storage, and utilization of acetylene in cylinders shall be in...

2009-07-01

57

29 CFR 1910.102 - Acetylene.  

Code of Federal Regulations, 2010 CFR

...2009-07-01 2009-07-01 false Acetylene. 1910.102 Section 1910.102... Hazardous Materials § 1910.102 Acetylene. (a) Cylinders. The in-plant...handling, storage, and utilization of acetylene in cylinders shall be in...

2009-07-01

58

Ionic Reactions in Gaseous Acetylene.  

National Technical Information Service (NTIS)

Mass spectrometric studies of ionic reactions in acetylene have been made which gave rate constants of .9 and 1.3 x 10 to the -9th power cc/molecule-sec. for reaction of C2H2(+) and C2H(+). Consecutive ionic reactions were observed giving ionic species up...

M. S. B. Munson

1964-01-01

59

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...

60

Acetylene-terminated polyimide adhesives  

NASA Technical Reports Server (NTRS)

The nadic-encapped LARC-13 addition polyimide exhibits excellent flow, is easy to process, and can be utilized for short terms at temperatures up to 593 C. It retains good lap shear strength as an adhesive for titanium after aging in air up to 125 hours at 316 C; but lap shear strength degrades with longer exposures at that temperature. Thermid 600, an addition polyimide that is acetylene encapped, exhibits thermomechanical properties even after long term exposure in at air at 316 C. An inherent drawback of this system is that it has a narrow processing window. An acetylene encapped, addition polyimide which is a hybrid of these two systems was developed. It has good retention of strength after long term aging and is easily processed. The synthesis and characterization of various molecular weight oligomers of this system are discussed as well as the bonding, aging, and testing of lap shear adhesive samples.

Hanky, A. O.

1983-01-01

61

Growth of Nocardia rhodochrous on acetylene gas.  

PubMed Central

Soil sediment enrichment cultures yielded a coryneform bacterium capable of growing in a mineral salts solution with acetylene gas as its only source of carbon and energy. Based on morphological and physiological traits as well as on cell wall analysis, the bacterium was characterized as a strain of Nocardia rhodochrous. Maximal growth rates (generation time 2.7 to 3.0 h) on acetylene were obtained at 5 to 20% acetylene, 25 to 40% oxygen, pH 7.0 and 26 to 28 degrees C. Yields (grams of dry cells produced per gram of acetylene consumed) ranged between 90 and 110%. N. rhodochrous exhibits a growth factor requirement for the pyrimidine moiety of thiamine. Acetylene utilization is not an obligate trait, and a wide range of alternate carbon sources is utilized. Ethylene is neither produced nor consumed. The only previous report on acetylene utilization appeared in 1932. The Mycobacterium lacticola strain described in that report strongly resembles N. rhodochrous.

Kanner, D; Bartha, R

1979-01-01

62

Evaluation of Sorbents for Acetylene Separation in Atmosphere Revitalization Loop Closure  

NASA Technical Reports Server (NTRS)

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.

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

2011-01-01

63

Evaluation of Sorbents for Acetylene Separation in Atmosphere Revitalization Loop Closure  

NASA Technical Reports Server (NTRS)

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

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

2012-01-01

64

77 FR 13997 - Revising Standards Referenced in the Acetylene Standard  

Federal Register 2010, 2011, 2012, 2013

...Revising Standards Referenced in the Acetylene Standard AGENCY: Occupational Safety...its direct-final rule revising the Acetylene Standard for general industry. DATES...update the incorporated references in its Acetylene Standard for general industry at 29...

2012-03-08

65

77 FR 13969 - Revising Standards Referenced in the Acetylene Standard  

Federal Register 2010, 2011, 2012, 2013

...Revising Standards Referenced in the Acetylene Standard AGENCY: Occupational Safety...its direct final rule that revises the Acetylene Standard for general industry by updating...the Federal Register that revised the Acetylene Standard for general industry by...

2012-03-08

66

75 FR 5707 - Revising Standards Referenced in the Acetylene Standard  

Federal Register 2010, 2011, 2012, 2013

...Revising Standards Referenced in the Acetylene Standard AGENCY: Occupational Safety...its direct-final rule revising the Acetylene Standard for general industry. DATES...update the incorporated references in its Acetylene Standard for general industry at 29...

2010-02-04

67

46 CFR 154.1735 - Methyl acetylene-propadiene mixture.  

Code of Federal Regulations, 2010 CFR

...2009-10-01 2009-10-01 false Methyl acetylene-propadiene mixture. 154.1735...Requirements § 154.1735 Methyl acetylene-propadiene mixture. (a) The composition of the methyl acetylene-propadiene mixture at loading...

2009-10-01

68

46 CFR 154.1735 - Methyl acetylene-propadiene mixture.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 false Methyl acetylene-propadiene mixture. 154.1735...Requirements § 154.1735 Methyl acetylene-propadiene mixture. (a) The composition of the methyl acetylene-propadiene mixture at loading...

2010-10-01

69

Acetylene terminated aspartimides and resins therefrom  

NASA Technical Reports Server (NTRS)

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.

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

1989-01-01

70

Cholinergic activity of acetylenic imidazoles and related compounds.  

PubMed

A series of acetylenic imidazoles related to oxotremorine (1a) were prepared and evaluated as cholinergic agents with in vitro binding assays and in vivo pharmacological tests in mice. 1-[4-(1H-Imidazol-1-yl)-2-butynyl]-2-pyrrolidinone (1b) was a cholinergic agonist with one-half the potency of oxotremorine. Analogues of 1b with a 5- or 2-methyl substituent in the imidazole ring (compounds 1c and 1g) were cholinergic partial agonists. Analogues of 1b with a methyl substituent at the 5-position in the pyrrolidinone ring (7b) or at the alpha-position in the acetylenic chain (8b) were antagonists. Various analogues of these imidazole acetylenes where the pyrrolidinone ring was replaced by an amide, carbamate, or urea residue were prepared. Several compounds which contained 5-methylimidazole as the amine substituent were partial agonists. The activities of the imidazole compounds are compared with those of the related pyrrolidine and dimethylamine analogues. Agonist and antagonist conformations for these compounds at muscarinic receptors are proposed. PMID:1875333

Moon, M W; Chidester, C G; Heier, R F; Morris, J K; Collins, R J; Russell, R R; Francis, J W; Sage, G P; Sethy, V H

1991-08-01

71

Infrared Spectra of Complexes Containing ACETYLENE-d2  

NASA Astrophysics Data System (ADS)

Infrared spectra of the C_2D_2 dimer in the monomer ?b{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)

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

2011-06-01

72

Determination of rivaroxaban by different factor Xa specific chromogenic substrate assays: reduction of interassay variability  

Microsoft Academic Search

Rivaroxaban and other oral direct factor Xa inhibitors (ODiXa) are currently developed for prophylaxis and treatment of thromboembolic\\u000a diseases using fixed doses. Although routine monitoring is not required, assessing the intensity of anticoagulation may be\\u000a useful under certain clinical conditions. ODiXa prolong coagulation times of several clotting assays and, thus, their concentration\\u000a may be determined in factor Xa specific chromogenic

Job Harenberg; Roland Krämer; Christina Giese; Svetlana Marx; Christel Weiss; Martin Wehling

73

Reduction of misleading ("false") positive results in mammalian cell genotoxicity assays. II. Importance of accurate toxicity measurement.  

PubMed

In a previous publication, Fowler et al. [4] demonstrated that the seemingly high rate of false or misleading positive results obtained in in vitro cytogenesis assays for genotoxicity - when compared with in vivo genotoxicity or rodent carcinogenicity data - was greater when rodent cell lines were used that were also reported to have mutant or non-functional p53. As part of a larger project for improvement of in vitro mammalian cell assays, we have investigated the impact of different toxicity measures, commonly used in in vitro cytogenetic assays, on the occurrence of misleading positive results. From a list of 19 chemicals that produce "false" positive results in in vitro mammalian cell assays [10], six substances that had given positive responses in CHO, CHL and TK6 cells [4], were evaluated for micronucleus induction in vitro, with different measures of toxicity for selection of the top concentration. The data show that estimating toxicity by relative cell count (RCC) or replication index (RI) consistently underestimates the toxicity observed by other measures (Relative Population Doubling, RPD, or Relative Increase in Cell Count, RICC). RCC and RI are more likely to lead to selection of concentrations for micronucleus scoring that are highly cytotoxic and thus could potentially lead to artefacts of toxicity being scored (elevated levels of apoptosis and necrosis), generating misleading positive results. These results suggest that a further reduction in the frequency of misleading positive results in in vitro cytogenetic assays can be achieved with this set of chemicals, by avoiding the use of toxicity measures that underestimate the level of toxicity induced. PMID:22595317

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

2012-08-30

74

Measles immunity testing: Comparison of two measles IgG ELISAs with plaque reduction neutralisation assay  

Microsoft Academic Search

Two commercial IgG ELISAs, one based on recombinant nucleocapsid antigen and one based on cell culture grown native virus antigens, were evaluated for measles immunity testing by comparison with plaque reduction neutralisation test (PRNT). Qualitative results of the two ELISAs showed 92% agreement with those of PRNT. The sensitivity of the two ELISAs was 89.6%. False negative ELISA results were

B. J. Cohen; R. P. Parry; D. Doblas; D. Samuel; L. Warrener; N. Andrews; D. Brown

2006-01-01

75

Oligomers Terminated By Maleimide And Acetylene  

NASA Technical Reports Server (NTRS)

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.

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

1994-01-01

76

Evaluation of an Acetylene Terminated Sulfone Oligomer.  

National Technical Information Service (NTIS)

This paper describes the initial characterization and evaluation of a novel acetylene terminated oligomer 4, 4'-bis (3-ethynylphenoxy) diphenylsulfone (ATS). The approach uses a scientific interdisciplinary team concept to generate material properites. Th...

S. R. Eddy A. M. Lucarelli T. Helminiak W. B. Jones L. G. Picklesimer

1983-01-01

77

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

NASA Astrophysics Data System (ADS)

Acetylene (C2H2) is present in part per million quantities in the atmosphere of Titan; conceivably as an intermediate product of methane photolysis. Currently, Earth’s 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)?

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

2009-12-01

78

Acetylene-Terminated Aspartimides And Derived Resins  

NASA Technical Reports Server (NTRS)

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).

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

1989-01-01

79

Comparison of targeted peptide quantification assays for reductive dehalogenases by selective reaction monitoring (SRM) and precursor reaction monitoring (PRM).  

PubMed

Targeted absolute protein quantification yields valuable information about physiological adaptation of organisms and is thereby of high interest. Especially for this purpose, two proteomic mass spectrometry-based techniques namely selective reaction monitoring (SRM) and precursor reaction monitoring (PRM) are commonly applied. The objective of this study was to establish an optimal quantification assay for proteins with the focus on those involved in housekeeping functions and putative reductive dehalogenase proteins from the strictly anaerobic bacterium Dehalococcoides mccartyi strain CBDB1. This microbe is small and slow-growing; hence, it provides little biomass for comprehensive proteomic analysis. We therefore compared SRM and PRM techniques. Eleven peptides were successfully quantified by both methods. In addition, six peptides were solely quantified by SRM and four by PRM, respectively. Peptides were spiked into a background of Escherichia coli lysate and the majority of peptides were quantifiable down to 500 amol absolute on column by both methods. Peptide quantification in CBDB1 lysate resulted in the detection of 15 peptides using SRM and 14 peptides with the PRM assay. Resulting quantification of five dehalogenases revealed copy numbers of <10 to 115 protein molecules per cell indicating clear differences in abundance of RdhA proteins during growth on hexachlorobenzene. Our results indicated that both methods show comparable sensitivity and that the combination of the mass spectrometry assays resulted in higher peptide coverage and thus more reliable protein quantification. PMID:24220761

Schiffmann, Christian; Hansen, Rasmus; Baumann, Sven; Kublik, Anja; Nielsen, Per Halkjær; Adrian, Lorenz; von Bergen, Martin; Jehmlich, Nico; Seifert, Jana

2014-01-01

80

Comparative evaluation of the nitrate reduction assay, the MTT test, and the resazurin microtitre assay for drug susceptibility testing of clinical isolates of Mycobacterium tuberculosis  

Microsoft Academic Search

Objectives: To evaluate the performance of three rapid low-cost methods for the detection of resistance to first-line drugs in Mycobacterium tuberculosis. Methods: One hundred M. tuberculosis clinical isolates were tested by the nitrate reductase assay (NRA), the MTT test and the resazurin microtitre assay (REMA), and the results compared with those obtained with the gold standard proportion method (PM) on

Ernesto Montoro; Dihadenys Lemus; Miguel Echemendia; Anandi Martin

2005-01-01

81

Vapor pressures of acetylene at low temperatures  

NASA Technical Reports Server (NTRS)

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.

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

1990-01-01

82

Thermodynamics of acetylene van der Waals dimerization  

NASA Technical Reports Server (NTRS)

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.

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

1991-01-01

83

New incubation device for in situ measurement of acetylene-reducing activity in ricefields  

Microsoft Academic Search

A device forin situ estimation of biological nitrogen fixation in shallow-water ricefields was developed using the acetylene-reducing assay.\\u000a The device consists of a rigid transparent bottomless plastic bottle provided with an agitation system. Laboratory experiments\\u000a using flooded pots inoculated withAnabaena UAM 202 indicated that agitation significantly reduced the time needed to detect the production of ethylene by eliminating\\u000a the slow

Antonio Quesada; Eva Sanchez Maeso; Eduardo Fernandez Valiente

1989-01-01

84

Pyrolysis of Acetylene Initiated by Acetone.  

National Technical Information Service (NTIS)

A detailed, radical chain mechanism is used to model the pyrolysis of acetylene near 1000 K. The initiation process, C2H2 + C2H2 yields C4H3 + H, appears to be inconsistent with thermochemistry. Since experimental evidence indicates the presence of a chai...

M. B. Colket D. J. Seery H. B. Palmer

1989-01-01

85

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

PubMed

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

Rosner, B M; Schink, B

1995-10-01

86

Acetylene hydration on different Cd-zeolites  

Microsoft Academic Search

Various Cd-zeolite preparations, containing adsorbed water in controlled amounts, were contacted with acetylene in an IR cell at 0.03 bar. The activity of the zeolites was estimated from the formation rate of adsorbed acetaldehyde at 50 °C detected by FTIR. Cd-derivatives of MOR, MFI, and clinoptilolite were prepared by conventional ion exchange and by a novel method which is based

Gy. Onyestyák; G. Pál-Borbély; D. Kalló

2004-01-01

87

Cyclopolymerization of Acetylene to Benzyne and Naphthalene  

NASA Astrophysics Data System (ADS)

Reactions of acetylene (C_2H_2) with laser-vaporized La atoms produced La(C_6H_4) and La (C10H_8) in supersonic molecular beams. The organic fragments in these complexes were benzyne and naphthalene. The benzyne species was produced by the La-mediated cyclotrimerization of three acetylene molecules, whereas naphthalene was formed likely by the cyclization of the transient benzyne with two additional acetylene molecules. These cyclized products were identified by mass-analyzed threshold ionization mass spectroscopy, which measured adiabatic ionization energies and several vibrational frequencies. The measured ionization energies were 40875 (5) cm-1 for La(C_6H_4) and 36767 (5) cm-1 for La(C10H_8). The most active vibrational transitions of both complexes were metal-ligand stretching with 326 cm-1 for La(C_6H_4) and 286 cm-1 for La (C10H_8). By combining the spectra with theoretical calculations, the ground electronic states of the neutral complexes were determined to be ^2A_1 (C2v) and ^2A' (C_s) and those of the corresponding ions were ^1A_1 (C2v) and ^1A' (C_s) for La (C_6H_4) and La(C10H_8), respectively.

Hewage, Dilrukshi; Silva, Ruchira; Yang, Dong-Sheng

2012-06-01

88

Structure and electrochemical properties of track membranes with a polymer layer obtained by plasma polymerization of acetylene  

NASA Astrophysics Data System (ADS)

The structure and electrochemical properties of poly(ethylene terephthalate) track membrane modified by acetylene plasma were studied. It was found that polymer deposition on the surface of a track membrane by plasma polymerization of acetylene results in the creation of composite membranes that, in the case of formation of a thin semipermeable layer, possess an asymmetry of conductivity in electrolyte solutions – a rectification effect. It is caused by the reduction of the pores diameter due to the plasma polymer that results in changing the pore geometry, and as well due to the existence of an interface between the initial membrane and the polymer layer which have various concentrations of carboxyl groups.

Kravets, L. I.; Dmitriev, S. N.; Satulu, V.; Mitu, B.; Dinescu, G.

2014-06-01

89

High temperature polymer from maleimide-acetylene terminated monomers  

NASA Technical Reports Server (NTRS)

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.

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

1993-01-01

90

Electronic Spectroscopy and Dynamics of the Acetylene - Complex  

Microsoft Academic Search

The structures, intermolecular forces and excited state dynamics of acetylene(A) cdot Ar complex are investigated by combination of laser induced fluorescence spectroscopy pairwise potential model calculations. Acetylene is linear in the X state while trans-bent in the (A) state. Although only one structure has been known to exist for the acetylene(X) cdot Ar complex, two isomeric structures are determined for

Shan-Shan Ju

1994-01-01

91

High-resolution FTIR spectroscopy of the ?3 band of methyl acetylene-d  

NASA Astrophysics Data System (ADS)

The high-resolution Fourier transform spectrum of methyl acetylene-d1 (CH3CCD) at room temperature has been recorded in the region of the ?3 band (1980–2035 cm?1) at an apodized resolution of 0.004 cm?1. About 600 vibration–rotation transitions have been assigned, with J upto 36 and K upto 6. The spectrum shows the presence of several perturbations. The observed minus calculated deviation of the fit for K = 4 subband is much more than the expected, shows the presence of Fermi resonance with the nearby vibrational state.

Pal, Ayan Kumar; Kshirsagar, R. J.

2014-04-01

92

Both oxidative stress-dependent and independent effects of amyloid ? protein are detected by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) reduction assay  

Microsoft Academic Search

3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) reduction assay has been widely used for evaluating amyloid ? protein (A?) toxicity. However, the potency of A? in inhibiting cellular MTT reduction and the underlying mechanism have been reported with some discrepancies among researchers. To understand what makes such discrepancies, the effect of A? detected by MTT reduction assay was re-examined in detail by using cultured

Kazuho Abe; Hiroshi Saito

1999-01-01

93

Determination of the optimal conditions for filling of acetylene cylinders  

Microsoft Academic Search

In accordance with standards of the International Standards Organization (ISO), the types of tests for acetylene cylinders include a test for heating to 65~ and in this case hydraulic pressure should not appear in the cylinder, i.e., the volume of the solution of acetylene in acetone, during its expansion, should be less than or equal to the gas volume of

S. P. Neshumova; M. M. Grunina

1990-01-01

94

RECRYSTALLIZATION OF PMDA AND SYNTHESIS OF AN ACETYLENIC DIAMINE  

SciTech Connect

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.

Sanner, R; Cook, R C

2004-09-21

95

Optical properties of disubstituted acetylene polymers  

NASA Astrophysics Data System (ADS)

Optical properties and electronic energy structures of di- substituted acetylene polymers have been studied. Strong blue and green photoluminescence and electroluminescence have been observed in the poly(diphenylacetylene) derivatives and poly(1-alkyl-2-phenylacetylene) derivatives, contrary to trans-polyacetylene, in which only very weak photoluminescence are observed at infrared region. The dependence of optical properties of the di-substituted polyacetylene derivatives such as photoluminescence intensity and electroluminescence efficiency on the molecular structure of substituents and the change of optical properties upon electrochemical doping and their interpretation by soliton model have also bee discussed. Spectral narrowing in photoluminescence of some di- substituted polyacetylenes have also been studied.

Tada, Kazuya; Hidayat, Rahmat; Hirohata, Masaharu; Kajii, Hirotake; Tatsuhara, Satoshi; Fujii, Akihiko; Ozaki, Masanori; Teraguchi, Masahiro; Masuda, Toshio; Yoshino, Katsumi

1997-10-01

96

Free radical-induced carbonyl content in protein of estrogen-treated hamsters assayed by sodium boro[3H]hydride reduction.  

PubMed

Oxidative damage to proteins is known to occur via conversion of side chain amino groups to corresponding carbonyl derivatives. Such damage to enzymes and purified proteins has been quantified previously by reduction with sodium boro[3H]hydride and subsequent measurement of the incorporation of 3H into amino acid fractions. In this study, the NaB3H4 reduction assay was modified to permit the quantitation of free radical-mediated oxidative damage to proteins obtained from animals. Modifications included additional extractions of protein isolates with organic solvents to remove lipids and with nitric acid to remove metal ions. The modified assay has first been validated in vitro by measuring changes in levels of oxidative damage to bovine serum albumin exposed to xanthine plus xanthine oxidase (2-fold increase), to hydrogen peroxide and iron(II) sulfate (5-fold increase), or to gamma radiation (30-fold increase over controls, respectively). gamma radiation of isolated hamster kidney protein also raised the carbonyl content in a dose-dependent manner. The modified assay has then been validated in vivo by measuring the changes in oxidative damage to lung tissue in animals exposed to approximately 85% oxygen (2-fold increase) or to different doses of paraquat (5-fold increase with the high dose over controls, respectively). The assay was then used to examine free radical-mediated oxidation introduced by acute or chronic treatment of hamsters with estrogens, since both synthetic and natural estrogens induce kidney tumors in this species. Priming of hamsters for 3 days with 20 mg/kg/day diethylstilbestrol and treatment with 100 mg/kg of this drug on the 4th day resulted in a 160% increase in free radical modification of renal proteins. Oxidative damage to kidney proteins was also assayed in hamsters treated with estradiol implants for up to 7 months, a regimen known to induce kidney tumors. Significant increases in covalent oxidative modification to renal proteins over values in age-matched controls were detected after 1, 2, and 7 months of continuous estradiol exposure. It is concluded that the modification of the NaB3H4 reduction assay is a useful postlabeling method for monitoring free radical action in vivo. Furthermore, it is postulated that free radical damage in estrogen-treated hamster kidney plays a role in estrogen-induced carcinogenesis. PMID:1860852

Winter, M L; Liehr, J G

1991-08-01

97

Acetylene-Based Materials in Organic Photovoltaics  

PubMed Central

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.

Silvestri, Fabio; Marrocchi, Assunta

2010-01-01

98

Pressure-induced polymerization in substituted acetylenes  

SciTech Connect

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.

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

2012-04-10

99

Insights on antioxidant assays for biological samples based on the reduction of copper complexes-the importance of analytical conditions.  

PubMed

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 µM Trolox, (limit of detection 2.3 µM; limit of quantification 7.7 µM) 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

Marques, Sara S; Magalhães, Luís M; Tóth, Ildikó V; Segundo, Marcela A

2014-01-01

100

1,3-Dipolar cycloadditions of acetylenic sulfones in solution and on solid supports.  

PubMed

Several representative acetylenic sulfones were immobilized on a polymer support derived from Merrifield resin by means of ester linkers that were used to couple free carboxylic acid groups on the solid support with benzylic hydroxyl functions on the arylsulfonyl moieties of the acetylenes. Several examples of reversed ester linkers, using Merrifield resin directly, were also successfully prepared. The 1,3-dipolar cycloadditions of the solid-supported acetylenic sulfones were investigated with a series of 1,3-dipoles, including benzyl azide, ethyl diazoacetate, diazomethane, as well as representative nitrile oxides, nitrile imines, nitrile ylides, nitrones, azomethine imines, azomethine ylides, munchnones, and sydnones. In general, analogous cycloadditions were also performed with acetylenic sulfones in solution phase for comparison. The cycloadditions typically afforded good to excellent yields of the desired products in both solution and solid phase, although the latter reactions sometimes required more vigorous conditions. Except in the case of benzyl azide and diazo compounds, where mixtures of regioisomers were obtained, the other 1,3-dipoles reacted with high regioselectivity and afforded essentially unique regioisomers. Cleavage of the products from the resin was smoothly effected by alkaline hydrolysis, while several attempts at reductive desulfonylation with sodium amalgam or samarium diiodide-HMPA resulted in N-O or C-O scission, in addition to cleavage from the polymer. The method provides access to a number of important classes of heterocycles, including variously substituted and functionalized triazoles, pyrazoles, 1,2-oxazoles, pyrroles, as well as their dihydro and bicyclic analogues. The success of the cycloadditions on polymer supports paves the way to future investigations of sequential transformations leading to libraries of useful heterocycles. PMID:18798677

Gao, Detian; Zhai, Huimin; Parvez, Masood; Back, Thomas G

2008-10-17

101

Interpenetrating polymer networks from acetylene terminated materials  

NASA Technical Reports Server (NTRS)

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.

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

1989-01-01

102

High pressure chemistry of substituted acetylenes  

SciTech Connect

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.

Chellappa, Raja [Los Alamos National Laboratory; Dattelbaum, Dana [Los Alamos National Laboratory; Sheffield, Stephen [Los Alamos National Laboratory; Robbins, David [Los Alamos National Laboratory

2011-01-25

103

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

PubMed Central

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.

2014-01-01

104

Acetylenic acid analogues from the edible mushroom Chanterelle (Cantharellus cibarius) and their effects on the gene expression of peroxisome proliferator-activated receptor-gamma target genes.  

PubMed

A new acetylenic acid, (10E,14Z)-9-oxooctadeca-10,14-dien-12-ynoic acid (1), was isolated from the edible mushroom Chanterelle (Cantharellus cibarius), together with a known acetylenic acid, (10E,14Z)-9-hydroxyoctadeca-10,14-dien-12-ynoic acid (2) and their structures were determined through analysis of NMR and mass data. The new acetylenic acid (1) specifically activated peroxisome proliferator-activated receptor (PPAR)-? with an EC(50) value of 1.88 ?M as measured by a reporter gene assay. Expression of PPAR-? target genes were significantly altered as well, supporting the hypothesis that compound 1 is a PPAR-? potential agonist that regulates transcription of the PPAR-? target genes. PMID:22342624

Hong, Seong Su; Lee, Ji Hae; Jeong, Wonsik; Kim, Nahyun; Jin, Hui Zi; Hwang, Bang Yeon; Lee, Hak-Ju; Lee, Sung-Joon; Jang, Dae Sik; Lee, Dongho

2012-03-15

105

Pyrethrum stabilization by inactivation of natural acetylenic impurities  

SciTech Connect

This patent describes a mixture of naturally occurring pyrethroid substances and derivatives of naturally occurring polyacetylenic substances wherein the derivatives of polyacetylenic substances are formed by substantially inactivating the acetylenic functional groups to promote the stability of the pyrethroid substances.

Evans, A.J.

1989-01-17

106

An Acetylenic Alkaloid from the Calcareous Sponge Leucetta sp.  

PubMed Central

A new acetylenic alkaloid was isolated from the sponge Leucetta sp. The structure was established by analyzing spectroscopic data. The alkaloid showed cytotoxicity IC50 2.5 ?g/mL against NBT-T2 cells.

Hermawan, Idam; de Voogd, Nicole J.; Tanaka, Junichi

2011-01-01

107

46 CFR 154.1735 - Methyl acetylene-propadiene mixture.  

Code of Federal Regulations, 2011 CFR

...acetylene-propadiene mixture must have a refrigeration system without vapor compression or have a refrigeration system with the following features...separate cargo piping, vent piping, and refrigeration equipment for methyl...

2011-10-01

108

Theoretical study of acetylene adsorption on armchair nanotubes  

Microsoft Academic Search

We have performed first principles total energy calculations to investigate the adsorption of an acetylene molecule inside and outside carbon nanotubes (CNT). We have calculated the binding energies and the electronic properties of a single acetylene molecule interacting with (n,n) CNTs (n=4–7). The exchange-correlation potential energies were treated in the generalized gradient approximation (GGA) and the local density approximation (LDA).

G. Canto; E. Martínez-Guerra; Noboru Takeuchi

2008-01-01

109

Laser absorption diagnostic for measuring acetylene concentrations in shock tubes  

NASA Astrophysics Data System (ADS)

A fixed-wavelength direct absorption laser diagnostic for high-temperature measurements of acetylene concentration was developed. The diagnostic, based on a tunable continuous wave distributed feedback diode laser, was optimized primarily for studying chemical kinetics behind reflected shock waves. The center wavelength (3335.55 cm-1) of the tunable diagnostic was typically set at the peak of the 3300 cm-1 absorption band of acetylene at high temperatures. The absorption spectrum of acetylene diluted in argon was characterized using scanned-wavelength direct absorption measurements from 1070 to 1720 K and 0.8 to 4.0 atm. Line fitting of the measured absorption spectra was not possible due to the large number of transitions overlapped by pressure broadening that contribute to the spectrum. Instead, empirical fits for the peak absorption coefficient and its corresponding wavelength as a function of temperature and pressure were generated. Furthermore, in order to allow for characterization of interference absorption in kinetic studies, empirical fits for the acetylene absorption coefficient in the region around the primary absorption feature were developed. Absorption coefficient measurements of propyne and 1-butyne, which may be the primary interference candidates, reveal that their absorption coefficients are constant in the wavelength range of interest, and are much smaller than those of acetylene. Therefore, the acetylene concentration in the presence of these interfering species can be inferred using two-color techniques. The utility of the acetylene diagnostic was demonstrated by measuring acetylene mole fraction time-histories during the pyrolysis of propene and 1-butene.

Stranic, Ivo; Hanson, Ronald K.

2014-07-01

110

Electronic Spectroscopy and Dynamics of the Acetylene - Complex  

NASA Astrophysics Data System (ADS)

The structures, intermolecular forces and excited state dynamics of acetylene(A) cdot Ar complex are investigated by combination of laser induced fluorescence spectroscopy pairwise potential model calculations. Acetylene is linear in the X state while trans-bent in the (A) state. Although only one structure has been known to exist for the acetylene(X) cdot Ar complex, two isomeric structures are determined for the acetylene(A) cdot Ar complex from the rotational band shape analysis of the fluorescence excitation spectra. One of the isomers has the argon sitting in the molecular plane of C _2H_2 (A), 3.77 A away from the center-of-mass of acetylene, the other has the argon 3.71 A above the plane on the C_2 axis. Formulas useful for calculating axis switching angles in non-planar molecules have been derived and applied to the two isomeric structures. It was found that despite the acetylene geometry change from the (X) to the (A) state, the axis switching effect is negligible for the complex spectral calculation. A pair potential model with parameters directly extracted from the ones calculated for ethene (X) cdot Ar is able to produce the two structures. Based on the structures and the calculated potential surface, three of the vdW frequencies are assigned to be: upsilon_{rm stretch } = 28 cm^{-1} for the out-of-plane isomer, upsilon_ {rm bend1} = 11 cm^ {-1} (the in-plane bend) and upsilon_{rm bend2} = 8.5 cm^{-1} (the out -of-plane bend) for the in-plane isomer. The existence of the two isomers allowed the study of the orientation dependence in intersystem crossing (ISC) of acetylene(S _1) induced by interaction with argon. Similar ISC lifetimes (~100 ns) were observed for the two isomers, suggesting that the pi and pi^* orbitals are equally susceptible to spin-changing interactions with Ar.

Ju, Shan-Shan

111

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

PubMed Central

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)

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

1984-01-01

112

Saturn's Stratospheric Acetylene And Ethane Emission  

NASA Astrophysics Data System (ADS)

Hydrocarbons in the upper atmosphere of Saturn are known, from Voyager and early Cassini results, to vary in emission intensity with latitude. Of particular interest is the marked increase in temperature and hydrocarbon line intensity near the South Pole (Greathouse et al. 2005, Orton and Yanamandra-Fisher, 2005, Flasar et al. 2005). Latitudinal variations in hydrocarbon abundances can be determined from measurements of hydrocarbon emission lines using temperatures derived from Cassini’s Composite InfRared Spectrometer (CIRS). Latitudinal, temporal, and vertical variations of stratospheric hydrocarbons provide constraints on dynamics, seasonal climate models, and photochemical models. In an effort to monitor temporal and latitudinal variations of hydrocarbons in Saturn’s southern hemisphere we are conducting a ground-based campaign using Celeste, an infrared (5-25 ?m) high-resolution (<0.1 cm-1) cryogenic grating spectrometer. From 2005 to 2007, we have been mapping lines of ethane and acetylene at the McMath-Pierce telescope at Kitt Peak, AZ and the NASA Infrared Telescope Facility at Mauna Kea, HI. These observations are being used to infer molecular abundances for each species in the 1-10 mbar region across the southern hemisphere of Saturn. Updated results from these observations will be presented. This research was supported by a NASA Postdoctoral Program Fellowship appointment conducted at the Goddard Space Flight Center. References: Flasar et al., (2005) Science 307, 1247. Greathouse et al., (2005) Icarus 177, 18 Orton and Yanamandra-Fisher, (2005) Science 307, 696.

Hesman, Brigette E.; Jennings, D. E.; Sada, P. V.; Bjoraker, G. L.; Simon-Miller, A. A.; Nixon, C. A.; Boyle, R. J.; McCabe, G. H.

2007-05-01

113

Ion-induced dissociation dynamics of acetylene  

SciTech Connect

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.

De, Sankar [Inter-University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi-110067 (India); Department of Physics, University of Calcutta, 92, Acharya Prafulla Chandra Road, Kolkata-700009 (India); Rajput, Jyoti; Roy, A.; Safvan, C. P. [Inter-University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi-110067 (India); Ghosh, P. N. [Department of Physics, University of Calcutta, 92, Acharya Prafulla Chandra Road, Kolkata-700009 (India)

2008-02-15

114

Electron impact induced anion production in acetylene.  

PubMed

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

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

2014-02-28

115

Is acetylene essential for carbon dust formation?  

NASA Astrophysics Data System (ADS)

We have carried out an investigation of the chemical evolution of gas in different carbon-rich circumstellar environments. Previous studies have tended to invoke terrestrial flame chemistries, based on acetylene (C2H2) combustion to model the formation of carbon dust, via polycyclic aromatic hydrocarbons (PAHs). In this work, we pay careful attention to the accurate calculation of the molecular photoreaction rate coefficients to ascertain whether there is a universal formation mechanism for carbon dust in strongly irradiated astrophysical environments. A large number of possible chemical channels may exist for the formation of PAHs, so we have concentrated on the viability of the formation of the smallest building block species, C2H2, in a variety of carbon-rich stellar outflows. C2H2 is very sensitive to dissociation by UV radiation. This sensitivity is tested, using models of the time-dependent chemistry. We find that C2H2 formation is sensitive to some of the physical parameters and that in some known sources of dust formation it can never attain appreciable abundances. Therefore, multiple (and currently ill-defined) dust-formation channels must exist.

Dhanoa, H.; Rawlings, J. M. C.

2014-05-01

116

Ion-induced dissociation dynamics of acetylene  

NASA Astrophysics Data System (ADS)

We report on the results of dissociation dynamics of multiple charged acetylene molecules formed in collision with 1.2 MeV Ar8+ 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 diatomlike behavior of the C-C charged complex during dissociation of multiply charged C2H2 . 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.

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

2008-02-01

117

Photochemistry of acetylene at 1470 A. [with Jovian atmosphere application  

NASA Technical Reports Server (NTRS)

The considered study was conducted to assess the importance of the major primary photochemical process of acetylene at 1470 A, to clarify the role of the metastable excited state, and to obtain information on the rates of C2H reactions with H2 and CH4. Concerning the photodissociation process of acetylene, it was found that at acetylene pressures below 0.8 Torr the direct dissociation process (C2H2 yields C2H + H) is the most important primary photochemical process with a quantum yield of 0.3. Another primary process may be the production of H2 with a quantum yield of approximately 0.1 (C2H2 yields C2 + H2). At acetylene pressures above 0.8 Torr diacetylene is formed by the direct dissociation process followed by the reaction: C2H + C2H2 yields C4H2 + H. At pressures above 20 Torr benzene becomes an important product with a concomitant decrease of diacetylene. The role of acetylene in the photochemistry of the Jovian atmosphere is also considered

Okabe, H.

1981-01-01

118

49 CFR 173.303 - Charging of cylinders with compressed gas in solution (acetylene).  

Code of Federal Regulations, 2010 CFR

...cylinders with compressed gas in solution (acetylene). 173.303 Section...SHIPMENTS AND PACKAGINGS Gases; Preparation and Packaging § 173.303 Charging...cylinders with compressed gas in solution (acetylene). (a)...

2010-10-01

119

49 CFR 173.303 - Charging of cylinders with compressed gas in solution (acetylene).  

Code of Federal Regulations, 2010 CFR

...cylinders with compressed gas in solution (acetylene). 173.303 Section...SHIPMENTS AND PACKAGINGS Gases; Preparation and Packaging § 173.303 Charging...cylinders with compressed gas in solution (acetylene). (a)...

2009-10-01

120

Adsorption and Decomposition of Acetylene on Si(100)-(2x1).  

National Technical Information Service (NTIS)

The adsorption and decomposition of acetylene on Si(100) - (2x1) has been studied in ultrahigh vacuum by Auger spectroscopy, temperature programmed desorption and changes in the partial pressure of acetylene as measured by a quadruple mass spectrometer du...

P. A. Taylor R. M. Wallace C. C. Cheng W. H. Weinberg M. J. Dresser

1991-01-01

121

Biphenylene- and Phenyl-End-Capped Oligomeric Polyquinolines Containing Acetylene Linkages. Preparation, Processing, and Composite Application.  

National Technical Information Service (NTIS)

A series of oligomeric polyquinolines (DP=22) containing acetylene linkages and capped by biphenylene or phenyl groups was prepared. The monomer, 4,4'-diacetyldiphenylacetylene, was used to incorporate the acetylene linkages. Oligomers with 0, 12.5, 25, 5...

D. M. Sutherlin J. K. Stille W. B. Alston

1986-01-01

122

49 CFR 173.303 - Charging of cylinders with compressed gas in solution (acetylene).  

Code of Federal Regulations, 2013 CFR

... Charging of cylinders with compressed gas in solution (acetylene). 173.303...REQUIREMENTS FOR SHIPMENTS AND PACKAGINGS Gases; Preparation and Packaging § 173.303 Charging of cylinders with compressed gas in solution (acetylene). (a)...

2013-10-01

123

Chemistry and properties of blends of acetylene terminated materials  

NASA Technical Reports Server (NTRS)

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.

Connell, John W.; Hergenrother, Paul M.

1991-01-01

124

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

Code of Federal Regulations, 2010 CFR

...2009-10-01 false Fixed oxygen-acetylene distribution piping. 56.50-103...Systems § 56.50-103 Fixed oxygen-acetylene distribution piping. (a) This...installed for the distribution of oxygen and acetylene carried in cylinders as vessels...

2009-10-01

125

46 CFR 151.50-79 - Methyl acetylene-propadiene mixture.  

Code of Federal Regulations, 2010 CFR

...2009-10-01 2009-10-01 false Methyl acetylene-propadiene mixture. 151.50-79...Requirements § 151.50-79 Methyl acetylene-propadiene mixture. (a) The composition of the methyl acetylene-propadiene mixture at loading...

2009-10-01

126

46 CFR 151.50-79 - Methyl acetylene-propadiene mixture.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 false Methyl acetylene-propadiene mixture. 151.50-79...Requirements § 151.50-79 Methyl acetylene-propadiene mixture. (a) The composition of the methyl acetylene-propadiene mixture at loading...

2010-10-01

127

Strong-Field Dissociative Double Ionization of Acetylene  

NASA Astrophysics Data System (ADS)

We investigate dissociative double ionization of acetylene, one of the smallest organic molecules yet with a rich electronic structure, in strong laser fields by measuring two fragment ions and two electrons in coincidence. The two-body fragmentation channels are dominated by the removal of electrons from the lower-lying molecular orbitals rather than from the highest occupied one. The electron localization-assisted enhanced ionization mechanism plays a central role for the strong-field deprotonation ionization of acetylene by releasing the second electron from the up-field potential well of the hydrogen site at the internuclear distance near twice the equilibrium value of the C-H bond.

Gong, Xiaochun; Song, Qiying; Ji, Qinying; Pan, Haifeng; Ding, Jingxin; Wu, Jian; Zeng, Heping

2014-06-01

128

Tropospheric and lower stratospheric vertical profiles of ethane and acetylene  

Microsoft Academic Search

The first known vertical distributions of ethane and acetylene which extend into the lower stratosphere are reported. The average upper tropospheric concentrations, between 20,000 ft (6 km) and 35,000 ft (11 km), near 37°N-123°W were 1.2 mug\\/m3 (1.0 ppb) for ethane and 0.24 mug\\/m3 (0.23 ppb) for acetylene while the values near 9°N-80°W were 0.95 mug\\/m3 (0.77 ppb) and 0.09

Dagmar Cronn; Elmer Robinson

1979-01-01

129

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

SciTech Connect

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.}

Dube, P.; Ma, L.; Ye, J.; Jungner, P.; Hall, J.L. [JILA, University of Colorado and National Institute of Standards and Technology, Boulder, Colorado 80309-0440 (United States)

1996-09-01

130

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

NASA Astrophysics Data System (ADS)

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-Perot cavity of finesse 274 was filled with acetylene gas and illuminated with a titanium:sapphire laser tuned to the P(11) line of the nu 1+3 nu 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. .

Dubé, P.; Ma, L.-S.; Ye, J.; Jungner, P.; Hall, J. L.

1996-09-01

131

High yield of pure multiwalled carbon nanotubes from the catalytic decomposition of acetylene on in-situ formed cobalt nanoparticles.  

PubMed

For the first time, multiwalled carbon nanotubes (MWNTs) could be formed selectively in a high yield, free of any disordered carbon by-product, from the catalytic decomposition of acetylene at 600 degrees C on a CoxMg(1-x)O solid solution. Starting from 1 g of catalytic substrate, 4 g of pure MWNTs were obtained after its dissolution in boiling concentrated HCl, without any additional purification in strongly oxidizing medium, as is required for other methods of nanotube production. In situ reduction of CoO by dihydrogen liberated from acetylene decomposition allows highly divided metal particles to be continuously produced as synthesis proceeds. This is undoubtedly the reason for the good performance of the catalyst and for the ability to produce nanotubes in a narrow diameter range, namely from 10 to 15 nm. With the use of acetylene instead of methane, the synthesis proceeds at low temperature, which prevents the growth of carbon shells, in which the metal particles are generally embedded, decreasing their activity. Because of the very low specific surface area of the catalyst support, the amount of disordered carbon by-product formed is negligible. PMID:12908283

Delpeux, Sandrine; Szostak, Katarzyna; Frackowiak, Elzbieta; Bonnamy, Sylvie; Béguin, François

2002-10-01

132

Production of acetylene from coal using a new plasma gasifier  

SciTech Connect

Since the development of the plasma jet generator, temperatures above several thousand degrees Kelvin can be readily and steadily generated. The plasma jet has been used in various branches of high temperature technology. The authors discuss plasma chemistry, especially in the direct production of acetylene from coal.

Kikukawa, N.; Makino, M.

1984-04-01

133

Near-threshold vibrational excitation of acetylene by positron impact  

SciTech Connect

We report vibrational excitation cross sections for C-C and C-H symmetric stretch modes of acetylene by positron impact. The contribution of these infrared inactive modes to the annihilation parameter is also addressed. The Feshbach projection operator approach was employed to vibrationally resolve e{sup +}-acetylene scattering phase shifts obtained with the Schwinger multichannel method. The present results point out a virtual state pole at the equilibrium geometry of acetylene that becomes a bound state as either bond is stretched, in qualitative agreement with previous calculations for small hydrocarbons. The vibrational couplings are stronger for the C-C mode, giving rise to a bound state pole within the Franck-Condon region of the vibrational ground state. These bound and virtual states give rise to sharp threshold structures (vibrational resonances) in both the vibrational excitation cross sections and the annihilation parameter (Z{sub eff}). We found fair agreement between the present calculations and previously reported e{sup +}-acetylene vibrational excitation cross sections.

Oliveira, Eliane M. de; Lima, Marco A. P.; Sanchez, Sergio d'A.; Varella, Marcio T. do N. [Instituto de Fisica Gleb Wataghin, Universidade Estadual de Campinas, 13083-970 Campinas, Sao Paulo (Brazil); Universidade Federal do ABC, Centro de Ciencias Naturais e Humanas, Rua Santa Adelia 166, 09210-170 Santo Andre (Brazil)

2010-01-15

134

Near-threshold vibrational excitation of acetylene by positron impact  

NASA Astrophysics Data System (ADS)

We report vibrational excitation cross sections for C-C and C-H symmetric stretch modes of acetylene by positron impact. The contribution of these infrared inactive modes to the annihilation parameter is also addressed. The Feshbach projection operator approach was employed to vibrationally resolve e+-acetylene scattering phase shifts obtained with the Schwinger multichannel method. The present results point out a virtual state pole at the equilibrium geometry of acetylene that becomes a bound state as either bond is stretched, in qualitative agreement with previous calculations for small hydrocarbons. The vibrational couplings are stronger for the C-C mode, giving rise to a bound state pole within the Franck-Condon region of the vibrational ground state. These bound and virtual states give rise to sharp threshold structures (vibrational resonances) in both the vibrational excitation cross sections and the annihilation parameter (Zeff). We found fair agreement between the present calculations and previously reported e+-acetylene vibrational excitation cross sections.

de Oliveira, Eliane M.; Lima, Marco A. P.; Sanchez, Sergio D.'A.; Varella, Márcio T. Do N.

2010-01-01

135

Fatal carbon monoxide intoxication after acetylene gas welding of pipes.  

PubMed

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

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

2013-06-01

136

Thermoset Polymers Made by Blending Poly (Carborane-Siloxane/ Silane-Acetylene) and Poly (Siloxane/Silane-Acetylene).  

National Technical Information Service (NTIS)

An organoboron thermoset polymer precursor composition is made up of a mixture of a first linear polymer having a repeating unit comprising at least one carboranyl group, at least one silyl or siloxyl groups, and at least one acetylenic group, and a secon...

T. M. Keller D. Y. Son

1996-01-01

137

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

SciTech Connect

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.

Gan, L.S.

1986-01-01

138

Decoupling in the line mixing of acetylene infrared Q branches  

Microsoft Academic Search

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

A. S. Pine; J. P. Looney

1990-01-01

139

Total ionization cross-sections for fluoro acetylene molecule  

NASA Astrophysics Data System (ADS)

Total ionization cross-sections for Fluoro acetylene molecule is calculated by applying Binary Encounter Bethe (BEB) model by electron impact. The cross-sections are calculated in the energy range from ionization threshold to 2 keV. No experimental or theoretical work is reported in the literature to the best of my knowledge for comparison. Present work is a maiden attempt to find electron impact ionization cross section.

Pandya, C. V.

2014-04-01

140

Single Step Synthesis of Acetylene-Substituted Oxacalix[4]arenes.  

PubMed

Oxacalixarenes bearing acetylene groups are synthesized in a single step by nucleophilic aromatic substitution reactions of orcinol with various 1,5-diethynyl-2,4-difluorobenzenes. Thermodynamic equilibration of the cyclooligomer mixtures was accomplished for arylethynyl activating groups, leading to increased yields of the corresponding oxacalix[4]arenes. A 1,3-alternate macrocycle conformation is observed in the solid state, presenting a large V-shaped ?-surface. PMID:24831553

Wackerly, Jay Wm; Zhang, Mengfei; Nodder, Stephen T; Carlin, Stephen M; Katz, Jeffrey L

2014-06-01

141

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

SciTech Connect

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.

Bao, W.; Li, F.; Cai, G.; Lu, Y.; Chang, L. [Taiyuan University of Technology, Taiyuan (China)

2009-07-01

142

[Tunable fiber laser based photoacoustic spectroscopy for acetylene detection].  

PubMed

An acetylene detection system has been constructed with a tunable erbium-doped fiber laser (TEDFL) based photoacoustic spectrometer. Combining wavelength modulation and second harmonic signal detection technique, the system is able to effectively eliminate the background noise generated by absorption of the cell windows and the wall of the acoustic resonator. The system was applied to low concentration acetylene flowing measurement, through optimizing the systemic optics, acoustics and electron detection technique condition. The experimental results show that the second harmonic amplitude is directly proportional to gas concentration. Their linear pertinence coefficient is 0.999 53. The system sensitivity limit for acetylene detection is 0.3 ppm under atmosphere pressure with 100 ms time constant and 3. 5 mW average optical power. The TEDFL was used as light source in stead of the DFB diode laser which is relatively costly. The system appears promising as a basis for developing cheap, practical, portable spectroscopy instruments for trace gas detection. The detection sensitivity could be greatly improved by using multi-path cell or increasing the laser power with EDFA. PMID:19839300

Peng, Yong; Yu, Qing-Xu

2009-08-01

143

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

SciTech Connect

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.

Merkulov, A.A.; Ovsyannikov, A.A.; Polak, L.S.; Popov, V.T.; Pustilnikov, V.Yu. (Institute of Petrochemical Synthesis, Moscow (USSR))

1989-03-01

144

Models for reactions of acetylene on platinum (111): the. mu. /sub 3/-eta/sup 2/-acetylene derivative  

SciTech Connect

The reactions of acetylene with the Pt(111) surface have been studied in detail; the species Pt/sub 3/(..mu../sub 3/-eta/sup 2/-HCCH), Pt/sub 3/(..mu../sub 3/-eta/sup 2/-C=CH/sub 2/), and Pt/sub 3/(..mu../sub 3/-CCH/sub 3/) are formed sequentially, and theoretical studies of each species have been carried out. This article reports an attempt to mimic this chemistry by reaction of acetylene with the coordinatively unsaturated cluster (Pt/sub 3/(..mu../sub 3/-CO)(..mu..-dppm)/sub 3/)-(PF/sub 6/)/sub 2/ (1, dppm = Ph/sub 2/PCH/sub 2/PPh/sub 2/)/sup 5/ and the characterization of the first Pt/sub 3/(..mu../sub 3/-eta/sup 2/-HCCH) complexes. The chief chemical results are given here.

Douglas, G.; Manojlovic-Muir, L.; Muir, K.W.; Rashidi, M.; Anderson, C.M.; Puddephatt, R.J.

1987-10-14

145

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)

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.

Nadeem, Shahid; Dörsch, Peter; Bakken, Lars

2013-04-01

146

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

PubMed

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

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

2013-10-01

147

A mesofluidic platform integrating on-chip probe ultrasonication for multiple sample pretreatment involving denaturation, reduction, and digestion in protein identification assays by mass spectrometry.  

PubMed

The integration of ultrasound (US)-assisted sample processing on-chip in a lab-on-a-valve (LOV) format for automated high-throughput shotgun proteomic assays is herein presented for the first time. The proof of concept of this system was demonstrated with the analysis of three proteins and sera from patients with lymphoma or myeloma. PMID:24443721

Nunes-Miranda, J D; Núñez, Cristina; Santos, Hugo M; Vale, G; Reboiro-Jato, Miguel; Fdez-Riverola, Florentino; Lodeiro, Carlos; Miró, Manuel; Capelo, J L

2014-03-01

148

An infrared study of the bending region of acetylene  

NASA Astrophysics Data System (ADS)

Acetylene spectra observed with instrumental resolutions of 0.0025 and 0.005 cm-1 were obtained at The National Optical Astronomy Observatory, Tucson, Arizona using the FTS spectrometer at the National Solar Observatory McMath telescope facility. These resolutions are factors of 6 and 3 times, respectively, that of the best prior study in the literature. The higher resolution allowed the assignment of many more low-J Q-branch transitions. The range of optical densities available in this study also allowed the extension of observed and assigned transitions to significantly higher J-values than reported in prior studies. Availability of improved standard lines resulted in high quality transition wavenumbers which are accurate to approximately +/-0.0001 cm-1. Using proven combination difference techniques and analysis software, this study produces the best available molecular parameters for the ?4 and ?5 states of acetylene. In addition, because acetylene has no permanent dipole moment, this study extends the precision of available ground state parameters B0 and D0 and produces for the first time an estimator of H0. In addition to H0 values for both isotopic species treated, we have obtained for the first time a value for H5 for the dominant isotopmer. The value of H5 for the 13C12CH2 was not determined and thus thought to be significantly smaller than H5 for 12C2H2. This study also obtains l-doubling parameters for both degenerate fundamental states in the lesser isotopmer for the first time as well as H4 for both isotopmers and B4 and D4 for the lesser isotopmer. NASA/ASEE Summer Faculty Fellow, NASA/Goddard Space Flight Center, 1986, 1987 (during which periods a portion of this work was completed).

Hillman, J. J.; Jennings, D. E.; Halsey, G. W.; Nadler, Shachar; Blass, W. E.

1991-04-01

149

Electron-paramagnetic-resonance studies on nitrogenase of Klebsiella pneumoniae. Evidence for acetylene- and ethylene-nitrogenase transient complexes.  

PubMed Central

Klebsiella pneumoniae nitrogenase exhibited four new electron-paramagnetic-resonance signals during turnover at 10 degrees C, pH7.4, which were assigned to intermediates present in low concentrations in the steady state. 57Fe-substituted Mo--Fe protein showed that they arose from Fe--S clusters in the Mo--Fe protein of nitrogenase. The new signals are designated: Ic, g values at 4.67, 3.37 and approx. 2.0; VI, g values at 2.125, 2.000 and 2.000; VII, g values at 5.7 and 5.4; VIII, g values at 2.092, 1.974 and 1.933. The sharp axial signal VI arises from a Fe4S4 cluster at the --1 oxidation level. This signal was only detected in the presence of ethylene and provides the first evidence of an enzyme--product complex for nitrogenase. [13C]Acetylene and [13C]ethylene provided no evidence for direct binding of this substrate and product to the Fe--S clusters giving rise to these signals. The dependence of signal intensities on acetylene concentration indicated two types of binding site, with apparent dissociation constants K less than 16 micron and K approximately 13mM. A single binding site for ethylene (K=1.5mM) was detected. A scheme is proposed for the mechanism of reduction of acetylene to ethylene and inhibition of this reaction by CO.

Lowe, D J; Eady, R R; Thorneley, N F

1978-01-01

150

Development of an Acetylene Monitor at the Part Per Billion Level.  

National Technical Information Service (NTIS)

The purpose of this contract was to develop instrumentation for the collection and analysis of atmospheric acetylene at the part per billion level. The reason for measuring acetylene is that it comes primarily from vehicular exhausts and thus can be used ...

W. Dencker M. Robinson R. Villalobos

1974-01-01

151

Excited electronic states of protonated acetylene. II - Anisotropy of the potential energy surface  

Microsoft Academic Search

Extensive ab initio configuration interaction calculations have been carried out for different directions of approach of a proton to a rigid acetylene molecule. The calculated potential energy curves of several singlet states are presented. The anisotropy we found allows us to explain features of the charge transfer mechanism during proton-acetylene collisions as observed in recent molecular beam experiments. An important

F. Schneider; A. Palma; E. Semprini; F. A. Gianturco

1993-01-01

152

Modeling of acetylene pyrolysis under vacuum carburizing conditions of steel in a tubular ?ow reactor  

Microsoft Academic Search

In the present work, the pyrolysis of acetylene was studied under the conditions of vacuum carburizing of steel in a tubular ?ow reactor. The pyrolysis temperature ranges from 650 oC to 1050 oC . The partial pressure of acetylene in the feed mixture was 10 mbar and 20 mbar respectively while the rest of the mixture consisted of nitrogen. The

R. U. Khan; S. Bajohr; F. Graf; R. Reimert

153

Aromatic ring generation as a dust precursor in acetylene discharges  

SciTech Connect

Production of aromatic hydrocarbon compounds as an intermediate step for particle formation in low-pressure acetylene discharges is investigated via a kinetic approach. The detailed chemical reaction mechanism contains 140 reactions among 55 species. The cyclic hydrocarbon chemistry is mainly based on studies of polycyclic aromatic hydrocarbon formation in cosmic environments. The model explicitly includes organic chain, cyclic molecules, radicals, and ions up to a size of 12 carbon atoms. The calculated density profiles show that the aromatic formation yields are quite significant, suggesting that aromatic compounds play a role in the underlying mechanisms of particle formation in hydrocarbon plasmas.

Bleecker, Kathleen de; Bogaerts, Annemie; Goedheer, Wim [PLASMANT, Department of Chemistry, University of Antwerp, Universiteitsplein 1, 2610 Wilrijk (Belgium); FOM-Institute for Plasma Physics 'Rijnhuizen', Association EURATOM-FOM, Trilateral Euregio Cluster, P.O. Box 1207, 3430 BE Nieuwegein (Netherlands)

2006-04-10

154

Protonated acetylene - An important circumstellar and interstellar ion  

NASA Technical Reports Server (NTRS)

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.

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

1992-01-01

155

Ultrafast Extreme Ultraviolet Induced Isomerization of Acetylene Cations  

NASA Astrophysics Data System (ADS)

Ultrafast isomerization of acetylene cations ([HC=CH]+) in the low-lying excited A?g+2 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++CH2+ as a function of time between XUV-pump and -probe pulses, generated by a split-mirror device, we find an isomerization time of 52±15fs in a kinetic energy release (KER) window of 5.8

Jiang, Y. H.; Rudenko, A.; Herrwerth, O.; Foucar, L.; Kurka, M.; Kühnel, K. U.; Lezius, M.; Kling, M. F.; van Tilborg, J.; Belkacem, A.; Ueda, K.; Düsterer, S.; Treusch, R.; Schröter, C. D.; Moshammer, R.; Ullrich, J.

2010-12-01

156

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

PubMed

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 A(2)?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. PMID:23485298

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

2013-03-01

157

Nanosecond discharge ignition in acetylene-containing mixtures  

NASA Astrophysics Data System (ADS)

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.

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

2013-08-01

158

A gasdynamic laser using products of acetylene explosions  

NASA Astrophysics Data System (ADS)

A combustion pulse explosive gasdynamic laser (GDL) has been used to investigate the characteristics of acetylene-air fuel combustion products flow. The 2-liter GDL spherical explosion chamber was connected to the nozzle grid by a flat widening adapter. The chamber and adapter volumes were separated with a copper diaphragm. The explosion products escaped through the nozzle grid to the evacuated 200-liter damper tank with probe windows on the side walls. The nozzle grid (500 mm wide) consisted of ten variable nozzle blades. To obtain a uniform flow in the outlet section, the nozzles were profiled (0.35 mm nozzle throat and 140 area ratio). Gain measurement was carried out in two sections behind the nozzle grid edge. Experimental values of the gain, obtained over the pressure region from 5 to 100 atm at 1800 and 2500 K, is in satisfactory agreement with calculations. Acetylene, nitrogen, and nitrous oxide mixtures produced the best energy characteristics over the investigated experimental region. The specific stored energy values in such mixtures can be as high as 120 J/g, with the pressure from 6 to 10 atm and a temperature of 3100 K.

Britan, A. B.; Khmelevskii, A. N.; Levin, V. A.; Losev, S. A.; Lugovskoi, V. V.; Smekhov, G. D.; Starik, A. M.

159

Photo-double-ionization of ethylene and acetylene near threshold  

NASA Astrophysics Data System (ADS)

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.

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.; Schöffler, M.; Dörner, R.; Gassert, H.; Zeller, S.; Voigtsberger, J.; Cao, W.; Zohrabi, M.; Williams, J.; Gatton, A.; Reedy, D.; Nook, C.; Müller, Thomas; Landers, A. L.; Cocke, C. L.; Ben-Itzhak, I.; Jahnke, T.; Belkacem, A.; Weber, Th.

2014-01-01

160

The Acetylene Laboratory IR Spectrum: New Quantitative Studies  

NASA Astrophysics Data System (ADS)

The acetylene molecule 12C2H2 shows numerous vibration - rotation bands throughout the IR spectrum. Vibrational levels of C2H2 are grouped into clusters almost regularly spaced every 700 cm-1, from the fundamental ?5 band, at 13.6 ?m, up to the visible. Several IR spectral regions where C2H2 bands occur have been extensively studied in the past years, mainly in order to obtain absolute individual line intensities and to improve spectroscopic databases as HITRAN or GEISA. This quantitative spectroscopy work is performed with the aid of Fourier transform interferometers to obtain absorption spectra, and using a multispectrum fitting procedure to retrieve line parameters from these spectra. For usual applications, a semi-empirical model based on the Herman-Wallis factor is used to generate line lists dedicated to spectroscopic databases. This poster gives a summary of all the spectral regions studied for acetylene 12C2H2, pointing out the current state of the spectroscopic databases HITRAN/GEISA. Works in progress (around 1300 cm-1) and in project (0 - 500 cm-1) will also be presented. Data available in the literature, or obtained in the recent works, have been compiled to set up line lists usable for applications and dedicated to databases. On the whole the number of transitions is twice compared to the actual HITRAN 2004 database plus the 2007 updates and is ranging from 700 to 9600 cm-1.

Jaccquemart, D.; Lacome, N.; Gomez, L.; Mandin, J.

2011-12-01

161

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

PubMed

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

Oremland, Ronald S; Voytek, Mary A

2008-02-01

162

Determination of total antioxidant capacity by a new spectrofluorometric method based on Ce(IV) reduction: Ce(III) fluorescence probe for CERAC assay.  

PubMed

A Ce(IV)-based reducing capacity (CERAC) assay was developed to measure the total antioxidant capacity (TAC) of foods, in which Ce(IV) would selectively oxidize antioxidant compounds but not citric acid and reducing sugars which are not classified as antioxidants. The method is based on the electron-transfer (ET) reaction between Ce(IV) ion and antioxidants in optimized acidic sulphate medium (i.e., 0.3 M H(2)SO(4) and 0.7 M Na(2)SO(4)) and subsequent determination of the produced Ce(III) ions by a fluorometric method. The fluorescent product, Ce(III), exhibited strong fluorescence at 360 nm with an excitation wavelength of 256 nm, the fluorescence intensity being correlated to antioxidant power of the original sample. The linear concentration range for most antioxidants was quite wide, e.g., 5.0 × 10(-7)-1.0 × 10(-5) M for quercetin. The developed procedure was successfully applied to the TAC assay of antioxidant compounds such as trolox, quercetin, gallic acid, ascorbic acid, catechin, naringin, naringenin, caffeic acid, ferulic acid, glutathione, and cysteine. The proposed method was reproducible, additive in terms of TAC values of constituents of complex mixtures, and the trolox equivalent antioxidant capacities (TEAC coefficients) of the tested antioxidant compounds gave good correlations with those found by reference methods such as ABTS and CUPRAC. PMID:21617997

Ozyurt, Dilek; Demirata, Birsen; Apak, Resat

2011-11-01

163

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

NASA Astrophysics Data System (ADS)

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⋯? and C sbnd H⋯O interactions. In this complex boric acid acts as a proton donor to the acetylene ?-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.

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

2011-04-01

164

Copper-promoted reductive homocoupling of quasi-aromatic iron(II) clathrochelates: boosting the inhibitory activity in a transcription assay.  

PubMed

A copper-promoted reductive homocoupling reaction, for the first time used for a metal complex, allowed obtaining a new kind of complexes with the encapsulated metal ions, C-C conjugated bis-clathrochelates. These compounds demonstrate extremely high transcription inhibition activity in the T7 RNA polymerase system with values of IC50 reaching as low as the submicromolar range, which places them among the most potent metal-based transcription inhibitors. PMID:24516860

Varzatskii, O A; Novikov, V V; Shulga, S V; Belov, A S; Vologzhanina, A V; Negrutska, V V; Dubey, I Y; Bubnov, Yu N; Voloshin, Ya Z

2014-03-25

165

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

PubMed

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 ?8%, while mixed species are produced at low concentrations (?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 (C2H2)n(+). At the electron energies ?21.5 eV above the CH+CH(+) dissociative ionization limit of acetylene the fragment ions nominally labelled as (C2H2)nCH(+), n ? 2, are observed. For n ? 7 these fragments correspond to covalently bound ionic structures as suggested by the observed strong dehydrogenation [(C2H2)n - k × H](+) and [(C2H2)nCH - k × H](+). The dehydrogenation is significantly reduced in the mixed clusters where evaporation of Ar instead of hydrogen can stabilize the nascent molecular ion. The C3H3(+) ion was previously assigned to originate from the benzene molecular ion; however, the low appearance energy of ?13.7 eV indicates that a less rigid covalently bound structure of C6H6(+) ion must also be formed upon the acetylene cluster electron ionization. The appearance energy of Arn(C2H2)(+) fragments above ?15.1 eV indicates that the argon ionization is the first step in the fragment ion production, and the appearance energy of Arn?2(C2H2)m?2(+) at ?13.7 eV is discussed in terms of an exciton transfer mechanism. PMID:23556722

Ko?išek, J; Lengyel, J; Fárník, M

2013-03-28

166

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

NASA Astrophysics Data System (ADS)

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 ~8%, while mixed species are produced at low concentrations (~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 (C2H2)n+. At the electron energies >=21.5 eV above the CH+CH+ dissociative ionization limit of acetylene the fragment ions nominally labelled as (C2H2)nCH+, n >= 2, are observed. For n <= 7 these fragments correspond to covalently bound ionic structures as suggested by the observed strong dehydrogenation [(C2H2)n - k × H]+ and [(C2H2)nCH - k × H]+. The dehydrogenation is significantly reduced in the mixed clusters where evaporation of Ar instead of hydrogen can stabilize the nascent molecular ion. The C3H3+ ion was previously assigned to originate from the benzene molecular ion; however, the low appearance energy of ~13.7 eV indicates that a less rigid covalently bound structure of C6H6+ ion must also be formed upon the acetylene cluster electron ionization. The appearance energy of Arn(C2H2)+ fragments above ~15.1 eV indicates that the argon ionization is the first step in the fragment ion production, and the appearance energy of Arn>=2(C2H2)m>=2+ at ~13.7 eV is discussed in terms of an exciton transfer mechanism.

Ko?išek, J.; Lengyel, J.; Fárník, M.

2013-03-01

167

Assay of neutralizing antibody against variola virus by the degree of focus reduction on HeLa cell cultures and its application to revaccination with smallpox vaccines of various potencies  

PubMed Central

A method for assaying neutralizing antibody against variola virus was established by focus counting on HeLa cell cultures. The ND50 titre, i.e., the serum dilution endpoint to give a 50% reduction in the number of foci, was determined with excellent reproducibility. Groups of students 19-20 years of age were revaccinated by the multiple pressure method with serial 10-fold dilutions of a smallpox vaccine and their neutralizing antibody response was assayed by the focus counting assay system and was related to the local skin reactions on the seventh day after inoculation and to the potency of the vaccine administered. There was a significant rise in the antibody level even after inoculation with a vaccine whose potency was as low as 1.3 × 105 pock-forming units/ml. In general, the rise in the log antibody level was proportional to the diameter of the reddening, but a significant rise was found among individuals who had no detectable skin reaction. The skin reaction was greater among individuals with a lower initial antibody level when the vaccine administered had a potency lower than 1.3 × 106 pock-forming units/ml.

Kitamura, Takashi; Shinjo, Nagashige

1972-01-01

168

Inhibition of alkylbenzene biodegradation under denitrifying conditions by using the acetylene block technique.  

PubMed Central

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 degraded at a slower rate than usual. Benzene was not degraded in either case. Addition of acetylene to microcosms preexposed to nitrate and alkylbenzenes produced similar inhibition. These data indicate that the activities of microorganisms that degrade alkylbenzenes under denitrifying conditions may be suppressed if the standard acetylene block technique is used to verify denitrifying activity.

Hutchins, S R

1992-01-01

169

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

NASA Technical Reports Server (NTRS)

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.

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

1986-01-01

170

ESI-MS, DFT and Synthetic Studies on the H2-Mediated Coupling of Acetylene: Insertion of C=X Bonds into Rhodacyclopentadienes and Br?nsted Acid Cocatalyzed Hydrogenolysis of Organorhodium Intermediates  

PubMed Central

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 alternative reaction products. ESI-MS analysis of reaction mixtures from the hydrogen-mediated reductive coupling of acetylene to ?-ketoesters or N-benzenesulfonyl aldimines corroborate a catalytic mechanism involving C=X (X = O, NSO2Ph) insertion into a cationic rhodacyclopentadiene obtained by way of acetylene oxidative dimerization with subsequent Brønsted acid cocatalyzed hydrogenolysis of the resulting oxa- or azarhodacycloheptadiene. Hydrogenation of 1,6-diynes in the presence of ?-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 multi-stage collisional activated dissociation (CAD) ESI-MS 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 aldehyde in the absence of hydrogen or Brønsted acid cocatalyst provides the corresponding (Z)-butadienyl ketone, which arises from ?-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 Brønsted 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.

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

2009-01-01

171

Organogermanium Chemistry: Germacyclobutanes and digermane Additions to Acetylenes  

SciTech Connect

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.

Andrew Michael Chubb

2003-12-12

172

Acetylenic-terminated fluorinated polyimide, properties and applications  

SciTech Connect

A new line of acetylene-terminated, oligomeric polyimides has been introduced for aerospace and electronic applications. The oligomers are derived from the monomers 4,4'-hexafluoroisopropylidinebis(phthalic anhydride), 1,3'-bis(3-aminophenoxy)benzene, and 3-ethynylaniline. They are fully imidized and cure by reactions of the terminal ethynyl groups. These products have unique properties when compared with similar systems containing nonfluorinated dianhydrides. Studies have shown improved solubility in a variety of solvents and stable solutions at high concentrations. The glass transition temperature is in the 300-350 C range. Decomposition by thermal gravimetric analysis (TCA), occurs at about 550 C. The weight loss by isothermal TGA is less than 1.0 percent per hour at 400 C in air. The dielectric constants are less than 3.0 over a wide range of frequencies. 9 references.

Capo, D.J.; Schoenberg, J.E.

1987-04-01

173

Detection of acetylene in the infrared spectrum of comet Hyakutake.  

PubMed

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. PMID:8857534

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

1996-10-17

174

Mass spectra of acetylenic fatty acid methyl esters and derivatives.  

PubMed

A series of isomeric methyl octadecynoates was analyzed by mass spectrometry; each isomer gave a unique spectrum. The characteristic ions were those resulting from a McLafferty rearrangement of the allenic sites or of the already-rearranged allenic sites. The acetylenic esters were also subjected to oxymercuration whereupon a carbonyl group was formed at either of the original actylenic carbon atoms providing two oxostearates. Further reaction with NaBH4 formed hydroxy esters which, after silylation, gave diagnostic mass spectra indicative of the triple bond location. Applied to esters with both double and triple bonds, this procedure permitted differentiation between the two types of unsaturation. Methoxyl groups marked the original double bond locations and hydroxyls did so for triple bonds. PMID:972578

Kleiman, R; Bohannon, M B; Gunstone, F D; Barve, J A

1976-08-01

175

Acetylene fuel from atmospheric CO2 on Mars  

NASA Technical Reports Server (NTRS)

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.

Landis, Geoffrey A.; Linne, Diane L.

1992-01-01

176

Decoupling in the line mixing of acetylene infrared Q branches  

NASA Technical Reports Server (NTRS)

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.

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

1990-01-01

177

Detection of acetylene in the infrared spectrum of comet Hyakutake  

NASA Technical Reports Server (NTRS)

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.

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

1996-01-01

178

Kinetic tetrazolium microtiter assay  

NASA Technical Reports Server (NTRS)

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.

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

1992-01-01

179

One-pot synthesis of metalated pyridines from two acetylenes, a nitrile, and a titanium(II) alkoxide.  

PubMed

Four-component coupling process involving two acetylenes, a nitrile, and a divalent titanium alkoxide reagent, Ti(O-i-Pr)(4)/2i-PrMgCl, directly yielded titanated pyridines in a highly selective manner. The reaction can be classified into four categories: (i) a combination of an internal acetylene, a terminal acetylene, sulfonylnitrile, and the titanium reagent to yield alpha-titanated pyridines, (ii) a combination of an internal acetylene, a (sulfonylamino)acetylene, a nitrile, and the titanium reagent to yield alternative alpha-titanated pyridines, (iii) a combination of an internal acetylene, a (sulfonylamino)acetylene, a nitrile, and the titanium reagent to yield titanated aminopyridines, and (iv) a combination of an acetylenic amide, a terminal acetylene, a nitrile, and the titanium reagent to yield pyridineamides with their side chain titanated. Some of these reactions enabled virtually completely regioselective coupling of two different, unsymmetrical acetylenes and a nitrile to form a single pyridine. Synthetic applications of these reactions have been illustrated in the preparation of optically active pyridines and medicinally useful compounds. PMID:15913367

Tanaka, Ryoichi; Yuza, Akio; Watai, Yuko; Suzuki, Daisuke; Takayama, Yuuki; Sato, Fumie; Urabe, Hirokazu

2005-06-01

180

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

Code of Federal Regulations, 2013 CFR

...suitable pressure at the outlet stations. (c) Acetylene distribution...Relief devices shall discharge to a location in the weather at least 3 m (10 ft) from sources...spaces or tanks. (j) Outlet stations are to be provided with...

2013-10-01

181

46 CFR 151.50-79 - Methyl acetylene-propadiene mixture.  

Code of Federal Regulations, 2011 CFR

...acetylene-propadiene mixture must have a refrigeration system that does not compress the cargo vapor or have a refrigeration system with the following features...piping system, including the cargo refrigeration system, for tanks to be...

2011-10-01

182

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...

183

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...

184

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

Code of Federal Regulations, 2010 CFR

...pressure at the outlet stations. (c) Acetylene distribution piping and pipe fittings must be seamless steel. Copper alloys containing less than 65 percent copper may be used in connection with valves, regulators, gages, and other...

2010-10-01

185

Structure of the non-redox-active tungsten/[4Fe:4S] enzyme acetylene hydratase  

PubMed Central

The tungsten–iron–sulfur enzyme acetylene hydratase stands out from its class because it catalyzes a nonredox reaction, the hydration of acetylene to acetaldehyde. Sequence comparisons group the protein into the dimethyl sulfoxide reductase family, and it contains a bis-molybdopterin guanine dinucleotide-ligated tungsten atom and a cubane-type [4Fe:4S] cluster. The crystal structure of acetylene hydratase at 1.26 ? now shows that the tungsten center binds a water molecule that is activated by an adjacent aspartate residue, enabling it to attack acetylene bound in a distinct, hydrophobic pocket. This mechanism requires a strong shift of pKa of the aspartate, caused by a nearby low-potential [4Fe:4S] cluster. To access this previously unrecognized W–Asp active site, the protein evolved a new substrate channel distant from where it is found in other molybdenum and tungsten enzymes.

Seiffert, Grazyna B.; Ullmann, G. Matthias; Messerschmidt, Albrecht; Schink, Bernhard; Kroneck, Peter M. H.; Einsle, Oliver

2007-01-01

186

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

NASA Technical Reports Server (NTRS)

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.

Walch, Stephen P.; Taylor, Peter R.

1995-01-01

187

A copper-free palladium catalyzed cross coupling reaction of vinyl tosylates with terminal acetylenes  

Microsoft Academic Search

A copper-free palladium-catalyzed cross coupling of vinyl tosylate (2) and terminal acetylenes was investigated, affording a convenient and efficient method for construction of an sp–sp2 carbon?carbon bond. The tosylate (2) derived from 1,3-cyclohexanedione was reacted with terminal acetylene under the copper-free conditions at ambient temperature, in the presence of palladium acetate and triphenylphosphine, to provide the conjugated en-yn-one products in

Xiaoyong Fu; Shuyi Zhang; Jianguo Yin; Doris P. Schumacher

2002-01-01

188

Experiments on ceramic formation from liquid precursor spray axially injected into an oxy-acetylene flame  

Microsoft Academic Search

An aqueous ceramic precursor solution was sprayed axially into an oxy-acetylene flame to produce yttria-stabilized zirconia ceramic deposits. Temperature and velocity fields of the oxy-acetylene flame were characterized by chemiluminescence and particle image velocimetry. Deposit samples were extracted from the flame at several downstream locations to study deposit evolution. The deposit phase and morphology were determined from Raman spectroscopy and

Alper Ozturk; Baki M. Cetegen

2005-01-01

189

Adhesion of Natural Rubber Compounds to Plasma-Polymerized Acetylene Films  

Microsoft Academic Search

Plasma-polymerized acetylene films were shown to be novel, highly effective primers for rubber-to-steel bonding. However, the performance of the primers depended strongly on processing variables such as the substrate pretreatment and the carrier gas. Miniature lap joints were prepared by using natural rubber as an “adhesive” to bond together pairs of pretreated steel adherends primed with plasma-polymerized acetylene films which

Y. M. Tsai; F. J. Boerio; Dong K. Kim

1997-01-01

190

Predictive model for the carbon concentration profile of vacuum carburized steels with acetylene  

Microsoft Academic Search

A predictive model for the carbon concentration profile in vacuum carburized steels with acetylene was proposed. The model\\u000a involves the process and boundary conditions based on the characteristic of vacuum carburizing with acetylene and carbon diffusivity\\u000a with an alloying element effect. In order to verify the predictive model, the carbon concentration profile of a cylindrical\\u000a SCM415 steel specimen vacuum carburized

Minsu Jung; Sehoon Oh; Young-Kook Lee

2009-01-01

191

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

SciTech Connect

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.

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

1986-05-01

192

Storage and sorption properties of acetylene in jungle-gym-like open frameworks.  

PubMed

The acetylene-sorption properties of six porous coordination polymers (PCPs), [M(2)(L)(2)(dabco)](n) (dabco=1,4-diazabicyclo[2.2.2]octane, M=Cu(2+) (1), Zn(2+) (2), L=1,4-benzenedicarboxylate (bdc; 1 a, 2 a), 1,4-naphthalenedicarboxylate (ndc; 1 b, 2 b), 9,10-anthracenedicarboxylate (adc; 1 c, 2 c)), were investigated. The acetylene sorption isotherms of 1 and 2 measured at 195 K are of type I and show a steep increase at low relative pressures. The sorption properties of carbon dioxide at 195 K were also investigated. Compounds 1 and 2 showed a large difference in onset pressure between acetylene sorption isotherms, although the difference between the carbon dioxide sorption isotherms is not so significant. In particular, 2 c displayed a remarkable affinity for acetylene. The acetylene sorption isotherm at 298 K showed that the adsorption amounts for 2 c and 2 b at 298 K, 1 atm (101 and 106 mL g(-1), respectively) were higher than those of other conventional porous materials. Notably, of the compounds 1 and 2, the porous crystals 2 c had the highest affinity for acetylene. PMID:18618609

Tanaka, Daisuke; Higuchi, Masakazu; Horike, Satoshi; Matsuda, Ryotaro; Kinoshita, Yoshinori; Yanai, Nobuhiro; Kitagawa, Susumu

2008-09-01

193

NIR diode laser-based QEPAS for acetylene detection  

NASA Astrophysics Data System (ADS)

Quartz-enhanced photoacoustic spectroscopy with a near infrared distributed feedback diode laser at 1.53 ?m is demonstrated for acetylene detection at atmospheric pressure and room temperature. The P(9) absorption line in the ?1+?3 band of C2H2 is selected for light absorption and photoacoustic pressure wave excitation. A pair of resonant tubes with optimal dimensions is used in combination with a quartz tuning fork for photoacoustic signal enhancement. The wavelength of diode laser is modulated at half of the resonant frequency of tuning fork for second harmonic signal detection. The effect of residual amplitude modulation is theoretically analyzed and compared with the experimental results. A noise-limited minimum detectable concentration (1?) of 2 part-per-million (ppm) is achieved with a 7-mW laser power and a 1-s lock-in time constant, corresponding to a normalized noise equivalent absorption coefficient of 5.4×10-8 cm-1 W/?Hz.

Cao, Yingchun; Jin, Wei; Ho, Hoi Lut

2012-05-01

194

An improved processible acetylene-terminated polyimide for composites  

NASA Technical Reports Server (NTRS)

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.

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

1985-01-01

195

Acetylene-chromene terminated resins as high temperature thermosets  

NASA Technical Reports Server (NTRS)

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.

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

1990-01-01

196

Status on the Global Vibration-Rotation Model in Acetylene  

NASA Astrophysics Data System (ADS)

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. Cané, L. Fusina, F. Tamassia, A. Fayt, S. Robert, and M. Herman, J.Q.S.R.T., 109, 2846 (2008).

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

2009-06-01

197

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...

198

Effect of amendments, moisture and temperature on acetylene reduction in nile delta soils  

Microsoft Academic Search

Summary The pattern of N2-ase activity in clay-loam soil of Nile Delta was determined. However, unamended soil showed somewhat low activity: an amount of 18–95 mg N2 fixed\\/kg soil\\/year was calculated. Addition of glucose greatly enhanced such activity and efficiencies of N2-fixation increased with decreasing carbon source concentration. Highest activities (800 n moles C2H4\\/gh?1) and efficiencies (18.06 mg N2\\/g glucose

N. A. Hegazi; K. Vlassak; M. Monib

1979-01-01

199

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

SciTech Connect

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.

Kocisek, J.; Lengyel, J.; Farnik, M. [J. Heyrovsky Institute of Physical Chemistry v.v.i., Academy of Sciences of the Czech Republic, Dolejskova 3, 18223 Prague (Czech Republic)

2013-03-28

200

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

NASA Technical Reports Server (NTRS)

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.

McLaren, Ian A.; Wrobel, Jacek D.

1997-01-01

201

Catalytic conversion of acetylene to polycyclic aromatic hydrocarbons over particles of pyroxene and alumina.  

PubMed

Polycyclic aromatic hydrocarbons (PAHs) are known to be present in many astrophysical objects and environments, but our understanding of their formation mechanism(s) is far from satisfactory. In this paper, we describe an investigation of the catalytic conversion reaction of acetylene gas to PAHs over pyroxene and alumina. Crystalline silicates such as pyroxenes (with general formula [Mg, Fe]SiO?) and alumina (Al?O?) are observed astrophysically through their infrared spectra and are likely to promote grain surface chemical reactions. In the experiments reported here, gas-phase PAHs were produced by the catalytic reaction of acetylene over crystalline silicates and alumina using a pulsed jet expansion technique and the gaseous products detected using time-of-flight mass spectrometry. In a separate experiment, the catalytic formation of PAHs from acetylene was further confirmed with acetylene gas at atmospheric pressure flowing continuously through a fixed-bed reactor. The gas effluent and carbonaceous compounds deposited on the catalysts were dissolved separately in dichloromethane and analysed using gas chromatography-mass spectrometry. Among the samples studied, alumina showed higher activity than the pyroxene-type grains for the acetylene reaction. It is proposed that formation of the PAHs relies on the Mg²? ions in the pyroxenes and Al³? ions in alumina, where these ions act as Lewis acid sites. X-ray diffraction, Fourier transform infrared and high-resolution transmission electron microscopy techniques were used to characterize the structure and physical properties of the pyroxene and alumina samples. PMID:23734053

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

2013-07-13

202

Infrared Spectra and Optical Constants of Acetylene and Ethane Ices  

NASA Astrophysics Data System (ADS)

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 NASA’s Planetary Atmospheres, Outer Planets, and Cassini Data Analysis programs, and The Goddard Center for Astrobiology.

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

2012-10-01

203

Direct conversion of methane to acetylene or syngas at room temperature using non-equilibrium pulsed discharge  

Microsoft Academic Search

Non-catalytic direct conversion of methane to valuable products was studied using non-equilibrium pulsed discharge under the conditions of ambient temperature and atmospheric pressure. Acetylene was produced with 95% selectivity and 52% methane conversion. An addition of oxygen, carbon dioxide and steam contributed significantly to suppress the carbon deposition and produced carbon monoxide as well as acetylene. Methane conversion increased with

Shigeru Kado; Kohei Urasaki; Yasushi Sekine; Kaoru Fujimoto

2003-01-01

204

First-principles study of acetylene adsorption on Si(100):??The end-bridge structure  

NASA Astrophysics Data System (ADS)

We present the results of a first-principles study of the adsorption of acetylene on Si(100). In particular, we focus on a recent controversial issue concerning the occurrence of the “end-bridge” configuration in which an acetylene molecule bridges two adjacent surface Si dimers. At variance with recent theoretical calculations, we find that the lowest-energy “end-bridge” structure is stable and nonmetallic both at 0.5 ML and at 1.0 ML coverage. This leads to the conclusion that this configuration can be one of those observed in experiments. The results of first-principles calculations of the optical properties of different configurations of acetylene on Si(100) are also presented and discussed.

Silvestrelli, Pier Luigi; Pulci, Olivia; Palummo, Maurizia; del Sole, Rodolfo; Ancilotto, Francesco

2003-12-01

205

Building a parent iridabenzene structure from acetylene and dichloromethane on an iridium center.  

PubMed

Parenthood: The reaction of [TpIr(C2H4)2] (1) (Tp=hydrotris(pyrazolyl)borate) with acetylene in CH2 Cl2 affords a 1:1 mixture of the "parent" metallabenzene 2 (that is, all the ring carbon centers are CH units) and the ?-Cl substituted vinyl species 3. Generation of 2 is by the coupling of an iridacyclopentadiene (formed from two acetylene molecules at the Ir center) with the dichloromethane-derived chlorocarbene ":C(H)Cl" and a subsequent ?-Cl elimination event. PMID:23934753

Vivancos, Ángela; Paneque, Margarita; Poveda, Manuel L; Álvarez, Eleuterio

2013-09-16

206

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

NASA Technical Reports Server (NTRS)

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.

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

1994-01-01

207

Matrix infrared spectra of aluminum, gallium, and indium complexes with acetylene  

SciTech Connect

Aluminum, gallium, and indium atoms have been codeposited from thermal sources with C[sub 2]H[sub 2] at high dilution in argon on a 12[plus minus]1 K CsI window. The major products are best characterized as 1/1 [pi] complexes where the metal shares electron density from one acetylene [pi] orbital. Higher reagent concentrations give evidence for 1/2 and 2/1 metal-acetylene complexes. In the case of aluminum, photolysis induces insertion to form HAlC[sub 2]H and AlC[sub 2]H.

Burkholder, T.R.; Andrews, L. (Univ. of Virginia, Charlottesville (United States))

1993-05-26

208

Quantum-chemical modeling of ethylene and acetylene adsorption on gold clusters  

NASA Astrophysics Data System (ADS)

The interaction of ethylene and acetylene molecules with planar (2D) and nonplanar (3D) gold clusters Au n ( n = 10, 12, 20) was studied by the density functional theory (DFT) method. The coordination of hydrocarbons at the vertices, edges, and fragments of the Au3 cluster was shown to form ?, di-?, and ? type complexes, respectively. The standard Gibbs energy and the C-C bond length of the hydrocarbon change during its adsorption in the series ? > di-? > ? complexes. The highest selectivity in adsorption of acetylene relative to that of ethylene was achieved on Au12 (3D) and Au20 (2D) clusters.

Pichugina, D. A.; Nikolaev, S. A.; Mukhamedzyanova, D. F.; Kuz'menko, N. E.

2014-06-01

209

Meridional Variations of Acetylene and Ethane On Jupiter  

NASA Astrophysics Data System (ADS)

Hydrocarbons such as acetylene (C2H2) and ethane (C2H6) are important tracers in Jupiter's atmosphere, constraining our models of the chemical and dynamical processes. However, our knowledge of the vertical and meridional variations of their abundances has remained sparse. During the flyby of the Cassini spacecraft in December 2000, the Composite Infrared Spectrometer (CIRS) instrument was used to map the spatial variation of emissions from 10--1400 cm-1 (1000--7 ? m). We have analyzed a zonally-averaged set of CIRS spectra taken at the highest (0.5 cm-1) resolution, to infer atmospheric temperatures in the stratosphere at 0.5--20 mbar via the ? 4 band of CH4, and in the troposphere at 150--400 mbar, via the H2 absorption at 600--800 cm-1 . Simultaneously, we retrieve the abundances of C2H2 and C2H6 via the ? 5 and ? 9 bands respectively. We find that the column abundance of C2H2 decreases sharply towards the poles by a factor ˜4, while C2H6\\ is unchanged in the north and increasing in the south, by a factor ˜1.8. An explanation for the meridional trends is proposed in terms of a combination of photochemistry and dynamics. Poleward, the decreasing UV flux is predicted to decrease the abundances of C2H2 and C2H6 by factors 2.7 and 3.5 respectively at a latitude 70o. However, the lifetime of C2H6\\ in the stratosphere (5×109 s) is much longer than the dynamical timescale for meridional motions inferred from SL-9 debris (5×108 s), and therefore the constant or rising abundance towards high latitudes likely indicates that meridional mixing dominates over photochemical effects. For C2H2, the opposite occurs, with the relatively short photochemical lifetime (3×107 s), compared to meridional mixing times, ensuring that the expected photochemical trends are visible.

Nixon, C. A.; Teanby, N. A.; Irwin, P. G. J.; Achterberg, R. K.; Romani, P. N.; Cassini CIRS Team

2005-08-01

210

Heats of Formation of Triplet Ethylene, Ethylidene, and Acetylene  

SciTech Connect

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.

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

2007-06-28

211

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

PubMed

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

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

2013-07-01

212

Hexosaminidase assays.  

PubMed

beta-Hexosaminidases (EC 3.2.1.52) are lysosomal enzymes that remove terminal beta-glycosidically bound N-acetylglucosamine and N-acetylgalactosamine residues from a number of glycoconjugates. Reliable assay systems are particularly important for the diagnosis of a family of lysosomal storage disorders, the GM2 gangliosidoses that result from inherited beta-hexosaminidase deficiency. More recently, aberrant hexosaminidase levels have also been found to be associated with a variety of inflammatory diseases. Apart from patient testing and carrier screening, practical in vitro assays are indispensable for the characterization of knock-out mice with potentially altered hexosaminidase activities, for detailed structure-function studies aimed at elucidating the enzymatic mechanism, and to characterize newly described enzyme variants from other organisms. The purpose of this article is to discuss convenient hexosaminidase assay procedures for these and other applications, using fluorogenic or chromogenic artificial substrates as well as the physiological glycolipid substrate GM2. Attempts are also made to provide an overview of less commonly used alternative techniques and to introduce recent developments enabling high-throughput screening for enzyme inhibitors. PMID:18473163

Wendeler, Michaela; Sandhoff, Konrad

2009-11-01

213

Acetylene and Ethane Vertical Distribution on Saturn from Cassini/CIRS Observations  

NASA Astrophysics Data System (ADS)

Acetylene and ethane are the two major products of the CH4 photolysis in the stratosphere of Saturn. They are formed in the homopause region, and migrate to deeper levels under the influence of eddy mixing diffusion and possibly vertical advection. Ethane presents a lifetime longer than the mixing timescale. It is therefore a good tracer of transport processes in the stratosphere. Acetylene lifetime is shorter than that of ethane. For this reason it is more sensitive to chemical sources and sinks. We will present ethane and acetylene vertical profiles derived from Cassini/CIRS limb and nadir observations. The stratospheric temperature profile is retrieved from the CH4 ? 4 band, ethane and acetylene are observed in their ? 9 and ? 5 bands respectively. Limb observations yield a higher vertical resolution than nadir observations but are restricted to specific geographical points. The use of both nadir and limb observations will allow us to monitor any spatial changes on the vertical profiles that would provide insight into Saturn's stratospheric dynamics.

Fouchet, T.; Lellouch, E.; Bézard, B.; Howett, C.; Irwin, P. G. J.; Nixon, C. A.; Simon-Miller, A. A.; Flasar, F. M.; CIRS Team

2005-08-01

214

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 ...

215

Synthesis, Polymerization and Thermal Properties of a New Acetylene-Terminated Schiff Base.  

National Technical Information Service (NTIS)

A new acetylene-terminated Schiff base monomer, N, N1-(1,4-phenylenedimethylidyne)-bis-(4-ethynylaniline)(PPP), was synthesized and was characterized by nuclear magnetic resonance and infrared spectroscopy. This monomer was then polymerized to yield a new...

Y. Wei R. Hariharan J. K. Ray

1991-01-01

216

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...

217

Quantifying Momentum Transfer Due to Blast Waves from Oxy-Acetylene Driven Shock Tubes.  

National Technical Information Service (NTIS)

Shock tubes have been widely used since the 1950s to study physical phenomena such as shock waves, combustion chemistry, and the response of materiel to blast loading. Recently, laboratory-scale shock tubes driven by oxy- acetylene were described. It was ...

A. Courtney H. Her M. Courtney

2012-01-01

218

Acetylenic fatty acids, triglyceride and triterpenes from the leaves of Hymenodictyon excelsum.  

PubMed

Two new acetylenic fatty acids (1, 2), a new triglyceride (3), along with eleven known compounds including 3-oxo-11alpha,12alpha-epoxyurs-13beta,28-olide (4) previously reported as a synthetic compound, have been isolated from the leaves of Hymenodictyon excelsum. The structural identification was established from spectroscopic data. PMID:19652413

Nareeboon, Parichat; Komkhunthot, Wichan; Lekcharoen, Decha; Wetprasit, Nuanchawee; Piriyapolsart, Chudaporn; Sutthivaiyakit, Somyote

2009-08-01

219

Anthranilate sulfonamide hydroxamate TACE inhibitors. Part 2: SAR of the acetylenic P1' group.  

PubMed

The SAR of a series of potent sulfonamide hydroxamate TACE inhibitors bearing novel acetylenic P1' groups was explored. In particular, compound 4t bearing a butynyloxy P1' moiety has excellent in vitro potency against isolated TACE enzyme and in cells, good selectivity over MMP-1 and oral activity in an in vivo model of TNF-alpha production. PMID:11934588

Levin, J I; Chen, J M; Du, M T; Nelson, F C; Killar, L M; Skala, S; Sung, A; Jin, G; Cowling, R; Barone, D; March, C J; Mohler, K M; Black, R A; Skotnicki, J S

2002-04-22

220

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

NASA Technical Reports Server (NTRS)

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.

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

1989-01-01

221

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

ERIC Educational Resources Information Center

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…

Cox, Marilyn Blagg; Krause, Paul

1994-01-01

222

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...

223

Simulations of Shock-Induced Mixing and Combustion of an Acetylene Cloud in a Chamber.  

National Technical Information Service (NTIS)

In this paper we present numerical simulations of the interaction of a blast wave with an acetylene bubble in a closed chamber. We model the system using the inviscid Euler equations for a mixture of ideal gases. The formulation specifies the thermodynami...

J. B. Bell M. S. Day V. E. Beckner A. L. Kuhl P. Neuwald

2001-01-01

224

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

Microsoft Academic Search

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

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

1996-01-01

225

Species Densities and Temperatures in an Argon-Acetylene RF Plasma using Mass Energy Analysis  

NASA Astrophysics Data System (ADS)

We report species measurements made with a Hiden EQP Mass Energy Analyser in a Diamond like Carbon Plasma Enhanced Physical Vapour Deposition system. Argon/acetylene fractions of 0% to 100% argon, pressures from 3 to 20 mTorr and RF powers up to 180 W ( ˜500 V d.c. bias), were used, concentrating near optimum DLC deposition conditions (10 sccm argon, 20 sccm acetylene, 7 mTorr, 150 W, 450 V dc bias). Initial neutral species results show, for all RF powers, at constant chamber pressure, altering the argon fraction causes the expected linear variation in argon and acetylene count rate. For a 33% argon fraction at near constant pressure ( ˜7 mTorr), however, acetylene count rates fall significantly as RF power is raised, argon count rates are almost constant. If the drop in total count rate (and thus number density) at constant pressure is due to a neutral temperature rise, it implies a temperature of 300 C at 160 W. Ionic species/energy measurements and comparison of species density with deposition rate will also be presented.

Mahony, C. M. O.; McPeake, G. L.; Maguire, P. D.

2004-09-01

226

Synthesis of pyrrolo[2,1- a]isoquinolines from activated acetylenes, benzoylnitromethanes, and isoquinoline  

Microsoft Academic Search

Isoquinoline reacts smoothly with aroylnitromethanes in the presence of dialkyl acetylenedicarboxylates and dibenzoylacetylene to produce pyrrolo[2,1-a]isoquinolines in good yields. Quinoline and benzothiazole also react in a similar way. Pyridine and N-methylimidazole catalyze the reaction between nitromethane derivatives with electron-deficient acetylenes to produce highly functionalized isoxazoles.

Issa Yavari; Mohammad Piltan; Loghman Moradi

2009-01-01

227

Seasonal Variations of Temperature, Acetylene and Ethane in Saturn's Stratosphere from 2005 to 2010  

NASA Astrophysics Data System (ADS)

Acetylene (C2H2) and ethane (C2H6) exemplify by-products of complex photochemistry in Saturn’s stratosphere. Their relative stability together with their strong vertical gradients in concentration allow for their use as tracers of vertical motion in Saturn’s lower stratosphere. Earlier studies of Saturn's hydrocarbons have provided only a snapshot of their behaviour with temporal variations remaining to be determined. In this study, we investigate how the thermal structure and concentrations of acetylene and ethane have evolved on Saturn with the changing season. We use FIRMAP (15.5 cm-1 spectral resolution) Cassini-CIRS observations, initially retrieve temperature and subsequently retrieve the abundances of acetylene and ethane. In comparing 2005, 2009 and 2010 results, we observe the disappearance of Saturn's southern warm polar hood with cooling of up to 18.6 K ± 0.9 K at 1.1 mbar south of 75°S (planetographic). This suggests dissipation of Saturn's south polar vortex in addition to an autumnal cooling. We observe a 20% ± 9% enrichment of acetylene and a 30% ± 10% enrichment of ethane at 2.1 mbar at 25°N, together with a 14% ± 9% depletion of acetylene and an 18% ± 7% depletion of ethane at the same altitude at 15°S. This suggests the presence of localised downwelling and upwelling at these latitudes, respectively. These vertical motions are consistent with a recently-developed GCM (global circulation model) of Saturn's tropopause and stratosphere, which predicts this pattern of upwelling and downwelling as a result of seasonally-reversing Hadley circulation.

Sinclair, James; Irwin, P. G. J.; Fletcher, L. N.; Moses, J. I.; Greathouse, T. K.; Friedson, A. J.; Hesman, B.; Hurley, J.; Merlet, C.

2012-10-01

228

The reaction of the benzene cation with acetylenes for the growth of PAHs in the interstellar medium  

NASA Astrophysics Data System (ADS)

We investigated the formation of the naphthalene cation from the successive addition of two acetylenes on the benzene cation. A DFT approach was used for that purpose. The entry channel corresponding to the addition of the acetylenes is the energetically highest part of the entire reaction pathway. It was recalculated using the ab initio W1-F12 and G4 thermochemical protocols. At these levels, the energetically highest point in the entry channel is shown to be just below the energy of the free reactants. This Letter shows that the formation of the naphthalene cation from benzene and acetylenes should proceed in space.

Ghesquière, Pierre; Talbi, Dahbia; Karton, Amir

2014-03-01

229

Low stereoselectivity in methylacetylene and cyclopropene reductions by nitrogenase.  

PubMed Central

The stereochemistry of reductions catalyzed by nitrogenase in 2H2O has been investigated by using allene, methylacetylene, and cyclopropene as substrates. Deuterium labeling patterns in the reduction products were determined by mass spectroscopy, infrared spectroscopy, 2H-decoupled 220-MHz 1H NMR, and 1H-decoupled 30.7-MHz 2H NMR. Reduction of allene gave pure [2,3-2H2]propene. Reduction of methyl acetylene gave a 1.8:1.0 mixture of [cis- and [trans-1,2-2H2]propene. (Similar reduction of acetylene reportedly gave virtually all [cis-1,2-2H2]ethylene.) Reduction of cyclopropene gave [cis-1,2-2H2]cyclopropane and a mixture of [2H2]propenes. The major propene 2H2 isomers formed were [trans-1,3-2H2]-propene (approximately 2), [cis-1,3-2H2]propene (approximately 1) and [2,3-2H2]propene (approximately 1). Cyclopropene appears to be unique as a nitrogenase substrate in that it simultaneously undergoes parallel reductions, one of which proceeds with high stereoselectivity while the other proceeds with low stereoselectivity. The weakly selective stereochemistry observed in these reductions is not consistent with a completely concerted dual proton-dual electron transfer mechanism. The results provide a basis to probe stereochemical effects in nitrogenase and in biomimetic model systems.

McKenna, C E; McKenna, M C; Huang, C W

1979-01-01

230

Effects of acido-basic support properties on the catalytic hydrogenation of acetylene on gold nano-particles  

NASA Astrophysics Data System (ADS)

Metallic gold nanoparticles supported on gamma-Al2O 3 and magnesia-alumina mixed oxide, with different magnesia content have been prepared by sol-gel method and characterized by different techniques (inductive coupled plasma-mass spectroscopy (ICP-MS), XRD, BET surface area analysis, transmission electron microscopy (TEM), CO2 and NH 3 temperature programmed desorption (TPD), H2 temperature programmed reduction (TPR) and FTIR of adsorbed CO2). Such systems were found to produce catalysts with controllable acidity, varying from catalyst possessing large density of acidic and low density of basic sites, others with acidic and basic sites of equal strength and density, and others with large basic and low acid sites densities, respectively. The catalytic assessment of the generated acidity was carried out using 2-propanol decomposition as a test reaction. The results obtained indicate that the presence of magnesia and reduced gold nanopartilces has imparted the catalysts, 1%Au/4%Mg-Al 2O3 and 1%Au/8%Mg-Al2O3, with significant base-catalytic properties. Acetylene hydrogenation and formation of coke deposits were investigated on a gold catalyst supported on gamma-Al2O3 and gold supported on alumina-magnisia mixed oxide with different gold content; 1%Au/gamma-Al 2O3, 1%Au/15%Mg-Al2O3, 2%Au/15%Mg-Al 2O3 and 4%Au/15%Mg-Al2O3. The effect of the H2/C2H2 ratio was studied over a range of values. The catalytic activity and selectivity towards ethylene and other products were investigated at different reaction temperatures. Acetylene hydrogenation was investigated in the presence and absence of ethylene in stream. It is investigated that the adsorption of the triple bond is preferred over the double bond and during selective catalytic (SCR) of C2H2 the two hydrocarbons do not compete for the same adsorption sites. The deactivation of catalysts was studied by temperature programmed oxidation (TPO). Higher content of coke over 1%Au/Al2O3 catalyst was investigated in contrast to the other catalysts in which the basisity of magnesia-alumina supports could have played an important role in inhibiting the acidic carbon formation by possessing smaller number and/or weaker acid sites.

Manda, Abdullah Ahmed

231

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

NASA Astrophysics Data System (ADS)

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.

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

2014-06-01

232

Physiological sources of reductant for nitrogen fixation activity in Nostoc sp. strain UCD 7801 in symbiotic association with Anthoceros punctatus.  

PubMed Central

Pure cultures of the symbiotic cyanobacterium-bryophyte association with Anthoceros punctatus were reconstituted by using Nostoc sp. strain UCD 7801 or its 3-(3,4-dichlorophenol)-1,1-dimethylurea (DCMU)-resistant mutant strain, UCD 218. The cultures were grown under high light intensity with CO2 as the sole carbon source and then incubated in the dark to deplete endogenous reductant pools before measurements of nitrogenase activities (acetylene reduction). High rates of light-dependent acetylene reduction were obtained both before starvation in the dark and after recovery from starvation, regardless of which of the two Nostoc strains was reconstituted in the association. Rates of acetylene reduction by symbiotic tissue with the wild-type Nostoc strain decreased 99 and 96% after 28 h of incubation in the dark and after reexposure to light in the presence of 5 microM DCMU, respectively. Supplementation of the medium with glucose restored nitrogenase activity in the dark to a rate that was 64% of the illuminated rate. In the light and in the presence of 5 microM DCMU, acetylene reduction could be restored to 91% of the uninhibited rate by the exogenous presence of various carbohydrates. The rate of acetylene reduction in the presence of DCMU was 34% of the uninhibited rate of tissue in association with the DCMU-resistant strain UCD 218. This result implies that photosynthates produced immediately by the cyanobacterium can supply at least one-third of the reductant required for nitrogenase activity on a short-term basis in the symbiotic association. However, high steady-state rates of nitrogenase activity by symbiotic Nostoc strains appear to depend on endogenous carbohydrate reserves, which are presumably supplied as photosynthate from both A. punctatus tissue and the Nostoc strain.

Steinberg, N A; Meeks, J C

1991-01-01

233

Transparent, highly conductive graphene electrodes from acetylene-assisted thermolysis of graphite oxide sheets and nanographene molecules  

Microsoft Academic Search

Transparent and highly conductive graphene electrodes have been fabricated through acetylene-assisted thermolysis of graphite oxide (GO) sheets. This novel procedure uses acetylene as a supplemental carbon source to repair substantial defects within GO sheets, leading to the enhancement of graphitization of synthesized graphene electrodes. The as-prepared graphene on quartz substrates exhibits an electrical conductivity of 1425 S cm-1 with an

Yanyu Liang; Johannes Frisch; Linjie Zhi; Hassan Norouzi-Arasi; Xinliang Feng; Jürgen P. Rabe; Norbert Koch; Klaus Müllen

2009-01-01

234

Performance and regeneration studies of Pd–Ag\\/Al 2O 3 catalysts for the selective hydrogenation of acetylene  

Microsoft Academic Search

The selective hydrogenation of acetylene is one process to remove traces of acetylene from steam cracker cuts during the production of ethylene. Current disadvantages of commercially used Pd–Ag\\/Al2O3 catalysts applied in the C2-tail end-selective hydrogenation are relative short cycle time (fast deactivation) caused by green oil formation and deposition of coke. Long-term tests were performed in a laboratory reactor under

Axel Pachulski; Rainer Schödel; Peter Claus

2011-01-01

235

First-principles-based kinetic Monte Carlo simulation of the selective hydrogenation of acetylene over Pd(111)  

Microsoft Academic Search

The kinetics for the selective hydrogenation of acetylene over Pd(111) was investigated by using first-principles-based kinetic Monte Carlo simulations. Density functional theory (DFT) calculations were carried out to obtain intrinsic kinetic data for a Horiuti–Polanyi-type reaction mechanism involving the sequential hydrogenation of acetylene. The results were subsequently used to develop a detailed intrinsic kinetics database that includes the adsorption energies

Donghai Mei; Priyam A. Sheth; Matthew Neurock; C. Michael Smith

2006-01-01

236

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

NASA Technical Reports Server (NTRS)

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.

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

1992-01-01

237

The influence of Pd–Ag catalyst restructuring on the activation energy for ethylene hydrogenation in ethylene–acetylene mixtures  

Microsoft Academic Search

Hydrogenation of acetylene–ethylene mixtures was studied on Pd\\/SiO2 and Pd–Ag\\/SiO2 under conditions that correspond to “front-end” hydrogenation of acetylene. The presence of excess H2 under “front-end” hydrogenation conditions can lead to thermal runaway due to the exothermic reaction of ethylene and H2. In previous work, we found that activation energy was sensitive to catalyst pretreatment: high temperature treatment in H2

Hugo Zea; Kelvin Lester; Abhaya K. Datye; Ed Rightor; Robert Gulotty; Wendy Waterman; Michael Smith

2005-01-01

238

Latitudinal variations of acetylene and ethane in the stratosphere of Saturn from Cassini/CIRS observations  

NASA Astrophysics Data System (ADS)

Acetylene and ethane are formed in the stratosphere of Saturn by the photolysis of methane. Since their lifetime is short variations in their abundances can be used to infer information on the photochemical processes of hydrocarbons and transport systems within the stratosphere. Cassini's approach of Saturn in May 2004 allowed CIRS to map the entire southern hemisphere of the planet unobscured by the planet's rings, providing one of the most latitudinally complete maps of Saturn recorded to date. Variations in the abundance of acetylene and ethane in the stratosphere of Saturn's southern hemisphere have been retrieved from the nadir observations made by CIRS. The retrieved maps are compared to previously conducted, largely ground-based, studies.

Howett, C.; Irwin, P.; Calcutt, S.; Taylor, F.; Teanby, N.; Fouchet, T.; Simon-Miller, A.; CIRS Team

2005-08-01

239

An alternative role for acetylenes: activation of fluorobenzenes toward nucleophilic aromatic substitution.  

PubMed

Acetylenes are increasingly versatile functional groups for a range of complexity-building organic transformations and for the construction of desirable molecular architectures. Herein we disclose a previously underappreciated aspect of arylacetylene reactivity by utilizing alkynes as electron-withdrawing groups (EWG) for promoting nucleophilic aromatic substitution (S(N)Ar) reactions. Reaction rates for the substitution of 4-(fluoroethynyl)benzenes by p-cresol were determined by (1)H NMR spectroscopy, and these rate data were used to determine substituent (Hammett) constants for terminal and substituted ethynyl groups. The synthetic scope of acetylene-activated S(N)Ar reactions is broad; fluoroarenes bearing one or two ethynyl groups undergo high-yielding substitution with a variety of oxygen and arylamine nucleophiles. PMID:23692440

Bizier, Nicholas P; Wackerly, Jay Wm; Braunstein, Eric D; Zhang, Mengfei; Nodder, Stephen T; Carlin, Stephen M; Katz, Jeffrey L

2013-06-21

240

Effect of acetylene portion on the properties of high frequency discharge in argon  

NASA Astrophysics Data System (ADS)

The gas discharge in hydrocarbon mixtures is widely used for carbon film growth. These thin films are of great interest for a wide range of industrial applications due to their extraordinary material properties. Noble gases like argon and neon are often used as main background gases for hydrocarbon mixtures as their presence changes morphology of diamond like carbon films and leads to fewer crystalline defects. In this paper the numerical study of characteristics of high frequency discharge are performed with using PIC-MCC simulation for different portions of acetylene in the mixture with argon. We consider the formation of heavy ions and radicals which are precursors for nanoparticle growth in the discharge volume. The density of electrons, positive and negative ions are found to be nonmonotonic functions of the quantity of the acetylene in the mixture. The presence of the negative ions, the density of which is comparable with electron density, weakly affects the parameters of discharge.

Schweigert, Irina; Ariskin, Dmitry

2009-10-01

241

Cationic Oxazaborolidine Catalyzed Enantioselective Diels-Alder Reaction of ?,?-Unsaturated Acetylenic Ketones  

PubMed Central

Cationic oxazaborolidine 1 affords Diels-Alder adducts of ?,?-unsaturated acteylenic ketones with cyclic and acyclic dienes in excellent yields and enantioselectivities. Importantly, dienophiles lacking the typical hydrogen bonding motif as required for other oxazaborolidinium mediated reactions also provide uniformly high levels of asymmetric induction. Subsequently, mechanistic studies of this reaction were undertaken through X-ray crystallographic and computational studies of BF3-acetylene complexes which both indicate a strong preference for syn-coordination geometry of the Lewis acid relative to the alkyne. Thus, we postulate syn-coordination of the acetylene by 1 is operative, which precludes the necessity for hydrogen bonding and maintains close proximity of the reactive sp carbon centers to the chiral environment of the catalyst, ensuring high enantioselectivities.

Payette, Joshua N.; Akakura, Matsujiro; Yamamoto, Hisashi

2009-01-01

242

Cold-atmospheric pressure plasma polymerization of acetylene on wood flour for improved wood plastics composites  

NASA Astrophysics Data System (ADS)

Plastic composites have become a large class of construction material for exterior applications. One of the main disadvantages of wood plastic composites resides in the weak adhesion between the polar and hydrophilic surface of wood and the non-polar and hydrophobic polyolefin matrix, hindering the dispersion of the flour in the polymer matrix. To improve interfacial compatibility wood flour can be pretreated with environmentally friendly methods such as cold-atmospheric pressure plasma. The objective of this work is therefore to evaluate the potential of plasma polymerization of acetylene on wood flour to improve the compatibility with polyolefins. This presentation will describe the reactor design used to modify wood flour using acetylene plasma polymerization. The optimum conditions for plasma polymerization on wood particles will also be presented. Finally preliminary results on the wood flour surface properties and use in wood plastic composites will be discussed.

Lekobou, William; Pedrow, Patrick; Englund, Karl; Laborie, Marie-Pierre

2009-10-01

243

Time-resolved molecular frame photoelectron angular distribution: Snapshots of acetylene and ethylene isomerizations  

NASA Astrophysics Data System (ADS)

It has been proposed that chemical reactions can be imaged by detection of a photoelectron in the molecular fixed body frame (MFPAD), following either valence or K-shell photoionization. We will contrast these two techniques using acetylene and ethylene isomerization as examples. The ab initio calculations were carried out using the complex Kohn variational method. Our results indicate that while K-shell MFPADs are only sensitive to molecular geometry whereas valence MFPADs are sensitive to both geometry and the initial electronic state of the target. Both examples show that isomerization takes place via conical intersections. However, acetylene requires an excitation/ionization step, while ethylene undergoes isomerization following direct excitation of the neutral V state.

Douguet, Nicolas; Rescigno, Thomas; Orel, Ann

2012-06-01

244

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

PubMed

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

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

2007-01-01

245

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

NASA Technical Reports Server (NTRS)

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.

Walch, Stephen P.; Taylor, Peter R.

1995-01-01

246

Polyketide Assembly by Alkene-Alkyne Reductive Cross-Coupling: Spiroketals Through the Union of Homoallylic Alcohols  

PubMed Central

A reaction sequence composed of regioselective formal hydroalkynylation, reductive ene-yne cross-coupling and oxidative cyclization has been developed to prepare stereochemically dense spiroketals. Overall, the chemistry defines a three-component coupling process for the union of two homoallylic alcohol-based substrates with TMS-acetylene.

Canterbury, Daniel P.; Micalizio, Glenn C.

2010-01-01

247

Vacuum ultraviolet photolysis of acetylene in the 110- to 135-nm region  

SciTech Connect

State-specific photofragmentation of acetylene in the 110- to 135-nm region has been studied using vuv laser and synchrotron sources. Investigations have been focused on learning the spectroscopic identity of the excited photoproducts by examining their time-resolved fluorescence. Results of the quenching of the excited photofragment emission and the emission polarization measurements are presented. An interpretation of these results in relating the observed photoproducts to the vuv photodissociation process is discussed. 13 refs., 3 figs., 1 tab.

Tiee, J.J.; Sander, R.K.; Quick, C.R.; Estler, R.

1986-01-01

248

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

PubMed

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

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

2011-09-15

249

Spectroscopy and energetics of the acetylene molecule: dynamical complexity alongside structural simplicity  

Microsoft Academic Search

This article reviews laser-spectroscopic studies of the structure, energetics, and dynamics of processes involving small polyatomic molecules, particularly acetylene (ethyne, C2H2). The linear, centrosymmetric structure of C2H2 is deceptively simple, given that aspects of its optical spectra and dynamics have proved to be unusually complicated. The article focuses on the ground electronic state of C2H2, where rovibrational eigenstates are only

Brian J. Orr

2006-01-01

250

Methane conversion to ethylene and acetylene: Optimal control with chlorine, oxygen, and heat flux  

Microsoft Academic Search

In this paper, an optimal control strategy is applied to the problem of finding the flux profiles for the conversion of methane to ethylene and acetylene in a plug flow reactor. A chlorine-catalyzed oxidative pyrolysis mechanism is used in the calculations, in which two mechanistic pathways to the Câ products were examined. One involves CHâCl and\\/or CHâCl, and the other

Atipat Rojnuckarin; Christodoulos A. Floudas; Herschel Rabitz; Richard A. Yetter

1996-01-01

251

Rotational spectroscopy and molecular structure of the 1,1,2-trifluoroethylene-acetylene complex  

NASA Astrophysics Data System (ADS)

Guided by ab initio calculations, Fourier transform microwave rotational spectra in the 6-22 GHz region are obtained for the complex formed between 1,1,2-trifluoroethylene and acetylene, including the normal isotopomer, three of four singly substituted 13C species obtained in natural abundance, and using commercially available isotopic varieties of acetylene, species containing HCCD and H13C13CH. Although the ab initio calculations suggest two possible low energy planar arrangements for the molecules in the complex, only a single, unique structure is obtained from a combined analysis of the rotational constants derived from the spectra and atomic positions determined using Kraitchman [Am. J. Phys. 21, 17 (1953)] substitution coordinates. This structure is similar to that obtained for the CF2CHF-HF complex [H. O. Leung and M. D. Marshall, J. Chem. Phys. 126, 114310 (2007)] in which both the primary and secondary interactions occur between the HCCH molecule and a F atom and a H atom bonded to the same carbon of CF2CHF. The 2.748(15) A? hydrogen bond has acetylene as the donor and 1,1,2-trifluoroethylene as the acceptor and forms a 104.49(15)° C-F...H angle. The 2.8694(9) A? secondary interaction between the ? bond of acetylene and the H atom geminal to the acceptor F atom causes the hydrogen bond to deviate 69.24(67)° from linearity. This large deviation from linearity and the similarity of the two intermolecular bond lengths suggest that the two interactions are becoming comparable in importance.

Leung, Helen O.; Marshall, Mark D.; Cashion, Winn T.; Chen, Vincent L.

2008-02-01

252

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

NASA Technical Reports Server (NTRS)

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.

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

1990-01-01

253

Acetylene\\/Vinylidene Isomerization after Carbon K-shell PhotoIonization  

Microsoft Academic Search

Comprehensive study of the acetylene\\/vinylidene isomerization dynamics after the carbon k-shell photoionization followed by the Auger decay was performed by means of the COLTRIMS (COLd Target Recoil Ion Momentum Spectroscopy) technique. The Auger electrons, produced in this reaction, were detected in coincidence with the products of the Coulomb explosion of the dication C2H2^2+. Measurement of the 3d vector momenta for

Timut Osipov; T. Weber; T. Jahnke; A. Alnaser; A. Landers; M. Hertlein; O. Jagutzki; L. Schmidt; M. Schöffler; M. Prior; B. Feinberg; C. L. Cocke; R. Dörner; A. Belkacem

2006-01-01

254

Nonoxidative Methane Conversion to Acetylene over Zeolite in a Low Temperature Plasma  

Microsoft Academic Search

Previous investigations have found that the plasma catalytic conversion of methane is a low-temperature process for the activation of methane, the major component of natural gas. In this paper, the production of acetylene via plasma catalytic conversion of methane over NaY zeolite is discussed. Hydrogen is produced as a by-product during this plasma catalytic methane conversion. A methane\\/hydrogen feed with

Chang-jun Liu; Richard Mallinson; Lance Lobban

1998-01-01

255

Organic–inorganic nanotube hybrids: Organosilica-nanotubes containing ethane, ethylene and acetylene groups  

Microsoft Academic Search

The synthesis and characterization of novel organic–inorganic hybrid nanotubes containing silica and ethane (EtSNT), ethylene (ESNT) and acetylene (ASNT) units are presented. The unsaturated hydrocarbon linkers can be applied for a chemical functionalization of the surface of the silica nanotubes, e.g. for the grafting of organic\\/inorganic or organometallic molecules. These new materials are synthesized via a template method using V3O7·H2O

Christian E. Fischer; Alexander Raith; János Mink; Gabriele Raudaschl-Sieber; Mirza Cokoja; Fritz E. Kühn

2011-01-01

256

Effect of Molecular Oxygen on the Emission Spectra of Atomic Oxygen-Acetylene Flames  

Microsoft Academic Search

Studies have been made of the emission spectra (3000 to 6000 A) obtained from low-pressure atomic oxygen-acetylene flames diluted with varying amounts of molecular oxygen and molecular nitrogen. Added molecular oxygen greatly increased the OH emission while reducing CH and C2 emission. It also had an effect on the rotational intensity distribution of OH and on the vibrational intensity distribution

S. L. N. G. Krishnamachari; H. P. Broida

1961-01-01

257

Nanosecond Pulse Burst Ignition of Ethylene and Acetylene by Uniform Low-Temperature Plasmas1  

Microsoft Academic Search

Nanosecond pulse burst plasma ignition measurements and kinetic modeling calculations have been used to analyze kinetics of low-temperature plasma assisted ignition of hydrocarbon fuels. Uniform low-temperature plasmas have been generated by high voltage, nanosecond duration pulses at high pulse repetition rates. Pulse bursts of up to 1000 pulses have been used to ignite premixed ethylene-air and acetylene-air flows. Ignition delay

E. Mintusov; M. Nishihara; N. Jiang; I. Choi; M. Uddi; A. Dutta; W. R. Lempert; I. V. Adamovich

2008-01-01

258

Acetylenic cyclophanes: emerging carbon-rich compounds for molecular construction and practical applications  

Microsoft Academic Search

The preparation of simple acetylenic [2.2]parcyclophane ‘building blocks’ is described. These compounds are readily available from the commercially available [2.2]paracyclophane employing functionalization of the parent system and conversion of the resulting functional groups into triple bonds. For the incorporation of these structures into cyclophanes with ‘extended’ ?-systems, coupling reactions such as the Sonogashira or the Glaser coupling are particularly valuable.

Henning Hopf

2008-01-01

259

Rotational spectra of deuterated acetylenes: DCCH, D 13CCH and DC 13CH  

Microsoft Academic Search

Rotational spectra of deuterated acetylenes, DCCH, D13CCH and DC13CH, have been recorded in the millimeter- and submillimeter-wave frequency ranges. In spite of the small dipole moment (0.01001(15) D), 13C-containing species have been observed in natural abundance. The present investigation allowed us to provide improved ground state rotational and quartic centrifugal distortion constants for DCCH, D13CCH and DC13CH. The experimental investigation

Gabriele Cazzoli; Cristina Puzzarini; Luciano Fusina; Filippo Tamassia

2008-01-01

260

A thioannulation approach to substituted thiophenes from Morita-Baylis-Hillman acetates of acetylenic aldehydes.  

PubMed

A new protocol has been developed for the synthesis of substituted thiophenes under mild and metal-free reaction conditions via the base-promoted thioannulation of Morita-Baylis-Hillman acetates of acetylenic aldehydes with potassium thioacetate involving a tandem allylic substitution/deacetylative 5-exo-dig-thiocycloisomerization. The obtained products provide an entry to 4H-thieno[3,2-c]chromene and thieno[3,2-c]dihydroquinoline. PMID:23738898

Reddy, Chada Raji; Valleti, Reddi Rani; Reddy, Motatipally Damoder

2013-07-01

261

Epigenetic modifier-induced biosynthesis of novel acetylenic sterols from Cladosporium colocasiae.  

PubMed

The addition of an HDAC inhibitor, suberoylanilide hydroxamic acid (SBHA), to the culture medium of Cladosporium colocasiae, dramatically altered its metabolic profiles. Analysis of the culture broth extract led to the isolation of two new acetylenic sterols (1-2). The isolated compounds were further evaluated for their cytotoxic and antibacterial activities. Compound 1 showed activity against Bacillus subtilis, affording a zone of inhibition of 12mm at 100?g/disk. However, none of them showed noticeable growth inhibitory effects. PMID:24907456

Liu, Dong-Ze; Liang, Bo-Wen; Li, Xiao-Fei; Yu, Zhi-Yuan

2014-09-01

262

Special Features of Vacuum Carburizing of Heat-Resistant Steel in Acetylene  

Microsoft Academic Search

The mechanism of formation of the diffusion layer due to vacuum carburizing of complexly alloyed steel 16Kh3NVFMB-Sh (VKS5) in a medium of acetylene is considered. It is shown that the process of carburizing occurs in a self-regulation mode without the danger of carbon black due to the high rate of arrival of carbon from the gas medium as a result

N. M. Ryzhov; A. E. Smirnov; R. S. Fakhurtdinov; L. M. Mulyakaev; V. I. Gromov

2004-01-01

263

Molecular mechanisms in the cyclotrimerization of acetylene to benzene on palladium (111)  

Microsoft Academic Search

Multiplexed temperature programmed reaction measurements have been used to examine mechanistic details of the acetylene ..-->.. benzene reaction on Pd(111). Results obtained from (CâHâ + CâDâ) experiments are in quantitative accord with a nondissociative reaction pathway; H\\/D scrambling in the reactants is not of significance, but at higher temperatures some H\\/D scrambling is observed between product molecules. The effects of

Charles H. Patterson; Richard M. Lambert

1988-01-01

264

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

SciTech Connect

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.

Bao, W.; Cao, Q.; Lv, Y.; Chang, L. [Taiyuan University of Technology, Taiyuan (China)

2008-07-01

265

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

NASA Technical Reports Server (NTRS)

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.

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

1983-01-01

266

A spectroscopic study of the premixed acetylene-nitrous oxide flame  

SciTech Connect

Premixed flat flames of acetylene-nitrous oxide were stabilized on a perforated, water cooled burner, 3 in. in diameter. A rich flame (C/sub 2/H/sub 2/:27%, N/sub 2/O:73%) was stabilized at 20 mm Hg and a lean flame (C/sub 2/H/sub 2/:9%, N/sub 2/O:91%) at 45 mm Hg. Temperature profiles and concentration profiles of free radicals and of stable products of reaction were determined in the reaction and postreaction zones using spectroscopic techniques. NO, CN, NH, C/sub 2/, CH, and OH were measured by absorption using single rotational lines of their molecular spectra in the visible or ..mu..v regions. H/sub 2/O and CO/sub 2/ were measured using the integrated emission intensities of their infrared spectra. Results indicated that the combustion of acetylene-nitrous oxide flames occurs in two steps: decomposition of nitrous oxide into O/sub 2/, N/sub 2/, and NO followed by combustion of acetylene with oxygen. The presence of NO is responsible for the reactions.

Darian, S.T.; Vanpee, M.

1987-10-01

267

Biosynthesis of chlorosome proteins is not inhibited in acetylene-treated cultures of Chlorobium vibrioforme.  

PubMed

The composition, abundance and apparent molecular masses of chlorosome polypeptides from Chlorobium tepidum and Chlorobium vibrioforme 8327 were compared. The most abundant, low-molecular-mass chlorosome polypeptides of both strains had similar electrophoretic mobilities and abundances, but several of the larger proteins were different in both apparent mass and abundance. Polyclonal antisera raised against recombinant chlorosome proteins of Cb. tepidum recognized the homologous proteins in Cb. vibrioforme, and a one-to-one correspondence between the chlorosome proteins of the two species was confirmed. As previously shown [Ormerod et al. (1990) J Bacteriol 172: 1352-1360], acetylene strongly suppressed the synthesis of bacteriochlorophyll c in Cb. vibrioforme strain 8327. No correlation was found between the bacteriochlorophyll c content of cells and the cellular content of chlorosome proteins. Nine of ten chlorosome proteins were detected in acetylene-treated cultures, and the chlorosome proteins were generally present in similar amounts in control and acetylene-treated cells. These results suggest that the synthesis of chlorosome proteins and the assembly of the chlorosome envelope is constitutive. It remains possible that the synthesis of bacteriochlorophyll c and its insertion into chlorosomes might be regulated by environmental parameters such as light intensity. PMID:16228502

Vassilieva, Elena V; Ormerod, John G; Bryant, Donald A

2002-01-01

268

Infrared spectra of chemisorbed molecules5. Magnetic and infrared measurements on methane, ethane, ethylene, and acetylene adsorbed on silica-supported nickel  

Microsoft Academic Search

Magnetic measurements suggested that ethane, ethylene, and acetylene adsorbed on silica-supported nickel at 25°C at low coverage to form NiCH=CHNi species, which were not detected by IR spectroscopy. At higher surface concentrations, ethylene and acetylene formed surface alkyl groups by self-hydrogenation of the adsorbed species, according to IR evidence. At 25°C and high acetylene concentrations, physical adsorption, polymerization possibly to

J. Erkelens; W. J. Woesten

1978-01-01

269

A Potent Plant-Derived Antifungal Acetylenic Acid Mediates Its Activity by Interfering with Fatty Acid Homeostasis  

PubMed Central

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 were conducted using the model yeast Saccharomyces cerevisiae to investigate its mechanism of action. 6-NDA elicited a transcriptome response indicative of fatty acid stress, altering the expression of genes that are required for yeast growth in the presence of oleate. Mutants of S. cerevisiae lacking transcription factors that regulate fatty acid ?-oxidation showed increased sensitivity to 6-NDA. Fatty acid profile analysis indicated that 6-NDA inhibited the formation of fatty acids longer than 14 carbons in length. In addition, the growth inhibitory effect of 6-NDA was rescued in the presence of exogenously supplied oleate. To investigate the response of a pathogenic fungal species to 6-NDA, transcriptional profiling and biochemical analyses were also conducted in C. albicans. The transcriptional response and fatty acid profile of C. albicans were comparable to those obtained in S. cerevisiae, and the rescue of growth inhibition with exogenous oleate was also observed in C. albicans. In a fluconazole-resistant clinical isolate of C. albicans, a fungicidal effect was produced when fluconazole was combined with 6-NDA. In hyphal growth assays, 6-NDA inhibited the formation of long hyphal filaments in C. albicans. Collectively, our results indicate that the antifungal activity of 6-NDA is mediated by a disruption in fatty acid homeostasis and that 6-NDA has potential utility in the treatment of superficial Candida infections.

Xu, Tao; Tripathi, Siddharth K.; Feng, Qin; Lorenz, Michael C.; Wright, Marsha A.; Jacob, Melissa R.; Mask, Melanie M.; Baerson, Scott R.; Li, Xing-Cong; Clark, Alice M.

2012-01-01

270

Reactions of trans-3-chloroacrylic acid dehalogenase with acetylene substrates: consequences of and evidence for a hydration reaction.  

PubMed

Various soil bacteria use 1,3-dichloropropene, a component of the commercially available fumigants Shell D-D and Telone II, as a sole source of carbon and energy. One enzyme involved in the catabolism of 1,3-dichloropropene is trans-3-chloroacrylic acid dehalogenase (CaaD), which converts the trans-isomers of 3-bromo- and 3-chloroacrylate to malonate semialdehyde. Sequence analysis suggested a relationship between the heterohexameric CaaD and the bacterial isomerase, 4-oxalocrotonate tautomerase (4-OT), thereby distinguishing CaaD from a number of dehalogenases whose mechanisms proceed through an alkyl- or aryl-enzyme intermediate. In this study, the genes for the alpha- and beta-subunits of CaaD have been synthesized using a polymerase chain reaction-based strategy, cloned into separate plasmids, and the proteins expressed and purified as the functional heterohexamer. Subsequently, the product of the reaction was confirmed to be malonate semialdehyde by (1)H and (13)C NMR spectroscopy, and kinetic constants were determined using a UV spectrophotometric assay. In view of the proposed hydrolytic nature of the CaaD-catalyzed reaction, three acetylene compounds were investigated as substrates for the enzyme. One compound, 2-oxo-3-pentynoate, a potent active site-directed irreversible inhibitor of 4-OT, is a substrate for CaaD, and was processed to acetopyruvate with kinetic constants similar to those determined for the trans-isomers of 3-bromo- and 3-chloroacrylate. The remaining two compounds, 3-bromo- and 3-chloropropiolic acid, were transformed into potent irreversible inhibitors of CaaD. The inactivation observed for 3-bromopropiolic acid is due to the covalent modification of Pro-1 of the beta-subunit. The results provide evidence for a hydratase activity and set the stage to use the 3-halopropiolic acids as ligands in inactivated CaaD complexes that can be studied by X-ray crystallography. PMID:12873137

Wang, Susan C; Person, Maria D; Johnson, William H; Whitman, Christian P

2003-07-29

271

Polycyclic propargylamine and acetylene derivatives as multifunctional neuroprotective agents.  

PubMed

The aim of this study was to design drug-like molecules with multiple neuroprotective mechanisms which would ultimately inhibit N-methyl-d-aspartate (NMDA) receptors, block L-type voltage gated calcium channels (VGCC) and inhibit apoptotic processes as well as the monoamine oxidase-B (MAO-B) enzyme in the central nervous system. These types of compounds may act as neuroprotective and symptomatic drugs for disorders such as Alzheimer's and Parkinson's disease. In designing the compounds we focused on the structures of rasagiline and selegiline, two well known MAO-B inhibitors and proposed neuroprotective agents. Based on this consideration, the compounds synthesised all contain the propargylamine functional group of rasagiline and selegiline or a derivative thereof, conjugated to various polycyclic cage moieties. Being non-polar, these polycyclic moieties have been shown to aid in the transport of conjugated compounds across the blood-brain barrier, as well as cell membranes and have secondary positive neuroprotective effects. All novel synthesised polycyclic derivatives proved to have significant anti-apoptotic activity (p < 0.05) which was comparable to the positive control, selegiline. Four compounds (12, 15 and 16) showed promising VGCC and NMDA receptor channel inhibitory activity ranging from 18% to 59% in micromolar concentrations and compared favourably to the reference compounds. In the MAO-B assay, 8-phenyl-ethynyl-8-hydroxypentacycloundecane (10), exhibited MAO-B inhibition of 73.32% at 300 ?M. This compound also reduced the percentage of apoptotic cells by as much as 40% when compared to the control experiments. PMID:24769350

Zindo, Frank T; Barber, Quinton R; Joubert, Jacques; Bergh, Jacobus J; Petzer, Jacobus P; Malan, Sarel F

2014-06-10

272

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

NASA Technical Reports Server (NTRS)

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.

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

2000-01-01

273

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

NASA Technical Reports Server (NTRS)

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.

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

2001-01-01

274

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

NASA Technical Reports Server (NTRS)

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.

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

2001-01-01

275

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

PubMed

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

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

2014-01-01

276

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

NASA Astrophysics Data System (ADS)

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.

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

2014-04-01

277

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

PubMed

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

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

2006-09-27

278

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

SciTech Connect

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.

Komives, E.A.

1987-01-01

279

Infrared spectra and optical constants of astronomical ices: I. Amorphous and crystalline acetylene  

NASA Astrophysics Data System (ADS)

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 (?), 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.

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

2014-01-01

280

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

NASA Technical Reports Server (NTRS)

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.

Tannenbaum, Stanley

1957-01-01

281

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

NASA Astrophysics Data System (ADS)

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.

Oh, Daniel B.; Hovde, David Christian

1995-10-01

282

First principles potential for the acetylene dimer and refinement by fitting to experiments.  

PubMed

We report the definition and refinement of a new first principles potential for the acetylene dimer. The ab initio calculations were performed with the DFT-SAPT combination of symmetry-adapted intermolecular perturbation method and density functional theory, and fitted to a model site-site functional form. Comparison of the calculated microwave spectrum with experimental data revealed that the barriers to isomerization were too low. This potential was refined by fitting the model parameters in order to reproduce the observed transitions, an excellent agreement within ~1 MHz being achieved. PMID:22191874

Leforestier, Claude; Tekin, Adem; Jansen, Georg; Herman, Michel

2011-12-21

283

Formation of artificial pores in nano-TiO2 photo-electrode films using acetylene-black for high-efficiency, dye-sensitized solar cells  

PubMed Central

Acetylene-black paste without a light scattering layer was applied to meso-porous TiO2 photo-electrode films with a crystalline framework, a low residual carbon, and a tunable morphological pore size. The thermal-treated TiO2 photo-electrode films had an increased acetylene-black concentration with an increase in artificial pores and a decrease in residual carbon. The performance of dye-sensitized solar cells (DSSCs) was enhanced by the use of the TiO2 photo-anode pastes at various acetylene-black concentrations. The photo-conversion efficiency of the DSSCs using TiO2 photo-electrode films with 1.5 wt% acetylene-black was enhanced from 7.98 (no acetylene-black) to 9.75% without the integration of a light- scattering layer.

Cho, Tae-Yeon; Han, Chi-Whan; Jun, Yongseok; Yoon, Soon-Gil

2013-01-01

284

Photoluminescent, wide-bandgap aSiC:H alloy films deposited by Cat-CVD using acetylene  

Microsoft Academic Search

Hydrogenated amorphous silicon\\/carbon films (a-Si-C:H) are deposited from a silane and acetylene gas mixture by the catalytic chemical vapour deposition (Cat-CVD) technique. It is observed that under certain conditions of total gas pressure and filament temperature (TF), the optical bandgap varies non-linearly with the acetylene to silane (C2H2\\/SiH4) ratio, having a maximum value of 3.6 eV for a C2H2\\/SiH4 ratio

Alka Kumbhar; Samadhan B Patil; Sanjay Kumar; R Lal; R. O Dusane

2001-01-01

285

A new catalysis for benzene production from acetylene under UHV conditions: Sn\\/Pt(111) surface alloys  

Microsoft Academic Search

The adsorption and reaction of acetylene on Pt(111) and the p(2[times]2) and ([radical]3[times][radical]3)R30[degrees]Sn\\/Pt(111) surface alloys were investigated with low energy electron diffraction (LEED), temperature programmed desorption (TPD), and Auger electron spectroscopy (AES). The presence of Sn atoms at the surface of the p(2[times]2) and ([radical]3[times][radical]3)R30[degrees]Sn\\/Pt(111) surface alloys strongly suppressed the decomposition of acetylene (C[sub 2]D[sub 2]) to deuterium and adsorbed

Chen Xu; J. W. Peck; B. E. Koel

1993-01-01

286

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

SciTech Connect

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.

Zubrin, R.M. (Martin Marietta Astronautics Group, Denver, CO (United States))

1992-01-01

287

Molecular dynamics simulation studies on ethane and acetylene mixture in CuBTC metal organic framework  

NASA Astrophysics Data System (ADS)

Molecular Dynamics (MD) simulation studies have been carried out on the mixture containing ethane and acetylene molecules in 1:1 ratio at various concentrations of each species in CuBTC metal organic framework (MOF). MOFs are important class of materials which are tremendously useful for applications such as gas storage and separation. They have complex structure consisting of pore and pockets connected by windows. Results obtained from MD simulation showed that the self diffusivity of the ethane increases with the concentration while it decreases in case of acetylene. Correlation effects are responsible for this kind of phenomena. Pair distribution function showed the strong peaks at higher correlation length indicating the complex crystalline structure of the host matrix. We have also obtained the velocity auto correlation function (VACF) and velocity cross correlation functions (VCCF) at each studied concentration and found that the contribution from VCCF is almost negligible at lower concentration. Since the transport properties of mixture also depend on the mutual diffusivity and distinct diffusivity besides the self diffusivity, attempt has been made to quantify both the diffusivities. In the present system, at lower concentration, contribution to the mutual diffusivity comes from self diffusivities of species alone and distinct diffusivity contributes only at higher concentration.

Prabhudesai, S. A.; Sharma, V. K.; Mitra, S.; Mukhopadhyay, R.

2014-04-01

288

Critical points bifurcation analysis of high-l bending dynamics in acetylene  

NASA Astrophysics Data System (ADS)

The bending dynamics of acetylene with pure vibrational angular momentum excitation and quantum number l?0 are analyzed through the method of critical points analysis, used previously [V. Tyng and M. E. Kellman, J. Phys. Chem. B 110, 18859 (2006)] for l=0 to find new anharmonic modes born in bifurcations of the low-energy normal modes. Critical points in the reduced phase space are computed for continuously varied bend polyad number Nb=n4+n5 as l=l4+l5 is varied between 0 and 20. It is found that the local L, orthogonal O, precessional P, and counter-rotator CR families persist for all l. In addition, for l>=8, there is a fifth family of critical points which, unlike the previous families, has no fixed relative phase (``off great circle'' OGC). The concept of the minimum energy path in the polyad space is developed. With restriction to l=0 this is the local mode family L. This has an intuitive relation to the minimum energy path or reaction mode for acetylene-vinylidene isomerization. With l>=0 included as a polyad number, the l=0 minimum energy path forms a troughlike channel in the minimum energy surface in the polyad space, which consists of a complex mosaic of L, O, and OGC critical points. There is a division of the complete set of critical points into layers, the minimum energy surface forming the lowest.

Tyng, Vivian; Kellman, Michael E.

2009-12-01

289

Preparation of allenic sulfones and allenes from the selenosulfonation of acetylenes  

SciTech Connect

{beta}-(phenylseleno)vinyl sulfones 2 are readily obtained from the free-radical selenosulfonation of acetylenes. Compounds 2 isomerize to allyl sulfones 4 under base-catalyzed conditions in nearly quantitative yield, with high stereoselectivity favoring the Z configuration. Allyl sulfones 4 afford generally high yields of allenic sulfones 1 when subjected to oxidation with m-chloroperbenzoic acid or tert-butyl hydroperoxide, followed by selenoxide syn-elimination. The sulfone-stabilized anion intermediates in the isomerizations of 2 to 4 can be alkylated, deuterated, or silylated in the {alpha}-position prior to oxidation, providing allenic sulfones with an additional {alpha}-substituent. In some cases, spontaneous elimination of the phenylseleno group occurred, producing the allenic sulfone without the need for an oxidation step. Desulfonylation of allyl sulfones 4f, 4c, and 25 with sodium amalgam afforded vinyl selenides that were converted to allenes in moderate to good yields by oxidation-elimination. The copper-catalyzed coupling of allyl sulfones 4 with Grignard reagents comprises an alternative route to vinyl selenide precursors of allenes. These procedures permit the synthesis of various {alpha}- and {gamma}-substituted allenic sulfones and allenes from acetylenes.

Back, T.G.; Krishna, M.V.; Muralidharan, K.R. (Univ. of Calgary, Alberta (Canada))

1989-08-18

290

Time Resolved Infrared Emission from Vibrational Excited Acetylene Following Super Energy Transfer Collisions with Hot Hydrogen  

NASA Astrophysics Data System (ADS)

Can a molecule be activated with large amounts of energy transferred in a single collision between an atom and a molecule? If so, this type of collision will greatly affect molecular reactivity and equilibrium in systems including combustion where abundant hot atoms exist. Conventional expectation of translation to vibration (T-V) energy transfer is that probability decreases exponentially with energy transferred. We show, however, that in collisions between a pair of atom/molecule for which chemical reactions may occur, such as between a hyperthermal H atom and an ambient acetylene molecule, (T-V) energy transfer occurs with surprisingly high efficiency through chemical complex formation. Time-resolved infrared emission observations reveal that collisions between H atoms moving with 60 kcal/mole energy and acetylene molecules result in transfer of up to 70% of this energy into vibrational degrees of freedom. These experimental results are further supported by state of the art quasi-classical trajectory calculations performed by Bowman and coworkers.

Smith, J. M.; Nikow, M.; Dai, J. Ma Andh. L.

2013-06-01

291

Synthesis, Polymerization, and Thermal Properties of a New Acetylene-Terminated Schiff Base. (Reannouncement with New Availability Information).  

National Technical Information Service (NTIS)

A new acetylene-terminated Schiff base monomer, N,N'-(1,4-phenylene dimethylidyne) -bis-(4-ethynylaniline) (PPP), was synthesized and was characterized by nuclear magnetic resonance and infrared spectroscopy. This monomer was then polymerized to yield a n...

Y. Wei R. Hariharan J. K. Ray

1991-01-01

292

Abrasive wear behavior of thermally sprayed diamond reinforced composite coating deposited with both oxy-acetylene and HVOF techniques  

Microsoft Academic Search

Diamond and diamond-based coatings have long been studied for their exceptional properties. Although a great deal of research has been carried out in this field, little is known about their tribological wear behavior. In the present work, diamond reinforced composite (DRC) coatings of varying diamond content was deposited on mild steel substrates using both oxy-acetylene (OA) and high velocity oxy

K. Venkateswarlu; V. Rajinikanth; T. Naveen; Dhiraj Prasad Sinha; Atiquzzaman; Ajoy Kumar Ray

2009-01-01

293

Plasma polymerization of acetylene onto silica: an approach to control the distribution of silica in single elastomers and immiscible blends  

Microsoft Academic Search

Surface modification of silica by acetylene plasma polymerization is applied in order to improve the dispersion in and compatibility with single rubbers and their blends. Silica, used as a reinforcing filler for elastomers, is coated with a polyacetylene (PA) film under vacuum conditions. Water penetration measurements show a change in surface energy due to the PA-film deposition. The weight loss

M. Tiwari; J. W. M. Noordermeer; Wim J. van Ooij; W. K. Dierkes

2008-01-01

294

Comparative wear under four different tribological conditions of acetylene enhanced cross-linked ultra high molecular weight polyethylene  

Microsoft Academic Search

In this study, the wear of ultra high molecular weight polyethylene (UHMWPE) (Grade RCH 1000) crosslinked by gamma irradiation in acetylene was compared to virgin (non-irradiated) UHMWPE using four different wear configurations: (i) unidirectional motion with a smooth counterface, (ii) multidirectional motion with a smooth counterface, (iii) unidirectional motion with a rough counterface and (iv) multidirectional motion with a rough

H. Marrs; D. C. Barton; R. A. Jones; I. M. Ward; J. Fisher; C. Doyle

1999-01-01

295

Copper-free palladium-catalyzed sonogashira-type coupling of aryl halides and 1-aryl-2-(trimethylsilyl)acetylenes  

Microsoft Academic Search

A one-pot procedure for the direct coupling of 1-aryl-2-trimethylsilylacetylenes with aryl halides to give diaryl acetylenes is reported. The procedure does not involve the use of copper(I) iodide. Improvement in reaction yields has been obtained by replacing conventional oil bath heating with the use of microwave dielectric heating.

Ulrik S. Sørensen; Esteban Pombo-Villar

2005-01-01

296

New insights into the microstructure-separation properties of organosilica membranes with ethane, ethylene, and acetylene bridges.  

PubMed

Microporous organosilica membranes with ethane, ethylene, and acetylene bridges have been developed and the extensive microstructural characterization has been discussed in relation with separation properties of the membrane. The organosilica network structure and the membrane performances can be controlled by adjusting the flexibility, size, and electronic structure of the bridging groups. A relatively narrow size distribution was obtained for the novel acetylene-bridged sol by optimizing the sol synthesis. Incorporation of larger rigid bridges into organosilica networks resulted in a looser microstructure of the membrane, which was quantitatively evaluated by N2 sorption and positron annihilation lifetime (PAL) measurements. Molecular weight cutoff (MWCO) measurements indicated that the acetylene-bridged membrane had a larger effective separation pore size than ethane- and ethylene-bridged membranes, leading to a relatively low NaCl rejection in reverse osmosis. In quantum chemical calculations, a more open pore structure and increased polarization was observed for the acetylene-bridged networks, which led to a significant improvement in water permeability. The present study will offer new insight into design of high-performance molecular separation membranes. PMID:24873373

Xu, Rong; Ibrahim, Suhaina M; Kanezashi, Masakoto; Yoshioka, Tomohisa; Ito, Kenji; Ohshita, Joji; Tsuru, Toshinori

2014-06-25

297

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

NASA Technical Reports Server (NTRS)

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.

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

1991-01-01

298

Nitrogen fixation (acetylene reduction) in the sediments of the Pluss-See: with special attention to the role of sedimentation  

Microsoft Academic Search

Sediments of productive lakes are usually rich in organic matter and, except for a thin surficial layer, anaerobic. These conditions seem to be favourable for heterotrophic nitrogen fixation. However, these sediments also contain relatively high ammonium concentrations. Ammonium represses the synthesis of the enzyme nitrogenase. Moreover, ammonium inhibits the activity of the enzyme in aerobic nitrogen fixers. These effects of

T. S. Blauw

1987-01-01

299

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

NASA Technical Reports Server (NTRS)

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.

Walch, Stephen P.

1995-01-01

300

6-azauracil sensitivity assay for yeast.  

PubMed

INTRODUCTIONTreatment of yeast with 6-Azauracil (6AU) leads to a reduction of intracellular GTP levels. The reduction in GTP levels is not itself lethal, but can block yeast growth when combined with mutations that affect transcriptional elongation. 6AU sensitivity thus can be used as a crude assay to test for mutations that affect transcriptional elongation. The assay described here requires growing saturated cultures of yeast, counting, and spotting serial dilutions of yeast on both CSM and CSM + 6AU plates. PMID:22484669

Tansey, William P

2006-01-01

301

Formation of complex organics in the gas phase by sequential reactions of acetylene with the phenylium ion.  

PubMed

In this paper, we report a study on the reactivity of the phenylium ion with acetylene, by measuring product yield as a function of pressure and temperature using mass-selected ion mobility mass spectrometry. The reactivity is dominated by a rapid sequential addition of acetylene to form covalently bonded C8H7(+) and C10H9(+) ions with an overall rate coefficient of 7-5 × 10(-10) cm(3) s(-1), indicating a reaction efficiency of nearly 50% at room temperature. The covalent bonding nature of the product ions is confirmed by high temperature studies where enhanced production of these ions is observed at temperatures as high as 660 K. DFT calculations at the UPBEPBE/6-31++G** level identify the C8H7(+) adduct as 2-phenyl-ethenylium ion, the most stable C8H7(+) isomer that maintains the phenylium ion structure. A small barrier of 1.6 kcal/mol is measured and attributed to the formation of the second adduct C10H9(+) containing a four-membered ring connected to the phenylium ion. Evidence for rearrangement of the C10H9(+) adduct to the protonated naphthalene structure at temperatures higher than 600 K is provided and suggests further reactions with acetylene with the elimination of an H atom and an H2 molecule to generate 1-naphthylacetylene or acenaphthylene cations. The high reactivity of the phenylium ion toward acetylene is in sharp contrast to the low reactivity of the benzene radical cation with a reaction efficiency of 10(-4)-10(-5), confirming that the first step in the cation ring growth mechanism is the loss of an aromatic H atom. The observed reactions can explain the formation of complex organics by gas phase ion-molecule reactions involving the phenylium ion and acetylene under a wide range of temperatures and pressures in astrochemical environments. PMID:22889439

Soliman, Abdel-Rahman; Hamid, Ahmed M; Momoh, Paul O; El-Shall, M Samy; Taylor, Danielle; Gallagher, Lauren; Abrash, Samuel A

2012-09-13

302

Carbon material formation on SBA-15 and Ni-SBA-15 and residue constituents during acetylene decomposition.  

PubMed

Carbon materials including carbon spheres and nanotubes were formed from acetylene decomposition on hydrogen-reduced SBA-15 and Ni-SBA-15 at 650-850°C. The physicochemical characteristics of SBA-15, Ni-SBA-15 and carbon materials were analyzed by field emission scanning electronic microscopy (FE-SEM), Raman spectrometry, and energy dispersive spectrometry (EDS). In addition, the contents of polyaromatic hydrocarbons (PAHs) in the tar and residue and volatile organic compounds (VOCs) in the exhaust were determined during acetylene decomposition on SBA-15 and Ni-SBA-15. Spherical carbon materials were observed on SBA-15 during acetylene decomposition at 750 and 850°C. Carbon filaments and ball spheres were formed on Ni-SBA-15 at 650-850°C. Raman spectroscopy revealed peaks at 1290 (D-band, disorder mode, amorphous carbon) and 1590 (G-band, graphite sp(2) structure)cm(-1). Naphthalene (2 rings), pyrene (4 rings), phenanthrene (3 rings), and fluoranthene (4 rings) were major PAHs in tar and residues. Exhaust constituents of hydrocarbon (as propane), H2, and C2H2 were 3.9-2.6/2.7-1.5, 1.4-2.8/2.6-4.3, 4.2-2.4/3.2-1.7% when acetylene was decomposed on SBA-15/Ni-SBA-15, respectively, corresponding to temperatures ranging from 650 to 850°C. The concentrations of 52 VOCs ranged from 9359 to 5658 and 2488 to 1104ppm for SBA-15 and Ni-SBA-15 respectively, at acetylene decomposition temperatures from 650 to 850°C, and the aromatics contributed more than 87% fraction of VOC concentrations. PMID:24858051

Chiang, Hung-Lung; Wu, Trong-Neng; Ho, Yung-Shou; Zeng, Li-Xuan

2014-07-15

303

The skin-blanching assay.  

PubMed

The skin-blanching assay is used for the determination and bioequivalence of dermatologic glucocorticoids (GCs). The exact mechanism of the production of blanching is not fully understood, but it is considered that local vasoconstriction of the skin microvasculature and the consequent blood-flow reduction cause this phenomenon. Several factors influence skin blanching, including drug concentration, duration of application, nature of vehicle, occlusion, posture and location. The intensity of vasoconstriction can be measured in several ways: visual or quantitative methods, such as reflectance spectroscopy, thermography, laser Doppler velocimetry and chromametry. In literature, contradicting results in the correlation of the skin-blanching assay with different tests to determine GC sensitivity have been reported, limiting its clinical usefulness. PMID:22303935

Smit, P; Neumann, H A M; Thio, H B

2012-10-01

304

Analysis of the seed oil of Heisteria silvanii (Olacaceae)—A rich source of a novel C 18 acetylenic fatty acid  

Microsoft Academic Search

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\\u000a 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%)

Volker Spitzer; Werner Tomberg; Rudolf Hartmann; Reiner Aichholz

1997-01-01

305

Analysis for Mar Vel Black and acetylene soot low reflectivity surfaces for star tracker sunshade applications  

NASA Technical Reports Server (NTRS)

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.

Yung, E.

1974-01-01

306

Dynamics of intramolecular vibrational redistribution in terminal acetylene molecules studies by time-resolved Raman spectroscopy  

NASA Astrophysics Data System (ADS)

We report the first direct investigations of vibrational dynamics in isolated polyatomic molecules by means of Raman spectroscopy. A pump-probe experimental scheme is applied where laser pumping of one mode of a molecule is followed by probing its anti-Stokes Raman spectrum, so that a decrease ofRaman signal with the probe-pump delay time tells us about intramolecular vibrational redistribution (IVR) of the energy from the initially excited mode to the other modes. Experimental results for terminal acetylene molecules are presented and discussed. The principal observation is that IVR times in our studies are much shorter than those estimated previously for the same molecules from high-resolution spectroscopy ofthe cold molecular beams. We analyze this difference assuming that the rotational degrees of freedom, which are highly populated in our case of gas at room temperature, play an important role in mediating IVR in the molecules under consideration.

Malinovsky, Alexander L.; Makarov, Alexander A.; Ryabov, Evgeny A.

2006-12-01

307

Shape and optical properties of aerosols formed by photolysis of acetylene, ethylene, and hydrogen cyanide  

NASA Astrophysics Data System (ADS)

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.

Bar-Nun, A.; Kleinfeld, I.; Ganor, E.

1988-07-01

308

Analytic approximations of burning velocities and flame thicknessesof lean hydrogen, methane, ethylene, ethane, acetylene, and propaneflames  

Microsoft Academic Search

The objective of this study is to provide accurate analytical expressions\\u000d\\u000a\\u0009for the burning velocity and flame thickness of lean hydrogen, methane,\\u000d\\u000a\\u0009ethylene, ethane, acetylene, and propane flames. Starting from a\\u000d\\u000a\\u0009detailed kinetic mechanism of 82 elementary reactions, numerical\\u000d\\u000a\\u0009computations were performed for pressures between 1 and 40 bar, unburnt\\u000d\\u000a\\u0009temperatures between 298 K and 800 K (500 K for

J. Gottgens; F. Mauss; N. Peters

1992-01-01

309

Particle formation in acetylene very low-pressure high density magnetized plasmas  

NASA Astrophysics Data System (ADS)

Particle formation in cold plasmas is a matter of a large number of studies in capacitive, high-pressure, and low-density discharges. Conversely, under very-low working pressure and high plasma density conditions, as in microwave multipolar plasma excited at distributed electron cyclotron resonance (MMP-DECR), particle formation is generally not favored: the gas phase interaction probability is low due to the very-low working pressure. However, in this work, we report observations and analyses of particles formed in acetylene MMP-DECR discharges. It is proposed that the presence of the magnetic field compensates for the very-low working pressure inducing an increase in the gas phase interaction probability: negative ions are repelled by the sheath and confined within the magnetic field. Thus, particles can be formed similarly to in rf plasma.

Calafat, Maria; Escaich, David; Clergereaux, Richard; Raynaud, Patrice; Segui, Yvan

2007-10-01

310

Synthesis and magnetic properties of aligned carbon nanotubes by microwave-assisted pyrolysis of acetylene  

NASA Astrophysics Data System (ADS)

Aligned carbon nanotubes with high quality were synthesized at low temperature by microwave-assisted pyrolysis of acetylene in nitrogen atmosphere. The morphology and structure of the products were characterized by field-emission scanning electron microscopy, high resolution transmission electron microscopy, X-ray diffraction and Raman spectroscopy. The results indicated that the ACNTs with high crystallinity are densely packed, and some Fe3C nanoparticles are encapsulated in all parts of carbon tubes. In addition, the effect of the reaction temperature on the morphologies of the CNTs was also studied in detail. Magnetic measurements showed that the Fe3C-filled ACNTs display ferromagnetic properties at room temperature, and can be easily manipulated by an external magnetic field.

Fu, Dongju; Ma, Qing; Zeng, Xierong; Chen, Jianjun; Zhang, Weili; Li, Dongshuang

2013-12-01

311

Benzene···acetylene: a structural investigation of the prototypical CH···? interaction.  

PubMed

The structure of a prototype CH···? system, benzene···acetylene, has been determined in the gas phase using Fourier-transform microwave spectroscopy. The spectrum is consistent with an effective C(6v) structure with an H···? distance of 2.4921(1) Å. The HCCH subunit likely tilts by ~5° from the benzene symmetry axis. The dipole moment was determined to be 0.438(11) D from Stark effect measurements. The observed intermolecular distance is longer than in similar benzene···HX complexes and than the distances observed in the benzene···HCCH cocrystal and predicted by many high level ab initio calculations; however, the experimentally estimated binding energy of 7.1(7) kJ mol(-1) is similar to previously studied benzene···HX complexes. Several additional sets of transitions were observed in the rotational spectrum, likely corresponding to excited states arising from low energy intermolecular vibrational modes of the dimer. PMID:24686437

Ulrich, Nathan W; Seifert, Nathan A; Dorris, Rachel E; Peebles, Rebecca A; Pate, Brooks H; Peebles, Sean A

2014-05-21

312

The - CO_2--ACETYLENE Complex: Fundamental and Torsional Combination Band in the CO_2 ?_3 Region  

NASA Astrophysics Data System (ADS)

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.

Lauzin, C.; Oliaee, J. Norooz; Rezaei, M.; Moazzen-Ahmadi, N.

2011-06-01

313

Shock-tube pyrolysis of acetylene - Sensitivity analysis of the reaction mechanism for soot formation  

NASA Technical Reports Server (NTRS)

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.

Frenklach, M.; Clary, D. W.; Gardiner, W. C., Jr.; Stein, S. E.

1986-01-01

314

Tabletop imaging of structural evolutions in chemical reactions demonstrated for the acetylene cation.  

PubMed

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

Ibrahim, Heide; Wales, Benji; Beaulieu, Samuel; Schmidt, Bruno E; Thiré, Nicolas; Fowe, Emmanuel P; Bisson, Eric; Hebeisen, Christoph T; Wanie, Vincent; Giguére, Mathieu; Kieffer, Jean-Claude; Spanner, Michael; Bandrauk, André D; Sanderson, Joseph; Schuurman, Michael S; Légaré, François

2014-01-01

315

Emission spectra of nitrous oxide supported acetylene flames at atmospheric pressure.  

PubMed

The emission spectra of a premixed flame of acetylene supported by nitrous oxide have been recorded under different fuel-gas mixture conditions. The emission spectra in these flames of a series of metals, for which it is difficult to obtain a significant population of ground state atoms for atomic absorption spectroscopy in more conventional flames, have also been studied. The red secondary zone which is present in the fuel-rich flames shows emission attributable to long-lived CN and NH species which form a strongly reducing atmosphere to inhibit refractory oxide formation from elements such as molybdenum, titanium and aluminium introduced into the flame. An attempt has also been made to explain some of the reactions which may occur between the flame species above the primary reaction zone. PMID:18960164

Kirkbright, G F; Peters, M K; West, T S

1967-07-01

316

Analysis of Effluent Gases During the CCVD Growth of Multi Wall Carbon Nanotubes from Acetylene  

NASA Technical Reports Server (NTRS)

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.

Schmitt, T. C.; Biris, A. S.; Miller, D. W.; Biris, A. R.; Lupu, D.; Trigwell, S.; Rahman, Z. U.

2005-01-01

317

Infrared Spectra of Acetylene Diluted in Solid Nitrogen upon Irradiation with Vacuum Ultraviolet Light and Electrons  

NASA Astrophysics Data System (ADS)

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.

Wu, Yu-Jong; Chuang, Shiang-Jiun; Chen, Sian-Cong; Huang, Tzu-Ping

2014-05-01

318

Indene formation from alkylated aromatics: kinetics and products of the fulvenallene + acetylene reaction.  

PubMed

A novel reaction is described for formation of the polyaromatic hydrocarbon (PAH) indene in aromatic flames, via the reaction of fulvenallene with acetylene (C2H2). Fulvenallene has been recently identified as the major decomposition product of the benzyl radical, the dominant intermediate in the oxidation of alkylated aromatic hydrocarbons, yet it is not presently included in kinetic models for aromatic oxidation or PAH/soot formation. Ab initio calculations with the G3B3 theoretical method show that acetylene adds to fulvenallene with a barrier of around 27 kcal mol(-1). This forms an activated C9H8 adduct that can rearrange to indene and dissociate to 1-indenyl + H with energy barriers below that of the entrance channel. Master equation simulations across a range of temperature and pressure conditions demonstrate that for temperatures relevant to combustion indene is the dominant product at high pressures while 1-indenyl + H dominate at lower pressures. At low to moderate temperatures, the production of collision stabilized cyclopentadiene-fulvene intermediates is also significant. The results presented in this study provide a new pathway to cyclopenta-fused PAHs in aromatic combustion and are expected to improve modeling of PAH and soot formation. The formation of cyclopenta-fused C5-C6 structures is required to describe the flame synthesis of carbon nanoparticles like fullerenes and buckybowls (corannulene). Improved rate expressions are also reported for the 1-indenyl + H --> indene association reaction, and for the reverse dissociation, from variational transition state theory calculations. The new rate constants are significantly different than current estimates, primarily due to a re-evaluation of the indene C-H bond dissociation energy. PMID:19603772

da Silva, Gabriel; Bozzelli, Joseph W

2009-08-01

319

Soot Volume Fraction Maps for Normal and Reduced Gravity Laminar Acetylene Jet Diffusion Flames  

NASA Technical Reports Server (NTRS)

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.

Greenberg, Paul S.; Ku, Jerry C.

1997-01-01

320

Effect of the nature of carbonaceous supports on the bioelectrocatalytic activity of peroxidase, immobilized on the supports, in the hydrogen peroxide reduction reaction  

Microsoft Academic Search

Electrochemical properties of such disperse carbonaceous materials as acetylene black AD-100, finely divided colloidal graphite\\u000a (FCG), ultradisperse diamond (UDD), and carbon nanotubes (CNT) are examined. Effect of the nature of disperse carbonaceous\\u000a supports on bioelectrocatalytic activity of adsorbed peroxidase (POD) in the hydrogen peroxide reduction reaction is investigated.\\u000a It is shown that the hydrogen peroxide reduction on the biocatalysts studied

M. A. Osina; V. A. Bogdanovskaya

2006-01-01

321

ARC-Coal Acetylene Process Development Program. Phase 1B. Final Technical Progress Report, 15 September 1979-31 September 1980.  

National Technical Information Service (NTIS)

For many years, acetylene was a major feedstock in the chemical industry, being used for the manufacture of such important large-volume chemicals as vinyl chloride, vinyl acetate, acrylonitrile, acetaldehyde, and several others chemicals. Since the mid-19...

1980-01-01

322

Fungicide resistance assays for fungal plant pathogens.  

PubMed

Fungicide resistance assays are useful to determine if a fungal pathogen has developed resistance to a fungicide used to manage the disease it causes. Laboratory assays are used to determine loss of sensitivity, or resistance, to a fungicide and can explain fungicide failures and for developing successful fungicide recommendations in the field. Laboratory assays for fungicide resistance are conducted by measuring reductions in growth or spore germination of fungi in the presence of fungicide, or by molecular procedures. This chapter describes two techniques for measuring fungicide resistance, using the sugarbeet leaf spot fungus Cercospora beticola as a model for the protocol. Two procedures are described for fungicides from two different classes; growth reduction for triazole (sterol demethylation inhibitor; DMI) fungicides, and inhibition of spore germination for quinone outside inhibitor (QoI) fungicides. PMID:22183666

Secor, Gary A; Rivera, Viviana V

2012-01-01

323

Absolute nuclear material assay  

DOEpatents

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.

Prasad, Manoj K. (Pleasanton, CA); Snyderman, Neal J. (Berkeley, CA); Rowland, Mark S. (Alamo, CA)

2012-05-15

324

Absolute nuclear material assay  

DOEpatents

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.

Prasad, Manoj K. (Pleasanton, CA) [Pleasanton, CA; Snyderman, Neal J. (Berkeley, CA) [Berkeley, CA; Rowland, Mark S. (Alamo, CA) [Alamo, CA

2010-07-13

325

Factor XII assay  

MedlinePLUS

Hageman factor assay ... test if a family member was diagnosed with factor XII deficiency. ... Decreased factor XII activity may indicate: Inherited (congenital) deficiency of factor XII Liver disease

326

Growth of multiwalled carbon nanotubes from acetylene over in situ formed Co nanoparticles on MgO support  

NASA Astrophysics Data System (ADS)

The performance of Co catalysts supported on MgO at different Co loading (10%-75%) for the formation of carbon nanotubes through acetylene decomposition at 600 ?C with H 2/C 2H 2 mixture for 1 h is investigated. The yield of MWNTs increases with an increase in Co loading (up to 50%). Starting from 1 g of catalyst precursor, about 8 g of MWNTs was obtained. The XRD patterns of catalyst precursor indicate the presence of cobalt in oxidic phase that eventually transformed into the catalytically active Co nanoparticles (12-18 nm) under the influence of acetylene and was responsible for the growth of coiled-like multi-walled CNTs as revealed by SEM and HRTEM images. It is suggested that bending in coil shaped MWNTs has the potential for functionalization for its biomedical applications.

Singh, B. K.; Ryu, Hojin; Chikate, Rajeev C.; Hoa, Nguyen Duc; Park, Soo Jin; Kim, Seok; Lee, Jae Rock

2006-07-01

327

A geochemical model of non-ideal solutions in the methane-ethane-propane-nitrogen-acetylene system on Titan  

NASA Astrophysics Data System (ADS)

Saturn's largest moon, Titan, has an atmosphere and surface that are rich in organic compounds. Liquid hydrocarbons exist on the surface, most famously as lakes. Photochemical reactions produce solid organics in Titan's atmosphere, and these materials settle or snow onto the surface. At the surface, liquids can interact with solids, and geochemical processes can occur. The consequences of these processes can be explored using a thermodynamic model to calculate the solubilities of gases and solids in liquid hydrocarbons at cryogenic temperatures. The van Laar model developed in this study was parameterized using experimental phase equilibrium data, and accurately represents the data for the CH4-C2H6-C3H8-N2-C2H2 chemical system from 90 to 110 K. The model generally gives more accurate results than existing models. The model also features a suitable balance between accuracy and simplicity, and can serve as a foundation for studies of fluvial geochemistry on Titan because it can be extended to any number of components while maintaining thermodynamic consistency. Application of the model to Titan reveals that the equilibrium composition of surface liquids depends on the abundance of methane gas in the local atmosphere, consistent with prior studies. The concentration of molecular nitrogen in Titan's lakes varies inversely with the ethane content of the lakes. The model indicates that solid acetylene should be quite soluble in surface liquids, which implies that acetylene-rich sedimentary rocks would be susceptible to chemical erosion, and acetylene evaporites may form on Titan. The geochemical character of acetylene in liquid hydrocarbons on Titan appears to be intermediate to those of calcite and gypsum in surface waters on Earth. Specific recommendations are given of observational, experimental, and theoretical work that will lead to significant advancements in our knowledge of geochemical processes on Titan. This paper represents the beginning of a new kind of geochemistry, called cryogenic fluvial geochemistry, with Titan starring as the first example.

Glein, Christopher R.; Shock, Everett L.

2013-08-01

328

Catalyst-free synthesis of reduced graphene oxide-carbon nanotube hybrid materials by acetylene-assisted annealing graphene oxide  

NASA Astrophysics Data System (ADS)

A facile catalyst-free approach for synthesis of reduced graphene oxide-carbon nanotube (RGO-CNT) hybrid materials was presented by acetylene-assisted annealing graphene oxide. The weight ratio of CNTs to RGO can be adjusted by regulating the annealing temperature, and it can be tuned in a relatively wide range of 0.33 to 7.039. The catalyst-free method opens up the possibility for the synthesis of RGO-CNTs for various applications.

Liu, Fuchi; Li, Ming; Feng, Qian; Tang, Nujiang; Zhong, Wei; Huang, Wei; Du, Youwei

2012-09-01

329

Vibrationally highly excited acetylene as studied by dispersed fluorescence and stimulated emission pumping spectroscopy: Vibrational assignment of the feature states  

Microsoft Academic Search

The dispersed fluorescence (DF) and stimulated emission pumping (SEP) spectra of acetylene originating from single rovibronic levels of the A˜ 1Au state were measured with resolutions of 30 and 0.5 cm?1, respectively, in order to examine the vibrational level structure of the electronic ground X˜ 1?+g state. The SEP spectra revealed that the number of vibrational levels under each peak

Kaoru Yamanouchi; Naru Ikeda; Soji Tsuchiya; David M. Jonas; James K. Lundberg; George W. Adamson; Robert W. Field

1991-01-01

330

Laser induced transition from soot generation to shell shaped carbon nanoparticles in an acetylene flow: aerosol characterization  

Microsoft Academic Search

Shell shaped carbon nanoparticles were synthesized from acetylene flow injected inside an oxygen-hydrogen diffusion flame\\u000a when it was irradiated with a focused beam of a CW CO2 laser above a certain laser power and at a certain position [1]. In the present study, the evolution of carbon nanoparticles\\u000a generated under laser irradiation has been investigated together with a study on

Young Jeong Kim; Sanghoon Lee; Peter Pikhitsa; Mansoo Choi

2008-01-01

331

Acetylene - Argon Plasmas Measured at a Biased Substrate Electrode for Diamond-Like Carbon Deposition. Part 1: Mass Spectroscopy  

Microsoft Academic Search

We report, for the first time, quadrupole mass spectrometry of neutral and\\u000apositive ionic hydrocarbon species measured at the rf biased substrate\\u000aelectrode of an inductively coupled plasma for acetylene rich C2H2:Ar mixtures\\u000aunder various bias, frequency and pressure conditions. It has been observed\\u000athat, irrespective of initial gas mixture, the resultant plasma is dominated by\\u000aargon neutrals and ions.

A. Baby; C M O Mahony; P. D. Maguire

2008-01-01

332

Spectroscopy in separated flames-III Use of the separated nitrous oxide-acetylene flame in thermal emission spectroscopy.  

PubMed

The separation of a premixed nitrous oxide-acetylene flame at a modified commercial burner is described. The reducing interconal zone of the fuel-rich separated flame exhibits low radiative background. The reducing atmosphere and high temperature of this flame result in an effective medium for the excitation of the atomic line spectra of the refractory elements. The use of the fuel-rich flame in the flame photometry of these elements has been investigated. PMID:18960318

Kirkbright, G F; Semb, A; West, T S

1968-05-01

333

Kinetics of OH Radicals from Flame Emission Spectra V. A Study of the Acetylene-Oxygen Flame  

Microsoft Academic Search

The inner cone of the acetylene-oxygen flame burning lean (1:5), stoichiometric (2:5), and rich (4:5) at atmospheric pressure has been studied spectroscopically with the object of gaining some information about the elementary processes occurring in this flame. The rotational, vibrational, and electronic distributions of OH(2?+) have been determined for each fuel mixture. The analysis of the data showed a rotational

K. E. Shuler; H. P. Broida

1952-01-01

334

The influences of alloy elements on the carburized layer in steels using vacuum carburization in an acetylene atmosphere  

Microsoft Academic Search

In this article, three commercial steels, JIS SCM 415, JIS SNCM 220 and AISI 1008 were carburized in a two-chamber vacuum furnace at temperature ranging between 900 and 1050°C in an acetylene atmosphere. Steel SCM 415 consists of mainly 0.12% C, 1.0% Cr and 0.17% Mo, steel SNCM 220 consists of 0.18% C, 0.55% Mo, 0.42% Cr and 0.17% Mo,

Lee-Der Liu; Fan-Shiong Chen

2003-01-01

335

Ultrafast hydrogen scrambling in methylacetylene and methyl-d3-acetylene ions induced by intense laser fields.  

PubMed

Three-body Coulomb explosion processes of triply charged positive ions of methylacetylene (CH(3)-C?C-H) and its isotopomer, methyl-d(3)-acetylene (CD(3)-C?C-H), induced by an ultrashort intense laser field (790 nm, ?40 fs, 5.0 × 10(13) W cm(-2)) are investigated by the coincidence momentum imaging method. Two types of three-body decomposition processes accompanying the ejection of a proton are identified for methylacetylene, and six types of three-body decomposition processes accompanying the ejection of a proton or a deuteron are identified for methyl-d(3)-acetylene. From the observed momentum vectors of all the three fragment ions for each decomposition pathway, the proton and deuteron distributions are constructed in the coordinate space, and the hydrogen migration processes are investigated. It was shown that the hydrogen migration proceeds more efficiently from the methyl group than from the methine group. In addition to the decomposition pathways accompanying the migration of one H (or D) atom, the decomposition pathways accompanying the migration of two light atoms (H/D exchange and 2D migration) are identified. Furthermore, the decomposition pathways ascribable to the migration of three light atoms (H/D exchange followed by D migration) are identified, showing the high intramolecular mobilities of H and D atoms within methylacetylene and methyl-d(3)-acetylene in an intense laser field, resulting in the H/D scrambling. PMID:22751449

Okino, Tomoya; Watanabe, Anri; Xu, Huailiang; Yamanouchi, Kaoru

2012-08-14

336

Angular and energy distribution of fragment ions in dissociative double photoionization of acetylene molecules at 39 eV  

SciTech Connect

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.

Alagia, M. [IOM CNR Laboratorio TASC, I-34012 Trieste (Italy); Callegari, C.; Richter, R. [Sincrotrone Trieste, Area Science Park, 34149 Basovizza, Trieste (Italy); Candori, P.; Falcinelli, S.; Vecchiocattivi, F. [Dipartimento di Ingegneria Civile ed Ambientale, 06125 Perugia (Italy); Pirani, F. [Dipartimento di Chimica dell'Universita di Perugia, 06123 Perugia (Italy); Stranges, S. [IOM CNR Laboratorio TASC, I-34012 Trieste (Italy); Dipartimento di Chimica, Universita di Roma ''La Sapienza'', 00185 Roma (Italy)

2012-05-28

337

Tuberosity Reduction  

MedlinePLUS

... forming. Tuberosity reductions are less common today because dental implants are becoming more popular. In addition, fewer people lose all their teeth and require upper dentures. However, some people with teeth and some who ...

338

Breast reduction  

MedlinePLUS

... smoke, you must stop. Women who smoke after breast surgery have a higher risk of poor healing, infection, ... likely to have a very good outcome from breast reduction surgery. You may feel better about your appearance and ...

339

Uremia Toxin Assay.  

National Technical Information Service (NTIS)

The purpose of the research was to find assay systems which could be used in attempts to isolate the supposed toxins of uremia. A total of 14 enzyme assay systems were tested against fractions of plasma, dialysate, and urine from both uremic subjects unde...

C. E. Cook

1970-01-01

340

Analyte detection assay  

US Patent & Trademark Office Database

A rapid and sensitive analyte detection assay is based on whispering gallery modes of fluorescently labelled microspheroidal particles. Ligands for the analyte, such as nucleic acids, are anchored to the particles. The fluorescent labels may comprise fluorophores or quantum dots. In the latter case, the particles may comprise melamine formaldehyde. The assay may be used to detect analytes in aqueous samples.

2013-12-31

341

Quantum Chemical Evaluation of the Astrochemical Significance of Reactions between S Atom and Acetylene or Ethylene  

NASA Technical Reports Server (NTRS)

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.

Woon, David E.

2007-01-01

342

Single-cell assays  

PubMed Central

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 microfabrication—conventional or otherwise—and 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.

Ryan, Declan; Ren, Kangning; Wu, Hongkai

2011-01-01

343

APPLICABILITY OF MICROBIAL TOXICITY ASSAYS TO ASSESSMENT PROBLEMS  

EPA Science Inventory

Microbial assays of dissolved oxygen (DO) uptake and resazurin reduction (RR) assays were compared with regard to applicability for hazard assessment schemes and determination of bioactive residues in soil and biota. The DO method is simpler and less expensive but is less sensiti...

344

Seasonal variations of temperature, acetylene and ethane in Saturn's atmosphere from 2005 to 2010, as observed by Cassini-CIRS  

NASA Astrophysics Data System (ADS)

Acetylene (C2H2) and ethane (C2H6) are by-products of complex photochemistry in the stratosphere of Saturn. Both hydrocarbons are important to the thermal balance of Saturn's stratosphere and serve as tracers of vertical motion in the lower stratosphere. Earlier studies of Saturn's hydrocarbons using Cassini-CIRS observations have provided only a snapshot of their behaviour. Following the vernal equinox in August 2009, Saturn's northern and southern hemispheres have entered spring and autumn, respectively, however the response of Saturn's hydrocarbons to this seasonal shift remains to be determined. In this paper, we investigate how the thermal structure and concentrations of acetylene and ethane have evolved with the changing season on Saturn. We retrieve the vertical temperature profiles and acetylene and ethane volume mixing ratios from ??˜=15.5cm-1 Cassini-CIRS observations. In comparing 2005 (solar longitude, Ls ˜ 308°), 2009 (Ls ˜ 3°) and 2010 (Ls ˜ 15°) results, we observe the disappearance of Saturn's warm southern polar hood with cooling of up to 17.1 K ± 0.8 K at 1.1 mbar at high-southern latitudes. Comparison of the derived temperature trend in this region with a radiative climate model (Section 4 of Fletcher et al., 2010 and Greathouse et al. (2013, in preparation)) indicates that this cooling is radiative although dynamical changes in this region cannot be ruled out. We observe a 21 ± 12% enrichment of acetylene and a 29 ± 11% enrichment of ethane at 25°N from 2005 to 2009, suggesting downwelling at this latitude. At 15°S, both acetylene and ethane exhibit a decrease in concentration of 6 ± 11% and 17 ± 9% from 2005 to 2010, respectively, which suggests upwelling at this latitude (though a statistically significant change is only exhibited by ethane). These implied vertical motions at 15°S and 25°N are consistent with a recently-developed global circulation model of Saturn's tropopause and stratosphere(Friedson and Moses, 2012), which predicts this pattern of upwelling and downwelling as a result of a seasonally-reversing Hadley circulation. Ethane exhibits a general enrichment at mid-northern latitudes from 2005 to 2009. As the northern hemisphere approaches summer solstice in 2017, this feature might indicate an onset of a meridional enrichment of ethane, as has been observed in the southern hemisphere during/after southern summer solstice.

Sinclair, J. A.; Irwin, P. G. J.; Fletcher, L. N.; Moses, J. I.; Greathouse, T. K.; Friedson, A. J.; Hesman, B.; Hurley, J.; Merlet, C.

2013-07-01

345

Phase Space Exploration of Acetylene at Energies up to 13,000 Cm-1  

NASA Astrophysics Data System (ADS)

The rotation-vibration Hamiltonian of acetylene is known in detail up to 13,000 Cm-1 in the electronic ground state, allows the calculation of time-dependent dynamics for postulated excitations of certain bright states. Three different measures of phase space exploration are examined including the participation number, Gruebele's dispersion, and the Shannon entropy. The time scales for phase space exploration span the range from 20 fs to 10 ps. The volume of phase space explored by the dynamics increases with energy and the rotational quantum number, J reaching about 90% of the (GOE) statistical limit at 12,000 Cm-1 and J = 100. At low and intermediate J, the extent of phase space exploration is reduced for the local bender and counter-rotator bright states as compared to their normal mode counterparts. However, the phase space exploration of the local mode CH stretch state is similar to that of the corresponding normal mode vibration. These calculations shed light on the applicability of the energy randomization assumption that is at the heart of the Rice-Rampsberger-Kassel-Marcus (RRKM) theory of unimolecular reactions.

Perry, David S.; Martens, Jonathan; Herman, Michel; Amyay, Badr

2011-06-01

346

Photolysis of phosphine in the presence of acetylene and propyne, gas mixtures of planetary interest.  

PubMed

Phosphine (PH3) 1 has been observed in the atmospheres of Jupiter and Saturn. We have studied the photochemical reactions of this compound with acetylene (C2H2), an alkyne also detected in these atmospheres. The volatile products formed in these reactions were characterized by H, 31P and 13C NMR. The ethenylphosphine 2 is the first product formed in the photolysis of PH3 in the presence Of C2H2. Photolysis of PH3 in the presence of propyne (C3H4) led to the formation of the Z- and E-prop-1-enylphosphines and traces of 1-methylethenylphosphine. A reaction pathway is proposed. The initial step is the dissociation of PH3 to hydrogen and PH2 radicals. Addition of the phosphinyl radical on alkyne occurs as the next step. Vinylphosphines are then formed by radical combination. This proposed reaction pathway takes into account the nature of the products and studies devoted to the photolysis of germane (GeH4) or hydrogen sulfide (H2S) in the presence of alkyne. Attempts to detect the methylidynephosphine HC triple bond P (the isoelectronic compound of HC triple bond N), in the photolysis products of PH3-C2H2 mixtures were unsuccessful. The application of these findings to Jovian and Saturn atmospheric chemistry is discussed. PMID:11543539

Guillemin, J C; Janati, T; Lassalle, L

1995-01-01

347

Molecular Heterogeneous Catalysis: a Single-Site Zeolite-Supported Rhodium Complex for Acetylene Cyclotrimerization  

SciTech Connect

By anchoring metal complexes to supports, researchers have attempted to combine the high activity and selectivity of molecular homogeneous catalysis with the ease of separation and lack of corrosion of heterogeneous catalysis. However, the intrinsic nonuniformity of supports has limited attempts to make supported catalysts truly uniform. We report the synthesis and performance of such a catalyst, made from [Rh(C{sub 2}H{sub 4}){sub 2}(CH{sub 3}COCHCOCH{sub 3})] and a crystalline support, dealuminated Y zeolite, giving {l_brace}Rh(C{sub 2}H{sub 4}){sub 2}{r_brace} groups anchored by bonds to two zeolite oxygen ions, with the structure determined by extended X-ray absorption fine structure (EXAFS) spectroscopy and the uniformity of the supported complex demonstrated by {sup 13}C NMR spectroscopy. When the ethylene ligands are replaced by acetylene, catalytic cyclotrimerization to benzene ensues. Characterizing the working catalyst, we observed evidence of intermediates in the catalytic cycle by NMR spectroscopy. Calculations at the level of density functional theory confirmed the structure of the as-synthesized supported metal complex determined by EXAFS spectroscopy. With this structure as an anchor, we used the computational results to elucidate the catalytic cycle (including transition states), finding results in agreement with the NMR spectra.

Kletnieks, P.W.; Liang, A.J.; Craciun, R.; Ehresmann, J.O.; Marcus, D.M.; Bhirud, V.A.; Klaric, M.M.; Hayman, M.J.; Guenther, D.R.; Bagatchenko, O.P.; Dixon, D.A.; Gates, B.C.; Haw, J.F.

2009-06-01

348

Infrared spectroscopy and Mie scattering of acetylene aerosols formed in a low temperature diffusion cell  

NASA Technical Reports Server (NTRS)

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.

Dunder, T.; Miller, R. E.

1990-01-01

349

Ion enhanced deposition by dual titanium and acetylene plasma immersion ion implantation  

NASA Astrophysics Data System (ADS)

Plasma immersion ion implantation and deposition (PIII-D) offers a non-line-of-sight fabrication method for various types of thin films on steels to improve the surface properties. In this work, titanium films were first deposited on 9Cr18 (AISI440) stainless bearing steel by metal plasma immersion ion implantation and deposition (MePIII-D) using a titanium vacuum arc plasma source. Afterwards, carbon implantation and carbon film deposition were performed by acetylene (C2H2) plasma immersion ion implantation. Multiple-layered structures with superior properties were produced by conducting Ti MePIII-D + C2H2 PIII successively. The composition and structure of the films were investigated employing Auger electron spectroscopy and Raman spectroscopy. It is shown that the mixing for Ti and C atoms is much better when the target bias is higher during Ti MePIII-D. A top diamond-like carbon layer and a titanium oxycarbide layer are formed on the 9Cr18 steel surface. The wear test results indicate that this dual PIII-D method can significantly enhance the wear properties and decrease the surface friction coefficient of 9Cr18 steel.

Zeng, Z. M.; Tian, X. B.; Chu, P. K.

2003-01-01

350

Acetylene Dynamics at Energies up to 13,000 Cm-1  

NASA Astrophysics Data System (ADS)

The rotation-vibration Hamiltonian of acetylene is known in detail up to 13,000 Cm-1 in the electronic ground state and allows the calculation of time-dependent dynamics for postulated excitations of certain bright states. The spectroscopic Hamiltonian, derived by Herman, includes four types of off-diagonal interactions: vibrational l-resonances, rotational l-resonances, anharmonic coupling, and Coriolis coupling. At high energies, hundreds of states may be coupled in each polyad and the rate and extent of intramolecular vibrational redistribution (IVR) increase substantially with rotational excitation. As each coupling mechanism becomes active, a hierarchical, sequential flow of probability through the different regions of phase space occurs on timescales ranging from 20 fs to 10 ps. As the energy is increased from one polyad to the next, the dynamics of similar bright states are similar; however, the dynamics depend critically on the nature of the bright state excited within a given polyad. The rotationally-mediated dynamics of the local CH stretch, the local bender and counter-rotator bright states are qualitatively similar to their normal mode counterparts. Didriche, K. & Herman, M., Chem. Phys. Lett. 496, 1-7 (2010)

Martens, Jonathan; Perry, David S.; Herman, Michel; Amyay, Badr

2011-06-01

351

MPI photoelectron spectroscopy of ungerade excited states of acetylene: Intermediate state mixing and ion state selection  

SciTech Connect

Three photon resonant, four photon (3+1) ionization spectroscopy and photoelectron spectroscopy have been used to study the ungerade excited states of acetylene in the energy range from 74 500 to 90 000 cm/sup -1/. Sharp bands from the nR (..pi../sup 3//sub u/ nssigma/sub g/) and /sup 1/Phi/sub u/ (..pi../sup 3//sub u/ nddelta/sub g/) Rydberg series dominate the MPI spectrum. A large number of Rydberg and valence states which are prominent in VUV absorption spectra are absent or weak in MPI studies. These weak bands are only observable under high power conditions, which suggests that nonradiative decay is rapid enough to depopulate these states before ionization occurs. The photoelectron results provide further insight into the nature of the excited states. Ionization through the sharp bands occurs via ..delta nu.. = 0 Franck--Condon transitions, resulting in ions in a single vibrational state. Ionization through bands which are mixed results in complicated ion vibrational distributions including excitation of both cis and trans bends.

Orlando, T.M.; Anderson, S.L.; Appling, J.R.; White, M.G.

1987-07-15

352

Theoretical and practical limitations of the acetylene inhibition technique to determine total denitrification losses  

NASA Astrophysics Data System (ADS)

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.

Felber, R.; Conen, F.; Flechard, C. R.; Neftel, A.

2012-10-01

353

Cycloheximide prevents the de novo polypeptide synthesis required to recover from acetylene inhibition in Nitrosopumilus maritimus.  

PubMed

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 (C2 H2 )-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 C2 H2 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

Vajrala, Neeraja; Bottomley, Peter J; Stahl, David A; Arp, Daniel J; Sayavedra-Soto, Luis A

2014-06-01

354

Production of ethane, ethylene, and acetylene from halogenated hydrocarbons by methanogenic bacteria  

SciTech Connect

Several methanogenic bacteria were shown to produce ethane, ethylene, and acetylene when exposed to the halogenated hydrocarbons bromoethane, dibromo- or dichloroethane, and 1,2-dibromoethylene, respectively. They also produced ethylene when exposed to the coenzyme M analog and specific methanogenic inhibitor bromoethanesulfonic acid. The production of these gases from halogenated hydrocarbons has a variety of implications concerning microbial ecology, agriculture, and toxic waste treatment. All halogenated aliphatic compounds tested were inhibitory to methanogens. Methanococcus thermolithotrophicus, Methanococcus deltae, and Methanobacterium thermoautotrophicum ..delta..H and Marburg were completely inhibited by 7 ..mu..M 1,2-dibromoethane and, to various degrees, by 51 to 1084 ..mu..M 1,2-dichloroethane, 1,2-dibromoethylene, 1,2-dichloroethylene, and trichloroethylene. In general, the brominated compounds were more inhibitory. The two Methanococcus species were fully inhibited by 1 ..mu..M bromoethanesulfonic acid, whereas both Methanobacterium strains were only partly inhibited by 2124 ..mu..M. Coenzyme M protected cells from bromoethanesulfonic acid but not from any of the other inhibitors.

Belay, N.; Daniels, L.

1987-07-01

355

Photolysis of phosphine in the presence of acetylene and propyne, gas mixtures of planetary interest  

NASA Astrophysics Data System (ADS)

Phosphine (PH_3) 1 has been observed in the atmospheres of Jupiter and Saturn. We have studied the photochemical reactions of this compound with acetylene (C_2H_2), an alkyne also detected in these atmospheres. The volatile products formed in these reactions were characterized by ^1H, ^31P and ^13C NMR. The ethenylphosphine 2 is the first product formed in the photolysis of PH_3 in the presence of C_2H_2. Photolysis of PH_3 in the presence of propyne (C_3H_4) led to the formation of the Z- and E-prop-1-enylphosphines and traces of 1-methylethenylphosphine. A reaction pathway is proposed. The initial step is the dissociation of PH_3 to hydrogen and PH_2 radicals. Addition of the phosphinyl radical on alkyne occurs as the next step. Vinylphosphines are then formed by radical combination. This proposed reaction pathway takes into account the nature of the products and studies devoted to the photolysis of germane (GeH_4) or hydrogen sulfide (H_2S) in the presence of alkyne. Attempts to detect the methylidynephosphine HC=P (the isoelectronic compound of HC=N), in the photolysis products of PH_3-C_2H_2 mixtures were unsuccessful. The application of these findings to Jovian and Saturn atmospheric chemistry is discussed.

Guillemin, J.-C.; Janati, T.; Lassalle, L.

1995-08-01

356

Human Health Effects Assays.  

National Technical Information Service (NTIS)

The use of assays to evaluate and assist in predicting potentially adverse human health effects associated with exposure to pollutants in water (that is, municipal wastewater, sewage sludge, ambient water, and drinking water) is the focus of the review.

L. Fradkin C. Sonich-Mullin M. Cerny C. Kruger F. Cavender

1989-01-01

357

Factor V assay  

MedlinePLUS

The factor V assay is a blood test to measure the activity of factor V. This is a substances involved in blood clotting ( ... Decreased factor V activity may be related to: Deficiency of factor ... at birth (congenital) Disseminated intravascular coagulation ( ...

358

New Rapid Spore Assay  

NASA Astrophysics Data System (ADS)

The presentation will detail approved Planetary Protection specifications for the Rapid Spore Assay for spacecraft components and subsystems. Outlined will be the research and studies on which the specifications were based. The research, funded by ESA and NASA/JPL, was conducted over a period of two years and was followed by limited cleanroom studies to assess the feasibility of this assay during spacecraft assembly.

Kminek, Gerhard; Conley, Catharine

2012-07-01

359

Doped colorimetric assay liposomes  

DOEpatents

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.

Charych, Deborah (Albany, CA); Stevens, Raymond C. (Albany, CA)

2001-01-01

360

Noise reduction  

NASA Technical Reports Server (NTRS)

The turbofan engine's noise-producing components are discussed in terms of efficient and economical noise reduction techniques that do not penalize the engine performance or weight significantly. Specific topics covered include fan noise, acoustic suppression, jet noise technology, combustor noise, and aircraft noise prediction.

Feiler, C. E.; Groeneweg, J. F.; Montegani, F. J.; Raney, J. P.; Rice, E. J.; Stone, J. R.

1979-01-01

361

Waste Reduction.  

ERIC Educational Resources Information Center

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…

Bray, Marilyn; And Others

1996-01-01

362

Regioselectivity in the reaction of tantalum-unsymmetrical acetylene complexes with carbonyl compounds. Stereoselective preparation of 1-alkenyl sulfides, [alpha],[beta]-unsaturated esters, and amides  

SciTech Connect

Tantalum-alkyne complexes, derived by treatment of aklynes with low-valent tantalum (TaCl[sub 5] and zinc), react in situ with carbonyl compounds to give (E)-allylic alcohols stereoselectively. When unsymmetrical acetylenes are employed in the reaction, two regioisomeric allylic alcohols are produced. The regioselectivity of the reaction depends on the steric and electronic effects of the substituents on the acetylenes. For example, treatment of tantalum-allkyne complexes derived from methyl alkynyl sulfides with carbonyl compounds yields (E)-3-hydroxy-1-propenyl methyl sulfides in a regioselective manner. Tantalum-alkyne complexes derived from acetylenic esters react with carbonyl compounds regioselectively at the [alpha]-position of the esters to give Z-isomers of trisubstituted [alpha],[beta]-unsaturated esters. In contract, tantalum-alkyne complexes derived from acetylenic amides react with carbonyl compounds predominantly at the [beta]-position of the amides. The regioselectivity of the reaction between acytylenic amides and aldehydes, however, cannot be explained solely in terms of the steric and electronic effects of the substituents. Strong coordination of the amide group to the tantalum center could also be responsible for the observed selectivity, which is opposite to that observed with tantalum-acetylenic ester complexes. 18 refs., 1 tab.

Kataoka, Yasutaka; Miyai, Jiro; Tezuka, Makoto; Takai, Kazuhiko; Utimoto, Kiitiro (Kyoto Univ., Yoshida (Japan))

1992-12-04

363

Methane Post-Processor Development to Increase Oxygen Recovery beyond State-of-the-Art Carbon Dioxide Reduction Technology  

NASA Technical Reports Server (NTRS)

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.

Abney, Morgan; Miller, Lee; Greenwood, Zach; Iannantuono, Michelle; Jones, Kenny

2013-01-01

364

Methane Post-Processor Development to Increase Oxygen Recovery beyond State-of-the-Art Carbon Dioxide Reduction Technology  

NASA Technical Reports Server (NTRS)

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

Abney, Morgan B.; Greenwood, Zachary; Miller, Lee A.; Alvarez, Giraldo; Iannantuono, Michelle; Jones, Kenny

2013-01-01

365

A rapid, multiwell colorimetric assay for chemotaxis.  

PubMed

This paper describes a colorimetric assay for the rapid quantification of chemotaxis in multiple samples. In this assay, cells that have migrated through polycarbonate membrane filters are collected onto the bottom wells of a chemotaxis chamber after centrifugation then the number of viable cells collected in the bottom well is quantified by measurement of the reduction of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenol tetrazolium bromide (MTT). The degree of MTT reduction, which corresponds to the relative cell number, is measured automatically with an ELISA reader. The MTT method of quantitation is as sensitive as the standard manual method, is especially useful for large numbers of samples and requires no specialized laboratory equipment. PMID:8370922

Shi, Y; Kornovski, B S; Savani, R; Turley, E A

1993-09-15

366

An experimental and theoretical study of nitrogen-broadened acetylene lines  

NASA Astrophysics Data System (ADS)

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 C2H2-N2 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 Q- and 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.

Thibault, Franck; Martínez, Raúl Z.; Bermejo, Dionisio; Ivanov, Sergey V.; Buzykin, Oleg G.; Ma, Qiancheng

2014-07-01

367

Uranium Reduction  

SciTech Connect

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.

Wall, J.D.; Krumholz, L.R.

2007-04-02

368

Nitrate reduction  

DOEpatents

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.

Dziewinski, Jacek J. (Los Alamos, NM); Marczak, Stanislaw (Los Alamos, NM)

2000-01-01

369

Chromogenic factor VIII activity assay.  

PubMed

Factor VIII (FVIII) may be measured by three different methodologies in the clinical laboratory: one-stage clotting assay, two-stage clotting assay, and chromogenic assay. These assays differ in ease of use, variety of reagents available, sensitivity to mild hemophilia A, and interference from lupus anticoagulants. This review will outline the methodology for each of the FVIII activity assays, with a discussion of assay interferences and variability. In some cases, chromogenic FVIII activity assays may be preferable to clot-based assays, and these clinical situations will be reviewed as well. Am. J. Hematol. 89:781-784, 2014. © 2014 Wiley Periodicals, Inc. PMID:24676945

Moser, Karen A; Adcock Funk, Dorothy M

2014-07-01

370

Differential inhibition of thromboxane B2 and leukotriene B4 biosynthesis by two naturally occurring acetylenic fatty acids.  

PubMed

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

Croft, K D; Beilin, L J; Ford, G L

1987-10-17

371

A guide to Sonogashira cross-coupling reactions: the influence of substituents in aryl bromides, acetylenes, and phosphines.  

PubMed

The conversion-time data for 168 different Pd/Cu-catalyzed Sonogashira cross-coupling reactions of five arylacetylenes (phenylacetylene; 1-ethynyl-2-ethylbenzene; 1-ethynyl-2,4,6-R(3)-benzene (R = Me, Et, i-Pr)) and Me(3)SiCCH with seven aryl bromides (three 2-R-bromobenzenes (R = Me, Et, i-Pr); 2,6-Me(2)-bromobenzene and three 2,4,6-R(3)-bromobenzenes (R = Me, Et, i-Pr)) with four different phosphines (P-t-Bu(3), t-Bu(2)PCy, t-BuPCy(2), PCy(3)) were determined using quantitative gas chromatography. The stereoelectronic properties of the substituents in the aryl bromides, acetylenes, and phosphines were correlated with the performance in Sonogashira reactions. It was found that the nature of the most active Pd/PR(3) complex for a Sonogashira transformation is primarily determined by the steric bulk of the acetylene; ideal catalysts are: Pd/P-t-Bu(3) or Pd/t-Bu(2)PCy for sterically undemanding phenylacetylene, Pd/t-BuPCy(2) for 2- and 2,6-substituted arylacetylenes or Me(3)SiCCH and Pd/PCy(3) for extremely bulky acetylenes and aryl bromides. Electron-rich and sterically demanding aryl bromides with substituents in the 2- or the 2,6-position require larger amounts of catalyst than 4-substituted aryl bromides. The synthesis of tolanes with bulky groups at one of the two aryl rings is best done by placing the steric bulk at the arylacetylene, which is also the best place for electron-withdrawing substituents. PMID:22390837

Schilz, Marc; Plenio, Herbert

2012-03-16

372

Reactions of gas phase H atoms with ethylene, acetylene and ethane adsorbed on Ni( 1 1 1 )  

NASA Astrophysics Data System (ADS)

The products of the reaction of the most energetic form of hydrogen, gas phase H atoms, with ethylene, acetylene and ethane adsorbed on a Ni(1 1 1) surface at 60 K are probed. Adsorbed ethylidyne (CCH 3) is identified by high resolution electron energy loss spectroscopy to be the major product (30% yield) in all three cases. Adsorbed acetylene is a minor product (3% yield) and arises as a consequence of a dynamic equilibrium between CCH 3 and C 2H 2 in the presence of gas phase H atoms. The observation of the same product for the reaction of H atoms with all three hydrocarbons implies that CCH 3 is the most stable C 2 species in the presence of coadsorbed hydrogen. The rates of CCH 3 production are measured as a function of the time of exposure of H atoms to each hydrocarbon. A simple kinetic model treating each reaction as a pseudo-first order reaction in the hydrocarbon coverage is fit to these data. A mechanism for the formation of CCH 3 via a CHCH 2 intermediate common to all three reactants is proposed to describe this model. The observed instability of the CH 2CH 3 species relative to C 2H 4 plays a role in the formulation of this mechanism as does the observed stability of CHCH 2 species in the presence of coadsorbed hydrogen. The CH 2CH 3 and the CHCH 2 species are produced by the translational activation of ethane and the dissociative ionization of ethane and ethylene, respectively. In addition, the binding energy and the vibrational spectrum of ethane adsorbed on Ni(1 1 1) are determined and exceptionally high resolution vibrational spectra of adsorbed ethylene and acetylene are presented.

Bürgi, T.; Trautman, T. R.; Gostein, M.; Lahr, D. L.; Haug, K. L.; Ceyer, S. T.

2002-03-01

373

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)

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.

Stiegman, A. E.; Graham, Eva; Khundkar, Lutfur R.; Perry, Joseph W.; Cheng, L.-T.; Perry, Kelly J.

1991-01-01

374

Heat of Combustion of the Product Formed by the Reaction of Acetylene and Diborane (LFPL-CZ-3)  

NASA Technical Reports Server (NTRS)

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.

Allen, Harrison, Jr.; Tannenbaum, Stanley

1957-01-01

375

Separation of esbiothrin and D-acetylene C permethrin in electric-mosquito coils by gas chromatography  

Microsoft Academic Search

A simple and sensitive gas chromatography method for the simultaneous determination of esbiothrin and D-acetylene C permethrin\\u000a in electric-mosquito coils using palmitic acid isopropyl as an internal standard was developed. The electric-mosquito coil\\u000a samples were extracted with petroleum ether (60–90 °C) and then centrifuged at 2,000 r\\/min for 2.0 min. The supernatant liquids\\u000a were collected into a glass bottle and

Junyu Liu; Kyung Ho Row

2010-01-01

376

Assays for calcitonin receptors  

SciTech Connect

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.

Teitelbaum, A.P.; Nissenson, R.A.; Arnaud, C.D.

1985-01-01

377

Automated phantom assay system  

SciTech Connect

This paper describes an automated phantom assay system developed for assaying phantoms spiked with minute quantities of radionuclides. The system includes a computer-controlled linear-translation table that positions the phantom at exact distances from a spectrometer. A multichannel analyzer (MCA) interfaces with a computer to collect gamma spectral data. Signals transmitted between the controller and MCA synchronize data collection and phantom positioning. Measured data are then stored on disk for subsequent analysis. The automated system allows continuous unattended operation and ensures reproducible results.

Sisk, D.R.; Nichols, L.L.; Olsen, P.C.

1991-11-01

378

Lateral flow strip assay  

DOEpatents

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.

Miles, Robin R. (Danville, CA) [Danville, CA; Benett, William J. (Livermore, CA) [Livermore, CA; Coleman, Matthew A. (Oakland, CA) [Oakland, CA; Pearson, Francesca S. (Livermore, CA) [Livermore, CA; Nasarabadi, Shanavaz L. (Livermore, CA) [Livermore, CA

2011-03-08

379

Adsorption and reaction of acetylene on clean and oxygen-precovered Pd(100) studied with high-resolution X-ray photoelectron spectroscopy  

NASA Astrophysics Data System (ADS)

We investigated the adsorption and thermal evolution of acetylene on clean Pd(100) and Pd(100) precovered with 0.25 ML oxygen. The measurements were performed in situ by fast XPS at the synchrotron radiation facility BESSY II. On Pd(100) acetylene molecularly adsorbs at 130 K. Upon heating transformation to a CCH species occurs around 390 K along with the formation of a completely dehydrogenated carbon species. On the oxygen-precovered surface partial CCH formation already occurs upon adsorption at 130 K, and the dehydrogenation temperature and the stability range of CCH are shifted to lower temperatures by ~200 K.

Höfert, O.; Lorenz, M. P. A.; Streber, R.; Zhao, W.; Bayer, A.; Steinrück, H.-P.; Papp, C.

2013-10-01

380

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

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.

Yue, Dawei; Yao, Tuanli

2008-01-01

381

Mouse Oocyte Toxicity Assay.  

National Technical Information Service (NTIS)

A standard toxicity assay based on the mouse oocyte system is described. Its application to toxicity determinations of complex mixtures as well as of pure compounds is shown. Because its oocytes are especially sensitive, the juvenile mouse is used. To fac...

J. S. Felton R. L. Dobson

1982-01-01

382

Broad-band frequency references in the near-infrared: Accurate dual comb spectroscopy of methane and acetylene  

NASA Astrophysics Data System (ADS)

The Doppler-limited spectra of methane between 176 THz and 184 THz (5870-6130 cm-1) and acetylene between 193 THz and 199 THz (6430-6630 cm-1) are acquired via comb-tooth resolved dual comb spectroscopy with frequency accuracy traceable to atomic standards. A least squares analysis of the measured absorbance and phase line shapes provides line center frequencies with absolute accuracy of 0.2 MHz, or less than one thousandth of the room temperature Doppler width. This accuracy is verified through comparison with previous saturated absorption spectroscopy of 37 strong isolated lines of acetylene. For the methane spectrum, the center frequencies of 46 well-isolated strong lines are determined with similar high accuracy, along with the center frequencies for 1107 non-isolated lines at lower accuracy. The measured methane line-center frequencies have an uncertainty comparable to the few available laser heterodyne measurements in this region but span a much larger optical bandwidth, marking the first broad-band measurements of the methane 2?3 region directly referenced to atomic frequency standards. This study demonstrates the promise of dual comb spectroscopy to obtain high resolution broadband spectra that are comparable to state-of-the-art Fourier-transform spectrometer measurements but with much improved frequency accuracy.Work of the US government, not subject to US copyright.

Zolot, A. M.; Giorgetta, F. R.; Baumann, E.; Swann, W. C.; Coddington, I.; Newbury, N. R.

2013-03-01

383

Quantum Chemical Simulations Reveal Acetylene-Based Growth Mechanisms in the Chemical Vapor Deposition Synthesis of Carbon Nanotubes  

SciTech Connect

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.

Eres, Gyula [ORNL] [ORNL; Wang, Ying [Nagoya University, Japan] [Nagoya University, Japan; Gao, Xingfa [Institute of High Energy Physics, Chinese Academy of Sciences, China] [Institute of High Energy Physics, Chinese Academy of Sciences, China; Qian, Hu-Jun [Jilin University, Changchun] [Jilin University, Changchun; Ohta, Yasuhito [Fukui Institute of Fundamental Chemistry, Kyoto University, Kyoto 606-8103, Japan] [Fukui Institute of Fundamental Chemistry, Kyoto University, Kyoto 606-8103, Japan; Wu, Xiaona [Nagoya University, Japan] [Nagoya University, Japan; Morokuma, Keiji [Fukui Institute of Fundamental Chemistry, Kyoto University, Kyoto 606-8103, Japan] [Fukui Institute of Fundamental Chemistry, Kyoto University, Kyoto 606-8103, Japan; Irle, Stephan [WPI-Institute of Transformative Bio-Molecules and Department of Chemistry, Nagoya University, Japan] [WPI-Institute of Transformative Bio-Molecules and Department of Chemistry, Nagoya University, Japan

2014-01-01

384

Rapid analysis of dissolved methane, ethylene, acetylene and ethane using partition coefficients and headspace-gas chromatography.  

PubMed

Analysis of dissolved methane, ethylene, acetylene, and ethane in water is crucial in evaluating anaerobic activity and investigating the sources of hydrocarbon contamination in aquatic environments. A rapid chromatographic method based on phase equilibrium between water and its headspace is developed for these analytes. The new method requires minimal sample preparation and no special apparatus except those associated with gas chromatography. Instead of Henry's Law used in similar previous studies, partition coefficients are used for the first time to calculate concentrations of dissolved hydrocarbon gases, which considerably simplifies the calculation involved. Partition coefficients are determined to be 128, 27.9, 1.28, and 96.3 at 30°C for methane, ethylene, acetylene, and ethane, respectively. It was discovered that the volume ratio of gas-to-liquid phase is critical to the accuracy of the measurements. The method performance can be readily improved by reducing the volume ratio of the two phases. Method validation shows less than 6% variation in accuracy and precision except at low levels of methane where interferences occur in ambient air. Method detection limits are determined to be in the low ng/L range for all analytes. The performance of the method is further tested using environmental samples collected from various sites in Nova Scotia. PMID:21682997

Lomond, Jasmine S; Tong, Anthony Z

2011-01-01

385

Rationally tuned micropores within enantiopure metal-organic frameworks for highly selective separation of acetylene and ethylene  

SciTech Connect

Separation of acetylene and ethylene is an important industrial process because both compounds are essential reagents for a range of chemical products and materials. Current separation approaches include the partial hydrogenation of acetylene into ethylene over a supported Pd catalyst, and the extraction of cracked olefins using an organic solvent; both routes are costly and energy consuming. Adsorption technologies may allow separation, but microporous materials exhibiting highly selective adsorption of C{sub 2}H{sub 2}/C{sub 2}H{sub 4} have not been realized to date. Here, we report the development of tunable microporous enantiopure mixed-metal-organic framework (M'MOF) materials for highly selective separation of C{sub 2}H{sub 2} and C{sub 2}H{sub 4}. The high selectivities achieved suggest the potential application of microporous M'MOFs for practical adsorption-based separation of C{sub 2}H{sub 2}/C{sub 2}H{sub 4}.

Xiang, Sheng-Chang [University of Texas at San Antonio (UTSA); Zhang, Zhangjing [University of Texas at San Antonio (UTSA); Zhao, Cong-Gui [University of Texas at San Antonio (UTSA); Hong, Kunlun [ORNL; Zhao, Xuebo [University of Newcastle upon Tyne; Ding, De-Rong [University of Texas at San Antonio (UTSA); Xie, Ming-Hua [University of Texas, Pan American, Edinburg, TX; Wu, Chuan-De [University of Texas, Pan American, Edinburg, TX; Madhab, Das [University of Texas at San Antonio (UTSA); Gill, Rachel [University of Newcastle upon Tyne; Thomas, K Mark [University of Newcastle upon Tyne; Chen, Banglin [University of Texas at San Antonio (UTSA)

2011-01-01

386

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)

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.

Blass, William E.; Daunt, Stephen J.; Peters, Antoni V.; Weber, Mark C.

1990-01-01

387

In situ TDLAS measurement of absolute acetylene concentration profiles in a non-premixed laminar counter-flow flame  

NASA Astrophysics Data System (ADS)

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 ?) in the flame, resulting in temperature-dependent acetylene detection limits for the P17e line at 6513 cm-1 of up to 2.1 ppm?m. Absolute C2H2 concentration profiles were obtained by translating the burner through the laser beam using a DC motor with 100 ?m 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.

Wagner, S.; Klein, M.; Kathrotia, T.; Riedel, U.; Kissel, T.; Dreizler, A.; Ebert, V.

2012-06-01

388

Titan haze: structure and properties of cyanoacetylene and cyanoacetylene-acetylene photopolymers  

NASA Technical Reports Server (NTRS)

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.

Clarke, D. W.; Ferris, J. P.

1997-01-01

389

Differential solubility of ethylene and acetylene in room-temperature ionic liquids: a theoretical study.  

PubMed

The room-temperature ionic liquids (RTILs) have potential in realizing the ethylene (C(2)H(4)) and acetylene (C(2)H(2)) separation and avoiding solvent loss and environmental pollution compared with traditional solvents. The interaction mechanisms between gases and RTILs are important for the exploration of new RTILs for gas separation; thus, they were studied by quantum chemical calculation and molecular dynamics simulation in this work. The optimized geometries were obtained for the complexes of C(2)H(4)/C(2)H(2) with anions (Tf(2)N(-), BF(4)(-), and OAc(-)), cation (bmim(+)), and their ion pairs, and the analysis for geometry, interaction energy, natural bond orbital (NBO), and atoms in molecules (AIM) was performed. The quantum chemical calculation results show that the hydrogen-bonding interaction between the gas molecule and anion is the dominant factor in determining the solubility of C(2)H(2) in RTILs. However, the hydrogen-bonding interaction, the p-? interaction in C(2)H(4)-anion, and the ?-? interaction in C(2)H(4)-cation are weak and comparable, which all affect the solubility of C(2)H(4) in RTILs with comparable contribution. The calculated results for the distance of H(gas)···X (X = O or F in anions), the BSSE-corrected interaction energy, the electron density of H(gas)···X at the bond critical point (?(BCP)), and the relative second-order perturbation stabilization energy (E(2)) are consistent with the experimental data that C(2)H(2) is more soluble than C(2)H(4) in the same RTILs and the solubility of C(2)H(4) in RTILs has the following order: [bmim][Tf(2)N] > [bmim][OAc] > [bmim][BF(4)]. The calculated results also agree with the order of C(2)H(2) solubility in different RTILs that [bmim][OAc] > [bmim][BF(4)] > [bmim][Tf(2)N]. Furthermore, the calculation results indicate that there is strong C(2)H(2)-RTIL interaction, which cannot be negligible compared to the RTIL-RTIL interaction; thus, the regular solution theory is probably not suitable to correlate C(2)H(2) solubility in RTILs. The molecular dynamics simulation results show that the hydrogen bond between the H in C2 of the imidazolium cation and the anion will weaken the hydrogen-bonding interaction of the gas molecule and anion in a realistic solution condition, especially in the C(2)H(4)-RTIL system. PMID:22414155

Zhao, Xu; Xing, Huabin; Yang, Qiwei; Li, Rulong; Su, Baogen; Bao, Zongbi; Yang, Yiwen; Ren, Qilong

2012-04-01

390

Nitrous oxide reduction in nodules: denitrification or N/sub 2/ fixation  

SciTech Connect

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.

Coyne, M.S.; Focht, D.D.

1987-05-01

391

Assessment of biological nitrogen fixation  

Microsoft Academic Search

The four commonly used methods for measuring biological nitrogen fixation (BNF) in plants are: the total nitrogen difference (TND) method, acetylene reduction assay (ARA) technique, xylem-solute (or ureide production) method and the use of15N labelled compounds.

S. K. A. Danso

1995-01-01

392

Kinetic Tetrazolium Microtiter Assay  

NASA Technical Reports Server (NTRS)

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.

Pierson, Duane L.; Stowe, Raymond; Koenig, David

1993-01-01

393

Arabidopsis assay for mutagenicity.  

PubMed

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

Gichner, T; Badayev, S A; Demchenko, S I; Relichová, J; Sandhu, S S; Usmanov, P D; Usmanova, O; Velemínský, J

1994-10-16

394

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

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…

Sharpless, William D.; Peng Wu; Hansen, Trond Vidar; Lindberg, James G.

2005-01-01

395

The treatment of electron correlation in aperiodic systems. II. Applications to poly(Li 2H 2) and poly(acetylene, carbyne) chains  

NASA Astrophysics Data System (ADS)

A new method for the calculation of the density of states of aperiodic polymers at the quasiparticle level (electronic structure with correlation) has been applied to poly (Li 2H 2) and to poly (acetylene, carbyne) chains. Both the periodic and the aperiodic copolymers have been studied.

Liegener, C.-M.; Bakhshi, A. K.; Sutjianto, A.; Otto, P.

1989-05-01

396

The small-scale production of (U-14C)acetylene from Ba14CO3: Application to labeling of ammonia monooxygenase in autotrophic nitrifying bacteria  

SciTech Connect

A small-scale method has been adapted from an established procedure for the generation of (U-14C)acetylene from inexpensive and commonly available precursors. The method involves the fusing of Ba14CO3 with excess barium metal to produce Ba14C2. The BaC2 is reacted with water to generate acetylene which is then selectively dissolved into dimethyl sulfoxide (DMSO). The results presented demonstrate the effect of Ba:BaCO3 ratio on the concentrations of various gases released during the hydrolysis reaction and quantify the selectivity of the DMSO-trapping process for each gas. (U-14C)Acetylene generated by this method has been used to inactivate ammonia monooxygenase in three species of autotrophic nitrifying bacteria: Nitrosomonas europaea, Nitrosococcus oceanus, and Nitrosolobus multiformis. Our results demonstrate that acetylene inactivation of this enzyme in all three species results in the covalent incorporation of radioactive label into a polypeptide of apparent Mr of 25,000-27,000, as determined by sodium dodecylsulfate-polyacrylamide gel electrophoresis and fluorography.

Hyman, M.R.; Arp, D.J. (Oregon State Univ., Corvallis (USA))

1990-11-01

397

Coupling of chiral 1-bromo-1,2-dienes with zinc-based cuprates: a new procedure for the regio and stereoselective synthesis of functionalized acetylenic compounds  

Microsoft Academic Search

Zinc alkylcyanocuprates (Knochel reagents) are found to be active in the cross-coupling reaction with allenic bromides affording acetylenic products with a high regio and stereoselective 1,3-anti substitution. The coupling process, which has been successfully extended to functionalized cuprates, can also be performed with alkylzinc chlorides in the presence of catalytic amounts of cuprous salts.

Anna Maria Caporusso; Sara Filippi; Federica Barontini; Piero Salvadori

2000-01-01

398

Synthesis of substituted 3-furanoates from MBH-acetates of acetylenic aldehydes via tandem isomerization-deacetylation-cycloisomerization: access to Elliott's alcohol.  

PubMed

A new method for the synthesis of 5-substituted furan-3-carboxylates from Morita-Baylis-Hillman acetates of acetylenic aldehydes is reported. The process involves palladium-catalyzed isomerization followed by base-promoted deacetylation and cycloisomerization reactions. The utility of this chemistry is further demonstrated by the synthesis of Elliott's alcohol, a key intermediate of the pyrethroid resmethrins. PMID:24492976

Reddy, Chada Raji; Krishna, Gaddam; Reddy, Motatipally Damoder

2014-03-14

399

The role of tin-promoted Pd/MWNTs via the management of carbonaceous species in selective hydrogenation of high concentration acetylene  

NASA Astrophysics Data System (ADS)

In the present study, Pd/MWNTs are synthesized using polyol process and modified by tin as a promoter for selective hydrogenation of high concentrated acetylene feedstock. Polyol method results in highly dispersed nanoparticles with a depletion of particle size for tin-promoted Pd catalysts as characterized by TEM. Tin promoter plays a considerable role in hydrogenation of pure acetylene stream. This is attributed to formation of Pd2Sn structural phase, confirmed by XRD and TPR techniques, composed mainly of intermetallic species. Catalytic behavior of tin-promoted Pd catalysts is affected by geometric and electronic factors which are more pronounced in the case of Sn/Pd = 0.25. A discontinuity in Arrhenius plots for the Sn-promoted catalysts is appeared, which seems to be due to a kinetic factor as a result of change in acetylene coverage on Pd metallic ensembles at low and high temperature ranges. Higher selectivity of the catalysts to ethylene is attributed to the presence of more isolated adsorption sites on the catalyst surface originated from both intermetallic compounds confirmed by XPS and the ones formed via the carbonaceous species upon the acetylene hydrogenation reaction.

Esmaeili, Elaheh; Mortazavi, Yadollah; Khodadadi, Abbas Ali; Rashidi, Ali Morad; Rashidzadeh, Mehdi

2012-12-01

400

2,5Bis(butyltelluro) thiophene as a convenient precursor for the synthesis of 2,5-bis-(acetylenic) thiophenes  

Microsoft Academic Search

Both symmetrically and unsymmetrically substituted 2,5-bis-(acetylenic) thiophene derivatives were obtained in good yields under mild conditions through palladium-catalyzed cross coupling reaction of 2,5-bis-(butyltelluro) thiophene 2 and terminal alkynes. The methodology represents a general and efficient protocol for carrying out the synthesis of thiophene derivatives with potential biological activities.

Gilson Zeni; Cristina W. Nogueira; Dagoberto O. Silva; Paulo H. Menezes; Antonio L. Braga; Hélio A. Stefani; João B. T. Rocha

2003-01-01

401

Rapid Colorimetric Assay for Antimicrobial Susceptibility Testing of Pseudomonas aeruginosa  

Microsoft Academic Search

A colorimetric assay based on the reduction of a tetrazolium salt {2,3-bis(2-methyloxy-4-nitro-5-sulfophe- nyl)-2H-tetrazolium-5-carboxanilide (XTT)} for rapidly determining the susceptibility of Pseudomonas aerugi- nosa isolates to bactericidal antibiotics is described. There was excellent agreement between the tobramycin and ofloxacin MICs determined after 5 h using the XTT assay and after 18 h using conventional methods. The data suggests that an XTT-based

Michael M. Tunney; Gordon Ramage; T. R. Field; Thomas F. Moriarty; D. G. Storey

2004-01-01

402

Farnesyl diphosphate synthase assay.  

PubMed

Farnesyl diphosphate synthase (FPS) catalyzes the sequential head-to-tail condensation of isopentenyl diphosphate (IPP, C5) with dimethylallyl diphosphate (DMAPP, C5) and geranyl diphosphate (GPP, C10) to produce farnesyl diphosphate (FPP, C15). This short-chain prenyl diphosphate constitutes a key branch-point of the isoprenoid biosynthetic pathway from which a variety of bioactive isoprenoids that are vital for normal plant growth and survival are produced. Here we describe a protocol to obtain highly purified preparations of recombinant FPS and a radiochemical assay method for measuring FPS activity in purified enzyme preparations and plant tissue extracts. PMID:24777789

Arró, Montserrat; Manzano, David; Ferrer, Albert

2014-01-01

403

COMPUTATIONAL MODELING AND EXPERIMENTAL STUDIES ON NOx REDUCTION UNDER PULVERIZED COAL COMBUSTION CONDITIONS  

SciTech Connect

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.

Subha K. Kumpaty; Kannikeswaran Subramanian; Victor P. Nokku; Tyrus L. Hodges; Adel Hassouneh; Ansumana Darboe; Sravan K. Kumpati

1998-06-01

404

The Breathing Orbital Valence Bond Method in Diffusion Monte Carlo: C-H Bond Dissociation ofAcetylene  

SciTech Connect

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).

Domin, D.; Braida, Benoit; Lester Jr., William A.

2008-05-30

405

Line-shape models testing on six acetylene transitions in the ?1+?3 band broadened by N2  

NASA Astrophysics Data System (ADS)

We present a line-shape study of six absorption lines P(21), P(16), P(19), R(16), R(19) and R(21) in the ?1+?3 band of the acetylene perturbed by nitrogen. The spectra were recorded using a 3-channel diode laser spectrometer. For each transition studied, the N2-broadening, N2-narrowing, N2-pressure induced line shift and N2-line mixing coefficients were retrieved using several line-shape models. Moreover, we compare the N2-narrowing parameter to the dynamical friction parameter. The spectra were recorded over a pressure range from 5 to 250 Torr, and were analyzed using the Voigt, Rautian, Correlated Rautian, Galatry, Rautian-Galatry, Speed Dependent Voigt, Speed Dependent Rautian and Correlated Speed Dependent Rautian line-shape models. Furthermore, we have studied the influence of the type of interaction potential in our analysis for line-shape models that take into account speed dependent effects.

Hashemi, Robab; Rozario, Hoimonti; Povey, Chad; Predoi-Cross, Adriana

2014-06-01

406

A DFT study of the possible role of vinylidene and carbene intermediates in the mechanism of the enzyme acetylene hydratase.  

PubMed

The mode of action of the tungstoprotein, acetylene hydratase, is unresolved at present.We have carried out density functional theory (DFT) calculations to investigate two proposed mechanisms, and also propose a new mechanism based on our calculations. We find that the previously proposed single step mechanisms which involve the attack of a water molecule, catalysed by Asp13, have barriers greater than 40 kcal mol(-1). We propose a new mechanism which involves two tungsten complexes, a vinylidene and a carbene, as stable intermediates. We calculate the potential energy surfaces for their formation, and for the decomposition of the carbene complex to yield acetaldehyde. All the barriers along the pathway are less than 30 kcal mol(-1), except for the barrier to carbene formation which is 34 kcal mol(-1). PMID:20369217

Vincent, Mark A; Hillier, Ian H; Periyasamy, Ganga; Burton, Neil A

2010-04-28

407

A microporous metal-organic framework for highly selective separation of acetylene, ethylene, and ethane from methane at room temperature.  

PubMed

A novel three-dimensional microporous metal-organic framework Zn(4)L(DMA)(4) (UTSA-33, H(8) L=1,2,4,5-tetra(5-isophthalic acid)benzene, DMA=N,N'-dimethylacetamide) with small pores of about 4.8 to 6.5 Å was synthesized and structurally characterized as a non-interpenetrated (4,8)-connected network with the flu topology (Schläfli symbol: (4(12)6(12)8(4))(4(6))(2)). The activated UTSA-33a exhibits highly selective separation of acetylene, ethylene, and ethane from methane with the adsorption selectivities of 12 to 20 at 296 K, which has been established exclusively by the sorption isotherms and simulated breakthrough experiments, thus methane can be readily separated from their binary and even ternary mixtures at room temperature. PMID:22162259

He, Yabing; Zhang, Zhangjing; Xiang, Shengchang; Fronczek, Frank R; Krishna, Rajamani; Chen, Banglin

2012-01-01

408

Upconversion enhanced degenerate four-wave mixing in the mid-infrared for sensitive detection of acetylene in gas flows  

NASA Astrophysics Data System (ADS)

We present a new background free method for in situ gas detection that combines degenerate four-wave mixing with an infra-red light detector based on parametric frequency upconversion of infra-red light. The system is demonstrated at mid infrared wavelengths for low concentration measurements of acetylene diluted in a N2 gas flow at ambient conditions. It is demonstrated that the system is able to cover more than 100 nm in scanning range and detect concentrations as low as 3 ppm based on the R9e line. A major issue in small signal measurements is scattered light and it is showed how a spatial analysis can be used to reduce this level.

Høgstedt, Lasse; Dam, Jeppe Seidelin; Sahlberg, Anna-Lena; Li, Zhongshan; Aldén, Marcus; Pedersen, Christian; Tidemand-Lichtenberg, Peter

2014-02-01

409

Isotope effect in acetylene C2H2 and C2D2 rotations on Cu(001)  

NASA Astrophysics Data System (ADS)

A comprehensive analysis of the elementary processes behind the scanning tunneling microscope controlled rotation of C2H2 and C2D2, isotopologues of a single acetylene molecule adsorbed on the Cu(001) surface, is given, with a focus on the isotope effects. With the help of density-functional theory we calculate the vibrational modes of C2H2 and C2D2 on Cu(001) and estimate the anharmonic couplings between them, using a simple strings-on-rods model. The probability of the elementary processes, nonlinear and combination band, is estimated using the Keldysh diagram technique. This allows us to clarify the main peculiarities and the isotope effects of the C2H2 and C2D2 on Cu(001) rotation, discovered in the pioneering work [B. C. Stipe et al., Phys. Rev. Lett. 81, 1263 (1998), 10.1103/PhysRevLett.81.1263], which have not been previously understood.

Shchadilova, Yulia E.; Tikhodeev, Sergei G.; Paulsson, Magnus; Ueba, Hiromu

2014-04-01

410

Indenyl effect due to metal slippage? Computational exploration of rhodium-catalyzed acetylene [2+2+2] cyclotrimerization.  

PubMed

The mechanism of CpRh (Cp=cyclopentadienyl) and IndRh (Ind=indenyl)-catalyzed acetylene [2+2+2] cyclotrimerization has been revisited aiming at finding an explanation for the better performance of the latter catalyst found experimentally. The hypothesis that an ancillary ligand of the precatalyst remains bonded to the metal center throughout the whole catalytic cycle, based on the experimental evidence that the nature of this ligand can exert some control in cocyclotrimerization of different alkynes, is considered. Strong hapticity variations occur in both the CpRh- and IndRh-catalyzed processes. As the Ind ligand undergoes a more facile slippage than Cp, the energy profile is far smoother in the IndRh-catalyzed cyclotrimerization. This difference in the energetics of the process translates into an enhanced activity of the IndRh catalyst, in nice agreement with experiment. PMID:24273097

Orian, Laura; Swart, Marcel; Bickelhaupt, F Matthias

2014-01-13

411

A bond-bond description of the intermolecular interaction energy: the case of the weakly bound acetylene-hydrogen complex.  

PubMed

A new semiempirical potential energy surface (PES) for the acetylene-hydrogen system has been derived by using the recently introduced bond-bond methodology. The proposed PES, expressed in an analytic form suitable for molecular dynamics simulations, involves a limited number of parameters, each one having a physical meaning and allowing the accurate description of the system also in the less stable configurations. The analysis of novel integral cross sections data, measured with nearly effusive molecular beams, combined with that of available pressure broadening coefficients of isotropic Raman lines at 143 K and IR lines at 173 and 295 K of C(2)H(2) in H(2), provides a test of the reliability of the proposed PES and suggests also some refinements. An extensive comparison with a recent ab initio potential is also exploited. PMID:19842658

Thibault, F; Cappelletti, D; Pirani, F; Bartolomei, M

2009-12-31

412

ABSORPTION CROSS SECTION OF GASEOUS ACETYLENE AT 85 K IN THE WAVELENGTH RANGE 110-155 nm  

SciTech Connect

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.

Cheng, Bing-Ming; Chen, Hui-Fen; Lu, Hsiao-Chi; Chen, Hong-Kai; Alam, M. S.; Chou, Sheng-Lung; Lin, Meng-Yeh, E-mail: bmcheng@nsrrc.org.tw [National Synchrotron Radiation Research Center, No. 101, Hsin-Ann Road, Hsinchu Science Park, Hsinchu 30076, Taiwan (China)

2011-09-01

413

Improving shuffler assay accuracy  

SciTech Connect

Drums of uranium waste should be disposed of in an economical and environmentally sound manner. The most accurate possible assays of the uranium masses in the drums are required for proper disposal. The accuracies of assays from a shuffler are affected by the type of matrix material in the drums. Non-hydrogenous matrices have little effect on neutron transport and accuracies are very good. If self-shielding is known to be a minor problem, good accuracies are also obtained with hydrogenous matrices when a polyethylene sleeve is placed around the drums. But for those cases where self-shielding may be a problem, matrices are hydrogenous, and uranium distributions are non-uniform throughout the drums, the accuracies are degraded. They can be greatly improved by determining the distributions of the uranium and then applying correction factors based on the distributions. This paper describes a technique for determining uranium distributions by using the neutron count rates in detector banks around the waste drum and solving a set of overdetermined linear equations. Other approaches were studied to determine the distributions and are described briefly. Implementation of this correction is anticipated on an existing shuffler next year.

Rinard, P.M.

1995-07-01

414

Ground Based Maps of Acetylene and Ethane Emission in Jupiter's Atmosphere at the Time of the Cassini Encounter  

NASA Astrophysics Data System (ADS)

Cassini's flyby of Jupiter in 2000-2001 provided a unique opportunity to coordinate Earth-based and spacecraft observations of that planet. In particular, the Composite Infrared Spectrometer, CIRS, mapped Jupiter globally at 600-1400 cm-1 during early January 2001. The spectra produced by CIRS covered spectral emission features due to several hydrocarbons with spatial coverage and resolution not previously achieved in the mid-infrared, together with moderate 2.17 cm-1 spectral resolution. We carried out ground based observations that recorded jovian maps of specific emission features of C2H2 (?5 R(5) line at 743.2 cm-1) and C2H6 (?9 RQ0 branch at 822.3 cm-1) at high spectral resolution during late January 2001, shortly after Cassini's closest approach. We used the large echelle cryogenic spectrometer Celeste, developed at Goddard Space Flight Center, at the McMath-Pierce telescope at Kitt Peak. These ground-based maps covered most of the globe with a spatial resolution about half that of CIRS and with superior spectral resolution. We have reduced and modeled the observed spectral emission intensities and from these we have derived meridional hydrocarbon abundance variations and global maps which we can compare with coeval CIRS observations. Our results show that ethane is enhanced in emission in the northern hemisphere mainly due to higher atmospheric temperatures. Its meridional abundance profile shows only slight enhancement in the northern hemisphere and a decrease of a factor of two towards the poles. Acetylene also shows a greater northern hemisphere temperature-induced emission. Its meridional abundance profile is also slightly enhanced in the northern hemisphere and also decreases towards the poles, but by a factor of three. In both hydrocarbons the north polar "hot spot” is evident as a localized emission enhancement, with acetylene being more sensitive to its presence.

Sada, Pedro; Boyle, R. J.; Jennings, D. E.; Bjoraker, G. L.; Hesman, B. E.; Nixon, C. A.; McCabe, G. H.; Edwards, M.

2009-09-01

415

Frequency Comb-Referenced Measurements of - and Nitrogen-Perturbed Line Shape Parameters in the ?_1 + ?_3 Band of Acetylene  

NASA Astrophysics Data System (ADS)

Using an extended cavity diode laser locked to a single component of an Er-fiber-based femtosecond frequency comb, we have made precise measurements of absorption spectral line shapes in a temperature controlled cell. Varying pressures of acetylene and nitrogen were used to determine the N_2 pressure-dependent parameters for the P(11) line in the ?_1 + ?_3 combination band of acetylene at 195 739.649 513(8) GHz. The temperature dependence of the line shape was determined from measurements at several temperatures, varying from 296 K to 125 K. With the absolute frequency positions at each point on the frequency scale determined by the comb, each experimental data set has better than 10-4 fractional error. Parameters describing the line shape, such as pressure-dependent broadening, narrowing and shift coefficients, can be obtained with standard deviations less that 0.1%. The data have been used to test various line shape models beyond the standard Voigt approximation including those with narrowing parameters (Rautian and Galatry models) and those with speed-dependence (Speed-dependent Voigt and Speed-dependent Nelkin-Ghatak models). Fitting results will be presented and the relative performance of the models will be discussed. Acknowledgements:Acknowledgement is made to the Donors of the American Chemical Society Petroleum Research Fund for partial support of this research. CPM gratefully acknowledges support by DOE EPSCoR grant DOE-07ER46361 for work conducted at the University of Oklahoma. The measurements and analyses were performed under grants NNX09AJ93G and NNX08AO78G from the NASA Planetary and Atmospheres program.

Cich, Matthew J.; Lopez, Gary V.; Sears, Trevor J.; McRaven, C. P.; Mantz, A. W.; Hurtmans, Daniel

2012-06-01

416

A Simple Assay Method for Melanosome Transfer  

PubMed Central

Pigmentation is induced by production of melanin in specialized organelles termed melanosomes and by transfer of these organelles from melanocytes to surrounding keratinocytes. The chemical basis of melanogenesis is relatively well known but the mechanism of melanosome transfer is not well studied. Various pigmentary disorders and cosmetic applications require the use of depigmenting agents. Currently available topical agents used for the reduction of pigmentation mainly include tyrosinase inhibitors and/or melanocyte-cytotoxic agents. Recently, several agents have been introduced to inhibit melanosome transfer from melanocytes to keratinocytes. However, an experimental model for melanosome transfer is not well established. In this study, a simple assay method using flow cytometry is described.

Choi, Hye Ryung; Park, So-Hee; Choi, Jae Woo; Kim, Dong-Seok

2012-01-01

417

Cholesterol Efflux Assay  

PubMed Central

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.

Low, Hann; Hoang, Anh; Sviridov, Dmitri

2012-01-01

418

Reduction of nitrogen in a system consisting of Mo(III), Ti(III), pyrocatechol, and sodium amalgam in aqueous solution  

SciTech Connect

Water-soluble complexes of Mo(III) and Ti(III) ions with pyrocatechol (PC) catalyze the electrochemical reduction of a series of unsaturated compounds (CO, CO/sub 2/, CN, MeCN, and acetylene) to form CH/sub 4/. This paper studies the reduction of nitrogen in this system. The experimental set up is described. In contrast to nitrogen fixation of complex hydroxide systems also containing Ti(III) and Mo(III) ions, preliminary data indicate that soluble clusters, which may be reversible reduced, are formd in this system. This permits a detailed study of the reaction mechanism.

Petrova, G.N.; Denisov, N.T.; Efimov, O.N.

1986-01-01

419

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

National Technical Information Service (NTIS)

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 current...

K. Barton L. A. Miller M. B. Abney

2012-01-01

420

Cost of gentamicin assays carried out by microbiology laboratories.  

PubMed Central

AIMS--To assess the current range of prices charged for gentamicin assays in United Kingdom laboratories; and to examine the laboratories' likely response to increases or decreases in the demand for the service. METHODS--A postal survey of the 420 members of the Association of Medical Microbiologists was used to establish the range of prices charged for aminoglycoside assays. Additionally, eight private institutions were contacted to determine what the private sector was charging for aminoglycoside assays. Reagent costs in the NHS laboratories were calculated by dividing the total cost of all aminoglycoside assay kits by the number of samples analysed. RESULTS--The NHS and the private institutions both showed a wide price variation. Prices charged to an in-hospital requester for a peak and trough assay ranged from 5.00 pounds to 68.20 pounds (n = 44), and to an external private hospital, under a bulk service contract, from 5.00 pounds to 96.00 pounds (n = 47). Prices charged by private laboratories ranged from 49.00 pounds to 84.00 pounds (n = 8). There was a log linear correlation in the NHS laboratories between the reagent costs per assay and the number of assays performed per year, and most laboratories thought that their price per assay would be sensitive to increases or decreases in demand. Laboratories which had purchased their assay machines had lower reagent costs per assay but higher repair and maintenance costs. Overall, number of assays performed and method of payment for assay machinery only accounted for 44.8% of the observed variation in assay kit costs. CONCLUSIONS--The price range for gentamicin assays in the United Kingdom is wide and is only partially explained by the number of assays performed. Most laboratories believe that they would experience a reduction in unit cost as output increases. The currently offered range of prices is, in part, due to variation in the laboratories' approach to costing the service provided and some laboratories charge prices which do not even cover the cost of assay kits. Overall, we believe that prices charged should be as close as possible to the marginal cost of the tests performed.

Vacani, P F; Malek, M M; Davey, P G

1993-01-01

421

Perpetual Reductions in Orthogonal Combinatory Reduction Systems.  

National Technical Information Service (NTIS)

A strategy that, for any given term t in an Orthogonal Combinatory Reduction System (OCRS) (that is, a term rewriting system with bound variables and substitutions), constructs a longest reduction starting from t if t is strongly normalizable, and constru...

Z. Khasidashvili

1993-01-01

422

Synthesis of 3-iodoindoles by the Pd/Cu-catalyzed coupling of N,N-dialkyl-2-iodoanilines and terminal acetylenes, followed by electrophilic cyclization.  

PubMed

[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

Yue, Dawei; Yao, Tuanli; Larock, Richard C

2006-01-01

423

Ensemble and ligand effects on the acetylene adsorption on ordered Pd(x)Ag(1-x)/Pd(100) surface alloys investigated by periodic DFT study.  

PubMed

The interactions of acetylene with structurally ordered PdxAg1-x/Pd(100) (x = 1, 0.75, 0.5, 0.25) surface alloys, in which Ag is presented only in the first layer as the computational model system, were investigated by gradient corrected periodic density functional calculations to unravel and understand contributions from electronic strain, electronic ligand and geometric ensemble effects. The calculated adsorption energies indicate that the hollow sites are always found to be more stable than any others and more sensitive to the Ag atoms because of the strong ensemble effect. However, the ligand effect plays a significant role in both the top and bridge adsorption sites. The electrons transferred to the acetylene molecules from the surface increase with increasing concentration of the surface atomic Ag. PMID:24170141

Li, Qiang; Song, Lijuan; Pan, Lihong; Zhuang, Xinling; Ling, Mingli; Duan, Linhai

2013-12-14

424

Autophagy: assays and artifacts  

PubMed Central

Autophagy is a fundamental and phylogenetically conserved self-degradation process that is characterized by the formation of double-layered vesicles (autophagosomes) around intracellular cargo for delivery to lysosomes and proteolytic degradation. The increasing significance attached to autophagy in development and disease in higher eukaryotes has placed greater importance on the validation of reliable, meaningful and quantitative assays to monitor autophagy in live cells and in vivo in the animal. To date, the detection of processed LC3B-II by western blot or fluorescence studies, together with electron microscopy for autophagosome formation, have been the mainstays for autophagy detection. However, LC3 expression levels can vary markedly between different cell types and in response to different stresses, and there is also concern that over-expression of tagged versions of LC3 to facilitate imaging and detection of autophagy interferes with the process itself. In addition, the realization that it is not sufficient to monitor static levels of autophagy but to measure ‘autophagic flux’ has driven the development of new or modified approaches to detecting autophagy. Here, we present a critical overview of current methodologies to measure autophagy in cells and in animals.

Barth, Sandra; Glick, Danielle; Macleod, Kay F

2010-01-01

425

NCI Launches Proteomics Assay Portal  

Cancer.gov

In a paper recently published by the journal Nature Methods, Investigators from the National Cancer Institute’s Clinical Proteomic Tumor Analysis Consortium (NCI-CPTAC) announced the launch of a proteomics Assay Portal for multiple reaction monitoring-mass spectrometry (MRM-MS) assays. This community web-based repository for well-characterized quantitative proteomic assays currently consists of 456 unique peptide assays to 282 unique proteins and serves as a public resource of methodologies and data related to cancer associated targets.

426

Low optical insertion-loss and vacuum-pressure all-fiber acetylene cell based on hollow-core photonic crystal fiber.  

PubMed

We report a novel and easy-to-implement hollow-core photonic crystal fiber cell fabrication technique based on helium diffusion through silica. The formed gas cells combine low optical insertion loss (1.8 dB) and vacuum acetylene pressure (microbar regime). The estimates of the final gas pressure, using both Voigt interpolation and electromagnetically induced transparency, show a good match with the initial fitting pressure. PMID:16902611

Light, P S; Couny, F; Benabid, F

2006-09-01

427

Submicro Determination of Copper and Zinc in Needle Biopsy-Sized Cardiac and Skeletal Muscles by Atomic Absorption Spectroscopy Using Stoichiometric Air-Acetylene Flame  

Microsoft Academic Search

A highly sensitive and rapid procedure is described for submicro quantitation of copper and zinc contents from the nitric acid extract of fat free-dry-tissue (FFDT) by a double beam atomic absorption spectrophotometer using stoichiometric air-acetylene flame. Simultaneous background correction was afforded with a deuterium lamp for Zn analysis to eliminate interferences from non-atomic absorption at 213.9 nm. Cu and Zn

Syamal K. Bhattacharya; Tena G. Goodwin; Alice J. Crawford

1984-01-01

428

Statistical Reexamination of Some Interference Patterns in the Determination of Calcium in Wheat (Triticum) by Atomic Absorption Spectrophotometry in an Air\\/Acetylene Flame  

Microsoft Academic Search

The paper aims to statistically reexamine some interfereces that appear in the analysis of calcium by flame atomic absorption spectrophotometry in wheat (Triticum) sample, in the first vegetation stage.The statistical study shows that in the air\\/acetylene flame for ourtype of samples the interference due to phosphorus is not significant (r=0.19). A strong significant interference is due to the presence of

Dan I. Seracu

1984-01-01

429

Determination of halogens via molecules in the air–acetylene flame using high-resolution continuum source absorption spectrometry, Part II: Chlorine  

Microsoft Academic Search

As continuation of the work on fluorine, the second part of the studies of halogens in the air–acetylene flame attends to the determination of chlorine using high-resolution continuum source absorption spectrometry and molecular absorption. In case of chlorine, the diatomic InCl molecule proved to be a suitable species. For an excess of In in the flame, chlorine is converted to

Mao Dong Huang; Helmut Becker-Ross; Stefan Florek; Uwe Heitmann; Michael Okruss

2006-01-01

430

A study of gas chemistry during hot-filament vapor deposition of diamond films using methane\\/hydrogen and acetylene\\/hydrogen gas mixtures  

Microsoft Academic Search

The composition of the reaction gases in a hot-filament reactor for chemical vapor deposition of diamond films was analyzed using a gas chromatograph coupled with a quartz microprobe. Concentrations of several hydrocarbons were determined as functions of filament temperature (FT) and the position of the probe relative to the filament for two feed gases, methane\\/hydrogen and acetylene\\/hydrogen. The diamond growth

Ching-Hsong Wu; M. A. Tamor; T. J. Potter; E. W. Kaiser

1990-01-01

431

An Acetylene Tracer-Based Approach to Quantifying Methane Emissions from Distributed Sources Using Wavelength-Scanned Cavity Ring-Down Spectroscopy  

NASA Astrophysics Data System (ADS)

The quantification of fugitive methane emissions from extended sources such as landfills is problematic due to the high temporal variability and spatial inhomogeneity of the emission. Additionally, the relationship between the emission rate and the gas concentration at a given location is dependent on the meteorological conditions and local topography, preventing accurate quantification of the emission rate. When the total source emission is of interest, tracer methods allow quantitative measurements to be made using a single, mobile gas analyzer located in the far field of the source (i.e., at a distance that is large compared with the size of the extended source). Making measurements in the far field enables both the extended source and the tracer to be approximated as point sources. By releasing a tracer gas at a known rate at or near the center of the extended area source, the far-field measurement of the ratio of concentrations yields the ratio of emission rates, since the effects of atmospheric dispersion are the same for both species. An ultra-sensitive, dual species gas analyzer based on wavelength scanned cavity ring-down spectroscopy has been developed to measure the concentrations of methane and acetylene with the required sensitivity and speed. Acetylene has been selected as a tracer gas due to its low concentration in the environment and the high detection sensitivity that can be achieved. We present field measurements of landfill methane plumes and overlapped acetylene plumes using this new instrument. Both mobile and fixed-point field data obtained with this analyzer are presented that demonstrate simplicity and robustness of the method. Both the strengths and the limitations of the acetylene tracer-based method are discussed.

Rella, C.; Crosson, E.; Thoma, E.; Hater, G.; Merrill, R.; Tan, S.; Green, R.

2009-12-01

432

Effect of macroamounts of aluminum, magnesium, nickel, and chromium on the degree of yttrium and lanthanum atomization in an acetylene-nitrous oxide flame  

SciTech Connect

Using the method of measuring absolute intensities in emission spectra, they have calculated the degree of atomization of yttrium and lanthanum in an acetylene-nitrous oxide flame, and have provided a quantitative appraisal of the effect of Al, Mg, Ni, and Cr on the number of yttrium and lanthanum atoms, ions, and molecules. Hypotheses are expressed concerning the mechanism of the effect of the principal elements in the flame.

Semenenko, K.A.; Osipova, V.A.; Panov, V.A.; Kuzyakov, Yu.Ya.

1987-09-20

433

AssayFinder--an online database for clinical chemistry assays.  

PubMed

AssayFinder is an electronic database of clinical chemistry assays. It currently holds 1300 entries from 63 laboratories. It was developed for hospital clinical chemistry laboratories that need to send patient samples to reference centres for complex analysis. AssayFinder anticipated use of the Internet for transmitting information between hospitals. It started as a disc containing individual hypertext markup language files. From the beginning AssayFinder was designed for Web browser software, usable even in laboratories without Internet access. Later, files were generated automatically from a database package, (FileMaker-Pro, Claris, Santa Clara, USA.). Direct on-line access to the database has now been achieved using the World Wide Web. In the future sites will submit new assays in electronic form. In addition, links to other relevant specialist web-sites will further increase its value to the clinical chemistry community. PMID:10023817

Falconer-Smith, J F

1998-12-01

434

Application of Firefly Luciferase Assay for Adenosine Triphosphate (ATP) to Antimicrobial Drug Sensitivity Testing.  

National Technical Information Service (NTIS)

The development of a rapid method for determining microbial susceptibilities to antibiotics using the firefly luciferase assay for adenosine triphosphate (ATP) is documented. The reduction of bacterial ATP by an antimicrobial agent was determined to be a ...

G. L. Picciolo S. Tuttle C. G. Schrock J. W. Deming M. Barza

1977-01-01

435

A simple high-content cell cycle assay reveals frequent discrepancies between cell number and ATP and MTS proliferation assays.  

PubMed

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

Chan, Grace Ka Yan; Kleinheinz, Tracy L; Peterson, David; Moffat, John G

2013-01-01

436

A Simple High-Content Cell Cycle Assay Reveals Frequent Discrepancies between Cell Number and ATP and MTS Proliferation Assays  

PubMed Central

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.

Chan, Grace Ka Yan; Kleinheinz, Tracy L.; Peterson, David; Moffat, John G.

2013-01-01

437

Reduction of Norwalk Virus, Poliovirus 1, and Bacteriophage MS2 by Ozone Disinfection of Water  

PubMed Central

Norwalk virus and other human caliciviruses (noroviruses) are major agents of gastroenteritis, and water is a major route of their transmission. In an effort to control Norwalk virus in drinking water, Norwalk virus reduction by bench-scale ozone disinfection was determined using quantitative reverse transcription (RT)-PCR for virus assays. Two other enteric viruses, poliovirus 1 and coliphage MS2, were included for comparison, and their reductions were assayed by infectivity assays as well as by RT-PCR. Virus reductions by ozone were determined using a dose of 0.37 mg of ozone/liter at pH 7 and 5°C for up to 5 min. Based on two RT-PCR assays, the reductions of Norwalk virus were >3 log10 within a contact time of 10 s, and these were similar to the reductions of the other two viruses determined by the same assay methods. Also, the virus reductions detected by RT-PCR assays were similar to those detected by infectivity assays, indicating that the RT-PCR assay is a reliable surrogate assay for both culturable and nonculturable viruses disinfected with ozone. Overall, the results of this study indicate that Norwalk virus as well as other enteric viruses can be reduced rapidly and extensively by ozone disinfection and that RT-PCR is a useful surrogate assay for both culturable and nonculturable viruses disinfected with ozone.

Shin, Gwy-Am; Sobsey, Mark D.

2003-01-01

438

Asymmetric reductive amination.  

PubMed

Asymmetric reductive amination (ARA) affords synthetically valuable chiral amines straightforwardly. This chapter reviews the recent advances made in the area, focusing on ARA by hydrogenation, transfer hydrogenation, organocatalytic reduction, and biocatalytic reduction. PMID:24158548

Wang, Chao; Xiao, Jianliang

2014-01-01

439

Intracellular Refolding Assay  

PubMed Central

This protocol describes a method to measure the enzymatic activity of molecular chaperones in a cell-based system and the possible effects of compounds with inhibitory/stimulating activity. Molecular chaperones are proteins involved in regulation of protein folding1 and have a crucial role in promoting cell survival upon stress insults like heat shock2, nutrient starvation and exposure to chemicals/poisons3. For this reason chaperones are found to be involved in events like tumor development, chemioresistance of cancer cells4 as well as neurodegeneration5. Design of small molecules able to inhibit or stimulate the activity of these enzymes is therefore one of the most studied strategies for cancer therapy7 and neurodegenerative disorders9. The assay here described offers the possibility to measure the refolding activity of a particular molecular chaperone and to study the effect of compounds on its activity. In this method the gene of the molecular chaperone investigated is transfected together with an expression vector encoding for the firefly luciferase gene. It has been already described that denaturated firefly luciferase can be refolded by molecular chaperones10,11. As normalizing transfection control, a vector encoding for the renilla luciferase gene is transfected. All transfections described in this protocol are performed with X-treme Gene 11 (Roche) in HEK-293 cells. In the first step, protein synthesis is inhibited by treating the cells with cycloheximide. Thereafter protein unfolding is induced by heat shock at 45°C for 30 minutes. Upon recovery at 37°C, proteins are re-folded into their active conformation and the activity of the firefly luciferase is used as read-out: the more light will be produced, the more protein will have re-gained the original conformation. Non-heat shocked cells are set as reference (100% of refolded luciferase).

Walther, Tamara Vanessa; Maddalo, Danilo

2012-01-01

440

[Immunoenzyme assay for histamine].  

PubMed

In order to produce monoclonal antibody to histamine, mice are immunized with histamine conjugated to bovine serum albumin (BSA) by the 1,4-benzoquinone method. After an initial screening using ovalbumin (OVA) and histamine-OVA conjugate as antigens to identify monoclonal antibody secreting clones, the hybridomas are isolated by limiting dilution cloning and grown in ascites. The specificity of selected monoclonal antibody (D22) is studied using a direct enzyme immunoassay and an ELISA-inhibition test. D22 antibody reacts with histamine-protein conjugates prepared by the 1,4-benzoquinone coupling procedure. On the contrary, this antibody is unreactive with native proteins, 1,4-benzoquinone treated proteins or various amine-protein conjugates. Free unconjugated histamine significantly inhibits antibody binding to histamine-OVA and 50% inhibition (IC50) is recorded at 5 X 10(-3) M. On a histamine molar concentration basis a much more lower inhibitory potency of free histamine is recorded, as compared to histamine-benzoquinone derivative (IC50 = 2 X 10(-8) M) and to histamine-OVA (IC50 = 7 X 10(-10) M). It is our interpretation that for the D22 antibody, the main epitope encompasses the 2-histaminyl-1,4-benzoquinone moiety and that this points to the importance of polyvalent ligands for efficient bivalent binding of the IgG antibodies. Using the D22 antibody we set up a competitive enzyme immunoassay for measuring histamine in various biological samples. In this assay, the histamine to be quantified is chemically modified by 1,4-benzoquinone and allowed to compete with a histamine-peroxidase conjugate for binding to a limited amount of monoclonal antibody which is used to coat the wells of a microtitration plate.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2462888

Guesdon, J L; Chevrier, D; Fadel, R; Avrameas, S

1988-11-01

441

Intracellular refolding assay.  

PubMed

This protocol describes a method to measure the enzymatic activity of molecular chaperones in a cell-based system and the possible effects of compounds with inhibitory/stimulating activity. Molecular chaperones are proteins involved in regulation of protein folding and have a crucial role in promoting cell survival upon stress insults like heat shock, nutrient starvation and exposure to chemicals/poisons. For this reason chaperones are found to be involved in events like tumor development, chemioresistance of cancer cells as well as neurodegeneration. Design of small molecules able to inhibit or stimulate the activity of these enzymes is therefore one of the most studied strategies for cancer therapy and neurodegenerative disorders. The assay here described offers the possibility to measure the refolding activity of a particular molecular chaperone and to study the effect of compounds on its activity. In this method the gene of the molecular chaperone investigated is transfected together with an expression vector encoding for the firefly luciferase gene. It has been already described that denaturated firefly luciferase can be refolded by molecular chaperones. As normalizing transfection control, a vector encoding for the renilla luciferase gene is transfected. All transfections described in this protocol are performed with X-treme Gene (Roche) in HEK-293 cells. In the first step, protein synthesis is inhibited by treating the cells with cycloheximide. Thereafter protein unfolding is induced by heat shock at 45°C for 30 minutes. Upon recovery at 37°C, proteins are re-folded into their active conformation and the activity of the firefly luciferase is used as read-out: the more light will be produced, the more protein will have re-gained the original conformation. Non-heat shocked cells are set as reference (100% of refolded luciferase). PMID:22297799

Walther, Tamara Vanessa; Maddalo, Danilo

2012-01-01

442

The primer extension assay.  

PubMed

In the primer extension assay, the transcription start site for a gene is determined experimentally by identifying the 5' end of the encoded messenger RNA (mRNA). The protocol begins with a primer, usually a synthetic oligonucleotide of about 20 residues, that is complementary to an mRNA sequence ?50-150 nucleotides downstream of the anticipated 5' end. The primer is 5'-end-labeled using [?-(32)P]ATP and T4 polynucleotide kinase and is annealed to the specific mRNA molecules within an RNA sample. Reverse transcriptase (RT), deoxyribonucleoside triphosphates, and appropriate buffer components are added to the primer-mRNA hybrids to catalyze elongation of the primer to the 5' end of the mRNA. The resulting radiolabeled complementary DNA (cDNA) products are analyzed by denaturing polyacrylamide gel electrophoresis, followed by autoradiography. The sizes of the bands detected on the gel, as compared to an adjacent sequencing ladder or molecular weight standards, provide a measure of the distance from the 5' end of the synthetic oligonucleotide to the beginning of the mRNA transcripts. In theory, the 3' end of the cDNA will coincide with the 5' end of the mRNA. Thus, the size of the radiolabeled cDNAs should represent the distance from the labeled 5' end of the primer to the 5' end of the mRNA (i.e., the 3' end of the cDNA). If the labeled cDNA products are within the resolution range of the gel, the transcription start site can be determined with an accuracy of plus or minus one nucleotide. PMID:23378648

Carey, Michael F; Peterson, Craig L; Smale, Stephen T

2013-02-01

443

Low-energy electron irradiation studies of acetonitrile and acetonitrile/acetylene ices relevant to Titan's atmospheric and surface chemistry  

NASA Astrophysics Data System (ADS)

The observation of organic-rich rivers and lakes on Titan has generated much interest concerning possible prebiotic reactions occurring at the surface and in the atmosphere. Acetonitrile (CH3CN) has been detected in the upper atmosphere and stratosphere by the international 30 meter radio telescope in the Spanish Sierra Nevada (operated by IRAM) and on the surface in dark terrain regions by Cassini's Visual and Infrared Mapping Spectrometer (VIMS) [1]. In addition, acetylene (C2H2) has been detected in the atmosphere by the Composite Infrared Spectrometer (CIRS) and the Ion and Neutral Mass Spectrometer (INMS) aboard the Cassini spacecraft [1]. Low-energy electrons are also known to be present at low altitudes and in the near surface regions. At altitudes of 1200 km, the electron flux has been estimated to be 102-105 cm-2s-1eV-1 with energies in the range of 0.1-1 KeV [2], and at lower altitudes appreciable electron densities were measured by the Huygens Probe [3]. In order to examine the reactions induced by low-energy electron irradiation of acetonitrile and acetylene ices, studies have been performed on pure CH3CN ices and CH3CN/C2D2 ice mixtures. These ices were exposed to irradiation by 80-1000 eV electrons and reaction products were detected using temperature programmed desorption (TPD) and reflection/absorption infrared spectroscopy (RAIRS). After irradiation of pure CH3CN ices, desorption of CH4 and HCN was observed with TPD. With CH3CN/C2D2 mixed ices, desorption of neutral H2 was observed, indicating increased availability of hydrogen in the ices. Thermal desorption of C2D2 and CH3CN peak at 90 and 147 K, respectively, in pure ices. However, an additional desorption peak was observed at 110 K in the ice mixture. This suggests desorption of a weakly bound CH3CN-C2D2 complex. Exploring the reactions of these hydrocarbon ices is crucial to determining Titan's role as a prebiotic chemical system in the outer solar system.

Dawley, M. M.; McLain, J.; Abbott, H. L.; Orlando, T. M.

2011-12-01

444

New low-viscosity overlay medium for viral plaque assays  

PubMed Central

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 h