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Sample records for situ reaction study

  1. In situ reaction furnace for real-time XRD studies.

    PubMed

    Riello, Pietro; Lausi, Andrea; Macleod, Jennifer; Plaisier, Jasper Rikkert; Zerauschek, Giulio; Fornasiero, Paolo

    2013-01-01

    The new furnace at the Materials Characterization by X-ray Diffraction beamline at Elettra has been designed for powder diffraction measurements at high temperature (up to 1373 K at the present state). Around the measurement region the geometry of the radiative heating element assures a negligible temperature gradient along the capillary and can accommodate either powder samples in capillary or small flat samples. A double capillary holder allows flow-through of gas in the inner sample capillary while the outer one serves as the reaction chamber. The furnace is coupled to a translating curved imaging-plate detector, allowing the collection of diffraction patterns up to 2θ ≃ 130°.

  2. Combined in-situ dilatometer and contact angle studies of interfacial reaction kinetics in brazing.

    SciTech Connect

    Dave, V. R.; Javernick, D. A.; Thoma, D. J.; Cola, M. J.; Hollis, K. J.; Smith, F. M.; Dauelsberg, L. B.

    2001-01-01

    Multi-component dissimilar material braze joints as shown in Figure 1 consisting of dissimilar base materials, filler materials and wetting agents are of tantamount importance in a wide variely of applications. This work combines dilatometry and contact angle measurements to characterize in-situ the multiple interfacial reaction pathways that occur in such systems. Whereas both of these methods are commonly used tools in metallurgical investigation, their combined use within the context of brazing studies is new and offers considerable additional insight. Applications are discussed to joints made between Beryllium and Monel with TiH{sub 2} as the wetting agent and Cu-28%Ag as the filler material.

  3. In Situ Ambient Pressure X-ray Photoelectron Spectroscopy Studies of Lithium-Oxygen Redox Reactions

    NASA Astrophysics Data System (ADS)

    Lu, Yi-Chun; Crumlin, Ethan J.; Veith, Gabriel M.; Harding, Jonathon R.; Mutoro, Eva; Baggetto, Loïc; Dudney, Nancy J.; Liu, Zhi; Shao-Horn, Yang

    2012-10-01

    The lack of fundamental understanding of the oxygen reduction and oxygen evolution in nonaqueous electrolytes significantly hinders the development of rechargeable lithium-air batteries. Here we employ a solid-state Li4+xTi5O12/LiPON/LixV2O5 cell and examine in situ the chemistry of Li-O2 reaction products on LixV2O5 as a function of applied voltage under ultra high vacuum (UHV) and at 500 mtorr of oxygen pressure using ambient pressure X-ray photoelectron spectroscopy (APXPS). Under UHV, lithium intercalated into LixV2O5 while molecular oxygen was reduced to form lithium peroxide on LixV2O5 in the presence of oxygen upon discharge. Interestingly, the oxidation of Li2O2 began at much lower overpotentials (~240 mV) than the charge overpotentials of conventional Li-O2 cells with aprotic electrolytes (~1000 mV). Our study provides the first evidence of reversible lithium peroxide formation and decomposition in situ on an oxide surface using a solid-state cell, and new insights into the reaction mechanism of Li-O2 chemistry.

  4. In Situ Ambient Pressure X-ray Photoelectron Spectroscopy Studies of Lithium-Oxygen Redox Reactions

    PubMed Central

    Lu, Yi-Chun; Crumlin, Ethan J.; Veith, Gabriel M.; Harding, Jonathon R.; Mutoro, Eva; Baggetto, Loïc; Dudney, Nancy J.; Liu, Zhi; Shao-Horn, Yang

    2012-01-01

    The lack of fundamental understanding of the oxygen reduction and oxygen evolution in nonaqueous electrolytes significantly hinders the development of rechargeable lithium-air batteries. Here we employ a solid-state Li4+xTi5O12/LiPON/LixV2O5 cell and examine in situ the chemistry of Li-O2 reaction products on LixV2O5 as a function of applied voltage under ultra high vacuum (UHV) and at 500 mtorr of oxygen pressure using ambient pressure X-ray photoelectron spectroscopy (APXPS). Under UHV, lithium intercalated into LixV2O5 while molecular oxygen was reduced to form lithium peroxide on LixV2O5 in the presence of oxygen upon discharge. Interestingly, the oxidation of Li2O2 began at much lower overpotentials (~240 mV) than the charge overpotentials of conventional Li-O2 cells with aprotic electrolytes (~1000 mV). Our study provides the first evidence of reversible lithium peroxide formation and decomposition in situ on an oxide surface using a solid-state cell, and new insights into the reaction mechanism of Li-O2 chemistry. PMID:23056907

  5. In situ infrared (FTIR) study of the mechanism of the borohydride oxidation reaction.

    PubMed

    Concha, B Molina; Chatenet, M; Maillard, F; Ticianelli, E A; Lima, F H B; de Lima, R B

    2010-10-07

    Early reports stated that Au was a catalyst of choice for the BOR because it would yield a near complete faradaic efficiency. However, it has recently been suggested that gold could yield to some extent the heterogeneous hydrolysis of BH, therefore lowering the electron count per BH, especially at low potential. Actually, the blur will exist regarding the BOR mechanism on Au as long as no physical proof regarding the reaction intermediates is not put forward. In that frame, in situ physical techniques like FTIR exhibit some interest to study the BOR. Consequently, in situ infrared reflectance spectroscopy measurements (SPAIRS technique) have been performed in 1 M NaOH/1 M NaBH(4) on a gold electrode with the aim to detect the intermediate species. We monitored several bands in B-H (nu ∼ 1180, 1080 and 972 cm(-1)) and B-O bond regions (nu = 1325 and ∼1425 cm(-1)), which appear sequentially as a function of the electrode polarization. These absorption bands are assigned to BH(3), BH(2) and BO species. At the light of the experimental results, possible initial elementary steps of the BOR on gold electrode have been proposed and discussed according to the relevant literature data.

  6. The Oxford-Diamond In Situ Cell for studying chemical reactions using time-resolved X-ray diffraction.

    PubMed

    Moorhouse, Saul J; Vranješ, Nenad; Jupe, Andrew; Drakopoulos, Michael; O'Hare, Dermot

    2012-08-01

    A versatile, infrared-heated, chemical reaction cell has been assembled and commissioned for the in situ study of a range of chemical syntheses using time-resolved energy-dispersive X-ray diffraction (EDXRD) on Beamline I12 at the Diamond Light Source. Specialized reactor configurations have been constructed to enable in situ EDXRD investigation of samples under non-ambient conditions. Chemical reactions can be studied using a range of sample vessels such as alumina crucibles, steel hydrothermal autoclaves, and glassy carbon tubes, at temperatures up to 1200 °C.

  7. The Oxford-Diamond In Situ Cell for studying chemical reactions using time-resolved X-ray diffraction

    NASA Astrophysics Data System (ADS)

    Moorhouse, Saul J.; Vranješ, Nenad; Jupe, Andrew; Drakopoulos, Michael; O'Hare, Dermot

    2012-08-01

    A versatile, infrared-heated, chemical reaction cell has been assembled and commissioned for the in situ study of a range of chemical syntheses using time-resolved energy-dispersive X-ray diffraction (EDXRD) on Beamline I12 at the Diamond Light Source. Specialized reactor configurations have been constructed to enable in situ EDXRD investigation of samples under non-ambient conditions. Chemical reactions can be studied using a range of sample vessels such as alumina crucibles, steel hydrothermal autoclaves, and glassy carbon tubes, at temperatures up to 1200 °C.

  8. Theoretical study of piezoelectrochemical reactions in molecular compression chambers: In-situ generation of molecular hydrogen

    NASA Astrophysics Data System (ADS)

    Pichierri, Fabio

    2016-09-01

    Nitrogen-containing molecular compression chambers (MCCs) undergo stepwise protonation followed by a 2-electron reduction step which affords molecular hydrogen in situ. This piezoelectrochemical reaction is favored by the high compression that characterizes the molecular skeleton of MCC and its fluorinated analogue. Besides H2, the MCCs are also capable of trapping molecular fluorine and the small monoatomic gases helium and neon. A topological analysis of the electronic charge density reveals the presence of closed-shell interactions between hosts and guests.

  9. Preliminary experiments on apparatus for in situ studies of microwave-driven reactions by small angle neutron scattering

    NASA Astrophysics Data System (ADS)

    Whittaker, A. G.; Harrison, A.; Oakley, G. S.; Youngson, I. D.; Heenan, R. K.; King, S. M.

    2001-01-01

    In this article we describe apparatus for the study of the microwave-driven growth of particles in solution by in situ small angle neutron scattering (SANS). This apparatus has enabled the first preliminary experiments using microwave-activated in situ diffraction. We take iron oxide as the prototype system, but the technique may be extended to a wide variety of chemical reactions that deposit solids from solution. The key features of the apparatus are a microwave cavity with a modular construction that may be adapted to the geometric constraints of the diffractometer, and a computer-controlled microwave generator that may be set to maintain either constant pressure or temperature in the reaction vessel. In this particular piece of equipment the reaction vessel is adapted so that part of the sample fills a cell of identical construction to those commonly used in SANS measurements for optimal transmission of the neutron beam.

  10. In situ quantitative and kinetic study by Fourier transform raman spectroscopy of reaction between nitriles and hydroperoxides

    NASA Astrophysics Data System (ADS)

    Vacque, V.; Dupuy, N.; Sombret, B.; Huvenne, J. P.; Legrand, P.

    1997-06-01

    The reaction of nitrile with alkaline hydrogen peroxide has been studied kinetically by means of iodometry several times. We proposed to set up an in situ analytical method to follow the consumption of nitrile. We applied FT-Raman spectroscopy coupled with a partial least-squares quantitative method to the study the reactions of hydrogen peroxide or tert-butyl hydroperoxide on benzonitrile and acetonitrile. The results obtained led us to conclusions on the reactivity of the hydroperoxides and on the rate of consumption of nitrile. Our study made also clear that FT-Raman spectroscopy was a convenient tool for controlling industrial processes.

  11. In situ high pressure and temperature carbon-13 nmr for the study of carbonation reactions of carbon dioxide

    NASA Astrophysics Data System (ADS)

    Surface, James Andrew

    The aqueous reactions of carbon dioxide with various Mg-containing minerals [MgO, Mg(OH)2, and Mg2SiO4] at several different pressures (1-200 bar) and temperatures (25-150C) have been studied using a novel, elevated pressure and temperature 13C NMR probe. Critical observations about reaction rates, chemical exchange, and pH measurements throughout these reactions and the implications of the in situ measurements made during these reactions are discussed. A new method is used to elucidate pH under high pressure and temperature conditions which utilizes a calculation scheme wherein experimental data and a computational model are combined. Additionally, a 1D pH imaging method is employed to observe pH gradient effects across mineral samples during their reaction with CO2. Finally, other experimental details are discussed including ex situ analysis on carbonate products using pXRD, Raman, and MAS NMR. Detailed discussion outlines how to use 13C NMR to study CO2 mineralization reactions.

  12. Development of a reaction cell for in-situ/operando studies of surface of a catalyst under a reaction condition and during catalysis.

    PubMed

    Nguyen, Luan; Tao, Franklin Feng

    2016-06-01

    Tracking surface chemistry of a catalyst during catalysis is significant for fundamental understanding of catalytic performance of the catalyst since it allows for establishing an intrinsic correlation between surface chemistry of a catalyst at its working status and its corresponding catalytic performance. Ambient pressure X-ray photoelectron spectroscopy can be used for in-situ studies of surfaces of different materials or devices in a gas. To simulate the gaseous environment of a catalyst in a fixed-bed a flowing gaseous environment of reactants around the catalyst is necessary. Here, we report the development of a new flowing reaction cell for simulating in-situ study of a catalyst surface under a reaction condition in gas of one reactant or during catalysis in a mixture of reactants of a catalytic reaction. The homemade reaction cell is installed in a high vacuum (HV) or ultrahigh vacuum (UHV) environment of a chamber. The flowing gas in the reaction cell is separated from the HV or UHV environment through well sealings at three interfaces between the reaction cell and X-ray window, sample door and aperture of front cone of an energy analyzer. Catalyst in the cell is heated through infrared laser beam introduced through a fiber optics interfaced with the reaction cell through a homemade feedthrough. The highly localized heating on the sample holder and Au-passivated internal surface of the reaction cell effectively minimizes any unwanted reactions potentially catalyzed by the reaction cell. The incorporated laser heating allows a fast heating and a high thermal stability of the sample at a high temperature. With this cell, a catalyst at 800 °C in a flowing gas can be tracked readily.

  13. Development of a reaction cell for in-situ/operando studies of surface of a catalyst under a reaction condition and during catalysis

    NASA Astrophysics Data System (ADS)

    Nguyen, Luan; Tao, Franklin Feng

    2016-06-01

    Tracking surface chemistry of a catalyst during catalysis is significant for fundamental understanding of catalytic performance of the catalyst since it allows for establishing an intrinsic correlation between surface chemistry of a catalyst at its working status and its corresponding catalytic performance. Ambient pressure X-ray photoelectron spectroscopy can be used for in-situ studies of surfaces of different materials or devices in a gas. To simulate the gaseous environment of a catalyst in a fixed-bed a flowing gaseous environment of reactants around the catalyst is necessary. Here, we report the development of a new flowing reaction cell for simulating in-situ study of a catalyst surface under a reaction condition in gas of one reactant or during catalysis in a mixture of reactants of a catalytic reaction. The homemade reaction cell is installed in a high vacuum (HV) or ultrahigh vacuum (UHV) environment of a chamber. The flowing gas in the reaction cell is separated from the HV or UHV environment through well sealings at three interfaces between the reaction cell and X-ray window, sample door and aperture of front cone of an energy analyzer. Catalyst in the cell is heated through infrared laser beam introduced through a fiber optics interfaced with the reaction cell through a homemade feedthrough. The highly localized heating on the sample holder and Au-passivated internal surface of the reaction cell effectively minimizes any unwanted reactions potentially catalyzed by the reaction cell. The incorporated laser heating allows a fast heating and a high thermal stability of the sample at a high temperature. With this cell, a catalyst at 800 °C in a flowing gas can be tracked readily.

  14. An in situ electron microscopy technique for the study of thermally activated reactions in multilayered materials

    SciTech Connect

    Wall, M.A.; Barbee, T.W. Jr.; Weihs, T.P.

    1995-04-14

    A novel in situ transmission electron microscopy technique for the observation of reaction processes in multilayered materials is reported. The technique involves constant heating rate experiments of multilayered materials in image and diffraction modes. Because the fine scale microstructure of multilayered materials is typically a small fraction of the TEM specimen thickness, realistic comparison of the microstructural evolution with that of similarly processed thick foil samples is possible. Such experiments, when well designed, can provide rapid characterization of phase transformations and stability of nano-structured materials. The results of these experiments can be recorded in both video and micrograph format. The results and limitations of this technique will be shown for the Al/Zr and Al/Monel multilayered systems.

  15. Reaction of Formic Acid over Amorphous Manganese Oxide Catalytic Systems: An In Situ Study

    SciTech Connect

    J Durand; S Senanayake; S Suib; D Mullins

    2011-12-31

    The interaction of formic acid with amorphous manganese oxide (AMO) is investigated using in situ photoelectron and infrared spectroscopy techniques. Soft X-ray photoelectron spectroscopy (sXPS) and in situ FTIR illustrate two possible modes of formate bound species at the AMO surface. Two peaks in the IR region from 1340-1390 cm{sup -1} are indicative of formate species bound to the surface in a bidentate configuration. However, a 224 cm{sup -1} band gap between v{sub s}OCO and v{sub as}OCO suggests formate is bound in a bridging configuration. Temperature-programmed desorption studies confirm the formate bound species desorbs as carbon dioxide from the surface at multiple binding sites. At temperatures above 700 K, the presence of K{sup +} {hor_ellipsis} OC complex suggests the bound species interacts at vacant sites related to framework oxygen and cation mobility.

  16. Reaction of Formic Acid over Amorphous Manganese Oxide Catalytic Systems: An In Situ Study

    SciTech Connect

    Durand, Jason; Senanayake, Sanjaya D; Mullins, David R; Suib, Steven

    2010-01-01

    The interaction of formic acid with amorphous manganese oxide (AMO) is investigated using in situ photoelectron and infrared spectroscopy techniques. Soft X-ray photoelectron spectroscopy (sXPS) and in situ FTIR illustrate two possible modes of formate bound species at the AMO surface. Two peaks in the IR region from 1340-1390 cm{sup -1} are indicative of formate species bound to the surface in a bidentate configuration. However, a 224 cm{sup -1} band gap between v{sub s}OCO and v{sub as}OCO suggests formate is bound in a bridging configuration. Temperature-programmed desorption studies confirm the formate bound species desorbs as carbon dioxide from the surface at multiple binding sites. At temperatures above 700 K, the presence of K{sup +} {hor_ellipsis} OC complex suggests the bound species interacts at vacant sites related to framework oxygen and cation mobility.

  17. In situ high-resolution transmission electron microscopy study of interfacial reactions of Cu thin films on amorphous silicon

    NASA Astrophysics Data System (ADS)

    Lee, Sung Bo; Choi, Duck-Kyun; Phillipp, Fritz; Jeon, Kyung-Sook; Kim, Chang Kyung

    2006-02-01

    Interfacial reactions of Cu with amorphous silicon (a-Si) in the Cu /a-Si/glass system are studied by in situ high-resolution transmission electron microscopy at 550°C. Various Cu silicides, such as η-Cu3Si, Cu15Si4, and Cu5Si, and Cu particles are observed. The formation of the Cu particles can be attributed to a heating effect from electron beam irradiation. Around the Cu silicides, crystallization of a-Si occurs. Around the Cu particles, however, crystallization does not occur. Crystallization appears to be enhanced by Cu dissolved in a-Si.

  18. In situ EPR studies of reaction pathways in Titania photocatalyst-promoted alkylation of alkenes.

    PubMed

    Rhydderch, Shona; Howe, Russell F

    2015-03-03

    In situ EPR spectroscopy at cryogenic temperatures has been used to observe and identify paramagnetic species produced when titania is irradiated in the presence of reactants used in the photocatalytic alkylation of maleimide with t-butyl carboxylic acid or phenoxyacetic acid. It is shown that maleimide acts as an acceptor of conduction band electrons. Valence band holes oxidise t-butyl carboxylic acid to the t-butyl radical and phenoxyacetic acid to the phenoxyacetic acid radical cation. In the presence of maleimide, the phenoxymethyl radical is formed from phenoxyacetic acid. The relevance of these observations to the mechanisms of titania photocatalyst-promoted alkylation of alkenes is discussed.

  19. A straightforward implementation of in situ solution electrochemical ¹³C NMR spectroscopy for studying reactions on commercial electrocatalysts: ethanol oxidation.

    PubMed

    Huang, L; Sorte, E G; Sun, S-G; Tong, Y Y J

    2015-05-11

    Identifying and quantifying electrocatalytic-reaction-generated solution species, be they reaction intermediates or products, are highly desirable in terms of understanding the associated reaction mechanisms. We report herein a straightforward implementation of in situ solution electrochemical (13)C NMR spectroscopy for the first time that enables in situ studies of reactions on commercial fuel-cell electrocatalysts (Pt and PtRu blacks). Using ethanol oxidation reaction (EOR) as a working example, we discovered that (1) the complete oxidation of ethanol to CO2 only took place dominantly at the very beginning of a potentiostatic chronoamperometric (CA) measurement and (2) the PtRu had a much higher activity in catalysing oxygen insertion reaction that leads to acetic acid.

  20. A microwave-heated infrared reaction cell for the in situ study of heterogeneous catalysts.

    PubMed

    Silverwood, Ian P; McDougall, Gordon S; Gavin Whittaker, A

    2006-12-14

    A transmission infrared microreactor cell which holds a pressed disc in a controlled atmosphere and allows microwave and conventional heating up to 423 K is demonstrated using the oxidation of carbon monoxide over the standard catalyst EUROPT-1. Optical characteristics are determined by the choice of CaF2 as the window material, allowing transmission from 77,000-1000 cm(-1). An oscillating microwave power regime with a peak height of 200 W is used and time-resolved infrared spectra and mass spectrometry show oscillations in the reaction which correspond to the microwave heating.

  1. In-situ time resolved synchrotron powder diffraction studies of synthesis and chemical reactions

    SciTech Connect

    Norby, P.

    1995-09-01

    Equipment for time and temperature dependent powder diffraction has been developed, especially in order to be able to study hydrothermal syntheses of zeolites. The system is very versatile and has so far been used to study e.g. hydrothermal syntheses of zeolites and aluminophosphates, syntheses of layered phosphates, formation of Sorel cements, dehydration and phase transformations of zeolites, solid state synthesis of lanthanum manganites, ion exchange of zeolites using molten salt, and oxidation/reduction of lanthanum manganites at high temperatures. The sample is contained in quartz capillaries and is heated using a stream of hot air. External pressure can be applied allowing hydrothermal syntheses at temperatures up to 200 C to be performed. Controlled atmosphere is obtained by flowing gas or a mixture of gases through the capillary.

  2. Study on the Electrochemical Reaction Mechanism of ZnFe2O4 by In Situ Transmission Electron Microscopy

    PubMed Central

    Su, Qingmei; Wang, Shixin; Yao, Libing; Li, Haojie; Du, Gaohui; Ye, Huiqun; Fang, Yunzhang

    2016-01-01

    A family of mixed transition–metal oxides (MTMOs) has great potential for applications as anodes for lithium ion batteries (LIBs). However, the reaction mechanism of MTMOs anodes during lithiation/delithiation is remain unclear. Here, the lithiation/delithiation processes of ZnFe2O4 nanoparticles are observed dynamically using in situ transmission electron microscopy (TEM). Our results suggest that during the first lithiation process the ZnFe2O4 nanoparticles undergo a conversion process and generate a composite structure of 1–3 nm Fe and Zn nanograins within Li2O matrix. During the delithiation process, volume contraction and the conversion of Zn and Fe take place with the disappearance of Li2O, followed by the complete conversion to Fe2O3 and ZnO not the original phase ZnFe2O4. The following cycles are dominated by the full reversible phase conversion between Zn, Fe and ZnO, Fe2O3. The Fe valence evolution during cycles evidenced by electron energy–loss spectroscopy (EELS) techniques also exhibit the reversible conversion between Fe and Fe2O3 after the first lithiation, agreeing well with the in situ TEM results. Such in situ TEM observations provide valuable phenomenological insights into electrochemical reaction of MTMOs, which may help to optimize the composition of anode materials for further improved electrochemical performance. PMID:27306189

  3. [In situ diffuse reflectance FTIR spectroscopy study of the selective catalytic reduction reaction of NO over Ag/SAPO-34 catalysis].

    PubMed

    Zhang, Ping; Wang, Le-fu; Xu, Jian-chang

    2003-02-01

    An in situ diffuse reflectance FTIR spectroscopy (DRIFTS) study of the selective catalytic reduction (SCR) of NO with propene in the presence of excess O2 was carried out over Ag/SAPO-34 catalyst. The SCR reaction was investigated at temperatures from 573 to 773 K, and the role of oxygen in the NO reduction process was determined by comparing experiments using an initial reaction mixture containing oxygen and without oxygen. The results show that both NO and propene are easily activated in oxygen. Furthermore, the presence of oxygen is necessary to form organo-NOx adsorbed species. Based on these experiments, a reaction mechanism is proposed that NO, propene and oxygen react to form organo-nitro and organo-nitrito adsorbed species as key intermediates, and then these intermediates decompose to nitrogen.

  4. A reaction cell with sample laser heating for in situ soft X-ray absorption spectroscopy studies under environmental conditions.

    PubMed

    Escudero, Carlos; Jiang, Peng; Pach, Elzbieta; Borondics, Ferenc; West, Mark W; Tuxen, Anders; Chintapalli, Mahati; Carenco, Sophie; Guo, Jinghua; Salmeron, Miquel

    2013-05-01

    A miniature (1 ml volume) reaction cell with transparent X-ray windows and laser heating of the sample has been designed to conduct X-ray absorption spectroscopy studies of materials in the presence of gases at atmospheric pressures. Heating by laser solves the problems associated with the presence of reactive gases interacting with hot filaments used in resistive heating methods. It also facilitates collection of a small total electron yield signal by eliminating interference with heating current leakage and ground loops. The excellent operation of the cell is demonstrated with examples of CO and H2 Fischer-Tropsch reactions on Co nanoparticles.

  5. In situ Raman and pulse reaction study on the partial oxidation of methane to synthesis gas over a Pt/Al2O3 catalyst.

    PubMed

    Wang, Mei-Liu; Zheng, Hao-Zhuan; Li, Jian-Mei; Weng, Wei-Zheng; Xia, Wen-Sheng; Huang, Chuan-Jing; Wan, Hui-Lin

    2011-02-01

    Catalytic partial oxidation of methane (POM) to synthesis gas (syngas) over Pt/Al(2)O(3) was investigated by in situ microprobe Raman and pulse reaction methods with attention focused on the mechanism of syngas formation in the oxidation zone (i.e., the catalyst zone in which O(2) was still available in the reaction feed). It was found that the amount of platinum oxide in the catalyst under POM conditions was below the detection level of Raman spectroscopy. Raman bands of carbon species that originated from methane dissociation were detected at the entrance of the catalyst bed under working conditions. The results of the pulse reaction study on POM as well as steam and CO(2) reforming of methane at 700 °C with a contact time of less than 1 ms over the catalyst suggest that pyrolysis of methane on reduced platinum sites followed by coupling of two surface hydrogen atoms to H(2) and partial oxidation of surface carbon species to CO are the major reactions responsible for syngas formation in the oxidation zone. Under the experimental conditions, steam and CO(2) reforming of methane play only a minor role in syngas formation in the same reaction zone. The contribution of the last two reactions increases with increasing contact time.

  6. An in situ sample environment reaction cell for spatially resolved x-ray absorption spectroscopy studies of powders and small structured reactors

    SciTech Connect

    Zhang, Chu; Gustafson, Johan; Merte, Lindsay R.; Evertsson, Jonas; Norén, Katarina; Carlson, Stefan; Svensson, Håkan; Carlsson, Per-Anders

    2015-03-15

    An easy-to-use sample environment reaction cell for X-ray based in situ studies of powders and small structured samples, e.g., powder, pellet, and monolith catalysts, is described. The design of the cell allows for flexible use of appropriate X-ray transparent windows, shielding the sample from ambient conditions, such that incident X-ray energies as low as 3 keV can be used. Thus, in situ X-ray absorption spectroscopy (XAS) measurements in either transmission or fluorescence mode are facilitated. Total gas flows up to about 500 ml{sub n}/min can be fed while the sample temperature is accurately controlled (at least) in the range of 25–500 °C. The gas feed is composed by a versatile gas-mixing system and the effluent gas flow composition is monitored with mass spectrometry (MS). These systems are described briefly. Results from simultaneous XAS/MS measurements during oxidation of carbon monoxide over a 4% Pt/Al{sub 2}O{sub 3} powder catalyst are used to illustrate the system performance in terms of transmission XAS. Also, 2.2% Pd/Al{sub 2}O{sub 3} and 2% Ag − Al{sub 2}O{sub 3} powder catalysts have been used to demonstrate X-ray absorption near-edge structure (XANES) spectroscopy in fluorescence mode. Further, a 2% Pt/Al{sub 2}O{sub 3} monolith catalyst was used ex situ for transmission XANES. The reaction cell opens for facile studies of structure-function relationships for model as well as realistic catalysts both in the form of powders, small pellets, and coated or extruded monoliths at near realistic conditions. The applicability of the cell for X-ray diffraction measurements is discussed.

  7. Combined temperature-programmed reaction and in-situ x-ray scattering studies of size-selected silver clusters under realistic reaction conditions in the epoxidation of propene.

    SciTech Connect

    Vajda, S.; Lee, S.; Sell, K.; Barke, I.; Kleibert, A.; von Oeynhausen, V.; Meiwes-Broer, K. H.; Rodriguez, A. F.; Elam, J. W.; Pellin, M. M.; Lee, B.; Seifert, S.; Winans, R. W.; Yale Univ.; Univ. Rostock; Swiss Light Source

    2009-09-28

    The catalytic activity and dynamical shape changes in size-selected nanoclusters at work are studied under realistic reaction conditions by using a combination of simultaneous temperature-programmed reaction with in situ grazing-incidence small angle x-ray scattering. This approach allows drawing a direct correlation between nanocatalyst size, composition, shape, and its function under realistic reaction conditions for the first time. The approach is illustrated in a chemical industry highly relevant selective partial oxidation of propene on a monodisperse silver nanocatalyst. The shape of the catalyst undergoes rapid change already at room temperature upon the exposure to the reactants, followed by a complex evolution of shape with increasing temperature. Acrolein formation is observed around 50 C while the formation of the propylene oxide exhibits a sharp onset at 80 C and is leveling off at 150 C. At lower temperatures acrolein is produced preferentially to propylene oxide; at temperatures above 100 C propylene oxide is favored.

  8. In situ infrared and mass spectroscopic study of the reaction of WF6 with hydrogenated amorphous silicon

    NASA Astrophysics Data System (ADS)

    Wadayama, Toshimasa; Shibata, Hironobu; Ohtani, Tsutomu; Hatta, Aritada

    1992-08-01

    The reaction process of tungsten hexafluoride (WF6) with photochemically deposited hydrogenated amorphous silicon was studied by polarization modulation infrared spectroscopy and quadruple mass spectrometry. Infrared absorption bands due to species (SiH3 and SiH2) incorporated in the hydrogenated amorphous silicon were decreased in intensity during exposure of WF6. The reduction rate was faster for the SiH3 species than for the SiH2 species. The mass spectrometric analysis revealed that evolution of hydrogen into the gas phase took place prior to that of silicon fluorides. These results strongly suggest that WF6 reacts preferentially with the SiH3 species present in the hydrogen-rich surface layer.

  9. A study of plasma reaction mechanisms and kinetics in glow discharges of methyl methacrylate and related precursors using in situ FTIR spectroscopy

    NASA Astrophysics Data System (ADS)

    Pan, Yu-Chi Vickie

    In order to understand plasma deposition processes, it is important to have a knowledge of the plasma gas-phase reactions. In this project, in situ Fourier Transform Infrared Spectroscopy (FTIR) was utilized to study the plasma gas-phase chemistry in a capacitively coupled glow discharge. Gas-phase measurements of a number of organic plasmas were performed. The precursors include methyl methacrylate (MMA), methyl crotonate, methyl isobutyrate, ethyl methacrylate, vinyl acetate, isopropanol, methanol, tetramethyl cyclobutanedione and formaldehyde. However, MMA was studied most extensively. In addition to the gas-phase study, plasma polymerized films were also characterized. A number of dissociation products were detected by FTIR in the plasmas. Calibration curves of these products and some monomers were prepared to determine the species concentrations and gas-phase composition. Plasma reaction kinetics were studied in closed systems to determine parameters such as dissociation pathway efficiencies, monomer decomposition rate coefficients, and intermediate species decomposition rate coefficients. The study shows that there are two major electron-impact induced dissociation pathways in MMA plasmas: the C-O bond cleavage reaction and decarboxylations. The C-O bond cleavage reaction accounts for approximately half of the MMA dissociation, and neutral formaldehyde and dimethyl ketene (DMK) molecules are produced via intramolecular rearrangement. Decarboxylation reactions produce CO, COsb2 and a number of radicals that subsequently stabilize to form neutral molecules, such as propylene, allene and methanol. These intermediate species then further dissociate in the plasma to small hydrocarbons (methane, acetylene and ethylene), CO, COsb2 and Hsb2. The reaction mechanisms in the plasmas of other alpha ,beta-unsaturated esters and vinyl acetate were found to be similar to the MMA mechanisms. However, the saturated ester (methyl isobutyrate) and isopropanol plasmas were found

  10. Fast in situ x-ray-diffraction studies of chemical reactions: A synchrotron view of the hydration of tricalcium aluminate

    NASA Astrophysics Data System (ADS)

    Jupe, A. C.; Turrillas, X.; Barnes, P.; Colston, S. L.; Hall, C.; Häusermann, D.; Hanfland, M.

    1996-06-01

    We report observations on the early hydration of tricalcium aluminate, the most reactive component of Portland cement, using rapid-energy dispersive diffraction on a high brilliance synchrotron source. In situ observations of the hydration process over short time scales, and through bulk samples, reveal an intermediate calcium aluminate hydrate appearing just prior to the formation of the final stable hydrate, demonstrating the nucleating role of this intermediate. The superior quality of the data is sufficient to yield concentration versus time plots for each phase over the whole hydration sequence. This improvement derives from being able to use smaller diffracting volumes and consequent removal of time smearing due to inhomogenetics, and thus now offers the possibility of extending the technique in terms of time resolution and diversity of system.

  11. In situ study on the effect of thermomigration on intermetallic compounds growth in liquid-solid interfacial reaction

    SciTech Connect

    Qu, Lin; Zhao, Ning; Ma, Haitao Zhao, Huijing; Huang, Mingliang

    2014-05-28

    Synchrotron radiation real-time imaging technology was carried out in situ to observe and characterize the effect of thermomigration on the growth behavior of interfacial intermetallic compounds (IMCs) in Cu/Sn/Cu solder joint during soldering. The thermomigration resulted in asymmetrical formation and growth of the interfacial IMCs. Cu{sub 6}Sn{sub 5} and Cu{sub 3}Sn IMCs formed at the cold end and grew rapidly during the whole soldering process. However, only Cu{sub 6}Sn{sub 5} IMC formed at the hot end and remained relatively thin until solidification. The IMCs at the cold end were nearly seven times thicker than that at the hot end after solidification. The Cu dissolution at the cold end was significantly restrained, while that at the hot end was promoted, which supplied Cu atoms to diffuse toward the cold end under thermomigration to feed the rapid IMC growth. Moreover, the thermomigration also caused asymmetrical morphology of the interfacial IMCs at the cooling stage, i.e., the Cu{sub 6}Sn{sub 5} IMC at the cold end transformed into facet structure, while that at the hot end remained scallop-type. The asymmetrical growth behavior of the interfacial IMCs was analyzed from the view point of kinetics.

  12. Monitoring enzymatic reactions with in situ sensors

    NASA Astrophysics Data System (ADS)

    Young, Ian T.; Iordanov, V.; Kroon, Arthur; Dietrich, Heidi R. C.; Moerman, R.; van den Doel, L. R.; van Dedem, G. W. K.; Bossche, Andre; Gray, Bonnie L.; Sarro, Lina; Verbeek, Piet W.; van Vliet, Lucas J.

    2003-07-01

    In previous publications and presentations we have described our construction of a laboratory-on-a-chip based on nanoliter capacity wells etched in silicon. We have described methods for dispensing reagents as well as samples, for preventing evaporation, for embedding electronics in each well to measure fluid volume per well in real-time, and for monitoring the production or consumption of NADH in enzyme-catalyzed reactions such as those found in the glycolytic pathway of yeast. In this paper we describe the use of light sensors (photodiodes) in each well to measure both fluorescence (such as that evidenced in NADH) as well as bioluminescence (such as evidenced in ATP assays). We show that our detection limit for NADH fluorescence in 100 μM and for ATP/luciferase bioluminescence is 2.4 μM.

  13. Gas sensing properties and in situ diffuse reflectance infrared Fourier transform spectroscopy study of trichloroethylene adsorption and reactions on SnO2 films

    NASA Astrophysics Data System (ADS)

    Zhang, Zhenxin; Huang, Kaijin; Yuan, Fangli; Xie, Changsheng

    2014-05-01

    The detection of trichloroethylene has attracted much attention because it has an important effect on human health. The sensitivity of the SnO2 flat-type coplanar gas sensor arrays to 100 ppm trichloroethylene in air was investigated. The adsorption and surface reactions of trichloroethylene were investigated at 100-200 °C by in-situ diffuse reflection Fourier transform infrared spectroscopy (DIRFTS) on SnO2 films. Molecularly adsorbed trichloroethylene, dichloroacetyl chloride (DCAC), phosgene, HCl, CO, H2O, CHCl3, Cl2 and CO2 surface species are formed during trichloroethylene adsorption at 100-200 °C. A possible mechanism of the reaction process is discussed.

  14. In situ analysis of copper electrodeposition reaction using unilateral NMR sensor

    NASA Astrophysics Data System (ADS)

    Gomes, B. F.; Nunes, L. M. S.; Lobo, C. M. S.; Carvalho, A. S.; Cabeça, L. F.; Colnago, L. A.

    2015-12-01

    The uses of high-resolution NMR spectroscopy and imaging (MRI) to study electrochemical reactions in situ have greatly increased in the last decade. However, most of these applications are limited to specialized NMR laboratories and not feasible for routine analysis. Recently we have shown that a bench top, time domain NMR spectrometer can be used to monitor in situ copper electrodeposition reaction and the effect of Lorentz force in the reaction rate. However these spectrometers limit the cell size to the magnet gap and cannot be used with standard electrochemical cells. In this paper we are demonstrating that unilateral NMR sensor (UNMR), which does not limit sample size/volume, can be used to monitor electrodeposition of paramagnetic ions in situ. The copper electrodeposition reaction was monitored remotely and in situ, placing the electrochemical cell on top of the UNMR sensor. The Cu2+ concentration was measured during three hours of the electrodeposition reactions, by using the transverse relaxation rate (R2) determined with the Carr-Purcell-Meiboom-Gill pulse sequence. The reaction rate increased fourfold when the reaction was performed in the presence of a magnetic field (in situ), in comparison to the reactions in the absence of the magnetic field (ex situ). The increase of reaction rate, in the presence of the UNMR magnet, was related to the magneto hydrodynamic force (FB) and magnetic field gradient force (F∇B). F∇B was calculated to be one order of magnitude stronger than FB. The UNMR sensor has several advantages for in situ measurements when compared to standard NMR spectrometers. It is a low cost, portable, open system, which does not limit sample size/volume and can be easily be adapted to standard electrochemical cells or large industrial reactors.

  15. In-situ studies of nanocatalysis.

    PubMed

    Zhang, Shiran; Nguyen, Luan; Zhu, Yuan; Zhan, Sihui; Tsung, Chia-Kuang Frank; Tao, Franklin Feng

    2013-08-20

    A heterogeneous catalyst in industry consists of nanoparticles with variable crystallite sizes, shapes, and compositions. Its catalytic performance (activity, selectivity, and durability) derives from surface chemistry of catalyst nanoparticles during catalysis. However, the surface chemistry of the catalyst particles during catalysis, termed in-situ information, is a "black box" because of the challenges in characterizing the catalysts during catalysis. The lack of such in-situ information about catalysts has limited the understanding of catalytic mechanisms and the development of catalysts with high selectivity and activity. The challenges in understanding heterogeneous catalysis include measurement of reaction kinetics, identification of reaction intermediates, bridging pressure gap and materials gap. The pressure gap is the difference in surface structure and chemistry between a catalyst during catalysis and under an ultrahigh vacuum (UHV) condition. The materials gap represents the difference between the structural and compositional complexity of industrial catalysts and the well-defined surface of model catalysts of metals or oxides. Development of in-situ characterization using electron spectroscopy and electron microscopy in recent decades has made possible studies of surface chemistry and structure of nanocatalysts under reaction conditions or during catalysis at near ambient pressure. In this Account, we review the new chemistries and structures of nanocatalysts during reactions revealed with in-situ analytical techniques. We discuss changes observed during catalysis including the evolution of composition, oxidation state, phase, and geometric structure of the catalyst surface, and the sintering of catalysts. These surface chemistries and structures have allowed researchers to build a correlation between surface chemistry and structure of active nanocatalysts and their corresponding catalytic performances. Such a correlation provides critical insights for

  16. In situ infrared reflection and transmission absorption spectroscopy study of surface reactions in selective chemical-vapor deposition of tungsten using WF6 and SiH4

    NASA Astrophysics Data System (ADS)

    Kobayashi, Nobuyoshi; Nakamura, Yoshitaka; Goto, Hidekazu; Homma, Yoshio

    1993-05-01

    The adsorption of tungsten hexafluoride (WF6) and monosilane (SiH4) in selective chemical-vapor deposition (CVD) of tungsten (W) is investigated in situ using Fourier-transform infrared reflection and transmission absorption spectroscopy (FTIR RAS and TMS). The selectivity for W growth is found to originate from the dissociation of SiH4 on a W surface. That is, SiH4 dissociates on a W surface to form Si-containing adsorbed species when the W surface is exposed to SiH4 at temperatures higher than 110 °C, whereas SiH4 does not dissociate on a SiO2 surface. On the other hand, when W and SiO2 surfaces are exposed to WF6 at temperatures from 20 to 300 °C, no adsorbed species are observed by FTIR RAS. However, WF6 can easily react with the Si-containing adsorbed species on a W surface to form W and byproduct gases of SiHF3 and SiF4. The main surface reaction of selective W CVD can be expressed as WF6+2SiH4=W+2SiHF3+3H2. These experimental results support the selective W-CVD mechanism previously proposed, which shows that dissociation of SiH4 and not the dissociation of WF6 has a central role in this process.

  17. New large volume hydrothermal reaction cell for studying chemical processes under supercritical hydrothermal conditions using time-resolved in situ neutron diffraction

    NASA Astrophysics Data System (ADS)

    Ok, Kang Min; O'Hare, Dermot; Smith, Ronald I.; Chowdhury, Mohammed; Fikremariam, Hanna

    2010-12-01

    The design and testing of a new large volume Inconel pressure cell for the in situ study of supercritical hydrothermal syntheses using time-resolved neutron diffraction is introduced for the first time. The commissioning of this new cell is demonstrated by the measurement of the time-of-flight neutron diffraction pattern for TiO2 (Anatase) in supercritical D2O on the POLARIS diffractometer at the United Kingdom's pulsed spallation neutron source, ISIS, Rutherford Appleton Laboratory. The sample can be studied over a wide range of temperatures (25-450 °C) and pressures (1-355 bar). This novel apparatus will now enable us to study the kinetics and mechanisms of chemical syntheses under extreme environments such as supercritical water, and in particular to study the crystallization of a variety of technologically important inorganic materials.

  18. New large volume hydrothermal reaction cell for studying chemical processes under supercritical hydrothermal conditions using time-resolved in situ neutron diffraction.

    PubMed

    Ok, Kang Min; O'Hare, Dermot; Smith, Ronald I; Chowdhury, Mohammed; Fikremariam, Hanna

    2010-12-01

    The design and testing of a new large volume Inconel pressure cell for the in situ study of supercritical hydrothermal syntheses using time-resolved neutron diffraction is introduced for the first time. The commissioning of this new cell is demonstrated by the measurement of the time-of-flight neutron diffraction pattern for TiO(2) (Anatase) in supercritical D(2)O on the POLARIS diffractometer at the United Kingdom's pulsed spallation neutron source, ISIS, Rutherford Appleton Laboratory. The sample can be studied over a wide range of temperatures (25-450 °C) and pressures (1-355 bar). This novel apparatus will now enable us to study the kinetics and mechanisms of chemical syntheses under extreme environments such as supercritical water, and in particular to study the crystallization of a variety of technologically important inorganic materials.

  19. In-situ Studies of the Reactions of Bifunctional and Heterocyclic Molecules over Noble Metal Single Crystal and Nanoparticle Catalysts Studied with Kinetics and Sum-Frequency Generation Vibrational Spectroscopy

    SciTech Connect

    Kliewer, Christopher J.

    2009-06-30

    Sum frequency generation surface vibrational spectroscopy (SFG-VS) in combination with gas chromatography (GC) was used in-situ to monitor surface bound reaction intermediates and reaction selectivities for the hydrogenation reactions of pyrrole, furan, pyridine, acrolein, crotonaldehyde, and prenal over Pt(111), Pt(100), Rh(111), and platinum nanoparticles under Torr reactant pressures and temperatures of 300K to 450K. The focus of this work is the correlation between the SFG-VS observed surface bound reaction intermediates and adsorption modes with the reaction selectivity, and how this is affected by catalyst structure and temperature. Pyrrole hydrogenation was investigated over Pt(111) and Rh(111) single crystals at Torr pressures. It was found that pyrrole adsorbs to Pt(111) perpendicularly by cleaving the N-H bond and binding through the nitrogen. However, over Rh(111) pyrrole adsorbs in a tilted geometry binding through the {pi}-aromatic orbitals. A surface-bound pyrroline reaction intermediate was detected over both surfaces with SFG-VS. It was found that the ring-cracking product butylamine is a reaction poison over both surfaces studied. Furan hydrogenation was studied over Pt(111), Pt(100), 10 nm cubic platinum nanoparticles and 1 nm platinum nanoparticles. The product distribution was observed to be highly structure sensitive and the acquired SFG-VS spectra reflected this sensitivity. Pt(100) exhibited more ring-cracking to form butanol than Pt(111), while the nanoparticles yielded higher selectivities for the partially saturated ring dihydrofuran. Pyridine hydrogenation was investigated over Pt(111) and Pt(100). The α-pyridyl surface adsorption mode was observed with SFG-VS over both surfaces. 1,4-dihydropyridine was seen as a surface intermediate over Pt(100) but not Pt(111). Upon heating the surfaces to 350K, the adsorbed pyridine changes to a flat-lying adsorption mode. No evidence was found for the pyridinium cation. The hydrogenation of the

  20. Spatially resolved in situ reaction dynamics of graphene via optical microscopy.

    PubMed

    Wojcik, Michal; Li, Yunqi; Li, Wan; Xu, Ke

    2017-04-05

    The potential of rising two-dimensional materials, such as graphene, can be substantially expanded through chemistry. However, it has been a challenge to study how chemical reactions of two-dimensional materials progress. Existing techniques offer limited signal contrast and/or spatial-temporal resolution, and are difficult to apply to in situ studies. Here we employ an optical approach to quantitatively monitor the redox reaction dynamics of graphene and graphene oxide (GO) in situ with diffraction-limited (~300 nm) spatial resolution and video-rate time resolution. Remarkably, we found that the oxidation kinetics of graphene is characterized by a seeded, autocatalytic process that gives rise to unique, wave-like propagation of reaction in two dimensions. The reaction is initially slow and confined to highly localized, nanoscale hot spots associated with structural defects, but then self-accelerates while propagating outwards, hence flower-like, micrometer-sized reaction patterns over the entire sample. In contrast, the reduction of GO is spatially homogeneous and temporally pseudo-first-order, and through in situ data we further identify pH as a key reaction parameter.

  1. Nuclear reaction studies

    SciTech Connect

    Alexander, J.M.; Lacey, R.A.

    1994-11-01

    Research focused on the statistical and dynamical properties of ``hot`` nuclei formed in symmetric heavy-ion reactions. Theses included ``flow`` measurements and the mechanism for multifragment disassembly. Model calculations are being performed for the reactions C+C, Ne+Al, Ar+Sc, Kr+Nb, and Xe+La. It is planned to study {sup 40}Ar reactions from 27 to 115 MeV/nucleon. 2 figs., 41 refs.

  2. Insights into reaction mechanisms in heterogeneous catalysis revealed by in situ NMR spectroscopy.

    PubMed

    Blasco, Teresa

    2010-12-01

    This tutorial review intends to show the possibilities of in situ solid state NMR spectroscopy in the elucidation of reaction mechanisms and the nature of the active sites in heterogeneous catalysis. After a brief overview of the more usual experimental devices used for in situ solid state NMR spectroscopy measurements, some examples of applications taken from the recent literature will be presented. It will be shown that in situ NMR spectroscopy allows: (i) the identification of stable intermediates and transient species using indirect methods, (ii) to prove shape selectivity in zeolites, (iii) the study of reaction kinetics, and (iv) the determination of the nature and the role played by the active sites in a catalytic reaction. The approaches and methodology used to get this information will be illustrated here summarizing the most relevant contributions on the investigation of the mechanisms of a series of reactions of industrial interest: aromatization of alkanes on bifunctional catalysts, carbonylation reaction of methanol with carbon monoxide, ethylbenzene disproportionation, and the Beckmann rearrangement reaction. Special attention is paid to the research carried out on the role played by carbenium ions and alkoxy as intermediate species in the transformation of hydrocarbon molecules on solid acid catalysts.

  3. In–situ Spatiotemporal Chemical Reactions at Water-Solid Interfacial Processes using Microelectrode Techniques: from Biofilm to Metal Corrosion

    EPA Science Inventory

    Recent developments in microscale sensors allows the non-destructive and in–situ measurement of both the absolute and changes in chemical concentrations in engineered and natural aquatic systems. Microelectrodes represent a unique tool for studying in–situ chemical reactions in b...

  4. In situ alkali-silica reaction observed by x-ray microscopy

    SciTech Connect

    Kurtis, K.E.; Monteiro, P.J.M.; Brown, J.T.; Meyer-Ilse, W.

    1997-04-01

    In concrete, alkali metal ions and hydroxyl ions contributed by the cement and reactive silicates present in aggregate can participate in a destructive alkali-silica reaction (ASR). This reaction of the alkalis with the silicates produces a gel that tends to imbibe water found in the concrete pores, leading to swelling of the gel and eventual cracking of the affected concrete member. Over 104 cases of alkali-aggregate reaction in dams and spillways have been reported around the world. At present, no method exists to arrest the expansive chemical reaction which generates significant distress in the affected structures. Most existing techniques available for the examination of concrete microstructure, including ASR products, demand that samples be dried and exposed to high pressure during the observation period. These sample preparation requirements present a major disadvantage for the study of alkali-silica reaction. Given the nature of the reaction and the affect of water on its products, it is likely that the removal of water will affect the morphology, creating artifacts in the sample. The purpose of this research is to observe and characterize the alkali-silica reaction, including each of the specific reactions identified previously, in situ without introducing sample artifacts. For observation of unconditioned samples, x-ray microscopy offers an opportunity for such an examination of the alkali-silica reaction. Currently, this investigation is focusing on the effect of calcium ions on the alkali-silica reaction.

  5. In situ reaction kinetic analysis of dental restorative materials

    NASA Astrophysics Data System (ADS)

    Younas, Basma; Samad Khan, Abdul; Muzaffar, Danish; Hussain, Ijaz; Chaudhry, Aqif Anwar; Rehman, Ihtesham Ur

    2013-12-01

    The objective of this study was to evaluate in situ structural and thermal changes of dental restorative materials at periodical time intervals. The commercial materials included zinc oxide eugenol (ZOE), zinc phosphate type I (ZnPO4), glass ionomer cement type II (GIC) and resin-based nano-omposite (Filtek Z350 XT). These materials were processed according to manufacturer's instructions. For the structural analysis Fourier transform infrared spectroscopy (FTIR) was used at high resolution. TGA was used to evaluate thermal weight-loss. The FTIR spectra were collected at periodic time intervals. FTIR spectra showed that with time passing all materials exhibited an increase in peak intensities and a new appearance of shoulders and shifting of peaks for example, ZnPO4 (P-O), ZOE (C═O, C═N, C-O-C), GIC (COO-, C-H, Si-OH), composites (C═O, C═C, C═N, C-N-H). The peaks were replaced by bands and these bands became broader with time interval. Composites showed a degree of conversion and new peaks corresponded to the cross-linking of polymer composites. TGA analysis showed that significant changes in weight loss of set materials were observed after 24 h, where ZOE showed continuous changes in thermal degradation. The spectral changes and thermal degradation with time interval elucidated in situ setting behaviour and understanding of their bonding compatibility with tooth structure and change in relation to time.

  6. In situ detection of specific p53 mutations in cultured cells using the amplification refractory mutation system polymerase chain reaction.

    PubMed

    Low, E O; Gibbins, J R; Walker, D M

    2000-12-01

    Accurate molecular detection of genetic mutations involved in tumorigenesis has been based predominantly on analysis of extracted DNA, but this does not provide detailed information on the location, number, type or clonal distribution of mutated cells and their precise anatomic location and clonal distribution. This study has used a sensitive and specific application of the amplification refractory mutation system (ARMS)-polymerase chain reaction (PCR) in situ, combined with in situ hybridization to localize and identify cells with defined p53 mutations. The ARMS-PCR was performed in situ in SW480 cells in suspension and in cells either cultured or cytospun onto glass slides. Amplified mutant DNA PCR products were detected in SW480 cells using digoxigenin-labeled probes, visually identifying cells harboring specific mutations in the p53 gene. In situ hybridization alone of the mutant cells without the amplification step was negative. Normal human fibroblasts or endothelial cells were refractory to in situ amplification. This reaction was mutation-specific as CEM cells with different p53 mutations reacted negatively. Mutant messenger RNA (mRNA) in tumor cells was also selectively amplified in situ by ARMS-PCR following reverse transcription (RT). This study demonstrates the potential of in situ ARMS-PCR or RT-ARMS-PCR for mutation analysis in situ and could have useful clinical applications.

  7. Following the Transient Reactions in Lithium-Sulfur Batteries Using In an In Situ Nuclear Magnetic Resonance Technique

    SciTech Connect

    Xiao, Jie; Hu, Jian Z.; Chen, Honghao; Vijayakumar, M.; Zheng, Jianming; Pan, Huilin; Walter, Eric D.; Hu, Mary Y.; Deng, Xuchu; Feng, Ju; Liaw, Bor Yann; Gu, Meng; Deng, Zhiqun; Lu, Dongping; Xu, Suochang; Wang, Chong M.; Liu, Jun

    2015-05-13

    Li-S batteries hold great potential for next-generation, large-format power source applications; yet, the fundamental understanding of the electrochemical reaction pathways remains lacking to enable their functionality as promised. Here, in situ NMR technique employing a specially designed cylindrical micro battery was used to monitor the chemical environments around Li+ ions during repetitive charge-discharge process and track the transient electrochemical and chemical reactions occurring in the whole Li-S system. The in situ NMR provides real time, quantitative information related to the temporal concentration variations of the polysulfides with various chain lengths, providing important clues for the reaction pathways during both discharge and charge processes. The in-situ technique also reveals that redox reactions may involve transient species that are difficult to detect in ex-situ NMR study. Intermediate species such as charged free radicals may play an important role in the formation of the polysulfide products. Additionally, in situ NMR measurement simultaneously reveals vital information on the 7Li chemical environments in the electrochemical and parasitic reactions on the lithium anode that promotes the understanding of the failure mechanism in the Li-S system. These new insights could help design effective strategies to accelerate the development of Li-S battery technology.

  8. In Situ Environmental TEM in Imaging Gas and Liquid Phase Chemical Reactions for Materials Research.

    PubMed

    Wu, Jianbo; Shan, Hao; Chen, Wenlong; Gu, Xin; Tao, Peng; Song, Chengyi; Shang, Wen; Deng, Tao

    2016-11-01

    Gas and liquid phase chemical reactions cover a broad range of research areas in materials science and engineering, including the synthesis of nanomaterials and application of nanomaterials, for example, in the areas of sensing, energy storage and conversion, catalysis, and bio-related applications. Environmental transmission electron microscopy (ETEM) provides a unique opportunity for monitoring gas and liquid phase reactions because it enables the observation of those reactions at the ultra-high spatial resolution, which is not achievable through other techniques. Here, the fundamental science and technology developments of gas and liquid phase TEM that facilitate the mechanistic study of the gas and liquid phase chemical reactions are discussed. Combined with other characterization tools integrated in TEM, unprecedented material behaviors and reaction mechanisms are observed through the use of the in situ gas and liquid phase TEM. These observations and also the recent applications in this emerging area are described. The current challenges in the imaging process are also discussed, including the imaging speed, imaging resolution, and data management.

  9. Next-Generation in Situ Hybridization Chain Reaction: Higher Gain, Lower Cost, Greater Durability

    PubMed Central

    2014-01-01

    Hybridization chain reaction (HCR) provides multiplexed, isothermal, enzyme-free, molecular signal amplification in diverse settings. Within intact vertebrate embryos, where signal-to-background is at a premium, HCR in situ amplification enables simultaneous mapping of multiple target mRNAs, addressing a longstanding challenge in the biological sciences. With this approach, RNA probes complementary to mRNA targets trigger chain reactions in which metastable fluorophore-labeled RNA hairpins self-assemble into tethered fluorescent amplification polymers. The properties of HCR lead to straightforward multiplexing, deep sample penetration, high signal-to-background, and sharp subcellular signal localization within fixed whole-mount zebrafish embryos, a standard model system for the study of vertebrate development. However, RNA reagents are expensive and vulnerable to enzymatic degradation. Moreover, the stringent hybridization conditions used to destabilize nonspecific hairpin binding also reduce the energetic driving force for HCR polymerization, creating a trade-off between minimization of background and maximization of signal. Here, we eliminate this trade-off by demonstrating that low background levels can be achieved using permissive in situ amplification conditions (0% formamide, room temperature) and engineer next-generation DNA HCR amplifiers that maximize the free energy benefit per polymerization step while preserving the kinetic trapping property that underlies conditional polymerization, dramatically increasing signal gain, reducing reagent cost, and improving reagent durability. PMID:24712299

  10. Next-generation in situ hybridization chain reaction: higher gain, lower cost, greater durability.

    PubMed

    Choi, Harry M T; Beck, Victor A; Pierce, Niles A

    2014-05-27

    Hybridization chain reaction (HCR) provides multiplexed, isothermal, enzyme-free, molecular signal amplification in diverse settings. Within intact vertebrate embryos, where signal-to-background is at a premium, HCR in situ amplification enables simultaneous mapping of multiple target mRNAs, addressing a longstanding challenge in the biological sciences. With this approach, RNA probes complementary to mRNA targets trigger chain reactions in which metastable fluorophore-labeled RNA hairpins self-assemble into tethered fluorescent amplification polymers. The properties of HCR lead to straightforward multiplexing, deep sample penetration, high signal-to-background, and sharp subcellular signal localization within fixed whole-mount zebrafish embryos, a standard model system for the study of vertebrate development. However, RNA reagents are expensive and vulnerable to enzymatic degradation. Moreover, the stringent hybridization conditions used to destabilize nonspecific hairpin binding also reduce the energetic driving force for HCR polymerization, creating a trade-off between minimization of background and maximization of signal. Here, we eliminate this trade-off by demonstrating that low background levels can be achieved using permissive in situ amplification conditions (0% formamide, room temperature) and engineer next-generation DNA HCR amplifiers that maximize the free energy benefit per polymerization step while preserving the kinetic trapping property that underlies conditional polymerization, dramatically increasing signal gain, reducing reagent cost, and improving reagent durability.

  11. In situ studies of solvothermal synthesis of energy materials.

    PubMed

    Jensen, Kirsten M Ø; Tyrsted, Christoffer; Bremholm, Martin; Iversen, Bo B

    2014-06-01

    Solvothermal and hydrothermal synthesis, that is, synthesis taking place in a solvent at elevated temperature and pressure, is a powerful technique for the production of advanced energy materials as it is versatile, cheap, and environmentally friendly. However, the fundamental reaction mechanisms dictating particle formation and growth under solvothermal conditions are not well understood. In order to produce tailor-made materials with specific properties for advanced energy technologies, it is essential to obtain an improved understanding of these processes and, in this context, in situ studies are an important tool as they provide real time information on the reactions taking place. Here, we present a review of the use of powder diffraction and total scattering methods for in situ studies of synthesis taking place under solvothermal and hydrothermal conditions. The experimental setups used for in situ X-ray and neutron studies are presented, and methods of data analysis are described. Special attention is given to the methods used to extract structural information from the data, for example, Rietveld refinement, whole powder pattern modelling and pair distribution function analysis. Examples of in situ studies are presented to illustrate the types of chemical insight that can be obtained.

  12. In Situ Vitrification Treatability Study Work Plan

    SciTech Connect

    Charboneau, B.L.; Landon, J.L.

    1989-03-01

    The Buried Waste Program was established in October, 1987 to accelerate the studies needed to develop a recommended long-term management plan for the buried mixed waste at the Radioactive Waste Management Complex at the Idaho National Engineering Laboratory. The In Situ Vitrification Project is being conducted in a Comprehensive Environmental Response, Compensation, and Liability Act Feasibility Study format to identify methods for the long-term management of the mixed waste buried. This In Situ Vitrification Treatability Study Work Plan gives a brief description of the site, work breakdown structure, and project organization: the in situ vitrification technology; the purpose of the tests and demonstrations; and the equipment and materials required for the tests and demonstration. 5 refs., 6 figs., 3 tabs.

  13. Following the transient reactions in lithium-sulfur batteries using an in situ nuclear magnetic resonance technique.

    PubMed

    Xiao, Jie; Hu, Jian Zhi; Chen, Honghao; Vijayakumar, M; Zheng, Jianming; Pan, Huilin; Walter, Eric D; Hu, Mary; Deng, Xuchu; Feng, Ju; Liaw, Bor Yann; Gu, Meng; Deng, Zhiqun Daniel; Lu, Dongping; Xu, Suochang; Wang, Chongmin; Liu, Jun

    2015-05-13

    A fundamental understanding of electrochemical reaction pathways is critical to improving the performance of Li-S batteries, but few techniques can be used to directly identify and quantify the reaction species during disharge/charge cycling processes in real time. Here, an in situ (7)Li NMR technique employing a specially designed cylindrical microbattery was used to probe the transient electrochemical and chemical reactions occurring during the cycling of a Li-S system. In situ NMR provides real time, semiquantitative information related to the temporal evolution of lithium polysulfide allotropes during both discharge/charge processes. This technique uniquely reveals that the polysulfide redox reactions involve charged free radicals as intermediate species that are difficult to detect in ex situ NMR studies. Additionally, it also uncovers vital information about the (7)Li chemical environments during the electrochemical and parasitic reactions on the Li metal anode. These new molecular-level insights about transient species and the associated anode failure mechanism are crucial to delineating effective strategies to accelerate the development of Li-S battery technologies.

  14. Spectroscopic detection of aqueous contaminants using in situ corona reactions.

    PubMed

    Johnson, M

    1997-04-01

    An apparently novel technique to aid the detection of a variety of inorganic and organic compounds in environmental and drinking water samples is described. Background absorbance due to optical scattering, cell fouling, and a variety of contaminants is suppressed by combining UV spectroscopy with chemical reactions initiated by reactive species generated in a high-voltage corona discharge. Injection of the reactive species takes place through a free water surface from the "corona wind". Initial measurements on aqueous chlorine in drinking water and BTEX (benzene, toluene, ethylbenzene, and xylene) in unfiltered river water down to parts-per-million concentration are given which show, by comparison with a conventional UV absorption measurement, good background suppression. The experimental arrangement is simpler than that in typical fluorescence detection systems, and the geometrical flexibility means that corona "dosing" can be applied also to Raman and other spectroscopies, to electrochemical detection schemes, and to planar and windowless geometries.

  15. One-pot lipase-catalyzed aldol reaction combination of in situ formed acetaldehyde.

    PubMed

    Wang, Na; Zhang, Wei; Zhou, Long-Hua; Deng, Qing-Feng; Xie, Zong-Bo; Yu, Xiao-Qi

    2013-12-01

    A facile tandem route to α,β-unsaturated aldehydes was developed by combining the two catalytic activities of the same enzyme in a one-pot strategy for the aldol reaction and in situ generation of acetaldehyde. Lipase from Mucor miehei was found to have conventional and promiscuous catalytic activities for the hydrolysis of vinyl acetate and aldol condensation with in situ formed acetaldehyde. The first reaction continuously provided material for the second reaction, which effectively reduced the volatilization loss, oxidation, and polymerization of acetaldehyde, as well as avoided a negative effect on the enzyme of excessive amounts of acetaldehyde. After optimizing the process, several substrates participated in the reaction and provided the target products in moderate to high yields using this single lipase-catalyzed one-pot biotransformation.

  16. Photocatalytic removal of soot: unravelling of the reaction mechanism by EPR and in situ FTIR spectroscopy.

    PubMed

    Smits, Marianne; Ling, Yun; Lenaerts, Silvia; Van Doorslaer, Sabine

    2012-12-21

    Photocatalytic soot oxidation is studied on P25 TiO(2) as an important model reaction for self-cleaning processes by means of electron paramagnetic resonance (EPR) and Fourier transform infrared (FTIR) spectroscopy. Contacting of carbon black with P25 leads on the one hand to a reduction of the local dioxygen concentration in the powder. On the other hand, the weakly adsorbed radicals on the carbon particles are likely to act as alternative traps for the photogenerated conduction-band electrons. We find furthermore that the presence of dioxygen and oxygen-related radicals is vital for the photocatalytic soot degradation. The complete oxidation of soot to CO(2) is evidenced by in situ FTIR spectroscopy, no intermediate CO is detected during the photocatalytic process.

  17. A modified protocol for the detection of three different mRNAs with a new-generation in situ hybridization chain reaction on frozen sections.

    PubMed

    Sui, Qian-Qian; Zhu, Jiao; Li, Xiangnan; Knight, Gillian E; He, Cheng; Burnstock, Geoffrey; Yuan, Hongbin; Xiang, Zhenghua

    2016-12-01

    A new multiple fluorescence in situ hybridization method based on hybridization chain reaction was recently reported, enabling simultaneous mapping of multiple target mRNAs within intact zebrafish and mouse embryos. With this approach, DNA probes complementary to target mRNAs trigger chain reactions in which metastable fluorophore-labeled DNA hairpins self-assemble into fluorescent amplification polymers. The formation of the specific polymers enhances greatly the sensitivity of multiple fluorescence in situ hybridization. In this study we describe the optimal parameters (hybridization chain reaction time and temperature, hairpin and salt concentration) for multiple fluorescence in situ hybridization via amplification of hybridization chain reaction for frozen tissue sections. The combined use of fluorescence in situ hybridization and immunofluorescence, together with other control experiments (sense probe, neutralization and competition, RNase treatment, and anti-sense probe without initiator) confirmed the high specificity of the fluorescence in situ hybridization used in this study. Two sets of three different mRNAs for oxytocin, vasopressin and somatostatin or oxytocin, vasopressin and thyrotropin releasing hormone were successfully visualized via this new method. We believe that this modified protocol for multiple fluorescence in situ hybridization via hybridization chain reaction would allow researchers to visualize multiple target nucleic acids in the future.

  18. Michael-type addition reactions for the in situ formation of poly(vinyl alcohol)-based hydrogels.

    PubMed

    Tortora, Mariarosaria; Cavalieri, Francesca; Chiessi, Ester; Paradossi, Gaio

    2007-01-01

    Michael-type addition reactions offer the possibility to obtain in situ formation of polymeric hydrogels in the absence of a radical mechanism for the networking process. We explored such a synthetic route for obtaining a poly(vinyl alcohol) (PVA)-based hydrogel as a potential biomaterial for applications in vitro-retinal replacement surgery. The presence of radicals in the reaction medium can represent a risk for in situ surgical treatment. To circumvent this problem we have applied nucleophilic addition to ad hoc modified PVA macromers. The gel formation has been studied with respect to the timing required in this surgery and in terms of the structural characteristics of the obtained network.

  19. In situ characterization of catalysts and membranes in a microchannel under high-temperature water gas shift reaction conditions

    NASA Astrophysics Data System (ADS)

    Cavusoglu, G.; Dallmann, F.; Lichtenberg, H.; Goldbach, A.; Dittmeyer, R.; Grunwaldt, J.-D.

    2016-05-01

    Microreactor technology with high heat transfer in combination with stable catalysts is a very attractive approach for reactions involving major heat effects such as methane steam reforming and to some extent, also the high temperature water gas shift (WGS) reaction. For this study Rh/ceria catalysts and an ultrathin hydrogen selective membrane were characterized in situ in a microreactor specially designed for x-ray absorption spectroscopic measurements under WGS conditions. The results of these experiments can serve as a basis for further development of the catalysts and membranes.

  20. Observing Metal-Catalyzed Chemical Reactions in Situ Using Surface-Enhanced Raman Spectroscopy on Pd–Au Nanoshells

    PubMed Central

    Heck, Kimberly N.; Janesko, Benjamin G.; Scuseria, Gustavo E.

    2016-01-01

    Insight into the nature of transient reaction intermediates and mechanistic pathways involved in heterogeneously catalyzed chemical reactions is obtainable from a number of surface spectroscopic techniques. Carrying out these investigations under actual reaction conditions is preferred but remains challenging, especially for catalytic reactions that occur in water. Here, we report the direct spectroscopic study of the catalytic hydrodechlorination of 1,1-dichloroethene in H2O using surface-enhanced Raman spectroscopy (SERS). With Pd islands grown on Au nanoshell films, this reaction can be followed in situ using SERS, exploiting the high enhancements and large active area of Au nanoshell SERS substrates, the transparency of Raman spectroscopy to aqueous solvents, and the catalytic activity enhancement of Pd by the underlying Au metal. The formation and subsequent transformation of several adsorbate species was observed. These results provide the first direct evidence of the room-temperature catalytic hydrodechlorination of a chlorinated solvent, a potentially important pathway for groundwater cleanup, as a sequence of dechlorination and hydrogenation steps. More broadly, the results highlight the exciting prospects of studying catalytic processes in water in situ, like those involved in biomass conversion and proton-exchange membrane fuel cells. PMID:19554693

  1. Direct detection of infectious bursal disease virus from clinical samples by in situ reverse transcriptase-linked polymerase chain reaction.

    PubMed

    Cardoso, Tereza C; Rosa, Ana C G; Astolphi, Rafael D; Vincente, Rafael M; Novais, Juliana B; Hirata, Karina Y; Luvizotto, Maria Cecilia R

    2008-08-01

    The presence of the very virulent (vv) Brazilian strain of infectious bursal disease virus (IBDV) was determined in the bursa of Fabricius, thymus and liver of 2-week-old broilers from a flock with a higher than expected mortality. For this purpose, a direct in situ reverse transcriptase (RT)-linked polymerase chain reaction (PCR) method was developed using specific primers for vvIBDV. Unlabelled forward and reverse biotinylated oligonucleotides were used for RT-PCR in a one-step method and the respective products were revealed by a direct enzymatic reaction. The results were compared with those obtained by standard RT-PCR using general primers for IBDV and virus isolation. The virus isolation, RT-PCR and in situ RT-PCR revealed positive results on the bursa of Fabricius in 86%, 80% and 100%, respectively. The in situ RT-PCR detected vvIBDV in all tested thymus and liver samples, whereas the standard RT-PCR detected virus in 80% and 90% of the samples, respectively. After three consecutive passages on chicken embryonated eggs, IBDV was isolated from 64% of the thymus samples and 30% of the liver samples. In the present study, no classical or antigenic variants of IBDV were detected. The developed in situ RT-PCR assay was able to detect the very virulent strain of IBDV with a higher sensitivity than the conventional RT-PCR and virus isolation.

  2. [The surface adsorption and selective catalytic reaction of NO on Cu-ZSM-5 using in situ DRIFTS].

    PubMed

    Zhang, Ping; Wang, Le-Fu; Chen, Yong-Heng

    2007-06-01

    The prepared Cu-ZSM-5 catalyst presents higher activity at low temperature during the selective catalytic reduction (SCR) of NO, and the conversion from NO to N2 is 70.6% at 613 K. The in situ diffuse reflectance FTIR spectroscopy (in situ DRIFTS) is an important method for studying surface adsorption of catalyst and mechanism of catalytic reaction, and was used to study the surface adsorbed species and the selective catalytic reduction reaction of NO on Cu-ZSM-5 catalyst in the presence of propene as reductant, with excess O2 and at 298-773 K. Based on the in-situ DRIFTS, a reaction mechanism is proposed that on Cu-ZSM-5, NO is first transformed to a series of NO(x) surface adsorbates, then these species react with the activating species of propene (C(x)H(y) or C(x)H(y)O(x)) to form organo-intermediates, including a process from organo-NH to organo-CN again to organo-NO(x) (organo-nitro or organo-nitrito), and finally these key intermediates react to form nitrogen. The role of Cu is to promote NO(x) content. Propene is easily activated on Cu-ZSM-5 with oxygen, and furthermore, the presence of oxygen is necessary to form organo-NO(x) intermediates.

  3. Real-time and in situ monitoring of mechanochemical milling reactions.

    PubMed

    Friščić, Tomislav; Halasz, Ivan; Beldon, Patrick J; Belenguer, Ana M; Adams, Frank; Kimber, Simon A J; Honkimäki, Veijo; Dinnebier, Robert E

    2013-01-01

    Chemical and structural transformations have long been carried out by milling. Such mechanochemical steps are now ubiquitous in a number of industries (such as the pharmaceutical, chemical and metallurgical industries), and are emerging as excellent environmentally friendly alternatives to solution-based syntheses. However, mechanochemical transformations are typically difficult to monitor in real time, which leaves a large gap in the mechanistic understanding required for their development. We now report the real-time study of mechanochemical transformations in a ball mill by means of in situ diffraction of high-energy synchrotron X-rays. Focusing on the mechanosynthesis of metal-organic frameworks, we have directly monitored reaction profiles, the formation of intermediates, and interconversions of framework topologies. Our results reveal that mechanochemistry is highly dynamic, with reaction rates comparable to or greater than those in solution. The technique also enabled us to probe directly how catalytic additives recently introduced in the mechanosynthesis of metal-organic frameworks, such as organic liquids or ionic species, change the reactivity pathways and kinetics.

  4. In situ visualization of metallurgical reactions in nanoscale Cu/Sn diffusion couples.

    PubMed

    Yin, Qiyue; Gao, Fan; Gu, Zhiyong; Stach, Eric A; Zhou, Guangwen

    2015-03-21

    The Cu-Sn metallurgical soldering reaction in two-segmented Cu-Sn nanowires is studied by in situ transmission electron microscopy. By varying the relative lengths of Cu and Sn segments, we show that the metallurgical reaction results in a Cu-Sn solid solution for small Sn/Cu length ratio while Cu-Sn intermetallic compounds (IMCs) for larger Sn/Cu length ratios. Upon heating the nanowires to ∼500 °C, two phase transformation pathways occur, η-Cu6Sn5 → ε-Cu3Sn → δ-Cu41Sn11 for nanowires with a long Cu segment and η-Cu6Sn5 → ε-Cu3Sn → γ-Cu3Sn with a short Cu segment. The evolution of Kirkendall voids in the nanowires demonstrates that Cu diffuses faster than Sn in IMCs. Void growth results in the nanowire breakage that shuts off the inter-diffusion of Cu and Sn and thus leads to changes in the phase transformation pathway in the IMCs.

  5. Real-time and in situ monitoring of mechanochemical milling reactions

    NASA Astrophysics Data System (ADS)

    Friščić, Tomislav; Halasz, Ivan; Beldon, Patrick J.; Belenguer, Ana M.; Adams, Frank; Kimber, Simon A. J.; Honkimäki, Veijo; Dinnebier, Robert E.

    2013-01-01

    Chemical and structural transformations have long been carried out by milling. Such mechanochemical steps are now ubiquitous in a number of industries (such as the pharmaceutical, chemical and metallurgical industries), and are emerging as excellent environmentally friendly alternatives to solution-based syntheses. However, mechanochemical transformations are typically difficult to monitor in real time, which leaves a large gap in the mechanistic understanding required for their development. We now report the real-time study of mechanochemical transformations in a ball mill by means of in situ diffraction of high-energy synchrotron X-rays. Focusing on the mechanosynthesis of metal-organic frameworks, we have directly monitored reaction profiles, the formation of intermediates, and interconversions of framework topologies. Our results reveal that mechanochemistry is highly dynamic, with reaction rates comparable to or greater than those in solution. The technique also enabled us to probe directly how catalytic additives recently introduced in the mechanosynthesis of metal-organic frameworks, such as organic liquids or ionic species, change the reactivity pathways and kinetics.

  6. In situ synthesis studies of silicon clathrates

    NASA Astrophysics Data System (ADS)

    Hutchins, Peter Thomas

    Solid state clathrates have shown considerable potential as a new class of materials over the past 30 years. Experimental and theoretical studies have shown that precise tuning and synthetic control of these materials, may lead to desirable properties. Very little is known about the mechanism of formation of the clathrates and so the desire to have accurate synthetic control was, until now, unrealistic. This thesis address the problem using in situ synchrotron x-ray techniques. In this study, experiments were designed to utilise time-resolved in situ diffraction techniques and high temperature 23Na NMR, in efforts to understand the mechanism of formation for this class of expanded framework materials. A complex high vacuum capillary synthesis cell was designed for loading under inert conditions and operation under high vacuum at station 6.2 of the SRS Daresbury. The cell was designed to operate in conjunction with a custom made furnace capable of temperatures in excess of 1000 C, as well as a vacuum system capable of 10"5 bar. The clathrate system was studied in situ, using rapid data collection to elucidate the mechanism of formation. The data were analysed using Rietveld methods and showed a structural link between the monoclinic, C2/c, Zintl precursors and the cubic, Pm3n, clathrate I phase. The phases were found to be linked by relation of the sodium planes in the silicide and the sodium atoms resident at cages centres in the clathrate system. This evidence suggests the guest species is instrumental in formation of the clathrate structure by templating the formation of the cages in the structure. Solid state 23Na NMR was utilised to complete specially design experiments, similar to those complete in situ using synchrotron x-ray techniques. The experiments showed increased spherical symmetry of the alkali metal sites and suggested increased mobility of the guest atoms during heating. In addition, cyclic heating experiments using in situ diffraction showed

  7. Mechanistic studies of malonic acid-mediated in situ acylation.

    PubMed

    Chandra, Koushik; Naoum, Johnny N; Roy, Tapta Kanchan; Gilon, Chaim; Gerber, R Benny; Friedler, Assaf

    2015-09-01

    We have previously introduced an easy to perform, cost-effective and highly efficient acetylation technique for solid phase synthesis (SPPS). Malonic acid is used as a precursor and the reaction proceeds via a reactive ketene that acetylates the target amine. Here we present a detailed mechanistic study of the malonic acid-mediated acylation. The influence of reaction conditions, peptide sequence and reagents was systematically studied. Our results show that the methodology can be successfully applied to different types of peptides and nonpeptidic molecules irrespective of their structure, sequence, or conformation. Using alkyl, phenyl, and benzyl malonic acid, we synthesized various acyl peptides with almost quantitative yields. The ketenes obtained from the different malonic acid derived precursors were characterized by in situ (1) H-NMR. The reaction proceeded in short reaction times and resulted in excellent yields when using uronium-based coupling agents, DIPEA as a base, DMF/DMSO/NMP as solvents, Rink amide/Wang/Merrifield resins, temperature of 20°C, pH 8-12 and 5 min preactivation at inert atmosphere. The reaction was unaffected by Lewis acids, transition metal ions, surfactants, or salt. DFT studies support the kinetically favorable concerted mechanism for CO2 and ketene formation that leads to the thermodynamically stable acylated products. We conclude that the malonic acid-mediated acylation is a general method applicable to various target molecules.

  8. Addition of CFCl3 to Aromatic Aldehydes via in Situ Grignard Reaction

    SciTech Connect

    Barkakaty, Balaka; Talukdar, Bandana; Lokitz, Bradley

    2015-08-18

    In the case of synthetic modification of trichlorofluoromethane (CFCl3) to non-volatile and useful fluorinated precursors, we realized that it is a cost-effective and an environmentally benign strategy for the safe consumption/destruction of the ozone depleting potential of the reagent. In our report, we present a novel method for in situ Grignard reaction using magnesium powder and CFCl3 for synthesis of dichlorofluoromethyl aromatic alcohols.

  9. Addition of CFCl3 to Aromatic Aldehydes via in Situ Grignard Reaction

    DOE PAGES

    Barkakaty, Balaka; Talukdar, Bandana; Lokitz, Bradley

    2015-08-18

    In the case of synthetic modification of trichlorofluoromethane (CFCl3) to non-volatile and useful fluorinated precursors, we realized that it is a cost-effective and an environmentally benign strategy for the safe consumption/destruction of the ozone depleting potential of the reagent. In our report, we present a novel method for in situ Grignard reaction using magnesium powder and CFCl3 for synthesis of dichlorofluoromethyl aromatic alcohols.

  10. Four unexpected lanthanide coordination polymers involving in situ reaction of solvent N, N-Dimethylformamide

    SciTech Connect

    Jin, Jun-Cheng; Tong, Wen-Quan; Fu, Ai-Yun; Xie, Cheng-Gen; Chang, Wen-Gui; Wu, Ju; Xu, Guang-Nian; Zhang, Ya-Nan; Li, Jun; Li, Yong; Yang, Peng-Qi

    2015-05-15

    Four unexpected 2D lanthanide coordination polymers have been synthesized through in situ reactions of DMF solvent under solvothermal conditions. The isostructural complexes 1–3 contain four types of 2{sub 1} helical chains. While the Nd(III) ions are bridged through μ{sub 2}-HIDC{sup 2−} and oxalate to form a 2D sheet along the bc plane without helical character in 4. Therefore, complex 1 exhibits bright red solid-state phosphorescence upon exposure to UV radiation at room temperature. - Graphical abstract: Four unexpected 2D lanthanide coordination polymers have been synthesized through in situ reactions of solvent DMF to formate acid or oxalic acid under solvothermal conditions. The isostructural complexes 1–3 contain four types of different 2{sub 1} helical chains in the 2D layer and 1 exhibits bright red solid-state phosphorescence upon UV radiation. - Highlights: • Four unexpected 2D lanthanide coordination compounds have been synthesized through in situ reactions under solvothermal conditions. • The complexes 1–3 contain four types of 2{sub 1} helical chains in the layer. • Complex 1 exhibits bright red solid-state phosphorescence upon exposure to UV radiation at room temperature.

  11. Salmonellae in fish feces analyzed by in situ hybridization and quantitative polymerase chain reaction.

    PubMed

    Sha, Qiong; Forstner, Michael R J; Bonner, Timothy H; Hahn, Dittmar

    2013-09-01

    The potential of fish to transfer salmonellae from heterogeneous aquatic biofilms into feces was assessed in controlled aquarium studies with Suckermouth Catfish Hypostomus plecostomus and with biofilms inoculated with salmonellae. Neither the presence of catfish nor inoculation with salmonellae had detectable effects on the abundance of the microbial community. Densities of the microbial community were about 10(5) cells/mL in the water during a 1-week period, whereas densities of the microbial community increased 10-fold (10(6) to 10(7) cells/mg) in catfish feces during the same period. Salmonellae were detected by both quantitative polymerase chain reaction (qPCR) and situ hybridization in water samples immediately after inoculation, in numbers of about 10(4) cells/mL, representing up to 20% of the cells of the microbial community. Numbers decreased by three orders of magnitude within the first 3 d of the study, which represented only 0.01% of the community, and became undetectable after day 5. In catfish feces, numbers of Salmonella initially increased to up to 6% of the cells of the community but then declined. These results suggest that Salmonella are not biomagnified during gut passage, and thus, fish only provide a means for the translocation of this pathogen.

  12. In Situ FTIR Spectroscopic Monitoring of Electrochemically Controlled Organic Reactions in a Recycle Reactor

    PubMed Central

    O'Brien, Alexander. G.; Luca, Oana. R.; Baran, Phil. S.

    2015-01-01

    An electrochemical cell coupled with a recycle loop through a transmission FTIR cell is employed in studies of two free radical organic reactions, the oxidation of allylic alcohols and the trifluoromethylation of heteroarenes. Rapid mixing through the recycle loop allows continuous monitoring of reaction progress. Electrochemical generation of free radicals allows their controlled mediation into the reaction mixture for more efficient reaction. Kinetic profiles provide mechanistic insight into reactions under electrochemical control. PMID:27069673

  13. In Situ FTIR Spectroscopic Monitoring of Electrochemically Controlled Organic Reactions in a Recycle Reactor.

    PubMed

    O'Brien, Alexander G; Luca, Oana R; Baran, Phil S; Blackmond, Donna G

    2016-02-01

    An electrochemical cell coupled with a recycle loop through a transmission FTIR cell is employed in studies of two free radical organic reactions, the oxidation of allylic alcohols and the trifluoromethylation of heteroarenes. Rapid mixing through the recycle loop allows continuous monitoring of reaction progress. Electrochemical generation of free radicals allows their controlled mediation into the reaction mixture for more efficient reaction. Kinetic profiles provide mechanistic insight into reactions under electrochemical control.

  14. Theoretical Studies of Reaction Surfaces

    DTIC Science & Technology

    2007-11-02

    31 Aug 97 4. TITLE AND SUBTITLE 5 . FUNDING NUMBERS AASERT93 THEORETICAL STUDIES OF REACTION SURFACES F49620-93-1-0556 3484/XS 6. AUTHOR(S) 61103D DR...DUNCAN AVE ROOM B115 BOLLING AFB DC 20332- 8050 DR MICHAEL R. BERMAN 11. SUPPLEMENTARY NOTES 12a. DISTRIBUTION i AVAILABILITY STATEMENT Approved f or pill...reaction14 , and solvation of electrolytes1 5 . The EFP method described in the previous section has one drawback: the repulsive 3 potential relies on

  15. In Situ Imidazole Activation of Ribonucleotides for Abiotic RNA Oligomerization Reactions

    NASA Astrophysics Data System (ADS)

    Burcar, Bradley T.; Jawed, Mohsin; Shah, Hari; McGown, Linda B.

    2015-06-01

    The hypothesis that RNA played a significant role in the origin of life requires effective and efficient abiotic pathways to produce RNA oligomers. The most successful abiotic oligomerization reactions to date have utilized high-energy, modified, or pre-activated ribonucleotides to generate strands of RNA up to 50-mers in length. In spite of their success, these modifications and pre-activation reactions significantly alter the ribonucleotides in ways that are highly unlikely to have occurred on a prebiotic Earth. This research seeks to address this problem by exploring an aqueous based method for activating the canonical ribonucleotides in situ using 1-Ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) and imidazole. The reactions were run with and without a montmorillonite clay catalyst and compared to reactions that used ribonucleotides that were pre-activated with imidazole. The effects of pH and ribonucleotide concentration were also investigated. The results demonstrate the ability of in situ activation of ribonucleotides to generate linear RNA oligomers in solution, providing an alternative route to produce RNA for use in prebiotic Earth scenarios.

  16. In situ Spectroscopy of Solid-State Chemical Reaction in PbBr2-Deposited CsBr Crystals

    NASA Astrophysics Data System (ADS)

    Kondo, Shin-ichi; Matsunaga, Toshihiro; Saito, Tadaaki; Asada, Hiroshi

    2003-09-01

    It is possible to measure the fundamental optical absorption spectra of CsPbBr3 and Cs4PbBr6, whose stability is predicted by the study of phase diagram in the binary system CsBr-PbBr2, by means of in situ optical absorption and reflection spectroscopy of thermally induced solid-state chemical reaction in PbBr2-deposited CsBr crystals. On heavy annealing of the crystals, the Pb2+ ions are uniformly dispersed in the crystal matrix. The present experiment provides a novel method for measuring intrinsic optical absorption of ternary metal halides and also for in situ monitoring of doping metal halide crystal with impurities (metal ions or halogen ions).

  17. Interfacial Reaction Studies Using ONIOM

    NASA Technical Reports Server (NTRS)

    Cardelino, Beatriz H.

    2003-01-01

    In this report, we focus on the calculations of the energetics and chemical kinetics of heterogeneous reactions for Organometallic vapor phase epitaxy (OMVPE). The work described in this report builds upon our own previous thermochemical and chemical kinetics studies. The first of these articles refers to the prediction of thermochemical properties, and the latter one deals with the prediction of rate constants for gaseous homolytic dissociation reactions. The calculations of this investigation are at the microscopic level. The systems chosen consisted of a gallium nitride (GaN) substrate, and molecular nitrogen (N2) and ammonia (NH3) as adsorbants. The energetics for the adsorption and the adsorbant dissociation processes were estimated, and reaction rate constants for the dissociation reactions of free and adsorbed molecules were predicted. The energetics for substrate decomposition was also computed. The ONIOM method, implemented in the Gaussian98 program, was used to perform the calculations. This approach has been selected since it allows dividing the system into two layers that can be treated at different levels of accuracy. The atoms of the substrate were modeled using molecular mechanics6 with universal force fields, whereas the adsorbed molecules were approximated using quantum mechanics, based on density functional theory methods with B3LYP functionals and 6-311G(d,p) basis sets. Calculations for the substrate were performed in slabs of several unit cells in each direction. The N2 and NH3 adsorbates were attached to a central location at the Ga-lined surface.

  18. Uranyl triazolate formation via an in situ Huisgen 1,3-dipolar cycloaddition reaction

    SciTech Connect

    Knope, Karah E.; Cahill, Christopher L.

    2010-08-27

    A two dimensional UO22+ coordination polymer, (UO2)3(C10H5N3O4)2(OH)2(H2O)2, has been synthesized under solvothermal conditions. The triazolate ligand, 1-(4-carboxyphenyl)-1H-1,2,3-triazole-4-carboxylic acid (CPTAZ) has been generated via a 1,3-dipolar cycloaddition of 4-azidobenzoic acid and propiolic acid. Reactions of the UO22+ cation with both the in situ generated triazolate ligand and the presynthesized ligand have been explored. The structure, fluorescent and thermal behaviour of this material are presented, as is a discussion of the utility of in situ ligand formation versus direct assembly.

  19. Fundamental studies of high-temperature corrosion reactions. Fifth annual progress report

    SciTech Connect

    Rapp, R.A.

    1980-02-01

    The in-situ study of metal oxidation reactions and the mechanism of the sulfidation of molybdenum by sulfur gases were studied. Equipment including a SEM microscope, heater and power supply which were used is described. (FS)

  20. In situ Regeneration of NADH via Lipoamide Dehydrogenase-catalyzed Electron Transfer Reaction Evidenced by Spectroelectrochemistry

    SciTech Connect

    Tam, Tsz Kin; Chen, Baowei; Lei, Chenghong; Liu, Jun

    2012-08-01

    NAD/NADH is a coenzyme found in all living cells, carrying electrons from one reaction to another. We report on characterizations of in situ regeneration of NADH via lipoamide dehydrogenase (LD)-catalyzed electron transfer reaction to regenerate NADH using UV-vis spectroelectrochemistry. The Michaelis-Menten constant (Km) and maximum velocity (Vmax) of NADH regeneration were measured as 0.80 {+-} 0.15 mM and 1.91 {+-} 0.09 {micro}M s-1 in a 1-mm thin-layer spectroelectrochemical cell using gold gauze as the working electrode at the applied potential -0.75 V (vs. Ag/AgCl). The electrocatalytic reduction of the NAD system was further coupled with the enzymatic conversion of pyruvate to lactate by lactate dehydrogenase to examine the coenzymatic activity of the regenerated NADH. Although the reproducible electrocatalytic reduction of NAD into NADH is known to be difficult compared to the electrocatalytic oxidation of NADH, our spectroelectrochemical results indicate that the in situ regeneration of NADH via LD-catalyzed electron transfer reaction is fast and sustainable and can be potentially applied to many NAD/NADH-dependent enzyme systems.

  1. Modeling and In-situ Probing of Surface Reactions in Atomic Layer Deposition.

    PubMed

    Zheng, Yuanxia; Hong, Sungwook; Psofogiannakis, George M; Rayner, G Bruce; Datta, Suman; van Duin, Adri C T; Engel-Herbert, Roman

    2017-04-05

    Atomic layer deposition (ALD) has matured into a preeminent and highly scalable thin film deposition technique, offering an economic route to integrate chemically dissimilar materials with excellent thickness control down to the sub-nanometer regime. Contrary to its extensive applications, a quantitative and comprehensive understanding of the reaction processes seems intangible. Complex and manifold reaction pathways are possible which are strongly affected by the surface chemical state. Here we report a combined modeling and experimental approach utilizing ReaxFF reactive force field simulation and in-situ real-time spectroscopic ellipsome-try to gain insights into the ALD process of Al2O3 from trimethylaluminum and water on hy-drogenated and oxidized Ge(100) surfaces. We deciphered the origin for the different peculiari-ties during initial ALD cycles for the deposition on both surfaces. While simulations predicted a nucleation delay for hydrogenated Ge(100), a self-cleaning effect was discovered on oxidized Ge(100) surfaces, forming an intermixed Al2O3/GeOx layer that effectively suppressed oxygen diffusion into Ge. In-situ spectroscopic ellipsometry in tandem with ex-situ atomic force mi-croscopy and X-ray photoelectron spectroscopy confirmed these simulation results. Electrical impedance characterizations evidenced the critical role of the intermixed Al2O3/GeOx layer to achieve electrically well behaved dielectric/Ge interfaces with low interface trap density. The combined approach can be generalized to comprehend the deposition and reaction kinetics of other ALD precursor and surface chemistry, offering a path towards a theory-aided rational de-sign of ALD processes at a molecular level.

  2. The design of dextran-based hypoxia-inducible hydrogels via in situ oxygen consuming reaction

    PubMed Central

    Park, Kyung Min; Blatchley, Michael R.; Gerecht, Sharon

    2014-01-01

    Hypoxia plays a critical role in development and the wound healing process, as well as a number of pathological conditions. Here, we report dextran–based hypoxia–inducible (Dex–HI) hydrogels formed with in situ oxygen consumption via laccase–medicated reaction. Oxygen levels and gradients were accurately predicted by mathematical simulation. We demonstrate that Dex–HI hydrogels provide prolonged hypoxic conditions up to 12 h. The Dex–HI hydrogel offers an innovative approach to delineate not only the mechanism by which hypoxia regulates cellular responses, but may facilitate the discovery of new pathways involved in the generation of hypoxic and oxygen gradient environments. PMID:25303104

  3. Laser scanning confocal microscopy for in situ monitoring of alkali-silica reaction.

    PubMed

    Collins, C L; Ideker, J H; Kurtis, K E

    2004-02-01

    Alkali-silica reaction (ASR) occurs in concrete between reactive siliceous components in the aggregate and the strongly alkaline pore solution, resulting in the formation of a potentially expansive gel product. Lithium additives have been shown to reduce expansion associated with ASR, but the mechanism(s) by which lithium reduces expansion have not been understood. Therefore, development of an in situ method to observe reactions associated with ASR is highly desirable, as it will allow for non-destructive observation of the reaction product formation and damage evolution over time, as the reaction progresses. A technique to image into mortar through glass aggregate by laser scanning confocal microscopy (LSCM), producing three-dimensional representations of the sample was developed. This LSCM technique was utilized to monitor the progress of alkali-silica reaction in mortar samples prepared with alkali-reactive glass aggregate both in the presence and in the absence of lithium additives: LiNO3, LiCl or LiOH. The method proved to be effective in qualitatively monitoring crack formation and growth and product formation, within cracks and at the paste/aggregate interface. In particular, dendritic products were observed at the paste/aggregate interface only in those samples containing lithium, suggesting that these products may play a role in ASR mitigation.

  4. Diagnosis of feline herpesvirus infection by immunohistochemistry, polymerase chain reaction, and in situ hybridization.

    PubMed

    Suchy, A; Bauder, B; Gelbmann, W; Löhr, C V; Teifke, J P; Weissenböck, H

    2000-03-01

    An adult domestic shorthair cat had severe chemosis due to purulent and necrotizing blepharitis and conjunctivitis. Purulent rhinitis, necrotizing glossitis, and dermatitis were also diagnosed. The cat was positive for feline immunodeficiency virus and feline leukemia virus. Histologically, intranuclear Cowdry type A inclusions were found within numerous epithelial cells adjacent to the lesions in skin, conjunctiva, and tongue. Electron microscopic examination revealed herpesviral particles within the lesions. Paraffin-embedded skin and tongue tissues were processed in a polymerase chain reaction, using primers to amplify a 306-bp region of the thymidine kinase gene of feline herpesvirus type 1, resulting in a distinct amplification product of the predicted size. The distribution of feline herpesvirus was demonstrated by immunohistochemistry and nonradioactive in situ hybridization. Positive immunostaining was found in nuclei and cytoplasm of numerous epithelial cells within and next to the lesions, whereas in situ hybridization, performed with a digoxigenin-labeled double-stranded DNA probe, revealed hybridization signal only in nuclei of intact epithelial cells. Neither immunohistochemistry nor in situ hybridization showed feline herpesvirus type 1 in tissues of lungs, liver, spleen, intestine, or brain.

  5. The in-situ characterization of a transesterification reaction using electrical impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Cho, Sungjin

    Impedance Spectroscopy has been used in the in-situ monitoring of a transesterfication reaction of soybean biodiesel. This paper describes the application of Electrical Impedance Spectroscopy (EIS) to observe and characterize the transesterfication reaction and its interfacial behavior phenomena electrically. In particular, the dielectric properties of soybean biodiesel were measured at broad range frequencies from 10-2 to 106 Hz at different temperatures, methanol molar ratio to biodiesel, concentration of catalyst and reaction time. Measurement of dielectric property have provided an important approach to understanding the structure of matter. Measurements of the dielectric properties are a reliable and efficient method for evaluating the biodiesel production to determine their quality and yield for reducing the production cost. The dielectric constant (epsilon') and loss (epsilon") are the most convenient indicators for quality control in commercial biodiesel manufacturing. Dielectric properties were correlated with chemically measured changes in soybean oil such as free fatty acids, amount of catalyst and alcohols at different temperatures as well as reaction times. It was observed that there is a good correlation between the dielectric constant (epsilon') and loss (epsilon") in soybean biodiesel. The result indicated that the dielectric properties increased with the (1) increasing temperature (2) increasing methanol; (3) increasing catalyst; (4) increasing reaction time. Dielectric properties was a useful index for the rapid quality evaluation of soybean biodiesel. Dielectric properties were compared to conventional methods of analysis (Infrared Spectroscopy) for evaluating the quality of soybean biodiesel. The results indicated that dielectric constant and dielectric loss are essential measurement for predicting the best biodiesel yield. Moreover, the electrical impedance parameters such as bulk resistance (Rb), bulk capacitance (Cb) and time constant(tau b

  6. In situ visualization of metallurgical reactions in nanoscale Cu/Sn diffusion couples

    DOE PAGES

    Yin, Qiyue; Stach, Eric A.; Gao, Fan; ...

    2015-02-10

    The Cu–Sn metallurgical soldering reaction in two-segmented Cu–Sn nanowires is visualized by in-situ transmission electron microscopy. By varying the relative lengths of Cu and Sn segments, we show that the metallurgical reaction starts at ~ 200 ° with the formation of a Cu–Sn solid solution for the Sn/Cu length ratio smaller than 1:5 while the formation of Cu–Sn intermetallic compounds (IMCs) for larger Sn/Cu length ratios. Upon heating the nanowires up to ~ 500 °C, two phase transformation pathways occur, η-Cu₆Sn₅ → ε-Cu₃Sn → δ-Cu₄₁Sn₁₁ for nanowires with a long Cu segment and η-Cu₆Sn₅ → ε-Cu₃Sn → γ-Cu₃Sn with amore » short Cu segment. The dynamic in situ TEM visualization of the evolution of Kirkendall voids demonstrates that Cu diffuses faster both in Sn and IMCs than that of Sn in Cu₃ and IMCs, which is the underlying cause of the dependence of the IMC formation and associated phase evolution on the relative lengths of the Cu and Sn segments.« less

  7. In situ visualization of metallurgical reactions in nanoscale Cu/Sn diffusion couples

    SciTech Connect

    Yin, Qiyue; Stach, Eric A.; Gao, Fan; Zhou, Guangwen; Gu, Zhiyong

    2015-02-10

    The Cu–Sn metallurgical soldering reaction in two-segmented Cu–Sn nanowires is visualized by in-situ transmission electron microscopy. By varying the relative lengths of Cu and Sn segments, we show that the metallurgical reaction starts at ~ 200 ° with the formation of a Cu–Sn solid solution for the Sn/Cu length ratio smaller than 1:5 while the formation of Cu–Sn intermetallic compounds (IMCs) for larger Sn/Cu length ratios. Upon heating the nanowires up to ~ 500 °C, two phase transformation pathways occur, η-Cu₆Sn₅ → ε-Cu₃Sn → δ-Cu₄₁Sn₁₁ for nanowires with a long Cu segment and η-Cu₆Sn₅ → ε-Cu₃Sn → γ-Cu₃Sn with a short Cu segment. The dynamic in situ TEM visualization of the evolution of Kirkendall voids demonstrates that Cu diffuses faster both in Sn and IMCs than that of Sn in Cu₃ and IMCs, which is the underlying cause of the dependence of the IMC formation and associated phase evolution on the relative lengths of the Cu and Sn segments.

  8. Structure and properties of composites synthesized in situ using solid state displacement reactions

    SciTech Connect

    Henager, C.H. Jr.; Brimhall, J.L.

    1993-10-01

    Solid state displacement reactions can produce in situ intermetallic and ceramic matrix composites in a process where an intermetallic or ceramic phase(s) and a potential reinforcing phase(s) are grown together during a solid state reaction. Interpenetrating and dispersed microstructures, important for desirable composite properties, have been produced by means of displacement reaction processing techniques. Two such composites have been synthesized which exhibit two distinct microstructures: MoSi{sub 2} reinforced with SiC particles, which exhibits a dispersed-phase structure, and NiAl/Ni{sub 3}Al reinforced with Al{sub 2}O{sub 3}, which exhibits an interpenetrating-phase structure. Strength in bending and chevron-notch fracture toughness have been determined as a function of temperature, and measured properties compare favorably with composites produced by other means. The measured properties are discussed with regard to the observed microstructures. The potential for displacement reaction processing is assessed, and it appears to be a cost-effective synthesis method compared to others.

  9. Synthesis of porous zinc gallate prisms composed of highly oriented nanoparticles by an in situ conversion reaction.

    PubMed

    Zhou, Wenli; Yang, Xianfeng; Huang, Lin; Wang, Jing; Tang, Jinke; Liang, Hongbin

    2012-04-23

    Porous ZnGa(2)O(4) prisms assembled by highly oriented nanoparticles have been fabricated by an in situ chemical conversion approach. We report, for the first time, that a solid α-Ga(2)O(3) precursor can be directly converted into ZnGa(2)O(4) rather than through the intermediate GaOOH. Based on a detailed study of the evolution of ZnGa(2)O(4) prisms, a growth mechanism is proposed for the in situ conversion reaction. During this conversion process, the precursor morphology can be highly retained, which is attributed to the similar atomic arrangements of the Ga and O atoms and excellent matching of the lattice spacing between the α-Ga(2)O(3) and ZnGa(2)O(4) prisms. The direct reaction between the precursor α-Ga(2)O(3) and Zn(2+) ions is more efficient than that between the byproduct GaOOH and Zn(2+) ions. Moreover, the photoluminescent color of the ZnGa(2)O(4) phosphor can be tuned by doping with Mn(2+) ions. Efficient energy transfer (ET) from the host lattice to the Mn(2+) centers is observed, whereas ET from the defects to the Mn(2+) ions is prohibited. The fabricated ZnGa(2)O(4) products have potential in the field of display applications.

  10. In situ Fe2N@N-doped porous carbon hybrids as superior catalysts for oxygen reduction reaction.

    PubMed

    Huang, Xiaoxiao; Yang, Ziyu; Dong, Bing; Wang, Yazhou; Tang, Tianyu; Hou, Yanglong

    2017-03-22

    Developing efficient and economical noble-metal free catalysts for oxygen reduction reaction (ORR) is one of the essential factors for the industrialization of fuel cells. Recent studies on transition metal ORR catalysts have become the priority to practical low-temperature fuel cells. Herein, we proposed a novel in situ design, Fe2N nanoparticles (NPs) in an N doped porous carbon matrix (Fe2N@NPC) derived from metal organic frameworks (MOFs) as high-performance ORR catalysts. The decorated Fe2N NPs increase the amount of Fe-N/C bonding as catalytic site. Meanwhile, the coated NPC facilitates the mass transport of the reaction and improves the conductivity simultaneously. The catalyst exhibits an onset potential of -0.038 V, a half-wave potential of -0.175 V in 0.1 M KOH, and superior stabilities and methanol tolerance performances to commercial Pt/C catalysts. More importantly, the proposed in situ 'two-step' annealing route provides potential possibilities for producing other non-precious metal catalysts for ORR.

  11. LONG TERM IN SITU DISPOSAL ENGINEERING STUDY

    SciTech Connect

    ADAMS; CARLSON; BROCKMAN

    2003-07-23

    Patent application pulled per Ken Norris (FH General Counsel). The objective of this study is to devise methods, produce conceptual designs, examine and select alternatives, and estimate costs for the demonstration of long-term (300-year) in situ disposal of an existing waste disposal site. The demonstration site selected is the 216-A-24 Crib near the 200 East Area. The site contains a fission product inventory and has experienced plant, animal, and inadvertent than intrusion. Of the potential intrusive events and transport pathways at the site, potential human intrusion has been given primary consideration in barrier design. Intrusion by wind, plants, and animals has been given secondary consideration. Groundwater modeling for a number of barrier configurations has been carried out to help select a barrier that will minimize water infiltration and waste/water contact time. The estimated effective lifetime and cost of 20 barrier schemes, using a variety of materials, have been evaluated. The schemes studied include single component surface barriers, multicomponent barriers, and massively injected grout barriers. Five barriers with high estimated effective lifetimes and relatively low costs have been selected for detailed evaluation. They are basalt riprap barriers, massive soil barriers, salt basin barriers, multi-component fine/coarse barriers, and cemented basalt barriers. A variety of materials and configurations for marking the site have also been considered. A decision analysis was completed to select a barrier scheme for demonstration. The analysis indicated that the basalt riprap alternative would be the preferred choice for a full-scale demonstration. The recommended approach is to demonstrate the basalt riprap barrier at the 216-A-24 Crib as soon as possible. Methods and costs of assessing effectiveness of the demonstration are also described. Preliminary design modifications and costs for applying the five selected barrier schemes to other site types are

  12. In situ surface characterization and oxygen reduction reaction on shape-controlled gold nanoparticles.

    PubMed

    Hernández, J; Solla-Gullón, J; Herrero, E; Feliu, J M; Aldaz, A

    2009-04-01

    Gold nanoparticles of different shapes/surface structures were synthesized and electrochemically characterized. An in-situ surface characterization of the Au nanoparticles, which was able to obtain qualitative information about the type and relative sizes of the different facets present in the surface of the Au nanoparticles, was carried out by using Pb Under Potential Deposition (UPD) in alkaline solutions as a surface sensitive tool. The results obtained show that the final atomic arrangement on the surface can be different from that expected from the bulk structure of the well-defined shape Au nanoparticles. In this way, the development of precise in-situ methods to measure the distribution of the different sites on the nanoparticle surface, as lead UPD on gold surfaces, is highlighted. Oxygen Reduction Reaction (ORR) was performed on the different Au nanoparticles. In agreement with the particular sensitivity of the oxygen reduction to the presence of Au(100) surface domains, cubic Au nanoparticles show much better electrocatalytic activity for ORR than small spherical particles and long nanorods, in agreement with the presence of a great fraction of (100) terrace sites on the surface of cubic gold nanoparticles.

  13. In situ analysis of the interfacial reactions between MCMB electrode and organic electrolyte solutions

    NASA Astrophysics Data System (ADS)

    Morigaki, Ken-ichi

    The interfacial phenomena between graphite (mesocarbon-microbeads (MCMB)) electrode and organic electrolyte solution were analyzed by in situ atomic force microscopy (AFM) and Fourier transform infrared (FTIR) spectroscopy. The influence of lithium salts (anion species), LiPF 6, LiBF 4, and LiClO 4, on the interfacial reaction, including lithium intercalation into graphite, was investigated in EC+DMC solutions. In situ AFM observation disclosed that morphological changes are quite different from one another depending on the kind of lithium salt (anion). A large expansion of MCMB particle was observed particularly in LiPF 6/EC+DMC. An expansion of MCMB particle started above 1.0 V versus Li/Li + and this expansion seemed to be caused by the decomposition of ternary graphite intercalation compound (GIC) ( C nLi(sol) y), because the expansion remained after de-intercalation of lithium. IRAS spectra of each electrolyte solution showed different behaviors and different reduction products of solvents. double modulation FTIR (DMFTIR) spectra on graphite electrode, which emphasize the surface species, indicated relatively small changes after cathodic polarization. Therefore, the observed morphological changes were caused mainly by the expansion of graphene layers and not by the precipitation of reduction products.

  14. Optimizing Metalloporphyrin-Catalyzed Reduction Reactions for In Situ Remediation of DOE Contaminants

    SciTech Connect

    Schlautman, Mark A.

    2013-07-14

    Past activities have resulted in a legacy of contaminated soil and groundwater at Department of Energy facilities nationwide. Uranium and chromium are among the most frequently encountered and highest-priority metal and radionuclide contaminants at DOE installations. Abiotic chemical reduction of uranium and chromium at contaminated DOE sites can be beneficial because the reduced metal species are less soluble in water, less mobile in the environment, and less toxic to humans and ecosystems. Although direct biological reduction has been reported for U(VI) and Cr(VI) in laboratory studies and at some field sites, the reactions can sometimes be slow or even inhibited due to unfavorable environmental conditions. One promising approach for the in-situ remediation of DOE contaminants is to develop electron shuttle catalysts that can be delivered precisely to the specific subsurface locations where contaminants reside. Previous research has shown that reduction of oxidized organic and inorganic contaminants often can be catalyzed by electron shuttle systems. Metalloporphyrins and their derivatives are well known electron shuttles for many biogeochemical systems, and thus were selected to study their catalytic capabilities for the reduction of chromium and uranium in the presence of reducing agents. Zero valent iron (ZVI) was chosen as the primary electron donor in most experimental systems. Research proceeded in three phases and the key findings of each phase are reported here. Phase I examined Cr(VI) reduction and utilized micro- and nano-sized ZVI as the electron donors. Electron shuttle catalysts tested were cobalt- and iron-containing metalloporphyrins and Vitamin B12. To aid in the recycle and reuse of the nano-sized ZVI and soluble catalysts, sol-gels and calcium-alginate gel beads were tested as immobilization/support matrices. Although the nano-sized ZVI could be incorporated within the alginate gel beads, preliminary attempts to trap it in sol-gels were not

  15. Experimental Study of Serpentinization Reactions

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

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

  16. [3 + 2] Cycloaddition Reaction of in Situ Formed Azaoxyallyl Cations with Aldehydes: An Approach to Oxazolidin-4-ones.

    PubMed

    Zhang, Kaifan; Yang, Chi; Yao, Hequan; Lin, Aijun

    2016-09-16

    A novel [3 + 2] cycloaddition reaction between in situ formed azaoxyallyl cations and aldehydes has been developed. This concise method allows the rapid formation of a number of oxazolidin-4-ones in high yields with good functional group tolerance at room temperature. Further transformation and late-stage modifications of drug molecules could also be achieved in good yields, highlighting the potential utility of the reaction.

  17. Investigation of CaO-CO₂ reaction kinetics by in-situ XRD using synchrotron radiation

    SciTech Connect

    Biasin, A.; Segre, C. U.; Salviulo, G.; Zorzi, F.; Strumendo, M.

    2015-02-05

    In this work, in-situ synchrotron radiation x-ray powder diffraction (SR-XRPD), performed at the Advanced Photon Source (APS) facilities of the Argonne National Laboratory, was applied to investigate the CaO–CO2 reaction. A set of CO2 absorption experiments were conducted in a high temperature reaction capillary with a controlled atmosphere (CO2 partial pressure of 1 bar), in the temperature range between 450 °C and 750 °C using CaO based sorbents obtained by calcination of commercial calcium carbonate. The evolution of the crystalline phases during CO2 uptake by the CaO solid sorbents was monitored for a carbonation time of 20 min as a function of the carbonation temperature and of the calcination conditions. The Rietveld refinement method was applied to estimate the calcium oxide conversion during the reaction progress and the average size of the initial (at the beginning of carbonation) calcium oxide crystallites. The measured average initial carbonation rate (in terms of conversion time derivative) of 0.280 s-1 (±13.2% standard deviation) is significantly higher than the values obtained by thermo-gravimetric analysis and reported thus far in the literature. Additionally, a dependence of the conversion versus time curves on the initial calcium oxide crystallite size was observed and a linear relationship between the initial CaO crystallite size and the calcium oxide final conversion was identified.

  18. Kinetic studies of elementary chemical reactions

    SciTech Connect

    Durant, J.L. Jr.

    1993-12-01

    This program concerning kinetic studies of elementary chemical reactions is presently focussed on understanding reactions of NH{sub x} species. To reach this goal, the author is pursuing experimental studies of reaction rate coefficients and product branching fractions as well as using electronic structure calculations to calculate transition state properties and reaction rate calculations to relate these properties to predicted kinetic behavior. The synergy existing between the experimental and theoretical studies allow one to gain a deeper insight into more complex elementary reactions.

  19. Detection of HTLV-1 by polymerase chain reaction in situ hybridization in adult T-cell leukemia/lymphoma.

    PubMed

    Setoyama, M; Kerdel, F A; Elgart, G; Kanzaki, T; Byrnes, J J

    1998-03-01

    A method for nonradioactive polymerase chain reaction in situ hybridization was developed and used to determine the distribution of human T-lymphotropic virus type I (HTLV-I) proviral DNA in paraffin-embedded surgical specimens of adult T-cell leukemia/lymphoma (ATLL). As controls, we used biopsy samples of five cases of mycosis fungoides, cells of an HTLV-I-infected cell line (MT2), as well as HTLV-1-negative cells (YAS). We successfully detected the amplicon of the HTLV-1 tax sequence in the nuclei of the cutaneous infiltrating lymphoid cells in 90% (9/10) of ATLL cases. Studies also revealed the existence of HTLV-1 provirus DNA in nuclei of sweat gland epithelial cells and vascular endothelial cells as well as lymphoid cells in ATLL patients. Mycosis fungoides and YAS cells were negative for the HTLV-I tax sequence, but MT2 cells were strongly positive. The results indicated that this technique was more sensitive in detecting intracellular amplicons than was the previous in situ hybridization method. Through its use, we were able to easily determine the distribution of HTLV-I-positive cells among the various cells and tissues of paraffin-embedded archival materials.

  20. In situ synchrotron x-ray spectroscopy of ruthenium nanoparticles modified with selenium for an oxygen reduction reaction.

    SciTech Connect

    Inukai, J.; Cao, D.; Wieckowski, A.; Chang, K.-C.; Menzel, A.; Komanicky, V.; You, H.; Univ. Illinois; Univ. Yamanashi

    2007-11-15

    We used in situ Se K-edge X-ray spectroscopy to characterize Ru nanoparticles chemically modified with submonolayers of selenium (Se/Ru) [Cao et al. J. Electrochem. Soc. 2006, 153, A869]. X-ray powder diffraction verified that the Se/Ru catalyst had metallic Ru cores. The in situ X-ray absorption near edge structure taken at the open circuit potential showed that there were both elemental and oxidized selenium on the as-prepared Se/Ru samples. All selenium oxide was reduced to the elemental form of selenium by applying negative potentials. By applying positive potentials, selenium was subsequently reoxidized. The analysis of the extended X-ray absorption fine structure shows the appearance of selenium hydration (Se-OH{sub 2}) in a deaerated solution, which was not observed during the oxygen reduction reaction. We present evidence that Se-free Ru atoms play an important role in the ORR activity of the Se/Ru catalyst studied in this paper.

  1. In-situ synchrotron x-ray spectroscopy of ruthenium nanoparticles modified with selenium for oxygen reduction reaction.

    SciTech Connect

    Inukai, J.; Cao, D.; Wieckowski, A.; Chang, K.-C.; Menzel, A.; Komanicky, V.; You, H.; Materials Science Division; Univ. of Illinois; Univ. of Yamanashi

    2007-11-15

    We used in situ Se K-edge X-ray spectroscopy to characterize Ru nanoparticles chemically modified with submonolayers of selenium (Se/Ru) [Cao et al. J. Electrochem. Soc. 2006, 153, A869]. X-ray powder diffraction verified that the Se/Ru catalyst had metallic Ru cores. The in situ X-ray absorption near edge structure taken at the open circuit potential showed that there were both elemental and oxidized selenium on the as-prepared Se/Ru samples. All selenium oxide was reduced to the elemental form of selenium by applying negative potentials. By applying positive potentials, selenium was subsequently reoxidized. The analysis of the extended X-ray absorption fine structure shows the appearance of selenium hydration (Se-OH{sub 2}) in a deaerated solution, which was not observed during the oxygen reduction reaction. We present evidence that Se-free Ru atoms play an important role in the ORR activity of the Se/Ru catalyst studied in this paper.

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

    PubMed

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

    2015-09-28

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

  3. In situ nucleophilic substitution reaction of N,N-dialkylaminoethyl-2-chlorides monitored by gas chromatography/mass spectrometry.

    PubMed

    Lakshmi, V V S; Reddy, T Jagadeshwar; Murty, M R V S; Prabhakar, S; Vairamani, M

    2006-01-01

    The detection and identification of degradation products of scheduled chemicals, which are characteristic markers of Chemical Warfare agents (CWAs), plays a key role in verification analysis. Identification of such non-scheduled but specific markers of CWAs helps in deciphering the kind of agent that was present in the sample submitted for off-site analysis. This paper describes the stability of N,N-dialkylaminoethyl-2-chlorides, which are precursors for highly toxic chemicals like VX, in different solvents. These compounds are stable in chloroform, acetonitrile, hexane and dichloromethane but tend to undergo in situ nucleophilic substitution reaction in the presence of alcohols giving the corresponding alkyl ether. The study shows that N,N-dialkylaminoethyl alkyl ethers can be used as markers of N,N-dialkylaminoethyl-2-chlorides. A detailed degradation study of these compounds in the presence of alcohols was carried out and it was found that the reaction follows pseudo-first order kinetics. Electron ionization mass spectral data for the methyl ethers of all the compounds are briefly discussed.

  4. MEMS Lubrication by In-Situ Tribochemical Reactions From the Vapor Phase.

    SciTech Connect

    Dugger, Michael Thomas; Asay, David B.; Kim, Seong H.

    2008-01-01

    Vapor Phase Lubrication (VPL) of silicon surfaces with pentanol has been demonstrated. Two potential show stoppers with respect to application of this approach to real MEMS devices have been investigated. Water vapor was found to reduce the effectiveness of VPL with alcohol for a given alcohol concentration, but the basic reaction mechanism observed in water-free environments is still active, and devices operated much longer in mixed alcohol and water vapor environments than with chemisorbed monolayer lubricants alone. Complex MEMS gear trains were successfully lubricated with alcohol vapors, resulting in a factor of 104 improvement in operating life without failure. Complex devices could be made to fail if operated at much higher frequencies than previously used, and there is some evidence that the observed failure is due to accumulation of reaction products at deeply buried interfaces. However, if hypothetical reaction mechanisms involving heated surfaces are valid, then the failures observed at high frequency may not be relevant to operation at normal frequencies. Therefore, this work demonstrates that VPL is a viable approach for complex MEMS devices in conventional packages. Further study of the VPL reaction mechanisms are recommended so that the vapor composition may be optimized for low friction and for different substrate materials with potential application to conventionally fabricated, metal alloy parts in weapons systems. Reaction kinetics should be studied to define effective lubrication regimes as a function of the partial pressure of the vapor phase constituent, interfacial shear rate, substrate composition, and temperature.

  5. Microbial Studies Supporting Implementation of In Situ Bioremediation at TAN

    SciTech Connect

    Barnes, Joan Marie; Matthern, Gretchen Elise; Rae, Catherine; Ely, R. L.

    2000-11-01

    The Idaho National Engineering and Environmental Laboratory is evaluating in situ bioremediation of contaminated groundwater at its Test Area North Facility. To determine feasibility, microcosm and bioreactor studies were conducted to ascertain the ability of indigenous microbes to convert trichloroethene and dichloroethene to non-hazardous byproducts under aerobic and anaerobic conditions, and to measure the kinetics of microbial reactions associated with the degradation process. Microcosms were established from core samples and groundwater obtained from within the contaminant plume. These microcosms were amended with nutrients, under aerobic and anaerobic conditions, to identify electron donors capable of stimulating the degradation process. Results of the anaerobic microcosm studies showed that lactate, acetate and propionate amendments stimulated indigenous cell growth and functioned as effective substrates for reductive degradation of chloroethenes. Bioreactors inoculated with cultures from these anaerobic microcosms were operated under a batch mode for 42 days then converted to a fed-batch mode and operated at a 53-day hydraulic residence time. It was demonstrated that indigenous microbes capable of complete anaerobic reductive dechlorination are present in the subject well. It was also demonstrated that aerobic microbes capable of oxidizing chlorinated compounds produced by anaerobic reductive dechlorination are present. Kinetic data suggest that controlling the type and concentration of electron donors can increase trichlorethene conversion rates. In the event that complete mineralization of trichlorethene does not occur following stimulation, and anaerobic/aerobic treatment scheme is feasible.

  6. Configuring robust DNA strand displacement reactions for in situ molecular analyses

    PubMed Central

    Duose, Dzifa Y.; Schweller, Ryan M.; Zimak, Jan; Rogers, Arthur R.; Hittelman, Walter N.; Diehl, Michael R.

    2012-01-01

    The number of distinct biomolecules that can be visualized within individual cells and tissue sections via fluorescence microscopy is limited by the spectral overlap of the fluorescent dye molecules that are coupled permanently to their targets. This issue prohibits characterization of important functional relationships between different molecular pathway components in cells. Yet, recent improved understandings of DNA strand displacement reactions now provides opportunities to create programmable labeling and detection approaches that operate through controlled transient interactions between different dynamic DNA complexes. We examined whether erasable molecular imaging probes could be created that harness this mechanism to couple and then remove fluorophore-bearing oligonucleotides to and from DNA-tagged protein markers within fixed cell samples. We show that the efficiency of marker erasing via strand displacement can be limited by non-toehold mediated stand exchange processes that lower the rates that fluorophore-bearing strands diffuse out of cells. Two probe constructions are described that avoid this problem and allow efficient fluorophore removal from their targets. With these modifications, we show one can at least double the number of proteins that can be visualized on the same cells via reiterative in situ labeling and erasing of markers on cells. PMID:22156404

  7. Single-Molecule Imaging of Iron-Phthalocyanine-Catalyzed Oxygen Reduction Reaction by in Situ Scanning Tunneling Microscopy.

    PubMed

    Gu, Jing-Ying; Cai, Zhen-Feng; Wang, Dong; Wan, Li-Jun

    2016-09-27

    We report herein an in situ electrochemical scanning tunneling microscopy (ECSTM) investigation of iron-phthalocyanine (FePc)-catalyzed oxygen reduction reaction (ORR). A highly ordered FePc adlayer is revealed on a Au(111) electrode. The center ions in the FePc adlayer show uniform high contrast in an oxygen-saturated electrolyte, which is attributed to the formation of an FePc-O2 complex. In situ STM results reveal the sharp contrast change upon shifting the electrode potential to trigger the ORR. Theoretical simulation has supplied further evidence for the contrast difference of the adsorbed FePc species.

  8. Electron transport between plastoquinone and chlorophyll Ai in chloroplasts. II. Reaction kinetics and the function of plastocyanin in situ.

    PubMed

    Haehnel, W

    1977-03-11

    The light-induced reaction kinetics of electron carriers between the two light reactions were studied in spinach chloroplasts. 1. The difference spectrum of the absorbance changes of plastocyanin in situ was separated from superimposing absorbance changes by flash titration described in the preceding paper (Haehnel, W. (1973) Biochim. Biophys. Acta 305, 618-631). Relative amounts of 2 : 1 electron equivalents were observed for plastocyanin and chlorophyll a1 (P-700). 2. A balance of the electron equivalents released from reduced plastoquinone and simultaneously accepted by oxidized plastocyanin, cytochrome f and chlorophyll a1 indicated a quantitative electron transfer. Additional electron carriers between plastoquinone and light reaction I can be excluded with an accuracy of about +/-0.3 electron equivalents per light reaction II. 3. The time course of the absorbance changes of plastocyanin was measured at 584 nm with negligible interference with other absorbance changes. The reduction kinetics show an initial lag followed by a rise with a half time of about 20 ms. The redox states of plastocyanin and chlorophyll a1 during this reduction via the rate-limiting step between the light reactions and during oxidation by weak far-red light suggest a true equilibrium constant of about 20. 4. The simultaneous oxidation and reduction kinetics of plastoquinone, cytochrome f, plastocyanin and chlorophyll a1 induced by two successive groups of saturating flashes after far-red illumination were measured. The oxidation kinetics of plastocyanin and the simultaneous reduction kinetics of chlorophyll a1 after the single flashes indicate a quantitative electron transfer with a half time of 200 mus. 5. The fast reduction of chlorophyll a1 by plastocyanin showed no effect of the inhibitors 3-(3',4'-dichlorophenyl)-1,1-dimethylurea and 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone or of reduced phenazine methosulfate. But it was completed inhibited after KCN incubation. 6. The

  9. In Situ and Ex Situ TEM Study of Lithiation Behaviours of Porous Silicon Nanostructures

    PubMed Central

    Shen, Chenfei; Ge, Mingyuan; Luo, Langli; Fang, Xin; Liu, Yihang; Zhang, Anyi; Rong, Jiepeng; Wang, Chongmin; Zhou, Chongwu

    2016-01-01

    In this work, we study the lithiation behaviours of both porous silicon (Si) nanoparticles and porous Si nanowires by in situ and ex situ transmission electron microscopy (TEM) and compare them with solid Si nanoparticles and nanowires. The in situ TEM observation reveals that the critical fracture diameter of porous Si particles reaches up to 1.52 μm, which is much larger than the previously reported 150 nm for crystalline Si nanoparticles and 870 nm for amorphous Si nanoparticles. After full lithiation, solid Si nanoparticles and nanowires transform to crystalline Li15Si4 phase while porous Si nanoparticles and nanowires transform to amorphous LixSi phase, which is due to the effect of domain size on the stability of Li15Si4 as revealed by the first-principle molecular dynamic simulation. Ex situ TEM characterization is conducted to further investigate the structural evolution of porous and solid Si nanoparticles during the cycling process, which confirms that the porous Si nanoparticles exhibit better capability to suppress pore evolution than solid Si nanoparticles. The investigation of structural evolution and phase transition of porous Si nanoparticles and nanowires during the lithiation process reveal that they are more desirable as lithium-ion battery anode materials than solid Si nanoparticles and nanowires. PMID:27571919

  10. In Situ and Ex Situ TEM Study of Lithiation Behaviours of Porous Silicon Nanostructures.

    PubMed

    Shen, Chenfei; Ge, Mingyuan; Luo, Langli; Fang, Xin; Liu, Yihang; Zhang, Anyi; Rong, Jiepeng; Wang, Chongmin; Zhou, Chongwu

    2016-08-30

    In this work, we study the lithiation behaviours of both porous silicon (Si) nanoparticles and porous Si nanowires by in situ and ex situ transmission electron microscopy (TEM) and compare them with solid Si nanoparticles and nanowires. The in situ TEM observation reveals that the critical fracture diameter of porous Si particles reaches up to 1.52 μm, which is much larger than the previously reported 150 nm for crystalline Si nanoparticles and 870 nm for amorphous Si nanoparticles. After full lithiation, solid Si nanoparticles and nanowires transform to crystalline Li15Si4 phase while porous Si nanoparticles and nanowires transform to amorphous LixSi phase, which is due to the effect of domain size on the stability of Li15Si4 as revealed by the first-principle molecular dynamic simulation. Ex situ TEM characterization is conducted to further investigate the structural evolution of porous and solid Si nanoparticles during the cycling process, which confirms that the porous Si nanoparticles exhibit better capability to suppress pore evolution than solid Si nanoparticles. The investigation of structural evolution and phase transition of porous Si nanoparticles and nanowires during the lithiation process reveal that they are more desirable as lithium-ion battery anode materials than solid Si nanoparticles and nanowires.

  11. In Situ and Ex Situ TEM Study of Lithiation Behaviours of Porous Silicon Nanostructures

    NASA Astrophysics Data System (ADS)

    Shen, Chenfei; Ge, Mingyuan; Luo, Langli; Fang, Xin; Liu, Yihang; Zhang, Anyi; Rong, Jiepeng; Wang, Chongmin; Zhou, Chongwu

    2016-08-01

    In this work, we study the lithiation behaviours of both porous silicon (Si) nanoparticles and porous Si nanowires by in situ and ex situ transmission electron microscopy (TEM) and compare them with solid Si nanoparticles and nanowires. The in situ TEM observation reveals that the critical fracture diameter of porous Si particles reaches up to 1.52 μm, which is much larger than the previously reported 150 nm for crystalline Si nanoparticles and 870 nm for amorphous Si nanoparticles. After full lithiation, solid Si nanoparticles and nanowires transform to crystalline Li15Si4 phase while porous Si nanoparticles and nanowires transform to amorphous LixSi phase, which is due to the effect of domain size on the stability of Li15Si4 as revealed by the first-principle molecular dynamic simulation. Ex situ TEM characterization is conducted to further investigate the structural evolution of porous and solid Si nanoparticles during the cycling process, which confirms that the porous Si nanoparticles exhibit better capability to suppress pore evolution than solid Si nanoparticles. The investigation of structural evolution and phase transition of porous Si nanoparticles and nanowires during the lithiation process reveal that they are more desirable as lithium-ion battery anode materials than solid Si nanoparticles and nanowires.

  12. In Situ and Ex Situ TEM Study of Lithiation Behaviours of Porous Silicon Nanostructures

    SciTech Connect

    Shen, Chenfei; Ge, Mingyuan; Luo, Langli; Fang, Xin; Liu, Yihang; Zhang, Anyi; Rong, Jiepeng; Wang, Chongmin; Zhou, Chongwu

    2016-08-30

    In this work, we study the lithiation behaviours of both porous silicon (Si) nanoparticles and porous Si nanowires by in situ and ex situ transmission electron microscopy (TEM) and compare them with solid Si nanoparticles and nanowires. The in situ TEM observation reveals that the critical fracture diameter of porous Si particles reaches up to 1.52 μm, which is much larger than the previously reported 150 nm for crystalline Si nanoparticles and 870 nm for amorphous Si nanoparticles. After full lithiation, solid Si nanoparticles and nanowires transform to crystalline Li15Si4 phase while porous Si nanoparticles and nanowires transform to amorphous LixSi phase, which is due to the effect of domain size on the stability of Li15Si4 as revealed by the first-principle molecular dynamic simulation. Ex situ TEM characterization is conducted to further investigate the structural evolution of porous and solid Si nanoparticles during the cycling process, which confirms that the porous Si nanoparticles exhibit better capability to suppress pore evolution than solid Si nanoparticles. The investigation of structural evolution and phase transition of porous Si nanoparticles and nanowires during the lithiation process reveal that they are more desirable as lithium-ion battery anode materials than solid Si nanoparticles and nanowires.

  13. Externally controlled pressure and temperature microreactor for in situ x-ray diffraction, visual and spectroscopic reaction investigations under supercritical and subcritial conditions

    SciTech Connect

    Diefenbacher, J.; McKelvy, M.; Chizemeshya, A.V.; Wolf, G.H.

    2010-07-13

    A microreactor has been developed for in situ, spectroscopic investigations of materials and reaction processes with full external pressure and temperature control from ambient conditions to 400 C and 310 bar. The sample chamber is in direct contact with an external manifold, whereby gases, liquids or fluids can be injected and their activities controlled prior to and under investigation conditions. The microreactor employs high strength, single crystal moissanite windows which allow direct probe beam interaction with a sample to investigate in situ reaction processes and other materials properties. The relatively large volume of the cell, along with full optical accessibility and external temperature and pressure control, make this reaction cell well suited for experimental investigations involving any combination of gas, fluid, and solid interactions. The microreactor's capabilities are demonstrated through an in situ x-ray diffraction study of the conversion of a meta-serpentine sample to magnesite under high pressure and temperature. Serpentine is one of the mineral candidates for the implementation of mineral carbonation, an intriguing carbon sequestration candidate technology.

  14. Externally controlled pressure and temperature microreactor for in situ x-ray diffraction, visual and spectroscopic reaction investigations under supercritical and subcritical conditions

    SciTech Connect

    Diefenbacher, Jason; McKelvy, Michael; Chizmeshya, Andrew V.G.; Wolf, George H.

    2005-01-01

    A microreactor has been developed for in situ, spectroscopic investigations of materials and reaction processes with full external pressure and temperature control from ambient conditions to 400 deg. C and 310 bar. The sample chamber is in direct contact with an external manifold, whereby gases, liquids or fluids can be injected and their activities controlled prior to and under investigation conditions. The microreactor employs high strength, single crystal moissanite windows which allow direct probe beam interaction with a sample to investigate in situ reaction processes and other materials properties. The relatively large volume of the cell, along with full optical accessibility and external temperature and pressure control, make this reaction cell well suited for experimental investigations involving any combination of gas, fluid, and solid interactions. The microreactor's capabilities are demonstrated through an in situ x-ray diffraction study of the conversion of a meta-serpentine sample to magnesite under high pressure and temperature. Serpentine is one of the mineral candidates for the implementation of mineral carbonation, an intriguing carbon sequestration candidate technology.

  15. Correlation Between in-situ Redox Reaction Rates and Microbial Biomass Distribution in Porous Media Influenced by Different Transport Regimes

    NASA Astrophysics Data System (ADS)

    Thullner, M.; Pallud, C.; van Cappellen, P.; Regnier, P.

    2004-12-01

    Microbially mediated redox transformations of organic carbon play an important role for the fate of reactive species in porous media. The terminal electron acceptors (TEAs) involved in such reactions depend on the amount and degradability of the organic carbon species and lead to a succession of redox reactions where the TEAs are used-up in a temporal or, in case transport is considered, spatial sequence of decreasing energy yields. A direct characterization of redox stratified systems is challenged by our ability to measure reaction rates in-situ. One novel approach consists in quantifying and characterizing microorganisms in aquifers and sediments and to use such results to predict in-situ redox reaction rates. However, the existence of a spatial correlation between microbial abundance and associated in-situ redox reaction rates should be questioned. Here, we investigate this correlation for porous media having different transport regimes. In the environment, these regimes vary between systems such as aquifers, where advective transport in the water phase is the dominant transport mechanism, and aquatic sediments, where close to the sediment water interface the mixing activity of benthic macrofauna contributes significantly to transport. Results from estuarine sediments show that for such systems, the spatial distributions of redox reaction rates and the associated microorganisms are not correlated. This observation is supported by reactive transport simulations, which show that the ratio of the time scale of the mixing processes to the time scale of microbial growth is controlling the spatial correlation between redox reaction rates and the distribution of microorganisms. For sediments highly affected by mixing, the correlation is missing or weak, while in advection controlled systems such as aquifers, a good correlation between redox rates and microbial biomass distribution can be expected.

  16. Physical organic studies of organometallic reactions

    SciTech Connect

    Bergman, Robert G.

    1981-01-01

    The mechanisms of reactions of organotransition metal complexes have only begun to be understood in detail during the last ten years. The complementary interaction of techniques and concepts developed earlier in studies of organic reaction mechanisms, with those commonly used in inorganic chetnistry, has played a crucial role in helping to elucidate organor.1etall.ic reaction mechanisms. A few systems in which this interaction has proved especially fruitful are discussed in this article.

  17. In-situ nanoelectrospray for high-throughput screening of enzymes and real-time monitoring of reactions.

    PubMed

    Yang, Yuhan; Han, Feifei; Ouyang, Jin; Zhao, Yunling; Han, Juan; Na, Na

    2016-01-01

    The in-situ and high-throughput evaluation of enzymes and real-time monitoring of enzyme catalyzed reactions in liquid phase is quite significant in the catalysis industry. In-situ nanoelectrospray, the direct sampling and ionization method for mass spectrometry, has been applied for high-throughput evaluation of enzymes, as well as the on-line monitoring of reactions. Simply inserting a capillary into a liquid system with high-voltage applied, analytes in liquid reaction system can be directly ionized at the capillary tip with small volume consumption. With no sample pre-treatment or injection procedure, different analytes such as saccharides, amino acids, alkaloids, peptides and proteins can be rapidly and directly extracted from liquid phase and ionized at the capillary tip. Taking irreversible transesterification reaction of vinyl acetate and ethanol as an example, this technique has been used for the high-throughput evaluation of enzymes, fast optimizations, as well as real-time monitoring of reaction catalyzed by different enzymes. In addition, it is even softer than traditional electrospray ionization. The present method can also be used for the monitoring of other homogenous and heterogeneous reactions in liquid phases, which will show potentials in the catalysis industry.

  18. In situ Scanning Electron Microscopy of Silicon Anode Reactions in Lithium-Ion Batteries during Charge/Discharge Processes.

    PubMed

    Chen, Chih-Yao; Sano, Teruki; Tsuda, Tetsuya; Ui, Koichi; Oshima, Yoshifumi; Yamagata, Masaki; Ishikawa, Masashi; Haruta, Masakazu; Doi, Takayuki; Inaba, Minoru; Kuwabata, Susumu

    2016-10-26

    A comprehensive understanding of the charge/discharge behaviour of high-capacity anode active materials, e.g., Si and Li, is essential for the design and development of next-generation high-performance Li-based batteries. Here, we demonstrate the in situ scanning electron microscopy (in situ SEM) of Si anodes in a configuration analogous to actual lithium-ion batteries (LIBs) with an ionic liquid (IL) that is expected to be a functional LIB electrolyte in the future. We discovered that variations in the morphology of Si active materials during charge/discharge processes is strongly dependent on their size and shape. Even the diffusion of atomic Li into Si materials can be visualized using a back-scattering electron imaging technique. The electrode reactions were successfully recorded as video clips. This in situ SEM technique can simultaneously provide useful data on, for example, morphological variations and elemental distributions, as well as electrochemical data.

  19. In situ Scanning Electron Microscopy of Silicon Anode Reactions in Lithium-Ion Batteries during Charge/Discharge Processes

    NASA Astrophysics Data System (ADS)

    Chen, Chih-Yao; Sano, Teruki; Tsuda, Tetsuya; Ui, Koichi; Oshima, Yoshifumi; Yamagata, Masaki; Ishikawa, Masashi; Haruta, Masakazu; Doi, Takayuki; Inaba, Minoru; Kuwabata, Susumu

    2016-10-01

    A comprehensive understanding of the charge/discharge behaviour of high-capacity anode active materials, e.g., Si and Li, is essential for the design and development of next-generation high-performance Li-based batteries. Here, we demonstrate the in situ scanning electron microscopy (in situ SEM) of Si anodes in a configuration analogous to actual lithium-ion batteries (LIBs) with an ionic liquid (IL) that is expected to be a functional LIB electrolyte in the future. We discovered that variations in the morphology of Si active materials during charge/discharge processes is strongly dependent on their size and shape. Even the diffusion of atomic Li into Si materials can be visualized using a back-scattering electron imaging technique. The electrode reactions were successfully recorded as video clips. This in situ SEM technique can simultaneously provide useful data on, for example, morphological variations and elemental distributions, as well as electrochemical data.

  20. In situ Scanning Electron Microscopy of Silicon Anode Reactions in Lithium-Ion Batteries during Charge/Discharge Processes

    PubMed Central

    Chen, Chih-Yao; Sano, Teruki; Tsuda, Tetsuya; Ui, Koichi; Oshima, Yoshifumi; Yamagata, Masaki; Ishikawa, Masashi; Haruta, Masakazu; Doi, Takayuki; Inaba, Minoru; Kuwabata, Susumu

    2016-01-01

    A comprehensive understanding of the charge/discharge behaviour of high-capacity anode active materials, e.g., Si and Li, is essential for the design and development of next-generation high-performance Li-based batteries. Here, we demonstrate the in situ scanning electron microscopy (in situ SEM) of Si anodes in a configuration analogous to actual lithium-ion batteries (LIBs) with an ionic liquid (IL) that is expected to be a functional LIB electrolyte in the future. We discovered that variations in the morphology of Si active materials during charge/discharge processes is strongly dependent on their size and shape. Even the diffusion of atomic Li into Si materials can be visualized using a back-scattering electron imaging technique. The electrode reactions were successfully recorded as video clips. This in situ SEM technique can simultaneously provide useful data on, for example, morphological variations and elemental distributions, as well as electrochemical data. PMID:27782200

  1. In Situ Optical Studies of Solid-Oxide Fuel Cells

    NASA Astrophysics Data System (ADS)

    Pomfret, Michael B.; Owrutsky, Jeffrey C.; Walker, Robert A.

    2010-07-01

    Thermal imaging and vibrational spectroscopy have become important tools for examining the physical and chemical changes that occur in real time in solid-oxide fuel cells (SOFCs). Imaging techniques can resolve temperature differences as fine as 0.1°C across a SOFC electrode at temperatures higher than 600°C. Vibrational spectroscopy can identify molecular species and changes in material phases in operating SOFCs. This review discusses the benefits and challenges associated with directly observing processes that are important to SOFC performance and durability. In situ optical methods can provide direct insight into reaction mechanisms that can be inferred only indirectly from electrochemical measurements such as voltammetry and electrochemical impedance spectroscopy and from kinetic models and postmortem, ex situ examinations of SOFC components. Particular attention is devoted to recent advances that, hopefully, will spur the development of new generations of efficient, versatile energy-producing devices.

  2. In situ optical studies of solid-oxide fuel cells.

    PubMed

    Pomfret, Michael B; Owrutsky, Jeffrey C; Walker, Robert A

    2010-01-01

    Thermal imaging and vibrational spectroscopy have become important tools for examining the physical and chemical changes that occur in real time in solid-oxide fuel cells (SOFCs). Imaging techniques can resolve temperature differences as fine as 0.1 degrees C across a SOFC electrode at temperatures higher than 600 degrees C. Vibrational spectroscopy can identify molecular species and changes in material phases in operating SOFCs. This review discusses the benefits and challenges associated with directly observing processes that are important to SOFC performance and durability. In situ optical methods can provide direct insight into reaction mechanisms that can be inferred only indirectly from electrochemical measurements such as voltammetry and electrochemical impedance spectroscopy and from kinetic models and postmortem, ex situ examinations of SOFC components. Particular attention is devoted to recent advances that, hopefully, will spur the development of new generations of efficient, versatile energy-producing devices.

  3. An in Situ Generated Palladium on Aluminum Oxide: Applications in Gram-Scale Matsuda-Heck Reactions.

    PubMed

    Pape, Simon; Daukšaitė, Lauryna; Lucks, Sandra; Gu, Xiaoting; Brunner, Heiko

    2016-12-16

    In situ generated palladium on aluminum oxide provides an active catalytic system for Matsuda-Heck reactions in gram-scale. The novel catalyst proceeded through a significantly higher catalytic activity compared to the classical Pd/C system. Based on the high catalytic activity the first α,β,β-triarylation of methyl acrylate in good yields could be provided in one-step.

  4. In situ electrochemical-electron spin resonance investigations of multi-electron redox reaction for organic radical cathodes

    SciTech Connect

    Huang, Qian; Walter, Eric D.; Cosimbescu, Lelia; Choi, Daiwon; Lemmon, John P.

    2016-02-29

    Organic radical batteries (ORBs) bearing robust radical polymers as energy storage species, are emerging promisingly with durable high energy and power characteristics by unique tunable redox properties. Here we report the development and application of in situ electrochemical-electron spin resonance (ESR) methodologies to identify the charge transfer mechanism of Poly(2,2,6,6- tetramethylpiperidinyloxy-4-yl methacrylate) (PTMA) based organic radical composite cathodes in the charge-discharge process of lithium half cells. The in situ experiments allow each electrochemical state to be associated with the chemical state (or environment) of the radical species upon the cell cycling. In situ ESR spectra of the composite cathode demonstrate a two-electron redox reaction of PTMA. Moreover, two different local environments of radical species are found in the composite electrode that includes both concentrated and isolated radicals. These two types of radicals show similarities during the redox reaction process while behave quite differently in the non-faradic reaction of ion sorption/desorption on the electrode surface.

  5. Grain rotation and lattice deformation during photoinduced chemical reactions revealed by in situ X-ray nanodiffraction.

    PubMed

    Huang, Zhifeng; Bartels, Matthias; Xu, Rui; Osterhoff, Markus; Kalbfleisch, Sebastian; Sprung, Michael; Suzuki, Akihiro; Takahashi, Yukio; Blanton, Thomas N; Salditt, Tim; Miao, Jianwei

    2015-07-01

    In situ X-ray diffraction (XRD) and transmission electron microscopy (TEM) have been used to investigate many physical science phenomena, ranging from phase transitions, chemical reactions and crystal growth to grain boundary dynamics. A major limitation of in situ XRD and TEM is a compromise that has to be made between spatial and temporal resolution. Here, we report the development of in situ X-ray nanodiffraction to measure high-resolution diffraction patterns from single grains with up to 5 ms temporal resolution. We observed, for the first time, grain rotation and lattice deformation in chemical reactions induced by X-ray photons: Br(-) + hv → Br + e(-) and e(-) + Ag(+) → Ag(0). The grain rotation and lattice deformation associated with the chemical reactions were quantified to be as fast as 3.25 rad s(-1) and as large as 0.5 Å, respectively. The ability to measure high-resolution diffraction patterns from individual grains with a temporal resolution of several milliseconds is expected to find broad applications in materials science, physics, chemistry and nanoscience.

  6. X-ray induced chemical reaction revealed by in-situ X-ray diffraction and scanning X-ray microscopy in 15 nm resolution (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Ge, Mingyuan; Liu, Wenjun; Bock, David; De Andrade, Vincent; Yan, Hanfei; Huang, Xiaojing; Marschilok, Amy; Takeuchi, Esther; Xin, Huolin; Chu, Yong S.

    2016-09-01

    The detection sensitivity of synchrotron-based X-ray techniques has been largely improved due to the ever increasing source brightness, which have significantly advanced ex-situ and in-situ research for energy materials, such as lithium-ion batteries. However, the strong beam-matter interaction arisen from the high beam flux can significantly modify the material structure. The parasitic beam-induced effect inevitably interferes with the intrinsic material property, which brings difficulties in interpreting experimental results, and therefore requires comprehensive evaluation. Here we present a quantitative in-situ study of the beam-effect on one electrode material Ag2VO2PO4 using four different X-ray probes with different radiation dose rate. The material system we reported exhibits interesting and reversible radiation-induced thermal and chemical reactions, which was further evaluated under electron microscopy to illustrate the underlying mechanism. The work we presented here will provide a guideline in using synchrotron X-rays to distinguish the materials' intrinsic behavior from extrinsic structure changed induced by X-rays, especially in the case of in-situ and operando study where the materials are under external field of either temperature or electric field.

  7. Design and development of an environmental cell for dynamic in situ observation of gas-solid reactions at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Deshmukh, Pushkarraj Vasant

    In situ monitoring of events in transmission electron microscopy provides information on how materials behave in their true state while varying environmental conditions (i.e. temperature and pressure) and exposure to reactant gas mixtures. In-situ results are usually different from static, post-reaction observations because they provide valuable real time---rather than post mortem---information. To facilitate applications that demand in situ observations, a transmission electron microscope specimen holder assembly has been developed in this dissertation. This assembly incorporates a gas flow and heating mechanism along with a novel window-type environmental cell. A controlled mixture of up to four different gases can be circulated through the cell during an experiment. In addition, the specimen can be heated up to a temperature of 1500°C using a specially designed carbon dioxide laser mechanism. This heating technique provides major advantages over conventional methods in terms of product life, specimen heating time and design size. The cell design incorporates a gas reaction chamber less than 1 mm in height, enclosed between a pair of 20 nm thick silicon nitride windows. The chamber can accommodate a specimen or a grid having a diameter of 3 mm and thicknesses in the range of 50 to 100 microns. The volume for the gas environment within the chamber is approximately 3 mm 3 and the gas path length is less than 1 mm. This holder has been designed by incorporating cutting edge heating and Si3N4 window fabrication technology to achieve excellent resolution along with a low thermal drift. Successful application of the holder has been shown to provide scientists with an economical alternative to dedicated transmission electron microscopes for a vast array of in situ applications. These applications include understanding the basic material properties, catalysis reactions, semiconductor device development, and nano structure fabrication.

  8. In situ electrochemical-electron spin resonance investigations of multi-electron redox reaction for organic radical cathodes

    NASA Astrophysics Data System (ADS)

    Huang, Qian; Walter, Eric D.; Cosimbescu, Lelia; Choi, Daiwon; Lemmon, John P.

    2016-02-01

    The multi-electron redox reaction of an organic radical based composite cathode comprised of poly(2,2,6,6- tetramethylpiperidinyloxy-4-yl methacrylate) (PTMA)-Ketjenblack is investigated using an in situ electrochemical-electron spin resonance (ESR) methodology. The experiments allow each electrochemical state to be associated with the chemical state (or environment) of the radical species upon the cell cycling. In situ ESR spectra of the composite cathode demonstrate a two-electron redox reaction of PTMA that is from an aminoxy anion (n-type, at 2.5-2.6 V vs. Li/Li+) via a radical (at 3.2-3.5 V vs. Li/Li+) to an oxoammonium cation (p-type, at 3.7-4.0 V vs. Li/Li+). In particular, an adjustable n-type doping process of PTMA is first observed during the discharging process. Moreover, two different local environments of radical species are found in the PTMA-Ketjenblack composite electrode that includes both concentrated and isolated radicals. These two types of radical species, showing similarities during the redox reaction process while behaving quite different in the non-faradic reaction of ion sorption/desorption on the electrode surface, govern the electrochemical behavior of PTMA based composite electrode.

  9. In situ and real-time monitoring of mechanochemical milling reactions using synchrotron X-ray diffraction.

    PubMed

    Halasz, Ivan; Kimber, Simon A J; Beldon, Patrick J; Belenguer, Ana M; Adams, Frank; Honkimäki, Veijo; Nightingale, Richard C; Dinnebier, Robert E; Friščić, Tomislav

    2013-09-01

    We describe the only currently available protocol for in situ, real-time monitoring of mechanochemical reactions and intermediates by X-ray powder diffraction. Although mechanochemical reactions (inducing transformations by mechanical forces such as grinding and milling) are normally performed in commercially available milling assemblies, such equipment does not permit direct reaction monitoring. We now describe the design and in-house modification of milling equipment that allows the reaction jars of the operating mill to be placed in the path of a high-energy (∼90 keV) synchrotron X-ray beam while the reaction is taking place. Resulting data are analyzed using conventional software, such as TOPAS. Reaction intermediates and products are identified using the Cambridge Structural Database or Inorganic Crystal Structure Database. Reactions are analyzed by fitting the time-resolved diffractograms using structureless Pawley refinement for crystalline phases that are not fully structurally characterized (such as porous frameworks with disordered guests), or the Rietveld method for solids with fully determined crystal structures (metal oxides, coordination polymers).

  10. Exploration of surface chemistry and structure of catalysts under reaction condition and during catalysis with surface-sensitive in-situ techniques

    NASA Astrophysics Data System (ADS)

    Tao, Franklin (Feng)

    2014-03-01

    In heterogeneous catalysis, each catalytic event occurs on a catalytic site. The catalytic site typically consists of a couple of or a few atoms of a catalyst which pack into a structure to offer specific electronic state to turn on a catalytic reaction. Surface structure and chemistry are the key for understanding a catalytic mechanism. From thermodynamic point of view, the surface structure of a catalyst depends on the environment of reactant gases or liquid around the catalyst. Thus, the surface chemistry and structure of a catalyst under a reaction condition or during catalysis (in an environment of reactant(s) with certainly pressure) could be different from those from ex-situ studies. In-situ surface science characterization techniques have been developed for disclosing the hidden surface chemistry and structure of catalysts under reaction conditions or during catalysis. In-situ ambient pressure XPS (AP-XPS) and ambient pressure STM (AP-STM) are two of these surface-sensitive techniques appropriate for exploring surface chemistry and structure, respectively. In this talk, I will present the origin of pressure dependent surface chemistry and structure from thermodynamic point of view. AP-XPS and AP-STM techniques will be introduced briefly. I will focus on (1) the evolution of surface composition and oxidation state of a reducible oxide and how the evolution is correlated to the corresponding catalytic performances, (2) the distribution of surface elements on surface of a bimetallic catalyst under a reaction condition and how a restructuring is used to generate a new surface with different catalytic performance, and (3) geometric restructuring of a metal catalyst surface at atomic scale and how it is related to its catalytic performances. This work is supported by the Chemical Sciences, Geosciences and Biosciences Division, Office of Basic Energy Sciences, Office of Science, U.S. Department of Energy under the grant DE-FG02-12ER1635.

  11. Cd-Based metal-organic frameworks from solvothermal reactions involving in situ aldimine condensation and the highly sensitive detection of Fe(3+) ions.

    PubMed

    Zhang, Xin; Wang, Zhong-Jie; Chen, Shu-Guang; Shi, Zhen-Zhen; Chen, Jin-Xi; Zheng, He-Gen

    2017-02-14

    Four Cd(ii)-based compounds (1-4) were synthesized from solvothermal reactions involving the in situ aldimine condensation of an o-diamino-functionalized precursor 3,6-di(4H-imidazol-4-yl)benzene-1,2-diamine (L), Cd(NO3)2·4H2O and aldehyde. Two modes of cycloaddition ([4 + 1] cycloaddition and [4 + 2] cycloaddition) occurred during condensation, causing the in situ generation of two benzimidazole derivative ligands (L1 and L3) and a quinoxaline derivative ligand (L2). Furthermore, the chemical selectivity of the condensation was studied, where the condensation of o-diamino and the aldehyde is more stable and easy to operate. This strategy enriches the synthesis method of MOFs. Additionally, compound 2 containing uncoordinated quinoxaline N atoms showed excellent luminescent sensitivity for Fe(3+) detection.

  12. Surface reactions, hydride kinetics and in situ boron doping of silicon and germanium

    NASA Astrophysics Data System (ADS)

    Gong, Bin

    1999-11-01

    A first principal model was developed for boron in situ doping during chemical vapor deposition, to explain and qualitatively predict the effect boron has on Si film growth rate. The study explored H2 desorption from Si(100), B/Si(100), Ge(100), B/Ge(100), and ion-roughened Si(100) surfaces. Diborane was chosen as the boron source. Hydrogen desorption from Si(100) surfaces with extremely low boron coverage (thetaB < 0.01 ML) showed there is no electronic effect leading to a lower energy monohydride or dihydride desorption state. Hydrogen desorption from B/Si(100) and B/Ge(100) containing 0.04 ML < thetaB < 0.5 ML reveals a boron-weakened trihydride state formation and induces a low temperature H2 desorption state. Boron is also shown to deactivate dangling bonds and inhibit adsorption of H. Growth rate changes with boron coverage are described using the trihydride state and deactivated dangling bonds.

  13. Uranyl Carboxyphosphonates Derived from Hydrothermal in Situ Ligand Reaction: Syntheses, Structures, and Computational Investigations.

    PubMed

    Wu, Dai; Bai, Xiaojing; Tian, Hong-Rui; Yang, Weiting; Li, Zewen; Huang, Qing; Du, Shiyu; Sun, Zhong-Ming

    2015-09-08

    Two uranyl carboxyphosphonates (H2dipy)[(UO2)3(H2O)2(H2DPTP)2]·2H2O (DPTP-U1) and (H2bbi)[(UO2)4(H2O)2(HDPTP)2] (DPTP-U2) [H6DPTP = 2,5-diphosphonoterephthalic acid, dipy = 4,4'-bipyridine, bbi = 1,1'-(1,4-butanediyl)bis(imidazole)] were synthesized under hydrothermal conditions. The carboxyphosphonate ligand was formed through the in situ oxidation of (2,5-dimethyl-1,4-phenylene)diphosphonic acid mediated by UO2(2+). Single-crystal X-ray diffraction analyses reveal that DPTP-U1 possesses uranyl carboxyphosphonate layers that are separated by protonated dipy cations. Whereas DPTP-U2 is in a three-dimensional framework structure with channels filled by protonated bbi cations. The computational investigations give an insight into the nature of bonding interactions between uranium(VI) and carboxyphosphonate ligand. The spectroscopic properties were also studied.

  14. Alpha resonant scattering for astrophysical reaction studies

    SciTech Connect

    Yamaguchi, H.; Kahl, D.; Nakao, T.; Wakabayashi, Y.; Kubano, S.; Hashimoto, T.; Hayakawa, S.; Kawabata, T.; Iwasa, N.; Teranishi, T.; Kwon, Y. K.; Binh, D. N.; Khiem, L. H.; Duy, N. G.

    2014-05-02

    Several alpha-induced astrophysical reactions have been studied at CRIB (CNS Radioactive Ion Beam separator), which is a low-energy RI beam separator at Center for Nuclear Study (CNS) of the University of Tokyo. One of the methods to study them is the α resonant scattering using the thick-target method in inverse kinematics. Among the recent studies at CRIB, the measurement of {sup 7}Be+α resonant scattering is discussed. Based on the result of the experiment, we evaluated the contributions of high-lying resonances for the {sup 7}Be(α,γ) reaction, and proposed a new cluster band in {sup 11}C.

  15. In-Situ Cure Monitoring of the Immidization Reaction of PMR-15

    NASA Technical Reports Server (NTRS)

    Cossins, Sheryl; Kellar, Jon J.; Winter, Robb M.

    1997-01-01

    Glass fiber reinforced polymer composites are becoming widely used in industry. With this increase in production, an in-situ method of quality control for the curing of the polymer is desirable. This would allow for the production of high-quality parts having more uniform properties.' Recently, in-situ fiber optic monitoring of polymer curing has primarily focused on epoxy resins and has been performed by Raman or fluorescence methods. In addition, some infrared (IR) investigations have been performed using transmission or ATR cells. An alternate IR approach involves using optical fibers as a sensor by utilizing evanescent wave spectroscopy.

  16. In situ probing of the active site geometry of ultrathin nanowires for the oxygen reduction reaction

    SciTech Connect

    Liu, Haiqing; Wong, Stanislaus S.; An, Wei; Li, Yuanyuan; Frenkel, Anatoly I.; Sasaki, Kotaro; Koenigsmann, Christopher; Su, Dong; Anderson, Rachel M.; Crooks, Richard M.; Adzic, Radoslav R.; Liu, Ping

    2015-09-24

    To create truly effective electrocatalysts for the cathodic reaction governing proton exchange membrane fuel cells (PEMFC), namely the oxygen reduction reaction (ORR), necessitates an accurate and detailed structural understanding of these electrocatalysts, especially at the nanoscale, and to precisely correlate that structure with demonstrable performance enhancement. To address this key issue, we have combined and interwoven theoretical calculations with experimental, spectroscopic observations in order to acquire useful structural insights into the active site geometry with implications for designing optimized nanoscale electrocatalysts with rationally predicted properties. Specifically, we have probed ultrathin (~2 nm) core–shell Pt~Pd9Au nanowires, which have been previously shown to be excellent candidates for ORR in terms of both activity and long-term stability, from the complementary perspectives of both DFT calculations and X-ray absorption spectroscopy (XAS). The combination and correlation of data from both experimental and theoretical studies has revealed for the first time that the catalytically active structure of our ternary nanowires can actually be ascribed to a PtAu~Pd configuration, comprising a PtAu binary shell and a pure inner Pd core. Moreover, we have plausibly attributed the resulting structure to a specific synthesis step, namely the Cu underpotential deposition (UPD) followed by galvanic replacement with Pt. Thus, the fundamental insights gained into the performance of our ultrathin nanowires from our demonstrated approach will likely guide future directed efforts aimed at broadly improving upon the durability and stability of nanoscale electrocatalysts in general.

  17. In Situ Probing of the Active Site Geometry of Ultrathin Nanowires for the Oxygen Reduction Reaction.

    PubMed

    Liu, Haiqing; An, Wei; Li, Yuanyuan; Frenkel, Anatoly I; Sasaki, Kotaro; Koenigsmann, Christopher; Su, Dong; Anderson, Rachel M; Crooks, Richard M; Adzic, Radoslav R; Liu, Ping; Wong, Stanislaus S

    2015-10-07

    To create truly effective electrocatalysts for the cathodic reaction governing proton exchange membrane fuel cells (PEMFC), namely the oxygen reduction reaction (ORR), necessitates an accurate and detailed structural understanding of these electrocatalysts, especially at the nanoscale, and to precisely correlate that structure with demonstrable performance enhancement. To address this key issue, we have combined and interwoven theoretical calculations with experimental, spectroscopic observations in order to acquire useful structural insights into the active site geometry with implications for designing optimized nanoscale electrocatalysts with rationally predicted properties. Specifically, we have probed ultrathin (∼2 nm) core-shell Pt∼Pd9Au nanowires, which have been previously shown to be excellent candidates for ORR in terms of both activity and long-term stability, from the complementary perspectives of both DFT calculations and X-ray absorption spectroscopy (XAS). The combination and correlation of data from both experimental and theoretical studies has revealed for the first time that the catalytically active structure of our ternary nanowires can actually be ascribed to a PtAu∼Pd configuration, comprising a PtAu binary shell and a pure inner Pd core. Moreover, we have plausibly attributed the resulting structure to a specific synthesis step, namely the Cu underpotential deposition (UPD) followed by galvanic replacement with Pt. Hence, the fundamental insights gained into the performance of our ultrathin nanowires from our demonstrated approach will likely guide future directed efforts aimed at broadly improving upon the durability and stability of nanoscale electrocatalysts in general.

  18. In situ probing of the active site geometry of ultrathin nanowires for the oxygen reduction reaction

    DOE PAGES

    Liu, Haiqing; Wong, Stanislaus S.; An, Wei; ...

    2015-09-24

    To create truly effective electrocatalysts for the cathodic reaction governing proton exchange membrane fuel cells (PEMFC), namely the oxygen reduction reaction (ORR), necessitates an accurate and detailed structural understanding of these electrocatalysts, especially at the nanoscale, and to precisely correlate that structure with demonstrable performance enhancement. To address this key issue, we have combined and interwoven theoretical calculations with experimental, spectroscopic observations in order to acquire useful structural insights into the active site geometry with implications for designing optimized nanoscale electrocatalysts with rationally predicted properties. Specifically, we have probed ultrathin (~2 nm) core–shell Pt~Pd9Au nanowires, which have been previously shownmore » to be excellent candidates for ORR in terms of both activity and long-term stability, from the complementary perspectives of both DFT calculations and X-ray absorption spectroscopy (XAS). The combination and correlation of data from both experimental and theoretical studies has revealed for the first time that the catalytically active structure of our ternary nanowires can actually be ascribed to a PtAu~Pd configuration, comprising a PtAu binary shell and a pure inner Pd core. Moreover, we have plausibly attributed the resulting structure to a specific synthesis step, namely the Cu underpotential deposition (UPD) followed by galvanic replacement with Pt. Thus, the fundamental insights gained into the performance of our ultrathin nanowires from our demonstrated approach will likely guide future directed efforts aimed at broadly improving upon the durability and stability of nanoscale electrocatalysts in general.« less

  19. Treatability study to evaluate in situ chlorinated solvent and pesticide bioremediation

    SciTech Connect

    Lige, J.E.; MacFarlane, I.D.; Hundt, T.R.

    1995-12-31

    Exploiting microbial reactions to remediate chlorinated solvents and pesticide contamination appeared to be an attractive remedial alternative for a site located at the Dover Air Force Base in Dover, Delaware. To generate data to evaluate the feasibility of implementing enhanced in situ bioremediation as a remedial technique, a relatively inexpensive and rapid treatability study was designed. Batch microcosm studies were used to mimic in situ redox conditions (oxygenated and unoxygenated) and methanotrophic conditions. No evidence of target compound degradation existed under either the amended or unamended aerobic conditions; however, the activity observed in some samples under anaerobic conditions suggested transformation of chlorinated compounds and pesticides. Results showed that biodegradation may be inducible under certain conditions, but time lags and efficiencies could be expected to vary considerably. A remedial alternative analysis could not be expected to achieve the degree of accuracy and precision necessary without the data resulting from this study.

  20. Theoretical studies of chemical reaction dynamics

    SciTech Connect

    Schatz, G.C.

    1993-12-01

    This collaborative program with the Theoretical Chemistry Group at Argonne involves theoretical studies of gas phase chemical reactions and related energy transfer and photodissociation processes. Many of the reactions studied are of direct relevance to combustion; others are selected they provide important examples of special dynamical processes, or are of relevance to experimental measurements. Both classical trajectory and quantum reactive scattering methods are used for these studies, and the types of information determined range from thermal rate constants to state to state differential cross sections.

  1. Single-Tube Reaction Using Perfluorocarbons: A Prerequisite Step Leading to the Whole-Slide In Situ Technique on Histopathological Slides

    PubMed Central

    Chen, Yi-Chang; Teng, Tsung-Han; Tsai, Jane S.-C.; Huang, Hsien-Da; Chang, Yih-Leong

    2016-01-01

    Developing a robust, novel method for performing multiple reactions in a single tube is not only time- and cost-saving but also critical for future high-throughput whole-slide in situ techniques on diseased tissues. In this study, we introduce the use of perfluorocarbons and compound-coated magnetic particles to create pseudochambers in a single tube, allowing different reactions to be performed in different phases. Perfluorocarbons also serve as cell lysis buffer and polymerase chain reaction (PCR) buffer owing to their highly penetrating, repellent and emulsifiable properties. Using this method, nucleic acids can be isolated and purified from various sample types and sizes, followed by PCR, real-time PCR, or multiplex PCR in the same tube. No incubation or enzyme digesting time is needed and the risk of cross-contamination is reduced. Tests can be performed in microemulsions (water-in-oil droplets) containing sequence-specific captures and probes for further high-throughput detection. We present a simple, quick, and robust procedure as a prerequisite step to future high-throughput in situ techniques. PMID:27336363

  2. Ultraviolet-Visible (UV-Vis) Microspectroscopic System Designed for the In Situ Characterization of the Dehydrogenation Reaction Over Platinum Supported Catalytic Microchannel Reactor.

    PubMed

    Suarnaba, Emee Grace Tabares; Lee, Yi Fuan; Yamada, Hiroshi; Tagawa, Tomohiko

    2016-11-01

    An ultraviolet visible (UV-Vis) microspectroscopic system was designed for the in situ characterization of the activity of the silica supported platinum (Pt) catalyst toward the dehydrogenation of 1-methyl-1,4-cyclohexadiene carried out in a custom-designed catalytic microreactor cell. The in situ catalytic microreactor cell (ICMC) with inlet/outlet ports was prepared using quartz cover as the optical window to facilitate UV-Vis observation. A fabricated thermometric stage was adapted to the UV-Vis microspectrophotometer to control the reaction temperature inside the ICMC. The spectra were collected by focusing the UV-Vis beam on a 30 × 30 µm area at the center of ICMC. At 393 K, the sequential measurement of the spectra recorded during the reaction exhibited a broad absorption peak with maximum absorbance at 260 nm that is characteristic for gaseous toluene. This result indicates that the silica supported Pt catalyst is active towards the dehydrogenation of 1-methyl-1,4-cyclohexadiene at the given experimental conditions. The onset of coke formation was also detected based on the appearance of absorption bands at 300 nm. The UV-Vis microspectroscopic system developed can be used further in studying the mechanism of the dehydrogenation reaction.

  3. Determination of redox reaction rates and orders by in situ liquid cell electron microscopy of Pd and Au solution growth

    DOE PAGES

    Sutter, Eli A.; Sutter, Peter W.

    2014-11-19

    In-situ liquid cell transmission and scanning transmission electron microscopy (TEM/STEM) experiments are important as they provide direct insight into processes in liquids, such as solution growth of nanoparticles among others. In liquid cell TEM/STEM redox reaction experiments the hydrated electrons e⁻aq created by the electron beam are responsible for the reduction of metal-ion complexes. Here we investigate the rate equation of redox reactions involving reduction by e⁻aq generated by the electron beam during in-situ liquid TEM/STEM. Specifically we consider the growth of Pd on Au seeds in aqueous solutions containing Pd-chloro complexes. From the quantification of the rate of Pdmore » deposition at different electron beam currents and as a function of distance from a stationary, nanometer-sized exciting beam, we determine that the reaction is first order with respect to the concentration of hydrated electrons, [e⁻aq]. In addition, by comparing Pd- and Au-deposition, we further demonstrate that measurements of the local deposition rate on nanoparticles in the solution via real-time imaging can be used to measure not only [e⁻aq] but also the rate of reduction of a metal-ion complex to zero-valent metal atoms in solution.« less

  4. Determination of redox reaction rates and orders by in situ liquid cell electron microscopy of Pd and Au solution growth

    SciTech Connect

    Sutter, Eli A.; Sutter, Peter W.

    2014-11-19

    In-situ liquid cell transmission and scanning transmission electron microscopy (TEM/STEM) experiments are important as they provide direct insight into processes in liquids, such as solution growth of nanoparticles among others. In liquid cell TEM/STEM redox reaction experiments the hydrated electrons e⁻aq created by the electron beam are responsible for the reduction of metal-ion complexes. Here we investigate the rate equation of redox reactions involving reduction by e⁻aq generated by the electron beam during in-situ liquid TEM/STEM. Specifically we consider the growth of Pd on Au seeds in aqueous solutions containing Pd-chloro complexes. From the quantification of the rate of Pd deposition at different electron beam currents and as a function of distance from a stationary, nanometer-sized exciting beam, we determine that the reaction is first order with respect to the concentration of hydrated electrons, [e⁻aq]. In addition, by comparing Pd- and Au-deposition, we further demonstrate that measurements of the local deposition rate on nanoparticles in the solution via real-time imaging can be used to measure not only [e⁻aq] but also the rate of reduction of a metal-ion complex to zero-valent metal atoms in solution.

  5. Design and Operation of a High Pressure Reaction Cell for in situ X-ray Absorption Spectroscopy

    SciTech Connect

    Bare,S.; Yang, N.; Kelly, S.; Mickelson, G.; Modica, F.

    2007-01-01

    X-ray absorption spectroscopy measurements of catalytic reactions have been instrumental in advancing the understanding of catalytic processes. These measurements require an in situ catalysis reaction cell with unique properties. Here we describe the design and initial operation of an in situ/operando catalysis reaction cell for transmission X-ray absorption spectroscopy measurements. The cell is designed: to be an ideal catalytic reactor with no mass transfer effects; to give the same conversion and selectivity under similar space velocities as standard laboratory micro-reactors; to be operational temperatures up to 600 {sup o}C and pressures up to 14 bar; to be X-ray transparent allowing XAS measurement to be collected in transmission for all elements with Z {>=} 23 (vanadium K-edge at 5.5 keV); to measure the actual catalyst bed temperature; to not use o-ring seals, or water cooling; to be robust, compact, easy to assemble, and use, and relatively low cost to produce. The heart of the cell is fabricated from an X-ray transparent beryllium tube that forms a plug flow reactor. XAFS data recorded during the reduction of a Re/{gamma}-A{sub 2}O{sub 3} catalyst as a function of hydrogen pressure from 0.05 to 8 bar, and from a Pt-Sn/{gamma}-A{sub 2}O{sub 3} catalyst during n-heptane reforming are given as initial examples of the versatility of the reactor.

  6. Combining direct residence time measurements and biogeochemistry to calculate in-situ reaction rates in the hyporheic zone

    NASA Astrophysics Data System (ADS)

    Pittroff, Marco; Gilfedder, Benjamin

    2015-04-01

    The hyporheic zone is an active interface between groundwater, riparian and surface water systems. Exchange and reaction of water, nutrients, and organic matter occur due to variations in surface and groundwater flow regimes, bed topography and active biogeochemistry fuelled by bioavailable carbon. There has been an increasing focus on coupling the residence time of surface water in the hyporheic zone with biogeochemical reactions. However, there are very few tracers that can be used to measure residence times in-situ, especially in complex groundwater-surface water settings. In this work we have used the natural radioisotope Radon (222Rn) as an in-situ tracer for river water residence time in a riffle-pool sequence (Rote Main River), and combined this information with biogeochemical parameters (DOC and C quality, O3, NO3, CO2). We can clearly observe a dependence of reaction progress on the water residence times, with oxygen and nitrate reduction following inverse logarithmic trends as a function of time. By comparing with initial concentrations (the river end member) with riverbed levels we have estimated first-order in-situ reduction rates for nitrate and oxygen. Nitrate reduction rates are at the higher end of published values, which is likely due to the continual supply of bioavailable carbon from the river system. This work helps to better understand the function and efficiency of the hyporheic zone as a natural filter for redox sensitive species such as nitrate at the groundwater - steam interface. It also provides a useful method for estimating residence times in complex, higher order river systems.

  7. An in situ study of resin-assisted solvothermal metal-organic framework synthesis

    SciTech Connect

    Moorhouse, Saul J.; Wu, Yue; O’Hare, Dermot

    2016-04-15

    A newly developed in situ monochromatic high-energy X-ray diffraction setup was used to investigate the synthesis of MOFs using cation-impregnated polymer resin beads as a ion source. The Co–NDC–DMF (NDC=2,6-naphthalenedicarboxylate; DMF=dimethylformamide) system was investigated, a system which is known to produce at least three distinct frameworks. It was found that the resin-assisted synthesis results in the preferential formation of a topology previously impossible to synthesise in bulk, while the comparable nitrate-salt synthesis appeared to form an alternative phases. It was also found that the resin-assisted synthesis is highly diffusion-controlled. - Graphical abstract: In situ monochromatic high-energy X-ray diffraction study of a MOF synthesis. - Highlights: • Resin-assisted solvothermal MOF synthesis was studied using in situ diffraction. • Full kinetics of reaction can be obtained from in situ data. • Kinetics show that this resin-assisted synthesis is diffusion controlled. • Resin-assisted synthesis enables the production of an alternative bulk phase.

  8. The design of dextran-based hypoxia-inducible hydrogels via in situ oxygen-consuming reaction.

    PubMed

    Park, Kyung Min; Blatchley, Michael R; Gerecht, Sharon

    2014-11-01

    Hypoxia plays a critical role in the development and wound healing process, as well as a number of pathological conditions. Here, dextran-based hypoxia-inducible (Dex-HI) hydrogels formed with in situ oxygen consumption via a laccase-medicated reaction are reported. Oxygen levels and gradients were accurately predicted by mathematical simulation. It is demonstrated that Dex-HI hydrogels provide prolonged hypoxic conditions up to 12 h. The Dex-HI hydrogel offers an innovative approach to delineate not only the mechanism by which hypoxia regulates cellular responses, but may facilitate the discovery of new pathways involved in the generation of hypoxic and oxygen gradient environments.

  9. Underwater microscopy for in situ studies of benthic ecosystems.

    PubMed

    Mullen, Andrew D; Treibitz, Tali; Roberts, Paul L D; Kelly, Emily L A; Horwitz, Rael; Smith, Jennifer E; Jaffe, Jules S

    2016-07-12

    Microscopic-scale processes significantly influence benthic marine ecosystems such as coral reefs and kelp forests. Due to the ocean's complex and dynamic nature, it is most informative to study these processes in the natural environment yet it is inherently difficult. Here we present a system capable of non-invasively imaging seafloor environments and organisms in situ at nearly micrometre resolution. We overcome the challenges of underwater microscopy through the use of a long working distance microscopic objective, an electrically tunable lens and focused reflectance illumination. The diver-deployed instrument permits studies of both spatial and temporal processes such as the algal colonization and overgrowth of bleaching corals, as well as coral polyp behaviour and interspecific competition. By enabling in situ observations at previously unattainable scales, this instrument can provide important new insights into micro-scale processes in benthic ecosystems that shape observed patterns at much larger scales.

  10. Underwater microscopy for in situ studies of benthic ecosystems

    NASA Astrophysics Data System (ADS)

    Mullen, Andrew D.; Treibitz, Tali; Roberts, Paul L. D.; Kelly, Emily L. A.; Horwitz, Rael; Smith, Jennifer E.; Jaffe, Jules S.

    2016-07-01

    Microscopic-scale processes significantly influence benthic marine ecosystems such as coral reefs and kelp forests. Due to the ocean's complex and dynamic nature, it is most informative to study these processes in the natural environment yet it is inherently difficult. Here we present a system capable of non-invasively imaging seafloor environments and organisms in situ at nearly micrometre resolution. We overcome the challenges of underwater microscopy through the use of a long working distance microscopic objective, an electrically tunable lens and focused reflectance illumination. The diver-deployed instrument permits studies of both spatial and temporal processes such as the algal colonization and overgrowth of bleaching corals, as well as coral polyp behaviour and interspecific competition. By enabling in situ observations at previously unattainable scales, this instrument can provide important new insights into micro-scale processes in benthic ecosystems that shape observed patterns at much larger scales.

  11. Underwater microscopy for in situ studies of benthic ecosystems

    PubMed Central

    Mullen, Andrew D.; Treibitz, Tali; Roberts, Paul L. D.; Kelly, Emily L. A.; Horwitz, Rael; Smith, Jennifer E.; Jaffe, Jules S.

    2016-01-01

    Microscopic-scale processes significantly influence benthic marine ecosystems such as coral reefs and kelp forests. Due to the ocean's complex and dynamic nature, it is most informative to study these processes in the natural environment yet it is inherently difficult. Here we present a system capable of non-invasively imaging seafloor environments and organisms in situ at nearly micrometre resolution. We overcome the challenges of underwater microscopy through the use of a long working distance microscopic objective, an electrically tunable lens and focused reflectance illumination. The diver-deployed instrument permits studies of both spatial and temporal processes such as the algal colonization and overgrowth of bleaching corals, as well as coral polyp behaviour and interspecific competition. By enabling in situ observations at previously unattainable scales, this instrument can provide important new insights into micro-scale processes in benthic ecosystems that shape observed patterns at much larger scales. PMID:27403715

  12. Synthesis and characterization of Ag nanoshells by a facile sacrificial template route through in situ replacement reaction.

    PubMed

    Chen, Minghai; Gao, Lian

    2006-06-26

    A facile in situ replacement reaction route was successfully introduced for synthesizing Ag nanoshells with outer diameters of 40-50 nm and inner diameters of 20-30 nm using Co nanoparticles as sacrificial templates. The products were characterized by XRD, TEM, SAED, and UV-vis absorption spectra. The formation mechanism was also discussed. The reaction driving force comes from the large reduction potential gap between the Ag+/Ag and Co2+/Co redox couples, which results in the consumption of Co cores and the formation of a hollow cavity of Ag nanoshells. The UV-vis spectrum of this nanostructure exhibits a distinct difference from that of solid nanoparticles, which makes it a good candidate for application in photothermal materials.

  13. In-situ x-ray absorption study of copper films in ground watersolutions

    SciTech Connect

    Kvashnina, K.O.; Butorin, S.M.; Modin, A.; Soroka, I.; Marcellini, M.; Nordgren, J.; Guo, J.-H.; Werme, L.

    2007-10-29

    This study illustrates how the damage from copper corrosion can be reduced by modifying the chemistry of the copper surface environment. The surface modification of oxidized copper films induced by chemical reaction with Cl{sup -} and HCO{sub 3}{sup -} in aqueous solutions was monitored by in situ X-ray absorption spectroscopy. The results show that corrosion of copper can be significantly reduced by adding even a small amount of sodium bicarbonate. The studied copper films corroded quickly in chloride solutions, whereas the same solution containing 1.1 mM HCO{sub 3}{sup -} prevented or slowed down the corrosion processes.

  14. In situ spectroscopy of ligand exchange reactions at the surface of colloidal gold and silver nanoparticles

    NASA Astrophysics Data System (ADS)

    Dinkel, Rebecca; Peukert, Wolfgang; Braunschweig, Björn

    2017-04-01

    Gold and silver nanoparticles with their tunable optical and electronic properties are of great interest for a wide range of applications. Often the ligands at the surface of the nanoparticles have to be exchanged in a second step after particle formation in order to obtain a desired surface functionalization. For many techniques, this process is not accessible in situ. In this review, we present second-harmonic scattering (SHS) as an inherently surface sensitive and label-free optical technique to probe the ligand exchange at the surface of colloidal gold and silver nanoparticles in situ and in real time. First, a brief introduction to SHS and basic features of the SHS of nanoparticles are given. After that, we demonstrate how the SHS intensity decrease can be correlated to the thiol coverage which allows for the determination of the Gibbs free energy of adsorption and the surface coverage.

  15. Laser Studies of Gas Phase Radical Reaction.

    DTIC Science & Technology

    1985-11-30

    1nai Irvest-aator Or.G. Hancock gn; FILE CO, Contr3ctor : Oxford University . Physical Chemistry Laboratory. South Parks Road.AD-A 193 689 Oxfor o~d...HIF spectrum and study of reaction of this and the CCI radical with atoms vi) sea;rchtrr; f(r FC) ’ndlict of the 0 *CF, reaction. OXFORD UNIVERSITY -. - SOUTH...0 Awtilability Codes I Avail ’and/or Dis Spcal0 Spoo OXFORD UNIVERSITY Tt SOUTH PARKS ROAD OXFCRD OXFORD � X3Z U.S. Army Contract DAJA45-85-C-0034

  16. Molecular Beam Studies of Low Energy Reactions.

    DTIC Science & Technology

    1983-03-31

    COMPLETING PORN . REPORT NUMBER 1 2. GOVT ACCESSION NO. S. RECIPIENT’S CATALOG NUMBER A D A Oaq J- 4. TITLE (And Subtitle) . TYPE OF REPORT & PERIOD COVERED...Gatlinburg, Tenn . in 1981. 2+ c) Studies were made of the charge transfer reaction Ar + Ar 4 2+ Ar + Ar at relative energies from 2 to 1000 eV. Reasons for

  17. Evaluation of a Cell Penetrating Prenylated Peptide Lacking an Intrinsic Fluorophore via in situ Click Reaction

    PubMed Central

    Ochocki, Joshua D.; Mullen, Daniel G.; Wattenberg, Elizabeth V.; Distefano, Mark D.

    2011-01-01

    Protein prenylation involves the addition of either a farnesyl (C15) or geranylgeranyl (C20) isoprenoid moiety onto the C-terminus of many proteins. This natural modification serves to direct a protein to the plasma membrane of the cell. A recently discovered application of prenylated peptides is that they have inherent cell-penetrating ability, and are hence termed cell penetrating prenylated peptides. These peptides are able to efficiently cross the cell membrane in an ATP independent, non-endocytotic manner and it was found that the sequence of the peptide does not affect uptake, so long as the geranylgeranyl group is still present. The present study investigates the effect of removing the fluorophore from the peptides and investigating the uptake by confocal microsopy and flow cytometry. Our results show that the fluorophore is not necessary for uptake of these peptides. This information is significant because it indicates that the prenyl group is the major determinant in allowing these peptides to enter cells; the hydrophobic fluorophore has little effect. Moreover, these studies demonstrate the utility of the Cu-catalyzed click reaction for monitoring the entry of nonfluorescent peptides into cells. PMID:21632248

  18. Evaluation of a cell penetrating prenylated peptide lacking an intrinsic fluorophore via in situ click reaction.

    PubMed

    Ochocki, Joshua D; Mullen, Daniel G; Wattenberg, Elizabeth V; Distefano, Mark D

    2011-09-01

    Protein prenylation involves the addition of either a farnesyl (C(15)) or geranylgeranyl (C(20)) isoprenoid moiety onto the C-terminus of many proteins. This natural modification serves to direct a protein to the plasma membrane of the cell. A recently discovered application of prenylated peptides is that they have inherent cell-penetrating ability, and are hence termed cell penetrating prenylated peptides. These peptides are able to efficiently cross the cell membrane in an ATP independent, non-endocytotic manner and it was found that the sequence of the peptide does not affect uptake, so long as the geranylgeranyl group is still present [Wollack, J. W.; Zeliadt, N. A.; Mullen, D. G.; Amundson, G.; Geier, S.; Falkum, S.; Wattenberg, E. V.; Barany, G.; Distefano, M. D. Multifunctional Prenylated Peptides for Live Cell Analysis. J. Am. Chem. Soc.2009, 131, 7293-7303]. The present study investigates the effect of removing the fluorophore from the peptides and investigating the uptake by confocal microscopy and flow cytometry. Our results show that the fluorophore is not necessary for uptake of these peptides. This information is significant because it indicates that the prenyl group is the major determinant in allowing these peptides to enter cells; the hydrophobic fluorophore has little effect. Moreover, these studies demonstrate the utility of the Cu-catalyzed click reaction for monitoring the entry of nonfluorescent peptides into cells.

  19. Envisioning an enzymatic Diels-Alder reaction by in situ acid-base catalyzed diene generation.

    PubMed

    Linder, Mats; Johansson, Adam Johannes; Manta, Bianca; Olsson, Philip; Brinck, Tore

    2012-06-07

    We present and evaluate a new and potentially efficient route for enzyme-mediated Diels-Alder reactions, utilizing general acid-base catalysis. The viability of employing the active site of ketosteroid isomerase is demonstrated.

  20. Laser Studies of Gas Phase Radical Reactions.

    DTIC Science & Technology

    1989-01-01

    Acremonium chrysogenum , was prepared according to the published procedure [6]. This fungal enzyme had a specific activity of 0.023 IUmg1, and was estimated to...Dist-lbitionj Avdielbiity Codes jAvail atidjor Dist 6a A-I . p -1- Laser Studies of Gas Phase Radical Reactions G. Hancock Physical Chemistry...some additional experiments concerning the formation of carbene radicals in liquid phase enzyme cleavage studies are described. Keywords Laser

  1. A novel fluorescence detection method for in situ hybridization, based on the alkaline phosphatase-fast red reaction.

    PubMed

    Speel, E J; Schutte, B; Wiegant, J; Ramaekers, F C; Hopman, A H

    1992-09-01

    We have used naphthol-ASMX-phosphate and Fast Red TR in combination with alkaline phosphatase (APase) to produce fluorescent precipitated reaction products in a non-radioactive in situ hybridization (ISH) method. To obtain optimal and discrete localization of the strongly red fluorescent ISH signals, the enzyme precipitation procedure was optimized. The optimal reaction time and the concentrations of substrate and capture agent were determined. Furthermore, polyvinyl alcohol (PVA) was used to increase the viscosity of the reaction mixture and thus to reduce diffusion of the reaction product. Our results show that the APase-Fast Red detection method has at least the same sensitivity as currently observed in other immunofluorescent detection systems. A single copy DNA sequence of 15.8 KB could be localized with high efficiency in metaphase spreads and in interphase nuclei. Double labeling procedures, in which the FITC- and azo-dye fluorescence are combined, are also feasible. The red fluorescent ISH signals showed hardly any fading as compared with FITC fluorescence on exposure to either light from the mercury-arc lamp or laser light. Therefore, these red fluorescent signals with a virtually permanent character allow a better analysis and three-dimensional localization of such cytochemically detected genomic fractions by means of confocal scanning laser microscopy as compared with the use of FITC, TRITC, or Texas Red as label.

  2. Early age hydration and pozzolanic reaction in natural zeolite blended cements: Reaction kinetics and products by in situ synchrotron X-ray powder diffraction

    SciTech Connect

    Snellings, R.; Mertens, G.; Cizer, O.; Elsen, J.

    2010-12-15

    The in situ early-age hydration and pozzolanic reaction in cements blended with natural zeolites were investigated by time-resolved synchrotron X-ray powder diffraction with Rietveld quantitative phase analysis. Chabazite and Na-, K-, and Ca-exchanged clinoptilolite materials were mixed with Portland cement in a 3:7 weight ratio and hydrated in situ at 40 {sup o}C. The evolution of phase contents showed that the addition of natural zeolites accelerates the onset of C{sub 3}S hydration and precipitation of CH and AFt. Kinetic analysis of the consumption of C{sub 3}S indicates that the enveloping C-S-H layer is thinner and/or less dense in the presence of alkali-exchanged clinoptilolite pozzolans. The zeolite pozzolanic activity is interpreted to depend on the zeolite exchangeable cation content and on the crystallinity. The addition of natural zeolites alters the structural evolution of the C-S-H product. Longer silicate chains and a lower C/S ratio are deduced from the evolution of the C-S-H b-cell parameter.

  3. XAFS characterization of industrial catalysts: in situ study of phase transformation of nickel sulfide

    NASA Astrophysics Data System (ADS)

    Wang, J.; Jia, Z.; Wang, Q.; Zhao, S.; Xu, Z.; Yang, W.; Frenkel, A. I.

    2016-05-01

    The online sulfiding process for nickel-contained catalyst often ends up with a nickel sulfide mixture in refinery plant. To elucidate the local environment of nickel and its corresponding sulfur species, a model catalyst (nickel sulfide) and model thermal process were employed to explore the possibilities for characterization of real catalysts in industrial conditions. The present investigation shows effectiveness of in situ XANES and EXAFS measurements for studying the phase stability and phase composition in these systems, which could be used to simulate real sulfiding process in industrial reactions, such as hydrodesulfurizations of oil.

  4. XAS/EXAFS studies of Ge nanoparticles produced by reaction between Mg 2 Ge and GeCl 4

    NASA Astrophysics Data System (ADS)

    Pugsley, Andrew J.; Bull, Craig L.; Sella, Andrea; Sankar, Gopinathan; McMillan, Paul F.

    2011-09-01

    We present results of an XAS and EXAFS study of the synthesis of Ge nanoparticles formed by a metathesis reaction between Mg 2Ge and GeCl 4 in diglyme (diethylene glycol dimethyl ether). The progress of the formation reaction and the products formed at various stages in the processing was characterised by TEM and optical spectroscopy as well as in situ XAS/EXAFS studies using specially designed reaction cells.

  5. Small-volume, ultrahigh-vacuum-compatible high-pressure reaction cell for combined kinetic and in situ IR spectroscopic measurements on planar model catalysts

    SciTech Connect

    Zhao, Z.; Diemant, T.; Haering, T.; Rauscher, H.; Behm, R.J.

    2005-12-15

    We describe the design and performance of a high-pressure reaction cell for simultaneous kinetic and in situ infrared reflection (IR) spectroscopic measurements on model catalysts at elevated pressures, between 10{sup -3} and 10{sup 3} mbars, which can be operated both as batch reactor and as flow reactor with defined gas flow. The cell is attached to an ultrahigh-vacuum (UHV) system, which is used for sample preparation and also contains facilities for sample characterization. Specific for this design is the combination of a small cell volume, which allows kinetic measurements with high sensitivity under batch or continuous flow conditions, the complete isolation of the cell from the UHV part during UHV measurements, continuous temperature control during both UHV and high-pressure operation, and rapid transfer between UHV and high-pressure stage. Gas dosing is performed by a designed gas-handling system, which allows operation as flow reactor with calibrated gas flows at adjustable pressures. To study the kinetics of reactions on the model catalysts, a quadrupole mass spectrometer is connected to the high-pressure cell. IR measurements are possible in situ by polarization-modulation infrared reflection-absorption spectroscopy, which also allows measurements at elevated pressures. The performance of the setup is demonstrated by test measurements on the kinetics for CO oxidation and the CO adsorption on a Au/TiO{sub 2}/Ru(0001) model catalyst film at 1-50 mbar total pressure.

  6. Small-volume, ultrahigh-vacuum-compatible high-pressure reaction cell for combined kinetic and in situ IR spectroscopic measurements on planar model catalysts

    NASA Astrophysics Data System (ADS)

    Zhao, Z.; Diemant, T.; Häring, T.; Rauscher, H.; Behm, R. J.

    2005-12-01

    We describe the design and performance of a high-pressure reaction cell for simultaneous kinetic and in situ infrared reflection (IR) spectroscopic measurements on model catalysts at elevated pressures, between 10-3 and 103mbars, which can be operated both as batch reactor and as flow reactor with defined gas flow. The cell is attached to an ultrahigh-vacuum (UHV) system, which is used for sample preparation and also contains facilities for sample characterization. Specific for this design is the combination of a small cell volume, which allows kinetic measurements with high sensitivity under batch or continuous flow conditions, the complete isolation of the cell from the UHV part during UHV measurements, continuous temperature control during both UHV and high-pressure operation, and rapid transfer between UHV and high-pressure stage. Gas dosing is performed by a designed gas-handling system, which allows operation as flow reactor with calibrated gas flows at adjustable pressures. To study the kinetics of reactions on the model catalysts, a quadrupole mass spectrometer is connected to the high-pressure cell. IR measurements are possible in situ by polarization-modulation infrared reflection-absorption spectroscopy, which also allows measurements at elevated pressures. The performance of the setup is demonstrated by test measurements on the kinetics for CO oxidation and the CO adsorption on a Au /TiO2/Ru(0001) model catalyst film at 1-50 mbar total pressure.

  7. In situ TEM observation of the Boudouard reaction: multi-layered graphene formation from CO on cobalt nanoparticles at atmospheric pressure.

    PubMed

    Bremmer, G Marien; Zacharaki, Eirini; Sjåstad, Anja O; Navarro, Violeta; Frenken, Joost W M; Kooyman, Patricia J

    2017-02-09

    Using a MEMS nanoreactor in combination with a specially designed in situ Transmission Electron Microscope (TEM) holder and gas supply system, we imaged the formation of multiple layers of graphene encapsulating a cobalt nanoparticle, at 1 bar CO : N2 (1 : 1) and 500 °C. The cobalt nanoparticle was imaged live in a TEM during the Boudouard reaction. The in situ/operando TEM studies give insight into the behaviour of the catalyst at the nanometer-scale, under industrially relevant conditions. When switching from Fischer-Tropsch syngas conditions (CO : H2 : N2 1 : 2 : 3 at 1 bar) to CO-rich conditions (CO : N2 1 : 1 at 1 bar), we observed the formation of multi-layered graphene on Co nanoparticles at 500 °C. Due to the high temperature, the surface of the Co nanoparticles facilitated the Boudouard reaction, causing CO dissociation and the formation of layers of graphene. After the formation of the first patches of graphene at the surface of the nanoparticle, more and more layers grew over the course of about 40 minutes. In its final state, around 10 layers of carbon capped the nanoparticle. During this process, the carbon shell caused mechanical stress in the nanoparticle, inducing permanent deformation.

  8. Analysis and modeling of PEM fuel cell stack performance: Effect of in situ reverse water gas shift reaction and oxygen bleeding

    NASA Astrophysics Data System (ADS)

    Karimi, G.; Li, Xianguo

    In this study the performance of a polymer electrolyte membrane (PEM) fuel cell stack is analyzed with a mathematical model when the stack operates on hydrocarbon reformate gas as the anode feed stream. It is shown that the effect of carbon dioxide dilution of the hydrogen dominated reformate gas has a minimal impact on the stack performance. However, the CO-poisoning effect due to the in situ reverse water gas shift reaction in the anode feed stream could have a very serious adverse impact on the stack performance, especially at high current densities. Thermodynamic calculations indicate that the equilibrium concentrations of CO could be as high as 100 ppm, generated by the in situ reverse water gas shift reaction, under the typical conditions of PEM fuel cell operation; and are influenced by the stack operating temperature and water content of the reformate anode feed. This CO-poisoning of the stack performance is shown mitigated effectively by introducing about 0.5-1% oxygen to the anode feed.

  9. Molecular beam studies of reaction dynamics

    SciTech Connect

    Lee, Y.T.

    1993-12-01

    The major thrust of this research project is to elucidate detailed dynamics of simple elementary reactions that are theoretically important and to unravel the mechanism of complex chemical reactions or photochemical processes that play important roles in many macroscopic processes. Molecular beams of reactants are used to study individual reactive encounters between molecules or to monitor photodissociation events in a collision-free environment. Most of the information is derived from measurement of the product fragment energy, angular, and state distributions. Recent activities are centered on the mechanisms of elementary chemical reactions involving oxygen atoms with unsaturated hydrocarbons, the dynamics of endothermic substitution reactions, the dependence of the chemical reactivity of electronically excited atoms on the alignment of excited orbitals, the primary photochemical processes of polyatomic molecules, intramolecular energy transfer of chemically activated and locally excited molecules, the energetics of free radicals that are important to combustion processes, the infrared-absorption spectra of carbonium ions and hydrated hydronium ions, and bond-selective photodissociation through electric excitation.

  10. Molecular beam studies of reaction dynamics

    SciTech Connect

    Lee, Yuan T.

    1991-03-01

    The major thrust of this research project is to elucidate detailed dynamics of simple elementary reactions that are theoretically important and to unravel the mechanism of complex chemical reactions or photochemical processes that play important roles in many macroscopic processes. Molecular beams of reactants are used to study individual reactive encounters between molecules or to monitor photodissociation events in a collision-free environment. Most of the information is derived from measurement of the product fragment energy, angular, and state distributions. Recent activities are centered on the mechanisms of elementary chemical reactions involving oxygen atoms with unsaturated hydrocarbons, the dynamics of endothermic substitution reactions, the dependence of the chemical reactivity of electronically excited atoms on the alignment of excited orbitals, the primary photochemical processes of polyatomic molecules, intramolecular energy transfer of chemically activated and locally excited molecules, the energetics of free radicals that are important to combustion processes, the infrared-absorption spectra of carbonium ions and hydrated hydronium ions, and bond-selective photodissociation through electric excitation.

  11. In Situ Reaction Kinetics and Microstructure Evolution in Preparing Particle-Containing Copper Alloys by Mechanical Alloying

    NASA Astrophysics Data System (ADS)

    Guo, Mingxing; Wang, Fei; Zhang, Yan; Zhang, Xukai

    2015-04-01

    To improve alloy properties and the distribution level of TiB2 particles in the alloy matrix, mechanical alloying was used to prepare the Cu-TiB2 alloy. But even after long-time ball milling, the in situ reaction between Cu-B and Cu-Ti alloy powders still cannot be observed in the whole process. The kinetics of the in situ reaction during high-temperature heat treatment was first investigated and led to the following results. With the increase of heat-treatment time t or diffusion depth X, both the moving speed Δ x/Δ t of reaction front edge and nucleation rate Z( x) of TiB2 particles decrease at a fast rate and finally stabilize at a very low level. The falling rate of moving speed Δ x/Δ t increases with the decrease of temperature. Although the C Ti' value of the Ti element gives a poor effect on the moving speed Δ x/Δ t, it significantly affects the nucleation rate of TiB2 particles, and its falling rate increases with a decreasing C Ti' value. And for the same diffusion depth X and C Ti', the nucleation rate of TiB2 decreases with increasing the heat-treatment temperature. These results were verified by the microstructure change after the heat treatments at temperatures of 773 K, 973 K, and 1173 K (500 °C, 700 °C, and 900 °C), respectively. Finally, the best combination of ball-milling and heat-treatment conditions was obtained.

  12. FALP and CRESU studies of ionic reactions

    NASA Astrophysics Data System (ADS)

    Rowe, B. R.; Canosa, A.; Le Page, V.

    1995-11-01

    Results obtained from the study of ionic reactions at the University of Rennes are reviewed. A brief description of the apparatus available in our laboratory is given. The historical evolution of the flowing afterglow device is emphasized as it is directly connected to one of the major puzzling questions in dissociative recombination studies: what is the rate coefficient for the dissociative recombination of H3+ in its ground state? Special attention is given to the dissociative recombination process which until recently was the main topic studied in Rennes. A compilation of our measurements of branching ratios and rate coefficients is presented. Results from other authors are also outlined with particular attention paid to H3+. Electron attachment and ion/molecule reactions studied with the flowing afterglow Langmuir probe mass spectrometer are presented. The first results of ion/molecule reactions at very low temperatures have been recently obtained with the CRESU apparatus available in Rennes. Comparison with measurements carried out in Meudon at lower pressures is made and discussed.

  13. ALDOL- AND MANNICH-TYPE REACTIONS VIA IN SITU OLEFIN MIGRATION IN IONIC LIQUID

    EPA Science Inventory


    An aldol-type and a Mannich-type reaction via the cross-coupling of aldehydes and imines with allylic alcohols catalyzed by RuCl2(PPh3)3 was developed with ionic liquid as the solvent. The solvent/catalyst system could be reused for at least five times with no loss of reactiv...

  14. Tracking the Fate of Surface Plasmon Resonance-Generated Hot Electrons by In Situ SERS Surveying of Catalyzed Reaction.

    PubMed

    Liu, Rui; He, Zuoliang; Sun, Jiefang; Liu, Jingfu; Jiang, Guibin

    2016-12-01

    Plasmonic catalysis is an emerging process that utilizes surface plasmon resonance (SPR) process to harnesses solar energy for the promotion of catalyzed reactions. In most cases, SPR generated hot electrons (HEs) play an indispensable role in this solar-chemical energy shift process. Therefore, understanding the effectiveness of the HEs in promoting chemical reactions, and identifying the key factors that contribute to this utilization efficiency is of profound importance. Herein, the authors outline an in situ surface enhanced Raman spectroscopy protocol to track the fate of HEs. This is based on the unheeded HEs-acceleration nature of the p-nitirothiophenol hydrogenation reaction. By this way, the authors discover that unlike Au@Pd nanostructures which experience a 20-fold increase in rate constant, HEs primary leak to surrounding H(+) /O species through Ag pinholes in Ag@Pd. This work sheds light on why Ag is seldom employed as a plasmonic cocatalyst, and provides a new viewpoint to design plasmonic nanocatalysts with efficient light utilization.

  15. In Situ-Forming Polyamidoamine Dendrimer Hydrogels with Tunable Properties Prepared via Aza-Michael Addition Reaction.

    PubMed

    Wang, Juan; He, Hongliang; Cooper, Remy C; Yang, Hu

    2017-03-29

    In this work, we describe synthesis and characterization of novel in situ-forming polyamidoamine (PAMAM) dendrimer hydrogels (DHs) with tunable properties prepared via highly efficient aza-Michael addition reaction. PAMAM dendrimer G5 was chosen as the underlying core and functionalized with various degrees of acetylation using acetic anhydride. The nucleophilic amines on the dendrimer surface reacted with α, β-unsaturated ester in acrylate groups of polyethylene glycol diacrylate (PEG-DA, Mn = 575 g/mol) via aza-Michael addition reaction to form dendrimer hydrogels without the use of any catalyst. The solidification time, rheological behavior, network structure, swelling, and degradation properties of the hydrogel were tuned by adjusting the dendrimer surface acetylation degree and dendrimer concentration. The DHs were shown to be highly cytocompatible and support cell adhesion and proliferation. We also prepared an injectable dendrimer hydrogel formulation to deliver the anticancer drug 5-fluorouracil (5-FU) and demonstrated that the injectable formulation efficiently inhibited tumor growth following intratumoral injection. Taken together, this new class of dendrimer hydrogel prepared by aza-Michael addition reaction can serve as a safe tunable platform for drug delivery and tissue engineering.

  16. Expedient construction of small molecule macroarrays via sequential palladium- and copper-mediated reactions and their ex situ biological testing†

    PubMed Central

    Frei, Reto; Breitbach, Anthony S.

    2012-01-01

    We report the highly efficient syntheses of a series of focused libraries in the small molecule macroarray format using Suzuki–Miyaura and copper-catalyzed azide–alkyne cycloaddition (or “click”) reactions. The libraries were based on stilbene and triazole scaffolds, which are known to have a broad range of biological activities, including quorum-sensing (QS) modulation in bacteria. The library products were generated in parallel on the macroarray in extremely short reaction times (~10–20 min) and isolated in excellent purities. Biological testing of one macroarray library post-cleavage (ex situ) revealed several potent agonists of the QS receptor, LuxR, in Vibrio fischeri. These synthetic agonists, in contrast to others that we have reported, were only active in the presence of the native QS signal in V. fischeri, which is suggestive of a different mode of activity. Notably, the results presented herein showcase the ready compatibility of the macroarray platform with chemical reactions that are commonly utilized in small molecule probe and drug discovery today. As such, this work serves to expand the utility of the small molecule macroarray as a rapid and operationally straightforward approach toward the synthesis and screening of bioactive agents. PMID:23198087

  17. Calcite dissolution: an in situ study in the Panama Basin

    SciTech Connect

    Thunell, R.C.; Keir, R.S.; Honjo, S.

    1981-05-08

    The results of an in situ study of calcite dissolution in the Panama Basin indicate that the rate of dissolution in the water column increases suddenly below a water depth of about 2800 meters. This coincides with the depth at which the calcium carbonate content of surface sediments begins to decrease rapidly or the sedimentary lysocline. Since this level of increased dissolution both in the water column and on the sea floor does not appear to be related to the transition from supersaturation to undersaturation with respect to carbonate, there may be a kinetic origin for the lysocline in this region.

  18. In situ STM studies of polycrystalline platinum electrodes

    NASA Astrophysics Data System (ADS)

    Szklarczyk, Marek; Bockris, John O'M.

    1991-01-01

    In situ scanning tunneling microscopy (STM) was applied in a 10 -2M NaClO 4 solution to study topographical changes of a platinum electrode surface due to its oxidation and reduction. Surface morphology depends on the electrode potential. There are two stages in surface reduction: the fast electrochemical charge transfer and the slow crystallographic reconstruction. Reconstruction during surface reduction tends to proceed in the direction of the topography obtained during the annealing process. Methods of avoiding Faradaic current flowing through the STM tip are discussed in detail.

  19. Calcite Dissolution: An in situ Study in the Panama Basin.

    PubMed

    Thunell, R C; Keir, R S; Honjo, S

    1981-05-08

    The results of an in situ study of calcite dissolution in the Panama Basin indicate that the rate of dissolution in the water column increases suddenly below a water depth of about 2800 meters. This coincides with the depth at which the calcium carbonate content of surface sediments begins to decrease rapidly or the sedimentary lysocline. Since this level of increased dissolution both in the water column and on the sea floor does not appear to be related to the transition from supersaturation to undersaturation with respect to carbonate, there may be a kinetic origin for the lysocline in this region.

  20. Fluorescent labelling of in situ hybridisation probes through the copper-catalysed azide-alkyne cycloaddition reaction.

    PubMed

    Hesse, Susann; Manetto, Antonio; Cassinelli, Valentina; Fuchs, Jörg; Ma, Lu; Raddaoui, Nada; Houben, Andreas

    2016-09-01

    In situ hybridisation is a powerful tool to investigate the genome and chromosome architecture. Nick translation (NT) is widely used to label DNA probes for fluorescence in situ hybridisation (FISH). However, NT is limited to the use of long double-stranded DNA and does not allow the labelling of single-stranded and short DNA, e.g. oligonucleotides. An alternative technique is the copper(I)-catalysed azide-alkyne cycloaddition (CuAAC), at which azide and alkyne functional groups react in a multistep process catalysed by copper(I) ions to give 1,4-distributed 1,2,3-triazoles at a high yield (also called 'click reaction'). We successfully applied this technique to label short single-stranded DNA probes as well as long PCR-derived double-stranded probes and tested them by FISH on plant chromosomes and nuclei. The hybridisation efficiency of differently labelled probes was compared to those obtained by conventional labelling techniques. We show that copper(I)-catalysed azide-alkyne cycloaddition-labelled probes are reliable tools to detect different types of repetitive sequences on chromosomes opening new promising routes for the detection of single copy gene. Moreover, a combination of FISH using such probes with other techniques, e.g. immunohistochemistry (IHC) and cell proliferation assays using 5-ethynyl-deoxyuridine, is herein shown to be easily feasible.

  1. Cleaning IF molten steel with dispersed in-situ heterophases induced by the composite sphere explosive reaction in RH ladles

    NASA Astrophysics Data System (ADS)

    Tang, Fu-Ping; Li, Zhen; Wang, Xiao-Feng; Chen, Ben-Wen; Fei, Peng

    2011-04-01

    A novel fine inclusion removal technology was put forward with dispersed in-situ heterophases induced by the composite sphere explosive reaction. A composite sphere with this function was designed and prepared using a laboratory scale batch-type balling disc (at 12 r/min), and the composite sphere was fed at the end of the RH refining process. The results indicate that inclusions in the IF molten steel can be removed effectively by feeding composite spheres in RH ladle. Compared with conventional inclusion removal technology, using this novel technology, the amount of oxide inclusions can be decreased to a lower level and the inclusion size becomes finer, the total oxygen content in the as-cast slab can approach 5×10-6, and the cost per ton of steel produced can be reduced by 5-12 Yuan RMB.

  2. Synthesis of iron aluminide-Al{sub 2}O{sub 3} composites by in-situ displacement reactions

    SciTech Connect

    Subramanian, R.; McKamey, C.G.; Buck, L.R.; Schneibel, J.H.

    1997-09-01

    Composites consisting of an iron aluminide matrix with ceramic particle reinforcements, such as alumina, could improve the high temperature strength without compromising the oxidation resistance. In this paper, the feasibility of processing Fe-Al alloy/Al{sub 2}O{sub 3} composites by an in-situ displacement reaction between Fe-40 at.% Al and iron oxide, Fe{sub 2}O{sub 3}, is investigated. Simple powder metallurgical processing was performed without resorting to an externally applied pressures or deformations during the high temperature processing step. The microstructural features of the composites are rationalized based on results from diffusion couples. Preliminary mechanical properties such as fracture toughness, yield strength and hardness are determined and compared with the values obtained for monolithic iron aluminide - Fe-28 at.% Al. Results suggest that a significant improvement in the properties is needed and further avenues for modifications, such as changes in the interface strength and externally applied forces during processing, are suggested.

  3. Reaction rate kinetics for in situ combustion retorting of Michigan Antrim oil shale

    USGS Publications Warehouse

    Rostam-Abadi, M.; Mickelson, R.W.

    1984-01-01

    The intrinsic reaction rate kinetics for the pyrolysis of Michigan Antrim oil shale and the oxidation of the carbonaceous residue of this shale have been determined using a thermogravimetric analysis method. The kinetics of the pyrolysis reaction were evaluated from both isothermal and nonisothermal rate data. The reaction was found to be second-order with an activation energy of 252.2 kJ/mole, and with a frequency factor of 9.25 ?? 1015 sec-1. Pyrolysis kinetics were not affected by heating rates between 0.01 to 0.67??K/s. No evidence of any reactions among the oil shale mineral constituents was observed at temperatures below 1173??K. However, it was found that the presence of pyrite in oil shale reduces the primary devolatilization rate of kerogen and increases the amount of residual char in the spent shale. Carbonaceous residues which were prepared by heating the oil shale at a rate of 0.166??K/s to temperatures between 923??K and 1073??K, had the highest reactivities when oxidized at 0.166??K/s in a gas having 21 volume percent oxygen. Oxygen chemisorption was found to be the initial precursor to the oxidation process. The kinetics governing oxygen chemisorption is (Equation Presented) where X is the fractional coverage. The oxidation of the carbonaceous residue was found also to be second-order. The activation energy and the frequency factor determined from isothermal experiments were 147 kJ/mole and 9.18??107 sec-1 respectively, while the values of these parameters obtained from a nonisothermal experiment were 212 kJ/mole and 1.5??1013 sec-1. The variation in the rate constants is attributed to the fact that isothermal and nonisothermal analyses represent two different aspects of the combustion process.

  4. In situ TEM studies of carbon and gold nanostructures

    NASA Astrophysics Data System (ADS)

    Casillas Garcia, Gilberto

    Properties of matter change as structures go down in size to the nanoscale, creating new possibilities for creating new functional materials with better properties than the bulk. In situ TEM techniques were used to probe the properties of two different materials: atomic carbon chains and gold nanoparticles. Carbon chains were synthesized by in situ TEM electron beam irradiation from few-layers-graphene (FLG) flakes. Several chains up to 5 nm long were observed. Aberration corrected TEM confirmed the dimerization of the linear chain as predicted by Peierls. Moreover, it was observed that two linear carbon chains can cross-bond every 9 atoms, and it was confirmed by DFT calculations. Five-fold nanoparticles are not supposed to be stable beyond 5 nm size. Here, decahedra with high index facets in the order of 300 nm were studied by TEM. It was found that the high index facets were only stable by adding a capping agent, otherwise, smooth edges were observed. In this case, a (5x1) hexagonal surface reconstruction was observed on the {001} surfaces, with the hexagonal strings along a [110] and a [410] direction. Additionally, mechanical properties of gold nanoparticles, with and without twin boundaries, under 100 nm were measured by in situ TEM compression experiments. All of the nanoparticles presented yield strengths in the order of GPa. Multi twinned nanoparticles were found to be more malleable, reaching real compressing strains of 100 %, while the single crystal nanoparticle presented less plastic flow. Molecular dynamics simulations revealed that the twin boundaries contribute to the malleability of the nanoparticles, at the same time it provides a mechanism to stop dislocations, hence, strain hardening the nanoparticle at later stages of compression. Finally, the behavior of a single grain boundary was studied by in situ TEM manipulation of nanoparticles. A liquid-like behavior of a grain boundary is observed after two 40 nm gold nanoparticles are brought to

  5. In situ microcalorimetry study of ZnFe2O4 nanoparticle formation under solvothermal conditions.

    PubMed

    Liu, Jun; Nan, Zhaodong; Gao, Shengli

    2015-10-21

    Solvothermal methods have been widely used to synthesize different kinds of materials. However, only little is known about how precursor solutions react to form solid precipitates via this method. In the present study, in situ microcalorimetry is first used to investigate the formation mechanism under solvothermal conditions, where ZnFe2O4 synthesized using a solvothermal method was selected as the model sample. Some novel results are obtained, such as with the experimental temperature increase, (1) the homogeneous solution transforms to a gel containing amorphous Fe2(C2H4O2)3 and ZnC2H4O2, and NaNO3 crystals; (2) the gel dissolves; (3) α-(Fe,Zn)OOH and α-Fe2O3 are synthesized; (4) the α-(Fe,Zn)OOH transforms to α-Fe2O3; (5) Fe(2+) is formed at about 159 °C, which acts as a catalyst for the formation of Fe3O4; (6) the Fe3O4 crystals are synthesized at about 200 °C; (7) the Fe3O4 is transformed to the ZnFe2O4 with the help of NO3(-), and the reaction was kept at 200 °C for about 20 h. This study shows a facile in situ method for the investigation of reaction processes of solvothermal methods.

  6. Reaction-driven cracking during hydration and carbonation of olivine: Implications for in situ CO2 capture and storage

    NASA Astrophysics Data System (ADS)

    Kelemen, P. B.; Hirth, G.

    2011-12-01

    Reactions forming serpentine and/or Mg-carbonates via reaction of fluid with olivine may increase the solid volume, due to increasing solid mass and decreasing solid density, provided that fluid is supplied in an open system, and that dissolution does not remove significant solid mass. Increasing solid volume can create deviatoric stress within a rock, potentially causing fracture. In turn, this can provide a positive feedback to the alteration process, maintaining or increasing permeability and reactive surface area. This could be important - or even essential - for proposed in situ mineral carbonation for CO2 storage, and potentially for geological CO2 capture from surface waters. We use several methods to estimate the 'force of crystallization' during hydration and carbonation of olivine. The free energy changes driving these processes can potentially generate overpressures of 100's to 1000's of MPa. These potential stresses are larger for a given temperature for carbonation compared to serpentinization. Thermodynamic upper bounds can be compared to estimates based on microstructure in natural samples. Evans (Int Geol Rev 2004) and Jamtveit et al. (EPSL 2008) provide microphotographs of igneous troctolites, with interstitial plagioclase surrounding rounded olivine grains. The olivine grains are partially serpentinized, and the plagioclase has closely spaced fractures interpreted as a result of expansion during serpentinization. Strain energy due to expansion should be greater than surface energy on new fractures. Spacing and length of fractures in plagioclase yields a minimum of about 260 MPa for the differential stress. Alternatively, if fractures did not form, elastic stress in the plagioclase resulting from expansion during serpentinization should be proportional to the strain. Because some strain could be accommodated by irreversible mechanisms, such as friction and dilation on cracks and/or viscous flow, this yields a maximum stress of 270 MPa. The close

  7. In situ studies and modeling the fracture of Zircaloy-4

    NASA Astrophysics Data System (ADS)

    Cockeram, B. V.; Chan, K. S.

    2009-09-01

    In situ fracture studies were performed on non-irradiated Zircaloy-4 using tensile specimens and pre-cracked Compact Tension (CT) specimens to clarify the mechanism for fracture initiation in the constrained and non-constrained state. Similar approaches have been taken in the literature to understand the role of hydrides on the fracture of Zircaloy-4, but hydride-free Zircaloy-4 has received little study. Both annealed and beta-treated Zircaloy-4 were tested in the longitudinal, transverse, and short-transverse orientations to study the role of microstructure and orientation. Unstable crack extension is shown to occur under plastic constraint by a process of void nucleation, growth, and coalescence initiating from the Laves phase particles in the microstructure. A micromechanical model is developed for ductile tearing by void growth and coalescence. Excellent agreement between the model and experiments are observed. Aspects of the fracture mechanism and model are discussed.

  8. Monitoring the Reaction Mechanism in Model Biogas Reforming by In Situ Transient and Steady-State DRIFTS Measurements.

    PubMed

    Bobadilla, Luis F; Garcilaso, Victoria; Centeno, Miguel A; Odriozola, José A

    2016-12-01

    In this work, the reforming of model biogas was investigated on a Rh/MgAl2 O4 catalyst. In situ transient and steady-state diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) measurements were used to gain insight into the reaction mechanism involved in the activation of CH4 and CO2 . It was found that the reaction proceeds through of an initial pathway in which methane and CO2 are both dissociated on Rh metallic sites and additionally a bifunctional mechanism in which methane is activated on Rh sites and CO2 is activated on the basic sites of the support surface via a formate intermediate by H-assisted CO2 decomposition. Moreover, this plausible mechanism is able to explain why the observed apparent activation energy of CO2 is much lower than that of CH4 . Our results suggest that CO2 dissociation facilitates CH4 activation, because the oxygen-adsorbed species formed in the decomposition of CO2 are capable of reacting with the CHx species derived from methane decomposition.

  9. Interphase fluorescence in situ hybridization and reverse transcription polymerase chain reaction as a diagnostic aid for synovial sarcoma.

    PubMed Central

    Shipley, J.; Crew, J.; Birdsall, S.; Gill, S.; Clark, J.; Fisher, C.; Kelsey, A.; Nojima, T.; Sonobe, H.; Cooper, C.; Gusterson, B.

    1996-01-01

    Identification of the t(X;18)(p11.2;q11.2) that is associated with a high proportion of synovial sarcoma can be a useful diagnostic aid. The translocation results in fusion of the SYT gene on chromosome 18 to either the SSX1 or the SSX2 gene, two homologous genes within Xp11.2. Two-color interphase fluorescence in situ hybridization and reverse transcription polymerase chain reaction were assessed as approaches to identify the rearrangement in well characterized cases. The presence of the translocation, and the specific chromosome X gene disrupted, were inferred from the configuration of signals from chromosome-specific centromere probes, paints, and markers flanking each gene in preparations of interphase nuclei. Rearrangement was found in two cell lines and eight of nine tumor samples, including analysis of five touch imprints. This was consistent with cytogenetic data in four cases and reverse transcription polymerase chain reaction analysis using primers known to amplify both SYT-SSX1 and SYT-SSX2 transcripts. The transcripts were distinguished by restriction with LspI and SmaI. Contrary to previous suggestions, there was no obvious correlation between histological subtype and involvement of the SSX1 or SSX2 gene. These approaches could also be applied to the identification of tumor-free margins and metastatic disease. Images Figure 1 Figure 3 PMID:8579118

  10. Identification of the origin of marker chromosomes by two-color fluorescence in situ hybridization and polymerase chain reaction in azoospermic patients.

    PubMed

    Wei, C L; Cheng, J L; Yang, W C; Li, L Y; Cheng, H C; Fu, J J

    2015-11-19

    Y chromosomal microdeletions at the azoospermia factor locus and chromosome abnormalities have been implicated as the major causes of idiopathic male infertility. A marker chromosome is a structurally abnormal chromosome in which no part can be identified by cytogenetics. In this study, to identify the origin of the marker chromosomes and to perform a genetic diagnosis of patients with azoospermia, two-color fluorescence in situ hybridization (FISH) and polymerase chain reaction (PCR) techniques were carried out. The marker chromosomes for the two patients with azoospermia originated in the Y chromosome; it was ascertained that the karyotype of both patients was 46,X, ish del(Y)(q11)(DYZ3+, DXZ1-). The combination of two-color FISH and PCR techniques is an important method for the identification of the origin of marker chromosomes. Thus, genetic counseling and a clear genetic diagnosis of patients with azoospermia before intracytoplasmic sperm injection or other clinical managements are important.

  11. Experimental studies of gas-aerosol reactions

    NASA Astrophysics Data System (ADS)

    Gupta, Anand

    1991-05-01

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

  12. Experimental Studies of Gas-Aerosol Reactions

    NASA Astrophysics Data System (ADS)

    Gupta, Anand

    1991-02-01

    The aqueous phase oxidation of SO_2 by H_2O_2 is believed to be the principle mechanism for atmospheric sulfate formation in cloud droplets. However, no studies in noncloud aerosol systems have been reported. The objective of this thesis is to quantify the importance of the noncloud liquid phase reactions of SO_2 by H_2O_2 in the atmosphere. In this thesis growth rates of submicron droplets exposed to SO_2 and H_2 O_2 were measured using the tandem differential mobility analyzer (TDMA) technique (Rader and McMurry, 1986). The technique uses differential mobility analyzers (DMAs) to generate monodisperse particles and to measure particle size after the reaction. To facilitate submicron monodisperse droplet production with the DMA, a low-ion-concentration charger capable of generating singly charged particles up to 1.0 μm was developed and experimentally evaluated. The experiments were performed using dry and deliquesced (NH_4)_2SO _4 particles with SO_2 and H_2O_2 concentrations from 0-860 ppb and 0-150 ppb, respectively. No growth was observed for dry particles. For droplets >=0.3 mum, the fractional diameter growth was independent of particle size and for droplets <=0.2 mum, it decreased as particle size decreased. The observed decrease is due to NH_3 evaporation. As ammonia evaporates, droplet pH decreases causing the oxidation rate to decrease, leading to a lower growth rate. To predict the size-dependent growth rates, a theoretical model was developed using solution thermodynamics, gas/particle equilibrium and chemical kinetics. The experimental and theoretical results are in reasonable agreement. For dry (NH_4) _2SO_4 particles exposed to SO_2, H_2O _2, NH_3 and H_2O vapor, surface reaction-controlled growth was observed. Particle growth was very sensitive to particle composition. No growth was observed for Polystyrene latex particles, whereas (NH_4) _2SO_4 particles doped with catalysts (Fe^{2+} , Fe^{3+}, Mn ^{2+}, Cu^{2+ }) in a molar ratio of 1:500 grew

  13. Maleimide cross-linked bioactive PEG hydrogel exhibits improved reaction kinetics and cross-linking for cell encapsulation and in-situ delivery

    PubMed Central

    Phelps, Edward A.; Enemchukwu, Nduka O.; Fiore, Vincent F.; Sy, Jay C.; Murthy, Niren; Sulchek, Todd A.; Barker, Thomas H.

    2012-01-01

    Engineered polyethylene glycol-maleimide matrices for regenerative medicine exhibit improved reaction efficiency and wider range of Young’s moduli by utilizing maleimide cross-linking chemistry. This hydrogel chemistry is advantageous for cell delivery due to the mild reaction that occurs rapidly enough for in situ delivery, while easily lending itself to “plug-and-play” design variations such as incorporation of enzyme-cleavable cross-links and cell-adhesion peptides. PMID:22174081

  14. Comparative Reactivity Study of Forsterite and Antigorite in Wet Supercritical CO2 by In Situ Infrared Spectroscopy

    SciTech Connect

    Thompson, Christopher J.; Loring, John S.; Rosso, Kevin M.; Wang, Zheming

    2013-10-01

    The carbonation reactions of forsterite (Mg2SiO4) and antigorite [Mg3Si2O5(OH)4], representatives of olivine and serpentine minerals, in dry and wet supercritical carbon dioxide (scCO2) at conditions relevant to geologic carbon sequestration (35 °C and 100 bar) were studied by in-situ Fourier transform infrared (FT-IR) spectroscopy. Our results confirm that water plays a critical role in the reactions between metal silicate minerals and scCO2. For neat scCO2, no reaction was observed in 24 hr for either mineral. When water was added to the scCO2, a thin water film formed on the minerals’ surfaces, and the reaction rates and extents increased as the water saturation level was raised from 54% to 116% (excess water). For the first time, the presence of bicarbonate, a key reaction intermediate for metal silicate reactions with scCO2, was observed in a heterogeneous system where mineral solids, an adsorbed water film, and bulk scCO2 co-exist. In excess-water experiments, approximately 4% of forsterite and less than 2% of antigorite transformed into hydrated Mg-carbonates. A precipitate similar to nesquehonite (MgCO3•3H2O) was observed for forsterite within 6 hr of reaction time, but no such precipitate was formed from antigorite until after water was removed from the scCO2 following a 24-hr reaction period. The reduced reactivity and carbonate-precipitation behavior of antigorite was attributed to slower, incongruent dissolution of the mineral and lower concentrations of Mg2+ and HCO3- in the water film. The in situ measurements employed in this work make it possible to quantify metal carbonate precipitates and key reaction intermediates such as bicarbonate for the investigation of carbonation reaction mechanisms relevant to geologic carbon sequestration.

  15. Concept And Laboratory Verification Of In-situ Reaction Barrier For CO2 Geological Storage

    NASA Astrophysics Data System (ADS)

    Ito, T.; Sakurai, M.; Sekine, K.

    2008-12-01

    In the Carbon dioxide Capture and Storage (CCS), the CO2 is captured from emission source and stored into geological reservoirs at a depth below 800 m. The injected CO2 is less dense than water, and as a result, it tends to migrate upward. For trapping to inhibit the upward migration of CO2, the reservoirs should be covered with a sufficiently impermeable seal, i.e. caprock. However, the caprock may contain imperfections such as faults and fractures which will play a role of a high permeability path to arise leakage of the injected CO2 from the reservoirs. We present here a concept to reduce the medium permeability along potential such leakage paths. An aqueous solution will be injected into the fractures and rocks through injection wells. The solution will have a low viscosity and will not impact formation permeability as long as the solution is left as it is, but when the solution encounters dissolved CO2, precipitation will occur due to chemical reaction. As a result, the permeability will be reduced by filling the pores and fractures in the rocks with the precipitates. We have demonstrated this concept in the laboratory experiments by using the solution of Ca(OH)2 in water. In this case, the chemical reaction between the Ca(OH)2 solution and CO2 should produce precipitation of calcium carbonate, CaCO3. We prepared a cylindrical pressure vessel filled with glass beads and water. The temperature and pressure inside the vessel were kept at 35 degC and 10 MPa respectively simulating subsurface condition at 1000 m deep. The Ca(OH)2 solution and CO2 were injected into the vessel separately, and the permeability of the analogous rock of glass beads was measured before and after the treatment respectively. As was expected, the permeability decreased to about 10 percent within one day after the treatment and it was stabilized at least for a week until the end of the experiment. This concept may be also applicable to prevent the leakage through abandoned wells, to

  16. In situ ellipsometric study of surface immobilization of flagellar filaments

    NASA Astrophysics Data System (ADS)

    Kurunczi, S.; Németh, A.; Hülber, T.; Kozma, P.; Petrik, P.; Jankovics, H.; Sebestyén, A.; Vonderviszt, F.; Fried, M.; Bársony, I.

    2010-10-01

    Protein filaments composed of thousands of subunits are promising candidates as sensing elements in biosensors. In this work in situ spectroscopic ellipsometry is applied to monitor the surface immobilization of flagellar filaments. This study is the first step towards the development of layers of filamentous receptors for sensor applications. Surface activation is performed using silanization and a subsequent glutaraldehyde crosslinking. Structure of the flagellar filament layers immobilized on activated and non-activated Si wafer substrates is determined using a two-layer effective medium model that accounted for the vertical density distribution of flagellar filaments with lengths of 300-1500 nm bound to the surface. The formation of the first interface layer can be explained by the multipoint covalent attachment of the filaments, while the second layer is mainly composed of tail pinned filaments floating upwards with the free parts. As confirmed by atomic force microscopy, covalent immobilization resulted in an increased surface density compared to absorption.

  17. Chemical redox reactions in ES-MS: Study of electrode reactions

    SciTech Connect

    Zhou, Feimeng; VAn Berkel, G.J.

    1995-12-31

    The authors previously demonstrated that chemical redox reactions can be used to ionize neutral commpounds for electrospray mass spectrometric (ES-MS) detection. Two different compounds, viz, C{sub 60}F{sub 48} and {beta}-carotene were used to demonstrate the utility of chemical redox reactions with on-line ES-MS for the elucidation of mechanisms of complicated electron transfer reactions and for the kinetic study of electrode reactions in which relatively short-lived intermediates are involved.

  18. In situ attenuated total reflectance Fourier transform infrared (ATR FT-IR) spectroscopy monitoring of 1,2-butylene oxide polymerization reaction by using iterative concentration-guided classical least squares.

    PubMed

    Chen, Xiaoyun; Pell, Randy; Sarsani, Sagar; Cramm, Brian; Villa, Carlos; Dixit, Ravindra

    2013-08-01

    There has been rapid growth in the application of in situ optical spectroscopy techniques for reaction and process monitoring recently in both academia and industry. Vibrational spectroscopies such as mid-infrared, near-infrared spectroscopy, and Raman spectroscopy have proven to be versatile and informative. Accurate determination of concentrations, based on highly overlapped spectra, remains a challenge. As an example, 1,2-butylene oxide (BO) polymerization, an important industrial reaction, initiated by propylene glycol (PG) and catalyzed by KOH, is studied in this work in a semi-batch fashion by using in situ attenuated total reflectance Fourier transform infrared spectroscopy (ATR FT-IR) monitoring. The weak BO absorbance, the constantly changing interference from the product oligomers throughout the course of the reaction, and the change in BO spectral features with system polarity posed challenges for quantitative spectral analysis based on conventional methods. An iterative concentration-guided classical least-squares (ICG-CLS) method was developed to overcome these challenges. Taking advantage of the concentration-domain information, ICG-CLS enabled the estimation of the pure oligomer product spectra at different stages of the semi-batch process, which in turn was used to construct valid CLS models. The ICG-CLS algorithm provides an in situ calibration method that can be broadly applied to reactions of known order. Caveats in its applications are also discussed.

  19. Versatile method for AFM-tip functionalization with biomolecules: fishing a ligand by means of an in situ click reaction.

    PubMed

    Kumar, Rakesh; Ramakrishna, Shivaprakash N; Naik, Vikrant V; Chu, Zonglin; Drew, Michael E; Spencer, Nicholas D; Yamakoshi, Yoko

    2015-04-21

    A facile and universal method for the functionalization of an AFM tip has been developed for chemical force spectroscopy (CFS) studies of intermolecular interactions of biomolecules. A click reaction between tripod-acetylene and an azide-linker-ligand molecule was successfully carried out on the AFM tip surface and used for the CFS study of ligand-receptor interactions.

  20. Employing CO2 as reaction medium for in-situ suppression of the formation of benzene derivatives and polycyclic aromatic hydrocarbons during pyrolysis of simulated municipal solid waste.

    PubMed

    Lee, Jechan; Choi, Dongho; Tsang, Yiu Fai; Oh, Jeong-Ik; Kwon, Eilhann E

    2017-02-28

    This study proposes a strategic principle to enhance the thermal efficiency of pyrolysis of municipal solid waste (MSW). An environmentally sound energy recovery platform was established by suppressing the formation of harmful organic compounds evolved from pyrolysis of MSW. Using CO2 as reaction medium/feedstock, CO generation was enhanced through the following: 1) expediting the thermal cracking of volatile organic carbons (VOCs) evolved from the thermal degradation of the MSWs and 2) directly reacting VOCs with CO2. This particular influence of CO2 on pyrolysis of the MSWs also led to the in-situ mitigation of harmful organic compounds (e.g., benzene derivatives and polycyclic aromatic hydrocarbons (PAHs)) considering that CO2 acted as a carbon scavenger to block reaction pathways toward benzenes and PAHs in pyrolysis. To understand the fundamental influence of CO2, simulated MSWs (i.e., various ratios of biomass to polymer) were used to avoid any complexities arising from the heterogeneous matrix of MSW. All experimental findings in this study suggested the foreseeable environmental application of CO2 to energy recovery from MSW together with disposal of MSW.

  1. A large volume cell for in situ neutron diffraction studies of hydrothermal crystallizations.

    PubMed

    Xia, Fang; Qian, Gujie; Brugger, Joël; Studer, Andrew; Olsen, Scott; Pring, Allan

    2010-10-01

    A hydrothermal cell with 320 ml internal volume has been designed and constructed for in situ neutron diffraction studies of hydrothermal crystallizations. The cell design adopts a dumbbell configuration assembled with standard commercial stainless steel components and a zero-scattering Ti-Zr alloy sample compartment. The fluid movement and heat transfer are simply driven by natural convection due to the natural temperature gradient along the fluid path, so that the temperature at the sample compartment can be stably sustained by heating the fluid in the bottom fluid reservoir. The cell can operate at temperatures up to 300 °C and pressures up to 90 bars and is suitable for studying reactions requiring a large volume of hydrothermal fluid to damp out the negative effect from the change of fluid composition during the course of the reactions. The capability of the cell was demonstrated by a hydrothermal phase transformation investigation from leucite (KAlSi(2)O(6)) to analcime (NaAlSi(2)O(6)⋅H(2)O) at 210 °C on the high intensity powder diffractometer Wombat in ANSTO. The kinetics of the transformation has been resolved by collecting diffraction patterns every 10 min followed by Rietveld quantitative phase analysis. The classical Avrami/Arrhenius analysis gives an activation energy of 82.3±1.1 kJ  mol(-1). Estimations of the reaction rate under natural environments by extrapolations agree well with petrological observations.

  2. A large volume cell for in situ neutron diffraction studies of hydrothermal crystallizations

    NASA Astrophysics Data System (ADS)

    Xia, Fang; Qian, Gujie; Brugger, Joël; Studer, Andrew; Olsen, Scott; Pring, Allan

    2010-10-01

    A hydrothermal cell with 320 ml internal volume has been designed and constructed for in situ neutron diffraction studies of hydrothermal crystallizations. The cell design adopts a dumbbell configuration assembled with standard commercial stainless steel components and a zero-scattering Ti-Zr alloy sample compartment. The fluid movement and heat transfer are simply driven by natural convection due to the natural temperature gradient along the fluid path, so that the temperature at the sample compartment can be stably sustained by heating the fluid in the bottom fluid reservoir. The cell can operate at temperatures up to 300 °C and pressures up to 90 bars and is suitable for studying reactions requiring a large volume of hydrothermal fluid to damp out the negative effect from the change of fluid composition during the course of the reactions. The capability of the cell was demonstrated by a hydrothermal phase transformation investigation from leucite (KAlSi2O6) to analcime (NaAlSi2O6ṡH2O) at 210 °C on the high intensity powder diffractometer Wombat in ANSTO. The kinetics of the transformation has been resolved by collecting diffraction patterns every 10 min followed by Rietveld quantitative phase analysis. The classical Avrami/Arrhenius analysis gives an activation energy of 82.3±1.1 kJ mol-1. Estimations of the reaction rate under natural environments by extrapolations agree well with petrological observations.

  3. In-situ early-age hydration study of sulfobelite cements by synchrotron powder diffraction

    SciTech Connect

    Álvarez-Pinazo, G.; Cuesta, A.; García-Maté, M.; Santacruz, I.; Losilla, E.R.; Fauth, F.; Aranda, M.A.G.; De la Torre, A.G.

    2014-02-15

    Eco-friendly belite calcium sulfoaluminate (BCSA) cement hydration behavior is not yet well understood. Here, we report an in-situ synchrotron X-ray powder diffraction study for the first hours of hydration of BCSA cements. Rietveld quantitative phase analysis has been used to establish the degree of reaction (α). The hydration of a mixture of ye'elimite and gypsum revealed that ettringite formation (α ∼ 70% at 50 h) is limited by ye'elimite dissolution. Two laboratory-prepared BCSA cements were also studied: non-active-BCSA and active-BCSA cements, with β- and α′{sub H}-belite as main phases, respectively. Ye'elimite, in the non-active-BCSA system, dissolves at higher pace (α ∼ 25% at 1 h) than in the active-BCSA one (α ∼ 10% at 1 h), with differences in the crystallization of ettringite (α ∼ 30% and α ∼ 5%, respectively). This behavior has strongly affected subsequent belite and ferrite reactivities, yielding stratlingite and other layered phases in non-active-BCSA. The dissolution and crystallization processes are reported and discussed in detail. -- Highlights: •Belite calcium sulfoaluminate cements early hydration mechanism has been determined. •Belite hydration strongly depends on availability of aluminum hydroxide. •Orthorhombic ye’elimite dissolved at a higher pace than cubic one. •Ye’elimite larger reaction degree yields stratlingite formation by belite reaction. •Rietveld method quantified gypsum, anhydrite and bassanite dissolution rates.

  4. SISGR - In situ characterization and modeling of formation reactions under extreme heating rates in nanostructured multilayer foils

    SciTech Connect

    Hufnagel, Todd C.

    2014-06-09

    Materials subjected to extreme conditions, such as very rapid heating, behave differently than materials under more ordinary conditions. In this program we examined the effect of rapid heating on solid-state chemical reactions in metallic materials. One primary goal was to develop experimental techniques capable of observing these reactions, which can occur at heating rates in excess of one million degrees Celsius per second. One approach that we used is x-ray diffraction performed using microfocused x-ray beams and very fast x-ray detectors. A second approach is the use of a pulsed electron source for dynamic transmission electron microscopy. With these techniques we were able to observe how the heating rate affects the chemical reaction, from which we were able to discern general principles about how these reactions proceed. A second thrust of this program was to develop computational tools to help us understand and predict the reactions. From atomic-scale simulations were learned about the interdiffusion between different metals at high heating rates, and about how new crystalline phases form. A second class of computational models allow us to predict the shape of the reaction front that occurs in these materials, and to connect our understanding of interdiffusion from the atomistic simulations to measurements made in the laboratory. Both the experimental and computational techniques developed in this program are expected to be broadly applicable to a wider range of scientific problems than the intermetallic solid-state reactions studied here. For example, we have already begun using the x-ray techniques to study how materials respond to mechanical deformation at very high rates.

  5. Possible intermediates of Cu(phen)-catalyzed C-O cross-coupling of phenol with an aryl bromide by in situ ESI-MS and EPR studies.

    PubMed

    Chen, Hong-Jie; Hsu, I-Jui; Tseng, Mei-Chun; Shyu, Shin-Guang

    2014-08-07

    The C-O coupling reaction between 2,4-dimethylphenol and 4-bromotoluene catalyzed by the CuI/K2CO3/phen system can be inhibited by the radical scavenger cumene. Complexes [Cu(i)(phen)(1-(2,4-dimethylphenoxy)-4-methylbenzene)](+) (denoted as A), {H[Cu(i)(phen)(2,4-dimethylphenoxy)]}(+) and [Cu(i)(2,4-dimethylphenoxy)2](-) (denoted as B) were observed by in situ electrospray ionization mass spectrometry (ESI-MS) analysis of the copper(i)-catalyzed C-O coupling reaction under the catalytic reaction conditions indicating that they could be intermediates in the reaction. The in situ EPR study of the reaction solution detected the Cu(ii) species with a fitted g value of 2.188. A catalytic cycle with a single electron transfer (SET) step was proposed based on these observations.

  6. In Situ Coupling of CoP Polyhedrons and Carbon Nanotubes as Highly Efficient Hydrogen Evolution Reaction Electrocatalyst.

    PubMed

    Wu, Can; Yang, Yijun; Dong, Duo; Zhang, Yuhang; Li, Jinghong

    2017-02-01

    Hydrogen evolution reaction (HER) from water electrolysis is an attractive technique developed in recent years for cost-effective clean energy. Although considerable efforts have been paid to create efficient catalysts for HER, the development of an affordable HER catalyst with superior performance under mild conditions is still highly desired. In this work, metal-organic frameworks (MOFs)-templated strategy is proposed for in situ coupling of cobalt phosphide (CoP) polyhedrons nanoparticles and carbon nanotubes (CNTs). Due to the synergistic catalytic effect between CoP polyhedrons and CNTs, the as-prepared CoP-CNTs hybrids show excellent HER performance. The resultant CoP-CNTs demonstrate excellent HER activity in 0.5 m H2 SO4 with Tafel slope of 52 mV dec(-1) , small onset overpotential of ≈64 mV, and a low overpotential of ≈139 mV at 10 mA cm(-2) . Additionally, the catalyst also manifests superior durability in acid media. Considering the structure diversity of MOFs, the strategy presented here can be extended for synthesizing other well-defined metal phosphides-CNTs hybrids, which may be used in the fields of catalysis, energy conversion and storage.

  7. A comparison of in situ hybridisation, reverse transcriptase-polymerase chain reaction (RT-PCR) and in situ-RT-PCR for the detection of canine distemper virus RNA in Paget's disease.

    PubMed

    Hoyland, Judith A; Dixon, Janet A; Berry, Jacqueline L; Davies, Michael; Selby, Peter L; Mee, Andrew P

    2003-05-01

    Previous evidence implicating Paramyxoviruses in the aetiopathology of Paget's disease of bone has proved controversial. Whilst several groups have demonstrated Paramyxoviruses using techniques such as in situ hybridisation (ISH), reverse transcriptase-polymerase chain reaction (RT-PCR), and in situ-RT-PCR (IS-RT-PCR), others have found no evidence of viruses using only RT-PCR. To investigate this latter finding, we have now compared detection of canine distemper virus by ISH, RT-PCR (three different methods) and IS-RT-PCR, in 10 patients with Paget's disease, and samples of non-diseased bone from four patients. Canine distemper virus was detectable in six of the samples by ISH, but only in five of the samples by RT-PCR, using one of the methods. Neither of the other RT-PCR methods detected canine distemper virus. IS-RT-PCR demonstrated canine distemper virus in all 10 samples. There was no evidence of virus in the control samples. We have shown that the ability to detect canine distemper virus in bone is dependent on the technique used. IS-RT-PCR clearly showed that canine distemper virus was present in 100% of Pagetic samples, whereas canine distemper virus was only found in 60% by ISH and in 50% using one particular RT-PCR method. These results provide conclusive evidence that canine distemper virus is present within Pagetic bone, and provide a possible explanation for the failure of some groups to detect Paramyxovirus sequences. These findings also have wider implications for other studies investigating viral expression.

  8. Study of char gasification in a reaction/adsorption apparatus

    SciTech Connect

    Sotirchos, S.V.; Crowley, J.A.

    1987-09-01

    The reaction of an activated carbon (coconut char) with CO/sub 2/ was studied in a reaction/adsorption apparatus which allows successive reactivity and physical adsorption measurements to be made on the same solid sample. Reaction and surface area evolution data were obtained in the temperature range from 800 to 900/sup 0/C. All reaction rate trajectories obtained in this study showed a maximum in the reaction rate, 2-3 times higher than the initial rate, at about 85% conversion. There was no correlation between these results and the evolution of the internal surface area although the reaction appeared to take place initially in the kinetically controlled regime.

  9. In situ transmission electron microscopy investigation of the interfacial reaction between Ni and Al during rapid heating in a nanocalorimeter

    SciTech Connect

    Grapes, Michael D. E-mail: david.lavan@nist.gov; LaGrange, Thomas; Reed, Bryan W.; Campbell, Geoffrey H.; Woll, Karsten; LaVan, David A. E-mail: david.lavan@nist.gov; Weihs, Timothy P. E-mail: david.lavan@nist.gov

    2014-11-01

    The Al/Ni formation reaction is highly exothermic and of both scientific and technological significance. In this report, we study the evolution of intermetallic phases in this reaction at a heating rate of 830 K/s. 100-nm-thick Al/Ni bilayers were deposited onto nanocalorimeter sensors that enable the measurement of temperature and heat flow during rapid heating. Time-resolved transmission electron diffraction patterns captured simultaneously with thermal measurements allow us to identify the intermetallic phases present and reconstruct the phase transformation sequence as a function of time and temperature. The results show a mostly unaltered phase transformation sequence compared to lower heating rates.

  10. Sample environment for in situ synchrotron corrosion studies of materials in extreme environments

    DOE PAGES

    Elbakhshwan, Mohamed S.; Gill, Simerjeet K.; Motta, Arthur T.; ...

    2016-10-25

    A new in situ sample environment has been designed and developed to study the interfacial interactions of nuclear cladding alloys with high temperature steam. The sample environment is particularly optimized for synchrotron X-ray diffraction (XRD) studies for in situ structural analysis. The sample environment is highly corrosion resistant and can be readily adapted for steam environments. The in situ sample environment design complies with G2 ASTM standards for studying corrosion in zirconium and its alloys and offers remote temperature and pressure monitoring during the in situ data collection. The use of the in situ sample environment is exemplified by monitoringmore » the oxidation of metallic zirconium during exposure to steam at 350°C. Finally, the in situ sample environment provides a powerful tool for fundamental understanding of corrosion mechanisms by elucidating the substoichiometric oxide phases formed during early stages of corrosion, which can provide a better understanding the oxidation process.« less

  11. EXAFS investigations of metal organic molecules with the goal of studying homogeneously catalytic systems in situ

    NASA Astrophysics Data System (ADS)

    Ertel, T. S.; Hörner, W.; Hückmann, S.; Kolb, U.; Abraham, I.; Bertagnolli, H.

    1995-02-01

    The investigations of Grignard compounds are very instructive for understanding the principles of getting structural information on highly complex and simultaneously metal activated systems by means of EXAFS spectroscopy. The structural investigations of a model system for Friedel-Crafts alkylation and some metal complexes (metal = Zr, Mo, W, Re), which activate carbonyl groups selectively with respect to the subsequent ring cleavage of axially prosterogenic biaryl lactones, are reported. As an actual field of metal organic research temperature dependent in situ EXAFS studies of the CH-activation of substituted olefins are presented. It was possible to observe the course of the rearrangement reaction of an iridium olefin complex to the corresponding hydrido (vinyl) iridium complex.

  12. Density functional study of chemical reaction equilibrium for dimerization reactions in slit and cylindrical nanopores

    NASA Astrophysics Data System (ADS)

    Malijevský, Alexandr; Lísal, Martin

    2009-04-01

    We present a theoretical study of the effects of confinement on chemical reaction equilibrium in slit and cylindrical nanopores. We use a density functional theory (DFT) to investigate the effects of temperature, pore geometry, bulk pressure, transition layering, and capillary condensation on a dimerization reaction that mimics the nitric oxide dimerization reaction, 2NO⇌(NO)2, in carbonlike slit and cylindrical nanopores in equilibrium with a vapor reservoir. In addition to the DFT calculations, we also utilize the reaction ensemble Monte Carlo method to supplement the DFT results for reaction conversion. This work is an extension of the previous DFT study by Tripathi and Chapman [J. Chem. Phys. 118, 7993 (2003)] on the dimerization reactions confined in the planar slits.

  13. In Situ Fabrication of PtCo Alloy Embedded in Nitrogen-Doped Graphene Nanopores as Synergistic Catalyst for Oxygen Reduction Reaction

    SciTech Connect

    Zhong, Xing; Wang, Lei; Zhou, Hu; Qin, Yingying; Xu, Wenlei; Jiang, Yu; Sun, Youyi; Shi, Zheqi; Zhuang, Guilin; Li, Xiaonian; Mei, Donghai; Wang, Jian-guo

    2015-11-23

    A novel PtCo alloy in situ etched and embedded in graphene nanopores (PtCo/NPG) as a high-performance catalyst for ORR was reported. Graphene nanopores were fabricated in situ while forming PtCo nanoparticles that were uniformly embedded in the graphene nanopores. Given the synergistic effect between PtCo alloy and nanopores, PtCo/NPG exhibited 11.5 times higher mass activity than that of the commercial Pt/C cathode electrocatalyst. DFT calculations indicated that the nanopores in NPG cannot only stabilize PtCo nanoparticles but can also definitely change the electronic structures, thereby change its adsorption abilities. This enhancement can lead to a favorable reaction pathway on PtCo/NPG for ORR. This study showed that PtCo/NPG is a potential candidate for the next generation of Pt-based catalysts in fuel cells. This study also offered a promising alternative strategy and enabled the fabrication of various kinds of metal/graphene nanopore nanohybrids with potential applications in catalysts and potential use for other technological devices. The authors acknowledge the financial support from the National Basic Research Program (973 program, No. 2013CB733501), Zhejiang Provincial Education Department Research Program (Y201326554) and the National Natural Science Foundation of China (No. 21306169, 21101137, 21136001, 21176221 and 91334013). D. Mei acknowledges the support from the US Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Division of Chemical Sciences, Geosciences & Biosciences. Pacific Northwest National Laboratory (PNNL) is a multiprogram national laboratory operated for DOE by Battelle. Computing time was granted by the grand challenge of computational catalysis of the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL) and by the National Energy Research Scientific Computing Center (NERSC).

  14. In situ studies of a platform for metastable inorganic crystal growth and materials discovery

    PubMed Central

    Shoemaker, Daniel P.; Hu, Yung-Jin; Chung, Duck Young; Halder, Gregory J.; Chupas, Peter J.; Soderholm, L.; Mitchell, J. F.; Kanatzidis, Mercouri G.

    2014-01-01

    Rapid shifts in the energy, technological, and environmental demands of materials science call for focused and efficient expansion of the library of functional inorganic compounds. To achieve the requisite efficiency, we need a materials discovery and optimization paradigm that can rapidly reveal all possible compounds for a given reaction and composition space. Here we provide such a paradigm via in situ X-ray diffraction measurements spanning solid, liquid flux, and recrystallization processes. We identify four new ternary sulfides from reactive salt fluxes in a matter of hours, simultaneously revealing routes for ex situ synthesis and crystal growth. Changing the flux chemistry, here accomplished by increasing sulfur content, permits comparison of the allowable crystalline building blocks in each reaction space. The speed and structural information inherent to this method of in situ synthesis provide an experimental complement to computational efforts to predict new compounds and uncover routes to targeted materials by design. PMID:25024201

  15. Raman spectroscopic study of reaction dynamics

    NASA Astrophysics Data System (ADS)

    MacPhail, R. A.

    1990-12-01

    The Raman spectra of reacting molecules in liquids can yield information about various aspects of the reaction dynamics. The author discusses the analysis of Raman spectra for three prototypical unimolecular reactions, the rotational isomerization of n-butane and 1,2-difluoroethane, and the barrierless exchange of axial and equatorial hydrogens in cyclopentane via pseudorotation. In the first two cases the spectra are sensitive to torsional oscillations of the gauche conformer, and yield estimates of the torsional solvent friction. In the case of cyclopentane, the spectra can be used to discriminate between different stochastic models of the pseudorotation dynamics, and to determine the relevant friction coefficients.

  16. Molecular beam studies of reaction dynamics

    SciTech Connect

    Lee, Y.T.

    1987-03-01

    Purpose of this research project is two-fold: (1) to elucidate detailed dynamics of simple elementary reactions which are theoretically important and to unravel the mechanism of complex chemical reactions or photo chemical processes which play an important role in many macroscopic processes and (2) to determine the energetics of polyatomic free radicals using microscopic experimental methods. Most of the information is derived from measurement of the product fragment translational energy and angular distributions using unique molecular beam apparati designed for these purposes.

  17. Soot Reaction Properties (Ground-Based Study)

    NASA Technical Reports Server (NTRS)

    Dai, Z.; El-Leathy, A. M.; Lin, K.-C.; Sunderland, P. B.; Xu, F.; Faeth, G. M.; Urban, D. L. (Technical Monitor); Yuan, Z.-G. (Technical Monitor)

    2000-01-01

    Three major soot reaction processes are needed to predict soot properties in flame environments: soot growth, or the formation of soot on soot nuclei and soot particles; soot oxidation, or the reaction of soot with oxidizing species to yield the combustion products of soot oxidation; and soot nucleation, or the formation of soot nuclei from soot precursors having large molecular weights (generally thought to be large and particularly stable PAH molecules in flame environments, called stabilomers). These processes are addressed in the following, considering soot growth, oxidation and nucleation, in turn, by exploiting the soot and flame structure results for premixed and diffusion flames already discussed in Section 2.

  18. Kinetic Study of the Heck Reaction: An Interdisciplinary Experiment

    ERIC Educational Resources Information Center

    Gozzi, Christel; Bouzidi, Naoual

    2008-01-01

    The aim of this experiment is to study and calculate the kinetic constant of a Heck reaction: the arylation of but-3-en-2-ol by iodobenzene catalyzed by palladium acetate in presence of triethylamine in DMF. The reaction leads to a mixture of two ketones. Students use GC analysis to quantify reagents and products of reaction. They control the…

  19. Amplified electrochemiluminescence of luminol based on hybridization chain reaction and in situ generate co-reactant for highly sensitive immunoassay.

    PubMed

    Xiao, Lijuan; Chai, Yaqin; Yuan, Ruo; Cao, Yaling; Wang, Haijun; Bai, Lijuan

    2013-10-15

    In this work, we described a simple and highly sensitive electrochemiluminescence (ECL) strategy for IgG detection. Firstly, L-cysteine functionalized reduced graphene oxide composite (L-cys-rGO) was decorated on the glassy carbon electrode (GCE) surface. Then anti-IgG was immobilized on the modified electrode surface through the interaction between the carboxylic groups of the L-cys-rGO and the amine groups in anti-IgG. And then biotinylated anti-IgG (bio-anti-IgG) was assembled onto the electrode surface based on the sandwich-type immunoreactions. By the conjunction of biotin and streptavidin (SA), SA was immobilized, which in turn, combined with the biotin labeled initiator strand (S1). In the presence of two single DNA strands of glucose oxidase labeled S2 (GOD-S2) and complementary strand (S3), S1 could trigger the hybridization chain reaction (HCR) among S1, GOD-S2 and S3. Herein, due to HCR, numerous GOD was efficiently immobilizated on the sensing surface and exhibited excellent catalysis towards glucose to in situ generate amounts of hydrogen peroxide (H2O2), which acted as luminol's co-reactant to significantly enhance the ECL signal. The proposed ECL immunosensor presented predominate stability and high sensibility for determination of IgG in the range from 0.1 pg mL(-1) to 100 ng mL(-1) with a detection limit of 33 fg mL(-1) (S/N=3). Additionally, the designed ECL immunosensor exhibited a promising application for other protein detection.

  20. The Saturn Ring Observer: In situ studies of planetary rings

    NASA Astrophysics Data System (ADS)

    Nicholson, P. D.; Tiscareno, M. S.; Spilker, L. J.

    2010-12-01

    As part of the Planetary Science Decadal Survey recently undertaken by the NRC's Space Studies Board for the National Academy of Sciences, studies were commissioned for a number of potential missions to outer planet targets. One of these studies examined the technological feasibility of a mission to carry out in situ studies of Saturn's rings, from a spacecraft placed in a circular orbit above the ring plane: the Saturn Ring Observer. The technical findings and background are discussed in a companion poster by T. R. Spilker et al. Here we outline the science goals of such a mission. Most of the fundamental interactions in planetary rings occur on spatial scales that are unresolved by flyby or orbiter spacecraft. Typical particle sizes in the rings of Saturn are in the 1 cm - 10 m range, and average interparticle spacings are a few meters. Indirect evidence indicates that the vertical thickness of the rings is as little as 5 - 10 m, which implies a velocity dispersion of only a few mm/sec. Theories of ring structure and evolution depend on the unknown characteristics of interparticle collisions and on the size distribution of the ring particles. The SRO could provide direct measurements of both the coefficient of restitution -- by monitoring individual collisions -- and the particles’ velocity dispersion. High-resolution observations of individual ring particles should also permit estimates of their spin states. Numerical simulations of Saturn’s rings incorporating both collisions and self-gravity predict that the ring particles are not uniformly distributed, but are instead clustered into elongated structures referred to as “self-gravity wakes”, which are continually created and destroyed on an orbital timescale. Theory indicates that the average separation between wakes in the A ring is of order 30-100 m. Direct imaging of self-gravity wakes, including their formation and subsequent dissolution, would provide critical validation of these models. Other

  1. Study of Reaction Mechanism in Tracer Munitions

    DTIC Science & Technology

    1974-12-01

    Regression Rates (Furnished by Frankford Arsenal) 35 13 Calculated Heat Fluxes and Energy Partitions 43 4 I NOMENCLATURE B = preexponential factor... anhydride disproportionates in a fast step: N2 0 3 - 2 + NO (4) so that the resulting dioxide can react with more nitrite in another fast reaction: Sr

  2. Post-Synthesis Modification of the Aurivillius Phase Bi2SrTa2O9 via In Situ Microwave-Assisted "Click Reaction".

    PubMed

    Wang, Yanhui; Delahaye, Emilie; Leuvrey, Cédric; Leroux, Fabrice; Rabu, Pierre; Rogez, Guillaume

    2016-10-03

    A new strategy for the functionalization of layered perovskites is presented, based on the in situ post-synthesis modification of a prefunctionalized phase by copper(I)-catalyzed alkyne-azide cycloaddition (CuAAC). The microwave-assisted protonation and grafting of an alkyne alcohol provides the alkyne-functionalized precursor within a few hours, starting from Bi2SrTa2O9. The subsequent microwave-assisted in situ "click reaction" allows the post-synthesis modification of the precursor within ∼2 h, providing a layered perovskite functionalized by an alcohol-grafted 1,4-disubstituted-1H-1,2,3-triazole. Two compounds are described here, bearing an aliphatic and an aromatic substituent, which illustrates the general application of the method. This work opens new perspectives for the functionalization of layered perovskites, going beyond mere insertion/grafting reactions, and thus broadens the design possibilities and the range of applications of these hybrid systems.

  3. In Situ Solid-State Reactions Monitored by X-ray Absorption Spectroscopy: Temperature-Induced Proton Transfer Leads to Chemical Shifts.

    PubMed

    Stevens, Joanna S; Walczak, Monika; Jaye, Cherno; Fischer, Daniel A

    2016-10-24

    The dramatic colour and phase alteration with the solid-state, temperature-dependent reaction between squaric acid and 4,4'-bipyridine has been probed in situ with X-ray absorption spectroscopy. The electronic and chemical sensitivity to the local atomic environment through chemical shifts in the near-edge X-ray absorption fine structure (NEXAFS) revealed proton transfer from the acid to the bipyridine base through the change in nitrogen protonation state in the high-temperature form. Direct detection of proton transfer coupled with structural analysis elucidates the nature of the solid-state process, with intermolecular proton transfer occurring along an acid-base chain followed by a domino effect to the subsequent acid-base chains, leading to the rapid migration along the length of the crystal. NEXAFS thereby conveys the ability to monitor the nature of solid-state chemical reactions in situ, without the need for a priori information or long-range order.

  4. Room temperature reaction of oxygen with gold: an in situ ambient-pressure X-ray photoelectron spectroscopy investigation

    SciTech Connect

    Jiang, Peng; Porsgaard, Soeren; Borondics, Ferenc; Kober, Mariana; Caballero, Alfonso; Bluhm, Hendrik; Besenbacher, Flemming; Salmeron, Miquel

    2010-02-01

    Gold is commonly regarded as the most inert element.1 However, the discovery of the exceptional catalytic properties of gold nanoparticles (NPs) for low temperature CO oxidation2 initiated great interest due to its promising applications and spawned a large number of studies devoted to the understanding of the reaction mechanism.3-6 Nevertheless, no consistent and conclusive picture has arisen.7-13

  5. In situ monitoring of the acetylene decomposition and gas temperature at reaction conditions for the deposition of carbon nanotubes using linear Raman scattering.

    PubMed

    Reinhold-López, Karla; Braeuer, Andreas; Popovska, Nadejda; Leipertz, Alfred

    2010-08-16

    To understand the reaction mechanisms taking place by growing carbon nanotubes via the catalytic chemical vapor deposition process, a strategy to monitor in situ the gas phase at reaction conditions was developed applying linear Raman spectroscopy. The simultaneous determination of the gas temperature and composition was possible by a new strategy of the evaluation of the Raman spectra. In agreement to the well-known exothermic decomposition of acetylene, a gas temperature increase was quantified when acetylene was added to the incident flow. Information about exhaust gas recirculation and location of the maximal acetylene conversion was derived from the composition measurements.

  6. In Situ Coral Reef Oxygen Metabolism: An Eddy Correlation Study

    PubMed Central

    Long, Matthew H.; Berg, Peter; de Beer, Dirk; Zieman, Joseph C.

    2013-01-01

    Quantitative studies of coral reefs are challenged by the three-dimensional hard structure of reefs and the high spatial variability and temporal dynamics of their metabolism. We used the non-invasive eddy correlation technique to examine respiration and photosynthesis rates, through O2 fluxes, from reef crests and reef slopes in the Florida Keys, USA. We assessed how the photosynthesis and respiration of different reef habitats is controlled by light and hydrodynamics. Numerous fluxes (over a 0.25 h period) were as high as 4500 mmol O2 m−2 d−1, which can only be explained by efficient light utilization by the phototrophic community and the complex canopy structure of the reef, having a many-fold larger surface area than its horizontal projection. Over diel cycles, the reef crest was net autotrophic, whereas on the reef slope oxygen production and respiration were balanced. The autotrophic nature of the shallow reef crests implies that the export of organics is an important source of primary production for the larger area. Net oxygen production on the reef crest was proportional to the light intensity, up to 1750 µmol photons m−2 s−1 and decreased thereafter as respiration was stimulated by high current velocities coincident with peak light levels. Nighttime respiration rates were also stimulated by the current velocity, through enhanced ventilation of the porous framework of the reef. Respiration rates were the highest directly after sunset, and then decreased during the night suggesting that highly labile photosynthates produced during the day fueled early-night respiration. The reef framework was also important to the acquisition of nutrients as the ambient nitrogen stock in the water had sufficient capacity to support these high production rates across the entire reef width. These direct measurements of complex reefs systems yielded high metabolic rates and dynamics that can only be determined through in situ, high temporal resolution measurements

  7. Degradation of Bimetallic Model Electrocatalysts ___ an in situ XAS Study

    SciTech Connect

    Friebel, Daniel

    2011-06-22

    One of the major challenges in the development of clean energy fuel cells is the performance degradation of the electrocatalyst, which, apart from poisoning effects, can suffer from corrosion due to its exposure to a harsh environment under high potentials. In this communication, we demonstrate how interactions of Pt with a transition metal support affect not only, as commonly intended, the catalytic activity, but also the reactivity of Pt towards oxide formation or dissolution. We use two well-defined single-crystal model systems, Pt/Rh(111) and Pt/Au(111) and a unique x-ray spectroscopy technique with enhanced energy resolution to monitor the potential-dependent oxidation state of Pt, and find two markedly different oxidation mechanisms on the two different substrates. This information can be of great significance for future design of more active and more stable catalysts. We have studied the potential-induced degradation of Pt monolayer model electrocatalysts on Rh(111) and Au(111) single-crystal substrates. The anodic formation of Pt oxides was monitored using in situ high energy resolution fluorescence detection x-ray absorption spectroscopy (HERFD XAS). Although Pt was deposited on both substrates in a three-dimensional island growth mode, we observed remarkable differences during oxide formation that can only be understood in terms of strong Pt-substrate interactions throughout the Pt islands. Anodic polarization of Pt/Rh(111) up to +1.6 V vs. RHE (reversible hydrogen electrode) leads to formation an incompletely oxidized passive layer, whereas formation of PtO2 and partial Pt dissolution is observed for Pt/Au(111).

  8. A laser flash photolysis kinetics study of the reaction OH + H2O2 yields HO2 + H2O

    NASA Technical Reports Server (NTRS)

    Wine, P. H.; Semmes, D. H.; Ravishankara, A. R.

    1981-01-01

    Absolute rate constants for the reaction are reported as a function of temperature over the range 273-410 K. OH radicals are produced by 266 nm laser photolysis of H2O2 and detected by resonance fluorescence. H2O2 concentrations are determined in situ in the slow flow system by UV photometry. The results confirm the findings of two recent discharge flow-resonance fluorescence studies that the title reaction is considerably faster, particularly at temperatures below 300 K, than all earlier studies had indicated. A table giving kinetic data from the reaction is included.

  9. Experimental Study of Stellar Reactions at CNS

    SciTech Connect

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

    2006-11-02

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

  10. Theoretical study of chemical reactions in solution

    SciTech Connect

    Yokogawa, D.

    2015-12-31

    Quantum chemical calculations in solution are becoming more and more important in chemistry. Reference interaction site model self-consistent field (RISM-SCF) is one of the powerful approaches to perform quantum chemical calculations in solution. In this work, we developed a new generation of RISM-SCF, where a robust fitting method was newly introduced. We applied the new method to tautomerization reaction of cytosine in aqueous phase. Our calculation reproduced experimentally obtained relative stabilities and relative free energies correctly.

  11. Direct Reactions studies at RIBF new facility

    NASA Astrophysics Data System (ADS)

    Motobayashi, Tohru

    2009-10-01

    The RIKEN RI Beam Factory (RIBF) is the firs realization of new-generation facilities with beams of unstable nuclei. It is based on heavy-ion primary beams accelerated to 345 MeV/nucleon for all elements up to uranium. When the goal intensity, 1 pμA, is reached, RIBF allows production of about thousand new isotopes with the yield higher than 1 particle par day. Since the RI beam energy after production by in-flight fission and/or projectile fragmentation is be around 200-300 MeV/nucleon, the direct reaction is one of the useful processes for spectroscopy of uncle very far from the stability. Several experiments were proposed and a few of them have been performed with intense (currently) ^48Ca primary beams. The ZeroDegree Spectrometer, which is already operational, can be used to identify the product of a direct reaction in inverse kinematics coupled with, for example, measurement of γ-rays from excited states in the product. Construction of SAMURAI, a large-acceptance spectrometer, has been started. Decays of unbound states or breakup products from various types of direct reaction will be measured in coincidence. Experimental and theoretical issues to be considered for the specific conditions in this new opportunity will be discussed together with brief overview of near-term research.

  12. Study of Catalytic Reaction at Electrode-Electrolyte Interfaces by a CV-XAFS Method

    NASA Astrophysics Data System (ADS)

    Kusano, Shogo; Matsumura, Daiju; Asazawa, Koichiro; Kishi, Hirofumi; Sakamoto, Tomokazu; Yamaguchi, Susumu; Tanaka, Hirohisa; Mizuki, Jun'ichiro

    2017-01-01

    A method combining cyclic voltammetry (CV) with x-ray absorption fine structure (XAFS) spectroscopy, viz. CV-XAFS, has been developed to enable in situ real-time investigation of atomic and electronic structures related to electrochemical reactions. We use this method to study the reaction of a Pt/C cathode catalyst in the oxygen reduction reaction (ORR) in an alkaline electrolyte, using x-ray energies near the Pt LIII edge for XAFS measurements. It was found that the current induced by the ORR was first observed at approximately 0.08 V versus Hg/HgO, although the Pt valence, which is reflected in the oxidation states, remained almost unchanged. The electronic structure of the catalytic surface in the ORR was observed to be different in the negative and positive scan directions of CV measurements. Hydrogen adsorption is also discussed on the basis of the observation of this spectral change. We have demonstrated that CV-XAFS provides dynamical structural and electronic information related to electrochemical reactions and can be used for in situ real-time measurements of a catalyst.

  13. Oral microemulsions of paclitaxel: in situ and pharmacokinetic studies.

    PubMed

    Nornoo, Adwoa O; Zheng, Haian; Lopes, Luciana B; Johnson-Restrepo, Boris; Kannan, Kurunthachalam; Reed, Rachel

    2009-02-01

    The overall goal of this study was to develop cremophor-free oral microemulsions of paclitaxel (PAC) to enhance its permeability and oral absorption. The mechanism of this enhancement, as well as characteristics of the microemulsions relevant to the increase in permeability and absorption of the low solubility, low permeability PAC was investigated. Phase diagrams were used to determine the macroscopic phase behavior of the microemulsions and to compare the efficiency of different surfactant-oil mixtures to incorporate water. The microemulsion region on the phase diagrams utilizing surfactant-myvacet oil combinations was in decreasing order: lecithin: butanol: myvacet oil (LBM, 48.5%)>centromix CPS: 1-butanol: myvacet oil (CPS, 45.15%)>capmul MCM: polysorbate 80: myvacet oil (CPM, 27.6%)>capryol 90: polysorbate 80: myvacet oil (CP-P80, 23.9%)>capmul: myvacet oil (CM, 20%). Oil-in-water (o/w) microemulsions had larger droplet sizes (687-1010 nm) than the water-in-oil (w/o) microemulsions (272-363 nm) when measured using a Zetasizer nano series particle size analyzer. Utilizing nuclear magnetic resonance spectroscopy (NMR), the self-diffusion coefficient (D) of PAC in CM, LBM and CPM containing 10% of deuterium oxide (D(2)O) was 2.24x10(-11), 1.97x10(-11) and 0.51x10(-11) m(2)/s, respectively. These values indicate the faster molecular mobility of PAC in the two w/o microemulsions (CM and LBM) than the o/w microemulsion--CPM. The in situ permeability of PAC through male CD-IGS rat intestine was 3- and 11-fold higher from LBM and CM, respectively, than that from the control clinical formulation, Taxol (CE, cremophor: ethanol) in a single pass perfusion study. PAC permeability was significantly increased in the presence of the pgp/CYP3A4 inhibitor cyclosporine A (CsA). This enhancement may be attributed to the pgp inhibitory effect of the surfactants, oil and/or the membrane perturbation effect of the surfactants. The oral disposition of PAC in CM, LBM and CPM compared

  14. In situ Raman study of Electrochemically Intercalted Bisulfate Ions in Carbon Nanotube Bundles

    NASA Astrophysics Data System (ADS)

    Sumanasekera, G. U.; Allen, J. L.; Rao, A. M.; Fang, S. L.; Eklund, P. C.

    1998-03-01

    We have investigated the electrochemical intercalation of bisulfate ions in single-walled carbon nanotubes (SWNT) using in situ Raman spectroscopy. SWNTs pressed onto a Pt plate was used as the working electrode, a Pt wire and Ag/AgCl were used, respectively, as the counter electrode and reference electrode. Sulfuric acid (95%) was used as the electrolyte. Using Raman scattering we have observed an apparent rapid spontaneous reaction involving charge transfer between ionically bonded HSO_4^- anions and the nanotubes. This is evidenced by an instantaneous shift of the Raman-active tangential mode frequency from 1593 cm -1 to 1604 cm-1 (It was not possible to reverse this shift electrochemically to 1593 cm-1, even at the expense of large reverse bias). In forward bias, after this initial instantaneous reaction, the tangential mode frequency again upshifted from 1604 cm-1 to 1614 cm-1 linearly with external electrochemical charge Q. From the slope of ω(Q) we found in this regime, δω/δ f= 1220 cm-1 (f = holes/carbon). Upon further charging, a second regime with slope δω/δ f = 118 cm-1 was observed where the frequency upshifted from 1614 cm-1 to 1620 cm-1. The results are compared to similar studies in C_p^+HSO_4^-.xH_2SO4 graphite intercalation compounds.

  15. In situ infrared study of adsorbed species during catalytic oxidation and carbon dioxide adsorption

    NASA Astrophysics Data System (ADS)

    Khatri, Rajesh A.

    2005-11-01

    Hydrogen is considered to be the fuel of the next century. Hydrogen can be produced by either water splitting using the solar or nuclear energy or by catalytic cracking and reforming of the fossil fuels. The water splitting process using solar energy and photovoltaics is a clean way to produce hydrogen, but it suffers from very low efficiency. A promising scheme to produce H 2 from natural gas involves following steps: (i) partial oxidation and reforming of natural gas to syngas, (ii) water-gas shift reaction to convert CO in the syngas to additional H2, (iii) separation of the H2 from CO2, and (iv) CO2 sequestration. The requirements for the above scheme are (i) a highly active coke resistant catalyst for generation of syngas by direct partial oxidation, (ii) a highly active sulfur tolerant catalyst for the water-gas shift reaction, and (iii) a low cost sorbent with high CO2 adsorption capacity for CO2 sequestration. This dissertation will address the mechanisms of partial oxidation, CO2 adsorption, and water-gas shift catalysis using in situ IR spectroscopy coupled with mass spectrometry (MS). The results from these studies will lead to a better understanding of the reaction mechanism and design of both the catalyst and sorbent for production of hydrogen with zero emissions. Partial oxidation of methane is studied over Rh/Al2O 3 catalyst to elucidate the reaction mechanism for synthesis gas formation. The product lead-lag relationship observed with in situ IR and MS results revealed that syngas is produced via a two-step reforming mechanism: the first step involving total oxidation of CH4 to CO2 and H 2O and the second step involving the reforming of unconverted methane with CO2 and H2O to form syngas. Furthermore, the Rh on the catalyst surface remains predominantly in the partially oxidized state (Rhdelta+ and Rh0). For the water-gas shift reaction, addition of Re to the Ni/CeO2 catalyst enhanced the water gas shift activity by a factor of three. The activity

  16. Studies on Pyridazine Azide Cyclisation Reactions

    SciTech Connect

    Allan, R.D.; Greenwood, J.; Hambley, T.; Hanrahan, J.R.; Hibbs, D.E.; Itani, S.; Tran, H.; Turner, P.

    2010-11-16

    Reaction of sodium azide with 4-methyl-3,5,6-tribromopyridazine results in the formation of 3,5,6-triazide intermediate which could cyclise to give two possible bicyclic products while ab initio calculations show that the formation of a tricyclic compound is extremely energetically unfavourable. However, experimentally, only one major product is isolated. The structure of this unstable product has been conclusively established by X-ray crystallography as 3,5-diazido-4-methyl[1,5-b]tetrazolopyridazine confirming theoretical predictions.

  17. Neutron-induced reaction studies using stored ions

    NASA Astrophysics Data System (ADS)

    Glorius, Jan; Litvinov, Yuri A.; Reifarth, René

    2015-11-01

    Storage rings provide unique possibilities for investigations of nuclear reactions. Radioactive ions can be stored if the ring is connected to an appropriate facility and reaction studies are feasible at low beam intensities because of the recycling of beam particles. Using gas jet or droplet targets, charged particle-induced reactions on short-lived isotopes can be studied in inverse kinematics. In such a system a high-flux reactor could serve as a neutron target extending the experimental spectrum to neutron-induced reactions. Those could be studied over a wide energy range covering the research fields of nuclear astrophysics and reactor safety, transmutation of nuclear waste and fusion.

  18. Behavior of Supported Palladium Oxide Nanoparticles under Reaction Conditions, Studied with near Ambient Pressure XPS.

    PubMed

    Jürgensen, Astrid; Heutz, Niels; Raschke, Hannes; Merz, Klaus; Hergenröder, Roland

    2015-08-04

    Near ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) is a promising method to close the "pressure gap", and thus, study the surface composition during heterogeneous reactions in situ. The specialized spectrometers necessary for this analytical technique have recently been adapted to operate with a conventional X-ray source, making it available for routine quantitative analysis in the laboratory. This is shown in the present in situ study of the partial oxidation of 2-propanol catalyzed with PdO nanoparticles supported on TiO2, which was investigated under reaction conditions as a function of gas composition (alcohol-to-oxygen ratio) and temperature. Exposure of the nanoparticles to 2-propanol at 30 °C leads to immediate partial reduction of the PdO, followed by a continuous reduction of the remaining PdO during heating. However, gaseous oxygen inhibits the reduction of PdO below 90 °C, and the oxidation of 2-propanol to carboxylates only occurs in the presence of oxygen above 90 °C. These results support the theory that metallic palladium is the active catalyst material, and they show that environmental conditions affect the nanoparticles and the reaction process significantly. The study also revealed challenges and limitations of this analytical method. Specifically, the intensity and fixed photon energy of a conventional X-ray source limit the spectral resolution and surface sensitivity of lab-based NAP-XPS, which affect precision and accuracy of the quantitative analysis.

  19. Dynamical observation of lithium insertion/extraction reaction during charge-discharge processes in Li-ion batteries by in situ spatially resolved electron energy-loss spectroscopy.

    PubMed

    Shimoyamada, Atsushi; Yamamoto, Kazuo; Yoshida, Ryuji; Kato, Takehisa; Iriyama, Yasutoshi; Hirayama, Tsukasa

    2015-12-01

    All-solid-state Li-ion batteries (LIBs) with solid electrolytes are expected to be the next generation devices to overcome serious issues facing conventional LIBs with liquid electrolytes. However, the large Li-ion transfer resistance at the electrode/solid-electrolyte interfaces causes low power density and prevents practical use. In-situ-formed negative electrodes prepared by decomposing the solid electrolyte Li(1+x+3z)Alx(Ti,Ge)(2-x)Si(3z)P(3-z)O12 (LASGTP) with an excess Li-ion insertion reaction are effective electrodes providing low Li-ion transfer resistance at the interfaces. Prior to our work, however, it had still been unclear how the negative electrodes were formed in the parent solid electrolytes. Here, we succeeded in dynamically visualizing the formation by in situ spatially resolved electron energy-loss spectroscopy in a transmission electron microscope mode (SR-TEM-EELS). The Li-ions were gradually inserted into the solid electrolyte region around 400 nm from the negative current-collector/solid-electrolyte interface in the charge process. Some of the ions were then extracted in the discharge process, and the rest were diffused such that the distribution was almost flat, resulting in the negative electrodes. The redox reaction of Ti(4+)/Ti(3+) in the solid electrolyte was also observed in situ during the Li insertion/extraction processes. The in situ SR-TEM-EELS revealed the mechanism of the electrochemical reaction in solid-state batteries.

  20. Synthesis of nitrate sodalite: An in situ scanning calorimetric study

    NASA Astrophysics Data System (ADS)

    Liu, Qingyuan; Navrotsky, Alexandra

    2007-04-01

    The formation of nitrate sodalite, an important constituent of the resilient heels at DOE nuclear waste storage sites, was closely followed by oven synthesis, in situ calorimetry as a function of heating rate from 0.01 to 0.1 °C/min and X-ray diffraction. A transition sequence of amorphous-zeolite A-sodalite-cancrinite was confirmed. For in situ synthesis calorimetry, the heat flow peaks related to zeolite A formation are shifted to higher temperatures as heating rate increases. Although the end products are mostly nitrate sodalite, no calorimetric signals associated with zeolite A to sodalite conversion are detected. This suggests that the enthalpy of formation of zeolite A and sodalite are very similar and the zeolite A to sodalite conversion enthalpy is small. This conclusion is in accord with previous measurements by oxide melt solution calorimetry.

  1. In situ TEM study of stability of TaRhx diffusion barriers using a novel sample preparation method.

    PubMed

    Dalili, Neda; Li, Peng; Kupsta, Martin; Liu, Qi; Ivey, Douglas G

    2014-03-01

    The atomic diffusion mechanisms associated with metallurgical failure of TaRhx diffusion barriers for Cu metallizations were studied by in situ transmission electron microscopy (TEM). The issues related to in situ heating of focused ion beam (FIB) prepared cross-sectional TEM samples that contain Cu thin films are discussed. The Cu layer in Si/(13 nm)TaRhx/Cu stacks showed grain growth and formation of voids at temperatures exceeding 550°C. For Si/(43 nm)TaRhx/Cu stacks, grain growth of Cu was delayed to higher temperatures, i.e., 700°C, and void formation was not observed. Extensive surface diffusion of Cu, however, preceded bulk diffusion. Therefore, a 10 nm film of electron beam evaporated C was deposited on both sides of the TEM lamellae to limit surface diffusion. This processing technique allowed for direct observation of atomic diffusion and reaction mechanisms across the TaRhx interface. Failure occurred by nucleation of orthorhombic RhSi particles at the Si/TaRhx interface. Subsequently, the barrier at areas adjacent to RhSi particles was depleted in Rh. This created lower density areas in the barrier, which facilitated diffusion of Cu to the Si substrate to form Cu3Si. The morphology of an in situ annealed lamella was compared with an ex situ bulk annealed sample, which showed similar reaction morphology. The sample preparation method developed in this study successfully prevented surface diffusion/delamination of the Cu layer and can be employed to understand the metallurgical failure of other potential diffusion barriers.

  2. Versatile method for AFM-tip functionalization with biomolecules: fishing a ligand by means of an in situ click reaction

    NASA Astrophysics Data System (ADS)

    Kumar, Rakesh; Ramakrishna, Shivaprakash N.; Naik, Vikrant V.; Chu, Zonglin; Drew, Michael E.; Spencer, Nicholas D.; Yamakoshi, Yoko

    2015-04-01

    A facile and universal method for the functionalization of an AFM tip has been developed for chemical force spectroscopy (CFS) studies of intermolecular interactions of biomolecules. A click reaction between tripod-acetylene and an azide-linker-ligand molecule was successfully carried out on the AFM tip surface and used for the CFS study of ligand-receptor interactions.A facile and universal method for the functionalization of an AFM tip has been developed for chemical force spectroscopy (CFS) studies of intermolecular interactions of biomolecules. A click reaction between tripod-acetylene and an azide-linker-ligand molecule was successfully carried out on the AFM tip surface and used for the CFS study of ligand-receptor interactions. Electronic supplementary information (ESI) available: Experimental details with synthesis and characterization of compounds. Procedures for modifications of Au surfaces and AFM tips. AFM images and full PM-IRRAS spectra of modified surfaces. Detailed procedure for QCM measurement. A table showing ligand-receptor interaction probability. NMR, IR and MS charts. See DOI: 10.1039/c5nr01495f

  3. Evolving Technologies for In-Situ Studies of Mars Ice

    NASA Technical Reports Server (NTRS)

    Carsey, F. D.; Hecht, M. H.

    2003-01-01

    Icy sites on Mars continue to be of high scientific importance. These sites include the polar caps, the southern mid-latitude subsurface permafrost, and the seasonal frost. These sites have interest due to their roles in climate processes, past climates, surface and near-surface water, astrobiology, geomorphology, and other topics. As is the case for many planetary features, remote sensing, while of great value, cannot answer all questions; in-situ examination is essential, and the motivation for in-situ observations generally leads to the subsurface, which, fortunately, is accessible on Mars. It is clear in fact that a Mars polar cap subsurface mission is both scientifically compelling and practical. Recent data from orbiting platforms has provided a remarkable level of information about the Mars ice caps; we know, for example, the size, shape and annual cycle of the cap topography as well as we know that of Earth, and we have more information on stratification that we have of, for example, the ice of East Antarctica. To understand the roles that the Mars polar caps play, it is necessary to gather information on the ice cap surface, strata, composition and bed. In this talk the status of in-situ operations and observations will be summarized, and, since we have conveniently at hand another planet with polar caps, permafrost and ice, the role of testing and validation of experimental procedures on Earth will be addressed.

  4. Holographic microscopy for in situ studies of microorganism motility

    NASA Astrophysics Data System (ADS)

    Nadeau, J.; Hu, S.; Jericho, S.; Lindensmith, C.

    2011-12-01

    Robust technologies for the detection and identification of microorganisms at low concentrations in complex liquid media are needed for numerous applications: environmental and medical microbiology, food safety, and for the search for microbial life elsewhere in the Solar System. The best current method for microbial enumeration is specific labeling with fluorescent dyes followed by high-resolution light microscopy. However, fluorescent techniques are difficult to use in situ in extreme environments (such as the Arctic and Antarctic or the open ocean) due to the fragility of the instruments and their high power demands. In addition, light microscopic techniques rarely provide insight into microbial motility behaviors. Tracking single cells would provide important insight into the physics of micron-scale motility as well as into key microbial phenomena such as surface attachment and invasiveness. An alternative to traditional light microscopy that is attracting increasing attention is holographic microscopy. Holographic microscopy works by illuminating the object of interest with coherent light from a laser. The light reflected from (or transmitted through) the object is then combined with a coherent reference beam to create an interference pattern that contains the phase and intensity information required to reconstruct a three dimensional image of the object. The interference pattern is recorded on a high resolution detector and can be used to computationally reconstruct a 3D image of the object. The lateral resolution of the image depends upon the wavelength of the light used, the laser power, camera quality, and external noise sources (vibration, stray light, and so forth). Although the principle is simple, technological barriers have prevented wider use of holographic microscopy. Laser sources and CCD cameras with the appropriate properties have only very recently become affordable. In addition, holographic microscopy leads to large data sets that are

  5. Amplification of papillomaviral DNA sequences from a high proportion of feline cutaneous in situ and invasive squamous cell carcinomas using a nested polymerase chain reaction.

    PubMed

    Munday, John S; Kiupel, Matti; French, Adrienne F; Howe, Laryssa

    2008-10-01

    Squamous cell carcinomas (SCCs) are common skin tumours of cats. Previous studies have suggested that papillomaviral (PV) DNA is detectible within some feline SCCs. A PV DNA sequence has been previously amplified from five feline bowenoid in situ carcinomas (BISCs). Primers specific for this sequence were used in a nested polymerase chain reaction to compare PV detection rates in SCCs to rates within non-SCC skin lesions. Papillomaviral DNA was amplified from 20 of 20 BISC, 17 of 20 invasive SCC and 3 of 17 non-SCC controls. The rate of PV amplification from feline cutaneous SCCs was significantly higher than from non-SCC lesions. These results confirm that feline cutaneous SCCs are associated with PV infection. In humans, there is evidence that PVs promote SCC development within sun-exposed skin. The demonstrated association between PVs and feline cutaneous SCCs suggests, but does not prove, that PVs may also promote feline SCC development. If PVs are oncogenic in cats, prevention of PV infection may reduce feline cutaneous SCC development. To the authors' knowledge, this is the first time that PV DNA has been amplified from a non-SCC sample of feline skin.

  6. Dehydrogenation and Sintering of TiH2: An In Situ Study

    NASA Astrophysics Data System (ADS)

    Chen, Gang; Liss, Klaus D.; Auchterlonie, Graeme; Tang, Huiping; Cao, Peng

    2017-03-01

    This first-ever study investigated dehydrogenation and microstructural evolution of TiH2 during sintering under vacuum using in situ neutron diffraction, in situ transmission electron microscopy, and ex situ neutron tomography. The densification behavior, microstructure, hydrogen concentration, and in situ phase transformation were reported. The shrinkage, weight loss percentage, and densification of the TiH2 powder compact monotonically increase with sintering temperature, while the open porosity behaves differently; porosity first increases at the initial sintering stage and then decreases during further sintering. The in situ phase transformation observations reveal that dehydrogenation starts from the outer area of either a particle or a powder compact and progressively carries forward into the interior of the particle or the compact. A shrinking core model was proposed to elucidate the dehydrogenation process for a single particle and a powder compact.

  7. NASTRAN buckling study of a linear induction motor reaction rail

    NASA Technical Reports Server (NTRS)

    Williams, J. G.

    1973-01-01

    NASTRAN was used to study problems associated with the installation of a linear induction motor reaction rail test track. Specific problems studied include determination of the critical axial compressive buckling stress and establishment of the lateral stiffness of the reaction rail under combined loads. NASTRAN results were compared with experimentally obtained values and satisfactory agreement was obtained. The reaction rail was found to buckle at an axial compressive stress of 11,400 pounds per square inch. The results of this investigation were used to select procedures for installation of the reaction rail.

  8. Theoretical Studies of Homogeneous and Heterogeneous Reactions in Silicon Systems

    DTIC Science & Technology

    1991-11-19

    and Si4 , and polymerization reactions leading to the higher silanes and silenes . Heterogeneous processes studied include sticking probabilities...to the higher silanes and silenes . Heterogeneous processes under study include sticking probabilities, scattering, and chemical reactions of H2 and...results for Si 2 in a silane CVD reactor have received qualitative experimental confirmation 24 . Consequently, our research group has devoted considerable

  9. A study to identify and compare airborne systems for in-situ measurements of launch vehicle effluents

    NASA Technical Reports Server (NTRS)

    Thomas, T. J.; Chace, A. S.

    1974-01-01

    An in-situ system for monitoring the concentration of HCl, CO, CO2, and Al2O3 in the cloud of reaction products that form as a result of a launch of solid propellant launch vehicle is studied. A wide array of instrumentation and platforms are reviewed to yield the recommended system. An airborne system suited to monitoring pollution concentrations over urban areas for the purpose of calibrating remote sensors is then selected using a similar methodology to yield the optimal configuration.

  10. In situ ESEM study of the thermal decomposition of chrysotile asbestos in view of safe recycling of the transformation product.

    PubMed

    Gualtieri, Alessandro F; Gualtieri, Magdalena Lassinantti; Tonelli, Massimo

    2008-08-15

    The thermal transformation of asbestos into non-hazardous crystalline phases and their recycling is a promising solution for the "asbestos problem". The most common asbestos-containing industrial material produced worldwide is cement-asbestos. Knowledge of the kinetics of thermal transformation of asbestos fibers in cement-asbestos is of paramount importance for the optimization of the firing process at industrial scale. Here, environmental scanning electron microscopy (ESEM) was used for the first time to follow in situ the thermal transformation of chrysotile fibers present in cement-asbestos. It was found that the reaction kinetics of thermal transformation of chrysotile was highly slowed down in the presence of water vapor in the experimental chamber with respect to He. This was explained by chemisorbed water on the surface of the fibers which affected the dehydroxylation reaction and consequently the recrystallization into Mg-silicates. In the attempt to investigate alternative and faster firing routes for the decomposition of asbestos, a low melting glass was mixed with cement-asbestos and studied in situ to assess to which extent the decomposition of asbestos is favored. It was found that the addition of a low melting glass to cement-asbestos greatly improved the decomposition reaction and decreased the transformation temperatures.

  11. The study on the reaction of rutile in Bayer liquor

    SciTech Connect

    Bi Shiwen; Li Dianfeng; Yang Yihong; Fu Gaofeng; Zhang Xin; Li Yan

    1996-10-01

    TiO{sub 2} is a harmful impurity in the digestion of producing alumina. TiO{sub 2} in bauxite usually exists in the forms of rutile, anatase and brookite. In this paper, the authors studied the reaction of rutile in sodium aluminate liquor, examined the effects of OH{sup {minus}} ion concentration, adding amount of CaO and temperature on the reaction, achieved the kinetics equation and calculated the activation energy of the reaction.

  12. Assessing denitrification in groundwater using natural gradient tracer tests with 15N: In situ measurement of a sequential multistep reaction

    USGS Publications Warehouse

    Smith, R.L.; Böhlke, J.K.; Garabedian, S.P.; Revesz, K.M.; Yoshinari, T.

    2004-01-01

    Denitrification was measured within a nitrate-contaminated aquifer on Cape Cod, Massachusetts, using natural gradient tracer tests with 15N nitrate. The aquifer contained zones of relatively high concentrations of nitrite (up to 77 ??M) and nitrous oxide (up to 143 ??M) and has been the site of previous studies examining ground water denitrification using the acetylene block technique. Small-scale (15-24 m travel distance) tracer tests were conducted by injecting 15N nitrate and bromide as tracers into a depth interval that contained nitrate, nitrite, nitrous oxide, and excess nitrogen gas. The timing of the bromide breakthrough curves at down-gradient wells matched peaks in 15N abundance above background for nitrate, nitrite, nitrous oxide, and nitrogen gas after more than 40 days of travel. Results were simulated with a one-dimensional transport model using linked reaction kinetics for the individual steps of the denitrification reaction pathway. It was necessary to include within the model spatial variations in background concentrations of all nitrogen oxide species. The model indicated that nitrite production (0.036-0.047 ??mol N (L aquifer)-1 d -1) was faster than the subsequent denitrification steps (0.013-0.016 ??mol N (L aquifer)-1 d-1 for nitrous oxide and 0.013-0.020 ??mol N (L aquifer)-1 d-1 for nitrogen gas) and that the total rate of reaction was slower than indicated by both acetylene block tracer tests and laboratory incubations. The rate of nitrate removal by denitrification was much slower than the rate of transport, indicating that nitrate would migrate several kilometers down-gradient before being completely consumed.

  13. Plans for Studies of (alpha,n) Reactions Relevant to Astrophysics via Inverse Reactions

    NASA Astrophysics Data System (ADS)

    Shima, T.; Nagai, Y.; Kii, T.; Kikuchi, T.; Baba, T.; Kobayashi, T.; Okazaki, F.

    1996-08-01

    (alpha,n) reactions in the keV energy region play important roles in astrophysical nucleosynthesis. In the primordial nucleosynthesis, it has been pointed out that a fluctuation of the baryon density distribution could be formed if the QCD phase transition from quark-gluon plasma to hadron gas occurred by first order. In that case the space was separated into the high density proton-rich zones and the low density neutron-rich ones, and in the neutron-rich zones nucleosynthesis could proceed beyond the mass gap at A = 8 via the reaction chains such as H-1(n,gamma)H-2(n,gamma)H-3(d,n)He-4(t,gamma)Li-7(n,gamma)Li-8(alpha,n)B- 11(n,ga mma)B-12(e(sup-)nu)C-12(n,gamma)C-13(n,gamma)C-14(n,gamma)C-15 ......, and so on. In the above nuclear reactions, the Li-8(alpha,n)B reaction plays quite a crucial role, because it can break through the mass gap at A = 8. (alpha,n) reactions of some light nuclei are also important as neutron sources for slow neutron capture process (s-process) of nucleosynthesis in stars. In low-mass and intermediate-mass (M < 10 Solar Mass) stars, neutrons are supposed to be supplied mainly by the C-13(alpha,n)O-16 reaction. On the other hand, the Ne-22(alpha,n)Mg-25 reaction is a candidate of the neutron source in massive stars with M > or = 10 Solar Mass. The contribution of the O-18(alpha,n)Ne-21 reaction to s-process in massive stars is still unknown. Since the temperatures of the above astrophysical sites correspond to the energy range of between a few ten and a few hundred keV, accurate data of the (alpha,n) reaction cross sections in the energy range are required for investigating nucleosynthesis. In order to measure these cross sections, not only direct (alpha,n) reactions but also inverse (n,alpha) reactions can be studied. In the following we would like to show experimental designs for studying several (alpha,n) reactions of astrophysical importance.

  14. Matrix isolation as a tool for studying interstellar chemical reactions

    NASA Technical Reports Server (NTRS)

    Ball, David W.; Ortman, Bryan J.; Hauge, Robert H.; Margrave, John L.

    1989-01-01

    Since the identification of the OH radical as an interstellar species, over 50 molecular species were identified as interstellar denizens. While identification of new species appears straightforward, an explanation for their mechanisms of formation is not. Most astronomers concede that large bodies like interstellar dust grains are necessary for adsorption of molecules and their energies of reactions, but many of the mechanistic steps are unknown and speculative. It is proposed that data from matrix isolation experiments involving the reactions of refractory materials (especially C, Si, and Fe atoms and clusters) with small molecules (mainly H2, H2O, CO, CO2) are particularly applicable to explaining mechanistic details of likely interstellar chemical reactions. In many cases, matrix isolation techniques are the sole method of studying such reactions; also in many cases, complexations and bond rearrangements yield molecules never before observed. The study of these reactions thus provides a logical basis for the mechanisms of interstellar reactions. A list of reactions is presented that would simulate interstellar chemical reactions. These reactions were studied using FTIR-matrix isolation techniques.

  15. IN SITU INFRARED STUDY OF CATALYTIC DECOMPOSITION OF NO

    SciTech Connect

    KHALID ALMUSAITEER; RAM KRISHNAMURTHY; STEVEN S.C. CHUANG

    1998-08-18

    The growing concerns for the environment and increasingly stringent standards for NO emission have presented a major challenge to control NO emissions from electric utility plants and automobiles. Catalytic decomposition of NO is the most attractive approach for the control of NO emission for its simplicity. Successful development of an effective catalyst for NO decomposition will greatly decrease the equipment and operation cost of NO control. Due to lack of understanding of the mechanism of NO decomposition, efforts on the search of an effective catalyst have been unsuccessful. Scientific development of an effective catalyst requires fundamental understanding of the nature of active site, the rate-limiting step, and an approach to prolong the life of the catalyst. Research is proposed to study the reactivity of adsorbates for the direct NO decomposition and to investigate the feasibility of two novel approaches for improving catalyst activity and resistance to sintering. The first approach is the use of silanation to stabilize metal crystallites and supports for Cu-ZSM-5 and promoted Pt catalysts; the second is utilization of oxygen spillover and desorption to enhance NO decomposition activity. An innovative infrared reactor system will be used to observe and determine the dynamic behavior and the reactivity of adsorbates during NO decomposition, oxygen spillover, and silanation. A series of experiments including X-ray diffraction, temperature programmed desorption, temperature programmed reaction, X-ray photoelectron spectroscopy will be used to characterized the catalysts. The information obtained from this study will provide a scientific basis for developing an effective catalyst for the NO decomposition under practical flue gas conditions.

  16. A quantified dosing ALD reactor with in-situ diagnostics for surface chemistry studies

    NASA Astrophysics Data System (ADS)

    Larrabee, Thomas J.

    A specialized atomic layer deposition (ALD) reactor has been constructed to serve as an instrument to simultaneously study the surface chemistry of the ALD process, and perform ALD as is conventionally done in continuum flow of inert gas. This reactor is uniquely useful to gain insight into the ALD process because of the combination of its precise, controllable, and quantified dosing/microdosing capability; its in-situ quadrupole mass spectrometer for gas composition analysis; its pair of highly-sensitive in-situ quartz crystal microbalances (QCMs); and its complete spectrum of pressures and operating conditions --- from viscous to molecular flow regimes. Control of the dose is achieved independently of the conditions by allowing a reactant gas to fill a fixed volume and measured pressure, which is held at a controlled temperature, and subsequently dosed into the system by computer controlled pneumatic valves. Absolute reactant exposure to the substrate and QCMs is unambiguously calculated from the molecular impingement flux, and its relationship to dose size is established, allowing means for easily intentionally reproducing specific exposures. Methods for understanding atomic layer growth and adsorption phenomena, including the precursor sticking probability, dynamics of molecular impingement, size of dose, and other operating variables are for the first time quantitatively related to surface reaction rates by mass balance. Extensive characterization of the QCM as a measurement tool for adsorption under realistic ALD conditions has been examined, emphasizing the state-of-the-art and importance of QCM system features required. Finally, the importance of dose-quantification and microdosing has been contextualized in view of the ALD literature, underscoring the significance of more precise condition specification in establishing a better basis for reactor and reactant comparison.

  17. In Situ Oxidation of Liquid Trichloroethylene by Permanganate Solutions: Preliminary Results of Column Studies

    SciTech Connect

    Schroth, Martin H.; Oostrom, Mart; Wietsma, Thomas W.; Istok, Jonathan D.; H.J. Morel-Seytoux

    2000-01-11

    In situ oxidation of liquid trichloroethylene by permanganate solutions: Preliminary results of column studies. In: Proceedings of the 19th American Geophysical Union Hydrology Days, H. J. Morel-Seytoux, ed., pp. 411-420. Hydrology Days Pub., Atherton, Ca.

  18. Xenon Implantation in Nanodiamonds: In Situ Transmission Electron Microscopy Study and Molecular Dynamics Simulations

    NASA Astrophysics Data System (ADS)

    Shiryaev, A. A.; Hinks, J.; Marks, N.; Greaves, G.; Donnelly, S.; Fisenko, A. V.; Kiwi, M.

    2016-08-01

    We present results of the first investigation of the Xe implantation process into nanodiamonds of various sizes studied in situ in transmission electron microscope (TEM), complemented by advanced molecular dynamics simulations.

  19. Chemical reactions in dense monolayers: in situ thermal cleavage of grafted esters for preparation of solid surfaces functionalized with carboxylic acids.

    PubMed

    Dugas, Vincent; Chevalier, Yves

    2011-12-06

    The thermodynamics of a chemical reaction confined at a solid surface was investigated through kinetic measurements of a model unimolecular reaction. The thermal cleavage of ester groups grafted at the surface of solid silica was investigated together with complementary physicochemical characterization of the grafted species. The ester molecules were chemically grafted to the silica surface and subsequently cleaved into the carboxylic acids. A grafting process of a reproducible monolayer was designed using the reaction of monofunctional organosilane from its gas phase. The thermal deprotection step of the ester end-group was investigated. The thermal deprotection reaction behaves in quite a specific manner when it is conducted at a surface in a grafted layer. Different organosilane molecules terminated by methyl, isopropyl and tert-butyl ester groups were grafted to silica surface; such functionalized materials were characterized by elemental analysis, IR and NMR spectroscopy, and thermogravimetric analysis, and the thermodynamic parameters of the thermal elimination reaction at the surface were measured. The limiting factor of such thermal ester cleavage reaction is the thermal stability of grafted ester group according to the temperature order: tert-butyl < i-propyl < methyl. Methyl ester groups were not selectively cleaved by temperature. The thermal deprotection of i-propyl ester groups took place at a temperature close to the thermal degradation of the organofunctional tail of the silane. The low thermolysis temperature of the grafted tert-butyl esters allowed their selective cleavage. There is a definite influence of the surface on the reaction. The enthalpy of activation is lower than in the gas phase because of the polarity of the reaction site. The major contribution is entropic; the negative entropy of activation comes from lateral interactions with the neighbor grafted molecules because of the high grafting density. Such reaction is an original strategy

  20. Fundamental studies of retrograde reactions in direct liquefaction

    SciTech Connect

    Serio, M.A.; Solomon, P.R.; Bassilakis, R.; Kroo, E.

    1989-01-01

    Most of the proposed processing schemes for improving liquefaction yields involve favoring bond-breaking and radical stabilization reactions over the retrograde reactions. The retrograde reactions are often encountered before liquefaction temperatures are reached. The objective of this program is to elucidate and model the retrograde reaction chemistry in direct coal liquefaction through the application of experimental techniques and theoretical models which have been successfully employed at Advanced Fuel Research (AFR) and SRI International (a subcontractor) to understand and predict coal reaction behavior. The study of retrograde reactions is being done using an integrated approach using extensive characterization of the liquefaction chemistry of three kinds of systems: (1) model polymers; (2) coal; and (3) modified coals.

  1. Transverse flow reactor studies of the dynamics of radical reactions

    SciTech Connect

    Macdonald, R.G.

    1993-12-01

    Radical reactions are in important in combustion chemistry; however, little state-specific information is available for these reactions. A new apparatus has been constructed to measure the dynamics of radical reactions. The unique feature of this apparatus is a transverse flow reactor in which an atom or radical of known concentration will be produced by pulsed laser photolysis of an appropriate precursor molecule. The time dependence of individual quantum states or products and/or reactants will be followed by rapid infrared laser absorption spectroscopy. The reaction H + O{sub 2} {yields} OH + O will be studied.

  2. Variational Flooding Study of a SN2 Reaction.

    PubMed

    Piccini, GiovanniMaria; McCarty, James J; Valsson, Omar; Parrinello, Michele

    2017-02-02

    We have studied the reaction dynamics of a prototypical organic reaction using a variationally optimized truncated bias to accelerate transitions between educt and product reactant states. The asymmetric SN2 nucleophilic substitution reaction of fluoromethane and chloromethane CH3F + Cl(-) ⇌ CH3Cl + F(-) is considered, and many independent biased molecular dynamics simulations have been performed at 600, 900, and 1200 K, collecting several hundred transitions at each temperature. The transition times and relative rate constants have been obtained for both reaction directions. The activation energies extracted from an Arrhenius plot compare well with standard static calculations.

  3. Multislice simulations for in-situ HRTEM studies of nanostructured magnesium hydride at ambient hydrogen pressure.

    PubMed

    Surrey, Alexander; Schultz, Ludwig; Rellinghaus, Bernd

    2017-01-31

    The use of transmission electron microscopy (TEM) for the structural characterization of many nanostructured hydrides, which are relevant for solid state hydrogen storage, is hindered due to a rapid decomposition of the specimen upon irradiation with the electron beam. Environmental TEM allows to stabilize the hydrides by applying a hydrogen back pressure of up to 4.5 bar in a windowed environmental cell. The feasibility of high-resolution TEM (HRTEM) investigations of light weight metals and metal hydrides in such a "nanoreactor" is studied theoretically by means of multislice HRTEM contrast simulations using Mg and its hydride phase, MgH2, as model system. Such a setup provides the general opportunity to study dehydrogenation and hydrogenation reactions at the nanoscale under technological application conditions. We analyze the dependence of both the spatial resolution and the HRTEM image contrast on parameters such as the defocus, the metal/hydride thickness, and the hydrogen pressure in order to explore the possibilities and limitations of in-situ experiments with windowed environmental cells. Such simulations may be highly valuable to pre-evaluate future experimental studies.

  4. Electromagnetic studies of nuclear structure and reactions

    SciTech Connect

    Hersman, F.W.; Dawson, J.F.; Heisenberg, J.H.; Calarco, J.R.

    1990-06-01

    This report contains papers on the following topics: giant resonance studies; deep inelastic scattering studies; high resolution nuclear structure work; and relativistic RPA; and field theory in the Schroedinger Representation.

  5. In situ SIMS analysis and reactions of surfaces prepared by soft landing of mass-selected cations and anions using an ion trap mass spectrometer.

    PubMed

    Nie, Zongxiu; Li, Guangtao; Goodwin, Michael P; Gao, Liang; Cyriac, Jobin; Cooks, R Graham

    2009-06-01

    Mass-selected polyatomic cations and anions, produced by electrosonic spray ionization (ESSI), were deposited onto polycrystalline Au or fluorinated self-assembled monolayer (FSAM) surfaces by soft landing (SL), using a rectilinear ion trap (RIT) mass spectrometer. Protonated and deprotonated molecules, as well as intact cations and anions generated from such molecules as peptides, inorganic catalysts, and fluorescent dyes, were soft-landed onto the surfaces. Analysis of the modified surfaces was performed in situ by Cs(+) secondary ion mass spectrometry (SIMS) using the same RIT mass analyzer to characterize the sputtered ions as that used to mass select the primary ions for SL. Soft-landing times as short as 30 s provided surfaces that yielded good quality SIMS spectra. Chemical reactions of the surfaces modified by SL were generated in an attached reaction chamber into which the surface was transferred under vacuum. For example, a surface on which protonated triethanolamine had been soft landed was silylated using vapor-phase chlorotrimethylsilane before being returned still under vacuum to the preparation chamber where SIMS analysis revealed the silyloxy functionalization. SL and vapor-phase reactions are complementary methods of surface modification and in situ surface analysis by SIMS is a simple way to characterize the products produced by either technique.

  6. Design study for a magnetically supported reaction wheel

    NASA Technical Reports Server (NTRS)

    Stocking, G.; Dendy, J.; Sabnis, A.

    1974-01-01

    Results are described of a study program in which the characteristics of a magnetically supported reaction wheel are defined. Tradeoff analyses are presented for the principal components, which are then combined in several reaction wheel design concepts. A preliminary layout of the preferred configuration is presented along with calculated design and performance parameters. Recommendations are made for a prototype development program.

  7. MOLAB, a Mobile Laboratory for In Situ Non-Invasive Studies in Arts and Archaeology

    NASA Astrophysics Data System (ADS)

    Brunetti, B. G.; Matteini, Mauro; Miliani, C.; Pezzati, L.; Pinna, D.

    Mobile laboratory (MOLAB) is a unique joint collection of portable equipment for non-destructive in situ measurements. MOLAB activities are carried out within the frame of the Eu-ARTECH Integrated Infrastructure Initiative of the sixth F.P. In situ measurement is quite useful because it eliminates any risk connected to moving artworks or other precious objects to a laboratory. MOLAB instruments are accessible to European researchers through a peer-review selection of proposals. Starting from July 2004, MOLAB enabled non-destructive in situ studies of many precious artworks, such as paintings by Perugino, Raphael and Leonardo.

  8. In situ anodization of aluminum surfaces studied by x-ray reflectivity and electrochemical impedance spectroscopy

    SciTech Connect

    Bertram, F. Evertsson, J.; Messing, M. E.; Mikkelsen, A.; Lundgren, E.; Zhang, F.; Pan, J.; Carlà, F.; Nilsson, J.-O.

    2014-07-21

    We present results from the anodization of an aluminum single crystal [Al(111)] and an aluminum alloy [Al 6060] studied by in situ x-ray reflectivity, in situ electrochemical impedance spectroscopy and ex situ scanning electron microscopy. For both samples, a linear increase of oxide film thickness with increasing anodization voltage was found. However, the slope is much higher in the single crystal case, and the break-up of the oxide film grown on the alloy occurs at a lower anodization potential than on the single crystal. The reasons for these observations are discussed as are the measured differences observed for x-ray reflectivity and electrochemical impedance spectroscopy.

  9. Relative sensitivity of immunohistochemistry, multiple reaction monitoring mass spectrometry, in situ hybridization and PCR to detect Coxsackievirus B1 in A549 cells

    PubMed Central

    Laiho, Jutta E.; Oikarinen, Maarit; Richardson, Sarah J.; Frisk, Gun; Nyalwidhe, Julius; Burch, Tanya C.; Morris, Margaret A.; Oikarinen, Sami; Pugliese, Alberto; Dotta, Francesco; Campbell-Thompson, Martha; Nadler, Jerry; Morgan, Noel G.; Hyöty, Heikki

    2017-01-01

    Background Enteroviruses (EVs) have been linked to the pathogenesis of several diseases and there is a collective need to develop improved methods for the detection of these viruses in tissue samples. Objectives This study evaluates the relative sensitivity of immunohistochemistry (IHC), proteomics, in situ hybridization (ISH) and RT-PCR to detect one common EV, Coxsackievirus B1 (CVB1), in acutely infected human A549 cells in vitro. Study design A549 cells were infected with CVB1 and diluted with uninfected A549 cells to produce a limited dilution series in which the proportion of infected cells ranged from 10−1 to 10−8. Analyses were carried out by several laboratories using IHC with different anti-EV antibodies, ISH with both ViewRNA and RNAScope systems, liquid chromatography multiple reaction monitoring mass spectrometry (LC/MRM/MS/MS), and two modifications of RT-PCR. Results RT-PCR was the most sensitive method for EV detection yielding positive signals in the most diluted sample (10−8). LC/MRM/MS/MS detected viral peptides at dilutions as high as 10−7. The sensitivity of IHC depended on the antibody used, and the most sensitive antibody (Dako clone 5D8/1) detected virus proteins at a dilution of 10−6, while ISH detected the virus at dilutions of 10−4. Conclusions All methods were able to detect CVB1 in infected A549 cells. RT-PCR was most sensitive followed by LC/MRM/MS/MS and then IHC. The results from this in vitro survey suggest that all methods are suitable tools for EV detection but that their differential sensitivities need to be considered when interpreting the results from such studies. PMID:26875099

  10. In situ infrared spectroscopic study of forsterite carbonation in wet supercritical CO2.

    PubMed

    Loring, John S; Thompson, Christopher J; Wang, Zheming; Joly, Alan G; Sklarew, Deborah S; Schaef, H Todd; Ilton, Eugene S; Rosso, Kevin M; Felmy, Andrew R

    2011-07-15

    Carbonation reactions are central to the prospect of CO(2) trapping by mineralization in geologic reservoirs. In contrast to the relevant aqueous-mediated reactions, little is known about the propensity for carbonation in the key partner fluid: supercritical carbon dioxide containing dissolved water ("wet" scCO(2)). We employed in situ mid-infrared spectroscopy to follow the reaction of a model silicate mineral (forsterite, Mg(2)SiO(4)) for 24 h with wet scCO(2) at 50 °C and 180 atm. The results show a dramatic dependence of reactivity on water concentration and the presence of liquid water on the forsterite particles. Exposure to neat scCO(2) showed no detectable carbonation reaction. At 47% and 81% water saturation, an Ångstrom-thick liquid-like water film was detected on the forsterite particles and less than 1% of the forsterite transformed. Most of the reaction occurred within the first 3 h of exposure to the fluid. In experiments at 95% saturation and with an excess of water (36% above water saturation), a nanometer-thick water film was detected, and the carbonation reaction proceeded continuously with approximately 2% and 10% conversion, respectively. Our collective results suggest constitutive links between water concentration, water film formation, reaction rate and extent, and reaction products in wet scCO(2).

  11. Reaction selectivity studies on nanolithographically-fabricated platinum model catalyst arrays

    SciTech Connect

    Grunes, Jeffrey Benjamin

    2004-05-01

    In an effort to understand the molecular ingredients of catalytic activity and selectivity toward the end of tuning a catalyst for 100% selectivity, advanced nanolithography techniques were developed and utilized to fabricate well-ordered two-dimensional model catalyst arrays of metal nanostructures on an oxide support for the investigation of reaction selectivity. In-situ and ex-situ surface science techniques were coupled with catalytic reaction data to characterize the molecular structure of the catalyst systems and gain insight into hydrocarbon conversion in heterogeneous catalysis. Through systematic variation of catalyst parameters (size, spacing, structure, and oxide support) and catalytic reaction conditions (hydrocarbon chain length, temperature, pressures, and gas composition), the data presented in this dissertation demonstrate the ability to direct a reaction by rationally adjusting, through precise control, the design of the catalyst system. Electron beam lithography (EBL) was employed to create platinum nanoparticles on an alumina (Al2O3) support. The Pt nanoparticle spacing (100-150-nm interparticle distance) was varied in these samples, and they were characterized using x-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and atomic force microscopy (AFM), both before and after reactions. The TEM studies showed the 28-nm Pt nanoparticles with 100 and 150-nm interparticle spacing on alumina to be polycrystalline in nature, with crystalline sizes of 3-5 nm. The nanoparticle crystallites increased significantly after heat treatment. The nanoparticles were still mostly polycrystalline in nature, with 2-3 domains. The 28-nm Pt nanoparticles deposited on alumina were removed by the AFM tip in contact mode with a normal force of approximately 30 nN. After heat treatment at 500 C in vacuum for 3 hours, the AFM tip, even at 4000 nN, could not remove the platinum

  12. Fundamental studies of retrograde reactions in direct liquefaction

    SciTech Connect

    Serio, M.A.; Solomon, P.R.; Kroo, E.; Charpenay, S.; Bassilakis, R.

    1991-12-17

    The overall objective of the program was to improve the understanding of retrograde reactions and their dependencies on coal rank and structure, and/or coal modifications and reaction conditions. Because retrograde reactions are competitive with bond breaking reactions, an understanding of both is required to shift the competition in favor of the latter. Related objectives were to clarify the conflicting observations reported in literature on such major topics as the role of oxygen groups in retrograde reactions and to provide a bridge from very fundamental studies on pure compounds to phenomenological studies on actual coal. This information was integrated into the FG-DVC model, which was improved and extended to the liquefaction context.

  13. In situ studies of microbial inactivation during high pressure processing

    NASA Astrophysics Data System (ADS)

    Maldonado, Jose Antonio; Schaffner, Donald W.; Cuitiño, Alberto M.; Karwe, Mukund V.

    2016-01-01

    High pressure processing (HPP) has been shown to reduce microbial concentration in foods. The mechanisms of microbial inactivation by HPP have been associated with damage to cell membranes. The real-time response of bacteria to HPP was measured to elucidate the mechanisms of inactivation, which can aid in designing more effective processes. Different pressure cycling conditions were used to expose Enterobacter aerogenes cells to HPP. Propidium iodide (PI) was used as a probe, which fluoresces after penetrating cells with damaged membranes and binding with nucleic acids. A HPP vessel with sapphire windows was used for measuring fluorescence in situ. Membrane damage was detected during pressurization and hold time, but not during depressurization. The drop in fluorescence was larger than expected after pressure cycles at higher pressure and longer times. This indicated possible reversible disassociation of ribosomes resulting in additional binding of PI to exposed RNA under pressure and its release after depressurization.

  14. In situ Raman cell for high pressure and temperature studies of metal and complex hydrides.

    PubMed

    Domènech-Ferrer, Roger; Ziegs, Frank; Klod, Sabrina; Lindemann, Inge; Voigtländer, Ralf; Dunsch, Lothar; Gutfleisch, Oliver

    2011-04-15

    A novel cell for in situ Raman studies at hydrogen pressures up to 200 bar and at temperatures as high as 400 °C is presented. This device permits in situ monitoring of the formation and decomposition of chemical structures under high pressure via Raman scattering. The performance of the cell under extreme conditions is stable as the design of this device compensates much of the thermal expansion during heating which avoids defocusing of the laser beam. Several complex and metal hydrides were analyzed to demonstrate the advantageous use of this in situ cell. Temperature calibration was performed by monitoring the structural phase transformation and melting point of LiBH(4). The feasibility of the cell in hydrogen atmosphere was confirmed by in situ studies of the decomposition of NaAlH(4) with added TiCl(3) at different hydrogen pressures and the decomposition and rehydrogenation of MgH(2) and LiNH(2).

  15. Advanced sample environments for in situ neutron diffraction studies of nuclear materials

    NASA Astrophysics Data System (ADS)

    Reiche, Helmut Matthias

    Generation IV nuclear reactor concepts, such as the supercritical-water-cooled nuclear reactor (SCWR), are actively researched internationally. Operating conditions above the critical point of water (374°C, 22.1 MPa) and fuel core temperature that potentially exceed 1850°C put a high demand on the surrounding materials. For their safe application, it is essential to characterize and understand the material properties on an atomic scale such as crystal structure and grain orientation (texture) changes as a function of temperature and stress. This permits the refinement of models predicting the macroscopic behavior of the material. Neutron diffraction is a powerful tool in characterizing such crystallographic properties due to their deep penetration depth into condensed matter. This leads to the ability to study bulk material properties, as opposed to surface effects, and allows for complex sample environments to study e.g. the individual contributions of thermo-mechanical processing steps during manufacturing, operating or accident scenarios. I present three sample environments for in situ neutron diffraction studies that provide such crystallographic information and have been successfully commissioned and integrated into the user program of the High Pressure -- Preferred Orientation (HIPPO) diffractometer at the Los Alamos Neutron Science Center (LANSCE) user facility. I adapted a sample changer for reliable and fast automated texture measurements of multiple specimens. I built a creep furnace combining a 2700 N load frame with a resistive vanadium furnace, capable of temperatures up to 1000°C, and manipulated by a pair of synchronized rotation stages. This combination allows following deformation and temperature dependent texture and strain evolutions in situ. Utilizing the presented sample changer and creep furnace we studied pressure tubes made of Zr-2.5wt%Nb currently employed in CANDURTM nuclear reactors and proposed for future SCWRs, acting as the primary

  16. [Spectrum characteristics of leaching components from co-contaminated loess in ex-situ column washing reaction].

    PubMed

    Fan, Chun-hui; Zhang, Ying-chao; Du, Bo; He, Lei; Wang, Jia-hong

    2015-02-01

    Soil contamination is regarded as one of the most serious issues to humanity all over the world. It is statistically believed that over one-fifth of the farmland, that is 20 million ha, is found to be contaminated by heavy metals in China. And the related issues, caused by soil contamination, of food safety, human health and eco-environmental quality attract much attention by public with more serious contamination than before. The technological approach for soil remediation is widely investigated. The technology of soil washing is effective for contaminants removal, while the treatment procedure might lead to component leaching from soil system, harmful for soil fertility, physicochemical properties and ecological functions. The study of spectral characteristics on leaching component is significant for decision-making of contaminated sites remediation and ecological function recovery, while the related investigation seems weaker nowadays. The paper mainly revealed the leaching characteristics of component from Pb/Cd contaminated loess in the washing process with Ethylene Diamine Tetraacetic Acid (EDTA) in reaction column, and the research objectives included base cations, loess nutrients, clay minerals and organic matter. The variation of clay minerals was analyzed by X-ray diffraction (XRD) and scanning electron microscope (SEM), and 3D-EEM fluorescence spectrum was used for the identification of dissolved organic matter (DOM). The experimental results showed: the leaching component from loess is detected in the washing reaction. The final removal efficiency (240 min) of Pb and Cd from loess are 49. 86% and 62.25%, respectively. The sodium ions and nitrate nitrogen are the most easily leaching component, and little difference of clay minerals is identified before and after washing reaction. The fulvic acid-like (FA-like) material was firstly (10 min) detected around E(ex/em) = 240-250/320-340 and E(ex/em) = 260-290/450-470 in 3D-EEM fluorescence spectrum, and the

  17. Direct studies of (α,p) reactions with HELIOS

    NASA Astrophysics Data System (ADS)

    Lai, Jianping; Blackmon, J. C.; Deibel, C. M.; Dimarco, D.; Gardiner, H.; Lauer, A.; Santiago-Gonzalez, D.; Williams, C.; Digiovine, B.; Greene, J.; Rohrer, J.; Helios Group At Argonne National Lab Collaboration

    2014-09-01

    In a variety of astrophysical processes, (α,p) type reactions have significant effects on final energy output and elemental abundances. However, only a handful of reactions have been measured due to technical limitations. Innovative new equipment and techniques, therefore, are necessary to extend measurement limits of these reactions rates. The HELIcal Orbit Spectrometer(HELIOS), serves as an important tool in studying reactions using radioactive ion beams at the Argonne Tandem Linac Accelerator System facility. With a specially designed gas target, we are able to study (α,p) reaction directly. HELIOS can separate protons from reactions with different energy states and the heavy recoils can be detected in coincidence by a high efficiency gas ionization detector. This combination has been successful in our pilot experiments. A series of (α,p) experiments using this setup in HELIOS are planned. We will start with 20Ne(α,p), which is crucial in Type Ia supernovae. A direct measurement of 30S(α,p), a key reaction in X ray burst, is also included in the near future plans and the beam development of 30S is in progress. Preliminary results will be presented. In a variety of astrophysical processes, (α,p) type reactions have significant effects on final energy output and elemental abundances. However, only a handful of reactions have been measured due to technical limitations. Innovative new equipment and techniques, therefore, are necessary to extend measurement limits of these reactions rates. The HELIcal Orbit Spectrometer(HELIOS), serves as an important tool in studying reactions using radioactive ion beams at the Argonne Tandem Linac Accelerator System facility. With a specially designed gas target, we are able to study (α,p) reaction directly. HELIOS can separate protons from reactions with different energy states and the heavy recoils can be detected in coincidence by a high efficiency gas ionization detector. This combination has been successful in our pilot

  18. Short-range plasmonic nanofocusing within submicron regimes facilitates in situ probing and promoting of interfacial reactions

    NASA Astrophysics Data System (ADS)

    Yu, Chen-Chieh; Lin, Keng-Te; Su, Pao-Yun; Wang, En-Yun; Yen, Yu-Ting; Chen, Hsuen-Li

    2016-02-01

    In this study, a simple configuration, based on high-index dielectric nanoparticles (NPs) and plasmonic nanostructures, is employed for the nanofocusing of submicron-short-range surface plasmon polaritons (SPPs). The excited SPPs are locally bound and focused at the interface between the dielectric NPs and the underlying metallic nanostructures, thereby greatly enhancing the local electromagnetic field. Taking advantage of the surface properties of the dielectric NPs, this system performs various functions. For example, the nanofocusing of submicron-short-range SPPs is used to enhance the Raman signals of gas molecules adsorbed on the dielectric NPs. In addition, the presence of the local strong electromagnetic field accelerates the rates of interfacial reactions on the surfaces of the dielectric NPs. Therefore, the proposed nanofocusing configuration can both promote and probe interfacial reactions simultaneously. Herein, the promotion and probing of the desorption of EtOH vapor are described, as well as the photodegradation of methylene blue. Moreover, the nanofocusing of SPPs is demonstrated on an aluminum surface in both the visible and UV regimes, a process that has not been achieved using conventional tapered waveguide nanofocusing structures. Therefore, the nanofocusing of submicron-short-range SPPs by dielectric NPs on plasmonic nanostructures is not limited to low-loss noble metals. Accordingly, this system has potential for use in light management and on-chip green devices and sensors.In this study, a simple configuration, based on high-index dielectric nanoparticles (NPs) and plasmonic nanostructures, is employed for the nanofocusing of submicron-short-range surface plasmon polaritons (SPPs). The excited SPPs are locally bound and focused at the interface between the dielectric NPs and the underlying metallic nanostructures, thereby greatly enhancing the local electromagnetic field. Taking advantage of the surface properties of the dielectric NPs, this

  19. In situ monitoring of brain tissue reaction of chronically implanted electrodes with an optical coherence tomography fiber system

    NASA Astrophysics Data System (ADS)

    Xie, Yijing; Hassler, Christina; Stieglitz, Thomas; Seifert, Andreas; Hofmann, Ulrich G.

    2014-03-01

    Neural microelectrodes are well established tools for delivering therapeutic electrical pulses, and recording neural electrophysiological signals. However, long term implanted neural probes often become functionally impaired by tissue encapsulation. At present, analyzing this immune reaction is only feasible with post-mortem histology; currently no means for specific in vivo monitoring exist and most applicable imaging modalities provide no sufficient resolution for a cellular measurement in deep brain regions. Optical coherence tomography (OCT) is a well developed imaging modality, providing cellular resolution and up to 1.2 mm imaging depth in brain tissue. Further more, a fiber based spectral domain OCT was shown to be capable of minimally invasive brain intervention. In the present study, we propose to use a fiber based spectral domain OCT to monitor the the progression of the tissue's immune response and scar encapsulation of microprobes in a rat animal model. We developed an integrated OCT fiber catheter consisting of an implantable ferrule based fiber cannula and a fiber patch cable. The fiber cannula was 18.5 mm long, including a 10.5 mm ceramic ferrule and a 8.0 mm long, 125 μm single mode fiber. A mating sleeve was used to fix and connect the fiber cannula to the OCT fiber cable. Light attenuation between the OCT fiber cable and the fiber cannula through the mating sleeve was measured and minimized. The fiber cannula was implanted in rat brain together with a microelectrode in sight used as a foreign body to induce the brain tissue immune reaction. Preliminary data showed a significant enhancement of the OCT backscattering signal during the brain tissue scarring process, while the OCT signal of the flexible microelectrode was getting weaker consequentially.

  20. Jet-A reaction mechanism study for combustion application

    NASA Technical Reports Server (NTRS)

    Lee, Chi-Ming; Kundu, Krishna; Acosta, Waldo

    1991-01-01

    Simplified chemical kinetic reaction mechanisms for the combustion of Jet A fuel was studied. Initially, 40 reacting species and 118 elementary chemical reactions were chosen based on a literature review. Through a sensitivity analysis with the use of LSENS General Kinetics and Sensitivity Analysis Code, 16 species and 21 elementary chemical reactions were determined from this study. This mechanism is first justified by comparison of calculated ignition delay time with the available shock tube data, then it is validated by comparison of calculated emissions from the plug flow reactor code with in-house flame tube data.

  1. Jet-A reaction mechanism study for combustion application

    NASA Technical Reports Server (NTRS)

    Lee, Chi-Ming; Kundu, Krishna; Acosta, Waldo

    1991-01-01

    Simplified chemical kinetic reaction mechanisms for the combustion of Jet A fuel are studied. Initially 40 reacting species and 118 elementary chemical reactions were chosen based on the literature review of previous works. Through a sensitivity analysis with the use of LSENS General Kinetics and Sensitivity Analysis Code, 16 species and 21 elementary chemical reactions were determined from this study. This mechanism is first justified by comparison of calculated ignition delay time with available shock tube data, then it is validated by comparison of calculated emissions from plug flow reactor code with in-house flame tube data.

  2. Theoretical Studies of Elementary Hydrocarbon Species and Their Reactions

    SciTech Connect

    Allen, Wesley D.; Schaefer, III, Henry F.

    2015-11-14

    This is the final report of the theoretical studies of elementary hydrocarbon species and their reactions. Part A has a bibliography of publications supported by DOE from 2010 to 2016 and Part B goes into recent research highlights.

  3. Theoretical Study of Sodium-Water Surface Reaction Mechanism

    NASA Astrophysics Data System (ADS)

    Kikuchi, Shin; Kurihara, Akikazu; Ohshima, Hiroyuki; Hashimoto, Kenro

    Computational study of the sodium-water reaction at the gas (water) - liquid (sodium) interface has been carried out using the ab initio (first-principle) method. A possible reaction channel has been identified for the stepwise OH bond dissociations of a single water molecule. The energetics including the binding energy of a water molecule on the sodium surface, the activation energies of the bond cleavages, and the reaction energies, have been evaluated, and the rate constants of the first and second OH bond-breakings have been compared. It was found that the estimated rate constant of the former was much larger than the latter. The results are the basis for constructing the chemical reaction model used in a multi-dimensional sodium-water reaction code, SERAPHIM, being developed by Japan Atomic Energy Agency (JAEA) toward the safety assessment of the steam generator (SG) in a sodium-cooled fast reactor (SFR).

  4. Severe Cutaneous Adverse Drug Reactions: A Clinicoepidemiological Study

    PubMed Central

    Sasidharanpillai, Sarita; Riyaz, Najeeba; Khader, Anza; Rajan, Uma; Binitha, Manikoth P; Sureshan, Deepthi N

    2015-01-01

    Background: Drug eruptions range from transient erythema to the life threatening severe cutaneous adverse reactions (SCAR) that encompass Stevens–Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), acute generalized exanthematous pustulosis (AGEP) and drug reaction with eosinophilia and systemic symptoms complex (DRESS). Aims and Objectives: To study the clinical and epidemiological aspects of cutaneous adverse drug reactions (CADR). Materials and Methods: Ethical clearance was obtained from the institutional ethics committee. All patients admitted in the Dermatology ward of our tertiary care hospital with CADR (those who fit in the category of probable or possible drug reaction as per WHO casuality assessment) from first September 2011 to 31st August 2012 were included in this cross sectional study after obtaining written informed consent. The drug reaction patterns observed in the study population were determined and the common offending drugs were identified. Results: In the study, population of males outnumbered females and the majority were between 46 and 60 years of age. The commonest reaction pattern observed was SJS- TEN spectrum of illness and aromatic anticonvulsants were the common offending drugs. Prompt withdrawal of the culprit drug and administration of systemic steroids with or without I/V Ig reverted the adverse reaction in all except one. Conclusion: Severe drug reactions predominated as the study population was comprised of inpatients of a tertiary referral centre. Though; previous authors had reported a mortality rate of up to 20% in DRESS, all our patients with this reaction pattern, responded well to treatment. The mortality rate among TEN cases was much lower than the previous reports. Early diagnosis, prompt withdrawal of the suspected drug, careful monitoring for development of complications and immediate intervention can improve the prognosis of CADR. PMID:25657416

  5. Epitaxial Growth of Multimetallic Pd@PtM (M = Ni, Rh, Ru) Core-Shell Nanoplates Realized by in Situ-Produced CO from Interfacial Catalytic Reactions.

    PubMed

    Yan, Yucong; Shan, Hao; Li, Ge; Xiao, Fan; Jiang, Yingying; Yan, Youyi; Jin, Chuanhong; Zhang, Hui; Wu, Jianbo; Yang, Deren

    2016-12-14

    Pt-based multimetallic core-shell nanoplates have received great attention as advanced catalysts, but the synthesis is still challenging. Here we report the synthesis of multimetallic Pd@PtM (M = Ni, Rh, Ru) nanoplates including Pd@Pt nanoplates, in which Pt or Pt alloy shells with controlled thickness epitaxially grow on plate-like Pd seeds. The key to achieve high-quality Pt-based multimetallic nanoplates is in situ generation of CO through interfacial catalytic reactions associated with Pd nanoplates and benzyl alcohol. In addition, the accurate control in a trace amount of CO is also of great importance for conformal growth of multimetallic core-shell nanoplates. The Pd@PtNi nanoplates exhibit substantially improved activity and stability for methanol oxidation reaction (MOR) compared to the Pd@Pt nanoplates and commercial Pt catalysts due to the advantages arising from plate-like, core-shell, and alloy structures.

  6. In situ X-ray Absorption Spectroscopic Investigation of the Electrochemical Conversion Reactions of CuF2-MoO3 Nanocomposite

    SciTech Connect

    A Mansour; F Badway; W Yoon; K Chung; G Amatucci

    2011-12-31

    We have used X-ray absorption spectroscopy at the Cu K-edge to investigate the electrochemical conversion reaction of 20 nm size 85 wt% CuF{sub 2}-15 wt% MoO{sub 3} nanocomposite under in situ conditions. The nanocomposite was prepared by high energy milling. Upon discharge, the lithiation reaction with the nanocomposite resulted in the formation of nanophase metallic Cu, which is consistent with the conversion of CuF{sub 2} into Cu and LiF. Based on XANES and Fourier transforms of EXAFS spectra, we show that the discharge process proceeded via the formation of highly dispersed Cu particles. Based on the coordination number of the first shell of Cu, the average size of the Cu particles was estimated to be in the 1-3 nm range in the fully discharged state.

  7. Effects of methanol-to-oil ratio, catalyst amount and reaction time on the FAME yield by in situ transesterification of rubber seeds (Hevea brasiliensis)

    NASA Astrophysics Data System (ADS)

    Abdulkadir, Bashir Abubakar; Uemura, Yoshimitsu; Ramli, Anita; Osman, Noridah B.; Kusakabe, Katsuki; Kai, Takami

    2014-10-01

    In this research, biodiesel is produced by in situ transesterification (direct transesterification) method from the rubber seeds using KOH as a catalyst. The influence of methanol to seeds mass ratio, duration of reaction, and catalyst loading was investigated. The result shows that, the best ratio of seeds to methanol is 1:6 (10 g seeds with 60 g methanol), 120 minutes reaction time and catalyst loading of 3.0 g. The maximum FAME yield obtain was 70 %. This findings support FAME production from the seeds of rubber tree using direct transesterifcation method from the seeds of rubber tree as an alternative to diesel fuel. Also, significant properties of biodiesel such as cloud point, density, pour point, specific gravity, and viscosity were investigated.

  8. In Situ Infrared Spectroscopic Study of Forsterite Carbonation in Wet Supercritical CO2

    SciTech Connect

    Loring, John S.; Thompson, Christopher J.; Wang, Zheming; Joly, Alan G.; Sklarew, Deborah S.; Schaef, Herbert T.; Ilton, Eugene S.; Rosso, Kevin M.; Felmy, Andrew R.

    2011-07-19

    Carbonation reactions are central to the prospect of CO2 trapping by mineralization in geologic reservoirs. In contrast to the relevant aqueous-mediated reactions, little is known about the propensity for carbonation in the long-term partner fluid: water-containing supercritical carbon dioxide (‘wet’ scCO2). We employed in situ mid-infrared spectroscopy to follow the reaction of a model silicate mineral (forsterite, Mg2SiO4) for 24 hr with wet scCO2 at 50°C and 180 atm, using water concentrations corresponding to 0%, 55%, 95%, and 136% saturation. Results show a dramatic dependence of reactivity on water concentration and the presence of liquid water on the forsterite particles. Exposure to neat scCO2 showed no detectable carbonation reaction. At 55% and 95% water saturation, a liquid-like thin water film was detected on the forsterite particles; less than 1% of the forsterite transformed, mostly within the first 3 hours of exposure to the fluid. At 136% saturation, where an (excess) liquid water film approximately several nanometers thick was intentionally condensed on the forsterite, the carbonation reaction proceeded continuously for 24 hr with 10% to 15% transformation. Our collective results suggest constitutive links between water concentration, water film formation, reaction rate and extent, and reaction products in wet scCO2.

  9. In situ X-ray diffraction monitoring of a mechanochemical reaction reveals a unique topology metal-organic framework

    NASA Astrophysics Data System (ADS)

    Katsenis, Athanassios D.; Puškarić, Andreas; Štrukil, Vjekoslav; Mottillo, Cristina; Julien, Patrick A.; Užarević, Krunoslav; Pham, Minh-Hao; Do, Trong-On; Kimber, Simon A. J.; Lazić, Predrag; Magdysyuk, Oxana; Dinnebier, Robert E.; Halasz, Ivan; Friščić, Tomislav

    2015-03-01

    Chemical and physical transformations by milling are attracting enormous interest for their ability to access new materials and clean reactivity, and are central to a number of core industries, from mineral processing to pharmaceutical manufacturing. While continuous mechanical stress during milling is thought to create an environment supporting nonconventional reactivity and exotic intermediates, such speculations have remained without proof. Here we use in situ, real-time powder X-ray diffraction monitoring to discover and capture a metastable, novel-topology intermediate of a mechanochemical transformation. Monitoring the mechanochemical synthesis of an archetypal metal-organic framework ZIF-8 by in situ powder X-ray diffraction reveals unexpected amorphization, and on further milling recrystallization into a non-porous material via a metastable intermediate based on a previously unreported topology, herein named katsenite (kat). The discovery of this phase and topology provides direct evidence that milling transformations can involve short-lived, structurally unusual phases not yet accessed by conventional chemistry.

  10. Novel microchip for in situ TEM imaging of living organisms and bio-reactions in aqueous conditions.

    PubMed

    Liu, Kuo-Liang; Wu, Chien-Chen; Huang, Ying-Jung; Peng, Hwei-Ling; Chang, Hwan-You; Chang, Pin; Hsu, Long; Yew, Tri-Rung

    2008-11-01

    A novel and disposable microchip (K-kit) with SiO(2) nano-membranes was developed and used as a specimen kit for in situ imaging of living organisms in an aqueous condition using transmission electron microscopy (TEM) without equipment modification. This K-kit enabled the successful TEM observation of living Escherichia coli cells and the tellurite reduction process in Klebsiella pneumoniae. The K. pneumoniae and Saccharomyces cerevisiae can stay alive in K-kit after continuous TEM imaging for up to 14 s and 42 s, respectively. Besides, different tellurite reduction profiles in cells grown in aerobic and anaerobic environments can be clearly revealed. These results demonstrate that the K-kit developed in this paper can be useful for observing living organisms and monitoring biological processes in situ.

  11. Studies of alpha-induced astrophysical reactions at CRIB

    SciTech Connect

    Yamaguchi, H.; Hashimoto, T.; Hayakawa, S.; Binh, D. N.; Kahl, D.; Kubono, S.

    2010-08-12

    CRIB (CNS Radioactive Ion Beam separator) is a low-energy RI beam separator at the Center for Nuclear Study (CNS) of the University of Tokyo. Using the RI beams at CRIB, many measurements on proton alpha resonance scatterings, ({alpha},p) reactions, and others were performed in recent years mainly for studying astrophysical reactions and exotic nuclear structure. Among them, the results on the {sup 7}Li+{alpha} resonance scatterings are presented.

  12. Alterations in juvenile flatfish gill epithelia induced by sediment-bound toxicants: A comparative in situ and ex situ study.

    PubMed

    Martins, Carla; Alves de Matos, António P; Costa, Maria H; Costa, Pedro M

    2015-12-01

    Juvenile Solea senegalensis were exposed in the laboratory (ex situ) and field (in situ) to different sediments of a moderately impacted estuary (the Sado, Portugal) for 28 days. A qualitative histopathological screening yielded scant lesions to gills, albeit alterations such as epithelial hyperplasia being evident and more frequent in fish exposed ex situ. Fully quantitative traits, namely chloride and goblet cell count and size revealed differences between the two bioassay approaches, with ex situ experiments likely enhancing bioavailability of toxicants. Chloride cells endured autolytic processes that could, at least in part, relate to contamination by mixed metals and polycyclic aromatic hydrocarbons (PAHs). Goblet cells did not reveal changes in the chemistry of mucous. Still, their number and size was reduced in fish exposed ex situ to the sediments most contaminated by PAHs, with evidence for adaptation. Also, copper histochemistry revealed the potential role of mucocytes in the regulation of metals.

  13. Crossed molecular beam studies of atmospheric chemical reaction dynamics

    SciTech Connect

    Zhang, Jingsong

    1993-04-01

    The dynamics of several elementary chemical reactions that are important in atmospheric chemistry are investigated. The reactive scattering of ground state chlorine or bromine atoms with ozone molecules and ground state chlorine atoms with nitrogen dioxide molecules is studied using a crossed molecular beams apparatus with a rotatable mass spectrometer detector. The Cl + O3 → ClO + O2 reaction has been studied at four collision energies ranging from 6 kcal/mole to 32 kcal/mole. The derived product center-of-mass angular and translational energy distributions show that the reaction has a direct reaction mechanism and that there is a strong repulsion on the exit channel. The ClO product is sideways and forward scattered with respect to the Cl atom, and the translational energy release is large. The Cl atom is most likely to attack the terminal oxygen atom of the ozone molecule. The Br + O3 → ClO + O2 reaction has been studied at five collision energies ranging from 5 kcal/mole to 26 kcal/mole. The derived product center-of-mass angular and translational energy distributions are quite similar to those in the Cl + O3 reaction. The Br + O3 reaction has a direct reaction mechanism similar to that of the Cl + O3 reaction. The electronic structure of the ozone molecule seems to play the central role in determining the reaction mechanism in atomic radical reactions with the ozone molecule. The Cl + NO2 → ClO + NO reaction has been studied at three collision energies ranging from 10.6 kcal/mole to 22.4 kcal/mole. The center-of-mass angular distribution has some forward-backward symmetry, and the product translational energy release is quite large. The reaction proceeds through a short-lived complex whose lifetime is less than one rotational period. The experimental results seem to show that the Cl atom mainly attacks the oxygen atom instead of the nitrogen atom of the NO2

  14. Atmospheric chemistry: Laboratory studies of kinetics of important reactions

    NASA Astrophysics Data System (ADS)

    Smith, S. J.

    Experiments to measure the rate constants for some reactions of the atmospherically important nitrate radical (NO3) are described using the discharge-flow technique. The nitrate radical was monitored by optical absorption at lambda = 662 nm. The reactions of NO3 with some stable organic and inorganic substrates are reported. The temperature dependences of some of the rate constants were also determined (298 less than T less than 523 K). In most cases, computer simulation was used to extract the rate constant for the primary process because the time-dependent behavior of (NO3) was affected by secondary reactions of NO3 with products of the primary interaction. The Arrhenius parameter for the reactions of NO3 with CH3CH3, CH2CH2, CH3OH, CHCl3, and HCl were determined. The activation energies for the reactions studied between NO3 and some alkynes are presented along with the corresponding pre-exponential factors. Some reactions were studied at room temperature (298 plus or minus 2 K) only and the rate constants found (in units of cubic cm/molecule sec) are: buta-1,3-diene (1.8 x 10 (exp -13), isobutene (2.8 x 10 (exp -13), HBr (1.3 x 10 (exp -15) and hex-2-yne (3.0 x 10 (exp -14). Non-Arrhenius behavior was found in the reactions of NO3 with n-butane, isobutane and propene. The empirical variation of these rate constants with temperature is presented. The curvature of the Arrhenius plots is discussed in terms of (1) a temperature-dependent pre-exponential factor, and (2) the possibility that two competing channels, possessing differing activation energies, exist for each reaction. The atmospheric implications of these reactions are discussed with reference to the nighttime production of nitric acid and the importance of the these reactions as loss processes for NO3.

  15. Probing Electrochemical Adsorbate Structure and Reactions with In-Situ Atomic-Resolution Scanning Microscopy: Some Progress and Prospects

    DTIC Science & Technology

    1992-10-01

    counterion would be of substantial value. An interesting example, examined recently by in-situ AFM, concerns underpotential deposited (upd) silver on...Au(lll)[31]. Markedly different symmetries of the deposited metal adlayer were observed, depending upon the nature of the electrolyte counteranion...with the common use of Au(lll) surfaces prepared by 19 vacuum metal deposition on mica or other suitable templates. The examination of ordered

  16. In situ quantitative study of nanoscale triboelectrification and patterning.

    PubMed

    Zhou, Yu Sheng; Liu, Ying; Zhu, Guang; Lin, Zong-Hong; Pan, Caofeng; Jing, Qingshen; Wang, Zhong Lin

    2013-06-12

    By combining contact-mode atomic force microscopy (AFM) and scanning Kevin probe microscopy (SKPM), we demonstrated an in situ method for quantitative characterization of the triboelectrification process at the nanoscale. We systematically characterized the triboelectric charge distribution, multifriction effect on charge transfer, as well as subsequent charge diffusion on the dielectric surface: (i) the SiO2 surface can be either positively or negatively charged through triboelectric process using Si-based AFM probes with and without Pt coating, respectively; (ii) the triboelectric charges accumulated from multifriction and eventually reached to saturated concentrations of (-150 ± 8) μC/m(2) and (105 ± 6) μC/m(2), respectively; (iii) the charge diffusion coefficients on SiO2 surface were measured to be (1.10 ± 0.03) × 10(-15) m(2)/s for the positive charge and (0.19 ± 0.01) × 10(-15) m(2)/s for the negative charges. These quantifications will facilitate a fundamental understanding about the triboelectric and de-electrification process, which is important for designing high performance triboelectric nanogenerators. In addition, we demonstrated a technique for nanopatterning of surface charges without assistance of external electric field, which has a promising potential application for directed self-assembly of charged nanostructures for nanoelectronic devices.

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

    SciTech Connect

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

    2014-05-09

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

  18. Development of microwave and impedance spectroscopy methods for in-situ nondestructive evaluation of alkali silica reaction in concrete

    NASA Astrophysics Data System (ADS)

    Heifetz, Alexander; Bakhtiari, Sasan; Lu, Juan; Aranson, Igor S.; Vinokur, Valerii M.; Bentivegna, Anthony F.

    2017-02-01

    Aging concrete degradation due to alkali silica reaction (ASR) is a challenge to sustainability of critical infrastructure, such as nuclear power plants. Currently, there is no standard, nondestructive method for detecting ASR in concrete. We report on the progress in developing electromagnetic (EM) methods, consisting of microwave and impedance spectroscopy techniques, for nondestructive detection of ASR. The microwave and impedance spectroscopy methods are complementary since they provide information about material electrical properties in GHz and Hz to KHz EM spectral bands, respectively. Preliminary studies were conducted using accelerated testing concrete prism specimens developed according to ASTM C1293 standard. Microwave and impedance spectroscopy measurements were performed on ASR specimens at the first and the second month maturity level, as well as on age-matched controls. Microwave tests consisted of reflection and transmission measurements using dielectric-loaded antennas, with the focus on X-band spectrum. Impedance measurements were performed using flexible electrode patches. Measurement results by both microwave and impedance spectroscopy methods indicate observable differences in electrical properties between reactive and non-reactive specimens. In addition, trends in measurement data obtained with the two complementary EM techniques are consistent and correlate with ASR progression in specimens.

  19. Catalytic behavior of metal catalysts in high-temperature RWGS reaction: In-situ FT-IR experiments and first-principles calculations

    NASA Astrophysics Data System (ADS)

    Choi, Sungjun; Sang, Byoung-In; Hong, Jongsup; Yoon, Kyung Joong; Son, Ji-Won; Lee, Jong-Ho; Kim, Byung-Kook; Kim, Hyoungchul

    2017-01-01

    High-temperature chemical reactions are ubiquitous in (electro) chemical applications designed to meet the growing demands of environmental and energy protection. However, the fundamental understanding and optimization of such reactions are great challenges because they are hampered by the spontaneous, dynamic, and high-temperature conditions. Here, we investigated the roles of metal catalysts (Pd, Ni, Cu, and Ag) in the high-temperature reverse water-gas shift (RWGS) reaction using in-situ surface analyses and density functional theory (DFT) calculations. Catalysts were prepared by the deposition-precipitation method with urea hydrolysis and freeze-drying. Most metals show a maximum catalytic activity during the RWGS reaction (reaching the thermodynamic conversion limit) with formate groups as an intermediate adsorbed species, while Ag metal has limited activity with the carbonate species on its surface. According to DFT calculations, such carbonate groups result from the suppressed dissociation and adsorption of hydrogen on the Ag surface, which is in good agreement with the experimental RWGS results.

  20. Catalytic behavior of metal catalysts in high-temperature RWGS reaction: In-situ FT-IR experiments and first-principles calculations

    PubMed Central

    Choi, Sungjun; Sang, Byoung-In; Hong, Jongsup; Yoon, Kyung Joong; Son, Ji-Won; Lee, Jong-Ho; Kim, Byung-Kook; Kim, Hyoungchul

    2017-01-01

    High-temperature chemical reactions are ubiquitous in (electro) chemical applications designed to meet the growing demands of environmental and energy protection. However, the fundamental understanding and optimization of such reactions are great challenges because they are hampered by the spontaneous, dynamic, and high-temperature conditions. Here, we investigated the roles of metal catalysts (Pd, Ni, Cu, and Ag) in the high-temperature reverse water-gas shift (RWGS) reaction using in-situ surface analyses and density functional theory (DFT) calculations. Catalysts were prepared by the deposition-precipitation method with urea hydrolysis and freeze-drying. Most metals show a maximum catalytic activity during the RWGS reaction (reaching the thermodynamic conversion limit) with formate groups as an intermediate adsorbed species, while Ag metal has limited activity with the carbonate species on its surface. According to DFT calculations, such carbonate groups result from the suppressed dissociation and adsorption of hydrogen on the Ag surface, which is in good agreement with the experimental RWGS results. PMID:28120896

  1. Catalytic behavior of metal catalysts in high-temperature RWGS reaction: In-situ FT-IR experiments and first-principles calculations.

    PubMed

    Choi, Sungjun; Sang, Byoung-In; Hong, Jongsup; Yoon, Kyung Joong; Son, Ji-Won; Lee, Jong-Ho; Kim, Byung-Kook; Kim, Hyoungchul

    2017-01-25

    High-temperature chemical reactions are ubiquitous in (electro) chemical applications designed to meet the growing demands of environmental and energy protection. However, the fundamental understanding and optimization of such reactions are great challenges because they are hampered by the spontaneous, dynamic, and high-temperature conditions. Here, we investigated the roles of metal catalysts (Pd, Ni, Cu, and Ag) in the high-temperature reverse water-gas shift (RWGS) reaction using in-situ surface analyses and density functional theory (DFT) calculations. Catalysts were prepared by the deposition-precipitation method with urea hydrolysis and freeze-drying. Most metals show a maximum catalytic activity during the RWGS reaction (reaching the thermodynamic conversion limit) with formate groups as an intermediate adsorbed species, while Ag metal has limited activity with the carbonate species on its surface. According to DFT calculations, such carbonate groups result from the suppressed dissociation and adsorption of hydrogen on the Ag surface, which is in good agreement with the experimental RWGS results.

  2. A four-component reaction involving in situ generated organometallic reagents: straightforward access to β-amino esters.

    PubMed

    Le Gall, Erwan; Léonel, Eric

    2013-04-22

    Four in one: A straightforward synthesis of β(2,3)-amino esters is described through a new zinc-mediated, cobalt-catalyzed four-component reaction between organic bromides, alkyl acrylates, amines, and aldehydes (see scheme). Synthesis involves a Mannich-related conjugate addition/aza-aldol domino sequence, allowing the formation of three single bonds in one step. A reaction mechanism, emphasizing the crucial role of zinc salts, is described.

  3. Miniaturized Environmental Scanning Electron Microscope for In Situ Planetary Studies

    NASA Technical Reports Server (NTRS)

    Gaskin, Jessica; Abbott, Terry; Medley, Stephanie; Gregory, Don; Thaisen, Kevin; Taylor , Lawrence; Ramsey, Brian; Jerman, Gregory; Sampson, Allen; Harvey, Ralph

    2010-01-01

    The exploration of remote planetary surfaces calls for the advancement of low power, highly-miniaturized instrumentation. Instruments of this nature that are capable of multiple types of analyses will prove to be particularly useful as we prepare for human return to the moon, and as we continue to explore increasingly remote locations in our Solar System. To this end, our group has been developing a miniaturized Environmental-Scanning Electron Microscope (mESEM) capable of remote investigations of mineralogical samples through in-situ topographical and chemical analysis on a fine scale. The functioning of an SEM is well known: an electron beam is focused to nanometer-scale onto a given sample where resulting emissions such as backscattered and secondary electrons, X-rays, and visible light are registered. Raster scanning the primary electron beam across the sample then gives a fine-scale image of the surface topography (texture), crystalline structure and orientation, with accompanying elemental composition. The flexibility in the types of measurements the mESEM is capable of, makes it ideally suited for a variety of applications. The mESEM is appropriate for use on multiple planetary surfaces, and for a variety of mission goals (from science to non-destructive analysis to ISRU). We will identify potential applications and range of potential uses related to planetary exploration. Over the past few of years we have initiated fabrication and testing of a proof-of-concept assembly, consisting of a cold-field-emission electron gun and custom high-voltage power supply, electrostatic electron-beam focusing column, and scanning-imaging electronics plus backscatter detector. Current project status will be discussed. This effort is funded through the NASA Research Opportunities in Space and Earth Sciences - Planetary Instrument Definition and Development Program.

  4. Experimental study on neptunium migration under in situ geochemical conditions

    NASA Astrophysics Data System (ADS)

    Kumata, M.; Vandergraaf, T. T.

    1998-12-01

    Results are reported for migration experiments performed with Np under in situ geochemical conditions over a range of groundwater flow rates in columns of crushed rock in a specially designed facility at the 240-level of the Underground Research Laboratory (URL) near Pinawa, Manitoba, Canada. This laboratory is situated in an intrusive granitic rock formation, the Lac du Bonnet batholith. Highly altered granitic rock and groundwater were obtained from a major subhorizontal fracture zone at a depth of 250 m in the URL. The granite was wet-crushed and wet-sieved with groundwater from this fracture zone. The 180-850-μm size fraction was selected and packed in 20-cm long, 2.54-cm in diameter Teflon™-lined stainless steel columns. Approximately 30-ml vols of groundwater containing 3HHO and 237Np were injected into the columns at flow rates of 0.3, 1, and 3 ml/h, followed by elution with groundwater, obtained from the subhorizontal fracture, at the same flow rates, for a period of 95 days. Elution profiles for 3HHO were obtained, but no 237Np was detected in the eluted groundwater. After terminating the migration experiments, the columns were frozen, the column material was removed and cut into twenty 1-cm thick sections and each section was analyzed by gamma spectrometry. Profiles of 237Np were obtained for the three columns. A one-dimensional transport model was fitted to the 3HHO breakthrough curves to obtain flow parameters for this experiment. These flow parameters were in turn applied to the 237Np concentration profiles in the columns to produce sorption and dispersion coefficients for Np. The results show a strong dependence of retardation factors ( Rf) on flow rate. The decrease in the retarded velocity of the neptunium ( Vn) varied over one order of magnitude under the geochemical conditions for these experiments.

  5. Synthesis and structural characterization of three copper coordination polymers with pyridine derivatives from hydro(solvo)thermal in situ decarboxylation reactions of 2,5-dicarboxylpyridine

    SciTech Connect

    Hou Qin; Xu Jianing; Yu Jiehui; Wang Tiegang; Yang Qingfeng; Xu Jiqing

    2010-07-15

    The hydro(solvo)thermal self-assembles of CuI, KI and 2,5-dicarboxylpyridine [2,5-(COOH){sub 2}py] in different molar ratios in H{sub 2}O/alcohol solutions produced three Cu coordination polymers as 2-D [N-C{sub 2}H{sub 5}py][Cu{sub 3}I{sub 4}] 1, 1-D [N-CH{sub 3}py][Cu{sub 2}I{sub 3}] 2 as well as 1-D [Cu(2-COOpy){sub 2}]{center_dot}H{sub 2}O 3 (N-C{sub 2}H{sub 5}py=N-ethylpyridine, N-CH{sub 3}py=N-methylpyridine, 2-COOpy=2-carboxylpyridine). N-C{sub 2}H{sub 5}py in 1 and N-CH{sub 3}py in 2 derived from the solvothermal in situ simultaneous decarboxylation and N-alkylation reactions of 2,5-(COOH){sub 2}py. The semi-decarboxylation reaction of 2,5-(COOH){sub 2}py into 2-COOpy occurred in the preparation of 3. X-ray single-crystal analysis revealed that CuI is transformed into a 2-D [Cu{sub 3}I{sub 4}]{sup -} layer in compound 1 and a 1-D chain in compound 2, templated by [N-C{sub 2}H{sub 5}py]{sup +} and [N-CH{sub 3}py]{sup +}, respectively. Compound 3 is a divalent Cu compound. The Cu(II) centers with a 4+2 geometry are coordinated by {mu}{sub 3}-mode 2-COOpy ligands. All of the title compounds were characterized by CHN analysis, IR spectrum analysis and TG analysis. Compounds 1 and 2 exhibit fluorescence properties with the maximum emissions at 581 nm for 1 and 537 nm for 2. - Graphical abstract: Three compounds were obtained via in situ metal-ligand hydro(solvo)thermal reactions of 2,5-(cooh){sub 2}py with cui. Three types of in situ reactions occurred for 2,5-(cooh){sub 2}py: decarboxylation n-ethylated in 1, n-methylated in 2 and semi-decarboxylation in 3.

  6. Platinum-cobalt catalysts for the oxygen reduction reaction in high temperature proton exchange membrane fuel cells - Long term behavior under ex-situ and in-situ conditions

    NASA Astrophysics Data System (ADS)

    Schenk, Alexander; Grimmer, Christoph; Perchthaler, Markus; Weinberger, Stephan; Pichler, Birgit; Heinzl, Christoph; Scheu, Christina; Mautner, Franz-Andreas; Bitschnau, Brigitte; Hacker, Viktor

    2014-11-01

    Platinum cobalt catalysts (Pt-Co) have attracted much interest as cathode catalysts for proton exchange membrane fuel cells (PEMFCs) due to their high activity toward oxygen reduction reaction (ORR). Many of the reported catalysts show outstanding performance in ex-situ experiments. However, the laborious synthesis protocols of these Pt-Co catalysts disable an efficient and economic production of membrane electrode assemblies (MEAs). We present an economic, flexible and continuous Pt-M/C catalyst preparation method as part of a large scale membrane electrode assembly manufacturing. In comparison, the as-prepared Pt-Co/C based high temperature (HT)-PEM MEA showed an equal performance to a commercially available HT-PEM MEA during 600 h of operation under constant load, although the commercial one had a significantly higher Pt loading at the cathode.

  7. Structural characterizaiton and gas reactions of small metal particles by high-resolution, in-situ TEM and TED

    NASA Technical Reports Server (NTRS)

    1984-01-01

    The existing in-situ transmission electron microscopy (TEM) facility was improved by adding a separately pumped mini-specimen chamber. The chamber contains wire-evaporation sources for three metals and a specimen heater for moderate substrate temperatures. A sample introduction device was constructed, installed, and tested, facilitating rapid introduction of a specimen into the mini-chamber while maintaining the background pressure in that chamber in the 10(-9) millibar range. Small particles and clusters of Pd, grown by deposition from the vapor phase in an in-situ TEM facility on amorphous and crystalline support films of alumina and on ultra-thin carbon films, were analyzed by conventional high-resolution TEM and image analysis in terms of detectability, number density, and size distribution. The smallest particles that could be detected and counted contained no more than 6 atoms; size determinations could be made for particles 1 nm in diameter. The influence of various oxygen plasma treatments, annealing treatments, and of increasing the substrate temperature during deposition was investigated. The TEM technique was employed to demonstrate that under otherwise identica l conditions the lattice parameter of Pd particles in the 1 to 2 nm size range and supported in random orientation on ex-situ prepared mica films is expanded by some 3% when compared to 5 nm size particles. It is believed that this expansion is neither a small-particle diffraction effect nor due to pseudomorphism, but that it is due to a annealing-induced transformation of the small as-deposited particles with predominantly composite crystal structures into larger particles with true f.c.c. structure and thus inherently smaller lattice parameter.

  8. Recent Direct Reaction Experimental Studies with Radioactive Tin Beams

    SciTech Connect

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

    2015-01-01

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

  9. Recent Direct Reaction Experimental Studies with Radioactive Tin Beams

    DOE PAGES

    Jones, K. L.; Ahn, S.; Allmond, J. M.; ...

    2015-01-01

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

  10. Molybdenum carbide nanocatalysts at work in the in situ environment: a density functional tight-binding and quantum mechanical/molecular mechanical study.

    PubMed

    Liu, Xingchen; Salahub, Dennis R

    2015-04-01

    Heterogeneous reactions catalyzed by transition-metal-containing nanoparticles represent a crucial type of reaction in chemical industry. Because of the existing gap in understanding heterogeneous catalysis between a cluster of a few atoms and a bulk model of periodic slabs, reactions catalyzed by transition-metal-containing nanoparticles are still not well understood. Herein, we provide a multiscale modeling approach to study the benzene hydrogenation reactions on molybdenum carbide nanoparticles (MCNPs) in the process of in situ heavy oil upgrading. By coupling the quantum mechanical (QM) density functional tight-binding (DFTB) method with a molecular mechanical (MM) force field, a QM/MM model was built to describe the reactants, the nanoparticles and the surroundings. Umbrella sampling (US) was used to calculate the free energy profiles of the benzene hydrogenation reactions in a model aromatic solvent in the in situ heavy oil upgrading conditions. By comparing with the traditional method in computational heterogeneous catalysis, the results reveal new features of the metallic MCNPs. Rather than being rigid, they are very flexible under working condition due to the entropic contributions of the MCNPs and the solvent, which greatly affect the free energy profiles of these nanoscale heterogeneous reactions.

  11. In situ detection of frequent and active infection of human cytomegalovirus in inflammatory abdominal aortic aneurysms: possible pathogenic role in sustained chronic inflammatory reaction.

    PubMed

    Yonemitsu, Y; Nakagawa, K; Tanaka, S; Mori, R; Sugimachi, K; Sueishi, K

    1996-04-01

    Inflammatory abdominal aortic aneurysm (IAAA) is histopathologically characterized by extensive adventitial fibrosis, mononuclear cell infiltration with lymph follicle formation, and severe atheromatous changes in the aneurysmal wall. We previously reported a frequent prevalence and immediate early gene expression of human cytomegalovirus (CMV) in IAAA by solution-phase PCR and reverse transcription PCR, respectively, and suggested that this virus might play a role in chronic inflammatory reaction in IAAA. To evaluate the pathogenic role of CMV infection, the frequency and distribution of CMV infected cells in IAAA were examined by in situ PCR, and compared with those in atherosclerotic aneurysms (AA) and control cases with minimal atherosclerotic changes. Human leukocyte antigen (HLA)-DR was simultaneously evaluated as a marker for immune response related to CMV infection. Immediate early gene expression was also detected by reverse transcription PCR and in situ hybridization, to certify whether the CMV infection in IAAA is active or latent. In the fibrously thickened adventitia of IAAA, CMV infected cells and HLA-DR-positive cells were more frequently encountered than in that of AA and control cases (p < 0.01). CMV infected cells were largely identified as macrophages, fibroblasts, endothelial cells, and lymphocytes. The expression of CMV immediate early mRNA, which suggests an active infection inducing active inflammatory reaction, was detected in most of the macrophages, endothelial cells, and fibroblasts. Our results strongly suggest that frequent and active infection of CMV in IAAA plays a significant role in the induction and acceleration of chronic inflammatory reaction in aortas of IAAA.

  12. In situ microliter-droplet anodic stripping voltammetry of copper stained on the gold label after galvanic replacement reaction enlargement for ultrasensitive immunoassay of proteins.

    PubMed

    Qin, Xiaoli; Xu, Aigui; Wang, Linchun; Liu, Ling; Chao, Long; He, Fang; Tan, Yueming; Chen, Chao; Xie, Qingji

    2016-05-15

    We report a new protocol for ultrasensitive electrochemical sandwich-type immunosensing, on the basis of signal amplification by gold-label/copper-staining, galvanic replacement reactions (GRRs), and in situ microliter-droplet anodic stripping voltammetry (ASV) after an enhanced cathodic preconcentration of copper. First, a sandwich-type immuno-structure is appropriately assembled at a glassy carbon electrode. Second, copper is selectively stained on the catalytic surfaces of second antibody-conjugated Au nanoparticles through CuSO4-ascorbic acid redox reaction, and the GRRs between HAuCl4 and the stained copper are used to amplify the quantity of copper. Finally, the corresponding antigen is determined based on simultaneous chemical-dissolution/cathodic-preconcentration of copper for in-situ ASV analysis directly at the immunoelectrode. Cyclic voltammetry, electrochemical impedance spectroscopy, quartz crystal microbalance and scanning electron microscopy are used for film characterization and/or process monitoring. Under optimized conditions, ultrasensitive analyses of human immunoglobulin G (IgG) and human carbohydrate antigen 125 (CA125) are achieved. The limits of detection are 0.3 fg mL(-1) (equivalent to 7 IgG molecules in the 6 μL sample employed) for IgG (S/N=3) and 1.3 nU mL(-1) for CA125 (S/N=3), respectively, which are amongst the best reported to date for the two proteins. The theoretical feasibility of such a single-molecule-level amperometric immunoassay is also discussed based on the immunological reaction thermodynamics.

  13. Revealing Stepwise Mechanisms in Dipolar Cycloaddition Reactions: Computational Study of the Reaction between Nitrones and Isocyanates.

    PubMed

    Darù, Andrea; Roca-López, David; Tejero, Tomás; Merino, Pedro

    2016-01-15

    The mechanism of cycloaddition reactions of nitrones with isocyanates has been studied using density functional theory (DFT) methods at the M06-2X/cc-pVTZ level of theory. The exploration of the potential energy surfaces associated with two reactive channels leading to 1,2,4-oxadiazolidin-5-ones and 1,4,2-dioxazolidines revealed that the cycloaddition reaction takes place through a concerted mechanism in gas phase and in apolar solvents but a stepwise mechanism in polar solvents. In stepwise mechanisms, the first step of the reaction is a rare case in which the nitrone oxygen acts as a nucleophile by attacking the central carbon atom of the isocyanate (interacting with the π-system of the C═O bond) to give an intermediate. The corresponding transition structure is stabilized by an attractive electrostatic interaction favored in a polar medium. The second step of the reaction is the rate-limiting one in which the formation of 1,2,4-oxadiazolidin-5-ones or 1,4,2-dioxazolidines is decided. Calculations indicate that formation of 1,2,4-oxadiazolidin-5-ones is favored both kinetically and thermodynamically independently of the solvent, in agreement with experimental observations. Noncovalent interactions (NCI) and topological analysis of the gradient field of electron localization function (ELF) bonding confirmed the observed interactions.

  14. Chromium Reaction Mechanisms for Speciation using Synchrotron in-Situ High-Temperature X-ray Diffraction.

    PubMed

    Low, Fiona; Kimpton, Justin; Wilson, Siobhan A; Zhang, Lian

    2015-07-07

    We use in situ high-temperature X-ray diffraction (HT-XRD), ex-situ XRD and synchrotron X-ray absorption near edge structure spectroscopy (XANES) to derive fundamental insights into mechanisms of chromium oxidation during combustion of solid fuels. To mimic the real combustion environment, mixtures of pure eskolaite (Cr(3+)2O3), lime (CaO) and/or kaolinite [Al2Si2O5(OH)4] have been annealed at 600-1200 °C in air versus 1% O2 diluted by N2. Our results confirm for the first time that (1) the optimum temperature for Cr(6+) formation is 800 °C for the coexistence of lime and eskolaite; (2) upon addition of kaolinite into oxide mixture, the temperature required to produce chromatite shifts to 1000 °C with a remarkable reduction in the fraction of Cr(6+). Beyond 1000 °C, transient phases are formed that bear Cr in intermediate valence states, which convert to different species other than Cr(6+) in the cooling stage; (3) of significance to Cr mobility from the waste products generated by combustion, chromatite formed at >1000 °C has a glassy disposition that prevents its water-based leaching; and (4) Increasing temperature facilitates the migration of eskolaite particles into bulk lime and enhances the extent to which Cr(3+) is oxidized, thereby completing the oxidation of Cr(3+) to Cr(6+) within 10 min.

  15. In situ heavy ion irradiation studies of nanopore shrinkage and enhanced radiation tolerance of nanoporous Au

    PubMed Central

    Li, Jin; Fan, C.; Ding, J.; Xue, S.; Chen, Y.; Li, Q.; Wang, H.; Zhang, X.

    2017-01-01

    High energy particle radiations induce severe microstructural damage in metallic materials. Nanoporous materials with a giant surface-to-volume ratio may alleviate radiation damage in irradiated metallic materials as free surface are defect sinks. Here we show, by using in situ Kr ion irradiation in a transmission electron microscope at room temperature, that nanoporous Au indeed has significantly improved radiation tolerance comparing with coarse-grained, fully dense Au. In situ studies show that nanopores can absorb and eliminate a large number of radiation-induced defect clusters. Meanwhile, nanopores shrink (self-heal) during radiation, and their shrinkage rate is pore size dependent. Furthermore, the in situ studies show dose-rate-dependent diffusivity of defect clusters. This study sheds light on the design of radiation-tolerant nanoporous metallic materials for advanced nuclear reactor applications. PMID:28045044

  16. Tissue microarray (TMA) technology: miniaturized pathology archives for high-throughput in situ studies.

    PubMed

    Bubendorf, L; Nocito, A; Moch, H; Sauter, G

    2001-09-01

    Tissue microarray (TMA) technology allows a massive acceleration of studies correlating molecular in situ findings with clinico-pathological information. In this technique, cylindrical tissue samples are taken from up to 1000 different archival tissue blocks and subsequently placed into one empty 'recipient' paraffin block. Sections from TMA blocks can be used for all different types of in situ tissue analyses including immunohistochemistry and in situ hybridization. Multiple studies have demonstrated that findings obtained on TMAs are highly representative of their donor tissues, despite the small size of the individual specimens (diameter 0.6 mm). It is anticipated that TMAs will soon become a widely used tool for all types of tissue-based research. The availability of TMAs containing highly characterized tissues will enable every researcher to perform studies involving thousands of tumours rapidly. Therefore, TMAs will lead to a significant acceleration of the transition of basic research findings into clinical applications.

  17. In situ heavy ion irradiation studies of nanopore shrinkage and enhanced radiation tolerance of nanoporous Au

    NASA Astrophysics Data System (ADS)

    Li, Jin; Fan, C.; Ding, J.; Xue, S.; Chen, Y.; Li, Q.; Wang, H.; Zhang, X.

    2017-01-01

    High energy particle radiations induce severe microstructural damage in metallic materials. Nanoporous materials with a giant surface-to-volume ratio may alleviate radiation damage in irradiated metallic materials as free surface are defect sinks. Here we show, by using in situ Kr ion irradiation in a transmission electron microscope at room temperature, that nanoporous Au indeed has significantly improved radiation tolerance comparing with coarse-grained, fully dense Au. In situ studies show that nanopores can absorb and eliminate a large number of radiation-induced defect clusters. Meanwhile, nanopores shrink (self-heal) during radiation, and their shrinkage rate is pore size dependent. Furthermore, the in situ studies show dose-rate-dependent diffusivity of defect clusters. This study sheds light on the design of radiation-tolerant nanoporous metallic materials for advanced nuclear reactor applications.

  18. In-situ powder X-ray diffraction investigation of reaction pathways for the BaCO(3)-CeO(2)-In(2)O(3) and CeO(2)-In(2)O(3) systems.

    PubMed

    Bhella, Surinderjit Singh; Shafi, Shahid P; Trobec, Francesca; Bieringer, Mario; Thangadurai, Venkataraman

    2010-02-15

    We report the first in-situ powder X-ray diffraction (PXRD) study of the BaCO(3)-CeO(2)-In(2)O(3) and CeO(2)-In(2)O(3) systems in air over a wide range of temperature between 25 and 1200 degrees C. Herein, we are investigating the formation pathway and chemical stability of perovskite-type BaCe(1-x)In(x)O(3-delta) (x = 0.1, 0.2, and 0.3) and corresponding fluorite-type Ce(1-x)In(x)O(2-delta) phases. The potential direct solid state reaction between CeO(2) and In(2)O(3) for the formation of indium-doped fluorite-type phase is not observed even up to 1200 degrees C in air. The formation of the BaCe(1-x)In(x)O(3-delta) perovskite structures was investigated and rationalized using in-situ PXRD. Furthermore the decomposition of the indium-doped perovskites in CO(2) is followed using high temperature diffraction and provides insights into the reaction pathway as well as the thermal stability of the Ce(1-x)In(x)O(3-delta) system. In CO(2) flow, BaCe(1-x)In(x)O(3-delta) decomposes above T = 600 degrees C into BaCO(3) and Ce(1-x)In(x)O(2-delta). Furthermore, for the first time, the in-situ PXRD confirmed that Ce(1-x)In(x)O(2-delta) decomposes above 800 degrees C and supported the previously claimed metastability. The maximum In-doping level for CeO(2) has been determined using PXRD. The lattice constant of the fluorite-type structure Ce(1-x)In(x)O(2-delta) follows the Shannon ionic radii trend, and crystalline domain sizes were found to be dependent on indium concentration.

  19. Mechanism study on the influence of in situ SOx removal on N2O emission in CFB boiler

    NASA Astrophysics Data System (ADS)

    Wu, Lingnan; Qin, Wu; Hu, Xiaoying; Dong, Changqing; Yang, Yongping

    2015-04-01

    The influence of in situ deSOx process on N2O emission in CFB boiler was studied using density functional theory calculations. The competitive adsorption of SO2 and N2O on pure CaO (1 0 0) surface was first studied and the reaction priority was determined. Results showed that SO2 was more likely to adsorb on CaO (1 0 0) surface O anion site, which hindered the catalytic decomposition of N2O on CaO (1 0 0) surface and sulfurized the CaO (1 0 0) surface under reducing atmosphere. Then a partially sulfurized CaO (1 0 0) surface was established to study the catalytic activity of deSOx reaction intermediate on N2O decomposition. The O atom transfer process and the surface recovery process were two key steps for N2O decomposition and the rate-determining step was the latter one. The sulfurization of the surface could deactivate its catalytic activity on N2O decomposition compared with pure CaO (1 0 0) surface but it was still better than that of pure CaS (1 0 0) surface. The free Gibbs energy was calculated to incorporate the temperature dependence of respective reactions. When temperature was higher than 373 K, the surface recovery was more likely to proceed via the LH route.

  20. The high - low-p clinoenstatite transition: in situ xrd and ultrasonic study

    NASA Astrophysics Data System (ADS)

    Müller, H. J.; Wunder, B.; Lathe, C.; Schilling, F. R.

    2003-04-01

    Using single-crystal X-ray diffraction analyses in a diamond anvil cell Angel et al. (1992) published the transformation of MgSiO_3 from LCEn to a C2/c-polymorph (HCEn) at around 5.5 - 8.0 GPa and room-T (RT)conditions. This LCEn - HCEn-transition is not quenchable. However, the knowledge of the exact phase boundary positions for the MgSiO_3-transitions is essential as pyroxene is an important component of the Earth's mantle and will significantly influence elastic properties (e.g. v_p, v_s) of the mantle. We determined the HCEn - LCEn-transition by in-situ XRD experiments under high P, T using the multi-anvil appar atus MAX80 at the synchrotron facility HASYLAB, Hamburg. Our preliminary results only represent the minimum P-conditions of the HCEn - LCEn phase boundary, which is approximated by equation P (GPa) = 0.0021T (/C) + 6.06. Nevertheless, our results are in good agreement to data published by Angel & Hugh-Jones (1994). The invariant point defined by the intersection of the HCEn - LCEn equilibrium determined within this study and the OEn - LCEn reaction after Angel &Hugh-Jones (1994) lies at about 7.9 GPa and 875/C. This is in contrast to earlier experimental results of Kanzaki (1991) and Ulmer &Stalder (2001). The samples for the ultrasonic interferometry experiments were prepared by hot-isostatic pressing also using the MAX80. Adjacent XRD ruled out any phase transition during the hip-process. For the ultrasonic measurements one of the six anvils of MAX80 were exchanged by an anvil equipped with lithium niobate p- and s-wave transducers of 33.3 MHz natural frequency (Mueller et al., 2002). Corresponding to the XRD experiments HCEn was formed by increasing the pressure at RT. The velocities of elastic compressional and shear waves were measured under in situ conditions using the classical digital sweep technique. After the phase transition to LCEn as a result of rising the temperature at given pressure the measurements were repeated. The newly developed

  1. Studies of complex fragment emission in heavy ion reactions

    SciTech Connect

    Charity, R.J.; Sobotka, L.G.

    1992-01-01

    Our work involves the study of intermediate energy heavy-ion nuclear reactions. This work has two foci. On the one hand, we desire to learn about the properties of nuclear matter under abnormal conditions, in this energy domain, predominately low densities. This purpose runs abreast of the second, which is the study of the relevant reaction mechanisms. The two objectives are inexorably linked because our experimental laboratory for studying nuclear matter properties is a dynamic one. We are forced to ask how nuclear matter properties, such as phase transitions, are reflected in the dynamics of the reactions. It may be that irrefutable information about nuclear matter will not be extracted from the reaction work. Nevertheless, we are compelled to undertake this effort not only because it is the only game in town and as yet we do not know that information cannot be extracted, but also because of our second objective. The process leads to an understanding of the reaction mechanism themselves and therefore to the response characteristics of finite, perhaps non-equilibrium, strongly interacting systems. Our program has been: To study energy, mass, and angular momentum deposition by studying incomplete fusion reactions. To gain confidence that we understand how highly excited systems decompose by studying all emissions from the highly excited systems. To push these kinds of studies into the intermediate energy domain, with excitation function studies. And attempt to learn about the dynamics of the decays using particle-particle correlations. In the last effort, we have decided to focus on simple systems, where we believe, definitive statements are possible. These avenues of research share a common theme, large complex fragment production.

  2. In situ and ex situ studies of materials with relevance to electrochemical energy storage and energy generation

    NASA Astrophysics Data System (ADS)

    Luo, Yu

    Surface analytical techniques have been employed for the preparation and characterization of modified surfaces of relevance to electrochemical energy storage and generation in ultrahigh vacuum environments. Complementary in situ spectroscopic studies were also performed using Raman microscopy for monitoring static and dynamic aspects of Li intercalation and deintercalation into transition metal oxides and graphitic materials. The most important conclusions emerging from this investigation can be summarized as follows: (i) Ruthenium-modified Pt(100) surfaces of very high purity and controlled stoichiometry were prepared in ultrahigh vacuum (UHV) by irradiating Ru3(CO)12 films condensed on cold Pt substrates at 150 K with X-rays, and subsequent annealing at ca. 620 K. Exposure of non-annealed Ru(thetaRu ≥0.22)/Pt(100) to large exposures of CO at ca. 200 K, yielded smaller theta CO, and temperature programmed desorption peaks ca. 50 K lower than those observed for bare Pt(100). (ii) Raman spectra of isolated single particles of technical grade LiMn2O4 embedded in Au foils were recorded in situ in 1M LiPF6 in EC/DMC solutions in real time during a voltammetric scan using a Raman microscope. Similar experiments involving single KS-44 carbon particles (8--50 mum in diameter) embedded into thermally annealed Ni foils in 1M LiClO4, ethylene carbonate (EC) diethyl carbonate (DEC) solutions allowed the average concentration of Li+ within the volume of the particle probed by the laser beam following application of a potential step to be monitored spectroscopically in real time. Analysis of these transient data yielded deintercalation time constants for Li+ for dilute stage 1 phase consistent with reported values of Li+ diffusion coefficients within graphitic materials. A new Raman band ascribed to bounding graphite layers was found upon continuous cycling of single KS-44 particles deep into the Li+-intercalation region. This feature was attributed to chemical modifications

  3. In Situ TEM Nanoindentation Studies on Stress-Induced Phase Transformations in Metallic Materials

    SciTech Connect

    Liu, Y.; Wang, H.; Zhang, X.

    2015-11-30

    Though abundant phase transformations are in general thermally driven processes, there are many examples wherein stresses can induce phase transformations. We applied numerous in situ techniques, such as in situ x-ray diffraction and neutron diffraction in order to reveal phase transformations. Recently, an in situ nanoindentation technique coupled with transmission electron microscopy demonstrated the capability to directly correlating stresses with phase transformations and microstructural evolutions at a submicron length scale. We briefly review in situ studies on stress-induced diffusional and diffusionless phase transformations in amorphous CuZrAl alloy and NiFeGa shape memory alloy. Moreover, in the amorphous CuZrAl, in situ nanoindentation studies show that the nucleation of nanocrystals (a diffusional process) occurs at ultra-low stresses manifested by a prominent stress drop. In the NiFeGa shape memory alloy, two distinctive types of martensitic (diffusionless) phase transformations accompanied by stress plateaus are observed, including a reversible gradual phase transformation at low stress levels, and an irreversible abrupt phase transition at higher stress levels.

  4. In Situ TEM Nanoindentation Studies on Stress-Induced Phase Transformations in Metallic Materials

    DOE PAGES

    Liu, Y.; Wang, H.; Zhang, X.

    2015-11-30

    Though abundant phase transformations are in general thermally driven processes, there are many examples wherein stresses can induce phase transformations. We applied numerous in situ techniques, such as in situ x-ray diffraction and neutron diffraction in order to reveal phase transformations. Recently, an in situ nanoindentation technique coupled with transmission electron microscopy demonstrated the capability to directly correlating stresses with phase transformations and microstructural evolutions at a submicron length scale. We briefly review in situ studies on stress-induced diffusional and diffusionless phase transformations in amorphous CuZrAl alloy and NiFeGa shape memory alloy. Moreover, in the amorphous CuZrAl, in situ nanoindentationmore » studies show that the nucleation of nanocrystals (a diffusional process) occurs at ultra-low stresses manifested by a prominent stress drop. In the NiFeGa shape memory alloy, two distinctive types of martensitic (diffusionless) phase transformations accompanied by stress plateaus are observed, including a reversible gradual phase transformation at low stress levels, and an irreversible abrupt phase transition at higher stress levels.« less

  5. Theoretical QM/MM studies of enzymatic pericyclic reactions.

    PubMed

    Martí, S; Andrés, J; Moliner, V; Silla, E; Tuñón, I; Bertrán, J

    2010-03-01

    The chorismate to prephenate enzyme catalyzed reaction has been used in this review as the conduit to show different theoretical approaches that have been used over the years in our laboratory to explain its molecular mechanism. This pericyclic reaction has the advantage that other protein scaffolds such as catalytic antibodies or some promiscuous enzymes present certain chorismate mutase activity. The obtained results on all these protein environments, by comparison with the uncatalyzed reaction in solution, have been used to propose, as a general conclusion, that the origin of enzyme catalysis is in the relative electrostatic stabilization of the transition state with respect to the Michaelis complex. This feature implies that reactants of catalyzed reaction were closer to the transition state than those of the non-catalyzed reaction. From this hypothesis, and considering the features of the wild type chorismate mutases as the optimal catalyst for the reaction, some mutations on both kinds of alternative proteins have been proposed which would presumably enhance the rate constant of the chemical step.The studies presented in this paper demonstrate that the improvements and developments of the methods and techniques of theoretical and computational chemistry are now mature enough to model physic-chemical properties of biological systems with good accuracy. The combination of a potent computational protocol with molecular engineering techniques can be a promising methodology to develop novel enzymes with new or more efficient catalytic functions.

  6. Reaction dynamics studies for the system 7Be+58Ni

    NASA Astrophysics Data System (ADS)

    Torresi, D.; Mazzocco, M.; Acosta, L.; Boiano, A.; Boiano, C.; Diaz-Torres, A.; Fierro, N.; Glodariu, T.; Grilj, L.; Guglielmetti, A.; Keeley, N.; La Commara, M.; Martel, I.; Mazzocchi, C.; Molini, P.; Pakou, A.; Parascandolo, C.; Parkar, V. V.; Patronis, N.; Pierroutsakou, D.; Romoli, M.; Rusek, K.; Sanchez-Benitez, A. M.; Sandoli, M.; Signorini, C.; Silvestri, R.; Soramel, F.; Stiliaris, E.; Strano, E.; Stroe, L.; Zerva, K.

    2015-04-01

    The study of reactions induced by exotic weakly bound nuclei at energies around the Coulomb barrier had attracted a large interest in the last decade, since the features of these nuclei can deeply affect the reaction dynamics. The discrimination between different reaction mechanisms is, in general, a rather difficult task. It can be achieved by using detector arrays covering high solid angle and with high granularity that allow to measure the reaction products and, possibly, coincidences between them, as, for example, recently done for stable weakly bound nuclei [1, 2]. We investigated the collision of the weakly bound nucleus 7Be on a 58Ni target at the beam energy of 1.1 times the Coulomb barrier, measuring the elastic scattering angular distribution and the energy and angular distributions of 3He and 4He. The 7Be radioactive ion beam was produced by the facility EXOTIC at INFN-LNL with an energy of 22 MeV and an intensity of ~3×105 pps. Results showed that the 4He yeld is about 4 times larger than 3He yield, suggesting that reaction mechanisms other than the break-up mostly produce the He isotopes. Theoretical calculations for transfer channels and compound nucleus reactions suggest that complete fusion accounts for (41±5%) of the total reaction cross section extracted from optical model analysis of the elastic scattering data, and that 3He and 4He stripping are the most populated reaction channels among direct processes. Eventually estimation of incomplete fusion contributions to the 3,4He production cross sections was performed through semi-classical calculations with the code PLATYPUS [3].

  7. In situ/operando studies for the production of hydrogen through the water-gas shift on metal oxide catalysts.

    PubMed

    Rodriguez, José A; Hanson, Jonathan C; Stacchiola, Dario; Senanayake, Sanjaya D

    2013-08-07

    In this perspective article, we show how a series of in situ techniques {X-ray diffraction (XRD), pair-distribution-function analysis (PDF), X-ray absorption fine structure (XAFS), environmental transmission electron microscopy (ETEM), infrared spectroscopy (IR), ambient-pressure X-ray photoelectron spectroscopy (AP-XPS)} can be combined to perform detailed studies of the structural, electronic and chemical properties of metal oxide catalysts used for the production of hydrogen through the water-gas shift reaction (WGS, CO + H2O → H2 + CO2). Under reaction conditions most WGS catalysts undergo chemical transformations that drastically modify their composition with respect to that obtained during the synthesis process. Experiments of time-resolved in situ XRD, XAFS, and PDF indicate that the active phase of catalysts which combine Cu, Au or Pt with oxides such as ZnO, CeO2, TiO2, CeOx/TiO2 and Fe2O3 essentially involves nanoparticles of the reduced noble metals. The oxide support undergoes partial reduction and is not a simple spectator, facilitating the dissociation of water and in some cases modifying the chemical properties of the supported metal. Therefore, to optimize the performance of these catalysts one must take into consideration the properties of the metal and oxide phases. IR and AP-XPS have been used to study the reaction mechanism for the WGS on metal oxide catalysts. Data of IR spectroscopy indicate that formate species are not necessarily involved in the main reaction path for the water-gas shift on Cu-, Au- and Pt-based catalysts. Thus, a pure redox mechanism or associative mechanisms that involve either carbonate-like (CO3, HCO3) or carboxyl (HOCO) species should be considered. In the last two decades, there have been tremendous advances in our ability to study catalytic materials under reaction conditions and we are moving towards the major goal of fully understanding how the active sites for the production of hydrogen through the WGS actually

  8. Bridging the pressure gap: In situ atomic-level investigations of model platinum catalyst surfaces under reaction conditions by scanning tunneling microscopy

    SciTech Connect

    McIntyre, Brian James

    1994-05-01

    Results of this thesis show that STM measurements can provide information about the surfaces and their adsorbates. Stability of Pt(110) under high pressures of H2, O2, and CO was studied (Chap. 4). In situ UHV and high vacuum experiments were carried out for sulfur on Pt(111) (Chap.5). STM studies of CO/S/Pt(111) in high CO pressures showed that the Pt substrate undergoes a stacking-fault-domain reconstruction involving periodic transitions from fcc to hcp stacking of top-layer atoms (Chap.6). In Chap.7, the stability of propylene on Pt(111) and the decomposition products were studied in situ with the HPSTM. Finally, in Chap.8, results are presented which show how the Pt tip of the HPSTM was used to locally rehydrogenate and oxidize carbonaceous clusters deposited on the Pt(111) surface; the Pt tip acted as a catalyst after activation by short voltage pulses.

  9. New Possibilities for the Accurate in Situ Determination of Chalcophile and Siderophile Trace Elements by Laser Ablation Collision and Reaction Cell ICP-MS

    NASA Astrophysics Data System (ADS)

    Mason, P. R.

    2004-05-01

    Our knowledge of how chalcophile and siderophile elements partition in minerals is limited, mainly due to the lack of suitable techniques for their accurate in situ determination. Host minerals (e.g. sulphides) are typically of small size (<30 μ m) and highly heterogeneous in composition, requiring analysis of high spatial resolution. Concentrations of chalcophile elements in silicates and oxides are low (sub μ gg-1) and thus challenging to measure. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), offering high sensitivity and good spatial resolution (10-100 μ m) is thus highly suited for this purpose. Unfortunately, the widespread use of this technique has been limited by enhanced problems specific to chalcophile and siderophile elements. These include inaccuracy due to the presence of spectral interferences, elemental fractionation during ablation/ionization and the lack of suitable calibration standards. Polyatomic spectral interferences, present either as a background component (e.g. O2+, ArAr+) or based around the recombination of matrix elements with argon (e.g. ArS+, ArNi+) hinder accurate analysis. These depend upon the relative concentrations of major matrix components and trace elements to be measured and are significant in many relevant minerals (e.g. sulphides). The use of a collision and reaction cells in ICP-MS is a new method for selective interference attenuation, significantly improving detection limits for elements such as Fe, S and Se by between 1 and 4 orders of magnitude. ArNi+ and ArCu+ interferences in sulphides can be attenuated by at least an order of magnitude leading to improved accuracy for the measurement of the Platinum Group elements Rh and Ru. Sulphur isotopes can be measured interference-free at m/z=32 and 34 by eliminating background O2+. These improvements open up new possibilities for the use of LA-ICP-MS in trace element and isotopic studies at the lowest concentration levels or where sample

  10. Theoretical study of reaction mechanism for NCO + HCNO

    NASA Astrophysics Data System (ADS)

    Zhang, Weichao; Du, Benni; Feng, Changjun

    2007-07-01

    A detailed quantum chemical study is performed on the mechanism of the NCO + HCNO reaction, which has never been studied by theory. The potential energy surface for this reaction is characterized at the B3LYP/6-311++G(d,p) level of theory, combined with high-level CBS-QB3 single point energy calculation. Four possible product channels have been investigated. From the calculations it can be seen that the formation of HCN + NO + CO is the dominant product channel, while the pathway to products of HCNN + CO 2 is expected to be minor one, and these conclusions are in good agreement with the experimental results.

  11. Comparison of culture, polymerase chain reaction, and fluorescent in situ hybridization for detection of Brachyspira hyodysenteriae and "Brachyspira hampsonii" in pig feces.

    PubMed

    Wilberts, Bailey L; Warneke, Hallie L; Bower, Leslie P; Kinyon, Joann M; Burrough, Eric R

    2015-01-01

    Swine dysentery is characterized by mucohemorrhagic diarrhea and can occur following infection by Brachyspira hyodysenteriae or "Brachyspira hampsonii ". A definitive diagnosis is often based on the isolation of strongly beta-hemolytic spirochetes from selective culture or by the application of species-specific polymerase chain reaction (PCR) assays directly to feces. While culture is highly sensitive, it typically requires 6 or more days to complete, and PCR, although rapid, can be limited by fecal inhibition. Fluorescent in situ hybridization (FISH) has been described in formalin-fixed tissues; however, completion requires approximately 2 days. Because of the time constraints of available assays, a same-day FISH assay was developed to detect B. hyodysenteriae and "B. hampsonii " in pig feces using previously described oligonucleotide probes Hyo1210 and Hamp1210 for B. hyodysenteriae and "B. hampsonii", respectively. In situ hybridization was simultaneously compared with culture and PCR on feces spiked with progressive dilutions of spirochetes to determine the threshold of detection for each assay at 0 and 48 hr. The PCR assay on fresh feces and FISH on formalin-fixed feces had similar levels of detection. Culture was the most sensitive method, detecting the target spirochetes at least 2 log-dilutions less when compared to other assays 48 hr after sample preparation. Fluorescent in situ hybridization also effectively detected both target species in formalin-fixed feces from inoculated pigs as part of a previous experiment. Accordingly, FISH on formalin-fixed feces from clinically affected pigs can provide same-day identification and preliminary speciation of spirochetes associated with swine dysentery in North America.

  12. Pulsed supercritical synthesis of anatase TiO₂ nanoparticles in a water-isopropanol mixture studied by in situ powder X-ray diffraction.

    PubMed

    Rostgaard Eltzholtz, Jakob; Tyrsted, Christoffer; Ørnsbjerg Jensen, Kirsten Marie; Bremholm, Martin; Christensen, Mogens; Becker-Christensen, Jacob; Brummerstedt Iversen, Bo

    2013-03-21

    A new step in supercritical nanoparticle synthesis, the pulsed supercritical synthesis reactor, is investigated in situ using synchrotron powder X-ray diffraction (PXRD) to understand the formation of nanoparticles in real time. This eliminates the common problem of transferring information gained during in situ studies to subsequent laboratory reactor conditions. As a proof of principle, anatase titania nanoparticles were synthesized in a 50/50 mixture of water and isopropanol near and above the critical point of water (P = 250 bar, T = 300, 350, 400, 450, 500 and 550 °C). The evolution of the reaction product was followed by sequentially recording PXRD patterns with a time resolution of less than two seconds. The crystallite size of titania is found to depend on both temperature and residence time, and increasing either parameter leads to larger crystallites. A simple adjustment of either temperature or residence time provides a direct method for gram scale production of anatase nanoparticles of average crystallite sizes between 7 and 35 nm, thus giving the option of synthesizing tailor-made nanoparticles. Modeling of the in situ growth curves using an Avrami growth model gave an activation energy of 66(19) kJ mol(-1) for the initial crystallization. The in situ PXRD data also provide direct information about the size dependent macrostrain in the nanoparticles and with decreasing crystallite size the unit cell contracts, especially along the c-direction. This agrees well with previous ex situ results obtained for hydrothermal synthesis of titania nanoparticles.

  13. Development of customised environmental chambers for time-resolved in situ diffraction studies

    NASA Astrophysics Data System (ADS)

    Styles, M. J.; Riley, D. P.

    2010-11-01

    In an effort to mitigate the expense and broaden the applicability of customised environment chambers, researchers at the University of Melbourne and the Australian Nuclear Science and Technology Organisation (ANSTO) have designed and are currently commissioning a modular reaction chamber, capable of separating the necessities of diffraction methodologies from those of the desired sample environment. The In Situ Reaction Chamber (ISRC) abstracts many of the details intrinsic to the diffractometer, allowing users to design inexpensive environmental inserts that may be readily customised to their individual needs. The first insert to be developed for use with the ISRC is a high temperature furnace capable of providing an oxidising sample environment up to 1600°C.

  14. How to design in situ studies: an evaluation of experimental protocols

    PubMed Central

    Sung, Young-Hye; Kim, Hae-Young; Son, Ho-Hyun

    2014-01-01

    Objectives Designing in situ models for caries research is a demanding procedure, as both clinical and laboratory parameters need to be incorporated in a single study. This study aimed to construct an informative guideline for planning in situ models relevant to preexisting caries studies. Materials and Methods An electronic literature search of the PubMed database was performed. A total 191 of full articles written in English were included and data were extracted from materials and methods. Multiple variables were analyzed in relation to the publication types, participant characteristics, specimen and appliance factors, and other conditions. Frequencies and percentages were displayed to summarize the data and the Pearson's chi-square test was used to assess a statistical significance (p < 0.05). Results There were many parameters commonly included in the majority of in situ models such as inclusion criteria, sample sizes, sample allocation methods, tooth types, intraoral appliance types, sterilization methods, study periods, outcome measures, experimental interventions, etc. Interrelationships existed between the main research topics and some parameters (outcome measures and sample allocation methods) among the evaluated articles. Conclusions It will be possible to establish standardized in situ protocols according to the research topics. Furthermore, data collaboration from comparable studies would be enhanced by homogeneous study designs. PMID:25110639

  15. A simple, fast and low-cost turn-on fluorescence method for dopamine detection using in situ reaction.

    PubMed

    Zhang, Xiulan; Zhu, Yonggang; Li, Xie; Guo, Xuhong; Zhang, Bo; Jia, Xin; Dai, Bin

    2016-11-09

    A simple, fast and low-cost method for dopamine (DA) detection based on turn-on fluorescence using resorcinol is developed. The rapid reaction between resorcinol and DA allows the detection to be performed within 5 min, and the reaction product (azamonardine) with high quantum yield generates strong fluorescence signal for sensitive optical detection. The detection exhibits a high sensitivity to DA with a wide linear range of 10 nM-20 μM and the limit of detection is estimated to be 1.8 nM (S/N = 3). This approach has been successfully applied to determine DA concentrations in human urine samples with satisfactory quantitative recovery of 97.84%-103.50%, which shows great potential in clinical diagnosis.

  16. Unified studies of structure and reactions in light unstable nuclei

    NASA Astrophysics Data System (ADS)

    Ito, Makoto

    2016-06-01

    The generalized two-center cluster model (GTCM), which can treat covalent, ionic and atomic configurations in general systems with two inert cores plus valence nucleons, is formulated in the basis of the microscopic cluster model. In this model, the covalent configurations constructed by the molecular orbital (MO) method and the atomic (or ionic) configuration obtained by the valence bonding (VB) method can be described in a consistent manner. GTCM is applied to the light neutron-rich system, 10,12Be = α + α + XN (X = 2,4), and the unified studies of the structural changes and the reaction problem are performed. In the structure study, the calculated energy levels are characterized in terms of the chemical bonding like structures, such as the covalent MO or ionic VB structures. The chemical bonding structures changes from level to level within a small energy interval. In the unbound region, the structure problem with the total system of α + α + XN and the reaction problem, induced by the collision of an asymptotic VB state of α+6,8He, are combined by GTCM. The properties of unbound resonant states are discussed in a close connection to the reaction mechanism, and some enhancement factors originated from the properties of the intrinsic states are predicted in the reaction observables. The unified calculation of the structures and the reactions is applied to the Coulomb shift problem in the mirror system, such the 10Be and 10C nuclei. The Coulomb displacement energy of the mirror systems are discussed.

  17. Singlet Oxygen Reactions with Flavonoids. A Theoretical – Experimental Study

    PubMed Central

    Morales, Javier; Günther, Germán; Zanocco, Antonio L.; Lemp, Else

    2012-01-01

    Detection of singlet oxygen emission, λmax = 1270 nm, following laser excitation and steady-state methods were employed to measure the total reaction rate constant, kT, and the reactive reaction rate constant, kr, for the reaction between singlet oxygen and several flavonoids. Values of kT determined in deuterated water, ranging from 2.4×107 M−1s−1 to 13.4×107 M−1s−1, for rutin and morin, respectively, and the values measured for kr, ranging from 2.8×105 M−1s−1 to 65.7×105 M−1s−1 for kaempferol and morin, respectively, being epicatechin and catechin chemically unreactive. These results indicate that all the studied flavonoids are good quenchers of singlet oxygen and could be valuable antioxidants in systems under oxidative stress, in particular if a flavonoid-rich diet was previously consumed. Analysis of the dependence of rate constant values with molecular structure in terms of global descriptors and condensed Fukui functions, resulting from electronic structure calculations, supports the formation of a charge transfer exciplex in all studied reactions. The fraction of exciplex giving reaction products evolves through a hydroperoxide and/or an endoperoxide intermediate produced by singlet oxygen attack on the double bond of the ring C of the flavonoid. PMID:22802966

  18. Use of Hybridization Chain Reaction-Fluorescent In Situ Hybridization To Track Gene Expression by Both Partners during Initiation of Symbiosis

    PubMed Central

    Nikolakakis, K.; Lehnert, E.

    2015-01-01

    The establishment of a productive symbiosis between Euprymna scolopes, the Hawaiian bobtail squid, and its luminous bacterial symbiont, Vibrio fischeri, is mediated by transcriptional changes in both partners. A key challenge to unraveling the steps required to successfully initiate this and many other symbiotic associations is characterization of the timing and location of these changes. We report on the adaptation of hybridization chain reaction-fluorescent in situ hybridization (HCR-FISH) to simultaneously probe the spatiotemporal regulation of targeted genes in both E. scolopes and V. fischeri. This method revealed localized, transcriptionally coregulated epithelial cells within the light organ that responded directly to the presence of bacterial cells while, at the same time, provided a sensitive means to directly show regulated gene expression within the symbiont population. Thus, HCR-FISH provides a new approach for characterizing habitat transition in bacteria and for discovering host tissue responses to colonization. PMID:25956763

  19. Computational Studies on Cinchona Alkaloid-Catalyzed Asymmetric Organic Reactions.

    PubMed

    Tanriver, Gamze; Dedeoglu, Burcu; Catak, Saron; Aviyente, Viktorya

    2016-06-21

    Remarkable progress in the area of asymmetric organocatalysis has been achieved in the last decades. Cinchona alkaloids and their derivatives have emerged as powerful organocatalysts owing to their reactivities leading to high enantioselectivities. The widespread usage of cinchona alkaloids has been attributed to their nontoxicity, ease of use, stability, cost effectiveness, recyclability, and practical utilization in industry. The presence of tunable functional groups enables cinchona alkaloids to catalyze a broad range of reactions. Excellent experimental studies have extensively contributed to this field, and highly selective reactions were catalyzed by cinchona alkaloids and their derivatives. Computational modeling has helped elucidate the mechanistic aspects of cinchona alkaloid catalyzed reactions as well as the origins of the selectivity they induce. These studies have complemented experimental work for the design of more efficient catalysts. This Account presents recent computational studies on cinchona alkaloid catalyzed organic reactions and the theoretical rationalizations behind their effectiveness and ability to induce selectivity. Valuable efforts to investigate the mechanisms of reactions catalyzed by cinchona alkaloids and the key aspects of the catalytic activity of cinchona alkaloids in reactions ranging from pharmaceutical to industrial applications are summarized. Quantum mechanics, particularly density functional theory (DFT), and molecular mechanics, including ONIOM, were used to rationalize experimental findings by providing mechanistic insights into reaction mechanisms. B3LYP with modest basis sets has been used in most of the studies; nonetheless, the energetics have been corrected with higher basis sets as well as functionals parametrized to include dispersion M05-2X, M06-2X, and M06-L and functionals with dispersion corrections. Since cinchona alkaloids catalyze reactions by forming complexes with substrates via hydrogen bonds and long

  20. In-situ study of interconnect failures by electromigration inside a scanning electron microscope

    SciTech Connect

    Wetzig, Klaus; Wendrock, Horst; Buerke, Axel; Koetter, Thomas

    1999-11-03

    The influence of microstructure on electromigration damage of Al and Cu interconnects with different width and morphology was studied. At first, grain boundaries and local grain orientations before electromigration were registered and correlated with defect places. The investigations focussed on in-situ electromigration tests inside a SEM under accelerated loading conditions, on the in-situ observation of defect formation, and on orientation measurements at the interconnect grains. The position of individual grain boundaries and the misorientation of their neighbored grains seem to be decisive factors for the interconnect failure because of different diffusivities. Whereas the failure behavior of polycrystalline interconnects is sufficiently understood, bamboo structures require further investigations.

  1. In situ study on the reorientation of polymer chains in operating polymer diodes

    NASA Astrophysics Data System (ADS)

    Guo, Tzung-Fang; Yang, Yang

    2002-01-01

    A reflection-absorption Fourier-transform infrared spectroscopy experiment has been designed to in situ monitor poly(2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylene vinylene) (MEH-PPV)-based polymer light-emitting diodes under stress test. This method enables the in situ study of the co-relation between device performance and the conformational transformation of a conjugated polymer. The experimental results indicate that the plane of the conjugated π-electron cloud in MEH-PPV tends to align parallel to the substrate. This rearrangement enhances the π-π electron coupling and lowers the device operating voltage under high current densities.

  2. Oxygen Reduction Reaction on Graphene in an Electro-Fenton System: In Situ Generation of H2 O2 for the Oxidation of Organic Compounds.

    PubMed

    Chen, Chen-Yu; Tang, Cheng; Wang, Hao-Fan; Chen, Cheng-Meng; Zhang, Xiaoyuan; Huang, Xia; Zhang, Qiang

    2016-05-23

    Fenton oxidation using an aqueous mixture of Fe(2+) and H2 O2 is a promising environmental remediation strategy. However, the difficulty of storage and shipment of concentrated H2 O2 and the generation of iron sludge limit its broad application. Therefore, highly efficient and cost-effective electrocatalysts are in great need. Herein, a graphene catalyst is proposed for the electro-Fenton process, in which H2 O2 is generated in situ by the two-electron reduction of the dissolved O2 on the cathode and then decomposes to generate (.) OH in acidic solution with Fe(2+) . The π bond of the oxygen is broken whereas the σ bond is generally preserved on the metal-free reduced graphene oxide owing to the high free energy change. Consequently, the oxygen is reduced to H2 O2 through a two-electron pathway. The thermally reduced graphene with a high specific surface area (308.8 m(2)  g(-1) ) and a large oxygen content (10.3 at %) exhibits excellent reactivity for the two-electron oxygen reduction reaction to H2 O2 . A highly efficient peroxide yield (64.2 %) and a remarkable decolorization of methylene blue (12 mg L(-1) ) of over 97 % in 160 min are obtained. The degradation of methylene blue with hydroxyl radicals generated in situ is described by a pseudo first-order kinetics model. This provides a proof-of-concept of an environmentally friendly electro-Fenton process using graphene for the oxygen reduction reaction in an acidic solution to generate H2 O2 .

  3. Reaction dynamics and mechanism of the Cl + HD(v = 1) reaction: a quantum mechanical study.

    PubMed

    González-Sánchez, L; Aldegunde, J; Jambrina, P G; Aoiz, F J

    2013-08-15

    Time-independent quantum mechanical calculations have been performed in order to characterize the dynamics and stereodynamics of Cl + HD reactive collisions. Calculations have been carried out at two different total energy values and for various initial states using the adiabatic potential energy surface by Bian and Werner [J. Chem. Phys. 2000, 112, 220]. Special attention has been paid to the reaction with HD(v = 1) for which integral and differential cross-sections have been calculated and the effect of vibrational vs translational energy on the reactivity has been examined. In addition, the reactant polarization parameters and polarization-dependent differential cross-sections have been determined. From these results, the spatial preferences of the reaction and the extent of the control of the cross sections achievable through a suitable preparation of the reactants have been also studied. The directional requirements are tighter for the HCl channel than for the DCl one. Formation of the products takes place preferentially when the rotational angular momentum of the HD molecule is perpendicular to the reactants approach direction. Cross-sections and polarization moments computed from the scattering calculations have been compared with experimental results by Kandel et al. [J. Chem. Phys. 2000, 112, 670] for the reaction with HD(v = 1) produced by stimulated Raman pumping. The agreement so obtained is good, and it improves the accordance found in previous calculations with other methodologies and potential energy surfaces.

  4. Detection of rare RNA sequences by single-enzyme in situ reverse transcription-polymerase chain reaction. High-resolution analyses of interleukin-6 mRNA in paraffin sections of lymph nodes.

    PubMed Central

    Peters, J.; Krams, M.; Wacker, H. H.; Carstens, A.; Weisner, D.; Hamann, K.; Menke, M.; Harms, D.; Parwaresch, R.

    1997-01-01

    To study the distribution pattern of interleukin-6 (IL-6)-producing cells in normal human lymph nodes, we applied the in situ reverse transcription-polymerase chain reaction technique. We describe a new modification of this technique for monitoring small amounts of specific nucleotide sequences in conventional paraffin sections. This technique differs in at least two respects from those described earlier. The two decisive steps are: 1) the reverse transcription of mRNA and the subsequent amplification of cDNA by polymerase chain reaction are performed by a new single enzyme capable of both reaction types in one and the same medium without buffer exchange; and 2) for the specific detection of the amplified cDNA, a modified version of the primed in situ labeling technique was used. The technique, carried out on normal human lymph nodes, traces a low load of IL-6 mRNA in fibroblasts, endothelial cells, and a minor population of T lymphocytes in the pulp region. High levels of expression were encountered in about 20% of perisinusoidal pulp macrophages. In addition, moderate activity was detectable in sinus lining cells. Because no major activity was found in the germinal centers of the lymphoid B follicles and in the T zone, it is suggested that the plasma cell differentiation ensuing from primary and secondary B-cell immunization is mainly effected by the sinus lining cells as well as perifollicular and perisinusoidal pulp macrophages capable of producing high amounts of IL-6. Images Figure 1 Figure 2 Figure 3 PMID:9033263

  5. Transport with Bimolecular Reactions: Applications to In-Situ Chemical Oxidation of DNAPLs by Permanganate in Fractured Rock

    NASA Astrophysics Data System (ADS)

    Arshadi, Masoud

    Chemical oxidation of dense nonaqueous-phase liquids (DNAPLs) by permanganate has emerged as an effective remediation strategy in fractured rock. Our objectives in this research were to carry out a sequence of experimental, computational and theoretical tasks aimed at improving current understanding of permanganate oxidation in fractured rock systems, and also develop modeling tools that can be used for preliminary design of oxidation schemes at field sites. Our research focused on both free-phase entrapped DNAPL in variable-aperture fractures and dissolved DNAPL in the rock matrix. In the first section of our research, we present high-resolution experimental investigations in transparent analog variable-aperture fractures to improve understanding of chemical oxidation of residual entrapped trichloroethylene (TCE) in fractures. Four experiments were performed with different permanganate concentrations, flow rates, and initial TCE phase geometry. The initial aperture field and evolving entrapped-phase geometry were measured quantitatively. We present results on the time-evolution of fracture-scale TCE consumption and DNAPL removal rates for all the experiments. In the next part of this work, we developed theoretical understanding of the reaction front dynamics in the case of chemical oxidation of aqueous-phase DNAPL within fracture-matrix system, backed up by numerical simulations. We also consider the influence of NOD consumption and contaminant sorption to solid aquifer materials in our models. Based on the results from this task we are able to propose simple strategies for remediation design (e.g. the time needed to degrade DNAPL inside the fracture-matrix system and the permanganate injection pattern) for a given set of conditions. Our numerical simulations of diffusion with bimolecular reaction in the rock matrix demonstrated a transition in the spatially integrated reaction rate - increasing with time initially, and transitioning to a decrease with time. We

  6. Nanolithographic Fabrication and Heterogeneous Reaction Studies ofTwo-Dimensional Platinum Model Catalyst Systems

    SciTech Connect

    Contreras, Anthony Marshall

    2006-05-20

    In order to better understand the fundamental components that govern catalytic activity, two-dimensional model platinum nanocatalyst arrays have been designed and fabricated. These catalysts arrays are meant to model the interplay of the metal and support important to industrial heterogeneous catalytic reactions. Photolithography and sub-lithographic techniques such as electron beam lithography, size reduction lithography and nanoimprint lithography have been employed to create these platinum nanoarrays. Both in-situ and ex-situ surface science techniques and catalytic reaction measurements were used to correlate the structural parameters of the system to catalytic activity.

  7. In situ ATR-FTIR study of the early stages of fly ash geopolymer gel formation.

    PubMed

    Rees, Catherine A; Provis, John L; Lukey, Grant C; van Deventer, Jannie S J

    2007-08-14

    The kinetics of geopolymer formation are monitored using a novel in situ attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopic technique. Reaction rates are determined from the intensity variation of the bands related to the geopolymer gel network and the unreacted fly ash particles. Comparison with deuterated geopolymer samples provides critical information regarding peak assignments. An initial induction (lag) period is observed to occur for hydroxide-activated geopolymers, followed by gel evolution according to an approximately linear reaction profile. The length of the lag period is reduced by increasing the concentration of NaOH. An increase in the rate of network formation also occurs with increasing NaOH concentration up to a maximum point, beyond which an increased NaOH concentration leads to a reduced rate of network formation. This trend is attributed to the competing effects of increased alkalinity and stronger ion pairing with an increase in NaOH concentration. In situ analysis also shows that the rate of fly ash dissolution is similar for all moderate- to high-alkali geopolymer slurries, which is attributed to the very highly water-deficient nature of these systems and is contrary to predictions from classical glass dissolution chemistry. This provides for the first time detailed kinetic information describing fly ash geopolymer formation kinetics.

  8. Sample environment for in situ synchrotron corrosion studies of materials in extreme environments

    SciTech Connect

    Elbakhshwan, Mohamed S.; Gill, Simerjeet K.; Motta, Arthur T.; Weidner, Randy; Anderson, Thomas; Ecker, Lynne E.

    2016-10-25

    A new in situ sample environment has been designed and developed to study the interfacial interactions of nuclear cladding alloys with high temperature steam. The sample environment is particularly optimized for synchrotron X-ray diffraction (XRD) studies for in situ structural analysis. The sample environment is highly corrosion resistant and can be readily adapted for steam environments. The in situ sample environment design complies with G2 ASTM standards for studying corrosion in zirconium and its alloys and offers remote temperature and pressure monitoring during the in situ data collection. The use of the in situ sample environment is exemplified by monitoring the oxidation of metallic zirconium during exposure to steam at 350°C. Finally, the in situ sample environment provides a powerful tool for fundamental understanding of corrosion mechanisms by elucidating the substoichiometric oxide phases formed during early stages of corrosion, which can provide a better understanding the oxidation process.

  9. Thermal decomposition of t-butylamine borane studied by in situ solid state NMR

    SciTech Connect

    Feigerle, J.; Smyrl, N. R.; Morrell, J. S.; Stowe, A. C.

    2010-03-18

    of the amine borane fuel more feasible [22]. In the present study, tert-butylamine borane is investigated by heteronuclear in situ solid state NMR to understand hydrogen release from a hydrocarbon containing amine borane. tbutylamine borane has similar physical properties to amine borane with a melting point of 96 C. A single proton has been replaced with a t-butylamine group resulting in a weakening of the dihydrogen bonding framework. t-butylamine borane has a theoretical gravimetric hydrogen density of 15.1%; however, isobutane can also be evolved rather than hydrogen. If decomposition yields one mole isobutane and two moles hydrogen, 4.5 wt% H2 gas will be evolved. More importantly for the present work, the resulting spent fuel should be comprised of both (BNH)n and (CBNH)n polyimidoboranes.

  10. Design, development, and demonstration of a fully LabVIEW controlled in situ electrochemical Fourier transform infrared setup combined with a wall-jet electrode to investigate the electrochemical interface of nanoparticulate electrocatalysts under reaction conditions.

    PubMed

    Nesselberger, Markus; Ashton, Sean J; Wiberg, Gustav K H; Arenz, Matthias

    2013-07-01

    We present a detailed description of the construction of an in situ electrochemical ATR-FTIR setup combined with a wall-jet electrode to investigate the electrocatalytic properties of nanoparticulate catalysts in situ under controlled mass transport conditions. The presented setup allows the electrochemical interface to be probed in combination with the simultaneous determination of reaction rates. At the same time, the high level of automation allows it to be used as a standard tool in electrocatalysis research. The performance of the setup was demonstrated by probing the oxygen reduction reaction on a platinum black catalyst in sulfuric electrolyte.

  11. Theoretical studies of the dynamics of chemical reactions

    SciTech Connect

    Wagner, A.F.

    1993-12-01

    Recent research effort has focussed on several reactions pertinent to combustion. The formation of the formyl radical from atomic hydrogen and carbon monoxide, recombination of alkyl radicals and halo-alkyl radicals with halogen atoms, and the thermal dissociation of hydrogen cyanide and acetylene have been studied by modeling. In addition, the inelastic collisions of NCO with helium have been investigated.

  12. Emotional Reactions of Students in Field Education: An Exploratory Study

    ERIC Educational Resources Information Center

    Litvack, Andrea; Mishna, Faye; Bogo, Marion

    2010-01-01

    An exploratory study using qualitative methodology was undertaken with recent MSW graduates (N=12) from 2 graduate social work programs to identify and describe the students' emotional reactions to experiences in field education. Significant and interrelated themes emerged including the subjective and unique definitions of emotionally charged…

  13. Study of Daedalus Interstellar Spacecraft Reaction Chamber and Thrust Structure

    NASA Astrophysics Data System (ADS)

    Reddy, S. K.; Benaroya, H.

    Project Daedalus was the 1978 trade study that proved the feasibility of space travel utilizing fusion-based propulsion (Inertial Confinement Fusion). This paper analyzes some of the key structural aspects of the Daedalus spacecraft, in particular, the reaction chamber and thrust structure that is integral to the Daedalus spacecraft, which supports the loads resulting from the fusion reactions. First, the reaction chamber is studied computationally in terms of static loading and vibrational characteristics utilizing the finite element method. Next, a proposed bracing system is integrated into the reaction chamber and the effects are studied. Lastly, the field coils with their supporting truss structure are added to the assembly. Concepts are introduced for actuators and course-correction mechanisms that ensure the spacecraft maintains the required trajectory to rendezvous with the target system. Present-day materials and manufacturing considerations are explored based on the assumptions made in the Daedalus study. Testing, qualification, and assembly of the spacecraft are also discussed. This paper is a summary of the first author's Master's Thesis at Rutgers University.

  14. [The contamination under polymerase chain reaction studies: problems and solutions].

    PubMed

    Titov, V N; Ameliushkina, V A; Rozhkova, T A

    2015-01-01

    The study was carried out to determine risk factors of false positive and false negative results under polymerase chain reaction-analysis of clinical material. The samples with high viral load can be the source of false positive results. The contamination with nucleic acids can occur at any section of polymerase chain reaction analysis. The study data permitted to establish that the most sensitive stage is isolation and purification of nucleic acids especially under manual mode of operation. The detection of positive signal in most samples of one setting indicates total contamination. The cases when only several samples are polluted are special challenge. The presence of sample with high concentration of viral nucleic acid and several samples with low concentration in one setting means necessity of repeated analysis beginning with stage of isolation of nucleic acid. The analysis of curves of accumulation of products of amplification, their forms and positioning on chart is the obligatory stage of polymerase chain reaction study in real time regimen. These actions permit to exclude the readouts of false negative testing results to departments. The study conclusions are equipotent for polymerase chain reaction testing of any nucleic acid targets.

  15. Palladium deuteride formation in the cathode of an electrochemical cell: An in situ neutron diffraction study

    SciTech Connect

    Rotella, F.J.; Richardson, J.W. Jr.; Redey, L.; Felcher, G.P.; Hitterman, R.L.; Kleb, R.

    1991-12-31

    In this report, neutron diffraction of palladium cathodes is utilized to reveal palladium deuteride formation within the crystal structure of the metal. The experiment described in this report demonstrates the efficacy of neutron powder diffraction as a tool for structural studies of metal deuterides/hydrides and the feasibility of in situ diffraction measurements from a working electrochemical cell. (JL)

  16. Palladium deuteride formation in the cathode of an electrochemical cell: An in situ neutron diffraction study

    SciTech Connect

    Rotella, F.J.; Richardson, J.W. Jr.; Redey, L.; Felcher, G.P.; Hitterman, R.L.; Kleb, R.

    1991-01-01

    In this report, neutron diffraction of palladium cathodes is utilized to reveal palladium deuteride formation within the crystal structure of the metal. The experiment described in this report demonstrates the efficacy of neutron powder diffraction as a tool for structural studies of metal deuterides/hydrides and the feasibility of in situ diffraction measurements from a working electrochemical cell. (JL)

  17. Surface phenomena revealed by in situ imaging: studies from adhesion, wear and cutting

    NASA Astrophysics Data System (ADS)

    Viswanathan, Koushik; Mahato, Anirban; Yeung, Ho; Chandrasekar, Srinivasan

    2017-03-01

    Surface deformation and flow phenomena are ubiquitous in mechanical processes. In this work we present an in situ imaging framework for studying a range of surface mechanical phenomena at high spatial resolution and across a range of time scales. The in situ framework is capable of resolving deformation and flow fields quantitatively in terms of surface displacements, velocities, strains and strain rates. Three case studies are presented demonstrating the power of this framework for studying surface deformation. In the first, the origin of stick-slip motion in adhesive polymer interfaces is investigated, revealing a intimate link between stick-slip and surface wave propagation. Second, the role of flow in mediating formation of surface defects and wear particles in metals is analyzed using a prototypical sliding process. It is shown that conventional post-mortem observation and inference can lead to erroneous conclusions with regard to formation of surface cracks and wear particles. The in situ framework is shown to unambiguously capture delamination wear in sliding. Third, material flow and surface deformation in a typical cutting process is analyzed. It is shown that a long-standing problem in the cutting of annealed metals is resolved by the imaging, with other benefits such as estimation of energy dissipation and power from the flow fields. In closure, guidelines are provided for profitably exploiting in situ observations to study large-strain deformation, flow and friction phenomena at surfaces that display a variety of time-scales.

  18. In-Situ Chemical Reduction and Oxidation of VOCs in Groundwater: Groundwater Treatability Studies

    NASA Technical Reports Server (NTRS)

    Keith, Amy; Glasgow, Jason; McCaleh, Rececca C. (Technical Monitor)

    2001-01-01

    This paper presents NASA Marshall Space Flight Center's treatability studies for volatile organic compounds in groundwater. In-Situ groundwater treatment technologies include: 1) Chemical Reduction(Ferox); 2) Chemical Oxidation (Fenton Reagents, Permanganate, and Persulfate); and 3) Thermal (Dynamic Underground Stripping, Six-Phase Heating). This paper is presented in viewgraph form.

  19. Toluene pyrolysis studies and high temperature reactions of propargyl chloride

    SciTech Connect

    Kern, R.D.; Chen, H.; Qin, Z.

    1993-12-01

    The main focus of this program is to investigate the thermal decompositions of fuels that play an important role in the pre-particle soot formation process. It has been demonstrated that the condition of maximum soot yield is established when the reaction conditions of temperature and pressure are sufficient to establish a radical pool to support the production of polyaromatic hydrocarbon species and the subsequent formation of soot particles. However, elevated temperatures result in lower soot yields which are attributed to thermolyses of aromatic ring structures and result in the bell-shaped dependence of soot yield on temperature. The authors have selected several acyclic hydrocarbons to evaluate the chemical thermodynamic and kinetic effects attendant to benzene formation. To assess the thermal stability of the aromatic ring, the authors have studied the pyrolyses of benzene, toluene, ethylbenzene, chlorobenzene and pyridine. Time-of-flight mass spectrometry (TOF) is employed to analyze the reaction zone behind reflected shock waves. Reaction time histories of the reactants, products, and intermediates are constructed and mechanisms are formulated to model the experimental data. The TOF work is often performed with use of laser schlieren densitometry (LS) to measure density gradients resulting from the heats of various reactions involved in a particular pyrolytic system. The two techniques, TOF and LS, provide independent and complementary information about ring formation and ring rupture reactions.

  20. A model study of sequential enzyme reactions and electrostatic channeling.

    PubMed

    Eun, Changsun; Kekenes-Huskey, Peter M; Metzger, Vincent T; McCammon, J Andrew

    2014-03-14

    We study models of two sequential enzyme-catalyzed reactions as a basic functional building block for coupled biochemical networks. We investigate the influence of enzyme distributions and long-range molecular interactions on reaction kinetics, which have been exploited in biological systems to maximize metabolic efficiency and signaling effects. Specifically, we examine how the maximal rate of product generation in a series of sequential reactions is dependent on the enzyme distribution and the electrostatic composition of its participant enzymes and substrates. We find that close proximity between enzymes does not guarantee optimal reaction rates, as the benefit of decreasing enzyme separation is countered by the volume excluded by adjacent enzymes. We further quantify the extent to which the electrostatic potential increases the efficiency of transferring substrate between enzymes, which supports the existence of electrostatic channeling in nature. Here, a major finding is that the role of attractive electrostatic interactions in confining intermediate substrates in the vicinity of the enzymes can contribute more to net reactive throughput than the directional properties of the electrostatic fields. These findings shed light on the interplay of long-range interactions and enzyme distributions in coupled enzyme-catalyzed reactions, and their influence on signaling in biological systems.

  1. Theoretical studies of atmospheric reaction mechanisms in the troposphere.

    PubMed

    Vereecken, Luc; Francisco, Joseph S

    2012-10-07

    The chemistry of the atmosphere encompasses a vast number of reactions acting on a plethora of intermediates. These reactions, occurring sequentially and in parallel, give rise to intertwined and irreducible mechanisms describing the complex chemical transformations of organic and inorganic compounds in the atmosphere. The complexity of this system is that it requires combined experimental, theoretical, and modeling approaches to elucidate the characteristics of the individual reactions, and their mutual interaction. In this review, we describe recent results from quantum chemical and theoretical kinetic studies of relevance to atmospheric chemistry. The review first summarizes the most commonly used theoretical methodologies. It then examines the VOC oxidation initiation channels by OH, O(3), NO(3) and Cl, followed by the reactions of the alkyl, alkoxy, alkylperoxy and Criegee intermediates active in the subsequent oxidation steps. Specific systems such as the oxidation of aromatics and the current state of knowledge on OH-regeneration in VOC oxidation are also discussed, as well as some inorganic reactions.

  2. Sum Frequency Generation Studies of Hydrogenation Reactions on Platinum Nanoparticles

    SciTech Connect

    Krier, James M.

    2013-08-31

    Sum Frequency Generation (SFG) vibrational spectroscopy is used to characterize intermediate species of hydrogenation reactions on the surface of platinum nanoparticle catalysts. In contrast to other spectroscopy techniques which operate in ultra-high vacuum or probe surface species after reaction, SFG collects information under normal conditions as the reaction is taking place. Several systems have been studied previously using SFG on single crystals, notably alkene hydrogenation on Pt(111). In this thesis, many aspects of SFG experiments on colloidal nanoparticles are explored for the first time. To address spectral interference by the capping agent (PVP), three procedures are proposed: UV cleaning, H2 induced disordering and calcination (core-shell nanoparticles). UV cleaning and calcination physically destroy organic capping while disordering reduces SFG signal through a reversible structural change by PVP.

  3. Studying the triple - α reaction in hyperspherical harmonic approach

    NASA Astrophysics Data System (ADS)

    Nguyen, Ngoc; Nunes, Filomena

    2010-11-01

    The triple-α reaction is studied by using hyperspherical harmonic (HH) method [1]. Starting from three body model, we determine the 2^+ state and the 0^+ resonance as well as the quadrupole strength function B(E2). The triple-α reaction rate are calculated. We also carefully consider the contributions of the nonresonant continuum states to the reaction rate at low temperature (T <=10^8 K). The results are compared with [2,3].[4pt] [1] I. J. Thompson, F. M. Nunes, B. V. Danilin, Comput.Phys.Comm. 161, 87-107 (2004).[0pt] [2] K.Ogata, M.Kan, M.Kamimura, Prog. Theor. Phys. 122, 1055 (2009).[0pt] [3] R. de Diego, E. Garrido, D.V. Fedorov, A.S. Jensen, arXiv:1005.5647v1.

  4. In situ measurement of activation energy for pyrolysis of ethanol as a first reaction in the synthesis of carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Ohga, Yosuke; Inoue, Shuhei; Matsumura, Yukihiko

    2015-10-01

    Using a quadrupole mass spectrometer we measured the activation energy of ethanol decomposition with various catalysts. In order to quantitatively evaluate the catalysts we subtracted their effect from that of the catalyst-free pyrolysis. As a result we derived the activation energies using iron, cobalt, nickel, and molybdenum catalysts. These metals are typical catalysts in carbon nanotube synthesis, with two of them usually mixed empirically. This empirical preparation and use of catalysts is consistent with our results. Among these catalysts, iron reduced the activation energy most. Conversely, cobalt achieved a reduction of only 0.3 eV compared to the catalyst-free reaction.

  5. Confocal microscopy indentation system for studying in situ chondrocyte mechanics.

    PubMed

    Han, Sang-Kuy; Colarusso, Pina; Herzog, Walter

    2009-10-01

    Chondrocytes synthesize extracellular matrix molecules, thus they are essential for the development, adaptation and maintenance of articular cartilage. Furthermore, it is well accepted that the biosynthetic activity of chondrocytes is influenced by the mechanical environment. Therefore, their response to mechanical stimuli has been studied extensively. Much of the knowledge in this area of research has been derived from testing of isolated cells, cartilage explants, and fixed cartilage specimens: systems that differ in important aspects from chondrocytes embedded in articular cartilage and observed during loading conditions. In this study, current model systems have been improved by working with the intact cartilage in real time. An indentation system was designed on a confocal microscope that allows for simultaneous loading and observation of chondrocytes in their native environment. Cell mechanics were then measured under precisely controlled loading conditions. The indentation system is based on a light transmissible cylindrical glass indentor of 0.17 mm thickness and 1.64 mm diameter that is aligned along the focal axis of the microscope and allows for real time observation of live cells in their native environment. The system can be used to study cell deformation and biological responses, such as calcium sparks, while applying prescribed loads on the cartilage surface. It can also provide novel information on the relationship between cell loading and cartilage adaptive/degenerative processes in the intact tissue.

  6. Shape-selected nanocrystals for in situ spectro-electrochemistry studies on structurally well defined surfaces under controlled electrolyte transport: A combined in situ ATR-FTIR/online DEMS investigation of CO electrooxidation on Pt

    PubMed Central

    Jusys, Zenonas; Behm, R Jürgen

    2014-01-01

    Summary The suitability and potential of shape selected nanocrystals for in situ spectro-electrochemical and in particular spectro-electrocatalytic studies on structurally well defined electrodes under enforced and controlled electrolyte mass transport will be demonstrated, using Pt nanocrystals prepared by colloidal synthesis procedures and a flow cell set-up allowing simultaneous measurements of the Faradaic current, FTIR spectroscopy of adsorbed reaction intermediates and side products in an attenuated total reflection configuration (ATR-FTIRS) and differential electrochemical mass spectrometry (DEMS) measurements of volatile reaction products. Batches of shape-selected Pt nanocrystals with different shapes and hence different surface structures were prepared and structurally characterized by transmission electron microscopy (TEM) and electrochemical methods. The potential for in situ spectro-electrocatalytic studies is illustrated for COad oxidation on Pt nanocrystal surfaces, where we could separate contributions from two processes occurring simultaneously, oxidative COad removal and re-adsorption of (bi)sulfate anions, and reveal a distinct structure sensitivity in these processes and also in the structural implications of (bi)sulfate re-adsorption on the CO adlayer. PMID:24991511

  7. Real-time studies of battery electrochemical reactions inside a transmission electron microscope.

    SciTech Connect

    Leung, Kevin; Hudak, Nicholas S.; Liu, Yang; Liu, Xiaohua H.; Fan, Hongyou; Subramanian, Arunkumar; Shaw, Michael J.; Sullivan, John Patrick; Huang, Jian Yu

    2012-01-01

    We report the development of new experimental capabilities and ab initio modeling for real-time studies of Li-ion battery electrochemical reactions. We developed three capabilities for in-situ transmission electron microscopy (TEM) studies: a capability that uses a nanomanipulator inside the TEM to assemble electrochemical cells with ionic liquid or solid state electrolytes, a capability that uses on-chip assembly of battery components on to TEM-compatible multi-electrode arrays, and a capability that uses a TEM-compatible sealed electrochemical cell that we developed for performing in-situ TEM using volatile battery electrolytes. These capabilities were used to understand lithiation mechanisms in nanoscale battery materials, including SnO{sub 2}, Si, Ge, Al, ZnO, and MnO{sub 2}. The modeling approaches used ab initio molecular dynamics to understand early stages of ethylene carbonate reduction on lithiated-graphite and lithium surfaces and constrained density functional theory to understand ethylene carbonate reduction on passivated electrode surfaces.

  8. Ammonium transport and reaction in contaminated groundwater: Application of isotope tracers and isotope fractionation studies

    USGS Publications Warehouse

    Böhlke, J.K.; Smith, R.L.; Miller, D.N.

    2006-01-01

    Ammonium (NH4+) is a major constituent of many contaminated groundwaters, but its movement through aquifers is complex and poorly documented. In this study, processes affecting NH4+ movement in a treated wastewater plume were studied by a combination of techniques including large-scale monitoring of NH4+ distribution; isotopic analyses of coexisting aqueous NH4+, NO3-, N2, and sorbed NH 4+; and in situ natural gradient 15NH 4+ tracer tests with numerical simulations of 15NH4+, 15NO3-, and 15N2 breakthrough data. Combined results indicate that the main mass of NH4+ was moving downgradient at a rate about 0.25 times the groundwater velocity. Retardation factors and groundwater ages indicate that much of the NH4+ in the plume was recharged early in the history of the wastewater disposal. NO3- and excess N2 gas, which were related to each other by denitrification near the plume source, were moving downgradient more rapidly and were largely unrelated to coexisting NH 4+. The ??15N data indicate areas of the plume affected by nitrification (substantial isotope fractionation) and sorption (no isotope fractionation). There was no conclusive evidence for NH 4+-consuming reactions (nitrification or anammox) in the anoxic core of the plume. Nitrification occurred along the upper boundary of the plume but was limited by a low rate of transverse dispersive mixing of wastewater NH4+ and O2 from overlying uncontaminated groundwater. Without induced vertical mixing or displacement of plume water with oxic groundwater from upgradient sources, the main mass of NH4+ could reach a discharge area without substantial reaction long after the more mobile wastewater constituents are gone. Multiple approaches including in situ isotopic tracers and fractionation studies provided critical information about processes affecting NH4+ movement and N speciation.

  9. [In-situ DRIFTS study of coupling partial oxidation of methane and carbon dioxide reforming].

    PubMed

    Ji, Hong-bing; Xu, Jian-hua; Xie, Jun-feng; Chen, Qing-lin

    2008-06-01

    8%Ru-5%Ce/gamma-Al2O3 catalyst exhibited excellent catalytic performance for low temperature activation of methane. Although the conversion rates of methane were 25.3% for exothermal partial oxidation of methane, and 0.8% for endothermal carbon dioxide reforming, whose activity was rather low, 38.8% of conversion rate of methane could be obtained for the obtained coupling reaction at 500 degrees C owing to the coupling intensification between endothermal carbon dioxide reforming reaction and exothermal partial oxidation of methane. The mechanism of coupling partial oxidation of methane and carbon dioxide reforming on supported Ru catalyst was investigated by in-situ DRIFTS. The adsorption of CO on 8%Ru-5%Ce/gamma-Al2O3 showed that two kinds of doublet peaks which were characteristic adsorption of the gaseous CO at 2167 cm(-1) (2118 cm(-1)) to form Ru(CO)2 at 2031 cm(-1) (2034 cm(-1)) to form Ce(CO)2 were observed. These CO adsorption species wee easy to be desorbed from the surface of the catalyst at high temperature. The results of in-situ DRIFTS showed that carbonate, formal (formate) and carbon monoxide formed on the surface of catalyst, and formal (formate) was intermediate for the methane partial oxidation. This intermediate was formed through the combination of the adsorption species of methane CHx and the lattice oxygen adsorption species on the surface of catalyst, and syngas was produced through the splitting of this intermediate. The DRIFTS researching on carbon dioxide reforming showed that there was no new adsorption species on the surface of the catalyst, which indicated that the mechanism for carbon dioxide reforming was through the dissociation of the adsorbed methane and carbon dioxide. During the reaction of the coupling of carbon dioxide reforming reaction and partial oxidation of methane, there was hydroxyl adsorption species on the surface of catalyst. The mechanism of coupling methane, carbon dioxide and oxygen might be composed of the above

  10. Functionalization of polyolefins via borane/oxygen chemistry: Synthesis and reaction mechanism study

    NASA Astrophysics Data System (ADS)

    Janvikul, Wanida

    This dissertation describes a novel method to functionalize polyolefins by the borane approach. Although the borane/oxygen chemistry has been extensively studied since 1950, its reaction mechanism is still ambiguous. It has been generally accepted that the reaction proceeds via a free radical process, and a boronperoxide is an initial product of the autoxidation of an alkylborane. Many speculations have been made on how this peroxide decomposes and how free radicals are formed at room temperature. We have studied the autoxidation of alkyl-9-BBN compounds by means of sp1H NMR, sp{13}C NMR, sp{11}B NMR and ESR. The alkyl-9-BBN compounds essentially differ from other alkylboranes in that they can be selectively oxidized by oxygen under a controlled condition. The oxidative selectivity was proved by sp{13}C NMR. The decomposition of the boronperoxide was trailed by ESR analysis. An alkoxyl radical, not an alkyl radical, was detected at room temperature, which was contradictory to the mechanism that has been postulated by several authors. The oxidated adducts from the alkyl-9-BBN/oxygen system were used as initiators in the polymerization of some vinyl monomers, i.e., methyl methacrylate (MMA), ethyl methacrylate, vinyl acetate, and t-butyl methacrylate. The polymerization, under a well-controlled condition, seemed to have a "pseudo-living" nature as the molecular weights of the resulting polymers increased with the reaction times. The synthese of polyolefin graft copolymers were carried out based on the autoxidation and polymerization studies. The process involves hydroboration of some commercial polymers containing unsaturation with 9-borabicyclononane (9-BBN). The resulting secondary alkyl-9-BBN moieties in the starting materials were then exposed to oxygen in the presence of free radical polymerizable monomers, i.e., MMA and acrylonitrile. Under certain conditions, the selective autoxidation reaction of secondary alkyl-9-BBN took place to create desirable polymeric

  11. Cost studies of thermally enhanced in situ soil remediation technologies

    SciTech Connect

    Bremser, J.; Booth, S.R.

    1996-05-01

    This report describes five thermally enhanced technologies that may be used to remediate contaminated soil and water resources. The standard methods of treating these contaminated areas are Soil Vapor Extraction (SVE), Excavate & Treat (E&T), and Pump & Treat (P&T). Depending on the conditions at a given site, one or more of these conventional alternatives may be employed; however, several new thermally enhanced technologies for soil decontamination are emerging. These technologies are still in demonstration programs which generally are showing great success at achieving the expected remediation results. The cost savings reported in this work assume that the technologies will ultimately perform as anticipated by their developers in a normal environmental restoration work environment. The five technologies analyzed in this report are Low Frequency Heating (LF or Ohmic, both 3 and 6 phase AC), Dynamic Underground Stripping (DUS), Radio Frequency Heating (RF), Radio Frequency Heating using Dipole Antennae (RFD), and Thermally Enhanced Vapor Extraction System (TEVES). In all of these technologies the introduction of heat to the formation raises vapor pressures accelerating contaminant evaporation rates and increases soil permeability raising diffusion rates of contaminants. The physical process enhancements resulting from temperature elevations permit a greater percentage of volatile organic compound (VOC) or semi- volatile organic compound (SVOC) contaminants to be driven out of the soils for treatment or capture in a much shorter time period. This report presents the results of cost-comparative studies between these new thermally enhanced technologies and the conventional technologies, as applied to five specific scenarios.

  12. [Electromagnetic studies of nuclear structure and reactions]. Progress summary

    SciTech Connect

    Not Available

    1992-12-31

    The experimental goals are focused on developing an understanding of strong interactions and the structure of hadronic systems by determination of the electromagnetic response; these goals will be accomplished through coincidence detection of final states. Nuclear modeling objectives are to organize and interpret the data through a consistent description of a broad spectrum of reaction observables; calculations are performed in a nonrelativistic diagrammatic framework as well as a relativistic QHD approach. Work is described according to the following arrangement: direct knockout reactions (completion of {sup 16}O(e,e{prime}p), {sup 12}C(e,e{prime}pp) progress, large acceptance detector physics simulations), giant resonance studies (intermediate-energy experiments with solid-state detectors, the third response function in {sup 12}C(e,e{prime}p{sub 0}) and {sup 16}O(e,e{prime}p{sub 0}), comparison of the {sup 12}C(e, e{prime}p{sub 0}) and {sup 16}O(e,e{prime}p{sub 3}) reactions, quadrupole strength in the {sup 16}O(e,e{prime}{alpha}{sub 0}) reaction, quadrupole strength in the {sup 12}C(e,e{prime}{alpha}) reaction, analysis of the {sup 12}C(e,e{prime}p{sub 1}) and {sup 16}O(e,e{prime}p{sub 3}) angular distributions, analysis of the {sup 40}Ca(e,e{prime}x) reaction at low q, analysis of the higher-q {sup 12}C(e,e{prime}x) data from Bates), models of nuclear structure (experimental work, Hartree-Fock calculations, phonon excitations in spherical nuclei, shell model calculations, variational methods for relativistic fields), and instrumentation development efforts (developments at CEBAF, CLAS contracts, BLAST developments).

  13. A thermostat chip of indium tin oxide glass substrate for static polymerase chain reaction and in situ real time fluorescence monitoring.

    PubMed

    Wu, Zhi-Yong; Chen, Kun; Qu, Bai-Yan; Tian, Xiao-Xi; Wang, Xiao-Jie; Fang, Fang

    2008-03-03

    A thermostat chip of indium-tin oxide glass substrate for static chip polymerase chain reaction (PCR) is, for the first time, introduced in this paper. The transparent conductive layer was used as an electro-heating element. Pulse width modulation and fuzzy proportional integration-differentiation algorithm were adopted in the temperature programming of the chip. The temperature distribution was investigated, and a dynamic control precision within +/-2 degrees C was achieved. The highest ramping rates were 37 degrees Cs(-1) for heating and 8 degrees Cs(-1) for cooling with an electric fan. The PCR reaction vials were constructed with polyethylene tubes or poly(dimethylsiloxane) directly on the thermostat chip; the chip had a typical size of 25 mm x 25 mm and a thickness of 1.1mm. Static chip PCR was successfully demonstrated either in a single vial or in an up to 8-parallel array vials. In situ real time fluorescence monitoring during PCR of a lambda DNA fragments (236bp) with SYBR Green I was demonstrated using a blue light emission diode as a light source and a photomultiplier as a detector. The method proposed here is characterized by open access, easy fabrication and low cost. This work could be the basis for developing a portable real time PCR system with disposable chips for point of care tests.

  14. A dynamical study of the Si(+) + H(2)O reaction.

    PubMed

    Flores, Jesús R

    2007-11-01

    A dynamical study of the Si(+) + H(2)O reaction has been carried out by means of a quasiclassical trajectory method that decomposes the reaction into a capture step, for which an accurate analytical potential is employed, and an unimolecular step, in which the evolution of the collision complex is studied through a direct dynamics BHandHLYP/6-31G(d,p) method. The capture rate coefficient has been computed for thermal conditions corresponding to temperatures ranging from 50 to 1000 K. It is concluded that the main reason why the reaction rate is about 10 times smaller than the capture rate (at T = 298 K) is the topology of the potential energy surface of the ground state. It is also concluded that the ratio between the rates of product and reactant generation from the collision complex decreases quite steeply with increasing temperature, and therefore, the reaction rate decreases even more sharply. Exciting the stretching normal modes of water substantially increases that ratio, and moderate rotational excitation does not appear to have a relevant effect. The collision complex is always initially SiOH(2)(+), but in some trajectories, it becomes HSiOH(+), which generates the products, although the former species is the main intermediate.

  15. In situ calibration of the Gamma Reaction History instrument using reference samples ("pucks") for areal density measurements

    NASA Astrophysics Data System (ADS)

    Hoffman, N. M.; Herrmann, H. W.; Kim, Y. H.; Hsu, H. H.; Horsfield, C. J.; Rubery, M. S.; Wilson, D. C.; Stoeffl, W. W.; Young, C. S.; Mack, J. M.; Miller, E. K.; Grafil, E.; Evans, S. C.; Sedillo, T. J.; Glebov, V. Yu.; Duffy, T.

    2013-11-01

    The introduction of a sample of carbon, for example a disk or "puck", near an imploding DT-filled capsule creates a source of 12C gamma rays that can serve as a reference for calibrating the response of the Gamma Reaction History (GRH) detector [1]. Such calibration is important in the measurement of ablator areal density ⟨ρR⟩abl in plastic-ablator DT-filled capsules at OMEGA [2], by allowing ⟨ρR⟩abl to be inferred as a function of ratios of signals rather than from absolute measurements of signal magnitudes. Systematic uncertainties in signal measurements and detector responses therefore cancel, permitting more accurate measurements of ⟨ρR⟩abl.

  16. Choline acetyltransferase: further studies on the reverse reaction

    SciTech Connect

    Hsu, L.L.; Chao, L.P.

    1982-01-01

    In order to further characterize the reaction mechanism of brain ChAc in its purified form, we have investigated the reverse reaction of ChAc in terms of pH optimum, salt effects, and substrate kinetics using a radiochemical assay. We directly measured the reaction product acetylcoenzyme A which was separated from the substrate ACh by a cation exchange column. Dowex 50W-X8 (Na+ form). The reverse reaction of ChAc was linear with incubation time up to 40 minutes, and with enzyme protein concentration up to 5 micrograms. It had a pH optimum at 7.0. At 0.22 M the monovalent chloride and bromide salts activated the reverse ChAc activity by 23-47% but the fluoride and iodide salts inhibited the reverse enzyme activity by 10-30%. Kinetic studies in the absence of salt showed that KACh was 0.62 +/- 0.06 mM, KCoA . SH was 12.68 +/- 1.21 microM, and Vmax was 11.6 +/- 1.0 nmol AcCoA/mg protein/min. These data are in disagreement with the values reported on partially purified ChAc from bovine brain by Glover and Potter (1971) and Hersh (1980). This indicates that further investigations are necessary to clarify or resolve these differences.

  17. Raman spectroscopic studies of gas/aerosol chemical reactions

    SciTech Connect

    Aardahl, C.L.; Davis, E.J.

    1995-12-31

    Reactions between sorbent particles and SO{sub 2} can be used to reduce atmospheric pollution either by {open_quotes}dry scrubbing{close_quotes} or {open_quotes}wet scrubbing{close_quotes} processes. This paper reports Raman spectroscopy results for single electrodynamically levitated droplets of NaOH reacting with SO{sub 2} and studies of the dehydration reactions of some hygroscopic salt species. The NaOH/SO{sub 2} reaction products and the liquid or solid state of the products are shown to depend on the gas phase SO{sub 2} concentration. Deliquesced particles of NaOH exhibit enhanced light scattering intensities associated with morphological resonances of the incident laser light, but crystalline materials show no such resonances. Raman-active hygroscopic salts exhibit bond frequencies characteristic of the stretching vibrations of the anionic group, but these frequencies are different in the presence of water because hydrogen bonding changes the bond force. This allows efficient tracking of the dehydration reactions in hygroscopic aerosols by Raman spectroscopy as the intensities of the two different modes are related to the degree of dehydration in the particle.

  18. Iron oxide mineral-water interface reactions studied by AFM

    SciTech Connect

    Hawley, M.E.; Rogers, P.S.Z.

    1994-07-01

    Natural iron mineral surfaces have been examined in air by atomic force (AFM) and scanning tunneling (STM) microscopies. A number of different surface features were found to be characteristic of the native surface. Even surfaces freshly exposed by crushing larger crystals were found to have a pebbly surface texture caused by the presence of thin coatings of what might be surface precipitates. This finding is interpreted as evidence for previous exposure to water, probably through an extensive network of microfractures. Surface reactions on the goethite crystals were studied by AFM at size resolutions ranging from microns to atomic resolution before, during, and after reaction with distilled water and 0.lN HCl. Immediate and extensive surface reconfiguration occurred on contact with water. In one case, after equilibration with water for 3 days, surface reprecipitation, etching and pitting were observed. Atomic resolution images taken under water were found to be disordered. The result of surface reaction was generally to increase the surface area substantially through the extension of surface platelet arrays, present prior to reaction. This work is being done in support of the site characterization project at Yucca Mountain.

  19. Molecular-dynamics study of detonation. II. The reaction mechanism

    NASA Astrophysics Data System (ADS)

    Rice, Betsy M.; Mattson, William; Grosh, John; Trevino, S. F.

    1996-01-01

    In this work, we investigate mechanisms of chemical reactions that sustain an unsupported detonation. The chemical model of an energetic crystal used in this study consists of heteronuclear diatomic molecules that, at ambient pressure, dissociate endothermically. Subsequent association of the products to form homonuclear diatomic molecules provides the energy release that sustains the detonation. A many-body interaction is used to simulate changes in the electronic bonding as a function of local atomic environment. The consequence of the many-body interaction in this model is that the intramolecular bond is weakened with increasing density. The mechanism of the reaction for this model was extracted by investigating the details of the molecular properties in the reaction zone with two-dimensional molecular dynamics. The mechanism for the initiation of the reaction in this model is pressure-induced atomization. There was no evidence of excitation of vibrational modes to dissociative states. This particular result is directly attributable to the functional form and choice of parameters for this model, but might also have more general applicability.

  20. Inertial confinement fusion reaction chamber and power conversion system study

    SciTech Connect

    Maya, I.; Schultz, K.R.; Battaglia, J.M.; Buksa, J.J.; Creedson, R.L.; Erlandson, O.D.; Levine, H.E.; Roelant, D.F.; Sanchez, H.W.; Schrader, S.A.

    1984-09-01

    GA Technologies has developed a conceptual ICF reactor system based on the Cascade rotating-bed reaction chamber concept. Unique features of the system design include the use of low activation SiC in a reaction chamber constructed of box-shaped tiles held together in compression by prestressing tendons to the vacuum chamber. Circulating Li/sub 2/O granules serve as the tritium breeding and energy transport material, cascading down the sides of the reaction chamber to the power conversion system. The total tritium inventory of the system is 6 kg; tritium recovery is accomplished directly from the granules via the vacuum system. A system for centrifugal throw transport of the hot Li/sub 2/O granules from the reaction chamber to the power conversion system has been developed. A number of issues were evaluated during the course of this study. These include the response of first-layer granules to the intense microexplosion surface heat flux, cost effective fabrication of Li/sub 2/O granules, tritium inventory and recovery issues, the thermodynamics of solids-flow options, vacuum versus helium-medium heat transfer, and the tradeoffs of capital cost versus efficiency for alternate heat exchange and power conversion system option. The resultant design options appear to be economically competitive, safe, and environmentally attractive.

  1. Transintestinal secretion of ciprofloxacin, grepafloxacin and sparfloxacin: in vitro and in situ inhibition studies.

    PubMed

    Rodríguez-Ibáñez, M; Nalda-Molina, R; Montalar-Montero, M; Bermejo, M V; Merino, V; Garrigues, T M

    2003-03-01

    The influence of the secretion process on the absorption of ciprofloxacin, grepafloxacin and sparfloxacin has been evaluated by means of inhibition studies. Two well known P-glycoprotein inhibitors (cyclosporine, verapamil), a mixed inhibitor of P-glycoprotein and the organic cation transporter OCT1 (quinidine) and a well established MRP substrate (p-aminohipuric acid) have been selected in order to distinguish the possible carriers implicated. An in situ rat gut perfusion model and CACO-2 permeability studies are used. Both methods suggest the involvement of several types of efflux transporters for every fluoroquinolone. The relevance of the secretory pathway depends on the intrinsic permeability of the quinolone. The in vitro model seems to be more suitable for discriminating mechanisms underlying the absorption process, while in situ studies are less sensitive to inhibition studies.

  2. A in Situ Study of Plasma Etching Surface Chemistry Using Reflection Infrared Spectroscopy

    NASA Astrophysics Data System (ADS)

    Lucchesi, Robert Peter

    Plasma etching is an important process in semiconductor manufacturing. The present work describes a means by which plasma etching surface chemistry may be studied in situ. The systems of interest were the sulfur hexafluoride plasma etching of silicon and tungsten in a diode reactor. A reflection infrared spectrometer was designed and constructed to be able to scan the frequency region from about 550cm ^{-1} to 1300cm ^{-1}, and a plasma etch reactor was modified to allow access to the infrared beam. Reflection infrared spectroscopy (RIS) allows the measurement of light absorbed by molecules adsorbed on a reflective surface selectively from light absorbed by molecules in the gas phase. RIS applied to heavily doped silicon substrates had limited success. While sulfur fluorine species were detected on the surface during plasma etching, no silicon fluorine species were ever detected. The sulfur fluorine species (referred to as SF_{rm x}) were not seen under any circumstances in the absence of an SF_6 plasma. Severe baseline drift of the infrared spectrometer during plasma etching was the main reason for the limited success. However, the results were significant in that they demonstrated the presence of sulfur fluorine species during the plasma etching of silicon in an SF_6 plasma. The baseline drift problems experienced with silicon were not found when tungsten was studied. The same SF _{rm x} feature detected on silicon was also found on tungsten during etching in an SF_6 plasma, but was never seen in the absence of the plasma. A detailed experimental and theoretical study was performed to show that the surface absorption feature seen was actually due to SF _{rm x} adsorbed on the surface. A hysteresis behavior was observed in the SF_ {rm x} concentration as the plasma power was ramped up and subsequently decreased. Finally, it could not be concluded if SF_{rm x} participated in the etch reaction by fluorinating the tungsten surface, but the presence of SF_ {rm x} on

  3. In-situ Study of Dynamic Phenomena at Metal Nanosolder Interfaces Using Aberration Corrected Scanning Transmission Electron Microcopy.

    SciTech Connect

    Lu, Ping

    2014-10-01

    Controlling metallic nanoparticle (NP) interactions plays a vital role in the development of new joining techniques (nanosolder) that bond at lower processing temperatures but remain viable at higher temperatures. The pr imary objective of this project is t o develop a fundamental understanding of the actual reaction processes, associated atomic mechanisms, and the resulting microstructure that occur during thermally - driven bond formation concerning metal - metal nano - scale (%3C50nm) interfaces. In this LDRD pr oject, we have studied metallic NPs interaction at the elevated temperatures by combining in - situ transmission electron microscopy (TEM ) using an aberration - corrected scanning transmission electron microscope (AC - STEM) and atomic - scale modeling such as m olecular dynamic (MD) simulations. Various metallic NPs such as Ag, Cu and Au are synthesized by chemical routines. Numerous in - situ e xperiments were carried out with focus of the research on study of Ag - Cu system. For the first time, using in - situ STEM he ating experiments , we directly observed t he formation of a 3 - dimensional (3 - D) epitaxial Cu - Ag core - shell nanoparticle during the thermal interaction of Cu and Ag NPs at elevated temperatures (150 - 300 o C). The reaction takes place at temperatures as low as 150 o C and was only observed when care was taken to circumvent the effects of electron beam irradiation during STEM imaging. Atomic - scale modeling verified that the Cu - Ag core - shell structure is energetically favored, and indicated that this phenomenon is a nano - scale effect related to the large surface - to - volume ratio of the NPs. The observation potentially can be used for developing new nanosolder technology that uses Ag shell as the "glue" that stic ks the particles of Cu together. The LDRD has led to several journal publications and numerous conference presentations, and a TA. In addition, we have developed new TEM characterization techniques and phase

  4. Ultrafast optical studies of surface reaction processes at semiconductor interfaces. Progress report

    SciTech Connect

    Miller, R.J.D.

    1994-10-01

    The DOE funded research has focused on the development of novel non-linear optical methods for the in situ study of surface reaction dynamics. In particular, the work has concentrated on interfacial charge transfer processes as this is the simplest of all surface reactions, i.e., no bonds are broken and the reaction is derived from nuclear repolarization. Interfacial charge transfer forms the basis for a number of important solar energy conversion strategies. In these studies, semiconductor liquid junctions provide a convenient system in which the interfacial charge transfer can be optically initiated. The all-optical approach necessitates that the dynamics of the charge transfer event itself be put in the proper context of the operating photophysical processes at the surface. There are at least four dynamical processes that are coupled in determining the overall rate of electron flux across the interface. In the limit that interfacial charge transfer approaches strong coupling, the time scale for transport of even field accelerated carriers within the space charge region becomes comparable to the charge transfer dynamics. The transport component needs to be convolved to probes of the carrier population at the surface. The other two dynamical processes, carrier thermalization and surface state trapping, determine the states which ultimately serve as the donor levels to the solution acceptor distribution. In terms of the hot carrier model, these latter two processes compete with direct unthermalized charge transfer. There is a fifth dynamical process which also needs consideration: the solvent modes that are coupled to the reaction coordinate. Ultimately, the dynamics of solvent relaxation determine the upper limit to the charge transfer process. Different optical techniques have been developed to follow all the above dynamical processes in which a real time view of charge transfer dynamics at semiconductor surfaces is emerging. These results are discussed here.

  5. Reaction cell for in situ soft x-ray absorption spectroscopy and resonant inelastic x-ray scattering measurements of heterogeneous catalysis up to 1 atm and 250 °C

    SciTech Connect

    Kristiansen, P. T.; Rocha, T. C. R.; Knop-Gericke, A.; Guo, J. H.; Duda, L. C.

    2013-11-15

    We present a novel in situ reaction cell for heterogeneous catalysis monitored in situ by x-ray absorption spectroscopy (XAS) and resonant inelastic x-ray scattering (RIXS). The reaction can be carried out at a total pressure up to 1 atm, a regime that has not been accessible to comparable in situ techniques and thus closes the pressure gap to many industrial standard conditions. Two alternate catalyst geometries were tested: (A) a thin film evaporated directly onto an x-ray transparent membrane with a flowing reaction gas mixture behind it or (B) a powder placed behind both the membrane and a gap of flowing reaction gas mixture. To illustrate the working principle and feasibility of our reaction cell setup we have chosen ethylene epoxidation over a silver catalyst as a test case. The evolution of incorporated oxygen species was monitored by total electron/fluorescence yield O K-XAS as well as O K-RIXS, which is a powerful method to separate contributions from inequivalent sites. We find that our method can reliably detect transient species that exist during catalytic reaction conditions that are hardly accessible using other spectroscopic methods.

  6. Reaction cell for in situ soft x-ray absorption spectroscopy and resonant inelastic x-ray scattering measurements of heterogeneous catalysis up to 1 atm and 250 °C.

    PubMed

    Kristiansen, P T; Rocha, T C R; Knop-Gericke, A; Guo, J H; Duda, L C

    2013-11-01

    We present a novel in situ reaction cell for heterogeneous catalysis monitored in situ by x-ray absorption spectroscopy (XAS) and resonant inelastic x-ray scattering (RIXS). The reaction can be carried out at a total pressure up to 1 atm, a regime that has not been accessible to comparable in situ techniques and thus closes the pressure gap to many industrial standard conditions. Two alternate catalyst geometries were tested: (A) a thin film evaporated directly onto an x-ray transparent membrane with a flowing reaction gas mixture behind it or (B) a powder placed behind both the membrane and a gap of flowing reaction gas mixture. To illustrate the working principle and feasibility of our reaction cell setup we have chosen ethylene epoxidation over a silver catalyst as a test case. The evolution of incorporated oxygen species was monitored by total electron/fluorescence yield O K-XAS as well as O K-RIXS, which is a powerful method to separate contributions from inequivalent sites. We find that our method can reliably detect transient species that exist during catalytic reaction conditions that are hardly accessible using other spectroscopic methods.

  7. Study on astrophysical reactions using low-energy RI beams

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Hidetoshi

    2009-10-01

    In recent years, low-energy RI beams can be produced in a good intensity and they have been used for studying many astrophysical reactions. One of the facilities producing low-energy RI beams is CRIB (CNS Radio-Isotope Beam separator) [1,2], an RI-beam separator of Center for Nuclear Study, University of Tokyo. Taking CRIB as an example, recent improvements on the RI-beam production and experimental results on astrophysical studies are presented. Several experimental approaches have been taken for the studies on astrophysical reactions.The feature of each method are discussed based on real measurements performed at CRIB. One is the direct method, applied for measurements of reactions such as (α,p) [3]. Another is the measurement of proton/alpha resonance scattering using the thick target method in inverse kinematics, by which we can obtain information on the resonances relevant in astrophysical reactions [4,5]. A recent fruitful result was from a measurement of proton resonance scattering using a ^7Be beam [5]. The energy level structure of ^8B, revealed by the experiment, is especially of interest as it is related with the ^7Be(p,γ) ^8B reaction, responsible for the production of ^8B neutrinos in the sun. We successfully determined parameters of resonances in ^8B below 6.7 MeV, which may affect the ^7Be(p,γ)^8B reaction rate at the solar temparature. Indirect methods, such as ANC and the Trojan Horse Method, were also used in some of the measurements.[4pt] [1] S. Kubono et al., Eur. Phys. J. A13 (2002) 217.[0pt] [2] Y. Yanagisawa et al., Nucl. Instrum. Meth. Phys. Res., Sect. A 539 (2005) 74.[0pt] [3] M. Notani et al., Nucl. Phys. A 764 (2004) 113c.[0pt] [4] T. Teranishi et al., Phys. Lett. B 650 (2007) 129.[0pt] [5] H. Yamaguchi et al., Phys. Lett. B 672 (2009) 230.

  8. Electrochemical and spectroscopic studies of fuel cell reactions

    NASA Astrophysics Data System (ADS)

    Shao, Minhua

    Fuel cells, especially proton exchange membrane fuel cells (PEMFCs) are expected soon to become a major source of clean energy. However, the sluggish kinetics of the fuel cell reactions, i.e., the fuel oxidation and oxygen reduction, hinders the wide-spread application of PEMFCs. These problems prompted our studies to focus on elucidating the nature of the reaction intermediates during the oxidation of fuels and the reduction of oxygen on electrocatalysts, and understanding the mechanisms of these reactions. The results from these studies will provide basic information for designing new electrocatalysts. In this dissertation, the oxidation reactions of ethanol and dimethyl ether (DME) on Pt were investigated by the surface enhanced infrared absorption spectroscopy with an attenuated total reflection configuration (ATR-SEIRAS). Various reaction intermediates were detected and their electrochemical behaviors were studied. We also benefited from advantages of the ATR-SEIRAS technique and observed superoxide anion (O2-) and hydrogen peroxide anion (H2-) as the intermediates in the oxygen reduction reaction (ORR) on Pt and Au electrodes for the first time. The other main goal of this study is design of new electrocatalysts for ORR with low cost and high activity. Two novel electrocatalysts were developed. One is Pt monolayer electrocatalysts consisting of a Pt monolayer formed by a red-ox replacement of the Cu monolayer by Pt atoms on non-noble metal-noble metal core-shell nanoparticles. In such catalyst, the total noble mass activity of the catalyst was 2--6 times larger that of commercial Pt catalyst. Another way of lowering the cost of catalysts and enhancing the ORR activity involves alloying less expensive noble metals with other non-noble elements. In this dissertation, the nano-structured Pd based alloy electrocatalysts have been explored. The results showed that their ORR activities surpass that of commercial Pt. The density functional theory (DFT) calculations

  9. Tuning the properties of copper-based catalysts based on molecular in situ studies of model systems.

    PubMed

    Stacchiola, Darío J

    2015-07-21

    and morphology can be followed during a reaction by a combination of in situ microscopy and spectroscopy. In addition to determining the active phase of a catalyst by in situ methods, the presence of weakly adsorbed surface species or intermediates generated only in the presence of reactants can be detected, allowing in turn the comparison of experimental results with first principle modeling of specific reaction mechanisms. Three reactions are used to exemplify the approach: CO oxidation (CO + 1/2O2 → CO2), water gas shift reaction (WGSR) (CO + H2O → CO2 + H2), and methanol synthesis (CO2 + 3H2 → CH3OH + H2O). During CO oxidation, the full conversion of Cu(0) to Cu(2+) deactivates an initially outstanding catalyst. This can be remedied by the formation of a TiCuOx mixed-oxide that protects the presence of active partially oxidized Cu(+) cations. It is also shown that for the WGSR a switch occurs in the reaction mechanism, going from a redox process on Cu(111) to a more efficient associative pathway at the interface of ceria nanoparticles deposited on Cu(111). Similarly, the activation of CO2 at the ceria/Cu(111) interface allows its facile hydrogenation to methanol. Our combined studies emphasize the need of searching for optimal metal/oxide interfaces, where multifunctional sites can lead to new efficient catalytic reaction pathways.

  10. Crossed-beam studies of the dynamics of radical reactions

    SciTech Connect

    Liu, K.

    1993-12-01

    The objective of this program is to characterize the detailed dynamics of elementary radical reactions and to provide a better understanding of radical reactivity in general. The radical beam is typically generated by a laser photolysis method. After colliding with the reacting molecule in a crossed-beam apparatus, the reaction product state distribution is interrogated by laser spectroscopic techniques. Several radicals of combustion significance, such as O, CH, OH, CN and NCO have been successfully generated and their collisional behavior at the state-to-state integral cross section level of detail has been studied in this manner. During the past year, the detection system has been converted from LIF to REMPI schemes, and the emphasis of this program shifted to investigate the product angular distributions. Both inelastic and reactive processes have been studied.

  11. A Nuclear Reaction Analysis study of fluorine uptake in flint

    SciTech Connect

    Jin, Jian-Yue; Weathers, D. L.; Picton, F.; Hughes, B. F.; Duggan, J. L.; McDaniel, F. D.; Matteson, S.

    1999-06-10

    Nuclear Reaction Analysis (NRA) using the {sup 19}F(p,{alpha}{gamma}){sup 16}O resonance reaction is a powerful method of fluorine depth profiling. We have used this method to study the fluorine uptake phenomenon in mineral flint, which could potentially develop into a method of dating archeological flint artifacts. Flint samples cut with a rock saw were immersed in aqueous fluoride solutions for different times for the uptake study. The results suggest that fluorine uptake is not a simple phenomenon, but rather a combination of several simultaneous processes. Fluorine surface adsorption appears to play an important role in developing the fluorine profiles. The surface adsorption was affected by several parameters such as pH value and fluorine concentration in the solution, among others. The problem of surface charging for the insulator materials during ion bombardment is also reported.

  12. Proton Transfer Reactions Studied Using the VANDLE Neutron Detector Array

    NASA Astrophysics Data System (ADS)

    Thornsberry, C. R.; Burcher, S.; Gryzwacz, R.; Jones, K. L.; Paulauskas, S. V.; Smith, K.; Vostinar, M.; Allen, J.; Bardayan, D. W.; Blankstein, D.; Deboer, J.; Hall, M.; O'Malley, P. D.; Reingold, C.; Tan, W.; Cizewski, J. A.; Lepailleur, A.; Walter, D.; Febbraro, M.; Pain, S. D.; Marley, S. T.

    2016-09-01

    Proton transfer reactions, such as (d,n), are powerful tools for the study of single particle proton states of exotic nuclei. Measuring the outgoing neutron allows for the extraction of spectroscopic information from the recoil nucleus. With the development of new radioactive ion beam facilities, such as FRIB in the U.S., comes the need for new tools for the study of reactions involving radioactive nuclei. Neutron detectors, such as VANDLE, are sensitive to gamma rays in addition to neutrons. This results in high background rates for measurements with high external trigger rates. The use of discriminating recoil particle detectors, such as phoswich detectors, allow for the selection of a clean recoil tag by separating the recoil nucleus of interest from unreacted RIB components. Developments of low energy proton transfer measurements in inverse kinematics and recent (d,n) results will be presented. This work supported in part by the U.S. Department of Energy and the National Science Foundation.

  13. Atmospheric Chemistry: Laboratory Studies of Kinetics of Important Reactions.

    NASA Astrophysics Data System (ADS)

    Smith, S. J.

    Available from UMI in association with The British Library. Requires signed TDF. This thesis describes the experiments to measure the rate constants for some reactions of the atmospherically important nitrate radical (NO_3) using the discharge-flow technique. The nitrate radical was monitored by optical absorption at lambda = 662 nm. The reactions of NO_3 with some stable organic and inorganic substrates are reported. The temperature dependences of some of the rate constants have also been determined (298 < T < 523 K). In most cases, computer simulation was used to extract the rate constant for the primary process because the time-dependent behaviour of (NO_3) was affected by secondary reactions of NO_3 with products of the primary interaction. The Arrhenius parameter in parentheses (E _{rm a}/kJ mol^ {-1}, A/cm^3 molecule ^{-1}s^ {-1} respectively) for the following reactions have been determined: ethane (37, 6.7 times 10^{-12}), ethylene (25.8, 6.3 times 10^ {-12}), CH_3OH (21.3, 1.2 times 10^ {-12}), CHCiota_3 (23.4, 8.6 times 10 ^{-13}) and HCl (27.7, 4 times 10^{-12}). The activation energies for the reactions studied between NO_3 and some alkynes are represented well by the value 25 +/- 3 kJ mol^{-1} and the corresponding pre-exponential factors (expressed as ln(10 ^{13}A/cm^3 molecule^{-1}s ^{-1}) are as follows: C_2H_2 (1.6 +/- 1.4), C_3H _4 (5.0 +/- 1.4), 1-C_4H_6 (5.8 +/- 1.0), 1-C_5 H_8 (5.7 +/- 0.6) and 1-C_6H _{10} (4.5 +/- 0.4). Some reactions were studied at room temperature _3(298 +/- 2 K) only and the rate constants found (in units of cm ^3 molecule^{ -1}s^{-1}) are: buta-1,3-diene (1.8 times 10 ^{-13}), isobutene (2.8 times 10^{-13 }), HBr (1.3 times 10 ^{-15}) and hex-2-yne (3.0 times 10^{-14 }). Non-Arrhenius behaviour was found in the reactions of NO_3 with n-butane, isobutane and propene. The empirical variation of these rate constants with temperature is well represented by the three parameter expressions:. k(T) = 1.2 times 10 ^{-46}T^{11

  14. In situ DNA hybridized chain reaction (FISH-HCR) as a better method for quantification of bacteria and archaea within marine sediment

    NASA Astrophysics Data System (ADS)

    Buongiorno, J.; Lloyd, K. G.; Shumaker, A.; Schippers, A.; Webster, G.; Weightman, A.; Turner, S.

    2015-12-01

    Nearly 75% of the Earth's surface is covered by marine sediment that is home to an estimated 2.9 x 1029 microbial cells. A substantial impediment to understanding the abundance and distribution of cells within marine sediment is the lack of a consistent and reliable method for their taxon-specific quantification. Catalyzed reporter fluorescent in situ hybridization (CARD-FISH) provides taxon-specific enumeration, but this process requires passing a large enzyme through cell membranes, decreasing its precision relative to general cell counts using a small DNA stain. In 2015, Yamaguchi et al. developed FISH hybridization chain reaction (FISH-HCR) as an in situ whole cell detection method for environmental microorganisms. FISH-HCR amplifies the fluorescent signal, as does CARD-FISH, but it allows for milder cell permeation methods that might prevent yield loss. To compare FISH-HCR to CARD-FISH, we examined bacteria and archaea cell counts within two sediment cores, Lille Belt (~78 meters deep) and Landsort Deep (90 meters deep), which were retrieved from the Baltic Sea Basin during IODP Expedition 347. Preliminary analysis shows that CARD-FISH counts are below the quantification limit for most depths across both cores. By contrast, quantification of cells was possible with FISH-HCR in all examined depths. When quantification with CARD-FISH was above the limit of detection, counts with FISH-HCR were up to 11 fold higher for Bacteria and 3 fold higher for Archaea from the same sediment sample. Further, FISH-HCR counts follow the trends of on board counts nicely, indicating that FISH-HCR may better reflect the cellular abundance within marine sediment than other quantification methods, including qPCR. Using FISH-HCR, we found that archaeal cell counts were on average greater than bacterial cell counts, but within the same order of magnitude.

  15. In situ metathesis reaction combined with liquid-phase microextraction based on the solidification of sedimentary ionic liquids for the determination of pyrethroid insecticides in water samples.

    PubMed

    Hu, Lu; Zhang, Panjie; Shan, Wanyu; Wang, Xuan; Li, Songqing; Zhou, Wenfeng; Gao, Haixiang

    2015-11-01

    A novel dispersion liquid-liquid microextraction method based on the solidification of sedimentary ionic liquids (SSIL-DLLME), in which an in situ metathesis reaction forms an ionic liquid (IL) extraction phase, was developed to determine four pyrethroid insecticides (i.e., permethrin, cyhalothrin, fenpropathrin, and transfluthrin) in water followed by separation using high-performance liquid chromatography. In the developed method, in situ DLLME was used to enhance the extraction efficiency and yield. After centrifugation, the extraction solvent, tributyldodecylphosphonium hexafluorophosphate ([P44412][PF6]), was easily collected by solidification in the bottom of the tube. The effects of various experimental parameters, the quantity of tributyldodecylphosphonium bromide ([P44412]Br), the molar ratio of [P44412]Br to potassium hexafluorophosphate (KPF6), the ionic strength, the temperature of the sample solution, and the centrifugation time, were optimized using a Plackett-Burman design to identify the significant factors that affected the extraction efficiency. These significant factors were then optimized using a central composite design. Under the optimized conditions, the recoveries of the four pyrethroid insecticides at four spiked levels ranged from 87.1% to 101.7%, with relative standard deviations (RSDs) ranging from 0.1% to 5.5%. At concentration levels between 1 and 500 µg/L, good linearity was obtained, with coefficients of determination greater than 0.9995. The limits of detection (LODs) for the four pyrethroid insecticides were in the range of 0.71-1.54 µg/L. The developed method was then successfully used for the determination of pyrethroid insecticides in environmental samples.

  16. In situ ATR FTIR studies of SO4 adsorption on goethite in the presence of copper ions.

    PubMed

    Beattie, D A; Chapelet, J K; Gräfe, M; Skinner, W M; Smith, E

    2008-12-15

    Despite the existence of many single ion sorption studies on iron and aluminum oxides, fewer studies have been reported that describe cosorption reactions. In this work, we present an in situ ATR FTIR study of synergistic adsorption of sulfate (SO4) and copper (Cu) on goethite, which is representative of the minerals and ions present in mine wastes, acid sulfate soils, and other industrial and agricultural settings. Sulfate adsorption was studied as a function of varying pH, and as a function of increasing concentration in the absence and presence of Cu. The presence of Cu ions in solution had a complex effect on the ability of SO4 ions to be retained on the goethite surface with increasing pH, with complete desorption occurring near pH 7 and 9 in the absence and presence of Cu, respectively. In addition, Cu ions altered the balance of inner vs outer sphere adsorbed SO4. The solid phase partitioning of SO4 at pH 3 and pH 5 was elevated by the presence of Cu; in both cases Cu increased the affinity of SO4 for the goethite surface. Complementary ex situ sorption edge studies of Cu on goethite in the absence and presence of SO4 revealed that the Cu adsorption edge shifted to lower pH (6.3 --> 5.6) in the presence of SO4, consistent with a decrease of the electrostatic repulsion between the goethite surface and adsorbing Cu. Based on the ATR FTIR and bulk sorption data we surmise that the cosorption products of SO4 and Cu at the goethite-water interface were not in the nature of ternary complexes under the conditions studied here. This information is critical for the evaluation of the onset of surface precipitates of copper-hydroxy sulfates as a function of pH and solution concentration.

  17. In-situ HRTEM study of the reactive carbide phase of Co/MoS2 catalyst.

    PubMed

    Ramos, Manuel; Ferrer, Domingo; Martinez-Soto, Eduan; Lopez-Lippmann, Hugo; Torres, Brenda; Berhault, Gilles; Chianelli, Russell R

    2013-04-01

    Hydrotreatment catalytic operations are commonly performed industrially by layered molybdenum sulfide promoted by cobalt or nickel in order to remove heteroelements (S, N, O) from fossil fuels and biofuels. Indeed, these heteroelements are responsible of the emission of pollutants when these fuels are used in vehicles. In this respect, previous studies made by our research group have shown that the active phase under steady state conditions is partially carbided while strong bending effects of MoS2 slabs were also observed. However, up to now, the morphology of the resulting Co/MoSxCy carbided catalyst has not been fully characterized. In the present study, for the first time, a chemical reaction between the carbon content of a TEM Cu/C grid and a freshly sulfide Co/MoS2 catalyst was in situ observed at 300 °C and 450 °C by HRTEM experimental techniques at ~10 nm of resolution. Results indicate that bending of MoS2 layers occurred due to carbon addition on MoS2 edge sites, as observed in stabilized catalysts after HDS reaction. Using a silicon grid, only cracks of MoS2 slabs were observed without bending effect confirming the role of structural-carbon in this change of morphology.

  18. New Pt/Alumina model catalysts for STM and in situ XPS studies

    NASA Astrophysics Data System (ADS)

    Nartova, Anna V.; Gharachorlou, Amir; Bukhtiyarov, Andrey V.; Kvon, Ren I.; Bukhtiyarov, Valerii I.

    2017-04-01

    The new Pt/alumina model catalysts for STM and in situ XPS studies based on thin alumina film formed over the conductive substrate are proposed. Procedure of platinum deposition developed for porous alumina was adapted for the model alumina support. The set of Pt/AlOx-film samples with the different mean platinum particle size was prepared. Capabilities of in situ XPS investigations of the proposed catalysts were demonstrated in study of NO decomposition on platinum nanoparticles. It is shown that proposed model catalysts behave similarly to Pt/γ-Al2O3 and provide the new opportunities for the instrumental studies of platinum catalysts due to resolving several issues (charging, heating, screening) that are typical for the investigation of the porous oxide supported catalysts.

  19. Materials testing for in situ stabilization treatability study of INEEL mixed wastes soils

    SciTech Connect

    Heiser, J.; Fuhrmann, M.

    1997-09-01

    This report describes the contaminant-specific materials testing phase of the In Situ Stabilization Comprehensive Environment Response, Compensation, and Liability Act (CERCLA) Treatability Study (TS). The purpose of materials testing is to measure the effectiveness of grouting agents to stabilize Idaho National Engineering and Environmental Laboratory (INEEL) Acid Pit soils and select a grout material for use in the Cold Test Demonstration and Acid Pit Stabilization Treatability Study within the Subsurface Disposal Area (SDA) at the Radioactive Waste Management Complex (RWMC). Test results will assist the selecting a grout material for the follow-on demonstrations described in Test Plan for the Cold Test Demonstration and Acid Pit Stabilization Phases of the In Situ Stabilization Treatability Study at the Radioactive Waste Management Complex.

  20. University Students' Situational Reaction Tendencies: Reflections on General Study Orientations, Learning Strategies, and Study Success

    ERIC Educational Resources Information Center

    Makinen, Jarkko; Olkinuora, Erkki

    2004-01-01

    The purpose of the study was to bridge the gap between situational and more general measures in investigating university students' studying. More precisely, the aim was to establish a connection between students' situational reaction tendencies and their general study orientations. Furthermore, situational reaction tendencies were related to the…

  1. In-situ spectroscopic ellipsometry study of copper selective-area atomic layer deposition on palladium

    SciTech Connect

    Jiang, Xiaoqiang; Wang, Han; Qi, Jie; Willis, Brian G.

    2014-07-01

    Selective area copper atomic layer deposition on palladium seed layers has been investigated with in-situ real-time spectroscopic ellipsometry to probe the adsorption/desorption and reaction characteristics of individual deposition cycles. The reactants are copper bis(2,2,6,6-tetramethyl-3,5-heptanedionate) vapor and hydrogen gas. Self-limiting atomic layer deposition was observed in the temperature range of 135–230 °C in a low pressure reactor. Under optimal conditions, growth occurs selectively on palladium and not on silicon dioxide or silicon nitride layers. Based on in-situ ellipsometry data and supporting experiments, a new mechanism for growth is proposed. In the proposed mechanism, precursor adsorption is reversible, and dissociatively adsorbed hydrogen are the stable surface intermediates between growth cycles. The mechanism is enabled by continuous diffusion of palladium from the seed layer into the deposited copper film and strong H* binding to palladium sites. Less intermixing can be obtained at low growth temperatures and short cycle times by minimizing Cu/Pd inter-diffusion.

  2. Demonstration testing and evaluation of in situ soil heating. Treatability study work plan (Revision 2)

    SciTech Connect

    Sresty, G.C.

    1994-12-30

    A Treatability Study planned for the demonstration of the in situ electromagnetic (EM) heating process to remove organic solvents is described in this Work Plan. The treatability study will be conducted by heating subsurface vadose-zone soils in an organic plume adjacent to the Classified Burial Ground K-1070-D located at K-25 Site, Oak Ridge. The test is scheduled to start during the fourth quarter of FY94 and will be completed during the first quarter of FY95. Over the last nine years, a number of Government agencies (EPA, Army, AF, and DOE) and industries sponsored further development and testing of the in situ heating and soil decontamination process for the remediation of soils containing hazardous organic contaminants. In this process the soil is heated in situ using electrical energy. The contaminants are removed from the soil due to enhanced vaporization, steam distillation and stripping. IITRI will demonstrate the EM Process for in situ soil decontamination at K-25 Site under the proposed treatability study. Most of the contaminants of concern are volatile organics which can be removed by heating the soil to a temperature range of 85{degrees} to 95{degrees}C. The efficiency of the treatment will be determined by comparing the concentration of contaminants in soil samples. Samples will be obtained before and after the demonstration for a measurement of the concentration of contaminants of concern. This document is a Treatability Study Work Plan for the demonstration program. The document contains a description of the proposed treatability study, background of the EM heating process, description of the field equipment, and demonstration test design.

  3. Study of the ( μ-, e +) reaction mediated by Majorana neutrinos

    NASA Astrophysics Data System (ADS)

    Vergados, J. D.; Ericson, M.

    1982-02-01

    The exotic lepton violating ( μ-, e +) reaction has been studied in a gauge theory model which assumes the existence of a Majorana neutral lepton. In addition to the usual mechanism involving only two nucleons, the reaction mechanisms which consider a virtual Δ++ present in the nucleus or pions in flight between the interacting nucleons have also been included. The total ( μ-, e +) branching ratio was computed as a function of the various parameters of the theory. It was found to be very sensitively dependent on the mass mσ of the Majorana particle and it becomes very small for mσ > 10 GeV/ c2. The dependence of the branching ratio on the other parameters of the theory is also discussed.

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

    SciTech Connect

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

    2015-10-15

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

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

    SciTech Connect

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

    2015-01-01

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

  6. A flow-through hydrothermal cell for in situ neutron diffraction studies of phase transformations

    NASA Astrophysics Data System (ADS)

    O'Neill, Brian; Tenailleau, Christophe; Nogthai, Yung; Studer, Andrew; Brugger, Joël; Pring, Allan

    2006-11-01

    A flow-through hydrothermal cell for the in situ neutron diffraction study of crystallisation and phase transitions has been developed. It can be used for kinetic studies on materials that exhibit structural transformations under hydrothermal conditions. It is specifically designed for use on the medium-resolution powder diffractometer (MRPD) at ANSTO, Lucas Heights, Sydney. But it is planned to adapt the design for the Polaris beamline at ISIS and the new high-intensity powder diffractometer (Wombat) at the new Australian reactor Opal. The cell will operate in a flow-through mode over the temperature range from 25-300 °C and up to pressures of 100 bar. The first results of a successful transformation of pentlandite (Fe,Ni) 9S 8 to violarite (Fe,Ni) 3S 4 under mild conditions (pH∼4) at 120 °C and 3 bar using in situ neutron diffraction measurements are presented.

  7. Acetone reactions over the surfaces of polycrystalline UO2: a kinetic and spectroscopic study.

    PubMed

    King, Richard; Idriss, Hicham

    2009-04-21

    The reaction of acetone is studied on the surfaces of polycrystalline UO2, prepared by hydrogen reduction of U3O8 at 770 K. The study is conducted by in situ Fourier transform infrared (FTIR) and temperature-programmed desorption (TPD). Acetone adsorption does not fit the simple Langmuir model, and adsorbate-adsorbate interactions are found to be significant. Acetone adsorbs molecularly on UO2 as evidenced by the nuCO of the eta1(O) mode at 1686 cm(-1). Part of acetone is reduced to the isopropoxide species ((CH3)2HC-O-U4+) upon heating (nu(CC), rho(CH3) at 1167 cm(-1) and nu(CO), rho(CH3) at 980 cm(-1)), and upon further heating, acetates (CH3COO(a), (a) for adsorbed) are observed. Detailed TPD studies indicated that the main reaction of acetone on UO2 is the deoxygenation to propene, driven by the oxophilic nature of UO2. Other reactions were also observed to a lesser extent, and these included reductive coupling to 2,3-dimethylbutene and condensation to mesityl oxide. An attempt to extract kinetic parameters from TPD data was conducted. Three models were studied: variation of heating rate, leading edge analysis (Habenschaden-Kuppers method), and complete analysis. The complete analysis provided the most plausible results, in particular, at low coverage. With this method, at nearly zero coverage the activation energy, Ed, for desorption was found to be close to 140 kJ/mol with a prefactor of 10(13) s(-1). Ed dropped sharply with increasing coverage, theta, to ca. 35 kJ/mol at theta=0.15 with a prefactor of 10(11) s(-1). The activation energy for the desorption of acetone on UO2(111) single crystals, at saturation coverage, was previously found to be equal to 65 kJ/mol using the leading edge analysis.

  8. Density Functional Theory and Reaction Kinetics Studies of the Water–Gas Shift Reaction on Pt–Re Catalysts

    SciTech Connect

    Carrasquillo-Flores, Ronald; Gallo, Jean Marcel R.; Hahn, Konstanze; Dumesic, James A.; Mavrikakis, Manos

    2013-11-05

    Periodic, self-consistent density functional theory calculations (DFT-GGA-PW91) on Pt(111) and Pt3Re(111) surfaces, reaction kinetics measurements, and microkinetic modeling are employed to study the mechanism of the water–gas shift (WGS) reaction over Pt and Pt–Re catalysts. The values of the reaction rates and reaction orders predicted by the model are in agreement with the ones experimentally determined; the calculated apparent activation energies are matched to within 6% of the experimental values. The primary reaction pathway is predicted to take place through adsorbed carboxyl (COOH) species, whereas formate (HCOO) is predicted to be a spectator species. We conclude that the clean Pt(111) is a good representation of the active site for the WGS reaction on Pt catalysts, whereas the active sites on the Pt–Re alloy catalyst likely contain partially oxidized metal ensembles.

  9. An in situ transmission electron microscope deformation study of the slip transfer mechanisms in metals

    SciTech Connect

    Lee, T.C.; Robertson, I.M.; Birnbaum, H.K. . Dept. of Materials Science and Engineering)

    1990-09-01

    The slip transfer mechanisms across grain boundaries in 310 stainless steel, high-purity aluminum, and a Ni-S alloy have been studied by using the in situ transmission electron microscope (TEM) deformation technique. Several interactions between mobile lattice dislocations and grain boundaries have been observed, including the transfer and generation of dislocations at grain boundaries and the nucleation and propagation of a grain boundary crack. Quantitative condition have been established to correctly predict the slip transfer mechanism.

  10. A Case Study in Chemical Kinetics: The OH + CO Reaction.

    ERIC Educational Resources Information Center

    Weston, Ralph E., Jr.

    1988-01-01

    Reviews some important properties of the bimolecular reaction between the hydroxyl radical and carbon monoxide. Investigates the kinetics of the reaction, the temperature and pressure dependence of the rate constant, the state-to-state dynamics of the reaction, and the reverse reaction. (MVL)

  11. Automated data extraction from in situ protein-stable isotope probing studies.

    PubMed

    Slysz, Gordon W; Steinke, Laurey; Ward, David M; Klatt, Christian G; Clauss, Therese R W; Purvine, Samuel O; Payne, Samuel H; Anderson, Gordon A; Smith, Richard D; Lipton, Mary S

    2014-03-07

    Protein-stable isotope probing (protein-SIP) has strong potential for revealing key metabolizing taxa in complex microbial communities. While most protein-SIP work to date has been performed under controlled laboratory conditions to allow extensive isotope labeling of the target organism(s), a key application will be in situ studies of microbial communities for short periods of time under natural conditions that result in small degrees of partial labeling. One hurdle restricting large-scale in situ protein-SIP studies is the lack of algorithms and software for automated data processing of the massive data sets resulting from such studies. In response, we developed Stable Isotope Probing Protein Extraction Resources software (SIPPER) and applied it for large-scale extraction and visualization of data from short-term (3 h) protein-SIP experiments performed in situ on phototrophic bacterial mats isolated from Yellowstone National Park. Several metrics incorporated into the software allow it to support exhaustive analysis of the complex composite isotopic envelope observed as a result of low amounts of partial label incorporation. SIPPER also enables the detection of labeled molecular species without the need for any prior identification.

  12. Automated data extraction from in situ protein stable isotope probing studies

    SciTech Connect

    Slysz, Gordon W.; Steinke, Laurey A.; Ward, David M.; Klatt, Christian G.; Clauss, Therese RW; Purvine, Samuel O.; Payne, Samuel H.; Anderson, Gordon A.; Smith, Richard D.; Lipton, Mary S.

    2014-01-27

    Protein stable isotope probing (protein-SIP) has strong potential for revealing key metabolizing taxa in complex microbial communities. While most protein-SIP work to date has been performed under controlled laboratory conditions to allow extensive isotope labeling of the target organism, a key application will be in situ studies of microbial communities under conditions that result in small degrees of partial labeling. One hurdle restricting large scale in situ protein-SIP studies is the lack of algorithms and software for automated data processing of the massive data sets resulting from such studies. In response, we developed Stable Isotope Probing Protein Extraction Resources software (SIPPER) and applied it for large scale extraction and visualization of data from short term (3 h) protein-SIP experiments performed in situ on Yellowstone phototrophic bacterial mats. Several metrics incorporated into the software allow it to support exhaustive analysis of the complex composite isotopic envelope observed as a result of low amounts of partial label incorporation. SIPPER also enables the detection of labeled molecular species without the need for any prior identification.

  13. Studies of a photochromic model system using NMR with ex-situ and in-situ irradiation devices.

    PubMed

    Wolff, Christiane; Kind, Jonas; Schenderlein, Helge; Bartling, Hanna; Feldmeier, Christian; Gschwind, Ruth M; Biesalski, Markus; Thiele, Christina M

    2016-06-01

    The switching behavior of a photochromic model system was investigated in detail via NMR spectroscopy in order to improve understanding of the compound itself and to provide ways to obtain insights into composition trends of a photo switchable (polymeric) material containing spiropyran/merocyanine units. In addition to the classical irradiation performed outside the magnet (ex-situ), a device for irradiation inside the NMR spectrometer (in-situ) was tested. Both setups are introduced, their advantages and disadvantages as well as their limits are described and the setup for future investigations of photochromic materials is suggested. The influence of different sample concentrations, irradiation procedures, and light intensities on the model system was examined as well as the dependence on solvent, temperature, and irradiation wavelengths. Using the recently published LED illumination device, it was even possible to record two-dimensional spectra on this model system with rather short half-life (7 min in DMSO). This way (13) C chemical shifts of the merocyanine form were obtained, which were unknown before. Copyright © 2016 John Wiley & Sons, Ltd.

  14. In situ control of atomic-scale Si layer with huge strain in the nanoheterostructure NiSi/Si/NiSi through point contact reaction.

    PubMed

    Lu, Kuo-Chang; Wu, Wen-Wei; Wu, Han-Wei; Tanner, Carey M; Chang, Jane P; Chen, Lih J; Tu, K N

    2007-08-01

    Nanoheterostructures of NiSi/Si/NiSi in which the length of the Si region can be controlled down to 2 nm have been produced using in situ point contact reaction between Si and Ni nanowires in an ultrahigh vacuum transmission electron microscope. The Si region was found to be highly strained (more than 12%). The strain increases with the decreasing Si layer thickness and can be controlled by varying the heating temperature. It was observed that the Si nanowire is transformed into a bamboo-type grain of single-crystal NiSi from both ends following the path with low-activation energy. We propose the reaction is assisted by interstitial diffusion of Ni atoms within the Si nanowire and is limited by the rate of dissolution of Ni into Si at the point contact interface. The rate of incorporation of Ni atoms to support the growth of NiSi has been measured to be 7 x 10(-4) s per Ni atom. The nanoscale epitaxial growth rate of single-crystal NiSi has been measured using high-resolution lattice-imaging videos. On the basis of the rate, we can control the consumption of Si and, in turn, the dimensions of the nanoheterostructure down to less than 2 nm, thereby far exceeding the limit of conventional patterning process. The controlled huge strain in the controlled atomic scale Si region, potential gate of Si nanowire-based transistors, is expected to significantly impact the performance of electronic devices.

  15. Femtosecond photodichroism studies of isolated photosystem II reaction centers.

    PubMed

    Wiederrecht, G P; Seibert, M; Govindjee; Wasielewski, M R

    1994-09-13

    Photosynthetic conversion of light energy into chemical potential begins in reaction center protein complexes, where rapid charge separation occurs with nearly unit quantum efficiency. Primary charge separation was studied in isolated photosystem II reaction centers from spinach containing 6 chlorophyll a, 2 pheophytin a (Pheo), 1 cytochrome b559, and 2 beta-carotene molecules. Time-resolved pump-probe kinetic spectroscopy was carried out with 105-fs time resolution and with the pump laser polarized parallel, perpendicular, and at the magic angle (54.7 degrees) relative to the polarized probe beam. The time evolution of the transient absorption changes due to the formation of the oxidized primary electron donor P680+ and the reduced primary electron acceptor Pheo- were measured at 820 nm and 545 nm, respectively. In addition, kinetics were obtained at 680 nm, the wavelength ascribed to the Qy transition of the primary electron donor P680 in the reaction center. At each measured probe wavelength the kinetics of the transient absorption changes can be fit to two major kinetic components. The relative amplitudes of these components are strongly dependent on the polarization of the pump beam relative to that of the probe. At the magic angle, where no photoselection occurs, the amplitude of the 3-ps component, which is indicative of the charge separation, dominates. When the primary electron acceptor Pheo is reduced prior to P680 excitation, the 3-ps component is eliminated.

  16. Neutrino-nucleus reactions based on recent structure studies

    SciTech Connect

    Suzuki, Toshio

    2015-05-15

    Neutrino-nucleus reactions are studied with the use of new shell model Hamiltonians, which have proper tensor components in the interactions and prove to be successful in the description of Gamow-Teller (GT) strengths in nuclei. The new Hamiltonians are applied to obtain new neutrino-nucleus reaction cross sections in {sup 12}C, {sup 13}C, {sup 56}Fe and {sup 56}Ni induced by solar and supernova neutrinos. The element synthesis by neutrino processes in supernova explosions is discussed with the new cross sections. The enhancement of the production yields of {sup 7}Li, {sup 11}B and {sup 55}Mn is obtained while fragmented GT strength in {sup 56}Ni with two-peak structure is found to result in smaller e-capture rates at stellar environments. The monopole-based universal interaction with tensor force of π+ρ meson exchanges is used to evaluate GT strength in {sup 40}Ar and ν-induced reactions on {sup 40}Ar. It is found to reproduce well the experimental GT strength in {sup 40}Ar.

  17. Femtosecond photodischroism studies of isolated photosystem II reaction centers

    SciTech Connect

    Wiederrecht, G.P.; Wasielewski, M.R.; Siebert, M.; Govindjee

    1994-09-13

    Photosynthetic conversion of light energy into chemical potential begins in reaction center protein complexes, where rapid charge separation occurs with nearly unit quantum efficiency. Primary charge separation was studied in isolated photosystem II reaction centers from spinach containing 6 chlorophyll a, 2 pheophytin a (Pheo), 1 cytochrome b{sub 559}, and 2 {beta}-carotene molecules. Time-resolved pump-probe kinetic spectroscopy was carried out with 105-fs time resolution and with the pump laser polarized parallel, perpendicular, and at the magic angle (54.7{degrees}) relative to the polarized probe beam. The time evolution of the oxidized primary electron donor P680{sup +} and the reduced primary electron acceptor Pheo{sup {minus}} were measured at 820 nm and 545 nm, respectively. In addition, kinetics were obtained at 680 nm, the wavelength ascribed to the Q{sub y} transition of the primary electron donor P680 in the reaction center. At each measured probe wavelength the kinetics of the transient absorption changes can be fit to two major kinetic components. The relative amplitudes of these components are strongly dependent on the polarization of the pump beam relative to that of the probe. At the magic angle, where no photoselection occurs, the amplitude of the 3-ps component, which is indicative of the charge separation, dominates. When the primary electron acceptor Pheo is reduced prior to P680 excitation, the 3-ps component is eliminated. 48 refs., 6 figs., 1 tab.

  18. Demonstration testing and evaluation of in situ soil heating. Treatability study work plan, Revision 1

    SciTech Connect

    Sresty, G.C.

    1994-07-07

    A Treatability Study planned for the demonstration of the in situ electromagnetic (EM) heating process to remove organic solvents is described in this Work Plan. The treatability study will be conducted by heating subsurface vadose-zone soils in an organic plume adjacent to the Classified Burial Ground K-1070-D located at K-25 Site, Oak Ridge. The test is scheduled to start during the fourth quarter of FY94 and will be completed during the first quarter of FY95. The EM heating process for soil decontamination is based on volumetric heating technologies developed during the `70s for the recovery of fuels from shale and tar sands by IIT Research Institute (IITRI) under a co-operative program with the US Department of Energy (DOE). Additional modifications of the technology developed during the mid `80s are currently used for the production of heavy oil and waste treatment. Over the last nine years, a number of Government agencies (EPA, Army, AF, and DOE) and industries sponsored further development and testing of the in situ heating and soil decontamination process for the remediation of soils containing hazardous organic contaminants. In this process the soil is heated in situ using electrical energy. The contaminants are removed from the soil due to enhanced vaporization, steam distillation and stripping. IITRI will demonstrate the EM Process for in situ soil decontamination at K-25 Site under the proposed treatability study. Most of the contaminants of concern are volatile organics which can be removed by heating the soil to a temperature range of 85 to 95 C. The efficiency of the treatment will be determined by comparing the concentration of contaminants in soil samples. Samples will be obtained before and after the demonstration for a measurement of the concentration of contaminants of concern.

  19. A case study of in situ oil contamination in a mangrove swamp (Rio De Janeiro, Brazil).

    PubMed

    Brito, Elcia M S; Duran, Robert; Guyoneaud, Rémy; Goñi-Urriza, Marisol; García de Oteyza, T; Crapez, Miriam A C; Aleluia, Irene; Wasserman, Julio C A

    2009-08-01

    Mangroves are sensitive ecosystems of prominent ecological value that lamentably have lost much of their areas across the world. The vulnerability of mangroves grown in proximity to cities requires the development of new technologies for the remediation of acute oil spills and chronic contaminations. Studies on oil remediation are usually performed with in vitro microcosms whereas in situ experiments are rare. The aim of this work was to evaluate oil degradation on mangrove ecosystems using in situ microcosms seeded with an indigenous hydrocarbonoclastic bacterial consortium (HBC). Although the potential degradation of oil through HBC has been reported, their seeding directly on the sediment did not stimulate oil degradation during the experimental period. This is probably due to the availability of carbon sources that are easier to degrade than petroleum hydrocarbons. Our results emphasize the fragility of mangrove ecosystems during accidental oil spills and also the need for more efficient technologies for their remediation.

  20. Photo-redox reactions of dicarboxylates and α-hydroxydicarboxylates at the surface of Fe(III)(hydr)oxides followed with in situ ATR-FTIR spectroscopy.

    PubMed

    Borer, Paul; Hug, Stephan J

    2014-02-15

    Colloidal mineral-phases play an important role in the adsorption, transport and transformation of organic and inorganic compounds in the atmosphere and in aqueous environments. Artificial UV-light and sunlight can induce electron transfer reactions between metal ions of the solid phases and adsorbed compounds, leading to their transformation and degradation. To investigate different possible photo-induced oxidation pathways of dicarboxylates adsorbed on iron(III)(hydr)oxide surfaces, we followed UV-A induced photoreactions of oxalate, malonate, succinate and their corresponding α-hydroxy analogues tartronate and malate with in situ ATR-FTIR spectroscopy in immersed particle layers of lepidocrocite, goethite, maghemite and hematite at pH 4. UV-A light (365 ± 5 nm) lead to fast degradation of oxalate, tartronate and malate, while malonate and succinate were photo-degraded at much slower rates. Efficient generation of OH-radicals can be excluded, as this would lead to fast and indiscriminate degradation of all tested compounds. Rapid photo-degradation of adsorbed oxalate and the α-hydroxydicarboxylates must be induced by direct ligand-to-metal charge transfer (LMCT) or by selectively oxidizing valence band holes, both processes requiring inner-sphere coordination with direct ligand-to-metal bonds to enable efficient electron-transfer. The slow photo-degradation of malonate and succinate can be explained by low-yield production of OH-radicals at the surface of the iron(III)(hydr)oxides.

  1. Bio-Based Artificial Nacre with Excellent Mechanical and Barrier Properties Realized by a Facile In Situ Reduction and Cross-Linking Reaction.

    PubMed

    Shahzadi, Kiran; Mohsin, Imran; Wu, Lin; Ge, Xuesong; Jiang, Yijun; Li, Hui; Mu, Xindong

    2017-01-24

    Demands for high strength integrated materials have substantially increased across various kinds of industries. Inspired by the relationship of excellent integration of mechanical properties and hierarchical nano/microscale structure of the natural nacre, a simple and facile method to fabricate high strength integrated artificial nacre based on sodium carboxymethylcellulose (CMC) and borate cross-linked graphene oxide (GO) sheets has been developed. The tensile strength and toughness of cellulose-based hybrid material reached 480.5 ± 13.1 MPa and 11.8 ± 0.4 MJm(-3) by a facile in situ reduction and cross-linking reaction between CMC and GO (0.7%), which are 3.55 and 6.55 times that of natural nacre. This hybrid film exhibits better thermal stability and flame retardancy. More interestingly, the hybrid material showed good water stability compared to that in the original water-soluble CMC. This type of hybrid has great potential applications in aerospace, artificial muscle, and tissue engineering.

  2. Fabrication of wear-resistant layers with lamellar eutectic structure by laser surface alloying using the in situ reaction between Cr and B4C

    NASA Astrophysics Data System (ADS)

    Sun, You-zheng; Li, Jin-bao; Wellburn, Daniel; Liu, Chang-sheng

    2016-11-01

    To improve the wear resistance of Cr5 steel, wear-resistant layers with lamellar eutectic microstructure were fabricated by laser surface alloying (LSA), which is dependent on the in situ reaction between Cr and B4C. Our results indicated that the hypoeutectic structures of the LSA layers were divided into interdendritic eutectic structures and dendrites. The area fraction of the eutectic structures increased with increasing laser scanning speed, which improved the hardness and wear resistance of the LSA layers. The average hardness of the LSA layer prepared at a scanning speed of 8 mm/s was HV0.2 883.9, which was 1.8 times greater than that of the traditional quenched layer (approximately HV 480). After sliding for 659.4 m, the specimen prepared at a scanning speed of 8 mm/s exhibited a volume loss of 0.0323 mm3, which was only 29.5% of the volume loss of the traditional quenched specimen.

  3. Highly active carbon supported palladium catalysts decorated by a trace amount of platinum by an in-situ galvanic displacement reaction for formic acid oxidation

    NASA Astrophysics Data System (ADS)

    Li, Zuopeng; Li, Muwu; Han, Mingjia; Wu, Xin; Guo, Yong; Zeng, Jianhuang; Li, Yuexia; Liao, Shijun

    2015-03-01

    Aimed at reducing platinum usage and improved catalytic activity for formic acid oxidation, a series of Pt decorated Pd/C catalysts are prepared by an in-situ galvanic displacement reaction between freshly prepared Pd/C ink and H2PtCl6 in an aqueous solution. The catalysts with 4 nm particle sizes and 20 wt.% loadings have been characterized by transmission electron microscopy, thermogravimetric analysis and X-ray photoelectron spectroscopy (XPS). The electrochemical evaluations by cyclic voltammetry are conducted to test out the CO tolerance and catalytic activities. In addition to XPS analysis, a theoretical calculation has been attempted the first time to find out the surface Pd/Pt molar ratios. The decay rate of the catalysts has been evaluated by the percentage of the forward/backward peak current retained using the value at the 20th cycle divided by that in the first cycle. Compared with a Pd/C benchmark, all Pt decorated Pd/C register enhanced activity while the cost remains virtually unchanged. The optimized catalyst is found to have a Pd/Pt molar ratio of 75:1 but with 2.5 times activity relative to that of Pd/C.

  4. A novel in situ polymerase chain reaction hybridisation assay for the direct detection of bovine herpesvirus type 5 in formalin-fixed, paraffin-embedded tissues.

    PubMed

    Cardoso, Tereza C; Gomes, Deriane E; Ferrari, Heitor F; Silva-Frade, Camila; Rosa, Ana C G; Andrade, Alexandre L; Luvizotto, Maria Cecília R

    2010-02-01

    An in situ polymerase chain reaction (IS-PCR) hybridisation assay was carried out on the brains of 20 cattle infected naturally with bovine herpesvirus type 5 (BoHV-5). Sections from the olfactory bulb and the frontal cortex of each sample were analysed using IS-PCR followed by hybridisation targeting the BoHV-5 US9 gene using a biotinylated primer. Each of the IS-PCR and hybridisation steps was optimised, and three different methods for detecting the virus were used. No false positive signals were observed in any negative control sample (n=20), resulting in a specificity of 100%. The results of IS-PCR hybridisation analysis of the olfactory bulb and the frontal cortex be compared directly with the results obtained using virus isolation, and the specificity and sensitivity were calculated. The most suitable method of visualisation was the peroxidase/3'-3-diaminobenzidine (DAB) detection system coupled with the use of the fluorescent dye Cy3. Using either of these methods, 80% of the positive samples (16 out of 20 samples) were identified using olfactory bulb sections. This is the first report using IS-PCR hybridisation for the direct detection of BoHV-5 DNA in clinical samples, and it provides an additional method for veterinary virology.

  5. Phthalic acid complexation and the dissolution of forsteritic glass studied via in situ FTIR and X-ray scattering

    NASA Astrophysics Data System (ADS)

    Morris, Peter M.; Wogelius, Roy A.

    2008-04-01

    Multiple Internal Reflection Fourier Transform Infra-Red (MIR-FTIR) spectroscopy was developed and used for in situ flow-through experiments designed to study the process of organic acid promoted silicate dissolution. In tandem with the FTIR analysis, ex situ X-ray scattering was used to perform detailed analyses of the changes in the surface structure and chemistry resulting from the dissolution process. Phthalic acid and forsteritic glass that had been Chemically Vapour Deposited (CVD) onto an internal reflection element were used as reactants, and the MIR-FTIR results showed that phthalic acid may promote dissolution by directly binding to exposed Mg metal ion centers on the solid surface. Integrated infrared absorption intensity as a function of time shows that phthalic acid attachment apparently follows a t1/2 dependence, indicating that attachment is a diffusive process. The diffusion coefficient of phthalic acid was estimated to be approximately 7 × 10 -6 cm 2 s -1 in the solution near the interface with the glass. Shifts in the infrared absorption structure of the phthalate complexed with the surface compared to the solute species indicate that phthalate forms a seven-membered ring chelate complex. This bidentate complex efficiently depletes Mg from the glass surface, such that after reaction as much as 95% of the Mg may be removed. Surface depletion in Mg causes adsorbate density to fall after an initial attachment stage for the organic ligand. In addition, the infrared analysis shows that silica in the near surface polymerizes after Mg removal, presumably to maintain charge balance. X-ray reflectivity shows that the dissolution rate of forsteritic glass at pH 4 based on Mg removal in such flow-through experiments was equal to 4 × 10 -12 mol cm -2 s -1 (geometric surface area normalized). Reflectivity also shows how the surface mass density decreases during reaction from 2.64 g cm -3 to 2.2 g cm -3, consistent with preferential loss of Mg from the

  6. Laser-induced reduction and in-situ optical spectroscopy of individual plasmonic copper nanoparticles for catalytic reactions

    NASA Astrophysics Data System (ADS)

    Di Martino, G.; Turek, V. A.; Braeuninger-Weimer, P.; Hofmann, S.; Baumberg, J. J.

    2017-02-01

    Copper (Cu) can provide an alternative to gold (Au) for the development of efficient, low-cost and low-loss plasmonic nanoparticles (NPs), as well as selective nanocatalysts. Unlike Au, the surface oxidation of Cu NPs can be an issue restricting their applicability. Here, we selectively reduce the Cu NPs by low power laser illumination in vacuum and use dark-field scattering to reveal in real time the optical signatures of the reduction process and its influence on the Cu NP plasmonic resonance. We then study reactive processes at the single particle level, using individual Cu catalyst nanoparticles for the selective laser-induced chemical vapour deposition of germanium nanostructures.

  7. Studies on the intercalation of naproxen into layered double hydroxide and its thermal decomposition by in situ FT-IR and in situ HT-XRD

    NASA Astrophysics Data System (ADS)

    Wei, Min; Shi, Shuxian; Wang, Ji; Li, Yong; Duan, Xue

    2004-07-01

    Layered double hydroxides, novel anionic clay, meet the first requirement as inorganic matrices for encapsulating functional drugs or biomolecules with negative charge in aqueous media. In this study, naproxen has been intercalated into Mg-Al layered double hydroxide by the methods of ion exchange. The structure and composition of the intercalated material have been studied by X-ray diffraction (XRD), UV-vis spectroscopy and inductively coupled plasma emission spectroscopy. A schematic model has been proposed. Furthermore, in situ Fourier transform infrared spectroscopy, in situ high-temperature XRD, and thermogravimetry (TG) have been used to characterize the thermal decomposition of the hybrid material. It has been found that the thermal stability of the intercalated naproxen is significantly enhanced compared with the pure form before intercalation, which suggests that this drug-inorganic layered material may have prospective application as the basis of a novel drug delivery system.

  8. Study of all Reaction Channels in Deuteron-Deuteron Scattering

    NASA Astrophysics Data System (ADS)

    Ramazani-Moghaddam-Arani, A.; Amir-Ahmadi, H. R.; Bacher, A. D.; Bailey, C. D.; Biegun, A.; Eslami-Kalantari, M.; Gašparić, I.; Joulaeizadeh, L.; Kalantar-Nayestanaki, N.; Kistryn, St.; Kozela, A.; Mardanpour, H.; Messchendorp, J. G.; Micherdzinska, A. M.; Moeini, H.; Shende, S. V.; Stephan, E.; Stephenson, E. J.; Sworst, R.

    Few-nucleon systems can be used as fundamental laboratories for studying details of the nuclear force effects. We performed a series of deuteron-deuteron scattering experiments at intermediate energies. The experiments exploited BINA and BBS experimental setups and polarized deuteron beams with kinetic energies of 65 and 90 MeV/nucleon. These experiments aim to measure differential cross sections, vector and tensor analyzing powers of all available reaction channels in deuteron-deuteron scattering. With these data we will provide a systematic database, which will be used to test present theoretical approximations and upcoming ab-initio calculations in four-nucleon system.

  9. Quantum chemical study of penicillin: Reactions after acylation

    NASA Astrophysics Data System (ADS)

    Li, Rui; Feng, Dacheng; Zhu, Feng

    The density functional theory methods were used on the model molecules of penicillin to determine the possible reactions after their acylation on ?-lactamase, and the results were compared with sulbactam we have studied. The results show that, the acylated-enzyme tetrahedral intermediate can evolves with opening of ?-lactam ring as well as the thiazole ring; the thiazole ring-open products may be formed via ?-lactam ring-open product or from tetrahedral intermediate directly. Those products, in imine or enamine form, can tautomerize via hydrogen migration. In virtue of the water-assisted, their energy barriers are obviously reduced.

  10. Physicochemical studies on the reaction between formaldehyde and DNA.

    PubMed

    FREIFELDER, D; DAVISON, P F

    1963-01-01

    The reaction between formaldehyde and phage T7 DNA has been studied by optical absorbance and sedimentation measurements. Through the course of denaturation, OD(200) and s(20, w) rise; after the attainment of full hyperchromicity the s(20, w) falls sharply, suggesting a decrease in molecular weight. Conditions in which formaldehyde causes cross-linking are defined. Some experimental applications of the denaturation technique are given. Evidence which suggests that preformed single-strand interruptions may exist in phage DNA is briefly discussed.

  11. Physicochemical Studies on the Reaction between Formaldehyde and DNA

    PubMed Central

    Freifelder, David; Davison, Peter F.

    1963-01-01

    The reaction between formaldehyde and phage T7 DNA has been studied by optical absorbance and sedimentation measurements. Through the course of denaturation, OD200 and s20, w rise; after the attainment of full hyperchromicity the s20, w falls sharply, suggesting a decrease in molecular weight. Conditions in which formaldehyde causes cross-linking are defined. Some experimental applications of the denaturation technique are given. Evidence which suggests that preformed single-strand interruptions may exist in phage DNA is briefly discussed. PMID:13959526

  12. Heck-type reactions of imine derivatives: a DFT study.

    PubMed

    Li, Zhe; Fu, Yao; Zhang, Song-Lin; Guo, Qing-Xiang; Liu, Lei

    2010-06-01

    The mechanism of a recently discovered intramolecular Heck-type coupling of oximes with aryl halides (Angew. Chem. Int. Ed. 2007, 46, 6325) was systematically studied by using density functional methods enhanced with a polarized continuum solvation model. The overall catalytic cycle of the reaction was found to consist of four steps: oxidative addition, migratory insertion, beta-H elimination, and catalyst regeneration, whereas an alternative base-promoted C-H activation pathway was determined to be less favorable. Migratory insertion was found to be the rate determining step in the catalytic cycle. The apparent activation barrier of migratory insertion of the (E)-oxime was +20.5 kcal mol(-1), whereas the barrier of (Z)-oxime was as high as +32.7 kcal mol(-1). However, (Z)-oxime could isomerize to form the more active (E)-oxime with the assistance of K(2)CO(3), so that both the (E)- and (Z)-oxime substrates could be transformed to the desired product. Our calculations also indicated that the Z product was predominant in the equilibrium of the isomerization of the imine double bond, which constituted the reason for the good Z-selectivity observed for the reaction. Furthermore, we examined the difference between the intermolecular Heck-type reactions of imines and of olefins. It was found that in the intermolecular Heck-type coupling of imines, the apparent activation barrier of migratory insertion was as high as +35 kcal mol(-1), which should be the main obstacle of the reaction. The analysis also revealed the main problem for the intermolecular Heck-type reactions of imines, which was that the breaking of a C=N pi bond was much more difficult than the breaking of a C=C pi bond. After systematic examination of a series of substituted imines, (Z)-N-amino imine and N-acetyl imine were found to have relatively low barriers of migratory insertion, so that they might be possible substrates for intermolecular Heck-type coupling.

  13. IN SITU MAGIC ANGLE SPINNING NMR FOR STUDYING GEOLOGICAL CO(2) SEQUESTRATION

    SciTech Connect

    Hoyt, David W.; Turcu, Romulus VF; Sears, Jesse A.; Rosso, Kevin M.; Burton, Sarah D.; Kwak, Ja Hun; Felmy, Andrew R.; Hu, Jian Z.

    2011-03-27

    Geological carbon sequestration (GCS) is one of the most promising ways of mitigating atmospheric greenhouse gases (1-3). Mineral carbonation reactions are potentially important to the long-term sealing effectiveness of caprock but remain poorly predictable, particularly in low-water supercritical CO2 (scCO2)-dominated environments where the chemistry has not been adequately explored. In situ probes that provide molecular-level information is desirable for investigating mechanisms and rates of GCS mineral carbonation reactions. MAS-NMR is a powerful tool for obtaining detailed molecular structure and dynamics information of a system regardless whether the system is in a solid, a liquid, a gaseous, or a supercritical state, or a mixture thereof (4,5). However, MAS NMR under scCO2 conditions has never been realized due to the tremendous technical difficulties of achieving and maintaining high pressure within a fast spinning MAS rotor (6,7), where non-metal materials must be used. In this work, we report development of a unique high pressure MAS NMR capability, and its application to mineral carbonation chemistry in scCO2 under geologically relevant temperatures and pressures.

  14. In situ studies of nanoscale electromechanical behavior of nacre under flexural stresses using band excitation PFM.

    PubMed

    Li, Tao; Chen, Lei; Zeng, Kaiyang

    2013-04-01

    In this paper, we have studied the electromechanical coupling behaviors of nacre under non-destructive flexural stresses. Band excitation piezoresponse force microscopy is used as the primary tool to characterize the piezoelectric properties of nacre. This method can differentiate various constituents in nacre at the nanoscale and track their in situ responses under tensile and compressive stresses. The local ferroelectric hysteresis behaviors of nacre are also studied. Based on the hysteresis loops observed under different stress states, various phenomena, including the stress-induced internal field and energy loss, are revealed in this study.

  15. In-situ bioventing: Two US EPA and Air Force sponsored field studies

    SciTech Connect

    Sayles, G.D.; Hinchee, R.E.; Brenner, R.C.; Vogel, C.M.; Miller, R.N.

    1992-01-01

    Bioventing is the process of delivering oxygen by forced air movement through organically contaminated unsaturated soils in order to stimulate in situ biodegradation in an otherwise oxygen-limited environment. The paper is a report on progress of two ongoing bioventing field studies involving JP-4 jet fuel contamination. The first investigation, at Eielson AFB near Fairbanks, Alaska, is a study of bioventing in shallow soils and cold climates in conjunction with an evaluation of soil warming techniques. The second study, at Hill AFB near Salt Lake City, Utah, is examining bioventing of large volumes of soil and determining biodegradation and volatilization rates as a function of air injection rate.

  16. Molecular beam mass spectrometer equipped with a catalytic wall reactor for in situ studies in high temperature catalysis research

    NASA Astrophysics Data System (ADS)

    Horn, R.; Ihmann, K.; Ihmann, J.; Jentoft, F. C.; Geske, M.; Taha, A.; Pelzer, K.; Schlögl, R.

    2006-05-01

    A newly developed apparatus combining a molecular beam mass spectrometer and a catalytic wall reactor is described. The setup has been developed for in situ studies of high temperature catalytic reactions (>1000°C), which involve besides surface reactions also gas phase reactions in their mechanism. The goal is to identify gas phase radicals by threshold ionization. A tubular reactor, made from the catalytic material, is positioned in a vacuum chamber. Expansion of the gas through a 100μm sampling orifice in the reactor wall into differentially pumped nozzle, skimmer, and collimator chambers leads to the formation of a molecular beam. A quadrupole mass spectrometer with electron impact ion source designed for molecular beam inlet and threshold ionization measurements is used as the analyzer. The sampling time from nozzle to detector is estimated to be less than 10ms. A detection time resolution of up to 20ms can be reached. The temperature of the reactor is measured by pyrometry. Besides a detailed description of the setup components and the physical background of the method, this article presents measurements showing the performance of the apparatus. After deriving the shape and width of the energy spread of the ionizing electrons from measurements on N2 and He we estimated the detection limit in threshold ionization measurements using binary mixtures of CO in N2 to be in the range of several hundreds of ppm. Mass spectra and threshold ionization measurements recorded during catalytic partial oxidation of methane at 1250°C on a Pt catalyst are presented. The detection of CH3• radicals is successfully demonstrated.

  17. Molecular beam mass spectrometer equipped with a catalytic wall reactor for in situ studies in high temperature catalysis research

    SciTech Connect

    Horn, R.; Ihmann, K.; Ihmann, J.; Jentoft, F.C.; Geske, M.; Taha, A.; Pelzer, K.; Schloegl, R.

    2006-05-15

    A newly developed apparatus combining a molecular beam mass spectrometer and a catalytic wall reactor is described. The setup has been developed for in situ studies of high temperature catalytic reactions (>1000 deg. C), which involve besides surface reactions also gas phase reactions in their mechanism. The goal is to identify gas phase radicals by threshold ionization. A tubular reactor, made from the catalytic material, is positioned in a vacuum chamber. Expansion of the gas through a 100 {mu}m sampling orifice in the reactor wall into differentially pumped nozzle, skimmer, and collimator chambers leads to the formation of a molecular beam. A quadrupole mass spectrometer with electron impact ion source designed for molecular beam inlet and threshold ionization measurements is used as the analyzer. The sampling time from nozzle to detector is estimated to be less than 10 ms. A detection time resolution of up to 20 ms can be reached. The temperature of the reactor is measured by pyrometry. Besides a detailed description of the setup components and the physical background of the method, this article presents measurements showing the performance of the apparatus. After deriving the shape and width of the energy spread of the ionizing electrons from measurements on N{sub 2} and He we estimated the detection limit in threshold ionization measurements using binary mixtures of CO in N{sub 2} to be in the range of several hundreds of ppm. Mass spectra and threshold ionization measurements recorded during catalytic partial oxidation of methane at 1250 deg. C on a Pt catalyst are presented. The detection of CH{sub 3}{center_dot} radicals is successfully demonstrated.

  18. In situ X-ray diffraction study of Na+ saturated montmorillonite exposed to variably wet super critical CO2.

    PubMed

    Ilton, Eugene S; Schaef, H Todd; Qafoku, Odeta; Rosso, Kevin M; Felmy, Andrew R

    2012-04-03

    Reactions involving variably hydrated super critical CO(2) (scCO(2)) and a Na saturated dioctahedral smectite (Na-STX-1) were examined by in situ high-pressure X-ray diffraction at 50 °C and 90 bar, conditions that are relevant to long-term geologic storage of CO(2). Both hydration and dehydration reactions were rapid with appreciable reaction occurring in minutes and near steady state occurring within an hour. Hydration occurred stepwise as a function of increasing H(2)O in the system; 1W, 2W-3W, and >3W clay hydration states were stable from ~2-30%, ~31-55 < 64%, and ≥ ~71% H(2)O saturation in scCO(2), respectively. Exposure of sub 1W clay to anhydrous scCO(2) caused interlayer expansion, not contraction as expected for dehydration, suggesting that CO(2) intercalated the interlayer region of the sub 1W clay, which might provide a secondary trapping mechanism for CO(2). In contrast, control experiments using pressurized N(2) and similar initial conditions as in the scCO(2) study, showed little to no change in the d(001) spacing, or hydration states, of the clay. A salient implication for cap rock integrity is that clays can dehydrate when exposed to wet scCO(2). For example, a clay in the ~3W hydration state could collapse by ~3 Å in the c* direction, or ~15%, if exposed to scCO(2) at less than or equal to about 64% H(2)O saturation.

  19. In situ SEM Study of Lithium Intercalation in individual V2O5 Nanowires

    DOE PAGES

    Strelcov, Evgheni; Cothren, Joshua E.; Leonard, Donovan N.; ...

    2015-01-08

    Progress in rational engineering of Li-ion batteries requires better understanding of the electrochemical processes and accompanying transformations in the electrode materials on multiple length scales. In spite of recent progress in utilizing transmission electron microscopy (TEM) to analyze these materials, in situ scanning electron microscopy (SEM) was mostly overlooked as a powerful tool that allows probing these phenomena on the nano and mesoscale. In this paper, we report on in situ SEM study of lithiation in a V2O5-based single-nanobelt battery with ionic liquid electrolyte. Coupled with cyclic voltammetry measurements, in situ SEM revealed the peculiarities of subsurface intercalation, formation ofmore » solid-electrolyte interface (SEI) and electromigration of liquid. We observed that single-crystalline vanadia nanobelts do not undergo large-scale amorphization or fracture during electrochemical cycling, but rather transform topochemically with only a slight shape distortion. Lastly, the SEI layer seems to have significant influence on the lithium ion diffusion and overall capacity of the single-nanobelt battery.« less

  20. Corrosion of an alloy studied in situ with synchrotron x-ray diffraction

    NASA Astrophysics Data System (ADS)

    Renner, Frank; Lee, Tien-Lin; Kolb, Dieter M.; Stierle, Andreas; Dosch, Helmut; Zegenhagen, Jorg

    2004-03-01

    Corrosion processes are mostly electrochemical in nature. For the basic understanding of corrosion and similar technical processes, in-situ structural methods capable of atomic resolution, such as scanning probe microscopy or hard X-ray techniques are necessary. We used in-situ X-ray diffraction and in addition ex-situ AFM, to study Cu_3Au(111) single crystal surfaces in 0.1M H_2SO4 electrolyte as a function of electrode potential in the sub-critical regime. This binary metal alloys serves as model systems for more complicated technically utilized metal alloys. During the initial electrochemical corrosion, Cu atoms are dissolved and a passivating layer is formed. The experiments show the formation of an epitaxial and highly strained ultra-thin Cu_xAu_1-x(111) phase on the surface at a potential where Cu dissolution starts. At higher potentials, thicker epitaxial Au islands are growing on the surface. AFM images reveal a surface, densely packed with Au islands of a homogeneous size-distribution. On a prolonged timescale, a percolating, porous morphology of the surface evolves by ripening, even at an electrode potential well below the critical potential.

  1. The applications of in situ electron energy loss spectroscopy to the study of electron beam nanofabrication.

    PubMed

    Chen, Shiahn J; Howitt, David G; Gierhart, Brian C; Smith, Rosemary L; Collins, Scott D

    2009-06-01

    An in situ electron energy loss spectroscopy (EELS) technique has been developed to investigate the dynamic processes associated with electron-beam nanofabrication on thin membranes. In this article, practical applications germane to e-beam nanofabrication are illustrated with a case study of the drilling of nanometer-sized pores in silicon nitride membranes. This technique involves successive acquisitions of the plasmon-loss and the core-level ionization-loss spectra in real time, both of which provide the information regarding the hole-drilling kinetics, including two respective rates for total mass loss, individual nitrogen and silicon element depletion, and the change of the atomic bonding environment. In addition, the in situ EELS also provides an alternative method for endpoint detection with a potentially higher time resolution than by imaging. On the basis of the time evolution of in situ EELS spectra, a qualitative working model combining knock-on sputtering, irradiation-induced mass transport, and phase separation can be proposed.

  2. In situ study of heavy ion irradiation response of immiscible Cu/Fe multilayers

    DOE PAGES

    Chen, Youxing; Li, Nan; Bufford, Daniel Charles; ...

    2016-04-09

    By providing active defect sinks that capture and annihilate radiation induced defect clusters immiscible metallic multilayers with incoherent interfaces can effectively reduce defect density in ion irradiated metals. Although it is anticipated that defect density within the layers should vary as a function of distance to the layer interface, there is, to date, little in situ TEM evidence to validate this hypothesis. In our study monolithic Cu films and Cu/Fe multilayers with individual layer thickness, h, of 100 and 5 nm were subjected to in situ Cu ion irradiation at room temperature to nominally 1 displacement-per-atom inside a transmission electronmore » microscope. Rapid formation and propagation of defect clusters were observed in monolithic Cu, whereas fewer defects with smaller dimensions were generated in Cu/Fe multilayers with smaller h. Moreover, in situ video shows that the cumulative defect density in Cu/Fe 100 nm multilayers indeed varies, as a function of distance to the layer interfaces, supporting a long postulated hypothesis.« less

  3. In situ study of heavy ion irradiation response of immiscible Cu/Fe multilayers

    SciTech Connect

    Chen, Youxing; Li, Nan; Bufford, Daniel Charles; Li, Jin; Hattar, Khalid Mikhiel; Wang, Haiyan; Zhang, Xinghang

    2016-04-09

    By providing active defect sinks that capture and annihilate radiation induced defect clusters immiscible metallic multilayers with incoherent interfaces can effectively reduce defect density in ion irradiated metals. Although it is anticipated that defect density within the layers should vary as a function of distance to the layer interface, there is, to date, little in situ TEM evidence to validate this hypothesis. In our study monolithic Cu films and Cu/Fe multilayers with individual layer thickness, h, of 100 and 5 nm were subjected to in situ Cu ion irradiation at room temperature to nominally 1 displacement-per-atom inside a transmission electron microscope. Rapid formation and propagation of defect clusters were observed in monolithic Cu, whereas fewer defects with smaller dimensions were generated in Cu/Fe multilayers with smaller h. Moreover, in situ video shows that the cumulative defect density in Cu/Fe 100 nm multilayers indeed varies, as a function of distance to the layer interfaces, supporting a long postulated hypothesis.

  4. In situ studies on ferroelectric BaTiO3 interface

    NASA Astrophysics Data System (ADS)

    Shin, Junsoo; Braun Nascimento, Von; Plummer, Ward; Zhang, Jiandi; Borisevich, Albina; Meunier, Vincent; Kalinin, Sergei; Baddorf, Arthur

    2012-02-01

    Ferroelectric phase stability in ferroelectric films is critically dependent on the surface and interface phenomena, especially governed by electrostatic depolarization energy. Predictions for the minimum critical film thickness for ferroelectricity have continuously decreased down to few unit cells. We have examined surface/interface atomic structures of ultrathin BaTiO3 (BTO) films grown on conductive SrRuO3 (SRO) and Nb-doped SrTiO3. The surface structure of BTO/SRO was refined using in-situ Low Energy Electron Diffraction (LEED) I-V, resulting to observation of polar distortion in ultrathin (>= 4 ML) BTO films. The in-situ Scanning Tunneling Microscopy (STM) has been performed prior and after BTO deposition on SRO. However, the unusual 2x2 reconstruction is observed for 1-2 ML BTO films and bare SRO by STM. The surface reconstruction of SRO bottom electrode is shown to affect the interface of films deposited subsequently which could be reflected in ultrathin film properties. The in-situ LEED I-V structural studies on 1-2 ML BTO interface have been performed without SRO layer, which kept ultrathin BTO films from the preclusion of reconstructed SRO films.

  5. An in situ approach to study trace element partitioning in the laser heated diamond anvil cell

    SciTech Connect

    Petitgirard, S.; Mezouar, M.; Borchert, M.; Appel, K.; Liermann, H.-P.; Andrault, D.

    2012-01-15

    Data on partitioning behavior of elements between different phases at in situ conditions are crucial for the understanding of element mobility especially for geochemical studies. Here, we present results of in situ partitioning of trace elements (Zr, Pd, and Ru) between silicate and iron melts, up to 50 GPa and 4200 K, using a modified laser heated diamond anvil cell (DAC). This new experimental set up allows simultaneous collection of x-ray fluorescence (XRF) and x-ray diffraction (XRD) data as a function of time using the high pressure beamline ID27 (ESRF, France). The technique enables the simultaneous detection of sample melting based to the appearance of diffuse scattering in the XRD pattern, characteristic of the structure factor of liquids, and measurements of elemental partitioning of the sample using XRF, before, during and after laser heating in the DAC. We were able to detect elements concentrations as low as a few ppm level (2-5 ppm) on standard solutions. In situ measurements are complimented by mapping of the chemical partitions of the trace elements after laser heating on the quenched samples to constrain the partitioning data. Our first results indicate a strong partitioning of Pd and Ru into the metallic phase, while Zr remains clearly incompatible with iron. This novel approach extends the pressure and temperature range of partitioning experiments derived from quenched samples from the large volume presses and could bring new insight to the early history of Earth.

  6. Identification of intermediates in zeolite-catalyzed reactions by in situ UV/Vis microspectroscopy and a complementary set of molecular simulations.

    PubMed

    Hemelsoet, Karen; Qian, Qingyun; De Meyer, Thierry; De Wispelaere, Kristof; De Sterck, Bart; Weckhuysen, Bert M; Waroquier, Michel; Van Speybroeck, Veronique

    2013-12-02

    The optical absorption properties of (poly)aromatic hydrocarbons occluded in a nanoporous environment were investigated by theoretical and experimental methods. The carbonaceous species are an essential part of a working catalyst for the methanol-to-olefins (MTO) process. In situ UV/Vis microscopy measurements on methanol conversion over the acidic solid catalysts H-SAPO-34 and H-SSZ-13 revealed the growth of various broad absorption bands around 400, 480, and 580 nm. The cationic nature of the involved species was determined by interaction of ammonia with the methanol-treated samples. To determine which organic species contribute to the various bands, a systematic series of aromatics was analyzed by means of time-dependent density functional theory (TDDFT) calculations. Static gas-phase simulations revealed the influence of structurally different hydrocarbons on the absorption spectra, whereas the influence of the zeolitic framework was examined by using supramolecular models within a quantum mechanics/molecular mechanics framework. To fully understand the origin of the main absorption peaks, a molecular dynamics (MD) study on the organic species trapped in the inorganic host was essential. During such simulation the flexibility is fully taken into account and the effect on the UV/Vis spectra is determined by performing TDDFT calculations on various snapshots of the MD run. This procedure allows an energy absorption scale to be provided and the various absorption bands determined from in situ UV/Vis spectra to be assigned to structurally different species.

  7. Model reaction for the in situ characterization of the hydrogenating and acid properties of industrial hydrocracking catalysts

    SciTech Connect

    Guisnet, M.; Thomazeau, C.; Lemberton, J.L.; Mignard, S.

    1995-01-01

    A kinetic study of o-xylene transformation was carried out on a sulfided NiMo on Y zeolite catalyst during the hydrocracking of a model compound (n-heptane) under the following conditions of the process: high hydrogen pressure (5.7 MPa), presence of nitrogen and sulfur-containing compounds. o-Xylene inhibits n-heptane transformation, which can be explained by a competition for the adsorption on the acid sites between o-xylene and the olefinic intermediates of hydrocracking. The products of o-xylene transformation are the following: p- and m-xylenes (isomerization), toluene and trimethylbenzenes (disproportionation), and saturated C{sub 8} naphthenes (dimethylcyclohexane and trimethylcyclopentanes). It is shown that 1,3- and 1,4-dimethylcyclohexanes (and trimethylcyclopentanes) result from the isomerization of m- and p-xylenes. Therefore, the hydrogenating activity of hydrocracking catalysts can be characterized by the formation of dimethylyclohexanes and trimethylcyclopentanes. Furthermore, the isomerization of xylenes, which occurs through an acid mechanism, can be used for characterizing the acid activity of hydrocracking catalysts. This is not the case for disproportion whose rate depends on hydrogen pressure. The validity of o-xylene transformation for characterizing the acid and hydrogenating activities of bifunctional hydrocracking catalysts was confirmed by the use of a series of catalysts having either the same content of NiMo and different contents of zeolite or the same content of zeolite and different contents of NiMo. While the isomerization activity is strictly proportional to the zeolite content and independent of the NiMo content, and the hydrogenating activity is proportional to the NiMo content and independent of the zeolite content. 27 refs., 17 figs., 3 tabs.

  8. Pulsed supercritical synthesis of anatase TiO2 nanoparticles in a water-isopropanol mixture studied by in situ powder X-ray diffraction

    NASA Astrophysics Data System (ADS)

    Eltzholtz, Jakob Rostgaard; Tyrsted, Christoffer; Jensen, Kirsten Marie Ørnsbjerg; Bremholm, Martin; Christensen, Mogens; Becker-Christensen, Jacob; Iversen, Bo Brummerstedt

    2013-02-01

    A new step in supercritical nanoparticle synthesis, the pulsed supercritical synthesis reactor, is investigated in situ using synchrotron powder X-ray diffraction (PXRD) to understand the formation of nanoparticles in real time. This eliminates the common problem of transferring information gained during in situ studies to subsequent laboratory reactor conditions. As a proof of principle, anatase titania nanoparticles were synthesized in a 50/50 mixture of water and isopropanol near and above the critical point of water (P = 250 bar, T = 300, 350, 400, 450, 500 and 550 °C). The evolution of the reaction product was followed by sequentially recording PXRD patterns with a time resolution of less than two seconds. The crystallite size of titania is found to depend on both temperature and residence time, and increasing either parameter leads to larger crystallites. A simple adjustment of either temperature or residence time provides a direct method for gram scale production of anatase nanoparticles of average crystallite sizes between 7 and 35 nm, thus giving the option of synthesizing tailor-made nanoparticles. Modeling of the in situ growth curves using an Avrami growth model gave an activation energy of 66(19) kJ mol-1 for the initial crystallization. The in situ PXRD data also provide direct information about the size dependent macrostrain in the nanoparticles and with decreasing crystallite size the unit cell contracts, especially along the c-direction. This agrees well with previous ex situ results obtained for hydrothermal synthesis of titania nanoparticles.A new step in supercritical nanoparticle synthesis, the pulsed supercritical synthesis reactor, is investigated in situ using synchrotron powder X-ray diffraction (PXRD) to understand the formation of nanoparticles in real time. This eliminates the common problem of transferring information gained during in situ studies to subsequent laboratory reactor conditions. As a proof of principle, anatase titania

  9. Chemistry at high pressures and temperatures: in-situ synthesis and characterization of {beta}-Si{sub 3}N{sub 4} by DAC X-ray/laser-heating studies

    SciTech Connect

    Yoo, C.-S.; Akella, J.; Nicol, M.

    1996-01-01

    We have developed in-situ XRD technique at high pressures and temperatures by integrating the angle-resolved synchrotron XRD method, laser-heating system, and diamond anvil cell together. Using this technique, we have studied the direct elementary reactions of nitrogen with Si, yielding technologically important {beta}-Si{sub 3}N{sub 4}. These reactions do not occur at ambient temperatures at high pressures up to 50 GPa, but proceed exothermically at high temperatures at moderate pressures. It implies that the reaction is kinetically limited by a large activation barrier.

  10. Photosynthetic reaction center of green sulfur bacteria studied by EPR

    SciTech Connect

    Nitschke, W.; Rutherford, A.W. ); Fieler, U. )

    1990-04-24

    Membrane preparations of two species of the green sulfur bacteria Chlorobium have been studied be EPR. Three signals were detected which were attributed to iron-sulfur centers acting as electron acceptors in the photosynthetic reaction center. (1) A signal from a center designated F{sub B}, was photoinduced at 4K. (2) A similar signal, F{sub A}, was photoinduced in addition to the F{sub B} signal upon a short period of illumination at 200 K. (3) Further illumination at 200 K resulted in the appearance of a broad feature at g=1.78. This is attributed to the g{sub x} component of an iron-sulfur center designated F{sub X}. The designations of these signals as F{sub B}, F{sub A}, and F{sub X} are based on their spectroscopic similarities to signals in photosystem I (PS I). The orientation dependence of these EPR signals in ordered Chlorobium membrane multilayers is remarkably similar to that of their PS I homologues. A magnetic interaction between the reduced forms of F{sub B} and F{sub A} occurs, which is also very similar to that seen in PS I. The triplet state of P{sub 840}, the primary electron donor, could be photoinduced at 4 K in samples which had been preincubated with sodium dithionite and methyl viologen and then preilluminated at 200 K. The preillumination reduces the iron-sulfur centers while the preincubation is thought to result in the inactivation of an earlier electron acceptor. Orientation studies of the triplet signal in ordered multilayers indicate that the bacteriochlorophylls which act as the primary electron donor in Chlorobium are arranged with a structural geometry almost identical with that of the special pair in purple bacteria. The Chlorobium reaction center appears to be similar in some respects to both PS I and to the purple bacterial reaction center. This is discussed with regard to the evolution of the different types of reaction centers from a common ancestor.

  11. First principle kinetic studies of zeolite-catalyzed methylation reactions.

    PubMed

    Van Speybroeck, Veronique; Van der Mynsbrugge, Jeroen; Vandichel, Matthias; Hemelsoet, Karen; Lesthaeghe, David; Ghysels, An; Marin, Guy B; Waroquier, Michel

    2011-02-02

    Methylations of ethene, propene, and butene by methanol over the acidic microporous H-ZSM-5 catalyst are studied by means of state of the art computational techniques, to derive Arrhenius plots and rate constants from first principles that can directly be compared with the experimental data. For these key elementary reactions in the methanol to hydrocarbons (MTH) process, direct kinetic data became available only recently [J. Catal.2005, 224, 115-123; J. Catal.2005, 234, 385-400]. At 350 °C, apparent activation energies of 103, 69, and 45 kJ/mol and rate constants of 2.6 × 10(-4), 4.5 × 10(-3), and 1.3 × 10(-2) mol/(g h mbar) for ethene, propene, and butene were derived, giving following relative ratios for methylation k(ethene)/k(propene)/k(butene) = 1:17:50. In this work, rate constants including pre-exponential factors are calculated which give very good agreement with the experimental data: apparent activation energies of 94, 62, and 37 kJ/mol for ethene, propene, and butene are found, and relative ratios of methylation k(ethene)/k(propene)/k(butene) = 1:23:763. The entropies of gas phase alkenes are underestimated in the harmonic oscillator approximation due to the occurrence of internal rotations. These low vibrational modes were substituted by manually constructed partition functions. Overall, the absolute reaction rates can be calculated with near chemical accuracy, and qualitative trends are very well reproduced. In addition, the proposed scheme is computationally very efficient and constitutes significant progress in kinetic modeling of reactions in heterogeneous catalysis.

  12. Cationic Pd(II)-catalyzed C-H activation/cross-coupling reactions at room temperature: synthetic and mechanistic studies.

    PubMed

    Nishikata, Takashi; Abela, Alexander R; Huang, Shenlin; Lipshutz, Bruce H

    2016-01-01

    Cationic palladium(II) complexes have been found to be highly reactive towards aromatic C-H activation of arylureas at room temperature. A commercially available catalyst [Pd(MeCN)4](BF4)2 or a nitrile-free cationic palladium(II) complex generated in situ from the reaction of Pd(OAc)2 and HBF4, effectively catalyzes C-H activation/cross-coupling reactions between aryl iodides, arylboronic acids and acrylates under milder conditions than those previously reported. The nature of the directing group was found to be critical for achieving room temperature conditions, with the urea moiety the most effective in promoting facile coupling reactions at an ortho C-H position. This methodology has been utilized in a streamlined and efficient synthesis of boscalid, an agent produced on the kiloton scale annually and used to control a range of plant pathogens in broadacre and horticultural crops. Mechanistic investigations led to a proposed catalytic cycle involving three steps: (1) C-H activation to generate a cationic palladacycle; (2) reaction of the cationic palladacycle with an aryl iodide, arylboronic acid or acrylate, and (3) regeneration of the active cationic palladium catalyst. The reaction between a cationic palladium(II) complex and arylurea allowed the formation and isolation of the corresponding palladacycle intermediate, characterized by X-ray analysis. Roles of various additives in the stepwise process have also been studied.

  13. Cationic Pd(II)-catalyzed C–H activation/cross-coupling reactions at room temperature: synthetic and mechanistic studies

    PubMed Central

    Nishikata, Takashi; Abela, Alexander R; Huang, Shenlin

    2016-01-01

    Summary Cationic palladium(II) complexes have been found to be highly reactive towards aromatic C–H activation of arylureas at room temperature. A commercially available catalyst [Pd(MeCN)4](BF4)2 or a nitrile-free cationic palladium(II) complex generated in situ from the reaction of Pd(OAc)2 and HBF4, effectively catalyzes C–H activation/cross-coupling reactions between aryl iodides, arylboronic acids and acrylates under milder conditions than those previously reported. The nature of the directing group was found to be critical for achieving room temperature conditions, with the urea moiety the most effective in promoting facile coupling reactions at an ortho C–H position. This methodology has been utilized in a streamlined and efficient synthesis of boscalid, an agent produced on the kiloton scale annually and used to control a range of plant pathogens in broadacre and horticultural crops. Mechanistic investigations led to a proposed catalytic cycle involving three steps: (1) C–H activation to generate a cationic palladacycle; (2) reaction of the cationic palladacycle with an aryl iodide, arylboronic acid or acrylate, and (3) regeneration of the active cationic palladium catalyst. The reaction between a cationic palladium(II) complex and arylurea allowed the formation and isolation of the corresponding palladacycle intermediate, characterized by X-ray analysis. Roles of various additives in the stepwise process have also been studied. PMID:27340491

  14. Isobaric Analogue States Studied in Mirrored Fragmentation and Knockout Reactions

    SciTech Connect

    Bentley, M.A.; Pritychenko, B.; Paterson,I.; Brown,J.R.; Taylor,M.J.; Digen,C.Aa.; Adrich,P.; Bazin,D.; Cook.J.M.; Gade,A.; Glasmacher,T.; McDaniel,S.; Ratkiewicz,A.; Siwek,K.; D.Weisshaar,D.; Pritychenko,B.; Lenzi,S.M.

    2010-05-21

    A Gamma-ray spectroscopic study of excited states of isobaric multiplets has been performed in recent years, with a view to gaining a quantitative understanding of energy differences between excited states in terms of a range of Coulomb and other isospin breaking phenomena. Recently, the experimental programme has been augmented by a study of isobaric analogue states of mirror nuclei populated in mirrored fragmentation reactions. In this presentation, recent results on the T = 3/2 analogue states in the T{sub z} = {+-} 3/2 mirror pair {sup 53}Ni/{sup 53}Mn will be summarised. In this work, further strong evidence is found for the need to include an anomalous isospin-breaking two-body matrix element for angular-momentum couplings of J = 2, in addition the expected Coulomb contribution, in order to account for the experimental data.

  15. Surface studies of lithium-oxygen redox reactions over HOPG

    NASA Astrophysics Data System (ADS)

    Marchini, Florencia; Herrera, Santiago E.; Calvo, Ernesto J.; Williams, Federico J.

    2016-04-01

    The O2/Li2O2 electrode reaction has been studied on low surface area HOPG electrodes in 0.1 M LiPF6 in dimethyl sulfoxide (DMSO) electrolyte. Studies were performed using electrochemical cells coupled to a XPS spectrometer and to an AFM microscope. AFM images after electrochemical treatment at cathodic potentials exhibited 20 to 100 nm in height features, whereas anodic treatment showed a thin film of about 1 nm thickness deposited over the HOPG electrode. XPS spectra after electrochemical treatment showed surface species due to DMSO and LiPF6 decomposition. These findings indicate the high reactivity of oxygen reduction products towards the electrolyte and the solvent. The unwanted deposits formed under electrochemical operation cannot be completely eliminated from the surface even after applying high anodic potentials. This highlights the known loss of capacity of Li-air batteries, issue that must be overcome for successful applications.

  16. A kinetic study of the CH2OO Criegee intermediate self-reaction, reaction with SO2 and unimolecular reaction using cavity ring-down spectroscopy.

    PubMed

    Chhantyal-Pun, Rabi; Davey, Anthony; Shallcross, Dudley E; Percival, Carl J; Orr-Ewing, Andrew J

    2015-02-07

    Criegee intermediates are important species formed during the ozonolysis of alkenes. Reaction of stabilized Criegee intermediates with various species like SO2 and NO2 may contribute significantly to tropospheric chemistry. In the laboratory, self-reaction can be an important loss pathway for Criegee intermediates and thus needs to be characterized to obtain accurate bimolecular reaction rate coefficients. Cavity ring-down spectroscopy was used to perform kinetic measurements for various reactions of CH2OO at 293 K and under low pressure (7 to 30 Torr) conditions. For the reaction CH2OO + CH2OO (8), a rate coefficient k8 = (7.35 ± 0.63) × 10(-11) cm(3) molecule(-1) s(-1) was derived from the measured CH2OO decay rates, using an absorption cross section value reported previously. A rate coefficient of k4 = (3.80 ± 0.04) × 10(-11) cm(3) molecule(-1) s(-1) was obtained for the CH2OO + SO2 (4) reaction. An upper limit for the unimolecular CH2OO loss rate coefficient of 11.6 ± 8.0 s(-1) was deduced from studies of reaction (4). SO2 catalysed CH2OO isomerization or intersystem crossing is proposed to occur with a rate coefficient of (3.53 ± 0.32) × 10(-11) cm(3) molecule(-1) s(-1).

  17. Theoretical and computational studies of organometallic reactions: successful or not?

    PubMed

    Sakaki, Shigeyoshi; Ohnishi, Yu-Ya; Sato, Hirofumi

    2010-03-01

    Theoretical and computational methods are powerful in studying transition metal complexes. Our theoretical studies of C-H sigma-bond activation of benzene by Pd(II)-formate complex and that of methane by Ti(IV)-imido complex successfully disclosed that these reactions are understood to undergo heterolytic sigma-bond activation and the driving force is the formation of strong O-H and N-H bonds in the former and the latter, respectively. Orbital interactions are considerably different from those of sigma-bond activation by oxidative addition. The transmetallation, which is a key process in the cross-coupling reaction, is understood to be heterolytic sigma-bond activation. Our theoretical study clarified how to accelerate this transmetallation. Also, we wish to discuss weak points in theoretical and computational studies of large systems including transition metal elements, such as the necessity to incorporate solvation effect and to present quantitatively correct numerical results. The importance of solvation effects is discussed in the oxidative addition of methyliodide to Pt(II) complex which occurs in a way similar to an S(N)2 substitution. To apply the CCSD(T) (coupled cluster singles and doubles with perturbative triples correction) method, which is the gold standard of electronic structure theory, to large system, we need to reduce the size of the system by employing a small model. But, such modeling induces neglects of electronic and steric effects of substituents which are replaced in the small model. Frontier-orbital-consistent quantum-capping potential (FOC-QCP) was recently proposed by our group to incorporate the electronic effects of the substituents neglected in the modeling. The CCSD(T) calculation with the FOC-QCP was successfully applied to large systems including transition metal elements.

  18. A Discrete Model to Study Reaction-Diffusion-Mechanics Systems

    PubMed Central

    Weise, Louis D.; Nash, Martyn P.; Panfilov, Alexander V.

    2011-01-01

    This article introduces a discrete reaction-diffusion-mechanics (dRDM) model to study the effects of deformation on reaction-diffusion (RD) processes. The dRDM framework employs a FitzHugh-Nagumo type RD model coupled to a mass-lattice model, that undergoes finite deformations. The dRDM model describes a material whose elastic properties are described by a generalized Hooke's law for finite deformations (Seth material). Numerically, the dRDM approach combines a finite difference approach for the RD equations with a Verlet integration scheme for the equations of the mass-lattice system. Using this framework results were reproduced on self-organized pacemaking activity that have been previously found with a continuous RD mechanics model. Mechanisms that determine the period of pacemakers and its dependency on the medium size are identified. Finally it is shown how the drift direction of pacemakers in RDM systems is related to the spatial distribution of deformation and curvature effects. PMID:21804911

  19. The human sunburn reaction: histologic and biochemical studies

    SciTech Connect

    Gilchrest, B.A.; Soter, N.A.; Stoff, J.S.; Mihm, M.C. Jr.

    1981-01-01

    The ultraviolet-induced erythema reaction was investigated histologically and biochemically in four subjects, utilizing suction blister aspirates, analyzed for histamine and prostaglandin E2 (PGE2), and Epon-embedded 1-mu skin biopsy sections from control skin and from irradiated skin at intervals for 72 hours after exposure to a Hanovia lamp. Major histologic alterations in the epidermis included dyskeratotic and vacuolated keratinocytes (sunburn cells), and disappearance of Langerhans cells. In the dermis the major changes were vascular, involving both the superficial and deep venular plexuses. Endothelial cell enlargement was first apparent within 30 minutes of irradiation, peaked at 24 hours, and persisted throughout the 72-hour study period. Mast cell degranulation and associated perivenular edema were first apparent at 1 hour and striking at the onset of erythema, 3 to 4 hours postirradiation; edema was absent and mast cells were again normal in number and granule content at 24 hours. Histamine levels rose approximately fourfold above control values immediately after the onset of erythema and returned to baseline within 24 hours. PGE2 levels were statistically elevated even before the onset of erythema and reached approximately 150% of the control value at 24 hours. These data provide the first evidence that histamine may mediate the early phase of the human sunburn reaction and increase our understanding of its complex histologic and biochemical sequelae.

  20. A discrete model to study reaction-diffusion-mechanics systems.

    PubMed

    Weise, Louis D; Nash, Martyn P; Panfilov, Alexander V

    2011-01-01

    This article introduces a discrete reaction-diffusion-mechanics (dRDM) model to study the effects of deformation on reaction-diffusion (RD) processes. The dRDM framework employs a FitzHugh-Nagumo type RD model coupled to a mass-lattice model, that undergoes finite deformations. The dRDM model describes a material whose elastic properties are described by a generalized Hooke's law for finite deformations (Seth material). Numerically, the dRDM approach combines a finite difference approach for the RD equations with a Verlet integration scheme for the equations of the mass-lattice system. Using this framework results were reproduced on self-organized pacemaking activity that have been previously found with a continuous RD mechanics model. Mechanisms that determine the period of pacemakers and its dependency on the medium size are identified. Finally it is shown how the drift direction of pacemakers in RDM systems is related to the spatial distribution of deformation and curvature effects.

  1. Space shuttle orbiter reaction control system jet interaction study

    NASA Technical Reports Server (NTRS)

    Rausch, J. R.

    1975-01-01

    The space shuttle orbiter has forward mounted and rear mounted Reaction Control Systems (RCS) which are used for orbital maneuvering and also provide control during entry and abort maneuvers in the atmosphere. The effects of interaction between the RCS jets and the flow over the vehicle in the atmosphere are studied. Test data obtained in the NASA Langley Research Center 31 inch continuous flow hypersonic tunnel at a nominal Mach number of 10.3 is analyzed. The data were obtained with a 0.01 scale force model with aft mounted RCS nozzles mounted on the sting off of the force model balance. The plume simulations were accomplished primarily using air in a cold gas simulation through scaled nozzles, however, various cold gas mixtures of Helium and Argon were also tested. The effect of number of nozzles was tested as were limited tests of combined controls. The data show that RCS nozzle exit momentum ratio is the primary correlating parameter for effects where the plume impinges on an adjacent surface and mass flow ratio is the parameter where the plume interaction is primarily with the external stream. An analytic model of aft mounted RCS units was developed in which the total reaction control moments are the sum of thrust, impingement, interaction, and cross-coupling terms.

  2. A study of the Sabatier-methanation reaction kinetics

    NASA Technical Reports Server (NTRS)

    Verostko, C. E.; Forsythe, R. K.

    1974-01-01

    The kinetics of the Sabatier methanation reaction, the reduction of carbon dioxide with hydrogen to methane and water, was investigated for 58 percent nickel on kieselguhr catalyst and 20 percent ruthenium on alumina catalyst. Differential rate data from an experimental program were correlated with a power function rate equation both for forward and reverse reactions. The kinetic parameters of activation energy, frequency rate constant and reaction order were determined for the rate equation. The values of these parameters were obtained from an Arrhenius plot of the experimental differential rate data. Also the carbon monoxide side reaction effect was measured and included in the correlation of parameters. The reaction was found to fit the rate equation experimentally within the temperature range 421 K, where the reaction effectively begins, the 800 K where the reaction rate drops and departs from the rate equation form.

  3. [Reaction mechanism studies of heavy ion induced nuclear reactions]. [Dept. of Chemistry and Biochemistry, Univ. of Maryland, College Park, Maryland

    SciTech Connect

    Mignerey, A.C.

    1993-02-01

    Completed work is summarized on the topics of excitation energy division in deep-inelastic reactions and the onset of multifragmentation in La-induced reactions at E/A = 45 MeV. Magnetic fields are being calculated for the PHOBOS detector system, a two-arm multiparticle spectrometer for studying low-transverse-momentum particles produced at the Relativistic Heavy Ion Collider. The Maryland Forward Array is being developed for detection of the reaction products from very peripheral collisions; it consists of two individual units of detectors: the annular silicon detector in front and the plastic phoswich detector at back.

  4. In-Situ X-Ray Diffraction Observations of Low Temperature Ag-Nanoink Sintering and High Temperature Eutectic Reaction with Copper

    SciTech Connect

    Elmer, J. W.; Specht, Eliot D

    2012-01-01

    Nanoinks, which contain nm sized metallic particles suspended in an organic dispersant fluid, are finding numerous microelectronic applications. Nanoinks sinter at much lower temperatures than bulk metals due to their high surface area to volume ratio and small radius of curvature, which reduces their melting points significantly below their bulk values. The unusually low melting and sintering temperatures have unique potential for materials joining since their melting points increase dramatically after initial sintering. In this paper Ag nanoink is studied using in-situ synchrotron based x-ray diffraction to follow the kinetics of the initial sintering step by analysis of diffraction patterns, and to directly observe the high remelt temperature of sintered nanoinks. Ag nanoink is further explored as a possible eutectic bonding medium with copper by tracking phase transformations to high temperatures where melting occurs at the Ag-Cu eutectic temperature, demonstrating nanoinks as a viable eutectic bonding medium.

  5. In situ hybridization study of CYP2D mRNA in the common marmoset brain

    PubMed Central

    Shimamoto, Yoshinori; Niimi, Kimie; Kitamura, Hiroshi; Tsubakishita, Sae; Takahashi, Eiki

    2016-01-01

    The common marmoset is a non-human primate that has increasingly employed in the biomedical research including the fields of neuroscience and behavioral studies. Cytochrome P450 (CYP) 2D has been speculated to be involved in psycho-neurologic actions in the human brain. In the present study, to clarify the role of CYP2D in the marmoset brain, we investigated the expression patterns of CYP2D mRNA in the brain using in situ hybridization (ISH). In addition, to identify the gene location of CYP2D19, a well-studied CYP2D isoform in the common marmoset, a fluorescence in situ hybridization (FISH) study was performed. Consistent with findings for the human brain, CYP2D mRNA was localized in the neuronal cells of different brain regions; e.g., the cerebral cortex, hippocampus, substantia nigra, and cerebellum. FISH analysis showed that the CYP2D19 gene was located on chromosome 1q, which is homologous to human chromosome 22 on which the CYP2D6 gene exists. These results suggest that CYP2D in the marmoset brain may play the same role as human CYP2D6 in terms of brain actions, and that the CYP2D19 gene is conserved in a syntenic manner. Taken together, these findings suggest that the common marmoset is a useful model for studying psychiatric disorders related to CYP2D dysfunction in the brain. PMID:27356856

  6. A novel cobalt tetranitrophthalocyanine/graphene composite assembled by an in situ solvothermal synthesis method as a highly efficient electrocatalyst for the oxygen reduction reaction in alkaline medium.

    PubMed

    Lv, Guojun; Cui, Lili; Wu, Yanying; Liu, Ying; Pu, Tao; He, Xingquan

    2013-08-21

    A novel micro/nano-composite, based on cobalt(II) tetranitrophthalocyanine (CoTNPc) grown on poly(sodium-p-styrenesulfonate) modified graphene (PGr), as a non-noble-metal catalyst for the oxygen reduction reaction (ORR), is fabricated by an in situ solvothermal synthesis method. The CoTNPc/PGr is characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), ultraviolet-visible (UV-vis) absorption spectroscopy, Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS), respectively. The electrocatalytic activity of the CoTNPc/PGr composite toward the ORR is evaluated using cyclic voltammetry and linear sweep voltammetry methods. The CoTNPc/PGr composite exhibits an unexpected, surprisingly high ORR activity compared to CoTNPc or PGr. The onset potential for ORR on CoTNPc/PGr is found to be around -0.10 V vs. SCE in 0.1 M NaOH solution, which is 30 mV and 70 mV more positive than that on PGr and CoTNPc, respectively. The peak current density on CoTNPc/PGr is about 2 times than that on PGr and CoTNPc, respectively. Rotating disk electrode (RDE) measurements reveal that the ORR mechanism is nearly via a four-electron pathway on CoTNPc/PGr. The current density for ORR on CoTNPc/PGr still remains 69.9% of its initial value after chronoamperometric measurements for 24 h. Pt/C catalyst, on the other hand, only retains 13.3% of its initial current. The peak potential shifts slightly and current barely changes when 3 M methanol is added. The fabricated composite catalyst for ORR displays high activity, good stability and excellent tolerance to the crossover effect, which may be used as a promising Pt-free catalyst in alkaline direct methanol fuel cells (DMFCs).

  7. In-situ metathesis reaction combined with ultrasound-assisted ionic liquid dispersive liquid-liquid microextraction method for the determination of phenylurea pesticides in water samples.

    PubMed

    Zhang, Jiaheng; Liang, Zhe; Li, Songqing; Li, Yubo; Peng, Bing; Zhou, Wenfeng; Gao, Haixiang

    2012-08-30

    A novel microextraction technique, named in-situ metathesis reaction, combined with ultrasound-assisted ionic liquid dispersive liquid-liquid microextraction was developed for the determination of five phenylurea pesticides (i.e., diuron, diflubenzuron, teflubenzuron, flufenoxuron, and chlorfluazuron) in environmental water samples. In the developed method, 360 μL LiNTf(2) aqueous solution (0.162 g/mL) was added to the sample solution containing a small amount of [C(6)MIM]Cl (0.034 g) to form a water-immiscible ionic liquid, [C(6)MIM]NTf(2), as extraction solution. The mixed solutions were placed in an ultrasonic water bath at 150 W for 4min and centrifuged at 3500 rpm for 10 min to achieve phase separation. After centrifugation, fine droplets of the extractant phase settled to the bottom of the centrifuge tube and were directly injected into the high-performance liquid chromatography system for analysis. The quantity of [C(6)MIM]Cl, the molar ratio of [C(6)MIM]Cl and LiNTf(2), ionic strength, ultrasound time, and centrifugation time, were optimized using a Plackett-Burman design. Significant factors obtained were optimized by employing a central composite design. The optimized technique provides good repeatability (RSD 2.4 to 3.5%), linearity (0.5 μg/L to 500 μg/L), low LODs (0.06 μg/L to 0.08 μg/L) and great enrichment factor (244 to 268). The developed method can be applied in routine analysis for the determining of phenylurea pesticides in environmental samples.

  8. Electro-deposition of Cu studied with in situ electrochemical scanning transmission x-ray microscopy

    NASA Astrophysics Data System (ADS)

    Hitchcock, A. P.; Qin, Z.; Rosendahl, S. M.; Lee, V.; Reynolds, M.; Hosseinkhannazer, H.

    2016-01-01

    Soft X-ray scanning transmission X-ray microscopy (STXM) was used to investigate Cu deposition onto, and stripping from a Au surface. Cu 2p spectromicroscopy was used to analyze initial and final states (ex situ processing) and follow the processes in situ. The in situ experiments were carried out using a static electrochemical cell with an electrolyte layer thickness of ˜1 μm. A new apparatus for in situ electrochemical STXM is described.

  9. Motorcyclists' reactions to safety helmet law: a qualitative study

    PubMed Central

    Zamani-Alavijeh, Fereshteh; Niknami, Shamsaddin; Mohammadi, Eesa; Montazeri, Ali; Ghofranipour, Fazlollah; Ahmadi, Fazlollah; Bazargan, Shahrzad Hejazi

    2009-01-01

    Background Extensive body of the literature reveals that proper use of helmets is an effective way to reduce the severity of injuries and fatalities among motorcyclists. However, many motorcyclists do not use safety helmet properly. This study aimed to empirically explore reactions of motorcyclists to the safety helmet laws, in Iran. Methods Qualitative data were collected via four focus groups and 11 in-depth interviews. Participants were 28 male motorcyclists who never used a safety helmet during rides, and 4 male police officers. All transcripts, codes and categories were read for several times to exhaust identifiable major themes. During this process data were reduced from text to codes and themes. Results Five major themes emerged from the data analyses, including themes related to the following: (1) circumventing or dodging police officers; (2) simulating a helmet wearing behavior; (3) accepting the probability of receiving a ticket; (4) taking advantage of the police neglect and carelessness; and (5) using a cheap or convenient helmet. Conclusion Our findings suggest certain levels of reckless driving among the participating motorcyclists in this study. They also point to a system of law enforcement that operates haphazardly and fails to consistently penalize those who deviate from it. Further studies are needed to investigate how "risks" are perceived and relate to "reactions", and how a 'culture of masculinity' may encourage risk tolerance and a disposition toward lawlessness and carelessness among male motorcyclists. Also, there is a need for the development and implementation of multidimensional interventions that would offer socio-culturally sensitive educational and motivational messages to the motorcyclists and the in-service traffic-enforcement officers in Iran. PMID:19843325

  10. Comparative Reactivity Study of Natural Silicate Minerals in Wet Supercritical CO2 By In Situ Infrared Spectroscopy

    NASA Astrophysics Data System (ADS)

    Thompson, C.; Schaef, T.; Miller, Q. R.; Loring, J. S.; Wang, Z.; Johnson, K. T.; McGrail, P.

    2012-12-01

    Long-term storage of CO2 in deep geologic reservoirs is one of the strategies being developed and implemented for reducing anthropogenic emissions of CO2 into the atmosphere. Reservoirs containing basalt or peridotite have the potential to permanently entrap the CO2 as silicate minerals react with the CO2 and formation waters to form stable carbonate minerals. Although the relevant reactions have been well studied in the aqueous phase, comparatively little work has focused on silicate mineral reactivity in the CO2-rich fluid containing dissolved water at conditions relevant to geologic carbon sequestration. In this study, we used in situ infrared spectroscopy to investigate the carbonation of naturally occurring samples of San Carlos olivine (Mg2SiO4), Bramble enstatite (MgSiO3), and a Hawaiian picritic basalt rich in olivine. To enhance reactivity, subsamples were micronized to obtain higher surface area materials, in the range of 14 to 23 m2g-1. Experiments were carried out at 50 °C and 91 bar by circulating a stream of dry or wet supercritical CO2 (scCO2) past a sample overlayer deposited on the window of a high-pressure infrared flow cell. Water concentrations ranged from 0% to 135% relative to saturation, and transmission-mode absorbance spectra were recorded as a function of time for 24 hours. In experiments with excess water, a controlled temperature gradient was used to intentionally condense a film of liquid water on the overlayers' surfaces. No discernible reaction was detected when the samples were exposed to dry scCO2. When water was added to the scCO2, a thin film of liquid-like water formed on the surfaces of each sample, followed by spectral evidence of carbonation. The extents of reaction were dependent on both the thickness of the water films and the materials being tested. The thinnest water film was associated with the Bramble enstatite, which also appeared minimally reactive. The Hawaiian picritic basalt was slightly more reactive but contained

  11. In situ study through electrical resistance of growth rate of trifluoroacetate-based solution-derived YBa2Cu3O7 films

    NASA Astrophysics Data System (ADS)

    Sánchez-Valdés, C. F.; Puig, T.; Obradors, X.

    2015-02-01

    In this work, we have studied by means of in situ electrical measurements the nucleation, growth and sintering stages of epitaxial YBa2Cu3O6+δ (YBCO) superconducting thin films prepared using a chemical solution deposition approach based on metal-organic trifluoroacetate-based (TFA) precursors. Single crystal substrates (LaAlO3 and CeO2/YSZ) were used in this study. Analysis of isothermal time dependences, at different temperatures, of in situ electrical resistance of films allowed to evidence that the growth rate G is strongly temperature dependent, i.e. G is enhanced by a factor ˜15 when going from 700 to 810 °C. Additionally, we demonstrate that adding Ag-TFA in the solution may enhance the growth rate by as much as 50%, as compared to pure YBCO, thus confirming previous assessments of the strong influence of Ag doping on YBCO film growth and microstructure. In situ electrical resistance measurements show as well that an incubation time exists and we infer the origin of its temperature dependence. Finally, a thermodynamic analysis allows proposing a single equation for the growth rate of YBCO films integrating all the relevant processing parameters. Our analysis has validated the solid-gas reaction-diffusion model describing the growth of YBCO films from TFA precursors and thus enlarges the knowledge required to enhance the control of the microstructure and superconducting properties of solution-derived YBCO films.

  12. In situ Hall-effect system for real-time electron-irradiation studies

    SciTech Connect

    Ziebro, B.S.; Look, D.C.; Hemsky, J.W.; Rice, W. )

    1990-01-01

    A unique system capable of taking {ital in} {ital situ} Hall-effect measurements during electron irradiation has been developed. The key element is a small, powerful rare-earth magnet. Measurements can be taken while the electron beam is on, resulting in a considerable time savings and eliminating problems associated with mounting and demounting the sample. High resolution electron concentration and mobility versus fluence data are quickly and easily obtained, making possible detailed defect production rate studies as functions of energy and flux.

  13. Silicate Carbonation in Supercritical CO2 Containing Dissolved H2O: An in situ High Pressure X-Ray Diffraction Study

    SciTech Connect

    Schaef, Herbert T.; Miller, Quin RS; Thompson, Christopher J.; Loring, John S.; Bowden, Mark E.; Arey, Bruce W.; McGrail, B. Peter; Rosso, Kevin M.

    2013-06-30

    Technological advances have been significant in recent years for managing environmentally harmful emissions (mostly CO2) resulting from combustion of fossil fuels. Deep underground geologic formations are emerging as reasonable options for long term storage of CO2 but mechanisms controlling rock and mineral stability in contact with injected supercritical fluids containing water are relatively unknown. In this paper, we discuss mineral transformation reactions occurring between supercritical CO2 containing water and the silicate minerals forsterite (Mg2SiO4), wollastonite (CaSiO3), and enstatite (MgSiO3). This study utilizes newly developed in situ high pressure x-ray diffraction (HXRD) and in situ infra red (IR) to examine mineral transformation reactions. Forsterite and enstatite were selected as they are important minerals present in igneous and mafic rocks and have been the subject of a large number of aqueous dissolution studies that can be compared with non-aqueous fluid tests in this study. Wollastonite, classified as a pyroxenoid (similar to a pyroxene), was chosen as a suitably fast reacting proxy for examining silicate carbonation processes associated with a wet scCO2 fluid as related to geologic carbon sequestration. The experiments were conducted under modest pressures (90 to 160 bar), temperatures between 35° to 70° C, and varying concentrations of dissolved water. Under these conditions scCO2 contains up to 3,500 ppm dissolved water.

  14. Reaction studies of hot silicon and germanium radicals. Progress report, September 1, 1979-August 31, 1980

    SciTech Connect

    Gaspar, P.P.

    1980-08-31

    The experimental approach to attaining the goals of this research program is briefly outlined and the progress made in the last year is reviewed in sections entitled: (a) primary steps in the reaction of recoiling silicon and germanium atoms and the identification of reactive intermediates in the recoil reactions; (b) thermally induced silylene and germylene reactions; (c) ion-molecule reaction studies.

  15. Computational Chemistry in the Undergraduate Laboratory: A Mechanistic Study of the Wittig Reaction

    ERIC Educational Resources Information Center

    Albrecht, Birgit

    2014-01-01

    The Wittig reaction is one of the most useful reactions in organic chemistry. Despite its prominence early in the organic chemistry curriculum, the exact mechanism of this reaction is still under debate, and this controversy is often neglected in the classroom. Introducing a simple computational study of the Wittig reaction illustrates the…

  16. Kinetic study of the reactions between chloramine disinfectants and hydrogen peroxide: temperature dependence and reaction mechanism.

    PubMed

    McKay, Garrett; Sjelin, Brittney; Chagnon, Matthew; Ishida, Kenneth P; Mezyk, Stephen P

    2013-09-01

    The temperature-dependent kinetics for the reaction between hydrogen peroxide and chloramine water disinfectants (NH2Cl, NHCl2, and NCl3) have been determined using stopped flow-UV/Vis spectrophotometry. Rate constants for the mono- and dichloramine-peroxide reaction were on the order of 10(-2)M(-1)s(-1) and 10(-5)M(-1)s(-1), respectively. The reaction of trichloramine with peroxide was negligibly slow compared to its thermal and photolytically-induced decomposition. Arrhenius expressions of ln(kH2O2-NH2Cl)=(17.3±1.5)-(51500±3700)/RT and ln(kH2O2-NHCl2)=(18.2±1.9)-(75800±5100)/RT were obtained for the mono- and dichloramine peroxide reaction over the temperature ranges 11.4-37.9 and 35.0-55.0°C, respectively. Both monochloramine and hydrogen peroxide were first-order in the rate-limiting kinetic step and concomitant measurements made using a chloride ion selective electrode showed that the chloride was produced quantitatively. These data will aid water utilities in predicting chloramine concentrations (and thus disinfection potential) throughout the water distribution system.

  17. Reaction between Chromium(III) and EDTA Ions: an Overlooked Mechanism of Case Study Reaction of Chemical Kinetics.

    PubMed

    Cerar, Janez

    2015-01-01

    Widely cited and accepted explanation of reaction mechanism of the case study reaction of chemical kinetics between Cr(III) ions and ethylenediaminetetraacetic acid (EDTA) contradicts modern chromium(III) coordination chemistry data. Absorption UV and visible light spectra were recorded during the reaction between aqueous solution of Cr(NO(3))(3) and EDTA in order to obtain new information about this reaction. Analysis of the spectra showed that only very small fraction of intermediates may be present in solution during the course of the reaction. The reaction scheme was established and according to it calculations based on a simplified model were carried out. Literature data for constants were used if known, otherwise, adjusted values of their sound estimates were applied. Reasonable agreement of the model calculations with the experimental data was obtained for pH values 3.8 and 4.5 but the model failed to reproduce measured rate of reaction at pH 5.5, probably due to the use of the oversimplified model.

  18. Mechanism of ceroid formation in atherosclerotic plaque: in situ studies using a combination of Raman and fluorescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Haka, Abigail S.; Kramer, John R.; Dasari, Ramachandra R.; Fitzmaurice, Maryann

    2011-01-01

    Accumulation of the lipid-protein complex ceroid is a characteristic of atherosclerotic plaque. The mechanism of ceroid formation has been extensively studied, because the complex is postulated to contribute to plaque irreversibility. Despite intensive research, ceroid deposits are defined through their fluorescence and histochemical staining properties, while their composition remains unknown. Using Raman and fluorescence spectral microscopy, we examine the composition of ceroid in situ in aorta and coronary artery plaque. The synergy of these two types of spectroscopy allows for identification of ceroid via its fluorescence signature and elucidation of its chemical composition through the acquisition of a Raman spectrum. In accordance with in vitro predictions, low density lipoprotein (LDL) appears within the deposits primarily in its peroxidized form. The main forms of modified LDL detected in both coronary artery and aortic plaques are peroxidation products from the Fenton reaction and myeloperoxidase-hypochlorite pathway. These two peroxidation products occur in similar concentrations within the deposits and represent ~40 and 30% of the total LDL (native and peroxidized) in the aorta and coronary artery deposits, respectively. To our knowledge, this study is the first to successfully employ Raman spectroscopy to unravel a metabolic pathway involved in disease pathogenesis: the formation of ceroid in atherosclerotic plaque.

  19. [In situ FTIR spectroscopic studies of the catalytic combustion of acid red B on CuFe2O4 in the presence and absence of O2].

    PubMed

    Wu, Rong-cheng; Qu, Jiu-hui; Yu, Yun-bo; He, Hong

    2005-02-01

    The reaction process of catalytic combustion of ARB on CuFe2O4 in the presence and absence of O2 was studied by in situ DRIFT spectroscopy. The results showed that the decomposition of the sulfonic group of ARB molecule was not affected by the reaction atmosphere, but the decompositions of azo group and aromatic ring were markedly affected by the presence or absence of O2. The catalytic combustion of ARB was faster in air atmosphere than that in N2 atmosphere, and ARB could be completely oxidized to CO2 and nitrate at 300 degrees C. But in N2 atmosphere, it was very difficult for the decomposition of ARB to complete at 300 degrees C, even though air was introduced following this process. The temperature required for the rapid and complete decomposition would be as high as 500 degrees C.

  20. On-Chip Bioorthogonal Chemistry Enables Immobilization of In Situ Modified Nanoparticles and Small Molecules for Label-Free Monitoring of Protein Binding and Reaction Kinetics

    PubMed Central

    Tassa, Carlos; Liong, Monty; Hilderbrand, Scott; Sandler, Jason E.; Reiner, Thomas; Keliher, Edmund J.; Weissleder, Ralph; Shaw, Stanley Y.

    2012-01-01

    Efficient methods to immobilize small molecules under continuous-flow microfluidic conditions would greatly improve label-free molecular interaction studies using biosensor technology. At present, small-molecule immobilization chemistries require special conditions and in many cases must be performed outside the detector and microfluidic system where real-time monitoring is not possible. Here, we have developed and optimized a method for on-chip bioorthogonal chemistry that enables rapid, reversible immobilization of small molecules with control over orientation and immobilization density, and apply this technique to surface plasmon resonance (SPR) studies. Immobilized small molecules reverse the orientation of canonical SPR interaction studies, and also enable a variety of new SPR applications including on-chip assembly and interaction studies of multicomponent structures such as functionalized nanoparticles, and measurement of bioorthogonal reaction rates. We use this approach to demonstrate that on-chip assembled functionalized nanoparticles show a preserved ability to interact with their target protein, and to measure rapid bioorthogonal reaction rates with k2 > 103 M−1 s−1. This method offers multiple benefits for microfluidic biological applications, including rapid screening of targeted nanoparticles with vastly decreased nanoparticle synthetic requirements, robust immobilization chemistry in the presence of serum, and a continuous flow technique that mimics biologic contexts better than current methods used to measure bioorthogonal reaction kinetics such as NMR or UV-vis spectroscopy (e.g., stopped flow kinetics). Taken together, this approach constitutes a flexible and powerful technique for evaluating a wide variety of reactions and intermolecular interactions for in vitro or in vivo applications. PMID:22760641

  1. On-chip bioorthogonal chemistry enables immobilization of in situ modified nanoparticles and small molecules for label-free monitoring of protein binding and reaction kinetics.

    PubMed

    Tassa, C; Liong, M; Hilderbrand, S; Sandler, J E; Reiner, T; Keliher, E J; Weissleder, R; Shaw, S Y

    2012-09-07

    Efficient methods to immobilize small molecules under continuous-flow microfluidic conditions would greatly improve label-free molecular interaction studies using biosensor technology. At present, small-molecule immobilization chemistries require special conditions and in many cases must be performed outside the detector and microfluidic system where real-time monitoring is not possible. Here, we have developed and optimized a method for on-chip bioorthogonal chemistry that enables rapid, reversible immobilization of small molecules with control over orientation and immobilization density, and apply this technique to surface plasmon resonance (SPR) studies. Immobilized small molecules reverse the orientation of canonical SPR interaction studies, and also enable a variety of new SPR applications including on-chip assembly and interaction studies of multicomponent structures, such as functionalized nanoparticles, and measurement of bioorthogonal reaction rates. We use this approach to demonstrate that on-chip assembled functionalized nanoparticles show a preserved ability to interact with their target protein, and to measure rapid bioorthogonal reaction rates with k(2) > 10(3) M(-1) s(-1). This method offers multiple benefits for microfluidic biological applications, including rapid screening of targeted nanoparticles with vastly decreased nanoparticle synthetic requirements, robust immobilization chemistry in the presence of serum, and a continuous flow technique that mimics biologic contexts better than current methods used to measure bioorthogonal reaction kinetics such as NMR or UV-vis spectroscopy (e.g., stopped flow kinetics). Taken together, this approach constitutes a flexible and powerful technique for evaluating a wide variety of reactions and intermolecular interactions for in vitro or in vivo applications.

  2. In Situ Synchrotron X-ray Study of Ultrasound Cavitation and Its Effect on Solidification Microstructures

    NASA Astrophysics Data System (ADS)

    Mi, Jiawei; Tan, Dongyue; Lee, Tung Lik

    2015-08-01

    Considerable progress has been made in studying the mechanism and effectiveness of using ultrasound waves to manipulate the solidification microstructures of metallic alloys. However, uncertainties remain in both the underlying physics of how microstructures evolve under ultrasonic waves, and the best technological approach to control the final microstructures and properties. We used the ultrafast synchrotron X-ray phase contrast imaging facility housed at the Advanced Photon Source, Argonne National Laboratory, US to study in situ the highly transient and dynamic interactions between the liquid metal and ultrasonic waves/bubbles. The dynamics of ultrasonic bubbles in liquid metal and their interactions with the solidifying phases in a transparent alloy were captured in situ. The experiments were complemented by the simulations of the acoustic pressure field, the pulsing of the bubbles, and the associated forces acting onto the solidifying dendrites. The study provides more quantitative understanding on how ultrasonic waves/bubbles influence the growth of dendritic grains and promote the grain multiplication effect for grain refinement.

  3. Coke forming reaction kinetic study on petroleum based feeds

    SciTech Connect

    Shigley, J.K.; Fu, Ta-Wei

    1988-08-01

    The carbonization of hydrocarbons is a very complex process. The pyrolysis reactions are predominantly free radical in nature and can be summarized as a polymerization process. The phase transitions from a 199% isotropic phase to an anisotropic mesophase during the carbonization of many feeds is an important and much studied phenomena. This phenomena is capitalized on in industry to produce needle or graphite coke. The kinetics of pitch polymerization and coke formation have historically been studied by measuring the solubility of the heat treated material in various solvents. The concentration of free radicals in the carbonized samples have also been used to investigate the mechanistic and kinetic aspects of the process. A very extensive study was conducted by Greinke using GPC techniques to measure the changes in narrow molecular weight ranges and the overall molecular weight distribution of a pitch during carbonization. This study focuses on the use of product volatile matter as the measure of extent of carbonization of two different feedstocks. It is ideally suited for use in commercial coking operations as a control or quality parameter of green coke.

  4. Copper phosphonatoethanesulfonates: temperature dependent in situ energy dispersive X-ray diffraction study and influence of the pH on the crystal structures.

    PubMed

    Feyand, Mark; Hübner, Annika; Rothkirch, André; Wragg, David S; Stock, Norbert

    2012-11-19

    The system Cu(2+)/H2O3P-C2H4-SO3H/NaOH was investigated using in situ energy dispersive X-ray diffraction (EDXRD) to study the formation and temperature induced phase transformation of previously described copper phosphonosulfonates. Thus, the formation of [Cu2(O3P-C2H4-SO3)(OH)(H2O)]·3H2O (4) at 90 °C is shown to proceed via a previously unknown intermediate [Cu2(O3P-C2H4-SO3)(OH)(H2O)]·4H2O (6), which could be structurally characterized from high resolution powder diffraction data. Increase of the reaction temperature to 150 °C led to a rapid phase transformation to [Cu2(O3P-C2H4-SO3)(OH)(H2O)]·H2O (1), which was also studied by in situ EDXRD. The comparison of the structures of 1, 4, and 6 allowed us to establish a possible reaction mechanism. In addition to the in situ crystallization studies, microwave assisted heating for the synthesis of the copper phosphonosulfonates was employed, which allowed the growth of larger crystals of [NaCu(O3P-C2H4-SO3)(H2O)2] (5) suitable for single crystal X-ray diffraction. Through the combination of force field calculations and Rietveld refinement we were able to determine the crystal structure of [Cu1.5(O3P-C2H4-SO3)] 2H2O (3) and thus structurally characterize all compounds known up to now in this well investigated system. With the additional structural data we are now able to describe the influence of the pH on the structure formation.

  5. In Situ X-ray Diffraction Studies of Cathode Materials in Lithium Batteries

    SciTech Connect

    Yang, X. Q.; Sun, X.; McBreen, J.; Mukerjee, S.; Gao, Yuan; Yakovleva, M. V.; Xing, X. K.; Daroux, M. L.

    1998-11-01

    There is an increasing interest in lithiated transition metal oxides because of their use as cathodes in lithium batteries. LiCoO{sub 2}, LiNiO{sub 2} and LiMn{sub 2}O{sub 4} are the three most widely used and studied materials, At present, although it is relative expensive and toxic, LiCoO{sub 2} is the material of choice in commercial lithium ion batteries because of its ease of manufacture, better thermal stability and cycle life. However, the potential use of lithium ion batteries with larger capacity for power tools and electric vehicles in the future will demand new cathode materials with higher energy density, lower cost and better thermal stability. LiNiO{sub 2} is isostructural with LiCoO{sub 2}. It offers lower cost and high energy density than LiCoO{sub 2}. However, it has much poorer thermal stability than LiCoO{sub 2}, in the charged (delithiated) state. Co, Al, and other elements have been used to partially replace Ni in LiNiO{sub 2} system in order to increase the thermal stability. LiMn{sub 2}O{sub 4} has the highest thermal stability and lowest cost and toxicity. However, the low energy density and poor cycle life at elevated temperature are the major obstacles for this material. In order to develop safer, cheaper, and better performance cathode materials, the in-depth understanding of the relationships between the thermal stability and structure, performance and structure are very important. The performance here includes energy density and cycle life of the cathode materials. X-ray diffraction (XRD) is one of the most powerful tools to study these relationships. The pioneer ex situ XRD work on cathode materials for lithium batteries was done by Ohzuku. His XRD studies on LiMn{sub 2}O{sub 4}, LiCoO{sub 2}, LiNiO{sub 2}, LiNi{sub 0.5}Co{sub 0.5}O{sub 2}, and LiAl{sub x}Ni{sub 1-x}O{sub 2} cathodes at different states of charge have provided important guidelines for the development of these new materials. However, the kinetic nature of the battery

  6. Direct coupling between stress, strain and adsorption reactions - A study on coal-CO2 systems

    NASA Astrophysics Data System (ADS)

    Hol, S.; Peach, C. J.; Spiers, C. J.

    2012-12-01

    Though it is well-known that adsorption reactions frequently assist deformation of porous rocks, very little understanding exists on the direct coupling with stress state and strain. One of the materials in which adsorption plays a large role is coal, as is observed in the particular case of Enhanced Coalbed Methane Production (ECBM), which involves the geological storage of CO2 and the recovery of CH4. In this case, adsorption and the associated swelling cause significant injectivity problems, which is experienced in almost all pilot field projects to date. This suggests that indeed a strong fundamental coupling exists between CO2 sorption, changes in the mechanical state of the coal matrix and changes in the transport properties of the system, and illustrates the need to understand coupled stress-strain-sorption behaviour. In this contribution, we describe several important observations made on coal-CO2 systems that can learn us about many other natural, stressed adsorbate-adsorbent systems. In our experiments, first of all, the adsorption of CO2 in the coal matrix gave rise to swelling. Although this is well-known, we found that the total volumetric strain occurring under unconfined conditions can be realistically modelled (up to at least 100 MPa) as the sum of an adsorption-related expansion term and an elastic compression term. Second, effective in situ stresses will directly reduce the sorption capacity, and associated swelling of the coal matrix significantly. Our general thermodynamic model for the effect of a 3D stress state on adsorbed CO2 concentration supports this observation, and also shows that "self-stressing", as a result of CO2 adsorption occurring under conditions of restricted or zero strain (i.e. fully constrained conditions), will more than double the expected in situ stresses. A constitutive equation was developed to describe the full coupling between stress state, total strain (i.e. combined strain of adsorption processes and poroelasticity

  7. Theoretical study on the reaction mechanisms of CH 2SH + NO reaction

    NASA Astrophysics Data System (ADS)

    Zhan, Peiying; Pan, Yaru; Tang, Yizhen

    2009-06-01

    The mechanisms for the CH2SH + NO reaction were investigated on both of the singlet and triplet PES at the BMC-CCSD//B3LYP/6-311+G(d,p) level. The results indicate that the singlet PES is much lower than the triplet PES energetically; therefore, the reaction occurs on the singlet PES dominantly. The most favorable channel on the singlet PES takes place by a barrierless addition of N atom to CH2SH radical to form HSCH2NO. Subsequently, the rearrangement of the initial adduct HSCH2NO (IM1) to form another intermediate IM3 via a four-center transition state, followed by the C-O bond fission in IM3 leading to the major product CH2S + HNO. Due to high barriers, other product including HC(N)SH + HO, HON + CH2S, and HNO + CHSH could be negligible. The direct abstraction channel was also determined to yield CH2S + HON. With high barrier (33.3 kcal/mol), it is not competitive with the addition channel, in which all stationary points are lower than reactant energetically. While on the triplet PES, with the lowest barrier height (18.8 kcal/mol), the direct N-abstracted channel to form CH2S + HNO is dominant. However, it is not competitive with the channels on the singlet PES. Our results are in good accordance with experimental conclusions that the reaction proceeds via addition mechanism.

  8. IN SITU STUDIES OF CORROSION USING X-RAY ABSORPTION NEAR SPECTROSCOPY (XANES)

    SciTech Connect

    ISAACS, H.S.; SCHMUKI, P.; VIRTANEN, S.

    2001-03-25

    Applications of x-ray absorption near-edge spectroscopy (XANES) and the design of cells for in situ corrosion studies are reviewed. Passive films studies require very thin metal or alloy layers be used having a thickness of the order of the films formed because of penetration of the x-ray beam into the metal substrate. The depth of penetration in water also limits the thickness of solutions that can be used because of water reduces the x-ray intensity. Solution thickness must also be limited in studies of conversion layer formation studies because the masking of the Cr in solution. Illustrative examples are taken from the anodic behavior of Al-Cr alloys, the growth of passive films on Fe and stainless steels, and the formation of chromate conversion layers on Al.

  9. In situ, simultaneous thermal imaging and infrared molecular emission studies of solid oxide fuel cell electrodes

    NASA Astrophysics Data System (ADS)

    Kirtley, J. D.; Qadri, S. N.; Steinhurst, D. A.; Owrutsky, J. C.

    2016-12-01

    Various in situ probes of solid oxide fuel cells (SOFCs) have advanced recently to provide detailed, real time data regarding materials and chemical processes that relate to device performance and degradation. These techniques offer insights into complex fuel chemistry at the anode in particular, especially in the context of model predictions. However, cell-to-cell variations can hinder mechanistic interpretations of measurements from separate, independent techniques. The present study describes an in situ technique that for the first time simultaneously measures surface temperature changes using near infrared thermal imaging and gas species using Fourier-transform infrared emission spectra at the anodes of operating SOFCs. Electrolyte-supported SOFCs with Ni-based anodes are operated at 700 °C with internal, dry-reformed methane at 75% maximum current and at open circuit voltage (OCV) while electrochemical and optical measurements are collected. At OCV, more cooling is observed coincident with more CO reforming products. Under load, CO decreases while the anode cools less, especially near the current collectors. The extent of cooling is more sensitive to polarization for electrolyte-supported cells because their anodes are thinner relative to anode-supported cells. This study exemplifies how this duplex technique can be a useful probe of electrochemical processes in SOFCs.

  10. Studies of ferroelectric heterostructure thin films and interfaces via in situ analytical techniques.

    SciTech Connect

    Auciello, O.; Dhote, A.; Gao, Y.; Gruen, D. M.; Im, J.; Irene, E. A.; Krauss, A. R.; Mueller, A. H.; Ramesh, R.

    1999-08-30

    The science and technology of ferroelectric thin films has experienced an explosive development during the last ten years. Low-density non-volatile ferroelectric random access memories (NVFRAMs) are now incorporated in commercial products such as ''smart cards'', while high permittivity capacitors are incorporated in cellular phones. However, substantial work is still needed to develop materials integration strategies for high-density memories. We have demonstrated that the implementation of complementary in situ characterization techniques is critical to understand film growth and interface processes, which play critical roles in film microstructure and properties. We are using uniquely integrated time of flight ion scattering and recoil spectroscopy (TOF-ISARS) and spectroscopic ellipsometry (SE) techniques to perform in situ, real-time studies of film growth processes in the high background gas pressure required to growth ferroelectric thin films. TOF-ISARS provides information on surface processes, while SE permits the investigation of buried interfaces as they are being formed. Recent studies on SrBi{sub 2}Ta{sub 2}O{sub 9} (SBT) and Ba{sub x}Sr{sub 1{minus}x}TiO{sub 3} (BST) film growth and interface processes are discussed.

  11. Hypersensitive radical probe studies of chloroperoxidase-catalyzed hydroxylation reactions.

    PubMed

    Toy, P H; Newcomb, M; Hager, L P

    1998-07-01

    The oxidation of hypersensitive radical probes by chloroperoxidase from Caldariomyces fumago (CPO) was studied in an attempt to "time" a putative radical intermediate. Oxidation of (trans-2-phenylcyclopropyl)methane, previously studied by Zaks and Dodds [Zaks, A., and Dodds, D. R. (1995) J. Am. Chem. Soc. 115, 10419-10424] was reinvestigated. Unrearranged oxidation products were found as previously reported, and control experiments demonstrated that the cyclic alcohol from oxidation at the cyclopropylcarbinyl position, while subject to further oxidation, survives CPO oxidation as detectable species. However, in contrast to the report by Zaks and Dodds, the rearranged alcohol product expected from ring opening of a cyclopropylcarbinyl radical intermediate was shown to be unstable toward the enzyme oxidation reaction. Because of this instability, two new hypersensitive radical probes, (trans-2-phenylcyclopropyl)ethane and 2-(trans-2-phenylcyclopropyl)propane, and their potential cyclic and acyclic products from oxidation at the cyclopropylcarbinyl position were synthesized and tested. Oxidation of both of these probes at the cyclopropylcarbinyl position by CPO gave unrearranged alcohol products only, but control experiments again demonstrated that the rearranged alcohol products were unstable toward CPO oxidation conditions. From the combination of the probe and control studies, the lifetime of a putative radical intermediate must be less than 3 ps. Whereas the results are consistent with an insertion mechanism for production of alcohol product, they do not exclude a very short-lived intermediate.

  12. Thermal degradation reaction mechanism of xylose: A DFT study

    NASA Astrophysics Data System (ADS)

    Huang, Jinbao; He, Chao; Wu, Longqin; Tong, Hong

    2016-08-01

    The thermal degradation reaction mechanism of xylose as hemicellulose model compound was investigated by using density functional theory methods M062X with the 6-31++G(d,p) basis set. Eight possible pyrolytic reaction pathways were proposed and the standard kinetic and thermodynamic parameters in all reaction pathways were calculated at different temperatures. In reaction pathway (1), xylose is first transformed into acyclic containing-carbonyl isomer, and then the isomer further decomposes through four possible pyrolysis pathways (1-1)-(1-4). Pathways (2) and (3) depict an immediate ring-opening process through the simultaneous breaking of C-O and C-C bonds. Pathways (4)-(7) describe the pyrolysis processes of various anhydro-xyloses through a direct ring-opening process. Pathway (8) gives the evolutionary process of pyranones. The calculation results show that reaction pathways (1), (2) and (5) are the major reaction channels and reaction pathways (3), (4), and (6)-(8) are the competitive reaction channels in pyrolysis of xylose. The major products of xylose pyrolysis are low molecular products such as 2-furaldehyde, glycolaldehyde, acetaldehyde, methylglyoxal and acetone, and the main competitive products are formaldehyde, formic acid, acetic acid, CO2, CH4, acetol, pyranone, and so on.

  13. Ion-Molecule Reaction Studies at Low Energies

    NASA Astrophysics Data System (ADS)

    Dheandhanoo, Seksan

    A variable temperature drift tube-mass spectrometer apparatus has been used to determine the forward rate coefficients for the association reactions of NO('+) ions with N(,2) and CO(,2), O(,2)('+) with N(,2), N('+) and N(,2)('+) with N(,2), and CH(,5)('+) and C(,2)H(,5)('+) with CH(,4) as a function of gas temperature. The measured rate coefficients were fitted to power laws of the form k(,+) = C(T/300)(' -x), where the exponents ranged from 2.0 to 4.3, i.e. a strong temperature dependence was observed in most of these three-body (clustering) reactions. The equilibrium constants K = k(,+)/k(,-) for the association reactions of CH(,5)('+) and C(,2)H(,5)('+) with CH(,4) were also measured as a function of gas temperature, allowing the reverse rate coefficients k(,-) for these two reactions to be determined. In a second set of measurements, rate coefficients for several two-body ion-molecule reactions involving hydrocarbons have been determined at thermal energies and above using a selected ion drift tube-mass spectrometer apparatus. The results indicate that the product yields of several of the fast ion-molecule reactions depend on ion energy (temperature), even though the total rate coefficients are independent of energy. The oxidation reaction of the metal ion Zr('+) has been found to be a fast reaction and the rate coefficient has been found to be independent of ion energy.

  14. Studies of the Atmospheric Chemsitry of Energy-Related Volatile Organic Compounds and of their Atmospheric Reaction Products

    SciTech Connect

    Roger Atkinson; Janet Arey

    2007-04-14

    The focus of this contract was to investigate selected aspects of the atmospheric chemistry of volatile organic compounds (VOCs) emitted into the atmosphere from energy-related sources as well as from biogenic sources. The classes of VOCs studied were polycyclic aromatic hydrocarbons (PAHs) and nitro-PAHs, the biogenic VOCs isoprene, 2-methyl-3-buten-2-ol and cis-3-hexen-1-ol, alkenes (including alkenes emitted from vegetation) and their oxygenated atmospheric reaction products, and a series of oxygenated carbonyl and hydroxycarbonyl compounds formed as atmospheric reaction products of aromatic hydrocarbons and other VOCs. Large volume reaction chambers were used to investigate the kinetics and/or products of photolysis and of the gas-phase reactions of these organic compounds with hydroxyl (OH) radicals, nitrate (NO3) radicals, and ozone (O3), using an array of analytical instrumentation to analyze the reactants and products (including gas chromatography, in situ Fourier transform infrared spectroscopy, and direct air sampling atmospheric pressure ionization tandem mass spectrometry). The following studies were carried out. The photolysis rates of 1- and 2-nitronaphthalene and of eleven isomeric methylnitronaphthalenes were measured indoors using blacklamp irradiation and outdoors using natural sunlight. Rate constants were measured for the gas-phase reactions of OH radicals, Cl atoms and NO3 radicals with naphthalene, 1- and 2-methylnaphthalene, 1- and 2-ethylnaphthalene and the ten dimethylnaphthalene isomers. Rate constants were measured for the gas-phase reactions of OH radicals with four unsaturated carbonyls and with a series of hydroxyaldehydes formed as atmospheric reaction products of other VOCs, and for the gas-phase reactions of O3 with a series of cycloalkenes. Products of the gas-phase reactions of OH radicals and O3 with a series of biogenically emitted VOCs were identified and quantified. Ambient atmospheric measurements of the concentrations of a

  15. In Situ Studies of Surface Mobility on Noble Metal Model Catalysts Using STM and XPS at Ambient Pressure

    SciTech Connect

    Butcher, Derek Robert

    2010-06-01

    are present on the Pt(100) hex reconstructed phase, but not the (1