WorldWideScience

Sample records for carbon 14 reactions

  1. Carbon-14 immobilization via the CO2-Ba(OH)2 hydrate gas-solid reaction

    International Nuclear Information System (INIS)

    Although no restrictions have been placed on the release of carbon-14, it has been identified as a potential health hazard due to the ease in which it may be assimilated into the biosphere. The intent of the Carbon-14 Immobilization Program, funded through the Airborne Waste Program Management Office, is to develop and demonstrate a novel process for restricting off-gas releases of carbon-14 from various nuclear facilities. The process utilizes the CO2-Ba(OH)2 hydrate gas-solid reaction to directly remove and immobilize carbon-14. The reaction product, BaCO3, possesses both the thermal and chemical stability desired for long-term waste disposal. The process is capable of providing decontamination factors in excess of 1000 and reactant utilization of greater than 99% in the treatment of high volumetric, airlike (330 ppM CO2) gas streams. For the treatment of an air-based off-gas stream, the use of packed beds of Ba(OH)2.8H2O flakes to remove CO2 has been demonstrated. However, the operating conditions must be maintained between certain upper and lower limits with respect to the partial pressure of water. If the water vapor pressure in the gas is less than the dissociation vapor pressure of Ba(OH)2.8H2O, the bed will deactivate. If the vapor pressure is considerably greater, pressure drop problems will increase with increasing humidity as the particles curl and degrade. Results have indicated that when operated in the proper regime, the bulk of the increase in pressure drop results from the conversion of Ba(OH)2.8H2O to BaCO3 and not from the hydration of the commercial Ba(OH)2.8H2O (i.e. Ba(OH)2.7.50H2O) to Ba(OH)2.8H2O

  2. Oxygen electrode reaction in molten carbonate fuel cells. Final report, September 15, 1987--September 14, 1990

    Energy Technology Data Exchange (ETDEWEB)

    Appleby, A.J.; White, R.E.

    1992-07-07

    Molten carbonate fuel cell system is a leading candidate for the utility power generation because of its high efficiency for fuel to AC power conversion, capability for an internal reforming, and a very low environmental impact. However, the performance of the molten carbonate fuel cell is limited by the oxygen reduction reaction and the cell life time is limited by the stability of the cathode material. An elucidation of oxygen reduction reaction in molten alkali carbonate is essential because overpotential losses in the molten carbonate fuel cell are considerably greater at the oxygen cathode than at the fuel anode. Oxygen reduction on a fully-immersed gold electrode in a lithium carbonate melt was investigated by electrochemical impedance spectroscopy and cyclic voltammetry to determine electrode kinetic and mass transfer parameters. The dependences of electrode kinetic and mass transfer parameters on gas composition and temperature were examined to determine the reaction orders and the activation energies. The results showed that oxygen reduction in a pure lithium carbonate melt occurs via the peroxide mechanism. A mass transfer parameter, D{sub O}{sup 1/2}C{sub O}, estimated by the cyclic voltammetry concurred with that calculated by the EIS technique. The temperature dependence of the exchange current density and the product D{sub O}{sup 1/2}C{sub O} were examined and the apparent activation energies were determined to be about 122 and 175 kJ/ mol, respectively.

  3. Coprecipitation of (14)C and Sr with carbonate precipitates: The importance of reaction kinetics and recrystallization pathways.

    Science.gov (United States)

    Hodkin, David J; Stewart, Douglas I; Graham, James T; Burke, Ian T

    2016-08-15

    This study investigated the simultaneous removal of Sr(2+) and (14)CO3(2-) from pH>12 Ca(OH)2 solution by the precipitation of calcium carbonate. Initial Ca(2+):CO3(2-) ratios ranged from 10:1 to 10:100 (mM:mM). Maximum removal of (14)C and Sr(2+) both occurred in the system containing 10mM Ca(2+) and 1mM CO3(2-) (99.7% and 98.6% removal respectively). A kinetic model is provided that describes (14)C and Sr removal in terms of mineral dissolution and precipitation reactions. The removal of (14)C was achieved during the depletion of the initial TIC in solution, and was subsequently significantly affected by recrystallization of the calcite precipitate from an elongate to isotropic morphology. This liberated >46% of the (14)C back to solution. Sr(2+) removal occurred as Ca(2+) became depleted in solution and was not significantly affected by the recrystallization process. The proposed reaction could form the basis for low cost remediation scheme for (90)Sr and (14)C in radioactively contaminated waters (<$0.25 reagent cost per m(3) treated).

  4. Carbon-14 waste management

    International Nuclear Information System (INIS)

    Carbon-14 occurs in nature, but is also formed in nuclear reactors. Because of its long half-life and the biological significance of carbon, releases from nuclear facilities could have a significant radiological impact. Waste management strategies for carbon-14 are therefore of current concern. Carbon-14 is present in a variety of waste streams both at reactors and at reprocessing plants. A reliable picture of the production and release of carbon-14 from various reactor systems has been built up for the purposes of this study. A possible management strategy for carbon-14 might be the reduction of nitrogen impurity levels in core materials, since the activation of 14N is usually the dominant source of carbon-14. The key problem in carbon-14 management is its retention of off-gas streams, particularly in the dissolver off-gas stream at reprocessing plants. Three alternative trapping processes that convert carbon dioxide into insoluble carbonates have been suggested. The results show that none of the options considered need be rejected on the grounds of potential radiation doses to individuals. All exposures should be as low as reasonably achievable, economic and social factors being taken into account. If, on these grounds, retention and disposal of carbon-14 is found to be beneficial, then, subject to the limitations noted, appropriate retention, immobilization and disposal technologies have been identified

  5. Compilation of carbon-14 data

    Energy Technology Data Exchange (ETDEWEB)

    Paasch, R.A.

    1985-07-08

    A review and critical analysis was made of the original sources of carbon-14 in the graphite moderator and reflector zones of the eight Hanford production reactors, the present physical and chemical state of the carbon-14, pathways (other than direct combustion) by which the carbon-14 could be released to the biosphere, and the maximum rate at which it might be released under circumstances which idealistically favor the release. Areas of uncertainty are noted and recommendations are made for obtaining additional data in three areas: (1) release rate of carbon-14 from irradiated graphite saturated with aerated water; (2) characterization of carbon-14 deposited outside the moderator and reflector zones; and (3) corrosion/release rate of carbon-14 from irradiated steel and aluminum alloys.

  6. Compilation of carbon-14 data

    International Nuclear Information System (INIS)

    A review and critical analysis was made of the original sources of carbon-14 in the graphite moderator and reflector zones of the eight Hanford production reactors, the present physical and chemical state of the carbon-14, pathways (other than direct combustion) by which the carbon-14 could be released to the biosphere, and the maximum rate at which it might be released under circumstances which idealistically favor the release. Areas of uncertainty are noted and recommendations are made for obtaining additional data in three areas: (1) release rate of carbon-14 from irradiated graphite saturated with aerated water; (2) characterization of carbon-14 deposited outside the moderator and reflector zones; and (3) corrosion/release rate of carbon-14 from irradiated steel and aluminum alloys

  7. Carbon 14 dating; La datation par le carbone 14

    Energy Technology Data Exchange (ETDEWEB)

    Laj, C.; Mazaud, A.; Duplessy, J.C. [CEA Saclay, Lab. des Sciences du Climat et de l' Environnement, 91 - Gif-sur-Yvette (France)

    2004-03-01

    In this article time dating based on carbon 14 method is reviewed, its limits are explained and recent improvements are presented. Carbon 14 is a by-product of the interactions of cosmic protons with air molecules. The fluctuations of the quantity of carbon 14 present in the atmosphere are responsible for the shift observed between the result given by the method and the real age. This shift appears for ages greater than 2000 years and is estimated to 1000 years for an age of 10.000 years. As a consequence carbon 14 dating method requires calibration by comparing with other methods like dendrochronology (till 11.000 years) and time dating of fossil corals (till 26.000 years and soon till 50.000 years). It is assumed that the fluctuations of carbon 14 in the atmosphere are due to: - the changes in the intensity and composition of cosmic radiations itself (due to the motion of the sun system through the galaxy or due to the explosion of a super-novae in the surroundings of the sun system); - the changes of the earth magnetic field that diverts cosmic rays; and - the changes in the interactions between the atmosphere and the oceans knowing that 40 tons of carbon 14 are dissolved in seas while only 1 ton belongs to the atmosphere. (A.C.)

  8. Carbon 14 dating method

    International Nuclear Information System (INIS)

    This document gives a first introduction to 14C dating as it is put into practice at the radiocarbon dating centre of Claude-Bernard university (Lyon-1 univ., Villeurbanne, France): general considerations and recalls of nuclear physics; the 14C dating method; the initial standard activity; the isotopic fractioning; the measurement of samples activity; the liquid-scintillation counters; the calibration and correction of 14C dates; the preparation of samples; the benzene synthesis; the current applications of the method. (J.S.)

  9. Elastic Scattering of CARBON-14 + CARBON-12, Carbon -14 + OXYGEN-16, and CARBON-14 + OXYGEN-18.

    Science.gov (United States)

    Sterbenz, Stephen Michael

    -nucleon transfer reactions. We have also applied recent group theoretical models of heavy-ion scattering to our data. The single -channel models involving the SO(3,2) and SO(3,1) dynamical symmetries were found to be somewhat more flexible than standard optical models, but were still not able to provide an acceptable gross description of the ^ {14}C+^{12}C and ^{14}C+^ {16}O data. However, a two-channel SO(3,1) dynamical symmetry model in which the elastic transfer amplitude is obtained as the second channel has provided very good fits to individual highly structured angular distributions and better overall reproduction of the datasets than the other models which we have studied.

  10. 1,4-Diketones from Cross-Conjugated Dienones: Potassium Permanganate-Interrupted Nazarov Reaction.

    Science.gov (United States)

    Kwon, Yonghoon; Schatz, Devon J; West, Frederick G

    2015-08-17

    A domino potassium permanganate-interrupted Nazarov reaction to yield syn-2,3-disubstituted 1,4-diketones via a decarbonylative cleavage of the Nazarov oxyallyl intermediate, believed to be without precedent, is presented. This process allows syn substituents to be established stereospecifically on the 2-carbon bridge connecting the ketone carbonyl carbons, and the formation of one carbon-carbon and two carbon-oxygen bonds. Two carbon-carbon bonds are cleaved in this process. PMID:26138361

  11. Cascade enzymatic reactions for efficient carbon sequestration.

    Science.gov (United States)

    Xia, Shunxiang; Zhao, Xueyan; Frigo-Vaz, Benjamin; Zheng, Wenyun; Kim, Jungbae; Wang, Ping

    2015-04-01

    Thermochemical processes developed for carbon capture and storage (CCS) offer high carbon capture capacities, but are generally hampered by low energy efficiency. Reversible cascade enzyme reactions are examined in this work for energy-efficient carbon sequestration. By integrating the reactions of two key enzymes of RTCA cycle, isocitrate dehydrogenase and aconitase, we demonstrate that intensified carbon capture can be realized through such cascade enzymatic reactions. Experiments show that enhanced thermodynamic driving force for carbon conversion can be attained via pH control under ambient conditions, and that the cascade reactions have the potential to capture 0.5 mol carbon at pH 6 for each mole of substrate applied. Overall it manifests that the carbon capture capacity of biocatalytic reactions, in addition to be energy efficient, can also be ultimately intensified to approach those realized with chemical absorbents such as MEA. PMID:25708541

  12. Carbon-14 Bomb-Pulse Dating

    Energy Technology Data Exchange (ETDEWEB)

    Buchholz, B A

    2007-12-16

    Atmospheric testing of nuclear weapons during the 1950s and early 1960s doubled the concentration of carbon-14 atmosphere and created a pulse that labeled everything alive in the past 50 years as carbon moved up the food chain. The variation in carbon-14 concentration in time is well-documented and can be used to chronologically date all biological materials since the mid-1950s.

  13. The carbon 14 and environment; Le carbone 14 et l'environnement

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2007-07-01

    This article resume the history and the properties of the carbon 14 ({sup 14}C). We also find the different origins and the produced quantities. The carbon transfers in environment are explained and so the {sup 14}C. The biological effects and the sanitary aspects are clarified. The measurements of carbon 14 are given as well its application through the dating. The waste management is tackled. (N.C.)

  14. Reactions on carbon anodes in aluminium electrolysis

    Energy Technology Data Exchange (ETDEWEB)

    Eidet, Trygve

    1997-12-31

    The consumption of carbon anodes and energy in aluminium electrolysis is higher than what is required theoretically. This thesis studies the most important of the reactions that consume anode materials. These reactions are the electrochemical anode reaction and the airburn and carboxy reactions. The first part of the thesis deals with the kinetics and mechanism of the electrochemical anode reaction using electrochemical impedance spectroscopy. The second part deals with air and carboxy reactivity of carbon anodes and studies the effects of inorganic impurities on the reactivity of carbon anodes in the aluminium industry. Special attention is given to sulphur since its effect on the carbon gasification is not well understood. Sulphur is always present in anodes, and it is expected that the sulphur content of available anode cokes will increase in the future. It has also been suggested that sulphur poisons catalyzing impurities in the anodes. Other impurities that were investigated are iron, nickel and vanadium, which are common impurities in anodes which have been reported to catalyze carbon gasification. 88 refs., 92 figs., 24 tabs.

  15. Capture reactions on C-14 in nonstandard big bang nucleosynthesis

    Science.gov (United States)

    Wiescher, Michael; Gorres, Joachim; Thielemann, Friedrich-Karl

    1990-01-01

    Nonstandard big bang nucleosynthesis leads to the production of C-14. The further reaction path depends on the depletion of C-14 by either photon, alpha, or neutron capture reactions. The nucleus C-14 is of particular importance in these scenarios because it forms a bottleneck for the production of heavier nuclei A greater than 14. The reaction rates of all three capture reactions at big bang conditions are discussed, and it is shown that the resulting reaction path, leading to the production of heavier elements, is dominated by the (p, gamma) and (n, gamma) rates, contrary to earlier suggestions.

  16. Synthesis of carbon-14 labeled Taxol (paclitaxel)

    International Nuclear Information System (INIS)

    Reductive cleavage of the C13 side chain of Taxol (1, paclitaxel) followed by regioselective silylation gave 7-triethylsilylbaccatin III (4). 3-O-Triethysilylation of 5 and subsequent reaction with benzoyl chloride-C7-14C gave azetidinone 7. Coupling of 4 and 7 followed by deprotection gave 1.26 g of Taxol-N3'-14C (11) having a specific activity of 26.5 mCi/mmol and a radiochemical purity of 95%. (author)

  17. Evaluation of carbon-14 life cycle in reactors VVER-1000

    International Nuclear Information System (INIS)

    This work is aimed at the evaluation of carbon-14 life cycle in light water reactors VVER-1000. Carbon-14 is generated as a side product in different systems of nuclear reactors and has been an issue not only in radioactive waste management but mainly in release into the environment in the form of gaseous effluents. The principal sources of this radionuclide are in primary cooling water and fuel. Considerable amount of C-14 is generated by neutron reactions with oxygen 17O and nitrogen 14N present in water coolant and fuel. The reaction likelihood and consequently volume of generated radioisotope depends on several factors, especially on the effective cross-section, concentrations of parent elements and conditions of power plant operating strategies. Due to its long half-life and high capability of integration into the environment and thus into the living species, it is very important to monitor the movement of carbon-14 in all systems of nuclear power plant and to manage its release out of NPP. The dominant forms of radioactive carbon-14 are the hydrocarbons owing to the combinations with hydrogen used for absorption of radiolytic oxygen. These organic compounds, such as formaldehyde, methyl alcohol, ethyl alcohol and formic acid can be mostly retained on ion exchange resins used in the system for purifying primary cooling water. The gaseous carbon compounds (CH4 and CO2) are released into the atmosphere via the ventilation systems of NPP. Based on the information and data obtained from different sources, it has been designed a balance model of possible carbon-14 pathways throughout the whole NPP. This model includes also mass balance model equations for each important node in system and available sampling points which will be the background for further calculations. This document is specifically not to intended to describe the best monitoring program attributes or technologies but rather to provide evaluation of obtained data and find the optimal way to upgrade

  18. Synthesis of carbon-14 labeled doxylamine succinate

    International Nuclear Information System (INIS)

    Doxylamine succinate, N,N-dimethyl-2-[1-phenyl-1-(2-pyridinyl)-ethoxy]ethanamine succinate is an antihistamine used primarily as a sedative. Carbon-14 labeled doxylamine succinate, required for toxicological studies, was synthesized in two steps starting from 2-benzoyl pyridine. (author)

  19. Some Organic Reactions in Supercritical Carbon Dioxide

    Institute of Scientific and Technical Information of China (English)

    JIANG Huan-feng; YANG Xiao-yue; LI Guo-ping; ZOU Gang

    2004-01-01

    Organic reactions in supercritical carbon dioxide (scCO2) have facilitated great progress in recent years 1. ScCO2, as an environmentally friendly reaction medium, may be a substitute for volatile and toxic organic solvents and show some special advantages. Firstly, CO2 is inexpensive,nonflammable, nontoxic and chemical inert under many conditions. Secondly, scCO2 possesses hybrid properties of both liquid and gas, to the advantage of some reactions involving gaseous reagents. Control of the solvent density by variation of the temperature and pressure enables the solvent properties to be "tuned" to reactants. Finally, separating of CO2 from the reaction mixture is energy-efficient and simple. Here we disclose our new work on some organic reactions involving small molecules in scCO2.The results showed that the upper reactions in scCO2 could be carried out smoothly and thepressure of CO2 had a remarkable effect on the conversion and selectivity.

  20. Carbon encapsulated magnetic nanoparticles produced by hydrothermal reaction

    Institute of Scientific and Technical Information of China (English)

    Nong Yue He; Ya Fei Guo; Yan Deng; Zhi Fei Wang; Song Li; Hong Na Liu

    2007-01-01

    Carbon encapsulated magnetic nanoparticles (CEMNs) were synthesized by heating an aqueous glucose solution containing FeAu (Au coated Fe nanoparticles) nanoparticles at 160-180 ℃ for 2 h. This novel hydrothermal approach is not only simple but also provides the surface of CEMNs with functional groups like-OH. The formation of carbon encapsulated magnetic nanoparticles was not favored when using pure Fe nanoparticles as cores because of the oxidation of Fe nanoparticles by H2O during the reaction and,therefore, the surfaces of the naked Fe nanoparticles had to be coated by Au shell in advance. TEM, XRD, XPS and VSM measurments characterized that they were uniform carbon spheres containing some embedded Fe-Au nanoparticles, with a saturation of 14.6 emu/g and the size of the typical product is ~350 nm.

  1. A detective from the past called carbon 14

    International Nuclear Information System (INIS)

    The analysis is carried out using Radiometry or Accelerator mass spectrometry. After the system allowing to date the age of any organic rest - whether a fossil, a wood fragment, a parchment or a seed - is an isotope called carbon-14. An atom that comes from reactions nuclear produced in the atmosphere and cosmic-ray-induced they interact with oxygen to form carbon dioxide. This element they absorb it plants in photosynthesis and then passes to the animals remained almost unchanged during the life of the organism. to the meet the initial ratio of c-14 that had been in the atmosphere before his death, the remains that are left in it determine the elapsed time. (Author)

  2. Removal of carbon-14 from irradiated graphite

    Science.gov (United States)

    Dunzik-Gougar, Mary Lou; Smith, Tara E.

    2014-08-01

    Approximately 250,000 tonnes of irradiated graphite waste exists worldwide and that quantity is expected to increase with decommissioning of Generation II reactors and deployment of Generation IV gas-cooled, graphite moderated reactors. This situation indicates the need for a graphite waste management strategy. On of the isotopes of great concern for long-term disposal of irradiated graphite is carbon-14 (14C), with a half-life of 5730 years. Study of irradiated graphite from some nuclear reactors indicates 14C is concentrated on the outer 5 mm of the graphite structure. The aim of the research presented here is to develop a practical method by which 14C can be removed. In parallel with these efforts, the same irradiated graphite material is being characterized to identify the chemical form of 14C in irradiated graphite. A nuclear-grade graphite, NBG-18, and a high-surface-area graphite foam, POCOFoam®, were exposed to liquid nitrogen (to increase the quantity of 14C precursor) and neutron-irradiated (1013 neutrons/cm2/s). During post-irradiation thermal treatment, graphite samples were heated in the presence of an inert carrier gas (with or without the addition of an oxidant gas), which carries off gaseous products released during treatment. Graphite gasification occurs via interaction with adsorbed oxygen complexes. Experiments in argon only were performed at 900 °C and 1400 °C to evaluate the selective removal of 14C. Thermal treatment also was performed with the addition of 3 and 5 vol% oxygen at temperatures 700 °C and 1400 °C. Thermal treatment experiments were evaluated for the effective selective removal of 14C. Lower temperatures and oxygen levels correlated to more efficient 14C removal.

  3. A gaseous measurement system for carbon-14 dioxide and carbon-14 methane: An analytical methodology to be applied in the evaluation of the carbon-14 dioxide and carbon-14 methane produced via microbial activity in volcanic tuff

    International Nuclear Information System (INIS)

    The objectives of this study were to develop a gaseous measurement system for the carbon-14 dioxide and carbon-14 methane produced via microbial activity or geochemical action on leachate in tuff; to determine the trapping efficiency of the system for carbon-14 dioxide; to determine the trapping efficiency of the system for carbon-14 methane; to apply the experimentally determined factors regarding the system's trapping efficiency for carbon-14 dioxide and carbon-14 methane to a trapping algorithm to determine the activity of the carbon-14 dioxide and carbon-14 methane in a mixed sample; to determine the minimum detectable activity of the measurement process in picocuries per liter; and to determine the lower limit or detection of the measurement process in counts per minute

  4. LDEO Carbon 14 Data from Selected Sea floor Cores

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Carbon-14 data in this file were compiled by W.F. Ruddiman and staff at the Lamont-Doherty Earth Observatory of Columbia University. Data include 974 carbon-14...

  5. Soil metabolic transformations of carbon-14-myo-inositol, carbon-14-phytic acid and carbon-14-iron(III) phytate

    International Nuclear Information System (INIS)

    Uniformly labelled 14C-phytic acid and 14C-iron(III) phytate were synthesized from uniformly labelled 14C-myo-inositol. The three compounds were incubated in an Andosol sandy loam at 70% field capacity and 36.50C for a 12-day period. Myo-inositol, phytic acid and iron(III) phytate underwent a 61.0, 1.9 and 0% microbial oxidation respectively to CO2 during the incubation period. The rate of fixation of 14C-phytic acid was illustrated by its rapid decline in metabolism in the 12-day period. The metabolism rate of phytic was considerably reduced by the presumed formation of iron(III) and aluminium phytate. The metabolism rate of myo-inositol was reduced nine-fold after an initial rapid metabolism during the first day of incubation. The following mechanisms were observed in the soil metabolism of myo-inositol: (1) soil mineral-inositol carbon adsorption, (2) humic acid-inositol carbon adsorption, (3) the phosphorylation of myo-inositol, and (4) the epimerization of myo-inositol to chiro-inositol. The formation of (1) and (2) was found to be highly dependent upon microbial activity. Interactions (1), (2) and (3)are considered as possible mechanisms for the inhibition of the microbial oxidation of myo-inositol. The inhibition of myo-inositol oxidation via adsorption or phosphorylation is considered to be due to the chemical blockage of the stereo-specific microbial oxidative attack on the axial hydroxyl group. (author)

  6. A detective from the past called carbon 14; Un detective del pasado llamado carbono 14

    Energy Technology Data Exchange (ETDEWEB)

    Trintan, R. M.

    2015-07-01

    The analysis is carried out using Radiometry or Accelerator mass spectrometry. After the system allowing to date the age of any organic rest - whether a fossil, a wood fragment, a parchment or a seed - is an isotope called carbon-14. An atom that comes from reactions nuclear produced in the atmosphere and cosmic-ray-induced they interact with oxygen to form carbon dioxide. This element they absorb it plants in photosynthesis and then passes to the animals remained almost unchanged during the life of the organism. to the meet the initial ratio of c-14 that had been in the atmosphere before his death, the remains that are left in it determine the elapsed time. (Author)

  7. Effective Permeability Change in Wellbore Cement with Carbon Dioxide Reaction

    Energy Technology Data Exchange (ETDEWEB)

    Um, Wooyong; Jung, Hun Bok; Martin, Paul F.; McGrail, B. Peter

    2011-11-01

    Portland cement, a common sealing material for wellbores for geological carbon sequestration was reacted with CO{sub 2} in supercritical, gaseous, and aqueous phases at various pressure and temperature conditions to simulate cement-CO{sub 2} reaction along the wellbore from carbon injection depth to the near-surface. Hydrated Portland cement columns (14 mm diameter x 90 mm length; water-to-cement ratio = 0.33) including additives such as steel coupons and Wallula basalt fragments were reacted with CO{sub 2} in the wet supercritical (the top half) and dissolved (the bottom half) phases under carbon sequestration condition with high pressure (10 MPa) and temperature (50 C) for 5 months, while small-sized hydrated Portland cement columns (7 mm diameter x 20 mm length; water-to-cement ratio = 0.38) were reacted with CO{sub 2} in dissolved phase at high pressure (10 MPa) and temperature (50 C) for 1 month or with wet CO{sub 2} in gaseous phase at low pressure (0.2 MPa) and temperature (20 C) for 3 months. XMT images reveal that the cement reacted with CO{sub 2} saturated groundwater had degradation depth of {approx}1 mm for 1 month and {approx}3.5 mm for 5 month, whereas the degradation was minor with cement exposure to supercritical CO{sub 2}. SEM-EDS analysis showed that the carbonated cement was comprised of three distinct zones; the innermost less degraded zone with Ca atom % > C atom %, the inner degraded zone with Ca atom % {approx} C atom % due to precipitation of calcite, the outer degraded zone with C atom % > Ca atom % due to dissolution of calcite and C-S-H, as well as adsorption of carbon to cement matrix. The outer degraded zone of carbonated cement was porous and fractured because of dissolution-dominated reaction by carbonic acid exposure, which resulted in the increase in BJH pore volume and BET surface area. In contrast, cement-wet CO{sub 2}(g) reaction at low P (0.2 MPa)-T (20 C) conditions for 1 to 3 months was dominated by precipitation of micron

  8. Study on Utilization of Carboxyl Group Decorated Carbon Nanotubes and Carbonation Reaction for Improving Strengths and Microstructures of Cement Paste

    Directory of Open Access Journals (Sweden)

    Xiantong Yan

    2016-08-01

    Full Text Available Carbon nanotubes (CNTs have excellent mechanical properties and can be used to reinforce cement-based materials. On the other hand, the reaction product of carbonation with hydroxides in hydrated cement paste can reduce the porosity of cement-based materials. In this study, a novel method to improve the strength of cement paste was developed through a synergy of carbon nanotubes decorated with carboxyl group and carbonation reactions. The experimental results showed that the carboxyl group (–COOH of decorated carbon nanotubes and the surfactant can control the morphology of the calcium carbonate crystal of carbonation products in hydrated cement paste. The spindle-like calcium carbonate crystals showed great morphological differences from those observed in the conventional carbonation of cement paste. The spindle-like calcium carbonate crystals can serve as fiber-like reinforcements to reinforce the cement paste. By the synergy of the carbon nanotubes and carbonation reactions, the compressive and flexural strengths of cement paste were significantly improved and increased by 14% and 55%, respectively, when compared to those of plain cement paste.

  9. Reaction from Dimethyl Carbonate to Diphenyl Carbonate. 1. Experimental Determination of the Chemical Equilibria

    NARCIS (Netherlands)

    Haubrock, J.; Raspe, M.; Versteeg, G.F.; Kooijman, H.A.; Taylor, R.; Hogendoorn, J.A.

    2008-01-01

    New experimental equilibrium data of the reaction of dimethyl carbonate (DMC) and phenol to methyl phenyl carbonate (MPC) and the subsequent disproportion and transesterification reaction of MPC to diphenyl carbonate (DPC) are presented and interpreted in terms of the reaction equilibrium coefficien

  10. Dissolved Organic Carbon 14C in Southern Nevada Groundwater and Implications for Groundwater Travel Times

    Energy Technology Data Exchange (ETDEWEB)

    Hershey, Ronald L.; Fereday, Wyall; Thomas, James M

    2016-08-01

    Dissolved inorganic carbon (DIC) carbon-14 (14C) ages must be corrected for complex chemical and physical reactions and processes that change the amount of 14C in groundwater as it flows from recharge to downgradient areas. Because of these reactions, DIC 14C can produce unrealistically old ages and long groundwater travel times that may, or may not, agree with travel times estimated by other methods. Dissolved organic carbon (DOC) 14C ages are often younger than DIC 14C ages because there are few chemical reactions or physical processes that change the amount of DOC 14C in groundwater. However, there are several issues that create uncertainty in DOC 14C groundwater ages including limited knowledge of the initial (A0) DOC 14C in groundwater recharge and potential changes in DOC composition as water moves through an aquifer. This study examines these issues by quantifying A0 DOC 14C in recharge areas of southern Nevada groundwater flow systems and by evaluating changes in DOC composition as water flows from recharge areas to downgradient areas. The effect of these processes on DOC 14C groundwater ages is evaluated and DOC and DIC 14C ages are then compared along several southern Nevada groundwater flow paths. Twenty-seven groundwater samples were collected from springs and wells in southern Nevada in upgradient, midgradient, and downgradient locations. DOC 14C for upgradient samples ranged from 96 to 120 percent modern carbon (pmc) with an average of 106 pmc, verifying modern DOC 14C ages in recharge areas, which decreases uncertainty in DOC 14C A0 values, groundwater ages, and travel times. The HPLC spectra of groundwater along a flow path in the Spring Mountains show the same general pattern indicating that the DOC compound composition does not change along this flow path. Although DOC concentration decreases from recharge-area to downgradient groundwater, the organic compounds are similar, indicating that DOC 14C is unaffected by other processes such as microbial

  11. Carbon compounds in the atmosphere and their chemical reactions

    OpenAIRE

    Martišová, Petra

    2013-01-01

    The essay dissert on compounds of carbon in the atmosphere and its reaction. The most important are carbon dioxide, carbon monoxide and methane. Included among important compounds of carbon are volatile organic substances, polycyclic aromatic hydrocarbon and dioxin. Carbon dioxide and methane representing greenhouse gases have also indispensable meaning. As they, together with water vapour, nitrogen monoxide and other gases are causing the major part of greenhouse effect. Primarily because of...

  12. The Path of Carbon in Photosynthesis IX. Photosynthesis, Photoreduction, and the Hydrogen-Oxygen-Carbon Dioxide Dark Reaction

    Science.gov (United States)

    Badin, E. J.; Calvin, M.

    1950-02-01

    A comparison of the rates of fixation of Carbon 14 dioxide in algae for the processes of photosynthesis, photoreduction and the hydrogen-oxygen-carbon dioxide dark reaction has been made. For the same series of experiments, rates of incorporation of tracer carbon into the separate soluble components using the radiogram method have been determined. The mechanism of carbon dioxide uptake has been shown to occur via two distinct paths. In all cases studied, essentially the same compounds appear radioactive. The distribution with time, however, differs markedly.

  13. Carbon dioxide as a carbon source in organic transformation: carbon-carbon bond forming reactions by transition-metal catalysts.

    OpenAIRE

    Tsuji, Yasushi; Fujihara, Tetsuaki

    2012-01-01

    Recent carbon-carbon bond forming reactions of carbon dioxide with alkenes, alkynes, dienes, aryl zinc compounds, aryl boronic esters, aryl halides, and arenes having acidic C-H bonds are reviewed in which transition-metal catalysts play an important role.

  14. Reaction from Dimethyl Carbonate (DMC) to Diphenyl Carbonate (DPC). 2. Kinetics of the Reactions from DMC via Methyl Phenyl Carbonate to DPC

    NARCIS (Netherlands)

    Haubrock, J.; Wermink, W.; Versteeg, G.F.; Kooijman, H.A.; Taylor, R.; Sint Annaland, M. van; Hogendoorn, J.A.

    2008-01-01

    The kinetics of the reaction of dimethyl carbonate (DMC) and phenol to methyl phenyl carbonate (MPC) and the subsequent disproportion and transesterification reaction of methyl phenyl carbonate (MPC) to diphenyl carbonate (DPC) have been studied. Experiments were carried out in a closed batch reacto

  15. The lichens, tritium and carbon 14 integrators; Les lichens, integrateurs de tritium et de carbone 14

    Energy Technology Data Exchange (ETDEWEB)

    Daillant, O

    2007-07-01

    The present report concerns a research for the tritium and for the carbon 14 in lichens in a spirit of bio-indication: the first results appear in Daillant and al (2004 ) and additional results were presented to the congress B.I.O.M.A.P. in Slovenia, organized collectively by the institute Josef Stefan from Ljubljana and the international atomic energy agency from Vienna (Daillant and al 2003). (N.C.)

  16. The optimization of the estimation of carbon-14 in urine

    International Nuclear Information System (INIS)

    The urinalysis method for carbon-14 currently used by the bioassay laboratory of the Dosimetric Research Branch at CRNL has been tested and optimized for both sensitivity and efficiency. Urine is first treated with an enzyme that catalyses the hydrolysis of urea, the major carbon-containing component of urine; carbon dioxide is then liberated by the measured addition of excess acid and collected in 2-aminoethanol. The aminoethanol can be directly counted by the addition of a liquid scintillation cocktail. This method can be used to measure both the specific activity, (Bq/g-carbon) or the total activity of carbon-14 released from the urine sample

  17. Ultra-Low-Temperature Reactions of Carbon Atoms with Hydrogen Molecules

    CERN Document Server

    Krasnokutski, S A; Renzler, M; Jäger, C; Henning, Th; Scheier, P

    2016-01-01

    The reactions of carbon atoms with dihydrogen have been investigated in liquid helium droplets at $T$ = 0.37 K. A calorimetric technique was applied to monitor the energy released in the reaction. The barrierless reaction between a single carbon atom and a single dihydrogen molecule was detected. Reactions between dihydrogen clusters and carbon atoms have been studied by high-resolution mass spectrometry. The formation of hydrocarbon cations of the type C$_m$H$_n^+$, with $m$ = 1-4 and $n$ = 1-15 was observed. With enhanced concentration of dihydrogen, the mass spectra demonstrated the main "magic" peak assigned to the CH$_5^+$ cation. A simple formation pathway and the high stability of this cation suggest its high abundance in the interstellar medium.

  18. Aminolysis Reaction of Glycerol Carbonate in Organic and Hydroorganic Medium

    OpenAIRE

    Nohra, Bassam; Candy, Laure; Blanco, Jean-François; Raoul, Yann; Mouloungui, Zephirin

    2012-01-01

    Aminolysis reaction of glycerol carbonate with primary amine in organic and hydroorganic media leads to the formation of two hydroxyurethane isomers and a partial decomposition of glycerol carbonate into glycerol. Aminolysis with a secondary amine promotes the condensation reaction and limits the formation of glycerol. The ratio of α versus β was determined by zgig 13C NMR. This technique permits computing the yield of α and β products in the medium. The quantity of glycerol was determined by...

  19. Laboratory Experiments to Evaluate Matrix Diffusion of Dissolved Organic Carbon Carbon-14 in Southern Nevada Fractured-rock Aquifers

    Energy Technology Data Exchange (ETDEWEB)

    Hershey, Ronald L. [Nevada University, Reno, NV (United States). Desert Research Institute; Fereday, Wyatt [Nevada University, Reno, NV (United States). Desert Research Institute

    2016-05-01

    Dissolved inorganic carbon (DIC) carbon-14 (14C) is used to estimate groundwater ages by comparing the DIC 14C content in groundwater in the recharge area to the DIC 14C content in the downgradient sampling point. However, because of chemical reactions and physical processes between groundwater and aquifer rocks, the amount of DIC 14C in groundwater can change and result in 14C loss that is not because of radioactive decay. This loss of DIC 14C results in groundwater ages that are older than the actual groundwater ages. Alternatively, dissolved organic carbon (DOC) 14C in groundwater does not react chemically with aquifer rocks, so DOC 14C ages are generally younger than DIC 14C ages. In addition to chemical reactions, 14C ages may also be altered by the physical process of matrix diffusion. The net effect of a continuous loss of 14C to the aquifer matrix by matrix diffusion and then radioactive decay is that groundwater appears to be older than it actually is. Laboratory experiments were conducted to measure matrix diffusion coefficients for DOC 14C in volcanic and carbonate aquifer rocks from southern Nevada. Experiments were conducted using bromide (Br-) as a conservative tracer and 14C-labeled trimesic acid (TMA) as a surrogate for groundwater DOC. Outcrop samples from six volcanic aquifers and five carbonate aquifers in southern Nevada were used. The average DOC 14C matrix diffusion coefficient for volcanic rocks was 2.9 x 10-7 cm2/s, whereas the average for carbonate rocks was approximately the same at 1.7 x 10-7 cm2/s. The average Br- matrix diffusion coefficient for volcanic rocks was 10.4 x 10-7 cm2/s, whereas the average for carbonate rocks was less at 6.5 x 10-7 cm2/s. Carbonate rocks exhibited greater variability in

  20. Combined reactions and separations using ionic liquids and carbon dioxide

    NARCIS (Netherlands)

    Kroon, M.C.

    2006-01-01

    A new and general type of process for the chemical industry is presented using ionic liquids and supercritical carbon dioxide as combined reaction and separation media. In this process, the carbon dioxide pressure controls the miscibility of reactants, products, catalyst and ionic liquid, enabling f

  1. Differential monitoring of tritium and carbon-14 compounds

    International Nuclear Information System (INIS)

    A gaseous sampling system was developed to differentially collect all major volatile forms of tritium and carbon-14 according to chemical class. These chemical forms include: tritiated forms of water, hydrogen and organics; as well as 14C-containing carbon monoxide, carbon dioxide and organics. Sampling campaigns involving the use of this differential 3H and 14C collection system have been successfully conducted at a high level liquid waste solidification plant, at a spent fuel storage facility and in the vicinity of power reactors

  2. Effect of Carbon Containing Materials on Pure Carbon Reaction-bonded SiC

    Institute of Scientific and Technical Information of China (English)

    JI Xiaoli; WEI Lei; SUN Feng

    2008-01-01

    Petroleum coke, graphite, gas carbon and lower sulfur carbon black were used to prepare reaction-bonded silicon carbide. The influences of different carbon containing materials on properties of carbonaceous precursors, sintering process, and microstructure of the prepared SiC were researched. The results show that:(1)With the density of carbon containing materials increasing, the porosity of carbonaceous precursors decreases and the infiltrating process of liquid silicon is more difficult.(2)The reaction between carbon containing materials and liquid silicon, the volume effect is more obvious with the density of carbon containing materials increasing.(3)As the carbon containing materials density decreasing, residual carbon in reaction bonded SiC also decreases.

  3. Reactions of carbon cluster ions stored in an RF trap

    International Nuclear Information System (INIS)

    Reactions of carbon cluster ions with O2 were studied by using an RF ion trap in which cluster ions of specific size produced by laser ablation could be stored selectively. Reaction rate constants for positive and negative carbon cluster ions were estimated. In the case of the positive cluster ions, these were consistent with the previous experimental results using FTMS. Negative carbon cluster ions C-n (n=4-8) were much less reactive than positive cluster ions. The CnO- products were seen only in n=4 and 6. (orig.)

  4. Modeling Corrosion Reactions of Steel in a Dilute Carbonate Solution

    Science.gov (United States)

    Eliyan, Faysal Fayez; Alfantazi, Akram

    2016-02-01

    This research models the corrosion reactions of a high-strength steel in an aerated, dilute, carbonate solution during a single-cycle voltammetry. Based on a previous study (Eliyan et al. in J Mater Eng Perform 24(6):1-8, 2015) and a literature survey, the corrosion reactions of the cathodic reduction, anodic dissolution, and passivation, as well as the interfacial interactions and the chemistry of the corrosion products are illustrated in schematics. The paper provides a visual guide on the corrosion reactions for steel in carbonate solutions based on the available mechanistic details that were reported and are still being investigated in literature.

  5. Reaction studies of hot silicon, germanium and carbon atoms

    Energy Technology Data Exchange (ETDEWEB)

    Gaspar, P.P.

    1990-11-01

    The goal of this project was to increase the authors understanding of the interplay between the kinetic and electronic energy of free atoms and their chemical reactivity by answering the following questions: (1) what is the chemistry of high-energy carbon silicon and germanium atoms recoiling from nuclear transformations; (2) how do the reactions of recoiling carbon, silicon and germanium atoms take place - what are the operative reaction mechanisms; (3) how does the reactivity of free carbon, silicon and germanium atoms vary with energy and electronic state, and what are the differences in the chemistry of these three isoelectronic atoms This research program consisted of a coordinated set of experiments capable of achieving these goals by defining the structures, the kinetic and internal energy, and the charge states of the intermediates formed in the gas-phase reactions of recoiling silicon and germanium atoms with silane, germane, and unsaturated organic molecules, and of recoiling carbon atoms with aromatic molecules. The reactions of high energy silicon, germanium, and carbon atoms created by nuclear recoil were studied with substrates chosen so that their products illuminated the mechanism of the recoil reactions. Information about the energy and electronic state of the recoiling atoms at reaction was obtained from the variation in end product yields and the extent of decomposition and rearrangement of primary products (usually reactive intermediates) as a function of total pressure and the concentration of inert moderator molecules that remove kinetic energy from the recoiling atoms and can induce transitions between electronic spin states. 29 refs.

  6. Optical Excitation of Carbon Nanotubes Drives Localized Diazonium Reactions.

    Science.gov (United States)

    Powell, Lyndsey R; Piao, Yanmei; Wang, YuHuang

    2016-09-15

    Covalent chemistries have been widely used to modify carbon nanomaterials; however, they typically lack the precision and efficiency required to directly engineer their optical and electronic properties. Here, we show, for the first time, that visible light which is tuned into resonance with carbon nanotubes can be used to drive their functionalization by aryldiazonium salts. The optical excitation accelerates the reaction rate 154-fold (±13) and makes it possible to significantly improve the efficiency of covalent bonding to the sp(2) carbon lattice. Control experiments suggest that the reaction is dominated by a localized photothermal effect. This light-driven reaction paves the way for precise nanochemistry that can directly tailor carbon nanomaterials at the optical and electronic levels.

  7. Heterogeneously Catalysed Chemical Reactions in Carbon Dioxide Medium

    DEFF Research Database (Denmark)

    Musko, Nikolai E.

    the selective hydrogenation of unsaturated aldehydes in carbon dioxide medium. It was found that supported tungstosilicic acid catalysts and acidic resin Amberlyst-15 are very effective for performing aldol reactions. The positive influence of temperature and CO2-content on catalyst activity was studied...... useful for the phase behaviour investigations. The direct synthesis of dimethyl carbonate from methanol and CO2 has been investigated for quite a long time, however hardly any sufficiently active catalysts have been found so far. Nevertheless, optimisation of the phase equilibria of the reaction mixture...... studies of catalytic chemical reactions in dense and supercritical carbon dioxide have been complemented by the theoretical calculations of phase equilibria using advanced thermodynamic models. In the recent years, the use of compressed carbon dioxide as innovative, non-toxic and non-flammable, cheap...

  8. Biomass carbon-14 ratio measured by accelerator mass spectrometry

    International Nuclear Information System (INIS)

    Measurement methods of a biomass carbon ratio in biomass products based on 14C-radiocarbon concentration have been reviewed. Determination of the biomass carbon ratio in biomass products is important to secure the reliance in the commercial market, because the 'biomass products' could contain products from petroleum. The biomass carbon ratio can be determined from percent Modern Carbon (pMC) using ASTM D6866 methods. The pMC value is calculated from the comparison between the 14C in sample and 14C in reference material. The 14C concentration in chemical products can be measured by liquid scintillation counter (LSC) and accelerator mass spectrometry (AMS). LSC can be applicable to determine the biomass carbon ratio for liquid samples such as gasoline with bioethanol (E5 or E10). On the other hand, AMS can be used to determine the biomass carbon ratio for almost all kinds of organic and inorganic compounds such as starch, cellulose, ethanol, gasoline, or polymer composite with inorganic fillers. AMS can accept the gaseous and solid samples. The graphite derived from samples included in solid phase is measured by AMS. The biomass carbon of samples derived from wood were higher than 100% due to the effect of atomic bomb test in the atmosphere around 1950 which caused the artificial 14C injection. Exact calculation methods of the biomass carbon ratio from pMC will be required for the international standard (ISO standard). (author)

  9. The preparation of glucose uniformly labelled with carbon-14

    International Nuclear Information System (INIS)

    The plant, (Zea mais, L) and culture conditions for an optimum production of glucose has been chosen. To achieve the labelling of glucose, photosynthesis and carboxylation are carried on, under an artificial atmosphere of 14CO2 produced from 14C-barium carbonate. Following photosynthesis the sugars are extracted, and then the extract purified by several methods. The purified glucose is finally, degraded and the specific radioactivity is determined in each of its carbon atoms. (Author) 37 refs

  10. Controllable-nitrogen doped carbon layer surrounding carbon nanotubes as novel carbon support for oxygen reduction reaction

    Energy Technology Data Exchange (ETDEWEB)

    Kuo, P.L.; Hsu, C.H.; Wu, H.M.; Hsu, W.S. [Department of Chemical Engineering, National Cheng Kung University, Tainan (China); Kuo, D. [Department of Biochemistry, University of Washington, Seattle, WA (United States)

    2012-08-15

    Novel nitrogen-doped carbon layer surrounding carbon nanotubes composite (NC-CNT) (N/C ratio 3.3-14.3 wt.%) as catalyst support has been prepared using aniline as a dispersant to carbon nanotubes (CNTs) and as a source for both carbon and nitrogen coated on the surface of the CNTs, where the amount of doped nitrogen is controllable. The NC-CNT so obtained were characterized with scanning electron microscopy (SEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and nitrogen adsorption and desorption isotherms. A uniform dispersion of Pt nanoparticles (ca. 1.5-2.0 nm) was then anchored on the surface of NC-CNT by using aromatic amine as a stabilizer. For these Pt/NC-CNTs, cyclic voltammogram measurements show a high electrochemical activity surface area (up to 103.7 m{sup 2} g{sup -1}) compared to the commercial E-TEK catalyst (55.3 m{sup 2} g{sup -1}). In single cell test, Pt/NC-CNT catalyst has greatly enhanced catalytic activity toward the oxygen reduction reaction, resulting in an enhancement of ca. 37% in mass activity compared with that of E-TEK. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  11. Carbon-Carbon Cross Coupling Reactions in Ionic Liquids Catalysed by Palladium Metal Nanoparticles

    OpenAIRE

    Martin H. G. Prechtl; Scholten, Jackson D.; Jairton Dupont

    2010-01-01

    A brief summary of selected pioneering and mechanistic contributions in the field of carbon-carbon cross-coupling reactions with palladium nanoparticles (Pd-NPs) in ionic liquids (ILs) is presented. Five exemplary model systems using the Pd-NPs/ILs approach are presented: Heck, Suzuki, Stille, Sonogashira and Ullmann reactions which all have in common the use of ionic liquids as reaction media and the use of palladium nanoparticles as reservoir for the catalytically active palladium species.

  12. Reactions of carbon atoms in pulsed molecular beams

    Energy Technology Data Exchange (ETDEWEB)

    Reisler, H. [Univ. of Southern California, Los Angeles (United States)

    1993-12-01

    This research program consists of a broad scope of experiments designed to unravel the chemistry of atomic carbon in its two spin states, P and D, by using well-controlled initial conditions and state-resolved detection of products. Prerequisite to the proposed studies (and the reason why so little is known about carbon atom reactions), is the development of clean sources of carbon atoms. Therefore, in parallel with the studies of its chemistry and reaction dynamics, the authors continuously explore new, state-specific and efficient ways of producing atomic carbon. In the current program, C({sup 3}P) is produced via laser ablation of graphite, and three areas of study are being pursued: (i) exothermic reactions with small inorganic molecules (e.g., O{sub 2}, N{sub 2}O, NO{sub 2}) that can proceed via multiple pathways; (ii) the influence of vibrational and translational energy on endothermic reactions involving H-containing reactants that yield CH products (e.g., H{sub 2}O H{sub 2}CO); (iii) reactions of C({sup 3}P) with free radicals (e.g., HCO, CH{sub 3}O). In addition, the authors plan to develop a source of C({sup 1}D) atoms by exploiting the pyrolysis of diazotetrazole and its salts in the ablation source. Another important goal involves collaboration with theoreticians in order to obtain relevant potential energy surfaces, rationalize the experimental results and predict the roles of translational and vibrational energies.

  13. Oxygen electrode reaction in molten carbonate fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Appleby, A.J.; White, R.E.

    1992-07-07

    Molten carbonate fuel cell system is a leading candidate for the utility power generation because of its high efficiency for fuel to AC power conversion, capability for an internal reforming, and a very low environmental impact. However, the performance of the molten carbonate fuel cell is limited by the oxygen reduction reaction and the cell life time is limited by the stability of the cathode material. An elucidation of oxygen reduction reaction in molten alkali carbonate is essential because overpotential losses in the molten carbonate fuel cell are considerably greater at the oxygen cathode than at the fuel anode. Oxygen reduction on a fully-immersed gold electrode in a lithium carbonate melt was investigated by electrochemical impedance spectroscopy and cyclic voltammetry to determine electrode kinetic and mass transfer parameters. The dependences of electrode kinetic and mass transfer parameters on gas composition and temperature were examined to determine the reaction orders and the activation energies. The results showed that oxygen reduction in a pure lithium carbonate melt occurs via the peroxide mechanism. A mass transfer parameter, D{sub O}{sup 1/2}C{sub O}, estimated by the cyclic voltammetry concurred with that calculated by the EIS technique. The temperature dependence of the exchange current density and the product D{sub O}{sup 1/2}C{sub O} were examined and the apparent activation energies were determined to be about 122 and 175 kJ/ mol, respectively.

  14. In-phantom dosimetry using the 13C(d,n)14N reaction for BNCT (boron neutron capture therapy)

    International Nuclear Information System (INIS)

    The use of the 13 C(d,n)14 N reaction at Ed =1.5 MeV for accelerator-based boron neutron capture therapy is investigated. The 13 C(d,n)14 N reaction presents the advantages of carbon as a target material and its large cross section. The deuteron beam was produced by a tandem accelerator at MIT's Laboratory for Accelerator Beam Applications. The resulting neutron spectra were evaluated in terms of RBE-dose rates at different depths inside a water-filled brain phantom using a heavy water moderator and lead reflector assembly. All results were simulated using the code MCNP. (author)

  15. Pattern Formation and Reaction Textures during Dunite Carbonation

    Science.gov (United States)

    Lisabeth, H. P.; Zhu, W.

    2015-12-01

    Alteration of olivine-bearing rocks by fluids is one of the most pervasive geochemical processes on the surface of the Earth. Serpentinized and/or carbonated ultramafic rocks often exhibit characteristic textures on many scales, from polygonal mesh textures on the grain-scale to onion-skin or kernel patterns on the outcrop scale. Strong disequilibrium between pristine ultramafic rocks and common geological fluids such as water and carbon dioxide leads to rapid reactions and coupled mechanical and chemical feedbacks that manifest as characteristic textures. Textural evolution during metasomatic reactions can control effective reaction rates by modulating dynamic porosity and therefore reactant supply and reactive surface area. We run hydrostatic experiments on thermally cracked dunites saturated with carbon dioxide bearing brine at 15 MPa confining pressure and 150°C to explore the evolution of physical properties and reaction textures as carbon mineralization takes place in the sample. Compaction and permeability reduction are observed throughout experiments. Rates of porosity and permeability changes are sensitive to pore fluid chemistry. After reaction, samples are imaged in 3-dimension (3D) using a dual-beam FIB-SEM. Analysis of the high resolution 3D microstructure shows that permeable, highly porous domains are created by olivine dissolution at a characteristic distance from pre-existing crack surfaces while precipitation of secondary minerals such as serpentine and magnesite is limited largely to the primary void space. The porous dissolution channels provide an avenue for fluid ingress, allow reactions to continue and could lead to progressive hierarchical fracturing. Initial modeling of the system indicates that this texture is the result of coupling between dissolution-precipitation reactions and the local stress state of the sample.

  16. Adverse reactions in treatment with lithium carbonate and haloperidol.

    Science.gov (United States)

    Baastrup, P C; Hollnagel, P; Sorensen, R; Schou, M

    1976-12-01

    Hospital records of 425 patients who had been treated simultaneously with lithium carbonate and haloperidol were examined. Adverse reactions in these patients were the same as in patients given lithium alone or haloperidol alone. None of the patients developed a syndrome resembling that described by others in patients treated with a lithium and haloperidol combination. PMID:1036539

  17. Effects of hydrolysis and carbonization reactions on hydrochar production.

    Science.gov (United States)

    Fakkaew, K; Koottatep, T; Polprasert, C

    2015-09-01

    Hydrothermal carbonization (HTC) is a thermal conversion process which converts wet biomass into hydrochar. In this study, a low-energy HTC process named "Two-stage HTC" comprising of hydrolysis and carbonization stages using faecal sludge as feedstock was developed and optimized. The experimental results indicated the optimum conditions of the two-stage HTC to be; hydrolysis temperature of 170 °C, hydrolysis reaction time of 155 min, carbonization temperature of 215 °C, and carbonization reaction time of 100 min. The hydrolysis reaction time and carbonization temperature had a statistically significant effect on energy content of the produced hydrochar. Energy input of the two-stage HTC was about 25% less than conventional HTC. Energy efficiency of the two-stage HTC for treating faecal sludge was higher than that of conventional HTC and other thermal conversion processes such as pyrolysis and gasification. The two-stage HTC could be considered as a potential technology for treating FS and producing hydrochar. PMID:26051497

  18. The 14N(p,gamma)15O reaction studied with a composite germanium detector

    CERN Document Server

    Marta, M; Bemmerer, D; Broggini, C; Caciolli, A; Corvisiero, P; Costantini, H; Elekes, Z; Fulop, Zs; Gervino, G; Guglielmetti, A; Gustavino, C; Gyurky, Gy; Imbriani, G; Junker, M; Lemut, A; Limata, B; Mazzocchi, C; Menegazzo, R; Prati, P; Roca, V; Rolfs, C; Alvarez, C Rossi; Somorjai, E; Straniero, O; Strieder, F; Terrasi, F; Trautvetter, H P; Vomiero, A

    2011-01-01

    The rate of the carbon-nitrogen-oxygen (CNO) cycle of hydrogen burning is controlled by the 14N(p,gamma)15O reaction. The reaction proceeds by capture to the ground states and several excited states in O-15. In order to obtain a reliable extrapolation of the excitation curve to astrophysical energy, fits in the R-matrix framework are needed. In an energy range that sensitively tests such fits, new cross section data are reported here for the four major transitions in the 14N(p,gamma)15O reaction. The experiment has been performed at the Laboratory for Underground Nuclear Astrophysics (LUNA) 400 kV accelerator placed deep underground in the Gran Sasso facility in Italy. Using a composite germanium detector, summing corrections have been considerably reduced with respect to previous studies. The cross sections for capture to the ground state and to the 5181, 6172, and 6792 keV excited states in O-15 have been determined at 359, 380, and 399 keV beam energy. In addition, the branching ratios for the decay of the...

  19. Dissolved Organic Carbon 14C in Southern Nevada Groundwater and Implications for Groundwater Travel Times

    Energy Technology Data Exchange (ETDEWEB)

    Hershey, Ronald L. [Nevada University, Reno, NV (United States). Desert Research Institute; Fereday, Wyall [Nevada University, Reno, NV (United States). Desert Research Institute; Thomas, James M [Nevada University, Reno, NV (United States). Desert Research Institute

    2016-08-01

    Dissolved inorganic carbon (DIC) carbon-14 (14C) ages must be corrected for complex chemical and physical reactions and processes that change the amount of 14C in groundwater as it flows from recharge to downgradient areas. Because of these reactions, DIC 14C can produce unrealistically old ages and long groundwater travel times that may, or may not, agree with travel times estimated by other methods. Dissolved organic carbon (DOC) 14C ages are often younger than DIC 14C ages because there are few chemical reactions or physical processes that change the amount of DOC 14C in groundwater. However, there are several issues that create uncertainty in DOC 14C groundwater ages including limited knowledge of the initial (A0) DOC 14C in groundwater recharge and potential changes in DOC composition as water moves through an aquifer. This study examines these issues by quantifying A0 DOC 14C in recharge areas of southern Nevada groundwater flow systems and by evaluating changes in DOC composition as water flows from recharge areas to downgradient areas. The effect of these processes on DOC 14C groundwater ages is evaluated and DOC and DIC 14C ages are then compared along several southern Nevada groundwater flow paths. Twenty-seven groundwater samples were collected from springs and wells in southern Nevada in upgradient, midgradient, and downgradient locations. DOC 14C for upgradient samples ranged from 96 to 120 percent modern carbon (pmc) with an average of 106 pmc, verifying modern DOC 14C ages in recharge areas, which decreases uncertainty in DOC 14C A0 values, groundwater ages, and travel times. The HPLC spectra of groundwater along a flow path in the Spring Mountains show the same general pattern indicating that the DOC compound composition does not change along this flow path

  20. Heterogeneously Catalysed Aldol Reactions in Supercritical Carbon Dioxide as Innovative and Non-Flammable Reaction Medium

    DEFF Research Database (Denmark)

    Musko, Nikolai; Grunwaldt, Jan-Dierk

    2011-01-01

    Aldol reactions of several aldehydes have been investigated over acidic and basic catalysts in supercritical carbon dioxide at 180 bar and 100 °C. Both acidic (Amberlyst-15, tungstosilicic acid (TSA) on SiO2 and MCM-41) and basic (hydrotalcite) materials showed interesting performance...

  1. Preparation of 14C-Labeled Multi-walled Carbon Nano-tubes for Biodistribution Investigations

    International Nuclear Information System (INIS)

    A new method allowing the 14C-labeling of carboxylic acid functions of carbon nano-tubes is described. The key step of the labeling process is a de-carbonylation reaction that has been developed and optimized with the help of a screening method. The optimized process has been successfully applied to multi-walled carbon nano-tubes (MWNTs), and the corresponding 14C-labeled nano-tubes were used to investigate their in vivo behavior. Preliminary results obtained after i.v. contamination of rats revealed liver as the main target organ. Radiolabeling of NTs with a long-life radioactive nucleus like 14C, coupled to a highly sensitive autoradiographic method, that provides a unique detection threshold, will make it possible to determine for a long time period whether or not NTs remain in any organs after animal exposure. (authors)

  2. Diffusion-reaction compromise the polymorphs of precipitated calcium carbonate

    Institute of Scientific and Technical Information of China (English)

    Han Wang; Wenlai Huang; Yongsheng Han

    2013-01-01

    Diffusion is seldom considered by chemists and materialists in the preparation of materials while it plays an important role in the field of chemical engineering.If we look at crystallization at the atomic level,crystal growth in a solution starts from the diffusion of ions to the growing surface followed by the incorporation of ions into its lattice.Diffusion can be a rate determining step for the growth of crystals.In this paper,we take the crystallization of calcium carbonate as an example to illustrate the microscopic processes of diffusion and reaction and their compromising influence on the morphology of the crystals produced.The diffusion effect is studied in a specially designed three-cell reactor.Experiments show that a decrease of diffusion leads to retardation of supersaturation and the formation of a continuous concentration gradient in the reaction cell,thus promoting the formation of cubic calcite particles.The reaction rate is regulated by temperature.Increase of reaction rate favors the formation of needle-like aragonite particles.When diffusion and reaction play joint roles in the reaction system,their compromise dominates the formation of products,leading to a mixture of cubic and needle-like particles with a controllable ratio.Since diffusion and reaction are universal factors in the preparation of materials,the finding of this paper could be helpful in the controlled synthesis of other materials.

  3. Carbon-14 geochemistry at the Savannah River Site

    Energy Technology Data Exchange (ETDEWEB)

    Roberts, Kimberly A.; Kaplan, Daniel I.

    2013-05-10

    Carbon-14 is among the key radionuclides driving risk at the E-Area Low-Level Waste Disposal Facility on the Savannah River Site (SRS). Much of this calculated risk is believed to be the result of having to make conservative assumptions in risk calculations because of the lack of site-specific data. The original geochemical data package (Kaplan 2006) recommended that performance assessments and composite analyses for the SRS assume that {sup 14}C did not sorbed to sediments or cementitious materials, i.e., that C-14 K{sub d} value (solid:liquid concentration ratio) be set to 0 mL/g (Kaplan 2006). This recommendation was based primarily on the fact that no site-specific experimental work was available and the assumption that the interaction of anionic {sup 14}C as CO{sub 2}{sup 2-}) with similarly charged sediments or cementitious materials would be minimal. When used in reactive transport equations, the 0 mL/g Kd value results in {sup 14}C not interacting with the solid phase and moving quickly through the porous media at the same rate as water. The objective of this study was to quantify and understand how aqueous {sup 14}C, as dissolved carbonate, sorbs to and desorbs from SRS sediments and cementitious materials. Laboratory studies measuring the sorption of {sup 14}C, added as a carbonate, showed unequivocally that {sup 14}C-carbonate K{sub d} values were not equal to 0 mL/g for any of the solid phases tested, but they required several months to come to steady state. After six months of contact, the apparent K{sub d} values for a clayey sediment was 3,000 mL/g, for a sandy sediment was 10 mL/g, for a 36-year-old concrete was 30,000 mL/g, and for a reducing grout was 40 mL/g. Furthermore, it was demonstrated that (ad)sorption rates were appreciably faster than desorption rates, indicating that a kinetic sorption model, as opposed to the steady-state K{sub d} model, may be a more accurate description of the {sup 14}C-carbonate sorption process. A second study

  4. Chemical Reactions in the Processing of Mosi2 + Carbon Compacts

    Science.gov (United States)

    Jacobson, Nathan S.; Lee, Kang N.; Maloy, Stuart A.; Heuer, Arthur H.

    1993-01-01

    Hot-pressing of MoSi2 powders with carbon at high temperatures reduces the siliceous grain boundary phase in the resultant compact. The chemical reactions in this process were examined using the Knudsen cell technique. A 2.3 wt pct oxygen MoSi2 powder and a 0.59 wt pct oxygen MoSi2 powder, both with additions of 2 wt pct carbon, were examined. The reduction of the siliceous grain boundary phase was examined at 1350 K and the resultant P(SiO)/P(CO) ratios interpreted in terms of the SiO(g) and CO(g) isobars on the Si-C-O predominance diagram. The MoSi2 + carbon mixtures were then heated at the hot-pressing temperature of 2100 K. Large weight losses were observed and could be correlated with the formation of a low-melting eutectic and the formation and vaporization of SiC.

  5. Carbon-14 in neutron-irradiated graphite for graphite-moderated reactors. Joint research

    Energy Technology Data Exchange (ETDEWEB)

    Fujii, Kimio [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment; Matsuo, Hideto [Radioactive Waste Management and Nuclear Facility Decommissioning Technology Center, Tokyo (Japan)

    2002-12-01

    The graphite moderated gas cooled reactor operated by the Japan Atomic Power Company was stopped its commercial operation on March 1998, and the decommissioning process has been started. Graphite material is often used as the moderator and the reflector materials in the core of the gas cooled reactor. During the operation, a long life nuclide of {sup 14}C is generated in the graphite by several transmutation reactions. Separation of {sup 14}C isotope and the development of the separation method have been recognized to be critical issues for the decommissioning of the reactor core. To understand the current methodologies for the carbon isotope separation, literature on the subject was surveyed. Also, those on the physical and chemical behavior of {sup 14}C were surveyed. This is because the larger part of the nuclides in the graphite is produced from {sup 14}N by (n,p) reaction, and the location of them in the material tends to be different from those of the other carbon atoms. This report summarizes the result of survey on the open literature about the behavior of {sup 14}C and the separation methods, including the list of the literature on these subjects. (author)

  6. Carbon 14 dating method; Methode de datation par le carbone 14

    Energy Technology Data Exchange (ETDEWEB)

    Fortin, Ph

    2000-07-01

    This document gives a first introduction to {sup 14}C dating as it is put into practice at the radiocarbon dating centre of Claude-Bernard university (Lyon-1 univ., Villeurbanne, France): general considerations and recalls of nuclear physics; the {sup 14}C dating method; the initial standard activity; the isotopic fractioning; the measurement of samples activity; the liquid-scintillation counters; the calibration and correction of {sup 14}C dates; the preparation of samples; the benzene synthesis; the current applications of the method. (J.S.)

  7. Method for producing bio-fuel that integrates heat from carbon-carbon bond-forming reactions to drive biomass gasification reactions

    Science.gov (United States)

    Cortright, Randy D.; Dumesic, James A.

    2011-01-18

    A low-temperature catalytic process for converting biomass (preferably glycerol recovered from the fabrication of bio-diesel) to synthesis gas (i.e., H.sub.2/CO gas mixture) in an endothermic gasification reaction is described. The synthesis gas is used in exothermic carbon-carbon bond-forming reactions, such as Fischer-Tropsch, methanol, or dimethylether syntheses. The heat from the exothermic carbon-carbon bond-forming reaction is integrated with the endothermic gasification reaction, thus providing an energy-efficient route for producing fuels and chemicals from renewable biomass resources.

  8. Cluster correlation effects in 12C+12C and 14N+10B fusion-evaporation reactions

    Directory of Open Access Journals (Sweden)

    Morelli L.

    2015-01-01

    Full Text Available The decay of highly excited states of 24Mg is studied in fusion evaporation events completely detected in charge in the reactions 12C+12C and 14N+10B at 95 and 80 MeV incident energy respectively. The comparison of light charged particles measured spectra with statistical model predictions suggests that the dominant reaction mechanism is compound nucleus (CN formation and decay. However, in both reactions, a discrepancy with statistical expectations is found for α particles detected in coincidence with Carbon, Oxigen and Neon residues. The comparison between the two reactions shows that this discrepancy is only partly explained by an entrance channel effect. Evidence for cluster correlations in excited 24Mg CN is suggested by the comparison between the measured and calculated branching ratios for the channels involving α particles.

  9. Progressive extraction method applied to isotopic exchange of carbon-14

    International Nuclear Information System (INIS)

    Isotopic exchange in natural settings is essentially an irreversible process, so that it progresses continuously until there is complete isotopic equilibrium. In soils, this process involves interaction between isotopes in the liquid and solid phases, and complete isotopic equilibrium may take a very long time. Measurements after partial isotopic exchange have been used to characterize the labile fraction of elements in soils. We describe a method to characterize the extent of isotopic exchange, with application here to incorporation of inorganic carbon-14 (14C) into mineral carbonates and organic matter in soils. The procedure uses a continuous addition of extractant, acid, or H2O2in the examples presented here, coupled with sequential sampling. The method has been applied to demonstrate the degree of isotopic exchange in soil. The same strategy could be applied to many other elements, including plant nutrients. (author)

  10. Carbon budget of a marine phytoplankton-herbivore system with carbon-14 as a tracer

    Energy Technology Data Exchange (ETDEWEB)

    Copping, A.E.; Lorenzen, C.J.

    1980-09-01

    Adult female and stage V Calanus pacificus were fed /sup 14/C-labeled phytoplankton in the laboratory in the form of monospecific cultures and natural populations. A carbon budget was constructed by following the /sup 14/C activity and the specific activity, over 48 h, in the phytoplankton, copepod, dissolved organic, dissolved inorganic, and fecal carbon compartments. The average incorporation of carbon into the copepod's body was 45% of the phytoplankton carbon available. Of the phytoplankton carbon, 27% appeared as dissolved organic carbon, 24% as dissolved inorganic carbon, and 3 to 4% in the form of fecal pellets. All of the tracer was recovered at the end of the experiments. The specific activity of the phytoplankton compartment was constant throughout each experiment. The other compartments had initial specific activities of zero, or close to zero, and increased throughout the experiment. In most experiments, the copepod specific activity equalled that of the phytoplankton at the end of 48 h, while the dissolved organic carbon, dissolved inorganic carbon, and fecal specific activities remained well below that of the phytoplankton.

  11. Synthesis of carbon-14 labeled Taxol (paclitaxel). [Anticancer agent

    Energy Technology Data Exchange (ETDEWEB)

    Walker, D.G.; Swigor, J.E. (Bristol-Myers Squibb Co., Syracuse, NY (United States). Pharmaceutical Research Inst.); Kant, Joydeep; Schroeder, D.R. (Bristol-Myers Squibb Co., Wallingford, CT (United States). Pharmaceutical Research Inst.)

    1994-10-01

    Reductive cleavage of the C13 side chain of Taxol (1, paclitaxel) followed by regioselective silylation gave 7-triethylsilylbaccatin III (4). 3-O-Triethysilylation of 5 and subsequent reaction with benzoyl chloride-C7-[sup 14]C gave azetidinone 7. Coupling of 4 and 7 followed by deprotection gave 1.26 g of Taxol-N3'-[sup 14]C (11) having a specific activity of 26.5 mCi/mmol and a radiochemical purity of 95%. (author).

  12. Radiative Neutron Capture on Carbon-14 in Effective Field Theory

    OpenAIRE

    Rupak, Gautam; Fernando, Lakma; Vaghani, Akshay

    2012-01-01

    The cross section for radiative capture of neutron on carbon-14 is calculated using the model-independent formalism of halo effective field theory. The dominant contribution from E1 transition is considered, and the cross section is expressed in terms of elastic scattering parameters of the effective range expansion. Contributions from both resonant and non-resonant interaction are calculated. Significant interference between these leads to a capture contribution that deviates from simple Bre...

  13. Study of redox reactions to split water and carbon dioxide

    Science.gov (United States)

    Arifin, Darwin

    The development of carbon-neutral, environmentally-sustainable energy carrier is a technological imperative necessary to mitigate the impact of anthropogenic carbon dioxide on earth's climate. One compelling approach rapidly gaining international attention is the conversion of solar energy into renewable fuels, such as H2 or CO, via a two-step thermochemical cycle driven by concentrated solar power. In accordance with the increased interest in this process, there is a need to better understand the gas splitting chemistry on the metal oxide intermediates encountered in such solar-driven processes. Here we measured the H2 and CO production rates during oxidation by H2O and CO2 in a stagnation flow reactor. Redox cycles were performed over various metal oxide chemistries such as hercynite and ceria based materials that are thermally reduced by laser irradiation. In addition to cycle capacity evaluation, reaction kinetics intrinsic to the materials were extracted using a model-based analytical approach to account for the effects of mixing and dispersion in the reactor. Investigation of the "hercynite chemistry" with raman spectroscopy verifies that, at the surface, the cycle proceeds by stabilizing the reduced and oxidized moieties in two different compounds, which allows the thermal reduction reaction to occur to a greater extent at a temperature 150 °C lower than a similarly prepared CoFe2O4-coated m-ZrO2. Investigation of the ceria cycle shows that the water splitting reaction, in the range of 750 - 950 °C and 20 - 40 vol.% H2O, can best be described by a first-order kinetic model with low apparent activation energy (29 kJ/mol). The carbon dioxide splitting reaction, in the range of 650 - 875 °C and 10 - 40 vol.% CO2, is a more complex surface-mediated phenomena that is controlled by a temperature-dependent surface site blocking mechanism involving adsorbed carbon. Moreover, we find that lattice substitution of ceria with zirconium can increase H2 production by

  14. Sarcoidosis patient: an unexpected reaction to carbonic anhydrase enzyme inhibitor

    OpenAIRE

    Khedr, Yahya A H; Khedr, Abdulla H

    2013-01-01

    Ocular diseases are very common in many of the systemic diseases such as sarcoidosis, and may sometimes be the presenting symptom of the disease. In this case report, we present an unusual reaction of the sarcoid granuloma to carbonic anhydrase enzyme inhibitors (CAIs), which was encountered in a patient with ocular sarcoidosis. This observation was taken after a 2-week interval between a CT scan orbits and an MRI orbits which showed a decrease in size from 4×3×4 cm to 2.5×2.5×2 cm, respectiv...

  15. Utilization of Tritium and Carbon-14 in Studies of Isotope Effects

    International Nuclear Information System (INIS)

    The utility of tritium in organic research has been augmented by the development of a simple method for determining C14 and tritium in the same sample. The non-volatile, radioactive material, in a film that is 'infinitely thick' to tritium radiation, is counted in a windowless, gas-fiow proportional counter; the film is then re-counted when covered with a screen that stops all radiation from tritium but allows a fraction of that from C14 to pass. By introduction of one isotope at a point removed from the reaction centre, an isotope effect for the other can be determined from changes in the tritium-C14 ratio in the reactant and/or products as the reaction proceeds. Carriers of reactant, products or derivatives can be added at any point to facilitate isolation, because the analytical method depends primarily on the tritium-C14 ratio. Methods for utilizing the double-label technique will be illustrated by a study of isotope effects in the oxidation of the penultimate carbon of certain labelled polyols with Acetobacter suboxydans. Six D-mannitols position-labelled either with C14 or with tritium at C1, C2 or C3 were prepared. For these, isotope effects (k*/k) of 0.93, 0.23, and 0.71, respectively, were found with C14 at C2, tritium at C2, and tritium at C3; no detectable isotope effects were found for the remaining Dmannitols. In the oxidation of position-labelled D-glucitols, an isotope effect of 0.24 was found for tritium at C5; no detectable effect was found for either C14 or tritium at C1. The techniques are suitable for studying a variety of chemical and biological reactions. (author)

  16. Mineral carbonation of gaseous carbon dioxide using a clay-hosted cation exchange reaction.

    Science.gov (United States)

    Kang, Il-Mo; Roh, Ki-Min

    2013-01-01

    The mineral carbonation method is still a challenge in practical application owing to: (1) slow reaction kinetics, (2) high reaction temperature, and (3) continuous mineral consumption. These constraints stem from the mode of supplying alkaline earth metals through mineral acidification and dissolution. Here, we attempt to mineralize gaseous carbon dioxide into calcium carbonate, using a cation exchange reaction of vermiculite (a species of expandable clay minerals). The mineralization is operated by draining NaCI solution through vermiculite powders and continuously dropping into the pool of NaOH solution with CO2 gas injected. The mineralization temperature is regulated here at 293 and 333 K for 15 min. As a result of characterization, using an X-ray powder diffractometer and a scanning electron microscopy, two types of pure CaCO3 polymorphs (vaterite and calcite) are identified as main reaction products. Their abundance and morphology are heavily dependent on the mineralization temperature. Noticeably, spindle-shaped vaterite, which is quite different from a typical vaterite morphology (polycrystalline spherulite), forms predominantly at 333 K (approximately 98 wt%).

  17. Methods for synthesizing diethyl carbonate from ethanol and supercritical carbon dioxide by one-pot or two-step reactions in the presence of potassium carbonate

    OpenAIRE

    Gasc, Fabien; Thiebaud-Roux, Sophie; Mouloungui, Zephirin

    2009-01-01

    Carbon dioxide sequestration was studied by synthesizing diethyl carbonate (DEC) from ethanol and CO2 under supercritical conditions in the presence of potassium carbonate as a base. The co-reagent was ethyl iodide or a concentrated strong acid. This sequestration reaction occurs in two steps, which were studied separately and in a one-pot reaction. An organic-inorganic carbonate hybrid, potassium ethyl carbonate (PEC) is generated at the end of the first step. This intermediate was character...

  18. Effect of carbon on the Ni catalyzed methane cracking reaction: A DFT study

    Energy Technology Data Exchange (ETDEWEB)

    Li, Jingde; Croiset, Eric; Ricardez–Sandoval, Luis, E-mail: laricard@uwaterloo.ca

    2014-08-30

    Highlights: • Effect of carbon deposition on kinetic properties of methane dissociation is studied. • Existence of surface and subsurface C atoms destabilized CH{sub x} species adsorption. • CH{sub x} activation is hindered with the deposition of C on and in the Ni (1 1 1) surface. - Abstract: To understand the effects of carbon atoms on the Ni catalyzed methane cracking reactions, methane dissociation on clean, surface-carbon-covered, and subsurface-carbon-accumulated Ni(1 1 1) surfaces were investigated using density functional theory (DFT). The results show that the existence of surface and subsurface C atoms destabilized the adsorption of the surface hydrocarbon species when compared to the clean Ni(1 1 1) surface. The projected density state (PDOS) analysis shows that the deposition of C atoms on and into the Ni surface modified the electronic structure of the Ni surface, and thus reduced the catalytic activity of the bonded Ni atoms. Moreover, it was found that the presence carbon atoms increase the CH{sub x} (x = 4–1) species activation barriers especially on the surface carbon covered (1/4 ML) Ni(1 1 1) surface, where CH{sub x} (x = 4–1) species encounter highest energy barrier for dissociation due to the electronic deactivation induced by C-Ni bonding and the strong repulsive carbon -CH{sub x} interaction. The calculations also show that CH{sub x} dissociation barriers are not affected by its neighboring C atom at low surface carbon coverage (1/9 ML). This work can be used to estimate more realistic kinetic parameters for this system.

  19. Carbon and oxygen isotope separation by plasma chemical reactions in carbon monoxide glow discharge

    International Nuclear Information System (INIS)

    The separation of carbon and oxygen isotopes in CO glow discharge has been studied. The isotope enrichment in the products was measured by quadru-pole mass spectrometer. The reaction yield and empirical formula of solid phase products were determined by the gas-volumetric analysis. The stable products obtained in our experiment are CO2 and solid polymers formed on the discharge wall. The polymer consists of both carbon and oxygen and the oxygen/carbon mole ratio in the polymer is 0.35±0.05. Thi isotope enrichment coefficients show a strong negative dependence on discharge current though the relative reaction yields have an opposite tendency. Consequently, the maximum isotope enrichment coefficients for 13C in wall deposit of 2.31 and for 18O in CO2 of 1.37 are obtained when the discharge current and the reaction yields are minimum in our experimental range. The experimental results of isotope enrichment have been compared with theoretical values estimated by an analytical model of literature. The dilution mechanism of the isotope enrichment of stable products is inferred from the isotopic distributions of 13C and 18O in products and theoretical predictions for isotope enrichment. (author)

  20. Carbon-coated magnetic palladium: applications in partial oxidation of alcohols and coupling reactions.

    Science.gov (United States)

    Magnetic carbon supported Pd catalyst has been synthesized via in situ generation of nanoferrites and incorporation of carbon from renewable cellulose via calcination; catalyst can be used for oxidation of alcohols, amination reaction and arylation of aryl halides (cross coupli...

  1. Synthesis of beta carbon nitride nanosized crystal through mechanochemical reaction

    CERN Document Server

    Yin Long Wei; Liu Yu Xian; Sui Jin Ling; Wang Jing Min

    2003-01-01

    Nanosized beta carbon nitride (beta-C sub 3 N sub 4), of grain size several tens of nanometres, has been synthesized by mechanochemical reaction processing. The low-cost synthetic method developed facilitates the novel and effective synthesis of nanosized crystalline beta-C sub 3 N sub 4 (a = 6.36 A, c = 4.648 A) powders. The graphite powders were first milled to a nanoscale state, then the nanosized graphite powders were milled in an atmosphere of NH sub 3 gas. It was found that nanosized beta-C sub 3 N sub 4 was formed after high-energy ball milling under an NH sub 3 atmosphere. After thermal annealing, the shape of the beta-C sub 3 N sub 4 changes from flake-like to sphere-like. The nanosized beta-C sub 3 N sub 4 formed was characterized by x-ray diffraction, Fourier transformation infrared spectroscopy, and transmission electron microscopy. A solid-gas reaction mechanism was proposed for the formation of nanosized beta-C sub 3 N sub 4 at room temperature induced by mechanochemical activation.

  2. Behavior of shungite carbon in reactions simulating thermal transformations of coal

    Energy Technology Data Exchange (ETDEWEB)

    Grigor' eva, E.N.; Rozhkova, N.N. [Russian Academy of Science, Moscow (Russian Federation)

    2000-07-01

    The catalytic activity of shungite carbon in reactions of model compounds (tetralin and benzyl phenyl ether) simulating thermolysis of coal was studied. The orders, rate constants, and activation energies of reactions were determined.

  3. {sup 14}Be(p,n){sup 14}B reaction at 69 MeV in inverse kinematics

    Energy Technology Data Exchange (ETDEWEB)

    Satou, Y., E-mail: satou@snu.ac.k [Department of Physics and Astronomy, Seoul National University, 599 Gwanak, Seoul 151-742 (Korea, Republic of); Nakamura, T.; Kondo, Y.; Matsui, N.; Hashimoto, Y.; Nakabayashi, T.; Okumura, T.; Shinohara, M. [Department of Physics, Tokyo Institute of Technology, 2-12-1 Oh-Okayama, Meguro, Tokyo 152-8551 (Japan); Fukuda, N.; Sugimoto, T.; Otsu, H.; Togano, Y.; Motobayashi, T.; Sakurai, H.; Yanagisawa, Y.; Aoi, N.; Takeuchi, S.; Gomi, T.; Ishihara, M. [RIKEN Nishina Center, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Kawai, S. [Department of Physics, Rikkyo University, 3 Nishi-Ikebukuro, Toshima, Tokyo 171-8501 (Japan)

    2011-03-21

    A Gamow-Teller (GT) transition from the drip-line nucleus {sup 14}Be to {sup 14}B was studied via the (p,n) reaction in inverse kinematics using a secondary {sup 14}Be beam at 69 MeV/nucleon. The invariant mass method is employed to reconstruct the energy spectrum. A peak is observed at an excitation energy of 1.27(2) MeV in {sup 14}B, together with bumps at 2.08 and 4.06(5) MeV. The observed forward peaking of the state at 1.27 MeV and a good description for the differential cross section, obtained with a DWBA calculation provide support for the 1{sup +} assignment to this state. By extrapolating the cross section to zero momentum transfer the GT-transition strength is deduced. The value is found to compare well with that reported in a {beta}-delayed neutron emission study.

  4. Template-free synthesis of porous graphitic carbon nitride/carbon composite spheres for electrocatalytic oxygen reduction reaction.

    Science.gov (United States)

    Fu, Xiaorui; Hu, Xiaofei; Yan, Zhenhua; Lei, Kaixiang; Li, Fujun; Cheng, Fangyi; Chen, Jun

    2016-01-28

    Porous graphitic carbon nitride/carbon composite spheres were synthesized using melamine and cyanuric acid, and glucose as the carbon nitride and carbon precursor, respectively. The 3D hierarchical composites efficiently catalyzed the oxygen reduction reaction with an onset potential of 0.90 V and a kinetic current density of 23.92 mA cm(-2). These merit their promising applications in fuel cells and metal-air batteries.

  5. Biosphere structure, carbon sequestering potential and the atmospheric C-14 carbon record

    Energy Technology Data Exchange (ETDEWEB)

    Goudriaan, J.

    1992-08-01

    The behaviour of a numerical model for the global carbon cycle is elucidated by a simple analytical model for the biosphere. In the period 1980-1990 the ocean is estimated to have absorbed 33% of the total CO{sub 2} emission to the atmosphere in that same period. Net deforestation was responsible for 12-17% of this total emission rate, whereas the CO{sub 2}-fertilization effect caused a re-absorption of 20-25%. Aggregation of the above-ground biosphere into a single pool in the model caused an overestimation of the CO{sub 2}-fertilization effect. Also, the estimate of this rate increased when the fraction of carbon assumed to remain after the transformation of litter into humus was increased, but the rate was little influenced by the model structure for soil organic carbon. A larger estimate for carbon uptake in the biosphere (Tans, Fung, and Takahashi, 1990) must be compensated by a reduced uptake in the ocean to arrive at a carbon balance. To do this, either the exchange rate between the upper mixed ocean layer and deep sea, or between ocean surface and atmosphere, should be reduced. In addition, a good match to the observed time-course of C-14 carbon in the atmosphere must be preserved by the model. The C-14 time-course did not remain well-matched if the atmosphere-ocean surface exchange was reduced, but it was hardly disturbed at all if the exchange rate with the deep sea was reduced.

  6. Application of the Trojan Horse Method to study neutron induced reactions: the 17O(n, α14C reaction

    Directory of Open Access Journals (Sweden)

    Gulino M.

    2014-03-01

    Full Text Available The reaction 17O(n, α14C was studied using virtual neutrons coming from the quasi-free deuteron break-up in the three body reaction 17O+d → α+14C+p. This technique, called virtual neutron method, extends the Trojan Horse method to neutron-induced reactions allowing to study the reaction cross section avoiding the suppression effects coming from the penetrability of the centrifugal barrier. For incident neutron energies from thermal up to a few hundred keV, direct experiments have shown the population of two out of three expected excited states at energies 8213 keV and 8282 keV and the influence of the sub-threshold level at 8038 keV. In the present experiment the 18O excited state at E* = 8.125 MeV, missing in the direct measurement, is observed. The angular distributions of the populated resonances have been measured for the first time. The results unambiguously indicate the ability of the method to overcome the centrifugal barrier suppression effect and to pick out the contribution of the bare nuclear interaction.

  7. Application of the Trojan Horse Method to study neutron induced reactions: the 17O(n, α)14C reaction

    Science.gov (United States)

    Gulino, M.; Spitaleri, C.; Tang, X. D.; Guardo, G. L.; Lamia, L.; Cherubini, S.; Bucher, B.; Burjan, V.; Couder, M.; Davies, P.; deBoer, R.; Fang, X.; Goldberg, V. Z.; Hons, Z.; Kroha, V.; Lamm, L.; La Cognata, M.; Li, C.; Ma, C.; Mrazek, J.; Mukhamedzhanov, A. M.; Notani, M.; O'Brien, S.; Pizzone, R. G.; Rapisarda, G. G.; Roberson, D.; Sergi, M. L.; Tan, W.; Thompson, I. J.; Wiescher, M.

    2014-03-01

    The reaction 17O(n, α)14C was studied using virtual neutrons coming from the quasi-free deuteron break-up in the three body reaction 17O+d → α+14C+p. This technique, called virtual neutron method, extends the Trojan Horse method to neutron-induced reactions allowing to study the reaction cross section avoiding the suppression effects coming from the penetrability of the centrifugal barrier. For incident neutron energies from thermal up to a few hundred keV, direct experiments have shown the population of two out of three expected excited states at energies 8213 keV and 8282 keV and the influence of the sub-threshold level at 8038 keV. In the present experiment the 18O excited state at E* = 8.125 MeV, missing in the direct measurement, is observed. The angular distributions of the populated resonances have been measured for the first time. The results unambiguously indicate the ability of the method to overcome the centrifugal barrier suppression effect and to pick out the contribution of the bare nuclear interaction.

  8. Highly vibrationally excited CO generated in a low-temperature chemical reaction between carbon vapor and molecular oxygen

    Science.gov (United States)

    Jans, E.; Frederickson, K.; Yurkovich, M.; Musci, B.; Rich, J. W.; Adamovich, I. V.

    2016-08-01

    A chemical flow reactor is used to study the vibrational population distribution of CO produced by a reaction between carbon vapor generated in an arc discharge and molecular oxygen. The results demonstrate formation of highly vibrationally excited CO, up to vibrational level v = 14, at low temperatures, T = 400-450 K, with population inversion at v = 4-7, in a collision-dominated environment, 15-20 Torr. The average vibrational energy per CO molecule formed by the reaction is 0.6-1.2 eV/molecule, which corresponds to 10-20% of reaction enthalpy. The results show feasibility of development of a new CO chemical laser using carbon vapor and oxygen as reactants.

  9. The kinetics of the O2/CO2 reaction in molten carbonate - Reaction orders for O2 and CO2 on NiO. [in fuel cells

    Science.gov (United States)

    Winnick, J.; Ross, P. N.

    1980-01-01

    The kinetics of the O2/CO2 reaction in molten carbonate is investigated using paste electrolytes and nickel sinter electrodes. A two-step approach to the determination of reaction orders is employed. First, exchange currents at various P(CO2) and P(O2) were measured using the low polarization method. Second, alpha(+) and alpha(-) values were obtained from the slope of the Allen-Hickling plot for current densities low enough so that concentration polarization within the electrode can be neglected. The reaction orders are + 1/4 in CO2 and + 5/8 in O2 in the cathodic direction, and - 3/4 in CO2 and + 1/8 in O2 in the anodic direction.

  10. The preparation of glucose uniformly labelled with carbon-14; Preparacion de glucosa uniformemente marcada con carbono-14

    Energy Technology Data Exchange (ETDEWEB)

    Garcia, M. D.; Suarez, C.; Rodrigo, M. E.

    1978-07-01

    The plant, (Zea mais, L) and culture conditions for an optimum production of glucose has been chosen. To achieve the labelling of glucose, photosynthesis and carboxylation are carried on, under an artificial atmosphere of 14CO{sub 2} produced from 14{sup C}-barium carbonate. Following photosynthesis the sugars are extracted, and then the extract purified by several methods. The purified glucose is finally, degraded and the specific radioactivity is determined in each of its carbon atoms. (Author) 37 refs.

  11. High-Throughput Screening of the Asymmetric Decarboxylative Alkylation Reaction of Enolate-Stabilized Enol Carbonates

    KAUST Repository

    Stoltz, Brian

    2010-06-14

    The use of high-throughput screening allowed for the optimization of reaction conditions for the palladium-catalyzed asymmetric decarboxylative alkylation reaction of enolate-stabilized enol carbonates. Changing to a non-polar reaction solvent and to an electron-deficient PHOX derivative as ligand from our standard reaction conditions improved the enantioselectivity for the alkylation of a ketal-protected,1,3-diketone-derived enol carbonate from 28% ee to 84% ee. Similar improvements in enantioselectivity were seen for a β-keto-ester derived- and an α-phenyl cyclohexanone-derived enol carbonate.

  12. Carbon dioxide sequestration via olivine carbonation: Examining the formation of reaction products

    Science.gov (United States)

    King, H. E.; Plümper, O.; Putnis, A.

    2009-04-01

    Due to its abundance and natural ability to sequester CO2, olivine has been proposed as one mineral that could be used in the control of CO2 emissions into the atmosphere (Metz, 2005). Large scale peridotite deposits found in locations such as the Western Gneiss Region in Norway could provide in-situ sites for sequestration or the raw materials for ex-situ mineral carbonation. Determining the conditions under which magnesite (MgCO3) forms most efficiently is crucial to conduct a cost effective process. Understanding the development of secondary minerals is particularly important for in-situ methods as these phases can form passivating layers and affect the host rock porosity. The final solution of flow-through experiments conducted at alkaline pH have been shown to be supersaturated with respect to talc and chrysotile (Giammer et al., 2005), although these phases were not found to have precipitated the formation of a passivating, amorphous silica layer has been observed on reacted olivine surfaces (Bearat et al., 2006). By studying magnesite and other products produced during the carbonation of olivine within Teflon lined steel autoclaves we have begun to form a more comprehensive understanding of how these reactions would proceed during sequestration processes. We have performed batch experiments using carbonated saline solutions in the presence of air or gaseous CO2 from 80 to 200 ˚ C. X-ray powder diffraction was used to identify magnesite within the reaction products. Crystals of magnesite up to 20 m in diameter can be observed on olivine grain surfaces with scanning electron microscopy. Secondary reaction products formed a platy layer on olivine surfaces in reactions above 160 ˚ C and below pH 12. Energy dispersive X-ray analysis of the platy layer revealed an increase in Fe concentration. The macroscopically observable red colouration of the reaction products and Raman spectroscopy indicate that hematite is present in these layers. For experiments with

  13. Inelastic Branch of the Stellar Reaction $^{14}$O$(\\alpha,p)^{17}$F

    CERN Multimedia

    Hass, M; Van duppen, P L E

    2002-01-01

    We propose to use the upgraded REX-ISOLDE beam energy to study the astrophysically important $^{14}$O($\\alpha$, p)$^{17}$F reaction in time reverse kinematics. In particular, we will use the highly efficient miniball + CD detection system to measure the previously undetermined inelastic proton branch of the 1$^-$ state at 6.15 MeV in $^{18}$Ne. This state dominates the reaction rate under X-ray burster conditions.

  14. Hybrid direct carbon fuel cells and their reaction mechanisms - a review

    DEFF Research Database (Denmark)

    Deleebeeck, Lisa; Kammer Hansen, Kent

    2014-01-01

    with carbon capture and storage (CCS) due to the high purity of CO2 emitted in the exhaust gas. Direct carbon (or coal) fuel cells (DCFCs) are directly fed with solid carbon to the anode chamber. The fuel cell converts the carbon at the anode and the oxygen at the cathode into electricity, heat and reaction...... is discussed on the fuel cell stack and system levels. The range of DCFC types can be roughly broken down into four fuel cell types: aqueous hydroxide, molten hydroxide, molten carbonate and solid oxide fuel cells. Emphasis is placed on the electrochemical reactions occurring at the anode and the proposed...... mechanism(s) of these reactions for molten carbonate, solid oxide and hybrid direct carbon fuel cells. Additionally, the criteria of choosing the ‘best’ DCFC technology is explored, including system design (continuous supply of solid fuel), performance (power density, efficiency), environmental burden...

  15. Correlation between carbon-carbon bond length and the ease of retro Diels-Alder reaction

    Indian Academy of Sciences (India)

    Sambasivarao Kotha; Shaibal Banerjee; Mobin Shaikh

    2014-09-01

    The bond length between C8-C9 in (1′R,4′S,4a′R,8a′S)-6′,7′-dimethyl-1′,4′,4a′,8a′-tetrahydrospiro [cyclopropane-1,9′-[1,4]methanonaphthalene]-5′,8′-dione is 1.571 (2) Å and between C7-C12 is 1.567 (2) Å which are longer than the corresponding bond length for saturated bicyclic systems (1.531-1.535Å). This paper reports the correlation between bond length and the ease of retro Diels−Alder reaction.

  16. Kinetic study of the reaction of uranium with various carbon-containing gases; Etude cinetique de la reaction sur l'uranium de differents gaz carbones

    Energy Technology Data Exchange (ETDEWEB)

    Feron, G. [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

    1963-09-15

    The kinetic study of the reaction U + CO{sub 2} and U + CO has been performed by a thermogravimetric method on a spherical uranium powder, in temperature ranges respectively from 460 to 690 deg. C and from 570 to 850 deg. C. The reaction with carbon dioxide leads to uranium dioxide. A carbon deposition takes place at the same time. The global reactions is the result of two reactions: U + 2 CO{sub 2} {yields} UO{sub 2} + 2 CO U + CO{sub 2} {yields} UO{sub 2} + C The reaction with carbon monoxide leads to a mixture of dioxide UO{sub 2}, dicarbide UC{sub 2} and free carbon. The main reaction can be written. U + CO {yields} 1/2 UO{sub 2} + 1/2 UC{sub 2} The free carbon results of the disproportionation of the carbon monoxide. A remarkable separation of the two phases UO{sub 2} and UC{sub 2} can be observed. A mechanism accounting for the phenomenon has been proposed. The two reactions U + CO{sub 2} and U + CO begin with a long germination period, after which, the reaction velocity seems to be limited in both cases by the ionic diffusion of oxygen through the uranium dioxide. (author) [French] L'etude cinetique des reactions U sol + CO{sub 2} gaz et U sol + CO gaz a ete effectuee par thermogravirnetrie sur une poudre d'uranium a grains spheriques, les domaines de temperature etudies s'etendant respectivement de 460 a 690 deg. C et de 570 a 850 deg. C. L'action du dioxyde de carbone conduit au dioxyde d'uranium UO{sub 2}; il se produit en meme temps un depot de carbone. La reaction globale resulte des deux reactions: U + 2 CO{sub 2} {yields} UO{sub 2} + 2 CO U + CO{sub 2} {yields} UO{sub 2} + C Le mono-oxyde de carbone conduit a un melange de dioxyde UO{sub 2}, de dicarbure UC{sub 2} et de carbone libre. La reaction principale s'ecrit: U + CO {yields} 1/2 UO{sub 2} + 1/2 UC{sub 2} Le carbone libre provient de la dismutation du mono-oxyde de carbone. On observe une separation remarquable des deux phases UO{sub 2} et UC{sub 2}; un mecanisme

  17. Synthesis of deleobuvir, a potent hepatitis C virus polymerase inhibitor, and its major metabolites labeled with carbon-13 and carbon-14.

    Science.gov (United States)

    Latli, Bachir; Hrapchak, Matt; Chevliakov, Maxim; Li, Guisheng; Campbell, Scot; Busacca, Carl A; Senanayake, Chris H

    2015-05-30

    Deleobuvir, (2E)-3-(2-{1-[2-(5-bromopyrimidin-2-yl)-3-cyclopentyl-1-methyl-1H-indole-6-carboxamido]cyclobutyl}-1-methyl-1H-benzimidazol-6-yl)prop-2-enoic acid (1), is a non-nucleoside, potent, and selective inhibitor of hepatitis C virus NS5B polymerase. Herein, we describe the detailed synthesis of this compound labeled with carbon-13 and carbon-14. The synthesis of its three major metabolites, namely, the reduced double bond metabolite (2) and the acyl glucuronide derivatives of (1) and (2), is also reported. Aniline-(13) C6 was the starting material to prepare butyl (E)-3-(3-methylamino-4-nitrophenyl-(13) C6 )acrylate [(13) C6 ]-(11) in six steps. This intermediate was then used to obtain [(13) C6 ]-(1) and [(13) C6 ]-(2) in five and four more steps, respectively. For the radioactive synthesis, potassium cyanide-(14) C was used to prepare 1-cylobutylaminoacid [(14) C]-(23) via Buchrer-Bergs reaction. The carbonyl chloride of this acid was then used to access both [(14) C]-(1) and [(14) C]-(2) in four steps. The acyl glucuronide derivatives [(13) C6 ]-(3), [(13) C6 ]-(4) and [(14) C]-(3) were synthesized in three steps from the acids [(13) C6 ]-(1), [(13) C6 ]-(2) and [(14) C]-(1) using known procedures. PMID:25964148

  18. FUSION-LIKE PROCESSES IN THE N-14+TH-232 REACTION AT 30 MEV NUCLEON

    NARCIS (Netherlands)

    LEEGTE, HKW; BOONSTRA, AL; HINNEFELD, JD; KOLDENHOF, EE; SIEMSSEN, RH; SIWEKWILCZYNSKA, K; SOSIN, Z; WILCZYNSKI, J; WILSCHUT, HW

    1992-01-01

    Fusionlike processes were studied in the N-14 + Th-232 reaction at 30 MeV per nucleon. Partition of the fusionlike cross section was determined by detecting nonequilibrium charged particles with an array of phoswich detectors (plastic wall) in coincidence with fission fragments for which the folding

  19. Graphitic mesoporous carbon based on aromatic polycondensation as catalyst support for oxygen reduction reaction

    Science.gov (United States)

    Liu, Peng; Kong, Jiangrong; Liu, Yaru; Liu, Qicheng; Zhu, Hongze

    2015-03-01

    Mesoporous carbon is constructed by monolithic polyaromatic mesophase deriving from the hexane insoluble of coal-tar pitch. This carbon material exhibits spherical morphology and layered crystallite, and thereby can be graphitized at 900 °C without destroying the mesoporous structure. Electrochemical measurements indicate that graphitic mesoporous carbon (GMC) support not only improves the activity of Pt electrocatalyst to oxygen reduction reaction (ORR), but also shows higher corrosion resistance than commercial XC-72 carbon black in the acid cathode environment.

  20. Kinetic study of the reaction of uranium with various carbon-containing gases

    International Nuclear Information System (INIS)

    The kinetic study of the reaction U + CO2 and U + CO has been performed by a thermogravimetric method on a spherical uranium powder, in temperature ranges respectively from 460 to 690 deg. C and from 570 to 850 deg. C. The reaction with carbon dioxide leads to uranium dioxide. A carbon deposition takes place at the same time. The global reactions is the result of two reactions: U + 2 CO2 → UO2 + 2 CO U + CO2 → UO2 + C The reaction with carbon monoxide leads to a mixture of dioxide UO2, dicarbide UC2 and free carbon. The main reaction can be written. U + CO → 1/2 UO2 + 1/2 UC2 The free carbon results of the disproportionation of the carbon monoxide. A remarkable separation of the two phases UO2 and UC2 can be observed. A mechanism accounting for the phenomenon has been proposed. The two reactions U + CO2 and U + CO begin with a long germination period, after which, the reaction velocity seems to be limited in both cases by the ionic diffusion of oxygen through the uranium dioxide. (author)

  1. Measurement of pion double charge exchange on carbon-13, carbon-14, magnesium-26, and iron-56

    Energy Technology Data Exchange (ETDEWEB)

    Seidl, P.A.

    1985-02-01

    Cross sections for the /sup 13,14/C,/sup 26/Mg,/sup 56/Fe(..pi../sup +/,..pi../sup -/)/sup 13,14/O,/sup 26/Si,/sup 56/Ni reactions were measured with the Energetic Pion Channel and Spectrometer at the Clinton P. Anderson Meson Physics Facility for 120 less than or equal to T/sub ..pi../ less than or equal to 292 MeV and 0 less than or equal to theta less than or equal to 50. The double isobaric analog states (DIAS) are of primary interest. In addition, cross sections for transitions to /sup 14/O(0/sup +/, 5.92 MeV), /sup 14/O(2/sup +/, 7.77 MeV), /sup 56/Ni(gs), /sup 13/O(gs), and /sup 13/O(4.21 MeV) are presented. The /sup 13/O(4.21 MeV) state is postulated to have J/sup ..pi../ = 1/2/sup -/. The data are compared to previously measured double-charge-exchange cross sections on other nuclei, and the systematics of double charge exchange on T greater than or equal to 1 target nuclei leading to the DIAS are studied. Near the ..delta../sub 33/ resonance, cross sections for the DIAS transitions are in disagreement with calculations in which the reaction is treated as sequential charge exchange through the free pion-nucleon amplitude, while for T/sub ..pi../ > 200 MeV the anomalous features of the 164 MeV data are not apparent. This is evidence for significant higher order contributions to the double-charge-exchange amplitude near the reasonable energy. Two theoretical approaches that include two nucleon processes are applied to the DIAS data. 64 references.

  2. Nuclear reactions with 11C and 14O radioactive ion beams

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Fanqing

    2004-12-09

    Radioactive ion beams (RIBs) have been shown to be a useful tool for studying proton-rich nuclides near and beyond the proton dripline and for evaluating nuclear models. To take full advantage of RIBs, Elastic Resonance Scattering in Inverse Kinematics with Thick Targets (ERSIKTT), has proven to be a reliable experimental tool for investigations of proton unbound nuclei. Following several years of effort, Berkeley Experiments with Accelerated Radioactive Species (BEARS), a RIBs capability, has been developed at the Lawrence Berkeley National Laboratory's 88-Inch Cyclotron. The current BEARS provides two RIBs: a 11C beam of up to 2x108 pps intensity on target and an 14O beam of up to 3x104 pps intensity. While the development of the 11C beam has been relatively easy, a number of challenges had to be overcome to obtain the 14O beam. The excellent 11C beam has been used to investigate several reactions. The first was the 197Au(11C,xn)208-xnAt reaction, which was used to measure excitation functions for the 4n to 8n exit channels. The measured cross sections were generally predicted quite well using the fusion-evaporation code HIVAP. Possible errors in the branching ratios of ?? decays from At isotopes as well as the presence of incomplete fusion reactions probably contribute to specific overpredictions. 15F has been investigated by the p(14O,p)14O reaction with the ERSIKTT technology. Several 14O+p runs have been performed. Excellent energy calibration was obtained using resonances from the p(14N,p)14N reaction in inverse kinematics, and comparing the results to those obtained earlier with normal kinematics. The differences between 14N+p and 14O+p in the stopping power function have been evaluated for better energy calibration. After careful calibration, the energy levels of 15F were fitted with an R-matrix calculation. Spins and parities were assigned to the two observed resonances. This new measurement of the 15F ground state supports the disappearance of the Z

  3. Nuclear reactions with 11C and 14O radioactive ion beams

    International Nuclear Information System (INIS)

    Radioactive ion beams (RIBs) have been shown to be a useful tool for studying proton-rich nuclides near and beyond the proton dripline and for evaluating nuclear models. To take full advantage of RIBs, Elastic Resonance Scattering in Inverse Kinematics with Thick Targets (ERSIKTT), has proven to be a reliable experimental tool for investigations of proton unbound nuclei. Following several years of effort, Berkeley Experiments with Accelerated Radioactive Species (BEARS), a RIBs capability, has been developed at the Lawrence Berkeley National Laboratory's 88-Inch Cyclotron. The current BEARS provides two RIBs: a 11C beam of up to 2x108 pps intensity on target and an 14O beam of up to 3x104 pps intensity. While the development of the 11C beam has been relatively easy, a number of challenges had to be overcome to obtain the 14O beam. The excellent 11C beam has been used to investigate several reactions. The first was the 197Au(11C,xn)208-xnAt reaction, which was used to measure excitation functions for the 4n to 8n exit channels. The measured cross sections were generally predicted quite well using the fusion-evaporation code HIVAP. Possible errors in the branching ratios of ?? decays from At isotopes as well as the presence of incomplete fusion reactions probably contribute to specific overpredictions. 15F has been investigated by the p(14O,p)14O reaction with the ERSIKTT technology. Several 14O+p runs have been performed. Excellent energy calibration was obtained using resonances from the p(14N,p)14N reaction in inverse kinematics, and comparing the results to those obtained earlier with normal kinematics. The differences between 14N+p and 14O+p in the stopping power function have been evaluated for better energy calibration. After careful calibration, the energy levels of 15F were fitted with an R-matrix calculation. Spins and parities were assigned to the two observed resonances. This new measurement of the 15F ground state supports the disappearance of the Z = 8

  4. Synthesis of carbon-14 labelled indolic 5HT{sub 1} receptor agonists

    Energy Technology Data Exchange (ETDEWEB)

    Waterhouse, Ian; Cable, K.M.; Fellows, Ian; Wipperman, M.D.; Sutherland, D.R. [Glaxo Wellcome Research and Development, Stevenage (United Kingdom). Isotope Chemistry Unit

    1996-11-01

    Syntheses of carbon-14 labelled versions of indolic 5HT{sub 1} agonists sumatriptan (GR43175), GR40370 and naratriptan (GR85548) are described. Introduction of the label via cyanation of ketoformanilides, formed by oxidative cleavage of an indole ring, ensured incorporation of carbon-14 at the metabolically stable C-2 position of the indole. (author).

  5. Effect of dead carbon on the 14C dating of the speleothem

    Institute of Scientific and Technical Information of China (English)

    CAI Yanjun; Warren Beck; PENG Zicheng; ZHANG Zhaofeng

    2005-01-01

    Based on the comparison of dating results among high-precision TIMS U-series and AMS 14C as well as the published 14C dating results and their band counting ages (i.e. calendar ages), this paper discusses the effect of dead carbon on the speleothem 14C dating. The result shows that the fraction of incorporated dead carbon during the formation of speleothem varies. The change in the fraction of dead carbon would result in big deviation in the 14C age of the speleothem. It is indispensable to take the dead carbon into consideration when dating the speleothem using the 14C method or studying the atmospheric 14C concentration during the past with the speleothem.

  6. Studies of reductive elimination reactions to form carbon-oxygen bonds from Pt(IV) complexes.

    Science.gov (United States)

    Williams, B S; Goldberg, K I

    2001-03-21

    The platinum(IV) complexes fac-L(2)PtMe(3)(OR) (L(2) = bis(diphenylphosphino)ethane, o-bis(diphenylphosphino)benzene, R = carboxyl, aryl; L = PMe(3), R = aryl) undergo reductive elimination reactions to form carbon-oxygen bonds and/or carbon-carbon bonds. The carbon-oxygen reductive elimination reaction produces either methyl esters or methyl aryl ethers (anisoles) and L(2)PtMe(2), while the carbon-carbon reductive elimination reaction affords ethane and L(2)PtMe(OR). Choice of reaction conditions allows the selection of either type of coupling over the other. A detailed mechanistic study of the reductive elimination reactions supports dissociation of the OR(-) ligand as the initial step for the C-O bond formation reaction. This is followed by a nucleophilic attack of OR(-) upon a methyl group bound to the Pt(IV) cation to produce the products MeOR and L(2)PtMe(2). C-C reductive elimination proceeds from L(2)PtMe(3)(OR) by initial L (L = PMe(3)) or OR(-) (L(2) = dppe, dppbz) dissociation, followed by C-C coupling from the resulting five-coordinate intermediate. Our studies demonstrate that both C-C and C-O reductive elimination reactions from Pt(IV) are more facile in polar solvents, in the presence of Lewis acids, and for OR(-) groups that contain electron withdrawing substituents. PMID:11456927

  7. Carbon dioxide released from subduction zones by fluid-mediated reactions

    Science.gov (United States)

    Ague, Jay J.; Nicolescu, Stefan

    2014-05-01

    The balance between the subduction of carbonate mineral-bearing rocks into Earth's mantle and the return of CO2 to the atmosphere by volcanic and metamorphic degassing is critical to the carbon cycle. Carbon is thought to be released from subducted rocks mostly by simple devolatilization reactions. However, these reactions will also retain large amounts of carbon within the subducting slab and have difficulty in accounting for the mass of CO2 emitted from volcanic arcs. Carbon release may therefore occur via fluid-induced dissolution of calcium carbonate. Here we use carbonate δ18O and δ13C systematics, combined with analyses of rock and fluid inclusion mineralogy and geochemistry, to investigate the alteration of the exhumed Eocene Cycladic subduction complex on the Syros and Tinos islands, Greece. We find that in marble rocks adjacent to two fluid conduits that were active during subduction, the abundance of calcium carbonate drastically decreases approaching the conduits, whereas silicate minerals increase. Up to 60-90% of the CO2 was released from the rocks--far greater than expected via simple devolatilization reactions. The δ18O of the carbonate minerals is 5-10 lighter than is typical for metamorphosed carbonate rocks, implying that isotopically light oxygen was transported by fluid infiltration from the surroundings. We suggest that fluid-mediated carbonate mineral removal, accompanied by silicate mineral precipitation, provides a mechanism for the release of enormous amounts of CO2 from subduction zones.

  8. Effect of industrial fuel combustion on the carbon-14 level of atmospheric CO2

    International Nuclear Information System (INIS)

    As was previously noticed in 1953 by SUESS, the radiocarbon content of atmospheric CO2 was slightly lower in the 20th century (before the increase in the carbon-14 level due to the addition of artificial 14C) than at the time before the beginning of the industrial revolution in the 19th century. An exact knowledge of the magnitude of this effect is of interest in connection with the question of the rate of isotope exchange between atmospheric CO2 and the bicarbonates of the oceans. However, the radiocarbon level in the CO2 of the atmosphere is also subject to natural fluctuations caused by a variable cosmic-ray production rate of carbon-14. To investigate this the authors have cross-correlated sunspot numbers (as indicators of cosmic-ray activity) with the carbon-14 level in wood, and have detected a significant coherence between the two time series. The observed coherence permits an extrapolation of the natural carbon-14 values beyond the time of the beginning of artificial combustion of fossil fuel, around 1880. The results show that the observed small decrease in the carbon-14 level is somewhat affected by the increase of the production rate of carbon-14, as a consequence of relatively low solar activity during the preceding decades. The effect of industrial fuel combustion upon the carbon-14 level of the atmosphere can then be estimated for the Northern Hemisphere to be in the vicinity of -3%. (author)

  9. Dilepton spectroscopy at intermediate energies; the carbon - carbon reaction at 1 GeV/A

    International Nuclear Information System (INIS)

    The Physics context of this work is heavy ion collisions at relativistic energies where di-electron provide informations on the produced hot and dense nuclear matter. The experiment is performed by the DiLepton Spectrometer (DLS) Collaboration at the Lawrence Berkeley's Bevalac. After a description of the apparatus, we review the whole program and the main results so far obtained: first evidence of a significant di-electron signal at energies above 1 GeV/A; improvement of the understanding of di-electron production (electromagnetic decays of hadrons, π+π- annihilation and hadronic Bremsstrahlung). The results of p-p, p-d reactions from 1 to 4.9 GeV/A show that hadronic Bremsstrahlung (pp, pn) should be reformulated. Our analysis, optimized on the reaction Carbon-Carbon at 1 GeV/A, has been applied to α-Ca and d-Ca. We have developed two main aspects: improvement of the time resolution (500 ps) in order to eliminate all of the protons. Improvement of the space resolution (300 μ) for better mass resolution, in particular in the ρ region. We obtain the cross section of di-electron production as a function of mass, transverse momentum and rapidity from the C-C, α-Ca and d-Ca reactions at 1 GeV/A. We also compare the cross section for all of the measured systems at 1 GeV/A, including Ca-Ca, and we show a (ApAt)α dependence with α ≅ 1.1. A study of the associated multiplicity has also been performed. Nevertheless, the limited acceptance of the DLS and its poor mass resolution to identify the ρ, ω vector mesons, do not allow to conclude on hadron behaviour in nuclear matter. This point is one of the main goal of the HADES project at GSI (Darmstadt), which we give a brief description of the main features. (authors). 60 refs

  10. Resonance strengths in the 14N(p,gamma)15O and 15N(p,alpha gamma)12C reactions

    CERN Document Server

    Marta, Michele; Bemmerer, Daniel; Beyer, Roland; Broggini, Carlo; Caciolli, Antonio; Erhard, Martin; Fülöp, Zsolt; Grosse, Eckart; Gyürky, György; Hannaske, Roland; Junghans, Arnd R; Menegazzo, Roberto; Nair, Chithra; Schwengner, Ronald; Szücs, Tamás; Vezzú, Simone; Wagner, Andreas; Yakorev, Dmitry

    2010-01-01

    The 14N(p,gamma)15O reaction is the slowest reaction of the carbon-nitrogen-oxygen cycle of hydrogen burning in stars. As a consequence, it determines the rate of the cycle. The 15N(p,alpha gamma)12C reaction is frequently used in inverse kinematics for hydrogen depth profiling in materials. The 14N(p,gamma)15O and 15N(p,alpha gamma)12C reactions have been studied simultaneously, using titanium nitride targets of natural isotopic composition and a proton beam. The strengths of the resonances at Ep = 1058 keV in 14N(p,gamma)15O and at Ep = 897 and 430 keV in 15N(p,alpha gamma)12C have been determined with improved precision, relative to the well-known resonance at Ep = 278 keV in 14N(p,gamma)15O. The new recommended values are \\omega\\gamma = 0.352$\\pm$0.018, 362$\\pm$20, and 22.0$\\pm$0.9\\,eV for their respective strengths. In addition, the branching ratios for the decay of the Ep = 1058 keV resonance in 14N(p,gamma)15O have been redetermined. The data reported here should facilitate future studies of off-resona...

  11. First measurements of the ^16O(e,e'pn)^14N reaction

    CERN Document Server

    Middleton, D G; Barbieri, C; Barneo, P; Bartsch, P; Bauman, D; Bermuth, J; Bosnar, D; Blok, H P; Böhm, R; Ding, M; Distler, M O; Elsner, D; Friedrich, J; Giusti, C; Glazier, D I; Grabmayr, P; Grozinger, S; Hehl, T; Heim, J; Hesselink, W H A; Jans, E; Klein, F; Köhl, M; Lapikas, L; MacGregor, I J D; Martin, I; McGeorge, J C; Merkel, H; Merle, P; Moschini, F; Müller, U; Pospischil, T; Rosner, G; Schmieden, H; Seimetz, M; Sule, A; De Vries, H; Walcher, T; Watts, D P; Weis, M; Zihlmann, B; Pospischil, Th.; Walcher, Th.

    2006-01-01

    This paper reports on the first measurement of the ^16O(e,e'pn)^14N reaction. Data were measured in kinematics centred on a super-parallel geometry at energy and momentum transfers of 215 MeV and 316 MeV/c. The experimental resolution was sufficient to distinguish groups of states in the residual nucleus but not good enough to separate individual states. The data show a strong dependence on missing momentum and this dependence appears to be different for two groups of states in the residual nucleus. Theoretical calculations of the reaction using the Pavia code do not reproduce the shape or the magnitude of the data.

  12. Cross section measurement for (n,n{alpha}) reactions by 14 MeV neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Kasugai, Y.; Ikeda, Y.; Uno, Y. [Japan Atomic Energy Research Inst., Naka, Ibaraki (Japan). Naka Fusion Research Establishment; Yamamoto, H.; Kawade, K.

    1997-03-01

    Nine (n,n{alpha}) cross sections for (n,n{alpha}) reactions induced by 13.5-14.9 MeV neutrons were measured for {sup 51}V, {sup 65}Cu, {sup 71}Ga, {sup 76}Ge, {sup 87}Rb, {sup 91}Zr, {sup 93}Nb, {sup 96}Zr and {sup 109}Ag isotopes by using Fusion Neutronics Source (FNS) at JAERI. The reactions for 91Zr and 96Zr were measured for the first time. The evaluated data of JENDL-3 and ENDF/B-VI were compared with the present data. Some of the evaluated values are much different from our data by a factor more than ten. (author)

  13. The role of carbon in the photocatalytic reaction of carbon/TiO{sub 2} photocatalysts

    Energy Technology Data Exchange (ETDEWEB)

    Teng, Feng; Zhang, Guozhi; Wang, Youqing; Gao, Caitian; Chen, Lulu; Zhang, Peng; Zhang, Zhenxing, E-mail: zhangzx@lzu.edu.cn; Xie, Erqing, E-mail: xieeq@lzu.edu.cn

    2014-11-30

    Graphical abstract: - Highlights: • Carbon/TiO{sub 2} composites were fabricated by one-step carbonization method. • Carbon was generated by the dehydration carbonation effect of polymers. • Carbon was formed inside and outside of the TiO{sub 2} nanoparticles. • The photocatalytic activities of the composites depend on the coating carbon. - Abstract: The carbon/TiO{sub 2} nanocomposites were fabricated by a simple one-step carbonization method with different polymers as precursors. Due to the dehydration carbonation effect of polymers, carbon was formed inside and outside of the TiO{sub 2} nanoparticles. The photo-degradation study of rhodamine B was carried out under UV–vis light irradiation, and the photocatalytic activities of carbon/TiO{sub 2} nanocomposites are affected severely by the state of carbon, including dopants and coatings. The results show that the carbon on the surface plays more important role in the photocatalytic process.

  14. Stellar reactions with short-lived nuclei : {sup 17}F(p,a){sup 14}O.

    Energy Technology Data Exchange (ETDEWEB)

    Harss, B.; Greene, J. P.; Henderson, D.; Janssens, R. V. F.; Jiang, C. L.; Nolen, J.; Pardo, R. C.; Rehm, K. E.; Schiffer, J. P.; Sonzogni, A. A.; Uusitalo, J.; Wiendenhoever, I.; Paul, W.; Wang, T. F.; Borasi, F.; Segel, R. E.; Blackmon, J.; Smith, M.; Chen, A.; Parker, P.; Physics; Hebrew Univ.; LLNL; Northwestern Univ.; ORNL; Yale Univ.

    1999-05-01

    A method has been developed that can provide beams of many short-lived nuclei of interest in nucleosynthesis along the rp process path. With a {sup 17}F beam (T{sub 1/2} = 64 s) the excitation function of the {sup 17}F(p,a){sup 14}O reaction was measured to determine properties of excited states in {sup 18}Ne. These states influence the rate of the {sup 14}O(a,p){sup 17}F reaction which is important for understanding energy generation and nucleosynthesis in x-ray bursts. The present direct measurements yield a pattern of resonances and cross sections which differ substantially from previous estimates.

  15. The US nuclear reaction data network. Summary of the first meeting, March 13 & 14 1996

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-03-01

    The first meeting of the US Nuclear Reaction Data Network (USNRDN) was held at the Colorado School of Mines, March 13-14, 1996 chaired by F. Edward Cecil. The Agenda of the meeting is attached. The Network, its mission, products and services; related nuclear data and data networks, members, and organization are described in Attachment 1. The following progress reports from the members of the USNRDN were distributed prior to the meeting and are given as Attachment 2. (1) Measurements and Development of Analytic Techniques for Basic Nuclear Physics and Nuclear Applications; (2) Nuclear Reaction Data Activities at the National Nuclear Data Center; (3) Studies of nuclear reactions at very low energies; (4) Nuclear Reaction Data Activities, Nuclear Data Group; (5) Progress in Neutron Physics at Los Alamos - Experiments; (6) Nuclear Reaction Data Activities in Group T2; (7) Progress Report for the US Nuclear Reaction Data Network Meeting; (8) Nuclear Astrophysics Research Group (ORNL); (9) Progress Report from Ohio University; (10) Exciton Model Phenomenology; and (11) Progress Report for Coordination Meeting USNRDN.

  16. The US nuclear reaction data network. Summary of the first meeting, March 13 ampersand 14 1996

    International Nuclear Information System (INIS)

    The first meeting of the US Nuclear Reaction Data Network (USNRDN) was held at the Colorado School of Mines, March 13-14, 1996 chaired by F. Edward Cecil. The Agenda of the meeting is attached. The Network, its mission, products and services; related nuclear data and data networks, members, and organization are described in Attachment 1. The following progress reports from the members of the USNRDN were distributed prior to the meeting and are given as Attachment 2. (1) Measurements and Development of Analytic Techniques for Basic Nuclear Physics and Nuclear Applications; (2) Nuclear Reaction Data Activities at the National Nuclear Data Center; (3) Studies of nuclear reactions at very low energies; (4) Nuclear Reaction Data Activities, Nuclear Data Group; (5) Progress in Neutron Physics at Los Alamos - Experiments; (6) Nuclear Reaction Data Activities in Group T2; (7) Progress Report for the US Nuclear Reaction Data Network Meeting; (8) Nuclear Astrophysics Research Group (ORNL); (9) Progress Report from Ohio University; (10) Exciton Model Phenomenology; and (11) Progress Report for Coordination Meeting USNRDN

  17. Report on Carbon-14 generation and release at some of the Hanford reactors

    Energy Technology Data Exchange (ETDEWEB)

    Barton, G.B.

    1964-12-14

    The Hanford graphite-moderated reactors have an enclosed gas circulation system to maintain control of the composition of gas atmosphere in the graphite stack. This investigation was undertaken to answer several questions concerning the generation and release of Carbon-14 in the operation of these graphite moderated reactors. The principle question was: Will an increase in the nitrogen content of the reactor atmosphere increase the release of Carbon-14 sufficiently to create a health hazard. Other questions were: (1) What are the main sources and the main release routes. (2) How much does carbon-14 build up in the graphite in the reactor stack. and (3) Is the total release of carbon-14 to the atmosphere sufficient to enhance the /sup 14/C levels in the vegetation surrounding the reactors.

  18. Somewhere beyond the sea? The oceanic - carbon dioxide - reactions

    Science.gov (United States)

    Meisinger, Philipp; Wittlich, Christian

    2014-05-01

    In correlation to climate change and CO2 emission different campaigns highlight the importance of forests and trees to regulate the concentration of carbon dioxide in the earths' atmosphere. Seeing millions of square miles of rainforest cut down every day, this is truly a valid point. Nevertheless, we often tend to forget what scientists like Spokes try to raise awareness for: The oceans - and foremost deep sea sections - resemble the second biggest deposit of carbon dioxide. Here carbon is mainly found in form of carbonate and hydrogen carbonate. The carbonates are needed by corals and other sea organisms to maintain their skeletal structure and thereby to remain vital. To raise awareness for the protection of this fragile ecosystem in schools is part of our approach. Awareness is achieved best through understanding. Therefore, our approach is a hands-on activity that aims at showing students how the carbon dioxide absorption changes in relation to the water temperature - in times of global warming a truly sensitive topic. The students use standard syringes filled with water (25 ml) at different temperatures (i.e. 10°C, 20°C, 40°C). Through a connector students inject carbon dioxide (25ml) into the different samples. After a fixed period of time, students can read of the remaining amount of carbon dioxide in relation to the given water temperature. Just as with every scientific project, students need to closely monitor their experiments and alter their setups (e.g. water temperature or acidity) according to their initial planning. A digital template (Excel-based) supports the analysis of students' experiments. Overview: What: hands-on, minds -on activity using standard syringes to exemplify carbon dioxide absorption in relation to the water temperature (Le Chatelier's principle) For whom: adjustable from German form 11-13 (age: 16-19 years) Time: depending on the prior knowledge 45-60 min. Sources (extract): Spokes, L.: Wie Ozeane CO2 aufnehmen. Environmental

  19. Biocatalytic carbon capture via reversible reaction cycle catalyzed by isocitrate dehydrogenase.

    Science.gov (United States)

    Xia, Shunxiang; Frigo-Vaz, Benjamin; Zhao, Xueyan; Kim, Jungbae; Wang, Ping

    2014-09-12

    The practice of carbon capture and storage (CCS) requires efficient capture and separation of carbon dioxide from its gaseous mixtures such as flue gas, followed by releasing it as a pure gas which can be subsequently compressed and injected into underground storage sites. This has been mostly achieved via reversible thermochemical reactions which are generally energy-intensive. The current work examines a biocatalytic approach for carbon capture using an NADP(H)-dependent isocitrate dehydrogenase (ICDH) which catalyzes reversibly carboxylation and decarboxylation reactions. Different from chemical carbon capture processes that rely on thermal energy to realize purification of carbon dioxide, the biocatalytic strategy utilizes pH to leverage the reaction equilibrium, thereby realizing energy-efficient carbon capture under ambient conditions. Results showed that over 25 mol of carbon dioxide could be captured and purified from its gas mixture for each gram of ICDH applied for each carboxylation/decarboxylation reaction cycle by varying pH between 6 and 9. This work demonstrates the promising potentials of pH-sensitive biocatalysis as a green-chemistry route for carbon capture.

  20. Influence of reaction parameters on the attachment of a carbon nanofiber layer on Ni foils

    NARCIS (Netherlands)

    Pacheco Benito, Sergio; Lefferts, Leon

    2012-01-01

    Dense carbon (C) and entangled carbon nanofiber (CNF) layers were deposited on nickel foils by decomposition of ethylene in presence of different H2 concentrations at 450 °C for different reaction times. Both C and CNF layer thicknesses increase with time, but samples pre-oxidized at 500 °C normally

  1. New Condensation Reaction of β-keto-δ-valerolactones, Carbon Disulfide and Alkyl Halides

    Institute of Scientific and Technical Information of China (English)

    You Ming WANG; Yu Xin LI; Su Hua WANG; Zheng Ming LI

    2004-01-01

    β-Keto-δ-valerolactones, which were obtained by reaction of acetoacetate with aldehydes or ketones, reacted with carbon disulfide, alkyl halides and a new condensation reaction was developed. The structures of the products 3 were confirmed by 1HNMR spectra and elemental analysis.

  2. Analytical evaluation of the solid rocket motor nozzle surface recession by the alumina-carbon reaction

    OpenAIRE

    Matsukawa, Yutaka; Sato, Yutaka; 松川 豊; 佐藤 裕

    2008-01-01

    A theoretical model describing the chemical ablation of a solid rocket motor nozzle ablator by the alumina-carbon reaction is presented. An application of it to a typical solid rocket motor with a graphite nozzle ablator indicates a large influence of the reaction on the nozzle surface recession.

  3. Pd-catalyzed cascade reactions between o-iodo-N-alkenylanilines and tosylhydrazones: novel approaches to the synthesis of polysubstituted indoles and 1,4-dihydroquinolines.

    Science.gov (United States)

    Paraja, Miguel; Valdés, Carlos

    2016-05-01

    Two different Pd-catalyzed cascade reactions between o-iodo-N-alkenylanilines and tosylhydrazones are described. The outcome of the cascade processes is determined by the substitution on the N-alkenyl fragment. The reactions with N-tosyl-N-ethylene-o-iodoanilines lead to indoles through a sequence that involves the sequential migratory insertions of a carbene ligand and a C-C double bond, featuring a 5-exo-trig cyclization. The reactions with N-alkyl-N-alkenyl-o-iodoanilines provide 1,4-dihydroquinolines through a cascade reaction that includes a formal 6-endo-trig cyclization. In both cases the benzofused heterocycles are built through the formation of two C-C bonds on the hydrazonic carbon atom. PMID:27087628

  4. Stable Isotopic Evidence for a Pedogenic Origin of Carbonates in Trench 14 near Yucca Mountain, Nevada.

    Science.gov (United States)

    Quade, J; Cerling, T E

    1990-12-14

    Layered carbonate and silica encrust fault fractures exposed in Trench 14 near Yucca Mountain, site of the proposed high-level nuclear waste repository in southern Nevada. Comparison of the stable carbon and oxygen isotopic compositions of the fracture carbonates with those of modern soil carbonates in the area shows that the fracture carbonates are pedogenic in origin and that they likely formed in the presence of vegetation and rainfall typical of a glacial climate. Their isotopic composition differs markedly from that of carbonate associated with nearby springs. The regional water table therefore remained below the level of Trench 14 during the time that the carbonates and silica precipitated, a period probably covering parts of at least the last 300,000 years. PMID:17818282

  5. Preparation of hollow carbon nanospheres at low temperature via new reaction route

    International Nuclear Information System (INIS)

    Hollow carbon nanospheres were obtained at 200oC via a new reaction route, by using magnesium, hexachloroethane and aluminum trichloride as starting materials and benzene as solvent. The products were characterized with X-ray diffraction pattern, transmission electron microscope, high-resolution transmission electron microscope images and Raman spectrum. The reaction conditions are easy to be maintained and controlled. They may provide a new method to produce other carbonaceous materials. A possible mechanism of reaction was proposed

  6. Carbon-14 in lunar soil and in meteorites

    Science.gov (United States)

    Fireman, E. L.

    1978-01-01

    C-14 was measured in grain-size fractions of lunar soil 10084 and in samples of the Bruderheim chondrite and of several meteorites recently found in Antarctica (Allan Hills no. 5, 6, and 8). Temperature-release patterns were investigated. It was found that C-14 is released at temperatures below melting from small soil grains (less than 74 microns), but not from meteorites or from large soil grains. Below-melting C-14 contents increase with decreasing grain size in a manner similar to solar-wind-implanted rare-gas isotope contents (Eberhardt et al., 1970), whereas the C-14 released above melting temperatures is independent of grain size, suggesting that below-melting C-14 is solar-wind-implanted and above-melting C-14 is the result of cosmic ray spallations. The activity of C-14 in lunar samples is half that measured in the Bruderheim meteorite, which fell on May 4, 1970. No C-14 activity was observed in the Allan Hills chondrites; the C-14 limits suggest that these meteorites fell more than 25,000 years ago.

  7. Measurement and calculation of 238U fission reaction rates induced by neutrons reflected by carbon material

    International Nuclear Information System (INIS)

    To check the data of carbon material reflecting neutrons, the distribution of 238U fission reaction rates induced by D-T fusion neutrons reflected by carbon material was measured by using the small depleted uranium fission chamber and the capturing detector. For comparison, 238U fission rates without carbon material was measured too. The combined standard uncertainty of 238U fission reaction rate is 5.1%-6.4%. The measured results are consistent with the calculated ones with MCNP/4A code and ENDF/B-IV library data in the range of the error

  8. A kinetic study of the reaction of water vapor and carbon dioxide on uranium

    International Nuclear Information System (INIS)

    The kinetic study of the reaction of water vapour and carbon dioxide with uranium has been performed by thermogravimetric methods at temperatures between 160 and 410 deg G in the first case, 350 and 1050 deg C in the second: Three sorts of uranium specimens were used: uranium powder, thin evaporated films, and small spheres obtained from a plasma furnace. The experimental results led in the case of water vapour, to a linear rate of reaction controlled by diffusion at the lower temperatures, and by a surface reaction at the upper ones. In the case of carbon dioxide, a parabolic law has been found, controlled by diffusional processes. (author)

  9. Base-promoted reactions of bridged ketones and 1,3- and 1,4-haloalkyl azides: competitive alkylation vs azidation reactions of ketone enolates.

    Science.gov (United States)

    Yao, Lei; Smith, Brenton T; Aubé, Jeffrey

    2004-03-01

    The reactions of 1,3- and 1,4-haloalkyl azides with enolates of 2-norbornanone (and a ring-expanded analog) afford polycyclic 1,2,3-triazolines in good yields. The reaction occurs by the initial azidation of the ketone enolate, followed in order by triazoline formation and O-alkylation. An interesting element of this process is the preferential reaction of the alkyl azide with an enolate anion as opposed to the more familiar reaction of the alkyl halide (including Cl and I derivatives). Reactions of acyclic or monocyclic enolates generally lead to 1,2,3-triazoles but none of the alternative C-alkylation product. PMID:14987033

  10. Mechanochemical Reaction of Lanthanum Carbonate with Sodium Hydroxide and Preparation of Lanthanum Oxide Nanoparticle

    Institute of Scientific and Technical Information of China (English)

    李永绣; 周雪珍; 王志强

    2002-01-01

    The preparation of nano sized La2O3 powder by mechanochemical reaction of lanthanum carbonate with sodium hydroxide and subsequent heat treatment was studied using X-ray diffraction, differential thermal and thermo gravimetric analysis and transmission electron microscopy. It was found that the mechanochemical reaction process can be divided into two steps: the first step is the multi-phases mechanochemical reaction of lanthanum carbonate with NaOH to form amorphous lanthanum basic carbonate and lanthanum hydroxide, and the second step is the crystallization of basic lanthanum carbonate with the formula of La2(OH)2(CO3)2*H2O under a quasi-hydrothermal synthesis condition caused by the mechanical ball-milling. The synthesized La2O3 powder appears clearly separated spherical-like monodisperse nano-size particles in which particle size ranges from 30 to 50 nm.

  11. Radiocarbon 14C differentiation of sparkling and carbonated wines

    International Nuclear Information System (INIS)

    Specific 14C-activities, percent of modern 14C-activity, and calculated percent of fermentation CO2 are presented for CO2 contained in commercial sparkling wines, labeled as champagne or produced by the bulk (charmat) process. These data are given for the production years 1976-1982. The survey encompassed effervescent wines produced in Spain, Italy, West Germany, California, and New York. Addition of synthetic CO2 to approximately 40 samples represented as sparkling wines was indicated by low 14C-activities of CO2 in these wines. Data for 14C-activity were also presented for the ethanol distilled from sparkling wines for the years 1977-1980. In all cases, the 14C-activity of ethanol was appropriate to the year of vintage

  12. Synthesis of the monosodium salt of carbon-14 labeled paclitaxel (Taxol) 2`-ethyl carbonate 7-phosphonooxymethyl ether, a potential prodrug of paclitaxel

    Energy Technology Data Exchange (ETDEWEB)

    Dischino, D.D.; Shuhui Chen; Golik, Jerzy; Walker, D.W.; Wong, H.S.L. [Bristol-Myers Squibb Co., Richard L. Gelb Center for Research and Development, Wallingford, CT (United States)

    1997-02-01

    The monosodium salt of carbon-14 labeled paclitaxel (Taxol) [N3`-{sup 14}COPh] 2`-ethyl carbonate 7-phosphonooymethyl ether, was prepared from C-14 labeled paclitaxel [N3`-{sup 14}COPh] in 5 steps. The radiochemical purity of the final product was greater than 99% and the specific activity was 25 {mu}Ci/mg. (author).

  13. Carbon Isotopic Fractionation in Fischer-Tropsch Type Reactions and Relevance to Meteorite Organics

    Science.gov (United States)

    Johnson, Natasha M; Elsila, Jamie E.; Kopstein, Mickey; Nuth, Joseph A., III

    2012-01-01

    Fischer-Tropsch-Type (FTT) reactions have been hypothesized to contribute to the formation of organic compounds in the early solar system, but it has been difficult to identify a signature of such reactions in meteoritic organics. The work reported here examined whether temperature-dependent carbon isotopic fractionation of FTT reactions might provide such a signature. Analyses of bulk organic deposits resulting from FTT experiments show a slight trend towards lighter carbon isotopic ratios with increasing temperature. It is unlikely, however, that these carbon isotopic signatures could provide definitive provenance for organic compounds in solar system materials produced through FTT reactions, because of the small scale of the observed fractionations and the possibility that signatures from many different temperatures may be present in any specific grain.

  14. Synthesis of δ-aminolevulic acid. Application to the introduction of carbon-14 and of tritium

    International Nuclear Information System (INIS)

    Several new syntheses of δ aminolevulic acid (δ A.L.A.) have been studied. 14C-4 δ - aminolevulic acid has been obtained from 14C allylacetic carboxylic acid with a yield of 30 per cent with respect to barium carbonate and with a specific activity of 32 mCi/mM. The 14C-1 or 14C-2 δ-A.L.A. has been prepared from the 14C-1 or 14C-2 acetate with a yield of 55 per cent with respect to the acetate. Finally the tritiated δ-A.L.A. has been obtained for the first time by tritiation of ethyl phthalimidodehydrolevulate. (author)

  15. Tracing terrestrial carbon: a novel application of ∆14C in a humic lake

    Science.gov (United States)

    Keaveney, Evelyn; Reimer, Paula J.; Foy, Robert H.

    2016-04-01

    Lakes play an important yet underrated role in global carbon cycles. Terrestrial carbon (C) is buried and/or remineralised in significant quantities, and lake function may also be affected by catchment inputs with potential feedbacks for regional and global C cycling. Changing deposition chemistry, land use and climate induced impacts on hydrology will affect soil biogeochemistry, terrestrial C export, and hence lake ecology. Autochthonous production in lakes is based on dissolved inorganic C (DIC). DIC in alkaline lakes is partially derived from weathering of carbonaceous bedrock, a proportion of which is 14C-free. The low 14C activity yields an artificial age offset leading samples to appear hundreds to thousands of years older than their actual age. Dissolved organic carbon (DOC) and particulate organic carbon (POC) can contain terrestrial inputs. The terrestrial inputs can be labile or detrital and their age depends to a first order on their depth in catchment soil/peat stocks. We present a pilot study that uses the radiocarbon (∆14C) method to determine the source of carbon buried in the surface sediment of Lower Lough Erne, a humic, alkaline lake in northwest Ireland. ∆14C, δ13C and δ15N values were measured from phytoplankton and other biota, dissolved inorganic, dissolved organic and particulate organic carbon. A novel radiocarbon method, Stepped Combustion1 was used to estimate the degree of the burial of terrestrial carbon in surface sediment, collected in 2011. The ∆14C values of the low temperature fractions were comparable to algal ∆14C, while the high temperature fractions were 14C-depleted (older than bulk sediment). The ∆14C end-member model indicated that ~64% of carbon in surface sediment was derived from detrital terrestrial carbon. The same proportion of detrital/labile carbon was found in surface sediment of Upper Lough Erne in 2014, despite the differences in lake type and collection date. The use of ∆14C in conjunction with

  16. Carbon Isotopic Fractionation During Formation of Macromolecular Organic Grain Coatings via FTT Reactions

    Science.gov (United States)

    Nuth, J. A.; Johnson, N. M.; Elsila-Cook, J.; Kopstein, M.

    2011-01-01

    Observations of carbon isotopic fractionation of various organic compounds found in meteorites may provide useful diagnostic information concerning the environments and mechanisms that were responsible for their formation. Unfortunately, carbon has only two stable isotopes, making interpretation of such observations quite problematic. Chemical reactions can increase or decrease the C-13/C-12 ratio by various amounts, but the final ratio will depend on the total reaction pathway followed from the source carbon to the final product, a path not readily discernable after 4.5 billion years. In 1970 Libby showed that the C-13/C-12 ratios of terrestrial and meteoritic carbon were similar by comparing carbon from the Murchison meteorite to that of terrestrial sediments. More recent studies have shown that the C-13/C-12 ratio of the Earth and meteorites may be considerably enriched in C-13 compared to the ratio observed in the solar wind [2], possibly suggesting that carbon produced via ion-molecule reactions in cold dark clouds could be an important source of terrestrial and meteoritic carbon. However, meteoritic carbon has been subjected to parent body processing that could have resulted in significant changes to the C-13/C-12 ratio originally present while significant variation has been observed in the C-13/C-12 ratio of the same molecule extracted from different terrestrial sources. Again we must conclude that understanding the ratio found in meteorites may be difficult.

  17. Research of Hydrogen Preparation with Catalytic Steam-Carbon Reaction Driven by Photo-Thermochemistry Process

    Directory of Open Access Journals (Sweden)

    Xiaoqing Zhang

    2013-01-01

    Full Text Available An experiment of hydrogen preparation from steam-carbon reaction catalyzed by K2CO3 was carried out at 700°C, which was driven by the solar reaction system simulated with Xenon lamp. It can be found that the rate of reaction with catalyst is 10 times more than that without catalyst. However, for the catalytic reaction, there is no obvious change for the rate of hydrogen generation with catalyst content range from 10% to 20%. Besides, the conversion efficiency of solar energy to chemical energy is more than 13.1% over that by photovoltaic-electrolysis route. An analysis to the mechanism of catalytic steam-carbon reaction with K2CO3 is given, and an explanation to the nonbalanced [H2]/[CO + 2CO2] is presented, which is a phenomenon usually observed in experiment.

  18. Determination of tritium and carbon-14 in accelerator waste

    Energy Technology Data Exchange (ETDEWEB)

    Argentini, M.; Weinreich, R. [Lab. of Radio- and Environmental Chemistry, Paul Scherrer Inst., Villigen-PSI (Switzerland)

    2003-07-01

    In dismounted parts of the accelerator facilities of paul scherrer institute, tritium and {sup 14}C were determined by low-level counting after chemical separation. In graphite targets used for the production of {pi}-mesons, tritium amounts from 1.7.10{sup 8} to 6.10{sup 8} Bq/g were found; the corresponding {sup 14}C data were 6 and 9 Ci/g, respectively. In the dismantled copper beam dump of Target E, the tritium content extended up to 2.8.10{sup 6} Bq/g, but no {sup 14}C could be detected. In mechanical parts of the beam dump, consisting of iron and stainless steel, respectively, the tritium amount ranged up to 5.3.10{sup 3} Bq/g, the {sup 14}C amount from 1 to 800 Bq/g. The separation procedures are described in detail. (orig.)

  19. Reactions between sodium and various carbon bearing compounds

    International Nuclear Information System (INIS)

    The presence of carbon bearing materials in liquid sodium is undesirable because of their ability to carburise stainless steel components. It has been demonstrated for example that carbon taken up by stainless steels can affect their mechanical properties and that thinner sectioned material such as fuel cladding and the tubing of intermediate heat exchanger may be more sensitive to such effects. Generally speaking, there are a number of potential carbon sources in reactor systems. Some of the sources such as the graphite in neutron shield rods, boron carbide in control rods and carbide fuels are part of the reactor designs while others such as oil in mechanical pumps arid 'coupling-fluids' used to inspect plant components are associated with the respective operation arid inspection of the plant. In this paper it is intended to discuss in general terms the way these various compounds behave in liquid sodium and to assess what effect their presence will have on the materials of construction in fast reactor systems. The paper also reviews the chemistry of the environment in relation to the types of carburizing species which may exist in sodium systems

  20. Asphalt in carbon-14-dated archaeological samples from Terqa, Syria

    International Nuclear Information System (INIS)

    The results are reported of an organic geochemical study to verify contamination in 14C dated archaeological samples, which could account for much older apparent ages than expected. The data indicate that ancient asphalt must be the source of contamination, showing that caution should be exercised, in interpreting 14C dates of archaeological samples from areas containing asphalt or other fossil fuel deposits. (U.K.)

  1. Results of interagency effort to determine carbon-14 source term in low-level radioactive waste

    International Nuclear Information System (INIS)

    A preliminary estimate of the risks from the shallow land disposal of low-level radioactive wastes by EPA in 1984-1985 indicated that Carbon-14 caused virtually all of the risk and that these risks were relatively high. Therefore, an informal interagency group, which included the US Department of Energy, US Geological Survey, US Nuclear Regulatory Commission, and US Environmental Protection Agency, formed in 1985 to obtain up-to-date information on the activity and chemical form of Carbon-14 in the different types of LLW and how Carbon-14 behaves after disposal. The EPA acted as a focal point for collating the information collected by all of the Agencies and will publish a report in Fall 1986 on the results of the Carbon-14 data collection effort. Of particular importance, the study showed that Carbon-14 activity in LLW was overestimated approximately 2000%. This paper summarizes results of the Carbon-14 data collection effort. 40 references, 1 figure, 3 tables

  2. Chemical Reactions and Kinetics of the Carbon Monoxide Coupling in the Presence of Hydrogen

    Institute of Scientific and Technical Information of China (English)

    Fandong Meng; Genhui Xu; Zhenhua Li; Pa Du

    2002-01-01

    The chemical reactions and kinetics of the catalytic coupling reaction of carbon monoxide to diethyl oxalate were studied in the presence of hydrogen over a supported palladium catalyst in the gaseous phase at the typical coupling reaction conditions. The experiments were performed in a continuous flow fixed-bed reactor. The results indicated that hydrogen only reacts with ethyl nitrite to form ethanol, and kinetic studies revealed that the rate-determining step is the surface reaction of adsorbed hydrogen and the ethoxy radical (EtO-). A kinetic model is proposed and a comparison of the observed and calculated conversions showed that the rate expressions are of rather high confidence.

  3. Study of the {sup 17}O(n,α){sup 14}C reaction: Extension of the Trojan Horse Method to neutron induced reactions

    Energy Technology Data Exchange (ETDEWEB)

    Guardo, G. L.; Lamia, L.; Spitaleri, C.; Cherubini, S.; Rapisarda, G. G.; Sergi, M. L. [INFN - Laboratori Nazionali del Sud, Catania, Italy and Department of Physics and Astronomy, University of Catania, Catania (Italy); Gulino, M. [INFN - Laboratori Nazionali del Sud, Catania, Italy and University of Enna (Italy); Tang, X. D.; Bucher, B.; Couder, M.; Davies, P.; Boer, R. de; Fang, X.; Lamm, L.; Ma, C.; Notani, M.; OBrien, S.; Roberson, D.; Tan, W.; Wiescher, M. [Department of Physics and Joint Institute for Nuclear Astrophysics, University of Notre Dame, IN (United States); and others

    2014-05-02

    The experimental study of the {sup 17}O(n,α){sup 14}C reaction has been performed in the energy range 0-350 keV. This reaction could play an important role in explaining heavy elements (s-process) nucleosynthesis in various astrophysical scenario. To overcome the practical problems arising from the neutrons production, a new application of the Trojan Horse Method has been recently suggested. In more details, the {sup 17}O(n,α){sup 14}C reaction has been studied using the quasi-free {sup 2}H({sup 17}O,α{sup 14}C){sup 1}H reaction, induced at an energy of 43.5 MeV. The measurement allows one to investigate the ℓ=3, 75 keV resonance (E*=8.125 MeV, J{sup π}=5{sup −}), absent in the available direct measurements because of centrifugal suppression effects.

  4. Study of the 17O(n,α)14C reaction: Extension of the Trojan Horse Method to neutron induced reactions

    Science.gov (United States)

    Guardo, G. L.; Lamia, L.; Spitaleri, C.; Gulino, M.; Tang, X. D.; Bucher, B.; Burjan, V.; Cherubini, S.; Couder, M.; Davies, P.; deBoer*, R.; Fang, X.; Goldberg, V. Z.; Hons, Z.; Kroha, V.; Lamm, L.; La Cognata, M.; Li, C.; Ma, C.; Mrazek, J.; Mukhamedzhanov, A. M.; Notani, M.; OBrien, S.; Pizzone, R. G.; Rapisarda, G. G.; Roberson, D.; Sergi, M. L.; Tan, W.; Thompson, I. J.; Wiescher, M.

    2014-05-01

    The experimental study of the 17O(n,α)14C reaction has been performed in the energy range 0-350 keV. This reaction could play an important role in explaining heavy elements (s-process) nucleosynthesis in various astrophysical scenario. To overcome the practical problems arising from the neutrons production, a new application of the Trojan Horse Method has been recently suggested. In more details, the 17O(n,α)14C reaction has been studied using the quasi-free 2H(17O,α14C)1H reaction, induced at an energy of 43.5 MeV. The measurement allows one to investigate the ℓ=3, 75 keV resonance (E*=8.125 MeV, Jπ=5-), absent in the available direct measurements because of centrifugal suppression effects.

  5. Carbon 14 absorption and translocation in sugar cane

    International Nuclear Information System (INIS)

    Plant-cane stools were labelled with sup(14) CO sub(2), in the field, at Goiana-PE, Brazil, when 3, 7 and 11 months old. Each stool was enclosed in a chamber with sup(14) CO sub(2) for 90 minutes. The sub(14) C photosynthetic were measured in leaves, stalks, roots and soil 24 hours after labelling. Roots were divided into alive and dead and soil into rhizosphere and outer soil. At the end of the labelling period at 3, 7 and 11 months, 2, 19 and 1% of the initial sup(14) CO sub(2) were recovered in the plant and the soil. The low recovery of sub(14) C at 3 months could be attribute to losses by respiration and lack of sampling of the top growing point. The low CO sub(2) fixation and losses at first sampling in the 7 month old labelling were attributed to low light intensity during the day of labelling. Most of the recovered sub(14) C (>80%) was founded in the leaves but all plant parts received labelled photosynthetic. At 3 months, most of the sub(14) C translocated from the leaves went to the living roots (83%); at 7 and 11 months it went to the stalks (69 and 66%). While the roots received less than 2%. Root masses did not vary consistently along the plant cycle and dead root masses were always less than 10% of the total root mass. Radioactivity in the dead roots was always very low. These results suggest that the root system have a low turnover rate after 3 months old. (author)

  6. Effect of temperature on kinetic parameters of decomposition reaction of calcium carbonate

    Institute of Scientific and Technical Information of China (English)

    CHEN Hongwei; CHEN Jiangtao; WEI Riguang; SUO Xinliang

    2013-01-01

    In order to investigate the influence of temperature on behavior of calcium carbonate decomposition,especially on kinetic parameters of the decomposition reaction,the analytically pure calcium carbonate was calcined on a self-built large dose thermogravimetric analyzer.The results indicated that,with an increase in the reaction temperature,the reactivity index of calcium carbonate decomposition increased at stage state while the kinetic parameters decreased at stage state.Moreover,both the reaction indices and the kinetic parameters can be divided into three stages and the temperature turning points in different stages were the same.The phase boundary reaction (cylindrical symmetry) theory was more suitable for calcium carbonate calcination under N2 atmosphere.The change trend of the logarithm of reaction activation with temperature was similar as that of the pre-exponential factor.There existed good liner relationship and kinetic compensation effect between them.The isokinetic temperature of the CaCO3 calcination was 842 ℃ and the reaction rate constant was 0.104 9 min-1 derived by the compensation coefficients.

  7. Atmospheric nuclear weapons test history narrated by carbon-14 in human teeth

    International Nuclear Information System (INIS)

    The atmospheric testing of nuclear weapons since 1945 caused a significant increase in the concentration of atmospheric 14C. The 14C concentration in plants that assimilate 14C directly by photosynthesis reflects the atmospheric 14C concentration. Carbon-14 is then transferred into the human body through the food chain. Based on animal experiments, the collagen in human teeth is metabolically inert after its formation. This implies that the collagen of each tooth retains the 14C concentration which reflects the 14C concentration in the blood at the time collagen metabolism ceased. The distribution of the 14C concentration in the collagen of teeth from subjects of various ages would follow a pattern similar to that shown by soft tissues. In this paper the authors elucidate the relationship between the number of nuclear weapon tests and the distribution of 14C concentration in teeth

  8. First measurements of the {sup 16}O(e,e'pn){sup 14}N reaction

    Energy Technology Data Exchange (ETDEWEB)

    Middleton, D.G.; Annand, J.R.M.; Glazier, D.I.; MacGregor, I.J.D.; McGeorge, J.C.; Rosner, G. [University of Glasgow, Department of Physics and Astronomy, Scotland (United Kingdom); Barbieri, C. [Gesellschaft fuer Schwerionenforschung, Darmstadt (Germany); Barneo, P.; Blok, H.P.; Jans, E.; Lapikas, L.; de Vries, H. [NIKHEF, P.O. Box 41882, Amsterdam (Netherlands); Boehm, R.; Distler, M.O.; Friedrich, J.; Kohl, M.; Merkel, H.; Seimetz, M.; Walcher, T. [Universitaet Mainz, Institut fuer Kernphysik (Germany); Giusti, C. [Dipartimento di Fisica Nucleare e Teorica dell' Universita degli Studi di Pavia and Istituto Nazionale di Fisica Nucleare, Sezione di Pavia, Pavia (Italy); Grabmayr, P.; Hehl, T.; Heim, J.; Martin, I.; Moschini, F. [Universitaet Tuebingen, Physikalisches Institut (Germany); Hesselink, W.H.A. [NIKHEF, Ammsterdam (Netherlands); Physikalisches Institut, Universitaet Tuebingen (Germany); Watts, D.P. [Department of Physics and Astronomy, University of Glasgow (United Kingdom); School of Physics, University of Edingburgh (United Kingdom); Zihlmann, B. [NIKHEF, Amsterdam (Netherlands); Vrije Universiteit, Amsterdam (Netherlands)

    2006-09-15

    This paper reports on the first measurement of the {sup 16}O(e,e'pn){sup 14}N reaction. Data were measured in kinematics centred on a super-parallel geometry at energy and momentum transfers of 215 MeV and 316 eV/c. The experimental resolution was sufficient to distinguish groups of states in the residual nucleus but not good enough to separate individual states. The data show a strong dependence on missing momentum and this dependence appears to be different for two groups of states in the residual nucleus. Theoretical calculations of the reaction using the Pavia code do not reproduce the shape or the magnitude of the data. (orig.)

  9. Low energy proton capture study of the 14N(p, gamma)15O reaction

    Science.gov (United States)

    Daigle, Stephen Michael

    The 14N(p,gamma)15O reaction regulates the rate of energy production for stars slightly more massive than the sun throughout stable hydrogen burning on the main sequence. The 14N(p,gamma)15O reaction rate also determines the luminosity for all stars after leaving the main sequence when their cores have exhausted hydrogen fuel, and later when they become red giant stars. The significant role that this reaction plays in stellar evolution has far-reaching consequences, from neutrino production in our Sun, to age estimates of globular clusters in our Galaxy. The weak cross section and inherent coincidence summing in the 15O gamma-ray decay scheme make a precision measurement of the astrophysical S-factor especially challenging, particularly for the ground-state transition. The present study, performed in the Laboratory for Experimental Nuclear Astrophysics (LENA), was aimed at measuring the ground-state transition at low energy by utilizing a new 24-element, position-sensitive, NaI(Tl) detector array. Because the array is highly segmented, the 14N( p,gamma)15O S-factor was evaluated for transitions to the ground, 5.18, 6.18, and 6.79 MeV states without the need for coincidence summing corrections. Additionally, the position-sensitivity of the detector was exploited to measure the angular correlation of the two-photon cascades. Software cuts were made to the data in order to identify single and coincident gamma-ray events and a fraction fit analysis technique was used to extract the characteristic 15O peaks from the composite gamma-ray spectrum. The results from the current work demonstrated a new approach to measuring weak nuclear cross sections near astrophysically relevant energies that, with refinements, has broader applications in gamma-ray spectroscopy.

  10. Reaction of folic acid with single-walled carbon nanotubes

    Science.gov (United States)

    Ellison, Mark D.; Chorney, Matthew

    2016-10-01

    The oxygen-containing functional groups on oxidized single-walled carbon nanotubes (SWNTs) are used to covalently bond folic acid molecules to the SWNTs. Infrared spectroscopy confirms intact molecular binding to the SWNTs through the formation of an amide bond between a carboxylic acid group on an SWNT and the primary amine group of folic acid. The folic acid-functionalized SWNTs are readily dispersible in water and phosphate-buffered saline, and the dispersions are stable for a period of two weeks or longer. These folic acid-functionalized SWNTs offer potential for use as biocompatible SWNTs.

  11. Cross Section of Heavy Ion Reaction (14.5 MeV/u) 132Xe + Bi

    Institute of Scientific and Technical Information of China (English)

    G. Sher; M. I. Shahzad; M. Hussain; M. A. Rana; E. U. Khan

    2006-01-01

    @@ We investigate the cross section of the heavy ion reaction (14.5 MeV/u) 132Xe + Bi by using a CR-39 plastic track detector. The target-detector assembly is exposed at UNILAC beam facility of GSI, Germany. After etching under appropriate etching conditions, the detector is scanned for multipronged events produced as a result of interactions of projectile ions with target atoms. The elastic events are separated from binary events and used for the determination of the quarter-point angle..

  12. Investigation of thermochemistry associated with the carbon-carbon coupling reactions of furan and furfural using ab initio methods.

    Science.gov (United States)

    Liu, Cong; Assary, Rajeev S; Curtiss, Larry A

    2014-06-26

    Upgrading furan and small oxygenates obtained from the decomposition of cellulosic materials via formation of carbon-carbon bonds is critical to effective conversion of biomass to liquid transportation fuels. Simulation-driven molecular level understanding of carbon-carbon bond formation is required to design efficient catalysts and processes. Accurate quantum chemical methods are utilized here to predict the reaction energetics for conversion of furan (C4H4O) to C5-C8 ethers and the transformation of furfural (C5H6O2) to C13-C26 alkanes. Furan can be coupled with various C1 to C4 low molecular weight carbohydrates obtained from the pyrolysis via Diels-Alder type reactions in the gas phase to produce C5-C8 cyclic ethers. The computed reaction barriers for these reactions (∼25 kcal/mol) are lower than the cellulose activation or decomposition reactions (∼50 kcal/mol). Cycloaddition of C5-C8 cyclo ethers with furans can also occur in the gas phase, and the computed activation energy is similar to that of the first Diels-Alder reaction. Furfural, obtained from biomass, can be coupled with aldehydes or ketones with α-hydrogen atoms to form longer chain aldol products, and these aldol products can undergo vapor phase hydrocycloaddition (activation barrier of ∼20 kcal/mol) to form the precursors of C26 cyclic hydrocarbons. These thermochemical studies provide the basis for further vapor phase catalytic studies required for upgrading of furans/furfurals to longer chain hydrocarbons.

  13. Carbon-14 ages of Allan Hills meteorites and ice

    Science.gov (United States)

    Fireman, E. L.; Norris, T.

    1982-01-01

    Allan Hills is a blue ice region of approximately 100 sq km area in Antarctica where many meteorites have been found exposed on the ice. The terrestrial ages of the Allan Hills meteorites, which are obtained from their cosmogenic nuclide abundances are important time markers which can reflect the history of ice movement to the site. The principal purpose in studying the terrestrial ages of ALHA meteorites is to locate samples of ancient ice and analyze their trapped gas contents. Attention is given to the C-14 and Ar-39 terrestrial ages of ALHA meteorites, and C-14 ages and trapped gas compositions in ice samples. On the basis of the obtained C-14 terrestrial ages, and Cl-36 and Al-26 results reported by others, it is concluded that most ALHA meteorites fell between 20,000 and 200,000 years ago.

  14. Aligned carbon nanotube with electro-catalytic activity for oxygen reduction reaction

    Science.gov (United States)

    Liu, Di-Jia; Yang, Junbing; Wang, Xiaoping

    2010-08-03

    A catalyst for an electro-chemical oxygen reduction reaction (ORR) of a bundle of longitudinally aligned carbon nanotubes having a catalytically active transition metal incorporated longitudinally in said nanotubes. A method of making an electro-chemical catalyst for an oxygen reduction reaction (ORR) having a bundle of longitudinally aligned carbon nanotubes with a catalytically active transition metal incorporated throughout the nanotubes, where a substrate is in a first reaction zone, and a combination selected from one or more of a hydrocarbon and an organometallic compound containing an catalytically active transition metal and a nitrogen containing compound and an inert gas and a reducing gas is introduced into the first reaction zone which is maintained at a first reaction temperature for a time sufficient to vaporize material therein. The vaporized material is then introduced to a second reaction zone maintained at a second reaction temperature for a time sufficient to grow longitudinally aligned carbon nanotubes over the substrate with a catalytically active transition metal incorporated throughout the nanotubes.

  15. Surface reactions of molecular and atomic oxygen with carbon phosphide films.

    Science.gov (United States)

    Gorham, Justin; Torres, Jessica; Wolfe, Glenn; d'Agostino, Alfred; Fairbrother, D Howard

    2005-11-01

    The surface reactions of atomic and molecular oxygen with carbon phosphide films have been studied using X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Carbon phosphide films were produced by ion implantation of trimethylphosphine into polyethylene. Atmospheric oxidation of carbon phosphide films was dominated by phosphorus oxidation and generated a carbon-containing phosphate surface film. This oxidized surface layer acted as an effective diffusion barrier, limiting the depth of phosphorus oxidation within the carbon phosphide film to phosphorus atoms as well as the degree of phosphorus oxidation. For more prolonged AO exposures, a highly oxidized phosphate surface layer formed that appeared to be inert toward further AO-mediated erosion. By utilizing phosphorus-containing hydrocarbon thin films, the phosphorus oxides produced during exposure to AO were found to desorb at temperatures >500 K under vacuum conditions. Results from this study suggest that carbon phosphide films can be used as AO-resistant surface coatings on polymers.

  16. Characterization of the major reactions during conversion of lignin to carbon fiber

    Directory of Open Access Journals (Sweden)

    Hendrik Mainka

    2015-10-01

    Full Text Available Lightweight design is an essential part of the overall Volkswagen strategy for reducing the CO2 emissions. The use of carbon fiber offers an enormous lightweight potential. In comparison to steel enabling a mass reduction of up to 70% in automotive parts without a degradation of the functionalities is possible. Today, the use of carbon fiber is limited in mass series applications of the automotive industry by the cost of the conventional C-fiber precursor polyacrylonitrile (PAN. 50% of the cost of a conventional carbon fiber already belongs to the cost of the PAN precursor. Lignin as a precursor for carbon fiber production can realize enormous savings in cost. For qualifying lignin-based carbon fiber for automotive mass production a detailed characterization of this new material is necessary. Therefore, nuclear magnetic resonance spectroscopy and Fourier transform infrared spectroscopy are used. Using the results of these experiments, the major reactions during conversion of lignin to carbon fiber are proposed.

  17. Synthesis and processing of beta silicon carbide powder by silicon - carbon reaction

    International Nuclear Information System (INIS)

    SiC is an important structural ceramic and finds applications in nuclear industry. Processing of SiC ceramic components for such applications require sinter-active beta silicon carbide powders. Various novel methods have been reported for the synthesis of beta SiC powder based on silica - carbon and silicon - carbon reactions. In this research, beta-silicon carbide (β-SiC) was synthesized from the reaction of Si and C. In this research, beta-silicon carbide (β-SiC) was synthesized from the reaction of Si and C. Stoichiometric amount of silicon and petroleum coke having agglomerate size ∼ 5-8μ were planetarily wet mixed, dried, granulated and compacted to reaction specimens

  18. β-Sialon Produced by Carbon Thermal Nitriding Reaction of Bauxite

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    β-Sialon was produced by carbon thermal nitriding reaction in N2 gas atmosphere when the mixtures of bauxite and anthracite were put into vertical furnace. According to the mass loss of raw materials and the result of X-ray diffration (XRD) of products, the influences of the process parameters on the compositions and relative contents of products, such as the fixed carbon content, the flow of N2, the soaking time and the temperature, were researched.

  19. The Reaction of Carbonates in Contact with Superheated Silicate Melts: New Insights from MEMIN Laser Melting Experiments

    Science.gov (United States)

    Hamann, C.; Hecht, L.; Schäffer, S.; Deutsch, A.; Lexow, B.

    2016-08-01

    The reaction of carbonates in contact with silicate impact melts is discussed quite controversially in the impact community. Here, we discuss four MEMIN laser melting experiments involving carbonates in contact with superheated silicate melts.

  20. Displacement of carbon-14 labelled amino acids from leaves

    International Nuclear Information System (INIS)

    The displacement of amino acids from nature leaves was investigated. The amino acids (Ala, Asn, Asp, Glu, Gln, Val, Leu, Lys, Ser, Pro) were applied on the leaves in L-form, uniformly labelled with 14C, and the type and direction of displacement have been observed. Most of the studies have been carried out on bush beans aged 3 to 4 weeks. The experiments were carried out in climatic chambers; in one case, barley plants just reaching maturity were used. In order to find out whether the applied amino acids were also displaced in their original form, freeze-dried plants were extracted and the 14C activity of the various fraction was determined. The radioactivity of some free amino acids was determined after two-dimensional separation by thin film chromatography. (orig./HK)

  1. Determination of carbon-14 in environmental level, solid reference materials

    Energy Technology Data Exchange (ETDEWEB)

    Blowers, Paul, E-mail: paul.blowers@cefas.co.uk [Cefas Lowestoft Laboratory, Pakefield Road, Lowestoft, Suffolk, NR33 0HT (United Kingdom); Caborn, Jane, E-mail: jane.a.caborn@nnl.co.uk [NNL, Springfields, Salwick, Preston, Lancashire, PR4 0XJ (United Kingdom); Dell, Tony [Veterinary Laboratories Agency, New Haw, Addlestone, Surrey, KT15 3NB (United Kingdom); Gingell, Terry [DSTL, Radiation Protection Services, Crescent Road, Alverstoke, Gosport, Hants, PO12 2DL (United Kingdom); Harms, Arvic [National Physical Laboratory, Hampton Road, Teddington, Middlesex, TW11 0LW (United Kingdom); Long, Stephanie [Radiological Protection Institute of Ireland, 3 Clonskeagh Square, Clonskeagh Road, Dublin 14, Ireland (United Kingdom); Sleep, Darren [Centre for Ecology and Hydrology, Lancaster Environment Centre, Library Avenue, Bailrigg, Lancaster, LA1 4AP (United Kingdom); Stewart, Charlie [UKAEA (Waste Management Group), Chemical Support Services, D1310/14, Dounreay, Thurso, Caithness, KW14 7TZ (United Kingdom); Walker, Jill [Radiocarbon Dating, The Old Stables, East Lockinge, Wantage, Oxon OX12 8QY (United Kingdom); Warwick, Phil E. [GAU-Radioanalytical, National Oceanography Centre Southampton, European Way, Southampton, SO14 3ZH (United Kingdom)

    2011-10-15

    An intercomparison exercise to determine the {sup 14}C activity concentrations in a range of solid, environmental level materials was conducted between laboratories in the UK. IAEA reference materials, C2, C6 and C7, and an in-house laboratory QA material were dispatched in 2006 to ten laboratories comprising of members of the Analyst Informal Working Group (AIWG) and one other invited party. The laboratories performed the determinations using a number of techniques, and using the results each one was evaluated in terms of levels of precision, sensitivity and limits of detection. The results of the study show that all techniques are capable of successfully analysing {sup 14}C in environmental level materials, however, a shortage of certified environmental reference materials exists. The suitability of the IAEA reference materials and other material for use as reference materials was also assessed.

  2. Determination of carbon-14 in environmental level, solid reference materials

    International Nuclear Information System (INIS)

    An intercomparison exercise to determine the 14C activity concentrations in a range of solid, environmental level materials was conducted between laboratories in the UK. IAEA reference materials, C2, C6 and C7, and an in-house laboratory QA material were dispatched in 2006 to ten laboratories comprising of members of the Analyst Informal Working Group (AIWG) and one other invited party. The laboratories performed the determinations using a number of techniques, and using the results each one was evaluated in terms of levels of precision, sensitivity and limits of detection. The results of the study show that all techniques are capable of successfully analysing 14C in environmental level materials, however, a shortage of certified environmental reference materials exists. The suitability of the IAEA reference materials and other material for use as reference materials was also assessed.

  3. Epoxidation and oxidation reactions using 1,4-butanediol dimethacrylate crosslinked polystyrene-supported tertiary butyl hydroperoxide

    Indian Academy of Sciences (India)

    M S Sheela; K Sreekumar

    2004-11-01

    1,4-Butanediol dimethacrylate (1,4-BDDMA) crosslinked polystyrene-supported -butyl hydroperoxide was employed in the epoxidation of olefins and oxidation of alcohols to carbonyl compounds. The reagent proved to be successful as a recyclable solid phase organic reagent with as much or more efficiency when compared to its monomeric counterpart. The extent of reaction was found to be dependent on various reaction parameters like solvent, temperature, molar concentration and presence of catalyst.

  4. Determination of Carbon-14 in environmental samples by mixing 14CO{sub 2} with a liquid scintillator; Determinacion de carbono-14 en muestras ambientales por incorporacion de 14CO{sub 2} a un centelleador liquido

    Energy Technology Data Exchange (ETDEWEB)

    Garcia, M. R.; Gomez, V.; Heras, M. C.; Beltran, M. A.

    1990-07-01

    A method for the determination of Carbon-14 (14CO2) in environmental samples has been developed. The method use the direct absorption of the carbon dioxide into Carbosorb, followed with incorporation of the mixture (Carbosorb-CO2) to the liquid scintillator. The results obtained to apply this method and the benzene synthesis, usual in our laboratory, are discussed and compared. The method of collection of atmospheric samples is also described. (Author) 10 refs.

  5. Initial reaction between CaO and SO2 under carbonating and non-carbonating conditions

    DEFF Research Database (Denmark)

    Rasmussen, Martin Hagsted; Wedel, Stig; Pedersen, Kim H.;

    2015-01-01

    The initial kinetics of the CaO/SO2 reaction have been investigated for reaction times shorter than 1s and in the temperature interval between 450 and 600°C under both carbonating and non-carbonating conditions (0-20 vol% CO2) to clarify how recirculating CaO influences the emission of SO2 from...... showed that the CaO conversion with respect to SO2 declined when the CO2 concentration was increased. Under all conditions, larger specific surface areas of CaO gave higher reaction rates with SO2. Higher temperatures had a positive effect on the reaction between SO2 and CaO under non...... a modern dry kiln preheater system for cement production. Calcined Faxe Bryozo limestone with a particle size smaller than 400μm was utilized as CaO source. It was shown, both theoretically and experimentally, that the observed reaction rates were influenced by mass transport limitations. The results...

  6. Method of carbon chain extension using novel aldol reaction

    Energy Technology Data Exchange (ETDEWEB)

    Silks, Louis A; Gordon, John C; Wu, Ruilan; Hangson, Susan Kloek

    2013-08-13

    Method of producing C.sub.8-C.sub.15 hydrocarbons comprising providing a ketone starting material; providing an aldol starting material comprising hydroxymethylfurfural; mixing the ketone starting material and the aldol starting material in a reaction in the presence of a proline-containing catalyst selected from the group consisting of Zn(Pro).sub.2, Yb(Pro).sub.2, and combinations thereof, or a catalyst having one of the structures (I), (II) or (III), and in the presence of a solvent, wherein the solvent comprises water and is substantially free of organic solvents, where (I), (II) and (III) respectively are: ##STR00001## where R.sub.1 is a C.sub.1-C.sub.6 alkyl moiety, X=(OH) and n=2. ##STR00002## In (III), X may be CH.sub.2, sulfur or selenium, M may be Zn, Mg, or a lanthanide, and R.sub.1 and R.sub.2 each independently may be a methyl, ethyl, phenyl moiety.

  7. The process of dimethyl carbonate to diphenyl carbonate: thermodynamics, reaction kinetics and conceptual process design

    NARCIS (Netherlands)

    Haubrock, Jens

    2007-01-01

    Diphenyl carbonate (DPC) is a precursor in the production of Polycarbonate (PC), a widely employed engineering plastic. To overcome the drawbacks of the traditional PC process - e.g. phosgene as a reactant and methylene chloride as solvent- a new process route starting from Dimethyl carbonate (DMC)

  8. Characteristics of 14C and 13C of carbonate aerosols in dust storm events in China

    Science.gov (United States)

    Chen, Bing; Jie, Dongmei; Shi, Meinan; Gao, Pan; Shen, Zhenxing; Uchida, Masao; Zhou, Liping; Liu, Kexin; Hu, Ke; Kitagawa, Hiroyuki

    2015-10-01

    In contrast with its decrease in western China deserts, the dust storm event in eastern China, Korea, and Japan shows an increase in frequency. Although the drylands in northeastern China have been recognized as an important dust source, the relative contributions of dust transport from the drylands and deserts are inconclusive, thus the quantification of dust storm sources in downwind area remains a challenge. We measured the 14C and 13C contents in carbonates of dust samples from six sites in China, which were collected for the duration of dust storm events in drylands, deserts, and urban areas. The δ13C of the dryland dust samples considerably varied in a range of - 9.7 to - 5.0‰, which partly overlapped the desert dust carbonate δ13C ranges. The 14C content of the dryland dust carbonates showed a narrow range of 60.9 ± 4.0 (as an average and 1 SD of five samples) percent modern carbon (pMC), indicating the enrichment of modern carbonate. Dust samples in desert regions contained relatively aged carbonates with the depleting 14C showing of 28.8 ± 3.3 pMC. After the long-range transport of the western China desert dust plume, the carbonates collected at the southern China remained the depletion of 14C (33.5 ± 5.3 pMC) as in the desert regions. On the other hand, the samples of dust storm events at the urban areas of eastern China showed an enrichment of 14C contents (46.2 ± 5.0 pMC, n = 7), which might be explained by the stronger contribution of modern-carbonate-rich dryland dust.

  9. Two dimensional model study of atmospheric transport using carbon-14 and strontium-90 as inert tracers

    International Nuclear Information System (INIS)

    This study tests the transport processes in the LLNL two-dimensional chemical-radiative-transport model using recently reanalyzed carbon-14 and strontium-90 data. These radioactive tracers were produced bythe atmospheric nuclear bomb tests of 1952--58 and 1961--62, and they were measured at a few latitudes up to 35 kilometers over the period 1955--1970. Selected horizontal and vertical eddy diffusion coefficients were varied in the model to test their sensitivity to short and long term transpose of carbon-14. A sharp transition of Kzz and Kyy through the tropopause, as opposed to a slow transition between the same limiting values, shows a distinct improvement in the calculated carbon-14 distributions, a distinct improvement in the calculated seasonal and latitudinal distribution of ozone columns (relative to TOMS observations), and a very large difference in the calculated ozone reduction by a possible fleet of High Speed Civil Transports. Calculated northern hemisphere carbon-14 is more sensitive to variation of Kyy than are global ozone columns. Strontium-90 was used to test the LLNL tropopause height at four different latitudes. Starting with the 1960 background distribution of carbon-14, we calculate the input of carbon-14 as the sum of each nuclear test of the 1961--62 series, using two bomb-cloud rise models. With the Seitz bomb-rise formulation in the LLNL model, we find good agreement between calculated and observedcarbon-14 (with noticeable exceptions at the north polar tropopause and the short-term mid-latitude mid-stratosphere) between 1963 and 1970

  10. Characteristics study of a system for carbon 14 dating

    International Nuclear Information System (INIS)

    The developing of a radiocarbon dating laboratory, specially built to deal with carbonate samples from underground water, at the Institute de Energia Atomica, required the optimization of a benzene synthetizer, and also of the operative conditions of the liquid scintillator counter, used in sample measurements. An average yield of about 70% was obtained in our benzenic synthesis. If more refined conditions were used, better results could have been obtained, but the reported yield is good enough for our necessities. A comparison of the ages of several shell samples was done between the Geochronology Laboratory, belonging to the Instituto de Geociencias, at Sao Paulo University and our dating laboratory. The agreement between the results was fairly good, according to the precision required

  11. Synthesis of carbon-14 labelled CD 271 (6-[3-(1-adamantyl)-4-methoxyphenyl]-2-naphthoic acid): a potential new agent for dermatology

    International Nuclear Information System (INIS)

    6-[3-(1-Adamantyl)-4-methoxyphenyl]-2-naphthoic acid, a promising new compound for the treatment of disorders of keratinization, has been synthesized in [14C]-labelled form from barium[14C]-carbonate via labelled benzene. Benzene-[U-14C] was converted to 4-bromo-methoxybenzene-[phenyl-U-14C] in six steps. Introduction of the adamantyl ring was carried out using 1-acetoxyadamantane under acid catalysis. 2-(1-Adamantyl)-4-bromo-methoxybenzene-[phenyl-U-14C] was converted to a zincate and coupled with methyl 6-bromo-2-naphthoate using a nickel catalyst. The product of the aryl coupling reaction was then saponified to give 6-[3-(1-adamantyl)-4-methoxyphenyl-[phenyl-U-14C

  12. Heterogeneous reactions of gaseous methanesulfonic acid with calcium carbonate and kaolinite particles

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Heterogeneous reactions of gaseous methanesulfonic acid (MSA) with calcium carbonate (CaCO3) and kaolinite particles at room temperature were investigated using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and ion chromatography (IC).Methanesulfonate (MS-) was identified as the product in the condensed phase,in accordance with the product of the reaction of gaseous MSA with NaCl and sea salt particles.When the concentration of gaseous MSA was 1.34 × 10-13 molecules cm-3,the uptake coefficient was (1.21 ± 0.06) × 10-8 (1) for the reaction of gaseous MSA with CaCO3 and (4.10 ± 0.65) × 10 10 (1) for the reaction with kaolinite.Both uptake coefficients were significantly smaller than those of the reactions of gaseous MSA with NaCl and sea salt particles.

  13. Carboxylic Group Embedded Carbon Balls as a New Supported Catalyst for Hydrogen Economic Reactions.

    Science.gov (United States)

    Bordoloi, Ankur

    2016-03-01

    Carboxylic group functionalized carbon balls have been successfully synthesized by using a facile synthesis method and well characterized with different characterization techniques such as XPS, MAS NMR, SEM, ICP and N2 physi-sorption analysis. The synthesized material has been effectively utilized as novel support to immobilized ruthenium catalyst for hydrogen economic reactions. PMID:27455763

  14. Mechanisms of oxygen reduction reactions for carbon alloy catalysts via first principles molecular dynamics

    International Nuclear Information System (INIS)

    Carbon alloy catalysts (CACs) are one of promising candidates for platinum-substitute cathode catalysts for polymer electrolyte fuel cells. We have investigated possible mechanisms of oxygen reduction reactions (ORRs) for CACs via first-principles-based molecular dynamics simulations. In this contribution, we review possible ORRs at likely catalytic sites of CACs suggested from our simulations. (author)

  15. Carbophilic versus thiophilic attack in the reaction of metallated aromates and heteroaromates with carbon disulfide

    NARCIS (Netherlands)

    Verkruijsse, H.D.; Brandsma, L.

    1987-01-01

    Copper(I) halides catalyse the formation of carbodithioates RCSSLi in the reaction of aryl- or heteroaryl-lithium reagents with carbon disulfide. Subsequent addition of methyl iodide gives the dithioesters RCSSCH3 in high yields. Appreciable amounts of the methyl sulfides RSCH3 and tars are obtained

  16. Direct Electrochemical Reaction of Horseradish Peroxidase Immobilized on the Surface of Active Carbon Powders

    Institute of Scientific and Technical Information of China (English)

    Dong Mei SUN; Chen Xin CAI; Wei XING; Tian Hong LU

    2004-01-01

    It is reported for the first time that horseradish peroxidase(HRP)immobilized on the active carbon can undergo a direct quasi-reversible electrochemical reaction. In addition,the immobilized HRP showed the stable bioelectrocatalytic activity for the reduction of H2O2.

  17. Carboxylic Group Embedded Carbon Balls as a New Supported Catalyst for Hydrogen Economic Reactions.

    Science.gov (United States)

    Bordoloi, Ankur

    2016-03-01

    Carboxylic group functionalized carbon balls have been successfully synthesized by using a facile synthesis method and well characterized with different characterization techniques such as XPS, MAS NMR, SEM, ICP and N2 physi-sorption analysis. The synthesized material has been effectively utilized as novel support to immobilized ruthenium catalyst for hydrogen economic reactions.

  18. Oxalyl chloride as a practical carbon monoxide source for carbonylation reactions

    DEFF Research Database (Denmark)

    Hansen, Steffen V F; Ulven, Trond

    2015-01-01

    A method for generation of high-quality carbon monoxide by decomposition of oxalyl chloride in an aqueous hydroxide solution is described. The usefulness of the method is demonstrated in the synthesis of heterocycles and for hydroxy-, alkoxy-, amino-, and reductive carbonylation reactions, in sev...

  19. N, S co-doped carbon dots with orange luminescence synthesized through polymerization and carbonization reaction of amino acids

    International Nuclear Information System (INIS)

    Graphical abstract: N, S co-doped CDs with orange luminescence were synthesized through one-pot polymerization and carbonization reactions under hydrothermal conditions, using two different amino acids as raw materials. - Highlights: • N, S co-doped CDs were synthesized by one-pot carbonization reactions, using two different amino acids as raw materials. • The as-obtained N, S co-doped CDs showed unique orange fluorescence under excitation at room temperature. • The products could be applied in the imaging of peritoneal macrophages of mice without any functionalization. - Abstract: For practical application, it is highly desirable to obtain carbon dots (CDs) through environmentally benign synthetic route, using green raw materials. On the other hand, at present, most of CDs reported in the literature showed blue, green and yellow emission. Therefore it is still necessary to develop new strategy to obtain CDs with longer wavelength emission in order to expand their application range. Toward this end, in this study, N, S co-doped CDs were synthesized through one-pot condensation polymerization and carbonization reactions under hydrothermal conditions, using two different amino acids as raw materials. Taking the reaction of L-serine with L-cystine as an example, the as-obtained products were characterized by various techniques such as transmission electron microscopy, elemental analysis, Fourier-transform infrared spectrum, X-ray photoelectron spectra, and so on. Interestingly, N, S co-doped CDs displayed unique orange emission at room temperature. The possible photoluminescence mechanism of N, S co-doped CDs was proposed. Furthermore, the as-synthesized N, S co-doped CDs were directly applied in the imaging of peritoneal macrophages of mice

  20. N, S co-doped carbon dots with orange luminescence synthesized through polymerization and carbonization reaction of amino acids

    Energy Technology Data Exchange (ETDEWEB)

    Zeng, Ya-Wen [Nanomaterials and Chemistry Key Laboratory, Wenzhou University, Wenzhou, Zhejiang 325027 (China); Ma, De-Kun, E-mail: dkma@wzu.edu.cn [Nanomaterials and Chemistry Key Laboratory, Wenzhou University, Wenzhou, Zhejiang 325027 (China); Wang, Wei; Chen, Jing-Jing; Zhou, Lin; Zheng, Yi-Zhou [Department of Hematology, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou, Zhejiang 325027 (China); Yu, Kang, E-mail: yukang62@126.com [Department of Hematology, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou, Zhejiang 325027 (China); Huang, Shao-Ming, E-mail: smhuang@wzu.edu.cn [Nanomaterials and Chemistry Key Laboratory, Wenzhou University, Wenzhou, Zhejiang 325027 (China)

    2015-07-01

    Graphical abstract: N, S co-doped CDs with orange luminescence were synthesized through one-pot polymerization and carbonization reactions under hydrothermal conditions, using two different amino acids as raw materials. - Highlights: • N, S co-doped CDs were synthesized by one-pot carbonization reactions, using two different amino acids as raw materials. • The as-obtained N, S co-doped CDs showed unique orange fluorescence under excitation at room temperature. • The products could be applied in the imaging of peritoneal macrophages of mice without any functionalization. - Abstract: For practical application, it is highly desirable to obtain carbon dots (CDs) through environmentally benign synthetic route, using green raw materials. On the other hand, at present, most of CDs reported in the literature showed blue, green and yellow emission. Therefore it is still necessary to develop new strategy to obtain CDs with longer wavelength emission in order to expand their application range. Toward this end, in this study, N, S co-doped CDs were synthesized through one-pot condensation polymerization and carbonization reactions under hydrothermal conditions, using two different amino acids as raw materials. Taking the reaction of L-serine with L-cystine as an example, the as-obtained products were characterized by various techniques such as transmission electron microscopy, elemental analysis, Fourier-transform infrared spectrum, X-ray photoelectron spectra, and so on. Interestingly, N, S co-doped CDs displayed unique orange emission at room temperature. The possible photoluminescence mechanism of N, S co-doped CDs was proposed. Furthermore, the as-synthesized N, S co-doped CDs were directly applied in the imaging of peritoneal macrophages of mice.

  1. Empirical relation and establishment of shell effects in (, 2) reaction cross-sections at 14 MeV

    Indian Academy of Sciences (India)

    Sneh Lata Goyal; Pratibha Gur

    2009-02-01

    The experimental data for (, 2) reaction cross-sections around 14 MeV neutron energy have been collected from the literature and analysed for the isotopes having 1 ≤ ≤ 82. The empirical relations for the reaction cross-sections have been obtained, which show fairly good fits with the experimental values. The shell effects have been established at magic nucleon numbers for (, 2) reaction cross-sections around 14 MeV neutron energy. The odd–even effects have also been observed as the cross-sections for odd-mass nuclei are higher than their neighbouring even–even nuclei.

  2. Mineral carbonation: energy costs of pretreatment options and insights gained from flow loop reaction studies

    Energy Technology Data Exchange (ETDEWEB)

    Penner, Larry R.; O' Connor, William K.; Dahlin, David C.; Gerdemann, Stephen J.; Rush, Gilbert E.

    2004-01-01

    Sequestration of carbon as a stable mineral carbonate has been proposed to mitigate environmental concerns that carbon dioxide may with time escape from its sequestered matrix using alternative sequestration technologies. A method has been developed to prepare stable carbonate products by reacting CO2 with magnesium silicate minerals in aqueous bicarbonate/chloride media at high temperature and pressure. Because this approach is inherently expensive due to slow reaction rates and high capital costs, studies were conducted to improve the reaction rates through mineral pretreatment steps and to cut expenses through improved reactor technology. An overview is given for the estimated cost of the process including sensitivity to grinding and heating as pretreatment options for several mineral feedstocks. The energy costs are evaluated for each pretreatment in terms of net carbon avoided. New studies with a high-temperature, high-pressure flow-loop reactor have yielded information on overcoming kinetic barriers experienced with processing in stirred autoclave reactors. Repeated tests with the flow-loop reactor have yielded insights on wear and failure of system components, on challenges to maintain and measure flow, and for better understanding of the reaction mechanism.

  3. Carbon nanohybrids used as catalysts and emulsifiers for reactions in biphasic aqueous/organic systems

    Institute of Scientific and Technical Information of China (English)

    Daniel E. Resasco

    2014-01-01

    This mini-review summarizes some novel aspects of reactions conducted in aqueous/organic emul-sions stabilized by carbon nanohybrids functionalized with catalytic species. Carbon nanohybrids represent a family of solid catalysts that not only can stabilize water-oil emulsions in the same fash-ion as Pickering emulsions, but also catalyze reactions at the liquid/liquid interface. Several exam-ples are discussed in this mini-review. They include (a) aldol condensation-hydrodeoxygenation tandem reactions catalyzed by basic (MgO) and metal (Pd) catalysts, respectively; (b) Fischer-Tropsch synthesis catalyzed by carbon-nanotube-supported Ru;and (c) emulsion polymerization of styrene for the production of conductive polymer composites. Conducting these reactions in emul-sion generates important advantages, such as increased liquid/liquid interfacial area that conse-quently means faster mass transfer rates of molecules between the two phases, effective separation of products from the reaction mixture by differences in the water-oil solubility, and significant changes in product selectivity that can be adjusted by modifying the emulsion characteristics.

  4. Carbon-14 transfer into rice plants from a continuous atmospheric source: observations and model predictions

    International Nuclear Information System (INIS)

    Carbon-14 (14C) is one of the most important radionuclides from the perspective of dose estimation due to the nuclear fuel cycle. Ten years of monitoring data on 14C in airborne emissions, in atmospheric CO2 and in rice grain collected around the Tokai reprocessing plant (TRP) showed an insignificant radiological effect of the TRP-derived 14C on the public, but suggested a minor contribution of the TRP-derived 14C to atmospheric 14C concentrations, and an influence on 14C concentrations in rice grain at harvest. This paper also summarizes a modelling exercise (the so-called rice scenario of the IAEA's EMRAS program) in which 14C concentrations in air and rice predicted with various models using information on 14C discharge rates, meteorological conditions and so on were compared with observed concentrations. The modelling results showed that simple Gaussian plume models with different assumptions predict monthly averaged 14C concentrations in air well, even for near-field receptors, and also that specific activity and dynamic models were equally good for the prediction of inter-annual changes in 14C concentrations in rice grain. The scenario, however, offered little opportunity for comparing the predictive capabilities of these two types of models because the scenario involved a near-chronic release to the atmosphere. A scenario based on an episodic release and short-term, time-dependent observations is needed to establish the overall confidence in the predictions of environmental 14C models

  5. Sampling and monitoring of carbon-14 in gaseous effluents from nuclear facilities

    International Nuclear Information System (INIS)

    This study reviews the possibilities from sampling and monitoring C-14 in gaseous effluents from nuclear facilities. After oxidation of various forms of carbon-14 in the off-gas into CO2 three main processes for trapping are used either separately or in combination. These are sorption, freezing and chemical processes. Absorption in alkaline solutions or solids or molecular sieve adsorption are the most frequently used methods. The main counting methods used are gas proportional counting and liquid scintillation counting

  6. Carbon-14 production compared to oxygen isotope records from Camp Century, Greenland and Devon Island, Canada

    International Nuclear Information System (INIS)

    Carbon-14 production rate variations that are not explainable by geomagnetic changes are thought to be in antiphase with solar activity and as such should be in antiphase with paleotemperature records or proxy temperature histories such as those obtainable from oxygen isotope analyses of ice cores. Oxygen isotope records from Camp Century, Greeland and Devon Island Ice Cap are in phase with each other over thousands of years and in antiphase to the 14C production rate residuals. (Auth.)

  7. Shrinkage Cracking: A mechanism for self-sustaining carbon mineralization reactions in olivine rocks

    Science.gov (United States)

    Zhu, W.; Fusseis, F.; Lisabeth, H. P.; Xing, T.; Xiao, X.; De Andrade, V. J. D.; Karato, S. I.

    2015-12-01

    The hydration and carbonation of olivine results in an up to ~44% increase in solid molar volume, which may choke off of fluid supply and passivate reactive surfaces, thus preventing further carbonation reactions. The carbonation of olivine has ben studied extensively in the laboratory. To date, observations from these experimental studies indicate that carbonation reaction rates generally decrease with time and the extent of carbonation is limited in olivine rocks. Field studies, however, show that 100% hydration and carbonation occur naturally in ultramafic rocks. The disagreement between the laboratory results under controlled conditions and the field observations underlines the lack of understanding of the mechanisms responsible for the self-sustaining carbonation interaction in nature. We developed a state-of-the-art pressurized hydrothermal cell that is transparent to X-rays to characterize the real-time evolution of pore geometry during fluid-rock interaction using in-situ synchrotron-based X-ray microtomography. Through a time series of high-resolution 3-dimensional images, we document the microstructural evolution of a porous olivine aggregate reacting with a sodium bicarbonate solution at elevated pressure and temperature conditions. We observed porosity increases, near constant rate of crystal growth, and pervasive reaction-induced fractures. Based on the nanometer scale tomography data, we propose that shrinkage cracking is the mechanism responsible for producing new reactive surface and keep the carbonation reaction self-sustaining in our experiment. Shrinkage cracks are commonly observed in drying mud ponds, cooling lava flows and ice wedge fields. Stretching of a contracting surface bonded to a substrate of nearly constant dimensions leads to a stress buildup in the surface layer. When the stress exceeds the tensile strength, polygonal cracks develop in the surface layer. In our experiments, the stretching mismatch between the surface and interior of

  8. Proportion of biogenic carbon in flue gas by carbon-14 measurement; Biohiili2: Biohiilen mittaus savukaasusta hiili-14-menetelmaellae

    Energy Technology Data Exchange (ETDEWEB)

    Lehtomaeki, J.; Antson, O.; Hongisto, M.; Knuuttila, M.; Roine, J.; Raesaenen, J.; Tormonen, K. [VTT Technical Research Centre of Finland, Espoo (Finland); Jungner, H. [Helsinki Univ. (Finland)

    2007-07-01

    The subject of this project is closely related to EU's emissions trading system and to the current and future monitoring needs therein. The determination of fossil part of emissions originated from various fuels by stack measurements or by laboratory analyses could possibly find users also in other fields outside the ETS (e.g. waste incineration). After the market analysis and preliminary measurements carried out in the previous Biocarbon project this project focused on the development of the sampling method for stack measurements and to the validation of isotope measurements. The results obtained for fossil proportion of the fuel by current methods will be compared to those obtained by isotope measurements. The operation of the sampling system was tested in long period tests in plant conditions. Moreover, the sample preparation methods and isotope measurements were validated by measuring the proportions of biogenic and fossil carbon of known traffic fuel mixtures. The developed service concept can also be utilised as a fraud prevention measure related to the expanding international biofuels-trade. (orig.)

  9. Reaction engineering for materials processing in space: Reduction of ilmenite by hydrogen and carbon monoxide

    Science.gov (United States)

    Zhao, Y.; Shadman, F.

    1991-01-01

    Oxygen is a consumable material which needs to be produced continuously in most space missions. Its use for propulsion as well as life support makes oxygen one of the largest volume chemicals to be produced in space. Production of oxygen from lunar materials is of particular interest and is very attractive possibility. The kinetics and mechanism of reduction of ilmenite by carbon monoxide and hydrogen at 800 to 1100 C were investigated. The temporal profiles of conversion for carbon monoxide have a sigmoidal shape and indicate the presence of three different stages (induction, acceleration, and deceleration) during the reduction reaction. The apparent activation energy decreases from 18 kcal/mole at 10 percent conversion to 10 kcal/mole at 50 percent conversion. The reaction is first order with respect to carbon monoxide under the experimental conditions studied. Both SEM and EDX analysis show that the diffusion of Fe product away from the reaction front and through the TiO2 phase, followed by the nucleation and growth of a separate Fe phase are important steps affecting the process kinetics. The results from hydrogen reduction show that the mechanism of ilmenite reduction by hydrogen is similar to that by carbon monoxide. However, the titanium dioxide can be further reduced by hydrogen at 800 to 1000 C. The detailed comparison and theoretical modeling of both reduction processes is presented.

  10. Changes in a coke structure due to reaction with carbon dioxide

    Energy Technology Data Exchange (ETDEWEB)

    Pusz, S.; Majewska, J.; Pilawa, B. [Centre of Polymer and Carbon Materials, Polish Academy of Sciences, M. Curie-Sklodowskiej 34, PL-41819 Zabrze (Poland); Krzesinska, M. [Centre of Polymer and Carbon Materials, Polish Academy of Sciences, M. Curie-Sklodowskiej 34, PL-41819 Zabrze (Poland); Silesian Technical University, Department of Electron Technology, Institute of Physics, Krzywoustego 2, PL-44100 Gliwice (Poland); Smedowski, L. [Silesian Technical University, Department of Electron Technology, Institute of Physics, Krzywoustego 2, PL-44100 Gliwice (Poland); Kwiecinska, B. [AGH-University of Science and Technology, Aleja Mickiewicza 30, PL-30059 Krakow (Poland)

    2010-04-01

    Technological properties of a coke directly depend on a coke structure, i.e., on carbon matrix (a solid phase in a porous medium) and on pore system. Coke structure is deeply transformed during blast furnace operation and one of the most important factors responsible for that is the CO{sub 2} gasification. The objective of this work was to investigate changes of the physical structure of a coke upon the reaction with carbon dioxide to evaluate the effects of structural transformations on technological properties of a coke. Selected physical parameters of cokes produced in a laboratory scale were carried out prior to and after the reaction with CO{sub 2}. The following physical methods were used for the study: helium gas densitometry, physical adsorption of N{sub 2}, optical microscopy, transmission electron microscopy (TEM), ultrasonic measurements and electron paramagnetic resonance spectroscopy (EPR). The results showed that the reaction with CO{sub 2} distinctly affects the physical structure of coke. Coke solid matrix becomes better ordered, with greater structural units, while development of pore structure consists in the enlargement and coalescence of pores and the increase of specific surface area. Great increase of coke porosity after the reaction with CO{sub 2} seems to be more affecting the final strength and reactivity of coke than the transformation of carbon matrix. (author)

  11. Sulfur reactions and cryptic cross-linkages to oxygen, iron, and carbon cyclin

    Science.gov (United States)

    Druschel, G.; Kafantaris, F. C. A.; Fike, D. A.; Schmitt-Kopplin, P.; Dvorski, S.; Oduro, H.

    2014-12-01

    Sulfur speciation in any setting is controlled by a complex series of redox reactions, polymerization, and complexation reactions that are affected by both biotic and abiotic processes. Additionally there are several crossroads of reactions with oxygen, carbon, and iron in which polysulfide molecules serve as a key reaction component that affects not only sulfur speciation, but the speciation, solubility, and bioavailability of these elements as well. Utilizing a combination of analytical approaches including electrochemistry, spectroscopy, mass spectrometry, and chromatography, we have started to unravel the interconnections between sulfur and other key elements, and how microorganisms may be either direct or indirect contributors to these chemical and mineralogical signatures. In microbial mats, we have observed microbial production of significant hydrogen peroxide under UV-stressed conditions. This peroxide interaction with hydrogen sulfide changes the kinetics and the pathways of abiotic sulfur reactions, potentially affecting the overall bioavailability and isotopic fractionations for specific reactions via a change in the linkage between oxygen and sulfur cycling. In systems containing significant iron, we have observed the production of an electroactive form of ferrous iron and sulfide (FeS(aq)) that is of a size that can be described between a dissolved molecular cluster and a small nanoparticle. This FeS(aq) can be a significant fraction of the dissolved iron or sulfide in a system, and is a key part of both the solubility of iron and sulfur and the pathways potentially important for pyritization reactions. In systems where we investigate the links between sulfur and carbon, laboratory and field experiments indicate a wide range of large and more reduced organic compounds are highly reactive towards polysulfide. Utilizing Fourier-transform ion cyclotron resonance mass spectrometry in conjunction with electrochemistry and chromatography, we are seeing a

  12. CaCO3, its reaction and carbonate rocks: terahertz spectroscopy investigation

    Science.gov (United States)

    Zhan, Honglei; Wu, Shixiang; Zhao, Kun; Bao, Rima; Xiao, Lizhi

    2016-10-01

    Carbonate-rich rocks cover a primary part of the earth’s petroleum geology reservoir. The study of carbonate has special significance and more effective study methods are now needed. In order to improve the availability of carbonate rock detection, terahertz (THz) spectroscopy was employed to investigate relevant materials in Na2CO3  +  CaCl2  =  CaCO3  +  2NaCl, which is often used to generate CaCO3. By comparing the materials composited with different ions, it can be revealed that Ca2+, \\text{CO}32- , Na+ and Cl- have respective absorption features at different frequencies. Furthermore, by utilizing a conservation equation it can be observed that the average refractive indices of Na2CO3 as well as CaCl2 equal those of CaCO3 and NaCl in the entire range. Combining the absorption and refractive effect of the materials in the reaction can comprehensively characterize the different substances and reveal the inner interaction during the reaction. THz spectra can deduce the process of molecule rearrangement in the chemical reaction of long-term rock evolution. Besides, the absorption features of the real carbonate rock collected from the nearest town of Sinan county, Guizhou province in Yunnan-Guizhou plateau validate the peaks’ central frequencies of ions and the principal components of carbonates, which can be in agreement with the SEM-EDS analysis. This research will supply a spectral tool to identify the particles in the rock and deduce an evolution of petroleum carbonate reservoir.

  13. Fabrication and characterization of reaction bonded silicon carbide/carbon nanotube composites

    International Nuclear Information System (INIS)

    Carbon nanotubes have generated considerable excitement in the scientific and engineering communities because of their exceptional mechanical and physical properties observed at the nanoscale. Carbon nanotubes possess exceptionally high stiffness and strength combined with high electrical and thermal conductivities. These novel material properties have stimulated considerable research in the development of nanotube-reinforced composites (Thostenson et al 2001 Compos. Sci. Technol. 61 1899, Thostenson et al 2005 Compos. Sci. Technol. 65 491). In this research, novel reaction bonded silicon carbide nanocomposites were fabricated using melt infiltration of silicon. A series of multi-walled carbon nanotube-reinforced ceramic matrix composites (NT-CMCs) were fabricated and the structure and properties were characterized. Here we show that carbon nanotubes are present in the as-fabricated NT-CMCs after reaction bonding at temperatures above 1400 deg. C. Characterization results reveal that a very small volume content of carbon nanotubes, as low as 0.3 volume %, results in a 75% reduction in electrical resistivity of the ceramic composites. A 96% decrease in electrical resistivity was observed for the ceramics with the highest nanotube volume fraction of 2.1%

  14. 14.7% efficient mesoscopic perovskite solar cells using single walled carbon nanotubes/carbon composite counter electrodes

    Science.gov (United States)

    Li, Hao; Cao, Kun; Cui, Jin; Liu, Shuangshuang; Qiao, Xianfeng; Shen, Yan; Wang, Mingkui

    2016-03-01

    A single walled carbon nanotube (SWCNT) possesses excellent hole conductivity. This work communicates an investigation of perovskite solar cells using a mesoscopic TiO2/Al2O3 structure as a framework in combination with a certain amount of SWCNT-doped graphite/carbon black counter electrode material. The CH3NH3PbI3-based device achieves a power conversion efficiency of 14.7% under AM 1.5G illumination. Detailed investigations show an increased charge collection in this device compared to that without the SWCNT additive.A single walled carbon nanotube (SWCNT) possesses excellent hole conductivity. This work communicates an investigation of perovskite solar cells using a mesoscopic TiO2/Al2O3 structure as a framework in combination with a certain amount of SWCNT-doped graphite/carbon black counter electrode material. The CH3NH3PbI3-based device achieves a power conversion efficiency of 14.7% under AM 1.5G illumination. Detailed investigations show an increased charge collection in this device compared to that without the SWCNT additive. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr07347b

  15. Synthesis of graphitic carbon nitride through pyrolysis of melamine and its electrocatalysis for oxygen reduction reaction

    Institute of Scientific and Technical Information of China (English)

    He-Sheng Zhai; Lei Cao; Xing-Hua Xia

    2013-01-01

    Graphitic carbon nitride (g-C3N4) was synthesized via direct pyrolysis of melamine and its electrocatalysis toward oxygen reduction reaction was studied.The morphology and structures of the products were characterized by scanning electron microscope and X-ray powder diffractometer.It was found that higher pyrolysis temperature resulted in more perfect crystalline structure of the graphitic carbon nitride product.Electrochemical characterizations show that the g-C3N4 has electrocatalytic activity toward ORR through a two-step and two-electron process.

  16. Practical Aspects of Carbon-Carbon Cross-Coupling Reactions Using Heteroarenes

    NARCIS (Netherlands)

    Slagt, Vincent F.; Vries, André H.M. de; Vries, Johannes G. de; Kellogg, Richard M.

    2010-01-01

    The use of cross-coupling reactions for the preparation of alkylated and arylated heteroaromatic compounds has increased tremendously over the past two decades. This has been driven on the one hand by the increasingly complex structures of new drugs, most of which contain one or more heterocyclic mo

  17. A Brief Review of the Application of 14C in Terrestrial Carbon Cycle Studies

    Energy Technology Data Exchange (ETDEWEB)

    Guilderson, T; Mcfarlane, K

    2009-10-22

    An over-arching goal of the DOE TCP program is to understand the mechanistic controls over the fate, transport, and residence time of carbon in the terrestrial biosphere. Many of the modern process and modeling studies focus on seasonal to interannual variability. However, much of the carbon on the landscape and in soils is in separate reservoirs with turnover times that are multi-decadal to millennial. It is the controls on these longer term pools or reservoirs that is a critical unknown in the face of rising GHGs and climate change and uncertainties of the terrestrial biosphere as a future global sink or source of atmospheric CO{sub 2} [eg., Friedlingstein et al., 2006; Govindasamy et al., 2005; Thompson et al., 2004]. Radiocarbon measurements, in combination with other data, can provide insight into, and constraints on, terrestrial carbon cycling. Radiocarbon (t{sub 1/2} 5730yrs) is produced naturally in the stratosphere when secondary neutrons generated by cosmic rays collide with {sup 14}N atoms [Libby 1946; Arnold and Libby, 1949]. Upon formation, {sup 14}C is rapidly oxidized to CO and then to CO{sub 2}, and is incorporated into the carbon cycle. Due to anthropogenic activities, the amount of {sup 14}C in the atmosphere doubled in the mid/late 1950s and early 1960s from its preindustrial value of {sup 14}C/{sup 12}C ratio of 1.18 x 10{sup -12} [eg., Nydal and Lovseth, 1983]. Following the atmospheric weapons test ban in 1963, the {sup 14}C/{sup 12}C ratio, has decreased due to the net isotopic exchange between the ocean and terrestrial biosphere [eg., Levin and Hessheimer, 2000] and a dilution effect due to the burning of {sup 14}C-free fossil fuel carbon, the 'Suess Effect' [Suess, 1955]. In the carbon cycle literature, radiocarbon measurements are generally reported as {Delta}{sup 14}C, which includes a correction for mass dependent fractionation [Stuiver and Polach, 1977]. In the context of carbon cycle studies radiocarbon measurements can be

  18. Synthesis of propylene carbonate from urea and propylene glycol over zinc oxide: A homogeneous reaction

    OpenAIRE

    Dengfeng Wang; Xuelan Zhang; Tingting Cheng; Jing Wu; Qijun Xue

    2014-01-01

    In this work, several metal oxides and zinc salts were used to catalyze propylene carbonate (PC) synthesis from urea and propylene glycol (PG). According to the results of catalytic test and characterization, the catalytic pattern of ZnO was different from that of other metal oxides such as CaO, MgO and La2O3, but similar to that of zinc salts. In fact, the leaching of Zn species took place during reaction for ZnO. And ZnO was found to be the precursor of homogenous catalyst for reaction of u...

  19. tert-Butanesulfinamides as Nitrogen Nucleophiles in Carbon-Nitrogen Bond Forming Reactions.

    Science.gov (United States)

    Ramirez Hernandez, Johana; Chemla, Fabrice; Ferreira, Franck; Jackowski, Olivier; Oble, Julie; Perez-Luna, Alejandro; Poli, Giovanni

    2016-01-01

    The use of tert-butanesulfinamides as nitrogen nucleophiles in carbon-nitrogen bond forming reactions is reviewed. This field has grown in the shadow of the general interest in N-tert-butanesulfinyl imines for asymmetric synthesis and occupies now an important place in its own right in the chemistry of the chiral amine reagent tert-butanesulfinamide. This article provides an overview of the area and emphasizes recent contributions wherein the tert-butanesulfinamides act as chiral auxiliaries or perform as nitrogen donors in metal-catalyzed amination reactions. PMID:26931222

  20. Variation of 14C, 137Cs and stable carbon composition in forest soil and its implications

    International Nuclear Information System (INIS)

    In Japan, about 70% of land area is covered by forest. Therefore, forest ecosystem plays a vital role in ultimate fate of radionuclides and carbon cycle in terrestrial environment. Three undisturbed forest soil profiles were collected from Ibaraki Prefecture, Japan. The 137Cs data illustrate that maximum fallout deposition of 137Cs took place around 1964. 14C determination shows that 14C also has peak values in the top 10 cm of the soil profiles ascribed to the highest bomb 14C level in 1960's. The 13C data show that the turnover dynamics of soil organic carbon could be described very well by progressive enrichment values of δ13C. (author)

  1. Capture cross-section and rate of the 14C(, )15C reaction from the Coulomb dissociation of 15C

    Indian Academy of Sciences (India)

    Shubhchintak; Neelam; R Chatterjee

    2014-10-01

    We calculate the Coulomb dissociation of 15C on a Pb target at 68 MeV/u incident beam energy within the fully quantum mechanical distorted wave Born approximation formalism of breakup reactions. The capture cross-section and the subsequent rate of the 14C(, )15C reaction are calculated from the photodisintegration of 15C, using the principle of detailed balance. Our theoretical model is free from the uncertainties associated with the multipole strength distributions of the projectile.

  2. Photosynthesis and assimilate partitioning characteristics of the coconut palm as observed by carbon-14 labelling

    International Nuclear Information System (INIS)

    A technique was developed on the use of carbon dioxide(carbon-14 labelled) rapid labelling of foliage and to ascertain photosynthesis and partitioning characteristics of labelled assimilate into other parts of the coconut palm. An eight-year-old Tall x Tall young coconut palm growing under field conditions at Bandirippuwa Estate and with six developing bunches , was selected for this study. The labelling was carried out on a bright sunny day and soil was at field capacity. Seventh leaf from the youngest open leaf was used for labelling with 5 mCi of sodium bi carbonate (Carbon-14 labelled). The results revealed that within 24 hours, 60% of the labelled assimilate was partitioned into other parts of the palm and at the end of the seventh day about 18% of the labelled assimilate still remained in the labelled leaf. Among the developing bunches fifth and sixth bunches from the youngest developing bunch received more labelled assimilate than young developing bunches above them. It was revealed that partitioning of assimilate into various ''sinks'' is determined by the developmental stage or activeness of the ''sink''. The proportion of C-14 labelled carbon assimilate, partitioned into developing bunches was substantially low compared to the total amount of labelled carbon fixed by the labelled leaf. Further, it was observed that partitioning of assimilated labelled carbon into the young leaves above, as well as the mature leaves below the labelled leaf. The complex vascular anatomy of the palms could be attributed to this pattern of partitioning of assimilates into upper and lower leaves from the labelled leaf

  3. Reservoir-Condition Pore-Scale Imaging of Reaction in Carbonates using Synchrotron Fast Tomography

    Science.gov (United States)

    Menke, H. P.; Andrew, M. G.; Bijeljic, B.; Blunt, M. J.

    2015-12-01

    Carbon capture and storage in carbonate reservoirs is essential for mitigating climate change. Supercritical CO2 mixed with host brine is acidic and can dissolve the surrounding pore structure and change flow dynamics. However, the type, speed, and magnitude of the dissolution are dependent on both the reactive transport properties of the pore-fluid and the intrinsic properties of the rock. Understanding how changes in the pore structure, chemistry, and flow properties affect dissolution is vital for successful predictive modelling both on the pore-scale and for up-scaled reservoir simulations. Reaction in carbonates has been studied at the pore-scale but has never been imaged dynamically in situ. We present an experimental method whereby both lab-based benchtop instruments and 'Pink Beam' synchrotron radiation are used in X-ray microtomography to investigate pore structure changes during supercritical CO2 injection at reservoir conditions. Three types of pure limestone rock with broadly varying rock topology were imaged under the same reservoir conditions. Flow-rate and brine acidity was varied in successive experiments by half an order of magnitude to gain insight into the impact of flow, transport, and physical heterogeneity. The images were binarized and the magnitude of dissolution was identified on a voxel-by-voxel basis to extract pore-by-pore dissolution data. The impact of dissolution on flow characteristics was studied by computing the evolution of the pore-scale velocity fields with a flow solver. We found that increasing rock heterogeneity increased channelized flow [Figure 1] through preferential pathways and that higher flow rate increased total dissolution. Additionally, decreasing reaction rate lowered overall reaction rate and made axial flow less uniform. Experimentally measured reaction rates in real rocks are at least an order of magnitude lower when compared to batch experiments. We provide evidence that this can be due to transport limitations

  4. Cycloaddition Reaction of Carbon Dioxide to Epoxides Catalyzed by Polymer-Supported Quaternary Phosphonium Salts

    Directory of Open Access Journals (Sweden)

    Yubing Xiong

    2013-01-01

    Full Text Available Polymer-supported quaternary phosphonium salt (PS-QPS was explored as effective catalyst for the coupling reaction of carbon dioxide with epoxides. The results indicated that cyclic carbonates with high yields (98.6% and excellent selectivity (100% could be prepared at the conditions of 5 MPa CO2, 150°C, and 6 h without the addition of organic solvents or cocatalysts. The effects of various reaction conditions on the catalytic performance were investigated in detail. The catalyst is applicable to a variety of epoxides, producing the corresponding cyclic carbonates in good yields. Furthermore, the catalyst could be recovered easily and reused for five times without loss of catalytic activity obviously. A proposed mechanism for synthesis of cyclic carbonate in the presence of PS-QPS was discussed. The catalyst was characterized by thermogravimetric analysis (TGA, scanning electron microscopy (SEM, and Fourier transform infrared (FT-IR spectrum. It is believed that PS-QPS is of great potential for CO2 fixation applications due to its unusual advantages, such as easy preparation, high activity and selectivity, stability, low cost, and reusability.

  5. Factors affecting carbon-14 activity of unsaturated zone CO2 and implications for groundwater dating

    Science.gov (United States)

    Wood, Cameron; Cook, Peter G.; Harrington, Glenn A.; Meredith, Karina; Kipfer, Rolf

    2014-11-01

    Unsaturated zone processes may influence the carbon-14 (14C) activity of infiltrating groundwater and thus introduce error in derived groundwater residence times. However unsaturated zone 14C activities are rarely measured and there is little understanding of how they may vary spatially in a groundwater basin. In this study we measured 14C activity in unsaturated zone gas at five sites with different watertable depths (8.2-31.5 m) in the arid Ti Tree Basin, central Australia. We observed a relatively uniform decrease in 14C activity of unsaturated zone gas with depth at most sites, with variation in unsaturated zone depths leading to variation in 14C activities directly above the watertable at each site (ranging from 54 to 106 percent Modern Carbon (pMC)). Through modelling we show that the profiles are influenced by CO2 production at different depths from sources with different isotopic ratios, including production of ‘modern' CO2 in the root zone and production of ‘old' CO2 above the watertable. Scenario modelling showed that these processes are independent of recharge when recharge is low (0-10 mm y-1) but that higher recharge rates (>100 mm y-1) result in more advective transport of atmospheric CO2 to the watertable. The variation in 14C above the watertable was more sensitive to watertable depth and shallow and deep CO2 production rates. These findings offer insight into how unsaturated zone 14C activities may vary spatially and provide guidance as to when 14C depletion in unsaturated zone CO2 may become important for groundwater dating, particularly in arid settings.

  6. Theoretical study of the P-Ylide reaction in the carbon nanotube

    Institute of Scientific and Technical Information of China (English)

    XIAO Bo; ZHAO JingXiang; DING YiHong; SUN ChiaChung

    2009-01-01

    Recent studies have shown that the inner phase of carbon nanotubes (CNTs) can not only change the properties of molecules inside the tube,but also enhance or restrain the S_N2 reactions.Thus,the CNTs can be considered a form of solid solvent.In this paper,we study the[2+2]cycloaddition reaction between CH_2O and PH_3CH_2 in the gas phase,benzene solution and inner phase of CNT using the density functional theory (DFT).The results indicate that the inner phase of CNT has little effect on the[2+2]cycloaddition reaction.This can be explained as that while taking the linear arrangement for S_N2 reaction,the reactants do not possess the axial symmetry for the studied[2+2]cycloaddition reaction.Therefore,although the CNT has large axial polarizability,it can exert little influence on the[2+2]cycloaddition reaction.Our studies will be helpful for further understanding of the inner phase chemistry of CNTs.

  7. The neighboring effect of isosorbide and its epimers in their reactions with dimethyl carbonate

    Directory of Open Access Journals (Sweden)

    Fabio Aricò

    2014-10-01

    Full Text Available The reactions of isosorbide and its epimers, isomannide and isoidide, with dimethyl carbonate have been herein investigated as easy access to bio-based products by a free-halogen chemistry approach. Isosorbide and its epimers show a different reactivity in bimolecular nucleophilic substitution with dimethyl carbonate (DMC. Carboxymethylation reaction was carried out in the presence of DMC and a weak base resulting in the high-yielding synthesis of dicarboxymethyl derivatives. Isomannide was the most reactive anydro sugar due to the less sterically hindered exo position of the OH groups. On the other hand, methylation of isosorbide and its epimers, conducted in the presence of a strong base and DMC, showed the higher reactivity of the endo hydroxyl group, isoidide being the most reactive epimer. This result has been ascribed to the neighboring effect due to the combination of the oxygen in β-position and the intramolecular hydrogen bond within the anhydro sugar structure. Methylation reactions were also conducted in autoclave at high temperature with the amphoteric catalyst hydrotalcite using DMC as reagent and solvent. In this case, the reactivity of the epimers resulted quite differently with isosorbide being the most reactive reagent possibly as a result of the structure of hydrotalcite comprising of both acidic and basic sites. The neighboring effect was observed with good evidence in these methylation reactions.

  8. Synthesis of propylene carbonate from urea and propylene glycol over zinc oxide: A homogeneous reaction

    Directory of Open Access Journals (Sweden)

    Dengfeng Wang

    2014-11-01

    Full Text Available In this work, several metal oxides and zinc salts were used to catalyze propylene carbonate (PC synthesis from urea and propylene glycol (PG. According to the results of catalytic test and characterization, the catalytic pattern of ZnO was different from that of other metal oxides such as CaO, MgO and La2O3, but similar to that of zinc salts. In fact, the leaching of Zn species took place during reaction for ZnO. And ZnO was found to be the precursor of homogenous catalyst for reaction of urea and PG. Thus, the relationship between the amount of dissolved zinc species and the catalytic performance of employed ZnO was revealed. In addition, a possible reaction mechanism over ZnO was discussed based on the catalytic runs and the characterization of XRD, FTIR, and element analysis.

  9. 14例红花注射液致不良反应分析%Analysis on 14 Cases of Adverse Drug Reaction by Carthamus Injection

    Institute of Scientific and Technical Information of China (English)

    吴康郁; 朱群娣; 黄志辉; 张建环

    2013-01-01

    Objective To explore the rules and causes of adverse reactions by using Carthamus Injection. Methods Analysing 14 patients' basic, primary disease, the incidence of adverse reactions who causing adverse drug reactions by Carthamus Injection. Result 14 cases of Carthamus injection adverse reactions in patients with women slightly more than men, but there is no statistical significant(p>0.05); 60 years old or more accounted for 12 cases of adverse reactions in patients, under the age of 60 accounted for 2 cases, with statisticaly significant(p45min group, the difference was statistical significant(p<0.05); clinical manifestations of adverse reactions included the skin and appendages (7 cases), systemic reactions (5 cases), cardiovascular system damage (two cases). Conclusion Carthamus injection adverse reactions caused no significant relationship with patients' gender, adverse reactions mostly occurred in patients over the age of 60, the adverse reaction time more appear in 30min after administration, adverse reactions more performance for the damage to the skin and its appendages, systemic reactions and cardiovascular system damage.%  目的探讨使用红花注射液后发生不良反应的特点及规律。方法对本院14例使用红花注射液后出现不良反应的患者的基本情况、原发疾病、不良反应发生情况进行分析。结果红花注射液所致14例不良反应患者女性较男性稍多,但没有统计学差异(p>0.05);不良反应患者中60以上的占12例,60岁以下的占2例,具有统计学差异(p<0.05);14例患者原发病均属于心脑血管疾病;不良反应出现在15min-45min者占13例,与<15min组及>45min组相比差异具有统计学意义(p<0.05);不良反应临床表现为皮肤及附件损害(7例),全身反应(5例),心血管系统损害(2例)。结论红花注射液致不良反应与患者性别无明显关系,不良反应多发生在60岁以上患者

  10. Multiphase Carbon-14 Transport in a Near-Field-Scale Unsaturated Column of Natural Sediments

    Energy Technology Data Exchange (ETDEWEB)

    D. T. Fox; Mitchell A. Plummer; Larry C. Hull; D. Craig Cooper

    2004-03-01

    Wastes buried at the Subsurface Disposal Area (SDA) of the Idaho National Engineering and Environmental Laboratory include activated metals that release radioactive carbon-14 (14C) as they corrode. To better understand 14C phase partitioning and transport in the SDA sediments, we conducted a series of transport experiments using 14C (radio-labeled sodium carbonate) and nonreactive gas (sulfur hexafluoride) and aqueous (bromide and tritiated water) tracers in a large (2.6-m high by 0.9-m diameter) column of sediments similar to those used as cover material at the SDA. We established steady-state unsaturated flow prior to injecting tracers into the column. Tracer migration was monitored using pore-water and pore-gas samples taken from co-located suction lysimeters and gas ports inserted at ~0.3-m intervals along the column’s length. Measurements of 14C discharged from the sediment to the atmosphere (i.e., 14CO2 flux) indicate a positive correlation between CO2 partial pressure (pCO2) in the column and changes in 14CO2 flux. Though 14CO2 diffusion is expected to be independent of pCO2, changes of pCO2 affect pore water chemistry sufficiently to affect aqueous/gas phase 14C partitioning and consequently 14C2 flux. Pore-water and -gas 14C activity measurements provide an average aqueous/gas partitioning ratio, Kag, of 4.5 (±0.3). This value is consistent with that calculated using standard carbonate equilibrium expressions with measured pH, suggesting the ability to estimate Kag from carbonate equilibrium. One year after the 14C injection, the column was cored and solid-phase 14C activity was measured. The average aqueous/solid partition coefficient, Kd, (1.6 L kg-1) was consistent with those derived from small-scale and short-term batch and column experiments using SDA sediments, suggesting that bench-scale measurements are a valid means of estimating aqueous/solid partitioning at the much larger spatial scale considered in these meso-scale experiments. However

  11. The Development and Application of Two-Chamber Reactors and Carbon Monoxide Precursors for Safe Carbonylation Reactions.

    Science.gov (United States)

    Friis, Stig D; Lindhardt, Anders T; Skrydstrup, Troels

    2016-04-19

    , an array of low-pressure carbonylations were developed applying only near stoichiometric amounts of carbon monoxide. Importantly, carbon isotope variants of the CO precursors, such as (13)COgen, Sila(13)COgen, or even (14)COgen, provide a simple means for performing isotope-labeling syntheses. Finally, the COware applicability has been extended to reactions with other gases, such as hydrogen, CO2, and ethylene including their deuterium and (13)C-isotopically labeled versions where relevant. The COware system has been repeatedly demonstrated to be a valuable reactor for carrying out a wide number of transition metal-catalyzed transformations, and we believe this technology will have a significant place in many organic research laboratories.

  12. Carbon-14 in waste packages for spent fuel in a tuff repository

    International Nuclear Information System (INIS)

    Carbon-14 is produced naturally by cosmic ray neutrons in the upper atmosphere. It is also produced in nuclear reactors, in amounts much smaller than the global inventory. About one-third of this is released directly to the atmosphere, and the other two-thirds remains in the spent fuel. Both the Environmental Protection Agency and the Nuclear Regulatory Commission have established limits on release of the 14C in spent fuel. This is of particular concern for the proposed repository in tuff, because of the unsaturated conditions and the consequent possibility of gaseous transport of 14C as CO2. Existing measurements and calculations of the 14C inventory in spent fuel are reviewed. The physical distribution and chemical forms of the 14C are discussed. Available data on the release of 14C from spent fuel in aqueous solutions and in gaseous environments of air, nitrogen, and helium are reviewed. Projected 14C behavior in a tuff repository is described. It is concluded that 14C release measurements from spent fuel into moist air at temperatures both above and below the in situ boiling point of water as well as detailed transport calculations for the tuff geological environment will be needed to determine whether the 10CFR60 and 40CFR191 requirements can be met. 56 refs., 1 tab

  13. Modelling the Environmental Transfer of Tritium and Carbon-14 to Biota and Man. Report of the Tritium and Carbon-14 Working Group of EMRAS Theme 1

    International Nuclear Information System (INIS)

    Hydrogen and carbon are biologically-regulated, essential elements that are highly mobile in the environment and the human body. As isotopes of these elements, tritium and 14C enter freely into water (in the case of tritium), plants, animals and humans. This complex behaviour means that there are substantial uncertainties in the predictions of models that calculate the transfer of tritium and 14C through the environment. The EMRAS Tritium/C14 Working Group (WG) was set up to establish the confidence that can be placed in the predictions of such models, to recommend improved modelling approaches, and to encourage experimental work leading to the development of data sets for model testing. The activities of the WG focused on the assessment of models for organically bound tritium (OBT) formation and translocation in plants and animals, the area where model uncertainties are largest. Environmental 14C models were also addressed because the dynamics of carbon and OBT are similar. The goals of the WG were achieved primarily through nine test scenarios in which model predictions were compared with observations obtained in laboratory or field studies. Seven of the scenarios involved tritium, covering terrestrial and aquatic ecosystems and steady-state and dynamic conditions. The remaining two scenarios concerned 14C, one addressing steady-state concentrations in plants and the other time-dependent concentrations in animals. The WG also considered one model intercomparison exercise involving the calculation of doses following a hypothetical, short-term release of tritium to the atmosphere in a farming area. Finally, the WG discussed the nature of OBT and proposed a definition to promote common understanding and usage within the international tritium community. The models used by the various participants varied in complexity from simple specific activity approaches to dynamic compartment models and process-oriented models, in which the various transfer processes were

  14. Thermodynamic Data for Geochemical Modeling of Carbonate Reactions Associated with CO2 Sequestration – Literature Review

    Energy Technology Data Exchange (ETDEWEB)

    Krupka, Kenneth M. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Cantrell, Kirk J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); McGrail, B. Peter [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2010-09-01

    Permanent storage of anthropogenic CO2 in deep geologic formations is being considered as a means to reduce the concentration of atmospheric CO2 and thus its contribution to global climate change. To ensure safe and effective geologic sequestration, numerous studies have been completed of the extent to which the CO2 migrates within geologic formations and what physical and geochemical changes occur in these formations when CO2 is injected. Sophisticated, computerized reservoir simulations are used as part of field site and laboratory CO2 sequestration studies. These simulations use coupled multiphase flow-reactive chemical transport models and/or standalone (i.e., no coupled fluid transport) geochemical models to calculate gas solubility, aqueous complexation, reduction/oxidation (redox), and/or mineral solubility reactions related to CO2 injection and sequestration. Thermodynamic data are critical inputs to modeling geochemical processes. The adequacy of thermodynamic data for carbonate compounds has been identified as an important data requirement for the successful application of these geochemical reaction models to CO2 sequestration. A review of thermodynamic data for CO2 gas and carbonate aqueous species and minerals present in published data compilations and databases used in geochemical reaction models was therefore completed. Published studies that describe mineralogical analyses from CO2 sequestration field and natural analogue sites and laboratory studies were also reviewed to identify specific carbonate minerals that are important to CO2 sequestration reactions and therefore require thermodynamic data. The results of the literature review indicated that an extensive thermodynamic database exists for CO2 and CH4 gases, carbonate aqueous species, and carbonate minerals. Values of ΔfG298° and/or log Kr,298° are available for essentially all of these compounds. However, log Kr,T° or heat capacity values at temperatures above 298 K exist for less than

  15. Algal C-14 and total carbon metabolisms 2. Experimental observations with the diatom Skeletonema costatum

    DEFF Research Database (Denmark)

    Williams, P.J.L.; Robinson, C.; Søndergaard, M.;

    1996-01-01

    of 2-3), C-14 uptake into the particulate plus the dissolved fractions approximated to net photosynthesis. Rate constants derived from the chemically determined changes were used to parameterize models that accounted for the respiration of photosynthetic products and for the recycling of respiratory CO......Three sets of comparisons of net and gross inorganic carbon assimilation and C-14 uptake were made with an axenic culture of Skeletonema costatum. The comparisons showed that in the physiological window studied (10-20% of the intrinsic generation time and gross photosynthesis/respiration ratios......2. The conclusion drawn was that over the time scale studied, the C-14 technique was measuring net photosynthesis, consistent with essentially 100% recycling of respiratory CO2. The study has shown that we now possess the basis to make a rigorous analysis of net, gross CO2 fixation and net C-14...

  16. Polyaniline-Derived Ordered Mesoporous Carbon as an Efficient Electrocatalyst for Oxygen Reduction Reaction

    Directory of Open Access Journals (Sweden)

    Kai Wan

    2015-06-01

    Full Text Available Nitrogen-doped ordered mesoporous carbon was synthesized by using polyaniline as the carbon source and SBA-15 as the template. The microstructure, composition and electrochemical behavior were extensively investigated by the nitrogen sorption isotherm, X-ray photoelectron spectroscopy, cyclic voltammetry and rotating ring-disk electrode. It is found that the pyrolysis temperature yielded a considerable effect on the pore structure, elemental composition and chemical configuration. The pyrolysis temperature from 800 to 1100 °C yielded a volcano-shape relationship with both the specific surface area and the content of the nitrogen-activated carbon. Electrochemical tests showed that the electrocatalytic activity followed a similar volcano-shape relationship, and the carbon catalyst synthesized at 1000 °C yielded the best performance. The post-treatment in NH3 was found to further increase the specific surface area and to enhance the nitrogen doping, especially the edge-type nitrogen, which favored the oxygen reduction reaction in both acid and alkaline media. The above findings shed light on electrocatalysis and offer more strategies for the controllable synthesis of the doped carbon catalyst.

  17. Evaluating reaction pathways of hydrothermal abiotic organic synthesis at elevated temperatures and pressures using carbon isotopes

    Science.gov (United States)

    Fu, Qi; Socki, Richard A.; Niles, Paul B.

    2015-04-01

    Experiments were performed to better understand the role of environmental factors on reaction pathways and corresponding carbon isotope fractionations during abiotic hydrothermal synthesis of organic compounds using piston cylinder apparatus at 750 °C and 5.5 kbars. Chemical compositions of experimental products and corresponding carbon isotopic values were obtained by a Pyrolysis-GC-MS-IRMS system. Alkanes (methane and ethane), straight-chain saturated alcohols (ethanol and n-butanol) and monocarboxylic acids (formic and acetic acids) were generated with ethanol being the only organic compound with higher δ13C than CO2. CO was not detected in experimental products owing to the favorable water-gas shift reaction under high water pressure conditions. The pattern of δ13C values of CO2, carboxylic acids and alkanes are consistent with their equilibrium isotope relationships: CO2 > carboxylic acids > alkanes, but the magnitude of the fractionation among them is higher than predicted isotope equilibrium values. In particular, the isotopic fractionation between CO2 and CH4 remained constant at ∼31‰, indicating a kinetic effect during CO2 reduction processes. No "isotope reversal" of δ13C values for alkanes or carboxylic acids was observed, which indicates a different reaction pathway than what is typically observed during Fischer-Tropsch synthesis under gas phase conditions. Under constraints imposed in experiments, the anomalous 13C isotope enrichment in ethanol suggests that hydroxymethylene is the organic intermediate, and that the generation of other organic compounds enriched in 12C were facilitated by subsequent Rayleigh fractionation of hydroxymethylene reacting with H2 and/or H2O. Carbon isotope fractionation data obtained in this study are instrumental in assessing the controlling factors on abiotic formation of organic compounds in hydrothermal systems. Knowledge on how environmental conditions affect reaction pathways of abiotic synthesis of organic

  18. Mechanism and kinetics of the reaction of 1,4-thioxane with O3 in the atmosphere - A theoretical study

    Science.gov (United States)

    Sandhiya, L.; Kolandaivel, P.; Senthilkumar, K.

    2012-02-01

    A theoretical investigation of the atmospheric oxidation of a cyclic organosulfur compound 1,4-thioxane by O3 is performed. The pathways for the reaction of 1,4-thioxane with O3 have been modeled using B3LYP, M06-2X, MPW1K and MP2 level of theories with 6-31G(d,p), 6-311G(d,p) and 6-31+G(d,p) basis sets. The reaction is initiated by the formation of a primary ozonide, followed by a biradical, which on subsequent reactions with other atmospheric species produces hydroxyl radical, hydrogen peroxides and organic peroxides. The results obtained from DFT calculations were subsequently used to perform canonical variational transition-state theory calculations to determine the rate constant. The calculated rate constant is in good agreement with the available experimental data.

  19. Electrocatalytic Activity of Carbonized Nanostructured Polyanilines for Oxidation Reactions: Sensing of Nitrite Ions and Ascorbic Acid

    International Nuclear Information System (INIS)

    Highlights: • Carbonized PANIs prepared from various nanostructured PANI precursors • Electroanalytical performances of carbonized PANIs evaluated using voltammetry • Study of carbonized PANIs physico-chemical properties related to electroactivity • The lowest over-potential for NO2− oxidation at c-PANI (+0.87 V vs. SCE) • The lowest over-potential for ascorbic acid oxidation at both c-PANI and c-PANI-SSA - Abstract: A comparative study of the electrocatalytic activity of nitrogen-containing carbon nanomaterials, prepared by the carbonization of nanostructured polyaniline (PANI) salts, for the electrooxidation reactions is presented. Nanostructured PANI salts were synthesized by the oxidative polymerization of aniline with ammonium peroxydisulfate in an aqueous solution in the presence of 5-sulfosalicylic acid (PANI-SSA), 3,5-dinitrosalicylic acid (PANI-DNSA) as well as without added acid (PANI), and subsequently carbonized to c-PANI-SSA, c-PANI-DNSA and c-PANI, respectively. Glassy carbon tip was modified with nanostructured c-PANIs and used for the investigation of sensing of nitrite and ascorbic acid in aqueous solutions as model analytes by linear sweep voltammetry. All three types of the investigated c-PANIs gave excellent response to the nitrite ions and ascorbic acid electrooxidation. The lowest peak potential for nitrite ion oxidation exhibited c-PANI (+0.87 V vs. SCE), and for ascorbic acid oxidation both c-PANI and c-PANI-SSA (ca. + 0.13 V vs. SCE). Electrochemical data were correlated with structural and textural data obtained by Raman spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, elemental and nitrogen sorption analysis

  20. The influence of carbon surface chemistry on supported palladium nanoparticles in heterogeneous reactions.

    Science.gov (United States)

    Ding, Yuxiao; Zhang, Liyun; Wu, Kuang-Hsu; Feng, Zhenbao; Shi, Wen; Gao, Qiang; Zhang, Bingsen; Su, Dang Sheng

    2016-10-15

    The surface chemistry of nanocarbon support can tailor chemical properties of precious metal nanoparticle/nanocarbon hybrid catalyst in heterogeneous reactions. We report on modified reduced graphene oxide (rGO) support with ionic liquid-derived carbonaceous surface for palladium nanoparticle (Pd NPs) decoration and their actions in different heterogeneous reactions. The surface chemistry of support materials was characterized in detail, and the influence of which on the formation and distribution of metal particles was further investigated. Three different types of reactions including Suzuki-Miyaura coupling reaction, CO oxidation and phenol reduction were examined in terms of reactivity and selectivity. The roles of substituted nitrogen in graphitic lattice and grafted groups on the carbon surface were exploited. Nitrogen-doping can give rise to changes in electronic properties of supported metals, and the Lewis basicity of the doped nitrogen atoms can favor the adsorption of acidic reactants in phenol reduction. The grafted groups derived a negative impact to the Suzuki-Miyaura coupling reaction, due to the involvement of larger reactant molecules, despite that they could prevent significant sintering of Pd NPs in the CO oxidation. PMID:27442144

  1. On the labelling of insuline and insuline derivatives with tritium and carbon-14

    International Nuclear Information System (INIS)

    Two different labelling methods were investigated. By means of the Wilzbach labelling with diaminosuberoylinsuline the insuline is irreversibly altered. As a second method the reductive methylation was used, in doing so it was possible to distinguish between mono and dimethylated parts of the reaction product by using C-14 labelled formaldehyde. Furthermore four N,N-dimethylated insuline derivatives were isolated with yields of 25 until 35%. By using C-14 and h-3 labelled reagents insuline can be labelled doubly. Moreover N-terminal amino groups could be protected irreversibly with this method. Furthermore structure-function investigations and investigations concerning the insuline metabolism were done. (SPI)

  2. Reexposure and advection of C-14-depleted organic carbon from old deposits at the upper continental slope

    OpenAIRE

    Tesi, Tommaso; Goñi, Miguel A.; Langone, Leonardo; Puig, Pere; Canals, Miquel; Nittrouer, Charles A.; Durrieu De Madron, Xavier; Calafat, Antoni; Palanques, Albert; Heussner, Serge; Davies, Maureen H.; Drexler, Tina M.; Fabres, Joan; Miserocchi, Stefano

    2010-01-01

    Outcrops of old strata at the shelf edge resulting from erosive gravity-driven flows have been globally described on continental margins. The reexposure of old strata allows for the reintroduction of aged organic carbon (OC), sequestered in marine sediments for thousands of years, into the modern carbon cycle. This pool of reworked material represents an additional source of C-14-depleted organic carbon supplied to the ocean, in parallel with the weathering of fossil organic carbon delivered ...

  3. Unique Sandwiched Carbon Sheets@Ni-Mn Nanoparticles for Enhanced Oxygen Evolution Reaction.

    Science.gov (United States)

    Zhang, Yan; Zhang, Huijuan; Yang, Jiao; Bai, Yuanjuan; Qiu, Huajun; Wang, Yu

    2016-05-11

    A unique sandwich-like architecture, where Ni-Mn nanoparticles are enveloped in coupled carbon sheets (CS@Ni-Mn), has been successfully fabricated. In the synthesis process, a great quantity of uniform NiMnO3 nanosheets generated by a universal hydrothermal method acts as precursors and templates and the cheap, environmentally friendly and recyclable glucose functions as a green carbon source. Via subsequent hydrothermal reaction and thermal annealing, sandwiched nanocomposites with Ni-Mn nanoparticles embedded inside and carbon sheets encapsulating outside can be massively prepared. The novel sandwich-like CS@Ni-Mn possesses numerous advantages, such as an intrinsic porous feature, large specific surface area, and enhanced electronic conductivity. Moreover, as a promising NiMn-based oxygen evolution reaction (OER) catalyst, the special sandwiched nanostructure demonstrates improved electrochemical properties in 1 M KOH, including a low overpotential of about 250 mV, a modest Tafel slope of 40 mV dec(-1), excellent stability over 2000 cycles, and durability for 40 h. PMID:27101350

  4. Thin film solid-state reactions forming carbides as contact materials for carbon-containing semiconductors

    Science.gov (United States)

    Leroy, W. P.; Detavernier, C.; Van Meirhaeghe, R. L.; Lavoie, C.

    2007-03-01

    Metal carbides are good candidates to contact carbon-based semiconductors (SiC, diamond, and carbon nanotubes). Here, we report on an in situ study of carbide formation during the solid-state reaction between thin films. The solid-state reaction was examined between 11 transition metals (W, Mo, Fe, Cr, V, Nb, Mn, Ti, Ta, Zr, and Hf) and an amorphous carbon layer. Capping layers (C or TiN) of different thicknesses were applied to prevent oxidation. Carbide formation is evidenced for nine metals and the phases formed have been identified (for a temperature ranging from 100to1100°C). W first forms W2C and then WC; Mo forms Mo2C; Fe forms Fe3C; Cr first forms metastable phases Cr2C and Cr3C2-x, and finally forms Cr3C2; V forms VCx; Nb transforms into Nb2C followed by NbC; Ti forms TiC; Ta first forms Ta2C and then TaC; and Hf transforms into HfC. The activation energy for the formation of the various carbide phases has been obtained by in situ x-ray diffraction.

  5. A synthetic approach to carbon-14 labeled anti-bacterial naphthyridine and quinolone carboxylic acids

    Energy Technology Data Exchange (ETDEWEB)

    Ekhato, I.V.; Huang, C.C. (Parke, Davis and Co., Ann Arbor, MI (United States))

    1993-09-01

    Labeled versions of (S)-clinafloxacin (1) and two napththyridine carboxylic acid anti-bacterial compounds 2 and 3 which are currently in development were synthesized. Preparations started from hitherto unknown bromo compounds 22 and 10, from which the corresponding [sup 14]C-labeled aromatic carboxylic acids 23 and 12 were generated by metal-halogen exchange followed by carboxylation reaction. Details of these preparations are given. (author).

  6. Mass Transfer and Reaction Kinetics in the Carbonization of Magnesium Oxide from Light Calcined Magnesia with Mechanical Force Enhancement

    Institute of Scientific and Technical Information of China (English)

    张焕军; 朱国才

    2004-01-01

    The carbonization of magnesium oxide particles by CO2 was investigated using a stirring mill reactor.The effects of the system temperature, stirring rotation speed, influx rate of CO2 and initial diameter of the magnesium oxide particles on the carbonization process were determined. The results show that the system temperature and the stirring rotation speed are the most significant influencing factors on the carbonization rate. The determination of critical decomposition temperature (CDT) gives the maximum carbonization rate with other conditions fixed. A theoretical model involving mass transfer and reaction kinetics was presented for the carbonization process.The apparent activation energy was calculated to be 32.8kJ·mo1-1. The carbonization process is co-controlled by diffusive mass transfer and chemical reaction. The model fits well with the experimental results.

  7. Modelling of dead carbon fraction in speleothems: a step towards reliable speleothem 14C-chronologies

    Science.gov (United States)

    Lechleitner, Franziska A.; Jamieson, Robert A.; McIntyre, Cameron; Baldini, Lisa M.; Baldini, James U. L.; Eglinton, Timothy I.

    2015-04-01

    Over the past two decades, speleothems have become one of the most versatile and promising archives for the study of past continental climate. Very precise absolute dating is often possible using the U-Th method, resulting in paleoclimate records of exceptional resolution and accuracy. However, not all speleothems are amenable to this dating method for a variety of reasons (e.g. low U concentrations, high detrital Th etc). This has lead researchers to exclude many otherwise suitable speleothems and cave sites from further investigation. 14C-dating of speleothems has so far not been applicable, due to the 'dead carbon' problem. As drip water percolates through the karst, dissolving CaCO3, a variable amount of 14C-dead carbon is added to the solution. This results in a temporally variable and site-specific reservoir effect, ultimately undermining the development of speleothem 14C -chronologies. However, a number of recent studies have shown a clear link between karst hydrology and associated proxies (e.g., Mg/Ca and δ13C) and this 'dead carbon fraction' (DCF). We take advantage of this relationship to model DCF and its changes using Mg/Ca, δ13C and 14C data from published speleothem records. Using one record for calibration purposes, we build a transfer function for the DCF in relation to δ13C and Mg/Ca, which we then apply to other 14C records. Initial model results are promising; we are able to reconstruct general long-term average DCF within uncertainties of the calculated DCF from the U-Th chronology. Large shifts in DCF related to hydrology are also often detected. In a second step, we apply the model to a speleothem from southern Poland, which so far could not be dated, due to very low U-concentrations. To construct a 14C chronology, the stalagmite was sampled at 5 mm intervals. CaCO3 powders were graphitized and measured by Accelerator Mass Spectrometry (MICADAS) at ETH Zurich. Additional high-resolution (0.1 mm/sample) 14C measurements were performed on

  8. 14C Activity and Global Carbon Cycle Changes over the Past 50,000 Years

    Science.gov (United States)

    Hughen, K.; Lehman, S.; Southon, J.; Overpeck, J.; Marchal, O.; Herring, C.; Turnbull, J.

    2004-01-01

    A series of 14C measurements in Ocean Drilling Program cores from the tropical Cariaco Basin, which have been correlated to the annual-layer counted chronology for the Greenland Ice Sheet Project 2 (GISP2) ice core, provides a high-resolution calibration of the radiocarbon time scale back to 50,000 years before the present. Independent radiometric dating of events correlated to GISP2 suggests that the calibration is accurate. Reconstructed 14C activities varied substantially during the last glacial period, including sharp peaks synchronous with the Laschamp and Mono Lake geomagnetic field intensity minimal and cosmogenic nuclide peaks in ice cores and marine sediments. Simulations with a geochemical box model suggest that much of the variability can be explained by geomagnetically modulated changes in 14C production rate together with plausible changes in deep-ocean ventilation and the global carbon cycle during glaciation.

  9. Source terms; isolation and radiological consequences of carbon-14 waste in the Swedish SFR repository

    International Nuclear Information System (INIS)

    The source term, isolation capacity, and long-term radiological exposure of 14C from the Swedish underground repository for low and intermediate level waste (SFR) is assessed. The prospective amount of 14C in the repository is assumed to be 5 TBq. Spent ion exchange resins will be the dominant source of 14C. The pore water in the concrete repository is expected to maintain a pH of >10.5 for a period of at least 106 y. The cement matrix of the repository will retain most of the 14CO32- initially present. Bacterial production of CO2 and CH4 from degradation of ion-exchange resins and bitumen may contribute to 14C release to the biosphere. However, CH4 contributes only to a small extent to the overall carbon loss from freshwater ecosystems. The individual doses to local and regional individuals peaked with 5x10-3 and regional individuals peaked with 5x10-3 and 8x10-4 μSv y-1 respectively at about 2.4x104 years. A total leakage of 8.4 GBq of 14C from the repository will cause a total collective dose commitment of 1.1 manSv or 130 manSv TBq-1. (authors)

  10. Comparative temporal analysis of multiwalled carbon nanotube oxidation reactions: Evaluating chemical modifications on true nanotube surface

    Science.gov (United States)

    Pacheco, Flávia G.; Cotta, Alexandre A. C.; Gorgulho, Honória F.; Santos, Adelina P.; Macedo, Waldemar A. A.; Furtado, Clascídia A.

    2015-12-01

    The influence of extensive purification on oxidized multiwalled carbon nanotube surface composition was studied through the characterization and differentiation of the actual surface submitted to three oxidation methods: microwave-assisted acid oxidation, hydrogen peroxide reflux, and Fenton reaction. The oxidized samples were purified by a multi-step procedure including the sequential use of basic reflux and dispersion in dimethylformamide (DMF). The results showed a significant increase in the amount of oxidation debris with hydrogen peroxide and Fenton reaction times longer than 8 h and strong surface characteristic modification. With regard to sample purification, basic reflux led to a reduction in oxygenated group concentration of only 10% in the samples treated by acid oxidation. On the other hand, the subsequent use of DMF led to a further decrease in concentration of 39%, proving to be a more efficient method for the removal of oxidation debris.

  11. Dilepton spectroscopy at intermediate energies; the carbon - carbon reaction at 1 GeV/A; Spectroscopie des dileptons aux energies intermediaires; la reaction carbone - carbone A 1 GeV/A

    Energy Technology Data Exchange (ETDEWEB)

    Prunet, M.

    1995-06-01

    The Physics context of this work is heavy ion collisions at relativistic energies where di-electron provide informations on the produced hot and dense nuclear matter. The experiment is performed by the DiLepton Spectrometer (DLS) Collaboration at the Lawrence Berkeley`s Bevalac. After a description of the apparatus, we review the whole program and the main results so far obtained: first evidence of a significant di-electron signal at energies above 1 GeV/A; improvement of the understanding of di-electron production (electromagnetic decays of hadrons, {pi}{sup +}{pi}{sup -} annihilation and hadronic Bremsstrahlung). The results of p-p, p-d reactions from 1 to 4.9 GeV/A show that hadronic Bremsstrahlung (pp, pn) should be reformulated. Our analysis, optimized on the reaction Carbon-Carbon at 1 GeV/A, has been applied to {alpha}-Ca and d-Ca. We have developed two main aspects: improvement of the time resolution (500 ps) in order to eliminate all of the protons. Improvement of the space resolution (300 {mu}) for better mass resolution, in particular in the {rho} region. We obtain the cross section of di-electron production as a function of mass, transverse momentum and rapidity from the C-C, {alpha}-Ca and d-Ca reactions at 1 GeV/A. We also compare the cross section for all of the measured systems at 1 GeV/A, including Ca-Ca, and we show a (ApAt){sup {alpha}} dependence with {alpha} {approx_equal} 1.1. A study of the associated multiplicity has also been performed. Nevertheless, the limited acceptance of the DLS and its poor mass resolution to identify the {rho}, {omega} vector mesons, do not allow to conclude on hadron behaviour in nuclear matter. This point is one of the main goal of the HADES project at GSI (Darmstadt), which we give a brief description of the main features. (authors). 60 refs.

  12. Hetero-atom doped carbon nanotubes for dye degradation and oxygen reduction reaction

    Energy Technology Data Exchange (ETDEWEB)

    Nandan, Ravi, E-mail: aerawat27@gmail.com; Nanda, Karuna Kar [Materials Research Centre, Indian Institute of Science, Bangalore-560012 (India)

    2015-06-24

    We report the synthesis of nitrogen doped vertically aligned multi-walled (MWNCNTs) carbon nanotubes by pyrolysis and its catalytic performance for degradation of methylene blue (MB) dye & oxygen reduction reaction (ORR). The degradation of MB was monitored spectrophotometrically with time. Kinetic studies show the degradation of MB follows a first order kinetic with rate constant k=0.0178 min{sup −1}. The present rate constant is better than that reported for various supported/non-supported semiconducting nanomaterials. Further ORR performance in alkaline media makes MWNCNTs a promising cost-effective, fuel crossover tolerance, metal-free, eco-friendly cathode catalyst for direct alcohol fuel cell.

  13. Hetero-atom doped carbon nanotubes for dye degradation and oxygen reduction reaction

    International Nuclear Information System (INIS)

    We report the synthesis of nitrogen doped vertically aligned multi-walled (MWNCNTs) carbon nanotubes by pyrolysis and its catalytic performance for degradation of methylene blue (MB) dye & oxygen reduction reaction (ORR). The degradation of MB was monitored spectrophotometrically with time. Kinetic studies show the degradation of MB follows a first order kinetic with rate constant k=0.0178 min−1. The present rate constant is better than that reported for various supported/non-supported semiconducting nanomaterials. Further ORR performance in alkaline media makes MWNCNTs a promising cost-effective, fuel crossover tolerance, metal-free, eco-friendly cathode catalyst for direct alcohol fuel cell

  14. Stepwise Quenching of Exciton Fluorescence in Carbon Nanotubes by Single Molecule Reactions

    CERN Document Server

    Cognet, Laurent; Rocha, John-David R; Doyle, Condell D; Tour, James M; Weisman, R Bruce

    2007-01-01

    Single-molecule chemical reactions with individual single-walled carbon nanotubes were observed through near-infrared photoluminescence microscopy. The emission intensity within distinct submicrometer segments of single nanotubes changes in discrete steps after exposure to acid, base, or diazonium reactants. The steps are uncorrelated in space and time, and reflect the quenching of mobile excitons at localized sites of reversible or irreversible chemical attack. Analysis of step amplitudes reveals an exciton diffusional range of about 90 nanometers, independent of nanotube structure. Each exciton visits approximately 104 atomic sites during its lifetime, providing highly efficient sensing of local chemical and physical perturbations.

  15. Analytical Validation of Accelerator Mass Spectrometry for Pharmaceutical Development: the Measurement of Carbon-14 Isotope Ratio.

    Energy Technology Data Exchange (ETDEWEB)

    Keck, B D; Ognibene, T; Vogel, J S

    2010-02-05

    Accelerator mass spectrometry (AMS) is an isotope based measurement technology that utilizes carbon-14 labeled compounds in the pharmaceutical development process to measure compounds at very low concentrations, empowers microdosing as an investigational tool, and extends the utility of {sup 14}C labeled compounds to dramatically lower levels. It is a form of isotope ratio mass spectrometry that can provide either measurements of total compound equivalents or, when coupled to separation technology such as chromatography, quantitation of specific compounds. The properties of AMS as a measurement technique are investigated here, and the parameters of method validation are shown. AMS, independent of any separation technique to which it may be coupled, is shown to be accurate, linear, precise, and robust. As the sensitivity and universality of AMS is constantly being explored and expanded, this work underpins many areas of pharmaceutical development including drug metabolism as well as absorption, distribution and excretion of pharmaceutical compounds as a fundamental step in drug development. The validation parameters for pharmaceutical analyses were examined for the accelerator mass spectrometry measurement of {sup 14}C/C ratio, independent of chemical separation procedures. The isotope ratio measurement was specific (owing to the {sup 14}C label), stable across samples storage conditions for at least one year, linear over 4 orders of magnitude with an analytical range from one tenth Modern to at least 2000 Modern (instrument specific). Further, accuracy was excellent between 1 and 3 percent while precision expressed as coefficient of variation is between 1 and 6% determined primarily by radiocarbon content and the time spent analyzing a sample. Sensitivity, expressed as LOD and LLOQ was 1 and 10 attomoles of carbon-14 (which can be expressed as compound equivalents) and for a typical small molecule labeled at 10% incorporated with {sup 14}C corresponds to 30 fg

  16. Rapid Access to Spirocyclized Indolenines via Palladium-Catalyzed Cascade Reactions of Tryptamine Derivatives and Propargyl Carbonate

    OpenAIRE

    Montgomery, Thomas D.; Nibbs, Antoinette E.; Zhu, Ye; Rawal, Viresh H.

    2014-01-01

    We report the intermolecular palladium-catalyzed reaction of tert-butyl propargyl carbonate with tryptamine derivatives or other indole-containing bis-nucleophiles. The reaction proceeds under mild conditions and with low catalyst loadings to afford novel spiroindolenine products in good to high yields.

  17. Palladium on Carbon-Catalyzed Suzuki-Miyaura Coupling Reaction Using an Efficient and Continuous Flow System

    Directory of Open Access Journals (Sweden)

    Tomohiro Hattori

    2015-01-01

    Full Text Available The continuous flow Suzuki-Miyaura reaction between various haloarenes and arylboronic acids was successfully achieved within only ca. 20 s during the single-pass through a cartridge filled with palladium on carbon (Pd/C. No palladium leaching was observed in the collected reaction solution by atomic absorption spectrometry (detection limit: 1 ppm.

  18. Benzyl alcohol oxidation in supercritical carbon dioxide: spectroscopic insight into phase behaviour and reaction mechanism.

    Science.gov (United States)

    Caravati, Matteo; Grunwaldt, Jan-Dierk; Baiker, Alfons

    2005-01-21

    Selective oxidation of benzyl alcohol to benzaldehyde with molecular oxygen over an alumina-supported palladium catalyst was performed with high rate at about 95% selectivity in supercritical carbon dioxide. The experiments in a continuous flow fixed-bed reactor showed that the pressure has a strong influence on the reaction rate. A marked increase of the rate (turnover frequency) from 900 h(-1) to 1800 h(-1) was observed when increasing the pressure from 140 to 150 bar. Video monitoring of the bulk fluid phase behavior and the simultaneous investigation by transmission and attenuated total reflection (ATR) infrared spectroscopy at two positions of the view cell showed that the sharp increase in activity is correlated to a transition from a biphasic to a monophasic reaction mixture. In the single phase region, both oxygen and benzyl alcohol are dissolved in the supercritical CO2 phase, which leads to a reduction of the mass transport resistances (both in the external fluid film and in the catalyst pores) and thus to the high reaction rate measured in the catalytic experiments. The phase transition could be effectively and easily monitored by transmission and ATR-IR spectroscopy despite the small concentration of the dense liquid like phase. Deposition of the Pd/Al2O3 catalyst on the ATR-crystal at the bottom of the view cell allowed to gain insight into the chemical changes and mass transfer processes occurring in the solid/liquid interface region during reaction. Analyzing the shift of the upsilon2 bending mode of CO2 gave information on the fluid composition in and outside the catalyst pores. Moreover, the catalytic reaction could be investigated in situ in this spectroscopic batch reactor cell by monitoring simultaneously the reaction progress, the phase behaviour and the catalytic interface. PMID:19785149

  19. Proportion of biogenic carbon in flue gas by carbon-14 measurement - part 2; Biohiili 2

    Energy Technology Data Exchange (ETDEWEB)

    Lehtomaeki, J.; Antson, O.; Hongisto, M. (VTT Technical Research Centre of Finland, Espoo (Finland)) (and others)

    2009-07-01

    The subject of this project is closely related to EU's emissions trading system and to the current and future monitoring needs therein. The determination of fossil part of emissions originated from various fuels by stack measurements or by laboratory analyses could possibly find users also in other fields outside the ETS - Emission Trading Scheme (e.g. waste incineration). After the market analysis and preliminary measurements carried out in the previous Biocarbon project this project focused on the development of the sampling method for stack measurements and to the validation of isotope measurements. The results obtained for fossil proportion of the fuel by current methods will be compared to those obtained by isotope measurements. The operation of the sampling system was tested in long period tests in plant conditions. Moreover, the sample preparation methods and isotope measurements were validated by measuring the proportions of biogenic and fossil carbon of known traffic fuel mixtures. The developed method can also be utilised as a fraud prevention measure related to the expanding international biofuels-trade. (orig.)

  20. A simultaneous evaluation of neutron induced reaction cross sections for 56Fe at En = 14.1 MeV

    International Nuclear Information System (INIS)

    A simultaneous evaluation of neutron induced reaction (i.e., (n,total), (n,n), (n,non), (n,n'), (n,2n), (n,nα), (n,np), (n,γ), (n,p), (n,d), (n,α), (n,n-em), (n,p-em), (n,d-em) and (n,α-em) reaction) cross sections on 56Fe at En = 14.1 MeV is carried out. The evaluated cross sections are compared with the corresponding measured values and the evaluations for CENDL-2, ENDF/B-6, JEF-2.2, JENDL-3 and BROND-2. (9 tabs., 1 fig)

  1. Resonance strength measurement at astrophysical energies: The 17O(p,α)14N reaction studied via Trojan Horse Method

    International Nuclear Information System (INIS)

    In recent years, the Trojan Horse Method (THM) has been used to investigate the low-energy cross sections of proton-induced reactions on 17O nuclei, overcoming extrapolation procedures and enhancement effects due to electron screening. We will report on the indirect study of the 17O(p,α)14N reaction via the THM by applying the approach developed for extracting the resonance strength of narrow resonance in the ultralow energy region. Two measurements will be described and the experimental THM cross sections will be shown for both experiments

  2. Resonance Strength Measurement at Astrophysical Energies: The 17O(p,α)14N Reaction Studied via THM

    Science.gov (United States)

    Sergi, M. L.; Spitaleri, C.; La Cognata, M.; Lamia, L.; Pizzone, R. G.; Rapisarda, G. G.; Mukhamedzhanov, A.; Irgaziev, B.; Tang, X. D.; Wischer, M.; Mrazek, J.; Kroha, V.

    2016-05-01

    In recent years, the Trojan Horse Method (THM) has been used to investigate the low-energy cross sections of proton-induced reactions on 17O nuclei, overcoming extrapolation procedures and enhancement effects due to electron screening. We will report on the indirect study of the 17O(p,α)14N reaction via the Trojan Horse Method by applying the approach developed for extracting the resonance strength of narrow resonance in the ultralow energy region. The mean value of the strengths obtained in the two measurements was calculated and compared with the direct data available in literature.

  3. Resonance strength measurement at astrophysical energies: The 17O(p,α)14N reaction studied via Trojan Horse Method

    Science.gov (United States)

    Sergi, M. L.; Spitaleri, C.; La Cognata, M.; Lamia, L.; Pizzone, R. G.; Rapisarda, G. G.; Mukhamedzhanov, A.; Irgaziev, B.; Tang, X. D.; Wiescher, M.; Mrazek, J.; Kroha, V.

    2015-10-01

    In recent years, the Trojan Horse Method (THM) has been used to investigate the low-energy cross sections of proton-induced reactions on 17O nuclei, overcoming extrapolation procedures and enhancement effects due to electron screening. We will report on the indirect study of the 17O(p,α)14N reaction via the THM by applying the approach developed for extracting the resonance strength of narrow resonance in the ultralow energy region. Two measurements will be described and the experimental THM cross sections will be shown for both experiments.

  4. Resonance Strength Measurement at Astrophysical Energies: The 17O(p,α)14N Reaction Studied via THM

    OpenAIRE

    Sergi M.L.; Spitaleri C.; La Cognata M.; Lamia L.; Pizzone R.G.; Rapisarda G.G.; Mukhamedzhanov A.; Irgaziev B.; Tang X.D.; Wischer M.; Mrazek J.; Kroha V.

    2016-01-01

    In recent years, the Trojan Horse Method (THM) has been used to investigate the low-energy cross sections of proton-induced reactions on 17O nuclei, overcoming extrapolation procedures and enhancement effects due to electron screening. We will report on the indirect study of the 17O(p,α)14N reaction via the Trojan Horse Method by applying the approach developed for extracting the resonance strength of narrow resonance in the ultralow energy region. The mean value of the strengths obtained in ...

  5. Resonance Strength Measurement at Astrophysical Energies: The 17O(p,α14N Reaction Studied via THM

    Directory of Open Access Journals (Sweden)

    Sergi M.L.

    2016-01-01

    Full Text Available In recent years, the Trojan Horse Method (THM has been used to investigate the low-energy cross sections of proton-induced reactions on 17O nuclei, overcoming extrapolation procedures and enhancement effects due to electron screening. We will report on the indirect study of the 17O(p,α14N reaction via the Trojan Horse Method by applying the approach developed for extracting the resonance strength of narrow resonance in the ultralow energy region. The mean value of the strengths obtained in the two measurements was calculated and compared with the direct data available in literature.

  6. Theoretical and Experimental Study on Reaction Coupling: Dehydrogenation of Ethylbenzene in the Presence of Carbon Dioxide

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Dehydrogenation of ethylbenzene (EB) to styrene (ST) in the presence of CO2, in which EB dehydrogenation is coupled with the reverse water-gas shift (RWGS), was investigated extensively through both theoretical analysis and experimental characterization. The reaction coupling proved to be superior to the single dehydrogenation in several respects. Thermodynamic analysis suggests that equilibrium conversion of EB can be improved greatly by reaction coupling due to the simultaneous elimination of the hydrogen produced from dehydrogenation. Catalytic tests proved that iron and vanadium supported on activated carbon or Al2O3 with certain promoters are potential catalysts for this coupling process.The catalysts of iron and vanadium are different in the reaction mechanism, although ST yield is always associated with CO2 conversion over various catalysts. The two-step pathway plays an important role in the coupling process over Fe/Al2O3, while the one-step pathway dominates the reaction over V/Al2O3.Coke deposition and deep reduction of active components are the major causes of catalyst deactivation.CO2 can alleviate the catalyst deactivation effectively through preserving the active species at high valence in the coupling process, though it can not suppress the coke deposition.

  7. Two-neutron transfer reaction mechanisms in $^{12}$C($^6$He,$^{4}$He)$^{14}$C using a realistic three-body $^{6}$He model

    CERN Document Server

    Smalley, D; Nunes, F M; Brown, B A; Adsley, P; Al-Falou, H; Andreoiu, C; Baartman, B; Ball, G C; Blackmon, J C; Boston, H C; Catford, W N; Chagnon-Lessard, S; Chester, A; Churchman, R M; Cross, D S; Diget, C Aa; Di Valentino, D; Fox, S P; Fulton, B R; Garnsworthy, A; Hackman, G; Hager, U; Kshetri, R; Orce, J N; Orr, N A; Paul, E; Pearson, M; Rand, E T; Rees, J; Sjue, S; Svensson, C E; Tardiff, E; Varela, A Diaz; Williams, S J; Yates, S

    2014-01-01

    The reaction mechanisms of the two-neutron transfer reaction $^{12}$C($^6$He,$^4$He) have been studied at 30 MeV at the TRIUMF ISAC-II facility using the SHARC charged-particle detector array. Optical potential parameters have been extracted from the analysis of the elastic scattering angular distribution. The new potential has been applied to the study of the transfer angular distribution to the 2$^+_2$ 8.32 MeV state in $^{14}$C, using a realistic 3-body $^6$He model and advanced shell model calculations for the carbon structure, allowing to calculate the relative contributions of the simultaneous and sequential two-neutron transfer. The reaction model provides a good description of the 30 MeV data set and shows that the simultaneous process is the dominant transfer mechanism. Sensitivity tests of optical potential parameters show that the final results can be considerably affected by the choice of optical potentials. A reanalysis of data measured previously at 18 MeV however, is not as well described by th...

  8. Synthesis of a polycyclic aromatic hydrocarbon marked with carbon-14: (b, d e f) dibenzo-chrysene {sup 14}C-7,14; Synthese d'un hydrocarbure aromatique polycyclique marque au carbone 14: le dibenzo (b, d e f) chrysene {sup 14}C-7,14

    Energy Technology Data Exchange (ETDEWEB)

    Chatelain, G. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1965-07-01

    (b, d e f) dibenzo-chrysene C-7,14 has been synthesized from radioactive carbon dioxide and the organic magnesium compound derived from 1,5 dibromo naphthalene. The product has been purified by a very precise series of fractionated chromatographs on alumina having a chromatographic activity. This has necessitated the development of a special technique. (author) [French] Le dibenzo (b, d e f) chrysene 14C-7,14 a ete synthetise au depart de gaz carbonique radioactif et de bis-organomagnesien derive du dibromo-1,5 naphtalene. Le produit a ete purifie par une serie de chromatographies fractionnees sur alumine d'activite chromatographique tres precise. Ceci a fait l'objet d'une mise au point de technique. (auteur)

  9. Study of 16O(12C,α20Ne)α for the investigation of carbon-carbon fusion reaction via the Trojan Horse Method

    Science.gov (United States)

    Rapisarda, G. G.; Spitaleri, C.; Bordeanu, C.; Hons, Z.; Kiss, G. G.; La Cognata, M.; Mrazek, J.; Nita, C.; Pantelica, D.; Petrascu, H.; Pizzone, R. G.; Romano, S.; Szücs, T.; Trache, L.; Tumino, A.; Velisa, G.

    2016-04-01

    Carbon-carbon fusion reaction represents a nuclear process of great interest in astrophysics, since the carbon burning is connected with the third phase of massive stars (M > 8 M⊙) evolution. In spite of several experimental works, carbon-carbon cross section has been measured at energy still above the Gamow window moreover data at low energy present big uncertainty. In this paper we report the results about the study of the 16O(12C,α 20Ne)α reaction as a possible three-body process to investigate 12C(12C,α)20Ne at astrophysical energy via Trojan Horse Method (THM). This study represents the first step of a program of experiments aimed to measure the 12C+12C cross section at astrophysical energy using the THM.

  10. The reaction of carbon disulphide with -haloketones and primary amines in the presence of potassium iodide as catalyst

    Indian Academy of Sciences (India)

    Javad Safaei-Ghomi; Fariba Salimi; Ali Ramazani

    2013-09-01

    A simple, mild and convenient method has been developed for the synthesis of 3,4,5-trialkyl-1,3-thiazole-2(3)-thione derivatives through one pot three-component reaction between a primary amine, carbon disulphide, and -haloketone in the presence of potassium iodide at room temperature conditions. The products were obtained with excellent yield and appropriate reaction times. This reaction represents a rapid and unprecedented route to the described molecules that have biological specifications.

  11. Multimolecular tracers of terrestrial carbon transfer across the pan-Arctic : 14C characteristics of sedimentary carbon components and their environmental controls

    NARCIS (Netherlands)

    Feng, Xiaojuan; Gustafsson, Örjan; Holmes, R. Max; Vonk, Jorien E.; Van Dongen, Bart E.; Semiletov, Igor P.; Dudarev, Oleg V.; Yunker, Mark B.; Macdonald, Robie W.; Wacker, Lukas; Montluçon, Daniel B.; Eglinton, Timothy I.

    2015-01-01

    Distinguishing the sources, ages, and fate of various terrestrial organic carbon (OC) pools mobilized from heterogeneous Arctic landscapes is key to assessing climatic impacts on the fluvial release of carbon from permafrost. Through molecular 14C measurements, including novel analyses of suberin- a

  12. Validation test for carbon-14 migration and accumulation in a Canadian shield lake

    International Nuclear Information System (INIS)

    This particular BIOMOVS II Technical Report is concerned with modelling the transfer of C-14 through the aquatic food chain following release to a Canadian shield lake. Model performance has been tested against field data supplied by Atomic Energy of Canada Limited. Carbon-14 was added in 1978 to the epilimnion of a small Canadian Shield lake to investigate primary production and carbon dynamics. Data from this experiment were used within BIOMOVS II to provide a validation test, which involved modelling the fate of the C-14 added to the lake. The nature of the spike and the subsequent monitoring allowed the investigation of both short-term processes relevant to evaluation of the impacts of accidental releases as well as longer-term processes relevant to routine release and to solid waste disposal. Four models participated in the scenario: 1) a simple mass balance model of a lake (AECL, Whiteshell Laboratories, Canada); 2) a relatively complex deterministic dynamic compartment model (QuantiSci Ltd.,UK); 3) a complex deterministic model (Studsvik Model A) and a more complex probabilistic model (Studsvik Model B; Studsvik Eco and Safety AB, Sweden). Endpoints were C-14 concentrations in water, sediment and whitefish over a thirteen year period. Each model produced reasonable predictions when compared to the observed data and when uncertainty is taken into consideration. About 0.2 to 0.4% of the initial C-14 inventory to the lakes remained in the water at the end of the study, because of internal recycling of C-14 from sediments. The simple AECL model did not account for this internal recycling of C-14 and, in this respect, its predictions were not as realistic as those of the QuantiSci and Studsvik models for concentrations in water. However, the AECL model predictions for the C-14 inventory remaining in lake sediment were closest to the observed values. Overall, Studsvik Model B was the most accurate in simulating C-14 concentrations in water and in whitefish, but

  13. Stellar Reactions with Short-Lived Nuclei: {sup 17}F ( p,thinsp{alpha}){sup 14}O

    Energy Technology Data Exchange (ETDEWEB)

    Harss, B.; Greene, J.P.; Henderson, D.; Janssens, R.V.; Jiang, C.L.; Nolen, J.; Pardo, R.C.; Rehm, K.E.; Schiffer, J.P.; Siemssen, R.H.; Sonzogni, A.A.; Uusitalo, J.; Wiedenhoever, I. [Argonne National Laboratory, Argonne, Illinois 60439 (United States); Paul, M. [Hebrew University, Jerusalem (Israel); Wang, T.F. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Borasi, F.; Segel, R.E. [Northwestern University, Evanston, Illinois 60439 (United States); Blackmon, J.C.; Smith, M.S. [Physics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6354 (United States); Chen, A.; Parker, P. [Wright Nuclear Structure Laboratory, Yale University, New Haven, Connecticut 06520-8124 (United States)

    1999-05-01

    A method has been developed that can provide beams of many short-lived nuclei of interest in nucleosynthesis along the rp process path. With a {sup 17}F beam (T{sub 1/2}=64 s ) the excitation function of the {sup 17}F( p,thinsp{alpha}){sup 14} O reaction was measured to determine properties of excited states in {sup 18}Ne . These states influence the rate of the {sup 14}O( {alpha},thinspp){sup 17} F reaction which is important for understanding energy generation and nucleosynthesis in x-ray bursts. The present direct measurements yield a pattern of resonances and cross sections which differ substantially from previous estimates. {copyright} {ital 1999} {ital The American Physical Society}

  14. Elucidation of the involvement of p14, a sperm protein during maturation, capacitation and acrosome reaction of caprine spermatozoa.

    Directory of Open Access Journals (Sweden)

    Pinki Nandi

    Full Text Available Mammalian sperm capacitation is an essential prerequisite to fertilization. Although progress is being made in understanding the physiology and biochemistry of capacitation, little has been yet explored about the potential role(s of individual sperm cell protein during this process. Therefore elucidation of the role of different sperm proteins in the process of capacitation might be of great importance to understand the process of fertilization. The present work describes the partial characterization of a 14-kDa protein (p14 detected in goat spermatozoa using an antibody directed against the purified protein. Confocal microscopic analysis reveals that the protein is present in both the intracellular and extracellular regions of the acrosomal and postacrosomal portion of caudal sperm head. Though subcellular localization shows that p14 is mainly cytosolic, however it is also seen to be present in peripheral plasma membrane and soluble part of acrosome. Immuno-localization experiment shows change in the distribution pattern of this protein upon induction of capacitation in sperm cells. Increased immunolabeling in the anterior head region of live spermatozoa is also observed when these cells are incubated under capacitating conditions, whereas most sperm cells challenged with the calcium ionophore A23187 to acrosome react, lose their labeling almost completely. Intracellular distribution of p14 also changes significantly during acrosome reaction. Interestingly, on the other hand the antibody raised against this 14-kDa sperm protein enhances the forward motility of caprine sperm cells. Rose-Bengal staining method shows that this anti-p14 antibody also decreases the number of acrosome reacted cells if incubated with capacitated sperm cells before induction of acrosome reaction. All these results taken together clearly indicate that p14 is intimately involved and plays a critical role in the acrosomal membrane fusion event.

  15. INTERMEDIATE-MASS FRAGMENTS IN N-14+TB-159/AG-NAT/CU-NAT REACTIONS AT 22 MEV/U

    NARCIS (Netherlands)

    SOSIN, Z; BRZYCHCZYK, J; GROTOWSKI, K; HINNEFELD, JD; KOLDENHOF, EE; KOZIK, T; LEEGTE, HKW; LUKASIK, J; MICEK, S; PLANETA, R; SIEMSSEN, RH; WIELOCH, A; WILSCHUT, HW

    1994-01-01

    The yields of intermediate-mass fragments from the reactions N-14 + Tb-159/(nat)Ag/(nat)Cu have been measured at 22 MeV/u. A complete set of double-differential cross sections d2sigma/dE dOMEGA ranging from 15-degrees to 165-degrees and with low-energy thresholds has been obtained. The evolution of

  16. Multipolarity analysis for 14C high-energy resonance populated by (18O,16O) two-neutron transfer reaction

    International Nuclear Information System (INIS)

    The 12C(18O,16O)14C reaction at 84 MeV incident energy has been explored up to high excitation energy of the residual nucleus thanks to the use of the MAGNEX spectrometer to detect the ejectiles. In the region above the two-neutron separation energy, a resonance has been observed at 16.9 MeV. A multipolarity analysis of the cross section angular distribution indicates an L = 0 character for such a transition

  17. The first chiral diene-based metal-organic frameworks for highly enantioselective carbon-carbon bond formation reactions

    Energy Technology Data Exchange (ETDEWEB)

    Sawano, Takahiro; Ji, Pengfei; McIsaac, Alexandra R.; Lin, Zekai; Abney, Carter W.; Lin, Wenbin [UC

    2016-02-01

    We have designed the first chiral diene-based metal–organic framework (MOF), E₂-MOF, and postsynthetically metalated E₂-MOF with Rh(I) complexes to afford highly active and enantioselective single-site solid catalysts for C–C bond formation reactions. Treatment of E₂-MOF with [RhCl(C₂H₄)₂]₂ led to a highly enantioselective catalyst for 1,4-additions of arylboronic acids to α,β-unsaturated ketones, whereas treatment of E₂-MOF with Rh(acac)(C₂H₄)₂ afforded a highly efficient catalyst for the asymmetric 1,2-additions of arylboronic acids to aldimines. Interestingly, E₂-MOF·Rh(acac) showed higher activity and enantioselectivity than the homogeneous control catalyst, likely due to the formation of a true single-site catalyst in the MOF. E₂-MOF·Rh(acac) was also successfully recycled and reused at least seven times without loss of yield and enantioselectivity.

  18. Effect of denitrifying bacteria on the electrochemical reaction of activated carbon fiber in electrochemical biofilm system

    Institute of Scientific and Technical Information of China (English)

    YING Diwen; JIA Jinping; ZHANG Lehua

    2007-01-01

    An electrochemical-activated denitrifying biofilm system consisting of activated carbon fiber electrodes immobilized with denitrifying bacteria film as cathode was studied.A revised model for an electrochemical-activated denitrifying biofilm was developed and validated by electrochemical analysis of cathodal polarization curves and nitrate consumption rate.The cathodal polarization curve and nitrate consumption rate were introduced to verify the rate of electrochemical reaction and the activity of denitrifying bacteria,respectively.It was shown that the denitrification process effectively strengthened the electrochemical reaction while the electron also intensified denitrification activity.Electron was transferred between electrochemical process and biological process not only by hydrogen molecule but also by new produced active hydrogen atom.Additionally,a parameter of apparent exchange current density was deprived from the cathodal polarization curve with high overpotential,and a new bio-effect current density was defined through statistical analysis,which was linearly dependent to the activity of denitrification bacteria.Activated carbon fiber (ACF) electrode was also found to be more suitable to the electrochemical denitrifying system compared with graphite and platinum.

  19. Neutron multiplicity distributions for 30 MeVu sup 14 N reactions with the indicated targets

    Energy Technology Data Exchange (ETDEWEB)

    1992-06-01

    This report contains short papers on the following topics: Heavy ion reactions; nuclear structure and fundamental interactions; nuclear theory; atomic molecular and materials science; and superconducting cyclotron and instrumentation. (LSP)

  20. Neutron multiplicity distributions for 30 MeVu 14N reactions with the indicated targets

    International Nuclear Information System (INIS)

    This report contains short papers on the following topics: Heavy ion reactions; nuclear structure and fundamental interactions; nuclear theory; atomic molecular and materials science; and superconducting cyclotron and instrumentation

  1. Interfacial Cu+ promoted surface reactivity: Carbon monoxide oxidation reaction over polycrystalline copper-titania catalysts

    Science.gov (United States)

    Senanayake, Sanjaya D.; Pappoe, Naa Adokaley; Nguyen-Phan, Thuy-Duong; Luo, Si; Li, Yuanyuan; Xu, Wenqian; Liu, Zongyuan; Mudiyanselage, Kumudu; Johnston-Peck, Aaron C.; Frenkel, Anatoly I.; Heckler, Ilana; Stacchiola, Dario; Rodriguez, José A.

    2016-10-01

    We have studied the catalytic carbon monoxide (CO) oxidation (CO + 0.5O2 → CO2) reaction using a powder catalyst composed of both copper (5 wt.% loading) and titania (CuOx-TiO2). Our study was focused on revealing the role of Cu, and the interaction between Cu and TiO2, by systematic comparison between two nanocatalysts, CuOx-TiO2 and pure CuOx. We interrogated these catalysts under in situ conditions using X-ray diffraction (XRD), X-ray absorption fine structure (XAFS) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) to probe the structure and electronic properties of the catalyst at all stages of the reaction and simultaneously probe the surface states or intermediates of this reaction. With the aid of several ex situ characterization techniques including transmission electron microscopy (TEM), the local catalyst morphology and structure were also studied. Our results show that a CuOx-TiO2 system is more active than bulk CuOx for the CO oxidation reaction due to its lower onset temperature and better stability at higher temperatures. Our results also suggest that surface Cu+ species observed in the CuOx-TiO2 interface are likely to be a key player in the CO oxidation mechanism, while implicating that the stabilization of this species is probably associated with the oxide-oxide interface. Both in situ DRIFTS and XAFS measurements reveal that there is likely to be a Cu(Ti)-O mixed oxide at this interface. We discuss the nature of this Cu(Ti)-O interface and interpret its role on the CO oxidation reaction.

  2. Observation and analysis of incomplete fusion reactions induced by (12C, 14N, 16O, 22Ne) ions

    International Nuclear Information System (INIS)

    The mechanism of the reactions induced by heavy ions has been studied. The experiments were concerned with incident channels which lead to the formation of intermediate nuclei with atomic mass (6412C, 14N, 16O, 22Ne) as projectiles respectively. The detection of light fragments (2< Z<12) is studied. A three solid-state-detector telescope, with associated electronics is used which allows the separation of reaction products according to their charge. The main features of deep inelastic collisions are discussed: large kinetic energy loss, and important nucleon transfer as a function of the angular detection. The time evolution of the reaction has been studied, then the results are compared with a scattering model suggested by Noremberg. A theoretical calculation based on both classical and statistical approaches giving the total cross-sections for any exit channel has been proposed

  3. Application of bis-(L zinc prolinate (II on the synthesis reactions of some 1,4-dyhidropyridines

    Directory of Open Access Journals (Sweden)

    Cristiane R. Winck

    2012-06-01

    Full Text Available The 1,4-Dyhidropyridine (DHP is a class of substances that presents a wide spectrum of biological activities. Among these applications, it can be applied on the treatment of cardiovascular diseases e.g. hypertension. This project proposes the synthesis of some DHPs through multicomponent reactions (one pot using bis-(L zinc prolinate (II as catalyst. Initially the synthesis of the precursor enamine was held using the catalyst and later, there was an addition of cinnmaldehyde to the same reaction media. Such procedure resulted on the formation of the compound of interest (Figure 1. Another important factor is that the ultrasound was used to reach the results, which makes such reactions highly convergent and coherent with the principles of the Green Chemistry.

  4. Matrix isolation study of the ozonolysis of 1,3- and 1,4-cyclohexadiene: identification of novel reaction pathways.

    Science.gov (United States)

    Pinelo, Laura; Gudmundsdottir, Anna D; Ault, Bruce S

    2013-05-23

    The ozonolysis reactions of 1,3- and 1,4-cyclohexadiene have been studied using a combination of matrix isolation, infrared spectroscopy, and theoretical calculations. Experimental and theoretical results demonstrate that these reactions predominantly do not follow the long-accepted Criegee mechanism. Rather, the reaction of O3 with 1,4-cyclohexadiene leads to the essentially barrierless formation of benzene, C6H6, and H2O3. These two species are then trapped in the same argon matrix cage and weakly interact to form a molecular complex. There is also evidence for the formation of a small amount of the primary ozonide as a minor product, formed through a transition state that is slightly higher in energy. The reaction of O3 with 1,3-cyclohexadiene follows two pathways, one of which is the Criegee mechanism through a low energy transition state leading to formation of the primary ozonide. In addition, with a similar barrier, ozone abstracts a single hydrogen from C5 while adding to C1, forming a hydroperoxy intermediate. This study presents two of the rare cases in which the Criegee mechanism is not the dominant pathway for the ozonolysis of an alkene as well as the first evidence for dehydrogenation of an alkene by ozone. PMID:23638640

  5. Heating Treated Carbon Nanotubes As Highly Active Electrocatalysts for Oxygen Reduction Reaction

    International Nuclear Information System (INIS)

    Graphical abstract: Heating treatment for multi-walled carbon nanotubes in the air introduces abundant structure defects which improve catalytic performances for oxygen reduction reaction (ORR). There is a positive correlation between the defect levels and ORR activities. The product shows better methanol tolerance and long-term durability than commercial Pt/C which makes it applicable in fuel cells. - Abstract: Carbon nanotubes (CNTs) have been widely developed for electrochemical energy conversion and storage devices for replacement of high-cost Pt-based catalysts. In this paper, a simple and convenient method is developed for improving the catalytic activity of CNTs in a controlled way. By simple heating treatment in the air, the multi-walled carbon nanotubes (MWCNTs) change with special morphologies, compositions and abundant defects (denoted as h-CNT). Those defects significantly improve the electrocatalytic performances for oxygen reduction reaction (ORR) which proceeds in a nearly four-electron pathway. The heating conditions have important effects on the structures and defect properties of h-CNTs which show a positive correlation between the defect levels and ORR performances. The small amounts of iron residues originated from nanotube growth and nitrogen doping during heating treatment also contribute to some catalytic activity. The inner walls of h-CNT remain intact during heating treatment and provide sufficient conductivity which facilitates charge transport during ORR. The h-CNT electrocatalyst shows better methanol tolerance and long-term durability than commercial Pt/C in alkaline media which makes it an alternative cathode catalyst in fuel cells

  6. N-doped carbon nanomaterials are durable catalysts for oxygen reduction reaction in acidic fuel cells.

    Science.gov (United States)

    Shui, Jianglan; Wang, Min; Du, Feng; Dai, Liming

    2015-02-01

    The availability of low-cost, efficient, and durable catalysts for oxygen reduction reaction (ORR) is a prerequisite for commercialization of the fuel cell technology. Along with intensive research efforts of more than half a century in developing nonprecious metal catalysts (NPMCs) to replace the expensive and scarce platinum-based catalysts, a new class of carbon-based, low-cost, metal-free ORR catalysts was demonstrated to show superior ORR performance to commercial platinum catalysts, particularly in alkaline electrolytes. However, their large-scale practical application in more popular acidic polymer electrolyte membrane (PEM) fuel cells remained elusive because they are often found to be less effective in acidic electrolytes, and no attempt has been made for a single PEM cell test. We demonstrated that rationally designed, metal-free, nitrogen-doped carbon nanotubes and their graphene composites exhibited significantly better long-term operational stabilities and comparable gravimetric power densities with respect to the best NPMC in acidic PEM cells. This work represents a major breakthrough in removing the bottlenecks to translate low-cost, metal-free, carbon-based ORR catalysts to commercial reality, and opens avenues for clean energy generation from affordable and durable fuel cells.

  7. Cu,N-codoped Hierarchical Porous Carbons as Electrocatalysts for Oxygen Reduction Reaction.

    Science.gov (United States)

    Yu, Haiyan; Fisher, Adrian; Cheng, Daojian; Cao, Dapeng

    2016-08-24

    It remains a huge challenge to develop nonprecious electrocatalysts with high activity to substitute commercial Pt catalysts for oxygen reduction reactions (ORR). Here, the Cu,N-codoped hierarchical porous carbon (Cu-N-C) with a high content of pyridinic N was synthesized by carbonizing Cu-containing ZIF-8. Results indicate that Cu-N-C shows excellent ORR electrocatalyst properties. First of all, it nearly follows the four-electron route, and its electron transfer number reaches 3.92 at -0.4 V. Second, both the onset potential and limited current density of Cu-N-C are almost equal to those of a commercial Pt/C catalyst. Third, it exhibits a better half-wave potential (∼16 mV) than a commercial Pt/C catalyst. More importantly, the Cu-N-C displays better stability and methanol tolerance than the Pt/C catalyst. All of these good properties are attributed to hierarchical structure, high pyridinic N content, and the synergism of Cu and N dopants. The metal-N codoping strategy can significantly enhance the activity of electrocatalysts, and it will provide reference for the design of novel N-doped porous carbon ORR catalysts. PMID:27490846

  8. N-doped carbon nanomaterials are durable catalysts for oxygen reduction reaction in acidic fuel cells

    Science.gov (United States)

    Shui, Jianglan; Wang, Min; Du, Feng; Dai, Liming

    2015-01-01

    The availability of low-cost, efficient, and durable catalysts for oxygen reduction reaction (ORR) is a prerequisite for commercialization of the fuel cell technology. Along with intensive research efforts of more than half a century in developing nonprecious metal catalysts (NPMCs) to replace the expensive and scarce platinum-based catalysts, a new class of carbon-based, low-cost, metal-free ORR catalysts was demonstrated to show superior ORR performance to commercial platinum catalysts, particularly in alkaline electrolytes. However, their large-scale practical application in more popular acidic polymer electrolyte membrane (PEM) fuel cells remained elusive because they are often found to be less effective in acidic electrolytes, and no attempt has been made for a single PEM cell test. We demonstrated that rationally designed, metal-free, nitrogen-doped carbon nanotubes and their graphene composites exhibited significantly better long-term operational stabilities and comparable gravimetric power densities with respect to the best NPMC in acidic PEM cells. This work represents a major breakthrough in removing the bottlenecks to translate low-cost, metal-free, carbon-based ORR catalysts to commercial reality, and opens avenues for clean energy generation from affordable and durable fuel cells. PMID:26601132

  9. Cu,N-codoped Hierarchical Porous Carbons as Electrocatalysts for Oxygen Reduction Reaction.

    Science.gov (United States)

    Yu, Haiyan; Fisher, Adrian; Cheng, Daojian; Cao, Dapeng

    2016-08-24

    It remains a huge challenge to develop nonprecious electrocatalysts with high activity to substitute commercial Pt catalysts for oxygen reduction reactions (ORR). Here, the Cu,N-codoped hierarchical porous carbon (Cu-N-C) with a high content of pyridinic N was synthesized by carbonizing Cu-containing ZIF-8. Results indicate that Cu-N-C shows excellent ORR electrocatalyst properties. First of all, it nearly follows the four-electron route, and its electron transfer number reaches 3.92 at -0.4 V. Second, both the onset potential and limited current density of Cu-N-C are almost equal to those of a commercial Pt/C catalyst. Third, it exhibits a better half-wave potential (∼16 mV) than a commercial Pt/C catalyst. More importantly, the Cu-N-C displays better stability and methanol tolerance than the Pt/C catalyst. All of these good properties are attributed to hierarchical structure, high pyridinic N content, and the synergism of Cu and N dopants. The metal-N codoping strategy can significantly enhance the activity of electrocatalysts, and it will provide reference for the design of novel N-doped porous carbon ORR catalysts.

  10. The key role of metal dopants in nitrogen-doped carbon xerogel for oxygen reduction reaction

    Science.gov (United States)

    Liu, Sisi; Deng, Chengwei; Yao, Lan; Zhong, Hexiang; Zhang, Huamin

    2014-12-01

    Highly active non-precious metal catalysts based on nitrogen-doped carbon xerogel (NCX) for the oxygen reduction reaction (ORR) is prepared with resorcinol(R)-formaldehyde (F) resin as carbon precursor and NH3 as nitrogen source. NCX samples doped with various transition metal species are investigated to elucidate the effect of transition metals on the structure and ORR activity of the products. As-prepared NCX catalysts with different metals are characterized using nitrogen-adsorption analysis, X-ray diffractometry, X-ray photoelectron spectroscopy, and Raman spectroscopy. The structural properties and ORR activities of the catalysts are altered by addition of different metals, and NCX doped with iron exhibits the best ORR activity. Metal doping evidently promotes the formation of more micropores and mesopores. Raman and XPS studies reveal that iron, cobalt, and nickel can increase pyridinic-N contents and that iron can catalyse the formation of graphene structures and enhance quaternary-N contents. Whereas the total N-content does not determine ORR activity, Metal-N4/C-like species generated from the interaction of the metals with nitrogen and carbon atoms play important roles in achieving high ORR activity.

  11. Prise en compte du carbone 14 dans le modèle PASIM

    OpenAIRE

    Duclos, Etienne

    2010-01-01

    J'ai effectué mon stage de fin d'étude d'ingénieur ISIMA au sein de l'Institut National de la Recherche Agronomique (INRA), dans l'Unité de Recherche sur l'Ecosystème Prairial (UREP). Mon stage a été effectué en collaboration avec l'Institut de Radioprotection et de Sûreté Nucléaire (IRSN). J'ai été chargé d'ajouter la gestion du carbone 14 au sein de PaSim, modèle de simulation de prairie gérant déjà les flux de carbone et d'azote. Il m'a donc fallu faire la distinction, au...

  12. Effect of Reaction Temperature on Carbon Yield and Morphology of CNTs on Copper Loaded Nickel Nanoparticles

    Directory of Open Access Journals (Sweden)

    Hu Ming

    2016-01-01

    Full Text Available This investigation was attempted to introduce carbon nanotubes (CNTs onto surface of copper powders in order to improve heat transfer performance of copper matrix for engineering application of electrical packaging materials. The Ni/MgO catalyst was formed on the copper powders surface by means of codeposition method. CVD technique was executed to fabricate uniform CNTs on copper powders and effect of reaction temperature on the morphology of CNTs was surveyed. The results showed that CNTs products on the copper powder surface were distributed uniformly even if reaction temperature was different. The diameter dimension of CNTs was within the scope of 30~60 nm. Growth behaviors of CNTs by CVD method were considered to be “tip-growth” mechanism. Raman spectra of CNTs proved that intensity ratio of D-band to G-band (ID/IG increased as deposition reaction temperature increased, which implied that order degree of graphitic structure in synthesized CNTs improved.

  13. Revealing Brown Carbon Chromophores Produced in Reactions of Methylglyoxal with Ammonium Sulfate

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Peng; Laskin, Julia; Nizkorodov, Sergey A.; Laskin, Alexander

    2015-12-15

    Atmospheric brown carbon (BrC) is an important contributor to light absorption and climate forcing by aerosols. Reactions between small water-soluble carbonyls and ammonia or amines have been identified as one of the potential pathways of BrC formation. However, detailed chemical characterization of BrC chromophores has been challenging and their formation mechanisms are still poorly understood. Understanding BrC formation is impeded by the lack of suitable methods which can unravel the variability and complexity of BrC mixtures. This study applies high performance liquid chromatography (HPLC) coupled to photodiode array (PDA) detector and high resolution mass spectrometry (HRMS) to investigate optical properties and chemical composition of individual BrC components produced through reactions of methylglyoxal (MG) and ammonium sulfate (AS), both of which are abundant in the atmospheric environment. A direct relationship between optical properties and chemical composition of 30 major BrC chromophores was established. Nearly all of these chromophores are nitrogen-containing compounds that account for >70% of the overall light absorption by the MG+AS system in the 300-500 nm range. These results suggest that reduced-nitrogen organic compounds formed in reactions between atmospheric carbonyls and ammonia/amines are important BrC chromophores. It is also demonstrated that improved separation of BrC chromophores by HPLC will significantly advance understanding of BrC chemistry.

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

    Science.gov (United States)

    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

  15. Synthesis of {delta}-aminolevulic acid. Application to the introduction of carbon-14 and of tritium; Syntheses de l'acide {delta} aminolevulique. Application a l'introduction de carbone 14 et de tritium

    Energy Technology Data Exchange (ETDEWEB)

    Loheac, J. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1966-06-01

    Several new syntheses of {delta} aminolevulic acid ({delta} A.L.A.) have been studied. {sup 14}C-4 {delta} - aminolevulic acid has been obtained from {sup 14}C allylacetic carboxylic acid with a yield of 30 per cent with respect to barium carbonate and with a specific activity of 32 mCi/mM. The {sup 14}C-1 or {sup 14}C-2 {delta}-A.L.A. has been prepared from the {sup 14}C-1 or {sup 14}C-2 acetate with a yield of 55 per cent with respect to the acetate. Finally the tritiated {delta}-A.L.A. has been obtained for the first time by tritiation of ethyl phthalimidodehydrolevulate. (author) [French] Plusieurs syntheses nouvelles de l'acide {delta}-aminolevulique ont ete etudiees. L'acide {delta}-aminolevulique {sup 14}C-4 a ete obtenu a partir d'acide allylacetique carboxylique {sup 14}C, avec un rendement global de 30 pour cent par rapport au carbonate de baryum a une activite specifique de 32 mCi/M. Le {delta}-A.A.L. {sup 14}C-1 ou {sup 14}C-2 a ete obtenu a partir d'acetate {sup 14}C-1 ou {sup 14}C-2 avec un rendement de 55 pour cent par rapport a l'acetate. Enfin le {delta}-A.A.L. tritie a ete obtenu pour la premiere fois par tritiation du phtalimidodehydrolevulate d'ethyle. (auteur)

  16. Tritium- and carbon-14-contents of wines of different vintage from the northern and southern hemisphere

    International Nuclear Information System (INIS)

    The carbon-14 and tritium radioactivity contents of up to 19 vintages of German and Southafrican wines were compared. A similar large dependence of the 14C- and of the 3H-activity in the German wine on the nuclear weapon tests of the years 1962/63 was found out. The radioactivity level is also 1977/78 still essentially higher than before 1950. The Southafrican wines have been influenced considerably less by nuclear explosions. The highest 3H-values were found in the vintage 1963 of the German wine with 5910 pCi/litre and in the vintage 1964 of the Southafrican wine with 510 pCi/litre. (orig.)

  17. First direct measurement of the 11C (α ,p )14N stellar reaction by an extended thick-target method

    Science.gov (United States)

    Hayakawa, S.; Kubono, S.; Kahl, D.; Yamaguchi, H.; Binh, D. N.; Hashimoto, T.; Wakabayashi, Y.; He, J. J.; Iwasa, N.; Kato, S.; Komatsubara, T.; Kwon, Y. K.; Teranishi, T.

    2016-06-01

    The 11C(α,p ) 14N reaction is an important α -induced reaction competing with β -limited hydrogen-burning processes in high-temperature explosive stars. We directly measured its reaction cross sections both for the ground-state transition (α ,p0) and the excited-state transitions (α ,p1) and (α ,p2) at relevant stellar energies 1.3-4.5 MeV by an extended thick-target method featuring time of flight for the first time. We revised the reaction rate by numerical integration including the (α ,p1) and (α ,p2) contributions and also low-lying resonances of (α ,p0) using both the present and the previous experimental data which were totally neglected in the previous compilation works. The present total reaction rate lies between the previous (α ,p0) rate and the total rate of the Hauser-Feshbach statistical model calculation, which is consistent with the relevant explosive hydrogen-burning scenarios such as the ν p process.

  18. Localized surface grafting reactions on carbon nanofibers induced by gamma and e-beam irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Evora, M.C., E-mail: cecilia@ieav.cta.br [Institute for Advanced Studies-IEAV/DCTA, Av. Cel Jose Alberto Albano do Amarante, 1-Putim, 12228-001 São Jose dos Campos, SP (Brazil); Araujo, J.R., E-mail: jraraujo@inmetro.gov.br [Instituto Nacional de Metrologia, Qualidade e Tecnologia, Av. Nossa Sra. das Graças, 50, 25250-020 Duque de Caxias, RJ (Brazil); Ferreira, E.H.M. [Instituto Nacional de Metrologia, Qualidade e Tecnologia, Av. Nossa Sra. das Graças, 50, 25250-020 Duque de Caxias, RJ (Brazil); Strohmeier, B.R. [Thermo Fisher Scientific, 5225 Verona Road, Madison, WI 53711 (United States); Silva, L.G.A., E-mail: lgasilva@ipen.br [Institute for Nuclear and Energy Research- IPEN, Av. Prof lineu Prestes, 2242- Cidade Universitaria, 05508-000 SP (Brazil); Achete, C.A. [Instituto Nacional de Metrologia, Qualidade e Tecnologia, Av. Nossa Sra. das Graças, 50, 25250-020 Duque de Caxias, RJ (Brazil)

    2015-04-30

    Graphical abstract: - Highlights: • Methodology for the functionalization of carbon nanofibers was investigated. • Two radiation sources were used to promote grafting reactions: gamma and electron beam. • We report the optimum inhibitor concentration to achieve the functionalization. • Surface of carbon nanofibers showed an increase of oxygen content after irradiation. • The radiation-induced graphitization did not damage the overall sp{sup 2} structure. - Abstract: Electron beam and gamma-ray irradiation have potential application to modify the carbon fiber nanostructures in order to produce useful defects in the graphitic structure and create reactive sites. In this study, the methodology to functionalize carbon nanofiber (CNF), via a radiation process and using acrylic acid as a source of oxygen functional groups, was investigated. The samples were submitted to a direct grafting radiation process with electron beam and gamma-ray source. Several parameters were changed such as: acrylic acid concentration, radiation dose and percentage of inhibitor necessary to achieve functionalization, with higher percentage of oxygen functional groups on CNF surface, and better dispersion. The better results achieved were when mixing CNF in a solution of acrylic acid with 6% of inhibitor (FeSO{sub 4}·7H{sub 2}O) and irradiated at 100 kGy. The samples were characterized by X-ray photoelectron spectroscopy and the surface composition (atomic%) showed a significant increase of oxygen content for the samples after irradiation. Also, the dispersion of the functionalized CNF in water was stable during months which may be a good indication that the functionalization process of CNF via ionizing radiation was successful.

  19. Final Report: The Impact of Carbonate on Surface Protonation, Electron Transfer and Crystallization Reactions in Iron Oxide Nanoparticles and Colloids

    Energy Technology Data Exchange (ETDEWEB)

    Dixon, David Adams [The University of Alabama

    2013-07-02

    This project addresses key issues of importance in the geochemical behavior of iron oxides and in the geochemical cycling of carbon and iron. For Fe, we are specifically studying the influence of carbonate on electron transfer reactions, solid phase transformations, and the binding of carbonate to reactive sites on the edges of particles. The emphasis on carbonate arises because it is widely present in the natural environment, is known to bind strongly to oxide surfaces, is reactive on the time scales of interest, and has a speciation driven by acid-base reactions. The geochemical behavior of carbonate strongly influences global climate change and CO{sub 2} sequestration technologies. Our goal is to answer key questions with regards to specific site binding, electron transfer reactions, and crystallization reactions of iron oxides that impact both the geochemical cycling of iron and CO{sub 2} species. Our work is focused on the molecular level description of carbonate chemistry in solution including the prediction of isotope fractionation factors. We have also done work on critical atmospheric species.

  20. Up-Scaling Geochemical Reaction Rates for Carbon Dioxide (CO2) in Deep Saline Aquifers

    Energy Technology Data Exchange (ETDEWEB)

    Peters, Catherine A

    2013-02-28

    Geochemical reactions in deep subsurface environments are complicated by the consolidated nature and mineralogical complexity of sedimentary rocks. Understanding the kinetics of these reactions is critical to our ability to make long-term predictions about subsurface processes such as pH buffering, alteration in rock structure, permeability changes, and formation of secondary precipitates. In this project, we used a combination of experiments and numerical simulation to bridge the gap between our knowledge of these reactions at the lab scale and rates that are meaningful for modeling reactive transport at core scales. The focus is on acid-driven mineral dissolution, which is specifically relevant in the context of CO2-water-rock interactions in geological sequestration of carbon dioxide. The project led to major findings in three areas. First, we modeled reactive transport in pore-network systems to investigate scaling effects in geochemical reaction rates. We found significant scaling effects when CO2 concentrations are high and reaction rates are fast. These findings indicate that the increased acidity associated with geological sequestration can generate conditions for which proper scaling tools are yet to be developed. Second, we used mathematical modeling to investigate the extent to which SO2, if co-injected with CO2, would acidify formation brines. We found that there exist realistic conditions in which the impact on brine acidity will be limited due to diffusion rate-limited SO2 dissolution from the CO2 phase, and the subsequent pH shift may also be limited by the lack of availability of oxidants to produce sulfuric acid. Third, for three Viking sandstones (Alberta sedimentary basin, Canada), we employed backscattered electron microscopy and energy dispersive X-ray spectroscopy to statistically characterize mineral contact with pore space. We determined that for reactive minerals in sedimentary consolidated rocks, abundance alone is not a good predictor of

  1. Analysis and Characterization of Organic Carbon in Early Holocene Wetland Paleosols using Ramped Pyrolysis 14C and Biomarkers

    Science.gov (United States)

    Vetter, L.; Schreiner, K. M.; Fernandez, A.; Rosenheim, B. E.; Tornqvist, T. E.

    2014-12-01

    Radiocarbon analyses are a key tool for quantifying the dynamics of carbon cycling and storage in both modern soils and Quaternary paleosols. Frequently, bulk 14C dates of paleosol organic carbon provide ages older than the time of soil burial, and 14C dates of geochemical fractions such as alkali and acid extracts (operationally defined as humic acids) can provide anomalously old ages when compared to coeval plant macrofossil dates. Ramped pyrolysis radiocarbon analysis of sedimentary organic material has been employed as a tool for investigating 14C age spectra in sediments with multiple organic carbon sources. Here we combine ramped pyrolysis 14C analysis and biomarker analysis (lignin-phenols and other cupric oxide products) to provide information on the source and diagenetic state of the paleosol organic carbon. We apply these techniques to immature early Holocene brackish wetland entisols from three sediment cores in southeastern Louisiana, along with overlying basal peats. Surprisingly, we find narrow 14C age spectra across all thermal aliquots from both paleosols and peats. The weighted bulk 14C ages from paleosols and overlying peats are within analytical error, and are comparable to independently analyzed 14C AMS dates from charcoal fragments and other plant macrofossils from each peat bed. Our results suggest high turnover rates of carbon in soils relative to input of exogenous carbon sources. These data raise broader questions about processes within the active soil and during pedogenesis and burial of paleosols that can effectively homogenize radiocarbon content in soils across the thermochemical spectrum. The concurrence of paleosol and peat 14C ages also suggests that, in the absence of peats with identifiable plant macrofossils, ramped pyrolysis 14C analyses of paleosols may be used to provide ages for sea-level indicators.

  2. The influence of experimental setup on the spectroscopy investigation of $^{\\mathrm{14}}$Be by Coulomb breakup reaction

    CERN Document Server

    Song, Yu-Shou; Hu, Li-Yuan; Liu, Hui-Lan; Wu, Hong-Yi

    2015-01-01

    The two-body core+$2n$ cluster structure was implemented to describe the two-neutron halo nucleus $^{\\mathrm{14}}\\mathrm{Be}$, where the core$^{\\mathrm{12}}\\mathrm{Be}$ was assumed inert and at ground state and the dineutron was assumed at pure $2S_0$ state. Based on such a structure the three-body continuum-discretized coupled-channel (CDCC) calculation was successfully used to deal with the $^{\\mathrm{14}}\\mathrm{Be}$ breakup reactions of $^{\\mathrm{14}}\\mathrm{Be}+^{\\mathrm{12}}\\mathrm{C}$ at 68~MeV/nucleon and $^{\\mathrm{14}}\\mathrm{Be}+ $Pb at 35~MeV/nucleon.Consequently, we modeled the kinematically complete measurement experiment of $^{\\mathrm{14}}\\mathrm{Be}$ (35~MeV/nucleon) Coulomb breakup at a lead target with the help of Geant4. From the simulation data the relative energy spectrum was constructed by the invariant mass method and $B(E1)$ spectrum was extracted using virtual photon model. The influence of the target thickness and detector performance on the spectroscopy was investigated.

  3. Carbon cycling in primary production bottle incubations: inferences from grazing experiments and photosynthetic studies using 14C and 18O in the Arabian Sea

    Science.gov (United States)

    Laws, Edward A.; Landry, Michael R.; Barber, Richard T.; Campbell, Lisa; Dickson, Mary-Lynn; Marra, John

    Estimates of photosynthesis based on the incorporation of 14C-labeled inorganic carbon into particulate carbon were compared to estimates of gross photosynthesis based on net O 2 production and the production of 18O2 from H218O during the US Joint Global Ocean Flux Study (US JGOFS) Arabian Sea process cruises. For samples incubated below the surface and at optical depthsMehler reaction, photorespiration, dark respiration, excretion, and grazing effects on the two estimates of photosynthesis. The 14C uptake : gross photosynthesis ratio was distinctly higher (0.62) for samples incubated at the surface. This result is likely due to UV light effects, since the O 2 and 14C incubations were done in quartz and polysulfone bottles, respectively. The 14C uptake : gross photosynthesis ratio was lower (0.31) for bottles incubated at optical depths>3. This result probably reflects an increase in the ratio of dark respiration to net photosynthesis in the vicinity of the compensation light level.

  4. Study of carbon nitride compounds synthesised by co-implantation of 13C and 14N in copper at different temperatures

    International Nuclear Information System (INIS)

    Research highlights: → Simultaneous implantation of 13C and 14N in copper were performed to synthesise CNx compounds. → The formation of fullerene-like CNx compounds was highlighted by XPS and TEM. → Only about 20% of the implanted 14N atoms are contained in the FL CxNy structures. → The exceeding of implanted nitrogen precipitates in large N2 gas bubbles. → A growth model for the FL CxNy structures is proposed. - Abstract: Carbon nitride compounds have been synthesised in copper by simultaneous high fluence (1018 at. cm-2) implantation of 13C and 14N ions. During the implantation process, the substrate temperature was maintained at 25, 250, 350 or 450 deg. C. Depth profiles of 13C and 14N were determined using the non-resonant nuclear reactions (NRA) induced by a 1.05 MeV deuteron beam. The retained doses were deduced from NRA measurements and compared to the implanted fluence. The chemical bonds between carbon and nitrogen were studied as a function of depth and temperature by X-ray photoelectron spectroscopy (XPS). The curve fitting of C 1s and N 1s core level photoelectron spectra reveal different types of C-N bonds and show the signature of N2 molecules. The presence of nitrogen gas bubbles in copper was highlighted by mass spectroscopy. The structure of carbon nitride compounds was characterised by transmission electron microscopy (TEM). For that purpose, cross-sectional samples were prepared using a focused ion beam (FIB) system. TEM observations showed the presence of small amorphous carbon nitride 'nano-capsules' and large gas bubbles in copper. Based on our observations, we propose a model for the growth of these nano-objects. Finally, the mechanical properties of the implanted samples were investigated by nano-indentation.

  5. Mountain scale modeling of transient, coupled gas flow, heat transfer and carbon-14 migration

    International Nuclear Information System (INIS)

    We simulate mountain-scale coupled heat transfer and gas flow at Yucca Mountain. A coupled rock-gas flow and heat transfer model, TGIF2, is used to simulate mountain-scale two-dimensional transient heat transfer and gas flow. The model is first verified against an analytical solution for the problem of an infinite horizontal layer of fluid heated from below. Our numerical results match very well with the analytical solution. Then, we obtain transient temperature and gas flow distributions inside the mountain. These distributions are used by a transient semianalytical particle tracker to obtain carbon-14 travel times for particles starting at different locations within the repository. Assuming that the repository is filled with 30-year-old waste at an initial areal power density of 57 kw/acre, we find that repository temperatures remain above 60 degrees C for more than 10,000 years. Carbon-14 travel times to the surface are mostly less than 1000 years, for particles starting at any time within the first 10,000 years

  6. Cobalt diselenide nanoparticles embedded within porous carbon polyhedra as advanced electrocatalyst for oxygen reduction reaction

    Science.gov (United States)

    Wu, Renbing; Xue, Yanhong; Liu, Bo; Zhou, Kun; Wei, Jun; Chan, Siew Hwa

    2016-10-01

    Highly efficient and cost-effective electrocatalyst for the oxygen reduction reaction (ORR) is crucial for a variety of renewable energy applications. Herein, strongly coupled hybrid composites composed of cobalt diselenide (CoSe2) nanoparticles embedded within graphitic carbon polyhedra (GCP) as high-performance ORR catalyst have been rationally designed and synthesized. The catalyst is fabricated by a convenient method, which involves the simultaneous pyrolysis and selenization of preformed Co-based zeolitic imidazolate framework (ZIF-67). Benefiting from the unique structural features, the resulting CoSe2/GCP hybrid catalyst shows high stability and excellent electrocatalytic activity towards ORR (the onset and half-wave potentials are 0.935 and 0.806 V vs. RHE, respectively), which is superior to the state-of-the-art commercial Pt/C catalyst (0.912 and 0.781 V vs. RHE, respectively).

  7. Just a Chemical Reaction. The Science Club. Ages 10-14. [CD-ROM].

    Science.gov (United States)

    1999

    This CD-ROM allows students to discover the key factors and major dates in the development of the science of chemistry. It includes 93 scientific concepts, 20 minutes of narration with animation, 14 interactive activities, an illustrated periodic table, a complete Portable Document Format (PDF) user guide, a dictionary explaining over 40 terms, a…

  8. Metal-Organic Framework Derived Hierarchically Porous Nitrogen-Doped Carbon Nanostructures as Novel Electrocatalyst for Oxygen Reduction Reaction

    Energy Technology Data Exchange (ETDEWEB)

    Fu, Shaofang; Zhu, Chengzhou; Zhou, Yazhou; Yang, Guohai; Jeon, Ju Won; Lemmon, John P.; Du, Dan; Nune, Satish K.; Lin, Yuehe

    2015-10-01

    The hierarchically porous nitrogen-doped carbon materials, derived from nitrogen-containing isoreticular metal-organic framework-3 (IRMOF-3) through direct carbonization, exhibited excellent electrocatalytic activity in alkaline solution for oxygen reduction reaction (ORR). This high activity is attributed to the 10 presence of high percentage of quaternary and pyridinic nitrogen, the high surface area as well as good conductivity. When IRMOF-3 was carbonized at 950 °C (CIRMOF-3-950), it showed four-electron reduction pathway for ORR and exhibited better stability (about 78.5% current density was maintained) than platinum/carbon (Pt/C) in the current durability test. In addition, CIRMOF-3-950 presented high selectivity to cathode reactions compared to commercial Pt/C.

  9. Synthesis, Characterization, and Biodegradation Studies of Poly(1,4-cyclohexanedimethylene-adipate-carbonates

    Directory of Open Access Journals (Sweden)

    Ajay S. Chandure

    2014-01-01

    Full Text Available Aliphatic/alicyclic poly(1,4-cyclohexanedimethylene-adipate-carbonates (PCACs were synthesized by a transesterification from 1,4-cyclohexamethylendimethanol (1,4-CHDM, adipic acid (AA, diethyl carbonate (DEC, and titanium butoxide Ti(OBu4 as a transesterification catalyst. The synthesized PCACs were characterized by the Fourier transform infrared (FTIR, X-ray diffraction analysis (XRD, solubility, solution viscosity, gel permeation chromatography (GPC, differential scanning calorimetry (DSC, thermogravimetric analysis (TGA, and scanning electron microscope (SEM for their structural, physical, thermal, and morphological investigation. The structure of synthesized PCACs was confirmed by FTIR. All TGA curves of PCACs shows 10% weight loss above 270°C, and they reveal good thermal stability. Biodegradability of PCACs was investigated by hydrolytic degradation at (pH 7.2 and 11.5, enzymatic degradation using Rhizopus delemar lips at 37°C in phosphate buffer solution (PBS, and soil burial degradation at 30°C. The hydrolytic degradation shows the greater rate of weight loss in PBS at pH-11.5 than pH-7.2. The hydrolytic and soil burial degradation shows faster rate of weight loss as compared to enzymatic degradation. Biodegradation rate of PCACs follows the order: PCAC-20 > PCAC-40 > PCAC-60. SEM images show that degradation occurred all over the film surface, creating holes and cracks. These biodegradable PCACs may be able to replace conventional polymer in the fabrication of packaging film in near future.

  10. Formation of tungsten carbide nanoparticles on graphitized carbon to facilitate the oxygen reduction reaction

    Science.gov (United States)

    Yan, Zaoxue; He, Guoqiang; Cai, Mei; Meng, Hui; Shen, Pei Kang

    2013-11-01

    Tungsten carbide nanoparticles with the average size less than 5 nm uniformly dispersed on the graphitized carbon matrix have been successfully synthesized by a one-step ion-exchange method. This route is to locally anchor the interested species based on an ionic level exchange process using ion-exchange resin. The advantage of this method is the size control of targeted nanomaterial as well as the graphitization of resin at low temperatures catalyzed by iron salt. The Pt nanoparticles coupled with tungsten carbide nanoparticles on graphitized carbon nanoarchitecture form a stable electrocatalyst (Pt/WC-GC). The typical Pt/WC-GC electrocatalyst gives a Pt-mass activity of 247.7 mA mgPt-1, which is much higher than that of commercial Pt/C electrocatalyst (107.1 mA mgPt-1) for oxygen reduction reaction due to the synergistic effect between Pt and WC. The presented method is simple and could be readily scaled up for mass production of the nanomaterials.

  11. Effect of Co in the efficiency of the methanol electrooxidation reaction on carbon supported Pt

    Energy Technology Data Exchange (ETDEWEB)

    Hernandez-Fernandez, P.; Montiel, M.; Ocon, P. [Dpto. Quimica-Fisica Aplicada, Facultad de Ciencias, Universidad Autonoma de Madrid (UAM), C/Francisco Tomas y Valiente 7, 28049 Madrid (Spain); Fierro, J.L.G.; Rojas, S. [Grupo de Energia y Quimica Sostenibles, Instituto de Catalisis y Petroleoquimica (CSIC), C/ Marie Curie 2, 28049 Madrid (Spain); Wang, H.; Abruna, H.D. [Department of Chemistry and Chemical Biology, Cornell University. Ithaca, NY 14853 (United States)

    2010-12-15

    The effect of Co addition to carbon nanotubes supported Pt in the methanol oxidation reaction has been investigated by means of differential electrochemical mass spectrometry (DEMS). It has been observed that the CO{sub 2} efficiency increases in carbon nanotubes supported PtCo compared to its homologous Pt catalysts, especially at potentials lower than 0.55 V. Despite of this, the Faradaic current reached by the bimetallic catalysts in the methanol electrooxidation was lower than those recorded on the monometallic samples. This is because Co addition difficult finding enough Pt vicinal sites for methanol dehydrogenation. On the other hand, it has been found that alloying Pt with Co, shifts down the d-band center of the larger element, so the strength of the interaction with adsorbates decreases. Consequently, it will be easier to oxidize CO{sub ad} on the bimetallic surface. Furthermore, the necessary -OH{sub ad} species for the CO{sub ad} oxidation to CO{sub 2} will be provided by the CNTs themselves. (author)

  12. One-pot synthesis of S-alkyl dithiocarbamates via the reaction of N-tosylhydrazones, carbon disulfide and amines.

    Science.gov (United States)

    Sha, Qiang; Wei, Yun-Yang

    2013-09-14

    A new, convenient and efficient transition metal-free synthesis of S-alkyl dithiocarbamates through one-pot reaction of N-tosylhydrazones, carbon disulfide and amines is reported. Tosylhydrazones derived from various aromatic and aliphatic ketones or aldehydes were tested and gave dithiocarbamates in good to excellent yields. The tosylhydrazones can be generated in situ without isolation, which provides a simpler one-pot method to synthesize dithiocarbamates via the reaction of carbonyl compounds, carbon disulfide and amines in the presence of 4-methylbenzenesulfonohydrazide. PMID:23863979

  13. Method for increasing -SiC yield on solid state reaction of coal fly ash and activated carbon powder

    Indian Academy of Sciences (India)

    Sulardjaka; Jamasri; M W Wildan; Kusnanto

    2011-07-01

    A novel process for increasing -SiC yield on solid state reaction of coal fly ash and micro powder activated carbon powder has been proposed. -SiC powder was synthesized at temperature 1300°C for 2 h under vacuum condition with 1 l/min argon flow. Cycling synthesis process has been developed for increasing -SiC yield on solid state reaction of coal fly ash and activated carbon powder. Synthesized products were analyzed by XRD with Cu-K radiation, FTIR spectrometer and SEM fitted with EDAX. The results show that the amount of relative -SiC is increased with the number of cycling synthesis.

  14. Bio-mass derived mesoporous carbon as superior electrode in all vanadium redox flow battery with multicouple reactions

    Science.gov (United States)

    Ulaganathan, Mani; Jain, Akshay; Aravindan, Vanchiappan; Jayaraman, Sundaramurthy; Ling, Wong Chui; Lim, Tuti Mariana; Srinivasan, Madapusi P.; Yan, Qingyu; Madhavi, Srinivasan

    2015-01-01

    We first report the multi-couple reaction in all vanadium redox flow batteries (VRFB) while using bio-mass (coconut shell) derived mesoporous carbon as electrode. The presence of V3+/V4+ redox couple certainly supplies the additional electrons for the electrochemical reaction and subsequently provides improved electrochemical performance of VRFB system. The efficient electro-catalytic activity of such coconut shell derived high surface area mesoporous carbon is believed for the improved cell performance. Extensive power and electrochemical studies are performed for VRFB application point of view and described in detail.

  15. Finite range distorted wave analysis of 101.3 MeV 16O(p, pd)14N* reaction

    International Nuclear Information System (INIS)

    Experimental and theoretical studies of cluster knockout reactions have been progressing for the past several decades. This is to study the cluster structure as well as to yield the cluster spectroscopic factor in the light-medium mass nuclei using quasi-free (p, pα), (α, 2α), (p, pd), (α, αd) type of reactions. The spectroscopic factors deduced from the (α, 2α) reactions are found be almost 100 times larger than expected from the conventional shell model estimates. These values were deduced by comparing the experimental data with the predictions of the conventional Zero Range-Distorted Wave Impulse Approximation (ZR-DWIA) calculations. Analysis using the FR-DWIA formalism has been performed for the 101.3 MeV 16O(p, pd)14N* quasi-free reaction using all-through attractive (A) and an L-dependent attractive plus repulsive core (A+R) (of 2.5 fm) between the p and d potential

  16. A simultaneous evaluation of neutron induced reaction cross sections for 56Fe at En = 14.1 MeV

    International Nuclear Information System (INIS)

    A simultaneous evaluation of neutron induced reaction (i.e., (n,total), (n,n), (n,non), (n,n'), (n,2n), (n,nα), (n,np), (n,γ), (n,p), (n,d), (n,α), (n,n-em), (n,p-em), (n,d-em) and (n,α-em) reaction) cross sections on 56Fe at En = 14.1 MeV is carried out. The evaluated cross sections are compared with the corresponding measured values and the evaluations for CENDL-2, ENDF/B-6, JEF-2.2, JENDL-3 and BROND-2. (author). 27 refs, 1 fig., 8 tabs

  17. Heteropoly Acid/Nitrogen Functionalized Onion-like Carbon Hybrid Catalyst for Ester Hydrolysis Reactions.

    Science.gov (United States)

    Liu, Wei; Qi, Wei; Guo, Xiaoling; Su, Dangsheng

    2016-02-18

    A novel heteropoly acid (HPA)/nitrogen functionalized onion-like carbon (NOLC) hybrid catalyst was synthesized through supramolecular (electrostatic and hydrogen bond) interactions between the two components. The chemical structure and acid strength of the HPA/NOLC hybrid have been fully characterized by thermogravimetric analysis, IR spectroscopy, X-ray photoelectron spectroscopy, NH3 temperature-programmed desorption and acid-base titration measurements. The proposed method for the fabrication of the HPA/NOLC hybrid catalyst is a universal strategy for different types of HPAs to meet various requirements of acidic or redox catalysis. The hydrophobic environment of NOLC effectively prevents the deactivation of HPA in an aqueous system, and the combination of uniformly dispersed HPA clusters and the synergistic effect between NOLC and HPA significantly promotes its activity in ester hydrolysis reactions, which is higher than that of bare PWA as homogeneous catalyst. The kinetics of the hydrolysis reactions indicate that the aggregation status of the catalyst particles has great influence on the apparent activity. PMID:26606266

  18. Removal of Cr (VI) with wheat-residue derived black carbon: Reaction mechanism and adsorption performance

    International Nuclear Information System (INIS)

    The removal of Cr (VI) from aqueous solutions using black carbon (BC) isolated from the burning residues of wheat straw was investigated as a function of pH, contact time, reaction temperature, supporting electrolyte concentration and analytical initial Cr (VI) concentration in batch studies. The effect of surface properties on the adsorption behavior of Cr (VI) was investigated with scanning electron microscope (SEM) equipped with the energy dispersive X-ray spectroscope (EDS) and Fourier transform-infrared (FTIR) spectroscopy. The removal mechanism of Cr (VI) onto the BC was investigated and the result showed that the adsorption reaction consumed a large amount of protons along the reduction of Cr (VI) to Cr (III). The oxidation of the BC took place concurrently to the chromium reduction and led to the formation of hydroxyl and carboxyl functions. An initial solution pH of 1.0 was most favorable for Cr (VI) removal. The adsorption process followed the pseudo-second order equation and Freundlich isotherm very well. The Cr (VI) adsorption was temperature-dependent and almost independent on the sodium chloride concentrations. The maximum adsorption capacity for Cr (VI) was found at 21.34 mg/g in an acidic medium, which is comparable to other low-cost adsorbents.

  19. Fusion Reaction of 16O+14N and Its Implication for the Production of 26Al in Explosive Oxygen Burning

    Institute of Scientific and Technical Information of China (English)

    WANG Peng; PENG Qiu-He; ZHANG Shui-Nai; LUO Xin-Lian

    2006-01-01

    We suggest that the fusion reaction 16 O+14 N may be a new way to produce 26A1 in interstellar medium. Adopting different mixing modes, we investigate the impact on the production of 26Al in explosive oxygen burning and find that the result is extremely sensitive to mixing mechanisms. In some cases, we obtain an encouraging result, for example, the greatest final abundance of 26Al reaches 7.779×10-6, which means that the explosive oxygen burning may be a new origin of 26Al.

  20. The 65 keV resonance in the {sup 17}O(p,alpha){sup 14}N thermonuclear reaction

    Energy Technology Data Exchange (ETDEWEB)

    Sergi, M.L. [Laboratori Nazionali del Sud, Catania (Italy); Dipartimento di Metodologie Fisiche e Chimiche per l' Ingegneria, Universita di Catania, Catania (Italy); Centro Siciliano di Fisica Nucleare e Struttura della Materia, Catania (Italy); Spitaleri, C. [Laboratori Nazionali del Sud, Catania (Italy); Dipartimento di Metodologie Fisiche e Chimiche per l' Ingegneria, Universita di Catania, Catania (Italy); Coc, A. [CSNSM, UMR 8609, CNRS/IN2P3and Universite Paris Sud 11, Batiment 104, 91405 Orsay Campus (France); Mukhamedzhanov, A. [Cyclotron Institute, Texas A and M University, College Station, TX 77843 (United States); Burjan, S.V. [Nuclear Physics Institute of ASCR Rez near Prague (Czech Republic); Gulino, M. [Laboratori Nazionali del Sud, Catania (Italy); Dipartimento di Metodologie Fisiche e Chimiche per l' Ingegneria, Universita di Catania, Catania (Italy); Hammache, F. [IPN, IN2P3-CNRS et Universite de Paris-Sud 11, 91406 Orsay Cedex (France); Hons, Z. [Nuclear Physics Institute of ASCR Rez near Prague (Czech Republic); Irgaziev, B. [GIK Institute of Engineering Sciences and Technology Topi District Swabi NWFP (Pakistan); Kiss, G.G. [Laboratori Nazionali del Sud, Catania (Italy); Dipartimento di Metodologie Fisiche e Chimiche per l' Ingegneria, Universita di Catania, Catania (Italy); Kroha, V. [Nuclear Physics Institute of ASCR Rez near Prague (Czech Republic); La Cognata, M. [Laboratori Nazionali del Sud, Catania (Italy); Dipartimento di Metodologie Fisiche e Chimiche per l' Ingegneria, Universita di Catania, Catania (Italy); Centro Siciliano di Fisica Nucleare e Struttura della Materia, Catania (Italy); Lamia, L.; Pizzone, R.G. [Laboratori Nazionali del Sud, Catania (Italy); Dipartimento di Metodologie Fisiche e Chimiche per l' Ingegneria, Universita di Catania, Catania (Italy); Sereville, N. de [IPN, IN2P3-CNRS et Universite de Paris-Sud 11, 91406 Orsay Cedex (France); Somorjai, E. [ATOMKI, Debrecen (Hungary)

    2010-03-01

    The indirect measurement of {sup 17}O(p,alpha){sup 14}N cross section was performed by means of the Trojan Horse Method. This approach allowed to investigate the ultra-low energy range (E{sub c.m.}=0-300 keV) relevant for several astrophysics environments, where two resonant levels of {sup 18}F at E{sub c.m.}{sup R}=65 keV and E{sub c.m.}{sup R}=183 keV play a significant role in the reaction rate determination.

  1. Synthesis of carbon C-14 labelled 2-phenyl-4-alpha-alkylaminomethyl-quinolinemethanol: a potential anti-leishmaniasis agent

    Energy Technology Data Exchange (ETDEWEB)

    Wang, T.S.T.; Fawwaz, R.A.; Heertum, R.L.van [Columbia Univ., New York, NY (United States). Coll. of Physicians and Surgeons

    1995-07-01

    Using sodium acetate, [1-{sup 14}C] as a starting material, a total of seven steps were required to synthesize the title compound. This involved acylation of ortho-dichlorobenzene to form dichloroacetophenone, [2-{sup 14}C] (I). The 2-phenyl-4-quinoline carboxylic acid, [2-{sup 14}C] (II) was prepared by the Pfitzinger reaction from (1) and dichloroisatin. Compound 11 was converted to the acid chloride (III) by reaction with SOCl{sub 2} in benzene. Grignard condensation reaction of (III) yielded 4-quinolylmethylketone, [2-{sup 14}C] (IV) which was then converted to the bromomethylketone (V). Compound V was reacted with NaBH{sub 4} to form the ethylene oxide (VI). Alkylation of the oxide yielded the title compound (VII). The overall radiochemical yield was 10.1% and the specific activity was 3.0 mCi/mmol, with a radiochemical purity of >99.5%. (author).

  2. Carbon-14 immobilization via the CO2-Ba(OH)2 hydrate gas-solid reaction

    International Nuclear Information System (INIS)

    For the treatment of an air-based off-gas stream, the use of packed beds of Ba(OH)2.8H2O flakes to remove CO2 has been demonstrated. However, the operating conditions must be maintained between certain upper and lower limits with respect to the partial pressure of water. If the water vapor pressure in the gas is less than the dissociation vapor pressure of Ba(OH)2.8H2O, the bed will deactivate. If the vapor pressure is considerably greater, pressure drop problems will increase with increaseing humidity as the particles curl and degrade. Results have indicted that when operated in the proper regime, the bulk of the increase in pressure drop results from the conversion of Ba(OH)2.8H2O to BaCO3 and not from the hydration of the commercial Ba(OH)2.8H2O (i.e., Ba(OH)2.7.50H2O) to Ba(OH)2.8H2O

  3. A kinetic study of the reaction of water vapor and carbon dioxide on uranium; Cinetique de la reaction de la vapeur d'eau et du dioxyde de carbone sur l'uranium

    Energy Technology Data Exchange (ETDEWEB)

    Santon, J.P. [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

    1964-09-15

    The kinetic study of the reaction of water vapour and carbon dioxide with uranium has been performed by thermogravimetric methods at temperatures between 160 and 410 deg G in the first case, 350 and 1050 deg C in the second: Three sorts of uranium specimens were used: uranium powder, thin evaporated films, and small spheres obtained from a plasma furnace. The experimental results led in the case of water vapour, to a linear rate of reaction controlled by diffusion at the lower temperatures, and by a surface reaction at the upper ones. In the case of carbon dioxide, a parabolic law has been found, controlled by diffusional processes. (author) [French] L'etude cinetique de la reaction de la vapeur d'eau et du dioxyde de carbone sur l'uranium a ete entreprise au moyen de methodes thermogravimetriques, dans te premier cas entre 160 et 410 deg C et dans le second entre 350 et 1050 deg C. Le materiau utilise se presentait sous trois formes: poudres, couches minces evaporees et billes obtenues par fusion en chalumeau a plasma. Les resultats experimentaux ont permis de mettre en evidence, dans le cas de la vapeur d'eau, une cinetique lineaire controlee par la diffusion a basse temperature et d'interface a haute temperature. Dans le cas du dioxyde de carbone par contre, on trouve une cinetique parabolique controlee par la diffusion. (auteur)

  4. Reproducibly creating hierarchical 3D carbon to study the effect of Si surface functionalization on the oxygen reduction reaction

    Science.gov (United States)

    Zeng, Yuze; Flores, Jose F.; Shao, Yu-Cheng; Guo, Jinghua; Chuang, Yi-De; Lu, Jennifer Q.

    2016-06-01

    We report a new method to reproducibly fabricate functional 3D carbon structures directly on a current collector, e.g. stainless steel. The 3D carbon platform is formed by direct growth of upright arrays of carbon nanofiber bundles on a roughened surface of stainless steel via the seed-assisted approach. Each bundle consists of about 30 individual carbon nanofibers with a diameter of 18 nm on average. We have found that this new platform offers adequate structural integrity. As a result, no reduction of the surface area during downstream chemical functionalization was observed. With a fixed and reproducible 3D structure, the effect of the chemistry of the grafted species on the oxygen reduction reaction has been systematically investigated. This investigation reveals for the first time that non-conductive Si with an appropriate electronic structure distorts the carbon electronic structure and consequently enhances ORR electrocatalysis. The strong interface provides excellent electron connectivity according to electrochemical analysis. This highly reproducible and stable 3D platform can serve as a stepping-stone for the investigation of the effect of carbon surface functionalization on electrochemical reactions in general.We report a new method to reproducibly fabricate functional 3D carbon structures directly on a current collector, e.g. stainless steel. The 3D carbon platform is formed by direct growth of upright arrays of carbon nanofiber bundles on a roughened surface of stainless steel via the seed-assisted approach. Each bundle consists of about 30 individual carbon nanofibers with a diameter of 18 nm on average. We have found that this new platform offers adequate structural integrity. As a result, no reduction of the surface area during downstream chemical functionalization was observed. With a fixed and reproducible 3D structure, the effect of the chemistry of the grafted species on the oxygen reduction reaction has been systematically investigated. This

  5. Non-destructive testing of proteins in single seeds using the 14N(d,p)15N and 14N(d,∝)12C reactions

    International Nuclear Information System (INIS)

    A non-destructive nuclear technique aimed for the analysis of proteins in single seeds using the 14N(d,p)15N and 14N(d,∝)12C reactions is implemented. This work was performed at the ININ's Tandem Van der Graaff facility, using a 6 MeV deuteron beam and a surface barrier solid state detector with its associated electronics for the pulse height analysis of the charged particles backscattered from the samples. Well defined populations of five varieties of wheat, and four of corn were used as samples in order to optimize the experimental conditions for the analysis, these results were compared with those obtained using an analytical chemical method (Kjeldahl). The linear regression coefficient (''r'') obtained from the results of these two methods was: r = 0.9 in the case of wheat, and r = 0.7 in the case of corn, which we consider adequate figures for using the non-destructive nuclear technique as an aid or support in agricultural seed protein improvement programs. In adequate geometrical conditions the analysis per seed can take a few seconds, and the exposure to the germ can be as low as ≅1 Rad. (author)

  6. Catalytic hydrogenation of carbon monoxide. Progress report, December 15, 1991--December 14, 1992

    Energy Technology Data Exchange (ETDEWEB)

    Wayland, B.B.

    1992-12-01

    This project is focused on developing strategies to accomplish the reduction and hydrogenation of carbon monoxide to produce organic oxygenates at mild conditions. Our approaches to this issue are based on the recognition that rhodium macrocycles have unusually favorable thermodynamic values for producing a series of intermediate implicated in the catalytic hydrogenation of CO. Observations of metalloformyl complexes produced by reactions of H{sub 2} and CO, and reductive coupling of CO to form metallo {alpha}-diketone species have suggested a multiplicity of routes to organic oxygenates that utilize these species as intermediates. Thermodynamic and kinetic-mechanistic studies are used in constructing energy profiles for a variety of potential pathways, and these schemes are used in guiding the design of new metallospecies to improve the thermodynamic and kinetic factors for individual steps in the overall process. Variation of the electronic and steric effects associated with the ligand arrays along with the influences of the reaction medium provide the chemical tools for tuning these factors. Emerging knowledge of the factors that contribute to M-H, M-C and M-O bond enthalpies is directing the search for ligand arrays that will expand the range of metal species that have favorable thermodynamic parameters to produce the primary intermediates for CO hydrogenation. Studies of rhodium complexes are being extended to non-macrocyclic ligand complexes that emulate the favorable thermodynamic features associated with rhodium macrocycles, but that also manifest improved reaction kinetics. Multifunctional catalyst systems designed to couple the ability of rhodium complexes to produce formyl and diketone intermediates with a second catalyst that hydrogenates these imtermediates are promising approaches to accomplish CO hydrogenation at mild conditions.

  7. 14CO2-assimilation, translocation of 14C, and 14C-carbonate uptake in different organs of spring barley plants in relation to adult-plant resistance to powdery mildew

    International Nuclear Information System (INIS)

    The cultivar Peruvian of spring barley, which is susceptible at all growth stages, and Asse, which exhibits adult-plant resistance to powdery mildew, were compared in 14CO2 assimilation, distribution of 14C, and 14C-carbonate uptake in different organs of healthy and infected plants. The reduction of 14CO2 assimilation in infected plants at the first and fourth leaf stages was greater in Peruvian than in Asse. In Peruvian, the 14C which was fixed by the infected third leaf of plants with mildew on the lower 3 leaves remained in the third leaves with very little translocation to other parts of the plant. Infection of the lower three leaves at the fourth leaf stage reduced 14CO2 assimilation in noninfected fourth leaves of Asse less than that of Peruvian, but the flow of 14C from the healthy fourth leaves into other plant parts such as leaf sheaths was markedly stimulated in Peruvian compared to Asse. Infection also reduced the uptake of 14C-carbonate by seedling roots, the reduction being greater in Peruvian than Asse. A greater proportion of the 14C absorbed by roots of Asse was translocated to the infected leaves than that of Peruvian. It was concluded that powdery mildew disrupted the normal pattern of photosynthesis and translocation of metabolites in a susceptible cultivar more markedly than in an adult-plant-resistant cultivar of spring barley. (author)

  8. Platinum Nanoparticles Supported on Nitrobenzene-Functionalized Multiwalled Carbon Nanotube as Efficient Electrocatalysts for Methanol Oxidation Reaction

    International Nuclear Information System (INIS)

    Graphical abstract: Multiwalled carbon nanotube was functionalized with nitrobenzene as a promising support material for Pt-based electrocatalysts (Pt-NB-MWCNT) for methanol oxidation. The as-prepared catalysts have higher electrocatalytic activity in terms of both mass and specific activities, and improved durability for methanol oxidation reaction than as compared to the undoped materials. - Highlights: • Multiwalled carbon nanotube was functionalized with nitrobenzene as a support material for Pt-based electrocatalysts for methanol oxidation. • The electronic properties of carbon nanotubes were modified by the nitrobenzene functionalization. • Nitrobenzene-functionalized electrocatalysts revealing the improved electrocatalytic performance of Pt-NB-MWCNT catalyst for the methanol oxidation reaction. - Abstract: A novel method of molecular covalently functionalized multiwalled carbon nanotube using nitrobenzene group is prepared and used as a promising support material of Pt-based electrocatalysts (denoted as Pt-NB-MWCNT) for methanol oxidation reaction. The physical and chemical characteristics are performed by X-ray powder diffraction, transmission electron microscopy, Raman spectroscopy, thermogravimetric and X-ray photoelectron spectroscopy. The electrocatalytic are evaluated by cyclic voltammetry and chronoamperometry techniques. Compared with the un-functionalized Pt-MWCNT catalyst, Pt-NB-MWCNTs show more uniform particle dispersion, smaller particle size, improved activity and durability for methanol oxidation reaction. The nitrobenzene group is demonstrated to promote the electrocatalytic activity of Pt-MWCNT for methanol oxidation significantly. The results represent a novel approach to functionalize MWCNT in a simple and economic way to prepare efficient electrocatalysts for methanol oxidation

  9. Microcalorimetric Adsorption of Alumina Oxide Catalysts for Combination of Ethylbenzene dehydrogenation and carbon Dioxide Shift-reaction

    Institute of Scientific and Technical Information of China (English)

    GE Xin; SHEN Jian-yi

    2004-01-01

    Styrene (STY) is now produced industrially in fairly large quantities by the dehydrogenation of ethylbenzene (EB) using promoted iron oxide catalyst with superheated steam.In this case, small amount of carbon dioxide formed as a by-product was known to inhibit the catalytic activity of commercial catalyst. Recently, there have been some reports which carbon dioxide showed positive effects to promote catalytic activities on the reaction over several catalysts.In this study, we attempted to combine the dehydrogenation of EB to STY with the carbon dioxide shift-reaction. The combine reaction (EB + CO2 → STY + H2O + CO) can be considered as one of the ways of using CO2 resources and can yield simultaneously STY and Carbon oxide.Alumina oxide catalysts such as Al2O3, Na2O/Al2O3 and K2O/Al2O3 were prepared by the usual impregnation method with an aqueous solution of NaNO3 and KNO3, and then calcined at 650℃ for 5 h in a stream of air. The reaction condition is 600℃, flow of CO2 38ml/mon and space velocity (EB) 1.28h-1.

  10. Introducing the global carbon cycle to middle school students with a 14C research project

    Science.gov (United States)

    Brodman Larson, L.; Phillips, C. L.; LaFranchi, B. W.

    2012-12-01

    Global Climate Change (GCC) is currently not part of the California Science Standards for 7th grade. Required course elements, however, such as the carbon cycle, photosynthesis, and cellular respiration could be linked to global climate change. Here we present a lesson plan developed in collaboration with scientists from Lawrence Livermore National Laboratory, to involve 7th grade students in monitoring of fossil fuel emissions in the Richmond/San Pablo area of California. -The lesson plan is a Greenhouse Gas/Global Climate Change Unit, with an embedded research project in which students will collect plant samples from various locals for analysis of 14C, to determine if there is a correlation between location and how much CO2 is coming from fossil fuel combustion. Main learning objectives are for students to: 1) understand how fossil fuel emissions impact the global carbon cycle, 2) understand how scientists estimate fossil CO2 emissions, and 3) engage in hypothesis development and testing. This project also engages students in active science learning and helps to develop responsibility, two key factors for adolescentsWe expect to see a correlation between proximity to freeways and levels of fossil fuel emissions. This unit will introduce important GCC concepts to students at a younger age, and increase their knowledge about fossil fuel emissions in their local environment, as well as the regional and global impacts of fossil emissions.

  11. Measurement of the Erc .m .=259 keV resonance in the 14N(p ,γ )15O reaction

    Science.gov (United States)

    Daigle, S.; Kelly, K. J.; Champagne, A. E.; Buckner, M. Q.; Iliadis, C.; Howard, C.

    2016-08-01

    The 14N(p ,γ )15O reaction regulates the power generated by the CN cycle and thus impacts the structure and evolution of every star at some point in its life. The lowest positive-energy resonance in this reaction is located at Erc .m .=259 keV, too high in energy to strongly influence quiescent stellar burning. However, the strength of this resonance is used as a cross-section normalization for lower-energy measurements of this reaction. We report on new measurements of the energy, strength, and γ -ray branching ratios for the 259-keV resonance, using different detection and data-analysis schemes. We have also reevaluated previous results, where possible. Our new recommended strength of ω γ =12.6 (3 ) meV is in agreement with the previous value of 13.1(6) meV, but is more precise and thus provides a more reliable normalization for low-energy (p ,γ ) measurements.

  12. Probing the statistical decay and alpha-clustering effects in 12c+12c and 14n+10b reactions

    CERN Document Server

    Morelli, Luca; Agostino, M D; Bruno, M; Gulminelli, F; Cinausero, M; Degerlier, M; Fabris, D; Gramegna, F; Marchi, T; Barlini, S; Bini, M; Casini, G; Gelli, N; Lopez, A; Pasquali, G; Piantelli, S; Valdre', S

    2013-01-01

    An experimental campaign has been undertaken at INFN Laboratori Nazionali di Legnaro, Italy, in order to progress in our understanding of the statistical properties of light nuclei at excitation energies above particle emission threshold, by measuring exclusive data from fusion-evaporation reactions. A first reaction 12C+12C at 7.9 AMeV beam energy has been measured, using the GARFIELD+Ring Counter experimental setup. Fusion-evaporation events have been exclusively selected. The comparison to a dedicated Hauser-Feshbach calculation allows us to give constraints on the nuclear level density at high excitation energy for light systems ranging from C up to Mg. Out-of-equilibrium emission has been evidenced and attributed both to entrance channel effects favoured by the cluster nature of reaction partners and, in more dissipative events, to the persistence of cluster correlations well above the 24Mg threshold for 6 alphas decay. The 24Mg compound nucleus has been studied with a new measurement 14N + 10B at 5.7 AM...

  13. Radial deformation of single-walled carbon nanotubes on quartz substrates and the resultant anomalous diameter-dependent reaction selectivity

    Institute of Scientific and Technical Information of China (English)

    Juan Yang; Yu Liu; Daqi Zhang; Xiao Wang; Ruoming Li; Yan Li

    2015-01-01

    Owing to the unique conjugated structure, the chemical-reaction selectivity of single-walled carbon nanotubes (SWNTs) has attracted great attention. By utilizing the radial deformation of SWNTs caused by the strong interactions with the quartz lattice, we achieve an anomalous diameter-dependent reaction selectivity of quartz lattice-oriented SWNTs in treatment with iodine vapor; this is distinctly different from the widely reported and well accepted higher reaction activity in small-diameter tubes compared to large-diameter tubes. The radial deformation of SWNTs on quartz substrate is verified by detailed Raman spectroscopy and mappings in both G-band and radial breathing mode. Due to the strong interaction between SWNTs and the quartz lattice, large-diameter tubes present a larger degree of radial deformation and more delocalized partial electrons are distributed at certain sidewall sites with high local curvature. It is thus easier for the carbon--carbon bonds at these high-curvature sites on large-diameter tubes to break down during reaction. This anomalous reaction activity offers a novel approach for selective removal of small-band~aD large-diameter tubes.

  14. Simulation Experiments on the Reaction of CH4-CaSO4 and Its Carbon Kinetic Isotope Fractionation

    Institute of Scientific and Technical Information of China (English)

    YueChangtao; LiShuyuan; DingKangle; ZhongNingning

    2005-01-01

    Thermochemical sulfate reduction (TSR) in geological deposits can account for the accumulation of H,S in deep sour gas reservoirs. In this paper, thermal simulation experiments on the reaction of CH4-CaSO4 were carried out using an autoclave at high temperatures and high pressures. The products were characterized with analytical methods including carbon isotope analysis. It is found that the reaction can proceed to produce H2S, H2O and CaCO3 as the main products. Based on the experimental results, the carbon kinetic isotope fractionation was investigated, and the value of Ki(kinetic isotope effect) was calculated. The results obtained in this paper can provide useful information to explain the occurrence of H2S in deep carbonate gas reservoirs.

  15. Amorphous Molybdenum Sulfide on Graphene-Carbon Nanotube Hybrids as Highly Active Hydrogen Evolution Reaction Catalysts.

    Science.gov (United States)

    Pham, Kien-Cuong; Chang, Yung-Huang; McPhail, David S; Mattevi, Cecilia; Wee, Andrew T S; Chua, Daniel H C

    2016-03-01

    In this study, we report on the deposition of amorphous molybdenum sulfide (MoSx, with x ≈ 3) on a high specific surface area conductive support of Graphene-Carbon Nanotube hybrids (GCNT) as the Hydrogen Evolution Reaction (HER) catalysts. We found that the high surface area GCNT electrode could support the deposition of MoSx at much higher loadings compared with simple porous carbon paper or flat graphite paper. The morphological study showed that MoSx was successfully deposited on and was in good contact with the GCNT support. Other physical characterization techniques suggested the amorphous nature of the deposited MoSx. With a typical catalyst loading of 3 mg cm(-2), an overpotential of 141 mV was required to obtain a current density of 10 mA cm(-2). A Tafel slope of 41 mV decade(-1) was demonstrated. Both measures placed the MoSx-deposited GCNT electrode among the best performing molybdenum sulfide-based HER catalysts reported to date. The electrode showed a good stability with only a 25 mV increase in overpotential required for a current density of 10 mA cm(-2), after undergoing 500 potential sweeps with vigorous bubbling present. The current density obtained at -0.5 V vs SHE (Standard Hydrogen Electrode potential) decreased less than 10% after the stability test. The deposition of MoSx on high specific surface area conductive electrodes demonstrated to be an efficient method to maximize the catalytic performance toward HER. PMID:26864503

  16. Role of reaction resistance in limiting carbon monoxide uptake in rabbit lungs.

    Science.gov (United States)

    Heller, H; Schuster, K

    1998-06-01

    The contribution of reaction resistance to overall resistance to pulmonary carbon monoxide (CO) uptake [DLCO/(ThetaCO . Vc), where DLCO is lung CO diffusing capacity, ThetaCO is CO uptake conductance of erythrocytes, and Vc is pulmonary capillary blood volume] was determined in 10 anesthetized, paralyzed, and artificially ventilated rabbits. On the basis of the classical double-reciprocal equation of F. G. W. Roughton and R. E. Forster (J. Appl. Physiol. 11: 290-302, 1957), DLCO/(ThetaCO . Vc) was obtained by solving the relation DLCO/(ThetaCO . Vc) = 1 - 2/(DLNO/DLCO), where DLNO/DLCO represents the ratio between the respective single-breath diffusing capacities (DL) of nitric oxide (NO) and CO pulmonary capillary blood. The lungs of eight rabbits were inflated, starting from residual volume, by using 55 ml of indicator gas mixture (0.2% CO and 0.05% NO in nitrogen). DL values were calculated by taking the end-tidal partial pressures of CO and NO as analyzed by using a respiratory mass spectrometer. The overall value was DLCO/(ThetaCO . Vc) = 0.4 +/- 0.025 (mean +/- SD). Because of the use of O2-free indicator gas mixtures, the end-tidal O2 partial pressures were approximately 21 Torr. In one other rabbit, the application of 0.2% CO and 0.001% NO yielded DLCO/(ThetaCO . Vc) = 0.39; in the tenth rabbit, however, inspiratory volume was varied, and an identical value was found at functional residual capacity. We conclude that the contribution of reaction resistance to overall resistance to pulmonary CO uptake is independent of the inspiratory NO concentration used, including, with respect to the pertinent literature, the conclusion that in rabbits, dogs, and humans this contribution amounts to 40% when determined at functional residual capacity.

  17. Experimental Study on Hydrocarbon Formation Due to Reactions Between Carbonates and Water or Water—Bearing Minerals in Deep Earth

    Institute of Scientific and Technical Information of China (English)

    翁克难; 汪本善; 等

    1999-01-01

    In order to investigate the mechanism of formation of abiogenetic hydrocarbons at the depth of the Earth,experimental research on reactions between carbonates and water or waterbearing minerals was carried out at the pressure of about 1GPa and the temperature range of 800-1500℃.The reactions took place in an open and nonequilibrium state.Chromatographic analyses of the gas products indicate that in the experiments there were generated CH4-dominated hydrocarbons,along with some CO2 and CO.Accordingly,we think there is no essential distinction between free-state water and hydroxy in the minerals in the process of hydrocarbon formation.This study indicates that reactions between carbonates and water or water-bearing minerals should be an important factor leading to the formation of abiogenetic hydrocarbons at the Earth's depth.

  18. Reaction products from the chlorination of seawater. Final report 15 Jul 75-14 Jul 80

    Energy Technology Data Exchange (ETDEWEB)

    Carpenter, J.H.; Smith, C.A.; Zika, R.G.

    1981-03-01

    Chemical treatment of natural waters, in particular the use of chlorine as a biocide, modifies the chemistry of these waters in ways that are not fully understood. The research described in this report examined both inorganic and organic reaction products from the chlorination of seawater using a variety of analytical approaches. Some analytical methods in widespread current use underestimate the residual oxidants in chlorinated seawater by as much as 70% depending upon the detail of the procedures. The chlorination of seawater in the presence of light produces substantial quantities of bromate ions which can influence standard analytical procedures and represents an unknown factor in estuarine and coastal waters. The copper complexing capacity of Biscayne Bay, Florida water was found to be substantially reduced with the addition of chlorine. Analysis was made by anodic stripping voltammetry on water samples after successive additions of copper sulfate solution. Laboratory chlorination of water from the intake of the Port Everglades, Florida power plant produces bromoform levels comparable to that found in the plant discharge. These results are in contrast to results reported in the literature for a power plant on the Patuxent estuary in Maryland, so that bromoform production appears to be site-specific. Chloroform extracts of chlorinated Biscayne Bay water are found to contain halogenated compounds which are new and different, and which pose unusual analytical problems. Studies using GC/ECD, GC/MS, HPLC, H NMR, differential pulsed polarography and other techniques on natural extracts and synthesized compounds are reported.

  19. In vivo uptake of carbon-14-colchicine for identification of tumor multidrug resistance

    Energy Technology Data Exchange (ETDEWEB)

    Mehta, B.M.; Rosa, E.; Biedler, J.L. [Nuclear Medicine Research Lab., New York, NY (United States)] [and others

    1994-07-01

    A major limitation in the treatment of cancer with natural product chemotherapeutic agents is the development of multidrug resistance (MDR). Multidrug resistance is attributed to enhanced expression of the multidrug resistance gene MDR1. Colchicine (CHC) is known to be one of the MDR drugs. The authors have previously demonstrated that it is possible to distinguish multidrug resistant tumors from the multidrug-sensitive tumors in vivo on the basis of tritium ({sup 3}H) uptake following injection of {sup 3}H-CHC. The present studies were carried out in xenografted animals using {sup 14}C-CHC which may be more indicative of {sup 11}C-labeled CHC distribution with regard to circulating metabolites, since metabolic processes following injection of (ring C, methoxy-{sup 11}C)-CHC may produce significant amounts of circulating 1l-carbon fragments (i.e., methanol and/or formaldehyde). Experiments were carried out at a dose of 2 mg/kg. Activity concentration per injected dose was approximately twice as great in sensitive as in resistant tumors (p < 0.05) at 60 min following intravenous injection of {sup 14}C-CHC. About 75% of total activity was CHC in the sensitive tumors. The findings are further confirmed by the quantitative autoradiographic evaluation of resistant and sensitive tumors. These studies confirm our previous observations that it is possible to noninvasively distinguish multidrug-resistant tumors from sensitive tumors in vivo based on uptake of an injected MDR drug using a{sup 14}C-labeled CHC at the same position and of comparable specific activity to a {sup 11}C-CHC tracer used for PET imaging. 16 refs., 5 figs., 2 tabs.

  20. Probing the Statistical Decay and α-clustering effects in 12C + 12C and 14N + 10B reactions

    Science.gov (United States)

    Morelli, L.; Baiocco, G.; D'Agostino, M.; Bruno, M.; Gulminelli, F.; Cinausero, M.; Degerlier, M.; Fabris, D.; Gramegna, F.; Marchi, T.; Barlini, S.; Bini, M.; Casini, G.; Gelli, N.; Lopez, A.; Pasquali, G.; Piantelli, S.; Valdrè, S.

    2014-03-01

    An experimental campaign has been undertaken at Laboratori Nazionali di Legnaro (LNL INFN), Italy, in order to progress in our understanding of the statistical properties of light nuclei at excitation energies above particle emission threshold, by measuring exclusive data from fusion-evaporation reactions. On the experimental side, a first reaction: 12C+12C at 95 MeV beam energy has been measured, using the GARFIELD + Ring Counter (RCo) apparatuses. Fusion-evaporation events have been exclusively selected out of the entire data set. The comparison to a dedicated Hauser-Feshbach calculation allows us to give constraints on the nuclear level density at high excitation energy for light systems ranging from C up to Mg. Out-of-equilibrium aα emission has been evidenced and attributed both to an entrance channel effect (favoured by the cluster nature of reaction partners), and, in more dissipative events, to the persistence of cluster correlations well above the 24Mg threshold for 6 α's decay. In order to study the same 24Mg compound nucleus at similar excitation energy with respect to this first reaction a new measurement, 14N + 10B at 5.7 A.MeV, was performed at LNL laboratories with the same experimental setup. The comparison between the two systems would allow us to further constrain the level density of light nuclei in the mass-excitation energy range of interest. In this perspective, deviations from a statistical behaviour can be used as a tool to get information on nuclear clustering, both in the ground-state for projectile and target and in the hot source formed in the collision.

  1. Probing the Statistical Decay and α-clustering effects in 12C + 12C and 14N + 10B reactions

    Directory of Open Access Journals (Sweden)

    Morelli L.

    2014-03-01

    Full Text Available An experimental campaign has been undertaken at Laboratori Nazionali di Legnaro (LNL INFN, Italy, in order to progress in our understanding of the statistical properties of light nuclei at excitation energies above particle emission threshold, by measuring exclusive data from fusion-evaporation reactions. On the experimental side, a first reaction: 12C+12C at 95 MeV beam energy has been measured, using the GARFIELD + Ring Counter (RCo apparatuses. Fusion-evaporation events have been exclusively selected out of the entire data set. The comparison to a dedicated Hauser-Feshbach calculation allows us to give constraints on the nuclear level density at high excitation energy for light systems ranging from C up to Mg. Out-of-equilibrium aα emission has been evidenced and attributed both to an entrance channel effect (favoured by the cluster nature of reaction partners, and, in more dissipative events, to the persistence of cluster correlations well above the 24Mg threshold for 6 α’s decay. In order to study the same 24Mg compound nucleus at similar excitation energy with respect to this first reaction a new measurement, 14N + 10B at 5.7 A.MeV, was performed at LNL laboratories with the same experimental setup. The comparison between the two systems would allow us to further constrain the level density of light nuclei in the mass-excitation energy range of interest. In this perspective, deviations from a statistical behaviour can be used as a tool to get information on nuclear clustering, both in the ground-state for projectile and target and in the hot source formed in the collision.

  2. Science Letters: Nitrogen doping of activated carbon loading Fe2O3 and activity in carbon-nitric oxide reaction

    Institute of Scientific and Technical Information of China (English)

    WAN Xian-kai; ZOU Xue-quan; SHI Hui-xiang; WANG Da-hui

    2007-01-01

    Nitrogen doping of activated carbon loading Fe2O3 was performed by annealing in ammonia, and the activity of the modified carbon for NO reduction was studied in the presence of oxygen. Results show that Fe2O3 enhances the amount of surface oxygen complexes and facilitates nitrogen incorporation in the carbon, especially in the form of pyridinic nitrogen. The modified carbon shows excellent activity for NO reduction in the low temperature regime (<500 ℃) because of the cooperative effect of Fe2O3 and the surface nitrogen species.

  3. In situ observation of the reaction of scandium and carbon by neutron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Juarez-Arellano, Erick A., E-mail: eajuarez@unpa.edu.m [Institut fuer Geowissenschaften, Universitaet Frankfurt, Altenhoeferallee 1, 60438 Frankfurt a.M. (Germany); Universidad del Papaloapan, Circuito Central 200, Parque Industrial, Tuxtepec 68301 (Mexico); Winkler, Bjorn [Institut fuer Geowissenschaften, Universitaet Frankfurt, Altenhoeferallee 1, 60438 Frankfurt a.M. (Germany); Vogel, Sven C. [Los Alamos National Laboratory, Lujan Center. Mail Stop H805, Los Alamos, NM 87545 (United States); Senyshyn, Anatoliy [Forschungsneutronenquelle Heinz Maier-Leibnitz (FRM II), Technische Universitaet Muenchen, Lichtenbergstr. 1, D-85747 Garching (Germany); Materialwissenschaft, TU Darmstadt, Petersensstr. 23, D-64287 Darmstadt (Germany); Kammler, Daniel R. [Sandia National Laboratories, Albuquerque, NM 87185 (United States); Avalos-Borja, Miguel [CNyN, UNAM, A. Postal 2681, Ensenada, B.C. (Mexico)

    2011-01-05

    Research highlights: {yields} Exist two ScC cubic phases with B1-structure type differing in site occupancy of C. {yields} A new orthorhombic scandium carbide phase is formed at 1473(50) K. {yields} The recrystallization of alpha-Sc occurs between 1000 and 1223 K. - Abstract: The formation of scandium carbides by reaction of the elements has been investigated by in situ neutron diffraction up to 1823 K. On heating, the recrystallization of {alpha}-Sc occurs between 1000 and 1223 K. The formation of Sc{sub 2}C and ScC (NaCl-B1 type structure) phases has been detected at 1323 and 1373 K, respectively. The formation of a new orthorhombic scandium carbide phase was observed at 1473(50) K. Once the scandium carbides are formed they are stable upon heating or cooling. No other phases were detected in the present study, in which the system was always carbon saturated. The thermal expansion coefficients of all phases have been determined, they are constant throughout the temperature interval studied.

  4. Carbon nanotubes-supported palladium nanoparticles for the Suzuki reaction in supercritical carbon dioxide:A facile method for the synthesis of tetrasubstituted olefins

    Institute of Scientific and Technical Information of China (English)

    ZHOU Lei; ZHANG WeiDe; JIANG HuanFeng

    2008-01-01

    A facile and efficient method for the synthesis of tetrasubstituted olefins in supercritical carbon dioxide was developed by using carbon nanotubes-supported palladium nanoparticles (Pd/CNTs) as the cata-lyst. Compared with common Pd/C, Pd/CNTs could more effectively catalyze the reaction of di-bromo-substituted olefins with boronic acids, affording the corresponding tetrasubstituted olefins with moderate to good yields. This environmentally benign route with an easy-to-handle catalyst provides an appealing alternative to the currently available methods.

  5. Carbon nanotubes-supported palladium nanoparticles for the Suzuki reaction in supercritical carbon dioxide: A facile method for the synthesis of tetrasubstituted olefins

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    A facile and efficient method for the synthesis of tetrasubstituted olefins in supercritical carbon dioxide was developed by using carbon nanotubes-supported palladium nanoparticles (Pd/CNTs) as the catalyst. Compared with common Pd/C, Pd/CNTs could more effectively catalyze the reaction of dibromo-substituted olefins with boronic acids, affording the corresponding tetrasubstituted olefins with moderate to good yields. This environmentally benign route with an easy-to-handle catalyst provides an appealing alternative to the currently available methods.

  6. The {sup 14}N(p, {gamma}){sup 15}O reaction studied at low and high beam energy

    Energy Technology Data Exchange (ETDEWEB)

    Marta, Michele

    2012-07-01

    The Bethe-Weizsaecker cycle consists of a set of nuclear reactions that convert hydrogen into helium and release energy in the stars. It determines the luminosity of low-metal stars at their turn-off from the main-sequence in the Hertzsprung-Russel diagram, so its rate enters the calculation of the globular clusters' age, an independent lower limit on the age of the universe. The cycle contributes less than 1% to our Sun's luminosity, but it produces neutrinos that can in principle be measured on Earth in underground experiments and bring direct information of the physical conditions in the solar core, provided that the nuclear reaction rate is known with sufficient precision. The {sup 14}N(p,{gamma}){sup 15}O reaction is the slowest reaction of the Bethe-Weizsaecker cycle and establishes its rate. Its cross section is the sum of the contributions by capture to different excited levels and to the ground state in {sup 15}O. Recent experiments studied the region of the resonance at E{sub p} = 278 keV. Only one modern data set from an experiment performed in 1987 is available for the high-energy domain. Both energy ranges are needed to constrain the fit of the excitation function in the R-matrix framework and to obtain a reliable extrapolated S-factor at the very low astrophysical energies. The present research work studied the {sup 14}N(p,{gamma}){sup 15}O reaction in the LUNA (Laboratory for Underground Nuclear Astrophysics) underground facility at three proton energies 0.36, 0.38, 0.40MeV, and in Dresden in the energy range E{sub p} = 0.6 - 2MeV. In both cases, an intense proton beam was sent on solid titanium nitride sputtered targets, and the prompt photons emitted from the reaction were detected with germanium detectors. At LUNA, a composite germanium detector was used. This enabled a measurement with dramatically reduced summing corrections with respect to previous studies. The cross sections for capture to the ground state and to the excited states

  7. Oxygen-18 and carbon-13 records for the last 14,000 years from lacustrine carbonates of Siling-Co (lake) in the Qinghai-Tibetan Plateau

    Science.gov (United States)

    Morinaga, H.; Itota, C.; Isezaki, N.; Goto, H.; Yaskawa, K.; Kusakabe, M.; Liu, J.; Gu, Z.; Yuan, B.; Cong, S.

    1993-12-01

    To understand paleoenvironmental changes for the central Qinghai-Tibetan plateau, we analyzed stable isotopes of oxygen and carbon from calcium carbonates in a bottom sediment core collected from Siling-Co (lake). Five conventional and two Tandetron Acceleration Mass Spectrometry (TAMS) C-14 dates indicate that the core recovered sediments of the last 14,000 years. Calcium carbonates in the sediments seem to be primary carbonates precipitated chemically in the lake, and not clastic particles from limestones distributed around the lake, because of large variation of isotopic ratios, isotopic covariance since 6,000 yr BP and similarity between dates from total calcium carbonates and organic carbon. Their isotopic composition therefore reflects that of the lake water. We present the following paleoenvironmental history over the last 14,000 years in the central part of the plateau, from secular variations of delta O-18, delta C-13 and CaCO3 content throughout the core: (1) Desiccation was dominant during the latter part of the Last Glacial stage (14,000 to 11,000 yr BP). (2) The Last Glacial stage abruptly terminated at 11,000 yr BP. (3) A temperate and stable climate was dominant from 11,000 to 5,000 yr BP. (4) Climatic conditions fluctuated from 5,000 to the present, including two strong desiccation periods (5,000 to 4,000 yr BP and 3,000 to 2,000 yr BP) and an intermediate period of heavy rainfall (4,000 to 3,000 yr BP). This period is also characterized by a covariant O and C isotopic trend.

  8. Nano-Scale Au Supported on Carbon Materials for the Low Temperature Water Gas Shift (WGS Reaction

    Directory of Open Access Journals (Sweden)

    Paula Sánchez

    2011-12-01

    Full Text Available Au-based catalysts supported on carbon materials with different structures such as graphite (G and fishbone type carbon nanofibers (CNF-F were prepared using two different methods (impregnation and gold-sol to be tested in the water gas shift (WGS reaction. Atomic absorption spectrometry, transmission electron microscopy (TEM, temperature-programmed oxidation (TPO, X-ray diffraction (XRD, Raman spectroscopy, elemental analyses (CNH, N2 adsorption-desorption analysis, temperature-programmed reduction (TPR and temperature-programmed decomposition were employed to characterize both the supports and catalysts. Both the crystalline nature of the carbon supports and the method of gold incorporation had a strong influence on the way in which Au particles were deposited on the carbon surface. The higher crystallinity and the smaller and well dispersed Au particle size were, the higher activity of the catalysts in the WGS reaction was noted. Finally, catalytic activity showed an important dependence on the reaction temperature and steam-to-CO molar ratio.

  9. Analysis of LMD data of core coming from Ta(15C, 14C+n)Ta Coulomb breakup reaction

    International Nuclear Information System (INIS)

    It is well established fact that the neutron-halo nucleus is a loosely bound exotic nuclear state where in the valence neutron is found mostly at a much larger distance from the remaining core. The development of radioactive ion beams (RI) has provided a great opportunity to explore various peculiar properties of such nuclear systems. Consequently lots of efforts have been made on theoretical and experimental fronts to understand the exotic features of halo nuclei. One of the clear manifestations of exotic properties of isotopes lying near neutron drip line is the loss of magicity and the tendency to posses prolate deformation. In this conference contribution, we study Ta(15C, 14C+n)Ta Coulomb breakup reaction with a special emphasis on the study of effects of deformation and to investigate the possibility of occupying d-orbital by valence neutron in 15 C

  10. Luminosity determination for the pd reaction at 2.14 GeV with WASA-at-COSY

    Institute of Scientific and Technical Information of China (English)

    ZHENG Chuan; M. Büscher; P. Fedorets; V.Hejny; H. Str(o)her; XU Hu-Shan; YUAN Xiao-Hua

    2012-01-01

    The luminosity for a WASA-at-COSY experiment involving the pd reaction at 2.14 GeV protonbeam energy is determined by the forward pd elastic scattering,which yields an average beam-on-target value of [5.2±0.3(stat)±0.3(syst)] × 1030s-1 cm-2.In addition,the forward pd elastic-scattering angular distribution is obtained with four-momentum transfer squared -t between 0.16 (GeV/c)2 and 0.78 (GeV/c)2 at this beam energy,which is compared with other experimental data and the pd double scattering model.

  11. Semi-empirical systematics of (n, p) reaction cross sections for 14.5 MeV neutrons

    International Nuclear Information System (INIS)

    A new semi-empirical formula for the calculation of the (n, p) cross section at 14.5 MeV neutron energy is obtained. Derived from the evaporation statistical model, the new formula includes five parameters and shows for the first time a strong dependence of the (n, p) cross section on terms of the parameter (2Z-1)/A. Fitting this formula to the existing cross section data on 161 nuclei with 40≤A≤209, the adjustable parameters have been determined and the systematics of the (n, p) reaction have been studied. The predictions of this formula are compared with those of the existing formulae and with the experimental data. The formula with five parameters is found to give a better fit to the data than the previous comparable formulae

  12. Diffusion-type model of the global carbon cycle for the estimation of dose to the world population from releases of carbon-14 to the atmosphere

    Energy Technology Data Exchange (ETDEWEB)

    Killough, G.G.

    1977-05-01

    A nonlinear dynamic model of the exchange of carbon among the atmosphere, terrestrial biosphere, and ocean is described and applied to estimating the radiation dose to the world's population from the release of /sup 14/C to the atmosphere from the nuclear power industry. A computer implementation of the model, written in the IBM Continuous System Modeling Program III (CSMP III) simulation language, is presented. The model treats the ocean as a diffusive medium with respect to vertical transport of carbon, and the nonlinear variation of CO/sub 2/ partial pressure with the total inorganic carbon concentration in surface waters is taken into account in calculating the transfer rate from ocean to atmosphere. Transfers between the atmosphere and terrestrial biosphere are represented by nonlinear equations which consider CO/sub 2/ fertilization and impose a constraint on the ultimate total carbon mass in the biosphere.

  13. Mechanistic aspects of the copolymerization reaction of carbon dioxide and epoxides, using a chiral salen chromium chloride catalyst.

    Science.gov (United States)

    Darensbourg, Donald J; Yarbrough, Jason C

    2002-06-01

    The air-stable, chiral (salen)Cr(III)Cl complex (3), where H(2)salen = N,N'-bis(3,5-di-tert-butyl-salicylidene)-1,2-cyclohexene diamine, has been shown to be an effective catalyst for the coupling of cyclohexene oxide and carbon dioxide to afford poly(cyclohexenylene carbonate), along with a small quantity of its trans-cyclic carbonate. The thus produced polycarbonate contained >99% carbonate linkages and had a M(n) value of 8900 g/mol with a polydispersity index of 1.2 as determined by gel permeation chromatography. The turnover number (TON) and turnover frequency (TOF) values of 683 g of polym/g of Cr and 28.5 g of polym/g of Cr/h, respectively for reactions carried out at 80 degrees C and 58.5 bar pressure increased by over 3-fold upon addition of 5 equiv of the Lewis base cocatalyst, N-methyl imidazole. Although this chiral catalyst is well documented for the asymmetric ring-opening (ARO) of epoxides, in this instance the copolymer produced was completely atactic as illustrated by (13)C NMR spectroscopy. Whereas the mechanism for the (salen)Cr(III)-catalyzed ARO of epoxides displays a squared dependence on [catalyst], which presumably is true for the initiation step of the copolymerization reaction, the rate of carbonate chain growth leading to copolymer or cyclic carbonate formation is linearly dependent on [catalyst]. This was demonstrated herein by way of in situ measurements at 80 degrees C and 58.5 bar pressure. Hence, an alternative mechanism for copolymer production is operative, which is suggested to involve a concerted attack of epoxide at the axial site of the chromium(III) complex where the growing polymer chain for epoxide ring-opening resides. Preliminary investigations of this (salen)Cr(III)-catalyzed system for the coupling of propylene oxide and carbon dioxide reveal that although cyclic carbonate is the main product provided at elevated temperatures, at ambient temperature polycarbonate formation is dominant. A common reaction pathway for

  14. Accelerated carbonation using municipal solid waste incinerator bottom ash and cold-rolling wastewater: Performance evaluation and reaction kinetics.

    Science.gov (United States)

    Chang, E-E; Pan, Shu-Yuan; Yang, Liuhanzi; Chen, Yi-Hung; Kim, Hyunook; Chiang, Pen-Chi

    2015-09-01

    Accelerated carbonation of alkaline wastes including municipal solid waste incinerator bottom ash (MSWI-BA) and the cold-rolling wastewater (CRW) was investigated for carbon dioxide (CO2) fixation under different operating conditions, i.e., reaction time, CO2 concentration, liquid-to-solid ratio, particle size, and CO2 flow rate. The MSWI-BA before and after carbonation process were analyzed by the thermogravimetry and differential scanning calorimetry, X-ray diffraction, and scanning electron microscopy equipped with energy dispersive X-ray spectroscopy. The MSWI-BA exhibits a high carbonation conversion of 90.7%, corresponding to a CO2 fixation capacity of 102g perkg of ash. Meanwhile, the carbonation kinetics was evaluated by the shrinking core model. In addition, the effect of different operating parameters on carbonation conversion of MSWI-BA was statistically evaluated by response surface methodology (RSM) using experimental data to predict the maximum carbonation conversion. Furthermore, the amount of CO2 reduction and energy consumption for operating the proposed process in refuse incinerator were estimated. Capsule abstract: CO2 fixation process by alkaline wastes including bottom ash and cold-rolling wastewater was developed, which should be a viable method due to high conversion.

  15. Formation of brown carbon via reactions of ammonia with secondary organic aerosols from biogenic and anthropogenic precursors

    Science.gov (United States)

    Updyke, Katelyn M.; Nguyen, Tran B.; Nizkorodov, Sergey A.

    2012-12-01

    Filter samples of secondary organic aerosols (SOA) generated from the ozone (O3)- and hydroxyl radical (OH)-initiated oxidation of various biogenic (isoprene, α-pinene, limonene, α-cedrene, α-humulene, farnesene, pine leaf essential oils, cedar leaf essential oils) and anthropogenic (tetradecane, 1,3,5-trimethylbenzene, naphthalene) precursors were exposed to humid air containing approximately 100 ppb of gaseous ammonia (NH3). Reactions of SOA compounds with NH3 resulted in production of light-absorbing "brown carbon" compounds, with the extent of browning ranging from no observable change (isoprene SOA) to visible change in color (limonene SOA). The aqueous phase reactions with dissolved ammonium (NH4+) salts, such as ammonium sulfate, were equally efficient in producing brown carbon. Wavelength-dependent mass absorption coefficients (MAC) of the aged SOA were quantified by extracting known amounts of SOA material in methanol and recording its UV/Vis absorption spectra. For a given precursor, the OH-generated SOA had systematically lower MAC compared to the O3-generated SOA. The highest MAC values, for brown carbon from SOA resulting from O3 oxidation of limonene and sesquiterpenes, were comparable to MAC values for biomass burning particles but considerably smaller than MAC values for black carbon aerosols. The NH3/NH4+ + SOA brown carbon aerosol may contribute to aerosol optical density in regions with elevated concentrations of NH3 or ammonium sulfate and high photochemical activity.

  16. Cross sections for 13.5-14.7 MeV neutron induced reactions on palladium isotopes

    CERN Document Server

    Kong Xiang Zhong; Wang Yong; Yang Jing Kan

    1999-01-01

    Cross sections for (n, p), (n, alpha) and (n, 2n) reactions have been measured on palladium isotopes at 13.5-14.7 MeV using the activation technique. Data are reported for the following reactions: sup 1 sup 0 sup 2 Pd(n, p) sup 1 sup 0 sup 2 sup m Rh, sup 1 sup 0 sup 2 Pd(n, p) sup 1 sup 0 sup 2 sup g Rh, sup 1 sup 0 sup 5 Pd(n, p) sup 1 sup 0 sup 5 Rh, sup 1 sup 0 sup 6 Pd(n, p) sup 1 sup 0 sup 6 Rh; sup 1 sup 0 sup 6 Pd(n, alpha) sup 1 sup 0 sup 3 Ru, sup 1 sup 0 sup 8 Pd(n, alpha) sup 1 sup 0 sup 5 Ru; sup 1 sup 0 sup 2 Pd(n, 2n) sup 1 sup 0 sup 1 Pd and sup 1 sup 1 sup 0 Pd(n, 2n) sup 1 sup 0 sup 9 Pd.

  17. Measurement method of activation cross-sections of reactions producing short-lived nuclei with 14 MeV neutrons

    CERN Document Server

    Kawade, K; Kasugai, Y; Shibata, M; Iida, T; Takahashi, A; Fukahori, T

    2003-01-01

    We describe a method for obtaining reliable activation cross-sections in the neutron energy range between 13.4 and 14.9 MeV for the reactions producing short-lived nuclei with half-lives between 0.5 and 30 min. We noted neutron irradiation fields and measured induced activities, including (1) the contribution of scattered low-energy neutrons, (2) the fluctuation of the neutron fluence rate during the irradiation, (3) the true coincidence sum effect, (4) the random coincidence sum effect, (5) the deviation in the measuring position due to finite sample thickness, (6) the self-absorption of the gamma-ray in the sample material and (7) the interference reactions producing the same radionuclides or the ones emitting the gamma-ray with the same energy of interest. The cross-sections can be obtained within a total error of 3.6%, when good counting statistics are achieved, including an error of 3.0% for the standard cross-section of sup 2 sup 7 Al (n, alpha) sup 2 sup 4 Na. We propose here simple methods for measuri...

  18. Highly Efficient Electrocatalysts for Oxygen Reduction Reaction Based on 1D Ternary Doped Porous Carbons Derived from Carbon Nanotube Directed Conjugated Microporous Polymers

    KAUST Repository

    He, Yafei

    2016-10-11

    © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.One-dimensional (1D) porous materials have shown great potential for gas storage and separation, sensing, energy storage, and conversion. However, the controlled approach for preparation of 1D porous materials, especially porous organic materials, still remains a great challenge due to the poor dispersibility and solution processability of the porous materials. Here, carbon nanotube (CNT) templated 1D conjugated microporous polymers (CMPs) are prepared using a layer-by-layer method. As-prepared CMPs possess high specific surface areas of up to 623 m2 g-1 and exhibit strong electronic interactions between p-type CMPs and n-type CNTs. The CMPs are used as precursors to produce heteroatom-doped 1D porous carbons through direct pyrolysis. As-produced ternary heteroatom-doped (B/N/S) 1D porous carbons possess high specific surface areas of up to 750 m2 g-1, hierarchical porous structures, and excellent electrochemical-catalytic performance for oxygen reduction reaction. Both of the diffusion-limited current density (4.4 mA cm-2) and electron transfer number (n = 3.8) for three-layered 1D porous carbons are superior to those for random 1D porous carbon. These results demonstrate that layered and core-shell type 1D CMPs and related heteroatom-doped 1D porous carbons can be rationally designed and controlled prepared for high performance energy-related applications.

  19. Carbonation rates of peridotite in the Samail Ophiolite, Sultanate of Oman, constrained through 14C dating and stable isotopes

    Science.gov (United States)

    Mervine, Evelyn M.; Humphris, Susan E.; Sims, Kenneth W. W.; Kelemen, Peter B.; Jenkins, William J.

    2014-02-01

    Detailed 14C dating as well as stable C and O isotope analyses were conducted on carbonates formed during alteration of the peridotite layer of the Samail Ophiolite, Sultanate of Oman. 14C results obtained in this and previous studies indicate that surface travertines range in age from modern to >45,000 yr BP, indicating long-term deposition and preservation. Travertine deposition rates in two localities were ˜0.1 to 0.3 mm/yr between ˜30,000 and 45,000 yr BP. Using an estimate of total travertine area, this would result in a maximum of ˜1000 to 3000 m3/yr of travertine being deposited throughout the ophiolite during this time period. This travertine deposition would have sequestered a maximum of ˜1 to 3 × 106 kg CO2/yr. Ca-rich carbonate veins that are associated with the surface travertine deposits have ages ranging from ˜4000 to 36,000 yr BP (average: 15,000 yr BP). Mg-rich carbonate veins exposed in outcrops have ages ranging from ˜8000 to 45,000 yr BP (average: 35,000 yr BP). Detailed sampling from numerous locations (3 locations in this study and 10 locations in the previous studies) indicates that no carbonate veins from the natural peridotite weathering surface are older than the ˜50,000 yr BP dating limit of 14C. However, 14C dating of Mg-rich carbonate veins from three roadcut exposures (Qafeefah, Fanja, and Al-Wuqbah) indicates that a significant number of roadcut veins are 14C dead (>50,000 yr BP). A location weighted average indicates that ˜40% of veins sampled at the three roadcuts are 14C dead. An average including veins sampled at both roadcuts and outcrops indicates that overall ˜8% of Mg-rich carbonate veins are 14C dead. Mg-rich carbonate veins are estimated to sequester on the order of 107 kg CO2/yr throughout the ophiolite.

  20. Release of (14)C-labelled carbon nanotubes from polycarbonate composites.

    Science.gov (United States)

    Rhiem, Stefan; Barthel, Anne-Kathrin; Meyer-Plath, Asmus; Hennig, Michael P; Wachtendorf, Volker; Sturm, Heinz; Schäffer, Andreas; Maes, Hanna M

    2016-08-01

    Waste disposal of carbon nanotube (CNT) containing products is expected to be the most important pathway for release of CNTs into the environment. In the present work, the use of radiolabelled CNTs ((14)C-CNT) for polycarbonate polymer nanocomposites with 1 wt% (14)C-CNT content allowed for the first time to quantify and differentiate the CNT release according to the type of impact along the materials' ageing history. After an initial exposure of the nanocomposite by solar-like irradiation, further environmental impacts were applied to composite material. They aimed at mimicking disposal site conditions that may induce further ageing effects and CNT release. This study included shaking in water, rapid temperature changes, soaking in humic acid solution as well as waste water effluent, and, finally, gentle mechanical abrasion. All ageing impacts were applied sequentially, both on pristine (control) and on solar-irradiated nanocomposites. All experiments were accompanied by absolute quantification of radioactive release as well as chemical and morphological analyses of the nanocomposite surfaces using infra-red (IR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The morphological analysis showed that spectral irradiation can uncover CNT networks on the outer nanocomposite surface layers by polymer degradation. After having subjected the solar-irradiated nanocomposite to all studied disposal site effect, the total radioactive release was quantified to amount to 64 mg CNT/m(2), whereas only 0.8 mg CNT/m(2) were found for the un-irradiated control sample. Solar degradation of polymers was thus found to significantly increase the propensity of the studied polymer nanocomposites to release CNTs during ageing effects at the product's end-of-life typical for disposal sites. PMID:27194367

  1. Towards a global understanding of vertical soil carbon dynamics: meta-analysis of soil 14C data

    Science.gov (United States)

    hatte, C.; Balesdent, J.; Guiot, J.

    2012-12-01

    Soil represents the largest terrestrial storage mechanism for atmospheric carbon from photosynthesis, with estimates ranging from 1600 Pg C within the top 1 meter to 2350 Pg C for the top 3 meters. These values are at least 2.5 times greater than atmospheric C pools. Small changes in soil organic carbon storage could result in feedback to atmospheric CO2 and the sensitivity of soil organic matter to changes in temperature, and precipitation remains a critical area of research with respect to the global carbon cycle. As an intermediate storage mechanism for organic material through time, the vertical profile of carbon generally shows an age continuum with depth. Radiocarbon provides critical information for understanding carbon exchanges between soils and atmosphere, and within soil layers. Natural and "bomb" radiocarbon has been used to demonstrate the importance and nature of the soil carbon response to climatic and human impacts on decadal to millennial timescales. Radiocarbon signatures of bulk, or chemically or physically fractionated soil, or even of specific organic compounds, offer one of the only ways to infer terrestrial carbon turnover times or test ecosystem carbon models. We compiled data from the literature on radiocarbon distribution on soil profiles and characterized each study according to the following categories: soil type, analyzed organic fraction, location (latitude, longitude, elevation), climate (temperature, precipitation), land use and sampling year. Based on the compiled data, soil carbon 14C profiles were reconstructed for each of the 226 sites. We report here partial results obtained by statistical analyses of portion of this database, i.e. bulk and bulk-like organic matter and sampling year posterior to 1980. We highlight here 14C vertical pattern in relationship with external parameters (climate, location and land use).

  2. Magnetic Carbon Supported Palladium Nanoparticles: An Efficient and Sustainable Catalyst for Hydrogenation Reactions

    Science.gov (United States)

    Magnetic carbon supported Pd catalyst has been synthesized via in situ generation of nanoferrites and incorporation of carbon from renewable cellulose via calcination; the catalyst can be used for the hydrogenation of alkenes and reduction of aryl nitro compounds.

  3. Distribution of {delta}{sup 14}C in western North Pacific and tracing carbons of human origin

    Energy Technology Data Exchange (ETDEWEB)

    Aramaki, Takafumi; Mizushima, Toshihiko; Togawa, Orihiko [Japan Atomic Energy Research Inst., Mutsu, Aomori (Japan). Mutsu Establishment; Watanabe, Shuichi; Tsunogai, Shizuo [Hokkaido Univ., Sapporo (Japan); Kuji, Tomoyuki [Japan marine Sience Fundation, Mutsu, Aomori (Japan)

    2001-02-01

    Seawater were collected at six points, 0deg to 48degN around 165degE. Dissolved inorganic carbonates was reduced into graphite. The ratio C-11/C-12 was measured by the accelerator mass analyzer. {sup 14}C concentration was calculated from {delta}{sup 13}C value calculated from the {sup 13}C/{sup 12}C ratio. {sup 14}C resulting from the nuclear weapon test was calculated by comparing estimated {sup 14}C and real {sup 14}C concentration. It was compared with that in 1970s. {sup 14}Cbomb has dissolved into North Pacific Intermediate Water in Arctic latitude, which has moved to Mid-latitude. (A. Yamamoto)

  4. Carbon and Oxygen Isotopic Stratigraphy of Mesoproterozoic Carbonate Sequences (1.6–1.4 Ga from Yanshan in North China

    Directory of Open Access Journals (Sweden)

    Kuang Hongwei

    2011-01-01

    Full Text Available In Yanshan, located in the northern part of North China, Mesoproterozoic carbonate sequences (1.6–1.4 Ga form a 10, 000 m thick succession in an aulacogen basin. Carbon and oxygen isotope (δ13O and δ18O, resp. data were obtained from 110 carbonate samples across three sections of these Mesoproterozoic deposits. From the early to late Mesoproterozoic, low negative values of δ13O appear, followed by low positive variation and then a stable increase. An abrupt decrease in δ13O values, with subsequent rapid increase, is found at the end of the Mesoproterozoic. During the whole Mesoproterozoic, δ18O shows a mainly negative trend and occasional highly negative isotopic shifts (from lower to upper deposits. Whole-rock carbon and oxygen isotopic compositions and profiles must be studied to provide a paleogeochemical record that can be associated with paleocean sedimentary environments, temperature, biological productivity, and sea-level fluctuations. Results of the present study correlate well with other international carbon and oxygen isotope profiles, suggesting that a global marine geochemical system existed during the interval of 1.6–1.4 Ga under a globally united tectonic, sedimentary, and geochemical background.

  5. Multimolecular tracers of terrestrial carbon transfer across the pan-Arctic: 14C characteristics of sedimentary carbon components and their environmental controls

    Science.gov (United States)

    Feng, Xiaojuan; Gustafsson, Örjan; Holmes, R. Max; Vonk, Jorien E.; Dongen, Bart E.; Semiletov, Igor P.; Dudarev, Oleg V.; Yunker, Mark B.; Macdonald, Robie W.; Wacker, Lukas; Montluçon, Daniel B.; Eglinton, Timothy I.

    2015-11-01

    Distinguishing the sources, ages, and fate of various terrestrial organic carbon (OC) pools mobilized from heterogeneous Arctic landscapes is key to assessing climatic impacts on the fluvial release of carbon from permafrost. Through molecular 14C measurements, including novel analyses of suberin- and/or cutin-derived diacids (DAs) and hydroxy fatty acids (FAs), we compared the radiocarbon characteristics of a comprehensive suite of terrestrial markers (including plant wax lipids, cutin, suberin, lignin, and hydroxy phenols) in the sedimentary particles from nine major arctic and subarctic rivers in order to establish a benchmark assessment of the mobilization patterns of terrestrial OC pools across the pan-Arctic. Terrestrial lipids, including suberin-derived longer-chain DAs (C24,26,28), plant wax FAs (C24,26,28), and n-alkanes (C27,29,31), incorporated significant inputs of aged carbon, presumably from deeper soil horizons. Mobilization and translocation of these "old" terrestrial carbon components was dependent on nonlinear processes associated with permafrost distributions. By contrast, shorter-chain (C16,18) DAs and lignin phenols (as well as hydroxy phenols in rivers outside eastern Eurasian Arctic) were much more enriched in 14C, suggesting incorporation of relatively young carbon supplied by runoff processes from recent vegetation debris and surface layers. Furthermore, the radiocarbon content of terrestrial markers is heavily influenced by specific OC sources and degradation status. Overall, multitracer molecular 14C analysis sheds new light on the mobilization of terrestrial OC from arctic watersheds. Our findings of distinct ages for various terrestrial carbon components may aid in elucidating fate of different terrestrial OC pools in the face of increasing arctic permafrost thaw.

  6. The history of ironware in Japan revealed by the AMS-carbon 14 age method

    International Nuclear Information System (INIS)

    This paper focuses on the influence what the AMS-carbon 14 age method attains to the history of the iron in the Japanese Islands. The research team in National Museum of Japanese History makes a clear that the Yayoi period began in 10 Cen. cal BC. However, there was a problem in this. It is iron. If the Yayoi period has started in the 10th Cen. BC, it means that the ironware in Japanese Islands had spread early rather than it spreads in China. The research team reexamined the ironware excavated from Magarita site in the Fukuoka Pref. considered to be the oldest ironware in Japan. Consequently, the excavation situation was indefinite and it turned out that we cannot specify the time to belong. Furthermore, 36 ironwares in the initial and early Yayoi were also already found by that time cannot be specified except for two points. Therefore, it turned out that Japanese ironware appeared in the 3rd century of B.C. What does this mean? Although it had been thought that the beginning of agriculture in Japan and the appearance of ironware were simultaneous, it turned out that agriculture has appeared early about in 700 years. Therefore, it became clear that agriculture of Japan started at the Stone Age. (author)

  7. Accelerated carbonation using municipal solid waste incinerator bottom ash and cold-rolling wastewater: Performance evaluation and reaction kinetics

    Energy Technology Data Exchange (ETDEWEB)

    Chang, E-E [Department of Biochemistry, Taipei Medical University, 250 Wu-Hsing Street, Taipei City, Taiwan 110, Taiwan, ROC (China); Pan, Shu-Yuan [Graduate Institute of Environmental Engineering, National Taiwan University, 71 Chou-Shan Rd., Taipei City, Taiwan 10673, Taiwan, ROC (China); Yang, Liuhanzi [School of Environment, Tsinghua University, Haidin District, Beijing 100084 (China); Chen, Yi-Hung [Department of Chemical Engineering and Biotechnology, National Taipei University of Technology, 1, Sec. 3, Zhongxiao E. Rd., Taipei City, Taiwan 10608, Taiwan, ROC (China); Kim, Hyunook [Department of Energy and Environmental System Engineering, University of Seoul (Korea, Republic of); Chiang, Pen-Chi, E-mail: pcchiang@ntu.edu.tw [Graduate Institute of Environmental Engineering, National Taiwan University, 71 Chou-Shan Rd., Taipei City, Taiwan 10673, Taiwan, ROC (China)

    2015-09-15

    Highlights: • Carbonation was performed using CO{sub 2}, wastewater and bottom ash in a slurry reactor. • A maximum capture capacity of 102 g CO{sub 2} per kg BA was achieved at mild conditions. • A maximum carbonation conversion of MSWI-BA was predicted to be 95% by RSM. • The CO{sub 2} emission from Bali incinerator could be expected to reduce by 6480 ton/y. • The process energy consumption per ton CO{sub 2} captured was estimated to be 180 kW h. - Abstract: Accelerated carbonation of alkaline wastes including municipal solid waste incinerator bottom ash (MSWI-BA) and the cold-rolling wastewater (CRW) was investigated for carbon dioxide (CO{sub 2}) fixation under different operating conditions, i.e., reaction time, CO{sub 2} concentration, liquid-to-solid ratio, particle size, and CO{sub 2} flow rate. The MSWI-BA before and after carbonation process were analyzed by the thermogravimetry and differential scanning calorimetry, X-ray diffraction, and scanning electron microscopy equipped with energy dispersive X-ray spectroscopy. The MSWI-BA exhibits a high carbonation conversion of 90.7%, corresponding to a CO{sub 2} fixation capacity of 102 g per kg of ash. Meanwhile, the carbonation kinetics was evaluated by the shrinking core model. In addition, the effect of different operating parameters on carbonation conversion of MSWI-BA was statistically evaluated by response surface methodology (RSM) using experimental data to predict the maximum carbonation conversion. Furthermore, the amount of CO{sub 2} reduction and energy consumption for operating the proposed process in refuse incinerator were estimated. Capsule abstract: CO{sub 2} fixation process by alkaline wastes including bottom ash and cold-rolling wastewater was developed, which should be a viable method due to high conversion.

  8. Boron Doped Multi-walled Carbon Nanotubes as Catalysts for Oxygen Reduction Reaction and Oxygen Evolution Reactionin in Alkaline Media

    International Nuclear Information System (INIS)

    The boron doped multi-walled carbon nanotubes (B-MWCNTs) were synthesized by thermal annealing multi-walled carbon nanotubes (MWCNTs) in the presence of boric acid. The transmission electron microscopy (TEM) and X-ray diffraction (XRD) results revealed that the structure of MWCNTs does not be destroyed during the doping process, and X-ray photoelectron spectroscopy (XPS) analysis demonstrated the boron atoms were successfully doped in the structure of MWCNTs. The electrocatalytic properties of B-MWCNTs are characterized by rotating disk electrode (RDE) methods. The results demonstrated that the B-MWCNTs catalyzed oxygen reduction reaction (ORR) in alkaline media by a 2 + 2 electron pathway and it showed good catalytic activity for oxygen evolution reaction (OER) as well

  9. Carboxyl functionalization of carbon fibers via aryl diazonium reaction in molten urea to enhance interfacial shear strength

    Science.gov (United States)

    Wang, Yuwei; Meng, Linghui; Fan, Liquan; Wu, Guangshun; Ma, Lichun; Zhao, Min; Huang, Yudong

    2016-01-01

    Using molten urea as the solvent, carbon fibers were functionalized with carboxylic acid groups via aryl diazonium reaction in 15 min to improve their interfacial bonding with epoxy resin. The surface functionalization was quantified by X-ray photoelectron spectroscopy, which showed that the relative surface coverage of carboxylic acid groups increased from an initial percentage of 3.17-10.41%. Mechanical property test results indicated that the aryl diazonium reaction in this paper could improve the interfacial shear strength by 66%. Meanwhile, the technique did not adopt any pre-oxidation step to produce functional groups prior to grafting and was shown to maintain the tensile strength of the fibers. This methodology provided a rapid, facile and economically viable route to produce covalently functionalized carbon fibers in large quantities with an eco-friendly method.

  10. Low temperature synthesis of high quality carbon nanospheres through the chemical reactions between calcium carbide and oxalic acid

    Energy Technology Data Exchange (ETDEWEB)

    Xie Yonggui, E-mail: xieyg2004@163.com [State Key Laboratory for Powder Metallurgy, Central South University, Changsha, Hunan 410083 (China); Huang Qizhong, E-mail: qzhuang@mail.csu.edu.cn [State Key Laboratory for Powder Metallurgy, Central South University, Changsha, Hunan 410083 (China); Huang Baiyun [State Key Laboratory for Powder Metallurgy, Central South University, Changsha, Hunan 410083 (China); Xie Xiangmin [Applied Chemistry Department, College of Science, Hunan Agricultural University, Changsha, Hunan 410128 (China)

    2010-11-01

    Carbon nanospheres (CNSs) were synthesized through the chemical reactions of calcium carbide and oxalic acid without using catalysts. The chemical reactions were carried out in a sealed stainless steel pressure vessel with various molar ratios at temperatures of 65-250 deg. C. The synthesized CNSs have been characterized using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) attached to the SEM, transmission electron microscopy (TEM), X-ray diffraction (XRD) and Raman spectroscopy. The total yield of carbonaceous materials relative to the starting material is about 4% (w/w). SEM and TEM results reveal that the percentage of CNSs is high (>95%). The CNSs that have been synthesized are roe-like spheres of relatively uniform size with diameters of 60-120 nm. The attached EDS result shows that the carbon content of CNSs reaches up to 98%.

  11. Synthesis of graphitic carbon nitride by reaction of melamine and uric acid

    Energy Technology Data Exchange (ETDEWEB)

    Dante, Roberto C., E-mail: rcdante@yahoo.com [Laboratorio de Tecnologias del Medio Ambiente, Departamento de Ingenieria Agricola y Forestal, Universidad de Valladolid, Avenida de Madrid 44, 34004 Palencia (Spain); Martin-Ramos, Pablo, E-mail: pablomartinramos@gmail.com [Laboratorio de Tecnologias del Medio Ambiente, Departamento de Ingenieria Agricola y Forestal, Universidad de Valladolid, Avenida de Madrid 44, 34004 Palencia (Spain); Correa-Guimaraes, Adriana, E-mail: acg@iaf.uva.es [Laboratorio de Tecnologias del Medio Ambiente, Departamento de Ingenieria Agricola y Forestal, Universidad de Valladolid, Avenida de Madrid 44, 34004 Palencia (Spain); Martin-Gil, Jesus, E-mail: jesusmartingil@gmail.com [Laboratorio de Tecnologias del Medio Ambiente, Departamento de Ingenieria Agricola y Forestal, Universidad de Valladolid, Avenida de Madrid 44, 34004 Palencia (Spain)

    2011-11-01

    Highlights: {yields} Graphitic carbon nitrides by CVD of melamine and uric acid on alumina. {yields} The building blocks of carbon nitrides are heptazine nuclei. {yields} Composite particles with alumina core and carbon nitride coating. - Abstract: Graphitic carbon nitrides were synthesized starting from melamine and uric acid. Uric acid was chosen because it thermally decomposes, and reacts with melamine by condensation at temperatures in the range of 400-600 deg. C. The reagents were mixed with alumina and subsequently the samples were treated in an oven under nitrogen flux. Alumina favored the deposition of the graphitic carbon nitrides layers on the exposed surface. This method can be assimilated to an in situ chemical vapor deposition (CVD). Infrared (IR) spectra, as well as X-ray diffraction (XRD) patterns, are in accordance with the formation of a graphitic carbon nitride with a structure based on heptazine blocks. These carbon nitrides exhibit poor crystallinity and a nanometric texture, as shown by transmission electron microscopy (TEM) analysis. The thermal degradation of the graphitic carbon nitride occurs through cyano group formation, and involves the bridging tertiary nitrogen and the bonded carbon, which belongs to the heptazine ring, causing the ring opening and the consequent network destruction as inferred by connecting the IR and X-ray photoelectron spectroscopy (XPS) results. This seems to be an easy and promising route to synthesize graphitic carbon nitrides. Our final material is a composite made of an alumina core covered by carbon nitride layers.

  12. Carbon Fibre and Its Reaction With Metals%碳纤维及其与金属的作用

    Institute of Scientific and Technical Information of China (English)

    赵浩峰; 王玲; 刘红梅; 韩世平

    2001-01-01

    本文介绍了金属基复合材料中常用增强物——碳纤维的结构及性能,特别总结讨论了碳纤维与常用金属的结合类型。%The paper deals with the structure and performance of carbon fibre used in MMCs and especially the reaction between it and some metals.

  13. Protective effect of application of carbon nanoparticles in thyroid cancer surgery and evaluation of inflammatory stress reaction degree

    Institute of Scientific and Technical Information of China (English)

    Qing-Sheng Zheng; Jun-Zheng Li; Wei-Xiong Hong; Jiao-Yuan Xu; Si-Yi Zhang

    2015-01-01

    Objective:To study the protective effect of application of carbon nanoparticles in thyroid cancer surgery and its influence on inflammatory stress reaction degree.Methods:Patients who received thyroid cancer surgery in our hospital from June 2013 to June 2014 were chosen for study and randomly divided into conventional group and nano-carbon group. Then contents of thyroid cancer related malignant molecules, pro-inflammation cytokines and inflammation inhibiting factors in serum were detected.Results:(1) Malignant molecules: compared with conventional group, mRNA levels of Wip1, gal-3, SATB1, LSD1, GDF-15 and TBX2 in serum of nano-carbon group were lower; (2) Inflammation inhibiting factors: compared with conventional group, serum MFG-E8 and Omentin-1 levels of nano-carbon group were higher; (3) Pro-inflammation cytokines: compared with conventional group, serum MIP-1, SGK-1 and β-EP levels of nano-carbon group were lower.Conclusion: Application of carbon nanoparticles in thyroid cancer surgery is helpful to reduce operative damage to thyroid tissue, prevent release of malignant biological molecules into bloodstream and relieve inflammatory response; it’s an ideal surgical method for thyroid cancer.

  14. Electrocatalytic oxygen evolution reaction at a FeNi composite on a carbon nanofiber matrix in alkaline media

    Institute of Scientific and Technical Information of China (English)

    Xianghua An; Dongyoon Shin; Joey D. Ocon; Jae Kwang Lee; Young-il Son; Jaeyoung Lee

    2014-01-01

    Non-noble metals such as Fe and Ni have comparable electrocatalytic activity and stability to that of Ir and Ru in an oxygen evolution reaction (OER). In this study, we synthesized carbon nanofibers with embedded FeNi composites (FeNi-CNFs) as OER electrocatalysts by a facile route comprising electrospinning and the pyrolysis of a mixture of metal precursors and a polymer solution. FeNi-CNFs demonstrated catalytic activity and stability that were better than that of 20 wt%Ir on Vulcan carbon black in oxidizing water to produce oxygen in an alkaline media. Physicochemical and electrochemical characterization revealed that Fe and Ni had synergistic roles that enhanced OER activity by the uniform formation and widening of pores in the carbon structure, while the CNF matrix also contributed to the increased stability of the catalyst.

  15. Evaluation of two decomposition schemes in Earth System Models against LIDET, C14 observations and global soil carbon maps

    Science.gov (United States)

    Ricciuto, D. M.; Yang, X.; Thornton, P. E.

    2015-12-01

    Soils contain the largest pool of carbon in terrestrial ecosystems. Soil carbon dynamics and associated nutrient dynamics play significant roles in regulating global carbon cycle and atmospheric CO2 concentrations. Our capability to predict future climate change depends to a large extent on a well-constrained representation of soil carbon dynamics in ESMs. Here we evaluate two decomposition schemes - converging trophic cascade (CTC) and Century - in CLM4.5/ACME V0 using data from the long-term intersite decomposition experiment team (LIDET), radiocarbon (14C) observations, and Harmonized World Soil Database (HWSD). For the evaluation against LIDET, We exercise the full CLM4.5/ ACME V0 land model, including seasonal variability in nitrogen limitation and environmental scalars (temperature, moisture, O2), in order to represent LIDET experiment in a realistic way. We show that the proper design of model experiments is crucial to model evaluation using data from field experiments such as LIDET. We also use 14C profile data at 10 sites to evaluate the performance of CTC and CENTURY decomposition scheme. We find that the 14C profiles at these sites are most sensitive to the depth dependent decomposition parameters, consistent with previous studies.

  16. Measurement of Carbon Fixation Rates in Leaf Samples — Use of carbon-14 labeled sodium bicarbonate to estimate photosynthetic rates

    OpenAIRE

    sprotocols

    2014-01-01

    Author: David R. Caprette ### Generation of a Light Curve To address the hypothesis concerning photosynthetic efficiency it is necessary to expose sun and shade leaves to a range of light intensities long enough for them to fix significant amounts of carbon. It is necessary to expose identical surface areas under favorable conditions which are identical for all leaves except for light intensity (the experimental variable). A means of measuring the rate of carbon fixation is also neces...

  17. Potassium-decorated active carbon supported Co-Mo-based catalyst for water-gas shift reaction

    Institute of Scientific and Technical Information of China (English)

    Yixin Lian; RuiFen Xiao; Weiping Fang; Yiquan Yang

    2011-01-01

    The effect of potassium-decoration was studied on the activity of water-gas shift(WGS)reaction over the Co-Mo-based catalysts supported on active carbon(AC),which was prepared by incipient wetness co-impregnation method.The decoration of potassium on active carbon in advance enhances the activities of the CoMo-K/AC catalysts for WGS reaction.Highest activity(about 92% conversion)was obtained at250 ℃ for the catalyst with an optimum K2O/AC weight ratio in the range from 0.12 to 0.15.The catalysts were characterized by TPR and EPR,and the results show that activated carbon decorated with potassium makes Co-Mo species highly dispersed,and thus easily reduced and sulfurized.XRD results show that an appropriate content of potassium-decoration on active carbon supports may favors the formation of highly dispersed Co9Ss-type structures which are situated on the edge or a site in contact with MoS2,K-Mo-O-S,Mo-S-K phase.Those active species are responsible for the high activity of CoMo-K/AC catalysts.

  18. THM determination of the 65 keV resonance strength intervening in the {sup 17}O(p,α){sup 14}N reaction rate

    Energy Technology Data Exchange (ETDEWEB)

    Sergi, M. L.; La Cognata, M.; Pizzone, R. G. [INFN-Laboratori Nazionali del Sud, Catania (Italy); Spitaleri, C.; Cherubini, S.; Puglia, S. M. R.; Rapisarda, G. G.; Romano, S. [Università di Catania, Catania, Italy and INFN-Laboratori Nazionali del Sud, Catania (Italy); Burjan, S. V.; Hons, Z.; Kroha, V. [Nuclear Physics Institute of ASCR Rez near Prague (Czech Republic); Coc, A. [CSNSM, UMR 8609, CNRS/IN2P3 and Universitè Paris Sud 11, Bâtiment 104, 91405 Orsay Campus (France); Gulino, M.; Tumino, A. [Università di Catania, Catania, Italy and INFN-Laboratori Nazionali del Sud, Catania, Italy and Universitá Kore di Enna, Enna (Italy); Hammache, F. [IPN, IN2P3-CNRS et Université de Paris-Sud 91406 Orsay Cedex (France); Irgaziev, B. [GIK Institute of Engineering Sciences and Technology Topi District Swabi NWFP (Pakistan); Kiss, G. G.; Somorjai, E. [ATOMKI, Debrecen (Hungary); Lamia, L. [Università di Catania, Catania (Italy); Mukhamedzhanov, A. [Cyclotron Institute,Texas A and M University College Station (United States); and others

    2015-02-24

    The {sup 17}O(p,α){sup 14}N reaction is of paramount importance for the nucleosynthesis in a number of stellar sites, including red giants (RG), asymptotic giant branch (AGB) stars, massive stars and classical novae. We report on the indirect study of the {sup 17}O(p,α){sup 14}N reaction via the Trojan Horse Method by applying the approach recently developed for extracting the resonance strength of the narrow resonance at E{sub c.m.}{sup R} = 65 keV (E{sub X} =5.673 MeV). The strength of the 65 keV resonance in the {sup 17}O(p,α){sup 14}N reaction, measured by means of the THM, has been used to renormalize the corresponding resonance strength in the {sup 17}O+p radiative capture channel.

  19. Domino Michael-Michael and Aldol-Aldol Reactions: Diastereoselective Synthesis of Functionalized Cyclohexanone Derivatives Containing Quaternary Carbon Center.

    Science.gov (United States)

    Ghorai, Manas K; Halder, Sandipan; Das, Subhomoy

    2015-10-01

    A simple strategy for the synthesis of highly functionalized cyclohexanone derivatives containing an all-carbon quaternary center from α-(aryl/alkyl)methylidene-β-keto esters or β-diketones via a K-enolate mediated domino Michael-Michael reaction sequence with moderate to good yield and excellent diastereoselectivity (de > 99%) is described. Interestingly, Li-base mediated reaction of α-arylmethylidene-β-diketones affords functionalized 3,5-dihydroxy cyclohexane derivatives as the kinetically controlled products via a domino aldol-aldol reaction sequence with excellent diastereoselectivity. Li-enolates of the β-keto esters or β-diketones undergo facile domino Michael-Michael reaction with nitro-olefins to afford the corresponding nitrocyclohexane derivatives in good yields and excellent diastereoselectivity (de > 99%). The formation of the products and the observed stereoselectivity were explained by plausible mechanisms and supported by extensive computational study. An asymmetric version of the protocol was explored with (L)-menthol derived nonracemic substrates, and the corresponding nonracemic cyclohexanone derivatives containing an all-carbon quaternary center were obtained with excellent stereoselectivity (de, ee > 99%).

  20. Application of {sup 14}N({sup 3}He,{sup 4}He){sup 13}N nuclear reaction to nitrogen profiling

    Energy Technology Data Exchange (ETDEWEB)

    Wielunski, L.S. [Commonwealth Scientific and Industrial Research Organisation (CSIRO), Lindfield, NSW (Australia). Div. of Applied Physics

    1996-12-31

    In this paper the {sup 14}N({sup 3}He,{sup 4}He){sup 1`}3N reaction is proposed for nitrogen profiling in metals and other materials. The beam energy is chosen to be 4.65 MeV in order to use the high cross section. Two types of particle filtering are used: a 25 {mu}m thick mylar in front of the detector to avoid backscattered particle pileup and reduced detector bias voltage to avoid full energy detection of high energy protons produced by competing reactions. The depth resolution is about 150-200 nm and the sensitivity is better than for the {sup 14}N(d,{sup 4}He){sup 12}C reaction. The low level of neutron radiation background allows use of this reaction in accelerator laboratories without radiation shielding. 11 refs., 5 figs.

  1. Carbon doped molybdenum disulfide nanosheets stabilized on graphene for the hydrogen evolution reaction with high electrocatalytic ability

    Science.gov (United States)

    Li, Yong; Wang, Jiao; Tian, Xike; Ma, Longlong; Dai, Chu; Yang, Chao; Zhou, Zhaoxin

    2016-01-01

    Fabricating a cost effective hydrogen evolution reaction catalyst without using precious metal elements is in crucial demand for environmentally-benign energy production. In this work, the thin and edge-rich molybdenum disulfide nanosheets, with carbon doped in the interlayers and decorated on graphene, were developed by a facile solvothermal process. The as-synthesized nanohybrids exhibited high catalytic ability for the hydrogen evolution electrochemical reaction with an onset overpotential of 0.165 mV and a Tafel slope of 46 mV dec-1. Furthermore, the prepared nanohybrids also showed better durability and stability. Our work may lead to a potential method for in situ production of metal carbide-sulphur hybrid nanomaterials with promising applications for the hydrogen evolution reaction.Fabricating a cost effective hydrogen evolution reaction catalyst without using precious metal elements is in crucial demand for environmentally-benign energy production. In this work, the thin and edge-rich molybdenum disulfide nanosheets, with carbon doped in the interlayers and decorated on graphene, were developed by a facile solvothermal process. The as-synthesized nanohybrids exhibited high catalytic ability for the hydrogen evolution electrochemical reaction with an onset overpotential of 0.165 mV and a Tafel slope of 46 mV dec-1. Furthermore, the prepared nanohybrids also showed better durability and stability. Our work may lead to a potential method for in situ production of metal carbide-sulphur hybrid nanomaterials with promising applications for the hydrogen evolution reaction. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr07370g

  2. Direct measurement of the breakout reaction {sup 11}C({alpha},p){sup 14}N in explosive hydrogen-burning process

    Energy Technology Data Exchange (ETDEWEB)

    Hayakawa, S.; Kubono, S.; Kahl, D.; Yamaguchi, H.; Binh, Dam N.; Hashimoto, T.; Wakabayashi, Y.; He, J. J.; Iwasa, N.; Kato, S.; Komatsubara, T.; Kwon, Y. K.; Teranishi, T.; Wanajo, S. [Center for Nuclear Study, Graduate of Science, University of Tokyo (Japan) and Institute of Physics (Japan); RCNP, Osaka University (Japan); Japan Atomic Energy Agency (Japan); Institute of Modern Physics (Japan); Department of Physics, Tohoku University (Japan); Department of Physics, Yamagata University (Japan); Department of Physics, University of Tsukuba (Japan); Department of Physics, Chung Ang University (Korea, Republic of); Department of Physics, Kyushu University (Japan); Institute for the Physics and Mathematics of the Universe, University of Tokyo (Japan)

    2012-11-12

    We determined the {sup 11}C({alpha},p){sup 14}N reaction rate relevant to the nucleosynthesis in explosive hydrogen-burning stars. The measurement was performed by means of the thick target method in inverse kinematics with {sup 11}C RI beams. We derived the excitation functions for the ground-state transition and excited-state transitions using time-of-flight information for the first time. The present reaction rate is compared to the previous one.

  3. Intermediate-mass fragments from nonbinary processes in the reaction of /sup 14/N on Ag at E/A = 35 MeV

    Energy Technology Data Exchange (ETDEWEB)

    Bougault, R.; Horn, D.; Chitwood, C.B.; Fields, D.J.; Gelbke, C.K.; Klesch, D.R.; Lynch, W.G.; Tsang, M.B.; Kwiatkowski, K.

    1987-08-01

    Angular distributions of recoil nuclei were measured in coincidence with low-energy intermediate-mass fragments emitted in /sup 14/N-induced reactions on Ag at E/A = 35 MeV. The measured correlations are inconsistent with a purely binary reaction mechanism. The incomplete linear momentum transfer mechanism alone does not reproduce the data, which show evidence for emission of additional matter to the same side of the beam axis as the intermediate-mass fragment.

  4. Transition metal/nitrogen dual-doped mesoporous graphene-like carbon nanosheets for the oxygen reduction and evolution reactions

    Science.gov (United States)

    Liu, Xiaobo; Amiinu, Ibrahim Saana; Liu, Shaojun; Cheng, Kun; Mu, Shichun

    2016-07-01

    The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) have been considered as a key step in energy conversion processes. Here, a novel and simple Mg(OH)2 nanocasting method is adopted to fabricate Co and N co-doped porous graphene-like carbon nanosheets (Co@N-PGCS) by using chitosan as both carbon and N sources. The as-obtained Co@N-PGCS shows a mesopore-dominated structure as well as a high specific surface area (1716 cm2 g-1). As a bifunctional electrocatalyst towards both the ORR and OER, it shows favorable ORR performance compared with the commercial Pt/C catalyst with an onset potential of -0.075 V and a half-wave potential of -0.151 V in 0.1 M KOH solutions. Furthermore, it also displays considerable OER properties compared with commercial IrO2. The effective catalytic activity could originate from the introduction of transition metal species and few-layer mesoporous carbon structures.The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) have been considered as a key step in energy conversion processes. Here, a novel and simple Mg(OH)2 nanocasting method is adopted to fabricate Co and N co-doped porous graphene-like carbon nanosheets (Co@N-PGCS) by using chitosan as both carbon and N sources. The as-obtained Co@N-PGCS shows a mesopore-dominated structure as well as a high specific surface area (1716 cm2 g-1). As a bifunctional electrocatalyst towards both the ORR and OER, it shows favorable ORR performance compared with the commercial Pt/C catalyst with an onset potential of -0.075 V and a half-wave potential of -0.151 V in 0.1 M KOH solutions. Furthermore, it also displays considerable OER properties compared with commercial IrO2. The effective catalytic activity could originate from the introduction of transition metal species and few-layer mesoporous carbon structures. Electronic supplementary information (ESI) available: The XPS fitted results, SEM and TEM images, the K-L equation, and some of the electrochemical

  5. A technique for measuring total-body nitrogen in clinical investigations using the 14N(n, 2n) 13N reaction

    International Nuclear Information System (INIS)

    The radioactivity induced in subjects by irradiation with 14 MeV neutrons is measured in a Whole-body Radiation Counter and analysed into its separate activities. Total-body nitrogen is estimated from the annihilation spectrum after corrections for interfering reactions and the subject's body build. Total-body potassium is also derived from the spectrum following irradiation but using the contribution from its natural activity. The method is compared with that at another centre which uses the 14N (n, γ) 15N reaction. The procedure is being used to investigate nitrogen metabolism in critically-ill surgical patients and those receiving hyperalimentation. (author)

  6. Metal-Carbon Hybrid Electrocatalysts Derived from Ion-Exchange Resin Containing Heavy Metals for Efficient Hydrogen Evolution Reaction.

    Science.gov (United States)

    Zhou, Yucheng; Zhou, Weijia; Hou, Dongman; Li, Guoqiang; Wan, Jinquan; Feng, Chunhua; Tang, Zhenghua; Chen, Shaowei

    2016-05-01

    Transition metal-carbon hybrids have been proposed as efficient electrocatalysts for hydrogen evolution reaction (HER) in acidic media. Herein, effective HER electrocatalysts based on metal-carbon composites are prepared by controlled pyrolysis of resin containing a variety of heavy metals. For the first time, Cr2 O3 nanoparticles of 3-6 nm in diameter homogeneously dispersed in the resulting porous carbon framework (Cr-C hybrid) is synthesized as efficient HER electrocatalyst. Electrochemical measurements show that Cr-C hybrids display a high HER activity with an onset potential of -49 mV (vs reversible hydrogen electrode), a Tafel slope of 90 mV dec(-1) , a large catalytic current density of 10 mA cm(-2) at -123 mV, and the prominent electrochemical durability. X-ray photoelectron spectroscopic measurements confirm that electron transfer occurs from Cr2 O3 into carbon, which is consistent with the reported metal@carbon systems. The obtained correlation between metals and HER activities may be exploited as a rational guideline in the design and engineering of HER electrocatalysts. PMID:27061759

  7. Designing nitrogen-enriched echinus-like carbon capsules for highly efficient oxygen reduction reaction and lithium ion storage.

    Science.gov (United States)

    Hu, Chuangang; Wang, Lixia; Zhao, Yang; Ye, Minhui; Chen, Qing; Feng, Zhihai; Qu, Liangti

    2014-07-21

    Both structural and compositional modulations are important for high-performance electrode materials in energy conversion/storage devices. Here hierarchical-structure nitrogen-rich hybrid porous carbon capsules with bamboo-like carbon nanotube whiskers (N-CC@CNTs) grown in situ have been specifically designed, which combine the advantageous features of high surface area, abundant active sites, easy access to medium and favorable mass transport. As a result, the newly prepared N-CC@CNTs show highly efficient catalytic activity in oxygen reduction reaction in alkaline media for fuel cells, which not only outperforms commercial Pt-based catalysts in terms of kinetic limiting current, stability and tolerance to methanol crossover effect, but is also better than most of the nanostructured carbon-based catalysts reported previously. On the other hand, as an anode material for lithium ion batteries, the N-CC@CNTs obtained also exhibit an excellent reversible capacity of ca. 1337 mA h g(-1) at 0.5 A g(-1), outstanding rate capability and long cycling stability, even at a current density of 20 A g(-1). The capacity is the highest among all the heteroatom-doped carbon materials reported so far, and is even higher than that of many of the composites of metal, metal oxides or metal sulfides with carbon materials. PMID:24906180

  8. The chemistry of subcritical water reactions of a hardwood derived lignin and lignin model compounds with nitrogen, hydrogen, carbon monoxide and carbon dioxide

    Science.gov (United States)

    Hill Bembenic, Meredith A.

    collected solids from the CO reactions appeared to be the most reacted (i.e., the most changed from the unreacted lignin) according to solid state 13C-NMR analysis, and the widest variety of products (methoxy-substituted phenolic compounds) were obtained when using CO according to GC/MS analysis. Therefore, reactions with CO were completed that varied the initial reaction pressure (300, 500 and 800 psi) in order to elucidate the effects of CO pressure. Similar conversion (≈54--58%) and DCM-soluble liquid product yields (≈53--62%) were obtained for the different pressure reactions, but the reactions with an initial pressure of 500 psi had the greatest change in aromaticity from the unreacted lignin. Additional reactions between Organosolv lignin and H2O with CO (initial pressure of 500 psi) were conducted where the reaction time was varied (15, 30 and 60 min.) to determine the effect of reaction time. Longer reaction time (60 min.) appeared to inhibit conversion to low molecular weight compounds (i.e., conversion and DCM-soluble yields were lower at ≈53% and ≈28%, respectively). Solid state 13C-NMR of collected residues also showed that there are losses in carbons representative of both guaiacyl and syringyl components as reaction time increases, which may indicate that methoxy groups are being cleaved or the products are reacting with each other (i.e., repolymerization) to form high molecular weight compounds as reaction time is increased. The role of H2O and the gases during the baseline reactions and the expanded CO reactions is not intuitive based on the results, so reactions with lignin model compounds (i.e., aromatic aldehydes represented by vanillin and syringaldehyde, aromatic ketones represented by acetovanillone and acetosyringone, and aromatic ethers represented by dibenzyl ether and 2-phenethyl phenyl ether) were completed to study this. From these results, the suggested reaction pathway of Organosolv lignin reactions in subcritical H2O with and without

  9. The present status of carbon 14 analysis and projects for beryllium 10 analysis at the Tandetron 1 accelerator, Nagoya University

    Energy Technology Data Exchange (ETDEWEB)

    Nakamura, Toshio; Oda, Hirotaka; Ikeda, Akiko; Niu, Etsuko [Nagoya Univ. (Japan)

    2001-02-01

    The operation experience in 1999 of the Tandetron accelerator age estimation system, Nagoya University, is reported, after the overview and the history of the accelerator is briefly described. Total number of carbon 14 environmental samples analyzed was 8567. The project of introducing new HVEE Tandetron for C-14 analysis, and modifying the present GIC Tandetron for Be-10 analysis is presented. Ion source shall be replaced, and the heavy ion detector shall be installed. Projected geological and archaeological studies using Be-10 are enumerated. (A. Yamamoto)

  10. Biochar, activated carbon, and carbon nanotubes have different effects on fate of (14)C-catechol and microbial community in soil.

    Science.gov (United States)

    Shan, Jun; Ji, Rong; Yu, Yongjie; Xie, Zubin; Yan, Xiaoyuan

    2015-10-30

    This study investigated the effects of biochar, activated carbon (AC)-, and single-walled and multi-walled carbon nanotubes (SWCNTs and MWCNTs) in various concentrations (0, 0.2, 20, and 2,000 mg/kg dry soil) on the fate of (14)C-catechol and microbial community in soil. The results showed that biochar had no effect on the mineralization of (14)C-catechol, whereas AC at all amendment rates and SWCNTs at 2,000 mg/kg significantly reduced mineralization. Particularly, MWCNTs at 0.2 mg/kg significantly stimulated mineralization compared with the control soil. The inhibitory effects of AC and SWCNTs on the mineralization were attributed to the inhibited soil microbial activities and the shifts in microbial communities, as suggested by the reduced microbial biomass C and the separated phylogenetic distance. In contrast, the stimulatory effects of MWCNTs on the mineralization were attributed to the selective stimulation of specific catechol-degraders by MWCNTs at 0.2 mg/kg. Only MWCNTs amendments and AC at 2,000 mg/kg significantly changed the distribution of (14)C residues within the fractions of humic substances. Our findings suggest biochar, AC, SWCNTs and MWCNTs have different effects on the fate of (14)C-catechol and microbial community in soil.

  11. Biochar, activated carbon, and carbon nanotubes have different effects on fate of 14C-catechol and microbial community in soil

    Science.gov (United States)

    Shan, Jun; Ji, Rong; Yu, Yongjie; Xie, Zubin; Yan, Xiaoyuan

    2015-10-01

    This study investigated the effects of biochar, activated carbon (AC)-, and single-walled and multi-walled carbon nanotubes (SWCNTs and MWCNTs) in various concentrations (0, 0.2, 20, and 2,000 mg/kg dry soil) on the fate of 14C-catechol and microbial community in soil. The results showed that biochar had no effect on the mineralization of 14C-catechol, whereas AC at all amendment rates and SWCNTs at 2,000 mg/kg significantly reduced mineralization. Particularly, MWCNTs at 0.2 mg/kg significantly stimulated mineralization compared with the control soil. The inhibitory effects of AC and SWCNTs on the mineralization were attributed to the inhibited soil microbial activities and the shifts in microbial communities, as suggested by the reduced microbial biomass C and the separated phylogenetic distance. In contrast, the stimulatory effects of MWCNTs on the mineralization were attributed to the selective stimulation of specific catechol-degraders by MWCNTs at 0.2 mg/kg. Only MWCNTs amendments and AC at 2,000 mg/kg significantly changed the distribution of 14C residues within the fractions of humic substances. Our findings suggest biochar, AC, SWCNTs and MWCNTs have different effects on the fate of 14C-catechol and microbial community in soil.

  12. Cross-section measurements for (n, 2n) reactions on stannum isotopes in the neutron energy range of 13.5 to 14.6 MeV

    Institute of Scientific and Technical Information of China (English)

    PU Zhong-Sheng; YAN Dong; MA Jun; DU Xiao-Fang; GUAN Qiu-Yun

    2008-01-01

    Cross-sections for (n, 2n) reactions have been measured on stannum isotopes at the neutron energies of 13.5 to 14.6 MeV using the activation technique. Data are reported for the following reactions:112Sn(n, 2n)111Sn, 118Sn(n, 2n)117Sn and 124Sn(n, 2n)123mSn. The neutron fluences were determined using the monitor reaction 93Nb(n, 2n)92mNb or 27Al(n, α)24Na. The results of present work were compared with data published previously.

  13. Bayesian calibration of a soil organic carbon model using Δ14C measurements of soil organic carbon and heterotrophic respiration as joint constraints

    Science.gov (United States)

    Ahrens, B.; Reichstein, M.; Borken, W.; Muhr, J.; Trumbore, S. E.; Wutzler, T.

    2014-04-01

    Soils of temperate forests store significant amounts of organic matter and are considered to be net sinks of atmospheric CO2. Soil organic carbon (SOC) turnover has been studied using the Δ14C values of bulk SOC or different SOC fractions as observational constraints in SOC models. Further, the Δ14C values of CO2 that evolved during the incubation of soil and roots have been widely used together with Δ14C of total soil respiration to partition soil respiration into heterotrophic respiration (HR) and rhizosphere respiration. However, these data have not been used as joint observational constraints to determine SOC turnover times. Thus, we focus on (1) how different combinations of observational constraints help to narrow estimates of turnover times and other parameters of a simple two-pool model, the Introductory Carbon Balance Model (ICBM); (2) whether relaxing the steady-state assumption in a multiple constraints approach allows the source/sink strength of the soil to be determined while estimating turnover times at the same time. To this end ICBM was adapted to model SOC and SO14C in parallel with litterfall and the Δ14C of litterfall as driving variables. The Δ14C of the atmosphere with its prominent bomb peak was used as a proxy for the Δ14C of litterfall. Data from three spruce-dominated temperate forests in Germany and the USA (Coulissenhieb II, Solling D0 and Howland Tower site) were used to estimate the parameters of ICBM via Bayesian calibration. Key findings are as follows: (1) the joint use of all four observational constraints (SOC stock and its Δ14C, HR flux and its Δ14C) helped to considerably narrow turnover times of the young pool (primarily by Δ14C of HR) and the old pool (primarily by Δ14C of SOC). Furthermore, the joint use of all observational constraints made it possible to constrain the humification factor in ICBM, which describes the fraction of the annual outflux from the young pool that enters the old pool. The Bayesian parameter

  14. Validation of ten-minute single sample carbon-14 urea breath test for diagnosis of Helicobacter pylori infection

    Energy Technology Data Exchange (ETDEWEB)

    Prabakaran, K.; Fernandes, V.; McDonald, J. [Illawarra Regional Hospital, Wollongong, NSW (Australia). Depts of Nuclear Medicine and Gastroenterology

    1996-09-01

    Helicobacter pylori infection is traditionally diagnosed by endoscopy followed by gastric biopsy and histologic demonstration of organisms, rapid urease test and culture. The non-invasive carbon-14-urea breath test has been widely accepted now for the diagnosis of this bacterium. This study was aimed to establish and validate normal and abnormal values for an Australian population, for a single sample carbon-14-urea breath test at ten minutes. A dose of 185 kBq was used in order to achieve reasonable counting statistics. The derived values were validated with the results of the rapid urease test. This method has a high sensitivity, specificity and greater patient acceptance, and could be used in many clinical settings as the first modality for the diagnosis of H. pylori infection and for documenting response or cure after antibiotic therapy for eradication. 11 refs., 1 tab., 4 figs.

  15. Validation of ten-minute single sample carbon-14 urea breath test for diagnosis of Helicobacter pylori infection

    International Nuclear Information System (INIS)

    Helicobacter pylori infection is traditionally diagnosed by endoscopy followed by gastric biopsy and histologic demonstration of organisms, rapid urease test and culture. The non-invasive carbon-14-urea breath test has been widely accepted now for the diagnosis of this bacterium. This study was aimed to establish and validate normal and abnormal values for an Australian population, for a single sample carbon-14-urea breath test at ten minutes. A dose of 185 kBq was used in order to achieve reasonable counting statistics. The derived values were validated with the results of the rapid urease test. This method has a high sensitivity, specificity and greater patient acceptance, and could be used in many clinical settings as the first modality for the diagnosis of H. pylori infection and for documenting response or cure after antibiotic therapy for eradication. 11 refs., 1 tab., 4 figs

  16. Cobalt nanoparticles embedded in N-doped carbon as an efficient bifunctional electrocatalyst for oxygen reduction and evolution reactions

    Science.gov (United States)

    Su, Yunhe; Zhu, Yihua; Jiang, Hongliang; Shen, Jianhua; Yang, Xiaoling; Zou, Wenjian; Chen, Jianding; Li, Chunzhong

    2014-11-01

    Cobalt based catalysts are promising bifunctional electrocatalysts for both oxygen reduction and oxygen evolution reactions (ORR and OER) in unitized regenerative fuel cells (URFCs) operating with alkaline electrolytes. Here we report a hybrid composite of cobalt nanoparticles embedded in nitrogen-doped carbon (Co/N-C) via a solvothermal carbonization strategy. With the synergistic effect arising from the N-doped carbon and cobalt nanoparticles in the composite, the Co/N-C hybrid catalyst exhibits highly efficient bifunctional catalytic activity and excellent stability toward both ORR and OER. The ΔE (oxygen electrode activity parameter for judging the overall electrocatalytic activity of a bifunctional electrocatalyst) value for Co/N-C is 0.859 V, which is smaller than those of Pt/C and most of the non-precious metal catalysts in previous studies. Furthermore, the Co/N-C composite also shows better bifunctional catalytic activity than its oxidative counterparts, which could be attributed to the high specific surface area and the efficient charge transfer ability of the composite, as well as the good synergistic effect between N-doped carbon and the Co nanoparticles in the Co/N-C composite.Cobalt based catalysts are promising bifunctional electrocatalysts for both oxygen reduction and oxygen evolution reactions (ORR and OER) in unitized regenerative fuel cells (URFCs) operating with alkaline electrolytes. Here we report a hybrid composite of cobalt nanoparticles embedded in nitrogen-doped carbon (Co/N-C) via a solvothermal carbonization strategy. With the synergistic effect arising from the N-doped carbon and cobalt nanoparticles in the composite, the Co/N-C hybrid catalyst exhibits highly efficient bifunctional catalytic activity and excellent stability toward both ORR and OER. The ΔE (oxygen electrode activity parameter for judging the overall electrocatalytic activity of a bifunctional electrocatalyst) value for Co/N-C is 0.859 V, which is smaller than those

  17. Nitrogen-Doped Carbon Nanoparticle-Carbon Nanofiber Composite as an Efficient Metal-Free Cathode Catalyst for Oxygen Reduction Reaction.

    Science.gov (United States)

    Panomsuwan, Gasidit; Saito, Nagahiro; Ishizaki, Takahiro

    2016-03-23

    Metal-free nitrogen-doped carbon materials are currently considered at the forefront of potential alternative cathode catalysts for the oxygen reduction reaction (ORR) in fuel cell technology. Despite numerous efforts in this area over the past decade, rational design and development of a new catalyst system based on nitrogen-doped carbon materials via an innovative approach still present intriguing challenges in ORR catalysis research. Herein, a new kind of nitrogen-doped carbon nanoparticle-carbon nanofiber (NCNP-CNF) composite with highly efficient and stable ORR catalytic activity has been developed via a new approach assisted by a solution plasma process. The integration of NCNPs and CNFs by the solution plasma process can lead to a unique morphological feature and modify physicochemical properties. The NCNP-CNF composite exhibits a significantly enhanced ORR activity through a dominant four-electron pathway in an alkaline solution. The enhancement in ORR activity of NCNP-CNF composite can be attributed to the synergistic effects of good electron transport from highly graphitized CNFs as well as abundance of exposed catalytic sites and meso/macroporosity from NCNPs. More importantly, NCNP-CNF composite reveals excellent long-term durability and high tolerance to methanol crossover compared with those of a commercial 20 wt % supported on Vulcan XC-72. We expect that NCNP-CNF composite prepared by this synthetic approach can be a promising metal-free cathode catalyst candidate for ORR in fuel cells and metal-air batteries. PMID:26908214

  18. The use of C-14 as tracer in the carbon flow assimilated by the plants (maize, sugar cane, bean)

    International Nuclear Information System (INIS)

    The flow of carbon in three different crops (maize, beans and sugar cane) was studied by use of C-14. The plants were exposed to an atmosphere with a constant concentration of the tracer for 12 hours in a biosynthesis chamber. The detection of the isotope permitted the distribution and concentration of the photosynthetates in the various organs of the plants to be followed. (M.A.C.)

  19. Flow characteristics and reaction properties of carbon dioxide in microtubules and porous media

    Institute of Scientific and Technical Information of China (English)

    ZHAO RenBao; YUE XiangAn; WU Ya Hong; XU ShaoLiang; WANG Fei; HOU YongLi

    2008-01-01

    Carbon dioxide reacts with porous media while flowing through them enhancing their permeability. Its flow behavior as well as the permeability enhancement effects were studied in synthetic cores, natural cores and microtubes with an inner diameter of 5 μm. The results show that the permeability of H2O-saturated cores (containing carbonate ingredients) was enhanced by increasing the injection volume of a CO2-H2O solution. This enhancement is attributable to carbon dioxide's corrosion, which is justified by SEM scanning. The same phenomenon occurs with a CO2-H2O solution in microtubes, but for a different reason. The gas flow velocity of carbon dioxide in microtubes was approximately 100% aster than that of nitrogen because of the scale and the squeezing effects. Carbon dioxide molecules dissolved in water accelerate the diffusion rate of water molecules within the boundary layer, which in turn diminishes the thickness of the water film and enlarges the effective pore size. This flow behavior facilitates the injection of carbon dioxide into low-permeability reservoirs for oil-displacement and formation energy buildup purposes. This behavior also increases the potential for carbon dioxide channeling or release from the formation.

  20. Graphite Carbon-Supported Mo2C Nanocomposites by a Single-Step Solid State Reaction for Electrochemical Oxygen Reduction.

    Directory of Open Access Journals (Sweden)

    K Huang

    Full Text Available Novel graphite-molybdenum carbide nanocomposites (G-Mo2C are synthesized by a typical solid state reaction with melamine and MoO3 as precursors under inert atmosphere. The characterization results indicate that G-Mo2C composites are composed of high crystallization and purity of Mo2C and few layers of graphite carbon. Mo2C nanoparticles with sizes ranging from 5 to 50 nm are uniformly supported by surrounding graphite layers. It is believed that Mo atom resulting from the reduction of MoO3 is beneficial to the immobilization of graphite carbon. Moreover, the electrocatalytic performances of G-Mo2C for ORR in alkaline medium are investigated by cyclic voltammetry (CV, rotating disk electrode (RDE and chronoamperometry test with 3M methanol. The results show that G-Mo2C has a considerable catalytic activity and superior methanol tolerance performance for the oxygen reduction reaction (ORR benefiting from the chemical interaction between the carbide nanoparticles and graphite carbon.

  1. Graphite Carbon-Supported Mo2C Nanocomposites by a Single-Step Solid State Reaction for Electrochemical Oxygen Reduction.

    Science.gov (United States)

    Huang, K; Bi, K; Liang, C; Lin, S; Wang, W J; Yang, T Z; Liu, J; Zhang, R; Fan, D Y; Wang, Y G; Lei, M

    2015-01-01

    Novel graphite-molybdenum carbide nanocomposites (G-Mo2C) are synthesized by a typical solid state reaction with melamine and MoO3 as precursors under inert atmosphere. The characterization results indicate that G-Mo2C composites are composed of high crystallization and purity of Mo2C and few layers of graphite carbon. Mo2C nanoparticles with sizes ranging from 5 to 50 nm are uniformly supported by surrounding graphite layers. It is believed that Mo atom resulting from the reduction of MoO3 is beneficial to the immobilization of graphite carbon. Moreover, the electrocatalytic performances of G-Mo2C for ORR in alkaline medium are investigated by cyclic voltammetry (CV), rotating disk electrode (RDE) and chronoamperometry test with 3M methanol. The results show that G-Mo2C has a considerable catalytic activity and superior methanol tolerance performance for the oxygen reduction reaction (ORR) benefiting from the chemical interaction between the carbide nanoparticles and graphite carbon.

  2. Nitrogen-doped carbon-embedded TiO2 nanofibers as promising oxygen reduction reaction electrocatalysts

    Science.gov (United States)

    Hassen, D.; Shenashen, M. A.; El-Safty, S. A.; Selim, M. M.; Isago, H.; Elmarakbi, A.; El-Safty, A.; Yamaguchi, H.

    2016-10-01

    The development of inexpensive and effective electrocatalysts for oxygen reduction reaction (ORR) as a substitute for commercial Pt/C catalyst is an important issue in fuel cells. In this paper, we report on novel fabrication of self-supported nitrogen-doped carbon-supported titanium nanofibers (Nsbnd TiO2@C) and carbon-supported titanium (TiO2@C) electrocatalysts via a facile electrospinning route. The nitrogen atom integrates physically and homogenously into the entire carbon-titanium structure. We demonstrate the catalytic performance of Nsbnd TiO2@C and TiO2@C for ORR under alkaline conditions in comparison with Pt/C catalyst. The Nsbnd TiO2@C catalyst shows excellent ORR reactivity and durability. Interestingly, among all the catalysts used in this ORR, Nsbnd TiO2@C-0.75 exhibits remarkable competitive oxygen reduction activity in terms of current density and onset potential, as well as superior methanol tolerance. Such tolerance attributes to maximizing the diffusion of trigger pulse electrons during catalytic reactions because of enhanced electronic features. Results indicate that our fabrication strategy can provide an opportunity to produce a simple, efficient, cost-effective, and promising ORR electrocatalyst for practical applications in energy conversion and storage technologies.

  3. Transition metal/nitrogen dual-doped mesoporous graphene-like carbon nanosheets for the oxygen reduction and evolution reactions.

    Science.gov (United States)

    Liu, Xiaobo; Amiinu, Ibrahim Saana; Liu, Shaojun; Cheng, Kun; Mu, Shichun

    2016-07-21

    The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) have been considered as a key step in energy conversion processes. Here, a novel and simple Mg(OH)2 nanocasting method is adopted to fabricate Co and N co-doped porous graphene-like carbon nanosheets (Co@N-PGCS) by using chitosan as both carbon and N sources. The as-obtained Co@N-PGCS shows a mesopore-dominated structure as well as a high specific surface area (1716 cm(2) g(-1)). As a bifunctional electrocatalyst towards both the ORR and OER, it shows favorable ORR performance compared with the commercial Pt/C catalyst with an onset potential of -0.075 V and a half-wave potential of -0.151 V in 0.1 M KOH solutions. Furthermore, it also displays considerable OER properties compared with commercial IrO2. The effective catalytic activity could originate from the introduction of transition metal species and few-layer mesoporous carbon structures. PMID:27341409

  4. Chemical behaviour of Pu and Am: Hydrolysis reaction in brine solutions, carbonate complexation, α-radiolysis, humate complexation and speciation

    International Nuclear Information System (INIS)

    The chemical behaviour of transuranic elements (Pu and Am) has been investigated in saline solution of different NaCl concentrations in the near neutral pH range. Important reactions considered are hydrolysis, carbonate complexation, redox reaction, alpha-radiolysis, colloid generation and humate complexation. Hydrolysis reactions are studied for Pu(VI) in 3.6 M NaCl and for Am(III) in 0.1 M and 0.6 M NaCl solution, whereas carbonate complexation of Pu(IV) and Am(III) is investigated in HCO3-/CO32- solution of varying pH. Consequences of alpha-radiolysis in NaCl solution are thoroughly analysed as for the Eh change due to Cl- oxidation and the oxidation of Pu(IV) and Am(III). In groundwaters colloid generation of Am(III), particularly pseudocolloids, is characterized and correlated with the concentration of humic substances. Humate complexation under discussion deals mainly with the stabilization of Am(III) in a given groundwater through its colloid generation. (orig.)

  5. Year-round probing of soot carbon and secondary organic carbon contributions and sources to the South Asian Atmospheric Brown Cloud using radiocarbon (14C) measurements

    Science.gov (United States)

    Kirillova, Elena; Sheesley, Rebecca J.; Andersson, August; Krusâ, Martin; Safai, P. D.; Budhavant, Krishnakant; Rao, P. S. P.; Praveen, P. S.; Gustafsson, Örjan

    2010-05-01

    South Asia is one region of vital importance for assessing human impact on radiative forcing by atmospheric aerosols. Previous research in the region has indicated that black carbon is a significant component of the regional aerosol load. In contrast, there is more ambiguous information regarding the contribution of secondary organic aerosols (SOA) to the total carbonaceous (TC) aerosol composition. Here we primarily address the SOA component of the South Asian Atmospheric Brown Cloud (ABC) by a combination of measurements of SOA concentrations and the 14C signature of TC. Atmospheric particulate matter was collected during fourteen-month continuous sampling campaigns Jan 2008 - March 2009 at both the Maldives Climate Observatory at Hannimaadho (MCO-H) and at the Sinhagad hilltop sampling site of the Indian Institute of Tropical Meteorology (SIN) in central-western India. The radiocarbon method is an ideal approach to identify fossil sources (14C "dead") compared to biogenic and biomass combustion products (with a contemporary 14C signal). The radiocarbon source apportionment of TC revealed very similar contribution from biogenic/biomass combustion (60-70%) for Indian SIN site and the MCOH receptor regions for much of the year. However, during the summer monsoon season biomass contribution to TC at the Indian Ocean site increases to 70-80%, while it decreases to 40-50% at the Indian site. Source apportionment of a soot carbon (SC) isolate (CTO-375 method; a tracer of black carbon) shows a similar trend. According to preliminary data in summer biomass contribution is higher at the MCOH receptor site (70%) compared to the SIN background site (45%). These unique year-round 14C data will be interpreted in view of the SOA concentration and the varying origin of the air masses.

  6. Synthesis and infrared spectra of alkaline earth metal carbonates formed by the reaction of metal salts with urea at high temperature

    Indian Academy of Sciences (India)

    S M Teleb; D El-Sayed Nassr; E M Nour

    2004-12-01

    The metal carbonate, MCO3 (M = Ca, Sr and Ba), was synthesized by a novel method of reacting aqueous solution of each of Ca2+, Sr2+ and Ba2+ salts with urea at high temperature, ∼ 80°C. The reaction products were characterized through elemental analysis and infrared spectra. The infrared spectra of the products are the same as those of the corresponding commercially obtained carbonates. A general reaction describing the formation of MCO3 is proposed.

  7. Total synthesis of cis-hydroazulene sesquiterpenes. Base-induced and -directed elimination and rearrangement reactions of perhydronaphthalene-1,4-diol monosulfonate esters.

    NARCIS (Netherlands)

    Jenniskens, L.H.D.

    1992-01-01

    The total synthesis of a number of cis-fused hydroazulene sesquiterpenes is described in this thesis. In this synthetic study, ample attention is paid to the mechanistic aspects of the base- induced and -directed rearrangement and elimination reactions of perhydronaphthalene-1,4-diol monosulfonate e

  8. The 17O(p,α)14N reaction measurement via the Trojan horse method and its application to 17O nucleosynthesis

    Science.gov (United States)

    Sergi, M. L.; Spitaleri, C.; Pizzone, R. G.; Burjan, S. V.; Cherubini, S.; Coc, A.; Gulino, M.; Hammache, F.; Hons, Z.; Irgaziev, B.; Kiss, G. G.; Kroha, V.; La Cognata, M.; Lamia, L.; Mukhamedzhanov, A.; Puglia, S. M. R.; Rapisarda, G. G.; Romano, S.; de Séréville, N.; Somorjai, E.; Tumino, A.

    2014-05-01

    The role of oxygen in astrophysics is related to different problems as novae nucleosynthesis and gamma-ray astronomy. In particular, owing to the still present uncertainties on its rate, the 17O(p,α)14N is one of the most important reaction to be studied in order to get more information about the fate of oxygen in different astrophysical scenarios.

  9. Ion exchange reactions in interaction of basic zirconium sulfate with sodium carbonate solution

    International Nuclear Information System (INIS)

    Basic zirconium sulfates, extracted from basic zirconium chloride solution and zirconium disulfate solution, as well as products of their interaction with sodium carbonate solution, which was exposed and not exposed to hydrolysis, were investigated by chemical and NMR spectroscopy methods. It has been established that the process of interaction of the basic zirconium sulfate with sodium carbonate solutions sulfatocarbonatozicrconates and carbonatozirconates of sodium are sequentially formed. In this case carbonate groups, due to different strenght of addition of hydroxogroups in initial basic sulfates, substitute either SOsub(h)sup(2)-)- groups and H2O or SO42--and OH--groups, and sodium ions substitute H3O+-groups. Carbonate groups, if they have substituted sulfato- or hydroxogroup, during hydrolysis of carbonatozirconates are splitted out to a less degree

  10. On the water promoted reaction of titanium isopropoxide with carbon dioxide

    OpenAIRE

    Ghosh, Rajshekhar; Nethaji, Munirathinam; Samuelson, Ashoka G

    2003-01-01

    Insertion of carbon dioxide into titanium isopropoxide takes place only in the presence of trace quantities of water to give an isopropyl carbonato cluster which has been crystallographically characterised.

  11. Preparation of tantalum carbide films by reaction of electrolytic carbon coating with the tantalum substrate

    OpenAIRE

    Massot, Laurent; Chamelot, Pierre; Taxil, Pierre

    2006-01-01

    This article demonstrates that coatings of tantalum carbide can be obtained by electrodeposition of carbon in molten fluorides on a tantalum substrate as an alternative to the CVD process. The structural characteristics of the carbon deposited by the electrolytic route lead to a high reactivity of this element towards a tantalum cathode to produce tantalum carbide. Mutual reactivity was shown to be enhanced if tantalum plate is replaced by an electrodeposited layer of tantalum, where th...

  12. Study on the Reaction Mechanism for Carbon Dioxide Reforming of Methane over supported Nickel Catalyst

    Institute of Scientific and Technical Information of China (English)

    Ling QIAN; Zi Feng YAN

    2003-01-01

    The adsorption and dissociation of methane and carbon dioxide for reforming on nickelcatalyst were extensively investigated by TPSR and TPD experiments. It showed that thedecomposition of methane results in the formation of at least three kinds of surface carbon specieson supported nickel catalyst, while CO2 adsorbed on the catalyst weakly and only existed in onekind of adsorption state. Then the mechanism of interaction between the species dissociatedfrom CH4 and CO2 during reforming was proposed.

  13. Velocity Map Imaging Study of Ion-Radical Chemistry: Charge Transfer and Carbon-Carbon Bond Formation in the Reactions of Allyl Radicals with C(.).

    Science.gov (United States)

    Pei, Linsen; Farrar, James M

    2016-08-11

    We present an experimental and computational study of the dynamics of collisions of ground state carbon cations with allyl radicals, C3H5, at a collision energy of 2.2 eV. Charge transfer to produce the allyl cation, C3H5(+), is exoergic by 3.08 eV and proceeds via energy resonance such that the electron transfer occurs without a significant change in nuclear velocities. The products have sufficient energy to undergo the dissociation process C3H5(+) → C3H4(+) + H. Approximately 80% of the reaction products are ascribed to charge transfer, with ∼40% of those products decaying via loss of a hydrogen atom. We also observe products arising from the formation of new carbon-carbon bonds. The experimental velocity space flux distributions for the four-carbon products are symmetric about the centroid of the reactants, providing direct evidence that the products are mediated by formation of a C4H5(+) complex living at least a few rotational periods. The primary four-carbon reaction products are formed by elimination of molecular hydrogen from the C4H5(+) complex. More than 75% of the nascent C4H3(+) products decay by C-H bond cleavage to yield a C4H2(+) species. Quantum chemical calculations at the MP2/6-311+g(d,p) level of theory support the formation of a nonplanar cyclic C4H5(+) adduct that is produced when the p-orbital containing the unpaired electron on C(+) overlaps with the unpaired spin density on the terminal carbon atoms in allyl. Product formation then occurs by 1,2-elimination of molecular hydrogen from the cyclic intermediate to form a planar cyclic C4H3(+) product. The large rearrangement in geometry as the C4H3(+) products are formed is consistent with high vibrational excitation in that product and supports the observation that the majority of those products decay to form the C4H2(+) species. PMID:27434380

  14. Simulation of Carbon-14 Migration Through a Thick Unsaturated Alluvial Basin Resulting from an Underground Nuclear Explosion

    Science.gov (United States)

    Martian, P.; Larentzos, J.

    2008-12-01

    Yucca Flat is one of several areas on the Nevada Test Site that was used for underground nuclear testing. Extensive testing performed in the unsaturated and saturated zones have resulted in groundwater contamination and surface subsidence craters in the vicinity of the underground test areas. Simulation of multiphase 14C transport through the thick Yucca Flat alluvial basin was performed to estimate the magnitude of radionuclide attenuation occurring within the unsaturated zone. Parameterization of the 14C transport in the multiphase flow and transport simulator (FEHM) was verified with experimental data collected from a large unsaturated soil column experiment. The experimental data included 14C as a radio-labeled bicarbonate solution, SF6 gas, and lithium bromide solution breakthroughs. Two representative simulation cases with working points located at shallow and deep depths relative to the water table were created to investigate the impact of subsidence crater-enhanced recharge, crater-playa areal extent, gas-phase partitioning, solid-phase partitioning, and a reduced permeability/porosity compressed zone created during the explosion on 14C transport. The representative shallow test had a detonation point located 175 m below land surface, and the deep test had a working point 435 m below land surface in a 500 m deep unsaturated zone. Carbon-14 transport is influenced by gas-phase diffusion and sorption within the alluvium. Gas-phase diffusion is an attenuation mechanism that transports 14C gas as 14CO2 throughout the unsaturated zone and exposes it to a large amount of soil moisture, resulting in dilute concentrations. The simulations indicated that the majority of the 14C inventory remains in the unsaturated zone over a 1,000-year time period after detonation because gas-phase diffusion moves the bulk of the 14C away from the higher recharge occurring in crater playas. Retardation also plays a role in slowing advective aqueous phase transport to the water

  15. Mechanism of ({sup 14}N, {sup 12}B) reactions at intermediate energy leading to large spin-polarization of {sup 12}B

    Energy Technology Data Exchange (ETDEWEB)

    Mitsuoka, Shin-ichi [Osaka Univ., Ibaraki (Japan). Research Center for Nuclear Physics; Shimoda, Tadashi; Miyatake, Hiroari [and others

    1996-05-01

    To study mechanisms of the ({sup 14}N, {sup 12}B) reactions at intermediate energies, double differential cross section and nuclear spin-polarization of the {sup 12}B projectile-like fragments have been measured as a function of longitudinal momentum in the angular range of 0deg - 9deg. Large spin-polarization of the reaction products {sup 12}B has been observed in the {sup 9}Be({sup 14}N, {sup 12}B) reaction at 39.3 MeV/u. The momentum distributions at forward angles exhibit characteristic features which can not be understood by the current projectile fragmentation picture. It is shown that by assuming the existence of direct two-proton transfer process in addition to the fragmentation process, both the cross section and polarization of {sup 12}B fragments are successfully explained. The target and incident energy dependence of the momentum distribution are also explained reasonably. (author)

  16. Use of carbon-14 for the study of elementary carbon exchange between methane and its chemisorption residues on metallic films

    International Nuclear Information System (INIS)

    After giving the results of the most recent work done with a view to providing a rational account of the exchanges between two gases in contact with a catalyst, the authors, using C14, proceed to study elementary exchange between methane and its chemisorption residues on molybdenum films. The surface is labelled in two ways: by chemisorption of C14H4 at different temperatures; or by exchange between C14H4 with a high specific activity and a metallic film previously treated with inactive methane. The C14 is counted in the form of CO2 in the Geiger region. The results show that the exchange rate is measurable from about 100o C onwards and that it reaches a maximum at about 250o C. Furthermore, the exchange is governed by laws which vary according to the prior treatment of the surface. On the basis of the results discussed, the authors suggest a methane displacement pattern which they compare with the CH4 and D2 exchange mechanisms suggested by Kemball. (author)

  17. Characterization of carbon-14 generated by the nuclear power industry. Final report

    International Nuclear Information System (INIS)

    This report describes an evaluation of C-14 production rates in light-water reactors (LWRs) and characterization of its chemical speciation and environmental behavior. The study estimated the total production rate of the nuclide in operating PWRs and BWRs along with the assessment of the C-14 content of solid radwaste. The major source of production of C-14 in both PWR's and BWRs was the activation of 0-17 in the water molecule and of N-14 dissolved in reactor coolant. The production of C-14 was estimated to range from 7 Ci/GW(e)-year to 11 Ci/GW(e)-year. The estimated range of the quantity of C-14 in LLW was 1-2 Ci/ reactor-year which compares favorably with data obtained from shipping manifests. The environmental behavior of C-14 associated with low-level waste (LLW) disposal is greatly dependent upon its chemical speciation. This scoping study was performed to help identify the occurrence of inorganic and organic forms of C-14 in reactor coolant water and in primary coolant demineralization resins. These represent the major source for C-14 in LLW from nuclear power stations. Also, the behavior of inorganic and two of the organic forms of C-14 on soil uptake was determined by measuring distribution coefficients (Kd's) on two soil types and a cement, using two different groundwater types. This study confirms that C-14 concentrations are significantly higher in the primary coolant from PWR stations compared to BWR stations. The C-14 followed trends of Co-60 generation during primary coolant demineralization at all but one of the stations examined. However, the C-14/Co-60 activity ratios measured by this study in resin samples through which samples of coolant were drawn were about 8 to 42 times higher than those reported for waste samples in the industry data base for PWR stations, and 15 to 730 times lower for the BWR stations

  18. A novel electrocatalyst for oxygen evolution reaction based on rational anchoring of cobalt carbonate hydroxide hydrate on multiwall carbon nanotubes

    Science.gov (United States)

    Zhang, Yuxia; Xiao, Qingqing; Guo, Xin; Zhang, Xiaoxue; Xue, Yifei; Jing, Lin; Zhai, Xue; Yan, Yi-Ming; Sun, Kening

    2015-03-01

    Cobalt carbonate hydroxide hydrate (CCHH) nanosheets have been densely and strongly anchored onto mildly oxidized multiwalled carbon nanotubes with the assistance of diethylenetriamine (DETA). The resulted hybrid (CCHH/MWCNT) is used as high efficient electrocatalyst for water oxidation with an extremely low onset potential of ∼1.47 V vs. RHE and an overpotential of 285 mV to achieve a current density of 10 mA cm-2 in 1.0 mol L-1 KOH. The CCHH/MWCNT electrode affords a Tafel slope of 51 mV/decade and an exchange current density of 2.5 × 10-7 A cm-2. Moreover, the CCHH/MWCNT catalyst delivers a high faradic efficiency of 95% and possesses remarkable stability for long-term electrolysis of water. By contrast, neither MWCNT nor CCHH exhibits apparent catalytical activity towards water oxidation. Importantly, we demonstrate that DETA plays crucial role in determining the morphology, structure of the CCHH/MWCNT, therefore resulting in an enhanced performance for water oxidation. This work not only provides a novel cobalt-based electrocatalyst for oxygen evolution, but also offers a useful and viable approach to deliberately synthesize functional nanocomposites for applications in energy conversion and storage.

  19. A Nodular Foreign Body Reaction in a Dialysis Patient Receiving Long-term Treatment With Lanthanum Carbonate.

    Science.gov (United States)

    Valika, Aziz K; Jain, Dhanpat; Jaffe, Phillip E; Moeckel, Gilbert; Brewster, Ursula C

    2016-01-01

    A 63-year-old man with HIV (human immunodeficiency virus) infection and end-stage renal disease, treated with lanthanum carbonate phosphate binder for 4 years, presented with anemia and an upper gastrointestinal bleed. Upper endoscopy revealed a nodular hyperplastic epithelium, with an endoscopic ultrasound confirming hyperechoic material within the nodules. Light microscopy showed collections of histiocytes and multinucleated giant cells containing brown granular cytoplasmic material and extracellular crystalline material, a finding confirmed by electron microscopy. Similar pathologic findings associated with lanthanum exposure have been described recently. In our patient, lanthanum carbonate treatment was withdrawn and gastrointestinal bleeding has since ceased. The patient was exposed to a high amount of lanthanum over a long period, which may explain his adverse reaction. However, other contributing factors, such as competing medications or comorbid conditions, also may have increased his sensitivity to the drug.

  20. Nitrogen-modified carbon-based catalysts for oxygen reduction reaction in polymer electrolyte membrane fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Subramanian, Nalini P.; Li, Xuguang; Nallathambi, Vijayadurda; Kumaraguru, Swaminatha P.; Colon-Mercado, Hector; Wu, Gang; Lee, Jong-Won; Popov, Branko N. [Center for Electrochemical Engineering, Department of Chemical Engineering, University of South Carolina, Columbia, SC 29208 (United States)

    2009-03-01

    Nitrogen-modified carbon-based catalysts for oxygen reduction were synthesized by modifying carbon black with nitrogen-containing organic precursors. The electrocatalytic properties of catalysts were studied as a function of surface pre-treatments, nitrogen and oxygen concentrations, and heat-treatment temperatures. On the optimum catalyst, the onset potential for oxygen reduction is approximately 0.76 V (NHE) and the amount of hydrogen peroxide produced at 0.5 V (NHE) is approximately 3% under our experimental conditions. The characterization studies indicated that pyridinic and graphitic (quaternary) nitrogens may act as active sites of catalysts for oxygen reduction reaction. In particular, pyridinic nitrogen, which possesses one lone pair of electrons in addition to the one electron donated to the conjugated {pi} bond, facilitates the reductive oxygen adsorption. (author)

  1. Evaluation of carbon-supported Pt and Pd nanoparticles for the hydrogen evolution reaction in PEM water electrolysers

    Science.gov (United States)

    Grigoriev, S. A.; Millet, P.; Fateev, V. N.

    Carbon-supported Pt and Pd nanoparticles (CSNs) were synthesized and electrochemically characterized in view of potential application in proton exchange membrane (PEM) water electrolysers. Electroactive metallic nanoparticles were obtained by chemical reduction of precursor salts adsorbed to the surface of Vulcan XC-72 carbon carrier, using ethylene glycol as initial reductant and with final addition of formaldehyde. CSNs were then coated over the surface of electron-conducting working electrodes using an alcoholic solution of perfluorinated polymer. Their electrocatalytic activities with regard to the hydrogen evolution reaction (HER) were measured in sulfuric acid solution using cyclic voltammetry, and in a PEM cell during water electrolysis. Results obtained show that palladium can be advantageously used as an alternative electrocatalyst to platinum for the HER in PEM water electrolysers. Developed electrocatalysts could also be used in PEM fuel cells.

  2. The 12C(3He,pγ)14N reaction cross section for γ-ray spectroscopy simulation of fusion plasmas

    International Nuclear Information System (INIS)

    High resolution γ-ray spectroscopy measurements were performed in JET (3He)D plasmas with high energy ion populations driven by radio-frequency (RF) heating. One of the first reactions investigated was 12C(3He,pγ)14N, which was observed at low 3He concentrations. In order to interpret the measurements in this work, cross section data for the 12C(3He,pγ)14N reaction are evaluated. Available data for the population of excited states in 14N up to the eighth level are assessed in the range E3He=0-5 MeV. Discrepancies and gaps in the database have been solved by means of interpolations and consistency analysis. The evaluated cross section data are used to predict the intensity ratio of characteristic 2.31 and 1.63 MeV γ-rays.

  3. In situ catalyzed Boudouard reaction of coal char for solid oxide-based carbon fuel cells with improved performance

    International Nuclear Information System (INIS)

    Highlights: • Industrial coal char was used as a fuel for solid oxide-based carbon fuel cells. • The Boudouard reactivity of coal char is higher than that of a commercial activated carbon. • The mineral matter in coal char has a catalytic effect on the Boudouard reaction. • Added catalysts and the inherent catalysts synergetically improved cell output. - Abstract: The use of industrial coal char as a fuel source for an anode-supported solid oxide-based carbon fuel cell (SO-CFC) with a yttrium-stabilized zirconia electrolyte and La0.8Sr0.2MnO3 cathode was investigated. Both the Boudouard reactivity and electrochemical performance of the coal char samples are higher than those of activated carbon samples under the same conditions. The inherent catalytic activity of the metal species (FemOn, CaO, etc.) in the coal char mineral matter leads to good cell performance, even in the absence of an external catalyst. For example, the peak power density of a cell fueled with pure coal char is 100 mW cm−2 at 850 °C, and that of a cell fueled with coal char impregnated with an FemOn-alkaline metal oxide catalyst is 204 mW cm−2. These results suggest that using coal char as the fuel in SO-CFCs might be an attractive way to utilize abundant coal resources cleanly and efficiently, providing an alternative for future power generation

  4. Up-Scaling Geochemical Reaction Rates for Carbon Dioxide (CO2) in Deep Saline Aquifers

    Energy Technology Data Exchange (ETDEWEB)

    Lindquist, W Brent

    2009-03-03

    The overall goal of the project was to bridge the gap between our knowledge of small-scale geochemical reaction rates and reaction rates meaningful for modeling transport at core scales. The working hypothesis was that reaction rates, determined from laboratory measurements based upon reactions typically conducted in well mixed batch reactors using pulverized reactive media may be significantly changed in in situ porous media flow due to rock microstructure heterogeneity. Specifically we hypothesized that, generally, reactive mineral surfaces are not uniformly accessible to reactive fluids due to the random deposition of mineral grains and to the variation in flow rates within a pore network. Expected bulk reaction rates would therefore have to be correctly up-scaled to reflect such heterogeneity. The specific objective was to develop a computational tool that integrates existing measurement capabilities with pore-scale network models of fluid flow and reactive transport. The existing measurement capabilities to be integrated consisted of (a) pore space morphology, (b) rock mineralogy, and (c) geochemical reaction rates. The objective was accomplished by: (1) characterizing sedimentary sandstone rock morphology using X-ray computed microtomography, (2) mapping rock mineralogy using back-scattered electron microscopy (BSE), X-ray dispersive spectroscopy (EDX) and CMT, (3) characterizing pore-accessible reactive mineral surface area, and (4) creating network models to model acidic CO{sub 2} saturated brine injection into the sandstone rock samples.

  5. Hydrogen evolution reaction at Ru-modified nickel-coated carbon fibre in 0.1 M NaOH

    Directory of Open Access Journals (Sweden)

    Pierożyński Bogusław

    2015-03-01

    Full Text Available The electrochemical activity towards hydrogen evolution reaction (HER was studied on commercially available (Toho-Tenax and Ru-modified nickel-coated carbon fibre (NiCCF materials. Quality and extent of Ru electrodeposition on NiCCF tows were examined by means of scanning electron microscopy (SEM. Kinetics of the hydrogen evolution reaction were investigated at room temperature, as well as over the temperature range: 20-50°C in 0.1 M NaOH solution for the cathodic overpotential range: -100 to -300 mV vs. RHE. Corresponding values of charge-transfer resistance, exchange current-density for the HER and other electrochemical parameters for the examined fibre tow composites were recorded.

  6. Reaction Mechanisms for the Limited Reversibility of Li-O2 Chemistry in Organic Carbonate Electrolytes

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Wu; Xu, Kang; Viswanathan, Vilayanur V.; Towne, Silas A.; Hardy, John S.; Xiao, Jie; Nie, Zimin; Hu, Dehong; Wang, Deyu; Zhang, Jiguang

    2011-11-15

    The Li-O2 chemistry in nonaqueous carbonate electrolytes and the underneath reason of its limited reversibility was exhaustively investigated. The discharge products collected from the air cathode in a Li-O2 battery at different depth of discharge (DOD) were systematically analyzed with X-ray diffraction. It is revealed that, independent of the discharge depth, lithium alkylcarbonate (either lithium propylenedicarbonate - LPDC, or lithium ethylenedicarbonate - LEDC, with other related derivatives) and lithium carbonate (Li2CO3) are always the main products, obviously originated from the electrolyte solvents propylene carbonate (PC) and ethylene carbonate (EC). These lithium alkylcarbonates are obviously generated from the single-electron reductive decomposition of the corresponding carbonate solvents initiated by the attack of superoxide radical anions. On the other hand, neither lithium peroxide (Li2O2) nor lithium oxide (Li2O) is detected. More significantly, from in situ gas chromatography/mass spectroscopy it is found that Li2CO3 and Li2O cannot be oxidized even when charged up to 4.6 V vs. Li/Li+, while LPDC, LEDC and Li2O2 are readily able to, with CO2 and CO released with the re-oxidation of LPDC and LEDC. It is therefore concluded that the quasi-reversibility of Li-O2 chemistry observed hitherto in an organic carbonate-based electrolyte is actually reliant on the formation of lithium alkylcarbonates through the reductive decomposition of carbonate solvents during discharge process and the subsequent oxidation of these same alkylcarbonates during charge process. It is the poor oxidizability of these alkylcarbonate species that constitutes the obstruction to an ideal rechargeable Li-O2 battery.

  7. A prediction model for concrete carbonation based on coupled CO²-H²O-ions transfers and chemical reactions

    OpenAIRE

    Thiery, M.; DANGLA, P; Villain, G.; Platret, G.

    2005-01-01

    It is a recognized fact that steel corrosion reduces the serviceability and safety performance of reinforced concrete. Usually high alkaline conditions in concrete lead to the formation of a passive layer at the steel surface. However the natural diffusion of the atmospheric carbon dioxide (CO²) into the concrete induces a decrease of the pore water pH value after reactions with hydrates such as portlandite Ca(OH)² and calcium silicate hydrates C-S-H. Under low-pH conditions, the passive laye...

  8. Synthesis and Characterization of Graphene and Graphene Oxide Based Palladium Nanocomposites and Their Catalytic Applications in Carbon-Carbon Cross-Coupling Reactions

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Minjae [Kunsan National Univ., Gunsan (Korea, Republic of); Kim, Bohyun; Lee, Yuna; Kim, Beomtae; Park, Joon B. [Chonbuk National Univ., Jeonju (Korea, Republic of)

    2014-07-15

    We have developed an efficient method to generate highly active Pd and PdO nanoparticles (NPs) dispersed on graphene and graphene oxide (GO) by an impregnation method combined with thermal treatments in H{sub 2} and O{sub 2} gas flows, respectively. The Pd NPs supported on graphene (Pd/G) and the PdO NPs supported on GO (PdO/GO) demonstrated excellent carbon-carbon cross-coupling reactions under a solvent-free, environmentally-friendly condition. The morphological and chemical structures of PdO/GO and Pd/G were fully characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). We found that the remarkable reactivity of the Pd/G and PdO/GO catalysts toward the cross-coupling reaction is attributed to the high degree of dispersion of the Pd and PdO NPs while the oxidative states of Pd and the oxygen functionalities of graphene oxide are not critical for their catalytic performance.

  9. A DFT study on the mechanism of palladium-catalyzed divergent reactions of 1,6-enyne carbonates

    Indian Academy of Sciences (India)

    Xing Hui Zhang; Zhi Yuan Geng; Teng Niu; Ke Tai Wang

    2015-03-01

    The reaction mechanisms of palladium-catalyzed divergent reactions of 1,6-enyne carbonates have been investigated using DFT calculations at the B3LYP/6-31G(d,p) (LanL2DZ for Pd) level. Solvent effects on these reactions have been considered by the polarizable continuum model (PCM) for the solvent (DMF). The formation of vinylidenepyridines and vinylidenepyrrolidines were generated through 5-exo-dig cyclization or 6-endo-dig cyclization. Our calculation results suggested the following: (i) The first step of the whole cycle is the rate-determining step, which causes allenic palladium intermediate through two plausible pathways. This intermediate provides the corresponding products and releases the palladium catalyst by a subsequent hydrogen transfer and elimination process. (ii) For the catalyst CH3OPdH, the reaction could occur through two possible pathways, but 5-exo-dig cyclization is favoured over 6-endo-dig cyclization. However, when the hydrogen atom is substituted with a phenyl group, the energy barriers for 5-exo-dig cyclization or 6-endo-dig cyclization become relatively high, 18.0–28.5 kcal/mol. The computational results provide good explanation for the experimental observations.

  10. In Situ Evaluation of Water-Rock Reactions during Carbon Dioxide Injection in Basaltic and Metasedimentary Rocks

    Science.gov (United States)

    Matter, J. M.; Assayag, N.; Goldberg, D.; Takahashi, T.

    2006-12-01

    Large differences between laboratory and field derived mineral reaction rates underscore the importance of evaluating mineral-fluid reactions under in situ conditions in a natural environment. This study investigates the extent of in situ water-rock reactions in basaltic and metasedimentary rocks (rich in Ca, Mg silicates) after the injection of CO2 enriched water, with the objective of providing information pertinent to permanent storage of anthropogenic CO2 in geologic reservoirs. CO2 injections were conducted using a single-well push-pull testing strategy. CO2 saturated water (pH 3.5) was injected into a hydraulically isolated and permeable aquifer in a 300-m experimental borehole. Water samples were retrieved after the CO2 injection. Mass transfer terms for Ca, Mg, Na, and Si were determined by using the measured ion concentrations. Using the mass balance, the weeks-long incubation time of the injected solution, and geometric estimates of the reactive surface area of the host rocks, in situ bulk rock dissolution rates of aquifer material were estimated. In addition, δ13C data coupled with total CO2 concentration were used as a tracer to quantitatively evaluate processes such as carbonate dissolution and precipitation, oxidation of organic matter and biological activity within the aquifer. Results show that the injected CO2 was neutralized within several days by two processes; mixing with aquifer water, and rock-water reactions. Calculated bulk rock dissolution rates decrease with increasing pH. The pH dependence of the dissolution rate for Ca is twice as large as for Mg, strongly favoring Ca release and possibly suggesting an additional source of Ca besides silicate minerals. Analyses of δ13C on water and rock samples confirm dissolution of calcium carbonates within the aquifer.

  11. Oxygène-18, carbone-13, carbone-14 et diatomées dans les quatre carottes du lac Huynamarca (Bolivie) : premiers résultats

    OpenAIRE

    Wirrmann, Denis; Servant Vildary, Simone; Fontes, J.C.

    1982-01-01

    L'étude de géochimie isotopique des carbonates coquilliers de quatre carottes du lac Huynamarca (Bolivie), ainsi que les datations au carbone-14 de quelques échantillons montrent qu'au cours des dix derniers millénaires le bilan hydrologique du lac Titicaca a considérablement varié. Une phase sèche, située entre 3650 et 5325 ans B.P. se traduit par une baisse du niveau du lac d'au moins dix mètres par rapport à l'actuel, avec comme corrolaire l'augmentation de la teneur en sels dissous dans l...

  12. Estimation of groundwater residence time using environmental radioisotopes (14C,T) in carbonate aquifers, southern Poland.

    Science.gov (United States)

    Samborska, Katarzyna; Różkowski, Andrzej; Małoszewski, Piotr

    2013-01-01

    Triassic carbonate aquifers in the Upper Silesia region, affected by intense withdrawal, have been investigated by means of isotopic analyses of (14)C, δ(13)C, δ(2)H, δ(18)O and (3)H. The isotopic examinations were carried out in the 1970s and in the early 1980s, and it was the first application of tracers to estimate age and vulnerability for the contamination of groundwater in this region. Similar isotopic analyses were conducted in 2007 and 2008 with the same Triassic carbonate formation. The isotopic examinations were performed within the confined part of the carbonate formation, wherein aquifers are covered by semi-permeable deposits. The direct recharge of the aquifer occurs in the outcrop areas, but it mainly takes place due to percolation of the water through aquitards and erosional windows. The Triassic aquifer has been intensively drained by wells and by lead-zinc mines. Nowadays, the declining water demand and closure of some mines have induced a significant increase in the water table level. The detailed analysis of the results, including the radiocarbon age corrections and the comparison of radioisotope activities, has made it possible to estimate the range of residence time within the carbonate Triassic aquifer. This range from several tens to several tens of thousands indicates that the recharge of aquifers might have occurred between modern times and the Pleistocene. The apparent age of the water estimated on the basis of (14)C activity was corrected considering the carbon isotope exchange and the diffusion between mobile water in fractures and stagnant water in micropores. The obtained corrected period of recharge corresponds to the result of investigations of noble gases, which were carried out in the 1990s. In almost half of the cases, groundwater is a mixture of young and old water. The mixing processes occur mainly in areas of heavy exploitation of the aquifer.

  13. Non-Enzymatic-Browning-Reaction: A Versatile Route for Production of Nitrogen-Doped Carbon Dots with Tunable Multicolor Luminescent Display

    OpenAIRE

    Weili Wei; Can Xu; Li Wu; Jiasi Wang; Jinsong Ren; Xiaogang Qu

    2014-01-01

    The non-enzymatic browning, namely Maillard reaction is commonly invoked to account for abiotic chemical transformations of organic matter. Here we report a new reaction pathway via the Maillard reaction to systematically synthesize a series of nitrogen-doped carbon dots (C-dots) with superhigh quantum yield (QY) and tunable multicolor luminescent displayment. The starting materials are glucose and the serial amino acid analogues which allow systemically controlling luminescent and physicoche...

  14. Electrochemical activity and durability of platinum nanoparticles supported on ordered mesoporous carbons for oxygen reduction reaction

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Shou-Heng [Institute of Atomic and Molecular Sciences, Academia Sinica, P.O. Box 23-166, Taipei 10617 (China); Chiang, Chien-Chang; Wu, Min-Tsung; Liu, Shang-Bin [Institute of Atomic and Molecular Sciences, Academia Sinica, P.O. Box 23-166, Taipei 10617 (China); Department of Chemistry, National Taiwan Normal University, Taipei 11677 (China)

    2010-08-15

    A facile procedure for synthesizing platinum nanoparticles (NPs) studded in ordered mesoporous carbons (Pt-OMCs) based on the organic-organic self-assembly (one-pot) approach is reported. These Pt-OMCs, which can be easily fabricated with controllable Pt loading, were found to possess high surface areas, highly accessible and stable active sites and superior electrocatalytic properties pertinent as cathode catalysts for hydrogen-oxygen fuel cells. The enhanced catalytic activity and durability observed for the Pt-OMC electrocatalysts are attributed to the strengthened interactions between the Pt catalyst and the mesoporous carbon that effectively precludes migration and/or agglomeration of Pt NPs on the carbon support. (author)

  15. A nitrogen-doped mesoporous carbon containing an embedded network of carbon nanotubes as a highly efficient catalyst for the oxygen reduction reaction.

    Science.gov (United States)

    Li, Jin-Cheng; Zhao, Shi-Yong; Hou, Peng-Xiang; Fang, Ruo-Pian; Liu, Chang; Liang, Ji; Luan, Jian; Shan, Xu-Yi; Cheng, Hui-Ming

    2015-12-01

    A nitrogen-doped mesoporous carbon containing a network of carbon nanotubes (CNTs) was produced for use as a catalyst for the oxygen reduction reaction (ORR). SiO2 nanoparticles were decorated with clusters of Fe atoms to act as catalyst seeds for CNT growth, after which the material was impregnated with aniline. After polymerization of the aniline, the material was pyrolysed and the SiO2 was removed by acid treatment. The resulting carbon-based hybrid also contained some Fe from the CNT growth catalyst and was doped with N from the aniline. The Fe-N species act as active catalytic sites and the CNT network enables efficient electron transport in the material. Mesopores left by the removal of the SiO2 template provide short transport pathways and easy access to ions. As a result, the catalyst showed not only excellent ORR activity, with 59 mV more positive onset potential and 30 mV more positive half-wave potential than a Pt/C catalyst, but also much longer durability and stronger tolerance to methanol crossover than a Pt/C catalyst.

  16. Measurement of low level carbon-14 in biologic specimens by wet ashing

    Energy Technology Data Exchange (ETDEWEB)

    Bucks, D.; Maibach, H.

    1981-10-01

    Pharmacokinetic studies of animal and human skin are often advantageously performed with low levels of C-14. We detail an efficient wet ashing mehtod capable of detecting 20 dpm per sample, equivalent to twice the background level, thus permitting complete kinetic assays with 1 ..mu..Ci or less of C-14 per subject.

  17. Effects of reaction conditions on hydrogen production and carbon nanofiber properties generated by methane decomposition in a fixed bed reactor using a NiCuAl catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Suelves, I.; Pinilla, J.L.; Lazaro, M.J.; Moliner, R. [Instituto de Carboquimica CSIC, Miguel Luesma Castan, 4, 50015 Zaragoza (Spain); Palacios, J.M. [Instituto de Catalisis y Petroleoquimica, CSIC, Cantoblanco, Marie Curie 2, 28049 Madrid (Spain)

    2009-07-01

    In this paper, the results obtained in the catalytic decomposition of methane in a fixed bed reactor using a NiCuAl catalyst prepared by the fusion method are presented. The influences of reaction temperature and space velocity on hydrogen concentration in the outlet gases, as well as on the properties of the carbon produced, have been investigated. Reaction temperature and the space velocity both increase the reaction rate of methane decomposition, but also cause an increase in the rate of catalyst deactivation. Under the operating conditions used, the carbon product is mainly deposited as nanofibers with textural properties highly correlated with the degree of crystallinity. (author)

  18. Interfacial Microstructure and Enhanced Mechanical Properties of Carbon Fiber Composites Caused by Growing Generation 1-4 Dendritic Poly(amidoamine) on a Fiber Surface.

    Science.gov (United States)

    Gao, Bo; Zhang, Ruliang; Gao, Fucheng; He, Maoshuai; Wang, Chengguo; Liu, Lei; Zhao, Lifen; Cui, Hongzhi

    2016-08-23

    In an attempt to improve the mechanical properties of carbon fiber composites, propagation of poly(amidoamine) (PAMAM) dendrimers by in situ polymerization on a carbon fiber surface was performed. During polymerization processes, PAMAM was grafted on carbon fiber by repeated Michael addition and amidation reactions. The changes in surface microstructure and the chemical composition of carbon fibers before and after modification were investigated by atomic force microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. All the results indicated that PAMAM was successfully grown on the carbon fiber surface. Such propagation could significantly increase the surface roughness and introduce sufficient polar groups onto the carbon fiber surface, enhancing the surface wettability of carbon fiber. The fractured surface of carbon fiber-reinforced composites showed a great enhancement of interfacial adhesion. Compared with those of desized fiber composites, the interlaminar shear strength and interfacial shear strength of PAMAM/fiber-reinforced composites showed increases of 55.49 and 110.94%, respectively.

  19. Measurement of high-threshold-energy activation reaction rates in combined materials with 14 MeV neutrons

    International Nuclear Information System (INIS)

    High-threshold-energy activation reaction rates were measured in cylindric combined materials bombarded by D-T neutrons with 6 threshold-energy detectors Fe, Al, Nb, F, Zr and Cu. The experimental results are discussed. MCNP/4B code was used to calculate the activation reaction rates on the experimental device. The calculated results are compared with the experimental ones. It shows that the discrepancies are 10%-30% except for the F activation reaction rate. (authors)

  20. Differentiation of Pigment in Eggs Using Carbon ((13)C/(12)C) and Nitrogen ((15)N/(14)N) Stable Isotopes.

    Science.gov (United States)

    Sun, Feng M; Shi, Guang Y; Wang, Hui W

    2016-07-01

    Consumers prefer natural and healthy food, but artificial pigments are often abused in egg products. The study aimed at differentiating the origin of pigments in eggs by applying the technique of carbon ((13)C/(12)C) and nitrogen ((15)N/(14)N) stable isotope analysis. Five hundred sixty laying hens were randomly distributed into 14 treatments, which were divided into four groups: maize, carophyll red pigment, carophyll yellow pigment, and a mixture of carophyll red and yellow pigments. Eggs were collected and pretreated to determe the values of the Roche Yolk Color Fan (RCF), δ(13)C, and δ(15)N. With increasing maize content, the RCF and δ(13)C values of yolks increased. Moreover, the RCF values in the three pigment groups were significantly influenced by the artificial colors, but δ(13)C values were not significantly different, regardless of the existence of pigment. The δ(15)N values in all treatments did not vary as regularly as the carbon stable isotope. A strong positive correlation was found between RCF and δ(13)C in the maize group, but no such correlation was be observed in the pigment groups. It is concluded that carbon stable isotope ratio analysis (δ(13)C) of the yolk can be used to differentiate the origin of the pigment added to eggs.

  1. Differentiation of Pigment in Eggs Using Carbon ((13)C/(12)C) and Nitrogen ((15)N/(14)N) Stable Isotopes.

    Science.gov (United States)

    Sun, Feng M; Shi, Guang Y; Wang, Hui W

    2016-07-01

    Consumers prefer natural and healthy food, but artificial pigments are often abused in egg products. The study aimed at differentiating the origin of pigments in eggs by applying the technique of carbon ((13)C/(12)C) and nitrogen ((15)N/(14)N) stable isotope analysis. Five hundred sixty laying hens were randomly distributed into 14 treatments, which were divided into four groups: maize, carophyll red pigment, carophyll yellow pigment, and a mixture of carophyll red and yellow pigments. Eggs were collected and pretreated to determe the values of the Roche Yolk Color Fan (RCF), δ(13)C, and δ(15)N. With increasing maize content, the RCF and δ(13)C values of yolks increased. Moreover, the RCF values in the three pigment groups were significantly influenced by the artificial colors, but δ(13)C values were not significantly different, regardless of the existence of pigment. The δ(15)N values in all treatments did not vary as regularly as the carbon stable isotope. A strong positive correlation was found between RCF and δ(13)C in the maize group, but no such correlation was be observed in the pigment groups. It is concluded that carbon stable isotope ratio analysis (δ(13)C) of the yolk can be used to differentiate the origin of the pigment added to eggs. PMID:27302905

  2. Supercritical carbon dioxide as an innovative reaction medium for selective oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Loeker, F.; Leitner, W. [Max-Planck-Institut fuer Kohlenforschung, Muelheim an der Ruhr (Germany)

    1998-12-31

    Although the catalytic efficiency of all catalytic oxidation processes studied in scCO{sub 2} up to now is far from being satisfactory, the principle possibility to carry out such reactions in this medium is clearly evident. Future research in our group will be directed towards the development of homogeneous and heterogeneous catalysts that are adopted to the special requirements of both the oxidation process and the supercritical reaction medium. Preliminary results from these studies regarding the epoxidation of olefins with molecular oxygen as oxidant will be presented on the conference poster. (orig.)

  3. EPR spectroscopy of catalytic systems based on nickel complexes of 1,4-diaza-1,3-butadiene (alpha-diimine) ligands in hydrogenation and polymerization reactions

    International Nuclear Information System (INIS)

    The catalytic systems based on .-diimine complexes of Ni(0) and Ni(II) of the general formulas NiBr2(DAD-R) (R = -C3H7 or -CH3) and Ni(DAD-CH3)2 (DAD(-C3H7) = 1,4-bis(2,6-diiso-propylphenyl)-2,3-(dimethyl-1,4-diazabuta-1,3-diene, DAD(-CH3) = 1,4-bis 2,6-dimethylphenyl)-2,3-dimethyl-1,4-diazabuta-1,3-diene), with Lewis acids (AlEt3, AlEt2Cl, AlEtCl2, B(F5C6)3, BF3 centre dot OEt2) in hydrogenation and polymerization reactions were investigated by the EPR spectroscopy method. The Ni(I) complexes of a (DAD-R)NiX2AlXy(C2H5)3-y composition (instead of the aluminum atom may be a boron atom) were identified where R = -CH3 or -C3H7, X = Br, X = Cl or -C2H5. The .-diimines radical-anions are included in the derivatives of aluminum or boron. It is found that there occur oxidation reactions between Ni(DAD-CH3)2 and aluminum organic compounds or boron derivatives, resulting in the formation of paramagnetic complexes. It is shown that there is no direct relationship between activity in polymerization or hydrogenation reactions and concentration of paramagnetic particles.

  4. Iron encapsulated within pod-like carbon nanotubes for oxygen reduction reaction.

    Science.gov (United States)

    Deng, Dehui; Yu, Liang; Chen, Xiaoqi; Wang, Guoxiong; Jin, Li; Pan, Xiulian; Deng, Jiao; Sun, Gongquan; Bao, Xinhe

    2013-01-01

    Chainmail for catalysts: a catalyst with iron nanoparticles confined inside pea-pod-like carbon nanotubes exhibits a high activity and remarkable stability as a cathode catalyst in polymer electrolyte membrane fuel cells (PEMFC), even in presence of SO(2). The approach offers a new route to electro- and heterogeneous catalysts for harsh conditions.

  5. Nitrogen and Sulfur Co-doped Mesoporous Carbon Materials as Highly Efficient Electrocatalysts for Oxygen Reduction Reaction

    International Nuclear Information System (INIS)

    Nitrogen and sulfur co-doped mesoporous carbon materials are synthesized by pyrolyzing FeSO4 + poly(ethyleneimine) + template SiO2 mixture at a high temperature without additional dopant precursors. For post-treatment, acid leaching is used to remove the metal, and the heat-treatment is tailored to optimize the catalytic activity of the catalysts toward the oxygen reduction reaction (ORR) in acidic solution. Scanning electron microscopy, X-ray diffraction, low-temperature N2 adsorption, X-ray photoelectron spectroscopy and inductively coupled plasma are used to characterize the catalysts' morphologies, structures, and compositions. Rotating disk electrode and rotating ring-disk electrode techniques are employed to quantitatively obtain the ORR kinetic constants and determine the reaction mechanisms. The ORR activity is highly improved by reheating the catalyst after H2SO4 leaching with improved half-wave potential of 0.68 V vs. RHE, and ORR electron number larger than 3.76. Moreover, increasing the catalyst loading of 800 μg cm−2 exhibits only ∼36 mV deviation from Pt/C. It is believed that the synergetic effect between the Fe-, N- and S-containing active sites and the modified carbon matrix structure due to H2SO4 leaching and reheating should make contribution to the high ORR activity

  6. Preliminary study of the impact of tritium and carbon 14 releases from the Saint-Alban nuclear power plant. CRIIRAD N.04-20 V1 Report

    International Nuclear Information System (INIS)

    After having recalled the results of previous studies on the radioactivity in surface water and land environments, and outlined the need of an investigation of the tritium and carbon 14 contamination, this report defines the objectives of this investigation, the adopted methodology (choice of plants, tritium and carbon 14 dose measurements, and sampling to study time variations). It recalls some aspects of tritium and carbon 14 releases (production of radionuclides, origins of emissions in the environment, assessments by EDF). It reports the investigation and the assessment of tritium activity in a land environment and in rain waters about the investigated site, and the investigation and the assessment of carbon 14 activity within the same environment. It reports preliminary results concerning the aquatic environment

  7. Modular, Catalytic Enantioselective Construction of Quaternary Carbon Stereocenters by Sequential Cross-Coupling Reactions.

    Science.gov (United States)

    Potter, Bowman; Edelstein, Emma K; Morken, James P

    2016-07-01

    The catalytic Suzuki-Miyaura cross-coupling with chiral γ,γ-disubstituted allylboronates in the presence of RuPhos ligand occurs with high regioselectivity and enantiospecificity, furnishing nonracemic compounds with quaternary centers. Mechanistic experiments suggest that the reaction occurs by transmetalation with allyl migration, followed by rapid reductive elimination.

  8. Reaction dynamics of {sup 34-38}Mg projectile with carbon target using Glauber model

    Energy Technology Data Exchange (ETDEWEB)

    Shama, Mahesh K., E-mail: maheshphy82@gmail.com [School of Physics and Material Sciences, Thapar University Patiala-147004 (India); Department of Applied Sciences, Chandigarh Engineering College, Landran Mohali-140307 (India); Panda, R. N. [Department of Physics, ITER, Shiksha O Anusandhan University, Bhubaneswar-751030 (India); Sharma, Manoj K. [School of Physics and Material Sciences, Thapar University Patiala-147004 (India); Patra, S. K. [Institute of Physics, Sachivalaya marg Bhubneswar-751005 (India)

    2015-08-28

    We have studied nuclear reaction cross-sections for {sup 34-38}Mg isotopes as projectile with {sup 12}C target at projectile energy 240AMeV using Glauber model with the conjunction of densities from relativistic mean filed formalism. We found good agreement with the available experimental data. The halo status of {sup 37}Mg is also investigated.

  9. Sustainable Ways of Combining Reactions and Separations Using Ionic Liquids and Carbon Dioxide

    NARCIS (Netherlands)

    Kazemi, S.

    2013-01-01

    Traditional chemical processes show shortcomings caused by using volatile organic compounds as solvents during reactions and separations. Therefore, it is necessary to address this issue by moving toward more environmentally friendly processes. This is possible by using less toxic and hazardous solv

  10. Resonance strength measurement at astrophysical energies: The {sup 17}O(p,α){sup 14}N reaction studied via Trojan Horse Method

    Energy Technology Data Exchange (ETDEWEB)

    Sergi, M. L., E-mail: sergi@lns.infn.it; La Cognata, M.; Pizzone, R. G. [INFN, Laboratori Nazionali del Sud, Catania (Italy); Spitaleri, C. [INFN, Laboratori Nazionali del Sud, Catania (Italy); Dipartimento di Fisica e Astronomia, Università degli studi di Catania, Catania (Italy); Lamia, L.; Rapisarda, G. G. [Dipartimento di Fisica e Astronomia, Università degli studi di Catania, Catania (Italy); Mukhamedzhanov, A. [Cyclotron Institute, Texas A& M University, College Station, Texas 77843 (United States); Irgaziev, B. [GIK Institute of Engineering Sciences and Technology, Topi, Districti Swabi, Khyber Pakhtunkhwa (Pakistan); Tang, X. D.; Wiescher, M. [Department of Physics, Joint Institute for Nuclear Astrophysics, University of Notre Dame, Notre Dame 46556, Indiana (United States); Mrazek, J.; Kroha, V. [Nuclear Physics Institute of ASCR, Rez (Czech Republic)

    2015-10-15

    In recent years, the Trojan Horse Method (THM) has been used to investigate the low-energy cross sections of proton-induced reactions on {sup 17}O nuclei, overcoming extrapolation procedures and enhancement effects due to electron screening. We will report on the indirect study of the {sup 17}O(p,α){sup 14}N reaction via the THM by applying the approach developed for extracting the resonance strength of narrow resonance in the ultralow energy region. Two measurements will be described and the experimental THM cross sections will be shown for both experiments.

  11. Strength, decay branching ratios, and angular distribution of the 0.987 MeV resonance in the {sup 14}N(p,{gamma}){sup 15}O reaction

    Energy Technology Data Exchange (ETDEWEB)

    Marta, Michele; Bemmerer, Daniel; Beyer, Roland; Erhard, Martin; Grosse, Eckart; Hannaske, Roland; Junghans, Arnd Rudolf; Nair, Chithra; Schwengner, R.; Trompler, Erik; Wagner, Andreas; Yakorev, Dmitry [Forschungszentrum Dresden-Rossendorf (FZD), Dresden (Germany); Broggini, Carlo; Caciolli, Antonio; Menegazzo, Roberto [INFN Sezione di Padova, Padova (Italy); Fueloep, Zsolt; Gyuerky, Gyoergy; Szuecs, Tamas [Atomki, Debrecen (Hungary)

    2009-07-01

    The {sup 14}N(p,{gamma}){sup 15}O reaction controls the rate of the hydrogen burning CNO cycle. This reaction has recently been re-studied at E<500 keV at different facilities, including LUNA. However, also data at higher energy play a role in determining the extrapolated cross section in the R-matrix framework. Here we report on a new measurement of the absolute strength, decay branching ratio, and angular distribution of the E=0.987 MeV (E{sub x} = 8.284 MeV) resonance carried out at the high-current FZD Tandetron.

  12. Study of the 20,22Ne+20,22Ne and 10,12,13,14,15C+12C Fusion Reactions with MUSIC

    Directory of Open Access Journals (Sweden)

    Avila M. L.

    2016-01-01

    Full Text Available A highly efficient MUlti-Sampling Ionization Chamber (MUSIC detector has been developed for measurements of fusion reactions. A study of fusion cross sections in the 10,12,13,14,15C+12C and 20,22Ne+20,22Ne systems has been performed at ATLAS. Experimental results and comparison with theoretical predictions are presented. Furthermore, results of direct measurements of the 17O(α, n20Ne, 23Ne(α, p26Mg and 23Ne(α, n26Al reactions will be discussed.

  13. Study of the 20,22Ne+20,22Ne and 10,12,13,14,15C+12C Fusion Reactions with MUSIC

    Science.gov (United States)

    Avila, M. L.; Rehm, K. E.; Almaraz-Calderon, S.; Carnelli, P. F. F.; DiGiovine, B.; Esbensen, H.; Hoffman, C. R.; Jiang, C. L.; Kay, B. P.; Lai, J.; Nusair, O.; Pardo, R. C.; Santiago-Gonzalez, D.; Talwar, R.; Ugalde, C.

    2016-05-01

    A highly efficient MUlti-Sampling Ionization Chamber (MUSIC) detector has been developed for measurements of fusion reactions. A study of fusion cross sections in the 10,12,13,14,15C+12C and 20,22Ne+20,22Ne systems has been performed at ATLAS. Experimental results and comparison with theoretical predictions are presented. Furthermore, results of direct measurements of the 17O(α, n)20Ne, 23Ne(α, p)26Mg and 23Ne(α, n)26Al reactions will be discussed.

  14. Two-neutron transfer reaction mechanisms in $^{12}$C($^6$He,$^{4}$He)$^{14}$C using a realistic three-body $^{6}$He model

    OpenAIRE

    Smalley, D.; F. Sarazin; Nunes, F. M.; Brown, B. A.; Adsley, P.; Al-Falou, H; Andreoiu, C.; Baartman, B.; Ball, G. C.; Blackmon, J. C.; Boston, H. C.; Catford, W. N.; Chagnon-Lessard, S.; Chester, A.; Churchman, R. M.

    2013-01-01

    The reaction mechanisms of the two-neutron transfer reaction $^{12}$C($^6$He,$^4$He) have been studied at 30 MeV at the TRIUMF ISAC-II facility using the SHARC charged-particle detector array. Optical potential parameters have been extracted from the analysis of the elastic scattering angular distribution. The new potential has been applied to the study of the transfer angular distribution to the 2$^+_2$ 8.32 MeV state in $^{14}$C, using a realistic 3-body $^6$He model and advanced shell mode...

  15. Synthesis of pyrrolizines by intramolecular capture of 1,4-dipolar intermediates in reactions of enamines with dimethyl acetylenedicarboxylate

    NARCIS (Netherlands)

    Verboom, W.; Visser, G.W.; Trompenaars, W.P.; Reinhoudt, D.N.; Harkema, S.; Hummel, van G.J.

    1981-01-01

    Solvent polarity and reaction temperature strongly influence the reactions of dimethyl acetylenedicar-boxylate (DMAD) with 1-pyrrolidinyl enamines of acyclic and cyclic ketones. Whereas DMAD and 1-[1-phenyl-2-(phenylthio)ethenyl]pyrrolidine (3) give only a mixture of the isomeric 1,3-butadienes (5)

  16. Light charged-particle production in 96 MeV neutron-induced reactions on carbon and oxygen

    International Nuclear Information System (INIS)

    In recent years, an increasing number of applications involving fast neutrons have been developed or are under consideration, e.g. radiation treatment of cancer, neutron dosimetry at commercial aircraft altitudes, soft-error effects in computer memories, accelerator-driven transmutation of nuclear waste and energy production and determination of the response of neutron detectors. Data on light-ion production in light nuclei such as carbon, nitrogen and oxygen are particularly important in calculations of dose distributions in human tissue for radiation therapy at neutron beams, and for dosimetry of high-energy neutrons produced by high-energy cosmic radiation interacting with nuclei (nitrogen and oxygen) in the atmosphere. When studying neutron dose effects, it is especially important to consider carbon and oxygen, since they are, by weight, the most abundant elements in human tissue. Preliminary experimental double-differential cross sections of inclusive light-ion (p, d, t, 3He and α) production in carbon induced by 96-MeV neutrons have been presented. Energy spectra were measured at eight laboratory angles: 20, 40, 60, 80, 100, 120, 140 and 160 deg.. Measurements were performed at The Svedberg Laboratory (TSL), Uppsala, using the dedicated MEDLEY experimental setup. The authors have earlier reported experimental double-differential cross sections of inclusive light-ion production in oxygen. In this paper, the deduced kerma coefficients for oxygen has been presented and compared with reaction model calculations. (authors)

  17. Enhanced catalysis of the electrochemical hydrogen evolution reaction using composites of molybdenum-based compounds, gold nanoparticles and carbon.

    Science.gov (United States)

    Joshi, Ubisha; Lee, Jing; Giordano, Cristina; Malkhandi, Souradip; Yeo, Boon Siang

    2016-08-21

    Molybdenum nitride has been recently reported to interact synergistically with gold to show an enhanced activity for the electrochemical hydrogen evolution reaction (2H(+) + 2e(-)→ H2, HER). In this work, we elucidated the roles of nitrogen, carbon, molybdenum and gold on this observed phenomenon. Composites of Mo-based compounds, carbon black (black pearl 2000) and/or Au nanoparticles (AuNP) were prepared, and their activities for the HER in a 0.5 M H2SO4 electrolyte were measured using linear sweep voltammetry. We show and discuss here for the first time that, while the presence of carbon is necessary for the synergy phenomenon, the nitrogen atoms present in the compounds play no apparent role in this synergy. In fact, all the compounds containing Mo, namely Mo2N, MoB and metallic Mo(0), exhibited extensive synergy with Au for the HER. A hypothesis for the enhanced catalysis of H2 evolution by the mixed metal composites is proposed and discussed. PMID:27424516

  18. Effect of reaction environments on the reactivity of PCB (2-chlorobiphenyl) over activated carbon impregnated with palladized iron

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Hyeok [Department of Civil Engineering, University of Texas at Arlington, 416 Yates Drive, Arlington, TX 76019-0308 (United States); Al-Abed, Souhail R., E-mail: al-abed.souhail@epa.gov [National Risk Management Research Laboratory, U.S. Environmental Protection Agency, 26 West Martin Luther King Drive, Cincinnati, OH 45268 (United States)

    2010-07-15

    Reactive activated carbon (RAC) impregnated with palladized iron nanoparticles has been developed to treat polychlorinated biphenyls (PCBs). In this study, we evaluated the effects of various reaction environments on the adsorption-mediated dechlorination of 2-chlorobiphenyl (2-ClBP) in the RAC system. The results were discussed in close connection to the implementation issue of the RAC system for the remediation of contaminated sites with PCBs. Adsorption event of 2-ClBP onto RAC limited the overall performance under condition with a 2-ClBP/RAC mass ratio of less than 1.0 x 10{sup -4} above which dechlorination of 2-ClBP adsorbed to RAC was the reaction rate-determining step. Acidic and basic conditions were harmful to 2-ClBP adsorption and iron stability while neutral pH showed the highest adsorption-promoted dechlorination of 2-ClBP and negligible metal leaching. Coexisting natural organic matter (NOM) slightly inhibited 2-ClBP adsorption onto RAC due to the partial partitioning of 2-ClBP into NOM in the liquid phase while the 2-ClBP absorbed into NOM, which also tended to adsorb onto RAC, was less available for the dechlorination reaction. Common anions slowed down 2-ClBP adsorption but adsorbed 2-ClBP was almost simultaneously dechlorinated. Some exceptions included strong inhibitory effect of carbonate species on 2-ClBP adsorption and severe detrimental effect of sulfite on 2-ClBP dechlorination. Results on treatment of 2-ClBP spiked to actual sediment supernatants implied site-specific reactivity of RAC.

  19. Spatial Distribution and Dynamics of Carbon-14 in a Wetland Ecosystem

    Energy Technology Data Exchange (ETDEWEB)

    Yankovich, Tamara L. [International Atomic Energy Agency, P.O. Box 100, 1400 Vienna (Austria); Carr, James; King-Sharp, K.; Doug Killey, R.W. [Atomic Energy of Canada Limited, Chalk River Laboratories, Chalk River, Ontario, K0J 1J0 (Canada); Robertson, Erin [201 21st Street East, Saskatoon, SK S7K 0B8 (Canada); Beresford, Nicholas A. [NERC Centre for Ecology and Hydrology, Lancaster Environment Center, Bailrigg, Lancaster, LA14AP (United Kingdom); School of Environment and Life Sciences, University of Salford, Manchester, M44WT (United Kingdom); Wood, Michael D. [School of Environment and Life Sciences, University of Salford, Manchester, M44WT (United Kingdom)

    2014-07-01

    There is significant interest in assessing the impact of {sup 14}C releases from nuclear facilities, radioactive waste management areas, and geologic disposal facilities. As a result, there is a general need to gain understanding of {sup 14}C dynamics, especially in complex interface ecosystems, such as wetlands. This paper summarizes the key findings of two studies undertaken in Duke Swamp, a circa 0.1 km{sup 2} area of wetland consisting of marsh, fen and swamp habitats, on the Atomic Energy of Canada Limited (AECL)'s Chalk River Laboratories Site. The swamp receives radionuclides, such as {sup 14}C and tritium, from an up-gradient waste management area. The first study was an extensive field sampling campaign, involving collection of surface vegetation at 69 locations on a 50 m x 50 m grid, to evaluate the spatial distribution of {sup 14}C in Duke Swamp. Representative receptor plants and animals, and corresponding environmental media (including air, soil, and plant) samples were then collected, as part of a second study, at a subset of six locations with {sup 14}C specific activities that spanned the range present in Duke Swamp and also represented the different wetland habitats occurring there. The highest specific activity concentrations in surface vegetation were highly localized, representing a surface area of only about 150 m{sup 2}. The spatial distribution of {sup 14}C in the swamp seemed to be at least partly accounted for by the physical attributes of the Duke Swamp habitat. In general, it was found that specific activities of {sup 14}C in biota tissues reflected those measured in surface vegetation collected from the same sampling location. Such information provides needed insight for biosphere assessments, as well as for the development of monitoring programs that demonstrate protection of biota in areas where exposure to {sup 14}C is elevated. (authors)

  20. Usefulness of long-distance inverse polymerase chain reaction for molecular detection of 14q32 translocation in a clinical setting.

    OpenAIRE

    Ishizaki, Akiko; Sugahara, Kazuyuki; Tsuruda, Kazuto; Hasegawa, Hiroo; Yanagihara, Katsunori; Tsukasaki, Kunihiro; Yamada, Yasuaki; Kamihira, Shimeru

    2008-01-01

    All mature B-cell leukaemias and lymphomas have a clonal Ig gene recombination, and half of them have a reciprocal chromosomal translocation involving the 14q32 locus. The 14q32 translocation partners are variable, such as BCL-2, BCL-1 and BCL-6, thus accounting for the difficulty in molecular detection by the current genomic polymerase chain reaction (PCR) method. To identify B-cell clones efficiently with an Ig gene rearrangement and reciprocal inter-chromosomal translocation, we verified t...

  1. Preparation of carbon nitride fine powder by laser induced gas-phase reactions

    Science.gov (United States)

    Alexandrescu, R.; Huisken, F.; Pugna, G.; Crunteanu, A.; Petcu, S.; Cojocaru, S.; Cireasa, R.; Morjan, I.

    We present the possibility of carbon nitride fine powder synthesis by sensitized laser pyrolysis of acethylene/nitrous oxide/ammonia mixtures. The powders were analyzed using X-ray diffraction, X-ray photoelectron spectroscopy (XPS) and IR transmission measurements. It was found that nitrogen was incorporated in powders and that in the carbon-nitrogen phases formed, the presence of the triple bonded C≡N was not detected. The majority of X-ray diffraction data suggests the presence of a mixture of the predicted α- and β-C3N4 structure, with an α-C3N4-like form being prevalent. The powders were found to be slightly contaminated by SF6 sensitizer products. Our results suggest that by improving the experimental parameters this contamination might be reduced and that the laser pyrolysis method offers possibilities for production of CxNy materials, with controlled composition.

  2. Biodegradation of poly(butylene succinate) powder in a controlled compost at 58°C evaluated by naturally-occurring carbon 14 amounts in evolved CO(2) based on the ISO 14855-2 method.

    Science.gov (United States)

    Kunioka, Masao; Ninomiya, Fumi; Funabashi, Masahiro

    2009-10-01

    The biodegradabilities of poly(butylene succinate) (PBS) powders in a controlled compost at 58 degrees C have been studied using a Microbial Oxidative Degradation Analyzer (MODA) based on the ISO 14855-2 method, entitled "Determination of the ultimate aerobic biodegradability of plastic materials under controlled composting conditions-Method by analysis of evolved carbon dioxide-Part 2: Gravimetric measurement of carbon dioxide evolved in a laboratory-scale test". The evolved CO(2) was trapped by an additional aqueous Ba(OH)(2) solution. The trapped BaCO(3) was transformed into graphite via a serial vaporization and reduction reaction using a gas-tight tube and vacuum manifold system. This graphite was analyzed by accelerated mass spectrometry (AMS) to determine the percent modern carbon [pMC (sample)] based on the (14)C radiocarbon concentration. By using the theory that pMC (sample) was the sum of the pMC (compost) (109.87%) and pMC (PBS) (0%) as the respective ratio in the determined period, the CO(2) (respiration) was calculated from only one reaction vessel. It was found that the biodegradabilities determined by the CO(2) amount from PBS in the sample vessel were about 30% lower than those based on the ISO method. These differences between the ISO and AMS methods are caused by the fact that part of the carbons from PBS are changed into metabolites by the microorganisms in the compost, and not changed into CO(2). PMID:20057944

  3. Porous Carbon-Supported Gold Nanoparticles for Oxygen Reduction Reaction: Effects of Nanoparticle Size.

    Science.gov (United States)

    Wang, Likai; Tang, Zhenghua; Yan, Wei; Yang, Hongyu; Wang, Qiannan; Chen, Shaowei

    2016-08-17

    Porous carbon-supported gold nanoparticles of varied sizes were prepared using thiolate-capped molecular Au25, Au38, and Au144 nanoclusters as precursors. The organic capping ligands were removed by pyrolysis at controlled temperatures, resulting in good dispersion of gold nanoparticles within the porous carbons, although the nanoparticle sizes were somewhat larger than those of the respective nanocluster precursors. The resulting nanocomposites displayed apparent activity in the electroreduction of oxygen in alkaline solutions, which increased with decreasing nanoparticle dimensions. Among the series of samples tested, the nanocomposite prepared with Au25 nanoclusters displayed the best activity, as manifested by the positive onset potential at +0.95 V vs RHE, remarkable sustainable stability, and high numbers of electron transfer at (3.60-3.92) at potentials from +0.50 to +0.80 V. The performance is comparable to that of commercial 20 wt % Pt/C. The results demonstrated the unique feasibility of porous carbon-supported gold nanoparticles as high-efficiency ORR catalysts. PMID:27454707

  4. [Tritium- and carbon-14-contents of wines of different vintage from the northern and southern hemisphere (author's transl)].

    Science.gov (United States)

    Fischer, E; Möller, H; Rapp, A; Steffan, H

    1980-10-01

    The carbon-14 and tritium radioactivity contents of up to 19 vintages of German and South African wines were compared. A similar large dependence of the 14C- and of the 3H-activity in the German wine on the nuclear weapon tests of the years 1962/63 was found out. The radioactivity level is also 1977/78 still essential higher than before 1950. The South African wines have been influenced considerably smaller by nuclear explosions. The highest 3H-values were found in the vintage 1963 of the German wine with 5910 pCi/litre and in the vintage 1964 of the South African wine with 510 pCi/litre.

  5. Study on the reaction of carbon disulfide with hydroxyl radical in aqueous solution

    Institute of Scientific and Technical Information of China (English)

    FANG Haojie; OUYANG Bin; QIN Yan; DONG Wenbo; HOU Huiqi

    2005-01-01

    The laser flash photolysis technique is employed to investigate the reaction mechanism of CS2 with ·OH in the nitrogen-saturated aqueous solution. By comparison of the transient absorption spectra obtained at different phases and pHs and through the addition of proper radical cation scavenger, CS2 is determined to react with ·OH to form ·CS2OH adduct, instead of the CS2+ radical cation. At pH 1-5, ·CS2OH decomposes into COS and ·HS, while at pH>5, it further reacts with OH- to form CS2O-. The temperature dependent kinetics for the reaction CS2 + ·OH →·CS2OH is also reported in this paper with an estimated activation energy of (26.9±1.0) kJ·mol1.

  6. 碳酸乙二酯与二醇反应制备聚碳酸酯二元醇%Synthesis of Polycarbonate Diol Through the Reaction of Ethylene Carbonate with Diol

    Institute of Scientific and Technical Information of China (English)

    李金丽; 周宏勇; 李云庆; 王家喜

    2012-01-01

    A series of linear aliphatic polycarbonate diols (APC) with defined structure were synthesized by using ethylene carbonate (EC), 1,4-butanediol, and 1,6-hexanediol as the raw materials promoted by zinc acetate or zinc nitrate. The effect of reaction temperature, time and the amount of catalyst on the structure and number average molecular weight of polycarbonate was investigated. The structures and number average molecular weight were characterized and calculated by means of NMR spectroscopy. The number average molecular weight (Mn) of polycarbonate with l]-hydroxylethyl and/or c0-hydroxylalkyl as end groups is in range of 300 to 560 for reaction of 1, 4-butanediol and 700 to 980 for reaction of 1,6-hexanediol. The ether unit from the reaction of 1,4-butandiol can be less than 3%(mol). While the ether unit from the reaction of 1,6-hexandiol can be less up to 0.24% (tool). The reaction mechanism of ethylene carbonate with diol is proposed.%以碳酸乙二酯、1,4-丁二醇和1,6-己二醇为原料,醋酸锌、硝酸锌为催化剂,考察了反应温度、反应时间等条件对碳酸乙二酯与二元醇反应的影响,制备出结构规整的以β-羟乙基、ω-羟烷氧基为端基的聚碳酸酯二元醇。产物经核磁共振波谱表征,1,4-丁二醇反应的聚碳酸酯二元醇的数均分子量为300-560,产物中由脱羰基反应形成的醚键链段含量可小于3%,1,6-己二醇反应的聚碳酸酯二元醇的数均分子量为700-980,产物中醚键链段含量可降低至0.24%。最后探讨了碳酸乙二酯与二元醇的反应机理。

  7. Improving the durability of methanol oxidation reaction electro-catalysts through the modification of carbon architectures

    Science.gov (United States)

    Wood, Kevin N.

    Carbon materials represent one of the largest areas of studied research today, having integrated applications stretching from energy production and storage to medical use and far beyond. One of these many intriguing applications is fuel cells, which offers the promise of clean electricity through a direct electrochemical energy conversion process. Unfortunately, at the present time the cost per watt-hour produced by fuel cells is more expensive than conventional methods of energy production/storage (i.e. combustion engines, batteries, etc.). Under the umbrella of fuel cell systems, methanol is a promising fuel source because of its high energy density and convenience of direct liquid fuel operation. In this field, recent advancements are bringing direct methanol fuel cells (DMFCs) closer to commercial viability. However, just as in other fuel cell systems, further improvements are greatly needed, particularly in the area of catalyst durability. This need for improved durability has led to increased research activity focused on improving catalyst stability and utilization. This thesis explores one of the most promising areas of enhancing catalyst-support interactions; namely, modification of carbon support architectures. Through the use of heteroatom modifiers, such as nitrogen, fuel cell support systems can be enhanced in such a way as to improve metal nucleation and growth, catalyst durability and catalytic activity. To this end, this thesis employs advanced characterization techniques to study the changes in catalyst particle morphology before and after nitrogen modification of the support structure. These results clearly show the beneficial effects of nitrogen moieties on carbon structures and help elucidate the effects of nitrogen on the stability of supported catalytic nanoparticles systems. Similarly, the novel concept of post-modifying commercially available supported catalysts with nitrogen ion implantation gives further insight into the behavior of

  8. Backward emitted high-energy neutrons in hard reactions of p and pi^+ on carbon

    OpenAIRE

    Malki, A.; Alster, J.; Asryan, G.; Barton, D; Baturin, V.; Buchkojarova, N.; Carroll, A.; Chtchetkovski, A.; Heppelmann, S.; Kawabata, T.; Leksanov, A.; Makdisi, Y.; Minina, E.; Navon, I.; Nicholson, H.

    2000-01-01

    Beams of protons and pions of 5.9 GeV/c were incident on a C target. Neutrons emitted into the back hemisphere, in the laboratory system, were detected in (triple) coincidence with two emerging $p_t>$0.6 GeV/c particles. We present the momentum spectra of the backward going neutrons, which have the same universal shape observed in earlier (inclusive) reactions induced by hadrons, $\\gamma$, $\

  9. Assessment of the apparent activation energies for gas/solid reactions-carbonate decomposition

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The guidelines for assessing the apparent activation energies of gas/solid reactions have been proposed based on the ex-perimental results from literatures. In CO2 free inlet gas flow, CaCO3 decomposition between 950 and 1250 K with thin sample layercould be controlled by the interfacial chemical reaction with apparent activation energy E = (215+10) kJ/mol and E = (200±10)kJ/mol at T = 813 to 1020 K, respectively. With relatively thick sample layer between 793 and 1273 K, the CaCO3 decompositioncould be controlled by one or more steps involving self-cooling, nucleation, intrinsic diffusion and heat transfer of gases, and E couldvary between 147 andl90 kJ/mol. In CO2 containing inlet gas flow (5%-100% of CO2), E was determined to be varied from 949 to2897 kJ/mol. For SrCO3 and BaCO3 decompositions controlled by the interfacial chemical reaction, E was (213+15) kJ/mol (1000-1350 K) and (305+15) kJ/mol (1260-1400 K), respectively.

  10. Concentration and 14C Content of Total Organic Carbon and Black Carbon in Small (<100 ug C) Samples from Low-Latitude Alpine Ice Cores

    Science.gov (United States)

    Kehrwald, N. M.; Czimczik, C. I.; Santos, G. M.; Thompson, L. G.; Ziolkowski, L.

    2008-12-01

    Many low latitude glaciers are receding with consequences for the regional energy budget and hydrology. Ice loss has been linked to climate change and the deposition of organic aerosols such as black carbon (BC) which is formed during incomplete combustion. Little is known about how the contents of BC and total organic carbon (TOC) in aerosols change over time and how anthropogenic activities (e.g. land-use change) impact this variability. Low-latitude ice cores are located closer to population centers than polar ice caps and can provide a regional synthesis of TOC and BC variability. Radiocarbon (14C) may be used to partition BC aerosols into fossil (>50 kyrs) and modern sources (e.g. fossil-fuels vs. wildfires). We quantified TOC, BC, and their 14C content in three low-latitude ice cores: Naimona'nyi (30°27'N, 81°91'E) and Dasuopu (28°23'N, 85°43'E), Tibet, and Quelccaya (13°56'S; 70°50'W), Peru. Aerosols (52-256 g ice on filters) were separated into TOC and BC using thermal oxidation (CTO- 375). 14C was measured by AMS. TOC contents were 0.11-0.87, 0.05-0.43, and 0.06-0.19 μg C (g ice) -1 for Naimona'nyi, Dasuopu, and Quelccaya, respectively. BC contents were 18±8, 27±4, and 29±12 %TOC. Procedural blanks were 0.8 ± 0.4 μg C (TOC) and 1.2 ± 0.6 μg C (BC). In ice cores well dated through annual layer counting and/or independent ages (e.g. volcanic horizons) such as Quelccaya, the ability to separate BC from TOC, as well as partition BC into fossil and modern contributions has potential for reconstructing pre- and post-industrial changes in aerosol composition and their impact on the energy budget.

  11. Carbon and 14C distribution in tropical and subtropical agricultural soils

    Science.gov (United States)

    Prastowo, Erwin; Grootes, Pieter; Nadeau, Marie

    2016-04-01

    Paddy soil management affects, through the alternating anoxic and oxic conditions it creates, the transport and stabilisation of soil organic matter (SOM). Irrigation water may percolate more organic materials - dissolved (DOM) and colloidal - into the subsoil during anoxic conditions. Yet a developed ploughpan tends to prevent C from going deeper in the subsoil and partly decouple C distribution in top and sub soil. We investigate the influence of different soil type and environment. We observed the C and 14C distribution in paddy and non-paddy soil profiles in three different soil types from four different climatic regions of tropical Indonesia, and subtropical China. Locations were Sukabumi (Andosol, ca. 850 m a.s.l), Bogor (clayey Alisol, ca. 240 m a.s.l), and Ngawi (Vertisol, ca. 70 m a.s.l) in Jawa, Indonesia, and Cixi (Alisol(sandy), ca. 4 - 6 m a.s.l) in Zhejiang Province, China. We compared rice paddies with selected neighbouring non-paddy fields and employed AMS 14C as a tool to study C dynamics from bulk, alkali soluble-humic, and insoluble humin samples, and macrofossils (plant remains, charcoal). Our data suggest that vegetation type determines the quantity and quality of biomass introduced as litter and root material in top and subsoil, and thus contributes to the soil C content and profile, which fits the 14C signal distribution, as well as 13C in Ngawi with C4 sugar cane as upland crop. 14C concentrations for the mobile humic acid fraction were generally higher than for bulk samples from the same depth, except when recent plant and root debris led to high 14C levels in near-surface samples. The difference in sampling, - averaged layer for bulk sample and 1-cm layer thickness for point sample - shows gradients in C and 14C across the layers, which could be a reason for discrepancies between the two. High 14C concentrations - in Andosol Sukabumi up to 111 pMC - exceed the atmospheric 14CO2concentration in the sampling year in 2012 (˜ 103 pMC) and

  12. Formation of 1,4- and 1,5-regioisomers of triazolines in reactions of 2-ethoxyethyl azide with monosubstituted ethylenes

    International Nuclear Information System (INIS)

    The structural specificity of the reactions of 2-ethoxyethyl azide with alkenes RCH=CH2 [R = CH2C6H5, CH2OC6H13, CH(OC2H5)2, C6H5] was studied. The formation of 1,4- and 1,5-substituted triazolines and the high stabilities of the latter were demonstrated by PMR spectroscopy, data from gas-liquid chromatography (GLC), and the kinetics of thermolysis

  13. Evaluation of carbon-14 (C{sup 14}) levels of terrestrial and marine food products of the environment of the site of Cogema La Hague; Evaluation des niveaux de carbone-14 ({sup 14}C) des denrees alimentaires terrestres et marines de l'environnement du site de COGEMA - La Hague

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2006-04-15

    This evaluation has for object to inform about the levels in carbon 14 in the environment of the factories of La Hague. Two sectors were differentiated on one hand the terrestrial environment, and on the other hand the marine environment. The investigations concerned first and foremost food products stemming as the vegetable culture (vegetables) or individual breeding (milk, eggs) but also foodstuffs stemming from the local agriculture (cereal). In touch with the second sector, the marine environment, the sampling concerned the accessible products of the sea by all and those locally marketed (fishes, molluscs, shellfishes). The different results are presented in tables. (N.C.)

  14. A General Method for the Rapid Determination of Carbon-14- and Hydrogen-3-Labelled Substances by Gas Chromatography

    International Nuclear Information System (INIS)

    A method is described for the determination of 14C- and 3H- labelled substances by gas chromatography using different size flow counters. The method of cracking substances in a current of hydrogen gas is especially suitable for 3H-labelled compounds because it is free from the disadvantages encountered when the substances are first oxidized and the water formed subsequently converted. The general applicability of this method is shown for different classes of compounds. The analysis is independent of the chemical composition of the compound. By using a part oi the apparatus very rapid analyses of vaporizable 14C- and apparently all 3H-labelled substances can be made by direct injection into the reaction chamber. The apparatus can also be used for the oxidation procedure. (author)

  15. Radiobiological half-lives for carbon-14 and hydrogen-3 leucine in man

    International Nuclear Information System (INIS)

    In vivo estimates of protein metabolism in many are often made by oral or intravenous administration of leucine or its ∼-ketoacid, ∼-ketoisocaproate, labeled with 14C or 3H. Previous estimates of radiation dose from such tracers have been based on the measurement of 14CO2 in breath. Using measurements of the decay of 3H or 14C leucine from plasma proteins, longer biological half-lives for these compounds were obtained. The estimated total-body radiation absorbed dose is 0.97 mrad/uCi for [1-14C]KIC (or [1-14C]leucine) and 0.11 mrad/+Ci for ]4,5-3H]leucine (or [3H]KIC). Assuming administered doses of 100 μCi each, the total-body radiation absorbed dose is still well within the limits set by the FDA for Radioactive Drug Research Committees. 12 references, 3 figures, 3 tables

  16. Semi-empirical systematics of (n, 2n), (n, α) reactions cross sections at 14–15 MeV neutron energy

    International Nuclear Information System (INIS)

    In this study we propose new semi-empirical formulas by modifying the formula of Levkovskii with the new parameters for (n, 2n) and (n, α) reactions cross-sections at 14–15 MeV neutron incident energy. The cross sections have been calculated using the asymmetry parameter depending on empirical formulas for the incoming energies of 14–15 MeV neutrons. The parameters obtained by modifying the original formula of Levkovskii and Konno et al. have been determined by applying the least squares fitting method to the experimental cross sections, and the systematics of the (n, 2n) and (n, α) reactions have been studied. We have also suggested different parameters for the empirical formula to reproduce the cross sections of the (n, 2n) and (n, α) reactions for the neutron incident energy of 14–15 MeV. The modified formulas yielded cross sections representing markedly smaller chi-square (χ2) deviations from experimental values, and values much closer to units as compared with those calculated using Levkovskii's and Konno et al. original formulas. The results obtained have been discussed and compared with the other empirical formulas, and found to be well in agreement when used to correlate the available experimental σ(n, 2n) and σ(n, σ) data of different nuclei. (author)

  17. Contribution of sorption, DOC transport and microbial interactions to the 14C age of a soil organic carbon profile: Insights from a calibrated process model

    NARCIS (Netherlands)

    Ahrens, B.; Braakhekke, M.C.; Guggenberger, G.; Schrumpf, M.; Reichstein, M.

    2015-01-01

    Profiles of soil organic carbon (SOC) are often characterized by a steep increase of 14C age with depth, often leading to subsoil 14C ages of more than 1000 years. These observations have generally been reproduced in SOC models by introducing a SOC pool that decomposes on the time-scale of millennia

  18. A comet could not produce the carbon-14 spike in the 8th century

    CERN Document Server

    Usoskin, Ilya

    2014-01-01

    A mysterious increase of radiocarbon 14C ca. 775 AD in the Earth's atmosphere has been recently found by Miyake et al. (Nature, 486, 240, 2012). A possible source of this event has been discussed widely, the most likely being an extreme solar energetic particle event. A new exotic hypothesis has been presented recently by Liu et al. (Nature Sci. Rep., 4, 3728, 2014) who proposed that the event was caused by a comet bringing additional 14C to Earth. Here we calculated a realistic mass and size of such a comet to show that it would have been huge (~100 km across and 10^{14}-10^{15} ton of mass) and would have produced a disastrous impact on Earth. Such an impact could not remain unnoticed in the geological records and chronicles. The absence of an evidence for such a dramatic event makes this hypothesis invalid.

  19. Synthesis of Bridged Heterocycles via Sequential 1,4- and 1,2-Addition Reactions to α,β-Unsaturated N-Acyliminium Ions: Mechanistic and Computational Studies.

    Science.gov (United States)

    Yazici, Arife; Wille, Uta; Pyne, Stephen G

    2016-02-19

    Novel tricyclic bridged heterocyclic systems can be readily prepared from sequential 1,4- and 1,2-addition reactions of allyl and 3-substituted allylsilanes to indolizidine and quinolizidine α,β-unsaturated N-acyliminium ions. These reactions involve a novel N-assisted, transannular 1,5-hydride shift. Such a mechanism was supported by examining the reaction of a dideuterated indolizidine, α,β-unsaturated N-acyliminium ion precursor, which provided specifically dideuterated tricyclic bridged heterocyclic products, and from computational studies. In contrast, the corresponding pyrrolo[1,2-a]azepine system did not provide the corresponding tricyclic bridged heterocyclic product and gave only a bis-allyl adduct, while more substituted versions gave novel furo[3,2-d]pyrrolo[1,2-a]azepine products. Such heterocyclic systems would be expected to be useful scaffolds for the preparation of libraries of novel compounds for new drug discovery programs. PMID:26816207

  20. Thermophysical properties and reaction kinetics of γ-irradiated poly allyl diglycol carbonates nuclear track detector

    Science.gov (United States)

    Elmaghraby, Elsayed K.; Seddik, Usama

    2015-07-01

    Kinetic thermogravimetric technique was used to study the effect of gamma irradiation on the poly allyl diglycol carbonates (PADC) within the dose range from 50 to ? Gy. The approach of Coats-Redfern was used to analyze the data. Results showed that low doses around 50 Gy make the polymer slightly more resistive to heat treatment. Higher radiation doses cause severe effects in the samples accompanied by the formation of lower molecular mass species and consequent crosslinking. Results support the domination of re-polymerization and crosslinking for the γ radiation interaction PADC at dose below about ? Gy, while the situation is inverted above ? Gy in which chain secession dominates.

  1. Carbon dioxide activation and reaction induced by electron transfer at an oxide-metal interface.

    Science.gov (United States)

    Calaza, Florencia; Stiehler, Christian; Fujimori, Yuichi; Sterrer, Martin; Beeg, Sebastian; Ruiz-Oses, Miguel; Nilius, Niklas; Heyde, Markus; Parviainen, Teemu; Honkala, Karoliina; Häkkinen, Hannu; Freund, Hans-Joachim

    2015-10-12

    A model system has been created to shuttle electrons through a metal-insulator-metal (MIM) structure to induce the formation of a CO2 anion radical from adsorbed gas-phase carbon dioxide that subsequently reacts to form an oxalate species. The process is completely reversible, and thus allows the elementary steps involved to be studied at the atomic level. The oxalate species at the MIM interface have been identified locally by scanning tunneling microscopy, chemically by IR spectroscopy, and their formation verified by density functional calculations.

  2. A palladium-doped ceria@carbon core-sheath nanowire network: a promising catalyst support for alcohol electrooxidation reactions

    Science.gov (United States)

    Tan, Qiang; Du, Chunyu; Sun, Yongrong; Du, Lei; Yin, Geping; Gao, Yunzhi

    2015-08-01

    A novel palladium-doped ceria and carbon core-sheath nanowire network (Pd-CeO2@C CSNWN) is synthesized by a template-free and surfactant-free solvothermal process, followed by high temperature carbonization. This hierarchical network serves as a new class of catalyst support to enhance the activity and durability of noble metal catalysts for alcohol oxidation reactions. Its supported Pd nanoparticles, Pd/(Pd-CeO2@C CSNWN), exhibit >9 fold increase in activity toward the ethanol oxidation over the state-of-the-art Pd/C catalyst, which is the highest among the reported Pd systems. Moreover, stability tests show a virtually unchanged activity after 1000 cycles. The high activity is mainly attributed to the superior oxygen-species releasing capability of Pd-doped CeO2 nanowires by accelerating the removal of the poisoning intermediate. The unique interconnected one-dimensional core-sheath structure is revealed to facilitate immobilization of the metal catalysts, leading to the improved durability. This core-sheath nanowire network opens up a new strategy for catalyst performance optimization for next-generation fuel cells.A novel palladium-doped ceria and carbon core-sheath nanowire network (Pd-CeO2@C CSNWN) is synthesized by a template-free and surfactant-free solvothermal process, followed by high temperature carbonization. This hierarchical network serves as a new class of catalyst support to enhance the activity and durability of noble metal catalysts for alcohol oxidation reactions. Its supported Pd nanoparticles, Pd/(Pd-CeO2@C CSNWN), exhibit >9 fold increase in activity toward the ethanol oxidation over the state-of-the-art Pd/C catalyst, which is the highest among the reported Pd systems. Moreover, stability tests show a virtually unchanged activity after 1000 cycles. The high activity is mainly attributed to the superior oxygen-species releasing capability of Pd-doped CeO2 nanowires by accelerating the removal of the poisoning intermediate. The unique

  3. Intermediate- and high-energy reactions of uranium with neon and carbon

    International Nuclear Information System (INIS)

    Target fragment production from the interactions of 1.0, 3.0, 4.8, and 12 GeV 12C and 5.0, 8.0, 20, and 42 GeV 20Ne with uranium has been measured using off-line gamma-ray spectroscopic techniques. The experimental charge and mass yield distributions are generally consistent with the concepts of limiting fragmentation and factorization at energies of 3.0 GeV and above. The total projectile kinetic energy was found to be the relevant scaling parameter for the comparison of reactions induced by projectiles of different sizes. Light fragments with mass number less than 60 were found to violate limiting fragmentation, and had excitation functions that were strongly increasing with projectile energy until 8.0 to 12.0 GeV. With the 1.0 GeV 12C beam the pattern of mass yields was quite different from that of all the other reactions, with the normal peak in the fission mass region (80 < A < 145), but with much lower yields below mass number 60 and between mass numbers 145 and 210, indicating that these fragments are formed primarily in very energetic reactions in which large excitation energies are transferred to and significant amounts of mass are removed from the target nucleus. Theoretical predictions of the intra-nuclear cascade, nuclear fireball, and nuclear firestreak models are compared with the experimental results. The intra-nuclear cascade and nuclear firestreak models are both able to predict the general shapes of the experimental distributions, with the exception of the yields for the lightest fragments

  4. Carbon beam extraction with 14.5 GHz electron cyclotron resonance ion source at Korea Atomic Energy Research Institute

    Science.gov (United States)

    Lee, Cheol Ho; Oh, Byung-Hoon; Chang, Dae-Sik; Jeong, Sun-Chan

    2014-02-01

    A 14.5 GHz Electron Cyclotron Resonance ion source (ECRIS) has been made to produce C4+ beam for using a carbon therapy facility and recently tested at KAERI. Highly charged carbon ions have been successfully extracted. When using only CO2 gas, the beam current of C4+ was almost 14 μA at 15 kV extraction voltage. To get higher current of the C4+ beam, while optimizing confinement magnetic field configuration (e.g., axial strengths at minimum and extraction side), gas-mixing (CO2/He), and biased disk were introduced. When the gas mixing ratio of the CO2/He gas is 1:8 at an operational pressure of 5 × 10-7 mbar and the disk was biased to -150 V relative to the ion source body, the highest current of the C4+ beam was achieved to be 50 μA, more than three times higher than previously observed only with CO2 gas. Some details on the operating conditions of the ECRIS were discussed.

  5. TiO2-sludge carbon enhanced catalytic oxidative reaction in environmental wastewaters applications.

    Science.gov (United States)

    Athalathil, Sunil; Erjavec, Boštjan; Kaplan, Renata; Stüber, Frank; Bengoa, Christophe; Font, Josep; Fortuny, Agusti; Pintar, Albin; Fabregat, Azael

    2015-12-30

    The enhanced oxidative potential of sludge carbon/TiO2 nano composites (SNCs), applied as heterogeneous catalysts in advanced oxidation processes (AOPs), was studied. Fabrification of efficient SNCs using different methods and successful evaluation of their catalytic oxidative activity is reported for the first time. Surface modification processes of hydrothermal deposition, chemical treatment and sol-gel solution resulted in improved catalytic activity and good surface chemistry of the SNCs. The solids obtained after chemical treatment and hydrothermal deposition processes exhibit excellent crystallinity and photocatalytic activity. The highest photocatalytic rate was obtained for the material prepared using hydrothermal deposition technique, compared to other nanocomposites. Further, improved removal of bisphenol A (BPA) from aqueous phase by means of catalytic ozonation and catalytic wet air oxidation processes is achieved over the solid synthesized using chemical treatment method. The present results demonstrate that the addition of TiO2 on the surface of sludge carbon (SC) increases catalytic oxidative activity of SNCs. The latter produced from harmful sludge materials can be therefore used as cost-effective and efficient sludge derived catalysts for the removal of hazardous pollutants. PMID:26223014

  6. Localized surface grafting reactions on carbon nanofibers induced by gamma and e-beam irradiation

    Science.gov (United States)

    Evora, M. C.; Araujo, J. R.; Ferreira, E. H. M.; Strohmeier, B. R.; Silva, L. G. A.; Achete, C. A.

    2015-04-01

    Electron beam and gamma-ray irradiation have potential application to modify the carbon fiber nanostructures in order to produce useful defects in the graphitic structure and create reactive sites. In this study, the methodology to functionalize carbon nanofiber (CNF), via a radiation process and using acrylic acid as a source of oxygen functional groups, was investigated. The samples were submitted to a direct grafting radiation process with electron beam and gamma-ray source. Several parameters were changed such as: acrylic acid concentration, radiation dose and percentage of inhibitor necessary to achieve functionalization, with higher percentage of oxygen functional groups on CNF surface, and better dispersion. The better results achieved were when mixing CNF in a solution of acrylic acid with 6% of inhibitor (FeSO4·7H2O) and irradiated at 100 kGy. The samples were characterized by X-ray photoelectron spectroscopy and the surface composition (atomic%) showed a significant increase of oxygen content for the samples after irradiation. Also, the dispersion of the functionalized CNF in water was stable during months which may be a good indication that the functionalization process of CNF via ionizing radiation was successful.

  7. Dissolved Organic Carbon Determination Using FIA and Photo-Fenton Reaction

    Directory of Open Access Journals (Sweden)

    Kondo Márcia M.

    2002-01-01

    Full Text Available The FIA-photo-Fenton system is based on the flow oxidation of the organic matter. A small amount of the sample containing H2O2 is injected into the acidic flow solution of Fe2+, which passes through a tubular PTFE reactor irradiated with UV light. The generated CO2 is quantified by a conductometric detector and is directly proportional to the dissolved organic carbon concentration in the sample. The optimization studies were performed using EDTA solutions. The average recovery of organic carbon was 83% with a relative standard deviation of 3.7% using a 1:5 molar ratio of Fe2+:H2O2, pH 2.0, 100 muL of sample injection and a liquid flow of 1 mL min-1. After optimization, the DOC concentration was quantified using 13 different organic compounds, where the average recovery was 90%. The rate of the analysis was in average 50 samples hour-1.

  8. Nitrogen, carbon, and sulfur isotopic change during heterotrophic (Pseudomonas aureofaciens) and autotrophic (Thiobacillus denitrificans) denitrification reactions

    Science.gov (United States)

    Hosono, Takahiro; Alvarez, Kelly; Lin, In-Tian; Shimada, Jun

    2015-12-01

    In batch culture experiments, we examined the isotopic change of nitrogen in nitrate (δ15NNO3), carbon in dissolved inorganic carbon (δ13CDIC), and sulfur in sulfate (δ34SSO4) during heterotrophic and autotrophic denitrification of two bacterial strains (Pseudomonas aureofaciens and Thiobacillus denitrificans). Heterotrophic denitrification (HD) experiments were conducted with trisodium citrate as electron donor, and autotrophic denitrification (AD) experiments were carried out with iron disulfide (FeS2) as electron donor. For heterotrophic denitrification experiments, a complete nitrate reduction was accomplished, however bacterial denitrification with T. denitrificans is a slow process in which, after seventy days nitrate was reduced to 40% of the initial concentration by denitrification. In the HD experiment, systematic change of δ13CDIC (from - 7.7‰ to - 12.2‰) with increase of DIC was observed during denitrification (enrichment factor εN was - 4.7‰), suggesting the contribution of C of trisodium citrate (δ13C = - 12.4‰). No SO42 - and δ34SSO4 changes were observed. In the AD experiment, clear fractionation of δ13CDIC during DIC consumption (εC = - 7.8‰) and δ34SSO4 during sulfur use of FeS2-S (around 2‰), were confirmed through denitrification (εN = - 12.5‰). Different pattern in isotopic change between HD and AD obtained on laboratory-scale are useful to recognize the type of denitrification occurring in the field.

  9. Carbon-14 based determination of the biogenic fraction of industrial CO2 emissions : Application and validation

    NARCIS (Netherlands)

    Palstra, S. W. L.; Meijer, H. A. J.

    2010-01-01

    The C-14 method is a very reliable and sensitive method for industrial plants, emission authorities and emission inventories to verify data estimations of biogenic fractions of CO2 emissions. The applicability of the method is shown for flue gas CO2 samples that have been sampled in I-h intervals at

  10. Carbon-14 labelled nitrogen heterocycles; the syntheses of three phosphodiesterase inhibitors

    International Nuclear Information System (INIS)

    The syntheses of three heterocyclic phosphodiesterase inhibitors are described from a common radiolabelled precursor, namely 2-propoxybenzo[cyano-14C] nitrile. Conversion of the nitrile to the corresponding methyl ketone or amidine allows elaboration of the heterocycles radiolabelled within the ring systems. (Author)

  11. Constraints on emissions of carbon monoxide, methane, and a suite of hydrocarbons in the Colorado Front Range using observations of 14CO2

    OpenAIRE

    LaFranchi, B. W; Pétron, G.; Miller, J. B.; S. J. Lehman; Andrews, A. E; E. J. Dlugokencky; Hall, B.; Miller, B. R.; Montzka, S. A.; W. Neff; P. C. Novelli; C. Sweeney; J. C. Turnbull; D. E. Wolfe; P. P. Tans

    2013-01-01

    Atmospheric radiocarbon (14C) represents an important observational constraint on emissions of fossil-fuel derived carbon into the atmosphere due to the absence of 14C in fossil fuel reservoirs. The high sensitivity and precision that accelerator mass spectrometry (AMS) affords in atmospheric 14C analysis has greatly increased the potential for using such measurements to evaluate bottom-up emissions inventories of fossil fuel CO2 (CO2ff), as well as those for other co-emitte...

  12. STUDIES ON THE CATALYTIC REACTION OF NITROGEN OXIDE ON METAL MODIFIED ACTIVATED CARBON FIBERS

    Institute of Scientific and Technical Information of China (English)

    FU Ruowen; DU Xiuying; LIN Yuansheng; XU Hao; HU Yiongjun

    2003-01-01

    The catalytic reaction of NO with CO and decomposition of NO over metal modified ACFs were investigated and compared with other carriers supported catalysts. It is demonstrated that Pd/ACF and Pd/Cu/ACF have high catalytic activity for the reaction of NO/CO, while Pt/ACF.Pt/Cu/ACF and Co/Cu/ACF have very Iow catalytic activity in similar circumstance. Pd-modified ACF possesses high catalytic decomposition of NO at 300 ℃. Pd/CB and Pd/GAC present good catalytic decomposition ability for NO only at low flowrate. Pd/G, Pd/ZMS and Pd/A however, do not show any catalytic activity for NO decomposition even at 400 ℃. Catalytic temperature, NO flowrate and loading of metal components affect the decomposition rate of NO. The coexistence of Cu with Pd on Cu/Pd/ACF leads to crystalline of palladium to more unperfected so as to that increase the catalytic activity.

  13. Interactive effects between carbon allotropes on the mechanical reinforcement of nanocomposites based on poly(1,4-cis-isoprene)

    Science.gov (United States)

    Musto, Sara; Cipolletti, Valeria; Barbera, Vincenzina; Agnelli, Silvia; Pandini, Stefano; Galimberti, Maurizio

    2014-05-01

    Interactive effects of carbon allotropes on the mechanical reinforcement of polymer nanocomposites were investigated by using, as the polymer matrix, poly(1,4-cis-isoprene) (PI) samples from industrial synthesis and from natural sources. Carbon nanotubes (CNT) and nano-graphite with high shape anisotropy (nanoG) were melt blended with PI, as the only fillers or in combination with carbon black (CB), measuring the shear modulus at low strain amplitudes. The nanofiller was found to increase the low amplitude storage modulus of the matrix, with or without CB, by a factor depending on nanofiller type and content. The filler-polymer interfacial area was able to correlate modulus data of composites with CNT, CB and with the hybrid filler system, leading to the construction of a common master curve. The filler networking phenomenon was found to be affected by type and amount of low molecular mass products of PI from natural sources. The correlation between chemical composition, dynamic mechanical and ultimate properties of nanocomposites was investigated. In particular, it was found that low molecular mass components control the ability of elastomeric nano-composites to store or dissipate energy.

  14. An electrochemical immunosensor based on covalent immobilization of okadaic acid onto screen printed carbon electrode via diazotization-coupling reaction.

    Science.gov (United States)

    Hayat, Akhtar; Barthelmebs, Lise; Sassolas, Audrey; Marty, Jean-Louis

    2011-07-15

    In this work, an electrochemical method based on the diazonium-coupling reaction mechanism for the immobilization of okadaic acid (OA) on screen printed carbon electrode was developed. At first, 4-carboxyphenyl film was grafted by electrochemical reduction of 4-carboxyphenyl diazonium salt, followed by terminal carboxylic group activation by N-hydroxysuccinimide (NHS), N-(3-dimethylaminopropyle)-N'-ethyle-carbodiimide hydrochloride (EDC). Hexamethyldiamine was then covalently bound by one of its terminal amine group to the activated carboxylic group. The carboxyl group of okadaic acid was activated by EDC/NHS and then conjugated to the second terminal amine group on other side of the hexamethyldiamine through amide bond formation. After immobilization of OA, an indirect competitive immunoassay format was employed to detect OA. The immunosensor obtained using this novel approach allowed detection limit of 1.44 ng/L of OA, and was also validated with certified reference mussel samples. PMID:21645734

  15. Reaction of carbon tetrachloride with methane in a non-equilibrium plasma at atmospheric pressure, and characterisation of the polymer thus formed.

    Science.gov (United States)

    Gaikwad, Vaibhav; Kennedy, Eric; Mackie, John; Holdsworth, Clovia; Molloy, Scott; Kundu, Sazal; Stockenhuber, Michael; Dlugogorski, Bogdan

    2014-09-15

    In this paper we focus on the development of a methodology for treatment of carbon tetrachloride utilising a non-equilibrium plasma operating at atmospheric pressure, which is not singularly aimed at destroying carbon tetrachloride but rather at converting it to a non-hazardous, potentially valuable commodity. This method encompasses the reaction of carbon tetrachloride and methane, with argon as a carrier gas, in a quartz dielectric barrier discharge reactor. The reaction is performed under non-oxidative conditions. Possible pathways for formation of major products based on experimental results and supported by quantum chemical calculations are outlined in the paper. We elucidate important parameters such as carbon tetrachloride conversion, product distribution, mass balance and characterise the chlorinated polymer formed in the process.

  16. High energy halogen atom reactions activated by nuclear transformations. Progress report, February 15, 1978--February 14, 1979

    International Nuclear Information System (INIS)

    High energy reactions of halogen atoms or ions, activated by nuclear transformations, were studied in gaseous, high pressure and condensed phase saturated and unsaturated hydrocarbons, halomethanes and other organic systems in order to better understand the mechanisms and dynamics of high energy monovalent species. The experimental and theoretical program consists of six interrelated areas: (1) the reactions of iodine with alkenes and alkynes activated by radiative neutron capture and isomeric transition in low pressure gaseous systems employing additives and rare gas moderators, high pressure and liquid systems; (2) the gas to condensed state transition in halogen high chemistry, involving bromine activated by the (n,γ) and (I.T.) processes in ethane was investigated in more detail; (3) systematics of halogen hot atom reactions. The reactions of 80Br/sup m/, 80Br, 82Br/sup m/ + 82Br, 82Br, 128I, 130I, and 130I/sup m/ + 130I activated by radiative neutron capture or isomeric transition in hydrocarbons and halo-substituted alkanes in low pressure and high pressure gaseous systems employing additives and rare gas moderators; (4) kinetic theory applications of high energy reactions and mathematical development of caging mechanisms were developed; (5) the sterochemistry of 38Cl substitution reactions involving diastereomeric 1,2-dichloro-1,2-difluorethane in liquid mixtures was completed, suggesting that the stereochemical course of the substitution process is controlled by the properties of the solvent molecules; and (6) the applications of high energy chemistry techniques and theory to neutron activation analysis of biological systems was continued, especially involving aluminum and vanadium trace determinations

  17. Improvement of the high-accuracy 17O(p ,α )14N reaction-rate measurement via the Trojan Horse method for application to 17O nucleosynthesis

    Science.gov (United States)

    Sergi, M. L.; Spitaleri, C.; La Cognata, M.; Lamia, L.; Pizzone, R. G.; Rapisarda, G. G.; Tang, X. D.; Bucher, B.; Couder, M.; Davies, P.; deBoer, R.; Fang, X.; Lamm, L.; Ma, C.; Notani, M.; O'Brien, S.; Roberson, D.; Tan, W.; Wiescher, M.; Irgaziev, B.; Mukhamedzhanov, A.; Mrazek, J.; Kroha, V.

    2015-06-01

    The 17O(p ,α )14N and 17O(p ,γ )18F reactions are of paramount importance for the nucleosynthesis in a number of stellar sites, including red giants (RGs), asymptotic giant branch (AGB) stars, massive stars, and classical novae. In particular, they govern the destruction of 17O and the formation of the short-lived radioisotope 18F, which is of special interest for γ -ray astronomy. At temperatures typical of the above-mentioned astrophysical scenario, T =0.01 -0.1 GK for RG, AGB, and massive stars and T =0.1 -0.4 GK for a classical nova explosion, the 17O(p ,α )14N reaction cross section is dominated by two resonances: one at about ERc m=65 keV above the 18F proton threshold energy, corresponding to the EX=5.673 MeV level in 18F, and another one at ERc m=183 keV (EX=5.786 MeV). We report on the indirect study of the 17O(p ,α )14N reaction via the Trojan Horse method by applying the approach recently developed for extracting the strength of narrow resonance at ultralow energies. The mean value of the strengths obtained in the two measurements was calculated and compared with the direct data available in literature. This value was used as input parameter for reaction-rate determination and its comparison with the result of the direct measurement is also discussed in the light of the electron screening effect.

  18. Reaction of erythromycin with dissolved oxygen on gold nanoparticle-modified glassy carbon electrodes

    Institute of Scientific and Technical Information of China (English)

    LI Xue; FU Ying; WANG Jian-xiu; L(U) Hui-dan; XU Mao-tian

    2008-01-01

    Cyclic voltammetry was used to investigate the reaction of erythromycin (EM) with dissolved oxygen on gold nanoparticle-modified electrodes prepared via electrodeposition. A well-defined reduction peak at -0.420 V and a reoxidation peak at -0.055V were observed. With the addition of EM into the NaOH solution containing dissolved oxygen, the oxidation peak at -0.055 V was still indiscernible. However, a new oxidation peak at 0.200V appeared, which suggests the interaction between EM and dissolved oxygen. Therefore, this method can be used for the analysis of EM in tablets. The present method is simple, reproducible,and does not require complex analytical instruments.

  19. Rates of hydroxyl radical reactions with some HFCs. [HydroFluoroCarbons

    Science.gov (United States)

    Demore, William B.

    1993-01-01

    Relative rate constants for OH reactions with some HFCs have been determined at 298 K by a technique which measures the loss of HFC greater than OH. The following ratios were determine: k(152a)/k(CH4) = 5.2 +/- 0.5, k(CH4)/k(125) = 3.9 +/- 0.5, k(CH4)/k(134a) = 2.1 +/- 0.2, k(134a)/k(125) = 2.0 +/- 0.2, and k(C2H6)/k(152a) = 6.2 +/- 1.0. These results are in good agreement with literature values for the absolute rate constants except for HFC 134a, where a slower rate constant is indicated.

  20. Effect of SiO2 on the Preparation and Properties of Pure Carbon Reaction Bonded Silicon Carbide Ceramics

    Institute of Scientific and Technical Information of China (English)

    WU Qi-de; GUO Bing-jian; YAN Yong-gao; ZHAO Xiu-jian; HONG Xiao-lin

    2004-01-01

    Effect of SiO2 content and sintering process on the composition and properties of Pure CarbonReaction Bonded Silicon Carbide (PCRBSC) ceramics prepared with C - SiO2 green body by infiltrating siliconwas presented. The infiltrating mechanism of C - SiO2 preform was also explored. The experimental results indicatethat the shaping pressure increases with the addition of SiO2 to the preform, and the pore size of the body turnedfiner and distributed in a narrower range, which is beneficial to decreasing the residual silicon content in the sin-tered materials and to avoiding shock off, thus increasing the conversion rate of SiC. SiO2 was deoxidized by car-bon at a high temperature and the gaseous SiO and CO produced are the main reason to the crack of the body atan elevated temperature. If the green body is deposited at 1800℃ in vacuum before infiltration crack will not beproduced in the preform and fully dense RBSC can be obtained. The ultimate material has the following properties:a density of3.05-3.12g/cm3 ,a strength of 580±32MPa and a hardness of (HRA)91-92.3.

  1. Gas/solid carbon branching ratios in surface-mediated reactions and the incorporation of carbonaceous material into planetesimals

    Science.gov (United States)

    Nuth, Joseph A.; Johnson, Natasha M.; Ferguson, Frank T.; Carayon, Alicia

    2016-07-01

    We report the ratio of the initial carbon available as CO that forms gas-phase compounds compared to the fraction that deposits as a carbonaceous solid (the gas/solid branching ratio) as a function of time and temperature for iron, magnetite, and amorphous iron silicate smoke catalysts during surface-mediated reactions in an excess of hydrogen and in the presence of N2. This fraction varies from more than 99% for an amorphous iron silicate smoke at 673 K to less than 40% for a magnetite catalyst at 873 K. The CO not converted into solids primarily forms methane, ethane, water, and CO2, as well as a very wide range of organic molecules at very low concentration. Carbon deposits do not form continuous coatings on the catalytic surfaces, but instead form extremely high surface area per unit volume "filamentous" structures. While these structures will likely form more slowly but over much longer times in protostellar nebulae than in our experiments due to the much lower partial pressure of CO, such fluffy coatings on the surfaces of chondrules or calcium aluminum inclusions could promote grain-grain sticking during low-velocity collisions.

  2. Gas/solid carbon branching ratios in surface-mediated reactions and the incorporation of carbonaceous material into planetesimals

    Science.gov (United States)

    Nuth, Joseph A.; Johnson, Natasha M.; Ferguson, Frank T.; Carayon, Alicia

    2016-06-01

    We report the ratio of the initial carbon available as CO that forms gas-phase compounds compared to the fraction that deposits as a carbonaceous solid (the gas/solid branching ratio) as a function of time and temperature for iron, magnetite, and amorphous iron silicate smoke catalysts during surface-mediated reactions in an excess of hydrogen and in the presence of N2. This fraction varies from more than 99% for an amorphous iron silicate smoke at 673 K to less than 40% for a magnetite catalyst at 873 K. The CO not converted into solids primarily forms methane, ethane, water, and CO2, as well as a very wide range of organic molecules at very low concentration. Carbon deposits do not form continuous coatings on the catalytic surfaces, but instead form extremely high surface area per unit volume "filamentous" structures. While these structures will likely form more slowly but over much longer times in protostellar nebulae than in our experiments due to the much lower partial pressure of CO, such fluffy coatings on the surfaces of chondrules or calcium aluminum inclusions could promote grain-grain sticking during low-velocity collisions.

  3. Hybrid capacitors utilizing halogen-based redox reactions at interface between carbon positive electrode and aqueous electrolytes

    Science.gov (United States)

    Yamazaki, Shigeaki; Ito, Tatsuya; Murakumo, Yuka; Naitou, Masashi; Shimooka, Toshiharu; Yamagata, Masaki; Ishikawa, Masashi

    2016-09-01

    We propose novel hybrid capacitors (HCs) with electrolyte-involved redox reactions of bromide or iodide species by pretreatment of an activated carbon positive electrode. The treatment is simple; impregnation of pores at an activated carbon fiber cloth (ACFC) as a positive electrode with bromine- or iodine-containing water before cell assembly. The treated positive electrode is applied to a HC cell with a non-treated negative electrode of ACFC and its electrochemical performance is investigated by galvanostatic cycling and leakage current tests. Few studies on such "electrolytic" charge storage systems have provided acceptable capacitor performance because of inevitable self-discharge caused by diffusion of charged species form an electrode to the other one through an electrolyte. Nevertheless, our electrolyte-redox-based HCs show excellent performance without undesirable diffusion of charged species. Moreover, the present HC utilizing a bromide redox system fulfills a practical cell voltage of 1.8 V in spite of an aqueous electrolyte system. This high voltage provides excellent energy density, which is 5 times higher than that in a conventional aqueous electric double-layer capacitor (EDLC), and 1.2 times higher even than that in a 2.7 V-class non-aqueous EDLC, while keeping high charge-discharge rate capability.

  4. Stereoselective synthesis of C-fused pyranoindoles, pyranobenzofurans and pyranobenzothiophene scaffolds using oxa-Pictet-Spengler type reaction of vinylogous carbonates.

    Science.gov (United States)

    Gharpure, Santosh J; Prasath, V

    2014-10-01

    C-fused pyranoheterocycles can be readily assembled using an intramolecular oxa-Pictet-Spengler type reaction of vinylogous carbonates in a highly stereoselective manner. Required indole and benzofuran rings tethered to vinylogous carbonates are prepared by a tandem Sonogashira coupling-nucleopalladation reaction. The entire process can also be carried out in a 'one-pot' manner starting from homopropargyl alcohol. The C-fused pyranoindoles could be converted to spirooxindoles as well as to ring expanded products under oxidative conditions. PMID:25137156

  5. Radiosensitivity of pimonidazole-unlabelled intratumour quiescent cell population to γ-rays, accelerated carbon ion beams and boron neutron capture reaction.

    OpenAIRE

    Masunaga, S; Sakurai, Y.; Tanaka, H.; Hirayama, R; Matsumoto, Y; Uzawa, A; Suzuki, M.; Kondo, N; Narabayashi, M.; Maruhashi, A; Ono, K.

    2013-01-01

    [Objectives] To detect the radiosensitivity of intratumour quiescent (Q) cells unlabelled with pimonidazole to accelerated carbon ion beams and the boron neutron capture reaction (BNCR). [Methods] EL4 tumour-bearing C57BL/J mice received 5-bromo-2′-deoxyuridine (BrdU) continuously to label all intratumour proliferating (P) cells. After the administration of pimonidazole, tumours were irradiated with γ-rays, accelerated carbon ion beams or reactor neutron beams with the prior administration of...

  6. Composite of TiN nanoparticles and few-walled carbon nanotubes and its application to the electrocatalytic oxygen reduction reaction

    KAUST Repository

    Isogai, Shunsuke

    2011-11-30

    Nanoparticles meet nanotubes! Direct synthesis of TiN nanoparticles in a three-dimensional network of few-walled carbon nanotubes (FWCNTs) was achieved by using mesoporous graphitic carbon nitride (C 3N 4) as both a hard template and a nitrogen source. The TiN/FWCNT composite showed high performance for the oxygen reduction reaction in acidic media. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Characterization of airborne particulates by pyrolysis/mass spectrometry and carbon-14 analysis

    Energy Technology Data Exchange (ETDEWEB)

    Voorhees, K.J. (Colorado School of Mines, Golden); Durfee, S.L.; Currie, L.A.; Klouda, G.A.

    1981-08-01

    Pyrolysis/mass spectrometry (Py/MS) has been used to characterize the composition of organics in an ambient air particulate sample from the eastern Utah oil shale lands. The procedure involved collection of the individual contributors, pyrolysis of these samples, and finally a least-squares fitting of the individual contributor spectra to the pyrolysis mass spectrum of the ambient sample. The Py/MS results were verified by using /sup 14/C analysis.

  8. Effects of entrainment through Oconee Nuclear Station on carbon-14 assimilation rates of phytoplankton

    International Nuclear Information System (INIS)

    Carbon assimilation rates of phytoplankton communities entrained through Oconee Nuclear Station were measured on six dates during 1974. Thermal, mechanical, condenser, and multiple entrainment effects on uptake rates were compared by incubating samples in vitro in controlled-temperature water baths. Duplicate light and dark bottles containing water from four cooling-system locations were exposed to temperatures approximating intake and discharge temperatures. The relationships were variable, but exposure of the hypolimnetic intake water at near-discharge temperatures (thermal effect) stimulated primary productivity in four of six experiments. Multiple entrainment and mechanical effects caused no consistent change in assimilation rates

  9. Structure of carbon-supported Pt-Ru nanoparticles and their electrocatalytic behavior for hydrogen oxidation reaction

    Energy Technology Data Exchange (ETDEWEB)

    Velazquez, Amado; Centellas, Francesc; Garrido, Jose Antonio; Arias, Conchita; Rodriguez, Rosa Maria; Brillas, Enric; Cabot, Pere-Lluis [Laboratori d' Electroquimica dels Materials i del Medi Ambient, Departament de Quimica Fisica, Universitat de Barcelona, Marti i Franques 1-11, 08028 Barcelona (Spain)

    2010-02-01

    The electrochemical activity towards hydrogen oxidation reaction (HOR) of a high performance carbon-supported Pt-Ru electrocatalyst (HP 20 wt.% 1:1 Pt-Ru alloy on Vulcan XC-72 carbon black) has been studied using the thin-film rotating disk electrode (RDE) technique. The physical properties of the Pt-Ru nanoparticles in the electrocatalyst were previously determined by transmission electron microscopy (TEM), high resolution TEM, fast Fourier transform (FFT), electron diffraction and X-ray diffraction (XRD). The corresponding compositional and size-shape analyses indicated that nanoparticles generally presented a 3D cubo-octahedral morphology with about 26 at.% Ru in the lattice positions of the face-centred cubic structure of Pt. The kinetics for HOR was studied in a hydrogen-saturated 0.5 M H{sub 2}SO{sub 4} solution using thin-film electrodes prepared by depositing an ink of the electrocatalyst with different Nafion contents in a one-step process on a glassy carbon electrode. A maximum electrochemically active surface area (ECSA) of 119 m{sup 2} g Pt{sup -1} was found for an optimum Nafion composition of the film of about 35 wt.%. The kinetic current density in the absence of mass transfer effects was 21 mA cm{sup -2}. A Tafel slope of 26 mV dec{sup -1}, independent of the rotation rate and Nafion content, was always obtained, evidencing that HOR behaves reversibly. The exchange current density referred to the ECSA of the Pt-Ru nanoparticles was 0.17 mA cm{sup -2}, a similar value to that previously found for analogous inks containing pure Pt nanoparticles. (author)

  10. Nitrogen-doped carbon dots originating from unripe peach for fluorescent bioimaging and electrocatalytic oxygen reduction reaction.

    Science.gov (United States)

    Atchudan, Raji; Edison, Thomas Nesakumar Jebakumar Immanuel; Lee, Yong Rok

    2016-11-15

    This paper reports the robust hydrothermal synthesis of nitrogen doped carbon dots (N-CDs) using the unripe fruit of Prunus persica (peach) as the carbon precursor and aqueous ammonia as the nitrogen source. The optical properties of synthesized N-CDs were characterized by ultraviolet visible (UV-Vis) and fluorescence spectroscopy techniques. The synthesized N-CDs were emitted blue light when excitated with a portable UV lamp. The materials with the optical properties were characterized further by high resolution transmission electron microscope (HRTEM), X-ray diffraction (XRD), Raman, Fourier transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS). The mean size of the N-CDs was approximately 8nm, as calculated from the HRTEM image. The d-spacing of N-CDs, calculated using Bragg law, was approximately 0.21nm, which was consistent with the interlayer distance calculated from the HRTEM image. FT-IR spectroscopy and XPS revealed the presence of the phytoconstituents functionalities of peach fruit over the N-CDs surface and a high level of nitrogen doping on carbon dots (CDs) was confirmed by XPS studies. These results suggest that the unripe fruit extract of peach is an ideal candidate for the preparation of N-CDs. The resulting N-CDs showed excellent optical properties in water. The synthesized N-CDs exhibited a high fluorescence quantum yield and low cytotoxicity, and can be used as fluorescence imaging probes. In addition, the N-CDs were catalytically activite towards the oxygen reduction reaction (ORR). The N-CDs exhibited good catalytic activity in an alkaline medium (0.1M KOH) with a remarkable ORR of approximately 0.72V vs reversible hydrogen electrode (RHE), and O2 reduction follows mainly a 2 electron pathway by being reduced to hydrogen peroxide. The 2-electron reduction pathway is used in industry for H2O2 production. PMID:27479911

  11. Enantioselective organocatalyzed Oxa-Michael-Aldol cascade reactions: Construction of chiral 4H-chromenes with a trifluoromethylated tetrasubstituted carbon stereocenter

    KAUST Repository

    Zhang, Jing

    2015-03-13

    The first organocatalytic asymmetric synthesis of 4H-chromenes bearing a trifluoromethylated tetrasubstituted carbon center is presented. Chiral secondary amines promote the oxa-Michael-aldol cascade reaction between alkynals and 2-trifluoroacetylphenols via iminium-allenamine activation to produce pharmaceutically important heterocycles with excellent enantioselectivities. The proposed reaction can be scaled-up easily with maintenance of the excellent enantioselectivity. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. High energy halogen atom reactions activated by nuclear transformations. Progress report, February 15, 1980-February 14, 1981

    International Nuclear Information System (INIS)

    The stereochemistry of high energy 18F, /sup 34m/Cl, and 76Br substitution reactions involving enantiomeric molecules in the gas and condensed phase is studied. The gas to condensed state transition in halogen high energy chemistry, involving chlorine, bromine, and iodine activated by the (n,γ) and (I.T.) processes in halomethanes, saturated and unsaturated hydrocarbons is being investigated in more detail. Special attention is given to defining the nature of the enhancement yields in the condensed phase. High energy halogen reactions in liquid and frozen aqueous solutions of organic and biomolecular solutes are studied in an attempt to learn more about these reactions. The applications of high energy chemistry techniques and theory to neutron activation analysis of biological systems are being continued. Special attention is given to developing procedures for trace molecular determinations in biological systems. The applications of hot halogen atoms as indicators of solute-solute interactions in liquid and frozen aqueous solutions of halogenated bases and nucleosides are being developed. Experiments are designed to explain the mechanisms of the radioprotection offered biomolecular solutes trapped within the frozen ice lattice. Reactions of bromine and iodine activated by isomeric transition with halogenated biomolecular solutes in liquid and frozen aqueous solutions are studied. The high energy reactions of iodine with the isomers of pentene have been studied in low pressure gaseous systems employing additives and rare gas moderators and liquid systems. Reactivity of excited complex formation and structural effects of electrophilic iodine attack on the pi-bond systems are studied

  13. High energy halogen atom reactions activated by nuclear transformations. Progress report, February 15, 1979-February 14, 1980

    International Nuclear Information System (INIS)

    The program consists of six interrelated areas: (1) Reactions of iodine with alkenes and alkynes activated by radiative neutron capture and isomeric transition in low pressure gaseous systems employing additives and rare gas moderators, high pressure, and liquid systems. Special attention was given to the reactivity of excited complex formation and structural effects of electrophilic iodine attack on various pi-bond systems. (2) The gas-to-condensed phase transition in halogen high energy chemistry. Current interest involves the study of caging effects of an ice lattice on recombination reactions involving neutron-irradiated frozen aqueous solutions of halogenated organic and biochemical solutes in order to learn more about kinetic energy effects, halogen size, solute molecule size, steric effects and hydrogen bonding within an ice lattice cage. (3) Systematics of halogen hot atom reactions. The reactions of /sup 80m/Br, 80Br, /sup 82m/Br + 82Br, 82Br, 82Br, 128I, 130I, and /sup 130m/I + 130I activated by radiative neutron capture or isomeric transition in hydrocarbons and halo-substituted alkanes in low pressure and high pressure gaseous systems employing additives and rare gas moderators are currently being studied. (4) Mathematical and computer simulation studies of caging events within an ice lattice are being investigated. (5) At Brookhaven National Laboratory, cyclotron-produced chlorine and fluorine hot atoms substitution reactions with molecules possessing a single chiral center are under investigation. (6) The applications of high energy techniques and concepts to neutron activation analysis for trace elements and trace molecule determinations in biological systems was continued

  14. Chemiluminescence behavior of sodium hydrogen carbonate in the potassium permanganate-hydrogen peroxide reaction

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Chemiluminescence (CL) phenomenon of hydrogen peroxide with potassium permanganate in the presence of sodium hydrogen carbonate was reported.Effects of the surfactant on the CL system were investigated.Nonionic surfactants could effectively increase the CL signal.Radical scavengers and organic reagents such as nitro blue tetrazolium chloride (NBT),cytochrome c,sodium azide,ascorbic acid,thiourea,tert-butanol and dimethyl sulphoxide were used to study the emitting species.CL emission spectrum was recorded and the results showed that the maximal emission wavelengths of NaHCO3-H2O2-KMnO4 system were 440 and 634 nm.The mechanism was discussed based on electron spin resonance (ESR) spectra,fluorescence spectra and UV-vis absorption spectra.The addition of rhodamine B or uranine into this CL system enhanced the CL signal.It was due to part of the energy transfer from singlet oxygen and excited triplet dimers of two CO2 molecules to rhodamine B or uranine.The CL could be induced by excited rhodamine B or uranine.

  15. Crossed-beam reaction of carbon atoms with hydrocarbon molecules. V. Chemical dynamics of n-C4H3 formation from reaction of C(3Pj) with allene, H2CCCH2(X 1A1)

    Science.gov (United States)

    Kaiser, R. I.; Mebel, A. M.; Chang, A. H. H.; Lin, S. H.; Lee, Y. T.

    1999-06-01

    The crossed molecular beams technique was employed to investigate the reaction between ground state carbon atoms, C(3Pj), and allene, H2CCCH2(X 1A1), at two averaged collision energies of 19.6 and 38.8 kJ mol-1. Product angular distributions and time-of-flight spectra of C4H3 were recorded. Forward-convolution fitting of the data yields weakly polarized center-of-mass angular flux distributions isotropic at lower, but forward scattered with respect to the carbon beam at a higher collision energy. The maximum translational energy release and the angular distributions combined with ab initio and RRKM calculations are consistent with the formation of the n-C4H3 radical in its electronic ground state. The channel to the i-C4H3 isomer contributes less than 1.5%. Reaction dynamics inferred from the experimental data indicate that the carbon atom attacks the π-orbitals of the allenic carbon-carbon double bond barrierless via a loose, reactant-like transition state located at the centrifugal barrier. The initially formed cyclopropylidene derivative rotates in a plane almost perpendicular to the total angular momentum vector around its C-axis and undergoes ring opening to triplet butatriene. At higher collision energy, the butatriene complex decomposes within 0.6 ps via hydrogen emission to form the n-C4H3 isomer and atomic hydrogen through an exit transition state located 9.2 kJ mol-1 above the products. The explicit identification of the n-C4H3 radical under single collision represents a further example of a carbon-hydrogen exchange in reactions of ground state carbon atoms with unsaturated hydrocarbons. This channel opens a barrierless route to synthesize extremely reactive hydrocarbon radicals in combustion processes, interstellar chemistry, and hydrocarbon-rich atmospheres of Jupiter, Saturn, Titan, as well as Triton.

  16. Study of reaction mechanisms in 40Ar+68Zn interaction at 14.6 and 27.6 MeV/N

    International Nuclear Information System (INIS)

    The competing mechanisms in the 40Ar+68Zn reaction have been investigated at two bombarding energies: 14.6 and 27.6 MeV/nucleon. Mass, charge and energy spectra of the reaction products have been measured in a large angular range (30 0). The results show that important changes occur in this energy region. At 14.6 MeV/nucleon the production of the projectile-like fragments results mainly from deep inelastic and direct nucleon transfer reactions; while at 27.6 MeV/nucleon a strong component corresponding to process similar to projectile fragmentation is also observed. A distinction between the fragmentation process and direct transfer of few nucleons has been possible by analysing the linear momentum distributions of the detected fragments. The energy dependance of the fusion cross section indicates that this process should disappear for incident energies E/A > approximately 30 MeV/nucleon. The maximum temperature reached by the compound nucleus has been deduced i.e. Tmax approximately equal 7 MeV; this value is in agreement with recent theoretical predictions

  17. Carbon-14 ages of Antarctic meteorites with accelerator and small-volume counting techniques

    International Nuclear Information System (INIS)

    C-14 measurements were made on six Yamato and Victoria Land meteorites using tandem accelerator mass spectroscopy. The studies brought to 27 the number of Antarctic meteorites that have been examined for terrestrial aging. Details of the spectroscopic method are provided, along with the results in combinations with the data from the other 21 meteorites. It is found that the Yamato meteorites are younger than those found at Allan Hills, implying that two mechanisms may exist for the abundant Antarctic meteorites: exposure where falling due to a paucity of ice, and transport and exposure by sublimating ice

  18. Age determination of ground-waters by means of carbon 14

    International Nuclear Information System (INIS)

    At present the age determination of ground-waters aged between 1,500 and approximately 40,000 years is only possible by measuring their 14C content. A precise age assignment can be established in slightly mineralised waters, whereas it becomes vague in mineralised waters, particularly in acidulous springs. In general, additional information and data are required about the 13C, D, 18O, 3H, 85Kr and the 39Ar contents, about the ph value, temperature and the principal ions. (DG)

  19. Backward emitted high-energy neutrons in hard reactions of p and π+ on carbon

    Science.gov (United States)

    Malki, A.; Alster, J.; Asryan, G.; Averichev, Y.; Barton, D.; Baturin, V.; Bukhtoyarova, N.; Carroll, A.; Heppelmann, S.; Kawabata, T.; Leksanov, A.; Makdisi, Y.; Minina, E.; Navon, I.; Nicholson, H.; Ogawa, A.; Panebratsev, Yu.; Piasetzky, E.; Schetkovsky, A.; Shimanskiy, S.; Tang, A.; Watson, J. W.; Yoshida, H.; Zhalov, D.

    2002-01-01

    Beams of protons and pions of 5.9 GeV/c were incident on a C target. Neutrons emitted into the backward hemisphere, in the laboratory system, were detected in (triple) coincidence with two emerging particles of tranverse momenta pt>0.6 GeV/c. We determined that for (46.5+/-3.7)% of the proton-induced events and for (40.8+/-4.5)% of the pion-induced events with the two high-pt particles, there is also at least one backward emitted neutron with momentum greater than 0.32 GeV/c. This observation is in sharp contrast to a well- established universal pattern from a large variety of earlier inclusive measurements with hadrons, electrons, photons, neutrinos, and antineutrinos where the probability for backward nucleon emission was in the 5 to 10 % range. We present also a measurement of the momentum spectra for the backward going neutrons. The spectra have the same universal shape observed in the inclusive reactions. We speculate that the enhanced backward neutron emission in this semi-inclusive region could be an indication for a strong dependence of the cross section on the squared total center-of-mass energy (s) and for the importance of short-range nucleon-nucleon correlations.

  20. Carbon Nanotube and Nanofiber Exposure Assessments: An Analysis of 14 Site Visits.

    Science.gov (United States)

    Dahm, Matthew M; Schubauer-Berigan, Mary K; Evans, Douglas E; Birch, M Eileen; Fernback, Joseph E; Deddens, James A

    2015-07-01

    Recent evidence has suggested the potential for wide-ranging health effects that could result from exposure to carbon nanotubes (CNT) and carbon nanofibers (CNF). In response, the National Institute for Occupational Safety and Health (NIOSH) set a recommended exposure limit (REL) for CNT and CNF: 1 µg m(-3) as an 8-h time weighted average (TWA) of elemental carbon (EC) for the respirable size fraction. The purpose of this study was to conduct an industrywide exposure assessment among US CNT and CNF manufacturers and users. Fourteen total sites were visited to assess exposures to CNT (13 sites) and CNF (1 site). Personal breathing zone (PBZ) and area samples were collected for both the inhalable and respirable mass concentration of EC, using NIOSH Method 5040. Inhalable PBZ samples were collected at nine sites while at the remaining five sites both respirable and inhalable PBZ samples were collected side-by-side. Transmission electron microscopy (TEM) PBZ and area samples were also collected at the inhalable size fraction and analyzed to quantify and size CNT and CNF agglomerate and fibrous exposures. Respirable EC PBZ concentrations ranged from 0.02 to 2.94 µg m(-3) with a geometric mean (GM) of 0.34 µg m(-3) and an 8-h TWA of 0.16 µg m(-3). PBZ samples at the inhalable size fraction for EC ranged from 0.01 to 79.57 µg m(-3) with a GM of 1.21 µg m(-3). PBZ samples analyzed by TEM showed concentrations ranging from 0.0001 to 1.613 CNT or CNF-structures per cm(3) with a GM of 0.008 and an 8-h TWA concentration of 0.003. The most common CNT structure sizes were found to be larger agglomerates in the 2-5 µm range as well as agglomerates >5 µm. A statistically significant correlation was observed between the inhalable samples for the mass of EC and structure counts by TEM (Spearman ρ = 0.39, P 1 μg m(-3). Until more information is known about health effects associated with larger agglomerates, it seems prudent to assess worker exposure to airborne CNT and CNF