Intersystem return on investment in public mental health: Positive externality of public mental health expenditure for the jail system in the U.S.

Science.gov (United States)

Yoon, Jangho; Luck, Jeff

2016-12-01

This study examines the extent to which increased public mental health expenditures lead to a reduction in jail populations and computes the associated intersystem return on investment (ROI). We analyze unique panel data on 44 U.S. states and D.C. for years 2001-2009. To isolate the intersystem spillover effect, we exploit variations across states and over time within states in per capita public mental health expenditures and average daily jail inmates. Regression models control for a comprehensive set of determinants of jail incarcerations as well as unobserved determinants specific to state and year. Findings show a positive spillover benefit of increased public mental health spending on the jail system: a 10% increase in per capita public inpatient mental health expenditure on average leads to a 1.5% reduction in jail inmates. We also find that the positive intersystem externality of increased public inpatient mental health expenditure is greater when the level of community mental health spending is lower. Similarly, the intersystem spillover effect of community mental health expenditure is larger when inpatient mental health spending is lower. We compute that overall an extra dollar in public inpatient mental health expenditure by a state would yield an intersystem ROI of a quarter dollar for the jail system. There is significant cross-state variation in the intersystem ROI in both public inpatient and community mental health expenditures, and the ROI overall is greater for inpatient mental health spending than for community mental health spending. Copyright © 2016. Published by Elsevier Ltd.

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

KAUST Repository

Hu, Tong-Liang

2015-06-04

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.

Solvent-dependent excited-state hydrogen transfer and intersystem crossing in 2-(2′-hydroxyphenyl)-benzothiazole

KAUST Repository

Aly, Shawkat Mohammede

2015-02-12

The excited-state intramolecular hydrogen transfer (ESIHT) of 2-(2′-hydroxyphenyl) benzothiazole (HBT) has been investigated in a series of nonpolar, polar aprotic, and polar protic solvents. A variety of state-of-the-art experimental methods were employed, including femto- and nanosecond transient absorption and fluorescence upconversion spectroscopy with broadband capabilities. We show that the dynamics and mechanism of ESIHT of the singlet excited HBT are strongly solvent-dependent. In nonpolar solvents, the data demonstrate that HBT molecules adopt a closed form stabilized by O-H⋯N chelated hydrogen bonds with no twisting angle, and the photoinduced H transfer occurs within 120 fs, leading to the formation of a keto tautomer. In polar solvents, owing to dipole-dipole cross talk and hydrogen bonding interactions, the H transfer process is followed by ultrafast nonradiative deactivation channels, including ultrafast internal conversion (IC) and intersystem crossing (ISC). This is likely to be driven by the twisting motion around the C-C bond between the hydroxyphenyl and thiazole moieties, facilitating the IC back to the enol ground state or to the keto triplet state. In addition, our femtosecond time-resolved fluorescence experiments indicate, for the first time, that the lifetime of the enol form in ACN is approximately 280 fs. This observation indicates that the solvent plays a crucial role in breaking the H bond and deactivating the excited state of the HBT. Interestingly, the broadband transient absorption and fluorescence up-conversion data clearly demonstrate that the intermolecular proton transfer from the excited HBT to the DMSO solvent is about 190 fs, forming the HBT anion excited state.

Solvent-dependent excited-state hydrogen transfer and intersystem crossing in 2-(2′-hydroxyphenyl)-benzothiazole

KAUST Repository

Aly, Shawkat Mohammede; Usman, Anwar; Alzayer, Maytham; Hamdi, Ghada A.; Alarousu, Erkki; Mohammed, Omar F.

2015-01-01

The excited-state intramolecular hydrogen transfer (ESIHT) of 2-(2′-hydroxyphenyl) benzothiazole (HBT) has been investigated in a series of nonpolar, polar aprotic, and polar protic solvents. A variety of state-of-the-art experimental methods were employed, including femto- and nanosecond transient absorption and fluorescence upconversion spectroscopy with broadband capabilities. We show that the dynamics and mechanism of ESIHT of the singlet excited HBT are strongly solvent-dependent. In nonpolar solvents, the data demonstrate that HBT molecules adopt a closed form stabilized by O-H⋯N chelated hydrogen bonds with no twisting angle, and the photoinduced H transfer occurs within 120 fs, leading to the formation of a keto tautomer. In polar solvents, owing to dipole-dipole cross talk and hydrogen bonding interactions, the H transfer process is followed by ultrafast nonradiative deactivation channels, including ultrafast internal conversion (IC) and intersystem crossing (ISC). This is likely to be driven by the twisting motion around the C-C bond between the hydroxyphenyl and thiazole moieties, facilitating the IC back to the enol ground state or to the keto triplet state. In addition, our femtosecond time-resolved fluorescence experiments indicate, for the first time, that the lifetime of the enol form in ACN is approximately 280 fs. This observation indicates that the solvent plays a crucial role in breaking the H bond and deactivating the excited state of the HBT. Interestingly, the broadband transient absorption and fluorescence up-conversion data clearly demonstrate that the intermolecular proton transfer from the excited HBT to the DMSO solvent is about 190 fs, forming the HBT anion excited state.

First-principles method for calculating the rate constants of internal-conversion and intersystem-crossing transitions.

Science.gov (United States)

Valiev, R R; Cherepanov, V N; Baryshnikov, G V; Sundholm, D

2018-02-28

A method for calculating the rate constants for internal-conversion (k IC ) and intersystem-crossing (k ISC ) processes within the adiabatic and Franck-Condon (FC) approximations is proposed. The applicability of the method is demonstrated by calculation of k IC and k ISC for a set of organic and organometallic compounds with experimentally known spectroscopic properties. The studied molecules were pyrromethene-567 dye, psoralene, hetero[8]circulenes, free-base porphyrin, naphthalene, and larger polyacenes. We also studied fac-Alq 3 and fac-Ir(ppy) 3 , which are important molecules in organic light emitting diodes (OLEDs). The excitation energies were calculated at the multi-configuration quasi-degenerate second-order perturbation theory (XMC-QDPT2) level, which is found to yield excitation energies in good agreement with experimental data. Spin-orbit coupling matrix elements, non-adiabatic coupling matrix elements, Huang-Rhys factors, and vibrational energies were calculated at the time-dependent density functional theory (TDDFT) and complete active space self-consistent field (CASSCF) levels. The computed fluorescence quantum yields for the pyrromethene-567 dye, psoralene, hetero[8]circulenes, fac-Alq 3 and fac-Ir(ppy) 3 agree well with experimental data, whereas for the free-base porphyrin, naphthalene, and the polyacenes, the obtained quantum yields significantly differ from the experimental values, because the FC and adiabatic approximations are not accurate for these molecules.

Tracing Acetylene Dissolved in Transformer Oil by Tunable Diode Laser Absorption Spectrum.

Science.gov (United States)

Ma, Guo-Ming; Zhao, Shu-Jing; Jiang, Jun; Song, Hong-Tu; Li, Cheng-Rong; Luo, Ying-Ting; Wu, Hao

2017-11-02

Dissolved gas analysis (DGA) is widely used in monitoring and diagnosing of power transformer, since the insulation material in the power transformer decomposes gases under abnormal operation condition. Among the gases, acetylene, as a symbol of low energy spark discharge and high energy electrical faults (arc discharge) of power transformer, is an important monitoring parameter. The current gas detection method used by the online DGA equipment suffers from problems such as cross sensitivity, electromagnetic compatibility and reliability. In this paper, an optical gas detection system based on TDLAS technology is proposed to detect acetylene dissolved in transformer oil. We selected a 1530.370 nm laser in the near infrared wavelength range to correspond to the absorption peak of acetylene, while using the wavelength modulation strategy and Herriott cell to improve the detection precision. Results show that the limit of detection reaches 0.49 ppm. The detection system responds quickly to changes of gas concentration and is easily to maintenance while has no electromagnetic interference, cross-sensitivity, or carrier gas. In addition, a complete detection process of the system takes only 8 minutes, implying a practical prospect of online monitoring technology.

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

International Nuclear Information System (INIS)

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

2015-01-01

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 ν 4 band of methane and the ν 4 +ν 5 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. - Highlights: • Methane measured at the peak of Q(12) transition in the ν 4 band. • Acetylene measured at the peak of P(23) transition in the ν 4 +ν 5 band. • Differential absorption strategy employed to eliminate broadband interference absorption. • Absorption cross-sections measured over 1200–2200 K and 1–4 atm. • Methane and acetylene time-histories measured during the pyrolysis of n-pentane

Plasma Thermal Conversion of Methane to Acetylene

International Nuclear Information System (INIS)

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

2002-01-01

This paper describes a re-examination of a known process for the direct plasma thermal conversion of methane to acetylene. Conversion efficiencies (% methane converted) approached 100% and acetylene yields in the 90-95% range with 2-4% solid carbon production were demonstrated. Specificity for acetylene was higher than in prior work. Improvements in conversion efficiency, yield, and specificity were due primarily to improved injector design and reactant mixing, and minimization of temperature gradients and cold boundary layers. At the 60-kilowatt scale cooling by wall heat transfer appears to be sufficient to quench the product stream and prevent further reaction of acetylene resulting in the formation of heavier hydrocarbon products or solid carbon. Significantly increasing the quenching rate by aerodynamic expansion of the products through a converging-diverging nozzle led to a reduction in the yield of ethylene but had little effect on the yield of other hydrocarbon products. While greater product selectivity for acetylene has been demonstrated, the specific energy consumption per unit mass of acetylene produced was not improved upon. A kinetic model that includes the reaction mechanisms resulting in the formation of acetylene and heavier hydrocarbons, through benzene, is described

Thermal Conversion of Methane to Acetylene

Energy Technology Data Exchange (ETDEWEB)

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.

46 CFR 147.70 - Acetylene.

Science.gov (United States)

2010-10-01

... 46 Shipping 5 2010-10-01 2010-10-01 false Acetylene. 147.70 Section 147.70 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) DANGEROUS CARGOES HAZARDOUS SHIPS' STORES Stowage and Other... standard cubic feet) of acetylene may be on board a vessel engaged in industrial operations, if it is...

Studies on panax acetylenes: absolute structure of a new panax acetylene, and inhibitory effects of related acetylenes on the growth of L-1210 cells.

Science.gov (United States)

Satoh, Yoshio; Satoh, Mitsuru; Isobe, Kimiaki; Mohri, Kunihiko; Yoshida, Yuki; Fujimoto, Yasuo

2007-04-01

A new Panax acetylene, 3-oxo-PQ-1 (1), was isolated from Panax quinquefolium. The absolute configurations of 3-oxo-PQ-1 (1) and PQ-1 (2) were determined to be (9R,10R) and (3R,9R,10R), respectively, by synthesizing 1 and 2 starting from D-(-)-diethyl tartrate, and by synthesizing their stereoisomers from L-(+)-diethyl tartrate. The growth inhibitory effects of Panax acetylenes (1-8) and their stereoisomers against leukemia cells were tested. Unnatural acetylenes having the (3S)-configuration (2, 5, 6, 7, 8; IC(50)=0.01-0.1 microg/ml) were found to be approximately ten times more potent than natural acetylenes (IC(50)=0.1-1.0 microg/ml) with the (3R)-configuration. Potency differences due to the configuration at C-9 and C-10 were unrelated to this stereochemistry. The C(14)-polyacetylenes, PQ-8 (4) and its isomer (IC(50)=1.0-10.0 microg/ml), were found to exhibit weaker cytotoxicity than the C(17)-polyacetylenes.

Synthesis and kinetics of non-isothermal degradation of acetylene terminated silazane

Institute of Scientific and Technical Information of China (English)

Wei Jian Han; Li Ye; Ji Dong Hu; Tong Zhao

2011-01-01

Novel acetylene terminated silazane compounds, with three types of substituent, were synthesized by the aminolysis of dichlorosilane with 3-aminophenylacetylene (3-APA). Thermal property of the compounds is studied by thermogravimetry analysis (TGA). It shows that the acetylene terminated silazane has high temperature resistance. The char yield at 1000℃ is 77.6, 81.9 and 68.7 wt% for methyl, vinyl, and phenyl substituted silazane, respectively. The pyrolysis kinetics of the silazane is investigated by non-isothermal thermogravimetric measurement. The pyrolysis undergoes three stages, which is resolved by PEAKFIT. The kinetic parameters are calculated by the Kissinger method. The role of functionalities on the thermal resistance is discussed. The vinyl-silazane exhibits higher thermal stability because of higher cross-linking density.

Intersystem crossing and dynamics in O(3P) + C2H4 multichannel reaction: Experiment validates theory

Science.gov (United States)

Fu, Bina; Han, Yong-Chang; Bowman, Joel M.; Angelucci, Luca; Balucani, Nadia; Leonori, Francesca; Casavecchia, Piergiorgio

2012-01-01

The O(3P) + C2H4 reaction, of importance in combustion and atmospheric chemistry, stands out as a paradigm reaction involving triplet- and singlet-state potential energy surfaces (PESs) interconnected by intersystem crossing (ISC). This reaction poses challenges for theory and experiments owing to the ruggedness and high dimensionality of these potentials, as well as the long lifetimes of the collision complexes. Primary products from five competing channels (H + CH2CHO, H + CH3CO, H2 + CH2CO, CH3 + HCO, CH2 + CH2O) and branching ratios (BRs) are determined in crossed molecular beam experiments with soft electron-ionization mass-spectrometric detection at a collision energy of 8.4 kcal/mol. As some of the observed products can only be formed via ISC from triplet to singlet PESs, from the product BRs the extent of ISC is inferred. A new full-dimensional PES for the triplet state as well as spin-orbit coupling to the singlet PES are reported, and roughly half a million surface hopping trajectories are run on the coupled singlet-triplet PESs to compare with the experimental BRs and differential cross-sections. Both theory and experiment find almost equal contributions from the two PESs to the reaction, posing the question of how important is it to consider the ISC as one of the nonadiabatic effects for this and similar systems involved in combustion chemistry. Detailed comparisons at the level of angular and translational energy distributions between theory and experiment are presented for the two primary channel products, CH3 + HCO and H + CH2CHO. The agreement between experimental and theoretical functions is excellent, implying that theory has reached the capability of describing complex multichannel nonadiabatic reactions. PMID:22665777

Measurements of acetylene in air extracted from polar ice cores

Science.gov (United States)

Nicewonger, M. R.; Aydin, M.; Montzka, S. A.; Saltzman, E. S.

2016-12-01

Acetylene (ethyne) is a non-methane hydrocarbon emitted during combustion of fossil fuels, biofuels, and biomass. The major atmospheric loss pathway of acetylene is oxidation by hydroxyl radical with a lifetime estimated at roughly two weeks. The mean annual acetylene levels over Greenland and Antarctica are 250 ppt and 20 ppt, respectively. Firn air measurements suggest atmospheric acetylene is preserved unaltered in polar snow and firn. Atmospheric reconstructions based on firn air measurements indicate acetylene levels rose significantly during the twentieth century, peaked near 1980, then declined to modern day levels. This historical trend is similar to that of other fossil fuel-derived non-methane hydrocarbons. In the preindustrial atmosphere, acetylene levels should primarily reflect emissions from biomass burning. In this study, we present the first measurements of acetylene in preindustrial air extracted from polar ice cores. Air from fluid and dry-drilled ice cores from Summit, Greenland and WAIS-Divide Antarctica is extracted using a wet-extraction technique. The ice core air is analyzed using gas chromatography and high-resolution mass spectrometry. Between 1400 to 1800 C.E., acetylene levels over Greenland and Antarctica varied between roughly 70-120 ppt and 10-30 ppt, respectively. The preindustrial Greenland acetylene levels are significantly lower than modern levels, reflecting the importance of northern hemisphere fossil fuel sources today. The preindustrial Antarctic acetylene levels are comparable to modern day levels, indicating similar emissions in the preindustrial atmosphere, likely from biomass burning. The implications of the preindustrial atmospheric acetylene records from both hemispheres will be discussed.

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

KAUST Repository

Sajid, M.B.

2015-04-01

The mid-infrared wavelength region near 8 mu m 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 v(4) band of methane and the v(4)+v(5) 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. (C) 2015 Elsevier Ltd. All rights reserved.

The Intersystem Model of Psychotherapy: An Integrated Systems Treatment Approach

Science.gov (United States)

Weeks, Gerald R.; Cross, Chad L.

2004-01-01

This article introduces the intersystem model of psychotherapy and discusses its utility as a truly integrative and comprehensive approach. The foundation of this conceptually complex approach comes from dialectic metatheory; hence, its derivation requires an understanding of both foundational and integrational constructs. The article provides a…

How different is the borazine-acetylene dimer from the benzene-acetylene dimer? A matrix isolation infrared and ab initio quantum chemical study

Science.gov (United States)

Verma, Kanupriya; Viswanathan, K. S.; Majumder, Moumita; Sathyamurthy, N.

2017-11-01

The 1:1 dimer of borazine-acetylene has been studied for the first time, both experimentally and computationally. The borazine-acetylene dimer was trapped in Ar and N2 matrices, and studied using infrared spectroscopy. Our experiments clearly revealed two isomers of the borazine-acetylene complex, one in which the N-H of borazine interacted with the carbon of acetylene, and another in which the C-H of acetylene formed a hydrogen bond with a nitrogen atom of borazine. The formation of both isomers in the matrix was evidenced by shifts in the vibrational frequencies of the appropriate modes. Reassuringly, the experimental observations were corroborated by our computations using the second-order Møller-Plesset perturbation theoretic method and coupled-cluster singles, doubles and perturbative triples method in conjunction with different Dunning basis sets, which indicated both these isomers to be stable minima, with the N-HṡṡṡC complex being the global minimum. Atoms-in-molecules and energy decomposition analysis were also carried out for the different isomers of the dimer. These studies reveal that replacing the three C-C linkages in benzene with three B-N linkages in borazine modifies the interaction in the dimer sufficiently, to result in a different potential energy landscape for the borazine-acetylene system when compared with the benzene-acetylene system.

Acetylene Resembling Effect of Ethylene on Seed Germination: Evaluating the Effect of Acetylene Released from Calcium Carbide

Directory of Open Access Journals (Sweden)

Kambiz MASHAYEKHI

2015-09-01

Full Text Available Some vegetable seeds need a very long time to germinate. In these kinds of seeds the second phase of germination is very long. As acetylene’s chemical structure is almost similar to the gaseous hormone ethylene, its’ physiological effect on seed germination should be very similar as well. Therefore, an experiment was established in order to enhance seed germination, by treating seeds with acetylene released from interaction of calcium carbide (CaC2 with water (H2O. A simple system was designed for efficient and proper use of gaseous acetylene resulted from the two substrates interaction, which conducted the produced gas obtained inside the interaction chamber into a sealed container wherein seeds were floating in water. This experiment aimed to evaluate the effect of one concentration of acetylene with different exposure periods (between 1 to 8 hours on parsley, celery and Swees chard seeds’ germination (chosen as late germinating vegetables. The effect of acetylene on seed germination speed and percent was investigated. There were significant differences in both percent and speed of germination within the various treatments. By floating for 3, 5 and 3 hours for parsley, celery and Swiss chard respectively, the highest germination rates were observed. The highest germination speed was achieved by 5, 5 and 3 hours floating respectively for parsley, celery and Swiss chard. Based on the results obtained, the current experiment suggests that acetylene has positive effect on enhancing seed germination of named vegetables, and played the role of ethylene, its effects resembling in regard to seed germination process.

Modelling non-redox enzymes: Anaerobic and aerobic acetylene ...

Indian Academy of Sciences (India)

Administrator

Modelling non-redox enzymes: Anaerobic and aerobic acetylene hydratase. SABYASACHI SARKAR. Department of Chemistry, Indian Institute of Technology, Kanpur 208 016,. India. Acetaldehyde is the first metabolite produced during acetylene degradation by bacteria either aerobically or anaerobically. Conversion of ...

Orientation dependence in collision induced electronic relaxation studied through van der Waals complexes with isomeric structures. Invited feature article

International Nuclear Information System (INIS)

Cheng, P.Y.; Lapierre, L.; Ju, S.S.; DeRose, P.; Dai, H.L.

1994-01-01

Weakly bound molecular complexes with more than one well-defined structures provide us with an unique opportunity to investigate dynamic processes induced by intermolecular interactions with specific orientations. The relative orientation of the two interacting molecules or atoms is defined by the complex structure. The effect of the orientation in the spin changing collisions glyoxal (S 1 ) + Ar → glyoxal (T 1 ) + Ar and acetylene (S 1 ) + Ar → acetylene (T) + Ar have been studied by measuring the intersystem crossing (ISC) rates of the glyoxal(S 1 ).Ar and acetylene(S 1 ).Ar complexes with different isomeric structures. Results show that there is a strong orientation dependence in the ISC of glyoxal(S 1 ) induced by interaction with the Ar atom: the Ar atom positioned in the molecular plane is much more effective than in the out-of-plane position in inducing the S 1 → T 1 transition of glyoxal. On the other hand, studies of acetylene(S 1 ).Ar complexes indicate that the Ar-induced ISC rates are nearly identical for the in-plane and out-of-plane positions. Orientation dependence in the collision induced vibrational relaxation process C 2 H 2 (S 1 , v i ) + Ar → C 2 H 2 (S 1 , v f i ) + Ar is also studied by measuring the vibrational predissociation rates of the acetylene(S 1 ).Ar complex isomers. The results indicate that collisions of C 2 H 2 (S 1 , v 3 = 3, 4) with Ar at two orthogonal orientations are equally effective in causing vibrational relaxation of C 2 H 2 . (orig.)

Intersystem LOCA risk assessment: methodology and results

International Nuclear Information System (INIS)

Galyean, W.J.; Kelly, D.L.; Schroeder, J.A.; Auflick, L.J.; Blackman, H.S.; Gertman, D.I.; Hanley, L.N.

1994-01-01

The United States Nuclear Regulatory Commission is sponsoring a research program to develop an improved understanding of the human factors, hardware and accident consequence issues that dominate the risk from an intersystem loss-of-coolant accident (ISLOCA) at a nuclear power plant. To accomplish the goals of this program, a mehtodology has been developed for estimating ISLOCA core damage frequency and risk. The steps in this methodology are briefly described, along with the results obtained from an application of the methodology at three pressurized water reactors. Also included are the results of a screening study of boiling water reactors. ((orig.))

Positron collisions with acetylene calculated using the R-matrix with pseudo-states method

Science.gov (United States)

Zhang, Rui; Galiatsatos, Pavlos G.; Tennyson, Jonathan

2011-10-01

Eigenphase sums, total cross sections and differential cross sections are calculated for low-energy collisions of positrons with C2H2. The calculations demonstrate that the use of appropriate pseudo-state expansions very significantly improves the representation of this process giving both realistic eigenphases and cross sections. Differential cross sections are strongly forward peaked in agreement with the measurements. These calculations are computationally very demanding; even with improved procedures for matrix diagonalization, fully converged calculations are too expensive with current computer resources. Nonetheless, the calculations show clear evidence for the formation of a virtual state but no indication that acetylene actually binds a positron at its equilibrium geometry.

Positron collisions with acetylene calculated using the R-matrix with pseudo-states method

Energy Technology Data Exchange (ETDEWEB)

Zhang Rui; Galiatsatos, Pavlos G; Tennyson, Jonathan, E-mail: j.tennyson@ucl.ac.uk [Department of Physics and Astronomy, University College London, Gower St., London WC1E 6BT (United Kingdom)

2011-10-14

Eigenphase sums, total cross sections and differential cross sections are calculated for low-energy collisions of positrons with C{sub 2}H{sub 2}. The calculations demonstrate that the use of appropriate pseudo-state expansions very significantly improves the representation of this process giving both realistic eigenphases and cross sections. Differential cross sections are strongly forward peaked in agreement with the measurements. These calculations are computationally very demanding; even with improved procedures for matrix diagonalization, fully converged calculations are too expensive with current computer resources. Nonetheless, the calculations show clear evidence for the formation of a virtual state but no indication that acetylene actually binds a positron at its equilibrium geometry.

Intersystem Interference Reduction for Overlaid HAPS-Terrestrial CDMA System

Science.gov (United States)

Huang, Jeng-Ji; Wang, Wei-Ting; Li, Mingfu; Shiung, David; Ferng, Huei-Wen

In this letter, we propose that directional antennas, combined with power management, be incorporated to reduce intersystem interference in a shared band overlaid high altitude platform station (HAPS)-terrestrial code division multiple access (CDMA) system. To eliminate the HAPS to terrestrial interference, the HAPS is accessed only via directional antennas under the proposed scheme. By doing so, the uplink power to the HAPS can accordingly be increased, so that the terrestrial to HAPS interference is also effectively suppressed.

Recent New Methodologies for Acetylenic Polymers with Advanced Functionalities.

Science.gov (United States)

Qiu, Zijie; Han, Ting; Lam, Jacky W Y; Tang, Ben Zhong

2017-08-01

Polymers synthesized from acetylenic monomers often possess electronically unsaturated fused rings and thus show versatile optoelectronic properties and advanced functionalities. To expand the family of acetylenic polymers, development of new catalyst systems and synthetic routes is critically important. We summarize herein recent research progress on development of new methodologies towards functional polymers using alkyne building blocks since 2014. The polymerizations are categorized by the number of monomer components, namely homopolymerizations, two-component polymerizations, and multicomponent polymerizations. The properties and applications of acetylenic polymers, such as aggregation-induced emission, fluorescent photopatterning, light refraction, chemosensing, mechanochromism, chain helicity, etc., are also discussed.

Ab initio dynamics and photoionization mass spectrometry reveal ion-molecule pathways from ionized acetylene clusters to benzene cation.

Science.gov (United States)

Stein, Tamar; Bandyopadhyay, Biswajit; Troy, Tyler P; Fang, Yigang; Kostko, Oleg; Ahmed, Musahid; Head-Gordon, Martin

2017-05-23

The growth mechanism of hydrocarbons in ionizing environments, such as the interstellar medium (ISM), and some combustion conditions remains incompletely understood. Ab initio molecular dynamics (AIMD) simulations and molecular beam vacuum-UV (VUV) photoionization mass spectrometry experiments were performed to understand the ion-molecule growth mechanism of small acetylene clusters (up to hexamers). A dramatic dependence of product distribution on the ionization conditions is demonstrated experimentally and understood from simulations. The products change from reactive fragmentation products in a higher temperature, higher density gas regime toward a very cold collision-free cluster regime that is dominated by products whose empirical formula is (C 2 H 2 ) n + , just like ionized acetylene clusters. The fragmentation products result from reactive ion-molecule collisions in a comparatively higher pressure and temperature regime followed by unimolecular decomposition. The isolated ionized clusters display rich dynamics that contain bonded C 4 H 4 + and C 6 H 6 + structures solvated with one or more neutral acetylene molecules. Such species contain large amounts (>2 eV) of excess internal energy. The role of the solvent acetylene molecules is to affect the barrier crossing dynamics in the potential energy surface (PES) between (C 2 H 2 ) n + isomers and provide evaporative cooling to dissipate the excess internal energy and stabilize products including the aromatic ring of the benzene cation. Formation of the benzene cation is demonstrated in AIMD simulations of acetylene clusters with n > 3, as well as other metastable C 6 H 6 + isomers. These results suggest a path for aromatic ring formation in cold acetylene-rich environments such as parts of the ISM.

Ab initio dynamics and photoionization mass spectrometry reveal ion–molecule pathways from ionized acetylene clusters to benzene cation

Science.gov (United States)

Stein, Tamar; Bandyopadhyay, Biswajit; Troy, Tyler P.; Fang, Yigang; Kostko, Oleg

2017-01-01

The growth mechanism of hydrocarbons in ionizing environments, such as the interstellar medium (ISM), and some combustion conditions remains incompletely understood. Ab initio molecular dynamics (AIMD) simulations and molecular beam vacuum-UV (VUV) photoionization mass spectrometry experiments were performed to understand the ion–molecule growth mechanism of small acetylene clusters (up to hexamers). A dramatic dependence of product distribution on the ionization conditions is demonstrated experimentally and understood from simulations. The products change from reactive fragmentation products in a higher temperature, higher density gas regime toward a very cold collision-free cluster regime that is dominated by products whose empirical formula is (C2H2)n+, just like ionized acetylene clusters. The fragmentation products result from reactive ion–molecule collisions in a comparatively higher pressure and temperature regime followed by unimolecular decomposition. The isolated ionized clusters display rich dynamics that contain bonded C4H4+ and C6H6+ structures solvated with one or more neutral acetylene molecules. Such species contain large amounts (>2 eV) of excess internal energy. The role of the solvent acetylene molecules is to affect the barrier crossing dynamics in the potential energy surface (PES) between (C2H2)n+ isomers and provide evaporative cooling to dissipate the excess internal energy and stabilize products including the aromatic ring of the benzene cation. Formation of the benzene cation is demonstrated in AIMD simulations of acetylene clusters with n > 3, as well as other metastable C6H6+ isomers. These results suggest a path for aromatic ring formation in cold acetylene-rich environments such as parts of the ISM. PMID:28484019

Reactions of acetylenes with hypophosphorous and phosphonous acids

International Nuclear Information System (INIS)

Nifant'ev, E.E.; Solovetskaya, L.A.; Maslennikova, V.I.; Magdeeva, R.K.; Sergeev, N.M.

1986-01-01

Alkenylphosphonous, alkenylphosphinic, and alkylenebisphosphinic acids were prepared for the first time. The course of the hydrophosphorylation of 1-alkynes depends on the form of the reagent used. The homolytic hydrophosphorylation of acetylenes with hypophosphorous acid proceeds mainly with the participation of one molecule of the acid. The addition of phosphonous acids to acetylenic hydrocarbons leads to both mono- and di-phosphorylated adducts. The nature of the phosphonous acid taken has a substantial influence on the readiness with which the alkylenebisphosphinic acids are formed. Study of the stereoselectivity of the reactions showed that in the case of the monoaddition of hypophosphorous and phosphonous acids to acetylenes mixtures of cis and trans isomeric products are always formed. Phosphorous 31 and carbon 13 NMR spectra are analyzed

Design and experimental investigations on six-stroke SI engine using acetylene with water injection.

Science.gov (United States)

Gupta, Keshav; Suthar, Kishanlal; Jain, Sheetal Kumar; Agarwal, Ghanshyam Das; Nayyar, Ashish

2018-06-02

In the present study, a four-stroke cycle gasoline engine is redesigned and converted into a six-stroke cycle engine and experimental study has been conducted using gasoline and acetylene as fuel with water injection at the end of the recompression stroke. Acetylene has been used as an alternative fuel along with gasoline and performance of the six-stroke spark ignition (SI) engine with these two fuels has been studied separately and compared. Brake power and thermal efficiency are found to be 5.18 and 1.55% higher with acetylene as compared to gasoline in the six-stroke engine. However, thermal efficiency is found to be 45% higher with acetylene in the six-stroke engine as compared to four-stroke SI engine. The CO and HC emissions were found to be reduced by 13.33 and 0.67% respectively with acetylene as compared to gasoline due to better combustion of acetylene. The NO x emission was reduced by 5.65% with acetylene due to lower peak temperature by water injection. The experimental results showed better engine performance and emissions with acetylene as fuel in the six-stroke engine.

Probabilistic based design rules for intersystem LOCAS in ABWR piping

International Nuclear Information System (INIS)

Ware, A.G.; Wesley, D.A.

1993-01-01

A methodology has been developed for probability-based standards for low-pressure piping systems that are attached to the reactor coolant loops of advanced light water reactors (ALWRs) which could experience reactor coolant loop temperatures and pressures because of multiple isolation valve failures. This accident condition is called an intersystem loss-of-coolant accident (ISLOCA). The methodology was applied to various sizes of carbon and stainless steel piping designed to advanced boiling water reactor (ABWR) temperatures and pressures

Assessing the long-term variability of acetylene and ethane in the stratosphere of Jupiter

Science.gov (United States)

Melin, Henrik; Fletcher, L. N.; Donnelly, P. T.; Greathouse, T. K.; Lacy, J. H.; Orton, G. S.; Giles, R. S.; Sinclair, J. A.; Irwin, P. G. J.

2018-05-01

Acetylene (C2H2) and ethane (C2H6) are both produced in the stratosphere of Jupiter via photolysis of methane (CH4). Despite this common source, the latitudinal distribution of the two species is radically different, with acetylene decreasing in abundance towards the pole, and ethane increasing towards the pole. We present six years of NASA IRTF TEXES mid-infrared observations of the zonally-averaged emission of methane, acetylene and ethane. We confirm that the latitudinal distributions of ethane and acetylene are decoupled, and that this is a persistent feature over multiple years. The acetylene distribution falls off towards the pole, peaking at ∼ 30°N with a volume mixing ratio (VMR) of ∼ 0.8 parts per million (ppm) at 1 mbar and still falling off at ± 70° with a VMR of ∼ 0.3 ppm. The acetylene distributions are asymmetric on average, but as we move from 2013 to 2017, the zonally-averaged abundance becomes more symmetric about the equator. We suggest that both the short term changes in acetylene and its latitudinal asymmetry is driven by changes to the vertical stratospheric mixing, potentially related to propagating wave phenomena. Unlike acetylene, ethane has a symmetric distribution about the equator that increases toward the pole, with a peak mole fraction of ∼ 18 ppm at about ± 50° latitude, with a minimum at the equator of ∼ 10 ppm at 1 mbar. The ethane distribution does not appear to respond to mid-latitude stratospheric mixing in the same way as acetylene, potentially as a result of the vertical gradient of ethane being much shallower than that of acetylene. The equator-to-pole distributions of acetylene and ethane are consistent with acetylene having a shorter lifetime than ethane that is not sensitive to longer advective timescales, but is augmented by short-term dynamics, such as vertical mixing. Conversely, the long lifetime of ethane allows it to be transported to higher latitudes faster than it can be chemically depleted.

Anaerobic oxidation of acetylene by estuarine sediments and enrichment cultures

International Nuclear Information System (INIS)

Culbertson, C.W.; Zehnder, A.J.B.; Oremland, R.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 chloroamphenicol, air, and autoclaving. Addition of 14 C 2 H 2 to slurries resulted in the formation of 14 CO 2 and the transient appearance of 14 C-soluble intermediates, of which acetate was a major component. Acetylene oxidation stimulated sulfate reduction; however, sulfate reduction was not required for the loss of C 2 H 2 to occur. Enrichment cultures were obtained which grew anaerobically at the expense of C 2 H 2

Ethane and acetylene abundances in the Jovian atmosphere

Science.gov (United States)

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

1976-01-01

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

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

OpenAIRE

Rosner, Bettina M.; Schink, Bernhard

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 prote...

BASF and acetylene. 70 years of reppe chemistry - long-standing reliability and promising future - and now, the only natural gas based clean technology for acetylene production

Energy Technology Data Exchange (ETDEWEB)

Vicari, M. [BASF SE, Ludwigshafen (Germany)

2013-11-01

Acetylene is still an attractive intermediate synthesis component because carbon in methane from natural gas comes at a lower price than carbon in naphtha from crude oil or coal. Acetylene can be understood as a product of C-C coupling and functionalization. Beginning in the 1950s, BASF developed the partial oxidation (Pox) process, in addition to the electric arc process dating from the 1930s and the submerged flame process. The originally developed Pox process came along with severe emissions of hydrocarbons to the environment. Nowadays it is extremely important to have a clean, environmentally friendly technology. So in the 1990s a closed water-quench process was developed and built in the United States. The presentation focuses on the ways of making acetylene, the use of acetylene and BASF's closed water-quench process based on natural gas. This process will be presented including some important safety aspects. The process is available for licensing. (orig.)

Efficient separation of ethylene from acetylene/ethylene mixtures by a flexible-robust metalorganic framework

NARCIS (Netherlands)

Li, L.; Lin, R.-B.; Krishna, R.; Wang, X.; Li, B.; Wu, H.; Li, J.; Zhou, W.; Chen, B.

2017-01-01

During the production of polymer-grade ethylene, trace amounts of acetylene (about 1%) in the ethylene feed need to be reduced to 40 parts per million (ppm). We herein report a metal–organic framework (MOF) of flexible-robust nature for the efficient removal of acetylene from acetylene/ethylene

Efficient triplet application in exciplex delayed-fluorescence OLEDs using a reverse intersystem crossing mechanism based on a ΔES-T of around zero.

Science.gov (United States)

Zhang, Tianyou; Chu, Bei; Li, Wenlian; Su, Zisheng; Peng, Qi Ming; Zhao, Bo; Luo, Yongshi; Jin, Fangming; Yan, Xingwu; Gao, Yuan; Wu, Hairuo; Zhang, Feng; Fan, Di; Wang, Junbo

2014-08-13

We demonstrate highly efficient exciplex delayed-fluorescence organic light-emitting diodes (OLEDs) in which 4,4',4″-tris[3-methylphenyl(phenyl)aminotriphenylamine (m-MTDATA) and 4,7-diphenyl-1,10-phenanthroline (Bphen) were selected as donor and acceptor components, respectively. Our m-MTDATA:Bphen exciplex electroluminescence (EL) mechanism is based on reverse intersystem crossing (RISC) from the triplet to singlet excited states. As a result, an external quantum efficiency (EQE) of 7.79% at 10 mA/cm(2) was observed, which increases by 3.2 and 1.5 times over that reported in Nat. Photonics 2012, 6, 253 and Appl. Phys. Lett. 2012, 101, 023306, respectively. The high EQE would be attributed to a very easy RISC process because the energy difference between the singlet and triplet excited states is almost around zero. The verdict was proven by photoluminescence (PL) rate analysis at different temperatures and time-resolved spectral analysis. Besides, the study of the transient PL process indicates that the presence of an unbalanced charge in exciplex EL devices is responsible for the low EQE and high-efficiency roll-off. When the exciplex devices were placed in a 100 mT magnetic field, the permanently positive magnetoelectroluminescence and magnetoconductivity were observed. The magnetic properties confirm that the efficient exciplex EL only originates from delayed fluorescence via RISC processes but is not related to the triplet-triplet annihilation process.

Fuzzy logic control for selective hydrogenation of acetylene in ethylene rich streams using visual basic

International Nuclear Information System (INIS)

Malik, S.R.; Suleman, H.; Khan, J.R.

2010-01-01

Presence of acetylene is technically disadvantageous in the ethylene rich gas streams from steam crackers. Acetylene tends to polymerize and inactivates the transition metal catalysts, forming highly explosive compounds. The acetylene content has to be selectively reduced to less than one part per million for such streams. The acetylene hydrogenation unit requires stringent control parameters and needs specialized process control techniques for its operation. This study is concerned with application of Fuzzy Logic Control to manipulate and control the process plant with higher precision and greater simplicity. The control program has been written in visual Basic and entails all major scenarios of work modes for successful hydrogenation of Acetylene. (author)

Evaluation of Sorbents for Acetylene Separation in Atmosphere Revitalization Loop Closure

Science.gov (United States)

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

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

KAUST Repository

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

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

Stability improvement of the Nieuwland catalyst in the dimerization of acetylene to monovinylacetylene

Institute of Scientific and Technical Information of China (English)

Jianguo Liu; Yizan Zuo; Minghan Han; Zhanwen Wang; Dezheng Wang

2012-01-01

In the process of dimerization of acetylene to produce monovinylacetylene (MVA),the loss of active component CuCl in the Nieuwland catalyst due to the formation of a dark red precipitate was investigated.The formula of the precipitate was CuCl·2C2H2·1/5NH3,and it was presumed to be formed by the combination of NH3,C2H2 and [Cu]-acetylene π-complex,which was an intermediate in the dimerization reaction.The addition of hydrochloric acid into the catalyst can reduce the formation of precipitate,whereas excessive H+ is unfavorable to the dimerization reaction of acetylene.To balance between high acetylene conversion and low loss rate of CuCl,the optimum mass percentage of HCl in the added hydrochloric acid was determined.The result showed the optimum mass percentage of HCl decreased from 5.0％ to 3.2％ when the space velocity of acetylene was from 140 h-1 to 360 h-1.The result in this work also indicated the pH of the Nieuwland catalyst should be kept in the range of 5.80-5.97 during the reaction process,which was good for both catalyst life and acetylene conversion.

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

Science.gov (United States)

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.

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

Science.gov (United States)

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.

Leukotriene B4 omega-hydroxylase in human polymorphonuclear leukocytes. Suicidal inactivation by acetylenic fatty acids.

Science.gov (United States)

Shak, S; Reich, N O; Goldstein, I M; Ortiz de Montellano, P R

1985-10-25

Human polymorphonuclear leukocytes (PMN) not only generate and respond to leukotriene B4 (LTB4), but also catabolize this mediator of inflammation rapidly and specifically by omega-oxidation (probably due to the action of a cytochrome P-450 enzyme). To develop pharmacologically useful inhibitors of the LTB4 omega-hydroxylase in human PMN, we devised a general scheme for synthesizing terminal acetylenic fatty acids based on the "acetylenic zipper" reaction. We found that the LTB4 omega-hydroxylase in intact PMN and in PMN sonicates is inactivated in a concentration-dependent fashion by terminal acetylenic analogues of lauric, palmitic, and stearic acids (i.e. 11-dodecynoic, 15-hexadecynoic, and 17-octadecynoic acids). Consistent with a suicidal process, inactivation of the LTB4 omega-hydroxylase requires molecular oxygen and NADPH, is time-dependent, and follows pseudo-first-order kinetics. Inactivation of the omega-hydroxylase by acetylenic fatty acids also is dependent on the terminal acetylenic moiety and the carbon chain length. Saturated fatty acids lacking a terminal acetylenic moiety do not inactivate the omega-hydroxylase. In addition, the two long-chain (C16, C18) acetylenic fatty acids inactivate the omega-hydroxylase at much lower concentrations (less than 5.0 microM) than those required for inactivation by the short-chain (C12) terminal acetylenic fatty acid (100 microM). Potent suicidal inhibitors of the LTB4 omega-hydroxylase in human PMN will help elucidate the roles played by LTB4 and its omega-oxidation products in regulating PMN function and in mediating inflammation.

Ion structure and sequence of ion formation in acetylene flames

Energy Technology Data Exchange (ETDEWEB)

Larionova, I.A.; Fialkov, B.S.; Kalinich, K.YA.; Fialkov, A.B.; Ospanov, B.S.

1993-06-01

Results of a study of the ion composition of acetylene-air flames burning at low pressures are reported. Data on ion formation are compared for flames of saturated hydrocarbons, oxygen-containing fuels, and acetylene. It is shown that the characteristics of ion formation in the flame front and directly ahead of it are similar to those observed in flames of other fuels. These characteristics, however, are different in the low-temperature region. 9 refs.

Acetylene diffusion in Na-Y zeolite

Indian Academy of Sciences (India)

ideal guest molecule to start with. Here we ... In that case the incoherent scattering law, Sinc(Q, ω), alone describes the dynamics. Q(=k−k0) is the .... The results of QENS measurements to study the diffusion of acetylene gas in zeolite. Na-Y at ...

Potent In Vitro Antifungal Activities of Naturally Occurring Acetylenic Acids▿

Science.gov (United States)

Li, Xing-Cong; Jacob, Melissa R.; Khan, Shabana I.; Ashfaq, M. Khalid; Babu, K. Suresh; Agarwal, Ameeta K.; ElSohly, Hala N.; Manly, Susan P.; Clark, Alice M.

2008-01-01

Our continuing effort in antifungal natural product discovery has led to the identification of five 6-acetylenic acids with chain lengths from C16 to C20: 6-hexadecynoic acid (compound 1), 6-heptadecynoic acid (compound 2), 6-octadecynoic acid (compound 3), 6-nonadecynoic acid (compound 4), and 6-icosynoic acid (compound 5) from the plant Sommera sabiceoides. Compounds 2 and 5 represent newly isolated fatty acids. The five acetylenic acids were evaluated for their in vitro antifungal activities against Candida albicans, Candida glabrata, Candida krusei, Candida tropicalis, Candida parapsilosis, Cryptococcus neoformans, Aspergillus fumigatus, Aspergillus flavus, Aspergillus niger, Trichophyton mentagrophytes, and Trichophyton rubrum by comparison with the positive control drugs amphotericin B, fluconazole, ketoconazole, caspofungin, terbinafine, and undecylenic acid. The compounds showed various degrees of antifungal activity against the 21 tested strains. Compound 4 was the most active, in particular against the dermatophytes T. mentagrophytes and T. rubrum and the opportunistic pathogens C. albicans and A. fumigatus, with MICs comparable to several control drugs. Inclusion of two commercially available acetylenic acids, 9-octadecynoic acid (compound 6) and 5,8,11,14-eicosatetraynoic acid (compound 7), in the in vitro antifungal testing further demonstrated that the antifungal activities of the acetylenic acids were associated with their chain lengths and positional triple bonds. In vitro toxicity testing against mammalian cell lines indicated that compounds 1 to 5 were not toxic at concentrations up to 32 μM. Furthermore, compounds 3 and 4 did not produce obvious toxic effects in mice at a dose of 34 μmol/kg of body weight when administered intraperitoneally. Taking into account the low in vitro and in vivo toxicities and significant antifungal potencies, these 6-acetylenic acids may be excellent leads for further preclinical studies. PMID:18458131

Potent in vitro antifungal activities of naturally occurring acetylenic acids.

Science.gov (United States)

Li, Xing-Cong; Jacob, Melissa R; Khan, Shabana I; Ashfaq, M Khalid; Babu, K Suresh; Agarwal, Ameeta K; Elsohly, Hala N; Manly, Susan P; Clark, Alice M

2008-07-01

Our continuing effort in antifungal natural product discovery has led to the identification of five 6-acetylenic acids with chain lengths from C(16) to C(20): 6-hexadecynoic acid (compound 1), 6-heptadecynoic acid (compound 2), 6-octadecynoic acid (compound 3), 6-nonadecynoic acid (compound 4), and 6-icosynoic acid (compound 5) from the plant Sommera sabiceoides. Compounds 2 and 5 represent newly isolated fatty acids. The five acetylenic acids were evaluated for their in vitro antifungal activities against Candida albicans, Candida glabrata, Candida krusei, Candida tropicalis, Candida parapsilosis, Cryptococcus neoformans, Aspergillus fumigatus, Aspergillus flavus, Aspergillus niger, Trichophyton mentagrophytes, and Trichophyton rubrum by comparison with the positive control drugs amphotericin B, fluconazole, ketoconazole, caspofungin, terbinafine, and undecylenic acid. The compounds showed various degrees of antifungal activity against the 21 tested strains. Compound 4 was the most active, in particular against the dermatophytes T. mentagrophytes and T. rubrum and the opportunistic pathogens C. albicans and A. fumigatus, with MICs comparable to several control drugs. Inclusion of two commercially available acetylenic acids, 9-octadecynoic acid (compound 6) and 5,8,11,14-eicosatetraynoic acid (compound 7), in the in vitro antifungal testing further demonstrated that the antifungal activities of the acetylenic acids were associated with their chain lengths and positional triple bonds. In vitro toxicity testing against mammalian cell lines indicated that compounds 1 to 5 were not toxic at concentrations up to 32 muM. Furthermore, compounds 3 and 4 did not produce obvious toxic effects in mice at a dose of 34 mumol/kg of body weight when administered intraperitoneally. Taking into account the low in vitro and in vivo toxicities and significant antifungal potencies, these 6-acetylenic acids may be excellent leads for further preclinical studies.

Diamond growth in oxygen-acetylene flame

International Nuclear Information System (INIS)

Haga, Mario S.; Nagai, Y. Ernesto; Suzuki, Carlos K.

1995-01-01

What was supposed to be a laboratory curiosity in the 80's, in recent years the low pressure process for the production of man-made diamond turned out to be a major target for research and development of many high-tech companies. The main reason for such an interest stems on the possibility of coating many materials with a diamond film possessing the same amazing properties of the bulk natural diamond. Polycrystalline diamond film has been deposited on Mo substrate by using oxygen-acetylene flame of a welding torch. The substrate temperature has been held constant about 700 d eg C by means of a water cooled mount designed properly. Precision flowmeters have been used to control the flow ratio oxygen/acetylene, a key parameter for the success in diamond growth. Diamond has been detected by X-ray diffraction, a fast foolproof technique for crystal identification. Another method of analysis often used in Raman spectroscopy, which is able to exhibit amorphous structure besides crystalline phase. (author)

Safety assessment of inter-channel / inter-system digital communications: A defensive measures approach

International Nuclear Information System (INIS)

Thuy, N. N. Q.

2006-01-01

Inappropriately designed inter-channel and inter-system digital communications could initiate common cause failure of multiple channels or multiple systems. Defensive measures were introduced in EPRI report TR-1002835 (Guideline for Performing Defense-in-Depth and Diversity Assessments for Digital Upgrades) to assess, on a deterministic basis, the susceptibility of digital systems architectures to common-cause failures. This paper suggests how this approach could be applied to assess inter-channel and inter-system digital communications from a safety standpoint. The first step of the approach is to systematically identify the so called 'influence factors' that one end of the data communication path can have on the other. Potential factors to be considered would typically include data values, data volumes and data rates. The second step of the approach is to characterize the ways possible failures of a given end of the communication path could affect these influence factors (e.g., incorrect data values, excessive data rates, time-outs, incorrect data volumes). The third step is to analyze the designed-in measures taken to guarantee independence of the other end. In addition to classical error detection and correction codes, typical defensive measures are one-way data communication, fixed-rate data communication, fixed-volume data communication, validation of data values. (authors)

Mechanism-based inactivation of benzo[a]pyrene hydroxylase by aryl acetylenes and aryl olefins

International Nuclear Information System (INIS)

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

1986-01-01

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, 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

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

International Nuclear Information System (INIS)

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

2016-01-01

Graphical abstract: - Highlights: • For the first time, we succeeded in the LPCVD growth of monolayer graphene using acetylene as the precursor gas. • The growth rate is very high when acetylene is used as the source gas. Our process has exhibited the potential to shorten the growth time of CVD graphene. • We found that the domain size, defects density, layer number and the sheet resistance of graphene can be changed by changing the acetylene flow rates. • We found that it is also possible to form bilayer graphene using acetylene. However, further study are necessary to reduce the defects density. - Abstract: 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.

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

Energy Technology Data Exchange (ETDEWEB)

Yang, Meng, E-mail: youmou@rift.mech.tohoku.ac.jp [Department of Nanomechanics, Graduate School of Engineering, Tohoku University, Sendai 980-8579 (Japan); Sasaki, Shinichirou [Department of Nanomechanics, Graduate School of Engineering, Tohoku University, Sendai 980-8579 (Japan); Suzuki, Ken; Miura, Hideo [Fracture and Reliability Research Institute, Tohoku University, Sendai 980-8579 (Japan)

2016-03-15

Graphical abstract: - Highlights: • For the first time, we succeeded in the LPCVD growth of monolayer graphene using acetylene as the precursor gas. • The growth rate is very high when acetylene is used as the source gas. Our process has exhibited the potential to shorten the growth time of CVD graphene. • We found that the domain size, defects density, layer number and the sheet resistance of graphene can be changed by changing the acetylene flow rates. • We found that it is also possible to form bilayer graphene using acetylene. However, further study are necessary to reduce the defects density. - Abstract: 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.

Pore chemistry and size control in hybrid porous materials for acetylene capture from ethylene

KAUST Repository

Cui, X.

2016-05-20

The trade-off between physical adsorption capacity and selectivity of porous materials is a major barrier for efficient gas separation and purification through physisorption. We report control over pore chemistry and size in metal coordination networks with hexafluorosilicate and organic linkers for the purpose of preferential binding and orderly assembly of acetylene molecules through cooperative host-guest and/or guest-guest interactions. The specific binding sites for acetylene are validated by modeling and neutron powder diffraction studies. The energies associated with these binding interactions afford high adsorption capacity (2.1 millimoles per gram at 0.025 bar) and selectivity (39.7 to 44.8) for acetylene at ambient conditions. Their efficiency for the separation of acetylene/ethylene mixtures is demonstrated by experimental breakthrough curves (0.73 millimoles per gram from a 1/99 mixture).

Experimental investigation on dual fuel operation of acetylene in a DI diesel engine

Energy Technology Data Exchange (ETDEWEB)

Lakshmanan, T. [Department of Mechanical Engineering, Rajarajeswari Engineering College, Adayalampattu, Chennai, 600095 (India); Nagarajan, G. [Internal Combustion Engineering Division, College of Engineering, Anna University, Chennai, 600025 (India)

2010-05-15

Depletion of fossils fuels and environmental degradation have prompted researchers throughout the world to search for a suitable alternative fuel for diesel engine. One such step is to utilize renewable fuels in diesel engines by partial or total replacement of diesel in dual fuel mode. In this study, acetylene gas has been considered as an alternative fuel for compression ignition engine, which has excellent combustion properties. Investigation has been carried out on a single cylinder, air cooled, direct injection (DI), compression ignition engine designed to develop the rated power output of 4.4 kW at 1500 rpm under variable load conditions, run on dual fuel mode with diesel as injected primary fuel and acetylene inducted as secondary gaseous fuel at various flow rates. Acetylene aspiration resulted in lower thermal efficiency. Smoke, HC and CO emissions reduced, when compared with baseline diesel operation. With acetylene induction, due to high combustion rates, NO{sub x} emission significantly increased. Peak pressure and maximum rate of pressure rise also increased in the dual fuel mode of operation due to higher flame speed. It is concluded that induction of acetylene can significantly reduce smoke, CO and HC emissions with a small penalty on efficiency. (author)

[CHANGE OF CHARACTER OF INTERSYSTEMIC INTERACTIONS IN NEWBORN RAT PUPS UNDER CONDITIONS OF A DECREASE OF MOTOR ACTIVITY].

Science.gov (United States)

Sizonov, V A; Dmitrieva, L E; Kuznetsov, S V

2015-01-01

Interaction of slow-wave.rhythmic components of cardiac, respiratory.and motor activity was investigated in newborn rat pups on the first day after birth under normal conditions and after pharmacological depression of spontaneous periodic motor activity (SPMA) produced by injecting myocuran (myanesin) at low (100 mg/pg, i/p) and maximal (235 mg/pg, i/p) dosages. The data obtained allow to infer that in rat pups after birth the intersystemic interactions are realized mainly via slow-wave oscillations of about-one- and many-minute ranges whereas the rhythms of decasecond range do not play a significant role in integrative processes. Injection of miocuran at a dose causing no muscle relaxation and no inhibition of motor activity produces changes of the cardiac and respiratory rhythms as well as a transitory decrease of the magnitude of coordinate relations mediated by the rhythms of about-one- and many-minute ranges. The consequences of muscle relaxant injection were found to be more significant for intersystemic interactions with participation of the respiratory system. An increase of the dosage and, correspondingly, the total inhibition of SPMA is accompanied by reduction of the slow-wave components from the pattern of cardiac and respiratory rhythms. The cardiorespiratory interactions, more expressed in intact rat pups, are reduced in the about-one- and many-minute ranges of modulation whereas in the decasecond range of modulation they are slightly increased. Key words: early ontogenesis, intersystemic interactions, cardiac rhythm, respiration, motor activity, myocuran (myanesin).

Detonation engine fed by acetylene-oxygen mixture

Science.gov (United States)

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.

Ab initio and matrix isolation study of the acetylene-furan dimer

International Nuclear Information System (INIS)

Sanchez-Garcia, Elsa; Mardyukov, Artur; Tekin, Adem; Crespo-Otero, Rachel; Montero, Luis A.; Sander, Wolfram; Jansen, Georg

2008-01-01

Five acetylene-furan dimer structures are identified using ab initio calculations at the second-order Moller-Plesset (MP2) level of theory. The structures are stabilized by two basic types of intermolecular interactions: the CH...O and the CH...π interaction. The CH...π interaction appears in two variants, depending on which molecule provides the hydrogen atom and which molecule the π system. The MP2 results indicate that the CH...π interaction between one of the hydrogen atoms of acetylene and the π system of furan as found in structure A is the strongest interaction, followed by the in-plane CH...O interaction in the second most stable acetylene-furan dimer structure B. A matrix isolation study shows the acetylene-furan dimer to exist in an argon matrix, but likely rather as structure B than as A. High level coupled cluster calculations with up to triple excitations (CCSD(T)) yield the interaction energy of structure A as about -2.4 kcal/mol in the complete basis set limit and find structure B to be nearly isoenergetic with -2.3 kcal/mol. This is confirmed in calculations employing the density functional theory combined with symmetry adapted intermolecular perturbation theory (DFT-SAPT) approach yielding interaction energies of -2.3 and -2.0 kcal/mol for A and B, respectively. DFT-SAPT also helps to understand the importance of the electrostatic, induction and dispersion interaction energies and their respective exchange counterparts for the stability of the various acetylene-furan dimer structures. The CH...O and CH...π interactions are furthermore analyzed with the help of the atoms in molecules (AIM) theory

Acetylene on Titan

Science.gov (United States)

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).

Exchange reaction of acetylene-d2 with hydrogen chloride

International Nuclear Information System (INIS)

Bopp, A.F.; Kern, R.D.

1975-01-01

A mixture containing 3 percent each of the reactants C 2 D 2 and HCl in an Ne--Ar diluent was studied over the temperature range 1650 to 2600 0 K utilizing a shock tube coupled to a time-of-flight mass spectrometer. Plots of the mole fractions f of the exchange products, DCl and C 2 HD, revealed two distinct regions of growth: (a) an initial low conversion region characterized by an induction period t/sub i/; and (b) a region of accelerated exchange during which exchange products were formed with a quadratic dependence of the reaction time. These two regions labeled a and b were combined using two empirical equations, 1 - f/sub a//f/sub eq,a/ = exp [-k/sub a/[M]t], where t less than or equal to t/sub i/, and 1 - f/sub b//f/sub eq,b/ = exp [-k/sub b/[M](t - t/sub i/) 2 ], in order to represent the entire reaction profile at any given temperature within the interval investigated. The Arrhenius parameters for k/sub a/ and k/sub b/ were determined to be 10 11 . 15+-0 . 30 exp (-19990 +- 2850/RT) and 10 16 . 40+-0 . 41 exp (-31480 +- 4200/RT), respectively, for DCl and 10 11 . 69+-0 . 29 exp (-19150 +- 2740/RT) and 10 15 . 24+-0 . 34 exp (-17620 +- 3480/RT) for C 2 HD. The units for k/sub a/ are cm 3 mol -1 sec -1 and cm 3 mol -1 sec -2 for k/sub b/. Activation energies are reported in cal mol -1 . Comparison with the profiles obtained for acetylene pyrolysis strongly suggests that the mechanism for the exchange is atomic. Furthermore, the exchange experiments indicate that the initial step in the pyrolysis of acetylene is the disproportionation reaction, 2C 2 H 2 → C 2 H + C 2 H 3

Synthesis of acetylenic derivatives of hydroxynaphthoquinone

International Nuclear Information System (INIS)

Sanchez Kopper, Andres

2010-01-01

The acetylene derivatives synthesis 2-hydroxy-1 ,4-naphthoquinones was studied using different reaction conditions: coupling with copper and silver acetylides, Sonogashira reaction with and without CU (I) as cocatalyst. The reaction conditions are optimized for coupling of iodine lawson and ylide phenyl lawsone of iodine with various terminal acetylenes: phenyl acetylene, propargyl alcohol, 1-heptin and 2-methyl-3-butyne-2-ol. Also, reactants such as bromides of hidroxinaphthoquinones were used with protecting groups such as acetate, methoxy, phenyloxy, benzyloxy and tricloroetoxy. The synthesis of 2-hydroxy-3-(3-hydroxy-3-ynyl-1-methylbutane)-1,4-naphthoquinone, 2-methoxy-3-(2-phenylethynyl) -1,4-naphthoquinone and 2-(2-phenylethynyl)-3-(2,2,2-tricloroetoxy)-1,4-naphthoquinone was performed with rates of return of 22%, 57% and 67% respectively. The reaction of the yodolawsona was obtained with 3-chloro-3-methyl-1-butyne in the presence of CuI, CsI and Cs 2 Co 3 obtaining the enol ether: 3,3-dimethyl-2-methyl-2 ,3-dihydronaphto [2 ,3-b]furan-4,9-dione (dehydro-α-dunion), with a rate of return of 58%. This enol ether was used as a reactant for the formation, through a regioselective hydrogenation with PtO 2 /t-butanol of α-dunion with a yield of 50%. Furthermore, by acid hydrolysis with H 2 SO 4 has been possible to obtain a percentage yield of 75% streptocarpone. Both, α-dunion and streptocarpone, natural products extracted from Streptocarpus dunni shrub, with antiparasitic activity, and which so far had not presented an efficient synthesis. A mechanism is proposed for the reaction of formation of the enol ether where it is presumed the presence of a zwitterion-vinyl carbene as key intermediate of the reaction. All products were characterized by spectroscopy 1 H and 13 C-NMR, UV-Vis and IR. (author) [es

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

International Nuclear Information System (INIS)

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

Analysis of the polymeric film and fine dust obtained in plasma of acetylene and acetylene-nitrogen

International Nuclear Information System (INIS)

Rojas, Andres F; Ortiz, Jairo A; Devia Alfonso

1998-01-01

The results are presented from the resistance analyses to the corrosion of the polymeric covering obtained in plasma of acetylene, on a substrata of aluminum alloy, with the techniques of metallographic analysis, infrared and electrochemical, as much for the fine dust as for the grown film on aluminum. Also, the results of the electrochemical test of polarization made to these films will be shown, which demonstrated an improvement of 2.6 and 4.6 times in the resistance to the corrosion when the material treaty is exposed NaCl 0.2 N and Na H2 PO4 01 M, respectively, in comparison with the substrata without recovering. For the movie obtained in acetylene /nitrogen plasma on steel 1016 the micrographs of the superficial structure of the material they will be shown before and after being treated, which were used to measure the thickness of the cover; also, it will be given to know the results of the tests of adhesion and qualitative analysis of resistance before diverse chemical agents (such as: Benzene, Toluene, H2SO4, HNO3, NaCl, CACO3 NaOH and KOH) and the resistance results are presented from the cover to them

Influence of soil composition in the determination of chromium by atomic absorption spectrometry with flame air / acetylene

International Nuclear Information System (INIS)

Duran Sosa, Ibis; Granda Valdes, Mayra; Pomares Alfonso, Mario Simeon

2014-01-01

The Air-acetylene Flame Atomic Absorption determination of chromium is a complex task, being strongly influenced by sample composition and instrumental conditions. The objective of this work was to study the influence of Al, Ca, Fe, K, Mg, and Na on the absorption of chromium in the air-acetylene flame, both separately and combined in solution, when acetylene flow and burner height vary. Dissolutions of the mixtures simulated the composition of four soils from the Quibu River Basin in Havana, Cuba. Chromium absorption first increased and then decreased with increment of acetylene flow for shorter burner heights (∼ 2-4 mm); while a continuous increase was observed for larger heights (> 4 mm). This behavior was the same in the presence and absence of interfering chemical element, mentioned above. On the other hand, the dependence of the magnitude of the interference with acetylene flow and burner height was complex and dependent on the interfering element, particularly at larger heights where the behavior of Al was remarkably different. The interference of the four mixtures of Al, Ca, K, Fe, Mg and Na decreased in comparison to individual interfering effects and was less dependent on acetylene flow and burner height. Finally, a significant reduction of interference on chromium determination in soil samples was achieved by an adequate selection of acetylene flow and burner height

Investigation of supercapacitors with carbon electrodes obtained from argon-acetylene arc plasma

OpenAIRE

Kavaliauskas, Žydrūnas

2010-01-01

The dissertation examines topics related to the formation of supercapacitors using plasma technology and their analysis. Plasma spray technology was used to form supercapacitors electrodes. Carbon was deposited on stainless steel surface using the atmospheric pressure argon-acetylene plasma. The deposition of nickel oxide on the surface of carbon electrodes was made using magnetron sputtering method. The influence of acetylene amount to the supercapacitors electrodes and the electrical charac...

A Convenient Synthesis of Conjugated Acetylenic Ketones by Copper(l)-Catalyzed under Microwave Irradiation

Institute of Scientific and Technical Information of China (English)

WANG; JinXian

2001-01-01

Alkynyl ketones are useful precursors and intermediates in synthetic organic chemistry1 and has evoked considerable interest. A number of methods for the synthesis of conjugated acetylenic ketones involve the reaction a metal acetylide with an acyl chlorides or another carboxylic acid derivative have been developed 2. Recently, the synthesis of α, β-conjugated acetylenic ketones catalyzed by Pd(Ⅱ) or by copper(Ⅰ)pd(Ⅱ) reaction of 1-alkynes and acyl chlorides have been described. The acylation of terminal alkynes by acyl chlorides in the presence of catalytic amounts copper(Ⅰ) salts leading to α, β-conjugated acetylenic ketones has also been reported. However, many of these reactions suffer from lack of high pressure (17 atm), long reaction time (30 h)and require low temperatures (-78℃). Our work involves the synthesis of conjugated acetylenic ketones via the reaction of terminal alkynes with aroyl chlorides in the presence of cuprous iodide under microwave irradiation conditions.……

A Convenient Synthesis of Conjugated Acetylenic Ketones by Copper(l)-Catalyzed under Microwave Irradiation

Institute of Scientific and Technical Information of China (English)

WANG JinXian; WEI BangGuo; ZHAO LianBiao; HU YuLai; KANG LiQing

2001-01-01

@@ Alkynyl ketones are useful precursors and intermediates in synthetic organic chemistry1 and has evoked considerable interest. A number of methods for the synthesis of conjugated acetylenic ketones involve the reaction a metal acetylide with an acyl chlorides or another carboxylic acid derivative have been developed 2. Recently, the synthesis of α, β-conjugated acetylenic ketones catalyzed by Pd(Ⅱ) or by copper(Ⅰ)pd(Ⅱ) reaction of 1-alkynes and acyl chlorides have been described. The acylation of terminal alkynes by acyl chlorides in the presence of catalytic amounts copper(Ⅰ) salts leading to α, β-conjugated acetylenic ketones has also been reported. However, many of these reactions suffer from lack of high pressure (17 atm), long reaction time (30 h)and require low temperatures (-78℃). Our work involves the synthesis of conjugated acetylenic ketones via the reaction of terminal alkynes with aroyl chlorides in the presence of cuprous iodide under microwave irradiation conditions.

Study on using acetylene in dual fuel mode with exhaust gas recirculation

International Nuclear Information System (INIS)

Lakshmanan, T.; Nagarajan, G.

2011-01-01

Interest in employing gaseous fuels to internal combustion (IC) engines whether for stationary or mobile automotive applications has gained importance because of the economical, sustainable and environmental technical features associated with their usage. However, the incidence of preignition and knock remains a significant barrier in achieving their optimum performance potential. With the advent of latest technologies, the above barriers are eliminated. One such technique is timed manifold injection (TMI) of the gaseous fuel, which is controlled electronically to precisely monitor the induction of fuel to overcome the preignition problem in the intake. In the present investigation, acetylene was injected in the intake manifold in a single cylinder diesel engine, with a gas flow rate of 240 g/h, start of injection time is 10 o aTDC and 90 o CA (9.9 ms) duration, operated in dual fuel mode. In order to decrease the NOx emissions from acetylene-diesel engine, cooled EGR was employed. The cylinder pressure, brake thermal efficiency and emissions such as NOx, smoke, CO, HC, CO 2 and exhaust gas temperature were studied. Dual fuel operation with acetylene induction coupled with cooled EGR results in lowered NOx emissions and improved part load performance. -- Highlights: → Acetylene was tried in SI engines, but due to backfire further research was hindered as an alternative fuel. → But it is not tried in CI engine. Timed manifold injection was tried in diesel engine in the present work to combat backfire. → Author was successful in running the diesel engine in dual fuel mode. → 21% maximum diesel replacement was achieved. Author is confident that acetylene will be commercialised as a fuel for diesel engine in future.

Triplet state photochemistry and the three-state crossing of acetophenone within time-dependent density-functional theory

Energy Technology Data Exchange (ETDEWEB)

Huix-Rotllant, Miquel, E-mail: miquel.huix@gmail.com; Ferré, Nicolas, E-mail: nicolas.ferre@univ-amu.fr [Institut de Chimie Radicalaire (UMR-7273), Aix-Marseille Université, CNRS, 13397 Marseille Cedex 20 (France)

2014-04-07

Even though time-dependent density-functional theory (TDDFT) works generally well for describing excited states energies and properties in the Franck-Condon region, it can dramatically fail in predicting photochemistry, notably when electronic state crossings occur. Here, we assess the ability of TDDFT to describe the photochemistry of an important class of triplet sensitizers, namely, aromatic ketones. We take acetophenone as a test molecule, for which accurate ab initio results exist in the literature. Triplet acetophenone is generated thanks to an exotic three-state crossing involving one singlet and two triplets states (i.e., a simultaneous intersystem crossing and triplet conical intersection), thus being a stringent test for approximate TDDFT. We show that most exchange-correlation functionals can only give a semi-qualitative picture of the overall photochemistry, in which the three-state crossing is rather represented as a triplet conical intersection separated from the intersystem crossing. The best result overall is given by the double hybrid functional mPW2PLYP, which is even able to reproduce quantitatively the three-state crossing region. We rationalize this results by noting that double hybrid functionals include a larger portion of double excitation character to the excited states.

The Preparation of Cu-g-C3N4/AC Catalyst for Acetylene Hydrochlorination

Directory of Open Access Journals (Sweden)

Wenli Zhao

2016-12-01

Full Text Available A novel catalyst based on g-C3N4/activated carbon was prepared by adding CuCl2. The catalytic performance of the as-prepared catalyst was investigated in the acetylene hydrochlorination reaction. X-ray photoelectron spectroscopy, temperature programmed desorption, low temperature N2 adsorption/desorption (Brunauer–Emmett–Teller, and thermal gravity analysis showed that Cu-g-C3N4/AC significantly enhanced the catalytic performance of the original catalyst by increasing the relative pyrrolic N content. Cu-g-C3N4/AC also affected the adsorption of hydrogen chloride and acetylene, as well as inhibited the coke deposition during acetylene hydrochlorination.

Morphological reason for enhancement of electrochemical double layer capacitances of various acetylene blacks by electrochemical polarization

International Nuclear Information System (INIS)

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

2008-01-01

Enhancement of electrochemical capacitance and morphological variations of various acetylene blacks caused by electrochemical polarization are presented. Acetylene blacks of different mean particle diameters were modified by air-oxidation and heat treatment to diversify the morphologies of the acetylene blacks before electrochemical polarization. The various acetylene blacks were electrochemically oxidized at 1.6 V (vs. Ag/AgCl) for 10 s and the polarization step was repeated until the capacitance values did not change any longer. These polarization steps enhanced the capacitances of the acetylene blacks and the specific enhancement factors range from 2 to 5.5. Such an enhancement is strongly related to morphological modification as revealed by transmission electron microscopic observations. The electrochemical polarization resulted in formation of tiny graphene sheets on the wide graphitic carbon surfaces, which were most responsible for the observed capacitive enhancement. Although the pseudo-capacitance increased after polarization by forming oxygenated species on the surfaces, its contribution to the total capacitance was less than 10%. The mechanism of the formation of the tiny graphene sheets during the electrochemical oxidation is described schematically

Geometric detection of coupling directions by means of inter-system recurrence networks

International Nuclear Information System (INIS)

Feldhoff, Jan H.; Donner, Reik V.; Donges, Jonathan F.; Marwan, Norbert; Kurths, Jürgen

2012-01-01

We introduce a geometric method for identifying the coupling direction between two dynamical systems based on a bivariate extension of recurrence network analysis. Global characteristics of the resulting inter-system recurrence networks provide a correct discrimination for weakly coupled Rössler oscillators not yet displaying generalised synchronisation. Investigating two real-world palaeoclimate time series representing the variability of the Asian monsoon over the last 10,000 years, we observe indications for a considerable influence of the Indian summer monsoon on climate in Eastern China rather than vice versa. The proposed approach can be directly extended to studying K>2 coupled subsystems.

Pressure-induced polymerization in substituted acetylenes

Energy Technology Data Exchange (ETDEWEB)

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

2012-04-10

A fundamental understanding of shock-induced chemical reactions in organics is still lacking and there are limited studies devoted to determining reaction mechanisms, evolution of bonding, and effect of functional group substitutions. The fast timescale of reactions occurring during shock compression create significant experimental challenges (diagnostics) to fully quantify the mechanisms involved. Static compression combined with temperature provides a complementary route to investigate the equilibrium phase space and metastable intermediates under extreme P-T conditions. In this study, we present our results from our ongoing high pressure in situ synchrotron x-ray diffraction experiments on substituted acetylenes: tert-butyl acetylene [TBA: (CH{sub 3}){sub 3}-C=CH] and ethynyl trimethylsilane [ETMS: (CH{sub 3}){sub 3}-SiC=CH]. We observed that the onset pressure of chemical reactions (at room temperature) in these compounds is higher under static compression (TBA: 12 GPa and ETMS: 17.6 GPa) when compared to shock input pressures (TBA: 6.1 GPa and ETMS: 6.6 GPa). At elevated temperatures, reactivity was observed to occur at pressures comparable to shock conditions. The products were polymeric in nature, recovered to ambient conditions with little degradation.

Up-Conversion Intersystem Crossing Rates in Organic Emitters for Thermally Activated Delayed Fluorescence: Impact of the Nature of Singlet vs Triplet Excited States

KAUST Repository

Samanta, Pralok Kumar

2017-02-28

The rates for up-conversion intersystem crossing (UISC) from the T1 state to the S1 state are calculated for a series of organic emitters with an emphasis on thermally activated delayed fluorescence (TADF) materials. Both the spin-orbit coupling and the energy difference between the S1 and T1 states (ΔEST) are evaluated, at the density functional theory (DFT) and time-dependent DFT levels. The calculated UISC rates and ΔEST values are found to be in good agreement with available experimental data. Our results underline that small ΔEST values and sizable spin-orbit coupling matrix elements have to be simultaneously realized in order to facilitate UISC and ultimately TADF. Importantly, the spatial separation of the highest occupied and lowest unoccupied molecular orbitals of the emitter, a widely accepted strategy for the design of TADF molecules, does not necessarily lead to a sufficient reduction in ΔEST; in fact, either a significant charge-transfer (CT) contribution to the T1 state or a minimal energy difference between the local-excitation and charge-transfer triplet states is required to achieve a small ΔEST. Also, having S1 and T1 states of a different nature is found to strongly enhance spin-orbit coupling, which is consistent with the El-Sayed rule for ISC rates. Overall, our results indicate that having either similar energies for the local-excitation and charge-transfer triplet states or the right balance between a substantial CT contribution to T1 and somewhat different natures of the S1 and T1 states, paves the way toward UISC enhancement and thus TADF efficiency improvement.

Aromatic Radicals-Acetylene Particulate Matter Chemistry

Science.gov (United States)

2011-12-01

solutions include deactivated fused silica-lined tubing provided by Sigma-Aldrich. The internal wall of these tubes is covered by a thin layer of fused... Ser 809 S. Marshfield, RM 520, Chicago, IL 60612 USACE HUMPHREYS ENGR CTR SPT ACTIVITY Attn: CECT-HC 7701 Telegraph Road Alexandria, VA 22315...Model, m-Xylene Oxidation, Phenyl + Acetylene, Phenyl Pyrolysis, Gas Chromatography , Potential Energy Surface, Ab-Initio Calculations. None 133

Inter-system LOCA risk assessment

International Nuclear Information System (INIS)

Galyean, W.J.; Kelly, D.L.; Schroeder, J.A.

1991-01-01

Inter-systems loss-of-coolant accidents (ISLOCAs) have been included in probabilistic risk assessments (PRAs) since WASH-1400. While estimated as being relatively low contributors to core damage frequency, ISLOCAs have been identified as major contributors to risk at nuclear power plants (NPPs). They have the potential to result in core melt and containment bypass, which may lead to the early release of large quantities of fission products. Recent events at several operating reactors have been identified as ISLOCA precursors. The occurrence of these events have raised concerns that the frequency of ISLOCA sequences might be underestimated in current state-of-the-art PRAs. In order to expand the current state-of-the-art, a Nuclear Regulatory Commission research program is being conducted by ED and G Idaho, Inc. at the Idaho National Engineering Laboratory. The objective of the ISLOCA research program is to generate qualitative and quantitative information on the hardware, human factors, and accident consequence issues that dominate nuclear power plant risks for ISLOCA. To meet this objective, the approach being taken includes analysis of all interfaces between the primary reactor coolant system and other, lower pressure systems. This historical experience (primarily, licensee event reports) has provided the basis for determining the scope of the analysis with respect to potential failure mechanisms of the pressure isolation boundary. It is important to note that in the vast majority of these events, the dominant failure was a human error. Because of their significance, human errors are given particular attention in the present analysis

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

Science.gov (United States)

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.

Modeling, simulation, and optimization of a front-end system for acetylene hydrogenation reactors

Directory of Open Access Journals (Sweden)

R. Gobbo

2004-12-01

Full Text Available The modeling, simulation, and dynamic optimization of an industrial reaction system for acetylene hydrogenation are discussed in the present work. The process consists of three adiabatic fixed-bed reactors, in series, with interstage cooling. These reactors are located after the compression and the caustic scrubbing sections of an ethylene plant, characterizing a front-end system; in contrast to the tail-end system where the reactors are placed after the de-ethanizer unit. The acetylene conversion and selectivity profiles for the reactors are optimized, taking into account catalyst deactivation and process constraints. A dynamic optimal temperature profile that maximizes ethylene production and meets product specifications is obtained by controlling the feed and intercoolers temperatures. An industrial acetylene hydrogenation system is used to provide the necessary data to adjust kinetics and transport parameters and to validate the approach.

Synthesis of chirals regioisomers from D-mannitol: obtainment of a acetylenic alcohols mixture

International Nuclear Information System (INIS)

Cito, Antonia Maria das Gracas Lopes; Araujo, Bruno Quirino; Lopes, Jose Arimateia Dantas; Magalhes, Aderbal Farias; Magalhes, Eva Goncalves

2009-01-01

The synthesis of chiral acetylenic regioisomers was described by using an appropriate intermediate such as isopropylidene glycerol, a synthon widely used in the enantioselective syntheses. This intermediate was prepared from D-mannitol. The nine obtained compounds have been characterized by their respective spectral data. The mixture of chiral acetylenic alcohols showed activity against Escherichia coli when tested through the monitoring of CO 2 released during microbial respiration by using a conductimetric system. (author)

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

Science.gov (United States)

Rosner, B M; Schink, B

1995-10-01

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.

Cryosolution infrared study of hydrogen bonded halothane acetylene complex

Science.gov (United States)

Melikova, S. M.; Rutkowski, K. S.; Rospenk, M.

2018-05-01

The interactions between halothane (2-bromo-2-chloro-1,1,1-trifluoroethane) and acetylene (C2H2) are studied by FTIR spectroscopy. Results obtained in liquid cryosolutions in Kr suggest weak complex formation stabilized by H - bond. The complexation enthalpy (∼11 kJ/mol) is evaluated in a series of temperature measurements (T ∼ 120-160 K) of integrated intensity of selected bands performed in liquefied Kr. The quantum chemical MP2/6-311++G(2d,2p) calculations predict four different structures of the complex. The most stable and populated (94% at T∼120 K) structure corresponds to the H - bond between H atom of halothane and pi-electron of triple bond between C atoms of acetylene. Wave numbers of vibrational bands of the most stable structure are calculated in anharmonic approximation implemented in Gaussian program.

Simultaneous measurements of acetylene and soot during the pyrolysis of ethylene and benzene in a shock tube

KAUST Repository

KC, Utsav

2016-10-12

Acetylene is one of the most important precursors of soot and contributes to soot growth by the hydrogen-abstraction acetylene-addition (HACA) mechanism. In this work, we undertake time-resolved simultaneous measurements of acetylene and soot behind reflected shock waves at temperatures of 1600-2200. K and pressures of 3-5. bar. Acetylene mole fraction time-histories are measured from the absorption of a quantum-cascade laser operating around 13.6. μm. The soot volume fraction, particle size and number densities are calculated from the extinction and scattering of a cw Nd:Yag laser at 532. nm. Acetylene and soot are generated from the pyrolysis of 1% benzene in argon, 2.35% ethylene in argon, and binary mixtures of ethylene with propane/methane in argon. We note that acetylene time-histories exhibit a two-stage growth during the pyrolysis of benzene, which can be correlated to the initial rapid increase of soot volume fraction and a later plateauing. In comparison to ethylene pyrolysis, the pyrolysis of benzene results in larger values of the soot volume fraction, particle diameter and number density. We compare the measured data against the values simulated using the method-of-moments routine in Chemkin-Pro and a detailed PAH mechanism based on KM2 [1] and AramcoMech 1.3 [2]. Large discrepancies are observed between the measured and predicted values of the soot parameters. The data obtained from our experiments may assist future validation and development of soot mechanisms.

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

Energy Technology Data Exchange (ETDEWEB)

Chiang, Hung-Lung, E-mail: hlchiang@mail.cmu.edu.tw [Department of Risk Management, China Medical University, Taichung 40402, Taiwan (China); Wu, Trong-Neng [Department of Public Health, China Medical University, Taichung 40402, Taiwan (China); Ho, Yung-Shou [Department of Applied Chemistry and Materials Science, Fooyin University, Kaohsiung 831, Taiwan (China); Zeng, Li-Xuan [Department of Risk Management, China Medical University, Taichung 40402, Taiwan (China)

2014-07-15

Highlights: • Acetylene was decomposed on SBA-15 and Ni-SBA-15 at 650–850 °C. • Carbon spheres and filaments were formed after acetylene decomposition. • PAHs were determined in tar and residues. • Exhaust constituents include CO{sub 2}, H{sub 2}, NO{sub x} and hydrocarbon species. - Abstract: 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{sup 2} structure) cm{sup −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), H{sub 2}, and C{sub 2}H{sub 2} 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 1104 ppm 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.

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

International Nuclear Information System (INIS)

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

2016-01-01

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. (paper)

Two new acetylenic compounds from Asparagus officinalis.

Science.gov (United States)

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.

Acetylene-Based Materials in Organic Photovoltaics

Directory of Open Access Journals (Sweden)

Fabio Silvestri

2010-04-01

Full Text Available 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 (polyarylacetylenes that have been used in the field. A general introduction to (polyarylacetylenes, 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, (copolymers containing triple bonds, and metallopolyyne polymers as p-type semiconductor materials. The last section will deal with hybrids in which oligomeric/polymeric structures incorporating acetylenic linkages such as phenylene ethynylenes have been attached onto C60, and their use as the active materials in photovoltaic devices.

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

Science.gov (United States)

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

2009-02-12

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

Solid-State Polymerization of Acetylene under Pressure: {ital Ab Initio} Simulation

Energy Technology Data Exchange (ETDEWEB)

Bernasconi, M.; Parrinello, M. [Max-Planck-Institut fuer Festkoerperforschung, Heisenbergstr.1, D-70569 Stuttgart (Germany); Bernasconi, M. [Istituto Nazionale Fisica della Materia and Dipartimento di Fisica, Universita di Milano, Via Celoria 16, 20133 Milano (Italy); Chiarotti, G.; Focher, P.; Tosatti, E. [Istituto Nazionale Fisica della Materia and International School for Advanced Studies, Via Beirut 4, I-34014 Trieste (Italy); Tosatti, E. [International Centre for Theoretical Physics (ICTP), P.O.Box 586, I-34014 Trieste (Italy)

1997-03-01

We have simulated by {ital ab initio} constant pressure molecular dynamics the solid-state polymerization of acetylene recently observed experimentally in the pressure range 3.5{endash}14 GPa. We have found a massive polymerization only at much higher pressure (25 GPa). However, we have also found that a triplet exciton self-trapped on a single, {ital cis}-bent molecule in crystalline acetylene is a very effective polymerization seed at lower pressure ({lt}9GPa), much closer to the experimental threshold. Therefore, we propose that the polymerization observed experimentally is possibly catalyzed by a similar seed. We predict that injection of triplet excitons would greatly enhance the polymerization rate. {copyright} {ital 1997} {ital The American Physical Society}

Facile synthesis and electrochemical performances of binder-free flexible graphene/acetylene black sandwich film

International Nuclear Information System (INIS)

Xu, Juan; Wei, Xicheng; Cao, Jianyu; Dong, Yuanzhu; Wang, Guoxin; Xue, Yufei; Wang, Wenchang; Chen, Zhidong

2015-01-01

Graphene/acetylene black sandwich film was fabricated by a simple vacuum filtration procedure using a stable complex suspension of graphene oxide (GO) and acetylene black followed by a hydroiodic acid (HI) immersion process to fully reduce the GO to graphene sheets. The self-restacking of individual graphene sheets were greatly alleviated and electric conductivity was obviously improved using the acetylene black nanoparticles as both effective spacers to expand the inter-layer interval of the individual graphene sheets during the film assembly course and highly conducting bridges to facilitate the electron/ion transfer between the upper and lower graphene sheets. The flexible graphene/acetylene black film was utilized as supercapacitor electrode without additional conductive additives, binders and current collectors, which achieved an obviously higher specific capacitance (ca. 136.6 F g −1 at 0.5 A g −1 ) and much better specific capacitance retention at high current densities than that of the pure graphene film electrode, indicating that such a novel sandwich film structure allows for a higher charge storage capability. More importantly, the assembled symmetric supercapacitor device displayed a satisfactory specific capacitance of 59.2 F g −1 at 0.1 A g −1 , 47.6 F g −1 at 0.5 A g −1 and 42.8 F g −1 at 1 A g −1 , and only negligible 4.05% capacitance degradation have been found after 1000 continuous charge-discharge cycles at 0.5 A g −1 , revealing outstanding rate capability, excellent electrochemical reversibility and long-term cyclability. These results proved that such a flexible and highly conductive graphene/acetylene black film can be promising electroactive materials in the development of advanced electrochemical energy storage devices

Short exposure to acetylene to distinguish between nitrifier and denitrifier nitrous oxide production in soil and sediment samples

NARCIS (Netherlands)

Kester, R.A.; Boer, W. de; Laanbroek, H.J.

1996-01-01

The contribution of nitrifiers and denitrifiers to the nitrous oxide production in slurries of calcareous silt loam and river bank sediment at different oxygen concentrations was determined using acetylene as nitrification inhibitor. The addition of 10 Pa acetylene resulted in inhibition of

Short exposure to acetylene to distinguish between nitrifier and denitrifier nitrous oxide production in soil and sediment samples

NARCIS (Netherlands)

Kester, R.A.; De Boer, W.; Laanbroek, H.J.

1996-01-01

The contribution of nitrifiers and denitrifiers to the nitrous oxide production in slurries of calcareous silt loam and river bank sediment at different oxygen concentrations was determined using acetylene as nitrification inhibitor. The addition of 10 Pa acetylene resulted in inhibition of nitrous

Ring current models for acetylene and ethylene molecules

International Nuclear Information System (INIS)

Pelloni, Stefano; Lazzeretti, Paolo

2009-01-01

Spatial models of the current density vector field, induced in the electronic cloud of the acetylene and ethylene molecules by a uniform, time-independent magnetic field, are discussed in terms of topological stagnation graphs and three-dimensional streamline plots. The models are validated by documenting their ability to explain magnetic susceptibility and nuclear magnetic shieldings of carbon and hydrogen via related shielding density maps

Pulsed-induced electromagnetically induced transparency in the acetylene-filled hollow-core fibers

Science.gov (United States)

Rodríguez, Nayeli Casillas; Stepanov, Serguei; Miramontes, Manuel Ocegueda; Hernández, Eliseo Hernández

2017-06-01

Experimental results on pulsed excitation of electromagnetically induced transparency (EIT) in the acetylene-filled hollow-core photonic crystal fiber (HC-PCF) at pressures 0.1-0.4 Torr are reported. The EIT was observed both in Λ and V interaction configurations with the continuous probe wave tuned to R9 (1520.08 nm) acetylene absorption line and with the control pulses tuned to P11 (1531.58 nm) and P9 (1530.37 nm) lines, respectively. The utilized control pulses were of up to 40 ns duration with EIT was up to 40 and 15% for the co- and counter-propagation of the probe and control waves, respectively, and importance of the waves polarization matching was demonstrated. For a qualitative explanation of reduction in the counter-propagation EIT efficiency a simple model of the accelerated mismatch of the two-frequency EIT resonance with deviation of the molecule thermal velocity from the resonance value was utilized. It was shown experimentally that the EIT efficiencies in both configurations do not depend on the longitudinal velocity of the molecules. The characteristic relaxation time of the of the EIT response was found to be about 9 ns, i.e., is close to the relaxation times T 1,2 of the acetylene molecules under the utilized experimental conditions.

Experimental and theoretical studies of the O(3P) + C2H4 reaction dynamics: Collision energy dependence of branching ratios and extent of intersystem crossing

Science.gov (United States)

Fu, Bina; Han, Yong-Chang; Bowman, Joel M.; Leonori, Francesca; Balucani, Nadia; Angelucci, Luca; Occhiogrosso, Angela; Petrucci, Raffaele; Casavecchia, Piergiorgio

2012-12-01

The reaction of O(3P) with C2H4, of importance in combustion and atmospheric chemistry, stands out as paradigm reaction involving not only the indicated triplet state potential energy surface (PES) but also an interleaved singlet PES that is coupled to the triplet surface. This reaction poses great challenges for theory and experiment, owing to the ruggedness and high dimensionality of these potentials, as well as the long lifetimes of the collision complexes. Crossed molecular beam (CMB) scattering experiments with soft electron ionization detection are used to disentangle the dynamics of this polyatomic multichannel reaction at a collision energy Ec of 8.4 kcal/mol. Five different primary products have been identified and characterized, which correspond to the five exothermic competing channels leading to H + CH2CHO, H + CH3CO, CH3 + HCO, CH2 + H2CO, and H2 + CH2CO. These experiments extend our previous CMB work at higher collision energy (Ec ˜ 13 kcal/mol) and when the results are combined with the literature branching ratios from kinetics experiments at room temperature (Ec ˜ 1 kcal/mol), permit to explore the variation of the branching ratios over a wide range of collision energies. In a synergistic fashion, full-dimensional, QCT surface hopping calculations of the O(3P) + C2H4 reaction using ab initio PESs for the singlet and triplet states and their coupling, are reported at collision energies corresponding to the CMB and the kinetics ones. Both theory and experiment find almost an equal contribution from the triplet and singlet surfaces to the reaction, as seen from the collision energy dependence of branching ratios of product channels and extent of intersystem crossing (ISC). Further detailed comparisons at the level of angular distributions and translational energy distributions are made between theory and experiment for the three primary radical channel products, H + CH2CHO, CH3 + HCO, and CH2 + H2CO. The very good agreement between theory and

Acetylene Gas-Sensing Properties of Layer-by-Layer Self-Assembled Ag-Decorated Tin Dioxide/Graphene Nanocomposite Film

Directory of Open Access Journals (Sweden)

Chuanxing Jiang

2017-09-01

Full Text Available This paper demonstrates an acetylene gas sensor based on an Ag-decorated tin dioxide/reduced graphene oxide (Ag–SnO2/rGO nanocomposite film, prepared by layer-by-layer (LbL self-assembly technology. The as-prepared Ag–SnO2/rGO nanocomposite was characterized by scanning electron microscopy (SEM, transmission electron microscopy (TEM, X-ray diffraction (XRD and Raman spectrum. The acetylene sensing properties were investigated using different working temperatures and gas concentrations. An optimal temperature of 90 °C was determined, and the Ag–SnO2/rGO nanocomposite sensor exhibited excellent sensing behaviors towards acetylene, in terms of response, repeatability, stability and response/recovery characteristics, which were superior to the pure SnO2 and SnO2/rGO film sensors. The sensing mechanism of the Ag–SnO2/rGO sensor was attributed to the synergistic effect of the ternary nanomaterials, and the heterojunctions created at the interfaces between SnO2 and rGO. This work indicates that the Ag–SnO2/rGO nanocomposite is a good candidate for constructing a low-temperature acetylene sensor.

Acetylene Gas-Sensing Properties of Layer-by-Layer Self-Assembled Ag-Decorated Tin Dioxide/Graphene Nanocomposite Film

Science.gov (United States)

Jiang, Chuanxing; Yin, Nailiang; Yao, Yao; Shaymurat, Talgar; Zhou, Xiaoyan

2017-01-01

This paper demonstrates an acetylene gas sensor based on an Ag-decorated tin dioxide/reduced graphene oxide (Ag–SnO2/rGO) nanocomposite film, prepared by layer-by-layer (LbL) self-assembly technology. The as-prepared Ag–SnO2/rGO nanocomposite was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and Raman spectrum. The acetylene sensing properties were investigated using different working temperatures and gas concentrations. An optimal temperature of 90 °C was determined, and the Ag–SnO2/rGO nanocomposite sensor exhibited excellent sensing behaviors towards acetylene, in terms of response, repeatability, stability and response/recovery characteristics, which were superior to the pure SnO2 and SnO2/rGO film sensors. The sensing mechanism of the Ag–SnO2/rGO sensor was attributed to the synergistic effect of the ternary nanomaterials, and the heterojunctions created at the interfaces between SnO2 and rGO. This work indicates that the Ag–SnO2/rGO nanocomposite is a good candidate for constructing a low-temperature acetylene sensor. PMID:28927021

乙炔提浓装置高级炔管线堵塞原因浅析%Analysis on causes of higher acetylene pipe blocking of acetylene concentration system

Institute of Scientific and Technical Information of China (English)

谢全兵

2011-01-01

Causes of higher alkyne pipe blocking of acetylene concentration system in the natural gas-based acetylene production plant were found out by analyzing higher alkyne gas component concentration variation. Corresponding measures were proposed to prevent higher alkyne polymerization in the pipe and thus prolong the equipment operation cycle.%通过对高级炔气体组分含量变化进行分析,找出天然气制乙炔装置乙炔浓缩系统高级炔管线堵塞的原因,并提出了防止高级炔气体在管线内聚合、延长装置运行周期的措施.

Synthesis of trifluoromethylated acetylenes via copper-catalyzed trifluoromethylation of alkynyltrifluoroborates

KAUST Repository

Zheng, Huidong

2012-12-01

A new method for the synthesis of trifluoromethylated acetylenes is developed which involves the copper-catalyzed trifluoromethylation of alkynyltrifluoroborates with an electrophilic trifluoromethylating reagent. This method offers significant advantages such as efficiency and mild and base-free reaction conditions. A plausible mechanism is proposed. © 2012 Elsevier Ltd. All rights reserved.

Synthesis of trifluoromethylated acetylenes via copper-catalyzed trifluoromethylation of alkynyltrifluoroborates

KAUST Repository

Zheng, Huidong; Huang, Yuanyuan; Wang, Zhiwei; Li, Huaifeng; Huang, Kuo-Wei; Yuan, Yaofeng; Weng, Zhiqiang

2012-01-01

A new method for the synthesis of trifluoromethylated acetylenes is developed which involves the copper-catalyzed trifluoromethylation of alkynyltrifluoroborates with an electrophilic trifluoromethylating reagent. This method offers significant advantages such as efficiency and mild and base-free reaction conditions. A plausible mechanism is proposed. © 2012 Elsevier Ltd. All rights reserved.

The X-ray emission spectrum of gaseous acetylene

International Nuclear Information System (INIS)

Brammer, R.; Rubensson, J.E.; Wassdahl, N.; Nordgren, J.

1987-01-01

The X-ray emission spectrum of acetylene in the gas phase has been recorded using a 10 m grazing incidence spectrometer. Analysis of the spectrum is made based on calculations of total energies, potential curves and Franck-Condon vibrational intensities. Four emission bands are seen with the 1 π u band exhibiting vibrational structure. Analysis of the vibrations gives the CIs ionization energy. High energy satellite structure is observed and interpreted. (orig.)

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

International Nuclear Information System (INIS)

Han, Huixian; Li, Anyang; Guo, Hua

2014-01-01

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

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

Science.gov (United States)

Han, Huixian; Li, Anyang; Guo, Hua

2014-12-01

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

A first principles study of the acetylene-water interaction

International Nuclear Information System (INIS)

Tzeli, Demeter; Mavridis, Aristides; Xantheas, Sotiris S.

2000-01-01

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

Heterocycles by Transition Metals Catalyzed Intramolecular Cyclization of Acetylene Compounds

International Nuclear Information System (INIS)

Vizer, S.A.; Yerzhanov, K.B.; Dedeshko, E.C.

2003-01-01

Review shows the new strategies in the synthesis of heterocycles, having nitrogen, oxygen and sulfur atoms, via transition metals catalyzed intramolecular cyclization of acetylenic compounds on the data published at the last 30 years, Unsaturated heterocyclic compounds (pyrroles and pyrroline, furans, dihydro furans and benzofurans, indoles and iso-indoles, isoquinolines and isoquinolinones, aurones, iso coumarins and oxazolinone, lactams and lactones with various substitutes in heterocycles) are formed by transition metals, those salts [PdCl 2 , Pd(OAc) 2 , HgCl 2 , Hg(OAc) 2 , Hg(OCOCF 3 ) 2 , AuCl 3 ·2H 2 O, NaAuCl 4 ·2H 2 O, CuI, CuCl], oxides (HgO) and complexes [Pd(OAc) 2 (PPh 3 )2, Pd(PPh 3 ) 4 , PdCl 2 (MeCN) 2 , Pd(OAc ) 2 /TPPTS] catalyzed intramolecular cyclization of acetylenic amines, amides, ethers, alcohols, acids, ketones and βdiketones. More complex hetero polycyclic systems typical for natural alkaloids can to obtain similar. Proposed mechanisms of pyrroles, isoquinolines, iso indoles and indoles, benzofurans and iso coumarins, thiazolopyrimidinones formation are considered. (author)

A DFT study and micro-kinetic analysis of acetylene selective hydrogenation on Pd-doped Cu(111) surfaces

International Nuclear Information System (INIS)

Ma, Ling-Ling; Lv, Cun-Qin; Wang, Gui-Chang

2017-01-01

Semi-hydrogenation of acetylene in a hydrogen-rich stream is an industrially important process. Inspired by the recent experiments that Cu(111) surface doped by a small number of Pd atoms can exhibit excellent catalytic performance toward the dissociation of H_2 molecule as well as the high selective hydrogenation of acetylene as compared with pure Cu and Pd metal alone at low-temperature, here we performed systematic first-principles calculations to investigate the corresponding reaction mechanism related to the acetylene hydrogenation processes on single atom alloys (SAAs) and monolayer Pd/Cu(111) (i.e.,1.00 ML Pd/Cu(111)) model catalysts in detail, and to explore the possible factors controlling the high selectivity on SAAs. Our results clearly demonstrate that the SAA catalyst has higher selectivity for the ethylene formation than that of 1.00 ML Pd/Cu(111), and lower activity for the acetylene conversion compared with that of 1.00 ML Pd/Cu(111). The relatively high selectivity on SAA is mainly due to the facile desorption of ethylene and moderate activity in the dissociation of molecular H_2. The main factor which lowers the selectivity towards the ethylene formation on 1.00 ML Pd/Cu(111) is that this system has a higher capacity to promote the breaking of C−H/C−C bonds, which leads to the formation of carbonaceous deposits and polymers such as benzene, and thus reduces the selectivity for the ethylene formation. Meanwhile, it was found that the desorption energy of ethylene on these two surfaces was smaller than the energy barrier of further hydrogenation, which results in the absence of ethane on these two systems. Micro-kinetic model analysis provides a further valuable insight into the evidence for the key factors controlling the catalytic activity and selectivity towards the selective hydrogenation of acetylene. Our findings may help people to design a highly selective hydrogenation catalyst by controlling the balance between the H_2 dissociation and

A DFT study and micro-kinetic analysis of acetylene selective hydrogenation on Pd-doped Cu(111) surfaces

Science.gov (United States)

Ma, Ling-Ling; Lv, Cun-Qin; Wang, Gui-Chang

2017-07-01

Semi-hydrogenation of acetylene in a hydrogen-rich stream is an industrially important process. Inspired by the recent experiments that Cu(111) surface doped by a small number of Pd atoms can exhibit excellent catalytic performance toward the dissociation of H2 molecule as well as the high selective hydrogenation of acetylene as compared with pure Cu and Pd metal alone at low-temperature, here we performed systematic first-principles calculations to investigate the corresponding reaction mechanism related to the acetylene hydrogenation processes on single atom alloys (SAAs) and monolayer Pd/Cu(111) (i.e.,1.00 ML Pd/Cu(111)) model catalysts in detail, and to explore the possible factors controlling the high selectivity on SAAs. Our results clearly demonstrate that the SAA catalyst has higher selectivity for the ethylene formation than that of 1.00 ML Pd/Cu(111), and lower activity for the acetylene conversion compared with that of 1.00 ML Pd/Cu(111). The relatively high selectivity on SAA is mainly due to the facile desorption of ethylene and moderate activity in the dissociation of molecular H2. The main factor which lowers the selectivity towards the ethylene formation on 1.00 ML Pd/Cu(111) is that this system has a higher capacity to promote the breaking of Csbnd H/Csbnd C bonds, which leads to the formation of carbonaceous deposits and polymers such as benzene, and thus reduces the selectivity for the ethylene formation. Meanwhile, it was found that the desorption energy of ethylene on these two surfaces was smaller than the energy barrier of further hydrogenation, which results in the absence of ethane on these two systems. Micro-kinetic model analysis provides a further valuable insight into the evidence for the key factors controlling the catalytic activity and selectivity towards the selective hydrogenation of acetylene. Our findings may help people to design a highly selective hydrogenation catalyst by controlling the balance between the H2 dissociation and

Acetylenes bearing Aromatic Terminal Groups. : II 13C-NMR Spectra of Monosubstituted Diphenylacetylenes

OpenAIRE

野本, 健雄; Nomoto, Takeo

1986-01-01

Six monosubstituted diphenylacetylenes, p-X-C6H4-C≡C-C6H5 1 (Ⅹ=NMe2, NH2, OMe, Cl, and NO2), were synthesized, and 13C-NMR spectra of their acetylenic carbons were measured. Hammett plots of the chemical shifts of the acetylenic α-13C and β-13C (against substituent constants σ) respectively showed a linear relationship, eXCept for β-13C on NMe2 and NH2 groups. The effects of substituents on 13C-Chemical shifts of diphenylacetylenes and effeciency of the C≡C bonds in transmitting the substitue...

Acetylene Gas-Sensing Properties of Layer-by-Layer Self-Assembled Ag-Decorated Tin Dioxide/Graphene Nanocomposite Film

OpenAIRE

Jiang, Chuanxing; Zhang, Dongzhi; Yin, Nailiang; Yao, Yao; Shaymurat, Talgar; Zhou, Xiaoyan

2017-01-01

This paper demonstrates an acetylene gas sensor based on an Ag-decorated tin dioxide/reduced graphene oxide (Ag–SnO2/rGO) nanocomposite film, prepared by layer-by-layer (LbL) self-assembly technology. The as-prepared Ag–SnO2/rGO nanocomposite was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and Raman spectrum. The acetylene sensing properties were investigated using different working temperatures and gas concentrations. A...

Dual fuel operation of used transformer oil with acetylene in a DI diesel engine

International Nuclear Information System (INIS)

Behera, Pritinika; Murugan, S.; Nagarajan, G.

2014-01-01

Highlights: • Utilisation of Used transformer oil (UTO) as a fuel in a diesel engine. • UTO with acetylene in a diesel engine, on a dual fuel mode technique. • Analysis of combustion characteristics of the diesel engine. • Analysis of performance and emission characteristics of the diesel engine. - Abstract: Used transformer oil (UTO) is a waste oil obtained from power transformers and welding transformers. It possesses considerable heating value and properties similar to diesel fuel. A preliminary investigation on the utilization of the UTO in a single cylinder, four stroke small powered direct injection (DI) diesel engine revealed that at an optimum injection timing of 20°CA the engine exhibited lower nitric oxide (NO) and higher smoke emissions, compared to that of diesel operation. In order to improve the performance and reduce the smoke emission, a dual fuel operation was attempted in the present investigation. Acetylene was inducted as a primary fuel at four different flow rates viz 132 g/h, 198 g/h, 264 g/h and 330 g/h along with the air, to study the combustion, performance and emission behavior of a four-stroke, 4.4 kW diesel engine, while the UTO was injected as pilot fuel with the optimized injection timing. The experimental results were compared with diesel-acetylene dual fuel operation in the same engine. Acetylene aspiration reduced the ignition delay and maximum cylinder pressure by about 3°CA, and 25% respectively at full load in comparison with the sole UTO operation. Higher thermal efficiency and lower exhaust gas were also observed at full load. Smoke was reduced by about 13.7%, in comparison with the UTO operation at full load

A model for the ethylene and acetylene adsorption on the surface of Cu{sub n}(n = 10–15) nanoclusters: A theoretical study

Energy Technology Data Exchange (ETDEWEB)

Farmanzadeh, Davood, E-mail: d.farmanzad@umz.ac.ir; Abdollahi, Tahereh

2016-11-01

Highlights: • The most stable structures of Cu{sub n} (n = 10–15) were structures with C{sub S} symmetry. • It is expected that even clusters are better electron donors than the odd clusters. • Acetylene and ethylene adsorb molecularly on the Cu nanoclusters surface. • Acetylene never orient toward di-σ mode for Cu−Cu bond in odd copper nanoclusters. • For di- σ-Cu{sub n}C{sub 2}H{sub 4}, no stable structure is identified. - Abstract: In this work, we report the results of density functional theory calculations of ethylene and acetylene adsorption on the most stable Cu{sub n} (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 Cu−Cu bond in odd copper nanoclusters. Also, for di- σ-Cu{sub n}C{sub 2}H{sub 4}, no stable structure is identified. The highest interaction and deformation energies are seen for the adsorption of acetylene and ethylene on Cu{sub 11} in π-mode.

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

International Nuclear Information System (INIS)

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

2012-01-01

Highlights: ► Synthesis of highly active tin-promoted catalysts by polyol method for selective hydrogenation of high concentration of acetylene. ► A positive change in the catalytic activities of tin-promoted catalysts results from distinct geometric and electronic effects. ► Change in the coverage of acetylenic overlayers for different temperature regions corresponds to the change of the number of isolated adsorption sites. ► The isolated adsorption sites are responsible for the enhancement of selectivity to ethylene with increased temperatures, via the management of the carbonaceous species over the catalyst surface. - Abstract: 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 Pd 2 Sn 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.

Short exposure to acetylene to distinguish between nitrifier and denitrifier nitrous oxide production in soil and sediment samples

OpenAIRE

Kester, R.A.; Boer, W. de; Laanbroek, H.J.

1996-01-01

The contribution of nitrifiers and denitrifiers to the nitrous oxide production in slurries of calcareous silt loam and river bank sediment at different oxygen concentrations was determined using acetylene as nitrification inhibitor. The addition of 10 Pa acetylene resulted in inhibition of nitrous oxide production at oxic conditions, but strongly enhanced the nitrous oxide production at oxygen-poor and anoxic conditions. Inhibition of nitrification by short exposure (1 to 24 h) to high conce...

Effects of acetylene and carbon monoxide on long-term hydrogen production by Mastigocladus laminosus, a thermophilic blue-green alga

Energy Technology Data Exchange (ETDEWEB)

Miura, Y; Yokoyama, H; Takahara, K; Miyamoto, K

1982-01-01

Long-term H/sub 2/ production by a thermophilic and heterocystous blue-green alga (cyanobacterium) Mastigocladus laminosus was studied under the conditions when acetylene and carbon monoxide were supplemented to the gas phase of the culture vessel. The addition of both gases enhanced H/sub 2/ evolution by nitrogen-starved cells. The concentrations of acetylene and carbon monoxide in the gas phase of argon/CO/sub 2/ (97.5/2.5) were 10% and 0.2 to 1%, respectively, for the maximum H/sub 2/ production. Renewals of the gas phase, in addition to the addition of acetylene and carbon monoxide, were necessary for durable H/sub 2/ production. Since the concentrations of both H/sub 2/ and O/sub 2/ accumulated in the gas phase were minimized after the renewals, the H/sub 2/ uptake activity, which was not completely inhibited by acetylene and carbon monoxide, was reduced and thereby H/sub 2/ evolution was restored. Under such conditions, H/sub 2/ production for up to 20 days was observed under argon and N/sub 2/ atmospheres with average rats of 3.9 and 3.3..mu..l/mg dry wt/h, respectively. H/sub 2/ evolution for 15 days was observed even under an air atmosphere containing acetylene and carbon monoxide. It was thus shown that prolonged production of H/sub 2/ was possible by the use of a blue-green alga which exhibits a high activity of H/sub 2/ uptake under nitrogen-starved conditions.

Is the tungsten(IV complex (NEt42[WO(mnt2] a functional analogue of acetylene hydratase?

Directory of Open Access Journals (Sweden)

Matthias Schreyer

2017-11-01

Full Text Available The tungsten(IV complex (Et4N2[W(O(mnt2] (1; mnt = maleonitriledithiolate was proposed (Sarkar et al., J. Am. Chem. Soc. 1997, 119, 4315 to be a functional analogue of the active center of the enzyme acetylene hydratase from Pelobacter acetylenicus, which hydrates acetylene (ethyne; 2 to acetaldehyde (ethanal; 3. In the absence of a satisfactory mechanistic proposal for the hydration reaction, we considered the possibility of a metal–vinylidene type activation mode, as it is well established for ruthenium-based alkyne hydration catalysts with anti-Markovnikov regioselectivity. To validate the hypothesis, the regioselectivity of tungsten-catalyzed alkyne hydration of a terminal, higher alkyne had to be determined. However, complex 1 was not a competent catalyst for the hydration of 1-octyne under the conditions tested. Furthermore, we could not observe the earlier reported hydration activity of complex 1 towards acetylene. A critical assessment of, and a possible explanation for the earlier reported results are offered. The title question is answered with "no".

Synthesis of Novel E-2-Chlorovinyltellurium Compounds Based on the Stereospecific Anti-addition of Tellurium Tetrachloride to Acetylene

Directory of Open Access Journals (Sweden)

Svetlana V. Amosova

2012-05-01

Full Text Available The reaction of tellurium tetrachloride with acetylene proceeds in a stereospecific anti-addition manner to afford the novel products E-2-chlorovinyltellurium trichloride and E,E-bis(2-chlorovinyltellurium dichloride. Reaction conditions for the selective preparation of each of these products were found. The latter was obtained in 90% yield in CHCl₃ under a pressure of acetylene of 10–15 atm, whereas the former product was formed in up to 72% yield in CCl₄ under a pressure of acetylene of 1–3 atm. Synthesis of the previously unknown E,E-bis(2-chlorovinyl telluride, E,E-bis(2-chlorovinyl ditelluride, E-2-chlorovinyl 1,2,2-trichloroethyl telluride and E,E-bis(2-chlorovinyl-tellurium dibromide is described.

A DFT study and micro-kinetic analysis of acetylene selective hydrogenation on Pd-doped Cu(111) surfaces

Energy Technology Data Exchange (ETDEWEB)

Ma, Ling-Ling [Department of Chemistry, Key Laboratory of Advanced Energy Materials Chemistry (Ministry of Education) and Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Nankai University, Tianjin 300071 (China); Lv, Cun-Qin, E-mail: lcq173@126.com [College of Chemistry and Environmental Engineering, Shanxi Datong University, Datong 037009, Shanxi Province (China); Wang, Gui-Chang, E-mail: wangguichang@nankai.edu.cn [Department of Chemistry, Key Laboratory of Advanced Energy Materials Chemistry (Ministry of Education) and Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Nankai University, Tianjin 300071 (China)

2017-07-15

Semi-hydrogenation of acetylene in a hydrogen-rich stream is an industrially important process. Inspired by the recent experiments that Cu(111) surface doped by a small number of Pd atoms can exhibit excellent catalytic performance toward the dissociation of H{sub 2} molecule as well as the high selective hydrogenation of acetylene as compared with pure Cu and Pd metal alone at low-temperature, here we performed systematic first-principles calculations to investigate the corresponding reaction mechanism related to the acetylene hydrogenation processes on single atom alloys (SAAs) and monolayer Pd/Cu(111) (i.e.,1.00 ML Pd/Cu(111)) model catalysts in detail, and to explore the possible factors controlling the high selectivity on SAAs. Our results clearly demonstrate that the SAA catalyst has higher selectivity for the ethylene formation than that of 1.00 ML Pd/Cu(111), and lower activity for the acetylene conversion compared with that of 1.00 ML Pd/Cu(111). The relatively high selectivity on SAA is mainly due to the facile desorption of ethylene and moderate activity in the dissociation of molecular H{sub 2}. The main factor which lowers the selectivity towards the ethylene formation on 1.00 ML Pd/Cu(111) is that this system has a higher capacity to promote the breaking of C−H/C−C bonds, which leads to the formation of carbonaceous deposits and polymers such as benzene, and thus reduces the selectivity for the ethylene formation. Meanwhile, it was found that the desorption energy of ethylene on these two surfaces was smaller than the energy barrier of further hydrogenation, which results in the absence of ethane on these two systems. Micro-kinetic model analysis provides a further valuable insight into the evidence for the key factors controlling the catalytic activity and selectivity towards the selective hydrogenation of acetylene. Our findings may help people to design a highly selective hydrogenation catalyst by controlling the balance between the H{sub 2

Structure, Stabilities, Thermodynamic Properties, and IR Spectra of Acetylene Clusters (C2H2)n=2-5.

Science.gov (United States)

Karthikeyan, S; Lee, Han Myoung; Kim, Kwang S

2010-10-12

There are no clear conclusions over the structures of the acetylene clusters. In this regard, we have carried out high-level calculations for acetylene clusters (C2H2)2-5 using dispersion-corrected density functional theory (DFT-D), Møller-Plesset second-order perturbation theory (MP2); and coupled-cluster theory with single, double, and perturbative triple excitations [CCSD(T)] at the complete basis set limit. The lowest energy structure of the acetylene dimer has a T-shaped structure of C2v symmetry, but it is nearly isoenergetic to the displaced stacked structure of C2h symmetry. We find that the structure shows the quantum statistical distribution for configurations between the T-shaped and displaced stacked structures for which the average angle (|θ̃|) between two acetylene molecules would be 53-78°, close to the T-shaped structure. The trimer has a triangular structure of C3h symmetry. The tetramer has two lowest energy isomers of S4 and C2h symmetry in zero-point energy (ZPE)-uncorrected energy (ΔEe), but one lowest energy isomer of C2v symmetry in ZPE-corrected energy (ΔE0). For the pentamer, the global minimum structure is C1 symmetry with eight sets of T-type π-H interactions and a set of π-π interactions. Our high-level ab initio calculations are consistent with available experimental data.

A first principles study of the acetylene-water interaction

Energy Technology Data Exchange (ETDEWEB)

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

2000-04-08

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

Autoxidation and acetylene-accelerated oxidation of NO in a 2-phase system; implications for the expression of denitrification in ex situ experiments

Science.gov (United States)

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

Spectrum of acetylene fluorescence excited by single XUV photons

International Nuclear Information System (INIS)

Schmieder, R.W.

1982-01-01

The spectrum of visible emission from photofragments of acetylene excited by single 16.85 eV photons has been recorded for the first time. The spectrum is dominated by the Swan and Deslandres-d'Azambuja bands of C 2 and the 431.5 nm band of CH. The yields of these emissions are of the order 10 -3 photons per absorbed incident photon. The experimental conditions suggest that the emission results from primary C* 2 and CH* photofragments

Synthesis of acetylene alcohols of heterocyclic type and the acyl derivatives

Directory of Open Access Journals (Sweden)

Moldir Dyusebaeva

2015-03-01

Full Text Available A synthesis of potentially biologically active heterocyclic amino alcohols of acetylene (Piperidine and Morpholine under the conditions of Mannich reaction accomplished and received their acyl derivatives. Pharmacological activity (antibacterial and antispasmotic of synthesized compounds, also acute toxicological characteristics studied. The study showed that the combination of DMAE-4 has antispasmodic activity with low toxicity.

Promising SiC support for Pd catalyst in selective hydrogenation of acetylene to ethylene

Science.gov (United States)

Guo, Zhanglong; Liu, Yuefeng; Liu, Yan; Chu, Wei

2018-06-01

In this study, SiC supported Pd nanoparticles were found to be an efficient catalyst in acetylene selective hydrogenation reaction. The ethylene selectivity can be about 20% higher than that on Pd/TiO2 catalyst at the same acetylene conversion at 90%. Moreover, Pd/SiC catalyst showed a stable catalytic life at 65 °C with 80% ethylene selectivity. With the detailed characterization using temperature-programmed reduction (H2-TPR), powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), N2 adsorption/desorption analysis, CO-chemisorption and thermo-gravimetric analysis (TGA), it was found that SiC owns a lower surface area (22.9 m2/g) and a broad distribution of meso-/macro-porosity (from 5 to 65 nm), which enhanced the mass transfer during the chemical process at high reaction rate and decreased the residence time of ethylene on catalyst surface. Importantly, SiC support has the high thermal conductivity, which favored the rapid temperature homogenization through the catalyst bed and inhabited the over-hydrogenation of acetylene. The surface electronic density of Pd on Pd/SiC catalyst was higher than that on Pd/TiO2, which could promote desorption of ethylene from surface of the catalyst. TGA results confirmed a much less coke deposition on Pd/SiC catalyst.

Solution processed organic light-emitting diodes using the plasma cross-linking technology

Energy Technology Data Exchange (ETDEWEB)

He, Kongduo [Department of Light Sources and Illuminating Engineering, Fudan University, Shanghai 200433 (China); Liu, Yang [Department of Light Sources and Illuminating Engineering, Fudan University, Shanghai 200433 (China); Engineering Research Center of Advanced Lighting Technology, Ministry of Education, Shanghai 200433 (China); Gong, Junyi; Zeng, Pan; Kong, Xun; Yang, Xilu; Yang, Cheng; Yu, Yan [Department of Light Sources and Illuminating Engineering, Fudan University, Shanghai 200433 (China); Liang, Rongqing [Department of Light Sources and Illuminating Engineering, Fudan University, Shanghai 200433 (China); Engineering Research Center of Advanced Lighting Technology, Ministry of Education, Shanghai 200433 (China); Ou, Qiongrong, E-mail: qrou@fudan.edu.cn [Department of Light Sources and Illuminating Engineering, Fudan University, Shanghai 200433 (China); Engineering Research Center of Advanced Lighting Technology, Ministry of Education, Shanghai 200433 (China)

2016-09-30

Highlights: • Mixed acetylene and Ar plasma treatment makes the organic film surface cross-linked. • The plasma treatment for 30 s does not affect the performance of OLEDs. • Cross-linking surface can resist rinsing and corrosion of organic solvent. • The surface morphology is nearly unchanged after plasma treatment. • The plasma cross-linking method can realize solution processed multilayer OLEDs. - Abstract: Solution processed multilayer organic light-emitting diodes (OLEDs) present challenges, especially regarding dissolution of the first layer during deposition of a second layer. In this work, we first demonstrated a plasma cross-linking technology to produce a solution processed OLED. The surfaces of organic films can be cross-linked after mixed acetylene and Ar plasma treatment for several tens of seconds and resist corrosion of organic solvent. The film thickness and surface morphology of emissive layers (EMLs) with plasma treatment and subsequently spin-rinsed with chlorobenzene are nearly unchanged. The solution processed triple-layer OLED is successfully fabricated and the current efficiency increases 50% than that of the double-layer OLED. Fluorescent characteristics of EMLs are also observed to investigate factors influencing the efficiency of the triple-layer OLED. Plasma cross-linking technology may open up a new pathway towards fabrication of all-solution processed multilayer OLEDs and other soft electronic devices.

Computational Screening of MOFs for Acetylene Separation.

Science.gov (United States)

Nemati Vesali Azar, Ayda; Keskin, Seda

2018-01-01

Efficient separation of acetylene (C 2 H 2 ) from CO 2 and CH 4 is important to meet the requirement of high-purity acetylene in various industrial applications. Metal organic frameworks (MOFs) are great candidates for adsorption-based C 2 H 2 /CO 2 and C 2 H 2 /CH 4 separations due to their unique properties such as wide range of pore sizes and tunable chemistries. Experimental studies on the limited number of MOFs revealed that MOFs offer remarkable C 2 H 2 /CO 2 and C 2 H 2 /CH 4 selectivities based on single-component adsorption data. We performed the first large-scale molecular simulation study to investigate separation performances of 174 different MOF structures for C 2 H 2 /CO 2 and C 2 H 2 /CH 4 mixtures. Using the results of molecular simulations, several adsorbent performance evaluation metrics, such as selectivity, working capacity, adsorbent performance score, sorbent selection parameter, and regenerability were computed for each MOF. Based on these metrics, the best adsorbent candidates were identified for both separations. Results showed that the top three most promising MOF adsorbents exhibit C 2 H 2 /CO 2 selectivities of 49, 47, 24 and C 2 H 2 /CH 4 selectivities of 824, 684, 638 at 1 bar, 298 K and these are the highest C 2 H 2 selectivities reported to date in the literature. Structure-performance analysis revealed that the best MOF adsorbents have pore sizes between 4 and 11 Å, surface areas in the range of 600-1,200 m 2 /g and porosities between 0.4 and 0.6 for selective separation of C 2 H 2 from CO 2 and CH 4 . These results will guide the future studies for the design of new MOFs with high C 2 H 2 separation potentials.

Computational Screening of MOFs for Acetylene Separation

Science.gov (United States)

Nemati Vesali Azar, Ayda; Keskin, Seda

2018-02-01

Efficient separation of acetylene (C2H2) from CO2 and CH4 is important to meet the requirement of high-purity acetylene in various industrial applications. Metal organic frameworks (MOFs) are great candidates for adsorption-based C2H2/CO2 and C2H2/CH4 separations due to their unique properties such as wide range of pore sizes and tunable chemistries. Experimental studies on the limited number of MOFs revealed that MOFs offer remarkable C2H2/CO2 and C2H2/CH4 selectivities based on single-component adsorption data. We performed the first large-scale molecular simulation study to investigate separation performances of 174 different MOF structures for C2H2/CO2 and C2H2/CH4 mixtures. Using the results of molecular simulations, several adsorbent performance evaluation metrics, such as selectivity, working capacity, adsorbent performance score, sorbent selection parameter and regenerability were computed for each MOF. Based on these metrics, the best adsorbent candidates were identified for both separations. Results showed that the top three most promising MOF adsorbents exhibit C2H2/CO2 selectivities of 49, 47, 24 and C2H2/CH4 selectivities of 824, 684, 638 at 1 bar, 298 K and these are the highest C2H2 selectivities reported to date in the literature. Structure-performance analysis revealed that the best MOF adsorbents have pore sizes between 4-11 Å, surface areas in the range of 600-1,200 m2/g and porosities between 0.4-0.6 for selective separation of C2H2 from CO2 and CH4. These results will guide the future studies for the design of new MOFs with high C2H2 separation potentials.

Computational Screening of MOFs for Acetylene Separation

Directory of Open Access Journals (Sweden)

Ayda Nemati Vesali Azar

2018-02-01

Full Text Available Efficient separation of acetylene (C2H2 from CO2 and CH4 is important to meet the requirement of high-purity acetylene in various industrial applications. Metal organic frameworks (MOFs are great candidates for adsorption-based C2H2/CO2 and C2H2/CH4 separations due to their unique properties such as wide range of pore sizes and tunable chemistries. Experimental studies on the limited number of MOFs revealed that MOFs offer remarkable C2H2/CO2 and C2H2/CH4 selectivities based on single-component adsorption data. We performed the first large-scale molecular simulation study to investigate separation performances of 174 different MOF structures for C2H2/CO2 and C2H2/CH4 mixtures. Using the results of molecular simulations, several adsorbent performance evaluation metrics, such as selectivity, working capacity, adsorbent performance score, sorbent selection parameter, and regenerability were computed for each MOF. Based on these metrics, the best adsorbent candidates were identified for both separations. Results showed that the top three most promising MOF adsorbents exhibit C2H2/CO2 selectivities of 49, 47, 24 and C2H2/CH4 selectivities of 824, 684, 638 at 1 bar, 298 K and these are the highest C2H2 selectivities reported to date in the literature. Structure-performance analysis revealed that the best MOF adsorbents have pore sizes between 4 and 11 Å, surface areas in the range of 600–1,200 m2/g and porosities between 0.4 and 0.6 for selective separation of C2H2 from CO2 and CH4. These results will guide the future studies for the design of new MOFs with high C2H2 separation potentials.

New 2-Methoxy Acetylenic Acids and Pyrazole Alkaloids from the Marine Sponge Cinachyrella sp.

Directory of Open Access Journals (Sweden)

Amin Mokhlesi

2017-11-01

Full Text Available Three new 2-methoxy acetylenic acids (1–3 and a known derivative (4, in addition to three new natural pyrazole alkaloids (5–7 were isolated from an Indonesian marine sponge of the genus Cinachyrella. Compounds 5 and 6 have previously been reported as synthetic compounds. The structures of the new compounds were established on the basis of one- and two-dimensional NMR spectroscopy as well as by mass spectrometric data. The absolute configuration of the new acetylenic acid derivatives (1–3 was established by ECD spectroscopy. All isolated compounds were evaluated for their cytotoxicity against L5178Y mouse lymphoma cells. Compounds 1–4 exhibited strong activity with an IC50 value of 0.3 µM. A plausible biosynthetic pathway for the pyrazole metabolites 5–7 is proposed.

Shock tube/laser absorption measurements of methane, acetylene and ethylene during the pyrolysis of n-pentane and iso-pentane

KAUST Repository

Sajid, Muhammad Bilal

2015-11-09

Pentane isomers are important constituents of distillate gasoline, compressed natural gas and liquefied petroleum gas. Pentane chemistry is integral component of the chemical kinetic mechanisms of larger hydrocarbons. Existing kinetic mechanisms differ in their predictions of the oxidative and pyrolysis behavior of pentane isomers. This work provides new species time-history data to validate and improve pentane chemistry models. Methane, acetylene and ethylene are measured during the high-temperature pyrolysis of n-pentane and iso-pentane. Experiments are performed behind reflected shock waves over 1400–2100 K and pressures near 1 atm. Methane and acetylene are measured using a quantum cascade laser operating near 8 µm, whereas ethylene is measured with a CO2 gas laser operating near 10.6 µm. A two-color technique is used to eliminate broadband interference caused by large hydrocarbons. Measurements are compared with predictions of existing chemical kinetic mechanisms which underpredict the formation of methane and acetylene but overpredict ethylene formation.

Conductance mechanism in a linear non-conjugated trimethylsilyl-acetylene molecule: tunneling through localized states

NARCIS (Netherlands)

Petrov, E.G.; Marchenko, A.; Kapitanchuk, O.; Katsonis, Nathalie Hélène; Fichou, D.

2014-01-01

The conductance properties of 1,3-(trimethylsilyl)-1-tridecene-6,12-diyne, a non-conjugated trimethylsil-acetylene molecule have been investigated both experimentally and theoretically. Based on scanning tunnelling spectroscopy experiments, a discussion on the mechanisms controlling the charge

TINGKAT KEPUASAN PENGGUNA APLIKASI INTERSYSTEM BUSINESS SOLUTION (IBS PADA PT CITAJAYA INFINITE SYSTEM

Directory of Open Access Journals (Sweden)

Anderes Gui

2009-05-01

Full Text Available Use of applications to assist business processes to be completed faster, saat have been very widely adopted by companies so that good performance yang applications and meet the needs of users will be very important. The purpose of this research is to find the application user expectations Intersystem Business Solution (IBS in PT Citajaya Infinite System and find out how the performance of these applications after implemented so that will be generated an output, which form the level of satisfaction from the use of applications by managers and employees at the company. Data collection methods used were observation, interviews, and questionnaires. Manual methods used in data processing, Microsoft Excel 2003, and SPSS version 13.0. While the analysis method using gap analysis to determine the scale and range of satisfaction levels. So, one conclusion that can be drawn from this study is the performance of this application is sufficient to meet user expectations.Keywords: level of satisfaction, users, IBS applicationABSTRAKPenggunaan aplikasi untuk membantu proses bisnis agar menjadi lebih cepat diselesaikan, saat ini sudah sangat banyak diterapkan oleh perusahaan-perusahaan sehingga kinerja aplikasi yang baik dan memenuhi kebutuhan dari pengguna akan sangat penting sekali. Tujuan dari penelitian ini adalah untuk mencari harapan pengguna aplikasi Intersystem Business Solution (IBS pada PT Citajaya Infinite System dan mengetahui bagaimana kinerja aplikasi ini setelah diimplementasikan sehingga akan dihasilkan sebuah output, yang berupa tingkat kepuasan dari penggunaan aplikasi oleh para manajer dan karyawan di perusahaan tersebut. Metode pengumpulan data yang digunakan adalah observasi, wawancara, dan kuesioner. Metode pengolahan datanya menggunakan manual, Microsoft Excel 2003, dan SPSS versi 13.0. Sedangkan metode analisisnya menggunakan gap analysis dan rentang skala untuk menentukan tingkat kepuasan. Jadi, salah satu simpulan yang dapat diambil

2-methyl-3-butyn-2-ol as an acetylene precursor in the Mannich reaction. A new synthesis of suicide inactivators of monoamine oxidase

International Nuclear Information System (INIS)

Fowler, J.S.

1977-01-01

A two-step reaction process is reported for the synthesis of 11 C, 13 C, or 14 C-labelled propargylamines in moderate yields. The propargylamines were prepared by a modified Mannich scheme without the use of acetylene. The reaction scheme involved the use of 2-methyl-3-butyn-2-ol followed by KOH-catalyzed elimination of acetone from the acetylenic carbinols

RETRAN analysis of inter-system LOCA within the primary coolant pump

International Nuclear Information System (INIS)

Gangadharan, A.; Pratt, G.F.

1992-01-01

One example of an inter-system loss of coolant accident is the failure of the tubing within the primary coolant pump (PCP) thermal barrier heat exchanger. Such a failure would result in the entry of primary coolant into the component cooling water (CCW) system. The primary coolant flowrate through the break would rapidly pressurize the CCW system when the relief valves are too small. The piping in the CCW system at Palisades has a low pressure rating. Failures in this system outside the containment boundary could lead to primary coolant release to the atmosphere. RETRAN-02 was used to perform a simulation of the break in the PCP integral heat exchanger. The model included a detailed nodalization of the Byron-Jackson primary coolant pump internals leading up to the CCW system relief valves. Preliminary studies show the need for increased relief capacity in the CCW system. A case was run using a larger relief valve. Critical flow in the system upstream of the relief valves maintains the pressures in those volumes above the CCW design pressure. The pressures downstream from the relief valves and outside containment will be at or below the design pressure. This paper presents the results of the transient analysis

Component evaluation for intersystem loss-of-coolant accidents in advanced light water reactors

International Nuclear Information System (INIS)

Ware, A.G.

1994-07-01

Using the methodology outlined in NUREG/CR-5603 this report evaluates (on a probabilistic basis) design rules for components in ALWRs that could be subjected to intersystem loss-of-coolant accidents (ISLOCAs). The methodology is intended for piping elements, flange connections, on-line pumps and valves, and heat exchangers. The NRC has directed that the design rules be evaluated for BWR pressures of 7.04 MPa (1025 psig), PWR pressures of 15.4 MPa (2235 psig), and 177 degrees C (350 degrees F), and has established a goal of 90% probability that system rupture will not occur during an ISLOCA event. The results of the calculations in this report show that components designed for a pressure of 0.4 of the reactor coolant system operating pressure will satisfy the NRC survival goal in most cases. Specific recommendations for component strengths for BWR and PWR applications are made in the report. A peer review panel of nationally recognized experts was selected to review and critique the initial results of this program

Nine acetylenic alcohols isolated from the Okinawan marine sponge of the genus Petrosia (Strongylophora).

NARCIS (Netherlands)

Watanabe, K.; Mori, G.; Iguchi, K.; Suzuki, M.; van Soest, R.W.M.

2007-01-01

Nine new acetylenic alcohols 1-9 were isolated from a marine sponge belonging to the genus Petrosia (Strongylophora). The structures were elucidated mainly based on the analysis of one-and two-dimensional NMR spectral data. To determine the position of the central double bonds in 1-8, each compound

Reactivity differences of Pt0 phosphine complexes in C-C bond activation of asymmetric acetylenes

NARCIS (Netherlands)

Gunay, A.; Müller, C.; Lachicotte, R.J.; Brennessel, W.W.; Jones, W.D.

2009-01-01

Carbon-carbon bond activation reactions of asymmetric acetylene derivatives of the type L2Pt(PhC=CR) were studied with 1,2-bis(diisopropylphosphino)ethane (dippe), 1,2-bis(di-tert-butylphosphino)ethane (dtbpe), and 1-diisopropylphosphino-2-dimethylaminoethane (dippdmae) chelates.

Enthalpies of vaporization of some acetylene peroxy derivatives of carboranes-12

International Nuclear Information System (INIS)

Dibrivnyj, V.N.; Pistun, Z.E.; Van-Chin-Syan, Yu.Ya.; Yuvchenko, A.P.; Zvereva, T.D.

1999-01-01

Temperature dependences of saturated vapor pressure and vaporization enthalpies of five acetylene peroxy derivatives of carboranes-12 are determined by the Knudsen effusion method. Enthalpies and melting points of crystals, as well as temperatures of liquid compounds decomposition start are determined by the method of differential scanning calorimetry. Comparison of evaporation enthalpies determined in the study confirms the conclusions on non-additive character of intermolecular interaction in carboranes and their derivatives, which have been made previously [ru

On the Role of Surface Modifications of Palladium Catalysts in the Selective Hydrogenation of Acetylene

DEFF Research Database (Denmark)

Studt, Felix; Abild-Pedersen, Frank; Bligaard, Thomas

2008-01-01

Summing Me up: DFT calculations have shown that alloying, subsurface carbon, and hydride formation, all increase the selectivity of Pd catalysts for acetylene hydrogenation by weakening the surface–adsorbate bond. A simple descriptor—the adsorption energy of a methyl group—has been used to quanti...

Interpenetrating polymer networks from acetylene terminated materials

Science.gov (United States)

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

1989-01-01

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

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

International Nuclear Information System (INIS)

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, 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

Excited-state dynamics of acetylene excited to individual rotational level of the V04K01 subband

Science.gov (United States)

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

2006-01-01

Dynamics of the IR emission induced by excitation of the acetylene molecule using the (32Ka0,1,2,ÃAu1←41la1,X˜Σg+1) transition was investigated. The observed IR emission was assigned to transitions between the ground-state vibrational levels. Acetylene fluorescence quenching induced by external electric and magnetic fields acting upon the system prepared using the (34Ka1,ÃAu1←00la0,X˜Σg+1) excitation was also studied. External electric field creates an additional radiationless pathway to the ground-state levels, coupling levels of the ÃAu1 excited state to the quasiresonant levels of the X˜Σg+1 ground state. The level density of the ground state in the vicinity of the excited state is very high, thus the electric-field-induced transition is irreversible, with the rate constant described by the Fermi rule. Magnetic field alters the decay profile without changing the fluorescence quantum yield in collisionless conditions. IR emission from the CCH transient was detected, and was also affected by the external electric and magnetic fields. Acetylene predissociation was demonstrated to proceed by the direct S1→S0 mechanism. The results were explained using the previously developed theoretical approach, yielding values of the relevant model parameters.

Intra- and inter-molecular energy transfer studies. Progress report, 1 June 1974--31 May 1975

International Nuclear Information System (INIS)

Nicol, M.F.

1975-01-01

The analysis of pressure-induced effects on the intersystem crossing in anthracene; determination of the influence of hydrogen-bonding on the intersystem crossing rate and phosphorescence of azines; experimental studies of the kinetics of high-pressure structural transitions in Teflon; testing of liquid helium temperature high-pressure optical cells; excimer production in compound crystalline aromatic hydrocarbons; and studies of the structure and chemistry of dianthracene at high pressures are described. (6 figs.) (GHT)

Acetylene and carbon monoxide oxidation over a Pt/Rh/CeO2/γ-Al2O3 automotive exhaust gas catalyst: kinetic modelling of transient experiments

NARCIS (Netherlands)

Harmsen, J.M.A.; Hoebink, J.H.B.J.; Schouten, J.C.

2001-01-01

The transient kinetics of acetylene (C2H2) conversion by oxygen over a commercial Pt/Rh/CeO2/¿-Al2O3 three-way catalyst have been modelled. Experiments to validate the model were carried out in a fixed-bed reactor with two separate inlets, enabling alternate feeding of acetylene and oxygen.

Theoretical insights into acetylene adsorption on nanoporous gold surfaces: Role of residual silver

Science.gov (United States)

Luo, Yafei; Chen, Zhongzhu; Xu, Zhigang; Yang, Donglin; Zhang, Jin; Tang, Dianyong

2018-03-01

Unveiling the acetylene adsorption is crucial for designing novel and highly active catalyst for the semihydrogenation of alkyne. In order to achieve this goal, we have studied C2H2 adsorption on the various nanoporous gold models in detail, including the Au(100), Au(111) and Au(321) slab models. The calculated results indicate that the C atoms of C2H2 experience rehybridization from sp toward sp2/sp3 when the adsorption occurs on bridge and hollow sites, which can be illustrated via the projected density of state (PDOS) and crystal orbital Hamilton population (COHP). Meanwhile, the formation of σ(Ausbnd C) bond is beneficial for facilitating acetylene adsorption and the kink Au atom plays an important role for the C2H2 adsorption. In addition, for C2H2 adsorption on the Ag doped nanoporous gold, the configurations strongly depend on the position of superficial unsubstituted Au atoms. Further, the inversely relationship has been found between the adsorption energies and number of the Ag substituents, demonstrating that the superficial Ag substituents are harmful for C2H2 adsorption and activation.

Separation of Acetylene from Carbon Dioxide and Ethylene by a Water-Stable Microporous Metal-Organic Framework with Aligned Imidazolium Groups inside the Channels.

Science.gov (United States)

Lee, Jaechul; Chuah, Chong Yang; Kim, Jaheon; Kim, Youngsuk; Ko, Nakeun; Seo, Younggyu; Kim, Kimoon; Bae, Tae Hyun; Lee, Eunsung

2018-04-24

Separation of acetylene from carbon dioxide and ethylene is challenging in view of their similar sizes and physical properties. Metal-organic frameworks (MOFs) in general are strong candidates for these separations owing to the presence of functional pore surfaces that can selectively capture a specific target molecule. Here, we report a novel 3D microporous cationic framework named JCM-1. This structure possesses imidazolium functional groups on the pore surfaces and pyrazolate as a metal binding group, which is well known to form strong metal-to-ligand bonds. The selective sorption of acetylene over carbon dioxide and ethylene in JCM-1 was successfully demonstrated by equilibrium gas adsorption analysis as well as dynamic breakthrough measurement. Furthermore, its excellent hydrolytic stability makes the separation processes highly recyclable without a substantial loss in acetylene uptake capacity. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

KAUST Repository

Sajid, M.B.; Javed, Tamour; Farooq, Aamir

2015-01-01

The mid-infrared wavelength region near 8 mu m 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 v(4) band of methane and the v(4

Intersystem-crossing and phosphorescence rates in fac-Ir{sup III}(ppy){sub 3}: A theoretical study involving multi-reference configuration interaction wavefunctions

Energy Technology Data Exchange (ETDEWEB)

Kleinschmidt, Martin; Marian, Christel M., E-mail: Christel.Marian@hhu.de [Institute of Theoretical and Computational Chemistry, Heinrich-Heine-University Düsseldorf, Universitätsstraße 1, 40225 Düsseldorf (Germany); Wüllen, Christoph van [Fachbereich Chemie and Forschungszentrum OPTIMAS, Technical University of Kaiserslautern, Erwin-Schrödinger-Straße 52, 67663 Kaiserslautern (Germany)

2015-03-07

We have employed combined density functional theory and multi-reference configuration interaction methods including spin–orbit coupling (SOC) effects to investigate the photophysics of the green phosphorescent emitter fac-tris-(2-phenylpyridine)iridium (fac-Ir(ppy){sub 3}). A critical evaluation of our quantum chemical approaches shows that a perturbational treatment of SOC is the method of choice for computing the UV/Vis spectrum of this heavy transition metal complex while multi-reference spin–orbit configuration interaction is preferable for calculating the phosphorescence rates. The particular choice of the spin–orbit interaction operator is found to be of minor importance. Intersystem crossing (ISC) rates have been determined by Fourier transformation of the time correlation function of the transition including Dushinsky rotations. In the electronic ground state, fac-Ir(ppy){sub 3} is C{sub 3} symmetric. The calculated UV/Vis spectrum is in excellent agreement with experiment. The effect of SOC is particularly pronounced for the metal-to-ligand charge transfer (MLCT) band in the visible region of the absorption spectrum which does not only extend its spectral onset towards longer wavelengths but also experiences a blue shift of its maximum. Pseudo-Jahn-Teller interaction leads to asymmetric coordinate displacements in the lowest MLCT states. Substantial electronic SOC and a small energy gap make ISC an ultrafast process in fac-Ir(ppy){sub 3}. For the S{sub 1}↝T{sub 1} non-radiative transition, we compute a rate constant of k{sub ISC} = 6.9 × 10{sup 12} s{sup −1} which exceeds the rate constant of radiative decay to the electronic ground state by more than six orders of magnitude, in agreement with the experimental observation of a subpicosecond ISC process and a triplet quantum yield close to unity. As a consequence of the geometric distortion in the T{sub 1} state, the T{sub 1} → S{sub 0} transition densities are localized on one of the

Detailed modeling of hydrocarbon nanoparticle nucleation in acetylene discharges

International Nuclear Information System (INIS)

Bleecker, Kathleen de; Bogaerts, Annemie; Goedheer, Wim

2006-01-01

The initial stage of nanoparticle formation and growth in radiofrequency acetylene (C 2 H 2 ) plasmas is investigated by means of a self-consistent one-dimensional fluid model. A detailed chemical kinetic scheme, containing electron impact, ion-neutral, and neutral-neutral reactions, has been developed in order to predict the underlying dust growth mechanisms and the most important dust precursors. The model considers 41 different species (neutrals, radicals, ions, and electrons) describing hydrocarbons (C n H m ) containing up to 12 carbon atoms. Possible routes for particle growth are discussed. Both positive and negative ion reaction pathways are considered, as consecutive anion- and cation-molecule reactions seem to lead to a fast build up of the carbon skeleton

Effect of injection pressure on performance, emission, and combustion characteristics of diesel-acetylene-fuelled single cylinder stationary CI engine.

Science.gov (United States)

Srivastava, Anmesh Kumar; Soni, Shyam Lal; Sharma, Dilip; Jain, Narayan Lal

2018-03-01

In this paper, the effect of injection pressure on the performance, emission, and combustion characteristics of a diesel-acetylene fuelled single cylinder, four-stroke, direct injection (DI) diesel engine with a rated power of 3.5 kW at a rated speed of 1500 rpm was studied. Experiments were performed in dual-fuel mode at four different injection pressures of 180, 190, 200, and 210 bar with a flow rate of 120 LPH of acetylene and results were compared with that of baseline diesel operation. Experimental results showed that highest brake thermal efficiency of 27.57% was achieved at injection pressure of 200 bar for diesel-acetylene dual-fuel mode which was much higher than 23.32% obtained for baseline diesel. Carbon monoxide, hydrocarbon, and smoke emissions were also measured and found to be lower, while the NO x emissions were higher at 200 bar in dual fuel mode as compared to those in other injection pressures in dual fuel mode and also for baseline diesel mode. Peak cylinder pressure, net heat release rate, and rate of pressure rise were also calculated and were higher at 200 bar injection pressure in dual fuel mode.

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

International Nuclear Information System (INIS)

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

1987-01-01

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

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

Science.gov (United States)

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

2013-12-15

Power transformers are essential for a functioning electrical system and therefore require special attention by maintenance programs because a fault can harm both the company and society. The temperature inside a power transformer and the dissolved gases, which are primarily composed of acetylene, are the two main parameters monitored when detecting faults. This paper describes the development of a device for analyzing the acetylene content in insulating oil using spectrofluorimetry. Using this device introduces a new methodology for the maintaining and operating power transformers. The prototype is currently operating in a substation. The results presented by this system were satisfactory; when compared to chromatographic data, the errors did not exceed 15%. This prototype may be used to confirm the quality of an insulating oil sample to detect faults in power transformers. © 2013 Elsevier B.V. All rights reserved.

Resonance and intersystem transition lines of astrophysical importance in neutral sulfur

International Nuclear Information System (INIS)

Deb, N C; Hibbert, A

2006-01-01

A systematic study of S I levels belonging to 3s 2 3p 4 , 3s3p 5 , 3s 2 3p 3 ( 4 S o , 2 D o , 2 P o )nl, where nl = 4s, 5s, 6s, 4p, 5p, 6p, 3d, 4d, 5d, 4f and 5f configurations and optically allowed and intersystem transitions among them are presented. A very large set of basis functions are generated using up to three electron promotions from the ground configurations for each of the 24 symmetries considered belonging to two parities. Many of the levels are reported for the first time. Relativistic effects are included through the Breit-Pauli Hamiltonian. The resulting fine-structure levels and oscillator strengths for some astrophysically important transitions are then presented and compared with the available measured and calculated values. Excellent agreement between the present lifetimes and the measurement of Berzinsh et al (1997 Phys. Rev. A 55 1836) and Beideck et al (1994 Astrophys. J. 428 393) are achieved for the 3s 2 3p 3 ( 4 S o )ns( 3 S 1 o ), 4 ≤ n ≤ 6, 3s 2 3p 3 ( 4 S o )4p( 3 P 0,1,2 o ) and 3s 2 3p 3 ( 2 P o )4s( 3 P 0,1,2 o ) levels, respectively

Organogermanium Chemistry: Germacyclobutanes and digermane Additions to Acetylenes

Energy Technology Data Exchange (ETDEWEB)

Chubb, Andrew Michael [Iowa State Univ., Ames, IA (United States)

2003-01-01

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.

Coupled Hartree-Fock calculation of {sup 13} C shielding tensors in acetylene clusters

Energy Technology Data Exchange (ETDEWEB)

Craw, John Simon; Nascimento, Marco Antonio Chaer [Universidade Federal, Rio de Janeiro, RJ (Brazil). Inst. de Quimica

1992-12-31

The coupled Hartree Fock method has been used to calculate ab-initio carbon magnetic shielding tensors for small clusters of acetylene molecules. The chemical shift increases from the monomer to the dimer and trimer. This is mainly due increased diamagnetism, which is imperfectly cancelled by increased paramagnetism due to loss of axial symmetry. Anisotropic effects are shown to be small in both the dimer the and trimer. (author) 21 refs., 2 tabs.

Influence of soil composition in the determination of chromium by atomic absorption spectrometry with flame air / acetylene; Influencia de la composicion del suelo en la determinacion de cromo por espectrometria de absorcion atomica con llama aire/acetileno

Energy Technology Data Exchange (ETDEWEB)

Duran Sosa, Ibis; Granda Valdes, Mayra [Departamento de Quimica Analitica, Facultad de Quimica, Universidad de La Habana, La Habana (Cuba); Pomares Alfonso, Mario Simeon, E-mail: mpomares@imre.oc.uh.cu [Instituto de Ciencias y Tecnologia de Materiales, Universidad de La Habana, La Habana (Cuba)

2014-07-01

The Air-acetylene Flame Atomic Absorption determination of chromium is a complex task, being strongly influenced by sample composition and instrumental conditions. The objective of this work was to study the influence of Al, Ca, Fe, K, Mg, and Na on the absorption of chromium in the air-acetylene flame, both separately and combined in solution, when acetylene flow and burner height vary. Dissolutions of the mixtures simulated the composition of four soils from the Quibu River Basin in Havana, Cuba. Chromium absorption first increased and then decreased with increment of acetylene flow for shorter burner heights (∼ 2-4 mm); while a continuous increase was observed for larger heights (> 4 mm). This behavior was the same in the presence and absence of interfering chemical element, mentioned above. On the other hand, the dependence of the magnitude of the interference with acetylene flow and burner height was complex and dependent on the interfering element, particularly at larger heights where the behavior of Al was remarkably different. The interference of the four mixtures of Al, Ca, K, Fe, Mg and Na decreased in comparison to individual interfering effects and was less dependent on acetylene flow and burner height. Finally, a significant reduction of interference on chromium determination in soil samples was achieved by an adequate selection of acetylene flow and burner height.

Toward power scaling in an acetylene mid-infrared hollow-core optical fiber gas laser: effects of pressure, fiber length, and pump power

Science.gov (United States)

Weerasinghe, H. W. Kushan; Dadashzadeh, Neda; Thirugnanasambandam, Manasadevi P.; Debord, Benoît.; Chafer, Matthieu; Gérôme, Frédéric; Benabid, Fetah; Corwin, Kristan L.; Washburn, Brian R.

2018-02-01

The effect of gas pressure, fiber length, and optical pump power on an acetylene mid-infrared hollow-core optical fiber gas laser (HOFGLAS) is experimentally determined in order to scale the laser to higher powers. The absorbed optical power and threshold power are measured for different pressures providing an optimum pressure for a given fiber length. We observe a linear dependence of both absorbed pump energy and lasing threshold for the acetylene HOFGLAS, while maintaining a good mode quality with an M-squared of 1.15. The threshold and mode behavior are encouraging for scaling to higher pressures and pump powers.

An Empirical Spectroscopic Database for Acetylene in the Regions of 5850-9415 CM^{-1}

Science.gov (United States)

Campargue, Alain; Lyulin, Oleg

2017-06-01

Six studies have been recently devoted to a systematic analysis of the high-resolution near infrared absorption spectrum of acetylene recorded by Cavity Ring Down spectroscopy (CRDS) in Grenoble and by Fourier-transform spectroscopy (FTS) in Brussels and Hefei. On the basis of these works, in the present contribution, we construct an empirical database for acetylene in the 5850 - 9415 \\wn region excluding the 6341-7000 \\wn interval corresponding to the very strong νb{1}+ νb{3} manifold. The database gathers and extends information included in our CRDS and FTS studies. In particular, the intensities of about 1700 lines measured by CRDS in the 7244-7920 \\wn are reported for the first time together with those of several bands of ^{12}C^{13}CH_{2} present in natural isotopic abundance in the acetylene sample. The Herman-Wallis coefficients of most of the bands are derived from a fit of the measured intensity values. A recommended line list is provided with positions calculated using empirical spectroscopic parameters of the lower and upper energy vibrational levels and intensities calculated using the derived Herman-Wallis coefficients. This approach allows completing the experimental list by adding missing lines and improving poorly determined positions and intensities. As a result the constructed line list includes a total of 10973 lines belonging to 146 bands of ^{12}C_{2}H_{2} and 29 bands of ^{12}C^{13}CH_{2}. For comparison the HITRAN2012 database in the same region includes 869 lines of 14 bands, all belonging to ^{12}C_{2}H_{2}. Our weakest lines have an intensity on the order of 10^{-29} cm/molecule,about three orders of magnitude smaller than the HITRAN intensity cut off. Line profile parameters are added to the line list which is provided in HITRAN format. The comparison to the HITRAN2012 line list or to results obtained using the global effective operator approach is discussed in terms of completeness and accuracy.

Simultaneous measurements of acetylene and soot during the pyrolysis of ethylene and benzene in a shock tube

KAUST Repository

KC, Utsav; Beshir, Mohamed; Farooq, Aamir

2016-01-01

reflected shock waves at temperatures of 1600-2200. K and pressures of 3-5. bar. Acetylene mole fraction time-histories are measured from the absorption of a quantum-cascade laser operating around 13.6. μm. The soot volume fraction, particle size and number

An empirical spectroscopic database for acetylene in the regions of 5850-6341 cm-1 and 7000-9415 cm-1

Science.gov (United States)

Lyulin, O. M.; Campargue, A.

2017-12-01

Six studies have been recently devoted to a systematic analysis of the high-resolution near infrared absorption spectrum of acetylene recorded by Cavity Ring Down spectroscopy (CRDS) in Grenoble and by Fourier-transform spectroscopy (FTS) in Brussels and Hefei. On the basis of these works, in the present contribution, we construct an empirical database for acetylene in the 5850-9415 cm-1 region excluding the 6341-7000 cm-1 interval corresponding to the very strong ν1+ν3 manifold. Our database gathers and extends information included in our CRDS and FTS studies. In particular, the intensities of about 1700 lines measured by CRDS in the 7244-7920 cm-1 region are reported for the first time together with those of several bands of 12C13CH2 present in natural isotopic abundance in the acetylene sample. The Herman-Wallis coefficients of most of the bands are derived from a fit of the measured intensity values. A recommended line list is provided with positions calculated using empirical spectroscopic parameters of the lower and upper energy vibrational levels and intensities calculated using the derived Herman-Wallis coefficients. This approach allows completing the experimental list by adding missing lines and improving poorly determined positions and intensities. As a result the constructed line list includes a total of 11113 transitions belonging to 150 bands of 12C2H2 and 29 bands of 12C13CH2. For comparison the HITRAN database in the same region includes 869 transitions of 14 bands, all belonging to 12C2H2. Our weakest lines have an intensity on the order of 10-29 cm/molecule, about three orders of magnitude smaller than the HITRAN intensity cut off. Line profile parameters are added to the line list which is provided in HITRAN format. The comparison of the acetylene database to the HITRAN2012 line list or to results obtained using the global effective operator approach is discussed in terms of completeness and accuracy.

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

Science.gov (United States)

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.

Momentum-imaging investigations of the dissociation of D2+ and the isomerization of acetylene to vinylidene by intense short laser pulses

International Nuclear Information System (INIS)

Alnaser, A S; Litvinyuk, I; Osipov, T; Ulrich, B; Landers, A; Wells, E; Maharjan, C M; Ranitovic, P; Bochareva, I; Ray, D; Cocke, C L

2006-01-01

We present momentum images of the ionic products from the ionization of D 2 and C 2 H 2 by short laser pulses. For D 2 , we use a pump-probe approach to investigate the dependence of the enhanced ionization on the internuclear distance. Evidence for two (not well separated) regions of enhancement is found near internuclear distances of 6 and 10 au. In the case of acetylene, we report clear evidence for the production of both acetylene and vinylidene dications with kinetic energy releases similar to those reported earlier by core electron removal. We also find very different angular distributions for the fragments in the two channels, consistent with a finite time for the isomerization

Shock tube/laser absorption measurements of methane, acetylene and ethylene during the pyrolysis of n-pentane and iso-pentane

KAUST Repository

Sajid, Muhammad Bilal; Javed, Tamour; Farooq, Aamir

2015-01-01

differ in their predictions of the oxidative and pyrolysis behavior of pentane isomers. This work provides new species time-history data to validate and improve pentane chemistry models. Methane, acetylene and ethylene are measured during the high

Creation and behavior of radicals and ions in the Acetylene/Argon microwave ECR discharge

Czech Academy of Sciences Publication Activity Database

Pokorný, Petr; Musil, Jindřich; Novotný, Michal; Lančok, Ján; Fitl, Přemysl; Vlček, Jan

2017-01-01

Roč. 14, č. 12 (2017), s. 1-9, č. článku 1700062. ISSN 1612-8850 R&D Projects: GA ČR GA17-13427S; GA MŠk LO1409; GA MŠk LM2015088 Institutional support: RVO:68378271 Keywords : acetylene * ECR discharge * ions * mass spectrometry * radicals Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 2.846, year: 2016

Denitrification rate determined by nitrate disapperance is higher than determined by nitrous oxide production with acetylene blockage

DEFF Research Database (Denmark)

Yu, Kewei; Struwe, Sten; Kjøller, Annelise

2008-01-01

A mixed beech and spruce forest soil was incubated under potential denitrification assay (PDA) condition with 10% acetylene (C2H2) in the headspace of soil slurry bottles. Nitrous oxide (N2O) concentration in the headspace, as well as nitrate, nitrite and ammonium concentrations in the soil slurr...

Dictating photoreactivity through restricted bond rotations: cross-photoaddition of atropisomeric acrylimide derivatives under UV/visible-light irradiation.

Science.gov (United States)

Iyer, Akila; Jockusch, Steffen; Sivaguru, J

2014-11-13

Nonbiaryl atropisomeric acrylimides underwent facile [2 + 2] photocycloaddition leading to cross-cyclobutane adducts with very high stereospecificity (enantiomeric excess (ee): 99% and diastereomeric excess (de): 99%). The photoreactions proceeded smoothly in isotropic media for both direct and triplet sensitized irradiations. The reactions were also found to be very efficient in the solid state where the same cross-cyclobutane adduct was observed. Photophysical studies enabled us to understand the excited-state photochemistry of acrylimides. The triplet energy was found to be ∼63 kcal/mol. The reactions proceeded predominantly via a singlet excited state upon direct irradiation with very poor intersystem crossing that was ascertained by quantification of the generated singlet oxygen. The reactions progressed smoothly with triplet sensitization with UV or visible-light irradiations. Laser flash photolysis experiments established the triplet transient of atropisomeric acrylimides with a triplet lifetime at room temperature of ∼40 ns.

Selected properties of GPS and Galileo-IOV receiver intersystem biases in multi-GNSS data processing

International Nuclear Information System (INIS)

Paziewski, Jacek; Sieradzki, Rafał; Wielgosz, Paweł

2015-01-01

Two overlapping frequencies—L1/E1 and L5/E5a—in GPS and Galileo systems support the creation of mixed double-differences in a tightly combined relative positioning model. On the other hand, a tightly combined model makes it necessary to take into account receiver intersystem bias, which is the difference in receiver hardware delays. This bias is present in both carrier-phase and pseudorange observations. Earlier research showed that using a priori knowledge of earlier-calibrated ISB to correct GNSS observations has significant impact on ambiguity resolution and, therefore, precise positioning results. In previous research concerning ISB estimation conducted by the authors, small oscillations in phase ISB time series were detected. This paper investigates this effect present in the GPS–Galileo-IOV ISB time series. In particular, ISB short-term temporal stability and its dependence on the number of Galileo satellites used in the ISB estimation was examined. In this contribution we investigate the amplitude and frequency of the detected ISB time series oscillations as well as their potential source. The presented results are based on real observational data collected on a zero baseline with the use of different sets of GNSS receivers. (paper)

Selected properties of GPS and Galileo-IOV receiver intersystem biases in multi-GNSS data processing

Science.gov (United States)

Paziewski, Jacek; Sieradzki, Rafał; Wielgosz, Paweł

2015-09-01

Two overlapping frequencies—L1/E1 and L5/E5a—in GPS and Galileo systems support the creation of mixed double-differences in a tightly combined relative positioning model. On the other hand, a tightly combined model makes it necessary to take into account receiver intersystem bias, which is the difference in receiver hardware delays. This bias is present in both carrier-phase and pseudorange observations. Earlier research showed that using a priori knowledge of earlier-calibrated ISB to correct GNSS observations has significant impact on ambiguity resolution and, therefore, precise positioning results. In previous research concerning ISB estimation conducted by the authors, small oscillations in phase ISB time series were detected. This paper investigates this effect present in the GPS-Galileo-IOV ISB time series. In particular, ISB short-term temporal stability and its dependence on the number of Galileo satellites used in the ISB estimation was examined. In this contribution we investigate the amplitude and frequency of the detected ISB time series oscillations as well as their potential source. The presented results are based on real observational data collected on a zero baseline with the use of different sets of GNSS receivers.

ACETYLENE ON TITAN’S SURFACE

International Nuclear Information System (INIS)

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

2016-01-01

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 (C 2 H 2 ) net production in the atmosphere is predicted to be larger than any other compound and C 2 H 2 has been speculated to exist on the surface of Titan. C 2 H 2 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 C 2 H 2 on the surface of Titan by detecting absorption bands at 1.55 and 4.93 μ m 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 C 2 H 2 is preferentially detected in low-albedo areas, such as sand dunes and near the Huygens landing site. The specific location of the C 2 H 2 detections suggests that C 2 H 2 is mobilized by surface processes, such as surface weathering by liquids through dissolution/evaporation processes.

Al or Si decorated graphene-oxide: A promising material for capture and activation of ethylene and acetylene

Science.gov (United States)

Esrafili, Mehdi D.; Dinparast, Leila

2018-06-01

In this work, quantum chemical calculations are performed to compare adsorption behavior of ethylene and acetylene molecules over Al- or Si-decorated graphene oxide (Al/Si-GO). The corresponding adsorption energies, geometrical parameters and net charge-transfer values are calculated using the dispersion-corrected DFT calculations. The obtained large adsorption energies of the Al and Si atoms over GO suggest that both Al-GO and Si-GO are stable enough to be used as a stable substrate to capture and activate ethylene or acetylene. The results show that the adsorption of C2H4 or C2H2 on Al-GO is more favorable than over Si-GO surface, mainly due to the orbital interactions between the adsorbate and surface. Also, the DFT calculations reveal that the interaction of C2H2 with both surfaces is stronger than that of C2H4. Our findings are applicable for future theoretical and experimental studies about the interaction of hydrocarbons with light metal decorated graphene-based materials as well as heterogeneous catalysis.

Acetylene and oxygen as inhibitors of nitrous oxide production in Nitrosomonas europaea and Nitrosospira briensis: a cautionary tale

NARCIS (Netherlands)

Wrage, N.; Velthof, G.L.; Oenema, O.; Laanbroek, H.J.

2004-01-01

Autotrophic ammonia-oxidizing bacteria produce nitrous oxide (N2O) as a by-product of nitrification or as an intermediate of nitrifier denitrification. In soil incubations, acetylene (C2H2) and large partial pressures of oxygen (O2) are used to distinguish between these sources. C2H2 inhibits

Cross-Layer Design of the Inter-RAT Handover between UMTS and WiMAX

Directory of Open Access Journals (Sweden)

Bertin Philippe

2010-01-01

Full Text Available In future mobile networks, different radio access technologies will have to coexist. IEEE 802.21 MIH (Media-Independent Handover provides primitive mechanisms that ease the implementation of a seamless vertical handover (inter-RAT handover between different radio access technologies. However, it does not specify any handover execution mechanism. The first objective of this paper is to propose a novel MIHF (Media-Independent Handover Function variant, which is renamed interworking (IW sublayer. IW sublayer provides a seamless inter-RAT handover procedure between UMTS and WiMAX systems. It relies on a new intersystem retransmission mechanism with cross-layer interaction ability providing lossless handover while keeping acceptable delays. The second objective of this paper is to design a new TCP snoop agent (TCP Snoop, which interacts with the IW layer in order to mitigate BDP (Bandwidth Delay Product mismatch and to solve spurious RTO (Retransmission TimeOut problems. The cross-layer effects on the handover performance are evaluated by simulations. Our results show that cross-layer interaction between IW layer and TCP Snoop smoothes the handover procedure for TCP traffics. Additionally, this novel inter-RAT cross-layer scheme has the merit of keeping existing TCP protocol stacks unchanged.

ACETYLENE ON TITAN’S SURFACE

Energy Technology Data Exchange (ETDEWEB)

Singh, S.; McCord, T. B.; Combe, J-Ph. [Bear Fight Institute, 22 Fiddlers Rd, Winthrop, WA 98862 (United States); Rodriguez, S.; Maltagliati, L. [Laboratoire Astrophysique, Instrumentation et Modélisation (AIM), CNRS-UMR 7158, Université Paris-Diderot, CEA-SACLAY, F-91191 Gif sur Yvette (France); Cornet, T. [European Space Agency (ESA), European Space Astronomy Centre (ESAC), P.O. BOX 78, E-28691 Villanueva de la Caada, Madrid (Spain); Mouélic, S. Le [Laboratoire de Planétologie et Géodynamique de Nantes, Université de Nantes, UMR 6112 CNRS, 2 rue de la Houssiniére BP92208, Nantes Cedex 3 (France); Clark, R. N. [U.S. Geological Survey, Denver Federal Center, Denver, CO 80225 (United States); Chevrier, V. F., E-mail: ssingh@bearfightinstitute.com [Arkansas Center for Space and Planetary Science, University of Arkansas, Fayetteville, AR 72701 (United States)

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 (C{sub 2}H{sub 2}) net production in the atmosphere is predicted to be larger than any other compound and C{sub 2}H{sub 2} has been speculated to exist on the surface of Titan. C{sub 2}H{sub 2} 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 C{sub 2}H{sub 2} on the surface of Titan by detecting absorption bands at 1.55 and 4.93 μ m 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 C{sub 2}H{sub 2} is preferentially detected in low-albedo areas, such as sand dunes and near the Huygens landing site. The specific location of the C{sub 2}H{sub 2} detections suggests that C{sub 2}H{sub 2} is mobilized by surface processes, such as surface weathering by liquids through dissolution/evaporation processes.

Self-broadening coefficients and positions of acetylene around 1.533 μm studied by high-resolution diode laser absorption spectrometry

International Nuclear Information System (INIS)

Li Jingsong; Durry, Georges; Cousin, Julien; Joly, Lilian; Parvitte, Bertrand; Zeninari, Virginie

2010-01-01

The self-broadening coefficients of acetylene at room temperature have been measured for 10 lines in the P branch of the ν 1 +ν 3 (Σ u + )-0(Σ g + ) bands of 12 C 2 H 2 and 13 C 12 CH 2 near 1.533 μm, using a high resolution tunable diode laser spectrometer developed for the Martian space mission PHOBOS-Grunt. The collisional widths are obtained by fitting each recorded line with the Voigt profile as well as the Rautian profile accounting for the collisional Dicke narrowing effect. The standard Voigt model provides slightly smaller broadening coefficients than the Rautian model. Our data are thoroughly compared to the main atmospheric molecule database HITRAN and previous values in various bands of acetylene. Moreover, it is worth noting that a large number of new transitions not listed in the latest HITRAN08 were measured and identified for the first time.

Plasma Polymerization of Acetylene onto silica: and Approach to control the distribution of silica in single elastomers and immiscible blends

NARCIS (Netherlands)

Tiwari, M.; Noordermeer, Jacobus W.M.; Ooij, W.J.; Dierkes, Wilma K.

2008-01-01

Surface modification of silica by acetylene plasma polymerization is applied in order to improve the dispersion in and compatibility with single rubbers and their blends. Silica, used as a reinforcing filler for elastomers, is coated with a polyacetylene (PA) film under vacuum conditions. Water

Frequency metrology of the acetylene lines near 789 nm from lamb-dip measurements

Science.gov (United States)

Tao, Lei-Gang; Hua, Tian-Peng; Sun, Yu R.; Wang, Jin; Liu, An-Wen; Hu, Shui-Ming

2018-05-01

Lamb-dips of the ro-vibrational lines of 12C2H2 near 789 nm were recorded using cavity ring-down saturation spectroscopy. Calibrated by an optical frequency comb, frequencies of 45 acetylene lines were determined with an accuracy of 1.1 ×10-7 cm-1 (δν / ν = 8 ×10-12), which is over two orders of magnitude more accurate than previous Doppler-limited studies. An averaged shift of about 0.01 cm-1 were found by comparing the upper energies obtained in this work to those recently presented by Chubb et al. from a MARVEL analysis.

Pressure-induced amorphization and reactivity of solid dimethyl acetylene probed by in situ FTIR and Raman spectroscopy

Science.gov (United States)

Guan, Jiwen; Daljeet, Roshan; Kieran, Arielle; Song, Yang

2018-06-01

Conjugated polymers are prominent semiconductors that have unique electric conductivity and photoluminescence. Synthesis of conjugated polymers under high pressure is extremely appealing because it does not require a catalyst or solvent used in conventional chemical methods. Transformation of acetylene and many of its derivatives to conjugated polymers using high pressure has been successfully achieved, but not with dimethyl acetylene (DMA). In this work, we present a high-pressure study on solid DMA using a diamond anvil cell up to 24.4 GPa at room temperature characterized by in situ Fourier transform infrared and Raman spectroscopy. Our results show that solid DMA exists in a phase II crystal structure and is stable up to 12 GPa. Above this pressure, amorphization was initiated and the process was completed at 24.4 GPa. The expected polymeric transformation was not evident upon compression, but only observed upon decompression from a threshold compression pressure (e.g. 14.4 GPa). In situ florescence measurements suggest excimer formation via crystal defects, which induces the chemical reactions. The vibrational spectral analysis suggests the products contain the amorphous poly(DMA) and possibly additional amorphous hydrogenated carbon material.

Studies on synthesis and hydrogenation behaviour of graphitic nanofibres prepared through palladium catalyst assisted thermal cracking of acetylene

International Nuclear Information System (INIS)

Gupta, Bipin Kumar; Tiwari, R.S.; Srivastava, O.N.

2004-01-01

The nano-variants of carbon including graphitic nanofibres (GNF) have recently been considered to be exotic (light weight, high storage capacity) hydrogen storage materials. In the present paper, we report growth of aligned bundles of GNF. The length and width of cross-section of the bundles is ∼50 and ∼25 μm, respectively. The length of individual GNF is ∼50 μm and diameter ∼0.25 μm. The GNFs have been synthesized through thermal decomposition of acetylene using palladium (Pd) sheets as catalyst. This represents a new form of catalyst. The GNFs bundles grown by the present method are easier to hydrogenate. They adsorb hydrogen at a lower pressure of ∼80 atm as against ∼120 atm for the GNF grown in the earlier studies. The storage capacity obtained in the present investigation is ∼17 wt.%. Electron microscopic investigations reveal that as against the as grown GNF, the hydrogenated version embodies microstructures exhibiting fragmentation of graphitic layer bundles. The reasons for the growth of GNF in the form of aligned bundles, the ease of hydrogenation and relevance of GNF fragmentation after hydrogenation have been outlined

Studies on synthesis and hydrogenation behaviour of graphitic nanofibres prepared through palladium catalyst assisted thermal cracking of acetylene

Energy Technology Data Exchange (ETDEWEB)

Gupta, Bipin Kumar; Tiwari, R.S.; Srivastava, O.N

2004-11-03

The nano-variants of carbon including graphitic nanofibres (GNF) have recently been considered to be exotic (light weight, high storage capacity) hydrogen storage materials. In the present paper, we report growth of aligned bundles of GNF. The length and width of cross-section of the bundles is {approx}50 and {approx}25 {mu}m, respectively. The length of individual GNF is {approx}50 {mu}m and diameter {approx}0.25 {mu}m. The GNFs have been synthesized through thermal decomposition of acetylene using palladium (Pd) sheets as catalyst. This represents a new form of catalyst. The GNFs bundles grown by the present method are easier to hydrogenate. They adsorb hydrogen at a lower pressure of {approx}80 atm as against {approx}120 atm for the GNF grown in the earlier studies. The storage capacity obtained in the present investigation is {approx}17 wt.%. Electron microscopic investigations reveal that as against the as grown GNF, the hydrogenated version embodies microstructures exhibiting fragmentation of graphitic layer bundles. The reasons for the growth of GNF in the form of aligned bundles, the ease of hydrogenation and relevance of GNF fragmentation after hydrogenation have been outlined.

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

Science.gov (United States)

Lomond, Jasmine S; Tong, Anthony Z

2011-01-01

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

Selective hydrogenation of acetylene on SiO{sub 2} supported Ni-In bimetallic catalysts: Promotional effect of In

Energy Technology Data Exchange (ETDEWEB)

Chen, Yanjun; Chen, Jixiang, E-mail: jxchen@tju.edu.cn

2016-11-30

Graphical abstract: A suitable Ni/In ratio remarkably enhanced the acetylene conversion, the selectivity to ethylene and the catalyst stability. Display Omitted - Highlights: • There was a promotional effect of In on the performance of Ni/SiO{sub 2}. • A suitable Ni/In ratio was required for good performance of Ni{sub x}In/SiO{sub 2}. • Both geometrical and electronic effects of In contributed to good performance. • Ni/SiO{sub 2} deactivation is mainly owing to phase change from Ni to nickel carbide. • The carbonaceous deposit was the main reason for Ni{sub x}In/SiO{sub 2} deactivation. - Abstract: Ni/SiO{sub 2} and the bimetallic Ni{sub x}In/SiO{sub 2} 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 N{sub 2}-sorption, H{sub 2}-TPR, XRD, TEM, XPS, H{sub 2} chemisorption, C{sub 2}H{sub 4}-TPD, NH{sub 3}-TPD, FT-IR of adsorbed pyridine, and TG/DTA and Raman. A promotional effect of In on the performance of Ni/SiO{sub 2} was found, and Ni{sub x}In/SiO{sub 2} with a suitable Ni/In ratio gave much higher acetylene conversion, ethylene selectivity and catalyst stability than Ni/SiO{sub 2}. 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 C−C hydrogenolysis and the polymerizations of acetylene and the intermediate compounds. On the whole, Ni{sub 6}In/SiO{sub 2} and Ni{sub 10}In/SiO{sub 2} 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

Effect of Iminodiacetic Acid-Modified Nieuwland Catalyst on the Acetylene Dimerization Reaction

Directory of Open Access Journals (Sweden)

Yanhe You

2017-12-01

Full Text Available The iminodiacetic acid-modified Nieuwland catalyst not only improves the conversion of acetylene but also increases the selectivity of monovinylacetylene (MVA. A catalyst system containing 4.5% iminodiacetic acid exhibited excellent performance, and the yield of MVA was maintained at 32% after 24 h, producing an increase in the yield by 12% relative to the Nieuwland catalyst system. Based on a variety of characterization methods analysis of the crystal precipitated from the catalyst solution, it can be inferred that the outstanding performance and lifetime of the catalyst system was due to the presence of iminodiacetic acid, which increases the electron density of Cu+ and adjusts the acidity of the catalytic solution.

Indirect determination of uranium by atomic-absorption spectrophotometry using an air-acetylene flame

International Nuclear Information System (INIS)

Alder, J.F.; Das, B.C.

1977-01-01

An indirect method has been developed for the determination of uranium by atomic-absorption spectrophotometry using an air-acetylene flame. Use is made of the reduction of copper(II) by uranium(IV) followed by complex formation of the copper(I) ions so produced with neocuproine (2,9-dimethyl-1,10-phenanthroline) and finally the determination of copper in this complex by atomic-absorption spectrophotometry. The results show that the method can be recommended, provided that care is taken to ensure the complete reduction of uranium(VI) to uranium(IV). The sensitivity of the method is 4.9 μg of uranium and the upper limit 500 μg without dilution. (author)

Experimental investigation of timed manifold injection of acetylene in direct injection diesel engine in dual fuel mode

International Nuclear Information System (INIS)

Lakshmanan, T.; Nagarajan, G.

2010-01-01

The increase in demand and decrease in availability of fossil fuels with more stringent emission norms have led to research in finding an alternative fuel for internal combustion (IC) engines. Among the alternative fuels, gaseous fuels find a great potential. The gaseous fuel taken up for the present study is acetylene, which possesses excellent combustion properties. Preignition is the major problem with this fuel. In the present study, timed manifold injection technique is adopted to induct the fuel into the IC engine. A four-stroke, 4.4 kW diesel engine is selected, with slight modification in intake manifold for holding the gas injector, which is controlled by an electronic control unit (ECU). By using an ECU, an optimized injection timing of 10 o after top dead center and 90 o crank angle duration are arrived. At this condition, experiments were conducted for the various gas flow rates of 110 g/s, 180 g/s and 240 g/s. The performance was nearer to diesel at full load. Oxides of nitrogen, hydrocarbon and carbon monoxide emission decreased due to lean operation with marginal increase in smoke emission. To conclude, a safe operation of acetylene replacement up to 24% was possible with reduction in emission parameters.

Extraordinary Separation of Acetylene-Containing Mixtures with Microporous Metal-Organic Frameworks with Open O Donor Sites and Tunable Robustness through Control of the Helical Chain Secondary Building Units

KAUST Repository

Yao, Zizhu; Zhang, Zhangjing; Liu, Lizhen; Li, Ziyin; Zhou, Wei; Zhao, Yunfeng; Han, Yu; Chen, Banglin; Krishna, Rajamani; Xiang, Shengchang

2016-01-01

Acetylene separation is a very important but challenging industrial separation task. Here, through the solvothermal reaction of CuI and 5-triazole isophthalic acid in different solvents, two metal-organic frameworks (MOFs, FJU-21 and FJU-22) with open O donor sites and controllable robustness have been obtained for acetylene separation. They contain the same paddle-wheel {Cu2(COO2)4} nodes and metal-ligand connection modes, but with different helical chains as secondary building units (SBUs), leading to different structural robustness for the MOFs. FJU-21 and FJU-22 are the first examples in which the MOFs' robustness is controlled by adjusting the helical chain SBUs. Good robustness gives the activated FJU-22 a, which has higher surface area and gas uptakes than the flexible FJU-21 a. Importantly, FJU-22 a shows extraordinary separation of acetylene mixtures under ambient conditions. The separation capacity of FJU-22 a for 50:50 C2H2/CO2 mixtures is about twice that of the high-capacity HOF-3, and its actual separation selectivity for C2H2/C2H4 mixtures containing 1 % acetylene is the highest among reported porous materials. Based on first-principles calculations, the extraordinary separation performance of C2H2 for FJU-22 a was attributed to hydrogen-bonding interactions between the C2H2 molecules with the open O donors on the wall, which provide better recognition ability for C2H2 than other functional sites, including open metal sites and amino groups. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Extraordinary Separation of Acetylene-Containing Mixtures with Microporous Metal-Organic Frameworks with Open O Donor Sites and Tunable Robustness through Control of the Helical Chain Secondary Building Units

KAUST Repository

Yao, Zizhu

2016-03-02

Acetylene separation is a very important but challenging industrial separation task. Here, through the solvothermal reaction of CuI and 5-triazole isophthalic acid in different solvents, two metal-organic frameworks (MOFs, FJU-21 and FJU-22) with open O donor sites and controllable robustness have been obtained for acetylene separation. They contain the same paddle-wheel {Cu2(COO2)4} nodes and metal-ligand connection modes, but with different helical chains as secondary building units (SBUs), leading to different structural robustness for the MOFs. FJU-21 and FJU-22 are the first examples in which the MOFs\\' robustness is controlled by adjusting the helical chain SBUs. Good robustness gives the activated FJU-22 a, which has higher surface area and gas uptakes than the flexible FJU-21 a. Importantly, FJU-22 a shows extraordinary separation of acetylene mixtures under ambient conditions. The separation capacity of FJU-22 a for 50:50 C2H2/CO2 mixtures is about twice that of the high-capacity HOF-3, and its actual separation selectivity for C2H2/C2H4 mixtures containing 1 % acetylene is the highest among reported porous materials. Based on first-principles calculations, the extraordinary separation performance of C2H2 for FJU-22 a was attributed to hydrogen-bonding interactions between the C2H2 molecules with the open O donors on the wall, which provide better recognition ability for C2H2 than other functional sites, including open metal sites and amino groups. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Mechanism of the Zn(IIPhthalocyanines’ Photochemical Reactions Depending on the Number of Substituents and Geometry

Directory of Open Access Journals (Sweden)

Leandro Henrique Zucolotto Cocca

2016-05-01

Full Text Available In this work, the synthesis and the nonlinear absorption and population dynamics investigation of a series of zinc phthalocyanines (ZnPcs dissolved in chloroform are reported. In order to determine the relevant spectroscopic parameters, such as absorption cross-sections of singlet and triplet excited states, fluorescence relaxation times, intersystem crossing, radiative decay and internal conversion, different optical and spectroscopic techniques were used. By single pulse and pulse train Z-scan techniques, respectively, singlet and triplet excited states‘ absorption cross-section were determined at 532 nm. Furthermore, the intersystem crossing time was obtained by using both techniques combined with the fluorescence lifetime determined by time-resolved fluorescence. The radiative and internal conversion rates were determined from the fluorescence quantum yield of the samples. Such spectroscopy parameters are fundamental for selecting photosensitizers used in photodynamic therapy, as well as for many other applications.

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

Science.gov (United States)

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.

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

Energy Technology Data Exchange (ETDEWEB)

Shi, Xuetao; Li, Wen; Schlegel, H. Bernhard, E-mail: hbs@chem.wayne.edu [Department of Chemistry, Wayne State University, Detroit, Michigan 48202 (United States)

2016-08-28

The hydrogens in protonated acetylene are very mobile and can easily migrate around the C{sub 2} 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 H{sub 2}CCH{sup +} ion requires only 4 kcal/mol. The effect of circularly polarized light on the migration of hydrogens in oriented C{sub 2}H{sub 3}{sup +} 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{sup 13} W/cm{sup 2} and 3.15 × 10{sup 13} W/cm{sup 2}, respectively. These linearly and circularly polarized pulses transfer similar amounts of energy and total angular momentum to C{sub 2}H{sub 3}{sup +}. 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 C{sub 2} 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 C{sub 2} core of protonated acetylene.

Direct synthesis of solid and hollow carbon nanospheres over NaCl crystals using acetylene by chemical vapour deposition

Energy Technology Data Exchange (ETDEWEB)

Chandra Kishore, S.; Anandhakumar, S.; Sasidharan, M., E-mail: sasidharan.m@res.srmuniv.ac.in

2017-04-01

Highlights: • Hollow and solid carbon nanospheres were synthesized by CVD method. • NaCl was used as template for direct growth of carbon nanospheres. • Separation of NaCl from the mixture is made easy by dissolving in water. • The hollow carbon nanospheres exhibit high specific capacity in Li-ion batteries than the graphite anodes. - Abstract: Carbon nanospheres (CNS) with hollow and solid morphologies have been synthesised by a simple chemical vapour deposition method using acetylene as a carbon precursor. Sodium chloride (NaCl) powder as a template was used for the direct growth of CNS via facile and low-cost approach. The effect of various temperatures (500 °C, 600 °C and 700 °C) and acetylene flow rates were investigated to study the structural evolution on the carbon products. The purified CNS thus obtained was characterized by various physicochemical techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), Raman spectroscopy, and cyclicvoltametry. The synthesised hollow nanospheres were investigated as anode materials for Li-ion batteries. After 25 cycles of repeated charge/discharge cycles, the discharge and charge capacities were found to be 574 mAh/g and 570 mAh/g, respectively which are significantly higher than the commercial graphite samples.

Acetylene Flow Rate as a Crucial Parameter of Vacuum Carburizing Process of Modern Tool Steels

Directory of Open Access Journals (Sweden)

Rokicki P.

2016-12-01

Full Text Available Carburizing is one of the most popular and wide used thermo-chemical treatment methods of surface modification of tool steels. It is a process based on carbon diffusive enrichment of the surface material and is applied for elements that are supposed to present higher hardness and wear resistance sustaining core ductility. Typical elements submitted to carburizing process are gears, shafts, pins and bearing elements. In the last years, more and more popular, especially in highly advanced treatment procedures used in the aerospace industry is vacuum carburizing. It is a process based on chemical treatment of the surface in lower pressure, providing much higher uniformity of carburized layer, lower process cost and much lesser negative impact on environment to compare with conventional carburizing methods, as for example gas carburizing in Endo atmosphere. Unfortunately, aerospace industry requires much more detailed description of the phenomena linked to this process method and the literature background shows lack of tests that could confirm fulfilment of all needed requirements and to understand the process itself in much deeper meaning. In the presented paper, authors focused their research on acetylene flow impact on carburized layer characteristic. This is one of the most crucial parameters concerning homogeneity and uniformity of carburized layer properties. That is why, specific process methodology have been planned based on different acetylene flow values, and the surface layer of the steel gears have been investigated in meaning to impact on any possible change in potential properties of the final product.

Measurements of linestrengths, N2-, Ar-, He- and self-broadening coefficients of acetylene in the ν4+ν5 combination band using a cw quantum cascade laser

KAUST Repository

Sajid, Muhammad Bilal

2014-11-01

Linestrengths, N2-, Ar-, He- and self-broadening coefficients of acetylene have been measured at 296K in the P branch of the ν4+ν5 combination band for 25 rotational transitions. The effect of gas temperature is studied over 296-683K for five transitions to allow the determination of the temperature dependent exponent n for N2- and Ar-broadening coefficients. These measurements were performed using a continuous-wave quantum cascade laser (cw-QCL) operating over 1253-1310cm-1. Spectroscopic parameters were obtained by fitting absorption spectra using Voigt, Galatry and Rautian profiles. Linestrength and broadening results are compared with previous studies available in literature for the ν4+ν5 combination band and other vibrational bands of acetylene. © 2014 Elsevier Ltd.

VISIBLE LIGHT INDUCED PHOTOCATALYTIC DEGRADATION OF ...

African Journals Online (AJOL)

a

Solar Energy and Photochemistry Laboratory, Department of Chemistry, University College ..... singlet state which then undergo intersystem crossing to their triplet state. ... are removed by the dissolved molecular oxygen to produce superoxide.

Substitution of Acetylene Black by Using Modified Flake Graphite Applied in Activated Carbon Supercapacitors

Directory of Open Access Journals (Sweden)

Zhao Peng

2018-01-01

Full Text Available Flake graphite was mechanically modified at different times in N-methyl pyrrolidone under normal pressure. The results of the scanning electron microscopy, X-ray diffraction, and transmission electron microscopy suggested that the structure of the flake graphite was modified. The crystallinity of the flake graphite, and many defects were introduced into the material. The evaluation of capacitor performance by cyclic voltammetry, galvanostatic charge/discharge tests, and electrochemical impedance spectroscopy was also performed. Results showed that the electrochemical performance of flake graphite was strongly enhanced, particularly when it was exfoliated for 6 h. Moreover, the electrochemical capacitive properties of activated carbon were obviously enhanced through the substitution of acetylene black by flake graphite modified for 6 h.

ASD-1000: High-resolution, high-temperature acetylene spectroscopic databank

Science.gov (United States)

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

2017-11-01

We present a high-resolution, high-temperature version of the Acetylene Spectroscopic Databank called ASD-1000. The databank contains the line parameters (position, intensity, Einstein coefficient for spontaneous emission, term value of the lower states, self- and air-broadening coefficients, temperature dependence exponents of the self- and air-broadening coefficients) of the principal isotopologue of C2H2. The reference temperature for line intensity is 296 K and the intensity cutoff is 10-27 cm-1/(molecule cm-2) at 1000 K. The databank has 33,890,981 entries and covers the 3-10,000 cm-1 spectral range. The databank is based on the global modeling of the line positions and intensities performed within the framework of the method of effective operators. The parameters of the effective Hamiltonian and the effective dipole moment operator have been fitted to the observed values of the line positions and intensities collected from the literature. The broadening coefficients as well as their temperature dependence exponents were calculated using the empirical equations. The databank is useful for studying high-temperature radiative properties of C2H2. ASD-1000 is freely accessible via the Internet site of V.E. Zuev Institute of Atmospheric Optics SB RAS ftp://ftp.iao.ru/pub/ASD1000/.

ACTIVATION OF ACETYLENE BY COORDINATION TO BIS-TRIPHENYLPHOSPHINE COMPLEX OF Pt(0: DFT STUDY

Directory of Open Access Journals (Sweden)

N. N. Gorinchoy

2009-06-01

Full Text Available The present work is devoted to the theoretical study of the activation of the acetylene molecule coordinated in the [Pt(PPh32C2H2] complex. By means of DFT calculations it is shown that the geometrical and electronic characteristics of the C2H2 are essentially changed due to its coordination. The subsequent detailed analysis of the molecular orbitals (MO of the active valence zone of this complex allows one to make important conclusion that this activation is being realized mainly due to the orbital back donation of 5d-electronic density from one of the occupied MOs of the complex [Pt(PPh32] to the unoccupied antibonding π*-MO of C2H2.

Cycloplatinated(II) complexes containing bridging bis(diphenylphosphino)acetylene: Photophysical study

Energy Technology Data Exchange (ETDEWEB)

Jamshidi, Mahboubeh [Department of Chemistry, College of Sciences, Shiraz University, Shiraz 71467-13565 (Iran, Islamic Republic of); Nabavizadeh, S. Masoud, E-mail: nabavizadeh@shirazu.ac.ir [Department of Chemistry, College of Sciences, Shiraz University, Shiraz 71467-13565 (Iran, Islamic Republic of); Sepehrpour, Hajar [Department of Chemistry, College of Sciences, Shiraz University, Shiraz 71467-13565 (Iran, Islamic Republic of); Hosseini, Fatemeh Niroomand [Department of Chemistry, Shiraz Branch, Islamic Azad University, Shiraz 71993-37635 (Iran, Islamic Republic of); Kia, Reza [Department of Chemistry, Sharif University of Technology, Tehran 11155-3516 (Iran, Islamic Republic of); Rashidi, Mehdi, E-mail: rashidi@chem.susc.ac.ir [Department of Chemistry, College of Sciences, Shiraz University, Shiraz 71467-13565 (Iran, Islamic Republic of)

2016-11-15

Reaction of the known cycloplatinated (II) complexes [PtAr(C^N)(SMe{sub 2})], in which Ar=p–MeC{sub 6}H{sub 4} or p–MeOC{sub 6}H{sub 4} and C^N= 2-phenylpyridinate (ppy) or benzo[h]quinolinate (bhq), with 0.5 equivalent of the bidentate phosphine ligand 1,1′–bis(diphenylphosphino)acetylene, dppac, in acetone at room temperature gave the symmetrical binuclear cycloplatinated(II) complexes [Pt{sub 2}Ar{sub 2}(C^N){sub 2}(μ–dppac)], 1–4, in which dppac acts as a bridging bidentate ligand. All the complexes were fully characterized using multinuclear ({sup 1}H, {sup 31}P and {sup 195}Pt) NMR spectroscopy and the complex [Pt{sub 2}(p–MeC{sub 6}H{sub 4}){sub 2}(ppy){sub 2}(μ–dppac)], 1, was further identified by single crystal X-ray structure determination. Additional information about the geometries and electronic spectra of these cycloplatinated (II) complexes are discussed. Effects of aryl and C^N ligands on the luminescent properties of the complexes were also investigated that are complying well with the related DFT/TD-DFT calculations.

Near-Unity Quantum Yields for Intersystem Crossing and Singlet Oxygen Generation in Polymethine-like Molecules: Design and Experimental Realization

Science.gov (United States)

2010-01-01

Florida, Cocoa , Florida 32922, ^Institute of Organic Chemistry, National Academy of Sciences, Kiev 03094, Ukraine, and #Physics and Optical Engineering...the time evolution of the S-S and T-Tabsorption and their cross sections (σSS and σTT). S-SandT-TESAspectra for SD-S7508are shown inFigure3a. SD-O

Large-scale synthesis of high-purity well-aligned carbon nanotubes using pyrolysis of iron(II) phthalocyanine and acetylene

Science.gov (United States)

Liu, B. C.; Lee, T. J.; Lee, S. H.; Park, C. Y.; Lee, C. J.

2003-08-01

Well-aligned carbon nanotubes (CNTs) with high purity have been produced by pyrolysis of iron(II) phthalocyanine and acetylene at 800 °C. The synthesized CNTs have a length of 75 μm and diameters ranging from 20 to 60 nm. The CNTs have a bamboo-like structure and exhibit good crystallinity of graphite sheets. The growth rate of the CNTs was rapidly increased with adding C 2H 2. Our results demonstrate that the proposed growth method is suitable to large-scale synthesis of high-purity well-aligned CNTs on various substrates.

Acetylene black paste electrode modified with a molecularly imprinted chitosan film for the detection of bisphenol A

International Nuclear Information System (INIS)

Deng, Peihong; Xu, Zhifeng; Li, Junhua; Kuang, Yunfei

2013-01-01

We report on a voltammetric sensor for bisphenol A (BPA) that is based on an acetylene-black paste electrode modified with a chitosan film molecularly imprinted for BPA. The sensor responds linearly to BPA in the 80 nM to 10 μM concentration range, and the detection limit is 60 nM (at an S/N of 3). The use of a molecular imprint provides an efficient way for eliminating interferences from potentially interfering substances. The high sensitivity, selectivity and stability of the sensor demonstrate its practical application for the determination of BPA in plastic samples. (author)

Rate Constants and H-Atom Product Yields for the Reactions of O(1D) Atoms with Ethane and Acetylene from 50 to 296 K.

Science.gov (United States)

Nunez-Reyes, Dianailys; Hickson, Kevin M

2018-05-01

The gas phase reactions of atomic oxygen in its first excited state with ethane and acetylene have been investigated in a continuous supersonic flow reactor over the temperature range 50 K to 296 K. O(1D) atoms were produced by pulsed laser photolysis of ozone at 266 nm. Two different types of experiments, kinetics measurements and H-atom product yield determinations, were performed by detecting O(1D) atoms and H(2S) atoms respectively by vacuum ultraviolet laser induced fluorescence. The measured rate constants are in agreement with previous work at room temperature and little or no temperature dependence was observed as the temperature is decreased to 50 K. H-atoms yields were found to be independent of temperature for the reaction of O(1D) with ethane. These product yields are discussed in the context of earlier dynamics measurements at higher temperature. Due to the influence of secondary reactions, no H-atom yields could be obtained for the reaction of O(1D) with acetylene.

Transition probabilities for the 3s2 3p(2P0)-3s3p2(4P) intersystem lines of Si II

Science.gov (United States)

Calamai, Anthony G.; Smith, Peter L.; Bergeson, S. D.

1993-01-01

Intensity ratios of lines of the spin-changing 'intersystem' multiplet of S II (4P yields 2P0) at 234 nm have been used to determine electron densities and temperatures in a variety of astrophysical environments. However, the accuracy of these diagnostic calculations have been limited by uncertainties associated with the available atomic data. We report the first laboratory measurement, using an ion-trapping technique, of the radiative lifetimes of the three metastable levels of the 3s3p2 4P term of Si II. Our results are 104 +/- 16, 406 +/- 33, and 811 +/- 77 micro-s for lifetimes of the J = 1/2, 5/2, and 3/2 levels, respectively. A-values were derived from our lifetimes by use of measured branching fractions. Our A-values, which differ from calculated values by 30 percent or more, should give better agreement between modeled and observed Si II line ratios.

Simultaneous detection of Ponceat 4R and tartrazine in food using adsorptive stripping voltammetry on an acetylene black nanoparticle-modified electrode.

Science.gov (United States)

Yang, Xiaofeng; Qin, Haibin; Gao, Miaomiao; Zhang, Huajie

2011-12-01

Ponceau 4R and tartrazine have been widely used in foodstuffs. However, they are pathogenic if they are excessively consumed. Therefore, the detection of Ponceat 4R and tartrazine is quite important. A sensitive and rapid electrochemical method was developed for the simultaneous detection of Ponceat 4R and tartrazine using anodic adsorptive stripping voltammetry and based on the strong enhancement effect of acetylene black nanoparticle. For Ponceat 4R, the linear range was from 0.05 to 4 mg kg(-1) , and the limit of detection was 0.03 mg kg(-1) . For tartrazine, the linear range was from 0.15 to 18 mg kg(-1) , and the limit of detection was 0.1 mg kg(-1) . The relative standard deviation was 3.8% and 4.7% for 10 successive measurements of 1 mg kg(-1) Ponceau 4R and tartrazine. The method was used to determine Ponceat 4R and tartrazine in soft drinks, and recovery was in the range of 92.4-104.8%. At the acetylene black nanoparticle-modified electrode, the oxidation current signal of Ponceau 4R and tartrazine greatly increase. This new method is sensitive, rapid, simple and feasible. Copyright © 2011 Society of Chemical Industry.

Stable Carbon Isotope Fractionation during Bacterial Acetylene Fermentation: Potential for Life Detection in Hydrocarbon-Rich Volatiles of Icy Planet(oid)s.

Science.gov (United States)

Miller, Laurence G; Baesman, Shaun M; Oremland, Ronald S

2015-11-01

We report the first study of stable carbon isotope fractionation during microbial fermentation of acetylene (C2H2) in sediments, sediment enrichments, and bacterial cultures. Kinetic isotope effects (KIEs) averaged 3.7 ± 0.5‰ for slurries prepared with sediment collected at an intertidal mudflat in San Francisco Bay and 2.7 ± 0.2‰ for a pure culture of Pelobacter sp. isolated from these sediments. A similar KIE of 1.8 ± 0.7‰ was obtained for methanogenic enrichments derived from sediment collected at freshwater Searsville Lake, California. However, C2H2 uptake by a highly enriched mixed culture (strain SV7) obtained from Searsville Lake sediments resulted in a larger KIE of 9.0 ± 0.7‰. These are modest KIEs when compared with fractionation observed during oxidation of C1 compounds such as methane and methyl halides but are comparable to results obtained with other C2 compounds. These observations may be useful in distinguishing biologically active processes operating at distant locales in the Solar System where C2H2 is present. These locales include the surface of Saturn's largest moon Titan and the vaporous water- and hydrocarbon-rich jets emanating from Enceladus. Acetylene-Fermentation-Isotope fractionation-Enceladus-Life detection.

Hydrogen Abstraction Acetylene Addition and Diels-Alder Mechanisms of PAH Formation:  A Detailed Study Using First Principles Calculations.

Science.gov (United States)

Kislov, V V; Islamova, N I; Kolker, A M; Lin, S H; Mebel, A M

2005-09-01

Extensive ab initio Gaussian-3-type calculations of potential energy surfaces (PES), which are expected to be accurate within 1-2 kcal/mol, combined with statistical theory calculations of reaction rate constants have been applied to study various possible pathways in the hydrogen abstraction acetylene addition (HACA) mechanism of naphthalene and acenaphthalene formation as well as Diels-Alder pathways to acenaphthalene, phenanthrene, and pyrene. The barrier heights; reaction energies; and molecular parameters of the reactants, products, intermediates, and transition states have been generated for all types of reactions involved in the HACA and Diels-Alder mechanisms, including H abstraction from various aromatic intermediates, acetylene addition to radical sites, ring closures leading to the formation of additional aromatic rings, elimination of hydrogen atoms, H disproportionation, C2H2 cycloaddition, and H2 loss. The reactions participating in various HACA sequences (e.g., Frenklach's, alternative Frenklach's, and Bittner and Howard's routes) are demonstrated to have relatively low barriers and high rate constants under combustion conditions. A comparison of the significance of different HACA mechanisms in PAH growth can be made in the future using PES and molecular parameters obtained in the present work. The results show that the Diels-Alder mechanism cannot compete with the HACA pathways even at high combustion temperatures, because of high barriers and consequently low reaction rate constants. The calculated energetic parameters and rate constants have been compared with experimental and theoretical data available in the literature.

Nuclear magnetic resonance study of the structure of simple molecules adsorbed on metal surfaces: acetylene on platinum

International Nuclear Information System (INIS)

Wang, P.K.

1984-01-01

We have used NMR to determine the structure of acetylene (HC - CH) adsorbed at room temperature on small platinum particles by studying the 13 C- 13 C, 13 C- 1 H, and 1 H- 1 H dipolar interactions among the nuclei in the adsorbed molecules. We find a model of 77% CCH 2 and 23% HCCH to be the only one consistent with all of our data. The C-C bond length of the majority species, CCH 2 , is determined as 1.44 +- 0.02 A, midway between a single and double bond, suggesting that both carbon atoms bond to the surface. 36 references, 29 figures, 1 table

Measurements of linestrengths, N2-, Ar-, He- and self-broadening coefficients of acetylene in the ν4+ν5 combination band using a cw quantum cascade laser

KAUST Repository

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

2014-01-01

Linestrengths, N2-, Ar-, He- and self-broadening coefficients of acetylene have been measured at 296K in the P branch of the ν4+ν5 combination band for 25 rotational transitions. The effect of gas temperature is studied over 296-683K for five

Synthesis of carbon nanotubes from acetylene on the FeCoMgO catalytic system obtained by ball milling

Energy Technology Data Exchange (ETDEWEB)

Biris, A R; Simon, S; Lupu, D; Misan, I [National Institute for Research and Development of Isotopic and Molecular Technologies, 65-103 Donath, 400293 Cluj-Napoca (Romania); Biris, A S; Dervishi, E; Li, Z; Watanabe, F [UALR Nanotechnology Center, University of Arkansas, 2801 S University Ave, Little Rock, AR 72204 (United States); Lucaci, M, E-mail: alexandru.biris@itim-cj.r [National Institute for Research and Development in Electrical Engineering ICPE-CA 313 Splaiul Unirii, 030138 Bucharest (Romania)

2009-08-01

Highly crystalline multi wall carbon nanotubes have been synthesized by RF-CVD from acetylene at 850{sup 0}C over a Fe:Co:MgO catalyst. The catalytic system was obtained by mixing for 100 h Fe, Co and MgO powders in a ball milling device under petroleum ether environment, followed by oxidation in air at 500{sup 0}C for 24 h. Most of the nanotubes had external diameters in order of dozens of nm and lengths of microns, resulting in an aspect ration of over 1000. Their external to internal diameter ratio varied between 2.5 and 3.

Picosecond phase conjugation in two-photon absorption in poly-di-acetylenes

International Nuclear Information System (INIS)

Nunzi, Dominique Jean-Michel

1990-01-01

Poly-di-acetylenes exhibit a large two-photon absorption at 1064 nm wavelength. Its different effects on phase-conjugate nonlinearity are described in the framework of picosecond experiments. In solutions, gels, and films (optically thin media), third-order susceptibility appears as an increasing intensity dependent function. Phase measurements by nonlinear interferometry with the substrate or with the solvent are compared with predictions of a resonantly driven three level system. Phase-conjugate response exhibits a multi-exponential decay. Polarization symmetries analysis shows a one-dimensional effect. Study under strong static electric field action reveals that we face charged species bound to photoconductive polymer chains. In PTS single crystals (optically thick media), response saturates and cancels at high light intensity. This is well accounted for by propagation equations solved in large two-photon absorption conditions. The effect is exploited in a phase conjugation experiment under external optical pump excitation. We thus demonstrate that enhanced nonlinearity is a two-photon absorption relayed and amplified by mid-gap absorbing species which have been created by this two-photon absorption. We formally face a four-photon absorption described by a positive imaginary seventh-order non-linearity. (author) [fr

Photoinduced Dynamics of Neutral, Cationic, and Anionic Species

DEFF Research Database (Denmark)

Stephansen, Anne Boutrup

. The investigations have primarily employed femtosecond time-resolved photoionization or photodetachment techniques. Intersystem crossing (ISC) in neutral organic species is conventionally assumed to be slow due to the spin-forbidden nature of the process; this assumption has been challenged during the past decade...

Time-dependent nonequilibrium soft x-ray response during a spin crossover

Science.gov (United States)

van Veenendaal, Michel

2018-03-01

A theoretical framework is developed for better understanding the time-dependent soft-x-ray response of dissipative quantum many-body systems. It is shown how x-ray absorption and resonant inelastic x-ray scattering (RIXS) at transition-metal L edges can provide insight into ultrafast intersystem crossings of importance for energy conversion, ultrafast magnetism, and catalysis. The photoinduced doublet-to-quartet spin crossover on cobalt in Fe-Co Prussian blue analogs is used as a model system to demonstrate how the x-ray response is affected by the nonequilibrium dynamics on a femtosecond time scale. Changes in local spin and symmetry and the underlying mechanism are reflected in strong broadenings, a collapse of clear selection rules during the intersystem crossing, fluctuations in the isotropic branching ratio in x-ray absorption, crystal-field collapse and/or oscillations, and time-dependent anti-Stokes processes in RIXS.

Triplet excited state properties in variable gap π-conjugated donor–acceptor–donor chromophores

KAUST Repository

Cekli, Seda; Winkel, Russell W.; Alarousu, Erkki; Mohammed, Omar F.; Schanze, Kirk S.

2016-01-01

A series of variable band-gap donor–acceptor–donor (DAD) chromophores capped with platinum(II) acetylide units has been synthesized and fully characterized by electrochemical and photophysical methods, with particular emphasis placed on probing triplet excited state properties. A counter-intuitive trend of increasing fluorescence quantum efficiency and lifetime with decreasing excited state energy (optical gap) is observed across the series of DAD chromophores. Careful study of the excited state dynamics, including triplet yields (as inferred from singlet oxygen sensitization), reveals that the underlying origin of the unusual trend in the fluorescence parameters is that the singlet–triplet intersystem crossing rate and yield decrease with decreasing optical gap. It is concluded that the rate of intersystem crossing decreases as the LUMO is increasingly localized on the acceptor unit in the DAD chromophore, and this result is interpreted as arising because the extent of spin–orbit coupling induced by the platinum heavy metal centers decreases as the LUMO is more localized on the acceptor. In addition to the trend in intersystem crossing, the results show that the triplet decay rates follow the Energy Gap Law correlation over a 1.8 eV range of triplet energy and 1000-fold range of triplet decay rates. Finally, femtosecond transient absorption studies for the DAD chromophores reveals a strong absorption in the near-infrared region which is attributed to the singlet excited state. This spectral band appears to be general for DAD chromophores, and may be a signature of the charge transfer (CT) singlet excited state.

Triplet excited state properties in variable gap π-conjugated donor–acceptor–donor chromophores

KAUST Repository

Cekli, Seda

2016-02-12

A series of variable band-gap donor–acceptor–donor (DAD) chromophores capped with platinum(II) acetylide units has been synthesized and fully characterized by electrochemical and photophysical methods, with particular emphasis placed on probing triplet excited state properties. A counter-intuitive trend of increasing fluorescence quantum efficiency and lifetime with decreasing excited state energy (optical gap) is observed across the series of DAD chromophores. Careful study of the excited state dynamics, including triplet yields (as inferred from singlet oxygen sensitization), reveals that the underlying origin of the unusual trend in the fluorescence parameters is that the singlet–triplet intersystem crossing rate and yield decrease with decreasing optical gap. It is concluded that the rate of intersystem crossing decreases as the LUMO is increasingly localized on the acceptor unit in the DAD chromophore, and this result is interpreted as arising because the extent of spin–orbit coupling induced by the platinum heavy metal centers decreases as the LUMO is more localized on the acceptor. In addition to the trend in intersystem crossing, the results show that the triplet decay rates follow the Energy Gap Law correlation over a 1.8 eV range of triplet energy and 1000-fold range of triplet decay rates. Finally, femtosecond transient absorption studies for the DAD chromophores reveals a strong absorption in the near-infrared region which is attributed to the singlet excited state. This spectral band appears to be general for DAD chromophores, and may be a signature of the charge transfer (CT) singlet excited state.

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

DEFF Research Database (Denmark)

Høgstedt, Lasse; Dam, Jeppe Seidelin; Sahlberg, Anna-Lena

2014-01-01

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

Disposition and biotransformation of the acetylenic retinoid tazarotene in humans.

Science.gov (United States)

Attar, Mayssa; Yu, Dale; Ni, Jinsong; Yu, Zhiling; Ling, Kah-Hiing John; Tang-Liu, Diane D-S

2005-10-01

Oral tazarotene, an acetylenic retinoid, is in clinical development for the treatment of psoriasis. The disposition and biotransformation of tazarotene were investigated in six healthy male volunteers, following a single oral administration of a 6 mg (100 microCi) dose of [14C]tazarotene, in a gelatin capsule. Blood levels of radioactivity peaked 2 h postdose and then rapidly declined. Total recovery of radioactivity was 89.2+/-8.0% of the administered dose, with 26.1+/-4.2% in urine and 63.0+/-7.0% in feces, within 7 days of dosing. Only tazarotenic acid, the principle active metabolite formed via esterase hydrolysis of tazarotene, was detected in blood. One major urinary oxidative metabolite, tazarotenic acid sulfoxide, accounted for 19.2+/-3.0% of the dose. The majority of radioactivity recovered in the feces was attributed to tazarotenic acid representing 46.9+/-9.9% of the dose and only 5.82+/-3.84% of dose was excreted as unchanged tazarotene. Thus following oral administration, tazarotene was rapidly absorbed and underwent extensive hydrolysis to tazarotenic acid, the major circulating species in the blood that was then excreted unchanged in feces. A smaller fraction of tazarotenic acid was further metabolized to an inactive sulfoxide that was excreted in the urine. Copyright (c) 2005 Wiley-Liss, Inc. and the American Pharmacists Association

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

International Nuclear Information System (INIS)

Cheng, Peifu; Hu, Yun Hang

2016-01-01

Graphical abstract: It was demonstrated that Dubinin-Astakhov equation can be exploited as a general isotherm model for C2H2 adsorption on metal-organic frameworks (MOFs), including MOF-5, ZIF-8, HKUST-1, and MIL-53. - Highlights: • Dubinin-Astakhov equation is demonstrated to be a general model for C_2H_2 adsorption on metal-organic frameworks (MOFs). • Surface areas obtained with Dubinin-Astakhov equation from C_2H_2 adsorption on MOFs are consistent with BET surface areas from N_2 adsorption. • C_2H_2 on MOF-5, ZIF-8, and MIL-53 is a physical adsorption, whereas its adsorption on HKUST-1 is due to a chemical bonding. - Abstract: Acetylene (C_2H_2) is explosive at a pressure above 29 psi, causing a safety issue for its storage and applications. C_2H_2 adsorption on metal-organic frameworks (MOFs) has been explored to solve the issue. However, a suitable isotherm equation for C_2H_2 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 C_2H_2 adsorption on MOF-5, ZIF-8, HKUST-1, and MIL-53. In contrast, commonly used Langmuir and BET models exhibited their inapplicability for C_2H_2 adsorption on those MOFs.

A New Acetylenic Compound and Other Bioactive Metabolites from a Shark Gill-derived Penicillium Strain

Directory of Open Access Journals (Sweden)

Yi Zhang

2017-01-01

Full Text Available Nine chiral compounds (1−9 were isolated from the static fermentation culture of a shark gill-derived fungus Penicillium polonicum AP2T1. These compounds include a new acetylenic aromatic ether (1 , (--WA , four alkaloids ( a urantiomide C ( 2 , fructigenine A (3, cyclopenin (4 and cyclopenol (5 and four oxygenated compounds ((R-penipratynolene (6, (3S,4S-3,4-dihydro-3,4,8-trihydroxyl-naphthalenone (7, verrucosidin (8 and norverrucosidin (9. Their structures were elucidated by MS, NMR , optical rotation and circular dichroism (CD . In antimicrobial tests , compounds 1–4, 6 and 8–9 showed weak antibacterial activity against Staphylococcus aureus, Bacillus subtilis, and/or Escherichia coli.Compounds 3, 8 and 9 also exhibited moderate toxicity against Artemia salina larva , and showed cytotoxicity against human colon cancer cell line HCT116.

Quenching mechanism of exciplex fluorescence by inverted micelles

International Nuclear Information System (INIS)

Sato, Chika; Kikuchi, Koichi

1992-01-01

Using an emission-absorption laser photolysis method, the quenching mechanism of the pyrene-N,N-dimethylaniline exciplex fluorscence by inverted micelles is studied. The rate of enhanced intersystem crossing depends upon water pool size and is reduced by external magnetic fields. 15 refs., 3 figs., 2 tabs

Time-resolved photoelectron imaging using a femtosecond UV laser and a VUV free-electron laser

OpenAIRE

Liu, S. Y.; Ogi, Yoshihiro; Fuji, Takao; Nishizawa, Kiyoshi; Horio, Takuya; Mizuno, Tomoya; Kohguchi, Hiroshi; Nagasono, Mitsuru; Togashi, Tadashi; Tono, Kensuke; Yabashi, Makina; Senba, Yasunori; Ohashi, Haruhiko; Kimura, Hiroaki; Ishikawa, Tetsuya

2010-01-01

A time-resolved photoelectron imaging using a femtosecond ultraviolet (UV) laser and a vacuum UV freeelectron laser is presented. Ultrafast internal conversion and intersystem crossing in pyrazine in a supersonic molecular beam were clearly observed in the time profiles of photoioinzation intensity and time-dependent photoelectron images.

Dissociation of Methanol and Acetylene by slow Highly Charged Ion Collision

International Nuclear Information System (INIS)

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

2007-01-01

We report here the results of dissociation of multiple charged methanol and acetylene molecules in collision with 1.2 MeV Ar 8+ projectiles. We observed a wide range of dissociation products from the TOF spectrum starting from undissociated molecular ions, fragments losing an hydrogen atom due to breakage of C-H and/or O-H bonds, to complete rupture of C-C and C-O skeletons for the respective molecules. From the coincidence map of the fragments, we could separate out the different dissociation channels between carbon and oxygen ionic fragments as well as complete two-body dissociation events. The most striking feature in the breakup of CH 3 OH is the formation of H 2 + and H 3 + due to intramolecular rearrangement of the C-H bonds within the methyl group. In dissociative ionization studies of C 2 H 2 , we observed a diatom-like behaviour of the C-C charged complex as evidenced from the measured slopes of the coincidence islands for carbon atomic charged fragments and theoretical values determined from the charge and momentum distribution of the correlated particles. The shape and orientation of the islands give further information about the momentum balance in the fragmentation process in two-body dissociation

Pressure-Induced Polymerization of Acetylene: Structure-Directed Stereoselectivity and a Possible Route to Graphane.

Science.gov (United States)

Sun, Jiangman; Dong, Xiao; Wang, Yajie; Li, Kuo; Zheng, Haiyan; Wang, Lijuan; Cody, George D; Tulk, Christopher A; Molaison, Jamie J; Lin, Xiaohuan; Meng, Yufei; Jin, Changqing; Mao, Ho-Kwang

2017-06-01

Geometric isomerism in polyacetylene is a basic concept in chemistry textbooks. Polymerization to cis-isomer is kinetically preferred at low temperature, not only in the classic catalytic reaction in solution but also, unexpectedly, in the crystalline phase when it is driven by external pressure without a catalyst. Until now, no perfect reaction route has been proposed for this pressure-induced polymerization. Using in situ neutron diffraction and meta-dynamic simulation, we discovered that under high pressure, acetylene molecules react along a specific crystallographic direction that is perpendicular to those previously proposed. Following this route produces a pure cis-isomer and more surprisingly, predicts that graphane is the final product. Experimentally, polycyclic polymers with a layered structure were identified in the recovered product by solid-state nuclear magnetic resonance and neutron pair distribution functions, which indicates the possibility of synthesizing graphane under high pressure. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

The origin of efficient triplet state population in sulfur-substituted nucleobases

Science.gov (United States)

Mai, Sebastian; Pollum, Marvin; Martínez-Fernández, Lara; Dunn, Nicholas; Marquetand, Philipp; Corral, Inés; Crespo-Hernández, Carlos E.; González, Leticia

2016-10-01

Elucidating the photophysical mechanisms in sulfur-substituted nucleobases (thiobases) is essential for designing prospective drugs for photo- and chemotherapeutic applications. Although it has long been established that the phototherapeutic activity of thiobases is intimately linked to efficient intersystem crossing into reactive triplet states, the molecular factors underlying this efficiency are poorly understood. Herein we combine femtosecond transient absorption experiments with quantum chemistry and nonadiabatic dynamics simulations to investigate 2-thiocytosine as a necessary step to unravel the electronic and structural elements that lead to ultrafast and near-unity triplet-state population in thiobases in general. We show that different parts of the potential energy surfaces are stabilized to different extents via thionation, quenching the intrinsic photostability of canonical DNA and RNA nucleobases. These findings satisfactorily explain why thiobases exhibit the fastest intersystem crossing lifetimes measured to date among bio-organic molecules and have near-unity triplet yields, whereas the triplet yields of canonical nucleobases are nearly zero.

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

Science.gov (United States)

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

2003-01-01

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

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

International Nuclear Information System (INIS)

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

2003-01-01

Plasma immersion ion implantation and deposition (PIII-D) offers a non-line-of-sight fabrication method for various types of thin films on steels to improve the surface properties. In this work, titanium films were first deposited on 9Cr18 (AISI440) stainless bearing steel by metal plasma immersion ion implantation and deposition (MePIII-D) using a titanium vacuum arc plasma source. Afterwards, carbon implantation and carbon film deposition were performed by acetylene (C 2 H 2 ) plasma immersion ion implantation. Multiple-layered structures with superior properties were produced by conducting Ti MePIII-D + C 2 H 2 PIII successively. The composition and structure of the films were investigated employing Auger electron spectroscopy and Raman spectroscopy. It is shown that the mixing for Ti and C atoms is much better when the target bias is higher during Ti MePIII-D. A top diamond-like carbon layer and a titanium oxycarbide layer are formed on the 9Cr18 steel surface. The wear test results indicate that this dual PIII-D method can significantly enhance the wear properties and decrease the surface friction coefficient of 9Cr18 steel

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

Energy Technology Data Exchange (ETDEWEB)

Cheng, Peifu; Hu, Yun Hang, E-mail: yunhangh@mtu.edu

2016-07-30

Graphical abstract: It was demonstrated that Dubinin-Astakhov equation can be exploited as a general isotherm model for C2H2 adsorption on metal-organic frameworks (MOFs), including MOF-5, ZIF-8, HKUST-1, and MIL-53. - Highlights: • Dubinin-Astakhov equation is demonstrated to be a general model for C{sub 2}H{sub 2} adsorption on metal-organic frameworks (MOFs). • Surface areas obtained with Dubinin-Astakhov equation from C{sub 2}H{sub 2} adsorption on MOFs are consistent with BET surface areas from N{sub 2} adsorption. • C{sub 2}H{sub 2} on MOF-5, ZIF-8, and MIL-53 is a physical adsorption, whereas its adsorption on HKUST-1 is due to a chemical bonding. - Abstract: Acetylene (C{sub 2}H{sub 2}) is explosive at a pressure above 29 psi, causing a safety issue for its storage and applications. C{sub 2}H{sub 2} adsorption on metal-organic frameworks (MOFs) has been explored to solve the issue. However, a suitable isotherm equation for C{sub 2}H{sub 2} 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 C{sub 2}H{sub 2} adsorption on MOF-5, ZIF-8, HKUST-1, and MIL-53. In contrast, commonly used Langmuir and BET models exhibited their inapplicability for C{sub 2}H{sub 2} adsorption on those MOFs.

Metastable argon atom density in complex argon/acetylene plasmas determined by means of optical absorption and emission spectroscopy

International Nuclear Information System (INIS)

Sushkov, Vladimir; Herrendorf, Ann-Pierra; Hippler, Rainer

2016-01-01

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(1s 5 ) 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(1s 3 ) 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. (paper)

Transition dipole-moment of the ν1 +ν3 band of acetylene measured with dual-comb Fourier-transform spectroscopy

Science.gov (United States)

Okubo, Sho; Iwakuni, Kana; Yamada, Koichi M. T.; Inaba, Hajime; Onae, Atsushi; Hong, Feng-Lei; Sasada, Hiroyuki

2017-11-01

The ν1 +ν3 vibration band of acetylene (C2H2) in the near infrared region was recorded with a dual-comb Fourier-transform spectrometer. We observed 56 transitions from P (26) to R (29) at six different column densities. The integral line intensity was determined for each recorded absorption line by fitting the line profile to Lambert-Beer's law with a Voigt function. Thanks to the outstanding capability of dual-comb spectroscopy to cover a broad spectrum in a relatively short time with high resolution and high frequency precision, we determined the reliable line strength for each ro-vibrational transition as well as the transition dipole moment for this band.

New catalysts for selective hydrogenation of diene and acetylene hydrocarbons into olefins

Energy Technology Data Exchange (ETDEWEB)

Frolov, V.M.; Parenago, O.P.; Shuikina, L.P.

1978-12-01

New catalysts for selective hydrogenation of diene and acetylene hydrocarbons into olefins were obtained by reacting aqueous palladium, rhodium, or nickel chloride (0.005-0.05 mole/l.) at 50/sup 0/C, in an argon atmosphere with chelating nitrogen compounds, i.e., o-phenanthroline, ..cap alpha..,..cap alpha..'-dipyridyl, sodium ethylenediaminetetracetate, morpholine, branched polyethylene imines, or amino acids such as glycine, ..cap alpha..-alanine, ..beta..-phenyl-..cap alpha..-alanine, tyrosine, or histidine, and treating the complexes so obtained with sodium borohydride at 1:1-1:5 NaBH/sub 4/-metal ratios, in an aqueous medium. Palladium-based complexes showed the highest activities (20-98Vertical Bar3< conversion) and selectivities (98-100Vertical Bar3<) in heterogeneous hydrogenation of cyclopentadiene, butadiene, 1-hexyne, 1,3-cyclohexadiene, or 1,3-cyclooctadiene at 20/sup 0/-60/sup 0/C and 0.5-15 atm hydrogen, carried out in a kinetic circulation reactor or a metallic autoclave. Thus, a catalytic system based on PdCl/sub 2/ and ..beta..-phenyl-..cap alpha..-alanine converted 98Vertical Bar3< of cyclopentadiene to cyclopentene with 99Vertical Bar3< selectivity. The palladium-based catalyst did not deactivate on the contact with air.

Photobleaching of Sn(IV) chlorine e6 dichloride trisodium salt in ...

African Journals Online (AJOL)

Jane

2011-06-24

Jun 24, 2011 ... conversion with loss of excess energy or by taking the inter-system crossing and transferring into the lowest triplet state, which has a lower energy level than the first excited state and emitted ... saline (PBS), fetal bovine serum (FBS) and bovine serum albumin. (BSA), was obtained from (GIBCO, Malaysia).

External heavy atom effect on intersystem crossing reactions of aromatic hydrocarbons

International Nuclear Information System (INIS)

Wojnarovits, L.; Foeldiak, G.

1988-01-01

The external heavy atom effect by xenon on the S 1 → T n and T 1 → S o transitions of naphthalene and pyrene was investigated in hydrocarbon solvents by fluorescence or absorption spectroscopy. The quencher forms a short-lived encounter complex (that may be called exciplex as well) with the excited molecules in equilibrium process. This exciplex formation in solutions with naphthalene leads to some deviation from the Stern-Volmer type concentration dependence of the quenching. (author)

Spectroscopy of vibrationally hot molecules: Hydrogen cyanide and acetylene

International Nuclear Information System (INIS)

Jonas, D.M.

1992-01-01

An efficient formula for calculating nuclear spin statistical weights is presented. New experimental methods to distinguish electric and magnetic multipole transitions are proposed and used to prove that the formaldehyde A - X 0-0 transition is a magnetic dipole transition. HIgh resolution vacuum ultraviolet studies of the A → X fluorescence excitation spectrum of hydrogen cyanide (HCN) have: (i) determined that only the (0,1,0) vibrational level of the HCN A-state has a sufficiently long fluorescence lifetime to be suitable for Stimulated Emission Pumping (SEP) studies; and (ii) measured the electric dipole moment of the A-state. Several transitions in the hydrogen cyanide A → X SEP spectrum are shown to be due to the axis-switching mechanism. From a Franck-Condon plot of the intensities and a comparison between sums of predicted rotational constants and sums of observed rotational constants, all of the remaining transitions in the SEP spectrum can be securly assigned. Two weak resonances; a 2:3 CH:CN stretch Fermi resonance and a 6:2 bend:CN stretch resonance appear in the SEP spectrum. Excitation of the CH stretching vibration is predicted and shown to be entirely absent, apart from resonances, in the HCN SEP spectrum. A → X SEP spectra of acetylene (HCCH) near E VIB = 7,000 cm -1 display a wealth of strong and fully assignable anharmonic resonances and forbidden rotational transitions. It is proved that Darling-Dennison resonance between the cis and trans bending vibrations is the crucial first step in a series of anharmonic resonances which can transfer nearly all the vibrational energy out of the initial CC stretch/trans-bend excitation at high vibrational energy. Secondary steps in the vibrational energy flow are vibrational-l-resonance and the '2345' Fermi resonance. For short times, the vibrational energy redistribution obeys very restrictive rules

Time-dependent nonequilibrium soft x-ray response during a spin crossover

Energy Technology Data Exchange (ETDEWEB)

van Veenendaal, Michel

2018-03-01

The rapid development of high-brilliance pulsed X-ray sources with femtosecond time resolution has created a need for a better theoretical understanding of the time-dependent soft-X-ray response of dissipative many-body quantum systems. It is demonstrated how soft-X-ray spectroscopies, such as X-ray absorption and resonant inelastic X-ray scattering at transition-metal L-edges, can provide insight into intersystem crossings, such as a spin crossover. The photoinduced doublet-to-quartet spin crossover on cobalt in Fe-Co Prussian blue analogues is used as an example to demonstrate how the X-ray response is affected by the dissipative nonequilibrium dynamics. The time-dependent soft-X-ray spectra provide a wealth of information that reflect the changes in the nonequilibrium initial state via continuously changing spectral lineshapes that cannot be decomposed into initial photoexcited and final metastable spectra, strong broadenings, a collapse of clear selection rules during the intersystem crossing, strong fluctuations in the isotropic branching ratio in X-ray absorption, and crystal-field collapse/oscillations and strongly time-dependent anti-Stokes processes in RIXS.

Triplet exciton formation in organic photovoltaics

Energy Technology Data Exchange (ETDEWEB)

Yang, Xudong; Westenhoff, Sebastian; Howard, Ian; Ford, Thomas; Friend, Richard; Hodgkiss, Justin; Greenham, Neil [Cavendish Laboratory, University of Cambridge (United Kingdom)

2009-07-01

We have recently found that the formation of triplet excitons can be an important loss mechanism in organic photovoltaics, particularly in donor-acceptor blends designed to have high open-circuit voltages. This can occur when the intrachain triplet state lies lower in energy than the charge-transfer state formed at the heterojunction. We find that in a blend based on the polyfluorene derivatives F8BT and PFB, triplet excitons are formed after photoexcitation with much higher efficiency than in the component polymers. We use transient absorption spectroscopy to study the dynamics of charges and triplet excitons on timescales from picoseconds to microseconds. This allows us to determine a characteristic time of {proportional_to} 40 ns for intersystem crossing in the charge-separated state, and to estimate that as many as 75% of photoexcitations lead to the formation of triplet states. To avoid losses to triplet excitons in photovoltaic devices, it is necessary to separate charge pairs before intersystem crossing can occur. We also present photophysical measurements of saturation and relaxation of the triplet excited state absorption used to quantify triplet populations.

{sup 77} Se NMR of deuteride vinyl and acetylene selenides; RMn de {sup 77} Se de selenetos vinilicos e acetilenicos deuterados

Energy Technology Data Exchange (ETDEWEB)

Roque, L C; Stefani, H A; Arruda Campos, I.P. de; Comasseto, J V [Sao Paulo Univ., SP (Brazil). Inst. de Quimica

1992-12-31

The main objective of this work is a contribution for establishing a data base sufficient for interpretation of the selenium organic compound spectra. Due to the short literature on acetylene and vinyl selenides, the investigation of these compounds using {sup 77} Se NMR has been considered interesting. Particularly, compounds containing the selenium phenyl group have been selected, as they are larger used in organic chemistry. Non usual deuterated compounds have been applied, viewing simplification of the experimental results interpretation, since the use of deuterium virtually eliminates the Se-H coupling constants, due to the protons of the selenium phenyl group 5 refs., 2 tabs.

[Change of character of intersystemic interactions in newborn rat pups under conditions of a decrease of central influences (urethane anesthesia)].

Science.gov (United States)

Kuznetsov, S V; Sizonov, V A; Dmitrieva, L E

2014-01-01

On newborn rat pups, for the first day after birth, there was studied the character of mutual influences between the slow-wave rhythmical components of the cardiac, respiratory, and motor activities reflecting interactions between the main functional systems of the developing organism. The study was carried out in norm and after pharmacological depression of the spontaneous periodical motor activity (SPMA) performed by narcotization of rat pups with urethane at low (0.5 g/kg, i/p) and maximal (1 g/kg, i/p) doses. Based on the complex of our obtained data, it is possible to conclude that after birth in rat pups the intersystemic interactions are realized mainly by the slow-wave oscillations of the near- and manyminute diapason. The correlational interactions mediated by rhythms of the decasecond diapason do not play essential role in integrative processes. Injection to the animals of urethane producing selective suppression of reaction of consciousness, but not affecting activating influences of reticular formation on cerebral cortex does not cause marked changes of autonomous parameters, but modulates structure and expression of spontaneous periodical motor activity. There occurs an essential decrease of mutual influences between motor and cardiovascular systems. In the case of preservation of motor activity bursts, a tendency for enhancement of correlational relations between the modulating rhythms of motor and somatomotor systems is observed. The cardiorespiratory interactions, more pronounced in intact rat pups in the near- and many-minute modulation diapason, under conditions of urethane, somewhat decrease, whereas the rhythmical components of the decasecond diapason--are weakly enhanced.

Ultrafast Wiggling and Jiggling: Ir2(1,8-diisocyanomenthane)4 2+

Czech Academy of Sciences Publication Activity Database

Pižl, Martin; Hunter, B. M.; Greetham, G. M.; Towrie, M.; Záliš, Stanislav; Gray, H. B.; Vlček, Antonín

2017-01-01

Roč. 121, č. 48 (2017), s. 9275-9283 ISSN 1089-5639 R&D Projects: GA ČR GA17-01137S; GA MŠk(CZ) LTC17052 Institutional support: RVO:61388955 Keywords : Coherent oscillations * Inter-system crossings * Optical spectroscopic Subject RIV: CF - Physical ; Theoretical Chemistry OBOR OECD: Physical chemistry Impact factor: 2.847, year: 2016

Diffusion air effects on the soot axial distribution concentration in a premixed acetylene/air flame

Energy Technology Data Exchange (ETDEWEB)

Fassani, Fabio Luis; Santos, Alex Alisson Bandeira; Goldstein Junior, Leonardo [Universidade Estadual de Campinas, SP (Brazil). Faculdade de Engenharia Mecanica. Dept. de Engenharia Termica e de Fluidos]. E-mails: fassani@fem.unicamp.br; absantos@fem.unicamp.br; leonardo@fem.unicamp.br; Ferrari, Carlos Alberto [Universidade Estadual de Campinas, SP (Brazil). Inst. de Fisica. Dept. de Eletronica Quantica]. E-mail: ferrari@ifi.unicamp.br

2000-07-01

Soot particles are produced during the high temperature pyrolysis or combustion of hydrocarbons. The emission of soot from a combustor, or from a flame, is determined by the competition between soot formation and its oxidation. Several factors affect these processes, including the type of fuel, the air-to-fuel ratio, flame temperature, pressure, and flow pattern. In this paper, the influence of the induced air diffusion on the soot axial distribution concentration in a premixed acetylene/air flame was studied. The flame was generated in a vertical axis burner in which the fuel - oxidant mixture flow was surrounded by a nitrogen discharge coming from the annular region between the burner tube and an external concentric tube. The nitrogen flow provided a shield that protected the flame from the diffusion of external air, enabling its control. The burner was mounted on a step-motor driven, vertical translation table. The use of several air-to-fuel ratios made possible to establish the sooting characteristics of this flame, by measuring soot concentration along the flame height with a non-intrusive laser light absorption technique. (author)

Dissimilatory reduction of nitrate and nitrite in the bovine rumen: nitrous oxide production and effect of acetylene.

Science.gov (United States)

Kaspar, H F; Tiedje, J M

1981-03-01

15N tracer methods and gas chromatography coupled to an electron capture detector were used to investigate dissimilatory reduction of nitrate and nitrite by the rumen microbiota of a fistulated cow. Ammonium was the only 15N-labeled end product of quantitative significance. Only traces of nitrous oxide were detected as a product of nitrate reduction; but in experiments with nitrite, up to 0.3% of the added nitrogen accumulated as nitrous oxide, but it was not further reduced. Furthermore, when 13NO3- was incubated with rumen microbiota virtually no [13N]N2 was produced. Acetylene partially inhibited the reduction of nitrite to ammonium as well as the formation of nitrous oxide. It is suggested that in the rumen ecosystem nitrous oxide is a byproduct of dissimilatory nitrite reduction to ammonium rather than a product of denitrification and that the latter process is absent from the rumen habitat.

Theoretical study on the photolysis mechanism of 2,3-diazabicyclo[2.2.2]oct-2-ene.

Science.gov (United States)

Chen, Hui; Li, Shuhua

2005-09-28

A CASPT2/CASSCF study has been carried out to investigate the mechanism of the photolysis of 2,3-diazabicyclo[2.2.2]oct-2-ene (DBO) under direct and triplet-sensitized irradiation. By exploring the detailed potential energy surfaces including intermediates, transition states, conical intersections, and singlet/triplet crossing points, for the first excited singlet (S(1)) and the low-lying triplet states (T(1), T(2), and T(3)), we provide satisfactory explanations of many experimental findings associated with the photophysical and photochemical processes of DBO. A key finding of this work is the existence of a significantly twisted S(1) minimum, which can satisfactorily explain the envelope of the broad emission band of DBO. It is demonstrated that the S(1) (n-pi*) intermediate can decay to the T(1) (n-pi*) state by undergoing intersystem crossing (rather inefficient) to the T(2) (pi-pi*) state followed by internal conversion to the T(1) state. The high fluorescence yield and the extraordinarily long lifetime of the singlet excited DBO are due to the presence of relatively high barriers, both for intersystem crossing and for C-N cleavage. The short lifetime of the triplet DBO is caused by fast radiationless decay to the ground state.

Comparative study of the monomer grafting: ethylene, acetylene, 1,3-butadiene and estyrene in the matrix of recycled polytetrafluoroethylene (PTFE)

International Nuclear Information System (INIS)

Ikari, Carolina T.; Rosner, Gerhardyne O.; Oliveira, Ana C.F.; Ferreto, Helio F.R.; Lima, Luiz F.C.P.; Lugao, Ademar B.; Moreira, Otavio M.

2009-01-01

In this study it is used the recycled polytetrafluoroethylene (PTFE), that with the gamma radiation under inert atmosphere or in presence of air, it is obtained free radicals and a posterior the monomer grafting (ethylene, acetylene, styrene or 1.3 butadiene), obtaining the copolymer polytetrafluoroethylene-g-monomer. It is studied the obtention of the polymer by two methods: by direct way, via grafting, where the polymer is irradiated in presence of monomer, and via grafting when the polymer is irradiated in absence of monomer and under inert or air. The characterization of the copolymer was performed by the techniques of infrared region absorption spectroscopy with Fourier transformation (FTIR), thermogravimetric (TGA) and derivative thermogravimetry (DTG), and percentage of mass grafting (DOG)

Peut-on envisager le remplacement de l'éthylène par l'acétylène à moyen terme ? Can the Substitution of Ethylene by Acetylene Be Imagined in the Medium Term?

Directory of Open Access Journals (Sweden)

Lefebvre G.

2006-11-01

Full Text Available L'accroissement considérable depuis 1973 du coût des énergies fossiles, notamment du pétrole, a fortement contribué au renchérissement du prix de l'éthylène alors que parallèlement l'acétylène fabriqué au départ de carbure de calcium ou par arc électrique pouvait espérer bénéficier d'un coût relatif plus faible de l'énergie électrique d'origine nucléaire. II ressort de la présente étude que malgré les hypothèses favorables suivantes : - taux de croissance moyen du prix du pétrole à monnaie constante 1982 de 7 % par an, - augmentation de celui du charbon limitée à 3 % par an, - énergie électrique disponible en permanence à 5 et 10 c/kWh, - capacité unitaire de production d'acétylène de l'ordre de 300 000 t/an comparable à celle de l'éthylène, il apparaît impossible que l'acétylène puisse concurrencer l'éthylène avant l'an 2000. Seul le chlorure de vinyle pourrait être fabriqué à partir d'acétylène favorisé par un important facteur d'échelle, à condition que l'électricité puisse être alimentée en permanence à 0,10 F le kWh. Cette constatation ne tient pas compte de la remise en cause des procédés pétrochimiques actuels d'obtention des intermédiaires de seconde génération dont la fabrication à partir d'acétylène nécessiterait la création d'installations de conception entièrement différente. Alors qu'en 1975 les procédés à l'arc électrique de production d'acétylène à partir de naphta apparaissaient plus économiques que la voie carbure de calcium, on constate actuellement une situation inverse, consécutive aux augmentations de prix du pétrole qui ont suivi. The considerable increase in the cost of fossil energy sources since 1973, and especially that of oil, has greatly helped drive up the price of ethylene, whereas at the same time acetylene manufactured initially from calcium carbide or by electric arc could have hoped to profit from the relative low price of electric

Acetylene black incorporated layered copper sulfide nanosheets for high-performance supercapacitor

International Nuclear Information System (INIS)

Huang, Ke-Jing; Zhang, Ji-Zong; Jia, Yu-Ling; Xing, Ke; Liu, Yan-Ming

2015-01-01

Highlights: • CuS/AB composites were synthesized by a simple solvothermal route. • Supercapacitor electrode based on CuS/AB was fabricated. • Microstructures and electrochemical properties of the electrodes were evaluated. • CuS/AB electrode exhibited ultrahigh specific capacitance and good cycling stability. - Abstract: Two-dimensional transition metal chalcogenides are attracting increasing attention in energy storage due to their unique structures and electronic properties. CuS has been demonstrated with a metal-like electronic conductivity and a high theoretical capacity. In this work, a facile strategy was reported for one-step synthesis of acetylene black (AB) incorporated layered CuS nanosheet via a simple solvothermal route. X-ray diffraction, Raman spectroscopy, scanning electron microscopy and transmission electron microscopy were used to investigate the morphologies and microstructures of the as-prepared materials. Electrochemical data showed that the CuS/AB composites displayed a high specific capacitance of 2981 F/g at 1.0 A/g and retained 64.6% (1924.5 F/g) at a high current density of 20 A/g, indicative of good rate capability. Furthermore, the composites retained approximately 92% of the initial specific capacitance after 600 cycles at a current density of 1.0 A/g, demonstrating good cycling stability. The outstanding electrochemical properties of the CuS/AB composite suggested that it had great potential for practical applications in high-performance supercapacitors and the present synthesis strategy maybe readily extended to the preparation of other composites based on CuS for potential applications in energy storage and conversion devices

Ploidy Variation in Hybrids from Interploid 3x X 2x Crosses in Musa

Directory of Open Access Journals (Sweden)

Osuji, JO.

1997-01-01

Full Text Available Hybrids were obtained after in vitro germination of embryos from interploid crosses between triploid 'French' plantain cultivars (Musa spp. AAB group 'Ntanga 2' and 'Bobby Tannap' with diploid banana (Ivlusa acuminata subsp. burmannicoidesj 'Calcutta 4'. Cross-pollinated bunches were harvested at full maturity and ripened with acetylene in a room for 4 days. Seeds were extracted from peeled ripe fruits by squashing. Embryos from the seeds were excised aseptically after 2 days and germinated in vitro. Seedlings were subsequently planted in early evaluation trials after acclimatising in the greenhouse. Chromosome counts were carried out on root tips of mature and maiden suckers to determine ploidy levels using a modified squashing technique. Counts showed that two of the hybrids were aneuploids (trisomies with somatic chromosome number of 2n = 2x + 1 = 23, one hybrid was diploid while the other two were tetraploids. Tetraploids are the most promising hybrids for the genetic improvement of plantains. Diploids are valuable material for further improvement of the plantain genome at this ploidy level. Trisomies provide means for further characterisation of the Musa genome and physical gene mapping in plantain and banana.

Superior mercury-free catalysts for acetylene hydrochlorination to VCM. Achieving high productivities and long catalyst life-time

Energy Technology Data Exchange (ETDEWEB)

Liebens, A.T.; Piccinini, M. [Solvay S.A., Bruxelles (Belgium)

2013-11-01

New mercury-free catalytic systems based on the use of ionic liquids (IL) and noble metals (e.g. Pd, Au) have been evaluated for the hydrochlorination reaction of acetylene to produce Vinyl Chloride Monomer (VCM). Two different approaches have been investigated: gas-liquid homogeneous catalytic systems in the presence of molten IL/Metal and heterogeneous gas-solid ones using solid materials. For the latter case, very positive results have been obtained using SILP-type catalysts (SILP: Supported Ionic Liquid Phase) where IL/Metal were deposited onto a solid mesoporous support. Remarkably, both systems display very high Space Time Yield (STY) and breakthrough life-time stability. No deactivation is observed even after 500 h on stream indicating the strong advantages of these new materials compared to most investigated Au/C supported systems. The development of heterogeneous catalysts was preferred as the scale-up of gas-liquid technology implies important CAPEX investments to convert current plants from gas-solid to gas-liquid equipment. (orig.)

Heats of Formation of Triplet Ethylene, Ethylidene, and Acetylene

Energy Technology Data Exchange (ETDEWEB)

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.

In situ acetylene reduction activity of Scytonema julianum in Vapor cave (Spain

Directory of Open Access Journals (Sweden)

Asencio Antonia Dolores

2011-01-01

Full Text Available Nitrogen fixation was measured in situ for the first time by acetylene reduction for a greyish mat composed of Scytonema julianum in cave- like environments. Mat-specific rates (129.9-215.7 nmol C2 H4 m-2 s-1 for daytime fixation and 65.1-120.6 nmol C2 H4 m-2 s-1 for nighttime fixation recorded in the Vapor cave differed considerably due to the energy reserves stored during photosynthesis being exhausted and used in the dark phase. The most influential environmental parameter for nitrogen fixation in the Vapor cave is temperature in the daytime and nighttime fixations. Nitrogen fixation by cyanobacteria may contribute considerably to the overall nitrogen cycle in harsh environments such as caves. Nitrogenase activity in Scytonema julianum was roughly 30 times higher than that of Scytonema mirabile, which also grew in cave environments, which is due to the characteristics of each site. The entrance of Vapour cave (Spain faces SE, measures 0.75 x 0.6 m and opens to shafts of a total depth of 80 m. Its dimensions and environmental conditions (relative humidity up to 100%; maximum temperature, 43oC imply that it is isolated from external influences, and that the microclimate differs substantially from that experienced externally. Nitrogen fixation, photon flux density, relative humidity and temperature in the Vapor cave were taken hourly over a 24-hour period in winter.

Molecular effects in carbon K-shell Auger-electron production by 0.6-2.0 MeV protons and extraction of an atomic cross section

International Nuclear Information System (INIS)

McDaniel, F.D.; Lapicki, G.

1987-01-01

Carbon K-shell Auger-electron production cross sections are reported for 0.6-2.0 MeV protons incident on CH 4 (methane), C 2 H 2 (acetylene), C 2 H 4 (ethylene), C 2 H 6 (ethane), n-C 4 H 10 (normal butane), i-C 4 H 10 (isobutane), C 6 H 6 (benzene), CO (carbon monoxide), and CO 2 (carbon dioxide). A constant-energy mode 45 0 parallel-plate electrostatic analyzer was used for detection of Auger electrons. The carbon KLL Auger-electron cross sections for all molecules were found to be lower than that found for CH 4 by 9-23%. All carbon KLL Auger-electron data could be brought into agreement when corrected for the chemical shift of the carbon K-shell binding energy in molecules and for intramolecular scattering. KLL Auger-electron production cross sections are compared to first Born and ECPSSR theories and show good agreement with both after the chemical shift of the carbon K-shell binding energy in molecules and the effects of intramolecular scattering are considered. (orig.)

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

Science.gov (United States)

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.

Mid-IR Absorption Cross-Section Measurements of Hydrocarbons

KAUST Repository

Alrefae, Majed Abdullah

2013-05-01

Laser diagnostics are fast-response, non-intrusive and species-specific tools perfectly applicable for studying combustion processes. Quantitative measurements of species concentration and temperature require spectroscopic data to be well-known at combustion-relevant conditions. Absorption cross-section is an important spectroscopic quantity and has direct relation to the species concentration. In this work, the absorption cross-sections of basic hydrocarbons are measured using Fourier Transform Infrared (FTIR) spectrometer, tunable Difference Frequency Generation laser and fixed wavelength helium-neon laser. The studied species are methane, methanol, acetylene, ethylene, ethane, ethanol, propylene, propane, 1-butene, n-butane, n-pentane, n-hexane, and n-heptane. The Fourier Transform Infrared (FTIR) spectrometer is used for the measurements of the absorption cross-sections and the integrated band intensities of the 13 hydrocarbons. The spectral region of the spectra is 2800 – 3400 cm-1 (2.9 – 3.6 μm) and the temperature range is 673 – 1100 K. These valuable data provide huge opportunities to select interference-free wavelengths for measuring time-histories of a specific species in a shock tube or other combustion systems. Such measurements can allow developing/improving chemical kinetics mechanisms by experimentally determining reaction rates. The Difference Frequency Generation (DFG) laser is a narrow line-width, tunable laser in the 3.35 – 3.53 μm wavelength region which contains strong absorption features for most hydrocarbons due to the fundamental C-H vibrating stretch. The absorption cross-sections of propylene are measured at seven different wavelengths using the DFG laser. The temperature range is 296 – 460 K which is reached using a Reflex Cell. The DFG laser is very attractive for kinetic studies in the shock tube because of its fast time response and the potential possibility of making species-specific measurements. The Fixed wavelength

Photoluminescence behavior of riboflavin and lumiflavin in liquid solutions and solid films

Energy Technology Data Exchange (ETDEWEB)

Penzkofer, A., E-mail: alfons.penzkofer@physik.uni-regensburg.de [Fakultaet fuer Physik, Universitaet Regensburg, Universitaetsstrasse 31, D-93053 Regensburg (Germany)

2012-05-25

Highlights: Black-Right-Pointing-Pointer Delayed fluorescence and phosphorescence spectra of flavins in starch films measured. Black-Right-Pointing-Pointer Quantum yield of singlet-triplet intersystem determined with a new approach. Black-Right-Pointing-Pointer Theory developed for determination of luminescence quantum yields of films. Black-Right-Pointing-Pointer Delayed fluorescence and phosphorescence lifetimes of flavins in starch films measured. Black-Right-Pointing-Pointer Singlet and triplet relevant parameters of riboflavin and lumiflavin determined. - Abstract: The absorption and emission behavior of riboflavin and lumiflavin in water, tetrahydrofuran (THF), water-starch, THF-polystyrene, starch films, and polystyrene films was studied at room temperature. Absorption cross-section spectra, fluorescence quantum distributions, and fluorescence quantum yields were determined. For the starch films additionally phosphorescence and delayed fluorescence spectra as well as phosphorescence lifetimes and delayed fluorescence lifetimes were measured and their quantum yields of intersystem-crossing, intrinsic triplet-based phosphorescence quantum yields, T{sub 1}-S{sub 0} radiative lifetimes, and S{sub 0}-T{sub 1} absorption strengths were calculated. A method of absolute intrinsic luminescence quantum distribution and quantum yield determination for dye doped films on transparent plates with a fluorimeter is described.

Characterization and reaction studies of dimeric molybdenum(III) complexes with bridging dithiolate ligands. Catalytic reduction of acetylene to ethylene

International Nuclear Information System (INIS)

DuBois, M.R.; Haltiwanger, R.C.; Miller, D.J.; Glatzmaier, G.

1979-01-01

The complexes [C 5 H 5 MoSC/sub n/H/sub 2n/S] 2 (where n = 2 and 3) have been prepared by the reaction of ethylene sulfide and propylene sulfide, respectively, with C 5 H 5 MoH(CO) 3 or with [C 5 H 5 Mo(CO) 3 ] 2 . Cyclic voltammetry shows that each complex undergoes two reversible oxidations at 0.13 and 0.79 V vs. SCE (in acetonitrile with 0.1 M Bu 4 NBF 4 ). Both the one-electron and two-electron oxidation products have been synthesized and characterized by spectral and magnetic data. Electrochemical data for the oxidized complexes support the conclusion that the complexes have the same gross structural features in all three oxidation states. A single crystal of the monocation [C 5 H 5 MoSC 3 H 6 S] 2 BF 4 has been characterized by an x-ray diffraction study. The compound crystallizes in the space group C2/c with a = 18.266 (1) A, b = 9.206 (4) A, c = 12.911 (5) A, β = 100.83 (3) 0 , and V = 2128 A 3 . The metal ions of the cation are bridged by two 1,2-propanedithiolate ligands. The four sulfur atoms of these ligands form a plane which bisects the metal-metal distance. The neutral dimeric complexes undergo a unique reaction with alkenes and alkynes in which the hydrocarbon portion of the bridging dithiolate ligands is exchanged. The reaction has been characterized with olefinswith both electron-withdrawing and electron-donating substituents. When [C 5 H 5 MoSC 2 H 4 S] 2 (1) is reacted with acetylene at 25 0 C, ethene is produced and the complex [C 5 H 5 MoSC 2 H 2 S] 2 is isolated. The latter complex is reduced by hydrogen (2 atm) at 60 0 C to re-form 1. The utility of these reactions in the catalytic reduction of acetylene to ethylene has been investigated. The role of the sulfur ligands in this catalytic cycle is discussed. 50 references, 2 figures, 5 tables

Strategic development of OJSC 'Krymenergo'- Energy of Crimea to the human

Energy Technology Data Exchange (ETDEWEB)

Gruba, Grygory

2010-09-15

Historically, electric networks in Crimea were designed and built by the Company taking into account objective considerations. Today we have the main power system based on 110 kV lines, which carry the main load in Crimea and Crimea energy iterflows. Because of the steep increase of the loads in AR Krym, the cross-section Ukraine-Crimea during the highest loads operates at the least allowable level. Further growth of the loads is hindered by this cross-section. This requires the system approach to the safety automation, strengthening intersystem links, own generation and corresponded investments.

Acetylene Black/Sulfur Composites Synthesized by a Solution Evaporation Concentration Crystallization Method and Their Electrochemical Properties for Li/S Batteries

Directory of Open Access Journals (Sweden)

Zhigao Yang

2013-07-01

Full Text Available A novel technique to prepare carbon/sulfur composites as cathode materials for Li/S batteries is proposed, which we call the ‘solution evaporation concentration crystallization’ method. Three composites with different S loadings were prepared, subject to two different solvent evaporation rates from acetylene black (AB/sulfur in carbon disulfide solutions. X-ray diffraction, environmental scanning electron microscopy, transmission electron microscopy, and Brunauer-Emmett-Teller measurements all show that the porous AB structure is well-filled with S. Composites prepared at a lower solvent evaporation rate with 50 wt % S content, had good electrochemical properties, with 1609.67 mAh g−1 after 100 cycles. Composites with better dispersibility at a low solvent evaporation rate can effectively prevent polysulfide from dissolving in the electrolyte, and serve to stabilize the structure of the S cathode during the charge-discharge process.

Superexcited states on ethylene and acetylene

International Nuclear Information System (INIS)

Azevedo e Souza, A.C. de; Souza, G.G.B. de

1988-01-01

Electron energy loss spectra were obtained for C 2 H 2 and C 2 H 4 in the energy loss range from 12 to 50 eV for 1 Kev electrons. Elastic and inelastic cross sections and generalized oscillator strengths for transitions at 13.3, 15.7 and 18.7 eV were obtained. (A.C.A.S.) [pt

Iridium complexes for the application of photodynamic therapy

Directory of Open Access Journals (Sweden)

SHI Min

2015-10-01

Full Text Available Photodynamic therapy can destruct tumor cells by singlet oxygen which is generated via a photodynamic reaction of the photosensitizer under a specfic excitation wavelength.Due to the heavy atom effect of metal iridium,iridiumcomplexes are excited by suitable light and then reach their excited triple state through intersystem crossing.The excited iridium complexes transfer energy to oxygen molecules to produce singlet oxygen for photodynamic therapy.

Heavy Atom Substituents as Molecular Probes for Solvent Effects on the Dynamics of Short-lived Triplet Exciplexes

OpenAIRE

Winter, Gerhard; Steiner, Ulrich

1980-01-01

The influence of heavy atom substituents (Br, I) in the electron donor aniline on the electron transfer reaction with thiopyronine triplet is investigated by flash spectroscopy in solvents of different viscosity and polarity. Triplet quenching constants and radical yields are determined. The results are analysed in terms of decay constants of an intermediate triplet exciplex where the heavy atom substituents significantly enhance the intersystem crossing process leading to singlet ground stat...

'Clicking' on the nanoscale: 1,3-dipolar cycloaddition of terminal acetylenes on azide functionalized, nanometric surface templates with nanometer resolution

International Nuclear Information System (INIS)

Haensch, Claudia; Hoeppener, Stephanie; Schubert, Ulrich S

2009-01-01

Electro-oxidative lithography is used as a tool to create chemical nanostructures on an n-octadecyltrichlorosilane (OTS) monolayer self-assembled on silicon. The use of a bromine precursor molecule, which is exclusively assembled on these chemical templates, can be used to further functionalize the nanostructures by the site-selective generation of azide functions and performing the highly effective 1,3-dipolar cycloaddition reaction with acetylene functionalized molecules. The versatility of this reaction scheme provides the potential to integrate a large variety of functional molecules, to tailor the surface properties of the nanostructures or to anchor molecular building blocks or particles in confined, pre-defined surface areas. The results demonstrated in the present study introduce a conceivable route towards the functionalization of chemically active surface templates with high fidelity and reliability. It is demonstrated that surface features with a lateral resolution of 50 nm functionalized with propargyl alcohol can be fabricated.

Study on optoelectronic properties of Spiro-CN for developing an efficient OLED

Science.gov (United States)

Mishra, Ashok Kumar

2018-05-01

There are a class of organic molecules and polymers which exhibit semiconductor behavior because of nearly free conjugate π-electrons. Hopping of these electrons in molecules forms different excited singlet and triplet states named as excitons. Some of these organic molecules can be set to emit photons by triplet-singlet excitonic transition via a process called Thermally Activated Delayed Fluorescence (TADF) which is exploited for designing the Organic Light Emitting diode (OLED.) Spiro-CN (spirobifluorene skeletons) Spiro is one of these reported noble metal-free TADF molecules which offers unique optical and electronic properties arising from the efficient transition and reverse intersystem crossing between the lowest singlet (S) and triplet (T) excited states. Its ability to harvest triplet excitons for fluorescence through facilitated reverse intersystem crossing (T→S) could directly impact their properties and performances, which is attractive for a wide variety of low-cost optoelectronic device. In the present study, the Spiro-CN compounds have been taken up for the investigation of various optoelectronic properties including the thermally activated delayed fluorescence (TADF) by using the Koopmans Method and Density Functional Theory. The present study discusses the utility of the Spiro-CN organic semiconductor as a suitable TADF material essential for developing an efficient Organic Light Emitting Diode (OLED).

Shorter Exciton Lifetimes via an External Heavy-Atom Effect: Alleviating the Effects of Bimolecular Processes in Organic Light-Emitting Diodes.

Science.gov (United States)

Einzinger, Markus; Zhu, Tianyu; de Silva, Piotr; Belger, Christian; Swager, Timothy M; Van Voorhis, Troy; Baldo, Marc A

2017-10-01

Multiexcited-state phenomena are believed to be the root cause of two exigent challenges in organic light-emitting diodes; namely, efficiency roll-off and degradation. The development of novel strategies to reduce exciton densities under heavy load is therefore highly desirable. Here, it is shown that triplet exciton lifetimes of thermally activated delayed-fluorescence-emitter molecules can be manipulated in the solid state by exploiting intermolecular interactions. The external heavy-atom effect of brominated host molecules leads to increased spin-orbit coupling, which in turn enhances intersystem crossing rates in the guest molecule. Wave function overlap between the host and the guest is confirmed by combined molecular dynamics and density functional theory calculations. Shorter triplet exciton lifetimes are observed, while high photoluminescence quantum yields and essentially unaltered emission spectra are maintained. A change in the intersystem crossing rate ratio due to increased dielectric constants leads to almost 50% lower triplet exciton densities in the emissive layer in the steady state and results in an improved onset of the photoluminescence quantum yield roll-off at high excitation densities. Efficient organic light-emitting diodes with better roll-off behavior based on these novel hosts are fabricated, demonstrating the suitability of this concept for real-world applications. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

International Nuclear Information System (INIS)

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

2012-01-01

The time evolution of the smallest anions (C 2 H - and H 2 CC - ), just after plasma ignition, is studied by means of microwave cavity resonance spectroscopy (MCRS) in concert with laser-induced photodetachment under varying gas pressure and temperature in an argon-acetylene radio-frequency (13.56 MHz) plasma. These anions act as an initiator for spontaneous dust particle formation in these plasmas. With an intense 355 nm Nd:YAG laser pulse directed through the discharge, electrons are detached only from these anions present in the laser path. This results in a sudden increase in the electron density in the plasma, which can accurately and with sub-microsecond time resolution be measured with MCRS. By adjusting the time after plasma ignition at which the laser is fired through the discharge, the time evolution of the anion density can be studied. We have operated in the linear regime: the photodetachment signal is proportional to the laser intensity. This allowed us to study the trends of the photodetachment signal as a function of the operational parameters of the plasma. The density of the smallest anions steadily increases in the first few milliseconds after plasma ignition, after which it reaches a steady state. While keeping the gas density constant, increasing the gas temperature in the range 30-120 °C limits the number of smallest anions and saturates at a temperature of about 90 °C. A reaction pathway is proposed to explain the observed trends.

Effect of in situ pyrolysis of acetylene (C2H2) gas as a carbon source on the electrochemical performance of LiFePO4 for rechargeable lithium-ion batteries

Science.gov (United States)

Saroha, Rakesh; Panwar, Amrish K.

2017-06-01

The intention of this work is to study the effect of in situ pyrolysis of acetylene (C2H2) gas used as a carbon source on the physicochemical and electrochemical performance of pristine LiFePO4 (LFP). Acetylene gas, which decomposed to carbon and methane along with some side products when exposed to high temperature (>625 °C), is used as a carbon source for coating over the surface of LFP particles. Thermogravimetric (TGA) measurements were performed in an air atmosphere, primarily to estimate the exact amount of carbon deposited on the surface of the olivine cathode material due to the decomposition of C2H2 gas. Raman and TGA results confirm the presence of carbon as coated on the surface of the prepared compositions. Among all the synthesized samples, LFP with 10 min C2H2 treatment (LFPC10) shows the highest discharge capacity at all C-rates and exhibits excellent rate performance. LFPC10 delivers a specific discharge capacity of 144 (±5) mAh g-1 (~85% of the theoretical capacity of 170 mAh g-1) at 0.1C rate. LFPC10 demonstrates the best cycling performance as it offers an initial discharge capacity of about 117 (±5) mAh g-1 (~69% of the theoretical capacity) at 1C-rate and has 97% capacity retention even after 100 charge/discharge cycles.

Organophotocatalysis: Insights into the Mechanistic Aspects of Thiourea-Mediated Intermolecular [2+2] Photocycloadditions.

Science.gov (United States)

Vallavoju, Nandini; Selvakumar, Sermadurai; Pemberton, Barry C; Jockusch, Steffen; Sibi, Mukund P; Sivaguru, Jayaraman

2016-04-25

Mechanistic investigations of the intermolecular [2+2] photocycloaddition of coumarin with tetramethylethylene mediated by thiourea catalysts reveal that the reaction is enabled by a combination of minimized aggregation, enhanced intersystem crossing, and altered excited-state lifetime(s). These results clarify how the excited-state reactivity can be manipulated through catalyst-substrate interactions and reveal a third mechanistic pathway for thiourea-mediated organo-photocatalysis. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Spin-selective depopulation of triplet sublevels in rapidly rotating triplet exciplexes detected by a heavy-atom-induced magnetic field effect

OpenAIRE

Steiner, Ulrich

1980-01-01

A mechanism is presented explaining a reported heavy-atom-induced magnetic field effect as a consequence of non-equilibrium triplet sublevel population in an intermediate exciplex. The triplet exciplex spin polarization is induced by sub-level-selective intersystem crossing from the exciplex triplet to its singlet ground state and is decreased by an external magnetic field. The theory accounts almost quantitatively for the observed influence of magnetic field strength and heavy-atom substitue...

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

Science.gov (United States)

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. Copyright © 2015 Elsevier Ltd. All rights reserved.

An enhanced sensitivity towards H2O2 reduction based on a novel Cu metal–organic framework and acetylene black modified electrode

International Nuclear Information System (INIS)

Meng, Wei; Xu, Shuang; Dai, Lei; Li, Yuehua; Zhu, Jing; Wang, Ling

2017-01-01

Highlights: • A novel Cu metal–organic framework (Cu-MOF) has been synthesized under hydrothermal condition. • The Cu-MOF modified electrode shows good electrocatalytic activity towards H 2 O 2 reduction in alkaline solution. • The addition of acetylene black improves the response performance of the modified electrode towards H 2 O 2 reduction. - Abstract: As a large class of highly crystalline hybrid materials, metal-organic frameworks (MOFs) have the potentials to act as electrochemical sensors due to their active metal sites and diverse structures. However, the poor electron-conductive property limits their application as electrocatalyst. An effective strategy is to introduce conductive phases to the MOFs. In this paper, a novel Cu metal–organic framework {[Cu 2 (bep)(ada) 2 ]·H 2 O} n (Cu-MOF) (beb = 1,4-bis(2-ethylbenzimidazol-1-ylmethyl) benzene, H 2 ada = 1,3-adamantanediacetic acid) was synthesized under hydrothermal condition. Single-crystal X-ray analysis revealed that the Cu-MOF was a three-dimensional pillar-layered framework with two kinds of paddle-wheel secondary building units. Subsequently, the Cu-MOF modified glassy carbon electrode (GCE) was applied in the H 2 O 2 detection in alkaline solution, and it exhibited the good electrocatalytic activity towards H 2 O 2 reduction. When acetylene black (AB) was added to the Cu-MOF, the electrocatalytic performance of the Cu-MOF modified electrode was greatly improved. The results of amperometric response to H 2 O 2 with different AB addition showed that the Cu-MOF/AB-2%/GCE exhibited a wide linear relationship in the H 2 O 2 concentration range of 0.05–3 μM with a rather high sensitivity of 5.56 μA μM −1 cm −2 , a low detection limit of 0.014 μM as well as a fast response time of 4 s. The Cu-MOF/AB-2%/GCE also exhibited the good selectivity towards H 2 O 2 reduction, and had no response to its normal co-existences of glucose, glycerin, alcohol and lactose. In addition, the modified

Excited-state dynamics of pentacene derivatives with stable radical substituents.

Science.gov (United States)

Ito, Akitaka; Shimizu, Akihiro; Kishida, Noriaki; Kawanaka, Yusuke; Kosumi, Daisuke; Hashimoto, Hideki; Teki, Yoshio

2014-06-23

The excited-state dynamics of pentacene derivatives with stable radical substituents were evaluated in detail through transient absorption measurements. The derivatives showed ultrafast formation of triplet excited state(s) in the pentacene moiety from a photoexcited singlet state through the contributions of enhanced intersystem crossing and singlet fission. Detailed kinetic analyses for the transient absorption data were conducted to quantify the excited-state characteristics of the derivatives. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

An Ideal Molecular Sieve for Acetylene Removal from Ethylene with Record Selectivity and Productivity.

Science.gov (United States)

Li, Bin; Cui, Xili; O'Nolan, Daniel; Wen, Hui-Min; Jiang, Mengdie; Krishna, Rajamani; Wu, Hui; Lin, Rui-Biao; Chen, Yu-Sheng; Yuan, Daqiang; Xing, Huabin; Zhou, Wei; Ren, Qilong; Qian, Guodong; Zaworotko, Michael J; Chen, Banglin

2017-12-01

Realization of ideal molecular sieves, in which the larger gas molecules are completely blocked without sacrificing high adsorption capacities of the preferred smaller gas molecules, can significantly reduce energy costs for gas separation and purification and thus facilitate a possible technological transformation from the traditional energy-intensive cryogenic distillation to the energy-efficient, adsorbent-based separation and purification in the future. Although extensive research endeavors are pursued to target ideal molecular sieves among diverse porous materials, over the past several decades, ideal molecular sieves for the separation and purification of light hydrocarbons are rarely realized. Herein, an ideal porous material, SIFSIX-14-Cu-i (also termed as UTSA-200), is reported with ultrafine tuning of pore size (3.4 Å) to effectively block ethylene (C 2 H 4 ) molecules but to take up a record-high amount of acetylene (C 2 H 2 , 58 cm 3 cm -3 under 0.01 bar and 298 K). The material therefore sets up new benchmarks for both the adsorption capacity and selectivity, and thus provides a record purification capacity for the removal of trace C 2 H 2 from C 2 H 4 with 1.18 mmol g -1 C 2 H 2 uptake capacity from a 1/99 C 2 H 2 /C 2 H 4 mixture to produce 99.9999% pure C 2 H 4 (much higher than the acceptable purity of 99.996% for polymer-grade C 2 H 4 ), as demonstrated by experimental breakthrough curves. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Donor-Acceptor Chromophores based on Acetylenic Scaffolds and Indenofluorenes

DEFF Research Database (Denmark)

Christensen, Mikkel Andreas

-valence salt). [BILLEDE UDELADT] In the third chapter the reactivity of chloroalkynes is explored. A number of chloroalkynes is prepared and subjected to palladium-catalyzed cross coupling with a terminal alkyne. The chloroalkynes turned out to couple very well using the same conditions as for the Sonogashira...... cross-coupling. The reactivity of chloroalkynes was compared to that of Sonogashira substrates and the chloroalkynes turned out to react as fast as an aryl iodide. Some of the couplings gave reductive homo-coupling of the chloroalkyne as a byproducts. This was avoided by using a large copper...

Crossed Molecular Beams and Quasiclassical Trajectory Surface Hopping Studies of the Multichannel Nonadiabatic O((3)P) + Ethylene Reaction at High Collision Energy.

Science.gov (United States)

Balucani, Nadia; Leonori, Francesca; Casavecchia, Piergiorgio; Fu, Bina; Bowman, Joel M

2015-12-17

The combustion relevant O((3)P) + C2H4 reaction stands out as a prototypical multichannel nonadiabatic reaction involving both triplet and singlet potential energy surfaces (PESs), which are strongly coupled. Crossed molecular beam (CMB) scattering experiments with universal soft electron ionization mass spectrometric detection have been used to characterize the dynamics of this reaction at the relatively high collision energy Ec of 13.7 kcal/mol, attained by crossing the reactant beams at an angle of 135°. This work is a full report of the data at the highest Ec investigated for this reaction. From laboratory product angular and velocity distribution measurements, angular and translational energy distributions in the center-of-mass system have been obtained for the five observed exothermic competing reaction channels leading to H + CH2CHO, H + CH3CO, CH3 + HCO, CH2 + H2CO, and H2 + CH2CO. The product branching ratios (BRs) have been derived. The elucidation of the reaction dynamics is assisted by synergic full-dimensional quasiclassical trajectory surface-hopping calculations of the reactive differential cross sections on coupled ab initio triplet/singlet PESs. This joint experimental/theoretical study extends and complements our previous combined CMB and theoretical work at the lower collision energy of 8.4 kcal/mol. The theoretically derived BRs and extent of intersystem crossing (ISC) are compared with experimental results. In particular, the predictions of the QCT results for the three main channels (those leading to vinoxy + H, methyl + HCO and methylene + H2CO formation) are compared directly with the experimental data in the laboratory frame. Good overall agreement is noted between theory and experiment, although some small, yet significant shortcomings of the theoretical differential cross section are noted. Both experiment and theory find almost an equal contribution from the triplet and singlet surfaces to the reaction, with a clear tendency of the

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

Science.gov (United States)

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

1988-01-01

1. The vanadium (V-) nitrogenase of Azobacter chroococcum transfers up to 7.4% of the electrons used in acetylene (C2H2) reduction for the formation of ethane (C2H6). The apparent Km for C2H2 (6 kPa) is the same for either ethylene (C2H4) or ethane (C2H6) formation and much higher than the reported Km values for C2H2 reduction to C2H4 by molybdenum (Mo-) nitrogenases. Reduction of C2H2 in 2H2O yields predominantly [cis-2H2]ethylene. 2. The ratio of electron flux yielding C2H6 to that yielding C2H4 (the C2H6/C2H4 ratio) is increased by raising the ratio of Fe protein to VFe protein and by increasing the assay temperature up to at least 40 degrees C. pH values above 7.5 decrease the C2H6/C2H4 ratio. 3. C2H4 and C2H6 formation from C2H2 by V-nitrogenase are not inhibited by H2. CO inhibits both processes much less strongly than it inhibits C2H4 formation from C2H2 with Mo-nitrogenase. 4. Although V-nitrogenase also catalyses the slow CO-sensitive reduction of C2H4 to C2H6, free C2H4 is not an intermediate in C2H6 formation from C2H2. 5. Propyne (CH3C identical to CH) is not reduced by the V-nitrogenase. 6. Some implications of these results for the mechanism of C2H6 formation by the V-nitrogenase are discussed. PMID:3162672

Level crossing analysis of chemically induced dynamic nuclear polarization: Towards a common description of liquid-state and solid-state cases

Energy Technology Data Exchange (ETDEWEB)

Sosnovsky, Denis V.; Ivanov, Konstantin L., E-mail: ivanov@tomo.nsc.ru [International Tomography Centre of SB RAS, Institutskaya 3a, 630090, Novosibirsk (Russian Federation); Novosibirsk State University, Pirogova 2, 630090, Novosibirsk (Russian Federation); Jeschke, Gunnar [Institut für Physikalische Chemie, ETH Zürich, Vladimir-Prelog-Weg 2, CH-8093 Zürich (Switzerland); Matysik, Jörg [Institut für Analytische Chemie, Universität Leipzig, Linnéstr. 3, D-04103 Leipzig (Germany); Vieth, Hans-Martin [International Tomography Centre of SB RAS, Institutskaya 3a, 630090, Novosibirsk (Russian Federation); Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, D-14195 Berlin (Germany)

2016-04-14

Chemically Induced Dynamic Nuclear Polarization (CIDNP) is an efficient method of creating non-equilibrium polarization of nuclear spins by using chemical reactions, which have radical pairs as intermediates. The CIDNP effect originates from (i) electron spin-selective recombination of radical pairs and (ii) the dependence of the inter-system crossing rate in radical pairs on the state of magnetic nuclei. The CIDNP effect can be investigated by using Nuclear Magnetic Resonance (NMR) methods. The gain from CIDNP is then two-fold: it allows one to obtain considerable amplification of NMR signals; in addition, it provides a very useful tool for investigating elusive radicals and radical pairs. While the mechanisms of the CIDNP effect in liquids are well established and understood, detailed analysis of solid-state CIDNP mechanisms still remains challenging; likewise a common theoretical frame for the description of CIDNP in both solids and liquids is missing. Difficulties in understanding the spin dynamics that lead to the CIDNP effect in the solid-state case are caused by the anisotropy of spin interactions, which increase the complexity of spin evolution. In this work, we propose to analyze CIDNP in terms of level crossing phenomena, namely, to attribute features in the CIDNP magnetic field dependence to Level Crossings (LCs) and Level Anti-Crossings (LACs) in a radical pair. This approach allows one to describe liquid-state CIDNP; the same holds for the solid-state case where anisotropic interactions play a significant role in CIDNP formation. In solids, features arise predominantly from LACs, since in most cases anisotropic couplings result in perturbations, which turn LCs into LACs. We have interpreted the CIDNP mechanisms in terms of the LC/LAC concept. This consideration allows one to find analytical expressions for a wide magnetic field range, where several different mechanisms are operative; furthermore, the LAC description gives a way to determine CIDNP sign

Effect of Fe2O3 and Binder on the Electrochemical Properties of Fe2O3/AB (Acetylene Black) Composite Electrodes

Science.gov (United States)

Anh, Trinh Tuan; Thuan, Vu Manh; Thang, Doan Ha; Hang, Bui Thi

2017-06-01

In an effort to find the best anode material for Fe/air batteries, a Fe2O3/AB (Acetylene Black) composite was prepared by dry-type ball milling using Fe2O3 nanoparticles and AB as the active and additive materials, respectively. The effects of various binders and Fe2O3 content on the electrochemical properties of Fe2O3/AB electrodes in alkaline solution were investigated. It was found that the content of Fe2O3 strongly affected the electrochemical behavior of Fe2O3/AB electrodes; with Fe2O3 nanopowder content reaching 70 wt.% for the electrode and showing improvement of the cyclability. When the electrode binder polytetrafluoroethylene (PTFE) was used, clear redox peaks were observed via cyclic voltammetry (CV), while polyvinylidene fluoride-containing electrodes provided CV curves with unobservable redox peaks. Increasing either binder content in the electrode showed a negative effect in terms of the cyclability of the Fe2O3/AB electrode.

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

International Nuclear Information System (INIS)

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

2005-01-01

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

Interactions between tetrathiafulvalene units in dimeric structures – the influence of cyclic cores

Directory of Open Access Journals (Sweden)

Huixin Jiang

2015-06-01

Full Text Available A selection of cyclic and acyclic acetylenic scaffolds bearing two tetrathiafulvalene (TTF units was prepared by different metal-catalyzed coupling reactions. The bridge separating the two TTF units was systematically changed from linearly conjugated ethyne, butadiyne and tetraethynylethene (trans-substituted units to a cross-conjugated tetraethynylethene unit, placed in either acyclic or cyclic arrangements. The cyclic structures correspond to so-called radiaannulenes having both endo- and exocyclic double bonds. Interactions between two redox-active TTF units in these molecules were investigated by cyclic voltammetry, UV–vis–NIR and EPR absorption spectroscopical methods of the electrochemically generated oxidized species. The electron-accepting properties of the acetylenic cores were also investigated electrochemically.

A novel approach for a C-11C bond formation: synthesis of 17α-([11C]prop-1-ynyl)-3-methoxy-3,17β-estradiol

International Nuclear Information System (INIS)

Wuest, F.; Zessin, J.

2002-01-01

A novel method for a 11 C-C bond formation was developed, employing a cross-coupling reaction between a terminal acetylene and [ 11 C]methyl iodide. The method was used for the synthesis of 17α-([ 11 C]prop-1-ynyl)-3-methoxy-3,17β-estadiol. (orig.)

Role of the reaction intermediates in determining PHIP (parahydrogen induced polarization) effect in the hydrogenation of acetylene dicarboxylic acid with the complex [Rh (dppb)]+ (dppb: 1,4-bis(diphenylphosphino)butane)

International Nuclear Information System (INIS)

Reineri, F.; Aime, S.; Gobetto, R.; Nervi, C.

2014-01-01

This study deals with the parahydrogenation of the symmetric substrate acetylene dicarboxylic acid catalyzed by a Rh(I) complex bearing the chelating diphosphine dppb (1,4-bis(diphenylphosphino)butane). The two magnetically equivalent protons of the product yield a hyperpolarized emission signal in the 1 H-NMR spectrum. Their polarization intensity varies upon changing the reaction solvent from methanol to acetone. A detailed analysis of the hydrogenation pathway is carried out by means of density functional theory calculations to assess the structure of hydrogenation intermediates and their stability in the two solvents. The observed polarization effects have been accounted on the basis of the obtained structures. Insights into the lifetime of a short-lived reaction intermediate are also obtained

Simultaneous voltammetric determination of 2-nitrophenol and 4-nitrophenol based on an acetylene black paste electrode modified with a graphene-chitosan composite

International Nuclear Information System (INIS)

Deng, Peihong; Xu, Zhifeng; Li, Junhua

2014-01-01

We describe a simple and sensitive voltammetric method for the simultaneous determination of 2-nitrophenol and 4-nitrophenol. It is based on the use of an acetylene black paste electrode modified with a graphene-chitosan composite film (denoted as Gr-Chit/ABPE). The reduction peak currents of 2-nitrophenol (at −252 mV) and of 4-nitrophenol (at −340 mV) in pH 1.0 solution increase significantly at the Gr-Chit/ABPE in comparison to a bare ABPE. Factors affecting sensitivity were optimized and a linear relationship is found between peak current and the concentrations of 2-nitrophenol (in the 0.4 μM to 80 μM range) and for 4-nitrophenol (in the 0.1 μM to 80 μM range). The detection limits (at an SNR of 3 and after a 30-s accumulation time) are 200 nM for 2-nitrophenol and 80 nM for 4-nitrophenol, respectively. The modified electrode was successfully applied to the direct and parallel determination of 2-nitrophenol and 4-nitrophenol in spiked water samples. (author)

Time-resolved photoelectron spectroscopy of nitrobenzene and its aldehydes

Science.gov (United States)

Schalk, Oliver; Townsend, Dave; Wolf, Thomas J. A.; Holland, David M. P.; Boguslavskiy, Andrey E.; Szöri, Milan; Stolow, Albert

2018-01-01

We report the first femtosecond time-resolved photoelectron spectroscopy study of 2-, 3- and 4-nitrobenzaldehyde (NBA) and nitrobenzene (NBE) in the gas phase upon excitation at 200 nm. In 3- and 4-NBA, the dynamics follow fast intersystem crossing within 1-2 picoseconds. In 2-NBA and NBE, the dynamics are faster (∼ 0.5 ps). 2-NBA undergoes hydrogen transfer similar to solution phase dynamics. NBE either releases NO2 in the excited state or converts internally back to the ground state. We discuss why these channels are suppressed in the other nitrobenzaldehydes.

Radiation Polymerization of Acetylene Hydrocarbons. Special Features; Particularites de la polymerisation radiochimique des hydrocarbures acetyleniques; Radiatsionnaya polimerizatsiya atsetilenovykh proizvodnykh; Particularidades de la radiopolimerizacion de los hidrocarburos acetilenicos

Energy Technology Data Exchange (ETDEWEB)

Barkalov, I. M.; Gol' danskij, V. I.; Go, Min' -Gao

1963-11-15

The synthesis and study of the properties of polymers with conjugated bond systems offers new and extremely promising prospects in the chemistry of high molecular compounds. A high degree of de-localization of p-electrons in the macromolecule is characteristic of such polymer systems. The decrease in the energy excited in the triplet state, just like the diminished ionization potential with large conjugated bonds, conditions the semiconductor and specific magnetic properties of such compounds. In addition, polymer systems with conjugated bonds have proved to be extremely effective stabilizers in the thermo- and photo-oxidation destruction of polymers. The radiation polymerization of acetylene derivatives offers one suitable method of obtaining such polymers and is the only one which ensures that the polymers obtained are free of contamination from initiators at low temperatures. The kinetics of the radiation polymerization of ethynyl benzene and other acetylene derivatives have a number of features typical of ion polymerization quite rare in radical polymerization (speed of polymerization linearly proportional to speed of initiation: very low activation energy; no oxygen inhibition). Nevertheless this polymerization is obviously radical. We reached that conclusion on the basis of a study of polymerization initiation for acetylene hydrocarbons by typical radical initiators - benzoyl peroxide and the dinitrile of azoisobutyric acid. They investigated the kinetic features and mechanism of peroxide decomposition in the presence of acetylene hydrocarbons (e.g. ethynyl benzene, deutero-ethynyl benzene and phenylpropyne). The kinetics of radiation co-polymerization of ethynyl benzene with different vinyl monomers and the composition of copolymers in different initial mixtures were also studied. These data and the results of a study of the kinetics of inhibited ethynyl benzene polymerization (benzoquinone initiator) indicate a small reactivity capacity of the ethynyl

Role of Fluid-Dynamics in Soot Formation and Microstructure in Acetylene-Air Laminar Diffusion Flames

Directory of Open Access Journals (Sweden)

Praveen Pandey

2015-03-01

Full Text Available Residence time and thermo-chemical environment are important factors in the soot-formation process in flames. Studies have revealed that flow-dynamics plays a dominant role in soot formation process. For understanding the effect of flow dynamics on soot formation and physical structure of the soot formed in different combustion environments two types of laminar diffusion flames of Acetylene and air, a normal diffusion flame (NDF and an inverse diffusion flame (IDF have been investigated. The fuel and air supply in the reaction zone in two flame types were kept constant but the interchange of relative position of fuel and air altered the burner exit Reynolds and Froude numbers of gases, fuel/air velocity ratio and flame shape. Soot samples were collected using thermophoretic sampling on transmission electron microscope (TEM grids at different flame heights and were analyzed off-line in a Transmission Electron Microscope. Soot primary particle size, soot aggregate size and soot volume fraction were measured using an image analysis software. In NDF the maximum flame temperature was about 1525 K and 1230 K for IDF. The soot primary particles are distinctly smaller in size in IDF (between 19 – 26 nm compared to NDF (between 29–34 nm. Both NDF and IDF show chainlike branched structure of soot agglomerate with soot particles of a nearly spherical shape. The average number of soot primary particles per aggregate in NDF was in the range of 24 to 40 and in IDF it varied between 16 to 24. Soot volume fraction was between 0.6 to 1.5 ppm in NDF where as it was less than 0.2 ppm in IDF. The change in sooting characteristics of the two flame types is attributed to changed fuel/air velocity ratio, entrainment of gas molecules and thermophoresis on soot particles.

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

Directory of Open Access Journals (Sweden)

V. P. Kanawade

2011-10-01

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

Carbon Domains on MoS2/TiO2 System via Catalytic Acetylene Oligomerization: Synthesis, Structure, and Surface Properties

Directory of Open Access Journals (Sweden)

Sara Cravanzola

2017-11-01

Full Text Available Carbon domains have been obtained at the surface of a MoS2/TiO2 (Evonik, P25 system via oligomerization and cyclotrimerization reactions involved in the interaction of the photoactive material with acetylene. Firstly, MoS2 nanosheets have been synthesized at the surface of TiO2, via sulfidation of a molybdenum oxide precursor with H2S (bottom-up method. Secondly, the morphology and the structure, the optical and the vibrational properties of the obtained materials, for each step of the synthesis procedure, have been investigated by microscopy and spectroscopy methods. In particular, transmission electron microscopy images provide a simple tool to highlight the effectiveness of the sulfidation process, thus showing 1L, 2L, and stacked MoS2 nanosheets anchored to the surface of TiO2 nanoparticles. Lastly, in-situ FTIR spectroscopy investigation gives insights into the nature of the oligomerized species, showing that the formation of both polyenic and aromatic systems can be taken into account, being their formation promoted by both Ti and Mo catalytic sites. This finding gives an opportunity for the assembly of extended polyenic, polyaromatic, or mixed domains firmly attached at the surface of photoactive materials. The presented approach, somehow different from the carbon adding or doping processes of TiO2, is of potential interest for the advanced green chemistry and energy conversion/transport applications.

Enhanced intersystem crossing via a high energy charge transfer state in a perylenediimide-perylenemonoimide dyad

NARCIS (Netherlands)

Veldman, D.; Chopin-Cado, S.M.A; Meskers, S.C.J.; Janssen, R.A.J.

2008-01-01

The electronic relaxation processes of a photoexcited linear perylenediimide-perylenemonoimide (PDI-PMI) acceptor-donor dyad were studied. PDI-PMI serves as a model compound for donor-acceptor systems in photovoltaic devices and has been designed to have a high-energy PDI--PMI + charge transfer (CT)

Інтелектуальна автоматизована система контролю знань студентів вищих навчальних закладів.

Directory of Open Access Journals (Sweden)

I. Katerynchuk

2009-11-01

Full Text Available Conception of construction of the intellectual automated systems of evaluation of knowledge’s. The offered system foresees the presence of such subsystems: functional subsystem of transformation of information from external representation in intersystem information; subsystems of transformation from intersystem presentation of information in external information; subsystems of representation of knowledge’s, which includes the block of forming of results and system of artificial intelligence.

Selective coupling reaction between 2,6-diiodoanisoles and terminal alkynes catalyzed by Pd(PPh32Cl2 and CuI

Directory of Open Access Journals (Sweden)

Allan F. C. Rossini

2012-06-01

Full Text Available The cross-coupling reaction between aryl halides and terminal alkynes, catalyzed by palladium complexes and copper (I salts, consists in an efficient synthetic tool for the formation of C-C bonds, resulting in disubstituted acetylenic compounds. Accordingly, in this work we present our preliminary results involving the selective cross-coupling reaction between 2,6-diiodoanisoles and terminal alkynes, catalyzed by Pd(PPh32Cl2 and CuI, in the formation of 2-iodo-alkynylanisoles (scheme 1.

QM/MM studies on the excited-state relaxation mechanism of a semisynthetic dTPT3 base.

Science.gov (United States)

Guo, Wei-Wei; Zhang, Teng-Shuo; Fang, Wei-Hai; Cui, Ganglong

2018-02-14

Semisynthetic alphabets can potentially increase the genetic information stored in DNA through the formation of unusual base pairs. Recent experiments have shown that near-visible-light irradiation of the dTPT3 chromophore could lead to the formation of a reactive triplet state and of singlet oxygen in high quantum yields. However, the detailed excited-state relaxation paths that populate the lowest triplet state are unclear. Herein, we have for the first time employed the QM(MS-CASPT2//CASSCF)/MM method to explore the spectroscopic properties and excited-state relaxation mechanism of the aqueous dTPT3 chromophore. On the basis of the results, we have found that (1) the S 2 ( 1 ππ*) state of dTPT3 is the initially populated excited singlet state upon near-visible light irradiation; and (2) there are two efficient relaxation pathways to populate the lowest triplet state, i.e. T 1 ( 3 ππ*). In the first one, the S 2 ( 1 ππ*) system first decays to the S 1 ( 1 nπ*) state near the S 2 /S 1 conical intersection, which is followed by an efficient S 1 → T 1 intersystem crossing process at the S 1 /T 1 crossing point; in the second one, an efficient S 2 → T 2 intersystem crossing takes place first, and then, the T 2 ( 3 nπ*) system hops to the T 1 ( 3 ππ*) state through an internal conversion process at the T 2 /T 1 conical intersection. Moreover, an S 2 /S 1 /T 2 intersection region is found to play a vital role in the excited-state relaxation. These new mechanistic insights help in understanding the photophysics and photochemistry of unusual base pairs.

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

Science.gov (United States)

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.

Manipulating charge transfer excited state relaxation and spin crossover in iron coordination complexes with ligand substitution

DEFF Research Database (Denmark)

Zhang, Wenkai; Kjær, Kasper Skov; Alonso-Mori, Roberto

2017-01-01

iron complexes with four cyanide (CN-;) ligands and one 2,2′-bipyridine (bpy) ligand. This enables MLCT excited state and metal-centered excited state energies to be manipulated with partial independence and provides a path to suppressing spin crossover. We have combined X-ray Free-Electron Laser (XFEL...... state lifetime of iron based complexes due to spin crossover-the extremely fast intersystem crossing and internal conversion to high spin metal-centered excited states. We revitalize a 30 year old synthetic strategy for extending the MLCT excited state lifetimes of iron complexes by making mixed ligand...

Low-pressure appraoch to the formation and study of exciplex systems

International Nuclear Information System (INIS)

Sanzone, G.

1977-11-01

Studies on the formation and properties of new materials for high-energy, gas-phase lasers are described. Attention is directed mainly to systems having bound excited states but unbound ground states. An important class of such excimer/exciplex systems has a van der Waals dimer/oligomer as its ground state. This research attempts to probe the relative rates of electron pumping of excited-state manifolds and the preferentially pumped vibronic states within each manifold. Reactive quenching of emission, resonant self-absorption of laser emissions, and collision- and noncollision-induced intersystem crossing are also considered. 11 figures, 2 tables

High-Efficiency Iron Photosensitizer Explained with Quantum Wavepacket Dynamics

DEFF Research Database (Denmark)

Pápai, Mátyás Imre; Vankó, György; Rozgonyi, Tamas

2016-01-01

designed to destabilize the MC states. Using first-principles quantum nuclear wavepacket simulations we achieve a detailed understanding of the photoexcited decay mechanism, demonstrating that it is dominated by an ultrafast intersystem crossing from 1MLCT–3MLCT proceeded by slower kinetics associated...... with the conversion into the 3MC states. The slowest component of the 3MLCT decay, important in the context of photosensitizers, is much longer than related Fe(II) complexes because the population transfer to the 3MC states occurs in a region of the potential where the energy gap between the 3MLCT and 3MC states...

Organic light-emitting diodes with a spacer enhanced exciplex emission

Science.gov (United States)

Yan, Fei; Chen, Rui; Sun, Handong; Wei Sun, Xiao

2014-04-01

By introducing a spacer molecule into the blended exciplex emissive layer, the performance of the bulk heterojunction exciplex organic light-emitting diodes (OLEDs) was improved dramatically; the maximum luminous efficiency was enhanced by about 22% from 7.9 cd/A to 9.7 cd/A, and the luminous efficiency drop was reduced by 28% at 400 mA/cm2. Besides the suppressed annihilation of exciton, the time-resolved photoluminescence measurements indicated that the spacer enhanced the delayed fluorescence through increasing the backward intersystem crossing rate from the triplet to singlet exciplex state. This method is useful for developing high performance exciplex OLEDs.

Third-order nonlinear optical properties of open-shell supermolecular systems composed of acetylene linked phenalenyl radicals.

Science.gov (United States)

Nakano, Masayoshi; Kishi, Ryohei; Yoneda, Kyohei; Inoue, Yudai; Inui, Tomoya; Shigeta, Yasuteru; Kubo, Takashi; Champagne, Benoît

2011-08-11

The third-order nonlinear optical (NLO) properties, at the molecular level, the static second hyperpolarizabilities, γ, of supermolecular systems composed of phenalenyl and pyrene rings linked by acetylene units are investigated by employing the long-range corrected spin-unrestricted density functional theory, LC-UBLYP, method. The phenalenyl based superethylene, superallyl, and superbutadiene in their lowest spin states have intermediate diradical characters and exhibit larger γ values than the closed-shell pyrene based superpolyene systems. The introduction of a positive charge into the phenalenyl based superallyl radical changes the sign of γ and enhances its amplitude by a factor of 35. Although such sign inversion is also observed in the allyl radical and cation systems in their ground state equilibrium geometries, the relative amplitude of γ is much different, that is, |γ(regular allyl cation)/γ(regular allyl radical)| = 0.61 versus |γ(phenalenyl based superallyl cation)/γ(phenalenyl based superallyl radical)| = 35. In contrast, the model ethylene, allyl radical/cation, and butadiene systems with stretched carbon-carbon bond lengths (2.0 Å), having intermediate diradical characters, exhibit similar γ features to those of the phenalenyl based superpolyene systems. This exemplifies that the size dependence of γ as well as its sign change by introducing a positive charge on the phenalenyl based superpolyene systems originate from their intermediate diradical characters. In addition, the change from the lowest to the highest π-electron spin states significantly reduces the γ amplitudes of the neutral phenalenyl based superpolyene systems. For phenalenyl based superallyl cation, the sign inversion of γ (from negative to positive) is observed upon switching between the singlet and triplet states, which is predicted to be associated with a modification of the balance between the positive and negative contributions to γ. The present study paves the way

Total synthesis of Ivorenolide A following a base-induced elimination protocol.

Science.gov (United States)

Mohapatra, Debendra K; Umamaheshwar, Gonela; Rao, R Nageshwar; Rao, T Srinivasa; R, Sudheer Kumar; Yadav, Jhillu S

2015-02-20

A concise and stereocontrolled first total synthesis of Ivorenolide A (1) is reported in 16 longest linear steps with a 13.4% overall yield starting from (+)-diethyl tartrate (DET). Key features are base-induced elimination protocol for the construction of chiral propargyl alcohols in both fragments, Pd-catalyzed cross-coupling of terminal acetylenes, and Shiina's 2-methyl-6-nitrobezoic anhydride (MNBA) mediated macrolactonization.

Visible-Light-Mediated Excited State Relaxation in Semi-Synthetic Genetic Alphabet: d5SICS and dNaM.

Science.gov (United States)

Bhattacharyya, Kalishankar; Datta, Ayan

2017-08-25

The excited state dynamics of an unnatural base pair (UBP) d5SICS/dNaM were investigated by accurate ab-initio calculations. Time-dependent density functional and high-level multireference calculations (MS-CASPT2) were performed to elucidate the excitation of this UBP and its excited state relaxation mechanism. After excitation to the bright state S 2 (ππ*), it decays to the S 1 state and then undergoes efficient intersystem crossing to the triplet manifold. The presence of sulfur atom in d5SICS leads to strong spin-orbit coupling (SOC) and a small energy gap that facilitates intersystem crossing from S 1 (n s π*) to T 2 (ππ*) followed by internal conversion to T 1 state. Similarly in dNaM, the deactivation pathway follows analogous trends. CASPT2 calculations suggest that the S 1 (ππ*) state is a dark state below the accessible S 2 (ππ*) bright state. During the ultrafast deactivation, it exhibits bond length inversion. From S 1 state, significant SOC leads the population transfer to T 3 due to a smaller energy gap. Henceforth, fast internal conversion occurs from T 3 to T 2 followed by T 1 . From time-dependent trajectory surface hopping dynamics, it is found that excited state relaxation occurs on a sub-picosecond timescale in d5SICS and dNaM. Our findings strongly suggest that there is enough energy available in triplet state of UBP to generate reactive oxygen species and induce phototoxicity with respect to cellular DNA. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Optoelectronic properties of CC2TA towards a good TADF material

Science.gov (United States)

Mishra, Ashok Kumar

2018-05-01

2,4-bis{f3-(9H-carbazol-9-yl)-9H-carbazol-9-yl}-6-phenyl-1,3,5-triazine (CC2TA) is a triazine derivatives in which the acceptor phenyltriazine unit is used as the central skeleton and donor bicarbazole units are bonded to both ends of the skeleton. Molecular orbital calculations exhibit that the HOMO and LUMO are locally allocated chiefly in the bicarbazole and phenyltriazine units, respectively. There are a class of organic molecules and polymers which exhibit semiconductor behavior because of nearly free conjugate π-electrons. Hopping of these electrons in molecules forms different excited singlet and triplet states named as excitons. Some of these organic molecules can be set to emit photons by triplet-singlet excitonic transition via a process called Thermally Activated Delayed Fluorescence (TADF) which is exploited for designing the Organic Light Emitting diode (OLED.) CC2TA is one of these reported noble metal-free TADF molecules which offers unique opto electronic properties arising from the reverse intersystem crossing between the lowest singlet (S) and triplet (T) excited states. Its ability to harvest triplet excitons for fluorescence through facilitated reverse intersystem crossing (T→S) could directly impact their properties and performances, which is attractive for a wide variety of low-cost optoelectronic device. In the present study, the CC2TA compounds have been taken up for the investigation of various optoelectronic properties including the thermally activated delayed fluorescence (TADF) by using the Koopmans Method and Density Functional Theory. The present study discusses the utility of the CC2TA organic semiconductor as a suitable TADF material essential for developing an efficient Organic Light Emitting Diode (OLED).

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

Science.gov (United States)

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.

Photophysics of aggregated 9-methylthiacarbocyanine bound to polyanions

Science.gov (United States)

Chibisov, Alexander K.; Görner, Helmut

2002-05-01

The photophysical properties of 3,3 '-diethyl-9-methylthiacarbocyanine (DTC) were studied in the presence of polystyrene sulfonate (PSS), polyacrylic acid (PAA) and polymethacrylic acid (PMA). The absorption spectra reflect a monomer/dimer equilibrium in neat aqueous solution and a shift towards bound H-aggregates, bound dimers and bound monomers on increasing the ratio of polyanion residue to dye concentrations ( r). These equilibria also determine the photodeactivation modes of DTC. The fluorescence intensity is reduced, when dimers and aggregates are present and strongly enhanced for low dye loading ( r=10 4). In contrast, the quantum yield of intersystem crossing is enhanced for bound dimers ( r=10 3).

The impact of Au doping on the charge carrier dynamics at the interfaces between cationic porphyrin and silver nanoclusters

KAUST Repository

Almansaf, Abdulkhaleq A.

2017-02-04

We explore the impact of Au doping on the charge transfer dynamics between the positively charged porphyrin (TMPyP) and negatively charged silver nanoclusters (Ag29 NCs). Our transient absorption (TA) spectroscopic results demonstrate that the interfacial charge transfer, the intersystem crossing and the triplet state lifetime of porphyrin can be tuned by the doping of Au atoms in Ag29 NCs. Additionally, we found that the electrostatic interaction between the negative charge of the cluster and the positive charge on the TMPyP is the driving force that brings them close to each other for complex formation and subsequently facilitates the transfer process.

Low-pressure approach to the formation and study of exciplex systems

International Nuclear Information System (INIS)

Sanzone, G.

1977-10-01

Studies on the formation and properties of new materials for high-energy, gas-phase lasers are described. Attention is directed mainly to systems having bound excited states but unbound ground states. An important class of such excimer/exciplex systems has a van der Waals dimer/oligomer as its ground state. This research attempts to probe the relative rates of electron pumping of excited-state manifolds and the preferentially pumped vibronic states within each manifold. Reactive quenching of emission, resonant self-absorption of laser emissions, and collision- and noncollision-induced intersystem crossing are also considered. Lists of personnel and facilities are included. 8 figures, 2 tables

Large magneto-conductance and magneto-electroluminescence in exciplex-based organic light-emitting diodes at room temperature

Science.gov (United States)

Ling, Yongzhou; Lei, Yanlian; Zhang, Qiaoming; Chen, Lixiang; Song, Qunliang; Xiong, Zuhong

2015-11-01

In this work, we report on large magneto-conductance (MC) over 60% and magneto-electroluminescence (MEL) as high as 112% at room temperature in an exciplex-based organic light-emitting diode (OLED) with efficient reverse intersystem crossing (ISC). The large MC and MEL are individually confirmed by the current density-voltage characteristics and the electroluminescence spectra under various magnetic fields. We proposed that this type of magnetic field effect (MFE) is governed by the field-modulated reverse ISC between the singlet and triplet exciplex. The temperature-dependent MFEs reveal that the small activation energy of reverse ISC accounts for the large MFEs in the present exciplex-based OLEDs.

Design of ortho-Substituted Donor-Acceptor Molecules as Highly Efficient Green Thermally Activated Delayed Fluorescent Emitters

Science.gov (United States)

Cha, Jae-Ryung; Gong, Myoung-Seon; Lee, Tak Jae; Ha, Tae Hoon; Lee, Chil Won

2018-04-01

The ortho-substituted donor-acceptor molecules 2-(4,6-diphenyl-1, 3, 5-triazin-2-yl)- N,Ndiphenylaniline (DPA- o-Trz) and 2-(4,6-diphenyl-1, 3, 5-triazine-2-yl)- N,N-di- p-tolylaniline (MPA- o-Trz) were designed, synthesized, and found to exhibit green fluorescence characteristics. Notably, the singlet-triplet energy gap was less than 0.1 eV, indicating that reverse intersystem crossing gave rise to thermally activated delayed fluorescence (TADF). The organic light-emitting device performance of MPA- o-Trz showed a high external quantum efficiency of 16.3% and good color stability from 0.1 cd/m2 to 5000 cd/m2.

The impact of Au doping on the charge carrier dynamics at the interfaces between cationic porphyrin and silver nanoclusters

KAUST Repository

Almansaf, Abdulkhaleq A.; Parida, Manas R.; Besong, Tabot M.D.; Maity, Partha; Bootharaju, Megalamane Siddaramappa; Bakr, Osman; Mohammed, Omar F.

2017-01-01

We explore the impact of Au doping on the charge transfer dynamics between the positively charged porphyrin (TMPyP) and negatively charged silver nanoclusters (Ag29 NCs). Our transient absorption (TA) spectroscopic results demonstrate that the interfacial charge transfer, the intersystem crossing and the triplet state lifetime of porphyrin can be tuned by the doping of Au atoms in Ag29 NCs. Additionally, we found that the electrostatic interaction between the negative charge of the cluster and the positive charge on the TMPyP is the driving force that brings them close to each other for complex formation and subsequently facilitates the transfer process.

Dynamical propagation of nanosecond pulses in Naphthalocyanines and Phthalocyanines

Energy Technology Data Exchange (ETDEWEB)

Miao, Quan, E-mail: qmiao2013@yahoo.com [College of Electronics, Communication and Physics, Shandong University of Science and Technology, Qingdao 266590, Shandong (China); Liang, Min; Liu, Qixin [College of Electronics, Communication and Physics, Shandong University of Science and Technology, Qingdao 266590, Shandong (China); College of Electrical Engineering and Automation, Shandong University of Science and Technology, Qingdao 266590, Shandong (China); Wang, Jing-Jing [College of Electronics, Communication and Physics, Shandong University of Science and Technology, Qingdao 266590, Shandong (China); Sun, Erping; Xu, Yan [College of Electronics, Communication and Physics, Shandong University of Science and Technology, Qingdao 266590, Shandong (China); College of Electrical Engineering and Automation, Shandong University of Science and Technology, Qingdao 266590, Shandong (China)

2016-11-30

Highlights: • We study the dynamical processes of nanoseconds lasers in Naphthalocyanines and Phthalocyanines. • We provide theoretical evidences of the main mechanism of optical power limiting. • The central metals play more important roles in the dynamical processes. • The main reason is the central metals enhance the spin–orbit coupling. - Abstract: Dynamical propagation and optical limiting of nanosecond pulses in peripherally substituted Naphthalocyanines (Npcs) and Phthalocyanines (Pcs) with central metals gallium and indium were theoretically studied using paraxial field and rate equations. The results demonstrated that both Npcs and Pcs have good optical limiting performances, and Npc with heavier central mental indium shows better optical limiting properities due to the stronger reverse saturable absorption, which is mainly strengthened by the larger one-photo absorption cross section of excited state and the faster intersystem crossing rate.

Intersystem Communications between Virtualized Agents

Directory of Open Access Journals (Sweden)

Ovidiu Gherman

2015-12-01

Full Text Available This paper presents an analysis of the main problems associated with data and command communications in virtualized environments. This aspect is very important in determining the performance and functionality of such systems. In this regard, an effective data communication brings obvious advantages for volume data transfer (images, backups, checkpointing information. If we are to refer to resource administration overhead, we can notice that direct connectivity - although important - is not the only factor which defines the performance of data transfers; resource administration, resource loading and load balancing are also extremely important. Furthermore, a command structure is very important to expand the capabilities of underlying software (platform. Even if a platform supports various functions, the system should have the capability to discover, asses, command, deploy and monitor various dynamic virtualized resources in order to correctly (and efficiently use those resources, either via predefined protocols or via a set of mission-defined parameters that are transferred and intelligently parsed and processed.

Are there differences in the catalytic activity per unit enzyme of recombinantly expressed and human liver microsomal cytochrome P450 2C9? A systematic investigation into inter-system extrapolation factors.

Science.gov (United States)

Crewe, H K; Barter, Z E; Yeo, K Rowland; Rostami-Hodjegan, A

2011-09-01

The 'relative activity factor' (RAF) compares the activity per unit of microsomal protein in recombinantly expressed cytochrome P450 enzymes (rhCYP) and human liver without separating the potential sources of variation (i.e. abundance of enzyme per mg of protein or variation of activity per unit enzyme). The dimensionless 'inter-system extrapolation factor' (ISEF) dissects differences in activity from those in CYP abundance. Detailed protocols for the determination of this scalar, which is used in population in vitro-in vivo extrapolation (IVIVE), are currently lacking. The present study determined an ISEF for CYP2C9 and, for the first time, systematically evaluated the effects of probe substrate, cytochrome b5 and methods for assessing the intrinsic clearance (CL(int) ). Values of ISEF for S-warfarin, tolbutamide and diclofenac were 0.75 ± 0.18, 0.57 ± 0.07 and 0.37 ± 0.07, respectively, using CL(int) values derived from the kinetic values V(max) and K(m) of metabolite formation in rhCYP2C9 + reductase + b5 BD Supersomes™. The ISEF values obtained using rhCYP2C9 + reductase BD Supersomes™ were more variable, with values of 7.16 ± 1.25, 0.89 ± 0.52 and 0.50 ± 0.05 for S-warfarin, tolbutamide and diclofenac, respectively. Although the ISEF values obtained from rhCYP2C9 + reductase + b5 for the three probe substrates were statistically different (p system, with the intrinsic clearance calculated from full kinetic data is recommended for generation of the CYP2C9 ISEF. Furthermore, as ISEFs have been found to be sensitive to differences in accessory proteins, rhCYP system specific ISEFs are recommended. Copyright © 2011 John Wiley & Sons, Ltd.

1,4-diphenylbutadiyne as a potential tritium getter

International Nuclear Information System (INIS)

Miller, H.H.; Bissell, E.E.; Tsugawa, R.T.; Souers, P.C.

1980-01-01

Research on the acetylene compound 1,4-diphenylbutadiyne is an effort to develop an air-operative tritium gas scavenger. T 2 adds to the acetylene bond of the organic in the presence of a metal catalyst. The catalyst also stimulates the oxidation reaction as well. The butadiyne compound has shown good reaction efficiency at 300 ppM T 2 in static dry air. At this concentration 75% of the scavenged tritium was in the organic. This work has expanded to the investigation of liquid acetylenes, metal acetylene complexes, organometallics and acetylene based alcohols. The best of these compounds has gettered 100% of 10 to 500 ppM T 2 for both static and dynamic air flow conditions

Synthesis of perdeuterophenylacetylene

International Nuclear Information System (INIS)

Kunjappu, J.T.; Prasad, C.V.C.; Gupta, H.M.; Rao, M.H.; Rao, K.N.

1986-01-01

The relative merits of feasible methods to synthesise phenyl acetylene-d 6 have been evaluated and a convenient path has been adopted for obtaining it in good isotopic purity. Detailed procedures for preparing the intermediate deuterated compounds like benzene-d 6 bromobenzene-d 5 , α-phenyl-d 5 -ethanol, phenyl-d 5 -ethylene, styrene dibromide-d 5 , phenyl-d 5 -acetylene, phenyl acetylene-d 6 and deuterosulphuric acid have been outlined. The infrared spectra of these deutero compounds in carbon tetrachloride solution scanned in sodium chloride liquid cells have been presented and they were used in quantitatively estimating their deuterium content. This compound is of potential use as a target material in nuclear fusion studies. (author)

The Synthesis and Photophysical Characterization of Porphyrin Photoactive Materials for Use as Sensitizers in Organic Photovoltaics and Photodynamic Therapy

Science.gov (United States)

Marin, Dawn Marie

Solar energy conversion and photodynamic therapy (PDT) are very different applications. However, both utilize very similar photoactive molecules called porphyrins. Porphyrins are structural analogs of chlorophyll and also function as prosthetic groups in some biological enzymes. Understanding the structure/function relationship of these molecules is crucial for enhancing the energy generation efficiency of molecular solar cells and improving chemotherapeutic activity in PDT. In this dissertation, two approaches were applied with the goal of increasing the efficiency of molecular semiconductors for these applications: the heavy atom effect and donor-acceptor molecules. We enhanced the efficiency of triplet excited state formation and singlet oxygen generation for porphyrin sensitizers using the heavy atom effect. The heavy atom effect induces spin-orbit coupling to promote intersystem crossing into the triplet state. In this study, a carbomethoxyphenyl substituent was replaced with either a bromophenyl or an iodophenyl substituent on 5,10,15,20-tetrakis(4-carbomethoxyphenyl)porphyrin. The longer lifetimes obtained from the increase in the triplet excited state allow for longer exciton diffusion lengths and lower recombination rates in photovoltaics. Also, the enhanced intersystem crossing is beneficial for photodynamic therapy because it increases singlet oxygen generation, which destroys tumor cells. Optimizing photovoltaic performance and PDT efficacy can also be accomplished with donor-acceptor molecules because they have extended electronic pi bond delocalization across the molecule, which causes the molecule to absorb longer wavelengths of light. Donor-acceptor molecules should produce photovoltaic devices that absorb more of the solar spectrum and produce sensitizers that absorb wavelengths of light that can penetrate through tissues. Donor-acceptor molecules were synthesized using 5,15-bis(4-carbomethoxyphenyl)porphyrin as the acceptor and thiazolo[5,4-d

Mechanistic photodecarboxylation of pyruvic acid: Excited-state proton transfer and three-state intersection

Science.gov (United States)

Chang, Xue-Ping; Fang, Qiu; Cui, Ganglong

2014-10-01

Photodissociation dynamics of pyruvic acid experimentally differs from that of commonly known ketones. We have employed the complete active space self-consistent field and its multi-state second-order perturbation methods to study its photodissociation mechanism in the S0, T1, and S1 states. We have uncovered four nonadiabatic photodecarboxylation paths. (i) The S1 system relaxes via an excited-state intramolecular proton transfer (ESIPT) to a hydrogen-transferred tautomer, near which an S1/S0 conical intersection funnels the S1 to S0 state. Then, some trajectories continue completing the decarboxylation reaction in the S0 state; the remaining trajectories via a reverse hydrogen transfer return to the S0 minimum, from which a thermal decarboxylation reaction occurs. (ii) Due to a small S1 -T1 energy gap and a large S1/T1 spin-orbit coupling, an efficient S1 → T1 intersystem crossing process happens again near this S1/S0 conical intersection. When decaying to T1 state, a direct photodecarboxylation proceeds. (iii) Prior to ESIPT, the S1 system first decays to the T1 state via an S1 → T1 intersystem crossing; then, the T1 system evolves to a hydrogen-transferred tautomer. Therefrom, an adiabatic T1 decarboxylation takes place due to a small barrier of 7.7 kcal/mol. (iv) Besides the aforementioned T1 ESIPT process, there also exists a comparable Norrish type I reaction in the T1 state, which forms the ground-state products of CH3CO and COOH. Finally, we have found that ESIPT plays an important role. It closes the S1-T1 and S1-S0 energy gaps, effecting an S1/T1/S0 three-state intersection region, and mediating nonadiabatic photodecarboxylation reactions of pyruvic acid.

Polymer Soft-Landing Isolation of Acetylene on Polystyrene and Poly(vinylpyridine): A Novel Approach to Probing Hydrogen Bonding in Polymers.

Science.gov (United States)

Li, Yike; Samet, Cindy

2015-09-17

Hydrogen-bonded complexes of acetylene (Ac) with the polymers polystyrene (PS), poly(4-vinylpyridine) (P4VP), and poly(2-vinylpyridine) (P2VP) have been characterized for the first time at 16 K in a "polymer soft-landing isolation" experiment which is being pioneered in our research laboratory. In particular, changes in vibrational modes of Ac provide ample evidence for hydrogen-bonded complexes between Ac and the phenyl groups of PS or the pyridyl groups of P4VP and P2VP. With PS, the proton on the top Ac molecule of the classic T-shaped Ac dimer interacts with the π cloud of the benzene (Bz) ring to form a C-H---π interaction, while the π cloud of the lower Ac forms a second C-H---π interaction with a proton on the Bz ring. An analogous (ring)1-(Ac)2 double interaction occurs between an Ac dimer and the pyridine (Pyr) rings on both P2VP and P4VP, yielding a C-H---N and C-H---π interaction. With P4VP and P2VP a second bridged (ring)2-(Ac)2 product is formed, with the Ac dimer forming nearly collinear C-H---N hydrogen bonds to adjacent Pyr rings. On P2VP this bridged product is the only one after extensive annealing. These complexes in which Ac acts as both proton donor and acceptor have not previously been observed in conventional matrix isolation experiments. This study is the second from our laboratory employing this method, which represents a slight modification of the traditional matrix isolation technique.

Comparative study of the monomer grafting: ethylene, acetylene, 1,3-butadiene and estyrene in the matrix of recycled polytetrafluoroethylene (PTFE); Estudo comparativo da enxertia dos monomeros: etileno, acetileno, 1,3-butadieno e estireno na matriz de politetrafluoroetileno (PTFE) reciclado

Energy Technology Data Exchange (ETDEWEB)

Ikari, Carolina T.; Rosner, Gerhardyne O.; Oliveira, Ana C.F. [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil). Centro de Quimica e Meio Ambiente (CQMA); Faculdades Oswaldo Cruz, Sao Paulo, SP (Brazil); Ferreto, Helio F.R.; Lima, Luiz F.C.P.; Lugao, Ademar B., E-mail: hferreto@ipen.b [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil). Centro de Quimica e Meio Ambiente (CQMA); Moreira, Otavio M. [Faculdades Oswaldo Cruz, Sao Paulo, SP (Brazil)

2009-07-01

In this study it is used the recycled polytetrafluoroethylene (PTFE), that with the gamma radiation under inert atmosphere or in presence of air, it is obtained free radicals and a posterior the monomer grafting (ethylene, acetylene, styrene or 1.3 butadiene), obtaining the copolymer polytetrafluoroethylene-g-monomer. It is studied the obtention of the polymer by two methods: by direct way, via grafting, where the polymer is irradiated in presence of monomer, and via grafting when the polymer is irradiated in absence of monomer and under inert or air. The characterization of the copolymer was performed by the techniques of infrared region absorption spectroscopy with Fourier transformation (FTIR), thermogravimetric (TGA) and derivative thermogravimetry (DTG), and percentage of mass grafting (DOG)

Are Nonadiabatic Reaction Dynamics the Key to Novel Organosilicon Molecules? The Silicon (Si(3P))-Dimethylacetylene (C4H6(X1A1g)) System as a Case Study.

Science.gov (United States)

Thomas, Aaron M; Dangi, Beni B; Yang, Tao; Kaiser, Ralf I; Lin, Lin; Chou, Tzu-Jung; Chang, Agnes H H

2018-06-06

The bimolecular gas phase reaction of ground-state silicon (Si; 3 P) with dimethylacetylene (C 4 H 6 ; X 1 A 1g ) was investigated under single collision conditions in a crossed molecular beams machine. Merged with electronic structure calculations, the data propose nonadiabatic reaction dynamics leading to the formation of singlet SiC 4 H 4 isomer(s) and molecular hydrogen (H 2 ) via indirect scattering dynamics along with intersystem crossing (ISC) from the triplet to the singlet surface. The reaction may lead to distinct energetically accessible singlet SiC 4 H 4 isomers ( 1 p8- 1 p24) in overall exoergic reaction(s) (-107 -20 +12 kJ mol -1 ). All feasible reaction products are either cyclic, carry carbene analogous silylene moieties, or carry C-Si-H or C-Si-C bonds that would require extensive isomerization from the initial collision complex(es) to the fragmenting singlet intermediate(s). The present study demonstrates the first successful crossed beams study of an exoergic reaction channel arising from bimolecular collisions of silicon, Si( 3 P), with a hydrocarbon molecule.

Improving the Working Efficiency of a Triboelectric Nanogenerator by the Semimetallic PEDOT:PSS Hole Transport Layer and Its Application in Self-Powered Active Acetylene Gas Sensing.

Science.gov (United States)

Uddin, A S M Iftekhar; Yaqoob, Usman; Chung, Gwiy-Sang

2016-11-09

Herein we report an enhanced triboelectric nanogenerator (TENG) based on the contact-separation mode between a patterned film of polydimethylsiloxane (PDMS) with a semimetallic elastomer of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and a nylon fiber film. The addition of ethylene glycol to the PEDOT:PSS film improves the functionality of the TENG significantly, yielding promising applicability in both indoor and outdoor (i.e., under sunlight) environments, with the maximum instantaneous power of 0.09 mW (indoors) and 0.2 mW (outdoors) for the load resistance of 3.8 MΩ. The device can also generate 11.2 V and 0.08 μA cm -2 in response to the forearm movement of a human. Additionally, by replacing the bare nylon fiber in the TENG design with a Ag@ZnO/nylon fiber film, a self-powered active sensor (triboelectric nanogenerator-based sensor; TENS) has been realized to detect acetylene (C 2 H 2 ) gas. The TENS exhibits excellent sensitivity of 70.9% (indoors) and 89% (outdoors) to C 2 H 2 gas of 1000 ppm concentration. The proposed approach for harvesting energy and sensing can be advantageous in practical applications and may stimulate new research that will enhance nanogenerators as well as wearable, self-powered active sensors.

Mechanism for the Coupled Photochemistry of Ammonia and Acetylene: Implications for Giant Planets, Comets and Interstellar Organic Synthesis

Science.gov (United States)

Keane, Thomas C.

2017-09-01

Laboratory studies provide a fundamental understanding of photochemical processes in planetary atmospheres. Photochemical reactions taking place on giant planets like Jupiter and possibly comets and the interstellar medium are the subject of this research. Reaction pathways are proposed for the coupled photochemistry of NH3 (ammonia) and C2H2 (acetylene) within the context Jupiter's atmosphere. We then extend the discussion to the Great Red Spot, Extra-Solar Giant Planets, Comets and Interstellar Organic Synthesis. Reaction rates in the form of quantum yields were measured for the decomposition of reactants and the formation of products and stable intermediates: HCN (hydrogen cyanide), CH3CN (acetonitrile), CH3CH = N-N = CHCH3 (acetaldazine), CH3CH = N-NH2 (acetaldehyde hydrazone), C2H5NH2 (ethylamine), CH3NH2 (methylamine) and C2H4 (ethene) in the photolysis of NH3/C2H2 mixtures. Some of these compounds, formed in our investigation of pathways for HCN synthesis, were not encountered previously in observational, theoretical or laboratory photochemical studies. The quantum yields obtained allowed for the formulation of a reaction mechanism that attempts to explain the observed results under varying experimental conditions. In general, the results of this work are consistent with the initial observations of Ferris and Ishikawa (1988). However, their proposed reaction pathway which centers on the photolysis of CH3CH = N-N = CHCH3 does not explain all of the results obtained in this study. The formation of CH3CH = N-N = CHCH3 by a radical combination reaction of CH3CH = N• was shown in this work to be inconsistent with other experiments where the CH3CH = N• radical is thought to form but where no CH3CH = N-N = CHCH3 was detected. The importance of the role of H atom abstraction reactions was demonstrated and an alternative pathway for CH3CH = N-N = CHCH3 formation involving nucleophilic reaction between N2H4 and CH3CH = NH is advanced.

49 CFR 178.59 - Specification 8 steel cylinders with porous fillings for acetylene.

Science.gov (United States)

2010-10-01

... being set at the calculated corresponding strain. (iv) Cross-head speed of the testing machine may not... percent of tensile strength. Elongation must be at least 40 percent in 2 inch or 20 percent in other cases...

Nitrogen fixation on a coral reef

Energy Technology Data Exchange (ETDEWEB)

Mague, T.H.; Holm-Hansen, O.

1975-06-01

Benthic, heterocystous blue-green algae (genera Calothrix, Hormothamnion and Nostoc) from Eniwetok Atoll were found to reduce acetylene at rapid rates. Slight acetylene reduction was associated with samples of Rhizoclonium (Chlorophyceae) and Oscillatoria (a cyanophyte lacking heterocysts), but this may have been due to contamination by epiphytes. There was virtually no acetylene reduction by phytoplankton, and nutrient enrichment experiments failed to selectively increase the numbers or activity of N/sub 2/-fixing algae in surface water samples. The Nostoc required light for acetylene reduction. Nitrogen fixation by this species could have supplied up to 11 ..mu..g N/cm/sup 2//day to the ecosystem. (auth)

An ab initio study of potential energy surfaces of CH 3COCN dissociation on the low-lying states

Science.gov (United States)

Ding, Wan-Jian; Fang, Wei-Hai; Liu, Ruo-Zhuang

2002-01-01

The C-CH 3 and C-CN bond dissociations of CH 3COCN on S 1 and T 1 surfaces are studied at the CAS(8,7)/cc-pVDZ level. The results show that the intersystem crossing from S 1 to T 1 is a favorable pathway of S 1 deactivation. Once on the T 1 surface, the system can dissociate adiabatically to CH3 ( X˜)+ OCCN ( X˜) or CN ( X˜)+ CH3CO ( X˜) , but the former has some preference over the latter. This mechanism is consistent with Cheng's presumption deduced from the experimental facts and theoretical considerations. A comparison with other asymmetrically substituted carbonyl compounds suggests that the selectivity of the α-bond cleavage is mainly dependent on the mechanism of dissociation.

(ajst) intersystem interference due to hydrometeor

African Journals Online (AJOL)

telecommunication services and to expand existing ones continues to receive ..... Theoretical Physics (ICTP), Trieste, Italy for travel support and the facilities used in ... Commission of the European Communities on Cooperation in the Fields of ...

Burn Injury Arise From Flying Balloon Toys

Directory of Open Access Journals (Sweden)

Yalcin Kulahci

2007-08-01

Full Text Available Many of peoples are faced minor or major burn injuries in their life. Even the most widespread burn cause is flame injuries, too different burn cause pointed out in literature like Acetylen burns. The cases which imply in literature, mostly causes from explosion of high pressure acetylene tube, metal oxygene patch flame or carbide lamp using from cave explorers. An interesting acetylene burn cause in Turkey was publised by the authors. This cases was to come into being from flying toy balloons flame. 80 person was injured from flying toy ballons flame in a meeting in 2002. Although this potential risks of acetylene, helium have not any of some risk. But helium was provided from other countries and have more price. The injuries which caused from acetylene burns like 1st -2nd degree burns. Consequently that was known helium is more avaliable for using in toy sector, and never cause burn injuries like this. [TAF Prev Med Bull. 2007; 6(4: 291-296

[Effects of organic and inorganic fertilizers on emission and sources of N2O in vegetable soils.

Science.gov (United States)

Lin, Wei; Ding, Jun Jun; Li, Yu Zhong; Xu, Chun Ying; Li, Qiao Zhen; Zheng, Qian; Zhuang, Shan

2018-05-01

To clarify the microbial pathway of the N 2 O production and consumption under different fertilizers and provide theoretical basis for the reduction of N 2 O emission and rational management of fertilization in vegetable soils, we examined dynamics of N 2 O flux and isotope signatures under different fertilizer treatments in the vegetable soils of Beijing, by setting up four treatments (organic-acetylene, organic-nonacetylene, inorganic-acetylene, inorganic-nonacetylene) and using the stable isotope technique of natural N 2 O abundance. The results showed that the cumulative N 2 O emission from organic-acetylene group, organic-nonacetylene group, inorganic-acetylene group and inorganic-nonacetylene group was (374±37), (283±34), (458±36), (355±41) g·m -2 in cabbage growing season, respectively. N 2 O fluxes were significantly lower in treatments with organic fertilizer than those with inorganic fertilizer and significantly higher in acetylene group than nonacetylene group. The degree of N 2 O reduction were similar in both fertilizer treatments, and higher nitrification was found in inorganic fertilizer than organic fertilizer treatments. Acetylene only inhibited partial nitrification and partial N 2 O reduction at the peak of N 2 O emission. When the emission was reduced, N 2 O reduction could be completely suppressed. Therefore, the inorganic fertilizer might trigger nitrification and promote higher N 2 O emission. The high concentration of N 2 O could withstand that acetylene to inhibite N 2 O reduction. Hence, using organic fertilizers instead of some inorganic ones could effectively reduce N 2 O emission in vegetable soils of Beijing. The N 2 O concentration threshold should be considered when we identify N 2 O source by acetylene inhibition method.

Mechanism for the Coupled Photochemistry of Ammonia and Acetylene: Implications for Giant Planets, Comets and Interstellar Organic Synthesis.

Science.gov (United States)

Keane, Thomas C

2017-09-01

Laboratory studies provide a fundamental understanding of photochemical processes in planetary atmospheres. Photochemical reactions taking place on giant planets like Jupiter and possibly comets and the interstellar medium are the subject of this research. Reaction pathways are proposed for the coupled photochemistry of NH 3 (ammonia) and C 2 H 2 (acetylene) within the context Jupiter's atmosphere. We then extend the discussion to the Great Red Spot, Extra-Solar Giant Planets, Comets and Interstellar Organic Synthesis. Reaction rates in the form of quantum yields were measured for the decomposition of reactants and the formation of products and stable intermediates: HCN (hydrogen cyanide), CH 3 CN (acetonitrile), CH 3 CH = N-N = CHCH 3 (acetaldazine), CH 3 CH = N-NH 2 (acetaldehyde hydrazone), C 2 H 5 NH 2 (ethylamine), CH 3 NH 2 (methylamine) and C 2 H 4 (ethene) in the photolysis of NH 3 /C 2 H 2 mixtures. Some of these compounds, formed in our investigation of pathways for HCN synthesis, were not encountered previously in observational, theoretical or laboratory photochemical studies. The quantum yields obtained allowed for the formulation of a reaction mechanism that attempts to explain the observed results under varying experimental conditions. In general, the results of this work are consistent with the initial observations of Ferris and Ishikawa (1988). However, their proposed reaction pathway which centers on the photolysis of CH 3 CH = N-N = CHCH 3 does not explain all of the results obtained in this study. The formation of CH 3 CH = N-N = CHCH 3 by a radical combination reaction of CH 3 CH = N• was shown in this work to be inconsistent with other experiments where the CH 3 CH = N• radical is thought to form but where no CH 3 CH = N-N = CHCH 3 was detected. The importance of the role of H atom abstraction reactions was demonstrated and an alternative pathway for CH 3 CH = N-N = CHCH 3 formation involving nucleophilic reaction

Infrared study of the nature of the copper ion--alkyne bond in Y zeolite

International Nuclear Information System (INIS)

Pichat, P.

1975-01-01

The infrared spectra of acetylene, deuterated acetylene, propyne, and but-2-yne, chemisorbed in Cu, Na--Y zeolites, which have undergone various treatments, were studied. It is concluded that the OH groups interact only with the weakly absorbed molecules, the Cu + ions are not involved, the acetylenic hydrogen atoms do not take part in the bonding, the Cu 2+ ion--alkyne bone results mainly from π donation from the unsaturated hydrocarbon to the metallic ion. (auth)

Quasi-solid polymer electrolytes using photo-cross-linked polymers. Lithium and divalent cation conductors and their applications

Science.gov (United States)

Ikeda, Shoichiro; Mori, Yoichi; Furuhashi, Yuri; Masuda, Hideki; Yamamoto, Osamu

In this report, we will present the results on the photo-cross-linked poly-(ethylene glycol) diacrylate (PEGDA) based quasi-solid, i.e. gel, polymer electrolyte systems with lithium, magnesium and zinc trifluoromethanesulfonates [triflate; M n(CF 3SO 3) n] and their preliminary applications to primary cells. The Celgard® membrane-impregnated electrolytes were prepared in the same manner as Abraham et al. [K.M. Abraham, M. Alamgir, D.K. Hoffman, J. Electrochem. Soc. 142 (1995) 683]. The precursor solutions were composed of metal triflates, ethylene carbonate, propylene carbonate, and tetraethylene glycol diacrylate. The Celgard® #3401 membrane was soaked overnight in the precursor solution, then clamped between two Pyrex glass plates and irradiated with UV light to form a gel electrolyte. The maxima of the conductivity obtained were 4.5×10 -4 S cm -1 at 12 mol% for LiCF 3SO 3, 1.7×10 -4 S cm -1 at 1 mol% for Mg(CF 3SO 3) 2, and 2.1×10 -4 S cm -1 at 4 mol% for Zn(CF 3SO 3) 2 system, respectively. The Arrhenius plots of the conductivities are almost linear between 268 and 338 K with 15-25 kJ/mol of activation energy for conduction. The cell, Li|LiCF 3SO 3-SPE+Celgard® #3401|(CH 3) 4NI 5+acetylene black, showed 2.86 V of OCV and could discharge up to 25% with respect to the cathode active material at a discharging current of 0.075 mA/cm 2.

Ultrafast Photoinduced Electron Transfer in Bimolecular Donor-Acceptor Systems

KAUST Repository

Alsulami, Qana A.

2016-11-30

The efficiency of photoconversion systems, such as organic photovoltaic (OPV) cells, is largely controlled by a series of fundamental photophysical processes occurring at the interface before carrier collection. A profound understanding of ultrafast interfacial charge transfer (CT), charge separation (CS), and charge recombination (CR) is the key determinant to improving the overall performances of photovoltaic devices. The discussion in this dissertation primarily focuses on the relevant parameters that are involved in photon absorption, exciton separation, carrier transport, carrier recombination and carrier collection in organic photovoltaic devices. A combination of steady-state and femtosecond broadband transient spectroscopies was used to investigate the photoinduced charge carrier dynamics in various donor-acceptor systems. Furthermore, this study was extended to investigate some important factors that influence charge transfer in donor-acceptor systems, such as the morphology, energy band alignment, electronic properties and chemical structure. Interestingly, clear correlations among the steady-state measurements, time-resolved spectroscopy results, grain alignment of the electron transporting layer (ETL), carrier mobility, and device performance are found. In this thesis, we explored the significant impacts of ultrafast charge separation and charge recombination at donor/acceptor (D/A) interfaces on the performance of a conjugated polymer PTB7-Th device with three fullerene acceptors: PC71BM, PC61BM and IC60BA. Time-resolved laser spectroscopy and high-resolution electron microscopy can illustrate the basis for fabricating solar cell devices with improved performances. In addition, we studied the effects of the incorporation of heavy metals into π-conjugated chromophores on electron transfer by monitoring the triplet state lifetime of the oligomer using transient absorption spectroscopy, as understanding the mechanisms controlling intersystem crossing and

Photodissociation dynamics of CH3C(O)SH in argon matrix: A QM/MM nonadiabatic dynamics simulation

Science.gov (United States)

Xia, Shu-Hua; Liu, Xiang-Yang; Fang, Qiu; Cui, Ganglong

2015-11-01

In this work, we have first employed the combined quantum mechanics/molecular mechanics (QM/MM) method to study the photodissociation mechanism of thioacetic acid CH3C(O)SH in the S1, T1, and S0 states in argon matrix. CH3C(O)SH is treated quantum mechanically using the complete active space self-consistent field and complete active space second-order perturbation theory methods; argon matrix is described classically using Lennard-Jones potentials. We find that the C-S bond fission is predominant due to its small barriers of ca. 3.0 and 1.0 kcal/mol in the S1 and T1 states. It completely suppresses the nearby C—C bond fission. After the bond fission, the S1 radical pair of CH3CO and SH can decay to the S0 and T1 states via internal conversion and intersystem crossing, respectively. In the S0 state, the radical pair can either recombine to form CH3C(O)SH or proceed to form molecular products of CH2CO and H2S. We have further employed our recently developed QM/MM generalized trajectory-based surface-hopping method to simulate the photodissociation dynamics of CH3C(O)SH. In 1 ps dynamics simulation, 56% trajectories stay at the Franck-Condon region; the S1 C—S bond fission takes place in the remaining 44% trajectories. Among all nonadiabatic transitions, the S1 → S0 internal conversion is major (55%) but the S1 → T1 intersystem crossing is still comparable and cannot be ignored, which accounts for 28%. Finally, we have found a radical channel generating the molecular products of CH2CO and H2S, which is complementary to the concerted molecular channel. The present work sets the stage for simulating photodissociation dynamics of similar thio-carbonyl systems in matrix.

Mechanistic photodecarboxylation of pyruvic acid: Excited-state proton transfer and three-state intersection

Energy Technology Data Exchange (ETDEWEB)

Chang, Xue-Ping; Fang, Qiu, E-mail: fangqiu917@bnu.edu.cn; Cui, Ganglong, E-mail: ganglong.cui@bnu.edu.cn [Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875 (China)

2014-10-21

Photodissociation dynamics of pyruvic acid experimentally differs from that of commonly known ketones. We have employed the complete active space self-consistent field and its multi-state second-order perturbation methods to study its photodissociation mechanism in the S{sub 0}, T{sub 1}, and S{sub 1} states. We have uncovered four nonadiabatic photodecarboxylation paths. (i) The S{sub 1} system relaxes via an excited-state intramolecular proton transfer (ESIPT) to a hydrogen-transferred tautomer, near which an S{sub 1}/S{sub 0} conical intersection funnels the S{sub 1} to S{sub 0} state. Then, some trajectories continue completing the decarboxylation reaction in the S{sub 0} state; the remaining trajectories via a reverse hydrogen transfer return to the S{sub 0} minimum, from which a thermal decarboxylation reaction occurs. (ii) Due to a small S{sub 1} −T{sub 1} energy gap and a large S{sub 1}/T{sub 1} spin-orbit coupling, an efficient S{sub 1} → T{sub 1} intersystem crossing process happens again near this S{sub 1}/S{sub 0} conical intersection. When decaying to T{sub 1} state, a direct photodecarboxylation proceeds. (iii) Prior to ESIPT, the S{sub 1} system first decays to the T{sub 1} state via an S{sub 1} → T{sub 1} intersystem crossing; then, the T{sub 1} system evolves to a hydrogen-transferred tautomer. Therefrom, an adiabatic T{sub 1} decarboxylation takes place due to a small barrier of 7.7 kcal/mol. (iv) Besides the aforementioned T{sub 1} ESIPT process, there also exists a comparable Norrish type I reaction in the T{sub 1} state, which forms the ground-state products of CH{sub 3}CO and COOH. Finally, we have found that ESIPT plays an important role. It closes the S{sub 1}-T{sub 1} and S{sub 1}-S{sub 0} energy gaps, effecting an S{sub 1}/T{sub 1}/S{sub 0} three-state intersection region, and mediating nonadiabatic photodecarboxylation reactions of pyruvic acid.

Photodissociation dynamics of CH{sub 3}C(O)SH in argon matrix: A QM/MM nonadiabatic dynamics simulation

Energy Technology Data Exchange (ETDEWEB)

Xia, Shu-Hua; Liu, Xiang-Yang; Fang, Qiu; Cui, Ganglong, E-mail: ganglong.cui@bnu.edu.cn [Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875 (China)

2015-11-21

In this work, we have first employed the combined quantum mechanics/molecular mechanics (QM/MM) method to study the photodissociation mechanism of thioacetic acid CH{sub 3}C(O)SH in the S{sub 1}, T{sub 1}, and S{sub 0} states in argon matrix. CH{sub 3}C(O)SH is treated quantum mechanically using the complete active space self-consistent field and complete active space second-order perturbation theory methods; argon matrix is described classically using Lennard-Jones potentials. We find that the C-S bond fission is predominant due to its small barriers of ca. 3.0 and 1.0 kcal/mol in the S{sub 1} and T{sub 1} states. It completely suppresses the nearby C—C bond fission. After the bond fission, the S{sub 1} radical pair of CH{sub 3}CO and SH can decay to the S{sub 0} and T{sub 1} states via internal conversion and intersystem crossing, respectively. In the S{sub 0} state, the radical pair can either recombine to form CH{sub 3}C(O)SH or proceed to form molecular products of CH{sub 2}CO and H{sub 2}S. We have further employed our recently developed QM/MM generalized trajectory-based surface-hopping method to simulate the photodissociation dynamics of CH{sub 3}C(O)SH. In 1 ps dynamics simulation, 56% trajectories stay at the Franck-Condon region; the S{sub 1} C—S bond fission takes place in the remaining 44% trajectories. Among all nonadiabatic transitions, the S{sub 1} → S{sub 0} internal conversion is major (55%) but the S{sub 1} → T{sub 1} intersystem crossing is still comparable and cannot be ignored, which accounts for 28%. Finally, we have found a radical channel generating the molecular products of CH{sub 2}CO and H{sub 2}S, which is complementary to the concerted molecular channel. The present work sets the stage for simulating photodissociation dynamics of similar thio-carbonyl systems in matrix.

Computational Investigation of the Influence of Halogen Atoms on the Photophysical Properties of Tetraphenylporphyrin and Its Zinc(II) Complexes.

Science.gov (United States)

De Simone, Bruna C; Mazzone, Gloria; Russo, Nino; Sicilia, Emilia; Toscano, Marirosa

2018-03-15

How the tetraphenylporphyrin (TPP) and its zinc(II) complexes (ZnTPP) photophysical properties (absorption energies, singlet-triplet energy gap and spin-orbit coupling contributions) can change due to the presence of an increasing number of heavy atoms in their molecular structures has been investigated by means of density functional theory and its time-dependent formulation. Results show that the increase of the atomic mass of the substituted halogen strongly enhances the spin-orbit coupling values, allowing a more efficient singlet-triplet intersystem crossing. Different deactivation channels have been considered and rationalized on the basis of El-Sayed and Kasha rules. Most of the studied compounds possess the appropriate properties to generate cytotoxic singlet molecular oxygen ( 1 Δ g ) and, consequently, they can be proposed as photosensitizers in photodynamic therapy.

Deep blue exciplex organic light-emitting diodes with enhanced efficiency; P-type or E-type triplet conversion to singlet excitons?

Science.gov (United States)

Jankus, Vygintas; Chiang, Chien-Jung; Dias, Fernando; Monkman, Andrew P

2013-03-13

Simple trilayer, deep blue, fluorescent exciplex organic light-emitting diodes (OLEDs) are reported. These OLEDs emit from an exciplex state formed between the highest occupied molecular orbital (HOMO) of N,N'-bis(1-naphthyl)N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine (NPB) and lowest unoccupied molecular orbital (LUMO) of 1,3,5-tri(1-phenyl-1H-benzo[d]imidazol-2-yl)phenyl (TPBi) and the NPB singlet manifold, yielding 2.7% external quantum efficiency at 450 nm. It is shown that the majority of the delayed emission in electroluminescence arises from P-type triplet fusion at NPB sites not E-type reverse intersystem crossing because of the presence of the NPB triplet state acting as a deep trap. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Highly efficient bilayer interface exciplex for yellow organic light-emitting diode.

Science.gov (United States)

Hung, Wen-Yi; Fang, Guan-Cheng; Chang, Yuh-Chia; Kuo, Ting-Yi; Chou, Pi-Tai; Lin, Shih-Wei; Wong, Ken-Tsung

2013-08-14

A simple three-layer interfacial-type yellow emission exciplex device with an external quantum efficiency as high as 7.7% has been successfully achieved by combining conformation compatible C3-symmetric hole-transporting TCTA and electron-transporting 3P-T2T. The excellent and balanced charge-transporting properties of TCTA and 3P-T2T and the large energy-levels offset (0.8 eV) of TCTA/3P-T2T interface play important roles for the efficient exciplexes formation, which are effectively confined around the interfacial region due to the high triplet energies (2.85 eV) of TCTA and 3P-T2T. The high-performance OLED was believed to be from the effective harvest of exciplex triplet excitons via reverse intersystem crossing process.

Magnetic enhancement of photoluminescence from blue-luminescent graphene quantum dots

Science.gov (United States)

Chen, Qi; Shi, Chentian; Zhang, Chunfeng; Pu, Songyang; Wang, Rui; Wu, Xuewei; Wang, Xiaoyong; Xue, Fei; Pan, Dengyu; Xiao, Min

2016-02-01

Graphene quantum-dots (GQDs) have been predicted and demonstrated with fascinating optical and magnetic properties. However, the magnetic effect on the optical properties remains experimentally unexplored. Here, we conduct a magneto-photoluminescence study on the blue-luminescence GQDs at cryogenic temperatures with magnetic field up to 10 T. When the magnetic field is applied, a remarkable enhancement of photoluminescence emission has been observed together with an insignificant change in circular polarization. The results have been well explained by the scenario of magnetic-field-controlled singlet-triplet mixing in GQDs owing to the Zeeman splitting of triplet states, which is further verified by temperature-dependent experiments. This work uncovers the pivotal role of intersystem crossing in GQDs, which is instrumental for their potential applications such as light-emitting diodes, photodynamic therapy, and spintronic devices.

Fixation of tritium in a highly stable polymer form

International Nuclear Information System (INIS)

Steinberg, M.; Colombo, P.; Pruzansky, J.

1977-01-01

A method for the fixation of tritium comprises reacting tritiated water with calcium carbide to produce calcium hydroxide and tritiated acetylene, polymerizing the acetylene, and then incorporating the polymer in a solidifying matrix. 2 claims

Selectivity in catalytic alkyne cyclotrimerization over chromium(VI): kinetic evaluation using the characteristics of radioactive carbon-11 decay for nondisruptive ultrasensitive detection of adsorbed species

International Nuclear Information System (INIS)

Ferrieri, R.A.; Wolf, A.P.

1984-01-01

The application of carbon-11 to kinetic measurements of molecular sorption is reported using positron annihilation surface detection (PASD). The technique is nondisruptive to dynamic processes and has the sensitivity to detect 10 -8 of a monolayer. In studies of alkyne cyclomerization on silica-alumina-supported Cr(VI), a high selectivity toward p-xylene formation was observed when acetylene-propyne mixtures were cotrimerized at monolayer total alkyne coverages. This selectivity was enhanced to 84% p-xylene, as the partial acetylene coverage was reduced to 1.0% of a monolayer. Competitive sorption studies utilized PASD to measure the surface concentration of [ 11 C]-acetylene coupled with macroscopic sorption measurements of propyne. Surface displacement of sorbed acetylene by propyne was observed with subsequent readsorption. The kinetics of this displacement were evaluated by using PASD in pulse-flow studies with various acetylene and propyne coverages and were modeled to a calculation of the isomeric xylene distribution. A near-identical fit was obtained between experimental and modeled results. This strongly suggested that the observed selectivity for p-xylene formation was due to sorbate interactions resulting in a specific molecular ordering of the alkyne mixture on the catalyst surface

Structural Control of (1)A(2u)-to-(3)A(2u) Intersystem Crossing in Diplatinum(II,II) Complexes

Czech Academy of Sciences Publication Activity Database

Durrell, A. C.; Keller, G. E.; Lam, Y.; Ch.; Sýkora, Jan; Vlček, Antonín; Gray, H. B.

2012-01-01

Roč. 134, č. 34 (2012), s. 14201-14207 ISSN 0002-7863 R&D Projects: GA MŠk(CZ) ME10124 Institutional support: RVO:61388955 Keywords : TRIPLET EXCITED-STATE * BINUCLEAR PLATINUM(II) PHOTOCHEMISTRY * ELECTRON-TRANSFER REACTIONS Subject RIV: CG - Electrochemistry Impact factor: 10.677, year: 2012

49 CFR 178.60 - Specification 8AL steel cylinders with porous fillings for acetylene.

Science.gov (United States)

2010-10-01

...) Cross-head speed of the testing machine may not exceed 1/8 inch per minute during yield strength... increment of tensile strength above 50,000 psi to a maximum of four such increments. (n) Weld tests...: (1) Tensile test. A specimen must be cut from one cylinder of each lot of 200 or less, or welded test...

African Journal of Science and Technology (AJST) REACTIONS OF ...

African Journals Online (AJOL)

opiyo

Acetylenic amines have been used in the synthesis of potential biologically active heterocyclic compounds. Recently the anticonvulsant activity of some acetylenic quinazolinone derivatives have been evaluated and most of them exhibited significant activity in the seizure threshold test with subcutaneous pentylenetetrazole.

Types of cross-cultural studies in cross-cultural psychology

NARCIS (Netherlands)

van de Vijver, F.J.R.; Lonner, W.J.; Dinnel, D.L.; Hayes, S.A.; Sattler, D.N.

2003-01-01

From a methodological perspective cross-cultural studies in psychology differ in three dimensions. First, cross-cultural psychological studies can be exploratory or test specific hypotheses. Second, some cross-cultural studies compare countries or ethnic groups while other cross-cultural studies

Border Crossing/Entry Data - Boarder Crossing

Data.gov (United States)

Department of Transportation — Border Crossing/Entry Data provides summary statistics for incoming crossings at the U.S.-Canadian and the U.S.-Mexican border at the port level. Data are available...

CrossWork: Software-assisted identification of cross-linked peptides

DEFF Research Database (Denmark)

Rasmussen, Morten; Refsgaard, Jan; Peng, Li

2011-01-01

Work searches batches of tandem mass-spectrometric data, and identifies cross-linked and non-cross-linked peptides using a standard PC. We tested CrossWork by searching mass-spectrometric datasets of cross-linked complement factor C3 against small (1 protein) and large (1000 proteins) search spaces, and show...

Kinetics of Hydrocarbon formation in a-C:H Film deposition plasmas

International Nuclear Information System (INIS)

Cal, E. de la; Tabares, F. L.

1993-01-01

The formation of C2 and Cp hydrocarbons during the PACVD of a-C:H films from admixtures of methane with H2 and He has been investigated by mass spectrometry under several deposition condition. The time evolution of the observed species indicates that the formation mechanisms of ethylene and acetylene are sensitive to the conditions of the wall during the growing of the film. Acetylene are sensitive to the conditions of the wall during the growing of the film. Acetylene formation was found to be directly related to the formation of the film on top of the carburized metal. (Author) 12 refs

Kinetics of Hydrocarbon formation in a- C:H Film deposition plasmas

Energy Technology Data Exchange (ETDEWEB)

Cal, E de la; Tabares, F L

1993-07-01

The formation of C2 and Cp hydrocarbons during the PACVD of a-C:H films from admixtures of methane with H2 and He has been investigated by mass spectrometry under several deposition condition. The time evolution of the observed species indicates that the formation mechanisms of ethylene and acetylene are sensitive to the conditions of the wall during the growing of the film. Acetylene are sensitive to the conditions of the wall during the growing of the film. Acetylene formation was found to be directly related to the formation of the film on top of the carburized metal. (Author) 12 refs.

Simple structured hybrid WOLEDs based on incomplete energy transfer mechanism: from blue exciplex to orange dopant

Science.gov (United States)

Zhang, Tianyou; Zhao, Bo; Chu, Bei; Li, Wenlian; Su, Zisheng; Yan, Xingwu; Liu, Chengyuan; Wu, Hairuo; Gao, Yuan; Jin, Fangming; Hou, Fuhua

2015-05-01

Exciplex is well known as a charge transfer state formed between electron-donating and electron-accepting molecules. However, exciplex based organic light emitting diodes (OLED) often performed low efficiencies relative to pure phosphorescent OLED and could hardly be used to construct white OLED (WOLED). In this work, a new mechanism is developed to realize efficient WOLED with extremely simple structure by redistributing the energy of triplet exciplex to both singlet exciplex and the orange dopant. The micro process of energy transfer could be directly examined by detailed photoluminescence decay measurement and time resolved photoluminescence analysis. This strategy overcomes the low reverse intersystem crossing efficiency of blue exciplex and complicated device structure of traditional WOLED, enables us to achieve efficient hybrid WOLEDs. Based on this mechanism, we have successfully constructed both exciplex-fluorescence and exciplex-phosphorescence hybrid WOLEDs with remarkable efficiencies.

Achievement report for fiscal 1981 on research under Sunshine Program. Basic research on plasma-aided coal gasification technology; 1981 nendo sushine keikaku kenkyu seika hokokusho. Sekitan no plasma gas ka gijutsu no kiso kenkyu

Energy Technology Data Exchange (ETDEWEB)

NONE

1982-03-01

Researches are conducted for the development of a technology of producing useful gases such as acetylene, hydrogen, carbon monoxide, etc., from coal by the use of the high temperature and high-density energy of the plasma jet. In an experiment using a 100kW 3-port plasma-aided gasification unit, rapid quenching tests are conducted using hydrogen and helium, where the reaction furnace is changed, the specimen feed device is changed, and the plasma torch head is replaced by a high-power head. In a test of the coal specimen, it is found that rapid quenching exerts a great effect on the prevention of re-decomposition of the generated acetylene into hydrogen and carbon black and that a rise in the hydrogen partial pressure results in a great decrease in the quantity of acetylene generated. The said torch head replacement increases the rate of the coal specimen infiltrating into the plasma flame, which brings about an increase in the quantity of acetylene generated. It is found after all that the conventional acetylene yield of 34g/kWh increases to 59g/kWh in a rapid quenching test in which the specimen is dried Akabira coal and the plasma is an argon gas plasma containing 40% hydrogen. (NEDO)

A subspecies of region crossing change, region freeze crossing change

OpenAIRE

Inoue, Ayumu; Shimizu, Ryo

2016-01-01

We introduce a local move on a link diagram named a region freeze crossing change which is close to a region crossing change, but not the same. We study similarity and difference between region crossing change and region freeze crossing change.

CrossFlow: Cross-Organizational Workflow Management in Dynamic Virtual Enterprises

NARCIS (Netherlands)

Grefen, P.W.P.J.; Aberer, Karl; Hoffner, Yigal; Ludwig, Heiko

In this report, we present the approach to cross-organizational workflow management of the CrossFlow project. CrossFlow is a European research project aiming at the support of cross-organizational workflows in dynamic virtual enterprises. The cooperation in these virtual enterprises is based on

CrossFlow : cross-organizational workflow management in dynamic virtual enterprises

NARCIS (Netherlands)

Grefen, P.W.P.J.; Aberer, K.; Hoffner, Y.

2000-01-01

This paper gives a detailed overview of the approach to cross-organizational workflow management developed in the CrossFlow project. CrossFlow is a European research project aiming at the support of cross-organizational workflows in dynamic virtual enterprises. The cooperation in these virtual

To cross or not to cross: modeling wildlife road crossings as a binary response variable with contextual predictors

Science.gov (United States)

Siers, Shane R.; Reed, Robert N.; Savidge, Julie A.

2016-01-01

Roads are significant barriers to landscape-scale movements of individuals or populations of many wildlife taxa. The decision by an animal near a road to either cross or not cross may be influenced by characteristics of the road, environmental conditions, traits of the individual animal, and other aspects of the context within which the decision is made. We considered such factors in a mixed-effects logistic regression model describing the nightly road crossing probabilities of invasive nocturnal Brown Treesnakes (Boiga irregularis) through short-term radiotracking of 691 snakes within close proximity to 50 road segments across the island of Guam. All measures of road magnitude (traffic volume, gap width, surface type, etc.) were significantly negatively correlated with crossing probabilities. Snake body size was the only intrinsic factor associated with crossing rates, with larger snakes crossing roads more frequently. Humidity was the only environmental variable affecting crossing rate. The distance of the snake from the road at the start of nightly movement trials was the most significant predictor of crossings. The presence of snake traps with live mouse lures during a portion of the trials indicated that localized prey cues reduced the probability of a snake crossing the road away from the traps, suggesting that a snake's decision to cross roads is influenced by local foraging opportunities. Per capita road crossing rates of Brown Treesnakes were very low, and comparisons to historical records suggest that crossing rates have declined in the 60+ yr since introduction to Guam. We report a simplified model that will allow managers to predict road crossing rates based on snake, road, and contextual characteristics. Road crossing simulations based on actual snake size distributions demonstrate that populations with size distributions skewed toward larger snakes will result in a higher number of road crossings. Our method of modeling per capita road crossing

Pramana – Journal of Physics | Indian Academy of Sciences

Indian Academy of Sciences (India)

Study of diffusivity of acetylene adsorbed in Na-Y zeolite by quasi-elastic neutron scattering (QENS) measurements at temperatures of 300, 325 and 350 K is reported. A model in which the acetylene molecules undergo random-walk diffusion characterized by a Gaussian distribution of jump lengths inside zeolite cages ...

WEB Services Implementation on The Report of Dengue Hemorrhagic Fever (DHF At Health Office Karanganyar

Directory of Open Access Journals (Sweden)

Ragil Saputra

2013-06-01

Full Text Available Abstract— Dengue Hemorrhagic Fever (DHF is one of the infectious diseases that frequently leads to Extraordinary Situation. The management of report is conducted by Health Community Center which subsequently gives report to Health Office. A problem arising from the report management is the fact that the report is conducted manually, therefore, the data is less valid and is not processed as quickly as possible. The quick and accurate data report system enables to lessen the risk of Dengue Hemorrhagic Fever. Due to this fact, it is undeniable necessary to provide an integrated inter-system of Dengue Fever report. This system includes an inter-system between one Health Community Center to another and to the system in Health Office. The integration of inter-system report is able to be conducted by the use of web service technology. Therefore, this research focuses on the development of Web Service based integrated system on the report of Dengue Fever. Data exchange is conducted in XML form by the application of SOAP and WSDL technologies. Library NuSOAP is necessary to provide class soapClient and soapServer. In other words, it functions as the listener whose functions are to receive and to respond at the access demand toward web service. The result is web service based report system which has dual functions since the system has functions to be either server or client. Keywords— web service, integration, SOAP, DHF.

Quasi-solid polymer electrolytes using photo-cross-linked polymers. Lithium and divalent cation conductors and their applications

Energy Technology Data Exchange (ETDEWEB)

Ikeda, Shoichiro; Mori, Yoichi; Furuhashi, Yuri; Masuda, Hideki [Nagoya Inst. of Tech. (Japan). Dept. of Applied Chemistry; Yamamoto, Osamu [Mie Univ., Tsu (Japan). Dept. of Chemistry

1999-09-01

In this report, we will present the results on the photo-cross-linked poly-(ethylene glycol) diacrylate (PEGDA) based quasi-solid, i.e. gel, polymer electrolyte systems with lithium, magnesium and zinc trifluoromethanesulfonates [triflate; M{sup n}(CF{sub 3}SO{sub 3}){sub n}] and their preliminary applications to primary cells. The Celgard{sup trademark} membrane-impregnated electrolytes were prepared in the same manner as Abraham et al. [K.M. Abraham, M. Alamgir, D.K. Hoffmann, J. Electrochem. Soc. 142 (1995) 683]. The precursor solutions were composed of metal triflates, ethylene carbonate, propylene carbonate, and tetraethylene glycol diacrylate. The Celgard{sup trademark} aa3401 membrane was soaked overnight in the precursor solution, then clamped between two Pyrex glass plates and irradiated with UV light to form a gel electrolyte. The maxima of the conductivity obtained were 4.5 x 10{sup -4} S cm{sup -1} at 12 mol% for LiCF{sub 3}SO{sub 3}, 1.7 x 10{sup -4} S cm{sup -1} at 1 mol% for Mg(CF{sub 3}SO{sub 3}){sub 2}, and 2.1 x 10{sup -4} S cm{sup -1} at 4 mol% Zn(CF{sub 3}SO{sub 3}){sub 2} system, respectively. The Arrhenius plots of the conductivities are almost linear between 268 and 338 K with 15-25 kJ/mol of activation energy for conduction. The cell, li vertical stroke LiCF{sub 3}SO{sub 3}-SPE+Celgard{sup trademark} aa3401 vertical stroke (CH{sub 3}){sub 4}NI{sub 5}+acetylene black, showed 2.86 V of OCV and could discharge up to 25% with respect to the cathode active material at a discharging current of 0.075 mA/cm{sup 2}. (orig.)

Effects of specific inhibitors on anammox and denitrification in marine sediments.

Science.gov (United States)

Jensen, Marlene Mark; Thamdrup, Bo; Dalsgaard, Tage

2007-05-01

The effects of three metabolic inhibitors (acetylene, methanol, and allylthiourea [ATU]) on the pathways of N2 production were investigated by using short anoxic incubations of marine sediment with a 15N isotope technique. Acetylene inhibited ammonium oxidation through the anammox pathway as the oxidation rate decreased exponentially with increasing acetylene concentration; the rate decay constant was 0.10+/-0.02 microM-1, and there was 95% inhibition at approximately 30 microM. Nitrous oxide reduction, the final step of denitrification, was not sensitive to acetylene concentrations below 10 microM. However, nitrous oxide reduction was inhibited by higher concentrations, and the sensitivity was approximately one-half the sensitivity of anammox (decay constant, 0.049+/-0.004 microM-1; 95% inhibition at approximately 70 microM). Methanol specifically inhibited anammox with a decay constant of 0.79+/-0.12 mM-1, and thus 3 to 4 mM methanol was required for nearly complete inhibition. This level of methanol stimulated denitrification by approximately 50%. ATU did not have marked effects on the rates of anammox and denitrification. The profile of inhibitor effects on anammox agreed with the results of studies of the process in wastewater bioreactors, which confirmed the similarity between the anammox bacteria in bioreactors and natural environments. Acetylene and methanol can be used to separate anammox and denitrification, but the effects of these compounds on nitrification limits their use in studies of these processes in systems where nitrification is an important source of nitrate. The observed differential effects of acetylene and methanol on anammox and denitrification support our current understanding of the two main pathways of N2 production in marine sediments and the use of 15N isotope methods for their quantification.

Nodulation of legumes, nitrogenase activity of roots and occurrence of nitrogen-fixing Azospirillum spp. In representative soils of central Amazonia

Energy Technology Data Exchange (ETDEWEB)

Sylvester-Bradley, R; De Oliverira, L A; De Podesta Filho, J A; John, T V

1980-12-01

Leguminosae do not predominate in the Brazilian Amazon rain forest, although they are among the five best represented families. Plant roots from various soils were examined for the presence of nodules, acetylene-reducing activity and N/sub 2/-fixing Azospirillum spp. Abundant nodulation was found in black earth (''terra preta dos indios'') and in one case on sandy soil under campinarana vegetation along a tributary of the upper Rio Negro. In sandy latosol some nodules occurred in secondary forest and fewer in primary forest. Legumes in disturbed clayey or sandy latosol showed more frequent nodulation. Primary forest on alluvial (''varzea'') soil, and in Bahia coastal rain forest on sandy latosol and Erythrina glauca used for shading cacao plantations were abundantly nodulated. Acetylene reduction assays showed no, or very little, nitrogenase activity of roots from primary or secondary forest on clayey latosol near Manaus. Nodulated roots from secondary forest on sandy latosol showed acetylene-reducing activity. High rates of acetylene reduction were observed in nodulated roots of primary forest on alluvial ''varzea'' soil. Root samples showed ethylene absorption in controls without acetylene which might interfere with the results of acetylene reduction tests. The incidence of Azospirillum was also higher in black earth than the other soils examined, and in soils with higher pH. The hypothesis that Azospirillum is associated with Trema micantha roots was refuted. Roots and soils collected under cultivated grasses showed a higher incidence of Azospirillum when fertilized with phosphorus and lime. Results indicate that nitrogen fixation did occur in association with roots in some soils, but not with roots of primary or secondary forest on clayey latosol in the vicinity of Manaus, which is the most common soil in Central Amazonia. The possible reasons for this are discussed.

The formation of ethane from carbon dioxide under cold plasma

International Nuclear Information System (INIS)

Zhang Xiuling; Zhang Lin; Dai Bin; Gong Weimin; Liu Changhou

2001-01-01

Pulsed-corona plasma has been used as a new method for ethane dehydrogenation at low temperature and normal pressure using carbon dioxide as an oxidant. The effect of carbon dioxide content in the feed, power input, and flow rate of the reactants on the ethane dehydrogenation has been investigated. The experimental results show that the conversion of ethane increases with the increasing in the amount of carbon dioxide in the feed. The yield of ethylene and acetylene decreases with the increasing in the yield of carbon monoxide, indicating that the increased carbon dioxide leads to the part of ethylene and acetylene being oxidized to carbon monoxide. Power input is primarily an electrical parameter in pulsed-corona plasma, which plays an important role in reactant conversion and product formation. When the power input reaches 16 W, ethane conversion is 41.0% and carbon dioxide conversion is 26.3%. The total yield of ethylene and acetylene is 15.6%. The reduced flow rate of feed improves the conversion of ethane, carbon dioxide and the yield of acetylene, and induces carbon deposit as well

Interplay between singlet and triplet excited states in a conformationally locked donor–acceptor dyad

KAUST Repository

Filatov, Mikhail A.

2015-10-13

The synthesis and photophysical characterization of a palladium(II) porphyrin – anthracene dyad bridged via short and conformationally rigid bicyclo[2.2.2]octadiene spacer were achieved. A spectroscopic investigation of the prepared molecule in solution has been undertaken to study electronic energy transfer in excited singlet and triplet states between the anthracene and porphyrin units. By using steady-state and time-resolved photoluminescence spectroscopy it was shown that excitation of the singlet excited state of the anthracene leads to energy transfer to the lower-lying singlet state of porphyrin. Alternatively, excitation of the porphyrin followed by intersystem crossing to the triplet state leads to very fast energy transfer to the triplet state of anthracene. The rate of this energy transfer has been determined by transient absorption spectroscopy. Comparative studies of the dynamics of triplet excited states of the dyad and reference palladium octaethylporphyrin (PdOEP) have been performed.

Multireference theoretical investigation on selectivity of the bond fissions in photodissociation of acetyl cyanide

Science.gov (United States)

Xiao, Hong-Yan; Liu, Ya-Jun; Fang, Wei-Hai

2007-12-01

The selectivity of the C -CH3 and C-CN bond fissions upon excitation of acetyl cyanide at 193nm has been investigated at the theoretical level of multistate complete active space self-consistent field second order perturbation. The calculated results indicated that the initially excited S3 state relaxes to S2 via ultrafast internal conversion. The S2 state could dissociate via two pathways. One, adiabatically dissociates to CH3CO(X˜)+CN(Ã). The other one internally converts to S1 before S1 intersystem crossing to T1. The T1 state subsequently dissociates to two groups of products: CH3(X˜)+OCCN(X˜) and CH3CO(X˜)+CN(X˜). The experimentally observed preference branching of CN elimination over CH3 one and bond selectivity are the results of the competition between the adiabatic and nonadiabatic dynamics of the S2 state.

Fluoresence quenching of riboflavin in aqueous solution by methionin and cystein

International Nuclear Information System (INIS)

Droessler, P.; Holzer, W.; Penzkofer, A.; Hegemann, P.

2003-01-01

The fluorescence quantum distributions, fluorescence quantum yields, and fluorescence lifetimes of riboflavin in methanol, DMSO, water, and aqueous solutions of the sulphur atom containing amino acids methionin and cystein have been determined. In methanol, DMSO, and water (pH=4-8) only dynamic fluorescence reduction due to intersystem crossing and internal conversion is observed. In aqueous methionin solutions of pH=5.25-9 a pH independent static and dynamic fluorescence quenching occurs probably due to riboflavin anion-methionin cation pair formation. In aqueous cystein solutions (pH range from 4.15 to 9) the fluorescence quenching increases with rising pH due to cystein thiolate formation. The cystein thiol form present at low pH does not react with neutral riboflavin. Cystein thiolate present at high pH seems to react with neutral riboflavin causing riboflavin deprotonation (anion formation) by cystein thiolate reduction to the cystein thiol form

The Paterno-Buchi reaction

DEFF Research Database (Denmark)

Brogaard, Rasmus Yding; Schalk, Oliver; Boguslavskiy, Andrey E.

2012-01-01

The Paternò-Büchi (PB) reaction between an excited carbonyl compound and an alkene has been widely studied, but so far little is known about the excited-state dynamics of the reaction. In this investigation, we used a compound in which a formyl and a vinyl group are attached to a [2.......2]paracyclophane in order to obtain a model system in pre-reactive conformation for the PB reaction. We studied the excited-state dynamics of the isolated molecule in a molecular beam using femtosecond time-resolved photoelectron spectroscopy and ab initio calculations. The results show that inter-system crossing...... within two picoseconds competes efficiently with the reaction in the singlet manifold. Thus, the PB reaction in this model system takes place in the triplet state on a time scale of nanoseconds. This result stresses the importance of triplet states in the excited-state pathway of the PB reaction...

Interplay between singlet and triplet excited states in a conformationally locked donor–acceptor dyad

KAUST Repository

Filatov, Mikhail A.; Etzold, Fabian; Gehrig, Dominik; Laquai, Fré dé ric; Busko, Dmitri; Landfester, Katharina; Baluschev, Stanislav

2015-01-01

The synthesis and photophysical characterization of a palladium(II) porphyrin – anthracene dyad bridged via short and conformationally rigid bicyclo[2.2.2]octadiene spacer were achieved. A spectroscopic investigation of the prepared molecule in solution has been undertaken to study electronic energy transfer in excited singlet and triplet states between the anthracene and porphyrin units. By using steady-state and time-resolved photoluminescence spectroscopy it was shown that excitation of the singlet excited state of the anthracene leads to energy transfer to the lower-lying singlet state of porphyrin. Alternatively, excitation of the porphyrin followed by intersystem crossing to the triplet state leads to very fast energy transfer to the triplet state of anthracene. The rate of this energy transfer has been determined by transient absorption spectroscopy. Comparative studies of the dynamics of triplet excited states of the dyad and reference palladium octaethylporphyrin (PdOEP) have been performed.

Prospects of Optical Single Atom Detection in Noble Gas Solids for Measurements of Rare Nuclear Reactions

Science.gov (United States)

Singh, Jaideep; Bailey, Kevin G.; Lu, Zheng-Tian; Mueller, Peter; O'Connor, Thomas P.; Xu, Chen-Yu; Tang, Xiaodong

2013-04-01

Optical detection of single atoms captured in solid noble gas matrices provides an alternative technique to study rare nuclear reactions relevant to nuclear astrophysics. I will describe the prospects of applying this approach for cross section measurements of the ^22Ne,,),25Mg reaction, which is the crucial neutron source for the weak s process inside of massive stars. Noble gas solids are a promising medium for the capture, detection, and manipulation of atoms and nuclear spins. They provide stable and chemically inert confinement for a wide variety of guest species. Because noble gas solids are transparent at optical wavelengths, the guest atoms can be probed using lasers. We have observed that ytterbium in solid neon exhibits intersystem crossing (ISC) which results in a strong green fluorescence (546 nm) under excitation with blue light (389 nm). Several groups have observed ISC in many other guest-host pairs, notably magnesium in krypton. Because of the large wavelength separation of the excitation light and fluorescence light, optical detection of individual embedded guest atoms is feasible. This work is supported by DOE, Office of Nuclear Physics, under contract DE-AC02-06CH11357.

Solvent-Dependent Dual Fluorescence of the Push-Pull System 2-Diethylamino-7-Nitrofluorene

KAUST Repository

Larsen, Martin A. B.

2018-01-31

The solvent-dependent excited state behavior of the molecular push-pull system 2-diethylamino-7-nitrofluorene has been explored using femtosecond transient absorption spectroscopy in combination with density functional theory calculations. Several excited state minima have been identified computationally, all possessing significant intramolecular charge transfer character. The experimentally observed dual fluorescence is suggested to arise from a planar excited state minimum and another minimum reached by twisting of the aryl-nitrogen bond of the amino group. The majority of the excited state population, however, undergo non-radiative transitions and potential excited deactivation pathways are assessed in the computational investigation. A third excited state conformer, characterized by twisting around the aryl-nitrogen bond of the nitro group, is reasoned to be responsible for the majority of the non-radiative decays and a crossing between the excited state and ground state is localized. Additionally, ultrafast intersystem crossing is observed in the apolar solvent cyclohexane and rationalized to occur via an El-Sayed assisted transition from one of the identified excited state minima. The solvent thus determines more than just the fluorescence lifetime and shapes the potential energy landscape, thereby dictating the available excited state pathways.

Solvent-Dependent Dual Fluorescence of the Push-Pull System 2-Diethylamino-7-Nitrofluorene

KAUST Repository

Larsen, Martin A. B.; Stephansen, Anne B.; Alarousu, Erkki; Pittelkow, Michael; Mohammed, Omar F.; Sø lling, Theis I

2018-01-01

The solvent-dependent excited state behavior of the molecular push-pull system 2-diethylamino-7-nitrofluorene has been explored using femtosecond transient absorption spectroscopy in combination with density functional theory calculations. Several excited state minima have been identified computationally, all possessing significant intramolecular charge transfer character. The experimentally observed dual fluorescence is suggested to arise from a planar excited state minimum and another minimum reached by twisting of the aryl-nitrogen bond of the amino group. The majority of the excited state population, however, undergo non-radiative transitions and potential excited deactivation pathways are assessed in the computational investigation. A third excited state conformer, characterized by twisting around the aryl-nitrogen bond of the nitro group, is reasoned to be responsible for the majority of the non-radiative decays and a crossing between the excited state and ground state is localized. Additionally, ultrafast intersystem crossing is observed in the apolar solvent cyclohexane and rationalized to occur via an El-Sayed assisted transition from one of the identified excited state minima. The solvent thus determines more than just the fluorescence lifetime and shapes the potential energy landscape, thereby dictating the available excited state pathways.

Triplet states of carotenoids from photosynthetic bacteria studied by nanosecond ultraviolet and electron pulse irradiation

International Nuclear Information System (INIS)

Bensasson, R.; Land, E.J.; Maudinas, B.

1976-01-01

Absorptions of the triplet excited states of five carotenoids (15,15'-cis phytoene, all-trans phytoene, zeta-carotene, spheroidene and spirillox-anthin), extracted from the photosynthetic bacteria Rhodopseudomonas spheroides and Rhodospirillum rubrum, have been detected in solution using pulse radiolysis and laser flash photolysis. Triplet lifetimes, extinction coefficients, lowest energy levels and quantum efficiencies of formation have been determined. Comparison of the carotenoid triplet energy levels with that of O 2 ('Δsub(g)) suggests that spirilloxanthin, spheroidene and possibly also zeta-carotene, would be expected to protect against photodynamic action caused by O 2 ('Δsub(g)), but not cis or trans phytoene. The S → T intersystem crossing efficiencies of all five polyenes were found to be low, being a few per cent or less. In their protective role these triplet states can only therefore be effectively reached via energy transfer from another triplet, except in the case of O 2 (Δsub(g)). The low crossover efficiencies also mean that light absorbed in such carotenoids in their possible role as accessory pigments would not be wasted in crossing over to the triplet state. (author)

Sonogashira reactions of alpha and beta-1-ethynyl-2-deoxyribosides: synthesis of acetylene-extended C-nucleosides

Czech Academy of Sciences Publication Activity Database

Bobula, T.; Hocek, Michal; Kotora, M.

2010-01-01

Roč. 66, č. 2 (2010), s. 530-536 ISSN 0040-4020 R&D Projects: GA MŠk 1M0508; GA AV ČR IAA400550902 Institutional research plan: CEZ:AV0Z40550506 Keywords : alkynes * C-nucleosides * aryl halides * cross-coupling reactions Subject RIV: CC - Organic Chemistry Impact factor: 3.011, year: 2010

Method development for the determination of fluorine in toothpaste via molecular absorption of aluminum mono fluoride using a high-resolution continuum source nitrous oxide/acetylene flame atomic absorption spectrophotometer.

Science.gov (United States)

Ozbek, Nil; Akman, Suleyman

2012-05-30

Fluorine was determined via the rotational molecular absorption line of aluminum mono fluoride (AlF) generated in C(2)H(2)/N(2)O flame at 227.4613 nm using a high-resolution continuum source flame atomic absorption spectrophotometer (HR-CS-FAAS). The effects of AlF wavelength, burner height, fuel rate (C(2)H(2)/N(2)O) and amount of Al on the accuracy, precision and sensitivity were investigated and optimized. The Al-F absorption band at 227.4613 nm was found to be the most suitable analytical line with respect to sensitivity and spectral interferences. Maximum sensitivity and a good linearity were obtained in acetylene-nitrous oxide flame at a flow rate of 210 L h(-1) and a burner height of 8mm using 3000 mg L(-1) of Al for 10-1000 mg L(-1)of F. The accuracy and precision of the method were tested by analyzing spiked samples and waste water certified reference material. The results were in good agreement with the certified and spiked amounts as well as the precision of several days during this study was satisfactory (RSD<10%). The limit of detection and characteristic concentration of the method were 5.5 mg L(-1) and 72.8 mg L(-1), respectively. Finally, the fluorine concentrations in several toothpaste samples were determined. The results found and given by the producers were not significantly different. The method was simple, fast, accurate and sensitive. Copyright © 2012 Elsevier B.V. All rights reserved.

Effect of Acetylene Black Content in Li4Ti5O12 Xerogel Solid-State Anode Materials on Half-Cell Li-ion Batteries Performance

Science.gov (United States)

Abdurrahman, N. M.; Priyono, B.; Syahrial, A. Z.; Subhan, A.

2017-07-01

The effect of Acetylene Black (AB) additive contents in lithium titanate/Li4Ti5O12 (LTO) anode on Li-ion Batteries performance is studied in this work. The LTO active material for Li-ion batteries anode was successfully synthesized using sol-gel method to form TiO2 xerogel continued by mixing process with LiOH in ball-mill and then sintered to obtain spinel LTO. The LTO powder is characterized by X-Ray Diffraction (XRD), scanning electron microscopy-Energy Dispersive Spectroscopy (SEM-EDS), and Brunauer-Emmett-Teller (BET). The spinel LTO and TiO2 rutile were detected by XRD diffractogram. The LTO powder is in the form of agglomerates structure. This powder then was mixed with PVDF binder (10%wt) and AB additives with various amount from 10%wt (LTO2 Ac-1), 12%wt (LTO2 Ac-2), and 15%wt (LTO2 Ac-3) of total weight solid content to form electrode sheet. Half-cell coin battery was made with lithium metal foil as a counter electrode. Cyclic voltammetry (CV), Electrochemical-impedance spectroscopy (EIS), and charge discharge (CD) test used to examine the battery performance. The highest resistance value is obtained in LTO2 Ac-3 sample with 15%wt of AB. It might be caused by the formation of side reaction product on electrode surface at initial cycle due to high reactivity of LTO2 Ac-3 electrode. The highest initial capacity at CV test and CD test was obtained in LTO2 Ac-1 (10%wt AB) sample, due to the best proportion of active material content in the compound. While, in the charge-discharge test at high current rate, the best sample rate-capability performance belongs to LTO2 Ac-3 sample (15%wt AB), which still have 24.12 mAh/g of discharge capacity at 10 C with 71.34% capacity loss.

Secondary Organic Aerosol Formation from Acetylene (C2H2: seed effect on SOA yields due to organic photochemistry in the aerosol aqueous phase

Directory of Open Access Journals (Sweden)

P. J. Ziemann

2009-03-01

Full Text Available The lightest Non Methane HydroCarbon (NMHC, i.e., acetylene (C2H2 is found to form secondary organic aerosol (SOA. Contrary to current belief, the number of carbon atoms, n, for a NMHC to act as SOA precursor is lowered to n=2 here. The OH-radical initiated oxidation of C2H2 forms glyoxal (CHOCHO as the highest yield product, and >99% of the SOA from C2H2 is attributed to CHOCHO. SOA formation from C2H2 and CHOCHO was studied in a photochemical and a dark simulation chamber. Further, the experimental conditions were varied with respect to the chemical composition of the seed aerosols, mild acidification with sulphuric acid (SA, 3

An Approach for Hydrogen Recycling in a Closed-loop Life Support Architecture to Increase Oxygen Recovery Beyond State-of-the-Art

Science.gov (United States)

Abney, Morgan B.; Miller, Lee; Greenwood, Zachary; Alvarez, Giraldo

2014-01-01

State-of-the-art atmosphere revitalization life support technology on the International Space Station is theoretically capable of recovering 50% of the oxygen from metabolic carbon dioxide via the Carbon Dioxide Reduction Assembly (CRA). When coupled with a Plasma Pyrolysis Assembly (PPA), oxygen recovery increases dramatically, thus drastically reducing the logistical challenges associated with oxygen resupply. The PPA decomposes methane to predominantly form hydrogen and acetylene. Because of the unstable nature of acetylene, a down-stream separation system is required to remove acetylene from the hydrogen stream before it is recycled to the CRA. A new closed-loop architecture that includes a PPA and downstream Hydrogen Purification Assembly (HyPA) is proposed and discussed. Additionally, initial results of separation material testing are reported.

Use of 15N in evaluating symbiotic N2 fixation of field-grown soybeans

International Nuclear Information System (INIS)

Ham, G.E.

1978-01-01

Various methods have been used to estimate N 2 fixation by legumes (i.e. Kjeldahl N and the acetylene-ethylene assay). Recently 'Asub(N)' values by the legume and a non-nodulating crop using 15 N-labelled N fertilizer were used to quantitatively estimate the amount of N 2 fixed by legume crops growing under field conditions. The objective of this research was to evaluate Kjeldahl N procedures, the acetylene-ethylene assay and the 'Asub(N)' technique as estimators of N 2 fixation by field-grown soybeans. The 'Asub(N)' value concept provided a reliable estimate of N 2 fixation by soybeans which agreed with acetylene-ethylene measurements made weekly and the values compared favourably with Kjeldahl N measurements. (author)

Cunqueiro in Catalonia: A Model of Intersystemic Relations

Directory of Open Access Journals (Sweden)

María Xesús Lama López

2012-12-01

Full Text Available Abstract: Panoramic study on Álvaro Cunqueiro and cunqueirian studies’ contact and exchanges with Catalan culture as a presentation of the context of intercultural relationships in which this monograph falls. The three areas dealt with, in a diverse criticism, are considered to be: personal relationships with Catalan cultural agents, allowing different collaborations and exchanges; professional relationships with the editorial and journalistic world, launching his work on the Spanish market; and repertorial relationships, shown in translations or in literary criticisms, made by the author of his own readings.

Two-mode chaos and its synchronization properties

DEFF Research Database (Denmark)

Postnov, D E; Shishkin, A V; Sosnovtseva, Olga

2005-01-01

Using a simple model with bimodal dynamics, we investigate the intra- and inter-system entrainment of the two different time scales involved in the chaotic oscillations. The transition between mode-locked and mode-unlocked chaos is analyzed for a single system. For coupled oscillators, we...

Light-induced cross-linking and post-cross-linking modification of polyglycidol.

Science.gov (United States)

Marquardt, F; Bruns, M; Keul, H; Yagci, Y; Möller, M

2018-02-08

The photoinduced radical generation process has received renewed interest due to its economic and ecological appeal. Herein the light-induced cross-linking of functional polyglycidol and its post-cross-linking modification are presented. Linear polyglycidol was first functionalized with a tertiary amine in a two-step reaction. Dimethylaminopropyl functional polyglycidol was cross-linked in a UV-light mediated reaction with camphorquinone as a type II photoinitiator. The cross-linked polyglycidol was further functionalized by quaternization with various organoiodine compounds. Aqueous dispersions of the cross-linked polymers were investigated by means of DLS and zeta potential measurements. Polymer films were evaluated by DSC and XPS.

Photo- and heterotrophic nitrogenase activity by the cyano-bacterium Nostoc in symbiosis with the bryophyte Anthoceros

International Nuclear Information System (INIS)

Steinberg, N.A.; Meeks, J.C.

1987-01-01

In symbiosis with Anthoceros, Nostoc is thought to do little or no photosynthesis. However, light-dependent 14 CO 2 fixation by symbiotic Nostoc, freshly isolated from pure cultures of the reconstituted Anthoceros-Nostoc association, was 16% of that by free-living Nostoc. A DCMU-resistant mutant of Nostoc was isolated that fixed CO 2 at rates comparable to wild-type in both symbiotic and free-living growth states. To determine if symbiotic Nostoc can use its photosynthate directly to fix nitrogen, acetylene reduction by Anthoceros associations reconstituted with wild-type Nostoc was compared to associations with the DCMU-resistant mutant. In wild-type Anthoceros-Nostoc acetylene reduction was inhibited 97% by 5 μM DCMU, while inhibition of the DCMU-resistant Nostoc association was only 63%. Additions of glucose, fructose, maltose or sucrose to wild-type associations completely restored DCMU-inhibited acetylene reduction in the light. Acetylene reduction in the dark was stimulated by glucose, attaining 84% of the uninhibited light-dependent value. The authors conclude that symbiotic Nostoc maintains a pool of photosynthate which supports nitrogenase activity. The pool can also be supplemented from plant sources

Two-mode chaos and its synchronization properties

DEFF Research Database (Denmark)

Postnov, D.E.; Shishkin, A.V.; Sosnovtseva, Olga

2005-01-01

Using a simple model with bimodal dynamics, we investigate the intra- and inter-system entrainment of the two different time scales involved in the chaotic oscillations. The transition between mode-locked and mode-unlocked chaos is analyzed for a single system. For coupled oscillators, we demonst...

Rhodamine dyes as potential agents for photochemotherapy of cancer in human bladder carcinoma cells

International Nuclear Information System (INIS)

Shea, C.R.; Chen, N.; Wimberly, J.; Hasan, T.

1989-01-01

The phototoxicity in vitro of rhodamine 123 and tetrabromo rhodamine 123 (TBR) was compared, in order to assess their photochemotherapeutic potential. Exposure to 514.5-nm radiation from an argon ion laser caused phototoxicity in MGH-U1 bladder carcinoma cells previously treated with either dye at 10 microM for 30 min. As assessed by colony formation and cellular morphology, TBR was markedly more phototoxic than rhodamine 123, reflecting increased intersystem crossing of TBR to the triplet manifold via spin-orbital coupling induced by the heavy bromine atoms. Photoreactions of TBR very efficiently generated singlet oxygen ( 1 O 2 ) in solution; furthermore, irradiation of TBR-treated cells was significantly more toxic when performed in the presence of deuterium oxide, an enhancer of damage caused by 1 O 2 . Retention of fluorescence in TBR-treated cells was enhanced by irradiation, indicating that a stable photoproduct may be formed in reaction with cellular components

Type II photoinitiator substituted zinc phthalocyanine: Synthesis, photophysical and photopolymerization studies

Energy Technology Data Exchange (ETDEWEB)

Korkut, Sibel Eken [Department of Chemistry, Yıldız Technical University, 34210 Davutpaşa, İstanbul (Turkey); Temel, Gokhan [Department of Polymer Engineering, Yalova University, 77100 Yalova (Turkey); Balta, Demet Karaca [Department of Chemistry, Yıldız Technical University, 34210 Davutpaşa, İstanbul (Turkey); Arsu, Nergis, E-mail: narsu@yildiz.edu.tr [Department of Chemistry, Yıldız Technical University, 34210 Davutpaşa, İstanbul (Turkey); Şener, M. Kasım, E-mail: mkasimsener@gmail.com [Department of Chemistry, Yıldız Technical University, 34210 Davutpaşa, İstanbul (Turkey)

2013-04-15

The novel 4-(9-oxo-9 H-thioxanthen-2yloxy) phthalonitrile (TX-Pht) and its peripherally tetra substituted zinc phthalocyanine complex (TX-ZnPc) have been prepared and characterized by spectroscopic and elemental analysis techniques. Photoinitiated polymerization of methyl methacrylate (MMA) with TX-ZnPc has been investigated in the presence and absence of a co-initiator. Fluorescence and phosphorescence measurements have been also performed to determine the photophysical properties. Low fluorescence quantum yield (Φ{sub F}=0.08) compared to the unsubstituted ZnPc has been found. This allows initiator to undergo intersystem crossing into the triplet state and the lowest triplet state possesses π-π{sup ⁎} configuration. Highlights: ► Zinc phthalocyanine (ZnPc), peripherally functionalized with photoactive thioxanthone (TX) groups was synthesized. ► The photophysical and photochemical properties of resulting photoinitiator were studied in DMF. ► Photoinitiated polymerization of MMA with TX-ZnPc was investigated in the presence and absence of co-initiator.

Can Expanded Bacteriochlorins Act as Photosensitizers in Photodynamic Therapy? Good News from Density Functional Theory Computations

Directory of Open Access Journals (Sweden)

Gloria Mazzone

2016-02-01

Full Text Available The main photophysical properties of a series of expanded bacteriochlorins, recently synthetized, have been investigated by means of DFT and TD-DFT methods. Absorption spectra computed with different exchange-correlation functionals, B3LYP, M06 and ωB97XD, have been compared with the experimental ones. In good agreement, all the considered systems show a maximum absorption wavelength that falls in the therapeutic window (600–800 nm. The obtained singlet-triplet energy gaps are large enough to ensure the production of cytotoxic singlet molecular oxygen. The computed spin-orbit matrix elements suggest a good probability of intersystem spin-crossing between singlet and triplet excited states, since they result to be higher than those computed for 5,10,15,20-tetrakis-(m-hydroxyphenylchlorin (Foscan© already used in the photodynamic therapy (PDT protocol. Because of the investigated properties, these expanded bacteriochlorins can be proposed as PDT agents.

Electronic and ionization spectra of 1,1-diamino-2,2-dinitroethylene, FOX-7.

Science.gov (United States)

Borges, Itamar

2014-03-01

Singlet, triplet and ionized states of the energetic molecule 1,1-diamino-2,2-dinitroethylene, known as FOX-7 or DADNE, were investigated using the symmetry-adapted-cluster configuration interaction (SAC-CI) ab initio wave function. The 20 computed singlet transitions, with 2 exceptions, were bright. The most intense singlet transitions were of the n₀→π type-typical of molecules having nitro groups. Fast intersystem crossing (ISC) from the 1¹A, 2¹A and 8¹A bright singlet transitions is possible. Other feasible ISC processes are discussed. The computed singlet and ionization spectra have similar features when compared to nitramide and N,N-dimethylnitramine molecules, which have only a nitro group. The ionization energies of the first 20 states have differences in comparison with Koopmans' energy values that can reach 3 eV. Moreover, the character of the first ionized states, dominated by single ionizations, is not the same when compared with the character resulting from application of Koopmans' theorem.

Mapping of upper electronic reaction surfaces by tuned laser photolysis and by absorption and emission spectroscopies

International Nuclear Information System (INIS)

Morgan, M.A.

1989-07-01

Potential energy surfaces for photorotamerization of two intramolecularly hydrogen-bonded molecules, o-hydroxybenzaldehyde (OHBA) and methyl salicylate (MS), isolated in cryogenic matrices have been spectroscopically mapped. In addition, the external heavy atom effect of krypton and xenon matrices on the coupling between the S 1 and T 1 surfaces of 4-(dimethylamino)benzonitrile has been examined. Heavy atom matrices are known to increase rates of spin-forbidden processes. The phosphorescence intensity of DMABN increases in krypton and xenon matrices, while the fluorescence intensity, and phosphorescence and fluorescence lifetimes, decrease. These effects are interpreted in terms of a model in which the phosphorescence rate constant increases 300-fold in xenon compared to argon, while the rate constants for intersystem crossing and nonradiative relaxation from the triplet state increase by factors of less than 5. Lifetime measurements in argon matrices doped with heavy atoms indicate that even one heavy atom neighbor has a significant effect on both singlet and triplet lifetimes. 78 refs., 35 figs., 15 tabs

Pharmacokinetics and pharmacodynamics of orally administered acetylenic tricyclic bis(cyanoenone), a highly potent Nrf2 activator with a reversible covalent mode of action

Energy Technology Data Exchange (ETDEWEB)

Kostov, Rumen V.; Knatko, Elena V.; McLaughlin, Lesley A.; Henderson, Colin J. [Jacqui Wood Cancer Centre, Division of Cancer Research, Medical Research Institute, University of Dundee, Dundee, DD1 9SY, Scotland (United Kingdom); Zheng, Suqing [Department of Chemistry and Institute of Chemical Biology & Drug Discovery, Stony Brook University, Stony Brook, NY, 11794 (United States); Huang, Jeffrey T.-J. [Jacqui Wood Cancer Centre, Division of Cancer Research, Medical Research Institute, University of Dundee, Dundee, DD1 9SY, Scotland (United Kingdom); Honda, Tadashi [Department of Chemistry and Institute of Chemical Biology & Drug Discovery, Stony Brook University, Stony Brook, NY, 11794 (United States); Dinkova-Kostova, Albena T., E-mail: a.dinkovakostova@dundee.ac.uk [Jacqui Wood Cancer Centre, Division of Cancer Research, Medical Research Institute, University of Dundee, Dundee, DD1 9SY, Scotland (United Kingdom); Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, 21205 (United States); Department of Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine, Baltimore, MD, 21205 (United States)

2015-09-25

The acetylenic tricyclic bis(cyanoenone) TBE-31 is a highly potent cysteine targeting compound with a reversible covalent mode of action; its best-characterized target being Kelch-like ECH-associated protein-1 (Keap1), the cellular sensor for oxidants and electrophiles. TBE-31 reacts with cysteines of Keap1, impairing its ability to target nuclear factor-erythroid 2 p45-related factor 2 (Nrf2) for degradation. Consequently, Nrf2 accumulates and orchestrates cytoprotective gene expression. In this study we investigated the pharmacokinetic and pharmacodynamic properties of TBE-31 in C57BL/6 mice. After a single oral dose of 10 μmol/kg (∼200 nmol/animal), the concentration of TBE-31 in blood exhibited two peaks, at 22.3 nM and at 15.5 nM, 40 min and 4 h after dosing, respectively, as determined by a quantitative stable isotope dilution LC-MS/MS method. The AUC{sub 0–24h} was 195.5 h/nmol/l, the terminal elimination half-life was 10.2 h, and the k{sub el} was 0.068 h{sup −1}. To assess the pharmacodynamics of Nrf2 activation by TBE-31, we determined the enzyme activity of its prototypic target, NAD(P)H:quinone oxidoreductase 1 (NQO1) and found it elevated by 2.4- and 1.5-fold in liver and heart, respectively. Continuous feeding for 18 days with diet delivering the same daily doses of TBE-31 under conditions of concurrent treatment with the immunosuppressive agent azathioprine had a similar effect on Nrf2 activation without any indications of toxicity. Together with previous reports showing the cytoprotective effects of TBE-31 in animal models of carcinogenesis, our results demonstrate the high potency, efficacy and suitability for chronic administration of cysteine targeting reversible covalent drugs. - Highlights: • TBE-31 is a cysteine targeting compound with a reversible covalent mode of action. • After a single oral dose, the blood concentration of TBE-31 exhibits two peaks. • Oral TBE-31 is a potent activator of Nrf2-dependent enzymes in

Preparation and comparison of a-C:H coatings using reactive sputter techniques

Energy Technology Data Exchange (ETDEWEB)

Keunecke, M., E-mail: martin.keunecke@ist.fraunhofer.d [Fraunhofer Institute for Surface Engineering and Thin Films (IST), Braunschweig (Germany); Weigel, K.; Bewilogua, K. [Fraunhofer Institute for Surface Engineering and Thin Films (IST), Braunschweig (Germany); Cremer, R.; Fuss, H.-G. [CemeCon AG, Wuerselen (Germany)

2009-12-31

Amorphous hydrogenated carbon (a-C:H) coatings are widely used in several industrial applications. These coatings commonly will be prepared by plasma activated chemical vapor deposition (PACVD). The main method used to prepare a-C:H coating in industrial scale is based on a glow discharge in a hydrocarbon gas like acetylene or methane using a substrate electrode powered with medium frequency (m.f. - some 10 to 300 kHz). Some aims of further development are adhesion improvement, increase of hardness and high coating quality on complex geometries. A relatively new and promising technique to fulfil these requirements is the deposition of a-C:H coatings by a reactive d.c. magnetron sputter deposition from a graphite target with acetylene as reactive gas. An advancement of this technique is the deposition in a pulsed magnetron sputter process. Using these three mentioned techniques a-C:H coatings were prepared in the same deposition machine. For adhesion improvement different interlayer systems were applied. The effect of different substrate bias voltages (d.c. and d.c. pulse) was investigated. By applying the magnetron sputter technique in the d.c. pulse mode, plastic hardness values up to 40 GPa could be reached. Besides hardness other mechanical properties like resistance against abrasive wear were measured and compared. Cross sectional SEM images showed the growth structure of the coatings.

Understanding Infidelity: An Interview with Gerald Weeks

Science.gov (United States)

Smith, Travis

2011-01-01

In this interview, Gerald Weeks shares his expertise on the topic of infidelity and couples counseling. Dr. Weeks defines infidelity, presents assessment strategies for treating the issue of infidelity, and discusses an intersystemic model for infidelity treatment when counseling couples. Dr. Weeks also provides insight into common mistakes made…

The Seven Deadly Sins of World University Ranking: A Summary from Several Papers

Science.gov (United States)

Soh, Kaycheng

2017-01-01

World university rankings use the weight-and-sum approach to process data. Although this seems to pass the common sense test, it has statistical problems. In recent years, seven such problems have been uncovered: spurious precision, weight discrepancies, assumed mutual compensation, indictor redundancy, inter-system discrepancy, negligence of…

Multifractal Cross Wavelet Analysis

Science.gov (United States)

Jiang, Zhi-Qiang; Gao, Xing-Lu; Zhou, Wei-Xing; Stanley, H. Eugene

Complex systems are composed of mutually interacting components and the output values of these components usually exhibit long-range cross-correlations. Using wavelet analysis, we propose a method of characterizing the joint multifractal nature of these long-range cross correlations, a method we call multifractal cross wavelet analysis (MFXWT). We assess the performance of the MFXWT method by performing extensive numerical experiments on the dual binomial measures with multifractal cross correlations and the bivariate fractional Brownian motions (bFBMs) with monofractal cross correlations. For binomial multifractal measures, we find the empirical joint multifractality of MFXWT to be in approximate agreement with the theoretical formula. For bFBMs, MFXWT may provide spurious multifractality because of the wide spanning range of the multifractal spectrum. We also apply the MFXWT method to stock market indices, and in pairs of index returns and volatilities we find an intriguing joint multifractal behavior. The tests on surrogate series also reveal that the cross correlation behavior, particularly the cross correlation with zero lag, is the main origin of cross multifractality.

Cross Selling Management

OpenAIRE

Nufer, Gerd; Kelm, Daniel

2011-01-01

Erfolgreiches Cross Selling Management bietet die Möglichkeit, die Profitabilität von Neu- oder Bestandskunden zu steigern und kann zur Verbesserung der Kundenzufriedenheit, Kundenbindung und Verlängerung des Kundenlebenszyklus beitragen. Um erfolgreiches Cross Selling Management zu betreiben, sind ein systematisches Vorgehen und die Bereitstellung von Unternehmensressourcen notwendig. Umfangreiche vorbereitende Maßnahmen stellen sicher, dass Cross Selling nicht dem Zufall überlassen wird. De...

Characterization of a rotating nanoparticle cloud in an inductively coupled plasma

International Nuclear Information System (INIS)

Schulze, M; Keudell, A von; Awakowicz, P

2006-01-01

Carbon clusters with diameters in the range of 10 to 50 nm are produced by injecting pulses of acetylene into an inductively coupled plasma in argon and helium. The injection causes plasma instability, which becomes visible as an oscillation of the emission intensity. The frequency of this oscillation can be uniquely correlated to the particle diameter. Consequently, the measurement of the oscillation frequency represents a method to determine particle diameters in situ. The oscillation corresponds to the rotation of a localized plasmoid and a particle cloud around the symmetry axis of the reactor. It is assumed that this rotation is driven by the ion wind crossing the interface between the plasmoid and the particle cloud

Cross-border versus cross-sector interconnectivity in renewable energy systems

DEFF Research Database (Denmark)

Thellufsen, Jakob Zinck; Lund, Henrik

2017-01-01

. The results show that while both measures increase the system utilisation of renewable energy and the system efficiency, the cross-sector interconnection gives the best system performance. To analyse the possible interaction between cross-sector and cross-border interconnectivity, two main aspects have......In the transition to renewable energy systems, fluctuating renewable energy, such as wind and solar power, plays a large and important role. This creates a challenge in terms of meeting demands, as the energy production fluctuates based on weather patterns. To utilise high amounts of fluctuating...... renewable energy, the energy system has to be more flexible in terms of decoupling demand and production. This paper investigates two potential ways to increase flexibility. The first is the interconnection between energy systems, for instance between two countries, labelled as cross-border interconnection...

Triazole: a unique building block for the construction of functional materials.

Science.gov (United States)

Juríček, Michal; Kouwer, Paul H J; Rowan, Alan E

2011-08-21

Over the past 50 years, numerous roads towards carbon-based materials have been explored, all of them being paved using mainly one functional group as the brick: acetylene. The acetylene group, or the carbon-carbon triple bond, is one of the oldest and simplest functional groups in chemistry, and although not present in any of the naturally occurring carbon allotropes, it is an essential tool to access their synthetic carbon-rich family. In general, two strategies towards the synthesis of π-conjugated carbon-rich structures can be employed: (a) either the acetylene group serves as a building block to access acetylene-derived structures or (b) it serves as a synthetic tool to provide other, usually benzenoid, structures. The recently discovered copper-catalysed azide-alkyne cycloaddition (CuAAC) reaction, however, represents a new powerful alternative: it transforms the acetylene group into a five-membered heteroaromatic 1H-1,2,3-triazole (triazole) ring and this gives rise to new opportunities. Compared with all-carbon aromatic non-functional rings, the triazole ring possesses three nitrogen atoms and, thus, can serve as a ligand to coordinate metals, or as a hydrogen bond acceptor and donor. This Feature Article summarises examples of using the triazole ring to construct conjugation- and/or function-related heteroaromatic materials, such as tuneable multichromophoric covalent ensembles, macrocyclic receptors or responsive foldamers. These recent examples, which open a new sub-field within organic materials, started to appear only few years ago and represent "a few more bricks" on the road to carbon-rich functional materials. This journal is © The Royal Society of Chemistry 2011

German cross-cultural psychology

OpenAIRE

Trommsdorff, Gisela

1986-01-01

The present study deals with German-language cross-cultural research in different fields of psychology which attempts to achieve one Or more goals of cross-cultural psychology. First, methodological problems are discussed, followed by a selective presentation of cross-cultural research in personality, clinical, ethological, developmental, and social psychology. The theoretical and methodological advancement of these studies is investigated with respect to four approaches - universals in cross...

Cross-border versus cross-sector interconnectivity in renewable energy systems

DEFF Research Database (Denmark)

Thellufsen, Jakob Zinck; Lund, Henrik

2017-01-01

renewable energy, the energy system has to be more flexible in terms of decoupling demand and production. This paper investigates two potential ways to increase flexibility. The first is the interconnection between energy systems, for instance between two countries, labelled as cross-border interconnection...... systems that represent Northern and Southern Europe. Both systems go through three developmental steps that increase the cross-sector interconnectivity. At each developmental step an increasing level of transmission capacities is examined to identify the benefits of cross-border interconnectivity...

Diacetylene time-temperature indicators

International Nuclear Information System (INIS)

Patel, G.N.; Yee, K.C.

1980-01-01

An improved recording device is described, useful for measuring the integrated time-temperature or integrated radiation-dosage history of an article, comprising a substrate onto which an acetylenic compound, containing at least two conjugated c*c groups, in an inactive form, is deposited. The inactive form is capable of being converted by melt or solvent recrystallization to an active form, which undergoes 1,4-addition polymerization resulting in an irreversible, progressive color change. The color change produced at any given point in time represents an integrated time-temperature history of thermal annealing or integrated radiation-dosage history of exposure to actinic radiation to which an article has been exposed. Also described is a process for producing an inactive form of the acetylenic compound. A film and a fiber, made from the inactive form of an acetylenic compound are also described

Cross-border versus cross-sector interconnectivity in renewable energy systems

International Nuclear Information System (INIS)

Thellufsen, Jakob Zinck; Lund, Henrik

2017-01-01

In the transition to renewable energy systems, fluctuating renewable energy, such as wind and solar power, plays a large and important role. This creates a challenge in terms of meeting demands, as the energy production fluctuates based on weather patterns. To utilise high amounts of fluctuating renewable energy, the energy system has to be more flexible in terms of decoupling demand and production. This paper investigates two potential ways to increase flexibility. The first is the interconnection between energy systems, for instance between two countries, labelled as cross-border interconnection, and the second is cross-sector interconnection, i.e., the integration between different parts of an energy system, for instance heat and electricity. This paper seeks to compare the types of interconnectivity and discuss to which extent they are mutually beneficial. To do this, the study investigates two energy systems that represent Northern and Southern Europe. Both systems go through three developmental steps that increase the cross-sector interconnectivity. At each developmental step an increasing level of transmission capacities is examined to identify the benefits of cross-border interconnectivity. The results show that while both measures increase the system utilisation of renewable energy and the system efficiency, the cross-sector interconnection gives the best system performance. To analyse the possible interaction between cross-sector and cross-border interconnectivity, two main aspects have to be clarified. The first part defines the approach and the second is the construction of the two archetypes. - Highlights: • A method to investigate system integration and system interconnection is suggested. • The implementation is investigated across a Northern and Southern energy system. • The study identifies benefits of system integration and system interconnection. • The performance of the energy system benefits most from system integration.

New Drugs for CML

Science.gov (United States)

2007-02-01

to a fulminant acute leukemic disorder in which patients die of bleeding and infection (1). Allogeneic bone marrow transplantation was the first...acetylenes were created in one step by the coupling of a propiolate anion and isocyanate. These acetylenes were then used as a precursor in the synthesis of...the furans. The furan synthesis was based on early research in the Austin laboratory, which was centered on the concept of adapting the 1,3-dipolar

Border Crossing/Entry Data - Border Crossing/Entry Data Time Series tool

Data.gov (United States)

Department of Transportation — The dataset is known as “Border Crossing/Entry Data.” The Bureau of Transportation Statistics (BTS) Border Crossing/Entry Data provides summary statistics to the...

Crossed modules of racks

OpenAIRE

Crans, Alissa S.; Wagemann, Friedrich

2014-01-01

We generalize the notion of a crossed module of groups to that of a crossed module of racks. We investigate the relation to categorified racks, namely strict 2-racks, and trunk-like objects in the category of racks, generalizing the relation between crossed modules of groups and strict 2-groups. Then we explore topological applications. We show that by applying the rack-space functor, a crossed module of racks gives rise to a covering. Our main result shows how the fundamental racks associate...

Cross of Lorraine and Cross of Caravaca: new IUD's with low expulsion rates.

Science.gov (United States)

Coutinho, E M; Mascarenhas, M J

1985-01-01

The Cross of Caravaca and Cross of Lorraine IUDs with double horizontal bar design were developed in an attempt to reduce expulsion and removal rates for pain and bleeding encountered with other IUDs. The devices were manufactured in radio-opaque plastic bearing copper wire or sleeves on the top arm. The Cross of Lorraine has the upper arm shorter than the lower arm whereas in the Cross of Caravaca the shorter is the lower arm. 748 women had insertion of the Cross of Caravaca and 412 had insertion of the Cross of Lorraine. For the Cross of Caravaca 486 women completed 1 year of use, 392 completed 2 years and 310 completed 3 years. For the Cross of Lorraine, 268 women completed the 1st year, 205 the 2nd, and 150 women completed 3 years of use. The combined number of observed months of use for the 2 devices at the end of 3 years was 24,963. Accidental pregnancy rates at the end of 3 years were 1.13% for Caravaca and 3.48% for Lorraine. Expulsion rates at the end of 3 years were nil for the Cross of Lorraine and 1.16% for the Cross of Caravaca. Pain and bleeding were the most common causes of termination for medical reasons, bleeding accounting for termination in 1.66% of Lorraine users at the end of 3 years of use and 2.75% of Caravaca users. Pain accounted for termination in 3.14% of Caravaca users and 2.02% of Lorraine users. Incidence of infection was 0.42% and nil for Caravaca and Lorraine users respectively. Total discontinuation rates at the end of 3 years were 25.39% for Caravaca and 16.67% for Lorraine.

CROPPER: a metagene creator resource for cross-platform and cross-species compendium studies.

Science.gov (United States)

Paananen, Jussi; Storvik, Markus; Wong, Garry

2006-09-22

Current genomic research methods provide researchers with enormous amounts of data. Combining data from different high-throughput research technologies commonly available in biological databases can lead to novel findings and increase research efficiency. However, combining data from different heterogeneous sources is often a very arduous task. These sources can be different microarray technology platforms, genomic databases, or experiments performed on various species. Our aim was to develop a software program that could facilitate the combining of data from heterogeneous sources, and thus allow researchers to perform genomic cross-platform/cross-species studies and to use existing experimental data for compendium studies. We have developed a web-based software resource, called CROPPER that uses the latest genomic information concerning different data identifiers and orthologous genes from the Ensembl database. CROPPER can be used to combine genomic data from different heterogeneous sources, allowing researchers to perform cross-platform/cross-species compendium studies without the need for complex computational tools or the requirement of setting up one's own in-house database. We also present an example of a simple cross-platform/cross-species compendium study based on publicly available Parkinson's disease data derived from different sources. CROPPER is a user-friendly and freely available web-based software resource that can be successfully used for cross-species/cross-platform compendium studies.

Cross-flow electrochemical reactor cells, cross-flow reactors, and use of cross-flow reactors for oxidation reactions

Science.gov (United States)

Balachandran, Uthamalingam; Poeppel, Roger B.; Kleefisch, Mark S.; Kobylinski, Thaddeus P.; Udovich, Carl A.

1994-01-01

This invention discloses cross-flow electrochemical reactor cells containing oxygen permeable materials which have both electron conductivity and oxygen ion conductivity, cross-flow reactors, and electrochemical processes using cross-flow reactor cells having oxygen permeable monolithic cores to control and facilitate transport of oxygen from an oxygen-containing gas stream to oxidation reactions of organic compounds in another gas stream. These cross-flow electrochemical reactors comprise a hollow ceramic blade positioned across a gas stream flow or a stack of crossed hollow ceramic blades containing a channel or channels for flow of gas streams. Each channel has at least one channel wall disposed between a channel and a portion of an outer surface of the ceramic blade, or a common wall with adjacent blades in a stack comprising a gas-impervious mixed metal oxide material of a perovskite structure having electron conductivity and oxygen ion conductivity. The invention includes reactors comprising first and second zones seprated by gas-impervious mixed metal oxide material material having electron conductivity and oxygen ion conductivity. Prefered gas-impervious materials comprise at least one mixed metal oxide having a perovskite structure or perovskite-like structure. The invention includes, also, oxidation processes controlled by using these electrochemical reactors, and these reactions do not require an external source of electrical potential or any external electric circuit for oxidation to proceed.

Structural and mechanical properties of amorphous carbon films deposited by the dual plasma technique

Institute of Scientific and Technical Information of China (English)

Yaohui Wang; Xu Zhang; Xianying Wu; Huixing Zhang; Xiaoji Zhang

2008-01-01

Direct current metal filtered cathodic vacuum are (FCVA) and acetylene gas (C2H2) were wielded to synthesize Ti-containing amorphous carbon films on Si (100). The influence of substrate bias voltage and acetylene gas on the microstructure and mechanical properties of the films were investigated. The results show that the phase of TiC in the (111) preferential crystallo-graphic orientation exists in the film, and rite main existing pattern of carbon is sp2. With increasing the acetylene flow rate, the con-tents of Ti and TiC phase of the film gradually reduce; however, the thickness of the film increases. When the substrate bias voltage reaches -600 V, the internal stress of the film reaches 1.6 GPa. The micro-hardness and elastic modulus of the film can reach 33.9 and 237.6 GPa, respectively, and the friction coefficient of the film is 0.25.

Cross-Platform Technologies

Directory of Open Access Journals (Sweden)

Maria Cristina ENACHE

2017-04-01

Full Text Available Cross-platform - a concept becoming increasingly used in recent years especially in the development of mobile apps, but this consistently over time and in the development of conventional desktop applications. The notion of cross-platform software (multi-platform or platform-independent refers to a software application that can run on more than one operating system or computing architecture. Thus, a cross-platform application can operate independent of software or hardware platform on which it is execute. As a generic definition presents a wide range of meanings for purposes of this paper we individualize this definition as follows: we will reduce the horizon of meaning and we use functionally following definition: a cross-platform application is a software application that can run on more than one operating system (desktop or mobile identical or in a similar way.

Standard cross-section data

International Nuclear Information System (INIS)

Carlson, A.D.

1984-01-01

The accuracy of neutron cross-section measurement is limited by the uncertainty in the standard cross-section and the errors associated with using it. Any improvement in the standard immediately improves all cross-section measurements which have been made relative to that standard. Light element, capture and fission standards are discussed. (U.K.)

Pullback and pushout crossed polymodules

Indian Academy of Sciences (India)

Crossed module; polygroup; crossed polymodule; action; pullback; pushout; fundamental relation. Mathematics Subject Classification. 13D99, 20N20, 18D35. 1. Introduction. Crossed module was defined by Whitehad in [21] and many have worked on this sub- ject. There are many examples of crossed module such as ...

Fabrication and evaluation of polymeric early-warning fire-alarm devices. [combustion products

Science.gov (United States)

Senturia, S. D.

1975-01-01

The electrical resistivities were investigated of some polymers known to be enhanced by the presence of certain gases. This was done to make a device capable of providing early warning to fire through its response with the gases produced in the early phases of combustion. Eight polymers were investigated: poly(phenyl acetylene), poly(p-aminophenyl acetylene), poly(p-nitrophenyl acetylene), poly(p-formamidophenyl acetylene), poly(ethynyl ferrocene), poly(ethynyl carborane), poly(ethynyl pyridine), and the polymer made from 1,2,3,6 tetramethyl pyridazine. A total of 40 usable thin-film sandwich devices and a total of 70 usable interdigitated-electrode lock-and-key devices were fabricated. The sandwich devices were used for measurements of contact linearity, polymer conductivity, and polymer dielectric constant. The lock-and-key devices were used to determine the response of the polymers to a spectrum of gases that included ammonia, carbon nonoxide, carbon dioxide, sulfur dioxide, ethylene, acrolein, water vapor, and normal laboratory air. Strongest responses were to water vapor, ammonia, and acrolein, and depending on the polymer, weaker responses to carbon dioxide, sulfur dioxide, and carbon monoxide were observed. A quantitative theory of device operation, capable of accounting for observed device leakage current and sensitivity, was developed. A prototype detection/alarm system was designed and built for use in demonstrating sensor performance.

Carboxymethyl chitosan/conducting polymer as water-soluble composite binder for LiFePO4 cathode in lithium ion batteries

Science.gov (United States)

Zhong, Haoxiang; He, Aiqin; Lu, Jidian; Sun, Minghao; He, Jiarong; Zhang, Lingzhi

2016-12-01

A water-soluble conductive composite binder consisting of carboxymethyl chitosan (CCTS) as a binder and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) as a conduction-promoting agent is reported for the LiFePO4 (LFP) cathode in Li-ion batteries. The introduction of conductive PEDOT:PSS as a conductive composite binder facilitates the formation of homogeneous and continuous conducting bridges throughout the electrode and raises the compaction density of the electrode sheet by decreasing the amounts of the commonly used conducting agent of acetylene black. The optimized replacement ratios of acetylene black with PEDOT:PSS (acetylene black/PEDOT:PSS = 1:1, by weight) are obtained by measuring electrical conductivity, peel strength and compaction density of the electrode sheets. The LFP half-cell with the optimized conductive binder exhibits better cycling and rate performance and more favorable electrochemical kinetics than that using only acetylene black conducting agent. The pilot application of PEDOT:PSS/CCTS binder in 10 Ah CCTS-LFP prismatic cell exhibits a comparable cycling performance, retaining 89.7% of capacity at 1 C/2 C (charge/discharge) rate as compared with 90% for commercial PVDF-LFP over 1000 cycles, and better rate capability than that of commercial PVDF-LFP, retaining 98% capacity of 1 C at 7 C rate as compared with 95.4% for PVDF-LFP.

Phylogeny of nodulation genes and symbiotic diversity of Acacia senegal (L.) Willd. and A. seyal (Del.) Mesorhizobium strains from different regions of Senegal.

Science.gov (United States)

Bakhoum, Niokhor; Galiana, Antoine; Le Roux, Christine; Kane, Aboubacry; Duponnois, Robin; Ndoye, Fatou; Fall, Dioumacor; Noba, Kandioura; Sylla, Samba Ndao; Diouf, Diégane

2015-04-01

Acacia senegal and Acacia seyal are small, deciduous legume trees, most highly valued for nitrogen fixation and for the production of gum arabic, a commodity of international trade since ancient times. Symbiotic nitrogen fixation by legumes represents the main natural input of atmospheric N2 into ecosystems which may ultimately benefit all organisms. We analyzed the nod and nif symbiotic genes and symbiotic properties of root-nodulating bacteria isolated from A. senegal and A. seyal in Senegal. The symbiotic genes of rhizobial strains from the two Acacia species were closed to those of Mesorhizobium plurifarium and grouped separately in the phylogenetic trees. Phylogeny of rhizobial nitrogen fixation gene nifH was similar to those of nodulation genes (nodA and nodC). All A. senegal rhizobial strains showed identical nodA, nodC, and nifH gene sequences. By contrast, A. seyal rhizobial strains exhibited different symbiotic gene sequences. Efficiency tests demonstrated that inoculation of both Acacia species significantly affected nodulation, total dry weight, acetylene reduction activity (ARA), and specific acetylene reduction activity (SARA) of plants. However, these cross-inoculation tests did not show any specificity of Mesorhizobium strains toward a given Acacia host species in terms of infectivity and efficiency as stated by principal component analysis (PCA). This study demonstrates that large-scale inoculation of A. senegal and A. seyal in the framework of reafforestation programs requires a preliminary step of rhizobial strain selection for both Acacia species.

Cross sections for atmospheric corrections

International Nuclear Information System (INIS)

Meyer, J.P.; Casse, M.; Westergaard, N.

1975-01-01

A set of cross sections for spallation of relativistic nuclei is proposed based on (i) the best available proton cross sections, (ii) an extrapolation to heavier nuclei of the dependence on the number of nucleons lost of the 'target factor' observed for C 12 and O 16 by Lindstrom et al. (1975), in analogy with Rudstam's formalism, and (iii) on a normalization of all cross sections to the total cross sections for production of fragments with Asub(f) >= 6. The obtained cross sections for peripheral interactions are not inconsistent with simple geometrical considerations. (orig.) [de

Kinetics of Hydrocarbon formation in a-C:H film deposition plasmas

International Nuclear Information System (INIS)

De la Cal, E.; Tabares, F.L.

1993-01-01

The formation of C 2 and C 3 hydrocarbons during the PACVD of a-C-H films from admixtures of methane with H 2 and He has been investigated by mass spectrometry under several deposition condition. The time evolution of the observed species indicates that the formation mechanism of ethylene and acetylene are sensitive to the conditions of the wall during the growing of the film. Acetylene are sensitive to the conditions of the wall during the growing of the carburized metal. (Author)

Cross-impact method

Directory of Open Access Journals (Sweden)

Suzić Nenad

2014-01-01

Full Text Available The paper displays the application of the Cross-Impact method in pedagogy, namely a methodological approach which crosses variables in a novel, but statistically justified manner. The method is an innovation in pedagogy as well as in research methodology of social and psychological phenomena. Specifically, events and processes are crossed, that is, experts' predictions of about future interaction of events and processes. Therefore, this methodology is futuristic; it concerns predicting future, which is of key importance for pedagogic objectives. The paper presents two instances of the cross-impact approach: the longer, displayed in fourteen steps, and the shorter, in four steps. They are both accompanied with mathematic and statistical formulae allowing for quantification, that is, a numerical expression of the probability of a certain event happening in the future. The advantage of this approach is that it facilitates planning in education which so far has been solely based on lay estimates and assumptions.

Generalized Cross-Gramian for Linear Systems

DEFF Research Database (Denmark)

Shaker, Hamid Reza

2012-01-01

The cross-gramian is a well-known matrix with embedded controllability and observability information. The cross-gramian is related to the Hankel operator and the Hankel singular values of a linear square system and it has several interesting properties. These properties make the cross...... square symmetric systems, the ordinary cross-gramian does not exist. To cope with this problem, a new generalized cross-gramian is introduced in this paper. In contrast to the ordinary cross-gramian, the generalized cross-gramian can be easily obtained for general linear systems and therefore can be used...

Cross-cultural organizational behavior.

Science.gov (United States)

Gelfand, Michele J; Erez, Miriam; Aycan, Zeynep

2007-01-01

This article reviews research on cross-cultural organizational behavior (OB). After a brief review of the history of cross-cultural OB, we review research on work motivation, or the factors that energize, direct, and sustain effort across cultures. We next consider the relationship between the individual and the organization, and review research on culture and organizational commitment, psychological contracts, justice, citizenship behavior, and person-environment fit. Thereafter, we consider how individuals manage their interdependence in organizations, and review research on culture and negotiation and disputing, teams, and leadership, followed by research on managing across borders and expatriation. The review shows that developmentally, cross-cultural research in OB is coming of age. Yet we also highlight critical challenges for future research, including moving beyond values to explain cultural differences, attending to levels of analysis issues, incorporating social and organizational context factors into cross-cultural research, taking indigenous perspectives seriously, and moving beyond intracultural comparisons to understand the dynamics of cross-cultural interfaces.

Academic Globalization: Cultureactive to Ice- the Cross-Cultural, Crossdisciplinary and Cross-Epistemological Transformation

Directory of Open Access Journals (Sweden)

Marta Szabo White

2010-12-01

Full Text Available Commensurate with the concept of Academic Globalization, coupled with the foray of Globalization, this paper underscores the cross-cultural, cross-disciplinary and cross-epistemological transformation from the first-generation Cultureactive to the second-generation InterCultural Edge [ICE]. The former is embedded in the experiential works of cross-cultural consultant. Richard Lewis and the latter is grounded in established theoretical frameworks. Both serve to underscore the impact of the Globalization Phenomenon, as manifested in and enabled by the acceleration of academic and practitioner cross-cultural activities. The contribution of this paper is the celebration of the longawaited arrival of ICE [InterCultural Edge]. While previous research streams have underscored global similarities and differences among cultures, a previous paper [19] established that cross-professional rather than cross-cultural differences are more paramount. Employing Cultureactive and the LMR framework, it was noted that business versus non-business predisposition had a more direct impact on one's individual cultural profile than did nationality. Regardless of culture, persons involved in business are characterized primarily by linear-active modes of communication, and persons involved in non-business activities typically employ more multiactive/hybrid and less linear modes of communication. The pivotal question is this: Now that we have a new and improved tool, are we in a better position to assess and predict leadership, negotiating styles, individual behaviors, etc., which are central to academic globalization and preparing global business leaders?

Cross-cultural nursing research.

Science.gov (United States)

Suhonen, Riitta; Saarikoski, Mikko; Leino-Kilpi, Helena

2009-04-01

International cross-cultural comparative nursing research is considered important for the advancement of nursing knowledge offering a global perspective for nursing. Although this is recognised in policy statements and quality standards, international comparative studies are rare in database citations. To highlight the need for cross-cultural comparative research in nursing and to share some of the insights gained after conducting three international/cross-cultural comparative studies. These are: an examination of patients' autonomy, privacy and informed consent in nursing interventions BIOMED 1998-2001, the ICProject International Patient Study 2002-2006 and the Ethical Codes in Nursing (ECN) project 2003-2005. There are three critical issues raised here for discussion from the international cross-cultural studies. These are: the planning and formulating of an international study, the conduct of cross-cultural research including the implementation of rigorous data collection and analysis and the reporting and implementing the results. International and cross-cultural nursing research is powerful tool for the improvement of clinical nursing practise, education and management and advancement of knowledge. Such studies should be carried out in order to improve European evidence based health care development in which the patients' perspective plays an important part in the evaluation and benchmarking of services.

Cross currency swap valuation

OpenAIRE

Boenkost, Wolfram; Schmidt, Wolfgang M.

2004-01-01

Cross currency swaps are powerful instruments to transfer assets or liabilities from one currency into another. The market charges for this a liquidity premium, the cross currency basis spread, which should be taken into account by the valuation methodology. We describe and compare two valuation methods for cross currency swaps which are based upon using two different discounting curves. The first method is very popular in practice but inconsistent with single currency swap valuation methods....

Language and Cross-Culture Understanding—Through Cross-Culture Study of the Word'Dragon'

Institute of Scientific and Technical Information of China (English)

周玲

2016-01-01

This essay contributes to the analysis of the significance of cross-culture understanding in connection with language. It is important and necessary to promote cross-cultural understanding in order to communicate with people from various cultural backgrounds with the development of globalization. This essay also gives the example of the word'dragon'to illustrate that the cross-culture understanding of language will make us communicate with each other more effectively.

Flow velocity measurement by using zero-crossing polarity cross correlation method

International Nuclear Information System (INIS)

Xu Chengji; Lu Jinming; Xia Hong

1993-01-01

Using the designed correlation metering system and a high accurate hot-wire anemometer as a calibration device, the experimental study of correlation method in a tunnel was carried out. The velocity measurement of gas flow by using zero-crossing polarity cross correlation method was realized and the experimental results has been analysed

Radiation cross-linked collagen/dextran dermal scaffolds: effects of dextran on cross-linking and degradation.

Science.gov (United States)

Zhang, Yaqing; Zhang, Xiangmei; Xu, Ling; Wei, Shicheng; Zhai, Maolin

2015-01-01

Ionizing radiation effectively cross-links collagen into network with enhanced anti-degradability and biocompatibility, while radiation-cross-linked collagen scaffold lacks flexibility, satisfactory surface appearance, and performs poor in cell penetration and ingrowth. To make the radiation-cross-linked collagen scaffold to serve as an ideal artificial dermis, dextran was incorporated into collagen. Scaffolds with the collagen/dextran (Col/Dex) ratios of 10/0, 7/3, and 5/5 were fabricated via (60)Co γ-irradiation cross-linking, followed by lyophilization. The morphology, microstructure, physicochemical, and biological properties were investigated. Compared with pure collagen, scaffolds with dextran demonstrated more porous appearance, enhanced hydrophilicity while the cross-linking density was lower with the consequence of larger pore size, higher water uptake, as well as reduced stiffness. Accelerated degradation was observed when dextran was incorporated in both the in vitro and in vivo assays, which led to earlier integration with cell and host tissue. The effect of dextran on degradation was ascribed to the decreased cross-linking density, looser microstructure, more porous and hydrophilic surface. Considering the better appearance, softness, moderate degradation rate due to controllable cross-linking degree and good biocompatibility as well, radiation-cross-linked collagen/dextran scaffolds are expected to serve as promising artificial dermal substitutes.

Border Crossing Entry Data

Data.gov (United States)

Department of Transportation — The Bureau of Transportation Statistics (BTS) Border Crossing/Entry Data provides summary statistics for inbound crossings at the U.S.-Canadian and the U.S.-Mexican...

Border Crossing/Entry Data

Data.gov (United States)

Department of Transportation — The dataset is known as “Border Crossing/Entry Data.” The Bureau of Transportation Statistics (BTS) Border Crossing/Entry Data provides summary statistics to the...

Cross-National Yardstick Comparisons

DEFF Research Database (Denmark)

Møller Hansen, Kasper; Leth Olsen, Asmus; Bech, Mickael

2015-01-01

performance comparisons—even when accounting for classic national sociotropic and egotropic items. Specifically, voters respond strongly to how the prospective wealth of Denmark evolves relative to the neighboring Sweden. Interestingly, voters are more negative in their response to cross-national losses......Comparing performance between countries is both a theoretically and intuitively useful yardstick for voters. Cross-national comparisons provide voters with heuristics that are less cognitively demanding, less ambiguous, and less uncertain than solely national, absolute performance measurements. We...... test this proposition using a unique, choice experiment embedded in the 2011 Danish National Election Study. This design allows to contrast cross-national comparisons with more traditional national sociotropic and egotropic concerns. The findings suggest that voters are strongly influenced by cross-national...

Multitrajectory eikonal cross sections

International Nuclear Information System (INIS)

Turner, R.E.

1983-01-01

With the use of reference and distorted transition operators, a time-correlation-function representation of the inelastic differential cross section has recently been used to obtain distorted eikonal cross sections. These cross sections involve straight-line and reference classical translational trajectories that are unaffected by any internal-state changes which have occurred during the collision. This distorted eikonal theory is now extended to include effects of internal-state changes on the translational motion. In particular, a different classical trajectory is associated with each pair of internal states. Expressions for these inelastic cross sections are obtained in terms of time-ordered cosine and sine memory functions using the Zwanzig-Feshbach projection-operator method. Explicit formulas are obtained in the time-disordered perturbation approximation

Using heavy atom rare gas matrix to control the reactivity of 4-methoxybenzaldehyde: A comparison with benzaldehyde

Energy Technology Data Exchange (ETDEWEB)

Kus, Nihal [Department of Chemistry, University of Coimbra, 3004-535 Coimbra (Portugal); Department of Physics, Anadolu University, 26470 Eskisehir (Turkey); Sharma, Archna; Reva, Igor; Fausto, Rui [Department of Chemistry, University of Coimbra, 3004-535 Coimbra (Portugal); Lapinski, Leszek [Institute of Physics, Polish Academy of Sciences, Warsaw (Poland)

2012-04-14

Different patterns of photochemical behavior were observed for 4-methoxybenzaldehyde (p-anisaldehyde) isolated in xenon and in argon matrices. Monomers of the compound isolated in solid Xe decarbonylate upon middle ultraviolet irradiation, yielding methoxybenzene (anisole), and CO. On the other hand, p-anisaldehyde isolated in an Ar matrix and subjected to identical irradiation, predominantly isomerizes to the closed-ring isomeric ketene (4-methoxycyclohexa-2,4-dien-1-ylidene) methanone. Experimental detection of a closed-ring ketene photoproduct, generated from an aromatic aldehyde, constitutes a rare observation. The difference between the patterns of photochemical transformations of p-anisaldehyde isolated in argon and xenon environments can be attributed to the external heavy-atom effect, where xenon enhances the rate of intersystem crossing from the singlet to the triplet manifold in which decarbonylation (via p-methoxybenzoyl radical) takes place. The parent compound, benzaldehyde, decarbonylates (to benzene + CO) when subjected to middle ultraviolet irradiation in both argon and xenon matrices. This demonstrates the role of the methoxy p-anisaldehyde substituent in activation of the reaction channel leading to the formation of the ketene photoproduct.

Drug Carrier for Photodynamic Cancer Therapy

Directory of Open Access Journals (Sweden)

Tilahun Ayane Debele

2015-09-01

Full Text Available Photodynamic therapy (PDT is a non-invasive combinatorial therapeutic modality using light, photosensitizer (PS, and oxygen used for the treatment of cancer and other diseases. When PSs in cells are exposed to specific wavelengths of light, they are transformed from the singlet ground state (S0 to an excited singlet state (S1–Sn, followed by intersystem crossing to an excited triplet state (T1. The energy transferred from T1 to biological substrates and molecular oxygen, via type I and II reactions, generates reactive oxygen species, (1O2, H2O2, O2*, HO*, which causes cellular damage that leads to tumor cell death through necrosis or apoptosis. The solubility, selectivity, and targeting of photosensitizers are important factors that must be considered in PDT. Nano-formulating PSs with organic and inorganic nanoparticles poses as potential strategy to satisfy the requirements of an ideal PDT system. In this review, we summarize several organic and inorganic PS carriers that have been studied to enhance the efficacy of photodynamic therapy against cancer.

Study of the Synchrotron Photoionization Oxidation of 2-Methylfuran Initiated by O(3P) under Low-Temperature Conditions at 550 and 650 K.

Science.gov (United States)

Fathi, Yasmin; Meloni, Giovanni

2017-09-21

The O-( 3 P)-initiated oxidation of 2-methylfuran (2-MF) was investigated using vacuum-ultraviolet synchrotron radiation from the Advanced Light Source at Lawrence Berkeley National Laboratory. Reaction species were studied by multiplexed photoionization mass spectrometry at 550 and 650 K. The oxygen addition pathway is favored in this reaction, forming four triplet diradicals that undergo intersystem crossing into singlet epoxide species that lead to the formation of products at m/z 30 (formaldehyde), 42 (propene), 54 (1-butyne, 1,3-butadiene, and 2-butyne), and 70 (2-butenal, methyl vinyl ketone, and 3-butenal). Mass-to-charge ratios, photoionization spectra, and adiabatic ionization energies for each primary reaction species were obtained and used to characterize their identities. In addition, by means of electronic structure calculations, potential energy surface scans of the different species produced throughout the oxidation were examined to further validate the primary chemistry occurring. Branching fractions for the formation of the primary products were calculated at the two temperatures and contribute 81.0 ± 21.4% at 550 K and 92.1 ± 25.5% at 650 K.

Relaxation Mechanisms of 5-Azacytosine.

Science.gov (United States)

Giussani, Angelo; Merchán, Manuela; Gobbo, João Paulo; Borin, Antonio Carlos

2014-09-09

The photophysics and deactivation pathways of the noncanonical 5-azacytosine nucleobase were studied using the CASPT2//CASSCF protocol. One of the most significant differences with respect to the parent molecule cytosine is the presence of a dark (1)(nNπ*) excited state placed energetically below the bright excited state (1)(ππ*) at the Franck-Condon region. The main photoresponse of the system is a presumably efficient radiationless decay back to the original ground state, mediated by two accessible conical intersections involving a population transfer from the (1)(ππ*) and the (1)(nNπ*) states to the ground state. Therefore, a minor contribution of the triplet states in the photophysics of the system is expected, despite the presence of a deactivation path leading to the lowest (3)(ππ*) triplet state. The global scenario on the photophysics and photochemistry of the 5-azacytosine system gathered on theoretical grounds is consistent with the available experimental data, taking especially into account the low values of the singlet-triplet intersystem crossing and fluorescence quantum yields observed.

New insights into the by-product fatigue mechanism of the photo-induced ring-opening in diarylethenes.

Science.gov (United States)

Mendive-Tapia, David; Perrier, Aurélie; Bearpark, Michael J; Robb, Michael A; Lasorne, Benjamin; Jacquemin, Denis

2014-09-14

The photochromic properties of diarylethenes, some of the most studied class of molecular switches, are known to be controlled by non-adiabatic decay at a conical intersection seam. Nevertheless, as their fatigue-reaction mechanism - leading to non-photochromic products - is yet to be understood, we investigate the photo-chemical formation of the so-called by-product isomer using three complementary computational methods (MMVB, CASSCF and CASPT2) on three model systems of increasing complexity. We show that for the ring-opening reaction a transition state on S1(2A) involving bond breaking of the penta-ring leads to a low energy S1(2A)/S0(1A) conical intersection seam, which lies above one of the transition states leading to the by-product isomer on the ground state. Therefore, radiationless decay and subsequent side-product formation can take place explaining the photo-degradation responsible for the by-product generation in diarylethene-type molecules. The effect of dynamic electron correlation and the possible role of inter-system crossing along the penta-ring opening coordinate are discussed as well.

Photophysics of BODIPY Dyes as Readily-Designable Photosensitisers in Light-Driven Proton Reduction

Directory of Open Access Journals (Sweden)

Laura Dura

2017-04-01

Full Text Available A series of boron dipyrromethene (BODIPY dyes was tested as photosensitisers for light-driven hydrogen evolution in combination with the complex [Pd(PPh3Cl2]2 as a source for catalytically-active Pd nanoparticles and triethylamine as a sacrificial electron donor. In line with earlier reports, halogenated dyes showed significantly higher hydrogen production activity. All BODIPYs were fully characterised using stationary absorption and emission spectroscopy. Time-resolved spectroscopic investigations on meso-mesityl substituted compounds revealed that reduction of the photo-excited BODIPY by the sacrificial agent occurs from an excited singlet state, while, in halogenated species, long-lived triplet states are present, determining electron transfer processes from the sacrificial agent. Quantum chemical calculations performed at the time-dependent density functional level of theory indicate that the differences in the photocatalytic performance of the present series of dyes can be correlated to the varying efficiency of intersystem crossing in non-halogenated and halogenated species and not to alterations in the energy levels introduced upon substitution.

Synthesis and Exciton Dynamics of Triplet Sensitized Conjugated Polymers

KAUST Repository

Andernach, Rolf

2015-07-22

We report the synthesis of a novel polythiophene-based host-guest copolymer incorporating a Pt-porphyrin complex (TTP-Pt) into the backbone for efficient singlet to triplet polymer exciton sensitization. We elucidated the exciton dynamics in thin films of the material by means of Transient Absorption Spectrosopcy (TAS) on multiple timescales and investigated the mechanism of triplet exciton formation. During sensitization, single exciton diffusion is followed by exciton transfer from the polymer backbone to the complex where it undergoes intersystem crossing to the triplet state of the complex. We directly monitored the triplet exciton back transfer from the Pt-porphyrin to the polymer and find that 60% of the complex triplet excitons are transferred with a time constant of 1087 ps. We propose an equilibrium between polymer and porphyrin triplet states as a result of the low triplet diffusion length in the polymer backbone and hence an increased local triplet population resulting in increased triplet-triplet annihilation. This novel system has significant implications for the design of novel materials for triplet sensitized solar cells and up-conversion layers.

Functionalizing carbon nitride with heavy atom-free spin converters for enhanced 1 O 2 generation

Energy Technology Data Exchange (ETDEWEB)

Wu, Wenting; Han, Congcong; Zhang, Qinhua; Zhang, Qinggang; Li, Zhongtao; Gosztola, David J.; Wiederrecht, Gary P.; Wu, Mingbo

2018-05-01

advanced photosensitizers for singlet oxygen (1O2) generation. However, the intersystem crossing (ISC) process is quite insufficient in carbon nitride, limiting the 1O2 generation. Here, we report a facile and general strategy to confined benzophenone as a heavy atom-free spin converter dopant in carbon nitride via the facile copolymerization. With proper energy level matching between the heavy atom-free spin converter and various ligands based on carbon nitride precursors, the proper combination can decrease the singlet-triplet energy gap (DEST) and hence generate 1O2 effectively. Due to its significant and selectivity for 1O2 generation, the as-prepared carbon nitride-based photosensitizer shows a high selective photooxidation activity for 1,5-dihydroxy-naphthalene (1,5-DHN). The product yield reached 71.8% after irradiation for 60 min, which was higher than that of cyclometalated PtII complexes (53.6%) in homogeneous photooxidation. This study can broaden the application of carbon nitride in the field of selective heterogeneous photooxidation due to simple operation, low cost, and high efficiency, making it a strong candidate for future industrialization.

Ultrafast Excited-State Dynamics of Diketopyrrolopyrrole (DPP)-Based Materials: Static versus Diffusion-Controlled Electron Transfer Process

KAUST Repository

Alsulami, Qana

2015-06-25

Singlet-to-triplet intersystem crossing (ISC) and photoinduced electron transfer (PET) of platinum(II) containing diketopyrrolopyrrole (DPP) oligomer in the absence and presence of strong electron-acceptor tetracyanoethylene (TCNE) were investigated using femtosecond and nanosecond transient absorption spectroscopy with broadband capabilities. The role of platinum(II) incorporation in those photophysical properties was evaluated by comparing the excited-state dynamics of DPP with and without the metal centers. The steady-state measurements reveal that platinum(II) incorporation facilitates dramatically the interactions between DPP-Pt(acac) and TCNE, resulting in charge transfer (CT) complex formation. The transient absorption spectra in the absence of TCNE reveal ultrafast ISC of DPP-Pt(acac) followed by their long-lived triplet state. In the presence of TCNE, PET from the excited DPP-Pt(acac) and DPP to TCNE, forming the radical ion pairs. The ultrafast PET which occurs statically from DPP-Pt(acac) to TCNE in picosecond regime, is much faster than that from DPP to TCNE (nanosecond time scale) which is diffusion-controlled process, providing clear evidence that PET rate is eventually controlled by the platinum(II) incorporation.

Controlling the orientation of spin-correlated radical pairs by covalent linkage to nanoporous anodic aluminum oxide membranes.

Science.gov (United States)

Chen, Hsiao-Fan; Gardner, Daniel M; Carmieli, Raanan; Wasielewski, Michael R

2013-10-07

Ordered multi-spin assemblies are required for developing solid-state molecule-based spintronics. A linear donor-chromophore-acceptor (D-C-A) molecule was covalently attached inside the 150 nm diam. nanopores of an anodic aluminum oxide (AAO) membrane. Photoexcitation of D-C-A in a 343 mT magnetic field results in sub-nanosecond, two-step electron transfer to yield the spin-correlated radical ion pair (SCRP) (1)(D(+)˙-C-A(-)˙), which then undergoes radical pair intersystem crossing (RP-ISC) to yield (3)(D(+)˙-C-A(-)˙). RP-ISC results in S-T0 mixing to selectively populate the coherent superposition states |S'> and |T'>. Microwave-induced transitions between these states and the unpopulated |T(+1)> and |T(-1)> states result in spin-polarized time-resolved EPR (TREPR) spectra. The dependence of the electron spin polarization (ESP) phase of the TREPR spectra on the orientation of the AAO membrane pores relative to the externally applied magnetic field is used to determine the overall orientation of the SCRPs within the pores at room temperature.

Eight energy and material flow characteristics of urban ecosystems.

Science.gov (United States)

Bai, Xuemei

2016-11-01

Recent decades have seen an expanding literature exploring urban energy and material flows, loosely branded as urban metabolism analysis. However, this has occurred largely in parallel to the mainstream studies of cities as ecosystems. This paper aims to conceptually bridge these two distinctive fields of research, by (a) identifying the common aspects between them; (b) identifying key characteristics of urban ecosystems that can be derived from energy and material flow analysis, namely energy and material budget and pathways; flow intensity; energy and material efficiency; rate of resource depletion, accumulation and transformation; self-sufficiency or external dependency; intra-system heterogeneity; intersystem and temporal variation; and regulating mechanism and governing capacity. I argue that significant ecological insight can be, or has the potential to be, drawn from the rich and rapidly growing empirical findings of urban metabolism studies to understand the behaviour of cities as human-dominated, complex systems. A closer intellectual linkage and cross pollination between urban metabolism and urban ecosystem studies will advance our scientific understanding and better inform urban policy and management practices.

Ultrafast Excited-State Dynamics of Diketopyrrolopyrrole (DPP)-Based Materials: Static versus Diffusion-Controlled Electron Transfer Process

KAUST Repository

Alsulami, Qana; Aly, Shawkat Mohammede; Goswami, Subhadip; Alarousu, Erkki; Usman, Anwar; Schanze, Kirk S.; Mohammed, Omar F.

2015-01-01

Singlet-to-triplet intersystem crossing (ISC) and photoinduced electron transfer (PET) of platinum(II) containing diketopyrrolopyrrole (DPP) oligomer in the absence and presence of strong electron-acceptor tetracyanoethylene (TCNE) were investigated using femtosecond and nanosecond transient absorption spectroscopy with broadband capabilities. The role of platinum(II) incorporation in those photophysical properties was evaluated by comparing the excited-state dynamics of DPP with and without the metal centers. The steady-state measurements reveal that platinum(II) incorporation facilitates dramatically the interactions between DPP-Pt(acac) and TCNE, resulting in charge transfer (CT) complex formation. The transient absorption spectra in the absence of TCNE reveal ultrafast ISC of DPP-Pt(acac) followed by their long-lived triplet state. In the presence of TCNE, PET from the excited DPP-Pt(acac) and DPP to TCNE, forming the radical ion pairs. The ultrafast PET which occurs statically from DPP-Pt(acac) to TCNE in picosecond regime, is much faster than that from DPP to TCNE (nanosecond time scale) which is diffusion-controlled process, providing clear evidence that PET rate is eventually controlled by the platinum(II) incorporation.

Absence of Intramolecular Singlet Fission in Pentacene-Perylenediimide Heterodimers: The Role of Charge Transfer State.

Science.gov (United States)

Wang, Long; Wu, Yishi; Chen, Jianwei; Wang, Lanfen; Liu, Yanping; Yu, Zhenyi; Yao, Jiannian; Fu, Hongbing

2017-11-16

A new class of donor-acceptor heterodimers based on two singlet fission (SF)-active chromophores, i.e., pentacene (Pc) and perylenediimide (PDI), was developed to investigate the role of charge transfer (CT) state on the excitonic dynamics. The CT state is efficiently generated upon photoexcitation. However, the resulting CT state decays to different energy states depending on the energy levels of the CT state. It undergoes extremely rapid deactivation to the ground state in polar CH 2 Cl 2 , whereas it undergoes transformation to a Pc triplet in nonpolar toluene. The efficient triplet generation in toluene is not due to SF but CT-mediated intersystem crossing. In light of the energy landscape, it is suggested that the deep energy level of the CT state relative to that of the triplet pair state makes the CT state actually serve as a trap state that cannot undergoes an intramolecular singlet fission process. These results provide guidance for the design of SF materials and highlight the requisite for more widely applicable design principles.

Magnetic and optical effects in TiO2 based dye sensitized solar cells

Science.gov (United States)

Kannan U., M.; Jammalamadaka, S. Narayana

2018-04-01

We report on the magnetic effects on the solar cell efficiency of TiO2 based dye sensitized solar cells (DSSC). The strong spin orbit coupling of rare earth Ho3+ ions introduced by the addition of Ho2O3 into the photoanode resulted in a 28% enhancement in the power conversion efficiency of DSSC. Such an enhancement in the efficiency may be attributed to the improved lifetime of photo generated excitons as a result of the accelerated intersystem crossing phenomenon. This observation is supported by our photoluminescence (PL) measurements where we could observe a decrease in the photo emission intensity with the addition of Ho2O3. In addition, we have used a low magnetic field of 100 Oe to further enhance the overall efficiency to 5.6%, which in turn proves that the Lorentz force plays a significant role in magnetic field controlled charge transport in DSSC. Finally, we have carried out a transfer matrix model based theoretical simulation for studying the optical properties of the multilayer device stack.

Gas-phase hydrolysis of triplet SO2: A possible direct route to atmospheric acid formation

Science.gov (United States)

Donaldson, D. James; Kroll, Jay A.; Vaida, Veronica

2016-07-01

Sulfur chemistry is of great interest to the atmospheric chemistry of several planets. In the presence of water, oxidized sulfur can lead to new particle formation, influencing climate in significant ways. Observations of sulfur compounds in planetary atmospheres when compared with model results suggest that there are missing chemical mechanisms. Here we propose a novel mechanism for the formation of sulfurous acid, which may act as a seed for new particle formation. In this proposed mechanism, the lowest triplet state of SO2 (3B1), which may be accessed by near-UV solar excitation of SO2 to its excited 1B1 state followed by rapid intersystem crossing, reacts directly with water to form H2SO3 in the gas phase. For ground state SO2, this reaction is endothermic and has a very high activation barrier; our quantum chemical calculations point to a facile reaction being possible in the triplet state of SO2. This hygroscopic H2SO3 molecule may act as a condensation nucleus for water, giving rise to facile new particle formation (NPF).

Solvent, isotope, and magnetic field effects in the geminate recombination of radical ion pairs

International Nuclear Information System (INIS)

Werner, H.; Staerk, H.; Weller, A.

1978-01-01

The magnetic field dependence of the geminate recombination triplet yield of radical ion pairs generated via photoinduced electron transfer in polar solvents is investigated for the systems pyrene/N,N-dimethylaniline (Py/DMA), pyrene/3,5-dimethoxy-N,N-dimethylaniline (Py/DMDMA), and the perdeuterated system Py-d 10 /DMA-d 11 . The magnetic field dependence characterized through its B/sub 1/2/ value is found to be dependent on the sum of the hyperfine coupling constants in the radical pair in agreement with previous theoretical predictions. A drastic reduction of the B/sub 1/2/ value is observed with the perdeuterated system. By means of measurements of the radical ion and triplet absorption signals with nanosecond time resolution, the influence of the solvent on the geminate singlet and triplet recombination yields is investigated. Complementary measurements of exciplex lifetimes and quantum yields are carried out in a series of solvents with different polarities in order to determine the rate constants of fluorescence emission and intersystem crossing in the exciplexes

FEMA DFIRM Cross Sections

Data.gov (United States)

Minnesota Department of Natural Resources — FEMA Cross Sections are required for any Digital Flood Insurance Rate Map database where cross sections are shown on the Flood Insurance Rate Map (FIRM). Normally...

Influence of External Nitrogen on Nitrogenase Enzyme Activity and Auxin Production in Herbaspirillum seropedicae (Z78).

Science.gov (United States)

Yin, Tan Tzy; Pin, Ui Li; Ghazali, Amir Hamzah Ahmad

2015-04-01

The production of nitrogenase enzyme and auxins by free living diazotrophs has the potential to influence the growth of host plants. In this study, diazotrophs were grown in the presence of various concentrations of nitogen (N) to determine the optimal concentration of N for microbial growth stimulation, promotion of gaseous N (N2) fixation, and phytohormone production. Therefore, we investigate whether different levels of N supplied to Herbaspirillum seropedicae (Z78) have significant effects on nitrogenase activity and auxin production. The highest nitrogenase activity and the lowest auxin production of H. seropedicae (Z78) were both recorded at 0 gL(-1) of NH4Cl. Higher levels of external N caused a significant decrease in the nitrogenase activity and an increased production of auxins. In a subsequent test, two different inoculum sizes of Z78 (10(6) and 10(12) cfu/ml) were used to study the effect of different percentages of acetylene on nitrogenase activity of the inoculum via the acetylene reduction assay (ARA). The results showed that the optimal amount of acetylene required for nitrogenase enzyme activity was 5% for the 10(6) cfu/ml inoculum, whereas the higher inoculum size (10(12) cfu/ml) required at least 10% of acetylene for optimal nitrogenase activity. These findings provide a clearer understanding of the effects of N levels on diazotrophic nitrogenase activity and auxin production, which are important factors influencing plant growth.

Crossed molecular beams

International Nuclear Information System (INIS)

Lee, Y.T.

1976-01-01

Research activities with crossed molecular beams at Lawrence Berkeley Laboratory during 1976 are described. Topics covered include: scattering of Ar*, Kr*, with Xe; metastable rare gas interactions, He* + H 2 ; an atomic and molecular halogen beam source; a crossed molecular beam study of the Cl + Br 2 → BrCl + Br reaction; O( 3 P) reaction dynamics, development of the high pressure plasma beam source; energy randomization in the Cl + C 2 H 3 Br → Br + C 2 H 3 Cl reaction; high resolution photoionization studies of NO and ICl; photoionization of (H 2 O)/sub n/ and (NH 3 ) 2 ; photoionization mass spectroscopy of NH 3 + and O 3 + ; photo fragmentation of bromine; and construction of chemiluminescence-laser fluorescence crossed molecular beam machine

Comparison of integral cross section values of several cross section libraries in the SAND-II format

International Nuclear Information System (INIS)

Zijp, W.L.; Nolthenius, H.J.

1976-09-01

A comparison of some integral cross-section values for several cross-section libraries in the SAND-II format is presented. The integral cross-section values are calculated with the aid of the spectrum functions for a Watt fission spectrum, a 1/E spectrum and a Maxwellian spectrum. The libraries which are considered here are CCC-112B, ENDF/B-IV, DETAN74, LAPENAS and CESNEF. These 5 cross-section libraries used have all the SAND-II format. Discrepancies between cross-sections in the different libraries are indicated but not discussed

Cross-tools and cross-media effects

NARCIS (Netherlands)

Voorveld, H.

2013-01-01

Effects of persuasive messages depend on the content of the message itself and on the media or tools that deliver the persuasive messages. Nowadays almost all campaigns make use of multiple media or multiple promotional tools. Therefore, it is important to study so-called cross-media (or

Cross-linking of polymeric materials

International Nuclear Information System (INIS)

Bloom, L.I.; Du Plessis, T.A.; Meij, G.O.

1991-01-01

The invention provides a method of producing a cured polymeric artifact from a polymeric thermoplastic starting material, the material of the artifact having reduced thermoplasticity relative to the starting material and exhibiting an enhanced degree of cross-linking relative to the starting material. The method includes subjecting a polymeric thermoplastic starting material, which is capable of being cross-linked by irradiation, to sufficient irradiation partially to cross-linked the starting material to produce a thermoplastic partially cross-linked intermediate material. The thermoplasticity of the intermediate material is then reduced by heating it to raise its melting point. The invention also provides a method of making a partially cross-linked feedstocks and a master batch for use in making such artifacts

Relativistic photon-Maxwellian electron cross sections

International Nuclear Information System (INIS)

Wienke, B.R.; Lathrop, B.L.; Devaney, J.J.

1986-01-01

Temperature corrected cross sections, complementing the Klein-Nishina set, are developed for astrophysical, plasma, and transport applications. The set is obtained from a nonlinear least squares fit to the exact photon-Maxwellian electron cross sections, using the static formula as the asymptotic basis. Two parameters are sufficient (two decimal places) to fit the exact cross sections over a range of 0-100 keV in electron temperature, and 0-1 MeV in incident photon energy. The fit is made to the total cross sections, yet the parameters predict both total and differential scattering cross sections well. Corresponding differential energy cross sections are less accurate. An extended fit to (just) the total cross sections, over the temperature and energy range 0-5 MeV, is also described. (author)

Spectroscopic studies of organometallic compounds on single crystal metal surfaces: Surface acetylides of silver (110)

Science.gov (United States)

Madix, Robert J.

The nature of compounds formed by the reaction of organic molecules with metal surfaces can be studied with a battery of analytical methods based on both physicals and chemical understanding. In this paper the application of UPS, XPS, LEED and EELS as well as temperature programmed reaction spectroscopy (TPRS) and chemical titration methods to the characterization of surface complexes is discussed. Particular emphasis is given to the reaction of acetylene with a single crystal surface of silver, Ag(110). Previous work has shown that this surface, when clean, is unreactive to hydrocarbons, alcohols and carboxylic acids under ultra high vacuum conditions. Preadsorption of oxygen, however, renders the surface reactive, and a wide variety of organometallic surface compounds can be formed. As expected then, no stable adsorption state and no reaction was observed with clean Ag(110) following room temperature exposure to acetylene. Following exposure at 150 K, however, a weekly bound chemisorption state was observed to desorb at 195 K, indicating a binding energy to the surface of approximately 12 kcal/gmole. Reaction with preadsorbed oxygen gave water formulation upon dosing and produced surface intermediates which yeilded two acetylene desorption states at 195 and 175 K. Heating above 300 K to completely desorb the higher temperature state produced new, well-defined LEED Features due to residual surface carbon which disappeared when the surface was heated above 550 K. Clearly, there were distinc changes in the nature of the absorbed layer at 195, 300 and 550 K. These changes were reflected in XPS. For the weakly chemisorbed acetylene a large C(ls) peak at 285.6 eV with a small, broad, indistinc shoulder at higher binding energy (288.2) was observed. The spectrum of the species following acetylene desorption at 275 K, however, showed the formulation of a large C(ls) peak at 283.6 eV in addition to peaks characteristics of the weakly chemisorbed state. This result

50 CFR 228.18 - Cross-examination.

Science.gov (United States)

2010-10-01

... 50 Wildlife and Fisheries 7 2010-10-01 2010-10-01 false Cross-examination. 228.18 Section 228.18...-examination. (a) The presiding officer may: (1) Require the cross-examiner to outline the intended scope of the cross-examination; (2) Prohibit parties from cross-examining witnesses unless the presiding...

Photoelectron Diffraction Imaging for C2H2 and C2H4 Chemisorbed on Si(100) Reveals a New Bonding Configuration

International Nuclear Information System (INIS)

Xu, S. H.; Keeffe, M.; Yang, Y.; Chen, C.; Yu, M.; Lapeyre, G. J.; Rotenberg, E.; Denlinger, J.; Yates, J. T. Jr.

2000-01-01

A new adsorption site for adsorbed acetylene on Si(100) is observed by photoelectron imaging based on the holographic principle. The diffraction effects in the carbon 1s angle-resolved photoemission are inverted (including the small-cone method) to obtain an image of the atom's neighboring carbon. The chemisorbed acetylene molecule is bonded to four silicon surface atoms. In contrast to the C 2 H 2 case, the image for adsorbed C 2 H 4 shows it bonded to two Si surface atoms. (c) 2000 The American Physical Society

Procedure for coating articles with pyrolytic carbon

International Nuclear Information System (INIS)

Adams, C.C.; Allen, C.L.; Besenbruch, G.E.A.

1976-01-01

A method to coat articles with pyrolytic carbon is described which is particularly suitable for small nuclear fuel particles as one obtains a very homogeneous layer. The pyrolytic carbon is produced according to the invention by decomposing a hydrocarbon gas mixture composed of an inert gas share (20-65 Vol%) and a mixture of acetylene and propylene. It is favourable to have the hydrocarbon mixture contain between 50 and 55 Vol% acetylene. Variations on the known procedure are given. The coating of spherical thorium dioxide particles is mentioned as an example. (UWI) [de

Multifaceted Strategy for the Synthesis of Diverse 2,2'-Bithiophene Derivatives

Directory of Open Access Journals (Sweden)

Stanisław Krompiec

2015-03-01

Full Text Available New catalytically or high pressure activated reactions and routes, including coupling, double bond migration in allylic systems, and various types of cycloaddition and dihydroamination have been used for the synthesis of novel bithiophene derivatives. Thanks to the abovementioned reactions and routes combined with non-catalytic ones, new acetylene, butadiyne, isoxazole, 1,2,3-triazole, pyrrole, benzene, and fluoranthene derivatives with one, two or six bithiophenyl moieties have been obtained. Basic sources of crucial substrates which include bithiophene motif for catalytic reactions were 2,2'-bithiophene, gaseous acetylene and 1,3-butadiyne.

Synchronization control of cross-strict feedback hyperchaotic system based on cross active backstepping design

International Nuclear Information System (INIS)

Wang Jing; Gao Jinfeng; Ma Xikui

2007-01-01

This Letter presents a novel cross active backstepping design method for synchronization control of cross-strict feedback hyperchaotic system, in which the ordinary backstepping design is unavailable. The proposed control method, combining backstepping design and active control approach, extends the application of backstepping technique in chaos control. Based on this method, different combinations of controllers can be designed to meet the needs of different applications. The proposed method is applied to achieve chaos synchronization of two identical cross-strict feedback hyperchaotic systems. Also it is used to implement synchronization between cross-strict feedback hyperchaotic system and Roessler hyperchaotic system. Numerical examples illustrate the validity of the control method

Triplet-State Dissolved Organic Matter Quantum Yields and Lifetimes from Direct Observation of Aromatic Amine Oxidation.

Science.gov (United States)

Schmitt, Markus; Erickson, Paul R; McNeill, Kristopher

2017-11-21

Excited triplet state chromophoric dissolved organic matter ( 3 CDOM*) is a short-lived mixture of excited-state species that plays important roles in aquatic photochemical processes. Unlike the study of the triplet states of well-defined molecules, which are amenable to transient absorbance spectroscopy, the study of 3 CDOM* is hampered by it being a complex mixture and its low average intersystem crossing quantum yield (Φ ISC ). This study is an alternative approach to investigating 3 CDOM* using transient absorption laser spectroscopy. The radical cation of N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD), formed through oxidation by 3 CDOM*, was directly observable by transient absorption spectroscopy and was used to probe basic photophysical properties of 3 CDOM*. Quenching and control experiments verified that TMPD •+ was formed from 3 CDOM* under anoxic conditions. Model triplet sensitizers with a wide range of excited triplet state reduction potentials and CDOM oxidized TMPD at near diffusion-controlled rates. This gives support to the idea that a large cross-section of 3 CDOM* moieties are able to oxidize TMPD and that the complex mixture of 3 CDOM* can be simplified to a single signal. Using the TMPD •+ transient, the natural triplet lifetime and Φ ISC for different DOM isolates and natural waters were quantified; values ranged from 12 to 26 μs and 4.1-7.8%, respectively.

Intracellular events regulating cross-presentation

Directory of Open Access Journals (Sweden)

Peter eCresswell

2012-06-01

Full Text Available Cross-presentation plays a fundamental role in the induction of CD8-T cell immunity. However, although more than three decades have passed since its discovery, surprisingly little is known about the exact mechanisms involved. Here we give an overview of the components involved at different stages of this process. First, antigens must be internalized into the cross-presenting cell. The involvement of different receptors, method of antigen uptake, and nature of the antigen can influence intracellular trafficking and access to the cross-presentation pathway. Once antigens access the endocytic system, different requirements for endosomal/phagosomal processing arise, such as proteolysis and reduction of disulfide bonds. The majority of cross-presented peptides are generated by proteasomal degradation. Therefore, antigens must cross a membrane barrier in a manner analogous to the fate of misfolded proteins in the endoplasmic reticulum (ER that are retrotranslocated into the cytosol for degradation. Indeed, some components of the ER-associated degradation (ERAD machinery have been implicated in cross-presentation. Further complicating the matter, endosomal and phagosomal compartments have been suggested as alternative sites to the ER for loading of peptides on MHC class I molecules. Finally, the antigen presenting cells involved, particularly dendritic cell subsets and their state of maturation, influence the efficiency of cross-presentation.

Internet and Cross Media Productions

DEFF Research Database (Denmark)

Petersen, Anja Bechmann

2006-01-01

, the Internet continues to play a minor role when compared to older media. The content of the cross media concepts and organizations' history are crucial elements in deciding the priority and use of platforms. Methodologically, the article approaches cross media and the roles of the Internet on a micro......Convergence is one of the hot topics in Internet studies. Recently, however, media organizations have turned their focus to cross media communication. Media organizations are interested in optimizing communication across platforms such as TV, radio, websites, mobile telephones and newspapers....... The aim of this article is to examine the roles of the Internet when emphasis is put on cross media rather than convergence. This article proposes not one unidirectional convergent tendency but manifold roles of the Internet in cross media communication. Inside the media organizations, however...

Opas CrossFit -harjoitteluun

OpenAIRE

Knaapi, Matti

2014-01-01

CrossFit on laji, joka pyrkii edistämään terveyttä ja kuntoa. CrossFit saleja löytyy mailmalta yli 10 000 kappaletta. CrossFit -harjoittelussa pyritään parantamaan ihmisen kuntoa mahdollisimman laajalla skaalalla kehittämällä mm. voimaa, kestävyyttä, tarkkuutta, tasapainoa ja eri aineenvaihduntareittejä samanaikaisesti. Terveyden ja kunnon kehittämiseen kuuluu kuntoilun lisäksi myös muita osa-alueita. Ruokavalio ja kehonhuolto ovat tärkeitä osa-alueita hyvän kunnon saavuttamiseksi. Ruokav...

Antigen Cross-Presentation of Immune Complexes

Science.gov (United States)

Platzer, Barbara; Stout, Madeleine; Fiebiger, Edda

2014-01-01

The ability of dendritic cells (DCs) to cross-present tumor antigens has long been a focus of interest to physicians, as well as basic scientists, that aim to establish efficient cell-based cancer immune therapy. A prerequisite for exploiting this pathway for therapeutic purposes is a better understanding of the mechanisms that underlie the induction of tumor-specific cytotoxic T-lymphocyte (CTL) responses when initiated by DCs via cross-presentation. The ability of humans DC to perform cross-presentation is of utmost interest, as this cell type is a main target for cell-based immunotherapy in humans. The outcome of a cross-presentation event is guided by the nature of the antigen, the form of antigen uptake, and the subpopulation of DCs that performs presentation. Generally, CD8α+ DCs are considered to be the most potent cross-presenting DCs. This paradigm, however, only applies to soluble antigens. During adaptive immune responses, immune complexes form when antibodies interact with their specific epitopes on soluble antigens. Immunoglobulin G (IgG) immune complexes target Fc-gamma receptors on DCs to shuttle exogenous antigens efficiently into the cross-presentation pathway. This receptor-mediated cross-presentation pathway is a well-described route for the induction of strong CD8+ T cell responses. IgG-mediated cross-presentation is intriguing because it permits the CD8− DCs, which are commonly considered to be weak cross-presenters, to efficiently cross-present. Engaging multiple DC subtypes for cross-presentation might be a superior strategy to boost CTL responses in vivo. We here summarize our current understanding of how DCs use IgG-complexed antigens for the efficient induction of CTL responses. Because of its importance for human cell therapy, we also review the recent advances in the characterization of cross-presentation properties of human DC subsets. PMID:24744762

Metoda Criss-Cross

OpenAIRE

Papež, Jan

2008-01-01

This thesis describes the criss-cross method, which solves the tasks of linear programming and does not need primar or dual feasibility of the basis. At first, the single-phase simplex method, that needs primal feasibility, gets described. After that, we describe the dual simplex method, which needs dual feasibility. The criss-cross method combines both of these methods. All of mentioned methods are explained and demonstrated in several examples.

Seeds of Cross-Media Production

DEFF Research Database (Denmark)

Bødker, Susanne; Petersen, Anja Bechmann

2007-01-01

separately and of cross-media production. Since cross-media production is in the making, we study the instruments currently used for planning and coordination, and analyze them as seeds that will eventually make cross-media production happen. Time and timing are important in news production in general......We present an empirical study of an organization that has recently moved from traditional newspaper production towards cross-media production involving the integrated digital production of newspaper, television, radio and web-news. The paper focuses on the daily production rhythms of the media...... with planning and coordination. We demonstrate how the production rhythms of the individual media collide with that of cross-media, and how product lifecycle rhythms add to the list of causes of problems that may jeopardize crossmedia production. We propose to strengthen planning and overview support elements...

CrossFit athletes exhibit high symmetry of fundamental movement patterns. A cross-sectional study.

Science.gov (United States)

Tafuri, Silvio; Notarnicola, Angela; Monno, Antonello; Ferretti, Francesco; Moretti, Biagio

2016-01-01

even if CrossFit training programs accounted actually more than 7500 gyms affiliated in the USA and more than 2000 in Europe and involved today more than 1 million of people, actually there were not several studies about the effect of the CrossFit on the health and sport performance. The aim of these research was to evaluate the performance in 7 fundamental movement patterns using a standardized methods, the Functional Movement Screen (FMS). we enrolled three groups of athletes (age 17-40 years; >6 months of training programs): CrossFitters, body builders and professional weightlifters. FMS test was performed to all people enrolled. Scores of FMS test was examined comparing three groups. no differences in the three groups were showed in the mean score values of each test and in total score, except for shoulder mobility test (higher among CrossFitters) and trunk stability push-up test (higher among weightlifter). Agreement between the test performed on the two sides was higher in CrossFit groups for hurdle step (93.2%), in line lung (86%), rotary stability test (95.3%) and shoulder mobility (90.7%; pCrossFit seems to produce marked symmetry in some fundamental movements compared to weightlifting and bodybuilding.

Academic Globalization: Universality of Cross-Cultural And Cross-Disciplinary LMR Perspectives

Directory of Open Access Journals (Sweden)

Marta Szabo White

2010-10-01

Full Text Available The contribution of this paper suggests that previous research underscoring cross-cultural differences may be misleading, when in fact it is cross-professional rather than cross-cultural differences that should be emphasized. Employing the LMR framework, this paper concludes that business or non-business predisposition has a more direct impact on one's individual cultural profile than does nationality. Regardless of culture, persons involved in business are characterized primarily by linear-active modes of communication, and persons not involved in business typically employ less linear and more multi-active/hybrid modes of communication. The linkages among individual characteristics, communication styles, work behaviors, and the extent to which the LMR constructs can facilitate and predict leadership, negotiating styles, individual behaviors, etc. are central to academic globalization and preparing global business leaders.

Integral nucleus-nucleus cross sections

International Nuclear Information System (INIS)

Barashenkov, V.S.; Kumawat, H.

2003-01-01

Expressions approximating the experimental integral cross sections for elastic and inelastic interactions of light and heavy nuclei at the energies up to several GeV/nucleon are presented. The calculated cross sections are inside the corridor of experimental errors or very close to it. Described in detail FORTRAN code and a numerical example of the cross section approximation are also presented

Comparison of integral cross section values of several cross section libraries in the SAND-II format

International Nuclear Information System (INIS)

Zijp, W.L.; Nolthenius, H.J.

1978-01-01

A comparison of some integral cross section values for several cross section libraries in the SAND-II format is presented. The integral cross section values are calculated with aid of the spectrum functions for a Watt fission spectrum, a 1/E spectrum and a Maxwellian spectrum. The libraries which are considered here are CCC-112B, ENDF/B-IV, DETAN74, LAPENAS and CESNEF. These 5 cross section libraries used have all the SAND-II format. (author)

Border Crossings, US-Mexico Border, 2010, NAVTEQ

Data.gov (United States)

U.S. Environmental Protection Agency — NAVTEQ Border Crossings for Region 9. The Border Crossing layer contains all international border crossings for all motorway crossings, as well as other important...

Various aspects of cross-cultural communication

OpenAIRE

Tsibulya, N.

2014-01-01

The author considers the main cultural dimensions and tendencies in cross-cultural communication studies from the 1950s till the present day. Using one’s own experience in carrying out research of non-verbal and prosodic aspects of cross-cultural interaction, the author suggests a system of exercises useful in teaching and learning cross-cultural communication and aimed at formation and developing cross-cultural competence.

Electron collision cross sections of mercury

International Nuclear Information System (INIS)

Suzuki, Susumu; Kuzuma, Kiyotaka; Itoh, Haruo

2006-01-01

In this paper, we propose a new collision cross section set for mercury which revises the original set summarized by Hayashi in 1989. Hanne reported three excitation collision cross sections (6 3 P 0 , 6 3 P 1 , 6 3 P 2 ) determined from an electron beam experiment in 1988. As a matter for regret, no attentive consideration was given to combining these three excitation cross sections with the cross section set of Hayashi. Therefore we propose a new set where these three excitation cross sections are included. In this study, other two excitation cross sections (6 1 P 1 , 6 3 D 3 ) except for the three excitation collision cross sections (6 3 P 0 , 6 3 P 1 , 6 3 P 2 ) are taken from the original set of Hayashi. The momentum transfer cross section and the ionization collision cross section are also taken from Hayashi. A Monte Carlo Simulation (MCS) technique is applied for evaluating our new cross section set. The present results of the electron drift velocity and the ionization coefficient are compared to experimental values. Agreement is secured in relation to the electron drift velocity for 1.5 Td 2 ) is the reduced electric field, E (V/cm) is the electric field, N (1/cm 3 ) is the number density of mercury atoms at 0degC, 1 Torr, E/N is also equal to 2.828 x 10 -17 E/p 0 from the relation of the ideal gas equation, p 0 (Torr) is gas pressure at 0degC, 1 Torr=1.33322 x 10 -2 N/cm -2 and 10 -17 V/cm 2 is called 1 Td. Thus it is ensured that our new cross section set is reasonable enough to be used up to 100 eV when considering with the electron drift velocity and the ionization coefficient. (author)

Cross-relaxation solid state lasers

International Nuclear Information System (INIS)

Antipenko, B.M.

1989-01-01

Cross-relaxation functional diagrams provide a high quantum efficiency for pumping bands of solid state laser media and a low waste heat. A large number of the cross-relaxation mechanisms for decay rare earth excited states in crystals have been investigated. These investigations have been a starting-point for development of the cross-relaxation solid state lasers. For example, the cross-relaxation interactions, have been used for the laser action development of LiYF 4 :Gd-Tb. These interactions are important elements of the functional diagrams of the 2 μm Ho-doped media sensitized with Er and Tm and the 3 μm Er-doped media. Recently, new efficient 2 μm laser media with cross-relaxation pumping diagrams have been developed. Physical aspects of these media are the subject of this paper. A new concept of the Er-doped medium, sensitized with Yb, is illustrated

Vibration atomic layer deposition for conformal nanoparticle coating

Energy Technology Data Exchange (ETDEWEB)

Park, Suk Won; Woo Kim, Jun; Jong Choi, Hyung; Hyung Shim, Joon, E-mail: shimm@korea.ac.kr [School of Mechanical Engineering, Korea University, Seoul 136-701 (Korea, Republic of)

2014-01-15

A vibration atomic layer deposition reactor was developed for fabricating a conformal thin-film coating on nanosize particles. In this study, atomic layer deposition of 10–15-nm-thick Al{sub 2}O{sub 3} films was conducted on a high-surface-area acetylene black powder with particle diameters of 200–250 nm. Intense vibration during the deposition resulted in the effective separation of particles, overcoming the interparticle agglomeration force and enabling effective diffusion of the precursor into the powder chunk; this phenomenon led to the formation of a conformal film coating on the nanopowder particles. It was also confirmed that the atomic layer deposition Al{sub 2}O{sub 3} films initially grew on the high-surface-area acetylene black powder particles as discrete islands, presumably because chemisorption of the precursor and water occurred only on a few sites on the high-surface-area acetylene black powder surface. Relatively sluggish growth of the films during the initial atomic layer deposition cycles was identified from composition analysis.

Controlled growth of carbon nanofibers using plasma enhanced chemical vapor deposition: Effect of catalyst thickness and gas ratio

International Nuclear Information System (INIS)

Saidin, M.A.R.; Ismail, A.F.; Sanip, S.M.; Goh, P.S.; Aziz, M.; Tanemura, M.

2012-01-01

The characteristics of carbon nanofibers (CNFs) grown, using direct current plasma enhanced chemical vapor deposition system reactor under various acetylene to ammonia gas ratios and different catalyst thicknesses were studied. Nickel/Chromium-glass (Ni/Cr-glass) thin film catalyst was employed for the growth of CNF. The grown CNFs were then characterized using Raman spectroscopy, field emission scanning electron microscopy and transmission electron microscopy (TEM). Raman spectroscopy showed that the Ni/Cr-glass with thickness of 15 nm and gas ratio acetylene to ammonia of 1:3 produced CNFs with the lowest I D /I G value (the relative intensity of D-band to G-band). This indicated that this catalyst thickness and gas ratio value is the optimum combination for the synthesis of CNFs under the conditions studied. TEM observation pointed out that the CNFs produced have 104 concentric walls and the residual catalyst particles were located inside the tubes of CNFs. It was also observed that structural morphology of the grown CNFs was influenced by acetylene to ammonia gas ratio and catalyst thickness.

Controlled growth of carbon nanofibers using plasma enhanced chemical vapor deposition: Effect of catalyst thickness and gas ratio

Energy Technology Data Exchange (ETDEWEB)

Saidin, M.A.R. [Advanced Membrane Technology Research Centre (AMTEC), Universiti Teknologi Malaysia, 81310 Skudai, Johor Bahru (Malaysia); Ismail, A.F., E-mail: afauzi@utm.my [Advanced Membrane Technology Research Centre (AMTEC), Universiti Teknologi Malaysia, 81310 Skudai, Johor Bahru (Malaysia); Sanip, S.M.; Goh, P.S.; Aziz, M. [Advanced Membrane Technology Research Centre (AMTEC), Universiti Teknologi Malaysia, 81310 Skudai, Johor Bahru (Malaysia); Tanemura, M. [Department of Frontier Material, Graduate School of Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan)

2012-01-31

The characteristics of carbon nanofibers (CNFs) grown, using direct current plasma enhanced chemical vapor deposition system reactor under various acetylene to ammonia gas ratios and different catalyst thicknesses were studied. Nickel/Chromium-glass (Ni/Cr-glass) thin film catalyst was employed for the growth of CNF. The grown CNFs were then characterized using Raman spectroscopy, field emission scanning electron microscopy and transmission electron microscopy (TEM). Raman spectroscopy showed that the Ni/Cr-glass with thickness of 15 nm and gas ratio acetylene to ammonia of 1:3 produced CNFs with the lowest I{sub D}/I{sub G} value (the relative intensity of D-band to G-band). This indicated that this catalyst thickness and gas ratio value is the optimum combination for the synthesis of CNFs under the conditions studied. TEM observation pointed out that the CNFs produced have 104 concentric walls and the residual catalyst particles were located inside the tubes of CNFs. It was also observed that structural morphology of the grown CNFs was influenced by acetylene to ammonia gas ratio and catalyst thickness.

Structure of MoCN films deposited by cathodic arc evaporation

Energy Technology Data Exchange (ETDEWEB)

Gilewicz, A., E-mail: adam.gilewicz@tu.koszalin.pl [Koszalin University of Technology, Faculty of Technology and Education, Sniadeckich 2, 75-453 Koszalin (Poland); Jedrzejewski, R.; Kochmanska, A.E. [West Pomeranian University of Technology Szczecin, Faculty of Mechanical Engineering and Mechatronics, 19 Piastów Ave., 70-313 Szczecin (Poland); Warcholinski, B. [Koszalin University of Technology, Faculty of Technology and Education, Sniadeckich 2, 75-453 Koszalin (Poland)

2015-02-27

Molybdenum carbonitride (MoCN) coatings were deposited onto HS6-5-2 steel substrate using pure Mo targets in mixed acetylene and nitrogen atmosphere by cathodic arc evaporation. The structural properties of MoCN coatings with different carbon contents (as an effect of the C{sub 2}H{sub 2} flow rate) were investigated systematically. Phase and chemical composition evolution of the coatings were characterized both by the glancing angle of X-ray diffraction (XRD) and wavelength dispersive spectrometry, respectively. These analyses have been supplemented by estimates of grain sizes and stress in the coatings. The XRD results show that the increase in acetylene flow rate causes the formation of molybdenum carbide (MoC) hexagonal phase in the coatings, a reduction of grain size and an increase in internal stress. - Highlights: • MoN and MoCN coatings were deposited by cathodic arc evaporation in nitrogen atmosphere. • MoCN coatings were formed using different acetylene flow rates. • Phase composition evolution was observed. • Crystallite size and stress were calculated.

Novel technique for coal pyrolysis and hydrogenation product analysis

Energy Technology Data Exchange (ETDEWEB)

Pfefferle, L.D.

1992-01-01

This report covers the last quarter of the last year of the three-year grant period. In the final project year, we concentrated on the pyrolysis and oxidative pyrolysis of large hydrocarbons and mixtures of large and small hydrocarbons in order to develop the VUV-MS technique for compounds more representative of those in coal pyrolysis applications. Special focus was directed at the pyrolysis and oxidative pyrolysis of benzene and benzene acetylene mixtures. The acetylene/benzene mixtures were used to gain a better understanding of the mechanisms of molecular growth in such systems specifically to look at the kinetics of aryl-aryl reactions as opposed to small molecule addition to phenyl radicals. Sarofim and coworkers at MIT have recently demonstrated the importance of these reactions in coal processing environments. In the past, the growth mechanism for the formation of midsized PAH has been postulated to involve primarily successive acetylene additions to phenyl-type radicals, our work confmns this as an important mechanism especially for smaller PAH but also investigates conditions where biaryl formation can play an important role in higher hydrocarbon formation.

Novel technique for coal pyrolysis and hydrogenation product analysis. Quarterly report, June 1, 1992

Energy Technology Data Exchange (ETDEWEB)

Pfefferle, L.D.

1992-12-31

This report covers the last quarter of the last year of the three-year grant period. In the final project year, we concentrated on the pyrolysis and oxidative pyrolysis of large hydrocarbons and mixtures of large and small hydrocarbons in order to develop the VUV-MS technique for compounds more representative of those in coal pyrolysis applications. Special focus was directed at the pyrolysis and oxidative pyrolysis of benzene and benzene acetylene mixtures. The acetylene/benzene mixtures were used to gain a better understanding of the mechanisms of molecular growth in such systems specifically to look at the kinetics of aryl-aryl reactions as opposed to small molecule addition to phenyl radicals. Sarofim and coworkers at MIT have recently demonstrated the importance of these reactions in coal processing environments. In the past, the growth mechanism for the formation of midsized PAH has been postulated to involve primarily successive acetylene additions to phenyl-type radicals, our work confmns this as an important mechanism especially for smaller PAH but also investigates conditions where biaryl formation can play an important role in higher hydrocarbon formation.

Optimization, Yield Studies and Morphology of WO3Nano-Wires Synthesized by Laser Pyrolysis in C2H2and O2Ambients—Validation of a New Growth Mechanism

Directory of Open Access Journals (Sweden)

Sideras-Haddad E

2008-01-01

Full Text Available Abstract Laser pyrolysis has been used to synthesize WO3nanostructures. Spherical nano-particles were obtained when acetylene was used to carry the precursor droplet, whereas thin films were obtained at high flow-rates of oxygen carrier gas. In both environments WO3nano-wires appear only after thermal annealing of the as-deposited powders and films. Samples produced under oxygen carrier gas in the laser pyrolysis system gave a higher yield of WO3nano-wires after annealing than the samples which were run under acetylene carrier gas. Alongside the targeted nano-wires, the acetylene-ran samples showed trace amounts of multi-walled carbon nano-tubes; such carbon nano-tubes are not seen in the oxygen-processed WO3nano-wires. The solid–vapour–solid (SVS mechanism [B. Mwakikunga et al., J. Nanosci. Nanotechnol., 2008] was found to be the possible mechanism that explains the manner of growth of the nano-wires. This model, based on the theory from basic statistical mechanics has herein been validated by length-diameter data for the produced WO3nano-wires.

Carbon-based sputtered coatings for enhanced chitosan-based films properties

Science.gov (United States)

Fernandes, C.; Calderon V., S.; Ballesteros, Lina F.; Cerqueira, Miguel A.; Pastrana, L. M.; Teixeira, José A.; Ferreira, P. J.; Carvalho, S.

2018-03-01

In order to make bio-based packaging materials competitive in comparison to petroleum-based one, some of their properties need to be improved, among which gas permeability is of crucial importance. Thus, in this work, carbon-based coatings were applied on chitosan-based films by radiofrequency reactive magnetron sputtering aiming to improve their barrier properties. Chemical and morphological properties were evaluated in order to determine the effect of the coatings on the chemical structure, surface hydrophobicity and barrier properties of the system. Chemical analysis, performed by electron energy loss spectroscopy and Fourier transform infrared spectroscopy, suggests similar chemical characteristics among all coatings although higher incorporation of hydrogen as the acetylene flux increases was observed. On the other hand, scanning transmission electron microscopy revealed that the porosity of the carbon layer can be tailored by the acetylene flux. More importantly, the chitosan oxygen permeability showed a monotonic reduction as a function of the acetylene flux. This study opens up new opportunities to apply nanostructured coatings on bio-based polymer for enhanced oxygen barrier properties.

Background-cross-section-dependent subgroup parameters

International Nuclear Information System (INIS)

Yamamoto, Toshihisa

2003-01-01

A new set of subgroup parameters was derived that can reproduce the self-shielded cross section against a wide range of background cross sections. The subgroup parameters are expressed with a rational equation which numerator and denominator are expressed as the expansion series of background cross section, so that the background cross section dependence is exactly taken into account in the parameters. The advantage of the new subgroup parameters is that they can reproduce the self-shielded effect not only by group basis but also by subgroup basis. Then an adaptive method is also proposed which uses fitting procedure to evaluate the background-cross-section-dependence of the parameters. One of the simple fitting formula was able to reproduce the self-shielded subgroup cross section by less than 1% error from the precise evaluation. (author)

Photon-splitting cross sections

International Nuclear Information System (INIS)

Johannessen, A.M.; Mork, K.J.; Overbo, I.

1980-01-01

The differential cross section for photon splitting (scattering of one photon into two photons) in a Coulomb field, obtained earlier by Shima, has been integrated numerically to yield various differential cross sections. Energy spectra differential with respect to the energy of one of the outgoing photons are presented for several values of the primary photon energy. Selected examples of recoil momentum distributions and some interesting doubly or multiply differential cross sections are also given. Values for the total cross section are obtained essentially for all energies. The screening effect caused by atomic electrons is also taken into account, and is found to be important for high energies, as in e + e - pair production. Comparisons with various approximate results obtained by previous authors mostly show fair agreement. We also discuss the possibilities for experimental detection and find the most promising candidate to be a measurement of both photons, and their energies, at a moderately high energy

Electron-impact cross sections of Ne

International Nuclear Information System (INIS)

Tsurubuchi, S.; Arakawa, K.; Kinokuni, S.; Motohashi, K.

2000-01-01

Electron-impact absolute emission cross sections were measured for the 3p→3s transitions of Ne. Excitation functions of the 3s→2p first resonance lines were measured in the energy range from the threshold to 1000 eV by a polarization-free optical method and relative cross sections were normalized to the absolute values, (41.0±5.4)x10 -19 cm 2 for the 73.6 nm line and (7.1±1.0)x10 -19 cm 2 for the 74.4 nm line, which were determined at 500 eV. The integrated level-excitation cross sections of Suzuki et al for the 1s 2 and 1s 4 levels were combined with the corresponding 3p→3s cascade cross sections obtained in this paper to give absolute emission cross sections for the resonance lines. The level-excitation cross sections of the 1s 2 and 1s 4 states in Paschen notation were determined from the threshold to 1000 eV by subtracting 3p→3s cascade cross sections from the corresponding 3s→2p emission cross sections of the resonance lines. A large cascade contribution is found in the emission cross section of the resonance lines. It is 28.5% for the 73.6 nm line and 49.6% for the 74.4 nm line at 40 eV, and 17.0 and 61.8%, respectively, at 300 eV. (author)

Cross-section methodology in SIMMER

International Nuclear Information System (INIS)

Soran, P.D.

1975-11-01

The cross-section methodology incorporated in the SIMMER code is described. Data base for all cross sections is the ENDF/B system with various progressing computer codes to group collapse and modify the group constants which are used in SIMMER. Either infinitely dilute cross sections or the Bondarenko formalism can be used in SIMMER. Presently only a microscopic treatment is considered, but preliminary macroscopic algorithms have been investigated

Cross-section methodology in SIMMER

International Nuclear Information System (INIS)

Soran, P.D.

1976-05-01

The cross-section methodology incorporated in the SIMMER code is described. Data base for all cross sections is the ENDF/B system with various progressing computer codes to group collapse and modify the group constants which are used in SIMMER. Either infinitely dilute cross sections or the Bondarenko formalism can be used in SIMMER. Presently only a microscopic treatment is considered, but preliminary macroscopic algorithms have been investigated

Women Mentoring in the Academe: A Faculty Cross-Racial and Cross-Cultural Experience

Science.gov (United States)

Guramatunhu-Mudiwa, Precious; Angel, Roma B.

2017-01-01

Two women faculty members, one White from the southeastern United States and one Black African from Zimbabwe, purposefully explored their informal mentoring relationship with the goal of illuminating the complexities associated with their cross-racial, cross-cultural experience. Concentrating on their four-year mentor-mentee academic relationship…

Boundary Crossing in R&D Projects in Schools: Learning through Cross-Professional Collaboration

Science.gov (United States)

Schenke, Wouter; van Driel, Jan; Geijsel, Femke P.; Volman, Monique L. L.

2017-01-01

Background/Context: School leaders, teachers, and researchers are increasingly involved in collaborative research and development (R&D) projects in schools, which encourage crossing boundaries between the fields of school and research. It is not clear, however, what and how professionals in these projects learn through cross-professional…

Neutron cross sections: Book of curves

International Nuclear Information System (INIS)

McLane, V.; Dunford, C.L.; Rose, P.F.

1988-01-01

Neuton Cross Sections: Book of Curves represents the fourth edition of what was previously known as BNL-325, Neutron Cross Sections, Volume 2, CURVES. Data is presented only for (i.e., intergrated) reaction cross sections (and related fission parameters) as a function of incident-neutron energy for the energy range 0.01 eV to 200 MeV. For the first time, isometric state production cross sections have been included. 11 refs., 4 figs

Jet inclusive cross sections

International Nuclear Information System (INIS)

Del Duca, V.

1992-11-01

Minijet production in jet inclusive cross sections at hadron colliders, with large rapidity intervals between the tagged jets, is evaluated by using the BFKL pomeron. We describe the jet inclusive cross section for an arbitrary number of tagged jets, and show that it behaves like a system of coupled pomerons

Characterization of the degree of cross-linking in radiation cross-linked low and high density polyethylenes

International Nuclear Information System (INIS)

Posselt, K.; Haedrich, W.

1986-01-01

In practice the cross-linking of irradiated polyethylene is mostly characterized by solubility and thermomechanical data. The irradiation of samples of a LDPE and a HDPE yields very different gel-dose curves. But for a quantitative comparison the complicated connection between the gel values and the corresponding densities of cross-links, especially the dependence on the initial molecular size distribution, has to take into consideration. The analysis of the solubility data according to the statistical theory of cross-linking developed by Inokuti and Saito shows that at equal doses in both investigated PE types in spite of the different gel values nearly the same densities of cross-links are present. That result is confirmed by the densities of cross-links determined from stress-strain measurements at 423 K. (author)

Precise orbit determination of Multi-GNSS constellation including GPS GLONASS BDS and GALIEO

Science.gov (United States)

Dai, Xiaolei

2014-05-01

In addition to the existing American global positioning system (GPS) and the Russian global navigation satellite system (GLONASS), the new generation of GNSS is emerging and developing, such as the Chinese BeiDou satellite navigation system (BDS) and the European GALILEO system. Multi-constellation is expected to contribute to more accurate and reliable positioning and navigation service. However, the application of multi-constellation challenges the traditional precise orbit determination (POD) strategy that was designed usually for single constellation. In this contribution, we exploit a more rigorous multi-constellation POD strategy for the ongoing IGS multi-GNSS experiment (MGEX) where the common parameters are identical for each system, and the frequency- and system-specified parameters are employed to account for the inter-frequency and inter-system biases. Since the authorized BDS attitude model is not yet released, different BDS attitude model are implemented and their impact on orbit accuracy are studied. The proposed POD strategy was implemented in the PANDA (Position and Navigation Data Analyst) software and can process observations from GPS, GLONASS, BDS and GALILEO together. The strategy is evaluated with the multi-constellation observations from about 90 MGEX stations and BDS observations from the BeiDou experimental tracking network (BETN) of Wuhan University (WHU). Of all the MGEX stations, 28 stations record BDS observation, and about 80 stations record GALILEO observations. All these data were processed together in our software, resulting in the multi-constellation POD solutions. We assessed the orbit accuracy for GPS and GLONASS by comparing our solutions with the IGS final orbit, and for BDS and GALILEO by overlapping our daily orbit solution. The stability of inter-frequency bias of GLONASS and inter-system biases w.r.t. GPS for GLONASS, BDS and GALILEO were investigated. At last, we carried out precise point positioning (PPP) using the multi