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Sample records for acetylene black ab

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

    SciTech Connect

    Han, Huixian; Li, Anyang; Guo, Hua

    2014-12-28

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

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

    SciTech Connect

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

    2007-07-01

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

  3. Electrochemistry and voltammetric determination of colchicine using an acetylene black-dihexadecyl hydrogen phosphate composite film modified glassy carbon electrode.

    PubMed

    Zhang, Huajie

    2006-05-01

    The electrochemical behavior of colchicine at an acetylene black-dihexadecyl hydrogen phosphate (denoted as AB-DHP) composite film coated glassy carbon electrode (GCE) was investigated using cyclic voltammetry (CV), linear sweep voltammetry (LSV) and differential pulse voltammetry (DPV). Compared with the poor electrochemical signal at the unmodified GCE, the electrochemical response of colchicine at the AB-DHP film modified GCE was greatly improved, as confirmed from the significant peak current enhancement. The remarkable peak current enhancement indicates that the AB-DHP modified GCE has great potential in the sensitive determination of colchicine. Thus, all the experimental conditions, which influence the electrochemical response of colchicine, were studied and the optimum conditions were achieved. Finally, a sensitive and simple voltammetric method with a good linear relationship in the range of 1.0 x 10(-7) approximately 4.0 x 10(-5) mol/L, was developed for the determination of colchicine. The detection limit of colchicine was also examined and a low value of 4.0 x 10(-8) mol/L for 4-min accumulation was obtained (S/N=3). This electrode was successfully applied to detect colchicine in human urine samples.

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

    NASA Technical Reports Server (NTRS)

    Yung, E.

    1974-01-01

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

  5. What is Different Between Borazine-Acetylene and Benzene-Acetylene a Matrix Isolation and Ab-Initio Study.

    NASA Astrophysics Data System (ADS)

    Verma, Kanupriya; Viswanathan, K. S.

    2016-06-01

    Borazine (B_3N_3H_6)-C_2H_2 system was studied experimentally, using matrix isolation infrared spectroscopy and supported by ab-initio computations. B_3N_3H_6, also referred to as inorganic benzene, presents an interesting comparison with C_6H_6. While C_6H_6 has a delocalized π system, B_3N_3H_6 has electron density centered on the nitrogen atoms, while the boron atoms are electron deficient. In addition, B_3N_3H_6 can also serve as a proton donor through N-H group. Similarly, C_2H_2 can act both as a proton donor, using the hydrogen attached to the sp carbon or as a proton acceptor at its π-cloud. At the MP2/aug-cc-pVDZ level of theory, C_6H_6-C_2H_2 system showed three minimaThe. global minimum was a structure where the C_2H_2 was the proton donor to the C_6H_6 π system. The next was a local minimum where the C_6H_6 was the proton donor to C_2H_2 and the third was a π stacked structure. B_3N_3H_6-C_2H_2 also shows three minima at the same level of theory mentioned above. One was a structure where C_2H_2 donates a proton to B_3N_3H_6, approaching it from above the plane of the ring, much like in C_6H_6-C_2H_2. A second near degenerate structure was also located where the C_2H_2 serves as a proton acceptor towards the N-H group of B_3N_3H_6. A similar structure in C_6H_6-C_2H_2 was a local minimum. While in the case of C_6H_6-C_2H_2, the global minimum was the only one observed in the experiments, in the case of B_3N_3H_6-C_2H_2, both near degenerate minima mentioned above were observed in the matrix. B_3N_3H_6-C_2H_2 therefore reveals similarities and differences from the C_6H_6-C_2H_2 system. A π-stacked local minimum was also computationally indicated in the B_3N_3H_6-C_2H_2 system, though it was not observed in our experiments. Our earlier work comparing B_3N_3H_6-H_2O to C_6H_6-H_2O also yielded a similar behavioral pattern. Details of the experimental data and computational results will be presented. References: 1. M. Majumder, B. K. Mishra, N

  6. Performance of practical-sized membrane-electrode assemblies using titanium nitride-supported platinum catalysts mixed with acetylene black as the cathode catalyst layer

    NASA Astrophysics Data System (ADS)

    Shintani, Haruhiko; Kakinuma, Katsuyoshi; Uchida, Hiroyuki; Watanabe, Masahiro; Uchida, Makoto

    2015-04-01

    The performance of practical-sized membrane-electrode assemblies (MEAs) using titanium nitride-supported platinum (Pt/TiN) as the cathode catalysts was evaluated with the use of a practical single cell designed for microscale combined heat and power (CHP) applications. The performance can be controlled by adding acetylene black (AB), with the behavior being dominated by the percolation law. The electrical resistance of the MEAs drastically decreased for AB contents greater than 37 vol%. The Pt utilization percentage was close to 100% for Pt/TiN with percolated AB networks. It was also found that the percolated AB networks supplied effective gas transport pathways, which were not flooded by generated water, thus enhancing the oxygen mass transport. The practical-sized MEA using Pt/TiN + 47 vol% AB showed 1.5 times greater mass activity and a comparable performance under a practical operating condition for micro-CHP applications, compared with the MEA using a commercial graphitized carbon black-supported platinum catalyst.

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

    PubMed Central

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

    2013-01-01

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

  8. Zwitterionic Surfactant Modified Acetylene Black Paste Electrode for Highly Facile and Sensitive Determination of Tetrabromobisphenol A

    PubMed Central

    Wei, Xiaoyun; Zhao, Qiang; Wu, Weixiang; Zhou, Tong; Jiang, Shunli; Tong, Yeqing; Lu, Qing

    2016-01-01

    A electrochemical sensor for the highly sensitive detection of tetrabromobisphenol A (TBBPA) was fabricated based on acetylene black paste electrode (ABPE) modified with 3-(N,N-Dimethylpalmitylammonio) propanesulfonate (SB3-16) in this study. The peak current of TBBPA was significantly enhanced at SB3-16/ABPE compared with unmodified electrodes. To further improve the electrochemical performance of the modified electrode, corresponding experimental parameters such as the length of hydrophobic chains of zwitterionic surfactant, the concentration of SB3-16, pH value, and accumulation time were examined. The peak currents of TBBPA were found to be linearly correlated with its concentrations in the range of 1 nM to 1 µM, with a detection limit of 0.4 nM. Besides, a possible mechanism was also discussed, and the hydrophobic interaction between TBBPA and the surfactants was suggested to take a leading role in enhancing the responses. Finally, this sensor was successfully employed to detect TBBPA in water samples. PMID:27657078

  9. Ab initio calculations of one-electron-scattering properties of ethyne (acetylene) and ethylene molecules

    SciTech Connect

    Tripathi, A.N.; Smith, V.H. Jr. K7L3N6); Kaijser, P.; Siemens, A.G. ); Diercksen, G.H.F. )

    1990-03-01

    Isotropic scattering functions and Compton profiles together with their directional components for several directions relevant to the molecular structure of C{sub 2}H{sub 2} and C{sub 2}H{sub 4} have been evaluated for {ital ab} {ital initio} self-consistent field and configuration-interaction wave functions. The internally folded density (reciprocal form factor) {ital B}({ital r}) is calculated and discussed as are various momentum expectation values. Comparison is made with available experimental and other theoretical results.

  10. Fabrication of a Selective and Sensitive Sensor Based on Molecularly Imprinted Polymer/Acetylene Black for the Determination of Azithromycin in Pharmaceuticals and Biological Samples

    PubMed Central

    Zhou, Tingting; Tao, Yun; Jin, Hua; Song, Bin; Jing, Tao; Luo, Dan; Zhou, Yusun; Zhou, Yikai; Lee, Yong-Ill; Mei, Surong

    2016-01-01

    A new selective and sensitive sensor based on molecularly imprinted polymer/acetylene black (MIP/AB) was developed for the determination of azithromycin (AZM) in pharmaceuticals and biological samples. The MIP of AZM was synthesized by precipitation polymerization. MIP and AB were then respectively introduced as selective and sensitive elements for the preparation of MIP/AB-modified carbon paste (MIP/ABP) electrode. The performance of the obtained sensor was estimated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. Compared with non-molecularly imprinted polymer (NIP) electrodes, NIP/ABP electrodes, and MIP-modified carbon paste electrodes, MIP/ABP electrode exhibited excellent current response toward AZM. The prepared sensor also exhibited good selectivity for AZM in comparison with structurally similar compounds. The effect of electrode composition, extraction parameters, and electrolyte conditions on the current response of the sensor was investigated. Under the optimized conditions, the prepared sensor showed two dynamic linear ranges of 1.0 × 10−7 mol L−1 to 2.0 × 10−6 mol L−1 and 2.0 × 10−6 mol L−1 to 2.0 × 10−5 mol L−1, with a limit of detection of 1.1 × 10−8 mol L−1. These predominant properties ensured that the sensor exhibits excellent reliability for detecting AZM in pharmaceuticals and biological fluids without the assistance of any separation techniques. The results were validated by the high-performance liquid chromatography–tandem mass spectrometry method. PMID:26820753

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

    SciTech Connect

    Cazell, B.H.; Samuelson, L.J.; Seiler, J.R. )

    1990-05-01

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

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

    PubMed

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

    2015-08-01

    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 μM, 2.0-40 μM and 40-100 μM. The detection limit was 10nM. This sensor was used successfully for vanillin determination in various food samples.

  13. High temperature polymer from maleimide-acetylene terminated monomers

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

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

  14. Acetylene Black Induced Heterogeneous Growth of Macroporous CoV2O6 Nanosheet for High-Rate Pseudocapacitive Lithium-Ion Battery Anode.

    PubMed

    Zhang, Lei; Zhao, Kangning; Luo, Yanzhu; Dong, Yifan; Xu, Wangwang; Yan, Mengyu; Ren, Wenhao; Zhou, Liang; Qu, Longbing; Mai, Liqiang

    2016-03-23

    Metal vanadates suffer from fast capacity fading in lithium-ion batteries especially at a high rate. Pseudocapacitance, which is associated with surface or near-surface redox reactions, can provide fast charge/discharge capacity free from diffusion-controlled intercalation processes and is able to address the above issue. In this work, we report the synthesis of macroporous CoV2O6 nanosheets through a facile one-pot method via acetylene black induced heterogeneous growth. When applied as lithium-ion battery anode, the macroporous CoV2O6 nanosheets show typical features of pseudocapacitive behavior: (1) currents that are mostly linearly dependent on sweep rate and (2) redox peaks whose potentials do not shift significantly with sweep rate. The macroporous CoV2O6 nanosheets display a high reversible capacity of 702 mAh g(-1) at 200 mA g(-1), excellent cyclability with a capacity retention of 89% (against the second cycle) after 500 cycles at 500 mA g(-1), and high rate capability of 453 mAh g(-1) at 5000 mA g(-1). We believe that the introduction of pseudocapacitive properties in lithium battery is a promising direction for developing electrode materials with high-rate capability.

  15. Non-covalent C-Cl…π interaction in acetylene-carbon tetrachloride adducts: Matrix isolation infrared and ab initio computational studies

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

    Non-covalent halogen-bonding interactions between π cloud of acetylene (C2H2) and chlorine atom of carbon tetrachloride (CCl4) have been investigated using matrix isolation infrared spectroscopy and quantum chemical computations. The structure and the energies of the 1:1 C2H2-CCl4 adducts were computed at the B3LYP, MP2 and M05-2X levels of theory using 6-311 ++G(d,p) basis set. The computations indicated two minima for the 1:1 C2H2-CCl4 adducts; with the C-Cl…π adduct being the global minimum, where π cloud of C2H2 is the electron donor. The second minimum corresponded to a C-H…Cl adduct, in which C2H2 is the proton donor. The interaction energies for the adducts A and B were found to be nearly identical. Experimentally, both C-Cl…π and C-H…Cl adducts were generated in Ar and N2 matrixes and characterized using infrared spectroscopy. This is the first report on halogen bonded adduct, stabilized through C-Cl…π interaction being identified at low temperatures using matrix isolation infrared spectroscopy. Atoms in Molecules (AIM) and Natural Bond Orbital (NBO) analyses were performed to support the experimental results. The structures of 2:1 ((C2H2)2-CCl4) and 1:2 (C2H2-(CCl4)2) multimers and their identification in the low temperature matrixes were also discussed.

  16. Acetylenic carbon allotrope

    DOEpatents

    Lagow, Richard J.

    1998-01-01

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

  17. Acetylenic carbon allotrope

    DOEpatents

    Lagow, Richard J.

    1999-01-01

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

  18. Acetylenic carbon allotrope

    DOEpatents

    Lagow, R.J.

    1998-02-10

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

  19. Electron ionization of acetylene

    NASA Astrophysics Data System (ADS)

    King, Simon J.; Price, Stephen D.

    2007-11-01

    Relative partial ionization cross sections and precursor specific relative partial ionization cross sections for fragment ions formed by electron ionization of C2H2 have been measured using time-of-flight mass spectrometry coupled with a 2D ion-ion coincidence technique. We report data for the formation of H+, H2+, C2+, C+/C22+, CH +/C2H22+, CH2+, C2+, and C2H + relative to the formation of C2H2+, as a function of ionizing electron energy from 30-200eV. While excellent agreement is found between our data and one set of previously published absolute partial ionization cross sections, some discrepancies exist between the results presented here and two other recent determinations of these absolute partial ionization cross sections. We attribute these differences to the loss of some translationally energetic fragment ions in these earlier studies. Our relative precursor-specific partial ionization cross sections enable us, for the first time, to quantify the contribution to the yield of each fragment ion from single, double, and triple ionization. Analysis shows that at 50eV double ionization contributes 2% to the total ion yield, increasing to over 10% at an ionizing energy of 100eV. From our ion-ion coincidence data, we have derived branching ratios for charge separating dissociations of the acetylene dication. Comparison of our data to recent ab initio/RRKM calculations suggest that close to the double ionization potential C2H22+ dissociates predominantly on the ground triplet potential energy surface (Σg-3) with a much smaller contribution from dissociation via the lowest singlet potential energy surface (Δg1). Measurements of the kinetic energy released in the fragmentation reactions of C2H22+ have been used to obtain precursor state energies for the formation of product ion pairs, and are shown to be in good agreement with available experimental data and with theory.

  20. Acetylene terminated matrix resins

    NASA Technical Reports Server (NTRS)

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

    1985-01-01

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

  1. Acylamidation of acetylenes

    SciTech Connect

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

    1989-01-10

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

  2. Ab Initio Cosmological Simulations of CR7 as an Active Black Hole

    NASA Astrophysics Data System (ADS)

    Smidt, Joseph; Wiggins, Brandon K.; Johnson, Jarrett L.

    2016-09-01

    We present the first ab initio cosmological simulations of a CR7-like object that approximately reproduce the observed line widths and strengths. In our model, CR7 is powered by a massive (3.23× {10}7 {M}⊙ ) black hole (BH), the accretion rate of which varies between ≃0.25 and ≃0.9 times the Eddington rate on timescales as short as 103 years. Our model takes into account multi-dimensional effects, X-ray feedback, secondary ionizations, and primordial chemistry. We estimate Lyα line widths by post-processing simulation output with Monte Carlo radiative transfer and calculate emissivity contributions from radiative recombination and collisional excitation. We find the luminosities in the Lyα and He ii 1640 Å lines to be 5.0× {10}44 and 2.4× {10}43 erg s-1, respectively, in agreement with the observed values of \\gt 8.3× {10}43 and 2.0× {10}43 erg s-1. We also find that the BH heats the halo and renders it unable to produce stars as required to keep the halo metal free. These results demonstrate the viability of the BH hypothesis for CR7 in a cosmological context. Assuming the BH mass and accretion rate that we find, we estimate the synchrotron luminosity of CR7 to be P≃ {10}40{--}{10}41 erg s-1, which is sufficiently luminous to be observed in μJy observations and would discriminate this scenario from one where the luminosity is driven by Population III stars.

  3. Acetylene removal process

    SciTech Connect

    Mc Farland, C.G.

    1987-02-17

    This patent describes a vapor phase process for the preparation of unsaturated hydrocarbon monoolefins in diolefins comprising oxidative dehydrogenation of stream of C/sub 3/ to C/sub 9/ hydrocarbon compounds to produce a product stream comprising 3.5 to 80 mol percent of unsaturated hydrocarbon product and of about or from 0.0001 to 2.5 mol percent acetylenic compound impurity, about or from 0.0005 to 2.5 mol percent carbonyl compounds and 5 to 93 mol percent non-condensable gases. The improvement described here comprises contacting the product stream in vapor phase at a temperature in the range of 250/sup 0/ to 900/sup 0/C. and containing less than 5 mol percent fee oxygen with a solid catalyst for reducing the acetylenic compounds in the product stream. The catalyst consists essentially of a mixture of oxides, carbonates or hydroxides of Fe and Ni, Fe being present as the major metal component and Ni being present in the range of about 0.25 to 20 weight percent based on total catalyst, an alkaline earth metal oxide, carbonate or hydroxide of Mg, Ca, Sr or Ba, and about 0.5 to 30 weight percent of an alkali metal oxide, carbonate or hydroxide of Li, Na, K or Rb determined as metal and based on the other metallic elements, and recovering the stream having the amount of acetylenic compounds therein reduced.

  4. Acetylene: Synergy between theory and experiment

    NASA Astrophysics Data System (ADS)

    Lundberg, James K.; Field, Robert W.; Sherrill, C. David; Seidl, Edward T.; Xie, Yaoming; Schaefer, Henry F., III

    1993-06-01

    Six anomalous vibronic feature states [˜2 cm-1 full-width at half-maximum (FWHM), each consisting of ˜20 partially resolved eigenstates] have been observed in stimulated emission pumping (SEP) spectra of C2D2. Of the two plausible assignments for these features, the one most consistent with spectroscopic observations would imply that the lowest energy cis-bent triplet state of acetylene has T0≤25 820 cm-1, which is inconsistent with previous ab initio predictions. New higher level ab initio quantum mechanical methods have been used to predict the energy difference between X˜ 1Σg+ ground state and the cis-bent ã 3B2 lowest triplet state of acetylene. In conjunction with a triple zeta plus double polarization plus f function (TZ2Pf) basis set, the coupled cluster including single, double, and linearized triple excitations CCSD(T) method yields T0=ΔE(ã 3B2-X˜ 1Σg+)=30 500 cm-1. The true value of T0 for the ã 3B2 state is estimated to be ˜500 cm-1 higher. At the same level of theory the zero-point levels of the lowest triplet state of the trans-bent (ã 3Bu) and vinylidene (ã 3B2) isomers lie at still higher energies. This result conclusively rules out any triplet assignment for the anomalous feature states. The alternative assignment, as highly excited vibrational levels of the X˜ 1Σg+ state, is surprising in view of the Franck-Condon selectivity, dynamical stability, and nonselective relaxation of this special class of ``bright states'' observed in the SEP spectra. Such an assignment would be implausible in the absence of the present ab initio calculations. Previous experimental observations [Lisy and Klemperer, J. Chem. Phys. 72, 3880 (1980) and Wendt, Hippler, and Hunziker, J. Chem. Phys. 70, 4044 (1979)] of acetylene triplet states are discussed and shown to be completely consistent with each other and with the present ab initio ordering of the cis and trans isomeric minima on the T1 potential energy surface: cis ã 3B2 below trans ã 3Bu .

  5. Variability in antioxidant/detoxification enzymes of Labeo rohita exposed to an azo dye, acid black (AB).

    PubMed

    Kaur, Satinder; Kaur, Arvinder

    2015-01-01

    The aim of the present study was to evaluate effect of a highly toxic azo dye, acid black (AB) (CI: 20470, 96 h LC50=10 mg/L) on the biochemical responses of Labeo rohita. Antioxidant/detoxification enzymes such as glutathione-S-transferase (GST), glutathione reductase (GR), glutathione peroxidase (GPx), catalase (CAT), superoxide dismutase (SOD), acetylcholinesterase (AChE), lactate dehydrogenase (LDH), succinate dehydrogenase (SDH), acid phosphatase (AcP), alkaline phosphatase (AKP), alanine transaminase (ALT) and aspartate transaminase (AST) were determined in liver, kidney, gill, muscle and brain of L. rohita after 96 h exposure to 6 mg/L (LC10), 8 mg/L (LC30) and 10 mg/L (LC50) of dye with an aim to find out the target tissue and biomarker enzyme for AB. The fish were then kept for a recovery period of 90 days, and activity of the selected enzymes was determined at the end of this period. Present dye altered the activities of all these enzymes in the selected tissues of the experimental fish in a dose-dependent manner. SOD was the maximally affected enzyme, and liver was the most affected tissue. The results indicate that AB is very toxic to L. rohita as there was a significant effect of even 6 mg/L dose of the dye and the toxicity prolonged for a long time because the fish was not able to recover from the stress even 90 days after the exposure. The study suggests that SOD can be used as a biomarker enzyme and liver is the target tissue for AB.

  6. Acetylene on Titan

    NASA Astrophysics Data System (ADS)

    Singh, Sandeep; McCord, Thomas B.; Combe, Jean-Philippe; Rodriguez, Sebastien; Cornet, Thomas; Le Mouélic, Stéphane; Clark, Roger Nelson; Maltagliati, Luca; Chevrier, Vincent

    2016-10-01

    Saturn's moon Titan possesses a thick atmosphere that is mainly composed of N2 (98%), CH4 (2 % overall, but 4.9% close to the surface) and less than 1% of minor species, mostly hydrocarbons [1]. A dissociation of N2 and CH4 forms complex hydrocarbons in the atmsophere and acetylene (C2H2) and ethane (C2H6) are produced most abundently. Since years, C2H2 has been speculated to exist on the surface of Titan based on its high production rate in the stratosphere predicted by photochemical models [2,3] and from its detection as trace gas sublimated/evaporated from the surface after the landing of the Huygens probe by the Gas Chromatograph Mass Spectrometer (GCMS) [1]. Here we show evidence of acetylene (C2H2) on the surface of Titan by detecting absorption bands at 1.55 µm and 4.93 µm using Cassini Visual and Infrared Mapping Spectrometer (VIMS) [4] at equatorial areas of eastern Shangri-La, and Fensal-Aztlan/Quivira.An anti-correlation of absorption band strength with albedo indicates greater concentrations of C2H2 in the dark terrains, such as sand dunes and near the Huygens landing site. The specific location of the C2H2 detections suggests that C2H2 is mobilized by surface processes, such as surface weathering by liquids through dissolution/evaporation processes.References:[1]Niemann et al., Nature 438, 779–784 (2005).[2]Lavvas et al., Planetary and Space Science 56, 67 – 99 (2008).[3]Lavvas et al., Planetary and Space Science 56, 27 – 66 (2008).[4] Brown et al., The Cassini-Huygens Mission 111–168 (Springer, 2004).

  7. 29 CFR 1910.102 - Acetylene.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...., 2003). (b) Piped systems. (1) Employers must comply with Chapter 9 (“Acetylene Piping”) of NFPA 51A..., 2006, these employers may comply with the provisions of Chapter 7 (“Acetylene Piping”) of NFPA 51A-2001... (fill) acetylene cylinders comply with the provisions of NFPA 51A-2006 (“Standard for Acetylene...

  8. Acetylene removal process

    SciTech Connect

    Mc Farland, C.G.

    1987-04-14

    This patent describes a vapor phase process for the preparation of hydrocarbon monoolefins and diolefins comprising oxidative dehydrogenation of a stream of C/sub 3/ to C/sub 9/ hydrocarbon compounds to produce a product stream comprising, exclusive of any water present, 3.5 to 80 mol percent hydrocarbon monoolefins and diolefins and about from 0.0001 to 2.5 mol percent carbonyl compounds and 5 to 93 mol percent non-condensable gases. The improvement described here comprises contacting the product stream in vapor phase at a temperature in the range of 250/sup 0/ to 900/sup 0/C and containing less than 5 mol percent free oxygen with a solid catalyst for reducing the acetylene compounds in the product stream, the catalyst consisting essentially of zinc ferrite and nickel oxide. The Fe is the major metal component by weight, an alkaline earth metal oxide, carbonate or hydroxide of Mg, Ca, Sr or Ba, and about 0.5 to 30 weight percent of an alkali metal oxide, carbonate or hydroxide, based on the other metallic elements of Li, Na, K or Rh.

  9. Research in acetylene containing monomers

    NASA Technical Reports Server (NTRS)

    Ogliaruso, M. A.

    1976-01-01

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

  10. 29 CFR 1910.102 - Acetylene.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

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

  11. 29 CFR 1910.102 - Acetylene.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...). (b) Piped systems. (1) Employers must comply with Chapter 9 (“Acetylene Piping”) of NFPA 51A-2006... may comply with the provisions of Chapter 7 (“Acetylene Piping”) of NFPA 51A-2001 (“Standard for... comply with the provisions of NFPA 51A-2006 (“Standard for Acetylene Charging Plants”) (National...

  12. 29 CFR 1910.102 - Acetylene.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...). (b) Piped systems. (1) Employers must comply with Chapter 9 (“Acetylene Piping”) of NFPA 51A-2006... may comply with the provisions of Chapter 7 (“Acetylene Piping”) of NFPA 51A-2001 (“Standard for... comply with the provisions of NFPA 51A-2006 (“Standard for Acetylene Charging Plants”) (National...

  13. 41 CFR 50-204.66 - Acetylene.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 41 Public Contracts and Property Management 1 2010-07-01 2010-07-01 true Acetylene. 50-204.66 Section 50-204.66 Public Contracts and Property Management Other Provisions Relating to Public Contracts...) Plants for the generation of acetylene and the charging (filling) of acetylene cylinders shall...

  14. Nonradiative Electron--Hole Recombination Rate Is Greatly Reduced by Defects in Monolayer Black Phosphorus: Ab Initio Time Domain Study.

    PubMed

    Long, Run; Fang, Weihai; Akimov, Alexey V

    2016-02-18

    We report ab initio time-domain simulations of nonradiative electron-hole recombination and electronic dephasing in ideal and defect-containing monolayer black phosphorus (MBP). Our calculations predict that the presence of phosphorus divacancy in MBP (MBP-DV) substantially reduces the nonradiative recombination rate, with time scales on the order of 1.57 ns. The luminescence line width in ideal MBP of 150 meV is 2.5 times larger than MBP-DV at room temperature, and is in excellent agreement with experiment. We find that the electron-hole recombination in ideal MBP is driven by the 450 cm(-1) vibrational mode, whereas the recombination in the MBP-DV system is driven by a broad range of vibrational modes. The reduced electron-phonon coupling and increased bandgap in MBP-DV rationalize slower recombination in this material, suggesting that electron-phonon energy losses in MBP can be minimized by creating suitable defects in semiconductor device material. PMID:26821943

  15. Nonradiative Electron--Hole Recombination Rate Is Greatly Reduced by Defects in Monolayer Black Phosphorus: Ab Initio Time Domain Study.

    PubMed

    Long, Run; Fang, Weihai; Akimov, Alexey V

    2016-02-18

    We report ab initio time-domain simulations of nonradiative electron-hole recombination and electronic dephasing in ideal and defect-containing monolayer black phosphorus (MBP). Our calculations predict that the presence of phosphorus divacancy in MBP (MBP-DV) substantially reduces the nonradiative recombination rate, with time scales on the order of 1.57 ns. The luminescence line width in ideal MBP of 150 meV is 2.5 times larger than MBP-DV at room temperature, and is in excellent agreement with experiment. We find that the electron-hole recombination in ideal MBP is driven by the 450 cm(-1) vibrational mode, whereas the recombination in the MBP-DV system is driven by a broad range of vibrational modes. The reduced electron-phonon coupling and increased bandgap in MBP-DV rationalize slower recombination in this material, suggesting that electron-phonon energy losses in MBP can be minimized by creating suitable defects in semiconductor device material.

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

    PubMed

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

    2016-03-14

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

  17. Thermal Conversion of Methane to Acetylene

    SciTech Connect

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

    2000-01-01

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

  18. Acetylene terminated aspartimides and resins therefrom

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

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

  19. Quantum Dynamics of Vinylidene Photodetachment on an Accurate Global Acetylene-Vinylidene Potential Energy Surface.

    PubMed

    Guo, Lifen; Han, Huixian; Ma, Jianyi; Guo, Hua

    2015-08-01

    Vinylidene is a high-energy isomer of acetylene, and the rearrangement of bonds in the two species serves as a prototype for isomerization reactions. Here, a full-dimensional quantum mechanical study of the vinylidene vibration is carried out on a recently developed global acetylene-vinylidene potential energy surface by simulating the photodetachment dynamics of the vinylidene anion. Several low-lying vibrational levels of the anion were first determined on a new ab initio based potential energy surface, and their photoelectron spectra were obtained within the Condon approximation. The vibrational features of the vinylidene isomer are found to agree well with the experiment in both positions and intensities, validating the global acetylene-vinylidene potential energy surface.

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

    NASA Astrophysics Data System (ADS)

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

    2011-05-01

    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

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

    NASA Technical Reports Server (NTRS)

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

    2013-01-01

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

  2. Vapor pressures of acetylene at low temperatures

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

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

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

    PubMed Central

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

    2015-01-01

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

  4. 46 CFR 154.1735 - Methyl acetylene-propadiene mixture.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 5 2011-10-01 2011-10-01 false Methyl acetylene-propadiene mixture. 154.1735 Section... Operating Requirements § 154.1735 Methyl acetylene-propadiene mixture. (a) The composition of the methyl acetylene-propadiene mixture at loading must be within the following limits or specially approved by...

  5. 46 CFR 154.1735 - Methyl acetylene-propadiene mixture.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 5 2012-10-01 2012-10-01 false Methyl acetylene-propadiene mixture. 154.1735 Section... Operating Requirements § 154.1735 Methyl acetylene-propadiene mixture. (a) The composition of the methyl acetylene-propadiene mixture at loading must be within the following limits or specially approved by...

  6. 46 CFR 154.1735 - Methyl acetylene-propadiene mixture.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 5 2013-10-01 2013-10-01 false Methyl acetylene-propadiene mixture. 154.1735 Section... Operating Requirements § 154.1735 Methyl acetylene-propadiene mixture. (a) The composition of the methyl acetylene-propadiene mixture at loading must be within the following limits or specially approved by...

  7. 46 CFR 154.1735 - Methyl acetylene-propadiene mixture.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 5 2014-10-01 2014-10-01 false Methyl acetylene-propadiene mixture. 154.1735 Section... Operating Requirements § 154.1735 Methyl acetylene-propadiene mixture. (a) The composition of the methyl acetylene-propadiene mixture at loading must be within the following limits or specially approved by...

  8. Theoretical and Experimental Evidence of Hydrogen Migration rather than Isomerization in the Acetylene Dication

    NASA Astrophysics Data System (ADS)

    Liekhus-Schmaltz, Chelsea; Li, Zheng; Petrovic, Vladimir; Martinez, Todd; Bucksbaum, Phil; AMO75113 Collaboration

    2016-05-01

    Theoretical calculations and experimental results in the acetylene dication have long agreed that isomerization after x-ray excitation occurs in the first singlet state, where the carbon-carbon bond lives long enough for isomerization to complete. These same calculations predict that a large barrier to isomerization exists that would cause isomerization to occur in about a picosecond, while there is some evidence for ultrafast isomerization in under 100 fs. However, new ab initio calculations of the acetylene dication reveal that ultrafast isomerization after x-ray excitation is unlikely. In this talk, we present evidence that signatures of hydrogen migration observed in recent time resolved LCLS data are mostly due to hydrogen migration in an excited state which dissociates too quickly for isomerization to complete. This material is based upon work supported by the National Science Foundation under Grant No. PHY-0649578.

  9. Influence of and additives on acetylene detonation

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

    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.

  10. Living on acetylene. A primordial energy source.

    PubMed

    Ten Brink, Felix

    2014-01-01

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

  11. Hydration of Acetylene: A 125th Anniversary

    ERIC Educational Resources Information Center

    Ponomarev, Dmitry A.; Shevchenko, Sergey M.

    2007-01-01

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

  12. Two new acetylenic compounds from Asparagus officinalis.

    PubMed

    Li, Xue-Mei; Cai, Jin-Long; Wang, Wen-Xiang; Ai, Hong-Lian; Mao, Zi-Chao

    2016-01-01

    Two new acetylenic compounds, asparoffins A (1) and B (2), together with two known compounds, nyasol (3) and 3″-methoxynyasol (4), were isolated from stems of Asparagus officinalis. The structures of two new compounds were elucidated on the basis of detailed spectroscopic analyses (UV, IR, MS, 1D, and 2D NMR). All compounds were evaluated for their cytotoxicities against three human cancer cell lines. PMID:26558641

  13. Two new acetylenic compounds from Asparagus officinalis.

    PubMed

    Li, Xue-Mei; Cai, Jin-Long; Wang, Wen-Xiang; Ai, Hong-Lian; Mao, Zi-Chao

    2016-01-01

    Two new acetylenic compounds, asparoffins A (1) and B (2), together with two known compounds, nyasol (3) and 3″-methoxynyasol (4), were isolated from stems of Asparagus officinalis. The structures of two new compounds were elucidated on the basis of detailed spectroscopic analyses (UV, IR, MS, 1D, and 2D NMR). All compounds were evaluated for their cytotoxicities against three human cancer cell lines.

  14. Cyclopolymerization of Acetylene to Benzyne and Naphthalene

    NASA Astrophysics Data System (ADS)

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

    2012-06-01

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

  15. Spectroscopic study of acetylene and hydrogen cyanide

    NASA Astrophysics Data System (ADS)

    Rozario, Hoimonti Immaculata

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

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

    PubMed

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

    2011-01-21

    Guided by ab initio calculations, Fourier transform microwave spectra in the 6-21 GHz region are obtained for seven isotopomers of the complex formed between 1-chloro-1-fluoroethylene and acetylene. These include the four possible combinations of (35)Cl- and (37)Cl-containing CH(2)CClF with the most abundant acetylene isotopic modification, HCCH, and its H(13)C(13)CH analogue, as well as three singly substituted deuterated isotopomers. Analysis of the spectra determines the rotational constants and additionally, the complete chlorine quadrupole hyperfine coupling tensors in both the inertial and principal electric field gradient axis systems, and where appropriate, the diagonal components of the deuterium quadrupole coupling tensors. The inertial information contained in the rotational constants provides the structure for CH(2)CClF-HCCH: a primary, hydrogen bonding interaction existing between the HCCH donor and the F atom acceptor on the 1-chloro-1-fluoroethylene moiety, while a secondary interaction occurs between the acetylenic bond on the HCCH molecule and the H atom cis to the hydrogen-bonded F atom on the substituted ethylene, which causes the hydrogen bond to deviate from linearity. This is similar to the structure obtained for 1,1-difluoroethylene-HCCH [H. O. Leung and M. D. Marshall, J. Chem. Phys. 126, 154301 (2006)], and indeed, to within experimental uncertainty, the intermolecular interactions in CH(2)CClF-HCCH and its 1,1-difluoroethylene counterpart are practically indistinguishable, even though ab initio calculations at the MP2∕6-311G++(2d, 2p) level suggest that the former complex is more strongly bound. PMID:21261349

  17. Acetylenic polymers for hair styling products.

    PubMed

    Martiny, S

    2002-06-01

    This paper looks at the basic requirements of hair styling products from a consumer's perspective before moving onto a very brief outline of the various chemistries available to the formulator. It then discusses the manufacture of vinyl pyrrolidone from acetylene. The properties of polyvinyl pyrrolidone are described, followed by the features and benefits of some vinyl pyrrolidone copolymers and terpolymers. The instrumental analysis of the hold, flexibility, tack and combing properties of polymer films is discussed in some detail, along with the effect of application type on these measurable properties concentrating upon vinyl caprolactam/vinyl pyrrolidone/dimethylaminopropyl methacrylamide acrylates copolymer.

  18. RECRYSTALLIZATION OF PMDA AND SYNTHESIS OF AN ACETYLENIC DIAMINE

    SciTech Connect

    Sanner, R; Cook, R C

    2004-09-21

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

  19. Proton exchange membrane fuel cell cathode contamination - Acetylene

    NASA Astrophysics Data System (ADS)

    Zhai, Y.; St-Pierre, Jean

    2015-04-01

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

  20. Acetylene-based materials in organic photovoltaics.

    PubMed

    Silvestri, Fabio; Marrocchi, Assunta

    2010-04-08

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

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

    PubMed Central

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

    1981-01-01

    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

  2. Intramolecular competition between n-pair and π-pair hydrogen bonding: Microwave spectrum and internal dynamics of the pyridine-acetylene hydrogen-bonded complex.

    PubMed

    Mackenzie, Rebecca B; Dewberry, Christopher T; Coulston, Emma; Cole, George C; Legon, Anthony C; Tew, David P; Leopold, Kenneth R

    2015-09-14

    a-type rotational spectra of the hydrogen-bonded complex formed from pyridine and acetylene are reported. Rotational and (14)N hyperfine constants indicate that the complex is planar with an acetylenic hydrogen directed toward the nitrogen. However, unlike the complexes of pyridine with HCl and HBr, the acetylene moiety in HCCH-NC5H5 does not lie along the symmetry axis of the nitrogen lone pair, but rather, forms an average angle of 46° with the C2 axis of the pyridine. The a-type spectra of HCCH-NC5H5 and DCCD-NC5H5 are doubled, suggesting the existence of a low lying pair of tunneling states. This doubling persists in the spectra of HCCD-NC5H5, DCCH-NC5H5, indicating that the underlying motion does not involve interchange of the two hydrogens of the acetylene. Single (13)C substitution in either the ortho- or meta-position of the pyridine eliminates the doubling and gives rise to separate sets of spectra that are well predicted by a bent geometry with the (13)C on either the same side ("inner") or the opposite side ("outer") as the acetylene. High level ab initio calculations are presented which indicate a binding energy of 1.2 kcal/mol and a potential energy barrier of 44 cm(-1) in the C2v configuration. Taken together, these results reveal a complex with a bent hydrogen bond and large amplitude rocking of the acetylene moiety. It is likely that the bent equilibrium structure arises from a competition between a weak hydrogen bond to the nitrogen (an n-pair hydrogen bond) and a secondary interaction between the ortho-hydrogens of the pyridine and the π electron density of the acetylene.

  3. Three-Dimensional Carbon Allotropes Comprising Phenyl Rings and Acetylenic Chains in sp+sp(2) Hybrid Networks.

    PubMed

    Wang, Jian-Tao; Chen, Changfeng; Li, Han-Dong; Mizuseki, Hiroshi; Kawazoe, Yoshiyuki

    2016-01-01

    We here identify by ab initio calculations a new type of three-dimensional (3D) carbon allotropes that consist of phenyl rings connected by linear acetylenic chains in sp+sp(2) bonding networks. These structures are constructed by inserting acetylenic or diacetylenic bonds into an all sp(2)-hybridized rhombohedral polybenzene lattice, and the resulting 3D phenylacetylene and phenyldiacetylene nets comprise a 12-atom and 18-atom rhombohedral primitive unit cells in the symmetry, which are characterized as the 3D chiral crystalline modification of 2D graphyne and graphdiyne, respectively. Simulated phonon spectra reveal that these structures are dynamically stable. Electronic band calculations indicate that phenylacetylene is metallic, while phenyldiacetylene is a semiconductor with an indirect band gap of 0.58 eV. The present results establish a new type of carbon phases and offer insights into their outstanding structural and electronic properties.

  4. Three-Dimensional Carbon Allotropes Comprising Phenyl Rings and Acetylenic Chains in sp+sp2 Hybrid Networks

    NASA Astrophysics Data System (ADS)

    Wang, Jian-Tao; Chen, Changfeng; Li, Han-Dong; Mizuseki, Hiroshi; Kawazoe, Yoshiyuki

    2016-04-01

    We here identify by ab initio calculations a new type of three-dimensional (3D) carbon allotropes that consist of phenyl rings connected by linear acetylenic chains in sp+sp2 bonding networks. These structures are constructed by inserting acetylenic or diacetylenic bonds into an all sp2-hybridized rhombohedral polybenzene lattice, and the resulting 3D phenylacetylene and phenyldiacetylene nets comprise a 12-atom and 18-atom rhombohedral primitive unit cells in the symmetry, which are characterized as the 3D chiral crystalline modification of 2D graphyne and graphdiyne, respectively. Simulated phonon spectra reveal that these structures are dynamically stable. Electronic band calculations indicate that phenylacetylene is metallic, while phenyldiacetylene is a semiconductor with an indirect band gap of 0.58 eV. The present results establish a new type of carbon phases and offer insights into their outstanding structural and electronic properties.

  5. Three-dimensional carbon allotropes comprising phenyl rings and acetylenic chains in sp+sp2 hybrid networks

    DOE PAGES

    Wang, Jian -Tao; Chen, Changfeng; Li, Han -Dong; Mizuseki, Hiroshi; Kawazoe, Yoshiyuki

    2016-04-18

    Here, we here identify by ab initio calculations a new type of three-dimensional (3D) carbon allotropes that consist of phenyl rings connected by linear acetylenic chains in sp+sp2 bonding networks. These structures are constructed by inserting acetylenic or diacetylenic bonds into an all sp2-hybridized rhombohedral polybenzene lattice, and the resulting 3D phenylacetylene and phenyldiacetylene nets comprise a 12-atom and 18-atom rhombohedral primitive unit cells R-3m symmetry, which are characterized as the 3D chiral crystalline modification of 2D graphyne and graphdiyne, respectively. Simulated phonon spectra reveal that these structures are dynamically stable. Electronic band calculations indicate that phenylacetylene is metallic, whilemore » phenyldiacetylene is a semiconductor with an indirect band gap of 0.58 eV. The present results establish a new type of carbon phases and offer insights into their outstanding structural and electronic properties.« less

  6. Three-Dimensional Carbon Allotropes Comprising Phenyl Rings and Acetylenic Chains in sp+sp2 Hybrid Networks

    PubMed Central

    Wang, Jian-Tao; Chen, Changfeng; Li, Han-Dong; Mizuseki, Hiroshi; Kawazoe, Yoshiyuki

    2016-01-01

    We here identify by ab initio calculations a new type of three-dimensional (3D) carbon allotropes that consist of phenyl rings connected by linear acetylenic chains in sp+sp2 bonding networks. These structures are constructed by inserting acetylenic or diacetylenic bonds into an all sp2-hybridized rhombohedral polybenzene lattice, and the resulting 3D phenylacetylene and phenyldiacetylene nets comprise a 12-atom and 18-atom rhombohedral primitive unit cells in the symmetry, which are characterized as the 3D chiral crystalline modification of 2D graphyne and graphdiyne, respectively. Simulated phonon spectra reveal that these structures are dynamically stable. Electronic band calculations indicate that phenylacetylene is metallic, while phenyldiacetylene is a semiconductor with an indirect band gap of 0.58 eV. The present results establish a new type of carbon phases and offer insights into their outstanding structural and electronic properties. PMID:27087405

  7. High pressure chemistry of substituted acetylenes

    SciTech Connect

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

    2011-01-25

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

  8. 46 CFR 151.50-79 - Methyl acetylene-propadiene mixture.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 5 2012-10-01 2012-10-01 false Methyl acetylene-propadiene mixture. 151.50-79 Section... acetylene-propadiene mixture. (a) The composition of the methyl acetylene-propadiene mixture at loading must... acetylene-propadiene mixture must have a refrigeration system that does not compress the cargo vapor or...

  9. 46 CFR 151.50-79 - Methyl acetylene-propadiene mixture.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 5 2013-10-01 2013-10-01 false Methyl acetylene-propadiene mixture. 151.50-79 Section... acetylene-propadiene mixture. (a) The composition of the methyl acetylene-propadiene mixture at loading must... acetylene-propadiene mixture must have a refrigeration system that does not compress the cargo vapor or...

  10. 46 CFR 151.50-79 - Methyl acetylene-propadiene mixture.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 5 2014-10-01 2014-10-01 false Methyl acetylene-propadiene mixture. 151.50-79 Section... acetylene-propadiene mixture. (a) The composition of the methyl acetylene-propadiene mixture at loading must... acetylene-propadiene mixture must have a refrigeration system that does not compress the cargo vapor or...

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

    USGS Publications Warehouse

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

    1981-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Beaulieu, Samuel; Ibrahim, Heide; Wales, Benji; Schmidt, Bruno E.; Thiré, Nicolas; Bisson, Éric; Hebeisen, Christoph T.; Wanie, Vincent; Giguere, Mathieu; Kieffer, Jean-Claude; Sanderson, Joe; Schuurman, Michael S.; Légaré, François

    2014-05-01

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

  13. Acetylene on Titan’s Surface

    NASA Astrophysics Data System (ADS)

    Singh, S.; McCord, T. B.; Combe, J.-Ph.; Rodriguez, S.; Cornet, T.; Le Mouélic, S.; Clark, R. N.; Maltagliati, L.; Chevrier, V. F.

    2016-09-01

    Titan’s atmosphere is opaque in the near-infrared due to gaseous absorptions, mainly by methane, and scattering by aerosols, except in a few “transparency windows.” Thus, the composition of Titan’s surface remains difficult to access from space and is still poorly constrained. Photochemical models suggest that most of the organic compounds formed in the atmosphere are heavy enough to condense and build up at the surface in liquid and solid states over geological timescales. Acetylene (C2H2) net production in the atmosphere is predicted to be larger than any other compound and C2H2 has been speculated to exist on the surface of Titan. C2H2 was detected as a trace gas sublimated/evaporated from the surface using the Gas Chromatograph Mass Spectrometer after the landing of the Huygens probe. Here we show evidence of C2H2 on the surface of Titan by detecting absorption bands at 1.55 and 4.93 μm using the Cassini Visual and Infrared Mapping Spectrometer at three different equatorial areas—Tui Regio, eastern Shangri La, and Fensal-Aztlan/Quivira. We found that C2H2 is preferentially detected in low-albedo areas, such as sand dunes and near the Huygens landing site. The specific location of the C2H2 detections suggests that C2H2 is mobilized by surface processes, such as surface weathering by liquids through dissolution/evaporation processes.

  14. Electron impact induced anion production in acetylene.

    PubMed

    Szymańska, Ewelina; Čadež, Iztok; Krishnakumar, E; Mason, Nigel J

    2014-02-28

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

  15. Acetylene on Titan’s Surface

    NASA Astrophysics Data System (ADS)

    Singh, S.; McCord, T. B.; Combe, J.-Ph.; Rodriguez, S.; Cornet, T.; Le Mouélic, S.; Clark, R. N.; Maltagliati, L.; Chevrier, V. F.

    2016-09-01

    Titan’s atmosphere is opaque in the near-infrared due to gaseous absorptions, mainly by methane, and scattering by aerosols, except in a few “transparency windows.” Thus, the composition of Titan’s surface remains difficult to access from space and is still poorly constrained. Photochemical models suggest that most of the organic compounds formed in the atmosphere are heavy enough to condense and build up at the surface in liquid and solid states over geological timescales. Acetylene (C2H2) net production in the atmosphere is predicted to be larger than any other compound and C2H2 has been speculated to exist on the surface of Titan. C2H2 was detected as a trace gas sublimated/evaporated from the surface using the Gas Chromatograph Mass Spectrometer after the landing of the Huygens probe. Here we show evidence of C2H2 on the surface of Titan by detecting absorption bands at 1.55 and 4.93 μm using the Cassini Visual and Infrared Mapping Spectrometer at three different equatorial areas—Tui Regio, eastern Shangri La, and Fensal–Aztlan/Quivira. We found that C2H2 is preferentially detected in low-albedo areas, such as sand dunes and near the Huygens landing site. The specific location of the C2H2 detections suggests that C2H2 is mobilized by surface processes, such as surface weathering by liquids through dissolution/evaporation processes.

  16. Mortality of workers at acetylene production plants.

    PubMed Central

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

    1988-01-01

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

  17. Process hydrogenates unwanted diolefins and acetylenes

    SciTech Connect

    Vora, B.V. )

    1988-12-05

    Diolefins and actetylenes in C/sub 3//C/sub 4/ olefin streams can be selectively hydrogenated to produce high-purity mono-olefins for downstream polyolefin production. C/sub 3//C/sub 4/ olefin sources, fluid catalytic cracking (FCC), steam crackers, and dehydrogenation of C/sub 3//C/sub 4/ paraffins, all contain these undesirable polyunsaturated compounds. Hydrogenation of these compounds in alkylation unit feeds can also improve the economics of the alkylation process. Production of high-purity mono-olefins for downstream polyolefins production requires a feedstock that is essentially free of dienes and acetylenes to minimize undesirable side reactions. Although alkylation units can tolerate some diolefins in the feed, economics dictate that these diolefins should be minimized. The selective hydrogenation process (SHP) developed by others at its Marl, West Germany, plant, has undergone additional development work since commercialization of the process in 1980. The unit was designed to feed 160,000 metric tons/year of clean C/sub 4/ raffinate from a steam cracker, with a maximum polyunsaturated content of 0.8 wt%.

  18. Ion-induced dissociation dynamics of acetylene

    SciTech Connect

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

    2008-02-15

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

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

    NASA Astrophysics Data System (ADS)

    Ibrahim, Heide; Wales, Benji; Beaulieu, Samuel; Schmidt, Bruno E.; 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

    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.

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

    PubMed

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

    2014-01-01

    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.

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

    PubMed

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

    2014-01-01

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

  2. Identification of Acetylene on Titan's Surface

    NASA Astrophysics Data System (ADS)

    Singh, S.; McCord, T. B.; Rodriguez, S.; Combe, J. P.; Cornet, T.; Le Mouelic, S.; Maltagliati, L.; Chevrier, V.; Clark, R. N.

    2015-12-01

    Titan's atmosphere is opaque in the near infrared due to gaseous absorptions, mainly by methane, and scattering by aerosols, except in a few "transparency windows" (e.g., Sotin et al., 2005). Thus, the composition of Titan surface remains difficult to access from space and is still poorly constrained, limited to ethane in the polar lakes (Brown et al., 2008) and a few possible organic molecules on the surface (Clark et al., 2010). Photochemical models suggest that most of the organic compounds formed in the atmosphere are heavy enough to condense and build up at the surface in liquid and solid states over geological timescale (Cordier et al., 2009, 2011). Acetylene (C2H2) is one of the most abundant organic molecules in the atmosphere and thus thought to present on the surface as well. Here we report direct evidence of solid C2H2 on Titan's surface using Cassini Visual and Infrared Mapping Spectrometer (VIMS) data. By comparing VIMS observations and laboratory measurements of solid and liquid C2H2, we identify a specific absorption at 1.55 µm that is widespread over Titan but is particularly strong in the brightest terrains. This surface variability suggests that C2H2 is mobilized by surface processes, such as surface weathering, topography, and dissolution/evaporation. The detection of C2H2 on the surface of Titan opens new paths to understand and constrain Titan's surface activity. Since C2H2 is highly soluble in Titan liquids (Singh et al. 2015), it can easily dissolve in methane/ethane and may play an important role in carving of fluvial channels and existence of karstic lakes at higher latitudes on Titan. These processes imply the existence of a dynamic surface with a continued history of erosion and deposition of C2H2 on Titan.

  3. A Model for Self-Assembly of Carbon Nanotubes from Acetylene Based on Real-Time Studies of Vertically Aligned Growth Kinetics

    SciTech Connect

    Eres, Gyula

    2009-01-01

    Time-resolved optical reflectivity was used to study the kinetics in the early stages of vertically aligned carbon nanotube array growth from a molecular beam of acetylene. The molecular beam environment was used to suppress gas phase reaction pathways and limit the growth to surface reactions specific to the molecular structure of acetylene. The observed acetylene flux dependent induction delay and the threshold for vertically aligned growth are characteristic features of heterogeneous chain reactions. Propagation of chain reactions requires regeneration of the active sites that can occur only if catalytic activity is transferred from the metal catalyst film to surface carbon species. After the active site transformation, acetylene self-assembles into carbon structures of progressively increasing size such as chains, graphene fragments, and nanotubes. In this paper we show that a conceptual framework supported by ab initio density functional theory calculations in which active carbon species facilitate incorporation of new carbon readily explains recent results in vertically aligned nanotube growth that are puzzling in the context of the diffusion/precipitation model.

  4. Microgravity Superagglomerates Produced By Silane And Acetylene

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

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

  5. Synthesis of functional acetylene derivatives from calcium carbide.

    PubMed

    Lin, Zhewang; Yu, Dingyi; Sum, Yin Ngai; Zhang, Yugen

    2012-04-01

    AHA Erlebnis: CaC(2), used to produce acetylene until several decades ago, is re-emerging as a cheap, sustainable resource synthesized from coal and lignocellulosic biomass. We report efficient catalytic protocols for the synthesis of functional acetylene derivatives from CaC(2) through aldehyde, alkyne, and amine (AAA) as well as alkyne, haloalkane, and amine (AHA) couplings, and in addition demonstrate its use in click and Sonogashira chemistry, showing that calcium carbide is a sustainable and cost-efficient carbon source.

  6. Theoretical determination of the structure of acetylene on Pt(111)

    NASA Astrophysics Data System (ADS)

    Anderson, Alfred B.; Hubbard, Arthur T.

    1980-09-01

    An atom superposition and electron delocalization technique applied to acetylene chemisorption on small cluster models for the Pt(111) surface shows preference for the triangular site as deduced from electron energy loss analyses by Ibach and Lehwald. This confirms the applicability of Badger's and related rules in this instance. Calculations on CCH 3 produce a structure in agreement with a dynamic LEED analysis at 400 K by Kesmodel, Dubois and Somorjai. Structures of CCH 2 and CHCH 2 are calculated and these species are found to be less stable than acetylene and CCH 3, respectively, when chemisorbed on Pt(111).

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

    Code of Federal Regulations, 2013 CFR

    2013-10-01

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

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

    Code of Federal Regulations, 2011 CFR

    2011-10-01

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

  9. 46 CFR 56.50-103 - Fixed oxygen-acetylene distribution piping.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

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

  10. 46 CFR 56.50-103 - Fixed oxygen-acetylene distribution piping.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

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

  11. 46 CFR 56.50-103 - Fixed oxygen-acetylene distribution piping.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

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

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

    PubMed

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

    2013-06-01

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

  13. 76 FR 75840 - Revising Standards Referenced in the Acetylene Standard

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-12-05

    ... language from outdated standards published by standards developing organizations (``SDO standards'') (69 FR... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF LABOR... rulemaking, the Agency is proposing to revise its Acetylene Standard for general industry by updating...

  14. 76 FR 75782 - Revising Standards Referenced in the Acetylene Standard

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-12-05

    ... on November 9, 2009. See 74 FR 57883. The Compressed Gas Association published a new edition of CGA G... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF LABOR... is revising its Acetylene Standard for general industry by updating a reference to a...

  15. 77 FR 13969 - Revising Standards Referenced in the Acetylene Standard

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-03-08

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

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

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 5 2010-10-01 2010-10-01 false Methyl acetylene-propadiene mixture. 154.1735 Section 154.1735 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) CERTAIN BULK DANGEROUS CARGOES SAFETY STANDARDS FOR SELF-PROPELLED VESSELS CARRYING BULK LIQUEFIED GASES Special Design...

  17. Acetylene absorption and binding in nonporous crystal lattice

    SciTech Connect

    Thallapally, Praveen K.; Dobrzanska, Liliana B.; Gingrich, Todd R.; Wirsig, Trevor B.; Barbour, Leonard J.; Atwood, Jerry L.

    2006-09-01

    Unusual storage: An organic nonporous material, p-tert-butylcalix[4]arene, sorbs acetylene with high storage density under ambient conditions. It is presumed that gas molecules diffuse through the seemingly nonporous lattice without disrupting the arrangement of the host molecules (see picture; red O, blue C, gray H, yellow void space).

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

    PubMed

    Brvar, Miran

    2014-01-01

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

  19. Nonradiative Relaxation of Photoexcited Black Phosphorus Is Reduced by Stacking with MoS2: A Time Domain ab Initio Study.

    PubMed

    Long, Run; Guo, Meng; Liu, Lihong; Fang, Weihai

    2016-05-19

    Black phosphorus (BP) is an appealing material for applications in electronics and optoelectronics because of its tunable direct band gap and high charge carrier mobility. For real optoelectronic device utilization, nonradiative electron-hole recombination should be slow because it constitutes a major pathway for charge and energy losses. Using time-domain density functional theory combined with nonadiabatic (NA) molecular dynamics, we show that nonradiative electron-hole recombination occurs within several tens of picoseconds in bilayer BP, agreeing well with experimental data. When a single layer of BP is stacked with monolayer MoS2, the recombination is reduced because of the increased band gap and reduced electron-phonon NA coupling compared to bilayer BP. The slow electron-phonon energy losses in BP-MoS2 van der Waals heterojunction relative to bilayer BP indicate that rationally stacking BP with other two-dimensional materials is an attractive route for designing novel and efficient photovoltaic materials. PMID:27132486

  20. Lipase-catalyzed hydrolysis of TG containing acetylenic FA.

    PubMed

    Jie, Marcel S F Lie Ken; Fua, Xun; Lau, Maureen M L; Chye, M L

    2002-10-01

    Hydrolysis of symmetrical acetylenic TG of type AAA [viz., glycerol tri-(4-decynoate), glycerol tri-(6-octadecynoate), glycerol tri-(9-octadecynoate), glycerol tri-(10-undecynoate), and glycerol tri-(13-docosynoate)] in the presence of eight microbial lipases was studied. Novozyme 435 (Candida antarctica), an efficient enzyme for esterification, showed a significant resistance in the hydrolysis of glycerol tri-(9-octadecynoate) and glycerol tri-(13-docosynoate). Hydrolysis of acetylenic TG with Lipolase 100T (Humicola lanuginosa) was rapidly accomplished. Lipase PS-D (Pseudomonas cepacia) showed a fair resistance toward the hydrolysis of glycerol tri-(6-octadecynoate) only, which reflected its ability to recognize the delta6 positional isomer of 18:1. Lipase CCL (Candida cylindracea, syn. C. rugosa) and AY-30 (C. rugosa) were able to catalyze the release of 10-undecynoic acid and 9-octadecynoic acid from the corresponding TG, but less readily the 13-docosynoic acid in the case of glycerol tri-(13-docosynoate). The two lipases CCL and AY-30 were able to distinguish the small difference in structure of fatty acyl moieties in the TG substrate. To confirm this trend, three regioisomers of mixed acetylenic TG of type ABC (containing one each of delta6, delta9, and delta13 acetylenic FA in various positions) were prepared and hydrolyzed with CCL and AY-40. The results reconfirmed the observation that AY-30 and CCL were able to distinguish the slight differences in the molecular structure (position of the acetylenic bond and chain length) of the acyl groups in the TG during the hydrolysis of such TG substrates.

  1. Intramolecular competition between n-pair and π-pair hydrogen bonding: Microwave spectrum and internal dynamics of the pyridine–acetylene hydrogen-bonded complex

    SciTech Connect

    Mackenzie, Rebecca B.; Dewberry, Christopher T.; Leopold, Kenneth R. E-mail: david.tew@bristol.ac.uk; Coulston, Emma; Cole, George C.; Legon, Anthony C. E-mail: david.tew@bristol.ac.uk Tew, David P. E-mail: david.tew@bristol.ac.uk

    2015-09-14

    a-type rotational spectra of the hydrogen-bonded complex formed from pyridine and acetylene are reported. Rotational and {sup 14}N hyperfine constants indicate that the complex is planar with an acetylenic hydrogen directed toward the nitrogen. However, unlike the complexes of pyridine with HCl and HBr, the acetylene moiety in HCCH—NC{sub 5}H{sub 5} does not lie along the symmetry axis of the nitrogen lone pair, but rather, forms an average angle of 46° with the C{sub 2} axis of the pyridine. The a-type spectra of HCCH—NC{sub 5}H{sub 5} and DCCD—NC{sub 5}H{sub 5} are doubled, suggesting the existence of a low lying pair of tunneling states. This doubling persists in the spectra of HCCD—NC{sub 5}H{sub 5}, DCCH—NC{sub 5}H{sub 5}, indicating that the underlying motion does not involve interchange of the two hydrogens of the acetylene. Single {sup 13}C substitution in either the ortho- or meta-position of the pyridine eliminates the doubling and gives rise to separate sets of spectra that are well predicted by a bent geometry with the {sup 13}C on either the same side (“inner”) or the opposite side (“outer”) as the acetylene. High level ab initio calculations are presented which indicate a binding energy of 1.2 kcal/mol and a potential energy barrier of 44 cm{sup −1} in the C{sub 2v} configuration. Taken together, these results reveal a complex with a bent hydrogen bond and large amplitude rocking of the acetylene moiety. It is likely that the bent equilibrium structure arises from a competition between a weak hydrogen bond to the nitrogen (an n-pair hydrogen bond) and a secondary interaction between the ortho-hydrogens of the pyridine and the π electron density of the acetylene.

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

    PubMed

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

    2015-10-26

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

  3. Enhanced Photoluminescence in Acetylene-Treated ZnO Nanorods.

    PubMed

    Jäppinen, Luke; Jalkanen, Tero; Sieber, Brigitte; Addad, Ahmed; Heinonen, Markku; Kukk, Edwin; Radevici, Ivan; Paturi, Petriina; Peurla, Markus; Shahbazi, Mohammad-Ali; Santos, Hélder A; Boukherroub, Rabah; Santos, Hellen; Lastusaari, Mika; Salonen, Jarno

    2016-12-01

    Zinc oxide (ZnO) nanorods were manufactured using the aqueous chemical growth (ACG) method, and the effect of thermal acetylene treatment on their morphology, chemical composition, and optical properties was investigated. Changes in the elemental content of the treated rods were found to be different than in previous reports, possibly due to the different defect concentrations in the samples, highlighting the importance of synthesis method selection for the process. Acetylene treatment resulted in a significant improvement of the ultraviolet photoluminescence of the rods. The greatest increase in emission intensity was recorded on ZnO rods treated at the temperature of 825 °C. The findings imply that the changes brought on by the treatment are limited to the surface of the ZnO rods.

  4. Detonation engine fed by acetylene-oxygen mixture

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

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

  5. Enhanced Photoluminescence in Acetylene-Treated ZnO Nanorods

    NASA Astrophysics Data System (ADS)

    Jäppinen, Luke; Jalkanen, Tero; Sieber, Brigitte; Addad, Ahmed; Heinonen, Markku; Kukk, Edwin; Radevici, Ivan; Paturi, Petriina; Peurla, Markus; Shahbazi, Mohammad-Ali; Santos, Hélder A.; Boukherroub, Rabah; Santos, Hellen; Lastusaari, Mika; Salonen, Jarno

    2016-09-01

    Zinc oxide (ZnO) nanorods were manufactured using the aqueous chemical growth (ACG) method, and the effect of thermal acetylene treatment on their morphology, chemical composition, and optical properties was investigated. Changes in the elemental content of the treated rods were found to be different than in previous reports, possibly due to the different defect concentrations in the samples, highlighting the importance of synthesis method selection for the process. Acetylene treatment resulted in a significant improvement of the ultraviolet photoluminescence of the rods. The greatest increase in emission intensity was recorded on ZnO rods treated at the temperature of 825 °C. The findings imply that the changes brought on by the treatment are limited to the surface of the ZnO rods.

  6. Enhanced Photoluminescence in Acetylene-Treated ZnO Nanorods.

    PubMed

    Jäppinen, Luke; Jalkanen, Tero; Sieber, Brigitte; Addad, Ahmed; Heinonen, Markku; Kukk, Edwin; Radevici, Ivan; Paturi, Petriina; Peurla, Markus; Shahbazi, Mohammad-Ali; Santos, Hélder A; Boukherroub, Rabah; Santos, Hellen; Lastusaari, Mika; Salonen, Jarno

    2016-12-01

    Zinc oxide (ZnO) nanorods were manufactured using the aqueous chemical growth (ACG) method, and the effect of thermal acetylene treatment on their morphology, chemical composition, and optical properties was investigated. Changes in the elemental content of the treated rods were found to be different than in previous reports, possibly due to the different defect concentrations in the samples, highlighting the importance of synthesis method selection for the process. Acetylene treatment resulted in a significant improvement of the ultraviolet photoluminescence of the rods. The greatest increase in emission intensity was recorded on ZnO rods treated at the temperature of 825 °C. The findings imply that the changes brought on by the treatment are limited to the surface of the ZnO rods. PMID:27644239

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

    PubMed

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

    2014-12-28

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

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

    PubMed

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

    1976-01-01

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

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

    PubMed

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

    1976-01-01

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

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

    SciTech Connect

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

    2009-07-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

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

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

    PubMed

    Petter, P J

    1989-02-01

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

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

    PubMed Central

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

    1975-01-01

    The role of photosynthesis and transpiration in the desiccation-induced inhibition of acetylene reduction (nitrogen fixation) was investigated in soybean (Glycine max [L.] Merr. var. Beeson) using an apparatus that permitted simultaneous measurements of acetylene reduction, net photosynthesis, and transpiration. The inhibition of acetylene reduction caused by low water potentials and their aftereffects could be reproduced by depriving shoots of atmospheric CO2 even though the soil remained at water potentials that should have favored rapid acetylene reduction. The inhibition of acetylene reduction at low water potentials could be partially reversed by exposing the shoots to high CO2 concentrations. When transpiration was varied independently of photosynthesis and dark respiration in plants having high water potentials, no effects on acetylene reduction could be observed. There was no correlation between transpiration and acetylene reduction in the CO2 experiments. Therefore, the correlation that was observed between transpiration and acetylene reduction during desiccation was fortuitous. We conclude that the inhibition of shoot photosynthesis accounted for the inhibition of nodule acetylene reduction at low water potentials. PMID:16659277

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

    PubMed

    Petter, P J

    1989-02-01

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

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

    PubMed

    Boyle, C D; Patriquin, D G

    1980-08-01

    Earlier studies indicated that bacteria responsible for nitrogenase activity of some grasses are located inside the roots. Those studies were conducted with excised roots in which a long, unexplained "lag phase" occurred before initiation of nitrogenase activity. When hydroponically maintained Spartina alterniflora Loisel. was incubated in a two-compartment system with acetylene, ethylene was produced following, at most, a 2-hour lag in both the upper (shoot) and lower (roots + water) phases. Ethylene production in the upper phase not attributable to leaf-associated acetylene-reducing activity or to diffusion of ethylene from around the roots is considered to represent "endorhizal acetylene-reducing activity," the internally produced ethylene diffusing into the upper phase via the lacunae. Ethylene produced in the lower phase is designated "exorhizal acetylene-reducing activity." The endorhizal acetylene-reducing activity, in comparison to exorhizal activity, was relatively insensitive to additions of HgCl(2), NH(4)Cl, or carbon sources to the lower phase. Post-lag acetylene-reducing activity of roots excised from plants growing in soil responded to additions in a manner similar to that of endorhizal acetylene-reducing activity, whereas post-lag acetylene-reducing activity of rhizosphere soil responded in a manner similar to that of exorhizal acetylene-reducing activity. PMID:16661421

  16. Assay of the deuterium enrichment of water via acetylene.

    PubMed

    Previs, S F; Hazey, J W; Diraison, F; Beylot, M; David, F; Brunengraber, H

    1996-06-01

    A technique is presented for measuring the 2H enrichment of water in biological samples when this enrichment is greater than 0.2%. The sample is reacted with calcium carbide to form acetylene gas, which is determined by gas chromatography electron impact ionization mass spectrometry. Ion-molecule reactions, resulting in proton abstraction, are minimized by lowering the electron ionization energy from the usual 70 eV to 45 eV. This technique is much more rapid and economical than the classical isotope ratio mass spectrometric assay of the enrichment of hydrogen gas derived from reduction of water.

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

    SciTech Connect

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

    1985-08-01

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

  18. Quantification and removal of some contaminating gases from acetylene used to study gas-utilizing enzymes and microorganisms.

    PubMed

    Hyman, M R; Arp, D J

    1987-02-01

    Acetylene generated from various grades of calcium carbide and obtained from commercial- and purified-grade acetylene cylinders was shown to contain high concentrations of various contaminants. Dependent on the source of acetylene, these included, at maximal values, H(2) (0.023%), O(2) (0.779%), N(2) (3.78%), PH(3) (0.06%), CH(4) (0.073%), and acetone (1 to 10%). The concentration of the contaminants in cylinder acetylene was highly dependent on the extent of cylinder discharge. Several conventional methods used to partially purify cylinder acetylene were compared. A small-scale method for extensively purifying acetylene is described. An effect of acetylene quality on acetylene reduction assays conducted with purified nitrogenase from Azotobacter vinelandii was demonstrated.

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

    PubMed Central

    Hyman, Michael R.; Arp, Daniel J.

    1987-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-02-01

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

  1. 46 CFR 151.50-79 - Methyl acetylene-propadiene mixture.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... suction line. (c) The piping system, including the cargo refrigeration system, for tanks to be loaded with methyl acetylene-propadiene mixture must be completely separate from piping and refrigeration systems for other tanks. If the piping system for the tanks to be loaded with methyl acetylene-propadiene mixture...

  2. 46 CFR 151.50-79 - Methyl acetylene-propadiene mixture.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... suction line. (c) The piping system, including the cargo refrigeration system, for tanks to be loaded with methyl acetylene-propadiene mixture must be completely separate from piping and refrigeration systems for other tanks. If the piping system for the tanks to be loaded with methyl acetylene-propadiene mixture...

  3. Modifications of carbon black nanoparticle surfaces modulate type II pneumocyte homoeostasis.

    PubMed

    Schreiber, Nicole; Ströbele, Michael; Hochscheid, Renate; Kotte, Elke; Weber, Petra; Bockhorn, Henning; Müller, Bernd

    2016-01-01

    Inhalation uptake of carbon black nanoparticles (CBNP) bears the risk of morphological and functional lung impairment attributed to the highly reactive particle surface area. Chemical particle surface modifications might affect particle-cell interactions; however, thus far these alterations have not been determined. This is the first in vivo study comparing particle-induced acute lung injury using Printex(®)90 (Pr90, 7 µg), Printex®90 covered by benzo[a]pyrene or 9-nitroanthracene (BaP-Pr90, NA-Pr90, 7 µg, 15% BaP or NA by weight), and acetylene carbon black (CB) with polycyclic aromatic hydrocarbons (PAH-AB, 7 µg, 20% PAH by weight). All particles were suspended in distilled water with bovine serum albumin (BSA). In addition, the influence of suspension media was tested using Printex®90 suspended without BSA (Pr90(-BSA), 7 µg). Quartz (DQ12, 7 µg), 70 µl saline (NaCl), and distilled water with or without BSA (H2O(+/-BSA)) were used as reference and controls. It was postulated that CBNP surface modifications trigger pulmonary responses. After oropharyngeal particle aspiration, lung functions were measured 2 d postexposure, followed by lung preparation for histological or bronchoalveolar lavage fluid (BALF) examinations and type II pneumocyte isolation on d 3. Head-out body plethysmography revealed reduced flow rates induced by PAH-AB. Examinations of BALF demonstrated reduced influx of macrophages after exposure to Pr90(-BSA) and decreased lymphocyte levels after Pr90(+BSA) or BaP-Pr90 treatment. Further, CBNP induced changes in mRNA expressions (surfactant proteins) in type II pneumocytes. These findings indicate that CBNP surface area and media modulate interactions between NP and lung cells in short-term experiments.

  4. Modifications of carbon black nanoparticle surfaces modulate type II pneumocyte homoeostasis.

    PubMed

    Schreiber, Nicole; Ströbele, Michael; Hochscheid, Renate; Kotte, Elke; Weber, Petra; Bockhorn, Henning; Müller, Bernd

    2016-01-01

    Inhalation uptake of carbon black nanoparticles (CBNP) bears the risk of morphological and functional lung impairment attributed to the highly reactive particle surface area. Chemical particle surface modifications might affect particle-cell interactions; however, thus far these alterations have not been determined. This is the first in vivo study comparing particle-induced acute lung injury using Printex(®)90 (Pr90, 7 µg), Printex®90 covered by benzo[a]pyrene or 9-nitroanthracene (BaP-Pr90, NA-Pr90, 7 µg, 15% BaP or NA by weight), and acetylene carbon black (CB) with polycyclic aromatic hydrocarbons (PAH-AB, 7 µg, 20% PAH by weight). All particles were suspended in distilled water with bovine serum albumin (BSA). In addition, the influence of suspension media was tested using Printex®90 suspended without BSA (Pr90(-BSA), 7 µg). Quartz (DQ12, 7 µg), 70 µl saline (NaCl), and distilled water with or without BSA (H2O(+/-BSA)) were used as reference and controls. It was postulated that CBNP surface modifications trigger pulmonary responses. After oropharyngeal particle aspiration, lung functions were measured 2 d postexposure, followed by lung preparation for histological or bronchoalveolar lavage fluid (BALF) examinations and type II pneumocyte isolation on d 3. Head-out body plethysmography revealed reduced flow rates induced by PAH-AB. Examinations of BALF demonstrated reduced influx of macrophages after exposure to Pr90(-BSA) and decreased lymphocyte levels after Pr90(+BSA) or BaP-Pr90 treatment. Further, CBNP induced changes in mRNA expressions (surfactant proteins) in type II pneumocytes. These findings indicate that CBNP surface area and media modulate interactions between NP and lung cells in short-term experiments. PMID:26914170

  5. Memories of AB

    NASA Astrophysics Data System (ADS)

    Vaks, V. G.

    2013-06-01

    I had the good fortune to be a student of A. B. Migdal - AB, as we called him in person or in his absence - and to work in the sector he headed at the Kurchatov Institute, along with his other students and my friends, including Vitya Galitsky, Spartak Belyayev and Tolya Larkin. I was especially close with AB in the second half of the 1950s, the years most important for my formation, and AB's contribution to this formation was very great. To this day, I've often quoted AB on various occasions, as it's hard to put things better or more precisely than he did; I tell friends stories heard from AB, because these stories enhance life as AB himself enhanced it; my daughter is named Tanya after AB's wife Tatyana Lvovna, and so on. In what follows, I'll recount a few episodes in my life in which AB played an important or decisive role, and then will share some other memories of AB...

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

    PubMed

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

    1996-10-17

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

  7. Organogermanium Chemistry: Germacyclobutanes and digermane Additions to Acetylenes

    SciTech Connect

    Andrew Michael Chubb

    2003-12-12

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

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

    NASA Technical Reports Server (NTRS)

    Hergenrother, P. M.

    1981-01-01

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

  9. Ultrafast Extreme Ultraviolet Induced Isomerization of Acetylene Cations

    SciTech Connect

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

    2011-06-17

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

  10. Acetylene fuel from atmospheric CO2 on Mars

    NASA Technical Reports Server (NTRS)

    Landis, Geoffrey A.; Linne, Diane L.

    1992-01-01

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

  11. Ultrafast Extreme Ultraviolet Induced Isomerization of Acetylene Cations

    SciTech Connect

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

    2010-12-31

    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

  12. An Experimental and Theoretical Study of Nitrogen-Broadened Acetylene Lines

    NASA Technical Reports Server (NTRS)

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

    2014-01-01

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

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

    USGS Publications Warehouse

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

    2008-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Oremland, Ronald S.; Voytek, Mary A.

    2008-02-01

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

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

    PubMed

    Oremland, Ronald S; Voytek, Mary A

    2008-02-01

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

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

    PubMed

    Oremland, Ronald S; Voytek, Mary A

    2008-02-01

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

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

    USGS Publications Warehouse

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

    1988-01-01

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

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

    NASA Technical Reports Server (NTRS)

    Walch, Stephen P.; Taylor, Peter R.

    1995-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2011-01-01

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

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

    SciTech Connect

    Meyer, M.K.

    1991-12-20

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

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

    SciTech Connect

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

    1986-05-01

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

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

    PubMed Central

    van Berkum, Peter; Sloger, Charles

    1979-01-01

    Excised roots of Spartina alterniflora Loisel. and corn reduced acetylene in air without the previously reported period of zero activity lasting 8 to 18 hours. The profiles of acetylene-dependent ethylene accumulation by excised roots and intact plants of S. alterniflora were similar. No significant change in the number of bacteria associated with the roots was detectable during the assay. Most of the nitrogenase activity was detected in the roots and rhizomes of the plants. The salt marsh sediment also was capable of reducing acetylene. Additional damage to roots by washing and cutting increased the rate of acetylene reduction with samples incubated in air. Low concentrations of nitrate significantly inhibited the nitrogenase activity associated with the sediment and excised roots, but not with intact plants. Rates of acetylene reduction by excised corn roots were low. Oxidation and endogenous production of ethylene in the absence of acetylene were negligible. Measurements made with excised grass roots as described probably reflect the occurrence and magnitude of nitrogenase activity associated with the plants in the field. PMID:16661045

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

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

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

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

    PubMed Central

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

    2015-01-01

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

  7. An improved processible acetylene-terminated polyimide for composites

    NASA Technical Reports Server (NTRS)

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

    1985-01-01

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

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

    PubMed

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

    2015-11-25

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

  9. Copper-catalyzed chlorination and condensation of acetylene and dichloroacetylene.

    PubMed

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

    2000-06-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2009-12-01

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

  11. The energy separation between the classical and nonclassical isomers of protonated acetylene - An extensive study in one- and n-particle space saturation

    NASA Technical Reports Server (NTRS)

    Lindh, Roland; Rice, Julia E.; Lee, Timothy J.

    1991-01-01

    The energy separation between the classical and nonclassical forms of protonated acetylene has been reinvestigated in light of the recent experimentally deduced lower bound to this value of 6.0 kcal/mol. The objective of the present study is to use state-of-the-art ab initio quantum mechanical methods to establish this energy difference to within chemical accuracy (i.e., about 1 kcal/mol). The one-particle basis sets include up to g-type functions and the electron correlation methods include single and double excitation coupled-cluster (CCSD), the CCSD(T) extension, multireference configuration interaction, and the averaged coupled-pair functional methods. A correction for zero-point vibrational energies has also been included, yielding a best estimate for the energy difference between the classical and nonclassical forms of 3.7 + or - 1.3 kcal/mol.

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

    NASA Astrophysics Data System (ADS)

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

    2012-10-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  14. Acetylene fuels reductive dechlorination of TCE by Dehalococcoides/Pelobacter-containing microbial consortia

    NASA Astrophysics Data System (ADS)

    Oremland, R. S.; Mao, X.; Mahandra, C.; Baesman, S. M.; Gushgari, S.; Alvarez-Cohen, L.; Liu, T.

    2015-12-01

    Groundwater contamination by trichloroethene (TCE) poses a threat to health and leads to the generation of vinyl chloride (VC), a carcinogen. Dehalococcoides mccartyi is the only bacterium that can completely dechlorinate TCE to ethene (C2H4). Acetylene (C2H2) occurs in TCE-contaminated sites as a consequence of chemical degradation of TCE. Yet acetylene inhibits a variety of microbial processes including methanogesis and reductive dechlorination. Pelobacter acetylenicus and related species can metabolize acetylene via acetylene hydratase and acetaldehyde dismutatse thereby generating acetate and H2 as endproducts, which could serve as electron donor and carbon source for growth of D. mccartyi. We found that 1mM acetylene (aqueous) inhibits growth of D. mccartyi strain 195 on 0.3 mM TCE, but that the inhibition was removed after 12 days with the addition of an acetylene-utilizing isolate from San Francisco Bay, Pelobacter strain SFB93. TCE did not inhibit the growth of this Pelobacter at the concentrations tested (0.1-0.5 mM) and TCE was not consumed by strain SFB93. Co-cultures of strain 195 with strain SFB93 at 5% inoculation were established in 120 mL serum bottles containing 40 mL defined medium. TCE was supplied at a liquid concentration of 0.1 mM, with 0.1 mM acetylene and N2/CO2 (90:10 v/v) headspace at 34 °C. Co-cultures were subsequently transferred (5% vol/vol inoculation) to generate subcultures after 20 μmol TCE was reduced to VC and 36 μmol acetylene was depleted. Aqueous H2 ranged from 114 to 217 nM during TCE-dechlorination, and the cell yield of strain 195 was 3.7 ±0.3 × 107 cells μmol-1 Cl- released. In a D. mccartyi-containing enrichment culture (ANAS) under the same conditions as above, it was found that inhibition of dechlorination by acetylene was reversed after 19 days by adding SFB93. Thus we showed that a co-culture of Pelobacter SFB93 and D. mccartyi 195 could be maintained with C2H2 as the electron donor and carbon source while TCE

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

    SciTech Connect

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

    2013-03-28

    Pure acetylene and mixed Ar-acetylene clusters are formed in supersonic expansions of acetylene/argon mixtures and analysed using reflectron time-of-flight mass spectrometer with variable electron energy ionization source. Acetylene clusters composed of more than a hundred acetylene molecules are generated at the acetylene concentration of Almost-Equal-To 8%, while mixed species are produced at low concentrations ( Almost-Equal-To 0.7%). The electron energy dependence of the mass spectra revealed the ionization process mechanisms in clusters. The ionization above the threshold for acetylene molecule of 11.5 eV results in the main ionic fragment progression (C{sub 2}H{sub 2}){sub n}{sup +}. At the electron energies Greater-Than-Or-Slanted-Equal-To 21.5 eV above the CH+CH{sup +} dissociative ionization limit of acetylene the fragment ions nominally labelled as (C{sub 2}H{sub 2}){sub n}CH{sup +}, n Greater-Than-Or-Slanted-Equal-To 2, are observed. For n Less-Than-Or-Slanted-Equal-To 7 these fragments correspond to covalently bound ionic structures as suggested by the observed strong dehydrogenation [(C{sub 2}H{sub 2}){sub n}-k Multiplication-Sign H]{sup +} and [(C{sub 2}H{sub 2}){sub n}CH -k Multiplication-Sign H]{sup +}. The dehydrogenation is significantly reduced in the mixed clusters where evaporation of Ar instead of hydrogen can stabilize the nascent molecular ion. The C{sub 3}H{sub 3}{sup +} ion was previously assigned to originate from the benzene molecular ion; however, the low appearance energy of Almost-Equal-To 13.7 eV indicates that a less rigid covalently bound structure of C{sub 6}H{sub 6}{sup +} ion must also be formed upon the acetylene cluster electron ionization. The appearance energy of Ar{sub n}(C{sub 2}H{sub 2}){sup +} fragments above Almost-Equal-To 15.1 eV indicates that the argon ionization is the first step in the fragment ion production, and the appearance energy of Ar{sub n{>=}2}(C{sub 2}H{sub 2}){sub m{>=}2}{sup +} at Almost-Equal-To 13

  16. Flexible band gap tuning of hexagonal boron nitride sheets interconnected by acetylenic bonds.

    PubMed

    Zhang, Hongyu; Luo, Youhua; Feng, Xiaojuan; Zhao, Lixia; Zhang, Meng

    2015-08-21

    The energetic and electronic properties of acetylenic-bond-interconnected hexagonal boron nitride sheets (BNyne), in which the number of rows of BN hexagonal rings (denoted as BN width) between neighboring arrays of acetylenic linkages increases consecutively, have been explored using first-principles calculations. Depending on the spatial position of B/N atoms with respect to the acetylenic linkages, there are two different types of configurations. The band structure features and band gap evolutions of BNyne structures as a function of the BN width can be categorized into two families, corresponding to two distinct types of configurations. In particular, for both types of BNyne structures, the band gap variations exhibit odd-even oscillating behavior depending on the BN width, which is related to the different symmetries of acetylenic chains in the unit cell. These results suggest that the embedded linear acetylenic chains can provide more flexibility for manipulation of the atomic and electronic properties of hexagonal boron nitride. These sp-sp(2) hybrid structures might promise importantly potential applications for developing nanoscale electronic and optoelectronic devices. PMID:26194068

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

    NASA Technical Reports Server (NTRS)

    McLaren, Ian A.; Wrobel, Jacek D.

    1997-01-01

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

  18. Highly enantioselective reductive cyclization of acetylenic aldehydes via rhodium catalyzed asymmetric hydrogenation.

    PubMed

    Rhee, Jong Uk; Krische, Michael J

    2006-08-23

    Catalytic hydrogenation of acetylenic aldehydes 1a-12a using chirally modified cationic rhodium catalysts enables highly enantioselective reductive cyclization to afford cyclic allylic alcohols 1b-12b. Using an achiral hydrogenation catalyst, the chiral racemic acetylenic aldehydes 13a-15a engage in highly syn-diastereoselective reductive cyclizations to afford cyclic allylic alcohols 13b-15b. Ozonolysis of cyclization products 7b and 9b allows access to optically enriched alpha-hydroxy ketones 7c and 9c. Reductive cyclization of enyne 7a under a deuterium atmosphere provides the monodeuterated product deuterio-7b, consistent with a catalytic mechanism involving alkyne-carbonyl oxidative coupling followed by hydrogenolytic cleavage of the resulting oxametallacycle. These hydrogen-mediated transformations represent the first examples of the enantioselective reductive cyclization of acetylenic aldehydes. PMID:16910650

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

    PubMed Central

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

    2015-01-01

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

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

    SciTech Connect

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

    1994-12-31

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  2. Omega-AB

    SciTech Connect

    Siirola, John D.; Slepoy, Alexander; Sprigg, Jr., James A.; Jorgensen, Craig R.; Selzler, Gene; Pryor, Richard J.

    2007-05-01

    A hierarchical, modular modeling environment for hybrid simulations of sequential-modular, systems dynamics, discrete-event, and agent-based paradigms Omega-AB models contain a hierarchically-defined module tree that specifies the execution logic for the simulation, and a multi-network graph that defines the environment within which the simulation occurs. Modules are the fundamental buildinig blocks of an Omega-AB model and can define anything from a basic mathematical operation to a complex behavioral response model. Modules rely on the "plug-in" concept which allows developers to build independent module libraries that are gathered, linked, and instantiated by the Omega-AB engine at run time. Inter-module communication occurs through two complimentary systems: pull-based "ports" for general computation patterns and push-based "plugs" for event processing. The simulation environment is an abstract graph of nodes and links. Agents (module sub-trees headed up by an Agent module) reside at nodes and relate to their neighbors through typed links. To facilitate the construction and visualization of complex, interacting networks with dramatically different structure, Omega-AB provides a system for organizing the nodes into hierarchica trees that describe "slices" of the overall network.

  3. Omega-AB

    2007-05-01

    A hierarchical, modular modeling environment for hybrid simulations of sequential-modular, systems dynamics, discrete-event, and agent-based paradigms Omega-AB models contain a hierarchically-defined module tree that specifies the execution logic for the simulation, and a multi-network graph that defines the environment within which the simulation occurs. Modules are the fundamental buildinig blocks of an Omega-AB model and can define anything from a basic mathematical operation to a complex behavioral response model. Modules rely on the "plug-in" conceptmore » which allows developers to build independent module libraries that are gathered, linked, and instantiated by the Omega-AB engine at run time. Inter-module communication occurs through two complimentary systems: pull-based "ports" for general computation patterns and push-based "plugs" for event processing. The simulation environment is an abstract graph of nodes and links. Agents (module sub-trees headed up by an Agent module) reside at nodes and relate to their neighbors through typed links. To facilitate the construction and visualization of complex, interacting networks with dramatically different structure, Omega-AB provides a system for organizing the nodes into hierarchica trees that describe "slices" of the overall network.« less

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

    PubMed Central

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

    1989-01-01

    Nitrogenase reduces deuterated acetylene primarily to cis dideuterated ethylene. This can be distinguished from undeuterated ethylene by the use of Fourier transform infrared spectroscopy. Characteristic bands in the region from 800 to 3,500 cm-1 can be used to identify and quantitate levels of these products. This technique is applicable to field studies of nitrogen fixation where ethylene biosynthesis by plants or bacteria is occurring. We have verified the reaction stoichiometry by using Klebsiella pneumoniae and Bradyrhizobium japonicum in soybeans. The most useful bands for quantitation of substrate purity and product distribution are as follows: acetylene-d0, 3,374 cm-1; acetylene-d1, 2,584 cm-1; acetylene-d2, 2,439 cm-1; cis-ethylene-d2, 843 cm-1; trans-ethylene-d2, 988 cm-1; ethylene-d1, 943 cm-1; ethylene-d0, 949 cm-1. (The various deuterated ethylenes and acetylenes are designated by a lowercase d and subscript to indicate the number, but not the position, of deuterium atoms in the molecule.) Mass spectrometry coupled to a gas chromatograph system has been used to assist in quantitation of the substrate and product distributions. Significant amounts of trans-ethylene-d2 were produced by both wild-type and nifV mutant K. pneumoniae. Less of this product was observed with the soybean system. PMID:2655535

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

    SciTech Connect

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

    1989-02-01

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

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

    SciTech Connect

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

    2007-06-28

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

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

    SciTech Connect

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

    2001-02-06

    In this paper we present numerical simulations of the interaction of a blast wave with an acetylene bubble in a closed chamber. We model the system using the inviscid Euler equations for a mixture of ideal gases. The formulation specifies the thermodynamic behavior of the system using a Chemkin interface and includes the capability to model combustion as the ambient air mixes with the acetylene. The simulations are performed using a three-dimensional adaptive mesh refinement algorithm based on a second-order Godunov integration scheme. Simulations are compared with experimental measurements for the same configuration.

  8. Synthesis of micro- and nanodiamonds by the method of oxy- acetylene combustion flame

    NASA Astrophysics Data System (ADS)

    Sabitov, S.; Mansurov, B.; Medyanova, B.; Partizan, G.; Koshanova, A.; Merkibayev, Ye; Mansurova, M.; Lesbayev, B.

    2016-08-01

    This work presents the results of experiments on synthesis of micro- and nanodiamonds by the method of oxy-acetylene torch on the surface of pre-deposited copper thin films. The influence of the thickness of the buffer copper film and the concentration ratio of oxygen and acetylene on the structure formation of the deposited samples was investigated during performed experiments. Studies by Raman scattering and scanning electron microscopy showed that the synthesis of micro- and nano-diamonds occurs under certain experimental conditions.

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

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

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

  10. Application of an oxygen-shielded air-acetylene flame to atomic spectroscopy.

    PubMed

    Stephens, R

    1973-08-01

    A burner has been designed which provides an oxygen-shielded air-acetylene flame for atomic-absorption work. The chemical reducing properties of the oxygen-shielded flame operated under fuel-rich conditions are enhanced by the higher C: O ratio obtainable in the flame and by the higher flame temperature just above the reaction zone. The flame is inherently essentially free from the risk of flashback, and is offered as an alternative to the nitrous oxide-acetylene flame for use with certain types of equipment and for particular applications.

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

    NASA Astrophysics Data System (ADS)

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

    2011-10-01

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

  12. Recent Line-Shape and Doppler Thermometry Studies Involving Transitions in the ν1 +ν3 Band of Acetylene

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

    The line positions for transitions in the ν1 +ν3 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 ν1 +ν3 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 ν1 +ν3 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

  13. Near-infrared spectra of liquid/solid acetylene under Titan relevant conditions and implications for Cassini/VIMS detections

    NASA Astrophysics Data System (ADS)

    Singh, S.; Cornet, T.; Chevrier, V. F.; Combe, J.-Ph.; McCord, T. B.; Roe, L. A.; Le Mouélic, S.; Le Menn, E.; Wasiak, F. C.

    2016-05-01

    Acetylene is thought to be abundant on Titan according to most photochemical models. While detected in the atmosphere, its likely presence at the surface still lacks physical evidence. It is thought that solid acetylene could be a major component of Titan's lakes shorelines and dry lakebed, detected as the 5 μm-bright deposits with the Cassini/VIMS instrument. Acetylene could also be present under its liquid form as dissolved solids in Titan's methane-ethane lakes, as emphasized by thermodynamics studies. This paper is devoted to the near-infrared spectroscopy study of acetylene under solid and liquid phases between 1 and 2.2 μm, synthesized in a Titan simulation chamber that is able to reproduce extreme temperature conditions. From experiments, we observed a ∼10% albedo increase between liquid acetylene at 193-188 K and solid acetylene at 93 K. Using the NIR spectroscopy technique we successfully calculated the reflectivity ratio of solid/liquid acetylene as 1.13. The second difference we observed between liquid and solid acetylene is a shift in the major absorption band detected at 1.54 μm, the shift of ∼0.01 μm occurring toward higher wavelength. In order to assess the detectability of acetylene on Titan using the Cassini/VIMS instrument, we adapted our spectra to the VIMS spectral resolution. The spectral band at 1.55 μm and a negative slope at 2.0 μm falls in the Cassini/VIMS atmospheric windows over several VIMS infrared spectels, thus Cassini/VIMS should be able to detect acetylene.

  14. Ab initio molecular dynamics.

    PubMed

    Laasonen, Kari

    2013-01-01

    In this chapter, an introduction to ab initio molecular dynamics (AIMD) has been given. Many of the basic concepts, like the Hellman-Feynman forces, the difference between the Car-Parrinello molecular dynamics and AIMD, have been explained. Also a very versatile AIMD code, the CP2K, has been introduced. On the application, the emphasis was on the aqueous systems and chemical reactions. The biochemical applications have not been discussed in depth.

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

    PubMed

    Quine, Zachary R; McNesby, Kevin L

    2009-06-01

    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

  16. Elimination kinetics of acetylene and Freon 22 in resting and active lungless salamanders.

    PubMed

    Feder, M E; Full, R J; Piiper, J

    1988-05-01

    To quantify diffusion limitation in cutaneous gas exchange, the elimination of two inert gases of different diffusivity, Freon 22 (CHC1F2) and acetylene (C2H2), was measured simultaneously in exclusively skin-breathing lungless salamanders, Desmognathus quadramaculatus. In resting salamanders, elimination of both gases could be described as the sum of three exponential terms. For both the medium and the slow exponential component, the ratio of the respective rate constants (k) for acetylene and Freon averaged 1.77. This value is between the values expected for perfusion limitation (1.00) and diffusion limitation (1.94), indicating combined diffusion and perfusion limitation. In salamanders stimulated to run on a treadmill, the elimination rates and the rate constants increased more for Freon than for acetylene. During spontaneous activity, the increase in elimination of Freon was larger than that of acetylene. These findings suggest an increase in the diffusing capacity of the skin during exercise. Thus the diffusing capacity of salamander skin for gases appears to be variable and to be adjusted to meet the increased O2 requirement during exercise.

  17. 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...

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

    ERIC Educational Resources Information Center

    Cox, Marilyn Blagg; Krause, Paul

    1994-01-01

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

  19. Technical opportunities for converting natural gas to acetylene-based chemicals

    SciTech Connect

    Cooke, N.E.; Ashraf, F.A.; Divanji, H.

    1987-01-01

    Canada has abundant natural gas and in some provinces such as Quebec, cheap and surplus electricity is also available. A techno-economic study has been carried out which indicates that it is economically attractive to manufacture acetylene via the electric-arc process from natural gas and electricity at the cost of raw materials prevailing at present in the Province of Quebec, Canada.

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

    PubMed

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

    2016-02-01

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

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

    PubMed

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

    2010-12-28

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

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

    PubMed

    Quine, Zachary R; McNesby, Kevin L

    2009-06-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2012-10-01

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

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

    PubMed Central

    Rosner, B M; Schink, B

    1995-01-01

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

  5. Black Consciousness

    ERIC Educational Resources Information Center

    Hraba, Joseph; Siegman, Jack

    1974-01-01

    Black militancy is treated as an instance of class consciousness with criteria and scales developed to measure black consciousness and "self-placement" into black consciousness. These dimensions are then investigated with respect to the social and symbolic participation in the ideology of the black movement on the part of a sample of black…

  6. Black holes

    PubMed Central

    Brügmann, B.; Ghez, A. M.; Greiner, J.

    2001-01-01

    Recent progress in black hole research is illustrated by three examples. We discuss the observational challenges that were met to show that a supermassive black hole exists at the center of our galaxy. Stellar-size black holes have been studied in x-ray binaries and microquasars. Finally, numerical simulations have become possible for the merger of black hole binaries. PMID:11553801

  7. 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...

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

    NASA Astrophysics Data System (ADS)

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

    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.

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

    NASA Technical Reports Server (NTRS)

    Walch, Stephen P.; Taylor, Peter R.

    1995-01-01

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

  10. Carbide sludge management in acetylene producing plants by using vacuum filtration.

    PubMed

    Ramasamy, Palanisamy; Periathamby, Agamuthu; Ibrahim, Shaliza

    2002-12-01

    Carbide sludge (10.4-11.5 tonnes day(-1)) is generated from the reaction of calcium carbide (900 kg) and water (6,000 L) in the production of acetylene (2,400 m3), in three selected acetylene manufacturing plants. The sludge (of pH 12.2 and containing Cu, Pb, Fe, Mn, Ni and Zn ions whose concentrations exceed the Department of Environment limits for industrial wastewater) was treated by vacuum filtration as a substitute for the ponding system, which is environmentally less acceptable. A similar system by flocculation was also developed. The filtration system represents an improvement over the ponding method, as shown by a pH of 7 for the clear filtrate; the solid cake, which contains 98% of the metals, can be conveniently disposed at an integrated scheduled waste treatment centre.

  11. Formation of Large Ag Clusters with Shells of Methane, Ethylene, and Acetylene in He Droplets.

    PubMed

    Loginov, Evgeny; Gomez, Luis F; Sartakov, Boris G; Vilesov, Andrey F

    2016-09-01

    Helium droplets were used to assemble composite metal-molecular clusters. Produced clusters have several hundreds of silver atoms in the core, immersed in a shell consisting of methane, ethylene, or acetylene molecules. The structure of the clusters was studied via infrared spectra of the C-H stretches of the hydrocarbon molecules. The spectra of the clusters containing methane and acetylene show two distinct features due to molecules on the interface with silver core and those in the volume of the neat molecular part of the clusters. The relative intensities of the peaks are in good agreement with the estimates based on the number of the captured particles. Experiments also suggest that selection rules for infrared transitions for molecules adsorbed on metal surfaces are also valid for silver clusters as small as 300 atoms. PMID:27500443

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

    DOE PAGES

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

    2012-01-01

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

  13. Application of the photoacoustic method to the measurement of acetylene reduction by nitrogenase enzyme

    NASA Astrophysics Data System (ADS)

    Schramm, D. U.; Sthel, M. S.; Carneiro, L. O.; Franco, A. A.; Campos, A. C.; Vargas, H.

    2005-06-01

    Nitrogenase is an enzyme responsible for the reduction of the atmospheric N2 into NH4^+, which represents the key entry point of the molecular nitrogen into the biogeochemical cycle of nitrogen. This enzyme is present in the rhizobial bacteroids, which are symbionts in a Leguminosae plant (Acacia Holosericea), and also reduces acetylene into ethylene at the same rate as the nitrogen reduction. Therefore, a CO2 Laser Photoacoustic system was used for detecting and monitoring the ethylene emission by the nitrogenase activity, in the rhizobial symbionts in Acacia Holosericea, when they are confined in test tubes with acetylene at two different volumes (0.1 and 0.5 ml). Ethylene concentrations are also determined in the ppm range.

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

    SciTech Connect

    Wang, H.; Frenklach, M.

    1997-07-01

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

  15. Groundwater remediation engineering sparging using acetylene--study on the flow distribution of air.

    PubMed

    Zheng, Yan-Mei; Zhang, Ying; Huang, Guo-Qiang; Jiang, Bin; Li, Xin-Gang

    2005-01-01

    Air sparging (AS) is an emerging method to remove VOCs from saturated soils and groundwater. Air sparging performance highly depends on the air distribution resulting in the aquifer. In order to study gas flow characterization, a two-dimensional experimental chamber was designed and installed. In addition, the method by using acetylene as the tracer to directly image the gas distribution results of AS process has been put forward. Experiments were performed with different injected gas flow rates. The gas flow patterns were found to depend significantly on the injected gas flow rate, and the characterization of gas flow distributions in porous media was very different from the acetylene tracing study. Lower and higher gas flow rates generally yield more irregular in shape and less effective gas distributions.

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

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

  17. Probing Ionic Complexes of Ethylene and Acetylene with Vacuum-Ultraviolet Radiation.

    PubMed

    Bandyopadhyay, Biswajit; Stein, Tamar; Fang, Yigang; Kostko, Oleg; White, Alec; Head-Gordon, Martin; Ahmed, Musahid

    2016-07-14

    Mixed complexes of acetylene-ethylene are studied using vacuum-ultraviolet (VUV) photoionization mass spectrometry and theoretical calculations. These complexes are produced and ionized at different distances from the exit of a continuous nozzle followed by reflectron time-of-flight mass spectrometry detection. Acetylene, with a higher ionization energy (11.4 eV) than ethylene (10.6 eV), allows for tuning the VUV energy and initializing reactions either from a C2H2(+) or a C2H4(+) cation. Pure acetylene and ethylene expansions are separately carried out to compare, contrast, and hence identify products from the mixed expansion: these are C3H3(+) (m/z = 39), C4H5(+) (m/z = 53), and C5H5(+) (m/z = 65). Intensity distributions of C2H2, C2H4, their dimers and reactions products are plotted as a function of ionization distance. These distributions suggest that association mechanisms play a crucial role in product formation closer to the nozzle. Photoionization efficiency (PIE) curves of the mixed complexes demonstrate rising edges closer to both ethylene and acetylene ionization energies. We use density functional theory (ωB97X-V/aug-cc-pVTZ) to study the structures of the neutral and ionized dimers, calculate their adiabatic and vertical ionization energies, as well as the energetics of different isomers on the potential energy surface (PES). Upon ionization, vibrationally excited clusters can use the extra energy to access different isomers on the PES. At farther ionization distances from the nozzle, where the number densities are lower, unimolecular decay is expected to be the dominant mechanism. We discuss the possible decay pathways from the different isomers on the PES and examine the ones that are energetically accessible. PMID:26983013

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

    SciTech Connect

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

    1996-12-31

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

  19. Phase-vanishing method with acetylene evolution and its utilization in several organic syntheses.

    PubMed

    Matake, Ryosuke; Niwa, Yuki; Matsubara, Hiroshi

    2015-05-15

    A novel quadraphasic phase-vanishing system in which acetylene is evolved from calcium carbide and directly applied in situ to the Sonogashira coupling reaction was developed. This method, which provides a safe, convenient, and one-pot means to utilize gaseous reagents without special equipment, was also applied to a Cu-catalyzed azide-alkyne cycloaddition (CuAAC) reaction and a three-component aldehyde-alkyne-amine (A(3)) coupling reaction with excellent results.

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

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

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

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

    PubMed

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

    2014-09-01

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

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

    PubMed Central

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

    2013-01-01

    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 η1-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

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

    NASA Technical Reports Server (NTRS)

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

    1983-01-01

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

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

    PubMed Central

    Winship, Lawrence J.; Tjepkema, John D.

    1982-01-01

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

  5. Dehalogenative Homocoupling of Terminal Alkynyl Bromides on Au(111): Incorporation of Acetylenic Scaffolding into Surface Nanostructures.

    PubMed

    Sun, Qiang; Cai, Liangliang; Ma, Honghong; Yuan, Chunxue; Xu, Wei

    2016-07-26

    On-surface C-C coupling reactions of molecular precursors with alkynyl functional groups demonstrate great potential for the controllable fabrication of low-dimensional carbon nanostructures/nanomaterials, such as carbyne, graphyne, and graphdiyne, which demand the incorporation of highly active sp-hybridized carbons. Recently, through a dehydrogenative homocoupling reaction of alkynes, the possibility was presented to fabricate surface nanostructures involving acetylenic linkages, while problems lie in the fact that different byproducts are inevitably formed when triggering the reactions at elevated temperatures. In this work, by delicately designing the molecular precursors with terminal alkynyl bromide, we introduce the dehalogenative homocoupling reactions on the surface. As a result, we successfully achieve the formation of dimer structures, one-dimensional molecular wires and two-dimensional molecular networks with acetylenic scaffoldings on an inert Au(111) surface, where the unexpected C-Au-C organometallic intermediates are also observed. This study further supplements the database of on-surface dehalogenative C-C coupling reactions, and more importantly, it provides us an alternative efficient way for incorporating the acetylenic scaffolding into low-dimensional surface nanostructures. PMID:27326451

  6. Dehalogenative Homocoupling of Terminal Alkynyl Bromides on Au(111): Incorporation of Acetylenic Scaffolding into Surface Nanostructures.

    PubMed

    Sun, Qiang; Cai, Liangliang; Ma, Honghong; Yuan, Chunxue; Xu, Wei

    2016-07-26

    On-surface C-C coupling reactions of molecular precursors with alkynyl functional groups demonstrate great potential for the controllable fabrication of low-dimensional carbon nanostructures/nanomaterials, such as carbyne, graphyne, and graphdiyne, which demand the incorporation of highly active sp-hybridized carbons. Recently, through a dehydrogenative homocoupling reaction of alkynes, the possibility was presented to fabricate surface nanostructures involving acetylenic linkages, while problems lie in the fact that different byproducts are inevitably formed when triggering the reactions at elevated temperatures. In this work, by delicately designing the molecular precursors with terminal alkynyl bromide, we introduce the dehalogenative homocoupling reactions on the surface. As a result, we successfully achieve the formation of dimer structures, one-dimensional molecular wires and two-dimensional molecular networks with acetylenic scaffoldings on an inert Au(111) surface, where the unexpected C-Au-C organometallic intermediates are also observed. This study further supplements the database of on-surface dehalogenative C-C coupling reactions, and more importantly, it provides us an alternative efficient way for incorporating the acetylenic scaffolding into low-dimensional surface nanostructures.

  7. The anomalous behavior of the Zeeman anticrossing spectra of à 1Au acetylene: Theoretical considerations

    NASA Astrophysics Data System (ADS)

    Vacek, George; Sherrill, C. David; Yamaguchi, Yukio; Schaefer, Henry F., III

    1996-02-01

    P. Dupré, R. Jost, M. Lombardi, P. G. Green, E. Abramson, and R. W. Field have observed anomalous behavior of the anticrossing density in the Zeeman anticrossing (ZAC) spectra of gas phase à 1Au acetylene in the 42 200 to 45 300 cm-1 energy range. To best explain this result, they hypothesize a large singlet-triplet coupling due to the existence of a linear isomerization barrier connecting a triplet-excited cis- and trans-acetylene in the vicinity of the studied energy range (˜45 500 cm-1). Theoretically such a linear stationary point, however, must have two different degenerate bending vibrational frequencies which are either imaginary or exactly zero. Neither case has yet been experimentally detected. Here, we have studied the two lowest-lying linear triplet-excited-state stationary points of acetylene, 3Σ+u and 3Δu, to see if they fit Dupré et al.'s hypothesis. We have completed geometry optimization and harmonic vibrational frequency analysis using complete-active-space self-consistent field (CASSCF) wave functions as well as determined energy points at those geometries using the second-order configuration interaction (SOCI) method. Harmonic vibrational analyses of both stationary points reveal two different doubly degenerate vibrational modes with imaginary vibrational frequencies (or negative force constants) indicating that they are indeed saddle points with a Hessian index of four. At the DZP SOCI//CASSCF level of theory with zero-point vibrational energy (ZPVE) correction, the 3Σ+u stationary point lies 35 840 cm-1 above the ground state of acetylene. This is much too low in energy to contribute to the ZAC spectral anomaly. At the same level of theory with ZPVE correction, the 3Δu stationary point lies 44 940 cm-1 above the ground state consistent with Dupré et al.'s hypothesis. Several solutions to the anomalous ZAC spectra are discussed. We propose that the anomaly may also be due to coupling with a nearly linear structure on the T3 surface of

  8. Black Appalachians.

    ERIC Educational Resources Information Center

    Waage, Fred, Ed.; Cabbell, Ed, Ed.

    1986-01-01

    This issue of "Now and Then" focuses on black Appalachians, their culture, and their history. It contains local histories, articles, and poems and short stories by Appalachian blacks. Articles include: "A Mountain Artist's Landscape," a profile of artist Rita Bradley by Pat Arnow; "A Part and Apart," a profile of black historian Ed Cabbell by Pat…

  9. Talking Black.

    ERIC Educational Resources Information Center

    Abrahams, Roger D.

    This book contains essays which focus on the systems of communication that operate within and between various social segments of Afro-American communities in the United States. The essays are presented under the following headings: (1) "Getting Into It: Black Talk, Black Life and the Academic," (2) "'Talking My Talk': Black Talk Varieties and…

  10. Black Students.

    ERIC Educational Resources Information Center

    Edwards, Harry

    The black student revolt did not start with the highly publicized activities of the black students at San Francisco State College. The roots of the revolt lie deeply imbedded within the history and structure of the overall black liberation struggle in America. The beginnings of this revolt can be found in the students of Southern Negro colleges in…

  11. Black Psychology.

    ERIC Educational Resources Information Center

    Jones, Reginald L., Ed.

    The contents of the present volume, designed to bring together in a single place writings by the new black psychologists and other black social and behavioral scientists, are organized in seven parts, as follows: Part I, "Black Psychology: Perspectives," includes articles by Cedric Clark, Wade W. Nobles, Doris P. Mosby, Joseph White, and William…

  12. Interpretation of PAN, acetone and acetylene measurements from the MIPAS-E

    NASA Astrophysics Data System (ADS)

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

    2009-04-01

    Emissions of anthropogenic pollution, from biomass burning events in particular, result in the injection of a wide range of carbon compounds into the atmosphere. Carbon monoxide (CO), methane (CH4) and volatile organic compounds (VOCs) are released in significant amounts, affecting both the oxidation capacity of the troposphere and ozone production. Upper troposphere (UT) measurements of PAN, acetone and acetylene have, in the past, been generally limited to sporadic in situ sampling during specialised campaign periods. The recent rapid progress in both the detection and retrieval of many VOC species from spaceborne instrumentation has been large. It has recently been established that the observation of the global distribution of VOCs in the UT can be made by measurements provided by instruments such as the Michelson Interferometer for Passive Atmospheric Sounding onboard ENVISAT (MIPAS-E) or the Atmospheric Chemistry Experiment (ACE) onboard SCISAT-1. In this work, we discuss the ability of MIPAS-E to provide new global measurements of acetone in the UT. We also describe both the distribution and seasonality observed in UT PAN volume mixing ratios (vmrs). From the MIPAS-E acetylene measurements, we analyse the extent and magnitude of the chemical isolation observed over the Middle East during August 2003. We show that this enhancement is due to fast westward transport from Asia via the Easterly Jet associated with the Asian monsoon anticyclone. A full error analysis is carried out for each of the three gases we analyse. Previous work has shown that characteristic infrared signatures of PAN, acetone and acetylene can be detected in MIPAS-E thermal emission spectra, with the 787-790 cm-1, 1216-1218 cm-1 and 776.0-776.15 cm-1 spectral ranges respectively being particularly sensitive to changes in each of the gases. We invert the measured MIPAS-E spectra into vmrs using an independent offline-retrieval scheme based on the optimal estimation approach which was

  13. Ab interno trabeculectomy.

    PubMed

    Pantcheva, Mina B; Kahook, Malik Y

    2010-10-01

    Anterior chamber drainage angle surgery, namely trabeculotomy and goniotomy, has been commonly utilized in children for many years. Its' reported success has ranged between 68% and 100% in infants and young children with congenital glaucoma. However, the long-term success of these procedures has been limited in adults presumably due to the formation of anterior synechiae (AS) in the postoperative phase. Recently, ab interno trabeculectomy with the Trabectome™ has emerged as a novel surgical approach to effectively and selectively remove and ablate the trabecular meshwork and the inner wall of the Schlemm's canal in an attempt to avoid AS formation or other forms of wound healing with resultant closure of the cleft. This procedure seems to have an appealing safety profile with respect to early hypotony or infection if compared to trabeculectomy or glaucoma drainage device implantation. This might be advantageous in some of the impoverish regions of the Middle East and Africa where patients experience difficulties keeping up with their postoperative visits. It is important to note that no randomized trial comparing the Trabectome to other glaucoma procedures appears to have been published to date. Trabectome surgery is not a panacea, however, and it is associated with early postoperative intraocular pressure spikes that may require additional glaucoma surgery as well as a high incidence of hyphema. Reported results show that postoperative intraocular pressure (IOP) remains, at best, in the mid-teen range making it undesirable in patients with low-target IOP goals. A major advantage of Trabectome surgery is that it does not preclude further glaucoma surgery involving the conjunctiva, such as a trabeculectomy or drainage device implantation. As prospective randomized long-term clinical data become available, we will be better positioned to elucidate the exact role of this technique in the glaucoma surgical armamentarium. PMID:21180426

  14. Autonomous Biological System (ABS) experiments.

    PubMed

    MacCallum, T K; Anderson, G A; Poynter, J E; Stodieck, L S; Klaus, D M

    1998-12-01

    Three space flight experiments have been conducted to test and demonstrate the use of a passively controlled, materially closed, bioregenerative life support system in space. The Autonomous Biological System (ABS) provides an experimental environment for long term growth and breeding of aquatic plants and animals. The ABS is completely materially closed, isolated from human life support systems and cabin atmosphere contaminants, and requires little need for astronaut intervention. Testing of the ABS marked several firsts: the first aquatic angiosperms to be grown in space; the first higher organisms (aquatic invertebrate animals) to complete their life cycles in space; the first completely bioregenerative life support system in space; and, among the first gravitational ecology experiments. As an introduction this paper describes the ABS, its flight performance, advantages and disadvantages.

  15. Studies on South-east Asian fireflies: Abscondita, a new genus with details of life history, flashing patterns and behaviour of Abs. chinensis (L.) and Abs. terminalis (Olivier) (Coleoptera: Lampyridae: Luciolinae).

    PubMed

    Ballantyne, Lesley; Fu, Xinhua; Lambkin, Christine; Jeng, Ming-Luen; Faust, Lynn; Wijekoon, M C D; Li, Daiqin; Zhu, Tengfui

    2013-01-01

    Abscondita, a new genus of fireflies from South-east Asia, is described from males and females of Abs. anceyi (Olivier 1883), Abs. cerata (Olivier 1911), Abs. chinensis (L. 1767), Abs. perplexa (Walker 1858), Abs. promelaena (Walker 1858) and Abs. terminalis (Olivier 1883), all transferred from Luciola Laporte. Both L. dubia Olivier 1903 and L. dejeani Gemminger 1870 are synonymised with Luciola perplexa (Walker), and L. aegrota Olivier 1891 and L. melaspis Bourgeois 1909 with L. promelaena Walker. Females are characterised by their bursa plates. Larvae are associated and described for Abs. anceyi (Olivier), Abs. chinensis (L.) and Abs. terminalis (Olivier). Taxonomic issues regarding the identification of species with very similar colouration of pale dorsum and black tipped elytra are addressed and in some cases resolved. A neotype for Luciola chinensis (L.) is erected and Luciola praeusta (Kiesenwetter 1874) is synonymised with L. chinensis (L.). Descriptions of life histories, biology and flashing patterns of populations of Abs. chinensis and Abs. terminalis from central China are included. A bs. terminalis is the first Asian firefly known to possess multiple flash trains where males are documented to display with repeating flash trains.

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

    USGS Publications Warehouse

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

    2013-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

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

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

    SciTech Connect

    Komives, E.A.

    1987-01-01

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

  1. (-)-Duryne and its homologues, cytotoxic acetylenes from a marine Sponge Petrosia sp.

    PubMed

    Hitora, Yuki; Takada, Kentaro; Okada, Shigeru; Ise, Yuji; Matsunaga, Shigeki

    2011-05-27

    Six linear acetylenes, (-)-duryne (1) and (-)-durynes B-F (2-6), were isolated from the marine sponge Petrosia sp. Their structures were elucidated by NMR and tandem FABMS analyses. The positions of the olefinic bonds were confirmed by ozonolysis experiments, and the absolute configurations were determined by the modified Mosher's method. Compound 1 was found to be the enantiomer of duryne, a previously reported sponge metabolite. Compounds 1-6 show cytotoxicity against HeLa cells with IC50 values between 0.08 and 0.50 μM. PMID:21534590

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

    PubMed

    Hatua, Kaushik; Nandi, Prasanta K

    2015-10-01

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

  3. The 2Πg shape resonance of acetylene anion: an investigation with the RAC method

    NASA Astrophysics Data System (ADS)

    Čurík, Roman; Paidarová, Ivana; Horáček, Jiří

    2016-07-01

    Recently developed method of regularized analytic continuation (RAC) is applied to determination of the 2Πg resonance of acetylene anion. The method is based on continuation of the electron affinities calculated for the anion in presence of an external perturbation field. Its independence on the correlation treatment of the many-electron system allows application of accurate coupled-clusters methods for electronic structure calculations utilized in determination of the resonance position and width. Contribution to the Topical Issue "Advances in Positron and Electron Scattering", edited by Paulo Limao-Vieira, Gustavo Garcia, E. Krishnakumar, James Sullivan, Hajime Tanuma and Zoran Petrovic.

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

    NASA Technical Reports Server (NTRS)

    Tannenbaum, Stanley

    1957-01-01

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

  5. Synthesis of (iso)quinoline, (iso)coumarin and (iso)chromene derivatives from acetylene compounds

    NASA Astrophysics Data System (ADS)

    Ryabukhin, D. S.; Vasilyev, A. V.

    2016-06-01

    Published data on the methods of synthesis of quinoline, isoquinoline, coumarin, isocoumarin, chromene and isochromene derivatives from acetylene compounds are summarized. The reactions catalyzed by metal complexes (Pd, Pt, Ru, Rh, Au, Ag, Ni, Cu, etc.) and transformations induced by various electrophilic reagents (Brynsted and Lewis acids) are considered. Moieties of the mentioned heterocyclic systems are present in many biologically active natural products and pharmaceutical agents. Besides, derivatives of these heterocycles are used in the manufacture of catalysts, dyes, perfumery and cosmetic products, corrosion inhibitors and so on. The bibliography includes 211 references.

  6. Effect of Varying Inert Gas and Acetylene Concentration on the Synthesis of Carbon Nanotubes.

    PubMed

    Afrin, Rahat; Abbas, Syed Mustansar; Shah, Nazar Abbas; Mustafa, Muhammad Farooq; Ali, Zulfiqar; Ahmad, Nisar

    2016-03-01

    The multiwalled carbon nanotubes (MWCNTs) with small diameter and high purity were achieved by chemical vapor deposition technique using silicon substrate. The introduction of specific concentration of inert gas with hydrocarbon played a key role in controlling morphology and diameter of MWCNTs. Nickel mixed ferrite nanoparticles were used as a catalyst for the growth of MWCNTs. Growth parameters like concentration of hydrocarbon source and inert gas flow, composition of catalyst particles and growth temperature were studied. In this work smaller diameter and twisted MWCNTs were formed by dilution of acetylene with argon gas. Electrical properties suggest a semimetallic behavior of synthesized MWCNTs. PMID:27455741

  7. Effect of Varying Inert Gas and Acetylene Concentration on the Synthesis of Carbon Nanotubes.

    PubMed

    Afrin, Rahat; Abbas, Syed Mustansar; Shah, Nazar Abbas; Mustafa, Muhammad Farooq; Ali, Zulfiqar; Ahmad, Nisar

    2016-03-01

    The multiwalled carbon nanotubes (MWCNTs) with small diameter and high purity were achieved by chemical vapor deposition technique using silicon substrate. The introduction of specific concentration of inert gas with hydrocarbon played a key role in controlling morphology and diameter of MWCNTs. Nickel mixed ferrite nanoparticles were used as a catalyst for the growth of MWCNTs. Growth parameters like concentration of hydrocarbon source and inert gas flow, composition of catalyst particles and growth temperature were studied. In this work smaller diameter and twisted MWCNTs were formed by dilution of acetylene with argon gas. Electrical properties suggest a semimetallic behavior of synthesized MWCNTs.

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

    PubMed

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

    2006-09-27

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

  9. Characterization of magnetically confined low-pressure plasmas produced by an electromagnetic field in argon-acetylene mixtures

    NASA Astrophysics Data System (ADS)

    Makdessi, G. Al; Margot, J.; Clergereaux, R.

    2016-10-01

    Dust particles formation was investigated in magnetically confined low-pressure plasma produced in argon-acetylene mixtures. The plasma characteristics were measured in order to identify the species involved in the dust particles formation. Their dependence on the operating conditions including magnetic field intensity, acetylene fraction in the gas mixture and operating pressure was examined. In contrast with noble gases, in the presence of acetylene, the electron temperature increases with the magnetic field intensity, indicating additional charged particles losses in the plasma. Indeed, in these conditions, larger hydrocarbon ions are produced leading to the formation of dust particles in the plasma volume. The observed dependence of positive ion mass distribution and density and relative negative ion density on the operating parameters suggests that the dust particles are formed through different pathways, where negative and positive ions are both involved in the nucleation.

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

    SciTech Connect

    Silvester, W.B.; Winship, L.J. )

    1990-02-01

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

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

    SciTech Connect

    Zubrin, R.M. )

    1992-01-01

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

  12. Global fitting of line intensities of acetylene molecule in the infrared using the effective operator approach

    NASA Astrophysics Data System (ADS)

    Perevalov, V. I.; Lyulin, O. M.; Jacquemart, D.; Claveau, C.; Teffo, J.-L.; Dana, V.; Mandin, J.-Y.; Valentin, A.

    2003-04-01

    The method of effective operators has been applied to the global fitting of line intensities of the acetylene molecule in the middle infrared. Simultaneous fittings of recently observed line intensities in the cold and hot bands lying in the 13.6, 7.8, and 5 μm regions have been performed. The eigenfunctions of the effective Hamiltonian developed for the global treatment of the vibration-rotation line positions of acetylene [O.M. Lyulin, V.I. Perevalov, S.A. Tashkun, J.-L. Teffo, in: Leonid N. Sinitsa (Ed.), 13th Symposium and School on High Resolution Molecular Spectroscopy, Proceedings of SPIE, vol. 4063, 2000, pp. 126-133] have been used in the calculations. The sets of effective dipole moment parameters obtained reproduce the observed line intensities within the experimental accuracy. The importance of l-type resonance, responsible for some large differences between intensities of the same lines in subbands having opposite parities, is exhibited and discussed.

  13. Preparation of allenic sulfones and allenes from the selenosulfonation of acetylenes

    SciTech Connect

    Back, T.G.; Krishna, M.V.; Muralidharan, K.R. )

    1989-08-18

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

  14. Nonoxidative methane conversion to acetylene over zeolite in a low temperature plasma

    SciTech Connect

    Liu, C.; Mallinson, R.; Lobban, L.

    1998-10-01

    Previous investigations have found that the plasma catalytic conversion of methane is a low-temperature process for the activation of methane, the major component of natural gas. In this paper, the production of acetylene via plasma catalytic conversion of methane over NaY zeolite is discussed. Hydrogen is produced as a by-product during this plasma catalytic methane conversion. A methane/hydrogen feed with oxygen as an additive and helium as a diluent has been studied in this investigation. The CH{sub 4}/H{sub 2}/O{sub 2} system is found to be more selective for the production of C{sub 2} hydrocarbons, compared to the CH{sub 4}/O{sub 2}, CH{sub 4}H{sub 2}O, and CH{sub 4}/CO{sub 2} systems reported previously. A higher hydrogen concentration feed is more favorable for acetylene formation. The selectivity and yield of C{sub 2} hydrocarbons are related to the hydrogen feed rate, gas temperature, concentration of oxygen additive, and flowrate. The highest yield of C{sub 2} hydrocarbons (32%) is obtained at the lowest flowrate used (10 cm{sup 3}/s; residence time {approximately}2.3 s). A reaction mechanism is also presented to explain the experimental results.

  15. Theoretical description of electronically excited vinylidene up to 10 eV: first high level ab initio study of singlet valence and Rydberg states.

    PubMed

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

    2014-11-01

    The first quantitative description of the Rydberg and valence singlet electronic states of vinylidene lying in the 0-10 eV region is performed by using large scale ab initio calculations. A deep analysis of Rydberg-valence interactions has been achieved thanks to the comprehensive information contained in the accurate Multi-Reference Configuration Interaction wavefunctions and an original population analysis highlighting the respective role played by orbital and state mixing in such interactions. The present theoretical approach is thus adequate for dealing with larger than diatomic Rydberg systems. The nine lowest singlet valence states have been optimized. Among them, some are involved in strong Rydberg-valence interactions in the region of the Rydberg state equilibrium geometry. The Rydberg states of vinylidene present a great similarity with the acetylene isomer, concerning their quantum defects and Rydberg molecular orbital character. As in acetylene, strong s-d mixing is revealed in the n = 3 s-d supercomplex. Nevertheless, unlike in acetylene, the close-energy of the two vinylidene ionic cores (2)A1 and (2)B1 results into two overlapped Rydberg series. These Rydberg series exhibit local perturbations when an accidental degeneracy occurs between them and results in avoided crossings. In addition, some Δl = 1 (s-p and p-d) mixings arise for some Rydberg states and are rationalized in term of electrostatic interaction from the electric dipole moment of the ionic core. The strongest dipole moment of the (2)B1 cationic state also stabilizes the lowest members of the n = 3 Rydberg series converging to this excited state, as compared to the adjacent series converging toward the (2)A1 ionic ground state. The overall energies of vinylidene Rydberg states lie above their acetylene counterpart. Finally, predictions for optical transitions in singlet vinylidene are suggested for further experimental spectroscopic characterization of vinylidene.

  16. Vibration-rotation pattern in acetylene. II. Introduction of Coriolis coupling in the global model and analysis of emission spectra of hot acetylene around 3 microm.

    PubMed

    Amyay, Badr; Robert, Séverine; Herman, Michel; Fayt, André; Raghavendra, Balakrishna; Moudens, Audrey; Thiévin, Jonathan; Rowe, Bertrand; Georges, Robert

    2009-09-21

    A high temperature source has been developed and coupled to a high resolution Fourier transform spectrometer to record emission spectra of acetylene around 3 mum up to 1455 K under Doppler limited resolution (0.015 cm(-1)). The nu(3)-ground state (GS) and nu(2)+nu(4)+nu(5) (Sigma(u) (+) and Delta(u))-GS bands and 76 related hot bands, counting e and f parities separately, are assigned using semiautomatic methods based on a global model to reproduce all related vibration-rotation states. Significantly higher J-values than previously reported are observed for 40 known substates while 37 new e or f vibrational substates, up to about 6000 cm(-1), are identified and characterized by vibration-rotation parameters. The 3 811 new or improved data resulting from the analysis are merged into the database presented by Robert et al. [Mol. Phys. 106, 2581 (2008)], now including 15 562 lines accessing vibrational states up to 8600 cm(-1). A global model, updated as compared to the one in the previous paper, allows all lines in the database to be simultaneously fitted, successfully. The updates are discussed taking into account, in particular, the systematic inclusion of Coriolis interaction.

  17. AB 1725: A Comprehensive Analysis.

    ERIC Educational Resources Information Center

    California Community Colleges, Sacramento. Board of Governors.

    A summary and analysis is provided of California Assembly Bill (AB) 1725, a reform bill that provides new direction and support for the state's community colleges. The analysis addresses each of the eight sections of the bill: (1) mission, highlighting reforms related to mission statements, transfer core curriculum, remedial limits, articulation…

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

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

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

  19. High-temperature measurements of methane and acetylene using quantum cascade laser absorption near 8 μm

    NASA Astrophysics Data System (ADS)

    Sajid, M. B.; Javed, T.; Farooq, A.

    2015-04-01

    The mid-infrared wavelength region near 8 μm contains absorption bands of several molecules such as water vapor, hydrogen peroxide, nitrous oxide, methane and acetylene. A new laser absorption sensor based on the ν4 band of methane and the ν4+ν5 band of acetylene is reported for interference-free, time-resolved measurements under combustion-relevant conditions. A detailed line-selection procedure was used to identify optimum transitions. Methane and acetylene were measured at the line centers of Q12 (1303.5 cm-1) and P23 (1275.5 cm-1) transitions, respectively. High-temperature absorption cross sections of methane and acetylene were measured at peaks (on-line) and valleys (off-line) of the selected absorption transitions. The differential absorption strategy was employed to eliminate interference absorption from large hydrocarbons. Experiments were performed behind reflected shock waves over a temperature range of 1200-2200 K, between pressures of 1-4 atm. The diagnostics were then applied to measure the respective species time-history profiles during the shock-heated pyrolysis of n-pentane.

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

    NASA Astrophysics Data System (ADS)

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

    2013-07-01

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

  1. Infrared Spectroscopy of Deuterated Acetylene in Solid Parahydrogen and the Helium Recovery Initiative

    NASA Astrophysics Data System (ADS)

    Strom, Aaron I.; Anderson, David T.

    2016-06-01

    The linear tetratomic organic molecule acetylene, HCCH, has been studied extensively throughout the past century via numerous spectroscopic experiments, exploiting wavelengths across the electromagnetic spectrum. Both the mono- and di-deutero acetylene isotopologues have also been widely studied, namely HCCD and DCCD. In this presentation, I will present the Fourier transform infrared (FTIR) spectroscopy of DCCD in solid parahydrogen (pH2) in the low-temperature regime (1.5-5.0 K). We intend to perform UV photochemical studies on DCCD doped solid pH2 and, therefore, the infrared spectroscopy must be characterized prior. The FTIR spectrum of DCCD isolated in solid pH2 exhibits rich fine structure in the νb{3} asymmetric C-D stretch region. Some of the observed peaks may arise from the formation of weakly bound acetylene dimers, or potentially even larger clusters. We can test this hypothesis by varying the DCCD concentration in separate experiments and temperature cycling the matrix to look for irreversible cluster growth. In preliminary experiments we observe trace amounts of the lighter isotopologues (HCCD and HCCH) and so these species can also cluster with DCCD, adding to the complexity of the spectra. We remark that ortho-hydrogen clustering to DCCD may also be occurring and we have ways to check that as well. In order to make better sense of the FTIR spectrum of DCCD doped pH2, a comparison with the simulated low temperature gas-phase spectrum will also be presented. This will allow us to address issues related to the extent of the rotational motion of DCCD in solid pH2. A liquid helium bath cryostat is used to grow and maintain the DCCD doped pH2 crystals for spectroscopic characterization. Helium is a non-renewable resource and in recent years the Anderson group has been building a helium recovery system. This Helium Recovery Initiative (HRI) will be discussed in an effort to describe how we implemented this new experimental system in our laboratory and to

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

    NASA Technical Reports Server (NTRS)

    Walch, Stephen P.

    1995-01-01

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

  3. Black Lawyers

    ERIC Educational Resources Information Center

    Ware, Gilbert

    1977-01-01

    Notes that blacks are destined to remain strangers in the land of opportunity and in the system of justice, except as persons suspected, accused, arrested, prosecuted, imprisoned, executed--all in disproportionate numbers. (Author/AM)

  4. Black tea

    MedlinePlus

    ... flow. Some people use black tea for preventing tooth decay and kidney stones. In combination with various other ... that men who get more phytoestrogens in their diet have a lower risk of developing lung cancer ...

  5. Black psyllium

    MedlinePlus

    Herbs and supplements that might lower blood sugarBlack psyllium might decrease blood sugar by decreasing how much ... absorbs from foods. Taking it along with other herbs and supplements that might also lower blood sugar ...

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

    PubMed

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

    2014-07-15

    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

  7. A novel metal-organic framework for high storage and separation of acetylene at room temperature

    NASA Astrophysics Data System (ADS)

    Duan, Xing; Wang, Huizhen; Ji, Zhenguo; Cui, Yuanjing; Yang, Yu; Qian, Guodong

    2016-09-01

    A novel 3D microporous metal-organic framework with NbO topology, [Cu2(L)(H2O)2]•(DMF)6·(H2O)2 (ZJU-10, ZJU = Zhejiang University; H4L =2‧-hydroxy-[1,1‧:4‧,1″-terphenyl]-3,3″,5,5″-tetracarboxylic acid; DMF =N,N-dimethylformamide), has been synthesized and structurally characterized. With suitable pore sizes and open Cu2+ sites, ZJU-10a exhibits high BET surface area of 2392 m2/g, as well as moderately high C2H2 volumetric uptake capacity of 132 cm3/cm3. Meanwhile, ZJU-10a is a promising porous material for separation of acetylene from methane and carbon dioxide gas mixtures at room temperature.

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

    PubMed

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

    2011-03-01

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

  9. Synthesis, structure and cytotoxic activity of acetylenic derivatives of betulonic and betulinic acids

    NASA Astrophysics Data System (ADS)

    Bębenek, Ewa; Chrobak, Elwira; Wietrzyk, Joanna; Kadela, Monika; Chrobak, Artur; Kusz, Joachim; Książek, Maria; Jastrzębska, Maria; Boryczka, Stanisław

    2016-02-01

    A series of acetylenic derivatives of betulonic and betulinic acids has been synthesized and characterized by 1H and 13C NMR, IR and MS spectroscopy. The structure of propargyl betulonate 4 and propargyl betulinate-DMF solvate 8A was solved by X-ray diffraction. Thermal properties were examined using a DSC technique. The resulting alkynyl derivatives, as well as betulin 1 and betulinic acid 3, were evaluated in vitro for their cytotoxic activity against human T47D breast cancer, CCRF/CEM leukemia, SW707 colorectal, murine P388 leukemia and BALB3T3 normal fibroblasts cell lines. Several of the obtained compounds have a favorable cytotoxic profile than betulin 1. Propargyl betulinate 8 was the most active derivative, being up to 3-fold more potent than betulin 1 against the human leukemia (CCRF/CEM) cell line, with an IC50 value of 3.9 μg/mL.

  10. Reactions of yttrium and scandium atoms with acetylene: a matrix isolation infrared spectroscopic and theoretical study.

    PubMed

    Teng, Yun-Lei; Xu, Qiang

    2010-09-01

    Laser-ablated yttrium and scandium metal atoms have been codeposited at 4 K with acetylene in excess argon. Products, Y(C(2)H(2)), HYCCH, HScCCH(-), and HScScCCH(-), have been formed in the present experiments and characterized using infrared spectroscopy on the basis of the results of the isotopic shifts, mixed isotopic splitting patterns, stepwise annealing, the change of reagent concentration and laser energy, and the comparison with theoretical predictions. Density functional theory calculations have been performed on these molecules. The agreement between the experimental and calculated vibrational frequencies, relative absorption intensities, and isotopic shifts supports the identification of these molecules from the matrix infrared spectra. Plausible reaction mechanisms have been proposed to account for the formation of these molecules.

  11. Reactions of group 14 metal atoms with acetylene: a matrix isolation infrared spectroscopic and theoretical study.

    PubMed

    Teng, Yun-Lei; Xu, Qiang

    2009-11-01

    Laser-ablated group 14 metal atoms have been codeposited at 4 K with acetylene in excess argon. Products, Ge(C2H2), HGeCCH, Sn(C2H2), Sn2CCH2, HSnCCH, and HPbCCH, have been formed in the present experiments and characterized using infrared spectroscopy on the basis of the results of the isotopic shifts, mixed isotopic splitting patterns, stepwise annealing, the change of reagent concentration and laser energy, and the comparison with theoretical predictions. Density functional theory calculations have been performed on these molecules. The agreement between the experimental and the calculated vibrational frequencies, relative absorption intensities, and isotopic shifts supports the identification of these molecules from the matrix infrared spectra. Plausible reaction mechanisms have been proposed to account for the formation of these molecules.

  12. Retrievals of the Abundances of Acetylene and other Hydrocarbons in Titan's Upper Atmosphere

    NASA Astrophysics Data System (ADS)

    Fan, Siteng; Shemansky, D. E.; Yung, Yuk

    2016-10-01

    Acetylene abundance in the Titan upper atmosphere has been extracted from Cassini Ultraviolet Imaging Spectrograph (UVIS) stellar occultations. The data reduction process is based on simulation of the discrete spectral absorption in the far ultraviolet (FUV) region between 110 and 190 nm. Pointing drift is corrected by instrument simulation of the stellar image location on the instrument detector. Latitude and seasonal dependence of the vertical profiles has been examined. The observed spectra have been compared to atmospheric chemical model calculations (KINETICS) by predicting the occultation spectra, allowing the imposition of constraints on the model, and directly establishing the level of uncertainty in the extraction process. Hydrocarbon and nitrile vertical profiles have been extracted, with limits set on the precursors to aerosols. Aerosol continuum spectral structure is recognized in the extinction spectra, but physical chemistry modeling of aerosol precursors to date indicate higher abundances than the upper limits set by observation.

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

    PubMed Central

    Chen, Weigen; Peng, Shudi; Zeng, Wen

    2014-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    1980-12-01

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

  15. Atom-economic catalytic amide synthesis from amines and carboxylic acids activated in situ with acetylenes

    PubMed Central

    Krause, Thilo; Baader, Sabrina; Erb, Benjamin; Gooßen, Lukas J.

    2016-01-01

    Amide bond-forming reactions are of tremendous significance in synthetic chemistry. Methodological research has, in the past, focused on efficiency and selectivity, and these have reached impressive levels. However, the unacceptable amounts of waste produced have led the ACS GCI Roundtable to label ‘amide bond formation avoiding poor atom economy' as the most pressing target for sustainable synthetic method development. In response to this acute demand, we herein disclose an efficient one-pot amide coupling protocol that is based on simple alkynes as coupling reagents: in the presence of a dichloro[(2,6,10-dodecatriene)-1,12-diyl]ruthenium catalyst, carboxylate salts of primary or secondary amines react with acetylene or ethoxyacetylene to vinyl ester intermediates, which undergo aminolysis to give the corresponding amides along only with volatile acetaldehyde or ethyl acetate, respectively. The new amide synthesis is broadly applicable to the synthesis of structurally diverse amides, including dipeptides. PMID:27282773

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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

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

  17. Atom-economic catalytic amide synthesis from amines and carboxylic acids activated in situ with acetylenes.

    PubMed

    Krause, Thilo; Baader, Sabrina; Erb, Benjamin; Gooßen, Lukas J

    2016-01-01

    Amide bond-forming reactions are of tremendous significance in synthetic chemistry. Methodological research has, in the past, focused on efficiency and selectivity, and these have reached impressive levels. However, the unacceptable amounts of waste produced have led the ACS GCI Roundtable to label 'amide bond formation avoiding poor atom economy' as the most pressing target for sustainable synthetic method development. In response to this acute demand, we herein disclose an efficient one-pot amide coupling protocol that is based on simple alkynes as coupling reagents: in the presence of a dichloro[(2,6,10-dodecatriene)-1,12-diyl]ruthenium catalyst, carboxylate salts of primary or secondary amines react with acetylene or ethoxyacetylene to vinyl ester intermediates, which undergo aminolysis to give the corresponding amides along only with volatile acetaldehyde or ethyl acetate, respectively. The new amide synthesis is broadly applicable to the synthesis of structurally diverse amides, including dipeptides. PMID:27282773

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

    NASA Technical Reports Server (NTRS)

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

    2005-01-01

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

  19. Synthesis, structure and cytotoxic activity of acetylenic derivatives of betulonic and betulinic acids

    NASA Astrophysics Data System (ADS)

    Bębenek, Ewa; Chrobak, Elwira; Wietrzyk, Joanna; Kadela, Monika; Chrobak, Artur; Kusz, Joachim; Książek, Maria; Jastrzębska, Maria; Boryczka, Stanisław

    2016-02-01

    A series of acetylenic derivatives of betulonic and betulinic acids has been synthesized and characterized by 1H and 13C NMR, IR and MS spectroscopy. The structure of propargyl betulonate 4 and propargyl betulinate-DMF solvate 8A was solved by X-ray diffraction. Thermal properties were examined using a DSC technique. The resulting alkynyl derivatives, as well as betulin 1 and betulinic acid 3, were evaluated in vitro for their cytotoxic activity against human T47D breast cancer, CCRF/CEM leukemia, SW707 colorectal, murine P388 leukemia and BALB3T3 normal fibroblasts cell lines. Several of the obtained compounds have a favorable cytotoxic profile than betulin 1. Propargyl betulinate 8 was the most active derivative, being up to 3-fold more potent than betulin 1 against the human leukemia (CCRF/CEM) cell line, with an IC50 value of 3.9 μg/mL.

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

    PubMed

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

    2009-02-24

    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 (S(1)) with 3 triplet states (T(1), T(2), and T(3)). Using high-energy (157-nm) photons from an F(2) laser to record excited-state photoelectron spectra, we have decomposed the mixed eigenstates into their S(1), T(3), T(2), and T(1) 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.

  1. Dynamics of proton-acetylene collisions at 30 eV

    NASA Astrophysics Data System (ADS)

    Malinovskaya, S. A.; Cabrera-Trujillo, R.; Sabin, John. R.; Deumens, E.; Ohrn, Y.

    2002-07-01

    Collisions of protons with ground state acetylene molecules at 30 eV are studied using the electron nuclear dynamics (END) theory. This time-dependent methodology for the study of molecular processes is a nonadiabatic approach to direct dynamics, which has been successfully applied to ion-atom and ion-molecule reactive collisions. Using the minimal END theory, we calculate the direct and charge-transfer differential cross sections. Different initial conditions lead to diverse product channels, such as charge transfer, proton exchange, and collision induced dissociation. Projectile energy loss is analyzed in terms of transfer into target electronic, translational, and rovibrational excitations. The comparison of the computed results with time-of-flight measurements is discussed.

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

    NASA Technical Reports Server (NTRS)

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

    1986-01-01

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

  3. Dubinin-Astakhov model for acetylene adsorption on metal-organic frameworks

    NASA Astrophysics Data System (ADS)

    Cheng, Peifu; Hu, Yun Hang

    2016-07-01

    Acetylene (C2H2) is explosive at a pressure above 29 psi, causing a safety issue for its storage and applications. C2H2 adsorption on metal-organic frameworks (MOFs) has been explored to solve the issue. However, a suitable isotherm equation for C2H2 adsorption on various MOFs has not been found. In this paper, it was demonstrated that Dubinin-Astakhov equation can be exploited as a general isotherm model to depict C2H2 adsorption on MOF-5, ZIF-8, HKUST-1, and MIL-53. In contrast, commonly used Langmuir and BET models exhibited their inapplicability for C2H2 adsorption on those MOFs.

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

    NASA Technical Reports Server (NTRS)

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

    2013-01-01

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

  5. Computational simulations of hydrogen circular migration in protonated acetylene induced by circularly polarized light.

    PubMed

    Shi, Xuetao; Li, Wen; Schlegel, H Bernhard

    2016-08-28

    The hydrogens in protonated acetylene are very mobile and can easily migrate around the C2 core by moving between classical and non-classical structures of the cation. The lowest energy structure is the T-shaped, non-classical cation with a hydrogen bridging the two carbons. Conversion to the classical H2CCH(+) ion requires only 4 kcal/mol. The effect of circularly polarized light on the migration of hydrogens in oriented C2H3 (+) has been simulated by Born-Oppenheimer molecular dynamics. Classical trajectory calculations were carried out with the M062X/6-311+G(3df,2pd) level of theory using linearly and circularly polarized 32 cycle 7 μm cosine squared pulses with peak intensity of 5.6 × 10(13) W/cm(2) and 3.15 × 10(13) W/cm(2), respectively. These linearly and circularly polarized pulses transfer similar amounts of energy and total angular momentum to C2H3 (+). The average angular momentum vectors of the three hydrogens show opposite directions of rotation for right and left circularly polarized light, but no directional preference for linearly polarized light. This difference results in an appreciable amount of angular displacement of the three hydrogens relative to the C2 core for circularly polarized light, but only an insignificant amount for linearly polarized light. Over the course of the simulation with circularly polarized light, this corresponds to a propeller-like motion of the three hydrogens around the C2 core of protonated acetylene. PMID:27586924

  6. Computational simulations of hydrogen circular migration in protonated acetylene induced by circularly polarized light

    NASA Astrophysics Data System (ADS)

    Shi, Xuetao; Li, Wen; Schlegel, H. Bernhard

    2016-08-01

    The hydrogens in protonated acetylene are very mobile and can easily migrate around the C2 core by moving between classical and non-classical structures of the cation. The lowest energy structure is the T-shaped, non-classical cation with a hydrogen bridging the two carbons. Conversion to the classical H2CCH+ ion requires only 4 kcal/mol. The effect of circularly polarized light on the migration of hydrogens in oriented C2H3+ has been simulated by Born-Oppenheimer molecular dynamics. Classical trajectory calculations were carried out with the M062X/6-311+G(3df,2pd) level of theory using linearly and circularly polarized 32 cycle 7 μm cosine squared pulses with peak intensity of 5.6 × 1013 W/cm2 and 3.15 × 1013 W/cm2, respectively. These linearly and circularly polarized pulses transfer similar amounts of energy and total angular momentum to C2H3+. The average angular momentum vectors of the three hydrogens show opposite directions of rotation for right and left circularly polarized light, but no directional preference for linearly polarized light. This difference results in an appreciable amount of angular displacement of the three hydrogens relative to the C2 core for circularly polarized light, but only an insignificant amount for linearly polarized light. Over the course of the simulation with circularly polarized light, this corresponds to a propeller-like motion of the three hydrogens around the C2 core of protonated acetylene.

  7. Controllable optical black hole in left-handed materials.

    PubMed

    Bai, Qiang; Chen, Jing; Shen, Nian-Hai; Cheng, Chen; Wang, Hui-Tian

    2010-02-01

    Halting and storing light by infinitely decelerating its speed, in the absence of any form of external control, is extremely di+/-cult to imagine. Here we present a theoretical prediction of a controllable optical black hole composed of a planar left-handed material slab. We reveal a criterion that the effective round-trip propagation length in one zigzag path is zero, which brings light to a complete standstill. Both theory and ab initio simulation demonstrate that this optical black hole has degrees flexible controllability for the speed of light. Surprisingly, the ab initio simulations reveal that our scheme has degrees flexible controllability for swallowing, holding, and releasing light. PMID:20174039

  8. Aharonov-Bohm Effect in a Rotating Acoustic Black Hole

    NASA Astrophysics Data System (ADS)

    Oliveira, E. S.; Crispino, L. C. B.; Dolan, S. R.

    2015-01-01

    A classical analogue to the Aharonov-Bohm (AB) effect occurs in a (idealized) draining bathtub (DBT) vortex system. The DBT vortex presents a sonic horizon, at which the flow rate exceeds the speed of sound. The sonic horizon is the analogue of a black hole event horizon. The DBT vortex also presents an ergoregion, similar to a rotating black hole. Because of the sonic event horizon, the AB effect is modified and has two tuning coefficients proportional to the flow draining and circulation couplings with the perturbation frequency.

  9. The Crisis in Black and Black.

    ERIC Educational Resources Information Center

    Hutchinson, Earl Ofari

    These essays explore why the historic conflict between blacks and whites in the United States has become a crisis that divides many African Americans. The changing racial dynamic is not marked by conflicts. between the black middle class and the poor, black men and women, the black intellectual elite and rappers, black politicians and the urban…

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

    PubMed Central

    White, Ian N. H.

    1978-01-01

    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 17α-ethynyl-17β-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 17β-hydroxy-17α-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

  11. Black Literature vs. Black Studies: Three Lynchings

    ERIC Educational Resources Information Center

    Williams, Melvin G.

    1977-01-01

    Considers three works by black authors, all dealing with lynchings, that may be used in a black literature course to introduce students to the esthetic dimension of black literature, as well as to its cultural and racial significance. (GW)

  12. A model for the ethylene and acetylene adsorption on the surface of Cun(n = 10-15) nanoclusters: A theoretical study

    NASA Astrophysics Data System (ADS)

    Farmanzadeh, Davood; Abdollahi, Tahereh

    2016-11-01

    In this work, we report the results of density functional theory calculations of ethylene and acetylene adsorption on the most stable Cun (n = 10-15) nanoclusters, in two π and di- σ adsorption modes. Both the hydrocarbons molecularly adsorbed on the surface. Our results show that the quality of interaction of ethylene and acetylene with odd copper nanoclusters (n = 11, 13, 15) is different from what is found on even copper nanoclusters (n = 10, 12, 14). One of the interesting features of this adsorption is that acetylene never orient toward di-σ mode for Cusbnd Cu bond in odd copper nanoclusters. Also, for di- σ-CunC2H4, no stable structure is identified. The highest interaction and deformation energies are seen for the adsorption of acetylene and ethylene on Cu11 in π-mode.

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

    NASA Astrophysics Data System (ADS)

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

    2012-05-01

    We studied the dynamics of intramolecular vibrational redistribution (IVR) from the initially excited mode ν1≈3330 cm-1 (acetylene-type H-C bond) in H{-}C\\equivC{-}CF_3 molecules in the gaseous phase by means of time-resolved anti-Stokes spontaneous Raman scattering. The time constant of this process was estimated as 2.3 ns—this is the slowest IVR time reported so far for the room-temperature gases. We have compared this result with earlier results on the other terminal acetylene molecules, and give an explanation of this low IVR rate. Our suggestion for it follows from an assumption that the most probable doorway state leading to IVR from \

  14. Counseling Blacks

    ERIC Educational Resources Information Center

    Vontress, Clemmont E.

    1970-01-01

    Blacks have developed unique environmental perceptions, values, and attitudes, making it difficult for counselors to establish and maintain positive rapport. This article examines attitudinal ingredients posited by Carl Rogers for relevance to this problem, and suggests in-service training to help counselors and other professionals relate…

  15. Black Cohosh

    MedlinePlus

    ... from the Women's Health Initiative randomized controlled trial. Journal of the American Medical Association 288: 321-333, 2002. [ PubMed abstract ] Gunn TR, Wright IM: The use of black and blue cohosh in labour. New Zealand Medical Journal 109: 410-411, 1996. [ PubMed abstract ] Finkle RS, ...

  16. Black English.

    ERIC Educational Resources Information Center

    Bailey, Charles-James N.

    This paper, presented as part of a military lecture series given by the Division of Continuing Education and Community Service Speakers' Bureau of the University of Hawaii to military personnel at Schofield Barracks and Fort Shafter, investigates the origins and present status of Black English. A discussion of early studies in the Gullah dialect…

  17. Black Adolescents.

    ERIC Educational Resources Information Center

    Jones, Reginald L., Ed.

    This volume presents an overview of contemporary black adolescents from social, psychological, economic, educational, medical, historical, and comparative perspectives, with most emphasizing the roles that race, socioeconomic status, and environmental forces play in this critical period. The volume includes 19 chapters by various authors arranged…

  18. Black Hills

    Atmospheric Science Data Center

    2014-05-15

    article title:  Drought in the Black Hills     View ... and western South Dakota remain in the midst of a severe drought. This set of images and maps from NASA's Multi-angle Imaging ... the 2000 and 2004 dates. As the vegetation faded with the drought, the  albedo  at the surface increased. Albedo measures the ...

  19. Black America.

    ERIC Educational Resources Information Center

    San Francisco Unified School District, CA.

    This is a selected bibliography of some good and some outstanding audio-visual educational materials in the library of the Educational Materials Bureau, Audio-Visual Education Section, that may be considered by particular interest in the study of black Americans. The bibliography is arranged alphabetically within these subject areas: I. African…

  20. Can Analysis of Acetylene and Its Biodegradation Products in Enceladus Plumes be Used to Detect the Presence of Sub-Surface Life?

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    The search for biosignatures of life on Earth includes measurement of the stable isotope fractionation of reactants and products attributed to enzymatic processes and comparison with the often smaller chemical (abiotic) fractionation. We propose that this approach might be applied to study the origin and fate of organic compounds contained in water vapor plumes emanating from Enceladus or other icy bodies, perhaps revealing information about the potential for biology occurring within a sub-surface "habitable" zone. Methanol and C2-hydrocarbons including ethylene, ethane and acetylene (C2H2) have been identified in the plumes of Enceladus. Biological degradation of acetylene proceeds by anaerobic fermentation via acetylene hydratase through acetaldehyde, with a second enzyme (acetaldehyde dismutase) forming acetate and ethanol. We found that incubation of cultures of acetylene-fermenting bacteria exhibit a kinetic isotope effect (KIE) associated with the net removal of C2H2. Consumption of acetylene by both growing and washed-cell cultures of bacteria closely related to Pelobacter acetylenicus (e.g, strain SFB93) was accompanied by a carbon isotopic fractionation of about 2 per mil (KIE = 1.8-2.7 ‰), a result we are examining with other cultures of acetylene fermenters. In addition, we are measuring the carbon isotopic composition of acetaldehyde, ethanol and acetate during fermentation to learn whether these products are fractionated sufficiently, relative to their substrate, to warrant measurement of their isotopic composition in Enceladus (or Europa) plumes to indicate enzymatic activity in liquid environments below the crust of these moons.

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

    NASA Technical Reports Server (NTRS)

    Woon, David E.

    2007-01-01

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

  2. Characterization and anti-inflammatory effects of iodinated acetylenic acids isolated from the marine sponges Suberites mammilaris and Suberites japonicus.

    PubMed

    Hwang, Buyng Su; Lee, Kyung; Yang, Cao; Jeong, Eun Ju; Rho, Jung-Rae

    2013-12-27

    The previously unknown compounds 1-4, acetylenic acids with one or two iodine atom(s), were isolated from the marine sponges Suberites mammilaris and Suberites japonicus. Their complete structures were determined using NMR and mass spectrometry. The methylated compounds 1a and 2a exhibited a strong NO inhibitory effect on RAW264.7 cells, while methylated 3a and 4a were inactive in RAW264.7 cells, but highly active in BV2 microglia cells.

  3. Triplet acetylenes as synthetic equivalents of 1,2-bicarbenes: phantom n,pi state controls reactivity in triplet photocycloaddition.

    PubMed

    Zeidan, Tarek A; Kovalenko, Serguei V; Manoharan, Mariappan; Clark, Ronald J; Ghiviriga, Ion; Alabugin, Igor V

    2005-03-30

    Diaryl acetylenes, in which one of the aryl groups is either a pyridine or a pyrazine, undergo efficient triplet state photocycloaddition to 1,4-cyclohexadiene with formation of 1,5-diaryl substituted tetracyclo[3.3.0.0(2,8).0(4,6)]octanes (homoquadricyclanes). In the case of pyrazinyl acetylenes, the primary homoquadricyclane products undergo a secondary photochemical rearangement leading to diaryl substituted tricyclo[3.2.1.0(4,6)]oct-2-enes. Mechanistic and photophysical studies suggest that photocycloaddition proceeds through an electrophilic triplet excited state whereas the subsequent rearrangement to the tricyclooctenes proceeds through a singlet excited state. Chemical and quantum yields for the cycloaddition, in general, correlate with the electron acceptor character of aryl substituents but are attenuated by photophysical factors, such as the competition between the conversion of acetylene singlet excited state into the reactive triplet excited states (intersystem crossing: ISC) and/or to the radical-anion (photoelectron transfer from the diene to the excited acetylene: PET). Dramatically enhanced ISC between pi-pi S(1) state and "phantom" n,pi triplet excited state is likely to be important in directing reactivity to the triplet pathway. The role of PET can be minimized by the judicious choice of reaction conditions (solvent, concentration, etc.). From a practical perspective, such reactions are interesting because "capping" of the triple bond with the polycyclic framework orients the terminal aryl (4-pyridyl, 4-tetrafluoropyridyl, phenyl, etc.) groups in an almost perfect 60 degrees angle and renders such molecules promising supramolecular building blocks, especially in the design of metal coordination polymers. PMID:15783209

  4. Large-core acetylene-filled photonic microcells made by tapering a hollow-core photonic crystal fiber.

    PubMed

    Wheeler, Natalie V; Grogan, Michael D W; Light, Philip S; Couny, Francois; Birks, Timothy A; Benabid, Fetah

    2010-06-01

    We report on kagomé-lattice photonic microcells with low losses, large outer diameters, and large cores. The large (40-70microm) cores are accommodated by tapering the fibers and splicing the reduced ends to a single-mode fiber. We demonstrate the repeatability of this process and obtain splice losses of 0.6dB by optimizing the taper transition length. Narrow electromagnetically induced transparencies and saturable absorption are demonstrated in an acetylene-filled photonic microcell.

  5. Absolute frequency measurement of an acetylene stabilized laser using a selected single mode from a femtosecond fiber laser comb.

    PubMed

    Ryu, Han Young; Lee, Sung Hun; Lee, Won Kyu; Moon, Han Seb; Suh, Ho Suhng

    2008-03-01

    We performed an absolute frequency measurement of an acetylene stabilized laser utilizing a femtosecond injection locking technique that can select one component among the fiber laser comb modes. The injection locking scheme has all the fiber configurations. Femtosecond comb lines of 250 MHz spacing based on the fiber femtosecond laser were used for injection locking of a distributed feedback (DFB) laser operating at 1542 nm as a frequency reference. The comb injected DFB laser serves as a selection filter of optical comb modes and an amplifier for amplification of the selected mode. The DFB laser injection locked to the desired comb mode was used to evaluate the frequency stability and absolute frequency measurement of an acetylene stabilized laser. The frequency stability of the acetylene stabilized laser was measured to be 1.1 x 10(-12) for a 1 s averaging time, improving to 6.9 x 10(-14) after 512 s. The absolute frequency of the laser stabilized on the P(16) transition of (13)C(2)H(2) was measured to be 194 369 569 385.7 kHz.

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

    NASA Astrophysics Data System (ADS)

    Reshetenko, Tatyana V.; St-Pierre, Jean

    2015-08-01

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

  7. Importance of surface carbide formation on the activity and selectivity of Pd surfaces in the selective hydrogenation of acetylene

    NASA Astrophysics Data System (ADS)

    Yang, Bo; Burch, Robbie; Hardacre, Christopher; Hu, P.; Hughes, Philip

    2016-04-01

    A recent experimental investigation (Kim et al. J. Catal. 306 (2013) 146-154) on the selective hydrogenation of acetylene over Pd nanoparticles with different shapes concluded that Pd(100) showed higher activity and selectivity than Pd(111) for acetylene hydrogenation. However, our recent density functional calculations (Yang et al. J. Catal. 305 (2013) 264-276) observed that the clean Pd(111) surface should result in higher activity and ethylene selectivity compared with the clean Pd(100) surface for acetylene hydrogenation. In the current work, using density functional theory calculations, we find that Pd(100) in the carbide form gives rise to higher activity and selectivity than Pd(111) carbide. These results indicate that the catalyst surface is most likely in the carbide form under the experimental reaction conditions. Furthermore, the adsorption energies of hydrogen atoms as a function of the hydrogen coverage at the surface and subsurface sites over Pd(100) are compared with those over Pd(111), and it is found that the adsorption of hydrogen atoms is always less favoured on Pd(100) over the whole coverage range. This suggests that the Pd(100) hydride surface will be less stable than the Pd(111) hydride surface, which is also in accordance with the experimental results reported.

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

    PubMed

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

    2016-01-01

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

  9. Development of a New Detection Scheme to Probe Predissociated Levels of the S_1 State of Acetylene

    NASA Astrophysics Data System (ADS)

    Jiang, Jun; Erickson, Trevor J.; Merer, Anthony; Field, Robert W.

    2016-06-01

    A new spectroscopic scheme has been developed to probe the predissociated levels of the S_1 state of acetylene. Our new scheme is based on detection of visible fluorescence that is a result of multi-photon excitation of acetylene (resonantly through single rovibronic S_1 levels). The new detection scheme is not subject to decreases in fluorescence quantum yield of S_1 levels that lie above the predissociation limit, and laser scatter-light can be easily eliminated by a long-pass filter with a cutoff in the visible range. For the S_1 predissociated levels, the new detection scheme offers much improved signal-to-noise ratio compared to the conventional laser-induced fluorescence technique, based on detection of UV fluorescence from the S_1 levels. The new method is also easier to implement than various H-atom detection schemes, which involve one additional laser of different wavelength than the excitation wavelength. Based on the power dependence and lifetime of the fluorescence signals, electronically excited C_2H and/or C_2 fragments are the likely emitters of the detected visible fluorescence. The new method is currently being used to extend the vibrational and rotational assignments of both gerade and ungerade levels of the S_1 state of acetylene in the region of the cis-trans isomerization barrier, >1000 cm-1 above the onset of S_1 predissociation.

  10. Chromophores from photolyzed ammonia reacting with acetylene: Application to Jupiters Great Red Spot

    NASA Technical Reports Server (NTRS)

    Carlson, Robert W.; Baines, Kevin H.; Anderson, M. S.; Filacchione, G.; Simon, A. A.

    2016-01-01

    The high altitude of Jupiter's Great Red Spot (GRS) may enhance the upward flux of gaseous ammonia (NH3 ) into the high troposphere, where NH3 molecules can be photodissociated and initiate a chain of chemical reactions with downwelling acetylene molecules (C2H2 ). These reactions, experimentally studied earlier by (Ferris and Ishikawa [1987] Nature 326, 777-778) and (Ferris and Ishikawa [1988] J. Amer. Chem. Soc. 110, 4306-4312), produce chromophores that absorb in the visible and ultraviolet regions. In this work we photolyzed mixtures of NH3 and C2H2 using ultraviolet radiation with a wavelength of 214 nm and measured the spectral transmission of the deposited films in the visible region (400-740 nm). From these transmission data we estimated the imaginary indices of refraction. Assuming that ammonia grains at the top of the GRS clouds are coated with this material, we performed layered sphere and radiative transfer calculations to predict GRS reflection spectra. Comparison of those results with observed and previously unreported Cassini visible spectra and with true-color images of the GRS show that the unknown GRS chromophore is spectrally consistent with the coupled NH3-C2H2 photochemical products produced in our laboratory experiments. Using high-resolution mass spectrometry and infrared spectroscopy we infer that the chromophore-containing residue is composed of aliphatic azine, azo, and diazo compounds.

  11. Root and nodule respiration in relation to acetylene reduction in intact nodulated peas.

    PubMed

    Mahon, J D

    1977-12-01

    Inoculated pea plants (Pisum sativum L.) were grown with N-free nutrients in a controlled environment room and rates of respiratory CO(2) evolution and C(2)H(2) reduction by the intact nodulated roots were determined. Experiments followed changes related to diurnal cycles, light and dark treatments, partial defoliation, aging of plants and NH(4)NO(3) addition. In all experiments, changes in C(2)H(2) reduction were associated with parallel changes in the respiration rate, although in all but the defoliation experiment there was a basal level of respiration which was independent of the rate of C(2)H(2) reduction. In conditions which affected growth or plant size as well as C(2)H(2) reduction, respiration changed by an average of 0.42 mg CO(2) (mumol C(2)H(2) reduced)(-1). However, some treatments decreased C(2)H(2) reduction without greatly changing the growth and in these conditions respiration was decreased by an average of 0.27 mg CO(2) (mumol C(2)H(2) reduced)(-1). While this value may also include some respiration associated with other processes, it is proposed that it more closely estimates respiration directly associated with energy utilization for acetylene reduction; whereas the higher value includes respiration related to maintenance and growth processes as well.

  12. Influence of nanoparticle formation on discharge properties in argon-acetylene capacitively coupled radio frequency plasmas

    NASA Astrophysics Data System (ADS)

    Wegner, Th.; Hinz, A. M.; Faupel, F.; Strunskus, T.; Kersten, H.; Meichsner, J.

    2016-02-01

    This contribution presents experimental results regarding the influence of nanoparticle formation in capacitively coupled radio frequency (13.56 MHz) argon-acetylene plasmas. The discharge is studied using non-invasive 160 GHz Gaussian beam microwave interferometry and optical emission spectroscopy. Particularly, the temporal behavior of the electron density from microwave interferometry is analyzed and compared with the changing plasma emission and self-bias voltage caused by nanoparticle formation. The periodic particle formation with a cycle duration between 30 s and 140 s starts with an electron density drop over more than one order of magnitude below the detection limit (8 × 1014 m-3). The electron density reduction is the result of electron attachment processes due to negative ions and nanoparticle formation. The onset time constant of nanoparticle formation is five times faster compared to the expulsion of the particles from the plasma due to multi-disperse size distribution. Moreover, the intensity of the argon transition lines increases and implies a rising effective electron temperature. The cycle duration of the particle formation is affected by the total gas flow rate and exhibits an inverse proportionality to the square of the total gas flow rate. The variation in the total gas flow rate influences the force balance, which determines the confinement time of the nanoparticles. As a further result, the cycle duration is dependent on the axial position of the powered electrode, which also corresponds to different distances relative to the fixed optical axis of the microwave interferometer.

  13. Production of Ethane, Ethylene, and Acetylene from Halogenated Hydrocarbons by Methanogenic Bacteria

    PubMed Central

    Belay, Negash; Daniels, Lacy

    1987-01-01

    Several methanogenic bacteria were shown to produce ethane, ethylene, and acetylene when exposed to the halogenated hydrocarbons bromoethane, dibromo- or dichloroethane, and 1,2-dibromoethylene, respectively. They also produced ethylene when exposed to the coenzyme M analog and specific methanogenic inhibitor bromoethanesulfonic acid. The production of these gases from halogenated hydrocarbons has a variety of implications concerning microbial ecology, agriculture, and toxic waste treatment. All halogenated aliphatic compounds tested were inhibitory to methanogens. Methanococcus thermolithotrophicus, Methanococcus deltae, and Methanobacterium thermoautotrophicum ΔH and Marburg were completely inhibited by 7 μM 1,2-dibromoethane and, to various degrees, by 51 to 1,084 μM 1,2-dichloroethane, 1,2-dibromoethylene, 1,2-dichloroethylene, and trichloroethylene. In general, the brominated compounds were more inhibitory. The two Methanococcus species were fully inhibited by 1 μM bromoethanesulfonic acid, whereas both Methanobacterium strains were only partly inhibited by 2,124 μM. Coenzyme M protected cells from bromoethanesulfonic acid but not from any of the other inhibitors. PMID:16347389

  14. Chromophores from photolyzed ammonia reacting with acetylene: Application to Jupiter's Great Red Spot

    NASA Astrophysics Data System (ADS)

    Carlson, R. W.; Baines, K. H.; Anderson, M. S.; Filacchione, G.; Simon, A. A.

    2016-08-01

    The high altitude of Jupiter's Great Red Spot (GRS) may enhance the upward flux of gaseous ammonia (NH3) into the high troposphere, where NH3 molecules can be photodissociated and initiate a chain of chemical reactions with downwelling acetylene molecules (C2H2). These reactions, experimentally studied earlier by (Ferris and Ishikawa [1987] Nature 326, 777-778) and (Ferris and Ishikawa [1988] J. Amer. Chem. Soc. 110, 4306-4312), produce chromophores that absorb in the visible and ultraviolet regions. In this work we photolyzed mixtures of NH3 and C2H2 using ultraviolet radiation with a wavelength of 214 nm and measured the spectral transmission of the deposited films in the visible region (400-740 nm). From these transmission data we estimated the imaginary indices of refraction. Assuming that ammonia grains at the top of the GRS clouds are coated with this material, we performed layered sphere and radiative transfer calculations to predict GRS reflection spectra. Comparison of those results with observed and previously unreported Cassini visible spectra and with true-color images of the GRS show that the unknown GRS chromophore is spectrally consistent with the coupled NH3-C2H2 photochemical products produced in our laboratory experiments. Using high-resolution mass spectrometry and infrared spectroscopy we infer that the chromophore-containing residue is composed of aliphatic azine, azo, and diazo compounds.

  15. Time- and isomer-resolved measurements of sequential addition of acetylene to the propargyl radical

    DOE PAGES

    Savee, John D.; Selby, Talitha M.; Welz, Oliver; Taatjes, Craig A.; Osborn, David L.

    2015-10-06

    Soot formation in combustion is a complex process in which polycyclic aromatic hydrocarbons (PAHs) are believed to play a critical role. Recent works concluded that three consecutive additions of acetylene (C2H2) to propargyl (C3H3) create a facile route to the PAH indene (C9H8). However, the isomeric forms of C5H5 and C7H7 intermediates in this reaction sequence are not known. We directly investigate these intermediates using time- and isomer-resolved experiments. Both the resonance stabilized vinylpropargyl (vp-C5H5) and 2,4-cyclopentadienyl (c-C5H5) radical isomers of C5H5 are produced, with substantially different intensities at 800 K vs 1000 K. In agreement with literature master equationmore » calculations, we find that c-C5H5 + C2H2 produces only the tropyl isomer of C7H7 (tp-C7H7) below 1000 K, and that tp-C7H7 + C2H2 terminates the reaction sequence yielding C9H8 (indene) + H. Lastly, this work demonstrates a pathway for PAH formation that does not proceed through benzene.« less

  16. Klebsiella pneumoniae nitrogenase. Mechanism of acetylene reduction and its inhibition by carbon monoxide.

    PubMed Central

    Lowe, D J; Fisher, K; Thorneley, R N

    1990-01-01

    The electron flux through the MoFe-protein of nitrogenase from Klebsiella pneumoniae determines the absolute and relative rates of 2H+ reduction to H2 and acetylene (C2H2) reduction to ethylene (C2H4) at saturating levels of reductant (Na2S2O4) and MgATP. High electron flux, induced by a high Fe-protein (Kp2)/MoFe protein (Kp1) ratio, favours C2H2 reduction. These data can be explained if ethylene, the two-electron reduction product of C2H2, is not released until three electrons have been transferred from Kp2 to Kp1. This explanation is also consistent with a pre-steady-state lag phase for C2H4 formation of 250 ms observed when functioning enzyme is quenched with acid. Electron flux through nitrogenase is inhibited by C2H2 at high protein concentrations. This is because the association rate between Kp1 and oxidized Kp2 is enhanced by C2H2, leading to an increased steady-state concentration of the inhibitory complex Kp2oxKp1C2H2. This effect is not relieved by CO. Thus CO and C2H2 (or C2H4) must be bound at the same time to distinct sites, presumably at Mo or Fe centres, on the enzyme. PMID:2268290

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

    NASA Technical Reports Server (NTRS)

    Dunder, T.; Miller, R. E.

    1990-01-01

    A method is described for forming and spectroscopically characterizing cryogenic aerosols formed in a low temperature gas cell. By adjusting the cell pressure, gas composition and flow rate, the size distribution of aerosol particles can be varied over a wide range. The combination of pressure and flow rate determine the residence time of the aerosols in the cell and hence the time available for the particles to grow. FTIR spectroscopy, over the range from 600/cm to 6000/cm, is used to characterize the aerosols. The particle size distribution can be varied so that, at one extreme, the spectra show only absorption features associated with the infrared active vibrational bands and, at the other, they display both absorption and Mie scattering. In the latter case, Mie scattering theory is used to obtain semiquantitative aerosol size distributions, which can be understood in terms of the interplay between nucleation and condensation. In the case of acetylene aerosols, the infrared spectra suggest that the particles exist in the high temperature cubic phase of the solid.

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

    SciTech Connect

    Jonas, D.M.; Solina, S.A.B.; Rajaram, B.; Silbey, R.J.; Field, R.W. ); Yamanouchi, K.; Tsuchiya, S. )

    1992-08-15

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

  19. The Methane-Acetylene Cycle Aerospace Plane: A potential option for inexpensive Earth to orbit transportation

    NASA Astrophysics Data System (ADS)

    Zubrin, Robert M.

    1994-06-01

    Methane, a cheap, soft cryogen with six times the density of hydrogen could be an ideal fuel for use in a hypersonic aerospace plane. However, it does not burn fast enough for efficient scramjet operation and it possesses an inadequate thermal heat sink to cool the aircraft effectively. This paper proposes a concept, termed the Methane-Acetylene Cycle Aerospace Plane (MACASP), that may overcome these difficulties. In the MACASP concept, methane fuel is run out within the wing leading edge in pipes which are allowed to rise in temperature to about 1800 K. Drag heating is used to drive the highly endothermic chemical reaction; 2CH4 = 3H2 + C2H2. The reaction occurs on a millisecond time scale and endows the methane with a heat sink per unit mass comparable to that possessed by liquid hydrogen. The reaction products are fed into a combustion chamber and burned in air, releasing as much energy per unit mass at as rapid a combustion rate as hydrogen. This paper explores the thermodynamics of the MACASP concept and theoretical feasibility is demonstrated. Potential problems and areas of concern are identified. A conceptual point design for a MACASP vehicle is advanced and mission analysis performed comparing the MACASP to a conventional hydrogen aerospace plane. It is shown that the MACASP concept offers significant promise for economical Earth to orbit transportation.

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

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

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

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

    SciTech Connect

    Gabrielson, F.C.

    1982-01-01

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

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

    SciTech Connect

    Gabrielson, F.C.

    1982-01-01

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

  3. Theoretical investigation of alignment-dependent intense-field fragmentation of acetylene

    NASA Astrophysics Data System (ADS)

    Doblhoff-Dier, Katharina; Kitzler, Markus; Gräfe, Stefanie

    2016-07-01

    We analyze the alignment-dependent dissociative and nondissociative ionization of acetylene, C2H2 . Numerical models describing the yield of the singly and doubly charged ions (C2H2+,C2H22 +) and several fragmentation and isomerization channels (C2H++H+ ,CH++CH+ ,CH2++C+ ) as a function of the relative alignment angle between the laser polarization axis and the molecular axis are presented. We apply and compare two different approaches. The first is based on time-dependent density functional theory. The second is a quasi-single-particle approach using the Dyson orbitals. We find good agreement between the results of both methods. A comparison of our theoretical predictions with experimental data allows us to show that the alignment-dependent yield of most reaction channels is described to high accuracy assuming sequential ionization. However, for some of the fragmentation channels, namely, CH++CH+ and C2H++H+ , we find non-negligible influence of recollisional ionization.

  4. DFT study of selective hydrogenation of acetylene to ethylene on Pd doping Ag nanoclusters

    NASA Astrophysics Data System (ADS)

    Liu, D.

    2016-11-01

    Recently, it has been reported that the reaction selectivity of catalytic hydrogenation of acetylene to ethylene can be significantly enhanced via the approach of Pd mono-atomic catalysis [Pei et al. ACS Catal. 5 (2015) 3717-3725]. To explain the catalytic mechanism of this binary alloy catalyst, C2H2 hydrogenation reactions on Pd doping Ag nanoclusters are studied using density functional theory simulations. The simulation results indicate that H2 and C2H2 can simultaneously bind with a single Pd doping atom no matter it is on vertex and edge sites of Ag clusters. The following H2 dissociation and C2H2 hydrogenation are not difficult since the corresponding reaction barrier values are no more than 0.58 eV. The generated C2H4 molecule can not be further hydrogenated since it locates on the top of Pd doping atom, which is the only adsorption site for H2. On two Pd doping atoms at contiguous sites of Ag clusters, C2H4 hydrogenation reactions can be carried out since there are enough sites for co-adsorption of H2 and C2H4.

  5. Time- and Isomer-Resolved Measurements of Sequential Addition of Acetylene to the Propargyl Radical.

    PubMed

    Savee, John D; Selby, Talitha M; Welz, Oliver; Taatjes, Craig A; Osborn, David L

    2015-10-15

    Soot formation in combustion is a complex process in which polycyclic aromatic hydrocarbons (PAHs) are believed to play a critical role. Recent works concluded that three consecutive additions of acetylene (C2H2) to propargyl (C3H3) create a facile route to the PAH indene (C9H8). However, the isomeric forms of C5H5 and C7H7 intermediates in this reaction sequence are not known. We directly investigate these intermediates using time- and isomer-resolved experiments. Both the resonance stabilized vinylpropargyl (vp-C5H5) and 2,4-cyclopentadienyl (c-C5H5) radical isomers of C5H5 are produced, with substantially different intensities at 800 K vs 1000 K. In agreement with literature master equation calculations, we find that c-C5H5 + C2H2 produces only the tropyl isomer of C7H7 (tp-C7H7) below 1000 K, and that tp-C7H7 + C2H2 terminates the reaction sequence yielding C9H8 (indene) + H. This work demonstrates a pathway for PAH formation that does not proceed through benzene. PMID:26722791

  6. Conformations of propargyl alcohol and its interaction with acetylene: A matrix isolation infrared and DFT computations

    NASA Astrophysics Data System (ADS)

    Sundararajan, K.; Gopi, R.; Ramanathan, N.

    2016-10-01

    Conformations of propargyl alcohol (PA) were studied using matrix isolation infrared spectroscopy. DFT computations using 6-311++G(d,p) basis set on the PA molecule identified two minima; gauche (g-PA) and trans (t-PA). Comparison of infrared spectra of PA trapped in Ar, N2 and Xe matrices with computations showed the evidence of the ground state g-PA conformer. Four minima were optimized on the potential energy surface for the hydrogen-bonded interaction of g-PA and acetylene (C2H2), corresponding to complex A (Csbnd H⋯O), complex B (Osbnd H⋯π) and complex C and D (Csbnd H⋯π). The structure, energies and the vibrational wavenumbers were computed for these complexes at B3LYP/6-311++G (d,p) level of theory. The infrared spectra of the hydrogen-bonded complexes between C2H2 and g-PA were studied in Ar matrix. The infrared spectra recorded under matrix isolation conditions revealed the formation of two types of complexes A (Csbnd H⋯O) and B (Osbnd H⋯π). Formation of these complexes was evidenced from the shifts in the vibrational wavenumber of the modes involving the C2H2 and PA submolecules.

  7. The Fourier transform absorption spectrum of acetylene between 8280 and 8700 cm-1

    NASA Astrophysics Data System (ADS)

    Lyulin, O. M.; Vander Auwera, J.; Campargue, A.

    2016-07-01

    High resolution (0.011 cm-1) room temperature (295 K) Fourier transform absorption spectra (FTS) of acetylene have been analyzed in the 8280-8700 cm-1 range dominated by the ν1+ν2+ν3 band at 8512 cm-1. Line positions and intensities were retrieved from FTS spectra recorded at 3.84 and 56.6 hPa. As a result, a list of 1001 lines was constructed with intensities ranging between about 2×10-26 and 10-22 cm/molecule. Comparison with accurate predictions provided by a global effective operator model led to the assignment of 629 12C2H2 lines. In addition, 114 lines of the 13C12CH2 isotopologue were assigned using information available in the literature. The 12C2H2 lines belong to thirteen bands, nine of which being newly reported. The 13C12CH2 lines belong to three bands, the intensities of which being reported for the first time. Spectroscopic parameters of the 12C2H2 upper vibrational levels were derived from band-by-band analyses of the line positions (typical rms are on the order of 0.002 cm-1). Three of the analyzed bands were found to be affected by rovibrational perturbations, which are discussed in the frame of a global effective Hamiltonian. The obtained line parameters are compared with those of the two bands included in the HITRAN 2012 database.

  8. Global modeling of vibration-rotation spectra of the acetylene molecule

    NASA Astrophysics Data System (ADS)

    Lyulin, O. M.; Perevalov, V. I.

    2016-07-01

    The global modeling of both line positions and intensities of the acetylene molecule in the 50-9900 cm-1 region has been performed using the effective operators approach. The parameters of the polyad model of effective Hamiltonian have been fitted to the line positions collected from the literature. The used polyad model of effective Hamiltonian takes into account the centrifugal distortion, rotational and vibrational ℓ-doubling terms and both anharmonic and Coriolis resonance interaction operators arising due to the approximate relations between the harmonic frequencies: ω1≈ω3≈5ω4≈5ω5 and ω2≈3ω4≈3ω5. The dimensionless weighted standard deviation of the fit is 2.8. The fitted set of 237 effective Hamiltonian parameters allowed reproducing 24,991 measured line positions of 494 bands with a root mean squares deviation 0.0037 cm-1. The eigenfunctions of the effective Hamiltonian corresponding to the fitted set of parameters were used to fit the observed line intensities collected from the literature for 15 series of transitions: ΔP = 0-13,15, where P=5V1+5V3 +3V2+V4+V5 is the polyad number (Vi are the principal vibrational quantum numbers). The fitted sets of the effective dipole moment parameters reproduce the observed line intensities within their experimental uncertainties 2-20%.

  9. Antitrypanosomal Acetylene Fatty Acid Derivatives from the Seeds of Porcelia macrocarpa (Annonaceae).

    PubMed

    de Á Santos, Luciana; Cavalheiro, Alberto J; Tempone, Andre G; Correa, Daniela S; Alexandre, Tatiana R; Quintiliano, Natalia F; Rodrigues-Oliveira, André F; Oliveira-Silva, Diogo; Martins, Roberto Carlos C; Lago, João Henrique G

    2015-05-07

    Chagas' disease is caused by a parasitic protozoan and affects the poorest population in the world, causing high mortality and morbidity. As a result of the toxicity and long duration of current treatments, the discovery of novel and more efficacious drugs is crucial. In this work, the hexane extract from seeds of Porcelia macrocarpa R.E. Fries (Annonaceae) displayed in vitro antitrypanosomal activity against trypomastigote forms of T. cruzi by the colorimetric MTT assay (IC50 of 65.44 μg/mL). Using chromatographic fractionation over SiO2, this extract afforded a fraction composed by one active compound (IC50 of 10.70 µg/mL), which was chemically characterized as 12,14-octadecadiynoic acid (macrocarpic acid). Additionally, two new inactive acetylene compounds (α,α'-dimacro-carpoyl-β-oleylglycerol and α-macrocarpoyl-α'-oleylglycerol) were also isolated from the hexane extract. The complete characterization of the isolated compounds was performed by analysis of NMR and MS data as well as preparation of derivatives.

  10. Synthesis and characterization of graphenated carbon nanotubes on IONPs using acetylene by chemical vapor deposition method

    NASA Astrophysics Data System (ADS)

    Atchudan, Raji; Perumal, Suguna; Edison, Thomas Nesakumar Jebakumar Immanuel; Pandurangan, Arumugam; Lee, Yong Rok

    2015-11-01

    The graphenated carbon nanotubes (G-CNTs) were synthesized on monodisperse spherical iron oxide nanoparticles (IONPs) using acetylene as carbon precursor by simple chemical vapor deposition method. The reaction parameters such as temperature and flow of carbon source were optimized in order to achieve G-CNTs with excellent quality and quantity. Transmission electron microscopy (TEM) clearly illustrated that the graphene flakes are forming along the whole length on CNTs. The degree of graphitization was revealed by X-ray diffraction (XRD) analysis and Raman spectroscopic techniques. The intensity of D to G value was less than one which confirms the obtained G-CNTs have high degree of graphitization. The optimum reaction temperature for the IONPs to form metallic clusters which in turn lead to the formation of G-CNTs with high carbon deposition yield is at 900 °C. The TEM shows the CNTs diameter is 50 nm with foiled graphene flakes of diameter around 70 nm. Our results advocate for IONPs as a promising catalytic template for quantitative and qualitative productivity of nanohybrid G-CNTs. The produced G-CNTs with high degree of graphitization might be an ideal candidate for nanoelectronic application like super capacitors and so on.

  11. AB INITIO AND CALPHAD THERMODYNAMICS OF MATERIALS

    SciTech Connect

    Turchi, P A

    2004-04-14

    Ab initio electronic structure methods can supplement CALPHAD in two major ways for subsequent applications to stability in complex alloys. The first one is rather immediate and concerns the direct input of ab initio energetics in CALPHAD databases. The other way, more involved, is the assessment of ab initio thermodynamics {acute a} la CALPHAD. It will be shown how these results can be used within CALPHAD to predict the equilibrium properties of multi-component alloys.

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

    NASA Astrophysics Data System (ADS)

    Rosales Lombardi, Pablo I.

    The molecular structure of the interface between plasma-polymerized acetylene films and steel was determined using in-situ reflection-absorption infrared spectroscopy (RAIR) and X-ray photoelectron spectroscopy (XPS). Plasma-polymerized acetylene films were deposited onto polished steel substrates in microwave (MW) and radio frequency (RF)-powered reactors. The films deposited in RF-powered reactors were characterized in-situ using XPS and FTIR spectrometers that were interfaced directly to the reactors. RAIR showed that the plasma polymerized films contained large numbers of methyl and methylene groups but only a small number of monosubstituted acetylene groups, indicating that there was substantial rearrangement of the monomer molecules during plasma polymerization. The rearrangement of the monomer molecules during plasma was also determined by optical emission spectroscopy (OES), where CH and C2 species predominated in the optical emission spectra. Bands were observed near 1020 and 885 cm-1 in the RAIR spectra that were attributed to skeletal stretching vibrations in C-C-O-Fe groups, indicating that the plasma-polymerized films interacted with the substrate through formation of alkoxide bonds. Another band was observed near 1565 cm-1 and attributed to carboxylate groups in the interface between films and the oxidized surface of the substrate. Results from XPS also confirmed the formation of alkoxide and carboxylate groups in the interface during plasma polymerization of acetylene. Results from XPS showed that the surface of steel substrates consisted mostly of a mixture of Fe2O3 and FeOOH and that iron was mostly present in the Fe(III) oxidation state. However, during plasma-polymerization of acetylene, there was a tendency for the concentration of Fe(II) to increase, due to the reducing nature of argon/acetylene plasmas. Natural rubber reacted with plasma-polymerized acetylene primers through unsaturated functional groups present in the film. The RAIR and XPS

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

    NASA Astrophysics Data System (ADS)

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

    2013-07-01

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

  14. The First Black Holes

    NASA Astrophysics Data System (ADS)

    Abel, T.

    Recently we have been able to ab initio simulate the formation of the very first stars in the universe in three dimensions using Eulerian adaptive mesh refinement. Starting from initial conditions drawn from a cosmological model for structure formation that is consistent with all observational data and a knowledge of primordial gas physics no free parameters remain in these models. Our simulations have covered 12 orders of magnitude in length and time scales and follow the formation of a protostar up to the point where it becomes optically thick to its own cooling radiation. At this time the proto star has one solar mass and acretes about 1 solar mass per century. This large accretion rate is a direct consequence of the higher gas temperature in primordial gas which are only allowed to cool down to ~ 200 K via molecular hydrogen. Fragmentation has not been found. This result has been found to be independent of numerical resolution, time step and refinement criteria or even and the hydrodynamic methods employed. Since the rapidly acreting protostar has little time to act back on the accretion flow we argue that a massive star must form. The UV output of this star destroys all molecular coolants in the host halo inhibiting the formation of any other stars in the 106 Ms dark matter halo in which it formed. The typical mass scales of the proto-stars, its acreting envelope, the ``molecular cloud'' within which it formed as well as the total mass of the systems can be understood analytically from chemical time scales and the properties of molecular hydrogen alone. Interestingly our accretion profiles indicate that within the lifetime of a massive primordial star of three million years at most about 600 solar masses may be acreted onto the protostar. Also within the first 10,000 years already about 70 solar masses will be acreted. This is much faster than the Kelvin Helmholtz contraction time of the star indicating a robust lower limit to the initial mass of the first

  15. Fundamental Dynamics of Black Hole Physics

    NASA Astrophysics Data System (ADS)

    Haramein, Nassim

    2002-04-01

    The dynamics of rotating, charged black holes, obeying the Kerr-Newman metric is presented. These dynamical high-density, gravitationally collapsing, black hole systems for stellar, galactic, intergalactic and cosmogenesis appear to obey similar constraints on their mass, apparent density and radius. Under these extreme conditions, the gravitational force becomes "balanced" with the larger coupling constant of the electromagnetic force. Thus, the gravitational attraction forms dynamic pseudo equilibrium with the plasma dynamics surrounding the black holes. Thermodynamic-type processes occupy a role in energy transfer between gravitational attraction and electro-dynamic repulsion. Solving the modified Einstein-Maxwell's equations under high magnetic field conditions, with additional thermodynamic conditions, leads to a good description of the processes occurring externally, near and in the event horizons of the Kerr-Newman geometry and leads to a unification possibility. Reference; N. Haramein, Bull. Amer. Phys. Soc. AB06, 1154(2001)

  16. Ultrasound Biomicroscopy Comparison of Ab Interno and Ab Externo Intraocular Lens Scleral Fixation.

    PubMed

    Horiguchi, Lie; Garcia, Patricia Novita; Malavazzi, Gustavo Ricci; Allemann, Norma; Gomes, Rachel L R

    2016-01-01

    Purpose. To compare ab interno and ab externo scleral fixation of posterior chamber intraocular lenses (PCIOL) using ultrasound biomicroscopy (UBM). Methods. Randomized patients underwent ab externo or ab interno scleral fixation of a PCIOL. Ultrasound biomicroscopy was performed 3 to 6 months postoperatively, to determine PCIOL centration, IOL distance to the iris at 12, 3, 6, and 9 hours, and haptics placement in relation to the ciliary sulcus. Results. Fifteen patients were enrolled in the study. The ab externo technique was used in 7 eyes (46.6%) and the ab interno in 8 eyes (53.3%). In the ab externo technique, 14 haptics were located: 4 (28.57%) in the ciliary sulcus; 2 (14.28%) anterior to the sulcus; and 8 (57.14%) posterior to the sulcus, 6 in the ciliary body and 2 posterior to the ciliary body. In the ab interno group, 4 haptics (25.0%) were in the ciliary sulcus, 2 (12.50%) anterior to the sulcus, and 10 (75.0%) posterior to the sulcus, 4 in the ciliary body and 6 posterior to the ciliary body. Conclusions. Ab externo and ab interno scleral fixation techniques presented similar results in haptic placement. Ab externo technique presented higher vertical tilt when compared to the ab interno.

  17. Ultrasound Biomicroscopy Comparison of Ab Interno and Ab Externo Intraocular Lens Scleral Fixation

    PubMed Central

    Horiguchi, Lie; Garcia, Patricia Novita; Malavazzi, Gustavo Ricci; Allemann, Norma

    2016-01-01

    Purpose. To compare ab interno and ab externo scleral fixation of posterior chamber intraocular lenses (PCIOL) using ultrasound biomicroscopy (UBM). Methods. Randomized patients underwent ab externo or ab interno scleral fixation of a PCIOL. Ultrasound biomicroscopy was performed 3 to 6 months postoperatively, to determine PCIOL centration, IOL distance to the iris at 12, 3, 6, and 9 hours, and haptics placement in relation to the ciliary sulcus. Results. Fifteen patients were enrolled in the study. The ab externo technique was used in 7 eyes (46.6%) and the ab interno in 8 eyes (53.3%). In the ab externo technique, 14 haptics were located: 4 (28.57%) in the ciliary sulcus; 2 (14.28%) anterior to the sulcus; and 8 (57.14%) posterior to the sulcus, 6 in the ciliary body and 2 posterior to the ciliary body. In the ab interno group, 4 haptics (25.0%) were in the ciliary sulcus, 2 (12.50%) anterior to the sulcus, and 10 (75.0%) posterior to the sulcus, 4 in the ciliary body and 6 posterior to the ciliary body. Conclusions. Ab externo and ab interno scleral fixation techniques presented similar results in haptic placement. Ab externo technique presented higher vertical tilt when compared to the ab interno. PMID:27293878

  18. Contemporary Black Theatre.

    ERIC Educational Resources Information Center

    Thomas, Pearl

    The distinguishable black theatre in America, mirroring a distinguishable black experience, is an artistic product which demands audience involvement. Both the Afro-American oral tradition and the art of gesture are integral aspects of black theatre. In addition, the tragedy found black theatre is not tragedy in the classic sense, as blacks feel…

  19. Smoking Cessation among Blacks.

    ERIC Educational Resources Information Center

    Stotts, R. Craig; And Others

    1991-01-01

    Lung cancer is a serious health problem among blacks, with a mortality rate of 119 per 100,000 black males, compared to 81 per 100,000 for white males. Smoking cessation efforts are most successful when tailored to the black community, using black community networks and broadcast media for black audiences. (SLD)

  20. H-π Beats n-σ in PHENYLACETYLENE-HCl Hydrogen Bonded Heterodimer: a Matrix Isolation Infrared and AB Initio Study

    NASA Astrophysics Data System (ADS)

    Karir, Ginny; Viswanathan, K. S.

    2016-06-01

    Hydrogen bonded complexes of phenylacetylene (PhAc) and HCl were studied using matrix isolation infrared spectroscopy and ab initio computations. An H…π complex was observed in our experiments, which was indicated to be the global minimum by our computations. In this complex, HCl serves as the proton donor to the acetylenic π cloud of PhAc. Computations also located two other minima on the PhAc-HCl potential surface. One was an H…π complex where the proton of HCl interacts with the π cloud of the phenyl ring, which was nearly isoenergetic with the global minimum. The other was an n-σ complex, where the acetylenic hydrogen in PhAc interacted with the chlorine of HCl. The phenylacetylene-HCl system was theoretically investigated, employing MP2 and M06-2X methods, with 6-311++G(d,p) and aug/cc-pVDZ basis sets. AIM, EDA and NBO analysis were also performed to explore the nature, physical origin and the strength of the noncovalent interactions. Experiments with phenylacetylene deuterated at the acetylenic hydrogen (PhAcD) were also performed, to confirm the above observation, through the isotopic effect. This work is part of a study of the hydrogen bonded interactions of phenylacetylene with various precursors, which provide an interesting interaction landscape ranging from a strong n-σ to a strong H-π interaction. As it turns out, HCl is at one end of this range, displaying a strong H-π interaction. While this presentation will give the details of the phenylacetylene-HCl complex, it will also summarize the landscape mentioned above, putting the present study in perspective. GK acknowledges fellowship from MHRD, India. Authors thank IISER, Mohali for facilities.

  1. Double resonant absorption measurement of acetylene symmetric vibrational states probed with cavity ring down spectroscopy.

    PubMed

    Karhu, J; Nauta, J; Vainio, M; Metsälä, M; Hoekstra, S; Halonen, L

    2016-06-28

    A novel mid-infrared/near-infrared double resonant absorption setup for studying infrared-inactive vibrational states is presented. A strong vibrational transition in the mid-infrared region is excited using an idler beam from a singly resonant continuous-wave optical parametric oscillator, to populate an intermediate vibrational state. High output power of the optical parametric oscillator and the strength of the mid-infrared transition result in efficient population transfer to the intermediate state, which allows measuring secondary transitions from this state with a high signal-to-noise ratio. A secondary, near-infrared transition from the intermediate state is probed using cavity ring-down spectroscopy, which provides high sensitivity in this wavelength region. Due to the narrow linewidths of the excitation sources, the rovibrational lines of the secondary transition are measured with sub-Doppler resolution. The setup is used to access a previously unreported symmetric vibrational state of acetylene, ν1+ν2+ν3+ν4 (1)+ν5 (-1) in the normal mode notation. Single-photon transitions to this state from the vibrational ground state are forbidden. Ten lines of the newly measured state are observed and fitted with the linear least-squares method to extract the band parameters. The vibrational term value was measured to be at 9775.0018(45) cm(-1), the rotational parameter B was 1.162 222(37) cm(-1), and the quartic centrifugal distortion parameter D was 3.998(62) × 10(-6) cm(-1), where the numbers in the parenthesis are one-standard errors in the least significant digits. PMID:27369508

  2. Infrared analysis of soot produced from an acetylene-rich flame

    NASA Astrophysics Data System (ADS)

    Pino, Thomas; Dartois, Emmanuel; Cao, Anh Tuan; D'Hendecourt, Louis; Bréchignac, Philippe

    The ubiquitous unidentified infrared emission bands (UIBs), now referred to as aromatic infrared bands (AIBs), observed from a variety of regions of interstellar space have been recognized to involve carbonaceous material with an aromatic character. It is now widely accepted that these interstellar "nanograins" should have sizes intermediate between those of the PAHs easily accessible to laboratory studies and of the "standard" interstellar grains (ca 0.05μm or 50 nm). The nanometer size is related to their capability of being transiently heated upon absorption of UV starlight photons. We will present the preliminary results obtained with a new experimental set-up, devoted to the formation of carbonaceous nanoparticles and the characterization of their spectral properties in absorption and in emission, in the solid phase and in the gas phase, isolated in a van der Waals matrix or free-flying. The production of the species uses laboratory techniques and conditioning under specific interstellar processes such as coupling a chemical reactor to stellar-like UV irradiation. We have used in particular an acetylene-rich, premixed and flat, low-pressure flame as a reactor. When operated under low-pressure conditions, the spatial development of the flame allows us to sample its content at various stages of the particles growth. The analysis can be made by transmission spectroscopy of thin film deposits under infrared microscope or in rare gas matrices under FTIR spectroscopy, and by Time-Of-Flight mass spectrometry. The preliminary results reveal a strong evolution from aromatic materials containing aliphatic substituents to large polymer-like soot particules. The spectrum in Figure 1 is that of a deposition taken from a sooting flame at a C/O=2, burning at a pressure of 26.5mb, and sampled at 12mm from the flat burner. A tentative assignment is given.

  3. Time- and isomer-resolved measurements of sequential addition of acetylene to the propargyl radical

    SciTech Connect

    Savee, John D.; Selby, Talitha M.; Welz, Oliver; Taatjes, Craig A.; Osborn, David L.

    2015-10-06

    Soot formation in combustion is a complex process in which polycyclic aromatic hydrocarbons (PAHs) are believed to play a critical role. Recent works concluded that three consecutive additions of acetylene (C2H2) to propargyl (C3H3) create a facile route to the PAH indene (C9H8). However, the isomeric forms of C5H5 and C7H7 intermediates in this reaction sequence are not known. We directly investigate these intermediates using time- and isomer-resolved experiments. Both the resonance stabilized vinylpropargyl (vp-C5H5) and 2,4-cyclopentadienyl (c-C5H5) radical isomers of C5H5 are produced, with substantially different intensities at 800 K vs 1000 K. In agreement with literature master equation calculations, we find that c-C5H5 + C2H2 produces only the tropyl isomer of C7H7 (tp-C7H7) below 1000 K, and that tp-C7H7 + C2H2 terminates the reaction sequence yielding C9H8 (indene) + H. Lastly, this work demonstrates a pathway for PAH formation that does not proceed through benzene.

  4. Adsorption of Acetylene and Formation of Benzene on Cosmic Dust in Titan's Atmosphere

    NASA Astrophysics Data System (ADS)

    Frankland, Victoria; James, Alexander; Carrillo Sanchez, Juan; Mangan, Thomas; Willacy, Karen; Plane, John

    2016-04-01

    The formation of the haze layers and tholins in Titan's atmosphere is unclear. One potential mechanism is that small precursors, such as acetylene (C2H2), adsorb onto un-ablated cosmic dust particles as they sediment through Titan's atmosphere. The uptake coefficient of C2H2 onto cosmic dust analogues was measured using low temperature dual flow tube apparatus. Synthesized olivines analogues (Mg2-2nFe2nSiO4 where 1 ≥ n ≥ 0) were used to represent the cosmic dust particles based on investigations of cometary dust. The results indicated that the adsorption of C2H2 was independent of the Mg:Fe ratio in the dust analogue with the mean uptake coefficient (at 181 K) as 1.7 × 10-4. In some cases, the uptake experiments were left until the surface had become saturated with C2H2. Here, a small benzene (C6H6) mass trace was detected indicating that cyclotrimerzation of C2H2 into C6H6 was occurring on the surface. Further experiments using ultrahigh vacuum apparatus were used to confirm this observation. The rate of C6H6 (formed through C2H2 cyclotrimerization) desorbing from un-ablated cosmic dust particles sedimenting through Titan's atmosphere was explored using a 1D model. The results revealed that this heterogeneous formation and desorption route was competitive with gaseous C6H6 formation rates suggesting that the dust could be acting as a seed for the formation of complex organic molecules (such as PAHs) and tholins and, through this, the formation of the haze layers.

  5. Double resonant absorption measurement of acetylene symmetric vibrational states probed with cavity ring down spectroscopy.

    PubMed

    Karhu, J; Nauta, J; Vainio, M; Metsälä, M; Hoekstra, S; Halonen, L

    2016-06-28

    A novel mid-infrared/near-infrared double resonant absorption setup for studying infrared-inactive vibrational states is presented. A strong vibrational transition in the mid-infrared region is excited using an idler beam from a singly resonant continuous-wave optical parametric oscillator, to populate an intermediate vibrational state. High output power of the optical parametric oscillator and the strength of the mid-infrared transition result in efficient population transfer to the intermediate state, which allows measuring secondary transitions from this state with a high signal-to-noise ratio. A secondary, near-infrared transition from the intermediate state is probed using cavity ring-down spectroscopy, which provides high sensitivity in this wavelength region. Due to the narrow linewidths of the excitation sources, the rovibrational lines of the secondary transition are measured with sub-Doppler resolution. The setup is used to access a previously unreported symmetric vibrational state of acetylene, ν1+ν2+ν3+ν4 (1)+ν5 (-1) in the normal mode notation. Single-photon transitions to this state from the vibrational ground state are forbidden. Ten lines of the newly measured state are observed and fitted with the linear least-squares method to extract the band parameters. The vibrational term value was measured to be at 9775.0018(45) cm(-1), the rotational parameter B was 1.162 222(37) cm(-1), and the quartic centrifugal distortion parameter D was 3.998(62) × 10(-6) cm(-1), where the numbers in the parenthesis are one-standard errors in the least significant digits.

  6. Acetylene as an essential building block for prebiotic formation of pyrimidine bases on Titan.

    PubMed

    Jeilani, Yassin A; Fearce, Chelesa; Nguyen, Minh Tho

    2015-10-01

    Prebiotic building blocks for the formation of biomolecules are important in understanding the abiotic origin of biomolecules. However, there is a limited choice of the building blocks as precursors for the biomolecules. Acetylene (HCCH) is found in Titan's atmosphere and is an abiotic-precursor of pyrimidine bases. HCCH reacts with urea to form both cytosine and uracil. The mechanisms for the formation of both cytosine and uracil were studied by density functional theory at B3LYP/6-311G(d,p) level. Ethynyl radicals (˙CCH) are relevant for the chemistry of Titan's atmosphere therefore both HCCH and ˙CCH were evaluated as carbon sources. The pathways, for both HCCH and ˙CCH, lead to intermediates with an unsaturated-group that facilitate the formation of the six-membered ring of the pyrimidine bases. The predicted structures for cytosine and uracil were compared with labeled cytosine and uracil that were formed from the reaction of DCCD with urea. The results suggest that cytosine is formed from HCCH while uracil is formed from ˙CCH. The mechanisms are energetically feasible and there is no conclusive evidence for the preferred pathway (HCCH or ˙CCH). The pathways were further extended for the formation of both uric acid and 8-oxoguanine from HCCH and urea, and demonstrate the utility of HCCH as a carbon source for diverse biomolecules. Biuret is identified as a precursor for the pyridimine bases, and it unifies the free radical pathways for the pyrimidine bases with those of triazines. The pathways are appropriate for the reducing atmosphere that creates both radicals and electrons due to ionizing radiation on Titan. The mechanisms are feasible for the extraterrestrial formation of the pyrimidine bases. PMID:26325173

  7. Uptake of acetylene on cosmic dust and production of benzene in Titan's atmosphere

    NASA Astrophysics Data System (ADS)

    Frankland, Victoria L.; James, Alexander D.; Sánchez, Juan Diego Carrillo; Mangan, Thomas P.; Willacy, Karen; Poppe, Andrew R.; Plane, John M. C.

    2016-11-01

    A low-temperature flow tube and ultra-high vacuum apparatus were used to explore the uptake and heterogeneous chemistry of acetylene (C2H2) on cosmic dust analogues over the temperature range encountered in Titan's atmosphere below 600 km. The uptake coefficient, γ, was measured at 181 K to be (1.6 ± 0.4) × 10-4, (1.9 ± 0.4) × 10-4 and (1.5 ± 0.4) × 10-4 for the uptake of C2H2 on Mg2SiO4, MgFeSiO4 and Fe2SiO4, respectively, indicating that γ is independent of Mg or Fe active sites. The uptake of C2H2 was also measured on SiO2 and SiC as analogues for meteoric smoke particles in Titan's atmosphere, but was found to be below the detection limit (γ < 6 × 10-8 and < 4 × 10-7, respectively). The rate of cyclo-trimerization of C2H2 to C6H6 was found to be 2.6 × 10-5 exp(-741/T) s-1, with an uncertainty ranging from ± 27 % at 115 K to ± 49 % at 181 K. A chemical ablation model was used to show that the bulk of cosmic dust particles (radius 0.02-10 μm) entering Titan's atmosphere do not ablate (< 1% mass loss through sputtering), thereby providing a significant surface for heterogeneous chemistry. A 1D model of dust sedimentation shows that the production of C6H6via uptake of C2H2 on cosmic dust, followed by cyclo-trimerization and desorption, is probably competitive with gas-phase production of C6H6 between 80 and 120 km.

  8. Double resonant absorption measurement of acetylene symmetric vibrational states probed with cavity ring down spectroscopy

    NASA Astrophysics Data System (ADS)

    Karhu, J.; Nauta, J.; Vainio, M.; Metsälä, M.; Hoekstra, S.; Halonen, L.

    2016-06-01

    A novel mid-infrared/near-infrared double resonant absorption setup for studying infrared-inactive vibrational states is presented. A strong vibrational transition in the mid-infrared region is excited using an idler beam from a singly resonant continuous-wave optical parametric oscillator, to populate an intermediate vibrational state. High output power of the optical parametric oscillator and the strength of the mid-infrared transition result in efficient population transfer to the intermediate state, which allows measuring secondary transitions from this state with a high signal-to-noise ratio. A secondary, near-infrared transition from the intermediate state is probed using cavity ring-down spectroscopy, which provides high sensitivity in this wavelength region. Due to the narrow linewidths of the excitation sources, the rovibrational lines of the secondary transition are measured with sub-Doppler resolution. The setup is used to access a previously unreported symmetric vibrational state of acetylene, ν 1 + ν 2 + ν 3 + ν4 1 + ν5 - 1 in the normal mode notation. Single-photon transitions to this state from the vibrational ground state are forbidden. Ten lines of the newly measured state are observed and fitted with the linear least-squares method to extract the band parameters. The vibrational term value was measured to be at 9775.0018(45) cm-1, the rotational parameter B was 1.162 222(37) cm-1, and the quartic centrifugal distortion parameter D was 3.998(62) × 10-6 cm-1, where the numbers in the parenthesis are one-standard errors in the least significant digits.

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

    PubMed

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

    2012-04-01

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

  10. Clickable Photoaffinity Ligands for Metabotropic Glutamate Receptor 5 Based on Select Acetylenic Negative Allosteric Modulators.

    PubMed

    Gregory, Karen J; Velagaleti, Ranganadh; Thal, David M; Brady, Ryan M; Christopoulos, Arthur; Conn, P Jeffrey; Lapinsky, David J

    2016-07-15

    G protein-coupled receptors (GPCRs) represent the largest class of current drug targets. In particular, small-molecule allosteric modulators offer substantial potential for selectively "tuning" GPCR activity. However, there remains a critical need for experimental strategies that unambiguously determine direct allosteric ligand-GPCR interactions, to facilitate both chemical biology studies and rational structure-based drug design. We now report the development and use of first-in-class clickable allosteric photoprobes for a GPCR based on metabotropic glutamate receptor 5 (mGlu5) negative allosteric modulator (NAM) chemotypes. Select acetylenic mGlu5 NAM lead compounds were rationally modified to contain either a benzophenone or an aryl azide as a photoreactive functional group, enabling irreversible covalent attachment to mGlu5 via photoactivation. Additionally, a terminal alkyne or an aliphatic azide was incorporated as a click chemistry handle, allowing chemoselective attachment of fluorescent moieties to the irreversibly mGlu5-bound probe via tandem photoaffinity labeling-bioorthogonal conjugation. These clickable photoprobes retained submicromolar affinity for mGlu5 and negative cooperativity with glutamate, interacted with the "common allosteric-binding site," displayed slow binding kinetics, and could irreversibly label mGlu5 following UV exposure. We depleted the number of functional mGlu5 receptors using an irreversibly bound NAM to elucidate and delineate orthosteric agonist affinity and efficacy. Finally, successful conjugation of fluorescent dyes via click chemistry was demonstrated for each photoprobe. In the future, these clickable photoprobes are expected to aid our understanding of the structural basis of mGlu5 allosteric modulation. Furthermore, tandem photoaffinity labeling-bioorthogonal conjugation is expected to be a broadly applicable experimental strategy across the entire GPCR superfamily. PMID:27115427

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

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-10-01

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

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

    SciTech Connect

    Kataoka, Yasutaka; Miyai, Jiro; Tezuka, Makoto; Takai, Kazuhiko; Utimoto, Kiitiro )

    1992-12-04

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

  14. Selective hydrogenation of acetylene on SiO2 supported Ni-In bimetallic catalysts: Promotional effect of In

    NASA Astrophysics Data System (ADS)

    Chen, Yanjun; Chen, Jixiang

    2016-11-01

    Ni/SiO2 and the bimetallic NixIn/SiO2 catalysts with different Ni/In ratios were tested for the selective hydrogenation of acetylene, and their physicochemical properties before and after the reaction were characterized by means of N2-sorption, H2-TPR, XRD, TEM, XPS, H2 chemisorption, C2H4-TPD, NH3-TPD, FT-IR of adsorbed pyridine, and TG/DTA and Raman. A promotional effect of In on the performance of Ni/SiO2 was found, and NixIn/SiO2 with a suitable Ni/In ratio gave much higher acetylene conversion, ethylene selectivity and catalyst stability than Ni/SiO2. This is ascribed to the geometrical isolation of the reactive Ni atoms with the inert In ones and the charge transfer from the In atoms to Ni ones, both of which are favorable for reducing the adsorption strength of ethylene and restraining the Csbnd C hydrogenolysis and the polymerizations of acetylene and the intermediate compounds. On the whole, Ni6In/SiO2 and Ni10In/SiO2 had better performance. Nevertheless, with increasing the In content, the selectivity to the C4+ hydrocarbons tended to increase due to the enhanced catalyst acidity because of the charge transfer from the In atoms to Ni ones. As the Lewis acid ones, the In sites could promote the polymerization. The catalyst deactivation was also analyzed. We propose that the Ni/SiO2 deactivation is mainly attributed to the phase change from metallic Ni to nickel carbide. The introduction of In inhibited the formation of nickel carbide. However, as the In content increased, the carbonaceous deposit became the main reason for the NixIn/SiO2 deactivation due to the enhanced catalyst acidity.

  15. Laser double-resonance studies of electronic spectroscopy and state-resolved collisional relaxation in highly vibrationally excited acetylene

    SciTech Connect

    Tobiason, J.D.

    1992-01-01

    Vibrational overtone excitation combined with laser-induced fluorescence detection of acetylene molecules permits rotation-selected spectroscopy of the ([tilde A][sup 1]A[sub u]) electronic state and direct, state-resolved measurements of collisional energy transfer in the highly vibrationally excited ground electronic state. The author assigns energies of 1,045 transitions to previously unobserved ungerade vibrational states 2800-4500 cm[sup [minus]1] above the [tilde A] state origin. An analysis yields frequencies of 2856.4 and 3894.3 cm[sup [minus]1] for [nu][sub v][prime] and [nu][sub 3][prime] + [nu][sub 5][prime]. The author performs the first normal coordinate analysis of [tilde A] state acetylene based only on directly observed fundamentals. The spectroscopy measurements enable double-resonance experiments on the collisional dynamics of highly vibrationally excited acetylene. The quenching rate for single rotational states is twice the Lennard-Jones gas kinetic rate and fairly independent of vibrational energy level. Collision-induced detection of vibrational overtone excitation under single collision conditions allows direct measurements of state-of-state rotational and vibrational energy transfer. A collision-induced spectrum obtained by this new technique immediately identifies transfer channels and the [Delta]J and [Delta]E dependence of the transfer rates. The author observes changes of [vert bar][Delta]J[vert bar] and [Delta]E [approx] 3kT in a single collision. Directly measured rates for one set of vibrational relaxation pathways account for [approximately]3% of the total relaxation rate. The author also observes other vibrational relaxation pathways. The available pathways suggest that vibrational relaxation accounts for the rest of the total relaxation. Changes of [vert bar]J[vert bar] = 18 and [vert bar][Delta]E[vert bar] [approximately] 500 cm[sup [minus]1] in a single collision are observed.

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

    PubMed

    Kroneck, Peter M H

    2016-03-01

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

  17. Recovery of acetylene absorption line profile basing on tunable diode laser spectroscopy with intensity modulation and photoacoustic spectroscopy

    NASA Astrophysics Data System (ADS)

    Li, Li; Thursby, Graham; Stewart, George; Arsad, Norhana; Uttamchandani, Deepak; Culshaw, Brian; Wang, Yiding

    2010-04-01

    A novel and direct absorption line recovery technique based on tunable diode laser spectroscopy with intensity modulation is presented. Photoacoustic spectroscopy is applied for high sensitivity, zero background and efficient acoustic enhancement at a low modulation frequency. A micro-electromechanical systems (MEMS) mirror driven by an electrothermal actuator is used for generating laser intensity modulation (without wavelength modulation) through the external reflection. The MEMS mirror with 10μm thick structure material layer and 100nm thick gold coating is formed as a circular mirror of 2mm diameter attached to an electrothermal actuator and is fabricated on a chip that is wire-bonded and placed on a PCB holder. Low modulation frequency is adopted (since the resonant frequencies of the photoacoustic gas cell and the electrothermal actuator are different) and intrinsic high signal amplitude characteristics in low frequency region achieved from measured frequency responses for the MEMS mirror and the gas cell. Based on the property of photoacoustic spectroscopy and Beer's law that detectable sensitivity is a function of input laser intensity in the case of constant gas concentration and laser path length, a Keopsys erbium doped fibre amplifier (EDFA) with opto-communication C band and high output power up to 1W is chosen to increase the laser power. High modulation depth is achieved through adjusting the MEMS mirror's reflection position and driving voltage. In order to scan through the target gas absorption line, the temperature swept method is adopted for the tunable distributed feed-back (DFB) diode laser working at 1535nm that accesses the near-infrared vibration-rotation spectrum of acetylene. The profile of acetylene P17 absorption line at 1535.39nm is recovered ideally for ~100 parts-per-million (ppm) acetylene balanced by nitrogen. The experimental signal to noise ratio (SNR) of absorption line recovery for 500mW laser power was ~80 and hence the

  18. Ab initio phonon limited transport

    NASA Astrophysics Data System (ADS)

    Verstraete, Matthieu

    We revisit the thermoelectric (TE) transport properties of two champion materials, PbTe and SnSe, using fully first principles methods. In both cases the performance of the material is due to subtle combinations of structural effects, scattering, and phase space reduction. In PbTe anharmonic effects are completely opposite to the predicted quasiharmonic evolution of phonon frequencies and to frequently (and incorrectly) cited extrapolations of experiments. This stabilizes the material at high T, but also tends to enhance its thermal conductivity, in a non linear manner, above 600 Kelvin. This explains why PbTe is in practice limited to room temperature applications. SnSe has recently been shown to be the most efficient TE material in bulk form. This is mainly due to a strongly enhanced carrier concentration and electrical conductivity, after going through a phase transition from 600 to 800 K. We calculate the transport coefficients as well as the defect concentrations ab initio, showing excellent agreement with experiment, and elucidating the origin of the double phase transition as well as the new charge carriers. AH Romero, EKU Gross, MJ Verstraete, and O Hellman PRB 91, 214310 (2015) O. Hellman, IA Abrikosov, and SI Simak, PRB 84 180301 (2011)

  19. Why Black-on-Black Homicide?

    ERIC Educational Resources Information Center

    Jeff, Morris F. X., Jr.

    1981-01-01

    The causes of homicides committed against Blacks by Blacks are examined. Major preventive measures are said to be equal opportunity, better jobs, reduction of racial discrimination, elimination of organized crime, removal of drugs from community, and better schools. (JCD)

  20. Experimental study on new route to acetylene by using powder of coal and limestone in plasma reactor

    SciTech Connect

    Wang, Z.; Jin, Z.; Tian, Z.; Yang, Z.; Hao, H.

    1996-12-31

    In this paper, a new route to acetylene is described to use coal and precrushed limestone powder to produce CaC{sub 2}. Also the plasma reactor design is given. The significant advantages over coke and CaO based routes are: (1) the system produces no effluent; (2) coal and limestone as raw material (isn`t CaO); (3) clean fuel gas (H{sub 2}, CO...) that can be burned to provide heat for electricity generator; and (4) calcium hydroxide can be treated with salt to give caustic soda and calcium chloride by products.

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

    NASA Astrophysics Data System (ADS)

    Malla, Pavani

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

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

    NASA Technical Reports Server (NTRS)

    Allen, Harrison, Jr.; Tannenbaum, Stanley

    1957-01-01

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

  3. Electrochemical Study of AISI C1018 Steel in Methanesulfonic Acid Containing an Acetylenic Alcohol-Based Corrosion Inhibitor Formulation.

    PubMed

    Finšgar, Matjaž; Jackson, Jennifer

    2016-10-01

    In this work, the electrochemical potentiodynamic behavior of AISI C1018 lower-grade steel material was investigated in 20 wt.% methanesulfonic acid (MSA) solutions with or without different components to design corrosion inhibitor formulations based on acetylenic alcohol, cinnamaldehyde, 1-dodecylpyridinium chloride, and methanol. MSA has recently been considered as a new potential acid to be used in the matrix stimulation procedure and in well cleaning. It is demonstrated that AISI C1018 steel MSA needs to be inhibited. Inhibition type is determined for single components as well as for formulations.

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

    PubMed

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

    2014-12-01

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

  5. The electronic structure and second-order nonlinear optical properties of donor-acceptor acetylenes - A detailed investigation of structure-property relationships

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

    A series of donor-acceptor acetylene compounds was synthesized in which systematic changes in both the conjugation length and the donor-acceptor strength were made. The effect of these structural changes on the spectroscopic and electronic properties of the molecules and, ultimately, on the measured second-order molecular hyperpolarizabilities (beta) was investigated. It was found that increases in the donor-acceptor strength resulted in increases in the magnitude of beta. For this class of molecules, the increase is dominated by the energy of the intramolecular charge-transfer transition, while factors such as the ground to excited-state dipole moment change and the transition-moment integral are much less important. Increasing the conjugation length from one to two acetylene linkers did not result in an increase in the value of beta; however, beta increased sharply in going from two acetylenes to three. This increase is attributed to the superposition of several nearly isoenergetic excited states.

  6. Untangling the reaction dynamics of the silylidyne radical (SiH; X2Π) with acetylene (C2H2; X1Σg+)

    NASA Astrophysics Data System (ADS)

    Yang, Tao; Dangi, Beni B.; Thomas, Aaron M.; Kaiser, Ralf I.

    2016-06-01

    The chemical reaction dynamics of silylidyne (SiH; X2Π) with acetylene (C2H2; X1Σg+) were studied exploiting the crossed molecular beam approach, and compared with previous studies on D1-silylidyne with acetylene. The reaction is initiated by a barrierless addition of silylidyne to one or both carbons of acetylene leading to 1-sila-1-propene-1,3-diylidene and/or the cyclic 1-silacyclopropenyl with the former isomerizing to the latter. 1-Silacyclopropenyl eventually loses atomic hydrogen yielding silacyclopropenylidene (c-SiC2H2) in an overall exoergic reaction (experiment: -14.7 ± 8.5 kJ mol-1; theory: -13 ± 3 kJ mol-1). The enthalpy of formation for silacyclopropenylidene is determined to be 421.4 ± 9.3 kJ mol-1.

  7. Ab Initio Study of Polonium

    SciTech Connect

    Zabidi, Noriza Ahmad; Kassim, Hasan Abu; Shrivastava, Keshav N.

    2008-05-20

    Polonium is the only element with a simple cubic (sc) crystal structure. Atoms in solid polonium sit at the corners of a simple cubic unit cell and no where else. Polonium has a valence electron configuration 6s{sup 2}6p{sup 4} (Z = 84). The low temperature {alpha}-phase transforms into the rhombohedral (trigonal) {beta} structure at {approx}348 K. The sc {alpha}-Po unit cell constant is a = 3.345 A. The beta form of polonium ({beta}-Po) has the lattice parameters, a{sub R} = 3.359 A and a rhombohedral angle 98 deg. 13'. We have performed an ab initio electronic structure calculation by using the density functional theory. We have performed the calculation with and without spin-orbit (SO) coupling by using both the LDA and the GGA for the exchange-correlations. The k-points in a simple cubic BZ are determined by R (0.5, 0.5, 0.5), {gamma} (0, 0, 0), X (0.5, 0, 0), M (0.5, 0.5, 0) and {gamma} (0, 0, 0). Other directions of k-points are {gamma} (0, 0, 0), X (0.5, 0, 0), R (0.5, 0.5, 0.5) and {gamma} (0, 0, 0). The SO splittings of p states at the {gamma} point in the GGA+SO scheme for {alpha}-Po are 0.04 eV and 0.02 eV while for the {beta}-Po these are 0.03 eV and 0.97 eV. We have also calculated the vibrational spectra for the unit cells in both the structures. We find that exchanging of a Po atom by Pb atom produces several more bands and destabilizes the {beta} phase.

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

    PubMed

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

    2013-10-28

    We investigated the adsorption and thermal evolution of acetylene on clean Pd(100) and Pd(100) precovered with 0.25 ML oxygen. The measurements were performed in situ by fast XPS at the synchrotron radiation facility BESSY II. On Pd(100) acetylene molecularly adsorbs at 130 K. Upon heating transformation to a CCH species occurs around 390 K along with the formation of a completely dehydrogenated carbon species. On the oxygen-precovered surface partial CCH formation already occurs upon adsorption at 130 K, and the dehydrogenation temperature and the stability range of CCH are shifted to lower temperatures by ∼200 K. PMID:24182063

  9. Modeling study of the ABS relay valve

    NASA Astrophysics Data System (ADS)

    Lei, Ming; Lin, Min; Guo, Bin; Luo, Zai; Xu, Weidong

    2011-05-01

    The ABS (anti-lock braking system) relay valve is the key component of anti-lock braking system in most commercial vehicles such as trucks, tractor-trailers, etc. In this paper, structure of ABS relay valve and its work theory were analyzed. Then a mathematical model of ABS relay valve, which was investigated by dividing into electronic part, magnetic part, pneumatic part and mechanical part, was set up. The displacement of spools and the response of pressure increasing, holding, releasing of ABS relay valve were simulated and analyzed under conditions of control pressure 500 KPa, braking pressure 600 KPa, atmospheric pressure 100 KPa and air temperature 310 K. Thisarticle provides reliable theory for improving the performance and efficiency of anti-lock braking system of vehicles.

  10. Modeling study of the ABS relay valve

    NASA Astrophysics Data System (ADS)

    Lei, Ming; Lin, Min; Guo, Bin; Luo, Zai; Xu, Weidong

    2010-12-01

    The ABS (anti-lock braking system) relay valve is the key component of anti-lock braking system in most commercial vehicles such as trucks, tractor-trailers, etc. In this paper, structure of ABS relay valve and its work theory were analyzed. Then a mathematical model of ABS relay valve, which was investigated by dividing into electronic part, magnetic part, pneumatic part and mechanical part, was set up. The displacement of spools and the response of pressure increasing, holding, releasing of ABS relay valve were simulated and analyzed under conditions of control pressure 500 KPa, braking pressure 600 KPa, atmospheric pressure 100 KPa and air temperature 310 K. Thisarticle provides reliable theory for improving the performance and efficiency of anti-lock braking system of vehicles.

  11. Photochemistry of acetylenic ketones in micellar solutions as studied by product-yield-detected ESR and transient absorption techniques.

    PubMed

    Polyakov, N E; Okazaki, M; Fukaya, H; Fujiwara, Y; Tanimoto, Y

    1995-06-01

    The electron spin resonance (ESR) spectra of the transient radical pairs in the photoreduction of 1,5-diphenyl-1,4-pentadiyn-3-one(I) and 1,3-diphenyl-2-propyn-1-one(II) in sodium dodecyl sulfate (SDS) micellar solutions have been obtained by using the product-yield-detected ESR (PYESR) technique. The PYESR spectra, detected by tracing the microwave effect on the spin-adduct yield as functions of the magnetic field, show the ESR spectra of the ketyl radical of the ketone and SDS radical as the components of the radical pairs. In addition, the growth and the decay processes of the radical pair were observed through detecting the effect of microwave pulse as functions of the delay period between a laser pulse and the off and on time, respectively, of a microwave pulse. The absorption spectra of transient species have also been obtained by using the laser flash photolysis technique. Through the analysis of these data and molecular orbital calculations, the role of acetylenic groups in the photoreactivity of acetylenic ketones is discussed.

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

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

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

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

    PubMed Central

    Dicker, Howard J.; Smith, David W.

    1980-01-01

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

  14. Infrared spectra reveal box-like structures for a pentamer and hexamer of mixed carbon dioxide-acetylene clusters.

    PubMed

    Rezaei, Mojtaba; Norooz Oliaee, J; Moazzen-Ahmadi, N; McKellar, A R W

    2016-01-21

    Except for a few cases like water and carbon dioxide, identification and structural characterization of clusters with more than four monomers is rare. Here, we provide experimental and theoretical evidence for existence of box-like structures for a pentamer and a hexamer of mixed carbon dioxide-acetylene clusters. Two mid-infrared cluster absorption bands are observed in the CO2ν3 band region using a tunable diode laser to probe a pulsed supersonic jet. Each requires the presence of both carbon dioxide and acetylene in the jet, and (from observed rotational spacings) involves clusters containing about 4 to 7 molecules. Structures are predicted for mixed CO2 + C2H2 clusters using a distributed multipole model, and the bands are assigned to a specific pentamer, (CO2)3-(C2H2)2, and hexamer, (CO2)4-(C2H2)2. The hexamer has a box-like structure whose D2d symmetry is supported by observed intensity alternation in the spectrum. The pentamer has a closely related structure which is obtained by removing one CO2 molecule from the hexamer. These are among the largest mixed molecular clusters to be assigned by high-resolution spectroscopy.

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

    NASA Astrophysics Data System (ADS)

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

    2012-06-01

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

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

    SciTech Connect

    Eres, Gyula; Wang, Ying; Gao, Xingfa; Qian, Hu-Jun; Ohta, Yasuhito; Wu, Xiaona; Morokuma, Keiji; Irle, Stephan

    2014-01-01

    Nonequilibrium quantum chemical molecular dynamics (QM/MD) simulation of early stages in the nucleation process of carbon nanotubes from acetylene feedstock on an Fe38 cluster was performed based on the density-functional tight-binding (DFTB) potential. Representative chemical reactions were studied by complimentary static DFTB and density functional theory (DFT) calculations. Oligomerization and cross-linking reactions between carbon chains were found as the main reaction pathways similar to that suggested in previous experimental work. The calculations highlight the inhibiting effect of hydrogen for the condensation of carbon ring networks, and a propensity for hydrogen disproportionation, thus enriching the hydrogen content in already hydrogen-rich species and abstracting hydrogen content in already hydrogen-deficient clusters. The ethynyl radical C2H was found as a reactive, yet continually regenerated species, facilitating hydrogen transfer reactions across the hydrocarbon clusters. The nonequilibrium QM/MD simulations show the prevalence of a pentagon-first nucleation mechanism where hydrogen may take the role of one arm of an sp2 carbon Y-junction. The results challenge the importance of the metal carbide formation for SWCNT cap nucleation in the VLS model and suggest possible alternative routes following hydrogen-abstraction acetylene addition (HACA)-like mechanisms commonly discussed in combustion synthesis.

  17. An ab initio MO study of butalene

    NASA Astrophysics Data System (ADS)

    Ohta, Katsuhisa; Shima, Toru

    1994-01-01

    Butalene as a structural isomer of p-benzyne has been studied by using an ab initio GVB wavefunction. The geometry of butalene, which is shown to be almost rectangular, is first optimized as a local minimum on the energy surface at the ab initio level. However, the energy barrier of conversion to p-benzyne is as small as 1.6 kcal/mol, and experimental isolation of butalene is predicted to be difficult from a force-constant analysis.

  18. Graduating Black Males

    ERIC Educational Resources Information Center

    Bell, Edward Earl

    2010-01-01

    Background: The graduation numbers for Black males are dismal, chilling, and undeniably pathetic. The nation graduates only 47% of Black males who enter the 9th grade. The infusion of federal dollars and philanthropic support will not stop the trajectory of Black males who drop out of school. Black males face an upheaval educational battle;…

  19. Black Teachers on Teaching.

    ERIC Educational Resources Information Center

    Foster, Michele

    The importance to the black community of teaching as a profession can be seen in reference material and other literature about blacks, but this book is unique in presenting the voices of black teachers themselves. The stories of 20 black teachers, born between 1905 and 1973, are told in their own voices. These 20 life interviews collect the…

  20. Aerobic biodegradation of azo dye Acid Black-24 by Bacillus halodurans.

    PubMed

    Prasad, A S Arun; Rao, K V Bhaskara

    2014-05-01

    Bacillus halodurans MTCC 865 was employed for decolorization of textile azo dye, Acid Black-24 (AB-24). Thousand mgl⁻¹ of AB-24 was decolorized with 90% efficiency by the strain within 6 hrs at pH 9 and 37 °C with 5% NaCl under static conditions in screening medium. Decolorization was evaluated by measuring the periodic decrease in absorbance at 557 nm (λ(max)). Biodegradation of Acid Black-24 was determined by FTIR and HPLC. The FTIR spectrum of the AB-24 dye suggests the presence of azo bond (-N = N-) peak at 1618.28 cm⁻¹. Absence of the azo bond in the degraded sample spectrum indicates biodegradation of the dye. Formation of metabolites with different retention times in HPLC analysis further confirmed degradation of the azo dye, Acid Black-24 by Bacillus halodurans.

  1. The Black Black Woman and the Black Middle Class.

    ERIC Educational Resources Information Center

    Jeffers, Trellie

    1981-01-01

    Reprint of a 1973 article that describes the discrimination that particularly dark-skinned Black women suffer, especially at the hands of a color-conscious Black middle class. Calls for dark women to look to the African appearance and working-class roots as sources of pride and strength. (GC)

  2. A model of ethylene and acetylene adsorption on the (111) surfaces of platinum and nickel

    NASA Astrophysics Data System (ADS)

    Felter, T. E.; Weinberg, W. H.

    1981-02-01

    Despite the application of a variety of surface sensitive techniques to the adsorption of simple hydrocarbons on well characterized metallic surfaces, no consistent picture has appeared. We review briefly the published spectroscopic results of ultraviolet photoelectron spectroscopy (UPS) and electron energy loss spectroscopy (EELS) which probe, respectively, the electronic and vibrational structure of the surface-molecular complex, and we consider appropriate free molecular analogues, not only in their ground state but also in their first excited states. A simplified approach to determine the chemisorption geometry from UPS level shifts and EELS is presented. The technique allows an isolation of distortion induced shifts from the total relaxation shift, and we find that the true relaxation shift is rather constant, approximately 2.1 eV for the cases considered. These shifts can then be used to estimate the distance of the molecule to the surface. We concentrate primarily on four systems, C 2H 2 and C 2H 4 on Ni(111) and Pt(111), adsorbed at low temperature (below the onset of dissociation). Depending on the metal, the hydrocarbon can adsorb in a di-σ arrangement or with a distortion resembling the lowest energy configuration of the first excited state of the free molecule. We also consider briefly C 2H 4 on Ag and Cu in which no distortion occurs. The distortions that resemble the first excited states might occur as a consequence of donation of bonding (backbonding) electrons from (to) the normally filled π (empty π ∗) to (from) the empty (filled) d-band states of the metal. The net effect on the hydrocarbon to partially empty the π level and fill the π ∗ level, is analogous to a low excitation of the free molecule, π → π ∗. For C 2H 4 (planar in the ground state), the lowest excitation is the triplet T-state (3-4 eV) of minimal energy for a 90° twisted configuration with a lengthened C-C bond. Acetylene is a linear molecule in the ground state, but

  3. The small-scale production of [U-14C]acetylene from Ba14CO3: application to labeling of ammonia monooxygenase in autotrophic nitrifying bacteria.

    PubMed

    Hyman, M R; Arp, D J

    1990-11-01

    A small-scale method has been adapted from an established procedure for the generation of [U-14C]acetylene from inexpensive and commonly available precursors. The method involves the fusing of Ba14CO3 with excess barium metal to produce Ba14C2. The BaC2 is reacted with water to generate acetylene which is then selectively dissolved into dimethyl sulfoxide (DMSO). The results presented demonstrate the effect of Ba:BaCO3 ratio on the concentrations of various gases released during the hydrolysis reaction and quantify the selectivity of the DMSO-trapping process for each gas. [U-14C]Acetylene generated by this method has been used to inactivate ammonia monooxygenase in three species of autotrophic nitrifying bacteria: Nitrosomonas europaea, Nitrosococcus oceanus, and Nitrosolobus multiformis. Our results demonstrate that acetylene inactivation of this enzyme in all three species results in the covalent incorporation of radioactive label into a polypeptide of apparent Mr of 25,000-27,000, as determined by sodium dodecylsulfate-polyacrylamide gel electrophoresis and fluorography. PMID:2291478

  4. 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)

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

    2012-12-01

    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.

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

    ERIC Educational Resources Information Center

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

    2005-01-01

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

  6. Indole synthesis by conjugate addition of anilines to activated acetylenes and an unusual ligand-free copper(II)-mediated intramolecular cross-coupling.

    PubMed

    Gao, Detian; Back, Thomas G

    2012-11-12

    A versatile new synthesis of indoles was achieved by the conjugate addition of N-formyl-2-haloanilines to acetylenic sulfones, ketones, and esters followed by a copper-catalyzed intramolecular C-arylation. The conjugate addition step was conducted under exceptionally mild conditions at room temperature in basic, aqueous DMF. Surprisingly, the C-arylation was performed most effectively by employing copper(II) acetate as the catalyst in the absence of external ligands, without the need for protection from air or water. An unusual feature of this process, for the case of acetylenic ketones, is the ability of the initial conjugate-addition product to serve as a ligand for the catalyst, which enables it to participate in the catalysis of its further transformation to the final indole product. Mechanistic studies, including EPR experiments, indicated that copper(II) is reduced to the active copper(I) species by the formate ion that is produced by the base-catalyzed hydrolysis of DMF. This process also served to recycle any copper(II) that was produced by the adventitious oxidation of copper(I), thereby preventing deactivation of the catalyst. Several examples of reactions involving acetylenic sulfones attached to a modified Merrifield resin demonstrated the feasibility of solid-phase synthesis of indoles by using this protocol, and tricyclic products were obtained in one pot by employing acetylenic sulfones that contain chloroalkyl substituents. PMID:23019064

  7. Serum PDGF-AB in pleural mesothelioma.

    PubMed

    Filiberti, Rosa; Marroni, Paola; Neri, Monica; Ardizzoni, Andrea; Betta, Pier Giacomo; Cafferata, Mara A; Canessa, Pier Aldo; Puntoni, Riccardo; Ivaldi, Giovanni Paolo; Paganuzzi, Michela

    2005-01-01

    Overexpression of platelet-derived growth factor (PDGF) has been observed in lung and pleural tumors. The aim of this study was to evaluate the diagnostic and prognostic role of serum PDGF in pleural mesothelioma (PM). Four groups of subjects were studied: 93 malignant PM patients, 33 primary non small cell lung cancer patients, 51 subjects exposed to asbestos, defined as high-risk controls, and 24 healthy controls. PDGF-AB mean concentration was higher in PM patients (45.8 ng/ml) than in high-risk controls (33.1 ng/ml) and healthy controls (26.8 ng/ml). Using the cut-off level of 49.8 ng/ml, corresponding to the mean+2SD of PDGF-AB in healthy controls, 43% of PM patients showed positive PDGF-AB levels. Survival was evaluated in 82 PM patients. At the end of the follow-up (median 9.8 months) 80.5% of patients had died. Median survival was 13.1 and 7.9 months for patients with PDGF-AB lower and higher than the cut-off, respectively. Adjusting for age, sex, histology and platelet count, positive PDGF-AB levels were associated with lower survival (OR=1.2, 95%CI: 0.9-1.6), even if not significantly so. In conclusion, serum PDGF may represent a useful additional parameter to prognostic factors already available for PM.

  8. Copper ion detection using novel silver nanoclusters stabilized with amido black 10B.

    PubMed

    Ma, Fangfang; Liang, Sheng; Peng, Yibo; Kuang, Yangfang; Zhang, Xing; Chen, Shu; Long, Yunfei; Zeng, Rongjin

    2016-05-01

    Novel fluorescent silver nanoclusters (AgNCs) were synthesized using amido black 10B (AB) as a stabilizing agent and then employed for the detection of copper ions (Cu(2+)). The AB-stabilized AgNCs (AB-AgNCs) were well dispersed in aqueous solution with an average diameter of around 1.3 nm and exhibited illustrious blue fluorescence emission. Moreover, the fluorescence of AB-AgNCs could be quenched efficiently by Cu(2+), which might be a result of the coordination between Cu(2+) and the free recognition group of AB on surfaces of AB-AgNCs, inducing the aggregation of AB-AgNCs. Based on the linear decrease of fluorescence intensity, the Cu(2+) concentration was determined in the range of 0.01-1.1 μmol L(-1) and the limit of detection (LOD) was 4.0 nΜ. In addition, the detection of Cu(2+) could be performed with AB-AgNCs in the presence of other ions, including 13 kinds of conventional metal ions and 11 kinds of anions. Based on the above experiment, the developed AB-AgNC probe was successfully further applied to detect Cu(2+) in three electroplating effluents, which showed high accuracy. PMID:26873219

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

    NASA Astrophysics Data System (ADS)

    Nadeem, Shahid; Dörsch, Peter; Bakken, Lars

    2013-04-01

    Denitrification allows microorganisms to sustain respiration under anoxic conditions. The typical niche for denitrification is an environment with fluctuating oxygen concentrations such as soils and borders between anoxic and oxic zones of biofilms and sediments. In such environments, the organisms need adequate regulation of denitrification in response to changing oxygen availability to tackle both oxic and anoxic spells. The regulation of denitrification in soils has environmental implications, since it affects the proportions of N2, N2O and NO emitted to the atmosphere. The expression of denitrification enzymes is regulated by a complex regulatory network involving one or several positive feedback loops via the intermediate nitrogen oxides. Nitric oxide (NO) is known to induce denitrification in model organisms, but the quantitative effect of NO and its concentration dependency has not been assessed for denitrification in soils. NO is chemically unstable in the presence of oxygen due to autoxidation, and the oxidation of NO is accelerated by acetylene (C2H2) which is commonly used as an inhibitor of N2O reductase in denitrification studies. As a first step to a better understanding of NO's role in soil denitrification, we investigated NO oxidation kinetics for a closed "two phase" system (i.e. liquid phase + headspace) typically used for denitrification experiments with soil slurries, with and without acetylene present. Models were developed to adequately predict autoxidation and acetylene-accelerated oxidation. The minimum oxygen concentration in the headspace ([O2]min, mL L-1) for acetylene-accelerated NO oxidation was found to increase linearly with the NO concentration ([NO], mL L-1); [O2]min= 0.192 + [NO]*0.1 (r2=0.978). The models for NO oxidation were then used to assess NO-oxidation rates in denitrification experiments with batches of bacterial cells extracted from soil. The batches were exposed to low initial oxygen concentrations in gas tight serum

  10. Atomic and electronic structure of exfoliated black phosphorus

    SciTech Connect

    Wu, Ryan J.; Topsakal, Mehmet; Jeong, Jong Seok; Wentzcovitch, Renata M.; Mkhoyan, K. Andre; Low, Tony; Robbins, Matthew C.; Haratipour, Nazila; Koester, Steven J.

    2015-11-15

    Black phosphorus, a layered two-dimensional crystal with tunable electronic properties and high hole mobility, is quickly emerging as a promising candidate for future electronic and photonic devices. Although theoretical studies using ab initio calculations have tried to predict its atomic and electronic structure, uncertainty in its fundamental properties due to a lack of clear experimental evidence continues to stymie our full understanding and application of this novel material. In this work, aberration-corrected scanning transmission electron microscopy and ab initio calculations are used to study the crystal structure of few-layer black phosphorus. Directly interpretable annular dark-field images provide a three-dimensional atomic-resolution view of this layered material in which its stacking order and all three lattice parameters can be unambiguously identified. In addition, electron energy-loss spectroscopy (EELS) is used to measure the conduction band density of states of black phosphorus, which agrees well with the results of density functional theory calculations performed for the experimentally determined crystal. Furthermore, experimental EELS measurements of interband transitions and surface plasmon excitations are also consistent with simulated results. Finally, the effects of oxidation on both the atomic and electronic structure of black phosphorus are analyzed to explain observed device degradation. The transformation of black phosphorus into amorphous PO{sub 3} or H{sub 3}PO{sub 3} during oxidation may ultimately be responsible for the degradation of devices exposed to atmosphere over time.

  11. Ab interno trabeculectomy: patient selection and perspectives.

    PubMed

    Vinod, Kateki; Gedde, Steven J

    2016-01-01

    Ab interno trabeculectomy is one among several recently introduced minimally invasive glaucoma surgeries that avoid a conjunctival incision and full-thickness sclerostomy involved in traditional glaucoma surgery. Ablation of the trabecular meshwork and inner wall of Schlemm's canal is performed in an arcuate fashion via a clear corneal incision, alone or in combination with phacoemulsification cataract surgery. Intraocular pressure reduction following ab interno trabeculectomy is limited by resistance in distal outflow pathways and generally stabilizes in the mid-to-high teens. Relief of medication burden has been demonstrated by some studies. A very low rate of complications, most commonly transient hyphema and intraocular pressure elevations in the immediate postoperative period, have been reported. However, available data are derived from small retrospective and prospective case series. Randomized, controlled trials are needed to better elucidate the potential merits of ab interno trabeculectomy in the combined setting versus phacoemulsification cataract surgery alone and to compare it with other minimally invasive glaucoma surgeries. PMID:27574396

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

    NASA Astrophysics Data System (ADS)

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

    2013-10-01

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

  13. Metastable argon atom density in complex argon/acetylene plasmas determined by means of optical absorption and emission spectroscopy

    NASA Astrophysics Data System (ADS)

    Sushkov, Vladimir; Herrendorf, Ann-Pierra; Hippler, Rainer

    2016-10-01

    Optical emission and absorption spectroscopy has been utilized to investigate the instability of acetylene-containing dusty plasmas induced by growing nano-particles. The density of Ar(1s5) metastable atoms was derived by two methods: tunable diode laser absorption spectroscopy and with the help of the branching ratio method of emitted spectral lines. Results of the two techniques agree well with each other. The density of Ar(1s3) metastable atoms was also measured by means of optical emission spectroscopy. The observed growth instability leads to pronounced temporal variations of the metastable and other excited state densities. An analysis of optical line ratios provides evidence for a depletion of free electrons during the growth cycle but no indication for electron temperature variations.

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

    SciTech Connect

    Cheng, Bing-Ming; Chen, Hui-Fen; Lu, Hsiao-Chi; Chen, Hong-Kai; Alam, M. S.; Chou, Sheng-Lung; Lin, Meng-Yeh

    2011-09-01

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

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

    PubMed

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

    2014-01-13

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

  16. Trapping aryl radicals with acetylene: Evidence for C{sub 2}-accretion as a mechanism for polycyclic aromatic hydrocarbon growth

    SciTech Connect

    Necula, A.; Scott, L.T.

    2000-02-23

    The formation of polycyclic aromatic hydrocarbons (PAH), fullerenes, soot, and other carbonaceous materials during the combustion or pyrolysis of low-molecular weight hydrocarbons requires, at a minimum, that small molecules and/or reactive intermediates somehow become joined to make larger ones. Most likely, more than one type of intermolecular C-C bond-forming reaction plays a role. The accretion of C{sub 2}-units has long been considered a probable pathway for the stepwise growth of PAH in flames, but evidence also points to the operation of bimolecular processes in which both partners can be relatively large. The experiments reported here address the former paradigm and provide clear support for a specific C{sub 2}-accretion pathway in which the key C-C bond-forming step involves the simple trapping of aryl radicals by acetylene (C{sub 2}H{sub 2}), both of which are abundant species in flames.

  17. Rapid Diamond Deposition on Ni and Co Coatings by Using Twin Acetylene/Oxygen Gas Welding Torches

    NASA Astrophysics Data System (ADS)

    Ando, Yasutaka; Noda, Yoshimasa; Adachi, Shin-ichiro

    2015-12-01

    Cermet coatings have been widely used because of their high hardness and excellent wear resistance even under high-temperature conditions. However, since cermet coatings include expensive materials such as WC, TiC, TiN and so on, low-cost hard particles as a dispersing agent need to be developed. In this study, in order to develop a low-cost diamond dispersion system for the creation of diamond/thermal sprayed metal hybrid coatings, diamond deposition on thermal sprayed Ni and Co coatings and Mo and Ni metal substrates by the combustion flame method using twin acetylene/oxygen gas welding torches was carried out. Consequently, even in cases of thermal sprayed Ni and Co coatings, diamond particles could be deposited within only 5 min. From these results, this technique is proved to have a high potential for rapid diamond deposition in order to create diamond/thermal sprayed metal hybrid coatings.

  18. Wavelength modulation spectroscopy at 1530.32 nm for measurements of acetylene based on Fabry-Perot tunable filter

    NASA Astrophysics Data System (ADS)

    Yun-Long, Li; Bing-Chu, Yang; Xue-Mei, Xu

    2016-02-01

    Sensitive detection of acetylene (C2H2) is performed by absorption spectroscopy and wavelength modulation spectroscopy (WMS) based on Fiber Fabry-Perot tunable filter (FFP-TF) at 1530.32 nm. After being calibrated by Fiber Bragg Grating (FBG), FFP-TF is frequency-multiplexed and modulated at 20 Hz and 2.5 kHz respectively to achieve wavelength modulation. The linearity with 0.9907 fitting coefficient is obtained by measuring different concentrations in a 100 ppmv-400 ppmv range. Furthermore, the stability of the system is analyzed by detecting 50 ppmv and 100 ppmv standard gases for 2 h under room temperature and ambient pressure conditions respectively. The precision of 11 ppmv is achieved by calculating the standard deviation. Therefore, the measuring system of C2H2 detection can be applied in practical applications. Project supported by the National Natural Science Foundation of China (Grant Nos. 61172047 and 61071025).

  19. Mid-Infrared Pumped Laser-Induced Thermal Grating Spectroscopy for Detection of Acetylene in the Visible Spectral Range.

    PubMed

    Sahlberg, Anna-Lena; Kiefer, Johannes; Aldén, Marcus; Li, Zhongshan

    2016-06-01

    We present mid-infrared laser-induced thermal grating spectroscopy (IR-LITGS) using excitation radiation around 3 µm generated by a simple broadband optical parametric oscillator (OPO). Acetylene as a typical small hydrocarbon molecule is used as an example target species. A mid-infrared broadband OPO pumped by the fundamental output of a neodymium-doped yttrium aluminum garnet (Nd:YAG) laser was used to generate the pump beams, with pulse energies of 6-10 mJ depending on the wavelength. The line width of the OPO idler beam was ∼5 cm(-1), which is large enough to cover up to six adjacent acetylene lines. The probe beam was the radiation of a 532 nm cw solid state laser with 190 mW output power. Signals were generated in atmospheric pressure gas flows of N2, air, CO2 and Ar with small admixtures of C2H2 A detection limit of less than 300 ppm was found for a point measurement of C2H2 diluted in N2 As expected, the oscillation frequency of the IR-LITGS signal was found to have a large dependency on the buffer gas, which allows determination of the speed of sound. Moreover, the results reveal a very strong collisional energy exchange between C2H2 and CO2 compared to the other gases. This manifests as significant local heating. In summary, the MIR-LITGS technique enables spectroscopy of fundamental vibrational transitions in the infrared via detection in the visible spectral range. PMID:27091904

  20. Fabrication and Characterization of Nanocarbon-Based Nanofluids by Using an Oxygen-Acetylene Flame Synthesis System

    NASA Astrophysics Data System (ADS)

    Teng, Tun-Ping; Wang, Wei-Ping; Hsu, Yu-Chun

    2016-06-01

    In this study, an oxygen-acetylene flame synthesis system was developed to fabricate nanocarbon-based nanofluids (NCBNFs) through a one-step synthesis method. Measured in liters per minute (LPM), the flame's fuel flows combined oxygen and acetylene at four ratios: 1.5/2.5 (P1), 1.0/2.5 (P2), 0.5/2.5 (P3), and 0/2.5 (P4). The flow rate of cooling water (base fluid) was fixed at 1.2 LPM to produce different nanocarbon-based materials (NCBMs) and various concentrations of NCBNFs. Tests and analyses were conducted for determining the morphology of NCBMs, NCBM material, optical characteristics, the production rate, suspension performance, average particle size, zeta potential, and other relevant basic characteristics of NCBNFs to understand the characteristics and materials of NCBNFs produced through different process parameters (P1-P4). The results revealed that the NCBMs mainly had flaky and spherical morphologies and the diameters of the spherical NCBMs measured approximately 20-30 nm. X-ray diffraction and Raman spectroscopy revealed that the NCBMs contained graphene oxide (GO) and amorphous carbon (AC) when the oxygen flow rate was lower than 1.0 LPM. In addition, the NCBMs contained reduced GO, crystalline graphite (graphite-2H), and AC when the oxygen flow rate was higher than 1.0 LPM. The process parameters of P1, P2, P3, and P4 resulted in NCBMs produced at concentrations of 0.010, 0.013, 0.040, and 0.023 wt%, respectively, in NCBNFs. All the NCBNFs exhibited non-Newtonian and shear-thinning rheological properties. The P4 ratio showed the highest enhancement rate of thermal conductivity for NCBNFs, at a rate 4.85 % higher than that of water.

  1. Fabrication and Characterization of Nanocarbon-Based Nanofluids by Using an Oxygen-Acetylene Flame Synthesis System.

    PubMed

    Teng, Tun-Ping; Wang, Wei-Ping; Hsu, Yu-Chun

    2016-12-01

    In this study, an oxygen-acetylene flame synthesis system was developed to fabricate nanocarbon-based nanofluids (NCBNFs) through a one-step synthesis method. Measured in liters per minute (LPM), the flame's fuel flows combined oxygen and acetylene at four ratios: 1.5/2.5 (P1), 1.0/2.5 (P2), 0.5/2.5 (P3), and 0/2.5 (P4). The flow rate of cooling water (base fluid) was fixed at 1.2 LPM to produce different nanocarbon-based materials (NCBMs) and various concentrations of NCBNFs. Tests and analyses were conducted for determining the morphology of NCBMs, NCBM material, optical characteristics, the production rate, suspension performance, average particle size, zeta potential, and other relevant basic characteristics of NCBNFs to understand the characteristics and materials of NCBNFs produced through different process parameters (P1-P4). The results revealed that the NCBMs mainly had flaky and spherical morphologies and the diameters of the spherical NCBMs measured approximately 20-30 nm. X-ray diffraction and Raman spectroscopy revealed that the NCBMs contained graphene oxide (GO) and amorphous carbon (AC) when the oxygen flow rate was lower than 1.0 LPM. In addition, the NCBMs contained reduced GO, crystalline graphite (graphite-2H), and AC when the oxygen flow rate was higher than 1.0 LPM. The process parameters of P1, P2, P3, and P4 resulted in NCBMs produced at concentrations of 0.010, 0.013, 0.040, and 0.023 wt%, respectively, in NCBNFs. All the NCBNFs exhibited non-Newtonian and shear-thinning rheological properties. The P4 ratio showed the highest enhancement rate of thermal conductivity for NCBNFs, at a rate 4.85 % higher than that of water. PMID:27295256

  2. What Black Business Leaders Can Do for the Black Community.

    ERIC Educational Resources Information Center

    Johnson, John H.

    1985-01-01

    The existence of viable Black businesses is a statement of productivity and hope for the Black community. Black business leaders can help Black America by giving, soliciting, and lending money; by setting examples; by advocating for Black economic progress and change; and by providing opportunities for Black youth. (GC)

  3. MELCOR 1.8.2 assessment: Aerosol experiments ABCOVE AB5, AB6, AB7, and LACE LA2

    SciTech Connect

    Souto, F.J.; Haskin, F.E.; Kmetyk, L.N.

    1994-10-01

    The MELCOR computer code has been used to model four of the large-scale aerosol behavior experiments conducted in the Containment System Test Facility (CSTF) vessel. Tests AB5, AB6 and AB7 of the ABCOVE program simulate the dry aerosol conditions during a hypothetical severe accident in an LMFBR. Test LA2 of the LACE program simulates aerosol behavior in a condensing steam environment during a postulated severe accident in an LWR with failure to isolate the containment. The comparison of code results to experimental data show that MELCOR is able to correctly predict most of the thermal-hydraulic results in the four tests. MELCOR predicts reasonably well the dry aerosol behavior of the ABCOVE tests, but significant disagreements are found in the aerosol behavior modelling for the LA2 experiment. These results tend to support some of the concerns about the MELCOR modelling of steam condensation onto aerosols expressed in previous works. During these analyses, a limitation in the MELCOR input was detected for the specification of the aerosol parameters for more than one component. A Latin Hypercube Sampling (LHS) sensitivity study of the aerosol dynamic constants is presented for test AB6. The study shows the importance of the aerosol shape factors in the aerosol deposition behavior, and reveals that MELCOR input/output processing is highly labor intensive for uncertainty and sensitivity analyses based on LHS.

  4. NASA Now: Black Holes

    NASA Video Gallery

    In this NASA Now episode, Dr. Daniel Patnaude talks about how his team discovered a baby black hole, why this is important and how black holes create tidal forces. Throughout his discussion, Patnau...

  5. Black widow spider (image)

    MedlinePlus

    ... the southern areas of the United States. The black widow makes her home in wood piles, under eaves, and other undisturbed places. The bite of a black widow can be serious and require medical attention. ...

  6. The Black Studies Boondoggle

    ERIC Educational Resources Information Center

    Long, Richard A.

    1970-01-01

    Indicates tendencies dangerous to the basic purpose of Black Studies, and identifies four external challeges--imperialism, paternalism, nihilism, and materialism. An internal challenge is considered to be the use of European and Establishment constructs to analyze black reality. (DM)

  7. Black and white psychiatrists: therapy with blacks.

    PubMed

    Jones, B E; Gray, B A

    1985-01-01

    This paper is one of a series of reports on the findings of a survey on psychotherapy with nonpsychotic black patients and black and white psychiatrists. The responses of the two groups of psychiatrists are presented and analyzed, focusing on their clinical experiences with their black patients. The differences between the two groups of psychiatrists on the presenting problems, unconscious conflicts, and role of racism with their black patients are among the clinical areas examined and discussed.The psychiatrists treated similar types of black male and female patients; however, the survey results indicate that a large proportion of white psychiatrists have little or no experience treating blacks. Although there were more similarities than differences in responses of black and white psychiatrists to clinical questions, there were differences in the frequency and order in which problems were rated. For example, both groups of psychiatrists rated developing new coping mechanisms as the most frequent problem in stages of the treatment process for both sexes. However, white psychiatrists rated a majority of the problems in stages of the treatment process as occurring more frequently than did black psychiatrists. The findings substantiate difficulties with clinical treatment by a therapist who has a racial, ethnic, or cultural background different from that of his patient.

  8. Black holes without firewalls

    NASA Astrophysics Data System (ADS)

    Larjo, Klaus; Lowe, David A.; Thorlacius, Larus

    2013-05-01

    The postulates of black hole complementarity do not imply a firewall for infalling observers at a black hole horizon. The dynamics of the stretched horizon, that scrambles and reemits information, determines whether infalling observers experience anything out of the ordinary when entering a large black hole. In particular, there is no firewall if the stretched horizon degrees of freedom retain information for a time of the order of the black hole scrambling time.

  9. Accelerating black diholes and static black dirings

    SciTech Connect

    Teo, Edward

    2006-01-15

    We show how a recently discovered black-ring solution with a rotating 2-sphere can be turned into two new solutions of Einstein-Maxwell-dilaton theory. The first is a four-dimensional solution describing a pair of oppositely charged, extremal black holes--known as a black dihole--undergoing uniform acceleration. The second is a five-dimensional solution describing a pair of concentric, static extremal black rings carrying opposite dipole charges--a so-called black diring. The properties of both solutions, which turn out to be formally very similar, are analyzed in detail. We also present, in an appendix, an accelerating version of the Zipoy-Voorhees solution in four-dimensional Einstein gravity.

  10. Marketing for Black Alums.

    ERIC Educational Resources Information Center

    Harris, Tracy A.

    1994-01-01

    Considers need for colleges and universities to develop effective marketing plan for recruitment of black students. Highlights advantages of designing marketing plan for recruitment of black alumni to assist in recruitment and retention of black students. Identifies key indicators that often hinder institutions in their recruitment of black…

  11. The Nearest Black Hole

    NASA Technical Reports Server (NTRS)

    Oliversen, Ronald (Technical Monitor); Garcia, Michael

    2005-01-01

    The goal of this program is to study black holes, both in our Galaxy and in nearby galaxies. We aim to study both 'stellar mass' x-ray binaries containing black holes (both in our Galaxy and in nearby galaxies), and super-massive black holes in nearby galaxies.

  12. The Non-Black Teacher, Black Literature, and Black Students

    ERIC Educational Resources Information Center

    Shepard, Ray Anthony

    1970-01-01

    Criticizes Keneth Kinnamon's advice in his article Afro-American Literature, the Black Revolution, and Ghetto High Schools," English Journal," vol. 5., no. 2 (February 1970), pp. 189-94 (see TE 200 536). (SW)

  13. Theoretical studies of neutral radical reactions including quasiclassical trajectory studies on the CH2 and HNO potential surfaces and statistical RRKM studies of reactions of C, CH, and CH2 with acetylene

    NASA Astrophysics Data System (ADS)

    Guadagnini, Renee Anna

    1998-11-01

    +NO nonreactive collisions, we obtain vibrational and rotational distributions that are somewhat closer to experiment than obtained previously by theory. We studied C, CH and CH2 reactions with acetylene using variational RRKM theory and ab initio potential surfaces. The resulting rate constants are in excellent agreement with experiment.

  14. Magnetized static black Saturn

    SciTech Connect

    Yazadjiev, Stoytcho S.

    2008-06-15

    We present a new static solution to the 5D Einstein-Maxwell equations describing a static black hole surrounded by a nonrotating dipole black ring. The configuration is kept in equilibrium by an external magnetic field interacting with the dipole charge of the black ring. The properties of the black Saturn-like configuration are studied and the basic physical quantities are calculated. The solution demonstrates 2-fold continuous nonuniqueness of the 5D magnetized static neutral black objects for fixed total mass and Melvin background.

  15. Black Hole Battery

    NASA Astrophysics Data System (ADS)

    Levin, Janna; D'Orazio, Daniel

    2016-03-01

    Black holes are dark dead stars. Neutron stars are giant magnets. As the neutron star orbits the black hole, an electronic circuit forms that generates a blast of power just before the black hole absorbs the neutron star whole. The black hole battery conceivably would be observable at cosmological distances. Possible channels for luminosity include synchro-curvature radiation, a blazing fireball, or even an unstable, short-lived black hole pulsar. As suggested by Mingarelli, Levin, and Lazio, some fraction of the battery power could also be reprocessed into coherent radio emission to populate a subclass of fast radio bursts.

  16. Searching for Black Holes

    NASA Technical Reports Server (NTRS)

    Garica, M.

    2001-01-01

    In 1995 we proposed to carry out ground-based observations in order to securely identify stellar mass black holes in our galaxy. This type 4 proposal under NASA's UV, Visible, and Gravitational Astrophysics program compliments NASA's space-based research by following up black hole candidates found and studied with space-based observatories, in order to determine if they are indeed black holes. While our primary goal is to securely identify black holes by measuring their masses, a secondary goal is identifying unique visible-range signatures for black holes.

  17. Nonstationary analogue black holes

    NASA Astrophysics Data System (ADS)

    Eskin, Gregory

    2014-12-01

    We study the existence of analogue nonstationary spherically symmetric black holes. The prime example is the acoustic model see Unruh (1981 Phys. Rev. Lett. 46 1351). We consider also a more general class of metrics that could be useful in other physical models of analogue black and white holes. We give examples of the appearance of black holes and of disappearance of white holes. We also discuss the relation between the apparent and the event horizons for the case of analogue black holes. In the end we study the inverse problem of determination of black or white holes by boundary measurements for the spherically symmetric nonstationary metrics.

  18. On the Strain Rate Sensitivity of Abs and Abs Plus Fused Deposition Modeling Parts

    NASA Astrophysics Data System (ADS)

    Vairis, A.; Petousis, M.; Vidakis, N.; Savvakis, K.

    2016-06-01

    In this work the effect of strain rate on the tensile strength of fused deposition modeling parts built with Acrylonitrile-butadiene-styrene (ABS) and ABS plus material is presented. ASTM D638-02a specimens were built with ABS and ABS plus and they were tested on a Schenck Trebel Co. tensile test machine at three different test speeds, equal, lower, and higher to the test speed required by the ASTM D638-02a standard. The experimental tensile strength results were compared and evaluated. The fracture surfaces of selected specimens were examined with a scanning electron microscope, to determine failure mode of the filament strands. It was found that, as the test speed increases, specimens develop higher tensile strength and have higher elastic modulus. Specimens tested in the highest speed of the experiment had on average about 10% higher elastic modulus and developed on average about 11% higher tensile strength.

  19. On the Strain Rate Sensitivity of Abs and Abs Plus Fused Deposition Modeling Parts

    NASA Astrophysics Data System (ADS)

    Vairis, A.; Petousis, M.; Vidakis, N.; Savvakis, K.

    2016-09-01

    In this work the effect of strain rate on the tensile strength of fused deposition modeling parts built with Acrylonitrile-butadiene-styrene (ABS) and ABS plus material is presented. ASTM D638-02a specimens were built with ABS and ABS plus and they were tested on a Schenck Trebel Co. tensile test machine at three different test speeds, equal, lower, and higher to the test speed required by the ASTM D638-02a standard. The experimental tensile strength results were compared and evaluated. The fracture surfaces of selected specimens were examined with a scanning electron microscope, to determine failure mode of the filament strands. It was found that, as the test speed increases, specimens develop higher tensile strength and have higher elastic modulus. Specimens tested in the highest speed of the experiment had on average about 10% higher elastic modulus and developed on average about 11% higher tensile strength.

  20. IMAGES OF BLACK AMERICANS

    PubMed Central

    Fiske, Susan T.; Bergsieker, Hilary B.; Russell, Ann Marie; Williams, Lyle

    2013-01-01

    Images of Black Americans are becoming remarkably diverse, enabling Barack Obama to defy simple-minded stereotypes and succeed. Understood through the Stereotype Content Model’s demonstrably fundamental trait dimensions of perceived warmth and competence, images of Black Americans show three relevant patterns. Stereotyping by omission allows non-Blacks to accentuate the positive, excluding any lingering negativity but implying it by its absence; specifically, describing Black Americans as gregarious and passionate suggests warmth but ignores competence and implies its lack. Obama’s credentials prevented him from being cast as incompetent, though the experience debate continued. His legendary calm and passionate charisma saved him on the warmth dimension. Social class subtypes for Black Americans differentiate dramatically between low-income Blacks and Black professionals, among both non-Black and Black samples. Obama clearly fit the moderately warm, highly competent Black-professional subtype. Finally, the campaign’s events (and nonevents) allowed voter habituation to overcome non-Blacks’ automatic emotional vigilance to Black Americans. PMID:24235974

  1. Masses and activity of AB Doradus B a/b. The age of the AB Dor quadruple system revisited

    NASA Astrophysics Data System (ADS)

    Wolter, U.; Czesla, S.; Fuhrmeister, B.; Robrade, J.; Engels, D.; Wieringa, M.; Schmitt, J. H. M. M.

    2014-10-01

    We present a multiwavelength study of the close binary AB Dor Ba/b (Rst137B). Our study comprises astrometric orbit measurements, optical spectroscopy, X-ray and radio observations. Using all available adaptive optics images of AB Dor B taken with VLT/NACO from 2004 to 2009, we tightly constrain its orbital period to 360.6 ± 1.5 days. We present the first orbital solution of Rst 137B and estimate the combined mass of AB Dor Ba+b as 0.69+0.02-0.24 M⊙, slightly exceeding previous estimates based on IR photometry. Our determined orbital inclination of Rst 137B is close to the axial inclination of AB Dor A inferred from Doppler imaging. Our VLT/UVES spectra yield high rotational velocities of ≥30 km s-1 for both components Ba and Bb, in accord with previous measurements, which corresponds to rotation periods significantly shorter than one day. Our combined spectral model, using PHOENIX spectra, yields an effective temperature of 3310 ± 50 K for the primary and approximately 60 K less for the secondary. The optical spectra presumably cover a chromospheric flare and show that at least one component of Rst 137B is significantly active. Activity and weak variations are also found in our simultaneous XMM-Newton observations, while our ATCA radio data yield constant fluxes at the level of previous measurements. Using evolutionary models, our newly determined stellar parameters confirm that the age of Rst 137B is between 50 and 100 Myr. Based on observations collected at the European Southern Observatory, Paranal, Chile, 383.D-1002(A) and the ESO Science Archive Facility. Using data obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member states and NASA. Using data obtained with the Australia Telescope Compact Array (ATCA) operated by the Commonwealth Scientific and Industrial Research Organisation (CSIRO).

  2. Prebiotic Atmospheric Chemistry on Titan: Formation Kinetics via Ab Initio Calculations for Potential Energy Surface (PES) Mapping

    NASA Astrophysics Data System (ADS)

    Gonzalez, Dayana; Mebel, Alexander

    2016-03-01

    It has been recently shown that Titan provides a unique perspective in our solar system: its atmosphere is comparable to a model of prebiotic Earth's. Provided the organic cationic and anionic molecular species identified by the Cassini spacecraft, this research characterizes reaction pathways for the reactions of methyl derivatives of the cyclopropenyl cation, the methyl cation with methyl- and dimethyl-acetylene, and reactions of resonance structures of protonated acrylonitrile with CH2NH. Isomerization and dissociation reactions involving methyl-cyclopropenyl cations, the perinaphthenyl cation and anion, and cations of pyrimidine and purine precursors of nucleobases will be examined to locate reaction pathways, intermediates, transition states, and products of the reactions. Gaussian '09 software is used for ab initio calculations to map out the PES. Geometry optimizations and vibrational frequency computations are preformed via the double-hybrid density functional B2PLYP-D3. Single-point energies are refined by use of the explicitly-correlated coupled-cluster CCSD(T)-F12 method. Rate constants are calculated using microcanonical RRKM theory, and pressure effects evaluated used the Master Equation approach; these allow for prediction of absolute rate constants and product branching ratios at different pressures and temperatures.

  3. Detection of acetylene impurities in ethylene and polyethylene manufacturing processes using tunable diode laser spectroscopy in the 3-μm range

    NASA Astrophysics Data System (ADS)

    Kluczynski, P.; Jahjah, M.; Nähle, L.; Axner, O.; Belahsene, S.; Fischer, M.; Koeth, J.; Rouillard, Y.; Westberg, J.; Vicet, A.; Lundqvist, S.

    2011-11-01

    Using recently developed GaInAsSb/AlGaInAsSb DFB lasers, tunable diode laser spectroscopy (TDLS) has been extended into the 3-μm wavelength region for the detection of acetylene impurities in hydrocarbon compounds encountered in ethylene manufacturing. Measurements of acetylene in pure polymer grade ethylene and in a gas mixture of ethylene and ethane typical of the process stream around a hydrogenation reactor have been performed. Using a procedure incorporating subtraction of a hydrocarbon background spectrum a detection limit of 5 ppb m was achieved under ordinary laboratory conditions. Under forced temperature cycling conditions, the detection limit deteriorated to 180 ppb m, due to temperature drift caused by optical interferences generated by reflections in the laser TO8 can.

  4. Xe-bearing hydrocarbon ions: Observation of Xe.acetylene+rad and Xe.benzene+rad radical cations and calculations of their ground state structures

    NASA Astrophysics Data System (ADS)

    Cui, Zhong-hua; Attah, Isaac K.; Platt, Sean P.; Aziz, Saadullah G.; Kertesz, Miklos; El-Shall, M. S.

    2016-04-01

    This work reports evidence for novel types of Xe-bearing hydrocarbon radical cations. The Xe.acetylene+rad radical cation adduct is observed at nearly room temperature using the mass-selected drift cell technique. The irreversible addition of the Xe atom and the lack of back dissociation to HCCH+rad + Xe is consistent with the calculated binding energy of 0.85 eV to be contrasted with the metastable nature of the neutral Xe.acetylene adduct. The observed Xe.benzene+rad radical cation appears to be a weakly bound complex stabilized mainly by ion-induced dipole interaction consistent with a calculated binding energy in the range of 0.14-0.17 eV.

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

    PubMed Central

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

    2015-01-01

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

  6. Observation of Coriolis Coupling between nu(2) + 4nu(4) and 7nu(4) in Acetylene &Xtilde;(1)Sigma(+)(g) by Stimulated Emission Pumping Spectroscopy.

    PubMed

    Moss; Duan; Jacobson; O'Brien; Field

    2000-02-01

    Stimulated emission pumping (SEP) spectroscopy has been used to examine a low energy region (E(vib) approximately 4400 cm(-1)) of &Xtilde;(1)Sigma(+)(g) acetylene at higher resolution than was possible in previous dispersed fluorescence studies. The expected bright state, nu(2) + 4nu(4), is observed to be coupled to the nearly degenerate 7nu(4) state by a Coriolis mechanism. A least-squares analysis yields values for zero-order vibrational energies, rotational constants, and a Coriolis-coupling coefficient that are all consistent with expectations. Calculated relative intensities of SEP transitions, accounting for interference due to axis-switching effects, are also consistent with observations. Implications of the observed Coriolis resonance with regard to global acetylene vibrational dynamics are also discussed. Copyright 2000 Academic Press.

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

    PubMed

    Liao, Rong-Zhen; Thiel, Walter

    2013-10-15

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

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

    NASA Astrophysics Data System (ADS)

    Manda, Abdullah Ahmed

    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

  9. Effect of Nitrate and Acetylene on nirS, cnorB, and nosZ Expression and Denitrification Activity in Pseudomonas mandelii▿

    PubMed Central

    Saleh-Lakha, Saleema; Shannon, Kelly E.; Henderson, Sherri L.; Zebarth, Bernie J.; Burton, David L.; Goyer, Claudia; Trevors, Jack T.

    2009-01-01

    Nitrate acts as an electron acceptor in the denitrification process. The effect of nitrate in the range of 0 to 1,000 mg/liter on Pseudomonas mandelii nirS, cnorB, and nosZ gene expression was studied, using quantitative reverse transcription-quantitative PCR. Denitrification activity was measured by using the acetylene blockage method and gas chromatography. The effect of acetylene on gene expression was assessed by comparing denitrification gene expression in P. mandelii culture grown in the presence or absence of acetylene. The higher the amount of NO3− present, the greater the induction and the longer the denitrification genes remained expressed. nirS gene expression reached a maximum at 2, 4, 4, and 6 h in cultures grown in the presence of 0, 10, 100, and 1,000 mg of KNO3/liter, respectively, while induction of nirS gene ranged from 12- to 225-fold compared to time zero. cnorB gene expression also followed a similar trend. nosZ gene expression did not respond to NO3− treatment under the conditions tested. Acetylene decreased nosZ gene expression but did not affect nirS or cnorB gene expression. These results showed that nirS and cnorB responded to nitrate concentrations; however, significant denitrification activity was only observed in culture with 1,000 mg of KNO3/liter, indicating that there was no relationship between gene expression and denitrification activity under the conditions tested. PMID:19525277

  10. Ab initio infrared and Raman spectra

    NASA Technical Reports Server (NTRS)

    Fredkin, D. R.; White, S. R.; Wilson, K. R.; Komornicki, A.

    1983-01-01

    It is pointed out that with increased computer power and improved computational techniques, such as the gradients developed in recent years, it is becoming practical to compute spectra ab initio, from the fundamental constants of nature, for systems of increasing complexity. The present investigation has the objective to explore several possible ab initio approaches to spectra, giving particular attention to infrared and nonresonance Raman. Two approaches are discussed. The sequential approach, in which first the electronic part and then later the nuclear part of the Born-Oppenheimer approximation is solved, is appropriate for small systems. The simultaneous approach, in which the electronic and nuclear parts are solved at the same time, is more appropriate for many-atom systems. A review of the newer quantum gradient techniques is provided, and the infrared and Raman spectral band contours for the water molecule are computed.

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

    SciTech Connect

    Gan, L.S.

    1986-01-01

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

  12. Ab interno trabeculectomy: patient selection and perspectives

    PubMed Central

    Vinod, Kateki; Gedde, Steven J

    2016-01-01

    Ab interno trabeculectomy is one among several recently introduced minimally invasive glaucoma surgeries that avoid a conjunctival incision and full-thickness sclerostomy involved in traditional glaucoma surgery. Ablation of the trabecular meshwork and inner wall of Schlemm’s canal is performed in an arcuate fashion via a clear corneal incision, alone or in combination with phacoemulsification cataract surgery. Intraocular pressure reduction following ab interno trabeculectomy is limited by resistance in distal outflow pathways and generally stabilizes in the mid-to-high teens. Relief of medication burden has been demonstrated by some studies. A very low rate of complications, most commonly transient hyphema and intraocular pressure elevations in the immediate postoperative period, have been reported. However, available data are derived from small retrospective and prospective case series. Randomized, controlled trials are needed to better elucidate the potential merits of ab interno trabeculectomy in the combined setting versus phacoemulsification cataract surgery alone and to compare it with other minimally invasive glaucoma surgeries. PMID:27574396

  13. Quantization of Black Holes

    NASA Astrophysics Data System (ADS)

    He, Xiao-Gang; Ma, Bo-Qiang

    We show that black holes can be quantized in an intuitive and elegant way with results in agreement with conventional knowledge of black holes by using Bohr's idea of quantizing the motion of an electron inside the atom in quantum mechanics. We find that properties of black holes can also be derived from an ansatz of quantized entropy Δ S = 4π k Δ R/{{-{λ }}}, which was suggested in a previous work to unify the black hole entropy formula and Verlinde's conjecture to explain gravity as an entropic force. Such an Ansatz also explains gravity as an entropic force from quantum effect. This suggests a way to unify gravity with quantum theory. Several interesting and surprising results of black holes are given from which we predict the existence of primordial black holes ranging from Planck scale both in size and energy to big ones in size but with low energy behaviors.

  14. Black branes as piezoelectrics.

    PubMed

    Armas, Jay; Gath, Jakob; Obers, Niels A

    2012-12-14

    We find a realization of linear electroelasticity theory in gravitational physics by uncovering a new response coefficient of charged black branes, exhibiting their piezoelectric behavior. Taking charged dilatonic black strings as an example and using the blackfold approach we measure their elastic and piezolectric moduli. We also use our results to draw predictions about the equilibrium condition of charged dilatonic black rings in dimensions higher than six.

  15. Naked black holes

    SciTech Connect

    Horowitz, G.T.; Ross, S.F.

    1997-08-01

    It is shown that there are large static black holes for which all curvature invariants are small near the event horizon, yet any object which falls in experiences enormous tidal forces {ital outside} the horizon. These black holes are charged and near extremality, and exist in a wide class of theories including string theory. The implications for cosmic censorship and the black hole information puzzle are discussed. {copyright} {ital 1997} {ital The American Physical Society}

  16. Black branes as piezoelectrics.

    PubMed

    Armas, Jay; Gath, Jakob; Obers, Niels A

    2012-12-14

    We find a realization of linear electroelasticity theory in gravitational physics by uncovering a new response coefficient of charged black branes, exhibiting their piezoelectric behavior. Taking charged dilatonic black strings as an example and using the blackfold approach we measure their elastic and piezolectric moduli. We also use our results to draw predictions about the equilibrium condition of charged dilatonic black rings in dimensions higher than six. PMID:23368298

  17. What Black Educators are Saying.

    ERIC Educational Resources Information Center

    Wright, Nathan, Jr., Ed.

    Contents of this book are comprised of five groups of articles: Part I. The Black Educator: "Education for black humanism; a way of approaching it," Preston Wilcox; "The new black dimension in our society," Olivia Pearl Stokes; "The black teacher and black Power," Leslie Campbell; and, "The difference," Leslie Campbell. Part II. The White…

  18. Stability of Black Holes and Black Branes

    NASA Astrophysics Data System (ADS)

    Hollands, Stefan; Wald, Robert M.

    2013-08-01

    We establish a new criterion for the dynamical stability of black holes in D ≥ 4 spacetime dimensions in general relativity with respect to axisymmetric perturbations: Dynamical stability is equivalent to the positivity of the canonical energy, {{E}}, on a subspace, {{T}}, of linearized solutions that have vanishing linearized ADM mass, momentum, and angular momentum at infinity and satisfy certain gauge conditions at the horizon. This is shown by proving that—apart from pure gauge perturbations and perturbations towards other stationary black holes—{{E}} is nondegenerate on {{T}} and that, for axisymmetric perturbations, {{E}} has positive flux properties at both infinity and the horizon. We further show that {{E}} is related to the second order variations of mass, angular momentum, and horizon area by {{E} = δ^2 M -sum_A Ω_A δ^2 J_A - κ/8πδ^2 A}, thereby establishing a close connection between dynamical stability and thermodynamic stability. Thermodynamic instability of a family of black holes need not imply dynamical instability because the perturbations towards other members of the family will not, in general, have vanishing linearized ADM mass and/or angular momentum. However, we prove that for any black brane corresponding to a thermodynamically unstable black hole, sufficiently long wavelength perturbations can be found with {{E} < 0} and vanishing linearized ADM quantities. Thus, all black branes corresponding to thermodynmically unstable black holes are dynamically unstable, as conjectured by Gubser and Mitra. We also prove that positivity of {{E}} on {{T}} is equivalent to the satisfaction of a " local Penrose inequality," thus showing that satisfaction of this local Penrose inequality is necessary and sufficient for dynamical stability. Although we restrict our considerations in this paper to vacuum general relativity, most of the results of this paper are derived using general Lagrangian and Hamiltonian methods and therefore can be

  19. Black nightshade poisoning

    MedlinePlus

    Nightshade poisoning; Morelle noire poisoning; Wonderberry poisoning ... Black nightshade poisoning can affect many areas of the body. EYES, EARS, NOSE, MOUTH, AND THROAT Dry mouth Enlarged (dilated) pupils ...

  20. Black stain - a review.

    PubMed

    Ronay, Valerie; Attin, Thomas

    2011-01-01

    The purpose of this review was to summarise the fundamentals about black stain, its diagnosis and possible differential diagnoses as well as its microbiology and therapy. In addition, various studies investigating the relationship between black stain and dental caries are examined. Many studies report lower caries prevalence in children with black stain, but this finding could not be confirmed by all authors. Also, a negative relation between degree of staining and caries severity has been described. Reasons for these results are not yet clear but it was speculated that they are related to the specific oral microflora described in black stain-affected individuals. PMID:21594205

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

    PubMed

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

    2013-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1984-01-01

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

  3. Abrasive Wear Behavior of WC Reinforced Ni-BASED Composite Coating Sprayed and Fused by Oxy-Acetylene Flame

    NASA Astrophysics Data System (ADS)

    Wang, Qun; Chen, Zhenhua; Ding, Zhang Xiong; Chen, Ding

    Microstructure of WC reinforced Ni-based self-fluxing alloy composite coating sprayed and fused by oxy-acetylene flame was investigated by scanning electron microscopy and energy dispersive X-ray Spectrometry, X-ray diffraction, and transmission electron microscopy. The wear performance of the coating was studied by a MLS-225 wet sand rubber wheel abrasive wear tester at various loads and sizes of abrasive particles. Also, the wear resistance of the coating was compared with uncoated ASTM1020 steel. The results indicated that the coating is bonded metallurgically to the substrate and has a homogeneous microstructure composed of both coarse WC and fine carbide and boride grains such as Cr7C3, Cr23C6, and Ni2B which disperse uniformly in the matrix of γ-Ni solid solution and Ni3B. The worn mass loss of the coating and ASTM1020 steel both increased with the load and size of abrasive particles, also, the coating has exhibited excellent abrasive wear resistance compared with ASTM1020 steel.

  4. Direct Observation of Cascade of Photoinduced Ultrafast Intramolecular Charge Transfer Dynamics in Diphenyl Acetylene Derivatives: Via Solvation and Intramolecular Relaxation.

    PubMed

    Karunakaran, Venugopal; Das, Suresh

    2016-07-21

    Interaction of light with electron donor-acceptor π-conjugated systems leading to intramolecular charge transfer (ICT) plays an essential role in transformation of light energy. Here the cascade of photoinduced ICT processes is directly observed by investigating the excited state relaxation dynamics of cyano and mono/di methoxy substituted diphenyl acetylene derivatives using femtosecond pump-probe spectroscopy and nanosecond laser flash photolysis. The femtosecond transient absorption spectra of the chromophores upon ultrafast excitation reveal the dynamics of intermediates involved in transition from initially populated Frank-Condon state to local excited state (LE). It also provides the dynamic details of the transition from the LE to the charge transfer state yielding the formation of the radical ions. Finally, the charge transfer state decays to the triplet state by geminate charge recombination. The latter dynamics are observed in the nanosecond transient absorption spectra. It is found that excited state relaxation pathways are controlled by different stages of solvation and intramolecular relaxation depending on the solvent polarity. The twisted ICT state is more stabilized (978 ps) in acetonitrile than cyclohexane where major components of transient absorption originate from the S1 state. PMID:27347705

  5. A stunning example for a spontaneous reaction with a complex mechanism: the vinylidene-acetylene cycloaddition reaction

    NASA Astrophysics Data System (ADS)

    Kraka, Elfi; Joo, Hyun; Cremer, Dieter

    2010-10-01

    The chelotropic addition reaction (1): singlet vinylidene + acetylene → methylenecyclopropene (MCP), was investigated using different levels of theory (B3LYP, CASSCF, CCSD(T), G2M) and different basis sets (6-31G(d,p), 6-311G(d,p), 6-311++G(3df,3pd), cc-pVTZ). The concerted reaction is spontaneous at room temperature (activation enthalpy of 3 kcal mol-1) and strongly exothermic (ΔE = -64 kcal mol-1; ΔH(298) = -59 kcal mol-1). Analysis of the reaction mechanism with the help of the Unified Reaction Valley approach reveals a complicated sequence of structural and electronic changes, which can be best described by partitioning the mechanism into seven phases: (1) van der Waals, (2) electrophilic attack, (3) biradical, (4) allene, (5) carbene, (6) ring closure, and (7) MCP formation phase. In the transient regions from one phase to the next, structures are located that possess properties of hidden transition states (TSs) or hidden intermediates, i.e. by variation of the electronic nature or the environment of the reaction complex, real TSs and/or real intermediates can be generated. There is indication that a given sequence of reaction phases is fixed for a wide variation in the electronic nature of the reaction complex and that other than just orbital symmetry principles play a decisive role for the reaction mechanism.

  6. Rotationally Resolved Vacuum Ultraviolet Resonance-Enhanced Multiphoton Ionization (VUV REMPI) of Acetylene via the G̃ Rydberg State.

    PubMed

    Schmidt-May, Alice F; Grütter, Monika; Neugebohren, Jannis; Kitsopoulos, T N; Wodtke, Alec M; Harding, Dan J

    2016-07-14

    We present a 1 + 1' resonance-enhanced multiphoton ionization (REMPI) scheme for acetylene via the linear G̃ 4sσ (1)Πu Rydberg state, offering partial rotational resolution and the possibility to detect excitation in both the cis- and trans-bending modes. The resonant transition to the G̃ state is driven by a vacuum ultraviolet (VUV) photon, generated by resonant four-wave mixing (FWM) in krypton. Ionization from the short-lived G̃ state then occurs quickly, driven by the high intensity of the residual light from the FWM process. We have observed nine bands in the region between 79 200 cm(-1) and 80 500 cm(-1) in C2H2 and C2D2. We compare our results with published spectra in this region and suggest alternative assignments for some of the Renner-Teller split bands. Similar REMPI schemes should be applicable to other small molecules with picosecond lifetime Rydberg states. PMID:27073931

  7. Synthesis of Highly Stable Silver-Loaded Vertical ZnO Nanowires Array and its Acetylene Sensing Properties

    NASA Astrophysics Data System (ADS)

    Uddin, Abu Sadat Mohammad Iftekhar; Chung, Gwiy-Sang

    2016-09-01

    A silver-loaded one-dimensional (1D) vertical ZnO nanowires (NWs) array synthesized by a facile seed mediated hydrothermal-RF magnetron sputtering method has been investigated for the fabrication of a highly stable and reproducible acetylene (C2H2) gas sensor. Successful immobilization of silver nanoparticles (NPs) as a sensitizer on the ZnO NWs array significantly enhanced the C2H2 sensing properties and showed a stable sensing performance. The grown structure exhibited high response magnitude (30.8 at 1000ppm), short response time (43s) and excellent selectivity at 220∘C. The enhanced performance can probably be accounted for the effect of combining the highly orientated ZnO NWs and catalytically active silver-based network. The superior sensing features toward C2H2 along with broad detection range (1-1000ppm), outstanding stability and excellent reproducibility indicate that the sensor is a promising candidate for practical applications.

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

    PubMed

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

    2012-03-22

    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)Π) + 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)Σ) + H(2) ((1)Σ(g)(+)). A computational kinetic study shows that, in agreement with the experimental evidence, the major products are PCCH(+)((2)Π) + H((2)S) at all temperatures. Only at very high temperatures is CCP(+)((1)Σ) + H(2) ((1)Σ(g)(+)) formed in non-negligible amounts. Therefore, only PCCH(+) should be formed in the interstellar medium.

  9. The Black Caucus Votes No

    ERIC Educational Resources Information Center

    Urban Review, 1972

    1972-01-01

    From a statement on media practices regarding the dissemination of a wide range of documentary and other programming about the state of Black America without any input, consultation, or decisions by black Americans, issued by the Congressional Black Caucus. (JM)

  10. Undoing Gender Through Legislation and Schooling: the Case of AB 537 and AB 394 IN California, USA

    NASA Astrophysics Data System (ADS)

    Knotts, Greg

    2009-11-01

    This article investigates California laws AB 537: The Student Safety and Violence Prevention Act of 2000, and the recently enacted AB 394: Safe Place to Learn Act. Both demand that gender identity and sexual orientation be added to the lexicon of anti-harassment protection in public education. However, despite these progressive measures, schools have an unconscious acceptance of heteronormativity and gendered norms, which undermines both the spirit and language of these laws. This paper examines how California schools can both change standard practices and realise the transformative social change that laws like AB 537 and AB 394 can instigate. I assert that the systemic implementation of these laws, through the adoption, enforcement and evaluation of existing AB 537 Task Force Recommendations, is necessary for their success. My second assertion is that AB 537 and AB 394 have the potential to change and reconstitute gender-based and heteronormative standards at school sites.

  11. 40 CFR 174.506 - Bacillus thuringiensis Cry34Ab1 and Cry35Ab1 proteins in corn; exemption from the requirement of...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... Cry35Ab1 proteins in corn; exemption from the requirement of a tolerance. 174.506 Section 174.506... thuringiensis Cry34Ab1 and Cry35Ab1 proteins in corn; exemption from the requirement of a tolerance. Residues of Bacillus thuringiensis Cry34Ab1 and Cry35Ab1 proteins in corn are exempted from the requirement of...

  12. 40 CFR 174.506 - Bacillus thuringiensis Cry34Ab1 and Cry35Ab1 proteins in corn; exemption from the requirement of...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... Cry35Ab1 proteins in corn; exemption from the requirement of a tolerance. 174.506 Section 174.506... thuringiensis Cry34Ab1 and Cry35Ab1 proteins in corn; exemption from the requirement of a tolerance. Residues of Bacillus thuringiensis Cry34Ab1 and Cry35Ab1 proteins in corn are exempted from the requirement of...

  13. 40 CFR 174.506 - Bacillus thuringiensis Cry34Ab1 and Cry35Ab1 proteins in corn; exemption from the requirement of...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... Cry35Ab1 proteins in corn; exemption from the requirement of a tolerance. 174.506 Section 174.506... thuringiensis Cry34Ab1 and Cry35Ab1 proteins in corn; exemption from the requirement of a tolerance. Residues of Bacillus thuringiensis Cry34Ab1 and Cry35Ab1 proteins in corn are exempted from the requirement of...

  14. Black Studies Year One.

    ERIC Educational Resources Information Center

    Long, Richard A.

    Though Dubois tried to begin a series of scientific studies on the Negro problem in America more than 70 years ago, only recently have attempts been made to present a true history of the Black man in institutions of higher learning. Until that time, the experience of the Black man was defined in Euro-American terms, or in most cases was completely…

  15. Black Males Left Behind

    ERIC Educational Resources Information Center

    Mincy, Ronald B., Ed.

    2006-01-01

    Despite the overall economic gains in the 1990s, many young black men continue to have the poorest life chances of anyone in our society. Joblessness and low earnings among these less-educated young adults are contributing to reductions in marriage, increases in nonmarital childbearing, and a host of other social problems. In "Black Males Left…

  16. The Black Woman's Burden

    ERIC Educational Resources Information Center

    Hayes, Dianne

    2012-01-01

    Not even the first lady of the most powerful nation in the world is immune to stereotypes that have plagued Black women since first setting foot on American soil. Stereotypes of being the "angry Black woman" and curiosity about differences in appearance still persist from the academy to 1600 Pennsylvania Ave. As African-American women rise in…

  17. Black English: Two Viewpoints.

    ERIC Educational Resources Information Center

    Kleederman, Frances

    This paper focuses on the two main schools of thought concerning the structure of Black English and its relationship to other dialects. One approach is that of the social dialectologists who claim that Black English shares features and origins of white non-standard Southern speech; the frequency with which specific features occur in actual speech…

  18. Learning Mathematics while Black

    ERIC Educational Resources Information Center

    Martin, Danny Bernard

    2012-01-01

    While research by scholars has contributed greatly to an emerging knowledge base on Black children and mathematics, there continues to be a dire need for insightful research that de-centers longstanding accounts that have contributed to the construction of Black children as mathematically illiterate and as less than ideal learners relative to…

  19. Black Families. Interdisciplinary Perspectives.

    ERIC Educational Resources Information Center

    Cheatham, Harold E., Ed.; Stewart, James B., Ed.

    Since the early 1960s, the black family has been characterized as pathological. This six-part collection of 18 research studies presents alternative approaches to understanding the special characteristics of black families. Part I, "Theoretical and Methodological Perspectives," comprises a comparison of the pioneering work of W. E. B. Du Bois and…

  20. Black Women in Sport.

    ERIC Educational Resources Information Center

    Green, Tina Sloan; And Others

    An overview of the achievements of black women in sports is presented in this collection of essays, biographical sketches, and philosophical investigations. The work is divided into five chapters, the first of which focuses on prejudice (racial and sexual), absence of black women as subjects in the research base, work/home/family pressures, black…

  1. Arbitrators, Blacks and Discipline

    ERIC Educational Resources Information Center

    Jennings, Kenneth

    1975-01-01

    A discussion of the handling of disciplinary problems of black employees concludes that management should be concerned because of the effect that grievance resolution may have on the company's overall employee discipline program and the additional appeal alternatives available to the black employee. (Author/EA)

  2. Black phosphorus gas sensors.

    PubMed

    Abbas, Ahmad N; Liu, Bilu; Chen, Liang; Ma, Yuqiang; Cong, Sen; Aroonyadet, Noppadol; Köpf, Marianne; Nilges, Tom; Zhou, Chongwu

    2015-05-26

    The utilization of black phosphorus and its monolayer (phosphorene) and few-layers in field-effect transistors has attracted a lot of attention to this elemental two-dimensional material. Various studies on optimization of black phosphorus field-effect transistors, PN junctions, photodetectors, and other applications have been demonstrated. Although chemical sensing based on black phosphorus devices was theoretically predicted, there is still no experimental verification of such an important study of this material. In this article, we report on chemical sensing of nitrogen dioxide (NO2) using field-effect transistors based on multilayer black phosphorus. Black phosphorus sensors exhibited increased conduction upon NO2 exposure and excellent sensitivity for detection of NO2 down to 5 ppb. Moreover, when the multilayer black phosphorus field-effect transistor was exposed to NO2 concentrations of 5, 10, 20, and 40 ppb, its relative conduction change followed the Langmuir isotherm for molecules adsorbed on a surface. Additionally, on the basis of an exponential conductance change, the rate constants for adsorption and desorption of NO2 on black phosphorus were extracted for different NO2 concentrations, and they were in the range of 130-840 s. These results shed light on important electronic and sensing characteristics of black phosphorus, which can be utilized in future studies and applications.

  3. Black Craftsmen Through History.

    ERIC Educational Resources Information Center

    Myers, Robin

    This report traces the evolution of the black craftsmen from ancient Egypt to the present. Special attention is given to the restricted use of black craftsmen under slavery, and the added problems they faced after being freed. Business and union discimination is described, along with recent government and private efforts to achieve equal…

  4. They Made Black History.

    ERIC Educational Resources Information Center

    Elward, Thomas J.

    1981-01-01

    Reviews the history of Black music education in the public schools of Washington, D.C., from 1869 through the 1920s. Appended (on pp38-39) are historical notes on Black composers James Weldon Johnson and John Rosamond Johnson, and their song "Lift Ev'ry Voice and Sing." (Author/SJL)

  5. Ab initio melting curve of osmium

    NASA Astrophysics Data System (ADS)

    Burakovsky, L.; Burakovsky, N.; Preston, D. L.

    2015-11-01

    The melting curve of osmium up to a pressure P of 500 GPa is obtained from an extensive suite of ab initio quantum molecular dynamics (QMD) simulations using the Z method. The ab initio P =0 melting point of Os is 3370 ±75 K; this range encompasses all of the available data in the literature and corroborates the conclusion of J. W. Arblaster [Platinum Metals Rev. 49, 166 (2005)], 10.1595/147106705X70264 that the melting temperature of pure Os is 3400 ±50 K and that the 3300 K typically quoted in the literature is the melting point of impure Os. The T =0 equation of state (EOS) of Os and the P dependence of the optimized c /a ratio for the hexagonal unit cell, both to pressures ˜900 GPa, are obtained in the ab initio approach as validation of its use. Although excellent agreement with the available experimental data (P ≲80 GPa) is found, it is the third-order Birch-Murnaghan EOS with B0'=5 rather than the more widely accepted B0'=4 that describes the QMD data to higher pressures, in agreement with the more recent experimental EOS by Godwal et al. The theoretical melting curve of Os obtained earlier by Joshi et al. is shown to be inconsistent with our QMD results, and the possible reason for this discrepancy is suggested. Regularities in the melting curves of Os and five other third-row transition metals (Ta, W, Re, Pt, Au) could be used to estimate the currently unknown melting curves of Hf and Ir.

  6. Contact dermatitis in blacks.

    PubMed

    Berardesca, E; Maibach, H I

    1988-07-01

    Black skin is characterized by structural and functional differences such as increased stratum corneum cohesion, melanin content, and stratum corneum layers. These differences seem to make black skin difficult for irritants and light to penetrate, thus explaining the common opinion that skin in blacks is harder and develops contact dermatitis less frequently. The paucity of interpretable epidemiologic data and of clinical and experimental studies does not permit confirmation of this hypothesis, and the few data available are controversial. This article describes the main physiologic differences between black and white barrier function and reviews the literature on irritation, sensitization, and transcutaneous penetration. We found that the data are still too incomplete to generalize on the resistance, or lack thereof, of black skin (versus white skin) to chemical irritation, sensitization, and penetration. PMID:3048818

  7. American Black Duck

    USGS Publications Warehouse

    Longcore, J.R.; Clugston, D.A.; Mac, Michael J.; Opler, Paul A.; Puckett Haecker, Catherine E.; Doran, Peter D.

    1998-01-01

    A brief summary of the annual cycle of the American Black duck (Anas rubripes) is presented. The history of the American black duck population is tracked by the Mid-Winter Index (MWI) and related to annual harvest. Previous to effective restrictions in the United States in 1982 and later in Canada, the MWI was declining significantly at about 4% annually. Since restrictions were established the black duck population has stabilized, but to reach the goal of 260,000 wintering black ducks in the Atlantic Flyway continued or even more restrictions will be necessary. If the number of breeding pairs can be increased from current levels the black duck population is expected to increase.

  8. Contact dermatitis in blacks.

    PubMed

    Berardesca, E; Maibach, H I

    1988-07-01

    Black skin is characterized by structural and functional differences such as increased stratum corneum cohesion, melanin content, and stratum corneum layers. These differences seem to make black skin difficult for irritants and light to penetrate, thus explaining the common opinion that skin in blacks is harder and develops contact dermatitis less frequently. The paucity of interpretable epidemiologic data and of clinical and experimental studies does not permit confirmation of this hypothesis, and the few data available are controversial. This article describes the main physiologic differences between black and white barrier function and reviews the literature on irritation, sensitization, and transcutaneous penetration. We found that the data are still too incomplete to generalize on the resistance, or lack thereof, of black skin (versus white skin) to chemical irritation, sensitization, and penetration.

  9. Ab-initio phasing in protein crystallography

    NASA Astrophysics Data System (ADS)

    van der Plas, J. L.; Millane, Rick P.

    2000-11-01

    The central problem in the determination of protein structures form x-ray diffraction dada (x-ray crystallography) corresponds to a phase retrieval problem with undersampled amplitude data. Algorithms for this problem that have an increased radius of convergence have the potential for reducing the amount of experimental work, and cost, involved in determining protein structures. We describe such an algorithm. Application of the algorithm to a simulated crystallographic problem shows that it converges to the correct solution, with no initial phase information, where currently used algorithms fail. The results lend support to the possibility of ab initio phasing in protein crystallography.

  10. Testing Distributed ABS System with Fault Injection

    NASA Astrophysics Data System (ADS)

    Trawczyński, Dawid; Sosnowski, Janusz; Gawkowski, Piotr

    The paper deals with the problem of adapting software implemented fault injection technique (SWIFI) to evaluate dependability of reactive microcontroller systems. We present an original methodology of disturbing controller operation and analyzing fault effects taking into account reactions of the controlled object and the impact of the system environment. Faults can be injected randomly (in space and time) or targeted at the most sensitive elements of the controller to check it at high stresses. This approach allows identifying rarely encountered problems, usually missed in classical approaches. The developed methodology has been used successfully to verify dependability of ABS system. Experimental results are commented in the paper.

  11. New challenges to medicare beneficiary access to mAbs

    PubMed Central

    Wilson, Andrew

    2009-01-01

    Precision binding of monoclonal antibodies (mAbs) to biological targets, their relative clinical success, and expansion of indications following initial approval, are distinctive clinical features. The relatively high cost of mAbs, together with the absence of a regulatory pathway to generics, stand out as distinctive economic features. Based on both literature review and primary data collection we enumerated mAb original approvals, supplemental indications and off-label uses, assessed payer formulary management of mAbs, and determined new challenges to Medicare beneficiary access to mAbs. We found that the FDA has approved 22 mAbs and 30 supplemental indications pertaining to the originally approved mAbs. In addition, there are 46 off-label use citations in officially recognized pharmaceutical compendia. Across Part B carriers and Part D plans, we found considerable variation in terms of coverage and conditions of reimbursement related to on- and off-label uses of mAbs. Our results point to four major challenges facing mAb developers, health care providers, Medicare beneficiaries, payers and policymakers. These include administrative price controls, coverage variation, projected shift from physician- to self-administered mAbs, and comparative effectiveness. We suggest more systematic use of “coverage with evidence development” as a means of optimally addressing these challenges. PMID:20046575

  12. Atmospheric characterization of the hot Jupiter Kepler-13Ab

    SciTech Connect

    Shporer, Avi; O'Rourke, Joseph G.; Knutson, Heather A.; Szabó, Gyula M.; Zhao, Ming; Burrows, Adam; Fortney, Jonathan; Agol, Eric; Cowan, Nicolas B.; Desert, Jean-Michel; Howard, Andrew W.; Isaacson, Howard; Lewis, Nikole K.; Showman, Adam P.; Todorov, Kamen O.

    2014-06-10

    Kepler-13Ab (= KOI-13.01) is a unique transiting hot Jupiter. It is one of very few known short-period planets orbiting a hot A-type star, making it one of the hottest planets currently known. The availability of Kepler data allows us to measure the planet's occultation (secondary eclipse) and phase curve in the optical, which we combine with occultations observed by warm Spitzer at 4.5 μm and 3.6 μm and a ground-based occultation observation in the K{sub s} band (2.1 μm). We derive a day-side hemisphere temperature of 2750 ± 160 K as the effective temperature of a black body showing the same occultation depths. Comparing the occultation depths with one-dimensional planetary atmosphere models suggests the presence of an atmospheric temperature inversion. Our analysis shows evidence for a relatively high geometric albedo, A {sub g} = 0.33{sub −0.06}{sup +0.04}. While measured with a simplistic method, a high A {sub g} is supported also by the fact that the one-dimensional atmosphere models underestimate the occultation depth in the optical. We use stellar spectra to determine the dilution, in the four wide bands where occultation was measured, due to the visual stellar binary companion 1.''15 ± 0.''05 away. The revised stellar parameters measured using these spectra are combined with other measurements, leading to revised planetary mass and radius estimates of M{sub p} = 4.94-8.09 M {sub J} and R{sub p} = 1.406 ± 0.038 R {sub J}. Finally, we measure a Kepler midoccultation time that is 34.0 ± 6.9 s earlier than expected based on the midtransit time and the delay due to light-travel time and discuss possible scenarios.

  13. Black holes and beyond

    SciTech Connect

    Mathur, Samir D.

    2012-11-15

    The black hole information paradox forces us into a strange situation: we must find a way to break the semiclassical approximation in a domain where no quantum gravity effects would normally be expected. Traditional quantizations of gravity do not exhibit any such breakdown, and this forces us into a difficult corner: either we must give up quantum mechanics or we must accept the existence of troublesome 'remnants'. In string theory, however, the fundamental quanta are extended objects, and it turns out that the bound states of such objects acquire a size that grows with the number of quanta in the bound state. The interior of the black hole gets completely altered to a 'fuzzball' structure, and information is able to escape in radiation from the hole. The semiclassical approximation can break at macroscopic scales due to the large entropy of the hole: the measure in the path integral competes with the classical action, instead of giving a subleading correction. Putting this picture of black hole microstates together with ideas about entangled states leads to a natural set of conjectures on many long-standing questions in gravity: the significance of Rindler and de Sitter entropies, the notion of black hole complementarity, and the fate of an observer falling into a black hole. - Highlights: Black-Right-Pointing-Pointer The information paradox is a serious problem. Black-Right-Pointing-Pointer To solve it we need to find 'hair' on black holes. Black-Right-Pointing-Pointer In string theory we find 'hair' by the fuzzball construction. Black-Right-Pointing-Pointer Fuzzballs help to resolve many other issues in gravity.

  14. Black Literature vs. Black Studies: Three Lynchings.

    ERIC Educational Resources Information Center

    Williams, Melvin G.

    When studying Afro-American literature, even in an English class rather than Black Studies class, both student interest and the topic tend to lead discussion toward sociological, not literary, aspects. However, the teacher should emphasize repeatedly the aesthetic dimensions of an artistic work as well as the various literary forms in which a…

  15. Ab initio Study of HZnF

    NASA Astrophysics Data System (ADS)

    Hayashi, S.; Léonard, C.; Chambaud, G.

    2009-11-01

    On the basis of highly correlated ab initio calculations, an accurate determination of the electronic structure and of the rovibrational spectroscopy has been performed for the electronic ground state of the HZnF system. Using effective core pseudopotentials for the Zn and F atoms and associated aug-cc-pVQZ basis sets, we have calculated, at the multireference configuration interaction level including the Davidson correction, the three-dimensional potential energy surface of the X1Σ+ ground state. The rovibrational energy levels have been obtained variationally, and the results have been discussed and compared with existing experimental data on the ground state of the close system HZnCl, which exhibits a complicated vibration-rotation spectrum. Our analysis shows that the nature of the H-ZnF bond is quite similar to that of the H-ZnCl bond, according to their bond lengths, harmonic frequencies of the H-Zn stretching mode, and dissociation energies into H and ZnF/ZnCl. The ab initio study of the electronic ground and excited states of ZnH and ZnH+ are also presented using similar level of calculations. Characteristic constants are given for the first bounded electronic states correlating to the first two dissociation asymptotes of the neutral and ionic diatomics.

  16. Longitudinal wheel slip during ABS braking

    NASA Astrophysics Data System (ADS)

    Hartikainen, Lassi; Petry, Frank; Westermann, Stephan

    2015-02-01

    Anti-lock braking system (ABS) braking tests with two subcompact passenger cars were performed on dry and wet asphalt, as well as on snow and ice surfaces. The operating conditions of the tyres in terms of wheel slip were evaluated using histograms of the wheel slip data. The results showed different average slip levels for different road surfaces. It was also found that changes in the tyre tread stiffness affected the slip operating range through a modification of the slip value at which the maximum longitudinal force is achieved. Variation of the tyre footprint length through modifications in the inflation pressure affected the slip operating range as well. Differences in the slip distribution between vehicles with different brake controllers were also observed. The changes in slip operating range in turn modified the relative local sliding speeds between the tyre and the road. The results highlight the importance of the ABS controller's ability to adapt to changing slip-force characteristics of tyres and provide estimates of the magnitude of the effects of different tyre and road operating conditions.

  17. Ab initio non-relativistic spin dynamics

    SciTech Connect

    Ding, Feizhi; Goings, Joshua J.; Li, Xiaosong; Frisch, Michael J.

    2014-12-07

    Many magnetic materials do not conform to the (anti-)ferromagnetic paradigm where all electronic spins are aligned to a global magnetization axis. Unfortunately, most electronic structure methods cannot describe such materials with noncollinear electron spin on account of formally requiring spin alignment. To overcome this limitation, it is necessary to generalize electronic structure methods and allow each electron spin to rotate freely. Here, we report the development of an ab initio time-dependent non-relativistic two-component spinor (TDN2C), which is a generalization of the time-dependent Hartree-Fock equations. Propagating the TDN2C equations in the time domain allows for the first-principles description of spin dynamics. A numerical tool based on the Hirshfeld partitioning scheme is developed to analyze the time-dependent spin magnetization. In this work, we also introduce the coupling between electron spin and a homogenous magnetic field into the TDN2C framework to simulate the response of the electronic spin degrees of freedom to an external magnetic field. This is illustrated for several model systems, including the spin-frustrated Li{sub 3} molecule. Exact agreement is found between numerical and analytic results for Larmor precession of hydrogen and lithium atoms. The TDN2C method paves the way for the ab initio description of molecular spin transport and spintronics in the time domain.

  18. Ab initio non-relativistic spin dynamics

    NASA Astrophysics Data System (ADS)

    Ding, Feizhi; Goings, Joshua J.; Frisch, Michael J.; Li, Xiaosong

    2014-12-01

    Many magnetic materials do not conform to the (anti-)ferromagnetic paradigm where all electronic spins are aligned to a global magnetization axis. Unfortunately, most electronic structure methods cannot describe such materials with noncollinear electron spin on account of formally requiring spin alignment. To overcome this limitation, it is necessary to generalize electronic structure methods and allow each electron spin to rotate freely. Here, we report the development of an ab initio time-dependent non-relativistic two-component spinor (TDN2C), which is a generalization of the time-dependent Hartree-Fock equations. Propagating the TDN2C equations in the time domain allows for the first-principles description of spin dynamics. A numerical tool based on the Hirshfeld partitioning scheme is developed to analyze the time-dependent spin magnetization. In this work, we also introduce the coupling between electron spin and a homogenous magnetic field into the TDN2C framework to simulate the response of the electronic spin degrees of freedom to an external magnetic field. This is illustrated for several model systems, including the spin-frustrated Li3 molecule. Exact agreement is found between numerical and analytic results for Larmor precession of hydrogen and lithium atoms. The TDN2C method paves the way for the ab initio description of molecular spin transport and spintronics in the time domain.

  19. Quantum phases of AB 2 fermionic chains

    NASA Astrophysics Data System (ADS)

    Murcia-Correa, L. S.; Franco, R.; Silva-Valencia, J.

    2016-02-01

    A fermionic chain is a one-dimensional system with fermions that interact locally and can jump between sites in the lattice, in particular an AB n chain type, where A and B are sites that exhibit a difference in energy level of Δ and site B is repeated n-times, such that the unit cell has n +1 sites. A limit case of this model, called the ionic Hubbard model (n = 1), has been widely studied due to its interesting physics and applications. In this paper, we study the ground state of an AB 2 chain, which describes the material R 4[Pt 2(P 2O5H2)4X] · nH 2 O. Specifically, we consider a filling with two electrons per unit cell, and using the density matrix renormalization group method we found that the system exhibits the band insulator and Mott correlated insulator phases, as well as an intermediate phase between them. For couplings of Δ = 2,10 and 20, we estimate the critical points that separate these phases through the structure factor and the energy gap in the sector of charge and spin, finding that the position of the critical point rises as a function of Δ.

  20. Biosorption of Acid Blue 290 (AB 290) and Acid Blue 324 (AB 324) dyes on Spirogyra rhizopus.

    PubMed

    Ozer, Ayla; Akkaya, Gönül; Turabik, Meral

    2006-07-31

    In this study, the biosorption of Acid Blue 290 and Acid Blue 324 on Spirogyra rhizopus, a green algae growing on fresh water, was studied with respect to initial pH, temperature, initial dye concentration and biosorbent concentration. The optimum initial pH and temperature values for AB 290 and AB 324 biosorption were found to be 2.0, 30 degrees C and 3.0, 25 degrees C, respectively. It was observed that the adsorbed AB 290 and AB 324 amounts increased with increasing the initial dye concentration up to 1500 and 750 mg/L, respectively. The Langmuir, Freundlich, Redlich-Peterson and Koble-Corrigan isotherm models were applied to the experimental equilibrium data and the isotherm constants were determined by using Polymath 4.1 software. The monolayer coverage capacities of S. rhizopus for AB 290 and AB 324 dyes were found as 1356.6 mg/g and 367.0 mg/g, respectively. The intraparticle diffusion model and the pseudo-second order kinetic model were applied to the experimental data in order to describe the removal mechanism of these acidic dyes by S. rhizopus. The pseudo-second order kinetic model described very well the biosorption kinetics of AB 290 and AB 324 dyes. Thermodynamic studies showed that the biosorption of AB 290 and AB 324 on S. rhizopus was exothermic in nature.

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

    PubMed

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

    2013-01-01

    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

  2. Characterization of nitrogen-fixing bacteria from a temperate saltmarsh lagoon, including isolates that produce ethane from acetylene.

    PubMed

    Tibbles, B J; Rawlings, D E

    1994-01-01

    Nitrogen-fixing bacteria were isolated from sediments and water of a saltmarsh lagoon on the west coast of South Africa, and characterized according to factors that regulate nitrogen fixation in the marine environment. The majority of isolates were assigned to the Photobacterium or Vibrio genera on the basis of physiological and biochemical characteristics. One isolate was further assigned to the species Vibrio diazotrophicus. Carbohydrate utilization by each diazotrophic isolate was examined. Abilities of the isolates to utilize a range of mono-, di-, and polysaccharides largely reflected the predicted availability of organic carbon and energy in the lagoon, except that chitin was not utilized. Biochemical tests on the utilization of combined nitrogen showed that one isolate could utilize nitrate, and that this strain was susceptible to full repression of nitrogenase activity by 10mM nitrate. Urease activity was not detected in any of the isolates. In the absence of molybdenum two of the isolates, a Photobacterium spp. and V. diazotrophicus, reduced acetylene to ethylene and ethane, a property frequently associated with the activity of alternative nitrogenases. Addition of 25µM molybdenum inhibited ethane production by V. diazotrophicus, but stimulated ethylene and ethane production by the Photobacterium isolate. Addition of 28µM vanadium did not appear to regulate ethane production by either strain. Assays of nitrogenase activity in sediments from which some isolates were obtained indicated that molybdenum was not limiting nitrogenase activity at naturally-occurring concentrations. Southern hybridizations of the chromosomes of these strains with the anfH and vnfH genes of Azotobacter vinelandii and the nifH gene of Klebsiella pneumoniae indicated the presence of only one nitrogenase in these isolates.

  3. Ac conductance and capacitance of carbon black polymer composites during thermal cycling and isothermal annealing

    NASA Astrophysics Data System (ADS)

    Jäger, K.-M.; McQueen, D. H.; Vilcáková, J.

    2002-05-01

    The ac electrical properties of acetylene black composites mixed into ethylene butylacrylate copolymer (EBA) and into poly (methyl methacrylate) (PMMA) have been measured in thermal cycling and isothermal annealing experiments. The results show that changes in electrical properties are due to rearrangement of gaps between the carbon black aggregates. This has been concluded using an exponent z that relates the critical frequency ωc denoting the crossover of the conductivity from the dc-plateau to its frequency-dependent part to the dc conductivity, σdc, according to ωc ∝σdcz. Below the melting range of EBA and the glass transition of PMMA z is about one corresponding to strong variation of the conductivity and weak dependence of the permittivity on the gaps. Above the melting range of EBA z is about 1.5, indicating strong dependence of both the conductivity and the permittivity on the gaps, as predicted by percolation theory. This was not found in the PMMA composites above the glass transition. We conclude that the polymer matrix affects the nature of the gaps between carbon black aggregates, either allowing their size to vary continuously (z about 1) or letting them open and close (z about 1.5).

  4. Untapped Resources: "Styling" in Black Students' Writing for Black Audiences.

    ERIC Educational Resources Information Center

    Redd, Teresa M.

    Two studies compared the impact of black and white audiences on black students' writing style. In the first study, eight students in an all-black intermediate composition class completed one argumentative draft addressed to black opponents and one addressed to white opponents on two different topics. The essays were examined for stylistic features…

  5. The next Black America: Obstacles amidst opportunities for Black families.

    PubMed

    Armah, Tichianaa

    2015-09-01

    In this article, the author offers personal accounts on how she feels about the current Black America and obstacles that people face reaching for opportunities for Black families. Focus relies on the current state of Black America, poverty, schools, academic achievement, raising children in the next Black America and much more. (PsycINFO Database Record

  6. The next Black America: Obstacles amidst opportunities for Black families.

    PubMed

    Armah, Tichianaa

    2015-09-01

    In this article, the author offers personal accounts on how she feels about the current Black America and obstacles that people face reaching for opportunities for Black families. Focus relies on the current state of Black America, poverty, schools, academic achievement, raising children in the next Black America and much more. (PsycINFO Database Record PMID:26460716

  7. Black Studies and Black People in the Future

    ERIC Educational Resources Information Center

    Stewart, James B.

    1976-01-01

    Suggests that the demise of Black Studies would foreshadow the future deterioration of the material conditions of black people, a situation which all elements of the black community want to preclude as a possible future for black people. (Author/AM)

  8. On the Charter Question: Black Marxism and Black Nationalism

    ERIC Educational Resources Information Center

    Stern, Mark; Hussain, Khuram

    2015-01-01

    This article brings two black intellectual traditions to bear on the question of charter schools: black Marxism and black nationalism. The authors examine the theoretical and rhetorical devices used to talk about charters schools by focusing on how notions of "black liberation" are deployed by the charter movement, and to what end. The…

  9. Structure, Biological Functions and Applications of the AB5 Toxins

    PubMed Central

    Beddoe, Travis; Paton, Adrienne W.; Le Nours, Jérôme; Rossjohn, Jamie; Paton, James C.

    2010-01-01

    AB5 toxins are important virulence factors for several major bacterial pathogens, including Bordetella pertussis, Vibrio cholerae, Shigella dysenteriae and at least two distinct pathotypes of Escherichia coli. The AB5 toxins are so termed because they comprise a catalytic A-subunit, which is responsible for disruption of essential host functions, and a pentameric B-subunit that binds to specific glycan receptors on the target cell surface. The molecular mechanisms by which these AB5 toxins cause disease have been largely unraveled, including recent insights into a novel AB5 toxin family, subtilase cytotoxin (SubAB). Furthermore, AB5 toxins have become a valuable tool for studying fundamental cellular functions, and are now being investigated for potential applications in the clinical treatment of human diseases. PMID:20202851

  10. ULTRAMASSIVE BLACK HOLE COALESCENCE

    SciTech Connect

    Khan, Fazeel Mahmood; Holley-Bockelmann, Kelly; Berczik, Peter E-mail: k.holley@vanderbilt.edu

    2015-01-10

    Although supermassive black holes (SMBHs) correlate well with their host galaxies, there is an emerging view that outliers exist. Henize 2-10, NGC 4889, and NGC 1277 are examples of SMBHs at least an order of magnitude more massive than their host galaxy suggests. The dynamical effects of such ultramassive central black holes is unclear. Here, we perform direct N-body simulations of mergers of galactic nuclei where one black hole is ultramassive to study the evolution of the remnant and the black hole dynamics in this extreme regime. We find that the merger remnant is axisymmetric near the center, while near the large SMBH influence radius, the galaxy is triaxial. The SMBH separation shrinks rapidly due to dynamical friction, and quickly forms a binary black hole; if we scale our model to the most massive estimate for the NGC 1277 black hole, for example, the timescale for the SMBH separation to shrink from nearly a kiloparsec to less than a parsec is roughly 10 Myr. By the time the SMBHs form a hard binary, gravitational wave emission dominates, and the black holes coalesce in a mere few Myr. Curiously, these extremely massive binaries appear to nearly bypass the three-body scattering evolutionary phase. Our study suggests that in this extreme case, SMBH coalescence is governed by dynamical friction followed nearly directly by gravitational wave emission, resulting in a rapid and efficient SMBH coalescence timescale. We discuss the implications for gravitational wave event rates and hypervelocity star production.

  11. Measuring Black Hole Spin

    NASA Astrophysics Data System (ADS)

    Garmire, Gordon

    1999-09-01

    WE PROPOSE TO CARRY OUT A SYSTEMATIC STUDY OF EMISSION AND ABSORPTION SPECTRAL FEATURES THAT ARE OFTEN SEEN IN X-RAY SPECTRA OF BLACK HOLE BINARIES. THE EXCELLENT SENSITIVITY AND ENERGY RESOLUTION OF THE ACIS/HETG COMBINATION WILL NOT ONLY HELP RESOLVE AMBIGUITIES IN INTERPRETING THESE FEATURES, BUT MAY ALLOW MODELLING OF THE EMISSION LINE PROFILES IN DETAIL. THE PROFILES MAY CONTAIN INFORMATION ON SUCH FUNDAMENTAL PROPERTIES AS THE SPIN OF BLACK HOLES. THEREFORE, THIS STUDY COULD LEAD TO A MEASUREMENT OF BLACK HOLE SPIN FOR SELECTED SOURCES. THE RESULT CAN THEN BE DIRECTLY COMPARED WITH THOSE FROM PREVIOUS STUDIES BASED ON INDEPENDENT METHODS.

  12. Color evaluation of seventeen European unifloral honey types by means of spectrophotometrically determined CIE L*Cab*h(ab)° chromaticity coordinates.

    PubMed

    Tuberoso, Carlo Ignazio Giovanni; Jerković, Igor; Sarais, Giorgia; Congiu, Francesca; Marijanović, Zvonimir; Kuś, Piotr Marek

    2014-02-15

    CIE (Commission Internationale de l'Eclairage) L(*)Cab(*)h(ab)° color coordinates for 305 samples of 17 unifloral honeys types (asphodel, buckwheat, black locust, sweet chestnut, citrus, eucalyptus, Garland thorn, honeydew, heather, lime, mint, rapeseed, sage, strawberry tree, sulla flower, savory and thistle) from different geographic locations in Europe were spectrophotometrically assessed and statistically evaluated. Preliminary separation of unifloral honeys was obtained by means of L(*)-C(ab)(*) color coordination correlation. Hierarchical Cluster Analysis (HCA) revealed an expected segregation of the honeys types according to their chromatic characteristics. Principal Component Analysis (PCA) allowed to obtain a more defined distinction of the 17 unifloral honey types, particularly when using 3D graphics. CIE L(*)C(ab)(*)hab(*) color coordinates were useful for the identification of several honey types. The proposed method represents a simple and efficient procedure that can be used as a basis for the authentication of unifloral honeys worldwide.

  13. Color evaluation of seventeen European unifloral honey types by means of spectrophotometrically determined CIE L*Cab*h(ab)° chromaticity coordinates.

    PubMed

    Tuberoso, Carlo Ignazio Giovanni; Jerković, Igor; Sarais, Giorgia; Congiu, Francesca; Marijanović, Zvonimir; Kuś, Piotr Marek

    2014-02-15

    CIE (Commission Internationale de l'Eclairage) L(*)Cab(*)h(ab)° color coordinates for 305 samples of 17 unifloral honeys types (asphodel, buckwheat, black locust, sweet chestnut, citrus, eucalyptus, Garland thorn, honeydew, heather, lime, mint, rapeseed, sage, strawberry tree, sulla flower, savory and thistle) from different geographic locations in Europe were spectrophotometrically assessed and statistically evaluated. Preliminary separation of unifloral honeys was obtained by means of L(*)-C(ab)(*) color coordination correlation. Hierarchical Cluster Analysis (HCA) revealed an expected segregation of the honeys types according to their chromatic characteristics. Principal Component Analysis (PCA) allowed to obtain a more defined distinction of the 17 unifloral honey types, particularly when using 3D graphics. CIE L(*)C(ab)(*)hab(*) color coordinates were useful for the identification of several honey types. The proposed method represents a simple and efficient procedure that can be used as a basis for the authentication of unifloral honeys worldwide. PMID:24128479

  14. The Price of "Black Dominance."

    ERIC Educational Resources Information Center

    Hoberman, John

    2000-01-01

    Discusses the harmful effects of stereotyping black males as athletes, noting that over-identification with athletes and the world of physical performance limits black children's development by discouraging academic achievement. Examines the negative influence of mass media focus on black athletes, rappers, and stylized ghetto blackness. Discusses…

  15. Black Managers in White Corporations.

    ERIC Educational Resources Information Center

    Fernandez, John P.

    The study examines the major determinants of the career patterns of black managers in white businesses and the effects of corporations on their black managers' identities and relationships to the black community. Analyzed were occupational mobility theories; white and black managers' career patterns, goals, and related factors; company employment…

  16. Anti-GD2 mAbs and next-generation mAb-based agents for cancer therapy.

    PubMed

    Horta, Zulmarie Perez; Goldberg, Jacob L; Sondel, Paul M

    2016-09-01

    Tumor-specific monoclonal antibodies (mAbs) have demonstrated efficacy in the clinic, becoming an important approach for cancer immunotherapy. Due to its limited expression on normal tissue, the GD2 disialogangloside expressed on neuroblastoma cells is an excellent candidate for mAb therapy. In 2015, dinutuximab (an anti-GD2 mAb) was approved by the US FDA and is currently used in a combination immunotherapeutic regimen for the treatment of children with high-risk neuroblastoma. Here, we review the extensive preclinical and clinical development of anti-GD2 mAbs and the different mechanisms by which they mediate tumor cell killing. In addition, we discuss different mAb-based strategies that capitalize on the targeting ability of anti-GD2 mAbs to potentially deliver, as monotherapy, or in combination with other treatments, improved antitumor efficacy.

  17. Biologically Active Acetylenic Amino Alcohol and N-Hydroxylated 1,2,3,4-Tetrahydro-β-carboline Constituents of the New Zealand Ascidian Pseudodistoma opacum.

    PubMed

    Wang, Jiayi; Pearce, A Norrie; Chan, Susanna T S; Taylor, Richard B; Page, Michael J; Valentin, Alexis; Bourguet-Kondracki, Marie-Lise; Dalton, James P; Wiles, Siouxsie; Copp, Brent R

    2016-03-25

    The first occurrence of an acetylenic 1-amino-2-alcohol, distaminolyne A (1), isolated from the New Zealand ascidian Pseudodistoma opacum, is reported. The isolation and structure elucidation of 1 and assignment of absolute configuration using the exciton coupled circular dichroism technique are described. In addition, a new N-9 hydroxy analogue (2) of the known P. opacum metabolite 7-bromohomotrypargine is also reported. Antimicrobial screening identified modest activity of 1 toward Escherichia coli, Staphylococcus aureus, and Mycobacterim tuberculosis, while 2 exhibited a moderate antimalarial activity (IC50 3.82 μM) toward a chloroquine-resistant strain (FcB1) of Plasmodium falciparum. PMID:26670413

  18. Reactions of organoaluminum compounds with acetylene as a method for the synthesis of aliphatic derivatives with a z-disubstituted double bond

    SciTech Connect

    Andreeva, N.I.; Kuchin, A.V.; Tolstikov, G.A.

    1985-11-01

    This paper develops a method for the synthesis of aliphatic compounds with a Z-disubstituted double bond, which are important synthons for the preparation of such natural products as insect pheromones, aromatic principles, etc. In the carbalumination reaction of acetylene Z-alkenyldialkylaluminums are formed selectively. A-Alkenyldialkylaluminums are highly reactive and can readily be converted into Z-allyl alcohols and their ethers, and into Z-iodovinyl derivatives. By the reactions of vinyl organoaluminum compounds with the complex CH/sub 3/COClhaAlCl/sub 3/ E-conjugated ketones were obtained.

  19. Secondary hydrogen isotope effects on the structure and stability of cation-pi complexes (cation = Li(+), Na(+), K(+) and pi = acetylene, ethylene, benzene).

    PubMed

    Moreno, Diego V; González, Sergio A; Reyes, Andrés

    2010-09-01

    Secondary hydrogen isotope effects on the geometries, electronic wave functions and binding energies of cation-pi complexes (cation = Li(+), Na(+), K(+) and pi = acetylene, ethylene, benzene) are investigated with NEO/HF and NEO/MP2 methods. These methods determine both electronic and nuclear wave functions simultaneously. Our results show that an increase of the hydrogen nuclear mass leads to the elongation of the cation-pi bond distance and the decrease in its binding energy. An explanation to this behavior is given in terms of the changes in the pi-molecule electronic structure and electrostatic potential induced by isotopic substitutions.

  20. Acetylene bridged porphyrin-monophthalocyaninato ytterbium(III) hybrids with strong two-photon absorption and high singlet oxygen quantum yield.

    PubMed

    Ke, Hanzhong; Li, Wenbin; Zhang, Tao; Zhu, Xunjin; Tam, Hoi-Lam; Hou, Anxin; Kwong, Daniel W J; Wong, Wai-Kwok

    2012-04-21

    Several acetylene bridged porphyrin-monophthalocyaninato ytterbium(III) hybrids, PZn-PcYb, PH(2)-PcYb and PPd-PcYb, have been prepared and characterized by (1)H and (31)P NMR, mass spectrometry, and UV-vis spectroscopy. Their photophysical and photochemical properties, especially the relative singlet oxygen ((1)O(2)) quantum yields and the two-photon absorption cross-section (σ(2)), were investigated. These three newly synthesized compounds exhibited very large σ(2) values and substantial (1)O(2) quantum yields upon photo-excitation, making them potential candidates as one- and two-photon photodynamic therapeutic agents.

  1. Introducing the Black Hole

    ERIC Educational Resources Information Center

    Ruffini, Remo; Wheeler, John A.

    1971-01-01

    discusses the cosmology theory of a black hole, a region where an object loses its identity, but mass, charge, and momentum are conserved. Include are three possible formation processes, theorized properties, and three way they might eventually be detected. (DS)

  2. Charging black Saturn?

    NASA Astrophysics Data System (ADS)

    Chng, Brenda; Mann, Robert; Radu, Eugen; Stelea, Cristian

    2008-12-01

    We construct new charged static solutions of the Einstein-Maxwell field equations in five dimensions via a solution generation technique utilizing the symmetries of the reduced Lagrangian. By applying our method on the multi-Reissner-Nordström solution in four dimensions, we generate the multi-Reissner-Nordström solution in five dimensions. We focus on the five-dimensional solution describing a pair of charged black objects with general masses and electric charges. This solution includes the double Reissner-Nordström solution as well as the charged version of the five-dimensional static black Saturn. However, all the black Saturn configurations that we found contain either a conical or naked singularity. We also obtain a non-extremal configuration of charged black strings that reduces in the extremal limit to a Majumdar-Papapetrou like solution in five dimensions.

  3. Tuberculosis in Blacks

    MedlinePlus

    ... the United States is declining, there is decreased awareness of TB signs and symptoms among health care ... working on projects designed to educate and raise awareness about TB in black communities. In one project, ...

  4. Illuminating black holes

    NASA Astrophysics Data System (ADS)

    Barr, Ian A.; Bull, Anne; O’Brien, Eileen; Drillsma-Milgrom, Katy A.; Milgrom, Lionel R.

    2016-07-01

    Two-dimensional shadows formed by illuminating vortices are shown to be visually analogous to the gravitational action of black holes on light and surrounding matter. They could be useful teaching aids demonstrating some of the consequences of general relativity.

  5. Black hole accretion.

    PubMed

    Narayan, Ramesh; Quataert, Eliot

    2005-01-01

    Black holes are most often detected by the radiation produced when they gravitationally pull in surrounding gas, in a process called accretion. The efficiency with which the hot gas radiates its thermal energy strongly influences the geometry and dynamics of the accretion flow. Both radiatively efficient thin disks and radiatively inefficient thick disks are observed. When the accreting gas gets close to the central black hole, the radiation it produces becomes sensitive to the spin of the hole and the presence of an event horizon. Analysis of the luminosities and spectra of accreting black holes has yielded tantalizing evidence for both rotating holes and event horizons. Numerical simulations imply that the relativistic jets often seen from accreting black holes may be powered in part by the spin of the hole. PMID:15637269

  6. Astrophysics: Monster black holes

    NASA Astrophysics Data System (ADS)

    Cappellari, Michele

    2011-12-01

    A combination of ground-based and spacecraft observations has uncovered two black holes of 10 billion solar masses in the nearby Universe. The finding sheds light on how these cosmic monsters co-evolve with galaxies.

  7. Janus black holes

    NASA Astrophysics Data System (ADS)

    Bak, Dongsu; Gutperle, Michael; Janik, Romuald A.

    2011-10-01

    In this paper Janus black holes in A dS 3 are considered. These are static solutions of an Einstein-scalar system with broken translation symmetry along the horizon. These solutions are dual to interface conformal field theories at finite temperature. An approximate solution is first constructed using perturbation theory around a planar BTZ blackhole. Numerical and exact solutions valid for all sets of parameters are then found and compared. Using the exact solution the thermodynamics of the system is analyzed. The entropy associated with the Janus black hole is calculated and it is found that the entropy of the black Janus is the sum of the undeformed black hole entropy and the entanglement entropy associated with the defect.

  8. The Illinois Black Codes.

    ERIC Educational Resources Information Center

    Bridges, Roger D.; Daley, Harry

    1996-01-01

    Presents an excellent lesson plan discussing the repressive racial legislation that remained enforced in Illinois even after the repeal of slavery. Background material also covers the black communities' response to these racist laws. Includes teaching suggestions, handouts, and activities. (MJP)

  9. Discovering chemistry with an ab initio nanoreactor

    PubMed Central

    Wang, Lee-Ping; Titov, Alexey; McGibbon, Robert; Liu, Fang; Pande, Vijay S.; Martínez, Todd J.

    2014-01-01

    Chemical understanding is driven by the experimental discovery of new compounds and reactivity, and is supported by theory and computation that provides detailed physical insight. While theoretical and computational studies have generally focused on specific processes or mechanistic hypotheses, recent methodological and computational advances harken the advent of their principal role in discovery. Here we report the development and application of the ab initio nanoreactor – a highly accelerated, first-principles molecular dynamics simulation of chemical reactions that discovers new molecules and mechanisms without preordained reaction coordinates or elementary steps. Using the nanoreactor we show new pathways for glycine synthesis from primitive compounds proposed to exist on the early Earth, providing new insight into the classic Urey-Miller experiment. These results highlight the emergence of theoretical and computational chemistry as a tool for discovery in addition to its traditional role of interpreting experimental findings. PMID:25411881

  10. Ab Initio Modeling of Molecular Radiation

    NASA Technical Reports Server (NTRS)

    Jaffe, Richard; Schwenke, David

    2014-01-01

    Radiative emission from excited states of atoms and molecules can comprise a significant fraction of the total heat flux experienced by spacecraft during atmospheric entry at hypersonic speeds. For spacecraft with ablating heat shields, some of this radiative flux can be absorbed by molecular constituents in the boundary layer that are formed by the ablation process. Ab initio quantum mechanical calculations are carried out to predict the strengths of these emission and absorption processes. This talk will describe the methods used in these calculations using, as examples, the 4th positive emission bands of CO and the 1g+ 1u+ absorption in C3. The results of these calculations are being used as input to NASA radiation modeling codes like NeqAir, HARA and HyperRad.

  11. Discovering chemistry with an ab initio nanoreactor

    SciTech Connect

    Wang, Lee-Ping; Titov, Alexey; McGibbon, Robert; Liu, Fang; Pande, Vijay S.; Martínez, Todd J.

    2014-11-02

    Chemical understanding is driven by the experimental discovery of new compounds and reactivity, and is supported by theory and computation that provides detailed physical insight. While theoretical and computational studies have generally focused on specific processes or mechanistic hypotheses, recent methodological and computational advances harken the advent of their principal role in discovery. Here we report the development and application of the ab initio nanoreactor – a highly accelerated, first-principles molecular dynamics simulation of chemical reactions that discovers new molecules and mechanisms without preordained reaction coordinates or elementary steps. Using the nanoreactor we show new pathways for glycine synthesis from primitive compounds proposed to exist on the early Earth, providing new insight into the classic Urey-Miller experiment. Ultimately, these results highlight the emergence of theoretical and computational chemistry as a tool for discovery in addition to its traditional role of interpreting experimental findings.

  12. Discovering chemistry with an ab initio nanoreactor

    DOE PAGES

    Wang, Lee-Ping; Titov, Alexey; McGibbon, Robert; Liu, Fang; Pande, Vijay S.; Martínez, Todd J.

    2014-11-02

    Chemical understanding is driven by the experimental discovery of new compounds and reactivity, and is supported by theory and computation that provides detailed physical insight. While theoretical and computational studies have generally focused on specific processes or mechanistic hypotheses, recent methodological and computational advances harken the advent of their principal role in discovery. Here we report the development and application of the ab initio nanoreactor – a highly accelerated, first-principles molecular dynamics simulation of chemical reactions that discovers new molecules and mechanisms without preordained reaction coordinates or elementary steps. Using the nanoreactor we show new pathways for glycine synthesis frommore » primitive compounds proposed to exist on the early Earth, providing new insight into the classic Urey-Miller experiment. Ultimately, these results highlight the emergence of theoretical and computational chemistry as a tool for discovery in addition to its traditional role of interpreting experimental findings.« less

  13. Dissecting the A-B personality type.

    PubMed

    Ray, J J; Bozek, R

    1980-06-01

    It is suggested that 'freneticism' might be an appropriate name for the type of personality said by Rosenman, Friedman and Jenkins to be at risk from coronary heart disease. In study 1 the measure of this personality type (the JAS) was given a uniform answer format and, as such, was found to give improved reliability. It was administered to a random postal sample of Australians. A short form of 24 items was also produced. In study 2 a similar sample received the 24-item form and scales to measure achievement motivation, dominance and extraversion. 'A' types were found to be very much achievement motivated and dominant. A factor analysis showed these two traits as the main components of the A-B concept with only a third factor of 'freneticism'. This factor was measured in a third study which showed that the factor could be used as a scale in its own right.

  14. Ab Initio Calculation of the Hoyle State

    SciTech Connect

    Epelbaum, Evgeny; Krebs, Hermann; Lee, Dean; Meissner, Ulf-G.

    2011-05-13

    The Hoyle state plays a crucial role in the helium burning of stars heavier than our Sun and in the production of carbon and other elements necessary for life. This excited state of the carbon-12 nucleus was postulated by Hoyle as a necessary ingredient for the fusion of three alpha particles to produce carbon at stellar temperatures. Although the Hoyle state was seen experimentally more than a half century ago nuclear theorists have not yet uncovered the nature of this state from first principles. In this Letter we report the first ab initio calculation of the low-lying states of carbon-12 using supercomputer lattice simulations and a theoretical framework known as effective field theory. In addition to the ground state and excited spin-2 state, we find a resonance at -85(3) MeV with all of the properties of the Hoyle state and in agreement with the experimentally observed energy.

  15. Helical superconducting black holes.

    PubMed

    Donos, Aristomenis; Gauntlett, Jerome P

    2012-05-25

    We construct novel static, asymptotically five-dimensional anti-de Sitter black hole solutions with Bianchi type-VII(0) symmetry that are holographically dual to superconducting phases in four spacetime dimensions with a helical p-wave order. We calculate the precise temperature dependence of the pitch of the helical order. At zero temperature the black holes have a vanishing entropy and approach domain wall solutions that reveal homogenous, nonisotropic dual ground states with an emergent scaling symmetry.

  16. Beyond Black and White.

    ERIC Educational Resources Information Center

    Comer, James P.

    Black and white conflict is a by-product of a more basic problem: the failure of this society to develop a social system that enables all people to meet their basic human needs at a reasonable level. Until this is done, we will not be able to move beyond black and white. The underlying problem is related to a sudden acceleration of human history…

  17. The T2 phase in the Nb-Si-B system studied by ab initio calculations and synchrotron X-ray diffraction

    SciTech Connect

    Joubert, J.-M.; Colinet, C.; Rodrigues, G.; Suzuki, P.A.; Nunes, C.A.; Coelho, G.C.; Tedenac, J.-C.

    2012-06-15

    The solid solution based on Nb{sub 5}Si{sub 3} (Cr{sub 5}B{sub 3} structure type, D8{sub l}, tI32, I4/mcm, No140, a=6.5767 A, c=11.8967 A) in the Nb-Si-B system was studied from the structural and thermodynamic point of view both experimentally and by ab initio calculations. Rietveld refinement of powder X-ray synchrotron data allowed to determine the boron to silicon substitution mechanism and the structural parameters. Ab initio calculations of different ordered compounds and selected disordered alloys allowed to obtain in addition to the enthalpy of formation of the solution, substitution mechanism and structural parameters which are in excellent agreement with the experimental data. The stability of the phase is discussed. - Graphial abstract: Valence-charge electron localization function in the z=0 plane of the D8{sub l} structure for the ordered compound Nb{sub 5}SiB{sub 2}. Highlights: Black-Right-Pointing-Pointer Coupling between ab initio data and experimental results from synchrotron powder diffraction. Black-Right-Pointing-Pointer Excellent agreement between the two techniques for the site occupancies and internal coordinates. Black-Right-Pointing-Pointer Explanation of the phase stability up to Nb{sub 5}SiB{sub 2}.

  18. Ab initio alpha-alpha scattering.

    PubMed

    Elhatisari, Serdar; Lee, Dean; Rupak, Gautam; Epelbaum, Evgeny; Krebs, Hermann; Lähde, Timo A; Luu, Thomas; Meißner, Ulf-G

    2015-12-01

    Processes such as the scattering of alpha particles ((4)He), the triple-alpha reaction, and alpha capture play a major role in stellar nucleosynthesis. In particular, alpha capture on carbon determines the ratio of carbon to oxygen during helium burning, and affects subsequent carbon, neon, oxygen, and silicon burning stages. It also substantially affects models of thermonuclear type Ia supernovae, owing to carbon detonation in accreting carbon-oxygen white-dwarf stars. In these reactions, the accurate calculation of the elastic scattering of alpha particles and alpha-like nuclei--nuclei with even and equal numbers of protons and neutrons--is important for understanding background and resonant scattering contributions. First-principles calculations of processes involving alpha particles and alpha-like nuclei have so far been impractical, owing to the exponential growth of the number of computational operations with the number of particles. Here we describe an ab initio calculation of alpha-alpha scattering that uses lattice Monte Carlo simulations. We use lattice effective field theory to describe the low-energy interactions of protons and neutrons, and apply a technique called the 'adiabatic projection method' to reduce the eight-body system to a two-cluster system. We take advantage of the computational efficiency and the more favourable scaling with system size of auxiliary-field Monte Carlo simulations to compute an ab initio effective Hamiltonian for the two clusters. We find promising agreement between lattice results and experimental phase shifts for s-wave and d-wave scattering. The approximately quadratic scaling of computational operations with particle number suggests that it should be possible to compute alpha scattering and capture on carbon and oxygen in the near future. The methods described here can be applied to ultracold atomic few-body systems as well as to hadronic systems using lattice quantum chromodynamics to describe the interactions of

  19. Ab initio alpha-alpha scattering.

    PubMed

    Elhatisari, Serdar; Lee, Dean; Rupak, Gautam; Epelbaum, Evgeny; Krebs, Hermann; Lähde, Timo A; Luu, Thomas; Meißner, Ulf-G

    2015-12-01

    Processes such as the scattering of alpha particles ((4)He), the triple-alpha reaction, and alpha capture play a major role in stellar nucleosynthesis. In particular, alpha capture on carbon determines the ratio of carbon to oxygen during helium burning, and affects subsequent carbon, neon, oxygen, and silicon burning stages. It also substantially affects models of thermonuclear type Ia supernovae, owing to carbon detonation in accreting carbon-oxygen white-dwarf stars. In these reactions, the accurate calculation of the elastic scattering of alpha particles and alpha-like nuclei--nuclei with even and equal numbers of protons and neutrons--is important for understanding background and resonant scattering contributions. First-principles calculations of processes involving alpha particles and alpha-like nuclei have so far been impractical, owing to the exponential growth of the number of computational operations with the number of particles. Here we describe an ab initio calculation of alpha-alpha scattering that uses lattice Monte Carlo simulations. We use lattice effective field theory to describe the low-energy interactions of protons and neutrons, and apply a technique called the 'adiabatic projection method' to reduce the eight-body system to a two-cluster system. We take advantage of the computational efficiency and the more favourable scaling with system size of auxiliary-field Monte Carlo simulations to compute an ab initio effective Hamiltonian for the two clusters. We find promising agreement between lattice results and experimental phase shifts for s-wave and d-wave scattering. The approximately quadratic scaling of computational operations with particle number suggests that it should be possible to compute alpha scattering and capture on carbon and oxygen in the near future. The methods described here can be applied to ultracold atomic few-body systems as well as to hadronic systems using lattice quantum chromodynamics to describe the interactions of

  20. Can Blacks Be Racists? Black-on-Black Principal Abuse in an Urban School Setting

    ERIC Educational Resources Information Center

    Khalifa, Muhammad

    2015-01-01

    This study examines Black student and parental perceptions of exclusionary practices of Black school principals. I ask why students and parents viewed two Black principals as contributing to abusive and exclusionary school environments that marginalized Black students. After a two-year ethnographic study, it was revealed that exclusionary…