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1

Field technique using the acetylene reduction method to assay nitrogenase activity and its association with the rice rhizosphere  

Microsoft Academic Search

A plastic bag, used as a field assay chamber, assisted in the investigation of the acetylene reduction method as a technique to measure nitrogen-fixing activity in rice paddy fields. A study of the change in volume of the plastic bag and of the loss of acetylene and ethylene from the bag provided evidence that this plastic bag method was feasible

Kuk-Ki Lee; Bonifacio Alimagno; Tomio Yoshida

1977-01-01

2

Nitrogen Fixation (Acetylene Reduction) Associated with Duckweed (Lemnaceae) Mats  

PubMed Central

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. N2-fixing microorganisms were enumerated by plating or most-probable-number techniques, using appropriate N-free media. Results of the investigations indicated that substantial N2-fixation (C2H2) was associated with duckweed mats in Texas and Florida. Acetylene reduction values ranged from 1 to 18 ?mol of C2H4 g (dry weight)?1 day?1 for samples incubated aerobically in light. Dark N2 fixation was always two- to fivefold lower. 3-(3,4-Dichlorophenyl)-1,1-dimethylurea (7 to 10 ?M) 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. N2-fixing heterotrophic bacteria (105 cells g [wet weight]?1 and cyanobacteria (105 propagules g [wet weight]?1 were associated with the duckweed mats. Azotobacter sp. was not detected in these investigations. One diazotrophic isolate was classified as Klebsiella.

Zuberer, D. A.

1982-01-01

3

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

4

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

5

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

6

Comparison of N(2) Fixation and Yields in Cajanus cajan between Hydrogenase-Positive and Hydrogenase-Negative Rhizobia by In Situ Acetylene Reduction Assays and Direct N Partitioning.  

PubMed

Pigeon peas [Cajanus cajan (L.) Millsp.] were grown in soil columns containing (15)N-enriched organic matter. Seasonal N(2) fixation activity was determined by periodically assaying plants for reduction of C(2)H(2). N(2) fixation rose sharply from the first assay period at 51 days after planting to a peak of activity between floral initiation and fruit set. N(2) fixation (acetylene reduction) activity dropped concomitantly with pod maturation but recovered after pod harvests. Analysis of (15)N content of plant shoots revealed that approximately 91 to 94% of plant N was derived from N(2) 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. H(2) was never detected, even in columns containing pigeon peas inoculated with hydrogenase-negative rhizobia. This was attributed to H(2) consumption by soil bacteria. Estimation of N(2) fixation by acetylene reduction activity was closest to the direct (15)N 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 (15)N 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. PMID:16663148

La Favre, J S; Focht, D D

1983-08-01

7

An assay technique of measurement of nitrogenase activity in root zone of rice for varietal screening by the acetylene reduction method  

Microsoft Academic Search

The feasibility of using a plastic bag was examined in a test to screen rice varieties for differences in the nitrogen-fixing activity in their root zones. The change in the volume of the plastic bag during 24 hours of incubation was not significant. Although the plastic bag was permeable to acetylene and ethylene, the amounts lost through permeation during 24

Kuk-Ki Lee; Tomio Yoshida

1977-01-01

8

Immediate Acetylene Reduction by Excised Grass Roots Not Previously Preincubated at Low Oxygen Tensions 1  

PubMed Central

Excised roots of Spartina alterniflora Loisel. and corn reduced acetylene in air without the previously reported period of zero activity lasting 8 to 18 hours. The profiles of acetylene-dependent ethylene accumulation by excised roots and intact plants of S. alterniflora were similar. No significant change in the number of bacteria associated with the roots was detectable during the assay. Most of the nitrogenase activity was detected in the roots and rhizomes of the plants. The salt marsh sediment also was capable of reducing acetylene. Additional damage to roots by washing and cutting increased the rate of acetylene reduction with samples incubated in air. Low concentrations of nitrate significantly inhibited the nitrogenase activity associated with the sediment and excised roots, but not with intact plants. Rates of acetylene reduction by excised corn roots were low. Oxidation and endogenous production of ethylene in the absence of acetylene were negligible. Measurements made with excised grass roots as described probably reflect the occurrence and magnitude of nitrogenase activity associated with the plants in the field.

van Berkum, Peter; Sloger, Charles

1979-01-01

9

Nitrogen fixation (acetylene reduction) on a coral reef  

NASA Astrophysics Data System (ADS)

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 various reef zones, based on these measurements, indicate that the sand-covered lagoon is responsible for more than 70% of the fixation in the reef. Consequently, the lagoon may serve as an important source of nitrogen for the coral reef community.

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

1994-07-01

10

Nitrogen Fixation (Acetylene Reduction) by Epiphytes of Freshwater Macrophytes  

PubMed Central

The involvement of epiphytic microorganisms in nitrogen fixation was investigated in a shallow freshwater pond near Ithaca, N.Y. The acetylene reduction technique was used to follow diel and seasonal cycles of nitrogen fixation by epiphytes of Myriophyllum spicatum. Acetylene-reducing activity was maximal between noon and 6 p.m., but substantial levels of activity relative to daytime rates continued through the night. Experiments with the seasonal course of activity showed a gradual decline during the autumn months and no activity in January or February. Activity commenced in May, with an abrupt increase to levels between 0.45 and 0.95 nmol of ethylene formed per mg (dry weight) of plant per h. Through most of the summer months, mean rates of acetylene reduction remained between 0.15 and 0.60 nmol/mg (dry weight) per h. It was calculated from diel and seasonal cycles that, in the pond areas studied, epiphytes were capable of adding from 7.5 to 12.5 ?g of N per mg of plant per year to the pond. This amount is significant relative to the total amount of nitrogen incorporated into the plant. Blue-green algae (cyanobacteria), particularly Gloeotrichia, appeared to bear prime responsibility for nitrogen fixation, but photosynthetic bacteria of the genus Rhodopseudomonas were isolated from M. spicatum and shown to support high rates of acetylene reduction.

Finke, Linda R.; Seeley, H. W.

1978-01-01

11

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

12

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

PubMed Central

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

Winship, Lawrence J.; Tjepkema, John D.

1982-01-01

13

Limitation of Acetylene Reduction (Nitrogen Fixation) by Photosynthesis in Soybean Having Low Water Potentials 1  

PubMed Central

The role of photosynthesis and transpiration in the desiccation-induced inhibition of acetylene reduction (nitrogen fixation) was investigated in soybean (Glycine max [L.] Merr. var. Beeson) using an apparatus that permitted simultaneous measurements of acetylene reduction, net photosynthesis, and transpiration. The inhibition of acetylene reduction caused by low water potentials and their aftereffects could be reproduced by depriving shoots of atmospheric CO2 even though the soil remained at water potentials that should have favored rapid acetylene reduction. The inhibition of acetylene reduction at low water potentials could be partially reversed by exposing the shoots to high CO2 concentrations. When transpiration was varied independently of photosynthesis and dark respiration in plants having high water potentials, no effects on acetylene reduction could be observed. There was no correlation between transpiration and acetylene reduction in the CO2 experiments. Therefore, the correlation that was observed between transpiration and acetylene reduction during desiccation was fortuitous. We conclude that the inhibition of shoot photosynthesis accounted for the inhibition of nodule acetylene reduction at low water potentials.

Huang, Chi-Ying; Boyer, John S.; Vanderhoef, Larry N.

1975-01-01

14

Acetylene - ethylene assay for Nâ fixation: laboratory and field evaluation  

Microsoft Academic Search

The methodology, characteristics and application of the sensitive CâHâ-CâHâ assay for Nâ fixation by nitrogenase preparations and bacterial cultures in the laboratory and by legumes and free-living bacteria in situ is presented in this comprehensive report. This assay is based on the Nâase-catalyzed reduction of CâHâ to CâHâ, gas chromatographic isolation of CâHâ and CâHâ, and quantitative measurement with a

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

1968-01-01

15

A comparison of nitrogen fixation (acetylene reduction) among three species of mangrove litter, sediments, and pneumatophores in south Florida, USA  

Microsoft Academic Search

Assays of nitrogen fixation (acetylene reduction method) were performed on fresh leaf litter (yellow leaves recently fallen\\u000a from the trees), aged leaf litter (brown leaves on the forest floor) of Rhizophora mangle, Avicennia germinans, and Laguncularia\\u000a racemosa; and in addition rates were measured on pneumatophores of A. germinans and mangrove sediment from two different sites\\u000a along the Shark River estuary

Sílvia P. Pelegraí; Victor H. Rivera-Monroy; Robert R. Twilley

1997-01-01

16

Acetylene Reduction (Nitrogen Fixation) and Metabolic Activities of Soybean Having Various Leaf and Nodule Water Potentials 1  

PubMed Central

An apparatus was designed that permitted acetylene reduction (N2 fixation) by root nodules to be measured in situ simultaneously with net photosynthesis, dark respiration, and transpiration of the shoot in soybean plants (Glycine max [L.] Merr. var. Beeson). Tests showed that acetylene reduction was linear with time for at least 5 hours, except for the first 30 to 60 minutes. Endogenous ethylene production did not affect the measurements. Successive determinations of acetylene reduction could be made without apparent aftereffects on the plant. This apparatus was used to investigate the effects of soil flooding and desiccation on acetylene reduction under conditions where soil, nodule, and leaf water potentials could be measured. No acetylene reduction was detectable in flooded soil or in soil desiccated to a water potential of ?19.5 bars. Between these extremes, acetylene reduction displayed a sharp optimum. Removing the soil eliminated the inhibitory effects of flooding, suggesting that rates of gas exchange were restricted between the nodules and the atnosphere at soil water potentials above ?2 bars. As the soil desiccated further, acetylene reduction decreased, and the decrease was correlated with decreases in photosynthesis and transpiration. Although dark respiration was inhibited, it was not affected to the extent that acetylene reduction, photosynthesis, or transpiration were. Consequently, it was concluded that photosynthesis, transpiration, or some direct effect on the nodules other than that caused by respiration were most likely to account for the inhibition of acetylene reduction at soil water potentials below ?2 bars.

Huang, Chi-Ying; Boyer, John S.; Vanderhoef, Larry N.

1975-01-01

17

Physiological ecology of acetylene reduction (nitrogen fixation) in a Delaware salt marsh  

Microsoft Academic Search

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 considerable decrease (85–95%) in activity late in the summer and early in the fall. Nitrate caused a near complete suppression of activity

Howard J. Dicker; David W. Smith

1980-01-01

18

Nitrate requirement for acetylene inhibition of nitrous oxide reduction in marine sediments  

Microsoft Academic Search

The inhibition of nitrous oxide (N2O) reduction by acetylene (C2H2) in saltmarsh sediment was temporary; we investigated this phenomenon and possible causes. The reduction of N2O in the presence of C2H2 was biological. N2O consumption in the presence of C2H2 began when nitrate concentration became very low. The time course of N2O consumption after periods of N2O accumulation was unaffected

Jennifer M. Slater; Douglas G. Capone

1989-01-01

19

Acetylene reduction by bryophyte-cyanobacteria associations on a Subantarctic island  

Microsoft Academic Search

Nineteen bryophyte species containing epiphytic cyanobacteria on Marion Island (46°54' S, 37°45' E) were investigated for their capacity to reduce acetylene in the field. Fourteen species exhibited reduction, varying from 0.36 to 310.57 nmol C2H2 g-1 dry weight h-1. These values are within the range of those reported from northern hemisphere subpolar sites. The highest reduction rate occurred at a

V. R. Smith; S. Russell

1982-01-01

20

Sulfide Alleviation of the Acetylene Inhibition of Nitrous Oxide Reduction in Soil  

PubMed Central

The alleviation of the acetylene blockage of nitrous oxide reduction by sulfide was studied in anaerobically incubated Brookston soil to better characterize the process. Removal of nitrate-derived nitrous oxide from soil amended with acetylene and sulfide occurred earlier in the presence of glucose than it did in its absence. This was attributed to the influence of glucose on nitrous oxide production rather than reduction during the early stages of the soil incubation. Glucose was found to have no effect on reduction of injected nitrous oxide in the presence of acetylene- and sulfide-amended soil, whereas carbon dioxide significantly stimulated reduction. It is suggested that the microorganism(s) involved may use carbon dioxide as a cellular carbon source. The sulfide added to the soil probably did not act solely as an electron donor, as the number of electrons required to reduce the added nitrous oxide in our systems was greater than the amount supplied by the sulfide. The soil pH at which the alleviation occurred was 6.7 and was not affected by the sulfide treatment.

Evans, David G.; Beauchamp, Eric; Trevors, Jack T.

1985-01-01

21

Response to Drought Stress of Nitrogen Fixation (Acetylene Reduction) Rates by Field-Grown Soybeans  

PubMed Central

The effects of drought stress on soybean nodule conductance and the maximum rate of acetylene reduction were studied with in situ experiments performed during two seasons and under differing field conditions. In both years drought resulted in decreased nodule conductances which could be detected as early as three days after water was withheld. The maximum rate of acetylene reduction was also decreased by drought and was highly correlated with nodule conductance (r = 0.95). Since nodule conductance is equal to the nodule surface area times the permeability, the relationship of these variables to both whole-plant and unit-nodule nitrogenase activity was explored. Drought stress resulted in a decrease in nodule gas permeability followed by decreases in nodule surface area when drought was prolonged. Under all conditions studied acetylene reduction on a unit-nodule surface area basis was highly correlated with nodule gas permeability (r = 0.92). A short-term oxygen enrichment study demonstrated nodule gas permeability may limit oxygen flux into both drought-stressed and well-watered nodules of these field-grown soybeans.

Weisz, P. Randall; Denison, Robert F.; Sinclair, Thomas R.

1985-01-01

22

Experimental and kinetic modeling of nitric oxide reduction by acetylene in an atmospheric pressure jet-stirred reactor  

Microsoft Academic Search

The reduction of nitric oxide (NO) by acetylene in simulated conditions of the reburning zone has been undertaken in a fused silica jet-stirred reactor operating at 1atm, at temperatures ranging from 1050 to 1300K. In the present experiment, the initial mole fraction of NO was 1000ppm, and that of acetylene was 4400ppm. The equivalence ratio has been varied from 0.75

P Dagaut; F Lecomte; S Chevailler; M Cathonnet

1999-01-01

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

2009-03-13

24

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 Central

For evaluating N2 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 N2-fixing soil bacteria generally show only trace acetylene reduction activity. Here, we report that use of a N2 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 N2-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 N2 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.

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

2009-01-01

25

Acetylene Reduction (Nitrogen Fixation) by Enterobacteriaceae Isolated from Paper Mill Process Waters  

PubMed Central

Using selective media containing galactitol, over 130 Enterobacteriaceae have been isolated from paper mill process waters collected from different localities. These bacteria were extensively characterized and tested for acetylene-reducing (nitrogen-fixing) activity under anaerobic conditions. High activity was found in representatives of Klebsiella pneumoniae, Enterobacter aerogenes, Enterobacter cloacae, Erwinia herbicola, Citrobacter freundii, Citrobacter intermedius, and Escherichia coli. Under argon, nitrogenase synthesis was generally not repressed by 5 mM l-glutamate, l-aspartate, l-leucine or Casamino Acids (0.5 g/liter). In many strains, both the specific activities (nanomoles of C2H4 per minute per milligram of protein) and the activities (nanomoles of C2H4 per minute) had considerably declined after 24 h. In three selected strains, activity in intact cells grown under nitrogen was unaffected by the presence during assay of 10 mM l-amino acids or ammonium acetate. All of the strains examined were tolerant towards inactivation of nitrogen-fixing activity by 1.8% (vol/vol) oxygen during assay, and inactivation by up to 10% oxygen was partly reversible. Representatives of the six taxa synthesized nitrogenase in stirred aerobic cultures, though the protein concentrations attained were lower than under anaerobic conditions. It seems reasonable to suggest that under natural conditions, nitrogen fixation is able to contribute significantly to the nitrogen economy of the cells.

Neilson, A. H.; Sparell, L.

1976-01-01

26

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

PubMed Central

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

Haahtela, Kielo; Wartiovaara, Tuula; Sundman, Veronica; Skujins, J.

1981-01-01

27

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

PubMed Central

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

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

1968-01-01

28

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

PubMed Central

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

Hyman, Michael R.; Arp, Daniel J.

1987-01-01

29

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

PubMed Central

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

van Berkum, Peter; Sloger, Charles

1981-01-01

30

Relationship between Ureide N and N(2) Fixation, Aboveground N Accumulation, Acetylene Reduction, and Nodule Mass in Greenhouse and Field Studies with Glycine max L. (Merr).  

PubMed

The relationship between ureide N and N(2) 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 N(2) fixation in soybean and lima bean correlated with ureide N. In soybean, N(2) fixation, ureide N, acetylene reduction, and nodule mass were correlated when N(2) fixation was inhibited by applying KNO(3) 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 N(2) fixation. Ureide N determinations in field studies with soybean correlated with N(2) fixation, aboveground N accumulation, nodule weight, and acetylene reduction. N(2) fixation was estimated by (15)N 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 N(2) fixation and ureide N across strains were variable. Acetylene reduction in soybean across host-strain combinations did not correlate with N(2) fixation and ureide N. N(2) 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 N(2) fixation in soybean. Ureide-N measurements also may be useful to rank strains of B. japonicum for effectiveness of N(2) fixation. PMID:16664027

van Berkum, P; Sloger, C; Weber, D F; Cregan, P B; Keyser, H H

1985-01-01

31

Effects of CaSO4, CaCl2, and NaCl on leaf nitrogen, nodule weight, and acetylene reduction activity in Phaseolus vulgaris L  

Microsoft Academic Search

Two forms of calcium were used to ameliorate the harmful effects of sodium chloride (NaCl) on total leaf nitrogen, nodule weight, and acetylene reduction activity in snapbeans, Phaseolus vulgaris L., cv Contender, Plants were grown in pots under greenhouse conditions and were irrigated with water containing NaCl with a salinity of 0, 44, 88, or 132 mM., In addition, either

W. F. Campbell; J. J. Jurinak; L. M. Dudley

1991-01-01

32

Production of multiply labeled polyunsaturated fatty acids by selective reduction of their acetylene derivatives with gaseous tritium  

SciTech Connect

The selective catalytic hydrogenation of acetylenic analogs of polyunsaturated fatty acids by gaseous tritium was studied without the use of deactivating amines. The possiblity of preparative synthesis of multiple labeled polyenic acids with a high chemical yield was demonstrated. Methods of purification of tritium-labeled fatty acids with the use of silver-plated carriers are discussed. The biosynthesis of prostaglandin E/sub 2/ was carried out on the basis of labeled arachidonic acid. The stability of multiple labeled prostaglandin E/sub 2/ under various conditions of storage was investigated.

Shevchenko, V.P.; Lazurkina, T.Y.; Myagkova, G.I.; Myasoedov, N.F.; Nagaev, I.Y.; Yakusheva, L.A.

1986-09-01

33

Acetylene degradation by new isolates of aerobic bacteria and comparison of acetylene hydratase enzymes  

Microsoft Academic Search

Aerobic acetylene-degrading bacteria were isolated from soil samples. Two isolates were assigned to the species Rhodococcus opacus, two others to Rhodococcus ruber and Gordona sp. They were compared with known strains of aerobic acetylene-, cyanide-, or nitrile-utilizing bacteria. The acetylene hydratases of R. opacus could be measured in cell-free extracts only in the presence of a strong reductant like titanium(III)

Bettina M Rosner; Frederick A Rainey; Reiner M Kroppenstedt; Bernhard Schink

1997-01-01

34

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

35

Bioactive acetylenic metabolites.  

PubMed

This article focuses on anticancer, and other biological activities of acetylenic metabolites obtained from plants and fungi. Acetylenic compounds belong to a class of molecules containing triple bond(s). Naturally occurring acetylenics are of particular interest since many of them display important biological activities and possess antitumor, antibacterial, antimicrobial, antifungal, and immunosuppressive properties. There are of great interest for medicine, pharmacology, medicinal chemistry, and pharmaceutical industries. This review presents structures and describes cytotoxic activities of more than 100 acetylenic metabolites, including fatty alcohols, ketones, and acids, acetylenic cyclohexanoids, spiroketal enol ethers, and carotenoids isolated from fungi and plants. PMID:23871125

Kuklev, Dmitry V; Domb, Abraham J; Dembitsky, Valery M

2013-07-16

36

Catalytic and stoichiometric multielectron reduction of hydrazine to ammonia and acetylene to ethylene with clusters that contain the MFe 3S 4 cores (M?Mo, V). Relevance to the function of nitrogenase  

Microsoft Academic Search

A functional model for nitrogenase is currently sought in our laboratory in reactivity studies using various single cubane clusters that possess the [MFe3S4]n+ core, (M?Mo, n = 3; M?V, n = 2). These clusters are used as catalysts for the reduction of enzymatically relevant substrates. Substrates such as hydrazine and acetylene are catalytically reduced by (NEt4)2[(Cl4-cat) (CH3CN) MoFe3S4Cl3], I, to

Dimitri Coucouvanis; Konstantinos D. Demadis; Steven M. Malinak; Patrick E. Mosier; Marni A. Tyson; Les J. Laughlin

1996-01-01

37

Dynamics of the Formation of a Charge Transfer State in 1,2-Bis(9-anthryl)acetylene in Polar Solvents: Symmetry Reduction with the Participation of an Intramolecular Torsional Coordinate.  

PubMed

We have studied 1,2-bis(9-anthryl)acetylene as a model compound for the characterization of the process of solvent-mediated symmetry reduction in an excited state. Thanks to the acetylenic bridge that joins the two anthracenic moieties, this system maintains minimal steric hindrance between the end chromophores in comparison with the classic 9,9'-bianthryl model compound. The acetylenic bridge also allows for significant electronic coupling across the molecule, which permits a redistribution of electron density after light absorption. Femtosecond resolved fluorescence measurements were used to determine the spectral evolution in acetonitrile and cyclohexane solutions. We observed that, for 1,2-bis(9-anthryl)acetylene, the formation of a charge transfer state occurs in a clear bimodal fashion with well separated time scales. Specifically, the evolution of the emission spectrum involves a first solvent-response mediated subpicosecond stage where the fluorescence changes from that typical of nonpolar solvents (locally excited) to an intermediate, partial charge transfer state. The second stage of the evolution into a full charge transfer state occurs with a much longer time constant of 37.3 ps. Since in this system the steric hindrance is minimized, this molecule can undergo much larger amplitude motions for the torsion between the two anthracenic moieties associated with the charge redistribution in comparison with the typical model compound 9,9'-bianthryl. Clearly, the larger range of motions of 1,2-bis(9-anthryl)acetylene gives the opportunity to study the electron transfer process with a good separation of the time scales for the formation of a partial charge transfer state, determined by the speed of solvent response, and the intramolecular changes associated with the formation of the fully equilibrated charge transfer state. PMID:24016357

Gutiérrez-Arzaluz, Luis; Guarin, Cesar A; Rodríguez-Córdoba, William; Peon, Jorge

2013-09-27

38

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

39

Molecular Structure of Acetylene  

NSDL National Science Digital Library

Acetylene is an odorless and colorless gas that was discovered in England by E. Davy. This gas can be made from limestone and coal or from other petrochemical processes. The combustion of acetylene and pure oxygen produces the hottest flame temperature possible of 3300oC. As a result, it is an important fuel for welding and cutting metals. In addition, this chemical can be used as an anesthetic, however overexposure is hazardous. Nowadays acetylene is used for carburization (i.e. hardening) of steel. Research in the last ten years came to the conclusion, that acetylene is the best hydrocarbon available for this purpose.

2002-08-14

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

2012-08-01

41

Effects of long-term treatment with acetylene on nitrogen-fixing microorganisms.  

PubMed Central

Long periods of experimental incubation with acetylene led to a multifold enhancement of acetylene-reducing activity in Anabaena cylindrica, Anabaenopsis circularis, Rhodospirillum rubrum, and Azotobacter vinelandii. Rates of acetylene reduction showed a gradual increase and reached a peak after 2 to 6 h of continuous incubation under acetylene. Thereafter, enzyme activity rapidly declined. A similar enhancement of ethylene production was observed when pretreatment with acetylene was interrupted periodically by a brief exposure to ambient (or oxygen-free) atmosphere without acetylene although the decline of acetylene-reducing activity was less rapid. Pretreatment with acetylene depressed photosynthetic 14CO2 fixation and 15N2 incorporation in Anabaena cylindrica. It is concluded that assessments based on long-term experimental incubation with acetylene may grossly overestimate the actual quantities of fixed nitrogen in the field.

David, K A; Fay, P

1977-01-01

42

Acetylenic carbon allotrope  

SciTech Connect

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.

NONE

1999-11-16

43

Use of immunomagnetic reduction for C-reactive protein assay in clinical samples  

PubMed Central

Background: Magnetic nanoparticles biofunctionalized with antibodies are able to recognize and bind to the corresponding antigens. In this work, anti-C-reactive protein (CRP) antibody was covalently conjugated onto the surface of magnetic nanoparticles to label CRP specifically in serum. Methods: The level of serum CRP was detected by immunomagnetic reduction (IMR) assay, which identifies the changes in the magnetic signal representing the level of interaction between antibody-conjugated magnetic nanoparticles and CRP proteins. To investigate the feasibility of IMR for clinical application, pure CRP solutions and 40 human serum samples were tested for IMR detection of CRP to characterize sensitivity, specificity, and interference. Results: In comparison with the immunoturbidimetry assay, the results of the IMR assay indicated higher sensitivity and had a high correlation with those of the current immunoturbidimetry assay. Conclusion: We have developed a novel and promising way to assay CRP in human serum using immunomagnetic reduction in clinical diagnosis.

Chang, Chien-Hsi; Lai, Zhi-Xian; Lin, Hsiu-Li; Yang, Che-Chuan; Chen, Hsin-Hsien; Yang, Shieh-Yueh; Horng, Herng-Er; Hong, Chin-Yih; Yang, Hong-Chang; Lin, Hsiu-Chen

2012-01-01

44

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

45

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

46

Development of a novel efficient fluorescence-based plaque reduction microneutralization assay for measles virus immunity.  

PubMed

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 automated readout, using a recombinant measles virus engineered to express enhanced green fluorescent protein. The assay is performed in micro format, requires less time to complete (2 versus 4 to 7 days), and is less labor-intensive and less costly than the classical plaque reduction neutralization (PRN) test, widely accepted as the "gold standard" in measles serology. Two available WHO international anti-measles virus standards and one in-house reference serum were used to develop and standardize the new assay. The mean PRMN values from repeated assays were found to be similar to those reported in the literature or assigned to the WHO standards by the classical PRN assay. For validation, we used three groups of low, moderate, and high measles virus vaccine responders' sera with moderate values of correlation in antibody levels (mIU/ml) between PRMN and the Dade Behring immunoglobulin G enzyme immunoassay (EIA). The PRMN assay was more sensitive at low antibody levels and more informative in terms of protection than this commercial EIA. In conclusion, we have developed and validated a sensitive and high-throughput measles virus-specific PRMN that can be readily used in large population-based measles studies. PMID:18463223

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

2008-05-07

47

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

48

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

49

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

50

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

51

Molecular Structure of Divinyl acetylene  

NSDL National Science Digital Library

In 1920, while doing research on acetylene, Dr. Nieuwland, Professor of Organic Chemistry at University of Notre Dame, found a yellowish oil in addition to the gas. The oil is identified as divinyl acetylene, which, when left alone, will thicken into a jelly and then into a hard resin which tends to explode when handled. It is a highly reactive and explosive chemical. It is sensitive to shocks, sparks, mechanical friction, heat or other accidental ignition. It is far more shock sensitive than primary explosives such as TNT. It is mainly used in manufacturing of synthetic rubber.

2002-10-09

52

Measurement of Denitrification in Two Freshwater Sediments by an In Situ Acetylene Inhibition Method  

PubMed Central

An acetylene inhibition method was satisfactorily used for the in situ measurement of denitrification in two sediment-water systems incubated for not more than 22 h. In the presence of added nitrate, denitrification acted as a source of nitrous oxide in a drainage pond, but acted as a sink in its absence. The averaged rates of nitrous oxide accumulation with nitrate enrichment in the absence and presence of acetylene were 0.15 and 0.30 mg of N m?2h?1, respectively. Acetylene reduction at an average rate of 0.07 mmol of C2H4 formed m?2h?1 was simultaneously measured in the absence of added nitrate. In a small eutrophic lake where nitrogen was nonlimiting, the in situ rates of sediment denitrification were 0.09 and 0.11 mg of N m?2h?1 in the presence and absence of macrophytes, respectively, and no acetylene reduction activity was found.

Chan, Yiu-Kwok; Knowles, Roger

1979-01-01

53

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

54

Accidental death resulting from acetylene cylinder impact.  

PubMed

Acetylene is an inflammable gas commonly used for welding in small-scale industries. We present a case of a 34-year-old male welder who died following injuries sustained from explosion of an acetylene gas-welding cylinder. In this case report, we discuss the circumstances leading to the explosion of the welding cylinder, the autopsy findings, and a brief review of the literature on deaths resulting from blasts of acetylene cylinders. PMID:15894853

Rani, Mukta; Gupta, Avneesh; Dikshit, P C; Aggrawal, Anil; Setia, Puneet; Dhankar, Vijay

2005-06-01

55

Thermal Conversion of Methane to Acetylene  

SciTech Connect

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

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

2000-01-01

56

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

57

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

58

Comparative evaluation under routine conditions of the nitrate reduction assay, the proportion assay and the MGIT 960 assay for drug susceptibility testing of clinical isolates of Mycobacterium tuberculosis.  

PubMed

The performance of the nitrate reductase assay (NRA) was compared with the proportion method (PM) on Lowenstein-Jensen medium and the BACTEC MGIT960 assay under routine conditions using 160 clinical isolates of Mycobacterium tuberculosis with a high proportion of resistant strains. The mean time to obtain results was 8.8 days and the overall agreements between NRA and PM and NRA and M960 were 95% and 94%, respectively. NRA was easy to perform and represents a useful tool for the rapid screening of drug-resistant M. tuberculosis strains in low-resource countries. PMID:22310549

Fonseca, Leila de Souza; Vieira, Gisele Betzler de Oliveira; Sobral, Luciana Fonseca; Ribeiro, Elizabete Oliveira; Marsico, Anna Grazia

2012-02-01

59

Acetylene-based chemicals from coal and other natural resources  

Microsoft Academic Search

The economic and technological changes which have affected acetylene directly are examined. Commodity chemicals, which were manufactured from acetylene more than thirty years ago, are now made almost entirely from hydrocarbons such as ethylene, propylene, or butadiene. During this period, calcium carbide acetylene was displaced by petrochemical acetylene, the latter was gradually displaced by less expensive olefins and alkanes. The

Tedeschi

1982-01-01

60

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

NASA Astrophysics Data System (ADS)

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 optical transmittance of more than 70% at a wavelength of 500 nm. Such an acetylene-assisted thermal treatment approach is also adopted to fabricate graphene electrodes from synthetic nanographene molecules, with an almost five times increase in conductivity compared to samples prepared by the common thermal reduction.

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

2009-10-01

61

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

62

Comparison of motility, recovery, and methyl-thiazolyl-tetrazolium reduction assays for use in screening plant products for anthelmintic activity  

Microsoft Academic Search

The primary objective of these experiments was to compare the effectiveness of motility, recovery, and methyl-thiazolyl-tetrazolium\\u000a (MTT) reduction assays for determining anthelmintic activity of plant extracts and purified compounds from these extracts.\\u000a Caenorhabditis elegans was used as the test organism. High-performance liquid chromatography (HPLC) grade water and M9 medium were used as the solvents.\\u000a Copper, a common metal pollutant, and

Robert A. Smith; Laura Pontiggia; Carrie Waterman; Meghan Lichtenwalner; Jared Wasserman

2009-01-01

63

New Acetylene-Terminated Quinoxaline Oligomers.  

National Technical Information Service (NTIS)

A series of acetylene-terminated quinoxaline oligomers have been synthesized by methods for using a minimum amount of tetraamine, the most expensive component in the system. Samples of the oligomers have been furnished to the Materials Laboratory for furt...

K. Ishizu U. D. G. Prabhu D. Draney C. S. Marvel

1982-01-01

64

Acetylene as an Inhibitor of Methanogenic Bacteria  

Microsoft Academic Search

Growth of six pure cultures of methanogens was inhibited by low concentrations of dissolved acetylene (C2H2); other archaebacteria (three Halobacterium species) and several eubacteria were not similarly affected. The minimum concentration of dissolved C2H2 required to inhibit growth of Methanospirillum hungatei completely was about 8 p~; dissolved ethylene at 20 p~ had little effect on growth. Dissolved acetylene (33 p~)

G. D. Sprott; K. F. Jarrell; K. M. SHAWl; R. Knowles

1982-01-01

65

Time reduction of vitamin B(6) and inositol assay by using lyophilized Saccharomyces cerevisiae ATCC 9080.  

PubMed

The purpose of this study was to improve the efficiency of the microbiological assays for vitamin B(6) and inositol by using lyophilized cells from Saccharomyces cerevisiae ATCC 9080. The use of lyophilized cells as an inoculum was assessed to avoid time-consuming processes like cell precultivation and washing. The authors also examined the effects of various protectants such as skim milk, lactose, maltose, and trehalose on the assay. The viable cell counts of the lyophilized cells were approximately equal. The standard curves for vitamin B(6) and inositol concentrations obtained using lyophilized cells with maltose and intact cells gave similar linear ranges. Furthermore, the measured vitamin concentrations of the standard reference material 1849 were in the range of the established values. Therefore, lyophilized cells with maltose are potential alternative inocula for the turbidimetric method. This will increase the overall convenience associated with microbiological assays. PMID:22790574

Tsuda, Harutoshi; Matsumoto, Teruki; Ishimi, Yoshiko

2012-01-01

66

Property and reactivity of fluoro(silyl)acetylenes and fluoro(stannyl)acetylenes.  

PubMed

Fluoro(silyl)acetylenes and fluoro(stannyl)acetylenes underwent a radical addition reaction of THF to furnish the corresponding fluorinated cyclic ethers in moderate to good yields. These intriguing addition reaction proved to proceed via a radical reaction mechanism. PMID:21067194

Shiosaki, Masahiro; Unno, Masashi; Hanamoto, Takeshi

2010-11-10

67

Comparison of two assays, a faecal egg count reduction test (FECRT) and a coproantigen reduction test (CRT), for the diagnosis of resistance to triclabendazole in Fasciola hepatica in sheep  

Microsoft Academic Search

A sheep trial was performed to evaluate two diagnostic assays, a faecal egg count reduction test (FECRT) and a coproantigen reduction test (CRT), for the diagnosis of resistance of Fasciola hepatica to triclabendazole (TCBZ). The FECRT defines successful TCBZ treatment as a 95% or greater reduction in fluke faecal egg counts (FECs) at 14 days post-treatment (dpt). The CRT defines

A. Flanagan; H. W. J. Edgar; A. Gordon; R. E. B. Hanna; G. P. Brennan; I. Fairweather

2011-01-01

68

Dengue Plaque Reduction Neutralization Test (PRNT) in Primary and Secondary Dengue Virus Infections: How Alterations in Assay Conditions Impact Performance  

PubMed Central

Dengue virus (DENV) infection is a worsening global health problem. The plaque reduction neutralization test (PRNT) is currently considered to be the “gold standard” to characterize and quantify circulating levels of anti-DENV neutralizing antibody (NAb). Many variations of the PRNT are currently in use and neither the assay nor its performance conditions have been standardized or harmonized between laboratories. We used a well-characterized panel of acute and late convalescent follow-up sera samples from children experiencing primary and secondary DENV infections to evaluate the performance of the dengue PRNT under a variety of testing conditions. Investigators varied cell type, control virus passage, and the use of complement across multiple assay runs of the same sample panel. Our findings indicate wide variation in PRNT titer results in response to varied testing conditions.

Thomas, Stephen J.; Nisalak, Ananda; Anderson, Kathryn B.; Libraty, Daniel H.; Kalayanarooj, Siripen; Vaughn, David W.; Putnak, Robert; Gibbons, Robert V.; Jarman, Richard; Endy, Timothy P.

2010-01-01

69

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

2012-05-15

70

Comparing Denitrification Estimates for a Texas Estuary by Using Acetylene Inhibition and Membrane Inlet Mass Spectrometry  

PubMed Central

Characterizing denitrification rates in aquatic ecosystems is essential to understanding how systems may respond to increased nutrient loading. Thus, it is important to ensure the precision and accuracy of the methods employed for measuring denitrification rates. The acetylene (C2H2) inhibition method is a simple technique for estimating denitrification. However, potential problems, such as inhibition of nitrification and incomplete inhibition of nitrous oxide reduction, may influence rate estimates. Recently, membrane inlet mass spectrometry (MIMS) has been used to measure denitrification in aquatic systems. Comparable results were obtained with MIMS and C2H2 inhibition methods when chloramphenicol was added to C2H2 inhibition assay mixtures to inhibit new synthesis of denitrifying enzymes. Dissolved-oxygen profiles indicated that surface layers of sediment cores subjected to the MIMS flowthrough incubation remained oxic whereas cores incubated using the C2H2 inhibition methods did not. Analysis of the microbial assemblages before and after incubations indicated significant changes in the sediment surface populations during the long flowthrough incubation for MIMS analysis but not during the shorter incubation used for the C2H2 inhibition method. However, bacterial community changes were also small in MIMS cores at the oxygen transition zone where denitrification occurs. The C2H2 inhibition method with chloramphenicol addition, conducted over short incubation intervals, provides a cost-effective method for estimating denitrification, and rate estimates are comparable to those obtained by the MIMS method.

Bernot, Melody J.; Dodds, Walter K.; Gardner, Wayne S.; McCarthy, Mark J.; Sobolev, Dmitri; Tank, Jennifer L.

2003-01-01

71

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

72

Detonation of acetylene near the limit  

Microsoft Academic Search

concentration of condensed phase in the reactive gas and the increased h\\/d indicate a detonation structure different from the standard one [3]. The measurements were made with technical acetylene in a stainless steel tube of length 4 m and internal diameter 32 mm; one end of the tube was 10 cm below the other. Before use, the tube was evacuated

V. I. Manzhalei

1975-01-01

73

Hydration of Acetylene: A 125th Anniversary  

ERIC Educational Resources Information Center

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

Ponomarev, Dmitry A.; Shevchenko, Sergey M.

2007-01-01

74

Intracellular DNA Damage by Lysine-Acetylene Conjugates  

PubMed Central

Previously, we reported the design and properties of alkyne C-lysine conjugates, a powerful and tunable family of DNA cleaving reagents. We also reported that, upon photoactivation, these molecules are capable of inducing cancer cells death. To prove that the cell death stems from DNA cleavage by the conjugates, we investigated intracellular DNA damage induced by these molecules in LNCap cancer cells using single cell gel electrophoresis (SCGE) assays. The observation of highly efficient DNA damage confirmed that lysine acetylene conjugate is capable of cleaving the densely compacted intracellular DNA. This result provides a key mechanistic link between efficient DNA cleavage and cytotoxicity towards cancer cells for this family of light-activated anticancer agents.

Yang, Wang-Yong; Cao, Qiang; Callahan, Catherine; Galvis, Catalina; Sang, Qing-Xiang; Alabugin, Igor V.

2010-01-01

75

Acetylene inhibition of Azotobacter vinelandii hydrogenase: Acetylene binds tightly to the large subunit  

SciTech Connect

Acetylene is a slow-binding inhibitor of the Ni- and Fe-containing dimeric hydrogenase isolated from Azotobacter vinelandii. Acetylene was released from hydrogenase during the recovery from inhibition. This indicates that no transformation of acetylene to another compound occurred as a result of the interaction with hydrogenase. However, the release of C{sub 2}H{sub 2} proceeds more rapidly than the recovery of activity, which indicates that release of C{sub 2}H{sub 2} is not sufficient for recovery of activity. Acetylene binds tightly to native hydrogenase; hydrogenase and radioactivity coelute from a gel permeation column following inhibition with {sup 14}C{sub 2}H{sub 2}. Acetylene, or a derivative, remains bound to the large 65,000 MW subunit (and not to the small 35,000 MW subunit) of hydrogenase following denaturation as evidence by SDS-PAGE and fluorography of {sup 14}C{sub 2}H{sub 2}-inhibited hydrogenase. This result suggests that C{sub 2}H{sub 2}, and by analogy H{sub 2}, binds to and is activated by the large subunit of this dimeric hydrogenase. Radioactivity is lost from {sup 14}C{sub 2}H{sub 2}-inhibited protein during recovery. The inhibition is remarkably specific for C{sub 2}H{sub 2}; propyne, butyne, and ethylene are not inhibitors.

Jinhua Sun; Hyman, M.R.; Arp, D.J. (Oregon State Univ., Corvallis (United States))

1992-03-31

76

Selective hydrogenation of acetylene on Nanosized catalysts  

Microsoft Academic Search

The use of unconventional methods for the preparation of Nanosized catalysts for the selective hydrogenation of acetylene\\u000a and its homologs is considered. Based on published data and experimental data obtained in this work, it is shown that catalysts\\u000a based on nanoparticles of palladium have a high activity, although their selectivity and stability are low. Bimetallic palladium-containing\\u000a systems are more promising.

L. A. Tyurina; S. A. Nikolaev; S. A. Gurevich; V. M. Kozhevin; V. V. Smirnov; K. L. Zanaveskin

2009-01-01

77

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

78

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

EPA Science Inventory

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

79

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

PubMed

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 optical transmittance of more than 70% at a wavelength of 500 nm. Such an acetylene-assisted thermal treatment approach is also adopted to fabricate graphene electrodes from synthetic nanographene molecules, with an almost five times increase in conductivity compared to samples prepared by the common thermal reduction. PMID:19801755

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

2009-10-02

80

Acetylene-based chemicals from coal and other natural resources  

SciTech Connect

The economic and technological changes which have affected acetylene directly are examined. Commodity chemicals, which were manufactured from acetylene more than thirty years ago, are now made almost entirely from hydrocarbons such as ethylene, propylene, or butadiene. During this period, calcium carbide acetylene was displaced by petrochemical acetylene, the latter was gradually displaced by less expensive olefins and alkanes. The calcium carbide process viewed in terms of its abundant raw materials, might again become an attractive technology as petroleum-based feedstocks become scarcer and more expensive. With improved furnace design and solids handling, further economics in this process may be possible. The greatest growth area for acetylene is now in Reppe-type chemicals such as butyndiol, tetrahydrofuran, N-methyl-2-pyrrolidone, vinyl pyrrolidone, and polyvinyl pyrrolidone, and a variety of acetylenic alcohols and glycols. The technology and applications for large-volume acetylenic products and their derivatives are outlined. Acetylene production processes purification, stability and guidelines for its safe use in chemical operations are described. 327 references, 30 figures, 19 tables.

Tedeschi, R.J.

1982-01-01

81

Chemistry of acetylene on platinum (111) and (100) surfaces  

PubMed Central

An ultra-high vacuum experimental study of acetylene chemisorption on Pt(111) and Pt(100) and of the reaction of hydrogen with the acetylene adsorbate has established distinguishing features of carbon-hydrogen bond breaking and making processes as a function of pressure, temperature, and surface crystallography. The rates for both processes are substantially higher on the Pt(100) surface. Net acetylene-hydrogen processes, in the temperature range of 20°C to ?130°C, are distinctly different on the two surfaces: on Pt(100) the net reaction is hydrogen exchange (1H-2H exchange) and on Pt(111) the only detectable reaction is hydrogenation. Stereochemical differences in the acetylene adsorbate structure are considered to be a contributing factor to the differences in acetylene chemistry on these two surfaces. Images

Muetterties, E. L.; Tasi, M.-C.; Kelemen, S. R.

1981-01-01

82

Colorimetric microbial viability assay based on reduction of water-soluble tetrazolium salts for antimicrobial susceptibility testing and screening of antimicrobial substances  

Microsoft Academic Search

The applicability of a colorimetric microbial viability assay based on reduction of a tetrazolium salt {2-(2-methoxy-4-nitrophenyl)-3-(4-nitrophenyl)-5-(2,4-disulfophenyl)-2H-tetrazolium, monosodium salt [WST-8]} via 2-methyl-1,4-naphthoquinone (2-methyl-1,4-NQ) as an electron mediator for determining the susceptibility of various bacteria to antibiotics and screening antimicrobial substances was investigated. The measurement conditions, which include the effects of the concentration of 2-methyl-1,4-NQ, were optimized for proliferation assays of gram-negative

Tadayuki Tsukatani; Tomoko Higuchi; Hikaru Suenaga; Tetsuyuki Akao; Munetaka Ishiyama; Takatoshi Ezoe; Kiyoshi Matsumoto

2009-01-01

83

Metabolic activation of acetylenic substituents to derivatives in the rat causing the loss of hepatic cytochrome P-450 and haem  

PubMed Central

1. A number of acetylenic-substituted steroidal and non-steroidal compounds, including 2,2-dipropargylacetamide, pregna-2,4-dien-20-yno[2,3-d]isoxazol-17-ol (Danazol) and acetylene gas, when administered to rats in vivo brought about a decrease in the concentrations of hepatic microsomal cytochrome P-450 and haem. Abnormal haem-breakdown products, `green pigments', and porphyrins accumulated in the livers of these animals. 2. For loss of microsomal cytochrome P-450 to occur in vitro, metabolic activation of the acetylenic substituent was necessary. The enzyme system responsible required NADPH and air, and was induced by pretreatment of rats with phenobarbitone; these are characteristics typical of the microsomal mixed-function oxidases. 3. When rats were dosed with 17?-ethynyl-17?-hydroxyandrost-4-en-3-one (ethynyltestosterone, 1mmol/kg) the pattern of green pigments extracted from the liver 4h after dosing and separated by t.l.c. was quite different from that in rats given 17?-hydroxy-17?-vinylandrost-4-en-3-one (vinyltestosterone), suggesting that reduction of the unsaturated triple bond to a double bond is not normally part of the metabolic activation pathway of the acetylenic substituent. 4. The green pigments extracted from the livers of rats 4h after the administration of the acetylenic-substituted compounds (1mmol/kg) when separated by silica-gel t.l.c. had variable RF values. The number and distribution of green pigments was characteristic for each compound examined. There was little correlation between the total loss of hepatic microsomal haem and the apparent intensity of the green pigments seen on the thin-layer chromatograms. 5. After incubation of [14C]acetylene in vitro with microsomal preparations from phenobarbitone-pretreated rats and a NADPH-generating system, no significant covalent binding to microsomal protein was detected over a 30min incubation period, although under similar conditions there was a significant loss of cytochrome P-450.

White, Ian N. H.

1978-01-01

84

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

85

Acetylene-based materials in organic photovoltaics.  

PubMed

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

Silvestri, Fabio; Marrocchi, Assunta

2010-04-08

86

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

87

Conducting Acetylene-Terminated Polyaniline Oligomers  

NASA Astrophysics Data System (ADS)

Short polyaniline oligomers terminated with acetylene groups were synthesized and characterized. Synthesis was by adaptation of the procedures of Wudl, et al. (JACS 109, 3677 (1987)) and Manassen and Khalif. (JACS 88, 1943 (1966)) The as-synthesized materials were in oxidation states between fully reduced leucoemeraldine and half- oxidized emeraldine. Further oxidation was with O2. Typical conductivities were on the order of 0.01 S/cm. The oligomers were characterized using several spectroscopic methods including UV-vis, FTIR, and ESR. Oxidation states were determined by recording the total coulombs required to convert the partially-oxidized conducting forms to fully-reduced forms. Conductivity was monitored as a function of time at 150 C. Data from conventional high molecular weight polyaniline were collected for comparison.

Wilbur, J.; Sandreczki, T. C.; Park, J.; Zhong, Z.; Brown, I. M.; Leopold, D. J.

1996-03-01

88

Synthesis of Linear Acetylenic Carbon: The "sp" Carbon Allotrope  

NASA Astrophysics Data System (ADS)

A carbon allotrope based on "sp" hybridization containing alternating triple and single bonds (an acetylenic or linear carbon allotrope) has been prepared. Studies of small (8 to 28 carbon atoms) acetylenic carbon model compounds show that such species are quite stable (130^circ to 140^circC) provided that nonreactive terminal groups or end caps (such as tert-butyl or trifluoromethyl) are present to stabilize these molecules against further reactions. In the presence of end capping groups, laser-based synthetic techniques similar to those normally used to generate fullerenes, produce thermally stable acetylenic carbon species capped with trifluoromethyl or nitrile groups with chain lengths in excess of 300 carbon atoms. Under these conditions, only a negligible quantity of fullerenes is produced. Acetylenic carbon compounds are not particularly moisture or oxygen sensitive but are moderately light sensitive.

Lagow, Richard J.; Kampa, Joel J.; Wei, Han-Chao; Battle, Scott L.; Genge, John W.; Laude, David A.; Harper, Carla J.; Bau, Robert; Stevens, Raymond C.; Haw, James F.; Munson, Eric

1995-01-01

89

Three New Vinyl Acetylenes from the Marine Red Alga 'Laurencia'.  

National Technical Information Service (NTIS)

The structures of three new halogenated vinyl acetylenes are described which are natural products from various species of the red seaweed Laurencia. The structure of chlorofucin isolated from Laurencia snyderae was determined by X-ray diffration analysis....

B. M. Howard G. R. Shulte W. Fenical B. Solheim J. Clardy

1979-01-01

90

Tropospheric and lower stratospheric vertical profiles of ethane and acetylene  

NASA Astrophysics Data System (ADS)

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 µg/m³ (1.0 ppb) for ethane and 0.24 µg/m³ (0.23 ppb) for acetylene while the values near 9°N - 80°W were 0.95 µg/m³ (0.77 ppb) and 0.09 µg/m³ (0.09 ppb), respectively. Detectable quantities of both ethane and acetylene are present in the lower stratosphere. There is a sharp decrease in the levels of these two compounds as one crosses the tropopause and ascends into the lower stratosphere. The observed levels of ethane and acetylene may allow some impact on the background chemistry of the troposphere and stratosphere.

Cronn, Dagmar; Robinson, Elmer

91

Ion-molecule reactions in sooting acetylene-oxygen flames  

Microsoft Academic Search

Ion concentration profiles up to mass 557 amu were measured in a sooting acetylene-oxygen flame at an equivalence ratio of 3.0, a total pressure of 2.67 kPa, and an unburned gas velocity of 50 cm s. The mass spectrometer was calibrated for mass by seeding flames with isotopes of several metals and by using deuterated acetylene, which also allowed us

H. F. Calcote; D. G. Keil

1988-01-01

92

Single molecule thermal rotation and diffusion: Acetylene on Cu(001)  

Microsoft Academic Search

A variable temperature scanning tunneling microscope was used to directly observe the thermally induced rotation of a single acetylene molecule between two equivalent orientations on Cu(001) above 68 K. Measurements of the rotation rate as a function of temperature yielded an energy barrier of 169+\\/-3 meV and a preexponential factor of 1011.8+\\/-0.2 s-1. Thermal diffusion of individual acetylene molecules was

L. J. Lauhon; W. Ho

1999-01-01

93

Characterization of carbon nanotubes and carbon nanofibers prepared by catalytic decomposition of acetylene in a fluidized bed reactor  

Microsoft Academic Search

This article describes the synthesis of carbon nanotubes (CNTs) and carbon nanofibers (CNFs) by the catalytic decomposition of acetylene at 973 K over several Fe\\/silica catalysts (sol–gel method prepared) in a fluidized bed reactor. Characterization of the catalysts and the products was performed by chemical analyses, N2 adsorption isotherms (BET surface area), temperature-programmed reduction (TPR), CO volumetric chemisorption, X-ray diffraction (XRD),

M. Pérez-Cabero; I. Rodr??guez-Ramos; A. Guerrero-Ru??z

2003-01-01

94

Acetylene; a new reducing agent used in scr of NO on zeolite catalysts in an oxygen-rich atmosphere  

Microsoft Academic Search

Summary For the first time acetylene was investigated as a reducing agent for the selective catalytic reduction (SCR) of NO in the presence of excess oxygen on metal-exchanged ZSM-5 zeolite catalysts. By using C2H2 as reducing agent, 76% NO conversion to N2 was achieved over In-H-ZSM-5 catalyst under the reaction conditions of 325oC, 1600 ppm NO, 800 ppm C2H2, and

Chong Wang; Xinping Wang; Shanshan Yu; Yan Xu

2005-01-01

95

Characterization of a reduction-sensitive factor from human plasma responsible for apparent false activity in competitive assays for antibody to hepatitis B core antigen.  

PubMed

Addition of reducing agents to competitive assays for antibody to hepatitis B core antigen (anti-HBc) eliminates apparent false reactivity of specimens obtained from individuals with no prior history of hepatitis B virus (HBV) infection and without other serological markers of HBV infection. We have purified and characterized a reduction-sensitive factor (RSF) isolated from the plasma of several volunteer blood donors. Column fractions were assayed fro anti-HBc by using a highly sensitive chemiluminescence assay with a detection of 0.15 Paul Ehrlich Institut units per ml at 50% inhibition. Gel filtration on Sephacryl S-300 indicated that reductant-sensitive samples possessed anti-HBc activity that was associated with immunoglobulin M (IgM), whereas reductant-stable activity was associated with IgG. Gel filtration followed by metal chelate affinity chromatography resulted in a 55-fold purification and demonstrated that RSF activity copurifies with IgM. RSF was recovered from a recombinant hepatitis B core antigen matrix and shown to be an IgM species by immunoblot. In addition, RSF activity coeluted with IgM protein from anti-mu-chain Sepharose. Discrepancies between enzyme immunoassay and radioimmunoassay procedures for anti-HBc (Corzyme and Corab, respectively: Abbott Laboratories, North Chicago, Ill.) appear to be due to the relative sensitivity of the enzyme immunoassay for IgM anti-HBc (sevenfold greater than the radioimmunoassay using a specific panel). The biological basis for the occurrence of low levels of nonspecific IgM anti-HBc reactivity in individuals not previously exposed to HBV remains to be elucidated. PMID:2037679

Robertson, E F; Weare, J A; Randell, R; Holland, P V; Madsen, G; Decker, R H

1991-03-01

96

Characterization of a reduction-sensitive factor from human plasma responsible for apparent false activity in competitive assays for antibody to hepatitis B core antigen.  

PubMed Central

Addition of reducing agents to competitive assays for antibody to hepatitis B core antigen (anti-HBc) eliminates apparent false reactivity of specimens obtained from individuals with no prior history of hepatitis B virus (HBV) infection and without other serological markers of HBV infection. We have purified and characterized a reduction-sensitive factor (RSF) isolated from the plasma of several volunteer blood donors. Column fractions were assayed fro anti-HBc by using a highly sensitive chemiluminescence assay with a detection of 0.15 Paul Ehrlich Institut units per ml at 50% inhibition. Gel filtration on Sephacryl S-300 indicated that reductant-sensitive samples possessed anti-HBc activity that was associated with immunoglobulin M (IgM), whereas reductant-stable activity was associated with IgG. Gel filtration followed by metal chelate affinity chromatography resulted in a 55-fold purification and demonstrated that RSF activity copurifies with IgM. RSF was recovered from a recombinant hepatitis B core antigen matrix and shown to be an IgM species by immunoblot. In addition, RSF activity coeluted with IgM protein from anti-mu-chain Sepharose. Discrepancies between enzyme immunoassay and radioimmunoassay procedures for anti-HBc (Corzyme and Corab, respectively: Abbott Laboratories, North Chicago, Ill.) appear to be due to the relative sensitivity of the enzyme immunoassay for IgM anti-HBc (sevenfold greater than the radioimmunoassay using a specific panel). The biological basis for the occurrence of low levels of nonspecific IgM anti-HBc reactivity in individuals not previously exposed to HBV remains to be elucidated.

Robertson, E F; Weare, J A; Randell, R; Holland, P V; Madsen, G; Decker, R H

1991-01-01

97

Determination of water-soluble vitamins using a colorimetric microbial viability assay based on the reduction of water-soluble tetrazolium salts  

Microsoft Academic Search

A method for the determination of water-soluble vitamins using a colorimetric microbial viability assay based on the reduction of the tetrazolium salt {2-(2-methoxy-4-nitrophenyl)-3-(4-nitrophenyl)-5-(2,4-disulfophenyl)-2H-tetrazolium, monosodium salt (WST-8)} via 2-methyl-1,4-napthoquinone (NQ) was developed. Measurement conditions were optimized for the microbiological determination of water-soluble vitamins, such as vitamin B6, biotin, folic acid, niacin, and pantothenic acid, using microorganisms that have a water-soluble vitamin

Tadayuki Tsukatani; Hikaru Suenaga; Munetaka Ishiyama; Takatoshi Ezoe; Kiyoshi Matsumoto

2011-01-01

98

Mortality of workers at acetylene production plants.  

PubMed Central

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

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

1988-01-01

99

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

100

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

101

The Synthesis and Isothermal Aging Behavior of Oxygen-Free Acetylene Terminated Quinoxalines.  

National Technical Information Service (NTIS)

Acetylene-terminated resins prepared to date have contained phenyl ether groups, limiting their thermooxidative stability to 315 C, as determined by isothermal aging in air. In order to determine whether the thermooxidative stability of the acetylene cure...

F. L. Hedberg F. E. Arnold

1981-01-01

102

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

103

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 173.303...cylinders with compressed gas in solution (acetylene). (a) Cylinder, filler and solvent...applicable parts of Specification 8 and 8AL). Acetylene gas must be shipped in...

2010-10-01

104

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 173.303...cylinders with compressed gas in solution (acetylene). (a) Cylinder, filler and solvent...applicable parts of Specification 8 and 8AL). Acetylene gas must be shipped in...

2009-10-01

105

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

106

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

107

Transport of methane, acetylene, and acetaldehyde through activated carbon  

SciTech Connect

The outlet concentration as a function of time for pulsed and stepped inputs of 100 ppm concentrations of methane, acetylene, and acetaldehyde adsorptives in helium at 1 atm pressure through columns of activated carbon at 25{degree}C were measured and correlated with the solutions to a longitudinal-diffusion model with a linear isotherm. The solutions provided good fits to the experimental data for adsorptives with linear and almost linear isotherms, viz., methane and acetylene, respectively. The nonlinear isotherm of acetaldehyde precludes the determination of the longitudinal diffusion coefficient.

Forsythe, R.; Madey, R.; Photinos, P.J. (Kent State Univ., OH (USA))

1990-05-01

108

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

Microsoft Academic Search

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

Ronald S. Oremland; Mary A. Voytek

2008-01-01

109

The Explosion of a Mixture of Acetylene and Oxygen  

Microsoft Academic Search

WITH reference to your note in last week's NATURE, I may say that, whilst the thanks of chemists, and particularly of those whose duty it is to perform lecture-experiments, are due to Prof. Lothar Meyer for once more drawing attention to the dangerously explosive nature of mixtures of acetylene and oxygen, it may be assumed that the facts already known

T. E. THORPE T. E

1894-01-01

110

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

111

Turbulent Autoignition of Hydrogen and Acetylene in a Duct  

Microsoft Academic Search

This paper presents experimental data on the autoignition of hydrogen and acetylene jets in a turbulent co-flow of hot air. The aim is to understand better how turbulence affects autoignition of non-premixed flows and to obtain data for validating modelling approaches. The conditions under which flashback is observed following autoignition have been quantified as a function of air and jet

C. N. Markides; E. Mastorakos

112

Submicron Particle Size Measurements in an Acetylene-Oxygen Flame  

Microsoft Academic Search

Diffusion broadening spectroscopy has been used to make in situ size measurements of submicron aerosol particles in an acetylene-oxygen flame. Making use of the spectral broadening of scattered laser light due to random particle motion, this optical technique has been demonstrated to be suitable for application in unsteady high temperature environments of 2200 °K in flowing gases. Particle sizes were

J. F. DRISCOLL; D. M MANN; W K. McGREGOR

1979-01-01

113

Exceptionally high acetylene uptake in a microporous metal-organic framework with open metal sites.  

PubMed

Six prototype microporous metal-organic frameworks (MOFs) HKUST-1, MOF-505, MOF-508, MIL-53, MOF-5, and ZIF-8 with variable structures and porosities were examined for their acetylene storage, highlighting HKUST-1 as the highest acetylene storage material ever reported with an uptake of 201 cm(3)/g at 295 K and 1 atm. To locate the acetylene binding sites within HKUST-1, neutron powder diffraction studies on acetylene loaded HKUST-1 were carried out and have conclusively established the significant contribution of open Cu(2+) sites for acetylene storage by their strong preferred interactions with acetylene molecules. The binding properties of acetylene gas at different sites were further investigated by first-principles calculations. PMID:19705919

Xiang, Shengchang; Zhou, Wei; Gallegos, Jose M; Liu, Yun; Chen, Banglin

2009-09-01

114

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

NASA Astrophysics Data System (ADS)

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

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

2003-04-01

115

The ozonolysis of acetylene--a quantum chemical investigation.  

PubMed

The ozonolysis of acetylene was investigated using CCSD(T), CASPT2, and B3LYP-DFT in connection with a 6-311+G(2d,2p) basis set. The reaction is initiated by the formation of a van der Waals complex followed by a [4pi + 2pi] cycloaddition between ozone and acetylene (activation enthalpy DeltaH(a)(298) = 9.6 kcal/mol; experiment, 10.2 kcal/mol), yielding 1,2,3-trioxolene, which rapidly opens to alpha-ketocarbonyl oxide 5. Alternatively, an O atom can be transferred from ozone to acetylene (DeltaH(a)(298) = 15.6 kcal/mol), thus leading to formyl carbene, which can rearrange to oxirene or ketene. The key compound in the ozonolysis of acetylene is 5 because it is the starting point for the isomerization to the corresponding dioxirane 19 (DeltaH(a)(298) = 16.9 kcal/mol), for the cyclization to trioxabicyclo[2.1.0]pentane 10 (DeltaH(a)(298) = 19.5 kcal/mol), for the formation of hydroperoxy ketene 15 (DeltaH(a)(298) = 20.6 kcal/mol), and for the rearrangement to dioxetanone 9 (DeltaH(a)(298) = 23.6 kcal/mol). Compounds 19, 10, 15, and 9 rearrange or decompose with barriers between 13 and 16 kcal/mol to yield as major products formanhydride, glyoxal, formaldehyde, formic acid, and (to a minor extent) glyoxylic acid. Hence, the ozonolysis of acetylene possesses a very complicated reaction mechanism that deserves intensive experimental studies. PMID:11414847

Cremer, D; Crehuet, R; Anglada, J

2001-06-27

116

Acetylene-expanded dendralene segments with exotopic phosphaalkene units.  

PubMed

Bis-TMS protected C,C-diacetylenic phosphaalkene (A(2)PA) 1 (Mes*P=C(C?CTMS)(2); Mes* = 2,4,6-tBu(3)Ph) has been used as a building block for the construction of butadiyne-expanded dendralene fragments in which phosphaalkenes feature as exotopic double bonds. Treatment of 1 with CuCl gives rise to a Cu(I) acetylide that is selectively formed at the acetylene trans to the Mes* group. The cis-TMS-acetylene engages in similar chemistry, albeit at higher temperatures and longer reaction times. The differentiation between the two acetylene termini of 1 allows for the controlled synthesis of the title compounds by a variety of different Cu- and Pd-catalyzed oxidative acetylene homo- and heterocoupling protocols. Crystallographic characterization of A(2)PA 1 and dimeric Mes*P=C(C?CR(1))C(4)(R(2) C?C)C=PMes* (3b, R(1) = R(2) = Ph; 6, R(1) = R(2) = TMS), and 10 (R(1) = R(2) = C?CPh) verifies that the stereochemistry across the P=C bond is conserved during the coupling reactions, whereas spectroscopic evidence reveals cis/trans isomerization in an iodo-substituted A(2)PA intermediate 4 (Mes*P=C(C?CTMS)(C?CI). UV/Vis spectroscopic and electrochemical studies reveal that efficient ? conjugation operates through the entire acetylenic phosphaalkene framework, even in the cross-conjugated dimeric structures. The P centers contribute considerably to the frontier molecular orbitals of the compounds, thereby leading to smaller HOMO-LUMO gaps than in all-carbon-based congeners. Phenyl- and/or ethynylphenyl substituents at the A(2)PA framework influence the HOMO and LUMO to a varying degree depending on their relationship to the Mes* group, thus enabling a fine-tuning of the frontier molecular orbitals of the compounds. PMID:21915927

Geng, Xue-Li; Ott, Sascha

2011-09-14

117

Laboratory Experiments of Condensed-phase Acetylene Mixtures with Astrophysical Applications  

NASA Astrophysics Data System (ADS)

Studies of molecular hot cores and proto-stellar environments have shown that there are some chemical enhancements of molecules due to the newly heated material. In particular, acetylene (C2H2) has been observed toward various proto-stars with column densities as high as 1016 cm-2. Chemical models try to reproduce the observed column densities, but the observed values cannot be matched from acetylene production only via gas phase reactions. Models that assume some icy acetylene component on grain mantles are able to produce the observed values of gas phase acetylene. While it may be possible that some acetylene is sublimating from grain mantles, there has been no direct observations of acetylene ice features on grains. In the Cosmic Ice Laboratory at the NASA Goddard Space Flight Center, we have studied the changes to the infrared spectrum of condensed-phase acetylene as a function of temperature and as a function of concentration. We present the results of these experiments for various binary ice mixtures of acetylene mixed with water, carbon monoxide, carbon dioxide, and methane. We explore the relation between concentration and peak position of the acetylene features. In addition, we explore changes in the features of the other molecules in the presence of acetylene. Funding from the Goddard Center for Astrobiology is acknowledged.

Knez, Claudia; Moore, M.; Ferrante, R.; Hudson, R.

2009-05-01

118

The viscosity of carbon dioxide and acetylene at atmospheric pressure  

Microsoft Academic Search

The viscosities of carbon dioxide and acetylene have been determined to temperatures of 700 and 600 K respectively using the method of capillary flow. The viscometer was a continuous-flow instrument incorporating a differential mercury manometer and a soap-film flow meter. A determination of the constant m in the kinetic energy term of the Hagen-Poiseuille equation, showed it to have a

B J Bailey

1970-01-01

119

The IR acetylene spectrum in HITRAN: update and new results  

Microsoft Academic Search

The 2000 HITRAN edition, with the updates of 2001, contains improved and new data on the acetylene molecule. The main changes concern the 13.6- and 7.5-?m spectral regions (improved line intensities), and the 5-?m region (previously absent from the database). These changes are reviewed, and the key problem of the validation of line intensities is dealt with. The status of

D. Jacquemart; J.-Y. Mandinb; V. Dana; C. Claveau; J. Vander Auwera; M. Herman; L. S. Rothmana; L. Regalia-Jarlot; A. Barbe

2003-01-01

120

Direct polymerization of acetylene to give living polyenes  

SciTech Connect

Polyacetylene has been of great interest in the past decade as (inter alia) a potential organic conductor, but so far it has not been possible to prepare polyacetylene or shorter oligomers in a controlled polymerization of acetylene. There is good evidence that this should be possible under the right circumstances by using an alkylidene complex (eq 1). The authors report here the preparation of living polyenes of moderate length and block copolymers containing polyene sequences by this method.

Schlund, R.; Schrock, R.R.; Crowe, W.E. (Massachusetts Institute of Technology, Cambridge (USA))

1989-11-27

121

Meridional Variations of Acetylene and Ethane On Jupiter  

Microsoft Academic Search

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

C. A. Nixon; N. A. Teanby; P. G. J. Irwin; R. K. Achterberg; P. N. Romani

2005-01-01

122

Low temperature Raman study of bis(trimethylsilyl)acetylene  

Microsoft Academic Search

Low temperature Raman spectroscopy was applied in study of bis(trimethylsilyl)acetylene (BTMSA), a known catalyst with very low barrier for the internal rotation of methyl groups – less than 10cal\\/mol (Sipachev et al. J. Mol. Struct. 523 (2000) 1). Since crystals consisting of flexible molecules often show polymorphism, it was of interest to find out if it is the case of

Vlasta Mohacek-Grosev; Krešimir Furi?

2007-01-01

123

Interaction of pi-Electrons in the Acetylene Molecule  

Microsoft Academic Search

The acetylene molecule has been treated as a system of four pi-electrons, and its lower excited energy levels have been calculated using both MO method with configuration interaction and the HL method including ionic-homopolar resonance. The Slater 2ppi atomic orbitals with effective charge 3.18 have been used in each calculation. The results show that the effects of configuration interaction in

Takashi Nakamura; Kimio Ohno; Masao Kotani; Katsunori Hijikata

1952-01-01

124

Conversion of Natural Gas to Liquids via Acetylene as an Intermediate  

SciTech Connect

This paper describes an experimental investigation of the conversion of natural gas to liquid transportation fuels through acetylene as an intermediate. The first step is the direct thermal conversion of methane to acetylene utilizing a thermal plasma heat source to dissociate the methane. The dissociation products react to form a mixture of acetylene and hydrogen. Significant improvements over the prior art were observed; these improvements may be attributed to an improved methane injection configuration and minimization of radial temperature gradients. Conversion efficiencies (percent methane converted) approached 100% and acetylene yields in the 90–95% range with 2–4% solid carbon production were obtained. A variety of methods were examined for the second step, the conversion of acetylene to liquid products. The most promising technology was the reaction of acetylene with hydrogen over a shape-selective zeolite to form C3–C5+ aliphatics.

Fincke, James Russell; Anderson, Raymond Paul; Taylor, C. E.

2002-05-01

125

Renner-teller effect at the initial acetylene thermal transformation stages  

Microsoft Academic Search

It is shown that the vibrational excitation of the acetylene molecule is accompanied by the transformation of its linear structure\\u000a into a transoid structure because of the Renner-Teller effect. The electron density distribution in transoid acetylene was\\u000a calculated by nonempirical quantum-chemical methods. It was shown that this structure corresponded to a 1,2-biradicaloid.\\u000a The intense light absorption in the acetylene spectrum

I. V. Bilera; Yu. A. Borisov; N. N. Buravtsev; Yu. A. Kolbanovskii

2007-01-01

126

Acetylene as a substrate in the development of primordial bacterial communities  

NASA Astrophysics Data System (ADS)

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

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

1988-12-01

127

[Mechanism of the "acetylene effect" during interaction of organophosphorus compounds with cholinesterases].  

PubMed

Here we present data on the anticholinesterase activity of 58 synthesized ethers of phosphorus thioacids with an acetylene bond in the thioether group. Anticholinesterase activity of the compounds, with acetylene group in beta and especially alpha position, in the thioether radical is many times that of their saturated analogs. Reaction between the enzymes and acetylene organophosphorous inhibitors, as well as their saturated analogs, results in phosphorylated enzyme. The triple bond plays a significant role in the acceleration of cholinesterases phosphorylation. Antienzyme activity of acetylene organophosphorous inhibitors is discussed. PMID:10581870

Kabachnik, M I; Godovikov, N N; Vikhreva, L A; Pudova, T A; Brestkin, A P; Rozengart, V I

128

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

129

Regioselectivity of metabolic activation of acetylenic steroids by hepatic cytochrome P450 isozymes.  

PubMed

Liver cytochrome P450 monooxygenases (P450), a group of isozymes that catalyze the reductive cleavage of molecular oxygen, dominate hepatic metabolism of xenobiotic lipophilic substances. These P450 enzymes exhibit broad and overlapping substrate specificities, in contrast to the P450 isozymes of the steroid biosynthetic pathways, which are highly substrate specific. Hepatic heme pigments, N-alkylated porphyrins, accumulate following the self-catalyzed destruction of P450 by the metabolic activation of 17 alpha-ethynyl steroids. Acetylenic substituted steroidal aromatase inactivators, norethisterone (NET), and 10-(2-propynyl)estr-4-ene-3,17-dione (MDL 18,962) were administered to rats to determine if the acetylenic substituent was activated by hepatic P450 mixed-function oxidases. This metabolism could result in the formation of a reactive species that would alkylate a pyrrole nitrogen atom of heme. Male Sprague-Dawley rats were treated with 0, 10, 30, or 100 mg/kg NET or MDL 18,962 intraperitoneally. Four hours later, these animals received 40 mg/kg sodium pentobarbital and their sleeping times were recorded. On arousal, the rats were killed and their livers were taken for determination of P450 content and formation of N-alkylated porphyrins (green pigments). Norethisterone inhibited hepatic P450 isozymes, resulting in a dose-related increased sleeping time (89.2 +/- 3.5 to 156.3 +/- 7.6 minutes) and decreased P450 levels (maximum 25% decrease at 100 mg/kg), and the amount of green pigments increased with doses of 10 to 100 mg/kg. In contrast, MDL 18,962 treatment did not increase sleeping time and caused only a 15% decrease in hepatic P450 content at 100 mg/kg, with no detectable green pigments.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:1871782

Johnston, J O; Wright, C L; Leeson, G A

1991-04-01

130

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

131

Formation of HCN and acetylene oligomers by photolysis of ammonia in the presence of acetylene: applications to the atmospheric chemistry of Jupiter  

SciTech Connect

HCN is formed by the photolysis of ammonia in the presence of acetylene at room temperature. There is a 70% decrease in the yield of HCN when the temperature is lowered to 178 K and two new reaction products, acetonitrile and acetaldehyde ethylidenehydrazone (6), are formed. Photolysis of 6 yields acetonitrile, and the hydrogen atom initiated decomposition of acetonitrile yields HCN. Aziridine, a predicted reaction intermediate, was not detected at 298 or 178 K. Oligomers of acetylene are also formed. Oligomers formed by the photolysis of ammonia in the presence of acetylene were shown by Fourier transform infrared spectroscopy to contain NH groupings and to differ from those produced by the direct photolysis of acetylene. The possible role of these photochemical processes on the formation of HCN and chromophores on Jupiter, Titan, and comets is discussed.

Ferris, J.P.; Ishikawa, Y.

1988-06-22

132

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

133

Pore topology and diffusion of acetylene in CuBTC metal organic framework  

NASA Astrophysics Data System (ADS)

Here we report molecular dynamics simulation study to investigate the dynamical behaviour of acetylene adsorbed in CuBTC MOF. CuBTC has complex network structures consisting of main pores and side pockets connected by windows. Diffusivity of the acetylene molecules adsorbed in CuBTC is found to increase with increase in concentration of the acetylene molecules. It was found that average time spent in pockets by the acetylene molecules increases with increase in concentration suggesting faster saturation of the pockets. At higher concentration, acetylene molecules prefer to diffuse through the connecting windows rather than the pockets. Calculation of the potential energy landscape showed that molecules experience less energy barrier while diffusing through the connecting windows compared to that through the pockets.

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

2013-02-01

134

Retention of long-chain acetylenic hydrocarbons on non-polar stationary phases.  

PubMed

The retention indices of methyl and trimethylsilyl esters of octadeca-, eicosa- and tricosa-ynoic fatty acids containing acetylenic bonds were measured on non-polar stationary phase (dimethylsilicone with 5% phenyl groups). An unusually large increase in retention is observed for compounds containing conjugated and methylene interrupted acetylenic bonds. The additional increase in retention index as a result of the presence of one conjugated acetylenic bond is roughly equivalent to the retention increase caused by lengthening of the hydrocarbon chain for one carbon atom. The increase in retention for methylene interrupted bonds constitutes approximately 50% increase for conjugated triple bonds. A further increase in interruption substantially decreases the effect. Based on available literature data and the results of this work, the contributions of conjugated acetylenic and olefinic bonds, and methylene interrupted acetylenic bonds to retention were estimated. PMID:19095239

Tretyakov, K V; Babushok, V I

2008-12-06

135

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

136

Numerical study of ethylene and acetylene laminar flame speeds  

SciTech Connect

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

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

1995-03-01

137

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

2013-08-27

138

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

NASA Astrophysics Data System (ADS)

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

Oremland, Ronald S.; Voytek, Mary A.

2008-02-01

139

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

140

A first principles study of the acetylene-water interaction  

SciTech Connect

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

Tzeli, Demeter [Laboratory of Physical Chemistry, Department of Chemistry, National and Kapodistrain University of Athens, P.O. Box 64 004, 157 10 Zografou, Athens, (Greece); Mavridis, Aristides [Laboratory of Physical Chemistry, Department of Chemistry, National and Kapodistrain University of Athens, P.O. Box 64 004, 157 10 Zografou, Athens, (Greece); Xantheas, Sotiris S. [Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, 906 Battelle Boulevard, P.O. Box 999, MS K8-91, Richland, Washington 99352 (United States)

2000-04-08

141

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

142

Ultrafast dynamics in acetylene clocked in a femtosecond XUV stopwatch  

NASA Astrophysics Data System (ADS)

Few-photon induced ultrafast dynamics in acetylene (C2H2) leading to several dissociation channels—deprotonation (H++C2H+ and H++C2H2+), symmetric break-up (CH++CH+) and isomerization (C++CH2+)--were investigated employing the (XUV; extreme ultra-violet)-pump-(XUV extreme ultra-violet)-probe scheme at the free-electron laser in Hamburg, combined with multi-hit coincidence detection. The kinetic energy releases and fragment-ion momentum distributions for various decay channels are presented. The C++CH2+ and H++C2H2+ channels reveal clear signatures of ultrafast molecular mechanisms, demonstrating potential applications of our pump-probe technique to complex systems in order to study a large variety of ultrafast phenomena in the XUV regime.

Jiang, Y. H.; Senftleben, A.; Kurka, M.; Rudenko, A.; Foucar, L.; Herrwerth, O.; Kling, M. F.; Lezius, M.; Tilborg, J. V.; Belkacem, A.; Ueda, K.; Rolles, D.; Treusch, R.; Zhang, Y. Z.; Liu, Y. F.; Schröter, C. D.; Ullrich, J.; Moshammer, R.

2013-08-01

143

Ultrafast Extreme Ultraviolet Induced Isomerization of Acetylene Cations  

SciTech Connect

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

Jiang, Y. H.; Kurka, M.; Kuehnel, K. U.; Schroeter, C. D.; Moshammer, R. [Max-Planck-Institut fuer Kernphysik, 69117 Heidelberg (Germany); Rudenko, A.; Foucar, L. [Max-Planck Advanced Study Group at CFEL, 22607 Hamburg (Germany); Herrwerth, O.; Lezius, M.; Kling, M. F. [Max-Planck-Institut fuer Quantenoptik, 85748 Garching (Germany); Tilborg, J. van; Belkacem, A. [Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Ueda, K. [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 980-8577 Sendai (Japan); Duesterer, S.; Treusch, R. [DESY, 22607 Hamburg (Germany); Ullrich, J. [Max-Planck-Institut fuer Kernphysik, 69117 Heidelberg (Germany); Max-Planck Advanced Study Group at CFEL, 22607 Hamburg (Germany)

2010-12-31

144

Ignition of acetylene by high-voltage nanosecond discharge  

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

145

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

146

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

PubMed Central

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

Muller, Michael M.; Sundman, Veronica; Skujins, J.

1980-01-01

147

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...

148

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...

149

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

SciTech Connect

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

Meyer, M.K.

1991-12-20

150

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

Microsoft Academic Search

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

1991-01-01

151

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

National Technical Information Service (NTIS)

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

M. K. Meyer

1991-01-01

152

Diode laser spectrometry for monitoring acetylene on-line in a liquefaction plant  

SciTech Connect

A diode laser source infrared spectrometer has been acquired for use as an on-line monitor for acetylene in the rich (oxygen-enriched) liquid stream of the ORGDP liquefaction plant. The liquefaction plant produces high purity liquid nitrogen.

Maddox, W.L.; Turner, C.M.

1983-11-18

153

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

SciTech Connect

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

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

1986-06-10

154

On the reaction pathway for the hydrogenation of acetylene and vinylidene on Pd(111)  

Microsoft Academic Search

The pathways for the hydrogenation of adsorbed acetylene and vinylidene on Pd(111) are investigated using temperature-programmed desorption and infrared reflection-absorption spectroscopies. The chemistry of the vinyl intermediate formed by the hydrogenation of both species is investigated by adsorbing vinyl iodide on Pd(111) where it is found that vinyl species hydrogenate more rapidly than adsorbed acetylene, indicating that the rate-limiting step

S. Azad; M. Kaltchev; D. Stacchiola; G. Wu; W. T. Tysoe

2000-01-01

155

Rapid discharge performance of composite electrode of hydrated sodium manganese oxide and acetylene black  

Microsoft Academic Search

Hydrated sodium manganese oxide was synthesized by reducing permanganate ion using ethanol by a sol–gel method. By including acetylene black in the synthetic reaction, we obtained composite materials in which sodium manganese oxide hydrate particles were small and mixed well with the acetylene black. We evaluated those composites as a lithium battery cathode and found that they showed 170mAhg?1 under

Mitsuhiro Hibino; Hirokazu Kawaoka; Haoshen Zhou; Itaru Honma

2004-01-01

156

Infrared Spectroscopy of Interphases Between Model Rubber Compounds and Plasma Polymerized Acetylene Films  

Microsoft Academic Search

Thin (? 750 Å) plasma polymerized films of acetylene deposited onto polished steel substrates are promising primers for rubber-to-metal bonding. The as-deposited films contained mono- and di-substituted acetylene groups, aromatic groups, and groups such as carbonyl which apparently resulted from reaction of residual free radicals with oxygen when the films were exposed to the atmosphere. There was some evidence for

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

1995-01-01

157

Effect of surface free energy of acetylene black powder on air electrode performance  

Microsoft Academic Search

The effects of acetylene black powder surface free energy on air electrode electrochemical performance and lifetime were studied. The acetylene black was immersed in 30% H2O2 at room temperature and the changes of functional groups and surface free energy were investigated by X-ray Photoelectron Spectros-copy (XPS) and powder contact angle (CA). The air electrode performance was characterized by the potential

Xiuqin OU; Shuguang LIU; Guangchuan LIANG; Ying LI; Xiaoke ZHI; Bin HAN

2006-01-01

158

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

NASA Astrophysics Data System (ADS)

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

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

2012-03-01

159

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

PubMed

The formation mechanism of polycyclic aromatic hydrocarbon (PAH) molecules in interstellar and circumstellar environments is not well understood although the presence of these molecules is widely accepted. In this paper, addition and aromatization reactions of acetylene over astrophysically relevant nesosilicate particles are reported. Gas-phase PAHs produced from exposure of acetylene gas to crystalline silicates using pulsed supersonic jet expansion (SJE) conditions were detected by time-of-flight mass spectrometry (TOF-MS). The PAHs produced were further confirmed in a separate experiment using a continuous flow fixed-bed reactor in which acetylene was introduced at atmospheric pressure. The gas-phase effluent and solutions of the carbonaceous compounds deposited on the nesosilicate particles were analyzed using gas chromatography-mass spectrometry (GC-MS). A mechanism for PAH formation is proposed in which the Mg(2+) ions in the nesosilicate particles act as Lewis acid sites for the acetylene reactions. Our studies indicate that the formation of PAHs in mixed-chemistry astrophysical environments could arise from acetylene interacting with olivine nano-particles. These nesosilicate particles are capable of providing catalytic centres for adsorption and activation of acetylene molecules that are present in the circumstellar environments of mass-losing carbon stars. The structure and physical properties of the particles were characterized by means of X-ray diffraction (XRD), Fourier transform infrared (FT-IR) and high-resolution transmission electron microscopy (HRTEM) techniques. PMID:22460553

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

2012-03-29

160

Studies on a Heat-Labile Variola Virus Inhibitor in Normal Sera. I. Detection by the Variola Focus Reduction Assay and its General Characteristics  

Microsoft Academic Search

Summary A heat-labile inhibitor (HLI) capable of neutralizing the infectivity of variola virus, as measured by reduction of focus-forming and plaque-forming activity, was detected in normal human, guinea pig, rabbit and monkey sera. HLI lost its activity on incubation at 56° for 30 min, and showed different behaviors from complement in heat inactivation curves as well as in specific absorption

Takashi Kitamura; Yoshiko Miyagawa; Yukië Tanaka

1973-01-01

161

Human urothelial micronucleus assay to assess genotoxic recovery by reduction of arsenic in drinking water: a cohort study in West Bengal, India.  

PubMed

Chronic exposure to arsenic through drinking water affects nearly 26 million individuals in West Bengal, India. Cytogenetic biomarkers like urothelial micronucleus (MN) are extensively used to monitor arsenic exposed population. In 2004-2005, 145 arsenic exposed individuals and 60 unexposed controls were surveyed of which 128 exposed individuals and 54 unexposed controls could be followed up in 2010-2011. In 2004-2005, the extent of arsenic content in the drinking water was 348.23 ± 102.67 ?g/L, which was significantly lowered to 5.60 ± 10.83 ?g/L in 2010-2011. Comparing the data obtained between 2004-2005 and 2010-2011, there was a significant decline in the MN frequency, when assayed in 2010-2011 compared to 2004-2005. Hence, we infer that urothelial MN can be utilized as a good biomarker in detecting remedial effects from toxicity of the low dose of arsenic through drinking water. PMID:23907726

Paul, Somnath; Bhattacharjee, Pritha; Mishra, Prafulla K; Chatterjee, Debmita; Biswas, Anirban; Deb, Debasree; Ghosh, Aloke; Guha Mazumder, D N; Giri, Ashok K

2013-08-02

162

A highly regio- and stereo-selective hydrostannation reaction of various fluorine-containing internal acetylene derivatives  

Microsoft Academic Search

The hydrostannation reaction of various fluoroalkylated acetylene derivatives with tributyltin hydride was investigated using a variety of catalysts in toluene. Among them, the Et3B-induced hydrostannation reaction gave the highest regio- and stereo-selectivity. Their selectivity was mostly influenced upon the difference of the substituent X at the aromatic ring of the aryl-substituted internal acetylenes. Thus, the acetylenes having a halogen atom

Jungha Chae; Tsutomu Konno; Masashi Kanda; Takashi Ishihara; Hiroki Yamanaka

2003-01-01

163

Development of Pd–Cu catalyzed cross-coupling of terminal acetylenes with sp 2-carbon halides  

Microsoft Academic Search

The Pd-catalyzed cross coupling reactions between sp2-C halides and terminal acetylenes have been independently reported by Heck, Cassar and us in 1975. The former two methods have been developed as an extension of the Heck reaction to an acetylenic CH-bond. Ours has been discovered on the base of combination of Pd-catalyzed cross-coupling of sp2-C halides with terminal acetylenes and Cu-catalyzed

Kenkichi Sonogashira

2002-01-01

164

Endorhizal and Exorhizal Acetylene-reducing Activity in a Grass (Spartina alterniflora Loisel.)-Diazotroph Association 1  

PubMed Central

Earlier studies indicated that bacteria responsible for nitrogenase activity of some grasses are located inside the roots. Those studies were conducted with excised roots in which a long, unexplained “lag phase” occurred before initiation of nitrogenase activity. When hydroponically maintained Spartina alterniflora Loisel. was incubated in a two-compartment system with acetylene, ethylene was produced following, at most, a 2-hour lag in both the upper (shoot) and lower (roots + water) phases. Ethylene production in the upper phase not attributable to leaf-associated acetylene-reducing activity or to diffusion of ethylene from around the roots is considered to represent “endorhizal acetylene-reducing activity,” the internally produced ethylene diffusing into the upper phase via the lacunae. Ethylene produced in the lower phase is designated “exorhizal acetylene-reducing activity.” The endorhizal acetylene-reducing activity, in comparison to exorhizal activity, was relatively insensitive to additions of HgCl2, NH4Cl, or carbon sources to the lower phase. Post-lag acetylene-reducing activity of roots excised from plants growing in soil responded to additions in a manner similar to that of endorhizal acetylene-reducing activity, whereas post-lag acetylene-reducing activity of rhizosphere soil responded in a manner similar to that of exorhizal acetylene-reducing activity.

Boyle, C. David; Patriquin, David G.

1980-01-01

165

Structural trends in transition metal cation-acetylene complexes revealed through the C-H stretching fundamentals.  

PubMed

Metal cation-acetylene complexes (M = V, Fe, Co, Ni) are produced in molecular beams and studied with infrared photodissociation spectroscopy in the C-H stretching region. Each complex has two vibrational bands corresponding to the symmetric and asymmetric stretches of acetylene that are shifted to the red of these vibrations in the isolated acetylene molecule. Density functional theory reveals the sources of the red-shifted vibrations and their relative magnitudes. Fe+, Co+, and Ni+ form pi-complexes with acetylene, while V+(C2H2) is a metallacycle. PMID:15669839

Walters, Richard S; Schleyer, Paul V R; Corminboeuf, Clemence; Duncan, Michael A

2005-02-01

166

Copper-catalyzed chlorination and condensation of acetylene and dichloroacetylene.  

PubMed

The chlorination and condensation of acetylene at low temperatures is demonstrated using copper chlorides as chlorinated agents coated to model borosilicate surfaces. Experiments with and without both a chlorine source and borosilicate surfaces indicate the absence of gas-phase and gas-surface reactions. Chlorination and condensation occur only in the presence of the copper catalyst. C2 through C8 organic products were observed in the effluent; PCDD/F were only observed from extraction of the borosilicate surfaces. A global reaction model is proposed that is consistent with the observed product distributions. Similar experiments with dichloroacetylene indicate greater reactivity in the absence of the copper catalyst. Reaction is observed in the gas-phase and in the presence of borosilicate surfaces at low temperatures. The formation of hexachlorobenzene is only observed in the presence of a copper catalyst. PCDD/F were only observed from extraction of the borosilicate surfaces. A global reaction model is proposed for the formation of hexachlorobenzene from dichloroacetylene. PMID:10789968

Taylor, P H; Wehrmeier, A; Sidhu, S S; Lenoir, D; Schramm, K W; Kettrup, A

2000-06-01

167

Long-term measurements of light alkanes and acetylene in the Antarctic troposphere  

NASA Astrophysics Data System (ADS)

Between 1982 and 1989, biweekly whole air samples were collected at the German Antarctic station 'Georg von Neumayer.' In addition, a smaller number of samples were taken in 1988 and 1989 at Scott Base, the New Zealand Antarctic station. These samples were analyzed for several light hydrocarbons and halocarbons. For the light alkanes and acetylene, the average results from the two stations which are located at opposite coasts of Antarctica agree. The annual mean values for ethane, propane, n-butane, i-pentane and acetylene are 380 +/- 8 ppt, 84 +/- 4 ppt, 50 +/- 4 ppt, 15 +/- 2 ppt, and 17 +/- 1 ppt, respectively. The mixing ratios of ethane, propane, and i-pentane show a seasonal cycle with a peak in August, a minimum in February and an average maximum to minimum variation of 40 percent-50 percent. Acetylene also shows a maximum around August, but its seasonal variation is higher by a factor of three. For ethane, propane and acetylene, the measurements indicate that during the last few years, the average mixing ratios in austral winter have slightly increased. A possible explanation of this secular trend is the increase of biomass burning in the Southern Hemisphere. This is also consistent with the assumption that part of the seasonal variation found for ethane, propane and acetylene reflects the seasonal dependence of biomass burning.

Rudolph, J.; Khedim, A.; Clarkson, T.; Wagenbach, D.

1992-09-01

168

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...

169

Topoisomerase Assays  

PubMed Central

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

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

2012-01-01

170

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

171

Mechanism and Kinetics of the Silane Decomposition in the Presence of Acetylene and in the Presence of Olefins.  

National Technical Information Service (NTIS)

Kinetic data and product studies are reported for the silane pyrolysis in the presence of olefins and acetylene. The kinetics of silane loss in the presence of acetylene was found to be identical to the initial gas phase silane decomposition step (SiH4 + ...

J. W. Erwin M. A. Ring H. E. O'Neal

1985-01-01

172

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

SciTech Connect

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

Lin-Vien, D.; Fateley, W.G.; Davis, L.C. (Kansas State Univ., Manhattan (USA))

1989-02-01

173

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

PubMed Central

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

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

1989-01-01

174

Palladium-catalyzed coupling of heteroaromatic triflates with acetylene and its application for a dynemicin a intermediate  

Microsoft Academic Search

An acetylene moiety was introduced to a carbonyl carbon of amide group via its triflate in the presence of palladium catalyst. The reaction proceeded smoothly under mild conditions. Utilizing this methodology, a model compound of dynemicin A bearing acetylene group was synthesized.

Takaaki Okita; Minoru Isobe

1995-01-01

175

Synthesis of acetylenic azomethines from imidoyl chlorides and copper(I) acetylides, catalyzed by palladium compounds  

SciTech Connect

The synthesis of acetylenic azomethines from N-phenylbenzimidoyl chloride and copper butylacetylide in the presence of lithium iodide, from imidoyl chlorides and copper and silver acetylides in boiling acetonitrile, and from imidoyl chloride and trimethylsilylacetylene with lead acetate and triphenylphosphine as catalyst (80/degree/C, 2 h) has been described. The authors have found that acetylenic azomethines are formed readily from imidoyl chlorides and copper acetylides at room temperature in the presence of the phosphine complexes of Pd(0), produced in situ.

Ukhin, L.Yu.; Orlova, Zh.I.; Tokarskaya, O.A.

1988-04-20

176

Simulations of shock-induced mixing& combustion of an acetylene cloud in a chamber  

SciTech Connect

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 thermodynamic behavior of the system using a Chemkin interface and includes the capability to model combustion as the ambient air mixes with the acetylene. The simulations are performed using a three-dimensional adaptive mesh refinement algorithm based on a second-order Godunov integration scheme. Simulations are compared with experimental measurements for the same configuration.

Bell, J B; Day, M S; Beckner, V E; Kuhl, A L; Neuwald, P; Reichenbach, H

2001-02-06

177

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

2013-08-09

178

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

179

Cellulase Assays  

NASA Astrophysics Data System (ADS)

Cellulose is a heterogeneous polysaccharide, and its enzymatic hydrolysis requires endoglucanase, exoglucanase (cellobiohydrolase), and ?-glucosidase to work together. We summarize the most commonly used assays for individual enzymes and cellulase mixture.

Zhang, Y. H. Percival; Hong, Jiong; Ye, Xinhao

180

Fluorinated 5- and 7-membered carbacycle motifs by reaction of difluorocarbene with acetylene ethers.  

PubMed

The reaction of acetylene ethers with difluorocarbene (CF(2)), generated from the Ruppert-Prakash reagent, unexpectedly gave rise to co-produced fluorinated bicyclic [2.1.1]-hex-2-ene and cyclohepta-1,4-diene ring products. PMID:23385787

Chia, Poh Wai; Bello, Davide; Slawin, Alexandra M Z; O'Hagan, David

2013-03-18

181

Phase Transfer Catalytic Nucleophilic Addition Reactions: Synthesis of Polymers and Acetylenic Terminated Resins.  

National Technical Information Service (NTIS)

Solid-liquid phase transfer catalysis (SLPTC) was studied to facilitate the preparation of acetylene-terminated (AT) resins. 3-Ethylphenol, as a model system, was found to react with p,p'-difluorobenzophenone and p,p'-difluorodiphenylsulfone in refluxing ...

D. K. Klapprott R. Kellman

1992-01-01

182

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...

183

The Origin of Light Emission in the Atomic Hydrogen-Acetylene Flame  

Microsoft Academic Search

Acetylene catalyzes the gas phase recombination of hydrogen atoms, and frequently the reaction is accompanied by a bright flame. It is shown that the light emission is not the result of the catalytic recombination, but is caused by traces of water in the hydrogen. The possible reactive intermediates, OH, HO_2 and atomic oxygen, have been individually generated and added to

K. D. Bayes; R. E. W. Jansson

1964-01-01

184

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

Microsoft Academic Search

A computational study was performed for the formation and growth of polycyclic aromatic hydrocarbons (PAHs) in laminar premixed acetylene and ethylene flames. A new detailed reaction mechanism describing fuel pyrolysis and oxidation, benzene formation, and PAH mass growth and oxidation is presented and critically tested. It is shown that the reaction model predicts reasonably well the concentration profiles of major

Michael Frenklach

1997-01-01

185

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

Microsoft Academic Search

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-? production.

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

2002-01-01

186

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

NASA Astrophysics Data System (ADS)

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

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

2003-06-01

187

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

188

Carbon scaffolding: building acetylenic all-carbon and carbon-rich compounds  

Microsoft Academic Search

The preparation of acetylenic molecular and polymeric carbon allotropes and carbon-rich nanometre-sized structures opens new avenues of fundamental and technological research at the interface between chemistry and materials science. Unusual structures, high stability and useful electrical and nonlinear optical properties are some of the desirable characteristics of these materials.

François Diederich

1994-01-01

189

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 ...

190

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

191

Identification of Non-Precious Metal Alloy Catalysts for Selective Hydrogenation of Acetylene  

Microsoft Academic Search

The removal of trace acetylene from ethylene is performed industrially by palladium hydrogenation catalysts (often modified with silver) that avoid the hydrogenation of ethylene to ethane. In an effort to identify catalysts based on less expensive and more available metals, density functional calculations were performed that identified relations in heats of adsorption of hydrocarbon molecules and fragments on metal surfaces.

Felix Studt; Frank Abild-Pedersen; Thomas Bligaard; Rasmus Z. Sørensen; Claus H. Christensen; Jens K. Nørskov

2008-01-01

192

Hot atom reactive scattering and photodissociation experiments with acetylene and ethylene.  

National Technical Information Service (NTIS)

Two different experimental techniques, chemical activation and photofragment translational spectroscopy, are used to study acetylene, ethylene, and their associated radicals: C(sub 2), C(sub 2)H, C(sub 2)H(sub 3), and C(sub 2)H(sub 5). The experiments are...

B. A. Balko

1991-01-01

193

Laminar Burning Velocities for Hydrogen, Methane, Acetylene, and Propane-Nitrous Oxide Flames  

Microsoft Academic Search

Mixtures of four fuels (hydrogen, methane, acetylene and propane) with nitrous oxide were studied to experimentally and numerically determine the laminar flame speeds at near atmospheric pressure (0.8 atm). Using the flat flame method, laminar flame speeds for these nitrous oxide flames were determined for different levels of dilution with nitrogen. A comprehensive hydrocarbon oxidation mechanism in the literature was integrated

O. A. Powell; P. Papas; C. Dreyer

2009-01-01

194

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

PubMed

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

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

2013-10-31

195

Influence of CF3H and CCl4 additives on acetylene detonation  

NASA Astrophysics Data System (ADS)

The influence of CF3 H and CCl4 admixtures (known as detonation suppressors for combustible mixtures) on the development of acetylene detonation was experimentally investigated in a shock tube. The time-resolved images of detonation wave development and propagation were registered using a high-speed streak camera. Shock wave velocity and pressure profiles were measured by five calibrated piezoelectric gauges and the formation of condensed particles was detected by laser light extinction. The induction time of detonation development was determined as the moment of a pressure rise at the end plate of the shock tube. It was shown that CF3H additive had no influence on the induction time. For CCl4, a significant promoting effect was observed. A simplified kinetic model was suggested and characteristic rates of diacetylene C4H2 formation were estimated as the limiting stage of acetylene polymerisation. An analysis of the obtained data indicated that the promoting species is atomic chlorine formed by CCl4 pyrolysis, which interacts with acetylene and produces C2H radical, initiating a chain mechanism of acetylene decomposition. The results of kinetic modelling agree well with the experimental data.

Drakon, A.; Emelianov, A.; Eremin, A.

2013-06-01

196

Control of soot emitted from acetylene diffusion flames by applying an electric field  

Microsoft Academic Search

This paper deals with the control of soot emission from acetylene diffusion flames by applying an electric field. The effects of applied voltage, polarity, and spacing of electrodes on soot emissions were investigated experimentally. The results showed that the shape of the flame changed remarkably with increasing applied voltage. The polarity of the applied voltage influenced the shape of the

Masahiro Saito; Toshihiro Arai; Masataka Arai

1999-01-01

197

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...

198

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

199

Electrochemical oxidation and detection of paeonol on modified electrode with acetylene black nanoparticles  

Microsoft Academic Search

With an aim to construct a sensing platform for the electrochemical detection of paeonol, we modified the glassy carbon electrode with acetylene black nanoparticle (AB). A sensitive oxidation peak of paeonol was observed with remarkably increased peak current on the modified electrode because the electrode has a big surface area due to three dimensional structure of AB nanoparticles. The optimization

Huajie Zhang; Miaomiao Gao; Xiaofeng Yang

2011-01-01

200

FAST TRACK COMMUNICATION: Fragmentation pathways for selected electronic states of the acetylene dication  

Microsoft Academic Search

Coincident measurement of the Auger electron and fragment ion momenta emitted after carbon core-level photoionization of acetylene has yielded new understanding of how the dication fragments. Ab initio calculations and experimental data, including body-frame Auger angular distributions, are used to identify the parent electronic states and together yield a comprehensive map of the dissociation pathways which include surface crossings and

T. Osipov; T. N. Rescigno; T. Weber; S. Miyabe; T. Jahnke; A. S. Alnaser; M. P. Hertlein; O. Jagutzki; L. Ph H. Schmidt; M. Schöffler; L. Foucar; S. Schössler; T. Havermeier; M. Odenweller; S. Voss; B. Feinberg; A. L. Landers; M. H. Prior; R. Dörner; C. L. Cocke; A. Belkacem

2008-01-01

201

Sensitive voltammetric determination of tryptophan using an acetylene black paste electrode modified with a Schiff's base derivative of chitosan.  

PubMed

Chitosan was modified by salicylaldehyde via Schiff's base reaction and the resulting product was modified on the surface of an acetylene black paste electrode (ABPE) by the drop-coating method. In 0.5 mol L(-1) acetate buffer (pH 4.2), a substantial increase in the anodic stripping peak current of tryptophan (Trp) (compared to conventional bare carbon paste electrode (CPE) and bare ABPE) is observed at the Schiff's base chitosan-modified electrode. The parameters influencing voltammetric determination of Trp have been optimized. Under the selected conditions, the linearity between the anodic peak currents and concentrations of Trp demonstrated a wide range of 6.0 × 10(-8) mol L(-1) to 2.0 × 10(-6) mol L(-1), 2.0 × 10(-6) mol L(-1) to 4.0 × 10(-5) mol L(-1) and 4.0 × 10(-5) mol L(-1) to 1.0 × 10(-4) mol L(-1), a low detection limit of 2.0 × 10(-9) mol L(-1) was obtained after a 60 s accumulation. In addition, the developed electrochemical sensor has been successfully applied for the determination of Trp in pharmaceutical and biological samples with satisfactory assay results. PMID:22010111

Deng, Peihong; Fei, Junjie; Feng, Yonglan

2011-10-19

202

Competitive Inhibition of Abscisic Acid-Regulated Gene Expression by Stereoisomeric Acetylenic Analogs of Abscisic Acid.  

PubMed Central

The properties of two enantiomeric synthetic acetylenic abscisic acid (ABA) analogs (PBI-51 and PBI-63) in relation to ABA-sensitive gene expression are reported. Using microspore-derived embryos of Brassica napus as the biological material and their responsiveness to ABA in the expression of genes encoding storage proteins as a quantitative bioassay, we measured the biological activity of PBI-51 and PBI-63. Assays to evaluate agonistic activity of either compound applied individually showed a dose-dependent increase in napin gene expression on application of PBI-63. Maximal activity of about 40 [mu]M indicated that PBI-63 was an agonist, although somewhat weaker than ABA. PBI-63 has a similar stereochemistry to natural ABA at the junction of the ring and side chain. In contrast, PBI-51 showed no agonistic effects until applied at 40 to 50 [mu]M. Even then, the response was fairly weak. PBI-51 has the opposite stereochemistry to natural ABA at the junction of the ring and side chain. When applied concurrently with ABA, PBI-63 and PBI-51 had distinctly different properties. PBI-63 (40 [mu]M) and ABA (5 [mu]M) combined gave results similar to the application of either compound separately with high levels of induction of napin expression. PBI-51 displayed a reversible antagonistic effect with ABA, shifting the typical ABA dose-response curve by a factor of 4 to 5. This antagonism was noted for the expression of two ABA-sensitive genes, napin and oleosin. To test whether this antagonism was at the level of ABA recognition or uptake, ABA uptake was monitored in the presence of PBI-51 or PBI-63. Neither compound decreased ABA uptake. Treatments with either PBI-51 or PBI-63 showed an effect on endogenous ABA pools by permitting increases of 5- to 7-fold. It is hypothesized that this increase occurs because of competition for ABA catabolic enzymes by both compounds. The fact that ABA pools did not decrease in the presence of PBI-51 suggests that PBI-51 must exert its antagonistic properties through direct competition with ABA at a hormone-recognition site.

Wilen, R. W.; Hays, D. B.; Mandel, R. M.; Abrams, S. R.; Moloney, M. M.

1993-01-01

203

Luciferase assay.  

PubMed

When a transient or stable transfection assay is developed for a promoter, a primary objective is to quantify promoter strength. Because transfection efficiency in such assays can be low, promoters are commonly fused to heterologous reporter genes that encode enzymes that can be quantified using highly sensitive assays. The reporter protein's activity or fluorescence within a transfected cell population is approximately proportional to the steady-state mRNA level. A commonly used reporter gene is the luciferase gene from the firefly Photinus pyralis. This gene encodes a 61-kDa enzyme that oxidizes D-luciferin in the presence of ATP, oxygen, and Mg(++), yielding a fluorescent product that can be quantified by measuring the released light. Including coenzyme A in the reaction enhances the sensitivity of the assay and provides a sustained light reaction. In this protocol, cells transfected with a luciferase reporter plasmid are lysed using a detergent-containing buffer. Cell debris is removed by microcentrifugation and luciferase activity is measured using a luminometer. Some luminometers directly inject the reagents into the cell lysate. Such automation allows the signal to be measured at a precise time following injection, which can increase the consistency of the results. For manual luminometers, the substrate solution is mixed by hand with the cell lysate, and the fluorescence is read at a defined time following mixing. The luciferase assay is extremely rapid, simple, relatively inexpensive, sensitive, and possesses a broad linear range. PMID:20439408

Smale, Stephen T

2010-05-01

204

The effect of strain rate on polycyclic aromatic hydrocarbon (PAH) formation in acetylene diffusion flames  

SciTech Connect

Acetylene is a ubiquitous combustion intermediate that is also believed to be the major precursor for aromatic, polycyclic aromatic hydrocarbon (PAH), and soot formation in both hydrocarbon and halogenated hydrocarbon flames. However, in spite of its important role as a flame intermediate, the detailed chemical structures of acetylene diffusion flames have not been studied in the past. Here the detailed chemical structures of counterflow diffusion flames of acetylene at strain rates of 37.7 and 50.3 s{sup -1} are presented. Both flames possessed the same carbon density of 0.37 g/L corresponding to an acetylene mole fraction of 0.375 in argon on the fuel side, and an oxygen mole fraction of 0.22 in argon on the oxidizer side. Concentration profiles of a large number of major, minor, and trace species, including a wide spectrum of aromatics and PAH, have been determined by direct sampling from flames using a heated quartz microprobe coupled to an online gas chromatograph/mass selective detector (GC/MSD). Temperature profiles were made using a thermocouple and the rapid insertion technique. Although the major species concentrations were nearly the same in the two flames, the mole fraction profiles of trace combustion by-products were significantly lower in the higher-strain-rate flame, by nearly two orders of magnitude for PAH. These comparative results provide new information on the trace chemistries of acetylene flames and should be useful for the development and validation of detailed chemical kinetic mechanisms describing the formation of toxic by-products in the combustion of hydrocarbons and halogenated hydrocarbons. (author)

Yamamoto, Manabu; Duan, Shici; Senkan, Selim [Department of Chemical Engineering, University of California, Los Angeles, CA 90095 (United States)

2007-11-15

205

Anthranilate sulfonamide hydroxamate TACE inhibitors. Part 1: Structure-based design of novel acetylenic P1? groups  

Microsoft Academic Search

The structure-based design of potent sulfonamide hydroxamate TACE inhibitors bearing novel acetylenic P1? groups has led to compounds with excellent in vitro potency against TACE and selectivity over MMP-1.

James M. Chen; Guixian Jin; Amy Sung; Jeremy I. Levin

2002-01-01

206

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

PubMed

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

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

2012-02-02

207

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

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

208

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

209

First principles calculations of the adsorption of acetylene on the Si(0 0 1) surface at low and full coverage  

NASA Astrophysics Data System (ADS)

The adsorption of acetylene on the Si(0 0 1)-c(2 × 4) surface at low and full coverage is studied by first principles density functional calculations using the generalized gradient approximation. For a single acetylene molecule, the most stable configuration corresponds to the di-? site, on-top of a silicon dimer. This configuration is 0.36 eV more stable than the end-bridge site between two adjacent Si dimers. However, if there are two acetylene molecules, the paired end bridge configuration becomes the most stable. We have also studied the kinetics of the adsorption of a single acetylene molecule. Our calculations show that the reaction is barrier-free for adsorption in the di-? configuration, while there is an energy barrier of 0.19 eV for adsorption in the end-bridge site. At monolayer coverage, the most stable configuration corresponds to acetylene molecules in the pair-end bridge configuration, in agreement with previous calculations. We have found a noticeable coverage dependence only for the end-bridge site, but not for the di-?. Our results show that to have an accurate picture of the adsorption of acetylene on the Si(0 0 1) surface, a large unit cell is needed.

Takeuchi, Noboru

2007-08-01

210

Kinetics of formation of pyrolytic carbon from acetylene, vinylacetylene, and diacetylene  

SciTech Connect

The direct gravimetric measurement of the rate of formation of pyrolytic carbon during thermal decomposition of vinyl-, divinyl-, and diacetylene in the 450-1000/sup 0/ region was carried out. It was shown that the rates of formation of pyrolytic carbon from vinyl- and divinylacetylene coincide with one another, and at 600/sup 0/C are higher by one order of magnitude than that from acetylene. The rate of formation of pyrolytic carbon from diacetylene at 600/sup 0/C is higher than that of acetylene by two orders of magnitude. The activation energy of the formation process of pyrolytic carbon from vinyl- and divinylacetylene and diacetylene is 115 and 62 kJ/mole, respectively.

Tesner, P.A.; Shein, O.G.

1987-12-01

211

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

SciTech Connect

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

Wang, H. [Univ. of Delaware, Newark, DE (United States). Dept. of Mechanical Engineering; Frenklach, M. [Univ. of California, Berkeley, CA (United States). Dept. of Mechanical Engineering

1997-07-01

212

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

213

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

214

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

215

Synthesis of carbon nanotubes by CVD: Effect of acetylene pressure on nanotubes characteristics  

Microsoft Academic Search

The effect of acetylene partial pressure on the structural and morphological properties of multi-walled carbon nanotubes (MWCNTs) synthesized by CVD on iron nanoparticles dispersed in a SiO2 matrix as catalyst was investigated. The general growing conditions were: 110cm3\\/min flow rate, 690°C synthesis temperature, 180Torr over pressure and two gas compositions: 2.5% and 10% C2H2\\/N2. The catalyst and nanotubes were characterized

Mariano Escobar; M. Sergio Moreno; Roberto J. Candal; M. Claudia Marchi; Alvaro Caso; Pablo I. Polosecki; Gerardo H. Rubiolo; Silvia Goyanes

2007-01-01

216

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

217

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

218

The infrared-ultraviolet dispersed fluorescence spectrum of acetylene: New classes of bright states  

Microsoft Academic Search

Single rotational levels of ungerade vibrational levels, 2nu3'+nu6' and 3nu3'+nu6' (both with bu symmetry), in the A~ 1Au electronically excited state of acetylene were excited by an IR-UV double resonance scheme via the nu3'' fundamental level in the X~ 1Sigmag+ state, and the rotationally resolved dispersed fluorescence (DF) spectra were recorded at 3.2-4.5 cm-1 resolution. The term values of the

Kennosuke Hoshina; Atsushi Iwasaki; Kaoru Yamanouchi; Matthew P. Jacobson; Robert W. Field

2001-01-01

219

Inhibition by acetylene of conventional hydrogenase in nitrogen-fixing bacteria  

Microsoft Academic Search

ONE of the earliest observations associated with nitrogen fixation was that all nitrogen-fixing organisms contained hydrogenase and nitrogenase1. We show here that acetylene, which is widely used as a substrate for nitrogenase, inhibits conventional hydrogenase activity and thus prevents the uptake of H2 formed by nitrogenase in the presence of CO. Our evidence also suggests that azotobacter nitrogenase forms H2

Linda A. Smith; Susan Hill; M. G. Yates

1976-01-01

220

Gas-solid chromatography: longitudinal and intraparticle diffusion of acetylene in activated carbon  

Microsoft Academic Search

The time-dependent transmission of 100 ppm acetylene in helium at 1 atm through columns of Columbia 4LXC 12\\/28 activated carbon at 25\\/degrees\\/C was measured at several flow rates in the range from about 1 to 7 cm³\\/s. Transmission is the gas-phase concentration at the column outlet divided by the input concentration. The gas- and adsorbed-phase diffusion coefficients were calculated from

R. Forsythe; R. Madey; P. J. Photinos; D. Rothstein; J. C. Huang

2009-01-01

221

Gas-Solid Chromatography: Longitudinal and Intraparticle Diffusion of Acetylene in Activated Carbon  

Microsoft Academic Search

The time-dependent transmission of 100 ppm acetylene in helium at 1 atm through columns of Columbia 4LXC 12\\/28 activated carbon at 25°C was measured at several flow rates in the range from about 1 to 7 cm\\/s. Transmission is the gas-phase concentration at the column outlet divided by the input concentration. The gas-and adsorbed-phase diffusion coefficients were calculated from a

R. Forsythe; R. Madey; P. J. Photinos; D. Rothstein; J. C. Huang

1988-01-01

222

Analysis of effluent gases during the CCVD growth of multi-wall carbon nanotubes from acetylene  

Microsoft Academic Search

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

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

2006-01-01

223

A structure-property study of the dynamic surface tension of three acetylenic diol surfactants  

Microsoft Academic Search

Three acetylenic diol surfactants are compared using the pendant bubble technique. The surfactants studied are the highly branched surfactant Surfynol 104, a smaller branched diol, 2,7 dimethyl-4-octyn-3,6-diol, (DMOD) and a diol with linear alkyl chains, 7-tetradecyn-6,9-diol (TDD) which is a structural isomer of Surfynol 104. The molecules differ significantly in terms of both their equilibrium and dynamic surface tension. For

James K. Ferri; Kathleen J. Stebe

1999-01-01

224

Dissociation of Methanol and Acetylene by slow Highly Charged Ion Collision  

Microsoft Academic Search

We report here the results of dissociation of multiple charged methanol and acetylene molecules in collision with 1.2 MeV Ar8+ projectiles. We observed a wide range of dissociation products from the TOF spectrum starting from undissociated molecular ions, fragments losing an hydrogen atom due to breakage of C-H and\\/or O-H bonds, to complete rupture of C-C and C-O skeletons for

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

2007-01-01

225

Fullerene-acetylene hybrids: Towards a novel class of molecular carbon allotropes  

Microsoft Academic Search

The synthesis and complete characterization of 17 new fullerene-acetylene covalent derivatives is described. Reaction of 3-bromo-1,5-bis(trimethylsilyl)penta-1,4-diyne (5) with C60 gave bis-protected diethynylmethanofullerene 4 in 56% yield. Unsymmetrically bis-protected diethynylmethanofullerene 6 was synthesized in 53% yield from tosylhydrazone 7 and C60. Proto-desilylation of 4 and 6 gave the corresponding free alkynes 3 and 8 in 83% and 69% yield, respectively. Partial

Peter Timmerman; Harry L. Anderson; Rüdiger Faust; JeandashFrançois Nierengarten; Tilo Habicher; Paul Seiler; François Diederich

1996-01-01

226

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

NASA Astrophysics Data System (ADS)

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

Fogg, Peter G. T.

2013-03-01

227

Palladium–gallium intermetallic compounds for the selective hydrogenation of acetylene  

Microsoft Academic Search

The intermetallic compounds PdGa and Pd3Ga7 are introduced as selective catalysts for the hydrogenation of acetylene. Single phase PdGa and Pd3Ga7 can readily be prepared by the appropriate thermal treatment of the stoichiometric mixtures of the corresponding elements. The initial low surface areas of the as-prepared materials can be increased by careful mechanical treatment without decomposition. Detailed investigations of PdGa

Jürgen Osswald; Rainer Giedigkeit; Rolf E. Jentoft; Marc Armbrüster; Frank Girgsdies; Kirill Kovnir; Thorsten Ressler; Yuri Grin; Robert Schlögl

2008-01-01

228

Atmospheric acetylene and its relationship with CO as an indicator of air mass age  

Microsoft Academic Search

Acetylene (C2H2) and CO originating from combustion are strongly correlated in atmospheric observations, offering constraints on atmospheric dilution and chemical aging. We examine here the C2H2-CO relationships in aircraft observations worldwide, and interpret them with simple models as well as with a global chemical transport model (GEOS-Chem). A C2H2 global source of 6.6 Tg yr?1 in GEOS-Chem simulates the ensemble

Yaping Xiao; Daniel J. Jacob; Solene Turquety

2007-01-01

229

Synthesis of tungsten carbide by dynamic shock compression of a tungsten–acetylene black powder mixture  

Microsoft Academic Search

In order to synthesize tungsten carbide as a high-temperature structural element by a shock wave technique, a tungsten–acetylene black powder mixture was shock-compressed. The retrieved sample was examined by X-ray diffraction analysis and optical\\/electron microscopy. A rodlike compact consisting of rounded particles, plates and dendritic particles of WC having a hexagonal structure was formed in the central region of the

Kenjiro Yamada

2000-01-01

230

Carbon fiber formation on Pd and Ni catalysts by acetylene decomposition  

Microsoft Academic Search

In this study, carbon fibers were formed from acetylene decomposition on hydrogen-reduced Pd and Ni catalysts at 450–700°C. X-ray diffraction (XRD) was used to examine the crystal characteristics of catalysts and carbon fibers. The carbon fibers were also examined both by scanning electron microscopy (SEM) and Raman spectroscopy to define their appearance and structure. Little amount of carbon fibers were

Hung-Lung Chiang; Yung-Shou Ho; Kuo-Hsiung Lin; Chih-Hsing Leu

2007-01-01

231

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

232

Discovery of acetylene hydratase activity of the iron-sulphur protein IspH  

PubMed Central

The final step of the methylerythritol phosphate isoprenoid biosynthesis pathway is catalysed by the iron–sulphur enzyme IspH, producing the universal precursors of terpenes: isopentenyl diphosphate and dimethylallyl diphosphate. Here we report an unforeseen reaction discovered during the investigation of the interaction of IspH with acetylene inhibitors by X-ray crystallography, Mößbauer, and nuclear magnetic resonance spectroscopy. In addition to its role as a 2H+/2e? reductase, IspH can hydrate acetylenes to aldehydes and ketones via anti-Markovnikov/Markovnikov addition. The reactions only occur with the oxidised protein and proceed via ?1-O-enolate intermediates. One of these is characterized crystallographically and contains a C4 ligand oxygen bound to the unique, fourth iron in the 4Fe-4S cluster: this intermediate subsequently hydrolyzes to produce an aldehyde product. This unexpected side to IspH reactivity is of interest in the context of the mechanism of action of other acetylene hydratases, as well as in the design of antiinfectives targeting IspH.

Wang, Weixue; Zhang, Yonghui; Bacher, Adelbert; Eisenreich, Wolfgang; Li, Kai; Schulz, Charles; Oldfield, Eric; Groll, Michael

2013-01-01

233

Pulse-induced nonequilibrium dynamics of acetylene inside carbon nanotube studied by an ab initio approach  

PubMed Central

Nanoscale molecular confinement substantially modifies the functionality and electronic properties of encapsulated molecules. Many works have approached this problem from the perspective of quantifying ground-state molecular changes, but little is known about the nonequilibrium dynamics of encapsulated molecular system. In this letter, we report an analysis of the nonequilibrium dynamics of acetylene (C2H2) inside a semiconducting carbon nanotube (CNT). An ultrashort high-intense laser pulse (2 fs width and 1015 W/cm2 intensity) brings the systems out of equilibrium. This process is modeled by comprehensive first-principles time-dependent density-functional simulations. When encapsulated, acetylene dimer, unlike a single acetylene molecule, exhibits correlated vibrational dynamics (C–C bond rotation and H–C–C bending) that is markedly different from the dynamics observed in the gas phase. This result highlights the role of CNT in modulating the optical electric field within the tube. At longer simulation timescales (> 20 fs) in the largest-diameter tube studied here [CNT(14,0)], we observe synchronized rotation about the C–C axes in the dimer and ultimately ejection of one of the four hydrogen atoms. Our results illustrate the richness of photochemical phenomena in confined geometries.

Miyamoto, Yoshiyuki; Zhang, Hong; Rubio, Angel

2012-01-01

234

An autopsy case of suicide by acetylene explosion: a case report.  

PubMed

We report an autopsy case of a male welder in his thirties who was found dead in an exploded truck cabin. The roof, windows and doors of the cabin had been blown up to 50 metres away. An oxygen cylinder and an acetylene cylinder, both unexploded, were found in the back of the truck. The deceased was lying on the driver's seat. His entire body was burnt, carbonised and partially skeletonised. There was a small amount of soot in his oesophagus and stomach and a large volume of bloody fluid in the trachea and bronchi. There was an extensive haemorrhage in the posterior thoracic wall. No drugs were detected in the blood. Hardly any carbon monoxide and combustion-related gases were detected in the blood, therefore he was not considered to have died from the fire. Acetylene was detected in his blood (21.5 microg/ml in the femoral vein blood) and urine (7.49 microg/ml), with marked haemorrhaging in his back. We therefore concluded that the victim died because of an acetylene explosion in the cabin and also that this was a suicide. PMID:19537452

Kashiwagi, Masayuki; Hara, Kenji; Takamoto, Mutsuo; Kageura, Mitsuyoshi; Matsusue, Aya; Sugimura, Tomoko; Kubo, Shin-ichi

2009-04-01

235

Pulse-induced nonequilibrium dynamics of acetylene inside carbon nanotube studied by an ab initio approach.  

PubMed

Nanoscale molecular confinement substantially modifies the functionality and electronic properties of encapsulated molecules. Many works have approached this problem from the perspective of quantifying ground-state molecular changes, but little is known about the nonequilibrium dynamics of encapsulated molecular system. In this letter, we report an analysis of the nonequilibrium dynamics of acetylene (C(2)H(2)) inside a semiconducting carbon nanotube (CNT). An ultrashort high-intense laser pulse (2 fs width and 10(15) W/cm(2) intensity) brings the systems out of equilibrium. This process is modeled by comprehensive first-principles time-dependent density-functional simulations. When encapsulated, acetylene dimer, unlike a single acetylene molecule, exhibits correlated vibrational dynamics (C-C bond rotation and H-C-C bending) that is markedly different from the dynamics observed in the gas phase. This result highlights the role of CNT in modulating the optical electric field within the tube. At longer simulation timescales (> 20 fs) in the largest-diameter tube studied here [CNT(14,0)], we observe synchronized rotation about the C-C axes in the dimer and ultimately ejection of one of the four hydrogen atoms. Our results illustrate the richness of photochemical phenomena in confined geometries. PMID:22615352

Miyamoto, Yoshiyuki; Zhang, Hong; Rubio, Angel

2012-05-21

236

Chemistry of polycyclic aromatic hydrocarbons formation from phenyl radical pyrolysis and reaction of phenyl and acetylene.  

PubMed

An experimental investigation of phenyl radical pyrolysis and the phenyl radical + acetylene reaction has been performed to clarify the role of different reaction mechanisms involved in the formation and growth of polycyclic aromatic hydrocarbons (PAHs) serving as precursors for soot formation. Experiments were conducted using GC/GC-MS diagnostics coupled to the high-pressure single-pulse shock tube present at the University of Illinois at Chicago. For the first time, comprehensive speciation of the major stable products, including small hydrocarbons and large PAH intermediates, was obtained over a wide range of pressures (25-60 atm) and temperatures (900-1800 K) which encompass the typical conditions in modern combustion devices. The experimental results were used to validate a comprehensive chemical kinetic model which provides relevant information on the chemistry associated with the formation of PAH compounds. In particular, the modeling results indicate that the o-benzyne chemistry is a key factor in the formation of multi-ring intermediates in phenyl radical pyrolysis. On the other hand, the PAHs from the phenyl + acetylene reaction are formed mainly through recombination between single-ring aromatics and through the hydrogen abstraction/acetylene addition mechanism. Polymerization is the common dominant process at high temperature conditions. PMID:22339468

Comandini, A; Malewicki, T; Brezinsky, K

2012-03-02

237

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

238

Diastereoselective synthesis of syn-1,3-diols by titanium-mediated reductive coupling of propargylic alcohols.  

PubMed

A titanium-mediated, hydroxy-directed reductive coupling reaction of propargylic alcohols and aldehydes/ketones is described. Excellent diastereoselectivity and synthetically useful yields have been obtained for a range of substrates. This transformation has enabled a highly convergent three-component approach to syn-1,3-diols using (trimethylsilyl)acetylene as a C1 linchpin. PMID:19961149

Tian, Guo-Qiang; Kaiser, Thomas; Yang, Jiong

2010-01-15

239

Formation of Complex Organics by Gas Phase and Intracluster Ion-Molecule Reactions Involving Acetylene and Hydrogen Cyanide  

NASA Astrophysics Data System (ADS)

Many complex organics including polycyclic aromatic hydrocarbons are present in flames and combustion processes as well as in interstellar clouds and solar nebulae. Here, we present evidence for the formation of complex covalent organics by gas phase and intracluster reactions of the benzene, phenylium, pyridine, pyrimidine, phenylacetylene and benzonitrile cations with acetylene and hydrogen cyanide molecules. These reactions are studied using mass-selected ion mobility, chemical reactivity, collisional dissociation, and ab initio calculations. Measurements of collision cross sections in helium provide structural information on the adducts and allow probing structural changes at different temperatures (isomerization). We observed multiple additions of five acetylene molecules on the pyridine cation at room temperature. This is a remarkable result considering that only two acetylene molecules were added to the phenyl cation and no addition was observed on the benzene cation at room temperature. The experimental results are in full agreement with the ab initio calculations which predict that the first and second acetylenes add to the pyridine ion in barrierless, highly exothermic reactions. Similar reactions have been observed for the pyrimidine radical cation although the extent of the addition reactions is limited to only two acetylene molecules at room temperature. The results provide the first evidence for the incorporation of nitrogen in the formation cyclic hydrocarbons via the gas phase reactions of pyridine and pyrimidine ions with acetylene molecules. In addition, the formation of covalent adducts in the ionized acetylene/HCN system will be reported for the first time. Sequential reactions leading to the formation of pyridine and pyrimidine radical cations and higher adducts are observed over a wide range of temperature and pressure. The formation of these covalent adducts may represent a general class of addition reactions that can form complex heterocyclic species in ionizing environments.

El-Shall, S.; Hamed, A.; Soliman, A. R.; Momoh, P. O.

2011-05-01

240

Improved benzodiazepine radioreceptor assay using the MultiScreen® Assay System  

Microsoft Academic Search

In this article, an improved benzodiazepine radioreceptor assay is described, which allows substantial reduction in assay time. The filtration in this method was performed by using the MultiScreen® Assay System. The latter consists of a 96-well plate with glass fibre filters sealed at the bottom, which allows both the incubation and the filtration of the specimen in the same plate.

M. J. Janssen; K. Ensing; R. A. de Zeeuw

1999-01-01

241

Theoretical studies on the acetylene-vinylidene rearrangement with a metal atom (Li, Be, B, Na, Mg, and Al)  

SciTech Connect

Reaction mechanisms of 1,26-hydrogen migration of neutral and anionic acetylene to form corresponding vinylidenes are investigated with the ab initio Hartree-Fock method, the second- and third-order Moeller-Plesset perturbation theory, and the localized molecular orbital (LMO) analysis. The LMO analysis shows that in the neutral system the migrating hydrogen behaves like a hydride (H/sup -/) along the reaction path, while in the anion system it moves as a hydrogen atom. Reaction mechanisms of 1,2-hydrogen migration of neutral acetylene in the presence of a metal atom (Li, Be, B, Na, Mg, and Al) are also studied. The metal-catalyzed acetylene-vinylidene rearrangement can be classified based on the above two mechanisms of the metal-free reaction. In the presence of Li and Na atoms, the reaction mechanism is essentially that of the neutral acetylene, whereas with B, Be(/sup 3/P), Mg(/sup 3/P), and Al atoms, the reaction is similar to that of the acetylene anion. This difference has been related to the fact that in the latter atoms an odd electron is in a p orbital, whereas in the former no odd electron exists in a p orbital.

Sakai, S.; Morokuma, K.

1987-06-18

242

Spectrophotometric Assay for Superoxide Dismutase Based on Tetrazolium Salt 3?-{1-[(Phenylamino)-carbonyl]-3,4-tetrazolium}-bis(4-methoxy-6-nitro)benzenesulfonic Acid Hydrate Reduction by Xanthine–Xanthine Oxidase  

Microsoft Academic Search

XTT (3?-{1-[(phenylamino)-carbonyl]-3,4-tetrazolium}bis(4-methoxy-6-nitro)benzenesulfonic acid hydrate) was reduced to a water-soluble product with an absorbance maximum at about 470 nm by superoxide anion generated by xanthine–xanthine oxidase (XO). The rate of XTT reduction was linearly related to XO activity and the reduction was inhibited by superoxide dismutase (SOD). A perfect inhibition of the reduction of XTT by SOD was achieved, suggesting that

Hiroyuki Ukeda; Susumu Maeda; Toshinao Ishii; Masayoshi Sawamura

1997-01-01

243

Rotational spectroscopy and molecular structure of the 1-chloro-1-fluoroethylene-acetylene complex  

NASA Astrophysics Data System (ADS)

Guided by ab initio calculations, Fourier transform microwave spectra in the 6-21 GHz region are obtained for seven isotopomers of the complex formed between 1-chloro-1-fluoroethylene and acetylene. These include the four possible combinations of 35Cl- and 37Cl-containing CH2CClF with the most abundant acetylene isotopic modification, HCCH, and its H13C13CH analogue, as well as three singly substituted deuterated isotopomers. Analysis of the spectra determines the rotational constants and additionally, the complete chlorine quadrupole hyperfine coupling tensors in both the inertial and principal electric field gradient axis systems, and where appropriate, the diagonal components of the deuterium quadrupole coupling tensors. The inertial information contained in the rotational constants provides the structure for CH2CClF-HCCH: a primary, hydrogen bonding interaction existing between the HCCH donor and the F atom acceptor on the 1-chloro-1-fluoroethylene moiety, while a secondary interaction occurs between the acetylenic bond on the HCCH molecule and the H atom cis to the hydrogen-bonded F atom on the substituted ethylene, which causes the hydrogen bond to deviate from linearity. This is similar to the structure obtained for 1,1-difluoroethylene-HCCH [H. O. Leung and M. D. Marshall, J. Chem. Phys. 126, 154301 (2006)], and indeed, to within experimental uncertainty, the intermolecular interactions in CH2CClF-HCCH and its 1,1-difluoroethylene counterpart are practically indistinguishable, even though ab initio calculations at the MP2/6-311G++(2d, 2p) level suggest that the former complex is more strongly bound.

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

2011-01-01

244

Using saturated absorption spectroscopy on acetylene-filled hollow-core fibers for absolute frequency measurements  

NASA Astrophysics Data System (ADS)

Current portable near-infrared optical frequency references offer modest accuracy and instability compared to laboratory references. Low pressure reference cells are necessary to realize features narrower than the Doppler broadened overtone transitions, and most setups to date have occurred in free-space. Hollow-core photonic crystal fibers offer a potential alternative to free-space setups through their small cores (˜10's of mum) and low-loss guidance. Furthermore, HC-PCF can be made into fiber cells that could be directly integrated into existing telecommunications networks. Efforts were made to fabricate these fiber cells with a low pressure of molecules trapped inside, but this has proven to be quite challenging. Therefore, investigation of these fibers is conducted by placing the ends of the fiber inside vacuum chambers loaded with acetylene (12C2H2). The linewidths of several P branch nu1 +nu3 transitions (near 1.5 mum) are investigated as a function of acetylene pressure and optical pump power in three different HC-PCFs. Frequency modulation spectroscopy is then implemented on the acetylene-filled HC-PCF to generate sub-Doppler dispersion features that are useful for frequency stabilization using standard servo electronics. Instability and accuracy of this near-IR optical reference were then determined by analysis of heterodyne experiments conducted with frequency combs referenced to a GPS-disciplined rubidium oscillator. The instability and accuracy of this HC-PCF reference are within an order of magnitude of free-space experiments, as expected based on the ratio of linewidths observed in the two experiments. Therefore, HC-PCF has been shown to be suitable for potential frequency references. Further work is necessary to fabricate gas fiber cells with high optical transmission and low molecular contamination.

Knabe, Kevin

245

Single-Molecule Phenyl-Acetylene-Macrocycle-Based Optoelectronic Switch Functioning as a Quantum-Interference-Effect Transistor  

NASA Astrophysics Data System (ADS)

This work proposes a new type of optoelectronic switch, the phenyl-acetylene-macrocycle-based single-molecule transistor, which utilizes photon-assisted tunneling and destructive quantum interference. The analysis uses single-particle Green’s functions along with Floquet theory. Without the optical field, phenyl-acetylene-macrocycle exhibits a wide range of strong antiresonance between its frontier orbitals. The simulations show large on-off ratios (over 104) and measurable currents (˜10-11A) enabled by photon-assisted tunneling in a weak optical field (˜2×105V/cm) and at a small source-drain voltage (˜0.05V). Field amplitude power scaling laws and a range of field intensities are given for operating one- and two-photon assisted tunneling in phenyl-acetylene-macrocycle-based single-molecule transistors. This development opens up a new direction for creating molecular switches.

Hsu, Liang-Yan; Rabitz, Herschel

2012-11-01

246

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

PubMed

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

Hsu, Liang-Yan; Rabitz, Herschel

2012-10-31

247

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

NASA Astrophysics Data System (ADS)

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.

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

2011-12-01

248

Bromotheoynic acid, a brominated acetylenic acid from the marine sponge Theonella swinhoei.  

PubMed

A new brominated C(17) acetylenic acid (1) designated as bromotheoynic acid has been isolated from the marine sponge Theonella swinhoei, collected off the coast of Tanegashima, Kagoshima Prefecture, Japan. The structure was determined on the basis of the analysis of its extensive 2D NMR spectroscopic data as well as HRMS. Bromotheoynic acid (1) inhibited maturation of starfish oocytes and cell division of fertilised starfish eggs. Bromotheoynic acid (1) also inhibited proliferation of human leukaemia U937 and HL60 cells, human lung cancer A549 and H1299 cells, and human embryonic kidney 293 (HEK293) cells. PMID:22324431

Aoki, Nobuwa; Yamamoto, Kazuyuki; Ogawa, Takayuki; Ohta, Emi; Ikeuchi, Toshitaka; Kamemura, Kazuo; Ikegami, Susumu; Ohta, Shinji

2012-02-10

249

Designing zeolite catalysts for size- and shape-selective reactions: Selective hydrogenation of acetylene in the presence of butadiene and ethylene  

SciTech Connect

In the production of ethylene from the steam cracking of natural gas, small amounts of acetylene and butadiene are produced. Downstream, acetylene can present a hazard in a cryogenic separation process while nonselective hydrogenation removes acetylene as well as valuable ethylene and butadiene. With the aid of adsorption measurements, a selective hydrogenation catalyst has been designed. Small-pore zeolites, which serve as catalytic supports and provide reactant selective control, were ion-exchanged with Ni{sup 2+} and subsequently reduced. Compared to a commercial catalyst in which 60% of butadiene and all of the acetylene are hydrogenated, these new catalysts totally hydrogenate acetylene with only 10-20% hydrogenation of the butadiene and almost no hydrogenation of ethylene. To achieve selective hydrogenation, poisoning of the metal sites on the external zeolite surface is essential in order to obtain a product spectrum dominated by catalytic sites within the zeolite framework.

Corbin, D.R.; Abrams, L.; Bonifaz, C. (E.I. du Pont de Nemours Company, Wilmington, DE (USA))

1989-02-01

250

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

PubMed

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. PMID:23511122

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

2013-03-20

251

Acetylenic Linkers in Lead Compounds: A Study of the Stability of the Propargyl-Linked Antifolates  

PubMed Central

Propargyl-linked antifolates that target dihydrofolate reductase are potent inhibitors of several species of pathogenic bacteria and fungi. This novel class of antifolates possesses a relatively uncommon acetylenic linker designed to span a narrow passage in the enzyme active site and join two larger functional domains. Because the use of alkyne functionality in drug molecules is limited, it was important to evaluate some key physicochemical properties of these molecules and specifically to assess the overall stability of the acetylene. Herein, we report studies on four compounds from our lead series that vary specifically in the environment of the alkyne. We show that the compounds are soluble, chemically stable in water, as well as simulated gastric and intestinal fluids with half-lives of approximately 30 min after incubation with mouse liver microsomes. Their primary in vitro route of metabolism involves oxidative transformations of pendant functionality with little direct alteration of the alkyne. Identification of several major metabolites indicated the formation of N-oxides; the rate of formation of these oxides was highly influenced by branching substitutions around the propargyl linker. On the basis of the lessons of these metabolic studies, a more advanced inhibitor was designed, synthesized, and shown to have increased (t1/2 = 65 min) metabolic stability while maintaining potent enzyme inhibition.

Zhou, Wangda; Viswanathan, Kishore; Hill, Dennis; Anderson, Amy C.

2012-01-01

252

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

253

Comparison of diazotroph community structure in Lyngbya sp. and Microcoleus chthonoplastes dominated microbial mats from Guerrero Negro, Baja, Mexico  

Microsoft Academic Search

The nitrogenase activity and phylogenetic diversity of nitrogen fixing microorganisms in several different cyanobacterial mat types from Guerrero Negro, Baja California, Mexico were investigated by acetylene reduction assay, and by amplification and sequencing of the nitrogenase nifH gene. Acetylene reduction assays performed on a Lyngbya sp. and two Microcoleus chthonoplastes dominated microbial mats showed a typical diel pattern of nitrogenase

Enoma O Omoregie; Lori L Crumbliss; Brad M Bebout; Jonathan P Zehr

2004-01-01

254

Nitrification, Denitrification and Nitrate Reduction Rates in the Sediment of Hiroshima Bay, Japan  

Microsoft Academic Search

Nitrification, denitrification and nitrate reduction rates in the sediments at two stations in Hiroshima Bay were studied seasonally from August 1994 to May 1995. The acetylene (C2H2) inhibition technique was used to evaluate the rate of these processes. The seasonal average of nitrification and denitrification rates ranged from 0.00 to 299 µg atN m-2h-1 and 0.00 to 69.0 µg atN

DO-HEE KIM; OSAMU MATSUDA; TAMIJI YAMAMOTO

255

Chemisorption and thermal decomposition of acetylene on Pd(110): Electron energy loss spectroscopy and thermal desorption studies  

SciTech Connect

The adsorbed states of acetylene on Pd(110) at 90 K and its thermal decomposition in the temperature region up to 700 K have been investigated by using high-resolution electron energy loss spectroscopy and multiplexed thermal desorption spectroscopy. For a small exposure (0.5 langmuir) at 90 K, acetylene is chemisorbed molecularly in a single state (disorderedly) and it located in the {mu}{sub 2}-site with its C-C bond axis inclined to the surface plane; one of the CH groups is hydrogen-bonded to the surface and gives the softened CH stretching vibration. Upon heating to 180 K, acetylene (C{sub 2}H{sub 2}) is dissociated into ethynyl (CCH) species and H adatoms. For a large exposure (5 langmuirs) at 90 K, acetylene is adsorbed in several states. A part of the C{sub 2}H{sub 2} admolecules are desorbed intact at 100 K. Upon heating to 200 K, the rest are mainly dissociated into CCH species and H adatoms. The C{sub 2}H{sub 4} and {beta}-H{sub 2} desorptions occur at 265 and 320 K, respectively.

Yoshinobu, J.; Sekitani, T.; Onchi, M.; Nishijima, M. (Kyoto Univ. (Japan))

1990-05-17

256

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

National Technical Information Service (NTIS)

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-de...

S. P. Walch

1995-01-01

257

A combined experimental and theoretical study of the catalytic dissociation of methane by the photolysis of acetylene at 185 nm  

Microsoft Academic Search

Experimental irradiations of CH4–C2H2 (1000 : 1) gas mixtures, at 185 nm, have been carried out in order to test the catalytic scheme of dissociation of methane, via the photolysis of acetylene, that is supposed to occur in Titans stratosphere. The theoretical evolution of such a system has been investigated using three chemical models, and the predictions compared with our

N. S. Smith; M.-C. Gazeau; A. Khelifi; F. Raulin

1998-01-01

258

Acetylene-argon plasmas measured at a biased substrate electrode for diamond-like carbon deposition: I. Mass spectrometry  

NASA Astrophysics Data System (ADS)

We report, for the first time, quadrupole mass spectrometry of neutral and positive ionic hydrocarbon species measured at the rf-biased substrate electrode of an inductively coupled plasma for acetylene rich C2H2 : Ar mixtures under various bias, frequency and pressure conditions. It has been observed that, irrespective of initial gas mixture, the resultant plasma is dominated by argon neutrals and ions. This is attributed to highly efficient conversion of acetylene to C2H due to the enhanced electron density compared with a standard capacitive plasma where the acetylene (neutral and ion) species remain dominant. This conversion may be crucial to film formation via inert rather than hydrocarbon ion bombardment. In addition, the transient formation of CH4 from acetylene has been discovered using IR absorption spectroscopy with time constants similar to observed pressure variations. Rate coefficients and rates for many of the reaction mechanisms, calculated using measured electron energy distribution functions and species densities, are given. These results have important application in plasma models and growth studies for hydrogenated amorphous or diamond-like carbon film deposition. Film growth under similar plasma conditions is reported in an associated paper along with ion energy distributions for important growth species. .

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

2011-02-01

259

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 C(8)H(7)(+) and C(10)H(9)(+) 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 C(8)H(7)(+) adduct as 2-phenyl-ethenylium ion, the most stable C(8)H(7)(+) 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 C(10)H(9)(+) containing a four-membered ring connected to the phenylium ion. Evidence for rearrangement of the C(10)H(9)(+) 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 H(2) 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

2012-08-28

260

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

PubMed Central

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

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

1981-01-01

261

Nitrogen Fixation (Acetylene Reduction) in a Salt Marsh Amended with Sewage Sludge and Organic Carbon and Nitrogen Compounds 1  

PubMed Central

Seasonal distribution of nitrogen fixation by Spartina alterniflora epiphytes and in surface and soil samples was investigated in a Georgia salt marsh which was amended with sewage sludge or with glucose and/or ammonium nitrate. There was no significant difference between the rates of fixation in the unamended and sewage sludge plots. Additional perturbation experiments suggested that nitrogen addition indirectly stimulates nitrogen fixation by enhancing Spartina production and root exudation. Glucose additions, on the other hand, suppressed nitrogen fixation on a long-term basis. It is suggested that the microbial population in the soil out-competed the plants for the available nitrogen and in turn suppressed plant production and possibly root exudation. A comparison of nitrogen fixation in clipped and unclipped Spartina plots substantiated the suggestion that root exudation probably supports nitrogen fixation. Fixation in the clipped plots was significantly lower (P < 0.05) than the rates in the unclipped plots.

Hanson, Roger B.

1977-01-01

262

An improved choline monooxygenase assay  

SciTech Connect

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

Lafontaine, P.J.; Hanson, A.D. (Michigan State Univ. Plant Research Lab., East Lansing (United States))

1991-05-01

263

In situ monitoring of the acetylene decomposition and gas temperature at reaction conditions for the deposition of carbon nanotubes using linear Raman scattering.  

PubMed

To understand the reaction mechanisms taking place by growing carbon nanotubes via the catalytic chemical vapor deposition process, a strategy to monitor in situ the gas phase at reaction conditions was developed applying linear Raman spectroscopy. The simultaneous determination of the gas temperature and composition was possible by a new strategy of the evaluation of the Raman spectra. In agreement to the well-known exothermic decomposition of acetylene, a gas temperature increase was quantified when acetylene was added to the incident flow. Information about exhaust gas recirculation and location of the maximal acetylene conversion was derived from the composition measurements. PMID:20721212

Reinhold-López, Karla; Braeuer, Andreas; Popovska, Nadejda; Leipertz, Alfred

2010-08-16

264

Estrogen receptor-beta potency-selective ligands: structure-activity relationship studies of diarylpropionitriles and their acetylene and polar analogues.  

PubMed

Through an effort to develop novel ligands that have subtype selectivity for the estrogen receptors alpha (ERalpha) and beta (ERbeta), we have found that 2,3-bis(4-hydroxyphenyl)propionitrile (DPN) acts as an agonist on both ER subtypes, but has a 70-fold higher relative binding affinity and 170-fold higher relative potency in transcription assays with ERbeta than with ERalpha. To investigate the ERbeta affinity- and potency-selective character of this DPN further, we prepared a series of DPN analogues in which both the ligand core and the aromatic rings were modified by the repositioning of phenolic hydroxy groups and by the addition of alkyl substituents and nitrile groups. We also prepared other series of DPN analogues in which the nitrile functionality was replaced with acetylene groups or polar functions, to mimic the linear geometry or polarity of the nitrile, respectively. To varying degrees, all of the analogues show preferential binding affinity for ERbeta (i.e., they are ERbeta affinity-selective), and many, but not all of them, are also more potent in activating transcription through ERbeta than through ERalpha (i.e., they are ERbeta potency-selective). meso-2,3-Bis(4-hydroxyphenyl)succinonitrile and dl-2,3-bis(4-hydroxyphenyl)succinonitrile are among the highest ERbeta affinity-selective ligands, and they have an ERbeta potency selectivity that is equivalent to that of DPN. The acetylene analogues have higher binding affinities but somewhat lower selectivities than their nitrile counterparts. The polar analogues have lower affinities, and only the fluorinated polar analogues have substantial affinity selectivities. This study suggests that, in this series of ligands, the nitrile functionality is critical to ERbeta selectivity because it provides the optimal combination of linear geometry and polarity. Furthermore, the addition of a second nitrile group beta to the nitrile in DPN or the addition of a methyl substitutent at an ortho position on the beta-aromatic ring increases the affinity and selectivity of these compounds for ERbeta. These ERbeta-selective compounds may prove to be valuable tools in understanding the differences in structure and biological function of ERalpha and ERbeta. PMID:11708925

Meyers, M J; Sun, J; Carlson, K E; Marriner, G A; Katzenellenbogen, B S; Katzenellenbogen, J A

2001-11-22

265

An investigation on parallel, divergent and convergent acetylene dual jet diffusion flames  

SciTech Connect

Turbulent jet diffusion flames are quite common in industrial applications. Because of the large flow rates involved, usually the fuel gas is discharged through multiple burners and the mutual interaction between the jets determines flame shape, length, and general characteristics. Results are presented and discussed of an experimental investigation on acetylene turbulent dual jet diffusion flames. The study includes parameters of flames in parallel, divergent and convergent configurations. Tests with two parallel jets with addition of helium in the fuel stream were also performed and analyzed. The variation of overall flame length and of other flame physical characteristics, such as width, volume and conditions for lifting, are presented as functions of burner tip Reynolds number, jet distance from each other and inclination angle. The effects of diluent concentration in the fuel gas stream are presented for single and two parallel jets.

Abdalla, V.R.; Carvalho, J.A. Jr.; Ferreira, M.A.

1999-11-01

266

Urea-acetylene dicarboxylic acid reaction: A likely pathway for prebiotic uracil formation  

NASA Astrophysics Data System (ADS)

A number of routes have been suggested for the prebiotic synthesis of uracil involving the reaction of urea with malic acid, propiolic acid, cyanoacetylene and others. Cyanoacetylene has been detected in the interstellar medium as well as simulated prebiotic experiments. It is therefore plausible that dicyanoacetylene and its hydrolytic product acetylene dicarboxylic acid, (ADCA) may have played a role in chemical evolution. This aspect has been examined in the present work for the synthesis of uracil from ADCA and urea reaction. It was found that when ADCA reacted with urea, uracil was formed only in the presence of phosphoric acid and phosphates. Ammonium phosphates gave higher yields of uracil than other phosphates. In the absence of phosphoric acid or phosphates no uracil formation took place. This type of synthesis could have taken place in prebiotic oceans which contained ammonium phosphates and other salts.

Subbaraman, A. S.; Kazi, Z. A.; Choughuley, A. S. U.; Chadha, M. S.

1980-12-01

267

Urea-acetylene dicarboxylic acid reaction: a likely pathway for prebiotic uracil formation.  

PubMed

A number of routes have been suggested for the prebiotic synthesis of uracil involving the reaction of urea with malic acid, propiolic acid, cyanoacetylene and others. Cyanoacetylene has been detected in the interstellar medium as well as simulated prebiotic experiments. It is therefore plausible that dicyanoacetylene and its hydrolytic product acetylene dicarboxylic acid (ADCA) may have played a role in chemical evolution. This aspect has been examined in the present work for the synthesis of uracil from ADCA and urea reaction. It was found that when ADCA reacted with urea, uracil was formed only in the presence of phosphoric acid and phosphates. ammonium phosphates gave higher yields of uracil than other phosphates. In the absence of phosphoric acid or phosphates no uracil formation took place. This type of synthesis could have taken place in prebiotic oceans which contained ammonium phosphates and other salts. PMID:7454254

Subbaraman, A S; Kazi, Z A; Choughuley, A S; Chadha, M S

1980-12-01

268

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

269

Scanning tunneling microscope investigation of carbon nanotubes produced by catalytic decomposition of acetylene  

NASA Astrophysics Data System (ADS)

A detailed scanning tunneling microscopy (STM) study of carbon nanotubes prepared by catalytic decomposition of acetylene over a supported transition metal catalyst is reported. Nanotubes with diameters in the 10-nm range and others with diameters as small as 1 nm were found. The mechanism of STM image formation and image deconvolution with respect to the tip shape are discussed, as well as the corrections which have to be applied when measuring by STM nanotube diameters in the ranges of 10 nm and of 1 nm, respectively. The behavior of a nanotube crossing steps on the graphite surface is analyzed. Modified height values measured on a single-wall nanotube in regions where it was subjected to strong mechanical stresses indicate changes in the electrical conductivity by several orders of magnitude. Carbon nanotubes are found to be good candidates to be used for STM tip shape characterization in the nm range.

Biró, L. P.; Lazarescu, S.; Lambin, Ph.; Thiry, P. A.; Fonseca, A.; Nagy, J. B.; Lucas, A. A.

1997-11-01

270

Isotope effects on the stability of the nitrogen—acetylene van der Waals dimer  

NASA Astrophysics Data System (ADS)

Harmonic vibrational frequencies for various isotopomers of the nitrogen—acetylene van der Waals dimer are calculated at the SCF and MP2 ab initio levels of theory, using large basis sets. The relative stabilities of the dimers N 2…HCCD and N 2…DCCH are determined from differences in the zero-point energies. It is found that the D-bonded species are energetically favoured over the H-bonded species by 8.9 cm -1 with our largest basis set at MP2. We also computed a zero-point energy difference of about 0.6 cm -1 favouring N 2…H 13CCH over N 2…HC 13CH and 14N 15N…HCCH over 15N 14N…HCCH. These calculations are consistent with most, although not all, recent experimental observations of Legon, Wallwork and Fowler

McDowell, Sean A. C.; David Buckingham, A.

1993-04-01

271

Unusual sesquiterpene lactones with a new carbon skeleton and new acetylenes from Ajania przewalskii  

Microsoft Academic Search

Four new compounds, a noreudesmanolide (1), a guaianolide (4), and acetylenes (7–8), together with 16 other known compounds, were isolated from Ajania przewalskii. The novel sesquiterpenolide (1) possesses a rare carbon skeleton. Acetylation of 1 gave 1a. New compounds were elucidated as 1?-hydroxyl-2-noreudesm-4(15)-en-5?,6?,7?,11?H-12,6-olide (1), 1?-acetoxyoxyl-2-noreudesm-4(15)-en-5?,6?,7?,11?H-12,6-olide (1a), 8?-angeloyloxyl-3?,4?-dihydroxyguaia-1,9,11(13)-trien-6,12-olide (4), (E)-3?,4?-dihydroxyl-2-(2?,4?-hexadiynylidene)-1,6-dioxaspiro[4,5]decane (7) and 2-hydroxyl-2-[(E)-1?,2?,3-trihydroxyl-3-nonaene-5,7-diyne]-4H-pyran (8), by chemical and spectroscopic methods, including HRESIMS,

Ying Zhu; Li-Xia Zhang; Yan Zhao; Guo-Du Huang

2010-01-01

272

Metallaborane reaction chemistry. Part 12. Some interactions of acetylenes and isocyanides with selected metallaboranes  

Microsoft Academic Search

Compared to the chemistry associated with the basic syntheses and structures of the metallaboranes, their reaction chemistry is relatively uninvestigated. To illustrate the potential variety of such reaction chemistry, a linked overview of some previously reported and previously unreported reactions of the nido-6-metalladecaboranes [(PPh3)2HIrB9H13], [(PPh3)(Ph2PC6H4)HIrB9H12], [(?6-C6Me6)RuB9H13], [(?6-MeC6H4isoPr)RuB9H13] and [(?5-C5Me5)RhB9H13] with acetylenes and isocyanides is presented, together with some related chemistry

Jonathan Bould; Mark Bown; Richard J. Coldicott; Evert J. Ditzel; Norman N. Greenwood; Ian Macpherson; Peter MacKinnon; Mark Thornton-Pett; John D. Kennedy

2005-01-01

273

Synthesis and transformations of bis(trialkylstannyl)acetylenes containing tert-butyl radicals  

SciTech Connect

When studying the transformations of tri-tert-butylstannyl trimethylstannyl acetylene (I) they found the activity of the Sn-C/sub sp/ bond varying (depending on the configuration of the alkyl radicals near the atom of tin) with the reagents, e.g., halogens, that rupture these bonds by an ion mechanism. Thus, iodination or bromination of compound (I) occurs mainly at the Me/sub 3/Sn-C/sub sp/ bond with the formation of tri-tert-butylstannyl halogenoacetyelens. When compound (I) was iodinated in ether at -40/sup 0/C, the ratio of the tri-tert-butylstannyl iodoacetylene to the tri-tert-butylstannyl iodide was found to be approximately 9:1. Bromination of compound (I) in pentane at -70/sup 0/C resulted in the formation of tri-tert-butylstannyl bromoacetylene and tri-tert-butylstannyl bromide in the ratio of 7:3.

Girbasova, N.V.; Bogoradovskii, E.T.; Zavgorodnii, V.S.

1986-03-10

274

Interference in acetylene intersystem crossing acts as the molecular analog of Young's double-slit experiment  

PubMed Central

We report on an experimental approach that reveals crucial details of the composition of singlet-triplet mixed eigenstates in acetylene. Intersystem crossing in this prototypical polyatomic molecule embodies the mixing of the lowest excited singlet state (S1) with 3 triplet states (T1, T2, and T3). Using high-energy (157-nm) photons from an F2 laser to record excited-state photoelectron spectra, we have decomposed the mixed eigenstates into their S1, T3, T2, and T1 constituent parts. One example of the interpretive power that ensues from the selective sensitivity of the experiment to the individual electronic state characters is the discovery and examination of destructive interference between two doorway-mediated intersystem crossing pathways. This observation of an interference effect in nonradiative decay opens up possibilities for rational coherent control over molecular excited state dynamics.

de Groot, Mattijs; Field, Robert W.; Buma, Wybren J.

2009-01-01

275

Microstructure and performance of titanium oxide coatings sprayed by oxygen-acetylene flame.  

PubMed

TiO(2) nano-powders were agglomerated by a spray drying process for application to thermal spraying. A conventional oxygen-acetylene flame torch was used to deposit porous partially nanostructured TiO(2) coatings. Steel substrates were used as a support for tested samples. Scanning electron microscopy, X-ray microanalysis and X-ray diffraction were performed to study the morphology and the crystalline phases of the titania coatings. Optical bandgap and kinetics of the acetone decomposition were also studied. The best results were obtained for the powder which is available as a commercial spray feedstock. This powder seems to be most resistant against the reducing atmosphere in the jet of combustive gases. PMID:20938550

Ctibor, Pavel; Stengl, Vaclav; Zahalka, Frantisek; Murafa, Nataliya

2010-10-12

276

Lipase specificity toward some acetylenic and olefinic alcohols in the esterification of pentanoic and stearic acids  

Microsoft Academic Search

The esterification of five medium- and long-chain acetylenic alcohols (2-nonyn-1-ol, 10-undecyn-1-ol, 6-octadecyn-1-ol, 9-octadecyn-1-ol,\\u000a and 13-docosyn-1-ol), seven olefinic alcohols (cis-3-nonen-1-ol, 10-undecen-1-ol, cis-6-octadecen-1-ol, cis-9-octadecen-1-ol, trans-9-octadecen-1-ol, trans-9, trans-11-octadecadien-1-ol, cis-9, cis-12-octadecadien-1-ol), and four short-chain unsaturated alcohols (allyl alcohol, 3-butyn-1-ol, 3-pentyn-1-ol, and cis-2-penten-1-ol) with pentanoic or stearic acid in the presence of various lipase preparations was studied. With the exception\\u000a of 2-nonyn-1-ol, where Lipase AY-30

Marcel S. F. Lie Ken Jie; Xun Fu

1998-01-01

277

Acetylene and Ethane distributions in the Jovian stratosphere from Cassini CIRS observations  

NASA Astrophysics Data System (ADS)

During the recent encounter of the Cassini spacecraft with Jupiter on 30th December 2000, the Composite Infrared Spectrometer (CIRS) was used to map the planet from pole to pole at a spectral resolution of 3 cm-1, from 10 to 1400 cm-1. This paper describes preliminary results from modelling of spectral data in the region 600--850 cm-1. This rich wavenumber range encompasses part of the S(1) hydrogen band, as well as features due to a variety of hydrocarbons (C2H2, C2H6, C6H6, C4H2, C3H4, CH3). The vertical temperature profile and abundances of gaseous species in the stratosphere were simultaneously retrieved. The paper will focus on the meridional variations of acetylene and ethane, with an emphasis on the enhancements seen in the polar auroral regions.

Nixon, C. A.; Jennings, D. J.; Irwin, P. G. J.; Parrish, P. D.; Fouchet, T.; Achterberg, R. K.; Simon-Miller, A. A.; CIRS Team

2001-11-01

278

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

279

The absorption spectrum of acetylene by CRDS between 7244 and 7918 cm?1  

NASA Astrophysics Data System (ADS)

The absorption spectrum of acetylene has been recorded using high sensitivity cavity ring down spectroscopy (?min~5×10?11 cm?1) in the 7244–7918 cm?1 interval corresponding to a weak absorption region. The CRDS spectra revealed new bands which were identified on the basis of a global effective Hamiltonian model (Lyulin OM, Perevalov VI, Teffo JL. Proc. SPIE 2004;5311:134–43). Overall, about 2100 lines were rovibrationally assigned in the investigated interval. They belong to 26 new bands and to the eight already known bands of the region, for which additional J-lines were assigned. The spectroscopic parameters were derived from a band by band fit of the line positions. Part of the analyzed bands was found affected by strong rovibrational perturbations which are discussed. These new data will be valuable to refine the global effective Hamiltonian of 12C2H2 at higher energy.

Lyulin, O. M.; Campargue, A.; Mondelain, D.; Kassi, S.

2013-11-01

280

Visualizing Recurrently Migrating Hydrogen in Acetylene Dication by Intense Ultrashort Laser Pulses  

NASA Astrophysics Data System (ADS)

We demonstrate the visualization of ultrafast hydrogen migration in deuterated acetylene dication (C2D22+) by employing the pump-probe Coulomb explosion imaging with sub-10-fs intense laser pulses (9 fs, 0.13PW/cm2, 800 nm). It is shown, from the temporal evolution of the momenta of the fragment ions produced by the three-body explosion, C2D23+?D++C++CD+, that the migration proceeds in a recurrent manner: The deuterium atom first shifts from one carbon site to the other in a short time scale (˜90fs) and then migrates back to the original carbon site by 280 fs, in competition with the molecular dissociation.

Hishikawa, Akiyoshi; Matsuda, Akitaka; Fushitani, Mizuho; Takahashi, Eiji J.

2007-12-01

281

Speed-dependent and correlation effects on the line shape of acetylene  

SciTech Connect

In this work we present the main results concerning an accurate line shape analysis on acetylene lines in the spectral region around 3 {mu}m. We clearly demonstrate the influence of Dicke narrowing as well as correlations between velocity-changing and dephasing collisions and the speed-dependent effects on Xe-broadened lines. In the low pressure regime the correlations are the main effect responsible for the line asymmetry while for high pressure (several hundred Torr) the speed-dependent effects predominate. This work constitutes the experimental evidence of the influence of such kind of effects on the line profiles of a nonpolar molecule, except H{sub 2}. The influence of the choice of the theoretical profile describing the line shape on the fitted line parameters is also discussed and the Xe-broadening and shift parameters were found for six C{sub 2}H{sub 2} lines.

Lisak, Daniel [Instytut Fizyki, Uniwersytet Mikolaja Kopernika, ul. Grudziadzka 5/7, 87-100 Torun (Poland); Rusciano, Giulia; Sasso, Antonio [INFM and Universita di Napoli 'Federico II'-Dipartimento di Scienze Fisiche, Complesso Universitario Monte S. Angelo, Via Cinthia, I-80126 Naples (Italy)

2005-07-15

282

Clinical Assay Development Program (CADP)  

Cancer.gov

Skip to Content Search this site Clinical Assay Development Program (CADP) Do you need: Advice on further development of a cancer diagnostics assay? Assay optimization? Design or implementation of assay controls, assay standards or assay calibrators? Determination

283

Growth of carbon nanocoils from K and Ag cooperative bicatalyst assisted thermal decomposition of acetylene.  

PubMed

Growth of amorphous carbon nanocoil (CNC) from acetylene on Si substrates was achieved by using nanosized Ag and K as the catalysts. The deposition of CNC was carried out inside a hot-wall reactor at 723 K using H2 as the carrier gas. Based on the observed results, we propose a cooperative bimetal catalyst enhanced vapor-liquid-solid (VLS) growth mechanism to rationalize the CNC growth. In the reaction, the liquid phase metallic K dehydrogenated acetylene into the solid-state carbon, while the Ag nanoparticle assisted the extension of carbon one-dimensionally (1-D) via a tip-growth mechanism. Due to the adhesive force between the K liquid and the carbon, the 1-D solid curled along the C-K interface into the nanocoil shape. Some CNC samples were further heat-treated at 1423 K and showed very good field emission properties. They emitted electrons (10 microA/cm2) at a turn-on field Eto of 2.51 V/microm, while Jmax reached 17.71 mA/cm2 at 5.64 V/microm. The field enhancement factor beta was calculated to be 2124, comparable to other carbon nanotube (CNT) and CNC based emitters. The CNC was also characterized by using the electrochemical behavior of K3[Fe(CN)6] via cyclic voltammetry (CV). The electrochemical surface area of a CNC electrode (geometric surface area 0.078 cm2) was calculated to be 0.143 cm2. These properties suggest that the CNC electrodes may have potential applications in field emission and electrochemical devices. PMID:20527809

Liu, Wen-Chih; Lin, Huang-Kai; Chen, Yu-Liang; Lee, Chi-Young; Chiu, Hsin-Tien

2010-07-27

284

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

285

Platinum\\/multiwalled carbon nanotubes-platinum\\/carbon composites as electrocatalysts for oxygen reduction reaction in proton exchange membrane fuel cell  

Microsoft Academic Search

Pt-loaded multiwalled carbon nanotubes (Pt\\/MWCNTs) have been prepared by chemical reduction method using functionalized MWCNT synthesized by pyrolysis of acetylene over MmNi2 (Mm denotes misch metal) hydride catalyst. Composites of Pt\\/MWCNT and commercial Pt-loaded carbon black (Pt\\/C) have been used as electrocatalysts for oxygen reduction reaction in proton exchange membrane fuel cell (PEMFC). Cathode catalyst with 50% Pt\\/MWCNT and 50%

M. M. Shaijumon; S. Ramaprabhu; N. Rajalakshmi

2006-01-01

286

Surface characterization of the interfaces from plasma-polymerized acetylene films deposited onto cold-rolled steel for rubber-to-metal bonding  

Microsoft Academic Search

The molecular structure of the interface between plasma-polymerized acetylene films and steel was determined using in-situ reflection-absorption infrared spectroscopy (RAIR) and X-ray photoelectron spectroscopy (XPS). Plasma-polymerized acetylene films were deposited onto polished steel substrates in microwave (MW) and radio frequency (RF)-powered reactors. The films deposited in RF-powered reactors were characterized in-situ using XPS and FTIR spectrometers that were interfaced directly

Pablo I. Rosales Lombardi

2007-01-01

287

Room temperature O 2 plasma treatment of SiO 2 supported Au catalysts for selective hydrogenation of acetylene in the presence of large excess of ethylene  

Microsoft Academic Search

Supported gold nanoparticles have been proven to be active in the hydrogenation of the acetylene. In this work, we applied gold nanoparticles supported on silica for the selective hydrogenation of acetylene in excess ethylene that was close to current industrial practices. Amine group surface-functionalized silica was used to absorb the gold precursor AuCl4-, and small size-controlled gold nanoparticles are formed

Xiaoyan Liu; Chung-Yuan Mou; Szetsen Lee; Yanan Li; Jeremiah Secrest; Ben W.-L. Jang

288

Kohn-Sham density-functional study of the adsorption of acetylene and vinylidene on iron clusters, Fen\\/Fen+ (n=1-4)  

Microsoft Academic Search

This is the first paper in a series dealing with the formation of benzene from acetylene on iron clusters, Fen\\/Fen+ (n=1-4). In the present study, we have performed all-electron Kohn-Sham density-functional theory calculations on the adsorption of acetylene and vinylidene on small iron clusters. Many starting structures were fully optimized without geometric and symmetric constraints for at least three different

Steeve Chrétien; Dennis R. Salahub

2003-01-01

289

Kohn–Sham density-functional study of the adsorption of acetylene and vinylidene on iron clusters, Fen\\/Fen+(n=1–4)  

Microsoft Academic Search

This is the first paper in a series dealing with the formation of benzene from acetylene on iron clusters, Fen\\/Fen+(n=1–4). In the present study, we have performed all-electron Kohn–Sham density-functional theory calculations on the adsorption of acetylene and vinylidene on small iron clusters. Many starting structures were fully optimized without geometric and symmetric constraints for at least three different spin

Steeve Chre´tien; Dennis R. Salahub

2003-01-01

290

Slow intramolecular vibrational redistribution: the latest results for trifluoropropyne, a comparison with the other terminal acetylenes and the mechanism*  

NASA Astrophysics Data System (ADS)

We studied the dynamics of intramolecular vibrational redistribution (IVR) from the initially excited mode ?1?3330?cm-1 (acetylene-type H-C bond) in H{-}C\\equivC{-}CF_3 molecules in the gaseous phase by means of time-resolved anti-Stokes spontaneous Raman scattering. The time constant of this process was estimated as 2.3?ns—this is the slowest IVR time reported so far for the room-temperature gases. We have compared this result with earlier results on the other terminal acetylene molecules, and give an explanation of this low IVR rate. Our suggestion for it follows from an assumption that the most probable doorway state leading to IVR from \

Malinovsky, A. L.; Makarov, A. A.; Ryabov, E. A.

2012-05-01

291

Solvent effects on the spin-spin coupling constants of acetylene revisited: supermolecular and polarizable continuum model calculations.  

PubMed

The solvent shifts of the spin-spin coupling constants of acetylene were calculated using the polarizable continuum model (PCM) for solvents ranging in polarity from cyclohexane to water, using both density functional theory (DFT) and the complete active space self-consistent field (CASSCF) method. The spin-spin coupling constants were also calculated for complexes of acetylene with water, acetonitrile, acetone and benzene using DFT/B3LYP. It is demonstrated that PCM reproduces the substantial experimental solvent shifts of the (1)J(C,C) and (1)J(C,H) couplings with great accuracy. The sign and approximate magnitude are also rendered correctly by the supermolecular method, in spite of the limitation of the models, which included only one or two solvent molecules. PMID:15366048

Pecul, Magdalena; Ruud, Kenneth

2004-10-01

292

Vinyl acetate formation in the reaction of acetylene with acetic acid catalyzed by zinc acetate supported on porous carbon spheres  

NASA Astrophysics Data System (ADS)

A kind of porous carbon spheres (PCS) was prepared by the carbonization of poly(vinylidene chloride) synthesized by suspension polymerization. Structure analyses revealed the existence of bumps and holes on the surface of PCS. The PCS, with the pore size between 0.8-1.2 nm, could be used as the support of zinc acetate because of the regular shape, high specific surface area, and good mechanical strength. Vinyl acetate was produced from acetylene and acetic acid using the PCS-supported zinc acetate (PCS-Zn) under mild conditions. In a single-pass operation performed at 220°C, the conversions of acetic acid and acetylene reached 22.6 and 5.3% respectively while the activity of vinyl acetate formation was above 1000 g mol-1 h-1.

Yan, Feng-Wen; Guo, Cun-Yue; Yan, Fang; Li, Feng-Bo; Qian, Qing-Li; Yuan, Guo-Qing

2010-05-01

293

The Fantasio Set-Up (ii): High Resolution Overtone Spectroscopy of Acetylene Containing Van Der Waals Dimers  

NASA Astrophysics Data System (ADS)

We have used the CW-CRDS facility in the FANTASIO set-up described in the previous presentation to investigate acetylene-containing dimers formed in a supersonic expansion, in the 1.5 microns range. Ab initio calculations were also performed in some cases. The acetylene partners so far include argon, carbon dioxide and nitrous oxide. The results will be illustrated. C. Lauzin, K. Didriche, P. Macko, J. Demaison, J. Liévin, and M. Herman, J. Phys. Chem. A, in press (2009). C. Lauzin, K. Didriche, J. Liévin, M. Herman, and A. Perrin, J. Chem. Phys, submitted (2009). K. Didriche, C. Lauzin, P. Macko, M. Herman, and W.J. Lafferty, Chem. Phys. Letters, doi:10.1016/j.cplett.2008.12.037 (2008).

Lauzin, C.; Demaison, J.; Didriche, K.; Macko, P.; Lievin, J.; Herman, M.; Perrin, A.; Lafferty, W. J.

2009-06-01

294

Acetylene-vinylidene isomerization in ultrashort intense laser fields studied by triple ion-coincidence momentum imaging  

NASA Astrophysics Data System (ADS)

The isomerization of acetylene via hydrogen migration in intense laser fields (8×1014 W/cm2) has been investigated by coincidence momentum imaging of the three-body Coulomb explosion process, C2H23+-->H++C++CH+. When ultrashort (9 fs) laser pulses are used, the angle between the momenta of C+ and H+ fragments exhibits a sharp distribution peaked at a small angle (~20°), showing that the hydrogen atom remains near the original carbon site in the acetylene configuration. On the other hand, a significantly broad distribution extending to larger momentum angles (~120°) is observed when the pulse duration is increased to 35 fs, indicating that the ultrafast isomerization to vinylidene is induced in the longer laser pulse.

Hishikawa, Akiyoshi; Matsuda, Akitaka; Takahashi, Eiji J.; Fushitani, Mizuho

2008-02-01

295

A Rapid Fluorescence-based Assay for Soluble Methane Monooxgyenase  

SciTech Connect

A fluorescence-based assay was developed to estimate soluble methane monooxygenase (sMMO) activity in solution. Whole cells of Methylosinus trichosporium OB3b expressing sMMO were used to oxidize various compounds to screen for fluorescent products. Of the 12 compounds tested, only coumarin yielded a fluorescent product. The UV absorbance spectrum of the product matches that of 7-hydroxycoumarin, and this identification was confirmed by 13C-NMR spectroscopy. The dependence of the fluorescent reaction on sMMO activity was investigated by pre-incubation with acetylene, a known inhibitor of sMMO activity. Apparent kinetic parameters for whole cells were determined to be Km(app)=262 µM and Vmax(app)=821 nmol 7-hydroxycoumarin min–1 mg protein–1. The rate of coumarin oxidation by sMMO correlates well with those of trichloroethylene degradation and naphthalene oxidation. Advantages of the fluorescence-based coumarin oxidation assay over the naphthalene oxidation assay include a more stable product, direct detection of the product without additional reagents, and greater speed and convenience.

Miller, Amber Reese; Keener, William Kelvin; Roberto, Francisco Figueroa; Watwood, Maribeth E.

2002-01-01

296

Liquid-vapor equilibrium in systems formed by hydrogen chloride with ethane, propane, acetylene, and ethyl chloride  

Microsoft Academic Search

1.The liquid-vapor equilibrium was studied in the systems hydrogen chloride-acetylene, hydrogen chloride-ethane, hydrogen chloride-propane, and hydrogen chloride-ethyl chloride, and the dependence of the coefficient of separation on the temperature was investigated in the interval from -112 to -90°, and the dependence on the concentration of the trace impurity from 5·10-3 to 5·10-1 vol. %. These systems obey Henry's law within

G. G. Devyatykh; V. Ya. Dudorov; N. Kh. Agliulov; V. M. Stepanov; M. I. Smirnov

1972-01-01

297

Acetylene - Argon Plasmas Measured at a Biased Substrate Electrode for Diamond-Like Carbon Deposition. Part 2: Ion Energy Distributions  

Microsoft Academic Search

Ion energy distributions have been determined at the rf-bias electrode in an\\u000ainductively-coupled acetylene-argon plasma for various substrate bias voltages\\u000aand frequencies under conditions suitable for film deposition. These are\\u000acompared with those obtained at the grounded wall of a capacitively coupled\\u000aplasma. In the former, for pressures up to 25 mTorr, the IEDs exhibit bimodal\\u000astructures with peak separation

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

2008-01-01

298

Acetylene - Argon Plasmas Measured at a Biased Substrate Electrode for Diamond-Like Carbon Deposition. Part 2: Ion Energy Distributions  

Microsoft Academic Search

Ion energy distributions have been determined at the rf-bias electrode in an inductively-coupled acetylene-argon plasma for various substrate bias voltages and frequencies under conditions suitable for film deposition. These are compared with those obtained at the grounded wall of a capacitively coupled plasma. In the former, for pressures up to 25 mTorr, the IEDs exhibit bimodal structures with peak separation

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

2008-01-01

299

Pressure dependence of the reaction of chlorine atoms with ethene and acetylene in air at 295 K  

Microsoft Academic Search

The relative rate technique has been used to determine rate constants for the reaction of chlorine atoms with ethene and acetylene over the pressure ranges 10-3,000 and 10-5,800 Torr, respectively, of synthetic air at 295 K. The decays of the reactants were measured relative to that of either ethane or chloroethane or both. Using a pressure-independent value of 5.7 Ã

T. J. Wallington; J. M. Andino; I. M. Lorkovic; E. W. Kaiser; G. Marston

1990-01-01

300

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

301

Comparison between methane and acetylene as carbon sources for C-rich aSiC: H films  

Microsoft Academic Search

Films of a-SiC: H were deposited using an ultrahigh vacuum plasma-enhanced CVD system from SiH4 + CH4 and SiH4 + C2H2 gas mixtures. The compositional, optical, structural and photoluminescence properties of the films were characterized. We have shown that using an acetylene plasma it is possible to grow films having an optical gap in the range 2.3–3.3 eV, high uniformity

F. Demichelis; G. Crovini; F. Giorgis; C. F. Pirri; E. Tresso

1995-01-01

302

Deposition of carbon nanofibers on a low carbon steel substrate using an oxy-acetylene reducing flame  

Microsoft Academic Search

Carbon nanofiber (CNF) coatings were successfully deposited on a low carbon steel substrate that was pretreated by con-centrated nitric acid using an oxy-acetylene reducing flame. The morphologies and the microstructures of the CNF coatings were char-acterized using scanning electron microscopy, X-ray diffraction, and Raman spectroscopy. The CNFs were compact, entangled with each other, and highly graphitized with diameters from 80

Shu-mei LEI; Tong-chun KUANG; Xiao-ling CHENG; Shi-heng YIN; Hong-mei ZHU

2007-01-01

303

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

304

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

NASA Astrophysics Data System (ADS)

The two-body dissociation reactions of the dication, C2H22+, 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 C2H++H+ products occurs through a metastable dication with a lifetime of 108 +/- 22 ns, and a kinetic energy release (KER) distribution exhibiting a maximum at ~4.3 eV with a full width at half maximum (FWHM) of about 60%. The reaction leading to CH2++C+ occurs in a time shorter than the typical rotational period of the acetylene molecules (of the order of 10-12 s). The KER distribution of product ions for this reaction, exhibits a maximum at ~4.5 eV with a FWHM of about 28%. The symmetric dissociation, leading to CH+ + CH+, exhibits a KER distribution with a maximum at ~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.; Callegari, C.; Candori, P.; Falcinelli, S.; Pirani, F.; Richter, R.; Stranges, S.; Vecchiocattivi, F.

2012-05-01

305

Complexes of acetylene–fluoroform: A matrix isolation and computational study  

NASA Astrophysics Data System (ADS)

Hydrogen-bonded complexes of C2H2 and CHF3 have been investigated using matrix isolation infrared spectroscopy and ab initio computations. The complexes were trapped in both solid argon and nitrogen matrices at 12 K. The structure of the complexes and the energies were computed at the B3LYP and MP2 levels of theory using a 6-311++G(d,p) basis set and at the MP2/aug-cc-pvdz level. Our computations indicated two minima for the 1:1 C2H2–CHF3 complex, with the C–H…? complex being the global minimum, where CHF3 is the proton donor. The second minimum corresponded to a relatively less exothermic C–H…F complex, in which C2H2 is the proton donor. Experimentally, we observed only the C–H…? complex in our matrix, which was evidenced by the shifts in the vibrational frequencies of the modes involving the C2H2 and CHF3 sub-molecules. The increase in the blue shift of the C–H stretching frequency in going from CHCl3–acetylene complex to CHF3–acetylene complex with corresponding increase in the interaction energy helps to place these two complexes on the left hand end of the qualitative diagram (Fig. 1). We also performed computations to study the higher complexes of C2H2 and CHF3. One minimum was found for the 1:2 C2H2–CHF3 complexes and two minima for the 2:1 C2H2–CHF3 complexes, at all levels of theory. Experimentally we observed the features corresponding to the 1:2 and 2:1 C2H2–CHF3 complexes in the N2 matrix. The computed vibrational frequencies of C2H2–CHF3 complexes at B3LYP and MP2/6-311++G(d,p) level corroborated well with the experimental frequencies. Interestingly, no experimental evidence for the formation of higher complexes was observed in the Ar matrix.

Sundararajan, K.; Ramanathan, N.; Viswanathan, K. S.; Vidya, K.; Jemmis, Eluvathingal D.

2013-10-01

306

Quantum chemical evaluation of the astrochemical significance of reactions between S atom and acetylene or ethylene.  

PubMed

Addition-elimination reactions of S atom in its 3P 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 that either reaction might play a general role in astrochemistry or a specific role in the formation of S2 (X3Sigmag-) via a mechanism proposed by Saxena, P. P.; Misra, A. Mon. Not. R. Astron. Soc. 1995, 272, 89. The acetylene and ethylene reactions proceed through C2H2S (3A' ') and C2H4S (3A' ') intermediates, respectively, to yield HCCS (2Pi) and C2H3S (2A'). 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 are formed and stabilized efficiently under cometary or dense interstellar cloud conditions, they could serve as temporary reservoirs for the S atom and participate in reactions such as S + C2H2S --> S2 + C2H2 or S + C2H4S --> 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. PMID:17536790

Woon, David E

2007-05-31

307

Surface characterization of the interfaces from plasma-polymerized acetylene films deposited onto cold-rolled steel for rubber-to-metal bonding  

NASA Astrophysics Data System (ADS)

The molecular structure of the interface between plasma-polymerized acetylene films and steel was determined using in-situ reflection-absorption infrared spectroscopy (RAIR) and X-ray photoelectron spectroscopy (XPS). Plasma-polymerized acetylene films were deposited onto polished steel substrates in microwave (MW) and radio frequency (RF)-powered reactors. The films deposited in RF-powered reactors were characterized in-situ using XPS and FTIR spectrometers that were interfaced directly to the reactors. RAIR showed that the plasma polymerized films contained large numbers of methyl and methylene groups but only a small number of monosubstituted acetylene groups, indicating that there was substantial rearrangement of the monomer molecules during plasma polymerization. The rearrangement of the monomer molecules during plasma was also determined by optical emission spectroscopy (OES), where CH and C2 species predominated in the optical emission spectra. Bands were observed near 1020 and 885 cm-1 in the RAIR spectra that were attributed to skeletal stretching vibrations in C-C-O-Fe groups, indicating that the plasma-polymerized films interacted with the substrate through formation of alkoxide bonds. Another band was observed near 1565 cm-1 and attributed to carboxylate groups in the interface between films and the oxidized surface of the substrate. Results from XPS also confirmed the formation of alkoxide and carboxylate groups in the interface during plasma polymerization of acetylene. Results from XPS showed that the surface of steel substrates consisted mostly of a mixture of Fe2O3 and FeOOH and that iron was mostly present in the Fe(III) oxidation state. However, during plasma-polymerization of acetylene, there was a tendency for the concentration of Fe(II) to increase, due to the reducing nature of argon/acetylene plasmas. Natural rubber reacted with plasma-polymerized acetylene primers through unsaturated functional groups present in the film. The RAIR and XPS results showed the presence of amino groups at the early steps of the vulcanization process. Activator products such as sulfenamide groups were found at the rubber/plasma-polymerized acetylene interface, the absorption bands near 1560 cm-1 in the RAIR spectra was due to the C=N stretching mode of the sulfenamide fragments of the accelerator. The band found in the RAIR spectra near 1143 cm -1 is characteristic from aliphatic secondary amines. Similarly, the presence of zinc was also found in the early stages of the vulcanization of natural rubber onto acetylene films. Zinc stearate reacted with accelerator and sulfur to form an accelerator complex. The zinc complex eventually reacted with natural rubber, sulfur, and the plasma-polymerized acetylene film to form rubber-bound intermediates.

Rosales Lombardi, Pablo I.

308

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

2012-02-04

309

Nitrogen Fixation in Arctic Coastal Tundra in Relation to Vegetation and MicroRelief  

Microsoft Academic Search

A study to estimate nitrogen fixation input. in arctie cmtd tundra was carried out using the acetylene reduction assay. Areal estimation was attempted by high intensity sampling over a limited area of tundra containing both high-centred and low- centred polygons with their corresponding variations in micro-vegetation. The highest average rates of acetylene reduction were obtained from cores in damp interpolygonal

DONALD M. SCHELL; VERA ALEXANDER

310

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

311

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

312

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

313

Dissociation of Methanol and Acetylene by slow Highly Charged Ion Collision  

NASA Astrophysics Data System (ADS)

We report here the results of dissociation of multiple charged methanol and acetylene molecules in collision with 1.2 MeV Ar8+ projectiles. We observed a wide range of dissociation products from the TOF spectrum starting from undissociated molecular ions, fragments losing an hydrogen atom due to breakage of C-H and/or O-H bonds, to complete rupture of C-C and C-O skeletons for the respective molecules. From the coincidence map of the fragments, we could separate out the different dissociation channels between carbon and oxygen ionic fragments as well as complete two-body dissociation events. The most striking feature in the breakup of CH3OH is the formation of H2+ and H3+ due to intramolecular rearrangement of the C-H bonds within the methyl group. In dissociative ionization studies of C2H2, we observed a diatom-like behaviour of the C-C charged complex as evidenced from the measured slopes of the coincidence islands for carbon atomic charged fragments and theoretical values determined from the charge and momentum distribution of the correlated particles. The shape and orientation of the islands give further information about the momentum balance in the fragmentation process in two-body dissociation.

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

2007-09-01

314

Influence of the acetylenic substituent on the intramolecular carbolithiation of alkynes: a DFT theoretical study.  

PubMed

A theoretical study of the intramolecular 5-exo-dig carbolithiation of substituted propargyl o-lithioaryl ethers, leading to dihydrobenzofurans, has been performed. The results show that a DFT description of the reaction (B3P86, 6-31G**) matches the experimental data provided that an explicit solvation by two molecules of THF is considered. To take place, the cyclization also implies that the acetylenic chain adopts a conformation in which a significant interaction arises between the lithium and the C?C triple bond. Reaching the cyclization TS requires the passage of an activation barrier that should not be higher than 12-13 kcal mol(-1). From a thermodynamic point of view, the reaction is exothermic whatever the substituent R (from approximately -40 to -62 kcal mol(-1)). In the starting substrate, a supplementary interaction between the Li and a substituent at the propargylic position can develop, influencing the future double-bond configuration. Thus, derivatives exhibiting an R-Li interaction tend to provide E olefins. In contrast, when no coordination between the lithium cation and the terminal R occurs, syn carbolithiation takes place, and the configuration of the exocyclic olefin is likely to be Z. This hypothesis accounts for most of the experimental results published before. PMID:23987301

Fressigné, Catherine; Lhermet, Rudy; Girard, Anne-Lise; Durandetti, Muriel; Maddaluno, Jacques

2013-09-16

315

Electrochemical oxidation and detection of paeonol on modified electrode with acetylene black nanoparticles.  

PubMed

With an aim to construct a sensing platform for the electrochemical detection of paeonol, we modified the glassy carbon electrode with acetylene black nanoparticle (AB). A sensitive oxidation peak of paeonol was observed with remarkably increased peak current on the modified electrode because the electrode has a big surface area due to three dimensional structure of AB nanoparticles. The optimization of detection conditions was performed, including pH value of the buffer, the amount of AB nanoparticles on the electrode surface, the accumulation potential and time of paeonol. Under the optimized conditions, the oxidation peak current of paeonol increased linearly with its concentration over the range from 5×10(-7) to 1×10(-4) M. The detection limit was calculated to be 1×10(-7) M. The modified electrode was successfully applied to detect the content of paeonol in cortex moutan, a common traditional Chinese medicine. The method is new, sensitive, rapid and convenient for the detection of paeonol. PMID:21684728

Zhang, Huajie; Gao, Miaomiao; Yang, Xiaofeng

2011-06-01

316

Anion dynamics in the first 10 milliseconds of an argon-acetylene radio-frequency plasma  

NASA Astrophysics Data System (ADS)

The time evolution of the smallest anions (C2H- and H2CC-), just after plasma ignition, is studied by means of microwave cavity resonance spectroscopy (MCRS) in concert with laser-induced photodetachment under varying gas pressure and temperature in an argon-acetylene radio-frequency (13.56 MHz) plasma. These anions act as an initiator for spontaneous dust particle formation in these plasmas. With an intense 355 nm Nd?:?YAG laser pulse directed through the discharge, electrons are detached only from these anions present in the laser path. This results in a sudden increase in the electron density in the plasma, which can accurately and with sub-microsecond time resolution be measured with MCRS. By adjusting the time after plasma ignition at which the laser is fired through the discharge, the time evolution of the anion density can be studied. We have operated in the linear regime: the photodetachment signal is proportional to the laser intensity. This allowed us to study the trends of the photodetachment signal as a function of the operational parameters of the plasma. The density of the smallest anions steadily increases in the first few milliseconds after plasma ignition, after which it reaches a steady state. While keeping the gas density constant, increasing the gas temperature in the range 30-120 °C limits the number of smallest anions and saturates at a temperature of about 90 °C. A reaction pathway is proposed to explain the observed trends.

van de Wetering, F. M. J. H.; Beckers, J.; Kroesen, G. M. W.

2012-12-01

317

Colorimetric protein assay techniques.  

PubMed

There has been an increase in the number of colorimetric assay techniques for the determination of protein concentration over the past 20 years. This has resulted in a perceived increase in sensitivity and accuracy with the advent of new techniques. The present review considers these advances with emphasis on the potential use of such technologies in the assay of biopharmaceuticals. The techniques reviewed include Coomassie Blue G-250 dye binding (the Bradford assay), the Lowry assay, the bicinchoninic acid assay and the biuret assay. It is shown that each assay has advantages and disadvantages relative to sensitivity, ease of performance, acceptance in the literature, accuracy and reproducibility/coefficient of variation/laboratory-to-laboratory variation. A comparison of the use of several assays with the same sample population is presented. It is suggested that the most critical issue in the use of a chromogenic protein assay for the characterization of a biopharmaceutical is the selection of a standard for the calibration of the assay; it is crucial that the standard be representative of the sample. If it is not possible to match the standard with the sample from the perspective of protein composition, then it is preferable to use an assay that is not sensitive to the composition of the protein such as a micro-Kjeldahl technique, quantitative amino acid analysis or the biuret assay. In a complex mixture it might be inappropriate to focus on a general method of protein determination and much more informative to use specific methods relating to the protein(s) of particular interest, using either specific assays or antibody-based methods. The key point is that whatever method is adopted as the 'gold standard' for a given protein, this method needs to be used routinely for calibration. PMID:10075906

Sapan, C V; Lundblad, R L; Price, N C

1999-04-01

318

Reductive capacity of natural reductants.  

PubMed

Reductive capacities of soil minerals and soil for Cr(VI) and chlorinated ethylenes were measured and characterized to provide basic knowledge for in-situ and ex-situ treatment using these natural reductants. The reductive capacities of iron-bearing sulfide (pyrite), hydroxide (green rust; GR(SO4)), and oxide (magnetite) minerals for Cr(VI) and tetrachloroethylene (PCE) were 1-3 orders of magnitude greater than those of iron-bearing phyllosilicates (biotite, vermiculite, and montmorillonite). The reductive capacities of surface soil collected from the plains of central Texas were similar and slightly greater than those of iron-bearing phyllosilicates. The reductive capacity of iron-bearing soil minerals for Cr(VI) was roughly 3-16 times greater than that for PCE, implying that Cr(VI) is more susceptible to being reduced by soil minerals than is PCE. GR(SO4) has the greatest reductive capacity for both Cr(VI) and PCE followed by magnetite, pyrite, biotite, montmorillonite, and vermiculite. This order was the same for both target compounds, which indicates that the relative reductive capacities of soil minerals are consistent. The reductive capacities of pyrite and GR(SO4) for chlorinated ethylenes decreased in the order: trichloroethylene (TCE) > PCE > cis-dichloroethylene (c-DCE) > vinyl chloride (VC). Fe(II) content in soil minerals was directly proportional to the reductive capacity of soil minerals for Cr(VI) and PCE, suggesting that Fe(II) content is an important factor that significantly affects reductive transformations of target contaminants in natural systems. PMID:12630469

Lee, Woojin; Batchelor, Bill

2003-02-01

319

Breast reduction  

MedlinePLUS

... smoke, you must stop. Women who smoke after breast surgery have a greater chance of slow wound healing, ... likely to have a very good outcome from breast reduction surgery. You may feel better about your appearance and ...

320

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

321

Factor XII assay  

MedlinePLUS

Hageman factor assay ... one of your blood relatives was diagnosed with factor XII deficiency. ... Decreased factor XII activity may indicate: Inherited (congenital) deficiency of factor XII Liver disease

322

A Colorimetric Assay for Quantification of Defective Interfering Particles of Respiratory Syncytial Virus  

Microsoft Academic Search

SUMMARY A colorimetric assay for defective interfering (DI) particles of respiratory syncytial (RS) virus was developed. This quantitative biological assay is based on neutral red dye uptake by DI particle-protected cells that survive standard virus challenge. This assay was more sensitive than the reduction of infectious yield (RIY) assay and was capable of detecting 1 x 104 to 2 x

MARY W. TREUHAFT

1983-01-01

323

Thermal decomposition mechanisms of the methoxyphenols: formation of phenol, cyclopentadienone, vinylacetylene, and acetylene.  

PubMed

The pyrolyses of the guaiacols or methoxyphenols (o-, m-, and p-HOC(6)H(4)OCH(3)) have been studied using a heated SiC microtubular (?-tubular) reactor. The decomposition products are detected by both photoionization time-of-flight mass spectroscopy (PIMS) and matrix isolation infrared spectroscopy (IR). Gas exiting the heated SiC ?-tubular reactor is subject to a free expansion after a residence time of approximately 50-100 ?s. The PIMS reveals that, for all three guaiacols, the initial decomposition step is loss of methyl radical: HOC(6)H(4)OCH(3) ? HOC(6)H(4)O + CH(3). Decarbonylation of the HOC(6)H(4)O radical produces the hydroxycyclopentadienyl radical, C(5)H(4)OH. As the temperature of the ?-tubular reactor is raised to 1275 K, the C(5)H(4)OH radical loses a H atom to produce cyclopentadienone, C(5)H(4)?O. Loss of CO from cyclopentadienone leads to the final products, acetylene and vinylacetylene: C(5)H(4)?O ? [CO + 2 HC?CH] or [CO + HC?C-CH?CH(2)]. The formation of C(5)H(4)?O, HCCH, and CH(2)CHCCH is confirmed with IR spectroscopy. In separate studies of the (1 + 1) resonance-enhanced multiphoton ionization (REMPI) spectra, we observe the presence of C(6)H(5)OH in the molecular beam: C(6)H(5)OH + ?(275.1 nm) ? [C(6)H(5)OH Ã] + ?(275.1nm) ? C(6)H(5)OH(+). From the REMPI and PIMS signals and previous work on methoxybenzene, we suggest that phenol results from a radical/radical reaction: CH(3) + C(5)H(4)OH ? [CH(3)-C(5)H(4)OH]* ? C(6)H(5)OH + 2H. PMID:21928823

Scheer, Adam M; Mukarakate, Calvin; Robichaud, David J; Nimlos, Mark R; Ellison, G Barney

2011-10-21

324

Oxy-acetylene driven laboratory scale shock tubes for studying blast wave effects  

NASA Astrophysics Data System (ADS)

This paper describes the development and characterization of modular, oxy-acetylene driven laboratory scale shock tubes. Such tools are needed to produce realistic blast waves in a laboratory setting. The pressure-time profiles measured at 1 MHz using high-speed piezoelectric pressure sensors have relevant durations and show a true shock front and exponential decay characteristic of free-field blast waves. Descriptions are included for shock tube diameters of 27-79 mm. A range of peak pressures from 204 kPa to 1187 kPa (with 0.5-5.6% standard error of the mean) were produced by selection of the driver section diameter and distance from the shock tube opening. The peak pressures varied predictably with distance from the shock tube opening while maintaining both a true blast wave profile and relevant pulse duration for distances up to about one diameter from the shock tube opening. This shock tube design provides a more realistic blast profile than current compression-driven shock tubes, and it does not have a large jet effect. In addition, operation does not require specialized personnel or facilities like most blast-driven shock tubes, which reduces operating costs and effort and permits greater throughput and accessibility. It is expected to be useful in assessing the response of various sensors to shock wave loading; assessing the reflection, transmission, and absorption properties of candidate armor materials; assessing material properties at high rates of loading; assessing the response of biological materials to shock wave exposure; and providing a means to validate numerical models of the interaction of shock waves with structures. All of these activities have been difficult to pursue in a laboratory setting due in part to lack of appropriate means to produce a realistic blast loading profile.

Courtney, Amy C.; Andrusiv, Lubov P.; Courtney, Michael W.

2012-04-01

325

Oxy-acetylene driven laboratory scale shock tubes for studying blast wave effects.  

PubMed

This paper describes the development and characterization of modular, oxy-acetylene driven laboratory scale shock tubes. Such tools are needed to produce realistic blast waves in a laboratory setting. The pressure-time profiles measured at 1 MHz using high-speed piezoelectric pressure sensors have relevant durations and show a true shock front and exponential decay characteristic of free-field blast waves. Descriptions are included for shock tube diameters of 27-79 mm. A range of peak pressures from 204 kPa to 1187 kPa (with 0.5-5.6% standard error of the mean) were produced by selection of the driver section diameter and distance from the shock tube opening. The peak pressures varied predictably with distance from the shock tube opening while maintaining both a true blast wave profile and relevant pulse duration for distances up to about one diameter from the shock tube opening. This shock tube design provides a more realistic blast profile than current compression-driven shock tubes, and it does not have a large jet effect. In addition, operation does not require specialized personnel or facilities like most blast-driven shock tubes, which reduces operating costs and effort and permits greater throughput and accessibility. It is expected to be useful in assessing the response of various sensors to shock wave loading; assessing the reflection, transmission, and absorption properties of candidate armor materials; assessing material properties at high rates of loading; assessing the response of biological materials to shock wave exposure; and providing a means to validate numerical models of the interaction of shock waves with structures. All of these activities have been difficult to pursue in a laboratory setting due in part to lack of appropriate means to produce a realistic blast loading profile. PMID:22559580

Courtney, Amy C; Andrusiv, Lubov P; Courtney, Michael W

2012-04-01

326

Acetylene ^1^2C_2H_2 Laboratory Measurements for Astrophysical Applications  

NASA Astrophysics Data System (ADS)

The acetylene molecule is important for atmospheric, planetary, and astrophysical applications. This organic molecule, known as a precursor of amino acids, shows numerous vibration-rotation bands in the IR. Two recent works on line intensities measurements will be presented. A study around 7.7 ?m was motivated by SPITZER observations of C_2H_2 in this spectral region that cannot be modeled using the current line list of HITRAN/GEISA due to the lack of data. High resolution spectra have been recorded with the Bruker HR IFS 120 of the LADIR and analyzed to deduce absolute line intensities of several bands included the one present in HITRAN, the (?_4+?_5)^0_+ strong band. On the whole, line intensities of 2 cold bands and 15 hot bands have been studied, and a complete line list has been generated. Another study using SOLEIL synchrotron will be presented in the spectral region around 100 cm^-^1 of interest for astrophysical applications (SPITZER, ALMA, HERSCHEL...). High resolution spectra have been recorded with the Bruker HR IFS 125 of SOLEIL. For accurate line intensities measurement based on the FIR beam of the synchrotron, the strong wavenumber dependence of the beam radius had to be modeled in the apparatus function calculation. Absolute line intensities of the intense ?_5-?_4 band have been measured, and those of the 4 weaker hot bands are in progress. M. Matzuura et al. Non. Not. R. Astron. Soc. 371, 415-420, 2006. J. Vander Auwera. J. Mol. Spectrosc. 242, 25-30, 2007. L. Gomez, D. Jacquemart, N. Lacome and J.-Y. Mandin. JQSRT 110, 2102-2114, 2009. D. Jacquemart, L. Gomez, N. Lacome, J.-Y. Mandin, O. Pirali and P. Roy. JQSRT in press.

Jacquemart, D.; Gomez, L.; Lacome, N.; Mandin, J.-Y.; Pirali, O.; Roy, P.

2010-06-01

327

Living polymerization of (o-(trimethylsilyl) phenyl)acetylene by molybdenum imido alkylidene complexes  

SciTech Connect

syn-Mo(CHCMe{sub 2}Ph)(NAd) [OCH(CF{sub 3}){sub 2}]{sub 2}(2,4-lutidine) (2a; Ad = 1-adamantyl) reacts with (o-(trimethylsilyl) phenyl)acetylene(o-TMSPA) solely via formation of an {alpha}-substituted metallacyclobutene intermediate ({alpha} addition) that opens to give a single rotamer of a disubstituted alkylidene complex. o-TMSPA is smoothly polymerized at a rate k{sub 2a}[2a]{sub 0}[o-TMSPA] when [2a] < 1 mM with a propagation rate constant k{sub 2a} = 0.30 s{sup -1} M{sup -1}. Additional studies confirmed that the disubstituted alkylidene propagating species is essentially base-free and that the propagating species is stable under catalytic conditions (25{degree}C). Other versions of the Mo(CHCMe{sub 2}Ph)(NAd)[OCH(CF{sub 3}){sub 2}]{sub 2}(base) catalyst are either inactive (base = pyridine) or unstable (base = 2-(3-pentyl)pyridine). Low-polydispersity polyenes containing up to 150 equiv of o-TMSPA can be obtained readily using either catalyst. The thermodynamically most stable form of poly(o-TMSPA), which contains nearly 25 double bonds, is air-sensitive and has a significantly red-shifted {lambda}{sub max}. o-t-BuPA also can be polymerized to give highly conjugated polyenes, but o-i-PrPa, o-MePA, and phenylacetylene itself add to initiator 2a with decreasing {alpha} regiospecificity (73%, 60%, and 56%, respectively). 35 refs., 6 figs., 10 tabs.

Schrock, R.R.; Luo, S.; Lee, J.C. Jr.; Zanetti, N.C.; Davis, W.M. [Massachusetts Inst. of Technology, Cambridge, MA (United States)

1996-04-24

328

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

329

Infrared bands of acetone in solid argon and the structure II clathrate 2acetylene/acetone/17water  

SciTech Connect

The vibrational bands of acetone in solid argon and in the structure II 2acetylene/acetone/17water clathrates are presented. The results show that the band frequencies for enclathrated acetone are not greatly different from the unperturbed acetone frequencies. The acetone does not rotate on the IR time scale, and little evidence for site effects was observed (except for possibly lifting the degeneracy of an antisymmetric stretch of CH/sub 3/). Both of the C-C stretches of acetone undergo small blue shifts, though the reason is unclear.

Consani, K.

1987-10-22

330

Proline Fed to Intact Soybean Plants Influences Acetylene Reducing Activity and Content and Metabolism of Proline in Bacteroids 1  

PubMed Central

Supplying l-proline to the root system of intact soybean (Glycine max [L.] Merr.) plants stimulated acetylene reducing activity to the same extent as did supplying succinate. Feeding l-proline also caused an increase in bacteroid proline dehydrogenase activity that was highly correlated with the increase in acetylene-reducing activity. Twenty-four hours after irrigating with l-proline, endogenous proline content had increased in host cell cytoplasm and bacteroids, about three- and eightfold, respectively. In bacteroids, proline concentration was calculated to be at least 3.5 millimolar. In experiments in which [U-14C]l-proline was supplied to uprooted, intact plants incubated in aerated solution, 14C-labeled products of proline metabolism, as well as [14C]proline itself, accumulated in both host cells and bacteroids. When plants were incubated in aerated solutions containing [5-3H]l-proline, 3H-labeled proline was found in host cells and bacteroids. [3H] Pyrroline-5-carboxylate was found in bacteroids, but not host cells, after a 2-hour incubation in [5-3H]l-proline. When [U-14C]l-proline was supplied for 24 hours, a significant amount of [14C] pyrroline-5-carboxylate was found in the host cells, in contrast with the results from the shorter incubation in [5-3H]proline, although the amount in the host cells was only about half the quantity found in the bacteroids. Taken as a whole, these results indicate that proline crosses both plant and bacterial membranes under the in vivo experimental conditions utilized and are consistent with a significant role for proline as an energy source in support of bacteroid functioning. In spite of the increase in acetylene-reducing activity when proline was supplied to the root system of intact plants, proline application did not rescue stemgirdled plants from loss of acetylene-reducing activity, although succinate application did. This suggests a nonphloem route for succinate, but not proline, from roots to nodules.

Zhu, Yuxian; Shearer, Georgia; Kohl, Daniel H.

1992-01-01

331

Simplifying reductions  

Microsoft Academic Search

We present optimization techniques for high level equational pro- grams that are generalizations of affine control loops (ACLs). Sig- nificant parts of the SpecFP and PerfectClub benchmarks are ACLs. They often contain reductions: associative and commutative opera- tors applied to a collection of values. They also often exhibit reuse: intermediate values computed or used at different index points be- ing

Gautam Gupta; Sanjay V. Rajopadhye

2006-01-01

332

Diagnostic assays used to control small ruminant lentiviruses  

Technology Transfer Automated Retrieval System (TEKTRAN)

The serological diagnostic tests such as the agar gel immunodiffusion (AGID) assay and various types of enzyme linked immunosorbent assays (ELISAs) have contributed to the reduction of small ruminant lentivirus infections worldwide. Since there are no treatments or efficacious vaccines, the serolog...

333

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...

334

Synthesis and X-ray crystallographic structural determination of the acetylene complex (eta5-C5H5)2W2(CO)4(C2H2)  

Microsoft Academic Search

Reaction of photogenerated (ETA5-C5H5)2W2(CO)4 with acetylene at 25 yields a complex of the formula (ETA5-C5H5)2W2(CO)4(C2H2). The crystal structure of the complex shows it to have a tetrahedrane-like W2C2 core. The C-C bond distance of the C2H2 unit is 1.35 Angstrom which is close to that of ethylene, considerably longer than the 1.20 Angstrom for acetylenes. The W-W distance is 2.973

D. S. Ginley; C. R. Bock; M. S. Wrighton; B. Fischer; R. Bau

1977-01-01

335

DFT functional benchmarking on the energy splitting of chromium spin states and mechanistic study of acetylene cyclotrimerization over the Phillips Cr(II)/silica catalyst.  

PubMed

In this work, a two-state reaction mechanism for the acetylene cyclotrimerization over a cluster model for the Phillips Cr(II)/silica catalyst were systematically investigated using density functional theory (DFT). Since spin crossover phenomenon was confirmed in the catalytic cycle, an accurate prediction of the energy gap between low- and high-spin states is crucial for the description of a reaction involving a two-state reactivity. Therefore, a massive DFT functional benchmarking test has been conducted on the cluster model by taking a CASPT2 energy gap as a reference. Consequently, B3PW91* with 28% Hartree-Fock exchange energy was selected for the following mechanistic investigation. Each of the possible potential energy surface including singlet, triplet, and quintet surfaces was explored. On the quintet surface, the reaction begins with a coordination of an acetylene on the chromium center to generate a ?-coordinated complex. The following oxidative coupling through further coordination with a second acetylene was predicted to be a two-step reaction to generate a chromacyclopentadiene species. This transformation was found to be energetically prohibitive by the presence of the transition state (5)TS[C-E] (?G(‡) = 31.1 kcal/mol). On the triplet surface, however, the coordination of an acetylene generates a chromacyclopropene species without showing any activation barrier. The second acetylene incorporation proceeding via a coordination on the chromium center followed by an insertion into a Cr-C ?-bond of the chromacyclopropene was predicted to be a facile reaction pathway (?G(‡) = 10.2 kcal/mol). The third acetylene was captured by the cluster model through the formation of a hydrogen bond. The later transformation on the triplet surface was found to be an intermolecular [4 + 2] cycloaddition to finish the cyclization. The lack of the aromaticity of the benzene ring in (3)L results in an uncompleted reaction pathway on a single triplet surface. Consequently, a two-state reaction pathway that is connected by two low-lying minimum-energy crossing points (MECPs) of the two surfaces is thus described. It is worthy of note that the third acetylene in the tri(acetylene)chromium complex captured by the cluster model only through the formation of a hydrogen bond rules out the [2 + 2 + 2] concerted one-step reaction pathway proposed by Zecchina et al. [Phys. Chem. Chem. Phys.2003, 5, 4414]. The singlet reaction profile is far higher in energy compared with that proceeded on the triplet and quintet surfaces. PMID:22697502

Liu, Zhen; Cheng, Ruihua; He, Xuelian; Wu, Xiaojun; Liu, Boping

2012-07-05

336

Chaos and dynamics on 0. 5--300 ps time scales in vibrationally excited acetylene: Fourier transform of stimulated-emission pumping spectrum  

SciTech Connect

A recently proposed technique based on the Fourier transform of the spectrum is applied to the stimulated-emission pumping spectrum of acetylene at --26 500 cm/sup -1/ above the vibrational ground state. Correlations on two different time scales (--3 and --45 ps) were found from analysis of low-resolution (0.3 cm/sup -1/) and high-resolution (0.05 cm/sup -1/) spectra, respectively. Additional structure produced dynamic information on a wider (0.5--300 ps) time scale. The results show that acetylene at 26 500 cm/sup -1/ is in the transition from the regular to the chaotic regime.

Pique, J.P.; Chen, Y.; Field, R.W.; Kinsey, J.L.

1987-02-02

337

Experimental and kinetic modeling study of the reduction of NO by hydrocarbons and interactions with SO 2 in a JSR at 1 atm  

Microsoft Academic Search

The reduction of nitric oxide (NO) by a mixture of methane, ethylene and acetylene with and without addition of SO2 has been studied in a fused silica jet-stirred reactor operating at 1atm in simulated conditions of the reburning zone. The temperatures were ranging from 800 to 1400K. In these experiments, the initial mole fractions of NO and SO2 were 0

Philippe Dagaut; Franck Lecomte

2003-01-01

338

21 CFR 864.7360 - Erythrocytic glucose-6-phosphate dehydrogenase assay.  

Code of Federal Regulations, 2013 CFR

...dehydrogenase deficiency. This generic device includes assays based on fluorescence, electrophoresis, methemoglobin reduction, catalase inhibition, and ultraviolet kinetics. (b) Classification. Class II (performance standards). [45 FR...

2013-04-01

339

Pressure-induced shift and broadening of acetylene lines in the region 6580-6600 cm-1.  

PubMed

Highly accurate measurements of pressure shift and broadening parameters of acetylene absorption lines in the region 6580-6600 cm-1 have been performed by tunable diode laser spectroscopy (TDLS). For these purposes the three channel spectrometer with distributed-feedback diode laser, operated at 1.53 microm was used. The laser is generating pulses of 4-10 ms duration at a repetition frequency of 40 Hz. A temperature-stabilization system, using a thermoelectric cooling unit affords a temperature stability of the order of 10(-4)K in the temperature range from -15 to +50 degrees C. A three channels acquisition system ensured simultaneous real time recording of the sample gas absorption spectrum and of two spectral calibration signals (Fabry-Perot fringes and low-pressure reference lines). We have measured the pressure-induced self-shift and broadening coefficients for six lines of the R-branch in the nu1+nu3 rotation-vibration band of acetylene 12C2H2. The self-shift coefficients have been determined for these lines in the wide pressure region. A non-linear behavior of the pressure dependence of the shift was observed. The temperature exponent n of pressure-induced broadening and shift are reported. PMID:17185027

Nadezhdinskii, A I; Ponurovskii, Ya Ya

2006-10-27

340

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

341

Cavity Ringdown Laser Asorption Spectroscopy(crlas) of Isotopically Labeled Acetylene Between 12,500 - 13,600 wn  

NASA Astrophysics Data System (ADS)

About five years ago, Arkansas State University created the Arkansas Center for Laser Applications and Science (ArCLAS) with the intention of making it a state-of-the-art facility for laser-based research and optical spectroscopy in the midSouth. Since that time, University and DoD support has lead to the acquisition of numerous laser based spectrometers including a novel three color picosecond system utilized primarily for STIRAP measurements of bulk gas samples. Over the past few months, we have begun collecting near infrared overtone and combination band spectra for the acetylene molecule with a pulsed cavity ringdown laser absorption spectrometer (CRDLAS) as part of the STIRAP support effort. Certainly acetylene has been extensively studied by a number of different spectroscopic methods. During these CRDLAS investigations a 13C_2H_2 band was discovered which we believe has not been previously reported. Here a complete rovibrational analysis of this band will be presented. See for example, Michel Herman, Jacques lievin, Jean Vander Auwera, and Alain Campargue, in Global and Accurate Vibration Hamiltonians from High Resolution Molecular Spectroscopy, Advances in Chemical Physics Volume 108, John Wiley and Sons, NY, NY (1999) and references therein.

Lue, Christopher J.; Sullivan, Michael N.; Draganjac, Mark E.; Reeve, Scott W.

2011-06-01

342

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

343

Observations of upper tropospheric acetylene on Saturn: No apparent correlation with 2000 km-sized thunderstorms  

NASA Astrophysics Data System (ADS)

Thunderstorm activity has been observed on Saturn via radio emissions from lightning discharges and optical detections of the lightning flashes on the planet's nightside. Thunderstorms provide extreme environments in which specific atmospheric chemistry can be induced—namely through energy release via lightning discharges, and fast vertical transport resulting in rapid advection of tropospheric species. It is thus theorised that certain atmospheric trace species - such as C2H2, HCN, and CO - can be generated in the troposphere by large bursts of energy in the form of lightning, and transported upward towards the upper troposphere by the extreme dynamics of thunderstorms, where they should be observable by satellite instruments. In this work, high-spectral-resolution Cassini/CIRS observations from October 2005 through April 2009 are used to study whether there is an observable increase in upper tropospheric acetylene in regions of known normal thunderstorm activity. Using both individual measurements in which there is known thunderstorm activity, as well as large coadditions of data to study latitudinal-dependencies over the full disc, no systematic enhancement in upper tropospheric (100 mbar) C2H2 was detected around regions in which there are known occurrences of normally sized (2000 km) thunderstorms, or in normally sized thunderstorm-prone regions such as 40°S. It is likely that the magnitude of the enhancement theorised is too generous or that enhancements are not advected into the upper troposphere as vertical mixing rates in models would suggest, since Cassini/CIRS can only detect C2H2 above the 200 mbar level—although the massive northern hemisphere thunderstorm of 2010/2011 seems able to decrease stratospheric concentrations of C2H2. From this, it can be asserted that lightning from normal thunderstorm activity cannot be the key source for upper tropospheric C2H2 on Saturn, since the upper-tropospheric concentrations retrieved agree with the concentrations stemming from the photolysis of CH4 (2-3 ppbv) from solar radiation penetrating through the Saturnian atmosphere, with an upper limit for lightning-induced C2H2 volume mixing ratio of 10-9.

Hurley, J.; Irwin, P. G. J.; Fletcher, L. N.; Moses, J. I.; Hesman, B.; Sinclair, J.; Merlet, C.

2012-05-01

344

SiC formation by reaction of Si(001) with acetylene: Electronic structure and growth mode  

SciTech Connect

The carbonization process of a single domain 2{times}1-reconstructed Si(001) vicinal surface (5{degree} off axis from [001] in the [{bar 1}10] direction) in acetylene has been studied by combining in situ surface science techniques (x-ray photoemission spectroscopy, x-ray photoelectron diffraction, reflection-electron energy loss spectroscopy, low-energy electron diffraction) and ex situ analytical techniques ({sup 12}C and {sup 2}H dosing by nuclear reaction analysis, scanning electron microscopy, and reflection high-energy electron diffraction). It is found that at a growth temperature of about 820{degree}C a variety of growth mechanisms can be observed, particularly during the first step of carbonization. An analysis of C1s and Si2p core-level shifts and of the respective intensities of them, combined with the examination of photoelectron diffraction curves, gives evidence for a penetration of C atoms into the silicon substrate, to form a nonstoichiometric compound. Contemporaneously 3C-SiC nuclei form, aligned with respect to the substrate. Then a quasicontinuous 3C-SiC film grows heteroepitaxially (cube on cube unstrained growth) on the substrate up to a thickness of {approximately}40{Angstrom}. C1s and Si2p photoelectron diffraction patterns, compared with calculated ones, show that the single domain initial surface does not necessarily force a preferential alignment of one of the two inequivalent SiC{l_brace}110{r_brace} planes with respect to the (110) Si plane. Consequently, such vicinal Si(001) surfaces are not necessarily templates for the growth of crystalline films free of antiphase boundary domains. Finally, we have observed that an imperfect coalescence of 3C-SiC nuclei leaves easy paths for Si out migration from the substrate and SiC polycrystalline growth, even at a temperature as low as 820{degree}C. The current models of Si(001) carbonization are examined and compared to our experimental findings. (Abstract Truncated)

Dufour, G.; Rochet, F. [Laboratoire de Chimie Physique, Universite Pierre et Marie Curie, 11 rue Pierre et Marie Curie, 75231 Paris, Cedex 05 (France); Stedile, F.C. [Departamento de Fisico-quimica, Instituto de Quimica, UFRGS, Av. Bento Goncalves, 9500 Porto Alegre, Rio Grande do Sul (Brazil); Poncey, C. [Laboratoire de Chimie Physique, Universite Pierre et Marie Curie, 11 rue Pierre et Marie Curie, 75231 Paris Cedex 05 (France); De Crescenzi, M.; Gunnella, R. [Dipartimento di Matematica e Fisica, Unita dellIstituto Nazionale di Fisica della Materia, Universita di Camerino, 62032 Camerino (Italy); Froment, M. [Laboratoire de Physique des Liquides et Electrochimie, Universite Pierre et Marie Curie, Tour 22, 4 place Jussieu, 75230 Paris Cedex 05 (France)

1997-08-01

345

Titan Haze: Structure and Properties of Cyanoacetylene and Cyanoacetylene-Acetylene Photopolymers  

NASA Astrophysics Data System (ADS)

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 HC_3N 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 HC_3N is photolyzed in the presence of Titan's other atmospheric constituents (CH_4, C_2H_6, C_2H_2, 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 HC_3N and acetylene (C_2H_2). Even in experiments where C_2H_2 was absorbing nearly all of the incident photons, the ratio of C_2H_2 to HC_3N 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 ?m in diameter, polycyanoacetylenes appear to be strands of rough, solid particles slightly smaller in size. The copolymer of HC_3N and C_2H_2 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 HC_3N, into the polyacetylenes are expected to have optical constants more comparable to those of the Titan haze.

Clarke, David W.; Ferris, James P.

1997-05-01

346

Structure and hydration of the C4H4?+ ion formed by electron impact ionization of acetylene clusters.  

PubMed

Here we report ion mobility experiments and theoretical studies aimed at elucidating the identity of the acetylene dimer cation and its hydrated structures. The mobility measurement indicates the presence of more than one isomer for the C(4)H(4)(?+) ion in the cluster beam. The measured average collision cross section of the C(4)H(4)(?+) isomers in helium (38.9 ± 1 A?(2)) is consistent with the calculated cross sections of the four most stable covalent structures calculated for the C(4)H(4)(?+) ion [methylenecyclopropene (39.9 A?(2)), 1,2,3-butatriene (41.1 A?(2)), cyclobutadiene (38.6 A?(2)), and vinyl acetylene (41.1 A?(2))]. However, none of the single isomers is able to reproduce the experimental arrival time distribution of the C(4)H(4)(?+) ion. Combinations of cyclobutadiene and vinyl acetylene isomers show excellent agreement with the experimental mobility profile and the measured collision cross section. The fragment ions obtained by the dissociation of the C(4)H(4)(?+) ion are consistent with the cyclobutadiene structure in agreement with the vibrational predissociation spectrum of the acetylene dimer cation (C(2)H(2))(2)(?+) [R. A. Relph, J. C. Bopp, J. R. Roscioli, and M. A. Johnson, J. Chem. Phys. 131, 114305 (2009)]. The stepwise hydration experiments show that dissociative proton transfer reactions occur within the C(4)H(4)(?+)(H(2)O)(n) clusters with n ? 3 resulting in the formation of protonated water clusters. The measured binding energy of the C(4)H(4)(?+)H(2)O cluster, 38.7 ± 4 kJ/mol, is in excellent agreement with the G3(MP2) calculated binding energy of cyclobutadiene(?+)·H(2)O cluster (41 kJ/mol). The binding energies of the C(4)H(4)(?+)(H(2)O)(n) clusters change little from n = 1 to 5 (39-48 kJ/mol) suggesting the presence of multiple binding sites with comparable energies for the water-C(4)H(4)(?+) and water-water interactions. A significant entropy loss is measured for the addition of the fifth water molecule suggesting a structure with restrained water molecules, probably a cyclic water pentamer within the C(4)H(4)(?+)(H(2)O)(5) cluster. Consequently, a drop in the binding energy of the sixth water molecule is observed suggesting a structure in which the sixth water molecule interacts weakly with the C(4)H(4)(?+)(H(2)O)(5) cluster presumably consisting of a cyclobutadiene(?+) cation hydrogen bonded to a cyclic water pentamer. The combination of ion mobility, dissociation, and hydration experiments in conjunction with the theoretical calculations provides strong evidence that the (C(2)H(2))(2)(?+) ions are predominantly present as the cyclobutadiene cation with some contribution from the vinyl acetylene cation. PMID:21639448

Momoh, Paul O; Hamid, Ahmed M; Abrash, Samuel A; El-Shall, M Samy

2011-05-28

347

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

348

Effects of transient anaerobic conditions in the presence of acetylene on subsequent aerobic respiration and N 2O emission by soil aggregates  

Microsoft Academic Search

Our objective was to assess the effect of anaerobic conditioning in the presence of acetylene on subsequent aerobic respiration and N2O emission at the scale of soil aggregates. Nitrous oxide production was measured in intact soil aggregates ? (compacted aggregates without visible porosity) and ? (aggregates with visible porosity) incubated under oxic conditions, with or without anaerobic conditioning for 6

K. Khalil; P. Renault; B. Mary

2005-01-01

349

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

350

Temperature-dependent growth of carbon nanotubes by pyrolysis of ferrocene and acetylene in the range between 700 and 1000 °C  

Microsoft Academic Search

Aligned carbon nanotubes were grown by pyrolysis of ferrocene and acetylene in the temperature range 700–1000 °C. The average diameter is constantly 20 nm for all growth temperatures. As the temperature increases, the growth rate increases by 60 times. The length reaches up to 3 mm at 1000 °C. These long carbon nanotubes exhibit a cylindrical structure. The relative amount

Yun Tack Lee; Nam Seo Kim; Jae Beom Han; Young Sang Choi; Hyun Ryu; Hwack Joo Lee

2003-01-01

351

The combined use of SCF-MO calculations and experimental data in the evaluation of quadratic force fields MOCIC potential functions for fluoroform, methyl acetylene, and methyl cyanide  

Microsoft Academic Search

A semiempirical method combining SCF-MO calculations and limited vibrational data has been employed to evaluate the completely general quadratic potential fields of fluoroform, methyl acetylene, and acetonitrile. MOCIC (molecular orbital constraint using interaction coordinates) potential fields are presented for gas phase molecules of intermediate size. Here general harmonic force fields or excellent approximations utilizing extensive experimental data are available as

B. I. Swanson; T. H. Arnold; Y. Yamaguchi

1979-01-01

352

Hydrogen penetration and corrosion of iron and high strength steels. Effect of halides, H/sub 2/S, sulfur containing organics and acetylenics  

SciTech Connect

Hydrogen penetration, hydrogen evolution and corrosion rates of Ferrovac E iron, 4130 and 4340 steels have been investigated by electrochemical methods. In particular, the effects of pH, temperature and various additives (halides, H/sub 2/S, some organo-sulfur compounds, acetylenic compounds) on hydrogen penetration (h.p.), hydrogen evolution reaction (h.e.r.) and corrosion have been studied.

Saito, Y.

1982-01-01

353

Diamond deposition in low-pressure acetylene flames: in situ temperature and species concentration measurements by laser diagnostics and molecular beam mass spectrometry  

Microsoft Academic Search

Diamond deposition in a flat, premixed acetylene–oxygen–argon flame at 50 mbar was investigated to characterize the reactive gas phase in the vicinity of the substrate. For this, flames with and without a substrate present were analyzed as a function of stoichiometry; also, the distance between the substrate and the burner was varied. Optimal conditions for the deposition of diamond films

A. G Löwe; A. T Hartlier; J Brand; B Atakan; K Kohse-Höinghaus

1999-01-01

354

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…

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

2005-01-01

355

PEG-mediated catalyst-free expeditious synthesis of polysubstituted anilines and benzenes via the reaction of malononitrile and ?-ketoester derivatives in the presence of activated acetylenes.  

PubMed

Poly(ethylene glycol) (PEG) has been used as a sustainable, non-volatile, and environmentally friendly reaction solvent for synthesis of functionalized anilines and benzenes via the reaction of malononitrile and ?-ketoester derivatives in the presence of activated acetylenes at 80° C. No additional solvent and catalyst are required. PMID:22292778

Piltan, Mohammad; Moradi, Loghman; Salimi, Hiwa; Zargoosh, Kiomars; Zarei, Seyed Amir

2012-08-01

356

Miniaturization of hydrolase assays in thermocyclers.  

PubMed

We adapted the protocols of reducing sugar measurements with dinitrosalicylic acid and bicinchoninic acid for thermocyclers and their use in enzymatic assays for hydrolases such as amylase and ?-1,3-glucanase. The use of thermocyclers for these enzymatic assays resulted in a 10 times reduction in the amount of reagent and volume of the sample needed when compared with conventional microplate protocols. We standardized absorbance readings from the polymerase chain reaction plates, which allowed us to make direct readings of the techniques above, and a ?-glycosidase assay was also established under the same conditions. Standardization of the enzymatic reaction in thermocyclers resulted in less time-consuming temperature calibrations and without loss of volume through leakage or evaporation from the microplate. Kinetic parameters were successfully obtained, and the use of the thermocycler allowed the measurement of enzymatic activities in biological samples from the field with a limited amount of protein. PMID:23123426

Lucena, Severino A; Moraes, Caroline S; Costa, Samara G; de Souza, Wanderley; Azambuja, Patrícia; Garcia, Eloi S; Genta, Fernando A

2012-10-30

357

Assaying hematopoiesis using zebrafish.  

PubMed

The zebrafish has become a commonly used model for studying hematopoiesis as a result of its unique attributes. Zebrafish are highly suitable for large-scale genetic and chemical screens compared to other vertebrate systems. It is now possible to analyze hematopoietic lineages in zebrafish and validate cell function via transplantation assays. Here, we review advancements over the past decade in forward genetic screens, chemical screens, fluorescence-activated cell sorting analysis, and transplantation assays. Integrating these approaches enables new chemical and genetic screens that assay cell function within the hematopoietic system. Studies in zebrafish will continue to contribute and expand our knowledge about hematopoiesis, and develop novel treatments for clinical applications. PMID:23916372

Boatman, Sonja; Barrett, Francesca; Satishchandran, Sruthi; Jing, Lili; Shestopalov, Ilya; Zon, Leonard I

2013-08-02

358

Dilution assay statistics.  

PubMed Central

A parametric method of statistical analysis for dilution assays is developed in detail from first principles of probability and statistics. The method is based on a simple product binomial model for the experiment and produces an estimate for the concentration of target entities, a confidence interval for this concentration, and an indicator of the quality of the assay called the p value for goodness of fit. The procedure is illustrated with data from a virologic quantitative micrococulture assay used to quantify free human immunodeficiency virus in clinical trials. The merits of the procedure versus those of nonparametric methods of estimating the dilution inducing a 50% response rate are discussed. Advantages of the proposed approach include plausibility of the underlying assumptions, ability to assess plausibility of specific experimental outcomes through their likelihood, and plausibility of confidence intervals.

Myers, L E; McQuay, L J; Hollinger, F B

1994-01-01

359

CH and C2 measurements imply a radical pool within a pool in acetylene flames.  

PubMed

Measured CH and C2 profiles show a striking resemblance as a function of time in a series of seven well-characterized fuel-rich (phi=1.2-2.0) non-sooting acetylene flames. This implied commonality and interrelationship are unexpected as these radicals have dissimilar chemical kinetic natures. As a result, a rigorous examination was undertaken of the behavior of each of the hydrocarbon species known to be present, C, CH, CH2, CH3, CH4, CHO, CHOH, CH2O, CH2OH, CH3O, CH3OH, C2, C2H, C2H2, CHCO, CH2CO, and C2O. This emphasized the main region where CH and C2 are observed (50-600 micros) and reduced the kinetic reactions to only those that operate efficiently and are dominant. It was immediately apparent that this region of the flame reflects the nature of a hydrogen flame heavily doped with CO and CO2 and containing traces of hydrocarbons. The radical species, H, OH, O, along with H2, H2O, and O2, form an important controlling radical pool that is in partial equilibrium, and the concentrations of each of the hydrocarbon radicals are minor to this, playing secondary roles. As a result, the dominant fast reactions are those between the hydrocarbons and the basic hydrogen/oxygen radicals. Hydrocarbon-hydrocarbon reactions are unimportant here at these equivalence ratios. CH and C2 are formed and destroyed on a sub-microsecond time scale so that their flame profiles are the reflection of a complex kinetically dynamic system. This is found to be the case for all of the hydrocarbon species examined. As might be expected, these rapidly form steady-state distributions. However, with the exceptions of C, CHO, CHOH, and CH2O, which are irreversibly being oxidized, the others all form an interconnected hydrocarbon pool that is under the control of the larger hydrogen radical pool. The hydrocarbon pool can rapidly adjust, and the CH and C2 decay together as the pool is drained. This is either by continuing oxidation in less rich mixtures, or in richer flames where this is negligible by the onset of hydrocarbon-hydrocarbon reactions. The implications of such a hydrocarbon pool are significant. It introduces a buffering effect on their distribution and provides the indirect connection between CH and C2. Moreover, because they are members of this radical pool, flame studies alone cannot answer questions concerning their specific importance in combustion other than their contributing role to this pool. The presence of such a pool modifies the exactness that is needed for kinetic mechanisms, and knowledge of every species in the system no longer is necessary. Furthermore, as rate constants become refined, it will allow for the calculation of the relative concentrations of the hydrocarbon species and facilitate reduced kinetic mechanisms. It provides an explanation for previous isotopically labeled experiments and illustrates the difficulty of exactly identifying in flames the role of individual species. It resolves the fact that differing kinetic models can show similar levels of accuracy and has implications for sensitivity analyses. It finally unveils the mechanism of the flame ionization detector and has implications for the differing interpretations of diamond formation mechanisms. PMID:17388296

Schofield, Keith; Steinberg, Martin

2007-02-28

360

Fluorometric assay for aflatoxins  

SciTech Connect

The method that is now widely adopted by the government laboratories for the assay of individual aflatoxin components (B/sub 1/, B/sub 2/, G/sub 1/, and G/sub 2/) utilizes a TLC technique. The extraction and clean-up steps of this technique were further researched but the method is still time consuming. It is, therefore, very important to develop a rapid and accurate assay technique for aflatoxins. The current research proposes a technique which utilizes a Turner Fluorometer.

Chakrabarti, A.G.

1984-11-01

361

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

362

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

2011-12-08

363

Small molecular inhibitors of miR-1 identified from photocycloadducts of acetylenes with 2-methoxy-1,4-naphthalenequinone.  

PubMed

Small molecules which can modulate endogenous microRNAs are important chemical tools to study microRNA regulational network. In this Letter we screened the [2+2] photocycloadducts of 2-methoxy-1,4-naphthalenequinone with a series of aryl acetylenes on their activity to modulate endogenous microRNAs. A potent inhibitor of the muscle-specific miR-1 which is closely related with cardiac development and disease was identified. The small molecular inhibitor was the cyclobutene type product derived from the photocycloaddition of 2-methoxy-1,4-naphthalenequinone with tert-butyl (5-(phenylethynyl)quinolin-8-yl) carbonate. Analogues of the small molecular inhibitor were then prepared using similar photocycloaddition reactions for evaluation on inhibition activity on miR-1 to provide structure-activity relationship of the miR-1 inhibitor. PMID:23685176

Tan, Su-Bee; Huang, Chengmei; Chen, Xuejiao; Wu, Yihan; Zhou, Mi; Zhang, Chenyu; Zhang, Yan

2013-04-30

364

Histrionicotoxins: Roentgen-Ray Analysis of the Novel Allenic and Acetylenic Spiroalkaloids Isolated from a Colombian Frog, Dendrobates histrionicus  

PubMed Central

The structures and absolute configuration of two unique alkaloids isolated from the Colombian frog, Dendrobates histrionicus, have been elucidated by Roentgen-ray (x-ray) crystallography. Histrionicotoxin is (2pR, 6S, 7pS, 8aS)-7-(cis-1-buten-3-ynyl)-8-hydroxy-2-(cis-2-penten-4- ynyl)-1-azaspiro[5.5] undecane, while in dihydro-isohistrionicotoxin the acetylenic 2-pentenynyl side chain is replaced by an allenic 2-(3,4 pentadienyl) substituent. Dendrobates histrionicus exhibits remarkable interpopulational variations in amounts and composition of skin toxins, in behavior, and in phenotypic characters, aspects of which are illustrated in a color plate. The histrionico-toxins are the third class of alkaloids isolated from the defensive skin secretions of Neotropical (Dendrobatidae) frogs. Images

Daly, John W.; Karle, Isabella; Myers, Charles W.; Tokuyama, Takashi; Waters, James A.; Witkop, Bernhard

1971-01-01

365

Direct measurements of collisional Raman line broadening in the S-branch transitions of acetylene (C2H2)  

NASA Astrophysics Data System (ADS)

We report direct measurements of the self- and N2-broadened Raman S-branch linewidths of acetylene (C2H2), obtained by employing time-resolved picosecond rotational coherent anti-Stokes Raman scattering spectroscopy. Using broadband 115-ps pump and Stokes pulses (~135 cm-1 bandwidth) and a spectrally narrowed 90-ps probe pulse (~0.2 cm-1 bandwidth), Raman-coherence lifetimes are measured at room temperature for the S-branch (?J = +2) transitions associated with rotational quantum number J = 3-25. These directly measured Raman-coherence lifetimes, when converted to collisional linewidth broadening coefficients, differ from the previously reported broadening coefficients extracted from theoretical calculations by 6%-35% for self-broadening for C2H2 and by up to 60% for N2-broadened C2H2.

Hsu, Paul S.; Stauffer, Hans U.; Jiang, Naibo; Gord, James R.; Roy, Sukesh

2013-10-01

366

Direct measurements of collisional Raman line broadening in the S-branch transitions of acetylene (C2H2).  

PubMed

We report direct measurements of the self- and N2-broadened Raman S-branch linewidths of acetylene (C2H2), obtained by employing time-resolved picosecond rotational coherent anti-Stokes Raman scattering spectroscopy. Using broadband 115-ps pump and Stokes pulses (?135 cm(-1) bandwidth) and a spectrally narrowed 90-ps probe pulse (?0.2 cm(-1) bandwidth), Raman-coherence lifetimes are measured at room temperature for the S-branch (?J = +2) transitions associated with rotational quantum number J = 3-25. These directly measured Raman-coherence lifetimes, when converted to collisional linewidth broadening coefficients, differ from the previously reported broadening coefficients extracted from theoretical calculations by 6%-35% for self-broadening for C2H2 and by up to 60% for N2-broadened C2H2. PMID:24160504

Hsu, Paul S; Stauffer, Hans U; Jiang, Naibo; Gord, James R; Roy, Sukesh

2013-10-21

367

Radioligand binding assay.  

PubMed

Characterization and cloning of the AT(1) and AT(2) receptors would not have been possible without an assay that could detect and measure the density and affinity of these receptors. The most frequently used, if not the only, methodological approach used to investigate these receptors is the radioligand binding assay performed either in a test tube with tissue-membrane preparations or cultured cells, or on tissue sections (the latter revealed by autoradiography). This chapter will only deal with the test-tube radioligand binding assay. In this assay, a radiolabeled ligand (labeled with (125)I or (3)H, for example) is incubated with a membrane preparation or cells in presence of receptor subtype-specific antagonist or agonist. After reaching equilibrium, the receptor-bound tracer is separated from the free tracer by rapid filtration through glass fiber filters or by centrifugation. The amount (cpm) of bound tracer is then used to calculate the density and affinity of each receptor subtype. Alternatively, other experiments can be designed to derive kinetics of association and dissociation or saturation. PMID:21331726

Thibault, G; L Schiffrin, E

2001-01-01

368

Buccal micronucleus cytome assay  

Microsoft Academic Search

The Buccal Micronucleus Cytome (BMCyt) assay is a minimally invasive method for studying DNA damage, chromosomal instability, cell death and the regenerative potential of human buccal mucosal tissue. This method is increasingly used in molecular epidemiological studies for investigating the impact of nutrition, lifestyle factors, genotoxin exposure and genotype on DNA damage, chromosome malsegregation and cell death. The biomarkers measured

Nina Holland; Claudia Bolognesi; Micheline Kirsch-Volders; Stefano Bonassi; Errol Zeiger; Siegfried Knasmueller; Philip Thomas; Michael Fenech

2009-01-01

369

Diagnostic assay device  

US Patent & Trademark Office Database

This invention relates to assays for an analyte in a liquid sample such as a body fluid. More particularly, the invention relates to a method and apparatus for the detection of a ligand in a body fluid such as urine or blood, which includes an immobilization zone for interfering agents in a sample.

Imrich; Michael Reece (Encinitas, CA)

2008-12-16

370

Interferon Assay Systems.  

National Technical Information Service (NTIS)

A number of human cell strains and lines, including those derived from normal tissues as well as tumors, were tested for suitability in interferon assays of different types. Cell strains of normal skin fibroblasts were the most sensitive cells tested, wit...

S. E. Grossberg P. Jameson J. J. Sedmak

1974-01-01

371

Aptima Combo2 Assay  

Center for Biologics Evaluation and Research (CBER)

Text Version... N. gonorrhoeae cells (250 fg/assay*). *The rRNA equivalents were calculated based on the genome size and estimated DNA:RNA ratio/cell of each ... More results from www.fda.gov/downloads/biologicsbloodvaccines/safetyavailability

372

Bacterial Assay of Urine.  

National Technical Information Service (NTIS)

The dip-slide technique for bacterial assay of urine has been found to be a competent method for isolating the usual organisms responsible for urinary tract infection. Being a simple device, reliable in transport, and commercially available, it would appe...

J. E. Sippel Z. Farid A. S. Diab

1972-01-01

373

Human health effects assays  

SciTech Connect

The literature review focuses on the potential health hazards of environmental chemicals. Environmental sampling of mercury, arsenic, cadmium, organic mercury, manganese, polychyclic aromatic hydrocarbons, chromium compounds, and dimethyl sulfate are included. Test systems used include Escherichia coli, Salmonella typhimurium, and Bacillus subtilis. Special aspects of bacterial assays are discussed. 142 references.

Sims, R.C.; Sims, J.L.; Dupont, R.R.

1984-06-01

374

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

375

Latitudinal Distribution of Ammonia and Upper Limits of Acetylene and Phosphine in Jupiter's Upper Troposphere and Lower Stratosphere  

NASA Astrophysics Data System (ADS)

Observations of the northern and southern hemispheres of Jupiter done with the Hubble Space Telescope Faint Object Spectrograph during May 19-25, 1992 and June 6, 1993 have been analyzed. Spectra at latitudes 6deg N, 15deg N, 20deg N, 25deg N, 48deg N, 65deg N, 12deg S, 25deg S, 33deg S, 48deg S, 65deg S, and the equator were taken along the central meridian. In addition features were observed, including an equatorial plume, the Great Red Spot, and the nearby SEB. The data were taken with the G190H grating, which covers a wavelength range of 180-230 nm, with several combinations of the 0.5" and 1" apertures and the red and blue detectors. A photochemical model combining the hydrocarbon, nitrogen, and phosphorus chemical cycles along with a rigorous multiple scattering radiative transfer model has been used to determine the altitude profiles of ammonia, acetylene, and phosphine as a function of latitude which are consistent with the measured albedos. It is found that up to midlatitudes, the altitude profiles of ammonia are fairly uniform with latitude. Hazes at high latitudes and the equatorial plume obscure molecular species and prevent their detection. Upper limits to the abundances of acetylene and phosphine are provided. Comparison of the Great Red Spot with other regions will also be presented. This analysis also yields constraints on the value of the vertical eddy diffusion coefficient between the ammonia cloud top and the tropopause. Our current best estimate for the value of K is 1.4x10(3) cm(2) s(-1) at 40 km above the 1 bar level and 1.5x10(4) cm(2) s(-1) at 17 km above 1 bar.

Edgington, S. G.; Atreya, S. K.; Trafton, L. M.; Caldwell, J. J.; Beebe, R. F.; Simon, A. A.; West, R. A.; Barnet, C.

1996-09-01

376

Rapid, sensitive, and validated method for detection of Salmonella in food by an enrichment broth culture – Nested PCR combination assay  

Microsoft Academic Search

A rapid nested PCR assay for detection of Salmonella from food was developed. The sensitivity of the assay developed was comparable to the traditional culture based methods with an advantage in reduction of assay time. The assay procedure with artificially contaminated samples was able to detect as low as 4CFU Salmonella\\/25g of food samples (sprout, carrot, cucumber and poultry meat).

Sunil D. Saroj; R. Shashidhar; Manisha Karani; Jayant R. Bandekar

2008-01-01

377

Exceptional reductions  

NASA Astrophysics Data System (ADS)

Starting from basic identities of the group E8, we perform progressive reductions, namely decompositions with respect to the maximal and symmetric embeddings of E7 × SU(2) and then of E6 × U(1). This procedure provides a systematic approach to the basic identities involving invariant primitive tensor structures of various irreps of finite-dimensional exceptional Lie groups. We derive novel identities for E7 and E6, highlighting the E8 origin of some well-known ones. In order to elucidate the connections of this formalism to four-dimensional Maxwell-Einstein supergravity theories based on symmetric scalar manifolds (and related to irreducible Euclidean Jordan algebras, the unique exception being the triality-symmetric {N}=2 stu model), we then derive a fundamental identity involving the unique rank-4 symmetric invariant tensor of the 0-brane charge symplectic irrep of U-duality groups, with potential applications in the quantization of the charge orbits of supergravity theories, as well as in the study of multi-center black hole solutions therein.

Marrani, Alessio; Orazi, Emanuele; Riccioni, Fabio

2011-04-01

378

MUTAGENICITY OF NITRO COMPOUNDS IN SALMONELLA TYPHIMURIUM IN THE PRESENCE OF FLAVIN MONONUCLEOTIDE IN A PREINCUBATION ASSAY  

EPA Science Inventory

A series of nitro compounds (18 aromatic and one aliphatic) was evaluated using a modification of the standard Salmonella typhimurium mutagenicity assay. reincubation protocol was used with flavin mononucleotide (FMN) incorporated into the assay mixture to facilitate nitro reduct...

379

Assay for superantigens.  

PubMed

This chapter describes a quantitative assay for the streptococcal superantigen, streptococcal pyrogenic exotoxin A (SPEA), which can be used in broth, tissue-culture media, and certain sera. The protocol can be adapted to allow measurement of any bacterial superantigen or protein toxin, using different oligonucleotides to amplify the coding sequences from bacterial DNA. Previously, measurement of bacterial toxins such as SPEA was limited by poor test sensitivity and test samples could only be analyzed if concentrated. Techniques included Ouchterlony immunodiffusion or enzyme-linked immuno-sorbent assay (ELISA), although the lower limit of detection was 100-fold greater than that achievable in this system. (1-3) Recent methods described have achieved improved sensitivities, some using sandwich ELISA techniques, others using competitive ELISA techniques. (4-8). PMID:21340965

Sriskandan, S

2000-01-01

380

Growth cone collapse assay.  

PubMed

Growth cone collapse is an easy and efficient test for detecting and characterizing axon guidance activities secreted or expressed by cells. It can also be used to dissect signaling pathways by axon growth inhibitors and to isolate therapeutic compounds that promote axon regeneration. Here, we describe a growth cone collapse assay protocol used to study signal transduction mechanisms of the repulsive axon guidance molecule ephrin-A5 in hippocampal neurons. PMID:23681632

Yue, Xin; Son, Alexander I; Zhou, Renping

2013-01-01

381

Radioreceptor assay for sirolimus  

Microsoft Academic Search

Objectives: To develop a radioreceptor assay (RRA) for sirolimus (rapamycin, RAPA).Methods: A direct methanol extraction was used to prepare 45 patient samples for the RRA. Results were compared to the results obtained previously using high-performance liquid chromatography (HPLC). Between-run precision, recovery, and drug interference studies were also performed.Results: The RRA is sensitive to 1.0 ?g\\/L RAPA equivalents in whole blood.

Nancy Goodyear; Kimberly L. Napoli; Jayasimha N. Murthy; Barry D. Kahan; Steven J. Soldin

1996-01-01

382

Assay for calcium channels  

Microsoft Academic Search

This chapter focuses on biochemical assays for Ca\\/sup 2 +\\/-selective channels in electrically excitable membranes which are blocked in electrophysiological and pharmacological experiments by verapamil, 1,4-dihydropyridines, diltiazen (and various other drugs), as well as inorganic di- or trivalent cations. The strategy employed is to use radiolabeled 1,4-dihydropyridine derivatives which block calcium channels with EDââ values in the nanomolar range. Although

H. Glossmann; D. R. Ferry

1985-01-01

383

Chloramphenicol acetyltransferase assay.  

PubMed

When a transient or stable transfection assay is developed for a promoter, a primary objective is to quantify promoter strength. Because transfection efficiency in such assays can be low, promoters are commonly fused to heterologous reporter genes that encode enzymes that can be quantified using highly sensitive assays. The reporter protein's activity or fluorescence within a transfected cell population is approximately proportional to the steady-state mRNA level. In this protocol, cells transfected with an Escherichia coli transposon chloramphenicol acetyltransferase (CAT) reporter plasmid are lysed by repeated cycles of freezing and thawing and cellular debris is removed by centrifugation. The lysate is incubated with [(14)C]chloramphenicol and acetyl-coenzyme A; CAT catalyzes the acetylation of chloramphenicol. The acetylated products and the unmodified reactants are separated from the aqueous solution by organic extraction with ethyl acetate. Acetylation is monitored by autoradiography following thin-layer chromatography (TLC) to separate the acetylated from the unacetylated forms. The percent conversion of [(14)C]chloramphenicol to acetyl-[(14)C]chloramphenicol can be measured by PhosphorImager analysis of the TLC plate, by excising the radioactive spots from the TLC plate and counting in a scintillation counter, or by densitometry analysis of an autoradiograph. The acetylated (14)C-labeled product can also be quantified without TLC by organic extraction and scintillation counting using reagent-grade chemicals. PMID:20439409

Smale, Stephen T

2010-05-01

384

Insect vector transmission assays.  

PubMed

Phytoplasmas are transmitted in a persistent propagative manner by phloem-feeding vectors belonging to the order Hemiptera, suborder Homoptera. Following acquisition from the infected source plant, there is a latent period before the vector can transmit, so transmission assays consist of three basic steps: acquisition, latency, and inoculation. More than 90 vector species (plant-, leafhoppers, and psyllids) have been discovered so far but many others are still undiscovered, and their role in spreading economically important crop diseases is neglected. Therefore, screening for vectors is an essential step in developing rational control strategies targeted against the actual vectors for phytoplasma-associated diseases. The mere detection of a phytoplasma in an insect does not imply that the insect is a vector; a transmission assay is required to provide conclusive evidence. Transmission experiments can be carried out using insects from phytoplasma-free laboratory colonies or field-collections. Moreover, transmission assays can be performed by feeding vectors on an artificial diet through Parafilm(®), after which phytoplasmas can be detected in the sucrose feeding medium by PCR. Transmission trials involve the use of different techniques according to the biology of the different vector species; planthoppers, leafhoppers, and psyllids. PMID:22987407

Bosco, Domenico; Tedeschi, Rosemarie

2013-01-01

385

Comparative Evaluation of Three Assays for Measurement of Dengue Virus Neutralizing Antibodies  

Microsoft Academic Search

Plaque reduction neutralization tests (PRNTs) are commonly used for measuring levels of dengue virus (DENV) neutralizing antibodies. However, these assays lack a standardized format, generally have a low sample throughput, and are labor-intensive. The objective of the present study was to evaluate two alternative DENV neutral- izing antibody assays: an enzyme-linked immunosorbent assay-based microneutralization (MN) assay, and a fluorescent antibody

J. Robert Putnak; Rafael de la Barrera; Timothy Burgess; Jorge Pardo; Francis Dessy; Dirk Gheysen; Yves Lobet; Sharone Green; Timothy P. Endy; Stephen J. Thomas; Kenneth H. Eckels; Bruce L. Innis; Wellington Sun

386

Pathways and kinetics of chlorinated ethylene and chlorinated acetylene reaction with Fe(O) particles  

Microsoft Academic Search

Pathways and kinetics through which chlorinated ethylenes and their daughter products react with Fe(O) particles were investigated through batch experiments. Substantial intra- and interspecies inhibitory effects were observed, requiring the use of a modified Langmuir-Hinshelwood-Hougen-Watson (LHHW) kinetic model in which species compete for a limited number of reactive sites at the particle-water interface. Results indicate that reductive β-elimination accounts for

William A. Arnold; A. Lynn Roberts

2000-01-01

387

Acetylene-argon plasmas measured at an rf-biased substrate electrode for diamond-like carbon deposition: II. Ion energy distributions  

Microsoft Academic Search

Ion energy distributions (IEDs) have been determined at the radio frequency (rf)-biased electrode in an inductively coupled acetylene-argon plasma for various substrate bias voltages and frequencies under conditions suitable for diamond-like carbon (DLC) and polymer-like film deposition. These are compared with those obtained at a capacitively coupled plasma grounded wall. In the former, for pressures <25 mTorr, the IEDs exhibit

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

2011-01-01

388

Synthesis and SAR of centrally active mGlu5 positive allosteric modulators based on an aryl acetylenic bicyclic lactam scaffold  

PubMed Central

This Letter describes the hit-to-lead progression and SAR of a series of biphenyl acetylene compounds derived from an HTS screening campaign targeting the mGlu5 receptor. ‘Molecular switches’ were identified that modulated modes of pharmacology, and several compounds within this series were shown to be efficacious in reversal of amphetamine induced hyperlocomotion in rats after i.p. dosing, a preclinical model that shows similar positive effects with known antipsychotic agents.

Williams, Richard; Manka, Jason T.; Rodriguez, Alice L.; Vinson, Paige N.; Niswender, Colleen M.; Weaver, C. David; Jones, Carrie K.; Conn, P. Jeffrey; Lindsley, Craig W.

2012-01-01

389

Acetylene-Substituted Two-Photon Absorbing Molecules With Rigid Elongated Pi-Conjugation: Synthesis, Spectroscopic Properties and Two-Photon Fluorescence Cell Imaging Applications  

Microsoft Academic Search

Two asymmetrical molecules with substituted acetylene as central rigid elongated conjugation are reported as potential chromophores\\u000a for two-photon microscopic imaging. These molecules consist of a typical D–?–A structure, have different donors (D), the same\\u000a ?-conjugated center (?) and the same acceptor (A). Structural characterization and spectroscopic properties, including single-photon\\u000a (linear) absorption, quantum yields, single-photon fluorescence, and two-photon absorption spectra, were

Bo Liu; Hai-Li Zhang; Jun Liu; Zhen-Li Huang; Yuan-Di Zhao; Qing-Ming Luo

2007-01-01

390

Numerical analysis of the effect of acetylene and benzene addition to low-pressure benzene-rich flat flames on polycyclic aromatic hydrocarbon formation  

SciTech Connect

A modification of the CHEMKIN II package has been proposed for modeling addition of an arbitrary species at an arbitrary temperature to an arbitrary distance from the burner along a flat flame. The modified program was applied to the problem of addition of acetylene or benzene to different positions of a 40-Torr, {phi}=2.4 benzene/O{sub 2}/40%-N{sub 2} premixed flame to reach final equivalence ratios of {phi}=2.5 and 2.681. The results obtained showed that acetylene addition to early positions of the flame led to significant increase in pyrene production rates, but pyrene concentrations were lower in the flames with acetylene addition in both the {phi}=2.5 and 2.681 cases. Addition of benzene to the flame did not alter pyrene production rates in either the {phi}=2.5 or 2.681 cases; however, for {phi}=2.5, pyrene concentrations increased with benzene addition, while for {phi}=2.681, pyrene contents decreased in comparison to the correspondent flames with no addition. Acetylene addition led to a significant increase in pyrene production rates, but the pyrene levels dropped due to increase in the flow velocity. Pyrene production rates were not sensitive to benzene addition, but pyrene contents increased with benzene addition when the flow velocity decreased. These results show that PAH concentration changes accompanying species addition to flames should be interpreted carefully, because an increase or decrease in the content of a PAH species does not necessarily reflect an effect on its formation rate or mechanism. (author)

Kunioshi, Nilson [Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871 (Japan); Komori, Seisaku [6th Group, Central Research Laboratory, Hamamatsu Photonics K. K. 500 Hirakuchi, Hamakita City, Shizuoka 434-8601 (Japan); Fukutani, Seishiro [Department of System Engineering, Okayama Prefectural University, 111 Kuboki, Soja, Okayama 719-1197 (Japan)

2006-10-15

391

Chemistry and kinetics of chemical vapor deposition of pyrocarbon—II pyrocarbon deposition from ethylene, acetylene and 1,3-butadiene in the low temperature regime  

Microsoft Academic Search

Pyrocarbon deposition from ethylene, acetylene and 1,3-butadiene was studied with a vertical hot-wall reactor at ambient pressure and 1000 °C; initial partial pressures of the hydrocarbons and residence time were varied. Steady-state pyrocarbon deposition rates and corresponding compositions of the gas-phase were determined. Reaction models describing homogeneous gas-phase and heterogeneous pyrocarbon deposition reactions were derived and applied for simulation of

A. Becker; K. J. Hüttinger

1998-01-01

392

Does Marcus-Hush theory really work Optical studies of intervalence transfer in acetylene-bridged biferrocene monocation at infinite dilution and at finite ionic strengths  

SciTech Connect

Intervalence charge-transfer data for acetylene-bridged biferrocene monocation (Bf{sup +}) have been collected in five solvents in the presence and absence of excess electrolyte and in the limit of infinite chromophore dilution. The study was motivated by earlier work which demonstrated that the intervalence absorption maximum for Bf{sup +} in methylene chloride could vary substantially with both chromophore concentration and added electrolyte concentration. In the present study similar (but smaller) variations are found in other solvents.

Blackbourn, R.L.; Hupp, J.T. (Northwestern Univ., Evanston, IL (USA))

1990-03-08

393

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

394

Synthesis and X-ray Crystallographic Structural Determination of the Acetylene Complex (ETA5-C5H5)2W2(CO)4(C2H2).  

National Technical Information Service (NTIS)

Reaction of photogenerated (ETA5-C5H5)2W2(CO)4 with acetylene at 25 yields a complex of the formula (ETA5-C5H5)2W2(CO)4(C2H2). The crystal structure of the complex shows it to have a tetrahedrane-like W2C2 core. The C-C bond distance of the C2H2 unit is 1...

D. S. Ginley C. R. Bock M. S. Wrighton B. Fischer R. Bau

1977-01-01

395

Comparison of two versions of the acetylene inhibition\\/soil core method for measuring denitrification loss from an irrigated wheat field  

Microsoft Academic Search

Two versions of the acetylene inhibition (AI)\\/soil core method were compared for the measurement of denitrification loss\\u000a from an irrigated wheat field receiving urea-N at a rate of 100?kg?ha–1. With AI\\/soil core method A, the denitrification rate was measured by analysing the headspace N2O, followed by estimation of N2O dissolved in the solution phase using Bunsen absorption coefficients. With AI\\/soil

T. Mahmood; R. Ali; F. Azam; K. A. Malik

1999-01-01

396

Three-step laser induced ionization of Ir and Hg atoms in an air-acetylene flame and a gas cell  

SciTech Connect

The feasibility and the application of three-step excitation and ionization schemes with excimer-pumped, pulsed dye lasers have been studied in the case of Iridium atoms in an air acetylene flame and of Mercury atoms in a gas cell. The detection limits obtained were 0.2 ng/ml in the case of Ir and 10{sup 7} atoms per cubic centimeter of air.

Matveev, Oleg I.; Cavalli, Paolo; Omenetto, Nicolo' [EC, Joint Research Centre Environment Institute, Ispra (Varese) (Italy)

1995-04-01

397

Efficient synthesis of stable phosphonate ylides and ?phosphonate esters: reaction between activated acetylenes and triphenylphosphite in the presence of sulfonamide and heterocyclic NH-acids.  

PubMed

An efficient synthesis of stable phosphonate ylides and phosphonate esters is described via a ?one-pot reaction between activated acetylenes and triphenylphosphite in the presence of sulfonamides and heterocyclic ?NH-acids. Single X-ray diffraction analysis and NMR studies were used in characterizing the ylides and phosphonate ester products. Dynamic NMR studies performed on a phosphonate ylide allowed the calculation of the free energy barrier for the inter-conversion between the geometrical isomers (E) and (Z). PMID:20673221

Charati, Faramarz Rostami; Maghsoodlou, Malek Taher; Habibi-Khorassani, Sayyed Mostafa; Hazeri, Nourallah; Ebrahimi, Ali; Hossaini, Zinatossadat; Ebrahimi, Pouneh; Maleki, Nariman; Adhamdoust, Sayyed Reza; Farahani, Fatemeh Vasheghani; Marandi, Ghasem; Sobolev, Alexandre; Makha, Mohamed

2011-01-01

398

Acetylene associates (C2H2)n (n = 2–4). IR-spectra in argon matrixes and quantum-chemical calculations  

NASA Astrophysics Data System (ADS)

IR Fourier acetylene spectra were obtained in argon matrixes over a wide range of dilutions at various temperatures of gas-phase deposition. (C2H2)n (n = 2–4) associate bands were identified. Referring is based on studying the dynamics of spectra and quantum-chemical calculations using MP-2 and B3LYP methods with 6-311++G (d,p) and cc-pVTZ bases.

Golovkin, A. V.; Davlyatshin, D. I.; Serebrennikova, A. L.; Serebrennikov, L. V.

2013-10-01

399

Chaos and dynamics on 0.5-300 ps time scales in vibrationally excited acetylene: Fourier transform of stimulated-emission pumping spectrum  

Microsoft Academic Search

A recently proposed technique based on the Fourier transform of the spectrum is applied to the stimulated-emission pumping spectrum of acetylene at ~26 500 cm-1 above the vibrational ground state. Correlations on two different time scales (~3 and ~45 ps) were found from analysis of low-resolution (0.3 cm-1) and high-resolution (0.05 cm-1) spectra, respectively. Additional structure produced dynamic information on

J. P. Pique; Y. Chen; R. W. Field; J. L. Kinsey

1987-01-01

400

Chaos and dynamics on 0. 5--300 ps time scales in vibrationally excited acetylene: Fourier transform of stimulated-emission pumping spectrum  

Microsoft Academic Search

A recently proposed technique based on the Fourier transform of the spectrum is applied to the stimulated-emission pumping spectrum of acetylene at --26 500 cm⁻¹ above the vibrational ground state. Correlations on two different time scales (--3 and --45 ps) were found from analysis of low-resolution (0.3 cm⁻¹) and high-resolution (0.05 cm⁻¹) spectra, respectively. Additional structure produced dynamic information on

J. P. Pique; Y. Chen; R. W. Field; J. L. Kinsey

1987-01-01

401

The Assignment of the Vibrational Spectra of the C4 Hydrocarbons Butyne1, Butene1 and Vinyl Acetylene, to the Normal Modes of Vibration of These Molecules  

Microsoft Academic Search

An attempt has been made to assign all the normal modes of vibration of the C4 hydrocarbons butyne?1, butene?1, and vinyl acetylene, in terms of frequencies observed in the infra-red and Raman spectra. It has been found to be possible to do this in a satisfactory manner which takes into account the structural similarities of these and other hydrocarbon molecules.

N. Sheppard

1949-01-01

402

Rubisco activase activity assays.  

PubMed

Ribulose-1,5-bisphosphate (RuBP) carboxylase/oxygenase (Rubisco) activase functions as a mechano-chemical motor protein using the energy from ATP hydrolysis to contort the structure of its target protein, Rubisco. This action modulates the activation state of Rubisco by removing tightly-bound inhibitory sugar-phosphates from Rubisco's catalytic sites, thereby restoring the sites to catalytic competence. This chapter reports methods developed for assaying the two activities of Rubisco activase: ATP hydrolysis and Rubisco activation. PMID:20960144

Barta, Csengele; Carmo-Silva, A Elizabete; Salvucci, Michael E

2011-01-01

403

Rapid Colorimetric Assay for Antimicrobial Susceptibility Testing of Pseudomonas aeruginosa  

PubMed Central

A colorimetric assay based on the reduction of a tetrazolium salt {2,3-bis[2-methyloxy-4-nitro-5-sulfophenyl]-2H-tetrazolium-5-carboxanilide (XTT)} for rapidly determining the susceptibility of Pseudomonas aeruginosa 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 assay could provide a useful method for rapidly determining the susceptibility of P. aeruginosa to bactericidal antibiotics.

Tunney, Michael M.; Ramage, Gordon; Field, Tyler R.; Moriarty, Thomas F.; Storey, Douglas G.

2004-01-01

404

Acetylene Dithiolate Linking up the [Tp'W(CO)(CN)] Moiety with Ru(II) or Pd(II.).  

PubMed

A series of heterodinuclear complexes with acetylene dithiolate (acdt(2-) ) as the bridging moiety were synthesised by a facile one-pot procedure that avoided use of the highly elusive acetylene dithiol. Generation of the W-Ru complex [Tp'W(CN)(CO)(C2 S2 )Ru(?(5) -C5 H5 )(PPh3 )] (Tp'=hydrotris(3,5-dimethylpyrazolyl)borate) and the W-Pd complexes [Tp'W(CN)(CO)(C2 S2 )Pd(dppe)] and [Tp'W(CO)2 (C2 S2 )Pd(dppe)][PF6 ] (dppe=1,2-bis(diphenylphoshino)ethane), which exhibit a [W(?(2) -?(2) -C2 S2 )M] core (M=Ru, Pd), was accomplished by using a transition-metal-assisted solvolytical removal of the Me3 Si-ethyl thiol protecting groups. All intermediate species of the reaction have been fully characterised. The highly coloured W-Ru complex [Tp'W(CN)(CO)(C2 S2 )Ru(?(5) -C5 H5 )(PPh3 )] shows reversible redox chemistry, as does the prototype complex [Tp'W(CO)2 (C2 S2 )Ru(?(5) -C5 H5 )(PPh3 )][PF6 ]. Single crystal X-ray diffraction and IR, EPR and UV/Vis spectroscopic studies in conjunction with DFT calculations prove the high electronic delocalisation of states over the acdt(2-) linker. Comparative studies revealed a higher donor strength and more pronounced dithiolate character of acdt(2-) in [Tp'W(CN)(CO)(C2 S2 )Ru(?(5) -C5 H5 )(PPh3 )] relative to [Tp'W(CO)2 (C2 S2 )Ru(?(5) -C5 H5 )(PPh3 )](+) . In addition, the influence of the overall complex charge on the metric parameters was investigated by single-crystal X-ray diffraction studies with the W-Pd complexes [Tp'WL2 (C2 S2 )Pd(dppe)] (L=(CN(-) )(CO) or (CO)2 ). The central [W(C2 S2 )Pd] units exhibit high structural similarity, which indicates the extensive delocalisation of charge over both metals. PMID:24026953

Seidel, Wolfram W; Dachtler, Woldemar; Semmler, Julia; Tänzler, Marco; Folk, Manuel; Villinger, Alexander

2013-09-11

405

On the effect of varying constraints in the quantum mechanics only modeling of enzymatic reactions: the case of acetylene hydratase.  

PubMed

Quantum mechanics only (QM-only) studies of enzymatic reactions employ a coordinate-locking scheme, in which certain key atoms at the periphery of the chosen cluster model are fixed to their crystal structure positions. We report a case study on acetylene hydratase to assess the uncertainties introduced by this scheme. Random displacements of 0.1, 0.15, and 0.2 Å were applied at the ten terminal atoms fixed in the chosen 116-atom cluster model to generate sets of ten distorted structures for each given displacement. The relevant stationary points were reoptimized under these modified constraints to determine the variations of the computed energies and geometries induced by the displacements of the fixed atoms. Displacements of 0.1 Å cause a relatively minor perturbation that can be accommodated during geometry optimization, resulting in rather small changes in key bond distances and relative energies (typically of the order of 0.01 Å and 1 kcal/mol), whereas displacements of 0.2 Å lead to larger fluctuations (typically twice as high) and may sometimes even cause convergence to different local minima during geometry optimization. A literature survey indicates that protein crystal structures with a resolution higher than 2.0 Å are normally associated with a coordinate error of less than 0.1 Å for the backbone atoms. Judging from the present results for acetylene hydratase, such uncertainties seem tolerable in the design of QM-only models with more than 100 atoms, which are flexible enough to adapt during geometry optimization and thus keep the associate uncertainties in the computed energies and bond distances at tolerable levels (around 1 kcal/mol and 0.01 Å, respectively). On the other hand, crystal structures with significantly lower resolution should be used with great caution when setting up QM-only models because the resulting uncertainties in the computational results may become larger than acceptable. The present conclusions are mostly based on systematic DFT(B3LYP) calculations with a medium-size basis set. Test calculations on selected structures confirm that similar results are obtained for larger basis sets, different functionals (?B97X, BMK, M06), and upon including solvation and zero-point corrections, even though the fluctuations in the computed relative energies become somewhat larger in some cases. PMID:23517056

Liao, Rong-Zhen; Thiel, Walter

2013-04-04

406

Convergence in the QM-only and QM/MM modeling of enzymatic reactions: A case study for acetylene hydratase.  

PubMed

We report systematic quantum mechanics-only (QM-only) and QM/molecular mechanics (MM) calculations on an enzyme-catalyzed reaction to assess the convergence behavior of QM-only and QM/MM energies with respect to the size of the chosen QM region. The QM and MM parts are described by density functional theory (typically B3LYP/def2-SVP) and the CHARMM force field, respectively. Extending our previous work on acetylene hydratase with QM regions up to 157 atoms (Liao and Thiel, J. Chem. Theory Comput. 2012, 8, 3793), we performed QM/MM geometry optimizations with a QM region M4 composed of 408 atoms, as well as further QM/MM single-point calculations with even larger QM regions up to 657 atoms. A charge deletion analysis was conducted for the previously used QM/MM model (M3a, with a QM region of 157 atoms) to identify all MM residues with strong electrostatic contributions to the reaction energetics (typically more than 2 kcal/mol), which were then included in M4. QM/MM calculations with this large QM region M4 lead to the same overall mechanism as the previous QM/MM calculations with M3a, but there are some variations in the relative energies of the stationary points, with a mean absolute deviation (MAD) of 2.7 kcal/mol. The energies of the two relevant transition states are close to each other at all levels applied (typically within 2 kcal/mol), with the first (second) one being rate-limiting in the QM/MM calculations with M3a (M4). QM-only gas-phase calculations give a very similar energy profile for QM region M4 (MAD of 1.7 kcal/mol), contrary to the situation for M3a where we had previously found significant discrepancies between the QM-only and QM/MM results (MAD of 7.9 kcal/mol). Extension of the QM region beyond M4 up to M7 (657 atoms) leads to only rather small variations in the relative energies from single-point QM-only and QM/MM calculations (MAD typically about 1-2 kcal/mol). In the case of acetylene hydratase, a model with 408 QM atoms thus seems sufficient to achieve convergence in the computed relative energies to within 1-2 kcal/mol.Copyright © 2013 Wiley Periodicals, Inc. PMID:23913757

Liao, Rong-Zhen; Thiel, Walter

2013-08-01

407

Zebrafish assays of ciliopathies.  

PubMed

In light of the growing list of human disorders associated with their dysfunction, primary cilia have recently come to attention as being important regulators of developmental signaling pathways and downstream processes. These organelles, present on nearly every vertebrate cell type, are highly conserved structures allowing for study across a range of species. Zebrafish, in particular, have emerged as useful organisms in which to explore the consequences of ciliary dysfunction and to model human ciliopathies. Here, we present a range of useful techniques that allow for investigation of various aspects of ciliary function. The described assays capitalize on the hallmark gastrulation defects associated with ciliary defects as well as relative ease of visualization of cilia in whole-mount embryos. Further, we describe our recently developed assay for querying functionality of human gene variants in live developing embryos. Finally, a current catalog of known zebrafish ciliary mutant lines is included. The techniques presented here provide a basic toolkit for in vivo investigation of both the biological and genetic mechanisms underlying a growing class of human diseases. PMID:21951534

Zaghloul, Norann A; Katsanis, Nicholas

2011-01-01

408

Measuring antioxidant potential in corals using the FRAP assay  

Microsoft Academic Search

In this paper, we standardized a method for determining antioxidant potential in corals. This was determined using a simple, reproducible and inexpensive method: the ferric reducing\\/antioxidant potential (FRAP) assay. This procedure involves the reduction of FeIII-TPTZ to a blue colored FeII-TPTZ by biological antioxidants and chemical reductants, some of which might have no antioxidant activity in a sample. The FRAP

Sean P. Griffin; Ranjeet Bhagooli

2004-01-01

409

High-throughput assays for sirtuin enzymes: A microfluidic mobility shift assay and a bioluminescence assay  

Microsoft Academic Search

Silent information regulator or sirtuin (SIRT) enzymes are ?-nicotinamide adenine dinucleotide (oxidized) (NAD+)-dependent class III histone deacetylases. In this paper, two distinct assays to measure SIRT1 activity are described: a microfluidic mobility shift assay utilizing a fluorophore-labeled peptide substrate and a bioluminescence assay based upon quantitation of remaining NAD+. The mobility shift assay involves the electrophoretic separation of an N-acetyl-lysine-containing

Yichin Liu; Raphaele Gerber; John Wu; Trace Tsuruda; John D. McCarter

2008-01-01

410

REDUCTIVE TRANSFORMATION OF TRICHLOROETHENE CATALYZED BY COBALAMIN: REACTIVITIES OF THE INTERMEDIATES, ACETYLENE, CHLOROACETYLENE, AND THE DCE ISOMERS. (R825689C073)  

EPA Science Inventory

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

411

Measurements of hydrogen cyanide (HCN) and acetylene (C2H2) from the Infrared Atmospheric Sounding Interferometer (IASI)  

NASA Astrophysics Data System (ADS)

Hydrogen cyanide (HCN) and acetylene (C2H2) are ubiquitous atmospheric trace gases with medium lifetime, which are frequently used as indicators of combustion sources and as tracers for atmospheric transport and chemistry. Because of their weak infrared absorption, overlapped by the CO2 Q-branch near 720 cm-1, nadir sounders have up to now failed to measure these gases routinely. Taking into account CO2 line mixing we provide for the first time extensive measurements of HCN and C2H2 total columns at Reunion Island (21° S; 55° E) and Jungfraujoch (46° N; 8° E) in 2009-2010 using observations from the Infrared Atmospheric Sounding Interferometer (IASI). These are compared with local ground-based Fourier Transform InfraRed (FTIR) measurements and we demonstrate that the seasonality is well captured, except for HCN at Jungfraujoch. We also examine a nonspecific biomass burning plume over austral Africa and show that the emission ratios with respect to CO agree with previously reported values.

Duflot, V.; Hurtmans, D.; Clarisse, L.; R'honi, Y.; Vigouroux, C.; De Mazière, M.; Mahieu, E.; Servais, C.; Clerbaux, C.; Coheur, P.-F.

2012-10-01

412

Double-slit experiment with a polyatomic molecule: vibrationally resolved C 1s photoelectron spectra of acetylene  

NASA Astrophysics Data System (ADS)

We report the first evidence for double-slit interferences in a polyatomic molecule, which we have observed in the experimental carbon 1s photoelectron spectra of acetylene (or ethyne). The spectra have been measured over the photon energy range of 310-930 eV and show prominent oscillations in the intensity ratios ?g(?)/?u(?) for the vibrational quantum numbers ? = 0,1 and for the ratios ?s(? = 1)/?s(? = 0) for the symmetry s = g,u. The experimental findings are in very good agreement with ab initio density functional theory (DFT) calculations and are compatible with the Cohen-Fano mechanism of coherent emission from two equivalent atomic centers. This interpretation is supported by the qualitative predictions of a simple model in which the effect of nuclear recoil is taken into account to the lowest order. Our results confirm the delocalized character of the core hole created in the primary photoionization event and demonstrate that intramolecular core-hole coherence can survive the decoherent influence associated with the asymmetric nuclear degrees of freedom which are characteristic of polyatomic molecules.

Argenti, L.; Thomas, T. D.; Plésiat, E.; Liu, X.-J.; Miron, C.; Lischke, T.; Prümper, G.; Sakai, K.; Ouchi, T.; Püttner, R.; Sekushin, V.; Tanaka, T.; Hoshino, M.; Tanaka, H.; Decleva, P.; Ueda, K.; Martín, F.

2012-03-01

413

Computational study of the reaction of P+ with acetylene: does spin-crossing play a significant role?  

PubMed

A computational study of the reaction of P(+)((3)P) with acetylene has been carried out. The only exothermic products correlating with the reactants are PCCH(+)((2)?) + H((2)S). Two different pathways leading to these products that are apparently barrier-free have been found. Both pathways involve isomerization into open-chain intermediates followed by direct elimination of a hydrogen atom. The possibility of spin-crossing has been considered because the species on the singlet surface are considerably more stable than those on the triplet one. On the singlet surface, there are other possible channels for the reaction, namely, cyclic PC(2)H(+)((2)A') + H((2)S) and CCP(+)((1)?) + H(2) ((1)?(g)(+)). A computational kinetic study shows that, in agreement with the experimental evidence, the major products are PCCH(+)((2)?) + H((2)S) at all temperatures. Only at very high temperatures is CCP(+)((1)?) + H(2) ((1)?(g)(+)) formed in non-negligible amounts. Therefore, only PCCH(+) should be formed in the interstellar medium. PMID:22352296

Cimas, Álvaro; Rayón, Víctor M; Largo, Antonio

2012-03-07

414

Synthesis and characterization of acetylene-linked bisphenalenyl and metallic-like behavior in its charge-transfer complex.  

PubMed

We prepared and isolated a phenalenyl-based neutral hydrocarbon (1 b) with a biradical index of 14%, as well as its charge-transfer (CT) complex 1 b-F(4)-TCNQ. The crystal structure and the small HOMO-LUMO gap assessed by electrochemical and optical methods support the singlet-biradical contribution to the ground state of the neutral 1 b. This biradical character suggests that 1 b has the electronic structure of phenalenyl radicals coupled weakly through an acetylene linker, that is, some independence of the two phenalenyl moieties. The monocationic species 1 b*+ was obtained by reaction with the organic electron acceptor F4-TCNQ. The cationic species has a small disproportionation energy deltaE for the reaction 2 x 1 b*+ <==> 1 b + 1 b2+, which presumably originates from the independence of the phenalenyl moieties. The small deltaE led to a small on-site Coulombic repulsion U(eff) = 0.61 eV in the CT complex. Moreover, a very effective orbital overlap of the phenalenyl rings between molecules afforded a relatively large transfer integral t = 0.09 eV. The small U(eff)/4t ratio (= 1.7) resulted in a metallic-like conductive behavior at around room temperature. Below 280 K, the CT complex showed a transition into a semiconductive state as a result of bond formation between phenalenyl and F4-TCNQ carbon atoms. PMID:17828719

Kubo, Takashi; Goto, Yuko; Uruichi, Mikio; Yakushi, Kyuya; Nakano, Masayoshi; Fuyuhiro, Akira; Morita, Yasushi; Nakasuji, Kazuhiro

2007-11-01

415

Optimization of Acetylene Black Conductive Additive andPolyvinylidene Difluoride Composition for High Power RechargeableLithium-Ion Cells  

SciTech Connect

Fundamental electrochemical methods were applied to study the effect of the acetylene black (AB) and the polyvinylidene difluoride (PVDF) polymer binder on the performance of high-power designed rechargeable lithium ion cells. A systematic study of the AB/PVDF long-range electronic conductivity at different weight ratios is performed using four-probe direct current tests and the results reported. There is a wide range of AB/PVDF ratios that satisfy the long-range electronic conductivity requirement of the lithium-ion cathode electrode; however, a significant cell power performance improvement is observed at small AB/PVDF composition ratios that are far from the long-range conductivity optimum of 1 to 1.25. Electrochemical impedance spectroscopy (EIS) tests indicate that the interfacial impedance decreases significantly with increase in binder content. The hybrid power pulse characterization results agree with the EIS tests and also show improvement for cells with a high PVDF content. The AB to PVDF composition plays a significant role in the interfacial resistance. We believe the higher binder contents lead to a more cohesive conductive carbon particle network that results in better overall all local electronic conductivity on the active material surface and hence reduced charge transfer impedance.

Liu, G.; Zheng, H.; Battaglia, V.S.; Simens, A.S.; Minor, A.M.; Song, X.

2007-07-01

416

Reactivity of free radical intermediates that form spontaneously during molecular chlorine action on acetylene and vinyl monomers at low temperatures  

NASA Astrophysics Data System (ADS)

In this study, ESR, UV, VIS and IR spectroscopy, as well as chromatography, calorimetry, and elemental analysis were employed to show the spontaneous formation of free radicals under low-temperature action of molecular chlorine on acetylene monomer p-diethynylbenzene and on vinyl monomer acrylamide. These radicals are able to initiate a chain reaction of polymerization of monomers at low temperatures. This reaction results in a completely soluble polymer with a 25% yield, while an insoluble cross-linked polymer has been obtained during polymerization of p-diethynylbenzene initiated by other means. For example, under radiolysis by 1000 kGy the soluble fraction of obtained polymer was ~1%, while the overall yield was ~10%. p-Diethynylbenzene polymerizes at temperatures close to the melting temperature of chlorine (170 K). Polymerization of acrylamide takes place in the temperature range of 180-210 K with a ~10% yield of polymer. The low-temperature chlorination of a 20% solution of acrylamide in glycerol enables a twofold increase of the polymer yield and a tenfold decrease of the chlorine content in it.

Gordon, D. A.; Volodina, V. A.; Mikhailov, A. I.

2013-06-01

417

A new cytotoxic brominated acetylenic hydrocarbon from the marine sponge Haliclona sp. with a selective effect against human breast cancer.  

PubMed

Three acetylenic brominated derivatives were isolated from a Red Sea sponge, Haliclona sp. One of them, 18-bromooctadeca-9(E),17(E)-dien-7,15-diynoic acid (3), is a known metabolite, and the other two are new compounds, (1E,5E,12E,19E)-1,22-dibromodocosa-1,5,12,19-tetraen-3,14,21-triyne (1) and methyl 18-bromooctadeca-9(E),17(E)-dien-7,15-diynoate (2) which was isolated for the first time as a natural metabolite. Structures of all compounds were determined based on extensive spectroscopic measurements [1D (1H, 13C and DEPT) and 2D (HSQC, HMBC and NOESY) NMR, MS, UV, and IR]. All compounds, except 3, were evaluated for their cytotoxicity employing four cancer cell lines, i.e. MCF-7 (human breast cancer), HepG2 (human hepatocellular carcinoma), WI-38 (skin carcinoma), and Vero (African green monkey kidney). Compounds 1 and 2 had potent selective antitumour activity towards MCF-7 cells with IC50 values of 32.5 and 50.8 microM, respectively. PMID:23659175

Alarif, Walied M; Abdel-Lateff, Ahmed; Al-Lihaibi, Sultan S; Ayyad, Seif-Eldin N; Badria, Farid A

418

Measurements of hydrogen cyanide (HCN) and acetylene (C2H2) from the Infrared Atmospheric Sounding Interferometer (IASI)  

NASA Astrophysics Data System (ADS)

Hydrogen cyanide (HCN) and acetylene (C2H2) are ubiquitous atmospheric trace gases with medium lifetime, which are frequently used as indicators of combustion sources and as tracers for atmospheric transport and chemistry. Because of their weak infrared absorption, overlapped by the CO2 Q branch near 720 cm-1, nadir sounders have up to now failed to measure these gases routinely. Taking into account CO2 line mixing, we provide for the first time extensive measurements of HCN and C2H2 total columns at Reunion Island (21° S, 55° E) and Jungfraujoch (46° N, 8° E) in 2009-2010 using observations from the Infrared Atmospheric Sounding Interferometer (IASI). A first order comparison with local ground-based Fourier transform infraRed (FTIR) measurements has been carried out allowing tests of seasonal consistency which is reasonably captured, except for HCN at Jungfraujoch. The IASI data shows a greater tendency to high C2H2 values. We also examine a nonspecific biomass burning plume over austral Africa and show that the emission ratios with respect to CO agree with previously reported values.

Duflot, V.; Hurtmans, D.; Clarisse, L.; R'honi, Y.; Vigouroux, C.; De Mazière, M.; Mahieu, E.; Servais, C.; Clerbaux, C.; Coheur, P.-F.

2013-04-01

419

Pyrene-fluorene hybrids containing acetylene linkage as color-tunable emitting materials for organic light-emitting diodes.  

PubMed

New blue- to yellow-emitting materials have been developed by incorporating fluorene-based chromophores on pyrene core with acetylene linkage and using multifold palladium-catalyzed cross-coupling reactions. Both mono- and tetrasubstituted derivatives have been synthesized and characterized. The tetrasubstituted derivatives displayed red-shifted emission when compared to the monosubstituted derivative indicative of an extended conjugation in the former. End-capping with a diphenylamine unit further red-shifted the absorption and emission profiles and imparted a weak dipolar character to the molecules. Amine-containing derivatives displayed positive solvatochromism in the fluorescence spectra indicating a more polar excited state due to an efficient charge migration from the diphenylamine donor to the pyrene ?-acceptor. All of the derivatives were tested as emitting dopants with host material 4,4'-bis(9H-carbazol-9-yl)biphenyl (CBP) in a multilayered OLED and found to exhibit bright blue or yellow electroluminescence. The device utilizing 1,3,6,8-tetrasubstituted pyrene derivative as a dopant emitter displayed highest maximum luminescence 4630 cd/m(2) with power efficiency 3.8 lm/W and current efficiency 7.1 cd/A at 100 cd/m(2) attributable to the proper alignment of energy levels that led to the efficient harvesting of excitons. All of the devices exhibited color purity over a wide range of operating voltages. PMID:22443338

Thomas, K R Justin; Kapoor, Neha; Bolisetty, M N K Prasad; Jou, Jwo-Huei; Chen, Yu-Lin; Jou, Yung-Cheng

2012-04-04

420

Bioassay-Directed Isolation and Identification of Phytotoxic and Fungitoxic Acetylenes from Conyza canadensis.  

PubMed

Conyza canadensis (L.) Cronquist syn. (horseweed) is a problematic and invasive weed with reported allelopathic properties. To identify the phytotoxic constituents of the aerial parts, a systematic bioactivity-guided fractionation of the dichloromethane extract was performed. Three active enyne derivatives, (2Z,8Z)-matricaria acid methyl ester, (4Z,8Z)-matricaria lactone, and (4Z)-lachnophyllum lactone, were identified. The lactones inhibited growth of the monocot Agrostis stolonifera (bentgrass) and the dicot Lactuca sativa (lettuce) at 1 mg mL(-1), while the (2Z,8Z)-matricaria acid methyl ester was less active. In a dose-response screening of the lactones for growth inhibitory activity against Lemna paucicostata , (4Z)-lachnophyllum lactone was the most active with an IC(50) of 104 ?M, while the (4Z,8Z)-matricaria lactone was less active (IC(50) of 220 ?M). In a fungal direct bioautography assay, the two lactones at 10 and 100 ?g/spot inhibited growth of the plant pathogenic fungi Colletotrichum acutatum , Colletotrichum fragariae , and Colletotrichum gloeosporioides . In a dose-response screening of the lactones against six different plant pathogenic fungi, (4Z,8Z)-matricaria lactone was more active than the commercial fungicide azoxystrobin on Col. acutatum , Col. fragariae , and Col. gloeosporioides at 30 ?M and about as active as the commercial fungicide captan against Col. gloeosporioides , while (4Z)-lachnophyllum lactone was less active. PMID:22612410

Queiroz, Sonia C N; Cantrell, Charles L; Duke, Stephen O; Wedge, David E; Nandula, Vijay K; Moraes, Rita M; Cerdeira, Antonio L

2012-05-31

421

Enzymatic reduction studies of nitroheterocycles.  

PubMed

The nitroimidazole derivative Megazol is a highly active compound used against several strains of Trypanosoma cruzi, the causative agent of Chagas' disease (American trypanomiasis). With the aim of gaining an insight into the probable mode of action, the interaction of Megazol with different redox enzymes was studied in comparison to that of Nifurtimox and Metronidazole. The three nitroaromatic compounds are reduced by L-lactate cytochrome c-reductase, adrenodoxin reductase, and NADPH:cytochrome P-450 reductase (EC 1.6.2.4), the efficiencies of the enzymatic reductions being roughly related to the reduction potentials of these pseudo-substrates. As the enzyme responsible for the reduction of Megazol within the parasite has not yet been identified, the nitroimidazole was assayed with T. cruzi lipoamide dehydrogenase and trypanothione reductase. Megazol did not inhibit the physiological reactions but proved to be a weak substrate of both flavoenzymes. The single electron reduction of the compound by NADPH:cytochrome P-450 reductase, by rat liver as well as by trypanosome microsomes was confirmed by ESR experiments. As shown here, Megazol interferes with the oxygen metabolism of the parasite, but its extra activity when compared to Nifurtimox may be related to other features not yet identified. PMID:9952319

Viodé, C; Bettache, N; Cenas, N; Krauth-Siegel, R L; Chauvière, G; Bakalara, N; Périé, J

1999-03-01

422

Neutron coincidence imaging for active and passive neutron assays  

Microsoft Academic Search

Neutron multiplicity assay algorithms for ²°Pu assume a point source of fission neutrons that are detected in a single detector channel. The ²°Pu in real waste, however, is more likely to be distributed throughout the container in some random way. For different reasons, this leads to significant errors when using either multiplicity or simpler coincidence analyses. Reduction of these errors

R. J. Estep; G. S. Brunson; S. G. Melton

2001-01-01

423

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

424

Biomolecular Interaction Assay  

SciTech Connect

Understanding the binding interactions of complexes of multiple proteins is an important area of medical research since many biological signaling pathways involve multiple protein complexes. A number of sensor technologies have been adapted to monitoring biomolecular interactions. Acoustic wave devices such as flexural plate wave devices, surface transverse waves, and quartz crystal microbalances detect the mass increase observed upon binding of a solution biomolecule to a surface bound biomolecule. However, these devices will also respond to changes in viscosity, temperature, liquid density, and viscoelastic effects, which may confound the interpretation of observed signals. Nonspecific binding is indistinguishable from specific binding. Several techniques for refractive index sensing, such as planar wave guides and surface plasmon resonance (SPR), can also be used to observe biomolecular interactions localized at a surface. Again, nonspecific binding is indistinguishable from specific binding. In addition, the derivatized surface must be very thin and uniform to obtain adequate sensitivity and reproducibility, and the technique is not suited for monitoring large multiple protein complexes since the measurement sensitivity decreases rapidly with distance from the sensor surface. All of these techniques use planar surfaces that are difficult to prepare and characterize, and must be prepared fresh for each assay.

Bruckner-Lea, Cindy J.; Brown, L; Holman, David A.; Olson, Lydia; Grate, Jay W.

2000-12-29

425

Cell aggregation assays.  

PubMed

Invasion of carcinoma cells is the result of a disequilibrium between invasion promoter and invasion suppressor gene products (Mareel and Van Roy, Anticancer Res 6:419-435, 1986). The E-cadherin/catenin complex is the most potent invasion suppressor at the cell membrane of epithelioid cells (Duffy et al., J Pathol 214:283-293, 2008). This complex consists of E-cadherin, a transmembrane glycoprotein of 120 kDa, which is linked to the actin cytoskeleton via the catenins (Behrens et al., J Cell Biol 108:2435-2447, 1989). Downregulation of the complex is a common feature in invasive carcinoma cells, and has been recognized at several levels, ranging from genomic mutations to functional deficiencies of an apparently intact complex (Ozawa et al., Proc Natl Acad Sci USA 87:4246-4250, 1990). Cell aggregation assays have been set up to test the functionality of the complex in epithelioid tumor cells. Functional integrity of the complex is a prerequisite for cell-cell adhesion between epithelial cells, and measuring cell aggregation in vitro has thus become another elegant tool to study differences between invasive and noninvasive cell types. PMID:24092433

Debruyne, Delphine; Boterberg, Tom; Bracke, Marc E

2014-01-01

426

Hydrogenase activity in Azospirillum brasilense is inhibited by nitrite, nitric oxide, carbon monoxide, and acetylene.  

PubMed Central

Nitrite, NO, CO, and C2H2 inhibited O2-dependent H2 uptake (H3H oxidation) in denitrifying Azospirillum brasilense Sp7 grown anaerobically on N2O or NO3-. The apparent Ki values for inhibition of O2-dependent H2 uptake were 20 microM for NO2-, 0.4 microM for NO, 28 microM for CO, and 88 microM for C2H2. These inhibitors also affected methylene blue-dependent H2 uptake, presumably by acting directly on the hydrogenase. Nitrite and NO inhibited H2 uptake irreversibly, whereas inhibition due to CO was easily reversed by repeatedly evacuating and backfilling with N2. The C2H2 inhibition was not readily reversed, partly due to difficulty in removing the last traces of this gas from solution. The NO2- inhibition of malate-dependent respiration was readily reversed by repeatedly washing the cells, in contrast to the effect of NO2- on H2-dependent respiration. These results suggest that the low hydrogenase activities observed in NO3(-)-grown cultures of A. brasilense may be due to the irreversible inhibition of hydrogenase by NO2- and NO produced by NO3- reduction.

Tibelius, K H; Knowles, R

1984-01-01

427

Assessment of plaque assay methods for alphaviruses.  

PubMed

Viruses from the Alphavirus genus are responsible for numerous arboviral diseases impacting human health throughout the world. Confirmation of acute alphavirus infection is based on viral isolation, identification of viral RNA, or a fourfold or greater increase in antibody titers between acute and convalescent samples. In convalescence, the specificity of antibodies to an alphavirus may be confirmed by plaque reduction neutralization test. To identify the best method for alphavirus and neutralizing antibody recognition, the standard solid method using a cell monolayer overlay with 0.4% agarose and the semisolid method using a cell suspension overlay with 0.6% carboxymethyl cellulose (CMC) overlay were evaluated. Mayaro virus, Una virus, Venezuelan equine encephalitis virus (VEEV), and Western equine encephalitis virus (WEEV) were selected to be tested by both methods. The results indicate that the solid method showed consistently greater sensitivity than the semisolid method. Also, a "semisolid-variant method" using a 0.6% CMC overlay on a cell monolayer was assayed for virus titration. This method provided the same sensitivity as the solid method for VEEV and also had greater sensitivity for WEEV titration. Modifications in plaque assay conditions affect significantly results and therefore evaluation of the performance of each new assay is needed. PMID:23085307

Juarez, Diana; Long, Kanya C; Aguilar, Patricia; Kochel, Tadeusz J; Halsey, Eric S

2012-10-17

428

Metal reduction by spores of Desulfotomaculum reducens.  

PubMed

The bioremediation of uranium-contaminated sites is designed to stimulate the activity of microorganisms able to catalyze the reduction of soluble U(VI) to the less soluble mineral UO(2). U(VI) reduction does not necessarily support growth in previously studied bacteria, but it typically involves viable vegetative cells and the presence of an appropriate electron donor. We characterized U(VI) reduction by the sulfate-reducing bacterium Desulfotomaculum reducens strain MI-1 grown fermentatively on pyruvate and observed that spores were capable of U(VI) reduction. Hydrogen gas - a product of pyruvate fermentation - rather than pyruvate, served as the electron donor. The presence of spent growth medium was required for the process, suggesting that an unknown factor produced by the cells was necessary for reduction. Ultrafiltration of the spent medium followed by U(VI) reduction assays revealed that the factor's molecular size was below 3 kDa. Pre-reduced spent medium displayed short-term U(VI) reduction activity, suggesting that the missing factor may be an electron shuttle, but neither anthraquinone-2,6-disulfonic acid nor riboflavin rescued spore activity in fresh medium. Spores of D. reducens also reduced Fe(III)-citrate under experimental conditions similar to those for U(VI) reduction. This is the first report of a bacterium able to reduce metals while in a sporulated state and underscores the novel nature of the mechanism of metal reduction by strain MI-1. PMID:19601961

Junier, Pilar; Frutschi, Manon; Wigginton, Nicholas S; Schofield, Eleanor J; Bargar, John R; Bernier-Latmani, Rizlan

2009-07-10

429

The MTT assay is a rapid and reliable quantitative method to assess Staphylococcus aureus induced endothelial cell damage.  

PubMed

We established the 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay to assess damage induced by Staphylococcus aureus in human umbilical vein endothelial cells (HUVECs). The MTT assay was comparable to the previously published (51)chromium release assay. MTT reduction by intracellular S. aureus was negligible and therefore permits assessment of S. aureus induced EC damage. PMID:23275136

Seidl, Kati; Zinkernagel, Annelies S

2012-12-28

430

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

431

The reduction of tetrazolium salts by plant mitochondria  

Microsoft Academic Search

Data has been obtained concerning the reduction of tetrazolium salts by mitochondria isolated from Jerusalem artichoke tubers with succinate as the substrate using a direct recording spectrophotometric method of assay. ATP was found to increase the rate of reduction of the tetrazolium salts, this being independent of the effect ATP had on the rate of oxygen uptake. The magnitude of

M. Kalina; J. M. Palmer

1968-01-01

432

Latitude Variations of the Abundances of Ammonia, Acetylene, and Phosphine and Vertical Mixing in the Atmospheres of Jupiter and Saturn  

NASA Astrophysics Data System (ADS)

Ultraviolet observations of Jupiter and Saturn performed in the past have typically suffered from poor spatial resolution and have therefore focused on either globally-averaged values or north-south asymmetries. Spectra taken with the Hubble Space Telescope Faint Object Spectrograph have a spatial resolution of 1 arc second, making it possible to sample the disk at several latitudes. The observations presented here were taken at latitudes along the Central Meridian of both Jupiter (65oS, 48oS, 33oS, 25oS, 12oS, 6oS, 0o, 6oN, 15oN, 20oN, 25oN, 48oN, 65oN, along with the Great Red Spot and the South Equatorial Belt) and Saturn (4oS, 4oN, 12oN, 20oN, 40oN, 48oN, 60oN, 79oN, 90oN). The wavelength interval covers a range from 180 nm to 240 nm. Albedos have been calculated by dividing the observations by intensity of the Sun at each planet. Removal of solar features reveals the presence of ammonia, acetylene, and continuum absorbers (e.g. phosphine and aerosols). With the use of a photochemical model which includes a multiple scattering radiative transfer code, the altitude profiles of these species have been generated by using the eddy diffusion coefficient as a free parameter. From the altitude profiles, synthetic spectra were calculated and compared with the observations at each latitude. This work reveals that a variation of ammonia, acetylene, phosphine, and the vertical mixing with altitude exists in both atmospheres. The presence of a strong ammonia signature in the Jovian spectra allows it to be used as a tracer for the dynamics near the tropopause. The value of the eddy mixing coefficient at 6oN increases rapidly with depth from a value of 5×102 cm2s-1 to 104 cm2s-1 between 90-150 mbar. Above the 90 mbar level, the value increases reaching a value of 8×102 cm2s-1 at 60 mbar. A latitudinal variation in the ammonia mixing ratio and eddy mixing profile is also derived from the FOS observations. In the northern hemisphere of Jupiter, the ammonia mixing ratio above the tropopause and the eddy mixing are found to decrease as one moves further north. In the southern hemisphere, however, there is more variation with latitude. The strongest vertical mixing and the largest abundance of ammonia is in the Great Red Spot region. On Saturn, phosphine can be assumed to provide the source of opacity for the continuum. Based on this assumption, the vertical distribution of phosphine and eddy mixing coefficients have been derived. The largest mixing ratio of phosphine and the strongest mixing ( 9× 103/ cm2s-1) are found near 12oN, with both decreasing monotonically away from 12oN.

Edgington, Scott G.

433

Terahertz Spectroscopy of the Bending Vibrations of Acetylene 12C2H2 and 12C2D2  

NASA Astrophysics Data System (ADS)

Several fundamental interstellar molecules, e.g., C2H2, CH4 and C3, are completely symmetric molecules and feature no permanent dipole moment and no pure rotation spectrum. As a result they have only previously been observed in the infrared. However, directly observing them with the rest of the molecular column especially when the source is spatially resolved would be very valuable in understanding chemical evolution. Vibrational difference bands provide a means to detect symmetric molecules with microwave precision using terahertz techniques. Herschel, SOFIA and ALMA have the potential to identify a number of vibrational difference bands of light symmetric species. This paper reports laboratory results on 12C2H2 and 12C2D2. Symmetric acetylene isotopologues have two bending modes, the trans bending and the cis bending. Their difference bands are allowed and occur in the microwave, terahertz, and far-infrared wavelengths, with band origins at 3500 GHz for 12C2H2 and 900 GHz for 12C2D2. Twenty 12C2H2 P branch high-J transitions and two hundred and fifty-one 12C2D2 P Q and R branch transitions have been measured in the 0.2 - 1.6 THz region with precision of 50 to 100 kHz. These lines were modeled together with prior data on the pure bending levels. Significantly improved molecular parameters were obtained for 12C2H2 and 12C2D2 with the combined data set, and new frequency and intensity predictions were made to support astrophysics applications. The research was performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. S. Y. was supported by an appointment to the NASA Postdoctoral Program, administrated by Oak Ridge Associated Universities through a contract with NASA.

Yu, Shanshan; Drouin, B.; Pearson, J.

2009-12-01

434

A DFT study on the mechanisms for the cycloaddition reactions between 1-aza-2-azoniaallene cations and acetylenes.  

PubMed

The mechanisms of cycloaddition reactions between 1-aza-2-azoniaallene cations 1 and acetylenes 2 have been investigated using the global electrophilicity and nucleophilicity of the corresponding reactants as global reactivity indexes defined within the conceptual density functional theory. The reactivity and regioselectivity of these reactions were predicted by analysis of the energies, geometries, and electronic nature of the transition state structures. The theoretical results revealed that the reaction features a tandem process: an ionic 1,3-dipolar cycloaddition to produce the cycloadducts 3?H-pyrazolium salts 3 followed by a [1,2]-shift affording the thermodynamically more stable adducts 4 or 5. The mechanism of the cycloaddition reactions can be described as an asynchronous concerted pathway with reverse electron demand. The model reaction has also been investigated at the QCISD/6-31++G(d,p) and CCSD(T)/6-31++G(d,p)//B3LYP/6-31++G(d,p) levels as well as by the DFT. The polarizable continuum model, at the B3LYP/6-31++G(d,p) level of theory, was used to study solvent effects on all the studied reactions. In solvent dichloromethane, all the initial cycloadducts 3 were obtained via direct ionic process as the result of the solvent effect. The consecutive [1,2]-shift reaction, in which intermediates 3 are rearranged to the five-membered heterocycles 4/5, is proved to be a kinetically controlled reaction, and the regioselectivity can be modulated by varying the migrant. The LOL function and RDG function based on localized electron analysis were used to analysis the covalent bond and noncovalent interactions in order to unravel the mechanism of the title reactions. PMID:22810049

Wang, Jing-mei; Li, Zhi-ming; Wang, Quan-rui; Tao, Feng-gang

2012-07-19

435

?,?-Acetylenic amino thiolester inhibitors of aldehyde dehydrogenases 1&3: suppressors of apoptogenic aldehyde oxidation and activators of apoptosis.  

PubMed

The aim of this minireview is to recapitulate the evidence in the literature supporting a role for the aldehyde dehydrogenases (ALDH1, ALDH2 and ALDH3) in controlling the levels of 3 endogenous apoptogenic aldehydes: methional, malondialdehyde (MDA) and 4-hydroxynonenal (HNE). All 3 aldehydes are formed during the metabolism of cellular constituents. Methional is derived from the oxidative decarboxylation of 4-methylthio-2-oxobutanoate coming from the methionine salvage pathway. MDA arises from the peroxidation of lipids and also from methional subjected to attack by reactive oxygen species (ROS). HNE is formed primarily from lipid peroxidation by ROS attack. One major origin of ROS is the dysfunctional electron transport chain in the mitochondria of cancer cells. As bifunctional electrophilic compounds, HNE forms adducts with cellular nucleophiles e.g. GSH, whilst MDA acts as a potent DNA/protein cross-linking agent in vitro and in vivo. Cancer cells protect themselves from the apoptogenic effect of these aldehydes by the ALDHs that oxidize them to their non-apoptogenic carboxylic acids. Indeed, the over-expression of ALDH3 protects cells from HNE-induced apoptosis. The inhibition of ALDH1 allows methional to reach its apoptogenic threshold in BAF3bcl2 that were resistant to methional-inducible apoptosis. One member of the ?,?-acetylenic N-substituted aminothiol ester family is an "active-enzyme-dependent", competitive, irreversible inhibitor of ALDH1 in vitro, an inhibitor of ALDH1 and ALDH3 in rat and human cancer cells in culture, an irreversible apoptogen on chemoresistant bcl2(+++) murine lymphoid and human epithelial cancer cells but a reversible cytostatic compound on human prostate epithelial normal cells in culture. PMID:23231347

Fournet, G; Martin, G; Quash, G

2013-01-01

436

Aldehyde Reduction by Cytochrome P450  

PubMed Central

This protocol describes the procedure for measuring the relative rates of metabolism of the ?,?-unsaturated aldehydes, 9-anthracene aldehyde (9-AA) and 4-hydroxy-trans-2-nonenal (4-HNE); specifically the aldehyde reduction reactions of cytochrome P450s (CYPs). These assays can be performed using either liver microsomal or other tissue fractions, spherosome preparations of recombinant CYPs, or recombinant CYPs from other sources. The method used here to study the reduction of a model ?,?-unsaturated aldehyde, 9-AA, by CYPs was adapted from the assay used to investigate 9-anthracene oxidation as reported by Marini et al. (Marini et al., 2003). For experiments measuring reduction of the endogenous aldehyde, 4-HNE, the substrate was incubated with CYP in the presence of oxygen and NADPH and the metabolites were separated by High Pressure Liquid Chromatograpy (HPLC), using an adaptation of the method of Srivastava et al. (Srivastava et al., 2010). For study of 9-AA and 4-HNE reduction, the first step involves incubation of the substrate with the CYP in appropriate media, followed by quantification of metabolites through either spectrofluorimetry or analysis by HPLC coupled with a radiometric assay, respectively. Metabolite identification can be achieved by HPLC GC-mass spectrometric analysis. Inhibitors of cytochrome P450 function can be utilized to show the role of the hemoprotein or other enzymes in these reduction reactions. The reduction reactions for CYP’s were not inhibited by either anaerobiosis or inclusion of CO in the gaseous phase of the reaction mixture. These character of these reactions are similar to those reported for some cytochrome P450-catalyzed azo reduction reactions.

Amunom, Immaculate; Srivastava, Sanjay; Prough, Russell A.

2011-01-01

437

Strength Reduction via SSAPRE  

Microsoft Academic Search

We present techniques that allow strength reduction to be performed concurrently with partial redundancy elimination in the SSAPRE framework. By sharing the characteristics inherent to SSAPRE, the resulting strength reduction algorithm exhibits many interesting attributes. We compare various aspects of the new strength reduction algorithm with previous strength reduction algorithms. We also outline and discuss our implementation of the closely

Robert Kennedy; Fred C. Chow; Peter Dahl; Shin-ming Liu; Raymond Lo; Mark Streich

1998-01-01

438

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

439

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

440

Improved benzodiazepine radioreceptor assay using the MultiScreen Assay System.  

PubMed

In this article, an improved benzodiazepine radioreceptor assay is described, which allows substantial reduction in assay time. The filtration in this method was performed by using the MultiScreen Assay System. The latter consists of a 96-well plate with glass fibre filters sealed at the bottom, which allows both the incubation and the filtration of the specimen in the same plate. After the filtration, the filters were punched out for quantitation of the bound labeled ligand [3H]flunitrazepam. The results obtained with the MultiScreen Assay System did not differ significantly from the data obtained with the conventional filtration manifold (48S): The Ki's of lorazepam were 2.4 +/- 0.30 and 1.9 +/- 0.15 nM, respectively. In case a radioactive label is replaced by a fluorescent label, the bound labeled-ligand usually cannot be determined in the presence of the receptor material. Here, the bound labeled-ligand has to be dissociated after the filtration step. To dissociate the ligand-receptor complex, Tris- HCl buffer, containing 10 microM flumazenil, was added to the filters and the second filtrates were collected containing the previously bound fractions in the absence of receptor material. This approach showed the same Ki for lorazepam, 2.5 +/- 0.04 nM as without dissociation, when using the radio-labeled benzodiazepine [3H]flunitrazepam. PMID:10701983

Janssen, M J; Ensing, K; de Zeeuw, R A

1999-09-01

441

REVIEW Colorimetric protein assay techniques  

Microsoft Academic Search

There has been an increase in the number of colori- metric assay techniques for the determination of pro- tein concentration over the past 20 years. This has resulted in a perceived increase in sensitivity and accuracy with the advent of new techniques. The present review considers these advances with emphasis on the potential use of such technologies in the assay

Christine V. Sapan; Roger L. Lundbladã; Nicholas C. Priceå

442

Comet assay and early apoptosis  

Microsoft Academic Search

The comet assay is a single cell gel electrophoresis test currently used as a qualitative and quantitative genotoxicity test. However, some of the results from this comet assay and current knowledge on apoptosis lead us to suspect the presence of some false positive results. The aim of this study was to ascertain if apoptotic cells can yield comet images that

P Choucroun; D Gillet; G Dorange; B Sawicki; J. D Dewitte

2001-01-01

443

Assay of potentially contaminated propellant  

Microsoft Academic Search

One of the decontamination and decommissioning projects within DOD is demilitarization of an aging stockpile of munitions. A large portion of the stockpile contains depleted uranium (DU) as an armor piercing core and so these munitions must be assayed for the presence of uranium in other components. The assay method must be fast and preferably easy to implement. Presence of

J. E. Koster; H. E. Williams; W. S. Scott

1995-01-01

444

Establishing Assay Cutoffs for HLA Antibody Screening of Apheresis Donors  

PubMed Central

BACKGROUND TRALI is the leading cause of transfusion-related deaths. Donor HLA antibodies have been implicated in TRALI cases. Blood centers are implementing TRALI risk reduction strategies based on HLA antibody screening of some subpopulations of ever-pregnant apheresis platelet donors. However, if screening assay