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1

Continuous, Automated Acetylene Reduction Assays Using Intact Plants 1  

PubMed Central

An automated method was developed for continuous, in situ determination of acetylene reduction (N2 fixation) by intact soybean plants (Glycine max [L.]). The culture vessel containing the roots of intact plants grown in sand culture is sealed at the surface and an air-acetylene mixture continuously injected into the root chamber. The effluent gas is automatically sampled and injected into a gas chromatograph. Continuous acetylene assay at intervals as short as 3.5 min may be made over a period of several days, without attention, except for plant watering. Adverse effects of prolonged exposure of the root system to acetylene were mitigated by pulse injection of acetylene for 20 min followed by 40 min of acetylene-free air. Bare root systems can be suspended in a reaction chamber and sprayed with water or nutrient solution; this permits periodic removal of the root system for sampling nodules. In studies lasting several diurnal cycles, acetylene reduction did not decline more than 50% of the maximum rate in light, thus nitrogenase activity depends on concomitant photosynthesis and on carbohydrate from storage pools. PMID:16659997

Mederski, Henry J.; Streeter, John G.

1977-01-01

2

Acetylene, Not Ethylene, Inactivates the Uptake Hydrogenase of Actinorhizal Nodules during Acetylene Reduction Assays.  

PubMed

Acetylene reduction assays were shown to inactivate uptake hydrogenase activity to different extents in one Casuarina and two Alnus symbioses. Inactivation was found to be caused by C(2)H(2) and not by C(2)H(4). Acetylene completely inactivated the hydrogenase activity of intact root systems of Alnus incana inoculated with Frankia strain Avcl1 in 90 minutes, as shown by a drop in the relative efficiency of nitrogenase from 1.0 to 0.73. The hydrogenase of Frankia preparations (containing vesicles) and of cell-free extracts (not containing vesicles) from the same symbiosis was much more susceptible to acetylene inactivation. Cell-free extracts lost all hydrogenase activity after 5 minutes of exposure to acetylene. The hydrogenase activity of intact root systems of Casuarina obesa was less sensitive to acetylene than that of root systems of A. incana, since the relative efficiency of nitrogenase changed only from 1.0 to 0.95 over 90 minutes. Frankia preparations and cell-free extracts of C. obesa still retained hydrogenase activity after a 10 minute-exposure to acetylene. PMID:16667724

Sellstedt, A; Winship, L J

1990-09-01

3

The acetylene reduction technique as an assay for nitrogenase activity in the methane oxidizing bacterium Methylococcus capsulatus strain bath  

Microsoft Academic Search

The use of acetylene as a convenient assay substrate for nitrogenase in methane oxidising bacteria is complicated by the observation that it is a potent inhibitor of the methane monooxygenase enzyme in both whole cells and cell-free extracts. If the cells were provided with alternative oxidisable carbon substrates other than methane then nitrogen fixing cells would reduce acetylene to ethylene.

Howard Dalton; Roger Whittenbury

1976-01-01

4

Acetylene reduction by nitrogen-fixing blue-green algae  

Microsoft Academic Search

Known nitrogen-fixing species of blue-green algae are capable of reducing acetylene to ethylene, but acetylene is not reduced by Anacystis nidulans, which does not fix nitrogen. Cycad root nodules which contain blue-green algae as endophytes reduce acetylene. Acetylene reduction is inhibited by carbon monoxide. Nitrate or ammonium-nitrogen has no immediate effect on algae reducing acetylene, but algae grown on nitrate-nitrogen

W. D. P. Stewart; G. P. Fitzgerald; R. H. Burris

1968-01-01

5

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. PMID:16345992

Zuberer, D. A.

1982-01-01

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

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. PMID:16661045

van Berkum, Peter; Sloger, Charles

1979-01-01

8

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. PMID:16345301

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

1978-01-01

9

Nitrogen fixation (acetylene reduction) by epiphytes of freshwater macrophytes.  

PubMed

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 mug 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. PMID:16345301

Finke, L R; Seeley, H W

1978-07-01

10

Contribution from nitrogen fixation (acetylene reduction) to the nitrogen budget of Lake Tohopekaliga (Florida)  

Microsoft Academic Search

Nitrogen fixation, as assayed by the acetylene reduction technique, provided 44% of the input of nitrogen to a lake in central Florida (Lake Tohopekaliga) during 1984. Ninety-four percent of the lake total fixation was found in the water column and associated with Anabaena spp. The lake-wide average nitrogen fixation rate of 5.7 g N\\/m2-yr amounted to a mass loading of

Forrest E. Dierberg; Michael M. ScheinkmatG

1987-01-01

11

Simultaneous measurement of acetylene reduction and respiratory gas exchange of attached root nodules.  

PubMed

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

Winship, L J; Tjepkema, J D

1982-08-01

12

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. PMID:16659276

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

1975-01-01

13

Growth and acetylene reduction activity by intact plants of Alnus incana under field conditions  

Microsoft Academic Search

The nitrogen-fixing grey alder,Alnus incana (L.) Moench, has a potential use in forest soil restoration and as part of energy forestry plantations. As a first step to estimate nitrogen fixation byA. incana under field conditions we performed studies on nitrogenase activity and its possible relation to abiotic factors and growth of the alders. Nitrogenase activity was measured as acetylene reduction

Kerstin Huss-Danell; Per-Olof Lundquist; Alf Ekblad

1989-01-01

14

Acetylene reduction, H2 evolution and (15)N 2 fixation in the Alnus incana-Frankia symbiosis.  

PubMed

Acetylene reduction, (15)N2 reduction and H2 evolution were measured in root systems of intact plants of grey alder (Alnus incana (L.) Moench) in symbiosis with Frankia. The ratios of C2H2: (15)N2 were compared with C2H2:N2 ratios calculated from C2H2 reduction and H2 evolution, and with C2H2:N2 ratios calculated from accumulated C2H4 production and nitrogen content. It was possible to calculate C2H2:N2 ratios from C2H2 reduction and H2 evolution because this source of Frankia did not show any hydrogenase activity. The ratios obtained using the different methods ranged from 2.72 to 4.42, but these values were not significantly different. It was also shown that enriched (15)N could be detected in the shoot after a 1-h incubation of the root-system. It is concluded that the measurement of H2 evolution in combination with C2H2 reduction represents a nondestructive assay for nitrogen fixation in a Frankia symbiosis which shows no detectable hydrogenase activity. PMID:24240308

Sellstedt, A

1986-03-01

15

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. PMID:19286791

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

2009-01-01

16

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

PubMed

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

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

2009-05-01

17

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

PubMed Central

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

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

2012-01-01

18

Acetylene hydrogenation over Ni-Cu nanoparticles supported on silica prepared by aqueous hydrazine reduction.  

PubMed

Non conventional nickel (1%) and nickel (1%)-copper (0.2-0.75%) catalysts supported on silica, prepared by aqueous hydrazine reduction of nickel acetate at 70 degrees C, were studied in acetylene hydrogenation, mainly at 60 degrees C. The obtained results show that the metal dispersion decreases whereas the conversion passes through a maximum with increasing copper content. The reaction produces ethylene, benzene, ethane, n-butane, small amounts of higher hydrocarbons and a paraffinic product. Ethylene and benzene are rather low temperature products (below 80 degrees C) whereas the saturated hydrocarbons, mainly ethane, are rather formed at higher temperature. The presence of water in the feed gas changed the catalyst performances. The carbonaceous deposit during acetylene hydrogenation was studied by means of temperature programmed surface reaction (TPSR). Analysis of the results obtained showed that the changes observed in conversion/selectivity may be correlated with changes in Ni-Cu interactions, chemisorption equilibria or/and coke deposit. A comparative study of classical/non classical Ni/SiO2 catalysts is reported. PMID:19504880

Boudjahem, Abdel-Ghani; Chettibi, Moussa; Monteverdi, Serge; Bettahar, Mohammed M

2009-06-01

19

Root-associated n(2) fixation (acetylene reduction) by enterobacteriaceae and azospirillum strains in cold-climate spodosols.  

PubMed

N(2) 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 C(2)H(2) reduction were those of Agrostis stolonifera, Calamagrostis lanceolata, Elytrigia repens, and Phalaris arundinacea, which produced 538 to 1,510 nmol of C(2)H(4).g (dry weight). h when incubated at pO(2) 0.04 with sucrose (pH 6.5), and 70 to 269 nmol of C(2)H(4). g (dry weight).h 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 N(2)-fixing organisms in associative symbiosis with plant roots found in a northern climatic region in acidic soils ranging down to pH 4.0. PMID:16345687

Haahtela, K; Wartiovaara, T; Sundman, V; Skuji?s, J

1981-01-01

20

Acetylene reduction, H 2 evolution and 15 N 2 fixation in the Alnus incana-Frankia symbiosis  

Microsoft Academic Search

Acetylene reduction, 15N2 reduction and H2 evolution were measured in root systems of intact plants of grey alder (Alnus incana (L.) Moench) in symbiosis with Frankia. The ratios of C2H2: 15N2 were compared with C2H2:N2 ratios calculated from C2H2 reduction and H2 evolution, and with C2H2:N2 ratios calculated from accumulated C2H4 production and nitrogen content. It was possible to calculate

A. Sellstedt

1986-01-01

21

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

PubMed Central

Peas (Pisum sativum L.) were inoculated with strains of Rhizobium leguminosarum having different levels of uptake hydrogenase (Hup) activity and were grown in sterile Leonard jars under controlled conditions. Rates of H2 evolution and acetylene reduction were determined for intact nodulated roots at intervals after the onset of darkness or after removal of the shoots. Hup activity was estimated using treatment plants or equivalent plants from the growth chamber, by measuring the uptake of H2 or 3H2 in the presence of acetylene. In all cases, the rate of H2 evolution was a continuous function of the rate of acetylene reduction. In symbioses with no demonstrable Hup activity, H2 evolution increased in direct proportion to acetylene reduction and the slopes were similar with the Hup? strains NA502 and 128C79. Hup activity was similar in strains 128C30 and 128C52 but significantly lower in strain 128C54. With these strains, the slopes of the H2 evolution versus acetylene reduction curves initially increased with acetylene reduction, but became constant and similar to those for the Hup? strains at high rates of acetylene reduction. On these parallel portions of the curves, the decreases in H2 evolution by Hup+ strains were similar in magnitude to their H2-saturated rates of Hup activity. The curvilinear relationship between H2 evolution and acetylene reduction for a representative Hup+ strain (128C52) was the same, regardless of the experimental conditions used to vary the nitrogenase activity. PMID:16664984

Mahon, John D.; Nelson, Louise M.

1986-01-01

22

Seasonal variations in nitrogen-fixation (acetylene reduction) and sulphate-reduction rates in the rhizosphere of Zostera noltii : nitrogen fixation by sulphate-reducing bacteria  

Microsoft Academic Search

Nitrogen-fixation (acetylene reduction) rates were measured over an annual cycle in meadows of the seagrass Zostera noltii Hornem in the Bassin d'Arcachon, south-west France, between March 1994 and February 1995, using both slurry and whole-core techniques. Measured rates using the slurry technique consistently overestimated those determined on whole cores, probably due to the release of labile organic carbon sources as

D. T. Welsh; S. Bourgués; R. Wit; R. A. Herbert

1996-01-01

23

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. PMID:16345687

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

1981-01-01

24

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

25

Acetylene Hydrogenation on Au-Based Catalysts  

Microsoft Academic Search

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

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

2003-01-01

26

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

27

Acetylenic carbon allotrope  

DOEpatents

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

Lagow, R.J.

1998-02-10

28

Acetylenic carbon allotrope  

DOEpatents

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

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

1999-01-01

29

Acetylenic carbon allotrope  

DOEpatents

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

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

1998-01-01

30

Acetylenic carbon allotrope  

Microsoft Academic Search

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

Lagow

1998-01-01

31

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

32

29 CFR 1910.102 - Acetylene.  

Code of Federal Regulations, 2011 CFR

...Chapter 9 (“Acetylene Piping”) of NFPA 51A-2006 (“Standard for Acetylene...Chapter 7 (“Acetylene Piping”) of NFPA 51A-2001 (“Standard for Acetylene Charging...cylinders comply with the provisions of NFPA 51A-2006 (“Standard for Acetylene...

2011-07-01

33

29 CFR 1910.102 - Acetylene.  

Code of Federal Regulations, 2010 CFR

...Chapter 9 (“Acetylene Piping”) of NFPA 51A-2006 (“Standard for Acetylene...Chapter 7 (“Acetylene Piping”) of NFPA 51A-2001 (“Standard for Acetylene Charging...cylinders comply with the provisions of NFPA 51A-2006 (“Standard for Acetylene...

2010-07-01

34

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. PMID:22915855

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

35

Acetylene-Terminated Polyimide Siloxanes  

NASA Technical Reports Server (NTRS)

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

St. Clair, Terry L.; Maudgal, Shubba

1987-01-01

36

A cobalt-based tetrazolium salts reduction test to assay polyphenols.  

PubMed

A novel assay was developed to measure the capacity of polyphenols to chelate cobalt(II) by using the reduction of the tetrazolium salts, NBT (nitroblue tetrazolium chloride), MTT (methylthiazolyldiphenyl-tetrazolium bromide), and XTT (2,3-bis[2-methoxy-4-nitro-5-sulfophenyl]-2H-tetrazolium-5-carboxanilide) to formazan products. The reduction of the salts is initiated by a cocktail comprised of cobalt(II), H(2)O(2), and selenium(IV), which generates hydroxyl radical, peroxide, and superoxide ions. However, because cobalt(II) could not be replaced either by Fe(II), Mn(II), or Cu(II), the classical Fenton transitional metals, it indicates that cobalt is the key player in the tetrazolium salt reduction. Micromolar concentrations of a large variety of antioxidant polyphenols and minute amounts of fruit beverages rich in polyphenols can readily chelate cobalt, resulting in the inhibition of the reduction of tetrazolium salt to formazan, in a dose-dependent manner. However, this method is unsuitable to measure low molecular weight antioxidants such as ascorbate, uric acid, and vitamin E since these have no chelating properties for cobalt(II). The newly described tetrazolium reduction method is as sensitive as the ferric ion reducing antioxidant power, 2,2-diphenyl-2-picrylhydrazyl hydrate, and the luminol-dependent chemiluminescence antioxidant assays. The practical advantages of using the newly described method to quantify polyphenol levels from various sources are briefly discussed. PMID:19722702

Koren, Erez; Kohen, Ron; Ginsburg, Isaac

2009-09-01

37

Research in acetylene containing monomers  

NASA Technical Reports Server (NTRS)

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

Ogliaruso, M. A.

1976-01-01

38

Acetylene-terminated polyimide adhesives  

NASA Technical Reports Server (NTRS)

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

Hanky, A. O.

1983-01-01

39

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

40

Acetylene terminated aspartimides and resins therefrom  

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

41

Evaluation of Sorbents for Acetylene Separation in Atmosphere Revitalization Loop Closure  

NASA Technical Reports Server (NTRS)

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

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

2012-01-01

42

Evaluation of Sorbents for Acetylene Separation in Atmosphere Revitalization Loop Closure  

NASA Technical Reports Server (NTRS)

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

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

2011-01-01

43

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

PubMed

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

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

2012-02-18

44

29 CFR 1910.102 - Acetylene.  

Code of Federal Regulations, 2013 CFR

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

2013-07-01

45

29 CFR 1910.102 - Acetylene.  

Code of Federal Regulations, 2012 CFR

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

2012-07-01

46

29 CFR 1910.102 - Acetylene.  

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

2014-07-01

47

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

NASA Astrophysics Data System (ADS)

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

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

2009-12-01

48

Thermodynamics of acetylene van der Waals dimerization  

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

49

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

Microsoft Academic Search

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

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

50

Hydration of Acetylenic Esters: Synthesis of ß-Keto-Esters  

Microsoft Academic Search

Acetylenic esters, which are easily prepared by carbethoxylation of terminal acetylenes, can be hydrated regioselectively to #-keto-esters. In this paper, the terminal acetylenes were prepared by addition of lithium acetylide (complexed with ethylenediamine) to epoxides of cyclopentane derivatives to produce compounds oxygenated at the same position as certain natural products from Otoba parvifolia. The hydration was carried out by two

Mauricio Gomes Constantino; Ivone Carvalho; Gil Valdo José da Silva; Fernando Costa Archanjo

1996-01-01

51

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

52

Influence of and additives on acetylene detonation  

NASA Astrophysics Data System (ADS)

The influence of and 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 additive had no influence on the induction time. For , a significant promoting effect was observed. A simplified kinetic model was suggested and characteristic rates of diacetylene 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 pyrolysis, which interacts with acetylene and produces 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.

2014-03-01

53

Hydrosilylation of organosilicon acetylenic carbonyl compounds  

Microsoft Academic Search

The H2PtCl6-catalyzed hydrosilylation of organosilicon acetylenic carbonyl compounds Me3SiC=CCOR (R=H, Me, Ph) with triethylsilane (XH) leads in moderate yield to the formation of the regioisomeric adducts Me3SiCH=CXCOR and Me3 SiCX=CHCOR in a 5:1 mole ratio.

V. B. Pukhnarevich; I. I. Tsykhanskaya; M. G. Voronkov

1984-01-01

54

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. PMID:16345392

Chan, Yiu-Kwok; Knowles, Roger

1979-01-01

55

Ion Induced Dissociation Dynamics of Acetylene  

NASA Astrophysics Data System (ADS)

We report the results of dissociation dynamics of multiply charged acetylene molecules formed in collision with 1.2 MeV Ar8+ projectiles. Using the coincidence map, we found the evidence for molecular deformation due to a vibrationally active transition state of multiply charged C2H2 under the impact of low energy projectiles. 'Butterfly-like' structures are observed in the coincidence spectra between hydrogen and carbon ionic fragments. Such structures can be generated by numerical simulations and are found to originate from the bending motion of the dissociating molecule. 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 acetylene. This is a signature of sequentiality in the breakup dynamics of this multiply charged molecular species.

De, Sankar

2009-03-01

56

Acetylene hydrogenation on Au-based catalysts T.V. Choudhary a;*, C. Sivadinarayana a  

E-print Network

with energy dispersive X-ray spectroscopy (EDS) showed that while the redox method produced bimetallic Au contains small quantities of acetylene (polymerization catalysts of polymerization catalysts, extremely high conversions of acetylene are required (concentration of acetylene

Goodman, Wayne

57

The noncellular reduction of MTT tetrazolium salt by TiO? nanoparticles and its implications for cytotoxicity assays.  

PubMed

We report results of noncellular tests, revealing the occurrence of photocatalytic interactions between titanium dioxide (TiO2, titania) nanoparticles and the MTT [3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium-bromide] cytotoxicity indicator. These interactions induce the reduction of MTT and formation of purple formazan under biologically relevant conditions. Classical MTT assays have been performed to evaluate the production of formazan in DMEM-F12 and RPMI-1640 cell culture media (containing 10% fetal bovine serum-FBS) treated with Degussa-P25 TiO2 nanoparticles, in the absence of cells. The colorimetric determinations revealed the noncellular MTT to formazan transformation induced by TiO2 nanoparticles, under conditions commonly used for in vitro cytotoxicity testing of nanomaterials. The formazan precipitation was found to be proportional to the TiO2 concentration, being enhanced under laboratory daylight exposure. The photocatalytic nature of the studied effect was assessed under UV irradiation at 365nm. The biological significance of the reported reaction was established with respect to cellular reference experiments performed on V79-4, HeLa and B16 cell lines. The results show false viability increases with up to 14% (for TiO2 concentrations generally higher than 50?g/ml), induced by the TiO2-MTT reaction. This type of artifacts may lead to underestimated toxicity or false proliferation results. PMID:23531555

Lupu, A R; Popescu, T

2013-08-01

58

A first principles study of the acetylene-water interaction  

Microsoft Academic Search

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

Demeter Tzeli; Aristides Mavridis; Sotiris S. Xantheas

2000-01-01

59

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

60

Acetylene-Based Materials in Organic Photovoltaics  

PubMed Central

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

Silvestri, Fabio; Marrocchi, Assunta

2010-01-01

61

Pressure-induced Polymerization in Substituted Acetylenes  

NASA Astrophysics Data System (ADS)

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 provides a complementary route to investigate the equilibrium phase space and metastable intermediates during high pressure chemistry, although at a much slower timescale. In this study, we present our results from our ongoing high pressure in situ synchrotron x-ray diffraction and vibrational spectroscopy experiments on substituted acetylenes: tert-butyl acetylene [TBA: (CH3)3-C?CH] and ethynyl trimethylsilane [ETMS: (CH3)3-Si?CH]. We observed that the onset pressure of chemical reactions (at room temperature) in these compounds is significantly higher in static compression (TBA: 11 GPa and ETMS: 26 GPa) when compared to shock input pressures (TBA: 6.1 GPa and ETMS: 6.6 GPa). The products were polymeric in nature, recovered to ambient conditions with little degradation and fully characterized using spectroscopy, calorimetry, and other techniques to identify reaction mechanisms.

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

2011-06-01

62

Pressure-induced polymerization in substituted acetylenes  

NASA Astrophysics Data System (ADS)

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: (CH3)3-C=CH] and ethynyl trimethylsilane [ETMS: (CH3)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; Dattelbaum, Dana M.; Sheffield, S. A.; Robbins, David L.

2012-03-01

63

Pressure-induced Polymerization in Substituted Acetylenes  

NASA Astrophysics Data System (ADS)

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 provides a complementary route to investigate the equilibrium phase space and metastable intermediates during high pressure chemistry, although at a much slower timescale. In this study, we present our results from our ongoing high pressure in situ synchrotron x-ray diffraction and vibrational spectroscopy experiments on substituted acetylenes: tert-butyl acetylene [TBA: (CH3)3-C?CH] and ethynyl trimethylsilane [ETMS: (CH3)3-SiC?CH]. We observed that the onset pressure of chemical reactions (at room temperature) in these compounds is significantly higher in static compression (TBA: 11 GPa and ETMS: 26 GPa) when compared to shock input pressures (TBA: 6.1 GPa and ETMS: 6.6 GPa). The products were polymeric in nature, recovered to ambient conditions with little degradation and fully characterized using spectroscopy, calorimetry, and other techniques to identify reaction mechanisms.

Chellappa, Raja; Dattelbaum, Dana; Sheffield, Stephen

2012-02-01

64

Carbon black formation from the mixture of acetylene and benzene  

SciTech Connect

Formation of carbon black during isothermal pyrolysis of acetylene, benzene, and their mixtures was studied at 1200{degrees}C. Induction times of carbon black formation from acetylene, benzene, and their mixture were measured. The specific surface area of the carbon black obtained by pyrolysis of acetylene and benzene was nearly the same (21.0 m{sup 2}/g). Pyrolysis of acetylene-benzene mixtures resulted in carbon black with a much lower specific surface area (7.0 - 10.0 m{sup 2}/g); the particles of carbon black were shown to be formed by acetylene decomposition, while benzene was consumed but for the growth of particles. The observed inhibition of the particle formation from benzene is accounted for by the difference in the induction times during carbon black formation.

Tesner, P.A.; Shurupov, S.V. [All-Russian Research Institute of Natural Gases and Gas Technologies, Moscow (Russian Federation)

1995-07-01

65

Gas chromatographic-mass spectrometric assay of tissue malondialdehyde, 4-hydroxynonenal, and other aldehydes after their reduction to stable alcohols.  

PubMed

Measurement of specific aldehydes such as malondialdehyde, hexanal, or 4-hydroxynonenal provides a method to evaluate the extent of lipid peroxidation. However, assay of aldehydes is complicated by their high reactivity toward other molecules and their chemical instability. In the proposed method, aldehydes are reduced to stable alcohols. Except for malondialdehyde, this is readily accomplished under neutral conditions at room temperature or at 4 degrees C with either sodium borodeuteride (NaB2H4) or sodium borohydride (NaBH4). Complete reduction of malondialdehyde requires a more powerful reducing agent, borane trimethylamine. After ether extraction and evaporation of the organic phase, the alcohols are converted to t-butyldimethylsilyl ethers and analyzed by selected ion monitoring gas chromatography-mass spectrometry in the positive chemical ionization mode for malondialdehyde and 4-hydroxynonenal and electron impact mode for all other aldehydes. Quantitation is achieved using internal standards of 1,3-[2H8]propanediol for MDA, of 4-[2-2H]hydroxynonenal for 4-hydroxynonenal, and of the corresponding saturated per-deuterated alcohols for all saturated aldehydes, for example and [2H13]hexanol for hexanal. Saturated per-deuterated alcohols also serve as external standards for their unsaturated aldehydes with same chain length. The detection limit for individual aldehydes is 0.5 nmol in a given sample. In addition to being highly sensitive and selective, the present method allows one to verify the identity of each aldehyde by observing a mass shift when aldehydes are reduced with either NaB2H4 or NaBH4. The usefulness of our method is demonstrated by measuring aldehyde accumulation in autoxidized arachidonic acid solutions and in heart homogenates before and after induction of peroxidation. PMID:8434785

Des Rosiers, C; Rivest, M J; Boily, M J; Jetté, M; Carrobé-Cohen, A; Kumar, A

1993-01-01

66

Evaluation of anthelmintic activity in captive wild ruminants by fecal egg reduction tests and a larval development assay.  

PubMed

The effectiveness of anthelmintics was evaluated in four herds of captive ruminants, wapiti (Cervus elaphus), Armenian red sheep (Ovis orientalis), giraffe (Giraffa camelopardalis), and pronghorn (Antilocapra americana), by the use of fecal egg reduction tests (FERTs) and a commercial larval development assay (LDA) designed to evaluate susceptibility or resistance of nematodes to anthelmintics. Haemonchus sp. was the predominant nematode in the red sheep, giraffe, and pronghorn herds, whereas Ostertagia sp. and Trichostrongylus sp. were predominant in the wapiti. The LDA data indicated susceptibility by the worms to benzimidazoles except in the red sheep flock, which showed a high level of resistance. High levels of resistance to levamisole were seen in the worm populations from the wapiti and red sheep, moderate resistance in the pronghorn herd, and susceptibility in the giraffe herd. Worms were susceptible in all four herds to a combination of benzimidazole/levamisole. There was suspected avermectin resistance by Trichostrongylus sp. in the wapiti herd and by Haemonchus sp. in the giraffe. The FERTs agreed with the LDA in showing the Haemonchus in the giraffe was susceptible to fenbendazole and had suspected resistance to ivermectin, whereas Haemonchus in the red sheep and pronghorn were susceptible to ivermectin. There was correlation between the tests evaluating anthelmintics. The LDA is useful as a screening test in the selection of an anthelmintic for use in grazing ruminants, but the effectiveness of a drug in a host species may depend as much on the dose used, and the method of administration, as it does on the parasite's sensitivity to the anthelmintic. PMID:11237142

Young, K E; Jensen, J M; Craig, T M

2000-09-01

67

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

68

On-chip background noise reduction for cell-based assays in droplets Pascaline Mary,a  

E-print Network

-throughput biological assays. Each droplet serves as a reaction vessel with a volume as small as a few picolitres to homogeneous assays as it is very difficult to wash reagents from the reaction vessel. To help overcome a major obstacle for performing multi-step reactions or integrating an online reaction and detection step

69

46 CFR 154.1735 - Methyl acetylene-propadiene mixture.  

Code of Federal Regulations, 2010 CFR

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

2010-10-01

70

Tropospheric and lower stratospheric vertical profiles of ethane and acetylene  

NASA Technical Reports Server (NTRS)

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 and 35,000 ft, near 37 deg N-123 deg W were 1.2 micrograms/cu m (1.0 ppb) for ethane and 0.24 micrograms /cu m (0.23 ppb) for acetylene while the values near 9 N-80 W were 0.95 micrograms/cu m (0.77 ppb) and 0.09 micrograms/cu m (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, D.; Robinson, E.

1979-01-01

71

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

USGS Publications Warehouse

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

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

2013-01-01

72

Laser absorption diagnostic for measuring acetylene concentrations in shock tubes  

NASA Astrophysics Data System (ADS)

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

Stranic, Ivo; Hanson, Ronald K.

2014-07-01

73

Acetylene structure and dynamics on Pd(111)  

SciTech Connect

Acetylene molecules adsorbed onto a Pd(111) crystal surface were imaged by scanning tunneling microscopy (STM) below 70 K. Single C{sub 2}H{sub 2} molecules appeared as a combination of a protrusion and a depression 3.5 {Angstrom} apart. This peculiar shape is due to the molecular {pi} orbital, which is oriented at a shallow angle out of the surface. Six orientations of the molecule with respect to the substrate were observed, indicating two different threefold hollow binding sites each with three possible rotational states. At 44 K, thermally activated rotation of the molecules between the three equivalent states on the same threefold hollow site occurs on the time scale of seconds. Diffusion of molecules between adjacent threefold sites began at {approximately}70K. The findings agree with the structure of the adsorption site determined by total-energy calculations and with the STM image calculated using the electron scattering quantum chemistry method. {copyright} {ital 1998} {ital The American Physical Society}

Dunphy, J.C.; Rose, M.; Behler, S.; Ogletree, D.F.; Salmeron, M. [Lawrence Berkeley National Laboratory, Materials Sciences Division, University of California, Berkeley, California 94720 (United States)] [Lawrence Berkeley National Laboratory, Materials Sciences Division, University of California, Berkeley, California 94720 (United States); Sautet, P. [Laboratoire de Chimie Theorique, ENS, 69364Lyon (France)] [Laboratoire de Chimie Theorique, ENS, 69364Lyon (France); [Institut de Recherches sur la Catalyse, CNRS, 69626Villeurbanne (France)

1998-05-01

74

Electrochromic poly(acetylene)s with switchable visible/near-IR absorption characteristics.  

PubMed

Ferrocene is incorporated into a poly(acetylene) derivative via the postpolymerization amidation of a polymer precursor bearing pentafluorophenyl ester-leaving groups with aminoferrocene. While the neutral polymer exhibits a strong absorbance at 553 nm due to its conjugated backbone, oxidation of the ferrocene moieties with silver tetrafluoroborate causes the material to absorb in the near-IR (? max ? 1215 nm). Subsequent reduction of the oxidized polymer with decamethylferrocene restores the initial absorbance profile, demonstrating that the material features switchable visible/near-IR absorption characteristics. PMID:23996218

Pauly, Anja C; Varnado, C Daniel; Bielawski, Christopher W; Theato, Patrick

2014-01-01

75

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

76

Ethane and acetylene abundances in the Jovian atmosphere  

NASA Technical Reports Server (NTRS)

The paper reports spectra of Jupiter in the spectral region from 755 to 850 kaysers, which covers the nu-9 fundamental of ethane and contains lines from the R branch of the nu-5 fundamental of acetylene. The monochromatic absorption coefficient of the central Q branch of the nu-9 fundamental of ethane, which was determined in the laboratory, is applied in a radiative-transfer calculation to evaluate the ethane mixing ratio in the Jovian atmosphere; the present data are also used to place an upper limit on the acetylene mixing ratio. For the radiative-transfer calculation, emission intensity is computed for the region above the 0.02-atm level assuming both an isothermal inversion layer and a previously reported temperature profile. The resulting maximum mixing ratios consistent with the observations are 0.00003 for ethane and 7.5 by 10 to the -8th power for acetylene.

Tokunaga, A.; Knacke, R. F.; Owen, T.

1976-01-01

77

Chemistry and properties of blends of acetylene terminated materials  

NASA Technical Reports Server (NTRS)

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

Connell, John W.; Hergenrother, Paul M.

1991-01-01

78

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

Code of Federal Regulations, 2010 CFR

...2010-10-01 false Charging of cylinders with compressed gas in solution (acetylene). 173.303 Section 173.303 Transportation... § 173.303 Charging of cylinders with compressed gas in solution (acetylene). (a) Cylinder, filler and solvent...

2010-10-01

79

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

Code of Federal Regulations, 2011 CFR

...2011-10-01 false Charging of cylinders with compressed gas in solution (acetylene). 173.303 Section 173.303 Transportation... § 173.303 Charging of cylinders with compressed gas in solution (acetylene). (a) Cylinder, filler and solvent...

2011-10-01

80

Siloxane containing addition polyimides. II - Acetylene terminated polyimides  

NASA Technical Reports Server (NTRS)

Acetylene terminated polyimide oligomers having a range of molecular weights have been synthesized by reacting bis (gamma-aminopropyl) tetramethyldisiloxane, aminophenylacetylene and 3, 3', 4, 4' benzophenonetetracarboxylic dianhydride in different molar ratios. The prepolymers were isolated and characterized for melt flow and cure properties. They show promise as adhesives for bonding titanium to titanium and as matrix resins for graphite cloth reinforced composites. The most promising system has been blended in varying proportions with Thermid 600, a commercially available acetylene terminated polyimide oligomer, and the mixtures have been tested for application as composite matrix resins.

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

1984-01-01

81

New Silica-Immobilized Nickel Catalysts for Cyclotrimerizations of Acetylenes  

E-print Network

New Silica-Immobilized Nickel Catalysts for Cyclotrimerizations of Acetylenes S. Reinhard, P. SÏoba.Bluemel@urz.uni-heidelberg.de Received: December 16, 2002; Accepted: February 6, 2003 Abstract: New dicarbonylnickel catalysts), have been synthesized and fully characterized, three of them by X-ray analyses. All the catalysts have

Bluemel, Janet

82

Fatal carbon monoxide intoxication after acetylene gas welding of pipes.  

PubMed

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

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

2013-06-01

83

Production of acetylene from coal using a new plasma gasifier  

SciTech Connect

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

Kikukawa, N.; Makino, M.

1984-04-01

84

An estimation of the isomerization energy of acetylene  

Microsoft Academic Search

An accurate prediction of the adiabatic energy difference separating acetylene and vinylidene is presented. The electronic energy contribution is estimated on the basis of CCSD(T) calculations using up to 400 contracted Gaussian basis functions together with extrapolation to the basis set limit; an additional correction is applied to account for residual electron correlation effects. Zero-point vibrational corrections are based on

John F. Stanton; Jürgen Gauss

1999-01-01

85

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

86

Detonation engine fed by acetylene-oxygen mixture  

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

87

Rapid synthesis of crowded aromatic architectures from silyl acetylenes.  

PubMed

Congested aromatic systems were prepared by benzannulating silyl-protected arylacetylenes. The silyl groups may be retained in the naphthalene products and transformed into iodides in high yield. The desirable attributes of this strategy, particularly its remarkable tolerance of sterically hindered alkynes, are showcased in the efficient synthesis of a congested, branched oligo(naphthalene). As such, benzannulations of diaryl and silyl-protected acetylenes show outstanding promise for accessing new aromatic architectures. PMID:25162976

Hein, Samuel J; Arslan, Hasan; Keresztes, Ivan; Dichtel, William R

2014-09-01

88

Butterfly structure: Signature of vibrational flopping in dissociative acetylene  

NASA Astrophysics Data System (ADS)

We report experimental evidence for molecular deformation due to a vibrationally active transition state of multiply charged acetylene molecules under the impact of low energy Ar8+ projectiles. "Butterflylike" structures are observed in the experimental coincidence spectra between hydrogen and carbon ionic fragments. Such structures can be generated by numerical simulations and are found to originate from the bending motion of the dissociating molecule. Angular distributions for dissociation products from triply charged C2H2 ion are reported.

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

2007-08-01

89

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

SciTech Connect

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

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

2009-07-01

90

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

SciTech Connect

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

Gan, L.S.

1986-01-01

91

Base-catalyzed domino cyclization of acetylenes with ketones to functionalized cyclopentenes.  

PubMed

Acetylene reacts with methylaryl(hetaryl)ketones in the presence of 6.5 mol % KOH in DMSO to give diastereoselectively in single operationally functionalized cyclopentenes. This domino cyclization involving two molecules of acetylene and two molecules of ketone proceeds with the formation of four C-C bonds. The complementary assembly of the cyclopentenes with similar functionalities from acetylenes and 1,5-diketones has been developed. PMID:25055028

Schmidt, Elena Yu; Trofimov, Boris A; Bidusenko, Ivan A; Cherimichkina, Natalia A; Ushakov, Igor' A; Protzuk, Nadezhda I; Gatilov, Yurii V

2014-08-01

92

[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

1999-01-01

93

Ultrafast Extreme Ultraviolet Induced Isomerization of Acetylene Cations  

NASA Astrophysics Data System (ADS)

Ultrafast isomerization of acetylene cations ([HC=CH]+) in the low-lying excited A?g+2 state, populated by the absorption of extreme ultraviolet (XUV) photons (38 eV), has been observed at the Free Electron Laser in Hamburg, (FLASH). Recording coincident fragments C++CH2+ as a function of time between XUV-pump and -probe pulses, generated by a split-mirror device, we find an isomerization time of 52±15fs in a kinetic energy release (KER) window of 5.8

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

2010-12-01

94

[The mechanism of anticholinesterase action of acetylene organophosphorus inhibitors].  

PubMed

Introduction of the triple bond in the leaving group of the organophosphorus inhibitor molecule gives a sharp raise of the inhibitor activity but does not change principal characteristics of the cholinesterase inhibition mechanism. The reactivation experiments suggest that inactivation of cholinesterases by these compounds occurs due to phosphorylating of the serine hydroxyl by the corresponding phosphoric acid. A close similarity was shown between acetylenic and saturated organophosphorus inhibitors in altering ka upon change of pH and tetraalkylammonium ions action. It is demonstrated that S-alkynyl esters of thioacetic acid are slowly hydrolyzed by acetylcholinesterase and cholinesterase without irreversible inhibition of the enzymes. PMID:1445434

Brestkin, A P; Zhukovski?, Iu G; Moralev, S N; Rozengart, V I; Sochilina, E E; Iagodina, O V; Vikhreva, L A; Godovikov, N N; Kabachnik, M I

1992-08-01

95

Photochemical reaction dynamics in SO2-acetylene complexes  

NASA Astrophysics Data System (ADS)

The dynamics of photoinduced reactions between electronically excited SO2 molecule (A~ 1A2<--X~ 1A1) and acetylene molecule (X~ 1?g+) in the SO2-acetylene van der Waals (vdW) complexes (clusters) was studied. The SO2 molecule was excited by frequency-doubled radiation of a tunable dye laser, and resonance enhancement multiphoton photoionization of the produced photofragments was induced by ArF (193 nm) laser radiation or by frequency-doubled radiation of a second tunable dye laser to observe the C2H radical. The HOSO radical was detected by its IR emission. We found that the main photodecomposition channel of the vdW complexes (clusters) involves the SO2*+C2H2-->HOSO+C2H reaction. Indeed, the analysis of the action spectra of the excitation laser radiation showed that the photofragments emerging in our experimental conditions (SO2, 5% C2H2, 5% and Xe; P0=2 atm) originate from the SO2...C2H2 vdW complex (cluster). We analyzed the structure of this vdW complex theoretically, obtaining Cs symmetry, with the acetylene molecule located above the OSO plane. The resonance-enhanced multiphoton photoionization action spectra of the C2H (A~<--X~) photofragmentation and the IR emission spectra of the HOSO radical allowed the authors to probe the energy distribution between the photofragments formed. The reaction that involves transition of the acetylene H atom to the SO2 oxygen should be the primary step of the process considered, followed by nonstatistic dissociation of the vdW complex (cluster), with the C2H radical formed in its vibrationless state and excited both rotationally and translationally, and the HOSO radical excited vibrationally, rotationally and translationally. The proposed reaction mechanism was discussed, employing transition-state and Rice-Ramsperger-Kassel-Marcus (RRKM) approaches. The kinetics of photofragment formation was investigated, yielding characteristic radical build-up time of 0.64 ?s.

Makarov, Vladimir I.; Kochubei, Sergei A.; Khmelinskii, Igor

2010-06-01

96

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

97

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

PubMed Central

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

Dicker, Howard J.; Smith, David W.

1980-01-01

98

On the Distribution of Energy in the Visible Spectrum of an Acetylene Flame  

Microsoft Academic Search

A knowledge of the distribution of energy in the visible spectrum of an acetylene flame has become important within the last few years through the use of this flame, in cylindrical form, in investigations of the visibility of radiation. It can be shown by computation that the data on acetylene published by Coblentz form a curve in the visible spectrum

E. P. Hyde; W. E. Forsythe; F. E. Cady

1919-01-01

99

Effects of oxidation and heat treatment of acetylene blacks on their electrochemical double layer capacitances  

Microsoft Academic Search

Correlations between the electrochemical double layer capacitances of various acetylene blacks modified by surface oxidation and heat treatment, and their morphologies are presented. The acetylene blacks were different from each other in primary structural unit size (equivalent to mean particle diameter). They were oxidized in air at 300°C for 1h to produce graphene sheets protruding from the surfaces of the

Taegon Kim; Chulho Ham; Choong Kyun Rhee; Seong-Ho Yoon; Masaharu Tsuji; Isao Mochida

2009-01-01

100

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

NASA Astrophysics Data System (ADS)

The bending dynamics of acetylene with pure vibrational angular momentum excitation and quantum number ? ?0 are analyzed through the method of critical points analysis, used previously [V. Tyng and M. E. Kellman, J. Phys. Chem. B 110, 18859 (2006)] for ? =0 to find new anharmonic modes born in bifurcations of the low-energy normal modes. Critical points in the reduced phase space are computed for continuously varied bend polyad number Nb=n4+n5 as ? =?4+?5 is varied between 0 and 20. It is found that the local L, orthogonal O, precessional P, and counter-rotator CR families persist for all ?. In addition, for ? ?8, there is a fifth family of critical points which, unlike the previous families, has no fixed relative phase ("off great circle" OGC). The concept of the minimum energy path in the polyad space is developed. With restriction to ? =0 this is the local mode family L. This has an intuitive relation to the minimum energy path or reaction mode for acetylene-vinylidene isomerization. With ? ?0 included as a polyad number, the ? =0 minimum energy path forms a troughlike channel in the minimum energy surface in the polyad space, which consists of a complex mosaic of L, O, and OGC critical points. There is a division of the complete set of critical points into layers, the minimum energy surface forming the lowest.

Tyng, Vivian; Kellman, Michael E.

2009-12-01

101

Ion induced dissociation dynamics of acetylene: Signature of vibrational flopping  

NASA Astrophysics Data System (ADS)

We report the results of dissociation dynamics of multiple charged acetylene molecules formed in collision with 1.2 MeV Ar^8+ projectiles. Using the coincidence map, we found the evidence for molecular deformation due to a vibrationally active transition state of multiply charged C2H2 under the impact of low energy projectiles. `Butterfly-like' structures are observed in the coincidence spectra [1] between hydrogen and carbon ionic fragments. Such structures can be generated by numerical simulations and are found to originate from the bending motion of the dissociating molecule. 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 behaviour of the C--C charged complex during dissociation of multiply charged acetylene [2]. This is a signature of sequentiality in the breakup dynamics of this multiply charged molecular species. The results will be compared with those obtained in pump-probe experiments using intense few cycle laser pulses. Ref: [1] S. De et al. JCP, 127, 051101 (2007); [2] S. De et. al. PRA (accepted)

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

2008-05-01

102

TOPICAL REVIEW: Plasma-chemical reactions: low pressure acetylene plasmas  

NASA Astrophysics Data System (ADS)

Reactive plasmas are a well-known tool for material synthesis and surface modification. They offer a unique combination of non-equilibrium electron and ion driven plasma chemistry, energetic ions accelerated in the plasma sheath at the plasma-surface interface, high fluxes of reactive species towards surfaces and a friendly environment for thermolabile objects. Additionally, small negatively charged clusters can be generated, because they are confined in the positive plasma potential. Plasmas in hydrocarbon gases, and especially in acetylene, are a good example for the discussion of different plasma-chemical processes. These plasmas are involved in a plethora of possible applications ranging from fuel conversion to formation of single wall carbon nanotubes. This paper provides a concise overview of plasma-chemical reactions (PCRs) in low pressure reactive plasmas and discusses possible experimental and theoretical methods for the investigation of their plasma chemistry. An up-to-date summary of the knowledge about low pressure acetylene plasmas is given and two particular examples are discussed in detail: (a) Ar/C2H2 expanding thermal plasmas with electron temperatures below 0.3 eV and with a plasma chemistry initiated by charge transfer reactions and (b) radio frequency C2H2 plasmas, in which the energetic electrons mainly control PCRs.

Benedikt, J.

2010-02-01

103

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

104

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

105

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)] [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)] [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)] [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

106

[The development of acetylene on-line monitoring technology based on laser absorption spectrum].  

PubMed

As one of the materials in organic chemical industry, acetylene has been used in many aspects of chemical industry. But acetylene is a very dangerous inflammable and explosive gas, so it needs in-situ monitoring during industrial storage and production. Tunable diode laser absorption spectroscopy (TDLAS) technology has been widely used in atmospheric trace gases detection, because it has a lot of advantageous characteristics, such as high sensitivity, good selectivity, and rapid time response. The distribution characteristics of absorption lines of acetylene in near infrared band were studied, and then the system designing scheme of acetylene on-line monitoring based on near infrared tunable diode laser absorption spectroscopy technology was discussed in detail. Moreover, the system of experiment measurement was set up and the method of signal detection and the algorithm of concentration inversion were studied. In addition, the sample cell with a path length of 10 cm, and the acetylene of different known concentrations were measured. As a result, the detection limit obtained reached 1.46 cm3 x m(-3). Finally the dynamic detection experiment was carried out, and the measurement result is stable and reliable, so the design of the system is practicable through experiment analysis. On-line acetylene leakage monitoring system was developed based on the experiment, and it is suitable for giving a leakage alarm of acetylene during its storage, transportation and use. PMID:19123378

He, Ying; Zhang, Yu-jun; Kan, Rui-feng; Xia, Hui; Wang, Min; Cui, Xiao-juan; Chen, Jiu-ying; Chen, Dong; Liu, Wen-qing; Liu, Jian-guo

2008-10-01

107

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

NASA Astrophysics Data System (ADS)

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

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

2011-04-01

108

Acetylene fuel from atmospheric CO2 on Mars  

NASA Technical Reports Server (NTRS)

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

Landis, Geoffrey A.; Linne, Diane L.

1992-01-01

109

Detection of acetylene in the infrared spectrum of comet Hyakutake  

NASA Technical Reports Server (NTRS)

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

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

1996-01-01

110

Watching the acetylene vinylidene intramolecular reaction in real time  

E-print Network

It is a long-standing dream of scientists to capture the ultra-fast dynamics of molecular or chemical reactions in real time and to make a molecular movie. With free-electron lasers delivering extreme ultraviolet (XUV) light at unprecedented intensities, in combination with pump-probe schemes, it is now possible to visualize structural changes on the femtosecond time scale in photo-excited molecules. In hydrocarbons the absorption of a single photon may trigger the migration of a hydrogen atom within the molecule. Here, such a reaction was filmed in acetylene molecules (C2H2) showing a partial migration of one of the protons along the carbon backbone which is consistent with dynamics calculations on ab initio potential energy surfaces. Our approach opens attractive perspectives and potential applications for a large variety of XUV-induced ultra-fast phenomena in molecules relevant to physics, chemistry, and biology.

Jiang, Y H; Rudenko, A; Madjet, M E; Vendrell, O; Kurka, M; Schnorr, K; Foucar, L; Kübel, M; Herrwerth, O; Lezius, M; Kling, M F; van Tilborg, J; Belkacem, A; Ueda, K; Düsterer, S; Treusch, R; Schröter, C D; Santra, R; Ullrich, J; Moshammer, R

2014-01-01

111

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

112

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 < KER < 8 eV, providing clear evidence for the existence of a fast, nonradiative decay channel.

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

2011-06-17

113

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

PubMed

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

Oremland, Ronald S; Voytek, Mary A

2008-02-01

114

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

USGS Publications Warehouse

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

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

2008-01-01

115

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

116

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

NASA Technical Reports Server (NTRS)

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

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

1986-01-01

117

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

NASA Technical Reports Server (NTRS)

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

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

1986-01-01

118

Detection of acetylene in the Saturnian atmosphere, using the IUE satellite  

NASA Technical Reports Server (NTRS)

Direct evidence for the presence of acetylene in the upper part of the Saturnian atmosphere is reported. This evidence consists of two spectra of Saturn obtained by using the low-dispersion mode of the short-wavelength spectrograph on the IUE satellite. A series of distinct absorption bands in the reflected solar radiation at 1750 A is attributed to acetylene. The reciprocal of the acetylene cross section at 1750 A is shown to imply 7 x 10 to the 17th molecules/sq cm in the reflecting layer. It is concluded that the radiation at 1750 A originates from less than 2.3 km-amagat within the atmosphere.

Moos, H. W.; Clarke, J. T.

1979-01-01

119

Acetylene as a substrate in the development of primordial bacterial communities  

USGS Publications Warehouse

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

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

1988-01-01

120

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

SciTech Connect

Addition of acetylene to microcosms simultaneously amended with nitrate and alkylbenzenes resulted in inhibition of the rate of alkylbenzene biodegradation under denitrifying conditions. Toluene, xylenes, and 1,2,4-trimethylbenzene were recalcitrant, whereas ethylbenzene was degraded at a slower rate than usual. Benzene was not degraded in either case. Addition of acetylene to microcosms preexposed to nitrate and alkylbenzenes produced similar inhibition. These data indicate that the activities of microorganisms that degrade alkylbenzenes under denitrifying conditions may be suppressed if the standard acetylene block technique is used to verify denitrifying activity.

Hutchins, S.R. (U.S. Environmental Protection Agency, Ada, OK (United States))

1992-10-01

121

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

Code of Federal Regulations, 2010 CFR

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

2010-10-01

122

Novel Linear Metallocene Polymers Containing Acetylenic and Inorganic Units and Thermosets and Ceramics Therefrom.  

National Technical Information Service (NTIS)

Transition metal containing ceramic or carbonaeous material are formed from novel linear polymers containing a random distribution of repeating acetylenic units, organotransition metal complexes, Siloxane, boron, Silicon, and/or carborane-siloxane units. ...

T. Keller, E. J. Houser

1997-01-01

123

Novel Linear Metallocene Polymers Containing Acetylenic and Inorganic Units and Thermosets and Ceramics Therefrom.  

National Technical Information Service (NTIS)

Thermally stable thermosets are formed from novel linear polymer containing acetylenic units and a random distribution of organotransition metal complexes, siloxane, boron, and/or carborane-siloxane units formed by crosslinking of the linear copolymers th...

T. Keller, E. J. Houser

1997-01-01

124

Spectroscopy and theory of cis-trans isomerization in the S? state of acetylene  

E-print Network

This thesis consists of parallel experimental and theoretical studies of the rovibrational structure and dynamics of the Si state of acetylene, C2H2 . This small molecule is a prototypical system for the study of cis-trans ...

Changala, P. Bryan (Peter Bryan)

2013-01-01

125

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...

126

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...

127

Decarboxylative elimination of enol triflates as a general synthesis of acetylenes.  

PubMed

The enol trifluoromethanesulfonates 4, 8, 12, 17 and 20 of tert-butyl beta-ketodiesters and beta-ketoesters can be hydrolysed to the corresponding carboxylic acids by dissolution in trifluoroacetic acid. The dicarboxylic acids undergo mild decarboxylative elimination to give the acetylenic acids 4 and 9 in aqueous sodium bicarbonate solution at room temperature. Similarly, the monocarboxylic acids give the terminal and mid-chain acetylenes 13, 18, 21, and 24 by refluxing in acetone with potassium carbonate. One of the substituents on the acetylenes can be methyl, primary alkyl, secondary alkyl or ethynyl, and the other can be a carboxylic acid, hydrogen or primary alkyl, but the enol trifluoromethanesulfonates could not be prepared when one of the substituents was tert-butyl, nor when both substituents on the precursor to the acetylene were secondary alkyl. PMID:15136807

Fleming, Ian; Ramarao, Chandrashekar

2004-05-21

128

Solid-state NMR studies of the adsorption of acetylene on platinum/alumina catalysts  

E-print Network

platinum. Using quantitative adsorption of acetylene and spin counting techniques, we find that an amount of "C equivalent to approximately 0. 3 monolayer coverage of the metal is unobsetvable in a standard "CMAS chemical shift spectnun. This latter... platinum. Using quantitative adsorption of acetylene and spin counting techniques, we find that an amount of "C equivalent to approximately 0. 3 monolayer coverage of the metal is unobsetvable in a standard "CMAS chemical shift spectnun. This latter...

Lambregts, Marsha Jo Lupher

2012-06-07

129

A review of acetylene, ethylene and ethane molecular spectroscopy for planetary applications  

NASA Technical Reports Server (NTRS)

Spectroscopic work in acetylene, ethylene and ethane, are of particular interest since the Voyager IRIS observations of Jupiter. Acetylene and ethane but not ethylene were observed in the Jovian spectrum. Two fundamental bands of the observed gases are used to determine the spatial distribution of these hydrocarbons on Jupiter and to illuminate the photochemistry of these species. The 100 to 1000 cm region is discussed and selected examples of current laboratory work are given.

Maguire, W. C.

1982-01-01

130

Slow and Superluminal Light Pulses Via EIT in a 20-m Acetylene-Filled Photonic Microcell  

Microsoft Academic Search

We have developed an all-fiber system where we generate electromagnetically induced transparencies in a 20-m acetylene-filled photonic microcell. Using this system, pulses of probe light were delayed and advanced by up to 5 and 1 ns, respectively. The delay\\/advance is tunable through the probe detuning and the coupling Rabi frequency. Through optimization of experimental parameters such as acetylene pressure, coupling

Natalie V. Wheeler; Philip S. Light; Francois Couny; Fetah Benabid

2010-01-01

131

The adsorption of acetylene on rhodium-modified colloidal silver, a surface-enhanced Raman study  

NASA Astrophysics Data System (ADS)

Surface-enhanced Raman scattering (SERS) from molecules adsorbed on rhodium-modified colloidal silver particles is reported for the first time. Deposition of thin layers of metallic rhodium on the silver surface led to fast aggregation of the sol and to modifications of its SERS spectrum. An intense new band, assigned to the Rh?O stretching vibration of citrate ions bound to rhodium sites, appeared at 530 cm -1 in the Raman spectrum after rhodium addition to the suspension. The spectra of acetylene adsorbed on both unmodified silver particles and silver modified by an overlayer of rhodium indicated that acetylene displaced the citrate ions from their adsorption sites. All acetylene spectra were characterized by weak bands at 1990, 2050 and 2150 cm -1 assigned to ? ?-complexes between acetylene and silver, by a silver acetylide peak at 1800 cm -1 and by an intense band at 1550 cm -1 due to C=C containing species formed on the surface. However, on the rhodium-modified colloid an additional band, attributed to acetylene ? ?-bound to rhodium sites, was observed at 1910-1920 cm -1. The intensity of the new band was a direct function of the amount of rhodium deposited on the silver. It increased immediately after acetylene adsorption, and later slowly diminished, while simultaneously the 1550 cm -1 peak became more important. This time evolution was ascribed to a reaction taking place on the surface.

Feilchenfeld, Hannah; Luckier, Miguel; Efron, Leah; Willner, Bilha

132

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

SciTech Connect

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

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

1986-05-01

133

An improved processible acetylene-terminated polyimide for composites  

NASA Technical Reports Server (NTRS)

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

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

1985-01-01

134

Topoisomerase assays.  

PubMed

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 enzymes, which make 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 for 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 to examine topoisomerase covalent complexes in vivo, and an assay for measuring DNA cleavage in vitro. PMID:22684721

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

2012-06-01

135

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

EPA Science Inventory

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

136

Kinetic tetrazolium microtiter assay  

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

137

Vacuum ultraviolet photochemistry of solid acetylene: a multispectral approach  

NASA Astrophysics Data System (ADS)

Aims: Gas phase acetylene (C2H2) and polyynes (H(-C?C-)mH) are ubiquitous in the interstellar medium. However, astrochemical models systematically underestimate the observed abundances, supporting the idea that enrichment from the solid state takes place. In this laboratory-based study, we investigate the role C2H2 plays in interstellar ice chemistry and we discuss the way its photoproducts may affect gas phase compositions. Methods: C2H2 ice is investigated under vacuum ultraviolet (VUV) irradiation in its pure form as present in the atmosphere of Titan and in a water-dominated ice as present on grain mantles in molecular clouds and on comets. To disentangle the photochemical network, a unique, complementary combination of infrared and ultraviolet-visible (UV-VIS) spectroscopy is used. Results: From the experimental results, it can be concluded that the VUV-induced solid state C2H2 reaction network is dominated by polymerization resulting in the formation of polyynes at least up to C20H2 and larger polyyne-like molecules. At low temperatures, this process takes place very efficiently and suggests low barriers. When extending this reaction scheme to a water-rich environment, the dominant reaction products are CO and CO2 but the simultaneous detection of polyyne like molecules is evidence that the reactions as observed in pure C2H2 ice persist. Conclusions: From the spectroscopic evidence as presented in this laboratory study, it is concluded that the formation of polyynes upon VUV irradiation of interstellar ices is a process that may contribute to at least part of the observed gas phase enrichment in space.

Cuylle, Steven H.; Zhao, Dongfeng; Strazzulla, Giovanni; Linnartz, Harold

2014-10-01

138

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

PubMed

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

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

2013-07-13

139

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...

140

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

SciTech Connect

Aquifers contaminated with gasoline and other fuels often exhibit levels of benzene, toluene, ethylbenzene, and xylenes (BTEX) in excess of regulatory limits mandated by the U.S. Environmental Protection Agency. Addition of acetylene to microcosms simultaneously amended with nitrate and alkylbenzenes resulted in inhibition of the rate of alkylbenzene biodegradation under denitrifying conditions. Toluene, xylenes, and 1,2,4-trimethylbenzene were recalcitrant, whereas ethylbenzene was degraded at a slower rate than usual. Benzene was not degraded in either case. Addition of acetylene to microcosms preexposed to nitrate and alkylbenzenes produced similar inhibition. These data indicate that the activities of microorganisms that degrade alkylbenzenes under denitrifying conditions may be suppressed if the standard acetylene block technique is used to verify denitrifying activity.

Hutchins, S.R.

1992-01-01

141

Transport of acetylene adsorbed in CuBTC metal organic framework  

NASA Astrophysics Data System (ADS)

Metal organic frameworks (MOFs) are an important class of material which has a potential to be used for variety of applications such as in storage materials, pollution control, etc. Here we report a molecular dynamics simulation study investigating dynamical behaviour of the smallest and linear hydrocarbon, acetylene, adsorbed in CuBTC MOF. CuBTC has complex network structure consisting of large pores and tetrahedral pockets connected by windows. Calculated mean squared displacements of the acetylene molecules adsorbed in CuBTC showed anomalous behaviour with change in concentration. This has been understood by studying the evolution of the trajectories and free energy map. There are two pathways for an acetylene molecule to diffuse inside CuBTC. One is through tetrahedral pockets and other is through large pores. It is found that tetrahedral pockets are potential minima sites and most of the molecules reside there at low concentration. Free energy map also showed that there exists a higher energy barrier if diffusion occurs through tetrahedral pockets rather than large pores. Relative population of acetylene molecules in large pores is found to increase with the concentration and since energy barrier is less while diffusing through large pores, it leads to increase in the average diffusivity at higher concentration. It is found that relative population of acetylene molecules diffusing through different pathways and collision between the molecules decide the average diffusivity of the molecules inside CuBTC. Analysis of intermediate scattering function indicated that there exist three time scales associated with the centre of mass diffusion of the acetylene molecules in CuBTC framework.

Prabhudesai, Swapnil Anil; Sharma, Veerendra Kumar; Mitra, Subhankur; Mukhopadhyay, Ramaprosad

2013-04-01

142

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. PMID:2655535

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

1989-01-01

143

Novel three-component route to diastereoselective synthesis of trisubstituted vinylphosphonates using phosphites, acetylenic esters, and aroyl chlorides.  

PubMed

Trisubstituted vinylphosphonates have been prepared via three-component reaction using phosphites, acetylenic esters, and aroyl chlorides in good yields. A variety of phosphites, activated acetylenes, and aroyl chlorides have been successfully employed in these reactions. In addition, three-component synthesis of vinylphosphonate provides exclusive E-olefin stereochemistry. PMID:19099427

Rostamnia, Sadegh; Alizadeh, Abdolali; Zhu, Long-Guan

2009-01-01

144

Tanacetum (Chrysanthemum) corymbosum seed oil--a rich source of a novel conjugated acetylenic acid.  

PubMed

A new conjugated trans,trans-diunsaturated acetylenic acid (17%), found for the first time in nature as a main component of the seed oil of Tanacetum (Chrysanthemum) corymbosum, was shown to be octadeca-8t,10t-dien-12-ynoic acid. Another already known naturally occurring acetylenic acid, crepenynic acid (10%), was found also in the seed oil. The structure of this new unusual fatty acid was confirmed by chromatographic (thin-layer chromatography, gas chromatography, high-performance liquid chromatography) and spectroscopic (infrared, ultraviolet, mass spectrometry) methods by using different chemical derivatizations (deuteration, preparation of picolinyl ester, dimethyloxazoline, and maleic anhydride adduct). PMID:9688176

Tsevegsuren, N; Christie, W W; Lösel, D

1998-07-01

145

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

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

146

Modelling of fixed-bed reactor: two models of industrial reactor for selective hydrogenation of acetylene  

Microsoft Academic Search

Modelling and simulation of operation conditions for a heterogeneous fixed-bed reactor are investigated on the basis of the industrial reactor for selective hydrogenation of acetylene on palladium catalyst (in ethylene production). Heterogeneous and pseudohomogeneous models of the above-mentioned reactor with their advantages and drawbacks are presented. It is shown, that the proper formulation of a pseudohomogeneous model allows for its

M. Szukiewicz; K. Kaczmarski; R. Petrus

1998-01-01

147

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

148

Association mechanisms of unsaturated C2 hydrocarbons with their cations: acetylene and ethylene.  

PubMed

The ion-molecule association mechanism of acetylene and ethylene with their cations is investigated by ab initio quantum chemical methods to understand the structures, association energies, and the vibrational and electronic spectra of the products. Stable puckered cyclic isomers are found as the result of first forming less stable linear and bridge isomers. The puckered cyclic complexes are calculated to be strongly bound, by 87, 35 and 56 kcal mol(-1) for acetylene-acetylene cation, ethylene-ethylene cation and acetylene-ethylene cation, respectively. These stable complexes may be intermediates that participate in further association reactions. There are no association barriers, and no significant inter-conversion barriers, so the initial linear and bridge encounter complexes are unlikely to be observable. However, the energy gap between the bridged and cyclic puckered isomers greatly differs from complex to complex: it is 44 kcal mol(-1) in C(4)H(4)(+), but only 6 kcal mol(-1) in C(4)H(8)(+). The accurate CCSD(T) calculations summarized above are also compared against less computationally expensive MP2 and density functional theory (DFT) calculations for structures, relative energies, and vibrational spectra. Calculated vibrational spectra are compared against available experiments for cyclobutadiene cation. Electronic spectra are also calculated using time-dependent DFT. PMID:23258256

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

2013-02-14

149

ICARUS 66, 610--618 (1986) Enhanced Acetylene Emission near the North Pole of Jupiter  

E-print Network

ICARUS 66, 610--618 (1986) Enhanced Acetylene Emission near the North Pole of Jupiter PIERRE emission lines near 13.3 /xm on Jupiter recorded at the NASA Infrared Telescope Facility in July 1984 of the spot was found to be constant over a 3-day period. Two interpretations are proposed to explain

Atreya, Sushil

150

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

151

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

152

Matrix Isolation and ab initio study of the noncovalent complexes between formamide and acetylene.  

PubMed

Matrix isolation spectroscopy in combination with ab initio calculations is a powerful technique for the identification of weakly bound intermolecular complexes. Here, weak complexes between formamide and acetylene are studied, and three 1:1 complexes with binding energies of -2.96, -2.46, and -1.79 kcal/mol have been found at the MP2 level of theory (MP2/cc-pVTZ + ZPE + BSSE). The two most stable dimers A and B are identified in argon and nitrogen matrices by comparison between the experimental and calculated infrared frequencies. Both complexes are stabilized by the formamide C=O...HC acetylene and H...pi interactions. Large shifts have been observed experimentally for the C-H stretching vibrations of the acetylene molecule, in very good agreement with the calculated values. Eight 1:2 FMA-acetylene trimers (T-A to T-H) with binding energies between -5.44 and -2.62 kcal/mol (MP2/aug-cc-pVDZ + ZPE + BSSE) were calculated. The two most stable trimers T-A and T-B are very close in energy and have similar infrared spectra. Several weak bands that are in agreement with the calculated frequencies of the trimers T-A and T-B are observed under matrix isolation conditions. However, the differences are too small for a definitive assignment. PMID:19159242

Mardyukov, Artur; Sánchez-García, Elsa; Sander, Wolfram

2009-02-12

153

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

154

Spectroscopic Studies of Low-Pressure Flames; Temperature Measurements in Acetylene Flames  

Microsoft Academic Search

Flames at very low pressure have a relatively thick reaction zone (or flame front) and are especially suitable for detailed study of the combustion processes and of the distribution of energy during the reaction. Temperature measurements have been made, by various spectroscopic methods, on flames of acetylene with air, oxygen and nitrous oxide, in some cases down to a pressure

A. G. Gaydon; H. G. Wolfhard

1948-01-01

155

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

156

An automated immunoradiometric assay for ferritin  

Microsoft Academic Search

A semi-automated method for the immunoradiometric assay of ferritin has been developed. Results obtained with serum samples show excellent correlation between this method and the previously described assay. A further useful reduction in the assay time may be achieved by incubating for 3 hours at 37 degrees C instead of 24 hours at 4 degrees C.

B. M. Jones; M. Worwood

1975-01-01

157

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

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

158

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

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

Ma, Jianyi [University of New Mexico, Albuquerque, NM, (United States); Xu, Dingguo [University of New Mexico, Albuquerque, NM, (United States) and Sichuan Univ. (China); Guo, Hua [University of New Mexico, Albuquerque, NM, (United States); Tyng, Vivian [Univ. of Oregon, Eugene, OR (United States); Kellman, Michael E. [Univ. of Oregon, Eugene, OR (United States)

2012-01-03

159

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

PubMed

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

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

2007-01-01

160

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

161

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

SciTech Connect

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

Kumpaty, S.K.; Nokku, V.P. [Rust Coll., Holly Springs, MS (United States); Subramanian, K. [Subramanian (Kannikeswaran), Houston, TX (United States)

1996-12-31

162

A new C-10 acetylene and A new triterpenoid from Conyza canadensis.  

PubMed

From the whole plants of Conyza canadensis (Compositae), a new C-10 acetylene, namely 8R, 9R-dihydroxymatricarine methyl ester (1), and a new triterpenoid, namely 3beta, 16beta, 20beta-trihydroxytaraxast-3-O-palmitoxyl ester (4), were isolated along with eleven known compounds (2, 3, 5-13). The structures of all 13 compounds were elucidated on the basis of their spectral data. The antibacterial activities of compounds 1-3 were evaluated. PMID:17615671

Xie, Wei Dong; Gao, Xue; Jia, Zhong Jian

2007-05-01

163

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

NASA Technical Reports Server (NTRS)

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

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

1990-01-01

164

9,12,15-octadecatrien-6-ynoic acid, new acetylenic acid from mosses  

Microsoft Academic Search

Lipids of the moss,Ceratodon purpureus, yield up to 25% of an acetylenic acid which was identified as allcis-9,12,15-octadecatrien-6-ynoic acid. The methyl ester of this acid was isolated in 95% purity by gas liquid chromatography.\\u000a Mass spectroscopy provided the mol wt and confirmed methyl stearate as product of hydrogenation. Ozonization indicated a triple\\u000a bond in position 6 and a double bond

Bengt Åndersson; Wayne H. Anderson; Jacques R. Chipault; Eldon C. Ellison; Stuart W. Fenton; Joanne L. Gellerman; John M. Hawkins; Hermann Schlenk

1974-01-01

165

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

Microsoft Academic Search

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

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

2008-01-01

166

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

Microsoft Academic Search

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

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

2004-01-01

167

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

168

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

PubMed Central

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

2012-01-01

169

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

SciTech Connect

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

Caporusso, A.M.; Iodice, A.; Lardicci, L.; Salvadori, P. [Chimica Industriale dell` Universita, Pisa (Italy)

1995-12-31

170

Soluble fluorinated polyimides that contain curable acetylene units in the backbone  

SciTech Connect

Soluble polyimides that contain internal acetylene groups in the backbone were prepared by reacting 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride with various ratio of bis(3-aminophenyl)acetylene and 4,4`-diaminodiphenyl ether. The polyimides were soluble in organic solvents such as N-methylpyrrolidone (NMP) and N,N-dimethylacetamide, and exhibited reduced viscosities in the range of 0.76-1.44 (in NMP at 30{degrees}C). The crosslinking behavior was examined by DSC. The onset of exotherm appeared at 321-345{degrees}C depending on the acetylene content. After thermal treatment at 350{degrees}C, the polyimides became insoluble in any organic solvents examined and in conc. sulfuric acid. The viscoelastic analyses showed the effect of crosslinking clearly. For example, Tg increased with thermal treatment, and was finally above 400{degrees}C. The drop of modulus at higher temperature also became very small. The TGA analyses also showed excellent thermal stability.

Takeichi, T.; Ogura, S. [Toyohashi Univ. of Technology, Aichi (Japan)

1993-12-31

171

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

172

Nitrogen oxide reduction in Wolinella succinogenes and Campylobacter species.  

PubMed Central

Wolinella succinogenes cells and extracts reduced nitric oxide, and cells, but not extracts, reduced nitrous oxide. Formate-reduced W. succinogenes extracts generated the 573-nm peak in difference spectra seen previously in response to nitric oxide in denitrifiers. The type strains of several Campylobacter species did not reduce either gaseous oxide. Cells, but not extracts, of C. fetus subspecies (fetus and venerealis) reduced nitrous oxide; acetylene inhibited reduction. Neither cells nor extracts reduced nitric oxide. PMID:7130133

Payne, W J; Grant, M A; Shapleigh, J; Hoffman, P

1982-01-01

173

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

SciTech Connect

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

Burris, D.R. [AFRL/MLQR, Tyndall AFB, FL (United States); Delcomyn, C.A. [Applied Research Associates, Inc., Tyndall AFB, FL (United States); Deng, B. [New Mexico Inst. of Mining and Technology, Socorro, NM (United States). Dept. of Mineral and Environmental Engineering; Buck, L.E. [Polytechnic Univ., Brooklyn, NY (United States). Dept. of Civil and Environmental Engineering; Hatfield, K. [Univ. of Florida, Gainesville, FL (United States). Dept. of Civil Engineering

1998-09-01

174

Thiophene acetylenes and furanosesquiterpenes from Xanthopappus subacaulis and their antibacterial activities.  

PubMed

In a search for naturally occurring antibacterial compounds in medicinal plants, six hitherto unknown thiophene acetylenes, named 10,11-threo-xanthopappin D, 10,11-erythro-xanthopappin D, 10,11-cis-xanthopappin B, 5-(but-4-chloro-3-hydroxy-1-ynyl)-2-(Z)-pent-3-ene-1-ynylthiophene, 5-(but-4-chloro-3-hydroxy-1-ynyl)-2-(E)-pent-3-ene-1-ynylthiophene, 5-(but-3,4-dihydroxy-1-ynyl)-2-(Z)-pent-3-ene-1-ynylthiophene and two furanosesquiterpenes, as well as fifteen known compounds, were isolated from Xanthopappus subacaulis, which has been used as a traditional Tibetan medicine in China. A biosynthetic pathway to thiophene acetylenes was proposed and, the isolated compounds were tested for their antibacterial activity against five bacteria. Within the series of thiophene acetylenes tested, 10,11-threo-xanthopappin D with a threo configuration exhibited strong activity against Bacillus subtilis, with a minimum inhibitory concentration (MIC) of 7.25?g/mL, whereas 10,11-erythro-xanthopappin D with erythro configuration possessed broad-spectrum antibacterial activity against Escherichia coli, Bacillus cereus, Staphylococcus aureus and Erwinia carotovora, with MICs of 12.5, 15.5, 7.25 and 7.25?g/mL, respectively. Meanwhile, the compounds 10,11-cis-xanthopappin B, xanthopappin B, 5-(but-4-chloro-3-hydroxy-1-ynyl)-2-(Z)-pent-3-ene-1-ynylthiophene and 5-(but-4-chloro-3-hydroxy-1-ynyl)-2-(E)-pent-3-ene-1-ynylthiophene substituted with a Cl atom at C-14 showed moderate inhibitory activity against E. coli, B. cereus, S. aureus, E. carotovora and B. subtilis, with MICs ranging from 31.25 to 62.5?g/mL. The structures of these compounds were elucidated through the comprehensive analysis of spectroscopic data, including UV, IR, MS and NMR. PMID:25096755

Zhang, Li; Chen, Chao-Jun; Chen, Jia; Zhao, Qian-Qian; Li, Ya; Gao, Kun

2014-10-01

175

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

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

176

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

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

177

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

NASA Technical Reports Server (NTRS)

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

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

2000-01-01

178

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

NASA Technical Reports Server (NTRS)

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

Tannenbaum, Stanley

1957-01-01

179

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

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

180

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

SciTech Connect

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

Komives, E.A.

1987-01-01

181

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

PubMed

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

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

2014-01-01

182

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

PubMed Central

Pure cultures of the symbiotic cyanobacterium-bryophyte association with Anthoceros punctatus were reconstituted by using Nostoc sp. strain UCD 7801 or its 3-(3,4-dichlorophenol)-1,1-dimethylurea (DCMU)-resistant mutant strain, UCD 218. The cultures were grown under high light intensity with CO2 as the sole carbon source and then incubated in the dark to deplete endogenous reductant pools before measurements of nitrogenase activities (acetylene reduction). High rates of light-dependent acetylene reduction were obtained both before starvation in the dark and after recovery from starvation, regardless of which of the two Nostoc strains was reconstituted in the association. Rates of acetylene reduction by symbiotic tissue with the wild-type Nostoc strain decreased 99 and 96% after 28 h of incubation in the dark and after reexposure to light in the presence of 5 microM DCMU, respectively. Supplementation of the medium with glucose restored nitrogenase activity in the dark to a rate that was 64% of the illuminated rate. In the light and in the presence of 5 microM DCMU, acetylene reduction could be restored to 91% of the uninhibited rate by the exogenous presence of various carbohydrates. The rate of acetylene reduction in the presence of DCMU was 34% of the uninhibited rate of tissue in association with the DCMU-resistant strain UCD 218. This result implies that photosynthates produced immediately by the cyanobacterium can supply at least one-third of the reductant required for nitrogenase activity on a short-term basis in the symbiotic association. However, high steady-state rates of nitrogenase activity by symbiotic Nostoc strains appear to depend on endogenous carbohydrate reserves, which are presumably supplied as photosynthate from both A. punctatus tissue and the Nostoc strain. PMID:1938924

Steinberg, N A; Meeks, J C

1991-01-01

183

Base-catalyzed highly stereoselective conversion of gamma-hydroxy-alpha,beta-acetylenic esters to gamma-acetoxy dienoates.  

PubMed

Gamma-hydroxy-alpha,beta-acetylenic esters can be conveniently prepared from the reaction of methyl propiolate with aldehydes in the presence of ZnEt(2) and N-methylimidazole at room temperature. It is discovered that the gamma-hydroxy-alpha,beta-acetylenic esters can be catalyzed by p-N,N-dimethylaminopyridine (DMAP) in acetic anhydride to generate the gamma-acetoxy dienoates with high stereo control. The mechanism of this conversion is investigated by NMR analyses and isotope labeling experiments. An intramolecular Diels-Alder reaction of a gamma-acetoxy dienoate is conducted to show the synthetic potential of these compounds. PMID:19322771

Yue, Yang; Yu, Xiao-Qi; Pu, Lin

2009-01-01

184

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

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

185

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

PubMed Central

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

Silvester, Warwick B.; Winship, Lawrence J.

1990-01-01

186

Transient responses of nitrogenase to acetylene and oxygen in actinorhizal nodules and cultured Frania  

SciTech Connect

Nitrogenase activity in root nodules of four species of actinorhizal plants showed varying declines in response to exposure to acetylene (10% v/v). Gymnostoma papuanum (S.Moore) L. Johnson. and Casuarina equisetifolia L. nodules showed a small decline (5-15%) with little or no recovery over 15 minutes. Myrica gale L. nodules showed a sharp decline followed by a rapid return to peak activity. Alnus incana ssp. rugosa (Du Roi) Clausen. nodules usually showed varying degrees of decline followed by a slower return to peak or near-peak activity. We call these effects acetylene-induced transients. Rapid increases in oxygen tension also caused dramatic transient decreases in nitrogenase activity in all species. The magnitude of the transient decrease was related to the size of the O{sub 2} partial pressure (pO{sub 2}) rise, to the proximity of the starting and ending oxygen tensions to the pO{sub 2} optimum, and to the time for which the plant was exposed to the lower pO{sub 2}. Oxygen-induced transients, induced both by step jumps in pO{sub 2} and by O{sub 2} pulses, were also observed in cultures of Frankia. The effects seen in nodules are purely a response by the bacterium and not a nodule effect per se. Oxygen-induced nitrogenase transients in actinorhizal nodules from the plant genera tested here do not appear to be a result of changes in nodule diffusion resistance.

Silvester, W.B.; Winship, L.J. (Harvard Univ., Petersham, MA (USA))

1990-02-01

187

Transient responses of nitrogenase to acetylene and oxygen in actinorhizal nodules and cultured frankia.  

PubMed

Nitrogenase activity in root nodules of four species of actinorhizal plants showed varying declines in response to exposure to acetylene (10% v/v). Gymnostoma papuanum (S. Moore) L. Johnson. and Casuarina equisetifolia L. nodules showed a small decline (5-15%) with little or no recovery over 15 minutes. Myrica gale L. nodules showed a sharp decline followed by a rapid return to peak activity. Alnus incana ssp. rugosa (Du Roi) Clausen. nodules usually showed varying degrees of decline followed by a slower return to peak or near-peak activity. We call these effects acetylene-induced transients. Rapid increases in oxygen tension also caused dramatic transient decreases in nitrogenase activity in all species. The magnitude of the transient decrease was related to the size of the O(2) partial pressure (pO(2)) rise, to the proximity of the starting and ending oxygen tensions to the pO(2) optimum, and to the time for which the plant was exposed to the lower pO(2). Oxygen-induced transients, induced both by step jumps in pO(2) and by O(2) pulses, were also observed in cultures of Frankia. The effects seen in nodules are purely a response by the bacterium and not a nodule effect per se. Oxygen-induced nitrogenase transients in actinorhizal nodules from the plant genera tested here do not appear to be a result of changes in nodule diffusion resistance. PMID:16667301

Silvester, W B; Winship, L J

1990-02-01

188

Polymerization in Substituted Acetylenes: A Comparison between Static, Medium-Strain Rate, and Shock Compression Studies.  

NASA Astrophysics Data System (ADS)

Fast timescale of reactions occurring during shock compression create significant diagnostics challenges to fully quantify the mechanisms involved. Static compression provides a complementary route to investigate the equilibrium phase space and metastable intermediates during high pressure chemistry. Intermediate strain rate compression (0.001/s or higher) with time-resolved probes is a novel way to extract reaction kinetics and underlying pathways. In this study, we present our results from high pressure in situ synchrotron x-ray diffraction (XRD) and infrared (IR) spectroscopy studies on substituted acetylenes: tert-butyl acetylene [TBA: (CH3)3-C?CH] and ethynyl trimethylsilane [ETMS: (CH3)3-SiC?CH]. We observed that the onset pressure of chemical reactions at room temperature (C?C -> C=C polymerization) in these compounds was typically higher in static compression (TBA: 11 GPa and ETMS: 26 GPa) when compared to shock input pressures (TBA: 6.1 GPa and ETMS: 6.6 GPa). Expectedly, thermal effects during heating drive the threshold pressure were close to shock conditions as observed during the high temperature measurements. Under compression at medium strain rate (1 GPa/s or higher), a clear progression of the chemical reaction was observed via time-resolved XRD patterns obtained at 0.5s intervals. It is noted that the reaction products were visually observed to be glassy and recovered to ambient conditions, remaining stable with no degradation.

Chellappa, Raja; Dattelbaum, Dana; Velisavljevic, Nenad; Liermann, Hanns-Peter

2013-03-01

189

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

NASA Astrophysics Data System (ADS)

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

Walker, Michael P.

190

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

PubMed Central

Acetylene-black paste without a light scattering layer was applied to meso-porous TiO2 photo-electrode films with a crystalline framework, a low residual carbon, and a tunable morphological pore size. The thermal-treated TiO2 photo-electrode films had an increased acetylene-black concentration with an increase in artificial pores and a decrease in residual carbon. The performance of dye-sensitized solar cells (DSSCs) was enhanced by the use of the TiO2 photo-anode pastes at various acetylene-black concentrations. The photo-conversion efficiency of the DSSCs using TiO2 photo-electrode films with 1.5 wt% acetylene-black was enhanced from 7.98 (no acetylene-black) to 9.75% without the integration of a light- scattering layer. PMID:23511122

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

2013-01-01

191

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

Microsoft Academic Search

A method is described for the preparation of cyanobacterial heterocysts with high nitrogen-fixation (acetylene-reduction) activity supported by endogenous reductants. The starting material was Anabaena variabilis ATCC 29413 grown in the light in the presence of fructose. Heterocysts produced from such cyanobacteria were more active than those from photoautotrophically-grown A. variabilis, presumably because higher reserves of carbohydrate were stored within the

Bent Borg Jensen; Raymond P. Cox; Robert H. Burris

1986-01-01

192

Electrocatalytic activity of non-precious metal catalyst Co–N\\/C toward oxygen reduction reaction  

Microsoft Academic Search

Metallic cobalt was deposited on acetylene black to synthesize a composite Co\\/C by chemical reduction method. A platinum-free electrocatalyst Co–N\\/C(800) for oxygen reduction reaction (ORR) was synthesized by mixing the composite Co\\/C with urea and heat-treating at 800°C. The results from linear sweep voltammograms indicated that the Co–N\\/C(800) is active to ORR. The ?-Co and cobalt oxides are not the

Yu Jun Si; Chang Guo Chen; Wei Yin; Hui Cai

2010-01-01

193

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

194

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

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

195

Gold(I)-Catalyzed Intramolecular Acetylenic Schmidt Reaction David J. Gorin, Nicole R. Davis, and F. Dean Toste*  

E-print Network

Gold(I)-Catalyzed Intramolecular Acetylenic Schmidt Reaction David J. Gorin, Nicole R. Davis, and F 10, 2005; E-mail: fdtoste@berkeley.edu Gold(I) complexes have seen increased utility as catalysts-bonding from gold into an electron-deficient intermediate may play a role in mediating the formation of bicyclo

Toste, Dean

196

Voltammetric Determination of Bisphenol A Using an Acetylene Black?Dihexadecyl Hydrogen Phosphate Composite Film?Modified Electrode  

Microsoft Academic Search

Herein, acetylene black (AB) was easily dispersed into water in the presence of dihexadecyl hydrogen phosphate (DHP), resulting in a stable and homogeneous AB?DHP suspension. Then, an AB?DHP composite film coated glassy carbon electrode (GCE) was constructed after evaporation of water. The electrochemical behavior of bisphenol A was investigated using cyclic voltammetry (CV), linear sweep voltammetry (LSV), and differential pulse

Wensheng Huang; Chunhai Yang

2007-01-01

197

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

Microsoft Academic Search

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

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

2009-01-01

198

PRESSURE BROADENING OF SINGLE VIBRATIONAL-ROTATIONAL TRANSITIONS OF ACETYLENE AT v = 5  

SciTech Connect

To understand the mechanism of pressure broadening one must have accurate values of the pressure broadening coefficients as a function of vibrational quantum number. Unfortunately, such data for polyatomic molecules are scarce. The coefficient for self-broadening of methane has been found to be the same for the R(0) and R(1) lines of the 2{nu}{sub 3} and 3{nu}{sub 3} bands and for an unidentified line of the 5{nu}{sub 1} + {nu}{sub 3} band at 6190 {angstrom} (1). Measurements have also been performed on the {nu}{sub 2} (2) and {nu}{sub 1} + {nu}{sub 3} (3) bands of acetylene. In the work described here, high resolution spectra of single vibrational-rotational lines of the 5{nu}{sub 3} band of acetylene at 15,600 cm{sup -1} have been taken to determine the coefficients for self-broadening at a much higher level of vibrational excitation. A single frequency cw dye laser (Spectra-Physics 580A) with Rhodamine B as the lasing medium is used as a narrow bandwidth light source. The laser is continuously scannable over a 10 GHz region with 30 MHz linewidth. The unfocused beam is chopped and directed through a small, nonresonant optoacoustic cell. The pressure of the acetylene (> 99.99% purity) in the cell is measured with a capacitance manometer. The optoacoustic signal is detected by a miniature electret microphone placed within the cell and is processed by a lock-in amplifier. The high resolution scans are calibrated ({+-} 5%) by monitoring the dye laser output with a spectrum analyzer equipped with 2 GHz FSR mirrors. All spectra were taken at room temperature (293 {+-} 2 K). At the relatively low pressures used in these experiments, the experimental linewidths are not more than three times the Doppler width (1.1 GHz FWHM). The method of Gronwall was used to calculate values of the Voigt lineshape. With these data, the pressure broadened widths, {Delta}{nu}{sub p}, were extracted from the experimental lineshapes and are plotted as a function of pressure for the R(3), R(9), and R(15) lines in Figure 1. The lines drawn through the data points were determined by the linear least squares method. The self-broadening coefficients, {gamma}, and their standard errors are summarized in Table 1 along with the results of other workers.

Wong, James S.

1980-02-01

199

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

PubMed

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

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

2014-07-15

200

Low temperature formation of benzene from acetylene on a Pd(111) surface  

NASA Astrophysics Data System (ADS)

Experiments with UPS, metastable noble gas deexcitation spectroscopy (MDS) and thermal desorption demonstrated that C 2H 2 adsorbed on Pd(111) at 140 K undergoes cyclotrimerisation to C 6H 6 after higher (? 100 L) exposures. If the surface is intermediately warmed up to 300 K, the low temperature state of adsorbed acetylene transforms irreversibly into another species which is unreactive. The surface species formed by reaction was identified by comparison with the electron spectroscopic data of C 6H 6 adsorbed from the gas phase as well as with those of free C 6H 6. The molecules are only weaky held on the surface and start to desorb already at about 150 K.

Sesselmann, W.; Woratschek, B.; Ertl, G.; Küppers, J.; Haberland, H.

1983-08-01

201

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

202

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

NASA Technical Reports Server (NTRS)

Catalytic chemical vapor deposition was used to grow multi-walled carbon nanotubes on a Fe:Co:CaCO3 catalyst from acetylene. The influent and effluent gases were analyzed by gas chromatography and mass spectrometry at different time intervals during the nanotubes growth process in order to better understand and optimize the overall reaction. A large number of byproducts were identified and it was found that the number and the level for some of the carbon byproducts significantly increased over time. The CaCO3 catalytic support thermally decomposed into CaO and CO2 resulting in a mixture of two catalysts for growing the nanotubes, which were found to have outer diameters belonging to two main groups 8 to 35 nm and 40 to 60 nm, respectively.

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

2005-01-01

203

Chiroptical detection of nonchromophoric, achiral guests by enantiopure alleno-acetylenic helicages.  

PubMed

Enantiopure alleno-acetylenic ligands assemble diastereoselectively upon the addition of a zinc(II) salt to form triple-stranded helicates, which provide a sufficiently large helical cage ("helicage") for the encapsulation of guests. The inclusion complexation of heteroalicycles is confirmed by ROESY and DOSY NMR spectroscopy and quantified in (1) H?NMR binding titrations. The ECD spectra of the helicates, which showed strong Cotton effects and exciton coupling, were found to be extremely sensitive to the nature of the guest molecules. Consequently, a series of nonchromophoric, achiral guests of different sizes as well as regioisomers (1,3- and 1,4-dioxane) became distinguishable on the basis of their induced CD (ICD) spectra. Molecular dynamics (MD) simulations show the adaptability of the cavity size to individual guest molecules and support the selective ICD output. Particularly high affinity towards 1,4-dioxane allowed its selective detection at parts-per-million (ppm) levels in aqueous solutions. PMID:25384621

Gidron, Ori; Ebert, Marc-Olivier; Trapp, Nils; Diederich, François

2014-12-01

204

Combination of a pulsed microwave plasma with a catalyst for acetylene oxidation  

NASA Astrophysics Data System (ADS)

The potential of an approach combining a pulsed microwave discharge with a catalytic packed bed reactor for the oxidation of volatile organic compounds (VOC) has been studied. The ignition of the plasma has been made possible by inserting ferroelectric BaTiO3 pellets inside the microwave excitator. As a test VOC molecule, acetylene (C2H2) in an amount of 200ppm in dry air was used. The total oxidation products CO and CO2 have been monitored downstream of the plasma region by tuneable diode laser absorption spectroscopy in the infrared region. The oxidative efficiency was found to increase linearly with the pulse repetition rate. The oxidative efficiency and the CO2/CO selectivity were considerably enhanced when the catalyst was located inside the plasma region, which shows the synergetic effect of the plasma-catalyst combination.

Rousseau, A.; Guaitella, O.; Röpcke, J.; Gatilova, L. V.; Tolmachev, Y. A.

2004-09-01

205

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

PubMed

The introduction of femto-chemistry has made it a primary goal to follow the nuclear and electronic evolution of a molecule in time and space as it undergoes a chemical reaction. Using Coulomb Explosion Imaging, we have shot the first high-resolution molecular movie of a to and fro isomerization process in the acetylene cation. So far, this kind of phenomenon could only be observed using vacuum ultraviolet light from a free-electron laser. Here we show that 266 nm ultrashort laser pulses are capable of initiating rich dynamics through multiphoton ionization. With our generally applicable tabletop approach that can be used for other small organic molecules, we have investigated two basic chemical reactions simultaneously: proton migration and C=C bond breaking, triggered by multiphoton ionization. The experimental results are in excellent agreement with the timescales and relaxation pathways predicted by new and quantitative ab initio trajectory simulations. PMID:25034613

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

2014-01-01

206

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

NASA Astrophysics Data System (ADS)

The introduction of femto-chemistry has made it a primary goal to follow the nuclear and electronic evolution of a molecule in time and space as it undergoes a chemical reaction. Using Coulomb Explosion Imaging, we have shot the first high-resolution molecular movie of a to and fro isomerization process in the acetylene cation. So far, this kind of phenomenon could only be observed using vacuum ultraviolet light from a free-electron laser. Here we show that 266?nm ultrashort laser pulses are capable of initiating rich dynamics through multiphoton ionization. With our generally applicable tabletop approach that can be used for other small organic molecules, we have investigated two basic chemical reactions simultaneously: proton migration and C=C bond breaking, triggered by multiphoton ionization. The experimental results are in excellent agreement with the timescales and relaxation pathways predicted by new and quantitative ab initio trajectory simulations.

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

2014-07-01

207

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

PubMed

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

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

2014-01-01

208

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

PubMed

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

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

2014-05-21

209

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

2011-03-01

210

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

211

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

212

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

PubMed Central

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

Chen, Weigen; Peng, Shudi; Zeng, Wen

2014-01-01

213

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

NASA Technical Reports Server (NTRS)

The study of soot particulate distribution inside gas jet diffusion flames is important to the understanding of fundamental soot particle and thermal radiative transport processes, as well as providing findings relevant to spacecraft fire safety, soot emissions, and radiant heat loads for combustors used in air-breathing propulsion systems. Compared to those under normal gravity (1-g) conditions, the elimination of buoyancy-induced flows is expected to significantly change the flow field in microgravity (O g) flames, resulting in taller and wider flames with longer particle residence times. Work by Bahadori and Edelman demonstrate many previously unreported qualitative and semi-quantitative results, including flame shape and radiation, for sooting laminar zas jet diffusion flames. Work by Ku et al. report soot aggregate size and morphology analyses and data and model predictions of soot volume fraction maps for various gas jet diffusion flames. In this study, we present the first 1-g and 0-g comparisons of soot volume fraction maps for laminar acetylene and nitrogen-diluted acetylene jet diffusion flames. Volume fraction is one of the most useful properties in the study of sooting diffusion flames. The amount of radiation heat transfer depends directly on the volume fraction and this parameter can be measured from line-of-sight extinction measurements. Although most Soot aggregates are submicron in size, the primary particles (20 to 50 nm in diameter) are in the Rayleigh limit, so the extinction absorption) cross section of aggregates can be accurately approximated by the Rayleigh solution as a function of incident wavelength, particles' complex refractive index, and particles' volume fraction.

Greenberg, Paul S.; Ku, Jerry C.

1997-01-01

214

The effect of vesicular-arbuscular mycorrhizae on growth and nitrogen fixation (acetylene reduction) by subterranean clover and pearl millet  

E-print Network

for symbiotic nitrogen fixation using subterranean clover (Trifolium sub- terraneum L. ) inoculated with Rhizobium trifolii and mycorrhizal fun- gi. Two additional experiments were performed using pearl millet (P 1 i 1 &L. ) K. Sd . ) t 1 t auth~A* t tll... and Enterobacter cloacae) and in the Trifolium subterra- neum-Rhizobium symbiosis in a low fertility soil of central Texas. LITERATURE REVIEW The rising cost of commercial nitrogen and phosphorus fertiliz- ers motivates researchers to find alternative methods...

Sherrod, Carole Cay

2012-06-07

215

Nitrogen fixation (acetylene reduction) in a salt marsh amended with sewage sludge and organic carbon and nitrogen compounds.  

PubMed

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. PMID:16345239

Hanson, R B

1977-04-01

216

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

Microsoft Academic Search

Besides some usual fatty acids (FA), two conjugated ene-yne acetylenic FA [trans-10-heptadecen-8-ynoic acid (pyrulic acid) (7.4%), and trans-11-octadecen-9-ynoic acid (ximenynic acid) (3.5%)], a novel ene-yne-ene acetylenic FA [cis-7, trans-11-octadecadiene-9-ynoic acid (heisteric acid) (22.6%)], and 9,10-epoxystearic acid (0.6%) could be identified in the seed\\u000a oil of Heisteria silvanii (Olacaceae). Two further conjugated acetylenic FA [9,11-octadecadiynoic acid (0.1%) and 13-octadecene-9,11-diynoic acid (0.4%)

Volker Spitzer; Werner Tomberg; Rudolf Hartmann; Reiner Aichholz

1997-01-01

217

Schultheiss, Schiepe, & Rawolle Hormone assays 1 Running head: HORMONE ASSAYS  

E-print Network

Schultheiss, Schiepe, & Rawolle Hormone assays 1 Running head: HORMONE ASSAYS Hormone assays Oliver: Schultheiss, O. C., Schiepe, A., & Rawolle, M. (2012). Hormone assays. In H. Cooper, P. M. Camic, D. L. Long Association. #12;Schultheiss, Schiepe, & Rawolle Hormone assays 2 Hormone assays Hormones can be assayed from

Schultheiss, Oliver C.

218

Chemically activated reactions on the C7H5 energy surface: propargyl + diacetylene, i-C5H3 + acetylene, and n-C5H3 + acetylene.  

PubMed

This study uses computational chemistry and statistical reaction rate theory to investigate the chemically activated reaction of diacetylene (butadiyne, C(4)H(2)) with the propargyl radical (C?H(2)CCH) and the reaction of acetylene (C(2)H(2)) with the i-C(5)H(3) (CH(2)CCCC?H) and n-C(5)H(3) (CHCC?HCCH) radicals. A detailed G3SX-level C(7)H(5) energy surface demonstrates that the C(3)H(3) + C(4)H(2) and C(5)H(3) + C(2)H(2) addition reactions proceed with moderate barriers, on the order of 10 to 15 kcal mol(-1), and form activated open-chain C(7)H(5) species that can isomerize to the fulvenallenyl radical with the highest barrier still significantly below the entrance channel energy. Higher-energy pathways are available leading to other C(7)H(5) isomers and to a number of C(7)H(4) species + H. Rate constants in the large multiple-well (15) multiple-channel (30) chemically activated system are obtained from a stochastic solution of the one-dimensional master equation, with RRKM theory for microcanonical rate constants. The dominant products of the C(4)H(2) + C(3)H(3) reaction at combustion-relevant temperatures and pressures are i-C(5)H(3) + C(2)H(2) and CH(2)CCHCCCCH + H, along with several quenched C(7)H(5) intermediate species below 1500 K. The major products in the n-C(5)H(3) + C(2)H(2) reaction are i-C(5)H(3) + C(2)H(2) and a number of C(7)H(4) species + H, with C(7)H(5) radical stabilization at lower temperatures. The i-C(5)H(3) + C(2)H(2) reaction predominantly leads to C(7)H(4) + H and to stabilized C(7)H(5) products. The title reactions may play an important role in polycyclic aromatic hydrocarbon (PAH) formation in combustion systems. The C(7)H(5) potential energy surface developed here also provides insight into several other important reacting gas-phase systems relevant to combustion and astrochemistry, including C(2)H + the C(3)H(4) isomers propyne and allene, benzyne + CH, benzene + C((3)P), and C(7)H(5) radical decomposition, for which some preliminary analysis is presented. PMID:21465038

da Silva, Gabriel; Trevitt, Adam J

2011-05-21

219

Development of a spectrofluorimetry-based device for determining the acetylene content in the oils of power transformers.  

PubMed

Power transformers are essential for a functioning electrical system and therefore require special attention by maintenance programs because a fault can harm both the company and society. The temperature inside a power transformer and the dissolved gases, which are primarily composed of acetylene, are the two main parameters monitored when detecting faults. This paper describes the development of a device for analyzing the acetylene content in insulating oil using spectrofluorimetry. Using this device introduces a new methodology for the maintaining and operating power transformers. The prototype is currently operating in a substation. The results presented by this system were satisfactory; when compared to chromatographic data, the errors did not exceed 15%. This prototype may be used to confirm the quality of an insulating oil sample to detect faults in power transformers. PMID:24209339

Quintella, Cristina M; Meira, Marilena; Silva, Weidson Leal; Filho, Rogério G D; Araújo, André L C; Júnior, Elias T S; Sales, Lindolfo J O

2013-12-15

220

Exploration of the electronic structure of dendrimerlike acetylene-bridged oligothiophenes by correlating Raman spectroscopy, electrochemistry, and theory.  

PubMed

A series of radial thiophene-based structures consisting of a central benzene or thiophene ring surrounded by acetylene-bridged terthienyl arms has been investigated by physical and theoretical methods. Fourier transform Raman spectroscopy of the neutral solids shows that the terthiophene arms are weakly coupled across the core (benzene plus acetylene groups) likely due to cross-conjugation or meta-conjugation effects that may prevent full delocalization. By increasing the number of arms around the central ring, the electronic structure of the molecules seems to be affected only at the core, whereas the outer terthiophene arms remain almost unaltered. Raman spectroelectrochemistry and quantum chemical calculations provide further insight into the charge delocalization of the oxidized species. There is no evidence to suggest that these oxidized forms, obtained upon electrochemical doping of the molecules, show charge delocalization across the core. PMID:15268221

Casado, Juan; Pappenfus, Ted M; Mann, Kent R; Hernández, Victor; López Navarrete, Juan T

2004-06-22

221

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

NASA Technical Reports Server (NTRS)

Addition-elimination reactions of S atom in its P-3 ground state with acetylene (C2H2) and ethylene (C2H4) were characterized with both molecular orbital and density functional theory calculations employing correlation consistent basis sets in order to assess the likelihood either reaction might play a general role in astrochemistry or a specific role in the formation of S2 (X (sup 3 SIGMA (sub g) (sup -)) via a mechanism proposed by Saxena and Misra (Mon. Not. R. Astron. Soc. 1995, 272, 89). The acetylene and ethylene reactions proceed through C2H2S ((sup 3)A")) and C2H4S ((sup 3)A")) intermediates, respectively, to yield HCCS ((sup 2)II)) and C2H3S ((sup 2)A')). Substantial barriers were found in the exit channels for every combination of method and basis set considered in this work, which effectively precludes hydrogen elimination pathways for both S + C2H2 and S + C2H4 in the ultracold interstellar medium where only very modest barriers can be surmounted and processes without barriers tend to predominate. However, if one or both intermediates is formed and stabilized efficiently under cometary or dense interstellar cloud conditions, they could serve as temporary reservoirs for S atom and participate in reactions such as S + C2H2S (right arrow) S2 = C2H2 or S + C2H4S (right arrow) S2 + C2H4. For formation and stabilization to be efficient, the reaction must possess a barrier height small enough to be surmountable at low temperatures yet large enough to prevent redissociation to reactants. Barrier heights computed with B3LYP and large basis sets are very low, but more rigorous QCISD(T) and RCCSD(T) results indicate that the barrier heights are closer to 3-4 kcal/mol. The calculations therefore indicate that S + C2H2 or S + C2H4 could contribute to the formation of S2 in comets and may serve as a means to gauge coma temperature. The energetics of the ethylene reaction are more favorable.

Woon, David E.

2007-01-01

222

Frequency Comb-Referenced Spectroscopy in the ?1 + ?3 Region of Acetylene  

NASA Astrophysics Data System (ADS)

class="MsoNormal">By using saturation dip absorption spectroscopy with an extended cavity diode laser locked to a frequency comb, we have measured the rest frequencies of transitions in the ?4 = 1 and ?5 = 1 hot bands in the ?1 + ?3 combination band of acetylene. The measured line frequencies are accurate to approximately 20 kHz i.e. approximately one part in 1011. Positions of the hot-band lines quoted in the HITRAN database, which are derived from the analysis of high-resolution FTIR spectra, are of the order of 10's of MHz in error. These measurements were undertaken because pressure broadened lineshape measurements of rotational lines in the combination band indicated that weak underlying hot band features were not correctly accounted for on the basis of their previously reported positions. As a result, measured line profiles in the band could not be accurately fit leading to errors of up to 1% in acetylene concentrations derived from the measurements. In addition, the pressure broadened P(11) line in the ?1 + ?3 combination band has been studied as a function of varying concentration of the absorber in nitrogen. Mixture concentrations of 1, 5 and 10% at 296 K and pressures between a few Torr and one atmosphere were made and the measurements analyzed using two different speeddependent broadening models. These experiments are designed to test the additivity of contributions to pressure broadening and shift in speed-dependent line-shape modeling, i.e. whether the lineshape parameters follow partial pressure weighting in the binary mixtures. P(11) is relatively isolated with respect to underlying hot band transitions and neighboring transitions of the same band, but it was found that the accurate positions of underlying hot-band transitions were crucial to the successful modeling of the observed line shapes, even though these lines are typically 100-1000 times weaker than P(11) itself and are many Doppler line widths removed from the line center. Acknowledgments: Work at Brookhaven National Laboratory was carried out under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy and supported by its Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences and Biosciences.

Cich, Matthew J.; Forthomme, Damien; Hall, Gregory E.; Mcraven, Christopher P.; Sears, Trevor J.; Twagirayezu, Sylvestre

2014-06-01

223

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

2007-11-01

224

Long-distance simultaneous detection of methane and acetylene by using diode lasers coupled with optical fibers  

Microsoft Academic Search

Remote simultaneous detection of methane and acetylene by using two single-mode diode lasers emitting at 1.66 and 1.53 ?m, respectively, coupled with 4-km optical fibers has been demonstrated by laboratory simulations. The lasers were modulated at different frequencies to measure in real time the absorption of the two chemical species without interference. The gases could be detected quantitatively by the

H. Tai; K. Yamamoto; M. Uchida; S. Osawa; K. Uehara

1992-01-01

225

Absolute UV and soft X-ray photoabsorption of acetylene by high resolution dipole (e,e) spectroscopy  

Microsoft Academic Search

Absolute photoabsorption oscillator strengths (cross sections) for the discrete electronic transitions of acetylene from 5.5 to 11.2 eV have been measured using high resolution ?0.05 eV FWHM) dipole (e,e) spectroscopy. This experimental resolution enabled absolute oscillator strengths for most of the individual vibronic transitions to be obtained. A broader range spectrum, obtained from 5.5 to 200 eV at a resolution

Glyn Cooper; Gordon R. Burton; C. E. Brion

1995-01-01

226

Sequential allylic substitution/Pauson-Khand reaction: a strategy to bicyclic fused cyclopentenones from MBH-acetates of acetylenic aldehydes.  

PubMed

An efficient approach for the construction of novel bicyclic fused cyclopentenones starting from Morita-Baylis-Hillman (MBH) acetates of acetylenic aldehydes with flexible scaffold diversity has been achieved using a two-step reaction sequence involving allylic substitution and the Pauson-Khand reaction. This strategy provided a facile access to various bicyclic cyclopentenones fused with either a carbocyclic or a heterocyclic ring system in good yield. PMID:25105763

Raji Reddy, Chada; Kumaraswamy, Paridala; Singarapu, Kiran K

2014-09-01

227

Absolute rate constant for the reaction of atomic hydrogen with acetylene over an extended pressure and temperature range  

Microsoft Academic Search

The technique of flash photolysis coupled with time resolved detection of H via resonance fluorescence has been used to obtain absolute rate parameters for the reaction of atomic hydrogen with acetylene, i.e., H+C2H2?C2H3* (1); C2H3*+M-->C2H3+M (2). The rate constant for the reaction is strongly pressure dependent and was measured over the pressure range 10 to 700 torr. The reaction was

W. A. Payne; L. J. Stief

1976-01-01

228

Growth of bridging carbon nanofibers in cracks formed by heat-treating iron oxide thin sheets in acetylene gas  

NASA Astrophysics Data System (ADS)

We produced novel carbon nanofibers (CNFs) by oxidizing high-purity iron foil and then carburizing it in acetylene gas flow. This formed cracks in the heat-treated iron foil with CNFs bridging the two walls of each crack. The CNFs were drawn out from the walls as the crack opened during heat treatment. This will be a new method to grow and arrange carbon nanotubes and nanosheets without using metal nanoparticles or template substrates.

Hikata, Takeshi; Okubo, Soichiro; Higashi, Yugo; Matsuba, Teruaki; Utsunomiya, Risa; Tsurekawa, Sadahiro; Murakami, Katsuhisa; Fujita, Jun-ichi

2013-04-01

229

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

Microsoft Academic Search

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

Lee-Der Liu; Fan-Shiong Chen

2003-01-01

230

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

231

Cardiac output measured by acetylene rebreathing technique at rest and during exercise. Comparison of results obtained by various calculation procedures.  

PubMed

Cardiac output (Qc) was measured by a rebreathing technique, using acetylene and a mass-spectrometer for analyzing. In addition the rate of pulmonary uptake of O2 (VO2) during the rebreathing period and during a preceding steady-state period were determined. Measurements were made on 8 adult humans at rest and at different levels of exercise up to maximum at two occasions. The ratio (VO2 during steady-state/VO2 during rebreathing) was found to be significantly below 1 when the steady-state VO2 was below about 21 . min-1 and to be about 0.55 for subjects at rest. This indicates that VO2, and hence Qc, is increased by the rebreathing procedure when this involves deeper and more frequent respirations than those of the preceding period. Accordingly, when VO2 was below about 21 . min-1, the Qc value, calculated exclusively from acetylene concentrations recorded during rebreathing, was multiplied by the above-mentioned VO2-ratio. It is shown that this correcting procedure gives more reasonable values than those obtained by acetylene data alone. It is pointed out in what respects this correcting procedure of calculation deviates from that originally used by Grollman, and it is shown that there are only moderate differences between the results obtained by the two procedures. PMID:7195567

Kanstrup, I L; Hallbäck, I

1981-05-01

232

Intramolecular vibrational relaxation and forbidden transitions in the SEP spectrum of acetylene  

SciTech Connect

{ital {tilde A}} {sup 1}{ital A}{sub {ital u}}{r arrow}{ital {tilde X}} {sup 1{Sigma}}{sub {ital g}}{sup +} SEP spectra of acetylene near {ital E}{sub VIB}=7000 cm{sup {minus}1} show that Darling--Dennison resonance between the {ital cis}- and {ital trans}-bending vibrations is the {ital first} {ital step} in a series of anharmonic resonances which can transfer nearly all the vibrational energy out of the Franck--Condon bright states at higher energy. In addition to allowed {vert bar}{Delta}{ital K}{vert bar}{equivalent to}{vert bar}{ital K}{prime}{minus}l{double prime}{vert bar}=1 rotational transitions, nominally forbidden {vert bar}{Delta}{ital K}{vert bar}=0,2,3 rotational transitions have also been observed due to axis-switching and rotational-l-resonance. Although the range of detectable fluorescence dips is only about 30, the range of detectable SEP intensities in these spectra is probably about 500.

Jonas, D.M.; Solina, S.A.B.; Rajaram, B.; Silbey, R.J.; Field, R.W. (Department of Chemistry and George R. Harrison Spectroscopy Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)); Yamanouchi, K.; Tsuchiya, S. (Department of Pure and Applied Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo 153 (Japan))

1992-08-15

233

Microwave spectrum and molecular structure of vinyl chloride-acetylene, a side binding complex.  

PubMed

The structure of the gas-phase bimolecular complex formed between vinyl chloride and acetylene is determined using a combination of broad-band, chirped-pulse, and narrow-band, Balle-Flygare Fourier transform microwave spectroscopy from 5.8 to 20.7 GHz. Although all previous examples of complexes formed between protic acids and haloethylenes are observed to have similar modes of binding regardless of the specific identity of the acid, HF, HCl, or HCCH, the vinyl chloride-HCCH complex has HCCH located at one end of the vinyl chloride with the secondary interaction occurring with the geminal hydrogen atom as opposed to the "top" binding configuration found for vinyl chloride-HF. Nevertheless, the details of the structure, such as hydrogen bond length (3.01 Å) and amount of deviation from linearity (58.5°), do reflect the strength of the interaction and show clear correlations with the gas-phase acidity. Comparison with analogous complexes allows the determination of the relative importance of electrostatic interactions and steric requirements in leading to the observed structures. PMID:23941559

Leung, Helen O; Marshall, Mark D; Feng, Fan

2013-12-19

234

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

PubMed

Developing methods to differentiate the relative contributions of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) to ammonia (NH3) oxidation has been challenging due to the lack of compounds that selectively inhibit AOA. In this study, we investigated the effects of specific bacteria- and eukaryote-selective protein synthesis inhibitors on the recovery of acetylene (C2H2)-inactivated NH3 oxidation in the marine AOA Nitrosopumilus maritimus and compared the results with recovery of the AOB Nitrosomonas europaea. C2 H2 irreversibly inhibited N. maritimus NH3 oxidation in a similar manner to what was observed previously with N. europaea. However, cycloheximide (CHX), a widely used eukaryotic protein synthesis inhibitor, but not bacteria-specific protein synthesis inhibitors (kanamycin and gentamycin), inhibited the recovery of NH3-oxidizing activity in N. maritimus. CHX prevented the incorporation of (14)CO2 -labeling into cellular proteins, providing further evidence that CHX acts as a protein synthesis inhibitor in N. maritimus. If the effect of CHX on protein synthesis can be confirmed among other isolates of AOA, the combination of C2H2 inactivation followed by recovery of NH3 oxidation either in the presence of bacteria-selective protein synthesis inhibitors or CHX might be used to estimate the relative contributions of AOB and AOA to NH3 oxidation in natural environments. PMID:24606542

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

2014-06-01

235

Discovery of long-lived excited electronic states of chlorobenzene, bromobenzene, benzonitrile, and phenyl acetylene cations  

NASA Astrophysics Data System (ADS)

Previously developed technique of charge exchange ionization in a collision cell outside the ion source, which detects ions originating from the collision gas in the cell, was used to find long-lived excited electronic states of monosubstituted benzene cations. The technique is based on the criterion that charge exchange between polyatomic species is efficient only when the energy of reaction is close to zero or negative (Delta]E[less-than-or-equal0), or the exoergicity rule. The B 2B2 states of chlorobenzene, bromobenzene, benzonitrile, and phenyl acetylene cations were found to have long lifetimes (10 microseconds or longer) while excited electronic states with long lifetime were not detected for fluorobenzene, iodobenzene, toluene, nitrobenzene, and styrene cations. The long-lived states found were those displaying well-resolved vibrational structures in the photoelectron spectra. In particular, these were the states generated by removal of an electron from the in-plane nonbonding p orbitals of halogens or in-plane pi orbitals of the triple bonds.

Youn, Yeu Young; Kwon, Chan Ho; Choe, Joong Chul; Kim, Myung Soo

2002-08-01

236

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

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

237

Breast reduction  

MedlinePLUS

Breast reduction surgery is usually done under general anesthesia (asleep and pain-free). For a breast reduction, the surgeon ... Breast reduction surgery is generally safe. Ask your doctor about these complications. Risks of any surgery are: Bleeding Infection ...

238

Absolute nuclear material assay  

DOEpatents

A method of absolute nuclear material assay of an unknown source comprising counting neutrons from the unknown source and providing an absolute nuclear material assay utilizing a model to optimally compare to the measured count distributions. In one embodiment, the step of providing an absolute nuclear material assay comprises utilizing a random sampling of analytically computed fission chain distributions to generate a continuous time-evolving sequence of event-counts by spreading the fission chain distribution in time.

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

2012-05-15

239

Immunochromatographic assay on thread.  

PubMed

Lateral-flow immunochromatographic assays are low-cost, simple-to-use, rapid tests for point-of-care screening of infectious diseases, drugs of abuse, and pregnancy. However, lateral flow assays are generally not quantitative, give a yes/no answer, and lack multiplexing. Threads have recently been proposed as a support for transporting and mixing liquids in lateral-flow immunochromatographic assays, but their use for quantitative high-sensitivity immunoassays has yet to be demonstrated. Here, we introduce the immunochromatographic assay on thread (ICAT) in a cartridge format that is suitable for multiplexing. The ICAT is a sandwich assay performed on a cotton thread knotted to a nylon fiber bundle, both of which are precoated with recognition antibodies against one target analyte. Upon sample application, the assay results become visible to the eye within a few minutes and are quantified using a flatbed scanner. Assay conditions were optimized, the binding curves for C-reactive protein (CRP) in buffer and diluted serum were established and a limit of detection of 377 pM was obtained. The possibility of multiplexing was demonstrated using three knotted threads coated with antibodies against CRP, osteopontin, and leptin proteins. The performance of the ICAT was compared with that of the paper-based and conventional assays. The results suggest that thread is a suitable support for making low-cost, sensitive, simple-to-use, and multiplexed diagnostic tests. PMID:22889381

Zhou, Gina; Mao, Xun; Juncker, David

2012-09-18

240

Infrared studies of acetylene dissolved in liquefied Ar, Kr, N 2, CO, and CO 2  

NASA Astrophysics Data System (ADS)

FTIR spectra of acetylene have been studied in liquefied Ar, Kr, N 2, CO and CO 2 in the range ˜1000-9000 cm -1. Width, position and absolute integral intensity of a set of fundamental and combination bands were determined. In the case of ?3 band an effect of vibrational resonance interaction of Fermi-type has been taken into account and the position of non-perturbed ?30 and ( ?2+ ?4+ ?5) 0 bands were evaluated in the solutions studied. Liquid to crystal state phase transition experiments, performed in Kr solutions, show reversible growth of self-associates when going to lower temperatures of C 2H 2 doped solid Kr. The ?3(? u+) C-H stretch band exhibits weak side shoulders in the case of CO and CO 2 solvents. New combination bands, attributed to ?2(C 2H 2)+ ?3(CO 2), ?3(C 2H 2)+ ?3(CO 2) and ?1(C 2H 2)+ ?3(CO 2) simultaneous transitions due to vibrational excitation of both the interacting partners have been revealed in the region of ˜4000-6000 cm -1. Detecting the ?3(C 2H 2)+ ?3(CO 2) combination band, which is forbidden in the frame of dipole approximation, suggests an appreciable role of mutual polarization due to dipole-quadrupole polarizability of molecular partners. The observed spectroscopic features are compared with the results of theoretical DFT/B3LYP and ab initio MP2 calculations utilizing the 6-311++G(3df,3pd) basis set, which predict weak heterodimer formation, with linear H-C?C-H⋯C?O and slipped parallel H- C? C- HO- C- Ostructures being favored.

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

2002-09-01

241

Chromophores from Photolyzed Ammonia Reacting with Acetylene: Application to Jupiter’s Great Red Spot  

NASA Astrophysics Data System (ADS)

The production mechanisms of chromophores at Jupiter, and notably at the Great Red Spot (GRS), have been long-standing puzzles. A clue to the formation of the GRS coloring agent may be the great height of this storm, which can upwell ammonia to pressure levels of a few hundred mbar where solar photons capable of dissociating NH3 penetrate. Acetylene formed at higher altitudes can diffuse down and react with the NH3 photodissociation products, forming a deposit that absorbs in the ultraviolet and visible region (Ferris and Ishikawa, J. Amer. Chem. Soc. 110, 4306-4312, 1988). We have investigated the system NH3 + C2H2 + CH4 using a Zn lamp emitting at 214 nm to produce NH2 + H and subsequent reaction products. The deposits produced in these reactions were analyzed by optical and infrared spectroscopy and soft-ionization (He*) time-of-flight mass spectroscopy. The combination of NH3 + CH4 produced no visibly absorbing material, but NH3 + C2H2 and NH3 + C2H2 + CH4 mixtures both produced a yellow-orange film whose transmission spectra are similar to that of the GRS obtained by Cassini VIMS. Infrared spectra show a strong band at 2056 wavenumbers which may arise from nitrile (-CN), isonitrile (-NC), or diazide (-CNN) functional groups. The high-resolution mass spectra are consistent with compounds of the form CnH2n+1Nm, similar to the products formed in NH3 + CH4 spark discharges (Molton and Ponnamperuma, Icarus 21, 166-174, 1974). We thank NASA's Planetary Atmospheres Program for support.

Carlson, Robert W.; Baines, K. H.; Anderson, M. S.; Filacchione, G.

2012-10-01

242

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

243

Full dimensional Franck-Condon factors for the acetylene A? (1)Au-X? ?g+1 transition. I. Method for calculating polyatomic linear-bent vibrational intensity factors and evaluation of calculated intensities for the gerade vibrational modes in acetylene.  

PubMed

Franck-Condon vibrational overlap integrals for the A? Au1-X? ?g+1 transition in acetylene have been calculated in full dimension in the harmonic normal mode basis. The calculation uses the method of generating functions first developed for polyatomic Franck-Condon factors by Sharp and Rosenstock [J. Chem. Phys. 41(11), 3453-3463 (1964)], and previously applied to acetylene by Watson [J. Mol. Spectrosc. 207(2), 276-284 (2001)] in a reduced-dimension calculation. Because the transition involves a large change in the equilibrium geometry of the electronic states, two different types of corrections to the coordinate transformation are considered to first order: corrections for axis-switching between the Cartesian molecular frames and corrections for the curvilinear nature of the normal modes at large amplitude. The angular factor in the wavefunction for the out-of-plane component of the trans bending mode, ?4 (?), is treated as a rotation, which results in an Eckart constraint on the polar coordinates of the bending modes. To simplify the calculation, the other degenerate bending mode, ?5 (?), is integrated in the Cartesian basis and later transformed to the constrained polar coordinate basis, restoring the conventional v and l quantum numbers. An updated A?-state harmonic force field obtained recently in the R. W. Field research group is evaluated. The results for transitions involving the gerade vibrational modes are in qualitative agreement with experiment. Calculated results for transitions involving ungerade modes are presented in Paper II of this series [G. B. Park, J. H. Baraban, and R. W. Field, "Full dimensional Franck-Condon factors for the acetylene A? Au1-X? ?g+1 transition. II. Vibrational overlap factors for levels involving excitation in ungerade modes," J. Chem. Phys. 141, 134305 (2014)]. PMID:25296803

Park, G Barratt

2014-10-01

244

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...

245

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

NASA Technical Reports Server (NTRS)

The heat of combustion of the product formed by the reaction acetylene and diborane was found to be 20,100 +/- 100 Btu per pound for the reaction of liquid fuel to gaseous carbon dioxide, gaseous water, and solid boric oxide. The measurements were made in a Parr oxygen-bomb calorimeter, and chemical analyses both of the sample and of the combustion products indicated combustion in the bomb calorimeter to have been 97 percent complete. The estimated net heat of combustion for complete combustion would therefore be 20,700 +/- 100 Btu per pound.

Allen, Harrison, Jr.; Tannenbaum, Stanley

1957-01-01

246

Absolute rate constant for the reaction of atomic hydrogen with acetylene over an extended pressure and temperature range  

Microsoft Academic Search

The technique of flash photolysis coupled with time resolved detection of H via resonance fluorescence has been used to obtain absolute rate parameters for the reaction of atomic hydrogen with acetylene, i.e., H+C2H2?C2H3* (1); C2H3*+M?C2H3+M (2). The rate constant for the reaction is strongly pressure dependent and was measured over the pressure range 10 to 700 torr. The reaction was

W. A. Payne; L. J. Stief

1976-01-01

247

Enantiopure laterally functionalized alleno-acetylenic macrocycles: synthesis, chiroptical properties, and self-assembly in aqueous media.  

PubMed

A family of shape-persistent alleno-acetylenic macrocycles (SPAAMs), peripherally decorated with structurally diverse pendant groups, has been synthesized and characterized in enantiomerically pure form. Their electronic circular dichroism (ECD) spectra feature a strong chiroptical response, which is more than two times higher than for open-chain tetrameric analogues. A water-soluble oligo(ethylene glycol)-appended SPAAM undergoes self-assembly in aqueous solution. Morphology studies by cryogenic transmission electron microscopy (cryo-TEM) revealed the formation of aggregates with fibrous fine structures that correspond to tubular, macrocyclic stacks. PMID:25346432

Tzirakis, Manolis D; Alberti, Mariza N; Weissman, Haim; Rybtchinski, Boris; Diederich, François

2014-12-01

248

Assays without Borders  

Cancer.gov

CPTAC researchers partner with international labs to demonstrate the ability of Targeted mass spectrometry–based assays to reproducibly quantify Human proteins across labs, countries and continents in a recently published journal article.

249

Microfluidic DNA hybridization assays  

Microsoft Academic Search

DNA hybridization is one of the most powerful techniques applied in diagnostic assays. Microfluidics provides a promising\\u000a means to analyse small sample volumes, reduce reagent consumption and cost, shorten processing time as well as develop fast,\\u000a sensitive and portable diagnostic tools. By coupling with the microfluidic technology, DNA hybridization assay can achieve\\u000a high sensitivity, enhance hybridization kinetics and decrease the

Xuan WengHai; Hai Jiang; Dongqing Li

250

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

251

Development of a varicella-zoster virus neutralization assay using a glycoprotein K antibody enzyme-linked immunosorbent spot assay.  

PubMed

Plaque-reduction assays have been used to detect varicella-zoster virus (VZV)-neutralizing antibodies in sera for many decades. The current study characterized the mouse monoclonal antibody (MAb) 18A10, specific for VZV envelope glycoprotein K (gK), and applied this antibody to a new type of neutralization assay in the VZV field. The procedure is called the neutralization enzyme-linked immunosorbent spot (N-ELISPOT) assay and evolved from the VZV immunoperoxidase focus assay. Optimization of the assay involved defining the optimum combination of virus plaque-forming units (PFU) and antibody dilution, which were found to be 0-100 PFU and 1:200, respectively. Furthermore, the N-ELISPOT assay produced results consistent with that obtained for the plaque-reduction neutralization assay. Considering that the plaque-reduction neutralization assay is time-consuming and labor-intensive, the VZV N-ELISPOT assay offers several advantages including reproducibility and applicability for high-throughput analysis of humoral immune responses to VZV. PMID:24486923

Chen, Lihong; Liu, Jian; Wang, Wei; Ye, Jianghui; Wen, Lanling; Zhao, Qinjian; Zhu, Hua; Cheng, Tong; Xia, Ningshao

2014-05-01

252

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

...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...

2014-04-01

253

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

Code of Federal Regulations, 2012 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...

2012-04-01

254

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

255

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

NASA Technical Reports Server (NTRS)

The structure and morphological properties of polymers produced photochemically from the UV irradiation of cyanoacetylene and cyanoacetylene mixtures have been examined to evaluate their possible contribution to the haze layers found on Titan. A structural analysis of these polymers may contribute to our understanding of the data returned from the Huygens probe of the Cassini mission that will pass through the atmosphere of Titan in the year 2004. Infrared analysis, elemental analysis, and thermal methods (thermogravimetric analysis, thermolysis, pyrolysis) were used to examine structures of polycyanoacetylenes produced by irradiation of the gas phase HC3N at 185 and 254 nm. The resulting brown to black polymer, which exists as small particles, is believed to be a branched chain of conjugated carbon-carbon double bonds, which, on exposure to heat, cyclizes to form a graphitic structure. Similar methods of analysis were used to show that when HC3N is photolyzed in the presence of Titan's other atmospheric constituents (CH4, C2H6, C2H2, and CO), a copolymer is formed in which the added gases are incorporated as substituents on the polymer chain. Of special significance is the copolymer of HC3N and acetylene (C2H2). Even in experiments where C2H2 was absorbing nearly all of the incident photons, the ratio of C2H2 to HC3N found in the resulting polymer was only 2:1. Scanning electron microscopy was used to visually examine the polymer particles. While pure polyacetylene particles are amorphous spheres roughly 1 micrometer in diameter, polycyanoacetylenes appear to be strands of rough, solid particles slightly smaller in size. The copolymer of HC3N and C2H2 exhibits characteristics of both pure polymers. This is particularly important as pure polyacetylenes do not match the optical constants measured for Titan's atmospheric hazes. The copolymers produced by the incorporation of other minor atmospheric constituents, like HC3N, into the polyacetylenes are expected to have optical constants more comparable to those of the Titan haze.

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

1997-01-01

256

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

NASA Astrophysics Data System (ADS)

Acetylene (C2H2), as an important precursor for chemiluminescence species, is a key to understand, simulate and model the chemiluminescence and the related reaction paths. Hence we developed a high resolution spectrometer based on direct Tunable Diode Laser Absorption Spectroscopy (TDLAS) allowing the first quantitative, calibration-free and spatially resolved in situ C2H2 measurement in an atmospheric non-premixed counter-flow flame supported on a Tsuji burner. A fiber-coupled distributed feedback diode laser near 1535 nm was used to measure several absolute C2H2 concentration profiles (peak concentrations up to 9700 ppm) in a laminar non-premixed CH4/air flame ( T up to 1950 K) supported on a modified Tsuji counter-flow burner with N2 purge slots to minimize end flames. We achieve a fractional optical resolution of up to 5×10-5 OD (1 ?) in the flame, resulting in temperature-dependent acetylene detection limits for the P17e line at 6513 cm-1 of up to 2.1 ppm?m. Absolute C2H2 concentration profiles were obtained by translating the burner through the laser beam using a DC motor with 100 ?m step widths. Intercomparisons of the experimental C2H2 profiles with simulations using our new hydrocarbon oxidation mechanisms show excellent agreement in position, shape and in the absolute C2H2 values.

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

2012-06-01

257

The Effect of Surface Finish on Low-Temperature Acetylene-Based Carburization of 316L Austenitic Stainless Steel  

NASA Astrophysics Data System (ADS)

We observed a strong influence of surface finish on the efficacy of low-temperature acetylene-based carburization of AISI 316L austenitic stainless steel. Steel coupons were prepared with different surface finishes prior to carburization, from P400 SiC grit paper to 1-µm-diameter-diamond-paste. The samples with the finer surface finish developed a thicker "case" (a carbon-rich hardened surface layer) and a larger surface carbon concentration. Transmission electron microscopy revealed that the differences arose mainly from the nature of the deformation-induced disturbed layer on the steel surface. A thick (>400 nm) disturbed layer consisting of nano-crystalline grains (?10 nm diameter) inhibits acetylene-based carburization. The experimental observations can be explained by assuming that during machining or coarse polishing, the surface oxide layer is broken up and becomes incorporated into the deformation-induced disturbed layer. The incorporated oxide-rich films retard or completely prevent the ingress of carbon into the stainless steel.

Ge, Yindong; Ernst, Frank; Kahn, Harold; Heuer, Arthur H.

2014-08-01

258

Spectroscopic characterization of the cured state of acetylene-terminated resin. Final report 1 Apr 1982-31 Mar 1983  

SciTech Connect

The acetylene-terminated resin, bis 4-(3-ethynylphenoxy)phenyl sulfone (AT) has been studied using Fourier transform infrared spectroscopy (FT-IR) and high resolution nuclear magnetic resonance spectroscopy of solids. Samples which were cured at different temperatures for various times were analyzed by FT-IR and the results interpreted using factor analysis. The analysis revealed that only two major components were involved in the curing mechanism, that is, only a single polymerization reaction occurred at low curing temperatures. The pure component spectra generated by the factor analysis procedure could be used to analyze the state of cure of the resin. The infrared spectrum of the polymer is consistent with a polydiene structure. The NMR results produced a similar structural result. The extent of cure of the AT resin as evidence by the disappearance of the acetylene carbon followed a similar path to the infrared results. Curve studies also focussed on the effect of high temperature post cures of the ATS resin. Structural changes were reflected by spectroscopic differences but the changes were small and precise assignments were not possible. Further model compound studies would allow a precise determination of the structural basis of these spectroscopic differences.

Koenig, J.L.

1983-08-01

259

Laboratory studies, analysis, and interpretation of the spectra of hydrocarbons present in planetary atmospheres including cyanoacetylene, acetylene, propane, and ethane  

NASA Technical Reports Server (NTRS)

Combining broadband Fourier transform spectrometers (FTS) from the McMath facility at NSO and from NRC in Ottawa and narrow band TDL data from the laboratories with computational physics techniques has produced a broad range of results for the study of planetary atmospheres. Motivation for the effort flows from the Voyager/IRIS observations and the needs of Voyager analysis for laboratory results. In addition, anticipation of the Cassini mission adds incentive to pursue studies of observed and potentially observable constituents of planetary atmospheres. Current studies include cyanoacetylene, acetylene, propane, and ethane. Particular attention is devoted to cyanoacetylen (H3CN) which is observed in the atmosphere of Titan. The results of a high resolution infrared laboratory study of the line positions of the 663, 449, and 22.5/cm fundamental bands are presented. Line position, reproducible to better than 5 MHz for the first two bands, are available for infrared astrophysical searches. Intensity and broadening studies are in progress. Acetylene is a nearly ubiquitous atmospheric constituent of the outer planets and Titan due to the nature of methane photochemistry. Results of ambient temperature absolute intensity measurements are presented for the fundamental and two two-quantum hotband in the 730/cm region. Low temperature hotband intensity and linewidth measurements are planned.

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

1990-01-01

260

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

261

Harm reduction  

PubMed Central

The “Harm Reduction” session was chaired by Dr. Jacques Normand, Director of the AIDS Research Program of the U.S. National Institute on Drug Abuse. The three presenters (and their presentation topics) were: Dr. Don Des Jarlais (High Coverage Needle/Syringe Programs for People Who Inject Drugs in Low and Middle Income Countries: A Systematic Review), Dr. Nicholas Thomson (Harm Reduction History, Response, and Current Trends in Asia), and Dr. Jih-Heng Li (Harm Reduction Strategies in Taiwan).

Normand, Jacques; Li, Jih-Heng; Thomson, Nicholas; Jarlais, Don Des

2014-01-01

262

Lateral flow strip assay  

DOEpatents

A lateral flow strip assay apparatus comprising a housing; a lateral flow strip in the housing, the lateral flow strip having a receiving portion; a sample collection unit; and a reagent reservoir. Saliva and/or buccal cells are collected from an individual using the sample collection unit. The sample collection unit is immersed in the reagent reservoir. The tip of the lateral flow strip is immersed in the reservoir and the reagent/sample mixture wicks up into the lateral flow strip to perform the assay.

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

2011-03-08

263

Assay of AHF concentrates and standards: failure to eliminate variability with a monographed assay.  

PubMed

Previous calibration studies have shown a high interlaboratory variability in the potency of the proposed Office of Biologics (National Center for Drugs and Biologics, US-FDA) AHF standard relative to the 2nd International Standard for Factor VIII (Factor VIII:C) (WHO 73/552). This led to the formation of an Industry Collaborative Study group whose objective was to reduce the assay variability. The group, in collaboration with the Office of Biologics and the National Institute for Biological Standards and Control (UK), designed a study based on a monographed one-stage assay protocol, which specified all materials, assay methods, equipment, dilution technique, reagents, assay order, and calculation methodology. All participants received common reagents and samples, with the exception of substrate plasma. It was felt that substrate plasma could not be a common reagent in a monographed assay. However, each laboratory prepared substrate plasma according to the protocol. All data were analyzed by an independent statistical staff. Preparations assayed included two 10-donor plasma pools, the 2nd International Standard for Factor VIII (WHO 73/552), the proposed OoB Lot A internal standard, the participants' own house standards, and commercial AHF concentrate material. The results show a statistically insignificant reduction in the interlaboratory variability, but intralaboratory consistency was generally maintained. The study shows that monographing an assay for Factor VIII. PMID:6412386

Heldebrant, C; Kleszynski, R; Short, M; Aronson, D; Brown, L; Jacoby, G; Lee, M; Thomas, D; Barrowcliffe, T; Howell, I; Johnson, R C

1983-05-15

264

The strong field photoelectron spectroscopy of acetylene: Evidence for short-lived 4p gerade states via electric field-induced  

E-print Network

1999; accepted 13 October 1999 We report the intense field photoelectron spectra of acetylene, excited of the single photon photoelectron spectra,6 displaying well-separated peaks with little vibrational struc- ture. Here, we study the intense field photoelectron spectra of C2H2 using ultrafast, near infrared laser

Levis, Robert J.

265

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

266

Tandem allylic substitution-5-exo-dig-carbocyclization: a [4 + 1]-annulation approach to arylidene cyclopentenes from MBH-acetates of acetylenic aldehydes.  

PubMed

A new entry for the synthesis of functionalized arylidene cyclopentenes under metal-free reaction conditions is disclosed via the base-promoted [4 + 1]-annulation of Morita-Baylis-Hillman acetates of acetylenic aldehydes with active methylene derivatives involving tandem allylic substitution followed by 5-exo-dig-carbocyclization. PMID:23085708

Reddy, Chada Raji; Kumaraswamy, Paridala; Reddy, Motatipally Damoder

2012-12-01

267

ESI-MS, DFT, and Synthetic Studies on the H2-Mediated Coupling of Acetylene: Insertion of CdX Bonds into  

E-print Network

ESI-MS, DFT, and Synthetic Studies on the H2-Mediated Coupling of Acetylene: Insertion of CdX Bonds-benzenesulfonyl aldimines corroborate a catalytic mechanism involving CdX (X ) O, NSO2Ph) insertion into a cationic

Baik, Mu-Hyun

268

Comparison of the experimental, semi-experimental and ab initio equilibrium structures of acetylene: Influence of relativisitic effects and of the diagonal Born-Oppenheimer corrections  

Microsoft Academic Search

The equilibrium structure of acetylene (also named ethyne) has been reinvestigated to resolve the small discrepancies noted between different determinations. The size of the system as well as the large amount of available experimental data provides the quite unique opportunity to check the magnitude and relevance of various contributions to equilibrium structure as well as to verify the accuracy of

J. Liévin; J. Demaison; M. Herman; A. Fayt; C. Puzzarini

2011-01-01

269

Prediction of the energy dependence of molecular fragmentation cross sections for collisions of swift protons with ethane and acetylene  

SciTech Connect

We report the energy-dependent fragmentation cross sections for several of the more likely fragmentation channels for protons with up to 10 keV impact energy colliding with acetylene and ethane. We find that the predominant channels are those which involve the dissociation of a carbon-hydrogen bond, and we find that the cross sections for these channels are maximum in the low-projectile-energy region. The cross sections for fragmentation involving dissociation of a C-C bond are an order of magnitude smaller and peak at somewhat higher projectile energy. Although there are no experimental values with which to compare, it appears that selection of projectile energy can be used to influence branching ratios in proton-hydrocarbon collisions and, by implication, in other ion-molecule and atom-molecule collisions.

Cabrera-Trujillo, Remigio; Sabin, John R.; Deumens, Erik; Oehrn, Yngve [Departments of Physics and Chemistry, University of Florida, Gainesville, Florida 32611-8435 (United States)

2005-04-01

270

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 PMID:5288773

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

1971-01-01

271

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

NASA Astrophysics Data System (ADS)

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

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

2014-02-01

272

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

273

Rat mesentery angiogenesis assay.  

PubMed

The adult rat mesentery window angiogenesis assay is biologically appropriate and is exceptionally well suited to the study of sprouting angiogenesis in vivo [see review papers], which is the dominating form of angiogenesis in human tumors and non-tumor tissues, as discussed in invited review papers(1,2). Angiogenesis induced in the membranous mesenteric parts by intraperitoneal (i.p.) injection of a pro-angiogenic factor can be modulated by subcutaneous (s.c.), intravenous (i.v.) or oral (p.o.) treatment with modifying agents of choice. Each membranous part of the mesentery is translucent and framed by fatty tissue, giving it a window-like appearance. The assay has the following advantageous features: (i) the test tissue is natively vascularized, albeit sparsely, and since it is extremely thin, the microvessel network is virtually two-dimensional, which allows the entire network to be assessed microscopically in situ; (ii) in adult rats the test tissue lacks significant physiologic angiogenesis, which characterizes most normal adult mammalian tissues; the degree of native vascularization is, however, correlated with age, as discussed in(1); (iii) the negligible level of trauma-induced angiogenesis ensures high sensitivity; (iv) the assay replicates the clinical situation, as the angiogenesis-modulating test drugs are administered systemically and the responses observed reflect the net effect of all the metabolic, cellular, and molecular alterations induced by the treatment; (v) the assay allows assessments of objective, quantitative, unbiased variables of microvascular spatial extension, density, and network pattern formation, as well as of capillary sprouting, thereby enabling robust statistical analyses of the dose-effect and molecular structure-activity relationships; and (vi) the assay reveals with high sensitivity the toxic or harmful effects of treatments in terms of decreased rate of physiologic body-weight gain, as adult rats grow robustly. Mast-cell-mediated angiogenesis was first demonstrated using this assay(3,4). The model demonstrates a high level of discrimination regarding dosage-effect relationships and the measured effects of systemically administered chemically or functionally closely related drugs and proteins, including: (i) low-dosage, metronomically administered standard chemotherapeutics that yield diverse, drug-specific effects (i.e., angiogenesis-suppressive, neutral or angiogenesis-stimulating activities(5)); (ii) natural iron-unsaturated human lactoferrin, which stimulates VEGF-A-mediated angiogenesis(6), and natural iron-unsaturated bovine lactoferrin, which inhibits VEGF-A-mediated angiogenesis(7); and (iii) low-molecular-weight heparin fractions produced by various means(8,9). Moreover, the assay is highly suited to studies of the combined effects on angiogenesis of agents that are administered systemically in a concurrent or sequential fashion. The idea of making this video originated from the late Dr. Judah Folkman when he visited our laboratory and witnessed the methodology being demonstrated. Review papers (invited) discussing and appraising the assay Norrby, K. In vivo models of angiogenesis. J. Cell. Mol. Med. 10, 588-612 (2006). Norrby, K. Drug testing with angiogenesis models. Expert Opin. Drug. Discov. 3, 533-549 (2008). PMID:21712799

Norrby, Klas C

2011-01-01

274

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

NASA Technical Reports Server (NTRS)

State-of-the-art life support carbon dioxide (CO2) reduction technology, based on the Sabatier reaction, is theoretically capable of 50% recovery of oxygen from metabolic CO2. This recovery is constrained by the limited availability of reactant hydrogen. Post-processing of the methane byproduct from the Sabatier reactor results in hydrogen recycle and a subsequent increase in oxygen recovery. For this purpose, a Methane Post-Processor Assembly containing three sub-systems has been developed and tested. The assembly includes a Methane Purification Assembly (MePA) to remove residual CO2 and water vapor from the Sabatier product stream, a Plasma Pyrolysis Assembly (PPA) to partially pyrolyze methane into hydrogen and acetylene, and an Acetylene Separation Assembly (ASepA) to purify the hydrogen product for recycle. The results of partially integrated testing of the sub-systems are reported

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

2013-01-01

275

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

NASA Technical Reports Server (NTRS)

State-of-the-art life support carbon dioxide (CO2) reduction technology, based on the Sabatier reaction, is theoretically capable of 50% recovery of oxygen from metabolic CO2. This recovery is constrained by the limited availability of reactant hydrogen. Post-processing of the methane byproduct from the Sabatier reactor results in hydrogen recycle and a subsequent increase in oxygen recovery. For this purpose, a Methane Post-Processor Assembly containing three sub-systems has been developed and tested. The assembly includes a Methane Purification Assembly (MePA) to remove residual CO2 and water vapor from the Sabatier product stream, a Plasma Pyrolysis Assembly (PPA) to partially pyrolyze methane into hydrogen and acetylene, and an Acetylene Separation Assembly (ASepA) to purify the hydrogen product for recycle. The results of partially integrated testing of the sub-systems are reported.

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

2013-01-01

276

Carbon Dioxide Reduction Post-Processing Sub-System Development  

NASA Technical Reports Server (NTRS)

The state-of-the-art Carbon Dioxide (CO2) Reduction Assembly (CRA) on the International Space Station (ISS) facilitates the recovery of oxygen from metabolic CO2. The CRA utilizes the Sabatier process to produce water with methane as a byproduct. The methane is currently vented overboard as a waste product. Because the CRA relies on hydrogen for oxygen recovery, the loss of methane ultimately results in a loss of oxygen. For missions beyond low earth orbit, it will prove essential to maximize oxygen recovery. For this purpose, NASA is exploring an integrated post-processor system to recover hydrogen from CRA methane. The post-processor, called a Plasma Pyrolysis Assembly (PPA) partially pyrolyzes methane to recover hydrogen with acetylene as a byproduct. In-flight operation of post-processor will require a Methane Purification Assembly (MePA) and an Acetylene Separation Assembly (ASepA). Recent efforts have focused on the design, fabrication, and testing of these components. The results and conclusions of these efforts will be discussed as well as future plans.

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

2012-01-01

277

Biosensors: Viruses for ultrasensitive assays  

NASA Astrophysics Data System (ADS)

A three-dimensional assay based on genetically engineered viral nanoparticles and nickel nanohairs can detect much lower levels of protein markers associated with heart attacks than conventional assays.

Donath, Edwin

2009-04-01

278

Gaseous nitrogen losses from fertilized soil during nitrification and denitrification using the acetylene blockage technique  

Microsoft Academic Search

A sandy soil amended with different forms and amounts of fertilizer nitrogen (urea, ammonium sulphate and potassium nitrate) was investigated in model experiments for N2O emission, which may be evolved during both oxidation of ammonia to nitrate and anaerobic respiration of nitrate. Since C2H2 inhibits both nitrification and the reduction of N2O to N2 during denitrification, the amount of N2O

S. Casella; C. Leporini; G. Picci

1986-01-01

279

Uranium reduction.  

PubMed

The dramatic decrease in solubility accompanying the reduction of U(VI) to U(IV), producing the insoluble mineral uraninite, has been viewed as a potential mechanism for sequestration of environmental uranium contamination. In the past 15 years, it has been firmly established that a variety of bacteria exhibit this reductive capacity. To obtain an understanding of the microbial metal metabolism, to develop a practical approach for the acceleration of in situ bioreduction, and to predict the long-term fate of environmental uranium, several aspects of the microbial process have been experimentally explored. This review briefly addresses the research to identify specific uranium reductases and their cellular location, competition between uranium and other electron acceptors, attempts to stimulate in situ reduction, and mechanisms of reoxidation of reduced uranium minerals. PMID:16704344

Wall, Judy D; Krumholz, Lee R

2006-01-01

280

A Chemical Assay for Renin  

Microsoft Academic Search

The investigation of renal hypertension has led to the enzyme renin. At present renin can only be properly assayed by bioassay with a live animal which as been fitted in some manner with a device for measuring blood pressure. One common method is the rat assay. This assay requires careful anaesthesia, skilled surgical preparation of the animal, and several hours

Bruce B. McDonald

1968-01-01

281

Waste Reduction.  

ERIC Educational Resources Information Center

Presents activities that focus on waste reduction in the school and community. The ideas are divided into grade level categories. Sample activities include Techno-Trash, where children use tools to take apart broken appliances or car parts, then reassemble them or build new creations. Activities are suggested for areas including language arts and…

Bray, Marilyn; And Others

1996-01-01

282

Synthesis of 3-iodoindoles by the Pd/Cu-catalyzed coupling of N,N-dialkyl-2-iodoanilines and terminal acetylenes, followed by electrophilic cyclization.  

PubMed

[reaction: see text] 3-Iodoindoles have been prepared in excellent yields by coupling terminal acetylenes with N,N-dialkyl-o-iodoanilines in the presence of a Pd/Cu catalyst, followed by an electrophilic cyclization of the resulting N,N-dialkyl-o-(1-alkynyl)anilines using I2 in CH2Cl2. Aryl-, vinylic-, alkyl-, and silyl-substituted terminal acetylenes undergo this process to produce excellent yields of 3-iodoindoles. The reactivity of the carbon-nitrogen bond cleavage during cyclization follows the following order: Me > n-Bu, Me > Ph, and cyclohexyl > Me. Subsequent palladium-catalyzed Sonogashira, Suzuki, and Heck reactions of the resulting 3-iodoindoles proceed smoothly in good yields. PMID:16388618

Yue, Dawei; Yao, Tuanli; Larock, Richard C

2006-01-01

283

Measurements of linestrengths, N2-, Ar-, He- and self-broadening coefficients of acetylene in the ?4+?5 combination band using a cw quantum cascade laser  

NASA Astrophysics Data System (ADS)

Linestrengths, N2-, Ar-, He- and self-broadening coefficients of acetylene have been measured at 296 K in the P branch of the ?4+?5 combination band for 25 rotational transitions. The effect of gas temperature is studied over 296-683 K for five transitions to allow the determination of the temperature dependent exponent n for N2- and Ar-broadening coefficients. These measurements were performed using a continuous-wave quantum cascade laser (cw-QCL) operating over 1253-1310 cm-1. Spectroscopic parameters were obtained by fitting absorption spectra using Voigt, Galatry and Rautian profiles. Linestrength and broadening results are compared with previous studies available in literature for the ?4+?5 combination band and other vibrational bands of acetylene.

Sajid, Muhammad Bilal; Es-sebbar, Et-touhami; Farooq, Aamir

2014-11-01

284

Changes in the course of reaction and regeneration of a Pd-Ag\\/Al 2 O 3 catalyst for the selective hydrogenation of acetylene  

Microsoft Academic Search

The samples of Pd-Ag\\/Al2O3 catalysts for the selective hydrogenation of acetylene impurities in an ethane-ethylene mixture were studied using the IR\\u000a spectroscopy of adsorbed CO, X-ray diffraction analysis, and thermogravimetry. In the course of reaction and regeneration,\\u000a the total concentration of the supported metals (Pd and Ag) changed only slightly. The degree of accessibility of silver atoms\\u000a to CO adsorption

A. A. Lamberov; S. R. Egorova; I. R. Il’yasov; Kh. Kh. Gil’manov; S. V. Trifonov; V. M. Shatilov; A. Sh. Ziyatdinov

2007-01-01

285

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

286

Acetylene???furan trimer formation at 0.37 K as a model for ultracold aggregation of non- and weakly polar molecules.  

PubMed

We have studied the aggregation process of (C(2)H(2))???furan trimers at ultracold temperatures (0.37 K) in helium nanodroplets. Computational sampling of the potential energy surface using the multiple-minima-hypersurface (MMH) approach yielded seven possible minimum structures, optimized at the MP2 level of theory with the cc-pVTZ and 6-311++G(d,p) basis sets. Experimentally, we could assign five transitions in the IR spectrum of acetylene-furan aggregates in the acetylene C-H(asym) stretch region between 3240 and 3300 cm(-1) to vibrational bands of the 2:1 acetylene-furan trimer. The transitions were assigned to three ring structures that all contain the T-shaped acetylene dimer as structural sub-motif. Two of the structures form a nonplanar ring involving a C-H(Ac) ????(Fu) bond, the third is a nearly planar ring containing a C-H(Ac) ???O(Fu) bond. This assignment was corroborated by quantum mechanical/molecular dynamics (QM/MD) simulations mimicking in detail the aggregation process of precooled monomers. The simulations provided evidence for a transition from a higher level local minimum to the global minimum state over a small barrier during the aggregation process. The experimentally observed structures can be explained by a step-by-step aggregation of moieties pre-cooled to 0.37 K that are steered by intermediate and short-range electrostatic interactions. Thus, we are able to unravel a special aggregation mechanism which differs from aggregation of molecules with large dipole moments where this aggregation process is dominated by long range 1/r(3) dipole-dipole interaction ("electrostatic steering"). This mechanism is expected to be a general mechanism in ultracold chemistry. PMID:21557433

Metzelthin, Anja; Sánchez-García, Elsa; Birer, Özgür; Schwaab, Gerhard; Thiel, Walter; Sander, Wolfram; Havenith, Martina

2011-07-11

287

Geometrical and electronic effects in the conversion of acetylene to benzene on Au(111)/Pd and Au/Pd surface alloys  

NASA Astrophysics Data System (ADS)

In contrast with Pd(111), Au(111) is totally inert towards acetylene cyclisation. However, Pd overlayers on Au(111) efficiently catalyse the trimerisation of acetylene to benzene, even at submonolayer thickness. The extent of acetylene conversion and the binding energy of the resulting benzene depend on the atomic composition, morphology and electronic properties of the surface. Thin, un-annealed films exhibit maximum benzene yield at ˜ 3 ML thickness. Annealing leads initially to increased ordering of the Pd overlayer and ultimately to Pd/Au alloy formation. For a given Pd film thickness, limited annealing leads to increased benzene formation. Rougher, thicker Pd films are less efficient catalysts than smoother, thinner ones and appear to give rise to a new binding site for the reactively formed benzene. For a given benzene yield, Au/Pd alloy formation induced by annealing has a major effect on the desorption temperature of reactively-formed benzene. The results are discussed in terms of geometric and electronic effects on the reaction mechanism.

Ormerod, R. Mark; Baddeley, Christopher J.; Lambert, Richard M.

1991-12-01

288

Geometrical and electronic effects in the conversion of acetylene to benzene on Au(111)/Pd and Au/Pd surface alloys  

NASA Astrophysics Data System (ADS)

In contrast with Pd(111), Au(111) is totally inert towards acetylene cyclisation. However, Pd overlayers on Au(111) efficiently catalyse the trimerisation of acetylene to benzene, even at submonolayer thickness. The extent of acetylene conversion and the binding energy of the resulting benzene depend on the atomic composition, morphology and electronic properties of the surface. Thin, un-annealed films exhibit maximum benzene yield at ˜ 3 ML thickness. Annealing leads initially to increased ordering of the Pd overlayer and ultimately to Pd/Au alloy formation. For a given Pd film thickness, limited annealing leads to increased benzene formation. Rougher, thicker Pd films are less efficient catalysts than smoother, thinner ones and appear to give rise to a new binding site for the reactively formed benzene. For a given benzene yield, Au/Pd alloy formation induced by annealing has a major effect on the desorption temperature of reactively-formed benzene. The results are discussed in terms of geometric and electronic effects on the reaction mechanism.

Mark Ormerod, R.; Baddeley, Christopher J.; Lambert, Richard M.

289

Rotational spectroscopy of the first excited state of the acetylenic C H stretch of 3-fluoropropyne performed by infrared-Fourier transform microwave microwave triple-resonance spectroscopy  

NASA Astrophysics Data System (ADS)

The rotational spectra of 3-fluoropropyne in the ground and first excited acetylenic C-H stretch vibrational state have been measured. The pure rotational spectrum of the normal species and the 13C isotopomers were measured using FTMW-cwMW double-resonance spectroscopy based on the Autler-Townes (AC Stark) effect. The lineshape properties of this measurement make it possible to determine the transition strength, ? J-selection rules, and the relative energy ordering of the quantum states. The frequency accuracy of this technique is tested against a previous pure rotational study of 3-fluoropropyne. The rotational spectrum of vibrationally excited state was obtained through IR-FTMW-cwMW methods. In this technique a single-longitudinal-mode pulsed infrared laser source vibrationally excites the acetylenic C-H stretch with J-selectivity. The rotational spectrum of the excited state is then obtained by FTMW and FTMW-cwMW double-resonance methods. The excited-state measurements have a signal-to-noise ratio comparable to the pure rotational spectrum. The residuals in the excited-state fit are larger than those obtained in the ground-state fit. This greater deviation from a standard asymmetric top spectrum is most likely due to weak perturbations to the acetylenic C-H spectrum.

Douglass, Kevin O.; Rees, Frances S.; Suenram, Richard D.; Pate, Brooks H.; Leonov, Igor

2005-03-01

290

Selective Hydrogenation of Acetylene in the Presence of Ethylene on K+ -beta-Zeolite Supported Pd and PdAg Catalysts  

SciTech Connect

The selective hydrogenation of acetylene in the presence of ethylene has been studied on K+ exchanged {beta}-zeolite supported Pd and PdAg catalysts. Results from batch reactor studies with Fourier transform infrared spectroscopy (FTIR) have shown that the K+-{beta}-zeolite support is more selective than the Al2O3 or Na+-{beta}-zeolite supports toward the hydrogenation of acetylene. The rate and equilibrium constants for Pd/K+-{beta}-zeolite and PdAg/K+-{beta}-zeolite were determined using a Langmuir-Hinshelwood model. The selectivity of the PdAg bimetallic catalyst is twice of that of the Pd catalyst. Results from flow reactor studies show that the PdAg/K+-{beta}-zeolite catalyst has higher selectivity but lower activity toward acetylene hydrogenation than the Pd/K+-{beta}-zeolite catalyst. The selectivity to the undesirable ethane by-product is inhibited on the bimetallic catalyst. Extended X-ray absorption fine structure (EXAFS) studies and transmission electron microscope (TEM) analysis confirm the formation of Pd-Ag bimetallic bonds in the PdAg/K+-{beta}-zeolite catalyst.

Huang,W.; Pyrz, W.; Lobo, R.; Chen, J.

2007-01-01

291

A DFT+U study of acetylene selective hydrogenation on oxygen defective anatase (101) and rutile (110) TiO2 supported Pd4 cluster  

NASA Astrophysics Data System (ADS)

The reaction mechanisms for selective acetylene hydrogenation on three different supports, Pd4 cluster, oxygen defective anatase (101), and rutile (110) titania supported Pd4, cluster are studied using the density functional theory calculations with a Hubbard U correction (DFT+U). The present calculations show that the defect anatase support binds Pd4 cluster more strongly than that of rutile titania due to the existence of Ti3+ in anatase titania. Consequently, the binding energies of adsorbed species such as acetylene and ethylene on Pd4 cluster become weaker on anatase supported catalysts compared to the rutile supported Pd4 cluster. Anatase catalyst has higher selectivity of acetylene hydrogenation than rutile catalyst. On the one hand, the activation energies of ethylene formation are similar on the two catalysts, while they vary a lot on ethyl formation. The rutile supported Pd catalyst with lower activation energy is preferable for further hydrogenation. On the other hand, the relatively weak adsorption energy of ethylene is gained on anatase surface, which means it is easier for ethylene desorption, hence getting higher selectivity. For further understanding, the energy decomposition method and micro-kinetic analysis are also introduced.

Yang, Jie; Lv, Cun-Qin; Guo, Yong; Wang, Gui-Chang

2012-03-01

292

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 IC50 of 104 ?M, while the (4Z,8Z)-matricaria lactone was less active (IC50 of 220 ?M). In a fungal direct bioautography assay, the two lactones at 10 and 100 ?g/spot inhibited growth of the plant pathogenic fungi Colletotrichum acutatum , Colletotrichum fragariae , and Colletotrichum gloeosporioides . In a dose-response screening of the lactones against six different plant pathogenic fungi, (4Z,8Z)-matricaria lactone was more active than the commercial fungicide azoxystrobin on Col. acutatum , Col. fragariae , and Col. gloeosporioides at 30 ?M and about as active as the commercial fungicide captan against Col. gloeosporioides , while (4Z)-lachnophyllum lactone was less active. PMID:22612410

Queiroz, Sonia C N; Cantrell, Charles L; Duke, Stephen O; Wedge, David E; Nandula, Vijay K; Moraes, Rita M; Cerdeira, Antonio L

2012-06-13

293

Nitrate reduction  

DOEpatents

Nitrates are reduced to nitrogen gas by contacting the nitrates with a metal to reduce the nitrates to nitrites which are then contacted with an amide to produce nitrogen and carbon dioxide or acid anions which can be released to the atmosphere. Minor amounts of metal catalysts can be useful in the reduction of the nitrates to nitrites. Metal salts which are formed can be treated electrochemically to recover the metals.

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

2000-01-01

294

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

295

Quantum-chemical approach to determining the high potency of clorgyline as an irreversible acetylenic monoamine oxidase inhibitor.  

PubMed

Density functional theory calculations were employed to investigate the nature of chemical bond formation between the flavin co-factor of the enzyme monoamine oxidase (MAO) and its irreversible acetylenic inhibitor clorgyline in its terminally deprotonated anionic form. Since MAOs regulate the level of neurotransmitters in living cells, this reaction is pharmacologically relevant for treating depression and other mood disorders. The results revealed that this pathway is associated with the activation free energy of ?G act (#) = 17.4 kcal mol(-1), which, together with our previous results, suggests that clorgyline is intrinsically a more effective MAO inhibitor than antiparkinsonian drugs rasagiline and selegiline considering the preferred MAO isoforms in each case, thus displaying a trend in agreement with experimental data. The reaction is facilitated by the pronounced electrophilic character of the flavin moiety, due to its ability to efficiently accommodate excess negative charge from the approaching anionic inhibitor through resonance effect. The investigated mechanism was additionally validated by the inspection of the geometry of the flavin moiety in the formed adduct, which exhibit distortion from planarity consistent with experimental observations. These results offer valuable insight for mechanistic studies on other flavoenzymes and for the design of new antidepressants and antiparkinsonian drugs. PMID:23546802

Pavlin, Matic; Mavri, Janez; Repi?, Matej; Vianello, Robert

2013-06-01

296

Atomization efficiencies in halocarbon-loaded acetylene-air flames—I. Monochlorides of readily volatilized elements  

NASA Astrophysics Data System (ADS)

Carbon tetrachloride vapour was introduced with a carrier air stream into the mixing chamber of an acetylene-air flame while nebulizing aqueous solutions of several metal salts. The atomic absorption signal was measured under increasing flow rate of the halocarbon vapour at constant fuel-to-oxidant ratio, and the latter parameter was also varied in separate experiments. By applying the theory developed by Sugden and Bulewicz, the exclusive formation of monochlorides in the gaseous phase (presented here, in Part I) and the additional formation of hydroxychlorides and dichlorides (presented in Part II) could be elucidated. From the decrease of the signal measured for the alkali elements of known monochloride dissociation constants and dissociation energies, the temperature and the chlorine concentration present in the observed flame zone could be calculated. It is inferred that only 19% of the total halogen introduced is converted to HCl and Cl species in a slightly fuel-rich flame. The signal depression is stronger in a fuel-lean flame of higher monoatomic chlorine concentration for those elements which have a relatively efficient atomization under these flame conditions. An increase of the electron concentration resulting from the introduction of the halocarbon in an alkali-containing flame was deduced from the experimental findings, in agreement with earlier observations.

Kántor, Tibor

1994-12-01

297

Cosolvent effect on the catalytic reductive dechlorination of PCE.  

PubMed

Reductive dechlorination of chlorinated organic contaminants is an effective approach to treat this widespread group of environmentally hazardous substances. Metalloporphyrins can be used to catalyze reduction reactions by shuttling electrons from a reducing agent (electron donor) to chlorinated organic contaminants, thus rendering them to non-chlorinated acetylene, ethylene or ethane as major products. Iron, nickel and vanadium oxide tetraphenyl porphyrins (TPPs) were used as models of non-soluble metalloporphyrins that are common in subsurface environments, and hence may inflect on the ability to use natural ones. The effect of cosolvents on metalloporphyrins is demonstrated to switch the reduction of tetrachlorethylene (PCE) from no reaction to complete PCE transformation within 24 h and the production of final non-chlorinated compounds. Variations in product distributions for the different metalloporphyrins indicate that changes in the core metal can influence reaction rates and effective pathways. Furthermore, different cosolvents can generate varied product distributions, again suggesting that different pathways and/or rates are operative in the reduction reactions. Comparison of different cosolvent effects on PCE reduction using vitamin B12--a soluble natural metalloporphyrinogen--as the catalyst shows less pronounced differences between reactions in various cosolvent solutions versus only aqueous solution. PMID:15519395

Dror, Ishai; Schlautman, Mark A

2004-12-01

298

NCI Launches Proteomics Assay Portal  

Cancer.gov

In a paper recently published by the journal Nature Methods, Investigators from the National Cancer Institute’s Clinical Proteomic Tumor Analysis Consortium (NCI-CPTAC) announced the launch of a proteomics Assay Portal for multiple reaction monitoring-mass spectrometry (MRM-MS) assays. This community web-based repository for well-characterized quantitative proteomic assays currently consists of 456 unique peptide assays to 282 unique proteins and serves as a public resource of methodologies and data related to cancer associated targets.

299

Effect of lime additions to acid strip-mine spoil on survival, growth and nitrogen fixation (acetylene reduction) of several woody legume and actinomycete-nodulated species  

Microsoft Academic Search

Summary An acid mine spoil in Southern Indiana was amended with lime (CaCO3) (0.0, 12.5, 25 and 39t\\/ha) and planted withElaegnus umbellata Thunb.,Alnus glutinosa Gaertn.,Robinia pseudoacacia L.,Robinia fertilis Ashe, ‘Arnot’,Myrica pensylvania Lois,Caragana arborescens L. andShepherdia argentea Nutt. Survival and soil data were collected periodically and plants were harvested 15 months after planting. Nodule and top dry weights were determined and

D. L. Hensley; P. L. Carpenter

1984-01-01

300

Assays of ADAMTS-13 activity  

Microsoft Academic Search

Various assays for determination of ADAMTS-13 activity in plasma have been developed, all comprising two steps. The first step consists of proteolyzing a substrate by ADAMTS-13. Substrates were either exogenous von Willebrand factor (VWF) (purified from human plasma concentrates or recombinant VWF [rVWF]), purified VWF fragments, or endogenous VWF (from the tested plasma sample). All assays required a step in

Agnès Veyradier; Jean-Pierre Girma

2004-01-01

301

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. PMID:23691072

Chan, Grace Ka Yan; Kleinheinz, Tracy L.; Peterson, David; Moffat, John G.

2013-01-01

302

Frequency Comb-Referenced Measurements of - and Nitrogen-Perturbed Line Shapes in the ?_1 + ?_3 Band of Acetylene  

NASA Astrophysics Data System (ADS)

Frequency comb technology has the potential to dramatically improve precision and accuracy in measured spectra, but few applications have yet been reported. One application that can benefit from the high stability of spectrometers referenced to frequency combs is the measurement of spectral line shapes. We have built an absorption spectrometer based on an extended cavity diode laser locked to an Er-fiber-based frequency comb operating near 1550 nm. Here we report the first measurements of line shapes using a frequency comb as a reference. We studied the P(11) line in the ?_1 + ?_3 combination band of acetylene at 195 739.649 513(8) GHz at several temperatures from 296K down to 175K. This talk focuses on the data taken at 296K. We used a hard collision model (Rautian-Sobel'man) fit to the measurements to determine self- and nitrogen- pressure broadening, pressure shift and Dicke narrowing parameters that are at least 2 orders of magnitude more precise than those reported in previous measurements. We compare these hard collision model results with those of two other widely-used models: the Galatry (soft collision) and the Voigt function. The temperature- and rotational level- dependence of these parameters have been measured and some of the results will be discussed in a separate talk. 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

2011-06-01

303

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

SciTech Connect

In this work, both computer simulation and experimental studies were conducted to investigate several strategies for NO{sub x} reduction under pulverized coal combustion conditions with an aim to meet the stringent environmental standards for NO{sub x} control. Both computer predictions and reburning experiments yielded favorable results in terms of NO{sub x} control by reburning with a combination of methane and acetylene as well as non-selective catalytic reduction of NO{sub x} with ammonia following reburning with methane. The greatest reduction was achieved at the reburning stoichiometric ratio of 0.9; the reduction was very significant, as clearly shown in Chapters III and V. Both the experimental and computational results favored mixing gases: methane and acetylene (90% and 10% respectively) and methane and ammonia (98% and 2%) in order to get optimum reduction levels which can not be achieved by individual gases at any amounts. Also, the above gaseous compositions as reburning fuels seemed to have a larger window of stoichiometric ratio (SR2 < 0.9) as opposed to just methane (SR2=0.9) so as to reduce and keep NO{sub x} at low ppm levels. From the various computational runs, it has been observed that although there are several pathways that contribute to NO{sub x} reduction, the key pathway is NO {r_arrow} HCN {r_arrow} NH{sub 3} {r_arrow} N{sub 2} + H{sub 2}. With the trends established in this work, it is possible to scale the experimental results to real time industrial applications using computational calculations.

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

1998-06-01

304

From Antenna to Assay  

PubMed Central

Conspectus Ligand-sensitized, luminescent lanthanide(III) complexes are of considerable importance because their unique photophysical properties (microsecond to millisecond lifetimes, characteristic and narrow emission bands, and large Stokes shifts) make them well suited as labels in fluorescence-based bioassays. The long-lived emission of lanthanide(III) cations can be temporally resolved from scattered light and background fluorescence to vastly enhance measurement sensitivity. One challenge in this field is the design of sensitizing ligands that provide highly emissive complexes with sufficient stability and aqueous solubility for practical applications. In this Account, we give an overview of some of the general properties of the trivalent lanthanides and follow with a summary of advances made in our laboratory in the development of highly luminescent Tb(III) and Eu(III) complexes for applications in biotechnology. A focus of our research has been the optimization of these compounds as potential commercial agents for use in Homogeneous Time-Resolved Fluorescence (HTRF) technology. Our approach involves developing high-stability octadentate Tb(III) and Eu(III) complexes that rely on all-oxygen donor atoms and using multi-chromophore chelates to increase molar absorptivity; earlier examples utilized a single pendant chromophore (that is, a single “antenna”). Ligands based on 2-hydroxyisophthalamide (IAM) provide exceptionally emissive Tb(III) complexes with quantum yield values up to ?60% that are stable at the nanomolar concentrations required for commercial assays. Through synthetic modification of the IAM chromophore and time-dependent density functional theory (TD-DFT) calculations, we have developed a method to predict absorption and emission properties of these chromophores as a tool to guide ligand design. Additionally, we have investigated chiral IAM ligands that yield Tb(III) complexes possessing both high quantum yield values and strong circularly polarized luminescence (CPL) activity. To efficiently sensitize Eu(III) emission, we have used the 1-hydroxypyridin-2-one (1,2-HOPO) chelate to create remarkable ligands that combine excellent photophysical properties and exceptional aqueous stabilities. A more complete understanding of this chromophore has been achieved by combining low-temperature phosphorescence measurements with the same TD-DFT approach used with the IAM system. Eu(III) complexes with strong CPL activity have also been obtained with chiral 1,2-HOPO ligands. We have also undertaken the kinetic analysis of radiative and non-radiative decay pathways for a series of Eu(III) complexes; the importance of the metal ion symmetry on the ensuing photophysical properties is clear. Lastly, we describe a Tb(III)-IAM compound—now carried through to commercial availability—that offers improved performance in the common HTRF platform and has the potential to vastly improve sensitivity. PMID:19323456

Moore, Evan G.; Samuel, Amanda P. S.; Raymond, Kenneth N.

2009-01-01

305

Calorimetric assay of minor actinides  

SciTech Connect

This paper reviews the principles of calorimetric assay and evaluates its potential application to the minor actinides (U-232-4, Am-241, Am- 243, Cm-245, Np-237). We conclude that calorimetry and high- resolution gamma-ray isotopic analysis can be used for the assay of minor actinides by adapting existing methodologies for Pu/Am-241 mixtures. In some cases, mixtures of special nuclear materials and minor actinides may require the development of new methodologies that involve a combination of destructive and nondestructive assay techniques.

Rudy, C.; Bracken, D.; Cremers, T.; Foster, L.A.; Ensslin, N.

1996-12-31

306

Homogeneous catalysts supported on soluble polymers: biphasic Sonogashira coupling of aryl halides and acetylenes using MeOPEG-bound phosphine-palladium catalysts for efficient catalyst recycling.  

PubMed

The Sonogashira coupling of various aryl bromides and iodides with different acetylenes was studied under biphasic conditions with soluble, polymer-modified catalysts to allow the efficient recycling of the homogeneous catalyst. For this purpose, several sterically demanding and electron-rich phosphines of the type R(P)PR(2) were synthesised. They are covalently linked to a monomethyl polyethylene glycol ether with a mass of 2000 Dalton (R(P)=MeOPEG(2000)) R(P)PR(2): -PR(2)= -CH(2)C(6)H(4)CH(2)P(1-Ad)(2), -C(6)H(4)-P(1-Ad)(2), -C(6)H(4)-PPh(2). To couple aryl iodides and acetylenes, the catalyst [(MeCN)(2)PdCl(2)]/2 R(P)-C(6)H(4)-PPh(2) was used in CH(3)CN/Et(3)N/n-heptane (5/2/5). The combined yields of coupling product over five reaction cycles are between 80-95 percent. There is no apparent leaching of the catalyst into n-heptane, as evidenced by (1)H NMR spectroscopy. The new catalyst [(MeCN)(2)PdCl(2)]/2 (1-Ad)(2)PBn can be used for room-temperature coupling of various aryl bromides and acetylenes in THF with HNiPr(2) as a base. A closely related catalyst Na(2)[PdCl(4)]/2 R(P)-CH(2)C(6)H(4)CH(2)P(1-Ad)(2) linked to the polymer was used to couple aryl bromides and acetylenes in DMSO or DMSO/n-heptane at 60 degrees C with 0.5 mol percent Na(2)[PdCl(4)], 1 mol percent R(P)PR(2) and 0.33 mol percent CuI. The combined yield of coupling products over five cycles is always greater than 90 percent, except for sterically hindered aryl bromides. The determination of the turnover frequency (TOF) of the catalyst indicates only a small decrease in activity over five cycles. Leaching of the catalyst into the product containing n-heptane solution could not be detected by means of (1)H NMR and TXRF; this is indicative of >99.995 percent catalyst retention in the DMSO solvent. PMID:12645031

Köllhofer, Axel; Plenio, Herbert

2003-03-17

307

Rapid nonchromatographic assay for aminopropyltransferases  

SciTech Connect

Aminopropyltransferases are key enzymes in the biosynthesis of the polyamines spermidine and spermine. A procedure is described for assaying these enzymes be differential charcoal adsorption of /sup 14/C-labeled decarboxylated adenosylmethionine substrate from the labeled polyamine product. This assay is linear with time and enzyme concentration, and is suitable for use with a variety of amine acceptors. This procedure has the advantage, over those previously used, that it is extremely rapid yet very sensitive.

Anton, D.L.

1986-01-01

308

Acetylene C2H 2 retrievals from MIPAS data and regions of enhanced upper tropospheric concentrations in August 2003  

NASA Astrophysics Data System (ADS)

Acetylene (C2H2) volume mixing ratios (VMRs) have been successfully retrieved from the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) Level 1B radiances during August 2003, providing the first global map of such data and ratios to CO in the literature. The data presented here contain most information between 300 hPa and 100 hPa with systematic errors less than 10% at the upper levels. Random errors per point are less than 15% at lower levels and are closer to 30% at 100 hPa. Global distributions of the C2H2 and C2H2/CO ratio confirm significant features associated with both the Asian monsoon anticyclone and biomass burning for this important hydrocarbon in a characteristic summer month (August 2003), showing tight correlations regionally, particularly at lower to medium values, but globally emphasising the differences between sources and lifetimes of CO and C2H2. The correlations are seen to be particularly disturbed in the regions of highest C2H2 concentrations, indicating variability in the surface emissions or fast processing. A strong isolation of C2H2 within the Asian monsoon anticyclone is observed, evidencing convective transport into the upper troposphere, horizontal advection within the anticyclone at 200 hPa, distinct gradients at the westward edge of the vortex and formation of a secondary dynamical feature from the eastward extension of the anticyclone outflow over the Asian Pacific. Ratios of C2H2/CO are consistent with the evidence from the cross-sections that the C2H2 is uplifted rapidly in convection. Observations are presented of enhanced C2H2 associated with the injection from biomass burning into the upper troposphere and the outflow from Africa at 200 hPa into both the Atlantic and Indian Oceans. In the biomass burning regions, C2H2 and CO are well correlated, but the uplift is less marked and peaks at lower altitudes compared to the strong effects observed in the Asian monsoon anticyclone. Ratios of C2H2/CO clearly decay along transport pathways for the outflow, indicating photochemical ageing of the plumes. Overall, the data show the distinctive nature of C2H2 distributions, confirm in greater detail than previously possible features of hydrocarbon enhancements in the upper troposphere and highlight the future use of MIPAS hydrocarbon data for testing model transport and OH decay regimes in the middle to upper troposphere.

Parker, R. J.; Remedios, J. J.; Moore, D. P.; Kanawade, V. P.

2011-10-01

309

Site Map | Clinical Assay Development Program (CADP)  

Cancer.gov

Skip to Content Search this site Site Map Home About CADP Mission Background CADP Resources for Assay Development CADN — Clinical Assay Development Network CADC — Clinical Assay Development Center SRS — Specimen Retrieval System Access to CADP Resources Eligibility Instructions Submit

310

A theoretical study on the reaction pathways and the mechanism of 1,3- dipolar cycloaddition of vinyl acetylene and methyl azide.  

PubMed

1,3-dipolar cycloaddition procedure is one of the most widely practiced methods in order to synthesize heterocyclic compounds. Although, it seems very simple, but, there are numerous precursors of heterocyclic molecules who have more than one positions to react with a 1,3-dipole species. As a result, while using a precursor with more than one position for reaction, it is probable to synthesize several products with different structures. This paper studies all possible interactions of vinyl acetylene, which has two positions for reaction, with methyl azide. This reaction could lead to the emergence of any 1,3-dipolar cycloaddition products. Our ultimate goal is to help researchers to find out how precursors containing both carbon-carbon double, and the triple bonds interact with 1,3- dipolar species. The present study used the DFT calculations at B3LYP/6-311++G(3df,pd) level to check all probable interactions between vinyl acetylene and methyl azide, and determined Potential Energy Surface, and optimized all species. PMID:24852164

Siadati, Seyyed Amir; Mahboobifar, Ali; Nasiri, Ramin

2014-01-01

311

Luminogenic cytochrome P450 assays.  

PubMed

Luminogenic cytochrome P450 (CYP) assays couple CYP enzyme activity to firefly luciferase luminescence in a technology called P450-Glo(TM) (Promega). Luminogenic substrates are used in assays of human CYP1A1, -1A2, -1B1, -2C8, -2C9, -2C19, -2D6, -2J2, -3A4, -3A7, -4A11, -4F3B, -4F12 and -19. The assays detect dose-dependent CYP inhibition by test compounds against recombinant CYP enzymes or liver microsomes. Induction or inhibition of CYP activities in cultured hepatocytes is measured in a nonlytic approach that leaves cells intact for additional analysis. Luminogenic CYP assays offer advantages of speed and safety over HPLC and radiochemical-based methods. Compared with fluorogenic methods the approach offers advantages of improved sensitivity and decreased interference between optical properties of test compound and CYP substrate. These homogenous assays are sensitive and robust tools for high-throughput CYP screening in early drug discovery. PMID:16859410

Cali, James J; Ma, Dongping; Sobol, Mary; Simpson, Daniel J; Frackman, Susan; Good, Troy D; Daily, William J; Liu, David

2006-08-01

312

Plaque Assay for Rickettsia rickettsii  

PubMed Central

A plaque technique for the assay of Rickettsia rickettsii is described. The method employs primary chick or green monkey kidney monolayer cell cultures with either an agarose or special Noble agar overlay. Plaques were counted in 6 days and resultant titers correlated well with ld50 end points obtained by a standard assay in embryonated eggs. Identification of the plaque-forming organisms was accomplished by direct observation of rickettsiae-like bodies in the monolayer lesions, inhibition of plaques by antibiotics, sensitivity of plaques to specific immune serum, and failure to cultivate other microorganisms from the infected cells. Versatility of the test was demonstrated by assaying samples of rickettsiae from several different sources commonly used in our laboratory. These included infected yolk sacs, various cell cultures, and infected guinea pig tissue. Sufficient numbers of viable rickettsiae were present in the cells of a single lesion to permit direct recovery. Images PMID:4977475

Weinberg, Edmund H.; Stakebake, Jack R.; Gerone, Peter J.

1969-01-01

313

Plaque assay for Rickettsia rickettsii.  

PubMed

A plaque technique for the assay of Rickettsia rickettsii is described. The method employs primary chick or green monkey kidney monolayer cell cultures with either an agarose or special Noble agar overlay. Plaques were counted in 6 days and resultant titers correlated well with ld(50) end points obtained by a standard assay in embryonated eggs. Identification of the plaque-forming organisms was accomplished by direct observation of rickettsiae-like bodies in the monolayer lesions, inhibition of plaques by antibiotics, sensitivity of plaques to specific immune serum, and failure to cultivate other microorganisms from the infected cells. Versatility of the test was demonstrated by assaying samples of rickettsiae from several different sources commonly used in our laboratory. These included infected yolk sacs, various cell cultures, and infected guinea pig tissue. Sufficient numbers of viable rickettsiae were present in the cells of a single lesion to permit direct recovery. PMID:4977475

Weinberg, E H; Stakebake, J R; Gerone, P J

1969-05-01

314

Plaque Assay for Murine Norovirus  

PubMed Central

Murine norovirus (MNV) is the only member of the Norovirus genus that efficiently grows in tissue culture 1, 2. Cell lysis and cytopathic effect (CPE) are observed during MNV-1 infection of murine dendritic cells or macrophages 1. This property of MNV-1 can be used to quantify the number of infectious particles in a given sample by performing a plaque assay 1. The plaque assay relies on the ability of MNV-1 to lyse cells and to form holes in a confluent cell monolayer, which are called plaques 3. Multiple techniques can be used to detect viral infections in tissue culture, harvested tissue, clinical, and environmental samples, but not all measure the number of infectious particles (e.g. qRT-PCR). One way to quantify infectious viral particles is to perform a plaque assay 3, which will be described in detail below. A variation on the MNV plaque assay is the fluorescent focus assay, where MNV antigen is immunostained in cell monolayers 4. This assay can be faster, since viral antigen expression precedes plaque formation. It is also useful for titrating viruses unable to form plaques. However, the fluorescent focus assay requires additional resources beyond those of the plaque assay, such as antibodies and a microscope to count focus-forming units. Infectious MNV can also be quantified by determining the 50% Tissue Culture Infective Dose (TCID50) 3. This assay measures the amount of virus required to produce CPE in 50% of inoculated tissue culture cells by endpoint titration 5. However, its limit of detection is higher compared to a plaque assay 4. In this article, we describe a plaque assay protocol that can be used to effectively determine the number of infectious MNV particles present in biological or environmental samples 1, 4, 6. This method is based on the preparation of 10-fold serial dilutions of MNV-containing samples, which are used to inoculate a monolayer of permissive cells (RAW 264.7 murine macrophage cells). Virus is allowed to attach to the cell monolayer for a given period of time and then aspirated before covering cells with a mixture of agarose and cell culture media. The agar enables the spread of viral progeny to neighboring cells while limiting spread to distantly located cells. Consequently, infected cells are lysed and form holes in the monolayer known as plaques. Upon sufficient spread of virus, plaques become visible following staining of cells with dyes, like neutral red, methylene blue, or crystal violet. At low dilutions, each plaque originates from one infectious viral particle and its progeny, which spread to neighboring cells. Thus, counting the number of plaques allows one to calculate plaque-forming units (PFU) present in the undiluted sample 3. PMID:22951568

Gonzalez-Hernandez, Mariam B.; Bragazzi Cunha, Juliana; Wobus, Christiane E.

2012-01-01

315

Biochemical Assays of Cultured Cells  

NASA Technical Reports Server (NTRS)

Subpopulations of human embryonic kidney cells isolated from continuous flow electrophoresis experiments performed at McDonnell Douglas and on STS-8 have been analyzed. These analyses have included plasminogen activator assays involving indirect methodology on fibrin plated and direct methodology using chromogenic substrates. Immunological studies were performed and the conditioned media for erythropoietin activity and human granulocyte colony stimulating (HGCSF) activity was analyzed.

Barlow, G. H.

1985-01-01

316

Polymerase Chain Reaction Assay and  

E-print Network

Polymerase Chain Reaction Assay and Bacterial Meningitis Surveillance in Remote Areas, Niger Fati reference laboratory for meningitis in Niger used polymerase chain reaction (PCR) to enhance) and the national reference center for menin- gitis in Niger. The polymerase chain reaction (PCR) method

Paris-Sud XI, Université de

317

Three dimensional colorimetric assay assemblies  

DOEpatents

A direct assay is described using novel three-dimensional polymeric assemblies which change from a blue to red color when exposed to an analyte, in one case a flu virus. The assemblies are typically in the form of liposomes which can be maintained in a suspension, and show great intensity in their color changes. Their method of production is also described.

Charych, Deborah (Albany, CA); Reichart, Anke (Albany, CA)

2000-01-01

318

Three dimensional colorimetric assay assemblies  

SciTech Connect

A direct assay is described using novel three-dimensional polymeric assemblies which change from a blue to red color when exposed to an analyte, in one case a flu virus. The assemblies are typically in the form of liposomes which can be maintained in a suspension, and show great intensity in their color changes. Their method of production is also described.

Charych, D.; Reichart, A.

2000-06-27

319

Full dimensional Franck-Condon factors for the acetylene tilde{{A}} 1Au—{tilde{X}} {^1? _g^+} transition. I. Method for calculating polyatomic linear—bent vibrational intensity factors and evaluation of calculated intensities for the gerade vibrational modes in acetylene  

NASA Astrophysics Data System (ADS)

Franck-Condon vibrational overlap integrals for the tilde{A} {^1A_u}—{tilde{X}} {^1? _g^+} transition in acetylene have been calculated in full dimension in the harmonic normal mode basis. The calculation uses the method of generating functions first developed for polyatomic Franck-Condon factors by Sharp and Rosenstock [J. Chem. Phys. 41(11), 3453-3463 (1964)], and previously applied to acetylene by Watson [J. Mol. Spectrosc. 207(2), 276-284 (2001)] in a reduced-dimension calculation. Because the transition involves a large change in the equilibrium geometry of the electronic states, two different types of corrections to the coordinate transformation are considered to first order: corrections for axis-switching between the Cartesian molecular frames and corrections for the curvilinear nature of the normal modes at large amplitude. The angular factor in the wavefunction for the out-of-plane component of the trans bending mode, ? _4^' ' }, is treated as a rotation, which results in an Eckart constraint on the polar coordinates of the bending modes. To simplify the calculation, the other degenerate bending mode, ? _5^' ' }, is integrated in the Cartesian basis and later transformed to the constrained polar coordinate basis, restoring the conventional v and l quantum numbers. An updated tilde{A}-state harmonic force field obtained recently in the R. W. Field research group is evaluated. The results for transitions involving the gerade vibrational modes are in qualitative agreement with experiment. Calculated results for transitions involving ungerade modes are presented in Paper II of this series [G. B. Park, J. H. Baraban, and R. W. Field, "Full dimensional Franck-Condon factors for the acetylene tilde{A} {^1A_u}—{tilde{X}} {^1? _g^+} transition. II. Vibrational overlap factors for levels involving excitation in ungerade modes," J. Chem. Phys. 141, 134305 (2014)].

Park, G. Barratt

2014-10-01

320

Automated high-throughput Vibrio fischeri assay for (eco)toxicity screening: application to ionic liquids.  

PubMed

An automated high-throughput Vibrio fischeri assay was developed and further applied to the evaluation of ionic liquids (ILs) (eco)toxicity. The assay was based on the reduction of bacterial bioluminescence in the presence of test compounds and the results were presented as EC(50). The assays were performed with eight commercially available ILs with distinct cationic head groups, alkyl side chains and anions. EC(50) values between 6.5 and 691.9 mmol L(-1) were obtained for the tested ILs, being hmim [Cl] the most toxic and bmim [Cl] the less toxic ones, confirming the influence of the different structural elements. Moreover, all the tested ILs exhibited a (eco)toxicity lower than Cu(II), used as a positive control during the optimization and analysis steps. The automated assay assured the precise control of the contact time between V. fischeri and test compound by means of a simple protocol that guaranteed adequate aspiration and handling of the solutions as well as the precise implementation of a computer controlled stop period. Furthermore, a significant reduction of the assay costs was achieved through automation mainly by a drastic reduction of the volume of bacterial suspension and test compound. The methodology was validated by comparison with a microplate assay; it was stated that the results, obtained after a 3min contact time, changed proportionally relatively to Cu(II) in both assays. This confirmed the applicability of the methodology as an (eco)toxicity screening assay, with reduction of time and increase of robustness and repeatability (n=10; rsd<1.1%). It is expected that due to its simplicity and reduced cost the developed assay can be integrated in the early stage of development of new compounds as a rapid screening test. PMID:22417674

Pinto, Paula C A G; Costa, Susana P F; Lima, José L F C; Saraiva, M Lúcia M F S

2012-06-01

321

Hydrogenation of Acetylene-Ethylene Mixtures over Pd and Pd-Ag Alloys: First-Principles Based Kinetic Monte Carlo Simulations  

SciTech Connect

The kinetics for the selective hydrogenation of acetylene-ethylene mixtures over model Pd(111) and bimetallic Pd-Ag alloy surfaces were examined using first principles based kinetic Monte Carlo (KMC) simulations to elucidate the effects of alloying as well as process conditions (temperature and hydrogen partial pressure). The mechanisms that control the selective and unselective routes which included hydrogenation, dehydrogenation and C-?C bond breaking pathways were analyzed using first-principle density functional theory (DFT) calculations. The results were used to construct an intrinsic kinetic database that was used in a variable time step kinetic Monte Carlo simulation to follow the kinetics and the molecular transformations in the selective hydrogenation of acetylene-ethylene feeds over Pd and Pd-Ag surfaces. The lateral interactions between coadsorbates that occur through-surface and through-space were estimated using DFT-parameterized bond order conservation and van der Waal interaction models respectively. The simulation results show that the rate of acetylene hydrogenation as well as the ethylene selectivity increase with temperature over both the Pd(111) and the Pd-Ag/Pd(111) alloy surfaces. The selective hydrogenation of acetylene to ethylene proceeds via the formation of a vinyl intermediate. The unselective formation of ethane is the result of the over-hydrogenation of ethylene as well as over-hydrogenation of vinyl to form ethylidene. Ethylidene further hydrogenates to form ethane and dehydrogenates to form ethylidyne. While ethylidyne is not reactive, it can block adsorption sites which limit the availability of hydrogen on the surface and thus act to enhance the selectivity. Alloying Ag into the Pd surface decreases the overall rated but increases the ethylene selectivity significantly by promoting the selective hydrogenation of vinyl to ethylene and concomitantly suppressing the unselective path involving the hydrogenation of vinyl to ethylidene and the dehydrogenation ethylidene to ethylidyne. This is consistent with experimental results which suggest only the predominant hydrogenation path involving the sequential addition of hydrogen to form vinyl and ethylene exists over the Pd-Ag alloys. Ag enhances the desorption of ethylene and hydrogen from the surface thus limiting their ability to undergo subsequent reactions. The simulated apparent activation barriers were calculated to be 32-44 kJ/mol on Pd(111) and 26-31 kJ/mol on Pd-Ag/Pd(111) respectively. The reaction was found to be essentially first order in hydrogen over Pd(111) and Pd-Ag/Pd(111) surfaces. The results reveal that increases in the hydrogen partial pressure increase the activity but decrease ethylene selectivity over both Pd and Pd-Ag/Pd(111) surfaces. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.

Mei, Donghai; Neurock, Matthew; Smith, C Michael

2009-10-22

322

Synthesis, characterization and antimicrobial evaluation of some new schiff, mannich and acetylenic mannich bases incorporating a 1,2,4-triazole nucleus.  

PubMed

A series of Schiff and Mannich bases derived from 4-amino-5-(3-fluoro-phenyl)-2,4-dihydro-3H-1,2,4-triazole-3-thione were synthesized. The alkylation of 4-phenyl-5-(3-fluorophenyl)-2,4-dihydro-3H-1,2,4-triazole-3-thione with propargyl bromide afforded the corresponding thiopropargylated derivative which upon treatment with the appropriate secondary amines in the presence of CuCl2 furnished the desired acetylenic Mannich bases. The synthesized compounds were characterized on the basis of their spectral (IR, 1H- and 13C-NMR) data and evaluated for their biological activities. Some of the compounds were found to exhibit significant antimicrobial activity. PMID:25412038

Aouad, Mohamed R

2014-01-01

323

Mechanism of Gold(I)-Catalyzed Rearrangements of Acetylenic Amine-N-Oxides: Computational Investigations Lead to a New Mechanism Confirmed by Experiment  

PubMed Central

Quantum mechanical studies of the mechanism of gold-catalyzed rearrangements of acetylenic amine-N-oxides to piperidinones or azepanones have revealed a new mechanism involving a concerted hetero-retroene reaction, formally a 1, 5 hydrogen shift from the N-alkyl groups to the vinyl position of a gold-coordinated methyleneisoxazolidinium or methyleneoxazinanium. Density functional calculations (B3LYP, B3LYP-D3) on the hetero-retroene mechanism reproduce experimental regioselectivities and provide an explanation as to why the hydrogen is transferred from the smaller amine substituent. In support of the proposed mechanism, new experimental investigations show that the hydrogen shift is concerted and that gold carbenes are not involved as reaction intermediates. PMID:22191473

Noey, Elizabeth L.; Luo, Yingdong; Zhang, Liming

2012-01-01

324

Silver-catalyzed oxidative coupling of aniline and ene carbonyl/acetylenic carbonyl compounds: an efficient route for the synthesis of quinolines.  

PubMed

An efficient silver-mediated coupling of aniline with ene carbonyl/acetylenic carbonyl compounds for the synthesis of quinolines is reported. The transformation is effective for a broad range of substrates, thus enabling the expansion of substituent architectures on the heterocyclic framework. The electronic properties of the substituents on the amine have been investigated. It was found that molecules with both electron-donating and electron-withdrawing substituents were suitable substrates for this transformation, and the expected products were obtained in moderate to excellent yields. The use of a single catalytic system to mediate chemical transformations in a synthetic operation is important for the development of new atom-economic strategies and this strategy is efficient in building complex structures from simple starting materials in an environmentally benign fashion. PMID:25195503

Zhang, Xu; Xu, Xuefeng

2014-11-01

325

Full dimensional Franck-Condon factors for the acetylene A? (1)Au-X? ?g+1 transition. II. Vibrational overlap factors for levels involving excitation in ungerade modes.  

PubMed

A full-dimensional Franck-Condon calculation has been applied to the A? (1)Au-X? ?g+1 transition in acetylene in the harmonic normal mode basis. Details of the calculation are discussed in Part I of this series. To our knowledge, this is the first full-dimensional Franck-Condon calculation on a tetra-atomic molecule undergoing a linear-to-bent geometry change. In the current work, the vibrational intensity factors for levels involving excitation in ungerade vibrational modes are evaluated. Because the Franck-Condon integral accumulates away from the linear geometry, we have been able to treat the out-of-plane component of trans bend (?4 ('')) in the linear X? state in the rotational part of the problem, restoring the ? Euler angle and the a-axis Eckart conditions. A consequence of the Eckart conditions is that the out-of-plane component of ?4 ('') does not participate in the vibrational overlap integral. This affects the structure of the coordinate transformation and the symmetry of the vibrational wavefunctions used in the overlap integral, and results in propensity rules involving the bending modes of the X? state that were not previously understood. We explain the origin of some of the unexpected propensities observed in IR-UV laser-induced fluorescence spectra, and we calculate emission intensities from bending levels of the A? state into bending levels of the X? state, using normal bending mode and local bending mode basis sets. Our calculations also reveal Franck-Condon propensities for the Cartesian components of the cis bend (?5 ('')), and we predict that the best A?-state vibrational levels for populating X?-state levels with large amplitude bending motion localized in a single C-H bond (the acetylene?vinylidene isomerization coordinate) involve a high degree of excitation in ?6 (') (cis-bend). Mode ?4 (') (torsion) populates levels with large amplitude counter-rotational motion of the two hydrogen atoms. PMID:25296804

Park, G Barratt; Baraban, Joshua H; Field, Robert W

2014-10-01

326

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 cutoffs are too sensitive, donation loss may adversely impact blood availability. STUDY DESIGN Pregnancy history and HLA antibody screening and single antigen bead (SAB) data from blood donors in the REDS-II Leukocyte Antibody Prevalence Study (LAPS) were evaluated for correlations between assay screening values, HLA antibody titer, and number of HLA antigen specificities. The probabilities of matching a cognate antigen in a recipient were calculated and examined in association with total number of specificities observed and screening values. The relative impact of imposing various screening assay cutoffs or pregnancy stratification was examined in relation to detection of HLA antibody reactive donations and loss of donors and donations. RESULTS We provide evidence that higher HLA Ab screening assay values are associated with maintaining higher screening signals upon dilution and an increased breadth of specificities compared with lower screening values; the latter correlated with an increased risk of a cognate antigen match in potential recipients. Depending upon the TRALI risk reduction strategy used, the potential loss of donations ranged between 0.9 and 6.0%. CONCLUSION This analysis should enable blood centers to decide upon a TRALI risk reduction strategy for apheresis platelets that is consistent with how much donation loss the blood center can tolerate. PMID:21332726

Carrick, Danielle M.; Norris, Philip J.; Endres, Robert O.; Pandey, Suchitra; Kleinman, Steven H.; Wright, David; Sun, Yu; Busch, Michael P.

2011-01-01

327

Telomere Overhang Assay-de Lange Lab Telomere Overhang Assay  

E-print Network

Overhang Assay- de Lange Lab 2 Denaturing Solution 1.5M NaCl 0.5M NaOH Mix: 1.75kg NaCl 400g NaOH Fill to 20 l with dH20. Mix on stir plate o/n to dissolve. Neutralizing Solution 3M NaCl 0.5M Tris-HCL pH 7.0 Mix: 3.5 kg NaCL 1.2 kg Tris 780 ml HCL (careful with this much acid) Fill to 20 l with dH20 and mix

de Lange, Titia

328

The Intercostal NMJ Assay: a new alternative to the conventional LD50 assay for the determination of the therapeutic potency of botulinum toxin preparations.  

PubMed

Therapeutic botulinum neurotoxin type A preparations have found an increasing number of clinical uses for a large variety of neuromuscular disorders and dermatological conditions. The accurate determination of potency in the clinical application of botulinum toxins is critical to ensuring clinical efficacy and safety, and is currently achieved by using a lethal dose (LD50) assay in mice. Ethical concerns and operational constraints associated with this assay have prompted the development of alternative assay systems that could potentially lead to its replacement. As one such alternative, we describe the development and evaluation of a novel ex vivo assay (the Intercostal Neuromuscular Junction [NMJ] Assay), which uses substantially fewer animals and addresses ethical concerns associated with the LD50 assay. The assay records the decay of force from electrically-stimulated muscle tissue sections in response to the toxin, and thus combines the important mechanisms of receptor binding, translocation, and the enzymatic action of the toxin molecule. Toxin application leads to a time-related and dose-related reduction in contractile force. A regression model describing the relationship between the applied dose and force decay was determined statistically, and was successfully tested as able to correctly predict the potency of an unknown sample. The tissue sections used were found to be highly reproducible, as determined through the innervation pattern and the localisation of NMJs in situ. Furthermore, the efficacy of the assay protocol to successfully deliver the test sample to the cellular target sites, was critically assessed by using molecular tracer molecules. PMID:18522482

Huber, Alexander; France, Richard M; Riccalton-Banks, Lisa; McLaren, Jane; Cox, Helen; Quirk, Robin A; Shakesheff, Kevin M; Thompson, David; Panjwani, Naveed; Shipley, Sarah; Pickett, Andy

2008-05-01

329

Reductive dechlorination of tetrachloroethylene and trichloroethylene catalyzed by vitamin B{sub 12} in homogeneous and heterogeneous systems  

SciTech Connect

The reduction of tetrachloroethylene (PCE) and trichloroethylene (TCE) catalyzed by vitamin B{sub 12} was examined in homogeneous and heterogeneous (B{sub 12} bound to agarose) batch systems using titanium(III) citrate as the bulk reductant. The solution and surface-mediated reaction rates at similar B{sub 12} loadings were comparable, indicating that binding vitamin B{sub 12} to a surface did not lower catalytic activity. No loss in PCE reducing activity was observed with repeated usage of surface-bound vitamin B{sub 12}. Carbon mass recoveries were 81-84% for PCE reduction and 89% for TCE reduction, relative to controls. In addition to sequential hydrogenolysis, a second competing reaction mechanism for the reduction of PCE and TCE by B{sub 12}, reductive {beta}-elimination, is proposed to account for the observation of acetylene as a significant reaction intermediate. Reductive {beta}-elimination should be considered as a potential pathway in other reactive systems involving the reduction of vicinal polyhaloethenes. Surface-bound catalysts such as vitamin B{sub 12} may have utility in the engineered degradation of aqueous phase chlorinated ethenes. 19 refs., 6 figs., 1 tab.

Burris, D.R.; Smith, M.H. [Armstrong Lab., Tyndall Air Force Base, FL (United States)] [Armstrong Lab., Tyndall Air Force Base, FL (United States); Delcomyn, C.A. [Applied Research Associates, Inc., Tyndall Air Force Base, FL (United States)] [Applied Research Associates, Inc., Tyndall Air Force Base, FL (United States); Roberts, A.L. [Johns Hopkins Univ., Baltimore, MD (United States)] [Johns Hopkins Univ., Baltimore, MD (United States)

1996-10-01

330

MULTIPLEXING SCHEMES FOR GENERIC SNP GENOTYPING ASSAYS  

E-print Network

MULTIPLEXING SCHEMES FOR GENERIC SNP GENOTYPING ASSAYS R. SHARAN International Computer Science� mally multiplexing SNP genotyping using generic assays. We devise a graph theoretic formulation need to be inferred. The development of efficient SNP detection, genotyping and measurement techniques

Sharan, Roded

331

Opportunity for Clinical Assay Development Support  

Cancer.gov

The NCI’s Division of Cancer Treatment and Diagnosis and the Cancer Diagnosis Program announce a request for applications for the Clinical Assay Development Program (CADP) for investigators seeking clinical assay development and validation resources.

332

Technology platforms for pharmacogenomic diagnostic assays  

Microsoft Academic Search

Rapid advances in the understanding of genomic variation affecting drug responses, and the development of multiplex assay technologies, are converging to form the basis for new in vitro diagnostic assays. These molecular diagnostic assays are expected to guide the therapeutic treatment of many diseases, by informing physicians about molecular subtypes of disease that require differential treatment, which drug has the

Walter H. Koch

2004-01-01

333

Data transformation methods for multiplexed assays  

DOEpatents

Methods to improve the performance of an array assay are described. A correlation between fluorescence intensity-related parameters and negative control values of the assay is determined. The parameters are then adjusted as a function of the correlation. As a result, sensitivity of the assay is improved without changes in its specificity.

Tammero, Lance F. Bentley; Dzenitis, John M; Hindson, Benjamin J

2013-07-23

334

Whole worm glycerol assay Reagents needed  

E-print Network

AND 15. 21. Solublize the protein pellet in 0.5ml of .2N NaOH (this can sometimes take a while; use ample this supernatant for the glycerol assay (For low glycerol concentrations, use 1-2ml/ assay. For high glycerol-reaction after 7 minutes and postreaction after 15 minutes) 29. For BCA assay, run the room temp protocol

Lamitina, Todd

335

Effect of bilirubin on the spectrophotometric and radionuclide assay for serum angiotensin-converting enzyme  

SciTech Connect

The effect of bilirubin on serum angiotensin-converting enzyme (ACE) activity was studied with spectrophotometric and radionuclide assays. In the spectrophotometric assay addition of bilirubin to normal serum from dog, mouse, and human produced a dose-related inhibition of ACE activity. A 50% decrease in human ACE activity was produced by the addition of approximately 250 mg/L in vitro. Serum from icteric patients with elevated bilirubin was also associated with a reduction in ACE activity in the spectrophotometric assay. A 50% decrease in ACE activity in these samples was associated with a serum bilirubin of approximately 220 mg/L. In the radionuclide assay, however, addition of bilirubin to normal human serum failed to reduce measured ACE activity. The use of a radionuclide assay for serum ACE in clinical samples offers the advantage of less interference from serum bilirubin.

Saxe, A.W.; Hollinger, M.A.; Essam, T.

1986-01-01

336

Rotor assembly and assay method  

DOEpatents

A rotor assembly for carrying out an assay includes a rotor body which is rotatable about an axis of rotation, and has a central chamber and first, second, third, fourth, fifth, and sixth chambers which are in communication with and radiate from the central chamber. The rotor assembly further includes a shuttle which is movable through the central chamber and insertable into any of the chambers, the shuttle including a reaction cup carrying an immobilized antigen or an antibody for transport among the chambers. A method for carrying out an assay using the rotor assembly includes moving the reaction cup among the six chambers by passing the cup through the central chamber between centrifugation steps in order to perform the steps of: separating plasma from blood cells, binding plasma antibody or antigen, washing, drying, binding enzyme conjugate, reacting with enzyme substrate and optically comparing the resulting reaction product with unreacted enzyme substrate solution. The movement of the reaction cup can be provided by attaching a magnet to the reaction cup and supplying a moving magnetic field to the rotor.

Burtis, Carl A. (Oak Ridge, TN); Johnson, Wayne F. (Loudon, TN); Walker, William A. (Knoxville, TN)

1993-01-01

337

SNO+ Scintillator Purification and Assay  

NASA Astrophysics Data System (ADS)

We describe the R&D on the scintillator purification and assay methods and technology for the SNO+ neutrino and double-beta decay experiment. The SNO+ experiment is a replacement of the SNO heavy water with liquid scintillator comprised of 2 g/L PPO in linear alkylbenzene (LAB). During filling the LAB will be transported underground by rail car and purified by multi-stage distillation and steam stripping at a flow rate of 19 LPM. While the detector is operational the scintillator can be recirculated at 150 LPM (full detector volume in 4 days) to provide repurification as necessary by either water extraction (for Ra, K, Bi) or by functional metal scavenger columns (for Pb, Ra, Bi, Ac, Th) followed by steam stripping to remove noble gases and oxygen (Rn, O2, Kr, Ar). The metal scavenger columns also provide a method for scintillator assay for ex-situ measurement of the U and Th chain radioactivity. We have developed "natural" radioactive spikes of Pb and Ra in LAB and use these for purification testing. Lastly, we present the planned operating modes and purification strategies and the plant specifications and design.

Ford, R.; Chen, M.; Chkvorets, O.; Hallman, D.; Vázquez-Jáuregui, E.

2011-04-01

338

Assay of potentially contaminated propellant  

SciTech Connect

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 DU is indicated by its alpha decay. The alpha particles in turn produce ions in the ambient air. If a significant fraction of these ions can escape the quantity of propellant, the ions can be detected instead of the alpha particles. As a test of the feasibility of detecting alpha emissions from DU somewhere within a cartridge of propellant, the transmission of ions through layers of real propellant was measured. The propellant is in the form of graphite-coated cylindrical pellets. A 105nun cartridge was modified for use as a pellet chamber. A check source served as an ion source. The ion detector consisted of a grid held at 300V coupled to an ammeter. Results confirm that this is a promising technique for testing the propellant for the presence of DU quickly yet with sensitivity.

Koster, J.E.; Williams, H.E. III [Los Alamos National Lab., NM (United States); Scott, W.S. [Savanna Army Depot Activity (United States)

1995-02-01

339

Assay Development for Histone Methyltransferases  

PubMed Central

Abstract Epigenetic modifications play a crucial role in human diseases. Unlike genetic mutations, however, they do not change the underlying DNA sequences. Epigenetic phenomena have gained increased attention in the field of cancer research, with many studies indicating that they are significantly involved in tumor establishment and progression. Histone methyltransferases (HMTs) are a large group of enzymes that specifically methylate protein lysine and arginine residues, especially in histones, using S-adenosyl-l-methionine (SAM) as the methyl donor. However, in general, HMTs have no widely accepted high-throughput screening (HTS) assay format, and reference inhibitors are not available for many of the enzymes. In this study, we describe the application of a miniaturized, radioisotope-based reaction system: the HotSpotSM platform for methyltransferases. Since this platform employs tritiated SAM as a cofactor, it can be applied to the assay of any HMT. The key advantage of this format is that any substrate can be used, including peptides, proteins, or even nucleosomes, without the need for labeling or any other modifications. Using this platform, we have determined substrate specificities, characterized enzyme kinetics, performed compound profiling for both lysine and arginine methyltransferases, and carried out HTS for a small-library LOPAC against DOT1L. After hit confirmation and profiling, we found that suramin inhibited DOT1L, NSD2, and PRMT4 with IC50 values at a low ?M range. PMID:23557020

Eason, Mia M.; Ferry, Joseph J.; Planck, Jamie L.; Walsh, Colin P.; Smith, Robert F.; Howitz, Konrad T.

2013-01-01

340

Assay development for histone methyltransferases.  

PubMed

Epigenetic modifications play a crucial role in human diseases. Unlike genetic mutations, however, they do not change the underlying DNA sequences. Epigenetic phenomena have gained increased attention in the field of cancer research, with many studies indicating that they are significantly involved in tumor establishment and progression. Histone methyltransferases (HMTs) are a large group of enzymes that specifically methylate protein lysine and arginine residues, especially in histones, using S-adenosyl-L-methionine (SAM) as the methyl donor. However, in general, HMTs have no widely accepted high-throughput screening (HTS) assay format, and reference inhibitors are not available for many of the enzymes. In this study, we describe the application of a miniaturized, radioisotope-based reaction system: the HotSpot(SM) platform for methyltransferases. Since this platform employs tritiated SAM as a cofactor, it can be applied to the assay of any HMT. The key advantage of this format is that any substrate can be used, including peptides, proteins, or even nucleosomes, without the need for labeling or any other modifications. Using this platform, we have determined substrate specificities, characterized enzyme kinetics, performed compound profiling for both lysine and arginine methyltransferases, and carried out HTS for a small-library LOPAC against DOT1L. After hit confirmation and profiling, we found that suramin inhibited DOT1L, NSD2, and PRMT4 with IC?? values at a low ?M range. PMID:23557020

Horiuchi, Kurumi Y; Eason, Mia M; Ferry, Joseph J; Planck, Jamie L; Walsh, Colin P; Smith, Robert F; Howitz, Konrad T; Ma, Haiching

2013-05-01

341

SNO+ Scintillator Purification and Assay  

SciTech Connect

We describe the R and D on the scintillator purification and assay methods and technology for the SNO+ neutrino and double-beta decay experiment. The SNO+ experiment is a replacement of the SNO heavy water with liquid scintillator comprised of 2 g/L PPO in linear alkylbenzene (LAB). During filling the LAB will be transported underground by rail car and purified by multi-stage distillation and steam stripping at a flow rate of 19 LPM. While the detector is operational the scintillator can be recirculated at 150 LPM (full detector volume in 4 days) to provide repurification as necessary by either water extraction (for Ra, K, Bi) or by functional metal scavenger columns (for Pb, Ra, Bi, Ac, Th) followed by steam stripping to remove noble gases and oxygen (Rn, O{sub 2}, Kr, Ar). The metal scavenger columns also provide a method for scintillator assay for ex-situ measurement of the U and Th chain radioactivity. We have developed ''natural'' radioactive spikes of Pb and Ra in LAB and use these for purification testing. Lastly, we present the planned operating modes and purification strategies and the plant specifications and design.

Ford, R.; Vazquez-Jauregui, E. [SNOLAB, Creighton Mine, Lively, P3Y 1N2 (Canada); Chen, M. [Department of Physics, Queen's University, Kingston, K7L 3N6 (Canada); Chkvorets, O.; Hallman, D. [Department of Physics, Laurentian University, Sudbury, P3E 2C6 (Canada)

2011-04-27

342

Comparison of Established and Emerging Biodosimetry Assays  

PubMed Central

Rapid biodosimetry tools are required to assist with triage in the case of a large-scale radiation incident. Here, we aimed to determine the dose-assessment accuracy of the well-established dicentric chromosome assay (DCA) and cytokinesis-block micronucleus assay (CBMN) in comparison to the emerging ?-H2AX foci and gene expression assays for triage mode biodosimetry and radiation injury assessment. Coded blood samples exposed to 10 X-ray doses (240 kVp, 1 Gy/min) of up to 6.4 Gy were sent to participants for dose estimation. Report times were documented for each laboratory and assay. The mean absolute difference (MAD) of estimated doses relative to the true doses was calculated. We also merged doses into binary dose categories of clinical relevance and examined accuracy, sensitivity and specificity of the assays. Dose estimates were reported by the first laboratories within 0.3–0.4 days of receipt of samples for the ?-H2AX and gene expression assays compared to 2.4 and 4 days for the DCA and CBMN assays, respectively. Irrespective of the assay we found a 2.5–4-fold variation of interlaboratory accuracy per assay and lowest MAD values for the DCA assay (0.16 Gy) followed by CBMN (0.34 Gy), gene expression (0.34 Gy) and ?-H2AX (0.45 Gy) foci assay. Binary categories of dose estimates could be discriminated with equal efficiency for all assays, but at doses ?1.5 Gy a 10% decrease in efficiency was observed for the foci assay, which was still comparable to the CBMN assay. In conclusion, the DCA has been confirmed as the gold standard biodosimetry method, but in situations where speed and throughput are more important than ultimate accuracy, the emerging rapid molecular assays have the potential to become useful triage tools. PMID:23862692

Rothkamm, K.; Beinke, C.; Romm, H.; Badie, C.; Balagurunathan, Y.; Barnard, S.; Bernard, N.; Boulay-Greene, H.; Brengues, M.; De Amicis, A.; De Sanctis, S.; Greither, R.; Herodin, F.; Jones, A.; Kabacik, S.; Knie, T.; Kulka, U.; Lista, F.; Martigne, P.; Missel, A.; Moquet, J.; Oestreicher, U.; Peinnequin, A.; Poyot, T.; Roessler, U.; Scherthan, H.; Terbrueggen, B.; Thierens, H.; Valente, M.; Vral, A.; Zenhausern, F.; Meineke, V.; Braselmann, H.; Abend, M.

2014-01-01

343

Comparison of established and emerging biodosimetry assays.  

PubMed

Rapid biodosimetry tools are required to assist with triage in the case of a large-scale radiation incident. Here, we aimed to determine the dose-assessment accuracy of the well-established dicentric chromosome assay (DCA) and cytokinesis-block micronucleus assay (CBMN) in comparison to the emerging ?-H2AX foci and gene expression assays for triage mode biodosimetry and radiation injury assessment. Coded blood samples exposed to 10 X-ray doses (240 kVp, 1 Gy/min) of up to 6.4 Gy were sent to participants for dose estimation. Report times were documented for each laboratory and assay. The mean absolute difference (MAD) of estimated doses relative to the true doses was calculated. We also merged doses into binary dose categories of clinical relevance and examined accuracy, sensitivity and specificity of the assays. Dose estimates were reported by the first laboratories within 0.3-0.4 days of receipt of samples for the ?-H2AX and gene expression assays compared to 2.4 and 4 days for the DCA and CBMN assays, respectively. Irrespective of the assay we found a 2.5-4-fold variation of interlaboratory accuracy per assay and lowest MAD values for the DCA assay (0.16 Gy) followed by CBMN (0.34 Gy), gene expression (0.34 Gy) and ?-H2AX (0.45 Gy) foci assay. Binary categories of dose estimates could be discriminated with equal efficiency for all assays, but at doses ?1.5 Gy a 10% decrease in efficiency was observed for the foci assay, which was still comparable to the CBMN assay. In conclusion, the DCA has been confirmed as the gold standard biodosimetry method, but in situations where speed and throughput are more important than ultimate accuracy, the emerging rapid molecular assays have the potential to become useful triage tools. PMID:23862692

Rothkamm, K; Beinke, C; Romm, H; Badie, C; Balagurunathan, Y; Barnard, S; Bernard, N; Boulay-Greene, H; Brengues, M; De Amicis, A; De Sanctis, S; Greither, R; Herodin, F; Jones, A; Kabacik, S; Knie, T; Kulka, U; Lista, F; Martigne, P; Missel, A; Moquet, J; Oestreicher, U; Peinnequin, A; Poyot, T; Roessler, U; Scherthan, H; Terbrueggen, B; Thierens, H; Valente, M; Vral, A; Zenhausern, F; Meineke, V; Braselmann, H; Abend, M

2013-08-01

344

Formation of condensed 1H-pyrrol-2-ylphosphonates and 1,2-dihydropyridin-2-ylphosphonates via Kabachnik-Fields reaction of acetylenic aldehydes and subsequent 5-exo-dig or 6-endo-dig cyclizations.  

PubMed

Kabachnik-Fields reactions of various carbocyclic or heterocyclic acetylenic aldehydes together with subsequent Lewis acid catalyzed cyclizations have been studied. It was found that 5-exo-dig versus 6-endo-dig cyclization mode strongly depends on the structure of starting materials. Thus, nonaromatic acetylenic ?-anilinomethylphosphonates underwent gold(III)-catalyzed or iodine-mediated 5-exo-dig cyclization to 1H-pyrrol-2-ylphosphonates. In contrast, electron-withdrawing heteroaromatic substrates formed 1,2-dihydropyridin-2-ylphosphonate ring containing materials via an exclusive 6-endo-dig ring-closure process. The dual mode of cyclization is possible only for ?-amino (2-alkynylphenyl)methylphosphonates containing a benzene ring. PMID:24956009

Bukšnaitien?, Rita; Urbanait?, Aurelija; ?ikotien?, Inga

2014-07-18

345

Sperm chromatin structure assay (SCSA®).  

PubMed

The SCSA(®) is the pioneering assay for the detection of damaged sperm DNA and altered proteins in sperm nuclei via flow cytometry of acridine orange (AO) stained sperm. The SCSA(®) is considered to be the most precise and repeatable test providing very unique, dual parameter data (red vs. green fluorescence) on a 1,024 × 1,024 channel scale, not only on DNA fragmentation but also on abnormal sperm characterized by lack of normal exchange of histones to protamines. Raw semen/sperm aliquots or purified sperm can be flash frozen, placed in a box with dry ice and shipped by overnight courier to an experienced SCSA(®) lab. The samples are individually thawed, prepared, and analyzed in ?10 min. Of significance, data on 5,000 individual sperm are recorded on a 1,024 × 1,024 dot plot of green (native DNA) and red (broken DNA) fluorescence. Repeat measurements have virtually identical dot plot patterns demonstrating that the low pH treatment that opens up the DNA strands at the sites of breaks and staining by acridine orange (AO) are highly precise and repeatable (CVs of 1-3%) and the same between fresh and frozen samples. SCSAsoft(®) software transforms the X-Y data to total DNA stainability versus red/red + green fluoresence (DFI) providing a more accurate determination of % DFI as well as the more sensitive value of standard deviation of DFI (SD DFI) as demonstrated by animal fertility and dose-response toxicology studies. The current established clinical threshold is 25% DFI for placing a man into a statistical probability of the following: (a) longer time to natural pregnancy, (b) low odds of IUI pregnancy, (c) more miscarriages, or (d) no pregnancy. Changes in lifestyle as well as medical intervention can lower the %DFI to increase the probability of natural pregnancy. Couples of men with >25% DFI are counseled to try ICSI and when in the >50% range may consider TESE/ICSI. The SCSA(®) simultaneously determines the % of sperm with high DNA stainability (%HDS) related to retained nuclear histones consistent with immature sperm; high HDS values are predictive of pregnancy failure.The SCSA(®) is considered to be the most technician friendly, time- and cost-efficient, precise and repeatable DNA fragmentation assay, with the most data and the only fragmentation assay with an accepted clinical threshold for placing a man at risk for infertility. SCSA(®) data are more predictive of male factor infertility than classical semen analyses. PMID:22992911

Evenson, Donald P

2013-01-01

346

Northwest Australia's Saladin crude assayed  

SciTech Connect

High-quality Saladin crude oil from offshore Western Australia has been assayed. The 48.2[degree] API, 0.02 wt % sulfur crude's characteristics--determined in 1990--are presented here for the first time. The estimated 30--40 million bbl field, south of Barrow Island, is produced from two platforms in 58 ft of water in block TP 3. Production began in late 1989 from three platforms with three wells each and from two wells drilled directionally from Thevenard Island. The paper lists data on the following properties: API gravity, density, sulfur content, pour point, flash point, viscosity, salinity, heat of combustion, ash content, asphaltene content, wax content, and metal content for the whole crude and various fractions.

Rhodes, A.K.

1993-10-18

347

The formation of cyclo-addition adducts in the reaction of an acetylene-terminated material with a bismaleimide: A model compound study for addition-type thermoplastics (ATTs) using metal catalysts  

SciTech Connect

A model compound study using an acetylene-terminated material and a bismaleimide has provided evidence that a diruthenium complex Ru{sub 2}(CO){sub 6}[1,2-({mu}-PPh){sub 2}C{sub 6}H{sub 4}] and a rhodium complex Rh(PPh{sub 3}){sub 3}Cl can catalyze a Diels-Alder type cycloaddition in which acetylene-terminated material acts as a diene and the bismaleimide is a dieneophile. The molten state reaction of N-(3-ethynylphenyl) phthalimide and N-(4-phenoxyphenyl) maleimide with Ru{sub 2}(CO){sub 6}[{mu}-(PhP){sub 2}C{sub 6}H{sub 4}] or Rh(PPh{sub 3}){sub 3}Cl heated to 170{degrees}C led to two major products. The spectral data for the first major product is consistent with a 2:1 Diels-Alder adduct formed from two molecules of the acetylene compound and one molecule of the maleimide. The spectral data for the second major product is consistent with a 2:2 Diels-Alder adduct formed from two molecules of each reactant.

Soucek, M.D., Pater, R.H.; Ritenour, S.L. [NASA Langley Research Center, Hampton, VA (United States)

1993-12-31

348

Optimizing parallel reduction operations  

SciTech Connect

A parallel program consists of sets of concurrent and sequential tasks. Often, a reduction (such as array sum) sequentially combines values produced by a parallel computation. Because reductions occur so frequently in otherwise parallel programs, they are good candidates for optimization. Since reductions may introduce dependencies, most languages separate computation and reduction. The Sisal functional language is unique in that reduction is a natural consequence of loop expressions; the parallelism is implicit in the language. Unfortunately, the original language supports only seven reduction operations. To generalize these expressions, the Sisal 90 definition adds user-defined reductions at the language level. Applicable optimizations depend upon the mathematical properties of the reduction. Compilation and execution speed, synchronization overhead, memory use and maximum size influence the final implementation. This paper (1) Defines reduction syntax and compares with traditional concurrent methods; (2) Defines classes of reduction operations; (3) Develops analysis of classes for optimized concurrency; (4) Incorporates reductions into Sisal 1.2 and Sisal 90; (5) Evaluates performance and size of the implementations.

Denton, S.M.

1995-06-01

349

Withdrawal assay monitoring at US Enrichment Facilities  

SciTech Connect

The United States Enrichment Corporation (USEC) controls two uranium enrichment facilities that produce enriched uranium for both military and commercial use. The process requires both feed and withdrawal operations. The withdrawal process requires both product (enriched uranium) withdrawal stations and tails (depleted uranium) withdrawal stations. A previous prototype system, ``X-330 Tails Cylinder Assay Monitor,`` was developed as a demonstration for the tails withdrawal station at the Portsmouth Gaseous Diffusion Plant (PORTS). The prototype system was done in response to potential problems with the original method for determining the hourly weighted assay averages that are used to calculate the final weighted assay of the cylinder. In the original method the {sup 235}U assay of uranium hexaflouride withdrawn from PORTS cascade into tails cylinders is determined every 5 min by measurements from an in-line assay mass spectrometer. An average value for a 1-h period is then calculated by area control room personnel and assigned to the accumulated weight in the cylinder for the period. A potential problem with this method is that cylinder weight is not automatically recorded as often as the assay. The assay and withdrawal rate can both vary during the given period. This variation results in inaccuracies in the hourly weighted assays that are used to calculate the final weighted assay of the cylinder. Laboratory analysis is considered to be the most accurate method for determining the final cylinder assay; however, the cost and safety considerations of redundant cylinder handling limit the number of cylinders sampled to less than 10%.

Smith, D.E.

1996-01-01

350

A High Sensitivity Micro Format Chemiluminescence Enzyme Inhibition Assay for Determination of Hg(II)  

PubMed Central

A highly sensitive and specific enzyme inhibition assay based on alcohol oxidase (AlOx) and horseradish peroxidase (HRP) for determination of mercury Hg(II) in water samples has been presented. This article describes the optimization and miniaturization of an enzymatic assay using a chemiluminescence reaction. The analytical performance and detection limit for determination of Hg(II) was optimized in 96 well plates and further extended to 384 well plates with a 10-fold reduction in assay volume. Inhibition of the enzyme activity by dissolved Hg(II) was found to be linear in the range 5–500 pg·mL?1 with 3% CV in inter-batch assay. Due to miniaturization of assay in 384 well plates, Hg(II) was measurable as low as 1 pg·mL?1 within 15 min. About 10-fold more specificity of the developed assay for Hg(II) analysis was confirmed by challenging with interfering divalent metal ions such as cadmium Cd(II) and lead Pb(II). Using the proposed assay we could successfully demonstrate that in a composite mixture of Hg(II), Cd(II) and Pb(II), inhibition by each metal ion is significantly enhanced in the presence of the others. Applicability of the proposed assay for the determination of the Hg(II) in spiked drinking and sea water resulted in recoveries ranging from 100–110.52%. PMID:22163555

Deshpande, Kanchanmala; Mishra, Rupesh K.; Bhand, Sunil

2010-01-01

351

Preparation of carbon nano-microcoils by Ni3S2-catalyzed pyrolysis of acetylene and its vapor-liquid-solid-solid growth mechanism.  

PubMed

Carbon microcoils are generally prepared by catalytic chemical vapor deposition of acetylene, using Ni as the catalyst and thiophene as the promoter. In this work, Ni3S2 was chosen as the catalyst on purpose to avoid the introducing of noxious and unpleasant thiophene during the reaction process. The products obtained in the temperature range of 1013-1033 K were pure, regular and had perfect morphology. Using transmission electron microscope, Raman spectrometer and X-ray diffractometer, the microstructure of the as-prepared carbon microcoils were characterized, furthmore, energy dispersive spectrum and selected area electron diffraction analysis reveal that the growth of carbon microcoils is always accomplished with the transformation of the catalyst from Ni3S2 to Ni3C. We first observed that the fiber constructing the carbon microcoil is composed of three sub-fibers, which strongly supports the proposition of vapor-liquid-solid-solid growth mechanism. In this mechanism, every catalyst particle is in the state of the coexistence of solid and liquid. Carbon atoms firstly permeate into the liquid portion from gas, then disperse into the solid portion, and finally deposit from the catalyst grain to form the carbon microcoil. PMID:17256329

Li, Wenjun; Guo, Yanchuan; Chen, Lijuan

2006-12-01

352

A novel acetylenic tricyclic bis-(cyano enone) potently induces phase 2 cytoprotective pathways and blocks liver carcinogenesis induced by aflatoxin  

PubMed Central

A novel acetylenic tricyclic bis-(cyano enone), TBE-31, is a lead compound in a series of tricyclic compounds with enone functionalities in rings A and C. Nanomolar concentrations of this potent multifunctional molecule suppress the induction of the inflammatory protein, iNOS; activate phase 2 cytoprotective enzymes in vitro and in vivo; block cell proliferation; and induce differentiation and apoptosis of leukemia cells. Oral administration of TBE-31 also significantly reduces formation of aflatoxin-DNA adducts and decreases size and number of aflatoxin-induced pre-neoplastic hepatic lesions in rats by more than 90%. Because of the two cyano enones in rings A and C, TBE-31 may directly interact with dithiothreitol and protein targets such as Keap1 that contain reactive cysteine residues. The above findings suggest that TBE-31 should also be tested for chemoprevention and chemotherapy in relevant models of cancer and against other chronic, degenerative diseases in which inflammation and oxidative stress contribute to disease pathogenesis. PMID:18701497

Liby, Karen; Yore, Mark M.; Roebuck, Bill D.; Baumgartner, Karen J.; Honda, Tadashi; Sundararajan, Chitra; Yoshizawa, Hidenori; Gribble, Gordon W.; Williams, Charlotte R.; Risingsong, Renee; Royce, Darlene B.; Dinkova-Kostova, Albena T.; Stephenson, Katherine K.; Egner, Patricia A.; Yates, Melinda S.; Groopman, John D.; Kensler, Thomas W.; Sporn, Michael B.

2008-01-01

353

Improvements of anti-corrosion and mechanical properties of NiTi orthopedic materials by acetylene, nitrogen and oxygen plasma immersion ion implantation  

NASA Astrophysics Data System (ADS)

Nickel-titanium shape memory alloys (NiTi) are useful materials in orthopedics and orthodontics due to their unique super-elasticity and shape memory effects. However, the problem associated with the release of harmful Ni ions to human tissues and fluids has been raising safety concern. Hence, it is necessary to produce a surface barrier to impede the out-diffusion of Ni ions from the materials. We have conducted acetylene, nitrogen and oxygen plasma immersion ion implantation (PIII) into NiTi alloys in an attempt to improve the surface properties. All the implanted and annealed samples surfaces exhibit outstanding corrosion and Ni out-diffusion resistance. Besides, the implanted layers are mechanically stronger than the substrate underneath. XPS analyses disclose that the layer formed by C 2H 2 PIII is composed of mainly TiC x with increasing Ti to C concentration ratios towards the bulk. The nitrogen PIII layer is observed to be TiN, whereas the oxygen PIII layer is composed of oxides of Ti 4+, Ti 3+ and Ti 2+.

Poon, Ray W. Y.; Ho, Joan P. Y.; Liu, Xuanyong; Chung, C. Y.; Chu, Paul K.; Yeung, Kelvin W. K.; Lu, William W.; Cheung, Kenneth M. C.

2005-08-01

354

Transient absorption studies of the photochromic behavior of 3H-naphtho[2,1-b]pyrans linked to thiophene oligomers via an acetylenic junction.  

PubMed

The photophysical and photochemical properties of four 3,3-diphenyl-3H-naphtho[2,1- b]pyrans substituted, via an acetylenic junction, to (thiophene) n oligomers (n = 0-3 units) were investigated by transient absorption in the femtosecond to microsecond time domain and by stationary absorption and fluorescence. The decay of the initially produced excited S1(pi pi*) state is found to occur via three competing processes: fluorescence, intersystem crossing, and a ring-opening reaction leading to a colored merocyanine product, with relative yields varying drastically with n. Whereas ultrafast (sub-picosecond) reaction dynamics and high product quantum yield are observed for n = 0 and 1, the reaction is considerably slowed down on going to the n = 2 (105 ps) compound and does not occur for n = 3. A reaction scheme that accounts for this behavior is proposed and the effect of the oligothiophenic chain length on the photoinduced properties is discussed. It is suggested that increasing the chain length from 1 to 3 thiophene units stabilizes the S1(pi pi*) state by pi conjugation and induces an excited-state potential barrier along the reaction pathway. PMID:18457379

Moine, Baptiste; Réhault, Julien; Aloïse, Stéphane; Micheau, Jean-Claude; Moustrou, Corinne; Samat, André; Poizat, Olivier; Buntinx, Guy

2008-05-29

355

Revisiting Mulliken's concepts about Rydberg states and Rydberg-valence interactions from large-scale Ab initio calculations on the acetylene molecule.  

PubMed

A quantitative characterization of the Rydberg and valence singlet electronic states of acetylene lying in the 5-10.7 eV region is performed by using large-scale ab initio calculations. A special attention is paid on the comparison between the present calculations and Mulliken's concepts for Rydberg states, based on single-electron and single-configuration description. Most of the properties of the Rydberg states have been qualitatively understood via this comparison, mainly shown by the shape and size of the outer Rydberg molecular orbital. More quantitatively, Rydberg-valence mixing has been evaluated in several excited energy regions, as for instance, the interaction between the ' (1pig)2 1Ag doubly excited valence state and the manifold of electronic components of the np series, or the interaction between the 1pig 1Bu valence state and the 3dpig 1Sigma(u)+ Rydberg state. The rapid predissociation of the lowest 3s(sigma) 1Piu Rydberg state has been interpreted as a case of Rydbergization, earlier predicted by Mulliken. PMID:19639976

Laruelle, Fabrice; Boyé-Péronne, Séverine; Gauyacq, Dolores; Liévin, Jacques

2009-11-26

356

Assay development status report for total cyanide  

SciTech Connect

A validated cyanide assay that is applicable to a variety of tank waste matrices is necessary to resolve certain waste tank safety issues and for purposes of overall waste characterization. The target for this effort is an assay with an applicable range of greater than 1,000 ppM (0.10 wt%) total cyanide and a confidence level greater than 80%. Figure 1 illustrates the operating regime of the proposed cyanide assay method. The Assay Development Status Report for Total Cyanide will summarize the past experience with cyanide analyses on-tank waste matrices and will rate the status of the analytical methods used to assay total cyanide (CN{sup {minus}} ion) in the tank waste matrices as acceptable or unacceptable. This paper will also briefly describe the current efforts for improving analytical resolution of the assays and the attempts at speciation.

Simpson, B.C. [Westinghouse Hanford Co., Richland, WA (United States); Jones, T.E.; Pool, K.H. [Pacific Northwest Lab., Richland, WA (United States)

1993-02-01

357

An experimental and theoretical investigation of the competition between chemical reaction and relaxation for the reactions of 1CH2 with acetylene and ethene: implications for the chemistry of the giant planets.  

PubMed

The temperature dependence of the branching ratios for H atom production from the reactions of the first excited state of methylene (a1A1 1CH2) with acetylene and ethene have been measured at approximately 1 Torr total pressure and temperatures of 195, 250 and 298 K by monitoring the production of H atoms using laser induced fluorescence, comparing the signal to that observed from a calibration reaction. For the reaction with acetylene the yield of H increases from 0.28 (195 K) to 0.53 (250 K) to 0.88 at 298 K. The H atom yield from the reaction of 1CH2 with ethene shows similar behaviour, the yields being 0.35 (195 K), 0.51 (250 K) and 0.71 (298 K). The co-products, propargyl (C3H3) and allyl (C3H5) are formed from the dissociation of chemically activated C3H4 and C3H6 intermediates respectively, and are important species in the formation of higher hydrocarbons, including benzene, in the atmospheres of the outer planets and Titan. H atom production is in competition with electronic relaxation to form ground state methylene (X3B1, 3CH2) and collisional stabilization to form C3H4 and C3H6. Master equation calculations have been carried out to demonstrate that for the reaction of 1CH2 with acetylene, collisional stabilization is insignificant under experimental conditions and hence the balance of reaction is due to electronic relaxation. Non-adiabatic transition state theory has been applied to the reaction of 1CH2 with acetylene. The calculations show reasonable agreement with experiment, generally being within the combined errors, and reproduce the negative temperature dependence for electronic relaxation. The implications of the temperature dependence of the absolute rate coefficients for 1CH2 reactions with inert gases, hydrogen, acetylene and ethene and of the branching ratios between chemical reaction and electronic relaxation are discussed. PMID:21302547

Gannon, Kelly L; Blitz, Mark A; Liang, Chi-Hsiu; Pilling, Michael J; Seakins, Paul W; Glowacki, David R; Harvey, Jeremy N

2010-01-01

358

Automated amperometric plutonium assay system  

SciTech Connect

The amperometric titration for plutonium assay has been used in the nuclear industry for over twenty years and has been in routine use at the Hanford Engineering Development Laboratory since 1976 for the analysis of plutonium oxide and mixed oxide fuel material for the Fast Flux Test Facility. It has proven itself to be an accurate and reliable method. The method may be used as a direct end point titration or an excess of titrant may be added and a back titration performed to aid in determination of the end point. Due to the slowness of the PuVI-FeII reaction it is difficult to recognize when the end point is being approached and is very time consuming if the current is allowed to decay to the residual value after each titrant addition. For this reason the back titration in which the rapid FeII-CrVI reaction occurs is used by most laboratories. The back titration is performed by the addition of excess ferrous solution followed by two measured aliquots of standard dichromate with measurement of cell current after each addition.

Burt, M.C.

1985-01-01

359

Passive neutron techniques for the nondestructive assay of nuclear material  

E-print Network

Three drums containing potentially contaminated lead bricks were assayed with the Segmented Gamma Scan Neutron Assay System (SGSNAS) at Pacific Northwest National Laboratory's (PNNL) Nondestructive Assay Center. The assay system reported...

Mapili, Gabriel

2012-06-07

360

Optimization and validation of the TZM-bl assay for standardized assessments of neutralizing antibodies against HIV-1.  

PubMed

The TZM-bl assay measures antibody-mediated neutralization of HIV-1 as a function of reductions in HIV-1 Tat-regulated firefly luciferase (Luc) reporter gene expression after a single round of infection with Env-pseudotyped viruses. This assay has become the main endpoint neutralization assay used for the assessment of pre-clinical and clinical trial samples by a growing number of laboratories worldwide. Here we present the results of the formal optimization and validation of the TZM-bl assay, performed in compliance with Good Clinical Laboratory Practice (GCLP) guidelines. The assay was evaluated for specificity, accuracy, precision, limits of detection and quantitation, linearity, range and robustness. The validated manual TZM-bl assay was also adapted, optimized and qualified to an automated 384-well format. PMID:24291345

Sarzotti-Kelsoe, Marcella; Bailer, Robert T; Turk, Ellen; Lin, Chen-li; Bilska, Miroslawa; Greene, Kelli M; Gao, Hongmei; Todd, Christopher A; Ozaki, Daniel A; Seaman, Michael S; Mascola, John R; Montefiori, David C

2014-07-01

361

Application of methylene blue dye reduction test (MBRT) to determine growth and death rates of microorganisms  

Microsoft Academic Search

An efficacy of a compound for antimicrobial characteristics is typically evaluated through experiments to obtain the minimum inhibitory concentration (MIC). Similarly, a minimum activating concentration (MAC) can be obtained for a compound necessary for growth. We report a protocol for the determination of MIC and MAC for antibiotic and exhibition assays, respectively using methylene blue reduction test. The assay has

Subir Kumar Nandy; K. V. Venkatesh

2010-01-01

362

Cytotoxicity of ambient air particles to rat lung macrophages: Comparison of cellular and functional assays  

Microsoft Academic Search

The biological reactivity of ambient air particles was studied in five in vitro lung macrophage assays, involving the release of cytoplasmic and lysosomal enzymes, cellular ATP, neutral red uptake, tetrazolium reduction, and chemiluminescence. Macrophages from rat lungs (2 × 105 cells; 1 cm2 attachment surface; 1 ml culture medium) were exposed for 18 hr to 0–100 ?g of (1) the

D. Nadeau; R. Vincent; P. Kumarathasan; J. Brook; A. Dufresne

1996-01-01

363

The Ferric Reducing Ability of Plasma (FRAP) as a Measure of “Antioxidant Power”: The FRAP Assay  

Microsoft Academic Search

A simple, automated test measuring the ferric reducing ability of plasma, the FRAP assay, is presented as a novel method for assessing “antioxidant power.” Ferric to ferrous ion reduction at low pH causes a colored ferrous-tripyridyltriazine complex to form. FRAP values are obtained by comparing the absorbance change at 593 nm in test reaction mixtures with those containing ferrous ions

Iris F. F. Benzie; J. J. Strain

1996-01-01

364

MULTIPLEXING SCHEMES FOR GENERIC SNP GENOTYPING ASSAYS  

E-print Network

MULTIPLEXING SCHEMES FOR GENERIC SNP GENOTYPING ASSAYS R. SHARAN International Computer Science- mally multiplexing SNP genotyping using generic assays. We devise a graph theoretic formulation. The development of e cient SNP detection, genotyping and measurement techniques is an active research area

Shamir, Ron

365

Strategic petroleum reserve crude oil assays  

SciTech Connect

This booklet provides background information on the purchase of crude oils for the Strategic Petroleum Reserve (SPR), procedures used to assess quality of the stored petroleum, and methods used in generating assays of the various streams which may be sold. Current assays of the eight SPR crude oil streams are included.

Not Available

1991-11-01

366

Oxidation/Reduction  

NSDL National Science Digital Library

Created by team members from Kapi'olani Community College and Leeward Community College, this site provides educators and students with a colorful background lesson in oxidation and reduction. The site is divided into concepts, exercises, and everyday examples of oxidation and reduction. Each exercise allows users to check all answers.

367

Academic Employee Reduction Procedure.  

ERIC Educational Resources Information Center

Criteria and procedures for dismissing full-time faculty at Grays Harbor College are listed. These procedures are to be followed for faculty dismissal because of program termination or reduction, decreases in enrollment, changes in educational policy or substantial evidence of a serious shortage of funds. All phases of the reduction process are…

Grays Harbor Coll., Aberdeen, WA.

368

Microbial reductive dehalogenation.  

PubMed Central

A wide variety of compounds can be biodegraded via reductive removal of halogen substituents. This process can degrade toxic pollutants, some of which are not known to be biodegraded by any other means. Reductive dehalogenation of aromatic compounds has been found primarily in undefined, syntrophic anaerobic communities. We discuss ecological and physiological principles which appear to be important in these communities and evaluate how widely applicable these principles are. Anaerobic communities that catalyze reductive dehalogenation appear to differ in many respects. A large number of pure cultures which catalyze reductive dehalogenation of aliphatic compounds are known, in contrast to only a few organisms which catalyze reductive dehalogenation of aromatic compounds. Desulfomonile tiedjei DCB-1 is an anaerobe which dehalogenates aromatic compounds and is physiologically and morphologically unusual in a number of respects, including the ability to exploit reductive dehalogenation for energy metabolism. When possible, we use D. tiedjei as a model to understand dehalogenating organisms in the above-mentioned undefined systems. Aerobes use reductive dehalogenation for substrates which are resistant to known mechanisms of oxidative attack. Reductive dehalogenation, especially of aliphatic compounds, has recently been found in cell-free systems. These systems give us an insight into how and why microorganisms catalyze this activity. In some cases transition metal complexes serve as catalysts, whereas in other cases, particularly with aromatic substrates, the catalysts appear to be enzymes. Images PMID:1406492

Mohn, W W; Tiedje, J M

1992-01-01

369

Fluorimetric DNA assay of cell number.  

PubMed

This fluorimetric assay has utility for the accurate assessment of cultured epidermal cell numbers by virtue of their deoxyribonucleic acid content, which is the most significant correlate available. The improvement in fluorochromes in the recent past makes PicoGreen the dye of choice for this, with its greatly increased sensitivity (+/- 50 cells) over the Hoechst and DAPI stains and which remains linear over several orders of magnitude with a single dye concentration. The assay involves minimal liquid handling to achieve cell disruption by sodium dodecyl sulfate in saline sodium citrate buffer, and PicoGreen staining is rapidly assayed by a multiwell plate reading fluorimeter, which can be automated for robotic high throughput use. Highly fibrous cells like epidermal keratinocytes can be disrupted using 8 M urea and assayed after dilution. The assay is also compatible with tritiated thymidine incorporation. PMID:15502190

Otto, William R

2005-01-01

370

Paper disk assay for glycosaminoglycan sulfotransferases  

SciTech Connect

A method is described for the assay of sulfotransferases, which transfer sulfate from 3'-phosphoadenosine-5'-phosphosulfate (PAPS) to glycosaminoglycan acceptors. Following the sulfation reactions, the (/sup 35/S)sulfate-labeled products are precipitated and then separated from a sulfate donor ((/sup 35/S)PAPS) and its degradation products by a paper disk method, and then the radioactivity remaining on the paper disk is subsequently determined by liquid scintillation counting. The rapidity and simplicity of the method are advantageous for multiple assays and have allowed us to establish assay conditions for serum sulfotransferases which introduce sulfate at position 6 of the internal N-acetylgalactosamine units of chondroitin, position 2 (amino group) of the glucosamine units of heparan sulfate and sugar units of keratan sulfate, respectively. The assay method will be applicable with modification to the assay of other glycosaminoglycan sulfotransferases and glycoprotein sulfotransferases.

Sugahara, K.; Ishii, T.; Yamashina, I.

1987-11-01

371

Bayesian supervised dimensionality reduction.  

PubMed

Dimensionality reduction is commonly used as a preprocessing step before training a supervised learner. However, coupled training of dimensionality reduction and supervised learning steps may improve the prediction performance. In this paper, we introduce a simple and novel Bayesian supervised dimensionality reduction method that combines linear dimensionality reduction and linear supervised learning in a principled way. We present both Gibbs sampling and variational approximation approaches to learn the proposed probabilistic model for multiclass classification. We also extend our formulation toward model selection using automatic relevance determination in order to find the intrinsic dimensionality. Classification experiments on three benchmark data sets show that the new model significantly outperforms seven baseline linear dimensionality reduction algorithms on very low dimensions in terms of generalization performance on test data. The proposed model also obtains the best results on an image recognition task in terms of classification and retrieval performances. PMID:23757527

Gönen, Mehmet

2013-12-01

372

Growth Hormone Determination in Children Using an Immunofunctional Assay in Comparison to Conventional Assays  

Microsoft Academic Search

Conventional assays for determination of growth hormone (GH) in serum measure immunoreactive molecules of a blood sample. The immunofunctional assay (IFA), on the other hand, is able to determine biologically active molecules. In our study, we evaluated GH determination in children with IFA to compare these data with clinical reliable data of conventional assay systems, since there is only insufficient

Simone Stark; Rolf Peter Willig

2007-01-01

373

ATP-independent substrate reduction by nitrogenase P-cluster variant  

PubMed Central

The P-cluster of nitrogenase is largely known for its function to mediate electron transfer to the active cofactor site during catalysis. Here, we show that a P-cluster variant (designated P*-cluster), which consists of paired [Fe4S4]-like clusters, can catalyze ATP-independent substrate reduction in the presence of a strong reductant, europium(II) diethylenetriaminepentaacetate [Eu(II)-DTPA]. The observation of a decrease of activity in the rank ?nifH, ?nifB?nifZ, and ?nifB MoFe protein, which corresponds to a decrease of the amount of P*-clusters in these cofactor-deficient proteins, firmly establishes P*-cluster as a catalytically active metal center in Eu(II)-DTPA–driven reactions. More excitingly, the fact that P*-cluster is not only capable of catalyzing the two-electron reduction of proton, acetylene, ethylene, and hydrazine, but also capable of reducing cyanide, carbon monoxide, and carbon dioxide to alkanes and alkenes, points to a possibility of developing biomimetic catalysts for hydrocarbon production under ambient conditions. PMID:22509042

Lee, Chi Chung; Hu, Yilin; Ribbe, Markus W.

2012-01-01

374

Feasibility studies for assaying alpha-fetoprotein using antibody-activated magnetic nanoparticles  

PubMed Central

Some previous reports have already shown the characterizations of immunomagnetic reduction (IMR). The assay technology involves the utilities of biofunctionalized magnetic nanoparticles to label target biomolecules. However, the detection threshold and interference tests for IMR have not been investigated in detail. In this study, alpha-fetoprotein (AFP) was used as a target biomolecule. The signals for AFP solutions of various concentrations, or with interfering materials, were detected via IMR. These samples were also used for characterizing the detection threshold and interference with enzyme-linked immunosorbent assay (ELISA). The results of assaying AFP level with IMR and ELISA were compared. The detection threshold for assaying AFP with IMR was found to be 3 ng/mL, which is 15 times lower than that of ELISA, and definitely suppresses false negative. For the interfering materials noted commonly in serum such as hemoglobin, bilirubin, triglyceride, and vascular endothelial growth factor, there was no detectable interfering effect when assaying AFP with IMR. Several serum samples from normal people and liver-tumor-bearing patients were used for the detections of AFP concentration via IMR. These results reveal the feasibilities of assaying AFP in blood using IMR, as well as achieving high-sensitive and high-specific assay for AFP. PMID:22619536

Huang, Kai-Wen; Yang, Shieh-Yueh; Hong, Yu-Wei; Chieh, Jen-Jie; Yang, Che-Chuan; Horng, Herng-Er; Wu, Chau-Chung; Hong, Chin-Yih; Yang, Hong-Chang

2012-01-01

375

Particle-induced artifacts in the MTT and LDH viability assays  

PubMed Central

In vitro testing is a common first step in assessing combustion generated and engineered nanoparticle related health hazards. Commercially available viability assays are frequently used to compare the toxicity of different particle types and to generate dose response data. Nanoparticles, well known for having large surface areas and chemically active surfaces, may interfere with viability assays, producing a false assessment of toxicity and making it difficult to compare toxicity data. The objective of this study is to measure the extent of particle interference in two common viability assays, the MTT reduction and the lactate dehydrogenase (LDH) release assays. Diesel particles, activated carbon, flame soot, oxidized flame soot, and titanium dioxide particles are assessed for interactions with the MTT and LDH assay under cell-free conditions. Diesel particles, at concentrations as low as 0.05 ?g/ml, reduce MTT. Other particle types reduce MTT only at a concentration of 50 ?g/ml and higher. The activated carbon, soot, and oxidized soot particles bind LDH to varying extents, reducing the concentration measured in the LDH assay. The interfering effects of the particles explain in part the different toxicities measured in human bronchial epithelial cells (16HBE14o). We conclude that valid particle toxicity assessments can only be assured after first performing controls to verify that the particles under investigation do not interfere with a specific assay at the expected concentrations. PMID:22799765

Holder, Amara L.; Goth-Goldstein, Regine; Lucas, Donald; Koshland, Catherine P.

2012-01-01

376

Rapid detection of oleander poisoning by Dimension Vista digoxin assay (Flex Reagent Cartridge).  

PubMed

Oleander poisoning can be detected by digoxin immunoassays and for last two decades the fluorescence polarization immunoassay (FPIA) has been used for rapid detection of oleander poisoning in clinical laboratories. Recently, Abbott Laboratories (Abbott Park, IL) discontinued this assay. Therefore, we explored the possibility of using another digoxin assay (Dimension Vista Flex Reagent Cartridge, Tina Quant, EMIT 2000 and old FPIA assay for comparison) for rapid detection of oleander poisoning. When aliquots of drug-free serum pools were supplemented with pure oleandrin or oleander extract, we observed the highest apparent digoxin values using Dimension Vista digoxin assay (Flex Reagent Cartridge). We also observed significant apparent digoxin values in vivo in sera of mice both 1 and 2 ?hr after feeding with oleander extract. When a serum pool prepared from patients taking digoxin was further supplemented with various amounts of oleander extract, the highest falsely elevated digoxin values were observed with Dimension Vista digoxin assay. Monitoring free digoxin using Dimension Vista digoxin assay (Flex Reagent Cartridge) did not eliminate this interference. Digibind neutralized digoxin-like factors of oleander extract and such effect can be monitored by observing significant reduction in apparent free digoxin levels in the presence of Digibind as measured in the protein-free ultrafiltrate using Dimension Vista digoxin assay (Flex Reagent Cartridge). PMID:21438002

Dasgupta, Amitava; Klein, Kimberley; Risin, Semyon A; Actor, Jeffrey K

2011-01-01

377

Molecular assays in breast cancer pathology.  

PubMed

Recent advances in understanding the molecular pathology of breast cancer offer significant potential to identify patients who may benefit from adjuvant therapies. To date, few of these advances are utilised in a routine setting. We review molecular assays that are currently in use or are in the advanced stages of development, which may be used as predictive or prognostic biomarkers in breast cancer.The only widely used breast cancer molecular assay is in situ hybridisation (ISH) for human epidermal growth factor receptor 2 (HER2) gene amplification and we highlight key issues with the interpretation of this assay, with particular attention to the difficulties of the equivocal category. New molecular assays such as ISH for the topoisomerase II alpha (TOP2A) gene and for the aberrations in the copy number of the centromeric region of chromosome 17 are readily performed in a standard histopathology laboratory, but to date there are insufficient data to support their routine use. We also review the current data on two commercially available multigene expression assays, Oncotype DX and MammaPrint and discuss their potential use. Overall, while new molecular assays have significant potential to improve patient selection for therapy, well-performed histopathology with reliable interpretation of standard hormone and HER2 assays provides the most important predictive and prognostic information in early breast cancer. PMID:21233672

O'Toole, Sandra A; Selinger, Christina I; Millar, Ewan K A; Lum, Trina; Beith, Jane M

2011-02-01

378

Human somatic mutation assays as biomarkers of carcinogenesis  

SciTech Connect

This paper describes four assays that detect somatic gene mutations in humans: the hypoxanthine-guanine phosphoribosyl transferase assay, the glycophorin A assay, the HLA-A assay, and the sickle cell hemoglobin assay. Somatic gene mutations can be considered a biomarker of carcinogenesis, and assays for somatic mutation may assist epidemiologists in studies that attempt to identify factors associated with increased risks of cancer. Practical aspects of the use of these assays are discussed.

Compton, P.J.E.; Smith, M.T. (Univ. of California, Berkeley (United States)); Hooper, K. (California Dept. of Health Services, Berkeley (United States))

1991-08-01

379

Kit-On-A-Lid-Assays for accessible self-contained cell assays.  

PubMed

Microscale methods for cell-based assays typically rely on macroscopic reagent handling and fluidic loading protocols that are technically challenging and do not scale with the number of assays favorably. Here, we demonstrate a microfluidic platform technology called "Kit-On-A-Lid-Assay" (KOALA), that enables the creation of self-contained microfluidic cell-based assays, integrating all the steps required to perform cell-based assays. The KOALA platform allows the pre-packaging of reagents, cryopreservation of cell suspensions, thawing of cell suspensions, culture of cells, and operation of whole cell-based assays. The operation of the KOALA platform is user-friendly and consists of bringing together a lid containing the microchannels, and a base containing the pre-packaged reagents, thereby causing fluidic exchange in all the channels simultaneously. We demonstrate that the KOALA cell-based assays can be simply operated from start to finish without any external laboratory equipment. PMID:23229806

Berthier, Erwin; Guckenberger, David J; Cavnar, Peter; Huttenlocher, Anna; Keller, Nancy P; Beebe, David J

2013-02-01

380

Summarizing FLARE assay images in colon carcinogenesis  

E-print Network

by observing populations that have a sh-based diet. Both Eskimos and Japanese shermen have a high intake of sh and low rates of colon cancer (Bartsch et al. 1999). While this is only an observation, and not conclusive evidence, experiments per- formed... oil, were found not to promote cancer, and possibly even have a cancer preventing (chemopreventive) e ect (Bartsch et al. 1999, Diggle 2002, Hong et al. 2002, Sugimura 2000). 1.6 FLARE Assay The FLARE assay, also known as the FPG-comet assay, is able...

Leyk Williams, Malgorzata

2006-04-12

381

Reduction redux of adinkras  

NASA Astrophysics Data System (ADS)

We show performing general "0-brane reduction" along an arbitrary fixed direction in space-time and applied to the starting point of minimal, off-shell 4D, 𝒩 = 1 irreducible supermultiplets, yields adinkras whose adjacency matrices are among some of the special cases proposed by Kuznetsova, Rojas and Toppan. However, these more general reductions also can lead to "Garden Algebra" structures beyond those described in their work. It is also shown that for light-like directions, reduction to the 0-brane breaks the equality in the number of fermions and bosons for dynamical theories. This implies that light-like reductions should be done instead to the space of 1-branes or equivalently to the worldsheet.

Gates, S. James; Randall, Stephen; Stiffler, Kory

2014-04-01

382

Reduction of the Fracture  

Microsoft Academic Search

A meticulous clinical and radiologic examination (analysis of the fracture type), an anatomic reduction, a properly executed\\u000a internal fixation and a correct rehabilitation (mobilization as early as possible with weight-bearing) are the most important\\u000a parts for any head-preserving treatment of neck fractures. We are in full agreement with authors who insist on the cardinal\\u000a role of reduction (Parker and Pryor,

J. Manninger; T. Salacz; K. Fekete

383

A photochemical study of the kinetics of the reactions of NH2 with phosphine, ethylene, and acetylene using flash photolysis-laser induced fluorescence. Ph.D. Thesis Catholic Univ. of America; [ammonia in the atmosphere of Jupiter  

NASA Technical Reports Server (NTRS)

The photochemistry of the reactions of NH2 was investigated in an attempt to explain the existence of an abundance of ammonia in the Jovian atmosphere. The production of ammonia reservoirs from the coupling of ammonia with other atmospheric constituents was considered. The rate constants for the reactions of NH2 radicals with phosphine, acetylene, and ethylene were measured. Flash photolysis was used for the production of NH2 radicals and laser induced fluorescence was employed for radical detection. It was determined that the rates of the reactions were too slow to be significant as a source of ammonia reservoirs in the Jovian atmosphere.

Bosco, S. R.

1982-01-01

384

Comparative response of Pisum sativum nodulated with indigenous soil Rhizobium populations and/or co-inoculated with a Rhizobium leguminosarum strain. I. Acetylene-reducing, dihydrogen- and carbon dioxide-evolving activities.  

PubMed

No significant differences in the acetylene-reducing activity and evolution of H2 and CO2 from nodulated roots of Pisum sativum inoculated with soil Rhizobium populations from two soils with different acidities (Ruzyn? soil 7.6; Lukavec soil 4.9) were observed. Rhizobium population from Lukavec soil formed nodules, exhibiting a higher H2 evolution. Co-inoculation with the Hup+ strain 128C30 (7 x 10(7) cells per seedling) eliminated, to some extent, the effect of soil populations on physiological activity. PMID:1841862

Skrdleta, V; N?mcová, M; Lisá, L; Novák, K; Kovárová, D

1991-01-01

385

Effects of ?-glucan polysaccharide revealed by the dominant lethal assay and micronucleus assays, and reproductive performance of male mice exposed to cyclophosphamide  

PubMed Central

?-glucan is a well-known polysaccharide for its chemopreventive effect. This study aimed to evaluate the chemopreventive ability of ?-glucan in somatic and germ cells through the dominant lethal and micronucleus assays, and its influence on the reproductive performance of male mice exposed to cyclophosphamide. The results indicate that ?-glucan is capable of preventing changes in DNA in both germ cells and somatic ones. Changes in germ cells were evaluated by the dominant lethal assay and showed damage reduction percentages of 46.46% and 43.79% for the doses of 100 and 150 mg/kg. For the somatic changes, evaluated by micronucleus assay in peripheral blood cells in the first week of treatment, damage reduction percentages from 80.63–116.32% were found. In the fifth and sixth weeks, the percentage ranged from 10.20–52.54% and ?0.95–62.35%, respectively. Besides the chemopreventive efficiency it appears that the ?-glucan, when combined with cyclophosphamide, is able to improve the reproductive performance of males verified by the significant reduction in rates of post-implantation losses and reabsorption in the mating of nulliparous females with males treated with cyclophosphamide. PMID:24688298

Oliveira, Rodrigo Juliano; Pesarini, Joao Renato; Sparca Salles, Maria Jose; Nakamura Kanno, Tatiane Yumi; dos Santos Lourenco, Ana Carolina; da Silva Leite, Vessia; da Silva, Ariane Fernanda; Matiazi, Hevenilton Jose; Ribeiro, Lucia Regina; Mantovani, Mario Sergio

2014-01-01

386

Effects of ?-glucan polysaccharide revealed by the dominant lethal assay and micronucleus assays, and reproductive performance of male mice exposed to cyclophosphamide.  

PubMed

?-glucan is a well-known polysaccharide for its chemopreventive effect. This study aimed to evaluate the chemopreventive ability of ?-glucan in somatic and germ cells through the dominant lethal and micronucleus assays, and its influence on the reproductive performance of male mice exposed to cyclophosphamide. The results indicate that ?-glucan is capable of preventing changes in DNA in both germ cells and somatic ones. Changes in germ cells were evaluated by the dominant lethal assay and showed damage reduction percentages of 46.46% and 43.79% for the doses of 100 and 150 mg/kg. For the somatic changes, evaluated by micronucleus assay in peripheral blood cells in the first week of treatment, damage reduction percentages from 80.63-116.32% were found. In the fifth and sixth weeks, the percentage ranged from 10.20-52.54% and -0.95-62.35%, respectively. Besides the chemopreventive efficiency it appears that the ?-glucan, when combined with cyclophosphamide, is able to improve the reproductive performance of males verified by the significant reduction in rates of post-implantation losses and reabsorption in the mating of nulliparous females with males treated with cyclophosphamide. PMID:24688298

Oliveira, Rodrigo Juliano; Pesarini, João Renato; Sparça Salles, Maria José; Nakamura Kanno, Tatiane Yumi; Dos Santos Lourenço, Ana Carolina; da Silva Leite, Véssia; da Silva, Ariane Fernanda; Matiazi, Hevenilton José; Ribeiro, Lúcia Regina; Mantovani, Mário Sérgio

2014-03-01

387

Developmental toxicity assays using the Drosophila model.  

PubMed

The fruit fly (Drosophila melanogaster) has long been a premier model for developmental biologists and geneticists. In toxicology studies, Drosophila has only recently gained broader recognition as a tool to elaborate molecular genetic mechanisms of toxic substances. In this article, two practical applications of Drosophila for developmental toxicity assays are described. The first assay takes advantage of newly developed methods to render the fly embryo accessible to small molecules, toxicants, and drugs. The second assay engages straightforward exposures to developing larvae and easy-to-score outcomes of adult development. With the extensive collections of flies that are publicly available and the ease of creating transgenic flies, these two assays have a unique power for identifying and characterizing molecular mechanisms and cellular pathways specific to the mode of action of a number of toxicants and drugs. Curr. Protoc. Toxicol. 59:1.12.1-1.12.20. © 2014 by John Wiley & Sons, Inc. PMID:24789363

Rand, Matthew D; Montgomery, Sara L; Prince, Lisa; Vorojeikina, Daria

2014-01-01

388

CONTROL ASSAY DEVELOPMENT: METHODOLOGY AND LABORATORY VERIFICATION  

EPA Science Inventory

The report describes Control Assay Development (CAD), a data acquisition program designed to evaluate the potential applicability of various treatment processes for the control of solid, liquid, and gaseous emissions from coal conversion plants. The CAD program described could be...

389

LIMITATIONS OF THE FLUORESCENT PROBE VIABILITY ASSAY  

EPA Science Inventory

Cell viability commonly is determined flow cytometrically by the carboxyfluorescein diacetate (CFDA)/propidium iodide (PI) assay. FDA is taken up by the viable cell and converted via cytoplasmic esterase-catalyzed hydrolysis to carboxyfluorescein (CF). F fluorescence intensity is...

390

BIOMARKER ASSAYS IN NIPPLE APIRATE FLUID  

EPA Science Inventory

ABSTRACT The noninvasive technique of nipple aspiration as a potential source of biomarkers of breast cancer risk was evaluated. The feasibility of performing mutagenesis assays, amplifying DNA and performing protein electrophoresis on nipple aspirate fluid was explored. ...

391

Assay for Arf GTP-binding Proteins  

Cancer.gov

The National Cancer Institute's Laboratory of Cellular and Molecular Biology is seeking statements of capability or interest from parties interested in collaborative research to further develop, evaluate, or commercialize an antibody-based proteomics assay.

392

Variables Affecting Two Electron Transport System Assays  

PubMed Central

Several methodological variables were critical in two commonly used electron transport activity assays. The dehydrogenase assay based on triphenyl formazan production exhibited a nonlinear relationship between formazan production (dehydrogenase activity) and sediment dilution, and linear formazan production occurred for 1 h in sediment slurries. Activity decreased with increased time of sediment storage at 4°C. Extraction efficiencies of formazan from sediment varied with alcohol type; methanol was unsatisfactory. Phosphate buffer (0.06 M) produced higher activity than did either U.S. Environmental Protection Agency reconstituted hard water or Tris buffer sediment diluents. Intracellular formazan crystals were dissolved within minutes when in contact with immersion oil. Greater crystal production (respiration) detected by a tetrazolium salt assay occurred at increased substrate concentrations. Test diluents containing macrophyte exudates produced greater activity than did phosphate buffer, U.S. Environmental Protection Agency water, or ultrapure water diluents. Both assays showed decreases in sediment or bacterial activity through time. PMID:16347067

Burton, G. Allen; Lanza, Guy R.

1986-01-01

393

21 CFR 864.7250 - Erythropoietin assay.  

... FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES HEMATOLOGY AND PATHOLOGY DEVICES Hematology Kits and Packages § 864.7250 Erythropoietin assay. (a) Identification. A...

2014-04-01

394

21 CFR 864.7490 - Sulfhemoglobin assay.  

Code of Federal Regulations, 2011 CFR

... FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES HEMATOLOGY AND PATHOLOGY DEVICES Hematology Kits and Packages § 864.7490 Sulfhemoglobin assay. (a) Identification. A...

2011-04-01

395

21 CFR 864.7525 - Heparin assay.  

Code of Federal Regulations, 2012 CFR

... FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES HEMATOLOGY AND PATHOLOGY DEVICES Hematology Kits and Packages § 864.7525 Heparin assay. (a) Identification. A heparin...

2012-04-01

396

21 CFR 864.7490 - Sulfhemoglobin assay.  

Code of Federal Regulations, 2012 CFR

... FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES HEMATOLOGY AND PATHOLOGY DEVICES Hematology Kits and Packages § 864.7490 Sulfhemoglobin assay. (a) Identification. A...

2012-04-01

397

21 CFR 864.7525 - Heparin assay.  

... FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES HEMATOLOGY AND PATHOLOGY DEVICES Hematology Kits and Packages § 864.7525 Heparin assay. (a) Identification. A heparin...

2014-04-01

398

21 CFR 864.7525 - Heparin assay.  

Code of Federal Regulations, 2011 CFR

... FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES HEMATOLOGY AND PATHOLOGY DEVICES Hematology Kits and Packages § 864.7525 Heparin assay. (a) Identification. A heparin...

2011-04-01

399

21 CFR 864.7250 - Erythropoietin assay.  

Code of Federal Regulations, 2010 CFR

... FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES HEMATOLOGY AND PATHOLOGY DEVICES Hematology Kits and Packages § 864.7250 Erythropoietin assay. (a) Identification. A...

2010-04-01

400

21 CFR 864.7525 - Heparin assay.  

Code of Federal Regulations, 2010 CFR

... FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES HEMATOLOGY AND PATHOLOGY DEVICES Hematology Kits and Packages § 864.7525 Heparin assay. (a) Identification. A heparin...

2010-04-01

401

21 CFR 864.7250 - Erythropoietin assay.  

Code of Federal Regulations, 2013 CFR

... FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES HEMATOLOGY AND PATHOLOGY DEVICES Hematology Kits and Packages § 864.7250 Erythropoietin assay. (a) Identification. A...

2013-04-01

402

21 CFR 864.7425 - Carboxyhemoglobin assay.  

Code of Federal Regulations, 2013 CFR

... FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES HEMATOLOGY AND PATHOLOGY DEVICES Hematology Kits and Packages § 864.7425 Carboxyhemoglobin assay. (a) Identification. A...

2013-04-01

403

21 CFR 864.7425 - Carboxyhemoglobin assay.  

... FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES HEMATOLOGY AND PATHOLOGY DEVICES Hematology Kits and Packages § 864.7425 Carboxyhemoglobin assay. (a) Identification. A...

2014-04-01

404

21 CFR 864.7525 - Heparin assay.  

Code of Federal Regulations, 2013 CFR

... FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES HEMATOLOGY AND PATHOLOGY DEVICES Hematology Kits and Packages § 864.7525 Heparin assay. (a) Identification. A heparin...

2013-04-01

405

21 CFR 864.7425 - Carboxyhemoglobin assay.  

Code of Federal Regulations, 2012 CFR

... FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES HEMATOLOGY AND PATHOLOGY DEVICES Hematology Kits and Packages § 864.7425 Carboxyhemoglobin assay. (a) Identification. A...

2012-04-01

406

21 CFR 864.7425 - Carboxyhemoglobin assay.  

Code of Federal Regulations, 2011 CFR

... FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES HEMATOLOGY AND PATHOLOGY DEVICES Hematology Kits and Packages § 864.7425 Carboxyhemoglobin assay. (a) Identification. A...

2011-04-01

407

Radiometric assays for glycerol, glucose, and glycogen  

Microsoft Academic Search

We have developed radiometric assays for small quantities of glycerol, glucose and glycogen, based on a technique described by Thorner and Paulus for the measurement of glycerokinase activity. In the glycerol assay, glycerol is phosphorylated with (32P)ATP and glycerokinase, residual (32P)ATP is hydrolyzed by heating in acid, and free (32P)phosphate is removed by precipitation with ammonium molybdate and triethylamine. Standard

D. C. Bradley; H. R. Kaslow

1989-01-01

408

Substrate capacity considerations in developing kinase assays.  

PubMed

In developing a screening assay for a serine/threonine kinase, we evaluated various formats of an in-plate enzyme-linked immunosorbent assay (ELISA), as well as solution-phase kinase assays using either ELISA or AlphaScreen detection. Substrate was available both as a biotinylated 15-residue peptide and as a 25-residue peptide containing the same sequence expressed as a glutathione S-transferase fusion protein. When increasing concentrations of either of these substrates were coated directly onto ELISA plates, the rates of the kinase reactions progressively increased. In contrast, when the biotin-peptide was captured onto NeutrAvidin-coated plates, the finite peptide binding capacity of the plates limited the amount of substrate that could be incorporated into the assay system and thereby limited the rate of the reaction at a given kinase concentration. Solution-phase kinase reactions can tolerate high substrate concentrations; however, analysis of kinase reaction samples containing biotin-peptide concentrations higher than the binding capacity of NeutrAvidin-coated plates resulted in an inability to detect differences between reactions run at different substrate concentrations. For AlphaScreen detection following solution-phase kinase reactions, limitations in the binding capacity of the donor and acceptor beads caused loss of signal for substrate concentrations above the maximum binding capacity. Overall, the solution-phase assays required significantly more kinase than the in-plate assays (1-4 microg/ml versus <100 ng/ml, respectively). These studies demonstrate that the amount of substrate that can be incorporated into an assay system substantially affects the rate of the kinase reaction and therefore the amount of kinase required for the assay. PMID:15165509

DeForge, Laura E; Cochran, Andrea G; Yeh, Sherry H; Robinson, Brian S; Billeci, Karen L; Wong, Wai Lee T

2004-04-01

409

Simultaneous measurement of multiple ear proteins with multiplex ELISA assays.  

PubMed

A recent advancement in enzyme-linked immunosorbent assay (ELISA) technology is the multiplex antibody array that measures multiple proteins simultaneously within a single sample. This allows reduction in sample volume, time, labor, and material costs, while increasing sensitivity over single ELISA. Current multiplex platforms include planar-based systems using microplates or slides, or bead-based suspension assay with microspheres. To determine the applicability of this technology for ear research, we used 3 different multiplex ELISA-based immunoassay arrays from 4 different companies to measure cytokine levels in mouse middle and inner ear tissue lysate extracts 24 h following transtympanic Haemophilus influenzae inoculation. Middle and inner ear tissue lysates were analyzed using testing services from Quansys Biosciences, Aushon Biosystems SearchLight (both microplate-based), MILLIPLEX MAP Sample (bead-based), and a RayBiotech, Inc (slide-based) kit. Samples were assayed in duplicate or triplicate. Results were compared to determine their relative sensitivity and reliability for measures of cytokines related to inflammation. The cytokine pg/ml amounts varied among the multiplex assays, so a comparison also was made of the mean fold increase in cytokines from untreated controls. Several cytokines and chemokines were elevated, the extent dependent upon the assay sensitivity. Those most significantly elevated were IL-1?, IL-1?, IL-6, TNF?, VEGF, and IL-8/MIP-2. The results of the multiplex systems were compared with single ELISA kits (IL-1?, IL-6) to assess sensitivity over the traditional method. Overall, the Quansys Biosciences and SearchLight arrays showed the greatest sensitivity, both employing the same multiplex methodology of a spotted array within a microplate well with chemiluminescent detection. They also were more sensitive than the traditional single ELISA performed with commercial kits and matched gene expression changes determined by quantitative RT-PCR. The Quansys array showed a limit of detection for ear IL-6 down to 2-4 pg/ml, indicating it is sufficiently sensitive to detect ear proteins present in low concentrations. Thus, the multiplex ELISA procedures appear suitable and reliable for the study of hearing related proteins, providing accurate, quantitative, reproducible results with considerable improvement in sensitivity and economy. PMID:21144888

Trune, Dennis R; Larrain, Barbara E; Hausman, Frances A; Kempton, J Beth; MacArthur, Carol J

2011-05-01

410

On the assay of brachytherapy sources.  

PubMed

In many of brachytherapy procedures, a large amount of radioactive sources are used to deliver desired doses to the target volume. It is both the federal regulation recommendation (U.S. Nuclear Regulatory Commission, 10 CFR 35.432) and recommendations of the American Association of Physicists in Medicine (AAPM) [Kutcher et al., Med. Phys. 21, 581-618 (1994); Nath et al., Med. Phys. 24, 1557-1598 (1997)] that users independently verify the sources' strength. Though the reports of AAPM Task Group 40 [Kutcher et al., Med. Phys. 21, 581-618 (1994)] and 56 [Nath et al., Med. Phys. 24, 1557-1598 (1997)] have made specific recommendations on the assay of brachytherapy sources, the relevant statistical significance of the recommendations remain unanswered. In this study, statistical theories were used and a method was presented to quantify the assay process of brachytherapy sources and to evaluate the recommendations. The results showed that the quality of a source assay process was dependent on the measured source strength deviation and number of assayed sources. Its dependence on the total number of sources becomes statistically insignificant if the total number is large enough. It was concluded that the assay process can be determined by the obtained assay information, instead of a preset percentage of total sources. It was further found that the use of manufacturer's stated strength value may possibly lead to bigger uncertainty in source strength accuracy, unless the manufacturer's stated strength is the measured mean value of all the ordered sources. PMID:17654900

Yue, Ning J; Haffty, Bruce G; Yue, Jinfeng

2007-06-01

411

Radioimmune assay of human platelet prostaglandin synthetase  

SciTech Connect

Normal platelet function depends, in part, on platelet PG synthesis. PG synthetase (cyclo-oxygenase) catalyzes the first step in PG synthesis, the formation of PGH/sub 2/ from arachidonic acid. Inhibition of the enzyme by ASA results in an abnormality in the platelet release reaction. Patients with pparent congenital abnormalities in the enzyme have been described, and the effects have been referred to as ''aspirin-like'' defects of the platelet function. These patients lack platelet PG synthetase activity, but the actual content of PG synthetase protein in these individuals' platelets is unknown. Therefore an RIA for human platelet PG synthetase would provide new information, useful in assessing the aspirin-like defects of platelet function. An RIA for human platelet PG synthetase is described. The assay utilizes a rabbit antibody directed against the enzyme and (/sup 125/I)-labelled sheep PG synthetase as antigen. The human platelet enzyme is assayed by its ability to inhibit precipitation of the (/sup 125/I)antigen. The assay is sensitive to 1 ng of enzyme. By the immune assay, human platelets contain approximately 1200 ng of PG synethetase protein per 1.5 mg of platelet protein (approximately 10/sup 9/ platelets). This content corresponds to 10,000 enzyme molecules per platelet. The assay provides a rapid and convenient assay for the human platelet enzyme, and it can be applied to the assessment of patients with apparent platelet PG synthetase (cyclo-oxygenase) deficiency.

Roth, G.J.; Machuga, E.T.

1982-02-01

412

Protein immobilization techniques for microfluidic assays  

PubMed Central

Microfluidic systems have shown unequivocal performance improvements over conventional bench-top assays across a range of performance metrics. For example, specific advances have been made in reagent consumption, throughput, integration of multiple assay steps, assay automation, and multiplexing capability. For heterogeneous systems, controlled immobilization of reactants is essential for reliable, sensitive detection of analytes. In most cases, protein immobilization densities are maximized, while native activity and conformation are maintained. Immobilization methods and chemistries vary significantly depending on immobilization surface, protein properties, and specific assay goals. In this review, we present trade-offs considerations for common immobilization surface materials. We overview immobilization methods and chemistries, and discuss studies exemplar of key approaches—here with a specific emphasis on immunoassays and enzymatic reactors. Recent “smart immobilization” methods including the use of light, electrochemical, thermal, and chemical stimuli to attach and detach proteins on demand with precise spatial control are highlighted. Spatially encoded protein immobilization using DNA hybridization for multiplexed assays and reversible protein immobilization surfaces for repeatable assay are introduced as immobilization methods. We also describe multifunctional surface coatings that can perform tasks that were, until recently, relegated to multiple functional coatings. We consider the microfluidics literature from 1997 to present and close with a perspective on future approaches to protein immobilization. PMID:24003344

Kim, Dohyun; Herr, Amy E.

2013-01-01

413

A modified chromogenic assay for the measurement of very low levels of factor VIII activity (FVIII:C).  

PubMed

A precise and sensitive chromogenic assay for the measurement of very low levels of factor VIII (FVIII) in plasma has been developed. The assay is based on modifications of a commercially available chromogenic assay. The modifications include reduction of sample final dilution factor and prolongation of the development period. The modified assay allows accurate and precise measurement of FVIII in the range of 0.001-0.02 IU mL(-1). The detection limit is 0.0005 IU mL(-1) and the quantitation limit is 0.0015 IU mL(-1). This assay can be used in research and to study the clinical efficacy of low circulating levels of FVIII in haemophilia A patients. PMID:16643210

Yatuv, R; Dayan, I; Baru, M

2006-05-01

414

Selection of non-destructive assay methods: Neutron counting or calorimetric assay?  

SciTech Connect

The transition of DOE facilities from production to D&D has lead to more measurements of product, waste, scrap, and other less attractive materials. Some of these materials are difficult to analyze by either neutron counting or calorimetric assay. To determine the most efficacious analysis method, variety of materials, impure salts and hydrofluorination residues have been assayed by both calorimetric assay and neutron counting. New data will be presented together with a review of published data. The precision and accuracy of these measurements are compared to chemistry values and are reported. The contribution of the gamma ray isotopic determination measurement to the overall error of the calorimetric assay or neutron assay is examined and discussed. Other factors affecting selection of the most appropriate non-destructive assay method are listed and considered.

Cremers, T.L.; Wachter, J.R.

1994-08-01

415

A double layer plaque assay using spread plate technique for enumeration of bacteriophage MS2.  

PubMed

Bacteriophage MS2 is used widely as a model organism to estimate pathogenic virus survival in various environments, and is usually quantified by plaque assay. Although current plaque assays work well in enumeration of MS2 in environmental samples, quantification of MS2 calls for better visibility and higher consistency. In an attempt to improve the visibility and consistency of the current plaque assay, spread plate technique was introduced, instead of the pour plate technique used commonly in existing methods. Other parameters that influence the outcome of the plaque assay were also compared. Using spread plate technique resulted in an increase of plaque size by approximately 50% and contributed to a better visibility. Addition of supplements (glucose, CaCl2 and thiamine); reduction of agar thickness and hardness, also contributed to enhanced plaque visibility and increased plaque count. Among all the conditions tested, a supplemented thin bottom agar (10ml 1% agar) and a supplemented thin top agar (10ml 0.45% agar) with spread plate technique gave the maximum countable plaques with a minimum standard deviation. When compared to other methods, it produced significantly higher plaque count and lower variation. The optimized plaque assay significantly improved visibility and consistency of the existing plaque assay methods and could be used in quantification of MS2. PMID:24211298

Cormier, Jiemin; Janes, Marlene

2014-02-01

416

A High-throughput Screening Assay for Determining Cellular Levels of Total Tau Protein  

PubMed Central

The microtubule-associated protein (MAP) tau has been implicated in the pathology of numerous neurodegenerative diseases. In the past decade, the hyperphosphorylated and aggregated states of tau protein have been important targets in the drug discovery field for the potential treatment of Alzheimer’s disease. Although several compounds have been reported to reduce the hyperphosphorylated state of tau or impact the stabilization of tau, their therapeutic activities are still to be validated. Recently, reduction of total cellular tau protein has emerged as an alternate intervention point for drug development and a potential treatment of tauopathies. We have developed and optimized a homogenous assay, using the AlphaLISA and HTRF assay technologies, for the quantification of total cellular tau protein levels in the SH-SY5Y neuroblastoma cell line. The signal-to-basal ratios were 375 and 5.3, and the Z’ factors were 0.67 and 0.60 for the AlphaLISA and HTRF tau assays, respectively. The clear advantages of this homogeneous tau assay over conventional total tau assays, such as ELISA and Western blot, are the elimination of plate wash steps and miniaturization of the assay into 1536-well plate format for the ultra–high-throughput screening of large compound libraries. PMID:23905996

Dehdashti, Seameen J.; Zheng, Wei; Gever, Joel R.; Wilhelm, Robert; Nguyen, Dac-Trung; Sittampalam, Gurusingham; McKew, John C.; Austin, Christopher P.; Prusiner, Stanley B.

2014-01-01

417

Rovibrational energy transfer in the 4nuCH manifold of acetylene, viewed by IR-UV double resonance spectroscopy. 5. Detailed kinetic model.  

PubMed

Time-resolved infrared-ultraviolet double resonance (IR-UV DR) spectroscopy provides a distinctive way to examine collision-induced state-to-state energy transfer between rotational J-levels in vibrational manifolds of small polyatomic molecules, such as acetylene (C2H2) in its electronic ground state X. We consider the 4nuCH rovibrational manifold of C2H2 at approximately 12,700 cm(-1), where the principal source of IR-brightness is the (nu1+3nu3) or (1 0 3 0 0)0 Sigma+u vibrational combination level. In this highly congested manifold, anharmonic, l-resonance, and Coriolis couplings affect the J-levels of interest, implicating them in a complicated variety of intramolecular dynamics. Previous papers of this series have reported several seemingly anomalous J-resolved phenomena induced by collisions in C2H2 gas at room temperature with pressures and IR-UV pump-probe delay intervals corresponding to remarkably high Lennard-Jones collisional efficiencies P: odd-DeltaJ rotational energy transfer (10(-3)

Payne, Mark A; Milce, Angela P; Frost, Michael J; Orr, Brian J

2007-12-13

418

Synthesis and antiproliferative assay of norcantharidin derivatives in cancer cells.  

PubMed

Diels-Alder reaction between furan and maleic anhydride resulted in 5,6-dehydro norcantharidin, then norcantharidin was obtained by reduction. The substituted-carboxylic acid was condensed with N-aminothiourea in presence of phosphorus oxychloride, yielding 2-amino-1,3,4-thiadiazole derivatives. Novel norcantharidin derivatives were synthesized with acylation, then intramolecular condensation using norcantharidin (or 5,6-dehydro norcantharidin) and 2-amino- 1,3,4-thiadiazole derivatives. All the target compounds were confirmed by IR, (1)HNMR, ESI-MS and were reported for the first time. Norcantharidin derivatives antiproliferative assay was tested by MTT method against A549 and PC-3 cell lines. The results showed that all the norcantharidin derivatives displayed moderate inhibitory activities. PMID:23909288

Tu, Guo Gang; Zhan, Jian Feng; Lv, Qiao Li; Wang, Jia Qi; Kuang, Bin Hai; Li, Shao Hua

2014-06-01

419

SWEPP assay system version 2.0 software requirements specification  

SciTech Connect

The INEL Stored Waste Examination Pilot Plant (SWEPP) operations staff use nondestructive analysis methods to characterize the radiological contents of contact-handled radioactive waste containers. Containers of waste from Rocky Flats Environmental Technology Site and other DOE sites are currently stored at SWEPP. Before these containers can be shipped to WIPP, SWEPP must verify compliance with storage, shipping, and disposal requirements. One part of the SWEPP program measures neutron emissions from the containers and estimates the mass of Pu and other transuranic isotopes present. The code NEUT2 was originally used to perform data acquisition and reduction; the SWEPP Assay System (SAS) code replaced NEUT2 in early 1994. This document specifies the requirements for the SAS software as installed at INEL and was written to comply with RWMC (INEL Radioactive Waste Management Complex) quality requirements.

Matthews, S.D.; East, L.V.; Marwil, E.S.; Ferguson, J.J.

1996-06-01

420

REDUCTIVE GROUP SCHEMES Brian Conrad  

E-print Network

REDUCTIVE GROUP SCHEMES Brian Conrad Abstract. -- We develop the relative theory of reductive group´ematique de France #12;2 BRIAN CONRAD Although the structure theory of connected reductive groups is developed

Conrad, Brian

421

21 CFR 864.7100 - Red blood cell enzyme assay.  

Code of Federal Regulations, 2013 CFR

... 2013-04-01 false Red blood cell enzyme assay. 864.7100 Section 864.7100...Packages § 864.7100 Red blood cell enzyme assay. (a) Identification. Red blood cell enzyme assay is a device used to measure...

2013-04-01

422

21 CFR 864.7040 - Adenosine triphosphate release assay.  

Code of Federal Regulations, 2011 CFR

...2011-04-01 2011-04-01 false Adenosine triphosphate release assay. 864...Hematology Kits and Packages § 864.7040 Adenosine triphosphate release assay. (a) Identification. An adenosine triphosphate release assay is a...

2011-04-01

423

Optimization of a colorimetric assay for glycosylated human serum albumin  

SciTech Connect

The thiobarbituric acid (TBA) assay has been used for several years to quantitate the amount of glucose which has been non-enzymatically linked to hemoglobin and other proteins. The ketoamine-protein adduct is converted to 5-hydroxymethylfurfural (HMF) by mild hydrolysis with oxalic acid. Reaction of HMF with TBA yields a colored product which has an absorbance maximum at 443 nm. Several modifications of the original procedure has been published, but none permit the unambiguous quantitation of glycosylated human serum albumin (glc-HSA). Problems relate to reagent preparation and stability, the time and temperature of hydrolysis, the choice of standards, and background color corrections. The authors have found that maximum color yield occurs after hydrolysis in an autoclave for 2 h. This increases the sensitivity 3-fold and cuts the assay time in half relative to hydrolysis for 4.5 h at 100/sup 0/C. A NaBH/sub 4/ reduction of a parallel protein sample must be performed to correct for variable background color associated with different sample sources and amounts. HMF can be used as a standard, however, corrections must be made for HMF degradation. Fructose is a better standard, but HMF formation from fructose is faster than formation from glc-HSA. This may result in an underestimate of percent glycosylation. The best standard appears to be glc-HSA prepared with (/sup 3/H)glucose. It appears that with proper controls and standards the TBA assay can be used to determine actual rather than relative percent glycosylation.

Bohney, J.P.; Feldhoff, R.C.

1986-05-01

424

Partial LLL Reduction  

E-print Network

The Lenstra-Lenstra-Lovasz (LLL) reduction has wide applications in digital communications. It can greatly improve the speed of the sphere decoding (SD) algorithms for solving an integer least squares (ILS) problem and the performance of the Babai integer point, a suboptimal solution to the ILS problem. Recently Ling and Howgrave-Graham proposed the so-called effective LLL (ELLL) reduction. It has less computational complexity than LLL, while it has the same effect on the performance of the Babai integer point as LLL. In this paper we propose a partial LLL (PLLL) reduction. PLLL avoids the numerical stability problem with ELLL, which may result in very poor performance of the Babai integer point. Furthermore, numerical simulations indicated that it is faster than ELLL. We also show that in theory PLLL and ELLL have the same effect on the search speed of a typical SD algorithm as LLL.

Xie, Xiaohu; Borno, Mazen Al

2012-01-01

425

Controlling variation in the comet assay  

PubMed Central

Variability of the comet assay is a serious issue, whether it occurs from experiment to experiment in the same laboratory, or between different laboratories analysing identical samples. Do we have to live with high variability, just because the comet assay is a biological assay rather than analytical chemistry? Numerous attempts have been made to limit variability by standardizing the assay protocol, and the critical steps in the assay have been identified; agarose concentration, duration of alkaline incubation, and electrophoresis conditions (time, temperature, and voltage gradient) are particularly important. Even when these are controlled, variation seems to be inevitable. It is helpful to include in experiments reference standards, i.e., cells with a known amount of specific damage to the DNA. They can be aliquots frozen from a single large batch of cells, either untreated (negative controls) or treated with, for example, H2O2 or X-rays to induce strand breaks (positive control for the basic assay), or photosensitiser plus light to oxidize guanine (positive control for Fpg- or OGG1-sensitive sites). Reference standards are especially valuable when performing a series of experiments over a long period—for example, analysing samples of white blood cells from a large human biomonitoring trial—to check that the assay is performing consistently, and to identify anomalous results necessitating a repeat experiment. The reference values of tail intensity can also be used to iron out small variations occurring from day to day. We present examples of the use of reference standards in human trials, both within one laboratory and between different laboratories, and describe procedures that can be used to control variation. PMID:25368630

Collins, Andrew R.; El Yamani, Naouale; Lorenzo, Yolanda; Shaposhnikov, Sergey; Brunborg, Gunnar; Azqueta, Amaya

2014-01-01

426

Cell Culture Assay for Human Noroviruses [response  

SciTech Connect

We appreciate the comments provided by Leung et al., in response to our recently published article “In Vitro Cell Culture Infectivity Assay for Human Noroviruses” by Straub et al. (1). The specific aim of our project was to develop an in vitro cell culture infectivity assay for human noroviruses (hNoV) to enhance risk assessments when they are detected in water supplies. Reverse transcription (RT) qualitative or quantitative PCR are the primary assays for waterborne NoV monitoring. However, these assays cannot distinguish between infectious vs. non-infectious virions. When hNoV is detected in water supplies, information provided by our infectivity assay will significantly improve risk assessment models and protect human health, regardless of whether we are propagating NoV. Indeed, in vitro cell culture infectivity assays for the waterborne pathogen Cryptosporidium parvum that supplement approved fluorescent microscopy assays, do not result in amplification of the environmentally resistant hard-walled oocysts (2). However, identification of life cycle stages in cell culture provides evidence of infectious oocysts in a water supply. Nonetheless, Leung et al.’s assertion regarding the suitability of our method for the in vitro propagation of high titers of NoV is valid for the medical research community. In this case, well-characterized challenge pools of virus would be useful for developing and testing diagnostics, therapeutics, and vaccines. As further validation of our published findings, we have now optimized RT quantitative PCR to assess the level of viral production in cell culture, where we are indeed finding significant increases in viral titer. The magnitude and time course of these increases is dependent on both virus strain and multiplicity of infection. We are currently preparing a manuscript that will discuss these findings in greater detail, and the implications this may have for creating viral challenge pools

Straub, Tim M.; Honer Zu Bentrup, Kerstin; Orosz Coghlan, Patricia; Dohnalkova, Alice; Mayer, Brooke K.; Bartholomew, Rachel A.; Valdez, Catherine O.; Bruckner-Lea, Cindy J.; Gerba, Charles P.; Abbaszadegan, Morteza A.; Nickerson, Cheryl A.

2007-07-01

427

Systematic analysis of bicistronic reporter assay data  

PubMed Central

Bicistronic reporter assay systems have become a mainstay of molecular biology. While the assays themselves encompass a broad range of diverse and unrelated experimental protocols, the numerical data garnered from these experiments often have similar statistical properties. In general, a primary dataset measures the paired expression of two internally controlled reporter genes. The expression ratio of these two genes is then normalized to an external control reporter. The end result is a ‘ratio of ratios’ that is inherently sensitive to propagation of the error contributed by each of the respective numerical components. The statistical analysis of this data therefore requires careful handling in order to control for the propagation of error and its potentially misleading effects. A careful survey of the literature found no consistent method for the statistical analysis of data generated from these important and informative assay systems. In this report, we present a detailed statistical framework for the systematic analysis of data obtained from bicistronic reporter assay systems. Specifically, a dual luciferase reporter assay was employed to measure the efficiency of four programmed ?1 frameshift signals. These frameshift signals originate from the L-A virus, the SARS-associated Coronavirus and computationally identified frameshift signals from two Saccharomyces cerevisiae genes. Furthermore, these statistical methods were applied to prove that the effects of anisomycin on programmed ?1 frameshifting are statistically significant. A set of Microsoft Excel spreadsheets, which can be used as templates for data generated by dual reporter assay systems, and an online tutorial are available at our website (http://dinmanlab.umd.edu/statistics). These spreadsheets could be easily adapted to any bicistronic reporter assay system. PMID:15561995

Jacobs, Jonathan L.; Dinman, Jonathan D.

2004-01-01

428

Measurement of dabigatran in standardly used clinical assays, whole blood viscoelastic coagulation, and thrombin generation assays.  

PubMed

Dabigatran, a direct thrombin inhibitor, is increasingly used clinically as one of the new oral anticoagulants. This review summarizes the assays available to measure its activity and includes the relative sensitivity of the different assays for this agent. In addition to plasma-based clotting tests, assays commonly used in surgical/emergency settings, such as activated clotting time and thromboelastometry/thromboelastography, are reviewed. In addition, the thrombin generation assay is discussed as an important method to determine the potential risk of thrombosis or bleeding and its relevance to the measurement of direct thrombin inhibitors. PMID:25168938

van Ryn, Joanne; Grottke, Oliver; Spronk, Henri

2014-09-01

429

REDUCTIONS WITHOUT REGRET: SUMMARY  

SciTech Connect

This paper briefly summarizes the series in which we consider the possibilities for losing, or compromising, key capabilities of the U.S. nuclear force in the face of modernization and reductions. The first of the three papers takes an historical perspective, considering capabilities that were eliminated in past force reductions. The second paper is our attempt to define the needed capabilities looking forward in the context of the current framework for force modernization and the current picture of the evolving challenges of deterrence and assurance. The third paper then provides an example for each of our undesirable outcomes: the creation of roach motels, box canyons, and wrong turns.

Swegle, J.; Tincher, D.

2013-09-16

430

Time, Chance, and Reduction  

NASA Astrophysics Data System (ADS)

List of contributors; 1. Introduction Gerhard Ernst and Andreas Hütteman; Part I. The Arrows of Time: 2. Does a low-entropy constraint prevent us from influencing the past? Mathias Frisch; 3. The part hypothesis meets gravity Craig Callender; 4. Quantum gravity and the arrow of time Claus Kiefer; Part II. Probability and Chance: 5. The natural-range conception of probability Jacob Rosenthal; 6. Probability in Boltzmannian statistical mechanics Roman Frigg; 7. Humean mechanics versus a metaphysics of powers Michael Esfeld; Part III. Reduction: 8. The crystallisation of Clausius's phenomenological thermodynamics C. Ulises Moulines; 9. Reduction and renormalization Robert W. Batterman; 10. Irreversibility in stochastic dynamics Jos Uffink; Index.

Ernst, Gerhard; Hüttemann, Andreas

2010-01-01

431

Aircraft engine emission reduction  

SciTech Connect

The paper discusses new concepts for combustion chambers to help create low pollution power plants and reduce engine emissions. Researchers see that internal combustion engines provide complete combustion when they are close to stoichiometry while gas turbines experience problems when they reach this ratio. It would be best to modify the equivalence ratio of the primary combustion zone which is responsible for the high level of NOx emissions. Reduction of pollutant emissions from aircraft engines are focused on three areas: (1) use of less polluting fuels; (2) modification of the combustion process; and (3) reduction of specific fuel consumption and consequently consumption overall.

Birch, S.

1994-01-01

432

Turbulent drag reduction research  

NASA Technical Reports Server (NTRS)

Research in the area of turbulent drag reduction for attached flows is summarized. The most promising passive techniques utilize non-planar geometry. Of particular interest is the suitability of these devices for retrofit of existing vehicles. Five methods for reducing turbulent skin friction drag on bodies/fuselages are discussed. They are: (1) large-eddy breakup devices; (2) riblets; (3) slot injection optimization; (4) control of Emmons spot generation; and (5) relaminarization through massive suction. Except for the Emmons spot work these methods all indicate the possibility of sizable net reductions in skin friction for laboratory conditions.

Bushnell, D. M.; Anders, J. B.; Walsh, M. J.; Mcinville, R. V.

1984-01-01

433

Forests and Poverty Reduction  

NSDL National Science Digital Library

"Close to 1.6 billion people - more than 25% of the world's population - rely on forest resources for their livelihoods and most of them (1.2 billion) use trees on farms to generate food and cash." Despite these figures, the Food and Agriculture Organization of the United Nations explains that data on these vital forest resources is "sketchy or not available." On the left hand side of the page visitors will find several interesting links including the FAO website which addresses the topic of forests and poverty reduction, the FAO forestry site which includes recent events and news topics, "Publications", information on "Workshops", and "Forestry and Poverty Reduction Strategies".

434

Novel Csbnd X⋯? halogen bonds in complexes of acetylene and its derivatives of Na and MPH3 (M = Cu, Ag, Au) with XCCF (X = Cl, Br, I)  

NASA Astrophysics Data System (ADS)

Ab initio calculations have been carried out for a variety of model systems with a T-shaped Csbnd X⋯? motif. The Csbnd X⋯? interaction of acetylene with the halogen donor molecule XCCF (X = Cl, Br, I) is invariably found to be weak with the interaction energy less than 11 kJ/mol in magnitude. Substitution of the two protons in acetylene with more electron-donating sodium atoms increases the ? electron density in the Ctbnd C bond and leads to a substantial enhancement in its interaction with the halogen donor. The calculated interaction energies increase to as much as 73 kJ/mol in the case of C2Na2-ICCF. The interaction of XCCF with a model coinage metal ethynide, H3PMCCMPH3 (M = Cu, Ag, Au), is intermediate between these two extremes, and the interaction energy is related to the nature of coinage metals. The Csbnd X⋯? halogen bonds have been analyzed with natural bond orbital, atoms in molecules, and energy decomposition.

Zhuo, Hongying; Liu, Mingjuan; Li, Qingzhong; Li, Wenzuo; Cheng, Jianbo

2014-06-01

435

Multigene assays in metastatic colorectal cancer.  

PubMed

Specific genomic colorectal cancer alterations are increasingly linked to prognosis and/or response to specific anticancer agents. The identification of KRAS mutations as markers of resistance to epidermal growth factor receptor (EGFR) inhibitors has paved the way to the interrogation of numerous other markers of resistance to anti-EGFR therapy, such as NRAS, BRAF, and PI3KCA mutations. Other genomic and protein expression alterations have recently been identified as potential targets of treatment or as markers of chemotherapy or targeted-therapy resistance, including ERCC1 expression, c-Met expression, PTEN expression, HER2 amplification, HER3 expression, and rare KRAS mutations. As the number of distinct validated intratumor genomic assays increases, numerous molecular assays will need to be compiled into one multigene panel assay. Several companies and academic centers are now offering multigene assays to patients with metastatic colorectal cancer and other solid tumors. This article discusses the technology behind multigene assays, its l