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Sample records for copolymerization reactions experimental

  1. Chain Copolymerization Reactions: An Algorithm to Predict the Reaction Evolution with Conversion

    ERIC Educational Resources Information Center

    Gallardo, Alberto; Aguilar, Maria Rosa; Abraham, Gustavo A.; Roman, Julio San

    2004-01-01

    An algorithm is developed to study and understand the behavior of chain copolymerization reactions. When a binary copolymerization reaction follows the terminal model, Conversion is able to predict the evolution of different parameters, such as instantaneous and cumulative copolymer molar fractions, or molar fractions of any sequence with the…

  2. Two-dimensional Raman correlation spectroscopy study of an emulsion copolymerization reaction process.

    PubMed

    Noda, Isao; Allen, William M; Lindberg, Seth E

    2009-02-01

    The emulsion copolymerization of styrene and 1,3-butadiene using an oligomeric nonionic surfactant as an emulsifier to make a styrene-butadiene rubber (SBR) copolymer latex was monitored by real-time in situ Raman spectroscopy. Time-resolved Raman spectra collected during the early stage of the polymerization reaction were subjected to a series of data analysis techniques, including two-dimensional (2D) correlation spectroscopy, multivariate self-modeling curve resolution (SMCR), and kernel analysis, to elucidate the fine details of the complex reaction process. Generalized 2D correlation analysis of time-resolved Raman spectra readily identified the characteristic Raman scattering bands for the monomers and copolymer. Cross-peaks appearing in 2D Raman correlation spectra showed that the decrease in the spectral intensity of Raman bands assignable to 1,3-butadiene occurs before the band intensity changes for styrene or SBR copolymer. The positions of asynchronous cross-peaks were used to identify a spectral region with the most distinct pattern of intensity variations, which in turn could be used as the starting point for the alternating least squares iteration of the SMCR analysis. SMCR analysis of the time-resolved Raman spectra generated a set of estimated pure component spectra and concentration profiles of styrene, 1,3-butadiene, and SBR copolymer without requiring independently measured calibration data. The estimated concentration profiles of monomers and copolymer indicated that the reaction of 1,3-butadiene started before the consumption of styrene and production of SBR copolymer. Kernel analysis of the estimated concentration profiles provided a succinct measure of the similarity and dissimilarity of the concentration changes of monomers and copolymer. PMID:19215653

  3. Graft copolymerization of acrylic acid to cassava starch--evaluation of the influences of process parameters by an experimental design method.

    PubMed

    Witono, J R; Noordergraaf, I W; Heeres, H J; Janssen, L P B M

    2012-11-01

    The graft copolymerization of cassava starch with acrylic acid was investigated using a free radical initiator system (Fe(2+)/H(2)O(2) redox system) in water. A comprehensive understanding of the important variables and their interaction has been obtained by applying an experimental design method. In this approach, two ('high' and 'low') values of selected variables are considered. Important result parameters are add-on and the grafting efficiency. Out of eight reaction variables, it was found that only temperature, starch concentration and the starch to monomer ratio have a pronounced influence on these response parameters. Moderate reaction temperature (40 °C) and high starch concentration (10%) give relatively good results of add-on and grafting efficiency. A low starch to monomer ratio favors add-on but decreases grafting efficiency. These findings can be used to optimize the production of cassava starch-acrylate copolymers and to gain insight in the process-product property interactions, for various applications. PMID:22944411

  4. Development of group IV molecular catalysts for high temperature ethylene-α-olefin copolymerization reactions.

    PubMed

    Klosin, Jerzy; Fontaine, Philip P; Figueroa, Ruth

    2015-07-21

    This Account describes our research related to the development of molecular catalysts for solution phase olefin polymerization. Specifically, a series of constrained geometry and nonmetallocene (imino-amido-type) complexes were developed for high temperature olefin polymerization reactions. We have discovered many highly active catalysts that are capable of operating at temperatures above 120 °C and producing copolymers with a useful range of molecular weights (from medium to ultrahigh depending on precatalyst identity and polymerization conditions) and α-olefin incorporation capability. Constrained geometry catalysts (CGCs) exhibit very high activities and are capable of producing a variety of copolymers including ethylene-propylene and ethylene-1-octene copolymers at high reactor temperatures. Importantly, CGCs have much higher reactivity toward α-olefins than classical Ziegler-Natta catalysts, thus allowing for the production of copolymers with any desired level of comonomer. In search of catalysts with improved performance, we discovered 3-amino-substituted indenyl-based CGCs that exhibit the highest activity and produce copolymers with the highest molecular weight within this family of catalysts. Phenanthrenyl-based CGCs were found to be outstanding catalysts for the effective production of high styrene content ethylene-styrene copolymers under industrially relevant conditions. In contrast to CGC ligands, imino-amido-type ligands are bidentate and monoionic, leading to the use of trialkyl group IV precatalysts. The thermal instability of imino-amido complexes was addressed by the development of imino-enamido and amidoquinoline complexes, which are not only thermally very robust, but also produce copolymers with higher molecular weights, and exhibit improved α-olefin incorporation. Imido-amido and imino-enamido catalysts undergo facile chain transfer reactions with metal alkyls, as evidenced by a sharp decrease in polymer molecular weight when the

  5. Monitoring of high solids content starved-semi-batch emulsion copolymerization reactions by Fourier transform Raman spectroscopy.

    PubMed

    Elizalde, Oihana; Asua, José M; Leiza, Jose R

    2005-10-01

    A high solids content n-butyl acrylate/methyl methacrylate emulsion copolymerization process carried out under starved semi-batch conditions was for the first time monitored on-line by means of Fourier transform (FT)-Raman spectroscopy. Partial least squares regression was employed to build calibration models that allowed relating the spectra with solids content (overall conversion), free amounts of both n-butyl acrylate (n-BA) and methyl methacrylate (MMA), and cumulative copolymer composition. In spite of the heterogeneous nature of the polymerization, the similarities of the spectra for MMA, n-BA, and for the copolymer, and the low monomer concentrations in the reactor, the FT-Raman spectroscopy has been shown to be a suitable noninvasive sensor to accurately monitor the process. Therefore, it is well suited for on-line control of all-acrylic polymerization systems. PMID:18028623

  6. Experimental Demonstrations in Teaching Chemical Reactions.

    ERIC Educational Resources Information Center

    Hugerat, Muhamad; Basheer, Sobhi

    2001-01-01

    Presents demonstrations of chemical reactions by employing different features of various compounds that can be altered after a chemical change occurs. Experimental activities include para- and dia-magnetism in chemical reactions, aluminum reaction with base, reaction of acid with carbonates, use of electrochemical cells for demonstrating chemical…

  7. Experimental Study of Serpentinization Reactions

    NASA Technical Reports Server (NTRS)

    Cohen, B. A.; Brearley, A. J.; Ganguly, J.; Liermann, H.-P.; Keil, K.

    2004-01-01

    Current carbonaceous chondrite parent-body thermal models [1-3] produce scenarios that are inconsistent with constraints on aqueous alteration conditions based on meteorite mineralogical evidence, such as phase stability relationships within the meteorite matrix minerals [4] and isotope equilibration arguments [5, 6]. This discrepancy arises principally because of the thermal runaway effect produced by silicate hydration reactions (here loosely called serpentinization, as the principal products are serpentine minerals), which are so exothermic as to produce more than enough heat to melt more ice and provide a self-sustaining chain reaction. One possible way to dissipate the heat of reaction is to use a very small parent body [e.g., 2] or possibly a rubble pile model. Another possibility is to release this heat more slowly, which depends on the alteration reaction path and kinetics.

  8. EXFOR Library of Experimental Nuclear Reaction Data

    DOE Data Explorer

    The EXFOR library contains an extensive compilation of experimental nuclear reaction data up to 1 GeV. Neutron reactions have been compiled systematically since the discovery of the neutron, while charged particle(up to carbon) and photon reactions have been covered less extensively. Files contain nuclear reaction data such as cross sections, spectra, angular distributions, polarizations, etc, along with information on experimental technique, error analysis, and applied standards. Numerous search parameters include: target, beam, product, experimental method, and even author and publication names. The library contains data from more than 20,000 experiments. (Specialized Interface)

  9. Development of Novel Polymeric Prodrugs Synthesized by Mechanochemical Solid-State Copolymerization of Hydroxyethylcellulose and Vinyl Monomers.

    PubMed

    Doi, Naoki; Sasai, Yasushi; Yamauchi, Yukinori; Adachi, Tetsuo; Kuzuya, Masayuki; Kondo, Shin-ichi

    2015-01-01

    Novel polymeric prodrugs were synthesized by mechanochemical solid-state copolymerization of hydroxyethylcellulose and the methacryloyloxy derivative of 5-fluorouracil (5-FU). Copolymerization was about 94% complete after 4 h, and the polymeric prodrug was quantitatively obtained after 14 h of reaction. The number average molecular weight (Mn) and polydispersity (H) of the polymeric prodrug were 39000 g/mol and 6.20, respectively. Mechanical fracturing of the polymer in a stainless steel twin-shell blender improved these properties (Mn=16000 g/mol and H=1.94). 5-FU was sustainably released from the polymeric prodrugs, and the rate was not affected by the molecular weight or molecular weight distribution of the prodrug under the experimental conditions used. These results suggest that novel polymeric prodrugs composed of a polysaccharide and a synthetic polymer can be fabricated by mechanochemical solid-state copolymerization under anaerobic conditions. PMID:26423117

  10. Recent Experimental Progress on Surrogate Reactions

    NASA Astrophysics Data System (ADS)

    Beausang, Cornelius

    2014-09-01

    Reactions on unstable nuclei are important in a wide variety of nuclear physics scenarios. Cross sections for neutron (or light charged particle) induced reactions on target nuclei spanning the chart of the nuclei are important for nuclear astrophysics (r-process, s-process rp- and p-processes etc.), for nuclear energy generation and for national security applications. Many such reactions occur on short-lived unstable nuclei. Even with the present generation of radioactive beam facilities, many such reactions are difficult, if not impossible, to measure directly. For these reactions, often the surrogate reaction technique provides the only option to provide some experimental guidance for the calculations. The experimental and theoretical techniques required are described in some detail in the recent review article by Escher et al.. Originally introduced in the 1970's the last decade has seen a resurgence of interest in the surrogate technique. Various ratio techniques, external, internal and hybrid, have been developed to minimize the effect of target contamination. In the actinide region, a large number of surrogate (n,f) cross sections have been measured. In general, these show agreement to within 5--10%, with directly measured (n,f) data where these data exist (benchmarking), for equivalent neutron energies ranging from ~100 keV up to tens of MeV. For (n, γ) reactions, measurements have been attempted for select nuclei in various mass regions (A ~ 90, 150 and 235) and for these the agreement with directly measured data is less good. The various experimental techniques employed will be described as well as the current state of the experimental data. Some future directions will be described. Reactions on unstable nuclei are important in a wide variety of nuclear physics scenarios. Cross sections for neutron (or light charged particle) induced reactions on target nuclei spanning the chart of the nuclei are important for nuclear astrophysics (r-process, s

  11. Experimental nuclear reaction data collection EXFOR

    SciTech Connect

    Semkova, V.; Otuka, N.; Simakov, S. P.; Zerkin, V.

    2011-07-01

    The International Network of Nuclear Reaction Data Centres (NRDC) constitutes a worldwide cooperation of 14 nuclear data centres. The main activity of the NRDC Network is collection and compilation of experimental nuclear reaction cross section data and the related bibliographic information in the EXFOR and CINDA databases as well as dissemination of nuclear reaction data and associated documentation to users. The database contains information and numerical data from more than about 19000 experiments consisting of more than 140000 datasets. EXFOR is kept up to date by constantly adding newly published experimental information. Tools developed for data dissemination utilise modern database technologies with fast online capabilities over the Internet. Users are provided with sophisticated search options, a user-friendly retrieval interface for downloading data in different formats, and additional output options such as improved data plotting capabilities. The present status of the EXFOR database will be presented together with the latest development for data access and retrieval. (authors)

  12. Fuel-rich, catalytic reaction experimental results

    NASA Technical Reports Server (NTRS)

    Rollbuhler, R. James

    1991-01-01

    Future aeropropulsion gas turbine combustion requirements call for operating at very high inlet temperatures, pressures, and large temperature rises. At the same time, the combustion process is to have minimum pollution effects on the environment. Aircraft gas turbine engines utilize liquid hydrocarbon fuels which are difficult to uniformly atomize and mix with combustion air. An approach for minimizing fuel related problems is to transform the liquid fuel into gaseous form prior to the completion of the combustion process. Experimentally obtained results are presented for vaporizing and partially oxidizing a liquid hydrocarbon fuel into burnable gaseous components. The presented experimental data show that 1200 to 1300 K reaction product gas, rich in hydrogen, carbon monoxide, and light-end hydrocarbons, is formed when flowing 0.3 to 0.6 fuel to air mixes through a catalyst reactor. The reaction temperatures are kept low enough that nitrogen oxides and carbon particles (soot) do not form. Results are reported for tests using different catalyst types and configurations, mass flowrates, input temperatures, and fuel to air ratios.

  13. Tuning the critical solution temperature of polymers by copolymerization

    SciTech Connect

    Schulz, Bernhard; Chudoba, Richard; Dzubiella, Joachim; Heyda, Jan

    2015-12-28

    We study statistical copolymerization effects on the upper critical solution temperature (CST) of generic homopolymers by means of coarse-grained Langevin dynamics computer simulations and mean-field theory. Our systematic investigation reveals that the CST can change monotonically or non-monotonically with copolymerization, as observed in experimental studies, depending on the degree of non-additivity of the monomer (A-B) cross-interactions. The simulation findings are confirmed and qualitatively explained by a combination of a two-component Flory-de Gennes model for polymer collapse and a simple thermodynamic expansion approach. Our findings provide some rationale behind the effects of copolymerization and may be helpful for tuning CST behavior of polymers in soft material design.

  14. Tuning the critical solution temperature of polymers by copolymerization

    NASA Astrophysics Data System (ADS)

    Schulz, Bernhard; Chudoba, Richard; Heyda, Jan; Dzubiella, Joachim

    2015-12-01

    We study statistical copolymerization effects on the upper critical solution temperature (CST) of generic homopolymers by means of coarse-grained Langevin dynamics computer simulations and mean-field theory. Our systematic investigation reveals that the CST can change monotonically or non-monotonically with copolymerization, as observed in experimental studies, depending on the degree of non-additivity of the monomer (A-B) cross-interactions. The simulation findings are confirmed and qualitatively explained by a combination of a two-component Flory-de Gennes model for polymer collapse and a simple thermodynamic expansion approach. Our findings provide some rationale behind the effects of copolymerization and may be helpful for tuning CST behavior of polymers in soft material design.

  15. Experimental studies of gas-aerosol reactions

    NASA Astrophysics Data System (ADS)

    Gupta, Anand

    1991-05-01

    The aqueous phase oxidation of SO2 by H2O2 is believed to the principle mechanism for atmospheric sulfate formation in cloud droplets. However, no studies in noncloud aerosol systems have been reported. The objective is to quantify the importance of the noncloud liquid phase reactions of SO2 by H2O2 in the atmosphere. Growth rates of submicron droplets exposed to SO2 and H2O2 were measured using the tandem differential mobility analyzer (TDMA) technique (Rader and McMurry, 1986). The technique uses differential mobility analyzers (DMA's) to generate monodisperse particles and to measure particle size after the reaction. To facilitate submicron monodisperse droplet production with the DMA, a low-ion-concentration charter capable of generating singly charged particles up to 1.0 microns was developed and experimentally evaluated. The experiments were performed using dry and deliquesced (NH4)2SO4 particles with SO2 and H2O2 concentrations from 0-860 ppb and 0-150 ppb, respectively. No growth was observed for dry particles. For droplets greater than or equal to 0.3 microns, the fractional diameter growth was independent of particle size and for droplets less than or equal to 0.2 microns, it decreased as particle size decreased. The observed decrease is due to NH3 evaporation. As ammonia evaporates, droplet pH decreases causing the oxidation rate to decrease, leading to a lower growth rate. To predict the size-dependent growth rates, a theoretical model was developed using solution thermodynamics, gas/particle equilibrium, and chemical kinetics. The experimental and theoretical results are in reasonable agreement. For dry (NH4)2SO4 particles exposed to SO2, H2O2, NH3, and H2O vapor, surface reaction-controlled growth was observed. Particle growth was very sensitive to particle composition. No growth was observed for Polystyrene latex particles, whereas (NH4)2SO4 particles doped with catalysts (Fe(2+), Fe(3+), Mn(2+) and Cu(2+)) in a molar ratio of 1:500 grew slower than

  16. Radiation copolymerization of N-vinylpyrrolidone with crotonic acid

    SciTech Connect

    Solovskii, M.V.; Ushakova, V.N.; Panarin, E.F.; Boimirzaev, A.S.; Nesterov, V.V.; Persinen, A.A.; Mikhal'chenko, G.A.

    1987-09-01

    It was experimentally shown that the method of radiation initiation of copolymerization can be used to synthesize copolymers of N-vinylpyrrolidone with crotonic acid with controlled composition, molecular weights, and molecular weight distribution. These copolymers also include those with characteristics that satisfy the requirements for synthetic polymers serving as modifiers of biologically active compounds.

  17. Direct Copolymerization of CO2 and Diols

    PubMed Central

    Tamura, Masazumi; Ito, Kazuki; Honda, Masayoshi; Nakagawa, Yoshinao; Sugimoto, Hiroshi; Tomishige, Keiichi

    2016-01-01

    Direct polymerization of CO2 and diols is promising as a simple and environmental-benign method in place of conventional processes using high-cost and/or hazardous reagents such as phosgene, carbon monoxide and epoxides, however, there are no reports on the direct method due to the inertness of CO2 and severe equilibrium limitation of the reaction. Herein, we firstly substantiate the direct copolymerization of CO2 and diols using CeO2 catalyst and 2-cyanopyridine promotor, providing the alternating cooligomers in high diol-based yield (up to 99%) and selectivity (up to >99%). This catalyst system is applicable to various diols including linear C4-C10 α,ω-diols to provide high yields of the corresponding cooligomers, which cannot be obtained by well-known methods such as copolymerization of CO2 and cyclic ethers and ring-opening polymerization of cyclic carbonates. This process provides us a facile synthesis method for versatile polycarbonates from various diols and CO2 owing to simplicity of diols modification. PMID:27075987

  18. Direct Copolymerization of CO2 and Diols

    NASA Astrophysics Data System (ADS)

    Tamura, Masazumi; Ito, Kazuki; Honda, Masayoshi; Nakagawa, Yoshinao; Sugimoto, Hiroshi; Tomishige, Keiichi

    2016-04-01

    Direct polymerization of CO2 and diols is promising as a simple and environmental-benign method in place of conventional processes using high-cost and/or hazardous reagents such as phosgene, carbon monoxide and epoxides, however, there are no reports on the direct method due to the inertness of CO2 and severe equilibrium limitation of the reaction. Herein, we firstly substantiate the direct copolymerization of CO2 and diols using CeO2 catalyst and 2-cyanopyridine promotor, providing the alternating cooligomers in high diol-based yield (up to 99%) and selectivity (up to >99%). This catalyst system is applicable to various diols including linear C4-C10 α,ω-diols to provide high yields of the corresponding cooligomers, which cannot be obtained by well-known methods such as copolymerization of CO2 and cyclic ethers and ring-opening polymerization of cyclic carbonates. This process provides us a facile synthesis method for versatile polycarbonates from various diols and CO2 owing to simplicity of diols modification.

  19. Porating anion-responsive copolymeric gels.

    PubMed

    England, Dustin; Yan, Feng; Texter, John

    2013-09-24

    A polymerizable ionic liquid surfactant, 1-(11-acryloyloxyundecyl)-3-methylimidiazolium bromide (ILBr), was copolymerized with methyl methacrylate (MMA) in aqueous microemulsions at 30% (ILBr w/w) and various water to MMA ratios. The ternary phase diagram of the ILBr/MMA/water system was constructed at 25 and 60 °C. Homopolymers and copolymers of ILBr and MMA were produced by thermally initiated chain radical microemulsion polymerization at various compositions in bicontinuous and reverse microemulsion subdomains. Microemulsion polymerization reaction products varied from being gel-like to solid, and these materials were analyzed by thermal and scanning electron microscopy methods. Microemulsion polymerized materials were insoluble in all solvents tested, consistent with light cross-linking. Ion exchange between Br(-) and PF6(-) in these copolymeric materials resulted in the formation of open-cell porous structures in some of these materials, as was confirmed by scanning electron microscopy (SEM). Several compositions illustrate the capture of prepolymerization nanoscale structure by thermally initiated polymerization, expanding the domain of compositions exhibiting this feat and yet to be demonstrated in any other system. Regular cylindrical pores in interpenetrating ILBr-co-MMA and PMMA networks are produced by anion exchange in the absence of templates. A percolating cluster/bicontinuous transition is "captured" by SEM after using anion exchange to visualize the mixed cluster/pore morphology. Some design principles for achieving this capture and for obtaining stimuli responsive solvogels are articulated, and the importance of producing solvogels in capturing the nanoscale is highlighted. PMID:23968242

  20. Direct Copolymerization of CO2 and Diols.

    PubMed

    Tamura, Masazumi; Ito, Kazuki; Honda, Masayoshi; Nakagawa, Yoshinao; Sugimoto, Hiroshi; Tomishige, Keiichi

    2016-01-01

    Direct polymerization of CO2 and diols is promising as a simple and environmental-benign method in place of conventional processes using high-cost and/or hazardous reagents such as phosgene, carbon monoxide and epoxides, however, there are no reports on the direct method due to the inertness of CO2 and severe equilibrium limitation of the reaction. Herein, we firstly substantiate the direct copolymerization of CO2 and diols using CeO2 catalyst and 2-cyanopyridine promotor, providing the alternating cooligomers in high diol-based yield (up to 99%) and selectivity (up to >99%). This catalyst system is applicable to various diols including linear C4-C10 α,ω-diols to provide high yields of the corresponding cooligomers, which cannot be obtained by well-known methods such as copolymerization of CO2 and cyclic ethers and ring-opening polymerization of cyclic carbonates. This process provides us a facile synthesis method for versatile polycarbonates from various diols and CO2 owing to simplicity of diols modification. PMID:27075987

  1. Copolymerization of carbon dioxide and butadiene via a lactone intermediate.

    PubMed

    Nakano, Ryo; Ito, Shingo; Nozaki, Kyoko

    2014-04-01

    Although carbon dioxide has attracted broad interest as a renewable carbon feedstock, its use as a monomer in copolymerization with olefins has long been an elusive endeavour. A major obstacle for this process is that the propagation step involving carbon dioxide is endothermic; typically, attempted reactions between carbon dioxide and an olefin preferentially yield olefin homopolymerization. Here we report a strategy to circumvent the thermodynamic and kinetic barriers for copolymerizations of carbon dioxide and olefins by using a metastable lactone intermediate, 3-ethylidene-6-vinyltetrahydro-2H-pyran-2-one, which is formed by the palladium-catalysed condensation of carbon dioxide and 1,3-butadiene. Subsequent free-radical polymerization of the lactone intermediate afforded polymers of high molecular weight with a carbon dioxide content of 33 mol% (29 wt%). Furthermore, the protocol was applied successfully to a one-pot copolymerization of carbon dioxide and 1,3-butadiene, and one-pot terpolymerizations of carbon dioxide, butadiene and another 1,3-diene. This copolymerization technique provides access to a new class of polymeric materials made from carbon dioxide. PMID:24651200

  2. Characteristics of vestibulosensory reactions studied by experimental caloric test

    NASA Technical Reports Server (NTRS)

    Kapranov, V. Z.

    1980-01-01

    Vestibulo-sensory reactions were studied in 135 workers who were in contact with nitroethers, by the method of an experimental caloric test. The response vestibulo-sensory reactions were recorded by means of an electroencephalograph. The changes in the sensory reaction depended on the duration of the workers' contact with toxic agents. A study of illusion reactions by the labyrinth calorization widens diagnostic possibilities in the examination of functional condition of the vestibular analyser considerably.

  3. Experimental Study of Stellar Reactions at CNS

    NASA Astrophysics Data System (ADS)

    Kubono, S.; Yamaguchi, H.; Wakabayashi, Y.; Amadio, G.; Hayakawa, S.; He, J. J.; Saito, A.; Teranishi, T.; Nishimura, S.; Fukunishi, N.; Iwasa, N.; Inafuku, K.; Kato, S.; Tanaka, M. H.; Fuchi, Y.; Moon, J. Y.; Kwon, K.; Lee, C. S.; Khiem, Le Hong; Chen, A.; Pearson, J.

    2006-11-01

    After a brief review on low-energy RI beam production technology, nuclear astrophysics programs at CNS are presented including a scope of the field in the Wako campus. The CRIB project involves a total development of the whole facility to maximize the low-energy RI beam intensities, including the ion source, the AVF cyclotron and the low-energy RI beam separator CRIB, Some recent nuclear astrophysics experiments performed with the RI beams were discussed, including the measurement of the 14O(α,p)17F reaction, the key stellar reaction for the onset of the high-temperature rp-process. The first experiment performed with a newly installed high-resolution magnetic spectrograph PA of CNS was also presented. Collaboration possibilities for nuclear astrophysics in the RIKEN campus are also touched.

  4. Experimental Study of Stellar Reactions at CNS

    SciTech Connect

    Kubono, S.; Yamaguchi, H.; Wakabayashi, Y.; Amadio, G.; Hayakawa, S.; He, J. J.; Saito, A.; Teranishi, T.; Nishimura, S.; Fukunishi, N.; Iwasa, N.; Inafuku, K.; Kato, S.; Tanaka, M. H.; Fuchi, Y.; Moon, J. Y.; Kwon, K.; Lee, C. S.; Khiem, Le Hong; Chen, A.

    2006-11-02

    After a brief review on low-energy RI beam production technology, nuclear astrophysics programs at CNS are presented including a scope of the field in the Wako campus. The CRIB project involves a total development of the whole facility to maximize the low-energy RI beam intensities, including the ion source, the AVF cyclotron and the low-energy RI beam separator CRIB, Some recent nuclear astrophysics experiments performed with the RI beams were discussed, including the measurement of the 14O({alpha},p)17F reaction, the key stellar reaction for the onset of the high-temperature rp-process. The first experiment performed with a newly installed high-resolution magnetic spectrograph PA of CNS was also presented. Collaboration possibilities for nuclear astrophysics in the RIKEN campus are also touched.

  5. Experimental research of reaction blading on air turbine VT-400

    NASA Astrophysics Data System (ADS)

    Klimko, Marek; Okresa, Daniel

    2016-03-01

    The article deals with testing a reaction blading on an experimental air turbine VT-400, which is situated at the Department of Power System Engineering at University of West Bohemia. Experiments were carried out in cooperation with an industrial partner Doosan Skoda Power. The outputs of these measurements are for example: results of the stage efficiency depending on the speed ratio u/c, the course of reaction, the input and output angles and profile losses along a blade.

  6. Experimental studies of reactions relevant for γ-process nucleosynthesis

    SciTech Connect

    Scholz, P.; Endres, J.; Hennig, A.; Mayer, J.; Netterdon, L.; Zilges, A.; Sauerwein, A.

    2014-05-09

    We report on our recent experimental studies of reactions relevant for the γ process nucleosynthesis. Applying the activation method using the Cologne Clover Counting Setup total cross sections of the reactions {sup 168}Yb(α,γ), {sup 168}Yb(α,n), and {sup 187}Re(α,n) could be obtained. Furthermore, the reaction {sup 89}Y(p,γ) was investigated via the in-beam technique with HPGe detectors at the high-efficiency g-ray spectrometer HORUS in Cologne in order to determine partial and total cross sections.

  7. Reactivity ratios, and mechanistic insight for anionic ring-opening copolymerization of epoxides.

    PubMed

    Lee, Bongjae F; Wolffs, Martin; Delaney, Kris T; Sprafke, Johannes K; Leibfarth, Frank A; Hawker, Craig J; Lynd, Nathaniel A

    2012-05-01

    Reactivity ratios were evaluated for anionic ring-opening copolymerizations of ethylene oxide (EO) with either allyl glycidyl ether (AGE) or ethylene glycol vinyl glycidyl ether (EGVGE) using a benzyl alkoxide initiator. The chemical shift for the benzylic protons of the initiator, as measured by (1)H NMR spectroscopy, were observed to be sensitive to the sequence of the first two monomers added to the initiator during polymer growth. Using a simple kinetic model for initiation and the first propagation step, reactivity ratios for the copolymerization of AGE and EGVGE with EO could be determined by analysis of the (1)H NMR spectroscopy for the resulting copolymer. For the copolymerization between EO and AGE, the reactivity ratios were determined to be r(AGE) = 1.31 ± 0.26 and r(EO) = 0.54 ± 0.03, while for EO and EGVGE, the reactivity ratios were r(EGVGE) = 3.50 ± 0.90 and r(EO) = 0.32 ± 0.10. These ratios were consistent with the compositional drift observed in the copolymerization between EO and EGVGE, with EGVGE being consumed early in the copolymerization. These experimental results, combined with density functional calculations, allowed a mechanism for oxyanionic ring-opening polymerization that begins with coordination of the Lewis-basic epoxide to the cation to be proposed. The calculated transition-state energies agree qualitatively with the observed relative rates for polymerization. PMID:23226879

  8. Implementation of high throughput experimentation techniques for kinetic reaction testing.

    PubMed

    Nagy, Anton J

    2012-02-01

    Successful implementation of High throughput Experimentation (EE) tools has resulted in their increased acceptance as essential tools in chemical, petrochemical and polymer R&D laboratories. This article provides a number of concrete examples of EE systems, which have been designed and successfully implemented in studies, which focus on deriving reaction kinetic data. The implementation of high throughput EE tools for performing kinetic studies of both catalytic and non-catalytic systems results in a significantly faster acquisition of high-quality kinetic modeling data, required to quantitatively predict the behavior of complex, multistep reactions. PMID:21902639

  9. Multifragment emission and the experimental characterization of breakup reactions

    SciTech Connect

    Martinez Heimann, D.; Pacheco, A. J.; Arazi, A.; Fernandez Niello, J. O.; Figueira, J. M.; Negri, A.; Capurro, O. A.; Carnelli, P.; Cardona, M. A.; Barbara, E. de; Fimiani, L.; Hojman, D. L.; Marti, G. V.

    2010-08-04

    The production of three or more particles in nuclear reactions is discussed in terms of physically meaningful variables for the description of the asymptotic exit-channel configuration. The emphasis is placed in a direct comparison between these basic variables obtained in a purely experimental way and the corresponding results of generic model calculations. Applications of this approach to a few examples of recent inclusive and exclusive measurements of breakup reactions in the {sup 6,7}Li+{sup 144}Sm systems are presented.

  10. Study Of Laser-Induced Copolymerization

    NASA Technical Reports Server (NTRS)

    Miner, Gilda A.; Meador, Willard E.; Chang, C. Ken

    1993-01-01

    Report describes experiments on photopolymerization of styrene/maleic anhydride copolymer published as part of Laser Polymerization Program at NASA Langley Research Center. Presents basic study of copolymerization of styrene and maleic anhydride under laser-induced initiation and polymerization. Helps to clarify different theories on such initiation and represents significant advances in understanding of basic processes.

  11. A DFT Study on the Co-polymerization of CO2 and Ethylene: Feasibility Analysis for the Direct Synthesis of Polyethylene Esters.

    PubMed

    Moha, Verena; Cozzula, Daniela; Hölscher, Markus; Leitner, Walter; Müller, Thomas E

    2016-07-01

    The co-polymerization of CO2 with the non-polar monomer ethylene, though highly desirable, still presents a challenge whereas the palladium-catalyzed CO/C2 H4 co-polymerization is well understood. Building on this analogy, the goal of this study was to elucidate the feasibility of developing suitable catalysts for co-polymerizing CO2 with ethylene to polyethylene esters. Computational methods based on density functional theory were hereby employed. In the search for new catalyst lead structures, a closed catalytic cycle was identified for the palladium-catalyzed CO2 /C2 H4 co-polymerization reaction. The computational study on palladium complexes with a substituted anionic 2-[bis(2,4-dimethoxyphenyl)-phosphine]-benzene-2-hydroxo ligand revealed key aspects that need to be considered when designing ligand sets for potential catalysts for the non-alternating co-polymerization of CO2 and ethylene. PMID:27322770

  12. Identifying Understudied Nuclear Reactions by Text-mining the EXFOR Experimental Nuclear Reaction Library

    NASA Astrophysics Data System (ADS)

    Hirdt, J. A.; Brown, D. A.

    2016-01-01

    The EXFOR library contains the largest collection of experimental nuclear reaction data available as well as the data's bibliographic information and experimental details. We text-mined the REACTION and MONITOR fields of the ENTRYs in the EXFOR library in order to identify understudied reactions and quantities. Using the results of the text-mining, we created an undirected graph from the EXFOR datasets with each graph node representing a single reaction and quantity and graph links representing the various types of connections between these reactions and quantities. This graph is an abstract representation of the connections in EXFOR, similar to graphs of social networks, authorship networks, etc. We use various graph theoretical tools to identify important yet understudied reactions and quantities in EXFOR. Although we identified a few cross sections relevant for shielding applications and isotope production, mostly we identified charged particle fluence monitor cross sections. As a side effect of this work, we learn that our abstract graph is typical of other real-world graphs.

  13. Influence of diosgenin structure on the polymerization kinetics of acrylamide: An experimental and theoretical approach

    NASA Astrophysics Data System (ADS)

    Odio, Oscar F.; Martínez, Ariel; Martínez, Ricardo; Crespo-Otero, Rachel; Montero-Cabrera, Luis A.

    2011-01-01

    The acrylamide polymerization in presence of diosgenin has been investigated by experimental and theoretical methods. NMR spectroscopy shows the absence of copolymerization. Viscosimetric and dilatometric experiments support the occurrence of transfer reactions that retard the polymerization. The mechanism was studied at the MPWB1K/6-31G(d,p)//B3LYP/6-31G(d,p) level of theory. Transfer, homopropagation, copolymerization and reinitiation reactions were considered either in gas or solution phase. According to results, the retardation seems to be originated by the formation of an allylic radical in the ring B of diosgenin that reinitiates acrylamide polymerization at slow rate.

  14. Kinetics and thermodynamics of first-order Markov chain copolymerization

    NASA Astrophysics Data System (ADS)

    Gaspard, P.; Andrieux, D.

    2014-07-01

    We report a theoretical study of stochastic processes modeling the growth of first-order Markov copolymers, as well as the reversed reaction of depolymerization. These processes are ruled by kinetic equations describing both the attachment and detachment of monomers. Exact solutions are obtained for these kinetic equations in the steady regimes of multicomponent copolymerization and depolymerization. Thermodynamic equilibrium is identified as the state at which the growth velocity is vanishing on average and where detailed balance is satisfied. Away from equilibrium, the analytical expression of the thermodynamic entropy production is deduced in terms of the Shannon disorder per monomer in the copolymer sequence. The Mayo-Lewis equation is recovered in the fully irreversible growth regime. The theory also applies to Bernoullian chains in the case where the attachment and detachment rates only depend on the reacting monomer.

  15. Kinetics and thermodynamics of first-order Markov chain copolymerization.

    PubMed

    Gaspard, P; Andrieux, D

    2014-07-28

    We report a theoretical study of stochastic processes modeling the growth of first-order Markov copolymers, as well as the reversed reaction of depolymerization. These processes are ruled by kinetic equations describing both the attachment and detachment of monomers. Exact solutions are obtained for these kinetic equations in the steady regimes of multicomponent copolymerization and depolymerization. Thermodynamic equilibrium is identified as the state at which the growth velocity is vanishing on average and where detailed balance is satisfied. Away from equilibrium, the analytical expression of the thermodynamic entropy production is deduced in terms of the Shannon disorder per monomer in the copolymer sequence. The Mayo-Lewis equation is recovered in the fully irreversible growth regime. The theory also applies to Bernoullian chains in the case where the attachment and detachment rates only depend on the reacting monomer. PMID:25084957

  16. Chain Transfer of Vegetable Oil Macromonomers in Acrylic Solution Copolymerization

    SciTech Connect

    Black, Micah; Messman, Jamie M; Rawlins, James

    2011-01-01

    Use of vegetable oil macromonomers (VOMMs) as comonomers in emulsion polymerization enables good film coalescence without the addition of solvents that constitute volatile organic compounds (VOCs). VOMMs are derived from renewable resources and offer the potential of post-application crosslinking via auto-oxidation. However, chain transfer reactions of VOMMs with initiator and/or polymer radicals during emulsion polymerization reduce the amount of allylic hydrogen atoms available for primary auto-oxidation during drying. Vegetable oils and derivatives were reacted in combination with butyl acrylate and methyl methacrylate via solution polymerization. The copolymerization was monitored using in situ infrared spectroscopy to determine the extent of chain transfer. 1H NMR spectroscopy was used to determine the loci of chain transfer and the molecular weight characteristics of the polymers were characterized by SEC. Solution polymerization was utilized to minimize temperature fluctuations and maintain polymer solubility during the initial characterization.

  17. Kinetics and thermodynamics of first-order Markov chain copolymerization

    SciTech Connect

    Gaspard, P.; Andrieux, D.

    2014-07-28

    We report a theoretical study of stochastic processes modeling the growth of first-order Markov copolymers, as well as the reversed reaction of depolymerization. These processes are ruled by kinetic equations describing both the attachment and detachment of monomers. Exact solutions are obtained for these kinetic equations in the steady regimes of multicomponent copolymerization and depolymerization. Thermodynamic equilibrium is identified as the state at which the growth velocity is vanishing on average and where detailed balance is satisfied. Away from equilibrium, the analytical expression of the thermodynamic entropy production is deduced in terms of the Shannon disorder per monomer in the copolymer sequence. The Mayo-Lewis equation is recovered in the fully irreversible growth regime. The theory also applies to Bernoullian chains in the case where the attachment and detachment rates only depend on the reacting monomer.

  18. Experimental techniques for in-ring reaction experiments

    NASA Astrophysics Data System (ADS)

    Mutterer, M.; Egelhof, P.; Eremin, V.; Ilieva, S.; Kalantar-Nayestanaki, N.; Kiselev, O.; Kollmus, H.; Kröll, T.; Kuilman, M.; Chung, L. X.; Najafi, M. A.; Popp, U.; Rigollet, C.; Roy, S.; von Schmid, M.; Streicher, B.; Träger, M.; Yue, K.; Zamora, J. C.; the EXL Collaboration

    2015-11-01

    As a first step of the EXL project scheduled for the New Experimental Storage Ring at FAIR a precursor experiment (E105) was performed at the ESR at GSI. For this experiment, an innovative differential pumping concept, originally proposed for the EXL recoil detector ESPA, was successfully applied. The implementation and essential features of this novel technical concept will be discussed, as well as details on the detectors and the infrastructure around the internal gas-jet target. With 56Ni(p, p)56Ni elastic scattering at 400 MeV u-1, a nuclear reaction experiment with stored radioactive beams was realized for the first time. Finally, perspectives for a next-generation EXL-type setup are briefly discussed.

  19. Role of the cocatalyst in the copolymerization of CO2 and cyclohexene oxide utilizing chromium salen complexes.

    PubMed

    Darensbourg, Donald J; Mackiewicz, Ryan M; Rodgers, Jody L

    2005-10-12

    The mechanism of the copolymerization of cyclohexene oxide and carbon dioxide to afford poly(cyclohexylene)carbonate catalyzed by (salen)CrN3 (H2salen = N,N,'-bis(3,5-di-tert-butylsalicylidene)-1,2-ethylene-diimine) in the presence of a broad range of cocatalysts has been studied. We have previously established the rate of copolymer formation to be very sensitive to both the electron-donating ability of the salen ligand and the [cocatalyst], where N-heterocyclic amines, phosphines, and ionic salts were effective cocatalysts. Significant increases in the rate of copolymerization have been achieved with turnover frequencies of approximately 1200 h(-1), thereby making these catalyst systems some of the most active and robust thus far uncovered. Herein we offer a detailed explanation of the role of the cocatalyst in the copolymerization of CO2 and cyclohexene oxide catalyzed by chromium salen derivatives. A salient feature of the N-heterocyclic amine- or phosphine-cocatalyzed processes is the presence of an initiation period prior to reaching the maximum rate of copolymerization. Importantly, this is not observed for comparable processes involving ionic salts as cocatalysts, e.g., PPN+ X-. In these latter cases the copolymerization reaction exhibits ideal kinetic behavior and is proposed to proceed via a reaction pathway involving anionic six-coordinate (salen)Cr(N3)X- derivatives. By way of infrared and 31P NMR spectroscopic studies, coupled with in situ kinetic monitoring of the reactions, a mechanism of copolymerization is proposed where the neutral cocatalysts react with CO2 and/or epoxide to produce inner salts or zwitterions which behave in a manner similar to that of ionic salts. PMID:16201825

  20. RAFT copolymerization of itaconic anhydride and 2-methoxyethyl acrylate: a multifunctional scaffold for preparation of "clickable" gold nanoparticles.

    PubMed

    Javakhishvili, Irakli; Kasama, Takeshi; Jankova, Katja; Hvilsted, Søren

    2013-05-25

    RAFT copolymerization of 2-methoxyethyl acrylate and itaconic anhydride - a monomer derived from renewable resources - is carried out in a controlled fashion. The copolymer allows preparation of gold nanoparticles with abundant surficial carboxyl and alkyne functional groups that are dendronized via Cu(I)-mediated "click" reaction. PMID:23588100

  1. Copper mediated controlled radical copolymerization of styrene and 2-ethylhexyl acrylate and determination of their reactivity ratios.

    NASA Astrophysics Data System (ADS)

    Koiry, Bishnu; Singha, Nikhil

    2014-10-01

    Copolymerization is an important synthetic tool to prepare polymers with desirable combination of properties which are difficult to achieve from the different homopolymers concerned. This investigation reports the copolymerization of 2-ethylhexyl acrylate (EHA) and styrene using copper bromide (CuBr) as catalyst in combination with N,N,N’,N”,N”- pentamethyldiethylenetriamine (PMDETA) as ligand and 1-phenylethyl bromide (PEBr) as initiator. Linear kinetic plot and linear increase in molecular weights versus conversion indicate that copolymerization reactions were controlled. The copolymer composition was calculated using 1H NMR studies. The reactivity ratio of styrene and EHA (r1 and r2) were determined using the Finemann-Ross (FR), inverted Finemann-Ross (FR) and Kelen-Tudos (KT) methods. Thermal properties of the copolymers were also studied by using TGA and DSC analysis.

  2. Copper mediated controlled radical copolymerization of styrene and 2-ethylhexyl acrylate and determination of their reactivity ratios.

    PubMed

    Koiry, Bishnu P; Singha, Nikhil K

    2014-01-01

    Copolymerization is an important synthetic tool to prepare polymers with desirable combination of properties which are difficult to achieve from the different homopolymers concerned. This investigation reports the copolymerization of 2-ethylhexyl acrylate (EHA) and styrene using copper bromide (CuBr) as catalyst in combination with N,N,N',N″,N″- pentamethyldiethylenetriamine (PMDETA) as ligand and 1-phenylethyl bromide (PEBr) as initiator. Linear kinetic plot and linear increase in molecular weights vs. conversion indicate that copolymerization reactions were controlled. The copolymer composition was calculated using (1)H NMR studies. The reactivity ratio of styrene and EHA (r1 and r2) were determined using the Finemann-Ross (FR), inverted Finemann-Ross (IFR), and Kelen-Tudos (KT) methods. Thermal properties of the copolymers were also studied by using TGA and DSC analysis. PMID:25368866

  3. Experimental study of η meson photoproduction reaction at MAMI

    NASA Astrophysics Data System (ADS)

    Kashevarov, V. L.

    2015-06-01

    New data for the differential cross sections, polarization observables T, F, and E in the reaction of η photoproduction on proton from the threshold up to a center-of-mass energy of W=1.9 GeV are presented. The data were obtained with the Crystal-Ball/TAPS detector setup at the Glasgow tagged photon facility of the Mainz Microtron MAMI. The polarization measurements were made using a frozen-spin butanol target and circularly polarized photon beam. The results are compared to existing experimental data and different PWA predictions. The data solve a long-standing problem related the angular dependence of older T data close to threshold. The unexpected relative phase motion between s- and d-wave amplitudes required by the old data is not confirmed. At higher energies, all model predictions fail to reproduce the new polarization data indicating a significant impact on our understanding of the underlying dynamics of η meson photoproduction. Furthermore, we present a fit of the new data and existing data from GRAAL for ∑ asymmetry based on an expansion in terms of associated Legendre polynomials. A Legendre decomposition shows the sensitivity to small partialwave contributions. The sensitivity of the Legendre coefficients to the nucleon resonance parameters is shown using the ηMAID isobar model.

  4. Experimental Guidance of ISB Corrections via Direct Nuclear Reactions

    NASA Astrophysics Data System (ADS)

    Leach, K. G.; Garrett, P. E.; Ball, G. C.; Bangay, J. C.; Bianco, L.; Demand, G. A.; Faestermann, T.; Finlay, P.; Green, K. L.; Hertenberger, R.; Kriicken, R.; Phillips, A. A.; Rand, E. T.; Sumithrarachchi, C. S.; Svensson, C. E.; Towner, I. S.; Triambak, S.; Wirth, H.-F.; Wong, J.

    2011-09-01

    The most recent isospin-symmetry-breaking corrections, δc, of Towner and Hardy for superallowed Fermi β-decay transitions, have included the opening of specific core orbitals. This change has resulted in significant deviations in some of the δc factors from their previous calculations, and an improved agreement of the individual corrected Script Ft values with the overall world average of the 13 most precise cases. While this is consistent with the conserved-vector-current (CVC) hypothesis of the Standard Model, these new calculations must be thoroughly tested, and guidance must be given for the improvement of calculations for the upper-pf shell nuclei. Using the (d,t) reaction mechanism to probe the single neutron wavefunction overlap, information regarding the relevant shell-model configurations needed in the calculation can be determined. An experiment was therefore performed with a 22 MeV polarized deuterium beam from the MP tandem Van de Graaff accelerator in Munich, Germany. Using the Q3D magnetic spectrograph, and a cathode-strip focal-plane detector, outgoing tritons were analyzed at 9 angles between 10° and 60°, up to an excitation energy of 4.8 MeV. This proceeding reports the motivational and experimental details for the 64Zn(d,t)63Zn transfer work presented.

  5. Spin-selective recombination reactions of radical pairs: Experimental test of validity of reaction operators

    SciTech Connect

    Maeda, Kiminori; Liddell, Paul; Gust, Devens; Hore, P. J.

    2013-12-21

    Spin-selective reactions of radical pairs are conventionally modelled using an approach that dates back to the 1970s [R. Haberkorn, Mol. Phys. 32, 1491 (1976)]. An alternative approach based on the theory of quantum measurements has recently been suggested [J. A. Jones and P. J. Hore, Chem. Phys. Lett. 488, 90 (2010)]. We present here the first experimental attempt to discriminate between the two models. Pulsed electron paramagnetic resonance spectroscopy has been used to investigate intramolecular electron transfer in the radical pair form of a carotenoid-porphyrin-fullerene molecular triad. The rate of spin-spin relaxation of the fullerene radical in the triad was found to be inconsistent with the quantum measurement description of the spin-selective kinetics, and in accord with the conventional model when combined with spin-dephasing caused by rotational modulation of the anisotropic g-tensor of the fullerene radical.

  6. Experimental Observation of Nuclear Reactions in Palladium and Uranium

    SciTech Connect

    J. Dufour; D. Murat; X. Dufour; J. Foos

    2001-11-12

    By submitting various metals (Pd, U) containing hydrogen (from 2000 to 700 000 atoms of hydrogen for 1 000 000 atoms of the host metal) to the combined action of electrical currents and magnetic fields, we have observed a sizeable exothermal effect (from 0.1 to 8 W for 500 mg of metal used). This effect is beyond experimental errors, the energy output being typically 130 to 250{percent} of the energy input and not of chemical origin (exothermal effect in the range of 7000 MJ/mol of metal in the case of palladium and of 60 MJ/mol in the case of uranium). New chemical species also appear in the processes metals. It has been shown by a QED calculation that resonances of long lifetime (s), nuclear dimensions (fm), and low energy of formation (eV) could exist. This concept seems to look like the 'shrunken hydrogen atoms' proposed by various authors. It is indeed very different in two ways (a) being a metastable state, it needs energy to be formed (a few eV) and reverts to normal hydrogen after a few seconds, liberating back its energy of formation (it is thus not the source of the energy observed); (b) its formation can be described as the electron spin/proton nuclear spin interaction becoming first order in the lattice environment (whereas it is third order in a normal hydrogen atom). Moreover, we consider that the hydrex cannot yield a neutron because this reaction is strongly endothermic. To explain our results, we put forward the following working hypothesis: In a metal lattice and under proper conditions, the formation of such resonances (metastable state) could be favored. We propose to call them HYDREX, and we assume that they are actually formed in cold fusion (CF) and low-energy nuclear reaction (LENR) experiments. Once formed, a number of HYDREX could gather around a nucleus of the lattice to form a cluster of nuclear size and of very long life time compared to nuclear time (10{sup -22} s). In this cluster, nuclear rearrangements could take place, yielding

  7. Fragmentation and Coagulation in Supramolecular (Co)polymerization Kinetics

    PubMed Central

    2016-01-01

    The self-assembly of molecular building blocks into one-dimensional supramolecular architectures has opened up new frontiers in materials science. Due to the noncovalent interactions between the monomeric units, these architectures are intrinsically dynamic, and understanding their kinetic driving forces is key to rationally programming their morphology and function. To understand the self-assembly dynamics of supramolecular polymerizations (SP), kinetic models based on aggregate growth by sequential monomer association and dissociation have been analyzed. However, fragmentation and coagulation events can also play a role, as evident from studies on peptide self-assembly and the fact that aggregations can be sensitive to mechanical agitations. Here, we analyze how fragmentation and coagulation events influence SP kinetics by theoretical analysis of self-assembling systems of increasing complexity. Our analysis starts with single-component systems in which aggregates are able to grow via an isodesmic or cooperative nucleation–elongation mechanism. Subsequently, equilibration dynamics in cooperative two-component supramolecular copolymerizations are investigated. In the final part, we reveal how aggregate growth in the presence of competing, kinetically controlled pathways is influenced by fragmentation and coagulation reactions and reveal how seed-induced growth can give rise to block copolymers. Our analysis shows how fragmentation and coagulation reactions are able to modulate SP kinetics in ways that are highly system dependent. PMID:27163054

  8. Improved homopolymer separation to enable the application of 1H NMR and HPLC for the determination of the reaction parameters of the graft copolymerization of acrylic acid onto starch.

    PubMed

    Witono, Judy R; Marsman, Jan Henk; Noordergraaf, Inge-Willem; Heeres, Hero J; Janssen, Leon P B M

    2013-04-01

    Graft copolymers of starch with acrylic acid are a promising green, bio based material with many potential applications. The grafting of acrylic acid onto cassava starch in an aqueous medium initiated by Fenton's reagent has been studied. Common grafting result parameters are add-on (yield) and graft efficiency (selectivity). However, the analysis of the reaction products and an accurate determination of these parameters stand or fall with a complete separation of the entangled but ungrafted homopolymer from the grafted product. Therefore, this separation is the core of the newly developed analytical procedure. An appropriate solvent has been selected with dedicated testing from the range methanol, ethanol, acetone, dioxane, 2-propanol, and 1-propanol. Acetone showed the best performance in many respects. It has a high dissolving power for the homopolymer, as well as the highest yield of precipitation for the starch derivatives and it is the most economical in use. After the successful separation, the precipitated graft copolymers could be analyzed quantitatively by nuclear magnetic resonance. The liquid with homopolymer and unreacted monomer was analyzed by high pressure liquid chromatography. Proof of grafting has been found by FTIR and TGA analyses. The mass balance calculation shows a systematic error which appears fairly consistent: 18.0±2.5 wt%. This was used as a correction factor in the calculation of the grafting parameters but more importantly, it means that the method we developed has a high level of repeatability, in the order of 97%. PMID:23435285

  9. Derivation of reaction cross sections from experimental elastic backscattering probabilities

    NASA Astrophysics Data System (ADS)

    Sargsyan, V. V.; Adamian, G. G.; Antonenko, N. V.; Gomes, P. R. S.

    2013-10-01

    The relationship between the backward elastic scattering probabilities and the reaction cross sections is derived. This is a very simple and useful method to extract reaction cross sections for heavy-ion systems. We compare the results of our method with those that use the traditional full elastic scattering angular distributions for several systems at energies near and above the Coulomb barrier. From the calculated reaction and capture cross sections that use the present method, we derive the cross sections of other mechanisms for weak nearly spherical systems.

  10. Recent Direct Reaction Experimental Studies with Radioactive Tin Beams

    SciTech Connect

    Jones, K. L.; Ahn, S.; Allmond, J. M.; Ayres, A.; Bardayan, D. W.; Baugher, T.; Bazin, D.; Berryman, J. S.; Bey, A.; Bingham, C.; Cartegni, L.; Cerizza, G.; Chae, K. Y.; Cizewski, J. A.; Gade, A.; Galindo-Uribarri, A.; Garcia-Ruiz, R. F.; Grzywacz, R.; Howard, M. E.; Kozub, R. L.; Liang, J. F.; Manning, B.; Matoš, M.; McDaniel, S.; Miller, D.; Nesaraja, C. D.; O'Malley, P. D.; Padgett, S.; Padilla-Rodal, E.; Pain, S. D.; Pittman, S. T.; Radford, D. C.; Ratkiewicz, A.; Schmitt, K. T.; Shore, A.; Smith, M. S.; Stracener, D. W.; Stroberg, S. R.; Tostevin, J.; Varner, R. L.; Weisshaar, D.; Wimmer, K.; Winkler, R.

    2015-01-01

    Direct reaction techniques are powerful tools to study the single-particle nature of nuclei. Performing direct reactions on short-lived nuclei requires radioactive ion beams produced either via fragmentation or the Isotope Separation OnLine (ISOL) method. Some of the most interesting regions to study with direct reactions are close to the magic numbers where changes in shell structure can be tracked. These changes can impact the final abundances of explosive nucleosynthesis. The structure of the chain of tin isotopes is strongly influenced by the Z = 50 proton shell closure, as well as the neutron shell closures lying in the neutron-rich, N = 82, and neutron-deficient, N = 50, regions. Here, we present two examples of direct reactions on exotic tin isotopes. The first uses a one-neutron transfer reaction and a low-energy reaccelerated ISOL beam to study states in Sn-131 from across the N = 82 shell closure. The second example utilizes a one-neutron knockout reaction on fragmentation beams of neutron-deficient Sn-106,108Sn. In conclusion, In both cases, measurements of γ rays in coincidence with charged particles proved to be invaluable.

  11. Recent Direct Reaction Experimental Studies with Radioactive Tin Beams

    DOE PAGESBeta

    Jones, K. L.; Ahn, S.; Allmond, J. M.; Ayres, A.; Bardayan, D. W.; Baugher, T.; Bazin, D.; Berryman, J. S.; Bey, A.; Bingham, C.; et al

    2015-01-01

    Direct reaction techniques are powerful tools to study the single-particle nature of nuclei. Performing direct reactions on short-lived nuclei requires radioactive ion beams produced either via fragmentation or the Isotope Separation OnLine (ISOL) method. Some of the most interesting regions to study with direct reactions are close to the magic numbers where changes in shell structure can be tracked. These changes can impact the final abundances of explosive nucleosynthesis. The structure of the chain of tin isotopes is strongly influenced by the Z = 50 proton shell closure, as well as the neutron shell closures lying in the neutron-rich, Nmore » = 82, and neutron-deficient, N = 50, regions. Here, we present two examples of direct reactions on exotic tin isotopes. The first uses a one-neutron transfer reaction and a low-energy reaccelerated ISOL beam to study states in Sn-131 from across the N = 82 shell closure. The second example utilizes a one-neutron knockout reaction on fragmentation beams of neutron-deficient Sn-106,108Sn. In conclusion, In both cases, measurements of γ rays in coincidence with charged particles proved to be invaluable.« less

  12. Electrocyclic reactions of siloles: a combined experimental and theoretical study.

    PubMed

    Meyer-Wegner, Frank; Wender, Josef H; Falahati, Konstantin; Porsch, Timo; Sinke, Tanja; Bolte, Michael; Wagner, Matthias; Holthausen, Max C; Lerner, Hans-Wolfram

    2014-04-14

    The reaction of 4-chloro-1,2-dimethyl-4-supersilylsila-1-cyclopentene (2 a) with Li[NiPr2] at -78 °C results in the formation of the formal 1,4-addition product of the silacyclopentadiene derivative 3,4-dimethyl-1-supersilylsila-1,3-cyclopentadiene (4 a) with 2,3-dimethyl-4-supersilylsila-1,3-cyclopentadiene (5 a). In addition the respective adducts of the Diels-Alder reactions of 4 a+4 a and 4 a+5 a were obtained. Compound 4 a, which displays an s-cis-silacyclopentadiene configuration, reacts with cyclohexene to form the racemate of the [4+2] cycloadduct of 4 a and cyclohexene (9). In the reaction between 4 a and 2,3-dimethylbutadiene, however, 4 a acted as silene as well as silacyclopentadiene to yield the [2+4] and [4+2] cycloadducts 10 and 11, respectively. The constitutions of 9, 10, and 11 were confirmed by NMR spectroscopy and their crystal structures were determined. Reaction of 4-chloro-1,2-dimethyl-4-tert-butyl-4-silacyclopent-1-ene (2 c) with KC8 yielded the corresponding disilane (12), which was characterized by X-ray crystal structure analysis (triclinic, P1). DFT calculations are used to unveil the mechanistic scenario underlying the observed reactivity. PMID:24615826

  13. Direct Reaction Experimental Studies with Beams of Radioactive Tin Ions

    SciTech Connect

    Jones, K. L.; Ahn, S.H.; Allmond, James M; Ayres, A.; Bardayan, Daniel W; Baugher, T.; Bazin, D.; Beene, James R; Berryman, J. S.; Bey, A.; Bingham, C. R.; Cartegni, L.; Chae, K. Y.; Gade, A.; Galindo-Uribarri, Alfredo {nmn}; Garcia-Ruiz, R.F.; Grzywacz, Robert Kazimierz; Howard, Meredith E; Kozub, R. L.; Liang, J Felix; Manning, Brett M; Matos, M.; McDaniel, S.; Miller, D.; Nesaraja, Caroline D; O'Malley, Patrick; Padgett, S; Padilla-Rodal, Elizabeth; Pain, Steven D; Pittman, S. T.; Radford, David C; Ratkiewicz, Andrew J; Schmitt, Kyle; Smith, Michael Scott; Stracener, Daniel W; Stroberg, S.; Tostevin, Jeffrey A; Varner Jr, Robert L; Weisshaar, D.; Wimmer, K.

    2015-01-01

    The tin chain of isotopes provides a unique region in which to investigate the evolution of single-particle structure, spreading from N = 50 at Sn-100, through 10 stable isotopes and the N = 82 shell closure at Sn-132 out into the r-process path. Direct reactions performed on radioactive ion beams are sensitive spectroscopic tools for studying exotic nuclei. Here we present one experiment knocking out neutrons from tin isotopes that are already neutron deficient and two reactions that add a neutron to neutron-rich Sn-130. Both techniques rely on selective particle identification and the measurement of gamma rays in coincidence with charged ions. We present the goals of the two experiments and the particle identification for the channels of interest. The final results will be presented in future publications.

  14. Direct reaction experimental studies with beams of radioactive tin ions

    SciTech Connect

    Jones, K. L. Ayres, A.; Bey, A.; Burcher, S.; Cartegni, L.; Cerizza, G.; Ahn, S.; Allmond, J. M.; Beene, J. R.; Galindo-Uribarri, A.; Liang, J. F.; Nesaraja, C. D.; Pain, S. D.; Radford, D. C.; Schmitt, K. T.; Smith, M. S.; Stracener, D. W.; Varner, R. L.; Bardayan, D. W.; Baugher, T.; and others

    2015-10-15

    The tin chain of isotopes provides a unique region in which to investigate the evolution of single-particle structure, spreading from N = 50 at {sup 100}Sn, through 10 stable isotopes and the N = 82 shell closure at {sup 132}Sn out into the r-process path. Direct reactions performed on radioactive ion beams are sensitive spectroscopic tools for studying exotic nuclei. Here we present one experiment knocking out neutrons from tin isotopes that are already neutron deficient and two reactions that add a neutron to neutron-rich {sup 130}Sn. Both techniques rely on selective particle identification and the measurement of γ rays in coincidence with charged ions. We present the goals of the two experiments and the particle identification for the channels of interest. The final results will be presented in future publications.

  15. Community reactions to helicopter noise - Results from an experimental study

    NASA Technical Reports Server (NTRS)

    Fields, James M.; Powell, Clemans A.

    1987-01-01

    Community reactions to low numbers of helicopter noise events (less than 50 per day) are investigated using a new type of study design. Although the effect of maximum noise level and number of noise events on helicopter noise annoyance was found to be similar to that represented by the energy summation principle contained in L(eq)-based noise indices, it is noted that the possibility that the number of noise events has only a small effect on annoyance cannot be rejected at the conventional p of less than 0.05 level. The effect of the duration of noise events was also shown to be consistent with L(eq)-based indices. After removing the effects of differences in duration and noise levels, little difference is found between reactions to impulsive and nonimpulsive types of helicopters.

  16. Monitoring the synthesis and properties of copolymeric polycations.

    PubMed

    González García, Gemma; Kreft, Tomasz; Alb, Alina M; de la Cal, José C; Asua, José M; Reed, Wayne F

    2008-11-20

    The kinetics; evolution of molar mass; solution conductivity, sigma; intrinsic viscosity; and average composition drift; and distribution were determined by monitoring the synthesis of copolymeric polycations of acrylamide (Am) and [2-(acryloyloxy)ethyl]-trimethylammonium chloride (Q9). The quantitative relationship between diminishing sigma and charged co-monomers incorporation was monitored for the first time and provided novel data on counterion condensation, which occurs gradually over a broad composition regime. This new capability allows predictions concerning the relationship between copolymer composition and linear charge density, xi, to be tested and models of trivariate mass, composition, and xi distributions to be built. This approach, hence, brings together the previously disparate fields of synthetic chemistry of copolymers and physical chemical properties of polyelectrolytes. Monitoring was achieved with a new implementation of the ACOMP (automatic continuous online monitoring of polymerization reactions) platform. Reactivity ratios determined by ACOMP were rQ9 = 0.47 and rAm = 1.10. Opposite trends in composition drift and final molar mass were found; low starting percentage of Q9 led to low composition drift and high molar mass, whereas the opposite was found at high starting percentage of Q9. Complementary end-product analysis by multidetector gel permeation chromatography supported the ACOMP results. End-product polyelectrolyte properties were characterized by automatic continuous mixing, revealing that combined electrostatic persistence length and excluded volume effects led to the expected large changes in polyelectrolyte conformation and interactions. These results set the groundwork for semibatch control of molar mass, composition, and xi, and eventually for monitoring and control for inverse emulsion-based reactions of this type. PMID:18783199

  17. Chemoselective Alternating Copolymerization of Limonene Dioxide and Carbon Dioxide: A New Highly Functional Aliphatic Epoxy Polycarbonate.

    PubMed

    Li, Chunliang; Sablong, Rafaël J; Koning, Cor E

    2016-09-12

    The alternating copolymerization of biorenewable limonene dioxide with carbon dioxide (CO2 ) catalyzed by a zinc β-diiminate complex is reported. The chemoselective reaction results in linear amorphous polycarbonates that carry pendent methyloxiranes and exhibit glass transition temperatures (Tg ) up to 135 °C. These polycarbonates can be efficiently modified by thiols or carboxylic acids in combination with lithium hydroxide or tetrabutylphosphonium bromide as catalysts, respectively, without destruction of the main chain. Moreover, polycarbonates bearing pendent cyclic carbonates can be quantitatively prepared by CO2 insertion catalyzed by lithium bromide. PMID:27529815

  18. Experimental Study of Level Density and {gamma}-strength Functions from Compound Nuclear Reactions

    SciTech Connect

    Voinov, A. V.; Grimes, S. M.; Brune, C. R.; Massey, T. N.; Schiller, A.; Guttormsen, M.; Siem, S.

    2008-04-17

    The current status of experimental study of level density and {gamma}-strength functions is reviewed. Three experimental techniques are used. These are measurements of particle evaporation spectra from compound nuclear reactions, the measurements of particle-{gamma} coincidences from inelastic scattering and pick-up reactions and the method of two-step {gamma}-cascades following neutron/proton radiative capture. Recent experimental data on level densities from neutron evaporation spectra are shown. The first results on the cascade {gamma}-spectrum from the {sup 59}Co(p,2{gamma}){sup 60}Ni reaction are presented.

  19. Experimental review of exclusive processes in two photon reactions

    SciTech Connect

    Ronan, M.T.

    1986-07-01

    Recent experimental results on exclusive final stated produced in photon-photon interactions are reviewed. Comparisons between experiments and with perturbative QCD calculations are made for meson and baryon pair production. New results on vector meson pair (rho/sup 0/rho/sup 0/,rho/sup 0/omega,rho/sup 0/phi,...) production and production of multiparticle (KK..pi pi..,K*K..pi..,...) final states are summarized. 34 refs.

  20. Development of the Experimental Photo-Nuclear Reaction Database in Hokkaido University

    NASA Astrophysics Data System (ADS)

    Makinaga, A.

    2015-10-01

    Nuclear databases are important tools to apply nuclear phenomena to various fields of nuclear engineering. It is now recognized that the databases must be further developed for photo-nuclear reaction data for nuclear security, safety and nonproliferation applications. Hokkaido University Nuclear Reaction Data Centre (JCPRG) has contributed to the Experimental Nuclear Reaction Data Library (EXFOR) which is developed by the International Network of Nuclear Reaction Data Centres under coordination by IAEA. We report here on the recent compilation of the nuclear data files for the photonuclear reaction.

  1. Catalysts for CO2/epoxide ring-opening copolymerization

    PubMed Central

    Trott, G.; Saini, P. K.; Williams, C. K.

    2016-01-01

    This article summarizes and reviews recent progress in the development of catalysts for the ring-opening copolymerization of carbon dioxide and epoxides. The copolymerization is an interesting method to add value to carbon dioxide, including from waste sources, and to reduce pollution associated with commodity polymer manufacture. The selection of the catalyst is of critical importance to control the composition, properties and applications of the resultant polymers. This review highlights and exemplifies some key recent findings and hypotheses, in particular using examples drawn from our own research. PMID:26755758

  2. Catalysts for CO2/epoxide ring-opening copolymerization.

    PubMed

    Trott, G; Saini, P K; Williams, C K

    2016-02-28

    This article summarizes and reviews recent progress in the development of catalysts for the ring-opening copolymerization of carbon dioxide and epoxides. The copolymerization is an interesting method to add value to carbon dioxide, including from waste sources, and to reduce pollution associated with commodity polymer manufacture. The selection of the catalyst is of critical importance to control the composition, properties and applications of the resultant polymers. This review highlights and exemplifies some key recent findings and hypotheses, in particular using examples drawn from our own research. PMID:26755758

  3. Patient reactions to personalized medicine vignettes: An experimental design

    PubMed Central

    Butrick, Morgan; Roter, Debra; Kaphingst, Kimberly; Erby, Lori H.; Haywood, Carlton; Beach, Mary Catherine; Levy, Howard P.

    2011-01-01

    Purpose Translational investigation on personalized medicine is in its infancy. Exploratory studies reveal attitudinal barriers to “race-based medicine” and cautious optimism regarding genetically personalized medicine. This study describes patient responses to hypothetical conventional, race-based, or genetically personalized medicine prescriptions. Methods Three hundred eighty-seven participants (mean age = 47 years; 46% white) recruited from a Baltimore outpatient center were randomized to this vignette-based experimental study. They were asked to imagine a doctor diagnosing a condition and prescribing them one of three medications. The outcomes are emotional response to vignette, belief in vignette medication efficacy, experience of respect, trust in the vignette physician, and adherence intention. Results Race-based medicine vignettes were appraised more negatively than conventional vignettes across the board (Cohen’s d = −0.51−0.57−0.64, P < 0.001). Participants rated genetically personalized comparably with conventional medicine (− 0.14−0.15−0.17, P = 0.47), with the exception of reduced adherence intention to genetically personalized medicine (Cohen’s d = −0.38−0.41−0.44, P = 0.009). This relative reluctance to take genetically personalized medicine was pronounced for racial minorities (Cohen’s d =−0.38−0.31−0.25, P = 0.02) and was related to trust in the vignette physician (change in R2 = 0.23, P < 0.001). Conclusions This study demonstrates a relative reluctance to embrace personalized medicine technology, especially among racial minorities, and highlights enhancement of adherence through improved doctor-patient relationships. PMID:21270639

  4. Cross-checking of Large Evaluated and Experimental Nuclear Reaction Databases

    SciTech Connect

    Zeydina, O.; Koning, A.J.; Soppera, N.; Raffanel, D.; Bossant, M.; Dupont, E.; Beauzamy, B.

    2014-06-15

    Automated methods are presented for the verification of large experimental and evaluated nuclear reaction databases (e.g. EXFOR, JEFF, TENDL). These methods allow an assessment of the overall consistency of the data and detect aberrant values in both evaluated and experimental databases.

  5. Experimental studies in vortex pair motion coincident with a liquid reaction

    NASA Technical Reports Server (NTRS)

    Karagozian, A. R.; Suganuma, Y.; Strom, B. D.

    1988-01-01

    An experimental examination of the coincidence of a liquid reaction (acid/base) with the formation of a vortex pair structure is described in which emphasis is placed on the evolution of the strained diffusion layer and reacted core structures. Flow visualization of the reaction process is achieved via the technique of chemically sensitive LIF. The observed growth of reacted core structures associated with each vortex is compared with theoretically predicted behavior (Marble, 1983; Karagozian and Marble, 1986). Vortex pair separation is also compared with theoretical correlations, and the relevance of the analogy between a fast liquid reaction and a gaseous reaction is discussed.

  6. Summary Report of the Workshop on The Experimental Nuclear Reaction Data Database

    SciTech Connect

    Semkova, V.; Pritychenko, B.

    2014-10-10

    The Workshop on the Experimental Nuclear Reaction Data Database (EXFOR) was held at IAEA Headquarters in Vienna from 6 to 10 October 2014. The workshop was organized to discuss various aspects of the EXFOR compilation process including compilation rules, different techniques for nuclear reaction data measurements, software developments, etc. A summary of the presentations and discussions that took place during the workshop is reported here.

  7. Evolution of composition, molar mass, and conductivity during the free radical copolymerization of polyelectrolytes.

    PubMed

    Alb, Alina M; Paril, Ahmet; Catalgil-Giz, Huceste; Giz, Ahmet; Reed, Wayne F

    2007-07-26

    Despite their importance in biological and technological contexts, copolymeric polyelectrolytes (or "copolyelectrolytes") continue to present challenges to theorists and experimentalists. The first results of a unified approach to the kinetics and mechanisms of copolyelectrolyte synthesis and the physical characteristics of the resulting polymers are presented. The free radical copolymerization of 4-vinylbenzenesulfonic acid sodium salt and acrylamide was monitored using automatic continuous online monitoring of polymerization reactions (ACOMP), from which the average bivariate composition and mass distributions were determined. Composition drift was related to the evolution of conductivity. In some cases bimodal populations of copolyelectrolyte and homopolymeric poly(acrylamide) resulted, i.e., blends of copolyelectrolyte and neutral homopolymer. The end-product scattering behavior depended on whether the end-product was bimodal or not, as demonstrated using automatic continuous mixing (ACM) in conjunction with light scattering and viscosity. Negative light-scattering third virial coefficients were found for bimodal end-products. This combined approach may allow connecting the synthesis kinetics to the resulting "trivariate" distribution of composition, molar mass, and linear charge density, which in turn controls the properties of end-product solutions, such as chain conformations, interparticle interactions, viscosity, interactions with colloids and other polymers, phase separation, etc. Unified results may allow testing and improvement of existing polyelectrolyte theories, development of new quantitative physicochemical models, provide advanced characterization methods, set the stage for studying more complex copolyelectrolytes, such as hydrophobically modified ones, and provide tools for ultimately controlling and tailoring the synthesis and properties of copolyelectrolytes. PMID:17441756

  8. Experimental studies of reactions relevant for γ-process nucleosynthesis

    NASA Astrophysics Data System (ADS)

    Scholz, P.; Endres, J.; Hennig, A.; Mayer, J.; Netterdon, L.; Sauerwein, A.; Zilges, A.

    2014-05-01

    We report on our recent experimental studies of reactions relevant for the γ process nucleosynthesis. Applying the activation method using the Cologne Clover Counting Setup total cross sections of the reactions 168Yb(α,γ), 168Yb(α,n), and 187Re(α,n) could be obtained. Furthermore, the reaction 89Y(p,γ) was investigated via the in-beam technique with HPGe detectors at the high-efficiency g-ray spectrometer HORUS in Cologne in order to determine partial and total cross sections.

  9. Experimental study to explore the 8Be-induced nuclear reaction via the Trojan horse method

    NASA Astrophysics Data System (ADS)

    Wen, Qun-Gang; Li, Cheng-Bo; Zhou, Shu-Hua; Irgaziev, Bakhadir; Fu, Yuan-Yong; Spitaleri, Claudio; La Cognata, Marco; Zhou, Jing; Meng, Qiu-Ying; Lamia, Livio; Lattuada, Marcello

    2016-03-01

    To explore a possible indirect method for 8Be induced astrophysical reactions, the 8Be=(8Be+n ) cluster structure has been studied via the Trojan horse method. For the first time a 8Be nucleus having an ultrashort lifetime is studied by the Trojan horse method and a 9Be nucleus in the ground state is used for this purpose. The 9Be nucleus is assumed to have a (8Be+n ) cluster structure and used as a Trojan horse nucleus. The 8Be nucleus acts as a participant, while the neutron is a spectator to the virtual 8Be+d →α +6Li reaction via the 3-body reaction 8Be+d →α +6Li+n . The experimental neutron momentum distribution inside 9Be has been reconstructed. The agreement between the experimental momentum distribution and the theoretical one indicates that a (8Be+n ) cluster structure inside 9Be is very likely. Therefore, the experimental study of 8Be induced reactions, for example, the measurement of the 8Be+α →12C reaction proceeding through the Hoyle state, is possible.

  10. Low-temperature radiation copolymerization of tetrafluoroethylene with perfluorovinyl ethers

    SciTech Connect

    Kim, I.P.; Pirozhnaya, L.N.; Loginova, N.N.; Barkalov, I.M.

    1986-12-01

    The copolymerization of perfluorovinyl ethers with tetrafluoroethylene at low temperature was studied and compared with the process conducted with chemical initiation in bulk or aqueous medium. A calorimetric method was used for studying the kinetics of copolymerization, the phase state of the system, and the phase transition dynamics. Ampules containing the samples of monomers and mixtures were irradiated at 77/sup 0/K with /sup 60/Co ..gamma.. rays with a dose rate of 25 kGy/h. Radiolysis in the solid phase at 77/sup 0/K with a 130 kGy dose resulted in the formation of 0.5-1.0 wt.% of a polymer, and this polymer was soluble in the monomer.

  11. Experimental studies of coherent structures in an advection-reaction-diffusion system.

    PubMed

    Gowen, Savannah; Solomon, Tom

    2015-08-01

    We present experimental studies of reaction front propagation in a single vortex flow with an imposed external wind. The fronts are produced by the excitable, ferroin-catalyzed Belousov-Zhabotinsky chemical reaction. The flow is generated using an electromagnetic forcing technique: an almost-radial electrical current interacts with a magnetic field from a magnet below the fluid layer to produce the vortex. The magnet is mounted on crossed translation stages allowing for movement of the vortex through the flow. Reaction fronts triggered in or in front of the moving vortex form persistent structures that are seen experimentally for time-independent (constant motion), time-periodic, and time-aperiodic flows. These results are examined with the use of burning invariant manifolds that act as one-way barriers to front motion in the flows. We also explore the usefulness of finite-time Lyapunov exponent fields as an instrument for analyzing front propagation behavior in a fluid flow. PMID:26328574

  12. Experimental studies of coherent structures in an advection-reaction-diffusion system

    NASA Astrophysics Data System (ADS)

    Gowen, Savannah; Solomon, Tom

    2015-08-01

    We present experimental studies of reaction front propagation in a single vortex flow with an imposed external wind. The fronts are produced by the excitable, ferroin-catalyzed Belousov-Zhabotinsky chemical reaction. The flow is generated using an electromagnetic forcing technique: an almost-radial electrical current interacts with a magnetic field from a magnet below the fluid layer to produce the vortex. The magnet is mounted on crossed translation stages allowing for movement of the vortex through the flow. Reaction fronts triggered in or in front of the moving vortex form persistent structures that are seen experimentally for time-independent (constant motion), time-periodic, and time-aperiodic flows. These results are examined with the use of burning invariant manifolds that act as one-way barriers to front motion in the flows. We also explore the usefulness of finite-time Lyapunov exponent fields as an instrument for analyzing front propagation behavior in a fluid flow.

  13. Experimental and computational studies of trialkylaluminum and alkylaluminum chloride reactions with silica.

    PubMed

    Blitz, Jonathan P; Diebel, Richard E; Deakyne, Carol A; Christensen, Jeannine M; Gun'ko, Vladimir M

    2005-03-31

    Reactions of trimethylaluminum, triethylaluminum, and diethylaluminum chloride and ethylaluminum dichloride with silica gel have been studied experimentally by infrared spectroscopy and elemental analysis. The silica gel was subjected to different pretreatments to alter surface functionalities prior to reaction. In all cases the extent of surface modification reaction follows the trend unmodified > 600 degrees C pretreated > hexamethyldisilazane (HMDZ) pretreated > 600 degrees C/HMDZ pretreated. All of the aluminum compounds studied completely react non-hydrogen-bonded silanols, while also reacting with hydrogen-bonded silanols and siloxanes. Primarily monomeric surface species result from the surface modification reaction. Ethylaluminum chlorides preferentially react with silanols through cleavage of the Al-C bond rather than the Al-Cl bond. Singly bonded Si(s)-O-AlCl(2) surface species are readily synthesized by reaction of ethylaluminum dichloride with HMDZ-pretreated silica gel. Bridged bonded (Si(s)-O)(2)-AlCl surface species are readily synthesized by reaction of diethylaluminum chloride with HMDZ-pretreated silica gel. Computational ab initio studies of the cluster Si(4)O(6)(OH)(4) as a model to study the reaction of monomeric and dimeric methylaluminum dichloride with a silica silanol are also described. Comparison of the potential energy surface (PES) of monomer and dimer indicates that the energetics favor monomer reaction, consistent with experimental results. The energy cost in the dimer reaction is primarily from cleavage of a bridged Al-Cl bond upon adsorption. This does not occur when the monomer adsorbs. A comparison of the PES for the two reaction pathways resulting from cleavage of either an Al-Cl or Al-C bond indicates that while the former reaction is slightly kinetically favored (E(a) = 23.1 kJ/mol for Al-Cl bond cleavage versus E(a) = 31.1 kJ/mol for Al-C bond cleavage), the latter is strongly thermodynamically favored with an overall free

  14. Radiopaque iodinated copolymeric nanoparticles for X-ray imaging applications.

    PubMed

    Aviv, Hagit; Bartling, Sonke; Kieslling, Fabian; Margel, Shlomo

    2009-10-01

    Recently we described iodinated homopolymeric radiopaque nanoparticles of 28.9+/-6.3 nm dry diameter synthesized by emulsion polymerization of 2-methacryloyloxyethyl(2,3,5-triiodobenzoate) (MAOETIB). The nanoparticle aqueous dispersion, however, was not stable and tended to agglomerate, particularly at weight concentration of dispersed nanoparticles above approximately 0.3%. The agglomeration rate increases as the concentration of nanoparticles in aqueous phase rises and prevents the potential in vivo use as contrast agent for medical X-ray imaging. Here we describe efforts to overcome this limitation by synthesis of iodinated copolymeric nanoparticles of 25.5+/-4.2 nm dry diameter, by emulsion copolymerization of the monomer, MAOETIB, with a low concentration of glycidyl methacrylate (GMA). The surface of resulting copolymeric nanoparticles is far more hydrophilic than that of polyMAOETIB (PMAOETIB) nanoparticles. Therefore, P(MAOETIB-GMA) nanoparticles are significantly more stable against agglomeration in aqueous continuous phase. After intravenous injection of P(MAOETIB-GMA) nanoparticles in rats and mice (including those with a liver cancer model) CT-imaging revealed a significant enhanced visibility of the blood pool for 30 min after injection. Later, lymph nodes, liver and spleen strongly enhanced due to nanoparticle uptake by the reticuloendothelial system. This favorably enabled the differentiation of cancerous from healthy liver tissue and suggests our particles for tumor imaging in liver and lymph nodes. PMID:19592085

  15. Experimental Study of Estimating the Subgrade Reaction Modulus on Jointed Rock Foundations

    NASA Astrophysics Data System (ADS)

    Lee, Jaehwan; Jeong, Sangseom

    2016-06-01

    The subgrade reaction modulus for rock foundations under axial loading is investigated by model footing tests. This study focuses on quantifying a new subgrade reaction modulus by considering rock discontinuities. A series of model-scale footing tests are performed to investigate the effects of the unconfined compressive strength, discontinuity spacing and inclination of the rock joint. Based on the experimental results, it is observed that the subgrade reaction modulus of the rock with discontinuities decreases by up to approximately 60 % of intact rock. In addition, it is found that the modulus of subgrade reaction is proportional to the discontinuity spacing, and it decreases gradually within the range of 0°-30° and tends to increase within the range of 30°-90°.

  16. CAMELOT: A machine learning approach for coarse-grained simulations of aggregation of block-copolymeric protein sequences

    NASA Astrophysics Data System (ADS)

    Ruff, Kiersten M.; Harmon, Tyler S.; Pappu, Rohit V.

    2015-12-01

    We report the development and deployment of a coarse-graining method that is well suited for computer simulations of aggregation and phase separation of protein sequences with block-copolymeric architectures. Our algorithm, named CAMELOT for Coarse-grained simulations Aided by MachinE Learning Optimization and Training, leverages information from converged all atom simulations that is used to determine a suitable resolution and parameterize the coarse-grained model. To parameterize a system-specific coarse-grained model, we use a combination of Boltzmann inversion, non-linear regression, and a Gaussian process Bayesian optimization approach. The accuracy of the coarse-grained model is demonstrated through direct comparisons to results from all atom simulations. We demonstrate the utility of our coarse-graining approach using the block-copolymeric sequence from the exon 1 encoded sequence of the huntingtin protein. This sequence comprises of 17 residues from the N-terminal end of huntingtin (N17) followed by a polyglutamine (polyQ) tract. Simulations based on the CAMELOT approach are used to show that the adsorption and unfolding of the wild type N17 and its sequence variants on the surface of polyQ tracts engender a patchy colloid like architecture that promotes the formation of linear aggregates. These results provide a plausible explanation for experimental observations, which show that N17 accelerates the formation of linear aggregates in block-copolymeric N17-polyQ sequences. The CAMELOT approach is versatile and is generalizable for simulating the aggregation and phase behavior of a range of block-copolymeric protein sequences.

  17. CAMELOT: A machine learning approach for coarse-grained simulations of aggregation of block-copolymeric protein sequences

    SciTech Connect

    Ruff, Kiersten M.; Harmon, Tyler S.; Pappu, Rohit V.

    2015-12-28

    We report the development and deployment of a coarse-graining method that is well suited for computer simulations of aggregation and phase separation of protein sequences with block-copolymeric architectures. Our algorithm, named CAMELOT for Coarse-grained simulations Aided by MachinE Learning Optimization and Training, leverages information from converged all atom simulations that is used to determine a suitable resolution and parameterize the coarse-grained model. To parameterize a system-specific coarse-grained model, we use a combination of Boltzmann inversion, non-linear regression, and a Gaussian process Bayesian optimization approach. The accuracy of the coarse-grained model is demonstrated through direct comparisons to results from all atom simulations. We demonstrate the utility of our coarse-graining approach using the block-copolymeric sequence from the exon 1 encoded sequence of the huntingtin protein. This sequence comprises of 17 residues from the N-terminal end of huntingtin (N17) followed by a polyglutamine (polyQ) tract. Simulations based on the CAMELOT approach are used to show that the adsorption and unfolding of the wild type N17 and its sequence variants on the surface of polyQ tracts engender a patchy colloid like architecture that promotes the formation of linear aggregates. These results provide a plausible explanation for experimental observations, which show that N17 accelerates the formation of linear aggregates in block-copolymeric N17-polyQ sequences. The CAMELOT approach is versatile and is generalizable for simulating the aggregation and phase behavior of a range of block-copolymeric protein sequences.

  18. Block Copolymerization of Lactide and an Epoxide Facilitated by a Redox Switchable Iron-Based Catalyst.

    PubMed

    Biernesser, Ashley B; Delle Chiaie, Kayla R; Curley, Julia B; Byers, Jeffery A

    2016-04-18

    A cationic iron(III) complex was active for the polymerization of various epoxides, whereas the analogous neutral iron(II) complex was inactive. Cyclohexene oxide polymerization could be "switched off" upon in situ reduction of the iron(III) catalyst and "switched on" upon in situ oxidation, which is orthogonal to what was observed previously for lactide polymerization. Conducting copolymerization reactions in the presence of both monomers resulted in block copolymers whose identity can be controlled by the oxidation state of the catalyst: selective lactide polymerization was observed in the iron(II) oxidation state and selective epoxide polymerization was observed in the iron(III) oxidation state. Evidence for the formation of block copolymers was obtained from solubility differences, GPC, and DOSY-NMR studies. PMID:26991820

  19. Experimental investigation of the 30S(α, p) thermonuclear reaction in x-ray bursts

    NASA Astrophysics Data System (ADS)

    Kahl, D.; Chen, A. A.; Kubono, S.; Yamaguchi, H.; Binh, D. N.; Chen, J.; Cherubini, S.; Duy, N. N.; Hashimoto, T.; Hayakawa, S.; Iwasa, N.; Jung, H. S.; Kato, S.; Kwon, Y. K.; Nishimura, S.; Ota, S.; Setoodehnia, K.; Teranishi, T.; Tokieda, H.; Yamada, T.; Yun, C. C.; Zhang, L. Y.

    2016-02-01

    We performed the first measurement of 30S+α resonant elastic scattering to experimentally examine the 30S(α, p) stellar reaction rate in type I x-ray bursts. These bursts are the most frequent thermonuclear explosions in the galaxy, resulting from thermonuclear runaway on the surface of accreting neutron star binaries. The 30S(α, p) reaction plays a critical role in burst models, yet very little is known about the compound nucleus 34Ar at these energies nor the reaction rate itself. We performed a measurement of alpha elastic scattering with a radioactive beam of 30S to experimentally probe the entrance channel. Utilizing a gaseous active target system and silicon detector array, we extracted the excitation function from 1.8 to 5.5 MeV near 160° in the center-of-mass frame. The experimental data were analyzed with an R-Matrix calculation, and we discovered several new resonances and extracted their quantum properties (resonance energy, width, spin, and parity). Finally, we calculated the narrow resonant thermonuclear reaction rate of 30S(α, p) for these new resonances.

  20. EXPERIMENTAL AND THEORETICAL STUDIES OF REACTIONS BETWEEN H ATOMS AND CARBANIONS OF INTERSTELLAR RELEVANCE

    SciTech Connect

    Yang Zhibo; Eichelberger, Brian; Carpenter, Marshall Y.; Martinez, Oscar; Bierbaum, Veronica M.; Snow, Theodore P. E-mail: BEichelberger@jbu.ed E-mail: Oscar.Martinez@colorado.ed E-mail: Theodore.Snow@colorado.ed

    2010-11-10

    The recent detection of molecular anions in the interstellar medium (ISM) has highlighted the need for laboratory studies of negative ion chemistry. Hydrogen atoms are the most abundant atomic species in the ISM, and the chemistry of H atoms with anions may contribute to molecular synthesis in interstellar clouds. This work is a combined experimental and computational study of a series of anions reacting with H atoms by associative detachment (A{sup -} + H {yields} AH + e {sup -}). The anions include deprotonated nitriles (CH{sub 2}CN{sup -}, CH{sub 3}CHCN{sup -}, and (CH{sub 3}){sub 2}CCN{sup -}), acetaldehyde (HC(O)CH{sub 2} {sup -}), acetone (CH{sub 3}C(O)CH{sub 2} {sup -}), ethyl acetate (CH{sub 3}CH{sub 2}OC(O)CH{sub 2} {sup -}), methanol (CH{sub 3}O{sup -}), and acetic acid (CH{sub 3}CO{sub 2} {sup -}). Experimental measurements of the reaction rate constants were made with the flowing afterglow-selected ion flow tube technique. Ab initio theoretical calculations were carried out to explore the reaction mechanism and investigate the factors influencing reaction efficiencies, which are largely proportional to reaction exothermicities. Other factors influencing reaction efficiencies include the charge density on the reactive site of the anion, the characteristics of the potential energy surfaces along the approach of the reactants, and angular momentum conservation of the anion-H atom collision.

  1. Reactivity of benzohydrazide derivatives towards acetylation reaction. Experimental and theoretical studies

    NASA Astrophysics Data System (ADS)

    Campodónico, Paola R.; Aliaga, Margarita E.; Santos, José G.; Castro, Enrique A.; Contreras, Renato

    2010-03-01

    We herein report an experimental and theoretical study on the acetylation reaction of benzohydrazide derivatives towards p-nitrophenyl acetate (NPA). The kinetic data are consistent with a stepwise mechanism with the nucleophilic attack as the rate determining step. From the theoretical analysis it is found that benzohydrazide derivatives establish intramolecular proton rearrangement. The enol form appears as the active species for nucleophilic attack. A reaction mechanism incorporating keto-enol pre-equilibria is proposed. The study is completed with a local reactivity analysis describing the most reactive centers for nucleophilic attack together with a site activation analysis describing inductive substituent effects.

  2. Experimental Investigation of the Stellar Reaction 30S(p,γ)31Cl via Coulomb Dissociation

    NASA Astrophysics Data System (ADS)

    Togano, Y.; Motobayashi, T.; Aoi, N.; Baba, H.; Bishop, S.; Cai, X.; Doornenbal, P.; Fang, D.; Furukawa, T.; Ieki, K.; Iwasa, N.; Kawabata, T.; Kanno, S.; Kobayashi, N.; Kondo, Y.; Kuboki, T.; Kume, N.; Kurita, K.; Kurokawa, M.; Ma, Y. G.; Matsuo, Y.; Murakami, H.; Matsushita, M.; Nakamura, T.; Okada, K.; Ota, S.; Satou, Y.; Shimoura, S.; Shioda, R.; Tanaka, K. N.; Takeuchi, S.; Tian, W.; Wang, H.; Wang, J.; Yamada, K.; Yamada, Y.; Yoneda, K.

    2011-09-01

    Coulomb dissociation of the proton-rich nucleus 31Cl was studied experimentally using a 31Cl beam at 58 MeV/nucleon with a lead target. The relative energy spectrum of 30S+p system was obtained from the measured momentum vectors of the reaction products detected in coincidence by the invariant mass method. The first excited state in 31Cl was observed which is relevant to the resonant capture in the stellar 30S(p,γ)31Cl reaction. Discussion for another observed state is also given.

  3. Experimental Study of the Cross Sections of {alpha}-Particle Induced Reactions on 209Bi

    SciTech Connect

    Hermanne, A.; Tarkanyi, F.; Takacs, S.; Szucs, Z.

    2005-05-24

    Alpha particle induced reactions for generation of 211At used in therapeutic nuclear medicine and possible contaminants were investigated with the stacked foil activation technique on natural bismuth targets up to E{alpha}=39 MeV. Excitation functions for the reactions 209Bi({alpha},2n)211At, 209Bi({alpha},3n)210At, 209Bi({alpha},x) 210Po obtained from direct alpha emission measurements and gamma spectra from decay products are compared with earlier literature values. Thick target yields have been deduced from the experimental cross sections.

  4. Population-reaction model and microbial experimental ecosystems for understanding hierarchical dynamics of ecosystems.

    PubMed

    Hosoda, Kazufumi; Tsuda, Soichiro; Kadowaki, Kohmei; Nakamura, Yutaka; Nakano, Tadashi; Ishii, Kojiro

    2016-02-01

    Understanding ecosystem dynamics is crucial as contemporary human societies face ecosystem degradation. One of the challenges that needs to be recognized is the complex hierarchical dynamics. Conventional dynamic models in ecology often represent only the population level and have yet to include the dynamics of the sub-organism level, which makes an ecosystem a complex adaptive system that shows characteristic behaviors such as resilience and regime shifts. The neglect of the sub-organism level in the conventional dynamic models would be because integrating multiple hierarchical levels makes the models unnecessarily complex unless supporting experimental data are present. Now that large amounts of molecular and ecological data are increasingly accessible in microbial experimental ecosystems, it is worthwhile to tackle the questions of their complex hierarchical dynamics. Here, we propose an approach that combines microbial experimental ecosystems and a hierarchical dynamic model named population-reaction model. We present a simple microbial experimental ecosystem as an example and show how the system can be analyzed by a population-reaction model. We also show that population-reaction models can be applied to various ecological concepts, such as predator-prey interactions, climate change, evolution, and stability of diversity. Our approach will reveal a path to the general understanding of various ecosystems and organisms. PMID:26747638

  5. Experimental and Theoretical Investigations of Reaction-Coupled Flow and Transport in Porous Media

    NASA Astrophysics Data System (ADS)

    Kim, J.; Schwartz, F. W.

    2004-12-01

    In some systems, it is possible to observe complex patterns of coupling between fluid and flow and mass transport when reactions involving a solid phase are operative. For example, dissolution and precipitation reactions can change a porous medium's physical properties such as porosity and permeability. These changes influence fluid flow, which affect the concentration of dissolved solids, the composition of solid phases, and the rate and direction of advective transport. Both experimental and modeling studies were conducted to investigate the coupling between flow and transport due to effects of fluid density, dissolution/precipitation reactions, and heterogeneity in medium properties. The complex chemical system is created by pumping a dilute Fe(ClO4)3 solution through a medium created by mixing glass beads and crushed calcite. Fe3+ rapidly hydrolyzes to produce hydroxo complexes and H+. As pH increases through reaction with calcite, a poorly crystallized solid, ferric oxyhydroxide precipitates. Two-dimensional flow tank studies are use to verify a novel modeling approach. In the model, there is full coupling of flow and transport due to permeability changes from dissolution/precipitation reactions. Further, TOUGHREACT is used to study reaction-front dynamics, and how the aqueous phase concentrations depend upon this pattern of evolution. Both the experimental and theoretical results highlight the complexity of coupling in systems with heterogeneous reactions. The important implication of this study is that details of interactions between pore fluid and the porous medium need to be well characterized in order to predict the changing aqueous concentrations.

  6. Experimental test of a method for determining causal connectivities of species in reactions.

    PubMed

    Torralba, Antonio S; Yu, Kristine; Shen, Peidong; Oefner, Peter J; Ross, John

    2003-02-18

    Theoretical analysis has shown the possibility of determining causal connectivities of reacting species and the reaction mechanism in complex chemical and biochemical reaction systems by applying pulse changes of concentrations of one or more species, of arbitrary magnitude, and measuring the temporal response of as many species as possible. This method, limited to measured and pulsed species, is given here an experimental test on a part of glycolysis including the sequence of reactions from glucose to fructose 1,6-biphosphate, followed by the bifurcation of that sequence into two branches, one ending in glycerol 3-phosphate, the other in glyceraldehyde 3-phosphate. Pulses of concentrations of one species at a time are applied to the open system in a non-equilibrium stationary state, and the temporal responses in concentrations of six metabolites are measured by capillary zone electrophoresis. From the results of these measurements and the use of the theory for their interpretation, we establish the causal connectivities of the metabolites and thus the reaction mechanism, including the bifurcation of one chain of reactions into two. In this test case of the pulse method, no prior knowledge was assumed of the biochemistry of this system. We conclude that the pulse method is relatively simple and effective in determining reaction mechanisms in complex systems, including reactants, products, intermediates, and catalysts and their effectors. The method is likely to be useful for substantially more complex systems. PMID:12576555

  7. Reactions to Ingroup and Outgroup Deviants: An Experimental Group Paradigm for Black Sheep Effect

    PubMed Central

    2015-01-01

    In the classic black sheep effect (BSE) an ingroup deviant member is usually evaluated more negatively than the corresponding outgroup deviant. This effect is usually obtained by using scenarios and asking people to imagine the situation as vividly as possible. The present study proposes a new method to investigate the BSE by considering the behavioral and physiological reactions to unfair behavior (aggressive game behavior) in a realistic experimental group-setting. The study involved 52 university students in a minimal group setting who performed a modified version of the competitive reaction time (CRT) task adapted to be played in groups of four people. The classic BSE was replicated for evaluation but not for the behavioral reactions (retaliate to aggression) to deviants. More interestingly, a negative relationship emerged in the ingroup deviant condition between the level of behavioral derogation and the systolic blood pressure level. PMID:25946148

  8. Experimental and theoretical investigation of the self-reaction of phenyl radicals.

    SciTech Connect

    Tranter, R. S.; Klippenstein, S. J.; Harding, L. B.; Giri, B. R.; Yang, X.; Kiefer, J. H.; Chemical Sciences and Engineering Division; Univ. of Illinois at Chicago

    2010-08-19

    A combination of experiment and theory is applied to the self-reaction kinetics of phenyl radicals. The dissociation of phenyl iodide is observed with both time-of-flight mass spectrometry, TOF-MS, and laser schlieren, LS, diagnostics coupled to a diaphragmless shock tube for temperatures ranging from 1276 to 1853 K. The LS experiments were performed at pressures of 22 {+-} 2, 54 {+-} 7, and 122 {+-} 6 Torr, and the TOF-MS experiments were performed at pressures in the range 500-700 Torr. These observations are sensitive to both the dissociation of phenyl iodide and to the subsequent self-reaction of the phenyl radicals. The experimental observations indicate that both these reactions are more complicated than previously assumed. The phenyl iodide dissociation yields {approx}6% C{sub 6}H{sub 4} + HI in addition to the major and commonly assumed C{sub 6}H{sub 5} + I channel. The self-reaction of phenyl radicals does not proceed solely by recombination, but also through disproportionation to benzene + o-/m-/p-benzynes, with comparable rate coefficients for both. The various channels in the self-reaction of phenyl radicals are studied with ab initio transition state theory based master equation calculations. These calculations elucidate the complex nature of the C{sub 6}H{sub 5} self-reaction and are consistent with the experimental observations. The theoretical predictions are used as a guide in the development of a model for the phenyl iodide pyrolysis that accurately reproduces the observed laser schlieren profiles over the full range of the observations.

  9. The BZ Reaction: Experimental and Model Studies in the Physical Chemistry Laboratory

    NASA Astrophysics Data System (ADS)

    Benini, Omar; Cervellati, Rinaldo; Fetto, Pasquale

    1996-09-01

    The paper illustrates integrated physical chemistry-computational lab experiments at the tertiary level on the "classic" Belousov-Zhabotinsky (BZ) oscillating reaction. The complete work was designed for studying the behavior of the Ce4+/Ce3+- and Fe(phen)32+/Fe(phen)33+-catalyzed BZ systems and developing a kinetic model to interpret the experimental data. The students prepared the appropriate reactant mixtures and followed spectrophotometrically the absorbance of Ce4+ and Fe(phen)32+ ions. Then they plot the period of oscillation as a function of the initial concentration of any one of the mixture components observing in particular the difference in the dependence of the oscillation period on the [Ce4+]o and [Fe(phen)32+]o respectively. These differences suggest that the two redox couples catalyze the BZ reaction by different mechanisms. A kinetic mathematical model based on the FKN mechanism for the cerium-catalyzed reaction is presented and discussed. The numerical intergration solutions of the resulting rate equations show that the model accounts satsfactorily for the oscillations of the Ce4+/Ce3+-catalyzed system but fails to reproduce the experimental behavior of the system catalyzed by the couple Fe(phen)32+/Fe(phen)33+. It has been proved that these integrated chemistry-computational lab experiments are a powerful tool in stimulating student interest in physical chemistry and in showing the importance of chemical kinetics in the elucidation of reaction mechanism.

  10. Matching of experimental and statistical-model thermonuclear reaction rates at high temperatures

    NASA Astrophysics Data System (ADS)

    Newton, Joseph; Longland, Richard; Iliadis, Christian

    2009-05-01

    Reliable reaction rates at high stellar temperatures are necessary for the study of advanced stellar burning stages, supernovae and x-ray bursts. We suggest a new procedure for extrapolating experimental thermonuclear reaction rates to these higher temperatures (T > 1 GK) using statistical model (Hauser-Feshbach) results. Current, generally accepted, procedures involve the use of the Gamow peak, which has been shown to be unreliable for narrow resonances at high stellar temperatures [1]. Our new approach defines the effective thermonuclear energy range (ETER) by using the 8^th, 50^th and 92^nd percentiles of the cumulative distribution of fractional resonant reaction contributions. The ETER is then used to define a reliable temperature for matching experimental rates to Hauser-Feshbach rates. The resulting matching temperature is often well above the previous result using the Gamow peak concept. Our new method should provide more accurate extrapolated rates since Hauser-Feshbach rates are more reliable at higher temperatures. These ideas are applied to 21 (p,γ), (p,α) and (α,γ) reactions on a range of A = 20-40 target nuclei and results will be presented. [0pt] [1] J. R. Newton, C. Iliadis, A. E. Champagne, A. Coc, Y. Parpottas and R. Ugalde, Phys. Rev. C 75, 045801 (2007).

  11. Concerning the deactivation of cobalt(III)-based porphyrin and salen catalysts in epoxide/CO2 copolymerization.

    PubMed

    Xia, Wei; Salmeia, Khalifah A; Vagin, Sergei I; Rieger, Bernhard

    2015-03-01

    Functioning as active catalysts for propylene oxide (PO) and carbon dioxide copolymerization, cobalt(III)-based salen and porphyrin complexes have drawn great attention owing to their readily modifiable nature and promising catalytic behavior, such as high selectivity for the copolymer formation and good regioselectivity with respect to the polymer microstructure. Both cobalt(III)-salen and porphyrin catalysts have been found to undergo reduction reactions to their corresponding catalytically inactive cobalt(II) species in the presence of propylene oxide, as evidenced by UV/Vis and NMR spectroscopies and X-ray crystallography (for cobalt(II)-salen). Further investigations on a TPPCoCl (TPP = tetraphenylporphyrin) and NaOMe system reveal that such a catalyst reduction is attributed to the presence of alkoxide anions. Kinetic studies of the redox reaction of TPPCoCl with NaOMe suggests a pseudo-first order in cobalt(III)-porphyrin. The addition of a co-catalyst, namely bis(triphenylphosphine)iminium chloride (PPNCl), into the reaction system of cobalt(III)-salen/porphyrin and PO shows no direct stabilizing effect. However, the results of PO/CO2 copolymerization by cobalt(III)-salen/porphyrin with PPNCl suggest a suppressed catalyst reduction. This phenomenon is explained by a rapid transformation of the alkoxide into the carbonate chain end in the course of the polymer formation, greatly shortening the lifetime of the autoreducible PO-ring-opening intermediates, cobalt(III)-salen/porphyrin alkoxides. PMID:25656829

  12. Chemical morphogenesis: recent experimental advances in reaction-diffusion system design and control.

    PubMed

    Szalai, István; Cuiñas, Daniel; Takács, Nándor; Horváth, Judit; De Kepper, Patrick

    2012-08-01

    In his seminal 1952 paper, Alan Turing predicted that diffusion could spontaneously drive an initially uniform solution of reacting chemicals to develop stable spatially periodic concentration patterns. It took nearly 40 years before the first two unquestionable experimental demonstrations of such reaction-diffusion patterns could be made in isothermal single phase reaction systems. The number of these examples stagnated for nearly 20 years. We recently proposed a design method that made their number increase to six in less than 3 years. In this report, we formally justify our original semi-empirical method and support the approach with numerical simulations based on a simple but realistic kinetic model. To retain a number of basic properties of real spatial reactors but keep calculations to a minimal complexity, we introduce a new way to collapse the confined spatial direction of these reactors. Contrary to similar reduced descriptions, we take into account the effect of the geometric size in the confinement direction and the influence of the differences in the diffusion coefficient on exchange rates of species with their feed environment. We experimentally support the method by the observation of stationary patterns in red-ox reactions not based on oxihalogen chemistry. Emphasis is also brought on how one of these new systems can process different initial conditions and memorize them in the form of localized patterns of different geometries. PMID:23919126

  13. Amphibole reaction rims as a record of pre-eruptive magmatic heating: An experimental approach

    NASA Astrophysics Data System (ADS)

    De Angelis, S. H.; Larsen, J.; Coombs, M.; Dunn, A.; Hayden, L.

    2015-09-01

    Magmatic minerals record the pre-eruptive timescales of magma ascent and mixing in crustal reservoirs and conduits. Investigations of the mineral records of magmatic processes are fundamental to our understanding of what controls eruption style, as ascent rates and magma mixing processes are well known to control and/or trigger potentially hazardous explosive eruptions. Thus, amphibole reaction rims are often used to infer pre-eruptive magma dynamics, and in particular to estimate magma ascent rates. However, while several experimental studies have investigated amphibole destabilization during decompression, only two investigated thermal destabilization relevant to magma mixing processes. This study examines amphibole decomposition experimentally through isobaric heating of magnesio-hornblende phenocrysts within a natural high-silica andesite glass. The experiments first equilibrated for 24 h at 870 °C and 140 MPa at H2O-saturated conditions and ƒO2 ∼ Re-ReO prior to rapid heating to 880, 900, or 920 °C and hold times of 3-48 h. At 920 °C, rim thicknesses increased from 17 μm after 3 h, to 55 μm after 12 h, and became pseudomorphs after longer durations. At 900 °C, rim thicknesses increased from 7 μm after 3 h, to 80 μm after 24 h, to pseudomorphs after longer durations. At 880 °C, rim thicknesses increased from 7 μm after 3 h, to 18 μm after 36 h, to pseudomorphs after 48 h. Reaction rim microlites vary from 5-16 μm in size, with no systematic relationship between crystal size and the duration or magnitude of heating. Time-averaged rim microlite growth rates decrease steadily with increasing experimental duration (from 3.97 ×10-7 mms-1 to 3.1 to 3.5 ×10-8 mms-1). Time-averaged microlite nucleation rates also decrease with increasing experimental duration (from 1.2 ×103mm-3s-1 to 5.3 mm-3 s-1). There is no systematic relationship between time-averaged growth or nucleation rates and the magnitude of the heating step. Ortho- and clinopyroxene

  14. Experimental deformation of a mafic rock - interplay between fracturing, reaction and viscous deformation

    NASA Astrophysics Data System (ADS)

    Marti, Sina; Stünitz, Holger; Heilbronner, Renée; Plümper, Oliver; Drury, Martyn

    2016-04-01

    Deformation experiments were performed on natural Maryland Diabase (˜ 55% Plg, 42% Px, 3% accessories, 0.18 wt.-% H2O added) in a Griggs-type deformation apparatus in order to explore the brittle-viscous transition and the interplay between deformation and mineral reactions. Shear experiments at strain rates of ˜ 2e-5 /s are performed, at T=600, 700 and 800°C and confining pressures Pc=1.0 and 1.5 GPa. Deformation localizes in all experiments. Below 700°C, the microstructure is dominated by brittle deformation with a foliation formed by cataclastic flow and high strain accommodated along 3-5 major ultracataclasite shear bands. At 700°C, the bulk of the material still exhibits abundant microfractures, however, deformation localizes into an anastomosing network of shear bands (SB) formed from a fine-grained (<< 1 μm) mixture of newly formed Plg and Amph. These reaction products occur almost exclusively along syn-kinematic structures such as fractures and SB. Experiments at 800°C show extensive mineral reactions, with the main reaction products Amph+Plg (+Zo). Deformation is localized in broad C' and C SB formed by a fine-grained (0.1 - 0.8 μm) mixture of Plg+Amph (+Zo). The onset of mineral reactions in the 700°C experiments shows that reaction kinetics and diffusional mass transport are fast enough to keep up with the short experimental timescales. While in the 700°C experiments brittle processes kinematically contribute to deformation, fracturing is largely absent at 800°C. Diffusive mass transfer dominates. The very small grain size within SB favours a grain size sensitive deformation mechanism. Due to the presence of water (and relatively high supported stresses), dissolution-precipitation creep is interpreted to be the dominant strain accommodating mechanism. From the change of Amph coronas around Px clasts with strain, we can determine that Amph is re-dissolved at high stress sites while growing in low stress sites, showing the ability of Amph to

  15. Lipase-catalyzed synthesis of aliphatic polyesters via copolymerization of lactone, dialkyl diester, and diol.

    PubMed

    Jiang, Zhaozhong

    2008-11-01

    Candida antarctica lipase (CALB) has been successfully used as catalyst for copolymerization of dialkyl diester with diol and lactone to form aliphatic polyesters. The polymerization reactions were performed using a two stage process: first stage oligomerization under low vacuum followed by second stage polymerization under high vacuum. Use of the two-stage process is required to obtain products with high molecular weights at high yields for the following reasons: (i) the first stage reaction ensures that the monomer loss via evaporation is minimized to maintain 1:1 diester to diol stoichiometric ratio, and the monomers are converted to nonvolatile oligomers; (ii) use of high vacuum during the second stage accelerates equilibrium transesterification reactions to transform the oligomers to high molecular weight polymers. Thus, terpolymers of omega-pentadecalactone (PDL), diethyl succinate (DES), and 1,4-butanediol (BD) with a M w of whole product (nonfractionated) up to 77000 and M w/ M n between 1.7 and 4.0 were synthesized in high yields (e.g., 95% isolated yield). A desirable reaction temperature for the copolymerizations was found to be around 95 degrees C. At 1:1:1 PDL/DES/BD monomer molar ratio, the resultant terpolymers contained equal moles of PDL, succinate, and butylene repeat units in the polymer chains. (1)H and (13)C NMR analyses were used to determine the polyester microstructures. The synthesized PDL-DES-BD terpolymers possessed near random structures with all possible combinations of PDL, succinate, and butylene units via ester linkages in the polymer backbone. Furthermore, thermal stability and crystallinity of a pure PDL-DES-BD terpolymer with 1:1:1 PDL to succinate to butylene unit ratio and M w of 85400 were studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The copolyester was found to be a semicrystalline material with a T g of -34 degrees C and a T m of 64 degrees C, which degrades in a single weight loss

  16. Experimental Approach to High-Temperature Stellar Reactions with Low-Energy RI Beams

    NASA Astrophysics Data System (ADS)

    Kubono, S.; Yamaguchi, H.; Amadio, G.; Hayakawa, S.; Wakabayashi, Y.; Kurihara, Y.; He, J. J.; Saito, A.; Fujikawa, H.; Khiem, Le Hong; Niikura, M.; Teranishi, T.; Nishimura, S.; Kato, S.; Lee, C. S.; Kwon, Y. K.; Hahn, I. S.; Kim, A.

    2008-04-01

    The experimental efforts for the stellar reactions under high-temperature and high densities have been made as the major program using the RI beams from the CNS low-energy in-flight RI beam separator (CRIB) of University of Tokyo, in order to understand the evolution of the universe as well as various stellar phenomena. Specifically, two subjects of hydrogen burning are discussed here. One is a reaction study of the pp-chain and the second is of the explosive hydrogen burning, the rp-process. Some s-wave resonances have been identified by the thick target method in the crucial reaction processes in the hydrogen burning. The resonant scattering with the thick target method also succeeded in identifying inelastic resonant scattering, giving proton widths for the first excited state of the target nucleus. This provides very efficiently the reaction rate estimate for the process under high-temperature equilibrium condition. Possibilities of the CRIB facility in near future are also briefly discussed.

  17. An experimental and theoretical study of reaction mechanisms between nitriles and hydroxylamine.

    PubMed

    Vörös, Attila; Mucsi, Zoltán; Baán, Zoltán; Timári, Géza; Hermecz, István; Mizsey, Péter; Finta, Zoltán

    2014-10-28

    The industrially relevant reaction between nitriles and hydroxylamine yielding amidoximes was studied in different molecular solvents and in ionic liquids. In industry, this procedure is carried out on the ton scale in alcohol solutions and the above transformation produces a significant amount of unexpected amide by-product, depending on the nature of the nitrile, which can cause further analytical and purification issues. Although there were earlier attempts to propose mechanisms for this transformation, the real reaction pathway is still under discussion. A new detailed reaction mechanistic explanation, based on theoretical and experimental proof, is given to augment the former mechanisms, which allowed us to find a more efficient, side-product free procedure. Interpreting the theoretical results obtained, it was shown that the application of specific imidazolium, phosphonium and quaternary ammonium based ionic liquids could decrease simultaneously the reaction time while eliminating the amide side-product, leading to the targeted product selectively. This robust and economic procedure now affords a fast, selective amide free synthesis of amidoximes. PMID:25185027

  18. Single particle refuse-derived fuel devolatilization: Experimental measurements of reaction products

    SciTech Connect

    Lai, Weichuan; Krieger-Brockett, B. . Dept. of Chemical Engineering)

    1993-11-01

    The authors present experimentally measured devolatilization product yields from single particles of refuse-derived fuel (RDF), a more uniform, transportable municipal solid waste. Disposal costs and environmental concerns have stimulated interest in thermochemical conversion of this material to chemicals and fuels. The composition, reaction conditions, and particle properties were systematically varied over the range found in practice to develop quantitative measures that rank the process controllables' influence on altering the product slate. Specialized regression methods and experimental designs enhanced the accuracy in view of the feed heterogeneity and offer a general method to extract real effects from experimental and sample noise''. The results have been verified successfully using actual commercial RDF and fabricated compositions that surpass those normally found in municipal waste to anticipate the influence of trends in recycling. The results show that the reaction conditions have a greater influence on altering fuel utilization and the relative yields of char, condensibles, and gases than does the composition over the range found in MSW and RDF.

  19. Experimental studies of stationary reaction fronts in a chain of vortices with imposed wind

    NASA Astrophysics Data System (ADS)

    Solomon, Tom; Boyer, Carleen

    2013-03-01

    We present experiments that study the behavior of the excitable Belousov-Zhabotinsky (BZ) reaction in a chain of alternating vortices with an imposed uniform wind. Previous experiments[2] have shown that fronts in this system are pinned for a wide range of imposed wind speeds, propagating neither forward against the wind nor in the downwind direction. We explain this behavior with a recent theory[3] that proposes the existence of burning invariant manifolds (BIMs) that act as local barriers to front propagation. Fronts are pinned when a BIM or a combination of BIMs spans the width of the vortex chain, blocking the reaction front. We show experimental measurements of the shape of the pinned front for a range of different wind speeds, and compare these shapes to the BIMs calculated theoretically. We also consider the dependence of the front shape on the location of the initial trigger for the front. Supported by NSF Grants DMR-0703635, DMR-1004744, and and PHY-1156964.

  20. Experimental studies of stationary reaction fronts in a chain of vortices

    NASA Astrophysics Data System (ADS)

    Boyer, Carleen; Solomon, Tom

    2012-11-01

    We present results of experiments studying the behavior of the excitable Belousov-Zhabotinsky (BZ) reaction in a chain of alternating vortices with an imposed uniform wind. Previous experiments have shown that fronts in this system are pinned for a wide range of imposed wind speeds, propagating neither forward against the wind nor in the downwind direction. We explain this behavior with a recent theory that proposes the existence of burning invariant manifolds (BIMs) that act as local barriers to front propagation. Fronts are pinned when a BIM or a combination of BIMs spans the width of the vortex chain, blocking the reaction front. We show experimental measurements of the shape of the pinned front for a range of different wind speeds, and compare these shapes to the BIMs calculated theoretically. We also consider the dependence of the front shape on the location of the initial trigger for the front. Supported by NSF Grants DMR-0703635, DMR-1004744, and and PHY-1156964.

  1. Alternating copolymerization of propylene oxide with biorenewable terpene-based cyclic anhydrides: a sustainable route to aliphatic polyesters with high glass transition temperatures.

    PubMed

    Van Zee, Nathan J; Coates, Geoffrey W

    2015-02-23

    The alternating copolymerization of propylene oxide with terpene-based cyclic anhydrides catalyzed by chromium, cobalt, and aluminum salen complexes is reported. The use of the Diels-Alder adduct of α-terpinene and maleic anhydride as the cyclic anhydride comonomer results in amorphous polyesters that exhibit glass transition temperatures (Tg ) of up to 109 °C. The polymerization conditions and choice of catalyst have a dramatic impact on the molecular weight distribution, the relative stereochemistry of the diester units along the polymer chain, and ultimately the Tg of the resulting polymer. The aluminum salen complex exhibits exceptional selectivity for copolymerization without transesterification or epimerization side reactions. The resulting polyesters are highly alternating and have high molecular weights and narrow polydispersities. PMID:25611489

  2. Fuel-rich, catalytic reaction experimental results. [fuel development for high-speed civil transport aircraft

    NASA Technical Reports Server (NTRS)

    Rollbuhler, Jim

    1991-01-01

    Future aeropropulsion gas turbine combustion requirements call for operating at very high inlet temperatures, pressures, and large temperature rises. At the same time, the combustion process is to have minimum pollution effects on the environment. Aircraft gas turbine engines utilize liquid hydrocarbon fuels which are difficult to uniformly atomize and mix with combustion air. An approach for minimizing fuel related problems is to transform the liquid fuel into gaseous form prior to the completion of the combustion process. Experimentally obtained results are presented for vaporizing and partially oxidizing a liquid hydrocarbon fuel into burnable gaseous components. The presented experimental data show that 1200 to 1300 K reaction product gas, rich in hydrogen, carbon monoxide, and light-end hydrocarbons, is formed when flowing 0.3 to 0.6 fuel to air mixes through a catalyst reactor. The reaction temperatures are kept low enough that nitrogen oxides and carbon particles (soot) do not form. Results are reported for tests using different catalyst types and configurations, mass flowrates, input temperatures, and fuel to air ratios.

  3. Experimental and theoretical study of the reactions between vanadium oxide cluster cations and water.

    PubMed

    Ma, Jia-Bi; Zhao, Yan-Xia; He, Sheng-Gui; Ding, Xun-Lei

    2012-03-01

    Vanadium oxide cluster cations V(x)O(y)(+) (x = 2-6) are prepared by laser ablation and are reacted with D(2)O in a fast flow reactor under room temperature conditions. A time-of-flight mass spectrometer is used to detect the cluster distribution before and after the reactions. Observation of the products (V(2)O(5))(1-3)D(+) indicates the deuterium atom abstraction reaction (V(2)O(5))(1-3)(+) + D(2)O → (V(2)O(5))(1-3)D(+) + OD. In addition, significant association products (V(2)O(5))(1-3)D(2)O(+) are also observed in the experiments. Density functional theory calculations are performed to study the reaction mechanisms of V(4)O(10)(+) with H(2)O. The calculated results are in agreement with the experimental observations and indicate that H(2)O is dissociatively rather than molecularly adsorbed in V(4)O(10)H(2)O(+) complex. PMID:22315964

  4. Modification of flax fibres by radiation induced emulsion graft copolymerization of glycidyl methacrylate

    NASA Astrophysics Data System (ADS)

    Moawia, Rihab Musaad; Nasef, Mohamed Mahmoud; Mohamed, Nor Hasimah; Ripin, Adnan

    2016-05-01

    Flax fibres were modified by radiation induced graft copolymerization of glycidyl methacrylate (GMA) by pre-irradiation method in an emulsion medium. The effect of reaction parameters on the degree of grafting (DOG) such as concentration of bleaching agent, absorbed dose, monomer concentration, temperature and reaction time were investigated. The DOG was found to be dependent on the investigated parameters. The incorporation of poly(GMA) grafts in the bleached flax fibres was confirmed by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The structural and mechanical changes were evaluated by X-ray diffraction (XRD) and mechanical tester, respectively. The results revealed that reacting bleached flax fibres irradiated with 20 kGy with 5% GMA emulsion containing 0.5% polyoxyethylene-sorbitan monolaurate (Tween 20) surfactant at 40 °C for 1 h led to a maximum DOG of 148%. The grafted fibres showed sufficient mechanical strength and hydrophobicity which make them promising precursors for development of adsorbents after appropriate chemical treatments.

  5. Direct Synthesis of Imidazolium-Functional Polyethylene by Insertion Copolymerization.

    PubMed

    Jian, Zhongbao; Leicht, Hannes; Mecking, Stefan

    2016-06-01

    Cationic imidazolium-functionalized polyethylene is accessible by insertion copolymerization of ethylene and allyl imidazolium tetrafluoroborate (AIm-BF4 ) with phosphinesulfonato palladium(II) catalyst precursors. Imidazolium-substituted repeat units are incorporated into the main chain and the initiating saturated chain end of the linear polymers, rather than the terminating unsaturated chain end. The counterion of the allyl imidazolium monomer is decisive, with the chloride analogue (AIm-Cl) no polymerization is observed. Stoichiometric studies reveal the formation of an inactive chloride complex from the catalyst precursor. An effect of moderate densities (0.5 mol%) of ionic groups on the copolymers' physical properties is exemplified by an enhanced wetting by water. PMID:27111477

  6. Dynamic optimization of a copolymerization reactor using tabu search.

    PubMed

    Anand, P; Rao, M Bhagvanth; Venkateswarlu, Ch

    2015-03-01

    A novel multistage dynamic optimization strategy based on meta-heuristic tabu search (TS) is proposed and evaluated through sequential and simultaneous implementation procedures by applying it to a semi-batch styrene-acrylonitrile (SAN) copolymerization reactor. The adaptive memory and responsive exploration features of TS are exploited to design the dynamic optimization strategy and compute the optimal control policies for temperature and monomer addition rate so as to achieve the desired product quality parameters expressed in terms of single and multiple objectives. The dynamic optimization results of TS sequential and TS simultaneous implementation strategies are analyzed and compared with those of a conventional optimization technique based on iterative dynamic programming (IDP). The simulation results demonstrate the usefulness of TS for optimal control of transient dynamic systems. PMID:25466914

  7. Experimental verification of a computational technique for determining ground reactions in human bipedal stance.

    PubMed

    Audu, Musa L; Kirsch, Robert F; Triolo, Ronald J

    2007-01-01

    We have developed a three-dimensional (3D) biomechanical model of human standing that enables us to study the mechanisms of posture and balance simultaneously in various directions in space. Since the two feet are on the ground, the system defines a kinematically closed-chain which has redundancy problems that cannot be resolved using the laws of mechanics alone. We have developed a computational (optimization) technique that avoids the problems with the closed-chain formulation thus giving users of such models the ability to make predictions of joint moments, and potentially, muscle activations using more sophisticated musculoskeletal models. This paper describes the experimental verification of the computational technique that is used to estimate the ground reaction vector acting on an unconstrained foot while the other foot is attached to the ground, thus allowing human bipedal standing to be analyzed as an open-chain system. The computational approach was verified in terms of its ability to predict lower extremity joint moments derived from inverse dynamic simulations performed on data acquired from four able-bodied volunteers standing in various postures on force platforms. Sensitivity analyses performed with model simulations indicated which ground reaction force (GRF) and center of pressure (COP) components were most critical for providing better estimates of the joint moments. Overall, the joint moments predicted by the optimization approach are strongly correlated with the joint moments computed using the experimentally measured GRF and COP (0.78 < or = r(2) < or = 0.99,median,0.96) with a best-fit that was not statistically different from a straight line with unity slope (experimental=computational results) for postures of the four subjects examined. These results indicate that this model-based technique can be relied upon to predict reasonable and consistent estimates of the joint moments using the predicted GRF and COP for most standing postures. PMID

  8. Deuteron induced reactions on Ho and La: Experimental excitation functions and comparison with code results

    NASA Astrophysics Data System (ADS)

    Hermanne, A.; Adam-Rebeles, R.; Tarkanyi, F.; Takacs, S.; Csikai, J.; Takacs, M. P.; Ignatyuk, A.

    2013-09-01

    Activation products of rare earth elements are gaining importance in medical and technical applications. In stacked foil irradiations, followed by high resolution gamma spectroscopy, the cross-sections for production of 161,165Er, 166gHo on 165Ho and 135,137m,137g,139Ce, 140La, 133m,133g,cumBa and 136Cs on natLa targets were measured up to 50 MeV. Reduced uncertainty is obtained by simultaneous remeasurement of the 27Al(d,x)24,22Na monitor reactions over the whole energy range. A comparison with experimental literature values and results from updated theoretical codes (ALICE-D, EMPIRE-D and the TENDL2012 online library) is discussed.

  9. Experimental investigation on material migration phenomena in micro-EDM of reaction-bonded silicon carbide

    NASA Astrophysics Data System (ADS)

    Liew, Pay Jun; Yan, Jiwang; Kuriyagawa, Tsunemoto

    2013-07-01

    Material migration between tool electrode and workpiece material in micro electrical discharge machining of reaction-bonded silicon carbide was experimentally investigated. The microstructural changes of workpiece and tungsten tool electrode were examined using scanning electron microscopy, cross sectional transmission electron microscopy and energy dispersive X-ray under various voltage, capacitance and carbon nanofibre concentration in the dielectric fluid. Results show that tungsten is deposited intensively inside the discharge-induced craters on the RB-SiC surface as amorphous structure forming micro particles, and on flat surface region as a thin interdiffusion layer of poly-crystalline structure. Deposition of carbon element on tool electrode was detected, indicating possible material migration to the tool electrode from workpiece material, carbon nanofibres and dielectric oil. Material deposition rate was found to be strongly affected by workpiece surface roughness, voltage and capacitance of the electrical discharge circuit. Carbon nanofibre addition in the dielectric at a suitable concentration significantly reduced the material deposition rate.

  10. Experimental cross-sections for proton-induced nuclear reactions on natMo

    NASA Astrophysics Data System (ADS)

    Červenák, Jaroslav; Lebeda, Ondřej

    2016-08-01

    In the framework of the Co-ordinated Research Project of the IAEA, we measured in detail cross-sections of the nuclear reactions natMo(p,x)93gTc, 93mTc, 93m+gTc, 94gTc, 94mTc, 95gTc, 95mTc, 96m+gTc, 97mTc, 99mTc, 90Mo, 93mMo, 99Mo, 88gNb, 88mNb, 89gNb, 89mNb, 90m+gNb, 90m+gNbcum, 91mNb, 92mNb, 95gNb, 95mNb, 95m+gNb, 96Nb, 97m+gNb, 88m+gZrcum and 89m+gZrcum in the energy range of 6.9-35.8 MeV. The data for formation of 97mTc, 88gNb, 88mNb and 89mNb are reported for the first time. The obtained results were compared to the prediction of the nuclear reaction model code TALYS adopted from the TENDL-2015 library and to the previously published cross-sections. The thick target yields for all the radionuclides were calculated from the measured data. We suggest recommended cross-sections and thick target yields for the 100Mo(p,2n)99mTc, 100Mo(p,x)99Mo and natMo(p,x)96m+gTc nuclear reactions deduced from the selected experimental data.

  11. Effects of edaravone on experimental brain injury in view of free radical reaction.

    PubMed

    Nakamura, H; Uzura, M; Uchida, K; Nakayama, H; Furuya, Y; Hayashi, T; Sekino, H; Ominato, M; Owada, S

    2003-01-01

    The purpose of this study is to clarify the influence of a novel free radical scavenger edaravone on experimental brain injury. Male Wistar rats were anesthetized with 1-2% halothane. Brain injury was produced using a controlled cortical impact injury device. Experimental rats were divided into 2 groups. In the edaravone group, edaravone (3 mg/kg) was twice administered intravenously for 30 minutes. In the saline group, saline solution was administered in the same way. This administration of edaravone or saline solution made it possible to evaluate the relative effects of edaravone by assessment of free radical reaction and water content. As a result, the level of oxygen free radicals at 50 minutes after brain injury was significantly lower in the edaravone group than in the saline group. The water content in the injured brain at 180 minutes was significantly lower in the edaravone group than in the saline group. Therefore, we propose that edaravone may be effective for treatment in head injury. PMID:14753459

  12. Experimental study of the reaction kinetics between CO2-bearing solution and picrite cubes

    NASA Astrophysics Data System (ADS)

    Zhang, S.; Wang, Z.; Qiu, L.; Karato, S.; Johnson, K. T.; Ague, J. J.; Oristaglio, M. L.; Bolton, E. W.; Bercovici, D. A.

    2013-12-01

    Shuang Zhang1*, Zhengrong Wang1, Lin Qiu1, Shun-ichiro Karato1, Kevin Johnson2, Jay Ague1, Michael Oristaglio1, Edward Bolton1, and David Bercovici1 1Department of Geology and Geophysics and Energy Science Institute, Yale University, New Haven, CT 06520, USA 2Department of Geology and Geophysics, University of Hawai';i at Mānoa, Honolulu, HI 96822, USA *presenting author: shuang.zhang@yale.edu Picrites are potential repositories for permanent storage of anthropogenic CO2 because they contain large amounts of olivine which dissolves faster than other coexisting minerals (e.g., clinopyroxene or plagioclase), and they have relatively higher porosity and permeability than ultramafic rocks. In order to understand the kinetics of reacting CO2-bearing fluid with picrites and its carbonation potential, this study investigated the reactions between CO2-bearing solution and picrite cubes under various experimental conditions, including temperature, the concentration of DIC, reaction time and water/rock ratio. Hawaiian picrite cubes (~ 4 mm × 4 mm) and different concentrations of NaHCO3 solution (0.5 M, 1 M, and 3 M) were sealed in gold capsules and placed in an autoclave at 100-200 oC for 5-10 days. After each run, the solids were dried and characterized by Scanning Electron Microprobe (SEM) and Electron Probe Micro Analyzer (EPMA). The coexisting solutions were titrated to quantify the consumption of dissolved inorganic carbon (DIC) during the carbonation process. Several phenomena have been observed from these experiments. First, high concentrations of DIC can significantly raise the carbonation fraction ((Mg+Fe+Ca (consumed by carbonate))/(Mg+Fe+Ca (in picrite before reaction))×100%) in these experiments. For example, the carbonation fraction (~ 0.5%) is negligible using the 0.5 or 1 M NaHCO3 even in experiments conducted at 200 oC for 10 days, but is significantly higher (~ 10%) than the detection limit of our titration method (0.5%) for 3 M NaHCO3. Second, most

  13. Experimental investigations of reactions of hot hydrogen atoms with molecular hydrogen and water

    SciTech Connect

    Adelman, D.E.

    1993-01-01

    The state-to-state integral rate constants were measured for the three reactions: (1) D + H[sub 2](vj) [yields] HD(v[prime] = 0,1,2;j) + H at E[sub rel] = 1.4 and 0.8 eV and (2) H + D[sub 2] [yields] HD(v[prime] = 1,j[prime]) + D at E[sub rel] = 2.2 and 2.5 eV, and (3) H + D[sub 2]O [yields] HD(v[prime],j[prime]), + OD at E[sub rel] = 2.7 eV. The reagents were either in the ground state, (v = 0,j), or for the D + H[sub 2] work prepared in the first excited vibrational state, (v = 1, j = 1), by stimulated Raman pumping. Translationally hot D(H) atoms were generated by UV photolysis of D(H)I. Resonance-enhanced multiphoton ionization and time-of-flight mass spectrometry were employed to detect the nascent HD product in a quantum-state-specific manner. For the reaction D + H[sub 2] we find that vibrational excitation of the H[sub 2] reagent results in: (1) substantial HD rotational excitation for each product vibrational state, (2) a [open quotes]heating[close quotes] of the vibrational product state distribution, and (3) almost no change in the total rate into HD(v[prime] = 0,1,2;j[prime]). The experimental results are consistent with a model in which internal energy of the reagents is conserved. Good to excellent agreement is found between the experiment and recent quantum-mechanical (QM) scattering calculations. The reaction H + D[sub 2] [yields] HD(v[prime] = 1,j[prime]) + D was studied at high collision energies. These experiments provide data that will be useful for determining the importance of the Jahn-Teller effect in reactive scattering systems and to the development of theoretical techniques in which the ground and first excited electronic surfaces are included in QM calculations. For the reaction H + D[sub 2]O, approximately 35% (12% in vibration, 23% in rotation) of the available energy is partitioned into the internal modes of the HD product.

  14. Experimental and Guided Theoretical Investigation of Complex Reaction Mechanisms in a Prins Reaction of Glyoxylic Acid and Isobutene

    ERIC Educational Resources Information Center

    Angelici, Gaetano; Nicolet, Stefan; Uda, Narasimha R.; Creus, Marc

    2014-01-01

    A laboratory experiment was designed for undergraduate students, in which the outcome of an easy single-step organic synthesis with well-defined conditions was not elucidated until the end of the exercise. In class, students predict and discuss the possible products using their knowledge of reaction mechanisms. In the laboratory, they learn how to…

  15. Experimental Cross Sections for Reactions of Heavy Ions and 208Pb, 209Bi, 238U, and 248Cm Targets

    SciTech Connect

    Patin, Joshua B.

    2002-05-24

    The study of the reactions between heavy ions and {sup 208}Pb, {sup 209}Bi, {sup 238}U, and {sup 248} Cm targets was performed to look at the differences between the cross sections of hot and cold fusion reactions. Experimental cross sections were compared with predictions from statistical computer codes to evaluate the effectiveness of the computer code in predicting production cross sections. Hot fusion reactions were studied with the MG system, catcher foil techniques and the Berkeley Gas-filled Separator (BGS). 3n- and 4n-exit channel production cross sections were obtained for the {sup 238}U({sup 18}O,xn){sup 256-x}Fm, {sup 238}U({sup 22}Ne,xn){sup 260-x}No, and {sup 248}Cm({sup 15}N,xn){sup 263-x}Lr reactions and are similar to previous experimental results. The experimental cross sections were accurately modeled by the predictions of the HIVAP code using the Reisdorf and Schaedel parameters and are consistent with the existing systematics of 4n exit channel reaction products. Cold fusion reactions were examined using the BGS. The {sup 208}Pb({sup 48}Ca,xn){sup 256-x}No, {sup 208}Pb({sup 50}Ti,xn){sup 258-x}Rf, {sup 208}Pb({sup 51}V,xn){sup 259-x}Db, {sup 209}Bi({sup 50}Ti,xn){sup 259-x}Db, and {sup 209}Bi({sup 51}V,xn){sup 260-x}Sg reactions were studied. The experimental production cross sections are in agreement with the results observed in previous experiments. It was necessary to slightly alter the Reisdorf and Schaedel parameters for use in the HIVAP code in order to more accurately model the experimental data. The cold fusion experimental results are in agreement with current 1n- and 2n-exit channel systematics.

  16. Homo- and co-polymerization of polysytrene-block-poly(acrylic acid)-coated metal nanoparticles.

    PubMed

    Wang, Hong; Song, Xiaohui; Liu, Cuicui; He, Jiating; Chong, Wen Han; Chen, Hongyu

    2014-08-26

    Amphiphilic block copolymers such as polystyrene-block-poly(acrylic acid) (PSPAA) give micelles that are known to undergo sphere-to-cylinder shape transformation. Exploiting this polymer property, core-shell nanoparticles coated in PSPAA can be "polymerized" into long chains following the chain-growth polymerization mode. This method is now extended to include a variety of different nanoparticles. A case study on the assembly process was carried out to understand the influence of the PAA block length, the surface ligand, and the size and morphology of the monomer nanoparticles. Shortening the PAA block promotes the reorganization of the amphiphilic copolymer in the micelles, which is essential for assembling large Au nanoparticles. Small Au nanoparticles can be directly "copolymerized" with empty PSPAA micelles into chains. The reaction time, acid quantity, and the [Au nanoparticles]/[PSPAA micelles] concentration ratio played important roles in controlling the sphere-cylinder-vesicle conversion of the PSPAA micelles, giving rise to different kinds of random "copolymers". With this knowledge, a general method is then developed to synthesize homo, random, and block "copolymers", where the basic units include small Au nanoparticles (d = 16 nm), large Au nanoparticles (d = 32 nm), Au nanorods, Te nanowires, and carbon nanotubes. Given the lack of means for assembling nanoparticles, advancing synthetic capabilities is of crucial importance. Our work provides convenient routes for combining nanoparticles into long-chain structures, facilitating rational design of complex nanostructures in the future. PMID:25000121

  17. Experimental and Theoretical Study of Reactions of OH Radicals with Hexenols: An Evaluation of the Relative Importance of the H-Abstraction Reaction Channel.

    PubMed

    Gai, Yanbo; Lin, Xiaoxiao; Ma, Qiao; Hu, Changjin; Gu, Xuejun; Zhao, Weixiong; Fang, Bo; Zhang, Weijun; Long, Bo; Long, Zhengwen

    2015-09-01

    C6 hexenols are one of the most significant groups of volatile organic compounds with biogenic emissions. The lack of corresponding kinetic parameters and product information on their oxidation reactions will result in incomplete atmospheric chemical mechanisms and models. In this paper, experimental and theoretical studies are reported for the reactions of OH radicals with a series of C6 hexenols, (Z)-2-hexen-1-ol, (Z)-3-hexen-1-ol, (Z)-4-hexen-1-ol, (E)-2-hexen-1-ol, (E)-3-hexen-1-ol, and (E)-4-hexen-1-ol, at 298 K and 1.01 × 10(5) Pa. The corresponding rate constants were 8.53 ± 1.36, 10.1 ± 1.6, 7.86 ± 1.30, 8.08 ± 1.33, 9.10 ± 1.50, and 7.14 ± 1.20 (in units of 10(-11) cm(3) molecule(-1) s(-1)), respectively, measured by gas chromatography with a flame ionization detector (GC-FID), using a relative technique. Theoretical calculations concerning the OH-addition and H-abstraction reaction channels were also performed for these reactions to further understand the reaction mechanism and the relative importance of the H-abstraction reaction. By contrast to previously reported results, the H-abstraction channel is a non-negligible reaction channel for reactions of OH radicals with these hexenols. The rate constants of the H-abstraction channel are comparable with those for the OH-addition channel and contribute >20% for most of the studied alcohols, even >50% for (E)-3-hexen-1-ol. Thus, H-abstraction channels may have an important role in the reactions of these alcohols with OH radicals and must be considered in certain atmospheric chemical mechanisms and models. PMID:26274814

  18. Towards a More Complete and Accurate Experimental Nuclear Reaction Data Library (EXFOR). International Collaboration Between Nuclear Reaction Data Centres (NRDC)

    SciTech Connect

    Otuka, N.; Pritychenko, B.; Otuka, N.; Dupont, E.; Semkova, V.; Pritychenko, B.; Blokhin, A. I.; Aikawa, M.; Babykina, S.; Bossant, M.; Chen, G.; Dunaeva, S.; Forrest, R. A.; Fukahori, T.; Furutachi, N.; Ganesan, S.; Ge, Z.; Gritzay, O. O.; Herman, M.; Hlavac, S.; Kato, K.; Lalremruata, B.; Lee, Y. O.; Makinaga, A.; Matsumoto, K.; Mikhaylyukova, M.; Pikulina, G.; Pronyaev, V. G.; Saxena, A.; Schwerer, O.; Simakov, S. P.; Soppera, N.; Suzuki, R.; Takacs, S.; Tao, X.; Taova, S.; Tarkanyi, F.; Varlamov, V. V.; Wang, J.; Yang, S. C.; Zerkin, V.; Zhuang, Y.

    2014-06-01

    The International Network of Nuclear Reaction Data Centres (NRDC) coordinated by the IAEA Nuclear Data Section (NDS) successfully collaborates in the maintenance and development of the EXFOR library. Likewise, as the scope of published data expands (e.g. to higher energy, to heavier projectile) to meet the needs of research and applications, it has become a challenging task to maintain both the completeness and accuracy of the EXFOR library. Evolution of the library highlighting recent developments is described.

  19. Towards a More Complete and Accurate Experimental Nuclear Reaction Data Library (EXFOR): International Collaboration Between Nuclear Reaction Data Centres (NRDC)

    SciTech Connect

    Otuka, N.; Dupont, E.; Semkova, V.; Pritychenko, B.; Blokhin, A.I.; Aikawa, M.; Babykina, S.; Bossant, M.; Chen, G.; Dunaeva, S.; Forrest, R.A.; Fukahori, T.; Furutachi, N.; Ganesan, S.; Ge, Z.; Gritzay, O.O.; Herman, M.; Hlavač, S.; and others

    2014-06-15

    The International Network of Nuclear Reaction Data Centres (NRDC) coordinated by the IAEA Nuclear Data Section (NDS) successfully collaborates in the maintenance and development of the EXFOR library. As the scope of published data expands (e.g. to higher energy, to heavier projectile) to meet the needs of research and applications, it has become a challenging task to maintain both the completeness and accuracy of the EXFOR library. Evolution of the library highlighting recent developments is described.

  20. Growth of polyphenyls via ion-molecule reactions: An experimental and theoretical mechanistic study

    SciTech Connect

    Aysina, Julia; Tosi, Paolo; Ascenzi, Daniela; Maranzana, Andrea; Tonachini, Glauco

    2013-05-28

    The reactivity of biphenylium cations C{sub 12}H{sub 9}{sup +} with benzene C{sub 6}H{sub 6} is investigated in a joint experimental and theoretical approach. Experiments are performed by using a triple quadruple mass spectrometer equipped with an atmospheric pressure chemical ion source to generate C{sub 12}H{sub 9}{sup +} via dissociative ionization of various isomers of the neutral precursor hydroxybiphenyl (C{sub 12}H{sub 10}O). C-C coupling reactions leading to hydrocarbon growth are observed. The most abundant ionic products are C{sub 18}H{sub 15}{sup +}, C{sub 18}H{sub 13}{sup +}, C{sub 17}H{sub 12}{sup +}, and C{sub 8}H{sub 7}{sup +}. The dependence of product ion yields on the kinetic energy of reagent ions, as well as further experiments performed using partial isotopic labelling of reagents, support the idea that the reaction proceeds via a long lived association product, presumably the covalently bound protonated terphenyl C{sub 18}H{sub 15}{sup +}. Its formation is found to be exothermic and barrierless and, therefore, might occur under the low pressure and temperature conditions typical of planetary atmospheres and the interstellar medium. Theoretical calculations have focussed on the channel leading to C{sub 8}H{sub 7}{sup +} plus C{sub 10}H{sub 8}, identifying, as the most probable fragments, the phenylethen-1-ylium cation and naphthalene, thus suggesting that the pathway leading to them might be of particular interest for the synthesis of polycyclic aromatic hydrocarbons. Both experiments and theory agree in finding this channel exoergic but hampered by small barriers of 2.7 and 3.7 kcal mol{sup -1} on the singlet potential energy surface.

  1. Theoretical and experimental cross sections for neutron reactions on /sup 64/Zinc

    SciTech Connect

    Rutherford, D.A.

    1988-03-01

    Accurate measurements of the /sup 64/Zn (n,2n)/sup 63/Zn and /sup 64/Zn (n,p)/sup 64/Cu cross sections at 14.8 MeV have been made using a Texas Nuclear Neutron Generator and the activation technique. A NaI(Tl) spectrometer (using two 6'' x 6'' NaI detectors/crystals) was ued to measure the gamma radiation emitted in coincidence from the positron-emitting decay products. The measurements were made relative to /sup 65/Cu (n,2n)/sup 64/Cu and /sup 63/Cu (n,2n)/sup 62/Cu cross sections, which have similar half-lives, radiation emission, and were previously measured to high accuracy (2%). The value obtained for the (n,2n) measurement was 199 +- 6 millibarns, and a value of 176 +- 4.5 millibarns was obtained for the (n,p) measurement. In concert, a theoretical analysis of neutron induced reactions on /sup 64/Zn was performed at Los Alamos National Laboratory using the Hauser-Feshbach statistical theory in the GNASH code over an energy range of 100 keV to 20 MeV. Calculations included width fluctuation corrections, direct reaction contributions, and preequilibrium corrections above 6 MeV. Neutron optical model potentials were determined for zinc. The theoretical values agree with the new 14.8 MeV measurements approximately within experimental error, with calculations of 201 millibarns for the (n,2n) cross section and 170 millibarns for the (n,p) cross section. Results from the analysis will be made available in National Evaluated Nuclear Data Format (ENDF/B) for fusion energy applications. 50 refs., 34 figs., 10 tabs.

  2. Evidence of alkali rich melt reactions with mantle peridotite : Natural observations and experimental analogues

    NASA Astrophysics Data System (ADS)

    Grant, T. B.; Milke, R.; Wunder, B.

    2012-04-01

    The Heldburg Phonolite, (Thuringia, Germany) is peculiar in its nature due to its absence of a Eu anomaly, and hence lack of feldspar fractionation, as well as the presence of spinel lherzolite xenocrysts. These observations suggest a higher than normal (mantle) pressure of origin, and its potential as a metasomatic agent at depth is explored in this work. Disequilibrium between the phonolite and its entrained upper mantle xenocrysts resulted in the development of secondary reaction rim assemblages of; (1) phlogopite + minor diopside around olivine, (2) pargasitic amphibole, phlogopite and minor diopside around orthopyroxene. We document both the natural rims and the attempts to reproduce them under experimental conditions, in order to elucidate the likely origin of the phonolite and its efficacy for metasomatising the upper mantle. Platinum capsules were loaded with mixtures of crushed mineral separates, (of pure synthetic forsterite, San Carlos olivine, synthetic enstatite or a natural enstatite from Kilosa, Tanzania) with a synthetic Fe-free phonolite melt in a 16:84% weight ratio, respectively. Experiments were run in a piston cylinder apparatus with CaF2 as the pressure medium. In addition to varying PT conditions, a wide range of water contents were tested (0-14wt%). It was found that pressures of 10-14 kbar, and temperatures of 900-1000°C, satisfy the conditions at which the reactions can form, thus, it is likely that the phonolite existed at upper mantle conditions. Water must be present to stabilize the desired hydrous phases, with >6wt% required at 900°C and 10 kbar. The destabilization of feldspar is also essential to the process, hence higher water contents are needed at the lowest PT conditions compared to 4-5 wt. % H2O at greater PT. The formation of amphibole around enstatite appears to be affected by sluggish reaction kinetics and the orientation of the host pyroxene, sometimes leading to diopside single rims. Furthermore we note some of the

  3. Melt-Peridotite Reaction Mechanism of North China Craton Destruction: Experimental Constrains

    NASA Astrophysics Data System (ADS)

    Wang, C.; Jin, Z.; Gao, S.; Zhang, J.; Zheng, S.

    2009-12-01

    Although the geoscientsts in the world have reached an agreement about the Mesozoic thinning of North China Craton, the dynamics of this process is still under debate, especially the thinning mechanism. There are two popular thinning mechanisms were proposed for the North China Craton, one is the delamination model and the other is thermo-mechanical erosion model. The delamination model has aroused great interests since Gao et al. use it to explain the formation of Xilonggou high Mg# andesite from Liaoxi region of Liaoning Province. These Lavas, which possessed an adakitic signature with high Mg#, were believed to origin by the interaction between silica rich and yttrium delepted melt, which are formed by partile melting of low crust eclogite, and asthenospheric peridotite. The discovery of zoned mantle olivine and pyroxene xenocrysts, especially zoned mantle peridotitic xenoliths in Mesozoic basaltic rocks from eastern North China, indicates that peridotite-melt reaction was widespread in Mesozoic lithospheric mantle beneath the southeastern North China craton. Such interaction could be an important mechanism for the compositional transformation and rapid enrichment of the lithospheric mantle. We conducted a series of experiments at a pressure of 2.0 GPa and temperatures of 1250-1400 °C using Bixiling eclogite and Damaping peridotite as starting materials to study the mechanism of melt-peridotite reaction. Our results show that olivine and orthopyroxene were dissolved in the reacting melts between eclogite and peridotite, resulting in clinopyroxene precipitation along the interface of melts and lherzolite. The experimental run products, possessing a lherzolite-pyroxenite-garnet pyroxenite sequence, are identical to the composite mantle xenoliths in the Neogene Hannuoba basalt of the North China craton. The later is considered as strong evidence of the maffic lower continental crust recycling into the mantle during the Mesozoic Era. The reacting melts have a high

  4. Electrochemical Synthesis of Phenol-aniline Copolymerization Coating on 304 Stainless Steel Anodes and Coating Microstructure Analysis

    NASA Astrophysics Data System (ADS)

    Bao, Li-yin; Xiong, Rong-chun; Zhang, Wen; Wei, Gang

    2011-02-01

    Electrochemical copolymerization of phenol and aniline was achieved on 304 stainless steel anodes in neutral water solution with an electrolyte of Na2SO4O4. Compared with pit corrosion potential of different copolymer coatings, the best solution composition was 0.09 mol/L phenol and 0.01 mol/L aniline. Through infrared spectrum analysis, polyaniline structure was proved in phenol-aniline copolymer, as well as more side chains. Scanning electron microscope was used to analyze microstructure of copolymer coating, taking advantage of part solubility of phenol-aniline copolymer in tetrahydrofuran, the bifurcate network structure was observed. The copolymer coating microstructure was summarized, compared with the performance of polyphenol coatings, the reasons of corrosion resistance enhancement with the addition of aniline in electropolymerization reaction was assumed as well.

  5. An experimental study of the organic molecules produced in cometary and interstellar ice analogs by thermal formaldehyde reactions

    NASA Technical Reports Server (NTRS)

    Schutte, W. A.; Allamandola, L. J.; Sandford, S. A.

    1993-01-01

    Results of an experimental study tracing thermal formaldehyde reactions in astrophysically relevant ices in dense molecular clouds are reported. The formaldehyde chemistry during warm-up of ices containing H2CO and one or more of the molecules H2O, CH3OH, CO, O2, and NH3 were monitored using IR spectroscopy. Conversion of H2CO into residues was observed to start at about 40 K for NH3:H2CO ices and at about 80 K in H2O-rich ices. A total of five different organic products of these reactions were distinguished: POM and reaction products of H2CO and H2O, CH3OH, and NH3. Given the measured reaction paths and efficiencies, it is estimated that on the order of 1 percent of the organics found in the coma of Comet P/Halley could have been produced by thermal formaldehyde reactions taking place in the nucleus.

  6. Experimental and Theoretical Study of Thermodynamics of the Reaction of Titania and Water at High Temperatures

    NASA Technical Reports Server (NTRS)

    Nguyen, Quynhgiao N.; Myers, Dwight L.; Jacobson, Nathan S.; Opila, Elizabeth J.

    2014-01-01

    The transpiration method was used to determine the volatility of titanium dioxide (TiO2) in water vapor-containing environments at temperatures between 1473 and 1673 K. Water contents ranged from 0 to 76 mole % in oxygen or argon carrier gases for 20 to 250 hr exposure times. Results indicate that oxygen is not a key contributor to volatilization and the primary reaction for volatilization in this temperature range is: TiO2(s) + H2O(g) = TiO(OH)2(g). Data were analyzed with both the second and third law methods to extract an enthalpy and entropy of formation. The geometry and vibrational frequencies of TiO(OH)2(g) were computed using B3LYP density functional theory, and the enthalpy of formation was computed using the coupled-cluster singles and doubles method with a perturbative correction for connected triple substitutions [CCSD(T)]. Thermal functions are calculated using both a structure with bent and linear hydroxyl groups. Calculated second and third heats show closer agreement with the linear hydroxyl group, suggesting more experimental and computational spectroscopic and structural work is needed on this system.

  7. Transfer reactions in inverse kinematics: An experimental approach for fission investigations

    NASA Astrophysics Data System (ADS)

    Rodríguez-Tajes, C.; Farget, F.; Derkx, X.; Caamaño, M.; Delaune, O.; Schmidt, K.-H.; Clément, E.; Dijon, A.; Heinz, A.; Roger, T.; Audouin, L.; Benlliure, J.; Casarejos, E.; Cortina, D.; Doré, D.; Fernández-Domínguez, B.; Jacquot, B.; Jurado, B.; Navin, A.; Paradela, C.; Ramos, D.; Romain, P.; Salsac, M. D.; Schmitt, C.

    2014-02-01

    Inelastic and multinucleon transfer reactions between a 238U beam, accelerated at 6.14 MeV/u, and a 12C target were used for the production of neutron-rich, fissioning systems from U to Cm. A Si telescope, devoted to the detection of the targetlike nuclei, provided a characterization of the fissioning systems in atomic and mass numbers, as well as in excitation energy. Cross sections and angular and excitation-energy distributions were measured for the inelastic and transfer channels. Possible excitations of the targetlike nuclei were experimentally investigated for the first time, by means of γ-ray measurements. The decays from the first excited states of 12C, 11B, and 10Be were observed with probabilities of 0.12-0.14, while no evidence for the population of higher-lying states was found. Moreover, the fission probabilities of 238U, 239Np and 240,241,242Pu and 244Cm were determined as a function of the excitation energy.

  8. Experimental and Estimated Rate Constants for the Reactions of Hydroxyl Radicals with Several Halocarbons

    NASA Technical Reports Server (NTRS)

    DeMore, W.B.

    1996-01-01

    Relative rate experiments are used to measure rate constants and temperature dependencies of the reactions of OH with CH3F (41), CH2FCl (31), CH2BrCl (30B1), CH2Br2 (3OB2), CHBr3 (2OB3), CF2BrCHFCl (123aBl(alpha)), and CF2ClCHCl2 (122). Rate constants for additional compounds of these types are estimated using an empirical rate constant estimation method which is based on measured rate constants for a wide range of halocarbons. The experimental data are combined with the estimated and previously reported rate constants to illustrate the effects of F, Cl, and Br substitution on OH rate constants for a series of 19 halomethanes and 25 haloethanes. Application of the estimation technique is further illustrated for some higher hydrofluorocarbons (HFCs), including CHF2CF2CF2CF2H (338pcc), CF3CHFCHFCF2CF3 (43-10mee), CF3CH2CH2CF3 (356ffa), CF3CH2CF2CH2CF3 (458mfcf), CF3CH2CHF2 (245fa), and CF3CH2CF2CH3 (365mfc). The predictions are compared with literature data for these compounds.

  9. Experimental Correlation of Substrate Position with Reaction Outcome in the Aliphatic Halogenase, SyrB2.

    PubMed

    Martinie, Ryan J; Livada, Jovan; Chang, Wei-chen; Green, Michael T; Krebs, Carsten; Bollinger, J Martin; Silakov, Alexey

    2015-06-01

    The iron(II)- and 2-(oxo)glutarate-dependent (Fe/2OG) oxygenases catalyze an array of challenging transformations, but how individual members of the enzyme family direct different outcomes is poorly understood. The Fe/2OG halogenase, SyrB2, chlorinates C4 of its native substrate, l-threonine appended to the carrier protein, SyrB1, but hydroxylates C5 of l-norvaline and, to a lesser extent, C4 of l-aminobutyric acid when SyrB1 presents these non-native amino acids. To test the hypothesis that positioning of the targeted carbon dictates the outcome, we defined the positions of these three substrates by measuring hyperfine couplings between substrate deuterium atoms and the stable, EPR-active iron-nitrosyl adduct, a surrogate for reaction intermediates. The Fe-(2)H distances and N-Fe-(2)H angles, which vary from 4.2 Å and 85° for threonine to 3.4 Å and 65° for norvaline, rationalize the trends in reactivity. This experimental correlation of position to outcome should aid in judging from structural data on other Fe/2OG enzymes whether they suppress hydroxylation or form hydroxylated intermediates on the pathways to other outcomes. PMID:25965587

  10. Experimental Correlation of Substrate Position with Reaction Outcome in the Aliphatic Halogenase, SyrB2

    PubMed Central

    Martinie, Ryan J.; Livada, Jovan; Chang, Wei-chen; Green, Michael T.; Krebs, Carsten; Bollinger, J. Martin; Silakov, Alexey

    2015-01-01

    The iron(II)- and 2-(oxo)glutarate-dependent (Fe/2OG) oxygenases catalyze an array of challenging transformations, but how individual members of the enzyme family direct different outcomes is poorly understood. The Fe/2OG halogenase, SyrB2, chlorinates C4 of its native substrate, L-threonine appended to the carrier protein, SyrB1, but hydroxylates C5 of L-norvaline and, to a lesser extent, C4 of L-aminobutyric acid when SyrB1 presents these non-native amino acids. To test the hypothesis that positioning of the targeted carbon dictates the outcome, we defined the positions of these three substrates by measuring hyperfine couplings between substrate deuterium atoms and the stable, EPR-active iron-nitrosyl adduct, a surrogate for reaction intermediates. The Fe-2H distances and N-Fe-2H angles, which vary from 4.2 Å and 85° for threonine to 3.4 Å and 65° for norvaline, rationalize the trends in reactivity. This experimental correlation of position to outcome should aid in judging from structural data on other Fe/2OG enzymes whether they suppress hydroxylation or form hydroxylated intermediates on the pathways to other outcomes. PMID:25965587

  11. Precise synthesis of thermoreversible block copolymers containing reactive furfuryl groups via living anionic polymerization: the countercation effect on block copolymerization behavior

    DOE PAGESBeta

    Kang, Beom-Goo; Pramanik, Nabendu; Singha, Nikhil K; Lee, Jae-Suk; Mays, Jimmy

    2015-01-01

    The anionic block copolymerization of 4,4 -vinylphenyl-N,N-bis(4-tert-butylphenyl)benzenamine (A) with furfuryl isocyanate (B) was carried out using potassium naphthalenide (K-Naph) in tetrahydrofuran at 78 and 98 C to prepare well-defined block copolymers containing furan groups for the formation of thermoreversible networks via a Diels Alder (DA) reaction. While no block copolymerization was observed in the absence of sodium tetraphenylborate (NaBPh4) due to side reactions, well-defined poly-(B-b-A-b-B) (PBAB) copolymers with controlled molecular weights (Mn = 18 700 19 500 g mol 1) and narrow molecular weight distributions (Mw/Mn = 1.08 1.17) were successfully synthesized in the presence of excess NaBPh4. The occurrencemore » of the undesirable side reactions during polymerization of B was effectively prevented by NaBPh4, which results in the change in the countercation from K+ to Na+ for further polymerization of B. The cross-linking via the DA reaction between the furan groups of PBAB and bismaleimide was proved by FT-IR and differential scanning calorimetry (DSC), and the thermoreversible properties of the cross-linked polymer were subsequently investigated using DSC and solubility testing.« less

  12. Precise synthesis of thermoreversible block copolymers containing reactive furfuryl groups via living anionic polymerization: the countercation effect on block copolymerization behavior

    SciTech Connect

    Kang, Beom-Goo; Pramanik, Nabendu; Singha, Nikhil K; Lee, Jae-Suk; Mays, Jimmy

    2015-01-01

    The anionic block copolymerization of 4,4 -vinylphenyl-N,N-bis(4-tert-butylphenyl)benzenamine (A) with furfuryl isocyanate (B) was carried out using potassium naphthalenide (K-Naph) in tetrahydrofuran at 78 and 98 C to prepare well-defined block copolymers containing furan groups for the formation of thermoreversible networks via a Diels Alder (DA) reaction. While no block copolymerization was observed in the absence of sodium tetraphenylborate (NaBPh4) due to side reactions, well-defined poly-(B-b-A-b-B) (PBAB) copolymers with controlled molecular weights (Mn = 18 700 19 500 g mol 1) and narrow molecular weight distributions (Mw/Mn = 1.08 1.17) were successfully synthesized in the presence of excess NaBPh4. The occurrence of the undesirable side reactions during polymerization of B was effectively prevented by NaBPh4, which results in the change in the countercation from K+ to Na+ for further polymerization of B. The cross-linking via the DA reaction between the furan groups of PBAB and bismaleimide was proved by FT-IR and differential scanning calorimetry (DSC), and the thermoreversible properties of the cross-linked polymer were subsequently investigated using DSC and solubility testing.

  13. Comparison of experimental and theoretical reaction rail currents, rail voltages, and airgap fields for the linear induction motor research vehicle

    NASA Technical Reports Server (NTRS)

    Elliott, D. G.

    1977-01-01

    Measurements of reaction rail currents, reaction rail voltages, and airgap magnetic fields in tests of the Linear Induction Motor Research Vehicle (LIMRV) were compared with theoretical calculations from the mesh/matrix theory. It was found that the rail currents and magnetic fields predicted by the theory are within 20 percent of the measured currents and fields at most motor locations in most of the runs, but differ by as much as a factor of two in some cases. The most consistent difference is a higher experimental than theoretical magnetic field near the entrance of the motor and a lower experimental than theoretical magnetic field near the exit. The observed differences between the theoretical and experimental magnetic fields and currents do not account for the differences of as much as 26 percent between the theoretical and experimental thrusts.

  14. Experimental study on controls on fluid chemistry and permeability evolution during serpentinization reactions

    NASA Astrophysics Data System (ADS)

    Farough, A.; Moore, D. E.; Lockner, D. A.; Lowell, R. P.

    2013-12-01

    Serpentinization plays a key role in hydrothermal processes and structural deformation at slow and ultraslow mid-ocean ridges, where it is commonly associated with the formation of oceanic core complexes and detachment faults. Many details of how serpentinization reactions progress at small scales and the links between the reactions and changes in permeability and stresses are poorly understood. To advance our understanding of the evolution of permeability and fluid chemistry accompanying serpentinization reactions and provide a framework for developing more realistic models at a larger scale, we performed a series of high-temperature permeability experiments on fractured solid ultramafic rock samples that reasonably simulate serpentinization in natural settings. Experimental conditions were 260°C, 50 MPa confining pressure, and 20×2 MPa pore pressure. Ultramafic rock types containing different proportions of olivine and pyroxene were tested, to investigate the effect of mineral assemblage on fluid-rock interaction and permeability. Samples were cylindrical cores of 18 mm diameter and 23 mm length that were split axially to form a well-mated tensile fracture, jacketed in a 0.5 mm thick teflon liner and inserted into a 0.4 mm thick annealed silver jacket. A 7.5 mm thick layer of the same rock, crushed and sieved (0.18-1.0 mm size range) was placed on the inlet side of the sample to produce a coarse-grained gouge. The gouge layer provided a heated fluid reservoir with which the deionized water, used as pore fluid, could equilibrate before entering the fracture. Routinely, about 1 cm3 of water was pumped through the sample each day and collected (without dropping sample pore pressure) for chemical analysis. Pore fluid flow was in one direction and the pore pressure change and flow rate were recorded to determine permeability. In most samples, the initial fracture permeability at 260°C was between 10-15 and 10-18 m2, and decreased by about 3 orders of magnitude in

  15. Palladium(II)-catalyzed copolymerization of styrenes with carbon monoxide: mechanism of chain propagation and chain transfer.

    PubMed

    Rix, Francis C; Rachita, Michael J; Wagner, Mark I; Brookhart, Maurice; Milani, Barbara; Barborak, James C

    2009-11-01

    A mechanistic interpretation of the [(1,10-phenanthroline)Pd(CH(3))(CH(3)CN)](+)[BArF](-) (1a) and [(2,2'-bipyridine)Pd(CH(3))(CH(3)CN)](+)[BArF](-) (1b) (BArF = 3,5-(CF(3))(2)-C(6)H(3)) catalyzed perfectly alternating copolymerization of styrenes with CO is reported. The copolymerization in CH(2)Cl(2) or chlorobenzene has been found to be first order in styrene and inverse first order in CO concentrations. The microscopic steps involved in the catalytic cycle have been studied via low temperature NMR techniques. Palladium alkyl chelate complex [(2,2'-bipyridine)Pd(CHArCH(2)C(O)CH(3)](+)[BArF](-) (5b sigma) and [(2,2'-bipyridine)Pd(eta(3)-CH(CH(2)C(O)CH(3))Ar)](+)[BArF](-) (5b pi), existing in equilibrium, were prepared. Treatment of 5b sigma,pi with (13)CO followed by 4-tert-butylstyrene at -78 degrees C allowed for (13)C NMR monitoring of the alternating chain growth of a series of palladium acyl carbonyl complexes. The acyl carbonyl species, representing the catalyst resting state, is in equilibrium with a palladium acyl styrene complex. The equilibrium constant, K(4), measured between [(phen)Pd(CO)(C(O)CH(3)](+)[BArF](-) (3a) and [(phen)Pd(C(O)CH(3))-(C(6)H(5)C=CH(2))](+)[BArF](-) (8a), was determined to be 2.84 +/- 2.8 x 10(-7) at -66 degrees C. The barrier to migratory insertion in 8a was determined (DeltaG(double dagger) (-66 degrees C) = 15.6 +/- 0.1 kcal mol(-1)). From the experimentally determined kinetic and thermodynamic data for the copolymerization of styrene with CO a mechanistic model has been constructed. The ability of this model to predict catalyst turnover frequency (TOF) was used as a test of its validity. A series of para-substituted styrenes, p-XC(6)H(4)CH=CH(2) (X = -OCH(3), -CH(3), -H, -Cl), were copolymerized with CO. A Hammett treatment of TOF for the series showed that electron-donating groups increase the rate of copolymerization (rho p = -0.8). The ratio of chain transfer to chain propagation was found to increase with styrene

  16. Semen characteristics and reaction time of Yankasa rams experimentally infected with Trypanosoma evansi infection.

    PubMed

    Ogundele, Francis Abidemi; Okubanjo, Oluyinka Oluseyi; Ajanusi, Olagunju Joseph; Fadason, Samuel Tanko

    2016-08-01

    Trypanosomosis is a serious, often fatal disease of domestic animals and humans, and a major constraint to livestock productivity and agricultural development in areas of Africa, Latin America, the Middle East, and Asia. It is caused by hemoflagelate protozoan of the genus Trypanosoma. Several species of Trypanosoma such as Trypanosoma congolense, Trypanosoma vivax, Trypanosoma brucei, and Trypanosoma evansi are known to infect domestic animals. Trypanosoma evansi is one of the most widespread pathogenic trypanosomes in the world causing disease known as "Surra" in animals. The effects of experimental T evansi infection on some aspects of reproduction in Yankasa rams were investigated over a 108-day period. Rams in the infected group A (n = 7) were each inoculated with 1 × 10(6) trypanosomes in 1 mL of donor blood via the jugular vein, whereas the control group B (n = 5) were administered 1 mL of normal saline. Semen volume, gross motility, live and/or dead sperm ratio, sperm morphologic abnormalities, and concentration as well as reaction time of infected and control rams were evaluated on a weekly basis. The results showed a nonsignificant (P > 0.05) decrease in semen volume and a significant (P < 0.05) decrease in concentration compared to the control rams. Reaction time showed considerable significant (P < 0.05) increase from preinfection values 26.7 ± 4.54 to 94.7 ± 7.54 seconds compared to control 32.9 ± 2.64 to 33.4 ± 4.78 seconds. Furthermore, semen gross motility for infected rams differed significantly (P < 0.05) from those of the control. There was a significant surge (P < 0.05) in the total sperm morphologic abnormalities in the infected rams to 90.75 ± 2.73% by week 20 (14 weeks after infection), compared to preinfection value of 20.9 ± 0.52%. The outcome of this study suggests that infection with T evansi in Yankasa rams has far reaching severe effects on their reproductive performance. PMID:27188633

  17. Copolymeric nanofilm platform for controlled and localized therapeutic delivery.

    PubMed

    Chow, Edward Kai-Hua; Pierstorff, Erik; Cheng, Genhong; Ho, Dean

    2008-01-01

    Nanomaterials such as block copolymeric membranes provide a platform for both cellular interrogation and biological mimicry. Their biomimetic properties are based upon the innate possession of hydrophilic and hydrophobic units that enable their integration with a broad range of therapeutic materials. As such, they can be engineered for specific applications in nanomedicine, including controlled/localized drug delivery. Here we describe a method for the functionalization of the polymethyloxazoline-polydimethylsiloxane-polymethyloxazoline (PMOXA-PDMS-PMOXA) block copolymer with anti-inflammatory molecules to develop copolymer-therapeutic hybrids, effectively conferring biological functionality to a versatile synthetic nanomembrane matrix and creating a platform for an anti-inflammatory drug delivery system. Utilizing self-assembly and Langmuir-Blodgett deposition methods, we mixed copolymers with dexamethasone (Dex), an anti-inflammatory glucocorticoid receptor agonist. The successful mixing of the copolymer with the drug was confirmed by surface pressure isotherms and fluorescence microscopy. Furthermore, at 4 nm thick per layer, orders of magnitude thinner than conventional drug delivery coatings, these dexamethasone-copolymer mixtures (PolyDex) suppressed in vitro expression of the inflammatory cytokines/signaling elements interleukin 6 (IL-6), interleukin 12 (IL-12), tumor necrosis factor alpha (TNFalpha), inducible nitric oxide synthase (iNOS), and interferon gamma inducible protein (IP-10). Finally, PolyDex maintained its anti-inflammatory properties in vivo confirmed through punch biopsies with tissue imagery via hematoxylin/eosin and macrophage specific staining using CD11b. Thus, we demonstrated that PolyDex may be utilized as a localized, highly efficient drug-copolymer composite for active therapeutic delivery to confer anti-inflammatory protection or as a platform material for broad drug elution capabilities. PMID:19206545

  18. Uncovering the Role of Metal Catalysis in Tetrazole Formation by an In Situ Cycloaddition Reaction: An Experimental Approach.

    PubMed

    Zhong, Di-Chang; Wen, Ya-Qiong; Deng, Ji-Hua; Luo, Xu-Zhong; Gong, Yun-Nan; Lu, Tong-Bu

    2015-09-28

    Using an experimental approach, the role of metal catalysis has been investigated in the in situ cycloaddition reaction of nitrile with azide to form tetrazoles. It has been shown that metal catalysis serves to activate the cyano group in the nitrile reagent by a coordinative interaction. PMID:26293313

  19. Growth of polyaromatic molecules via ion-molecule reactions: An experimental and theoretical mechanistic study

    SciTech Connect

    Ascenzi, Daniela; Aysina, Julia; Tosi, Paolo; Maranzana, Andrea; Tonachini, Glauco

    2010-11-14

    The reactivity of naphthyl cations with benzene is investigated in a joint experimental and theoretical approach. Experiments are performed by using guided ion beam tandem mass spectrometers equipped with electron impact or atmospheric pressure chemical ion sources to generate C{sub 10}H{sub 7}{sup +} with different amounts of internal excitation. Under single collision conditions, C-C coupling reactions leading to hydrocarbon growth are observed. The most abundant ionic products are C{sub 16}H{sub 13}{sup +}, C{sub 16}H{sub n}{sup +} (with n=10-12), and C{sub 15}H{sub 10}{sup +}. From pressure-dependent measurements, absolute cross sections of 1.0{+-}0.3 and 2{+-}0.6 A{sup 2} (at a collision energy of about 0.2 eV in the center of mass frame) are derived for channels leading to the formation of C{sub 16}H{sub 12}{sup +} and C{sub 15}H{sub 10}{sup +} ions, respectively. From cross section values a phenomenological total rate constant k=(5.8{+-}1.9)x10{sup -11} cm{sup 3} s{sup -1} at an average collision energy of about 0.27 eV can be estimated for the process C{sub 10}H{sub 7}{sup +}+C{sub 6}H{sub 6}{yields} all products. The energy behavior of the reactive cross sections, as well as further experiments performed using partial isotopic labeling of reagents, support the idea that the reaction proceeds via a long lived association product, presumably the covalently bound protonated phenylnaphthalene, from which lighter species are generated by elimination of neutral fragments (H, H{sub 2}, CH{sub 3}). A major signal relevant to the fragmentation of the initial adduct C{sub 16}H{sub 13}{sup +} belongs to C{sub 15}H{sub 10}{sup +}. Since it is not obvious how CH{sub 3} loss from C{sub 16}H{sub 13}{sup +} can take place to form the C{sub 15}H{sub 10}{sup +} radical cation, a theoretical investigation focuses on possible unimolecular transformations apt to produce it. Naphthylium can act as an electrophile and add to the {pi} system of benzene, leading to a barrierless

  20. Experimental study on the reaction between nuclear graphite IG-110 and carbon dioxide

    NASA Astrophysics Data System (ADS)

    Kim, Eung Soo; No, Hee Cheon

    2006-03-01

    With nuclear graphite IG-110, we measured various kinetic parameters and reaction rates of the C/CO 2 reaction. As a result, its activation energy is 295 ± 8 kJ/mol and the order of reaction is 0.9. It turns out that the rate of C/CO 2 reaction is much smaller than the rate of the C/O 2 reaction which is dominant in HTGR air-ingress below 1400 °C. Finally, we propose the following rate equation for the C/CO 2 reaction of IG-110: r(kg/m3s)=3.95×103·exp-{290 000}/{R·T}·(p)0.9.

  1. Temperature trends for reaction rates, hydrogen generation, and partitioning of iron during experimental serpentinization of olivine

    NASA Astrophysics Data System (ADS)

    McCollom, Thomas M.; Klein, Frieder; Robbins, Mark; Moskowitz, Bruce; Berquó, Thelma S.; Jöns, Niels; Bach, Wolfgang; Templeton, Alexis

    2016-05-01

    A series of laboratory experiments were conducted to examine how partitioning of Fe among solid reaction products and rates of H2 generation vary as a function of temperature during serpentinization of olivine. Individual experiments were conducted at temperatures ranging from 200 to 320 °C, with reaction times spanning a few days to over a year. The extent of reaction ranged from <1% to ∼23%. Inferred rates for serpentinization of olivine during the experiments were 50-80 times slower than older studies had reported but are consistent with more recent results, indicating that serpentinization may proceed more slowly than previously thought. Reaction products were dominated by chrysotile, brucite, and magnetite, with minor amounts of magnesite, dolomite, and iowaite. The chrysotile contained only small amounts of Fe (XFe = 0.03-0.05, with ∼25% present as ferric Fe in octahedral sites), and displayed little variation in composition with reaction temperature. Conversely, the Fe contents of brucite (XFe = 0.01-0.09) increased steadily with decreasing reaction temperature. Analysis of the reaction products indicated that the stoichiometry of the serpentinization reactions varied with temperature, but remained constant with increasing reaction progress at a given temperature. The observed distribution of Fe among the reaction products does not appear to be entirely consistent with existing equilibrium models of Fe partitioning during serpentinization, suggesting improved models that include kinetic factors or multiple reaction steps need to be developed. Rates of H2 generation increased steeply from 200 to 300 °C, but dropped off at higher temperatures. This trend in H2 generation rates is attributable to a combination of the overall rate of serpentinization reactions and increased partitioning of Fe into brucite rather than magnetite at lower temperatures. The results suggest that millimolal concentration of H2 could be attained in moderately hot hydrothermal

  2. Population of high spin states in very heavy ion transfer reactions. The experimental evidence

    SciTech Connect

    Guidry, M.W.

    1985-01-01

    Transfer reactions have been studied for some time with light heavy ions such as oxygen. Although states of spin I approx.10 h are sometimes populated in such reactions, it is assumed that collective excitation is small, and the transferred particles are responsible for the angular momentum transfer. In this paper we will discuss a qualitatively different kind of transfer reaction using very heavy ions (A greater than or equal to 40). In these reactions the collective excitation in both the entrance and exit channels is strong, and there may be appreciable angular momentum transfer associated with inelastic excitation. 12 refs., 13 figs.

  3. Heteroleptic tin(II) initiators for the ring-opening (co)polymerization of lactide and trimethylene carbonate: mechanistic insights from experiments and computations.

    PubMed

    Wang, Lingfang; Kefalidis, Christos E; Sinbandhit, Sourisak; Dorcet, Vincent; Carpentier, Jean-François; Maron, Laurent; Sarazin, Yann

    2013-09-27

    The tin(II) complexes {LO(x)}Sn(X) ({LO(x)}(-) =aminophenolate ancillary) containing amido (1-4), chloro (5), or lactyl (6) coligands (X) promote the ring-opening polymerization (ROP) of cyclic esters. Complex 6, which models the first insertion of L-lactide, initiates the living ROP of L-LA on its own, but the amido derivatives 1-4 require the addition of alcohol to do so. Upon addition of one to ten equivalents of iPrOH, precatalysts 1-4 promote the ROP of trimethylene carbonate (TMC); yet, hardly any activity is observed if tert-butyl (R)-lactate is used instead of iPrOH. Strong inhibition of the reactivity of TMC is also detected for the simultaneous copolymerization of L-LA and TMC, or for the block copolymerization of TMC after that of L-LA. Experimental and computational data for the {LO(x)}Sn(OR)complexes (OR=lactyl or lactidyl) replicating the active species during the tin(II)-mediated ROP of L-LA demonstrate that the formation of a five-membered chelate is largely favored over that of an eight-membered one, and that it constitutes the resting state of the catalyst during this (co)polymerization. Comprehensive DFT calculations show that, out of the four possible monomer insertion sequences during simultaneous copolymerization of L-LA and TMC: 1) TMC then TMC, 2) TMC then L-LA, 3) L-LA then L-LA, and 4) L-LA then TMC, the first three are possible. By contrast, insertion of L-LA followed by that of TMC (i.e., insertion sequence 4) is endothermic by +1.1 kcal mol(-1), which compares unfavorably with consecutive insertions of two L-LA units (i.e., insertion sequence 3) (-10.2 kcal mol(-1)). The copolymerization of L-LA and TMC thus proceeds under thermodynamic control. PMID:23955851

  4. Experimental and numerical investigation of the reflection coefficient and the distributions of Wigner's reaction matrix for irregular graphs with absorption.

    PubMed

    Lawniczak, Michał; Hul, Oleh; Bauch, Szymon; Seba, Petr; Sirko, Leszek

    2008-05-01

    We present the results of an experimental and numerical study of the distribution of the reflection coefficient P(R) and the distributions of the imaginary P(v) and the real P(u) parts of the Wigner reaction K matrix for irregular fully connected hexagon networks (graphs) in the presence of strong absorption. In the experiment we used microwave networks, which were built of coaxial cables and attenuators connected by joints. In the numerical calculations experimental networks were described by quantum fully connected hexagon graphs. The presence of absorption introduced by attenuators was modeled by optical potentials. The distribution of the reflection coefficient P(R) and the distributions of the reaction K matrix were obtained from measurements and numerical calculations of the scattering matrix S of the networks and graphs, respectively. We show that the experimental and numerical results are in good agreement with the exact analytic ones obtained within the framework of random matrix theory. PMID:18643145

  5. Statistical Ring Opening Metathesis Copolymerization of Norbornene and Cyclopentene by Grubbs' 1st-Generation Catalyst.

    PubMed

    Nikovia, Christiana; Maroudas, Andreas-Philippos; Goulis, Panagiotis; Tzimis, Dionysios; Paraskevopoulou, Patrina; Pitsikalis, Marinos

    2015-01-01

    Statistical copolymers of norbornene (NBE) with cyclopentene (CP) were prepared by ring-opening metathesis polymerization, employing the 1st-generation Grubbs' catalyst, in the presence or absence of triphenylphosphine, PPh₃. The reactivity ratios were estimated using the Finemann-Ross, inverted Finemann-Ross, and Kelen-Tüdos graphical methods, along with the computer program COPOINT, which evaluates the parameters of binary copolymerizations from comonomer/copolymer composition data by integrating a given copolymerization equation in its differential form. Structural parameters of the copolymers were obtained by calculating the dyad sequence fractions and the mean sequence length, which were derived using the monomer reactivity ratios. The kinetics of thermal decomposition of the copolymers along with the respective homopolymers was studied by thermogravimetric analysis within the framework of the Ozawa-Flynn-Wall and Kissinger methodologies. Finally, the effect of triphenylphosphine on the kinetics of copolymerization, the reactivity ratios, and the kinetics of thermal decomposition were examined. PMID:26343620

  6. The Inverse Demand Oxa-Diels-Alder Reaction of Resorcinarenes: An Experimental and Theoretical Analysis of Regioselectivity and Diastereoselectivity.

    PubMed

    Stefańska, Karolina; Jędrzejewska, Hanna; Wierzbicki, Michał; Szumna, Agnieszka; Iwanek, Waldemar

    2016-07-15

    The Diels-Alder reaction enables introduction of new functionalities onto the resorcinarene skeleton with simultaneous generation of new stereogenic centers and expansion of the internal cavity. We present highly regio- and diastereoselective inverse electron demand oxa-Diels-Alder reactions of resorcinarene ortho-quinone methide with benzofuran and indene, each generating 12 new stereogenic centers. The mechanism and reasons for regioselectivity and diastereoselectivity were analyzed using theoretical calculations (NBO charges, Fukui functions, transition state energies, and thermodynamic stability of the products). Enantiomers were separated, and their configurations were determined by comparison of experimental and theoretical electronic circular dichroism spectra. PMID:27336857

  7. Experimental study of exclusive $^2$H$(e,e^\\prime p)n$ reaction mechanisms at high $Q^2$

    SciTech Connect

    Kim Egiyan; Gegham Asryan; Nerses Gevorgyan; Keith Griffioen; Jean Laget; Sebastian Kuhn; Gary Adams; Moscov Amaryan; Pawel Ambrozewicz; Marco Anghinolfi; Gerard Audit; Harutyun AVAKIAN; Harutyun Avakian; Hovhannes Baghdasaryan; Nathan Baillie; Jacques Ball; Nathan Baltzell; Steve Barrow; Vitaly Baturin; Marco Battaglieri; Ivan Bedlinski; Ivan Bedlinskiy; Mehmet Bektasoglu; Matthew Bellis; Nawal Benmouna; Barry Berman; Angela Biselli; Lukasz Blaszczyk; Sylvain Bouchigny; Sergey Boyarinov; Robert Bradford; Derek Branford; William Briscoe; William Brooks; Stephen Bueltmann; Volker Burkert; Cornel Butuceanu; John Calarco; Sharon Careccia; Daniel Carman; Antoine Cazes; Shifeng Chen; Philip Cole; Patrick Collins; Philip Coltharp; Dieter Cords; Pietro Corvisiero; Donald Crabb; Volker Crede; John Cummings; Natalya Dashyan; Rita De Masi; Raffaella De Vita; Enzo De Sanctis; Pavel Degtiarenko; Haluk Denizli; Lawrence Dennis; Alexandre Deur; Kahanawita Dharmawardane; Richard Dickson; Chaden Djalali; Gail Dodge; Joseph Donnelly; David Doughty; Michael Dugger; Steven Dytman; Oleksandr Dzyubak; Hovanes Egiyan; Lamiaa Elfassi; Latifa Elouadrhiri; Paul Eugenio; Renee Fatemi; Gleb Fedotov; Gerald Feldman; Robert Feuerbach; Robert Fersch; Michel Garcon; Gagik Gavalian; Gerard Gilfoyle; Kevin Giovanetti; Francois-Xavier Girod; John Goetz; Atilla Gonenc; Christopher Gordon; Ralf Gothe; Michel Guidal; Matthieu Guillo; Hayko Guler; Lei Guo; Vardan Gyurjyan; Cynthia Hadjidakis; Kawtar Hafidi; Hayk Hakobyan; Rafael Hakobyan; Charles Hanretty; John Hardie; F. Hersman; Kenneth Hicks; Ishaq Hleiqawi; Maurik Holtrop; Charles Hyde-Wright; Yordanka Ilieva; David Ireland; Boris Ishkhanov; Eugeny Isupov; Mark Ito; David Jenkins; Hyon-Suk Jo; Kyungseon Joo; Henry Juengst; Narbe Kalantarians; James Kellie; Mahbubul Khandaker; Wooyoung Kim; Andreas Klein; Franz Klein; Alexei Klimenko; Mikhail Kossov; Zebulun Krahn; Laird Kramer; V. Kubarovsky; Joachim Kuhn; Sergey Kuleshov; Jeff Lachniet; Jorn Langheinrich; David Lawrence; Ji Li; Kenneth Livingston; Haiyun Lu; Marion MacCormick; Claude Marchand; Nikolai Markov; Paul Mattione; Simeon McAleer; Bryan McKinnon; John McNabb; Bernhard Mecking; Surik Mehrabyan; Joseph Melone; Mac Mestayer; Curtis Meyer; Tsutomu Mibe; Konstantin Mikhaylov; Ralph Minehart; Marco Mirazita; Rory Miskimen; Viktor Mokeev; Kei Moriya; Steven Morrow; Maryam Moteabbed; James Mueller; Edwin Munevar Espitia; Gordon Mutchler; Pawel Nadel-Turonski; Rakhsha Nasseripour; Silvia Niccolai; Gabriel Niculescu; Maria-Ioana Niculescu; Bogdan Niczyporuk; Megh Niroula; Rustam Niyazov; Mina Nozar; Grant O'Rielly; Mikhail Osipenko; Alexander Ostrovidov; Kijun Park; Evgueni Pasyuk; Craig Paterson; Sergio Pereira; Joshua Pierce; Nikolay Pivnyuk; Dinko Pocanic; Oleg Pogorelko; Sergey Pozdnyakov; Barry Preedom; John Price; Yelena Prok; Dan Protopopescu; Brian Raue; Gregory Riccardi; Giovanni Ricco; Marco Ripani; Barry Ritchie; Federico Ronchetti; Guenther Rosner; Patrizia Rossi; Franck Sabatie; Julian Salamanca; Carlos Salgado; Joseph Santoro; Vladimir Sapunenko; Reinhard Schumacher; Vladimir Serov; Youri Sharabian; Nikolay Shvedunov; Alexander Skabelin; Elton Smith; Lee Smith; Daniel Sober; Daria Sokhan; Aleksey Stavinskiy; Samuel Stepanyan; Stepan Stepanyan; Burnham Stokes; Paul Stoler; Steffen Strauch; Mauro Taiuti; David Tedeschi; Ulrike Thoma; Avtandil Tkabladze; Svyatoslav Tkachenko; Luminita Todor; Clarisse Tur; Maurizio Ungaro; Michael Vineyard; Alexander Vlassov; Daniel Watts; Lawrence Weinstein; Dennis Weygand; M. Williams; Elliott Wolin; Michael Wood; Amrit Yegneswaran; Lorenzo Zana; Jixie Zhang; Bo Zhao; Zhiwen Zhao

    2007-06-01

    The reaction {sup 2}H(e,e{prime} p)n has been studied with full kinematic coverage for photon virtuality 1.75 < 5.5 {approx} GeV{sup 2}. Comparisons of experimental data with theory indicate that for very low values of neutron recoil momentum (p{sub n} < 100 MeV/c) the neutron is primarily a spectator and the reaction can be described by the plane-wave impulse approximation. For 100 < 750 MeV/c proton-neutron rescattering dominates the cross section, while {Delta} production followed by the N{Delta} {yields} NN transition is the primary contribution at higher momenta.

  8. Experimental and calculated radionuclide production by photonuclear reactions using Bremsstrahlung photons produced by 150 MeV electrons

    SciTech Connect

    Wunstorf, R.; Bugg, W.M.; Parks, C.C.; Gabriel, T.A.; Lewis, T.A.; Dickens, J.K.

    1994-12-31

    We have developed an experimental apparatus to study radionuclide production by photonuclear reactions. A nearly neutron-free bremsstrahlung beam was created by incident electron interactions with a tantalum radiator. We studied photonuclear reactions in different samples, including the elements Be, Na, Si, Cl, and Ge. Decay gamma rays from radionuclides having half lives > 2 min were analysed. Using the PICA code, we calculated the yield of radionuclides for silicon. We have observed and assigned a new gamma ray transition, of E({gamma}) = 1153 keV, to the decay of 6.6 min 29-Al.

  9. Experimental and calculated radionuclide production by photonuclear reactions using bremsstrahlung photons produced by 150 MeV electrons

    SciTech Connect

    Wunstorf, R.; Bugg, W.M.; Parks, C.C.; Gabriel, T.A.; Lewis, T.A.; Dickens, J.K.

    1995-02-01

    The authors have developed an experimental apparatus to study radionuclide production by photonuclear reactions. A nearly neutron free bremsstrahlung beam was created by incident electron interactions with a tantalum radiator. They studied photonuclear reactions in different samples, including the elements Be, Na, Si, Cl, and Ge. Decay gamma rays from radionuclides having half lives > 2 min were analysed. Using the PICA code, the authors calculated the yield of radionuclides for silicon. They have observed and assigned a new gamma ray transition, of E(y) = 1153 keV, to the decay of 6.6 min 29-Al.

  10. Experimental study of exclusive 2H(e,e'p)n reaction mechanisms at high Q2.

    PubMed

    Egiyan, K S; Asryan, G; Gevorgyan, N; Griffioen, K A; Laget, J M; Kuhn, S E; Adams, G; Amaryan, M J; Ambrozewicz, P; Anghinolfi, M; Audit, G; Avakian, H; Bagdasaryan, H; Baillie, N; Ball, J P; Baltzell, N A; Barrow, S; Batourine, V; Battaglieri, M; Bedlinskiy, I; Bektasoglu, M; Bellis, M; Benmouna, N; Berman, B L; Biselli, A S; Blaszczyk, L; Bouchigny, S; Boiarinov, S; Bradford, R; Branford, D; Briscoe, W J; Brooks, W K; Bültmann, S; Burkert, V D; Butuceanu, C; Calarco, J R; Careccia, S L; Carman, D S; Cazes, A; Chen, S; Cole, P L; Collins, P; Coltharp, P; Cords, D; Corvisiero, P; Crabb, D; Crede, V; Cummings, J P; Dashyan, N; De Masi, R; De Vita, R; De Sanctis, E; Degtyarenko, P V; Denizli, H; Dennis, L; Deur, A; Dharmawardane, K V; Dickson, R; Djalali, C; Dodge, G E; Donnelly, J; Doughty, D; Dugger, M; Dytman, S; Dzyubak, O P; Egiyan, H; El Fassi, L; Elouadrhiri, L; Eugenio, P; Fatemi, R; Fedotov, G; Feldman, G; Feuerbach, R J; Fersch, R; Garçon, M; Gavalian, G; Gilfoyle, G P; Giovanetti, K L; Girod, F X; Goetz, J T; Gonenc, A; Gordon, C I O; Gothe, R W; Guidal, M; Guillo, M; Guler, N; Guo, L; Gyurjyan, V; Hadjidakis, C; Hafidi, K; Hakobyan, H; Hakobyan, R S; Hanretty, C; Hardie, J; Hersman, F W; Hicks, K; Hleiqawi, I; Holtrop, M; Hyde-Wright, C E; Ilieva, Y; Ireland, D G; Ishkhanov, B S; Isupov, E L; Ito, M M; Jenkins, D; Jo, H S; Joo, K; Juengst, H G; Kalantarians, N; Kellie, J D; Khandaker, M; Kim, W; Klein, A; Klein, F J; Klimenko, A V; Kossov, M; Krahn, Z; Kramer, L H; Kubarovsky, V; Kuhn, J; Kuleshov, S V; Lachniet, J; Langheinrich, J; Lawrence, D; Li, Ji; Livingston, K; Lu, H Y; Maccormick, M; Marchand, C; Markov, N; Mattione, P; McAleer, S; McKinnon, B; McNabb, J W C; Mecking, B A; Mehrabyan, S; Melone, J J; Mestayer, M D; Meyer, C A; Mibe, T; Mikhailov, K; Minehart, R; Mirazita, M; Miskimen, R; Mokeev, V; Moriya, K; Morrow, S A; Moteabbed, M; Mueller, J; Munevar, E; Mutchler, G S; Nadel-Turonski, P; Nasseripour, R; Niccolai, S; Niculescu, G; Niculescu, I; Niczyporuk, B B; Niroula, M R; Niyazov, R A; Nozar, M; O'Rielly, G V; Osipenko, M; Ostrovidov, A I; Park, K; Pasyuk, E; Paterson, C; Anefalos Pereira, S; Pierce, J; Pivnyuk, N; Pocanic, D; Pogorelko, O; Pozdniakov, S; Preedom, B M; Price, J W; Prok, Y; Protopopescu, D; Raue, B A; Riccardi, G; Ricco, G; Ripani, M; Ritchie, B G; Ronchetti, F; Rosner, G; Rossi, P; Sabatié, F; Salamanca, J; Salgado, C; Santoro, J P; Sapunenko, V; Schumacher, R A; Serov, V S; Sharabian, Y G; Shvedunov, N V; Skabelin, A V; Smith, E S; Smith, L C; Sober, D I; Sokhan, D; Stavinsky, A; Stepanyan, S S; Stepanyan, S; Stokes, B E; Stoler, P; Strauch, S; Taiuti, M; Tedeschi, D J; Thoma, U; Tkabladze, A; Tkachenko, S; Todor, L; Tur, C; Ungaro, M; Vineyard, M F; Vlassov, A V; Watts, D P; Weinstein, L B; Weygand, D P; Williams, M; Wolin, E; Wood, M H; Yegneswaran, A; Zana, L; Zhang, J; Zhao, B; Zhao, Z W

    2007-06-29

    The reaction 2H(e,e'p)n has been studied with full kinematic coverage for photon virtuality 1.75experimental data with theory indicate that for very low values of neutron recoil momentum (p(n)<100 MeV/c) the neutron is primarily a spectator and the reaction can be described by the plane-wave impulse approximation. For 100NN transition is the primary contribution at higher momenta. PMID:17678084

  11. Water vapor effect on the HNO3 yield in the HO2 + NO reaction: experimental and theoretical evidence.

    PubMed

    Butkovskaya, Nadezhda; Rayez, Marie-Thérèse; Rayez, Jean-Claude; Kukui, Alexandre; Le Bras, Georges

    2009-10-22

    The influence of water vapor on the production of nitric acid in the gas-phase HO(2) + NO reaction was determined at 298 K and 200 Torr using a high-pressure turbulent flow reactor coupled with a chemical ionization mass spectrometer. The yield of HNO(3) was found to increase linearly with the increase of water concentration reaching an enhancement factor of about 8 at [H(2)O] = 4 x 10(17) molecules cm(-3) ( approximately 50% relative humidity). A rate constant value k(1bw) = 6 x 10(-13) cm(3) molecule(-1) s(-1) was derived for the reaction involving the HO(2)xH(2)O complex: HO(2)xH(2)O + NO --> HNO(3) (1bw), assuming that the water enhancement is due to this reaction. k(1bw) is approximately 40 times higher than the rate constant of the reaction HO(2) + NO --> HNO(3) (1b), at the same temperature and pressure. The experimental findings are corroborated by density functional theory (DFT) calculations performed on the H(2)O/HO(2)/NO system. The significance of this result for atmospheric chemistry and chemical amplifier instruments is briefly discussed. An appendix containing a detailed consideration of the possible contribution from the surface reactions in our previous studies of the title reaction and in the present one is included. PMID:19780600

  12. A novel crosslinker for UV copolymerization of N-vinyl pyrrolidone and methacrylates

    SciTech Connect

    Lai, Yu-Chin

    1993-12-31

    Methacryloxyethyl vinyl carbonate, a novel crosslinker containing a vinyl carbonate and a methacrylate group which is capable of copolymerizing N-vinyl pyrrolidone and methacrylates, was prepared. With this crosslinker, N-vinyl pyrrolidone and methacrylates can copolymerize efficiently under strictly UV condition. Previously, polymeric systems containing N-vinyl pyrrolidone and methacrylates were prepared using thermal initiators, or a combination of thermal and UV initiators in the presence of crosslinkers such as allyl methacrylate or ethylene glycol dimethacrylate, These processes often led to polymers with inferior properties and less controllable quality. The use of this novel crosslinker represents a sharp improvement in polymerization conditions (UV vs heat) as well as product quality.

  13. Experimental study of the 12C ( K -stopped , π0 ) 12 Λ B reaction

    NASA Astrophysics Data System (ADS)

    Ahmed, M. W.; Cui, X.; Empl, A.; Hungerford, E. V.; Lan, K. J.; Youn, M.; Chrien, R. E.; Gill, R.; Pile, P.; Rusek, A.; Sutter, R.; Bjoraker, J.; Dehnhard, D.; O'Donnell, J. M.; Gerald, J.; Juengst, H.; Liu, J. H.; Peng, J. C.; Morris, C. L.; Riedel, C. M.; Thiessen, H. A.; Androic, D.; Bertovic, I.; Furic, M.; Petkovic, T.; Planinic, M.; Tang, L.; Zeps, V.

    2003-12-01

    The ( K -stopped , π0 ) strangeness and charge changing reaction was investigated by producing a 12 Λ B hypernucleus from a carbon target. The branching ratio for K- capture to the ground and p -shell states of this hypernucleus was found to be (0.28±0.08)× 10-3 and (0.35±0.09)× 10-3 , respectively, which after correction for isospin was lower than a previously measured value for the 12 C ( K -stopped , π- ) 12ΛC reaction, but still above the theoretical predictions for the ground state. The experiment obtained a missing-mass resolution comparable to in-flight reactions, however the higher background and lower selectivity of the K -stopped reaction limits its usefulness in the study of new hypernuclear species.

  14. Experimental study of the 13C+12C fusion reaction at deep sub-barrier energies

    NASA Astrophysics Data System (ADS)

    Tudor, D.; Chilug, A. I.; Straticiuc, M.; Trache, L.; Chesneanu, D.; Toma, S.; Ghita, D. G.; Burducea, I.; Margineanu, R.; Pantelica, A.; Gomoiu, C.; Zhang, N. T.; Tang, X.; Li, Y. J.

    2016-04-01

    Heavy-ion fusion reactions between light nuclei such as carbon and oxygen isotopes have been studied because of their significance for a wide variety of stellar burning scenarios. One important stellar reaction is 12C+12C, but it is difficult to measure it in the Gamow window because of very low cross sections and several resonances occurring. Hints can be obtained from the study of 13C+12C reaction. We have measured this process by an activation method for energies down to Ecm=2.5 MeV using 13C beams from the Bucharest 3 MV tandetron and gamma-ray deactivation measurements in our low and ultralow background laboratories, the latter located in a salt mine about 100 km north of Bucharest. Results obtained so far are shown and discussed in connection with the possibility to go even further down in energy and with the interpretation of the reaction mechanism at such deep sub-barrier energies.

  15. Compound-nuclear reactions with unstable nuclei: Constraining theory through innovative experimental approaches

    NASA Astrophysics Data System (ADS)

    Escher, J. E.; Tonchev, A. P.; Burke, J. T.; Bedrossian, P.; Casperson, R. J.; Cooper, N.; Hughes, R. O.; Humby, P.; Ilieva, R. S.; Ota, S.; Pietralla, N.; Scielzo, N. D.; Werner, V.

    2016-06-01

    Cross sections for compound-nuclear reactions involving unstable targets are important for many applications, but can often not be measured directly. Several indirect methods have recently been proposed to determine neutron capture cross sections for unstable isotopes. We consider three approaches that aim at constraining statistical calculations of capture cross sections with data obtained from the decay of the compound nucleus relevant to the desired reaction. Each method produces this compound nucleus in a different manner (via a light-ion reaction, a photon-induced reaction, or β-decay) and requires additional ingredients to yield the sought-after cross section. We give a brief outline of the approaches and employ preliminary results from recent measurements to illustrate the methods. We discuss the main advantages and challenges of each approach.

  16. Relevance of the H2 + O reaction pathway for the surface formation of interstellar water. Combined experimental and modeling study

    NASA Astrophysics Data System (ADS)

    Lamberts, T.; Cuppen, H. M.; Fedoseev, G.; Ioppolo, S.; Chuang, K.-J.; Linnartz, H.

    2014-10-01

    The formation of interstellar water is commonly accepted to occur on the surfaces of icy dust grains in dark molecular clouds at low temperatures (10-20 K), involving hydrogenation reactions of oxygen allotropes. As a result of the large abundances of molecular hydrogen and atomic oxygen in these regions, the reaction H2 + O has been proposed to contribute significantly to the formation of water as well. However, gas-phase experiments and calculations, as well as solid-phase experimental work contradict this hypothesis. Here, we use precisely executed temperature-programmed desorption (TPD) experiments in an ultra-high vacuum setup combined with kinetic Monte Carlo simulations to establish an upper limit of the water production starting from H2 and O. These reactants were brought together in a matrix of CO2 in a series of (control) experiments at different temperatures and with different isotopological compositions. The water detected with the quadrupole mass spectrometer upon TPD was found to originate mainly from contamination in the chamber itself. However, if water is produced in small quantities on the surface through H2 + O, this can only be explained by a combined classical and tunneled reaction mechanism. An absolutely conservative upper limit for the reaction rate was derived with a microscopic kinetic Monte Carlo model that converts the upper limit into the highest possible reaction rate. Incorporating this rate into simulation runs for astrochemically relevant parameters shows that the upper limit to the contribution of the reaction H2 + O in OH, and hence water formation, is 11% in dense interstellar clouds. Our combined experimental and theoretical results indicate, however, that this contribution is most likely much lower.

  17. Solid phase graft copolymerization of acrylic monomers onto thermoplastics and their use as blend compatibilizers

    NASA Astrophysics Data System (ADS)

    Subramanian, Srinivas

    This research work is an extension of some of the earlier work done on the development of solid phase grafting technique to graft various monomers onto polymers as well as postulation of the usefulness of the graft copolymers thus synthesized. Polystyrene grafted with acrylic acid, previously developed in bench scale, was synthesized in pilot-plant scale batches. Process parameter studies on the grafting of acrylic acid onto polypropylene and developmental studies on the grafting of maleic anhydride onto polystyrene were also done. Polymers grafted with polar molecules such as maleic anhydride and acrylic acid have been used to compatibilize immiscible blends of polar and non-polar polymers. On the same note, the applicability of the solid phase graft copolymers as blend compatibilizers were investigated and their performance was compared to commercially available compatibilizers. Solid phase graft copolymerization process is a technique to synthesize graft copolymers. Some of its salient features are use of minimal solvent to conduct the reaction and easy equipment modification. It is a low pressure and low temperature process. This technique provides a viable alternative to the environmentally hazardous, and time consuming conventional process currently in use. Hence, development of this technique could be beneficial not only to the plastics industry, but also to mankind. Also, this technique provides a low-cost and extremely easy method to develop graft copolymers such as acrylic acid functionalized polymers that are rapidly gaining popularity as blend compatibilizers and polymer reinforcing agents. A study that proves the potential of these solid phase graft copolymers as good blend compatibilizers for industrially important immiscible polymers will develop interest in the industries about this grafting process. The free radical solid phase graft copolymerization process was carried in a modified Brabender-type mixer fitted with specially designed blades to

  18. Experimental setup and procedure for the measurement of the 7Be(n,α)α reaction at n_TOF

    NASA Astrophysics Data System (ADS)

    Cosentino, L.; Musumarra, A.; Barbagallo, M.; Pappalardo, A.; Colonna, N.; Damone, L.; Piscopo, M.; Finocchiaro, P.; Maugeri, E.; Heinitz, S.; Schumann, D.; Dressler, R.; Kivel, N.; Aberle, O.; Andrzejewski, J.; Audouin, L.; Ayranov, M.; Bacak, M.; Barros, S.; Balibrea-Correa, J.; Bécares, V.; Bečvář, F.; Beinrucker, C.; Berthoumieux, E.; Billowes, J.; Bosnar, D.; Brugger, M.; Caamaño, M.; Calviani, M.; Calviño, F.; Cano-Ott, D.; Cardella, R.; Casanovas, A.; Castelluccio, D. M.; Cerutti, F.; Chen, Y. H.; Chiaveri, E.; Cortés, G.; Cortés-Giraldo, M. A.; Diakaki, M.; Domingo-Pardo, C.; Dupont, E.; Duran, I.; Fernandez-Dominguez, B.; Ferrari, A.; Ferreira, P.; Furman, W.; Ganesan, S.; García-Rios, A.; Gawlik, A.; Gheorghe, I.; Glodariu, T.; Göbel, K.; Gonc̗alves, I. F.; González-Romero, E.; Griesmayer, E.; Guerrero, C.; Gunsing, F.; Harada, H.; Heftrich, T.; Heyse, J.; Jenkins, D. G.; Jericha, E.; Käppeler, F.; Katabuchi, T.; Kavrigin, P.; Kimura, A.; Kokkoris, M.; Krtička, M.; Leal-Cidoncha, E.; Lerendegui, J.; Lederer, C.; Leeb, H.; Meo, S. Lo; Lonsdale, S.; Losito, R.; Macina, D.; Marganiec, J.; Martínez, T.; Massimi, C.; Mastinu, P.; Mastromarco, M.; Matteucci, F.; Mazzone, A.; Mendoza, E.; Mengoni, A.; Milazzo, P. M.; Mingrone, F.; Mirea, M.; Montesano, S.; Nolte, R.; Oprea, A.; Patronis, N.; Pavlik, A.; Perkowski, J.; Praena, J.; Quesada, J.; Rajeev, K.; Rauscher, T.; Reifarth, R.; Riego-Perez, A.; Rout, P.; Rubbia, C.; Ryan, J.; Sabate-Gilarte, M.; Saxena, A.; Schillebeeckx, P.; Schmidt, S.; Sedyshev, P.; Smith, A. G.; Stamatopoulos, A.; Tagliente, G.; Tain, J. L.; Tarifeño-Saldivia, A.; Tassan-Got, L.; Tsinganis, A.; Valenta, S.; Vannini, G.; Variale, V.; Vaz, P.; Ventura, A.; Vlachoudis, V.; Vlastou, R.; Vollaire, J.; Wallner, A.; Warren, S.; Weigand, M.; Weiß, C.; Wolf, C.; Woods, P. J.; Wright, T.; Z̆ugec, P.

    2016-09-01

    The newly built second experimental area EAR2 of the n_TOF spallation neutron source at CERN allows to perform (n, charged particles) experiments on short-lived highly radioactive targets. This paper describes a detection apparatus and the experimental procedure for the determination of the cross-section of the 7Be(n,α)α reaction, which represents one of the focal points toward the solution of the cosmological Lithium abundance problem, and whose only measurement, at thermal energy, dates back to 1963. The apparently unsurmountable experimental difficulties stemming from the huge 7Be γ-activity, along with the lack of a suitable neutron beam facility, had so far prevented further measurements. The detection system is subject to considerable radiation damage, but is capable of disentangling the rare reaction signals from the very high background. This newly developed setup could likely be useful also to study other challenging reactions requiring the detectors to be installed directly in the neutron beam.

  19. Experimental Observation of Nuclear Reactions in Palladium and Uranium - Possible Explanation by Hydrex Mode

    SciTech Connect

    Dufour, J.; Murat, D.; Dufour, X.; Foos, J

    2001-07-15

    Experiments with uranium are presented that show a highly exothermal reaction, which can only be of nuclear origin. One striking point of these results is that they clearly show that what is being observed is not some kind of fusion reaction of the deuterium present (only exceedingly small amounts of it are present). This is a strong indication that hydrogen can trigger nuclear reactions that seem to involve the nuclei of the lattice (which would yield a fission-like pattern of products). Confronted with a situation where some experiments in the field yield a fusion-like pattern of products (CF experiments) and others a fissionlike one (LENR experiments), one can reasonably wonder whether one is not observing two aspects of the same phenomenon. Thus, it is proposed to describe CF and LENR reactions as essentially the same phenomenon based on the possible existence of a still hypothetical proton/electron resonance, which would catalyze fissionlike reactions with a neutron sink. Finally, a series of experiments is proposed to assess this hypothesis.

  20. Fusion reactions and experimental approaches to the synthesis of superheavy nuclei

    SciTech Connect

    Yeremin, A. V.; Utyonkov, V. K.; Oganessian, Yu. Ts.

    1998-02-15

    The question whether the asymmetric actinide based heavy ion reactions could be used for the synthesis of heavy (Z{>=}106) nuclides is essential from the point of view of the study of limitation on fusion, it is also important in such reactions new nuclides close to the magic number N=162 can be produced. Thus as the problem of a hindrance to fusion still remains unsolved the high excitation energy of the compound nucleus looks to be an obvious obstacle to using these reactions. Using the gas-filled recoil separator and electrostatic recoil separator VAS-SILISSA installed at the beam lines of the U-400 heavy ion cyclotron of the FLNR JINR we investigated the fusion reactions leading to 102, 103, 104, 105 and heaviest isotopes of the 106, 108 and 110 elements. The analysis of the measured cross-sections did not reveal any evidence of a hindrance to fusion at the ion bombarding energy close to the Coulomb barrier. {sup 48}Ca+{sup 232}Th{yields}{sup 280}110*, {sup 48}Ca+{sup 238}U{yields}{sup 286}112*, {sup 48}Ca+{sup 244}Pu{yields}{sup 292}114* appear to be the best reactions from the point of view of their cross-sections.

  1. Experimental Study of p-11B Reaction Related to the Clean Fusion Fuel

    NASA Astrophysics Data System (ADS)

    Lin, Erh-kang; Wang, Chang-wan; Yuan, Jian; Liu, Xiao-dong; Li, Cheng-bo; Sun, Zu-xun; Zhang, Pei-hua; Chen, Jin-xiang; Yang, Qi-xiang; Wang, Jian-yong; Ling-hua, Gong

    1998-11-01

    Whole continuous α spectra of the p-11B three-body sequential decay reaction have been measured by using a charge particle time-of-flight (TOF) spectrometer with the high-resolution passivated implanted planar silicon detector. A characteristic shape of the saddle-type distribution was obtained. The Monte Carlo calculations show that observed α spectra can be interpreted by anisotropy sequential decay process of the intermediate nucleus 8Be (1) for the p-11B reaction. In the measurement, angular distributions were obtained for proton energies at 667 and 1370 keV, respectively. Total cross-sections for the 11B(p,α)8Be(2α) reaction related to the clean fusion fuel were also reported at two bombarding energies.

  2. Experimental study of the reactions of limonene with OH and OD radicals: kinetics and products.

    PubMed

    Braure, Tristan; Bedjanian, Yuri; Romanias, Manolis N; Morin, Julien; Riffault, Véronique; Tomas, Alexandre; Coddeville, Patrice

    2014-10-01

    The kinetics of the reactions of limonene with OH and OD radicals has been studied using a low-pressure flow tube reactor coupled with a quadrupole mass spectrometer: OH + C10H16 → products (1), OD + C10H16 → products (2). The rate constants of the title reactions were determined using four different approaches: either monitoring the kinetics of OH (OD) radicals or limonene consumption in excess of limonene or of the radicals, respectively (absolute method), and by the relative rate method using either the reaction OH (OD) + Br2 or OH (OD) + DMDS (dimethyl disulfide) as the reference one and following HOBr (DOBr) formation or DMDS and limonene consumption, respectively. As a result of the absolute and relative measurements, the overall rate coefficients, k1 = (3.0 ± 0.5) × 10(-11) exp((515 ± 50)/T) and k2 = (2.5 ± 0.6) × 10(-11) exp((575 ± 60)/T) cm(3) molecule(-1) s(-1), were determined at a pressure of 1 Torr of helium over the temperature ranges 220-360 and 233-353 K, respectively. k1 was found to be pressure independent over the range 0.5-5 Torr. There are two possible pathways for the reaction between OH (OD) and limonene: addition of the radical to one of the limonene double bonds (reactions 1a and 2a ) and abstraction of a hydrogen atom (reactions 1b and 2b ), resulting in the formation of H2O (HOD). Measurements of the HOD yield as a function of temperature led to the following branching ratio of the H atom abstraction channel: k2b/k2 = (0.07 ± 0.03) × exp((460 ± 140)/T) for T = (253-355) K. PMID:25211148

  3. Experimental Studies of Hydrogenation and Other Reactions on Surfaces Under Astrophysically Relevant Conditions

    NASA Technical Reports Server (NTRS)

    Vidali, Gianfranco

    1998-01-01

    The goal of our project is to study hydrogen recombination reactions on solid surfaces under conditions that are relevant in astrophysics. Laboratory experiments were conducted using low-flux, cold atomic H and D beams impinging on a sample kept under ultra high vacuum conditions. Realistic analogues of interstellar dust grains were used. Our results show that current models for hydrogen recombination reactions have to be modified to take into account the role of activated diffusion of H on surfaces even at low temperature.

  4. Experimental investigation and theoretical calculation for 3He induced nuclear reactions on vanadium

    NASA Astrophysics Data System (ADS)

    Ali, B. M.; Al-Abyad, M.; Seddik, U.; El-Kameesy, S. U.; Ditrói, F.; Takács, S.; Tárkányi, F.

    2016-04-01

    Using stacked-foil activation technique and gamma-ray spectrometry, excitation functions for 3He induced nuclear reactions on natV were measured. Cross-sections for natV(3He, xn)52m,gMn and natV(3He, pxn)51Cr nuclear reactions were measured up to 27 MeV utilizing the MGC-20E cyclotron of ATOMKI. The measurements establish for the first time consistent excitation curves. Comparisons with results for values derived from different theoretical codes were included. Integral yield were calculated.

  5. Experimental time scale of Gerischer's distribution curves for electron-transfer reactions at semiconductor electrodes

    SciTech Connect

    Willig, F.; Eichberger, R.; Sundaresan, N.S. ); Parkinson, B.A. )

    1990-03-28

    Fluorescence decay of adsorbed cresyl violet molecules was measured on n-SnS{sub 2} electrodes where their stationary photoelectrochemical current approached the yield of one electron per absorbed photon. At very low coverage, {theta} {approx} 10{sup {minus}2}, the fluorescence decay was faster than 10 ps and was identified with electron injection from excited dye monomers into the wide conduction band of the semiconductor. The reaction path was adiabatic or at least borderline to the adiabatic case. The measurement provides a time scale for Gerischer's distribution curves that are commonly applied in the discussion of electron-transfer reactions at electrodes.

  6. [Experimental and kinetic modeling of acid/base and redox reactions over oxide catalysts

    SciTech Connect

    Not Available

    1993-01-01

    The research has involved the characterization of catalyst acidity, [sup 2]D NMR studies of Bronsted acid sites, and kinetic, calorimetric, and spectroscopic studies of methylamine synthesis and related reactions over acid catalysts. Approach of this work was to explore quantitative correlations between factors that control the generation, type, strength, and catalytic properties of acid sites on zeolite catalysts. Microcalorimetry, thermogravimetric analysis, IR spectroscopy, and NMR spectroscopy have provided information about the nature and strength of acid sites in zeolites. This was vital in understanding the catalytic cycles involved in methylamine synthesis and related reactions over zeolite catalysts.

  7. A Case Study of the Mechanism of Alcohol-Mediated Morita Baylis–Hillman Reactions. The Importance of Experimental Observations

    PubMed Central

    2016-01-01

    The mechanism of the Morita Baylis–Hillman reaction has been heavily studied in the literature, and a long series of computational studies have defined complete theoretical energy profiles in these reactions. We employ here a combination of mechanistic probes, including the observation of intermediates, the independent generation and partitioning of intermediates, thermodynamic and kinetic measurements on the main reaction and side reactions, isotopic incorporation from solvent, and kinetic isotope effects, to define the mechanism and an experimental mechanistic free-energy profile for a prototypical Morita Baylis–Hillman reaction in methanol. The results are then used to critically evaluate the ability of computations to predict the mechanism. The most notable prediction of the many computational studies, that of a proton-shuttle pathway, is refuted in favor of a simple but computationally intractable acid–base mechanism. Computational predictions vary vastly, and it is not clear that any significant accurate information that was not already apparent from experiment could have been garnered from computations. With care, entropy calculations are only a minor contributor to the larger computational error, while literature entropy-correction processes lead to absurd free-energy predictions. The computations aid in interpreting observations but fail utterly as a replacement for experiment. PMID:25714789

  8. Experimental and theoretical analysis of the kinetics of the reaction of atomic bromine with 1,4-dioxane.

    PubMed

    Giri, Binod Raj; Roscoe, John M; González-García, Núria; Olzmann, Matthias

    2010-01-14

    The rate coefficient for the reaction of atomic bromine with 1,4-dioxane was measured from approximately 300 to 340 K using the relative rate method. Iso-octane and iso-butane were used as reference compounds, and the experiments were made in a bath of argon containing up to 210 Torr of O(2) at total pressures between 200 and 820 Torr. The rate coefficients were not affected by changes in pressure or O(2) concentration over our range of experimental conditions. The ratios of rate coefficients for the reaction of dioxane relative to the reference compound were put on an absolute basis by using the published absolute rate coefficients for the reference reactions. The variation of the experimentally determined rate coefficients with temperature for the reaction of Br with 1,4-dioxane can be given by k(1)(exp)(T) = (1.4 +/- 1.0) x 10(-11)exp[-23.0 +/- 1.8) kJ mol(-1)/(RT)] cm(3) molecule(-1) s(-1). We rationalized our experimental results in terms of transition state theory with molecular data from quantum chemical calculations. Molecular geometries and frequencies were obtained from MP2/aug-cc-pVDZ calculations, and single-point energies of the stationary points were obtained at CCSD(T)/CBS level of theory. The calculations indicate that the 1,4-dioxane + Br reaction proceeds in an overall endothermic addition-elimination mechanism via a number of intermediates. The rate-determining step is a chair-to-boat conformational change of the Br-dioxane adduct. The calculated rate coefficients, given by k(1)(calc)(T) = 5.6 x 10(-11)exp[-26.6 kJ mol(-1)/(RT)] cm(3) molecule(-1) s(-1), are in very good agreement with the experimental values. Comparison with results reported for the reactions of Br with other ethers suggests that this multistep mechanism differs significantly from that for abstraction of hydrogen from other ethers by atomic bromine. PMID:19848396

  9. Determination of the Molar Volume of Hydrogen from the Metal-Acid Reaction: An Experimental Alternative.

    ERIC Educational Resources Information Center

    de Berg, Kevin; Chapman, Ken

    1996-01-01

    Describes an alternative technique for determining the molar volume of hydrogen from the metal-acid reaction in which the metal sample is encased in a specially prepared cage and a pipette filler is used to fill an inverted burette with water. Eliminates some difficulties encountered with the conventional technique. (JRH)

  10. Experimental studies on the reaction kinetics of 1,1-dimethylhydrazine and oxygen

    NASA Technical Reports Server (NTRS)

    Just, T.

    1985-01-01

    Measurements behind shock waves in highly diluted 1,1 dimethylhydrazine-O2-Ar mixtures clearly showed a two-stage reaction. In the first stage, UDMH decomposes via a unimolecular step; in the second stage, clearly separated from the first one, the decay products react further with O2. Values for the rate constant of unimolecular decomposition were obtained.

  11. A theoretical and experimental study of unimolecular and biomolecular radical hydrogen transfer reactions

    SciTech Connect

    Franz, J.A.; Autrey, T.; Gleicher, G.J.; Camaioni, D.M; Ferris, K.F.

    1991-04-01

    We have examined the intramolecular radical hydrogen transfer (RHT) reaction of the 2-(2-phenylethyl)cyclohexadienyl radical. Intramolecular hydrogen shift from the cyclohexadienyl ring to the ipso position of the phenyl ring, followed by {beta}-scission would have given benzene and ethylbenzene as products. Competing with this reaction is {beta}-scission to give benzyl radical and isotoluene, or hydrogen loss to give bibenzyl. Studies to date suggest a barrier for thermoneutral hydrogen transfer in the RHT reaction between aromatic systems of ca. 18 kcal/mole. None of the studies of RHT or equivalent mechanisms have attempted to directly observe H{sub 2}, and direct determination of Arrhenius parameters and a detailed examination of the pathway of the hydrogen transfer process remains to be carried out. To better understand the structural and energetic aspects of RHT, we have carried out a semiempirical molecular orbital study of bimolecular and intramolecular RHT reactions for a variety of aromatic systems. We also examined in detail the energetics of hydrogen transfer between ethyl radical and ethylene via RHT, an addition/metathesis/scission pathway, and a hybrid concerted'' pathway. 11 refs., 1 fig., 4 tabs.

  12. Reaction kinetics of Cl atoms with limonene: An experimental and theoretical study

    NASA Astrophysics Data System (ADS)

    Dash, Manas Ranjan; Rajakumar, B.

    2014-12-01

    Rate coefficients for the reaction of Cl atoms with limonene (C10H16) were measured between 278-350 K and 800 Torr of N2, using the relative rate technique, with 1,3-butadiene (C4H6), n-nonane (C9H20), and 1-pentene (C5H10) as reference compounds. Cl atoms were generated by UV photolysis of oxalyl chloride ((COCl)2) at 254 nm. A gas chromatograph equipped with a flame ionization detector (GC-FID) was used for quantitative analysis of the organics. The rate coefficient for the reaction of Cl atoms with limonene at 298 K was measured to be (8.65 ± 2.44) × 10-10 cm3 molecule-1 s-1. The rate coefficient is an average value of the measurements, with two standard deviations as the quoted error, including uncertainties in the reference rate coefficients. The kinetic data obtained over the temperature range of 278-350 K were used to derive the following Arrhenius expression: k(T) = (9.75 ± 4.1) × 10-11 exp[(655 ± 133)/T] cm3 molecule-1 s-1. Theoretical kinetic calculations were also performed for the title reaction using conventional transition state theory (CTST) in combination with G3(MP2) theory between 275 and 400 K. The kinetic data obtained over the temperature range of 275-400 K were used to derive an Arrhenius expression: k(T) = (7.92 ± 0.82) × 10-13 exp[(2310 ± 34)/T] cm3 molecule-1 s-1. The addition channels contributes maximum to the total reaction and H-abstraction channels can be neglected in the range of studied pressures. The Atmospheric lifetime (τ) of limonene due to its reaction with Cl atoms was estimated and concluded that the reaction with chlorine atoms can be an effective tropospheric loss pathway in the marine boundary layer and in coastal urban areas.

  13. Experimental Constraints on Fluid-Rock Reactions during Incipient Serpentinization of Harzburgite

    NASA Astrophysics Data System (ADS)

    Klein, F.; Grozeva, N. G.; Seewald, J.; McCollom, T. M.; Humphris, S. E.; Moskowitz, B. M.; Berquo, T. S.; Kahl, W. A.

    2014-12-01

    The exposure of mantle peridotite to water at crustal levels leads to a cascade of interconnected dissolution-precipitation and reduction-oxidation reactions - a process referred to as serpentinization. These reactions have major implications for microbial life through the provision of hydrogen (H2). To simulate incipient serpentinization and the release of H2 under well-constrained conditions, we reacted uncrushed harzburgite with chemically modified seawater at 300°C and 35 MPa for ca. 1.5 years (13441 hours), monitored changes in fluid chemistry over time, and examined the secondary mineralogy at the termination of the experiment. Approximately 4 mol % of the protolith underwent alteration forming serpentine, accessory magnetite, chlorite, and traces of calcite and heazlewoodite. Alteration textures bear remarkable similarities to those found in partially serpentinized abyssal peridotites. Neither brucite nor talc precipitated during the experiment. Given that the starting material contained ~3.8 times more olivine than orthopyroxene on a molar basis, mass balance requires that dissolution of orthopyroxene was significantly faster than dissolution of olivine. However, the H2 release rate was not uniform, slowing from ~2 nmol H2(aq) gperidotite-1 s-1 at the beginning of the experiment to ~0.2 nmol H2(aq) gperidotite-1 s-1 at its termination. Serpentinization consumed water but did not release significant amounts of dissolved species (other than H2) suggesting that incipient hydration reactions involved a volume increase of ~40%. The reduced access of water to olivine surfaces due to filling of fractures and coating of primary minerals with alteration products led to decreased rates of serpentinization and H2 release. While this concept might seem at odds with completely serpentinized seafloor peridotites, reaction-driven fracturing offers an intriguing solution to the seemingly self-limiting nature of serpentinization. Indeed, the reacted sample revealed a

  14. Proton and deuteron induced reactions on natGa: Experimental and calculated excitation functions

    NASA Astrophysics Data System (ADS)

    Hermanne, A.; Adam-Rebeles, R.; Tárkányi, F.; Takács, S.; Ditrói, F.

    2015-09-01

    Cross-sections for reactions on natGa, induced by protons (up to 65 MeV) and deuterons (up to 50 MeV), producing γ-emitting radionuclides with half-lives longer than 1 h were measured in a stacked-foil irradiation using thin Ga-Ni alloy (70-30%) targets electroplated on Cu or Au backings. Excitation functions for generation of 68,69Ge, 66,67,68,72Ga and 65,69mZn on natGa are discussed, relative to the monitor reactions natAl(d,x)24,22Na, natAl(p,x)24,22Na, natCu(p,x)62Zn and natNi(p,x)57Ni. The results are compared to our earlier measurements, the scarce literature values and to the results of the code TALYS 1.6 (online database TENDL-2014).

  15. Reaction of trimethylsilylacetylenes with antimony pentafluoride under matrix isolation conditions: experimental and computational study.

    PubMed

    Cicak, Helena; Vancik, Hrvoj; Mihalić, Zlatko

    2010-10-15

    Reaction of trimethylsilylacetylenes Me(3)SiC≡CR with SbF(5) in the solid state was investigated using matrix isolation infrared spectroscopy and quantum-mechanical calculations. Two reaction pathways were detected. Replacement of the trimethylsilyl group with SbF(4) produces neutral antimony acetylides F(4)SbC≡CR. Acetylenic bond protonation produces silyl cation 6-R, fully bridged for R = H and SiMe(3). High total charges on the bridging SiMe(3) group and low Me(3)Si-C bond orders to acetylenic moiety, both calculated at the MP4(SDQ)/6-311G(d,p) level of theory, indicate high silyl cation character of these species. PMID:20857942

  16. Cycloaddition Reactions of Indanedioneketene with Electron-Rich Dienophiles: An Experimental and a Theoretical Study.

    PubMed

    Malamidou-Xenikaki, Elizabeth; Spyroudis, Spyros; Tsovaltzi, Erifili; Bakalbassis, Evangelos G

    2016-03-18

    Thermal decomposition of the phenyliodonium ylide of lawsone gives rise to a highly reactive cyclic α,α'-dioxoketene, indanedioneketene, which reacts with electron-rich dienophiles such as enol ethers to afford [4 + 2] cycloadducts. The initially formed 2,3-dihydro-2-alkoxy-indeno[1,2-b]pyrano-4,5-diones are labile compounds since through an opening of the pyranone ring upon heating they easily tautomerize to alkoxyallylidene-indenedione derivatives and under acid-catalysis they are additionally transformed to 2-(1,3-dihydroxyallylidene)-1H-indene-1,3(2H)-dione or by loss of alcohol to indeno[1,2-b]pyran-4,5-diones. A DFT study explains the polar nature of the cycloaddition reaction, the observed reactivity and suggests a possible mechanism operating in these reactions. PMID:26919033

  17. Experimental study of Three-Nucleon Dynamics in the dp breakup reaction

    NASA Astrophysics Data System (ADS)

    Kłos, B.; Ciepał, I.; Khatri, G.; Kistryn, S.; Kozela, A.; Magiera, A.; Parol, W.; Skwira-Chalot, I.; Stephan, E.; Szpik, K.

    2016-03-01

    An experiment to investigate the 1H(d,pp)n breakup reaction using a deuteron beam of 340, 380 and 400 MeV and the WASA detector has been performed at the Cooler Synchrotron COSY-Jülich. The main goal was a detailed study of various aspects of fewnucleon dynamics like the three nucleon force (3NF), the long-range Coulomb interaction or relativistic effects in the medium energy region. The relativistic effects and their interplay with 3NF become more important with increasing available energy in the three nucleon system. The almost 4π geometry of the WASA detector provides an unique possibility to study various aspects of dynamics. The studies of the 3N system dynamics in the breakup reaction with BINA detector are continued in the Cyclotron Center Bronowice.

  18. Experimental study of the asymmetric charge transfer reaction between Ar+ ions and Fe atoms.

    PubMed

    Korolov, I; Bánó, G; Donkó, Z; Derzsi, A; Hartmann, P

    2011-02-14

    We investigate the Ar(+)-Fe asymmetric charge transfer (ACT) reaction using a combination of plasma diagnostics methods and a kinetic model of the afterglow plasma, which allow monitoring of the temporal evolution of the densities of different species. The iron vapor is created inside a discharge cell by cathode sputtering; its density is measured by atomic absorption spectroscopy. The rate coefficient of the reaction is evaluated from the emission intensity decay of Fe(+)∗ lines pumped by the ACT process in the He-Ar-Fe and Ar-Fe afterglow plasmas. The measurements yield a rate coefficient k = 7.6( ± 3.0) × 10(-9) cm(3) s(-1) at T = 300 K. PMID:21322681

  19. Proposed experimental probes of chemical reaction molecular dynamics in solution: ICN photodissociation

    NASA Astrophysics Data System (ADS)

    Benjamin, I.; Wilson, Kent R.

    1989-04-01

    Knowledge of how translational and rotational motions are influenced by the solvent during the course of a photodissociation ``half-collision'' reaction in solution is of interest in itself and can also help our understanding of how thermally activated reactions take place in solution by means of fluctuations in translational and rotational motion. With this goal, the molecular dynamics of the photodissociation of the triatomic molecule ICN are compared in the gas phase and in Xe solution. The time evolution of the trajectories (particularly with respect to interfragment distance and CN orientation) and of the energy partitioning (particularly into fragment translational recoil and into rotation of the CN) are displayed. Two types of solution experiments are proposed and simulated, both closely related to recent gas phase studies by Dantus, Rosker, and Zewail. These experiments are designed to probe the detailed dynamics of chemical reactions in solution during the time period the reaction is in progress, in particular to reveal the dramatic effects of the solvent on translational motions and energies. Both are pump-probe experiments in which the first photon dissociates the ICN and the second induces fluorescence in the CN fragment. In the first type of experiment, which is particularly sensitive to fragment translational motion, the fluorescence intensity is measured as a function of photon energy and of time delay. In the second type of experiment, which is particularly sensitive to fragment rotation, in addition the angle between the polarizations of the pump and probe photons is varied. In the calculations presented here, the effect of the absorption of the photodissociation photon is treated using the classical Frank-Condon principle. The coupling between the assumed two upper electronic surfaces is taken into account semiclassically using a generalization to the condensed phase of the classical electron model of Miller and Meyer, which was applied to ICN

  20. Nuclear spin dependence of the reaction of H(3)+ with H2. II. Experimental measurements.

    PubMed

    Crabtree, Kyle N; Kauffman, Carrie A; Tom, Brian A; Beçka, Eftalda; McGuire, Brett A; McCall, Benjamin J

    2011-05-21

    The nuclear spin dependence of the chemical reaction H(3)(+)+ H(2) → H(2) + H(3)(+) has been studied in a hollow cathode plasma cell. Multipass infrared direct absorption spectroscopy has been employed to monitor the populations of several low-energy rotational levels of ortho- and para-H(3)(+) (o-H(3)(+) and p-H(3)(+)) in hydrogenic plasmas of varying para-H(2) (p-H(2)) enrichment. The ratio of the rates of the proton hop (k(H)) and hydrogen exchange (k(E)) reactions α ≡ k(H)/k(E) is inferred from the observed p-H(3)(+) fraction as a function of p-H(2) fraction using steady-state chemical models. Measurements have been performed both in uncooled (T(kin) ∼ 350 K) and in liquid-nitrogen-cooled (T(kin) ∼ 135 K) plasmas, marking the first time this reaction has been studied at low temperature. The value of α has been found to decrease from 1.6 ± 0.1 at 350 K to 0.5 ± 0.1 at 135 K. PMID:21599063

  1. Carbon sequestration via reaction with basaltic rocks: geochemical modeling and experimental results

    USGS Publications Warehouse

    Rosenbauer, Robert J.; Thomas, Burt; Bischoff, James L.; Palandri, James

    2012-01-01

    Basaltic rocks are potential repositories for sequestering carbon dioxide (CO2) because of their capacity for trapping CO2 in carbonate minerals. We carried out a series of thermodynamic equilibrium models and high pressure experiments, reacting basalt with CO2-charged fluids over a range of conditions from 50 to 200 °C at 300 bar. Results indicate basalt has a high reactivity to CO2 acidified brine. Carbon dioxide is taken up from solution at all temperatures from 50 to 200 °C, 300 bar, but the maximum extent and rate of reaction occurs at 100 °C, 300 bar. Reaction path simulations utilizing the geochemical modeling program CHILLER predicted an equilibrium carbonate alteration assemblage of calcite, magnesite, and siderite, but the only secondary carbonate identified in the experiments was a ferroan magnesite. The amount of uptake at 100 °C, 300 bar ranged from 8% by weight for a typical tholeite to 26% for a picrite. The actual amount of CO2 uptake and extent of rock alteration coincides directly with the magnesium content of the rock suggesting that overall reaction extent is controlled by bulk basalt Mg content. In terms of sequestering CO2, an average basaltic MgO content of 8% is equivalent to 2.6 × 108 metric ton CO2/km3 basalt.

  2. Experimental differential cross sections, level densities, and spin cutoffs as a testing ground for nuclear reaction codes

    DOE PAGESBeta

    Voinov, Alexander V.; Grimes, Steven M.; Brune, Carl R.; Burger, Alexander; Gorgen, Andreas; Guttormsen, Magne; Larsen, Ann -Cecilie; Massey, Thomas N.; Siem, Sunniva

    2013-11-08

    Proton double-differential cross sections from 59Co(α,p)62Ni, 57Fe(α,p)60Co, 56Fe(7Li,p)62Ni, and 55Mn(6Li,p)60Co reactions have been measured with 21-MeV α and 15-MeV lithium beams. Cross sections have been compared against calculations with the empire reaction code. Different input level density models have been tested. It was found that the Gilbert and Cameron [A. Gilbert and A. G. W. Cameron, Can. J. Phys. 43, 1446 (1965)] level density model is best to reproduce experimental data. Level densities and spin cutoff parameters for 62Ni and 60Co above the excitation energy range of discrete levels (in continuum) have been obtained with a Monte Carlo technique. Furthermore,more » excitation energy dependencies were found to be inconsistent with the Fermi-gas model.« less

  3. Experimental differential cross sections, level densities, and spin cutoffs as a testing ground for nuclear reaction codes

    NASA Astrophysics Data System (ADS)

    Voinov, A. V.; Grimes, S. M.; Brune, C. R.; Bürger, A.; Görgen, A.; Guttormsen, M.; Larsen, A. C.; Massey, T. N.; Siem, S.

    2013-11-01

    Proton double-differential cross sections from 59Co(α,p)62Ni, 57Fe(α,p)60Co, 56Fe(7Li,p)62Ni, and 55Mn(6Li,p)60Co reactions have been measured with 21-MeV α and 15-MeV lithium beams. Cross sections have been compared against calculations with the empire reaction code. Different input level density models have been tested. It was found that the Gilbert and Cameron [A. Gilbert and A. G. W. Cameron, Can. J. Phys.0008-420410.1139/p65-139 43, 1446 (1965)] level density model is best to reproduce experimental data. Level densities and spin cutoff parameters for 62Ni and 60Co above the excitation energy range of discrete levels (in continuum) have been obtained with a Monte Carlo technique. Excitation energy dependencies were found to be inconsistent with the Fermi-gas model.

  4. Experimental U.S. Census Bureau Race and Hispanic Origin Survey Questions: Reactions from Spanish Speakers

    ERIC Educational Resources Information Center

    Terry, Rodney L.; Fond, Marissa

    2013-01-01

    People of Hispanic origin, including monolingual Spanish speakers, have experienced difficulty identifying with a race category on U.S. demographic surveys. As part of a larger research effort by the U.S. Census Bureau to improve race and Hispanic origin questions for the 2020 Census, we tested experimental versions of race and Hispanic origin…

  5. Preparation of Thermo-Responsive Poly(ionic liquid)s-Based Nanogels via One-Step Cross-Linking Copolymerization.

    PubMed

    Zhang, Jing; Liu, Jingjiang; Zuo, Yong; Wang, Rongmin; Xiong, Yubing

    2015-01-01

    In this study, thermo-responsive polymeric nanogels were facilely prepared via one-step cross-linking copolymerization of ethylene glycol dimethacrylate/divinylbenzene and ionic liquid (IL)-based monomers, 1,n-dialkyl-3,3'-bis-1-vinyl imidazolium bromides ([CnVIm]Br; n = 6, 8, 12) in selective solvents. The results revealed that stable and blue opalescent biimidazolium (BIm)-based nanogel solutions could be obtained without any precipitation when the copolymerizations were conducted in methanol. Most importantly, these novel nanogels were thermo-response, and could reversibly transform to precipitation in methanol with temperature changes. Turbidity analysis and dynamic light scatting (DLS) measurement illustrated that PIL-based nanogel solutions presented the phase transform with upper critical solution temperature (UCST) in the range of 5-25 °C. The nanogels were characterized using Fourier transform infrared (FTIR), thermogravimetric analyses (TGA), and scanning electron microscopy (SEM). In addition, BIm-based nanogels could also be used as highly active catalysts in the cycloaddition reaction of CO₂ and epoxides. As a result, our attributes build a robust platform suitable for the preparation of polymeric nanomaterials, as well as CO₂ conversion. PMID:26393567

  6. Evolution of fracture permeability of ultramafic rocks at hydrothermal conditions: An experimental study on serpentinization reactions

    NASA Astrophysics Data System (ADS)

    Farough, A.; Moore, D. E.; Lockner, D. A.; Lowell, R. P.

    2014-12-01

    Serpentinization of ultramafic rocks, during which olivine and pyroxene minerals are replaced by serpentine, magnetite, brucite and talc, is associated with hydrothermal activity at slow and ultraslow mid-ocean ridges. Serpentinization reactions affect hydrothermal fluid circulation by changing permeability of the oceanic crust. To advance our understanding of the evolution of permeability accompanying serpentinization reactions, we performed a series of flow-through experiments at a temperature of 260˚C, a confining pressure of 50 MPa, and a pore pressure of 20±2 MPa on cylindrical cores of ultramafic rocks (18 mm in diameter and 23 mm length) containing a single through-going tensile fracture. Pore fluid flow was in one direction and was collected routinely for chemical analysis. A 7.5 mm thick layer of the same rock, crushed and sieved (0.18-1.0 mm) was placed on the inlet end of the sample to produce a reactive heated reservoir for the pore fluid before entering the fracture. Multiple peridotite samples were tested, to investigate the effect of mineral assemblage on fluid-rock interaction and permeability. The initial effective permeability of the samples varied between 10-(15-18)m2, and it decreased by about 2 orders of magnitude in 7-10 days, showing that serpentinization reactions result in an initially rapid decrease in permeability. The best fit equation for the observed rate of change in permeability (k) is in the form of dk/dt=Ae-0.01t, where A is a constant and t is time. This result suggests that the rate of serpentine formation is largely controlled by the initial permeability rather than the properties of the reacting rock. Assuming flow between parallel plates, we find the effective crack width decreases by approximately 2 orders of magnitude during the experiments. The fluid chemistry and mineralogy data support the occurrence of serpentinization reactions. The early peak and monotonic decrease in the concentration of Mg, and Si in pore fluid

  7. [An experimental unit for the recording of the escape reaction of a ground snail to tactile stimulation].

    PubMed

    Moskvitin, A A; Pivovarov, A S

    2003-01-01

    An original working experimental unit for noninvasive objective recording of the magnitude of escape reaction of a ground snail evoked by tactile stimulation is described. A. snail creeps upwards over the cylinder rotating around its horizontal axis. A watching device ensures a constant snail position relative to a light source and a photoelement. A device for tactile stimulation which provides graduated energy of an impact is constructed on the basis of the magnetic circuit of a loudspeaker. In response to a tactile stimulus a snail pulls in its feelers, head, and foot, and the area of snail's shadow decreases. These changes are indicated by the photoelement. PMID:12754854

  8. Experimental Measurements of the Chemical Reaction Zone of Detonating Liquid Explosives

    NASA Astrophysics Data System (ADS)

    Bouyer, Viviane; Sheffield, Stephen A.; Dattelbaum, Dana M.; Gustavsen, Richard L.; Stahl, David B.; Doucet, Michel; Decaris, Lionel

    2009-12-01

    We have a joint project between CEA-DAM Le Ripault and Los Alamos National Laboratory (LANL) to study the chemical reaction zone in detonating high explosives using several different laser velocimetry techniques. The short temporal duration of the von Neumann spike and early part of the reaction zone make these measurements difficult. Here, we report results obtained from detonation experiments using VISAR (velocity interferometer system for any reflector) and PDV (photon Doppler velocimetry) methods to measure the particle velocity history at a detonating nitromethane/PMMA interface. Experiments done at CEA were high-explosive-plane-wave initiated and those at LANL were gas-gun-projectile initiated with a detonation run of about 6 charge diameters in all experiments. The experiments had either glass or brass confinement. Excellent agreement of the interface particle velocity measurements at both Laboratories were obtained even though the initiation methods and the velocimetry systems were somewhat different. Some differences were observed in the peak particle velocity because of the ˜2 ns time resolution of the techniques—in all cases the peak was lower than the expected von Neumann spike. This is thought to be because the measurements were not high enough time resolution to resolve the spike.

  9. Experimental Measurements of the Chemical Reaction Zone of Detonating Liquid Explosives

    NASA Astrophysics Data System (ADS)

    Bouyer, Viviane; Sheffield, Stephen A.; Dattelbaum, Dana M.; Gustavsen, Richard L.; Stahl, David B.; Doucet, Michel

    2009-06-01

    We have a joint project between CEA-DAM Le Ripault and Los Alamos National Laboratory (LANL) to study the chemical reaction zone in detonating high explosives using several different laser velocimetry techniques. The short temporal duration of the features (von Neumann spike and sonic locus) of the reaction zone make these measurements difficult. Here, we report results obtained from using and PDV (photon Doppler velocimetry) methods to measure the particle velocity history at a detonating HE (nitromethane)/PMMA interface. Experiments done at CEA were high-explosive-plane-wave initiated and those at LANL were gas-gun-projectile initiated with a detonation run of about 6 charge diameters in all experiments, in either glass or brass confinement. Excellent agreement of the interface particle velocity measurements at both Laboratories were obtained even though the initiation systems and the velocimetry systems were different. Some differences were observed in the von Neumann spike height because of the approximately 2 nanosecond time resolution of the techniques -- in some or all cases the spike top was truncated.

  10. Experimental and theoretical studies of rate coefficients for the reaction O(3P)+CH3OH at high temperatures.

    PubMed

    Lu, Chih-Wei; Chou, Shen-Long; Lee, Yuan-Pern; Xu, Shucheng; Xu, Z F; Lin, M C

    2005-06-22

    Rate coefficients of the reaction O((3)P) + CH(3)OH in the temperature range of 835-1777 K were determined using a diaphragmless shock tube. O atoms were generated by photolysis of SO(2) with a KrF excimer laser at 248 nm or an ArF excimer laser at 193 nm; their concentrations were monitored via atomic resonance absorption excited by emission from a microwave-discharged mixture of O(2) and He. The rate coefficients determined for the temperature range can be represented by the Arrhenius equation, k(T) = (2.29 +/- 0.18) x 10(-10) exp[-(4210 +/- 100)T] cm(3) molecule(-1) s(-1); unless otherwise noted, all the listed errors represent one standard deviation in fitting. Combination of these and previous data at lower temperature shows a non-Arrhenius behavior described as the three-parameter equation, k(T) = (2.74 +/- 0.07) x 10(-18)T(2.25 +/- 0.13) exp[-(1500 +/- 90)T] cm(3)molecule(-1) s(-1). Theoretical calculations at the Becke-3-Lee-Yang-Parr (B3LYP)6-311 + G(3df,2p) level locate three transition states. Based on the energies computed with coupled clusters singles, doubles (triples) [CCSD(T)]/6-311 + G(3df,2p)B3LYP6-311 + G(3df,2p), the rate coefficients predicted with canonical variational transition state theory with small curvature tunneling corrections agree satisfactorily with the experimental observations. The branching ratios of two accessible reaction channels forming OH + CH(2)OH (1a) and OH + CH(3)O (1b) are predicted to vary strongly with temperature. At 300 K, reaction (1a) dominates, whereas reaction (1b) becomes more important than reaction (1a) above 1700 K. PMID:16035764

  11. Reaction cross-section calculations using new experimental and theoretical level structure data for deformed nuclei

    SciTech Connect

    Hoff, R.W.; Gardner, D.G.; Gardner, M.A.

    1984-10-05

    A technique for modeling quasiparticle excitation energies and rotational parameters in odd-odd deformed nuclei has been used to construct sets of discrete states with energy 0 to 1.5 MeV in /sup 176/Lu and /sup 236/Np. These data were used as part of the input for calculation of isomer production cross-section ratios in the /sup 175/Lu(n,..gamma..)/sup 176/Lu and /sup 237/Np(n,2n)/sup 236/Np reactions. In order to achieve agreement with experiment, it has been found necessary to include in the modeled set many rotational bands (35 to 95), which are comprised of hundreds of levels with their gamma-ray branching ratios. It is essential that enough bands be included to produce a representative selection of K quantum numbers in the de-excitation cascade. 20 refs., 3 figs., 3 tabs.

  12. Experimental Studies of Fast Protons Originated from Fusion Reactions in Plasma-Focus Discharges

    SciTech Connect

    Malinowska, A.; Malinowski, K.; Sadowski, M. J.; Zebrowski, J.; Szydlowski, A.

    2008-03-19

    The paper describes results of the recent measurements of fusion-reaction protons, which were performed within the PF-360 facility operated at the IPJ in Swierk, Poland. The main aim of those studies was to perform time-integrated measurements of fast protons (of energy of about 3 MeV) by means of ion-pinhole cameras, which were equipped with solid state nuclear track detectors (SSNTD) of the PM-355 type and absorption filters made of thin metal foils. In order to determine the spatial distribution of fusion-produced protons the use was made of several miniature pinhole cameras placed at different angles to the PF-360 axis. The irradiated and etched detectors were analyzed with an optical microscope coupled with a CCD camera and a PC unit.

  13. Combined Experimental and Computational Approach to Predict the Glass-Water Reaction

    SciTech Connect

    Pierce, Eric M.; Bacon, Diana H.

    2011-10-01

    The use of mineral and glass dissolution rates measured in laboratory experiments to predict the weathering of primary minerals and volcanic and nuclear waste glasses in field studies requires the construction of rate models that accurately describe the weathering process over geologic timescales. Additionally, the need to model the long-term behavior of nuclear waste glass for the purpose of estimating radionuclide release rates requires that rate models be validated with long-term experiments. Several long-term test methods have been developed to accelerate the glass-water reaction [drip test, vapor hydration test, product consistency test B, and pressurized unsaturated flow (PUF)], thereby reducing the duration required to evaluate long-term performance. Currently, the PUF test is the only method that mimics the unsaturated hydraulic properties expected in a subsurface disposal facility and simultaneously monitors the glass-water reaction. PUF tests are being conducted to accelerate the weathering of glass and validate the model parameters being used to predict long-term glass behavior. A one-dimensional reactive chemical transport simulation of glass dissolution and secondary phase formation during a 1.5-year-long PUF experiment was conducted with the Subsurface Transport Over Reactive Multiphases (STORM) code. Results show that parameterization of the computer model by combining direct bench scale laboratory measurements and thermodynamic data provides an integrated approach to predicting glass behavior over the length of the experiment. Over the 1.5-year-long test duration, the rate decreased from 0.2 to 0.01 g/(m2 day) based on B release for low-activity waste glass LAWA44. The observed decrease is approximately two orders of magnitude higher than the decrease observed under static conditions with the SON68 glass (estimated to be a decrease by four orders of magnitude) and suggests that the gel-layer properties are less protective under these dynamic

  14. Combined Experimental and Computational Approach to Predict the Glass-Water Reaction

    SciTech Connect

    Pierce, Eric M; Bacon, Diana

    2011-01-01

    The use of mineral and glass dissolution rates measured in laboratory experiments to predict the weathering of primary minerals and volcanic and nuclear waste glasses in field studies requires the construction of rate models that accurately describe the weathering process over geologic time-scales. Additionally, the need to model the long-term behavior of nuclear waste glass for the purpose of estimating radionuclide release rates requires that rate models are validated with long-term experiments. Several long-term test methods have been developed to accelerate the glass-water reaction [drip test, vapor hydration test, product consistency test-B, and pressurized unsaturated flow (PUF)], thereby reducing the duration required to evaluate long-term performance. Currently, the PUF test is the only method that mimics the unsaturated hydraulic properties expected in a subsurface disposal facility and simultaneously monitors the glass-water reaction. PUF tests are being conducted to accelerate the weathering of glass and validate the model parameters being used to predict long-term glass behavior. A one-dimensional reactive chemical transport simulation of glass dissolution and secondary phase formation during a 1.5-year long PUF experiment was conducted with the subsurface transport over reactive multi-phases code. Results show that parameterization of the computer model by combining direct bench-scale laboratory measurements and thermodynamic data provides an integrated approach to predicting glass behavior over the length of the experiment. Over the 1.5-year long test duration, the rate decreased from 0.2 to 0.01 g/(m2 d) base on B release. The observed decrease is approximately two orders of magnitude higher than the decrease observed under static conditions with the SON68 glass (estimated to be a decrease by 4 orders of magnitude) and suggest the gel-layer properties are less protective under these dynamic conditions.

  15. On the Way to Experimental Test of the Time Reversal Invariance in the Nuclear Reactions

    PubMed Central

    Skoy, Vadim R.; Ino, Takashi; Masuda, Yasuhiro; Muto, Suguru; Kim, Guinyun

    2005-01-01

    Time (T) violation can be related with charge-parity (CP) violation through the CPT theorem. The CP violation was discovered experimentally in the K0-meson decays about 35 years ago. The T violating interaction related with the CP violation violates parity as well. However, an extension of the theory beyond the locality of the interactions might violate the CPT theorem. The result of the CPLEAR experiment [1], which has given direct evidence of T violation in the elementary-particle phenomena, could be considered under assumption of the CPT invariance. PMID:27308170

  16. Experimental and theoretical studies on gas-phase reactions of NO3 radicals with three methoxyphenols: Guaiacol, creosol, and syringol

    NASA Astrophysics Data System (ADS)

    Yang, Bo; Zhang, Haixu; Wang, Youfeng; Zhang, Peng; Shu, Jinian; Sun, Wanqi; Ma, Pengkun

    2016-01-01

    Methoxyphenols, lignin pyrolysis products, are major biomass combustion components and are considered potential tracers for wood smoke emissions. Their atmospheric reactivity, however, has not been well characterized. Guaiacol, creosol, and syringol are three typical methoxyphenols generated in relatively high concentrations in fresh wood smoke. In this study, the gas-phase reactions of NO3 radicals with these methoxyphenols were investigated using a laboratory-built vacuum ultraviolet photoionization gas time-of-flight mass spectrometer (VUV-GTOFMS) and off-line GC-MS. By combining experimental and theoretical methods, 4-nitroguaiacol, 6-nitroguaiacol, and 4,6-dinitroguaiacol were determined as the primary degradation products for guaiacol; similarly, 6-nitrocreosol and 3-nitrosyringol were identified for creosol and syringol, respectively. Using the relative rate method, rate constants at 298 K and 1 atm for the gas-phase reactions of guaiacol, creosol, and syringol with NO3 radicals were measured to be 3.2 × 10-12, 2.4 × 10-13, and 4.0 × 10-13 cm3 molecule-1 s-1, respectively. At a typical tropospheric concentration of NO3 radicals (5 × 108 molecule cm-3), atmospheric lifetimes for guaiacol, creosol, and syringol toward NO3 radicals were 0.2, 2.3, and 1.4 h, respectively. These results indicate that the reaction with NO3 radicals can be a major sink for methoxyphenols at night.

  17. Experimental and Computational Induced Aerodynamics from Missile Jet Reaction Controls at Angles of Attack to 75 Degrees

    NASA Technical Reports Server (NTRS)

    Capone, Francis J.; Ashbury, Scott C.; Deere, Karen A.

    1996-01-01

    An investigation was conducted in the Langley 16-Foot Transonic Tunnel to determine induced aerodynamic effects from jet reaction controls of an advanced air-to-air missile concept. The 75-percent scale model featured independently controlled reaction jets located near the nose and tail of the model. Aerodynamic control was provided by four fins located near the tail of the model. This investigation was conducted at Mach numbers of 0.35 and 0.60, at angles of attack up to 75 deg and at nozzle pressure ratios up to 90. Jet-reaction thrust forces were not measured by the force balance but jet-induced forces were. In addition, a multiblock three-dimensional Navier-Stokes method was used to calculate the flowfield of the missile at angles of attack up to 40 deg. Results indicate that large interference effects on pitching moment were induced from operating the nose jets with the the off. Excellent correlation between experimental and computational pressure distributions and pitching moment were obtained a a Mach number of 0.35 and at angles of attack up to 40 deg.

  18. Experimental elaboration of faulting induced by fluid-releasing mineral reactions in subduction zones

    NASA Astrophysics Data System (ADS)

    Green, H.; Zhang, J.; Jung, H.; Dobrzinetskaya, L.

    2003-04-01

    Dehydration embrittlement has been cited repeatedly as a potential mechanism for triggering earthquakes at depths where unassisted brittle failure is impossible due to the normal-stress-dependence of friction. We are investigating two different aspects of this problem in the laboratory: (i) dehydration of antigorite under stress where the ΔV of reaction varies from strongly positive to distinctly negative; (ii) deformation of eclogite in which the nominally anhydrous minerals contain small amounts of dissolved H_2O that can lead to faulting induced by very small amounts of melting stimulated by exsolution of H_2O. (i) Antigorite has the largest stability field of the serpentines and is often cited as potentially being the source of most or all mantle earthquakes to a depth of over 200 km. However, like other low-pressure hydrous phases, the net volume change accompanying antigorite dehydration varies from strongly positive at low P to negative at P > ˜2-2.5 GPa. Fracture mechanics theory predicts that dehydration should not induce shear failure if ΔV<0. To test the effect of ΔV on faulting, we have deformed an extensively-serpentinized peridotite at P = 1-6 GPa. We conducted constant strain rate experiments in a Griggs-type apparatus at P = 1.0 - 3.4 GPa and rapid-pumping experiments in a Walker-type multianvil apparatus, culminating in pressures as high as 6 GPa. Independent of the sign of ΔV, specimens subjected to stress during dehydration yielded extremely thin zones of reaction products with shear offset across them. Some were clearly faults whereas others could be precursors to faulting. Fluid released at grain boundaries between antigorite and relict olivine locally produced Mode I cracks &fluid inclusions. (ii) Deformation of "wet" eclogite at 3 GPa and temperatures between the wet and dry solidi induced exsolution of H_2O and formation of very small amounts (<1%) of melt, leading to faulting. At lower temperature the rock was extremely strong but

  19. Fabrication of microarray of gel-immobilized compounds on a chip by copolymerization.

    SciTech Connect

    Vasiliskov, A. V.; Timofeev, E. N.; Surzhikov, S. A.; Drobyshev, A. L.; Shick, V. V.; Mirzabekov, A. D.; Biochip Technology Center; Engelhardt Inst. of Molecular Biology; Moscow Inst. of Physics and Technology

    1999-09-01

    The manufacturing of microchips containing oligonucleotides and proteins immobilized within gel pads, ranging in size from 10 x 10 to 100 x 100 {mu}m, is described. The microchips are produced by photo- or persulfate-induced copolymerization of unsaturated derivatives of biomolecules with acrylamide-bisacrylamide mixture. Oligonucleotides containing 5'-allyl or 5'-butenediol units were synthesized using standard phosphoramidite chemistry. Acryloyl residues were attached to a protein by a twostep procedure. Photopolymerization was induced by illumination of the monomer solution containing initiator with UV light through the mask. The mask was applied directly over the monomer solution or projected through a microscope. Alternatively, copolymerization was carried out in drops of aqueous solution of monomers containing ammonium persulfate. Drops with different allyl-oligonucleotides were distributed on a glass slide, and the polymerization was induced by diffusion of N,N,N',N'-tetramethylethylenediamine (TEMED) from a hexane solution that covered the aqueous drops.

  20. Anticancer drug release from poly(N-isopropylacrylamide/itaconic acid) copolymeric hydrogels

    NASA Astrophysics Data System (ADS)

    Taşdelen, B.; Kayaman-Apohan, N.; Güven, O.; Baysal, B. M.

    2005-08-01

    The drug uptake and release of anticancer drug from N-isopropylacrylamide/itaconic acid copolymeric hydrogels containing 0-3 mol% of itaconic acid irradiated at 48 kGy have been investigated. 5-Fluorouracil (5-FU) is used as a model anticancer drug. The effect of 5-FU solution on swelling characteristics of PNIPAAm and P(NIPAAm/IA) copolymeric hydrogels have also been studied. The percent swelling, equilibrium swelling, equilibrium water/5-FU content and diffusion constant values are evaluated for poly(N-isopropylacrylamide) (PNIPAAm) and poly(N-isopropylacrylamide/itaconic) (P(NIPAAm/IA)) hydrogels at 130 ppm of 5-FU solution at room temperature. Diffusion of 5-FU solution into the hydrogels has been found to be the non-Fickian type. Finally, the kinetics of drug release from the hydrogels are examined.

  1. Antimicrobial cotton containing N-halamine and quaternary ammonium groups by grafting copolymerization

    NASA Astrophysics Data System (ADS)

    Liu, Ying; Liu, Yin; Ren, Xuehong; Huang, T. S.

    2014-03-01

    The monomer (3-acrylamidopropyl)trimethylammonium chloride (APTMAC) was used to treat cotton fibers by grafting copolymerization. The grafted cotton fabrics were characterized by SEM image and FTIR spectra. The treated samples with quaternary ammonium groups could decrease 96.08% of Staphylococcus aureus and 48.74% of Escherichia coli O157:H7 within 30 min. After chlorination with dilute sodium hypochlorite, the treated cotton fabrics containing both N-halamine and quaternary ammonium groups effectively inactivated 100% (log reduction 5.82) of S. aureus and 100% (log reduction 6.26) of E. coli O157:H7 within 5 min of contact time. The grafting process of cotton fabric has small effect on the thermal stability and tensile strength, which favors the practical application. Compared to the traditional pad-dry-cure method to produce antibacterial materials, the radical grafting copolymerization method occurred in water without any organic solvents involved in the whole treatment.

  2. Toward a Unified Mechanism for Oxoammonium Salt-Mediated Oxidation Reactions: A Theoretical and Experimental Study Using a Hydride Transfer Model.

    PubMed

    Hamlin, Trevor A; Kelly, Christopher B; Ovian, John M; Wiles, Rebecca J; Tilley, Leon J; Leadbeater, Nicholas E

    2015-08-21

    A range of oxoammonium salt-based oxidation reactions have been explored computationally using density functional theory (DFT), and the results have been correlated with experimentally derived trends in reactivity. Mechanistically, most reactions involve a formal hydride transfer from an activated C-H bond to the oxygen atom of the oxoammonium cation. Several new potential modes of reactivity have been uncovered and validated experimentally. PMID:26167866

  3. [The effect of gamma-L-glutamylhistamine analogues on the severity of experimental anaphylactic reaction, hormonal status and liver cytochrome P450 system].

    PubMed

    Nebol'sin, V E; Zheltukhina, G A; Krzhechkovskaia, V V; Kovaleva, V L; Evstigneeva, R P

    2001-01-01

    The influence of gamma-L-glutamylhistamine analogues on the hexenal-induced sleeping, glucocorticoid hormone content in blood plasma and severity of experimental anaphylactic reaction was studied. It was observed that gamma-L-glutamylhistamine analogues caused decrease in the sleeping time and severity of experimental anaphylactic reaction, the elevation of glucocorticoids content in blood plasma. The present results indicate that substances have the wide spectrum of biological activity which depends on the length of the N-acyl radical. PMID:11558312

  4. Monodispersepoly[BMA-co-(COPS-I)] Particles by Soap-Free Emulsion Copolymerization and Its Optical Properties as Photonic Crystals.

    PubMed

    Lee, Ki Chang; Choo, Hun Seung

    2015-10-01

    In order to study the surfactant-free emulsion copolymerization of benzyl methacrylate (BMA) with sodium 1-allyloxy-2-hydroxypropane sulfonate (COPS-I) and the resulting optical properties, a series of experiments was carried out at various reaction conditions such as the changes of BMA concentration, COPS-I concentration, BMA concentration under a fixed COPS-I amount, initiator and divinyl benzene (DVB) concentration. All the latices showed highly monodispersed spherical particles in the size range of 144~435 nm and the respective shiny structural colors from their colloidal photonic crystals. It is found that the changes in such polymerization factors greatly affect the number of particles and particle diameter, polymerization rate, molecular weight, zeta-potential, and refractive indices. The increase of number of particles led to the increased rate of polymerization and zeta-potential of the latices, on the other hand, to the decreased molecular weight. Refractive indices and the reflectivity increased with COPS-I concentration, on the other hand, and decreased with DVB concentration. Especially, refractive indices of the resulting poly[BMA-co-(COPS-I)] colloidal photonic crystals showed much higher values of 1.65~2.21 than that of polystyrene, due to the formation of core-shell shaped morphology. Monodisperse and high refractive index of poly[BMA-co-(COPS-I)] particles prepared in this work could be used for the study in photonic crystals and electrophoretic display. PMID:26726393

  5. Porous polymer monoliths with large surface area and functional groups prepared via copolymerization of protected functional monomers and hypercrosslinking.

    PubMed

    Maya, Fernando; Svec, Frantisek

    2013-11-22

    A new approach to the preparation of porous polymer monoliths possessing both large surface area and functional groups has been developed. The chloromethyl groups of poly(styrene-co-4-acetoxystyrene-co-vinylbenzyl chloride-co-divinylbenzene) monolith enable post-polymerization hypercrosslinking catalyzed by ferric chloride in dichloroethane leading to a multitude of small pores thus enhancing the surface area. The acetoxy functionalities are easily deprotected using hydrazine to produce polar phenolic hydroxyl groups, which would be difficult to obtain by direct copolymerization of hydroxyl-containing monomers. The hypercrosslinking and deprotection reactions as well as their sequence were studied in detail with bulk polymer monoliths containing up to 50% 4-acetoxystyrene and its progress monitored by infrared spectrometry and nitrogen adsorption/desorption measurements. No significant difference was found for both possible successions. All monoliths were also prepared in a capillary column format, then deprotected and hypercrosslinked. Capillary columns were tested for the separation of small molecules using reversed phase and normal phase chromatographic modes. For polymer monoliths containing 50% deprotected 4-acetoxystyrene, column efficiencies of 40,000 plates/m for benzene in reversed phase mode and 31,800 plates/m for nitrobenzene in normal phase mode, were obtained. The percentage of hydroxyl groups in the monoliths enables modulation of polarity of the stationary phase. They also represent functionalities that are potentially suitable for further modifications and formation of new types of stationary phases for liquid chromatography. PMID:23910448

  6. Synthesis of α(1→4)-linked non-natural mannoglucans by α-glucan phosphorylase-catalyzed enzymatic copolymerization.

    PubMed

    Baba, Ryotaro; Yamamoto, Kazuya; Kadokawa, Jun-Ichi

    2016-10-20

    α-Glucan phosphorylase catalyzes enzymatic polymerization of α-d-glucose 1-phosphate (Glc-1-P) as a monomer from a maltooligosaccharide primer to produce α(1→4)-glucan, i.e., amylose, with liberating inorganic phosphate (Pi). Because of quite weak specificity for the recognition of substrates by thermostable α-glucan phosphorylase (from Aquifex aeolicus VF5), in this study, we investigated the enzymatic copolymerization of Glc-1-P with its analogue monomer, α-d-mannose 1-phosphate (Man-1-P) under the conditions for removal of Pi as the precipitate with ammonium and magnesium in ammonia buffer containing Mg(2+) ion to produce α(1→4)-linked non-natural mannoglucans composed of Glc/Man units. The reaction was conducted in different feed ratios using the maltotriose primer at 40°C for 7days. The MALDI-TOF mass and (1)H NMR spectra of the products fully supported the mannoglucan structures. PMID:27474652

  7. Tailored Living Block Copolymerization: Multiblock Poly(cyclohexene carbonate)s with Sequence Control

    SciTech Connect

    Kim, Jeung Gon; Cowman, Christina D.; LaPointe, Anne M.; Wiesner, Ulrich; Coates, Geoffrey W.

    2011-03-08

    In this Communication, the living block copolymerization of functionalized cyclohexene oxides and CO{sub 2} is described, yielding multiblock poly(cyclohexene carbonate)s [p(CHC)s] with a diverse range of functionality on the side chains and good control of block sequence and length. Unlike prior systems that contain stable vinyl backbones, the carbonate backbones of polymers reported herein are degradable, allowing possible applications where removable templates are required.

  8. Random and block copolymerization in metal oxide gel synthesis from metalorganic compounds

    NASA Technical Reports Server (NTRS)

    Mukherjee, S. P.

    1985-01-01

    The introduction and development of the block copolymerization concept in metal oxide gel synthesis will in the future generate a new class of glass/microcrystalline materials. By the year 2004, better scientific understanding of the chemical principles controlling the distribution of network formers or modifiers in silicate gels will permit the synthesis of architecturally well-defined block polymers with unique high-performance behavior.

  9. Experimental and Computational Studies of the Isomerization Reactions of Bidentate Phosphine Ligands in Triosmium Clusters

    SciTech Connect

    Xue, Zhang; Kandala, Srikanth; Yang, Li; Watson, William H.; Wang, Xiaoping; Hrovat, David A.

    2011-01-01

    The diphosphine ligand 1,2-bis(diphenylphosphino)benzene (dppbz) reacts with the activated cluster 1,2-Os{sub 3}(CO){sub 10}(MeCN){sub 2} (1) at room temperature to furnish a mixture of the triosmium clusters 1,2-Os{sub 3}(CO){sub 10}(dppbz) (2) and 1,1-Os{sub 3}(CO){sub 10}(dppbz) (3), along with a trace amount of the hydride cluster HOs{sub 3}(CO){sub 9}[{mu}-1,2-PhP(C{sub 6}H{sub 4}-{eta}{sup 1})C{sub 6}H{sub 4}PPh{sub 2}] (4). The dppbz-bridged cluster 2 forms as the kinetically controlled product and irreversibly transforms to the corresponding chelated isomer 3 at ambient temperature. The disposition of the dppbz ligand in 2 and 3 has been established by X-ray crystallography and {sup 31}P NMR spectroscopy, and the kinetics for the conversion 2 {yields} 3 have been followed by UV-vis spectroscopy in toluene over the temperature range 318-343 K. The calculated activation parameters ({Delta}H{sub {+-}} = 21.6(3) kcal/mol; {Delta}S{sub {+-}} = -11(1) eu) and lack of CO inhibition support an intramolecular isomerization mechanism that involves the simultaneous migration of phosphine and CO groups about the cluster polyhedron. The reaction between 1 and the fluorinated diphosphine ligand 1,2-bis(diphenylphosphino)tetrafluorobenzene (dppbzF{sub 4}) was examined under similar reaction conditions and was found to afford the chelated cluster 1,1-Os{sub 3}(CO){sub 10}(dppbzF{sub 4}) (6) as the sole observable product. The absence of the expected bridged isomer 1,2-Os{sub 3}(CO){sub 10}(dppbzF{sub 4}) (5) suggests that the dppbzF{sub 4} ligand destabilizes 5, thus accounting for the rapid isomerization of 5 to 6. Near-UV irradiation of clusters 3 and 6 leads to CO loss and ortho metalation of an ancillary aryl group. The resulting hydride clusters 4 and HOs{sub 3}(CO){sub 9}[{mu}-1,2-PhP(C{sub 6}H{sub 4}-{eta}{sup 1})C{sub 6}F{sub 4}PPh{sub 2}] (7) have been isolated and fully characterized by spectroscopic and X-ray diffraction analyses. Both 4 and 7 react with added

  10. Experimental study of the 66Ni(d ,p ) 67Ni one-neutron transfer reaction

    NASA Astrophysics Data System (ADS)

    Diriken, J.; Patronis, N.; Andreyev, A.; Antalic, S.; Bildstein, V.; Blazhev, A.; Darby, I. G.; De Witte, H.; Eberth, J.; Elseviers, J.; Fedosseev, V. N.; Flavigny, F.; Fransen, Ch.; Georgiev, G.; Gernhauser, R.; Hess, H.; Huyse, M.; Jolie, J.; Kröll, Th.; Krücken, R.; Lutter, R.; Marsh, B. A.; Mertzimekis, T.; Muecher, D.; Orlandi, R.; Pakou, A.; Raabe, R.; Randisi, G.; Reiter, P.; Roger, T.; Seidlitz, M.; Seliverstov, M.; Sotty, C.; Tornqvist, H.; Van De Walle, J.; Van Duppen, P.; Voulot, D.; Warr, N.; Wenander, F.; Wimmer, K.

    2015-05-01

    The quasi-SU(3) sequence of the positive parity ν g9 /2,d5 /2,s1 /2 orbitals above the N =40 shell gap are assumed to induce strong quadrupole collectivity in the neutron-rich Fe (Z =26 ) and Cr (Z =24 ) isotopes below the nickel region. In this paper the position and strength of these single-particle orbitals are characterized in the neighborhood of 68Ni (Z =28 ,N =40 ) through the 66Ni(d ,p )67Ni one-neutron transfer reaction at 2.95 MeV/nucleon in inverse kinematics, performed at the REX-ISOLDE facility in CERN. A combination of the Miniball γ -array and T-REX particle-detection setup was used and a delayed coincidence technique was employed to investigate the 13.3-μ s isomer at 1007 keV in 67Ni. Excited states up to an excitation energy of 5.8 MeV have been populated. Feeding of the ν g9 /2 (1007 keV) and ν d5 /2 (2207 keV and 3277 keV) positive-parity neutron states and negative parity (ν p f ) states have been observed at low excitation energy. The extracted relative spectroscopic factors, based on a distorted-wave Born approximation analysis, show that the ν d5 /2 single-particle strength is mostly split over these two excited states. The results are also compared to the distribution of the proton single-particle strength in the 90Zr region (Z =40 ,N =50 ) .

  11. Grafting copolymerization of acrylamides onto preirradiated PP films

    NASA Astrophysics Data System (ADS)

    Chen, Jie; Nho, Young Chang; Kwon, Oh Hyun; Hoffman, Allan S.

    1999-06-01

    Acrylamide (AAm), N,N-Dimethylacrylamide (DMAAm) and N-(3-Dimethylaminopropyl) methacrylamide (DMAPMAAm) were grafted onto polypropylene (PP) films by preirradiation grafting respectively. The effect of irradiation dose, solvent systems and reaction time on the degree of grafting were determined. The grafted sample films were verified by Fourier Transform Infrared (FTIR) spectroscopy in the attenuated total reflectance mode (ATR) and the determination of water contact angle. The blood compatibility of the grafted PP films were evaluated by the determination of platelet adsorption and thrombus. The blood compatibility of grafted PP films seems better than that of original PP films.

  12. Radiation-initiated emulsion copolymerization of styrene and carboxylic acid monomers. [Gamma radiation

    SciTech Connect

    Egusa, S.; Makuuchi, K.

    1982-03-01

    The emulsion copolymerization of styrene and carboxylic acid monomers such as acrylic, methacrylic, and itaconic acids (AAc, MAAc, IAc) was studied by using /sup 60/Co ..gamma..-rays as initiator and sodium dodecylsulfate as emulsifier. The polymerization behavior of these acid monomers was followed by simultaneous conductometric and potentiometric titrations for a latex sample taken in polymerization. The polymerization rate of these acid monomers increases in the following order of hydrophobicity: IAc < AAc < MAAc; this suggests that their polymerization sites are mainly the surface and/or subsurface regions of latex particles. The copolymerization rate of styrene and acid monomer increases with an increase in the acid monomer content for AAc and MAAc, whereas for IAc the rate decreases. The particle sizes determined by the stopped-flow method reveal that this variation of copolymerization rate cannot be explained by the number of growing particles and should be attributed to another factor; for instance, the transfer rate of styrene molecules from oil droplets to growing particles.

  13. Photomediated Controlled Radical Polymerization and Block Copolymerization of Vinylidene Fluoride.

    PubMed

    Asandei, Alexandru D

    2016-02-24

    This review summarizes recent research on novel photochemical methods for the initiation and control of the polymerization of main chain fluorinated monomers as exemplified by vinylidene fluoride (VDF) and for the synthesis of their block copolymers. Such reactions can be carried out at ambient temperature in glass tubes using visible light. Novel, original protocols include the use of hypervalent iodide carboxylates alone or in conjunction with molecular iodine, as well as the use of photoactive transition metal carbonyls in the presence of alkyl, fluoroalkyl, and perfluoroalkyl halides. An in-depth study of the reaction parameters highlights the use of dimethyl carbonate as a preferred polymerization solvent and outlines the structure-property relationship for hypervalent iodide carboxylates and halide initiators in both the free radical and iodine degenerative transfer controlled radical polymerization (IDT-CRP) of VDF. Finally, the rational selection of metal carbonyls that are successful not only as IDT mediators but, more importantly, in the quantitative activation of both PVDF-CH2-CF2-I and PVDF-CF2-CH2-I chain ends toward the synthesis of well-defined PVDF block copolymers is presented. PMID:26760676

  14. Simulation and Experimental Study on the Efficiency of Traveling Wave Direct Energy Conversion for Application to Aneutronic Fusion Reactions

    NASA Astrophysics Data System (ADS)

    Tarditi, Alfonso; Chap, Andrew; Miley, George; Scott, John

    2013-10-01

    A study based on both Particle-in-cell (PIC) simulation and experiments is being developed to study the physics of the Traveling Wave Direct Energy Converter (TWDEC,) with the perspective of application to aneutronic fusion reaction products and space propulsion. The PIC model is investigating in detail the key TWDEC physics process by simulating the time-dependent transfer of energy from the ion beam to an electric load connected to ring-type electrodes in cylindrical symmetry. An experimental effort is in progress on a TWDEC test article at NASA, Johnson Space Center with the purpose of studying the conditions for improving the efficiency of the direct energy conversion process. Using a scaled-down ion energy source, the experiment is primarily focused on the effect of the (bunched) beam density on the efficiency and on the optimization of the electrode design. The simulation model is guiding the development of the experimental configuration and will provide details of the beam dynamics for direct comparison with experimental diagnostics. Work supported by NASA, Johnson Space Center.

  15. Theoretical and experimental investigation of carnosine and its oxygenated adducts. The reaction with the nickel ion

    NASA Astrophysics Data System (ADS)

    Pavlos, Dimitrios; Petropouleas, Panayiotis; Hatzipanayioti, Despina

    2015-11-01

    DFT theoretical calculations at B3LYP/TZVP or LANL2DZ level of theory, for neutral, zwitterions, protonated and anionic carnosine, were performed. Energies, the structural and spectroscopic parameters were calculated in the gas phase and aqueous medium. Additional H-bonds stabilize the ionized forms of carnosine, creating "nests" into which metal ions or bio-molecules may be sheltered. Based on Fukui functions, the reactivity of the abovementioned forms of carnosine, with 1O2, may lead to oxygenated species. The theoretical spectroscopic parameters have been correlated to our experimental results. The effect of H2O2 and the electrochemistry of aqueous carnosine solutions were examined. Theoretical models containing Ni(II), carnosine and water were constructed. In the isolated mauve solid, formulated [Ni(carn)2(H2O)5], the COOsbnd , Nπ and/or NH2 were bonded. When H2O2 was added, the imidazole NMR signals disappeared. A redox couple clearly indicates one electron process, the electron coming from either the oxidation of imidazole ring or the nickel(II)/Ni(III) couple.

  16. The kinetics of clumped-isotope reactions in calcite and apatite from natural and experimental samples

    NASA Astrophysics Data System (ADS)

    Stolper, D. A.; Eiler, J. M.

    2014-12-01

    Measurements of clumped isotopes of carbonate-bearing minerals are a powerful tool for reconstructing past surface temperatures and thermal histories of shallow crustal rocks. Because the clumped-isotope thermometer is based on homogenous-phase equilibrium, a sample's clumped-isotope temperature is susceptible to resetting through, for example, intracrystalline diffusion and redistribution of C and O isotopes during (re)heating or slow cooling. Quantitative knowledge of the kinetics of this resetting have received increasing attention (1-3) and is critical for understanding the meaning of clumped-isotope temperatures of samples with complex burial histories. To better constrain these kinetics and complement previous work (1-3) we performed heating experiments (400-700°C) on optical calcites and carbonate-bearing apatites. As previously observed (2-3), calcites exhibit non-first-order kinetics. The data were fit using a model that incorporates both diffusion and isotope-exchange reactions (4). The kinetics derived with this model using the optical-calcite heating experiments of (2) and those measured here are indistinguishable. The model predicts that subtle changes (>10°C) in measured calcite clumped-isotope temperatures can occur at burial temperatures between 60-100°C on million-year timescales. Though small, such changes may have an impact on clumped-isotope-based reconstructions of past surface temperatures and thermal histories. The derived kinetics were compared to clumped-isotope measurements of cogenetic calcites and apatites from slowly cooled carbonatite intrusions. Apparent temperatures are 70-140°C for apatites and 120-190°C for calcites. Measured temperatures for calcites match modeled temperatures using reasonable geological cooling rates. Natural apatite samples yield lower apparent temperatures than predicted based on the model. We propose that this difference is the result of annealment of structural damage in apatites (e.g., generated by

  17. Experimental differential cross sections, level densities, and spin cutoffs as a testing ground for nuclear reaction codes

    SciTech Connect

    Voinov, Alexander V.; Grimes, Steven M.; Brune, Carl R.; Burger, Alexander; Gorgen, Andreas; Guttormsen, Magne; Larsen, Ann -Cecilie; Massey, Thomas N.; Siem, Sunniva

    2013-11-08

    Proton double-differential cross sections from 59Co(α,p)62Ni, 57Fe(α,p)60Co, 56Fe(7Li,p)62Ni, and 55Mn(6Li,p)60Co reactions have been measured with 21-MeV α and 15-MeV lithium beams. Cross sections have been compared against calculations with the empire reaction code. Different input level density models have been tested. It was found that the Gilbert and Cameron [A. Gilbert and A. G. W. Cameron, Can. J. Phys. 43, 1446 (1965)] level density model is best to reproduce experimental data. Level densities and spin cutoff parameters for 62Ni and 60Co above the excitation energy range of discrete levels (in continuum) have been obtained with a Monte Carlo technique. Furthermore, excitation energy dependencies were found to be inconsistent with the Fermi-gas model.

  18. Hydration of periclase at 350 ∘ C to 620 ∘ C and 200 MPa: experimental calibration of reaction rate

    NASA Astrophysics Data System (ADS)

    Kuleci, H.; Schmidt, C.; Rybacki, E.; Petrishcheva, E.; Abart, R.

    2016-02-01

    The hydration of periclase to brucite was investigated experimentally. Single crystals of periclase machined to millimeter sized cubes with (100) surfaces were reacted with distilled water at temperatures of 350 to 620 ∘C and a pressure of 200 MPa for run durations of 5 to 40 minutes. Hydration produced a layer of brucite covering the surface of periclase. While the shrinking periclase largely retained its cube shape a surface roughness developed on the μm scale and eventually outward pointing spikes bounded by (111) faces emerged on the retreating faces of the periclase due to kinetic selection of less reactive (111) and (110) surfaces. The periclase to brucite conversion followed a linear rate law, where the reaction rate increased from 350 to 530 ∘C and then decreased towards higher temperature and finally vanished at about 630 ∘C, where periclase, brucite, and water are in equilibrium at 200 MPa. The overall kinetics of the hydration reaction is conveniently described in terms of a phenomenological interface mobility. Measuring the velocity of the hydration front relative to the lattice of the reactant periclase, the temperature dependence of its mobility is described by an Arrhenius relation with pre-exponential factor 1.7.10-12 m 4/s.J and activation energy of E A =55 kJ/mol.

  19. Experimental and theoretical study on the reaction of N3-phenyl-(pyridin-2-yl)carbohydrazonamide with itaconic anhydride

    NASA Astrophysics Data System (ADS)

    Modzelewska-Banachiewicz, Bożena; Paprocka, Renata; Mazur, Liliana; Saczewski, Jarosław; Kutkowska, Jolanta; Stępień, Dorota K.; Cyrański, Michał

    2012-08-01

    Two new 1,2,4-triazole-containing alkenoic acid derivatives were obtained from the reaction of N-phenyl-(pyridin-2-yl)carbohydrazonamide with itaconic anhydride, depending on the reaction conditions. The structures of 2-((4-phenyl-5-(pyridin-2-yl)-4H-1,2,4-triazol-3-yl)methyl)acrylic acid or (E)-2-methyl-3(4-phenyl-5-(pyridine-2-yl)-4H-1,2,4-triazol-3-yl)acrylic acid were confirmed by means of 1D and 2D NMR spectroscopic data as well as by single-crystal X-ray diffraction analysis. The experiential 1H and 13C chemical shifts were compared with those calculated with B3LYP, EDF1, and EDF2 density functional theories. The theoretical study of the observed terminal-to-internal alkene isomerization was performed with density functional (DFT) B3LYP/6-31+G∗ method using SM8 water and DMF solvation models. Antimicrobial activities of the newly prepared alkenoic acid derivatives were verified experimentally by a broth microdilution method.

  20. Influence of experimental parameters on sonochemistry dosimetries: KI oxidation, Fricke reaction and H2O2 production.

    PubMed

    Merouani, Slimane; Hamdaoui, Oualid; Saoudi, Fethi; Chiha, Mahdi

    2010-06-15

    Central events of the ultrasonic action are the cavitation bubbles that can be considered as microreactors. Adiabatic collapse of cavitation bubbles leads to the formation of reactive species such as hydroxyl radicals (*OH), hydrogen peroxide (H(2)O(2)) and hydroperoxyl radicals (HOO*). Several chemical methods were used to detect the production of these reactive moieties in sonochemistry. In this work, the influence of several operational parameters on the sonochemistry dosimetries namely KI oxidation, Fricke reaction and H(2)O(2) production using 300 kHz ultrasound was investigated. The main experimental parameters showing significant effect in KI oxidation dosimetry were initial KI concentration, acoustic power and pH. The solution temperature showed restricted influence on KI oxidation. The acoustic power and liquid temperature highly affected Fricke reaction dosimetry. Operational conditions having important influence on H(2)O(2) formation were acoustic power, solution temperature and pH. For the three tested dosimetries, the sonochemical efficiency was independent of liquid volume. PMID:20211524

  1. Solar energy storage by the reversible reaction - N2O4 yields 2NO2 - Theoretical and experimental results

    NASA Astrophysics Data System (ADS)

    Ragaini, V.

    1982-01-01

    The suitability of the reversible reaction between N2O4 and 2NO2 for short term solar energy storage applications were examined theoretically and experimentally. N2O4 dissociates completely at 140 C, while NO2 seldom dissociates below 150 C. The heat storage capacity of the reaction 2NO2 yields N2O4 was calculated for the temperature intervals between 0-500 C, showing that a maximum of 195.7 kcal/l is available with liquified 2NO2, compared to 100 kcal/l with water. Nitrogen dioxide was tested in the gas phase in a solar collector. The results indicate a heat storage capacity from 3 to 1.7 times that of water, and its use for a domestic hot water energy source is described. Toxicity problems with 2nO2 and the formation of nitric acid are suggested to be solvable by use of nitrogen dioxide in anhydrous form and in stainless steel apparatus.

  2. Development of Highly Active and Regioselective Catalysts for the Copolymerization of Epoxides with Cyclic Anhydrides: An Unanticipated Effect of Electronic Variation.

    PubMed

    DiCiccio, Angela M; Longo, Julie M; Rodríguez-Calero, Gabriel G; Coates, Geoffrey W

    2016-06-01

    Recent developments in polyester synthesis have established several systems based on zinc, chromium, cobalt, and aluminum catalysts for the ring-opening alternating copolymerization of epoxides with cyclic anhydrides. However, to date, regioselective processes for this copolymerization have remained relatively unexplored. Herein we report the development of a highly active, regioselective system for the copolymerization of a variety of terminal epoxides and cyclic anhydrides. Unexpectedly, electron withdrawing substituents on the salen framework resulted in a more redox stable Co(III) species and longer catalyst lifetime. Using enantiopure propylene oxide, we synthesized semicrystalline polyesters via the copolymerization of a range of epoxide/anhydride monomer pairs. PMID:27171536

  3. Kinetic Study of the Gas-Phase Reactions of Nitrate Radicals with Methoxyphenol Compounds: Experimental and Theoretical Approaches.

    PubMed

    Lauraguais, Amélie; El Zein, Atallah; Coeur, Cécile; Obeid, Emil; Cassez, Andy; Rayez, Marie-Thérèse; Rayez, Jean-Claude

    2016-05-01

    The gas-phase reactions of five methoxyphenols (three disubstituted and two trisubstituted) with nitrate radicals were studied in an 8000 L atmospheric simulation chamber at atmospheric pressure and 294 ± 2 K. The NO3 rate constants were investigated with the relative kinetic method using PTR-ToF-MS and GC-FID to measure the concentrations of the organic compounds. The rate constants (in units of cm(3) molecule(-1) s(-1)) determined were: 2-methoxyphenol (guaiacol; 2-MP), k(2-MP) = (2.69 ± 0.57 × 10(-11); 3-methoxyphenol (3-MP), k(3-MP) = (1.15 ± 0.21) × 10(-11); 4-methoxyphenol (4-MP), k(4-MP) = (13.75 ± 7.97) × 10(-11); 2-methoxy-4-methylphenol, k(2-M-4-MeP) = (8.41 ± 5.58) × 10(-11) and 2,6-dimethoxyphenol (syringol; 2,6-DMP), k(2,6-DMP) = (15.84 ± 8.10) × 10(-11). The NO3 rate constants of the studied methoxyphenols are compared with those of other substituted aromatics, and the differences in the reactivity are construed regarding the substituents (type, number and position) on the aromatic ring. This study was also supplemented by a theoretical approach of the methoxyphenol reactions with nitrate radicals. The upper limits of the NO3 overall rate constants calculated were in the same order of magnitude than those experimentally determined. Theoretical calculations of the minimum energies of the adducts formed from the reaction of NO3 radicals with the methoxyphenols were also performed using a DFT approach (M06-2X/6-31G(d,p)). The results indicate that the NO3 addition reactions on the aromatic ring of the methoxyphenols are exothermic, with energy values ranging between -13 and -21 kcal mol(-1), depending on the environment of the carbon on which the oxygen atom of NO3 is attached. These energy values allowed identifying the most suitable carbon sites for the NO3 addition on the aromatic ring of the methoxyphenols: at the exception of the 3-MP, the NO3 ipso-addition to the hydroxyl group is one of the favored sites for all the studies compounds

  4. An experimental study of catalytic and non-catalytic reaction in heat recirculating reactors and applications to power generation

    NASA Astrophysics Data System (ADS)

    Ahn, Jeongmin

    An experimental study of the performance of a Swiss roll heat exchanger and reactor was conducted, with emphasis on the extinction limits and comparison of results with and without Pt catalyst. At Re<40, the catalyst was required to sustain reaction; with the catalyst self-sustaining reaction could be obtained at Re less than 1. Both lean and rich extinction limits were extended with the catalyst, though rich limits were extended much further. At low Re, the lean extinction limit was rich of stoichiometric and rich limit had equivalence ratios 80 in some cases. Non-catalytic reaction generally occurred in a flameless mode near the center of the reactor. With or without catalyst, for sufficiently robust conditions, a visible flame would propagate out of the center, but this flame could only be re-centered with catalyst. Gas chromatography indicated that at low Re, CO and non-C3 H8 hydrocarbons did not form. For higher Re, catalytic limits were slightly broader but had much lower limit temperatures. At sufficiently high Re, catalytic and gas-phase limits merged. Experiments with titanium Swiss rolls have demonstrated reducing wall thermal conductivity and thickness leads to lower heat losses and therefore increases operating temperatures and extends flammability limits. By use of Pt catalysts, reaction of propane-air mixtures at temperatures 54°C was sustained. Such low temperatures suggest that polymers may be employed as a reactor material. A polyimide reactor was built and survived prolonged testing at temperatures up to 500°C. Polymer reactors may prove more practical for microscale devices due to their lower thermal conductivity and ease of manufacturing. Since the ultimate goal of current efforts is to develop combustion driven power generation devices at MEMS like scales, a thermally self-sustaining miniature power generation device was developed utilizing a single-chamber solid-oxide-fuel-cell (SOFC) placed in a Swiss roll. With the single-chamber design

  5. Methyl iodide oxidative addition to [Rh(acac)(CO)(PPh3)]: an experimental and theoretical study of the stereochemistry of the products and the reaction mechanism.

    PubMed

    Conradie, Marrigje M; Conradie, Jeanet

    2011-08-28

    Density functional theory was used to investigate the oxidative addition and subsequent carbonyl insertion and deinsertion steps of the reaction of methyl iodide to a rhodium(I) acetylacetonato complex of the formula [Rh(acac)(CO)(PPh(3))] (Hacac = acetylacetone). This process has been studied experimentally for many rhodium β-diketonato complexes, but, to the best of our knowledge, this is the first systematic computational study of the complete reaction sequence. Experimental (1)H techniques complement the theoretical results on the stereochemistry of the reaction intermediates and products. (1)H NMR also revealed the existence of a second rhodium(III)-acyl product, which has not been previously observed in this reaction. The calculated Gibbs free energy of activation of the oxidative addition reaction is 71 kJ mol(-1), which is in agreement with the experimental value of 82(1) kJ mol(-1). The DFT-calculated oxidative addition corresponds to an associative S(N)2 nucleophilic attack by the rhodium metal centre on the methyl iodide, which is in agreement with calculated and experimental (in brackets) activation parameters of the reaction, 27 (38.8) kJ mol(-1) for ΔH((≠)) and -147 (-146) J K(-1) mol(-1) for ΔS((≠)). PMID:21761056

  6. Understanding reactivity and regioselectivity in Diels-Alder reactions of a sugar-derived dienophile bearing two competing EWGs. An experimental and computational study.

    PubMed

    Giri, Germán F; Sarotti, Ariel M; Spanevello, Rolando A

    2015-10-13

    The effect of an extra EWG in the reactivity and regioselectivity in Diels-Alder reactions of β-cyanolevoglucosenone and 4 different dienes was studied by a joint computational and experimental study. Conceptual DFT analysis successfully predicted an important enhancement in the reactivity, and correctly anticipated the regioselectivity in the reactions with isoprene. However, this static treatment failed when dealing the regiochemical preference of the reactions involving a substituted anthracene as diene. MPW1K/6-31G* calculations correctly reproduced the experimental observations. Based on the collected data, we found that when dealing with dienes and dienophiles with no clear electronically activated position, the ease of pyramidalization of the interacting atoms dictates the regioselectivity of the DA reaction. PMID:26318382

  7. Experimental study of the influence of chemical reactions on convective dissolution of CO2 in aqueous solutions.

    NASA Astrophysics Data System (ADS)

    Thomas, Carelle; Lemaigre, Lorena; Haudin, Florence; Zalts, Anita; D'Onofrio, Alejandro; De Wit, Anne

    2014-05-01

    Within the global context of climate change, carbon dioxide (CO2) sequestration into deep saline aquifers is one of the technologies being considered in order to tackle the accumulation of anthropogenic CO2 in the atmosphere. Upon injection of CO2 into these porous geological formations, the less dense CO2 rises above the aqueous phase, spreads laterally under the upper impermeable cap rock and starts to dissolve into the underlying brine. This leads to a buoyantly unstable stratification of denser CO2-enriched brine on top of less dense brine, which can give rise to density-driven convective fingering in the fluid. This hydrodynamic instability is a favorable process for CO2 sequestration as it accelerates the mixing of CO2 into the aqueous phase and therefore enhances the safety of the storage in the saline aquifer (by reducing the risks of leaks of CO2 to the atmosphere). The influence of chemical reactions and of the physico-chemical characteristics of the geological reservoir on the development of this instability is, however, still not completely understood. In this context, we study experimentally in a laboratory-scale reactor the influence of chemical reactions on convective fingering occurring during dissolution of CO2 in reactive aqueous solutions. Experiments are performed in Hele-Shaw cells (constructed of two vertical transparent plates separated by a thin gap) in which gaseous CO2 at atmospheric pressure flows above aqueous solutions containing chemical reactants. Dynamics occurring within the transparent fluids are visualized by Schlieren techniques, which track dynamical changes in refractive index related to density gradients in the solutions. We show that in some cases the convection can be enhanced by chemical reactions as they accelerate the development of the fingers, shorten their onset time and increase the number of fingers. In particular, we show that the presence of a color indicator (for instance bromocresol green) in the aqueous solution

  8. Relative rates for plasma homo- and copolymerizations of olefins in a homologous series of fluorinated ethylenes

    NASA Technical Reports Server (NTRS)

    Golub, M. A.; Wydeven, T.

    1997-01-01

    It is well known that the rate of plasma polymerization, or deposition rate, of a given monomer depends on various plasma process parameters, e.g., monomer flow rate, pressure, power, frequency (DC, rf or microwave), location of the substrate in the reactor, reactor geometry or configuration, and temperature. In contrast, little work has been done to relate deposition rates to monomer structures for a homologous series of monomers where the rates are obtained under identical plasma process parameters. For the particular series of fluorinated ethylenes (C2HxF4-x; x = 0-4), deposition rates were reported for ethylene (ET), vinyl fluoride, vinylidene fluoride and tetrafluoroethylene (TFE), but for plasma polymerizations carried out under different discharge conditions, e.g., pressure, current density, and electrode temperature. Apparently, relative deposition rates were reported for only two members of that series (ET, x = 4, and TFE, x = 0) for which the plasma polymerizations were conducted under identical conditions. We now present relative deposition rates for both homopolymerizations and copolymerizations of the entire series of fluorinated ethylenes (x = 0-4). Our interest in such rates stems from prior work on the plasma copolymerization of ET and TFE in which it was found that the deposition rates for the plasma copolymers, when plotted versus mol % TFE in the ET/TFE feed stock, followed a concave-downward curve situated above the straight line joining the deposition rates for the plasma homopolymers. This type of plot (observed also for an argon-ET/TFE plasma copolymerization) indicated a positive interaction between ET and TFE such that each monomer apparently "sensitized" the plasma copolymerization of the other. Since the shape of that plot is not altered if mol % TFE is replaced by F/C, the fluorine-to-carbon ratio, this paper aims (1) to show how the relative deposition rates for plasma copolymers drawn from all pairs of monomers in the C2HxF4-x series

  9. Experimental measurements of low temperature rate coefficients for neutral-neutral reactions of interest for atmospheric chemistry of Titan, Pluto and Triton: reactions of the CN radical.

    PubMed

    Morales, Sébastien B; Le Picard, Sébastien D; Canosa, André; Sims, Ian R

    2010-01-01

    The kinetics of the reactions of cyano radical, CN (X2sigma+) with three hydrocarbons, propane (CH3CH2CH3), propene (CH3CH=CH2) and 1-butyne (CH[triple band]CCH2CH3) have been studied over the temperature range of 23-298 K using a CRESU (Cinétique de Réaction en Ecoulement Supersonique Uniforme or Reaction Kinetics in Uniform Supersonic Flow) apparatus combined with the pulsed laser photolysis-laser induced fluorescence technique. These reactions are of interest for the cold atmospheres of Titan, Pluto and Triton, as they might participate in the formation of nitrogen and carbon bearing molecules, including nitriles, that are thought to play an important role in the formation of hazes and biological molecules. All three reactions are rapid with rate coefficients in excess of 10(-10) cm3 molecule(-1) s(-1) at the lowest temperatures of this study and show behaviour characteristic of barrierless reactions. Temperature dependences, different for each reaction, are compared to those used in the most recent photochemical models of Titan's atmosphere. PMID:21302546

  10. Catalytic Upgrading of Biomass-Derived Compounds via C-C Coupling Reactions. Computational and Experimental Studies of Acetaldehyde and Furan Reactions in HZSM-5

    SciTech Connect

    Liu, Cong; Evans, Tabitha J.; Cheng, Lei; Nimlos, Mark R.; Mukarakate, Calvin; Robichaud, David J.; Assary, Rajeev S.; Curtiss, Larry A.

    2015-10-02

    These catalytic C–C coupling and deoxygenation reactions are essential for upgrading of biomass-derived oxygenates to fuel-range hydrocarbons. Detailed understanding of mechanistic and energetic aspects of these reactions is crucial to enabling and improving the catalytic upgrading of small oxygenates to useful chemicals and fuels. Using periodic density functional theory (DFT) calculations, we have investigated the reactions of furan and acetaldehyde in an HZSM-5 zeolite catalyst, a representative system associated with the catalytic upgrading of pyrolysis vapors. Comprehensive energy profiles were computed for self-reactions (i.e., acetaldehyde coupling and furan coupling) and cross-reactions (i.e., acetaldehyde + furan) of this representative mixture. Major products proposed from the computations are further confirmed using temperature controlled mass spectra measurements. Moreover, the computational results show that furan interacts with acetaldehyde in HZSM-5 via an alkylation mechanism, which is more favorable than the self-reactions, indicating that mixing furans with aldehydes could be a promising approach to maximize effective C–C coupling and dehydration while reducing the catalyst deactivation (e.g., coke formation) from aldehyde condensation.

  11. Synthesis and structural characterization of double metal cyanides of iron and zinc: catalyst precursors for the copolymerization of carbon dioxide and epoxides.

    PubMed

    Darensbourg, Donald J; Adams, M Jason; Yarbrough, Jason C; Phelps, Andrea L

    2003-12-01

    Several synthetic approaches for the preparation of double metal cyanide (DMC) derivatives of iron(II) and zinc(II) are described. These include (1) metathesis reactions of ZnCl(2) or ZnI(2) with KCpFe(CN)(2)CO in aqueous solution, (2) reactions of KCpFe(CN)(2)CO and its phosphine-substituted analogues with Zn(CH(3)CN)(4)(BF(4))(2) and subsequent displacement of acetonitrile at the zinc centers by the addition of a neutral (phosphine) or anionic (phenoxide) ligand, and (3) reactions of the protonated HCpFe(CN)(2)(phosphine) complexes with Zn(N(SiMe(3))(2))(2), followed by the addition of phenols. All structures are based on a diamond-shaped planar arrangement of the Fe(2)(CN)(4)Zn(2) core with various appended ligands at the metal sites. Although attempts to replace the iodide ligands in [CpFe(mu-CN)(2)PPh(3)ZnI(THF)](2) with acetate using silver acetate failed, two novel cationic mixed-metal cyanide salts based on the [CpFe(PPh(3))(mu-CN)(2)Zn(NC(5)H(5))](2)(2+) framework were isolated from pyridine solution and their structures were defined by X-ray crystallography. The anionic ligand bound to zinc in these derivatives, which serve as an anionic polymerization initiator, was shown to be central to the catalytic copolymerization reaction of CO(2)/epoxide to provide polycarbonates and cyclic carbonates. The structurally stabilized phosphine-strapped complexes [CpFe(mu-CN)(2)Zn(X)THF](2)(mu-dppp), where X = I or phenolate, were shown to be thermally stable under the conditions (80 degrees C) of the copolymerization reaction by in situ infrared spectroscopy. Both of these derivatives were proposed to serve as mimics for the heterogeneous DMC catalysts in the patent literature, with the derivative where the initiator is a phenolate being more active for the production of polycarbonates. PMID:14632496

  12. Experimental study of the low-lying structure of {sup 94}Zr with the (n,n{sup '}{gamma}) reaction

    SciTech Connect

    Elhami, E.; Orce, J. N.; Scheck, M.; Mukhopadhyay, S.; Choudry, S. N.; McEllistrem, M. T.; Yates, S. W.; Angell, C.; Boswell, M.; Karwowski, H. J.; Fallin, B.; Howell, C. R.; Hutcheson, A.; Parpottas, Y.; Tonchev, A. P.; Tornow, W.; Kelley, J. H.

    2008-12-15

    The low-lying structure of {sub 40}{sup 94}Zr was studied with the (n,n{sup '}{gamma}) reaction, and a level scheme was established based on excitation function and {gamma}{gamma} coincidence measurements. Branching ratios, multipole mixing ratios, and spin assignments were determined from angular distribution measurements. Lifetimes of levels up to 3.4 MeV were measured by the Doppler-shift attenuation method, and for many transitions the reduced transition probabilities were determined. In addition to the anomalous 2{sub 2}{sup +} state, which has a larger B(E2;2{sub 2}{sup +}{yields}0{sub 1}{sup +}) value than the B(E2;2{sub 1}{sup +}{yields}0{sub 1}{sup +}), the experimental results revealed interesting and unusual properties of the low-lying states in {sup 94}Zr. In a simple interpretation, the excited states are classified in two distinct categories, i.e., those populating the 2{sub 2}{sup +} state and those decaying to the 2{sub 1}{sup +} state.

  13. Nitrogen Fixation on Early Mars and Other Terrestrial Planets: Experimental Demonstration of Abiotic Fixation Reactions to Nitrite and Nitrate

    NASA Astrophysics Data System (ADS)

    Summers, David P.; Khare, Bishun

    2007-05-01

    Understanding the abiotic fixation of nitrogen is critical to understanding planetary evolution and the potential origin of life on terrestrial planets. Nitrogen, an essential biochemical element, is certainly necessary for life as we know it to arise. The loss of atmospheric nitrogen can result in an incapacity to sustain liquid water and impact planetary habitability and hydrological processes that shape the surface. However, our current understanding of how such fixation may occur is almost entirely theoretical. This work experimentally examines the chemistry, in both gas and aqueous phases, that would occur from the formation of NO and CO by the shock heating of a model carbon dioxide/nitrogen atmosphere such as is currently thought to exist on early terrestrial planets. The results show that two pathways exist for the abiotic fixation of nitrogen from the atmosphere into the crust: one via HNO and another via NO2. Fixation via HNO, which requires liquid water, could represent fixation on a planet with liquid water (and hence would also be a source of nitrogen for the origin of life). The pathway via NO2 does not require liquid water and shows that fixation could occur even when liquid water has been lost from a planet's surface (for example, continuing to remove nitrogen through NO2 reaction with ice, adsorbed water, etc.).

  14. An experimental investigation of multiple sulfur isotope fractionations during heterogenous reactions between SO2 and activated carbon

    NASA Astrophysics Data System (ADS)

    Hamasaki, H.; Watanabe, Y.; Ohmoto, H.

    2010-12-01

    . We have recognized that the δ34S of SO2 in the system continuously decreased during the experiments from -0.6 to -1.4‰ (relative to the initial value) at 200 °C, and from -1.0 to -1.2 ‰ at 250 °C. The Δ33S of SO2 continued to decrease from 0 to -0.18 ‰ at 200 °C and 0.03 to -0.05 ‰ at 250 °C. Mass balance calculations suggest that the bulk S in activated carbon increased its δ34S value from 1.4 to 12.1 ‰ at 200 °C and 3.2 to 16.7 ‰ at 250 °C; and increased the Δ33S value from 0 to 0.18 ‰ at 200 °C and from 0.07 to 0.32 ‰ at 250 °C. Results of the sequential S extraction from the solid run products (activated C) indicate the total S content of 0.9 wt%, mostly in the forms of Cr-reductive S compounds (e.g., sulfites and polysulfides) and non Cr-reductive S compounds (e.g., organic sulfur, elemental sulfur, and sulfates). Our experimental results indicate that the adsorption of SO2, the reduction of S4+ to S0 (and/or Sx2-), and the oxidation of C0 to C4+ continued to occur during the reaction between SO2 and activated carbon at 200 °C and 250 °C, and that the redox reactions produced larger sulfur isotope effects (both in δ34S and Δ33S) compared to a simple adsorption process under our experimental conditions.

  15. Thermodynamic Properties of CO{sub 2} Capture Reaction by Solid Sorbents: Theoretical Predictions and Experimental Validations

    SciTech Connect

    Duan, Yuhua; Luebke, David; Pennline, Henry; Li, Liyu; King, David; Zhang,; Keling,; Zhao,; Lifeng,; Xiao, Yunhan

    2012-01-01

    It is generally accepted that current technologies for capturing CO{sub 2} are still too energy intensive. Hence, there is a critical need for development of new materials that can capture CO{sub 2} reversibly with acceptable energy costs. Accordingly, solid sorbents have been proposed to be used for CO{sub 2} capture applications through a reversible chemical transformation. By combining thermodynamic database mining with first principles density functional theory and phonon lattice dynamics calculations, a theoretical screening methodology to identify the most promising CO{sub 2} sorbent candidates from the vast array of possible solid materials has been proposed and validated. The calculated thermodynamic properties of different classes of solid materials versus temperature and pressure changes were further used to evaluate the equilibrium properties for the CO{sub 2} adsorption/desorption cycles. According to the requirements imposed by the pre- and post- combustion technologies and based on our calculated thermodynamic properties for the CO{sub 2} capture reactions by the solids of interest, we were able to screen only those solid materials for which lower capture energy costs are expected at the desired pressure and temperature conditions. These CO{sub 2} sorbent candidates were further considered for experimental validations. In this presentation, we first introduce our screening methodology with validating by solid dataset of alkali and alkaline metal oxides, hydroxides and bicarbonates which thermodynamic properties are available. Then, by studying a series of lithium silicates, we found that by increasing the Li{sub 2}O/SiO{sub 2} ratio in the lithium silicates their corresponding turnover temperatures for CO{sub 2} capture reactions can be increased. Compared to anhydrous K{sub 2}CO{sub 3}, the dehydrated K{sub 2}CO{sub 3}1.5H{sub 2}O can only be applied for post-combustion CO{sub 2} capture technology at temperatures lower than its phase transition (to

  16. Copolymerization of Epichlorohydrin and CO2 Using Zinc Glutarate: An Additional Application of ZnGA in Polycarbonate Synthesis.

    PubMed

    Sudakar, Padmanaban; Sivanesan, Dharmalingam; Yoon, Sungho

    2016-05-01

    The use of zinc glutarate (ZnGA) as a heterogeneous catalyst for the copolymerization of epichlorohydrin, an epoxide with an electron-withdrawing substituent, and CO2 is reported. This catalyst shows the highest selectivity (98%) for polycarbonate over the cyclic carbonate in epichlorohydrin/CO2 copolymerization under mild conditions. The (epichlorohydrin-co-CO2 ) polymer exhibits a high glass transition temperature (Tg ), 44 °C, which is the maximum Tg value obtained for the (epichlorohydrin-co-CO2 ) polymer to date. PMID:26991465

  17. Simulation of 3He(d,p) 4He reaction and recent results of the experimental investigation of dp breakup reaction

    NASA Astrophysics Data System (ADS)

    Janek, M.; Kurilkin, P. K.; Tarjanyiova, G.; Ladygin, V. P.; Gurchin, Yu V.; Isupov, A. Yu; Karachuk, J.-T.; Khrenov, A. N.; Kurilkin, A. K.; Livanov, A. N.; Martinska, G.; Piyadin, S. M.; Reznikov, S. G.; Merts, S. P.; Batyuk, P. N.; Terekhin, A. A.; Vnukov, I. E.

    2016-02-01

    The feasibility study for the measurements of the polarization observables in the 3He(d,p) 4He reaction for DSS project using a part of the BM@N setup have been performed. Deuteron beam with energy of 1.5 GeV, magnet, 12 stations GEM tracker and TOF wall were used in simulations in order to obtain momentum resolution and to prove the separation of the secondary protons and deuterons. Summarized results of the dp breakup reactions with detection of two protons in coincidence for some kinematic configurations at energies from 300 to 500 MeV obtained in Nuclotron are presented.

  18. Relative Rates for Plasma Homo- and Copolymerizations of Olefins in a Homologous Series of Fluorinated Ethylenes

    NASA Technical Reports Server (NTRS)

    Golub, Morton A.; Wydeven, Theodore; Kliss, Mark (Technical Monitor)

    1996-01-01

    The relative rates of plasma (co)polymerizations of ethylene, vinyl fluoride, vinylidene fluoride, trifluoroethylene and tetrafluoroethylene (VF(sub x); x = 0-4, respectively) were determined in an rf, capacitively coupled, tubular reactor with external electrodes using identical plasma parameters. The averages of deposition rates obtained by both microgravimetry and ellipsometry were plotted versus the F/C ratios of the monomers or monomer blends. The deposition rates for VF(sub x)(x = 1-3) and 20 monomer blends were all located above a straight line joining the rates for VF(sub 0) and VF(sub 4), following a concave-downward plot of deposition rate versus F/C ratio similar to that reported previously for VF(sub 0)/VF(sub 4) blends. The deposition rates for VF(sub m)/VF(sub n) blends (m = 3 or 4; n = 0-2) were all greater than expected for non-interacting monomers; those for VF(sub 0)/VF(sub 2) and VF(sub 1)/VF(sub 2) blends were all lower than expected; while those for VF(sub 0)/VF(sub 1) and VF(sub 3)/VF(sub 4) blends fen on a straightline plot versus F/C ratio, indicative of apparent non-interaction between monomers. The mechanisms for plasma (co)polymerizations of VF(sub x) monomers responsible for the wide range of relative deposition rates remain to be elucidated.

  19. Photo-induced alternating copolymerization of N-substituted maleimides and electron donor olefins

    NASA Astrophysics Data System (ADS)

    Jönsson, S.; Sundell, P. E.; Shimose, M.; Clark, S.; Miller, C.; Morel, F.; Decker, C.; Hoyle, C. E.

    1997-08-01

    Photo-initiated free radical polymerization of donor/acceptor type monomers have gained considerable interest due to the possibility of formulating UV curable non-acrylate systems. Recently, we described a photoinitiator free system based on donor/acceptor combinations [1-7]. Photoinitiator free nonacrylate based compositions will of course attain an enhanced interest and importance because of a broader selection of raw materials and combinations thereof, potential outdoor use, lower costs of formulations, improved odour, no formation of benzaldehyde, less extractables and so on. Recent developments of the direct photolysis of these acceptors and complexes, and their potential use in practical "UV curing" will be outlined. By a selective combination of A and D type monomers, a direct photolysis of the ground state complex (CTC) or the excitation of the acceptor, followed by the formation of an exciplex, will initiate a free radical copolymerization. A second route of direct initiation is based on inter- or intra-molecular H-abstraction from an excited state acceptor or exciplex. This paper will focus on the photochemistry as it relates to initiation of polymerization depending on acceptor and donor strength of the monomer system. Inherently different reactivities in air and nitrogen of donors and acceptors are compared to photoinitiator containing acrylates. Furthermore, the ratio of homo and alternating copolymerization as well as the 2 + 2 cycloaddition will be discussed.

  20. Reversion of pH-Induced Physiological Drug Resistance: A Novel Function of Copolymeric Nanoparticles

    PubMed Central

    Li, Rutian; Xie, Li; Zhu, Zhenshu; Liu, Qin; Hu, Yong; Jiang, Xiqun; Yu, Lixia; Qian, Xiaoping; Guo, Wanhua; Ding, Yitao; Liu, Baorui

    2011-01-01

    Aims The extracellular pH of cancer cells is lower than the intracellular pH. Weakly basic anticancer drugs will be protonated extracellularly and display a decreased intracellular concentration. In this study, we show that copolymeric nanoparticles (NPs) are able to overcome this “pH-induced physiological drug resistance” (PIPDR) by delivering drugs to the cancer cells via endocytosis rather than passive diffussion. Materials and Methods As a model nanoparticle, Tetradrine (Tet, Pka 7.80) was incorporated into mPEG-PCL. The effectiveness of free Tet and Tet-NPs were compared at different extracellular pHs (pH values 6.8 and 7.4, respectively) by MTT assay, morphological observation and apoptotic analysis in vitro and on a murine model by tumor volume measurement, PET-CT scanning and side effect evaluation in vivo. Results The cytotoxicity of free Tet decreased prominently (P<0.05) when the extracellular pH decreased from 7.4 to 6.8. Meanwhile, the cytotoxicity of Tet-NPs was not significantly influenced by reduced pH. In vivo experiment also revealed that Tet-NPs reversed PIPDR more effectively than other existing methods and with much less side effects. Conclusion The reversion of PIPDR is a new discovered mechanism of copolymeric NPs. This study emphasized the importance of cancer microenvironmental factors in anticancer drug resistance and revealed the superiority of nanoscale drug carrier from a different aspect. PMID:21966359

  1. A general theory of kinetics and thermodynamics of steady-state copolymerization.

    PubMed

    Shu, Yao-Gen; Song, Yong-Shun; Ou-Yang, Zhong-Can; Li, Ming

    2015-06-17

    Kinetics of steady-state copolymerization has been investigated since the 1940s. Irreversible terminal and penultimate models were successfully applied to a number of comonomer systems, but failed for systems where depropagation is significant. Although a general mathematical treatment of the terminal model with depropagation was established in the 1980s, a penultimate model and higher-order terminal models with depropagation have not been systematically studied, since depropagation leads to hierarchically-coupled and unclosed kinetic equations which are hard to solve analytically. In this work, we propose a truncation method to solve the steady-state kinetic equations of any-order terminal models with depropagation in a unified way, by reducing them into closed steady-state equations which give the exact solution of the original kinetic equations. Based on the steady-state equations, we also derive a general thermodynamic equality in which the Shannon entropy of the copolymer sequence is explicitly introduced as part of the free energy dissipation of the whole copolymerization system. PMID:25992648

  2. A joint experimental and theoretical investigation of kinetics and mechanistic study in a synthesis reaction between triphenylphosphine and dialkyl acetylenedicarboxylates in the presence of benzhydrazide.

    PubMed

    Kazemian, Mohammad Amin; Habibi-Khorassani, Sayyed Mostafa; Ebrahimi, Ali; Maghsoodlou, Malek Taher; Jahani, Peyman Mohammadzadeh; Ghahramaninezhad, Mahbobeh

    2012-12-01

    Stable crystalline phosphorus ylides were obtained in excellent yields from the 1:1:1 addition reaction between triphenylphosphine (TPP) and dialkyl acetylenedicarboxylates, in the presence of NH-acids, such as benzhydrazide. To determine the kinetic parameters of the reactions, they were monitored by UV spectrophotometery. The second order fits were automatically drawn and the values of the second order rate constant (k(2)) were calculated using standard equations within the program. At the temperature range studied the dependence of the second order rate constant (Ln k(2)) on reciprocal temperature was compatible with Arrhenius equation. This provided the relevant plots to calculate the activation energy of all reactions. Furthermore, useful information were obtained from studies of the effect of solvent, structure of reactants (different alkyl groups within the dialkyl acetylenedicarboxylates) and also concentration of reactants on the rate of reactions. On the basis of experimental data the proposed mechanism was confirmed according to the obtained results and a steady state approximation and the first step (k(2)) and third (k(3)) steps of the reactions were recognized as the rate determining steps, respectively. In addition, three speculative proposed mechanisms were theoretically investigated using quantum mechanical calculation. The results, arising from the second and third speculative mechanisms, were far from the experimental data. Nevertheless, there was a good agreement between the theoretical kinetic data, emerge from the first speculative mechanism, and experimental kinetic data of proposed mechanism. PMID:22752542

  3. 4′-CyanoPLP presents better prospect for the experimental detection of elusive cyclic intermediate radical in the reaction of lysine 5,6-aminomutase

    SciTech Connect

    Maity, Amarendra Nath; Ke, Shyue-Chu

    2015-02-06

    Graphical abstract: The results of our calculations suggest that the reaction of 4′-cyanoPLP with lysine 5,6-aminomutase offers better prospect for the experimental detection of elusive cyclic azacyclopropylcarbinyl radical, which is proposed to be a key intermediate in the reaction of pyridoxal-5′-phosphate dependent radical aminomutases. - Highlights: • 4′-CyanoI{sup ·} is the lowest energy radical intermediate in the reaction of 5,6-LAM. • 4′-CyanoPLP offers good prospect for the experimental observation of elusive I{sup ·}. • The calculated HFCCs would help to characterize 4′-cyanoI{sup ·} by EPR. - Abstract: The results of our calculations suggest that the reaction of 4′-cyanoPLP with lysine 5,6-aminomutase offers better prospect for the experimental detection of elusive cyclic azacyclopropylcarbinyl radical (I{sup ·}), which is proposed to be a key intermediate in the reaction of pyridoxal-5′-phosphate dependent radical aminomutases. We have calculated the corresponding hyperfine coupling constants (HFCCs) for {sup 14}N and {sup 13}C of cyano group using several basis sets to help the characterization of 4′-cyanoI{sup ·}.

  4. New Insights of the Fenton Reaction Using Glycerol as the Experimental Model. Effect of O2, Inhibition by Mg(2+), and Oxidation State of Fe.

    PubMed

    Vitale, Arturo Alberto; Bernatene, Eduardo A; Vitale, Martín Gustavo; Pomilio, Alicia Beatriz

    2016-07-21

    The use of iron ions as catalyst of oxidation with hydrogen peroxide, known as the Fenton reaction, is important for industry and biological systems. It has been widely studied since its discovery in the 19th century, but important aspects of the reaction as which is the oxidant, the role of oxygen, and the oxidation state of Fe still remain unclear. In this work new mechanistic insights of the oxidation of carbohydrates by the Fenton reaction using glycerol as experimental model are described. The reaction was studied by means of oxidation reduction potential (ORP) measures. The stoichiometry was measured, showing the important role of oxygen for lowering H2O2 consumption under aerobic conditions. Evidence is provided to demonstrate that in this system Fe(2+) generates a catalyst by reacting with a substrate to produce a complex, which gives rise to singlet oxygen after reacting with H2O2. This is the first time that the inhibitor effect of Mg(2+) is reported in this reaction, and its participation in the mechanism is described. A rational mechanism for the oxidation of glycerol using the Fenton reaction under these specific conditions is proposed. The role of oxygen, the participation of Fe(2+), and the inhibition by Mg(2+) are fully demonstrated experimentally. PMID:27340836

  5. Experimental study of the effects of CO{sub 2} on the noncatalytic reduction reaction of NO by carbonaceous materials

    SciTech Connect

    Weidong Fan; Zhengchun Lin; Youyi Li; Jinguo Kuang

    2009-05-15

    In a fixed bed reactor with a quartz tube, the effects of the concentration of CO{sub 2} in the feed gas on the uncatalyzed reaction between soot produced in a natural gas diffusion flame and NO were investigated. They were compared with CO{sub 2} effects on reactions involving candle soot and bituminous coal char. The presence of CO{sub 2} in the feed gas exerted no influence on the reaction of NO with natural gas soot. However, it did result in a lower initial temperature in the reaction of candle soot or coal char with NO, and separated the whole initial reaction process into two stages. At higher CO{sub 2} concentrations, more NO reduction occurred in the reaction with candle soot or coal char during the initial reaction process. However, no dramatic changes in the amount of NO reduction were observed for natural gas soot. The addition of CO{sub 2} seemed to have no effect on the apparent activation energy of the NO-natural gas soot reaction, while a lowering of the apparent activation energy was observed in the reaction of NO with candle soot or coal char as the CO{sub 2} concentration increased. The abundant C(O) complexes formed during sample gasification by CO{sub 2} were assumed to play an important role in the enhancement of the reaction. 20 refs., 12 figs., 2 tabs.

  6. Experimental study and chemical analysis of n-heptane homogeneous charge compression ignition combustion with port injection of reaction inhibitors

    SciTech Connect

    Lue, Xingcai; Ji, Libin; Zu, Linlin; Hou, Yuchun; Huang, Cheng; Huang, Zhen

    2007-05-15

    The control of ignition timing in the homogeneous charge compression ignition (HCCI) of n-heptane by port injection of reaction inhibitors was studied in a single-cylinder engine. Four suppression additives, methanol, ethanol, isopropanol, and methyl tert-butyl ether (MTBE), were used in the experiments. The effectiveness of inhibition of HCCI combustion with various additives was compared under the same equivalence ratio of total fuel and partial equivalence ratio of n-heptane. The experimental results show that the suppression effectiveness increases in the order MTBE < isopropanol << ethanol < methanol. But ethanol is the best additive when the operating ranges, indicated thermal efficiency, and emissions are considered. For ethanol/n-heptane HCCI combustion, partial combustion may be observed when the mole ratio of ethanol to that of total fuel is larger than 0.20; misfires occur when the mole ratio of ethanol to that of total fuel larger than 0.25. Moreover, CO emissions strongly depend on the maximum combustion temperature, while HC emissions are mainly dominated by the mole ratio of ethanol to that of total fuel. To obtain chemical mechanistic informations relevant to the ignition behavior, detailed chemical kinetic analysis was conducted. The simulated results also confirmed the retarding of the ignition timing by ethanol addition. In addition, it can be found from the simulation that HCHO, CO, and C{sub 2}H{sub 5}OH could not be oxidized completely and are maintained at high levels if the partial combustion or misfire occurs (for example, for leaner fuel/air mixture). (author)

  7. Review of Experimental Data on Alpha-Induced Reactions on Some Nuclei (Mg-24, Si-28, S-32, Ar-36, Ca-40) in Terms of Astrophysical Applications

    SciTech Connect

    Dunaeva, S.A.; McLane, V.; Savin, M.; Taova, S.

    2005-05-24

    The present report gives a detailed analysis of experimental works and a review of alpha-induced reaction cross-section data of five alpha-alpha nuclei, Mg-24, Si-28, S-32, Ar-36 and Ca-40, for incident alpha energy up to 20 MeV. Alpha-induced reactions play an important role in the helium burning stage of stars, novae, and supernovae. These reactions are basic to the CNO and Al-Mg cycles, and also to the production of neutrons producing S and R processes occurring in stars. Thus, the availability of cross-section data for these reactions is a prime need for the study of nuclear interactions taking place in stars.These data have been compiled as part of an international collaboration, funded in part by the Civilian Research and Development Foundation, and are available in the EXFOR databases.

  8. An experimental and theoretical study on the kinetic isotope effect of C2H6 and C2D6 reaction with OH

    NASA Astrophysics Data System (ADS)

    Khaled, Fethi; Giri, Binod Raj; Szőri, Milán; Viskolcz, Béla; Farooq, Aamir

    2015-11-01

    We report experimental and theoretical results for the deuterated kinetic isotope effect (DKIE) of the reaction of OH with ethane (C2H6) and deuterated ethane (C2D6). The reactions were investigated behind reflected shock waves over 800-1350 K by monitoring OH radicals near 306.69 nm using laser absorption. In addition, high level CCSD(T)/cc-pV(T,Q)Z//MP2/cc-pVTZ quantum chemical and statistical rate theory calculations were performed which agreed very well with the experimental findings. The results reported herein provide the first experimental evidence that DKIE asymptotes to a value of 1.4 at high temperatures.

  9. A theoretical and experimental study of the effects of silyl substituents in enantioselective reactions catalyzed by diphenylprolinol silyl ether.

    PubMed

    Hayashi, Yujiro; Okamura, Daichi; Yamazaki, Tatsuya; Ameda, Yasuto; Gotoh, Hiroaki; Tsuzuki, Seiji; Uchimaru, Tadafumi; Seebach, Dieter

    2014-12-15

    The effect of silyl substituents in diphenylprolinol silyl ether catalysts was investigated. Mechanistically, reactions catalyzed by diphenylprolinol silyl ether can be categorized into three types: two that involve an iminium ion intermediate, such as for the Michael-type reaction (type A) and the cycloaddition reaction (type B), and one that proceeds via an enamine intermediate (type C). In the Michael-type reaction via iminium ions (type A), excellent enantioselectivity is realized when the catalyst with a bulky silyl moiety is employed, in which efficient shielding of a diastereotopic face of the iminium ion is directed by the bulky silyl moiety. In the cycloaddition reaction of iminium ions (type B) and reactions via enamines (type C), excellent enantioselectivity is obtained even when the silyl group is less bulky and, in this case, too much bulk reduces the reaction rate. In other cases, the yield increases when diphenylprolinol silyl ethers with bulky substituents are employed, presumably by suppressing side reactions between the nucleophilic catalyst and the reagent. The conformational behaviors of the iminium and enamine species have been determined by theoretical calculations. These data explain the effect of the bulkiness of the silyl substituent on the enantioselectivity and reactivity of the catalysts. PMID:25348681

  10. The Introduction of High-Throughput Experimentation Methods for Suzuki-Miyaura Coupling Reactions in University Education

    ERIC Educational Resources Information Center

    Hoogenboom, Richard; Meier, Michael A. R.; Schubert, Ulrich S.

    2005-01-01

    A laboratory project permits for the discussion of the reaction mechanism of the Suzuki-Miyaura coupling reaction. The practical part of the project makes the students familiar with working under inert atmosphere but if the appropriate equipment for working under inert atmosphere is not available in a laboratory, novel catalysts that do not…

  11. Dinuclear and Trinuclear Nickel Complexes as Effective Catalysts for Alternating Copolymerization on Carbon Dioxide and Cyclohexene Oxide.

    PubMed

    Tsai, Chen-Yen; Cheng, Fu-Yin; Lu, Kuan-Yeh; Wu, Jung-Tsu; Huang, Bor-Hunn; Chen, Wei-An; Lin, Chu-Chieh; Ko, Bao-Tsan

    2016-08-15

    A series of novel nickel complexes 1-9 supported by NNO-tridentate Schiff-base derivatives have been synthesized and characterized. Treatment of the pro-ligands [L(1)-H = 2,4-di-tert-butyl-6-(((2-(dimethylamino)ethyl)imino)methyl)phenol, L(2)-H = 2-(((2-(dimethylamino)ethyl)imino)methyl)-4,6-bis(2-phenylpropan-2-yl)phenol, L(3)-H = 2-(((2-(dimethylamino)ethyl)imino)methyl)phenol] with Ni(OAc)2·4H2O in refluxing ethanol afforded mono- or bimetallic nickel complexes {[(L(1))Ni(OAc)] (1); (L(2))Ni(OAc)] (2); (L(3))2Ni2(OAc)2(H2O)] (3)}. Alcohol-solvated trimetallic nickel acetate complexes {[(L(3))2Ni3(OAc)4(MeOH)2] (4); (L(3))2Ni3(OAc)4(EtOH)2] (5)} could be generated from the reaction of L(3)-H and anhydrous nickel(II) acetate with a ratio of 2:3 in refluxing anhydrous MeOH or EtOH. The reaction of nickel acetate tetrahydrate and L(4)-H to L(6)-H [L(4)-H = 2-(((2-(dimethylamino)ethyl)imino)methyl)-5-methoxyphenol, L(5)-H = 2-(((2-(dimethylamino)ethyl)imino)methyl)-4-methoxy-phenol, L(6)-H = 2-(((2-(dimethylamino)ethyl)imino)(phenyl)methyl)phenol] produced, respectively, the alcohol-free trinuclear nickel complexes {[(L(4))2Ni3(OAc)4] (7); [(L(5))2Ni3(OAc)4] (8); [(L(6))2Ni3(OAc)4] (9)} with the same ratio in refluxing EtOH under the atmospheric environment. Interestingly, recrystallization of [(L(3))2Ni3(OAc)4(MeOH)] (4) or [(L(3))2Ni3(OAc)4(EtOH)] (5) in the mixed solvent of CH2Cl2/hexane gives [(L(3))2Ni3(OAc)4] (6), which is isostructural with analogues 7-9. All bi- and trimetallic nickel complexes exhibit efficient activity and good selectivity for copolymerization of CO2 with cyclohexene oxide, resulting in copolymers with a high alternating microstructure possessing ≥99% carbonate-linkage content. This is the first example to apply well-defined trinuclear nickel complexes as efficient catalysts for the production of perfectly alternating poly(cyclohexene carbonate). PMID:27479795

  12. Dynamics of alkali ions-neutral molecules reactions: Radio frequency-guided beam experimental cross-sections and direct quasiclassical trajectory studies

    SciTech Connect

    Aguilar, J.; Andres, J. de; Lucas, J. M.; Alberti, M.; Huarte-Larranaga, F.; Bassi, D.; Aguilar, A.

    2012-11-27

    Different reactive processes taking place in collisions between alkali ions and neutral i-C{sub 3}H{sub 7}Cl molecules in the low (center of mass frame) energy range have been studied using an octopole radiofrequency guided-ion-beam apparatus developed in our laboratory. Cross-section energy dependences for all these reactions have been obtained in absolute units. Ab initio electronic structure calculations for those colliding systems evolving on the ground single potential surface have given relevant information on the main topological features of the surfaces. For some of the reactions a dynamic study by 'on the fly' trajectories has complemented the available experimental and electronic structure information.

  13. Experimental determination of particle range and dose distribution in thick targets through fragmentation reactions of stable heavy ions

    NASA Astrophysics Data System (ADS)

    Inaniwa, Taku; Kohno, Toshiyuki; Tomitani, Takehiro; Urakabe, Eriko; Sato, Shinji; Kanazawa, Mitsutaka; Kanai, Tatsuaki

    2006-09-01

    In radiation therapy with highly energetic heavy ions, the conformal irradiation of a tumour can be achieved by using their advantageous features such as the good dose localization and the high relative biological effectiveness around their mean range. For effective utilization of such properties, it is necessary to evaluate the range of incident ions and the deposited dose distribution in a patient's body. Several methods have been proposed to derive such physical quantities; one of them uses positron emitters generated through projectile fragmentation reactions of incident ions with target nuclei. We have proposed the application of the maximum likelihood estimation (MLE) method to a detected annihilation gamma-ray distribution for determination of the range of incident ions in a target and we have demonstrated the effectiveness of the method with computer simulations. In this paper, a water, a polyethylene and a polymethyl methacrylate target were each irradiated with stable 12C, 14N, 16O and 20Ne beams. Except for a few combinations of incident beams and targets, the MLE method could determine the range of incident ions RMLE with a difference between RMLE and the experimental range of less than 2.0 mm under the circumstance that the measurement of annihilation gamma rays was started just after the irradiation of 61.4 s and lasted for 500 s. In the process of evaluating the range of incident ions with the MLE method, we must calculate many physical quantities such as the fluence and the energy of both primary ions and fragments as a function of depth in a target. Consequently, by using them we can obtain the dose distribution. Thus, when the mean range of incident ions is determined with the MLE method, the annihilation gamma-ray distribution and the deposited dose distribution can be derived simultaneously. The derived dose distributions in water for the mono-energetic heavy-ion beams of four species were compared with those measured with an ionization chamber

  14. Polylactide-based microspheres prepared using solid-state copolymerized chitosan and d,l-lactide.

    PubMed

    Demina, T S; Akopova, T A; Vladimirov, L V; Zelenetskii, A N; Markvicheva, E A; Grandfils, Ch

    2016-02-01

    Amphiphilic chitosan-g-poly(d,l-lactide) copolymers have been manufactured via solid-state mechanochemical copolymerization and tailored to design polyester-based microspheres for tissue engineering. A single-step solid-state reactive blending (SSRB) using low-temperature co-extrusion has been used to prepare these copolymers. These materials have been valorized to stabilize microspheres processed by an oil/water emulsion evaporation technique. Introduction of the copolymers either in water or in the oil phase of the emulsion allowed to replace a non-degradable emulsifier typically used for microparticle preparation. To enhance cell adhesion, these copolymers were also tailored to bring amino-saccharide positively charged segments to the microbead surface. Size distribution, surface morphology, and total microparticle yield have been studied and optimized as a function of the copolymer composition. PMID:26652381

  15. Atom Transfer Radical Copolymerization of Gradient Copolymers of HEMA/DMAEMA with Arbitrary Composition Profiles

    NASA Astrophysics Data System (ADS)

    Gallow, Keith; Loo, Yueh-Lin

    2009-03-01

    Gradient copolymers represent a new class of statistical copolymers where a non-uniform composition profile is controllably introduced along the length of the polymer chain. Gradient copolymers have thermal and mechanical properties that are different from random or block copolymers having the same average composition. Due to synthetic limitations, however, the introduction of arbitrary composition profiles remains challenging. Here, we demonstrate the ability to controllably introduce arbitrary composition profiles along copolymers of 2-hydroxyethyl methacrylate (HEMA) and 2-(dimethylamino)ethyl methacrylate (DMAEMA) by atom transfer radical copolymerization in a semi-batch reactor. Using gas chromatography to monitor monomer consumption, we have constructed a kinetic model which we use as a basis to synthesize copolymers with linear and parabolic composition profiles. The overall DMAEMA content and molecular weight of these gradient copolymers were determined using nuclear magnetic resonance spectroscopy and size exclusion chromatography, respectively, and both show good agreement with our model's predictions.

  16. Crystalline Isotactic Polar Polypropylene from the Palladium-Catalyzed Copolymerization of Propylene and Polar Monomers.

    PubMed

    Ota, Yusuke; Ito, Shingo; Kobayashi, Minoru; Kitade, Shinichi; Sakata, Kazuya; Tayano, Takao; Nozaki, Kyoko

    2016-06-20

    Moderately isospecific homopolymerization of propylene and the copolymerization of propylene and polar monomers have been achieved with palladium complexes bearing a phosphine-sulfonate ligand. Optimization of substituents on the phosphorus atom of the ligand revealed that the presence of bulky alkyl groups (e.g. menthyl) is crucial for the generation of high-molecular-weight polypropylenes (Mw ≈10(4) ), and the substituent at the ortho-position relative to the sulfonate group influences the molecular weight and isotactic regularity of the obtained polypropylenes. Statistical analysis suggested that the introduction of substituents at the ortho-position relative to the sulfonate group favors enantiomorphic site control over chain end control in the chain propagation step. The triad isotacticity could be increased to mm=0.55-0.59, with formation of crystalline polar polypropylenes, as supported by the presence of melting points and sharp peaks in the corresponding X-ray diffraction patterns. PMID:27161896

  17. Surface Modification of PET Fabric by Graft Copolymerization with Acrylic Acid and Its Antibacterial Properties

    PubMed Central

    Abdolahifard, M.; Bahrami, S. Hajir; Malek, R. M. A.

    2011-01-01

    Graft copolymerization of acrylic acid (AA) onto Poly(ethylene terephthalate) (PET) fabrics with the aid of benzoyl peroxide was carried out. The effect of polymerization parameters on the graft yield was studied. Percent grafting was enhanced significantly by increasing benzoyl peroxide (BP) concentrations up to 3.84 g/lit and then decreased upon further increase in initiator concentration. Preswelling of PET leads to changes in its sorption-diffusion properties and favors an increase in the degree of grafting. The antibiotics treated grafted fabrics showed antibacterial properties towards gram-positive and gram-negative microorganisms. FTIR and SEM were used to characterize AA-grafted polyester fabrics. PMID:24052819

  18. EXPERIMENTAL STUDY OF CO{sub 2} FORMATION BY SURFACE REACTIONS OF NON-ENERGETIC OH RADICALS WITH CO MOLECULES

    SciTech Connect

    Oba, Yasuhiro; Watanabe, Naoki; Kouchi, Akira; Hama, Tetsuya; Pirronello, Valerio

    2010-04-01

    Surface reactions between carbon monoxide and non-energetic hydroxyl radicals were carried out at 10 K and 20 K in order to investigate possible reaction pathways to yield carbon dioxide in dense molecular clouds. Hydroxyl radicals, produced by dissociating water molecules in microwave-induced plasma, were cooled down to 100 K prior to the introduction of CO. The abundances of species were monitored in situ using a Fourier transform infrared spectrometer. Formation of CO{sub 2} was clearly observed, even at 10 K, suggesting that reactions of CO with OH proceed with little or no activation barrier. The present results indicate that CO{sub 2} formation, due to reactions between CO and OH, occurs in tandem with H{sub 2}O formation, and this may lead to the formation of CO{sub 2} ice in polar environments, as typically observed in molecular clouds.

  19. Theoretical calculations for neutrino-induced charged current reactions in sup 12 C and recent experimental results

    SciTech Connect

    Mintz, S.L. ); Pourkaviani, M. )

    1989-12-01

    Theoretical calculations are presented for the reaction {nu}{sub {ital e}}+{sup 12}C{r arrow}{sup 12}N{sub g.s.} +{ital e}{sup {minus}} for {ital E}{sub {nu}} from threshold to 135 MeV, for the reaction {nu}{sub {mu}}+{sup 12}C{r arrow}{sup 12}N{sub g.s.} +{mu}{sup {minus}}, and the corresponding antineutrino reaction for {ital E}{sub {nu}} from threshold to 160 MeV. Use is made of updated form factors based on more recent data for {ital e}{sup {minus}}+{sup 12}C{r arrow}{sup 12}C{sup *}+{ital e}{prime} {minus} and {gamma}+{sup 12}C{r arrow}{sup 12}C{sup *}. The recent neutrino reaction experiments are discussed in light of these calculations.

  20. Experimental search for the radiative capture reaction d + d {yields} {sup 4}He + {gamma} from the dd{mu} muonic molecule state J = 1

    SciTech Connect

    Baluev, V. V.; Bogdanova, L. N.; Bom, V. R.; Demin, D. L.; Eijk, C. W. E. van; Filchenkov, V. V.; Grafov, N. N.; Grishechkin, S. K.; Gritsaj, K. I.; Konin, A. D.; Mikhailyukov, K. L.; Rudenko, A. I.; Vinogradov, Yu. I.; Volnykh, V. P.; Yukhimchuk, A. A.; Yukhimchuk, S. A.

    2011-07-15

    A search for the muon-catalyzed fusion reaction d + d {yields} {sup 4}He + {gamma} in the dd{mu} muonic molecule was performed using the experimental installation TRITON with BGO detectors for {gamma}-quanta. A high-pressure target filled with deuterium was exposed to the negative muon beam of the JINR Phasotron to detect {gamma}-quanta with the energy 23.8 MeV. An experimental estimation for the yield of radiative deuteron capture from the dd{mu} state J = 1 was obtained at the level of {eta}{sub {gamma}} {<=} 8 Multiplication-Sign 10{sup -7} per fusion.

  1. Experimental search for the radiative capture reaction d + d → 4He + γ from the ddμ muonic molecule state J = 1

    NASA Astrophysics Data System (ADS)

    Baluev, V. V.; Bogdanova, L. N.; Bom, V. R.; Demin, D. L.; van Eijk, C. W. E.; Filchenkov, V. V.; Grafov, N. N.; Grishechkin, S. K.; Gritsaj, K. I.; Konin, A. D.; Mikhailyukov, K. L.; Rudenko, A. I.; Vinogradov, Yu. I.; Volnykh, V. P.; Yukhimchuk, A. A.; Yukhimchuk, S. A.

    2011-07-01

    A search for the muon-catalyzed fusion reaction d + d → 4He + γ in the ddμ muonic molecule was performed using the experimental installation TRITON with BGO detectors for γ-quanta. A high-pressure target filled with deuterium was exposed to the negative muon beam of the JINR Phasotron to detect γ-quanta with the energy 23.8 MeV. An experimental estimation for the yield of radiative deuteron capture from the ddμ state J = 1 was obtained at the level of η γ ≤ 8 × 10-7 per fusion.

  2. Experimental study of neutron-rich nuclei near the N = 82 closed shell using the 4096Zr +50124Sn reaction with GASP and PRISMA-CLARA arrays

    NASA Astrophysics Data System (ADS)

    Rodríguez, W.; Torres, D. A.; Cristancho, F.; Medina, N. H.; Chapman, R.; Smith, J. F.; Mengoni, D.; Truesdale, V.; Grocutt, L.; Mulholland, K.; Kumar, V.; Hadinia, B.; Labiche, M.; Liang, X.; O'Donell, D.; Ollier, J.; Orlandi, R.; Smith, J. F.; Spohr, K. M.; Wady, P.; Wang, Z. M.; Gadea, A.; Ur, C. A.; Lenzi, S. M.; Capponi, L.; Michelangnoli, C.; Bazzacco, D.; Beghini, S.; Mǎrginean, R.; Mengoni, D.; Montagnoli, G.; Recchia, F.; Scarlassara, F.; Lunardi, S.; Kröll, T.; Napoli, D. R.; Corradi, L.; Fioretto, E.; de Angelis, G.; Mǎrginean, N.; Sahin, E.; Stefanini, A. M.; Valiente-Dobon, J. J.; Vedova, F. D.; Axiotis, M.; Martinez, T.; Szilner, S.; Freeman, S. J.; Smith, A. G.; Jones, G.; Thompson, N.; Pollarolo, G.

    2014-11-01

    In this contribution an experimental study of the deep-inelastic reaction 4096Zr +50124Sn at 530 MeV, using the GASP and PRISMA-CLARA arrays, is presented. The experiments populate a wealth of projectile-like and target-like binary fragments, in a large neutron-rich region around N ≥ 50 and Z ≈ 40. Preliminary results on the study of the yrast and near-yrast states for 95Nb will be shown, along with a comparison of the experimental yields obtained in the experiments.

  3. A theoretical DFT-based and experimental study of the transmetalation step in Au/Pd-mediated cross-coupling reactions.

    PubMed

    Hansmann, Max M; Pernpointner, Markus; Döpp, René; Hashmi, A Stephen K

    2013-11-01

    In this work a combined theoretical and experimental investigation of the cross-coupling reaction involving two metallic reaction centers, namely gold and palladium, is described. One metal center (Au) hereby is rather inert towards change in its oxidation state, whereas Pd undergoes oxidative insertion and reductive elimination steps. Detailed mechanistic and energetic studies of each individual step, with the focus on the key transmetalation step are presented and compared for different substrates and ligands on the catalytic Pd center. Different aryl halides (Cl, Br, I) and aryl triflates were investigated. Hereby the nature of the counteranion X turned out to be crucial. In the case of X=Cl and L=PMe3 the oxidative addition is rate-determining, whereas in the case of X=I the transmetalation step becomes rate-determining in the Au/Pd-cross-coupling mechanism. A variety of Au-Pd transmetalation reaction scenarios are discussed in detail, favoring a transition state with short intermetallic Au-Pd contacts. Furthermore, without a halide counteranion the transmetalation from gold(I) to palladium(II) is highly endothermic, which confirms our experimental findings that the coupling does not occur with aryl triflates and similar weakly coordinating counteranions--a conclusion that is essential in designing new Au-Pd catalytic cycles. In combination with experimental work, this corrects a previous report in the literature claiming a successful coupling potentially catalytic in both metals with weakly coordinating counteranions. PMID:24115258

  4. Experimental determination of the minimum onset temperature of runaway reaction from a radioactive salt disposal in asphalt.

    PubMed

    Li, Xin-Rui; Sun, Jin-Hua; Koseki, Hiroshi; Hasegawa, Kazutoshi

    2005-04-11

    In order to clarify the reason for the most hazardous explosion in the history of the Japanese nuclear power development by a radioactive salt disposal in asphalt, an adiabatic process was developed using a Dewar vessel to minimize the temperature difference between the reactants and the surroundings. By this means, the heat evolution from a reaction which is readily lost can be detected at a lower temperature imitating the accidental condition. A series of ambient temperature-tracking Dewar experiments on asphalt salt mixtures were conducted under different initial ambient temperatures, such as 230, 210, 190, and 170 degrees C, respectively. As a result, it was observed that from 190 degrees C the sample's temperature rose until a runaway reaction occurred. The minimum onset temperature for the runaway reaction of the asphalt salt mixture was determined to be 190 degrees C, which is close to the initial temperature of approximately 180 degrees C, the same temperature as the real accident. This implies that at near this operational temperature, initial faint chemical reactions may occur and lead to further rapid reactions if heat is accumulated at this stage. PMID:15811664

  5. An experimental investigation of the reaction of hydrogen chloride with lead oxide under simulated hazardous waste incineration conditions

    SciTech Connect

    Shor, J.T.; Frazier, G.C.

    1996-04-01

    To simulate the behavior of lead during hazardous waste incineration, pellets of sintered lead oxide were treated with hydrogen chloride at concentrations of 2000 and 4000 ppm in air in a laboratory tube furnace. The chemical reaction kinetics and mass transfer properties of the solid-gas and solid-liquid reactions were examined at temperatures between 260 and 680{degrees}C. Lead dichloride was found to form and became more volatile at elevated temperatures. At temperatures above 300{degrees}C, chemical reaction kinetic limitations were absent and mass transfer resistance in the developing liquid lead oxide, lead dichloride eutectic phases were controlling. Above 590{degrees}C, a curious anomaly occurred: The observed global reaction rate appeared to increase slightly while the volatilization of lead dichloride dropped during the initial stages of the reaction. A thick film of a lead oxychloride compound was found which displayed low lead dichloride activity. Below 590{degrees}C, a different lead oxychloride compound was identified by x-ray diffraction in which lead dichloride activity was high, and this compound was much more volatile than the oxychloride formed above 5900{degrees}C.

  6. Grafting of copolymer styrene maleic anhydride on poly(ethylene terephthalate) film by chemical reaction and by plasma method: Optimization of the grafting reaction using experimental design

    NASA Astrophysics Data System (ADS)

    Bigan, Muriel; Bigot, Julien; Mutel, Brigitte; Coqueret, Xavier

    2008-02-01

    This work deals with the chemical grafting of a styrene maleic anhydride copolymer on the surface of a previously hydrolyzed polyethylene terephthalate (PET) film 12 μm thick via covalent bond. Two different ways are studied. The first one involves an activation of the hydrolyzed PET by the triethylamine before the grafting step. In the second one, the copolymer reacts with the 4-dimethylaminopyridine in order to form maleinyl pyridinium salt which reacts with alcohol function of the hydrolyzed PET. Characterization and quantification of the grafting are performed by Fourier transform infrared spectroscopy. Factorial experiment designs are used to optimize the process and to estimate experimental parameters effects. The opportunity to associate the chemical process to a cold remote nitrogen plasma one is also examined.

  7. Metal-Catalyzed Cyclization Reactions of 2,3,4-Trien-1-ols: A Joint Experimental-Computational Study.

    PubMed

    Alcaide, Benito; Almendros, Pedro; Cembellín, Sara; Fernández, Israel; Martínez Del Campo, Teresa

    2016-08-01

    Controlled preparation of tri- and tetrasubstituted furans, as well as carbazoles has been achieved through chemo- and regioselective metal-catalyzed cyclization reactions of cumulenic alcohols. The gold- and palladium-catalyzed cycloisomerization reactions of cumulenols, including indole-tethered 2,3,4-trien-1-ols, to trisubstituted furans was effective, due to a 5-endo-dig oxycyclization by attack of the hydroxy group onto the central cumulene double bond. In contrast, palladium-catalyzed heterocyclization/coupling reactions with 3-bromoprop-1-enes furnished tetrasubstituted furans. Also studied was the palladium-catalyzed cyclization/coupling sequence involving protected indole-tethered 2,3,4-trien-1-ols and 3-bromoprop-1-enes that exclusively generated trisubstituted carbazole derivatives. These results could be explained through a selective 6-endo-dig cumulenic hydroarylation, followed by aromatization. DFT calculations were carried out to understand this difference in reactivity. PMID:27383332

  8. Experimental Plan of the 25Mg(p, γ)26Al Resonance Capture Reaction at Jinping Underground Laboratory

    NASA Astrophysics Data System (ADS)

    Li, Z. H.; Su, J.; Li, Y. J.; Guo, B.; Yan, S. Q.; Wang, Y. B.; Lian, G.; Zeng, S.; Zhang, Q. W.; He, G. Z.; Gan, L.; Zhou, C.; Liu, W. P.; Li, K. A.; Yu, X. Q.; Tang, X. D.; He, J. J.; Qian, Y. Z.

    The observation of 26Al is an useful tool for γ-ray astronomy and in studies of galactic chemical evolution. The most likely mechanism for 26A1 nucleosynthesis is in the hydrogen burning MgAl cycle, and the 26A1 production from the 25Mg(p, γ)26Al reaction at the important temperature range below T = 0.2 is still not well known. We present a proposal to measure the resonance strength of 58 keV resonance level of the 25Mg(p, γ)26Al reaction, and the effective counting rate is estimated for the direct measurement at Jinping underground laboratory.

  9. [Experimental and kinetic modeling of acid/base and redox reactions over oxide catalysts]. Technical progress report

    SciTech Connect

    Not Available

    1993-07-01

    The research has involved the characterization of catalyst acidity, {sup 2}D NMR studies of Bronsted acid sites, and kinetic, calorimetric, and spectroscopic studies of methylamine synthesis and related reactions over acid catalysts. Approach of this work was to explore quantitative correlations between factors that control the generation, type, strength, and catalytic properties of acid sites on zeolite catalysts. Microcalorimetry, thermogravimetric analysis, IR spectroscopy, and NMR spectroscopy have provided information about the nature and strength of acid sites in zeolites. This was vital in understanding the catalytic cycles involved in methylamine synthesis and related reactions over zeolite catalysts.

  10. Gas-phase reactions of aryl radicals with 2-butyne: experimental and theoretical investigation employing the N-methyl-pyridinium-4-yl radical cation.

    PubMed

    Lam, A K Y; Li, C; Khairallah, G; Kirk, B B; Blanksby, S J; Trevitt, A J; Wille, U; O'Hair, R A J; da Silva, G

    2012-02-21

    Aromatic radicals form in a variety of reacting gas-phase systems, where their molecular weight growth reactions with unsaturated hydrocarbons are of considerable importance. We have investigated the ion-molecule reaction of the aromatic distonic N-methyl-pyridinium-4-yl (NMP) radical cation with 2-butyne (CH(3)C≡CCH(3)) using ion trap mass spectrometry. Comparison is made to high-level ab initio energy surfaces for the reaction of NMP and for the neutral phenyl radical system. The NMP radical cation reacts rapidly with 2-butyne at ambient temperature, due to the apparent absence of any barrier. The activated vinyl radical adduct predominantly dissociates via loss of a H atom, with lesser amounts of CH(3) loss. High-resolution Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry allows us to identify small quantities of the collisionally deactivated reaction adduct. Statistical reaction rate theory calculations (master equation/RRKM theory) on the NMP+2-butyne system support our experimental findings, and indicate a mechanism that predominantly involves an allylic resonance-stabilized radical formed via H atom shuttling between the aromatic ring and the C(4) side-chain, followed by cyclization and/or low-energy H atom β-scission reactions. A similar mechanism is demonstrated for the neutral phenyl radical (Ph˙)+2-butyne reaction, forming products that include 3-methylindene. The collisionally deactivated reaction adduct is predicted to be quenched in the form of a resonance-stabilized methylphenylallyl radical. Experiments using a 2,5-dichloro substituted methyl-pyridiniumyl radical cation revealed that in this case CH(3) loss from the 2-butyne adduct is favoured over H atom loss, verifying the key role of ortho H atoms, and the shuttling mechanism, in the reactions of aromatic radicals with alkynes. As well as being useful phenyl radical analogues, pyridiniumyl radical cations may form in the ionosphere of Titan, where they could undergo rapid

  11. Tunable mechano-responsive organogels by ring-opening copolymerizations of N-carboxyanhydrides

    PubMed Central

    Fan, Jingwei; Zou, Jiong; He, Xun; Zhang, Fuwu; Zhang, Shiyi; Raymond, Jeffery E.; Wooley, Karen L.

    2013-01-01

    The simple copolymerization of N-carboxyanhydride (NCA) monomers is utilized to generate copolypeptides having a combination of α-helix and β-sheet sub-structures that, when grown from a solvophilic synthetic polymer block segment, are capable of driving mechano-responsive supramolecular sol-to-gel-to-sol and sol-to-gel-to-gel transitions reversibly, which allow also for injection-based processing and self-healing behaviors. A new type of polypeptide-based organogelator, methoxy poly(ethylene glycol)-block-poly(γ-benzyl-l-glutamate-co-glycine) (mPEG-b-P(BLG-co-Gly)), is facilely synthesized by statistical ring-opening copolymerizations (ROPs) of γ-benzyl-l-glutamate (BLG) and glycine (Gly) NCAs initiated by mPEG-amine. These systems exhibit tunable secondary structures and result in sonication stimulus responsiveness of the organogels with the polypeptide segment variation, controlled by varying the ratio of BLG NCA to Gly NCA during the copolymerizations. Attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) studies indicate the α-helical component decreases while the β-sheet content increases systematically with a higher mole fraction of Gly in the polypeptide segment. The supramolecular assembly of β-sheet nanofibrils, having a tunable width over the range of 10.4 – 14.5 nm with varied BLG to Gly ratio, are characterized by transmission electron microscopy (TEM). The further self-assembly of these nanostructures into 3-D gel networks within N,N-dimethylformamide (DMF) occurs at low critical gelation concentrations (CGC) (lowest ca. 0.6 wt %). Increased BLG to Gly ratios lead to an increase of the α-helical component in the secondary structures of the polypeptide segments, resulting in wider and more flexible nanofibrils. The presence of α-helical component in the polymers enhances the stability of the organogels against sonication, and instantaneous gel-to-gel transitions are observed as in situ reconstruction of networks

  12. Tunable mechano-responsive organogels by ring-opening copolymerizations of N-carboxyanhydrides.

    PubMed

    Fan, Jingwei; Zou, Jiong; He, Xun; Zhang, Fuwu; Zhang, Shiyi; Raymond, Jeffery E; Wooley, Karen L

    2014-01-01

    The simple copolymerization of N-carboxyanhydride (NCA) monomers is utilized to generate copolypeptides having a combination of α-helix and β-sheet sub-structures that, when grown from a solvophilic synthetic polymer block segment, are capable of driving mechano-responsive supramolecular sol-to-gel-to-sol and sol-to-gel-to-gel transitions reversibly, which allow also for injection-based processing and self-healing behaviors. A new type of polypeptide-based organogelator, methoxy poly(ethylene glycol)-block-poly(γ-benzyl-l-glutamate-co-glycine) (mPEG-b-P(BLG-co-Gly)), is facilely synthesized by statistical ring-opening copolymerizations (ROPs) of γ-benzyl-l-glutamate (BLG) and glycine (Gly) NCAs initiated by mPEG-amine. These systems exhibit tunable secondary structures and result in sonication stimulus responsiveness of the organogels with the polypeptide segment variation, controlled by varying the ratio of BLG NCA to Gly NCA during the copolymerizations. Attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) studies indicate the α-helical component decreases while the β-sheet content increases systematically with a higher mole fraction of Gly in the polypeptide segment. The supramolecular assembly of β-sheet nanofibrils, having a tunable width over the range of 10.4 - 14.5 nm with varied BLG to Gly ratio, are characterized by transmission electron microscopy (TEM). The further self-assembly of these nanostructures into 3-D gel networks within N,N-dimethylformamide (DMF) occurs at low critical gelation concentrations (CGC) (lowest ca. 0.6 wt %). Increased BLG to Gly ratios lead to an increase of the α-helical component in the secondary structures of the polypeptide segments, resulting in wider and more flexible nanofibrils. The presence of α-helical component in the polymers enhances the stability of the organogels against sonication, and instantaneous gel-to-gel transitions are observed as in situ reconstruction of networks

  13. Swelling and thermodynamic studies of temperature responsive 2-hydroxyethyl methacrylate/itaconic acid copolymeric hydrogels prepared via gamma radiation

    NASA Astrophysics Data System (ADS)

    Tomić, Simonida L. J.; Mićić, Maja M.; Filipović, Jovanka M.; Suljovrujić, Edin H.

    2007-08-01

    The copolymeric hydrogels based on 2-hydroxyethyl methacrylate (HEMA) and itaconic acid (IA) were synthesized by gamma radiation induced radical polymerization. Swelling and thermodynamic properties of PHEMA and copolymeric P(HEMA/IA) hydrogels with different IA contents (2, 3.5 and 5 mol%) were studied in a wide pH and temperature range. Initial studies of so-prepared hydrogels show interesting pH and temperature sensitivity in swelling and drug release behavior. Special attention was devoted to temperature investigations around physiological temperature (37 °C), where small changes in temperature significantly influence swelling and drug release of these hydrogels. Due to maximum swelling of hydrogels around 40 °C, the P(HEMA/IA) hydrogel containing 5 mol% of IA without and with drug-antibiotic (gentamicin) were investigated at pH 7.40 and in the temperature range 25-42 °C, in order to evaluate their potential for medical applications.

  14. Functional Degradable Polymers by Radical Ring-Opening Copolymerization of MDO and Vinyl Bromobutanoate: Synthesis, Degradability and Post-Polymerization Modification

    PubMed Central

    2015-01-01

    The synthesis of vinyl bromobutanoate (VBr), a new vinyl acetate monomer derivative obtained by the palladium-catalyzed vinyl exchange reaction between vinyl acetate (VAc) and 4-bromobutyric acid is reported. The homopolymerization of this new monomer using the RAFT/MADIX polymerization technique leads to the formation of novel well-defined and controlled polymers containing pendent bromine functional groups able to be modified via postpolymerization modification. Furthermore, the copolymerization of vinyl bromobutanoate with 2-methylene-1,3-dioxepane (MDO) was also performed to deliver a range of novel functional degradable copolymers, poly(MDO-co-VBr). The copolymer composition was shown to be able to be tuned to vary the amount of ester repeat units in the polymer backbone, and hence determine the degradability, while maintaining a control of the final copolymers’ molar masses. The addition of functionalities via simple postpolymerization modifications such as azidation and the 1,3-dipolar cycloaddition of a PEG alkyne to an azide is also reported and proven by 1H NMR spectroscopy, FTIR spectroscopy, and SEC analyses. These studies enable the formation of a novel class of hydrophilic functional degradable copolymers using versatile radical polymerization methods. PMID:25997518

  15. Enhancement of copolymerization of itaconic acid with N-vinyl 2-pyrrolidone by radiation in the presence of cross-linking agent

    NASA Astrophysics Data System (ADS)

    Şen, M.; Yakar, A.

    2005-06-01

    Enhancement of copolymerization of itaconic acid (IA) with N-vinyl 2-pyrrolidone (VP) by radiation in the presence of cross-linking agent was investigated. Hydrogels with varying IA content were prepared from the ternary systems N-vinyl 2-pyrrolidone/itaconic acid/water by irradiating with gamma-rays in the presence of a chemical cross-linker, ethylene glycol dimethacrylate (EGDMA) at ambient temperature. The incorporation of EGDMA into the ternary mixtures caused an increase in the amount of IA in the gel system up to a mole fraction of 13.7%. Hydrogels showed a typical pH response such as high pH swelling and low pH deswelling. Equilibrium volume swelling ratio at pH 7 was varied from 15-40 with changing the IA content in the gel system and irradiation dose. The equation recently modified by the authors for the determination of M is observed to describe the swelling behaviour of P(VP/IA/EGDMA) networks containing relatively higher amount of charged units very well. In addition to the evaluation of M from swelling data, the measurement of polymer solvent interaction parameter and the determination of the reaction yield of cross-links of the systems were examined.

  16. Functional Degradable Polymers by Radical Ring-Opening Copolymerization of MDO and Vinyl Bromobutanoate: Synthesis, Degradability and Post-Polymerization Modification.

    PubMed

    Hedir, Guillaume G; Bell, Craig A; O'Reilly, Rachel K; Dove, Andrew P

    2015-07-13

    The synthesis of vinyl bromobutanoate (VBr), a new vinyl acetate monomer derivative obtained by the palladium-catalyzed vinyl exchange reaction between vinyl acetate (VAc) and 4-bromobutyric acid is reported. The homopolymerization of this new monomer using the RAFT/MADIX polymerization technique leads to the formation of novel well-defined and controlled polymers containing pendent bromine functional groups able to be modified via postpolymerization modification. Furthermore, the copolymerization of vinyl bromobutanoate with 2-methylene-1,3-dioxepane (MDO) was also performed to deliver a range of novel functional degradable copolymers, poly(MDO-co-VBr). The copolymer composition was shown to be able to be tuned to vary the amount of ester repeat units in the polymer backbone, and hence determine the degradability, while maintaining a control of the final copolymers' molar masses. The addition of functionalities via simple postpolymerization modifications such as azidation and the 1,3-dipolar cycloaddition of a PEG alkyne to an azide is also reported and proven by (1)H NMR spectroscopy, FTIR spectroscopy, and SEC analyses. These studies enable the formation of a novel class of hydrophilic functional degradable copolymers using versatile radical polymerization methods. PMID:25997518

  17. Spontaneously Healable Thermoplastic Elastomers Achieved through One-Pot Living Ring-Opening Metathesis Copolymerization of Well-Designed Bulky Monomers.

    PubMed

    Yang, Ji-Xing; Long, Ying-Yun; Pan, Li; Men, Yong-Feng; Li, Yue-Sheng

    2016-05-18

    We report here a series of novel spontaneously healable thermoplastic elastomers (TPEs) with a combination of improved mechanical and good autonomic self-healing performances. Hard-soft diblock and hard-soft-hard triblock copolymers with poly[exo-1,4,4a,9,9a,10-hexahydro-9,10(1',2')-benzeno-l,4-methanoanthracene] (PHBM) as the hard block and secondary amide group containing norbornene derivative polymer as the soft block were synthesized via living ring-opening metathesis copolymerization by use of Grubbs third-generation catalyst through sequential monomer addition. The microstructure, mechanical, self-healing, and surface morphologies of the block copolymers were thoroughly studied. Both excellent mechanical performance and self-healing capability were achieved for the block copolymers because of the interplayed physical cross-link of hard block and dynamic interaction formed by soft block in the self-assembled network. Under an optimized hard block (PHBM) weight ratio of 5%, a significant recovery of tensile strength (up to 100%) and strain at break (ca. 85%) was achieved at ambient temperature without any treatment even after complete rupture. Moreover, the simple reaction operations and well-designed monomers offer versatility in tuning the architectures and properties of the resulting block copolymers. PMID:27136676

  18. Analysis of Experimental Data on the Reaction γN → ηN with an Exotic Narrow Resonance

    NASA Astrophysics Data System (ADS)

    Tryasuchev, V. A.

    2016-05-01

    The isospin structure of the well-established s-wave resonances N(1535)1/2- and N(1650)1/2- in the presence of a hypothesized narrow resonance N(1670)/1/2+ in the amplitude of the reaction γn → ηn is considered as a function of results of two different experiments on the photoproduction of η-mesons on deuterons.

  19. Kinetics of the Fischer-Tropsch reaction on a precipitated promoted iron catalyst. 1. Experimental procedure and results

    SciTech Connect

    Lox, E.S.; Froment, G.F. )

    1993-01-01

    The Fischer-Tropsch reaction on a commercial promoted precipitated iron catalyst was studied in a tubular reactor under non-deactivating conditions of temperatures between 523 and 623 K, pressures between 0.6 and 2.1 MPa, hydrogen to carbon monoxide feed ratios between 3.0 and 6.0 mol/mol, and W/F[degree][sub CO] values between 9.2 and 63.0 kg[center dot]s/mol. The selectivity for carbon dioxide, methane, and hydrocarbons of different functionality with 2-15 carbon atoms in the molecule was obtained as a function of the carbon monoxide conversion, the reactor temperature, and the total pressure. The initial rate of formation of these products was measured as a function of the total pressure and the partial pressures of hydrogen and carbon monoxide at the reactor inlet. These experiments, combined with the information gained from the catalyst characterization, indicated that carbon dioxide is formed by the water gas shift reaction. Methane, n-paraffins, and 1-olefins with two and more carbon atoms in the molecule are all primary products of the Fischer-Tropsch reaction. The composition of the hydrocarbon product fraction, as a function of the number of carbon atoms in the hydrocarbon molecule, could be described by the Schulz-Flory distribution, although it is shown that the latter only approximately holds for the effluent of an integral reactor.

  20. Nuclear spin dependence of the reaction of H{sub 3}{sup +} with H{sub 2}. II. Experimental measurements

    SciTech Connect

    Crabtree, Kyle N.; Kauffman, Carrie A.; Tom, Brian A.; Becka, Eftalda; McGuire, Brett A.; McCall, Benjamin J.

    2011-05-21

    The nuclear spin dependence of the chemical reaction H{sub 3}{sup +}+ H{sub 2}{yields} H{sub 2} +H{sub 3}{sup +} has been studied in a hollow cathode plasma cell. Multipass infrared direct absorption spectroscopy has been employed to monitor the populations of several low-energy rotational levels of ortho- and para-H{sub 3}{sup +} (o-H{sub 3}{sup +} and p-H{sub 3}{sup +}) in hydrogenic plasmas of varying para-H{sub 2} (p-H{sub 2}) enrichment. The ratio of the rates of the proton hop (k{sup H}) and hydrogen exchange (k{sup E}) reactions {alpha}{identical_to}k{sup H}/k{sup E} is inferred from the observed p-H{sub 3}{sup +} fraction as a function of p-H{sub 2} fraction using steady-state chemical models. Measurements have been performed both in uncooled (T{sub kin}{approx} 350 K) and in liquid-nitrogen-cooled (T{sub kin}{approx} 135 K) plasmas, marking the first time this reaction has been studied at low temperature. The value of {alpha} has been found to decrease from 1.6 {+-} 0.1 at 350 K to 0.5 {+-} 0.1 at 135 K.

  1. Experimental studies of the kinetics of the reaction of hydroxyl (OH) radicals with 3-methylfuran at low pressure

    NASA Astrophysics Data System (ADS)

    Liljegren, J. A.; Stevens, P. S.

    2011-12-01

    In addition to anthropogenic origins from fossil fuel combustion and biomass burning, 3-methylfuran is an atmospheric constituent of interest due to biogenic origins from the OH-initiated oxidation of isoprene. Although the yield of 3-methylfuran produced from the OH-initiated oxidation of isoprene is relatively small (approximately 5%), 3-methylfuran could contribute significantly to atmospheric chemistry due to the high emission rate of isoprene to the atmosphere. A knowledge of the rate constant for the reaction of OH radicals with 3-methylfuran under a variety of conditions is important for determining the overall impact of isoprene emissions on atmospheric chemistry. The rate constant for the reaction of OH with 3-methylfuran has been measured as a function of temperature at low pressure using discharge-flow techniques coupled with laser induced fluorescence detection of OH. These absolute measurements at room temperature will be compared to previous measurements using relative rate techniques. The measurements of the temperature dependence for this reaction are the first to be reported.

  2. First Experimental Measurement of the {sup 18}O(p,{alpha}){sup 15}N Reaction at Astrophysical Energies

    SciTech Connect

    La Cognata, M.; Sergi, M. L.; Spitaleri, C.; Cherubini, S.; Gulino, M.; Kiss, G.; Lamia, L.; Pizzone, R. G.; Romano, S.; Mukhamedzhanov, A.; Goldberg, V.; Tribble, R.; Coc, A.; Hammache, F.; Sereville, N. de; Tumino, A.

    2010-11-24

    The {sup 18}O(p,{alpha}){sup 15}N and {sup 17}O(p,{alpha}){sup 14}N reactions are of primary importance in several as-trophysical scenarios, including nucleosynthesis inside Asymptotic Giant Branch stars and oxygen and nitrogen isotopic ratios in meteorite grains. They are also key reactions to understand exotic systems such as R-Coronae Borealis stars and novae. Thus, the measurement of their cross sections in the low energy region can be crucial to reduce the nuclear uncertainty on theoretical predictions, because the resonance parameters are poorly determined. The Trojan Horse Method, in its newly developed form particularly suited to investigate low-energy resonances, has been applied to the {sup 2}H({sup 18}O,{alpha}{sup 15}N)n and {sup 2}H({sup 17}O,{alpha}{sup 14}N)n reactions to deduce the {sup 18}O(p,{alpha}){sup 15}N and {sup 17}O(p,{alpha}){sup 14}N cross sections at low energies. Resonances in the {sup 18}O(p,{alpha}){sup 15}N and {sup 17}O(p,{alpha}){sup 14}N excitation functions have been studied and the resonance parameters deduced.

  3. Swelling and drug release behavior of poly(2-hydroxyethyl methacrylate/itaconic acid) copolymeric hydrogels obtained by gamma irradiation

    NASA Astrophysics Data System (ADS)

    Tomić, S. Lj.; Mićić, M. M.; Filipović, J. M.; Suljovrujić, E. H.

    2007-05-01

    The new copolymeric hydrogels based on 2-hydroxyethyl methacrylate (HEMA) and itaconic acid (IA) were prepared by gamma irradiation, in order to examine the potential use of these hydrogels in controlled drug release systems. The influence of IA content in the gel on the swelling characteristics and the releasing behavior of hydrogels, and the effect of different drugs, theophylline (TPH) and fenethylline hydrochloride (FE), on the releasing behavior of P(HEMA/IA) matrix were investigated in vitro. The diffusion exponents for swelling and drug release indicate that the mechanisms of buffer uptake and drug release are governed by Fickian diffusion. The swelling kinetics and, therefore, the release rate depends on the matrix swelling degree. The drug release was faster for copolymeric hydrogels with a higher content of itaconic acid. Furthermore, the drug release for TPH as model drug was faster due to a smaller molecular size and a weaker interaction of the TPH molecules with(in) the P(HEMA/IA) copolymeric networks.

  4. Experimental and theoretical study on gas-phase ion/molecule reactions of silver trimer cation, Ag{sub 3}{sup +}, with 12-crown-4

    SciTech Connect

    Kumondai, Kousuke; Toyoda, Michisato; Ishihara, Morio; Katakuse, Itsuo; Takeuchi, Takae; Ikeda, Mai; Iwamoto, Kenichi

    2005-07-08

    The reaction mechanisms of silver trimer cation, Ag{sub 3}{sup +}, with 12-crown-4 (12C4) were studied experimentally and theoretically. Using a cylindrical ion trap time-of-flight mass spectrometer, gas-phase ion/molecule reactions of Ag{sub 3}{sup +} with 12C4 were observed. Metal-ligand complexes of [Ag(12C4)]{sup +}, [Ag{sub 3}(12C4)]{sup +} and [Ag{sub 3}(12C4){sub 2}]{sup +}, and of [Ag(12C4){sub 2}]{sup +} and [Ag{sub 3}(12C4){sub 3}]{sup +}, were observed as the reaction intermediates and terminal products, respectively. The formations of the [Ag(12C4)]{sup +} and [Ag(12C4){sub 2}]{sup +} complexes indicated that the neutral dimer (Ag{sub 2}) had been eliminated from the trimer cation. From the results of ab initio calculations at the HF/LanL2DZ level of theory and the experiments, it is suggested that three 12C4 molecules can attach to Ag{sub 3}{sup +} through consecutive reactions and that neutral Ag{sub 2} can be easily eliminated from [Ag{sub 3}(12C4)]{sup +}.

  5. Generation of 4-hydroxy-2,5-dimethyl-3(2H)-furanone from rhamnose as affected by reaction parameters: experimental design approach.

    PubMed

    Illmann, Silke; Davidek, Tomas; Gouézec, Elisabeth; Rytz, Andreas; Schuchmann, Heike P; Blank, Imre

    2009-04-01

    The formation of 4-hydroxy-2,5-dimethyl-3(2H)-furanone (HDMF) was studied in aqueous model systems containing L-rhamnose and L-lysine. The approach consisted in systematically varying four reaction parameters (rhamnose concentration, rhamnose to lysine ratio, pH, and phosphate concentration) at 3 levels. A fractional factorial design was used to reduce the number of trials. The degradation of rhamnose was followed by high performance anion exchange chromatography and the formation of HDMF by solid phase extraction in combination with GC/MS. The study permitted the identification of critical reaction parameters that affect the formation of HDMF from rhamnose in aqueous systems. Although all studied parameters have some impact on the HDMF formation and rhamnose degradation kinetics, the effect of phosphate is by far the most important, followed by concentration of precursors and pH. The experimental design approach permitted us, with a limited number of experiments, to accurately model the effects of the four investigated reaction parameters on the kinetics of rhamnose degradation and HDMF formation (R(2)>0.93). Overall, the results indicate that rhamnose can be an excellent precursor of HDMF (yield >40 mol%), if the reaction conditions are well mastered. PMID:19256512

  6. Closed-System One-Pot Block Copolymerization by Temperature-Modulated Monomer Segregation.

    PubMed

    Carmean, R Nicholas; Figg, C Adrian; Becker, Troy E; Sumerlin, Brent S

    2016-07-18

    A biphasic one-pot polymerization method enables the preparation of block copolymers from monomers with similar and competitive reactivities without the addition of external materials. AB diblock copolymers were prepared by encapsulating a frozen solution of monomer B on the bottom of a reaction vessel, while the solution polymerization of monomer A was conducted in a liquid layer above. Physical separation between the solid and liquid phases permitted only homopolymerization of monomer A until heating above the melting point of the lower phase, which released monomer B, allowing the addition of the second block to occur. The triggered release of monomer B allowed for chain extension without additional deoxygenation steps or exogenous monomer addition. A method for the closed (i.e., without addition of external reagents) one-pot synthesis of block copolymers with conventional glassware using straightforward experimental techniques has thus been developed. PMID:27258702

  7. Experimental determination of the {sup 26}Al(n,{alpha}){sup 23}Na reaction cross section and calculation of the Maxwellian averaged cross section at stellar temperatures

    SciTech Connect

    Smet, L. de; Wagemans, C.; Wagemans, J.; Heyse, J.; Gils, J. van

    2007-10-15

    The {sup 26}Al(n,{alpha}){sup 23}Na reaction cross section has been studied at the linear accelerator GELINA of the Institute for Reference Materials and Measurements in Geel, Belgium, and has been determined up to a neutron energy of about 100 keV using the time-of-flight technique. Six resonances could be observed in this energy region, whereas before only one had been identified experimentally. For four of them, resonance parameters such as resonance energy, total width, area, and spin of the state could be determined. From the obtained {sup 26}Al(n,{alpha}){sup 23}Na cross section data, Maxwellian averaged cross section (MACS) values were calculated by numerical integration. Since neutron induced reactions are among the major destruction mechanisms of {sup 26}Al in our Galaxy, these new MACS values contribute to a better understanding of the observed {sup 26}Al abundance.

  8. Open Experimentation on Phenomena of Chemical Reactions via the Learning Company Approach in Early Secondary Chemistry Education

    ERIC Educational Resources Information Center

    Beck, Katharina; Witteck, Torsten; Eilks, Ingo

    2010-01-01

    Presented is a case study on the implementation of open and inquiry-type experimentation in early German secondary chemistry education. The teaching strategy discussed follows the learning company approach. Originally adopted from vocational education, the learning company method is used to redirect lab-oriented classroom practice towards a more…

  9. Dinuclear Zinc Salen Catalysts for the Ring Opening Copolymerization of Epoxides and Carbon Dioxide or Anhydrides.

    PubMed

    Thevenon, Arnaud; Garden, Jennifer A; White, Andrew J P; Williams, Charlotte K

    2015-12-21

    A series of four dizinc complexes coordinated by salen or salan ligands, derived from ortho-vanillin and bearing (±)-trans-1,2-diaminocyclohexane (L1) or 2,2-dimethyl-1,3-propanediamine (L2) backbones, is reported. The complexes are characterized using a combination of X-ray crystallography, multinuclear NMR, DOSY, and MALDI-TOF spectroscopies, and elemental analysis. The stability of the dinuclear complexes depends on the ligand structure, with the most stable complexes having imine substituents. The complexes are tested as catalysts for the ring-opening copolymerization (ROCOP) of CO2/cyclohexene oxide (CHO) and phthalic anhydride (PA)/CHO. All complexes are active, and the structure/activity relationships reveal that the complex having both L2 and imine substituents displays the highest activity. In the ROCOP of CO2/CHO its activity is equivalent to other metal salen catalysts (TOF = 44 h(-1) at a catalyst loading of 0.1 mol %, 30 bar of CO2, and 80 °C), while for the ROCOP of PA/CHO, its activity is slightly higher than other metal salen catalysts (TOF = 198 h(-1) at a catalyst loading of 1 mol % and 100 °C). Poly(ester-block-carbonate) polymers are also afforded using the most active catalyst by the one-pot terpolymerization of PA/CHO/CO2. PMID:26605983

  10. Recent Development of Copolymeric Delivery System for Anticancer Agents Based on Cyclodextrin Derivatives.

    PubMed

    Feng, Runliang; Deng, Peizong; Teng, Fangfang; Song, Zhimei

    2016-01-01

    Core-shell structured aggregates of amphiphilic block copolymer are hopefully drug delivery system because of their ability to encapsulate hydrophobic drugs, and their hydrophilic shell can prolong retention time of drugs in the blood circulation system. Cyclodextrin is a kind of hydrophilic polysaccharide containing multiple hydroxyl groups, providing an inner hole that can load small molecule through host-guest interaction. These hydroxyl groups or their derived functional ones are utilized in conjugation with polymeric chains to form block copolymers. These copolymers can not only encapsulate hydrophobic drugs, but also encapsulate hydrophilic drugs (like DNA, protein, etc) through hydrophobic, host-guest or electrostatic interactions, which strengthen interaction between drugs and materials compared with general copolymers, indicating that formed drug delivery systems are more stable. By introduction of target molecule, they also achieve selective delivery of drugs to specific tissues or organs. So, several researchers are stimulated to carry out many studies for the development of cyclodextrin copolymeric drug delivery systems in recent. In this review, we focus the cyclodextrin copolymers' application in the anticancer agents' delivery. PMID:26349814

  11. Chemically induced graft copolymerization of 2-hydroxyethyl methacrylate onto polyurethane surface for improving blood compatibility

    NASA Astrophysics Data System (ADS)

    He, Chunli; Wang, Miao; Cai, Xianmei; Huang, Xiaobo; Li, Li; Zhu, Haomiao; Shen, Jian; Yuan, Jiang

    2011-11-01

    To improve hydrophilicity and blood compatibility properties of polyurethane (PU) film, we chemically induced graft copolymerization of 2-hydroxyethyl methacrylate (HEMA) onto the surface of polyurethane film using benzoyl peroxide as an initiator. The effects of grafting temperature, grafting time, monomer and initiator concentrations on the grafting yields were studied. The maximum grafting yield value was obtained 0.0275 g/cm2 for HEMA. Characterization of the films was carried out by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), water contact angle measurements. ATR-FTIR data showed that HEMA was successfully grafted onto the PU films surface. Water contact angle measurement demonstrated the grafted films possessed a relatively hydrophilic surface. The blood compatibility of the grafted films was preliminarily evaluated by a platelet-rich plasma adhesion test and hemolysis test. The results of platelet adhesion experiment showed that polyurethane grafted polymerization with monomer of 2-hydroxyethyl methacrylate had good blood compatibility featured by the low platelet adhesion. Hemolysis rate of the PU-g-PHEMA films was dramatically decreased than the ungrafted PU films. This kind of new biomaterials grafted with HEMA monomers might have a potential usage for biomedical applications.

  12. Multi-body simulation of a canine hind limb: model development, experimental validation and calculation of ground reaction forces

    PubMed Central

    2009-01-01

    Background Among other causes the long-term result of hip prostheses in dogs is determined by aseptic loosening. A prevention of prosthesis complications can be achieved by an optimization of the tribological system which finally results in improved implant duration. In this context a computerized model for the calculation of hip joint loadings during different motions would be of benefit. In a first step in the development of such an inverse dynamic multi-body simulation (MBS-) model we here present the setup of a canine hind limb model applicable for the calculation of ground reaction forces. Methods The anatomical geometries of the MBS-model have been established using computer tomography- (CT-) and magnetic resonance imaging- (MRI-) data. The CT-data were collected from the pelvis, femora, tibiae and pads of a mixed-breed adult dog. Geometric information about 22 muscles of the pelvic extremity of 4 mixed-breed adult dogs was determined using MRI. Kinematic and kinetic data obtained by motion analysis of a clinically healthy dog during a gait cycle (1 m/s) on an instrumented treadmill were used to drive the model in the multi-body simulation. Results and Discussion As a result the vertical ground reaction forces (z-direction) calculated by the MBS-system show a maximum deviation of 1.75%BW for the left and 4.65%BW for the right hind limb from the treadmill measurements. The calculated peak ground reaction forces in z- and y-direction were found to be comparable to the treadmill measurements, whereas the curve characteristics of the forces in y-direction were not in complete alignment. Conclusion In conclusion, it could be demonstrated that the developed MBS-model is suitable for simulating ground reaction forces of dogs during walking. In forthcoming investigations the model will be developed further for the calculation of forces and moments acting on the hip joint during different movements, which can be of help in context with the in silico development and

  13. Anti-Inflammatory Property of Plantago major Leaf Extract Reduces the Inflammatory Reaction in Experimental Acetaminophen-Induced Liver Injury.

    PubMed

    Hussan, Farida; Mansor, Adila Sofea; Hassan, Siti Nazihahasma; Tengku Nor Effendy Kamaruddin, Tg Nurul Tasnim; Budin, Siti Balkis; Othman, Faizah

    2015-01-01

    Hepatic injury induces inflammatory process and cell necrosis. Plantago major is traditionally used for various diseases. This study aimed to determine the anti-inflammatory property of P. major leaf extracts on inflammatory reaction following acetaminophen (APAP) hepatotoxicity. Thirty male Sprague-Dawley rats were divided into 5 groups, namely, normal control (C), APAP, aqueous (APAP + AQ), methanol (APAP + MT), and ethanol (APAP + ET) extract treated groups. All APAP groups received oral APAP (2 g/kg) at day 0. Then, 1000 mg/kg dose of P. major extracts was given for six days. The levels of liver transaminases were measured at day 1 and day 7 after APAP induction. At day 7, the blood and liver tissue were collected to determine plasma cytokines and tissue 11β-HSD type 1 enzyme. The in vitro anti-inflammatory activities of methanol, ethanol, and aqueous extracts were 26.74 ± 1.6%, 21.69 ± 2.81%, and 12.23 ± 3.15%, respectively. The ALT and AST levels were significantly higher in the APAP groups at day 1 whereas the enzyme levels of all groups showed no significant difference at day 7. The extracts treatment significantly reduced the proinflammatory cytokine levels and significantly increased the 11β-HSD type 1 enzyme activity (p < 0.05). In conclusion, the P. major extracts attenuate the inflammatory reaction following APAP-induced liver injury. PMID:26300946

  14. An experimental study on evolution of fracture permeability and rate of water-rock reactions in ultramafic rocks at hydrothermal conditions

    NASA Astrophysics Data System (ADS)

    Farough, A.; Lowell, R. P.

    2015-12-01

    We have performed experiments on the evolution of fracture permeability during serpentinization of ultramafic rocks. The experiments were performed using a flow-through triaxial machine on samples of ultramafic rocks with a well-mated through-going tensile fracture at hydrothermal conditions at effective pressure of 30 MPa and temperature of 260°C. By determining the flow rate under a pore pressure gradient during the experiments and assuming a cubic law relating fracture aperture and permeability, the results showed that fracture permeability decreased by one to two orders of magnitude during the 200 to 340 hour experiments. Electron microprobe data and SEM images indicated the formation of needle-shaped crystals of serpentine composition along the walls of the fracture. Assuming the dissolution and precipitation reactions occur simultaneously along the fracture walls we found that the rate of transformation at the beginning of the experiments is ~10-4-5 (molm-2hr-1) and decreases monotonically for about an order of magnitude towards the end of experiments. The rate of transformation is converted to rate of reaction of 10-5-7 s-1 at the beginning of the experiments, which is in agreement with estimates of Martin and Fyfe, [1970] of the rate of serpentinization reactions. The results suggest that the reaction rate slowed with increasing time as available reactive surface area decreased. The results also indicate that the water-rock reactions were the main mechanism contributing to the reduction in fracture aperture and cubic law is a reasonable first approximation for understanding evolution of fracture permeability. The experimental results suggest that the fracture network in long-lived hydrothermal circulation systems can be sealed rapidly as a result of mineral precipitation, and generation of new permeability resulting from a combination of tectonic and crystallization-induced stresses is required to maintain fluid circulation.

  15. Experimental Studies of the Coulomb Force Effects in Deuteron-Proton Break-up Reaction at Medium Energy Regime

    NASA Astrophysics Data System (ADS)

    Ciepał, I.; Parol, W.; Kalantar-Nayestanaki, N.; Khatri, G.; Kistryn, St.; Kłos, B.; Kozela, A.; Kulessa, P.; Messchendorp, J.; Skwira-Chalot, I.; Stephan, E.; Włoch, B.

    2016-03-01

    A set of differential cross-section data of the 1H(d, pp)n breakup reaction at 130 and 160 MeV deuteron beam energies has been measured in the forward polar angles domain. The data were collected with the use of the Germanium Wall (FZ Jülich) and BINA (KVI Groningen) detectors. This part of the phase-space is special with respect to the dominant Coulomb force influence on the system dynamics. The data are compared with the theoretical calculations based on the Argonne V18 potential supplemented with the long-range electromagnetic component. The predictions also include the Urbana IX three nucleon force model. The strongest Coulomb effects are found in regions where the relative energy of the two protons is the smallest.

  16. Experimentally constrained (p ,γ )89Y and (n ,γ )89Y reaction rates relevant to p -process nucleosynthesis

    NASA Astrophysics Data System (ADS)

    Larsen, A. C.; Guttormsen, M.; Schwengner, R.; Bleuel, D. L.; Goriely, S.; Harissopulos, S.; Bello Garrote, F. L.; Byun, Y.; Eriksen, T. K.; Giacoppo, F.; Görgen, A.; Hagen, T. W.; Klintefjord, M.; Renstrøm, T.; Rose, S. J.; Sahin, E.; Siem, S.; Tornyi, T. G.; Tveten, G. M.; Voinov, A. V.; Wiedeking, M.

    2016-04-01

    The nuclear level density and the γ -ray strength function have been extracted for 89Y by using the Oslo method on 89Y(p ,p'γ )89Y coincidence data. The γ -ray strength function displays a low-energy enhancement consistent with previous observations in this mass region (Mo-9893). Shell-model calculations support the conclusion that the observed enhancement is due to strong, low-energy M 1 transitions at high excitation energies. The data were further used as input for calculations of the 88Sr(p ,γ )89Y and 88Y(n ,γ )89Y cross sections with the talys reaction code. Comparison with cross-section data, where available, as well as with values from the BRUSLIB library, shows a satisfying agreement.

  17. Control of dissolved Al distributions in marine sediments by clay reconstitution reactions: Experimental evidence leading to a unified theory

    NASA Astrophysics Data System (ADS)

    Mackin, James E.

    1986-02-01

    A set of sediment "resuspension" experiments was designed to test various aspects of previously hypothesized clay reconstitution reactions in nearshore sediments. Aliquots of wet sediment of approximately equal weight from Flax Pond, Long Island Sound were suspended in stirred and aerated, high salinity solutions having variable adjusted initial dissolved Si concentrations but otherwise nearly identical properties. Dissolved Al and Si and the water pH were monitored over the course of three days. Dissolved Si was removed from solution in the high initial Si (325 and 650 μM) containers, while little change in Si concentration was observed in a "blank" and 0 Si-spike container. Short-term dissolved Al production in the experiments suggests that clay dissolution is important in these sediments. Long-term dissolved Al behavior agrees fairly well with quantitative predictions based upon previous studies of nearshore sediments, where authigenic clays were believed to cause observed inverse relationships between dissolved Al and Si. The unambiguous results give strong evidence that inverse Al-Si relations in dissolved Fe-poor sediments are a direct result of mineral precipitation, rather than being due to some fortuitous combination of unrelated reactions affecting Al and Si. The Si/Al composition of authigenic clay precipitates in marine sediments probably varies directly with the dissolved Si content of contacting waters. This indicates that a combination of "weathering" and "reverse weathering" of minerals may affect Si distributions, and provides a theoretical link between these two sets of previously suggested mechanisms for clay reconstitution in sediments.

  18. Calculational and Experimental Investigations of the Pressure Effects on Radical - Radical Cross Combinations Reactions: C2H5 + C2H3

    NASA Technical Reports Server (NTRS)

    Fahr, Askar; Halpern, Joshua B.; Tardy, Dwight C.

    2007-01-01

    Pressure-dependent product yields have been experimentally determined for the cross-radical reaction C2H5 + C2H3. These results have been extended by calculations. It is shown that the chemically activated combination adduct, 1-C4H8*, is either stabilized by bimolecular collisions or subject to a variety of unimolecular reactions including cyclizations and decompositions. Therefore the "apparent" combination/disproportionation ratio exhibits a complex pressure dependence. The experimental studies were performed at 298 K and at selected pressures between about 4 Torr (0.5 kPa) and 760 Torr (101 kPa). Ethyl and vinyl radicals were simultaneously produced by 193 nm excimer laser photolysis of C2H5COC2H3 or photolysis of C2H3Br and C2H5COC2H5. Gas chromatograph/mass spectrometry/flame ionization detection (GC/MS/FID) were used to identify and quantify the final reaction products. The major combination reactions at pressures between 500 (66.5 kPa) and 760 Torr are (1c) C2H5 + C2H3 yields 1-butene, (2c) C2H5 + C2H5 yields n-butane, and (3c) C2H3 + C2H3 yields 1,3-butadiene. The major products of the disproportionation reactions are ethane, ethylene, and acetylene. At moderate and lower pressures, secondary products, including propene, propane, isobutene, 2-butene (cis and trans), 1-pentene, 1,4-pentadiene, and 1,5-hexadiene are also observed. Two isomers of C4H6, cyclobutene and/or 1,2-butadiene, were also among the likely products. The pressure-dependent yield of the cross-combination product, 1-butene, was compared to the yield of n-butane, the combination product of reaction (2c), which was found to be independent of pressure over the range of this study. The [ 1-C4H8]/[C4H10] ratio was reduced from approx.1.2 at 760 Torr (101 kPa) to approx.0.5 at 100 Torr (13.3 kPa) and approx.0.1 at pressures lower than about 5 Torr (approx.0.7 kPa). Electronic structure and RRKM calculations were used to simulate both unimolecular and bimolecular processes. The relative importance

  19. Cationic germanium fluorides: 2. An experimental and theoretical investigation on the reaction between GeF+ and H2O [1

    NASA Astrophysics Data System (ADS)

    Antoniotti, Paola; Rabezzana, Roberto; Borocci, Stefano; Bronzolino, Nicoletta; Giordani, Maria; Grandinetti, Felice

    2006-11-01

    The reaction between singlet ground state GeF+ (1[Sigma]+) and H2O, with formation of Ge-OH+ and HF, was investigated by ion trap mass spectrometry (ITMS) and ab initio calculations at the MP2 and CCSD(T) level of theory. The process involves the initial formation of the addition product FGe+-OH2 (1), its interconversion into HOGe+-FH (2), and the eventual barrier-free dissociation into Ge-OH+ and HF. The activation barrier of the 1 --> 2 isomerization is comparable with the exothermicity (exoergicity) of the formation of 1, and this explains the relatively low efficiency of the process, experimentally evaluated as 0.14 from the ratio of the absolute rate constant, 3.2 x 10-10 cm3 molecule-1 s-1, and the collisional rate constant. The mechanism of the reaction between GeF+ and H2O is strictly analogue to that of the reaction between SiF+ and H2O, investigated so far by selected-ion flow tube (SIFT) mass spectrometry and ab initio calculations. From a general point of view, the conceivable occurrence of additional similarities between the still essentially unexplored reactivity of GeFn+ (n = 1-3) and the rich and variegated chemistry of SiFn+ suggests novel attractive opportunities in the gas-phase positive ion chemistry of germanium.

  20. An Experimental and Theoretical Investigation of the C((1)D) + N2 → C((3)P) + N2 Quenching Reaction at Low Temperature.

    PubMed

    Hickson, Kevin M; Loison, Jean-Christophe; Lique, François; Kłos, Jacek

    2016-04-28

    The gas-phase quenching reaction C((1)D) + N2 → C((3)P) + N2 has been investigated experimentally over the temperature range 50-296 K using a supersonic flow reactor. C((1)D) atoms were produced in situ by the pulsed multiphoton dissociation of CBr4 precursor molecules. Rate constants for this process were measured using a chemical tracer method whereby the C((1)D) + H2 → CH + H reaction was employed to follow C((1)D) decays by monitoring vacuum ultraviolet laser-induced fluorescence of the atomic hydrogen product at 121.567 nm. The deactivation rates are seen to increase at lower temperature, indicating the likely influence of the CNN intermediate complex lifetime on intersystem crossing for this system. We also performed electronic structure calculations of relevant C((3)P)-N2 and C((1)D)-N2 potential energy curves as well as triplet-singlet spin-orbit coupling terms using the explicitly correlated internally contracted multireference configuration interaction method (ic-MRCI-F12). The calculations were performed for the collinear and perpendicular approach of the C atom toward the N2 molecule, which allowed us to construct the approximate spherical (isotropic) potential model of C-N2(j = 0). The computed reduced dimensional potentials were used in quantum close coupling scattering calculations of the electronic quenching cross sections and rate constants. While the calculated potential energy curves form the basis for a good qualitative description of the reaction, the calculated rate constants are significantly smaller than the measured ones, and fail to reproduce the temperature dependence of the experimental results. Several possible reasons are provided to explain the origin of these differences. PMID:27046417

  1. Psychometric properties of reaction time based experimental paradigms measuring anxiety-related information-processing biases in children.

    PubMed

    Brown, H M; Eley, T C; Broeren, S; Macleod, C; Rinck, M; Hadwin, J A; Lester, K J

    2014-01-01

    Theoretical frameworks highlight the importance of threat-related information-processing biases for understanding the emergence of anxiety in childhood. The psychometric properties of several tasks measuring these biases and their associations with anxiety were examined in an unselected sample of 9-year-old children (N=155). In each task, threat bias was assessed using bias scores reflecting task performance on threat versus non-threat conditions. Reliability was assessed using split-half and test-retest correlations of mean reaction times (RTs), accuracy and bias indices. Convergence between measures was also examined. Mean RTs showed substantial split-half and test-retest correlations. Bias score reliability coefficients were near zero and non-significant, suggesting poor reliability in children of this age. Additionally, associations between bias scores and anxiety were weak and inconsistent and performance between tasks showed little convergence. Bias scores from RT based paradigms in the current study lacked adequate psychometric properties for measuring individual differences in anxiety-related information-processing in children. PMID:24486916

  2. Singly versus Doubly Reduced Nickel Porphyrins for Proton Reduction: Experimental and Theoretical Evidence for a Homolytic Hydrogen-Evolution Reaction.

    PubMed

    Han, Yongzhen; Fang, Huayi; Jing, Huize; Sun, Huiling; Lei, Haitao; Lai, Wenzhen; Cao, Rui

    2016-04-25

    A nickel(II) porphyrin Ni-P (P=porphyrin) bearing four meso-C6 F5 groups to improve solubility and activity was used to explore different hydrogen-evolution-reaction (HER) mechanisms. Doubly reduced Ni-P ([Ni-P](2-) ) was involved in H2 production from acetic acid, whereas a singly reduced species ([Ni-P](-) ) initiated HER with stronger trifluoroacetic acid (TFA). High activity and stability of Ni-P were observed in catalysis, with a remarkable ic /ip value of 77 with TFA at a scan rate of 100 mV s(-1) and 20 °C. Electrochemical, stopped-flow, and theoretical studies indicated that a hydride species [H-Ni-P] is formed by oxidative protonation of [Ni-P](-) . Subsequent rapid bimetallic homolysis to give H2 and Ni-P is probably involved in the catalytic cycle. HER cycling through this one-electron-reduction and homolysis mechanism has been proposed previously but rarely validated. The present results could thus have broad implications for the design of new exquisite cycles for H2 generation. PMID:27028563

  3. Experimental study of carbon sequestration reactions controlled by the percolation of CO2-rich brine through peridotites.

    PubMed

    Andreani, M; Luquot, L; Gouze, P; Godard, M; Hoisé, E; Gibert, B

    2009-02-15

    Carbonation of ultramafic rocks in geological reservoirs is, in theory, the most efficient way to trap CO2 irreversibly; however, possible feedback effects between carbonation reactions and changes in the reservoir permeability must be considered to realistically assess the efficiency and sustainability of this process. We investigated changes in the hydrodynamic properties of sintered dunite samples by means of percolation experiments, under conditions analogous to that of in situ carbonation. Our results show that carbonation efficiency is controlled by the local renewal of the reactants and the heterogeneity of the pore structure. Preferential flow zones are characterized by the formation of magnetite and of a silica-rich layer at the olivine surfaces, which eventually inhibits olivine dissolution. Conversely, sustainable olivine dissolution together with coprecipitation of magnesite, siderite, and minor Mg-TOT-phyllosilicates, occur in reduced-flow zones. Thus carbonate precipitation only decreases porosity in zones where diffusion-controlled transport is dominant. Consequently, while high flow rates will decrease the carbonation efficiency of the reservoir and low flow rates may reduce the permeability irreversibly close to the injection point, moderate injection rates will ensure a partial carbonation of the rock and maintain the reservoir permeability. PMID:19320184

  4. Experimental cross-sections for proton induced nuclear reactions on mercury up to 65 MeV

    NASA Astrophysics Data System (ADS)

    Hermanne, A.; Tárkányi, F.; Takács, S.; Ditrói, F.; Szücs, Z.; Brezovcsik, K.

    2016-07-01

    Cross-sections for formation of activation products induced by protons on natural mercury targets were measured. Results for 196m,196g,197g(cum), 198m,198g,199g(cum), 200g(cum), 201,202Tl, 194g(cum), 195g(cum), 196g(cum), 198m,199g(cum) Au and 195m,197m,203Hg are presented up to 65 MeV incident particle energy, many of these for the first time. The experimental data are compared with literature values and with the predictions of the TALYS 1.6 code (results taken from TENDL-2015 on-line library), thick target yields were derived and possible applications in biomedical sciences are discussed.

  5. The effects of stress concentrations on reaction progress: an example from experimental growth of magnesio-aluminate spinel at corundum - periclase interfaces under uniaxial load

    NASA Astrophysics Data System (ADS)

    Jerabek, Petr; Abart, Rainer; Rybacki, Erik; Habler, Gerlinde

    2014-05-01

    The study aims to understand the reaction progress and chemical, microstructural and textural evolution of magnesio-aluminate spinel reaction rims formed at varying experimental settings (load, temperature and experiment duration). The spinel rims were grown at the contacts between periclase and corundum at temperatures of 1250°C to 1350°C and dry atmosphere, maintained by a constant argon gas flow, under uniaxial load of 0.026 and 0.26 kN per 9 mm2 of initial contact area. Single crystals of periclase with [100] and of corundum with [0001] perpendicular to the polished reaction interface as well as polycrystalline corundum were used as starting materials. Two loading procedures, immediate application of the load before heating and loading after the desired temperature had been reached, were used. An important byproduct of our experiments stemmed from the immediate application of the load, which led to deformation twinning and fracturing of corundum. This internal deformation of corundum disturbed the reaction interface and introduced loci of concentrated stress due to opening of void spaces in between the reactant crystals. Whenever cracks formed in the initial stages of an experiment, the void space opened immediately and no spinel formed along these interface segments. In the case of deformation twinning, the decreased rim thickness indicates later opening of void spaces. This is because next to twins, the reaction interface is characterized by tight physical contact on the one side and less tight contact on the other side of the twin individual. The tight contacts are characterized by enhanced reaction progress which together with the overall positive volume change of the reaction and limits on plasticity of the studied phases led to the opening of void spaces at places characterized by less tight contacts. The thickness variations are less pronounced in our high load (0.26 kN) experiments where periclase behaves plastically and to some extent reduces the

  6. Determining Magma Mixing Duration Prior to the 1915 Eruption of Lassen Peak, California by Comparing Experimental Growth of Reaction Rims and Natural Olivine Crystals in Black Dacite

    NASA Astrophysics Data System (ADS)

    Graham, N. A.; Schwab, B. E.; Castro, J. M.; Clynne, M. A.

    2015-12-01

    Lassen Peak, located in northern California, last erupted in 1915 producing hybrid black dacite containing xenocrystic olivine grains with morphologically complex reaction rims of orthopyroxene. These rims are interpreted to have grown during magma mixing/mingling of admixed basaltic andesite and dacite reservoir magma prior to eruption. Reaction rim growth rates were determined from a series of hydrothermal experiments performed on starting materials consisting of powdered natural dacite pumice from the 1915 eruption and ~5 wt. % of Fo85 olivine separated from a spinel lherzolite xenolith (UM-5) from Kilbourne Hole, NM to constrain the length of time between magma recharge and eruption. Time series experiments were performed with run durations of 50, 100, 200, 400, and 600 hours at 50 and 100 MPa, 825oC and 875oC. The experiments produced a range in reaction rim growth rates where rim thickness generally increased with time. Average rim growth rate for each series is as follows: 0.031 μm²h-1 for 50 MPa at 825oC, 0.010 μm²h-1 for 50 MPa at 875oC, 0.158 μm²h-1 for 100 MPa at 825oC, and 0.088 μm²h-1 for 100 MPa at 875oC. Overall, the 100 MPa experiments resulted in faster growth rates and thicker reaction rims than the 50 MPa experiments. At a given pressure, the higher temperature (875 oC) experiments show slower average growth rates, but thicker reaction rims than the 825oC equivalents. This suggests that growth rate is not constant over time, but likely is more rapid at the early stages of the experiments/heating event, and then slows over time. Reaction rim widths on 100 olivine grains from samples of black dacite were determined by analysis of SEM BSE images and average 26.1 ± 21.7 μm. This average rim width corresponds to a range of mixing durations of 5.8 months (100 MPa, 825oC) to 93 months (50 MPa, 875oC). Average reaction duration of 10.6 months (at 100 MPa, 875oC) is most consistent with our previous experimental work on the 1915 dacite. Reaction

  7. Extension of the energy range of experimental activation cross-sections data of deuteron induced nuclear reactions on indium up to 50MeV.

    PubMed

    Tárkányi, F; Ditrói, F; Takács, S; Hermanne, A; Ignatyuk, A V

    2015-11-01

    The energy range of our earlier measured activation cross-sections data of longer-lived products of deuteron induced nuclear reactions on indium were extended from 40MeV up to 50MeV. The traditional stacked foil irradiation technique and non-destructive gamma spectrometry were used. No experimental data were found in literature for this higher energy range. Experimental cross-sections for the formation of the radionuclides (113,110)Sn, (116m,115m,114m,113m,111,110g,109)In and (115)Cd are reported in the 37-50MeV energy range, for production of (110)Sn and (110g,109)In these are the first measurements ever. The experimental data were compared with the results of cross section calculations of the ALICE and EMPIRE nuclear model codes and of the TALYS 1.6 nuclear model code as listed in the on-line library TENDL-2014. PMID:26226220

  8. Ultraviolet photoinitiated on-fiber copolymerization of ionic liquid sorbent coatings for headspace and direct immersion solid-phase microextraction.

    PubMed

    Ho, Tien D; Yu, Honglian; Cole, William T S; Anderson, Jared L

    2012-11-01

    A high-throughput method for the production of solid-phase microextraction (SPME) sorbent coatings via ultraviolet (UV) photoinitiated copolymerization of ionic liquid (IL) monomers on a fused silica support is described. The copolymerization of monocationic and dicationic IL cross-linkers was performed "on-fiber" using UV initiated free radical polymerization. Mixtures composed of various amounts of the IL cross-linker, UV initiator (DAROCUR 1173), and IL monomer were dip-coated onto an etched and derivatized fused silica support and placed in a high-capacity UV reactor. The method requires no organic dispersive solvent and is much more rapid compared to traditional methods in which polymeric ionic liquid (PIL) sorbent coatings are prepared by 2,2'-azobis(2-methylpropionitrile) (AIBN)-initiated polymerization. Two ionic liquid-based cross-linkers, namely, 1,8-di (3-vinylimidazolium) octane dibromide ([(VIM)(2)C(8)] 2[Br]) and 1,12-di (3-vinylimidazolium) dodecane dibromide ([(VIM)(2)C(12)] 2[Br]), were copolymerized with an ionic liquid monomer, 1-vinyl-3-hexylimidazolium chloride ([VHIM][Cl]), to produce polar cross-linked PIL-based SPME sorbent coatings. The cross-linking and immobilization of these coatings make them particularly applicable in direct immersion SPME. The coatings were applied in the extraction of polar analytes, including alcohols, aldehydes, and esters, from aqueous solutions using headspace and direct immersion SPME gas chromatography mass spectrometry (GC/MS). Compared to linear PIL-based sorbent coatings containing the same anions, the cross-linked PIL-based coatings exhibited higher thermal stability and lower bleed, making them ideal for GC/MS. Recovery experiments were performed in deionized, well, and river water. The structural integrity of the sorbent coatings, as well as their analytical precision, was not diminished after 90 extractions from complex samples using headspace and direct immersion SPME. PMID:22991947

  9. Computational Investigation of the Photochemical Reaction Path of Some Synthesized and Experimentally Analyzed Small-Chain Conjugated Nitrones.

    PubMed

    Saini, Praveen; Banerjee, Mainak; Chattopadhyay, Anjan

    2016-01-28

    This combined theoretical and experimental study has revealed the photochemistry of two small open-chain conjugated N-methylnitrone systems with phenyl substitutions at the C-terminal positions. The UV spectra of these synthesized nitrones have shown intense peaks around 330 nm while the new bands formed near 260 nm after their photoirradiation are predicted to be arising from the photoproduct oxaziridine. Photoexcitation of α-styryl N-methylnitrone populates the first excited singlet state which relaxes by 8 kcal/mol from the vertically excited state and subsequently goes toward the lowest-energy conical intersection (CI) geometry (situated 27-30 kcal/mol below) with a terminal CNO-kink. Following the gradient difference vectors of this CI, we have located the oxaziridine structure with its characteristic geometry at roughly 14 kcal/mol above the ground state. This whole process is triggered by a transfer of electronic cloud from oxygen to the conjugated chain side. On the other hand, the photoexcitation of the nonplanar 3,3-diphenylethylene N-methylnitrone has two strong singlet-singlet absorptions with almost 5 D transition moment values. Here the initial S2-S1 relaxation is followed by oxaziridine formation through the terminally twisted CI. However, the initially photoexcited S1 state in this nitrone is found to head toward some other direction with transfer of huge amount of nonbonding electron cloud of oxygen to the π* orbital, creating a stable excited state geometry with an elongated N-O bond which gets involved in a sloped CI with the ground state. PMID:26697926

  10. Ring-opening copolymerization of maleic anhydride with epoxides: a chain-growth approach to unsaturated polyesters.

    PubMed

    DiCiccio, Angela M; Coates, Geoffrey W

    2011-07-20

    We report the ring-opening copolymerization of maleic anhydride with a variety of epoxides catalyzed by a chromium(III) salen complex. Quantitative isomerization of the cis-maleate form of all polymers affords the trans-fumarate analogues. Addition of chain transfer reagents yields low M(n), narrow PDI polymer samples. This method provides access to a range of new unsaturated polyesters with versatile functionality, as well as the first synthesis of high molecular weight poly(propylene fumarate). PMID:21699247

  11. Uranyl ion uptake capacity of poly (N-isopropylacrylamide/maleic acid) copolymeric hydrogels prepared by gamma rays

    NASA Astrophysics Data System (ADS)

    Kam, Erol; Taşdelen, Betul; Osmanlioglu, A. Erdal

    2012-06-01

    The effect of gel composition, absorbed dose and pH of the solution on the uranyl ion uptake capacity of N-isopropylacrylamide/maleic acid copolymeric hydrogels containing 0-3 mol% of maleic acid at 48 kGy have been investigated. Uranyl uptake capacity of hydrogels are found to increase from 18.5 to 94.8 mg [UO22+]/g dry gel as the mole % of maleic acid content in the gel structure increased from 0 to 3. The percent swelling, equilibrium swelling and diffusion coefficient values have been evaluated for poly(N-isopropylacrylamide/maleic acid) hydrogels at 500 ppm of uranyl nitrate solution.

  12. Factors That Control the Reactivity of Cobalt(III)-Nitrosyl Complexes in Nitric Oxide Transfer and Dioxygenation Reactions: A Combined Experimental and Theoretical Investigation.

    PubMed

    Kumar, Pankaj; Lee, Yong-Min; Hu, Lianrui; Chen, Jianwei; Park, Young Jun; Yao, Jiannian; Chen, Hui; Karlin, Kenneth D; Nam, Wonwoo

    2016-06-22

    Metal-nitrosyl complexes are key intermediates involved in many biological and physiological processes of nitric oxide (NO) activation by metalloproteins. In this study, we report the reactivities of mononuclear cobalt(III)-nitrosyl complexes bearing N-tetramethylated cyclam (TMC) ligands, [(14-TMC)Co(III)(NO)](2+) and [(12-TMC)Co(III)(NO)](2+), in NO-transfer and dioxygenation reactions. The Co(III)-nitrosyl complex bearing 14-TMC ligand, [(14-TMC)Co(III)(NO)](2+), transfers the bound nitrosyl ligand to [(12-TMC)Co(II)](2+) via a dissociative pathway, {[(14-TMC)Co(III)(NO)](2+) → {(14-TMC)Co···NO}(2+)}, thus affording [(12-TMC)Co(III)(NO)](2+) and [(14-TMC)Co(II)](2+) as products. The dissociation of NO from the [(14-TMC)Co(III)(NO)](2+) complex prior to NO-transfer is supported experimentally and theoretically. In contrast, the reverse reaction, which is the NO-transfer from [(12-TMC)Co(III)(NO)](2+) to [(14-TMC)Co(II)](2+), does not occur. In addition to the NO-transfer reaction, dioxygenation of [(14-TMC)Co(III)(NO)](2+) by O2 produces [(14-TMC)Co(II)(NO3)](+), which possesses an O,O-chelated nitrato ligand and where, based on an experiment using (18)O-labeled O2, two of the three O-atoms in the [(14-TMC)Co(II)(NO3)](+) product derive from O2. The dioxygenation reaction is proposed to occur via a dissociative pathway, as proposed in the NO-transfer reaction, and via the formation of a Co(II)-peroxynitrite intermediate, based on the observation of phenol ring nitration. In contrast, [(12-TMC)Co(III)(NO)](2+) does not react with O2. Thus, the present results demonstrate unambiguously that the NO-transfer/dioxygenation reactivity of the cobalt(III)-nitrosyl complexes bearing TMC ligands is significantly influenced by the ring size of the TMC ligands and/or the spin state of the cobalt ion. PMID:27221953

  13. Main-Chain and Side-Chain Sequence-Regulated Vinyl Copolymers by Iterative Atom Transfer Radical Additions and 1:1 or 2:1 Alternating Radical Copolymerization.

    PubMed

    Soejima, Takamasa; Satoh, Kotaro; Kamigaito, Masami

    2016-01-27

    Main- and side-chain sequence-regulated vinyl copolymers were prepared by a combination of iterative atom transfer radical additions (ATRAs) of vinyl monomers for side-chain control and 1:1 or 2:1 alternating radical copolymerization of the obtained side-chain sequenced "oligomonomers" and vinyl comonomers for main-chain control. A complete set of sequence-regulated trimeric vinyl oligomers of styrene (S) and/or methyl acrylate (A) were first synthesized via iterative ATRAs of these monomers to a halide of monomeric S or A unit (X-S or X-A) under optimized conditions with appropriate ruthenium or copper catalysts, which were selected depending on the monomers and halides. The obtained halogen-capped oligomers were then converted into a series of maleimide (M)-ended oligomonomers with different monomer compositions and sequences (M-SSS, M-ASS, M-SAS, M-AAS, M-SSA, M-ASA, M-SAA, M-AAA) by a substitution reaction of the halide with furan-protected maleimide anion followed by deprotection of the furan units. These maleimide-ended oligomonomers were then radically copolymerized with styrene or limonene to enable the 1:1 or 2:1 monomer-sequence regulation in the main chain and finally result in the main- and side-chain sequence-regulated vinyl copolymers with high molecular weights in high yield. The properties of the sequence-regulated vinyl copolymers depended on not only the monomer compositions but also the monomer sequences. The solubility was highly affected by the outer monomer units in the side chains whereas the glass transition temperatures were primarily affected by the two successive monomer sequences. PMID:26761148

  14. Experimental validation of numerical study on thermoelectric-based heating in an integrated centrifugal microfluidic platform for polymerase chain reaction amplification.

    PubMed

    Amasia, Mary; Kang, Seok-Won; Banerjee, Debjyoti; Madou, Marc

    2013-01-01

    A comprehensive study involving numerical analysis and experimental validation of temperature transients within a microchamber was performed for thermocycling operation in an integrated centrifugal microfluidic platform for polymerase chain reaction (PCR) amplification. Controlled heating and cooling of biological samples are essential processes in many sample preparation and detection steps for micro-total analysis systems. Specifically, the PCR process relies on highly controllable and uniform heating of nucleic acid samples for successful and efficient amplification. In these miniaturized systems, the heating process is often performed more rapidly, making the temperature control more difficult, and adding complexity to the integrated hardware system. To gain further insight into the complex temperature profiles within the PCR microchamber, numerical simulations using computational fluid dynamics and computational heat transfer were performed. The designed integrated centrifugal microfluidics platform utilizes thermoelectrics for ice-valving and thermocycling for PCR amplification. Embedded micro-thermocouples were used to record the static and dynamic thermal responses in the experiments. The data collected was subsequently used for computational validation of the numerical predictions for the system response during thermocycling, and these simulations were found to be in agreement with the experimental data to within ∼97%. When thermal contact resistance values were incorporated in the simulations, the numerical predictions were found to be in agreement with the experimental data to within ∼99.9%. This in-depth numerical modeling and experimental validation of a complex single-sided heating platform provide insights into hardware and system design for multi-layered polymer microfluidic systems. In addition, the biological capability along with the practical feasibility of the integrated system is demonstrated by successfully performing PCR amplification of

  15. Experimental validation of numerical study on thermoelectric-based heating in an integrated centrifugal microfluidic platform for polymerase chain reaction amplification

    PubMed Central

    Amasia, Mary; Kang, Seok-Won; Banerjee, Debjyoti; Madou, Marc

    2013-01-01

    A comprehensive study involving numerical analysis and experimental validation of temperature transients within a microchamber was performed for thermocycling operation in an integrated centrifugal microfluidic platform for polymerase chain reaction (PCR) amplification. Controlled heating and cooling of biological samples are essential processes in many sample preparation and detection steps for micro-total analysis systems. Specifically, the PCR process relies on highly controllable and uniform heating of nucleic acid samples for successful and efficient amplification. In these miniaturized systems, the heating process is often performed more rapidly, making the temperature control more difficult, and adding complexity to the integrated hardware system. To gain further insight into the complex temperature profiles within the PCR microchamber, numerical simulations using computational fluid dynamics and computational heat transfer were performed. The designed integrated centrifugal microfluidics platform utilizes thermoelectrics for ice-valving and thermocycling for PCR amplification. Embedded micro-thermocouples were used to record the static and dynamic thermal responses in the experiments. The data collected was subsequently used for computational validation of the numerical predictions for the system response during thermocycling, and these simulations were found to be in agreement with the experimental data to within ∼97%. When thermal contact resistance values were incorporated in the simulations, the numerical predictions were found to be in agreement with the experimental data to within ∼99.9%. This in-depth numerical modeling and experimental validation of a complex single-sided heating platform provide insights into hardware and system design for multi-layered polymer microfluidic systems. In addition, the biological capability along with the practical feasibility of the integrated system is demonstrated by successfully performing PCR amplification of

  16. Synergistic effect on corrosion resistance of Phynox substrates grafted with surface-initiated ATRP (co)polymerization of 2-methacryloyloxyethyl phosphorylcholine (MPC) and 2-hydroxyethyl methacrylate (HEMA).

    PubMed

    Barthélémy, Bastien; Maheux, Simon; Devillers, Sébastien; Kanoufi, Frédéric; Combellas, Catherine; Delhalle, Joseph; Mekhalif, Zineb

    2014-07-01

    Phynox is of high interest for biomedical applications due to its biocompatibility and corrosion resistance. However, some Phynox applications require specific surface properties. These can be imparted with suitable surface functionalizations of its oxide layer. The present work investigates the surface-initiated atom transfer radical polymerization (ATRP) of 2-methacryloyoxyethyl phosphorylcholine (MPC), 2-hydroxyethyl methacrylate (HEMA), and ATRP copolymerization of (HEMA-co-MPC) (block and statistic copolymerization with different molar ratios) on grafted Phynox substrates modified with 11-(2-bromoisobutyrate)-undecyl-1-phosphonic acid (BUPA) as initiator. It is found that ATRP (co)polymerization of these monomers is feasible and forms hydrophilic layers, while improving the corrosion resistance of the system. PMID:24915233

  17. First accurate experimental study of Mu reactivity from a state-selected reactant in the gas phase: the Mu + H2{1} reaction rate at 300 K

    NASA Astrophysics Data System (ADS)

    Bakule, Pavel; Sukhorukov, Oleksandr; Ishida, Katsuhiko; Pratt, Francis; Fleming, Donald; Momose, Takamasa; Matsuda, Yasuyuki; Torikai, Eiko

    2015-02-01

    This paper reports on the experimental background and methodology leading to recent results on the first accurate measurement of the reaction rate of the muonium (Mu) atom from a state-selected reactant in the gas phase: the Mu + H2\\{1\\}\\to MuH + H reaction at 300 K, and its comparison with rigorous quantum rate theory, Bakule et al (2012 J. Phys. Chem. Lett. 3 2755). Stimulated Raman pumping, induced by 532 nm light from the 2nd harmonic of a Nd:YAG laser, was used to produce H2 in its first vibrational (v = 1) state, H2\\{1\\}, in a single Raman/reaction cell. A pulsed muon beam (from ‘ISIS’, at 50 Hz) matched the 25 Hz repetition rate of the laser, allowing data taking in equal ‘Laser-On/Laser-Off’ modes of operation. The signal to noise was improved by over an order of magnitude in comparison with an earlier proof-of-principle experiment. The success of the present experiment also relied on optimizing the overlap of the laser profile with the extended stopping distribution of the muon beam at 50 bar H2 pressure, in which Monte Carlo simulations played a central role. The rate constant, found from the analysis of three separate measurements, which includes a correction for the loss of {{H}2}\\{1\\} concentration due to collisional relaxation with unpumped H2 during the time of each measurement, is {{k}Mu}\\{1\\} = 9.9[(-1.4)(+1.7)] × 10-13 cm3 s-1 at 300 K. This is in good to excellent agreement with rigorous quantum rate calculations on the complete configuration interaction/Born-Huang surface, as reported earlier by Bakule et al, and which are also briefly commented on herein.

  18. The reaction of N{sub 2}O with phenylium ions C{sub 6}(H,D){sub 5}{sup +}: An integrated experimental and theoretical mechanistic study

    SciTech Connect

    Giordana, Anna; Ghigo, Giovanni; Tonachini, Glauco; Ascenzi, Daniela; Tosi, Paolo; Guella, Graziano

    2009-07-14

    The reaction of N{sub 2}O (known to be an O atom donor under several conditions) with the phenyl cation is studied by experimental and theoretical methods. Phenyl cation (or phenylium), C{sub 6}H{sub 5}{sup +}, and its perdeuterated derivative C{sub 6}D{sub 5}{sup +} are produced either by electron impact or by atmospheric pressure chemical ionization of adequate neutral precursors, and product mass spectra are measured in a guided ion beam tandem mass spectrometer. The ions C{sub 5}(H,D){sub 5}{sup +}, C{sub 6}(H,D){sub 5}O{sup +}, and C{sub 3}(H,D){sub 3}{sup +} are experimentally detected as the most relevant reaction products. In addition, the detection of the adduct (C{sub 6}H{sub 5}{center_dot}N{sub 2}O){sup +}, which is collisionally stabilized in the scattering cell of the mass spectrometer, is reported here for the first time. The reaction pathways, which could bring about the formation of the mentioned ions, are then explored extensively by density functional theory and, for the more promising pathways, by CASPT2/CASSCF calculations. The two reacting species (1) form initially a phenoxydiazonium adduct, C{sub 6}H{sub 5}ON{sub 2}{sup +} (2a), by involving the empty in-plane hybrid C orbital of phenylium. The alternative attack to the ring {pi} system to produce an epoxidic adduct 2c is ruled out on the basis of the energetics. Then, 2a loses N{sub 2} quite easily, thus affording the phenoxyl cation 3. This is only the first of several C{sub 6}H{sub 5}O{sup +} isomers (4-6 and 8-12), which can stem from 3 upon different cleavages and formations of C-C bond and/or H shifts. As regards the formation of C{sub 5}H{sub 5}{sup +}, among several conceivable pathways, a direct CO extrusion from 3 is discarded, while others appear to be viable to different extents, depending on the initial energy of the system. The easiest CO loss is from 4, with formation of the cyclopentadienyl cation 7. Formation of C{sub 3}H{sub 3}{sup +} is generally hindered and its detection

  19. Purification of polar compounds from Radix isatidis using conventional C18 column coupled with polar-copolymerized C18 column.

    PubMed

    Zeng, Jing; Guo, Zhimou; Xiao, Yuansheng; Wang, Chaoran; Zhang, Xiuli; Liang, Xinmiao

    2010-11-01

    Regarding hydrophilic interaction chromatography and normal phase liquid chromatography, RPLC is another choice used to separate polar compounds with the improvement of polar-modified C18 stationary phase. In this study, a method using conventional C18 column coupled with polar-copolymerized C18 column was successfully developed for the separation and purification of polar compounds from Radix isatidis, which is one of the most commonly used traditional Chinese medicines (TCMs). An XTerra MS C18 column was used to fractionate the extract of R. isatidis and a homemade polar-copolymerized C18 column was utilized for the final purification due to its good separation selectivity and high resolution for polar compounds. The established purification system demonstrated good orthogonality for the polar compounds. As a result, ten compounds were purified and three of them were identified as 3-methyl-5-vinyloxazolidin-2-one (compound A), 5-hydroxymethyl-2-furaldehyde (compound B) and 3-methylfuran-2-carboxylic acid (compound G) based on the MS, IR and extensive NMR data, respectively. It was demonstrated to be a feasible and powerful technique for the purification of polar compounds under RPLC mode and more chemical information of TCMs will be obtained to interpret the efficiency of TCMs. PMID:20886519

  20. Experimental and theoretical study of the ion-ion mutual neutralization reactions Ar(+)+SF(n)- (n=6, 5, and 4).

    PubMed

    Bopp, Joseph C; Miller, Thomas M; Viggiano, Albert A; Troe, Jürgen

    2008-08-21

    The ion-ion mutual neutralization reactions Ar(+)+SF(n) (-)-->Ar+SF(n) (n=6, 5, and 4) have been studied in a flowing afterglow-Langmuir probe (FALP) apparatus at 300 K and 1 Torr of He buffer gas. Electron concentrations and product ion fractions were measured, and neutralization rate constants of 4.0 x 10(-8), 3.8 x 10(-8), and 4 x 10(-8) cm(3) s(-1) for SF(6) (-), SF(5) (-), and SF(4) (-), respectively, were derived, with uncertainties of +/-25% (+/-35% for SF(4) (-)). During the neutralization process, excited neutrals are generated that are able to dissociate to neutral fragments. In the case of SF(6), the formation of SF(5) and SF(4), and similarly in the case of SF(5), the formation of SF(4) and SF(3) were observed and quantified. The mechanism of primary and secondary reaction was analyzed in detail, and rate constants for the dissociative electron attachments e(-)+SF(5)-->F(-)+SF(4) (k=3 x 10(-9) cm(3) s(-1),+/-40%) and e(-)+SF(3)-->F(-)+SF(2) (k=2 x 10(-8) cm(3) s(-1),+400%,-75%) were also derived. The experimental ion-ion neutralization rate constants were found to be in good agreement with estimates from an optimum two-state double-passage Landau-Zener model. It was also found that energy partitioning in the neutralization is related to the extent of electronic excitation of Ar generated by the electron transfer processes. PMID:19044768

  1. Reaction Progress of Olivine Alteration as a Function of Time and CO2 Supply at 150°C - An Experimental Study

    NASA Astrophysics Data System (ADS)

    Prikryl, J.; Stefansson, A.

    2014-12-01

    Increased anthropogenic CO2 emissions have caused an imbalance in the Earth's carbon cycle causing climate changes. Interaction of CO2 with water and rock plays important role in geochemical cycle of carbon and among potential ways of reducing atmospheric CO2 by sequestration into carbonates. Olivine, among the main constituents of mafic and ultramafic rocks, is rich in Mg and Fe that can react with CO2 to form Mg-Fe carbonates like siderite and magnesite. Laboratory experiments were performed in batch-type titanium reactors to study the interaction between CO2-rich water and olivine under hydrothermal conditions. The experimental were conducted at 150°C, for 1 to 4 weeks, the CO2 concentration was 5 to 30 mmol/kg and the initial pH was around neutral. The olivine used was forsterite 93% from Åheim Olivine Pit-Norway. The alteration products and fluid chemistry were monitored as a function of time. Moreover, the results were supported with reaction path modeling to further constrain the olivine alteration and carbonate mineral formation mechanism. Initially forsterite dissolved releasing elements into solution. During this stage limited alteration products were formed and the solution pH was buffered by H+ uptake by olivine dissolution and CO2 concentration. Upon further reactions secondary phases started to form including chrysotile, brusite and mainly solid solution of iron-containing magnesite. This resulted in decrease of CO2 concentrations and eventually increased solution pH. Experiments with higher initial CO2 concentrations required longer period until CO2was consumed. Furthermore experiments with longer duration had quantitatively larger amount of precipitated minerals. Findings of this research represent platform for kinetic numerical simulations of olivine alteration and therefore provide insight into carbon storage in mafic rocks under in-situ conditions.

  2. Experimental and theoretical study of the ion-ion mutual neutralization reactions Ar{sup +}+SF{sub n}{sup -} (n=6, 5, and 4)

    SciTech Connect

    Bopp, Joseph C.; Miller, Thomas M.; Viggiano, Albert A.; Troe, Juergen

    2008-08-21

    The ion-ion mutual neutralization reactions Ar{sup +}+SF{sub n}{sup -}{yields}Ar+SF{sub n} (n=6, 5, and 4) have been studied in a flowing afterglow-Langmuir probe (FALP) apparatus at 300 K and 1 Torr of He buffer gas. Electron concentrations and product ion fractions were measured, and neutralization rate constants of 4.0x10{sup -8}, 3.8x10{sup -8}, and 4x10{sup -8} cm{sup 3} s{sup -1} for SF{sub 6}{sup -}, SF{sub 5}{sup -}, and SF{sub 4}{sup -}, respectively, were derived, with uncertainties of {+-}25% ({+-}35% for SF{sub 4}{sup -}). During the neutralization process, excited neutrals are generated that are able to dissociate to neutral fragments. In the case of SF{sub 6}, the formation of SF{sub 5} and SF{sub 4}, and similarly in the case of SF{sub 5}, the formation of SF{sub 4} and SF{sub 3} were observed and quantified. The mechanism of primary and secondary reaction was analyzed in detail, and rate constants for the dissociative electron attachments e{sup -}+SF{sub 5}{yields}F{sup -}+SF{sub 4} (k=3x10{sup -9} cm{sup 3} s{sup -1},{+-}40%) and e{sup -}+SF{sub 3}{yields}F{sup -}+SF{sub 2} (k=2x10{sup -8} cm{sup 3} s{sup -1},+400%,-75%) were also derived. The experimental ion-ion neutralization rate constants were found to be in good agreement with estimates from an optimum two-state double-passage Landau-Zener model. It was also found that energy partitioning in the neutralization is related to the extent of electronic excitation of Ar generated by the electron transfer processes.

  3. Olivine-gabbros and olivine-rich troctolites genesis through melt-rock reactions in oceanic spreading lithosphere: an experimental study up to 0.7 GPa

    NASA Astrophysics Data System (ADS)

    Francomme, Justine E.; Fumagalli, Patrizia; Borghini, Giulio

    2016-04-01

    Extensive melt-rock reaction and melt impregnation significantly affect not only the physical and chemical properties at mantle-crust transition, but also control the evolution of migrating melts. We performed reactive dissolution and crystallization experiments at pressure ≤ 0.7 GPa in a piston-cylinder apparatus to provide experimental constraints on genesis of olivine-rich troctolites and olivine-gabbros at mantle-crust transition in oceanic spreading lithosphere by melt-rock reaction. Our experiments are carried out by using Salt-Pyrex-Graphite-Magnesium assemblies and graphite-lined platinum capsules. Experimental charges are prepared with three layers: (1) basalt powder, (2) fine powder (1-10μm) of San Carlos olivine (Fo90.1), and (3) carbon spheres used as a melt trap. Three synthetic MORB-type melts have been used, two tholeiitic basalts (Mg#: 0.62, SiO2: 47.70 wt%, Na2O: 2.28 wt% and Mg#: 0.58, SiO2: 49.25 wt%, Na2O: 2.49 wt%) and a primitive one (Mg#: 0.74, SiO2: 48.25 wt%, Na2O: 1.80 wt%), in order to investigate the effect of melt composition. A rock/melt ratio of 0.7 has been kept fixed. Experiments have been conducted at temperatures from 1200 to 1300°C, at both step cooling and isothermal conditions for different run durations (from 12 to 72 hrs). They resulted in layered samples in which all the initial San Carlos olivine powder, analog of a dunitic pluton infiltrated by basaltic melt, is replaced by different lithologies from olivine-rich troctolite to olivine gabbro. In isothermal experiments, reacted melts have been successfully trapped in the carbon spheres allowing their chemical analysis; as expected the reacted melt has a higher Mg# than the initial one (e.g. from Mg#=0.62 to 0.73). Across the different lithologies Mg# of olivine is decreasing from the olivine-rich troctolite to the gabbro. Replacive olivine-rich troctolite has a poikilitic texture with rounded euhedral olivine and interstitial poikilitic plagioclase and clinopyroxene

  4. First Experimental Constraints on the Interference of 3/2+ Resonances in the 18F(p, ?)15O Reaction

    SciTech Connect

    Chae, Kyung Yuk; Bardayan, Daniel W; Blackmon, Jeff C; Gregory, Darren R; Guidry, Mike W; Johnson, Micah; KOZUB, RAYMOND L; Livesay, Jake; Ma, Zhanwen; Nesaraja, Caroline D; Pain, Steven D; Paulauskas, Stanley V; Porter-Peden, Matthew D; Shriner, Jr., John F; Smith, Nathan A; Smith, Michael Scott; Thomas, Jeffrey S

    2006-06-01

    The interference effects among J{sup {pi}}=3/2+ resonances in the {sup 18}F+p system have not been previously measured. R-matrix calculations show that the cross sections above the E{sub c.m.}=665 keV resonance are sensitive to the interference between the E{sub c.m.}=8, 38, and 665 keV resonances. An excitation function for the {sup 1}H({sup 18}F,{alpha}){sup 15}O reaction has been measured in the energy range of E{sub c.m.}=663-877 keV using radioactive 18F beams at the Holifield Radioactive Ion Beam Facility (HRIBF). By comparing the observed cross sections with the R-matrix calculations, we provide the first experimental constraints on the interference. Upper limits on proton widths ({Gamma}{sub p}) of the E{sub c.m.}=827 and 842 keV resonances have been set as well.

  5. Mechanism of reaction in NaAlCl4 molten salt batteries with nickel felt cathodes and aluminum anodes. 2: Experimental results and comparison with model calculations

    NASA Astrophysics Data System (ADS)

    Knutz, B. C.; Berg, R. W.; Hjuler, H. A.; Bjerrum, N. J.

    1993-12-01

    The battery systems: Al/NaCl-AlCl3-Al2 X3/Ni-felt (X = S, Se, Te) and the corresponding system without chalcogen have been studied experimentally at 175 C. Charge/discharge experiments, performed on cells with NaCl saturated melts, show that advantages with regard to rate capability and cyclability can be obtained with systems containing dissolved chalcogen compared with the chalcogen-free system. Exchange of chalcogen between cathode and electrolyte during cycling was confirmed by performing gravimetric analysis and Raman spectroscopy of the electrolytes. Cathode reactions were studied by coulometric titrations (performed on cells with slightly acidic NaCl-AlCl3 melts and small amounts of chalcogen) and compared with model calculations. Cells containing chalcogen revealed at least three voltage plateaus during cycling. The lowest plateau is associated with formation/decomposition of essentially Ni(y)S(z) an d Ni(y)Se(z) in the sulfide and selenide system, respectively. Cells containing selenide revealed extra capacity below the Ni(y) Se(z)-plateau, most probably associated with a Al(v)Ni(y)Se(z) compound. On the second plateau of sulfide systems NiCl2 or a Ni(y)S(z) Cl(2y - 2z) compound with y greater than (4.4 +/- 0.2), z is formed during charging. Reduction of the formed compound to Ni takes place via consumption of sodium chloride.

  6. Reactions of titanocene bis(trimethylsilyl)acetylene complexes with carbodiimides: an experimental and theoretical study of complexation versus C-N bond activation.

    PubMed

    Haehnel, Martin; Ruhmann, Martin; Theilmann, Oliver; Roy, Subhendu; Beweries, Torsten; Arndt, Perdita; Spannenberg, Anke; Villinger, Alexander; Jemmis, Eluvathingal D; Schulz, Axel; Rosenthal, Uwe

    2012-09-26

    The reaction of the low valent metallocene(II) sources Cp'(2)Ti(η(2)-Me(3)SiC(2)SiMe(3)) (Cp' = η(5)-cyclopentadienyl, 1a or η(5)-pentamethylcyclopentadienyl, 1b) with different carbodiimide substrates RN═C═NR' 2-R-R' (R = t-Bu; R' = Et; R = R' = i-Pr; t-Bu; SiMe(3); 2,4,6-Me-C(6)H(2) and 2,6-i-Pr-C(6)H(3)) was investigated to explore the frontiers of ring strained, unusual four-membered heterometallacycles 5-R. The product complexes show dismantlement, isomerization, or C-C coupling of the applied carbodiimide substrates, respectively, to form unusual mono-, di-, and tetranuclear titanium(III) complexes. A detailed theoretical study revealed that the formation of the unusual complexes can be attributed to the biradicaloid nature of the unusual four-membered heterometallacycles 5-R, which presents an intriguing situation of M-C bonding. The combined experimental and theoretical study highlights the delicate interplay of electronic and steric effects in the stabilization of strained four-membered heterometallacycles, accounting for the isolation of the obtained complexes. PMID:22891968

  7. Orthogonal gradient networks via post polymerization reaction

    NASA Astrophysics Data System (ADS)

    Chinnayan Kannan, Pandiyarajan; Genzer, Jan

    2015-03-01

    We report a novel synthetic route to generate orthogonal gradient networks through post polymerization reaction using pentaflurophenylmethacrylate (PFPMAc) active ester chemistry. These chemoselective monomers were successfully copolymerized with 5 mole% of the photo (methacryloyloxybenzophenone) and thermal (styrenesulfonylazide) crosslinkers. Subsequently, the copolymers were modified by a series of amines having various alkyl chain lengths. The conversion of post polymerization reaction was monitored using Fourier Transform Infrared Spectroscopy (FT-IR) and noticed that almost all pentaflurophenyl moieties are substituted by amines within in an hour without affecting the crosslinkers. In addition, the incorporation of photo and thermal crosslinkers in the polymer enabled us to achieve stable and covalently surface-bound polymer gradient networks (PGN) in an orthogonal manner, i.e. complete control over the crosslink density of the network in two opposite directions (i.e. heat vs photo). The network properties such as wettability, swelling and tensile modulus of the gradient coatings are studied and revealed in the paper.

  8. Synthesis of nano-sized stereoselective imprinted polymer by copolymerization of (S)-2-(acrylamido) propanoic acid and ethylene glycol dimethacrylate in the presence of racemic propranolol and copper ion.

    PubMed

    Alizadeh, Taher; Bagherzadeh, Azam; Shamkhali, Amir Nasser

    2016-06-01

    A new chiral functional monomer of (S)-2-(acrylamido) propanoic acid was obtained by reaction of (l)-alanine with acryloyl chloride. The resulting monomer was characterized by FT-IR and HNMR and then utilized for the preparation of chiral imprinted polymer (CIP). This was carried out by copolymerization of (l)-alanine-derived chiral monomer and ethylene glycol dimethacrylate, in the presence of racemic propranolol and copper nitrate, via precipitation polymerization technique, resulting in nano-sized networked polymer particles. The polymer obtained was characterized by scanning electron microscopy and FT-IR. The non-imprinted polymer was also synthesized and used as blank polymer. Density functional theory (DFT) was also employed to optimize the structures of two diasterometric ternary complexes, suspected to be created in the pre-polymerization step, by reaction of optically active isomers of propranolol, copper ion and (S)-2-(acrylamido) propanoic acid. Relative energies and other characteristics of the described complexes, calculated by the DFT, predicted the higher stability of (S)-propranolol involved complex, compared to (R)-propranolol participated complex. Practical batch extraction test which employed CIP as solid phase adsorbent, indicated that the CIP recognized selectively (S)-propranolol in the racemic mixture of propranolol; whereas, the non-imprinted polymer (NIP) showed no differentiation capability between two optically active isomers of propranolol. PMID:27040217

  9. Cytoskeleton mimetic reinforcement of a self-assembled N,N'-dialkylimidazolium ionic liquid monomer by copolymerization.

    SciTech Connect

    Grubjesic, S.; Seifert, S.; Firestone, M. A.; Materials Science Division

    2009-08-11

    Preparation and photopolymerization of a decylmethylimidazolium ionic liquid (IL) that possesses an acrylate counteranion are described. This IL monomer self-assembles upon addition of water and can be copolymerized with poly(ethylene glycol) diacrylate (PEGDA) in the presence of a photoinitiator, forming a mechanically durable material that adopts a lamellar structure with in-plane hexagonally ordered pores, as evidenced by small-angle X-ray scattering (SAXS). Thermogravimetric analysis, the extent of polymerization, and solubility-swelling studies indicate the formation of a network copolymer of the IL monomer and the PEGDA. Additional evidence for the formation of a nanostructured copolymer is provided by evaluating the product formed by replacement of the IL monomer with the nonpolymerizable analogue, decylmethylimidazolium chloride. The results demonstrate the possibility of designing a self-assembled amiphiphilic bilayer architecture that is reinforced by polymerization and cross-linking.

  10. Kinetics of radiation-induced graft copolymerization of vinyl acetate onto ethylene-co-propylene rubber membranes

    NASA Astrophysics Data System (ADS)

    Yue-E, Fang; Lu Xiao Bing; Wang Shan Zhi; Xia, Zhao; Wang, Fang

    1997-02-01

    The kinetics of radiation-induced graft copolymerization of vinyl acetate onto ethylene-co-propylene rubber (EPR) membrane has been studied in methanol with a radiation source of cobalt-60. The effect of monomer concentration, dose rate, Cu 2+ concentration and temperature on the grafting rate were investigated. The results show that the functional relationship is dg 0/ dt = k[M] 01.95Ḋ[ Cu2+] 0.5. The apparent activation energy and collision frequency factor of the grafting polymerization are 49 kJ mol -1 and 8.9 × 10 8G% kGy -1h -1mol -2.45L 2.45, respectively. The work established the relationship of the initial grafting rate (d g0/d t) with various effect factors: ln(d g0/d t) = 20.61 - 5894(1/ T) + 1.95 ln[ M] 0 + ln D + 0.5 ln[Cu 2+].

  11. The reactions of N-methylformamide and N,N-dimethylformamide with OH and their photo-oxidation under atmospheric conditions: experimental and theoretical studies.

    PubMed

    Bunkan, Arne Joakim C; Hetzler, Jens; Mikoviny, Tomáš; Wisthaler, Armin; Nielsen, Claus J; Olzmann, Matthias

    2015-03-14

    The reactions of OH radicals with CH3NHCHO (N-methylformamide, MF) and (CH3)2NCHO (N,N-dimethylformamide, DMF) have been studied by experimental and computational methods. Rate coefficients were determined as a function of temperature (T = 260-295 K) and pressure (P = 30-600 mbar) by the flash photolysis/laser-induced fluorescence technique. OH radicals were produced by laser flash photolysis of 2,4-pentanedione or tert-butyl hydroperoxide under pseudo-first order conditions in an excess of the corresponding amide. The rate coefficients obtained show negative temperature dependences that can be parameterized as follows: kOH+MF = (1.3 ± 0.4) × 10(-12) exp(3.7 kJ mol(-1)/(RT)) cm(3) s(-1) and kOH+DMF = (5.5 ± 1.7) × 10(-13) exp(6.6 kJ mol(-1)/(RT)) cm(3) s(-1). The rate coefficient kOH+MF shows very weak positive pressure dependence whereas kOH+DMF was found to be independent of pressure. The Arrhenius equations given, within their uncertainty, are valid for the entire pressure range of our experiments. Furthermore, MF and DMF smog-chamber photo-oxidation experiments were monitored by proton-transfer-reaction time-of-flight mass spectrometry. Atmospheric MF photo-oxidation results in 65% CH3NCO (methylisocyanate), 16% (CHO)2NH, and NOx-dependent amounts of CH2[double bond, length as m-dash]NH and CH3NHNO2 as primary products, while DMF photo-oxidation results in around 35% CH3N(CHO)2 as primary product and 65% meta-stable (CH3)2NC(O)OONO2 degrading to NOx-dependent amounts of CH3N[double bond, length as m-dash]CH2 (N-methylmethanimine), (CH3)2NNO (N-nitroso dimethylamine) and (CH3)2NNO2 (N-nitro dimethylamine). The potential for nitramine formation in MF photo-oxidation is comparable to that of methylamine whereas the potential to form nitrosamine and nitramine in DMF photo-oxidation is larger than for dimethylamine. Quantum chemistry supported atmospheric degradation mechanisms for MF and DMF are presented. Rate coefficients and initial branching ratios

  12. Advanced Aromatic Polymers with Excellent Antiatomic Oxygen Performance Derived from Molecular Precursor Strategy and Copolymerization of Polyhedral Oligomeric Silsesquioxane.

    PubMed

    Wang, Pei; Tang, Yusheng; Yu, Zhen; Gu, Junwei; Kong, Jie

    2015-09-16

    In this contribution, the advanced aromatic polymers with excellent antiatomic oxygen (AO) performance were designed and synthesized using molecular precursor strategy and copolymerization of polyhedral oligomeric silsesquioxane (POSS). A soluble poly(p-phenylene benzobisoxazole) (PBO) precursor, that is, TBS-PBO (tert-butyldimethylsilyl was denoted as TBS), was designed to overcome the poor solubility of PBO in organic solvents. Then the new copolymer of TBS-PBO-POSS was synthesized by the copolymerization of TBS-PBO and POSS, which possessed good solubility and film-forming ability in common organic solvents, such as N-methylpyrrolidone, N,N-dimethylacetamide, and dimethyl sulfoxide. More importantly, the TBS-PBO-POSS films exhibited outstanding antiatomic oxygen properties because of the incorporation of POSS monomers with cagelike structure into the main chain of copolymer, which drastically reduced the AO-induced erosion owing to the formation of the passivating silica layer on the surface of polymers. When the TBS-PBO-POSS films were exposed to AO effective fluences of 1.5495×10(20) atom cm(-2) (5 h) and 4.6486×10(20) atom cm(-2) (15 h), the relative mass loss was merely 0.19% and 0.41%, respectively. This work provides a new perspective and efficient strategy for the molecular design of aromatic heterocyclic polymers possessing excellent combination properties including processing convenience and antioxidative and mechanical properties, which can be employed as potential candidates to endure the aggressive environment encountered in low earth orbits. PMID:26322523

  13. A combined experimental and DFT study of active structures and self-cycle mechanisms of mononuclear tungsten peroxo complexes in oxidation reactions

    NASA Astrophysics Data System (ADS)

    Jin, Peng; Wei, Donghui; Wen, Yiqiang; Luo, Mengfei; Wang, Xiangyu; Tang, Mingsheng

    2011-04-01

    Tungsten peroxo complexes have been widely used in olefin epoxidation, alcohol oxidation, Baeyer-Villiger oxidation and other oxidation reactions, however, there is still not a unanimous viewpoint for the active structure of mononuclear tungsten peroxo complex by now. In this paper, the catalysis of mononuclear tungsten peroxo complexes 0- 5 with or without acidic ligands for the green oxidation of cyclohexene to adipic acid in the absence of organic solvent and phase-transfer catalyst has been researched in experiment. Then we have suggested two possible kinds of active structures of mononuclear tungsten peroxo complexes including peroxo ring ( nA, n = 0-1) and hydroperoxo ( nB, n = 0-1) structures, which have been investigated using density functional theory (DFT). Moreover, the calculations on self-cycle mechanisms involving the two types of active structures of tungsten peroxo complexes with and without oxalic acid ligand have also been carried out at the B3LYP/[LANL2DZ/6-31G(d, p)] level. The highest energy barrier are 26.17 kcal/mol ( 0A, peroxo ring structure without oxalic acid ligand), 23.91 kcal/mol ( 1A, peroxo ring structure with oxalic acid ligand), 18.19 kcal/mol ( 0B, hydroperoxo structure without oxalic acid ligand) and 13.10 kcal/mol ( 1B, hydroperoxo structure with oxalic acid ligand) in the four potential energy profiles, respectively. The results indicate that both the energy barriers of active structure self-cycle processes with oxalic acid ligands are lower than those without oxalic acid ligands, so the active structures with oxalic acid ligands should be easier to recycle, which is in good agreement with our experimental results. However, due to the higher energy of product than that of the reactant, the energy profile of the self-cycle process of 1B shows that the recycle of 1B could not occur at all in theory. Moreover, the crystal data of peroxo ring structure with oxalic acid ligand could be found in some experimental references. Thus

  14. A selected reaction monitoring-based analysis of acute phase proteins in interstitial fluids from experimental equine wounds healing by secondary intention.

    PubMed

    Bundgaard, Louise; Bendixen, Emøke; Sørensen, Mette Aa; Harman, Victoria M; Beynon, Robert J; Petersen, Lars J; Jacobsen, Stine

    2016-05-01

    In horses, pathological healing with formation of exuberant granulation tissue (EGT) is a particular problem in limb wounds, whereas body wounds tend to heal without complications. Chronic inflammation has been proposed to be central to the pathogenesis of EGT. This study aimed to investigate levels of inflammatory acute phase proteins (APPs) in interstitial fluid from wounds in horses. A novel approach for absolute quantification of proteins, selected reaction monitoring (SRM)-based mass spectrometry in combination with a quantification concatamer (QconCAT), was used for the quantification of five established equine APPs (fibrinogen, serum amyloid A, ceruloplasmin, haptoglobin, and plasminogen) and three proposed equine APPs (prothrombin, α-2-macroglobulin, and α-1-antitrypsin). Wound interstitial fluid was recovered by large pore microdialysis from experimental body and limb wounds from five horses at days 1, 2, 7, and 14 after wounding and healing without (body) and with (limb) the formation of EGT. The QconCAT included proteotypic peptides representing each of the protein targets and was used to direct the design of a gene, which was expressed in Escherichia coli in a media supplemented with stable isotopes for metabolically labeling of standard peptides. Co-analysis of wound interstitial fluid samples with the stable isotope-labeled QconCAT tryptic peptides in known amounts enabled quantification of the APPs in absolute terms. The concentrations of fibrinogen, haptoglobin, ceruloplasmin, prothrombin, and α-1-antitrypsin in dialysate from limb wounds were significantly higher than in dialysate from body wounds. This is the first report of simultaneous analysis of a panel of APPs using the QconCAT-SRM technology. The microdialysis technique in combination with the QconCAT-SRM-based approach proved useful for quantification of the investigated proteins in the wound interstitial fluid, and the results indicated that there is a state of sustained inflammation in

  15. Comparison of the polymerase chain reaction and culture for the detection of feline Chlamydia psittaci in untreated and doxycycline-treated experimentally infected cats.

    PubMed

    Sykes, J E; Studdert, V P; Browning, G F

    1999-01-01

    The diagnostic sensitivity of the polymerase chain reaction (PCR) was compared with that of culture on conjunctival swabs over the course of infection in 4 doxycycline-treated and 4 untreated cats that were experimentally infected with feline Chlamydia psittaci. Treated cats were given 25 mg (5 mg/kg) of doxycycline orally twice daily for 3 weeks from day 6 after challenge. Clinical signs improved within 3 days of institution of treatment. Culture remained positive for 1 day and PCR remained positive for up to 5 days after treatment was commenced. No recurrence of clinical signs occurred and the organism could not be detected by either PCR or culture for 2 weeks after cessation of therapy. In the 4 untreated cats, conjunctival swabs were taken daily to day 14 and every 2nd weekday to day 64 after challenge. PCR was significantly more sensitive than culture in untreated cats overall (PCR 85.7%, culture 72.9%, P approximately 0) and for cats with clinical signs (PCR 89.2%, culture 79.2%, P = .008). PCR and culture had equivalent sensitivity (100%) for cats showing clinical signs in the 1st month of infection, whereas PCR was considerably more sensitive than culture for cats showing clinical signs in the 2nd month (PCR 72.9%, culture 47.9%, P = .028). Organisms were not detected by PCR in blood or any tissue collected from treated or untreated cats at postmortem. Thus, effective treatment of chlamydiosis in cats is possible with much shorter treatment regimens than currently recommended, and PCR is the more sensitive diagnostic method in chronically infected cats. PMID:10357101

  16. Initiation precursors and initiators in laser-induced copolymerization of styrene and maleic anhydride in acetone

    NASA Technical Reports Server (NTRS)

    Miner, Gilda A.; Meador, Willard E.; Chang, C. Ken

    1990-01-01

    The initiation step of photopolymerized styrene/maleic anhydride copolymer was investigated at 365 nm. UV absorption measurements provide decisive evidence that the styrene/maleic anhydride charge transfer complex is the sole absorbing species; however, key laser experiments suggest intermediate reactions lead to a monoradical initiating species. A mechanism for the photoinitiation step of the copolymer is proposed.

  17. Extension of the energy range of the experimental activation cross-sections data of longer-lived products of proton induced nuclear reactions on dysprosium up to 65MeV.

    PubMed

    Tárkányi, F; Ditrói, F; Takács, S; Hermanne, A; Ignatyuk, A V

    2015-04-01

    Activation cross-sections data of longer-lived products of proton induced nuclear reactions on dysprosium were extended up to 65MeV by using stacked foil irradiation and gamma spectrometry experimental methods. Experimental cross-sections data for the formation of the radionuclides (159)Dy, (157)Dy, (155)Dy, (161)Tb, (160)Tb, (156)Tb, (155)Tb, (154m2)Tb, (154m1)Tb, (154g)Tb, (153)Tb, (152)Tb and (151)Tb are reported in the 36-65MeV energy range, and compared with an old dataset from 1964. The experimental data were also compared with the results of cross section calculations of the ALICE and EMPIRE nuclear model codes and of the TALYS nuclear reaction model code as listed in the latest on-line libraries TENDL 2013. PMID:25644082

  18. A combined experimental and computational study of the catalytic dehydration of glycerol on microporous zeolites: an investigation of the reaction mechanism and acrolein selectivity.

    PubMed

    Lin, Xufeng; Lv, Yanhong; Qu, Yuanyuan; Zhang, Guodong; Xi, Yanyan; Phillips, David L; Liu, Chenguang

    2013-12-14

    The catalytic activity and the acrolein selectivity for liquid phase glycerol dehydration on β zeolites (HNa-β-k) were found to be dependent on the reaction temperature as well as on the amount of acid sites on the zeolites. An increase in the reaction temperature favors the acrolein selectivity. The acrolein selectivity increases with the Na(+)/H(+) ratio and the glycerol conversion decreases with it so that a maximum acrolein yield is obtained when a certain amount of acidic sites are replaced by non-active Na(+) sites. The computational results indicate that 3-hydoxylpropanal (HPA) is an important intermediate that determines the final product selectivity. The relative rates of the different reaction pathways for HAP can be affected by the amount of water molecules involved in its homogeneous reaction. Based on the reaction mechanism proposed, it was hypothesized that smaller pores reduce activity but increase selectivity to acrolein, and results of the H-MFI zeolite were consistent with this hypothesis. Our work provides important insight into the overall landscape of the reaction mechanism and can be used to help design reaction systems that have good acrolein selectivity for the liquid phase glycerol dehydration reactions. PMID:24158544

  19. Automatic, continuous online monitoring of polymerization reactions (ACOMP): Progress in characterization of polymers and polymerization reactions

    NASA Astrophysics Data System (ADS)

    Alb, Alina M.

    An original method is presented as an efficient technique for characterizing polymers, and understanding the kinetics of the polymerization reactions. The Automatic Continuous Online Monitoring of Polymerization Reactions (ACOMP) method developed at Tulane University involves following one or more characteristics of a polymerization reaction: monomer conversion, different molecular weight averages, intrinsic viscosity, etc. By performing an automatic withdrawal and dilution of the polymer solution to create a small stream which flows through a detector train, including light scattering, viscometer, refractive index, Ultraviolet/Visible detectors, a continuum of data points can be obtained, allowing powerful analysis methods to be developed. The goal of this work is to expand ACOMP to new polymerization reactions, such as free radical copolymerization, controlled radical polymerization, inverse emulsion polymerization, both to achieve a complete physical characterization of the polymers synthesized and a better understanding of the reaction mechanisms. For each of the reactions ACOMP brings significant innovations in the analysis of the kinetics. Other new methods, such as Automatic Continuous Mixing (ACM) and Simultaneous Multiple Sample Light Scattering (SMSLS) are also used, as well as traditional multi-detector Size Exclusion Chromatography (SEC). As an immediate consequence it is hoped that the information on reaction kinetics and mechanisms offer a better fundamental knowledge, control and ability to optimize reactions. At the industrial scale, online monitoring should allow a more efficient use of resources, energy, reactor and personnel time as well as a higher product quality.

  20. CO2 Reaction Induced Wettability Alteration and its Impacts on CO2 Storage: Pore to Core Scale Reservoir Condition Experimental Studies

    NASA Astrophysics Data System (ADS)

    Wan, J.; Tokunaga, T. K.; Kim, Y.; Jung, J.; Kim, T.; Dong, W.

    2013-12-01

    Wettability of the mineral surfaces plays an important role in subsurface multiphase flow and transport. Wettability affects the capillary pressure-saturation (Pc- S) relations, relative permeability (kr) of each fluid phase, and relative phase occupancy in reservoir pores. Although wettability issues have been studied extensively in other fields, significant knowledge gaps remain when applying the existing understanding to geological carbon sequestration; due largely to the unique physical-chemical properties of supercritical (sc) CO2 relative to other common non-wetting fluids such as air and oil. Here, we report our recent progress on wettability alteration upon reaction with CO2 and the resulting differences in capillary trapping of CO2 versus air. (1) Pore Scale Studies. There are conflict predictions in the literature concerning the effect of wettability on capillary trapping; some find that larger contact angles lead to lower capillary trapping while others have found opposite behavior. We hypothesized that spontaneous imbibition becomes energetically unfavorable with decreased wettability, so that increased residual trapping of scCO2 should occur during the post-injection inbibition stage. We developed a laboratory high-pressure and elevated temperature microscopic-micromodel system that is capable of controlling fine scale capillary pressure of scCO2-brine, and enabled us to conduct imbibition under controlled capillary pressures at the pore scale. We found that the de-wetting enhanced scCO2 capillary trapping is significant. These results suggest that scCO2 reaction induced dewetting can result in higher degrees of CO2 residual trapping in the post-injection stage than previously predicted. (2) Core Scale Studies. Capillary scaling is used routinely to predict Pc(S) relations for scCO2-brine systems at field scale, based on relations measured with air-water or mercury porosimetry. However, scaling-based predictions for CO2-brine systems have not been

  1. Gas-phase reactions of the bare Th2+ and U2+ ions with small alkanes, CH4, C2H6, and C3H8: experimental and theoretical study of elementary organoactinide chemistry.

    PubMed

    Di Santo, Emanuela; Santos, Marta; Michelini, Maria C; Marçalo, Joaquim; Russo, Nino; Gibson, John K

    2011-02-16

    The gas-phase reactions of two dipositive actinide ions, Th(2+) and U(2+), with CH(4), C(2)H(6), and C(3)H(8) were studied by both experiment and theory. Fourier transform ion cyclotron resonance mass spectrometry was employed to study the bimolecular ion-molecule reactions; the potential energy profiles (PEPs) for the reactions, both observed and nonobserved, were computed by density functional theory (DFT). The experiments revealed that Th(2+) reacts with all three alkanes, including CH(4) to produce ThCH(2)(2+), whereas U(2+) reacts with C(2)H(6) and C(3)H(8), with different product distributions than for Th(2+). The comparative reactivities of Th(2+) and U(2+) toward CH(4) are well explained by the computed PEPs. The PEPs for the reactions with C(2)H(6) effectively rationalize the observed reaction products, ThC(2)H(2)(2+) and UC(2)H(4)(2+). For C(3)H(8) several reaction products were experimentally observed; these and additional potential reaction pathways were computed. The DFT results for the reactions with C(3)H(8) are consistent with the observed reactions and the different products observed for Th(2+) and U(2+); however, several exothermic products which emerge from energetically favorable PEPs were not experimentally observed. The comparison between experiment and theory reveals that DFT can effectively exclude unfavorable reaction pathways, due to energetic barriers and/or endothermic products, and can predict energetic differences in similar reaction pathways for different ions. However, and not surprisingly, a simple evaluation of the PEP features is insufficient to reliably exclude energetically favorable pathways. The computed PEPs, which all proceed by insertion, were used to evaluate the relationship between the energetics of the bare Th(2+) and U(2+) ions and the energies for C-H and C-C activation. It was found that the computed energetics for insertion are entirely consistent with the empirical model which relates insertion efficiency to the

  2. Investigating Experimental Effects within the Framework of Structural Equation Modeling: An Example with Effects on Both Error Scores and Reaction Times

    ERIC Educational Resources Information Center

    Schweizer, Karl

    2008-01-01

    Structural equation modeling provides the framework for investigating experimental effects on the basis of variances and covariances in repeated measurements. A special type of confirmatory factor analysis as part of this framework enables the appropriate representation of the experimental effect and the separation of experimental and…

  3. Template copolymerization to control site structure around metal ions: Applications towards sensing and gas storage and release

    NASA Astrophysics Data System (ADS)

    Mitchell-Koch, Jeremy T.

    The development of functional materials for sensing and gas storage and release is useful in a number of chemical and biological applications. Investigating function of molecularly imprinted polymers (MIP), often used for these purposes, has relied on circumstantial evidence because direct examination of immobilized sites is not possible. Described in this dissertation is the design, synthesis, characterization and function studies of materials synthesized by template copolymerization methods. Metal ions exhibit unique spectroscopic properties and their utilization makes site examination more feasible. Ligand binding modulates these properties such that the event can be measured by spectroscopy. The metal ion's secondary coordination environment can also be tuned to increase or decrease function of the material. In Chapter Two the utilization of template copolymerization to immobilize a europium-containing compound for the detection of volatile organic compounds is described. Luminescence of the immobilized complex is quenched in the presence of volatile organic compounds (VOC). The quenching effect is dependent on concentration of VOC and the nature of polymeric host. Chapters Three and Four describe the development of materials for the photolytic release of nitric oxide (NO). In Chapter Three, a novel manipulation of the immobilized complex is employed to produce binding sites that contain ligands covalently embedded into the host in a position to bind the metal ion upon NO release in order to block rebinding. Incompatible binding affinities of the iron-containing templates made it impossible to study NO photo-release from this material. Second-row transition metals are more compatible with NO binding, and Chapter Four describes a ruthenium salen-containing polymer that releases NO in response to light. Additionally, transfer of NO to a metalloporphyrin and myoglobin has been achieved. This is the first report of photolytic heterogeneous NO transfer by a material

  4. Copolymerization and terpolymerization of carbon dioxide/propylene oxide/phthalic anhydride using a (salen)Co(III) complex tethering four quaternary ammonium salts

    PubMed Central

    Jeon, Jong Yeob; Eo, Seong Chan; Varghese, Jobi Kodiyan

    2014-01-01

    Summary The (salen)Co(III) complex 1 tethering four quaternary ammonium salts, which is a highly active catalyst in CO2/epoxide copolymerizations, shows high activity for propylene oxide/phthalic anhydride (PO/PA) copolymerizations and PO/CO2/PA terpolymerizations. In the PO/PA copolymerizations, full conversion of PA was achieved within 5 h, and strictly alternating copolymers of poly(1,2-propylene phthalate)s were afforded without any formation of ether linkages. In the PO/CO2/PA terpolymerizations, full conversion of PA was also achieved within 4 h. The resulting polymers were gradient poly(1,2-propylene carbonate-co-phthalate)s because of the drift in the PA concentration during the terpolymerization. Both polymerizations showed immortal polymerization character; therefore, the molecular weights were determined by the activity (g/mol-1) and the number of chain-growing sites per 1 [anions in 1 (5) + water (present as impurity) + ethanol (deliberately fed)], and the molecular weight distributions were narrow (M w/M n, 1.05–1.5). Because of the extremely high activity of 1, high-molecular-weight polymers were generated (M n up to 170,000 and 350,000 for the PO/PA copolymerization and PO/CO2/PA terpolymerization, respectively). The terpolymers bearing a substantial number of PA units (f PA, 0.23) showed a higher glass-transition temperature (48 °C) than the CO2/PO alternating copolymer (40 °C). PMID:25161738

  5. The influence of mixed activators on ethylene polymerization and ethylene/1-hexene copolymerization with silica-supported Ziegler-Natta catalyst.

    PubMed

    Senso, Nichapat; Khaubunsongserm, Supaporn; Jongsomjit, Bunjerd; Praserthdam, Piyasan

    2010-01-01

    This article reveals the effects of mixed activators on ethylene polymerization and ethylene/1-hexene copolymerization over MgCl₂/SiO₂-supported Ziegler-Natta (ZN) catalysts. First, the conventional ZN catalyst was prepared with SiO₂ addition. Then, the catalyst was tested for ethylene polymerization and ethylene/1-hexene (E/H) co-polymerization using different activators. Triethylaluminum (TEA), tri-n-hexyl aluminum (TnHA) and diethyl aluminum chloride (DEAC), TEA+DEAC, TEA+TnHA, TnHA+ DEAC, TEA+DEAC+TnHA mixtures, were used as activators in this study. It was found that in the case of ethylene polymerization with a sole activator, TnHA exhibited the highest activity among other activators due to increased size of the alkyl group. Further investigation was focused on the use of mixed activators. The activity can be enhanced by a factor of three when the mixed activators were employed and the activity of ethylene polymerization apparently increased in the order of TEA+ DEAC+TnHA > TEA+DEAC > TEA+TnHA. Both the copolymerization activity and crystallinity of the synthesized copolymers were strongly changed when the activators were changed from TEA to TEA+DEAC+TnHA mixtures or pure TnHA and pure DEAC. As for ethylene/1-hexene copolymerization the activity apparently increased in the order of TEA+DEAC+TnHA > TEA+TnHA > TEA+DEAC > TnHA+DEAC > TEA > TnHA > DEAC. Considering the properties of the copolymer obtained with the mixed TEA+DEAC+TnHA, its crystallinity decreased due to the presence of TnHA in the mixed activator. The activators thus exerted a strong influence on copolymer structure. An increased molecular weight distribution (MWD) was observed, without significant change in polymer morphology. PMID:21169883

  6. N-O versus N-N bond activation in reaction of N2O with carbon cluster ions: Experimental and ab initio studies of the effects of geometric and electronic structure

    NASA Astrophysics Data System (ADS)

    Resat, Marianne Sowa; Smolanoff, Jason N.; Goldman, Ilyse B.; Anderson, Scott L.

    1994-06-01

    We report a combined experimental and theoretical study of the reaction of small carbon cluster cations with N2O aimed at understanding the reaction mechanism and how it is affected by the electronic and geometric structure of the C+n reactants. Cross sections for reaction of C+n (n=3-12) with N2O were measured over a collision energy range from 0.1-10 eV, using a guided ion beam tandem mass spectrometer. Ab initio calculations were used to examine the structure and energetics of reactant and product species. Small clusters, which are linear, react with no activation barrier, resulting in either oxide or nitride formation. The branching between oxide and nitride channels shows a strong even-odd alternation, with even clusters preferentially forming nitrides. This appears to be correlated with an even/odd alternation in the ionization potential of the CnN. The larger, monocyclic C+n have activation barriers for reaction, and a completely different product distribution. Secondary reactions of the primary oxide and nitride products were studied at high N2O pressures. Products containing two O or two N atoms are not observed, but it is possible to add one of each. Possible reaction mechanisms are discussed and supported by thermochemistry derived from spin restricted ab initio calculations.

  7. In vitro drug release behavior, mechanism and antimicrobial activity of rifampicin loaded low molecular weight PLGA-PEG-PLGA triblock copolymeric nanospheres.

    PubMed

    Gajendiran, M; Divakar, S; Raaman, N; Balasubramanian, S

    2013-12-01

    Poly (lactic-co-glycolic acid) (PLGA (92:8)) and a series of PLGA-PEG-PLGA tri block copolymers were synthesized by direct melt polycondensation. The copolymers were characterized by FTIR, and 1HNMR spectroscopic techniques, viscosity, gel permeation chromatography (GPC) and powder x-ray diffraction (XRD). The rifampicin (RIF) loaded polymeric nanospheres (NPs) were prepared by ultrasonication-W/O emulsification technique. The NPs have been characterized by field emission scanning electron microscopy (FESEM), TEM, powder X-ray diffraction (XRD), UVvisible spectroscopy and DLS measurements. The drug loaded triblock copolymeric NPs have five folds higher drug content and drug loading efficiency than that of PLGA microspheres (MPs). The in vitro drug release study shows that the drug loaded NPs showed an initial burst release after that sustained release up to 72 h. All the triblock copolymeric NPs follow anomalous drug diffusion mechanism while the PLGA MPs follow non-Fickian super case-II mechanism up to 12 h. The overall in-vitro release follows second order polynomial kinetics up to 72 h. The antimicrobial activity of the RIF loaded polymer NPs was compared with that of pure RIF and tetracycline (TA). The RIF loaded triblock copolymeric NPs inhibited the bacterial growth more effectively than the pure RIF and TA. PMID:23701139

  8. Functional and surface-active membranes from poly(vinylidene fluoride)-graft-poly(acrylic acid) prepared via RAFT-mediated graft copolymerization.

    PubMed

    Ying, L; Yu, W H; Kang, E T; Neoh, K G

    2004-07-01

    Poly (vinylidene fluoride) (PVDF) with "living" poly (acrylic acid) (PAAc) side chains (PVDF-g-PAAc) was prepared by reversible addition-fragmentation chain transfer (RAFT)-mediated graft copolymerization of acrylic acid (AAc) with the ozone-pretreated PVDF. The chemical composition and structure of the copolymers were characterized by elemental analysis, Fourier transform infrared spectroscopy, and thermogravimetric analysis. The copolymer could be readily cast into pH-sensitive microfiltration (MF) membranes with enriched living PAAc graft chains on the surface (including the pore surfaces) by phase inversion in an aqueous medium. The surface composition of the membranes was determined by X-ray photoelectron spectroscopy. The morphology of the membranes was characterized by scanning electron microscopy. The pore size distribution of the membranes was found to be much more uniform than that of the corresponding membranes cast from PVDF-g-PAAc prepared by the "conventional" free-radical graft copolymerization process. Most important of all, the MF membranes with surface-tethered PAAc macro chain transfer agents, or the living membrane surfaces, could be further functionalized via surface-initiated block copolymerization with N-isopropylacrylamide (NIPAAM) to obtain the PVDF-g-PAAc-b-PNIPAAM MF membranes, which exhibited both pH- and temperature-dependent permeability to aqueous media. PMID:16459627

  9. Experimental cross-sections of deuteron-induced reaction on 89Y up to 20 MeV; comparison of natTi(d,x)48V and 27Al(d,x)24Na monitor reactions

    NASA Astrophysics Data System (ADS)

    Lebeda, Ondřej; Štursa, Jan; Ráliš, Jan

    2015-10-01

    We measured cross-sections of the deuteron-induced reactions on 89Y in the energy range of 3.9-19.5 MeV. Excitation functions for formation of 88Zr, 89mZr, 89Zr, 88Y, 90mY and 87mSr were determined and compared with previously published data and prediction of the TALYS code. Thick target yields for production of 88Zr, 89Zrcum, 88Y, 90mY and 87mSr were calculated from the measured cross-sections. Achievable activity versus radionuclidic purity of medically relevant 89Zr is discussed and compared with the production via the 89Y(p,n) reaction. Parallel use of titanium and aluminium beam monitors revealed systematic difference between the recommended cross-sections of both monitoring reactions and provided new cross-section data for formation of 24Na, 27Mg, 43Sc, 44mSc, 44Sc, 46Sc, 47Sc and 48Sc. The cross-sections for the natTi(d,x)46Sc reactions agree very well with recently proposed recommended values.

  10. Furfuralcohol Co-Polymerized Urea Formaldehyde Resin-derived N-Doped Microporous Carbon for CO2 Capture.

    PubMed

    Liu, Zhen; Yang, Yi; Du, Zhenyu; Xing, Wei; Komarneni, Sridhar; Zhang, Zhongdong; Gao, Xionghou; Yan, Zifeng

    2015-12-01

    Carbon-based adsorbent is considered to be one of the most promising adsorbents for CO2 capture form flue gases. In this study, a series of N-doped microporous carbon materials were synthesized from low cost and widely available urea formaldehyde resin co-polymerized with furfuralcohol. These N-doped microporous carbons showed tunable surface area in the range of 416-2273 m(2) g(-1) with narrow pore size distribution within less than 1 nm and a high density of the basic N functional groups (2.93-13.92 %). Compared with the carbon obtained from urea resin, the addition of furfuralcohol apparently changed the surface chemical composition and pore size distribution, especially ultramicropores as can be deduced from the X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR), and pore size distribution measurements and led to remarkable improvement on CO2 adsorption capacity. At 1 atm, N-doped carbons activated at 600 °C with KOH/UFFC weight ratio of 2 (UFFA-2-600) showed the highest CO2 uptake of 3.76 and 1.57 mmol g(-1) at 25 and 75 °C, respectively. PMID:26293492

  11. Synthesis and properties of antifouling poly(CL-co-zDMAEMA) zwitterionic copolymer by one-step hybrid copolymerization.

    PubMed

    Yan, Manqing; Yang, Hongjun; Zhang, Guangzhao

    2015-06-01

    A novel biocompatible and biodegradable copolymer was synthesized by one-step hybrid copolymerization of ε-caprolactone (CL) and 2-(N,N-dimethylamino) ethyl methacrylate (DMAEMA) employing (1-tert-butyl-4,4,4-tris(dimethylamino)-2,2-bis[tris(dimethylamino)phophoranylidenamino]-2Λ5,Λ5-catenadi(phosphazene) (t-BuP4) as a catalyst. The as-synthesized copolymer was betainizated resulting in a zwitterionic copolymer poly(CL-co-zDMAEMA) and the structure of the zwitterionic copolymer was confirmed by the FT-IR, NMR, and XPS measurements. The results of dynamic light scattering (DLS) show that this zwitterionic copolymer can self-assemble into stable micelles. The results of quartz crystal microbalance with dissipation (QCM-D) analysis and MTT measurement suggest that this zwitterionic copolymer possess better protein resistance and lower cell cytotoxicity in vitro in comparison with the cationic copolymer. The pyrene solubilization measurement of copolymers poly(CL-co-zDMAEMA) indicates an excellent pyrene solubilization capacity. These zwitterionic polymer micelles can release drugs in response to specific signals, such as temperature, pH, and enzymes and have a potential application in drug delivery and gene therapy due to their good antifouling, low cytotoxicity and high pyrene solubilization. PMID:25842125

  12. Radiation-induced graft copolymerization of poly(ethylene glycol) monomethacrylate onto deoxycholate-chitosan nanoparticles as a drug carrier

    NASA Astrophysics Data System (ADS)

    Pasanphan, Wanvimol; Rattanawongwiboon, Thitirat; Rimdusit, Pakjira; Piroonpan, Thananchai

    2014-01-01

    Poly(ethylene glycol) monomethacrylate-grafted-deoxycholate chitosan nanoparticles (PEGMA-g-DCCSNPs) were successfully prepared by radiation-induced graft copolymerization. The hydrophilic poly(ethylene glycol) monomethacrylate was grafted onto deoxycholate-chitosan in an aqueous system. The radiation-absorbed dose is an important parameter on degree of grafting, shell thickness and particle size of PEGMA-g-DCCSNPs. Owing to their amphiphilic architecture, PEGMA-g-DCCSNPs self-assembled into spherical core-shell nanoparticles in aqueous media. The particle size of PEGMA-g-DCCSNPs measured by TEM varied in the range of 70-130 nm depending on the degree of grafting as well as the irradiation dose. Berberine (BBR) as a model drug was encapsulated into the PEGMA-g-DCCSNPs. Drug release study revealed that the BBR drug was slowly released from PEGMA-g-DCCSNPs at a mostly constant rate of 10-20% in PBS buffer (pH 7.4) at 37 °C over a period of 23 days.

  13. Fabrication of Fluoropolymer Microtubes via RAFT Copolymerization of N,N'-Methylene Bisacrylamide Gel Fibers and Fluoromonomer.

    PubMed

    Li, Qi; Wang, Yi; Tang, Liming

    2015-06-01

    Fluoropolymer microtubes with a smooth surface were fabricated in more than 70 % yield via reversible addition fragmentation chain transfer (RAFT) co-polymerization of N,N'-methylene bisacrylamide (MBA) gel fibers as both template and monomer, 2-(perfluoro-3-methylbutyl)ethyl acrylate (R-3420) as co-monomer, and pentaerythritol tetraacrylate (PET4A) as cross-linker. The resulting fluoropolymer microtubes were characterized fully by SEM, TEM, EDS, XPS, and FT-IR. The influence of the monomer composition on the yields and morphologies of the tubes were investigated in detail. The results indicated that polymer microtubes with a smooth surface were obtained at suitable amounts of R-3420 and PET4A. Because of the decreased solubility of MBA gel fibers, the wall thickness increased as more R-3420 was used. In the presence of PET4A, the solution polymerization could be facilitated and more R-3420 could be attached onto the tubes based on FT-IR analysis. The water contact angle and swelling ratio measurements both revealed the low hydrophilicity and high lipophilicity of the fluoropolymer microtubes, which made the sample able to absorb toluene selectively in a water/toluene two-phase system. PMID:25786386

  14. Synthesis and characterization of transferrin-targeted chemotherapeutic delivery systems prepared via RAFT copolymerization of high molecular weight PEG macromonomers

    PubMed Central

    Roy, Debashish; Berguig, Geoffrey Y; Ghosn, Bilal; Lane, Daniel; Braswell, Scott; Stayton, Patrick S; Convertine, Anthony J

    2014-01-01

    Reversible addition-fragmentation chain transfer (RAFT) polymerization was employed to prepare a nanoparticulate drug delivery system for chemotherapeutics. The nanoparticles contain a PEG “stealth” corona as well as reactive anhydride functionality designed for conjugating targeting proteins. The multifunctional carrier functionality was achieved by controlling the copolymerization of the hydrophobic monomer lauryl methacrylate (LMA), with a reactive anhydride functional methacrylate (TMA), and a large polyethyleneglycol methacrylate monomer (Mn~950 Da) (O950). RAFT polymerization kinetics of O950 were evaluated as a function of target degrees of polymerization (DP), initial chain transfer agent to initiator ratio ([CTA]o/[I]o), and solvent concentration. Excellent control over the polymerization was observed for target DPs of 25 and 50 at [CTA]o/[I]o ratio of 10 as evidenced by narrow and symmetric molecular weight distributions and the ability to prepare block copolymers. The TMA-functional copolymers were conjugated to the tumor targeting protein transferrin (Tf). The targeted copolymer was shown to encapsulate docetaxel at concentrations comparable to the commercial single vial formulation of docetaxel (Taxotere). In vitro cytotoxicity studies conducted in HeLa cells show that the Tf targeting enhances the cancer killing properties relative to the polymer encapsulated docetaxel formulation. PMID:25221630

  15. Experimental study of neutron-rich nuclei near the N = 82 closed shell using the {sub 40}{sup 96}Zr+{sub 50}{sup 124}Sn reaction with GASP and PRISMA-CLARA arrays

    SciTech Connect

    Rodríguez, W.; Torres, D. A.; Cristancho, F.; Medina, N. H.; Chapman, R.; Smith, J. F.; Mengoni, D.; Truesdale, V.; Grocutt, L.; Mulholland, K.; Kumar, V.; Hadinia, B.; Labiche, M.; Liang, X.; O'Donell, D.; Ollier, J.; Orlandi, R.; Smith, J. F.; Spohr, K. M.; Wady, P.; and others

    2014-11-11

    In this contribution an experimental study of the deep-inelastic reaction {sub 40}{sup 96}Zr+{sub 50}{sup 124}Sn at 530 MeV, using the GASP and PRISMA-CLARA arrays, is presented. The experiments populate a wealth of projectile-like and target-like binary fragments, in a large neutron-rich region around N ≥ 50 and Z ≈ 40. Preliminary results on the study of the yrast and near-yrast states for {sup 95}Nb will be shown, along with a comparison of the experimental yields obtained in the experiments.

  16. Experimental study of the B11,12(n,γ) reactions and their influence on r-process nucleosynthesis of light elements

    NASA Astrophysics Data System (ADS)

    Lee, H. Y.; Greene, J. P.; Jiang, C. L.; Pardo, R. C.; Rehm, K. E.; Schiffer, J. P.; Wuosmaa, A. H.; Goodman, N. J.; Lighthall, J. C.; Marley, S. T.; Otsuki, K.; Patel, N.; Beard, M.; Notani, M.; Tang, X. D.

    2010-01-01

    We have studied the neutron-transfer reactions B11,12(d,p)B12,13 in inverse kinematics to obtain information about the neutron-capture reactions B11,12(n,γ). These capture reactions are suggested to play a role in seeding r-process nucleosynthesis through the production of light, neutron-rich nuclei. The neutron spectroscopic factors of the states in B12,13 were deduced and the branching ratio of the neutron-unbound state at EX=3.389 MeV in B12 was obtained to provide the ratio of partial widths, Γn/Γγ. The reaction rates for B11,12(n,γ) are estimated for direct captures and resonant captures and compared with previous compilations. The astrophysical implications, especially for neutrino-driven wind models in core-collapse supernovae, are discussed in the r-process network framework using our updated reaction rates.

  17. Experimental study of the {sup 11,12}B(n,gamma) reactions and their influence on r-process nucleosynthesis of light elements.

    SciTech Connect

    Lee, H. Y.; Greene, J. P.; Jiang, C. L.; Pardo, R. C.; Rehm , K. E.; Schiffer, J. P.; Wuosmaa, A. H.; Goodman, N. J.; Lighthall, J. C.; Marley, S. T.; Otsuki, K.; Patel, N.; Beard, M.; Notani, M.; Tang, X. D.; Physics; Western Michigan Univ.; GSI; Colorado School of Mines; Univ. of Notre Dame

    2010-01-01

    We have studied the neutron-transfer reactions {sup 11,12}B(d,p){sup 12,13}B in inverse kinematics to obtain information about the neutron-capture reactions {sup 11,12}B(n,{gamma}). These capture reactions are suggested to play a role in seeding r-process nucleosynthesis through the production of light, neutron-rich nuclei. The neutron spectroscopic factors of the states in {sup 12,13}B were deduced and the branching ratio of the neutron-unbound state at E{sub X} = 3.389 MeV in {sup 12}B was obtained to provide the ratio of partial widths, {Lambda}{sub n}/{Lambda}{sub {gamma}}. The reaction rates for {sup 11,12}B(n,{gamma}) are estimated for direct captures and resonant captures and compared with previous compilations. The astrophysical implications, especially for neutrino-driven wind models in core-collapse supernovae, are discussed in the r-process network framework using our updated reaction rates.

  18. Fabrication, modeling and characterization of multi-crosslinked methacrylate copolymeric nanoparticles for oral drug delivery.

    PubMed

    Ngwuluka, Ndidi C; Pillay, Viness; Choonara, Yahya E; Modi, Girish; Naidoo, Dinesh; du Toit, Lisa C; Kumar, Pradeep; Ndesendo, Valence M K; Khan, Riaz A

    2011-01-01

    Nanotechnology remains the field to explore in the quest to enhance therapeutic efficacies of existing drugs. Fabrication of a methacrylate copolymer-lipid nanoparticulate (MCN) system was explored in this study for oral drug delivery of levodopa. The nanoparticles were fabricated employing multicrosslinking technology and characterized for particle size, zeta potential, morphology, structural modification, drug entrapment efficiency and in vitro drug release. Chemometric Computational (CC) modeling was conducted to deduce the mechanism of nanoparticle synthesis as well as to corroborate the experimental findings. The CC modeling deduced that the nanoparticles synthesis may have followed the mixed triangular formations or the mixed patterns. They were found to be hollow nanocapsules with a size ranging from 152 nm (methacrylate copolymer) to 321 nm (methacrylate copolymer blend) and a zeta potential range of 15.8-43.3 mV. The nanoparticles were directly compressible and it was found that the desired rate of drug release could be achieved by formulating the nanoparticles as a nanosuspension, and then directly compressing them into tablet matrices or incorporating the nanoparticles directly into polymer tablet matrices. However, sustained release of MCNs was achieved only when it was incorporated into a polymer matrix. The experimental results were well corroborated by the CC modeling. The developed technology may be potentially useful for the fabrication of multi-crosslinked polymer blend nanoparticles for oral drug delivery. PMID:22016653

  19. Fabrication, Modeling and Characterization of Multi-Crosslinked Methacrylate Copolymeric Nanoparticles for Oral Drug Delivery

    PubMed Central

    Ngwuluka, Ndidi C.; Pillay, Viness; Choonara, Yahya E.; Modi, Girish; Naidoo, Dinesh; du Toit, Lisa C.; Kumar, Pradeep; Ndesendo, Valence M.K.; Khan, Riaz A.

    2011-01-01

    Nanotechnology remains the field to explore in the quest to enhance therapeutic efficacies of existing drugs. Fabrication of a methacrylate copolymer-lipid nanoparticulate (MCN) system was explored in this study for oral drug delivery of levodopa. The nanoparticles were fabricated employing multicrosslinking technology and characterized for particle size, zeta potential, morphology, structural modification, drug entrapment efficiency and in vitro drug release. Chemometric Computational (CC) modeling was conducted to deduce the mechanism of nanoparticle synthesis as well as to corroborate the experimental findings. The CC modeling deduced that the nanoparticles synthesis may have followed the mixed triangular formations or the mixed patterns. They were found to be hollow nanocapsules with a size ranging from 152 nm (methacrylate copolymer) to 321 nm (methacrylate copolymer blend) and a zeta potential range of 15.8–43.3 mV. The nanoparticles were directly compressible and it was found that the desired rate of drug release could be achieved by formulating the nanoparticles as a nanosuspension, and then directly compressing them into tablet matrices or incorporating the nanoparticles directly into polymer tablet matrices. However, sustained release of MCNs was achieved only when it was incorporated into a polymer matrix. The experimental results were well corroborated by the CC modeling. The developed technology may be potentially useful for the fabrication of multi-crosslinked polymer blend nanoparticles for oral drug delivery. PMID:22016653

  20. Ion-neutral reaction of the C2H2N+ cation with C2H2: An experimental and theoretical study

    NASA Astrophysics Data System (ADS)

    Fathi, P.; Geppert, W. D.; Kaiser, A.; Ascenzi, D.

    2016-03-01

    The ion-neutral reactions of the C2H2N+ cation with C2H2 have been investigated using a Guided Ion Beam Mass Spectrometer (GIB-MS). The following ionic products were observed: CH3+, C2H2+, C2H3+, HNC+ /HCN+ , HCNH+, C3H+ , C2N+ , C3H3+, HCCN+ and C4H2N+ . Theoretical calculations have been carried out to propose reaction pathways leading to the observed products. These processes are of relevance for the generation of long chain nitrogen-containing species and they may be of interest for the chemistry of Titan's ionosphere or circumstellar envelopes.

  1. Formation of plagioclase-bearing peridotite and a peridotite-wehrlite-gabbro suite through melt-rock reaction: An experimental study

    NASA Astrophysics Data System (ADS)

    Saper, L.; Liang, Y.

    2012-12-01

    Plagioclase-bearing peridotites are observed among abyssal peridotites, massif peridotites, and mantle sections of ophiolites of lherzolite subtype. Formation of plagioclase-bearing peridotites is often attributed to basalt impregnation into host harzburgite or lherzolite in a thermal boundary layer. During transport through asthenospheric mantle, melt generated in the deep mantle will inevitably interact with the overlying mantle column through reactive dissolution and may leave geochemical imprints on plagioclase-bearing peridotites. To assess the role of melt-rock reaction on the formation of plagioclase-bearing peridotites and its implications for lithosphere composition, we conducted dissolution experiments in which a 88% spinel lherzolite + 12% basalt starting mixture was juxtaposed against a primitive MORB in a graphite-lined molybdenum capsule. The reaction couples were run at 1300°C and 1 GPa for 1 or 24 hrs, and then stepped cooled to 1050°C and 0.7 GPa over the next several days. Cooling promotes in situ crystallization of interstitial melts, allowing us to better characterize the mineral compositional trends produced and observed by melt-rock reaction and crystallization. A gabbro and a plagioclase-bearing peridotite were observed in the two halves of the reaction couple after the experiments were completed. The peridotite from the 24 hr reaction experiment is mostly composed of subhedral to euhedral olivines (10-50 μm in size, Mg# 75-83), poikilitic clinopyroxene (~100 μm in size, Mg# 73-83) with olivine and spinel chadocrysts, and interstitial plagioclase (An# 68-78) and melt. In a control experiment quenched after a 24 hour reaction at 1300°C the basalt completely dissolved the pyroxenes and spinels leaving a residue of rounded olivine grains (10-100 μm in size) surrounded by a relatively large melt fraction. Textural results from the step-cooling experiments suggest the following crystallization sequence from the olivine+melt mush: olivine

  2. Experimental study of the knockout reaction mechanism using O14 at 60 MeV/nucleon

    NASA Astrophysics Data System (ADS)

    Sun, Y. L.; Lee, J.; Ye, Y. L.; Obertelli, A.; Li, Z. H.; Aoi, N.; Ong, H. J.; Ayyad, Y.; Bertulani, C. A.; Chen, J.; Corsi, A.; Cappuzzello, F.; Cavallaro, M.; Furono, T.; Ge, Y. C.; Hashimoto, T.; Ideguchi, E.; Kawabata, T.; Lou, J. L.; Li, Q. T.; Lorusso, G.; Lu, F.; Liu, H. N.; Nishimura, S.; Suzuki, H.; Tanaka, J.; Tanaka, M.; Tran, D. T.; Tsang, M. B.; Wu, J.; Xu, Z. Y.; Yamamoto, T.

    2016-04-01

    Background: For the deeply bound one-nucleon removal at intermediate energies using a Be9 or C12 target, a strong reduction of cross section was observed relative to the prediction of eikonal theoretical model. The large disagreement has not been explained and the systematic trend is inconsistent with results from transfer reactions. The recently observed asymmetric parallel momentum distribution of the knockout residue indicates the significant dissipative core-target interaction in the knockout reaction with a composite target, implying new reaction mechanisms beyond the eikonal reaction descriptions. Purpose: To investigate the reaction mechanism for deeply bound nucleon removal at intermediate energies. Method: Neutron removal from O14 using a C12 target at 60 MeV/nucleon was performed. Nucleon knockout cross sections were measured. The unbound excited states of O13 were reconstructed by using the invariant mass method with the residues and the associated decay protons measured in coincidence. The measured cross sections are compared with an intra-nuclear cascade (INC) prediction. Results: The measured cross section of (O14C11,) is 60(9) mb, which is 3.5 times larger than that of (O14O13,) channel. This 2 p n -removal cross section is consistent with INC prediction, which is 66 mb with the main contribution being non-direct reaction processes. On the other hand, the upper limit

  3. Swelling, ion uptake and biodegradation studies of PE film modified through radiation induced graft copolymerization

    NASA Astrophysics Data System (ADS)

    Kaur, Inderjeet; Gupta, Nitika; Kumari, Vandna

    2011-09-01

    An attempt to develop biodegradable polyethylene film grafting of mixture of hydrophilic monomers methacrylic acid (MAAc) and acrylamide (AAm) onto PE film has been carried out by preirradiation method using benzoyl peroxide as the radical initiator. Since ether linkages are susceptible to easy cleavage during degradation process, PE film was irradiated before the grafting reactions by γ-rays to introduce peroxidic linkages (PE-OO-PE) that offer sites for grafting. The effect of irradiation dose, monomer concentration, initiator concentration, temperature, time and amount of water on the grafting percent was determined. Maximum percentage of grafting of binary mixture (MAAc+AAm), (1792%) was obtained at a total concentration of binary monomer mixture=204.6×10 -2 mol/L ([MAAc]=176.5×10 -2 mol/L, [AAm]=28.1×10 -2 mol/L), [BPO]=8.3×10 -2 mol/L at 100 °C in 70 min. The grafted PE film was characterized by the Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric Analysis (TGA) and Scanning Electron Microscopic (SEM) methods. Some selective properties of grafted films such as swelling studies, ion uptake and biodegradation studies have been investigated. The grafted films show good swelling in water, ion uptake studies shows promising results for desalination of brackish water and the soil burial test shows that PE film grafted with binary monomer mixture degrades up to 47% within 50 days.

  4. Luminescent Nanocellulose Platform: From Controlled Graft Block Copolymerization to Biomarker Sensing.

    PubMed

    Navarro, Julien R G; Wennmalm, Stefan; Godfrey, Jamie; Breitholtz, Magnus; Edlund, Ulrica

    2016-03-14

    A strategy is devised for the conversion of cellulose nanofibrils (CNF) into fluorescently labeled probes involving the synthesis of CNF-based macroinitiators that initiate radical polymerization of methyl acrylate and acrylic acid N-hydroxysuccinimide ester producing a graft block copolymer modified CNF. Finally, a luminescent probe (Lucifer yellow derivative) was labeled onto the modified CNF through an amidation reaction. The surface modification steps were verified with solid-state (13)C nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy. Fluorescence correlation spectroscopy (FCS) confirmed the successful labeling of the CNF; the CNF have a hydrodynamic radius of about 700 nm with an average number of dye molecules per fibril of at least 6600. The modified CNF was also imaged with confocal laser scanning microscopy. Luminescent CNF proved to be viable biomarkers and allow for fluorescence-based optical detection of CNF uptake and distribution in organisms such as crustaceans. The luminescent CNF were exposed to live juvenile daphnids and microscopy analysis revealed the presence of the luminescent CNF all over D. magna's alimentary canal tissues without any toxicity effect leading to the death of the specimen. PMID:26789648

  5. Elemental and topographic characterization of LDPE based copolymeric films obtained by gamma irradiation

    NASA Astrophysics Data System (ADS)

    Ferreira, L. M.; Falcão, A. N.; Gil, M. H.

    2007-12-01

    The preparation of PE-g-HEMA (polyethylene-grafted-hydroxyethyl methacrylate) films by 60Co gamma irradiation has been optimized to produce a new material suitable for bioapplications. This paper reports the elemental and topographic analysis of PE-g-HEMA films with different grafting degrees, obtained under optimized experimental conditions, with the purpose to appraise their possible toxicological risk and their surface roughness properties. In this way a Nuclear Microprobe using PIXE (Proton Induced X-ray Emission) technique was used to assess the elemental analysis of the film samples prepared. Trace contaminations of elements heavier than Si (Ca, Cl, Fe, K, P, S, Si and Zn) were found, but their concentrations do not pose toxicological risk. Atomic Force Microscopy (AFM) and Scanning Electronic Microscopy (SEM) techniques were used to assess the morphological characterization of the films, revealing the roughness and 3D porous structure of their surface, which are ones of essential characteristics for bio-interaction or cell adhesion.

  6. A review on the radiation synthesis of copolymeric hydrogels for adsorption and separation purposes1

    NASA Astrophysics Data System (ADS)

    Güven, Olgun; Şen, Murat; Karadağ, Erdener; Saraydın, Dursun

    1999-10-01

    Recent theoretical and experimental work on the radiation synthesis, characterization and the use of hydrogels containing diprotic acid moieties have been reviewed. It is shown that upon incorporating vinyl monomers carrying diprotic acid groups randomly in the main chain, non-ionic hydrogels like poly(acryl amide) and poly(n-vinyl 2-pyrrolidone) acquired stimuli-responsive behaviours. The swelling behaviours of these hydrogels are shown to be predictable reliably under varying solution conditions by a theoretical expression derived recently. Examples are given for the utilization of these hydrogels in the adsorption and separation of biomolecules, dyes and metal ions in aqueous media and their ability to release drugs in stepwise manner in response to pH of the environment.

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

    NASA Astrophysics Data System (ADS)

    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

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

    PubMed

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

    2012-12-14

    The reaction of O((3)P) with C(2)H(4), 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 E(c) 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 + CH(2)CHO, H + CH(3)CO, CH(3) + HCO, CH(2) + H(2)CO, and H(2) + CH(2)CO. These experiments extend our previous CMB work at higher collision energy (E(c) ∼ 13 kcal∕mol) and when the results are combined with the literature branching ratios from kinetics experiments at room temperature (E(c) ∼ 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((3)P) + C(2)H(4) 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 + CH(2)CHO, CH(3) + HCO, and CH(2) + H(2)CO

  9. Reaction of CO2 with propylene oxide and styrene oxide catalyzed by a chromium(III) amine-bis(phenolate) complex.

    PubMed

    Dean, Rebecca K; Devaine-Pressing, Katalin; Dawe, Louise N; Kozak, Christopher M

    2013-07-01

    A diamine-bis(phenolate) chromium(III) complex, {CrCl[O2NN'](BuBu)}2 catalyzes the copolymerization of propylene oxide with carbon dioxide. The synthesis of this metal complex is straightforward and it can be obtained in high yields. This catalyst incorporates a tripodal amine-bis(phenolate) ligand, which differs from the salen or salan ligands typically used with Cr and Co complexes that have been employed as catalysts for the synthesis of such polycarbonates. The catalyst reported herein yields low molecular weight polymers with narrow polydispersities when the reaction is performed at room temperature. Performing the reaction at elevated temperatures causes the selective synthesis of propylene carbonate. The copolymerization activity for propylene oxide and carbon dioxide, as well as the coupling of carbon dioxide and styrene oxide to give styrene carbonate are presented. PMID:23192332

  10. Oxidation-Responsive and "Clickable" Poly(ethylene glycol) via Copolymerization of 2-(Methylthio)ethyl Glycidyl Ether.

    PubMed

    Herzberger, Jana; Fischer, Karl; Leibig, Daniel; Bros, Matthias; Thiermann, Raphael; Frey, Holger

    2016-07-27

    Poly(ethylene glycol) (PEG) is a widely used biocompatible polymer. We describe a novel epoxide monomer with methyl-thioether moiety, 2-(methylthio)ethyl glycidyl ether (MTEGE), which enables the synthesis of well-defined thioether-functional poly(ethylene glycol). Random and block mPEG-b-PMTEGE copolymers (Mw/Mn = 1.05-1.17) were obtained via anionic ring opening polymerization (AROP) with molecular weights ranging from 5 600 to 12 000 g·mol(-1). The statistical copolymerization of MTEGE with ethylene oxide results in a random microstructure (rEO = 0.92 ± 0.02 and rMTEG E = 1.06 ± 0.02), which was confirmed by in situ (1)H NMR kinetic studies. The random copolymers are thermoresponsive in aqueous solution, with a wide range of tunable transition temperatures of 88 to 28 °C. In contrast, mPEG-b-PMTEGE block copolymers formed well-defined micelles (Rh ≈ 9-15 nm) in water, studied by detailed light scattering (DLS and SLS). Intriguingly, the thioether moieties of MTEGE can be selectively oxidized into sulfoxide units, leading to full disassembly of the micelles, as confirmed by detection of pure unimers (DLS and SLS). Oxidation-responsive release of encapsulated Nile Red demonstrates the potential of these micelles as redox-responsive nanocarriers. MTT assays showed only minor effects of the thioethers and their oxidized derivatives on the cellular metabolism of WEHI-164 and HEK-293T cell lines (1-1000 μg·mL(-1)). Further, sulfonium PEG polyelectrolytes can be obtained via alkylation or alkoxylation of MTEGE, providing access to a large variety of functional groups at the charged sulfur atom. PMID:27375132

  11. Meniscal regeneration with copolymeric collagen scaffolds. In vitro and in vivo studies evaluated clinically, histologically, and biochemically.

    PubMed

    Stone, K R; Rodkey, W G; Webber, R; McKinney, L; Steadman, J R

    1992-01-01

    We sought to create a regeneration template for the meniscal cartilage of the knee to induce complete meniscal regeneration, and to develop the technique for implanting the prosthetic appliance in vivo. We designed a resorbable collagen-based scaffold and conducted in vitro and in vivo studies. In vivo, the scaffold was implanted in the knees of immature swine and mature canines and evaluated clinically, histologically, and biochemically. Because the canine stifle joint meniscus is more clinically relevant to the human meniscus, this paper emphasizes those results. We studied 24 mixed breed dogs (14 males and 10 females) with an average weight of 25.5 kg (range, 20 to 35) that were obtained from a USDA-licensed supplier. The dogs were deemed clinically and radiographically skeletally mature. None of the dogs had a preexisting knee joint abnormality. All dogs underwent an 80% subtotal resection of the medial meniscus bilaterally. A collagen template was implanted in one stifle (N = 24). The contralateral side served as a control: 12 dogs had a total resection alone and the other 12 dogs had an immediate replantation of the autologous meniscus. Results were tabulated at 3, 6, 9, and 12 months. At final evaluation, before the animals were euthanized, the results were submitted for statistical analysis as well as histologic and biochemical analyses. The results demonstrated that a copolymeric collagen-based scaffold can be constructed that is compatible with meniscal fibrochondrocyte growth in vitro and in vivo, that does not inhibit meniscal regeneration in an immature pig, and that may induce regeneration of the meniscus in the mature dog.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:1558234

  12. Application Of Phenol/Amine Copolymerized Film Modified Magnesium Alloys: Anticorrosion And Surface Biofunctionalization.

    PubMed

    Chen, Si; Zhang, Jiang; Chen, Yingqi; Zhao, Sheng; Chen, Meiyun; Li, Xin; Maitz, Manfred F; Wang, Jin; Huang, Nan

    2015-11-11

    Magnesium metal as degradable metallic material is one of the most researched areas, but its rapid degradation rate restricts its development. The current anticorrosion surface modification methods require expensive equipment and complicated operation processes and cannot continue to introduce biofunction on modified surface. In this study, the GAHD conversion coatings were fabricated on the surface of magnesium alloys (MZM) by incubating in the mixture solution of gallic acid (GA) and hexamethylenediamine (HD) to decrease the corrosion rate and provide primary amines (-NH2), carboxyl (-COOH), and quinone groups, which is supposed to introduce biomolecules on MZM. Chemical structures of the MZM-GAHD and MZM-HEP-GAHD were explored by analyzing the results of FTIR and XPS comprehensively. Furthermore, it was proved that the heparin (HEP) molecules were successfully immobilized on MZM-GAHD surface through carbodiimide method. The evaluation of platelet adhesion and clotting time test showed that MZM-HEP-GAHD had higher anticoagulation than MZM-GAHD. Through electrochemical detection (polarization curves and electrochemical impedance spectroscopy Nyquist spectrum) and immersion test (Mg(2+) concentration and weight loss), it was proved that compared to MZM, both the MZM-GAHD and MZM-HEP-GAHD significantly improved the corrosion resistance. Finally, in vivo experimentation indicated that mass loss had no significant difference between MZM-1:1, MZM-HEP-1:1, and MZM. However, the trend still suggested that MZM-1:1 and MZM-HEP-1:1 possessed corrosion resistance property. PMID:26479205

  13. Experimental investigation of the residues produced in the {sup 136}Xe+Pb and {sup 124}Xe+Pb fragmentation reactions at 1A GeV

    SciTech Connect

    Henzlova, D.; Schmidt, K.-H.; Ricciardi, M. V.; Kelic, A.; Henzl, V.; Pleskac, R.; Yordanov, O.; Napolitani, P.; Benlliure, J.; Casarejos, E.; Kurtukian, T.; Ordonez, M. F.; Pereira, J.; Boudard, A.; Ducret, J. E.; Leray, S.; Villagrasa, C.

    2008-10-15

    The nuclide cross sections and longitudinal velocity distributions of residues produced in the reactions of {sup 136}Xe and {sup 124}Xe at 1A GeV in a lead target were measured at the high-resolution magnetic spectrometer, the fragment separator (FRS) of GSI. The data cover a broad range of isotopes of the elements between Z=3 and Z=56 for {sup 136}Xe and between Z=5 and Z=55 for {sup 124}Xe, reaching down to cross sections of a few microbarns. The velocity distributions exhibit a Gaussian shape for masses above A=20, while more complex behavior is observed for lighter masses. The isotopic distributions for both reactions preserve a memory on the projectile N/Z ratio over the whole residue mass range.

  14. Experimental cross section of the 71Ga(n,γ)72Ga reaction at 0.0334 eV energy

    NASA Astrophysics Data System (ADS)

    Afroze, N.; Uddin, M. S.; Hossain, S. M.; Islam, M. A.; Shariff, M. A.; Zakaria, A. K. M.; Datta, T. K.; Azharul Islam, S. M.

    2014-10-01

    The cross section of the 71Ga(n,γ)72Ga reaction at 0.0334 eV was measured for the first time using monochromatic neutrons from powder diffractometer at TRIGA Mark II nuclear reactor. The 197Au(n,γ)198Au reaction was used to monitor the neutron beam intensity. The HPGe γ-ray spectrometry was used to determine the radioactivity of the product radionuclides. The obtained cross section value amounted 3.42 ± 0.27 b is about 95% consistent with JENDL-4, but about 17% and 14% lower than that of the ENDF/B-VII and TENDL-2012 data libraries, respectively. The measured value at 0.0334 eV and the previous measured value at 0.0536 eV would be useful to confirm the reliability of the data evaluated by 1/v relation in the above libraries.

  15. Experimental evidence suggesting that H2O2 is produced within the thylakoid membrane in a reaction between plastoquinol and singlet oxygen.

    PubMed

    Khorobrykh, Sergey A; Karonen, Maarit; Tyystjärvi, Esa

    2015-03-12

    Plastoquinol (PQH2-9) and plastoquinone (PQ-9) mediate photosynthetic electron transfer. We isolated PQH2-9 from thylakoid membranes, purified it with HPLC, subjected the purified PQH2-9 to singlet oxygen ((1)O2) and analyzed the products. The main reaction of (1)O2 with PQH2-9 in methanol was found to result in formation of PQ-9 and H2O2, and the amount of H2O2 produced was essentially the same as the amount of oxidized PQH2-9. Formation of H2O2 in the reaction between (1)O2 and PQH2-9 may be an important source of H2O2 within the lipophilic thylakoid membrane. PMID:25701589

  16. The bond-forming reaction between CF22+ and H2O/D2O: A computational and experimental study

    NASA Astrophysics Data System (ADS)

    Lambert, Natalie; Kaltsoyannis, Nikolas; Price, Stephen D.

    2003-07-01

    Ground-state stationary points on the potential energy surface of the reaction CF22++H2O→OCF++HF+H+ were calculated using the density-functional theory hybrid method B3LYP and the ab initio coupled cluster singles and doubles with perturbative triples [CCSD(T)] algorithm. The calculations reveal a reaction mechanism involving two transition states. The first transition state involves the migration of one hydrogen within the primary collision complex and the second corresponds to the loss of a proton. The neutral HF molecular product is formed in its stable ground 1Σ state. Comparison of activation energies for the reactions of CF22+ with H2O and with D2O, calculated from Becke three parameter Lee-Yang-Parr (B3LYP) zero-point energies, slightly favor the H2O pathway by 0.04 and 0.07 eV for the first and second activations, respectively. Rate constant calculations using Rice-Ramsperger-Kassel-Marcus/quasiequilibrium theory also kinetically favor the H2O pathway in comparison with the D2O pathway. However, the magnitudes of the calculated rate constants are so large (1012-1014 s-1) that the differences between the rates of reaction of CF22+ with H2O and with D2O should not be distinguished by a crossed-beam time-of-flight mass spectrometer experiment. Indeed, the ion yields reported in this paper from new collision experiments between CF22+ and D2O showed no isotope effect when compared with previous data from collisions of CF22+ with H2O.

  17. Herbert P. Broida Prize Talk: Experimental realization of coherent control of molecular dynamics and chemical reactions with feedback-optimized laser pulses--Quantum Control of Femtochemistry

    NASA Astrophysics Data System (ADS)

    Gerber, Gustav

    2009-05-01

    By using coherent control techniques we control the behavior of quantum systems on their natural fs-time scale by applying ultrashort coherent light fields in the wavelength range from the IR to the UV. These laser pulses can be variably shaped in space and time using a laser pulse shaper consisting of a liquid-crystal display. [1] Laser-optimized femtochemistry in the gas phase and liquid phase is one field in which this new technique is successfully employed. Automated optimization of branching ratios and total product yields of gas phase photodissociation reactions as well as chemically selective molecular excitation in the liquid phase is performed [2][3]. Structural changes of a molecule in the liquid phase have been controlled by laser-optimized photoisomerization of a cyanine dye molecule [4] and of retinal in bacteriorhodopsin [5]. So far, optimal control techniques have been restricted to gas phase and condensed phase optimization experiments. Recently we have demonstrated femtosecond laser-assisted catalytic reactions on a Pd(100) single crystal surface. By applying a closed-loop optimal control scheme, we manipulate these reactions and selectively optimize the ratio of different bond-forming reaction channels, in contrast to previous quantum control experiments aiming at bond-cleavage. The results represent a first step towards selective photocatalysis of molecules. [4pt] [1] T. Baumert et al, Appl. Phys. B 65, 779 (1997)[0pt] [2] A. Assion et al, Science 282, 919(1998); T. Brixner et al, J. Mod. Opt. 50, 539 (2003)[0pt] [3] T. Brixner et al, Nature, Vol. 414, 57 (2001) and J. Chem. Phys. 118, 3692 (2003)[0pt] [4] G. Krampert et al, Phys. Rev. Lett. 94, 068305 (2005)[0pt] [5] G. Vogt et al, Chem. Phys. Lett. 433, 211 (2006) P. Nuernberger et al, Phys. Chem. Chem. Phys. 9, 2470 (2007)

  18. THE FLUORINE DESTRUCTION IN STARS: FIRST EXPERIMENTAL STUDY OF THE {sup 19}F(p, {alpha}{sub 0}){sup 16}O REACTION AT ASTROPHYSICAL ENERGIES

    SciTech Connect

    La Cognata, M.; Spitaleri, C.; Indelicato, I.; Cherubini, S.; Gulino, M.; Kiss, G. G.; Lamia, L.; Pizzone, R. G.; Puglia, S. M. R.; Rapisarda, G. G.; Romano, S.; Mukhamedzhanov, A. M.; Aliotta, M.; Burjan, V.; Hons, Z.; Kroha, V.; Mrazek, J.; Piskor, S.; Coc, A.

    2011-10-01

    The {sup 19}F(p, {alpha}){sup 16}O reaction is an important fluorine destruction channel in the proton-rich outer layers of asymptotic giant branch (AGB) stars and it might also play a role in hydrogen-deficient post-AGB star nucleosynthesis. So far, available direct measurements do not reach the energy region of astrophysical interest (E {sub cm} {approx}< 300 keV), because of the hindrance effect of the Coulomb barrier. The Trojan Horse (TH) method was thus used to access this energy region, by extracting the quasi-free contribution to the {sup 2}H({sup 19}F, {alpha}{sup 16}O)n and the {sup 19}F({sup 3}He, {alpha}{sup 16}O)d reactions. The TH measurement of the {alpha}{sub 0} channel shows the presence of resonant structures not observed before, which cause an increase of the reaction rate at astrophysical temperatures up to a factor of 1.7, with potential consequences for stellar nucleosynthesis.

  19. Theoretical Analyses and Experimental Investigations of Selective Carbothermal Reactions of Vanadium-Bearing Titanomagnetite Concentrates for Preparation of Iron-Based Wear-Resistant Material

    NASA Astrophysics Data System (ADS)

    Zhang, Guangming; Feng, Keqin; Yue, Huifang

    2016-07-01

    Based on FACTSage® software, this paper focuses on the thermodynamic calculations of selective carbothermal reactions of vanadium-bearing titanomagnetite concentrates for preparing iron-based wear-resistant material directly from vanadium-bearing titanomagnetite concentrates. The calculations show that it was most likely to generate metallic iron, titanium carbide and vanadium carbide among all possible carbothermal reactions of vanadium-bearing titanomagnetite concentrates in a vacuum of 10 Pa. The equilibrium composition calculations indicate that Fe3O4 can be reduced to metallic iron by carbon above 400°C, FeTiO3 can be converted into TiC by carbon above 800°C and V2O5 can be converted into VC by carbon above 600°C in a vacuum of 10 Pa. The investigations demonstrated that the percentage of ferrous oxides reduced to metallic iron was about 96%, the conversion percentage of FeTiO3 into TiC was about 75% and the conversion percentage of V2O5 into VC was about 94% after the selective carbothermal reactions of vanadium-bearing titanomagnetite concentrates at 1300°C for 3 h in a vacuum of 10 Pa.

  20. The fluorine destruction in stars: First experimental study of the {sup 19}F(p,{alpha}){sup 16}O reaction at astrophysical energies

    SciTech Connect

    La Cognata, M.; Mukhamedzhanov, A.; Spitaleri, C.; Indelicato, I.; Aliotta, M.; Burjan, V.; Cherubini, S.; Coc, A.; Gulino, M.; Hons, Z.; Kiss, G. G.; Kroha, V.; Lamia, L.; Mrazek, J.; Palmerini, S.; Piskor, S.; Pizzone, R. G.; Puglia, S. M. R.; Rapisarda, G. G.; Romano, S.; and others

    2012-11-12

    The {sup 19}F(p,{alpha}){sup 16}O reaction is an important fluorine destruction channel in the proton-rich outer layers of asymptotic giant branch (AGB) stars and it might also play a role in hydrogendeficient post-AGB star nucleosynthesis. So far, available direct measurements do not reach the energy region of astrophysical interest (E{sub cm}{approx} 300 keV), because of the hindrance effect of the Coulomb barrier. The Trojan Horse (TH) method was thus used to access this energy region, by extracting the quasi-free contribution to the {sup 2}H({sup 19}F,{alpha}{sup 16}O)n reaction. The TH measurement of the {alpha}{sub 0} channel, which is the dominant one at such energies, shows the presence of resonant structures not observed before that cause an increase of the reaction rate at astrophysical temperatures up to a factor of 1.7, with potential important consequences for stellar nucleosynthesis.

  1. Experimental determination of the {sup 17}O(p,{alpha}){sup 14}N and {sup 17}O(p,{gamma}){sup 18}F reaction rates

    SciTech Connect

    Chafa, A.; Ouichaoui, S.; Tatischeff, V.; Coc, A.; Garrido, F.; Kiener, J.; Lefebvre-Schuhl, A.; Thibaud, J.-P.; Aguer, P.; Barhoumi, S.; Hernanz, M.; Jose, J.; Sereville, N. de

    2007-03-15

    The {sup 17}O(p,{alpha}){sup 14}N and {sup 17}O(p,{gamma}){sup 18}F reactions are of major importance to hydrogen-burning nucleosynthesis in a number of different stellar sites. In particular, {sup 17}O and {sup 18}F nucleosynthesis in classical novae is strongly dependent on the thermonuclear rates of these two reactions. The previously estimated rate for {sup 17}O(p,{alpha}){sup 14}N carries very large uncertainties in the temperature range of classical novae (T=0.01-0.4 GK), whereas a recent measurement has reduced the uncertainty of the {sup 17}O(p,{gamma}){sup 18}F rate. We report on the observation of a previously undiscovered resonance at E{sub c.m.}=183.3 keV in the {sup 17}O(p,{alpha}){sup 14}N reaction, with a measured resonance strength {omega}{gamma}{sub p{alpha}}=(1.6{+-}0.2)x10{sup -3} eV. We studied in the same experiment the {sup 17}O(p,{gamma}){sup 18}F reaction by an activation method, and the resonance strength was found to amount to {omega}{gamma}{sub p{gamma}}=(2.2{+-}0.4)x10{sup -6} eV. The excitation energy of the corresponding level in {sup 18}F was determined to be 5789.8{+-}0.3 keV in a Doppler shift attenuation method measurement, which yielded a value of {tau}<2.6 fs for the level lifetime. The {sup 17}O(p,{alpha}){sup 14}N and {sup 17}O(p,{gamma}){sup 18}F reaction rates were calculated using the measured resonance properties and reconsidering some previous analyses of the contributions of other levels or processes. The {sup 17}O(p,{alpha}){sup 14}N rate is now well established below T=1.5 GK, with uncertainties reduced by orders of magnitude in the temperature range T=0.1-0.4 GK. The uncertainty in the {sup 17}O(p,{gamma}){sup 18}F rate is somewhat larger because of remaining obscurities in the knowledge of the direct capture process. These new resonance properties have important consequences for {sup 17}O nucleosynthesis and {gamma}-ray emission of classical novae.

  2. Asking for work adjustments or initiating behavioural changes - what makes a 'problematic co-worker' score Brownie points? An experimental study on the reactions towards colleagues with a personality disorder.

    PubMed

    Muschalla, Beate; Fay, Doris; Seemann, Anne

    2016-10-01

    People with mental disorders, especially personality disorders, often face low acceptance at work. This is particularly problematic when returning to work after sick leave, because it impedes reintegration into the former workplace. This study explores colleagues' reactions towards a problematic worker dependent on the returning person's reintegration strategy: The returning person undertaking changes in their behaviour is compared with the person requesting adjustments of the workplace. In an experimental study, 188 employed persons read one of four vignettes that described a return-to-work-situation of a problematic co-worker. Across all vignettes, the co-worker was depicted as having previously caused problems in the work team. In the first vignette, the co-worker did not change anything (control condition) when she returned to work; in the second, she asked for workplace adjustments; in the third vignette she initiated efforts to change her own behaviour; and the fourth vignette combined both workplace adjustments and behavioural change. Study participants were asked for their reactions towards the problematic co-worker. Vignettes that included a behavioural change evoked more positive reactions towards the co-worker than vignettes without any behavioural change. Asking for workplace adjustments alone did not yield more positive reactions compared to not initiating any change. When preparing employees with interactional problems for their return to work, it is not effective to only instruct them on their statutory entitlement for workplace adjustments. Instead, it is advisable to encourage them to proactively strive for behaviour changes. PMID:26567587

  3. Reactions of laser-ablated Nb and Ta atoms with N2: experimental and theoretical study of M(NN)x (M = Nb, Ta; x = 1-4) in solid neon.

    PubMed

    Lu, Zhang-Hui; Jiang, Ling; Xu, Qiang

    2010-07-01

    Reactions of laser-ablated niobium and tantalum atoms with dinitrogen in solid neon have been investigated using matrix-isolation infrared spectroscopy. The Nb(NN)(x) and Ta(NN)(x) (x = 1-4) molecules formed during sample deposition or on annealing are the major products. The products are characterized on the basis of isotopic shifts, mixed isotopic splitting patterns, stepwise annealing, and change of reagent concentration and laser energy. Density functional theory calculations have been performed to understand the structures, ground electronic states, and bonding characteristics of niobium and tantalum dinitrogen complexes. The overall agreement between the experimental and calculated vibrational frequencies, relative absorption intensities, and isotopic shifts supports the identification of these species from the matrix infrared spectra. The molecular orbital analyses and plausible reaction pathways for the formation of the products are also discussed. PMID:20527869

  4. Reform of Reaction? An Experimental Analysis of the Effectiveness of "Power-Based" Strategies for Eliminating Sex Bias in California Schools. A Report.

    ERIC Educational Resources Information Center

    McDonald, Scott C.

    By means of a literature search and data from the California Coalition for Sex Equity in Education (CCSEE) questionnaire (the Title IX Implementation Assessment Instrument), this report presents the findings a 2-year (1978-80) study of sex bias and Title IX compliance in California at 23 experimental and 13 control school districts. The report…

  5. Experimental Validation of a Nested Polymerase Chain Reaction Targeting the Genetic Element ISMAP02 for Detection of Mycobacterium avium subspecies paratuberculosis in Bovine Colostrum

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Colostrum samples experimentally inoculated with Mycobacterium avium subsp. paratuberculosis (MAP) (strain K-10) at increasing concentrations between 1×10**1 and 1× 10**9 cells/mL were tested for recovery of MAP DNA using a modified nested ISMAP02 target PCR initially developed for detecting MAP DNA...

  6. Improving the cellular invasion into PHEMA sponges by incorporation of the RGD peptide ligand: the use of copolymerization as a means to functionalize PHEMA sponges.

    PubMed

    Paterson, Stefan M; Shadforth, Audra M A; Shaw, Jeremy A; Brown, David H; Chirila, Traian V; Baker, Murray V

    2013-12-01

    A monomer that contained the RGD ligand motif was synthesized and copolymerized with 2-hydroxyethyl methacrylate using polymerization-induced phase separation methods to form poly(2-hydroxyethyl methacrylate)-based hydrogel sponges. The sponges had morphologies of aggregated polymer droplets and interconnected pores, the pores having dimensions in the order of 10 μm typical of PHEMA sponges. RGD-containing moieties appeared to be evenly distributed through the polymer droplets. Compared to PHEMA sponges that were not functionalized with RGD, the new sponges containing RGD allowed greater invasion by human corneal epithelial cells, by advancing the attachment of cells to the surface of the polymer droplets. PMID:24094205

  7. Experimental investigations of certain side reactions and the initial voltage transient for FeS/sub 2/ cathodes in thermal batteries

    SciTech Connect

    Searcy, J. Q.; Delnick, F. M.; D'Angelo, J. C.

    1981-02-01

    The direct reaction of FeS/sub 2/ with stainless steel current collectors reduces the coulombic efficiency of thermal cell cathodes. When single cells are discharged in air, the reduction of O/sub 2/ at the FeS/sub 2/ cathode represents a significant fraction of the discharge current. At least five separate phenomena contribute to the initial voltage transient observed in thermal batteries which use FeS/sub 2/ for the cathode material. These five phenomena are: (1) a thermodynamic increase in the potential caused by the initial temperature peak which results from the heat pellets when ignited, (2) electrochemical participation of surface contaminants on the FeS/sub 2/, (3) electrochemical reduction of oxygen or reaction products of oxygen with FeS/sub 2/, (4) electrochemical reduction of elemental sulfur produced by the thermal decomposition of FeS/sub 2/, and (5) the voltage decrease which accompanies the saturation of the electrolyte with the electrochemical reduction product, or products. Mitigative techniques for the observed phenomena include: (1) performing single cell tests under an inert atmosphere, (2) using a nonreactive material for current collectors, (3) using an additive with the cathode to suppress the initial voltage transient, and (4) predischarging the cathodes.

  8. A Combined Experimental and Computational Investigation on the Unusual Molecular Mechanism of the Lossen Rearrangement Reaction Activated by Carcinogenic Halogenated Quinones

    PubMed Central

    2015-01-01

    The classic Lossen rearrangement is a well-known reaction describing the transformation of an O-activated hydroxamic acid into the corresponding isocyanate. In this study, we found that chlorinated benzoquinones (CnBQ) serve as a new class of agents for the activation of benzohydroxamic acid (BHA), leading to Lossen rearrangement. Compared to the classic one, this new kind of CnBQ-activated Lossen rearrangement has the following unique characteristics: (1) The stability of CnBQ-activated BHA intermediates was found to depend not only on the degree but also on the position of Cl-substitution on CnBQs, which can be divided into two subgroups. (2) It is the relative energy of the anionic CnBQ–BHA intermediates that determine the rate of this CnBQ-activated rearrangement, which is the rate-limiting step, and the Cl or H ortho to the reaction site at CnBQ is crucial for the stability of the anionic intermediates. (3) A pKa–activation energy correlation was observed, which can explain why the correlation exists between the rate of the rearrangement and the acidity of the conjugate acid of the anionic leaving group, the hydroxlated quinones. These findings may have broad implications for future research on halogenated quinoid carcinogens and hydroxamate biomedical agents. PMID:25470188

  9. First result of the experimental search for the 9.4 keV solar axion reactions with 83Kr in the copper proportional counter

    NASA Astrophysics Data System (ADS)

    Gavrilyuk, Yu. M.; Gangapshev, A. M.; Derbin, A. V.; Kazalov, V. V.; Kim, H. J.; Kim, Y. D.; Kobychev, V. V.; Kuzminov, V. V.; Ali, Luqman; Muratova, V. N.; Panasenko, S. I.; Ratkevich, S. S.; Semenov, D. A.; Tekueva, D. A.; Yakimenko, S. P.; Unzhakov, E. V.

    2015-03-01

    The experimental search for solar hadronic axions is started at the Baksan Neutrino Observatory of the Institute for Nuclear Researches of Russian Academy of Science (BNO INR RAS). It is assumed that axions are created in the Sun during M1 transition between the first thermally excited level at 9.4 keV and the ground state in 83Kr. The experiment is based on axion detection via resonant absorption process by the same nucleus in the detector. The big copper proportional counter filled with krypton is used to detect signals from axions. The experimental setup is situated in the deep underground low background laboratory. No evidence of axion detection were found after the 26.5 days data collection. Resulting new upper limit on axion mass is m A ≤ 130 eV at 95% C.L.

  10. Synthesis and characterization of sulfonated poly (arylene ether sulfone) copolymers via direct copolymerization: Candidates for proton exchange membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Harrison, William Lamont

    A designed series of directly copolymerized homo- and disulfonated copolymers containing controlled degrees of pendant sulfonic acid groups have been synthesized via nucleophilic step polymerization. Novel sulfonated poly (arylene ether sulfone) copolymers using 4,4'-bisphenol A, 4,4'-biphenol, hexafluorinated (6F) bisphenol AF, and hydroquinone, respectively, with dichlorodiphenyl sulfone (DCDPS) and 3,3'-disodiumsulfonyl-4,4'-dichlorodiphenylsulfone (SDCDPS) were investigated. Molar ratios of DCDPS and SDCDPS were systematically varied to produce copolymers of controlled compositions, which contained up to 70 mol% of disulfonic acid moiety. The goal is to identify thermally, hydrolytically, and oxidatively stable high molecular weight, film-forming, ductile ion conducting copolymers, which had properties desirable for proton exchange membranes (PEM) in fuel cells. Commercially available bisphenols were selected to produce cost effective alternative PEMs. Partially aliphatic bisphenol A and hexafluorinated (6F) bisphenol AF produced amorphous copolymers with different thermal oxidative and surface properties. Biphenol and hydroquinone was utilized to produce wholly aromatic copolymers. The sulfonated copolymers were prepared in the sodium-salt form and converted to the acid moiety via two different methodologies and subsequently investigated as proton exchange membranes for fuel cells. Hydrophilicity increased with the level of disulfonation, as expected. Moreover, water sorption increased with increasing mole percent incorporation of SDCDPS. The copolymers' water uptake was a function of both bisphenol structure and degree of disulfonation. Furthermore, the acidification procedures were shown to influence the Tg values, water uptake, and conductivity of the copolymers. Atomic force microscopy (AFM) in the tapping mode confirmed that the morphology of the copolymers could be designed to display nanophase separation in the hydrophobic and hydrophilic (sulfonated

  11. Experimental study of the halo nucleus {sup 6}He using the {sup 6}Li({gamma},{pi}{sup +}){sup 6}He reaction

    SciTech Connect

    Harrington, N. P.; Branford, D.; Foehl, K.; Roche, E.; Annand, J. R. M.; Livingston, K.; McGreorge, J. C.; MacGregor, I. J. D.; Monstad, K.; Waddell, S.; Watts, D. P.; Beck, R.; Hornidge, D.; Reiter, A.; Grabmayr, P.; Hehl, T.; Martin, I.; Moschini, F.; Young, S.

    2007-04-15

    The reaction {sup 6}Li({gamma},{pi}{sup +}){sup 6}He was studied over the angular range {theta}{sub {pi}}=40-150 degree sign with the aim of investigating the halo structure of {sup 6}He. Photons from a bremsstrahlung beam were tagged in the energy range E{sub {gamma}}=170-220 MeV at a resolution of {delta}E{sub {gamma}}=630 keV, and positively charged pions detected using high resolution stacked HpGe detectors. The measured angular distributions for the resolved {sup 6}He ground and 1.80 MeV excited states are compared to previous measurements and theoretical calculations based on the impulse approximation. It is deduced that the ground state rms radius of the {sup 6}He nucleus may be larger than previously thought and that the first excited 1.80 MeV state may also be a halo state.

  12. Copolymeric hexyl acrylate-methacrylic acid microspheres - surface vs. bulk reactive carboxyl groups. Coulometric and colorimetric determination and analytical applications for heterogeneous microtitration.

    PubMed

    Stelmach, Emilia; Maksymiuk, Krzysztof; Michalska, Agata

    2016-10-01

    Copolymeric acrylate microspheres were prepared from hexyl acrylate using different amounts of methacrylic acid, resulting in a series of microspheres of gradually changing properties. The distribution of carboxyl groups - between surface and bulk of microspheres was evaluated. Bulk reactive carboxyl groups were determined using reverse coulometric titration with H(+) ions, following hydroxide ions have been generated and allowed to react with microspheres in the first step. It was found that the number of reactive carboxyl groups available in copolymeric microspheres is lower compared to number of methacrylic acid units used for polymerization process. Moreover, there is correlation between the number of groups introduced and found to be reactive in microspheres. On the other hand, the number of surface reactive groups was proportional to the number of groups introduced in course of polymerization. Thus, the surface reactive groups can be used as reagent, in novel heterogeneous microtitration procedure, in which a constant number of microspheres of different carboxyl groups contents is introduced to the sample to react with the analyte. The applicability of novel proposed method was tested on the example of Ni(2+) determination. PMID:27474305

  13. Reaction between H2, CO, and H2S over Fe,Ni metal in the solar nebula: Experimental evidence for the formation of sulfur-bearing organic molecules and sulfides

    NASA Astrophysics Data System (ADS)

    Llorca, Jordi; Casanova, Ignasi

    2000-07-01

    Detailed laboratory studies have been carried out in order to simulate the interaction between nanometer-sized kamacite metal particles and different gas mixtures consisting of H2:H2S (250:0.1), H2:CO (250:1) and H2:CO:H2S (250:1:0.1) under nebular-type conditions (5x10-4 atm and 473 K). Reaction of H2+H2S with kamacite particles for 1000 h leads to the formation of pyrrhotite. Incorporation of CO into the gaseous reactant mixture results in the formation of both sulfide and carbide phases. At the same time, amorphous carbon is deposited onto the metal particles and organic molecules are evolved, namely hydrocarbons and thiols in the C1-C5 and C1-C2 range, respectively. Carbon deposition and production of organics are enhanced with respect to experiments performed with H2+CO, where a carbide phase is formed. There is no evidence for the existence of sulfur poisoning effects on the metal-catalysed hydrogenation of CO through Fischer-Tropsch-type reactions in nebular environments. In fact, it is experimentally demonstrated that sulfur-containing organic species could be synthesized by such reactions from nebular gas.

  14. An experimental evaluation of the reaction of granite with streamwater, seawater and NaCl solutions at 200°C

    NASA Astrophysics Data System (ADS)

    Savage, David; Bateman, Keith; Milodowski, Antoni E.; Hughes, Colin R.

    1993-10-01

    Experiments reacting granite with streamwater, seawater, and NaCl solutions have been conducted at 200°C, 50 MPa under batch conditions using direct-sampling autoclaves for durations up to 80 days. Granite-streamwater experiments at 10:1 and 2:1 water/rock ratios produced fluids of low TDS (<600 mg/l), alkaline pH (=9.2), with the solute load dominated by dissolved silica. Solid products of these experiments were a Ca-zeolite and a clay which ranged in composition from aluminous smectite to illite in the 2:1 water/rock ratio experiment. Clay in the 10:1 water/rock ratio experiment was an aluminous smectite. The difference in water/rock ratio of the experiments manifested itself in the rate of change of concentration with time (higher in the lower water/rock ratio experiment), and in the type and amount of solid products: more clay of a homogeneous composition was produced in the higher water/rock ratio experiment, and less zeolite. The amount of clay precipitated was directly related to the amount of Mg present in the initial system. The reaction of granite with seawater produced a fluid of low pH (≈ 3.5), and principal changes in the fluid chemistry as follows: a gain of SiO 2; and losses of sulphate, magnesium, and calcium. Appreciable mobilisation of heavy metals into the fluid phase such as Fe (up to 15 mg/l) and Mn (up to 2 mg/l) were noted. Solid precipitates consisted of anhydrite, caminite (magnesium hydroxide sulphate hydrate) and a mixed-layer smectite-chlorite clay. The low pH of the evolved fluid is attributed to the precipitation of the hydroxyl-consuming mineral phases, caminite and the smectite-chlorite clay. The reaction of granite with NaCl solutions (0.008 and 0.028 M) produced fluids which were similar to those of the streamwater experiments. However, pH was lower in the NaCl experiments (=7.4-7.8), so that the steady-state concentrations of a number of the cationic constituents of the fluids were slightly greater in these experiments compared

  15. Atmospheric fate of nitramines: an experimental and theoretical study of the OH reactions with CH3NHNO2 and (CH3)2NNO2.

    PubMed

    Maguta, Mihayo Musabila; Aursnes, Marius; Bunkan, Arne Joakim Coldevin; Edelen, Katie; Mikoviny, Tomáš; Nielsen, Claus Jørgen; Stenstrøm, Yngve; Tang, Yizhen; Wisthaler, Armin

    2014-05-15

    The rates of CH3NHNO2 and (CH3)2NNO2 reaction with OH radicals were determined relative to CH3OCH3 and CH3OH at 298 ± 2 K and 1013 ± 10 hPa in purified air by long path FTIR spectroscopy, and the rate coefficients were determined to be k(OH+CH3NHNO2) = (9.5 ± 1.9) × 10(-13) and k(OH+(CH3)2NNO2) = (3.5 ± 0.7) × 10(-12) (2σ) cm(3) molecule(-1) s(-1). Ozone was found to react very slowly with the two nitramines, k(O3+nitramine) < 10(-21) cm(3) molecule(-1) s(-1). Product formation in the photo-oxidation of CH3NHNO2 and (CH3)2NNO2 was studied by FTIR, PTR-ToF-MS, and quantum chemistry calculations; the major products in the OH-initiated degradation are the corresponding imines, CH2═NH and CH3N═CH2, and N-nitro amides, CHONHNO2 and CHON(CH3)NO2. Atmospheric degradation mechanisms are presented. PMID:24766577

  16. Experimental and density functional theoretical study of the effects of Fenton's reaction on the degradation of Bisphenol A in a high voltage plasma reactor.

    PubMed

    Dai, Fei; Fan, Xiangru; Stratton, Gunnar R; Bellona, Christopher L; Holsen, Thomas M; Crimmins, Bernard S; Xia, Xiaoyan; Mededovic Thagard, Selma

    2016-05-01

    A novel electrical discharge plasma reactor configuration with and without iron ions was evaluated for the degradation of 0.02 mM Bisphenol A (BPA). The pseudo-first-order reaction rate constant calculated for the plasma treatment of BPA with a stainless steel electrode in the presence of dissolved ferrous ion (Fe(2+)) salts (termed plasma/Fenton treatment) was higher than in the plasma treatment in the absence of iron salts. At the optimal ferrous ion concentration, longer plasma treatment times resulted in higher BPA degradation rates, likely due to increased hydroxyl (OH) radical concentration formed through the decomposition of H2O2. Replacing the stainless steel with a carbon steel grounded electrode resulted in the release of iron ions from the carbon steel thereby increasing the rate of BPA removal and eliminating the need for iron salts. After the plasma/Fenton treatment, >97% of the residual iron salts were removed by coagulation/flocculation/sedimentation. Byproduct identification coupled with density functional theory (DFT) calculations confirmed that OH radical attack on BPA's hydroxyl group is the primary pathway for byproduct formation. PMID:26874105

  17. Experimental identification of the active sites in pyrolyzed carbon-supported cobalt-polypyrrole-4-toluenesulfinic acid as electrocatalysts for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Sha, Hao-Dong; Yuan, Xianxia; Li, Lin; Ma, Zhong; Ma, Zi-Feng; Zhang, Lei; Zhang, Jiujun

    2014-06-01

    A series of carbon supported cobalt-polypyrrole-4-toluenesulfinic acid have been pyrolyzed in an argon atmosphere at 800 °C, then structurally characterized and electrochemically evaluated as oxygen reduction reaction (ORR) catalysts in aqueous 0.5 M sulfuric acid. The structures are cobalt bonded to nitrogen species (Co-Nx) along with metallic cobalt and cobalt oxide. When the cobalt loading in the compound is less than 1.0 wt%, the predominate form is Co-Nx, when the loading is higher than 1.0 wt%, metallic Co and Co oxide particles co-exist with the Co-Nx compound. At a Co loading of ∼1.0 wt%, the catalyst gives the best ORR activity. Both metallic Co and Co oxide are not active for catalyzing ORR, and block the catalytically active Co-Nx species from the surface and reduce the catalytic activity since the diffusion limiting current density on a rotating disk electrode (RDE) increases when the electrode blocking agents are washed away with acid.

  18. Mushroom tyrosinase: A model system to combine experimental investigation of enzyme-catalyzed reactions, data handling using R, and enzyme-inhibitor structural studies.

    PubMed

    Nairn, Robert; Cresswell, Will; Nairn, Jacqueline

    2015-01-01

    The activity of mushroom tyrosinase can be measured by monitoring the conversion of phenolic compounds into quinone derivatives using spectrophotometry. This article describes a series of experiments which characterize the functional properties of tyrosinase, the analysis of the resulting data using R to determine the kinetic parameters, and the exploration of the structural properties of tyrosinase-inhibitor complexes. Tyrosinase assay development and subsequent activity measurements, in the presence of varying pH, substrate concentration and inhibitors, offers the opportunity to learn the enzyme characterization skills relevant to a research laboratory setting. Combining the activity studies with an exploration of the nature of the tyrosinase-inhibitor interactions enables a structural understanding of the experimental observations. PMID:26331629

  19. The 18Ne(α,p)21Na breakout reaction in x-ray bursts: Experimental determination of spin-parities for α resonances in 22Mg via resonant elastic scattering of 21Na+p

    NASA Astrophysics Data System (ADS)

    He, J. J.; Zhang, L. Y.; Parikh, A.; Xu, S. W.; Yamaguchi, H.; Kahl, D.; Kubono, S.; Hu, J.; Ma, P.; Chen, S. Z.; Wakabayashi, Y.; Sun, B. H.; Wang, H. W.; Tian, W. D.; Chen, R. F.; Guo, B.; Hashimoto, T.; Togano, Y.; Hayakawa, S.; Teranishi, T.; Iwasa, N.; Yamada, T.; Komatsubara, T.

    2013-07-01

    The 18Ne(α,p)21Na reaction provides a pathway for breakout from the hot CNO cycles to the rp process in type-I x-ray bursts. To better determine this astrophysical reaction rate, the resonance parameters of the compound nucleus 22Mg have been investigated by measuring the resonant elastic scattering of 21Na+p. An 89 MeV 21Na radioactive ion beam was produced at the CNS Radioactive Ion Beam Separator and bombarded an 8.8 mg/cm2 thick polyethylene target. The recoiled protons were measured at scattering angles of θc.m.≈175∘ and 152∘ by three ΔE-E silicon telescopes. The excitation function was obtained with a thick-target method over energies Ex(22Mg) = 5.5-9.2 MeV. The resonance parameters have been determined through an R-matrix analysis. For the first time, the Jπ values for ten states above the α threshold in 22Mg have been experimentally determined in a single consistent measurement. We have made three new Jπ assignments and confirmed seven of the ten tentative assignments in the previous work. The 18Ne(α,p)21Na reaction rate has been recalculated, and the astrophysical impact of our new rate has been investigated through one-zone postprocessing x-ray burst calculations. We find that the 18Ne(α,p)21Na rate significantly affects the peak nuclear energy generation rate and the onset temperature of this breakout reaction in these phenomena.

  20. Jets in hadronic reactions

    SciTech Connect

    Paige, F.E.

    1983-01-01

    Recent experimental data on the properties of jets in hadronic reactions are reviewed and compared with theoretical expectations. Jets are clearly established as the dominant process for high E/sub T/ events in hadronic reactions. The cross section and the other properties of these events are in qualitative and even semiquantitative agreement with expectations based on perturbative QCD. However, we can not yet make precise tests of QCD, primarily because there are substantial uncertainties in the theoretical calculations. 45 references. (WHK)

  1. ''Subthreshold'' reactions involving nuclear fission

    SciTech Connect

    Goldhaber, M.; Shrock, R.

    2001-02-01

    We analyze reactions of several types that are naively below threshold but can proceed because of the release of binding energy from nuclear fission and occasionally the formation of Coulombic bound states. These reactions include (i) photofission with pion production and (ii) charged current neutrino-nucleus reactions that lead to fission and/or formation of a Coulomb bound state of a {mu}{sup -} with the nucleus of a fission fragment. We comment on the possible experimental observation of these reactions.

  2. Proposal for New Experimental Tests of the Bose-Einstein Condensation Mechanism for Low-Energy Nuclear Reaction and Transmutation Processes in Deuterium Loaded - and Nano-Scale Cavities

    NASA Astrophysics Data System (ADS)

    Kim, Yeong E.; Koltick, David S.; Reifenberger, Ronald G.; Zubarev, Alexander L.

    2006-02-01

    Most of experimental results of low-energy nuclear reaction (LENR) reported so far cannot be reproduced on demand. There have been persistent experimental results indicating that the LENR and transmutation processes in condensed matters (LENRTPCM) are surface phenomena rather than bulk phenomena. Recently proposed Bose-Einstein condensation (BEC) mechanism may provide a suitable theoretical description of the surface phenomena. New experiments are proposed and described for testing the BEC mechanism for LENR and transmutation processes in micro- and nano-scale traps. (1) We propose the use of micro- or nano-porous conducting materials as a cathode in electrolysis experiments with heavy water with or without Li in order to stabilize the active surface spots and to enhance the effect for the purpose of improving the reproducibility of excess heat generation and nuclear emission. (2) We propose new experimental tests of the BEC mechanism by measuring the pressure and temperature dependence of LENR events using deuterium gas and these deuterated metals with or without Li. If the LENRTPCM are surface phenomena, the proposed use of micro-/nano-scale porous materials is expected to enhance and scale up the LENRTPCM effects by many order of magnitude, and thus may lead to better reproductivity and theoretical understanding of the phenomena.

  3. A non-humanoid robot in the "uncanny valley": experimental analysis of the reaction to behavioral contingency in 2-3 year old children.

    PubMed

    Yamamoto, Kentaro; Tanaka, Saori; Kobayashi, Hiromi; Kozima, Hideki; Hashiya, Kazuhide

    2009-01-01

    Infants' sensitivity to social or behavioral contingency has been examined in the field of developmental psychology and behavioral sciences, mainly using a double video paradigm or a still face paradigm. These studies have shown that infants distinguish other individuals' contingent behaviors from non-contingent ones. The present experiment systematically examined if this ability extends to the detection of non-humanoids' contingent actions in a communicative context. We examined two- to three-year-olds' understanding of contingent actions produced by a non-humanoid robot. The robot either responded contingently to the actions of the participants (contingent condition) or programmatically reproduced the same sequence of actions to another participant (non-contingent condition). The results revealed that the participants exhibited different patterns of response depending on whether or not the robot responded contingently. It was also found that the participants did not respond positively to the contingent actions of the robot in the earlier periods of the experimental sessions. This might reflect the conflict between the non-humanlike appearance of the robot and its humanlike contingent actions, which presumably led the children to experience the uncanny valley effect. PMID:19759818

  4. Low-dose benznidazole treatment results in parasite clearance and attenuates heart inflammatory reaction in an experimental model of infection with a highly virulent Trypanosoma cruzi strain.

    PubMed

    Cevey, Ágata Carolina; Mirkin, Gerardo Ariel; Penas, Federico Nicolás; Goren, Nora Beatriz

    2016-04-01

    Chagas disease, caused by Trypanosoma cruzi, is the main cause of dilated cardiomyopathy in the Americas. Antiparasitic treatment mostly relies on benznidazole (Bzl) due to Nifurtimox shortage or unavailability. Both induce adverse drug effects (ADE) of varied severity in many patients, leading to treatment discontinuation or abandonment. Since dosage may influence ADE, we aimed to assess Bzl efficacy in terms of parasiticidal and anti-inflammatory activity, using doses lower than those previously reported. BALB/c mice infected with the T. cruzi RA strain were treated with different doses of Bzl. Parasitaemia, mortality and weight change were assessed. Parasite load, tissue infiltrates and inflammatory mediators were studied in the heart. Serum creatine kinase (CK) activity was determined as a marker of heart damage. The infection-independent anti-inflammatory properties of Bzl were studied in an in vitro model of LPS-treated cardiomyocyte culture. Treatment with 25 mg/kg/day Bzl turned negative the parasitological parameters, induced a significant decrease in IL-1β, IL-6 and NOS2 in the heart and CK activity in serum, to normal levels. No mortality was observed in infected treated mice. Primary cultured cardiomyocytes treated with Bzl showed that inflammatory mediators were reduced via inhibition of the NF-κB pathway. A Bzl dose lower than that previously reported for treatment of experimental Chagas disease exerts adequate antiparasitic and anti-inflammatory effects leading to parasite clearance and tissue healing. This may be relevant to reassess the dose currently used for the treatment of human Chagas disease, aiming to minimize ADE. PMID:26862474

  5. Low-dose benznidazole treatment results in parasite clearance and attenuates heart inflammatory reaction in an experimental model of infection with a highly virulent Trypanosoma cruzi strain

    PubMed Central

    Cevey, Ágata Carolina; Mirkin, Gerardo Ariel; Penas, Federico Nicolás; Goren, Nora Beatriz

    2015-01-01

    Chagas disease, caused by Trypanosoma cruzi, is the main cause of dilated cardiomyopathy in the Americas. Antiparasitic treatment mostly relies on benznidazole (Bzl) due to Nifurtimox shortage or unavailability. Both induce adverse drug effects (ADE) of varied severity in many patients, leading to treatment discontinuation or abandonment. Since dosage may influence ADE, we aimed to assess Bzl efficacy in terms of parasiticidal and anti-inflammatory activity, using doses lower than those previously reported. BALB/c mice infected with the T. cruzi RA strain were treated with different doses of Bzl. Parasitaemia, mortality and weight change were assessed. Parasite load, tissue infiltrates and inflammatory mediators were studied in the heart. Serum creatine kinase (CK) activity was determined as a marker of heart damage. The infection-independent anti-inflammatory properties of Bzl were studied in an in vitro model of LPS-treated cardiomyocyte culture. Treatment with 25 mg/kg/day Bzl turned negative the parasitological parameters, induced a significant decrease in IL-1β, IL-6 and NOS2 in the heart and CK activity in serum, to normal levels. No mortality was observed in infected treated mice. Primary cultured cardiomyocytes treated with Bzl showed that inflammatory mediators were reduced via inhibition of the NF-κB pathway. A Bzl dose lower than that previously reported for treatment of experimental Chagas disease exerts adequate antiparasitic and anti-inflammatory effects leading to parasite clearance and tissue healing. This may be relevant to reassess the dose currently used for the treatment of human Chagas disease, aiming to minimize ADE. PMID:26862474

  6. Experimental study of the dynamics of the H+D2 --> HD+D reaction at collision energies of 0.55 and 1.30 eV

    NASA Astrophysics Data System (ADS)

    Gerrity, Daniel P.; Valentini, James J.

    1984-08-01

    We report here experimental measurement of the nascent HD product quantum state distributions for the H+D2 → HD+D reaction. Pulsed laser photolysis of HI in an HI/D2 gas mixture produces hydrogen atoms giving H+D2 collision energies of 0.55 and 1.30 eV. Nanosecond-time-resolved coherent anti-Stokes Raman scattering (CARS) spectroscopy is used to record rotationally and vibrationally resolved spectra of the HD reaction product under nearly single-collision conditions. The spectra are analyzed to determine the nascent, single-collision HD product quantum state distributions. These distributions are compared to the results of related experiments by E. E. Marinero, C. T. Rettner, and R. N. Zare and to the results of recent quasiclassical trajectory calculations of N. C. Blais and D. G. Truhlar. Our results are in qualitative agreement with those of Marinero et al., but there are some quantitative differences. The trajectory calculations yield HD quantum state distributions which are very close to those we have measured. We find that our HD product quantum state distributions are fairly well summarized by a linear surprisal analysis with a rotational surprisal of 3.0 and a vibrational surprisal of 2.6. The quantum state distributions indicate that 71%±1% of the energy available to the products appears in translation, while 19%±2% is in HD rotation, and 10%±2% is in vibration. These results are discussed in terms of the dynamics of the reaction.

  7. An experimental guided-ion-beam and ab initio study of the ion-molecule gas-phase reactions between Li{sup +} ions and iso-C{sub 3}H{sub 7}Cl in their ground electronic state

    SciTech Connect

    Lucas, J. M.; Andres, J. de; Sogas, J.; Alberti, M.; Aguilar, A.; Bofill, J. M.; Bassi, D.; Ascenzi, D.; Tosi, P.

    2009-07-14

    Reactive collisions between Li{sup +} ions and i-C{sub 3}H{sub 7}Cl molecules have been studied in the 0.20-12.00 eV center-of-mass energy range using an octopole radio frequency guided-ion beam apparatus recently developed in our laboratory. At low collision energies, dehydrohalogenation reactions giving rise to Li(C{sub 3}H{sub 6}){sup +} and Li(HCl){sup +} are the main reaction channels, while at higher ones C{sub 3}H{sub 7}{sup +} and C{sub 2}H{sub 3}{sup +} become dominant, all their reactive cross sections having been measured as a function of the collision energy. To obtain information about the potential energy surfaces (PESs) on which the reactive processes take place, ab initio calculations at the MP2 level have been performed. For dehydrohalogenations, the reactive ground singlet PES shows ion-molecule adduct formation in both the reactant and product sides of the surface. Following the minimum energy path connecting both minima, an unstable intermediate and the corresponding barriers, both lying below the reactant's energy, have been characterized. The entrance channel ion-molecule adduct is also involved in the formation of C{sub 3}H{sub 7}{sup +}, which then generates C{sub 2}H{sub 3}{sup +} via an CH{sub 4} unimolecular elimination. A qualitative interpretation of the experimental results based on ab initio calculations is also included.

  8. Isoprene-styrene chain shuttling copolymerization mediated by a lanthanide half-sandwich complex and a lanthanidocene: straightforward access to a new type of thermoplastic elastomers.

    PubMed

    Valente, Andreia; Stoclet, Gregory; Bonnet, Fanny; Mortreux, André; Visseaux, Marc; Zinck, Philippe

    2014-04-25

    A lanthanide half-sandwich complex and a ansa lanthanidocene have been assessed for isoprene-styrene chain shuttling copolymerization with n-butylethylmagnesium (BEM). In the presence of 1 equiv BEM, a fully amorphous multiblock microstructure of soft and hard segments is achieved. The microstructure consists of poly(isoprene-co-styrene) blocks, with hard blocks rich in styrene and soft blocks rich in isoprene. The composition of the blocks and the resulting glass transition temperatures (Tg ) can be easily modified by changing the feed and/or the relative amount of the catalysts, highlighting a new class of thermoplastic elastomers (TPEs) with tunable transition temperatures. The materials self-organize into nanostructures in the solid state. PMID:24668565

  9. Penultimate effect in ethylene-styrene copolymerization and the discovery of highly active ethylene-styrene catalysts with increased styrene reactivity.

    PubMed

    Arriola, Daniel J; Bokota, Marilyn; Campbell, Richard E; Klosin, Jerzy; LaPointe, Robert E; Redwine, O David; Shankar, Ravi B; Timmers, Francis J; Abboud, Khalil A

    2007-06-01

    For the first time commercially relevant catalysts for the copolymerization of ethylene and styrene have been identified. The catalysts maintain very high copolymer efficiencies at relatively high reactor temperatures without sacrificing styrene comonomer reactivity. The observations which led to this discovery are based upon the kinetic analysis of ethylene-styrene copolymerization using constrained geometry catalyst (eta5-C5Me4)(SiMe2-N-t-Bu)TiMe2 (1). This analysis revealed a substantial styrene penultimate monomer effect. Inherent reactivity of 1 toward styrene is greatly improved when the penultimate monomer on the growing polymer chain is styrene rather than ethylene. The presence of a penultimate styrene effect led to the hypothesis that catalysts bearing aromatic moieties in close proximity to the active site could lead to enhancement of styrene reactivity for this catalyst family. This hypothesis was born out by two new constrained geometry catalysts, one having two phenyl substituents placed in the 3 and 3' positions of the Cp ring (2) and the other with a 2,2'-biphenyl fragment attached to the Cp ring (3). Both catalysts exhibit higher activity than that of 1 and, more importantly, much higher styrene reactivity leading to copolymers with substantially increased styrene content (21.5% for 2, 30.6% for 3) as compared to 1 (11%) under the same polymerization conditions. Analysis of the X-ray crystal structures of 2 and 3 shows no overriding structural arguments for the increased performance. Outstanding polymerization characteristics achieved with 3 make this catalyst a candidate for commercial production of ethylene-styrene resins in a solution process. PMID:17489593

  10. D5h [PhSiO1.5]10 synthesis via F(-) catalyzed rearrangement of [PhSiO1.5]n. An experimental/computational analysis of likely reaction pathways.

    PubMed

    Furgal, Joseph C; Goodson, Theodore; Laine, Richard M

    2016-01-21

    We describe here the synthesis and analysis of the reaction pathways leading to formation of the rare D5h decaphenylsilsesquioxane (SQ) [PhSiO1.5]10via F(-) catalyzed rearrangement of [PhSiO1.5]nn = 8, 12, and oligomers initially synthesized from PhSi(OEt)3. Isolated yields of ∼50% [PhSiO1.5]10 are obtained via rearrangement of all starting materials. The recovered starting materials can be re-equilibrated using catalytic F(-) to generate similar yields in second batches. These yields arise because [PhSiO1.5]10 exhibits higher solubility and better energy stabilization (10 kcal mol(-1) theory) in CH2Cl2 compared to [PhSiO1.5]8 or [PhSiO1.5]12. Reaction intermediates were identified using time dependent (19)F NMR and MALDI-ToF mass spectrometry eventually equilibrating to form the 8 : 10 : 12 cages in a 1 : 3 : 1.3 equilibrium in CH2Cl2. Experimental results coupled with modeling using the Gamess computational package provide multiple reasonable pathways for SQ rearrangements to [RSiO1.5]10, starting from [RSiO1.5]8. Heats of reaction for interconversion of the model intermediates [HSiO1.5]x determined computationally, were used to select the most reasonable reaction pathways. The findings support a mechanism involving activation and cleavage of a T8 cage corner by F(-) attachment, followed by the corners stepwise removal as [i.e. RSi(OH)3], followed thereafter by reinsertion forming [RSiO1.5]9-OH followed by, insertion of another corner to form [RSiO1.5]10-(OH)2 and finally condensation to give [RSiO1.5]10. The most enthalpically favorable path (-24 kcal mol(-1)) involves a hybrid mechanism. PMID:26648403

  11. Increased diversification of polyhydroxyalkanoates by modification reactions for industrial and medical applications.

    PubMed

    Hazer, Baki; Steinbüchel, Alexander

    2007-02-01

    A wide range of diverse polyhydroxyalkanoates, PHAs, is currently available due to the low substrate specificity of PHA synthases and subsequent modifications by chemical reactions. These polymers are promising materials for a number of different applications due to their biocompatibility and biodegradability. This review summarizes the large variability of PHAs regarding chemical structure and material properties that can be currently produced. In the first part, in vivo and in vitro biosynthesis processes for production of a large variety of different PHAs will be summarized with regard to obtaining saturated and unsaturated copolyesters and side chain functionalized polyesters, including brominated, hydroxylated, methyl-branched polyesters, and phenyl derivatives of polyesters. In the second part, established chemical modifications of PHAs will be summarized as that by means of grafting reactions and graft/block copolymerizations, as well as by chlorination, cross-linking, epoxidation, hydroxylation, and carboxylation, reactions yield further functionalized PHAs. PMID:17146652

  12. Reactions of Phenolphthalein at Various pH Values.

    ERIC Educational Resources Information Center

    Wittke, Georg

    1983-01-01

    Reactions of phenolphthalein with sodium hydroxide and sulfuric are discussed. Also discusses the sulfonation of phenolphthalein, listing experimental results related to the sulfonation reaction. (JN)

  13. Nuclear Reactions on Unstable Nuclei and the Surrogate Reaction Technique

    SciTech Connect

    Escher, J

    2004-03-01

    Determining reaction cross sections on short-lived nuclear species is a major challenge for nuclear physics and nuclear astrophysics. Many of these nuclei are too difficult to produce with currently available experimental techniques or too short-lived to serve as targets in present-day set-ups. Some nuclear reactions will remain immeasurable even at upcoming and planned radioactive beam facilities. It is therefore important to explore alternative methods for determining reaction cross sections on unstable nuclei.

  14. Structural femtochemistry: experimental methodology.

    PubMed Central

    Williamson, J C; Zewail, A H

    1991-01-01

    The experimental methodology for structural femtochemistry of reactions is considered. With the extension of femtosecond transition-state spectroscopy to the diffraction regime, it is possible to obtain in a general way the trajectories of chemical reactions (change of internuclear separations with time) on the femtosecond time scale. This method, considered here for simple alkali halide dissociation, promises many applications to more complex reactions and to conformational changes. Alignment on the time scale of the experiments is also discussed. Images PMID:11607189

  15. Highly efficient ring-opening reaction of azlactone-based copolymer platforms for the design of functionalized materials.

    PubMed

    Laquièvre, Aurélie; Allaway, Naomi S; Lyskawa, Joël; Woisel, Patrice; Lefebvre, Jean-Marc; Fournier, David

    2012-05-14

    Azlactone-based homopolymers and copolymers were successfully synthesized using the reversible addition-fragmentation chain transfer (RAFT) process. The functional monomer 2-styryl-4,4-dimethylazlactone (SDA) was first homopolymerized in bulk then copolymerized with styrene, leading to (co)polymers with low polydispersity indices (PDI = 1.10-1.20). The reactive azlactone rings, located along the backbone of the copolymers were subjected to highly efficient ring-opening reactions with functionalized primary amine derivatives incorporating a fluorescent (naphthalene) or an electrochemical (ferrocene) probes, a biological fragment (glutathione), a sugar unit (β-cyclodextrin), or an oligomeric fluorinated moiety, leading to materials with various interesting properties. PMID:22508541

  16. Radiative capture reactions in astrophysics

    SciTech Connect

    Brune, Carl R.; Davids, Barry

    2015-08-07

    Here, the radiative capture reactions of greatest importance in nuclear astrophysics are identified and placed in their stellar contexts. Recent experimental efforts to estimate their thermally averaged rates are surveyed.

  17. Code System to Calculate Integral Parameters with Reaction Rates from WIMS Output.

    Energy Science and Technology Software Center (ESTSC)

    1994-10-25

    Version 00 REACTION calculates different integral parameters related to neutron reactions on reactor lattices, from reaction rates calculated with WIMSD4 code, and comparisons with experimental values.

  18. Isosinglet approximation for nonelastic reactions

    NASA Technical Reports Server (NTRS)

    Wilson, J. W.

    1972-01-01

    Group theoretic relations are derived between different combinations of projectile and secondary particles which appear to have a broad range of application in spacecraft shielding or radiation damage studies. These relations are used to reduce the experimental effort required to obtain nuclear reaction data for transport calculations. Implications for theoretical modeling are also noted, especially for heavy-heavy reactions.

  19. Drug Reactions

    MedlinePlus

    Most of the time, medicines make our lives better. They reduce aches and pains, fight infections, and control problems such as high blood pressure or diabetes. But medicines can also cause unwanted reactions. One problem is ...

  20. Synthesis of a novel supermagnetic iron oxide nanocomposite hydrogel based on graft copolymerization of poly((2-dimethylamino)ethyl methacrylate) onto salep for controlled release of drug.

    PubMed

    Bardajee, Ghasem Rezanejade; Hooshyar, Zari; Asli, Maryam Jahanbakhsh; Shahidi, Fatemeh Emamjome; Dianatnejad, Nastaran

    2014-03-01

    In this research, a novel supermagnetic iron oxide nanocomposite hydrogel was prepared using simultaneous in situ formation of iron oxide nanoparticles (IONs) and three-dimensional cross-linked polymer networks based on graft copolymerization of poly((2-dimethylamino)ethyl methacrylate) (PDMA) onto salep (PDMA-g-salep). The prepared ION-PDMA-g-salep hydrogel was systematically characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDAX), transmission electron microscopy (TEM), thermal gravimetric analysis (TGA), X-ray diffraction (XRD), and vibrating sample magnetometer (VSM). In addition, the ION-PDMA-g-salep hydrogel exhibits favorable swelling properties that are sensitive to temperature, pH, and external magnetic field (EMF). The drug release behavior of the prepared hydrogel under EMF, different temperatures and pHs was also studied for the evaluation of the release mechanism and determination of diffusion coefficients. Finally, the antibacterial activity and cytotoxicity studies of the prepared hydrogel were examined. These results suggested that the ION-PDMA-g-salep hydrogel could be a promising candidate for biological dressing applications. PMID:24433913

  1. Radiation graft copolymerization of butyl methacrylate and acrylamide onto low density polyethylene and polypropylene films, and its application in wastewater treatment

    NASA Astrophysics Data System (ADS)

    Abdel Ghaffar, A. M.; El-Arnaouty, M. B.; Aboulfotouh, Maysara E.; Taher, N. H.; Taha, Ahmed A.

    2014-09-01

    Butyl methacrylate and acrylamide (BMA/AAm) comonomers were grafted onto low-density polyethylene (LDPE) and polypropylene (PP) films using the mutual gamma radiation grafting technique. The influences of grafting conditions such as solvent, monomer concentration, monomer composition, and irradiation dose on the grafting yield were determined. It was found that using dimethyl formamide as a solvent enhanced the copolymerization process. The grafting yield increases as the comonomer concentration increases up to 60%. Also it was found that the degree of grafting of BMA/AAm onto both LDPE and PP films increases as the AAm content increases till an optimum value at 50:50 wt%. The grafting yield of the comonomers was found to increase with increase in the radiation dose. It was observed that the degree of grafting of polyethylene films is higher than that of polypropylene (PP) films at the same conditions. Some selected properties of the graft copolymers, such as water uptake and thermal properties, were determined using thermogravimetric analysis. The morphology and structure of the grafted films were investigated using scanning electron microscopy, infra-red, and X-ray diffraction. Improvement in such properties of the prepared copolymers was observed which offers possible uses in some practical applications such as the removal of some heavy metals from wastewater. It was found that the maximum metal uptake by the copolymer followed the order Cu2+>Co2+>Ni2+ ions.

  2. Radiation induced graft copolymerization of n-butyl acrylate onto poly(ethylene terephthalate) (PET) films and thermal properties of the obtained graft copolymer

    NASA Astrophysics Data System (ADS)

    Ping, Xiang; Wang, Mozhen; Ge, Xuewu

    2011-05-01

    n-Butyl acrylate (BA) was successfully grafted onto poly(ethylene terephthalate) (PET) film using simultaneous radiation induced graft copolymerization with gamma rays. When BA concentration ranges from 20% to 30%, the Degree of Grafting (DG), measured by gravimetry and 1H NMR, increases with the monomer concentration and absorbed dose, but decreases with dose rate from 0.83 to 2.53 kGy/h. The maximum DG can reach up to 22.1%. The thermal transition temperatures such as glass-transition temperature ( Tg) and cold-crystallization temperature ( Tcc) of PET in grafted films were little different from those in original PET film, indicating that microphase separation occurred between PBA side chains and PET backbone. This work implied that if PET/elastomers (e.g., acrylate rubber) blends are radiated by high energy gamma rays under a certain condition, PET-g-polyacrylate copolymer may be produced in-situ, which will improve the compatibility between PET and the elastomers so as to improve the integral mechanical properties of PET based engineering plastic.

  3. Drug Reactions

    MedlinePlus

    ... using any of these products. Some types of food may also cause adverse drug reactions. For example, grapefruit and grapefruit juice, as well as alcohol and caffeine, may affect how drugs work. Every time your doctor ... interactions with any foods or beverages. What about medicines I've used ...

  4. A Mechanism of O-Demethylation of Aristolochic Acid I by Cytochromes P450 and Their Contributions to This Reaction in Human and Rat Livers: Experimental and Theoretical Approaches

    PubMed Central

    Stiborová, Marie; Bárta, František; Levová, Kateřina; Hodek, Petr; Schmeiser, Heinz H.; Arlt, Volker M.; Martínek, Václav

    2015-01-01

    Aristolochic acid I (AAI) is a plant alkaloid causing aristolochic acid nephropathy, Balkan endemic nephropathy and their associated urothelial malignancies. AAI is detoxified by cytochrome P450 (CYP)-mediated O-demethylation to 8-hydroxyaristolochic acid I (aristolochic acid Ia, AAIa). We previously investigated the efficiencies of human and rat CYPs in the presence of two other components of the mixed-functions-oxidase system, NADPH:CYP oxidoreductase and cytochrome b5, to oxidize AAI. Human and rat CYP1A are the major enzymes oxidizing AAI. Other CYPs such as CYP2C, 3A4, 2D6, 2E1, and 1B1, also form AAIa, but with much lower efficiency than CYP1A. Based on velocities of AAIa formation by examined CYPs and their expression levels in human and rat livers, here we determined the contributions of individual CYPs to AAI oxidation in these organs. Human CYP1A2 followed by CYP2C9, 3A4 and 1A1 were the major enzymes contributing to AAI oxidation in human liver, while CYP2C and 1A were most important in rat liver. We employed flexible in silico docking methods to explain the differences in AAI oxidation in the liver by human CYP1A1, 1A2, 2C9, and 3A4, the enzymes that all O-demethylate AAI, but with different effectiveness. We found that the binding orientations of the methoxy group of AAI in binding centers of the CYP enzymes and the energies of AAI binding to the CYP active sites dictate the efficiency of AAI oxidation. Our results indicate that utilization of experimental and theoretical methods is an appropriate study design to examine the CYP-catalyzed reaction mechanisms of AAI oxidation and contributions of human hepatic CYPs to this metabolism. PMID:26593908

  5. Kinetic studies of elementary chemical reactions

    SciTech Connect

    Durant, J.L. Jr.

    1993-12-01

    This program concerning kinetic studies of elementary chemical reactions is presently focussed on understanding reactions of NH{sub x} species. To reach this goal, the author is pursuing experimental studies of reaction rate coefficients and product branching fractions as well as using electronic structure calculations to calculate transition state properties and reaction rate calculations to relate these properties to predicted kinetic behavior. The synergy existing between the experimental and theoretical studies allow one to gain a deeper insight into more complex elementary reactions.

  6. Nuclear Structure and Reaction Mechanism Studies with Multinucleon Reactions

    SciTech Connect

    Regan, P. H.; Jones, G. A.; Podolyak, Zs.; Abdullah, M.; Gelletly, W.; Langdown, S. D.; Wollel, G.; De Angelis, G.; Gadea, A.; Kroell, Th.; Marginean, N.; Martinez, T.; Napoli, D. R.; Rusu, C.; Tonev, D.; Zhang, Y. H.; Ur, C. A.; Axiotis, M.; Bazzacco, D.; Farnea, E.

    2006-08-14

    This contribution reports on the results of an experiment to study the near-yrast states in selenium- and osmium-like nuclei, following their population in thick-target, multinucleon transfer reactions between an 82Se beam and a 192Os target. The experimental results for the level scheme for 84Se are presented together with investigations into the use of multi-dimensional gamma-ray energy gating to investigate angular momentum population in such heavy-ion binary reactions.

  7. Chemical Reactions in DSMC

    SciTech Connect

    Bird, G. A.

    2011-05-20

    DSMC simulations of chemically reacting gas flows have generally employed procedures that convert the macroscopic chemical rate equations to reaction cross-sections at the microscopic level. They therefore depend on the availability of experimental data that has been fitted to equations of the Arrhenius form. This paper presents a physical model for dissociation and recombination reactions and a phenomenological model for exchange and chain reactions. These are based on the vibrational states of the colliding molecules and do not require any experimentally-based data. The simplicity of the models allows the corresponding rate equations to be written down and, while these are not required for the implementation of the models, they facilitate their validation. The model is applied to a typical hypersonic atmospheric entry problem and the results are compared with the corresponding results from the traditional method. It is also used to investigate both spontaneous and forced ignition as well as the structure of a deflagration wave in an oxygen-hydrogen mixture.

  8. Chemical Reactions in DSMC

    NASA Astrophysics Data System (ADS)

    Bird, G. A.

    2011-05-01

    DSMC simulations of chemically reacting gas flows have generally employed procedures that convert the macroscopic chemical rate equations to reaction cross-sections at the microscopic level. They therefore depend on the availability of experimental data that has been fitted to equations of the Arrhenius form. This paper presents a physical model for dissociation and recombination reactions and a phenomenological model for exchange and chain reactions. These are based on the vibrational states of the colliding molecules and do not require any experimentally-based data. The simplicity of the models allows the corresponding rate equations to be written down and, while these are not required for the implementation of the models, they facilitate their validation. The model is applied to a typical hypersonic atmospheric entry problem and the results are compared with the corresponding results from the traditional method. It is also used to investigate both spontaneous and forced ignition as well as the structure of a deflagration wave in an oxygen-hydrogen mixture.

  9. Indirect techniques for astrophysical reaction rates determinations

    NASA Astrophysics Data System (ADS)

    Hammache, F.; Oulebsir, N.; Benamara, S.; De Séréville, N.; Coc, A.; Laird, A.; Stefan, I.; Roussel, P.

    2016-05-01

    Direct measurements of nuclear reactions of astrophysical interest can be challenging. Alternative experimental techniques such as transfer reactions and inelastic scattering reactions offer the possibility to study these reactions by using stable beams. In this context, I will present recent results that were obtained in Orsay using indirect techniques. The examples will concern various astrophysical sites, from the Big-Bang nucleo synthesis to the production of radioisotopes in massive stars.

  10. Experimental study of the {sup 238}U({sup 36}S,3-5n){sup 269-271}Hs reaction leading to the observation of {sup 270}Hs

    SciTech Connect

    Graeger, R.; Gorshkov, A.; Tuerler, A.; Yakushev, A.; Ackermann, D.; Duellmann, Ch. E.; Hessberger, F. P.; Huebner, A.; Jaeger, E.; Khuyagbaatar, J.; Kindler, B.; Krier, J.; Lommel, B.; Schaedel, M.; Schausten, B.; Chelnokov, M.; Chepigin, V.; Kuznetsov, A.; Petrushkin, O.; Dvorak, J.

    2010-06-15

    The deformed doubly magic nucleus {sup 270}Hs has so far only been observed as the four-neutron (4n) evaporation residue of the reaction {sup 26}Mg+{sup 248}Cm, where a maximum cross section of 3 pb was measured. Theoretical studies on the formation of {sup 270}Hs in the 4n evaporation channel of fusion reactions with different entrance channel asymmetry in the framework of a two-parameter Smoluchowski equation predict that the reactions {sup 48}Ca+{sup 226}Ra and {sup 36}S+{sup 238}U result in higher cross sections due to lower reaction Q values, in contrast to simple arguments based on the reaction asymmetry, which predict opposite trends. Calculations using hivap predict cross sections for the reaction {sup 36}S+{sup 238}U that are similar to those of the {sup 26}Mg+{sup 248}Cm reaction. Here, we report on the first measurement of evaporation residues formed in the complete nuclear fusion reaction {sup 36}S+{sup 238}U and the observation of {sup 270}Hs, which is produced in the 4n evaporation channel, with a measured cross section of 0.8{sub -0.7}{sup +2.6} pb at 51-MeV excitation energy. The one-event cross-section limits (68% confidence level) for the 3n, 4n, and 5n evaporation channels at 39-MeV excitation energy are 2.9 pb, while the cross-section limits of the 3n and 5n channel at 51 MeV are 1.5 pb. This is significantly lower than the 5n cross section of the {sup 26}Mg+{sup 248}Cm reaction at similar excitation energy.

  11. Tilting mode in nuclear reactions

    SciTech Connect

    Dossing, T.; Randrup, J.

    1986-02-01

    The relation between tilting relaxation and the reaction plane dynamics is discussed, providing an intuitive understanding of the expression for the cross section close to the beam direction, which has recently been derived. Second, the tilting relaxation time and the related wriggling relaxation time are discussed, based upon nucleon exchange transport (window friction). Finally, recent experimental information on the tilting mode relaxation is discussed, and the dynamics of the tilting mode is discussed qualitatively for the three different types of nuclear reactions considered, compound nucleus fission, quasifission, and damped nuclear reactions. 9 refs., 3 figs.

  12. Nuclear reactions at intermediate energies

    NASA Astrophysics Data System (ADS)

    Shyam, Radhey

    2016-05-01

    In the domain of Nuclear reactions at intermediate energies, the QCD coupling constant αs is large enough (~ 0.3 - 0.5) to render the perturbative calculational techniques inapplicable. In this regime the quarks are confined into colorless hadrons and it is expected that effective field theories of hadron interactions via exchange of hadrons, provide useful tools to describe such reactions. In this contribution we discuss the application of one such theory, the effective Lagrangian model, in describing the hadronic reactions at intermediate energies whose measurements are the focus of a vast international experimental program.

  13. Experimental and theoretical study of the reaction system of 2NO2 ↔ N2O4 and some fluorinated derivatives of tert-butanol in the gas phase

    NASA Astrophysics Data System (ADS)

    Kołodziejczyk, Wojciech; Wójcik-Pastuszka, Dorota; Berkowski, Ryszard

    2014-08-01

    The reversible reaction between NO2/N2O4 and CF3C(CH3)2OH has been studied using UV-Vis spectrophotometry. The final product -CF3C(CH3)2ONO- of this reaction was identified by its UV spectrum in the wavelength range of 340-420 nm. The absorption spectrum of CF3C(CH3)2ONO was recorded and the values of the absorption cross sections for prominent bands at 354.0; 367.5; 390.0 nm were derived. The kinetics of the reaction has been investigated in the temperature range of 298-358 K to follow the NO2 decay in a real time of the reaction. The rate constant for the forward k5 as well as for the reverse k6 reaction has been obtained and their values at 298 K are: 10-19 k5/cm3 molecule-1 s-1 1.4 ± 0.3 and 10-19 k6/cm3 molecule-1 s-1 15.0 ± 4.0. From the temperature dependence of the rate constants the activation energy for the forward E5 and for the reverse E6 reaction has been calculated. It was proposed that the reaction mechanism is complex and N2O4 is the reactive species. The UV-Vis spectra have for all studied compounds been calculated. The possible reason of absence of the reaction between (CF3)3COH, CH3C(CF3)2OH and N2O4 has been proposed. All possible stable conformers of studied moieties have been obtained. Molecular Electrostatic Potential Surfaces (MEPS) of all structures have been derived.

  14. Photoneutron reactions in astrophysics

    SciTech Connect

    Varlamov, V. V. Ishkhanov, B. S.; Orlin, V. N.; Peskov, N. N.; Stopani, K. A.

    2014-12-15

    Among key problems in nuclear astrophysics, that of obtaining deeper insight into the mechanism of synthesis of chemical elements is of paramount importance. The majority of heavy elements existing in nature are produced in stars via radiative neutron capture in so-called s- and r processes, which are, respectively, slow and fast, in relation to competing β{sup −}-decay processes. At the same time, we know 35 neutron-deficient so-called bypassed p-nuclei that lie between {sup 74}Se and {sup 196}Hg and which cannot originate from the aforementioned s- and r-processes. Their production is possible in (γ, n), (γ, p), or (γ, α) photonuclear reactions. In view of this, data on photoneutron reactions play an important role in predicting and describing processes leading to the production of p-nuclei. Interest in determining cross sections for photoneutron reactions in the threshold energy region, which is of particular importance for astrophysics, has grown substantially in recent years. The use of modern sources of quasimonoenergetic photons obtained in processes of inverse Compton laser-radiation scattering on relativistic electronsmakes it possible to reveal rather interesting special features of respective cross sections, manifestations of pygmy E1 and M1 resonances, or the production of nuclei in isomeric states, on one hand, and to revisit the problem of systematic discrepancies between data on reaction cross sections from experiments of different types, on the other hand. Data obtained on the basis of our new experimental-theoretical approach to evaluating cross sections for partial photoneutron reactions are invoked in considering these problems.

  15. Magnetic hydrophilic methacrylate-based polymer microspheres designed for polymerase chain reactions applications.

    PubMed

    Spanová, Alena; Horák, Daniel; Soudková, Eva; Rittich, Bohuslav

    2004-02-01

    Magnetic hydrophilic non-porous P(HEMA-co-EDMA), P(HEMA-co-GMA) and PGMA microspheres were prepared by dispersion (co)polymerization of 2-hydroxyethyl methacrylate (HEMA) and ethylene dimethacrylate (EDMA) or glycidyl methacrylate (GMA) in the presence of several kinds of magnetite. It was found that some components used in the preparation of magnetic carriers interfered with polymerase chain reaction (PCR). Influence of non-magnetic and magnetic microspheres, including magnetite nanoparticles and various components used in their synthesis, on the PCR course was thus investigated. DNA isolated from bacterial cells of Bifidobacterium longum was used in PCR evaluation of non-interfering magnetic microspheres. The method enabled verification of the incorporation of magnetite nanoparticles in the particular methacrylate-based polymer microspheres and evaluation of suitability of their application in PCR. Preferably, electrostatically stabilized colloidal magnetite (ferrofluid) should be used in the design of new magnetic methacrylate-based microspheres by dispersion polymerization. PMID:14698232

  16. qPCR (quantitative polymerase chain reaction) for the quantification of bacteriophages in stream water samples to investigate hydrological processes: a proof-of-concept study in the Huewelerbach experimental catchment (Luxembourg)

    NASA Astrophysics Data System (ADS)

    Antonelli, Marta; Narayanan Balasubramanian, Mukundh; Ogorzaly, Leslie; Pfister, Laurent

    2016-04-01

    Albeit recent technological developments (e.g. field deployable instruments operating at high temporal frequencies), experimental hydrology is a discipline that remains measurement limited. From this perspective, trans-disciplinary approaches may create valuable opportunities to enlarge the amount of tools available for investigating hydrological processes. Bacteriophages have been widely used in hydrology as biological tracer for investigating colloid transport and contamination of ground water systems. However, there are only a few studies focusing on the employability of bacteriophages as surface water tracers (i.e. phage transport, system functioning). Here, we present a proof-of-concept study carried out in the Huewelerbach catchment in Luxembourg in December 2015. The aim of this study was to investigate how viral particles can be used to detect hydrological connectivity between the riparian zone/river bank and the stream during rainfall events. Moreover, this study is one of the first attempts for applying the qPCR (quantitative polymerase chain reaction) technique for the quantification of bacteriophages in stream water samples to investigate hydrological processes. This technique is very sensitive and has a large dynamic range - enhancing ease and speed of phage detection. We used two different male-specific coliphages (GA phage, genogroup II and SP phage, genogroup IV). Two litres of GA phage were injected directly in the stream as a slug injection and two litres of SP phage were poured next to the river bank (alluvial deposition) close to the injection point. We also added NaCl (200 g) to both phage suspensions. We collected stream water samples 100 m and 500 m downstream (i.e. catchment outlet) of the injection point for one week. Phages were concentrated through ultracentrifugation of 100 ml of water sample followed by quantification via qPCR. Conductivity in stream water was monitored for the entire duration of the experiment. Discharge was monitored

  17. Exerting control over the helical chirality in the main chain of sergeants-and-soldiers-type poly(quinoxaline-2,3-diyl)s by changing from random to block copolymerization protocols.

    PubMed

    Nagata, Yuuya; Nishikawa, Tsuyoshi; Suginome, Michinori

    2015-04-01

    Chiral random poly(quinoxaline-2,3-diyl) polymers of the sergeants-and-soldiers-type (sergeant units bearing (S)-3-octyloxymethyl groups) adopt an M- or P-helical conformation in the presence of achiral units bearing propoxymethyl or butoxy groups (soldier units), respectively. Unusual bidirectional induction of the helical sense can be observed for a copolymer with butoxy soldier units upon changing the mole fraction of the sergeant units. In the presence of 16-20% of sergeant units, the selective induction of a P-helix was observed, while the selective induction of an M-helix was observed for a mole fraction of sergeant units of more than 60%. This phenomenon could be successfully employed to control the helical chirality of copolymers by applying either random or block copolymerization protocols. Random or block copolymerization of sergeant and soldier monomers in a 18:82 ratio resulted in the formation of 250mers with almost absolute P- or M-helical conformation, respectively (>99% ee). Incorporation of a small amount of coordination sites into the random and block copolymers resulted in chiral macromolecular ligands, which allowed the enantioselective synthesis of both enantiomers in the Pd-catalyzed asymmetric hydrosilylation of β-methylstyrene. PMID:25793617

  18. Surface treatment of poly(ethylene terephthalate) by gamma-ray induced graft copolymerization of methyl acrylate and its toughening effect on poly(ethylene terephthalate)/elastomer blend

    NASA Astrophysics Data System (ADS)

    Ma, Liang; Wang, Mozhen; Ge, Xuewu

    2013-09-01

    To improve the compatibility between ethylene-methyl acrylate-glycidyl methacrylate random terpolymer (E-MA-GMA) elastomer and poly(ethylene terephthalate) (PET), thereby enhance the toughening effect of E-MA-GMA on PET, γ-radiation-induced graft copolymerization technique was used to graft methyl acrylate (MA) monomer onto PET. The produced PET-g-PMA copolymer can be used as a self-compatibilizer in PET/E-MA-GMA blend since the copolymer contains the same segments, respectively, with PET and E-MA-GMA. The impact strength of PET/E-MA-GMA blend increased nearly by 30% in the presence of less than 0.1 wt% PET-g-PMA compared with that of the neat PET/elastomer blend, without loss of the tensile strength of the blends. This work proposed a potential application of radiation-induced grafting copolymerization technique on the in-situ compatibilization of PET/elastomer blends so as to improve the integral mechanical properties of PET based engineering plastic.

  19. Effective radii of deuteron-induced reactions

    SciTech Connect

    Hashimoto, Shintaro; Chiba, Satoshi; Yahiro, Masanobu; Ogata, Kazuyuki; Minomo, Kosho

    2011-05-15

    The continuum-discretized coupled-channels method (CDCC) for exclusive reactions and the eikonal reaction theory (ERT) as an extension of CDCC to inclusive reactions are applied to deuteron-induced reactions. The CDCC result reproduces experimental data on the reaction cross section for d+{sup 58}Ni scattering at 200 MeV/nucleon, and ERT provides data on the neutron-stripping cross section for inclusive {sup 7}Li(d,n) reaction at 40 MeV. For deuteron-induced reactions at 200 MeV/nucleon, target-dependence of the reaction, elastic-breakup, nucleon-stripping, nucleon-removal, and complete- and incomplete-fusion cross sections is clearly explained by simple formulas. Accuracy of the Glauber model is also investigated.

  20. Transfer reactions in nuclear astrophysics

    NASA Astrophysics Data System (ADS)

    Bardayan, D. W.

    2016-08-01

    To a high degree many aspects of the large-scale behavior of objects in the Universe are governed by the underlying nuclear physics. In fact the shell structure of nuclear physics is directly imprinted into the chemical abundances of the elements. The tranquility of the night sky is a direct result of the relatively slow rate of nuclear reactions that control and determines a star’s fate. Understanding the nuclear structure and reaction rates between nuclei is vital to understanding our Universe. Nuclear-transfer reactions make accessible a wealth of knowledge from which we can extract much of the required nuclear physics information. A review of transfer reactions for nuclear astrophysics is presented with an emphasis on the experimental challenges and opportunities for future development.

  1. The Mechanism of the Formaldehyde Clock Reaction.

    ERIC Educational Resources Information Center

    Burnett, M. G.

    1982-01-01

    Provides background information and problems with the formaldehyde clock reaction, including comparisons of experimental clock times reported in the literature and conditions for the reliable use of the formaldehyde clock based on a method discussed. (JN)

  2. Combined Experimental and Theoretical Study on the Formation of the Elusive 2-Methyl-1-silacycloprop-2-enylidene Molecule under Single Collision Conditions via Reactions of the Silylidyne Radical (SiH; X(2)Π) with Allene (H2CCCH2; X(1)A1) and D4-Allene (D2CCCD2; X(1)A1).

    PubMed

    Yang, Tao; Dangi, Beni B; Maksyutenko, Pavlo; Kaiser, Ralf I; Bertels, Luke W; Head-Gordon, Martin

    2015-12-17

    The crossed molecular beam reactions of the ground-state silylidyne radical (SiH; X(2)Π) with allene (H2CCCH2; X(1)A1) and D4-allene (D2CCCD2; X(1)A1) were carried out at collision energies of 30 kJ mol(-1). Electronic structure calculations propose that the reaction of silylidyne with allene has no entrance barrier and is initiated by silylidyne addition to the π electron density of allene either to one carbon atom (C1/C2) or to both carbon atoms simultaneously via indirect (complex forming) reaction dynamics. The initially formed addition complexes isomerize via two distinct reaction pathways, both leading eventually to a cyclic SiC3H5 intermediate. The latter decomposes through a loose exit transition state via an atomic hydrogen loss perpendicularly to the plane of the decomposing complex (sideways scattering) in an overall exoergic reaction (experimentally: -19 ± 13 kJ mol(-1); computationally: -5 ± 3 kJ mol(-1)). This hydrogen loss yields the hitherto elusive 2-methyl-1-silacycloprop-2-enylidene molecule (c-SiC3H4), which can be derived from the closed-shell cyclopropenylidene molecule (c-C3H2) by replacing a hydrogen atom with a methyl group and the carbene carbon atom by the isovalent silicon atom. The synthesis of the 2-methyl-1-silacycloprop-2-enylidene molecule in the bimolecular gas-phase reaction of silylidyne with allene enriches our understanding toward the formation of organosilicon species in the gas phase of the interstellar medium in particular via exoergic reactions of no entrance barrier. This facile route to 2-methyl-1-silacycloprop-2-enylidene via a silylidyne radical reaction with allene opens up a versatile approach to form hitherto poorly characterized silicon-bearing species in extraterrestrial environments; this reaction class might represent the missing link, leading from silicon-bearing radicals via organosilicon chemistry eventually to silicon-carbon-rich interstellar grains even in cold molecular clouds where temperatures are as

  3. Cu(II)-Gd(III) cryogenic magnetic refrigerants and Cu8Dy9 single-molecule magnet generated by in situ reactions of picolinaldehyde and acetylpyridine: experimental and theoretical study.

    PubMed

    Liu, Jun-Liang; Lin, Wei-Quan; Chen, Yan-Cong; Gómez-Coca, Silvia; Aravena, Daniel; Ruiz, Eliseo; Leng, Ji-Dong; Tong, Ming-Liang

    2013-12-16

    A series of heterometallic [Ln(III)(x)Cu(II)(y)] complexes, [Gd2Cu2]n (1), [Gd4Cu8] (2), [Ln9Cu8] (Ln=Gd, 3·Gd; Ln=Dy, 3·Dy), were successfully synthesized by a one-pot route at room temperature with three kinds of in situ carbonyl-related reactions: Cannizzaro reaction, aldol reaction, and oxidation. This strategy led to dysprosium analogues that behaved as single-molecule magnets (SMMs) and gadolinium analogues that showed significant magnetocaloric effect (MCE). In this study a numerical DFT approach is proposed by using pseudopotentials to calculate the exchange coupling constants in three polynuclear [Gd(x)Cu(y)] complexes; with these values exact diagonalization or quantum Monte Carlo simulations have been performed to calculate the variation of the magnetic entropy involved in the MCE. For the [Dy9Cu8] complexes, local magnetic properties of the Dy(III) centers have been determined by using the CASSCF+RASSI method. PMID:24265054

  4. Experimental study on the effect of SO2 on PCDD/F emissions: determination of the importance of gas-phase versus solid-phase reactions in PCDD/F formation.

    PubMed

    Ryan, Shawn P; Li, Xiao-Dong; Gullett, Brian K; Lee, C W; Clayton, Matt; Touati, Abderrahmane

    2006-11-15

    Cofiring coal in municipal solid waste incinerators (MSWls) has previously been reported to reduce polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDDs/Fs) emissions due to increasing the flue gas SO2 concentration. The present study was focused on understanding the primary mechanism responsible for the suppressant effect of SO2 on total PCDD/F formation and toxic equivalent (TEQ) emissions. The addition of SO2, simulating the effect of coal addition on the flue gas composition, resulted in significant reductions in the TEQ emissions due to reactions involving SO2 in the postcombustion zone. However, emissions of total PCDDs/Fs, unlike the TEQ value, were dependent upon the Cl2 and SO2 injection temperatures due to increases in non-TEQ correlated isomers. The conversion of metal chlorides in the fly ash to sulfates, thus reducing the sites responsible for chlorination/oxidation reactions, was concluded to be the main suppressant mechanism; proposed reactions for copper and iron are presented. This mechanism was found to be independent of combustion conditions and could have prolonged effects on PCDD/F emissions from deposits formed with high flue gas S/Cl ratios. PMID:17154014

  5. Bridging silyl groups in sigma-bond metathesis and [1, 2] shifts. An experimental and computational study of the reaction between cerium metallocenes and MeOSiMe3

    SciTech Connect

    Werkema, Evan; Yahia, Ahmed; Maron, Laurent; Eisenstein, Odile; Andersen, Richard

    2010-04-21

    The reaction of Cp'2CeH (Cp' = 1,2,4-(Me3C)3C5H2 ) with MeOSiMe3 gives Cp'2CeOMe and HSiMe3 and the reaction of the metallacycle, Cp'[(Me3C)2C5H2C(Me) 2CH2]Ce, with MeOSiMe3 yields Cp'2CeOCH2SiMe3, formed from hypothetical Cp'2CeCH2OSiMe3 by a [1, 2] shift also known as a silyl-Wittig rearrangement. Although both cerium products are alkoxides, they are formed by different pathways. DFT calculations on the reaction of the model metallocene, Cp2CeH, and MeOSiMe3 show that the lowest energy pathway is a H for OMe exchange at Ce that occurs by way of a sigma-bond metathesis transition state as SiMe3 exchanges partners. The formation of Cp2CeOCH2SiMe3 occurs by way of a low activation barrier [1, 2]shift of the SiMe3 group in Cp2CeCH2OSiMe3. Calculations on a model metallacycle, Cp[C5H4C(Me)2CH2]Ce, show that the metallacycle favors CH bond activation over sigma-bond metathesis involving the transfer of the SiMe3 group in good agreement with experiment. The sigma-bond metathesis involving the transfer of SiMe3 and the [1, 2]shift of SiMe3 reactions have in common a pentacoordinate silicon at the transition states. A molecular orbital analysis illustrates the connection between these two Si-O bond cleavage reactions and traces the reason why they occur for a silyl but not for an alkyl group to the difference in energy required to form a pentacoordinate silicon or carbon atom in the transition state. This difference clearly distinguishes a silyl from an alkyl group as shown in the study of"Pyrolysis of Tetramethylsilane Yielding Free d-orbitals by Seyferth and Pudvin in ChemTech 1981, 11, 230-233".

  6. Reactions of Monomeric [1,2,4-(Me3C)3C5H2]2CeH and CO with orwithout H2:An Experimental and Computational Study

    SciTech Connect

    Werkema, Evan L.; Maron, Laurent; Eisenstein, Odile; Andersen,Richard A.

    2006-09-07

    Addition of CO to [1,2,4-(Me3C)3C5H2]2CeH, Cp'2CeH, intoluene yields the cis (Cp'2Ce)2(mu-OCHCHO), in which the cis enediolategroup bridges the two metallocene fragments. The cis enediolatequantitatively isomerizes intramolecularly to the trans-enediolate inC6D6 at 100oC over seven months. When the solvent is pentane,Cp'2Ce(OCH2)CeCp'2 forms, in which the oxomethylene group or theformaldehyde dianion bridges the two metallocene fragments. The cisenediolate is suggested to form by insertion of CO into the Ce-C bond ofCp'2Ce(OCH2)CeCp'2 generating Cp'2CeOCH2COCeCp'2. The stereochemistry ofthe cis-enediolate is determined by a 1,2-hydrogen shift in the OCH2COfragment that has the OC(H2) bond anti periplanar relative to the carbenelone pair. The bridging oxomethylene complex reacts with H2, but not withCH4, to give Cp'2CeOMe, which is also the product of the reaction betweenCp'2CeH and a mixture of CO and H2. The oxomethylene complex reacts withCO to give the cis enediolate complex. DFT calculations on C5H5 modelmetallocenes show that the reaction of Cp2CeH with CO and H2 to giveCp2CeOMe is exoergic by 50 kcal mol-1. The net reaction proceeds by aseries of elementary reactions that occur after the formyl complex,Cp2Ce(eta-2 CHO), is formed by further reaction with H2. The key pointthat emerges from the calculated potential energy surface is thebifunctional nature of the metal formyl in which the carbon atom behavesas a donor and acceptor. Replacing H2 by CH4 increases the activationenergy barrier by 17 kcal mol-1.

  7. Reaction parameters for heavy-ion collisions

    SciTech Connect

    Wilcke, W.W.; Birkelund, J.R.; Wollersheim, H.J.; Hoover, A.D.; Huizenga, J.R.; Schroeder, W.U.; Tubbs, L.E.

    1980-09-01

    These tables present reaction parameters for all combinations of 27 projectile and 16 target nuclei in a laboratory bombarding energy range of 1--50 MeV/u. The reaction parameters are derived from the Fresnel model of heavy-ion scattering, the droplet model, and the rotating liquid-drop model, or from systematics of experimental data.

  8. Study of char gasification reactions

    SciTech Connect

    Ballal, G.D.

    1986-01-01

    A Texas lignite, an anthracite and two bituminous coals, Pittsburgh number8 and Illinois number6, were pyrolyzed in a nitrogen atmosphere to prepare chars. Optical microscopy, mercury porosimetry and gas adsorption techniques using nitrogen, CO/sub 2/ and CO, were employed for pore structure characterization. The lignite char exhibited the fastest rates of gaseous diffusion, followed in order of decreasing diffusivities by the Illinois number6, Pittsburgh number8 and anthracite chars. The changes in reactivities and pore structures of chars were measured experimentally during their reaction with oxygen (400-550C) and CO/sub 2/ (800-1000C). For a particular char-gas system, the normalized rate-conversion pattern was invariant with respect to temperature and gaseous concentration. In the case of lignite and Pittsburgh number8 chars, the rate-conversion pattern was similar during reaction with oxygen and CO/sub 2/. Adsorption experiments on partially reacted chars indicated that the micropores in the lignite char were accessible to both reactants. The micropores in the Illinois number6 char were, however, not accessible during its reaction with oxygen. The evolution of pore structure during reaction was modeled by using a probabilistic approach which accounts for overlapping pores with different shapes and sizes. The kinetics of gasification of the lignite and the Pittsburgh number8 chars was studied using a Langmuir-Hinshelwood type kinetic expression to correlate the experimental data. CO was found to inhibit the reaction substantially. The effect of a potassium carbonate catalyst on the reaction of these two chars was also investigated. Substantial increases in reaction rates were observed, and the enhancement was approximately proportional to the catalyst loading.

  9. A Combined Experimental and Theoretical Study on the Formation of the 2-Methyl-1-silacycloprop-2-enylidene Molecule via the Crossed Beam Reactions of the Silylidyne Radical (SiH; X(2)Π) with Methylacetylene (CH3CCH; X(1)A1) and D4-Methylacetylene (CD3CCD; X(1)A1).

    PubMed

    Yang, Tao; Dangi, Beni B; Kaiser, Ralf I; Bertels, Luke W; Head-Gordon, Martin

    2016-07-14

    The bimolecular gas-phase reactions of the ground-state silylidyne radical (SiH; X(2)Π) with methylacetylene (CH3CCH; X(1)A1) and D4-methylacetylene (CD3CCD; X(1)A1) were explored at collision energies of 30 kJ mol(-1) under single-collision conditions exploiting the crossed molecular beam technique and complemented by electronic structure calculations. These studies reveal that the reactions follow indirect scattering dynamics, have no entrance barriers, and are initiated by the addition of the silylidyne radical to the carbon-carbon triple bond of the methylacetylene molecule either to one carbon atom (C1; [i1]/[i2]) or to both carbon atoms concurrently (C1-C2; [i3]). The collision complexes [i1]/[i2] eventually isomerize via ring-closure to the c-SiC3H5 doublet radical intermediate [i3], which is identified as the decomposing reaction intermediate. The hydrogen atom is emitted almost perpendicularly to the rotational plane of the fragmenting complex resulting in a sideways scattering dynamics with the reaction being overall exoergic by -12 ± 11 kJ mol(-1) (experimental) and -1 ± 3 kJ mol(-1) (computational) to form the cyclic 2-methyl-1-silacycloprop-2-enylidene molecule (c-SiC3H4; p1). In line with computational data, experiments of silylidyne with D4-methylacetylene (CD3CCD; X(1)A1) depict that the hydrogen is emitted solely from the silylidyne moiety but not from methylacetylene. The dynamics are compared to those of the related D1-silylidyne (SiD; X(2)Π)-acetylene (HCCH; X(1)Σg(+)) reaction studied previously in our group, and from there, we discovered that the methyl group acts primarily as a spectator in the title reaction. The formation of 2-methyl-1-silacycloprop-2-enylidene under single-collision conditions via a bimolecular gas-phase reaction augments our knowledge of the hitherto poorly understood silylidyne (SiH; X(2)Π) radical reactions with small hydrocarbon molecules leading to the synthesis of organosilicon molecules in cold molecular

  10. Ultrafiltration membrane reactor for obtaining experimental reaction rates at defined concentrations of inhibiting sugars during enzymatic saccharifiction of alkali-pretreated sallow: formulation of a simple empirical rate equation

    SciTech Connect

    Frennesson, I.; Traegaardh, G.; Hahn-Haegerdal, B.

    1985-09-01

    The kinetics of the enzymatic hydrolysis of sodium hydroxide-pretreated sallow were studied in an ultrafiltration membrane reactor in the presence of different concentrations of glucose. In the UF membrane reactor low-molecular-weight products were continuously removed at a low dilution rate and replaced by a buffer solution that contained different concentrations of glucose, which made it possible to keep the inhibiting product concentration constant throughout an experiment. The reaction rate was related to the degree of substrate conversion and a mathematical relationship was formulated that describes the influence of the product concentration on the rate coefficient.

  11. Serpentinization reaction pathways: implications for modeling approach

    SciTech Connect

    Janecky, D.R.

    1986-01-01

    Experimental seawater-peridotite reaction pathways to form serpentinites at 300/sup 0/C, 500 bars, can be accurately modeled using the EQ3/6 codes in conjunction with thermodynamic and kinetic data from the literature and unpublished compilations. These models provide both confirmation of experimental interpretations and more detailed insight into hydrothermal reaction processes within the oceanic crust. The accuracy of these models depends on careful evaluation of the aqueous speciation model, use of mineral compositions that closely reproduce compositions in the experiments, and definition of realistic reactive components in terms of composition, thermodynamic data, and reaction rates.

  12. Effect of reactions in small eddies on biomass gasification with eddy dissipation concept - Sub-grid scale reaction model.

    PubMed

    Chen, Juhui; Yin, Weijie; Wang, Shuai; Meng, Cheng; Li, Jiuru; Qin, Bai; Yu, Guangbin

    2016-07-01

    Large-eddy simulation (LES) approach is used for gas turbulence, and eddy dissipation concept (EDC)-sub-grid scale (SGS) reaction model is employed for reactions in small eddies. The simulated gas molar fractions are in better agreement with experimental data with EDC-SGS reaction model. The effect of reactions in small eddies on biomass gasification is emphatically analyzed with EDC-SGS reaction model. The distributions of the SGS reaction rates which represent the reactions in small eddies with particles concentration and temperature are analyzed. The distributions of SGS reaction rates have the similar trend with those of total reactions rates and the values account for about 15% of the total reactions rates. The heterogeneous reaction rates with EDC-SGS reaction model are also improved during the biomass gasification process in bubbling fluidized bed. PMID:27010338

  13. Effects of small-scale chemical reactions between supercritical CO2 and arkosic sandstone on large-scale permeability fields: An experimental study with implications for geologic carbon sequestration

    NASA Astrophysics Data System (ADS)

    Luhmann, A. J.; Ding, K.; Saar, M. O.; Seyfried, W. E.

    2011-12-01

    During geologic carbon sequestration, small, pore-scale changes in mineralogy due to dissolution and precipitation reactions can modify bulk porosity. Porosity/permeability relationships are then typically used to infer large-scale permeability field changes. However, these relationships have limited use because they do not account for changes in pore geometry. Therefore, in connection with a DOE sponsored program, involving CO2 sequestration with geothermal energy usage, we constructed a novel hydrothermal flow system that allows simultaneous determination of changes in fluid chemistry and associated changes in permeability at elevated temperatures and high CO2 pressure. Initial experiments were conducted with an arkosic sandstone core of the Eau Claire Formation from southeastern Minnesota. The core was disaggregated and then wet sieved to yield a grain size distribution of 90-120 μm that was used to fill the Teflon sleeve held within the stainless steel pressure vessel. Initial water chemistry consisted of CO2 dissolved in deionized water. Outlet pressure was set to 11 MPa, and confinement pressure was 20 MPa. Flow rates produced inlet pressures between these two extremes, allowing CO2 solubility up to 1.1 mol/kg water. Rates of fluid flow ranged from 0.04 to 1.5 mL/min at a temperature of 21°C over the course of 33 days. Based on these data, the in-situ permeability of ~1E-14 to 9E-14 m2 for the arkosic sandstone was calculated. The reaction cell temperature was then increased to 50°C, and eventually 100°C. Each temperature step was associated with a sharp decrease in permeability, such that at 100°C the permeability had decreased by approximately three orders of magnitude from the starting condition. Fluid samples indicate release of dissolved Na, Ca, Mg, K, Al, SiO2, and Cl from minerals in the core, suggesting dissolution of primary mineral components. Charge balance constraints indicate a pH of approximately 4.2 at the highest temperature run condition

  14. Photonuclear reactions on titanium isotopes

    SciTech Connect

    Belyshev, S. S.; Dzhilavyan, L. Z.; Ishkhanov, B. S.; Kapitonov, I. M.; Kuznetsov, A. A. Orlin, V. N.; Stopani, K. A.

    2015-03-15

    The photodisintegration of titanium isotopes in the giant-dipole-resonance energy region is studied by the photon-activation method. Bremsstrahlung photons whose spectrum has the endpoint energy of 55 MeV is used. The yields and integrated cross sections are determined for photoproton reactions on the titanium isotopes {sup 47,48,49,50}Ti. The respective experimental results are compared with their counterparts calculated on the basis of the TALYS code and a combined photonucleon-reaction model. The TALYS code disregards the isospin structure of the giant dipole resonance and is therefore unable to describe the yield of photoproton reactions on the heavy titanium isotopes {sup 49,50}Ti.

  15. Method of uranium reclamation from aqueous systems by reactive ion exchange. [US DOE patent application; anion exchange resin of copolymerized divinyl-benzene and styrene having quarternary ammonium groups and bicarbonate ligands

    DOEpatents

    Maya, L.

    1981-11-05

    A reactive ion exchange method for separation and recovery of values of uranium, neptunium, plutonium, or americium from substantially neutral aqueous systems of said metals comprises contacting said system with an effective amount of a basic anion exchange resin of copolymerized divinyl-benzene and styrene having quarternary ammonium groups and bicarbonate ligands to achieve nearly 100% sorption of said actinyl ion onto said resin and an aqueous system practically free of said actinyl ions. The method is operational over an extensive range of concentrations from about 10/sup -6/ M to 1.0 M actinyl ion and a pH range of about 4 to 7. The method has particulr application to treatment of waste streams from Purex-type nuclear fuel reprocessing facilities and hydrometallurgical processes involving U, Np, P, or Am.

  16. Alpha particle induced reactions on natCr up to 39 MeV: Experimental cross-sections, comparison with theoretical calculations and thick target yields for medically relevant 52gFe production

    NASA Astrophysics Data System (ADS)

    Hermanne, A.; Adam Rebeles, R.; Tárkányi, F.; Takács, S.

    2015-08-01

    Thin natCr targets were obtained by electroplating, using 23.75 μm Cu foils as backings. In five stacked foil irradiations, followed by high resolution gamma spectroscopy, the cross sections for production of 52gFe, 49,51cumCr, 52cum,54,56cumMn and 48cumV in Cr and 61Cu,68Ga in Cu were measured up to 39 MeV incident α-particle energy. Reduced uncertainty is obtained by simultaneous remeasurement of the natCu(α,x)67,66Ga monitor reactions over the whole energy range. Comparisons with the scarce literature values and results from the TENDL-2013 on-line library, based on the theoretical code family TALYS-1.6, were made. A discussion of the production routes for 52gFe with achievable yields and contamination rates was made.

  17. Experimental determination of the {sup 36}Cl(n,p){sup 36}S and {sup 36}Cl(n,{alpha}){sup 33}P reaction cross sections and the consequences on the origin of {sup 36}S

    SciTech Connect

    Smet, L. de; Wagemans, C.; Goeminne, G.; Heyse, J.; Gils, J. van

    2007-03-15

    The {sup 36}Cl(n,p){sup 36}S and {sup 36}Cl(n,{alpha}){sup 33}P reaction cross sections have been studied with resonance neutrons at the linear accelerator GELINA of the IRMM in Geel (Belgium) and have been determined up to approximately 250 keV using the time-of-flight technique. In this energy region, 17 resonances were observed, whereas eight were identified before. For some resonances the resonance strength, the spin, and the total width could be determined. From the obtained cross section data, the MACS has been calculated by numerical integration. These updated MACS values were used in stellar models to trace the origin of the rare isotope {sup 36}S.

  18. Atmospheric pressure microwave assisted heterogeneous catalytic reactions.

    PubMed

    Chemat-Djenni, Zoubida; Hamada, Boudjema; Chemat, Farid

    2007-01-01

    The purpose of the study was to investigate microwave selective heating phenomena and their impact on heterogeneous chemical reactions. We also present a tool which will help microwave chemists to answer to such questions as "My reaction yields 90% after 7 days at reflux; is it possible to obtain the same yield after a few minutes under microwaves?" and to have an approximation of their reactions when conducted under microwaves with different heterogeneous procedures. This model predicting reaction kinetics and yields under microwave heating is based on the Arrhenius equation, in agreement with experimental data and procedures. PMID:17909495

  19. State- and bond-selected unimolecular reactions

    SciTech Connect

    Crim, F.F. )

    1990-09-21

    Unimolecular reactions are crucial chemical events that have been the focus of increasingly sophisticated investigation in the past decade. Unraveling their details is one fundamental goal of experimental and theoretical studies of chemical dynamics. New techniques are revealing the possibilities, and challenges, of eigenstate- and bond-specific unimolecular reactions. These experiments clearly demonstrate the intimate connection between intramolecular processes and unimolecular reaction dynamics and suggest means of exploiting molecular properties to study and control reactions at the level of individual quantum states. 55 refs., 3 figs.

  20. Experimental study of the dehydration reactions gypsum-bassanite and bassanite-anhydrite at high pressure: Indication of anomalous behavior of H2O at high pressure in the temperature range of 50-300 °C

    NASA Astrophysics Data System (ADS)

    Mirwald, Peter W.

    2008-02-01

    The system CaSO4-H2O, characterized by the three dehydration reactions gypsum-anhydrite, gypsum-bassanite, and bassanite-anhydrite, was reexamined by in situ differential pressure analysis in the temperature range of 60-350°C up to 3.5GPa pressure. The investigation revealed a fine structure in the dehydration boundaries of gypsum-bassanite and bassanite-anhydrite, each characterized by three inflections at 0.9-1.0, 1.9-2.0, and 2.6-28GPa. In addition, the phase transition of anhydrite high pressure anhydrite (monazite structure) was established for the first time at high P-T conditions intersecting the bassanite-anhydrite dehydration boundary at 2.15GPa /250°C. Furthermore, the triple point gypsum-bassanite-anhydrite was redetermined with 235MPa/80.5°C. The evaluation of the gypsum-bassanite dehydration boundary with respect to the volume and entropy change of the reaction, ΔVreact and ΔSreact, by means of the Clausius-Clapeyron relation yields for the entropy parameter an unusually large increase over the range of the noted inflections. This is interpreted as anomalous entropy behavior of H2O related presumably to a dramatic increase in fluctuations of the hydrogen network of the liquid leading possibly into a new structural state. The effect is strongly related to the three noted pressure levels of 0.9-1.0, 1.9-2.0, and 2.6-28GPa. In a synopsis of data including also a previous high pressure study in the temperature range between 0 and 80°C, a tentative P-T diagram of H2O is proposed.

  1. A MALDI-TOF MS analysis study of the binding of 4-(N,N-dimethylamino)pyridine to amine-bis(phenolate) chromium(III) chloride complexes: mechanistic insight into differences in catalytic activity for CO2/epoxide copolymerization.

    PubMed

    Kozak, Christopher M; Woods, April M; Bottaro, Christina S; Devaine-Pressing, Katalin; Ni, Kaijie

    2015-01-01

    Amine-bis(phenolato)chromium(III) chloride complexes, [LCrCl], are capable of catalyzing the copolymerization of cyclohexene oxide with carbon dioxide to give poly(cyclohexane) carbonate. When combined with 4-(N,N-dimethylamino)pyridine (DMAP) these catalyst systems yield low molecular weight polymers with moderately narrow polydispersities. The coordination chemistry of DMAP with five amine-bis(phenolato)chromium(III) chloride complexes was studied by matrix assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The amine-bis(phenolato) ligands were varied in the nature of their neutral pendant donor-group and include oxygen-containing tetrahydrofurfuryl and methoxyethyl moieties, or nitrogen-containing N,N-dimethylaminoethyl or 2-pyridyl moieties. The relative abundance of mono and bis(DMAP) adducts, as well as DMAP-free ions is compared under various DMAP : Cr complex ratios. The [LCr](+) cations show the ability to bind two DMAP molecules to form six-coordinate complex ions in all cases, except when the pendant group is N,N-dimethylaminoethyl (compound ). Even in the presence of a 4 : 1 ratio of DMAP to Cr, no ions corresponding to [L3Cr(DMAP)2](+) were observed for the complex containing the tertiary sp(3)-hybridized amino donor in the pendant arm. The difference in DMAP-binding ability of these compounds results in differences in catalytic activity for alternating copolymerization of CO2 and cyclohexene oxide. Kinetic investigations by infrared spectroscopy of compounds 2 and 3 show that polycarbonate formation by 3 is twice as fast as that of compound 2 and that no initiation time is observed. PMID:26388443

  2. Charge exchange reactions and applications to astrophysics

    NASA Astrophysics Data System (ADS)

    Cheoun, Myung-Ki; Ha, Eunja; Kajino, T.

    2012-11-01

    Neutrino-induced reactions have been known to play important roles as the neutrino process on the nucleosynthesis in core collapsing supernovae (SNe) explosions because expected neutrino flux and energy are sufficiently high enough to excite many relevant nuclei in spite of small cross sections of the weak interaction. However, we do not have enough data for the neutrino reaction to be exploited in the network calculation. Only a sparse data in the relevant energy range is known, in specific, for 12C. Therefore we have to rely on theoretical estimation of the reaction, which has two different modes, charge current (CC) and neutral current (NC). In particular, CC reactions are closely related to charge exchange reactions (CEXRs) which are feasible in the experiment, such as, (p,n) or (n,p) reactions. These CEXRs are usually dominated by the Gamow-Teller (GT) transition in the lower energy region. In this respect, any theoretical approaches for the neutrino reaction should be investigated for the CEXR because we have and expect more useful experimental data. After confirming our models to the GT strength deduced from the CEXR, we calculated neutrino-induced reactions in the energy range below the quasielastic region for nuclei of astrophysical importance. Our calculations are carried out with the Quasi-particle Random Phase Approximation (QRPA), which successfully described the nuclear beta decays of relevant nuclei. To describe neutrino-nucleus reactions, general multipole transitions by the weak interaction are considered for CC and NC reactions. Both reactions are described in a theoretical framework. Our results are shown to well reproduce the data from CEXRs and the sparse experimental data related to the neutrino-induced reaction, and further extended for neutrino reactions on various nuclear targets. Parts of the results are reported in this talk.

  3. An experimental and theoretical study on the formation of 2-methylnaphthalene (C11H10/C11H3D7) in the reactions of the para-tolyl (C7H7) and para-tolyl-d7 (C7D7) with vinylacetylene (C4H4).

    PubMed

    Parker, Dorian S N; Dangi, Beni B; Kaiser, Ralf I; Jamal, Adeel; Ryazantsev, Mikhail N; Morokuma, Keiji; Korte, André; Sander, Wolfram

    2014-04-17

    We present for the very first time single collision experimental evidence that a methyl-substituted polycyclic aromatic hydrocarbon (PAH)-2-methylnaphthalene-can be formed without an entrance barrier via indirect scattering dynamics through a bimolecular collision of two non-PAH reactants: the para-tolyl radical and vinylacetylene. Theory shows that this reaction is initiated by the addition of the para-tolyl radical to either the terminal acetylene carbon (C(4)) or a vinyl carbon (C(1)) leading eventually to two distinct radical intermediates. Importantly, addition at C(1) was found to be barrierless via a van der Waals complex implying this mechanism can play a key role in forming methyl substituted PAHs in low temperature extreme environments such as the interstellar medium and hydrocarbon-rich atmospheres of planets and their moons in the outer Solar System. Both reaction pathways involve a sequence of isomerizations via hydrogen transfer, ring closure, ring-opening and final hydrogen dissociation through tight exit transition states to form 2-methylnaphthalene in an overall exoergic process. Less favorable pathways leading to monocyclic products are also found. Our studies predict that reactions of substituted aromatic radicals can mechanistically deliver odd-numbered PAHs which are formed in significant quantities in the combustion of fossil fuels. PMID:24646186

  4. The Glyoxal Clock Reaction

    ERIC Educational Resources Information Center

    Ealy, Julie B.; Negron, Alexandra Rodriguez; Stephens, Jessica; Stauffer, Rebecca; Furrow, Stanley D.

    2007-01-01

    Research on the glyoxal clock reaction has led to adaptation of the clock reaction to a general chemistry experiment. This particular reaction is just one of many that used formaldehyde in the past. The kinetics of the glyoxal clock makes the reaction suitable as a general chemistry lab using a Calculator Based Laboratory (CBL) or a LabPro. The…

  5. Nonlocality in deuteron stripping reactions.

    PubMed

    Timofeyuk, N K; Johnson, R C

    2013-03-15

    We propose a new method for the analysis of deuteron stripping reactions, A(d,p)B, in which the nonlocality of nucleon-nucleus interactions and three-body degrees of freedom are accounted for in a consistent way. The model deals with equivalent local nucleon potentials taken at an energy shifted by ∼40  MeV from the "E(d)/2" value frequently used in the analysis of experimental data, where E(d) is the incident deuteron energy. The "E(d)/2" rule lies at the heart of all three-body analyses of (d, p) reactions performed so far with the aim of obtaining nuclear structure properties such as spectroscopic factors and asymptotic normalization coefficients that are crucial for our understanding of nuclear shell evolution in neutron- and proton-rich regions of the nuclear periodic table and for predicting the cross sections of stellar reactions. The large predicted shift arises from the large relative kinetic energy of the neutron and proton in the incident deuteron in those components of the n+p+A wave function that dominate the (d, p) reaction amplitude. The large shift reduces the effective d-A potentials and leads to a change in predicted (d, p) cross sections, thus affecting the interpretation of these reactions in terms of nuclear structure. PMID:25166525

  6. Combustion kinetics and reaction pathways

    SciTech Connect

    Klemm, R.B.; Sutherland, J.W.

    1993-12-01

    This project is focused on the fundamental chemistry of combustion. The overall objectives are to determine rate constants for elementary reactions and to elucidate the pathways of multichannel reactions. A multitechnique approach that features three independent experiments provides unique capabilities in performing reliable kinetic measurements over an exceptionally wide range in temperature, 300 to 2500 K. Recent kinetic work has focused on experimental studies and theoretical calculations of the methane dissociation system (CH{sub 4} + Ar {yields} CH{sub 3} + H + Ar and H + CH{sub 4} {yields} CH{sub 3} + H{sub 2}). Additionally, a discharge flow-photoionization mass spectrometer (DF-PIMS) experiment is used to determine branching fractions for multichannel reactions and to measure ionization thresholds of free radicals. Thus, these photoionization experiments generate data that are relevant to both reaction pathways studies (reaction dynamics) and fundamental thermochemical research. Two distinct advantages of performing PIMS with high intensity, tunable vacuum ultraviolet light at the National Synchrotron Light Source are high detection sensitivity and exceptional selectivity in monitoring radical species.

  7. Simultaneous Photoinduced ATRP and CuAAC Reactions for the Synthesis of Block Copolymers.

    PubMed

    Murtezi, Eljesa; Yagci, Yusuf

    2014-09-01

    Atom transfer radical polymerization (ATRP) and copper-catalyzed azide-alkyne cycloaddition (CuAAC) reactions, both utilizing copper(I) (Cu(I)) complexes, make a tremendous progress in synthetic polymer chemistry. Independently or in combination with other polymerization processes, they give access to the synthesis of polymers with well-defined structures, desired molecular architectures, and a wide variety of functionalities. Here, a novel in situ photoinduced formation of block copolymers is described by simultaneous ATRP and CuAAC processes. This approach relies on the direct reduction of initially charged copper(II) complexes to Cu(I) complexes to trigger both ATRP and CuAAC reactions coinciding under UV light at ambient temperature in one pot. Its synthetic utility is demonstrated on a model block copolymerization process by photoinduced ATRP of methyl methacrylate (MMA) using an initiator possessing acetylene functionality and concomitant click reaction between thus formed α-acetylene-poly(methyl methacrylate) (Ac-PMMA) and independently prepared azide functional polystyrene (PS-N3 ). Successful formation of PS-b-PMMA block copolymer is confirmed by FT-IR and (1) H NMR spectral analysis and gel permeation chromatography (GPC) measurements. PMID:25200624

  8. Experimental study on weathering of seafloor volcanic glass by bacteria (Pseudomonas fluorescens) - Implications for the contribution of bacteria to the wate-rock reaction at the Mid-Oceanic Ridge setting

    NASA Astrophysics Data System (ADS)

    Chen, Shun; Wu, Zijun; Peng, Xiaotong

    2014-08-01

    The biologically mediated weathering of the ocean crust has received increasing attention in recent decades, but the rates and the possible mechanism of elemental release during microbe-basalt interactions occurring below the seafloor have not been studied in detail. In this study, we established an experimental weathering study of seafloor natural basaltic glass comparing the effect of microbial activity (Pseudomonas fluorescens) in P-rich and P-poor media with parallel controls containing either nonviable cells or organic acid. The changes in the chemical parameters, including pH, bacterial densities, and ion concentrations (Ca, Mg, Si, Mn, Al, Fe, and P) in the solution, were examined during the different batch experiments. The results showed that the pH decreased from 7.0 to 3.5 and the bacterial density increased from 105 to 108 cells/ml during the first 120 h, and the cell numbers remained constant at 108 cells/ml and the pH increased from 3.5 to 6 between 120 h and 864 h in the P-bearing reactors containing bacteria. In contrast, during all the experimental time, the pH remained close to neutral condition in the abiotic control systems and the dissolution rates increased markedly with a decrease in pH and became minimal at near-neutral pH in P-bearing reactors containing bacteria, where Ca, Si, and Mg release rates were 2- to 4-fold higher than those obtained in chemical systems and biotic P-limited systems. Furthermore, the surfaces of the natural volcanic glass from the biotic systems were colonized by bacteria. Simultaneously, the etch pits were observed by Scanning Electron Microscope, which further indicate that the bacteria may promote the mineral dissolution for energy gain. Some elements (e.g., Fe, Mn, and Al) releasing from natural volcanic glass are likely an important source of the elemental budget in the ocean, and thus the element release and its possible mechanism conducted in this experimental study have potential implications on the

  9. Reaction Coordinates and Mechanistic Hypothesis Tests.

    PubMed

    Peters, Baron

    2016-05-27

    Reaction coordinates are integral to several classic rate theories that can (a) predict kinetic trends across conditions and homologous reactions, (b) extract activation parameters with a clear physical interpretation from experimental rates, and (c) enable efficient calculations of free energy barriers and rates. New trajectory-based rare events methods can provide rates directly from dynamical trajectories without a reaction coordinate. Trajectory-based frameworks can also generate ideal (but abstract) reaction coordinates such as committors and eigenfunctions of the master equation. However, rates and mechanistic insights obtained from trajectory-based methods and abstract coordinates are not readily generalized across simulation conditions or reaction families. We discuss methods for identifying physically meaningful reaction coordinates, including committor analysis, variational transition state theory, Kramers-Langer-Berezhkovskii-Szabo theory, and statistical inference methods that can use path sampling data to screen, mix, and optimize thousands of trial coordinates. Special focus is given to likelihood maximization and inertial likelihood maximization approaches. PMID:27090846

  10. Reaction Coordinates and Mechanistic Hypothesis Tests

    NASA Astrophysics Data System (ADS)

    Peters, Baron

    2016-05-01

    Reaction coordinates are integral to several classic rate theories that can (a) predict kinetic trends across conditions and homologous reactions, (b) extract activation parameters with a clear physical interpretation from experimental rates, and (c) enable efficient calculations of free energy barriers and rates. New trajectory-based rare events methods can provide rates directly from dynamical trajectories without a reaction coordinate. Trajectory-based frameworks can also generate ideal (but abstract) reaction coordinates such as committors and eigenfunctions of the master equation. However, rates and mechanistic insights obtained from trajectory-based methods and abstract coordinates are not readily generalized across simulation conditions or reaction families. We discuss methods for identifying physically meaningful reaction coordinates, including committor analysis, variational transition state theory, Kramers-Langer-Berezhkovskii-Szabo theory, and statistical inference methods that can use path sampling data to screen, mix, and optimize thousands of trial coordinates. Special focus is given to likelihood maximization and inertial likelihood maximization approaches.

  11. Practice Gaps: Drug Reactions.

    PubMed

    Wolverton, Stephen E

    2016-07-01

    The term "drug reactions" is relevant to dermatology in three categories of reactions: cutaneous drug reactions without systemic features, cutaneous drug reactions with systemic features, and systemic drugs prescribed by the dermatologist with systematic adverse effects. This article uses examples from each of these categories to illustrate several important principles central to drug reaction diagnosis and management. The information presented will help clinicians attain the highest possible level of certainty before making clinical decisions. PMID:27363888

  12. Reaction pathways of propene pyrolysis.

    PubMed

    Qu, Yena; Su, Kehe; Wang, Xin; Liu, Yan; Zeng, Qingfeng; Cheng, Laifei; Zhang, Litong

    2010-05-01

    The gas-phase reaction pathways in preparing pyrolytic carbon with propene pyrolysis have been investigated in detail with a total number of 110 transition states and 50 intermediates. The structure of the species was determined with density functional theory at B3PW91/6-311G(d,p) level. The transition states and their linked intermediates were confirmed with frequency and the intrinsic reaction coordinates analyses. The elementary reactions were explored in the pathways of both direct and the radical attacking decompositions. The energy barriers and the reaction energies were determined with accurate model chemistry method at G3(MP2) level after an examination of the nondynamic electronic correlations. The heat capacities and entropies were obtained with statistical thermodynamics. The Gibbs free energies at 298.15 K for all the reaction steps were reported. Those at any temperature can be developed with classical thermodynamics by using the fitted (as a function of temperature) heat capacities. It was found that the most favorable paths are mainly in the radical attacking chain reactions. The chain was proposed with 26 reaction steps including two steps of the initialization of the chain to produce H and CH(3) radicals. For a typical temperature (1200 K) adopted in the experiments, the highest energy barriers were found in the production of C(3) to be 203.4 and 193.7 kJ/mol. The highest energy barriers for the production of C(2) and C were found 174.1 and 181.4 kJ/mol, respectively. These results are comparable with the most recent experimental observation of the apparent activation energy 201.9 +/- 0.6 or 137 +/- 25 kJ/mol. PMID:20082392

  13. (Laser enhanced chemical reaction studies)

    SciTech Connect

    Not Available

    1992-01-01

    Experimental studies of dynamic molecular processes are described with particular emphasis on the use of a powerful infrared diode laser probe technique developed in our laboratory. This technique allows us to determine the final states of CO{sub 2} (and other molecules) produced by collisions, photofragmentation, or chemical reactions with a spectral resolution of 0.0003 cm{sup {minus}1} and a time resolution of 10{sup {minus}7} sec. Such high spectral resolution provides a detailed picture of the vibrational and rotational states of molecules produced by these dynamic events. We have used this experimental method to probe collisions between hot hydrogen/deuterium atoms and CO{sub 2}, between O({sup 1}D) atoms and CO{sub 2}, to study the final states of DC1 molecules produced as a result of the reactions of hot Cl atoms, and to investigate the dynamics of the reaction between OH and CO molecules. Advances in our techniques over the past two years have allowed us to identify and study more than 200 final rotational states in ten different vibrational levels of CO{sub 2} encompassing all 3 normal modes, many overtones, and combination states of the molecule. We have extended the technique to probe a variety of new molecules such as OCS, N{sub 2}O, DCl, and CS{sub 2}. All of this work is aimed at providing experimental tests for polyatomic molecule potential energy surfaces, chemical transition states in complex systems, and theories of reaction dynamic in molecules with more than 3 atoms.

  14. A study of the Sabatier-methanation reaction kinetics

    NASA Technical Reports Server (NTRS)

    Verostko, C. E.; Forsythe, R. K.

    1974-01-01

    The kinetics of the Sabatier methanation reaction, the reduction of carbon dioxide with hydrogen to methane and water, was investigated for 58 percent nickel on kieselguhr catalyst and 20 percent ruthenium on alumina catalyst. Differential rate data from an experimental program were correlated with a power function rate equation both for forward and reverse reactions. The kinetic parameters of activation energy, frequency rate constant and reaction order were determined for the rate equation. The values of these parameters were obtained from an Arrhenius plot of the experimental differential rate data. Also the carbon monoxide side reaction effect was measured and included in the correlation of parameters. The reaction was found to fit the rate equation experimentally within the temperature range 421 K, where the reaction effectively begins, the 800 K where the reaction rate drops and departs from the rate equation form.

  15. A Kinetic Study of the Diels-Alder Reaction. An Experiment Illustrating Simple Second-Order Reaction Kinetics.

    ERIC Educational Resources Information Center

    Silvestri, Michael G.; Dills, Charles E.

    1989-01-01

    Describes an organic chemistry experiment for teaching the basic concepts of chemical kinetics. Provides background information about first- and second-order reactions, experimental procedures of the Diels-Alder reaction between cyclopentadiene and dimethyl fumarate, and the experimental results. (YP)

  16. Experimental Pi.

    ERIC Educational Resources Information Center

    Corris, G.

    1990-01-01

    Discusses the calculation of pi by means of experimental methods. Polygon circle ratios, Archimedes' method, Buffon's needles, a Monte Carlo method, and prime number approaches are used. Presents three BASIC programs for the calculations. (YP)

  17. Microfluidic chemical reaction circuits

    DOEpatents

    Lee, Chung-cheng; Sui, Guodong; Elizarov, Arkadij; Kolb, Hartmuth C.; Huang, Jiang; Heath, James R.; Phelps, Michael E.; Quake, Stephen R.; Tseng, Hsian-rong; Wyatt, Paul; Daridon, Antoine

    2012-06-26

    New microfluidic devices, useful for carrying out chemical reactions, are provided. The devices are adapted for on-chip solvent exchange, chemical processes requiring multiple chemical reactions, and rapid concentration of reagents.

  18. Continuous detonation reaction engine

    NASA Technical Reports Server (NTRS)

    Lange, O. H.; Stein, R. J.; Tubbs, H. E.

    1968-01-01

    Reaction engine operates on the principles of a controlled condensed detonation rather than on the principles of gas expansion. The detonation results in reaction products that are expelled at a much higher velocity.

  19. Allergic reactions (image)

    MedlinePlus

    Allergic reaction is a sensitivity to a specific substance, called an allergen, that is contacted through the skin, inhaled into the lungs, swallowed or injected. The body's reaction to an allergen can be mild, such as ...

  20. Allergic reactions (image)

    MedlinePlus

    Allergic reaction can be provoked by skin contact with poison plants, chemicals and animal scratches, as well as by ... dust, nuts and shellfish, may also cause allergic reaction. Medications such as penicillin and other antibiotics are ...

  1. Microscale Thermite Reactions.

    ERIC Educational Resources Information Center

    Arnaiz, Francisco J.; Aguado, Rafael; Arnaiz, Susana

    1998-01-01

    Describes the adaptation of thermite (aluminum with metal oxides) reactions from whole-class demonstrations to student-run micro-reactions. Lists detailed directions and possible variations of the experiment. (WRM)

  2. Special Relativity and Reactions with Unstable Nuclei

    SciTech Connect

    Bertulani, C.A.

    2005-10-14

    Dynamical relativistic effects are often neglected in the description of reactions with unstable nuclear beams at intermediate energies (ELab {approx_equal} 100 MeV/nucleon). Evidently, this introduces sizable errors in experimental analysis and theoretical descriptions of these reactions. This is particularly important for the experiments held in GANIL/France, MSU/USA, RIKEN/Japan and GSI/Germany. I review a few examples where relativistic effects have been studied in nucleus-nucleus scattering at intermediate energies.

  3. Reaction cross sections of unstable nuclei

    SciTech Connect

    Ozawa, Akira

    2006-11-02

    Experimental studies on reaction cross sections are reviewed. The recent developments of radioactive nuclear beams have enabled us to measure reaction cross-sections for unstable nuclei. Using Glauber-model analysis, effective nuclear matter density distributions of unstable nuclei can be studied. Recent measurements in RIBLL at IMP and RIPS at RIKEN are introduced. The effective matter density distributions for 14-18C are also mentioned.

  4. Reaction coordinates for electron transfer reactions

    SciTech Connect

    Rasaiah, Jayendran C.; Zhu Jianjun

    2008-12-07

    The polarization fluctuation and energy gap formulations of the reaction coordinate for outer sphere electron transfer are linearly related to the constant energy constraint Lagrangian multiplier m in Marcus' theory of electron transfer. The quadratic dependence of the free energies of the reactant and product intermediates on m and m+1, respectively, leads to similar dependence of the free energies on the reaction coordinates and to the same dependence of the activation energy on the reorganization energy and the standard reaction free energy. Within the approximations of a continuum model of the solvent and linear response of the longitudinal polarization to the electric field in Marcus' theory, both formulations of the reaction coordinate are expected to lead to the same results.

  5. Catalytic diastereoselective petasis reactions.

    PubMed

    Muncipinto, Giovanni; Moquist, Philip N; Schreiber, Stuart L; Schaus, Scott E

    2011-08-22

    Multicomponent Petasis reactions: the first diastereoselective Petasis reaction catalyzed by chiral biphenols that enables the synthesis of syn and anti β-amino alcohols in pure form has been developed. The reaction exploits a multicomponent approach that involves boronates, α-hydroxy aldehydes, and amines. PMID:21751322

  6. Experimental and theoretical studies of the reactions of chlorine atoms with 1,2-dichloroethane and 1,2-dichloroethane-d4 in the gas phase. The kinetics of hydrogen atom abstraction from the -CH2Cl group in chloroethane and 1,2-dichloroethane

    NASA Astrophysics Data System (ADS)

    Sarzyński, Dariusz S.; Fojcik, Łukasz; Gola, Agnieszka A.; Berkowski, Ryszard; Jodkowski, Jerzy T.; Latajka, Zdzisław

    2014-03-01

    The rate constant for H-abstraction (kH) from CH2ClCH2Cl and D-abstraction (kD) from CD2ClCD2Cl by chlorine atoms is described by the expressions: kH = (1.99 ± 0.12) × 10-11 exp(-777 ± 23/T) cm3 molecule-1 s-1 and kD = (1.73 ± 0.12) × 10-11 exp(-1148 ± 16/T) cm3 molecule-1 s-1. The experiment revealed significant differences in the values of the rate constants for the abstraction of H-atom from the -CH2Cl group in chloroethane and 1,2-dichloroethane. The explanation of these differences was the subject of theoretical studies. The calculated potential energy barriers for the abstraction reaction confirmed the experimental results.

  7. Multichannel quench-flow microreactor chip for parallel reaction monitoring.

    PubMed

    Bula, Wojciech P; Verboom, Willem; Reinhoudt, David N; Gardeniers, Han J G E

    2007-12-01

    This paper describes a multichannel silicon-glass microreactor which has been utilized to investigate the kinetics of a Knoevenagel condensation reaction under different reaction conditions. The reaction is performed on the chip in four parallel channels under identical conditions but with different residence times. A special topology of the reaction coils overcomes the common problem arising from the difference in pressure drop of parallel channels having different length. The parallelization of reaction coils combined with chemical quenching at specific locations results in a considerable reduction in experimental effort and cost. The system was tested and showed good reproducibility in flow properties and reaction kinetic data generation. PMID:18030392

  8. Reaction efficiency effects on binary chemical reactions

    NASA Astrophysics Data System (ADS)

    Lazaridis, Filippos; Savara, Aditya; Argyrakis, Panos

    2014-09-01

    We study the effect of the variation of reaction efficiency in binary reactions. We use the well-known A + B → 0 model, which has been extensively studied in the past. We perform simulations on this model where we vary the efficiency of reaction, i.e., when two particles meet they do not instantly react, as has been assumed in previous studies, but they react with a probability γ, where γ is in the range 0 < γ < 1. Our results show that at small γ values the system is reaction limited, but as γ increases it crosses over to a diffusion limited behavior. At early times, for small γ values, the particle density falls slower than for larger γ values. This fall-off goes over a crossover point, around the value of γ = 0.50 for high initial densities. Under a variety of conditions simulated, we find that the crossover point was dependent on the initial concentration but not on the lattice size. For intermediate and long times simulations, all γ values (in the depleted reciprocal density versus time plot) converge to the same behavior. These theoretical results are useful in models of epidemic reactions and epidemic spreading, where a contagion from one neighbor to the next is not always successful but proceeds with a certain probability, an analogous effect with the reaction probability examined in the current work.

  9. Curing behavior and reaction kinetics of binder resins for 3D-printing investigated by dielectric analysis (DEA)

    NASA Astrophysics Data System (ADS)

    Möginger, B.; Kehret, L.; Hausnerova, B.; Steinhaus, J.

    2016-05-01

    3D-Printing is an efficient method in the field of additive manufacturing. In order to optimize the properties of manufactured parts it is essential to adapt the curing behavior of the resin systems with respect to the requirements. Thus, effects of resin composition, e.g. due to different additives such as thickener and curing agents, on the curing behavior have to be known. As the resin transfers from a liquid to a solid glass the time dependent ion viscosity was measured using DEA with flat IDEX sensors. This allows for a sensitive measurement of resin changes as the ion viscosity changes two to four decades. The investigated resin systems are based on the monomers styrene and HEMA. To account for the effects of copolymerization in the calculation of the reaction kinetics it was assumed that the reaction can be considered as a homo-polymerization having a reaction order n≠1. Then the measured ion viscosity curves are fitted with the solution of the reactions kinetics - the time dependent degree of conversion (DC-function) - for times exceeding the initiation phase representing the primary curing. The measured ion viscosity curves can nicely be fitted with the DC-function and the determined fit parameters distinguish distinctly between the investigated resin compositions.

  10. On the Violence of High Explosive Reactions

    SciTech Connect

    Tarver, C M; Chidester, S K

    2004-02-09

    High explosive reactions can be caused by three general energy deposition processes: impact ignition by frictional and/or shear heating; bulk thermal heating; and shock compression. The violence of the subsequent reaction varies from benign slow combustion to catastrophic detonation of the entire charge. The degree of violence depends on many variables, including the rate of energy delivery, the physical and chemical properties of the explosive, and the strength of the confinement surrounding the explosive charge. The current state of experimental and computer modeling research on the violence of impact, thermal, and shock-induced reactions is reviewed.

  11. Experimental philosophy.

    PubMed

    Knobe, Joshua; Buckwalter, Wesley; Nichols, Shaun; Robbins, Philip; Sarkissian, Hagop; Sommers, Tamler

    2012-01-01

    Experimental philosophy is a new interdisciplinary field that uses methods normally associated with psychology to investigate questions normally associated with philosophy. The present review focuses on research in experimental philosophy on four central questions. First, why is it that people's moral judgments appear to influence their intuitions about seemingly nonmoral questions? Second, do people think that moral questions have objective answers, or do they see morality as fundamentally relative? Third, do people believe in free will, and do they see free will as compatible with determinism? Fourth, how do people determine whether an entity is conscious? PMID:21801019

  12. Simulation as an aid to experimental design

    SciTech Connect

    Frazer, J.W.; Balaban, D.J.; Wang, J.L.

    1983-05-01

    A simulator of chemical reactions can aid the scientist in the design of experimentation. They are of great value when studying enzymatic kinetic reactions. One such simulator is a numerical ordinary differential equation solver which uses interactive graphics to provide the user with the capability to simulate an extremely wide range of enzyme reaction conditions for many types of single substrate reactions. The concentration vs. time profiles of any subset or all nine states of a complex reaction can be displayed with and without simulated instrumental noise. Thus the user can estimate the practicality of any proposed experimentation given known instrumental noise. The experimenter can readily determine which state provides the most information related to the proposed kinetic parameters and mechanism. A general discussion of the program including the nondimensionalization of the set of differential equations is included. Finally, several simulation examples are shown and the results discussed.

  13. Experimental Approaches to Studying Biological Electron Transfer.

    ERIC Educational Resources Information Center

    Scott, Robert A.; And Others

    1985-01-01

    Provides an overview on biological electron-transfer reactions, summarizing what is known about how distance, spatial organization, medium, and other factors affect electron transfer. Experimental approaches, including studies of bimolecular electron transfer reactions (electrostatic effects and precursor complexes), are considered. (JN)

  14. Modifying glass fiber surface with grafting acrylamide by UV-grafting copolymerization for preparation of glass fiber reinforced PVDF composite membrane.

    PubMed

    Luo, Nan; Zhong, Hui; Yang, Min; Yuan, Xing; Fan, Yaobo

    2016-01-01

    Experimental design and response surface methodology (RSM) were used to optimize the modification of conditions for glass surface grafting with acrylamide (AM) monomer for preparation of a glass fiber reinforced poly(vinylidene fluoride) (PVDF) composite membrane (GFRP-CM). The factors considered for experimental design were the UV (ultraviolet)-irradiation time, the concentrations of the initiator and solvent, and the kinds and concentrations of the silane coupling agent. The optimum operating conditions determined were UV-irradiation time of 25 min, an initiator concentration of 0-0.25 wt.%, solvent of N-Dimethylacetamide (DMAC), and silane coupling agent KH570 with a concentration of 7 wt.%. The obtained optimal parameters were located in the valid region and the experimental confirmation tests conducted showed good accordance between predicted and experimental values. Under these optimal conditions, the water absorption of the grafted modified glass fiber was improved from 13.6% to 23%; the tensile strength was enhanced and the peeling strength of the glass fiber reinforced PVDF composite membrane was improved by 23.7% and 32.6% with an AM concentration at 1 wt.% and 2 wt.%. The surface composition and microstructure of AM grafted glass fiber were studied via several techniques including Field Emission Scanning Electron Microscopy (FESEM), Fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR) and energy dispersive X-ray spectroscopy (EDX). The analysis of the EDX and FTIR-ATR results confirmed that the AM was grafted to the glass fiber successfully by detecting and proving the existence of nitrogen atoms in the GFRP-CM. PMID:26899659

  15. Clipped Random Wave Morphologies and the Analysis of the SAXS of an Ionomer Formed by Copolymerization of Tetrafluoroethylene and CF[subscript 2]=CFO(CF[subscript 2])[subscript 4]SO[subscript 3]H

    SciTech Connect

    Aieta, Niccolo V.; Stanis, Ronald J.; Horan, James L.; Yandrasits, Michael A.; Cookson, David J.; Ingham, Bridget; Toney, Michael F.; Hamrock, Steven J.; Herring, Andrew M.

    2009-09-15

    Using SAXS data, the microstructure of the ionomer formed by copolymerization of tetrafluoroethylene and CF{sub 2}=CFO(CF{sub 2}){sub 4}SO{sub 3}H films has been approached by two methods: a numerical method (the unified fit approach) utilizing a simple model of spherical scattering objects to determine the radius of gyration of different scattering features of the ionomer films and by a graphical method, the clipped random wave approach (CRW), using the scattering data and a porosity parameter to generate a random wave which is clipped to produce a real-space image of the microstructure. We studied films with EW of 733, 825, 900, and 1082 in both the as-cast and annealed 'dry' and boiled 'wet' states. The results of the two data analysis techniques are in good size agreement with each other. In addition, the CRW model show striking similarities to the structure proposed in a recent dissipative particle dynamic models. This has been the first time to our knowledge that the CRW technique has been applied to a PFSA type ionomer.

  16. Anaphylactic reactions to cinoxacin.

    PubMed Central

    Stricker, B. H.; Slagboom, G.; Demaeseneer, R.; Slootmaekers, V.; Thijs, I.; Olsson, S.

    1988-01-01

    During 1981 to mid-1988 three cases of anaphylactic shock after treatment with the quinolone derivative cinoxacin were reviewed by the Netherlands Centre for Monitoring of Adverse Reactions to Drugs and 17 cases of an anaphylactic type of reaction notified to the World Health Organisation Collaborating Centre for International Drug Monitoring. In five out of six patients for whom data were available the reaction began shortly after taking a single capsule of a second or next course of treatment. Cinoxacin is related to nalidixic acid, and one patient previously treated with that agent subsequently had an anaphylactoid reaction to cinoxacin and later developed a skin reaction to nalidixic acid. There were no deaths, and patients treated as an emergency with plasma expanders or with adrenaline and corticosteroids generally recovered promptly and uneventfully. In view of the potentially fatal consequences of anaphylactic reactions to cinoxacin and other quinolones doctors should take care when prescribing these drugs. PMID:3147004

  17. Reactions to radiocontrast media.

    PubMed

    Hong, Sandra J; Wong, Johnson T; Bloch, Kurt J

    2002-01-01

    Adverse reactions to radiocontrast media (RCM) occur unexpectedly and may be life-threatening. This article describes an anaphylactoid reaction (AR) in one patient. The term AR refers to a syndrome clinically similar to anaphylaxis, but these reactions are independent of immunoglobulin E antibody-mediated mast cell or basophil degranulation. This article briefly reviews the literature regarding RCMs and types of reactions to RCM. The risk factors for AR to RCM infusions will be discussed along with current concepts of the pathogenesis of RCM-induced ARs. This article also describes the therapeutic management of patients who have had a previous adverse reaction to RCM and provides an approach to patients who have breakthrough reactions despite adequate premedication, but require additional radiographic studies. PMID:12476546

  18. Noncanonical Reactions of Flavoenzymes

    PubMed Central

    Sobrado, Pablo

    2012-01-01

    Enzymes containing flavin cofactors are predominantly involved in redox reactions in numerous cellular processes where the protein environment modulates the chemical reactivity of the flavin to either transfer one or two electrons. Some flavoenzymes catalyze reactions with no net redox change. In these reactions, the protein environment modulates the reactivity of the flavin to perform novel chemistries. Recent mechanistic and structural data supporting novel flavin functionalities in reactions catalyzed by chorismate synthase, type II isopentenyl diphosphate isomerase, UDP-galactopyranose mutase, and alkyl-dihydroxyacetonephosphate synthase are presented in this review. In these enzymes, the flavin plays either a direct role in acid/base reactions or as a nucleophile or electrophile. In addition, the flavin cofactor is proposed to function as a “molecular scaffold” in the formation of UDP-galactofuranose and alkyl-dihydroxyacetonephosphate by forming a covalent adduct with reaction intermediates. PMID:23203060

  19. Mechanisms in Knockout Reactions

    NASA Astrophysics Data System (ADS)

    Bazin, D.; Charity, R. J.; de Souza, R. T.; Famiano, M. A.; Gade, A.; Henzl, V.; Henzlova, D.; Hudan, S.; Lee, J.; Lukyanov, S.; Lynch, W. G.; McDaniel, S.; Mocko, M.; Obertelli, A.; Rogers, A. M.; Sobotka, L. G.; Terry, J. R.; Tostevin, J. A.; Tsang, M. B.; Wallace, M. S.

    2009-06-01

    We report the first detailed study of the relative importance of the stripping and diffraction mechanisms involved in nucleon knockout reactions, by the use of a coincidence measurement of the residue and fast proton following one-proton knockout reactions. The measurements used the S800 spectrograph in combination with the HiRA detector array at the NSCL. Results for the reactions Be9(C9,B8+X)Y and Be9(B8,Be7+X)Y are presented and compared with theoretical predictions for the two reaction mechanisms calculated using the eikonal model. The data show a clear distinction between the stripping and diffraction mechanisms and the measured relative proportions are very well reproduced by the reaction theory. This agreement adds support to the results of knockout reaction analyses and their applications to the spectroscopy of rare isotopes.

  20. Animal experimentation.

    PubMed

    Kolar, Roman

    2006-01-01

    Millions of animals are used every year in often times extremely painful and distressing scientific procedures. Legislation of animal experimentation in modern societies is based on the supposition that this is ethically acceptable when certain more or less defined formal (e.g. logistical, technical) demands and ethical principles are met. The main parameters in this context correspond to the "3Rs" concept as defined by Russel and Burch in 1959, i.e. that all efforts to replace, reduce and refine experiments must be undertaken. The licensing of animal experiments normally requires an ethical evaluation process, often times undertaken by ethics committees. The serious problems in putting this idea into practice include inter alia unclear conditions and standards for ethical decisions, insufficient management of experiments undertaken for specific (e.g. regulatory) purposes, and conflicts of interest of ethics committees' members. There is an ongoing societal debate about ethical issues of animal use in science. Existing EU legislation on animal experimentation for cosmetics testing is an example of both the public will for setting clear limits to animal experiments and the need to further critically examine other fields and aspects of animal experimentation. PMID:16501652