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1

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

2

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

3

Acetylene inhibition of nitrous oxide reduction by denitrifying bacteria  

Microsoft Academic Search

Acetylene (0.1 atm) caused complete or almost complete inhibition of reduction of NâO by whole cell suspensions of Pseudomonas perfectomarinus, P. aeruginosa and Micrococcus denitrificans. Acetylene did not inhibit reduction of NOâ⁻ or NOâ⁻ by these organisms. In the presence of acetylene there was stoichiometric conversion of NOâ⁻ or NOâ⁻ to NâO with negligible subsequent reduction of the latter. In

T. Yoshinari; R. Knowles

1976-01-01

4

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

SciTech Connect

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

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

1985-08-01

5

Plant pathology Effect of nitrate on acetylene reduction  

E-print Network

Plant pathology Effect of nitrate on acetylene reduction and the activities of some enzymes October 1990) Summary — Soybean plants (Glycine max (L) Merr) cv Maple arrow were nodulated either infected by B japonicum USDA 311 b 138. Thus infecting soybean plants with either B japonicum USDA 311 b

Paris-Sud XI, Université de

6

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

7

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

8

Biological Dinitrogen Fixation (Acetylene Reduction) Associated with Florida Mangroves  

PubMed Central

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

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

1978-01-01

9

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

10

Conformational flexibility of fused tetracenedione propellers obtained from one-pot reductive dimerization of acetylenic quinones.  

PubMed

Reductive dimerization of acetylenic anthraquinones provides synthetic access to flexible nonplanar polyaromatics with a tetracenedione core. In solution, these nonplanar, contorted polycycles exist as equilibrating mixtures of two symmetric conformers. The fused tetracenediones are easily reduced and exhibit rich electrochemical behavior. PMID:25575160

Vasilevsky, Sergei F; Baranov, Denis S; Mamatyuk, Victor I; Fadeev, Dmitry S; Gatilov, Yurii V; Stepanov, Aleksandr A; Vasilieva, Nadezhda V; Alabugin, Igor V

2015-02-01

11

Effect of Temperature on H2 Evolution and Acetylene Reduction in Pea Nodules and in Isolated Bacteroids  

PubMed Central

Nitrogenase (EC 1.7.99.2) activity in pea (Pisum savitum) nodules formed after infection with Rhizobium leguminosarum (lacking uptake hydrogenase) was measured as acetylene reduction, H2 evolution in air and H2 evolution in Ar:O2. With detached roots the relative efficiency, calculated from acetylene reduction, showed a decrease (from 55 to below 0%) with increasing temperature. With excised nodules and isolated bacteroids similar results were obtained. However, the relative efficiency calculated from H2 evolution in Ar:O2 was unaffected by temperature. Measurements on both excised nodules and isolated bacteroids showed a marked difference between acetylene reduction and H2 evolution in Ar:O2 with increased temperature, indicating that either acetylene reduction or H2 evolution in Ar:O2 are inadequate measures of nitrogenase activity at higher temperature. PMID:16664054

Bertelsen, Hans

1985-01-01

12

Effects of sulfide and low redox potential on the inhibition of nitrous oxide reduction by acetylene in Pseudomonas nautica.  

PubMed

Membrane introduction mass spectrometry was used to investigate the inhibitory effect of acetylene on the nitrous oxide reductase activity of intact cells of Pseudomonas nautica. We studied the effects of the concentrations of nitrate and sulfide, and the redox potential, which have all been implicated in causing a decrease in the inhibitory effects of acetylene during measurements of denitrification in natural environments. There was no evidence that the concentration of nitrate influenced the effect of acetylene. Lowering the redox potential with the reductant Ti(III)-nitrilotriacetate caused a slight alleviation of acetylene inhibition. Much greater effects at the same redox potential were obtained with concentrations of sulfide in the range 1-10 microM. PMID:1526461

Jensen, K M; Cox, R P

1992-09-01

13

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

PubMed Central

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

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

1968-01-01

14

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

15

Acetylene reduction (nitrogen fixation) by pulp and paper mill effluents and by Klebsiella isolated from effluents and environmental situations.  

PubMed

High rates of acetylene (C(2)H(2)) reduction (nitrogenase activity) were observed in woodroom effluent from a neutral sulfite semi-chemical mill under aerobic (up to 644 nmol of C(2)H(4) produced per ml per h) and under anaerobic (up to 135 nmol of C(2)H(4) produced per ml per h) conditions. Pasteurized effluent developed C(2)H(2) reduction activity when incubated under anaerobic but not under aerobic conditions. Activities were increased by addition of 0.5 to 3.0% glucose or xylose. Enrichment and enumeration studies showed that N(2)-fixing Azotobacter and Klebsiella were abundant, and N(2)-fixing Bacillus was present. Of 129 isolates of Klebsiella from pulp mills, lakes, rivers, and drainage and sewage systems, 32% possessed nitrogen-fixing ability. PMID:4425455

Knowles, R; Neufeld, R; Simpson, S

1974-10-01

16

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

SciTech Connect

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

Gabrielson, F.C.

1982-01-01

17

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

SciTech Connect

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

Gabrielson, F.C.

1982-01-01

18

Immunomagnetic reduction assay for nervous necrosis virus extracted from groupers.  

PubMed

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

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

2012-04-01

19

A novel quantitative immunomagnetic reduction assay for Nervous necrosis virus.  

PubMed

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

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

2012-09-01

20

Acetylenic acids from mosses.  

PubMed

Two new acetylenic fatty acids, 9, 12-octadecadien-6-ynoic and 11, 14-eicosadien-8-ynoic, were identified from lipids of the moss, Fontinalis antipyretica. They resemble the previously identified 9,12,15-octadecatrien-6-ynoic acid by having a methylene interrupted unsaturated system. The C20 acetylenic acid shows that the capability of mosses to synthesize polyolefinic acids of this chain length applies, in certain species, also to olefinic-acetylenic acids. PMID:1160525

Anderson, W H; Gellerman, J L; Schlenk, H

1975-08-01

21

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

22

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

23

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

24

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

25

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

26

Acetylenic acids from mosses  

Microsoft Academic Search

Two new acetylenic fatty acids, 9, 12-octadecadien-6-ynoic and 11,14-eicosadien-8-ynoic, were identified from lipids of the\\u000a moss,Fontinalis antipyretica. They resemble the previously identified 9,12,15-octadecatrien-6-ynoic acid by having a methylene interrupted unsaturated\\u000a system. The C20 acetylenic acid shows that the capability of mosses to synthesize polyolefinic acids of this chain length applies, in certain\\u000a species, also to olefinic-acetylenic acids.

W. H. Anderson; J. L. Gellerman

1975-01-01

27

Anaerobic Oxidation of Acetylene by Estuarine Sediments and Enrichment Cultures  

PubMed Central

Acetylene disappeared from the gas phase of anaerobically incubated estuarine sediment slurries, and loss was accompanied by increased levels of carbon dioxide. Acetylene loss was inhibited by chloramphenicol, air, and autoclaving. Addition of 14C2H2 to slurries resulted in the formation of 14CO2 and the transient appearance of 14C-soluble intermediates, of which acetate was a major component. Acetylene oxidation stimulated sulfate reduction; however, sulfate reduction was not required for the loss of C2H2 to occur. Enrichment cultures were obtained which grew anaerobically at the expense of C2H2. PMID:16345714

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

1981-01-01

28

Acetylene terminated matrix resins  

NASA Technical Reports Server (NTRS)

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

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

1985-01-01

29

A Standardized Plaque Reduction Assay for Determination of Drug Susceptibilities of Cytomegalovirus Clinical Isolates  

PubMed Central

Twelve laboratories collaborated in formulating and testing a standardized plaque reduction assay for cytomegalovirus (CMV) cell-associated clinical isolates. Four characterized and plaque-purified CMV strains, as well as six coded clinical isolates obtained after antiviral therapy, were distributed and tested. Good agreement was obtained for four of the clinical isolates, but a broad distribution of results was obtained for two isolates. Analysis of these results indicates the problems associated with clinical isolates, including the large genetic variability and the highly cell-associated phenotype. This collaborative effort, by addressing these problems, represents a significant step toward the development of a standardized assay. PMID:10681339

Landry, Marie L.; Stanat, Sylvia; Biron, Karen; Brambilla, Donald; Britt, William; Jokela, Janet; Chou, Sunwen; Drew, W. Lawrence; Erice, Alejo; Gilliam, Bruce; Lurain, Nell; Manischewitz, Jody; Miner, Richard; Nokta, Mostafa; Reichelderfer, Patricia; Spector, Stephen; Weinberg, Adriana; Yen-Lieberman, Belinda; Crumpacker, Clyde

2000-01-01

30

A focus reduction neutralization assay for hepatitis C virus neutralizing antibodies  

Microsoft Academic Search

BACKGROUND\\/AIM: The role of humoral immunity in hepatitis C virus (HCV) infection is poorly understood. Nevertheless, there is increasing interest in characterizing the neutralizing antibodies in the serum of HCV-infected patients. Focus reduction assays have been widely used to evaluate neutralizing antibody responses against a range of non-cytopathic viruses. Based on the recent development of a HCV cell culture system

Carole Fournier; Gilles Duverlie; Catherine François; Aurelie Schnuriger; Sarah Dedeurwaerder; Etienne Brochot; Dominique Capron; Czeslaw Wychowski; Vincent Thibault; Sandrine Castelain

2007-01-01

31

Acetylene soot reaction with NO in the presence of CO.  

PubMed

The heterogeneous reaction of soot with NO can be considered as a means of reduction of the emissions of both pollutants from combustion systems. In this paper, the influence of the presence of CO in the soot-NO reaction is studied. Soot was obtained by pyrolysis at 1373 K of 5000 ppmv acetylene in nitrogen. The study of the influence of CO on the soot-NO reaction was performed in experiments fixing NO concentration at 900 ppmv and introducing different CO concentrations among 0 and 9900 ppmv. An increase in both the carbon consumption rate and NO reduction by acetylene soot was observed as the concentration of CO increases. These results can be explained by the oxide-stripping reaction, CO+C(f)(O)-->CO(2)+C(f). The direct reaction of CO with NO catalyzed by the carbon surface, CO+NO-->CO(2)+1/2N(2) may not be considered in this case the dominant process due to the absence of mineral impurities in the acetylene soot. The influence of CO in the acetylene soot-NO reaction was also tested in the presence of oxygen (250-5000 ppmv). In these conditions and for relatively high CO/O(2) ratios, CO seems to also contribute to NO reduction by the previous oxide-stripping reaction. PMID:19167157

Mendiara, T; Alzueta, M U; Millera, A; Bilbao, R

2009-07-30

32

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

33

Conducting Composites of Polymethylmethacrylate with Acetylene Black  

Microsoft Academic Search

Conducting composites of polymethylmethacrylate and acetylene black were prepared via potassium chromate–sodium arsenite initiated redox polymerization of methylmethacrylate in presence of a suspension of acetylene black in aqueous methanol medium at 60°C. Prolonged extraction of the composite by tetrahydrofuran failed to extract the polymethylmethacrylate completely from the acetylene black surface, as confirmed by Fourier Transform Infrared studies. Scanning electron microscopic

Arjun Maity; Mukul Biswas

2006-01-01

34

Molecular Structure of Divinyl acetylene  

NSDL National Science Digital Library

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

2002-10-09

35

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

36

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

37

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

38

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

39

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

40

Assessment of buffalo semen with the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide reduction assay.  

PubMed

The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, which measures the reduction of MTT, is commonly used to validate the viability of metabolically active cells. This study was conducted to evaluate and validate the MTT assay to assess the spermatozoal viability of Nili-Ravi buffalo bulls and compare the efficiency of the test with the supravital staining technique (eosin and nigrosin) and the hypoosmotic swelling test. Fresh semen samples from breeding Nili-Ravi buffalo bulls (n = 25) were collected using an artificial vagina. After assessing the quality of the semen for routine variables, the MTT assay was carried out in PBS. Results revealed a correlation (r = 0.979; P < 0.001) between the viability of spermatozoa and the rate of reduction of MTT. The other proportions of same semen samples showed a poor relationship between the eosin and nigrosin test (r = -0.25), the hypoosmotic swelling test (r = -0.12), and motility (r = -0.15). However, the MTT assay was found to be superior compared with other tests because it was able to determine those spermatozoa that were more than 90% viable. In conclusion, the MTT assay is a simple, robust test that can be used to select Nili-Ravi buffalo bulls on the basis of spermatozoa quality. PMID:20023142

Iqbal, M; Aleem, M; Ijaz, A; Rehman, H; Yousaf, M S

2010-03-01

41

Reduction of Diagnostic Window by New Fourth-Generation Human Immunodeficiency Virus Screening Assays  

Microsoft Academic Search

In order to reduce the diagnostic window between the time of human immunodeficiency virus (HIV) infection and laboratory diagnosis, new screening enzyme-linked immunosorbent assays (ELISAs) which permit the simultaneous detection of HIV antigen and antibody have been developed. Two fourth-generation assays, HIV DUO (Biomerieux) and HIV Combi (Boehringer Mannheim), for the combined detection of HIV antigen and antibody, were compared

BERNARD WEBER; ANNEMARIE BERGER; HANS WILHELM; Laboratoires Reunis

1998-01-01

42

Epoxy acetylenic lipids: their analogues and derivatives.  

PubMed

Currently, approximately 250 natural acetylenic epoxy structures are known. The present review describes research concerning biologically active epoxy acetylenic lipids and related compounds isolated from different sources. Intensive searches for new classes of pharmacologically potent agents produced by living organisms have resulted in the discovery of dozens of such compounds that possess high anticancer, cytotoxic, antibacterial, antiviral, and other activities. Acetylenic epoxides primarily belong to a class of molecules containing triple bond(s) and epoxy group(s) belonging to different lipid classes and/or other groups. This review emphasises natural and synthetic acetylenic epoxides and other related compounds as important sources of leads for drug discovery. The present review is the first article devoted to natural acetylenic epoxides. PMID:25193612

Kuklev, Dmitry V; Dembitsky, Valery M

2014-10-01

43

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

PubMed

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

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

2015-04-01

44

Measurement of measles virus-specific neutralizing antibodies: evaluation of the syncytium inhibition assay in comparison with the plaque reduction neutralization test  

Microsoft Academic Search

Plaque reduction neutralization (PRN) is the “gold-standard” for the measurement of measles-specific neutralizing antibodies. However, it is a complicated assay and tends to be operator-dependent. It has been suggested that the simpler syncytium inhibition assay (SIA) can give results comparable to the PRN test. We compared these two assays using 594 serum or plasma samples obtained from children at various

B. J Ward; S Aouchiche; N Martel; F. M. N Bertley; N Bautista-Lopez; B Serhir; S Ratnam

1999-01-01

45

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

46

Growth kinetics of Mycobacterium tuberculosis measured by quantitative resazurin reduction assay: a tool for fitness studies  

PubMed Central

We standardized a method to evaluate the growth kinetics of Mycobacterium tuberculosis by measuring quantitatively the reduction of resazurin by spectrophotometry. Growth curves and the rate of growth of twenty-one M. tuberculosis clinical isolates were determined. The method showed technical simplicity and is inexpensive to assess the fitness of each isolate. PMID:24031495

von Groll, Andrea; Martin, Anandi; Portaels, Françoise; da Silva, Pedro Eduardo Almeida; Palomino, Juan Carlos

2010-01-01

47

Resazurin reduction assay, a useful tool for assessment of heavy metal toxicity in acidic conditions.  

PubMed

Almost all bioassays have been designed only for pH levels around 7; however, some toxicant characteristics may be different at lower pH values. In this study, a modified resazurin reduction method was used to evaluate the toxicity of heavy metals and metal plating wastewater on acid-tolerant (AT) and conventional bacteria at the natural and acidic pH conditions. According to our optimized protocol, resazurin was rapidly reduced by both conventional and AT active microorganisms. Considering the 30-min median effective concentration (30 min EC50) values, conventional bacteria were comparatively more resistant than the acid-tolerant bacteria (ATB) in the case of exposure to Cd, Pb, Cr, and Zn, but the reverse case was found for Hg. After an exposure of 30 min, Cr and Hg showed the highest toxicity to ATB (30 min EC50 values were 0.34 and 17.02 ?mol/L, respectively), while Zn and Pb had a considerably lower toxicity. The modified resazurin reduction method successfully assessed the impact of metal plating wastewaters on the activities of conventional and AT bacteria. According to the findings where the wastewaters contain heavy metals, wastewater treatment facilities, which are dependent on ATB activity, should use bioassays at acidic pH values for better understanding of the effects of toxicants. PMID:25893751

Zare, Mohammadreza; Amin, Mohammad Mehdi; Nikaeen, Mahnaz; Bina, Bijan; Pourzamani, Hamidreza; Fatehizadeh, Ali; Taheri, Ensieh

2015-05-01

48

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

49

Vapor pressures of acetylene at low temperatures  

NASA Technical Reports Server (NTRS)

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

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

1990-01-01

50

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

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

Acetylenes and terpenoids of Bellis perennis  

Microsoft Academic Search

The essential oils of leaves and flowers from Bellis perennis, the common daisy, have been investigated. Polyacetylenes were one of the major chemical classes (18–21%) mainly consisting of two new C10 acetylenic compounds which were identified, by spectroscopic and chemical means, as methyl deca-4,6-diynoate (2,8-tetrahydromatricaria ester) and deca-4,6-diynoic acid.

Pinarosa Avato; Aldo Tava

1995-01-01

53

Serum Neutralization Assay Can Efficiently Replace Plaque Reduction Neutralization Test for Detection and Quantitation of West Nile Virus Antibodies in Human and Animal Serum Samples  

PubMed Central

A serum neutralization assay (SN) was compared with the official plaque reduction neutralization test for the quantitation of West Nile virus antibodies. A total of 1,348 samples from equid sera and 38 from human sera were tested by these two methods. Statistically significant differences were not observed, thus supporting the use of SN for routine purposes. PMID:25100824

Di Gennaro, Annapia; Casaccia, Claudia; Conte, Annamaria; Monaco, Federica; Savini, Giovanni

2014-01-01

54

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

EPA Science Inventory

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

55

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

PubMed Central

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

Rosner, B M; Schink, B

1995-01-01

56

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

NASA Astrophysics Data System (ADS)

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

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

2011-11-01

57

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

PubMed

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

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

2013-11-15

58

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

59

Synthesis of Functional Poly(disubstituted acetylene)s through the Post-Polymerization Modification Route.  

PubMed

We report the recent progress in the preparation of functional poly(disubstituted acetylene)s (PDSAs) through post-polymerization modification routes. The metathesis polymerization of disubstituted acetylene monomers activated by Mo/W-Sn complex catalysts, which do not tolerate highly polar functionalities, was assumed to be a key step in the polymer synthetic procedures. We and other groups have explored several approaches to prepare PDSAs with latent reactive functionalities, which are inactive to Mo/W-Sn complex catalysts but can be used as highly reactive sites for post-polymerization modification. Click chemistry, Michael-type addition reactions, the use of activated esters and other strategies are demonstrated by recently published examples. These works indicate that post-polymerization modification is an efficient route to the synthesis of various functional PDSAs. PMID:25707368

Gao, Yuan; Wang, Xiao; Sun, Jing Zhi; Tang, Ben Zhong

2015-04-01

60

Comparison of two cytotoxicity assays--tetrazolium derivative reduction (MTT) and tritiated thymidine uptake--on three malignant mouse cell lines using chemotherapeutic agents and investigational drugs.  

PubMed

Two different techniques [reduction of a tetrazolium derivative (MTT) and 3HTdR uptake assays] were compared in order to evaluate the cytotoxic effects of different chemotherapeutic agents in vitro. The cytotoxicities of Melphalan, hexamethylmelamine and seven derivatives, and daunorubicin were measured on P388D1 mouse macrophage-like cell line, RC mouse renal carcinoma cell line, and B16 mouse melanoma cell lines. Growth inhibition was determined after one hour as well as after continuous (48 hours) exposure to drugs. The IC50 was calculated using an appropriate algorithm (FADHA) which allowed within and between run variabilities to be taken into account. Optimal conditions had to be elucidated for culture conditions before assay: number of cells/well and assay duration for each line. The MTT and 3HTdR uptake assays were found to be similar in terms of sensitivity and reproducibility, both for adherent and floating cell lines. However, the MTT assay has the advantages of low cost and time saving. It also avoids problems related to radioactivity manipulation and counting. Both techniques rank the same chemicals as active or inactive. The algorithm Fadha was found to be a very powerful mathematical tool for comparing the IC50 values obtained by both assays. PMID:2334120

Arnould, R; Dubois, J; Abikhalil, F; Libert, A; Ghanem, G; Atassi, G; Hanocq, M; Lejeune, F J

1990-01-01

61

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

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false Fixed oxygen-acetylene distribution piping. 56...Specific Systems § 56.50-103 Fixed oxygen-acetylene distribution piping. ...piping installed for the distribution of oxygen and acetylene carried in cylinders...

2012-10-01

62

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

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Fixed oxygen-acetylene distribution piping. 56...Specific Systems § 56.50-103 Fixed oxygen-acetylene distribution piping. ...piping installed for the distribution of oxygen and acetylene carried in cylinders...

2013-10-01

63

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

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 false Fixed oxygen-acetylene distribution piping. 56...Specific Systems § 56.50-103 Fixed oxygen-acetylene distribution piping. ...piping installed for the distribution of oxygen and acetylene carried in cylinders...

2010-10-01

64

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

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false Fixed oxygen-acetylene distribution piping. 56...Specific Systems § 56.50-103 Fixed oxygen-acetylene distribution piping. ...piping installed for the distribution of oxygen and acetylene carried in cylinders...

2011-10-01

65

Vibrational excitation of acetylene by positron impact  

NASA Astrophysics Data System (ADS)

Vibrationally inelastic quantum calculations are carried out at low collision energies for the scattering of a beam of positrons off acetylene gaseous molecules. The normal mode analysis is assumed to be valid and the relative fluxes into the C C and C H symmetric vibrational modes are computed within a Body-Fixed (BF) formulation of the dynamics by solving the relevant vibrational Coupled Channels (VCC) equations. The clear dominance of the C C mode is observed near threshold and the implications of this finding are briefly considered in relation to more global indicators like the average vibrational energy transfer indices as obtained in the present work.

Franz, J.; Gianturco, F. A.

2006-09-01

66

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

PubMed Central

An ultra-high vacuum experimental study of acetylene chemisorption on Pt(111) and Pt(100) and of the reaction of hydrogen with the acetylene adsorbate has established distinguishing features of carbon-hydrogen bond breaking and making processes as a function of pressure, temperature, and surface crystallography. The rates for both processes are substantially higher on the Pt(100) surface. Net acetylene-hydrogen processes, in the temperature range of 20°C to ?130°C, are distinctly different on the two surfaces: on Pt(100) the net reaction is hydrogen exchange (1H-2H exchange) and on Pt(111) the only detectable reaction is hydrogenation. Stereochemical differences in the acetylene adsorbate structure are considered to be a contributing factor to the differences in acetylene chemistry on these two surfaces. Images PMID:16593110

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

1981-01-01

67

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

68

A two-fold reduction in measurement time for neutron assay: Initial tests of a prototype dual-gated shift register  

SciTech Connect

Neutron coincidence counting (NCC) is used routinely around the world for nondestructive mass assay of uranium and plutonium in many forms, including waste. Compared with other methods, NCC is generally the most flexible, economic, and rapid. Many applications of NCC would benefit from a reduction in counting time required for a fixed random error. We have developed and tested the first prototype of a dual- gated, shift-register-based electronics unit that offers the potential of decreased measurement time for all passive and active NCC applications.

Stewart, J.E.; Bourret, S.C.; Krick, M.S.; Hansen, W.J.; Harker, W.C.

1996-09-01

69

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

70

An investigation of multiple jet acetylene flames  

SciTech Connect

The interaction between turbulent acetylene flames was investigated experimentally by the analysis of their visible lengths. The study involved 1, 2, 3 and 5 turbulent flames formed by parallel vertical jets whose relative distance was varied. The tube internal diameters were 1, 2, 3 and 4.4 mm. The results quantify the increase of flame length of multiple jets of equal injection tube radii and equal initial velocities as the flame separation distance decreases and as the number of jets increases. An empirical formula relating the length of multiple jet flames to that of the individual flame of same burner diameter was derived. Results of experiments performed with parallel burners inclined of 45{degree} in relation to the vertical direction are also presented.

Leite, A.O.P. [Faculdade de Engenharia de Guaratingueta, Sao Paulo (Brazil). Dept. de Quimica] [Faculdade de Engenharia de Guaratingueta, Sao Paulo (Brazil). Dept. de Quimica; Ferreira, M.A.; Carvalho, J.A. Jr. [Inst. Nacional de Pesquisas Espaciais, Cachoeira Paulista, Sao Paulo (Brazil). Lab. Associado de Combustao e Propulsao] [Inst. Nacional de Pesquisas Espaciais, Cachoeira Paulista, Sao Paulo (Brazil). Lab. Associado de Combustao e Propulsao

1996-11-01

71

Interpenetrating polymer networks from acetylene terminated materials  

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

72

Reactions of Acetylene in Superbasic Media  

NASA Astrophysics Data System (ADS)

The results of studies of fundamentally new reactions of acetylene and its substituted derivatives in media of very high basicity are surveyed. They lead to hitherto unknown or relatively inaccessible monomers, reagents, and intermediates: 2-vinyloxybuta-1,3-diene, pyrroles, and N-vinylpyrroles, divinyl sulphide, divinyl telluride, 4-methylene-1,3-oxathiolan, di(buta-1,3-dienyl)sulphide, dihydrothiophen, 1-vinyl-2-thiabicyclo[3,2,0]hept-3-ene, etc. The most important properties of superbasic media consisting of an alkali metal hydroxide and a dipolar aprotic solvent as well as the probable mechanisms of their activating effect on anions and the triple bond are examined. An attempt is made to analyse these reactions in terms of coordination catalysis by alkali metal cations. The bibliography includes 199 references.

Trofimov, Boris A.

1981-02-01

73

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

74

Vertical profiles of acetylene in the troposphere and stratosphere  

NASA Astrophysics Data System (ADS)

Stratospheric measurements of acetylene up to altitudes of 30 km are presented. The air samples were collected during three different balloon flights, two of them at 44 deg N, and one at 32 deg N, using balloon-borne, liquid neon-cooled, cryosamplers. Their acetylene concentration was measured in the laboratory by flame ionization gas chromatography. The different profiles at 32 deg N and 44 deg N are discussed with respect to possible vertical exchange processes, and compared with published model calculations.

Rudolph, J.; Ehhalt, D. H.; Khedim, A.

75

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

76

Mortality of workers at acetylene production plants.  

PubMed Central

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

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

1988-01-01

77

Is acetylene essential for carbon dust formation?  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

78

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

PubMed Central

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

2014-01-01

79

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

Code of Federal Regulations, 2010 CFR

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

2010-10-01

80

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

Code of Federal Regulations, 2014 CFR

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

2014-10-01

81

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

Code of Federal Regulations, 2011 CFR

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

2011-10-01

82

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

Code of Federal Regulations, 2012 CFR

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

2012-10-01

83

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

Code of Federal Regulations, 2013 CFR

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

2013-10-01

84

Calculating the movement of a shut-off valve under the action of an acetylene explosion  

Microsoft Academic Search

The aim of this work is to calculate the movement of the shut-off valve under the action of an acetylene explosion. Assumes that the force of the acetylene explosion acts on the valve instantaneously. Compares the valve movements under the action of the shock wave and the acetylene decomposition products pressure. Finds that over a small distance equal to the

A. Yu. Potapov; A. Yu

1982-01-01

85

Thermodynamical Study on Production of Acetylene from Coal Pyrolysis in Hydrogen Plasma  

Microsoft Academic Search

The chemical thermodynamic equilibrium of acetylene production by coal pyrolysis in hydrogen plasma was studied. The thermodynamic equilibrium is obtained by using the method of free energy. Calculated results show that the hydrogen concentration in the equilibrium system is very important for the acetylene production by coal conversion and the energy consumption for the production of acetylene per-kilogram strongly depends

Fei Wang; Wenkang Guo; Xingqiu Yuan; Taize Zhao

2006-01-01

86

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

PubMed Central

1. A number of acetylenic-substituted steroidal and non-steroidal compounds, including 2,2-dipropargylacetamide, pregna-2,4-dien-20-yno[2,3-d]isoxazol-17-ol (Danazol) and acetylene gas, when administered to rats in vivo brought about a decrease in the concentrations of hepatic microsomal cytochrome P-450 and haem. Abnormal haem-breakdown products, `green pigments', and porphyrins accumulated in the livers of these animals. 2. For loss of microsomal cytochrome P-450 to occur in vitro, metabolic activation of the acetylenic substituent was necessary. The enzyme system responsible required NADPH and air, and was induced by pretreatment of rats with phenobarbitone; these are characteristics typical of the microsomal mixed-function oxidases. 3. When rats were dosed with 17?-ethynyl-17?-hydroxyandrost-4-en-3-one (ethynyltestosterone, 1mmol/kg) the pattern of green pigments extracted from the liver 4h after dosing and separated by t.l.c. was quite different from that in rats given 17?-hydroxy-17?-vinylandrost-4-en-3-one (vinyltestosterone), suggesting that reduction of the unsaturated triple bond to a double bond is not normally part of the metabolic activation pathway of the acetylenic substituent. 4. The green pigments extracted from the livers of rats 4h after the administration of the acetylenic-substituted compounds (1mmol/kg) when separated by silica-gel t.l.c. had variable RF values. The number and distribution of green pigments was characteristic for each compound examined. There was little correlation between the total loss of hepatic microsomal haem and the apparent intensity of the green pigments seen on the thin-layer chromatograms. 5. After incubation of [14C]acetylene in vitro with microsomal preparations from phenobarbitone-pretreated rats and a NADPH-generating system, no significant covalent binding to microsomal protein was detected over a 30min incubation period, although under similar conditions there was a significant loss of cytochrome P-450. PMID:728091

White, Ian N. H.

1978-01-01

87

Spectroscopy and energetics of the acetylene molecule  

NASA Astrophysics Data System (ADS)

This article reviews laser-spectroscopic studies of the structure, energetics, and dynamics of processes involving small polyatomic molecules, particularly acetylene (ethyne, C2H2). The linear, centrosymmetric structure of C2H2 is deceptively simple, given that aspects of its optical spectra and dynamics have proved to be unusually complicated. The article focuses on the ground electronic state of C2H2, where rovibrational eigenstates are only approximately described in normal-mode terms, because intramolecular processes (such as anharmonic mixing, ?-type resonances, and Coriolis coupling) introduce extensive global and local perturbations. These tend to spoil quantum numbers and symmetries that are well-defined in low-order basis states. Such effects within the rovibrational energy states of C2H2 are systematically characterized, together with dynamical descriptions in terms of polyad models and insight into photochemical or photophysical processes that may occur at high vibrational energies, without direct electronic excitation. Time-resolved optical double-resonance spectroscopy, probed by ultraviolet-laser-induced fluorescence and pumped by either infrared absorption or coherent Raman excitation, has proved particularly useful in exploring such effects in gas-phase C2H2; techniques of this type are discussed in detail, together with other laser-spectroscopic methods that provide complementary mechanistic information. A closely related topic concerns the area of optothermal molecular-beam spectroscopy, with particular emphasis on research by the late Roger E. Miller to whose memory this article is dedicated. Key publications by Miller and coworkers, in many of which C2H2 and its isotopomers play a central role, are reviewed. These cover the following themes: structure of molecular complexes and clusters, infrared predissociation spectra, rotational and vibrational energy transfer, differential scattering, photofragmentation of oriented complexes, superfluid-helium nanodroplet spectroscopy, aerosols formed in low-temperature diffusion cells, surface scattering experiments, optically selected mass spectrometry, and characterization of biomolecules. A unifying issue that links the assorted topics of this article is the role that intramolecular perturbations can play to enhance (and sometimes suppress) the efficiency of rovibrational energy transfer in colliding molecules or in molecular complexes and clusters; C2H2 and its isotopomers have been a rich source of insight in this regard, although they continue to pose challenges to our understanding.

Orr, Brian J.

88

Ionic structure and sequence of ion formation in acetylene flames  

Microsoft Academic Search

The principal results of a study on the ionic composition of acetylene—air flames at low pressures are presented. The results are compared with data on the ion formation in flames of saturated hydrocarbons and oxygen-containing substances. It is shown that the laws of ion formation at the front and immediately in front of it are similar to those which have

I. A. Larionova; B. S. Fialkov; K. Ya. Kalinich; A. B. Fialkov; B. S. Ospanov

1993-01-01

89

46 CFR 154.1735 - Methyl acetylene-propadiene mixture.  

Code of Federal Regulations, 2011 CFR

...composition is: (i) Maximum methyl acetylene and propadiene molar ratio of 3 to 1; (ii) Maximum combined concentration of...isobutane of 24 mole percent, of which at least one-third (on a molar basis) must be butanes and one-third propane; and...

2011-10-01

90

46 CFR 154.1735 - Methyl acetylene-propadiene mixture.  

Code of Federal Regulations, 2014 CFR

...composition is: (i) Maximum methyl acetylene and propadiene molar ratio of 3 to 1; (ii) Maximum combined concentration of...isobutane of 24 mole percent, of which at least one-third (on a molar basis) must be butanes and one-third propane; and...

2014-10-01

91

46 CFR 154.1735 - Methyl acetylene-propadiene mixture.  

Code of Federal Regulations, 2012 CFR

...composition is: (i) Maximum methyl acetylene and propadiene molar ratio of 3 to 1; (ii) Maximum combined concentration of...isobutane of 24 mole percent, of which at least one-third (on a molar basis) must be butanes and one-third propane; and...

2012-10-01

92

46 CFR 154.1735 - Methyl acetylene-propadiene mixture.  

Code of Federal Regulations, 2013 CFR

...composition is: (i) Maximum methyl acetylene and propadiene molar ratio of 3 to 1; (ii) Maximum combined concentration of...isobutane of 24 mole percent, of which at least one-third (on a molar basis) must be butanes and one-third propane; and...

2013-10-01

93

Butadiene from acetylene-ethylene cross-metathesis.  

PubMed

Acetylene to butadiene direct synthesis, via enyne cross-metathesis, is demonstrated with commercial ruthenium carbene catalysts. Using excess of ethylene, yields greater than 50% are obtained. High activity is observed in the first minute of the reaction (TOF > 800 h(-1) based on butadiene). Catalyst reusability and poisoning are discussed. PMID:25811306

Trotu?, Ioan-Teodor; Zimmermann, Tobias; Duyckaerts, Nicolas; Geboers, Jan; Schüth, Ferdi

2015-04-01

94

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

95

Reactions of acetylenes in superbasic media. Recent advances  

NASA Astrophysics Data System (ADS)

The main advances in the chemistry of acetylene in superbasic media achieved over the last five years are analyzed. Particular emphasis is placed on the ethynylation of aldehydes and ketones and C-, N- and O-vinylation. The cascade assembly of complex molecules in which ethynylation and vinylation are consecutive steps is considered. The bibliography includes 369 references.

Trofimov, B. A.; Schmidt, E. Yu

2014-07-01

96

Relative Abundance of Ureides and Nitrate in Plant Tissues of Soybean as a Quantitative Assay of Nitrogen Fixation 1  

PubMed Central

The relationship between the relative abundance of ureides ([ureide-N/ureide-N plus nitrate-N] × 100) in the shoot axis (stems plus petioles), nodulated roots and leaflets of “Bragg” soybean (Glycine max [L.] Merrill) and the symbiotic dependence of these plants was examined under glass-house conditions. Plants, inoculated with effective Rhizobium japonicum CB1809, were grown with their roots exposed continuously to a nutrient solution containing either 0, 1.5, 3.0, 6.0 or 12.0 millimolar NO3-N per liter. Nodulation and N2-acetylene fixation were correlated inversely with the level of nitrate. Seasonal acetylene reduction profiles for each of the nitrate treatments were integrated and the symbiotic dependence ([N2 fixed per total plant N] × 100) determined using a conversion ratio of 1.5:1 (acetylene reduced:N2 fixed), calculated from the zero NO3 treatment. Examination of the nitrogenous solutes of the shoot axis and nodulated roots showed linear relationships between the relative abundance of ureides and the symbiotic dependence of the plants. Two standard curves, depicting these relationships during vegetative and reproductive growth, were drawn for each plant part. The overriding effect of plant age invalidated any attempt to develop a standard relationship for leaflets. Data from two diurnal studies suggested that relative ureides were insensitive to diurnal fluctuations, thus simplifying sampling procedures. Plant material could be stored at ambient temperatures (20-30°C) for up to 24 h without affecting the relative concentration of ureides and nitrate. It is suggested that the shoot axis provides the most suitable target organ when using this technique as a quantitative assay for N2 fixation because of ease of sampling of these tissues, especially with field-grown plants. PMID:16662425

Herridge, David F.

1982-01-01

97

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

98

Enhanced acetylene emission near the north pole of Jupiter  

NASA Technical Reports Server (NTRS)

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

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

1986-01-01

99

Enhanced acetylene emission near the north pole of Jupiter  

NASA Technical Reports Server (NTRS)

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

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

1986-01-01

100

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

101

Methyl acetylene as a temperature probe for dense interstellar clouds  

SciTech Connect

Methyl acetylene (propyne) appears to be a convenient and reliable probe of kinetic temperature for dense (> or approx. =few +- 10/sup 4/ cm/sup -3/) molecular clouds. A method is presented for fitting a (J+1)-J K-multiplet to obtain the kinetic temperature from a single observation, facilitating the direct construction of kinetic temperature maps. Observations of Tau MC1, Ori MC1, Sgr B2, DR 21, DR 21 (OH), and S140 are presented to demonstrate the validity of the technique. Determination of methyl acetylene column densities requires, in addition, knowledge of the rotational excitation temperature. The relative abundance of CH/sub 3/CCH appears to be within a factor of 2 of 2.5 +- 10/sup -9/. Because of the large uncertainties in estimates of total gas column density, it is not clear whether there is genuine source-to-source variation in the CH/sub 2/CCH relative abundance.

Kuiper, T.B.H.; Kuiper, E.N.R.; Dickinson, D.F.; Turner, B.E.; Zuckerman, B.

1984-01-01

102

Methyl acetylene as a temperature probe for dense interstellar clouds  

NASA Technical Reports Server (NTRS)

Methyl acetylene (propyne) appears to be a convenient and reliable probe of kinetic temperature for dense (few x 10 to the 4th/ cu cm) molecular clouds. A method is presented for fitting a (J + 1) - J K-multiplet to obtain the kinetic temperature from a single observation, facilitating the direct construction of kinetic temperature maps. Observations of Tau MC1, Ori MC1, Sgr B2, DR 21, DR 21 (OH), and S140 are presented to demonstrate the validity of the technique. Determination of methyl acetylene column densities requires, in addition, knowledge of the rotational excitation temperature. The relative abundance of CH3CCH appears to be within a factor of 2 of 2.5 x 10 to the -9th. Because of the large uncertainties in estimates of total gas column density, it is not clear whether there is genuine source-to-source variation in the CH3CCH relative abundance.

Kuiper, T. B. H.; Kuiper, E. N. R.; Dickinson, D. F.; Turner, B. E.; Zuckerman, B.

1984-01-01

103

Method for production of methyl vinyl ketone from acetylene  

Microsoft Academic Search

A method is proposed for the synthesis of methyl vinyl ketone by hydration trimerization of acetylene followed by hydrolysis of the 2-vinloxy-1,3-butadiene formed under the action of a potassium hydroxide-potassium phosphate-DMSO catalyst system. The authors contend that this system eliminates the normal drawbacks associated with synthesis of the ketone, including low product yield, multistage operations, the presence of impurities that

O. A. Tarasova; B. A. Trofimov; S. V. Amosova; A. G. Tesler; M. G. Voronkov

1987-01-01

104

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

PubMed

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

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

2014-12-28

105

Acetylene is an active-site-directed, slow-binding, reversible inhibitor of Azotobacter vinelandii hydrogenase  

SciTech Connect

The inhibition of purified and membrane-bound hydrogenase from Azotobacter vinelandii by dihydrogen-free acetylene was investigated. The inhibition was a time-dependent process which exhibited first-order kinetics. Both H/sub 2/ and CO protected against the inhibition by acetylene. K/sub protect(app)/ values of 0.41 and 24 ..mu..M were derived for these gases, respectively. Both H/sub 2/-oxidizing activity and the tritium exchange capacity of the purified enzyme were inhibited at the same rate by acetylene. Removal of acetylene reversed the inhibition for both the purified and the membrane-associated form of the enzyme. The purified hydrogenases from both Rhizobium japonicum and Alcaligenes eutrophus H16 were also inhibited by acetylene in a time-dependent fashion. These findings suggest that acetylene is an active-site-directed, slow-binding, reversible inhibitor of some membrane-bound hydrogenases from aerobic bacteria.

Hyman, M.R.; Arp, D.J.

1987-10-06

106

Local mode behavior in the acetylene bending system  

SciTech Connect

The bending eigenfunctions of the acetylene {tilde X}{sup 1}{Sigma}{sub g}{sup +} state, as represented by our recently reported effective Hamiltonian [J. Chem. Phys. {bold 109}, 121 (1998)], are analyzed up to E{sub vib}=15thinsp000 cm{sup {minus}1}. A transition from normal to local mode behavior is observed around 8000{endash}10thinsp000 cm{sup {minus}1}, such that above these energies, the eigenstates are better described in terms of local mode quantum numbers. The local mode behavior in the bend degrees of freedom of acetylene that is described here is in many ways analogous to the local mode behavior that has been observed in the stretching degrees of freedom of many ABA molecules. However, the local mode behavior in the acetylene bend degrees of freedom, because it involves two two-dimensional rather than two one-dimensional vibrational modes, encompasses a richer range of motions. Specifically, in the {open_quotes}local{close_quotes} limit, the bending eigenfunctions are describable in terms of a continuum of motions ranging from local bend (one hydrogen bending) to counter-rotation (the two hydrogens executing rotations in opposite directions). {copyright} {ital 1999 American Institute of Physics.}

Jacobson, M.P.; Silbey, R.J.; Field, R.W. [Department of Chemistry and George R. Harrison Spectroscopy Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)] [Department of Chemistry and George R. Harrison Spectroscopy Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

1999-01-01

107

Chemiionization and ion-molecule reactions in fuel-rich acetylene flames  

Microsoft Academic Search

The objective of this study is to model the appearance and behavior of combustion-generated ions in rich flames of acetylene. A one-dimensional, laminar, flat flame of acetylene was developed that combines reactions for oxidation, pyrolysis, chemiionization, proton transfer, ion-molecule reactions, and charge recombination relevant to rich acetylene combustion. Four possible chemiionization reactions are included in the model. Ions other than

A. N. Eraslan; R. C. Brown

1988-01-01

108

Kinetics and Structure of Superagglomerates Produced by Silane and Acetylene  

NASA Technical Reports Server (NTRS)

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

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

1999-01-01

109

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

PubMed

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

Petter, P J

1989-02-01

110

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

PubMed

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

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

2015-04-01

111

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

PubMed

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

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

2013-10-01

112

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

NASA Astrophysics Data System (ADS)

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

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

2014-02-01

113

Mechanism of tungsten-dependent acetylene hydratase from quantum chemical calculations  

E-print Network

Mechanism of tungsten-dependent acetylene hydratase from quantum chemical calculations Rong hydratase is a tungsten-dependent enzyme that cata- lyzes the nonredox hydration of acetylene metalloenzyme cluster approach Tungsten is the heaviest metal in biology and plays prominent roles in carbon

Liao, Rongzhen

114

Structure of the non-redox-active tungsten/[4Fe:4S] enzyme acetylene hydratase Kroneck, and Oliver Einsle  

E-print Network

Structure of the non-redox-active tungsten/[4Fe:4S] enzyme acetylene hydratase Kroneck, and Oliver, see: Notes: #12;Structure of the non-redox-active tungsten/[4Fe:4S] enzyme acetylene hydratase Grazyna, and approved January 10, 2007 (received for review November 23, 2006) The tungsten­iron­sulfur enzyme acetylene

Ullmann, G. Matthias

115

Localized Tetrazolium Reduction in Relation to N2 Fixation, CO2 Fixation, and H2 Uptake in Aquatic Filamentous Cyanobacteria  

PubMed Central

The aquatic filamentous cyanobacteria Anabaena oscillarioides and Trichodesmium sp. reveal specific cellular regions of tetrazolium salt reduction. The effects of localized reduction of five tetrazolium salts on N2 fixation (acetylene reduction), 14CO2 fixation, and 3H2 utilization were examined. During short-term (within 30 min) exposures in A. oscillarioides, salt reduction in heterocysts occurred simultaneously with inhibition of acetylene reduction. Conversely, when salts failed to either penetrate or be reduced in heterocysts, no inhibition of acetylene reduction occurred. When salts were rapidly reduced in vegetative cells, 14CO2 fixation and 3H2 utilization rates decreased, whereas salts exclusively reduced in heterocysts were not linked to blockage of these processes. In the nonheterocystous genus Trichodesmium, the deposition of reduced 2,3,5-triphenyl-2-tetrazolium chloride (TTC) in the internal cores of trichomes occurs simultaneously with a lowering of acetylene reduction rates. Since TTC deposition in heterocysts of A. oscillarioides occurs contemporaneously with inhibition of acetylene reduction, we conclude that the cellular reduction of this salt is of use in locating potential N2-fixing sites in cyanobacteria. The possible applications and problems associated with interpreting localized reduction of tetrazolium salts in cyanobacteria are presented. Images PMID:16345923

Paerl, Hans W.; Bland, Patricia T.

1982-01-01

116

A new determination of the dissociation energy of acetylene  

SciTech Connect

A new {ital upper} {ital bound} for the dissociation energy of acetylene, {ital D}{sup 0}{sub 0}(HCC--H) =529.89({plus minus}0.01) kJ/mol, has been determined by Stark anticrossing spectroscopy. The zero-pressure extrapolated (unimolecular) decay rates of levels of {ital S}{sub 1} ({ital {tilde A}} {sup 1}{ital A}{sub {ital u}}) {ital v}{sup {prime}}{sub 3}=2 and 3 (quanta of the {ital trans}-bending vibration) {ital increase} upon application of an electric field of 113 kV/cm. We attribute this increase in molecular decay rate to {ital predissociation} rather than any other Stark-induced nonradiative or radiative phenomenon. The lowest level ({ital v}{sup {prime}}{sub 3} =2, {ital J}{prime}=2, {ital K}{prime}=1) from which we have observed an increase in decay rate (i.e., predissociation) has an internal energy of 44 295.65 cm{sup {minus}1} relative to {ital v}=0, {ital J}=0 of {ital S}{sub 0} ({ital {tilde X}} {sup 1}{Sigma}{sup +}{sub {ital g}}). This corresponds to a value about 24 kJ/mol lower then the consensus {ital upper bound} result from four different recent experimental determinations (including one of ours) as well as current {ital ab nitio} results. The new value agrees, however, with earlier work and with recent modeling studies of acetylene pyrolysis kinetics.

Green, P.G.; Kinsey, J.L.; Field, R.W. (Department of Chemistry and George R. Harrison Spectroscopy Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (US))

1989-11-01

117

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

NASA Astrophysics Data System (ADS)

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

Malla, Pavani

118

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

119

Investigation of Gallium promoted Palladium/Titanium dioxide catalysts for the selective hydrogenation of acetylene in the presence of ethylene  

NASA Astrophysics Data System (ADS)

Gallium is investigated as a promoter of supported Pd catalysts for the selective hydrogenation of acetylene in ethylene. TiO2 support is investigated with high (1%) and low (0.25%) Pd loadings. Reaction parameters, including reduction temperature, H2/C2H2 ratio and Pd/Ga ratio, were studied to optimize the performance of catalysts. The current results show that Ga promotes the selective hydrogenation of acetylene to ethylene over TiO2 supported Pd catalysts, but it is a function of Ga loading. In addition, non-thermal RF plasma has been used to modify and/or reduce promoted Pd catalysts to induce strong or unique interaction between Ga and Pd. Differential scanning calorimeter in hydrogen atmosphere (H2-DSC) was used as the main technique to gauge the interaction between Pd precursor and Ga on TiO2 surface, and will be used for the catalysts modified by plasmas. The catalytic performance of plasma modified catalysts will be systematically studied.

Pena Orduna, Luis

120

Opsonophagocytic assay.  

PubMed

The opsonophagocytic killing (OPK) assay is used as a correlate for protection to measure the functional capacities of vaccine-candidate-raised antibodies. This in vitro assay aids selecting promising vaccines by demonstrating whether the vaccine-induced antibodies drive efficient complement deposition and subsequent opsonophagocytic killing. Here, we describe two protocols for an OPK assay using either human-derived PMNs or cultured HL-60 cells. PMID:24218277

Dwyer, Markryan; Gadjeva, Mihaela

2014-01-01

121

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

122

Correlation between hydrogen bond basicity and acetylene solubility in room temperature ionic liquids.  

PubMed

Room temperature ionic liquids (RTILs) are proposed as the alternative solvents for the acetylene separation in ethylene generated from the naphtha cracking process. The solubility behavior of acetylene in RTILs was examined using a linear solvation energy relationship based on Kamlet-Taft solvent parameters including the hydrogen-bond acidity or donor ability (?), the hydrogen-bond basicity or acceptor ability (?), and the polarity/polarizability (?*). It is found that the solubility of acetylene linearly correlates with ? value and is almost independent of ? or ?*. The solubility of acetylene in RTILs increases with increasing hydrogen-bond acceptor (HBA) ability of the anion, but is little affected by the nature of the cation. Quantum mechanical calculations demonstrate that the acidic proton of acetylene specifically forms hydrogen bond with a basic oxygen atom on the anion of a RTIL. On the other hand, although C-H···? interaction is plausible, all optimized structures indicate that the acidic protons on the cation do not specifically associate with the ? cloud of acetylene. Thermodynamic analysis agrees well with the proposed correlation: the higher the ? value of a RTIL is, the more negative the enthalpy of acetylene absorption in the RTIL is. PMID:21218815

Palgunadi, Jelliarko; Hong, Sung Yun; Lee, Jin Kyu; Lee, Hyunjoo; Lee, Sang Deuk; Cheong, Minserk; Kim, Hoon Sik

2011-02-10

123

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...

124

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

125

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

PubMed Central

The catalytic mechanism of the hydrogen-mediated coupling of acetylene to carbonyl compounds and imines has been examined using three techniques: (a) ESI-MS and ESI-CAD-MS analyses, (b) computational modeling, and (c) experiments wherein putative reactive intermediates are diverted to alternative reaction products. ESI-MS analysis of reaction mixtures from the hydrogen-mediated reductive coupling of acetylene to ?-ketoesters or N-benzenesulfonyl aldimines corroborate a catalytic mechanism involving C=X (X = O, NSO2Ph) insertion into a cationic rhodacyclopentadiene obtained by way of acetylene oxidative dimerization with subsequent Brønsted acid cocatalyzed hydrogenolysis of the resulting oxa- or azarhodacycloheptadiene. Hydrogenation of 1,6-diynes in the presence of ?-ketoesters provides analogous coupling products. ESI mass spectrometric analysis again corroborates a catalytic mechanism involving carbonyl insertion into a cationic rhodacyclopentadiene. For all ESI-MS experiments, the structural assignments of ions are supported by multi-stage collisional activated dissociation (CAD) ESI-MS analyses. Further support for the proposed catalytic mechanism derives from experiments aimed at the interception of putative reactive intermediates and their diversion to alternate reaction products. For example, rhodium catalyzed coupling of acetylene to aldehyde in the absence of hydrogen or Brønsted acid cocatalyst provides the corresponding (Z)-butadienyl ketone, which arises from ?-hydride elimination of the proposed oxarhodacycloheptadiene intermediate, as corroborated by isotopic labeling. Additionally, the putative rhodacyclopentadiene intermediate obtained from the oxidative coupling of acetylene is diverted to the product of reductive [2+2+2] cycloaddition when N-p-toluenesulfonyl-dehydroalanine ethyl ester is used as the coupling partner. The mechanism of this transformation also is corroborated by isotopic labeling. Computer model studies based on density functional theory (DFT) support the proposed mechanism and identify Brønsted acid cocatalyst assisted hydrogenolysis to be the most difficult step. The collective studies provide new insight into the reactivity of cationic rhodacyclopentadienes, which should facilitate the design of related rhodium catalyzed C-C couplings. PMID:19845357

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

2009-01-01

126

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

127

On the C?H bond dissociation energy of acetylene  

NASA Astrophysics Data System (ADS)

Ab initio calculations, including extrapolation to the complete basis set limit, are reported for the C?H bond dissociation energy of acetylene. These calculations, which have a rms error of 0.51 kcal/mol per bond for the atomization energies of 13 well-known molecules, give D0(H-CCH) = 131.54 kcal/mol, in good agreement with previous results, but about 5 kcal/mol above the recent measurement of Green, Kinsey and Field ( D0 ? 126.647 ± 0.002 kcal/mol), and that of Segall, Lavi, Wen and Wittig ( D0 = 127 ± 1.5 kcal/mol). The electron affinity of CCH is calculated to be within 0.18 kcal/mol of the recent measurement of Ervin et al. (2.969 ± 0.010 eV)

Petersson, J. A. Montgomery G. A., Jr.

1990-04-01

128

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

129

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

130

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

SciTech Connect

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 flame and the soot emissions. When a positive voltage was applied to the nozzle electrode, the flame length became shorter and the width at the flame tip was spread at high voltages. More than 90% of the soot emission was suppressed at over 200 kV/m of electric field intensity. Also, the flame temperature increased with increasing applied voltage. In particular, in the case of voltages above 200 kV/m, the temperatures at the flame tip were about 500 C higher than in the absence of an electric field. The rise of flame temperature was caused by the air entrainment promoted by an ionic wind. It was concluded that the soot reduction by applying an electric field was due to the oxidation of soot particles. In contrast, when negative voltages were applied to the nozzle electrode, the efficiency of soot control was limited to about 70% because the flame temperature, even at high applied voltages, was comparable to that in the absence of the electric field.

Saito, Masahiro; Arai, Toshihiro; Arai, Masataka

1999-11-01

131

Hydration of 2-cyanoethyl ethers of acetylenic alcohols. Alcoholysis of the hydration products  

Microsoft Academic Search

1.The hydration of 2-cyanoethyl ethers of various acetylenic alcohols was carried out.2.The resulting 2-cyanoethyl ethers of a-hydroxy ketones were converted into the corresponding 2-(methoxycarbonyl) ethyl ethers.

I. N. Nazarov; G. A. Shvekhgeimer

1958-01-01

132

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

133

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

NASA Technical Reports Server (NTRS)

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

Walch, Stephen P.; Taylor, Peter R.

1995-01-01

134

High-performance supported catalysts with an ionic liquid layer for the selective hydrogenation of acetylene.  

PubMed

Pd-Ag shell catalysts impregnated with two different ionic liquids show considerable improvements both in ethylene selectivity and reduced ethane formation in the selective hydrogenation of acetylene under tail-end conditions. PMID:22008709

Herrmann, Tanja; Rössmann, Laura; Lucas, Martin; Claus, Peter

2011-12-01

135

Selective hydrogenation of acetylene over egg-shell palladium nano-catalyst.  

PubMed

A novel egg-shell Pd/PHSNs nano-catalyst was prepared by a wet impregnation method using self-synthesized porous hollow silica nanoparticles (PHSNs) as support and applied in selective hydrogenation of acetylene to remove acetylene from the ethylene feed. By controlling the preparing conditions and calcining temperature, the active metal particles were loaded evenly on the support with a size about 5 nm. Compared with conventional catalysts prepared with solid silica nanoparticles, solid Al2O3 millispheres and a commercial catalyst, the Pd/PHSNs catalyst showed higher acetylene conversion rates at same reaction temperatures, and the porous hollow nano structure of PHSNs allowed smoother diffusion of ethylene molecules within the catalyst matrix so that ethylene could migrate away from the active sites in time to avoid turning into ethane, which resulted in superior ethylene selectivity at high acetylene conversion rates. PMID:21133085

Zhu, Qiu-Feng; Gao, Jin; Chen, Jian-Feng; Wen, Li-Xiong

2010-09-01

136

VII. INFLUENCE OF THE ACETYLENIC BOND LOCATION ON THE EFFECTIVENESS OF ACYL CHAINS  

Microsoft Academic Search

Summary The ability of a series of 18 carbon acetylenic fatty acids to fulfill the unsat- urated fatty acid requirements of Escherichia coli and Saccharomyces cereuisiae was investigated. Despite their high melting points (>4O\\

WILLIAM E. M. LANDS; JOHN B. OHLROGGE; JOHN R. ROBINSON; ROGER W. SACKS; JOHN A. BARVE; FRANK D. GUNSTONE

1977-01-01

137

Cellulase Assays  

NASA Astrophysics Data System (ADS)

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

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

138

First overtone helium nanodroplet isolation spectroscopy of molecules bearing the acetylenic CH chromophore  

Microsoft Academic Search

High-resolution helium nanodroplet isolation spectra of the first overtone (2nu1) of the acetylenic stretch of several substituted acetylenes (RC?C-H) at T=0.38 K, have been observed for the first time. A tunable 1.5 mum laser is coupled, using a power buildup cavity, to a beam of He droplets seeded with the molecule to be studied. Absorption spectra are recorded by monitoring

C. Callegari; A. Conjusteau; I. Reinhard; K. K. Lehmann; G. Scoles

2000-01-01

139

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

140

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

PubMed

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

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

2015-06-01

141

Comparison and reliability of two non-invasive acetylene uptake techniques for the measurement of cardiac output  

Microsoft Academic Search

Comparison and reliability of two non-invasive acetylene uptake techniques for the measurement of cardiac output. Thirteen trained male cyclists performed CO2 rebreathing (CO2RB) at intensities from rest to 200 W, and open-circuit acetylene uptake (OpCirc) and single-breath acetylene uptake (SB) at intensities from rest to 300 W, with all procedures using 50 W increments. Oxygen consumption \\u000a cardiac output \\u000a and heart rate (HR), were

D. W. Dibski; D. J. Smith; R. Jensen; S. R. Norris; G. T. Ford

2005-01-01

142

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

PubMed

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

Avella, Joseph; Lehrer, Michael

2004-11-01

143

NIR diode laser-based QEPAS for acetylene detection  

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

144

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

145

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

SciTech Connect

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

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

2013-03-28

146

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

NASA Technical Reports Server (NTRS)

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

McLaren, Ian A.; Wrobel, Jacek D.

1997-01-01

147

Hexosaminidase assays  

Microsoft Academic Search

?-Hexosaminidases (EC 3.2.1.52) are lysosomal enzymes that remove terminal ?-glycosidically bound N-acetylglucosamine and N-acetylgalactosamine residues from a number of glycoconjugates. Reliable assay systems are particularly important for the\\u000a diagnosis of a family of lysosomal storage disorders, the GM2 gangliosidoses that result from inherited ?-hexosaminidase deficiency.\\u000a More recently, aberrant hexosaminidase levels have also been found to be associated with a variety

Michaela Wendeler; Konrad Sandhoff

2009-01-01

148

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

149

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

SciTech Connect

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

Hall, J.B.; Huggins, B.J.; Meyers, B.L. [Amoco Corp., Naperville, IL (United States); Kaminsky, M.P. [Amoco Chemical Co., Naperville, IL (United States)

1994-12-31

150

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...

151

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

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

152

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

E-print Network

SOLID-STATE NMR STUDIES OF THE ADSORPTION OF ACETYLENE ON PLATINUM/ALUMINA CATALYSTS A Thesis by MARSHA JO LUPHER LAMBREGTS Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements... for the degree of MASTER OF SCIENCE December 1991 Major Subject: Chemistry SOLID-STATE NMR STUDIES OF THE ADSORPTION OF ACETYLENE ON PLATINUM/ALUMINA CATALYSTS A Thesis by MARSHA JO LUPHER LAMBREGTS Approved as to style and content by: ames F. Haw...

Lambregts, Marsha Jo Lupher

1991-01-01

153

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

PubMed

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

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

2008-06-01

154

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

155

Cyclic Acetal Formation Between 2-Pyridinecarboxaldehyde and gamma-Hydroxy-alpha,beta-Acetylenic Esters.  

PubMed

A new transformation between 2-pyridinecarboxyaldehyde and gamma-hydroxy-alpha,beta-acetylenic esters to form highly functionalized cyclic acetals was discovered. This transformation proceeds under very mild conditions without any additives and is promoted by the basic nature of the pyridine ring. PMID:19907635

Osman, Sami; Koide, Kazunori

2008-11-10

156

Triplet Acetylenes as Synthetic Equivalents of 1,2-Bicarbenes: Phantom n,* State Controls Reactivity in  

E-print Network

. Clark, Ion Ghiviriga, and Igor V. Alabugin* Contribution from the Department of Chemistry: Diaryl acetylenes, in which one of the aryl groups is either a pyridine or a pyrazine, undergo efficient the photochemical transformation of benzannelated enediynes possessing electron-accepting sub- stituents

Alabugin, Igor

157

Structure and absolute configuration of new acetylenic compounds isolated from cultures of Clitocybe catinus.  

PubMed

Investigations of the extracts of a culture of Clitocybe catinus gave rise to the isolation of new acetylenic diols 1-3. Their structure was determined on the basis of 1H- and 13C-NMR evidence and the absolute configuration elucidated by means of the modified Mosher's method. PMID:10820836

Arnone, A; Nasini, G; Vajna de Pava, O

2000-04-01

158

A Microwave Investigation of the Ionization of Hydrogen-Oxygen and Acetylene-Oxygen Flames  

Microsoft Academic Search

The ionization of premixed hydrogen-oxygen and acetylene-oxygen flames burning at atmospheric pressure was studied by a microwave method. The attenuation of electromagnetic radiation by the flames was employed to determine the free electron concentration. To obtain a high sensitivity for these measurements, a microwave bridge operating slightly off balance was employed, with the flames positioned between two electromagnetic horns in

Kurt E. Shuler; Joseph Weber

1954-01-01

159

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

Code of Federal Regulations, 2011 CFR

...Composition 1 is: (i) Maximum methyl acetylene to propadiene molar ratio of 3 to 1; (ii) Maximum combined concentration of...isobutane of 24 mole percent, of which at least one-third (on a molar basis) must be butanes and one-third propane; and...

2011-10-01

160

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

Code of Federal Regulations, 2014 CFR

...Composition 1 is: (i) Maximum methyl acetylene to propadiene molar ratio of 3 to 1; (ii) Maximum combined concentration of...isobutane of 24 mole percent, of which at least one-third (on a molar basis) must be butanes and one-third propane; and...

2014-10-01

161

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

Code of Federal Regulations, 2010 CFR

...Composition 1 is: (i) Maximum methyl acetylene to propadiene molar ratio of 3 to 1; (ii) Maximum combined concentration of...isobutane of 24 mole percent, of which at least one-third (on a molar basis) must be butanes and one-third propane; and...

2010-10-01

162

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

Code of Federal Regulations, 2013 CFR

...Composition 1 is: (i) Maximum methyl acetylene to propadiene molar ratio of 3 to 1; (ii) Maximum combined concentration of...isobutane of 24 mole percent, of which at least one-third (on a molar basis) must be butanes and one-third propane; and...

2013-10-01

163

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

Code of Federal Regulations, 2012 CFR

...Composition 1 is: (i) Maximum methyl acetylene to propadiene molar ratio of 3 to 1; (ii) Maximum combined concentration of...isobutane of 24 mole percent, of which at least one-third (on a molar basis) must be butanes and one-third propane; and...

2012-10-01

164

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

165

Broad spectral features in the stimulated emission pumping spectrum of acetylene  

SciTech Connect

The vibrational spectrumof acetylene is reported. This is the stimulat emission pumping spectrum obtained by stimulated downward transition from an upper electronic state to the ground electronic surface.Broad band and high resolution spectra were recorded at 25840-27250 wave numbers.(AIP)

Pique, J.P.; Engel, Y.M.; Levine, R.D.; Chen, Y.; Field, R.W.; Kinsey, J.L.

1988-05-01

166

Acetylene measurement in flames by chirp-based quantum cascade laser spectrometry.  

PubMed

We have designed and characterized a mid-IR spectrometer built around a pulsed distributed-feedback quantum cascade laser using the characteristic frequency down-chirp to scan through the spectral region 6.5 cm(-1) spectral region. The behavior of this chirp is extensively measured. The accuracy and detection limits of the system as an absorption spectrometer are demonstrated first by measuring spectra of acetylene through a single pass 16 cm absorption cell in real time at low concentrations and atmospheric pressure. The smallest detectable peak is measured to be approximately 1.5 x 10(-4) absorbance units, yielding a minimum detectable concentration length product of 2.4 parts per million meter at standard temperature and pressure. This system is then used to detect acetylene within an ethylene-air opposed flow flame. Measurements of acetylene content as a function of height above the fuel source are presented, as well as measurements of acetylene produced in fuel breakdown as a function of preinjection fuel temperature. PMID:19488121

Quine, Zachary R; McNesby, Kevin L

2009-06-01

167

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

EPA Science Inventory

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

168

The influence of collision and vibrational energy on the reaction with acetylene  

E-print Network

The influence of collision and vibrational energy on the reaction of CH3CHO¿ with acetylene Ho-Tae Kim, Jianbo Liu, and Scott L. Anderson Department of Chemistry, University of Utah, Salt Lake City, Utah 84112-0850 Received 22 January 2001; accepted 21 February 2001 Reaction of acetaldehyde cations

Anderson, Scott L.

169

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

NASA Technical Reports Server (NTRS)

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

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

2013-01-01

170

Growth of diamond films using an enclosed methyl-acetylene and propadiene combustion flame  

E-print Network

1 Growth of diamond films using an enclosed methyl-acetylene and propadiene combustion flame K Abstract Diamond growth in low pressure combustion flames was studied using a safer, more economical and chemical kinetic time scales in the combustion reactor. 1 Present Address: 3M Corporation, Bldg. 60-1N-01

Dandy, David

171

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

EPA Science Inventory

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

172

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

NASA Astrophysics Data System (ADS)

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

Manda, Abdullah Ahmed

173

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

174

Comment on ``The overtone spectrum of acetylene: A rotational analysis based on a local model description''a)  

Microsoft Academic Search

Many serious errors in the recent article ‘‘The overtone spectrum of acetylene: A rotational analysis based on a local model description’’ by Bryan R. Henry, M. Ali Mohammadi, and Allan W. Tarr [J. Chem. Phys. 77, 3295 (1982)] are discussed.

Kevin K. Lehmann; George J. Scherer; W. Klemperer

1983-01-01

175

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

176

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

177

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

SciTech Connect

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

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

1997-07-01

178

Low pressure R.F. plasma reactions in light hydrocarbons. Ethylene and acetylene  

NASA Astrophysics Data System (ADS)

The results obtained in the plasmolysis of ethylene and acetylene in an inductively coupled radiofrequency glow discharge are reported. A static system at a constant initial pressure of 0.5 torr and input power of 50 W was used; the gaseous and polymeric products were evaluated and compared with previous data on ethane plasmolysis and other available literature data. The decomposition products of ethylene were similar to those obtained during the plasmolysis of ethane, with a different distribution and a smaller initial increase of the total pressure. The total pressure of acetylene quickly decreased to near zero value at small specific energy, due to rapid polymerization. No gaseous products were detected, except hydrogen and traces of diacetylene.

Canepa, Pietro; Castello, Gianrico; Nicchia, Mario; Munari, Stelio

179

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

NASA Technical Reports Server (NTRS)

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

Walch, Stephen P.; Taylor, Peter R.

1995-01-01

180

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

SciTech Connect

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

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

1987-12-01

181

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

DOE PAGESBeta

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

182

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

PubMed

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

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

2015-04-27

183

Computational study of the thermal reaction rate between S +( 4S) and acetylene  

NASA Astrophysics Data System (ADS)

The thermal reaction between S +( 4S) and acetylene has been studied in the framework of the statistical theories in order to extract informations concerning its actual efficiency at different temperatures and bath gas densities. The results of the present work are in reasonable agreement with the available experimental data concerning both the efficiency and the generated products. The spin-forbidden paths have been also re-addressed and their actual role within the overall process, discussed.

Aschi, Massimiliano; Largo, Antonio

2001-04-01

184

Ions in fuel-rich and sooting acetylene and benzene flames  

Microsoft Academic Search

Mass spectrometric measurements of flame ion concentration profiles have been made in low pressure rich and sooting acetylene\\/oxygen and benzene\\/oxygen flames. As both flames are made richer and approach sooting the predominant ion CâHâ\\/sup +\\/ is replaced by large positive aromatic ions with mass greater than 300. The profile of these ions corresponds with a previously identified class of ''soot

D. B. Olson; H. F. Calcote

1981-01-01

185

Electrochemical polymerization of acetylene on Rh electrodes probed by surface-enhanced Raman spectroscopy  

Microsoft Academic Search

By combining cyclic voltammetry (CV) and surface-enhanced Raman spectroscopy (SERS), the electrochemical behaviors of acetylene (C2H2) on a roughened Rh electrode in 0.1M HClO4 solution were studied. On both roughened and smooth Rh surfaces, a clear loop in the cyclic voltammogram was observed in the negative potential region, indicating the formation of a new phase. However, only on the roughened

Guo-kun Liu; Bin Ren; De-yin Wu; Jian-ming Lin; Ren-ao Gu; Zhong-qun Tian

2006-01-01

186

Use of hydrotalcites as catalytic precursors of multimetallic mixed oxides. Application in the hydrogenation of acetylene  

Microsoft Academic Search

The effect of the Ni\\/Zn molar ratio on the activity, selectivity, and coke formation of NiO·ZnO·Al2O3 catalysts (modified with Fe3+ or Cr3+) during acetylene hydrogenation has been studied. Coke formation is decreased significantly in the presence of ZnO, and a similar effect is also found when the catalysts are doped with Cr3+ instead of with Fe3+. An optimum Ni\\/Zn ratio

A. Monzón; E. Romeo; C. Royo; R. Trujillano; F. M. Labajos; V. Rives

1999-01-01

187

Synthesis and characterization of turbostratic carbons prepared by catalytic chemical vapour decomposition of acetylene  

Microsoft Academic Search

The turbostratic mesoporous carbon blacks were prepared by catalytic chemical vapour decomposition (CCVD) of acetylene using Ni\\/MgO catalysts prepared by co-precipitation. The relationship between deposition conditions and the nanostructures of resultant carbon black materials was investigated. It was found that the turbostratic and textural structures of carbon blacks are dependent on the deposition temperature and nickel catalyst loading. Higher deposition

Li Li; Z. H. Zhu; G. Q. Lu; Z. F. Yan; R. De Marco

2006-01-01

188

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

Microsoft Academic Search

Catalytic chemical vapor deposition was used to grow multi-walled carbon nanotubes on a Fe:Co:CaCO3 catalyst from acetylene. The influent and effluent gases were analyzed by gas chromatography and mass spectrometry at different time intervals during the nanotubes growth process in order to better understand and optimize the overall reaction. A large number of byproducts were identified and it was found

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

2006-01-01

189

Controlled degradation and crosslinking of polypropylene induced by gamma radiation and acetylene  

Microsoft Academic Search

Isotactic polypropylene (iPP) undergoes crosslinking and extensive main chain scissions when submitted to irradiation. The\\u000a simultaneous irradiation of PP and acetylene is able to control chain scission and produce grafting. The grafted PP further\\u000a reacts with PP radicals resulting in branching and crosslinking. In this work, commercial polypropylenes (iPP) of different\\u000a molecular weights were irradiated with a 60Co source at

Adriana Yoshiga; Harumi Otaguro; Duclerc Fernandes Parra; Luís Filipe C. P. Lima; Ademar B. Lugao

2009-01-01

190

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

PubMed

A new full-dimensional global potential energy surface (PES) for the acetylene-vinylidene isomerization on the ground (S0) electronic state has been constructed by fitting ?37,000 high-level ab initio points using the permutation invariant polynomial-neural network method with a root mean square error of 9.54 cm(-1). The geometries and harmonic vibrational frequencies of acetylene, vinylidene, and all other stationary points (two distinct transition states and one secondary minimum in between) have been determined on this PES. Furthermore, acetylene vibrational energy levels have been calculated using the Lanczos algorithm with an exact (J = 0) Hamiltonian. The vibrational energies up to 12,700 cm(-1) above the zero-point energy are in excellent agreement with the experimentally derived effective Hamiltonians, suggesting that the PES is approaching spectroscopic accuracy. In addition, analyses of the wavefunctions confirm the experimentally observed emergence of the local bending and counter-rotational modes in the highly excited bending vibrational states. The reproduction of the experimentally derived effective Hamiltonians for highly excited bending states signals the coming of age for the ab initio based PES, which can now be trusted for studying the isomerization reaction. PMID:25554156

Han, Huixian; Li, Anyang; Guo, Hua

2014-12-28

191

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

PubMed Central

The final step of the methylerythritol phosphate isoprenoid biosynthesis pathway is catalysed by the iron–sulphur enzyme IspH, producing the universal precursors of terpenes: isopentenyl diphosphate and dimethylallyl diphosphate. Here we report an unforeseen reaction discovered during the investigation of the interaction of IspH with acetylene inhibitors by X-ray crystallography, Mößbauer, and nuclear magnetic resonance spectroscopy. In addition to its role as a 2H+/2e? reductase, IspH can hydrate acetylenes to aldehydes and ketones via anti-Markovnikov/Markovnikov addition. The reactions only occur with the oxidised protein and proceed via ?1-O-enolate intermediates. One of these is characterized crystallographically and contains a C4 ligand oxygen bound to the unique, fourth iron in the 4Fe-4S cluster: this intermediate subsequently hydrolyzes to produce an aldehyde product. This unexpected side to IspH reactivity is of interest in the context of the mechanism of action of other acetylene hydratases, as well as in the design of antiinfectives targeting IspH. PMID:22948824

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

2013-01-01

192

Chemiionization and ion-molecule reactions in fuel-rich acetylene flames  

SciTech Connect

The objective of this study is to model the appearance and behavior of combustion-generated ions in rich flames of acetylene. A one-dimensional, laminar, flat flame of acetylene was developed that combines reactions for oxidation, pyrolysis, chemiionization, proton transfer, ion-molecule reactions, and charge recombination relevant to rich acetylene combustion. Four possible chemiionization reactions are included in the model. Ions other than CHO/sup +/ and C/sub 3/H/sub 3//sup +/ are assumed to form by proton transfer or by a series of ion-molecule reactions. The proposed model predicts total ion concentrations reasonably well over a wide range of stoichiometries. Total ion concentrations are very sensitive to the rate of the CH/sup */ + O chemiionization reaction. The dominant ion, C/sub 3/H/sub 3//sup +/, is found to be produced from CHO/sup +/ by ion-molecule reactions rather than by direct chemiionization. Computations show that only a limited number of ionic reactions are equilibrated in the flames. The ratio of large ions to small ions is predicted to increase sharply as the critical equivalence ratio for soot formation is approached.

Eraslan, A.N. (Dept. of Chemical Engineering, Iowa State Univ., Ames, IA (US)); Brown, R.C. (Dept. of Mechanical Engineering, Iowa State Univ., Ames, IA (US))

1988-10-01

193

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

NASA Astrophysics Data System (ADS)

A new full-dimensional global potential energy surface (PES) for the acetylene-vinylidene isomerization on the ground (S0) electronic state has been constructed by fitting ˜37 000 high-level ab initio points using the permutation invariant polynomial-neural network method with a root mean square error of 9.54 cm-1. The geometries and harmonic vibrational frequencies of acetylene, vinylidene, and all other stationary points (two distinct transition states and one secondary minimum in between) have been determined on this PES. Furthermore, acetylene vibrational energy levels have been calculated using the Lanczos algorithm with an exact (J = 0) Hamiltonian. The vibrational energies up to 12 700 cm-1 above the zero-point energy are in excellent agreement with the experimentally derived effective Hamiltonians, suggesting that the PES is approaching spectroscopic accuracy. In addition, analyses of the wavefunctions confirm the experimentally observed emergence of the local bending and counter-rotational modes in the highly excited bending vibrational states. The reproduction of the experimentally derived effective Hamiltonians for highly excited bending states signals the coming of age for the ab initio based PES, which can now be trusted for studying the isomerization reaction.

Han, Huixian; Li, Anyang; Guo, Hua

2014-12-01

194

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

195

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

PubMed

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

Comandini, A; Malewicki, T; Brezinsky, K

2012-03-15

196

Spectroscopic and dynamical studies of acetylene and hydrogen cyanide: S/sub 0/ surfaces, unstable isomers, and triplet states: Final technical report  

SciTech Connect

Progress is reported in the following areas of research: statistical properties of C/sub 2/H/sub 2/ spectra in the 28,000 cm/sup -1/ region; properties of C/sub 2/H/sub 2/ X-bar ..sigma../sub g//sup +/ levels in the 11,400-15,600 cm/sup -1/ region; a spectroscopic study of the acetylene-vinylidene isomerization; an unsuspected Fermi perturbation in the acetylene A-bar 'Au 3..nu../sub 3/ level; acetylene quantum beats and anticrossing spectroscopy; and unimolecular decomposition of acetylene; determination of the heat of formation of the CCH radical. (PLG)

Kinsey, J.L.; Field, R.W.

1987-01-01

197

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

NASA Astrophysics Data System (ADS)

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

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

2011-05-01

198

Polycyclic propargylamine and acetylene derivatives as multifunctional neuroprotective agents.  

PubMed

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

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

2014-06-10

199

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

200

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

201

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

202

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

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

203

Poly(acetylene) as a positive electrode in lithium sulfur oxyhalide cells  

NASA Astrophysics Data System (ADS)

Conductive poly(acetylene) film was employed as the positive electrode in primary lithium/thionyl chloride and lithium/sulfuryl chloride cells. Neutral (CH)x, doped to the metallic state upon in situ exposure to LiAlCl4/sulfur oxyhalide electrolytes, acts as a catalytic surface rather than as the active electrochemical element. Sulfur oxyhalides were reduced on(CH)x film at high rates as on PTFE-bonded Shawinigan carbon black felt. Electrode capacity was limited by the inability of the electrolyte to permeate the (CH)x film and the formation of a surface passive filmby discharge products.

Calvert, Jeffrey M.; Weiner, Bryndyn; Smith, Jerry J.; Nowak, Robert J.

1989-03-01

204

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

205

Excitation spectroscopy of the acetylene A--X transition in the 220 nm wavelength region  

SciTech Connect

The fluorescence excitation spectrum of the A /sup 1/A/sub u/--X /sup 1/..sigma../sup +//sub g/ transition of acetylene has been examined in the 220 nm wavelength region. Sharp lines were observed at frequencies that agree with earlier studies using absorption spectroscopy, and most lines previously reported as blended were well resolved. Time-resolved fluorescent decays following excitation in four of the peaks revealed suprisingly long lifetimes (2--5 ..mu..s in the low-pressure limit). Two of the levels exhibited modulation in their fluorescent decays.

Abramson, E.; Kittrell, C.; Kinsey, J.L.; Field, R.W.

1982-03-01

206

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

207

HCN formation on Jupiter - The coupled photochemistry of ammonia and Acetylene  

NASA Technical Reports Server (NTRS)

HCN formation in the upper troposphere and lower stratosphere of Jupiter is presently modeled in terms of UV pyrolysis of the C2H5N isomer aziridine, which is a product of the NH2 and C2H3 radicals that originate from ammonia photolysis and the addition of H atoms to acetylene, respectively. The sensitivity of the HCN column density to the individual rate constants and the eddy diffusion coefficient profile is considered, along with the possibility that additional HCN-yielding pathways may exist. Both ammonia and phosphine are strongly depleted by photolysis.

Kaye, J. A.; Strobel, D. F.

1983-01-01

208

CHINESE JOURNAL OF CHEMICAL PHYSICS VOLUME 21, NUMBER 5 OCTOBER 27, 2008 High-resolution Absorption Spectra of Acetylene in 142.8-152.3 nm  

E-print Network

syn- chrotron radiation as a light source [17,20,23]. More ac- curate absorption cross sections were to understand the photo- chemical behavior of acetylene in these cases. Moreover, acetylene is a very common) The ionization potential energy was measured by a later photoionization experiment [32]. Subsequently, Wilkin

Liu, Shilin

209

Potential Application of Nonstructural Protein NS1 Serotype-Specific Immunoglobulin G Enzyme-Linked Immunosorbent Assay in the Seroepidemiologic Study of Dengue Virus Infection: Correlation of Results with Those of the Plaque Reduction Neutralization Test  

Microsoft Academic Search

An NS1 serotype-specific indirect enzyme-linked immunosorbent assay (ELISA) was developed to differen- tiate primary and secondary dengue virus infections and serotypes of primary dengue virus infection. For this report, we carried out retrospective seroepidemiologic studies on serum samples collected from residents of Liuchiu Hsiang, Pingtung County, an isolated island in southern Taiwan during 1997-1998. The results demonstrated that good correlation

Pei-Yun Shu; Li-Kuang Chen; Shu-Fen Chang; Yi-Yun Yueh; Ling Chow; Li-Jung Chien; Chuan Chin; Hui-Hua Yang; Ting-Hsiang Lin; Jyh-Hsiung Huang

2002-01-01

210

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.

211

A DFT + U study of acetylene selective hydrogenation over anatase supported PdaAgb (a + b = 4) cluster.  

PubMed

It is well known that the addition of Ag into Pd can promote the selectivity of acetylene hydrogenation to ethylene, and early theoretical studies focus on ideal single crystal model catalysts, so it is worth studying relatively realistic catalyst models, such as metal oxide supported PdAg systems. In this work, the reaction mechanisms for acetylene selective hydrogenation on the anatase TiO2(101) supported PdaAgb (a + b = 4) cluster are studied by density functional theory calculations with a Hubbard U correction. The results show that Ag addition to the Pd4 cluster reduces the interaction between the PdAg cluster and the support, and the possible reason is that the amount of electron transfer from the TiO2 support to the PdAg cluster decreases with increasing number of Ag atoms. Consequently the adsorption energies of acetylene and ethylene would become smaller on the anatase supported PdAg cluster as compared to that on the anatase supported Pd4 cluster, and this may help to enhance the selectivity of ethylene formation. Moreover, the reaction kinetics study of acetylene hydrogenation on anatase TiO2(101) supported PdAg cluster shows that the activation energy of the hydrogenation step is higher on the PdAg cluster than that on the pure Pd4 cluster, and thus reduces its catalytic activity. Importantly, the present calculation results suggested that the selectivity of ethylene formation, which is defined as the energy difference between the adsorption energy of ethylene and the barrier for its further hydrogenation, varies with the ratio of Pd/Ag in the PdAg cluster: the Pd3Ag system shows relatively low selectivity compared to that of the pure Pd4 cluster, whereas Pd2Ag2/PdAg3 displays higher selectivity than that of the pure Pd4 cluster. Furthermore, our present results demonstrated that the anatase support plays a key role in the acetylene hydrogenation processes: on one hand, it reduces the reaction activity of acetylene hydrogenation processes compared to the Pd2Ag2/Pd(111) and Pd2Ag2 clusters; on the other hand, it enhances the selectivity of ethylene due to its lower desorption energy. It was also found that the carbon species inside the Pd2Ag2 cluster has little effect on the catalytic selectivity towards ethylene formation, whereas the hydrogenation catalytic activity is enhanced significantly. Finally the role of the Pd2Ag2-anatase interface on the catalytic properties of acetylene hydrogenation was studied, and it was found that the interface can increase the activity of acetylene hydrogenation but the selectivity is not improved. PMID:25026216

Meng, Ling-Dong; Wang, Gui-Chang

2014-09-01

212

DC Protein Assay Instruction  

E-print Network

DC Protein Assay Instruction Manual For Technical Service Call Your Local Bio-Rad Office and Principle The Bio-Rad DC Protein Assay is a colorimetric assay for protein concen- tration following preparation Spectrophotometer set to 750 nm 1 #12;Vortex mixer Plastic or glass cuvettes with 1 cm path length

Lebendiker, Mario

213

Length Dependence of Ionization Potentials of Trans-Acetylenes: Internally-Consistent DFT/GW Approach  

E-print Network

We follow the evolution of the Ionization Potential (IP) for the paradigmatic quasi-one-dimensional trans-acetylene family of conjugated molecules, from short to long oligomers and to the infinite polymer trans-poly-acetylene (TPA). Our results for short oligomers are very close to experimental available data. We find that the IP varies with oligomer length and converges to the given value for TPA with a smooth, coupled inverse-length-exponential behavior. Our prediction is based on an "internally-consistent" scheme to adjust the exchange mixing parameter $\\alpha$ of the PBEh hybrid density functional, so as to obtain a description of the electronic structure consistent with the quasiparticle approximation for the IP. This is achieved by demanding that the corresponding quasiparticle correction, in the GW@PBEh approximation, vanishes for the IP when evaluated at PBEh($\\alpha^{ic}$). We find that $\\alpha^{ic}$ is also system-dependent and converges with increasing oligomer length, allowing to capture the depen...

Pinheiro, Max; Rinke, Patrick; Blum, Volker; Scheffler, Matthias

2015-01-01

214

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.

215

Cryospectroscopic and ab initio anharmonic studies of acetylene-trimethylamine H-bonded complex  

NASA Astrophysics Data System (ADS)

The FTIR spectra of C 2H 2 in mixtures with trimethylamine (TMA) have been studied in liquefied Kr in the frequency range of ˜800-7000 cm -1. The data obtained for C 2H 2 subunit suggest the formation of 1:1 complexes stabilized by a moderate strength conventional H-bond. CH and CN stretching vibrations, related to the vicinal bonds of proton acceptor, were found to shift in opposite directions - blue in the former and red in the latter case. New weak bands, revealed in the range of ˜6000-7000 cm -1, were ascribed to the overtone and combination bands of C sbnd H stretching vibrations of acetylene which participates in the H-bond formation. The relative stability of the complex has been determined in a series of temperature ( T = 118-157 K) measurements of integrated intensities of vibrational bands ascribed to monomer and complex species. Ab initio MP2/6-311++G(2d,2p) a priory counterpoise corrected calculations, made for acetylene, TMA, and the complex reproduce the main spectroscopic observations. They suggest that the most stable non-linear structure of the complex is very floppy. Evaluations of anharmonic effects on position and integrated intensity of selected bands of C sbnd H stretching modes of C 2H 2 subunit have been made within perturbation theory on the basis of single point potential energy surface (PES) and dipole moment function calculations.

Rutkowski, K. S.; Melikova, S. M.; Janski, J.; Koll, A.

2010-09-01

216

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

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

217

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

218

266 Langmuir 1986,2, 266-281 acetylene dose due to the high supply of hydrogen.  

E-print Network

266 Langmuir 1986,2, 266-281 acetylene dose due to the high supply of hydrogen. Moreover, methane fragments. This observation clearly points to a Langmuir-Hinshelwood mechanism. The fact that methane the fragments react to deuterated methanes and ethanes (amu 26-36) corresponding to a Langmuir

Prentiss, Mara

219

[Characteristics of effects of acetylene amino alcohols M-cholinoreceptor blockers on the dopaminergic system in Daphnia magna].  

PubMed

Haloperidol and dimethpromide exhibit the properties of dopamine antagonists in the experiments on Daphnia magna Straus (Crustaceae family). Haloperidol, in contrast to dimethpromide, does not significantly influence the toxic effect of apomorphine. It is suggested that acetylene aminoalcohol derivatives are selective ligands for one of the subtypes of dopamine receptors. PMID:11202502

Kosmachev, A B; Tonkopi?, V D; Podosinovikova, N P; Zagrebin, A O; Evdokimova, E A; Libman, N M; Petrov, V V; Dolgo-Saburov, V B

2000-01-01

220

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

221

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

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

222

TiO2 supported Pd@Ag as highly selective catalysts for hydrogenation of acetylene in excess ethylene.  

PubMed

A novel TiO2 supported core-shell (Pd@Ag) bimetallic catalyst was fabricated via the sequential photodeposition method. The Ag shell effectively blocks the high coordination sites on the Pd core, and therefore pronouncedly enhances the ethylene selectivity for the catalytic hydrogenation of acetylene in excess ethylene. PMID:23929310

Han, Yuxiang; Peng, Du; Xu, Zhaoyi; Wan, Haiqin; Zheng, Shourong; Zhu, Dongqiang

2013-09-28

223

Photodestruction of PAHs in the interstellar medium. I. Photodissociation rates for the loss of an acetylenic group  

Microsoft Academic Search

We have developed a model for interstellar polycyclic aromatic hydrocarbons (PAHs) in order to estimate their rate of photodissociation in the interstellar medium. These photo-reactions include the loss of atomic and molecular hydrogen and the loss of the acetylene molecule. We have studied the stability of PAHs in the regions of high UV radiation where the infrared emission bands attributed

T. Allain; S. Leach; E. Sedlmayr

1996-01-01

224

Rhodium(III)-catalyzed C-H activation/annulation with vinyl esters as an acetylene equivalent.  

PubMed

The behavior of electron-rich alkenes in rhodium-catalyzed C-H activation/annulation reactions is investigated. Vinyl acetate emerges as a convenient acetylene equivalent, facilitating the synthesis of sixteen 3,4-unsubstituted isoquinolones, as well as select heteroaryl-fused pyridones. The complementary regiochemical preferences of enol ethers versus enol esters/enamides is discussed. PMID:25165993

Webb, Nicola J; Marsden, Stephen P; Raw, Steven A

2014-09-19

225

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

NASA Technical Reports Server (NTRS)

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

Walch, Stephen P.

1995-01-01

226

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

227

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

228

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

229

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

230

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

NASA Technical Reports Server (NTRS)

Mar Vel Black is a revolutionary new extremely low reflectivity anodized coating developed by Martin Marietta of Denver. It is of great interest in optics in general, and in star trackers specifically because it can reduce extraneous light reflections. A sample of Mar Vel Black was evaluated. Mar Vel Black looks much like a super black surface with many small peaks and very steep sides so that any light incident upon the surface will tend to reflect many times before exiting that surface. Even a high reflectivity surface would thus appear to have a very low reflectivity under such conditions. Conversely, acetylene soot does not have the magnified surface appearance of a super black surface. Its performance is, however, predictable from the surface structure, considering the known configuration of virtually pure carbon.

Yung, E.

1974-01-01

231

Selective synthesis of double-wall carbon nanotubes by CCVD of acetylene using zeolite supports  

NASA Astrophysics Data System (ADS)

Double-wall carbon nanotubes (DWNTs) have been synthesized in high-yield (>80%) by catalytic chemical vapor deposition (CCVD) of acetylene over well- dispersed metal particles (typically Co/Fe binary system) embedded in heat-resistant zeolites at temperatures above 900 °C. The synthetic yield of DWNTs has been sensitively affected by reaction conditions of the CCVD such as zeolite support materials, the sintering of the metal particles, hydrocarbon sources and reaction temperatures. High-resolution transmission electron microscopy together with Raman spectroscopy shows that the outer tube diameter varies from 3 to 6 nm with inner-outer tube separations of 0.36-0.37 nm, which is much larger than the interlayer distance of graphite (0.335 nm).

Hiraoka, Tatsuki; Kawakubo, Tomoju; Kimura, Junichi; Taniguchi, Risa; Okamoto, Atsuto; Okazaki, Toshiya; Sugai, Toshiki; Ozeki, Yuji; Yoshikawa, Masahito; Shinohara, Hisanori

2003-12-01

232

Efficient diode-pumped mid-infrared emission from acetylene-filled hollow-core fiber.  

PubMed

We report 3.1-3.2 ?m mid-infrared emission from acetylene-filled low loss antiresonant hollow-core fiber pumped with an amplified, modulated, narrowband, tunable 1.5 ?m diode laser. The maximum power conversion efficiency of ~30%, with respect to the absorbed pump power, is obtained with a 10.5 m length of fiber at 0.7 mbar. The maximum efficiency with respect to the total incident pump power (~20%) and the minimum pump laser energy required (<50 nJ) are both improved compared to similar work reported previously using an optical parametric oscillator as a pump source. This paper provides an effective route to obtain compact mid-infrared fiber lasers. PMID:25321562

Wang, Zefeng; Belardi, Walter; Yu, Fei; Wadsworth, William J; Knight, Jonathan C

2014-09-01

233

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

234

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

235

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

NASA Technical Reports Server (NTRS)

The impact of thermodynamic parameters on the sensitivity of model predictions of soot formation by shock-tube pyrolysis of acetylene were assessed analytically. The pyrolysis process was treated as having three components: initiation, the initial pyrolysis stages; cyclization, formation of larger molecules and radicals and small aromatic molecules; and polymerization, further growth of aromatic rings. Rate equations are reviewed for each component. Thermodynamic effects were assessed by varying the C2H-H and C2H3-H bond energies and the Ct-(Ct) group additivity value. Any change in the C2H-H bond energy had a significant impact on the temperature and the maximum amount of the soot yield. The findings underscore the necessity of using accurate thermodynamic data for modeling high-temperature chemical kinetics.

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

1986-01-01

236

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

PubMed Central

We report on an experimental approach that reveals crucial details of the composition of singlet-triplet mixed eigenstates in acetylene. Intersystem crossing in this prototypical polyatomic molecule embodies the mixing of the lowest excited singlet state (S1) with 3 triplet states (T1, T2, and T3). Using high-energy (157-nm) photons from an F2 laser to record excited-state photoelectron spectra, we have decomposed the mixed eigenstates into their S1, T3, T2, and T1 constituent parts. One example of the interpretive power that ensues from the selective sensitivity of the experiment to the individual electronic state characters is the discovery and examination of destructive interference between two doorway-mediated intersystem crossing pathways. This observation of an interference effect in nonradiative decay opens up possibilities for rational coherent control over molecular excited state dynamics. PMID:19179288

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

2009-01-01

237

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

238

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

239

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

PubMed

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

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

2014-01-01

240

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

PubMed

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

da Silva, Gabriel; Bozzelli, Joseph W

2009-08-01

241

Reaction of ketenyl radical with acetylene: a promising route for cyclopropenyl radical.  

PubMed

The reaction of the ketenyl radical (HCCO) with acetylene (C(2)H(2)) is very relevant to the oxygen-acetylene flames and fuel-rich combustion process for nitrogen-containing compounds. Unfortunately, except for several rate constant measurements, the mechanism is completely unknown for this reaction. In this paper, detailed theoretical investigations are performed for the HCCO + C(2)H(2) reaction at the G3B3 level using the B3LYP/6-31G(d), B3LYP/6-311++G(d,p), and QCISD/6-31G(d) geometries. The exclusive fragmentation channel is the formation of the cyclopropenyl radical (c-C(3)H(3)) and carbon monoxide (CO) via the chainlike OCCHCHCH and three-membered ring OC-cCHCHCH intermediates. Thus, the mass spectroscopic peak of C(3)H(3)(+) in a previous experiment can be explained. The calculated overall reaction barrier is 4.4, 4.4, and 5.3 kcal/mol at the G3B3//B3LYP/6-31G(d), G3B3//B3LYP/6-311++G(d,p), and G3B3//QCISD/6-31G(d) levels, respectively. The title reaction may provide an effective route for generating the long-sought cyclopropenyl radical in the laboratory, which has been the long-standing subject of numerous theoretical studies as the simplest cyclic conjugate radical, and its bulky derivatives were already known. Future experimental investigations for the HCCO + C(2)H(2) reaction are greatly desired to test the predicted fragmentation channel. The implication of the present study in combustion and interstellar processes is discussed. PMID:16737278

Xie, Hong-bin; Ding, Yi-hong; Sun, Chia-chung

2006-06-01

242

Diagnostic assays used to control small ruminant lentiviruses  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

243

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

E-print Network

is building which indicates that the symbiotic relationship between many fungi and roots of h1gher plants, a relationship referred to as mycorrh1zae (literally, "fungus root"), is instrumental in enhancing the uptake of many nutrients, particular- ly...

Sherrod, Carole Cay

1983-01-01

244

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

PubMed Central

Seasonal distribution of nitrogen fixation by Spartina alterniflora epiphytes and in surface and soil samples was investigated in a Georgia salt marsh which was amended with sewage sludge or with glucose and/or ammonium nitrate. There was no significant difference between the rates of fixation in the unamended and sewage sludge plots. Additional perturbation experiments suggested that nitrogen addition indirectly stimulates nitrogen fixation by enhancing Spartina production and root exudation. Glucose additions, on the other hand, suppressed nitrogen fixation on a long-term basis. It is suggested that the microbial population in the soil out-competed the plants for the available nitrogen and in turn suppressed plant production and possibly root exudation. A comparison of nitrogen fixation in clipped and unclipped Spartina plots substantiated the suggestion that root exudation probably supports nitrogen fixation. Fixation in the clipped plots was significantly lower (P < 0.05) than the rates in the unclipped plots. PMID:16345239

Hanson, Roger B.

1977-01-01

245

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

246

Rapid mercury assays  

SciTech Connect

We have developed rapid assays with the potential of detecting mercury in environmental samples. our methods combine the simple ELISA-format with the selective, high affinity complexation of mercuric ions by sulfur-containing ligands. The first assay is based on a sandwich chelate formed by a protein-bound ligand immobilized on the wells of a microliter plate, mercuric ion of the analyzed sample, and another ligand conjugated to a reporter enzyme. The second assay involves competition between mercuric ions and an organomercury-conjugate to bind to a chelating conjugate. Several sulfur containing chelators (e.g., dithiocarbamates) and organomercurials linked to macromolecular carriers have been investigated in these assay formats. The assays detect mercuric ions in ppb/high ppt concentrations with high selectivity.

Szurdoki, S.; Kido, H.; Hammock, B.D. [Univ. of California, Davis, CA (United States)

1996-10-01

247

CPTAC Assay Portal: a repository of targeted proteomic assays  

SciTech Connect

To address these issues, the Clinical Proteomic Tumor Analysis Consortium (CPTAC) of the National Cancer Institute (NCI) has launched an Assay Portal (http://assays.cancer.gov) to serve as a public repository of well-characterized quantitative, MS-based, targeted proteomic assays. The purpose of the CPTAC Assay Portal is to facilitate widespread adoption of targeted MS assays by disseminating SOPs, reagents, and assay characterization data for highly characterized assays. A primary aim of the NCI-supported portal is to bring together clinicians or biologists and analytical chemists to answer hypothesis-driven questions using targeted, MS-based assays. Assay content is easily accessed through queries and filters, enabling investigators to find assays to proteins relevant to their areas of interest. Detailed characterization data are available for each assay, enabling researchers to evaluate assay performance prior to launching the assay in their own laboratory.

Whiteaker, Jeffrey R.; Halusa, Goran; Hoofnagle, Andrew N.; Sharma, Vagisha; MacLean, Brendan; Yan, Ping; Wrobel, John; Kennedy, Jacob; Mani, DR; Zimmerman, Lisa J.; Meyer, Matthew R.; Mesri, Mehdi; Rodriguez, Henry; Abbateillo, Susan E.; Boja, Emily; Carr, Steven A.; Chan, Daniel W.; Chen, Xian; Chen, Jing; Davies, Sherri; Ellis, Matthew; Fenyo, David; Hiltket, Tara; Ketchum, Karen; Kinsinger, Christopher; Kuhn, Eric; Liebler, Daniel; Lin, De; Liu, Tao; Loss, Michael; MacCoss, Michael; Qian, Weijun; Rivers, Robert; Rodland, Karin D.; Ruggles, Kelly; Scott, Mitchell; Smith, Richard D.; Thomas, Stefani N.; Townsend, Reid; Whiteley, Gordon; Wu, Chaochao; Zhang, Hui; Zhang, Zhen; Paulovich, Amanda G.

2014-06-27

248

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

249

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

PubMed

Separation of acetylene and ethylene is an important industrial process because both compounds are essential reagents for a range of chemical products and materials. Current separation approaches include the partial hydrogenation of acetylene into ethylene over a supported Pd catalyst, and the extraction of cracked olefins using an organic solvent; both routes are costly and energy consuming. Adsorption technologies may allow separation, but microporous materials exhibiting highly selective adsorption of C(2)H(2)/C(2)H(4) have not been realized to date. Here, we report the development of tunable microporous enantiopure mixed-metal-organic framework (M'MOF) materials for highly selective separation of C(2)H(2) and C(2)H(4). The high selectivities achieved suggest the potential application of microporous M'MOFs for practical adsorption-based separation of C(2)H(2)/C(2)H(4). PMID:21343922

Xiang, Sheng-Chang; Zhang, Zhangjing; Zhao, Cong-Gui; Hong, Kunlun; Zhao, Xuebo; Ding, De-Rong; Xie, Ming-Hua; Wu, Chuan-De; Das, Madhab C; Gill, Rachel; Thomas, K Mark; Chen, Banglin

2011-01-01

250

Photodestruction of PAHs in the interstellar medium. I. Photodissociation rates for the loss of an acetylenic group.  

NASA Astrophysics Data System (ADS)

We have developed a model for interstellar polycyclic aromatic hydrocarbons (PAHs) in order to estimate their rate of photodissociation in the interstellar medium. These photo-reactions include the loss of atomic and molecular hydrogen and the loss of the acetylene molecule. We have studied the stability of PAHs in the regions of high UV radiation where the infrared emission bands attributed to PAHs are observed (reflection nebulae, planetary nebulae, active galactic nuclei, HII regions...) by comparing the rate of acetylene loss to the rate of accretion of carbon to PAHs. This comparison shows that only PAHs with more than 50 carbon atoms may survive the UV radiation field of these regions, whereas smaller PAHs such as coronene or ovalene are destroyed within a few years.

Allain, T.; Leach, S.; Sedlmayr, E.

1996-01-01

251

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.

252

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

253

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

254

Tracking hole localization in K -shell and core-valence-excited acetylene photoionization via body-frame photoelectron angular distributions  

NASA Astrophysics Data System (ADS)

Asymmetry in the molecular-frame photoelectron angular distributions from core-hole- or core-valence-excited polyatomic targets with symmetry-equivalent atoms can provide direct evidence for core-hole localization. Using acetylene as an example, we contrast the small asymmetry that can be seen in direct core-level ionization, due to the competition between two competing pathways to the continuum, with ionization from core-valence-excited HCCH, which offers the prospect of observing markedly greater asymmetry.

Rescigno, T. N.; Trevisan, C. S.; McCurdy, C. W.

2015-02-01

255

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

256

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

257

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

Microsoft Academic Search

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

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

2008-01-01

258

Rotational and Vibrational Energy Transfer from the First Overtone Strech of Acetylene  

NASA Astrophysics Data System (ADS)

Gas lasers that are optically pumped by solid state devices are currently being considered for applications that require high powers and high beam quality. Optical pumping in the 1-2 ?m region is of interest as there are efficient diode laser sources that operate in this spectral range. An optically pumped C_2H_2 laser was recently demonstrated by Wolfgang et al. at the University of New Mexico. Excitation of the CH overtone transition (v_C_H=2) at 1.52 ?m yielded lasing on an asymmetric stretch combination band centered at 3.1 ?m. Collisional energy transfer data for the v_C_H=2 level is needed for analysis and modeling of the laser performance. Although there have been numerous studies of energy transfer for vibrationally excited acetylene, the v_C_H=2 level has received very little attention. We are currently examining state-to-state ro-vibrational energy transfer processes for v_C_H=2 in self-collisions using a pulsed IR pump- UV probe technique. Pure rotational transfer has been characterized and rapid vibrational transfer has also been observed. Identification of the collisionally populated vibrational levels and measurements of the transfer rate constants are in progress.

Heaven, M. C.; Han, Jiande; Freel, Keith

2010-06-01

259

Assaying hematopoiesis using zebrafish.  

PubMed

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

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

2013-12-01

260

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

EPA Science Inventory

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

261

Clonogenic Assay: Adherent Cells  

PubMed Central

The clonogenic (or colony forming) assay has been established for more than 50 years; the original paper describing the technique was published in 19561. Apart from documenting the method, the initial landmark study generated the first radiation-dose response curve for X-ray irradiated mammalian (HeLa) cells in culture1. Basically, the clonogenic assay enables an assessment of the differences in reproductive viability (capacity of cells to produce progeny; i.e. a single cell to form a colony of 50 or more cells) between control untreated cells and cells that have undergone various treatments such as exposure to ionising radiation, various chemical compounds (e.g. cytotoxic agents) or in other cases genetic manipulation. The assay has become the most widely accepted technique in radiation biology and has been widely used for evaluating the radiation sensitivity of different cell lines. Further, the clonogenic assay is commonly used for monitoring the efficacy of radiation modifying compounds and for determining the effects of cytotoxic agents and other anti-cancer therapeutics on colony forming ability, in different cell lines. A typical clonogenic survival experiment using adherent cells lines involves three distinct components, 1) treatment of the cell monolayer in tissue culture flasks, 2) preparation of single cell suspensions and plating an appropriate number of cells in petri dishes and 3) fixing and staining colonies following a relevant incubation period, which could range from 1-3 weeks, depending on the cell line. Here we demonstrate the general procedure for performing the clonogenic assay with adherent cell lines with the use of an immortalized human keratinocyte cell line (FEP-1811)2. Also, our aims are to describe common features of clonogenic assays including calculation of the plating efficiency and survival fractions after exposure of cells to radiation, and to exemplify modification of radiation-response with the use of a natural antioxidant formulation. PMID:21445039

Rafehi, Haloom; Orlowski, Christian; Georgiadis, George T.; Ververis, Katherine; El-Osta, Assam; Karagiannis, Tom C.

2011-01-01

262

Clonogenic assay: adherent cells.  

PubMed

The clonogenic (or colony forming) assay has been established for more than 50 years; the original paper describing the technique was published in 1956. Apart from documenting the method, the initial landmark study generated the first radiation-dose response curve for X-ray irradiated mammalian (HeLa) cells in culture. Basically, the clonogenic assay enables an assessment of the differences in reproductive viability (capacity of cells to produce progeny; i.e. a single cell to form a colony of 50 or more cells) between control untreated cells and cells that have undergone various treatments such as exposure to ionising radiation, various chemical compounds (e.g. cytotoxic agents) or in other cases genetic manipulation. The assay has become the most widely accepted technique in radiation biology and has been widely used for evaluating the radiation sensitivity of different cell lines. Further, the clonogenic assay is commonly used for monitoring the efficacy of radiation modifying compounds and for determining the effects of cytotoxic agents and other anti-cancer therapeutics on colony forming ability, in different cell lines. A typical clonogenic survival experiment using adherent cells lines involves three distinct components, 1) treatment of the cell monolayer in tissue culture flasks, 2) preparation of single cell suspensions and plating an appropriate number of cells in petri dishes and 3) fixing and staining colonies following a relevant incubation period, which could range from 1-3 weeks, depending on the cell line. Here we demonstrate the general procedure for performing the clonogenic assay with adherent cell lines with the use of an immortalized human keratinocyte cell line (FEP-1811). Also, our aims are to describe common features of clonogenic assays including calculation of the plating efficiency and survival fractions after exposure of cells to radiation, and to exemplify modification of radiation-response with the use of a natural antioxidant formulation. PMID:21445039

Rafehi, Haloom; Orlowski, Christian; Georgiadis, George T; Ververis, Katherine; El-Osta, Assam; Karagiannis, Tom C

2011-01-01

263

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

264

Low-temperature synthesis of amorphous carbon nanocoils via acetylene coupling on copper nanocrystal surfaces at 468 K: a reaction mechanism analysis.  

PubMed

A new type of amorphous helical carbon nanofibers has been synthesized using copper nanocatalysts and an acetylene gas source at atmospheric pressure. The nanofibers are grown at 468 K, which is the lowest temperature by ordinary metal-catalyzed thermal chemical vapor deposition of hydrocarbon, and exhibit a symmetric growth mode in the form of twin helices. IR, XRD, Raman, and C/H molar ratio analyses reveal a polymer-like structure with a weak trans-polyacetylene feature. The nanofibers are a mixture of solid polymers and a small amount of carbon. A reaction mechanism has been proposed on the basis of the previous studies of acetylene adsorption, desorption properties, and surface reactions on copper (111), (110), and (001) planes under ultrahigh-vacuum (UHV) conditions as well as the results obtained in our study. The reaction mechanism of acetylene on copper single-crystal surfaces under UHV conditions indeed reflects the reaction mechanism under practical catalytic conditions at atmospheric pressure. The nanofibers grow mainly via acetylene coupling to solid polymers on copper nanocrystal surfaces. Acetylene also couples to yield small amounts of liquid oligomers and gaseous products, and undergoes slight carbon deposition during the fiber growth. PMID:16853825

Qin, Yong; Jiang, Xin; Cui, Zuolin

2005-11-24

265

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). PMID:25278732

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

2014-01-01

266

Acetylene-derived strong organic acceptors for planar and nonplanar push-pull chromophores.  

PubMed

Though investigated for decades, interest in push-pull chromophores (D-pi-A), strong electron donors (D) connected by pi-conjugating spacers to strong electron acceptors (A), continues to grow. Such chromophores are of substantial interest for optoelectronic devices such as waveguides. Also, strong donors and acceptors form bimolecular charge-transfer (CT) complexes and salts, some of which exhibit electrical conductivity and magnetic behavior. Furthermore, strong organic acceptors are increasingly explored as dopants in the fabrication of organic light-emitting diodes (OLEDs) and solar cells. This Account describes systematic efforts pursued over the past decade in our laboratory to generate new families of organic electron acceptors (A) and conjugate them via pi-spacers to electron donors (D) under formation of push-pull systems with intense intramolecular CT interactions and high third-order optical nonlinearities. First, we describe donor-acceptor-substituted tetraethynylethenes (TEEs). In these chromophores, the peripherally attached p-nitrophenyl acceptors and N,N-dimethylanilino donors behave as nearly independent redox centers. Acetylenic scaffolding using TEE building blocks produces large all-carbon sheets, such as perethynylated dehydroannulenes, expanded radialenes, and radiaannulenes with potent electron-acceptor properties. Arylated TEEs act as molecular switches allowing two-way photochemical interconversion that is not perturbed by thermal isomerization pathways. Upon sequential substitution of the acetylene moieties in TEEs, we formed another family of potent acceptors, the cyanoethynylethenes (CEEs). Donor-substituted CEEs are planar CT chromophores with very high third-order optical nonlinearities. Their high environmental stability allows for the formation of thin films by vapor-phase deposition. Through careful analysis of the physicochemical properties of CEEs, we established useful guidelines for evaluating and tuning the optical gap in strong push-pull chromophores: increasing the length of the pi-spacer in D-pi-A systems reduces ground-state D-A conjugation and lowers the HOMO-LUMO gap. By taking advantage of "click-chemistry"-type [2 + 2] cycloadditions of tetracyanoethene (TCNE) and 7,7,8,8-tetracyanoquinodimethane (TCNQ) with appropriately activated alkynes, followed by retro-electrocyclization, the formation of donor-substituted 1,1,4,4-tetracyanobuta-1,3-dienes (TCBDs), 1,1,2,4,4-pentacyanobuta-1,3-dienes (PCBDs), and novel TCNQ adducts is possible. Some of these stable, nonplanar CT chromophores form high optical quality amorphous thin films by vapor-phase deposition. Despite donor substitution, the new acceptors (TCBDs, PCBDs, and the TCNQ adducts) rival TCNE and TCNQ in their ease for reversible electron uptake. High-yielding cycloaddition/retro-electrocyclization cascades provide access to multivalent, dendritic chromophores acting as "molecular batteries" with a remarkable capacity for multiple electron uptake in a narrow potential range. Finally, we used a one-pot protocol for electronically controlled consecutive TCNE and tetrathiafulvalene (TTF) additions to end-capped polyynes to form [AB]-type oligomers with a dendralene-type backbone. PMID:19061332

Kivala, Milan; Diederich, François

2009-02-17

267

An Experimental and Theoretical Study of Nitrogen-Broadened Acetylene Lines  

NASA Technical Reports Server (NTRS)

We present experimental nitrogen-broadening coefficients derived from Voigt profiles of isotropic Raman Q-lines measured in the 2 band of acetylene (C2H2) at 150 K and 298 K, and compare them to theoretical values obtained through calculations that were carried out specifically for this work. Namely, full classical calculations based on Gordon's approach, two kinds of semi-classical calculations based on Robert Bonamy method as well as full quantum dynamical calculations were performed. All the computations employed exactly the same ab initio potential energy surface for the C2H2N2 system which is, to our knowledge, the most realistic, accurate and up-to-date one. The resulting calculated collisional half-widths are in good agreement with the experimental ones only for the full classical and quantum dynamical methods. In addition, we have performed similar calculations for IR absorption lines and compared the results to bibliographic values. Results obtained with the full classical method are again in good agreement with the available room temperature experimental data. The quantum dynamical close-coupling calculations are too time consuming to provide a complete set of values and therefore have been performed only for the R(0) line of C2H2. The broadening coefficient obtained for this line at 173 K and 297 K also compares quite well with the available experimental data. The traditional Robert Bonamy semi-classical formalism, however, strongly overestimates the values of half-width for both Qand R-lines. The refined semi-classical Robert Bonamy method, first proposed for the calculations of pressure broadening coefficients of isotropic Raman lines, is also used for IR lines. By using this improved model that takes into account effects from line coupling, the calculated semi-classical widths are significantly reduced and closer to the measured ones.

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

2014-01-01

268

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

269

Concentration Dependence of Line Shapes in the ?_1 + ?_3 Band of Acetylene  

NASA Astrophysics Data System (ADS)

Using an extended cavity diode laser locked to a frequency comb, the line shape of the P(11) line in the ?_1 + ?_3 combination band of acetylene 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 speed-dependent 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. 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. In parallel work, we have measured the positions of many of these lines by saturation dip spectroscopy. Progress in the analysis of the data and the new saturation dip line center measurements will be reported. [1] C. P. McRaven, et al. Paper RI05, 68th International Symposium on Molecular Spectroscopy, 2013 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; Forthomme, Damien; Hall, Gregory; McRaven, C.; Sears, Trevor

2014-06-01

270

Large scale contracted MC-CI calculations on acetylene and its dissociation into two CH(2?) radicals  

NASA Astrophysics Data System (ADS)

Large scale MC-CI calculations with up to 178 000 configurations have been performed on acetylene and its dissociation into two CH(2?) radicals with a newly developed contracted CI scheme. The geometry obtained for acetylene was RC-C = 1.208 Å (exptl. = 1.203 Å) and RC-H = 1.061 Å (1.060 Å). The dissociation energy into two CH(2?) was De = 10.00 eV (10.26 eV). The barrier along the linear dissociation path recently predicted by Raimondi et al. was confirmed but their value of 0.33 eV was raised to 0.57 eV and the location of the barrier was moved from 6.0 to 5.0 a.u. The origin of the barrier is an avoided crossing between the states dissociating into two CH(2?)—and two CH(4?-)—radicals. The energy difference between the states at the point of the avoided crossing was computed to be 0.19 eV from second root contracted CI calculations. The energy barrier was increased in going from MCSCF to CI and this unusual behavior is explained by the much larger amount of correlation energy in CH(2?) than in CH(4?-). The minimum energy path is however found to be nonlinear and has no energy barrier. A simple molecular orbital argument is given for why this should be so. The potential surface for acetylene is further found to exhibit irregular regions with double minima for bending which were not predicted in the surface given recently by Carter et al. All the presently performed calculations were done on a minicomputer VAX-11/780.

Siegbahn, Per E. M.

1981-09-01

271

Multiplexed Elispot assay.  

PubMed

Micron scale latex beads are well established as highly biocompatible reagents. Imbibing two fluorescent dyes into the interior of the beads enables the creation of a family of combinatorially colored labels. Previous use of such beads, in flow cytometry for example, has focused on beads of approximately 5 microm diameter. We show here that 280 nm combinatorially labeled particles can be used to create ELISA-style assays in 200 microm scale virtual wells, using digital microscopy as the readout. The utility of this technique is illustrated by profiling the secreted cytokine footprints of peripheral blood mononuclear cells in a multiparametric version of the popular Elispot assay. Doing so reveals noncanonical classes of T lymphocytes. We further show that the secreting cell type can be concurrently identified by surface staining with a cell type specific antibody conjugated to the same multiplexed beads. PMID:19084532

Harriman, William D; Collarini, Ellen J; Cromer, Remy G; Dutta, April; Strandh, Magnus; Zhang, Fen; Kauvar, Lawrence M

2009-02-28

272

Kinetic Tetrazolium Microtiter Assay  

NASA Technical Reports Server (NTRS)

Kinetic tetrazolium microtiter assay (KTMA) involves use of tetrazolium salts and Triton X-100 (or equivalent), nontoxic, in vitro color developer solubilizing colored metabolite formazan without injuring or killing metabolizing cells. Provides for continuous measurement of metabolism and makes possible to determine rate of action of antimicrobial agent in real time as well as determines effective inhibitory concentrations. Used to monitor growth after addition of stimulatory compounds. Provides for kinetic determination of efficacy of biocide, greatly increasing reliability and precision of results. Also used to determine relative effectiveness of antimicrobial agent as function of time. Capability of generating results on day of test extremely important in treatment of water and waste, disinfection of hospital rooms, and in pharmaceutical, agricultural, and food-processing industries. Assay also used in many aspects of cell biology.

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

1993-01-01

273

An approach to lauroxanes by iterative use of Co(2)(CO)(6)-acetylenic complexes. a formal synthesis of (+)-laurencin.  

PubMed

A new approach to lauroxanes by a powerful and highly convergent methodology based on iterative use of Co(2)(CO)(6)-acetylenic complexes is described. The strategy employs an intermolecular Nicholas reaction to form unsaturated branched linear ethers, a ring closing metathesis to obtain the cobalt complex cyclic ethers, and an isomerization promoted by montmorillonite K-10. A short synthesis of cyclic ethers of seven-, eight-, and nine-membered rings is described. Additionally, the methodology is exemplified by the formal synthesis of (+)-laurencin, a red algae metabolite. PMID:20809659

Ortega, Nuria; Martín, Victor S; Martín, Tomás

2010-10-01

274

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

PubMed Central

Supplying l-proline to the root system of intact soybean (Glycine max [L.] Merr.) plants stimulated acetylene reducing activity to the same extent as did supplying succinate. Feeding l-proline also caused an increase in bacteroid proline dehydrogenase activity that was highly correlated with the increase in acetylene-reducing activity. Twenty-four hours after irrigating with l-proline, endogenous proline content had increased in host cell cytoplasm and bacteroids, about three- and eightfold, respectively. In bacteroids, proline concentration was calculated to be at least 3.5 millimolar. In experiments in which [U-14C]l-proline was supplied to uprooted, intact plants incubated in aerated solution, 14C-labeled products of proline metabolism, as well as [14C]proline itself, accumulated in both host cells and bacteroids. When plants were incubated in aerated solutions containing [5-3H]l-proline, 3H-labeled proline was found in host cells and bacteroids. [3H] Pyrroline-5-carboxylate was found in bacteroids, but not host cells, after a 2-hour incubation in [5-3H]l-proline. When [U-14C]l-proline was supplied for 24 hours, a significant amount of [14C] pyrroline-5-carboxylate was found in the host cells, in contrast with the results from the shorter incubation in [5-3H]proline, although the amount in the host cells was only about half the quantity found in the bacteroids. Taken as a whole, these results indicate that proline crosses both plant and bacterial membranes under the in vivo experimental conditions utilized and are consistent with a significant role for proline as an energy source in support of bacteroid functioning. In spite of the increase in acetylene-reducing activity when proline was supplied to the root system of intact plants, proline application did not rescue stemgirdled plants from loss of acetylene-reducing activity, although succinate application did. This suggests a nonphloem route for succinate, but not proline, from roots to nodules. PMID:16668722

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

1992-01-01

275

NO A{sup 2}{Sigma}{sup +}-X{sup 2}II chemiluminescence produced from the reaction of excited NO{sub 2} with acetylene and its derivatives in their triplet states  

SciTech Connect

This paper discusses how reacting excited NO{sub 2} with acetylene and its derivatives produced NO(A{sup 2}{Sigma}{sup +}) by a NO A{sup 2}{sigma}{sup +}-X{sup 2}II chemiluminescence produced by a triplet-state mechanism, with acetylene > methylacetylene > ethylacetylene > phenylacetylene > benzene in terms of efficiency. 22 refs., 8 figs., 2 tabs.

Sisk, Wade; Endo; Hiromu; Shibuya, Kazuhiko; Obi, Kinichi [Tokyo Institute of Technology, Meguro, Tokyo (Japan)

1992-08-06

276

PathogenMip Assay: A Multiplex Pathogen Detection Assay  

Microsoft Academic Search

The Molecular Inversion Probe (MIP) assay has been previously applied to a large-scale human SNP detection. Here we describe the PathogenMip Assay, a complete protocol for probe production and applied approaches to pathogen detection. We have demonstrated the utility of this assay with an initial set of 24 probes targeting the most clinically relevant HPV genotypes associated with cervical cancer

Michael S. Akhras; Sreedevi Thiyagarajan; Andrea C. Villablanca; Ronald W. Davis; Pål Nyrén; Nader Pourmand; Sheila Bowyer

2007-01-01

277

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

SciTech Connect

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

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

1987-02-02

278

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

279

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

280

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

281

Reductive capacity of natural reductants.  

PubMed

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

Lee, Woojin; Batchelor, Bill

2003-02-01

282

Tuberosity Reduction  

MedlinePLUS

... denture stays in place because it makes a seal with your jaw and the roof of your mouth (palate). A large tuberosity can prevent this seal from forming. Tuberosity reductions are less common today ...

283

TOTAL CULTURABLE VIRUS QUANTAL ASSAY  

EPA Science Inventory

This chapter describes a quantal method for assaying culturable human enteric viruses from water matrices. The assay differs from the plaque assay described in Chapter 10 (December 1987 Revision) in that it is based upon the direct microscopic viewing of cells for virus-induced ...

284

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

285

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.

2014-12-01

286

Assays for ?-synuclein aggregation.  

PubMed

This review describes different ways to achieve and monitor reproducible aggregation of ?-synuclein, a key protein in the development of Parkinson's disease. For most globular proteins, aggregation is promoted by partially denaturing conditions which compromise the native state without destabilizing the intermolecular contacts required for accumulation of regular amyloid structure. As a natively disordered protein, ?-synuclein can fibrillate under physiological conditions and this process is actually stimulated by conditions that promote structure formation, such as low pH, ions, polyamines, anionic surfactants, fluorinated alcohols and agitation. Reproducibility is a critical issue since ?-synuclein shows erratic fibrillation behavior on its own. Agitation in combination with glass beads significantly reduces the variability of aggregation time curves, but the most reproducible aggregation is achieved by sub-micellar concentrations of SDS, which promote the rapid formation of small clusters of ?-synuclein around shared micelles. Although the fibrils produced this way have a different appearance and secondary structure, they are rich in cross-? structure and are amenable to high-throughput screening assays. Although such assays at best provide a very simplistic recapitulation of physiological conditions, they allow the investigator to focus on well-defined molecular events and may provide the opportunity to identify, e.g. small molecule inhibitors of aggregation that affect these steps. Subsequent experiments in more complex cellular and whole-organism environments can then validate whether there is any relation between these molecular interactions and the broader biological context. PMID:21163351

Giehm, Lise; Lorenzen, Nikolai; Otzen, Daniel E

2011-03-01

287

Test procedure for boxed waste assay system  

SciTech Connect

This document, prepared by Los Alamos National Laboratory`s NMT-4 group, details the test methodology and requirements for Acceptance/Qualification testing of a Boxed Waste Assay System (BWAS) designed and constructed by Pajarito Scientific Corporation. Testing of the BWAS at the Plutonium Facility (TA55) at Los Alamos National Laboratory will be performed to ascertain system adherence to procurement specification requirements. The test program shall include demonstration of conveyor handling capabilities, gamma ray energy analysis, and imaging passive/active neutron accuracy and sensitivity. Integral to these functions is the system`s embedded operating and data reduction software.

Wachter, J. [Los Alamos National Lab., NM (United States)

1994-12-07

288

Just Click It: Undergraduate Procedures for the Copper(I)-Catalyzed Formation of 1,2,3-Triazoles from Azides and Terminal Acetylenes  

ERIC Educational Resources Information Center

The click chemistry uses only the most reliable reactions to build complex molecules from olefins, electrophiles and heteroatom linkers. A variation on Huisgen's azide-alkyne 1,2,3-triazole synthesis, the addition of the copper (I), the premium example of the click reaction, catalyst strongly activates terminal acetylenes towards the 1,3-dipole in…

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

2005-01-01

289

Structure, dynamics, and reactivity of an alkoxy intermediate formed from acetylene on zeolite catalysts: An in situ solid-state NMR study  

SciTech Connect

Recently, there has been much interest in reactive intermediates formed by the adsorption of organic compounds on zeolites and alumina. In this communication, they present evidence for a vinyl alkoxy species, analogous to IV, which is formed at high temperatures from acetylene on zeolites HY and HZSM-5. Upon exposure of the catalyst to water, the intermediate was converted quantitatively to acetaldehyde.

Lazo, N.D.; White, J.L.; Munson, E.J.; Lambregts, M.; Haw, J.F. (Texas A and M Univ., College Station (USA))

1990-05-09

290

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

291

Cholesterol Efflux Assay  

PubMed Central

Cholesterol content of cells must be maintained within the very tight limits, too much or too little cholesterol in a cell results in disruption of cellular membranes, apoptosis and necrosis 1. Cells can source cholesterol from intracellular synthesis and from plasma lipoproteins, both sources are sufficient to fully satisfy cells' requirements for cholesterol. The processes of cholesterol synthesis and uptake are tightly regulated and deficiencies of cholesterol are rare 2. Excessive cholesterol is more common problem 3. With the exception of hepatocytes and to some degree adrenocortical cells, cells are unable to degrade cholesterol. Cells have two options to reduce their cholesterol content: to convert cholesterol into cholesteryl esters, an option with limited capacity as overloading cells with cholesteryl esters is also toxic, and cholesterol efflux, an option with potentially unlimited capacity. Cholesterol efflux is a specific process that is regulated by a number of intracellular transporters, such as ATP binding cassette transporter proteins A1 (ABCA1) and G1 (ABCG1) and scavenger receptor type B1. The natural acceptor of cholesterol in plasma is high density lipoprotein (HDL) and apolipoprotein A-I. The cholesterol efflux assay is designed to quantitate the rate of cholesterol efflux from cultured cells. It measures the capacity of cells to maintain cholesterol efflux and/or the capacity of plasma acceptors to accept cholesterol released from cells. The assay consists of the following steps. Step 1: labelling cellular cholesterol by adding labelled cholesterol to serum-containing medium and incubating with cells for 24-48 h. This step may be combined with loading of cells with cholesterol. Step 2: incubation of cells in serum-free medium to equilibrate labelled cholesterol among all intracellular cholesterol pools. This stage may be combined with activation of cellular cholesterol transporters. Step 3: incubation of cells with extracellular acceptor and quantitation of movement of labelled cholesterol from cells to the acceptor. If cholesterol precursors were used to label newly synthesized cholesterol, a fourth step, purification of cholesterol, may be required. The assay delivers the following information: (i) how a particular treatment (a mutation, a knock-down, an overexpression or a treatment) affects the capacity of cell to efflux cholesterol and (ii) how the capacity of plasma acceptors to accept cholesterol is affected by a disease or a treatment. This method is often used in context of cardiovascular research, metabolic and neurodegenerative disorders, infectious and reproductive diseases. PMID:22414908

Low, Hann; Hoang, Anh; Sviridov, Dmitri

2012-01-01

292

Adipose Tissue Angiogenesis Assay  

PubMed Central

Changes in adipose tissue mass must be accompanied by parallel changes in microcirculation. Investigating the mechanisms that regulate adipose tissue angiogenesis could lead to better understanding of adipose tissue function and reveal new potential therapeutic strategies. Angiogenesis is defined as the formation of new capillaries from existing microvessels. This process can be recapitulated in vitro, by incubation of tissue in extracellular matrix components in the presence of pro-angiogenic factors. Here, we describe a method to study angiogenesis from adipose tissue fragments obtained from mouse and human tissue. This assay can be used to define effects of diverse factors added in vitro, as well as the role of endogenously produced factors on angiogenesis. We also describe approaches to quantify angiogenic potential for the purpose of enabling comparisons between subjects, thus providing information on the role of physiological conditions of the donor on adipose tissue angiogenic potential. PMID:24480342

Rojas-Rodriguez, Raziel; Gealekman, Olga; Kruse, Maxwell E.; Rosenthal, Brittany; Rao, Kishore; Min, SoYun; Bellve, Karl D.; Lifshitz, Lawrence M.; Corvera, Silvia

2015-01-01

293

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

SciTech Connect

Detached cowpea nodules that contained a nitrous oxide reductase-positive (Nor/sup +/) rhizobium strain (8A55) and a nitrous oxide reductase-negative (Nor/sup -/) rhizobium strain (32H1) were incubated with 1% /sup 15/N/sub 2/O (95 atom% /sup 15/N) in the following three atmospheres: aerobic with C/sub 2/H/sub 2/ (10%), aerobic without C/sub 2/H/sub 2/, and anaerobic (argon atmosphere) without C/sub 2/H/sub 2/. The greatest production of /sup 15/N/sub 2/ occurred anaerobically with 8A55, yet very little was formed with 32H1. Although acetylene reduction activity was slightly higher with 32H1, about 10 times more /sup 15/N/sub 2/ was produced aerobically by 8A55 than by 32H1 in the absence of acetylene. The major reductive pathway of N/sub 2/O reduction by denitrifying rhizobium strain 8A55 is by nitrous oxide reductase rather than nitrogenase.

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

1987-05-01

294

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.

295

ABSORPTION CROSS SECTION OF GASEOUS ACETYLENE AT 85 K IN THE WAVELENGTH RANGE 110-155 nm  

SciTech Connect

Absorption spectra and absorption cross sections of gaseous acetylene, C{sub 2}H{sub 2}, at 298 and 85 K were measured in the wavelength range 110-155 nm with a slit-jet system coupled to a synchrotron as a source of vacuum ultraviolet light. Using published spectral parameters of C{sub 2}H{sub 2}, we simulated the absorption profile for the Rydberg transition to state 4R{sub 0} in the range 124.6-125.1 nm, according to which the temperature of the jet-expanded sample at stagnation pressure 200 Torr is 85 {+-} 5 K. Our cross sections of C{sub 2}H{sub 2} are applicable for determining properties sensitive to temperature for diagnostic work on Saturn and Titan.

Cheng, Bing-Ming; Chen, Hui-Fen; Lu, Hsiao-Chi; Chen, Hong-Kai; Alam, M. S.; Chou, Sheng-Lung; Lin, Meng-Yeh, E-mail: bmcheng@nsrrc.org.tw [National Synchrotron Radiation Research Center, No. 101, Hsin-Ann Road, Hsinchu Science Park, Hsinchu 30076, Taiwan (China)

2011-09-01

296

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

SciTech Connect

This study explores the use of breathing orbital valence bond (BOVB) trial wave functions for diffusion Monte Carlo (DMC). The approach is applied to the computation of the carbon-hydrogen (C-H) bond dissociation energy (BDE) of acetylene. DMC with BOVB trial wave functions yields a C-H BDE of 132.4 {+-} 0.9 kcal/mol, which is in excellent accord with the recommended experimental value of 132.8 {+-} 0.7 kcal/mol. These values are to be compared with DMC results obtained with single determinant trial wave functions, using Hartree-Fock orbitals (137.5 {+-} 0.5 kcal/mol) and local spin density (LDA) Kohn-Sham orbitals (135.6 {+-} 0.5 kcal/mol).

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

2008-05-30

297

Ir Spectra of Large Tailor-Made Ag-MOLECULE (methane, Ethane, Ethylene, Acetylene) Clusters Produced in Helium Nanodroplets  

NASA Astrophysics Data System (ADS)

Clusters of silver having up to about 10^4 atoms and molecules such as methane, ethane, ethylene and acetylene with up to 10^4 were obtained via sequential pickup of molecules by He droplets with average sizes in the range of 10^5 to 10^7 atoms. The formed clusters have been studied via infrared spectra in the C-H stretching range of the molecules. The spectra show two distinct features due to molecules on the boundary with silver atoms and those in the volume of the neat molecular part of the clusters. The relative intensities of the peaks allow obtaining of the cluster size, in good agreement with the estimates based on the known binding energies of the clusters. Experiments also suggest that selection rules for infrared transitions for molecules adsorbed on metal surfaces are also valid for silver clusters as small as 100 atoms.

Loginov, Evgeny; Gomez, Luis; Vilesov, Andrey

2010-06-01

298

Synthesis of Some Heterocycles of Expected Biological Activity Through the Action of Isatin3Thiosemicarbazone on Acetylenic Ketones and Esters  

Microsoft Academic Search

Isatin-3-thiosemicarbazone ( 1 ) reacted with 1-aryl-3-phenylprop-2-yn-1-ones ( 2a-c ) in n-butanol to give 4-aryl-6-phenyl-2-[2-oxo-2H,3H-benzo(b) pyrrolidine-3-iminyl]-imino-2H-1,3-thiazines ( 3a-c ). Similar treatment of 1 with acetylenic esters ( 4a-c ) gave the 6-substituted derivatives of 2-imino-3-[2-oxo-2H,3H-benzo(b)pyrrolidine-3-iminyl]-2,3-dihydro-4-oxo-1,3-thiazine ( 5a-c ). Treatment of 1 with 4a-c in the presence of sodium ethoxide in ethanol gave the 6-substituted derivatives of 3-[2-oxo-2H,3H-benzo(b)pyrrolidine-3-iminyl]-4-oxo-2-thioxo-1,2,4-trihydropyrimidine ( 6a-c ).

Ahmed S. A. Youssef

2002-01-01

299

Role of hydrogen abstraction acetylene addition mechanisms in the formation of chlorinated naphthalenes. 1. A quantum chemical investigation.  

PubMed

The addition of chloroacetylene or tetrachlorovinylacetylene to 2,4,5-trichlorophenyl radicals, leading to the formation of tetra-, penta-, and hexachloronaphthalene congeners, has been explored at the M06-2X/6-311+G(3df,3p)//B3LYP/6-31G(d) level of theory. The accuracy of this method was justified by comparing the barriers of several pertinent reactions against energies from single point calculations at the B3LYP/cc-pVDZ, CCSD(T)/6-31G(d), and G2MS levels. Bittner-Howard and Frenklach hydrogen abstraction acetylene addition mechanisms were developed, as was a channel based on acetylene additions to chlorinated [4.2.0]octa-1,3,5-trien-7-yl congeners. While the latter channel exhibits relatively high C2HCl addition barriers and may be a minor growth channel at best, both the Bittner-Howard and Frenklach sequences appear facile. In all mechanisms, the additions of C2HCl leading to a ?-chlorinated adduct is favored by ?15 kJ mol(-1) relative to the ?-chlorinated analogue, and the addition products typically access a variety of facile cyclization channels. The ?-chlorinated product of C2HCl addition to 2,4,5-trichlorophenyl, however, undergoes a particularly rapid Cl-loss leading to 1-ethynyl-2,4,5-trichlorobenzene, effectively shutting down further growth. Generalization implies that ?-chlorinated C6H5-CH?CH congeners do not participate in growth reactions. Addition of 2,4,5-trichlorophenyl to the C?C bond of tetrachlorovinylacetylene and subsequent cyclization is found to be a facile route to hexachloronaphthalene formation and may be operative in fully chlorinated systems where the C6Cl5-CCl?CCl congeners cannot participate in the major growth processes. PMID:25419897

McIntosh, Grant J; Russell, Douglas K

2014-12-26

300

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

301

Development of rapid pathogenicity assay for Verticillium dahliae using early flowering lettuce.  

Technology Transfer Automated Retrieval System (TEKTRAN)

Conventional assays of Verticillium wilt on lettuce require approximately three months from the time of seeding. A reduction in time required for analyses of symptom development would be useful in studies of the Verticillium dahliae-lettuce interaction. In this study, a growth chamber assay was ev...

302

A novel data mining method to identify assay-specific signatures in functional genomic studies  

Microsoft Academic Search

BACKGROUND:: The highly dimensional data produced by functional genomic (FG) studies makes it difficult to visualize relationships between gene products and experimental conditions (i.e., assays). Although dimensionality reduction methods such as principal component analysis (PCA) have been very useful, their application to identify assay-specific signatures has been limited by the lack of appropriate methodologies. This article proposes a new and

Derrick K. Rollins; Dongmei Zhai; Alrica L. Joe; Jack W. Guidarelli; Abhishek Murarka; Ramon Gonzalez

2006-01-01

303

J. Phycol. 38, 971982 (2002) FIELD ASSAYS FOR MEASURING NITRATE REDUCTASE ACTIVITY IN ENTEROMORPHA SP.  

E-print Network

.g. tissue metabolite levels) on nitrate reduction. Key index words: Enteromorpha sp.; estuary; Gelidium sp971 J. Phycol. 38, 971­982 (2002) FIELD ASSAYS FOR MEASURING NITRATE REDUCTASE ACTIVITY nitrate reductase (NR) activity assays designed for use in the field on Enteromorpha sp., Ulva sp

Sherman, Tim

304

Sulforhodamine B assay and chemosensitivity.  

PubMed

The sulforhodamine B (SRB) assay was developed by Skehan and colleagues to measure drug-induced cytotoxicity and cell proliferation for large-scale drug-screening applications. Its principle is based on the ability of the protein dye sulforhodamine B to bind electrostatically and pH dependent on protein basic amino acid residues of trichloroacetic acid-fixed cells. Under mild acidic conditions it binds to and under mild basic conditions it can be extracted from cells and solubilized for measurement. Results of the SRB assay were linear with cell number and cellular protein measured at cellular densities ranging from 1 to 200% of confluence. Its sensitivity is comparable with that of several fluorescence assays and superior to that of Lowry or Bradford. The signal-to-noise ratio is favorable and the resolution is 1000-2000 cells/well. It performed similarly compared to other cytotoxicity assays such as MTT or clonogenic assay. The SRB assay possesses a colorimetric end point and is nondestructive and indefinitely stable. These practical advances make the SRB assay an appropriate and sensitive assay to measure drug-induced cytotoxicity even at large-scale application. PMID:15901925

Voigt, Wieland

2005-01-01

305

PathogenMip assay: a multiplex pathogen detection assay.  

PubMed

The Molecular Inversion Probe (MIP) assay has been previously applied to a large-scale human SNP detection. Here we describe the PathogenMip Assay, a complete protocol for probe production and applied approaches to pathogen detection. We have demonstrated the utility of this assay with an initial set of 24 probes targeting the most clinically relevant HPV genotypes associated with cervical cancer progression. Probe construction was based on a novel, cost-effective, ligase-based protocol. The assay was validated by performing pyrosequencing and Microarray chip detection in parallel experiments. HPV plasmids were used to validate sensitivity and selectivity of the assay. In addition, 20 genomic DNA extracts from primary tumors were genotyped with the PathogenMip Assay results and were in 100% agreement with conventional sequencing using an L1-based HPV genotyping protocol. The PathogenMip Assay is a widely accessible protocol for producing and using highly discriminating probes, with experimentally validated results in pathogen genotyping, which could potentially be applied to the detection and characterization of any microbe. PMID:17311101

Akhras, Michael S; Thiyagarajan, Sreedevi; Villablanca, Andrea C; Davis, Ronald W; Nyrén, Pål; Pourmand, Nader

2007-01-01

306

Synthesis of indoles, benzofurans, and related heterocycles via an acetylene-activated SNAr/intramolecular cyclization cascade sequence in water or DMSO.  

PubMed

The synthesis of 2-substituted indoles and benzofurans was achieved by nucleophilic aromatic substitution, followed by subsequent 5-endo-dig cyclization between the nucleophile and an ortho acetylene. The acetylene serves the dual role of the electron withdrawing group to activate the substrate for SNAr, and the C1-C2 carbon scaffold for the newly formed 5-membered heteroaromatic ring. This method allows for the bond forming sequence of Ar-X-N/O-C1 to proceed in a single synthetic step, furnishing indoles and benzofurans in moderate to high yields. Since the method is not transition metal mediated, brominated and chlorinated substrates are tolerated, and benzofuran formation can be conducted using water or water-DMSO mixtures as solvent. PMID:25608594

Hudson, R; Bizier, N P; Esdale, K N; Katz, J L

2015-02-10

307

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

308

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

309

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

SciTech Connect

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

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

1995-04-01

310

Recent Line-Shape and Doppler Thermometry Studies Involving Transitions in the ?1 +?3 Band of Acetylene  

NASA Astrophysics Data System (ADS)

The line positions for transitions in the ?1 +?3 band are often used as a frequency standard by the telecom industry and also needed for planetary atmospheric studies. Four relevant studies have been recently carried out in our group and will be discussed briefly below. (1) N2-broadened line widths and N2-pressure induced line shifts have been measured for transitions in the ?1 +?3 band of acetylene at seven temperatures in the range 213333K to obtain the temperature dependences of broadening and shift coefficients. The Voigt and hard-collision line profile models were used to retrieve the line parameters. This study has been published in Molecular Physics, 110 Issue 21/22 (2012) 2645-2663. (2) Six nitrogen perturbed transitions of acetylene within the ?1 +?3 absorption band have been recorded using a 3-channel diode laser spectrometer. We have examined C2H2 spectra using a hard collision (Rautian) profile over a range of five temperatures (213 K-333 K). From these fits we have obtained the N2-broadening and narrowing coefficients of C2H2 and examined their temperature dependence. The experimentally measured narrowing coefficients have been used to estimate the nitrogen diffusion coefficients. The broadening coefficients and corresponding temperature dependence exponents have also been compared to that of calculations completed using a classical impact approach on an ab initio potential energy surface. We have observed a good agreement between our theoretical and experimental results. This study was published in Canadian Journal of Physics 91(11) 896-905 (2013). (3) An extension of the previous study was to analyze the room temperature for the same six transitions using the Voigt, Rautian, Galatry, RautianGalatry and Correlated Rautian profiles. For the entire pressure range, we have tested the applicability of these line-shape models. Except for Voigt profile, Dicke narrowing effect has been considered in all mentioned line-shape models. The experimental results for the narrowing parameters have been compared with calculated values based on the theory of diffusion. This study is in press in press in the Journal of Quantitative Spectroscopy and Radiative Transfer. (4) In this paper we present accurate measurements of the fundamental Boltzmann constant based on a lineshape analysis of acetylene spectra in the ?1 +?3 band recorded using a tunable diode laser. Experimental spectra recorded at low pressures have been analyzed using both the Voigt model and the Speed Dependent Voigt model that takes into account the molecular speed dependence effects. These line-shape models reproduces the experimental data with high accuracy and allow us to determine precise line-shape parameters for the transitions used, the Doppler-width and then determined the Boltzmann constant, kB. This study has been submitted for publication in the Journal of Chemical Physics. 1 1 Research described in this work was funded by NSERC, Canada.

Hashemi, Robab; Rozario, Hoimonti; Povey, Chad; Garber, Jolene; Derksen, Mark; Predoi-Cross, Adriana

2014-06-01

311

Real-time cytotoxicity assays.  

PubMed

Validation of new therapeutic targets calls for the advance in innovative assays that probe both spatial and temporal relationships in signaling networks. Cell death assays have already found a widespread use in pharmacological profiling of anticancer drugs. Such assays are, however, predominantly restricted to end point DEAD/LIVE parameter that provides only a snapshot of inherently stochastic process such as tumor cell death. Development of new methods that can offer kinetic real-time analysis would be highly advantageous for the pharmacological screening and predictive toxicology. In the present work we outline innovative protocols for the real-time analysis of tumor cell death, based on propidium iodide (PI) and SYTOX Green probes. These can be readily adapted to both flow cytometry and time-lapse fluorescence imaging. Considering vast time savings and kinetic data acquisition such assays have the potential to be applied in a number of areas including accelerated anticancer drug discovery and high-throughput screening routines. PMID:21516415

Wlodkowic, Donald; Faley, Shannon; Darzynkiewicz, Zbigniew; Cooper, Jonathan M

2011-01-01

312

Spectrophotometric assay for ornithine decarboxylase.  

PubMed

A rapid and sensitive spectrophotometric assay for ornithine decarboxylase is described. It is based on the observation that the product of ornithine decarboxylase, putrescine, reacts with 2,4,6-trinitrobenzenesulfonic acid to give a colored product soluble in 1-pentanol whereas ornithine does not. The amount of putrescine produced by the enzyme was determined by measuring the absorbance of the 1-pentanol extract of the reaction mixture at 420 nm, and by comparing the results to those obtained by the trapping of 14CO2 and by HPLC assays. The three assays were found to be equivalent in sensitivity, with the spectrophotometric assay having the advantages of being relatively rapid, requiring only common laboratory equipment, and not requiring the use of radioactive isotopes. PMID:3578755

Ngo, T T; Brillhart, K L; Davis, R H; Wong, R C; Bovaird, J H; Digangi, J J; Ristow, J L; Marsh, J L; Phan, A P; Lenhoff, H M

1987-02-01

313

Doug Berndt Evaluated Bacterial Assay  

USGS Multimedia Gallery

USGS microbiology technician evaluates a bacterial assay to determine the cause of a wildlife mortality. The USGS National Wildlife Health Center works to identify, track, and prevent wildlife disease....

314

Synthesis and biological evaluation of 1-(benzenesulfonamido)-2-[5-(N-hydroxypyridin-2(1H)-one)]acetylene regioisomers: a novel class of 5-lipoxygenase inhibitors.  

PubMed

A hitherto unknown class of linear acetylene regioisomers were designed such that a SO(2)NH(2) group was located at the ortho-, meta-, or para-position of the acetylene C-1 phenyl ring, and a N-hydroxypyridin-2(1H)-one moiety was attached via its C-5 position to the C-2 position on an acetylene template (scaffold). All three regioisomers inhibited 5-lipoxygenase (5-LOX), where the relative potency order was 2-SO(2)NH(2) (IC(50)=10 microM) >3-SO(2)NH(2) (IC(50)=15 microM) >4-SO(2)NH(2) (IC(50)=68 microM) relative to the reference drug nordihydroguaiaretic acid (NDGA; IC(50)=35 microM). The 2-SO(2)NH(2) regioisomer (ED(50)=86.0mg/kg po) exhibited excellent oral anti-inflammatory (AI) activity that was more potent than aspirin (ED(50)=128.9 mg/kg) and marginally less potent than ibuprofen (ED(50)=67.4 mg/kg). The N-hydroxypyridin-2(1H)one moiety provides a novel pharmacophore for the design of cyclic hydroxamic mimetics capable of chelating 5-LOX iron for exploitation in the design of 5-LOX inhibitory AI drugs. PMID:18541424

Chowdhury, Morshed Alam; Chen, Hua; Abdellatif, Khaled R A; Dong, Ying; Petruk, Kenneth C; Knaus, Edward E

2008-07-15

315

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

PubMed

The reaction mechanisms for selective acetylene hydrogenation on three different supports, Pd(4) cluster, oxygen defective anatase (101), and rutile (110) titania supported Pd(4), 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 Pd(4) cluster more strongly than that of rutile titania due to the existence of Ti(3+) in anatase titania. Consequently, the binding energies of adsorbed species such as acetylene and ethylene on Pd(4) cluster become weaker on anatase supported catalysts compared to the rutile supported Pd(4) 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. PMID:22423828

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

2012-03-14

316

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

317

Functional Assays for Ricin Detection  

NASA Astrophysics Data System (ADS)

In this review, we provide background information on ricin structure, present available functional assays for other toxins that are potential biothreat agents, and finish by describing the functional assay of ricin itself. Using appropriate sample preparation and optimized detection based on N-glycosidase activity, we demonstrate that specific detection of whole ricin at a level of around 0.1 ng/mL is possible and applicable to environmental samples.

Ezan, Eric; Duriez, Elodie; Fenaille, François; Becher, François

318

Protein tyrosine phosphatase: enzymatic assays  

Microsoft Academic Search

Activity assays for tyrosine phosphatases are based on the hydrolysis of a arylphosphate moiety from a synthetic substrate yielding a spectroscopically active product. Many different substrates can be used for these assays with p-nitrophenyl phosphate (pNPP), fluorescein diphosphate (FDP), and 6,8-difluoro-4-methylumbellyferyl phosphate (DiFMUP) being the most efficient and versatile. Equally, larger molecules such as phosphotyrosyl peptides can also be used

Jacqueline Montalibet; Kathryn I. Skorey; Brian P. Kennedy

2005-01-01

319

Calibration of quantitative PCR assays  

Microsoft Academic Search

Quantitative real-time PCR (polymerase chain reaction) assays are increasingly used to measure quantities of nucleic acids\\u000a in samples. They may be used to provide a high-throughput alternative to more traditional biological assays. In this case,\\u000a a calibration process may be required to convert the PCR measurements onto a more relevant scale. This is most commonly undertaken\\u000a using simple linear regression.

A. M. I. Roberts; C. M. Theobald; M. McNeil

2007-01-01

320

Methods to Assay Drosophila Behavior  

PubMed Central

Drosophila melanogaster, the fruit fly, has been used to study molecular mechanisms of a wide range of human diseases such as cancer, cardiovascular disease and various neurological diseases1. We have optimized simple and robust behavioral assays for determining larval locomotion, adult climbing ability (RING assay), and courtship behaviors of Drosophila. These behavioral assays are widely applicable for studying the role of genetic and environmental factors on fly behavior. Larval crawling ability can be reliably used for determining early stage changes in the crawling abilities of Drosophila larvae and also for examining effect of drugs or human disease genes (in transgenic flies) on their locomotion. The larval crawling assay becomes more applicable if expression or abolition of a gene causes lethality in pupal or adult stages, as these flies do not survive to adulthood where they otherwise could be assessed. This basic assay can also be used in conjunction with bright light or stress to examine additional behavioral responses in Drosophila larvae. Courtship behavior has been widely used to investigate genetic basis of sexual behavior, and can also be used to examine activity and coordination, as well as learning and memory. Drosophila courtship behavior involves the exchange of various sensory stimuli including visual, auditory, and chemosensory signals between males and females that lead to a complex series of well characterized motor behaviors culminating in successful copulation. Traditional adult climbing assays (negative geotaxis) are tedious, labor intensive, and time consuming, with significant variation between different trials2-4. The rapid iterative negative geotaxis (RING) assay5 has many advantages over more widely employed protocols, providing a reproducible, sensitive, and high throughput approach to quantify adult locomotor and negative geotaxis behaviors. In the RING assay, several genotypes or drug treatments can be tested simultaneously using large number of animals, with the high-throughput approach making it more amenable for screening experiments. PMID:22433384

Nichols, Charles D.; Becnel, Jaime; Pandey, Udai B.

2012-01-01

321

Continuous-flow automation of the Lactobacillus casei serum folate assay.  

PubMed Central

A method is described for the continuous-flow automation of the serum folate assay using Lactobacillus casei. The total incubation period is approximately four hours. The growth response of the organism to folate is estimated by measuring the rate of reduction of 2,3,5-triphenyl tetrazolium chloride (TTC). A simple continuous culture apparatus is used to grow the inoculum. Supplementation of the assay medium is necessary to obtain parallel results. A statistical assessment shows a favourable comparison with the whole-serum tube assay using a chloramphenicol resistant strain of L. casei. The method is less sensitive to inhibitory substances than the tube assay. PMID:415069

Tennant, G B

1977-01-01

322

Cis-trans isomerization in the S1 state of acetylene: Identification of cis-well vibrational levels  

NASA Astrophysics Data System (ADS)

A systematic analysis of the S1-trans ({tilde A}1Au) state of acetylene, using IR-UV double resonance along with one-photon fluorescence excitation spectra, has allowed assignment of at least part of every single vibrational state or polyad up to a vibrational energy of 4200 cm-1. Four observed vibrational levels remain unassigned, for which no place can be found in the level structure of the trans-well. The most prominent of these lies at 46 175 cm-1. Its 13C isotope shift, exceptionally long radiative lifetime, unexpected rotational selection rules, and lack of significant Zeeman effect, combined with the fact that no other singlet electronic states are expected at this energy, indicate that it is a vibrational level of the S1-cis isomer ({tilde A}1A2). Guided by ab initio calculations [J. H. Baraban, A. R. Beck, A. H. Steeves, J. F. Stanton, and R. W. Field, J. Chem. Phys. 134, 244311 (2011)], 10.1063/1.3570823 of the cis-well vibrational frequencies, the vibrational assignments of these four levels can be established from their vibrational symmetries together with the 13C isotope shift of the 46 175 cm-1 level (assigned here as cis-3161). The S1-cis zero-point level is deduced to lie near 44 900 cm-1, and the ?6 vibrational frequency of the S1-cis well is found to be roughly 565 cm-1; these values are in remarkably good agreement with the results of recent ab initio calculations. The 46 175 cm-1 vibrational level is found to have a 3.9 cm-1 staggering of its K-rotational structure as a result of quantum mechanical tunneling through the isomerization barrier. Such tunneling does not give rise to ammonia-type inversion doubling, because the cis and trans isomers are not equivalent; instead the odd-K rotational levels of a given vibrational level are systematically shifted relative to the even-K rotational levels, leading to a staggering of the K-structure. These various observations represent the first definite assignment of an isomer of acetylene that was previously thought to be unobservable, as well as the first high resolution spectroscopic results describing cis-trans isomerization.

Merer, Anthony J.; Steeves, Adam H.; Baraban, Joshua H.; Bechtel, Hans A.; Field, Robert W.

2011-06-01

323

21 CFR 864.7250 - Erythropoietin assay.  

Code of Federal Regulations, 2013 CFR

...assay. (a) Identification. A erythropoietin assay is a device that measures the concentration of erythropoietin (an enzyme that regulates the production of red blood cells) in serum or urine. This assay provides diagnostic information for the...

2013-04-01

324

Exceptional reductions  

NASA Astrophysics Data System (ADS)

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

Marrani, Alessio; Orazi, Emanuele; Riccioni, Fabio

2011-04-01

325

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

326

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

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

327

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

328

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

329

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

330

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

PubMed

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

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

2012-03-22

331

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

PubMed

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

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

2013-01-01

332

Temperature and pressure dependence of the absolute rate constant for the reactions of NH2 radicals with acetylene and ethylene  

NASA Technical Reports Server (NTRS)

The absolute rate constants for the reaction between the NH2 free radical and acetylene and ethylene is measured experimentally using a flash photolysis technique. The constant is considered to be a function of temperature and pressure. At each temperature level of the experiment, the observed pseudo-first-order rate constants were assumed to be independent of flash intensity. The results of the experiment indicate that the bimolecular rate constant for the NH2 + C2H2 reaction increases with pressure at 373 K and 459 K but not at lower temperatures. Results near the pressure limit conform to an Arrhenius expression of 1.11 (+ or -) 0.36 x 10 to the -13th over the temperature range from 241 to 459 K. For the reaction NH2 + C2H4, a smaller rate of increase in the bimolecular rate constant was observed over the temperature range 250-465 K. The implications of these results for current theoretical models of NH2 + C2H2 (or H4) reactions in the atmospheres of Jupiter and Saturn are discussed.

Bosco, S. R.; Nava, D. F.; Brobst, W. D.; Stief, L. J.

1984-01-01

333

Characterization of nitrogen-fixing moderate halophilic cyanobacteria isolated from saline soils of Songnen Plain in China  

Microsoft Academic Search

Twenty out of 200 isolates of cyanobacteria mainly from saline soils of Songnen Plain of China were successfully grown on BG11 N-free medium. The nitrogen-fixing activity was then demonstrated for the 20 isolates in modified BG11 medium using the acetylene reduction assay. All of them possessed appreciable nitrogenase activity (acetylene reduction) under non-saline conditions; however, at 5% NaCl only 60%

Wei Zhang; Yujie Feng

2008-01-01

334

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

335

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

336

Barcoded microchips for biomolecular assays.  

PubMed

Multiplexed assay of analytes is of great importance for clinical diagnostics and other analytical applications. Barcode-based bioassays with the ability to encode and decode may realize this goal in a straightforward and consistent manner. We present here a microfluidic barcoded chip containing several sets of microchannels with different widths, imitating the commonly used barcode. A single barcoded microchip can carry out tens of individual protein/nucleic acid assays (encode) and immediately yield all assay results by a portable barcode reader or a smartphone (decode). The applicability of a barcoded microchip is demonstrated by human immunodeficiency virus (HIV) immunoassays for simultaneous detection of three targets (anti-gp41 antibody, anti-gp120 antibody, and anti-gp36 antibody) from six human serum samples. We can also determine seven pathogen-specific oligonucleotides by a single chip containing both positive and negative controls. PMID:25513831

Zhang, Yi; Sun, Jiashu; Zou, Yu; Chen, Wenwen; Zhang, Wei; Xi, Jianzhong Jeff; Jiang, Xingyu

2015-01-20

337

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

338

Aldehyde Reduction by Cytochrome P450  

PubMed Central

This protocol describes the procedure for measuring the relative rates of metabolism of the ?,?-unsaturated aldehydes, 9-anthracene aldehyde (9-AA) and 4-hydroxy-trans-2-nonenal (4-HNE); specifically the aldehyde reduction reactions of cytochrome P450s (CYPs). These assays can be performed using either liver microsomal or other tissue fractions, spherosome preparations of recombinant CYPs, or recombinant CYPs from other sources. The method used here to study the reduction of a model ?,?-unsaturated aldehyde, 9-AA, by CYPs was adapted from the assay used to investigate 9-anthracene oxidation as reported by Marini et al. (Marini et al., 2003). For experiments measuring reduction of the endogenous aldehyde, 4-HNE, the substrate was incubated with CYP in the presence of oxygen and NADPH and the metabolites were separated by High Pressure Liquid Chromatograpy (HPLC), using an adaptation of the method of Srivastava et al. (Srivastava et al., 2010). For study of 9-AA and 4-HNE reduction, the first step involves incubation of the substrate with the CYP in appropriate media, followed by quantification of metabolites through either spectrofluorimetry or analysis by HPLC coupled with a radiometric assay, respectively. Metabolite identification can be achieved by HPLC GC-mass spectrometric analysis. Inhibitors of cytochrome P450 function can be utilized to show the role of the hemoprotein or other enzymes in these reduction reactions. The reduction reactions for CYP’s were not inhibited by either anaerobiosis or inclusion of CO in the gaseous phase of the reaction mixture. These character of these reactions are similar to those reported for some cytochrome P450-catalyzed azo reduction reactions. PMID:21553396

Amunom, Immaculate; Srivastava, Sanjay; Prough, Russell A.

2011-01-01

339

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

340

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

341

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

342

Recent advances in enzyme assays  

Microsoft Academic Search

Enzyme assays for high-throughput screening and enzyme engineering, which are often based on derivatives of coumarin, nitrophenol, fluorescein, nitrobenzofurazane or rhodamine dyes, can be divided into two categories: those that depend on labelled substrates, and those that depend on sensing the reactions of unmodified substrates. Labelled substrates include, for example, fluorogenic and chromogenic substrates that generate a reporter molecule by

Jean-Philippe Goddard; Jean-Louis Reymond

2004-01-01

343

Comparisons of a proposed five-seed assay method with the single-seed and batch assay methods for I-125 seeds in ultrasound-guided prostate implants.  

PubMed

A simple five-seed assay method was proposed and investigated. A commercial well ion chamber system with an NIST-traceable single-seed calibration constant was used for the single-seed assays. A batch seed holder was used for batch assays. For the five-seed assays, a second single-seed holder was modified such that all five seeds were loaded in a central region of the well ion chamber. Compared with the same seed in the standard single-seed holder, the relative chamber responses for the five seed positions were 0.993, 0.993, 1.000, 1.001, and 0.977, respectively, indicating little or no position-dependent chamber response and no self-attenuation among seeds. Subsequent comparison of assays with the single-seed and five-seed methods indicated only 0.4% difference in charge collection. The five-seed calibration constant was therefore taken to be the same as the single-seed calibration constant. The reproducibility of the five-seed assay method was found to be better than 0.8%. When a dummy seed replaced an active seed, a nearly 20% reduction in charge was found, indicating that the proposed five-seed assay method can detect a dead seed. Clinical comparison of all three assay methods showed that they produced qualitatively the same assay results when the batch assay method was performed with extra care. Compared with the single-seed assay method, the five-seed method is equally simple, rigid, and reproducible, but it demands much less assay time. Compared with the batch assay method, the five-seed method is much more reproducible and reliable because of its rigid assay geometry; it only demands a moderate amount of assay time and can detect dead seeds. The American Association of Physicists in Medicine Task Group 40 (AAPM TG40) states that, for brachytherapy, ideally every (i.e., 100%) loose seed should be calibrated. For procedures involving large number of loose seeds, it then recommends that 10% of seeds be calibrated. The proposed five-seed assay is very simple to implement. It will facilitate the compliance of the "10%" recommendation from the AAPM TG40; it will make the "ideally 100%" statement from AAPM TG40 a more realistic and practical QA procedure in seed assaying. PMID:10644061

Lee, P C; Starr, S J; Zuhlke, K; Moran, B J

1999-01-01

344

Rotational Dependence of Intramolecular Dynamics in Acetylene at Low Vibrational Excitation as Deduced from High Resolution Spectroscopy  

NASA Astrophysics Data System (ADS)

The link between energy-resolved spectra and time-resolved dynamics is explored quantitatively for acetylene (12C2H2), X1?g+ with up to 8,600 wn of vibrational energy. This comparison is based on the extensive knowledge of the vibration-rotation energy levels and on the model Hamiltonian used to fit them to high precision. Simulated intensity borrowing features in high resolution absorption spectra and predicted survival probabilities for intramolecular vibrational redistribution (IVR) are first investigated for the ?4+?5 and ?3 bright states, for J = 2, 30 and 100. The dependence of the results on the rotational quantum number and on the choice of vibrational bright state reflects the interplay of three kinds of off-diagonal resonances: anharmonic, rotational l-type, and Coriolis. The dynamical quantities used to characterize the calculated time-dependent dynamics are the dilution factor ?d, the IVR lifetime ?IVR, and the recurrence time ?rec. For the two bright states ?3+2?4 and 7?4, the collisionless dynamics for thermally averaged rotational distributions at T = 27, 270 and 500 K were calculated from the available spectroscopic data. For the 7?4 bright state, an apparent irreversible decay of is found. In all cases, the model Hamiltonian allows a detailed calculation of the energy flow among all of the coupled zeroth-order vibration-rotation states. B. Amyay, S. Robert, M. Herman, A. Fayt, B. Raghavendra, A. Moudens, J. Thiévin, B. Rowe, and R. Georges, J. Chem. Phys., 131, 114301 (2009).

Perry, David S.; Miller, Anthony; Amyay, B.; Fayt, A.; Herman, M.

2010-06-01

345

A DFT study on the mechanisms for the cycloaddition reactions between 1-aza-2-azoniaallene cations and acetylenes.  

PubMed

The mechanisms of cycloaddition reactions between 1-aza-2-azoniaallene cations 1 and acetylenes 2 have been investigated using the global electrophilicity and nucleophilicity of the corresponding reactants as global reactivity indexes defined within the conceptual density functional theory. The reactivity and regioselectivity of these reactions were predicted by analysis of the energies, geometries, and electronic nature of the transition state structures. The theoretical results revealed that the reaction features a tandem process: an ionic 1,3-dipolar cycloaddition to produce the cycloadducts 3?H-pyrazolium salts 3 followed by a [1,2]-shift affording the thermodynamically more stable adducts 4 or 5. The mechanism of the cycloaddition reactions can be described as an asynchronous concerted pathway with reverse electron demand. The model reaction has also been investigated at the QCISD/6-31++G(d,p) and CCSD(T)/6-31++G(d,p)//B3LYP/6-31++G(d,p) levels as well as by the DFT. The polarizable continuum model, at the B3LYP/6-31++G(d,p) level of theory, was used to study solvent effects on all the studied reactions. In solvent dichloromethane, all the initial cycloadducts 3 were obtained via direct ionic process as the result of the solvent effect. The consecutive [1,2]-shift reaction, in which intermediates 3 are rearranged to the five-membered heterocycles 4/5, is proved to be a kinetically controlled reaction, and the regioselectivity can be modulated by varying the migrant. The LOL function and RDG function based on localized electron analysis were used to analysis the covalent bond and noncovalent interactions in order to unravel the mechanism of the title reactions. PMID:22810049

Wang, Jing-mei; Li, Zhi-ming; Wang, Quan-rui; Tao, Feng-gang

2013-01-01

346

Gas Phase Molecular Spectroscopy: Electronic Spectroscopy of Combustion Intermediates, Chlorine Azide kinetics, and Rovibrational Energy Transfer in Acetylene  

NASA Astrophysics Data System (ADS)

This dissertation is composed of three sections. The first deals with the electronic spectroscopy of combustion intermediates that are related to the formation of polycyclic aromatic hydrocarbons. Absorption spectra for phenyl, phenoxy, benzyl, and phenyl peroxy radicals were recorded using the technique of cavity ring-down spectroscopy. When possible, molecular constants, vibrational frequencies, and excited state lifetimes for these radicals were derived from these data. The results were supported by theoretical predictions. The second section presents a study of electron attachment to chlorine azide (ClN3) using a flowing-afterglow Langmuir-probe apparatus. Electron attachment rates were measured to be 3.5x10-8 and 4.5x10-8 cm3s-1 at 298 and 400 K respectively. The reactions of ClN3 with eighteen cations and seventeen anions were characterized. Rate constants were measured using a selected ion flow tube. The ionization energy (>9.6eV), proton affinity (713+/-41 kJ mol-1), and electron affinity (2.48+/-0.2 eV) for ClN 3 were determined from these data. The third section demonstrates the use of double resonance spectroscopy to observe state-selected rovibrational energy transfer from the first overtone asymmetric stretch of acetylene. The total population removal rate constants from various rotational levels of the (1,0,1,00,00) vibrational state were determined to be in the range of (9-17) x 10 -10 cm3s-1. Rotational energy transfer accounted for approximately 90% of the total removal rate from each state. Therefore, the upper limit of vibrational energy transfer from the (1,0,1,0 0,00) state was 10%.

Freel, Keith A.

347

Reaction of phenyl radicals with acetylene: quantum chemical investigation of the mechanism and master equation analysis of the kinetics.  

PubMed

The mechanism of the C(6)H(5) + C(2)H(2) reaction has been investigated by various quantum chemical methods. Electrophilic addition to the CC triple bond is found to be the only important mode of phenyl radical attack on acetylene. The initially formed chemically activated C(6)H(5)C(2)H(2) adducts may follow several isomerization pathways in competition with collisional stabilization and H-elimination. Thermochemistry of various decomposition and isomerization channels is evaluated by the G2M method. For key intermediates, the following standard enthalpies of formation have been deduced from isodesmic reactions: 94.2 +/- 2.0 kcal/mol (C(6)H(5)CHCH), 86.4 +/- 2.0 kcal/mol (C(6)H(5)CCH(2)), and 95.5 +/- 1.8 kcal/ mol (o-C(6)H(4)C(2)H(3)). The accuracy of theoretical predictions was examined through extensive comparisons with available experimental and theoretical data. The kinetics and product branching of the C(6)H(5) + C(2)H(2) reaction have been evaluated by weak collision master equation/Rice-Ramsperger-Kassel-Marcus (RRKM) analysis of the truncated kinetic model including only kinetically important transformations of the isomeric C(8)H(7) radicals. Available experimental kinetic data can be quantitatively reproduced by calculation with a minor adjustment of the C(6)H(5) addition barrier from 3.7 to 4.1 kcal/mol. Our predicted total rate constant, k(R1) = (1.29 x 10(10))T(0.834) exp(-2320/T) cm(3) mol(-)(1) s(-)(1), is weakly dependent on P and corresponds to the phenylation process under combustion conditions (T > 1000 K). PMID:16220963

Tokmakov, I V; Lin, M C

2003-09-17

348

Spectroscopy in separated flames--VII: Determination of bismuth by atomic-fluorescence spectroscopy in a separated air-acetylene flame with electronically modulated electrodeless discharge tube sources.  

PubMed

The application of electronically modulated and unmodulated bismuth and iodine electrodeless discharge lamps as sources for the excitation of bismuth atomic fluorescence in conventional and nitrogen-separated air-acetylene flames has been investigated. Separation of the flame results in improved detection limits for bismuth even when a modulated source is employed. The effect of 500-fold weight excesses of foreign ions on the determination of bismuth at 302.46 nm with a modulated iodine source and separated flame has been studied; only calcium and zirconium are found to cause significant interference. The determination of bismuth in aluminium alloy samples is reported. PMID:18960956

Hobbs, R S; Kirkbright, G F; West, T S

1971-09-01

349

Influence of chlorine coordination number on the catalytic mechanism of ruthenium chloride catalysts in the acetylene hydrochlorination reaction: a DFT study.  

PubMed

The catalytic mechanism of Ru-based catalysts in the acetylene hydrochlorination reaction has been investigated via the density functional theory (DFT) method. To study the effect of the chlorine coordination number on the catalytic mechanism, Ru3Cl9, Ru3Cl7, Ru5Cl7, Ru3Cl3 and Ru3 clusters were chosen as the catalytic models. Our results show that the energy barrier for acetylene hydrochlorination on Ru3Cl9 was as high as 1.51 eV at 458 K. When the chlorine coordination number decreased, the energy barriers on Ru3Cl7, Ru5Cl7, Ru3Cl3 and Ru3 were 1.29, 0.89, 1.01 and 1.42 eV, respectively. On Ru3Cl9, the H and Cl atoms of HCl were simultaneously added to C2H2 to form C2H3Cl, while the reaction was divided into two steps on Ru3Cl7, Ru3Cl3 and Ru3 clusters. The first step was the addition of H atom of HCl to C2H2 to form C2H3?, and the second step was the addition of Cl atom to C2H3? to form C2H3Cl. The step involving the addition of Cl was the rate-controlling step during the whole reaction. On Ru5Cl7 cluster, there was an additional step before the steps involving the addition of H and Cl: the transfer of H atom from HCl to Ru atom. This step was the rate-controlling step during the reaction of acetylene hydrochlorination on Ru5Cl7 and its energy barrier was the lowest among all the above-mentioned catalytic models. Therefore, the Ru5Cl7 cluster played the most predominant role in acetylene hydrochlorination with the largest reaction rate constant kTST of 10(3). PMID:25712403

Han, You; Sun, Mengxia; Li, Wei; Zhang, Jinli

2015-03-11

350

Time-dependent density-functional study of the alignment-dependent ionization of acetylene and ethylene by strong laser pulses  

NASA Astrophysics Data System (ADS)

The alignment-dependent ionization of acetylene and ethylene in short laser pulses is investigated in the framework of the time-dependent density-functional theory coupled with Ehrenfest dynamics. The molecular alignment is found to have a substantial effect on the total ionization. Bond stretching is shown to cause an increase of the ionization efficiency, i.e., enhanced ionization, in qualitative agreement with previous theoretical investigations. It is also demonstrated that the enhanced ionization mechanism greatly enhances the ionization from the inner valence orbitals, and the ionization of the inner orbitals is primarily due to their extended weakly bound density tails.

Russakoff, Arthur; Bubin, Sergiy; Xie, Xinhua; Erattupuzha, Sonia; Kitzler, Markus; Varga, Kálmán

2015-02-01

351

Visible-to-near infrared standard source generation using acetylene ( 13C 2H 2)-stabilized comb-injection-locked technique  

NASA Astrophysics Data System (ADS)

An ultra-stable visible laser source (VLS) was generated by the second harmonic of a selectively injection-locked distributed feedback (DFB) laser from an optical frequency comb with acetylene-stabilized laser seeding. For the second-harmonic generation (SHG) of the injection-locked DFB laser, we used periodically poled lithium niobate (PPLN) crystal and generated the VLS at a region of 771 nm, which was discretely locked to a spacing of 25 GHz within the PPLN bandwidth (180 GHz). The frequency stability of this source was estimated to be 1.1 × 10 - 12 with an average time of 1 s.

Lee, S. H.; Ryu, H. Y.; Kim, Y. P.; Suh, H. S.; Eom, T. B.

2010-10-01

352

Fe(3+)-Fe(2+) transformation method: an important antioxidant assay.  

PubMed

If we look at the multitude of varied and interesting reaction that constitute biochemistry and bioorganic chemistry, it is possible to classify a great many as either oxidation or reduction reactions. The reducing agent transfers electrons to another substance and is thus it oxidized. And, because it gives electrons, it is also called an electron donor. Electron donors can also form charge transfer complexes with electron acceptors. Reductants in biochemistry are very diverse. For example ferric ions (Fe(3+)) are good reducing agents. Also, different bioanalytical reduction methods are available such as Fe(3+)-ferrous ions (Fe(2+)) reduction method, ferric reducing antioxidant power reducing assay. In this section, Fe(3+)-Fe(2+) transformation will be discussed. Recently there has been growing interest in research into the role of plant-derived antioxidants in food and human health. The beneficial influence of many foodstuffs and beverages including fruits, vegetables, tea, coffee, and cacao on human health has been recently recognized to originate from their antioxidant activity. For this purpose, the most commonly method used in vitro determination of reducing capacity of pure food constituents or plant extracts is Fe(3+) reducing ability. This commonly used reducing power method is reviewed and presented in this study. Also, the general chemistry underlying this assay was clarified. Hence, this overview provides a basis and rationale for developing standardized antioxidant capacity methods for the food, nutraceutical, and dietary supplement industries. In addition, the most important advantages of this method were detected and highlighted. The chemical principles of these methods are outlined and critically discussed. The chemical principles of methods of Fe(3+)-Fe(2+) transformation assay are outlined and critically discussed. PMID:25323511

Gülçin, ?lhami

2015-01-01

353

STATUS OF PORTABLE NON DESTRUCTIVE ASSAY (NDA) AT THE PLUTONIUM FINISHING PLANT (PFP)  

SciTech Connect

Collimated portable gamma-ray detectors are used to quantify the plutonium holdup in support of facility deactivation and decommissioning. The Generalized Geometry Holdup model recently has been implemented for data reduction to support a new decontamination and decommissioning mission. An approach to assess the total measurement uncertainty (TMU) has been developed. The TMU is added to the assay value for compliance with safety based limits. Details of the measurement techniques and comparisons to assays of materials removed are described.

KEELE, B.D.

2005-06-10

354

Assaying PTEN catalysis in vitro.  

PubMed

PTEN is a major tumour suppressor protein and a regulator of numerous diverse biological processes. It has an evolutionarily conserved role as a phosphoinositide lipid phosphatase, regulating the PI3K signalling pathway, but also has catalytic phosphatase activity against protein substrates, although the significance of this latter activity is less well understood. Unlike many tumour suppressors, even modest changes in PTEN activity can have strong effects on phenotypes, including tumour formation. Due to this recognised functional significance, several experimental platforms have been developed to assay the catalytic activity of PTEN against different substrates and are being applied to understand this cellular substrate diversity and the regulation of PTEN. Here we present and discuss methods to assay the phosphatase activity of PTEN in vitro. PMID:25461809

Spinelli, Laura; Leslie, Nicholas R

2015-05-01

355

SNO+ Scintillator Purification and Assay  

Microsoft Academic Search

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

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

2011-01-01

356

SNO+ Scintillator Purification and Assay  

Microsoft Academic Search

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

R. Ford; M. Chen; O. Chkvorets; D. Hallman; E. Va´zquez-Ja´uregui

2011-01-01

357

Northwest Australia's Saladin crude assayed  

Microsoft Academic Search

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

1993-01-01

358

Dehydrogenase activity of forest soils depends on the assay used  

NASA Astrophysics Data System (ADS)

Dehydrogenases are exclusively intracellular enzymes, which play an important role in the initial stages of oxidation of soil organic matter. One of the most frequently used methods to estimate dehydrogenase activity in soil is based on the use of triphenyltetrazolium chloride as an artificial electron acceptor. The purpose of this study was to compare the activity of dehydrogenases of forest soils with varied physicochemical properties using different triphenyltetrazolium chloride assays. The determination was carried out using the original procedure by Casida et al., a modification of the procedure which involves the use of Ca(OH)2 instead of CaCO3, the Thalmann method, and the assay by Casida et al. without addition of buffer or any salt. Soil dehydrogenase activity depended on the assay used. Dehydrogenase determined by the Casida et al. method without addition of buffer or any salt correlated with the pH values of soils. The autoclaved strongly acidic samples of control soils showed high concentrations of triphenylformazan, probably due to chemical reduction of triphenyltetrazolium chloride. There is, therefore, a need for a sterilization method other than autoclaving, ie a process that results in significant changes in soil properties, thus helping to increase the chemical reduction of triphenyltetrazolium chloride.

Januszek, Kazimierz; D?uga, Joanna; Socha, Jaros?aw

2015-01-01

359

Assay of deoxyhypusine synthase activity.  

PubMed

Deoxyhypusine synthase catalyzes an unusual protein modification reaction. A portion of spermidine is covalently added to one specific lysine residue of one eukaryotic protein, eIF5A (eukaryotic initiation factor 5A) to form a deoxyhypusine residue. The assay measures the incorporation of radioactivity from [1,8-(3)H]spermidine into the eIF5A protein. The enzyme is specific for the eIF5A precursor protein and does not work on short peptides (<50 amino acids). Optimum conditions for the reaction and four detection methods for the product, deoxyhypusine-containing eIF5A, are described in this chapter. The first, and most specific, method is the measurement of the amount of [(3)H]deoxyhypusine in the protein hydrolysate after its separation by ion exchange chromatography. However, this method requires some specialized equipment. The second method is counting the radioactivity in TCA-precipitated protein after thorough washing. The third method involves determining the radioactivity in the band of [(3)H]deoxyhypusine-containing eIF5A after separation by SDS-PAGE. The fourth method is a filter-binding assay. It is important to minimize nonspecific binding of [(3)H]spermidine to proteins in the assay mixture, especially for methods 2 and 4, as illustrated in a comparison figure in the chapter. PMID:21318875

Wolff, Edith C; Lee, Seung Bum; Park, Myung Hee

2011-01-01

360

Hydrocarbon growth via ion-molecule reactions: computational studies of the isomers of C?H2??, C?H?? and C?H?? and their formation paths from acetylene and its fragments.  

PubMed

We seek insight into the origin of observations made in plasma experiments mimicking interstellar and circumstellar conditions. To this end theory is applied to the low-energy isomers of C4H2(+), C6H2(+) and C6H4(+) and their formation paths from acetylene and its fragments. Ab initio molecular dynamics trajectories are performed to explore which isomers are readily accessible from acetylene and its ion fragments. Structural information at a high level of electronic structure theory [CCSD(T)/cc-pVTZ], as well as information on the vibrational [UMP2] and electronic spectra [?B97X] of the low-energy isomers is reported. PMID:25474483

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

2015-01-21

361

One-pot assembly of 4-methylene-3-oxa-1-azabicyclo[3.1.0]hexanes from alkyl aryl(hetaryl) ketoximes, acetylene, and aliphatic ketones: a new three-component reaction  

Microsoft Academic Search

A new three-component reaction between alkyl aryl(hetaryl)ketoximes, acetylene, and aliphatic ketones in the superbasic systems KOH\\/DMSO and LiOH\\/CsF\\/DMSO (70–90°C, initial acetylene pressure 13–15atm, 5–60min) affords novel 4-methylene-3-oxa-1-azabicyclo[3.1.0]hexanes in yields of up to 75%. Using KOH\\/DMSO, the side products of the reaction are O-vinylketoximes and 2-aryl(hetaryl)pyrroles, while with LiOH\\/CsF\\/DMSO, the reaction proves to be selective, only minor amounts of the corresponding

Boris A. Trofimov; Elena Yu. Schmidt; Al’bina I. Mikhaleva; Igor A. Ushakov; Nadezhda I. Protsuk; Elena Yu. Senotrusova; Olga N. Kazheva; Grigorii G. Aleksandrov; Oleg A. Dyachenko

2009-01-01

362

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

363

Comparison of rapid screening assays using organic chemicals  

SciTech Connect

In a continuation of a study presented last year using metals, the sensitivity of short term toxicity tests is examined using common organic chemicals. In toxicity testing, the focus has shifted from the traditional long-term studies utilizing the mortality of complex, multicellular eukaryotic organisms as the endpoint towards short-term studies in which transformation of biochemical pathways are monitored. The relative sensitivity of aquatic screening techniques are compared to the standardized 48-hr Daphnia magna and Ceriodaphnia dubia, 96-hr fathead minnow and 96-hr algal acute assays. The short-term test procedures investigated are: dehydrogenase enzyme activity assays utilizing triphenyltetrazolium chloride (TTC) and resazurin as the calorimetric indicators; TOXI-Chromotest, inhibition of {beta}-galactosidase; reduction in bioluminescence output utilizing the Microtox{reg_sign} test; nitrification inhibition assays with a commercial preparation of nitrifying bacteria (Nitroseed{trademark}) and municipal activated sludge; respiration inhibition assays with a commercial preparation of heterotrophic bacteria (Polytox{reg_sign}) and activated sludge; inhibition of root growth in terrestrial plants; and galactosidase inhibition through the use of a fluorometrically tagged substrate with the Daphnia magna IQ{trademark} test. Toxicity values generated by this laboratory on commonly used organic chemicals are compared.

Beach, S.A.; Robideau, R.R. [3M Environmental Lab., St. Paul, MN (United States)

1994-12-31

364

Enzymatic assay for GHB determination in forensic matrices.  

PubMed

Current procedures for the determination of gamma-hydroxybutyric acid (GHB) require time-consuming extraction and derivatization steps before chromatographic detection, making a high-throughput alternative desirable. Bühlmann Laboratories offers an enzymatic assay for the quantitative determination of GHB in urine and serum. We report the adaptation of this photometric assay to the Thermo Scientific MGC-240 analyzer and its use in the determination of GHB in forensic matrices including urine, whole blood and vitreous humour. Most matrices require only a brief centrifugation before analysis, while blood requires an additional protein precipitation step. A variety of cases (sexual assaults, impaired drivers and death investigations) have been analyzed alongside the gas chromatography-mass spectrometry (GC-MS) reference method. Correlation with the GC-MS has been found to be acceptable, with no false negatives and few false positives, although postmortem samples appear more prone to testing false positive than do antemortem samples. Simple sample preparation and high throughput allow for a significant reduction in analysis time relative to chromatographic methods. This assay is used as a screening method in our laboratory, with a quantitative GC-MS method serving for the confirmation of positive results. To our knowledge, this represents the first evaluation of an enzymatic assay for GHB in a forensic context. PMID:22722059

Grenier, Vincent; Huppé, Geneviève; Lamarche, Martine; Mireault, Pascal

2012-09-01

365

Circulating Tumor Cell Assay Frequently Asked Questions  

Cancer.gov

Version: July 2010 Circulating Tumor Cell Assay Frequently Asked Questions LHTP003.8.1 ?H2AX IMMUNOFLUORESCENCE ASSAY FOR CIRCULATING TUMOR CELLS USING THE CELLSEARCH SYSTEM 1. Do I need any prior experience before applying for the training

366

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.

367

Reactions between chlorine atom and acetylene in solid para-hydrogen: Infrared spectrum of the 1-chloroethyl radical  

SciTech Connect

We applied infrared matrix isolation spectroscopy to investigate the reactions between Cl atom and acetylene (C{sub 2}H{sub 2}) in a para-hydrogen (p-H{sub 2}) matrix at 3.2 K; Cl was produced via photodissociation at 365 nm of matrix-isolated Cl{sub 2} in situ. The 1-chloroethyl radical ({center_dot}CHClCH{sub 3}) and chloroethene (C{sub 2}H{sub 3}Cl) are identified as the main products of the reaction Cl + C{sub 2}H{sub 2} in solid p-H{sub 2}. IR absorption lines at 738.2, 1027.6, 1283.4, 1377.1, 1426.6, 1442.6, and 2861.2 cm{sup -1} are assigned to the 1-chloroethyl radical. For the reaction of Cl + C{sub 2}D{sub 2}, lines due to the {center_dot}CDClCH{sub 2}D radical and trans-CHDCDCl are observed; the former likely has a syn-conformation. These assignments are based on comparison of observed vibrational wavenumbers and {sup 13}C- and D-isotopic shifts with those predicted with the B3LYP/aug-cc-pVDZ and MP2/aug-cc-pVDZ methods. Our observation indicates that the primary addition product of Cl + C{sub 2}H{sub 2}, 2-chlorovinyl ({center_dot}CHCHCl) reacts readily with a neighboring p-H{sub 2} molecule to form {center_dot}CHClCH{sub 3} and C{sub 2}H{sub 3}Cl. Observation of {center_dot}CDClCH{sub 2}D and trans-CHDCDCl from Cl + C{sub 2}D{sub 2} further supports this conclusion. Although the reactivity of p-H{sub 2} appears to be a disadvantage for making highly reactive free radicals in solid p-H{sub 2}, the formation of 1-chloroethyl radical indicates that this secondary reaction might be advantageous in producing radicals that are difficult to prepare from simple photolysis or bimolecular reactions in situ.

Golec, Barbara [Department of Applied Chemistry and Institute of Molecular Science, National Chiao Tung University, Hsinchu 30010, Taiwan (China); Lee, Yuan-Pern [Department of Applied Chemistry and Institute of Molecular Science, National Chiao Tung University, Hsinchu 30010, Taiwan (China); Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan (China)

2011-10-28

368

Reactions between chlorine atom and acetylene in solid para-hydrogen: Infrared spectrum of the 1-chloroethyl radical  

SciTech Connect

We applied infrared matrix isolation spectroscopy to investigate the reactions between Cl atom and acetylene (C{sub 2}H{sub 2}) in a para-hydrogen (p-H{sub 2}) matrix at 3.2 K; Cl was produced via photodissociation at 365 nm of matrix-isolated Cl{sub 2} in situ. The 1-chloroethyl radical ({center_dot}CHClCH{sub 3}) and chloroethene (C{sub 2}H{sub 3}Cl) are identified as the main products of the reaction Cl + C{sub 2}H{sub 2} in solid p-H{sub 2}. IR absorption lines at 738.2, 1027.6, 1283.4, 1377.1, 1426.6, 1442.6, and 2861.2 cm{sup -1} are assigned to the 1-chloroethyl radical. For the reaction of Cl + C{sub 2}D{sub 2}, lines due to the {center_dot}CDClCH{sub 2}D radical and trans-CHDCDCl are observed; the former likely has a syn-conformation. These assignments are based on comparison of observed vibrational wavenumbers and {sup 13}C- and D-isotopic shifts with those predicted with the B3LYP/aug-cc-pVDZ and MP2/aug-cc-pVDZ methods. Our observation indicates that the primary addition product of Cl + C{sub 2}H{sub 2}, 2-chlorovinyl ({center_dot}CHCHCl) reacts readily with a neighboring p-H{sub 2} molecule to form {center_dot}CHClCH{sub 3} and C{sub 2}H{sub 3}Cl. Observation of {center_dot}CDClCH{sub 2}D and trans-CHDCDCl from Cl + C{sub 2}D{sub 2} further supports this conclusion. Although the reactivity of p-H{sub 2} appears to be a disadvantage for making highly reactive free radicals in solid p-H{sub 2}, the formation of 1-chloroethyl radical indicates that this secondary reaction might be advantageous in producing radicals that are difficult to prepare from simple photolysis or bimolecular reactions in situ.

Golec, Barbara [Department of Applied Chemistry and Institute of Molecular Science, National Chiao Tung University, Hsinchu 30010, Taiwan (China); Lee, Yuan-Pern [Department of Applied Chemistry and Institute of Molecular Science, National Chiao Tung University, Hsinchu 30010, Taiwan (China); Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan (China)

2011-11-07

369

A new route for the prebiotic synthesis of nucleobases and hydantoins in water/ice solutions involving the photochemistry of acetylene.  

PubMed

The origin of nucleobases and other heterocycles is a classic question in the chemistry of the origins of life. The construction of laboratory models for the abiotic synthesis of nitrogen heterocycles in plausible natural conditions also aids the understanding and prediction of chemical species in the Solar System. Here, we report a new explanation for the origin of hydantoins, purines, and pyrimidines in eutectic water/ice/urea solutions driven by ultraviolet irradiation (in the 185-254?nm range, UVC) of acetylene under anoxic conditions. An analysis of the products indicates the synthesis of hydantoin and 5-hydroxyhydantoin, the purines uric acid, xanthine, and guanine, and the pyrimidines uracil and cytosine. The synthesis occurred together with the photo-oxidation of bases in a complex process for which possible pathways are proposed. In conclusion, an acetylene-containing atmosphere could contribute to the origin of nucleobases in the presence of a urea/water system by an HCN-independent mechanism. The presence of ice has a dual role as a favorable medium for the synthesis of nucleobases and protection against degradation and as a source of free radicals for the synthesis of highly oxidized heterocycles. A mechanism for the origin of hydantoins and uracil from urea in plausible conditions for prebiotic chemistry is also proposed. PMID:23536286

Menor-Salván, César; Marín-Yaseli, Margarita R

2013-05-10

370

Effect of TiO2 crystalline phase composition on the physicochemical and catalytic properties of Pd/TiO(2) in selective acetylene hydrogenation.  

PubMed

Pd/TiO(2) catalysts have been prepared using TiO(2) supports consisting of various rutile/anatase crystalline phase compositions. Increasing percentages of rutile phase in the TiO(2) resulted in a decrease in Brunauer-Emmett-Teller surface areas, fewer Ti(3+) sites, and lower Pd dispersion. While acetylene conversions were found to be merely dependent on Pd dispersion, ethylene selectivity appeared to be strongly affected by the presence of Ti(3+) in the TiO(2) samples. When TiO(2) samples with 0-44% rutile were used, high ethylene selectivities (58-93%) were obtained whereas ethylene losses occurred for those supported on TiO(2) with 85% or 100% rutile phase. X-ray photoelectron spectroscopy and electron spin resonance experiments revealed that a significant amount of Ti(3+) existed in the TiO(2) samples composed of 0-44% rutile. The presence of Ti(3+) in contact with Pd can probably lower the adsorption strength of ethylene resulting in an ethylene gain. Among the five catalysts used in this study, the results for Pd/TiO(2)-R44 suggest an optimum anatase/rutile composition of the TiO(2) used to obtain high selectivity of ethylene in selective acetylene hydrogenation. PMID:16610902

Panpranot, Joongjai; Kontapakdee, Kunyaluck; Praserthdam, Piyasan

2006-04-20

371

Background Assay and Rejection in DRIFT  

E-print Network

The DRIFT-IId dark matter detector is a m$^3$-scale low-pressure TPC with directional sensitivity to WIMP-induced nuclear recoils. Its primary backgrounds were due to alpha decays from contamination on the central cathode. Efforts to reduce these backgrounds led to replacing the 20 \\mu m wire central cathode with one constructed from 0.9 \\mu m aluminized mylar, which is almost totally transparent to alpha particles. Detailed modeling of the nature and origin of the remaining backgrounds led to an in-situ, ppt-sensitive assay of alpha decay backgrounds from the central cathode. This led to further improvements in the thin-film cathode resulting in over 2 orders of magnitude reduction in backgrounds compared to the wire cathode. Finally, the addition of O$_2$ to CS$_2$ gas was found to produce multiple species of electronegative charge carriers, providing a method to determine the absolute position of nuclear recoils and reject all known remaining backgrounds while retaining a high efficiency for nuclear recoil detection.

Jeff Brack; Ed Daw; Alexei Dorofeev; Anthony Ezeribe; Jean-Luc Gauvreau; Michael Gold; John Harton; Randy Lafler; Robert Lauer; Eric R. Lee; Dinesh Loomba; John Matthews; Eric H. Miller; Alissa Monte; Alex Murphy; Sean Paling; Nguyen Phan; Steve Sadler; Andrew Scarff; Daniel Snowden-Ifft; Neil Spooner; Sam Telfer; Daniel Walker; Matt Williams; Leonid Yuriev

2014-04-08

372

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

373

Enhanced sensitivity growth hormone (GH) chemiluminescence assay reveals lower postglucose nadir GH concentrations in men than women  

Microsoft Academic Search

ABSTRACT Modifications,were,made,to a commercially,available,human,(h) GH chemiluminescence assay (Nichols Luma Tag hGH assay), which im- proved,its sensitivity,to,0.002 fig\\/L. The,results,of,this,assay,had,a high,correlation,with,those,of,the,Nichols,hGH,immunoradiometric assay,(IRMA; r = 0.91; P < 0.001). The,addition,of recombinant,hGH- binding,protein,(0.1-10 nmol\\/L),to,standards,and,serum,samples caused,a dose-responsive,reduction,in measured,GH in both,the,chemi- luminescence,assay,and,the,IRMA; at physiological,concentrations,of hGH-binding protein, a lo-20% reduction was observed. Fifteen nor- mal,young,adults,(nine,men,and,six,women),underwent,a standard 100-g oral glucose tolerance test, and plasma GH was measured from

I. M. Chapman; M. L. Hartman; M. Straume; M. L. Johnson; J. D. Veldhuisups

1994-01-01

374

Rapid prototyping of lateral flow assays.  

PubMed

Principles and characteristics of lateral flow strip assays are reviewed. Recent technology developments permit the use of inexpensive electronic readers for interrogating lateral flow strip test results, thus avoiding the inevitable variation and subjectivity of visual inspection to assess the capture of reporter-labeled analyte on test lines of the strip. Protocols for developing lateral flow assays are described, including two specific case studies for assaying cotinine (a small-molecule metabolite of nicotine) in a competitive format, and assaying HIV antibodies in a sandwich-type assay format. PMID:19159100

Volkov, Alexander; Mauk, Michael; Corstjens, Paul; Niedbala, R Sam

2009-01-01

375

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

376

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

377

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. 34 figures.

Burtis, C.A.; Johnson, W.F.; Walker, W.A.

1993-09-07

378

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

379

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

380

Phage Anti-Immunocomplex Assay for Clomazone: Two-Site Recognition Increasing Assay Specificity  

E-print Network

immunosorbent assay (ELISA), which showed excellent correlation with high-performance liquid chro- matographyPhage Anti-Immunocomplex Assay for Clomazone: Two-Site Recognition Increasing Assay Specificity show that phage anti- immunocomplex assay (PHAIA), a method that uses phage-borne peptides to detect

Hammock, Bruce D.

381

Homogeneous Cell and Bead-Based Assays for High Throughput Screening Using Fluorometric Microvolume Assay Technology  

Microsoft Academic Search

High throughput drug screening has become a critical component of the drug discovery process. The screening of libraries containing hundreds of thousands of compounds has resulted in a requirement for assays and instrumentation that are amenable to nonradioactive formats and that can be miniaturized. Homogeneous assays that minimize upstream automation of the individual assays are also preferable. Fluorometric microvolume assay

Sheri Miraglia; Elana E. Swartzman; Julia Mellentin-Michelotti; Lolita Evangelista; Christopher Smith; Iwan Gunawan; Kenton Lohman; Edward M. Goldberg; Bala Manian; Pau-Miau Yuan

1999-01-01

382

S-Tag Rapid Assay The SeTag rapid assay is based on the  

E-print Network

S-Tag Rapid Assay The SeTag rapid assay is based on the reconstitution of ribonucleolytic (RNase S to th e amount of recombinant protein present in the sample. T ypica l assay profil es are shown the conditions of the Rapid Assay. By comparing dIe absorbance profile of a known standard (provided in th e kit

Raines, Ronald T.

383

Evaluating 6 ricin field detection assays.  

PubMed

This study presents data showing the performance of 6 commercial detection assays against ricin around concentrations specified as detection limits by the producers. A 2-fold dilution series of 20?ng/ml ricin was prepared and used for testing the lateral-flow kits: BADD, Pro Strips™, ENVI, RAID DX, Ricin BioThreat Alert, and IMASS™ device. Three of the 6 tested field assays (IMASS™ device, ENVI assay, and the BioThreat Alert assay) were able to detect ricin, although differences in the measured detection limits compared to the official detection limits and false-negative results were observed. We were not able to get the BADD, Pro Strips™, and RAID assays to function in our laboratory. We conclude that when purchasing a field responder assay, there is large variation in the specificity of the assays, and a number of in-house tests must be performed to ensure functionality. PMID:24978020

Slotved, Hans-Christian; Sparding, Nadja; Tanassi, Julia Tanas; Steenhard, Nina R; Heegaard, Niels H H

2014-01-01

384

Factors Influencing the Microbiological Assay of Tobramycin  

PubMed Central

Tobramycin belongs to the aminoglycoside class of antibiotics. Assay procedures were investigated to determine the most suitable methods for the assay of tobramycin in blood, urine, and pharmaceutical preparations. The agar-plate assay was the method of choice for determinations in urine and serum. The turbidimetric assay was selected for the assay of pharmaceutical preparations. An extraction technique is described that minimizes problems encountered in the estimation of tobramycin in urine. Sample diluents, pH, and molarity were important and were variable depending on assay methods. Evidence is presented to show binding of tobramycin to ?-cellulose susceptibility discs. Iron and sodium ions demonstrated potential inhibition of tobramycin in all assay methods tested. PMID:4208898

Lamb, John W.; Mann, Jerry M.; Simmons, Richard J.

1972-01-01

385

Reductive dissolution of goethite by phenolic reductants  

SciTech Connect

The reductive dissolution of goethite ({alpha}-FeOOH) and hematite ({alpha}-Fe{sub 2}O{sub 3}) by phenolic reductants has been examined in order to improve the understanding of iron transformations in soils, sediments and aquifers. Rates of goethite reductive dissolution by hydroquinone increased as the pH was increased from pH 1.8 to 4.65, and the following reaction stoichiometry was obeyed: 2{alpha}-FeOOH + QH{sub 2} = 2Fe{sup 2+} + Q + 4OH{sup {minus}}. As the pH was increased from pH 4.5 to 6.0, the reductive dissolution rate decreased to below the detection limit. At pH 3.4, the reductive dissolution of hematite was two orders of magnitude slower than goethite. The relationship between structure and reactivity was examined for a series of mono-, di-, and tri-hydroxybenzene reductants. Rates of reductive dissolution decreased in the following order: catechol {approx equal} hydroquinone > 3,4-dihydroxybenzoic acid > resorcinol-phenol-4-hydroxybenzoic acid.

LaKind, J.S.; Stone, A.T. (Johns Hopkins Univ., Baltimore, MD (USA))

1989-05-01

386

Specific detection of membrane-toxic substances with a conductivity assay.  

PubMed

A conductivity assay that represents a new biotest able to detect the effects of membrane-toxic compounds, e.g., detergents, organic solvents, and radical formers, on various organisms was previously described and developed. The conductivity assay measures ion leakage from cells, tissues, or whole plant and animal organisms whose membrane systems have been damaged by membrane-toxic compounds. In this study the specificity of the conductivity assay for membrane-toxic compounds was tested by comparing the electrolyte efflux from Elodea canadensis leaves during incubation with a well-known detergent (benzalkonium chloride) using different plant physiological and biochemical techniques (photochemical efficiency, plasmolysis capacity, NBT reduction, and electron microscopy of membranes of E. canadensis leaves). The comparison of the different methods proved that the electrolyte loss during benzalkonium chloride incubation determined in the conductivity assay is due to membrane impairment. The observed electrolyte loss correlated with a reduction of photochemical efficiency and a decrease in both plasmolysis and NBT reduction capacity. Furthermore, a disintegration of the plasmalemma could be seen in the electron micrographs. These results indicate that the measured electrolyte loss in the conductivity assay is a specific effect of membrane-toxic compounds. PMID:10702340

Eich, J; Dürholt, H; Steger-Hartmann, T; Wagner, E

2000-03-01

387

Steroid Assays in Paediatric Endocrinology  

PubMed Central

Most steroid disorders of the adrenal cortex come to clinical attention in childhood and in order to investigate these problems, there are many challenges to the laboratory which need to be appreciated to a certain extent by clinicians. The analysis of sex steroids in biological fluids from neonates, over adrenarche and puberty present challenges of specificities and concentrations often in small sample sizes. Different reference ranges are also needed for interpretations. For around 40 years, quantitative assays for the steroids and their regulatory peptide hormones have been possible using immunoassay techniques. Problems are recognised and this review aims to summarise the benefits and failings of immunoassays and introduce where tandem mass spectrometry is anticipated to meet the clinical needs for steroid analysis in paediatric endocrine investigations. It is important to keep a dialogue between clinicians and the laboratory, especially when any laboratory result does not make sense in the clinical investigation. Conflict of interest:None declared. PMID:21274330

2010-01-01

388

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

389

A highly sensitive and versatile virus titration assay in the 96-well microplate format.  

PubMed

This report describes a fast, reproducible, inexpensive and convenient assay system for virus titration in the 96-well format. The micromethod substantially increases assay throughput and improves the data reproducibility. A highly simplified variant of virus quantification is based on immunohistochemical detection of virus amplification foci obtained without use of agarose or semisolid overlays. It can be incorporated into several types of routine virological assays successfully replacing the laborious and time-consuming conventional methods based on plaque formation under semisolid overlays. The method does not depend on the development of CPE and can be accommodated to assay viruses with substantial differences in growth properties. The use of enhanced immunohistochemical detection enabled a five- to six-fold reduction of the total assay time. The micromethod was specifically developed to take advantage of multichannel pipettor use to simplify handling of a large number of samples. The method performs well with an inexpensive low-power binocular, thus offering a routine assay system usable outside of specialized laboratory setting, such as for testing of clinical or field samples. When used in focus reduction-neutralization tests (FRNT), the method accommodates very small volumes of immune serum, which is often a decisive factor in experiments involving small rodent models. PMID:18079007

Borisevich, V; Nistler, R; Hudman, D; Yamshchikov, G; Seregin, A; Yamshchikov, V

2008-02-01

390

Predictive assay for cancer targets  

NASA Astrophysics Data System (ADS)

Early detection of cancer is a key element in successful treatment of the disease. Understanding the particular type of cancer involved, its origins and probable course, is also important. PhIP (2-amino-1- methyl-6 phenylimidazo [4,5-b]pyridine), a heterocyclic amine produced during the cooking of meat at elevated temperatures, has been shown to induce mammary cancer in female, Sprague-Dawley rats. Tumors induced by PhIP have been shown to contain discreet cytogenetic signature patterns of gains and losses using comparative genomic hybridization (CGH). To determine if a protein signature exists for these tumors, we are analyzing expression levels of the protein products of the above-mentioned tumors in combination with a new bulk protein subtractive assay. This assay produces a panel of antibodies against proteins that are either on or off in the tumor. Hybridization of the antibody panel onto a 2-D gel of tumor or control protein will allow for identification of a distinct protein signature in the tumor. Analysis of several gene databases has identified a number of rat homologs of human cancer genes located in these regions of gain and loss. These genes include the oncogenes c-MYK, ERBB2/NEU, THRA and tumor suppressor genes EGR1 and HDAC3. The listed genes have been shown to be estrogen-responsive, suggesting a possible link between delivery of bio-activated PhIP to the cell nucleus via estrogen receptors and gene-specific PhIP-induced DNA damage, leading to cell transformation. All three tumors showed similar silver staining patterns compared to each other, while they all were different than the control tissue. Subsequent screening of these genes against those from tumors know to be caused by other agents may produce a protein signature unique to PhIP, which can be used as a diagnostic to augment optical and radiation-based detection schemes.

Suess, Amanda; Nguyen, Christine; Sorensen, Karen; Montgomery, Jennifer; Souza, Brian; Kulp, Kris; Dugan, Larry; Christian, Allen

2005-11-01

391

Antioxidants and the Comet assay.  

PubMed

It is widely accepted that antioxidants, either endogenous or from the diet, play a key role in preserving health. They are able to quench radical species generated in situations of oxidative stress, either triggered by pathologies or xenobiotics, and they protect the integrity of DNA from genotoxicants. Nevertheless, there are still many compounds with unclear or unidentified prooxidant/antioxidant activities. This is of concern since there is an increase in the number of compounds synthesized or extracted from vegetables to which humans might be exposed. Despite the well-established protective effects of fruit and vegetables, the antioxidant(s) responsible have not all been clearly identified. There might also be alternative mechanisms contributing to the protective effects for which a comprehensive description is lacking. In the last two decades, the Comet assay has been extensively used for the investigation of the effects of antioxidants and many reports can be found in the literature. The Comet assay, a relatively fast, simple, and sensitive technique for the analysis of DNA damage in all cell types, has been applied for the screening of chemicals, biomonitoring and intervention studies. In the present review, several of the most well-known antioxidants are considered. These include: catalase, superoxide dismutase, glutathione peroxidase, selenium, iron chelators, melatonin, melanin, vitamins (A, B, C and E), carotenes, flavonoids, isoflavones, tea polyphenols, wine polyphenols and synthetic antioxidants. Investigations showing beneficial as well as non-beneficial properties of the antioxidants selected, either at the in vitro, ex vivo or in vivo level are discussed. PMID:18602333

Cemeli, Eduardo; Baumgartner, Adolf; Anderson, Diana

2009-01-01

392

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

393

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

394

Pollen tetrad-based visual assay for meiotic recombination in Arabidopsis  

E-print Network

), is a highly conserved feature of meiosis from fungi to mammals. Recombination helps ensure chromosome for meiosis, resulting in sterility. We have developed a visual assay capable of detecting Cos and GCs. cross-over meiosis tetrad gene conversion interference Meiosis, the reductive division of the genome

Copenhaver, Gregory P.

395

Validation of a Cell-Free Translation Assay for Detecting Shiga Toxin 2 in Bacterial Culture  

Technology Transfer Automated Retrieval System (TEKTRAN)

We have validated a cell-free translation (CFT) assay for detecting Shiga toxin (Stx). The limit of detection (LOD) for pure Stx2 (PStx2) and partially pure Stx2 (PPStx2) in water reached 20 pg/µl and 3.5 pg/µL respectively without the artificial process of proteolytic activation and reduction of th...

396

MCNP variance reduction overview  

SciTech Connect

The MCNP code is rich in variance reduction features. Standard variance reduction methods found in most Monte Carlo codes are available as well as a number of methods unique to MCNP. We discuss the variance reduction features presently in MCNP as well as new ones under study for possible inclusion in future versions of the code.

Hendricks, J.S.; Booth, T.E.

1985-01-01

397

Reduction of Poisson manifolds  

Microsoft Academic Search

Reduction in the category of Poisson manifolds is defined and some basic properties are derived. The context is chosen to include the usual theorems on reduction of symplectic manifolds, as well as results such as the Dirac bracket and the reduction to the Lie-Poisson bracket.

Jerrold E. Marsden; Tudor Ratiu

1986-01-01

398

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

2000-01-01

399

Line intensities of acetylene: Measurements in the 2.5-?m spectral region and global modeling in the ?p=4 and 6 series  

NASA Astrophysics Data System (ADS)

More than 670 line intensities of nine perpendicular bands of acetylene are measured in the 2.5-?m spectral region using a step-by-step interferometer. Absolute values of line intensities are obtained with an average accuracy of 5%. Vibrational transition dipole moment and Herman Wallis coefficients are determined for each studied band. These measured line intensities, and those previously measured in the 3.8-?m region [Jacquemart D, Lacome N, Mandin JY, Dana V, Lyulin OM, Perevalov VI. Multispectrum fitting of line parameters for 12C2H2 in the 3.8-?m spectral region. JQSRT, submitted for publication], are treated simultaneously within the framework of the effective operators approach. The sets of effective dipole moment parameters obtained reproduce the observed line intensities within the experimental uncertainty. The good predictive ability of the modele is demonstrated.

Lyulin, O. M.; Perevalov, V. I.; Mandin, J.-Y.; Dana, V.; Gueye, F.; Thomas, X.; von der Heyden, P.; Décatoire, D.; Régalia-Jarlot, L.; Jacquemart, D.; Lacome, N.

2007-02-01

400

Electrochemical behavior and voltammetric determination of vanillin based on an acetylene black paste electrode modified with graphene-polyvinylpyrrolidone composite film.  

PubMed

The graphene-polyvinylpyrrolidone composite film modified acetylene black paste electrode (GR-PVP/ABPE) was fabricated and used to determine vanillin. In 0.1M H3PO4 solution, the oxidation peak current of vanillin increased significantly at GR-PVP/ABPE compared with bare ABPE, PVP/ABPE and GR/ABPE. The oxidation mechanism was discussed. The experimental conditions that exert influence on the voltammetric determination of vanillin, such as supporting electrolytes, pH values, accumulation potential and accumulation time, were optimized. Besides, the interference, repeatability, reproducibility and stability measurements were also evaluated. Under the optimal experimental conditions, the oxidation peak current was proportional to vanillin concentration in the range of 0.02-2.0?M, 2.0-40?M and 40-100?M. The detection limit was 10nM. This sensor was used successfully for vanillin determination in various food samples. PMID:25766813

Deng, Peihong; Xu, Zhifeng; Zeng, Rongying; Ding, Chunxia

2015-08-01

401

Lack of activity of cadmium in in vitro estrogenicity assays  

SciTech Connect

Prompted by reports about strong estrogenic effects of cadmium, attempts were made to reproduce these observations using the yeast estrogen screen (YES) and the E-Screen assays. For the first time, possible activation of the Src/MAPK pathway was also investigated. In the YES, only a slight activation (10% of a maximal effect) of the estrogen receptor alpha (ER{alpha}) was observed at cadmium concentrations between 5 x 10{sup -7} M and 5 x 10{sup -6} M. In the E-Screen assay, carried out by two laboratories, the heavy metal was without observable cell proliferative effects when tested in the range between 6 x 10{sup -11} M and 1 x 10{sup -5} M. However, in both assays, cadmium led to a reduction of the effects of 17{beta}-estradiol (E2). Treatment of MCF-7 human breast cancer cells with 1 x 10{sup -7} M cadmium failed to induce phosphorylation of Src and the MAP kinases Erk1 and Erk2-effects shown to occur with E2 and epidermal growth factor (EGF). In summary, we were unable to confirm the strong estrogenicity of cadmium reported recently by a number of laboratories. This apparent absence of effects in our hands is not due to a lack of uptake of the metal or to effective protection against cadmium by high levels of glutathione or metallothionein, since toxicity and an antagonism of E2 responses were observed both in the YES and the E-Screen.

Silva, Elisabete [Centre for Toxicology, School of Pharmacy, University of London, 29-39 Brunswick Square, London WC1N 1AX (United Kingdom)]. E-mail: elisabete.silva@pharmacy.ac.uk; Lopez-Espinosa, Maria Jose [School of Medicine, Hospital Clinico, University of Granada, 18071-Granada (Spain); Molina-Molina, Jose-Manuel [School of Medicine, Hospital Clinico, University of Granada, 18071-Granada (Spain); Fernandez, Marieta [School of Medicine, Hospital Clinico, University of Granada, 18071-Granada (Spain); Olea, Nicolas [School of Medicine, Hospital Clinico, University of Granada, 18071-Granada (Spain); Kortenkamp, Andreas [Centre for Toxicology, School of Pharmacy, University of London, 29-39 Brunswick Square, London WC1N 1AX (United Kingdom)

2006-10-01

402

A nonradioactive iodide uptake assay for sodium iodide symporter function.  

PubMed

The standard assay for sodium iodide symporter (NIS) function is based on the measurement of radioiodide uptake ((125)I) in NIS-expressing cells. However, cost and safety issues have limited the method from being used widely. Here we describe a simple spectrophotometric assay for the determination of iodide accumulation in rat thyroid-derived cells (FRTL5) based on the catalytic effect of iodide on the reduction of yellow cerium(IV) to colorless cerium(III) in the presence of arsenious acid (Sandell-Kolthoff reaction). The assay is fast and highly reproducible with a Z' factor of 0.70. This procedure allows the screening of more than 800 samples per day and can easily be adapted to robotic systems for high-throughput screening of NIS function modulators. Using this method, the potency of several known inhibitors of NIS function was evaluated in a single day with high accuracy and reliability. Measured IC(50) values were essentially identical to those determined using Na(125)I. PMID:19733144

Waltz, Fanny; Pillette, Lucie; Ambroise, Yves

2010-01-01

403

Observation of mixed acetylene - Nitrous oxide trimers: Infrared spectra of C2H2-(N2O)2 and (C2H2)2-N2O  

NASA Astrophysics Data System (ADS)

Infrared spectra of the lowest energy isomers of C2H2-(N2O)2 and (C2H2)2-N2O were observed in the region of the ?1 fundamental band of the N2O monomer (?2224 cm-1) using a tunable diode laser and/or a CW quantum cascade laser to probe a pulsed supersonic slit jet expansion. One infrared band was measured for each trimer. The band for C2H2-(N2O)2 corresponds to the out-of-phase vibrations of the pair of equivalent N2O monomers. It is blue shifted by about 10 cm-1 with respect to the free N2O monomer. The band for (C2H2)2-N2O is slightly less blue shifted (centered at 2232.81 cm-1). It can be simulated as a predominately a-type band. In addition to the normal isotopologues, the corresponding bands for C2D2-(N2O)2 and (C2D2)2-N2O were also observed. The structures of these trimers are similar to those of the lowest energy isomers of the analogous OCS - acetylene trimers reported previously, that is, a twisted barrel with C2 symmetry for C2H2-(N2O)2 and a distorted T-shaped acetylene dimer with a coplanar N2O beside the stem of the T for (C2H2)2-N2O. Here, we present our observation and experimental results, which agree well with calculations based on distributed multipole pair potentials.

Sheybani-Deloui, S.; Yousefi, M.; Norooz Oliaee, J.; McKellar, A. R. W.; Moazzen-Ahmadi, N.

2014-12-01

404

Role of hydrogen abstraction acetylene addition mechanisms in the formation of chlorinated naphthalenes. 2. Kinetic modeling and the detailed mechanism of ring closure.  

PubMed

The dominant formation mechanisms of chlorinated phenylacetylenes, naphthalenes, and phenylvinylacetylenes in relatively low pressure and temperature (?40 Torr and 1000 K) pyrolysis systems are explored. Mechanism elucidation is achieved through a combination of theoretical and experimental techniques, the former employing a novel simplification of kinetic modeling which utilizes rate constants in a probabilistic framework. Contemporary formation schemes of the compounds of interest generally require successive additions of acetylene to phenyl radicals. As such, infrared laser powered homogeneous pyrolyses of dichloro- or trichloroethylene were perturbed with 1,2,4- or 1,2,3-trichlorobenzene. The resulting changes in product identities were compared with the major products expected from conventional pathways, aided by the results of our previous computational work. This analysis suggests that a Bittner-Howard growth mechanism, with a novel amendment to the conventional scheme made just prior to ring closure, describes the major products well. Expected products from a number of other potentially operative channels are shown to be incongruent with experiment, further supporting the role of Bittner-Howard channels as the unique pathway to naphthalene growth. A simple quantitative analysis which performs very well is achieved by considering the reaction scheme as a probability tree, with relative rate constants being cast as branching probabilities. This analysis describes all chlorinated phenylacetylene, naphthalene, and phenylvinylacetylene congeners. The scheme is then tested in a more general system, i.e., not enforcing a hydrogen abstraction/acetylene addition mechanism, by pyrolyzing mixtures of di- and trichloroethylene without the addition of an aromatic precursor. The model indicates that these mechanisms are still likely to be operative. PMID:25420011

McIntosh, Grant J; Russell, Douglas K

2014-12-26

405

Full dimensional Franck-Condon factors for the acetylene A? (1)Au-X? (1)?(g)(+) 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? 1?g+ 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

406

Two-dimensional simulation of an oxy-acetylene torch diamond reactor with a detailed gas-phase and surface mechanism  

NASA Astrophysics Data System (ADS)

A two-dimensional model is presented for the hydrodynamics and chemistry of an oxy-acetylene torch reactor for chemical vapor deposition of diamond, and it is validated against spectroscopy and growth rate data from the literature. The model combines the laminar equations for flow, heat, and mass transfer with combustion and deposition chemistries, and includes multicomponent diffusion and thermodiffusion. A two-step solution approach is used. In the first step, a lumped chemistry model is used to calculate the flame shape, temperatures and hydrodynamics. In the second step, a detailed, 27 species / 119 elementary reactions gas phase chemistry model and a 41 species / 67 elementary reactions surface chemistry model are used to calculate radicals and intermediates concentrations in the gas phase and at the surface, as well as growth rates. Important experimental trends are predicted correctly, but there are some discrepancies. The main problem lies in the use of the Miller-Melius hydrocarbon combustion mechanism for rich oxy-acetylene flames. [J. A. Miller and C. F. Melius, Combustion and Flame 91, 21 (1992)]. Despite this problem, some aspects of the diamond growth process are clarified. It is demonstrated that gas-phase diffusion limitations play a minor role in the diamond growth process, which is determined by surface kinetics. Except for atomic hydrogen, gas phase diffusion is also of minor importance for the transport of species in and behind the flame front. Finally, it is shown that penetration of nitrogen from the ambient air into the flame cannot explain the observed changes at the center of the diamond films as reported in the literature.

Okkerse, M.; Kleijn, C. R.; van den Akker, H. E. A.; de Croon, M. H. J. M.; Marin, G. B.

2000-10-01

407

A simple, rapid, inexpensive assay for toxic chemicals using a bacterial indicator  

SciTech Connect

A simple test for toxic chemicals has been developed. Rhizobium meliloti is combined with the toxic chemical. A tetrazolium dye, MTT (3-[4,5-Dimethylthiazol-2-yl]2,5-diphenyl-tetrazolium bromide) is added. The bacterium reduces this dye, causing the optical absorbance to increase dramatically. The increase can be determined with a simple spectrophotometer. Toxic chemicals and minerals inhibit the reduction of the dye. Presumably the dye serves as a terminal electron acceptor for electron transport. Toxic substances presumably damage the electron transport system. The results compare favorably with published results of tests using the Microtox{trademark} assay and with the Polytox{trademark} assay. This assay is simpler and requires no specialized equipment. It should be possible to use this assay in a third world situation.

Botsford, J.L.; Hillaker, T.; Robertson, B.; Gonzales, M.; Benavidez, M.; Jones, B.; Baker, R.; Steen, W.; Pacheco, F. [New Mexico State Univ., Las Cruces, NM (United States). Dept. of Biology; Homer, V.; Lucero, O.; Matthews, M.; Koehler, V.

1996-12-31

408

233U Assay A Neutron NDA System  

SciTech Connect

The assay of highly enriched {sup 233}U material presents some unique challenges. Techniques which apply to the assay of materials of Pu or enriched {sup 235}U do not convert easily over to the assay of {sup 233}U. A specialized neutron assay device is being fabricated to exploit the singles neutron signal, the weak correlated neutron signal, and an active correlated signal. These pieces of information when combined with {gamma} ray isotopics information should give a good overall determination of {sup 233}U material now stored in bldg. 3019 at the Oak Ridge National Laboratory.

Hensley, D.C.; Lucero, A.J.; Pierce, L.

1998-11-17

409

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

410

Detection and quantitation of infectious human adenoviruses and JC polyomaviruses in water by immunofluorescence assay.  

PubMed

Human adenoviruses (HAdV) and JC polyomaviruses (JCPyV) have been proposed as markers of fecal/urine contamination of human origin. An indirect immunofluorescence assay has been developed to quantify infectious human adenoviruses types 2 and 41 and JC polyomaviruses strain Mad-4 in water samples. The immunofluorescence assay was compared with other quantitative techniques used commonly such as plaque assay, tissue culture infectious dose-50 and quantitative PCR (qPCR). The immunofluorescence assays showed to be specific for the detection of infectious viruses, obtaining negative results when UV or heat-inactivated viruses were analyzed. The assays required less time and showed higher sensitivity for the detection of infectious viral particles than other cell culture techniques (1 log(10) more) evaluated. River water samples spiked previously with human adenoviruses and raw sewage samples were also analyzed using the proposed immunofluorescence assay as well as by qPCR. The results show quantitations with 2 log(10) reduction in the numbers of infectious viruses compared with the number of genome copies detected by qPCR. The immunofluorescence assay developed is fast, sensitive, specific, and a standardizable technique for the quantitation and detection of infectious viruses in water samples. PMID:20863853

Calgua, Byron; Barardi, Celia Regina Monte; Bofill-Mas, Silvia; Rodriguez-Manzano, Jesus; Girones, Rosina

2011-01-01

411

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

412

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

413

Assay of deoxyhypusine hydroxylase activity.  

PubMed

The eukaryotic translation initiation factor 5A (eIF5A) is the only cellular protein that contains an unusual amino acid, hypusine [N (?)-(4-amino-2-hydroxybutyl)-lysine]. eIF5A and its hypusine/deoxyhypusine modification are vital for eukaryotic cell proliferation. Hypusine is formed posttranslationally by two enzymatic steps catalyzed by deoxyhypusine synthase and deoxyhypusine hydroxylase. Deoxyhypusine hydroxylase catalyzes a stereo-specific hydroxylation of the deoxyhypusine residue in the eIF5A intermediate protein, eIF5A(Dhp). The enzyme is totally specific for this protein and does not act on short peptides (<50 amino acids). The assay measures the conversion of the radiolabeled deoxyhypusine residue to a hypusine residue in eIF5A. Optimum conditions for the reaction and two detection methods for the product, hypusine-containing eIF5A, are described in this chapter. The first, and most reliable, method is the measurement of the amount of [(3)H]hypusine in the protein hydrolysate after its separation from [(3)H]deoxyhypusine, by ion exchange chromatography. This method does require specialized equipment. The second method is based on counting the total TCA soluble radioactivity after sodium periodate oxidation of the reaction mixture, since the radiolabeled 4-amino-2-hydroxy butyl moiety of the hypusine residue is cleaved and is released from protein as radiolabeled ?-propionaldehyde and formaldehyde by periodate oxidation. PMID:21318876

Park, Jong Hwan; Wolff, Edith C; Park, Myung Hee

2011-01-01

414

Characterization of the quantitative HCV NASBA assay.  

PubMed

A quantitative nucleic acid sequence-based amplification assay (NASBA-QT) for detection of hepatitis C virus RNA (HCV-RNA) was evaluated and compared with the HCV branched-DNA (bDNA) assay (Chiron Corporation) and the HCV MONITOR assay (Roche Diagnostic Systems). For this evaluation five panels were designed: (1) serial dilutions of genotype 1b in-vitro HCV-RNA; (2) standards of in-vitro HCV-RNA genotypes 1a, 1b, 2, 3, 4, and 5; (3) a proficiency panel consisting of 12 HCV-RNA positive plasma samples of different genotypes and HCV-RNA concentrations and a genotype 1a and 1b 3-fold dilution series; (4) a panel of 67 HCV-RNA positive plasma samples obtained from patients with HCV infection and (5) an HCV-RNA positive control sample, diluted 50-fold in 25 different HCV-RNA negative plasma samples. The quantitative detection limit was found to be 10(3) copies per 100 microl and the qualitative detection limit 10(2.3) per 100 microl. The amplification efficiency was independent of the plasma matrix, but dependent on the HCV genotype. The HCV NASBA-QT assay was more than 10 times as sensitive as the bDNA assay while the quantitative results of both assays were highly concordant. The HCV NASBA-QT assay was comparable in sensitivity with the HCV MONITOR assay, but the HCV MONITOR assay yielded consistently lower values. It is concluded that the HCV NASBA-QT assay is a reliable assay for quantitative HCV-RNA detection in various settings. PMID:10507412

Damen, M; Sillekens, P; Cuypers, H T; Frantzen, I; Melsert, R

1999-09-01

415

Development of an upconverting chelate assay  

NASA Astrophysics Data System (ADS)

We report progress on performing a cell-based assay for the detection of EGFR on cell surfaces by using upconverting chelates. An upconversion microscope has been developed for performing assays and testing optical response. A431 cells are labeled with europium DOTA and imaged using this upconverting microscope.

Xiao, Xudong; Haushalter, Jeanne P.; Kotz, Kenneth T.; Faris, Gregory W.

2005-04-01

416

MULTIPLEXING SCHEMES FOR GENERIC SNP GENOTYPING ASSAYS  

E-print Network

MULTIPLEXING SCHEMES FOR GENERIC SNP GENOTYPING ASSAYS R. SHARAN International Computer Science yakhini@agilent.com. Abstract A generic genotyping assay utilizes a xed set of reagents, which with a genotyping experiment, it is desirable to design a set of experiments, which maximizes the number of SNPs

Shamir, Ron

417

MULTIPLEXING SCHEMES FOR GENERIC SNP GENOTYPING ASSAYS  

E-print Network

MULTIPLEXING SCHEMES FOR GENERIC SNP GENOTYPING ASSAYS R. SHARAN International Computer Science yakhini@agilent.com. Abstract A generic genotyping assay utilizes a fixed set of reagents, which with a genotyping experiment, it is desirable to design a set of experiments, which maximizes the number of SNPs

Sharan, Roded

418

Assays for mammalian tyrosinase: a comparative study  

Microsoft Academic Search

This work describes a comparative study of the tyrosinase activity determined using three methods which are the most extensively employed; two radiometric assays using L-tyrosine as substrate (tyrosine hydroxylase and melanin formation activities) and one spectrophotometric assay using L-dopa (dopa oxidase activity). The three methods were simultaneously employed to measure the activities of the soluble, melanosomal, and microsomal tyrosinase isozymes

JOSE R. JARA; FRANCISCO SOLANO; JOSE A. LOZANO

1988-01-01

419

The comet assay: a comprehensive review  

Microsoft Academic Search

The comet assay is a sensitive and rapid method for DNA strand break detection in individual cells. Its use has increased significantly in the past few years. This paper is a review of the studies published to date that have made use of the comet assay. The principles of strand break detection using both the alkaline and neutral versions of

Daryl W. Fairbairn; Peggy L. Olive; Kim L. O'Neill

1995-01-01

420

Improved immunoturbidimetric assay for cystatin C.  

PubMed

An immunoturbidimetric assay for cystatin C was optimized with respect to assay imprecision. After investigating the optimum pH, polyethylene glycol concentration and specimen volume, two modifications were introduced: an increase in specimen volume to 25 microL; and an extension of the pre-incubation period to 240 s. These modifications produced an assay with between-batch imprecision (coefficient of variation, n = 10 or 11) ranging from 3-9% at 0.72 mg/L to 1.3% at 5.29 mg/L. The assay was susceptible to interference from lipaemia and haemolysis but not bilirubinaemia in both the original and modified protocol. Extending the pre-incubation to 240 s improved tolerance to common interferences and retained assay applicability in the routine clinical setting. PMID:11269749

Lewis, A V; James, T J; McGuire, J B; Taylor, R P

2001-03-01

421

Interpretation of HLA single antigen bead assays.  

PubMed

The introduction of single antigen bead (SAB) assays for detection and quantitation of HLA antibodies has improved our ability to identify and manage allosensitized transplant candidates and recipients and to improve organ allocation, and was critical to the creation of national paired kidney exchanges. The principal limitations of the technology have been detailed in the literature and include artifacts resulting in non-specific background, variability, lack of standardization, and interpretive challenges. Accurate interpretation of SAB assays requires consideration of a number of factors, including identification of epitope reactivity patterns, mean fluorescence intensity (MFI) values, patient history, and appreciation of individual bead and assay nuances. The MFI value provides an estimate of relative HLA antibody levels although limited by saturation and epitope distribution effects. A better understanding of SAB assays and MFI values will be necessary to ensure appropriate application of these assays clinically and a higher quality of antibody data used in support of published clinical studies. PMID:23958238

Ellis, Thomas M

2013-10-01

422

Fluorometric assay for red blood cell antibodies  

SciTech Connect

A fluorometric assay is described for the detection of red blood cell antibodies. The assay reveals as little as 600 molecules of bound, fluoroesceinated rabbit anti-human IgG antibodies per erythrocyte. Eleven patients with possible autoimmune erythrocyte disorder and negative direct antiglobulin test were studied by the fluorometric assay. The outcome of the fluorometric assay was compared with that of the human allogeneic rosette test. Results obtained by the two methods were in complete agreement. Five of the patients were shown to possess unexpectedly high levels of erythrocyte-bound IgG in spite of a negative, direct antiglobulin test. These findings and the validity of the fluorometric assay are discussed.

Schreiber, A.B.; Lambermont, M.; Strosberg, A.D.; Wybran, J.

1981-03-01

423

Restraint reduction in orthopaedics.  

PubMed

Restraint reduction is a challenge, especially when working with an elderly population. This article describes one orthopaedic unit's successful restraint reduction program. The role of the nurses on the unit is discussed, along with forms that were helpful and the fact that the reduction program fit into the Performance Improvement Plan for the institution. The most frequently used and successful alternatives are discussed. A restraint/seclusion data collection form has been highlighted. Finally, areas for additional research are suggested. PMID:11153323

Zoellner-Hunter, J; Goetz, N; Czurylo, K

2000-01-01

424

Drag reduction in nature  

NASA Technical Reports Server (NTRS)

Recent studies on the drag-reducing shapes, structures, and behaviors of swimming and flying animals are reviewed, with an emphasis on potential analogs in vehicle design. Consideration is given to form drag reduction (turbulent flow, vortex generation, mass transfer, and adaptations for body-intersection regions), skin-friction drag reduction (polymers, surfactants, and bubbles as surface 'additives'), reduction of the drag due to lift, drag-reduction studies on porpoises, and drag-reducing animal behavior (e.g., leaping out of the water by porpoises). The need for further research is stressed.

Bushnell, D. M.; Moore, K. J.

1991-01-01

425

A quantitative real-time RT-PCR assay for mature C. albicans biofilms  

PubMed Central

Background Fungal biofilms are more resistant to anti-fungal drugs than organisms in planktonic form. Traditionally, susceptibility of biofilms to anti-fungal agents has been measured using the 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxyanilide (XTT) assay, which measures the ability of metabolically active cells to convert tetrazolium dyes into colored formazan derivatives. However, this assay has limitations when applied to high C. albicans cell densities because substrate concentration and solubility are limiting factors in the reaction. Because mature biofilms are composed of high cell density populations we sought to develop a quantitative real-time RT-PCR assay (qRT-PCR) that could accurately assess mature biofilm changes in response to a wide variety of anti-fungal agents, including host immune cells. Results The XTT and qRT-PCR assays were in good agreement when biofilm changes were measured in planktonic cultures or in early biofilms which contain lower cell densities. However, the real-time qRT-PCR assay could also accurately quantify small-medium size changes in mature biofilms caused by mechanical biomass reduction, antifungal drugs or immune effector cells, that were not accurately quantifiable with the XTT assay. Conclusions We conclude that the qRT-PCR assay is more accurate than the XTT assay when measuring small-medium size effects of anti-fungal agents against mature biofilms. This assay is also more appropriate when mature biofilm susceptibility to anti-fungal agents is tested on complex biological surfaces, such as organotypic cultures. PMID:21548962

2011-01-01

426

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

427

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

428

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

429

A bioluminescence assay for aldehyde dehydrogenase activity.  

PubMed

The aldehyde dehydrogenase (ALDH) family of enzymes is critical for cell survival and adaptation to cellular and environmental stress. These enzymes are of interest as therapeutic targets and as biomarkers of stem cells. This article describes a novel, homogeneous bioluminescence assay to study the activity of the ALDH enzymes. The assay is based on a proluciferin-aldehyde substrate that is recognized and utilized by multiple ALDH enzyme isoforms to generate luciferin. A detection reagent is added to inactivate ALDH and generate light from the luciferin product. The luminescent signal is dependent on the ALDH enzyme concentration and the incubation time in the ALDH reaction; moreover, the luminescent signal generated with the detection reagent is stable for greater than 2 h. This assay provides many advantages over standard NADH fluorescence assays. It is more sensitive and the signal stability provided allows convenient assay setup in batch mode-based high-throughput screens. The assay also shows an accurate pharmacological response for a common ALDH inhibitor and is robust, with a large assay window (S/B=64) and Z'=0.75. PMID:23219557

Duellman, Sarah J; Valley, Michael P; Kotraiah, Vinayaka; Vidugiriene, Jolanta; Zhou, Wenhui; Bernad, Laurent; Osterman, Jean; Kimball, Joshua J; Meisenheimer, Poncho; Cali, James J

2013-03-15

430

A fluorescent assay for ceramide synthase activity  

PubMed Central

The sphingolipids are a diverse family of lipids with important roles in membrane compartmentalization, intracellular signaling, and cell-cell recognition. The central sphingolipid metabolite is ceramide, formed by the transfer of a variable length fatty acid from coenzyme A to a sphingoid base, generally sphingosine or dihydrosphingosine (sphinganine) in mammals. This reaction is catalyzed by a family of six ceramide synthases (CerS1-6). CerS activity is usually assayed using either radioactive substrates or LC-MS/MS. We describe a CerS assay with fluorescent, NBD-labeled sphinganine as substrate. The assay is readily able to detect endogenous CerS activity when using amounts of cell or tissue homogenate protein that are lower than those reported for the radioactive assay, and the Michaelis-Menten constant was essentially the same for NBD-sphinganine and unlabeled sphinganine, indicating that NBD-sphinganine is a good substrate for these enzymes. Using our assay, we confirm that the new clinical immunosuppressant FTY720 is a competitive inhibitor of CerS activity, and show that inhibition requires the compound's lipid tail and amine headgroup. In summary, we describe a fluorescent assay for CerS activity that circumvents the need to use radioactive substrates, while being more accessible and cheaper than LC-MS based assays. PMID:22661289

Kim, Hyun Joon; Qiao, Qiao; Toop, Hamish D.; Morris, Jonathan C.; Don, Anthony S.

2012-01-01

431

Does Source Reduction Work?  

ERIC Educational Resources Information Center

Suggests that quantification is essential to establish the cost-effectiveness of source reduction (SR). Presents case studies of monitoring methods for seven different kinds of SR efforts: (1) packaging changes, (2) SR businesses, (3) waste exchanges, (4) individual nonresidential efforts, (5) variable garbage rates, (6) yard waste reduction, and…

Allaway, David

1992-01-01

432

Economics of Grade Reduction  

E-print Network

of this increase has little value in a report dealing with grade reduction. It is considered better, from a practical standpoint, to analyze the actual en- gine performance on the division in question and then to assume that after the grade reduction,lite per...

Neff, Paul J.

1914-02-10

433

Induction of Apoptosis by (Z)-Stellettic Acid C, an Acetylenic Acid from the Sponge Stelletta sp., Is Associated with Inhibition of Telomerase Activity in Human Leukemic U937 Cells  

Microsoft Academic Search

Background: (Z)-Stellettic acid C, an acetylenic acid from the marine sponge Stelletta sp., has been shown to have cytotoxic activity in some cancer cells; however, its mechanisms on malignant cell growth are not known. In this study, the potential of (Z)-stellettic acid C to induce apoptosis in human leukemic U937 cells and its effects on telomerase activity were investigated. Methods:

Cheol Park; Gi-Young Kim; Won Il Kim; Sang Hoon Hong; Dong Il Park; Nam Deuk Kim; Song-Ja Bae; Jee H. Jung; Yung Hyun Choi

2007-01-01

434

Methods for threshold determination in multiplexed assays  

DOEpatents

Methods for determination of threshold values of signatures comprised in an assay are described. Each signature enables detection of a target. The methods determine a probability density function of negative samples and a corresponding false positive rate curve. A false positive criterion is established and a threshold for that signature is determined as a point at which the false positive rate curve intersects the false positive criterion. A method for quantitative analysis and interpretation of assay results together with a method for determination of a desired limit of detection of a signature in an assay are also described.

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

2014-06-24

435

Fine-tuning control on CNT diameter distribution, length and density using thermal CVD growth at atmospheric pressure: an in-depth analysis on the role of flow rate and flow duration of acetylene (C2H2) gas  

NASA Astrophysics Data System (ADS)

An optimization control has been demonstrated to obtain carbon nanotubes having specific diameter distribution, length, homogeneity, and yield during its growth by thermal chemical vapor deposition technique under atmospheric pressure. Carbon nanotubes (CNTs) were grown on silicon wafer where a predeposition of iron catalyst of 2 nm thickness was made by sputtering. The growth was conducted under two variable parameters, i.e., flow rate and flow duration. Argon and hydrogen mixture was used for pretreatment of catalyst and as etching gas, and acetylene as a carbon precursor. In-depth analysis shows that increase in flow rate from 10 to 50 sccm resulted in increase in the concentration of amorphous carbon, CNTs diameter range and decrease in length, we found best result at 20 sccm flow rate of acetylene gas. On the other hand, as we varied flow duration from 6 to 14 min, with keeping flow rate of acetylene 20 sccm constant, dense homogeneous growth of horizontal CNTs network plus an increase in length and diameter range were observed. An optimization of flow rate and flow duration is presented here to obtain a selective diameter distribution and length as expected by this growth technique. Atomic force microscopy, field emission scanning electron microscopy and Raman spectroscopy were used to investigate the samples' morphologies in support of the observations made.

Tripathi, Nishant; Mishra, Prabhash; Harsh, Harsh; Islam, S. S.

2015-01-01

436

Homogeneous assays for single-nucleotide polymorphism typing using AlphaScreen.  

PubMed

AlphaScreen technology allows the development of high-throughput homogeneous proximity assays. In these assays, signal is generated when 680 nm laser light irradiates a donor bead in close proximity to an acceptor bead. For the detection of nucleic acids, donor and acceptor beads are brought into proximity by two bridging probes that hybridize simultaneously to a common target and to the generic oligonucleotides attached covalently to the beads. This method allows the detection of as little as 10 amole of a single-stranded DNA target. The combination of AlphaScreen with allele-specific amplification (ASA) and allele-specific hybridization (ASH) has allowed the development of two homogenous single-nucleotide polymorphism (SNP) genotyping platforms. Both types of assay are very robust, routinely giving accurate genotyping results with < 2 ng of genomic DNA per genotype. An AlphaScreen validation study was performed for 12 SNPs by using ASA assays and seven SNPs by using ASH assays. More than 580 samples were genotyped with accuracy >99%. The two assays are remarkably simple, requiring no post-PCR manipulations. Genotyping has been performed successfully in 96- and 384-well formats with volumes as small as 2 microL, allowing a considerable reduction in the amount of reagents and genomic DNA necessary for genotyping. These results show that the AlphaScreen technology can be successfully adapted to high-throughput genotyping. PMID:11282975

Beaudet, L; Bédard, J; Breton, B; Mercuri, R J; Budarf, M L

2001-04-01

437

Full dimensional Franck-Condon factors for the acetylene ˜{A} 1Au—{˜{X}} {^1? _g^+} transition. II. Vibrational overlap factors for levels involving excitation in ungerade modes  

NASA Astrophysics Data System (ADS)

A full-dimensional Franck-Condon calculation has been applied to the tilde{A} 1Au—tilde{X} ^1? _g^+ 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 tilde{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 tilde{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 tilde{A} state into bending levels of the tilde{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 tilde{A}-state vibrational levels for populating tilde{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.

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

2014-10-01

438

Homogeneous Cell- and Bead-Based Assays for High Throughput Screening Using Fluorometric Microvolume Assay Technology.  

PubMed

High throughput drug screening has become a critical component of the drug discovery process. The screening of libraries containing hundreds of thousands of compounds has resulted in a requirement for assays and instrumentation that are amenable to nonradioactive formats and that can be miniaturized. Homogeneous assays that minimize upstream automation of the individual assays are also preferable. Fluorometric microvolume assay technology (FMAT) is a fluorescence-based platform for the development of nonradioactive cell- and bead-based assays for HTS. This technology is plate format-independent, and while it was designed specifically for homogeneous ligand binding and immunological assays, it is amenable to any assay utilizing a fluorescent cell or bead. The instrument fits on a standard laboratory bench and consists of a laser scanner that generates a 1 mm(2) digitized image of a 100-µmm deep section of the bottom of a microwell plate. The instrument is directly compatible with a Zymark Twistertrade mark (Zymark Corp., Hopkinton, MA) for robotic loading of the scanner and unattended operation in HTS mode. Fluorescent cells or beads at the bottom of the well are detected as localized areas of concentrated fluorescence using data processing. Unbound flurophore comprising the background signal is ignored, allowing for the development of a wide variety of homogeneous assays. The use of FMAT for peptide ligand binding assays, immunofluorescence, apoptosis and cytotoxicity, and bead-based immunocapture assays is described here, along with a general overview of the instrument and software. PMID:10838439

Miraglia; Swartzman; Mellentin-Michelotti; Evangelista; Smith; Gunawan; Lohman; Goldberg; Manian; Yuan

1999-01-01

439

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...

440

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

441

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

442

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...

443

Developmental Toxicity Assays Using the Drosophila Model  

PubMed Central

The fruit fly (Drosophila melanogaster) has long been a premier model for developmental biologists and geneticists. The utility of Drosophila for toxicology studies 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 with which to create 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. PMID:24789363

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

2014-01-01

444

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. ...

445

Lack of standardized description of TRAb assays.  

PubMed

Anti-thyroid stimulating hormone (TSH) receptor antibodies (TRAb) exist as both stimulating and blocking antibodies. The current TRAb assays widely available to clinicians are receptor-binding assays. Bioassays that differentiate between stimulating and blocking TRAb are technically challenging and expensive. The terminology used to describe the different assays is confusing and a potential source of misinterpretation of TRAb results. In this article, we point out a typographical error in the 2011 American Thyroid Association and American Association of Clinical Endocrinologists' Guidelines on Hyperthyroidism where the term thyroid stimulating immunoglobulin (TSI) instead of thyroid binding inhibition immunoglobulin (TBII) was used in the description of TRAb results, to highlight the need to harmonize the terminology of TRAb assays to improve patient care. PMID:23179774

Tan, Karen; Loh, Tze Ping; Sethi, Sunil

2013-06-01

446

Iron Reduction and Carbonate Precipitation by Shewanella oneidensis  

NASA Astrophysics Data System (ADS)

This study is to contribute to better understanding of how Archean microbes induced carbonate diagenesis in mats and stromatolites. Previous studies showed sulfate reduction, a common promoter of carbonate precipitation in modern mats[1], is likely to have been less effective in Archean mats in marine fluids lower in sulfate[2]. Alternatively, iron reduction produces far more alkalinity per unit carbon respired than sulfate reduction. Therefore, we hypothesize iron reduction can promote much more carbonate precipitation than sulfate reduction. Our study might also have some relevance to banded iron formation on which microbial iron reduction played a potential role[3]. To test our hypothesis, Shewanella oneidensis MR-1, a dissimilatory iron reducing bacterium will be cultured anaerobically (79%N2, 20%CO2 and 1%H2) in basal medium to trigger iron reduction. Lactate will be used as electron donor, and the electron acceptor will be fresh ferrihydrite. Culture medium will be added with various metal ions, such as Ca2+ and Mg2+, to obtain potential carbonate precipitate. Escherichia coli (with fumarate added as an electron acceptor) will be used to provide a comparison to live but non-iron- reduction cells. After 20 days incubation, precipitate will be collected, washed and identified by X-ray diffraction (XRD). Besides, iron reduction rate (ferrozine assay)[4], PH and amount of precipitate (carbonate and oxidize fractions)[5] will be measured over time to well understand how S. oneidensis drives carbonate precipitation.

Zeng, Z.; Tice, M. M.

2011-12-01

447

Quantum dot-based cell motility assay  

Microsoft Academic Search

Motility and migration are measurable characteristics of cells that are classically associated with the invasive potential of cancer cells, but in vitro assays of invasiveness have been less than perfect. We previously developed an assay to monitor cell motility and migration using water-soluble CdSe\\/ZnS nanocrystals; cells engulf the fluorescent nanocrystals as they crawl across them and leave behind a fluorescent-free

Teresa Pellegrino; Wolfgang J. Parak; Rosanne Boudreau; Mark A. Le gros; Daniele Gerion; A. Paul Alivisatos; Carolyn A. Larabell

2003-01-01

448

Electrochemical Assay of Gold-Plating Solutions  

NASA Technical Reports Server (NTRS)

Gold content of plating solution is assayed by simple method that required only ordinary electrochemical laboratory equipment and materials. Technique involves electrodeposition of gold from solution onto electrode, the weight gain of which is measured. Suitable fast assay methods are economically and practically necessary in electronics and decorative-plating industries. If gold content in plating bath is too low, poor plating may result, with consequent economic loss to user.

Chiodo, R.

1982-01-01

449

A Flow Cytometric Assay for Lysosomal Glucocerebrosidase  

Microsoft Academic Search

A flow cytometric assay is described for the determination of glucocerebrosidase (GC) activity using fluorescein di-?-glucopyranoside (FDGlu). Fluorescent product is formed upon intracellular hydrolysis of FDGlu and is measured in the FL1 channel of a flow cytometer. We show that the assay is specific for lysosomal ?-glucosidase or glucocerebrosidase (1) by concentration-dependent inhibition of GC activity by conditurol-?-epoxide (CBE), a

Helmuth H. G. van Es; Marlon Veldwijk; Menzo Havenga; Dinko Valerio

1997-01-01

450

Pharmacokinetics of cefamandole using a HPLC assay  

Microsoft Academic Search

A pharmacokinetic study was carried out on six normal healthy adults with average creatinine clearances ranging from 94.8 to 129.3 ml\\/min. Cefamandole, 15 mg\\/kg, was administered intravenously over a period of 10 min. Frequent and prolonged samplings of blood and urine were made. Specimens were assayed by a sensitive, accurate, and reproducible HPLC assay. An excellent computer fit to a

Nik S. Aziz; John G. Gambertoglio; Emil T. Lin; Henry Grausz; Leslie Z. Benet

1978-01-01

451

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

452

Scintillation Proximity Assay of Arginine Methylation  

PubMed Central

Methylation of arginine residues, catalyzed by protein arginine methyltransferases (PRMTs), is one important protein post-translational modification involved in epigenetic regulation of gene expression. A fast and effective assay for PRMT can provide valuable information for dissecting the biological functions of PRMTs, as well as for screening small-molecule inhibitors of arginine methylation. Currently, among the methods used for PRMT activity measurement, many contain laborious separation procedures, which restrict the applications of these assays for high-throughput screening (HTS) in drug discovery. The authors report here a mix-and-measure method to measure PRMT activity based on the principle of scintillation proximity assay (SPA). In this assay, 3H-AdoMet was used as methyl donor, and biotin-modified histone H4 peptide served as a methylation substrate. Following the methylation reaction catalyzed by PRMTs, streptavidin-coated SPA beads were added to the reaction solution, and SPA signals were detected by a MicroBeta scintillation counter. No separation step is needed, which simplifies the assay procedure and greatly enhances the assay speed. Particularly, the miniaturization and robustness suggest that this method is suited for HTS of PRMT inhibitors. PMID:21821785

Wu, Jiang; Xie, Nan; Feng, You; Zheng, Y. George

2011-01-01

453

Baker's yeast assay procedure for testing heavy metal toxicity  

SciTech Connect

Baker's yeast (Saccharomyces cerevisiae) is microorganism which is commercially available and sold as packaged dry pellets in any food store at low cost. Studies have been undertaken on the effects of organic xenobiotics as well as heavy metals on yeast metabolism. This type of study has been generally useful in examining the mechanism(s) of chemical toxicity. However, a rapid and quantitative toxicity test using S. cerevisiae as the test organism has not been developed. The purpose of this study was to develop a toxicity assay for heavy metals, using commercial dry yeast as the test microorganism. This rapid and simple procedure is based on the reduction of 2-(p-iodophenyl)-3-(p-nitrophenyl)-5-phenyltetrazolium chloride (INT) to INT-formazan by the yeast electron transport system. The scoring of active cells following exposure to heavy metals was undertaken according to the MINT (malachite green-INT) method developed by Bitton and Koopman.

Bitton, G.; Koopman, B.; Wang, H.D.

1984-01-01

454

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

455

A novel coagulation assay incorporating adherent endothelial cells in thromboelastometry.  

PubMed

Following vascular injury or activation, endothelial cells (ECs) participate in the modulation of haemostasis and fibrinolysis. Viscoelastic tests (VETs) are a potent bedside monitoring tool that reports haemostatic parameters in real time. However, VETs neglect the influence of the surrounding endothelium. Our aim was therefore to establish an assay that incorporates ECs in a whole blood VET and to assess the impact of ECs on coagulation parameters. Outgrowth endothelial cells (OECs) and human umbilical vein endothelial cells (HUVECs) were seeded onto microbeads to create transferable EC-microcarriers. Microbeads were then added to citrated whole blood in the measurement cup of a thromboelastometry device (ROTEM). After the addition of CaCl2 (star-TEM®) to the blood sample (NATEM assay), standard ROTEM parameters were analysed. Scanning electron microscopy (SEM) was carried out to visualise the interactions of the beads, whole blood components and the ROTEM pin after clotting. SEM showed that the added microbeads were effectively incorporated into the final blood clot. In the presence of activated ECs, the clotting time (CT) of the blood was shortened fourfold compared to that in uncoated control beads. A significant reduction in CT was also observed in the presence of unstimulated ECs. Interestingly, CT was also reduced by the addition of purified EC culture supernatant. CT shortening was prevented by incubating the supernatant with an inhibiting antibody against tissue factor (TF). Our findings demonstrate that ECs can be incorporated into a ROTEM assay via coated microbeads, and whole blood clotting initiation is accelerated by non-activated and activated ECs. PMID:23494019

Zipperle, J; Schlimp, C J; Holnthoner, W; Husa, A-M; Nürnberger, S; Redl, H; Schöchl, H

2013-05-01

456

21 CFR 866.3305 - Herpes simplex virus serological assays.  

Code of Federal Regulations, 2012 CFR

...2012-04-01 false Herpes simplex virus serological assays. 866.3305 Section...Reagents § 866.3305 Herpes simplex virus serological assays. (a) Identification . Herpes simplex virus serological assays are devices...

2012-04-01

457

21 CFR 866.3305 - Herpes simplex virus serological assays.  

Code of Federal Regulations, 2011 CFR

...2011-04-01 false Herpes simplex virus serological assays. 866.3305 Section...Reagents § 866.3305 Herpes simplex virus serological assays. (a) Identification . Herpes simplex virus serological assays are devices...

2011-04-01

458

21 CFR 866.3305 - Herpes simplex virus serological assays.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 false Herpes simplex virus serological assays. 866.3305 Section...Reagents § 866.3305 Herpes simplex virus serological assays. (a) Identification . Herpes simplex virus serological assays are devices...

2013-04-