WorldWideScience

Sample records for chemical reactivity

  1. Interactive Chemical Reactivity Exploration

    OpenAIRE

    Haag, Moritz P.; Vaucher, Alain C.; Bosson, Mael; Redon, Stephane; Reiher, Markus

    2014-01-01

    Elucidating chemical reactivity in complex molecular assemblies of a few hundred atoms is, despite the remarkable progress in quantum chemistry, still a major challenge. Black-box search methods to find intermediates and transition-state structures might fail in such situations because of the high-dimensionality of the potential energy surface. Here, we propose the concept of interactive chemical reactivity exploration to effectively introduce the chemist's intuition into the search process. ...

  2. Interactive Chemical Reactivity Exploration

    CERN Document Server

    Haag, Moritz P; Bosson, Mael; Redon, Stephane; Reiher, Markus

    2014-01-01

    Elucidating chemical reactivity in complex molecular assemblies of a few hundred atoms is, despite the remarkable progress in quantum chemistry, still a major challenge. Black-box search methods to find intermediates and transition-state structures might fail in such situations because of the high-dimensionality of the potential energy surface. Here, we propose the concept of interactive chemical reactivity exploration to effectively introduce the chemist's intuition into the search process. We employ a haptic pointer device with force-feedback to allow the operator the direct manipulation of structures in three dimensions along with simultaneous perception of the quantum mechanical response upon structure modification as forces. We elaborate on the details of how such an interactive exploration should proceed and which technical difficulties need to be overcome. All reactivity-exploration concepts developed for this purpose have been implemented in the Samson programming environment.

  3. Fracture Reactivation in Chemically Reactive Rock Systems

    Science.gov (United States)

    Eichhubl, P.; Hooker, J. N.

    2013-12-01

    Reactivation of existing fractures is a fundamental process of brittle failure that controls the nucleation of earthquake ruptures, propagation and linkage of hydraulic fractures in oil and gas production, and the evolution of fault and fracture networks and thus of fluid and heat transport in the upper crust. At depths below 2-3 km, and frequently shallower, brittle processes of fracture growth, linkage, and reactivation compete with chemical processes of fracture sealing by mineral precipitation, with precipitation rates similar to fracture opening rates. We recently found rates of fracture opening in tectonically quiescent settings of 10-20 μm/m.y., rates similar to euhedral quartz precipitation under these conditions. The tendency of existing partially or completely cemented fractures to reactivate will vary depending on strain rate, mineral precipitation kinetics, strength contrast between host rock and fracture cement, stress conditions, degree of fracture infill, and fracture network geometry. Natural fractures in quartzite of the Cambrian Eriboll Formation, NW Scotland, exhibit a complex history of fracture formation and reactivation, with reactivation involving both repeated crack-seal opening-mode failure and shear failure of fractures that formed in opening mode. Fractures are partially to completely sealed with crack-seal or euhedral quartz cement or quartz cement fragmented by shear reactivation. Degree of cementation controls the tendency of fractures for later shear reactivation, to interact elastically with adjacent open fractures, and their intersection behavior. Using kinematic, dynamic, and diagenetic criteria, we determine the sequence of opening-mode fracture formation and later shear reactivation. We find that sheared fracture systems of similar orientation display spatially varying sense of slip We attribute these inconsistent directions of shear reactivation to 1) a heterogeneous stress field in this highly fractured rock unit and 2

  4. Quantum Entanglement and Chemical Reactivity.

    Science.gov (United States)

    Molina-Espíritu, M; Esquivel, R O; López-Rosa, S; Dehesa, J S

    2015-11-10

    The water molecule and a hydrogenic abstraction reaction are used to explore in detail some quantum entanglement features of chemical interest. We illustrate that the energetic and quantum-information approaches are necessary for a full understanding of both the geometry of the quantum probability density of molecular systems and the evolution of a chemical reaction. The energy and entanglement hypersurfaces and contour maps of these two models show different phenomena. The energy ones reveal the well-known stable geometry of the models, whereas the entanglement ones grasp the chemical capability to transform from one state system to a new one. In the water molecule the chemical reactivity is witnessed through quantum entanglement as a local minimum indicating the bond cleavage in the dissociation process of the molecule. Finally, quantum entanglement is also useful as a chemical reactivity descriptor by detecting the transition state along the intrinsic reaction path in the hypersurface of the hydrogenic abstraction reaction corresponding to a maximally entangled state. PMID:26894237

  5. Hydrophobic interactions and chemical reactivity

    OpenAIRE

    Otto, Sijbren; Engberts, Jan B.F.N.

    2003-01-01

    This perspective describes how kinetic studies of organic reactions can be used to increase our understanding of hydrophobic interactions. In turn, our understanding of hydrophobic interactions can be used as a tool to influence chemical reactions.

  6. Studying chemical reactivity in a virtual environment.

    Science.gov (United States)

    Haag, Moritz P; Reiher, Markus

    2014-01-01

    Chemical reactivity of a set of reactants is determined by its potential (electronic) energy (hyper)surface. The high dimensionality of this surface renders it difficult to efficiently explore reactivity in a large reactive system. Exhaustive sampling techniques and search algorithms are not straightforward to employ as it is not clear which explored path will eventually produce the minimum energy path of a reaction passing through a transition structure. Here, the chemist's intuition would be of invaluable help, but it cannot be easily exploited because (1) no intuitive and direct tool for the scientist to manipulate molecular structures is currently available and because (2) quantum chemical calculations are inherently expensive in terms of computational effort. In this work, we elaborate on how the chemist can be reintroduced into the exploratory process within a virtual environment that provides immediate feedback and intuitive tools to manipulate a reactive system. We work out in detail how this immersion should take place. We provide an analysis of modern semi-empirical methods which already today are candidates for the interactive study of chemical reactivity. Implications of manual structure manipulations for their physical meaning and chemical relevance are carefully analysed in order to provide sound theoretical foundations for the interpretation of the interactive reactivity exploration. PMID:25340884

  7. Steam-chemical reactivity for irradiated beryllium

    Energy Technology Data Exchange (ETDEWEB)

    Anderl, R.A.; McCarthy, K.A.; Oates, M.A.; Petti, D.A.; Pawelko, R.J.; Smolik, G.R. [Idaho National Engineering and Environmental Lab., Idaho Falls, ID (United States)

    1998-01-01

    This paper reports the results of an experimental investigation to determine the influence of neutron irradiation effects and annealing on the chemical reactivity of beryllium exposed to steam. The work entailed measurements of the H{sub 2} generation rates for unirradiated and irradiated Be and for irradiated Be that had been previously annealed at different temperatures ranging from 450degC to 1200degC. H{sub 2} generation rates were similar for irradiated and unirradiated Be in steam-chemical reactivity experiments at temperatures between 450degC and 600degC. For irradiated Be exposed to steam at 700degC, the chemical reactivity accelerated rapidly and the specimen experienced a temperature excursion. Enhanced chemical reactivity at temperatures between 400degC and 600degC was observed for irradiated Be annealed at temperatures of 700degC and higher. This reactivity enhancement could be accounted for by the increased specific surface area resulting from development of a surface-connected porosity in the irradiated-annealed Be. (author)

  8. Novel photochemical procedure in reactive chemical barrier

    Czech Academy of Sciences Publication Activity Database

    Lipšová, Hana; Jirkovský, Jaromír; Krystyník, Pavel; Datel, J. V.

    Ostrava : VŠB - TU Ostrava, 2011. s. 83-83. ISBN 978-80-248-2441-3. [Hydrogeochémia ´11. Mezinárodní věděcké konference /13./. 14.06.2011-15.06.2011, Ostrava] Institutional support: RVO:61388955 ; RVO:67985858 Keywords : reactive chemical barriers * contamined groundwater * old environmental burdens Subject RIV: CG - Electrochemistry

  9. Reactivity of Tourmaline by Quantum Chemical Calculations

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    ZnAb initio calculations on reactivity of tourmaline were performed using both Gaussian and density function theory discrete variation method (DFT-DVM). The HF, B3LYP methods and basis sets STO-3G(3d,3p),6-31G(3d,3p) and 6-311++G(3df,3pd) were used in the calculations. The experimental results show energy value obtained from B3LYP and 6-31++1G(3df,3pd) basis sets is more accurate than those from other methods. The highest occupied molecular orbital (HOMO) of the tourmaline cluster mainly consists of O atom of hydroxyl group with relative higher energy level, suggesting that chemical bond between those of electron acceptor and this site may readily form, indicating the higher reactivity of hydroxyl group. The lowest unoccupied molecular orbital (LUMO) of the tourmaline cluster are dominantly composed of Si, O of tetrahedron and Na with relative lower energy level, suggesting that these atoms may tend to form chemical bond with those of electron donor. The results also prove that the O atoms of the tourmaline cluster have stronger reactivity than other atoms.

  10. Chemical Reactivity as Described by Quantum Chemical Methods

    OpenAIRE

    De Proft, F.; Geerlings, P.

    2002-01-01

    Abstract: Density Functional Theory is situated within the evolution of Quantum Chemistry as a facilitator of computations and a provider of new, chemical insights. The importance of the latter branch of DFT, conceptual DFT is highlighted following Parr's dictum "to calculate a molecule is not to understand it". An overview is given of the most important reactivity descriptors and the principles they are couched in. Examples are given on the evolution of the structure-property-wave function t...

  11. Chemical Reactivity as Described by Quantum Chemical Methods

    Directory of Open Access Journals (Sweden)

    F. De Proft

    2002-04-01

    Full Text Available Abstract: Density Functional Theory is situated within the evolution of Quantum Chemistry as a facilitator of computations and a provider of new, chemical insights. The importance of the latter branch of DFT, conceptual DFT is highlighted following Parr's dictum "to calculate a molecule is not to understand it". An overview is given of the most important reactivity descriptors and the principles they are couched in. Examples are given on the evolution of the structure-property-wave function triangle which can be considered as the central paradigm of molecular quantum chemistry to (for many purposes a structure-property-density triangle. Both kinetic as well as thermodynamic aspects can be included when further linking reactivity to the property vertex. In the field of organic chemistry, the ab initio calculation of functional group properties and their use in studies on acidity and basicity is discussed together with the use of DFT descriptors to study the kinetics of SN2 reactions and the regioselectivity in Diels Alder reactions. Similarity in reactivity is illustrated via a study on peptide isosteres. In the field of inorganic chemistry non empirical studies of adsorption of small molecules in zeolite cages are discussed providing Henry constants and separation constants, the latter in remarkable good agreement with experiments. Possible refinements in a conceptual DFT context are presented. Finally an example from biochemistry is discussed : the influence of point mutations on the catalytic activity of subtilisin.

  12. Compatibility and reactivity between chemical compounds and water

    International Nuclear Information System (INIS)

    Chemical product reactivity with water is often underestimated as water is incorrectly considered as an inert compound. The Fuels Experimental Station (SSC) compiled a complete research, funded by CNR National Group for Protection from Chemical Industry and Ecological Risks, about the reactivity and compatibility of several compounds with water. This article is an excerpt of the final report. Consulting databases, scientific literature, chemical industrial catalogues and material safety data sheets, more than 300 potential reactive substances have been identified. A thermodynamical evaluation has been carried out using suitable software for about half of the detected compounds (the ones for which heat of formation has been found or calculated).

  13. Chemical reactivity test for thermal stability

    Energy Technology Data Exchange (ETDEWEB)

    Prokosch, D.W.; Garcia, F.

    1994-07-01

    Lawrence Livermore National Laboratory (LLNL) has developed a thermal stability test procedure that is currently being evaluated by the Department of Defense (DOD) Explosives Safety Board as an equivalent alternate test to the DOD Technical Bulletin 700-2 {open_quotes}Thermal Stability Test at 75{degrees}C{close_quotes}. The LLNL Chemical Reactivity Test (CRT) is significantly more severe than the existing {open_quotes}Thermal Stability Test at 75{degrees}C{close_quotes} and is also quantitative in nature. It has been approved by the Department of Energy (DOE) Explosives Safety Committee as an equivalent alternate thermal stability test and has been in use by LLNL for over 30 years. It is currently used by other DOE and DOD organizations as the standard small-scale safety test for determining thermal stability and material compatibility. The LLNL CRT is run on a 0.250 gm sample for 22 hours at 120{degrees}C rather than the 50 gm sample for 48 hours at 75{degrees}C as required for the Thermal Stability Test. Thus the CRT is a much more severe test since it is run at 120{degrees}C rather than 75{degrees}C. Simple Arrhenius kinetics predict a material decomposition rate of approximately 25 times greater at 120{degrees}C than at 75{degrees}C. Any material under test that exhibits gas evolution exceeding 4 cc/gm (approximately 0.8 % decomposition) is considered suspect and additional testing and/or evaluation is then performed to determine if the material is thermally unstable. In addition to the CRT being significantly more severe and quantitative, there are significant other advantages for using the CRT. These include: (1) the increased safety afforded to operating personnel and equipment by using a fraction of the test material, (2) the cost savings associated with reduced sample heating time and the use of less sample material, and (3) the reduced amount of post-test waste produced.

  14. Geometry, chemical reactivity and Raman spectra of gold clusters

    OpenAIRE

    Ngangbam Bedamani Singh; Utpal Sarkar

    2015-01-01

    Structures, stability, and chemical reactivity of Aun (n = 2-10) clusters are investigated using density functional theory (DFT). We have studied the reactivity parameters of the clusters in terms of relevant electronic structure principles. It is observed that stability and properties are strongly dependent on the cluster size. Clusters with an even number of atoms are found to be energetically and chemically more stable than odd-numbered clusters. Electronic structure of clusters has been i...

  15. Chemical reactor modeling multiphase reactive flows

    CERN Document Server

    Jakobsen, Hugo A

    2014-01-01

    Chemical Reactor Modeling closes the gap between Chemical Reaction Engineering and Fluid Mechanics.  The second edition consists of two volumes: Volume 1: Fundamentals. Volume 2: Chemical Engineering Applications In volume 1 most of the fundamental theory is presented. A few numerical model simulation application examples are given to elucidate the link between theory and applications. In volume 2 the chemical reactor equipment to be modeled are described. Several engineering models are introduced and discussed. A survey of the frequently used numerical methods, algorithms and schemes is provided. A few practical engineering applications of the modeling tools are presented and discussed. The working principles of several experimental techniques employed in order to get data for model validation are outlined. The monograph is based on lectures regularly taught in the fourth and fifth years graduate courses in transport phenomena and chemical reactor modeling, and in a post graduate course in modern reactor m...

  16. Reactive chemical dynamics through conical intersections

    Indian Academy of Sciences (India)

    S Ghosal; B Jayachander Rao; S Mahapatra

    2007-09-01

    Reaction dynamics of prototypical, D + H2 and Cl (2P) + H2, chemical reactions occurring through the conical intersections of the respective coupled multi-sheeted potential energy surfaces is examined here. In addition to the electronic coupling, nonadiabatic effects due to relativistic spin-orbit coupling are also considered for the latter reaction. A time-dependent wave packet propagation approach is undertaken and the quantum dynamical observables viz., energy resolved reaction probabilities, integral reaction cross-sections and thermal rate constants are reported.

  17. Spinodal decomposition of chemically reactive binary mixtures

    Science.gov (United States)

    Lamorgese, A.; Mauri, R.

    2016-08-01

    We simulate the influence of a reversible isomerization reaction on the phase segregation process occurring after spinodal decomposition of a deeply quenched regular binary mixture, restricting attention to systems wherein material transport occurs solely by diffusion. Our theoretical approach follows a diffuse-interface model of partially miscible binary mixtures wherein the coupling between reaction and diffusion is addressed within the frame of nonequilibrium thermodynamics, leading to a linear dependence of the reaction rate on the chemical affinity. Ultimately, the rate for an elementary reaction depends on the local part of the chemical potential difference since reaction is an inherently local phenomenon. Based on two-dimensional simulation results, we express the competition between segregation and reaction as a function of the Damköhler number. For a phase-separating mixture with components having different physical properties, a skewed phase diagram leads, at large times, to a system converging to a single-phase equilibrium state, corresponding to the absolute minimum of the Gibbs free energy. This conclusion continues to hold for the critical phase separation of an ideally perfectly symmetric binary mixture, where the choice of final equilibrium state at large times depends on the initial mean concentration being slightly larger or less than the critical concentration.

  18. Local Chemical Reactivity of a Metal Alloy Surface

    DEFF Research Database (Denmark)

    Hammer, Bjørk; Scheffler, Matthias

    1995-01-01

    The chemical reactivity of a metal alloy surface is studied by density functional theory investigating the interaction of H2 with NiAl(110). The energy barrier for H2 dissociation is largely different over the Al and Ni sites without, however, reflecting the barriers over the single component metal...

  19. The direct peptide reactivity assay: selectivity of chemical respiratory allergens.

    Science.gov (United States)

    Lalko, Jon F; Kimber, Ian; Gerberick, G Frank; Foertsch, Leslie M; Api, Anne Marie; Dearman, Rebecca J

    2012-10-01

    It is well known that some chemicals are capable of causing allergic diseases of the skin and respiratory tract. Commonly, though not exclusively, chemical allergens are associated with the selective development of skin or respiratory sensitization. The reason for this divergence is unclear, although it is hypothesized that the nature of interactions between the chemical hapten and proteins is influential. The direct peptide reactivity assay (DPRA) has been developed as a screen for the identification of skin-sensitizing chemicals, and here we describe the use of this method to explore whether differences exist between skin and respiratory allergens with respect to their peptide-binding properties. Known skin and respiratory sensitizers were reacted with synthetic peptides containing either lysine (Lys) or cysteine (Cys) for 24 h. The samples were analyzed by HPLC/UV, and the loss of peptide from the reaction mixture was expressed as the percent depletion compared with the control. The potential for preferential reactivity was evaluated by comparing the ratio of Lys to Cys depletion (Lys:Cys ratio). The results demonstrate that the majority of respiratory allergens are reactive in the DPRA, and that in contrast to most skin-sensitizing chemicals, preferentially react with the Lys peptide. These data suggest that skin and respiratory chemical allergens can result in different protein conjugates, which may in turn influence the quality of induced immune responses. Overall, these investigations reveal that the DPRA has considerable potential to be incorporated into tiered testing approaches for the identification and characterization of chemical respiratory allergens. PMID:22713598

  20. Geometry, chemical reactivity and Raman spectra of gold clusters

    Directory of Open Access Journals (Sweden)

    Ngangbam Bedamani Singh

    2015-12-01

    Full Text Available Structures, stability, and chemical reactivity of Aun (n = 2-10 clusters are investigated using density functional theory (DFT. We have studied the reactivity parameters of the clusters in terms of relevant electronic structure principles. It is observed that stability and properties are strongly dependent on the cluster size. Clusters with an even number of atoms are found to be energetically and chemically more stable than odd-numbered clusters. Electronic structure of clusters has been investigated using partial density of states (PDOS. PDOS analysis clearly shows that energy states of highest occupied molecular orbital and lowest unoccupied molecular orbital are predominantly contributed by s orbital. From time-dependent DFT calculations, it is shown that absorption spectra of even-numbered clusters are more intense and are observed at lower wavelength region than the odd-sized gold clusters.

  1. Physical Characterization and Steam Chemical Reactivity of Carbon Fiber Composites

    Energy Technology Data Exchange (ETDEWEB)

    Anderl, Robert Andrew; Pawelko, Robert James; Smolik, Galen Richard

    2001-05-01

    This report documents experiments and analyses that have been done at the Idaho National Engineering and Environmental Laboratory (INEEL) to measure the steam chemical reactivity of two types of carbon fiber composites, NS31 and NB31, proposed for use at the divertor strike points in an ITER-like tokamak. These materials are 3D CFCs constituted by a NOVOLTEX preform and densified by pyrocarbon infiltration and heat treatment. NS31 differs from NB31 in that the final infiltration was done with liquid silicon to reduce the porosity and enhance the thermal conductivity of the CFC. Our approach in this work was twofold: (1) physical characterization measurements of the specimens and (2) measurements of the chemical reactivity of specimens exposed to steam.

  2. The unique chemical reactivity of a graphene nanoribbon's zigzag edge

    CERN Document Server

    Jiang, D; Sumpter, B G; Dai, Sheng; Jiang, De-en; Sumpter, Bobby G.

    2007-01-01

    The zigzag edge of a graphene nanoribbon possesses a unique electronic state that is near the Fermi level and localized at the edge carbon atoms. We investigate the chemical reactivity of these zigzag edge sites by examining their reaction energetics with common radicals from first principles. A "partial radical" concept for the edge carbon atoms is introduced to characterize their chemical reactivity, and the validity of this concept is verified by comparing the dissociation energies of edge-radical bonds with similar bonds in molecules. In addition, the uniqueness of the zigzag-edged graphene nanoribbon is further demonstrated by comparing it with other forms of sp2 carbons, including a graphene sheet, nanotubes, and an armchair-edged graphene nanoribbon.

  3. The Use of Chemical Reactivity Assays in Toxicity Prediction

    OpenAIRE

    ASTURIOL David; Worth, Andrew

    2011-01-01

    The use of so-called “in chemico” methodology - abiotic assays that measure chemical reactivity - is gaining ground as relevant and reliable means of toxicity prediction. In this report we explain the basis of the in chemico approach to toxicity prediction and we review the studies that have developed the concept and its practical application since the 1930s, with special attention being paid to studies aimed at the development of Quantitative Structure-Activity Relationship (QSAR) models and...

  4. Multiple species reactive chemical transport in groundwater: A verification exercise

    International Nuclear Information System (INIS)

    Two multiple-species reactive chemical transport models (FASTCHEM and DYNAMIX) were tested against each other to check for consistency of solutions. For the particular problem studied, FASTCHEM and DYNAMIX led to differences in aqueous concentrations and mineral assemblages primarily because FASTCHEM ignores redox reactions in the transport phase of the calculations. Also, the spatial concentration profiles generated by FASTCHEM tend to be sharper than those generated by DYNAMIX because FASTCHEM is particularly designed to handle advection-dominated transport systems

  5. Chemical and Mechanical Alteration of Fractured Caprock Under Reactive Flow

    Science.gov (United States)

    Elkhoury, J. E.; Ameli, P.; Detwiler, R. L.

    2013-12-01

    Permeability evolution of fractures depends on chemical and mechanical processes. Stress perturbations lead to mechanical deformation and fracture propagation that can increase formation permeability. Chemical disequilibrium between fluids and resident minerals leads to dissolution and precipitation that further alter fracture porosity and permeability. The ability to predict whether these coupled chemical and mechanical processes will enhance or diminish fracture permeability remains elusive. Here, we present results from reactive-transport experiments in fractured anhydrite cores, with significant alteration of the rock matrix, where only the flow rate differed. For high flow rate, the transformation of anhydrite to gypsum occurred uniformly within the fracture leading to compaction and a two-order-of-magnitude decrease in permeability. For low flow rate, rock-fluid reactions proceeded to near equilibrium within the fracture with preferential flow paths persisting over the 6-month duration of the experiment and a negligible change in permeability. Anticipating such permeability evolution is critical for successful geologic CO2 sequestration and waste injection. Additionally, reactive alteration of the porous matrix bounding fractures will influence the strength of earthquake fault zones. Comparison of the aperture field before (a) and after (b) the reactive flow-through experiment at low flow rate. a) Aperture field from optical profilometry measurements of the fracture surfaces. b) Inferred aperture from x-ray computed tomography scans. Color scale I (blue) denotes mainly unaltered regions of the fracture and/or aperture 200 μm) leading to negligible change in permeability after a 6-month run.

  6. Reactive solute transport in physically and chemically heterogeneous porous media with multimodal reactive mineral facies: the Lagrangian approach.

    Science.gov (United States)

    Soltanian, Mohamad Reza; Ritzi, Robert W; Dai, Zhenxue; Huang, Chao Cheng

    2015-03-01

    Physical and chemical heterogeneities have a large impact on reactive transport in porous media. Examples of heterogeneous attributes affecting reactive mass transport are the hydraulic conductivity (K), and the equilibrium sorption distribution coefficient (Kd). This paper uses the Deng et al. (2013) conceptual model for multimodal reactive mineral facies and a Lagrangian-based stochastic theory in order to analyze the reactive solute dispersion in three-dimensional anisotropic heterogeneous porous media with hierarchical organization of reactive minerals. An example based on real field data is used to illustrate the time evolution trends of reactive solute dispersion. The results show that the correlation between the hydraulic conductivity and the equilibrium sorption distribution coefficient does have a significant effect on reactive solute dispersion. The anisotropy ratio does not have a significant effect on reactive solute dispersion. Furthermore, through a sensitivity analysis we investigate the impact of changing the mean, variance, and integral scale of K and Kd on reactive solute dispersion. PMID:25532767

  7. Reactive chromophores for sensitive and selective detection of chemical warfare agents and toxic industrial chemicals

    Science.gov (United States)

    Frye-Mason, Greg; Leuschen, Martin; Wald, Lara; Paul, Kateri; Hancock, Lawrence F.

    2005-05-01

    A reactive chromophore developed at MIT exhibits sensitive and selective detection of surrogates for G-class nerve agents. This reporter acts by reacting with the agent to form an intermediate that goes through an internal cyclization reaction. The reaction locks the molecule into a form that provides a strong fluorescent signal. Using a fluorescent sensor platform, Nomadics has demonstrated rapid and sensitive detection of reactive simulants such as diethyl chloro-phosphate (simulant for sarin, soman, and related agents) and diethyl cyanophosphate (simulant for tabun). Since the unreacted chromophore does not fluoresce at the excitation wavelength used for the cyclized reporter, the onset of fluo-rescence can be easily detected. This fluorescence-based detection method provides very high sensitivity and could enable rapid detection at permissible exposure levels. Tests with potential interferents show that the reporter is very selective, with responses from only a few highly toxic, electrophilic chemicals such as phosgene, thionyl chloride, and strong acids such as HF, HCl, and nitric acid. Dimethyl methyl phosphonate (DMMP), a common and inactive simu-lant for other CW detectors, is not reactive enough to generate a signal. The unique selectivity to chemical reactivity means that a highly toxic and hazardous chemical is present when the reporter responds and illustrates that this sensor can provide very low false alarm rates. Current efforts focus on demonstrating the sensitivity and range of agents and toxic industrial chemicals detected with this reporter as well as developing additional fluorescent reporters for a range of chemical reactivity classes. The goal is to produce a hand-held sensor that can sensitively detect a broad range of chemical warfare agent and toxic industrial chemical threats.

  8. Reactive solute transport in physically and chemically heterogeneous porous media with multimodal reactive mineral facies: The Lagrangian approach

    CERN Document Server

    Soltanian, Mohamad Reza; Dai, Zhenxue; Huang, Chaocheng

    2014-01-01

    Physical and chemical heterogeneities have a large impact on reactive transport in porous media. Examples of heterogeneous attributes affecting reactive mass transport are the hydraulic conductivity (K), and the equilibrium sorption distribution coefficient (Kd). This paper uses the Deng et al. (2013) conceptual model for multimodal reactive mineral facies and a Lagrangian-based stochastic theory in order to analyze the reactive solute dispersion in three-dimensional anisotropic heterogeneous porous media with hierarchical organization of reactive minerals. An example based on real field data is used to illustrate the time evolution trends of reactive solute dispersion. The results show that the correlation between the hydraulic conductivity and the equilibrium sorption distribution coefficient does have a significant effect on reactive solute dispersion. The anisotropy ratio does not have a significant effect on reactive solute dispersion. Furthermore, through a sensitivity analysis we investigate the impact...

  9. Nonlocal reactive transport with physical, chemical, and biological heterogeneity

    Science.gov (United States)

    Hu, Bill X.; Cushman, John H.; Deng, Fei-Wen

    When a natural porous medium is viewed from an eulerian perspective, incomplete characterization of the hydraulic conductivity, chemical reactivity, and biological activity leads to nonlocal constitutive theories, irrespective of whether the medium has evolving heterogeneity with fluctuations over all scales. Within this framework a constitutive theory involving nonlocal dispersive and convective fluxes and nonlocal sources/sinks is developed for chemicals undergoing random linear nonequilibrium reactions and random equilibrium first-order decay in a random conductivity field. The resulting transport equations are solved exactly in Fourier-Laplace space and then numerically inverted to real space. Mean concentration contours and various spatial moments are presented graphically for several covariance structures. 1997 Published by Elsevier Science Ltd. All rights reserved

  10. To Model Chemical Reactivity in Heterogeneous Emulsions, Think Homogeneous Microemulsions.

    Science.gov (United States)

    Bravo-Díaz, Carlos; Romsted, Laurence Stuart; Liu, Changyao; Losada-Barreiro, Sonia; Pastoriza-Gallego, Maria José; Gao, Xiang; Gu, Qing; Krishnan, Gunaseelan; Sánchez-Paz, Verónica; Zhang, Yongliang; Dar, Aijaz Ahmad

    2015-08-25

    Two important and unsolved problems in the food industry and also fundamental questions in colloid chemistry are how to measure molecular distributions, especially antioxidants (AOs), and how to model chemical reactivity, including AO efficiency in opaque emulsions. The key to understanding reactivity in organized surfactant media is that reaction mechanisms are consistent with a discrete structures-separate continuous regions duality. Aggregate structures in emulsions are determined by highly cooperative but weak organizing forces that allow reactants to diffuse at rates approaching their diffusion-controlled limit. Reactant distributions for slow thermal bimolecular reactions are in dynamic equilibrium, and their distributions are proportional to their relative solubilities in the oil, interfacial, and aqueous regions. Our chemical kinetic method is grounded in thermodynamics and combines a pseudophase model with methods for monitoring the reactions of AOs with a hydrophobic arenediazonium ion probe in opaque emulsions. We introduce (a) the logic and basic assumptions of the pseudophase model used to define the distributions of AOs among the oil, interfacial, and aqueous regions in microemulsions and emulsions and (b) the dye derivatization and linear sweep voltammetry methods for monitoring the rates of reaction in opaque emulsions. Our results show that this approach provides a unique, versatile, and robust method for obtaining quantitative estimates of AO partition coefficients or partition constants and distributions and interfacial rate constants in emulsions. The examples provided illustrate the effects of various emulsion properties on AO distributions such as oil hydrophobicity, emulsifier structure and HLB, temperature, droplet size, surfactant charge, and acidity on reactant distributions. Finally, we show that the chemical kinetic method provides a natural explanation for the cut-off effect, a maximum followed by a sharp reduction in AO efficiency with

  11. Steam chemical reactivity of Be pebbles and Be powder

    International Nuclear Information System (INIS)

    This paper reports the results of chemical reactivity experiments for Be pebbles (2 and 0.2 mm diameter) and Be powder (14-31 μm diameter) exposed to steam at elevated temperatures, 350-900 deg. C for pebbles and 400-500 deg. C for powders. We measured BET specific surface areas of 0.12 m2/g for 2 mm pebbles, 0.24 m2/g for 0.2 mm pebbles and 0.66-1.21 m2/g for Be powder samples. These experiments showed a complex reactivity behavior for the material, dependent primarily on the test temperature. Average H2 generation rates for powder samples, based on measured BET surface areas, were in good agreement with previous measurements for fully dense consolidated powder metallurgy (CPM)-Be. Rates for the Be pebbles, based on measured BET surface areas, were systematically lower than the CPM-Be rates, possibly because of different surface and bulk features for the pebbles, especially surface layer impurities, that contribute to the measured BET surface area and influence the oxidation process at the material surface

  12. Assessment of the extended Koopmans' theorem for the chemical reactivity: Accurate computations of chemical potentials, chemical hardnesses, and electrophilicity indices.

    Science.gov (United States)

    Yildiz, Dilan; Bozkaya, Uğur

    2016-01-30

    The extended Koopmans' theorem (EKT) provides a straightforward way to compute ionization potentials and electron affinities from any level of theory. Although it is widely applied to ionization potentials, the EKT approach has not been applied to evaluation of the chemical reactivity. We present the first benchmarking study to investigate the performance of the EKT methods for predictions of chemical potentials (μ) (hence electronegativities), chemical hardnesses (η), and electrophilicity indices (ω). We assess the performance of the EKT approaches for post-Hartree-Fock methods, such as Møller-Plesset perturbation theory, the coupled-electron pair theory, and their orbital-optimized counterparts for the evaluation of the chemical reactivity. Especially, results of the orbital-optimized coupled-electron pair theory method (with the aug-cc-pVQZ basis set) for predictions of the chemical reactivity are very promising; the corresponding mean absolute errors are 0.16, 0.28, and 0.09 eV for μ, η, and ω, respectively. PMID:26458329

  13. Lunar Dust Chemical, Electrical, and Mechanical Reactivity: Simulation and Characterization

    Science.gov (United States)

    VanderWal, Randy L.

    2008-01-01

    Lunar dust is recognized to be a highly reactive material in its native state. Many, if not all Constellation systems will be affected by its adhesion, abrasion, and reactivity. A critical requirement to develop successful strategies for dealing with lunar dust and designing tolerant systems will be to produce similar material for ground-based testing.

  14. Conservative or reactive? Mechanistic chemical perspectives on organic matter stability

    Science.gov (United States)

    Koch, Boris

    2016-04-01

    Carbon fixation by terrestrial and marine primary production has a fundamental seasonal effect on the atmospheric carbon content and it profoundly contributes to long-term carbon storage in form of organic matter (OM) in soils, water, and sediments. The efficacy of this sequestration process strongly depends on the degree of OM persistence. Therefore, one of the key issues in dissolved and particulate OM research is to assess the stability of reservoirs and to quantify their contribution to global carbon fluxes. Incubation experiments are helpful to assess OM stability during the first, early diagenetic turnover induced by sunlight or microbes. However, net carbon fluxes within the global carbon cycle also act on much longer time scales, which are not amenable in experiments. It is therefore critical to improve our mechanistic understanding to be able to assess potential future changes in the organic matter cycle. This session contribution highlights some achievements and open questions in the field. An improved mechanistic understanding of OM turnover particularly depends on the molecular characterization of biogeochemical processes and their kinetics: (i) in soils and sediments, aggregation/disaggregation of OM is primarily controlled by its molecular composition. Hence, the chemical composition determines the transfer of organic carbon from the large particulate to the small dissolved organic matter reservoir - an important substrate for microbial metabolism. (ii) In estuaries, dissolved organic carbon gradients usually suggest conservative behavior, whereas molecular-level studies reveal a substantial chemical modification of terrestrial DOM along the land-ocean interface. (iii) In the ocean, previous studies have shown that the recalcitrance of OM depends on bulk concentration and energy yield. However, ultrahigh resolution mass spectrometry in combination with radiocarbon analyses also emphasized that stability is tightly connected to molecular composition

  15. On the Inclusion of Inorganic Chemical Reactivity in High School Chemistry: The Reactivity Network.

    Science.gov (United States)

    Mellon, E. K.

    1989-01-01

    Reports the function of the Reactivity Network which is to translate reactivity data from the primary literature into some 30 reviews for high school teachers and curriculum developers and to disseminate that information nationwide. Discusses a needs assessment done for the project. (MVL)

  16. Chemical reactivity of alkali lignin modified with laccase

    International Nuclear Information System (INIS)

    The modification of alkali lignin with laccase was investigated. The structural change of lignin was analyzed. The sulfonation reactivity was measured by the content of sulfonic group. The results showed the sulfonation reactivity increased to some extent under the condition of atmosphere pressure, but decreased under the condition of 0.3 MPa oxygen pressure. The analysis of Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR) and gel permeation chromatography (GPC) showed the cleavage of various ether linkages and demethylation took place in the structure of lignin to certain extent during modification with laccase, which contributed to the improvement of sulfonation reactivity. Under the condition of 0.3 MPa oxygen pressure, the ratio of s/g (guaiacyl/syringyl) increased after modification, which reduced the sulfonation reactivity of lignin. Simultaneously partial polymerization reaction, such as 4-O-5′, β-5, 5-5 and other reaction in the aromatic ring decreased the activity sites of C2, C5 and C6. Abundant polymerization reaction of α-O increased steric hindrance of C2 and C6 in aromatic ring, resulting in low sulfonation reactivity of lignin. -- Highlights: ► The modification of alkali lignin with laccase was investigated. ► The sulfonation reactivity increased under the condition of atmosphere pressure. ► More content of guaiacyl and hydroxy, the less content of methoxyl, syringyl can enhance the sulfonation reactivity of lignin. ► Partial moieties polymerized each other with α-O linkgages during treatment with laccase under oxygen pressure. ► The steric hindrance on C2 and C6 in aromatic ring resulted in low sulfonation reaction reactivity of lignin

  17. Large-eddy simulation of chemically reactive pollutant transport from a point source in urban area

    OpenAIRE

    Du, T; Liu, CH

    2013-01-01

    Most air pollutants are chemically reactive so using inert scalar as the tracer in pollutant dispersion modelling would often overlook their impact on urban inhabitants. In this study, large-eddy simulation (LES) is used to examine the plume dispersion of chemically reactive pollutants in a hypothetical atmospheric boundary layer (ABL) in neutral stratification. The irreversible chemistry mechanism of ozone (O3) titration is integrated into the LES model. Nitric oxide (NO) is emitted from an ...

  18. Chemical reactivity of the compressed noble gas atoms and their reactivity dynamics during collisions with protons

    Indian Academy of Sciences (India)

    P K Chattaraj; B Maiti; U Sarkar

    2003-06-01

    Attempts are made to gain insights into the effect of confinement of noble gas atoms on their various reactivity indices. Systems become harder, less polarizable and difficult to excite as the compression increases. Ionization also causes similar effects. A quantum fluid density functional technique is adopted in order to study the dynamics of reactivity parameters during a collision between protons and He atoms in different electronic states for various projectile velocities and impact parameters. Dynamical variants of the principles of maximum hardness, minimum polarizability and maximum entropy are found to be operative.

  19. Strategies and chemical design approaches to reduce the potential for formation of reactive metabolic species.

    Science.gov (United States)

    Argikar, Upendra A; Mangold, James B; Harriman, Shawn P

    2011-01-01

    Metabolic activation of new chemical entities to reactive intermediates is routinely monitored in drug discovery and development. Reactive intermediates may bind to cellular macromolecules such as proteins, DNA and may eventually lead to cell death via necrosis, apoptosis or oxidative stress. The evidence that the ultimate outcome of metabolic activation is an adverse drug reaction manifested as in vivo toxicity, is at best circumstantial. However, understanding the process of bioactivation of structural alerts by trapping the reactive intermediates is critical to guide medicinal chemistry efforts in quest for safer and potent molecules. This commentary provides a brief introduction to adverse drug reactions and mechanisms of reactive intermediate formation for various functional groups, followed by a review of chemical design approaches, examples of such strategies, possible isosteric replacements for structural alerts and rationalization of laboratory approaches to determine reactive intermediates, as a guide to today's medicinal chemist. PMID:21320068

  20. Models for risk assessment of reactive chemicals in aquatic toxicology

    NARCIS (Netherlands)

    Freidig, Andreas Peter

    2001-01-01

    A quantitative structure property relationship (QSPR) for a,b-unsaturated carboxylates (mainly acrylates and methacrylates) was established in chapter 2. Chemical reaction rate constants were measured for 12 different chemicals with three different nucleophiles, namely H 2 O, OH - and glutathione (G

  1. Chemical reactivity of CVC and CVD SiC with UO2 at high temperatures

    International Nuclear Information System (INIS)

    Two types of silicon carbide (SiC) synthesized using two different vapor deposition processes were embedded in UO2 pellets and evaluated for their potential chemical reaction with UO2. While minor reactivity between chemical-vapor-composited (CVC) SiC and UO2 was observed at comparatively low temperatures of 1100 and 1300 °C, chemical-vapor-deposited (CVD) SiC did not show any such reactivity. However, both CVD and CVC SiCs showed some reaction with UO2 at a higher temperature (1500 °C). Elemental maps supported by phase maps obtained using electron backscatter diffraction indicated that CVC SiC was more reactive than CVD SiC at 1500 °C. Furthermore, this investigation indicated the formation of uranium carbides and uranium silicide chemical phases such as UC, USi2, and U3Si2 as a result of SiC reaction with UO2

  2. Metabolic activation of chemical carcinogens to reactive electrophiles

    International Nuclear Information System (INIS)

    Ionizing radiations and ultraviolet light constitute the principal known physical carcinogens. Likewise, a great variety and large number of chemicals and over 50 DNA and RNA viruses comprise the known chemical and viral carcinogens. These three categories of carcinogenic agents include the great majority of extrinsic agents known to induce cancer in mammals. Man is clearly susceptible to the action of physical and chemical carcinogens and, indeed, was the first species in which the activities of some of these agents were demonstated. It seems certain that viral carcinogenic information is involved in the etiology of at least some human tumors, but ethical and methodological problems have made it difficult to obtain unequivocal data. Given the long availability of experimental carcinogens of these three classes, there is surprisingly little known of their interrelationships in the production of cancer in experimental animals. The objective of this brief review is to present some salient aspects of experimental chemical carcinogenesis and an analysis of how some of these features relate to the mechanisms of action of radiation carcinogens

  3. Accelerating Wave Function Convergence in Interactive Quantum Chemical Reactivity Studies

    CERN Document Server

    Mühlbach, Adrian H; Reiher, Markus

    2015-01-01

    The inherently high computational cost of iterative self-consistent-field (SCF) methods proves to be a critical issue delaying visual and haptic feedback in real-time quantum chemistry. In this work, we introduce two schemes for SCF acceleration. They provide a guess for the initial density matrix of the SCF procedure generated by extrapolation techniques. SCF optimizations then converge in fewer iterations, which decreases the execution time of the SCF optimization procedure. To benchmark the proposed propagation schemes, we developed a test bed for performing quantum chemical calculations on sequences of molecular structures mimicking real-time quantum chemical explorations. Explorations of a set of six model reactions employing the semi-empirical methods PM6 and DFTB3 in this testing environment showed that the proposed propagation schemes achieved speedups of up to thirty percent as a consequence of a reduced number of SCF iterations.

  4. Accelerating Wave Function Convergence in Interactive Quantum Chemical Reactivity Studies.

    Science.gov (United States)

    Mühlbach, Adrian H; Vaucher, Alain C; Reiher, Markus

    2016-03-01

    The inherently high computational cost of iterative self-consistent field (SCF) methods proves to be a critical issue delaying visual and haptic feedback in real-time quantum chemistry. In this work, we introduce two schemes for SCF acceleration. They provide a guess for the initial density matrix of the SCF procedure generated by extrapolation techniques. SCF optimizations then converge in fewer iterations, which decreases the execution time of the SCF optimization procedure. To benchmark the proposed propagation schemes, we developed a test bed for performing quantum chemical calculations on sequences of molecular structures mimicking real-time quantum chemical explorations. Explorations of a set of six model reactions employing the semi-empirical methods PM6 and DFTB3 in this testing environment showed that the proposed propagation schemes achieved speedups of up to 30% as a consequence of a reduced number of SCF iterations. PMID:26788887

  5. Reactive formulations for a neutralization of toxic industrial chemicals

    Energy Technology Data Exchange (ETDEWEB)

    Tucker, Mark D. (Albuqueruqe, NM); Betty, Rita G. (Rio Rancho, NM)

    2006-10-24

    Decontamination formulations for neutralization of toxic industrial chemicals, and methods of making and using same. The formulations are effective for neutralizing malathion, hydrogen cyanide, sodium cyanide, butyl isocyanate, carbon disulfide, phosgene gas, capsaicin in commercial pepper spray, chlorine gas, anhydrous ammonia gas; and may be effective at neutralizing hydrogen sulfide, sulfur dioxide, formaldehyde, ethylene oxide, methyl bromide, boron trichloride, fluorine, tetraethyl pyrophosphate, phosphorous trichloride, arsine, and tungsten hexafluoride.

  6. Solution-phase synthesis of inorganic nanostructures by chemical transformation from reactive templates

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The solution-phase synthesis by chemical transformation from reactive templates has proved to be very effective in morphology-controlled synthesis of inorganic nanostructures. This review paper summarizes the recent progress in solution-phase synthesis of one-dimensional and hollow inorganic nanostructures via reactive templates, focusing on the approaches developed in our lab. The formation mechanisms based on reactive templates are discussed in depth to show the general concepts for the preparation processes. An outlook on the future development in this area is also presented.

  7. Importance of asparagine on the conformational stability and chemical reactivity of selected anti-inflammatory peptides

    Energy Technology Data Exchange (ETDEWEB)

    Soriano-Correa, Catalina, E-mail: csorico@comunidad.unam.mx [Química Computacional, Facultad de Estudios Superiores (FES)-Zaragoza, Universidad Nacional Autónoma de México (UNAM), Iztapalapa, C.P. 09230 México, D.F. (Mexico); Barrientos-Salcedo, Carolina [Laboratorio de Química Médica y Quimiogenómica, Facultad de Bioanálisis Campus Veracruz-Boca del Río, Universidad Veracruzana, C.P. 91700 Veracruz (Mexico); Campos-Fernández, Linda; Alvarado-Salazar, Andres [Química Computacional, Facultad de Estudios Superiores (FES)-Zaragoza, Universidad Nacional Autónoma de México (UNAM), Iztapalapa, C.P. 09230 México, D.F. (Mexico); Esquivel, Rodolfo O. [Departamento de Química, Universidad Autónoma Metropolitana-Iztapalapa (UAM-Iztapalapa), C.P. 09340 México, D.F. (Mexico)

    2015-08-18

    Highlights: • Asparagine plays an important role to anti-inflammatory effect of peptides. • The electron-donor substituent groups favor the formation of the hydrogen bonds, which contribute in the structural stability of peptides. • Chemical reactivity and the physicochemical features are crucial in the biological functions of peptides. - Abstract: Inflammatory response events are initiated by a complex series of molecular reactions that generate chemical intermediaries. The structure and properties of peptides and proteins are determined by the charge distribution of their side chains, which play an essential role in its electronic structure and physicochemical properties, hence on its biological functionality. The aim of this study was to analyze the effect of changing one central amino acid, such as substituting asparagine for aspartic acid, from Cys–Asn–Ser in aqueous solution, by assessing the conformational stability, physicochemical properties, chemical reactivity and their relationship with anti-inflammatory activity; employing quantum-chemical descriptors at the M06-2X/6-311+G(d,p) level. Our results suggest that asparagine plays a more critical role than aspartic acid in the structural stability, physicochemical features, and chemical reactivity of these tripeptides. Substituent groups in the side chain cause significant changes on the conformational stability and chemical reactivity, and consequently on their anti-inflammatory activity.

  8. Importance of asparagine on the conformational stability and chemical reactivity of selected anti-inflammatory peptides

    International Nuclear Information System (INIS)

    Highlights: • Asparagine plays an important role to anti-inflammatory effect of peptides. • The electron-donor substituent groups favor the formation of the hydrogen bonds, which contribute in the structural stability of peptides. • Chemical reactivity and the physicochemical features are crucial in the biological functions of peptides. - Abstract: Inflammatory response events are initiated by a complex series of molecular reactions that generate chemical intermediaries. The structure and properties of peptides and proteins are determined by the charge distribution of their side chains, which play an essential role in its electronic structure and physicochemical properties, hence on its biological functionality. The aim of this study was to analyze the effect of changing one central amino acid, such as substituting asparagine for aspartic acid, from Cys–Asn–Ser in aqueous solution, by assessing the conformational stability, physicochemical properties, chemical reactivity and their relationship with anti-inflammatory activity; employing quantum-chemical descriptors at the M06-2X/6-311+G(d,p) level. Our results suggest that asparagine plays a more critical role than aspartic acid in the structural stability, physicochemical features, and chemical reactivity of these tripeptides. Substituent groups in the side chain cause significant changes on the conformational stability and chemical reactivity, and consequently on their anti-inflammatory activity

  9. Effect of mechanical activation on structure changes and reactivity in further chemical modification of lignin.

    Science.gov (United States)

    Zhao, Xiaohong; Zhang, Yanjuan; Hu, Huayu; Huang, Zuqiang; Yang, Mei; Chen, Dong; Huang, Kai; Huang, Aimin; Qin, Xingzhen; Feng, Zhenfei

    2016-10-01

    Lignin was treated by mechanical activation (MA) in a customized stirring ball mill, and the structure and reactivity in further esterification were studied. The chemical structure and morphology of MA-treated lignin and the esterified products were analyzed by chemical analysis combined with UV/vis spectrometer, FTIR,NMR, SEM and particle size analyzer. The results showed that MA contributed to the increase of aliphatic hydroxyl, phenolic hydroxyl, carbonyl and carboxyl groups but the decrease of methoxyl groups. Moreover, MA led to the decrease of particle size and the increase of specific surface area and roughness of surface in lignin. The reactivity of lignin was enhanced significantly for the increase of hydroxyl content and the improvement of mass transfer in chemical reaction caused by the changes of molecular structure and morphological structure. The process of MA is green and simple, and is an effective method for enhancing the reactivity of lignin. PMID:27344951

  10. Steam chemical reactivity of plasma-sprayed beryllium

    Energy Technology Data Exchange (ETDEWEB)

    Anderl, R.A.; Pawelko, R.J.; Smolik, G.R. [Lockheed Martin Idaho Technologies Co., Idaho Falls, ID (United States). Idaho National Engineering and Environmental Lab.; Castro, R.G. [Los Alamos National Lab., NM (United States)

    1998-07-01

    Plasma-spraying with the potential for in-situ repair makes beryllium a primary candidate for plasma facing and structural components in experimental magnetic fusion machines. Deposits with good thermal conductivity and resistance to thermal cycling have been produced with low pressure plasma-spraying (LPPS). A concern during a potential accident with steam ingress is the amount of hydrogen produced by the reactions of steam with hot components. In this study the authors measure the reaction rates of various deposits produced by LPPS with steam from 350 C to above 1,000 C. They correlate these reaction rates with measurements of density, open porosity and BET surface areas. They find the reactivity to be largely dependent upon effective surface area. Promising results were obtained below 600 C from a 94% theoretical dense (TD) deposit with a BET specific surface area of 0.085 m{sup 2}/g. Although reaction rates were higher than those for dense consolidated beryllium they were substantially lower, i.e., about two orders of magnitude, than those obtained from previously tested lower density plasma-sprayed deposits.

  11. Transport of reactive chemicals in sediment-laden streams

    Science.gov (United States)

    Revelli, R.; Ridolfi, L.

    This paper deals with the transport of chemicals in a turbulent stream when both sorbing suspended load and decay reactions are present. These conditions, which can be found quite commonly in rivers, give rise to interesting behaviour. Important and not trivial processes are added and interact with the classical diffusive, advective, and dispersive mechanisms. Due to the sorption process, the chemical divides into an aqueous and a sorbed phase which follow different evolutions: the aqueous phase is regulated by turbulent diffusion, advection and shear, while the sorbed one undergoes the same fluid dynamic mechanisms but through the evolution of suspended sediment, which is also subjected to sedimentation. The evolutions of the two phases are not separate, as the sorption-desorption exchanges between the aqueous and sorbed phases connect their dynamics. In turn, the decay reactions, being able to modify the concentrations in the two phases, influence the sorption process and therefore the entire transport dynamics. A complex picture results where several nonlinear interactions occur. The main objective of the work is to obtain the one-dimensional partial differential equation that describes the temporal and spatial dynamics of the depth-averaged concentration of the chemical. Due to the existence of three well separated time scales in the whole transport process, the mathematical homogenization theory is adopted to average the two-dimensional model, and the most general case is dealt with in which sediment transport is unsteady while the reactions are nonlinear and different for the aqueous and sorbed phases. Finally, some examples of real cases are discussed where the influence of unsteady suspended sediment dynamics and the nonlinearity of reactions is analyzed, while the role of the several nonlinear differential terms in the model is highlighted.

  12. Modeling turbulence structure. Chemical kinetics interaction in turbulent reactive flows

    Energy Technology Data Exchange (ETDEWEB)

    Magnussen, B.F. [The Norwegian Univ. of Science and Technology, Trondheim (Norway)

    1997-12-31

    The challenge of the mathematical modelling is to transfer basic physical knowledge into a mathematical formulation such that this knowledge can be utilized in computational simulation of practical problems. The combustion phenomena can be subdivided into a large set of interconnected phenomena like flow, turbulence, thermodynamics, chemical kinetics, radiation, extinction, ignition etc. Combustion in one application differs from combustion in another area by the relative importance of the various phenomena. The difference in fuel, geometry and operational conditions often causes the differences. The computer offers the opportunity to treat the individual phenomena and their interactions by models with wide operational domains. The relative magnitude of the various phenomena therefore becomes the consequence of operational conditions and geometry and need not to be specified on the basis of experience for the given problem. In mathematical modelling of turbulent combustion, one of the big challenges is how to treat the interaction between the chemical reactions and the fluid flow i.e. the turbulence. Different scientists adhere to different concepts like the laminar flamelet approach, the pdf approach of the Eddy Dissipation Concept. Each of these approaches offers different opportunities and problems. All these models are based on a sound physical basis, however none of these have general validity in taking into consideration all detail of the physical chemical interaction. The merits of the models can only be judged by their ability to reproduce physical reality and consequences of operational and geometric conditions in a combustion system. The presentation demonstrates and discusses the development of a coherent combustion technology for energy conversion and safety based on the Eddy Dissipation Concept by Magnussen. (author) 30 refs.

  13. The effects of hazardous ions adsorption on the morphological and chemical properties of reactive cloth filter

    Energy Technology Data Exchange (ETDEWEB)

    Othman, Sameh H. [Nuclear Research Center, Atomic Energy Authority (Egypt)], E-mail: othman_sameh@yahoo.com; Sohsah, Moustfa A.; Ghoneim, Mohammad M. [Nuclear Research Center, Atomic Energy Authority (Egypt)

    2009-11-15

    Reactive cloth filter is fabricated by grafting of acrylonitrile/methacrylic acid onto cotton cloth, using mutual irradiation technique and the subsequent amidoximation of the reactive intermediate nitrile groups. The incorporation of the amidoxime/carboxyl groups was confirmed by different techniques. The effect of the hazardous ions chelation from radioactive waste on the morphological and chemical structure was studied. The cloth filter possessed good morphological and chemical stability suitable for practical use. The fabricated cloth filter can be used for low-level radioactive waste treatments.

  14. The effects of hazardous ions adsorption on the morphological and chemical properties of reactive cloth filter

    International Nuclear Information System (INIS)

    Reactive cloth filter is fabricated by grafting of acrylonitrile/methacrylic acid onto cotton cloth, using mutual irradiation technique and the subsequent amidoximation of the reactive intermediate nitrile groups. The incorporation of the amidoxime/carboxyl groups was confirmed by different techniques. The effect of the hazardous ions chelation from radioactive waste on the morphological and chemical structure was studied. The cloth filter possessed good morphological and chemical stability suitable for practical use. The fabricated cloth filter can be used for low-level radioactive waste treatments.

  15. Effective reactive surface area: An anisotropic property of physically and chemically heterogeneous porous media

    International Nuclear Information System (INIS)

    Although transport calculations are often formulated in terms of mass-based isotropic distribution coefficients, it is the abundance of reactive surface areas of subsurface materials that controls contaminant adsorption. In water-saturated homogeneous systems devoid of advective fluxes (e.g., batch experiments), the available reactive surface area is similar to the total surface area (as measured by conventional methods such as BET gas adsorption). However, in physically and chemically heterogeneous systems with advective fluxes, the effective reactive surface area (i.e., the surface area that a packet of advecting water interacts with) is smaller than the laboratory measured surface area and is a complex function of advective velocity and the correlation structures of the physical and chemical heterogeneities. Theoretical derivations for an important but simple type of heterogeneity (fine-scale horizontal layering) suggest that the effective reactive surface area is an anisotropic property of the medium and is inversely correlated with the anisotropy in hydraulic conductivity. The implications of reactive transport anisotropy include the concept that the retardation factor should be treated as a directional property rather than being treated as a constant. Furthermore, because of the inverse relationship between effective reactive surface area and hydraulic conductivity, batch adsorption experiments tend to overestimate the retention of contaminants relative to intact natural materials

  16. Chemical Characterization and Reactivity of Fuel-Oxidizer Reaction Product

    Science.gov (United States)

    David, Dennis D.; Dee, Louis A.; Beeson, Harold D.

    1997-01-01

    Fuel-oxidizer reaction product (FORP), the product of incomplete reaction of monomethylhydrazine and nitrogen tetroxide propellants prepared under laboratory conditions and from firings of Shuttle Reaction Control System thrusters, has been characterized by chemical and thermal analysis. The composition of FORP is variable but falls within a limited range of compositions that depend on three factors: the fuel-oxidizer ratio at the time of formation; whether the composition of the post-formation atmosphere is reducing or oxidizing; and the reaction or post-reaction temperature. A typical composition contains methylhydrazinium nitrate, ammonium nitrate, methylammonium nitrate, and trace amounts of hydrazinium nitrate and 1,1-dimethylhydrazinium nitrate. Thermal decomposition reactions of the FORP compositions used in this study were unremarkable. Neither the various compositions of FORP, the pure major components of FORP, nor mixtures of FORP with propellant system corrosion products showed any unusual thermal activity when decomposed under laboratory conditions. Off-limit thruster operations were simulated by rapid mixing of liquid monomethylhydrazine and liquid nitrogen tetroxide in a confined space. These tests demonstrated that monomethylhydrazine, methylhydrazinium nitrate, ammonium nitrate, or Inconel corrosion products can induce a mixture of monomethylhydrazine and nitrogen tetroxide to produce component-damaging energies. Damaging events required FORP or metal salts to be present at the initial mixing of monomethylhydrazine and nitrogen tetroxide.

  17. Lymphocyte reactivity of workers exposed to carcinogenic and non-carcinogenic chemicals.

    OpenAIRE

    Kumar, S.; Taylor, G; Hurst, W; Wilson, P.; Costello, C B

    1981-01-01

    Immunological studies have shown an increased lymphocyte reactivity in patients with early stage bladder cancer and individuals with pre-stage T1 exposed to bladder carcinogens (2-naphthylamine and industrial 1-naphthylamine containing 4-8% 2-naphthylamine) before 1952-that is, those at high risk of developing bladder cancer. Because of the close chemical similarity of Tobias acid (2-naphthylamine-1 sulphonic acid) to 2-naphthylamine, the lymphocytotoxicity of workers exposed to this chemical...

  18. Unifying principles of irreversibility minimization for efficiency maximization in steady-flow chemically-reactive engines

    International Nuclear Information System (INIS)

    Systems research has led to the conception and development of various steady-flow, chemically-reactive, engine cycles for stationary power generation and propulsion. However, the question that remains unanswered is: What is the maximum-efficiency steady-flow chemically-reactive engine architecture permitted by physics? On the one hand the search for higher-efficiency cycles continues, often involving newer processes and devices (fuel cells, carbon separation, etc.); on the other hand the design parameters for existing cycles are continually optimized in response to improvements in device engineering. In this paper we establish that any variation in engine architecture—parametric change or process-sequence change—contributes to an efficiency increase via one of only two possible ways to minimize total irreversibility. These two principles help us unify our understanding from a large number of parametric analyses and cycle-optimization studies for any steady-flow chemically-reactive engine, and set a framework to systematically identify maximum-efficiency engine architectures. - Highlights: • A unified thermodynamic model to study chemically-reactive engine architectures is developed. • All parametric analyses of efficiency are unified by two irreversibility-minimization principles. • Variations in internal energy transfers yield a net work increase that is greater than engine irreversibility reduced. • Variations in external energy transfers yield a net work increase that is lesser than engine irreversibility reduced

  19. Test results of chemical reactivity test (CRT) analysis of structural materials and explosives

    Energy Technology Data Exchange (ETDEWEB)

    Back, P.S.; Barnhart, B.V.; Walters, R.R.; Haws, L.D.; Collins, L.W.

    1980-03-21

    The chemical reactivity test, CRT, is a procedure used to screen the compatibility of component structure materials with explosives. This report contains the results of CRT materials evaluations conducted at Mound Facility. Data about materials combinations are catalogued both under the name of the explosive and the nonexplosive.

  20. Self-Decontaminating Fibrous Materials Reactive toward Chemical Threats.

    Science.gov (United States)

    Bromberg, Lev; Su, Xiao; Martis, Vladimir; Zhang, Yunfei; Hatton, T Alan

    2016-07-13

    Polymers that possess highly nucleophilic pyrrolidinopyridine (Pyr) and primary amino (vinylamine, VAm) groups were prepared by free-radical copolymerization of N,N-diallylpyridin-4-amine (DAAP) and N-vinylformamide (NVF) followed by acidic hydrolysis of NVF into VAm. The resulting poly(DAAP-co-VAm-co-NVF) copolymers were water-soluble and reacted with water-dispersible polyurethane possessing a high content of unreacted isocyanate groups. Spray-coating of the nylon-cotton (NYCO), rayon, and poly(p-phenylene terephthalamide) (Kevlar 119) fibers pretreated with phosphoric acid resulted in covalent bonding of the polyurethane with the hydroxyl groups on the fiber surface. A second spray-coating of aqueous solutions of poly(DAAP-co-VAm-co-NVF) on the polyurethane-coated fiber enabled formation of urea linkages between unreacted isocyanate groups of the polyurethane layer and the amino groups of poly(DAAP-co-VAm-co-NVF). Fibers with poly(DAAP-co-VAm-co-NVF) attached were compared with fibers modified by adsorption of water-insoluble poly(butadiene-co-pyrrolidinopyridine) (polyBPP) in terms of the stability against polymer leaching in aqueous washing applications. While the fibers modified by attachment of poly(DAAP-co-VAm-co-NVF) exhibited negligible polymer leaching, over 65% of adsorbed polyBPP detached and leached from the fibers within 7 days. Rayon fibers modified by poly(DAAP-co-VAm-co-NVF) were tested for sorption of dimethyl methylphosphonate (DMMP) in the presence of moisture using dynamic vapor sorption technique. Capability of the fibers modified with poly(DAAP-co-VAm-co-NVF) to facilitate hydrolysis of the sorbed DMMP in the presence of moisture was uncovered. The self-decontaminating property of the modified fibers against chemical threats was tested using a CWA simulant diisopropylfluorophosphate (DFP) in aqueous media at pH 8.7. Fibers modified with poly(DAAP-co-VAm-co-NVF) facilitated hydrolysis of DFP with the half-lives up to an order of magnitude

  1. Importance of asparagine on the conformational stability and chemical reactivity of selected anti-inflammatory peptides

    Science.gov (United States)

    Soriano-Correa, Catalina; Barrientos-Salcedo, Carolina; Campos-Fernández, Linda; Alvarado-Salazar, Andres; Esquivel, Rodolfo O.

    2015-08-01

    Inflammatory response events are initiated by a complex series of molecular reactions that generate chemical intermediaries. The structure and properties of peptides and proteins are determined by the charge distribution of their side chains, which play an essential role in its electronic structure and physicochemical properties, hence on its biological functionality. The aim of this study was to analyze the effect of changing one central amino acid, such as substituting asparagine for aspartic acid, from Cys-Asn-Ser in aqueous solution, by assessing the conformational stability, physicochemical properties, chemical reactivity and their relationship with anti-inflammatory activity; employing quantum-chemical descriptors at the M06-2X/6-311+G(d,p) level. Our results suggest that asparagine plays a more critical role than aspartic acid in the structural stability, physicochemical features, and chemical reactivity of these tripeptides. Substituent groups in the side chain cause significant changes on the conformational stability and chemical reactivity, and consequently on their anti-inflammatory activity.

  2. Computational Study of Chemical Reactivity Using Information-Theoretic Quantities from Density Functional Reactivity Theory for Electrophilic Aromatic Substitution Reactions.

    Science.gov (United States)

    Wu, Wenjie; Wu, Zemin; Rong, Chunying; Lu, Tian; Huang, Ying; Liu, Shubin

    2015-07-23

    The electrophilic aromatic substitution for nitration, halogenation, sulfonation, and acylation is a vastly important category of chemical transformation. Its reactivity and regioselectivity is predominantly determined by nucleophilicity of carbon atoms on the aromatic ring, which in return is immensely influenced by the group that is attached to the aromatic ring a priori. In this work, taking advantage of recent developments in quantifying nucleophilicity (electrophilicity) with descriptors from the information-theoretic approach in density functional reactivity theory, we examine the reactivity properties of this reaction system from three perspectives. These include scaling patterns of information-theoretic quantities such as Shannon entropy, Fisher information, Ghosh-Berkowitz-Parr entropy and information gain at both molecular and atomic levels, quantitative predictions of the barrier height with both Hirshfeld charge and information gain, and energetic decomposition analyses of the barrier height for the reactions. To that end, we focused in this work on the identity reaction of the monosubstituted-benzene molecule reacting with hydrogen fluoride using boron trifluoride as the catalyst in the gas phase. We also considered 19 substituting groups, 9 of which are ortho/para directing and the other 9 meta directing, besides the case of R = -H. Similar scaling patterns for these information-theoretic quantities found for stable species elsewhere were disclosed for these reactions systems. We also unveiled novel scaling patterns for information gain at the atomic level. The barrier height of the reactions can reliably be predicted by using both the Hirshfeld charge and information gain at the regioselective carbon atom. The energy decomposition analysis ensued yields an unambiguous picture about the origin of the barrier height, where we showed that it is the electrostatic interaction that plays the dominant role, while the roles played by exchange-correlation and

  3. Enhancing the design of in situ chemical barriers with multicomponent reactive transport modeling

    International Nuclear Information System (INIS)

    This paper addresses the need for systematic control of field-scale performance in the emplacement and operation of in situ chemical treatment barriers; in particular, it addresses the issue of how the local coupling of reaction kinetics and material heterogeneities at the laboratory or bench scale can be accurately upscaled to the field. The authors have recently developed modeling analysis tools that can explicitly account for all relevant chemical reactions that accompany the transport of reagents and contaminants through a chemically and physically heterogeneous subsurface rock or soil matrix. These tools are incorporated into an enhanced design methodology for in situ chemical treatment technologies, and the new methodology is demonstrated in the ongoing design of a field experiment for the In Situ Redox Manipulation (ISRM) project at the U.S. Department of Energy (DOE) Hanford Site. The ISRM design approach, which systematically integrates bench-scale and site characterization information, provides an ideal test for the new reactive transport techniques. The need for the enhanced chemistry capability is demonstrated by an example that shows how intra-aqueous redox kinetics can affect the transport of reactive solutes. Simulations are carried out on massively parallel computer architectures to resolve the influence of multiscale heterogeneities on multicomponent, multidimensional reactive transport. The technology will soon be available to design larger-scale remediation schemes

  4. The influence of zero-flux surface motion on chemical reactivity.

    Science.gov (United States)

    Morgenstern, Amanda; Morgenstern, Charles; Miorelli, Jonathan; Wilson, Tim; Eberhart, M E

    2016-02-21

    Visualizing and predicting the response of the electron density, ρ(r), to an external perturbation provides a portion of the insight necessary to understand chemical reactivity. One strategy used to portray electron response is the electron pushing formalism commonly utilized in organic chemistry, where electrons are pictured as flowing between atoms and bonds. Electron pushing is a powerful tool, but does not give a complete picture of electron response. We propose using the motion of zero-flux surfaces (ZFSs) in the gradient of the charge density, ∇ρ(r), as an adjunct to electron pushing. Here we derive an equation rooted in conceptual density functional theory showing that the movement of ZFSs contributes to energetic changes in a molecule undergoing a chemical reaction. Using a substituted acetylene, 1-iodo-2-fluoroethyne, as an example, we show the importance of both the boundary motion and the change in electron counts within the atomic basins of the quantum theory of atoms in molecules for chemical reactivity. This method can be extended to study the ZFS motion between smaller gradient bundles in ρ(r) in addition to larger atomic basins. Finally, we show that the behavior of ∇ρ(r) within atomic basins contains information about electron response and can be used to predict chemical reactivity. PMID:26832068

  5. Thermal chemical-mechanical reactive flow model of shock initiation in solid explosives

    International Nuclear Information System (INIS)

    The three dimensional Arbitrary Lagrange Eulerian hydrodynamic computer code ALE3D with fully coupled thermal-chemical-mechanical material models provides the framework for the development of a physically realistic model of shock initiation and detonation of solid explosives. The processes of hot spot formation during shock compression, subsequent ignition of reaction or failure to react, growth of reaction in individual hot spots, and coalescence of reacting hot spots during the transition to detonation can now be modeled using Arrhenius chemical kinetic rate laws and heat transfer to propagate the reactive flow. This paper discusses the growth rates of reacting hot spots in HMX and TATB and their coalescence during shock to detonation transition. Hot spot deflagration rates are found to be fast enough to consume explosive particles less than 10 mm in diameter during typical shock duration times, but larger particles must fragment and create more reactive surface area in order to be rapidly consumed

  6. The chemical reactivity and structure of collagen studied by neutron diffraction

    International Nuclear Information System (INIS)

    The chemical reactivity of collagen can be studied using neutron diffraction (a non-destructive technique), for certain reaction types. Collagen contains a number of lysine and hydroxylysine side chains that can react with aldehydes and ketones, or these side chains can themselves be converted to aldehydes by lysyl oxidase. The reactivity of these groups not only has an important role in the maintenance of mechanical strength in collagen fibrils, but can also manifest pathologically in the cases of aging, diabetes (reactivity with a variety of sugars) and alcoholism (reactivity with acetaldehyde). The reactivity of reducing groups with collagen can be studied by neutron diffraction, since the crosslink formed in the adduction process is initially of a Schiff base or keto-imine nature. The nature of this crosslink allows it to be deuterated, and the position of this relatively heavy scattering atom can be used in a process of phase determination by multiple isomorphous replacement. This process was used to study the following: the position of natural crosslinks in collagen; the position of adducts in tendon from diabetic rats in vivo and the in vitro position of acetaidehyde adducts in tendon

  7. The chemical reactivity and structure of collagen studied by neutron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Wess, T.J.; Wess, L.; Miller, A. [Univ. of Stirling (United Kingdom)

    1994-12-31

    The chemical reactivity of collagen can be studied using neutron diffraction (a non-destructive technique), for certain reaction types. Collagen contains a number of lysine and hydroxylysine side chains that can react with aldehydes and ketones, or these side chains can themselves be converted to aldehydes by lysyl oxidase. The reactivity of these groups not only has an important role in the maintenance of mechanical strength in collagen fibrils, but can also manifest pathologically in the cases of aging, diabetes (reactivity with a variety of sugars) and alcoholism (reactivity with acetaldehyde). The reactivity of reducing groups with collagen can be studied by neutron diffraction, since the crosslink formed in the adduction process is initially of a Schiff base or keto-imine nature. The nature of this crosslink allows it to be deuterated, and the position of this relatively heavy scattering atom can be used in a process of phase determination by multiple isomorphous replacement. This process was used to study the following: the position of natural crosslinks in collagen; the position of adducts in tendon from diabetic rats in vivo and the in vitro position of acetaidehyde adducts in tendon.

  8. Computational Nutraceutics: Chemical Reactivity Properties of the Flavonoid Naringin by Means of Conceptual DFT

    OpenAIRE

    Jorge Ignacio Martínez-Araya; Guillermo Salgado-Morán; Daniel Glossman-Mitnik

    2013-01-01

    The M06 family of density functionals has been assessed for the calculation of the molecular structure and properties of the Naringin molecule. The chemical reactivity descriptors have been calculated through Conceptual DFT. The active sites for nucleophilic and electrophilic attacks have been chosen by relating them to the Fukui function indices and the dual descriptor f(2)(r). A comparison between the descriptors calculated through vertical energy values and those arising from the Koopmans'...

  9. Efficient chemical equilibrium calculations for geochemical speciation and reactive transport modelling

    Science.gov (United States)

    Leal, Allan M. M.; Blunt, Martin J.; LaForce, Tara C.

    2014-04-01

    Chemical equilibrium calculations are essential for many environmental problems. It is also a fundamental tool for chemical kinetics and reactive transport modelling, since these applications may require hundreds to billions equilibrium calculations in a single simulation. Therefore, an equilibrium method for such critical applications must be very efficient, robust and accurate. In this work we demonstrate the potential effectiveness of a novel Gibbs energy minimisation algorithm for reactive transport simulations. The algorithm includes strategies to converge from poor initial guesses; capabilities to specify non-linear equilibrium constraints such as pH of an aqueous solution and activity or fugacity of a species; a rigorous phase stability test to determine the unstable phases; and a strategy to boost the convergence speed of the calculations to quadratic rates, requiring only few iterations to converge. We use this equilibrium method to solve geochemical problems relevant to carbon storage in saline aquifers, where aqueous, gaseous and minerals phases are present. The problems are formulated to mimic the ones found in kinetics and transport simulations, where a sequence of equilibrium calculations are performed, each one using the previous solution as the initial guess. The efficiency and convergence rates of the calculations are presented, which require an average of 1-2 iterations. These results indicate that critical applications such as chemical kinetics and reactive transport modelling can potentially benefit by using this multiphase equilibrium algorithm.

  10. Modeling accidental releases to the atmosphere of a dense reactive chemical (Uranium hexafluoride)

    Science.gov (United States)

    Hanna, Steven R.; Chang, Joseph C.; Zhang, Xiaoming J.

    In order to model the atmospheric transport and dispersion of dense reactive chemicals such as uranium hexafluoride (UF 6), it is necessary to include algorithms that account for heat exchanges due to chemical reactions and phase changes. UF 6 may be released accidentally at uranium-enrichment plants as a warm gas from a pipeline rupture, or as a flashing liquid from a pressurized tank or line break. The resulting plume is initially very dense due to the large molecular weight of UF 6, but may become lighter-than-air as the UF 6 reacts with water vapor to form HF, which has a molecular weight less than that of air, and which may cause an increase in plume temperature due to the exothermic reaction. The major chemical and thermodynamic processes related to UF 6 have been incorporated in a modified version of an existing dense gas model, HGSYSTEM. The same general approach could be used to include other reactive chemicals in the modeling system. New modules that are applicable to any type of chemical release have also been added to HGSYSTEM to account for building downwash, lift-off of warm plumes from the ground, and deposition. The revised HGSYSTEM/UF 6 model has been evaluated with field data from UF 6 tests. The sensitivities of the model predictions to variations in input parameters have been assessed.

  11. Chemical reactivity of graphene oxide towards amines elucidated by solid-state NMR

    Science.gov (United States)

    Vacchi, Isabella A.; Spinato, Cinzia; Raya, Jésus; Bianco, Alberto; Ménard-Moyon, Cécilia

    2016-07-01

    Graphene oxide (GO) is an attractive nanomaterial for many applications. Controlling the functionalization of GO is essential for the design of graphene-based conjugates with novel properties. But, the chemical composition of GO has not been fully elucidated yet. Due to the high reactivity of the oxygenated moieties, mainly epoxy, hydroxyl and carboxyl groups, several derivatization reactions may occur concomitantly. The reactivity of GO with amine derivatives has been exploited in the literature to design graphene-based conjugates, mainly through amidation. However, in this study we undoubtedly demonstrate using magic angle spinning (MAS) solid-state NMR that the reaction between GO and amine functions occurs via ring opening of the epoxides, and not by amidation. We also prove that there is a negligible amount of carboxylic acid groups in two GO samples obtained by a different synthesis process, hence eliminating the possibility of amidation reactions with amine derivatives. This work brings additional insights into the chemical reactivity of GO, which is fundamental to control its functionalization, and highlights the major role of MAS NMR spectroscopy for a comprehensive characterization of derivatized GO.Graphene oxide (GO) is an attractive nanomaterial for many applications. Controlling the functionalization of GO is essential for the design of graphene-based conjugates with novel properties. But, the chemical composition of GO has not been fully elucidated yet. Due to the high reactivity of the oxygenated moieties, mainly epoxy, hydroxyl and carboxyl groups, several derivatization reactions may occur concomitantly. The reactivity of GO with amine derivatives has been exploited in the literature to design graphene-based conjugates, mainly through amidation. However, in this study we undoubtedly demonstrate using magic angle spinning (MAS) solid-state NMR that the reaction between GO and amine functions occurs via ring opening of the epoxides, and not by

  12. Ab initio studies of equations of state and chemical reactions of reactive structural materials

    Science.gov (United States)

    Zaharieva, Roussislava

    The motivations for the research issues addressed in this thesis are based on the needs of the aerospace structural analysis and the design community. The specific focus is related to the characterization and shock induced chemical reactions of multi-functional structural-energetic materials that are also known as the reactive structural materials and their reaction capabilities. Usually motivation for selection of aerospace structural materials is to realize required strength characteristics and favorable strength to weight ratios. The term strength implies resistance to loads experienced during the service life of the structure, including resistance to fatigue loads, corrosion and other extreme conditions. Thus, basically the structural materials are single function materials that resist loads experienced during the service life of the structure. However, it is desirable to select materials that are capable of offering more than one basic function of strength. Very often, the second function is the capability to provide functions of sensing and actuation. In this thesis, the second function is different. The second function is the energetic characteristics. Thus, the choice of dual functions of the material are the structural characteristics and energetic characteristics. These materials are also known by other names such as the reactive material structures or dual functional structural energetic materials. Specifically the selected reactive materials include mixtures of selected metals and metal oxides that are also known as thermite mixtures, reacting intermetallic combinations and oxidizing materials. There are several techniques that are available to synthesize these structural energetic materials or reactive material structures and new synthesis techniques constitute an open research area. The focus of this thesis, however, is the characterization of chemical reactions of reactive material structures that involve two or more solids (or condensed matter). The

  13. Evidence for chemical and cellular reactivities of the formaldehyde releaser bronopol, independent of formaldehyde release.

    Science.gov (United States)

    Kireche, Mustapha; Peiffer, Jean-Luc; Antonios, Diane; Fabre, Isabelle; Giménez-Arnau, Elena; Pallardy, Marc; Lepoittevin, Jean-Pierre; Ourlin, Jean-Claude

    2011-12-19

    Formaldehyde and formaldehyde releasers are widely used preservatives and represent an important group of skin sensitizers. Formaldehyde is very often suspected to be the sensitizing agent of formaldehyde-releasers; however, many reported clinical cases of contact allergy to these molecules such as bronopol (2-bromo-2-nitropropane-1,3-diol) indicate negative skin reactions to formaldehyde suggesting a more complex mechanism. The aim of this study was to compare the chemical reactivity and biological activity of formaldehyde with those of two formaldehyde releasers: 2-bromo-2-nitropropane-1,3-diol and 1,3-dimethylol-5,5-dimethylhydantoin. A key step in the sensitization to chemicals is the formation of the hapten-protein antigenic complex via covalent binding between the chemical sensitizer and amino acids in proteins. The chemical reactivity of the three compounds was thus addressed using (13)C NMR analysis of adduct formation upon incubation with a set of nucleophilic amino acids. The biological activity was measured in two in vitro models based on dendritic cells and a monocytic cell line (CD34-DC and THP-1 model) through monitoring of a panel of biomarkers. The results obtained show that 2-bromo-2-nitropropane-1,3-diol produces low amount of free formaldehyde in physiological buffers but that its degradation generates various molecules including 2-bromoethanol. In addition, 2-bromo-2-nitropropane-1,3-diol also generates adducts with amino acids, not observed with formaldehyde alone, that could be explained by the reactivity of 2-bromoethanol. In parallel, in a cellular approach using the human monocytic THP-1 cell line, 2-bromo-2-nitropropane-1,3-diol activates THP-1 cells at concentrations that are not correlated to simple formaldehyde release. This observation is confirmed in the more physiological model CD34-DC. Moreover, in the THP-1 model, the expression profiles of several biomarkers are specific to 2-bromo-2-nitropropane-1,3-diol. Finally, the use in the

  14. Reactive chemically modified piezoelectric crystal detectors: A new class of high-selectivity sensors

    International Nuclear Information System (INIS)

    A great number of works have focused on the study of properties of modified piezoelectric quartz crystal detectors (PQCDs) coated with sorbing substrates and on applying sensors based on them for the analysis of diluted gas mixtures and solutions. This work offers a new class of gravemetric sensors characterized by a reversible chemical reaction that occurs on their surface. Silica films are proposed as a sorbing coating of quartz detectors, and a chemical modification of a surface is suggested for covalent fixation of the necessary compounds. PQCDs were chemically modified with reactive diene derivatives that can also act as dienophiles. Hexachlorocyclopentadiene (HCCPD, resonater I) and cyclopentadiene (CPD, resonator II) were fixed on a PQCD surface in several stages. After treatment with the resonaters, the PQCD in a CPD gas phase exhibited time dependent frequency shifts from 20-100 Hz. The results suggest that there is a reversible chemical reaction on the electrode surface of resonators I and II when they interact with CPD vapors. Therefore, PQCDs modified with reactive dienes were prepared for the first time and may be employed as selective sensors for CPD

  15. Chemical reactivity of PVD-coated WC-Co tools with steel

    Energy Technology Data Exchange (ETDEWEB)

    Gimenez, S. [Department of Metallurgy and Materials Engineering, Katholieke Universiteit Leuven, Kasteelpark Arenberg 44, B-3001 Heverlee (Belgium); Huang, S.G. [Department of Metallurgy and Materials Engineering, Katholieke Universiteit Leuven, Kasteelpark Arenberg 44, B-3001 Heverlee (Belgium); Van der Biest, O. [Department of Metallurgy and Materials Engineering, Katholieke Universiteit Leuven, Kasteelpark Arenberg 44, B-3001 Heverlee (Belgium); Vleugels, J. [Department of Metallurgy and Materials Engineering, Katholieke Universiteit Leuven, Kasteelpark Arenberg 44, B-3001 Heverlee (Belgium)]. E-mail: jozef.vleugels@mtm.kuleuven.be

    2007-01-30

    The chemical reactivity of CrN, ZrN, TiC {sub x}N{sub 1-x} and naCo (registered) PVD coatings on a WC-Co cemented carbide substrate with steel has been evaluated by means of the static interaction couples technique. Diffusion experiments with coated and uncoated tools were carried out at 900, 1100 and 1300 deg. C in order to establish the maximum temperature at which the substrate-coating-workpiece combinations are chemically stable. Computational equilibrium thermodynamics was used to identify the interaction products formed at elevated temperature and the chemical solubility of the different coating materials into iron. A metallic (Fe, Co) fcc solid solution was identified at the steel side of the interface from 1100 deg. C on for all the coated tools and from 900 deg. C for the uncoated carbide. In addition to this interaction product, the {eta}-carbide was identified at 1300 deg. C on the WC-Co side of the interface. Both of the experimental findings and thermodynamic equilibrium solubility calculations demonstrated that the PVD-coated WC-Co tools exhibit a lower chemical reactivity with respect to the uncoated tools.

  16. Chemical reactivity of PVD-coated WC-Co tools with steel

    International Nuclear Information System (INIS)

    The chemical reactivity of CrN, ZrN, TiC xN1-x and naCo (registered) PVD coatings on a WC-Co cemented carbide substrate with steel has been evaluated by means of the static interaction couples technique. Diffusion experiments with coated and uncoated tools were carried out at 900, 1100 and 1300 deg. C in order to establish the maximum temperature at which the substrate-coating-workpiece combinations are chemically stable. Computational equilibrium thermodynamics was used to identify the interaction products formed at elevated temperature and the chemical solubility of the different coating materials into iron. A metallic (Fe, Co) fcc solid solution was identified at the steel side of the interface from 1100 deg. C on for all the coated tools and from 900 deg. C for the uncoated carbide. In addition to this interaction product, the η-carbide was identified at 1300 deg. C on the WC-Co side of the interface. Both of the experimental findings and thermodynamic equilibrium solubility calculations demonstrated that the PVD-coated WC-Co tools exhibit a lower chemical reactivity with respect to the uncoated tools

  17. Investigation of the Reactivity of Oligodeoxynucleotides with Glyoxal and KMnO4 Chemical Probes by Electrospray Ionization Mass Spectrometry

    OpenAIRE

    Parr, Carol; Pierce, Sarah E.; Smith, Suncerae I.; Brodbelt, Jennifer S.

    2011-01-01

    The reactions of two well-known chemical probes, glyoxal and potassium permanganate (KMnO4), with oligodeoxynucleotides were monitored by electrospray ionization (ESI) mass spectrometry to evaluate the influence of the sequence of DNA, its secondary structure, and interactions with associated ligands on the reactivity of the two probes. Glyoxal, a guanine-reactive probe, incorporated a mass shift of 58 Da, and potassium permanganate (KMnO4) is a thymine-reactive probe that resulted in a mass ...

  18. Shock-induced solid-state chemical reactivity studies using time-resolved radiation pyrometry

    International Nuclear Information System (INIS)

    Time-resolved radiation pyrometry has been used to study materials which undergo solid-state chemical reactions due to shock loading. Shock-induced chemical reactivity in solids is fundamentally different than that in high explosives and other energetic materials because, if no volatiles are present, the reaction products end up in the condensed, rather than the vapor, state. Bulk property changes accompanying the solid-state reactions may therefore be too small to be observable with wave profile or shock-velocity measurements. However, some solid-state reactions, such as that between metallic nickel and aluminum, are exothermic enough to give rise to a measurable increase in temperature, so pyrometry can be used to detect the reactions. Unfortunately, these measurements are complicated by the large temperature increases generated by other sources. Possible mechanisms for generation of these high temperatures, and their effect on the chemical reaction, are suggested

  19. Bioassays for the detection of chemicals that can form bioactivation-dependent reactive free radicals

    Energy Technology Data Exchange (ETDEWEB)

    Sanderson, J.T.; Commandeur, J.N.M.; Wezel, A. van; Vermeulen, N.P.E. (Free Univ. of Amsterdam (Netherlands). Div. of Molecular Toxicology National Inst. for Coastal and Marine Management, Den Haag (Netherlands))

    1999-06-01

    In vitro bioassays were developed for the detection of chemicals that can be bioactivated to reactive free radical species in microsomal fractions. Two methods were deployed, a down-scaled spectrophotometric method for the detection of chemicals that can cause lipid peroxidation using the measurement of thiobarbituric acid-reactive substances (TBARS) and a fluorometric method for the detection of chemicals that can undergo redox cycling to generate superoxide radicals based on the detection of hydrogen peroxide. The response of these systems to prototypical and environmentally relevant chemicals, including tetrachloromethane and paraquat, was examined. The detection limit of the lipid peroxidation bioassay, based on the formation of TBARS, was about 1 [micro]M for tetrachloromethane; that of the bioassay for redox cyclers, based on the production of hydrogen peroxide, was about 2 [micro]M for paraquat and about 100-fold lower for the potent redox cycler 2,3,5,6-tetramethylbenzoquinone (TMBQ). Several binary mixtures of chemicals were tested for potential nonadditive effects in both in vitro systems. Some antagonistic effects among halogenated methanes were observed in the lipid peroxidation assay. In the hydrogen peroxide production assay, greater than additive effects were seen between small concentrations of paraquat and TMBQ. A number of surface water concentrates from several locations in The Netherlands, with various levels of chemical contamination, exhibited a weak response in the hydrogen peroxide production assay. Acetone was found to interfere with the response of the bioassay to redox cyclers and, therefore, the water concentrates (originally in acetone) were transferred to ethanol prior to testing. A good correlation was observed between the response of the water concentrates in the hydrogen peroxide production assay and their acute toxicity in Daphnia magna. No correlation was observed between this bioassay response and toxicity in the Microtox

  20. THE INTEGRATED USE OF COMPUTATIONAL CHEMISTRY, SCANNING PROBE MICROSCOPY, AND VIRTUAL REALITY TO PREDICT THE CHEMICAL REACTIVITY OF ENVIRONMENTAL SURFACES

    Science.gov (United States)

    In the last decade three new techniques scanning probe microscopy (SPM), virtual reality (YR) and computational chemistry ave emerged with the combined capability of a priori predicting the chemically reactivity of environmental surfaces. Computational chemistry provides the cap...

  1. XCHEM-1D: A Heat Transfer/Chemical Kinetics Computer Program for multilayered reactive materials

    Energy Technology Data Exchange (ETDEWEB)

    Gross, R.J.; Baer, M.R.; Hobbs, M.L.

    1993-10-01

    An eXplosive CHEMical kinetics code, XCHEM, has been developed to solve the reactive diffusion equations associated with thermal ignition of energetic materials. This method-of-lines code uses stiff numerical methods and adaptive meshing to resolve relevant combustion physics. Solution accuracy is maintained between multilayered materials consisting of blends of reactive components and/or inert materials. Phase change and variable properties are included in one-dimensional slab, cylindrical and spherical geometries. Temperature-dependent thermal properties have been incorporated and the modification of thermal conductivities to include decomposition effects are estimated using solid/gas volume fractions determined by species fractions. Gas transport properties, including high pressure corrections, have also been included. Time varying temperature, heat flux, convective and thermal radiation boundary conditions, and layer to layer contact resistances have also been implemented.

  2. Prediction of monomer reactivity in radical copolymerizations from transition state quantum chemical descriptors

    Directory of Open Access Journals (Sweden)

    Zhengde Tan

    2013-01-01

    Full Text Available In comparison with the Q-e scheme, the Revised Patterns Scheme: the U, V Version (the U-V scheme has greatly improved both its accessibility and its accuracy in interpreting and predicting the reactivity of a monomer in free-radical copolymerizations. Quantitative structure-activity relationship (QSAR models were developed to predict the reactivity parameters u and v of the U-V scheme, by applying genetic algorithm (GA and support vector machine (SVM techniques. Quantum chemical descriptors used for QSAR models were calculated from transition state species with structures C¹H3 - C²HR³• or •C¹H2 - C²H2R³ (formed from vinyl monomers C¹H²=C²HR³ + H•, using density functional theory (DFT, at the UB3LYP level of theory with 6-31G(d basis set. The optimum support vector regression (SVR model of the reactivity parameter u based on Gaussian radial basis function (RBF kernel (C = 10, ε = 10- 5 and γ = 1.0 produced root-mean-square (rms errors for the training, validation and prediction sets being 0.220, 0.326 and 0.345, respectively. The optimal SVR model for v with the RBF kernel (C = 20, ε = 10- 4 and γ = 1.2 produced rms errors for the training set of 0.123, the validation set of 0.206 and the prediction set of 0.238. The feasibility of applying the transition state quantum chemical descriptors to develop SVM models for reactivity parameters u and v in the U-V scheme has been demonstrated.

  3. The chemical and mechanical behaviors of polymer / reactive metal systems under high strain rates

    Science.gov (United States)

    Shen, Yubin

    As one category of energetic materials, impact-initiated reactive materials are able to release a high amount of stored chemical energy under high strain rate impact loading, and are used extensively in civil and military applications. In general, polymers are introduced as binder materials to trap the reactive metal powders inside, and also act as an oxidizing agent for the metal ingredient. Since critical attention has been paid on the metal / metal reaction, only a few types of polymer / reactive metal interactions have been studied in the literature. With the higher requirement of materials resistant to different thermal and mechanical environments, the understanding and characterization of polymer / reactive metal interactions are in great demand. In this study, PTFE (Polytetrafluoroethylene) 7A / Ti (Titanium) composites were studied under high strain rates by utilizing the Taylor impact and SHPB tests. Taylor impact tests with different impact velocities, sample dimensions and sample configurations were conducted on the composite, equipped with a high-speed camera for tracking transient images during the sudden process. SHPB and Instron tests were carried out to obtain the stress vs. strain curves of the composite under a wide range of strain rates, the result of which were also utilized for fitting the constitutive relations of the composite based on the modified Johnson-Cook strength model. Thermal analyses by DTA tests under different flow rates accompanied with XRD identification were conducted to study the reaction mechanism between PTFE 7A and Ti when only heat was provided. Numerical simulations on Taylor impact tests and microstructural deformations were also performed to validate the constitutive model built for the composite system, and to investigate the possible reaction mechanism between two components. The results obtained from the high strain rate tests, thermal analyses and numerical simulations were combined to provide a systematic study on

  4. Reactive chromophores for sensitive and selective detection of chemical warfare agents

    Science.gov (United States)

    Frye-Mason, Greg; Leuschen, Martin; la Grone, Marcus; Wald, Lara; Aker, Craig; Dock, Matt; Hancock, Lawrence F.; Fagan, Steve; Paul, Kateri

    2004-08-01

    A new sensor for highly toxic species including chemical warfare (CW) agents has been developed. This sensor is based on a unique CW indicating chromophore (CWIC) developed by Professor Tim Swager at MIT. The CWIC was designed to be sensitive to the reactivity that makes these chemicals so toxic. Since it requires the reactivity of the agent to be detected, the CWIC technology has shown remarkable selectivity for nerve agent surrogates and some other highly toxic species, thereby demonstrating the potential to provide low false alarm rate detection. Since the chromophore has mini-mal fluorescence prior to reaction with an electrophilic and toxic chemical, the sensor acts in a dark field fluorescence mode. This provides the sensor with exceptional sensitivity and a potential to detect priority analytes well below levels detected by current hand held sensors. Finally, it is based on a simple optical detection scheme that enables small and rugged sensors to be developed and produced at a low enough cost so they can be widely utilized.

  5. Chemical reactivity of thermo-hardenable steel weld joints investigated by electrochemical impedance spectroscopy

    International Nuclear Information System (INIS)

    The chemical reactivity of oxide-free weld joints made of thermo-hardened carbon steel in different electrolytes was investigated by chronopotentiometry, electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). The objective was to identify the role of different electrolyte constituents on the electrochemical behaviour of the different materials constituting the weld joint, namely the weld material, the heat affected zone (HAZ) and the base carbon steel. Hardness measurements by Vickers and nano-indentation techniques indicated that the weld material is harder than the heat affected zone and the base carbon steel due to a Widmanstaetten ferrite-type structure of the weld. Electrochemical measurements were performed on polished cross-sections on these weld joints in four electrolytes containing different additives. The weld joints are active in all tested electrolytes and the composition of the electrolytes dictates the dissolution even though the main chemical reactivity mechanism remains unaffected. A balanced presence of oxidative agent, inhibitor and HF in the electrolyte is necessary to obtain a homogeneous chemical attack on weld joint and Si-rich inclusion removal in weld material, while avoiding excessive attack roughening and/or pitting of the carbon steel

  6. Chemical Reactivity Testing for the National Spent Nuclear Fuel Program. Quality Assurance Project Plan

    Energy Technology Data Exchange (ETDEWEB)

    Newsom, H.C.

    1999-01-24

    This quality assurance project plan (QAPjP) summarizes requirements used by Lockheed Martin Energy Systems, Incorporated (LMES) Development Division at Y-12 for conducting chemical reactivity testing of Department of Energy (DOE) owned spent nuclear fuel, sponsored by the National Spent Nuclear Fuel Program (NSNFP). The requirements are based on the NSNFP Statement of Work PRO-007 (Statement of Work for Laboratory Determination of Uranium Hydride Oxidation Reaction Kinetics.) This QAPjP will utilize the quality assurance program at Y-12, QA-101PD, revision 1, and existing implementing procedures for the most part in meeting the NSNFP Statement of Work PRO-007 requirements, exceptions will be noted.

  7. Simulation of chemically reactive solute transport under conditions of changing temperature

    International Nuclear Information System (INIS)

    A numerical code, THCC, has been developed for simulation of multicomponent solute transport in saturated porous media with aqueous complexation and precipitation/dissolution of stable solid phases in the presence of variable temperature. THCC evolved from the isothermal code CHEMTRN and is capable of simulating the diffusion of solutes along a steady gradient of temperature and the mixing of fluids having different initial compositions and temperatures. Example calculations demonstrate the close coupling that can exist between temperature variations and the transport of chemically reactive solutes. This coupling can be an important consideration in the assessment of performance of nuclear waste repositories

  8. Chemical Reactivity Testing for the National Spent Nuclear Fuel Program. Quality Assurance Project Plan

    International Nuclear Information System (INIS)

    This quality assurance project plan (QAPjP) summarizes requirements used by Lockheed Martin Energy Systems, Incorporated (LMES) Development Division at Y-12 for conducting chemical reactivity testing of Department of Energy (DOE) owned spent nuclear fuel, sponsored by the National Spent Nuclear Fuel Program (NSNFP). The requirements are based on the NSNFP Statement of Work PRO-007 (Statement of Work for Laboratory Determination of Uranium Hydride Oxidation Reaction Kinetics.) This QAPjP will utilize the quality assurance program at Y-12, QA-101PD, revision 1, and existing implementing procedures for the most part in meeting the NSNFP Statement of Work PRO-007 requirements, exceptions will be noted

  9. Computational Nutraceutics: Chemical Reactivity Properties of the Flavonoid Naringin by Means of Conceptual DFT

    Directory of Open Access Journals (Sweden)

    Jorge Ignacio Martínez-Araya

    2013-01-01

    Full Text Available The M06 family of density functionals has been assessed for the calculation of the molecular structure and properties of the Naringin molecule. The chemical reactivity descriptors have been calculated through Conceptual DFT. The active sites for nucleophilic and electrophilic attacks have been chosen by relating them to the Fukui function indices and the dual descriptor f(2(r. A comparison between the descriptors calculated through vertical energy values and those arising from the Koopmans' theorem approximation has been performed in order to check for the validity of the last procedure.

  10. Density functional theory of chemical reactivity indices in some ion-molecule reaction systems

    International Nuclear Information System (INIS)

    Three isoelectronic reactions, proton transfer (PT), hydrogen abstraction (HA), and electron transfer (ET), of NH3+ with NH3, H2O, and HF have been studied using ab initio molecular orbital calculations. For the reaction of NH3+ + H2O, the energy of the transition state (TS) is higher than that of the reactants. This is consistent with the experimental observation that the rate constant is less than the average dipole orientation (ADO) rate constant. It seems reasonable that the reaction rate for the reaction NH3+ + H2O would hardly depend on the V2 mode of NH3+ at least for low-lying excited states (Eint≤ 0.714 eV) of the V2 mode, because the V2 contributes mainly to the normal mode orthogonal to the reaction coordinate at the TS. This is consistent with experimental observation. A similiar prediction can be made for the NH3+ + HF reaction. The electron transfer processes for the HA reactions have been examined in terms of the intrinsic reaction coordinate (IRC). The order of reactivity with NH3+ is NH3>H2O>HF. It is found that the degree of the electron transfer and the reactivity are correlated with the absolute hardness η of NH3, H2O, and HF. this is accord with the softness as the chemical reactivity index in the density functional theory. 25 refs., 6 fig., 4 tab

  11. Chemical reactivity trends of ergotamine and butenolide from electrostatic potentials and charge sensitivities

    International Nuclear Information System (INIS)

    A set of reactivity indices, including maps of the electrostatic potential and local and condensed Fukui function (FF) indices in the atomic resolution, are reported for two vasoconstricting mycotoxins: butenolide and ergotamine; both the finite difference approach of Parr and Yan as well as charge sensitivity analysis, determining the charge responses via the inversion of the hardness tensor, have been used to generate the FF data. These two routes of arriving at the atomic FF indices provide an opportunity to evaluate the available parametrizations of the semiempirical NDDO-type of methods which have been used to determine the input charge distribution; namely, the best parametrization should generate consistent FF predictions resulting from both approaches. For butenolide, the MNDO parametrization was found to fulfill this consistency requirement. The chemical reactivity information has been used to trace possible similarities in reactivity trends of the butenolide molecule and the related fragment of ergotamine, toward hypothetical nucleophilic, electrophilic, and radical attacks. These predictions have been compared to experimental data available for other unsaturated lactones. 13 refs., 18 figs., 1 tab

  12. Interactions between ingredients in IMX-101: Reactive Chemical Processes Control Insensitive Munitions Properties

    Energy Technology Data Exchange (ETDEWEB)

    Maharrey, Sean P. [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Wiese-Smith, Deneille [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Highley, Aaron M. [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Behrens, Richard [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Kay, Jeffrey J [Sandia National Lab. (SNL-CA), Livermore, CA (United States)

    2014-03-01

    Simultaneous Thermogravimetric Modulated Beam Mass Spectrometry (STMBMS) measurements have been conducted on a new Insensitive Munitions (IM) formulation. IMX-101 is the first explosive to be fully IM qualified under new NATO STANAG guidelines for fielded munitions. The formulation uses dinitroanisole (DNAN) as a new melt cast material to replace TNT, and shows excellent IM performance when formulated with other energetic ingredients. The scope of this work is to explain this superior IM performance by investigating the reactive processes occurring in the material when subjected to a well-controlled thermal environment. The dominant reactive processes observed were a series of complex chemical interactions between the three main ingredients (DNAN, NQ, and NTO) that occurs well below the onset of the normal decomposition process of any of the individual ingredients. This process shifts the thermal response of the formulations to a much lower temperature, where the kinetically controlled reaction processes are much slower. This low temperature shift has the effect of allowing the reactions to consume the reactive solids (NQ, NTO) well before the reaction rates increase and reach thermal runaway, resulting in a relatively benign response to the external stimuli. The main findings on the interaction processes are presented.

  13. Chemical reactivity trends of ergotamine and butenolide from electrostatic potentials and charge sensitivities

    Energy Technology Data Exchange (ETDEWEB)

    Mrozek, J.; Michalak, A. [Jagiellonian Univ., Cracow (Poland)

    1995-12-05

    A set of reactivity indices, including maps of the electrostatic potential and local and condensed Fukui function (FF) indices in the atomic resolution, are reported for two vasoconstricting mycotoxins: butenolide and ergotamine; both the finite difference approach of Parr and Yan as well as charge sensitivity analysis, determining the charge responses via the inversion of the hardness tensor, have been used to generate the FF data. These two routes of arriving at the atomic FF indices provide an opportunity to evaluate the available parametrizations of the semiempirical NDDO-type of methods which have been used to determine the input charge distribution; namely, the best parametrization should generate consistent FF predictions resulting from both approaches. For butenolide, the MNDO parametrization was found to fulfill this consistency requirement. The chemical reactivity information has been used to trace possible similarities in reactivity trends of the butenolide molecule and the related fragment of ergotamine, toward hypothetical nucleophilic, electrophilic, and radical attacks. These predictions have been compared to experimental data available for other unsaturated lactones. 13 refs., 18 figs., 1 tab.

  14. Notes on the KIVA-2 software and chemically reactive fluid mechanics

    Science.gov (United States)

    Holst, M. J.

    1992-09-01

    Working notes regarding the mechanics of chemically reactive fluids with sprays, and their numerical simulation with the KIVA-2 software are presented. KIVA-2 is a large FORTRAN program developed at Los Alamos National Laboratory for internal combustion engine simulation. It is our hope that these notes summarize some of the necessary background material in fluid mechanics and combustion, explain the numerical methods currently used in KIVA-2 and similar combustion codes, and provide an outline of the overall structure of KIVA-2 as a representative combustion program, in order to aid the researcher in the task of implementing KIVA-2 or a similar combustion code on a massively parallel computer. The notes are organized into three parts as follows. In Part 1, a brief introduction to continuum mechanics, to fluid mechanics, and to the mechanics of chemically reactive fluids with sprays is presented. In Part 2, a close look at the governing equations of KIVA-2 is taken, and the methods employed in the numerical solution of these equations is discussed. Some conclusions are drawn and some observations are made in Part 3.

  15. Measurements of nitric oxide and total reactive nitrogen in the Antarctic stratosphere: Observations and chemical implications

    International Nuclear Information System (INIS)

    Measurements of NO and the sum of reactive nitrogen species, NOy, were made as part of the Airborne Antarctic Ozone Experiment (AAOE) on flights of the NASA ER-2 aircraft over the Antarctic continent. Reactive nitrogen species include NO,NO2, NO3, N2O5, HNO3, and ClONO2. The technique utilized the conversion of NOy components to NO on a gold catalyst and the subsequent detection of NO by the chemiluminescent reaction of NO with O3. NO was measured on two of the flights by removing the catalyst from the sample line. The boundary of a chemically perturbed region (CPR) above the continent occurred on average near 66 degree S as indicated by a sharp increase in the level of ClO. Outside or equatorward of the CPR, NOy mixing ratios ranged between 6 and 12 parts per billion by volume (ppbv), with values increasing with latitude. At the edge of the CPR, large latitude gradients of NOyand NO were found with values decreasing poleward. Total NOy levels dropped to 4 ppbv or less within 5 degree poleward of the boundary. NO values were 0.1-0.2 ppbv outside and below the detection limit of 0.03 ppbv inside the CPR. The levels of NO and NOy observed preclude a chemical loss of ozone due to reaction with NO

  16. Chemical composition and photochemical reactivity of exhaust from aircraft turbine engines

    Directory of Open Access Journals (Sweden)

    T. F. Lyon

    Full Text Available Assessment of the environmental impact of aircraft emissions is required by planners and policy makers. Seveal areas of concern are: 1. exposure of airport workers and urban residents to toxic chemicals emitted when the engines operate at low power (idle and taxi on the ground; 2. contributions to urban photochemical air pollution of aircraft volatile organic and nitrogen oxides emissions from operations around airports; and 3. emissions of nitrogen oxides and particles during high-altitude operation. The environmental impact of chemicals emitted from jet aircraft turbine engines has not been firmly established due to lack of data regarding emission rates and identities of the compounds emitted. This paper describes an experimental study of two different aircraft turbine engines designed to determine detailed organic emissions, as well as emissions of inorganic gases. Emissions were measured at several engine power settings. Measurements were made of detailed organic composition from C1 through C17, CO, CO2, NO, NOx, and polycyclic aromatic hydrocarbons. Measurements were made using a multi-port sampling pro be positioned directly behind the engine in the exhaust exit plane. The emission measurements have been used to determine the organic distribution by carbon number and the distribution by compound class at each engine power level. The sum of the organic species was compared with an independent measurement of total organic carbon to assess the carbon mass balance. A portion of the exhaust was captured and irradiated in outdoor smog chambers to assess the photochemical reactivity of the emissions with respect to ozone formation. The reactivity of emissions from the two engines was apportioned by chemical compound class.

  17. Constraining chemical geothermometry with reactive transport models: An example study of the Dixie Valley geothermal area

    Science.gov (United States)

    Wanner, C.; Peiffer, L.; Spycher, N.; Sonnenthal, E. L.; Iovenitti, J. L.; Kennedy, B. M.

    2012-12-01

    In this study, 1D and 2D reactive transport simulations of the Dixie Valley geothermal area (Nevada, USA) were performed using Toughreact [1] to evaluate the fluid flow pathways and rates of equilibration of hydrothermal fluids. Modeling studies were combined with new multicomponent geothermometry, which is being used to estimate the temperature of geothermal reservoirs based on chemical analysis of geothermal springs. The concept is based on the assumption of chemical equilibrium between the thermal fluid and minerals of the reservoir rock [2]. If re-equilibration occurs between the reservoir at depth and the surface, then the 'deep' chemical signature of the fluid is lost and the obtained reservoir temperature is underestimated. The simulations were run for a vertical cross-section that has been structurally and geologically characterized. Model calibration was performed using available site information such as chemical analysis of geothermal springs, isotherms inferred from geothermal wells and results of a previous flow simulation study [3]. Model runs included the simulation of typical near-surface processes such as dilution, mixing and salt leaching occurring at the Dixie Valley geothermal area. Each reactive transport model produced 'synthetic' waters that were processed using the multicomponent chemical geothermometer code GeoT [4]. This code computes the saturation indices of reservoir minerals as a function of the temperature. Reservoir temperature is inferred when mineral saturation indices all cluster around zero. GeoT results were also compared with classical solute geothermometers (silica, Na-K-(Ca), K-Mg) [5]. Simulation results reveal that a minimum vertical fluid velocity on the order of a meter per day is needed to preserve the geochemical signature of a geothermal reservoir and to predict its temperature. The simulations also show that deep geochemical signatures are well preserved if fracture surfaces are partially coated by secondary minerals

  18. Chemical reactivity and ion beam irradiation behaviour of perovskite- and zirconolite-nuclear ceramics type

    International Nuclear Information System (INIS)

    Oxide ceramics of two neighboring families: perovskite A(II)B(IV)O3 and zirconolite A(II)B(IV)C(IV)2O7 have been synthesized by a classical solid route. Substitution of divalent cation (Ca) by trivalent cation (Nd) was tested on zirconolite compositions. Then, the ceramic pellets were submitted to aqueous leaching tests at 90 deg. C in deionized water. Some of them were previously ion irradiated with 150 keV Xe+ within a fluence range 5 x 1013-1 x 1015 cm-2 in order to study the effect of ion damaging on their intrinsic chemical reactivity. X-ray diffraction (XRD), electron microprobe analysis (EMA), scanning electron microscopy (SEM) and ion beam analysis (IBA) methods were used to characterize the evolution of the crystallinity level and the surface chemical composition of the ceramics after each step (synthesis, irradiation, leaching). The alteration mechanism of unirradiated titanate ceramics appears to be not uniform at the sample surface. Chemical durability of zirconolite is shown to be dependent both on the pH of the aqueous solution and the ceramic composition. Surface hydration only concerns a very thin layer, typically 200 nm and the hydrogen content does not go beyond 1-2 at.%. No differences have been detected in the leaching behaviour of unirradiated or irradiated perovskite samples

  19. Difference in low energy plasma excitation and chemical reactivity of rare gases

    International Nuclear Information System (INIS)

    The gas release behavior of heavy rare gases such as Xe and Kr formed as major fission products in fuel pellets plays an important role on the reliability of fuel claddings due to increase the internal pressure. To clarify the chemical characteristics of rare gases is useful to inhibit the gas release and to improve the radioactive waste management and to the industrial application. On this study, the chemical reactivity was examined using the low energy plasma excitation techniques and oxidation in oxygen atmosphere. Two types of RF sources of the induced couple and static capacity types were used as the low energy plasma source. The electron density in plasma of rare gases was dependent on the binding energy of each gas. The large difference in electron densities among rare gases was typically observed in the induced couple type plasma, because of the high production yield at wall surfaces covered with low energy electrons. It was suggested that the chemical compounds were formed in the condensed atmosphere as fuels tubes. (author)

  20. Probing the chemical reactivity of free titanium clusters by X-ray absorption spectroscopy

    International Nuclear Information System (INIS)

    Synchrotron radiation-based experimental techniques are largely employed for the characterization of the reactivity of finite size systems; in particular, X-ray absorption spectroscopy (XAS) is a suitable tool to shed light on the local electronic structure and chemical status of atoms in nano-objects, as it is very sensitive to the local bonding environment of the probed site. In supported clusters intrinsic properties and reactivity are largely distorted and obscured by the changes imposed by the growth procedure and by the influence of the substrate, so the attainability of experiments on free clusters reacting with species in the gas phase is a primary goal in the development of cluster science. In this paper we report a proof of principle of the applicability of gas phase XAS technique to titanium and titanium oxide, hydride and hydrate systems. Experiments are performed by coupling a pulsed microplasma cluster source (PMCS) with a third generation synchrotron light source, and measuring the intensity of the electron yield coming from the interaction of VUV photons with the clusters seeded in a supersonic beam. (orig.)

  1. Quantum mechanics of chemical reactions: Recent developments in reactive scattering and in reaction path Hamiltonians

    International Nuclear Information System (INIS)

    Two recent developments in the theory of chemical reaction dynamics are reviewed. First, it has recently been discovered that the S- matrix version of the Kohn variational principle is free of the ''Kohn anomalies'' that have plagued other versions and prevented its general use. This has considerably simplified quantum mechanical reactive scattering calculations, which provide the rigorous characterizations of bimolecular reactions. Second, a new kind of reaction path Hamiltonian has been developed, one based on the ''least motion'' path that interpolates linearly between the reactant and product geometry of the molecule (rather than the previously used minimum energy, or ''intrinsic'' reaction path). The form of Hamiltonian which results is much simpler than the original reaction path Hamiltonian, but more important is the fact that it provides a more physically correct description of hydrogen atom transfer reactions. 44 refs., 4 figs

  2. Chemical reactivity testing for the National Spent Nuclear Fuel Program. Revision 2

    International Nuclear Information System (INIS)

    This quality assurance project plan (QAPjP) summarizes requirements used by Lockheed Martin Energy Systems, Incorporated (LMES) Development Division at Y-12 for conducting chemical reactivity testing of Department of Energy (DOE) owned spent nuclear fuel, sponsored by the National Spent Nuclear Fuel Program (NSNFP). The requirements are based on the NSNFP Statement of work PRO-007 (Statement of Work for Laboratory Determination of Uranium Hydride Oxidation Reaction Kinetics.) This QAPjP will utilize the quality assurance program at Y-12, Y60-101PD, Quality Program Description, and existing implementing procedures for the most part in meeting the NSNFP Statement of Work PRO-007 requirements, exceptions will be noted. The project consists of conducting three separate series of related experiments, ''Passivation of Uranium Hydride Powder With Oxygen and Water'', ''Passivation of Uranium Hydride Powder with Surface Characterization'', and ''Electrochemical Measure of Uranium Hydride Corrosion Rate''

  3. Evaluating changes of transport properties of chemically degrading concrete using a coupled reactive transport model

    International Nuclear Information System (INIS)

    This paper presents a model to simulate chemical degradation of concrete due to leaching. The model considers simultaneously the multi-scale nature of concrete, a thermodynamic description of cement phases, and time-variable transport properties. It is implemented in the generic simulator HP1, which simulates the reactive transport in variably-saturated porous media. To illustrate the capabilities of the program, we simulate diffusive transport through concrete in contact with waters of different solution compositions (i.e., concentrations of major cations and anions and inorganic carbon contents) and use a homogenization scheme for up-scaling tortuosity. The simulations show the coupled effects between geochemical state variables, transport properties, and durability criteria for cementitious materials used in near-surface radioactive waste disposal facilities. (authors)

  4. Integrated atomistic chemical imaging and reactive force field molecular dynamic simulations on silicon oxidation

    International Nuclear Information System (INIS)

    In this paper, we quantitatively investigate with atom probe tomography, the effect of temperature on the interfacial transition layer suboxide species due to the thermal oxidation of silicon. The chemistry at the interface was measured with atomic scale resolution, and the changes in chemistry and intermixing at the interface were identified on a nanometer scale. We find an increase of suboxide (SiOx) concentration relative to SiO2 and increased oxygen ingress with elevated temperatures. Our experimental findings are in agreement with reactive force field molecular dynamics simulations. This work demonstrates the direct comparison between atom probe derived chemical profiles and atomistic-scale simulations for transitional interfacial layer of suboxides as a function of temperature

  5. Reactive Chemical Vapor Deposition Method as New Approach for Obtaining Electroluminescent Thin Film Materials

    Directory of Open Access Journals (Sweden)

    Valentina V. Utochnikova

    2012-01-01

    Full Text Available The new reactive chemical vapor deposition (RCVD method has been proposed for thin film deposition of luminescent nonvolatile lanthanide aromatic carboxylates. This method is based on metathesis reaction between the vapors of volatile lanthanide dipivaloylmethanate (Ln(dpm3 and carboxylic acid (HCarb orH2Carb′ and was successfully used in case of HCarb. Advantages of the method were demonstrated on example of terbium benzoate (Tb(bz3 and o-phenoxybenzoate thin films, and Tb(bz3 thin films were successfully examined in the OLED with the following structure glass/ITO/PEDOT:PSS/TPD/Tb(bz3/Ca/Al. Electroluminescence spectra of Tb(bz3 showed only typical luminescent bands, originated from transitions of the terbium ion. Method peculiarities for deposition of compounds of dibasic acids H2Carb′ are established on example of terbium and europium terephtalates and europium 2,6-naphtalenedicarboxylate.

  6. Integrated atomistic chemical imaging and reactive force field molecular dynamic simulations on silicon oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Dumpala, Santoshrupa; Broderick, Scott R.; Rajan, Krishna, E-mail: krajan@iastate.edu [Department of Materials Science and Engineering and Institute for Combinatorial Discovery, Iowa State University, 2220 Hoover Hall, Ames, Iowa 50011 (United States); Khalilov, Umedjon; Neyts, Erik C. [Department of Chemistry, PLASMANT Research Group, University of Antwerp, Universiteitsplein 1, B-2610 Wilrijk-Antwerp (Belgium); Duin, Adri C. T. van [Department of Mechanical and Nuclear Engineering, Penn State University, University Park, Pennsylvania 16801 (United States); Provine, J; Howe, Roger T. [Department of Electrical Engineering, Stanford University, 420 Via Palou Mall, Stanford, California 94305 (United States)

    2015-01-05

    In this paper, we quantitatively investigate with atom probe tomography, the effect of temperature on the interfacial transition layer suboxide species due to the thermal oxidation of silicon. The chemistry at the interface was measured with atomic scale resolution, and the changes in chemistry and intermixing at the interface were identified on a nanometer scale. We find an increase of suboxide (SiOx) concentration relative to SiO{sub 2} and increased oxygen ingress with elevated temperatures. Our experimental findings are in agreement with reactive force field molecular dynamics simulations. This work demonstrates the direct comparison between atom probe derived chemical profiles and atomistic-scale simulations for transitional interfacial layer of suboxides as a function of temperature.

  7. Basic and Reactive Dyes Sorption Enhancement of Rice Hull through Chemical Modification

    Directory of Open Access Journals (Sweden)

    Siew-Teng Ong

    2010-01-01

    Full Text Available Problem statement: Many studies have been conducted on the removal of either anionic or cationic dyes. However, as a mixture of dyes does commonly exist together in wastewater, therefore it is of great interest to have a material that can remove both types of dyes. Approach: To prepare an inexpensive and efficient sorbent by chemically modifying rice hull for the removal of both basic and reactive dyes. Different chemical modifications were performed on rice hull and a comparison study on the uptake of dyes was carried out. Optimization study was carried out on most promising modified rice hull. Surface morphology of modified rice hull was examined and the functional groups present were determined using FTIR. Results: From the results, it appeared that by using EDA modified rice hull, an appreciable amount of both dyes could be sorbed. Varying the EDA/NRH ratios and heating temperatures affected the uptake of BB3 and RO16. The investigated sorbents were non-porous materials, due to the absence of pores and cavities. Sorption-desorption study showed that a complete recovery of BB3 can be obtained using high concentrations of H2SO4 and HCl but the desorption experiments of RO16 using NH3 and NaOH were not successful. Conclusion: The modification of rice hull with EDA under the optimum conditions (in a ratio of 1.00 g of NRH to 0.02 mole of EDA in a well stirred water bath at 80°C for 2 h resulted in the formation of a sorbent (MRH that could be used successfully to remove Both Basic (BB3 and Reactive dyes (RO16.

  8. Formation and chemical reactivity of carbon fibers prepared by defluorination of graphite fluoride

    Science.gov (United States)

    Hung, Ching-Cheh

    1994-01-01

    Defluorination of graphite fluoride (CFX) by heating to temperatures of 250 to 450 C in chemically reactive environments was studied. This is a new and possibly inexpensive process to produce new carbon-based materials. For example, CF 0.68 fibers, made from P-100 carbon fibers, can be defluorinated in BrH2C-CH = CH-CH2Br (1,4-dibromo-2butene) heated to 370 C, and graphitized to produce fibers with an unusually high modulus and a graphite layer structure that is healed and cross-linked. Conversely, a sulfur-doped, visibly soft carbon fiber was produced by defluorinating CF 0.9 fibers, made from P-25, in sulfur (S) vapor at 370 C and then heating to 660 C in nitrogen (N2). Furthermore, defluorination of the CF 0.68 fibers in bromine (Br2) produced fragile, structurally damaged carbon fibers. Heating these fragile fibers to 1100 C in N2 caused further structural damage, whereas heating to 150 C in bromoform (CHBr3) and then to 1100 C in N2 healed the structural defects. The defluorination product of CFX, tentatively called activated graphite, has the composition and molecular structure of graphite, but is chemically more reactive. Activated graphite is a scavenger of manganese (Mn), and can be intercalated with magnesium (Mg). Also, it can easily collect large amounts of an alloy made from copper (Cu) and type 304 stainless steel to form a composite. Finally, there are indications that activated graphite can wet metals or ceramics, thereby forming stronger composites with them than the pristine carbon fibers can form.

  9. Solar energy combined with chemical reactive systems for the production and storage of sustainable energy. A review of thermodynamic principles

    International Nuclear Information System (INIS)

    Highlights: ► Solar radiation power. ► Chemical reactions for the production and storage of usable energy. ► Thermodynamics of solar power. ► Homogeneous and heterogeneous reactive systems. - Abstract: This review article deals with thermodynamics and thermochemistry of processes combining solar radiation power with chemical reactions for the production and storage of usable energy. Some of the most promising procedures of such processes discussed in the literature have been selected as representative examples and are analyzed on the basis of their thermodynamic principles rather than reporting on technical details and feasibility studies with respect to economic potentials. The examples studied involve pure gaseous as well as heterogeneous reactive systems where the shift of chemical equilibria at different temperatures is used to gain chemical energy. The majority of examples focusses on different multistep chemical processes for water splitting into H2 and O2 which have already been tested on laboratory and semi technical scale.

  10. Effect of chemical degradation on fluxes of reactive compounds – a study with a stochastic Lagrangian transport model

    Directory of Open Access Journals (Sweden)

    J. Rinne

    2012-06-01

    Full Text Available In the analyses of VOC fluxes measured above plant canopies, one usually assumes the flux above canopy to equal the exchange at the surface. Thus one assumes the chemical degradation to be much slower than the turbulent transport. We used a stochastic Lagrangian transport model in which the chemical degradation was described as first order decay in order to study the effect of the chemical degradation on above canopy fluxes of chemically reactive species. With the model we explored the sensitivity of the ratio of the above canopy flux to the surface emission on several parameters such as chemical lifetime of the compound, friction velocity, stability, and canopy density. Our results show that friction velocity and chemical lifetime affected the loss during transport the most. The canopy density had a significant effect if the chemically reactive compound was emitted from the forest floor. We used the results of the simulations together with oxidant data measured during HUMPPA-COPEC-2010 campaign at a Scots pine site to estimate the effect of the chemistry on fluxes of three typical biogenic VOCs, isoprene, α-pinene, and β-caryophyllene. Of these, the chemical degradation had a major effect on the fluxes of the most reactive species β-caryophyllene, while the fluxes of α-pinene were affected during nighttime. For these two compounds representing the mono- and sesquiterpenes groups, the effect of chemical degradation had also a significant diurnal cycle with the highest chemical loss at night. The different day and night time loss terms need to be accounted for, when measured fluxes of reactive compounds are used to reveal relations between primary emission and environmental parameters.

  11. Structure Chemical Composition And Reactivity Correlations during the In Situ Oxidation of 2-Propanol

    Energy Technology Data Exchange (ETDEWEB)

    K Paredis; L Ono; S Mostafa; L Li; Z Zhang; J Yang; L Barrio; A Frenkel; B Roldan Cuenya

    2011-12-31

    Unraveling the complex interaction between catalysts and reactants under operando conditions is a key step toward gaining fundamental insight in catalysis. We report the evolution of the structure and chemical composition of size-selected micellar Pt nanoparticles ({approx}1 nm) supported on nanocrystalline {gamma}-Al{sub 2}O{sub 3} during the catalytic oxidation of 2-propanol using X-ray absorption fine-structure spectroscopy. Platinum oxides were found to be the active species for the partial oxidation of 2-propanol (<140 C), while the complete oxidation (>140 C) is initially catalyzed by oxygen-covered metallic Pt nanoparticles, which were found to regrow a thin surface oxide layer above 200 C. The intermediate reaction regime, where the partial and complete oxidation pathways coexist, is characterized by the decomposition of the Pt oxide species due to the production of reducing intermediates and the blocking of O{sub 2} adsorption sites on the nanoparticle surface. The high catalytic activity and low onset reaction temperature displayed by our small Pt particles for the oxidation of 2-propanol is attributed to the large amount of edge and corner sites available, which facilitate the formation of reactive surface oxides. Our findings highlight the decisive role of the nanoparticle structure and chemical state in oxidation catalytic reactions.

  12. Local and linear chemical reactivity response functions at finite temperature in density functional theory

    International Nuclear Information System (INIS)

    We explore the local and nonlocal response functions of the grand canonical potential density functional at nonzero temperature. In analogy to the zero-temperature treatment, local (e.g., the average electron density and the local softness) and nonlocal (e.g., the softness kernel) intrinsic response functions are defined as partial derivatives of the grand canonical potential with respect to its thermodynamic variables (i.e., the chemical potential of the electron reservoir and the external potential generated by the atomic nuclei). To define the local and nonlocal response functions of the electron density (e.g., the Fukui function, the linear density response function, and the dual descriptor), we differentiate with respect to the average electron number and the external potential. The well-known mathematical relationships between the intrinsic response functions and the electron-density responses are generalized to nonzero temperature, and we prove that in the zero-temperature limit, our results recover well-known identities from the density functional theory of chemical reactivity. Specific working equations and numerical results are provided for the 3-state ensemble model

  13. Local and linear chemical reactivity response functions at finite temperature in density functional theory

    Energy Technology Data Exchange (ETDEWEB)

    Franco-Pérez, Marco, E-mail: francopj@mcmaster.ca, E-mail: ayers@mcmaster.ca, E-mail: jlgm@xanum.uam.mx, E-mail: avela@cinvestav.mx [Department of Chemistry and Chemical Biology, McMaster University, Hamilton, Ontario L8S 4M1 (Canada); Departamento de Química, Universidad Autónoma Metropolitana-Iztapalapa, Av. San Rafael Atlixco 186, México, D.F. 09340 (Mexico); Ayers, Paul W., E-mail: francopj@mcmaster.ca, E-mail: ayers@mcmaster.ca, E-mail: jlgm@xanum.uam.mx, E-mail: avela@cinvestav.mx [Department of Chemistry and Chemical Biology, McMaster University, Hamilton, Ontario L8S 4M1 (Canada); Gázquez, José L., E-mail: francopj@mcmaster.ca, E-mail: ayers@mcmaster.ca, E-mail: jlgm@xanum.uam.mx, E-mail: avela@cinvestav.mx [Departamento de Química, Universidad Autónoma Metropolitana-Iztapalapa, Av. San Rafael Atlixco 186, México, D.F. 09340 (Mexico); Vela, Alberto, E-mail: francopj@mcmaster.ca, E-mail: ayers@mcmaster.ca, E-mail: jlgm@xanum.uam.mx, E-mail: avela@cinvestav.mx [Departamento de Química, Centro de Investigación y de Estudios Avanzados (Cinvestav), Av. Instituto Politécnico Nacional 2508, México, D.F. 07360 (Mexico)

    2015-12-28

    We explore the local and nonlocal response functions of the grand canonical potential density functional at nonzero temperature. In analogy to the zero-temperature treatment, local (e.g., the average electron density and the local softness) and nonlocal (e.g., the softness kernel) intrinsic response functions are defined as partial derivatives of the grand canonical potential with respect to its thermodynamic variables (i.e., the chemical potential of the electron reservoir and the external potential generated by the atomic nuclei). To define the local and nonlocal response functions of the electron density (e.g., the Fukui function, the linear density response function, and the dual descriptor), we differentiate with respect to the average electron number and the external potential. The well-known mathematical relationships between the intrinsic response functions and the electron-density responses are generalized to nonzero temperature, and we prove that in the zero-temperature limit, our results recover well-known identities from the density functional theory of chemical reactivity. Specific working equations and numerical results are provided for the 3-state ensemble model.

  14. Accelerating moderately stiff chemical kinetics in reactive-flow simulations using GPUs

    CERN Document Server

    Niemeyer, Kyle E

    2014-01-01

    The chemical kinetics ODEs arising from operator-split reactive-flow simulations were solved on GPUs using explicit integration algorithms. Nonstiff chemical kinetics of a hydrogen oxidation mechanism (9 species and 38 irreversible reactions) were computed using the explicit fifth-order Runge-Kutta-Cash-Karp method, and the GPU-accelerated version performed faster than single- and six-core CPU versions by factors of 126 and 25, respectively, for 524,288 ODEs. Moderately stiff kinetics, represented with mechanisms for hydrogen/carbon-monoxide (13 species and 54 irreversible reactions) and methane (53 species and 634 irreversible reactions) oxidation, were computed using the stabilized explicit second-order Runge-Kutta-Chebyshev (RKC) algorithm. The GPU-based RKC implementation demonstrated an increase in performance of nearly 59 and 10 times, for problem sizes consisting of 262,144 ODEs and larger, than the single- and six-core CPU-based RKC algorithms using the hydrogen/carbon-monoxide mechanism. With the met...

  15. KIVA-2: A computer program for chemically reactive flows with sprays

    Science.gov (United States)

    Amsden, A. A.; Orourke, P. J.; Butler, T. D.

    1989-05-01

    This report documents the KIVA-2 computer program for the numerical calculation of transient, two- and three-dimensional, chemically reactive fluid flows with sprays. KIVA-2 extends and enhances the earlier KIVA code, improving its computational accuracy and efficiency and its ease-of-use. The KIVA-2 equations and numerical solution procedures are very general and can be applied to laminar or turbulent flows, subsonic or supersonic flows, and single-phase or dispersed two-phase flows. Arbitrary numbers of species and chemical reactions are allowed. A stochastic particle method is used to calculate evaporating liquid sprays, including the effects of droplet collisions and aerodynamic breakups. Although the initial and boundary conditions and mesh generation have been written for internal combustion engine calculations, the logic for these specifications can be easily modified for a variety of other applications. Following an overview of the principal features of the KIVA-2 program, we describe in detail the equations solved, the numerical solution procedure, and the structure of the computer program. Sixteen appendices provide additional details concerning the numerical solution procedure.

  16. Optimization of integrated chemical-biological degradation of a reactive azo dye using response surface methodology

    International Nuclear Information System (INIS)

    The integrated chemical-biological degradation combining advanced oxidation by UV/H2O2 followed by aerobic biodegradation was used to degrade C.I. Reactive Azo Red 195A, commonly used in the textile industry in Australia. An experimental design based on the response surface method was applied to evaluate the interactive effects of influencing factors (UV irradiation time, initial hydrogen peroxide dosage and recirculation ratio of the system) on decolourisation efficiency and optimizing the operating conditions of the treatment process. The effects were determined by the measurement of dye concentration and soluble chemical oxygen demand (S-COD). The results showed that the dye and S-COD removal were affected by all factors individually and interactively. Maximal colour degradation performance was predicted, and experimentally validated, with no recirculation, 30 min UV irradiation and 500 mg H2O2/L. The model predictions for colour removal, based on a three-factor/five-level Box-Wilson central composite design and the response surface method analysis, were found to be very close to additional experimental results obtained under near optimal conditions. This demonstrates the benefits of this approach in achieving good predictions while minimising the number of experiments required

  17. Chemical Imaging and Dynamical Studies of Reactivity and Emergent Behavior in Complex Interfacial Systems. Final Technical Report

    Energy Technology Data Exchange (ETDEWEB)

    Sibener, Steven J. [University of Chicago, IL (United States)

    2014-03-11

    This research program explored the efficacy of using molecular-level manipulation, imaging and scanning tunneling spectroscopy in conjunction with supersonic molecular beam gas-surface scattering to significantly enhance our understanding of chemical processes occurring on well-characterized interfaces. One program focus was on the spatially-resolved emergent behavior of complex reaction systems as a function of the local geometry and density of adsorbate-substrate systems under reaction conditions. Another focus was on elucidating the emergent electronic and related reactivity characteristics of intentionally constructed single and multicomponent atom- and nanoparticle-based materials. We also examined emergent chirality and self-organization in adsorbed molecular systems where collective interactions between adsorbates and the supporting interface lead to spatial symmetry breaking. In many of these studies we combined the advantages of scanning tunneling (STM) and atomic force (AFM) imaging, scanning tunneling local electronic spectroscopy (STS), and reactive supersonic molecular beams to elucidate precise details of interfacial reactivity that had not been observed by more traditional surface science methods. Using these methods, it was possible to examine, for example, the differential reactivity of molecules adsorbed at different bonding sites in conjunction with how reactivity is modified by the local configuration of nearby adsorbates. At the core of this effort was the goal of significantly extending our understanding of interfacial atomic-scale interactions to create, with intent, molecular assemblies and materials with advanced chemical and physical properties. This ambitious program addressed several key topics in DOE Grand Challenge Science, including emergent chemical and physical properties in condensed phase systems, novel uses of chemical imaging, and the development of advanced reactivity concepts in combustion and catalysis including carbon

  18. Methods for the mitigation of the chemical reactivity of beryllium in steam

    International Nuclear Information System (INIS)

    In the safety assessment of future fusion reactors, the reaction of beryllium with steam remains one of the main concerns. In this case of a loss of coolant accident (LOCA), the use of beryllium in combination with pressurized water as coolant can lead to excessive hydrogen production due to the reaction Be + H2O = BeO +H2 +heat. Because of the explosion hazard associated with this phenomenon, the hydrogen generation rate during a LOCA should be reduced as much as possible. Therefore, we started an R and D programme aimed at investigating mitigation methods for the beryllium/steam reaction. Beryllium samples were implanted in a 210 kV ion implanter at ITN (Institute Technologico e Nuclear) Lisbon, with calcium and aluminum ions respectively in a 210 kV ion implanter at ITN Lisbon. The average implantation depth was estimated at 100 nm for both elements. The chemical activity of these samples in steam was then measured at SCK-CEN (The Belgian Nuclear Research Center) in a dedicated experimental facility providing coupled thermogravimetry/mass spectrometry. The observed oxidation kinetics was parabolic. In comparison to reference un-doped material, the reactivity of doped beryllium after 30 minutes of exposure decreased with a factor 2 to 4. The mitigating effect was higher for calcium-doped than for aluminum-doped samples. As a second approach, beryllium pebbles were pre-oxidized in dry air at 400 degree C during ten hours. This did not result in an appreciable decrease in chemical activity. The results indicate that doping may be a viable means of mitigating the chemical activity of beryllium in steam. (author)

  19. Characterization of Dimethylsulfoxide / Glycerol Mixtures: A Binary Solvent System for the Study of "Friction-Dependent" Chemical Reactivity

    OpenAIRE

    Angulo Nunez, Gonzalo Manuel; Brucka, Marta; Gerecke, Mario; Grampp, Günter; Jeannerat, Damien; Milkiewicz, Jadwiga; Mitrev, Yavor; Radzewicz, Czesław; Rosspeintner, Arnulf; Vauthey, Eric; Wnuk, Paweł

    2016-01-01

    The properties of binary mixtures of dimethylsulfoxide and glycerol, measured by several techniques, are reported. Special attention is given to those properties contributing or affecting chemical reactions. In this respect the investigated mixture behaves as a relatively simple solvent and it is especially well suited for studies on the influence of viscosity in chemical reactivity. This is due to the relative invariance of the dielectric properties of the mixture. However, special caution m...

  20. Advanced Chemical Reduction of Reduced Graphene Oxide and Its Photocatalytic Activity in Degrading Reactive Black 5

    Directory of Open Access Journals (Sweden)

    Christelle Pau Ping Wong

    2015-10-01

    Full Text Available Textile industries consume large volumes of water for dye processing, leading to undesirable toxic dyes in water bodies. Dyestuffs are harmful to human health and aquatic life, and such illnesses as cholera, dysentery, hepatitis A, and hinder the photosynthetic activity of aquatic plants. To overcome this environmental problem, the advanced oxidation process is a promising technique to mineralize a wide range of dyes in water systems. In this work, reduced graphene oxide (rGO was prepared via an advanced chemical reduction route, and its photocatalytic activity was tested by photodegrading Reactive Black 5 (RB5 dye in aqueous solution. rGO was synthesized by dispersing the graphite oxide into the water to form a graphene oxide (GO solution followed by the addition of hydrazine. Graphite oxide was prepared using a modified Hummers’ method by using potassium permanganate and concentrated sulphuric acid. The resulted rGO nanoparticles were characterized using ultraviolet-visible spectrophotometry (UV-Vis, X-ray powder diffraction (XRD, Raman, and Scanning Electron Microscopy (SEM to further investigate their chemical properties. A characteristic peak of rGO-48 h (275 cm−1 was observed in the UV spectrum. Further, the appearance of a broad peak (002, centred at 2θ = 24.1°, in XRD showing that graphene oxide was reduced to rGO. Based on our results, it was found that the resulted rGO-48 h nanoparticles achieved 49% photodecolorization of RB5 under UV irradiation at pH 3 in 60 min. This was attributed to the high and efficient electron transport behaviors of rGO between aromatic regions of rGO and RB5 molecules.

  1. Atomistic-level non-equilibrium model for chemically reactive systems based on steepest-entropy-ascent quantum thermodynamics

    International Nuclear Information System (INIS)

    This paper outlines an atomistic-level framework for modeling the non-equilibrium behavior of chemically reactive systems. The framework called steepest- entropy-ascent quantum thermodynamics (SEA-QT) is based on the paradigm of intrinsic quantum thermodynamic (IQT), which is a theory that unifies quantum mechanics and thermodynamics into a single discipline with wide applications to the study of non-equilibrium phenomena at the atomistic level. SEA-QT is a novel approach for describing the state of chemically reactive systems as well as the kinetic and dynamic features of the reaction process without any assumptions of near-equilibrium states or weak-interactions with a reservoir or bath. Entropy generation is the basis of the dissipation which takes place internal to the system and is, thus, the driving force of the chemical reaction(s). The SEA-QT non-equilibrium model is able to provide detailed information during the reaction process, providing a picture of the changes occurring in key thermodynamic properties (e.g., the instantaneous species concentrations, entropy and entropy generation, reaction coordinate, chemical affinities, reaction rate, etc). As an illustration, the SEA-QT framework is applied to an atomistic-level chemically reactive system governed by the reaction mechanism F + H2 ↔ FH + H

  2. Chemical and Molecular Descriptors for the Reactivity of Amines with CO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Anita S.; Kitchin, John R.

    2012-10-24

    Amine-based solvents are likely to play an important role in CO{sub 2} capture applications in the future, and the identification of amines with superior performance will facilitate their use in CO{sub 2} capture. While some improvements in performance will be achieved through process modifications, modifying the CO{sub 2} capture performance of an amine also implies in part an ability to modify the reactions between the amine and CO{sub 2} through development of new functionalized amines. We present a computational study of trends in the reactions between CO{sub 2} and functionalized amines with a focus on identifying molecular descriptors that determine trends in reactivity. We examine the formation of bicarbonate and carbamate species on three classes of functionalized amines: alkylamines, alkanolamines, and fluorinated alkylamines including primary, secondary and tertiary amines in each class. These functional groups span electron-withdrawing to donating behavior, hydrogen-bonding, extent of functionalization, and proximity effects of the functional groups. Electron withdrawing groups tend to destabilize CO{sub 2} reaction products, whereas electron-donating groups tend to stabilize CO{sub 2} reaction products. Hydrogen bonding stabilizes CO{sub 2} reaction products. Electronic structure descriptors based on electronegativity were found to describe trends in the bicarbonate formation energy. A chemical correlation was observed between the carbamate formation energy and the carbamic acid formation energy. The local softness on the reacting N in the amine was found to partially explain trends carbamic acid formation energy.

  3. Toward Tetraradicaloid: The Effect of Fusion Mode on Radical Character and Chemical Reactivity.

    Science.gov (United States)

    Hu, Pan; Lee, Sangsu; Herng, Tun Seng; Aratani, Naoki; Gonçalves, Théo P; Qi, Qingbiao; Shi, Xueliang; Yamada, Hiroko; Huang, Kuo-Wei; Ding, Jun; Kim, Dongho; Wu, Jishan

    2016-01-27

    Open-shell singlet diradicaloids display unique electronic, nonlinear optical, and magnetic activity and could become novel molecular materials for organic electronics, photonics, and spintronics. However, design and synthesis of diradicaloids with a significant polyradical character is a challenging task for chemists. In this Article, we report our efforts toward a tetraradicaloid system. A series of potential tetraradicaloids by fusion of two p-quinodimethane (p-QDM) units with naphthalene or benzene rings in different modes were synthesized. Their model compounds containing one p-QDM moiety were also prepared and compared. Their ground-state structures, physical properties, and chemical reactivity were systematically investigated by various experimental methods such as steady-state and transient absorption, two-photon absorption, X-ray crystallographic analysis, electron spin resonance, superconducting quantum interference device, and electrochemistry, assisted by density functional theory calculations. It was found that their diradical and tetraradical characters show a clear dependence on the fusion mode. Upon the introduction of more five-membered rings, the diradical characters greatly decrease. This difference can be explained by the pro-aromaticity/antiaromaticity of the molecules as well as the intramolecular charge transfer. Our comprehensive studies provide a guideline for the design and synthesis of stable open-shell singlet polycyclic hydrocarbons with significant polyradical characters. PMID:26717263

  4. Chemical reactivity at buried-interfaces. II. Iron on nonstoichiometric and/or defected molybdenite

    Science.gov (United States)

    Zabinski, J. S.; George, T.; Tatarchuk, B. J.

    1991-01-01

    The role of defects and nonstoichioinetries in molybdenite substrates, and their influence on the chemical reactivity at buried MoS 2Fe interfaces, were investigated using conversion electron Mössbauer spectroscopy and X-ray photoelectron spectroscopy. Defects in the molybdenite crystal structure intentionally introduced by Ar + bombardment, or from the inherent structure of small MoS 2 crystallites, provide pathways for the diffusion and reaction of surface iron into the bulk of MoS 2 to form FeMo 2S 4. In comparison, iron overlayers do not react appreciably with undamaged molybdenite single crystals. Excess sulfur within molybdenite, when present, migrates towards deposited iron overlayers where it forms Fe 1- xs (pyrrhotite) and FeS (troilite). Annealing temperature determines the relative fraction of pyrrhotite to troilite and the orientational relationship between the ĉ-axis of the iron sulfide and the ĉ-axis of the molybdenite substrate. The stoichiometry of the molybdenite substrate, the presence of defects, and the annealing temperature provide a number of means to adjust the properties of the MoS 2Fe interface. Therefore, it may be possible to optimize/control processing conditions so as to impact either the tribochemical or catalytic properties of this important materials.

  5. Chemical Reactivity Probes for Assessing Abiotic Natural Attenuation by Reducing Iron Minerals.

    Science.gov (United States)

    Fan, Dimin; Bradley, Miranda J; Hinkle, Adrian W; Johnson, Richard L; Tratnyek, Paul G

    2016-02-16

    Increasing recognition that abiotic natural attenuation (NA) of chlorinated solvents can be important has created demand for improved methods to characterize the redox properties of the aquifer materials that are responsible for abiotic NA. This study explores one promising approach: using chemical reactivity probes (CRPs) to characterize the thermodynamic and kinetic aspects of contaminant reduction by reducing iron minerals. Assays of thermodynamic CRPs were developed to determine the reduction potentials (ECRP) of suspended minerals by spectrophotometric determination of equilibrium CRP speciation and calculations using the Nernst equation. ECRP varied as expected with mineral type, mineral loading, and Fe(II) concentration. Comparison of ECRP with reduction potentials measured potentiometrically using a Pt electrode (EPt) showed that ECRP was 100-150 mV more negative than EPt. When EPt was measured with small additions of CRPs, the systematic difference between EPt and ECRP was eliminated, suggesting that these CRPs are effective mediators of electron transfer between mineral and electrode surfaces. Model contaminants (4-chloronitrobenzene, 2-chloroacetophenone, and carbon tetrachloride) were used as kinetic CRPs. The reduction rate constants of kinetic CRPs correlated well with the ECRP for mineral suspensions. Using the rate constants compiled from literature for contaminants and relative mineral reduction potentials based on ECRP measurements, qualitatively consistent trends were obtained, suggesting that CRP-based assays may be useful for estimating abiotic NA rates of contaminants in groundwater. PMID:26814150

  6. Prospects of the use of chemically reactive working media in solar energy

    Energy Technology Data Exchange (ETDEWEB)

    Umarov, G.Ia.; Nesterenko, V.B.; Spivak, S.I.; Bubnov, V.P.; Umarov, A.G.

    1984-01-01

    The use of dissociating gases in solar and solar/fossil electric generating stations is shown to increase efficiency and to decrease cost. The advantages of gas and gas-liquid cycles with the heat transfer agent N2O4 as the working medium over both gas turbines using inert gases and steam turbines are presented. In the flow section of a high-pressure turbine of a gas-liquid cycle, high-pressure gas expands from 150 to 21 atm, and the gas temperature decreases from 450 to 300 C. Forty percent of the heat loss, transformed into useful turbine work, is formed due to the heat generated in the recombination of NO and O2. In the low-pressure turbine, 50 percent of the turbine work is formed in this way. The intensity of heat transfer processes in the chemically reactive system is 5-8 times higher than in air systems, and 3-4 times higher than in steam systems. 20 references.

  7. Towards Tetraradicaloid: The Effect of Fusion Mode on Radical Character and Chemical Reactivity

    KAUST Repository

    Hu, Pan

    2015-12-30

    Open-shell singlet diradicaloids display unique electronic, non-linear optical and magnetic activity and could become novel molecular materials for organic electronics, photonics and spintronics. However, design and synthesis of diradicaloids with a significant polyradical character is a challenging task for chemists. In this article, we report our efforts toward tetraradicaloid system. A series of potential tetraradicaloids by fusion of two p-quinodimethane (p-QDM) units with naphthalene or benzene rings in different modes were synthesized. Their model compounds containing one p-QDM moiety were also prepared and compared. Their ground-state structures, physical properties and chemical reactivity were systematically investigated by various exper-imental methods such as steady-state and transient absorption, two-photon absorption, X-ray crystallographic analysis, electron spin resonance, superconducting quantum interference device and electrochemistry, assisted by density functional theory calculations. It was found that their diradical and tetraradical characters show a clear dependence on the fusion mode. Upon the introducing of more five-membered rings, the diradical characters greatly decrease. This difference can be explained by the pro-aromaticity/anti-aromaticity of the molecules as well as the intramolecular charge transfer. Our comprehensive studies provide a guideline for the design and synthesis of stable open-shell singlet polycyclic hydrocarbons with significant polyradical characters.

  8. Theoretical study of some aspects of the nucleo-bases reactivity: definition of new theoretical tools for the study of chemical reactivity

    International Nuclear Information System (INIS)

    In this work, three kinds of nucleo-base damages were studied from a theoretical point of view with quantum chemistry methods based on the density-functional theory: the spontaneous deamination of cytosine and its derivatives, the formation of tandem lesion induced by hydroxyl radicals in anaerobic medium and the formation of pyrimidic dimers under exposition to an UV radiation. The complementary use of quantitative static methods allowing the exploration of the potential energy surface of a chemical reaction, and of 'conceptual DFT' principles, leads to information concerning the mechanisms involved and to the rationalization of the differences in the nucleo-bases reactivity towards the formation of a same kind of damage. At the same time, a reflexion was undertaken on the asynchronous concerted mechanism concept, in terms of physical meaning of the transition state, respect of the Maximum Hardness Principle, and determination of the number of primitive processes involved. Finally, a new local reactivity index was developed, relevant to understand the reactivity of a molecular system in an excited state. (author)

  9. Evaluation of specific ultraviolet absorbance as an indicator of the chemical composition and reactivity of dissolved organic carbon

    Science.gov (United States)

    Weishaar, J.L.; Aiken, G.R.; Bergamaschi, B.A.; Fram, M.S.; Fujii, R.; Mopper, K.

    2003-01-01

    Specific UV absorbance (SUVA) is defined as the UV absorbance of a water sample at a given wavelength normalized for dissolved organic carbon (DOC) concentration. Our data indicate that SUVA, determined at 254 nm, is strongly correlated with percent aromaticity as determined by 13C NMR for 13 organic matter isolates obtained from a variety of aquatic environments. SUVA, therefore, is shown to be a useful parameter for estimating the dissolved aromatic carbon content in aquatic systems. Experiments involving the reactivity of DOC with chlorine and tetramethylammonium hydroxide (TMAH), however, show a wide range of reactivity for samples with similar SUVA values. These results indicate that, while SUVA measurements are good predictors of general chemical characteristics of DOC, they do not provide information about reactivity of DOC derived from different types of source materials. Sample pH, nitrate, and iron were found to influence SUVA measurements.

  10. A toxicokinetic study of specifically acting and reactive organic chemicals for the prediction of internal effect concentrations in Scenedesmus vacuolatus.

    Science.gov (United States)

    Vogs, Carolina; Kühnert, Agnes; Hug, Christine; Küster, Eberhard; Altenburger, Rolf

    2015-01-01

    The toxic potency of chemicals is determined by using the internal effect concentration by accounting for differences in toxicokinetic processes and mechanisms of toxic action. The present study examines toxicokinetics of specifically acting and reactive chemicals in the green algae Scenedesmus vacuolatus by using an indirect method. Concentration depletion in the exposure medium was measured for chemicals of lower (log KOW  2-naphthylamine) hydrophobicity at 7 to 8 time points over 240 min or 360 min. Uptake and overall elimination rates were estimated by fitting a toxicokinetic model to the observed concentration depletions. The equilibrium of exposure concentrations was reached within minutes to hours or was even not observed within the exposure time. The kinetics of bioconcentration cannot be explained by the chemical's hydrophobicity only, but influential factors such as ionization of chemicals, the ion trapping mechanism, or the potential susceptibility for biotransformation are discussed. Internal effect concentrations associated with 50% inhibition of S. vacuolatus reproduction were predicted by linking the bioconcentration kinetics to the effect concentrations and ranged from 0.0480 mmol/kg wet weight to 7.61 mmol/kg wet weight for specifically acting and reactive chemicals. Knowing the time-course of the internal effect concentration may promote an understanding of toxicity processes such as delayed toxicity, carry-over toxicity, or mixture toxicity in future studies. PMID:25263251

  11. Melting and chemical reactivity of hydrocarbons under high pressure and temperature

    Science.gov (United States)

    Lobanov, S.; Chanyshev, A.; Chen, P.; Litasov, K.; Chen, X.; Goncharov, A.

    2013-12-01

    Hydrocarbons comprise roughly ⅓ of the icy mantles in interiors of icy giant planets and may determine the planetary physical properties. Here we present the results of laser heated diamond anvil cell experiments on hydrocarbon chemical reactivity at P up to 50 GPa and T up to 2000 K. Ethane (C2H6) and n-docosane (C22H46) were chosen as starting materials. Raman spectroscopy at high P was used to probe the C-H systems. Melting lines of the hydrocarbons were found by visual observations of fluid-solid interface. The melting lines lie below 1500 K at P1000 K and P25-30 GPa. Remarkably, free H2 was found in experiments at P>30-35 GPa. The interpretation of Raman spectra of quenched reaction products is uncertain. In general, P and T affect the lifetimes of C-H and C-C bonds. Temperature provides energy to brake C-H and C-C bonds, while stabilization of the bonds with pressure may be more pronounced for C-C bonds. The composition of C-H fluid is determined by the competition between C-C and C-H bonds. This competition can result in hydrocarbons with long C-C network. The role of C=C and C≡C bonds at high P cannot be ruled out from this study. It is possible that unsaturated hydrocarbons appear upon quenching from highly dissociated C-H fluid rather than being present in C-H fluid. n-docosane at 12 GPa Ethane at 34 GPa

  12. Colloidal stability and chemical reactivity of complex colloids containing Fe³⁺.

    Science.gov (United States)

    van Leeuwen, Y M; Velikov, K P; Kegel, W K

    2014-07-15

    The reactivity of iron contained within insoluble colloidal metal-pyrophosphate salts was determined and compared to the reactivity of a soluble iron salt (FeCl3). As a model system for the reactivity of iron in food products, the formation of an iron-polyphenol complex was followed with spectrophotometry. Three types of systems were prepared and their colloidal stability and reactivity studied: Fe(3+) pyrophosphate, protein-coated Fe(3+) pyrophosphate and mixed-metal pyrophosphates containing Fe(3+) and a second cation M. The additional cation used was either monovalent (sodium) or divalent (M(2+)). It was found that: (i) incorporating iron in a colloidal salt reduced its reactivity compared to free Fe(3+) ions; (ii) coating the particles with a layer of hydrophobic protein (zein) increased stability and further decreased the reactivity. Finally, the most surprising result was that (iii) a mixed system containing more Fe(3+) than M actually increased the reactivity of the contained iron, while the reverse, a system containing excess M, inhibited the reactivity completely. PMID:24594169

  13. Analysis of chemical reactivity of aminocyclopyrachlor herbicide through the Fukui function

    Directory of Open Access Journals (Sweden)

    Mendoza-Huizar Luis Humberto

    2015-01-01

    Full Text Available We have calculated global and local DFT reactivity descriptors for aminocyclopyrachlor herbicide at the MP2/6-311++G (2d,2p level of theory in the aqueous phase. Global reactivity descriptors such as ionization energy, molecular hardness, electrophilicity, and total energies were calculated to evaluate the aminocyclopyrachlor reactivity. Local reactivity was evaluated through the Fukui function. Our results suggest that the cationic and dipolar forms of aminocyclopyrachlor exhibit similar global reactivity and they are susceptible to deamination and decarboxylation. Also, the opening of the ring might become factible through free radical attacks to the neutral form, while a similar process is caused by nucleophilic attacks on the anionic form.

  14. Characterization of Dimethylsulfoxide / Glycerol Mixtures: A Binary Solvent System for the Study of "Friction-Dependent" Chemical Reactivity

    CERN Document Server

    Angulo, Gonzalo; Gerecke, Mario; Grampp, Günter; Jeannerat, Damien; Milkiewicz, Jadwiga; Mitrev, Yavor; Radzewicz, Czesław; Rosspeintner, Arnulf; Vauthey, Eric; Wnuk, Paweł

    2016-01-01

    The properties of binary mixtures of dimethylsulfoxide and glycerol, measured by several techniques, are reported. Special attention is given to those properties contributing or affecting chemical reactions. In this respect the investigated mixture behaves as a relatively simple solvent and it is especially well suited for studies on the influence of viscosity in chemical reactivity. This is due to the relative invariance of the dielectric properties of the mixture. However, special caution must be taken with specific solvation, as the hydrogen-bonding properties of the solvent changes with the molar fraction of glycerol.

  15. Characterization of dimethylsulfoxide/glycerol mixtures: a binary solvent system for the study of "friction-dependent" chemical reactivity.

    Science.gov (United States)

    Angulo, Gonzalo; Brucka, Marta; Gerecke, Mario; Grampp, Günter; Jeannerat, Damien; Milkiewicz, Jadwiga; Mitrev, Yavor; Radzewicz, Czesław; Rosspeintner, Arnulf; Vauthey, Eric; Wnuk, Paweł

    2016-07-21

    The properties of binary mixtures of dimethylsulfoxide and glycerol, measured using several techniques, are reported. Special attention is given to those properties contributing or affecting chemical reactions. In this respect the investigated mixture behaves as a relatively simple solvent and it is especially well suited for studies on the influence of viscosity on chemical reactivity. This is due to the relative invariance of the dielectric properties of the mixture. However, special caution must be taken with specific solvation, as the hydrogen-bonding properties of the solvent change with the molar fraction of glycerol. PMID:27339434

  16. Chemical reaction of sputtered Cu film with PI modified by low energy reactive atomic beam

    International Nuclear Information System (INIS)

    Polyimide (PMDA-ODA) surface was irradiated by low energy reactive atomic beam with energy 160-180 eV to enhance the adhesion with metal Cu film. O2+ and N2+ ions were irradiated at the fluence from 5 x 1015 to 1 x 1018 cm-2. Wetting angle 78o of distilled deionized (DI) water for bare PI was greatly reduced down to 2-4o after critical ion flounce, and the surface energy was increased from 37 to 81.2 erg/cm. From the analysis of O 1s core-level XPS spectra, such improvement seemed to result from the increment of hydrophilic carbonyl oxygen content on modified PI surface. To see more carefully correlation of the peel strength with interfacial reaction between Cu and PI, flexible copper clad laminate with Cu (9 μm)/Cu (200 nm) on modified PI substrate (25 μm) was fabricated by successive sputtering and electroplating. Firstly, peel strength was measured by using t-test and it was largely increased from 0.2 to 0.5 kgf/cm for Ar+ only irradiated PI to 0.72-0.8 kgf/cm for O2+ or N2O+ irradiated PI. Chemical reaction at the interface was reasoned by analyzing C 1s, O 1s, N 1s, and Cu 2p core-level X-ray photoelectron spectroscopy over the as-cleaved Cu-side and PI side surface through depth profiling. From the C 1s spectra of cleaved Cu-side, by the electron transfer from Cu to carbonyl oxygen, carbonyl carbon atom became less positive and as a result shifted to lower binding energy not reaching the binding energy of C2 and C3. The binding energy shift of the peak C4 as small as 1.7 eV indicates that carbonyl oxygen atoms were not completely broken. From the analysis of the O 1s spectra, it was found that new peak at 530.5 eV (O3) was occurred and the increased area of the peak O3 was almost the same with reduced area of the peak carbonyl oxygen peak O1. Since there was no change in the relative intensity of ether oxygen (O2) to carbonyl oxygen (O1), and thus O3 was believed to result from Cu oxide formation via a local bonding of Cu with carbonyl oxygen atoms

  17. Chemical Characterization and Reactivity Testing of Fuel-Oxidizer Reaction Product (Test Report)

    Science.gov (United States)

    1996-01-01

    The product of incomplete reaction of monomethylhydrazine (MMH) and nitrogen tetroxide (NTO) propellants, or fuel-oxidizer reaction product (FORP), has been hypothesized as a contributory cause of an anomaly which occurred in the chamber pressure (PC) transducer tube on the Reaction Control Subsystem (RCS) aft thruster 467 on flight STS-51. A small hole was found in the titanium-alloy PC tube at the first bend below the pressure transducer. It was surmised that the hole may have been caused by heat and pressure resulting from ignition of FORP. The NASA Johnson Space Center (JSC) White Sands Test Facility (WSTF) was requested to define the chemical characteristics of FORP, characterize its reactivity, and simulate the events in a controlled environment which may have lead to the Pc-tube failure. Samples of FORP were obtained from the gas-phase reaction of MMH with NTO under laboratory conditions, the pulsed firings of RCS thrusters with modified PC tubes using varied oxidizer or fuel lead times, and the nominal RCS thruster firings at WSTF and Kaiser-Marquardt. Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), accelerating rate calorimetry (ARC), ion chromatography (IC), inductively coupled plasma (ICP) spectrometry, thermogravimetric analysis (TGA) coupled to FTIR (TGA/FTIR), and mechanical impact testing were used to qualitatively and quantitatively characterize the chemical, thermal, and ignition properties of FORP. These studies showed that the composition of FORP is variable but falls within a limited range of compositions that depends on the fuel loxidizer ratio at the time of formation, composition of the post-formation atmosphere (reducing or oxidizing), and reaction or postreaction temperature. A typical composition contains methylhydrazinium nitrate (MMHN), ammonium nitrate (AN), methylammonium nitrate (MAN), and trace amounts of hydrazinium nitrate and 1,1-dimethylhydrazinium nitrate. The thermal decomposition

  18. Chemical exposure-response relationship between air pollutants and reactive oxygen species in the human respiratory tract.

    Science.gov (United States)

    Lakey, Pascale S J; Berkemeier, Thomas; Tong, Haijie; Arangio, Andrea M; Lucas, Kurt; Pöschl, Ulrich; Shiraiwa, Manabu

    2016-01-01

    Air pollution can cause oxidative stress and adverse health effects such as asthma and other respiratory diseases, but the underlying chemical processes are not well characterized. Here we present chemical exposure-response relations between ambient concentrations of air pollutants and the production rates and concentrations of reactive oxygen species (ROS) in the epithelial lining fluid (ELF) of the human respiratory tract. In highly polluted environments, fine particulate matter (PM2.5) containing redox-active transition metals, quinones, and secondary organic aerosols can increase ROS concentrations in the ELF to levels characteristic for respiratory diseases. Ambient ozone readily saturates the ELF and can enhance oxidative stress by depleting antioxidants and surfactants. Chemical exposure-response relations provide a quantitative basis for assessing the relative importance of specific air pollutants in different regions of the world, showing that aerosol-induced epithelial ROS levels in polluted megacity air can be several orders of magnitude higher than in pristine rainforest air. PMID:27605301

  19. Surface reactivity and layer analysis of chemisorbed reaction films in the surface-chemical environment of alkyl octadecenoates

    Indian Academy of Sciences (India)

    R B Choudhary; O N Anand; O S Tyagi

    2009-05-01

    Studies on surface reactivity of substrate iron (Fe-particles) were made in the tribo-chemical environment of alkyl octadecenoates. Two alkyl octadecenoates namely ethyl octadecenoate and methyl 12-hydroxy octadecenoate, slightly different in their chemical nature, were taken for preparing the chemisorbed reaction films (CRF) at the temperature 100 ± 5°C. The reaction products collected in the composite (amorphous) phase were isolated into three different solvent-soluble fractions (sub-layer films) using polar solvents of increasing polar strength. The FTIR analysis of these films showed that these were primarily organic in nature and were composed of alkyl and/or aryl hydroxy ethers, unsaturated hydroxy ketones, and aromatic structures chemically linked with iron surface. These reaction films also contained large amount of iron (Fe). Further, these film fractions also showed varying thermal behaviour during thermal decomposition in the temperature range of 50-800°C when thermally evaluated in the nitrogen environment.

  20. Chemical exposure-response relationship between air pollutants and reactive oxygen species in the human respiratory tract

    Science.gov (United States)

    Lakey, Pascale S. J.; Berkemeier, Thomas; Tong, Haijie; Arangio, Andrea M.; Lucas, Kurt; Pöschl, Ulrich; Shiraiwa, Manabu

    2016-01-01

    Air pollution can cause oxidative stress and adverse health effects such as asthma and other respiratory diseases, but the underlying chemical processes are not well characterized. Here we present chemical exposure-response relations between ambient concentrations of air pollutants and the production rates and concentrations of reactive oxygen species (ROS) in the epithelial lining fluid (ELF) of the human respiratory tract. In highly polluted environments, fine particulate matter (PM2.5) containing redox-active transition metals, quinones, and secondary organic aerosols can increase ROS concentrations in the ELF to levels characteristic for respiratory diseases. Ambient ozone readily saturates the ELF and can enhance oxidative stress by depleting antioxidants and surfactants. Chemical exposure-response relations provide a quantitative basis for assessing the relative importance of specific air pollutants in different regions of the world, showing that aerosol-induced epithelial ROS levels in polluted megacity air can be several orders of magnitude higher than in pristine rainforest air. PMID:27605301

  1. Fluctuations in reactive networks subject to extrinsic noise studied in the framework of the Chemical Langevin Equation

    CERN Document Server

    Berthoumieux, Hélène

    2016-01-01

    Theoretical and experimental studies have shown that the fluctuations of in vivo systems break the fluctuation-dissipation theorem. One can thus ask what information is contained in the correlation functions of protein concentrations and how they relate to the response of the reactive network to a perturbation. Answers to these questions are of prime importance to extract meaningful parameters from the in vivo fluorescence correlation spectroscopy data. In this paper we study the fluctuations of the concentration of a reactive species involved in a cyclic network that is in a non-equilibrium steady state perturbed by a noisy force, taking into account both the breaking of detailed balance and extrinsic noises. Using a generic model for the network and the extrinsic noise, we derive a Chemical Langevin Equation that describes the dynamics of the system, we determine the expressions of the correlation functions of the concentrations, estimate the deviation of the fluctuation-dissipation theorem and the range of...

  2. A coupling alternative to reactive transport simulations for long-term prediction of chemical reactions in heterogeneous CO2 storage systems

    OpenAIRE

    De Lucia, M.; Kempka, T.; Kühn, M.

    2014-01-01

    Fully-coupled, multi-phase reactive transport simulations of CO2 storage systems can be approximated by a simplified one-way coupling of hydrodynamics and reactive chemistry. The main characteristics of such systems, and hypotheses underlying the proposed alternative coupling, are (i) that the presence of CO2 is the only driving force for chemical reactions and (ii) that its migration in the reservoir is only marginally affected by immobilization due to chemical reac...

  3. A Simple Visualization of Double Bond Properties: Chemical Reactivity and UV Fluorescence

    Science.gov (United States)

    Grayson, Scott M.

    2012-01-01

    A simple, easily visualized thin-layer chromatography (TLC) staining experiment is presented that highlights the difference in reactivity between aromatic double bonds and nonaromatic double bonds. Although the stability of aromatic systems is a major theme in organic chemistry, the concept is rarely reinforced "visually" in the undergraduate…

  4. Chemical reactivity of hypervalent silicon compounds: The local hard and soft acids and bases principle viewpoint

    Indian Academy of Sciences (India)

    Francisco Méndez; María De L Romero; José L Gazquez

    2005-09-01

    The silicon atom may increase its coordination number to values greater than four, to form pentacoordinated compounds. It has been observed experimentally that, in general, pentacoordinated compounds show greater reactivity than tetracoordinated compounds. In this work, density functional theory is used to calculate the global softness and the condensed softness of the silicon atom for SiHF4- and SiHF$^{1-}_{5-n}$. The values obtained show that the global and condensed softness are greater in the pentacoordinated compounds than in the tetracoordinated compounds, a result that explains the enhanced reactivity. If the results are analysed through a local version of the hard and soft acids and bases principle, it is possible to suggest that in nucleophilic substitution reactions, soft nucleophiles preferably react with SiHF$^{1-}_{5-n}$, and hard nucleophiles with SiHF4-.

  5. Chemical conjugation of cowpea mosaic viruses with reactive HPMA-based polymers

    Czech Academy of Sciences Publication Activity Database

    Laga, Richard; Koňák, Čestmír; Šubr, Vladimír; Ulbrich, Karel; Suthiwangcharoen, N.; Niu, Q.; Wang, Q.

    2010-01-01

    Roč. 21, č. 12 (2010), s. 1669-1685. ISSN 0920-5063 R&D Projects: GA AV ČR KJB400500803; GA ČR GA202/09/2078; GA AV ČR KAN200200651 Institutional research plan: CEZ:AV0Z40500505 Keywords : acylthiazolidine-2-thione reactive groups * bioconjugation * coating Subject RIV: CD - Macromolecular Chemistry Impact factor: 1.842, year: 2010

  6. Physico-chemical characterization and oxidative reactivity evaluation of aged brake wear particles

    OpenAIRE

    Zhao Jiayuan; Lewinski Nastassja; Riediker Michael

    2015-01-01

    Brake wear dust is a significant component of traffic emissions and has been linked to adverse health effects. Previous research found a strong oxidative stress response in cells exposed to freshly generated brake wear dust. We characterized aged dust collected from passenger vehicles, using microscopy and elemental analyses. Reactive oxygen species (ROS) generation was measured with acellular and cellular assays using 2′7-dichlorodihydrofluorescein dye. Microscopy analyses revealed sam...

  7. Thermogravimetric study on the influence of structural, textural and chemical properties of biomass chars on CO2 gasification reactivity

    International Nuclear Information System (INIS)

    The present investigation aims to examine the influence of textural, structural and chemical properties of biomass chars on the CO2 gasification rate. Various lignocellulosic biomass chars were prepared under the same conditions. Different analytical techniques were used to determine the char properties such as Scanning Electronic Microscopy, nitrogen adsorption manometry, Raman spectroscopy and X Ray Fluorescence. Gasification tests were carried out in a thermobalance under 20% CO2 in nitrogen at 800 °C. Significant differences of the total average reactivity were observed with a factor of 2 between the prepared chars. Moreover, different behaviors of gasification rate profiles versus conversion were obtained. This difference of behavior appeared to be correlated with the biomass char properties. Hence, up to 70% of conversion, the gasification rate was shown to depend on the char external surface and the potassium content. At higher conversion ratio, a satisfactory correlation between the Catalytic Index and the average gasification rate was identified. The results highlight the importance of knowing both textural and structural properties and mineral contents of biomass chars to predict fuel reactivity during CO2 gasification processes. Such behavior prediction is highly important in the gasifiers design for char conversion. - Highlights: • CO2 gasification reactivity of various lignocellulosic chars were examined. • Chars properties affect strongly samples gasification behavior. • Initial gasification rate is affected by external surface, K content and D3/G ratio. • Gasification rate behavior depends on the Alkali index at high conversion

  8. Quantum chemical insight into the reactivity of 1,3-dipoles on coronene as model for nanographenes

    Science.gov (United States)

    Yuan, Yanli; Chen, Peiyu; Yang, Longhua; Ju, Yan; Wang, Hongming

    2016-01-01

    In this paper, we present a systematic investigation into reactivity of 1,3-dipoles on coronene as model for nanographenes using the density functional theory (DFT). The calculations show that the dipole nature mainly involving the structure and electrical effect is the major influence on reactivity. The 18-valence-electron azomethine ylides shows more active than the other two types of 1,3-dipoles with 16-valence-electron to NG, which may due to a smaller singlet-triple splitting. The more electronegative terminate group leads a higher stability and chemical inertness of the 1,3-dipole. There the reactivity order is oxide bonds of the 1,3-dipole increase in each series. The less electronegative terminate group leads the more electron-deficient and the less electron delocalization of the 1,3-dipole and even the more stable of the intermediate, which leads the cycloaddition proceed easier. The trend that the activation energy decreases as the strengths differences of the two new bonds of intermediate is also very clear in each series. All the reactivities are consistent analyzing in frontier molecular orbitals (FMO) theory. Unlike the 1,3-DC toward some other dipolarophiles, the vast majority of the studied 1,3-dipole cycloaddtions (DC) are of largely negative Gibbs free energies (Δ G ≠) values which are spontaneous at the temperature. There is correlation between the extent of spontaneous of reaction and the activation energy. There is also good relationship between the activation energy and the reaction energy, which follows the Hammond postulate.

  9. Size Dependence of Reactive Uptake Coefficient in Chemical Reactions on Aerosol Nanoparticles

    Czech Academy of Sciences Publication Activity Database

    Levdansky, Valerij Vladimirovič; Smolík, Jiří; Ždímal, Vladimír; Moravec, Pavel

    Praha : Česká aerosolová společnost, 2012 - (Vodička, P.; Zíková, N.), s. 77-78 ISBN 978-80-86186-40-5. [Výroční konference České aerosolové společnosti /13./. Třeboň (CZ), 25.10.2012-26.10.2012] R&D Projects: GA ČR GA101/09/1633; GA AV ČR IAA200760905 Institutional support: RVO:67985858 Keywords : reactive uptake coefficient * size effect * nanoscale aerosol particles Subject RIV: CF - Physical ; Theoretical Chemistry

  10. Programmable Thermal Dissociation of Reactive Gaseous Mercury, a Potential Approach to Chemical Speciation: Results from a Field Study§

    Directory of Open Access Journals (Sweden)

    Cheryl Tatum Ernest

    2014-08-01

    Full Text Available Programmable Thermal Dissociation (PTD has been used to investigate the chemical speciation of Reactive Gaseous Mercury (RGM, Hg2+. RGM was collected on denuders and analyzed using PTD. The technique was tested in a field campaign at a coal-fired power plant in Pensacola, Florida. Stack gas samples were collected from ducts located after the electrostatic precipitator and prior to entering the stack. An airship was used to sample from the stack plume, downwind of the stack exit. The PTD profiles from these samples were compared with PTD profiles of HgCl2. Comparison of stack and in-plume samples suggest that the chemical speciation are the same and that it is possible to track a specific chemical form of RGM from the stack and follow its evolution in the stack plume. Comparison of the measured plume RGM with the amount calculated from in-stack measurements and the measured plume dilution suggest that the stack and plume RGM concentrations are consistent with dilution. The PTD profiles of the stack and plume samples are consistent with HgCl2 being the chemical form of the sampled RGM. Comparison with literature PTD profiles of reference mercury compounds suggests no other likely candidates for the speciation of RGM.

  11. Chemical reactivity of hydrogen, nitrogen, and oxygen atoms at temperatures below 100 k

    Science.gov (United States)

    Mcgee, H. A., Jr.

    1973-01-01

    The synthesis of unusual compounds by techniques employing cryogenic cooling to retard their very extreme reactivity was investigated. Examples of such species that were studied are diimide (N2H2), cyclobutadiene (C4H4), cyclopropanone (C3H4O), oxirene (C2H2O), and many others. Special purpose cryogenically cooled inlet arrangements were designed such that the analyses incurred no warm-up of the cold, and frequently explosively unstable, compounds. Controlled energy electron impact techniques were used to measure critical potentials and to develop the molecular energetics and thermodynamics of these molecules and to gain some insight into their kinetic characteristics as well. Three and four carbon strained ring molecules were studied. Several reactions of oxygen and hydrogen atoms with simple molecules of H, N, C, and O in hard quench configurations were studied. And the quench stabilization of BH3 was explored as a model system in cryochemistry.

  12. Buoyancy-driven convection may switch between reactive states in three-dimensional chemical waves

    Czech Academy of Sciences Publication Activity Database

    Šebestíková, Lenka; Hauser, M. J. B.

    2012-01-01

    Roč. 85, č. 3 (2012), 036303. ISSN 1539-3755 R&D Projects: GA ČR GAP105/10/0919 Institutional research plan: CEZ:AV0Z20600510 Keywords : buoyancy-driven convection * chemical waves * iodate-arsenous acid reaction Subject RIV: BK - Fluid Dynamics Impact factor: 2.313, year: 2012

  13. A coupling alternative to reactive transport simulations for long-term prediction of chemical reactions in heterogeneous CO2 storage systems

    OpenAIRE

    De Lucia, M.; Kempka, T.; Kühn, M.

    2015-01-01

    Fully coupled, multi-phase reactive transport simulations of CO2 storage systems can be approximated by a simplified one-way coupling of hydrodynamics and reactive chemistry. The main characteristics of such systems, and hypotheses underlying the proposed alternative coupling, are (i) that the presence of CO2 is the only driving force for chemical reactions and (ii) that its migration in the reservoir is only marginally affected by immobilisation due to chem...

  14. An alternative to fully coupled reactive transport simulations for long-term prediction of chemical reactions in complex geological systems

    Science.gov (United States)

    De Lucia, Marco; Kempka, Thomas; Kühn, Michael

    2014-05-01

    Fully-coupled reactive transport simulations involving multiphase hydrodynamics and chemical reactions in heterogeneous settings are extremely challenging from a computational point of view. This often leads to oversimplification of the investigated system: coarse spatial discretization, to keep the number of elements in the order of few thousands; simplified chemistry, disregarding many potentially important reactions. A novel approach for coupling non-reactive hydrodynamic simulations with the outcome of single batch geochemical simulations was therefore introduced to assess the potential long-term mineral trapping at the Ketzin pilot site for underground CO2 storage in Germany [1],[2]. The advantage of the coupling is the ability to use multi-million grid non-reactive hydrodynamics simulations on one side and few batch 0D geochemical simulations on the other, so that the complexity of both systems does not need to be reduced. This contribution shows the approach which was taken to validate this simplified coupling scheme. The procedure involved batch simulations of the reference geochemical model, then performing both non-reactive and fully coupled 1D and 3D reactive transport simulations and finally applying the simplified coupling scheme based on the non-reactive and geochemical batch model. The TOUGHREACT/ECO2N [3] simulator was adopted for the validation. The degree of refinement of the spatial grid and the complexity and velocity of the mineral reactions, along with a cut-off value for the minimum concentration of dissolved CO2 allowed to originate precipitates in the simplified approach were found out to be the governing parameters for the convergence of the two schemes. Systematic discrepancies between the approaches are not reducible, simply because there is no feedback between chemistry and hydrodynamics, and can reach 20 % - 30 % in unfavourable cases. However, even such discrepancy is completely acceptable, in our opinion, given the amount of

  15. Drop drying on surfaces determines chemical reactivity - the specific case of immobilization of oligonucleotides on microarrays

    OpenAIRE

    Sobek, Jens; Aquino, Catharine; Weigel, Wilfried; Schlapbach, Ralph

    2013-01-01

    Background Drop drying is a key factor in a wide range of technical applications, including spotted microarrays. The applied nL liquid volume provides specific reaction conditions for the immobilization of probe molecules to a chemically modified surface. Results We investigated the influence of nL and μL liquid drop volumes on the process of probe immobilization and compare the results obtained to the situation in liquid solution. In our data, we observe a strong relationship between drop dr...

  16. Development of a Next-Generation Environmental Chamber Facility for Chemical Mechanism and VOC Reactivity Research

    OpenAIRE

    Carter, W P L; Fitz, D; D. R. Cocker III; Malkina, I L; Bumiller, K; Sauer, C G; Pisano, J T; Bufalino, C; Song, C.

    2005-01-01

    A new state-of-the-art indoor environmental chamber facility for the study of atmospheric processes leading to the formation of ozone and secondary organic aerosol (SOA) has been constructed and characterized. The chamber is designed for atmospheric chemical mechanism evaluation at low reactant concentrations under well-controlled environmental conditions. It consists of two collapsible 90 m3 FEP Teflon film reactors on pressure-controlled moveable frameworks inside a temperature-controlled e...

  17. Prediction of the Chapman-Jouguet chemical equilibrium state in a detonation wave from first principles based reactive molecular dynamics.

    Science.gov (United States)

    Guo, Dezhou; Zybin, Sergey V; An, Qi; Goddard, William A; Huang, Fenglei

    2016-01-21

    The combustion or detonation of reacting materials at high temperature and pressure can be characterized by the Chapman-Jouguet (CJ) state that describes the chemical equilibrium of the products at the end of the reaction zone of the detonation wave for sustained detonation. This provides the critical properties and product kinetics for input to macroscale continuum simulations of energetic materials. We propose the ReaxFF Reactive Dynamics to CJ point protocol (Rx2CJ) for predicting the CJ state parameters, providing the means to predict the performance of new materials prior to synthesis and characterization, allowing the simulation based design to be done in silico. Our Rx2CJ method is based on atomistic reactive molecular dynamics (RMD) using the QM-derived ReaxFF force field. We validate this method here by predicting the CJ point and detonation products for three typical energetic materials. We find good agreement between the predicted and experimental detonation velocities, indicating that this method can reliably predict the CJ state using modest levels of computation. PMID:26688211

  18. Octazethrene and Its Isomer with Different Diradical Characters and Chemical Reactivity: The Role of the Bridge Structure

    KAUST Repository

    Hu, Pan

    2016-03-11

    The fundamental relationship between structure and diradical character is important for the development of open-shell diradicaloid-based materials. In this work, we synthesized two structural isomers bearing a 2,6-naphthoquinodimethane or a 1,5-naphthoquinodimethane bridge and demonstrated that their diradical characters and chemical reactivity are quite different. The mesityl or pentafluorophenyl substituted octazethrene derivatives OZ-M/OZ-F and their isomer OZI-M (with mesityl substituents) were synthesized via an intramolecular Friedel-Crafts alkylation followed by oxidative dehydrogenation strategy from the key building blocks 4 and 11. Our detailed experimental and theoretical studies showed that both isomers have an open-shell singlet ground state with a remarkable diradical character (y0 = 0.35 and 0.34 for OZ-M and OZ-F, and y0 = 0.58 for OZI-M). Compounds OZ-M and OZ-F have good stability under the ambient environment while OZI-M has high reactivity and can be easily oxidized to a dioxo-product 15, which can be correlated to their different diradical characters. Additionally, we investigated the physical properties of OZ-M, OZ-F and 15.

  19. A case study of Asian dust storm particles: chemical composition, reactivity to SO2 and hygroscopic properties.

    Science.gov (United States)

    Ma, Qingxin; Liu, Yongchun; Liu, Chang; Ma, Jinzhu; He, Hong

    2012-01-01

    Mineral dust comprises a great fraction of the global aerosol loading, but remains the largest uncertainty in predictions of the future climate due to its complexity in composition and physico-chemical properties. In this work, a case study characterizing Asian dust storm particles was conducted by multiple analysis methods, including SEM-EDS, XPS, FT-IR, BET, TPD/mass and Knudsen cell/mass. The morphology, elemental fraction, source distribution, true uptake coefficient for SO2, and hygroscopic behavior were studied. The major components of Asian dust storm particles are aluminosilicate, SiO2 and CaCO3, with organic compounds and inorganic nitrate coated on the surface. It has a low reactivity towards SO2 with a true uptake coefficient, 5.767 x 10(-6), which limits the conversion of SO2 to sulfate during dust storm periods. The low reactivity also means that the heterogeneous reactions of SO2 in both dry and humid air conditions have little effect on the hygroscopic behavior of the dust particles. PMID:22783615

  20. Chemical Reactivity Window Determines Prodrug Efficiency toward Glutathione Transferase Overexpressing Cancer Cells.

    Science.gov (United States)

    van Gisbergen, Marike W; Cebula, Marcus; Zhang, Jie; Ottosson-Wadlund, Astrid; Dubois, Ludwig; Lambin, Philippe; Tew, Kenneth D; Townsend, Danyelle M; Haenen, Guido R M M; Drittij-Reijnders, Marie-José; Saneyoshi, Hisao; Araki, Mika; Shishido, Yuko; Ito, Yoshihiro; Arnér, Elias S J; Abe, Hiroshi; Morgenstern, Ralf; Johansson, Katarina

    2016-06-01

    Glutathione transferases (GSTs) are often overexpressed in tumors and frequently correlated to bad prognosis and resistance against a number of different anticancer drugs. To selectively target these cells and to overcome this resistance we previously have developed prodrugs that are derivatives of existing anticancer drugs (e.g., doxorubicin) incorporating a sulfonamide moiety. When cleaved by GSTs, the prodrug releases the cytostatic moiety predominantly in GST overexpressing cells, thus sparing normal cells with moderate enzyme levels. By modifying the sulfonamide it is possible to control the rate of drug release and specifically target different GSTs. Here we show that the newly synthesized compounds, 4-acetyl-2-nitro-benzenesulfonyl etoposide (ANS-etoposide) and 4-acetyl-2-nitro-benzenesulfonyl doxorubicin (ANS-DOX), function as prodrugs for GSTA1 and MGST1 overexpressing cell lines. ANS-DOX, in particular, showed a desirable cytotoxic profile by inducing toxicity and DNA damage in a GST-dependent manner compared to control cells. Its moderate conversion of 500 nmol/min/mg, as catalyzed by GSTA1, seems hereby essential since the more reactive 2,4-dinitrobenzenesulfonyl doxorubicin (DNS-DOX) (14000 nmol/min/mg) did not display a preference for GSTA1 overexpressing cells. DNS-DOX, however, effectively killed GSTP1 (20 nmol/min/mg) and MGST1 (450 nmol/min/mg) overexpressing cells as did the less reactive 4-mononitrobenzenesulfonyl doxorubicin (MNS-DOX) in a MGST1-dependent manner (1.5 nmol/min/mg) as shown previously. Furthermore, we show that the mechanism of these prodrugs involves a reduction in GSH levels as well as inhibition of the redox regulatory enzyme thioredoxin reductase 1 (TrxR1) by virtue of their electrophilic sulfonamide moiety. TrxR1 is upregulated in many tumors and associated with resistance to chemotherapy and poor patient prognosis. Additionally, the prodrugs potentially acted as a general shuttle system for DOX, by overcoming resistance

  1. Programmable thermal dissociation of reactive gaseous mercury – a potential approach to chemical speciation: results from a field study

    Directory of Open Access Journals (Sweden)

    C. Tatum Ernest

    2012-12-01

    Full Text Available The use of programmable thermal dissociation (PTD as an approach to investigating the chemical speciation of reactive gaseous mercury (RGM, Hg2+ has been explored in a field study. In this approach RGM is collected on a denuder and analyzed using PTD. The denuder is placed in an oven and the dissociation of the RGM is measured, as a function of temperature, by monitoring the evolution of elemental mercury (GEM, Hg0 in real time using laser-induced fluorescence (LIF. The technique was tested in a field campaign at a coal-fired power plant in Pensacola, Florida. Uncoated tubular denuders were used to obtain samples from the plant's stack exhaust gases and from the stack plume, downwind of the stack using an airship. The PTD profiles from these samples were compared with PTD profiles of HgCl2.

  2. Numerical modelling of shock-induced chemical reactions (SICR) in reactive powder mixtures using smoothed particle hydrodynamics (SPH)

    Science.gov (United States)

    S, Siva Prasad A. V.; Basu, Sumit

    2015-10-01

    Shock compaction of reactive powder mixtures to synthesize new materials is one of the oldest material processing techniques and has been studied extensively by several researchers over the past few decades. The quantitative connection between the shock energy imparted and the extent of reaction that can be completed in the small time window associated with the passage of the shock wave is complicated and depends on a large variety of parameters. In particular, our understanding of the complex interplay between the thermo-elasto-viscoplastic behaviour of the granular constituents and their temperature dependent, diffusion-limited reaction mechanism may be enriched through careful numerical simulations. A robust numerical model should be able to handle extremely large deformations coupled with diffusion mediated fast reaction kinetics. In this work, a meshfree discrete particle numerical method based on smoothed particle hydrodynamics (SPH) to simulate shock-induced chemical reactions (SICR) in reactive powder mixtures is proposed. We present a numerical strategy to carry out reactions between reactant powder particles and partition the obtained products between the particles in a manner that accounts for the requirement that the total mass of the entire system remains constant as the reactions occur. Instead of solving the reaction-diffusion problem, we propose a ‘pseudo-diffusion’ model in which a distance dependent reaction rate constant is defined to carry out chemical reaction kinetics. This approach mimics the actual reaction-diffusion process at short times. Our numerical model is demonstrated for the well-studied reaction system Nb  +  2Si \\rightleftharpoons NbSi 2 . The predicted mass fractions of the product obtained from the simulations are in agreement with experimental observations. Finally, the effects of impact speed, particle arrangement and mixing ratio on the predicted product mass fractions are discussed.

  3. Production of chemically reactive radioactive ion beams through on-line separation

    International Nuclear Information System (INIS)

    The ISOL (isotope separation on line) allows the production of secondary radioactive ion beams through spallation or fragmentation or fission reactions that take place in a thick target bombarded by a high intensity primary beam. The challenge is to increase the intensity and purity of the radioactive beam. The optimization of the system target/source requires the right choice of material for the target by taking into account the stability of the material, its reactivity and the ionization method used. The target is an essential part of the system because radioactive elements are generated in it and are released more or less quickly. Tests have been made in order to select the best fitted material for the release of S, Se, Te, Ge and Sn. Materials tested as target filling are: ZrO2, Nb, Ti, V,TiO2, CeOx, ThO2, C, ZrC4 and VC). Other molecules such as: COSe, COS, SeS, COTe, GeS, SiS, SnS have been studied to ease the extraction of recoil nuclei (Se, S, Te, Ge and Sn) produced inside the target

  4. Chemical Analysis of Organic Aerosols Using Reactive Nanospray Desorption Electrospray Ionization Mass Spectrometry

    Science.gov (United States)

    Laskin, A.; Laskin, J.; Nizkorodov, S.

    2013-12-01

    Nanospray Desorption Electrospray Ionization (nano-DESI) technique integrated with high resolution mass spectrometry (HR-MS) enables molecular level analysis of organic aerosol (OA) samples. In nano-DESI, analyte is desorbed into a small volume solvent bridge formed between two capillaries positioned in contact with analyte and enables fast and efficient characterization of OA collected on substrates without sample preparation. We report applications of the nano-DESI/HR-MS approach in a number of our recent studies focused on molecular identification of organic compounds in laboratory and in field collected OA samples. Reactive nano-DESI approach where selected reagent is added to the solvent is used for examining the presence of individual species containing specific functional groups and for their quantification within complex mixtures of OA. Specifically, we use the Girard's reagent T (GT) to probe and quantify carbonyl compounds in the SOA mixtures. We estimate for the first time the amounts of dimers and trimers in the SOA mixtures. We found that the most abundant dimer in limonene/O3 SOA was detected at the ˜0.5 pg level and the total amount of dimers and trimers in the analyzed sample was ˜11 pg. Understanding of the OA composition at the molecular level allowed us to identify key aging reactions, including the transformation of carbonyls to imines and carbonyl-imine oligomerization, that may contribute to the formation of brown carbon in the atmosphere.

  5. Chemical environment of iron atoms in iron oxynitride films synthesized by reactive magnetron sputtering

    International Nuclear Information System (INIS)

    An iron oxynitride film was deposited on silicon and glass substrates by magnetron sputtering in an Ar-N2-O2 reactive mixture. Rutherford back-scattering spectrometry was used to determine the film composition (Fe1.06O0.35N0.65). X-ray diffraction revealed the formation of a face-centred cubic (fcc) structure with a lattice parameter close to that of γ'''-FeN. X-ray photoelectron spectroscopy showed the occurrence of Fe-N and Fe-O bonds in the film. The local environment of iron atoms studied by 57Fe Moessbauer spectrometry at both 300 and 77 K gives clear evidence that the Fe1.06O0.35N0.65 is not a mixture of iron oxide and iron nitride phases. Despite a small amount of an iron nitride phase, the main sample consists of an iron oxynitride phase with an NaCl-type structure where oxygen atoms partially substitute for nitrogen atoms, thus indicating the formation of a iron oxynitride with an fcc structure

  6. Exploring chemical reactivity of complex systems with path-based coordinates: role of the distance metric.

    Science.gov (United States)

    Zinovjev, Kirill; Tuñón, Iñaki

    2014-09-01

    Path-based reaction coordinates constitute a valuable tool for free-energy calculations in complex processes. When a reference path is defined by means of collective variables, a nonconstant distance metric that incorporates the nonorthonormality of these variables should be taken into account. In this work, we show that, accounting for the correct metric tensor, these kind of variables can provide iso-hypersurfaces that coincide with the iso-committor surfaces and that activation free energies equal the value that would be obtained if the committor function itself were used as reaction coordinate. The advantages of the incorporation of the variable metric tensor are illustrated with the analysis of the enzymatic reaction catalyzed by isochorismate-pyruvate lyase. Hybrid QM/MM techniques are used to obtain the free energy profile and to analyze reactive trajectories initiated at the transition state. For this example, the committor histogram is peaked at 0.5 only when a variable metric tensor is incorporated in the definition of the path-based coordinate. PMID:24986052

  7. Molecular Beam Studies of Hot Atom Chemical Reactions: Reactive Scattering of Energetic Deuterium Atoms

    Science.gov (United States)

    Continetti, R. E.; Balko, B. A.; Lee, Y. T.

    1989-02-01

    A brief review of the application of the crossed molecular beams technique to the study of hot atom chemical reactions in the last twenty years is given. Specific emphasis is placed on recent advances in the use of photolytically produced energetic deuterium atoms in the study of the fundamental elementary reactions D + H{sub 2} -> DH + H and the substitution reaction D + C{sub 2}H{sub 2} -> C{sub 2}HD + H. Recent advances in uv laser and pulsed molecular beam techniques have made the detailed study of hydrogen atom reactions under single collision conditions possible.

  8. A chemical-detecting system based on a cross-reactive optical sensor array

    Science.gov (United States)

    Dickinson, Todd A.; White, Joel; Kauer, John S.; Walt, David R.

    1996-08-01

    THE vertebrate olfactory system has long been recognized for its extraordinary sensitivity and selectivity for odours. Chemical sensors have been developed recently that are based on analogous distributed sensing properties1-4, but although an association between artificial devices and the olfactory system has been made explicit in some previous studies4,5, none has incorporated comparable mechanisms into the mode of detection. Here we describe a multi-analyte fibre-optic sensor modelled directly on the olfactory system, in the sense that complex, time-dependent signals from an array of sensors provide a 'signature' of each analyte. In our system, polymer-immobilized dye molecules on the fibre tips give different fluorescent response patterns (including spectral shifts, intensity changes, spectral shape variations6 and temporal responses) on exposure to organic vapours, depending on the physical and chemical nature (for example, polarity, shape and size) of both the vapour and the polymer. We use video images of temporal responses of the multi-fibre tip as the input signals to train a neural network for vapour recognition. The system is able to identify individual vapours at different concentrations with great accuracy. 'Artificial noses' such as this should have wide potential application, most notably in environmental and medical monitoring.

  9. Transient analysis of diffusive chemical reactive species for couple stress fluid flow over vertical cylinder

    Institute of Scientific and Technical Information of China (English)

    H. P. RANI; G. J. REDDY; C. N. KIM

    2013-01-01

    The unsteady natural convective couple stress fluid flow over a semi-infinite vertical cylinder is analyzed for the homogeneous first-order chemical reaction effect. The couple stress fluid flow model introduces the length dependent effect based on the material constant and dynamic viscosity. Also, it introduces the biharmonic operator in the Navier-Stokes equations, which is absent in the case of Newtonian fluids. The solution to the time-dependent non-linear and coupled governing equations is carried out with an unconditionally stable Crank-Nicolson type of numerical schemes. Numerical results for the transient flow variables, the average wall shear stress, the Nusselt number, and the Sherwood number are shown graphically for both generative and destructive reactions. The time to reach the temporal maximum increases as the reaction constant K increases. The average values of the wall shear stress and the heat transfer rate decrease as K increases, while increase with the increase in the Sherwood number.

  10. The KIVA-2 computer program for transient multidimensional chemically reactive flows with sprays

    Science.gov (United States)

    Amsden, A. A.; Butler, T. D.; Orourke, P. J.

    Since its public release in 1985, the KIVA computer program has been utilized for the time dependent analysis of chemically reacting flows with sprays in two and three space dimensions. This paper describes some of the improvements to the original version that have been made since that time. The new code called KIVA-2 is planned for public release in early 1988. KIVA-2 improves the earlier version in the accuracy and efficiency of the computational procedure, the accuracy of the physics submodels, and in versatility and ease of use. Numerical improvements include the use of the ICE solution procedure in place of the acoustic subcycling method and the implementation of a quasi-second-order-accurate convection scheme. Major extensions to the physical submodels include the inclusion of an optional kappa-epsilon turbulence model, and several additions to the spray model. We illustrate some of the new capabilities by means of example solutions.

  11. Electron Transfer Reactivity Patterns at Chemically Modified Electrodes: Fundamentals and Application to the Optimization of Redox Recycling Amplification Systems

    Energy Technology Data Exchange (ETDEWEB)

    Adam Johan Bergren

    2006-05-01

    Electroanalytical chemistry is often utilized in chemical analysis and Fundamental studies. Important advances have been made in these areas since the advent of chemically modified electrodes: the coating of an electrode with a chemical film in order to impart desirable, and ideally, predictable properties. These procedures enable the exploitation of unique reactivity patterns. This dissertation presents studies that investigate novel reaction mechanisms at self-assembled monolayers on gold. In particular, a unique electrochemical current amplification scheme is detailed that relies on a selective electrode to enable a reactivity pattern that results in regeneration of the analyte (redox recycling). This regenerating reaction can occur up to 250 times for each analyte molecule, leading to a notable enhancement in the observed current. The requirements of electrode selectivity and the resulting amplification and detection limit improvements are described with respect to the heterogeneous and homogeneous electron transfer rates that characterize the system. These studies revealed that the heterogeneous electrolysis of the analyte should ideally be electrochemically reversible, while that for the regenerating agent should be held to a low level. Moreover, the homogeneous reaction that recycles the analyte should occur at a rapid rate. The physical selectivity mechanism is also detailed with respect to the properties of the electrode and redox probes utilized. It is shown that partitioning of the analyte into/onto the adlayer leads to the extraordinary selectivity of the alkanethiolate monolayer modified electrode. Collectively, these studies enable a thorough understanding of the complex electrode mechanism required for successful redox recycling amplification systems, Finally, in a separate (but related) study, the effect of the akyl chain length on the heterogeneous electron transfer behavior of solution-based redox probes is reported, where an odd-even oscillation

  12. Chemical reactivity of {alpha}-isosaccharinic acid in heterogeneous alkaline systems

    Energy Technology Data Exchange (ETDEWEB)

    Glaus, M. A.; Loon, L. R. Van

    2008-11-15

    Cellulose degradation under alkaline conditions is of relevance for the mobility of many radionuclides in the near-field of a cementitious repository for radioactive waste, because metal-binding degradation products may be formed. Among these, {alpha}-isosaccharinic acid ({alpha}-ISA) is the strongest complexant. The prediction of the equilibrium concentration of {alpha}-ISA in cement pore water is therefore an important step in the assessment of the influence of cellulose degradation products on the speciation of radionuclides in such environments. The present report focuses on possible chemical transformation reactions of {alpha}-ISA in heterogeneous alkaline model systems containing either Ca(OH){sub 2} or crushed hardened cement paste. The transformation reactions were monitored by measuring the concentration of {alpha}-ISA by high performance anion exchange chromatography and the formation of reaction products by high performance ion exclusion chromatography. The overall loss of organic species from solution was monitored by measuring the concentration of non-purgeable organic carbon. The reactions were examined in diluted and compacted suspensions, either at 25 {sup o}C or 90 {sup o}C, and under anaerobic atmospheres obtained by various methods. It was found that {alpha}-ISA was transformed under all conditions tested to some extent. Reaction products, such as glycolate, formate, lactate and acetate, all compounds with less complexing strength than {alpha}-ISA, were detected. The amount of reaction products identified by the chromatographic technique applied was {approx}50 % of the amount of {alpha}-ISA reacted. Sorption of {alpha}-ISA to Ca(OH){sub 2} contributed only to a minor extent to the loss of {alpha}-ISA from the solution phase. As the most important conclusion of the present work it was demonstrated that the presence of oxidising agents had a distinctive influence on the turnover of {alpha}-ISA. Under aerobic conditions {alpha}-ISA was

  13. Chemical reactivity of {alpha}-isosaccharinic acid in heterogeneous alkaline systems

    Energy Technology Data Exchange (ETDEWEB)

    Glaus, M. A.; Loon, L. R. Van

    2009-05-15

    Cellulose degradation under alkaline conditions is of relevance for the mobility of many radionuclides in the near-field of a cementitious repository for radioactive waste, because metal-binding degradation products may be formed. Among these, {alpha}- isosaccharinic acid ({alpha}-ISA) is the strongest complexant. The prediction of the equilibrium concentration of {alpha}-ISA in cement pore water is therefore an important step in the assessment of the influence of cellulose degradation products on the speciation of radionuclides in such environments. The present report focuses on possible chemical transformation reactions of {alpha}-ISA in heterogeneous alkaline model systems containing either Ca(OH){sub 2} or crushed hardened cement paste. The transformation reactions were monitored by measuring the concentration of {alpha}-ISA by high performance anion exchange chromatography and the formation of reaction products by high performance ion exclusion chromatography. The overall loss of organic species from solution was monitored by measuring the concentration of non-purgeable organic carbon. The reactions were examined in diluted and compacted suspensions, at either 25 {sup o}C or 90 {sup o}C, and under anaerobic atmospheres obtained by various methods. It was found that {alpha}-ISA was transformed under all conditions tested to some extent. Reaction products, such as glycolate, formate, lactate and acetate, all compounds with less complexing strength than {alpha}-ISA, were detected. The amount of reaction products identified by the chromatographic technique applied was {approx} 50 % of the amount of {alpha}-ISA reacted. Sorption of {alpha}-ISA to Ca(OH){sub 2} contributed only to a minor extent to the loss of {alpha}-ISA from the solution phase. As the most important conclusion of the present work it was demonstrated that the presence of oxidising agents had a distinctive influence on the turnover of {alpha}-ISA. Under aerobic conditions {alpha}-ISA was

  14. Chemical reactivity of α-isosaccharinic acid in heterogeneous alkaline systems

    International Nuclear Information System (INIS)

    Cellulose degradation under alkaline conditions is of relevance for the mobility of many radionuclides in the near-field of a cementitious repository for radioactive waste, because metal-binding degradation products may be formed. Among these, α- isosaccharinic acid (α-ISA) is the strongest complexant. The prediction of the equilibrium concentration of α-ISA in cement pore water is therefore an important step in the assessment of the influence of cellulose degradation products on the speciation of radionuclides in such environments. The present report focuses on possible chemical transformation reactions of α-ISA in heterogeneous alkaline model systems containing either Ca(OH)2 or crushed hardened cement paste. The transformation reactions were monitored by measuring the concentration of α-ISA by high performance anion exchange chromatography and the formation of reaction products by high performance ion exclusion chromatography. The overall loss of organic species from solution was monitored by measuring the concentration of non-purgeable organic carbon. The reactions were examined in diluted and compacted suspensions, at either 25 oC or 90 oC, and under anaerobic atmospheres obtained by various methods. It was found that α-ISA was transformed under all conditions tested to some extent. Reaction products, such as glycolate, formate, lactate and acetate, all compounds with less complexing strength than α-ISA, were detected. The amount of reaction products identified by the chromatographic technique applied was ∼ 50 % of the amount of α-ISA reacted. Sorption of α-ISA to Ca(OH)2 contributed only to a minor extent to the loss of α-ISA from the solution phase. As the most important conclusion of the present work it was demonstrated that the presence of oxidising agents had a distinctive influence on the turnover of α-ISA. Under aerobic conditions α-ISA was quantitatively converted to reaction products, whereas under strict anaerobic conditions, only small

  15. Chemical reactivity of α-isosaccharinic acid in heterogeneous alkaline systems

    International Nuclear Information System (INIS)

    Cellulose degradation under alkaline conditions is of relevance for the mobility of many radionuclides in the near-field of a cementitious repository for radioactive waste, because metal-binding degradation products may be formed. Among these, α-isosaccharinic acid (α-ISA) is the strongest complexant. The prediction of the equilibrium concentration of α-ISA in cement pore water is therefore an important step in the assessment of the influence of cellulose degradation products on the speciation of radionuclides in such environments. The present report focuses on possible chemical transformation reactions of α-ISA in heterogeneous alkaline model systems containing either Ca(OH)2 or crushed hardened cement paste. The transformation reactions were monitored by measuring the concentration of α-ISA by high performance anion exchange chromatography and the formation of reaction products by high performance ion exclusion chromatography. The overall loss of organic species from solution was monitored by measuring the concentration of non-purgeable organic carbon. The reactions were examined in diluted and compacted suspensions, either at 25 oC or 90 oC, and under anaerobic atmospheres obtained by various methods. It was found that α-ISA was transformed under all conditions tested to some extent. Reaction products, such as glycolate, formate, lactate and acetate, all compounds with less complexing strength than α-ISA, were detected. The amount of reaction products identified by the chromatographic technique applied was ∼50 % of the amount of α-ISA reacted. Sorption of α-ISA to Ca(OH)2 contributed only to a minor extent to the loss of α-ISA from the solution phase. As the most important conclusion of the present work it was demonstrated that the presence of oxidising agents had a distinctive influence on the turnover of α-ISA. Under aerobic conditions α-ISA was quantitatively converted to reaction products, whereas under strict anaerobic conditions, only small

  16. Applications of the Information Theory to Problems of Molecular Electronic Structure and Chemical Reactivity

    Directory of Open Access Journals (Sweden)

    Roman F. Nalewajski

    2002-04-01

    Full Text Available Abstract: Recent studies on applications of the information theoretic concepts to molecular systems are reviewed. This survey covers the information theory basis of the Hirshfeld partitioning of molecular electron densities, its generalization to many electron probabilities, the local information distance analysis of molecular charge distributions, the charge transfer descriptors of the donor-acceptor reactive systems, the elements of a “thermodynamic” description of molecular charge displacements, both “vertical” (between molecular fragments for the fixed overall density and “horizontal” (involving different molecular densities, with the entropic representation description provided by the information theory. The average uncertainty measures of bond multiplicities in molecular “communication” systems are also briefly summarized. After an overview of alternative indicators of the information distance (entropy deficiency, missing information between probability distributions the properties of the “stockholder” densities, which minimize the entropy deficiency relative to the promolecule reference, are summarized. In particular, the surprisal analysis of molecular densities is advocated as an attractive information-theoretic tool in the electronic structure theory, supplementary to the familiar density difference diagrams. The subsystem information density equalization rules satisfied by the Hirshfeld molecular fragments are emphasized: the local values of alternative information distance densities of subsystems are equal to the corresponding global value, characterizing the molecule as a whole. These local measures of the information content are semi-quantitatively related to the molecular density difference function. In the density functional theory the effective external potentials of molecular fragments are defined, for which

  17. [Studying the influence of some reactive oxygen species on physical and chemical parameters of blood].

    Science.gov (United States)

    Martusevich, A K; Martusevich, A A; Solov'eva, A G; Peretyagin, S P

    2014-01-01

    The aim of this work was to estimate the dynamics of blood physical and chemical parameters when blood specimens were processed by singlet oxygen in vitro. Our experiments were executed with whole blood specimens of healthy people (n=10). Each specimen was divided into five separate portions of 5 ml. The first portion was a control (without any exposures). The second one was processed by an oxygen-ozone mixture (at ozone concentration of 500 mcg/l, the third portion--by oxygen, and the fourth and fifth ones were processed by a gas mixture with singlet oxygen (50 and 100% of generator power). In blood samples after processing we studied the activity of lactate dehydrogenase, aldehyde dehydrogenase and superoxide dismutase, erythrocyte and plasma levels of glucose and lactate, acid-base balance and the partial pressure of gases in blood. It was found out, that blood processing by singlet oxygen leads to optimization of energy, detoxication and antioxidant enzymes functioning with changes in plasma and erythrocyte level of glucose and lactate, normalization of blood gases level and acid-base balance. Our results show, that the effect of singlet oxygen on enzyme activity is more pronounced than exposure to an oxygen-ozone gas mixture. PMID:25702489

  18. Exact Solutions of Chemically Reactive Solute Distribution in MHD Boundary Layer Flow over a Shrinking Surface

    International Nuclear Information System (INIS)

    An analytical study of the distribution of a reactant solute undergoing a first-order chemical reaction in the boundary layer flow of an electrically conducting incompressible fluid over a linearly shrinking surface is presented. The flow is permeated by an externally applied magnetic field normal to the plane of the flow. The equations governing the flow and concentration field are reduced into a set of nonlinear ordinary differential equations using similarity variables. Closed form exact solutions of the reduced concentration equation are obtained for both prescribed power-law surface concentration (PSC) and power-law wall mass flux (PMF) as boundary conditions. The study reveals that the concentration over a shrinking sheet is significantly different from that of a stretching surface. It is found that the solute boundary layer thickness is enhanced with the increasing values of the Schmidt number and the power-law index parameter, but decreases with enhanced values of magnetic and reaction rate parameters for the PSC case. For the PMF case, the solute boundary layer thickness decreases with the increase of the Schmidt number, magnetic and reaction rate parameter for power-law index parameter n = 0. Negative solute boundary layer thickness is observed for the PMF case when n = 1 and 2, and these facts may not be realized in real-world applications. (fundamental areas of phenomenology(including applications))

  19. Chemical reactivity of precursor materials during synthesis of glasses used for conditioning high-level radioactive waste: Experiments and models

    International Nuclear Information System (INIS)

    The glass used to store high-level radioactive waste is produced by reaction of a solid waste residue and a glassy precursor (glass frit). The waste residue is first dried and calcined (to lose water and nitrogen respectively), then mixed with the glass frit to enable vitrification at high temperature. In order to obtain a good quality glass of constant composition upon cooling, the chemical reactions between the solid precursors must be complete while in the liquid state, to enable incorporation of the radioactive elements into the glassy matrix. The physical and chemical conditions during glass synthesis (e.g. temperature, relative proportions of frit and calcine, amount of radioactive charge) are typically empirically adjusted to obtain a satisfactory final product. The aim of this work is to provide new insights into the chemical and physical interactions that take place during vitrification and to provide data for a mathematical model that has been developed to simulate the chemical reactions. The consequences of the different chemical reactions that involve solid, liquid and gaseous phases are described (thermal effects, changes in crystal morphology and composition, variations in melt properties and structure). In a first series of experiments, a simplified analogue of the calcine (NaNO3-Al2O3 ± MoO3/Nd2O3) has been studied. In a second series of experiments, the simplified calcines have been reacted with a simplified glass frit (SiO2-Na2O-B2O3-Al2O3) at high temperature. The results show that crystallization of the calcine may take place before interaction with the glass frit, but that the reactivity with the glass at high temperature is a function of the nature and stoichiometry of the crystalline phases which form at low temperature. The results also highlight how the mixing of the starting materials, the physical properties of the frit (viscosity, glass transition temperature) and the Na2O/Al2O3 of the calcine but also its crystallization all contribute

  20. Exact Solutions of Chemically Reactive Solute Distribution in MHD Boundary Layer Flow over a Shrinking Surface

    Institute of Scientific and Technical Information of China (English)

    Chandaneswar Midya

    2012-01-01

    An analytical study of the distribution of a reactant solute undergoing a first-order chemical reaction in the boundary layer flow of an electrically conducting incompressible Buid over a linearly shrinking surface is presented. The Row is permeated by an externally applied magnetic Geld normal to the plane of the flow. The equations governing the Row and concentration Reid are reduced into a set of nonlinear ordinary differential equations using similarity variables. Closed form exact solutions of the reduced concentration equation are obtained for both prescribed power-law surface concentration (PSC) and power-law wall mass flux (PMF) as boundary conditions. The study reveals that the concentration over a shrinking sheet is signiRcantly different from that of a stretching surface. It s found that te solute boundary layer thickness is enhanced with the increasing values of the Schmidt number and the power-law index parameter, but decreases with enhanced vaJues of magnetic and reaction rate parameters for the PSC case. For the PMF case, the solute boundary layer thickness decreases with the increase of the Schmidt number, magnetic and reaction rate parameter for power-law index parameter n = 0. Negative solute boundary layer thickness is observed for the PMF case when n = 1 and 2, and these facts may not be realized in real-world applications.%An analytical study of the distribution of a reactant solute undergoing a first-order chemical reaction in the boundary layer flow of an electrically conducting incompressible fluid over a linearly shrinking surface is presented.The flow is permeated by an externally applied magnetic field normal to the plane of the flow.The equations governing the flow and concentration field are reduced into a set of nonlinear ordinary differential equations using similarity variables.Closed form exact solutions of the reduced concentration equation are obtained for both prescribed power-law surface concentration (PSC) and power-law wall

  1. Reactibodies generated by kinetic selection couple chemical reactivity with favorable protein dynamics.

    Science.gov (United States)

    Smirnov, Ivan; Carletti, Eugénie; Kurkova, Inna; Nachon, Florian; Nicolet, Yvain; Mitkevich, Vladimir A; Débat, Hélène; Avalle, Bérangère; Belogurov, Alexey A; Kuznetsov, Nikita; Reshetnyak, Andrey; Masson, Patrick; Tonevitsky, Alexander G; Ponomarenko, Natalia; Makarov, Alexander A; Friboulet, Alain; Tramontano, Alfonso; Gabibov, Alexander

    2011-09-20

    Igs offer a versatile template for combinatorial and rational design approaches to the de novo creation of catalytically active proteins. We have used a covalent capture selection strategy to identify biocatalysts from within a human semisynthetic antibody variable fragment library that uses a nucleophilic mechanism. Specific phosphonylation at a single tyrosine within the variable light-chain framework was confirmed in a recombinant IgG construct. High-resolution crystallographic structures of unmodified and phosphonylated Fabs display a 15-Å-deep two-chamber cavity at the interface of variable light (V(L)) and variable heavy (V(H)) fragments having a nucleophilic tyrosine at the base of the site. The depth and structure of the pocket are atypical of antibodies in general but can be compared qualitatively with the catalytic site of cholinesterases. A structurally disordered heavy chain complementary determining region 3 loop, constituting a wall of the cleft, is stabilized after covalent modification by hydrogen bonding to the phosphonate tropinol moiety. These features and presteady state kinetics analysis indicate that an induced fit mechanism operates in this reaction. Mutations of residues located in this stabilized loop do not interfere with direct contacts to the organophosphate ligand but can interrogate second shell interactions, because the H3 loop has a conformation adjusted for binding. Kinetic and thermodynamic parameters along with computational docking support the active site model, including plasticity and simple catalytic components. Although relatively uncomplicated, this catalytic machinery displays both stereo- and chemical selectivity. The organophosphate pesticide paraoxon is hydrolyzed by covalent catalysis with rate-limiting dephosphorylation. This reactibody is, therefore, a kinetically selected protein template that has enzyme-like catalytic attributes. PMID:21896761

  2. Flow paths and chemical reactivity of CO2 in carbonates using Mercury-Intrusion Capillary Pressure data and dimensionless numbers

    Science.gov (United States)

    Vialle, S.; Dvorkin, J. P.; Mavko, G. M.

    2012-12-01

    Experiments performed earlier by Vialle and Vanorio (2011) [1] have showed that the injection of CO2-rich water (pH=3.2) in various calcite limestones lead to heterogeneous dissolution of the pore structure, inducing secondary porosity and changing the rock stiffness. The presence of oil in the pore space affects the magnitude of these changes by lowering the reactive surface area. We present here a semi-quantitative analysis at the mesoscale to investigate how different initial pore microgeometries and heterogeneities in pore microgeometry affect the fluid-rock interactions. In particular, we aim at quantitatively explaining (1) why, in clean samples, higher-porosity micrite with rounded grains appears to be more affected by dissolution than tight micrite and spar cement and (2) why, for the same number of pore volumes of fluid injected, the magnitude of the changes in porosity (and subsequently elastic properties) differs among the studied rock samples. Rock microgeometry is studied by classical rock-physics methods, He-pycnometry and Mercury-Intrusion Capillary Pressure (MICP) tests, as well as by Scanning Electron Microscopy (SEM) imaging. Experiments were performed on subsamples (~0.5cm3) extracted from core plugs (~12cm3): two Fontainebleau sandstones, to serve as benchmarks, and two calcite carbonates from two different geological formations. In order to relate pore microgeometry to flow paths and chemical reactivity of CO2 in carbonate rocks, we chose to work at a scale that lies between the pore scale and the core scale. The method consists of physically subdividing the core plugs under examination into subsets based on the pore-throat sizes; these subsets correspond to three types of microstructure: "macropores", "microporous rounded micrite", and "spar cement"/"tight micrite". The dimensionless Péclet (Pe) and Damkhöler (Da) numbers, defined as the ratio between the advection rate and the diffusion rate, and as the ratio between the reaction rate and

  3. Influence of the physicochemical and aromatic properties on the chemical reactivity and its relation with carcinogenic and anticoagulant effect of 17β-aminoestrogens

    Energy Technology Data Exchange (ETDEWEB)

    Soriano-Correa, Catalina, E-mail: socc@puma2.zaragoza.unam.mx [Química Computacional, FES-Zaragoza, Universidad Nacional Autónoma de México (UNAM), Iztapalapa, Mexico City (Mexico); Raya, Angélica [Unidad Profesional Interdisciplinaria de Ingeniería Campus Guanajuato, Instituto Politécnico Nacional (IPN), Silao de la Victoria, Guanajuato (Mexico); Barrientos-Salcedo, Carolina [Laboratorio de Química Médica y Quimiogenómica, Facultad de Bioanálisis Campus Veracruz - Boca del Río, Universidad Veracruzana, Veracruz (Mexico); Esquivel, Rodolfo O. [Departamento de Química, Universidad Autónoma Metropolitana-Iztapalapa (UAM-Iztapalapa), Mexico City (Mexico)

    2014-06-25

    Highlights: • The aromatic A-ring of 17β-aminoestrogens contribute to its anticoagulant effect. • The electron-donor substituent groups favored the basicity of 17β-aminoestrogens. • The physicochemical properties are important in the carcinogenic effect of anticoagulant molecules. - Abstract: Activity of steroid hormones is dependent upon a number of factors, as solubility, transport and metabolism. The functional differences caused by structural modifications could exert an influence on the chemical reactivity and biological effect. The goal of this work is to study the influence of the physicochemical and aromatic properties on the chemical reactivity and its relation with the carcinogenic risk that can associate with the anticoagulant effect of 17β-aminoestrogens using quantum-chemical descriptors at the DFT-B3LYP, BH and HLYP and M06-2X levels. The relative acidity of (H1) of the hydroxyl group increases with electron-withdrawing groups. Electron-donor groups favor the basicity. The steric hindrance of the substituents decreases the aromatic character and consequently diminution the carcinogenic effect. Density descriptors: hardness, electrophilic index, atomic charges, molecular orbitals, electrostatic potential and their geometric parameters permit analyses of the chemical reactivity and physicochemical features and to identify some reactive sites of 17β-aminoestrogens.

  4. Nanoscale multilayered and porous carbide interphases prepared by pressure-pulsed reactive chemical vapor deposition for ceramic matrix composites

    Energy Technology Data Exchange (ETDEWEB)

    Jacques, S., E-mail: jacques@lcts.u-bordeaux1.fr [LCTS, University of Bordeaux 1, CNRS, Herakles-Safran, CEA, 3 allee de la Boetie, F-33600 Pessac (France); Jouanny, I.; Ledain, O.; Maillé, L.; Weisbecker, P. [LCTS, University of Bordeaux 1, CNRS, Herakles-Safran, CEA, 3 allee de la Boetie, F-33600 Pessac (France)

    2013-06-15

    In Ceramic Matrix Composites (CMCs) reinforced by continuous fibers, a good toughness is achieved by adding a thin film called “interphase” between the fiber and the brittle matrix, which acts as a mechanical fuse by deflecting the matrix cracks. Pyrocarbon (PyC), with or without carbide sub-layers, is typically the material of choice to fulfill this role. The aim of this work was to study PyC-free nanoscale multilayered carbide coatings as interphases for CMCs. Nanoscale multilayered (SiC–TiC){sub n} interphases were deposited by pressure-Pulsed Chemical Vapor Deposition (P-CVD) on single filament Hi-Nicalon fibers and embedded in a SiC matrix sheath. The thicknesses of the carbide interphase sub-layers could be made as low as a few nanometers as evidenced by scanning and transmission electron microscopy. By using the P-ReactiveCVD method (P-RCVD), in which the TiC growth involves consumption of SiC, it was not only possible to obtain multilayered (SiC–TiC){sub n} films but also TiC films with a porous multilayered microstructure as a result of the Kirkendall effect. The porosity in the TiC sequences was found to be enhanced when some PyC was added to SiC prior to total RCVD consumption. Because the porosity volume fraction was still not high enough, the role of mechanical fuse of the interphases could not be evidenced from the tensile curves, which remained fully linear even when chemical attack of the fiber surface was avoided.

  5. Nanoscale multilayered and porous carbide interphases prepared by pressure-pulsed reactive chemical vapor deposition for ceramic matrix composites

    International Nuclear Information System (INIS)

    In Ceramic Matrix Composites (CMCs) reinforced by continuous fibers, a good toughness is achieved by adding a thin film called “interphase” between the fiber and the brittle matrix, which acts as a mechanical fuse by deflecting the matrix cracks. Pyrocarbon (PyC), with or without carbide sub-layers, is typically the material of choice to fulfill this role. The aim of this work was to study PyC-free nanoscale multilayered carbide coatings as interphases for CMCs. Nanoscale multilayered (SiC–TiC)n interphases were deposited by pressure-Pulsed Chemical Vapor Deposition (P-CVD) on single filament Hi-Nicalon fibers and embedded in a SiC matrix sheath. The thicknesses of the carbide interphase sub-layers could be made as low as a few nanometers as evidenced by scanning and transmission electron microscopy. By using the P-ReactiveCVD method (P-RCVD), in which the TiC growth involves consumption of SiC, it was not only possible to obtain multilayered (SiC–TiC)n films but also TiC films with a porous multilayered microstructure as a result of the Kirkendall effect. The porosity in the TiC sequences was found to be enhanced when some PyC was added to SiC prior to total RCVD consumption. Because the porosity volume fraction was still not high enough, the role of mechanical fuse of the interphases could not be evidenced from the tensile curves, which remained fully linear even when chemical attack of the fiber surface was avoided.

  6. Nanoscale multilayered and porous carbide interphases prepared by pressure-pulsed reactive chemical vapor deposition for ceramic matrix composites

    Science.gov (United States)

    Jacques, S.; Jouanny, I.; Ledain, O.; Maillé, L.; Weisbecker, P.

    2013-06-01

    In Ceramic Matrix Composites (CMCs) reinforced by continuous fibers, a good toughness is achieved by adding a thin film called "interphase" between the fiber and the brittle matrix, which acts as a mechanical fuse by deflecting the matrix cracks. Pyrocarbon (PyC), with or without carbide sub-layers, is typically the material of choice to fulfill this role. The aim of this work was to study PyC-free nanoscale multilayered carbide coatings as interphases for CMCs. Nanoscale multilayered (SiC-TiC)n interphases were deposited by pressure-Pulsed Chemical Vapor Deposition (P-CVD) on single filament Hi-Nicalon fibers and embedded in a SiC matrix sheath. The thicknesses of the carbide interphase sub-layers could be made as low as a few nanometers as evidenced by scanning and transmission electron microscopy. By using the P-ReactiveCVD method (P-RCVD), in which the TiC growth involves consumption of SiC, it was not only possible to obtain multilayered (SiC-TiC)n films but also TiC films with a porous multilayered microstructure as a result of the Kirkendall effect. The porosity in the TiC sequences was found to be enhanced when some PyC was added to SiC prior to total RCVD consumption. Because the porosity volume fraction was still not high enough, the role of mechanical fuse of the interphases could not be evidenced from the tensile curves, which remained fully linear even when chemical attack of the fiber surface was avoided.

  7. A coupling alternative to reactive transport simulations for long-term prediction of chemical reactions in heterogeneous CO2 storage systems

    Directory of Open Access Journals (Sweden)

    M. De Lucia

    2014-09-01

    Full Text Available Fully-coupled, multi-phase reactive transport simulations of CO2 storage systems can be approximated by a simplified one-way coupling of hydrodynamics and reactive chemistry. The main characteristics of such systems, and hypotheses underlying the proposed alternative coupling, are (i that the presence of CO2 is the only driving force for chemical reactions and (ii that its migration in the reservoir is only marginally affected by immobilization due to chemical reactions. In the simplified coupling, the exposure time to CO2 of each element of the hydrodynamic grid is estimated by non-reactive simulations and the reaction path of one single batch geochemical model is applied to each grid element during its exposure time. In heterogeneous settings, analytical scaling relationships provide the dependency of velocity and amount of reactions to porosity and gas saturation. The analysis of TOUGHREACT fully coupled reactive transport simulations of CO2 injection in saline aquifer, inspired to the Ketzin pilot site (Germany, both in homogeneous and heterogeneous settings, confirms that the reaction paths predicted by fully coupled simulations in every element of the grid show a high degree of self-similarity. A threshold value for the minimum concentration of dissolved CO2 considered chemically active is showed to mitigate the effects of the discrepancy between dissolved CO2 migration in non-reactive and fully coupled simulations. In real life, the optimal threshold value is unknown and has to be estimated, e.g., by means of 1-D or 2-D simulations, resulting in an uncertainty ultimately due to the process de-coupling. However, such uncertainty is more than acceptable given that the alternative coupling enables using grids in the order of million elements, profiting from much better description of heterogeneous reservoirs at a fraction of the calculation time of fully coupled models.

  8. A coupling alternative to reactive transport simulations for long-term prediction of chemical reactions in heterogeneous CO2 storage systems

    Science.gov (United States)

    De Lucia, M.; Kempka, T.; Kühn, M.

    2015-02-01

    Fully coupled, multi-phase reactive transport simulations of CO2 storage systems can be approximated by a simplified one-way coupling of hydrodynamics and reactive chemistry. The main characteristics of such systems, and hypotheses underlying the proposed alternative coupling, are (i) that the presence of CO2 is the only driving force for chemical reactions and (ii) that its migration in the reservoir is only marginally affected by immobilisation due to chemical reactions. In the simplified coupling, the exposure time to CO2 of each element of the hydrodynamic grid is estimated by non-reactive simulations and the reaction path of one single batch geochemical model is applied to each grid element during its exposure time. In heterogeneous settings, analytical scaling relationships provide the dependency of velocity and amount of reactions to porosity and gas saturation. The analysis of TOUGHREACT fully coupled reactive transport simulations of CO2 injection in saline aquifer, inspired to the Ketzin pilot site (Germany), both in homogeneous and heterogeneous settings, confirms that the reaction paths predicted by fully coupled simulations in every element of the grid show a high degree of self-similarity. A threshold value for the minimum concentration of dissolved CO2 considered chemically active is shown to mitigate the effects of the discrepancy between dissolved CO2 migration in non-reactive and fully coupled simulations. In real life, the optimal threshold value is unknown and has to be estimated, e.g. by means of 1-D or 2-D simulations, resulting in an uncertainty ultimately due to the process de-coupling. However, such uncertainty is more than acceptable given that the alternative coupling enables using grids of the order of millions of elements, profiting from much better description of heterogeneous reservoirs at a fraction of the calculation time of fully coupled models.

  9. A coupling alternative to reactive transport simulations for long-term prediction of chemical reactions in heterogeneous CO2 storage systems

    Directory of Open Access Journals (Sweden)

    M. De Lucia

    2015-02-01

    Full Text Available Fully coupled, multi-phase reactive transport simulations of CO2 storage systems can be approximated by a simplified one-way coupling of hydrodynamics and reactive chemistry. The main characteristics of such systems, and hypotheses underlying the proposed alternative coupling, are (i that the presence of CO2 is the only driving force for chemical reactions and (ii that its migration in the reservoir is only marginally affected by immobilisation due to chemical reactions. In the simplified coupling, the exposure time to CO2 of each element of the hydrodynamic grid is estimated by non-reactive simulations and the reaction path of one single batch geochemical model is applied to each grid element during its exposure time. In heterogeneous settings, analytical scaling relationships provide the dependency of velocity and amount of reactions to porosity and gas saturation. The analysis of TOUGHREACT fully coupled reactive transport simulations of CO2 injection in saline aquifer, inspired to the Ketzin pilot site (Germany, both in homogeneous and heterogeneous settings, confirms that the reaction paths predicted by fully coupled simulations in every element of the grid show a high degree of self-similarity. A threshold value for the minimum concentration of dissolved CO2 considered chemically active is shown to mitigate the effects of the discrepancy between dissolved CO2 migration in non-reactive and fully coupled simulations. In real life, the optimal threshold value is unknown and has to be estimated, e.g. by means of 1-D or 2-D simulations, resulting in an uncertainty ultimately due to the process de-coupling. However, such uncertainty is more than acceptable given that the alternative coupling enables using grids of the order of millions of elements, profiting from much better description of heterogeneous reservoirs at a fraction of the calculation time of fully coupled models.

  10. Accounting robustly for instantaneous chemical equilibriums in reactive transport: A numerical method and its application to liquid-liquid extraction modeling

    International Nuclear Information System (INIS)

    Reactive transport equations are used in numerous application fields: CO2 or nuclear waste storage monitoring, separation processes in chemical engineering. We present a general method to account robustly for instantaneous chemical equilibriums in reactive transport. This method is adapted to all kinds of hydraulic transport models including 1D to 3D convection-diffusion equations. This leads to the resolution of a bound constrained system of Differential Algebraic Equations (DAEs). The algebraic constraints come from the adjunction of mass action laws related to the equilibriums, whereas the bounds account for the positivity of the computed quantities. In order to solve the numerical system associated with our method, we use an adaptation of the DASSL solver, CDASSL, that can handle the resolution of bound constrained DAE systems. We present an application of this method to liquid-liquid extraction modeling. Numerical experiments demonstrate the interest of using the CDASSL solver to ensure the bound constraints are satisfied. (authors)

  11. A chemical probe technique for the determination of reactive halogen species in aqueous solution: Part 1 – bromide solutions

    Directory of Open Access Journals (Sweden)

    C. Anastasio

    2006-02-01

    Full Text Available Reactive halogen species (X*=X●, ●X2−, X2 and HOX, where X=Br, Cl, or I in seawater, sea-salt particles, and snowpacks play important roles in the chemistry of the marine boundary layer. Despite this, relatively little is known about the steady-state concentrations or kinetics of reactive halogens in these environmental samples. In part this is because there are few instruments or techniques that can be used to characterize aqueous reactive halogens. To better understand this chemistry, we have developed a chemical probe technique that can detect and quantify aqueous reactive bromine and chlorine species (Br*(aq and Cl*(aq. This technique is based on the reactions of short-lived X*(aq species with allyl alcohol (CH2=CHCH2OH to form stable 3-halo-1,2-propanediols that are analyzed by gas chromatography. Using this technique in conjunction with competition kinetics allows determination of the steady state concentrations of the aqueous reactive halogens and, in some cases, the rates of formation and lifetimes of X* in aqueous solutions. We report here the results of the method development for aqueous solutions containing only bromide (Br−.

  12. The coordination chemistry of boron porphyrin complexes B2OX2 (TYPP) (X = OH, F; Y = Cl, CH3) and their chemical reactivities

    Indian Academy of Sciences (India)

    G I Cárdenas-Jirón; F Espinoza-Leyton; T L Sordo

    2005-09-01

    The structure and coordination chemistry of boron porphyrin complexes B2OX2 (TYPP) (X = OH, F; Y = Cl, CH3) in connection with its chemical reactivity are analyzed at ab initio density functional theory B3LYP/6-31G∗ and restricted Hartree-Fock RHF/6-31G∗ levels of theory. Global reactivity and local selectivity descriptors are used as adequate tools to analyze the isomerism effect ( or isomer) and the substitution effect (X: in axial ligand; or Y: in porphyrin ligand). In all the cases, we find that the conformation is the most stable one, in agreement with X-ray results, and that a principle of maximum hardness in the isomerism analysis is fullfilled. In the substitution analysis, we find that the three global reactivity indexes (, , ) and the two local reactivity indexes (, electrostatic potential) used in this paper predict the same trend when an electron-withdrawing substituent is replaced by an electron donor. Finally, we show that substitution in the porphyrin ligand is slightly more significant than that in the axial ligand.

  13. From solution to in-cell study of the chemical reactivity of acid sensitive functional groups: a rational approach towards improved cleavable linkers for biospecific endosomal release.

    Science.gov (United States)

    Jacques, Sylvain A; Leriche, Geoffray; Mosser, Michel; Nothisen, Marc; Muller, Christian D; Remy, Jean-Serge; Wagner, Alain

    2016-06-01

    pH-Sensitive linkers designed to undergo selective hydrolysis at acidic pH compared to physiological pH can be used for the selective release of therapeutics at their site of action. In this paper, the hydrolytic cleavage of a wide variety of molecular structures that have been reported for their use in pH-sensitive delivery systems was examined. A wide variety of hydrolytic stability profiles were found among the panel of tested chemical functionalities. Even within a structural family, a slight modification of the substitution pattern has an unsuspected outcome on the hydrolysis stability. This work led us to establish a first classification of these groups based on their reactivities at pH 5.5 and their relative hydrolysis at pH 5.5 vs. pH 7.4. From this classification, four representative chemical functions were selected and studied in-vitro. The results revealed that only the most reactive functions underwent significant lysosomal cleavage, according to flow cytometry measurements. These last results question the acid-based mechanism of action of known drug release systems and advocate for the importance of an in-depth structure-reactivity study, using a tailored methodology, for the rational design and development of bio-responsive linkers. PMID:27169758

  14. Chemical alteration of cement materials in a radioactive waste repository environment. 3. Development of reactive transport computational code combined with incongruent dissolution model of calcium silicate hydrates

    International Nuclear Information System (INIS)

    For long-term performance assessment of a cementitious disposal system for TRU waste, a so-called reactive transport computational code, being a numerical simulation code coupled a geochemical model suited to the system includes cement hydrate and a solute transport model, so-called reactive transport computational code, has been developed. The thermodynamic model previously developed in our institute for incongruent dissolution of calcium silicate hydrate (C-S-H) gel, which is a principal product of hydrated cement phase, was incorporated into a geochemical code, Harphrq, to evaluate chemical equilibrium conditions containing cement hydrates. This modification of the code enables a user to evaluate adequately the chemical equilibrium of a system including cement hydrate, such as a dissolution/precipitation of C-S-H gel and/or a change of Ca/Si ratio in C-S-H gel. The modified geochemical code was coupled onto a simplified solute transport code using a compartment model. The coupled code could simulate the processes where various chemical species in aqueous phase migrate through the homogeneous porous materials while locally maintaining chemical equilibrium. The developed reactive transport computational code was verified by comparison with experimental results on batch-type dissolution tests and column-type alteration tests under flow-through conditions of ordinary Portland cement hydrate. Predictive calculation results by the developed code were reasonably accordant with the experimental results, e.g. the distribution of constituent minerals and the composition of pore water in altered ordinary Portland cement hydrate. The validity of the developed code was therefore verified. Analysis on the results by the calculation could indicates special features such as a distribution of Ca/Si ratio in C-S-H gel along the water-flow in the column, and a re-precipitation of C-S-H gel in the downstream side of the dissolution front of C-S-H gel. (author)

  15. Characterization of the chemical reactivity and nephrotoxicity of N-acetyl-S-(1,2-dichlorovinyl)-L-cysteine sulfoxide, a potential reactive metabolite of trichloroethylene

    Energy Technology Data Exchange (ETDEWEB)

    Irving, Roy M. [Molecular and Environmental Toxicology Center, University of Wisconsin-Madison, Madison, WI 53706 (United States); Pinkerton, Marie E. [Department of Pathobiological Sciences, University of Wisconsin-Madison, Madison, WI 53706 (United States); Elfarra, Adnan A., E-mail: elfarra@svm.vetmed.wisc.edu [Molecular and Environmental Toxicology Center, University of Wisconsin-Madison, Madison, WI 53706 (United States); Department of Comparative Biosciences, University of Wisconsin-Madison, Madison, WI 53706 (United States)

    2013-02-15

    N-Acetyl-S-(1,2-dichlorovinyl)-L-cysteine (NA-DCVC) has been detected in the urine of humans exposed to trichloroethylene and its related sulfoxide, N-acetyl-S-(1,2-dichlorovinyl)-L-cysteine sulfoxide (NA-DCVCS), has been detected as hemoglobin adducts in blood of rats dosed with S-(1,2-dichlorovinyl)-L-cysteine (DCVC) or S-(1,2-dichlorovinyl)-L-cysteine sulfoxide (DCVCS). Because the in vivo nephrotoxicity of NA-DCVCS was unknown, in this study, male Sprague–Dawley rats were dosed (i.p.) with 230 μmol/kg b.w. NA-DCVCS or its potential precursors, DCVCS or NA-DCVC. At 24 h post treatment, rats given NA-DCVC or NA-DCVCS exhibited kidney lesions and effects on renal function distinct from those caused by DCVCS. NA-DCVC and NA-DCVCS primarily affected the cortico-medullary proximal tubules (S{sub 2}–S{sub 3} segments) while DCVCS primarily affected the outer cortical proximal tubules (S{sub 1}–S{sub 2} segments). When NA-DCVCS or DCVCS was incubated with GSH in phosphate buffer pH 7.4 at 37 °C, the corresponding glutathione conjugates were detected, but NA-DCVC was not reactive with GSH. Because NA-DCVCS exhibited a longer half-life than DCVCS and addition of rat liver cytosol enhanced GSH conjugate formation, catalysis of GSH conjugate formation by the liver could explain the lower toxicity of NA-DCVCS in comparison with DCVCS. Collectively, these results provide clear evidence that NA-DCVCS formation could play a significant role in DCVC, NA-DCVC, and trichloroethylene nephrotoxicity. They also suggest a role for hepatic metabolism in the mechanism of NA-DCVC nephrotoxicity. - Highlights: ► NA-DCVCS and NA-DCVC toxicity are distinct from DCVCS toxicity. ► NA-DCVCS readily reacts with GSH to form mono- and di-GSH conjugates. ► Liver glutathione S-transferases enhance NA-DCVCS GSH conjugate formation. ► Renal localization of lesions suggests a role for NA-DCVCS in TCE nephrotoxicity.

  16. A chemical probe technique for the determination of reactive halogen species in aqueous solution: Part 2 – chloride solutions and mixed bromide/chloride solutions

    Directory of Open Access Journals (Sweden)

    C. Anastasio

    2006-02-01

    Full Text Available Although reactive halogen species (X*=X●, ●X2−, X2 and HOX, where X=Br, Cl, or I are important environmental oxidants, relatively little is known about their kinetics in condensed phases such as seawater and sea-salt particles. Here we describe a new technique to determine reactive chlorine and bromine species in aqueous solutions by using allyl alcohol (CH2=CHCH2OH as a chemical probe. This probe is combined with competition kinetics in order to determine steady state concentrations of X*(aq. In some cases the technique also can be used to determine the rates of formation and lifetimes of X* in aqueous solution. In a companion paper we reported the results of our method development for aqueous solutions containing only bromide (Br−. In this paper, we discuss method development for solutions containing chloride (Cl− alone, and for solutions containing both bromide and chloride.

  17. Direct measurement of the chemical reactivity of silicon electrodes with LiPF6-based battery electrolytes

    Energy Technology Data Exchange (ETDEWEB)

    Veith, Gabriel M [ORNL; Baggetto, Loic [ORNL; Sacci, Robert L [ORNL; Unocic, Raymond R [ORNL; Tenhaeff, Wyatt E [ORNL; Browning, Jim [ORNL

    2014-01-01

    We report the first direct measurement of the chemistry and extent of reactivity between a lithium ion battery electrode surface (Si) and a liquid electrolyte (1.2M LiPF6-3:7 wt% ethylene carbonate:dimethyl carbonate). This layer is estimated to be 3.6 nm thick and partially originates from the consumption of the silicon surface.

  18. Distillation and isolation of commodity chemicals from Bio-oil made by tail-gas reactive prolysis

    Science.gov (United States)

    Owing to instabilities, very little has been accomplished with regards to simple cost-effective separations of fast-pyrolysis bio-oil. However, recent developments in the use of tail-gas reactive pyrolysis (TGRP) (Mullen and Boateng 2013) provide higher quality bio-oils that are thermally stable. We...

  19. Hot spot formation and chemical reaction initiation in shocked HMX crystals with nanovoids: a large-scale reactive molecular dynamics study.

    Science.gov (United States)

    Zhou, Tingting; Lou, Jianfeng; Zhang, Yangeng; Song, Huajie; Huang, Fenglei

    2016-07-14

    We report million-atom reactive molecular dynamic simulations of shock initiation of β-cyclotetramethylene tetranitramine (β-HMX) single crystals containing nanometer-scale spherical voids. Shock induced void collapse and subsequent hot spot formation as well as chemical reaction initiation are observed which depend on the void size and impact strength. For an impact velocity of 1 km s(-1) and a void radius of 4 nm, the void collapse process includes three stages; the dominant mechanism is the convergence of upstream molecules toward the centerline and the downstream surface of the void forming flowing molecules. Hot spot formation also undergoes three stages, and the principal mechanism is kinetic energy transforming to thermal energy due to the collision of flowing molecules on the downstream surface. The high temperature of the hot spot initiates a local chemical reaction, and the breakage of the N-NO2 bond plays the key role in the initial reaction mechanism. The impact strength and void size have noticeable effects on the shock dynamical process, resulting in a variation of the predominant mechanisms leading to void collapse and hot spot formation. Larger voids or stronger shocks result in more intense hot spots and, thus, more violent chemical reactions, promoting more reaction channels and generating more reaction products in a shorter duration. The reaction products are mainly concentrated in the developed hot spot, indicating that the chemical reactivity of the hmx crystal is greatly enhanced by void collapse. The detailed information derived from this study can aid a thorough understanding of the role of void collapse in hot spot formation and the chemical reaction initiation of explosives. PMID:27307079

  20. Study of a new hybrid process combining slurry infiltration and Reactive Chemical Vapour Infiltration for the realisation of Ceramic Matrix Composites

    International Nuclear Information System (INIS)

    Ceramic matrix composites were originally developed for aerospace,military aeronautics or energy applications thanks to their good properties at high temperature. They are generally made by Chemical Vapor Infiltration (CVI). A new short hybrid process combining fiber preform slurry impregnation of ceramic powders with an innovative Reactive CVI (RCVI) route is proposed to reduce the production time. This route is based on the combination of Reactive Chemical Vapour Deposition (RCVD), which is often used to deposit coatings on fibres, with the Chemical Vapor Infiltration (CVI).In RCVD, the absence of one element of the deposited carbide in the initial gas phase involves the consumption/conversion of the solid substrate. In this work, the RCVD growth and the associated consumption were studied with different parameters in the Ti-H-Cl-C chemical system. The study has been completed with the chemical products analysis, combining XRD, XPS and FTIR. Then, the partial conversion of sub-micrometer carbon powders into titanium carbide and the consolidation of green bodies by RCVI from H2/TiCl4 gaseous infiltration were studied. The residual porosity and the final TiC content were measured in the bulk of the infiltrated powders by image analysis from scanning electron microscopy. Depending on temperature, few hundred micrometers-depth infiltrations are obtained.Finally, the results have been transposed to the RCVI into CMC-type pre-forms. Despite a minimal TiC content of 25% in the overall preform, the results shown a bad homogeneity of the infiltration and a poor cohesion of fibres with RCVI consolidated powder of their environment. (author)

  1. Chemical reactivity of Li17Pb83 with nitrogen and oxygen, and its compatibility with AISI 316L under known partial pressure of these gases

    International Nuclear Information System (INIS)

    The chemical reactivity of the lithium-lead eutectic with nitrogen and oxygen has been studied. While nitrogen is inert towards Li17Pb83 up to 1073 K, oxygen reacts, already at 750 K, with the lithium contained in the alloy. Compatibility tests at 873 K between AISI 316L stainless steel and Li17Pb83 under known partial pressures of nitrogen and oxygen have shown that the former gas does not influence the corrosion phenomenon while the latter greatly enhances it. (author)

  2. Chemical analysis of reactive species and antimicrobial activity of/nwater treated by nanosecond pulsed DBD air plasma

    Czech Academy of Sciences Publication Activity Database

    Laurita, R.; Barbieri, D.; Gherardi, M.; Colombo, V.; Lukeš, Petr

    2015-01-01

    Roč. 3, č. 2 (2015), s. 53-61. ISSN 2212-8166 R&D Projects: GA MŠk(CZ) LD14080 Grant ostatní: European Cooperation in Science and Technology(XE) COST TD1208 Institutional support: RVO:61389021 Keywords : Dielectric barrier discharge * Plasma activated water * Reactive species * Peroxynitrite * Phenol degradation * Candida albicans * Staphylococcus aureus * Antimicrobial activity * Nosocomial infections Subject RIV: BL - Plasma and Gas Discharge Physics http://www.sciencedirect.com/science/article/pii/S2212816615300081

  3. Host-cell reactivation of UV-irradiated and chemically-treated herpes simplex virus-1 by xeroderma pigmentosum, xp heterozygotes and normal skin fibroblasts

    International Nuclear Information System (INIS)

    The host-cell reactivation of UV-irradiated and N-acetoxy-2-acetylamino-fluorene-treated herpes simplex virus type 1 strain MP was studied in normal and xeroderma pigmentosum human skin fibroblasts. Virus treated with either agent demonstrated lower survival in XP cells from complementation groups A, B, C and D than in normal fibroblasts. The relative reactivation ability of XP cells from the different genetic complementation groups was found to be the same for both irradiated and chemically treated virus. In addition, the inactivation kinetics for virus treated with either agent in the XP variant were comparable to that seen in normal skin fibroblasts. The addition of 2 or 4 mmoles caffeine to the post-infection assay medium had no effect on the inactivation kinetics of virus treated by either agent in the XP variant or in XP cells from the different genetic complementation groups. Treatment of the virus with nitrogen mustard resulted in equivalent survival in normal and XP genetic complementation group D cells. No apparent defect was observed in the ability of XP heterozygous skin fibroblasts to repair virus damaged with up to 100 μg N-acetoxy-2-acetylaminofluorene per ml. These findings indicate that the repair of UV-irradiated and N-acetoxy-2-acetylaminofluorene-treated virus is accomplished by the same pathway or different pathways sharing a common intermediate step and that the excision defect of XP cells plays little if any role in the reactivation of nitrogen mustard treated virus. (Auth.)

  4. Dynamic behavior of chemical reactivity indices in density functional theory: A Bohn-Oppenheimer quantum molecular dynamics study

    Indian Academy of Sciences (India)

    Shubin Liu

    2005-09-01

    Dynamic behaviors of chemical concepts in density functional theory such as frontier orbitals (HOMO/LUMO), chemical potential, hardness, and electrophilicity index have been investigated in this work in the context of Bohn-Oppenheimer quantum molecular dynamics in association with molecular conformation changes. Exemplary molecular systems like CH$^{+}_{5}$ , Cl- (H2O)30 and Ca2+ (H2O)15 are studied at 300 K in the gas phase, demonstrating that HOMO is more dynamic than LUMO, chemical potential and hardness often fluctuate concurrently. It is argued that DFT concepts and indices may serve as a good framework to understand molecular conformation changes as well as other dynamic phenomena.

  5. Formulation of chemically reactive foams for the dissolution of oxides polluting the secondary circuits of steam generators

    International Nuclear Information System (INIS)

    The fouling of the Steam Generators (SG) secondary circuits, due to oxides deposits like magnetite (Fe3O4), induces the degradation of the internal SG equipment, the reduction of the plant power, implying to clean these circuits. This operation made in liquid phase generates an important volume of effluents with an expensive cost of treatment. The use of a reactive foam allows the reduction of this volume by ten. Among the reactive tested, oxalic acid is the most efficient to dissolve a magnetite quantity of 10 g.l-1, at ambient temperature for 24 hours, as imposed by the industrial wishes. The dissolution is not complete in our experimental conditions and is a complex reaction of autocatalytic type, composed of an acid attack, a reductive step, both followed by a slow diffusion. The surfactants generating the foam, which transport the reactive, are adsorbed on the magnetite but this affects weakly the dissolution. Its effectiveness is evaluated varying the experimental conditions. The wetting properties and the stability of the foam induce erosion and undissolved particles transport capacities, during its circulation into the SG. These particles trapped in the inter-bubble liquid films or carried by the piston effect of the foam bed, can be recovered on filters placed out of the SG. To quantify the transport, the influence of different parameters is studied: the more stable the foam is, the more important the transport is. Innocuousness tests showed that oxalic acid was not harmful for constitutive SG materials, either they were isolated or coupled. The cleaning by oxalic acid causes ferrous oxalates precipitation, representing 10 to 15 pc of the total iron quantity depending on the sample. A rinsing out with a foam containing 1 pc oxalic acid and 5 pc hydrogen peroxide allows the dissolution of these precipitates without corrosion problems. (author)

  6. Using laboratory flow experiments and reactive chemical transport modeling for designing waterflooding of the Agua Fria Reservoir, Poza Rica-Altamira Field, Mexico

    Energy Technology Data Exchange (ETDEWEB)

    Birkle, P.; Pruess, K.; Xu, T.; Figueroa, R.A. Hernandez; Lopez, M. Diaz; Lopez, E. Contreras

    2008-10-01

    Waterflooding for enhanced oil recovery requires that injected waters must be chemically compatible with connate reservoir waters, in order to avoid mineral dissolution-and-precipitation cycles that could seriously degrade formation permeability and injectivity. Formation plugging is a concern especially in reservoirs with a large content of carbonates, such as calcite and dolomite, as such minerals typically react rapidly with an aqueous phase, and have strongly temperature-dependent solubility. Clay swelling can also pose problems. During a preliminary waterflooding pilot project, the Poza Rica-Altamira oil field, bordering the Gulf coast in the eastern part of Mexico, experienced injectivity loss after five months of reinjection of formation waters into well AF-847 in 1999. Acidizing with HCl restored injectivity. We report on laboratory experiments and reactive chemistry modeling studies that were undertaken in preparation for long-term waterflooding at Agua Frma. Using analogous core plugs obtained from the same reservoir interval, laboratory coreflood experiments were conducted to examine sensitivity of mineral dissolution and precipitation effects to water composition. Native reservoir water, chemically altered waters, and distilled water were used, and temporal changes in core permeability, mineral abundances and aqueous concentrations of solutes were monitored. The experiments were simulated with the multi-phase, nonisothermal reactive transport code TOUGHREACT, and reasonable to good agreement was obtained for changes in solute concentrations. Clay swelling caused an additional impact on permeability behavior during coreflood experiments, whereas the modeled permeability depends exclusively on chemical processes. TOUGHREACT was then used for reservoir-scale simulation of injecting ambient-temperature water (30 C, 86 F) into a reservoir with initial temperature of 80 C (176 F). Untreated native reservoir water was found to cause serious porosity and

  7. Flows of Reactive Fluids

    CERN Document Server

    Prud'homme, Roger

    2010-01-01

    The modeling of reactive flows has progressed mainly with advances in aerospace, which gave birth to a new science called aerothermochemistry, as well as through developments in chemical and process engineering. The methods employed, the phenomena investigated, and the aims of modeling differ for each field; however, in all cases, the results obtained have considerably enriched the working knowledge of reactive flows. This work examines basic concepts and methods necessary to study reactive flows and transfer phenomena in areas such as fluid mechanics, thermodynamics, and chemistry. Specific topics covered include: * Equations of state * Transfer phenomena and chemical kinetics * Balance equations of reactive flows * Dimensionless numbers and similarity * Chemical reactors * Coupled phenomena * Turbulent flow concepts * Boundary layers and fluid layers * Reactive and nonreactive waves * Interface phenomena * Multiphase flow concepts The book presents tools of interest to graduate students, researchers in math...

  8. Investigating the Chemical Reactivity for Hydrogen in Siliciclastic Sediments: two Work Packages of the H2STORE Project

    Science.gov (United States)

    De Lucia, M.; Pilz, P.

    2014-12-01

    The H2STORE ("Hydrogen to Store") collaborative project, funded by the German government, investigates the feasibility of industrial-scale hydrogen storage from excess wind energy in siliciclastic depleted gas and oil reservoirs or suitable saline aquifers. In particular, two work packages (geochemical experiments and modelling) hosted at the German Research Centre for Geosciences (GFZ) focus on the possible impact of hydrogen on formation fluids and on the mineralogical, geochemical and petrophysical properties of reservoirs and caprocks. Laboratory experiments expose core samples from several potential reservoirs to pure hydrogen or hydrogen mixtures under site-specific conditions (temperatures up to 200 °C and pressure up to 300 bar). The resulting qualitative and, whereas possible, quantitative data are expected to ameliorate the precision of predictive geochemical and reactive transport modelling, which is also performed within the project. The combination of experiments and models will improve the knowledge about: (1) solubility model and mixing rule for of hydrogen and its gas mixtures in high saline formation fluids; (2) hydrogen reactivity in a broad spectrum of P-T conditions; (3) thermodynamics and kinetics of mineral dissolution or precipitation reactions and redox processes. It is known that under specific P-T conditions reactions between hydrogen and anorganic rock components such as carbonates can occur. However these conditions have never been precisely defined to date. A precise estimation of the hydrogen impact on reservoir behavior of different siliciclastic rock types is crucial for site selection and optimization of storage depth. Enhancing the overall understanding of such systems will benefit the operational reliability, the ecological tolerance, and the economic efficiency of future energy storing plants, crucial aspects for public acceptance and for industrial investors.

  9. In Chemico Evaluation of Tea Tree Essential Oils as Skin Sensitizers: Impact of the Chemical Composition on Aging and Generation of Reactive Species.

    Science.gov (United States)

    Avonto, Cristina; Chittiboyina, Amar G; Wang, Mei; Vasquez, Yelkaira; Rua, Diego; Khan, Ikhlas A

    2016-07-18

    Tea tree oil (TTO) is an essential oil obtained from the leaves of Melaleuca alternifolia, M. linariifolia, or M. dissitiflora. Because of the commercial importance of TTO, substitution or adulteration with other tea tree species (such as cajeput, niaouli, manuka, or kanuka oils) is common and may pose significant risks along with perceived health benefits. The distinctive nature, qualitative and quantitative compositional variation of these oils, is responsible for the various pharmacological as well as adverse effects. Authentic TTOs (especially aged ones) have been identified as potential skin sensitizers, while reports of adverse allergic reactions to the other tea trees essential oils are less frequent. Chemical sensitizers are usually electrophilic compounds, and in chemico methods have been developed to identify skin allergens in terms of their ability to bind to biological nucleophiles. However, little information is available on the assessment of sensitization potential of mixtures, such as essential oils, due to their complexity. In the present study, 10 "tea tree" oils and six major TTO constituents have been investigated for their sensitization potential using a fluorescence in chemico method. The reactivity of authentic TTOs was found to correlate with the age of the oils, while the majority of nonauthentic TTOs were less reactive, even after aging. Further thio-trapping experiments with DCYA and characterization by UHPLC-DAD-MS led to the identification of several possible DCYA-adducts which can be used to deduce the structure of the candidate reactive species. The major TTO components, terpinolene, α-terpinene, and terpinene-4-ol, were unstable under accelerated aging conditions, which led to the formation of several DCYA-adducts. PMID:27286037

  10. Lattice-Boltzmann simulation methods for chemically reactive systems in the micro area; Lattice Boltzmann Simulationsmethoden fuer chemisch reaktive Systeme im Microbereich - Schlussbericht

    Energy Technology Data Exchange (ETDEWEB)

    Karlin, I.; Frouzakis, Ch.; Boulouchos, K.

    2007-07-01

    This final report for the Swiss Federal Office of Energy (SFOE) reports on work done in 2007 at the Swiss Federal Institute of Technology ETH in Zurich on simulation methods for chemically reactive systems at the micrometer scale. The Lattice-Boltzmann method using lattice models is examined and the results obtained are discussed. A three-dimensional thermal model was developed and used to analyse flows with considerable temperature and density variations. The model was also used for the analysis of flows in diluted gases. A method for the reduction of complex reaction mechanisms was developed and tested for future combustion applications. 30 publications are noted and new possibilities for the analysis of flows in micro-channels and porous media - as used in reformers, catalyzers and fuel cells - are discussed.

  11. 具有高比表面积的稻壳灰的制备及其化学活性的研究%Study on Preparation of Rice Husk Ash with High Specific Surface Area and Its Chemical Reactivity

    Institute of Scientific and Technical Information of China (English)

    冯庆革; 林清宇; 童张法; S.Sugita

    2004-01-01

    Preparation of rice husk ash with high specific surface area and chemical reactivity of the product are reported in this paper. The amorphous rice husk ash with high specific surface area of 311 m2·g-1 was produced by heating acid treated rice husk at 700℃ for 4 h. The isotherms of rice husk ash are similar in shape to type Ⅱof Brunaner's classification with mesopores being predominant. The rice husk ash has a high chemical reactivity,especially that pretreated with acid. This chemical reactivity depends on ashing temperature and pretreatment conditions. There is an exponential relation between the specific surface area of rice husk ash and the change in the conductivity of saturated Ca(OH)2 solution with rice husk ash, from which the specific surface area can be known according to the conductivity change.

  12. Effect of temperature and residence time of calcination phosphate on the chemical reactivity: Application to the case of Bouchane phosphate (Morocco

    Directory of Open Access Journals (Sweden)

    El Mokhtar El Ouardi

    2013-10-01

    Full Text Available The calcination of phosphate consumes the fossil energy and generates greenhouse gas emissions. This later owed not only on the consumption of these energies, but also in the decomposition of carbonates and in the combustion of the organic matter. The energy consumption and the emission of gases require an optimization of the calcination depending on the residence time and temperature of calcination. These walking parameters influence the chemical reactivity and the solubility of finished product. To assist in that, we have studied the evolution of the main components of the control in the calcination (Corg, CO2, P2O5, CaO, the specific surface area and density of the ore according to the time and temperature. This treatment was performed in the laboratory in a fixed bed. The different analytical techniques that were applied are: sieve analysis, quantitative study by ICP, the mineralogical characterization by X-ray and differential thermal analysis coupled with thermogravimetric analysis. The obtained results show that mechanisms relative to the heat treatment of the phosphate are multiple and are strongly influenced by the nature of the matrix and the parameters of the treatment. The obtained product answers well the trade profiles and the requirements for use under the conditions of a temperature approximately of 800°C and a period of 30 minutes. In these conditions, we note a decrease of 89.29% organic carbon and carbon dioxide of 72.72% with the increase in weight of Bone Phosphate Lime to 12.63%. However, the chemical reactivity and the solubility are affected.

  13. Features in chemical kinetics. III. Attracting subspaces in a hyper-spherical representation of the reactive system

    Science.gov (United States)

    Ceccato, Alessandro; Nicolini, Paolo; Frezzato, Diego

    2015-12-01

    In this work, we deal with general reactive systems involving N species and M elementary reactions under applicability of the mass-action law. Starting from the dynamic variables introduced in two previous works [P. Nicolini and D. Frezzato, J. Chem. Phys. 138(23), 234101 (2013); 138(23), 234102 (2013)], we turn to a new representation in which the system state is specified in a (N × M)2-dimensional space by a point whose coordinates have physical dimension of inverse-of-time. By adopting hyper-spherical coordinates (a set of dimensionless "angular" variables and a single "radial" one with physical dimension of inverse-of-time) and by examining the properties of their evolution law both formally and numerically on model kinetic schemes, we show that the system evolves towards the equilibrium as being attracted by a sequence of fixed subspaces (one at a time) each associated with a compact domain of the concentration space. Thus, we point out that also for general non-linear kinetics there exist fixed "objects" on the global scale, although they are conceived in such an abstract and extended space. Moreover, we propose a link between the persistence of the belonging of a trajectory to such subspaces and the closeness to the slow manifold which would be perceived by looking at the bundling of the trajectories in the concentration space.

  14. Features in chemical kinetics. III. Attracting subspaces in a hyper-spherical representation of the reactive system

    International Nuclear Information System (INIS)

    In this work, we deal with general reactive systems involving N species and M elementary reactions under applicability of the mass-action law. Starting from the dynamic variables introduced in two previous works [P. Nicolini and D. Frezzato, J. Chem. Phys. 138(23), 234101 (2013); 138(23), 234102 (2013)], we turn to a new representation in which the system state is specified in a (N × M)2-dimensional space by a point whose coordinates have physical dimension of inverse-of-time. By adopting hyper-spherical coordinates (a set of dimensionless “angular” variables and a single “radial” one with physical dimension of inverse-of-time) and by examining the properties of their evolution law both formally and numerically on model kinetic schemes, we show that the system evolves towards the equilibrium as being attracted by a sequence of fixed subspaces (one at a time) each associated with a compact domain of the concentration space. Thus, we point out that also for general non-linear kinetics there exist fixed “objects” on the global scale, although they are conceived in such an abstract and extended space. Moreover, we propose a link between the persistence of the belonging of a trajectory to such subspaces and the closeness to the slow manifold which would be perceived by looking at the bundling of the trajectories in the concentration space

  15. Improving the chemical compatibility of sealing glass for solid oxide fuel cells: Blocking the reactive species by controlled crystallization

    Science.gov (United States)

    Zhang, Teng; Zou, Qi; Zeng, Fanrong; Wang, Shaorong; Tang, Dian; Yang, Hiswen

    2012-10-01

    The chemical compatibility of sealing glass is of great importance for Solid oxide fuel cell (SOFC). In this work, the interfacial reaction between sealing glass and Cr-containing interconnect alloy is characterized by reacting Cr2O3 powders with a representative SrO-containing glass crystallized by different heat-treatment schedules. The crystalline structure and crystalline content of sealing glass are determined by X-ray diffraction. The results show that the fraction of Cr6+ decreases from 39.8 ± 1.9% for quenched glass to 8.2 ± 0.4% for glass crystallized at 900 °C for 2 h. In addition, the interfacial reaction can be further reduced with increasing crystallization temperature and time as well as the addition of nucleation agent (TiO2). The formation of some Sr-containing crystalline phases, Sr2SiO4 and Sr(TiO3), contributes to the improvement of chemical compatibility of sealing glass, in agreement with the results of thermodynamic calculations.

  16. Structure sensitive chemical reactivity by palladium concave nanocubes and nanoflowers synthesised by a seed mediated procedure in aqueous medium

    Science.gov (United States)

    Sreedhala, S.; Sudheeshkumar, V.; Vinod, C. P.

    2014-06-01

    Palladium nanocubes and their transformation to concave nanocubes and nanoflowers are realised by a seed mediated procedure in aqueous medium and at room temperature using cationic surfactants. The concave nanocubes and nanoflowers were found to be enclosed by high index facets. The under co-ordinated atoms present on the high index facets make these nanostructures chemically more active towards Suzuki coupling and Heck coupling reactions compared to the conventional nanocubes and spherical nanoparticles of similar size.Palladium nanocubes and their transformation to concave nanocubes and nanoflowers are realised by a seed mediated procedure in aqueous medium and at room temperature using cationic surfactants. The concave nanocubes and nanoflowers were found to be enclosed by high index facets. The under co-ordinated atoms present on the high index facets make these nanostructures chemically more active towards Suzuki coupling and Heck coupling reactions compared to the conventional nanocubes and spherical nanoparticles of similar size. Electronic supplementary information (ESI) available: Additional HRTEM images, UV-Vis spectra and details of TOF calculation. See DOI: 10.1039/c4nr01283f

  17. Quantum chemical study of relative reactivities of a series of amines and nitriles - Relevance to prebiotic chemistry

    Science.gov (United States)

    Loew, G. H.; Berkowitz, D.; Chang, S.

    1975-01-01

    Using the Iterative Extended Huckel Theory (IEHT) calculations of the electron distribution and orbital energies of a series of thirteen amines, nitriles and amino-nitriles relevant to prebiotic and cosmo-chemistry have been carried out. Ground state properties such as the energy and nature of the highest occupied (HOMO) and lowest empty (LEMO) molecular orbitals, net atomic charges and number of nonbonding electrons have been identified as criteria for correlating the relative nucleophilicity of amine and nitrile nitrogens and the electrophilicity of nitrile and other unsaturated carbon atoms. The results of such correlations can be partially verified by known chemical behavior of these compounds and are used to predict and understand their role in prebiotic organic synthesis.

  18. Quantum chemical modelling of reactivity and selectivity of 1,2-dithiolanes towards retroviral and cellular zinc fingers

    Science.gov (United States)

    Topol, Igor A.; Nemukhin, Alexander V.; Burt, Stanley K.

    Interactions of 1,2-dithiolane species with zinc-containing sites, which mimic the zinc finger domains of retroviral and the cellular zinc finger proteins, have been investigated by quantum chemistry tools. According to the calculations, the immediate domains of zinc binding sites in the cellular and retroviral zinc fingers interact differently with such agents of the disulphide family. Thus, when approaching the model cellular-type domains, the molecules of 1,2-dithiolanes experience considerable potential barriers along the reaction path. However, these species react practically barrier-less with the model retroviral-type domains at the correlated DFT level. The results of the quantum chemical modelling provide firm support to the selectivity of 1,2-dithiolanes towards retroviral and cellular zinc fingers. This can be of great practical importance for the design of therapeutics that accomplish functional inactivation of the zinc fingers of the human immunodeficiency virus (HIV-1) retroviral type nucleocapsid protein NCp7.

  19. Enhancement of chemically induced reactive oxygen species production and DNA damage in human SH-SY5Y neuroblastoma cells by 872 MHz radiofrequency radiation

    International Nuclear Information System (INIS)

    The objective of the study was to investigate effects of 872 MHz radiofrequency (RF) radiation on intracellular reactive oxygen species (ROS) production and DNA damage at a relatively high SAR value (5 W/kg). The experiments also involved combined exposure to RF radiation and menadione, a chemical inducing intracellular ROS production and DNA damage. The production of ROS was measured using the fluorescent probe dichlorofluorescein and DNA damage was evaluated by the Comet assay. Human SH-SY5Y neuroblastoma cells were exposed to RF radiation for 1 h with or without menadione. Control cultures were sham exposed. Both continuous waves (CW) and a pulsed signal similar to that used in global system for mobile communications (GSM) mobile phones were used. Exposure to the CW RF radiation increased DNA breakage (p < 0.01) in comparison to the cells exposed only to menadione. Comparison of the same groups also showed that ROS level was higher in cells exposed to CW RF radiation at 30 and 60 min after the end of exposure (p < 0.05 and p < 0.01, respectively). No effects of the GSM signal were seen on either ROS production or DNA damage. The results of the present study suggest that 872 MHz CW RF radiation at 5 W/kg might enhance chemically induced ROS production and thus cause secondary DNA damage. However, there is no known mechanism that would explain such effects from CW RF radiation but not from GSM modulated RF radiation at identical SAR

  20. The impact of snow nitrate photolysis on boundary layer chemistry and the recycling and redistribution of reactive nitrogen across Antarctica and Greenland in a global chemical transport model

    Science.gov (United States)

    Zatko, Maria; Geng, Lei; Alexander, Becky; Sofen, Eric; Klein, Katarina

    2016-03-01

    The formation and recycling of reactive nitrogen (NO, NO2, HONO) at the air-snow interface has implications for air quality and the oxidation capacity of the atmosphere in snow-covered regions. Nitrate (NO3-) photolysis in snow provides a source of oxidants (e.g., hydroxyl radical) and oxidant precursors (e.g., nitrogen oxides) to the overlying boundary layer, and alters the concentration and isotopic (e.g., δ15N) signature of NO3- preserved in ice cores. We have incorporated an idealized snowpack with a NO3- photolysis parameterization into a global chemical transport model (Goddard Earth Observing System (GEOS) Chemistry model, GEOS-Chem) to examine the implications of snow NO3- photolysis for boundary layer chemistry, the recycling and redistribution of reactive nitrogen, and the preservation of ice-core NO3- in ice cores across Antarctica and Greenland, where observations of these parameters over large spatial scales are difficult to obtain. A major goal of this study is to examine the influence of meteorological parameters and chemical, optical, and physical snow properties on the magnitudes and spatial patterns of snow-sourced NOx fluxes and the recycling and redistribution of reactive nitrogen across Antarctica and Greenland. Snow-sourced NOx fluxes are most influenced by temperature-dependent quantum yields of NO3- photolysis, photolabile NO3- concentrations in snow, and concentrations of light-absorbing impurities (LAIs) in snow. Despite very different assumptions about snowpack properties, the range of model-calculated snow-sourced NOx fluxes are similar in Greenland (0.5-11 × 108 molec cm-2 s-1) and Antarctica (0.01-6.4 × 108 molec cm-2 s-1) due to the opposing effects of higher concentrations of both photolabile NO3- and LAIs in Greenland compared to Antarctica. Despite the similarity in snow-sourced NOx fluxes, these fluxes lead to smaller factor increases in mean austral summer boundary layer mixing ratios of total nitrate (HNO3+ NO3-), NOx, OH

  1. Reactive Nitrogen in Asian Continental Outflow over the Western Pacific: Results from the NASA Transport and Chemical Evolution over the Pacific (TRACE-P)Airborne Mission

    Science.gov (United States)

    Talbot, R.; Dibb, J.; Scheuer, E.; Seid, G.; Russo, R.; Sandholm, S.; Tan, D.; Blake, D.; Blake, N.; Singh, H.

    2003-01-01

    We present here results for reactive nitrogen species measured aboard the NASA DC-8 aircraft during the Transport and Chemical Evolution over the Pacific TRACE-P) mission. The large-scale distributions total reactive nitrogen (NO(sub y,sum) = NO + NO2 + HNO3 + PAN + C(sub 1)-C(sub 5) alkyl nitrates) and O3 and CO were better defined in the boundary layer with significant degradation of the relationships as altitude increased. Typically, NO(sub y,sum) was enhanced over background levels of approx.260 pptv by 20-to-30-fold. The ratio C2H2/CO had values of 1-4 at altitudes up to 10 km and as far eastward as 150degE, implying significant vertical mixing of air parcels followed by rapid advection across the Pacific. Analysis air parcels originating from five principal Asian source regions showed that HNO3 and PAN dominated NO(sub y,sum). Correlations of NO(sub y,sum) with C2Cl4 (urban tracer) were not well defined in any of the source regions, and they were only slightly better with CH3Cl (biomass tracer). Air parcels over the western Pacific contained a complex mixture of emission sources that are not easily resolvable as shown by analysis of the Shanghai mega-city plume. It contained an intricate mixture of pollution emissions and exhibited the highest mixing ratios of NO(sub y,sum) species observed during TRACE-P. Comparison of tropospheric chemistry between the earlier PEM-West B mission and the recent TRACE-P data showed that in the boundary layer significant increases in the mixing ratios of NO(sub y,sum)species have occurred, but the middle and upper troposphere seems to have been affected minimally by increasing emissions on the Asian continent over the last 7 years.

  2. PSI's 1kW imaging furnace-A tool for high-temperature chemical reactivity studies

    Energy Technology Data Exchange (ETDEWEB)

    Guesdon, C.; Alxneit, I.; Tschudi, H.R.; Wuillemin, D.; Brunner, Y.; Winkel, L.; Sturzenegger, M. [Laboratory for High-Temperature Solar Technology, Paul Scherrer Institut, 5232 Villigen PSI (Switzerland); Petrasch, J. [Professorship for Renewable Energy Carriers, ETHZ Zentrum, 8092 Zurich (Switzerland)

    2006-10-15

    A new experiment has been installed to conduct studies at temperatures as high as 2500K on chemical reactions that involve solids or melts and the release of condensable gases. The sample is radiatively heated by a 1kW xenon short arc lamp placed in the upper focus of a vertically oriented ellipsoid of revolution. The optimal optical configuration has been determined by a Monte-Carlo Ray tracing method. Several methods to machine the reflector have been evaluated by experimentally determining the optical quality of the surface of plane test pieces. In the imaging furnace the sample is placed on a water-cooled support and heated by the concentrated radiation. This arrangement allows for fast heating and impedes the reaction of the sample with crucible material. A remotely controlled hammer allows for freezing the high-temperature composition of the sample by a fast quench. Thus, the sample can be later analyzed by conventional methods such as XRD or TEM. To allow for measurements under defined atmospheres and to protect the ellipsoidal reflector from liberated condensable products, the entire sample stage is enclosed by a hemispherical glass dome. The dome itself is protected from condensable compounds by a laminar flow of inert gas. Experiments with an incense cone at the place of the sample to visualize the gas flow showed that a steady layer of inert gas protects the dome from smoke, if the inert gas flow is properly adjusted. Measured peak flux densities clearly exceed 500Wcm{sup -2} required to access temperatures of at least 2500K. Decomposition experiments on copper sulfides confirmed the operation of the furnace. In the near future flash assisted multi-wavelength pyrometry (FAMP) will be implemented to measure sample temperatures online. Though the imaging furnace was developed to study the decomposition of metal sulfides it is obviously suited to conduct high-temperature studies on most materials relevant for high-temperature solar technology. (author)

  3. CHEMICALS

    CERN Multimedia

    Medical Service

    2002-01-01

    It is reminded that all persons who use chemicals must inform CERN's Chemistry Service (TIS-GS-GC) and the CERN Medical Service (TIS-ME). Information concerning their toxicity or other hazards as well as the necessary individual and collective protection measures will be provided by these two services. Users must be in possession of a material safety data sheet (MSDS) for each chemical used. These can be obtained by one of several means : the manufacturer of the chemical (legally obliged to supply an MSDS for each chemical delivered) ; CERN's Chemistry Service of the General Safety Group of TIS ; for chemicals and gases available in the CERN Stores the MSDS has been made available via EDH either in pdf format or else via a link to the supplier's web site. Training courses in chemical safety are available for registration via HR-TD. CERN Medical Service : TIS-ME :73186 or service.medical@cern.ch Chemistry Service : TIS-GS-GC : 78546

  4. chemical studies on the reactivity of some organic extractants for extraction and separation of certain elements from aqueous solutions

    International Nuclear Information System (INIS)

    Lanthanide elements such as lanthanum and neodymium are important elements in photo-electronic and metallurgical industries as well as in nuclear technology. The main constituents of the spent nuclear fuel are actinides like uranium, thorium and various fission products including lanthanides. The co-ordination compounds of the trivalent lanthanum and neodymium continues to be an active research area, which includes the specific spectroscopic and magnetic properties of rare earth ions and their applications as super molecular device, contrast-enhancing agents in magnetic resonance imaging, optical signal amplifiers and electroluminescent (EL) devices. Hence, the separation and purification of these elements is of great concern. Solvent extraction technique is employed to separate and purify rare earth elements in an industrial scale, but the separation of lanthanum and neodymium is a difficult task, as lanthanide ions exhibit similar chemical and physical properties. They have generally common and stable +3 oxidation state that requires synthesis of certain extractants which are able to extract them from different aqueous solutions. During the last twenty years, different publications have pointed out the remarkable properties of alkyl amide in the field of separation chemistry. These extractants are able to form stable co-ordination compounds with different metallic ions. In this concern, this thesis deals with the synthesis of different amide extractants namely N, N diethylacetoamide (DEAA), N, N Teteraphenyl malonamide (TPMA), N, N diphenylbenzamide (DPBA), N, N' diphenylacetoamide (DPAA), and N, N' Teteraethyl malonamide (TEMA), which were synthesized, characterized and compared with Aliquat-336 in kerosene for extraction and separation of La (III) and Nd (III). The effect of the different parameters affecting the extraction of these metals from aqueous nitric acid medium in the different systems has been studied in terms of shaking time, nitric acid, hydrogen

  5. Calcium oxide/carbon dioxide reactivity in a packed bed reactor of a chemical heat pump for high-temperature gas reactors

    International Nuclear Information System (INIS)

    The thermal performance of a chemical heat pump that uses a calcium oxide/carbon dioxide reaction system was discussed as a heat storage system for utilizing heat output from high temperature gas reactors (HTGR). Calcium oxide/carbon dioxide reactivity for the heat pump was measured using a packed bed reactor containing 1.0 kg of reactant. The reactor was capable of storing heat at 900 deg. C by decarbonation of calcium carbonate and generating up to 997 deg. C by carbonation of calcium oxide. The amount of stored heat in the reactor was 800-900 kJ kg-1. The output temperature of the reactor could be controlled by regulating the carbonation pressure. The thermal storage performance of the reactor was superior to that of conventional sensible heat storage systems. A heat pump using this CaO/CO2 reactor is expected to contribute to thermal load leveling and to realize highly efficient utilization of HTGR output due to the high heat storage density and high-quality temperature output of the heat pump

  6. Collision induced dissociation of doubly-charged ions: Coulomb explosion vs. neutral loss in [Ca(urea)]2+ gas phase unimolecular reactivity via chemical dynamics simulations

    International Nuclear Information System (INIS)

    In this paper we report different theoretical approaches to study the gas-phase unimolecular dissociation of the doubly-charged cation [Ca(urea)]2+, in order to rationalize recent experimental findings. Quantum mechanical plus molecular mechanical (QM/MM) direct chemical dynamics simulations were used to investigate collision induced dissociation (CID) and rotational-vibrational energy transfer for Ar+ [Ca(urea)]2+ collisions. For the picosecond time-domain of the simulations, both neutral loss and Coulomb explosion reactions were found and the differences in their mechanisms elucidated. The loss of neutral urea subsequent to collision with Ar occurs via a shattering mechanism, while the formation of two singly-charged cations follows statistical (or almost statistical) dynamics. Vibrational-rotational energy transfer efficiencies obtained for trajectories that do not dissociate during the trajectory integration were used in conjunction with RRKM rate constants to approximate dissociation pathways assuming complete intramolecular vibrational energy redistribution (IVR) and statistical dynamics. This statistical limit predicts, as expected, that at long time the most stable species on the potential energy surface (PES) dominate. These results, coupled with experimental CID from which both neutral loss and Coulomb explosion products were obtained, show that the gas phase dissociation of this ion occurs by multiple mechanisms leading to different products and that reactivity on the complicated PES is dynamically complex. (authors)

  7. Phloroglucinols inhibit chemical mediators and xanthine oxidase, and protect cisplatin-induced cell death by reducing reactive oxygen species in normal human urothelial and bladder cancer cells.

    Science.gov (United States)

    Lin, Kai-Wei; Huang, A-Mei; Tu, Huang-Yao; Weng, Jing-Ru; Hour, Tzyh-Chyuan; Wei, Bai-Luh; Yang, Shyh-Chyun; Wang, Jih-Pyang; Pu, Yeong-Shiau; Lin, Chun-Nan

    2009-10-14

    Phloroglucinols, garcinielliptones HA-HE (1-5), and C (6) were studied in vitro for their inhibitory effects on chemical mediators released from mast cells, neutrophils, and macrophages. Compound 6 revealed significant inhibitory effect on release of lysozyme from rat neutrophils stimulated with formyl-Met-Leu-Phe (fMLP)/cytochalasin B (CB). Compounds 3, 4, and 6 showed significant inhibitory effects on superoxide anion generation in rat neutrophils stimulated with (fMLP)/(CB), while compounds 1 and 5 revealed inhibitory effects on tumor necrosis factor-alpha (TNF-alpha) formation in macrophages stimulated with lipopolysaccharide (LPS). Compounds 1 and 3-6 showed inhibitory effects on xanthine oxidase (XO) and could inhibit the DNA breakage caused by O2(-*). Treatment of NTUB1 with 2 to 60 microM compound 3 and 5 microM cisplatin and SV-HUC1 with 9 to 60 microM 3 and 5 microM cisplatin, respectively, resulted in an increase of viability of cells. These results indicated that compounds 1 and 3-6 showed anti-inflammatory effects and antioxidant activities. Compound 3 mediates through the suppression of XO activity and reduction of reactive oxygen species (ROS), and protection of subsequent cell death. PMID:19754119

  8. Chemical Characterization and Formation of Reactive Oxygen Species by PM2.5 during Summer in North China Plain of China

    Science.gov (United States)

    Zheng, M.; Li, X.; Kuang, X.; Yan, C.; Guo, X.; Paulson, S. E.

    2015-12-01

    Ambient particulate matter (PM) could cause adverse health effects by generating reactive oxygen species (ROS) including superoxide (·O2-), hydrogen peroxide (HOOH), and hydroxyl radical (·OH). A number of studies have shown that transition metals, quinones, as well as other unknown organics in particles, may contribute to ROS formation. North China Plain (NCP) is one of the most populated and polluted areas in the world, where Beijing, the capital of China, is located. NCP have been suffering from severe air pollution, and health effects of fine PM have drawn great attentions of both the government and the public. To study the chemical characterization and ROS generation of PM, airborne PM2.5 was collected at two sites, with one urban site on the campus of Peking University in Beijing and one suburban site in Wangdu, Hebei Province, which is located in the south of Beijing and was significantly influenced by biomass burning during the study period. Previous studies have shown that Beijing can be more influenced by regional transport when the prevailing wind is from the south. PM2.5 samples were collected on 47 mm Teflon filter and Quartz filter using the four-channel low-volume sampler, and organic carbon (OC), elemental carbon (EC), water soluble organic carbon (WSOC), soluble ions and trace metals have been analyzed. The formation of ·OH induced by PM2.5 was also measured to characterize the chemical generation of ROS from ambient particles in a cell-free solution. Preliminary analysis showed that during biomass burning periods, OC and EC concentrations in Wangdu were significantly higher than that in Beijing. The average concentration of WSOC in Beijing was comparable to that in Wangdu, while during biomass burning period, that in Wangdu was much higher than that in Beijing. Positive matrix factorization (PMF) was applied to identify the major contributing sources of PM2.5. More detailed information about chemical compositions, sources and ROS generation of

  9. Potential energy profile, structural, vibrational and reactivity descriptors of trans-2-methoxycinnamic acid by FTIR, FT-Raman and quantum chemical studies

    Science.gov (United States)

    Arjunan, V.; Anitha, R.; Thenmozhi, S.; Marchewka, M. K.; Mohan, S.

    2016-06-01

    The stable conformers of trans-2-methoxycinnamic acid (trans-2MCA) are determined by potential energy profile analysis. The energies of the s-cis and s-trans conformers of trans-2MCA determined by B3LYP/cc-pVTZ method are -612.9788331 Hartrees and -612.9780953 Hartrees, respectively. The vibrational and electronic investigations of the stable s-cis and s-trans conformers of trans-2-methoxycinnamic acid have been carried out extensively with FTIR and FT-Raman spectral techniques. The s-cis conformer (I) with a (C16-C17-C18-O19) dihedral angle equal to 0° is found to be more favoured relative to the one s-trans (II) with (C16-C17-C18-O19) = 180°, possibly due to delocalization, hydrogen bonding and steric repulsion effects between the methoxy and acrylic acid groups. The DFT studies are performed with B3LYP method by utilizing 6-311++G** and cc-pVTZ basis sets to determine the structure, thermodynamic properties, vibrational characteristics and chemical shifts of the compound. The total dipole moments of the conformers determined by B3LYP/cc-pVTZ method are 3.35 D and 4.87 D for s-cis and s-trans, respectively. It reveals the higher polarity of s-trans conformer of trans-2MCA molecule. The electronic and steric influence of the methoxy group on the skeletal frequencies has been analysed. The energies of the frontier molecular orbitals and the LUMO-HOMO energy gap have been determined. The MEP of s-cis conformer lie in the range +1.374e × 10-2 to -1.374e × 10-2 while for s-trans it is +1.591e × 10-2 to -1.591e × 10-2. The total electron density of s-cis conformer lie in the range +5.273e × 10-2 to -5.273e × 10-2 while for s-trans it is +5.403e × 10-2 to -5.403e × 10-2. The MEP and total electron density shows that the s-cis conformer is less polar, less reactive and more stable than the s-trans conformer. All the reactivity descriptors of the molecule have been discussed. Intramolecular electronic interactions and their stabilisation energies have analysed

  10. Reactive Transport Modeling of Chemical and Isotope Data to Identify Degradation Processes of Chlorinated Ethenes in a Diffusion-Dominated Media

    Science.gov (United States)

    Chambon, J. C.; Damgaard, I.; Jeannottat, S.; Hunkeler, D.; Broholm, M. M.; Binning, P. J.; Bjerg, P. L.

    2012-12-01

    Chlorinated ethenes are among the most widespread contaminants in the subsurface and a major threat to groundwater quality at numerous contaminated sites. Many of these contaminated sites are found in low-permeability media, such as clay tills, where contaminant transport is controlled by diffusion. Degradation and transport processes of chlorinated ethenes are not well understood in such geological settings, therefore risk assessment and remediation at these sites are particularly challenging. In this work, a combined approach of chemical and isotope analysis on core samples, and reactive transport modeling has been used to identify the degradation processes occurring at the core scale. The field data was from a site located at Vadsby, Denmark, where chlorinated solvents were spilled during the 1960-70's, resulting in contamination of the clay till and the underlying sandy layer (15 meters below surface). The clay till is heavily contaminated between 4 and 15 mbs, both with the mother compounds PCE/TCE and TCA and the daughter products (DCE, VC, ethene, DCA), indicating the occurrence of natural dechlorination of both PCE/TCE and TCA. Intact core samples of length 0.5m were collected from the source zone (between 6 and 12 mbs). Concentrations and stable isotope ratios of the mother compounds and their daughter products, as well as redox parameters, fatty acids and microbial data, were analyzed with discrete sub-sampling along the cores. More samples (each 5 mm) were collected around the observed higher permeability zones such as sand lenses, sand stringers and fractures, where a higher degradation activity was expected. This study made use of a reactive transport model to investigate the appropriateness of several conceptual models. The conceptual models considered the location of dechlorination and degradation pathways (biotic reductive dechlorination or abiotic β-elimination with iron minerals) in three core profiles. The model includes diffusion in the matrix

  11. Chemical Peels

    Science.gov (United States)

    ... pills, who subsequently become pregnant or have a history of brownish facial discoloration. Scarring Reactivation of cold sores What can I expect after having a chemical peel? All peels require some follow-up care: ...

  12. Wastewater treatment after reactive printing

    OpenAIRE

    Šostar-Turk, Sonja; Simonič, Marjana; Petrinić, Irena

    2012-01-01

    Membrane filtration of wastewater after textile printing with reactive dyes isdescribed. The wastewater from a Slovenian factory, whose output is approx. 80% reactive dyes printed and dyed on cotton, was studied. In particular, the presence of urea, sodium alginate, oxidation agent and reactive dyes, used forthe printing paste preparation, in the wastewater was studied. Chemical analyses of actual, non-purified, wastewater showed that many Slovenian regulations were exceeded. The study of mem...

  13. Prediction of in vivo potential for metabolic activation of drugs into chemically reactive intermediate: correlation of in vitro and in vivo generation of reactive intermediates and in vitro glutathione conjugate formation in rats and humans.

    Science.gov (United States)

    Masubuchi, Noriko; Makino, Chie; Murayama, Nobuyuki

    2007-03-01

    The covalent binding of reactive intermediates to macromolecules might have potential involvement in severe adverse drug reactions. Thus, quantification of reactive metabolites is necessary during the early stage of drug discovery to avoid serious toxicity. In this study, the relationship between covalent binding and glutathione (GSH) conjugate formation in rat and human liver microsomes were investigated using 10 representative radioactive compounds that have been reported as hepatotoxic or having other toxicity derived from their reactive intermediates: acetaminophen, amodiaquine, carbamazepine, clozapine, diclofenac, furosemide, imipramine, indomethacin, isoniazid, and tienilic acid, all at a concentration of 10 microM. The GSH conjugate formation rate correlates well with the covalent binding of radioactivity (both rat and human, r2 = 0.93), which suggests that quantification of the GSH conjugate can be used to estimate covalent binding. To quantify the GSH-conjugation rate with non-radiolabeled compounds in vitro, the validation study for the determination of GSH conjugate formation using 35S-GSH by radio-HPLC was useful to predict metabolic activation. Following oral administration of 20 mg/kg of the radiolabeled compounds to rats, radioactivity that covalently bound to plasma and liver proteins was determined. The in vivo maximum covalent binding level in liver based on the free fraction of plasma area under the concentration curve (AUC) and in vitro covalent binding rate was found to correlate well (r2 = 0.79). Therefore, this model for in vitro covalent binding studies in human and rat and in vivo rat studies might be useful in predicting human metabolic activation of compounds. PMID:17309281

  14. Reactive Arthritis

    Directory of Open Access Journals (Sweden)

    Eren Erken

    2013-06-01

    Full Text Available Reactive arthritis is an acute, sterile, non-suppurative and inflammatory arthropaty which has occured as a result of an infectious processes, mostly after gastrointestinal and genitourinary tract infections. Reiter syndrome is a frequent type of reactive arthritis. Both reactive arthritis and Reiter syndrome belong to the group of seronegative spondyloarthropathies, associated with HLA-B27 positivity and characterized by ongoing inflammation after an infectious episode. The classical triad of Reiter syndrome is defined as arthritis, conjuctivitis and urethritis and is seen only in one third of patients with Reiter syndrome. Recently, seronegative asymmetric arthritis and typical extraarticular involvement are thought to be adequate for the diagnosis. However, there is no established criteria for the diagnosis of reactive arthritis and the number of randomized and controlled studies about the therapy is not enough. [Archives Medical Review Journal 2013; 22(3.000: 283-299

  15. Reactive Safety

    OpenAIRE

    Rüdiger Ehlers; Bernd Finkbeiner

    2011-01-01

    The distinction between safety and liveness properties is a fundamental classification with immediate implications on the feasibility and complexity of various monitoring, model checking, and synthesis problems. In this paper, we revisit the notion of safety for reactive systems, i.e., for systems whose behavior is characterized by the interplay of uncontrolled environment inputs and controlled system outputs. We show that reactive safety is a strictly larger class of properties than standard...

  16. Reactivity measurements

    International Nuclear Information System (INIS)

    Digital reactivity meter, realized as an off-line Fortran program, the input to which is a record of 500 consecutive values of n(tsub(i)) obtained by on-line program on CDC 1700 from the linear power channel of the TRIGA reactor, has been tested at low powers at which the reactor fuel temperature feedback reactivity is negligible. Calibration of the meter by the regulating rod, the reactivity of which has been determined by the assymptotic reactor period, shows that the absolute error is below 1,6% for reactivities up to 1 $. The accuracy of the reactivity meter is proportional to the square of the product of the sampling interval and the period at which the neutron density changes. So the relative error of the reactivity remains at all operational states below 0.2% at 1 second sampling intervals and even at 3 seconds sampling it does not rises above 2.0%. The meter is useful for measurements of control rod drops into the reactor at sampling intervals of 0.1 sec. The meter sensitivity is 0.5 c/s at 1 sec sampling

  17. Host-cell reactivation of uv-irradiated and chemically treated Herpes simplex virus type 1 strain MP in normal and xeroderma pigmentosum skin fibroblasts

    International Nuclear Information System (INIS)

    The host-cell reactivation of UV-irradiated and N-acetoxy-2-acetylaminofluorene-treated herpes simplex virus type 1 strain mp was studied in normal human skin fibroblasts and xeroderma pigmentosum skin fibroblasts from XP genetic complementation groups A-D and in an XP variant. The increasing relative order for the host-cell reactivation of both types of damaged virus in the different complementation groups is A = D < B < C; XP variant = normal controls. XP complementation group D cells, which manifest the most severe inhibition of her ability for both UV-irradiated and N-acetoxy-2-acetylaminofluorene-treated virus, can reactivate nitrogen mustard treated HSV-1 mp to the same extent as normal cells. Together, these results indicate that (1) Excision repair of UV and N-acetoxy-2-acetylaminofluorene DNA damaged viruses share a common rate limiting enzymatic step and (2) The repair defect in xeroderma pigmentosum cells plays little or no role in the recovery of nitrogen mustard treated virus. The results of studies on the effect of caffeine on the survival of both UV- and N-acetoxy-2-acetylaminofluorene-treated virus in normal and XP cells imply that the reactivation of HSV-1 mp is mediated by an excision repair process with little if any recovery contributed by post-replication repair mechanisms. The host-cell reactivation of N-acetoxy-2-acetylaminofluorene-treated HSV-1 mp was also correlated with the defective UV-induced unscheduled DNA synthesis in two skin fibroblast strains established from a skin biopsy obtained from each of two juvenile females who had been clinically diagnosed as xeroderma pigmentosum. These findings are discussed in relation to the further characterization of the xeroderma pigmentosum phenotype and their possible utilization for the selection and isolation of new mammalian cell DNA repair mutants

  18. The synthesis and coupling of photoreactive collagen-based peptides to restore integrin reactivity to an inert substrate, chemically-crosslinked collagen

    OpenAIRE

    Malcor, Jean-Daniel; Bax, Daniel; Hamaia, Samir W.; Davidenko, Natalia; Best, Serena M.; Cameron, Ruth E.; Farndale, Richard W.; Bihan, Dominique

    2016-01-01

    Collagen is frequently advocated as a scaffold for use in regenerative medicine. Increasing the mechanical stability of a collagen scaffold is widely achieved by cross-linking using 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) and N-hydroxysuccinimide (NHS). However, this treatment consumes the carboxylate-containing amino acid sidechains that are crucial for recognition by the cell-surface integrins, abolishing cell adhesion. Here, we restore cell reactivity to a cross-linked type I c...

  19. One pot synthesis of Curcumin-NSAIDs prodrug, spectroscopic characterization, conformational analysis, chemical reactivity, intramolecular interactions and first order hyperpolarizability by DFT method

    Science.gov (United States)

    Srivastava, Sangeeta; Gupta, Preeti; Sethi, Arun; Singh, Ranvijay Pratap

    2016-08-01

    A novel Curcumin-NSAIDs prodrug 4-((1E, 3Z, 6E)-3-hydroxy-(4-hydroxy-3-methoxyphenyl)-5-oxohepta-1,3,3-trienyl)-2-methoxyphenyl-2-(4-isobutylphenyl) propanoate (2) derivative was synthesized by Steglich esterification in high yield and characterized with the help of 1H, 13C NMR, 1H-1H COSY, UV, FT-IR spectroscopy and mass spectrometry. The molecular geometry of synthesized compound was calculated in ground state by Density functional theory (DFT/B3LYP) using two different basis set 6-31G (d, p) and 6-311G (d, p). Conformational analysis of 2 was carried out to determine the most stable conformation. Stability of the molecule as a result of hyperconjugative interactions and electron delocalization were analysed using Natural bond orbital (NBO) analysis. Intramolecular interactions were analysed by AIM (Atom in molecule) approach. Global and local reactivity descriptors were calculated to study the reactive site within molecule. The electronic properties such as HOMO and LUMO energies were calculated using time dependent Density Functional Theory (TD-DFT). The vibrational wavenumbers were calculated using DFT method and assigned with the help of potential energy distribution (PED). First hyperpolarizability value has been calculated to describe the nonlinear optical (NLO) property of the synthesized compound. Molecular electrostatic potential (MEP) for synthesized compounds have also been determined to check their electrophilic or nucleophilic reactivity.

  20. Scale Alpha and Beta of Quantitative Convergence and Chemical Reactivity Analysis in Dual Cholinesterase/Monoamine Oxidase Inhibitors for the Alzheimer Disease Treatment Using Density Functional Theory (DFT

    Directory of Open Access Journals (Sweden)

    Alejandro Morales-Bayuelo

    2013-01-01

    Full Text Available Molecular quantum similarity descriptors and Density Functional Theory (DFT based reactivity descriptors were studied for a series of cholinesterase/monoamine oxidase inhibitors used for the Alzheimer's disease treatment (AD. This theoretical study is expected to shed some light onto some molecular aspects that could contribute to the knowledge of the molecular mechanics behind interactions of these molecules with acetylcholinesterase (AChE and butyrylcholinesterase (BuChE, as well as with monoamine oxidase (MAO A and B. The Topogeometrical Superposition Algorithm to handle flexible molecules (TGSA-Flex alignment method was used to solve the problem of the relative orientation in the quantum similarity (QS field. Using the molecular quantum similarity (MQS field and reactivity descriptors supported in the DFT was possible the quantification of the steric and electrostatic effects through of the Coulomb and Overlap quantitative convergence scales (alpha and beta. In addition, an analysis of reactivity indexes is development, using global and local descriptors, identifying the binding sites and selectivity in the (cholinesterase/monoamine oxidase inhibitors, understanding the retrodonor process, and showing new insight for drugs design in a disease of difficult control as Alzheimer.

  1. Reactive arthritis.

    Science.gov (United States)

    Keat, A

    1999-01-01

    Reactive arthritis is one of the spondyloarthropathy family of clinical syndromes. The clinical features are those shared by other members of the spondyloarthritis family, though it is distinguished by a clear relationship with a precipitating infection. Susceptibility to reactive arthritis is closely linked with the class 1 HLA allele B27; it is likely that all sub-types pre-dispose to this condition. The link between HLA B27 and infection is mirrored by the development of arthritis in HLA B27-transgenic rats. In this model, arthritis does not develop in animals maintained in a germ-free environment. Infections of the gastrointestinal, genitourinary and respiratory tract appear to provoke reactive arthritis and a wide range of pathogens has now been implicated. Although mechanistic parallels may exist, reactive arthritis is distinguished from Lyme disease, rheumatic fever and Whipple's disease by virtue of the distinct clinical features and the link with HLA B27. As in these conditions both antigens and DNA of several micro-organisms have been detected in joint material from patients with reactive arthritis. The role of such disseminated microbial elements in the provocation or maintenance of arthritis remains unclear. HLA B27-restricted T-cell responses to microbial antigens have been demonstrated and these may be important in disease pathogenesis. The importance of dissemination of bacteria from sites of mucosal infection and their deposition in joints has yet to be fully understood. The role of antibiotic therapy in the treatment of reactive arthritis is being explored; in some circumstances, both the anti-inflammatory and anti-microbial effects of certain antibiotics appear to be valuable. The term reactive arthritis should be seen as a transitory one, reflecting a concept which may itself be on the verge of replacement, as our understanding of the condition develops. Nevertheless it appropriately describes arthritis that is associated with demonstrable

  2. Double-stranded DNA-templated cleavage of oligonucleotides containing a P3'->N5' linkage triggered by triplex formation: the effects of chemical modifications and remarkable enhancement in reactivity.

    Science.gov (United States)

    Ito, Kosuke Ramon; Kodama, Tetsuya; Tomizu, Masaharu; Negoro, Yoshinori; Orita, Ayako; Osaki, Tomohisa; Hosoki, Noritsugu; Tanaka, Takaya; Imanishi, Takeshi; Obika, Satoshi

    2010-11-01

    We recently reported double-stranded DNA-templated cleavage of oligonucleotides as a sequence-specific DNA-detecting method. In this method, triplex-forming oligonucleotides (TFOs) modified with 5'-amino-2',4'-BNA were used as a DNA-detecting probe. This modification introduced a P3'→N5' linkage (P-N linkage) in the backbone of the TFO, which was quickly cleaved under acidic conditions when it formed a triplex. The prompt fission of the P-N linkage was assumed to be driven by a conformational strain placed on the linkage upon triplex formation. Therefore, chemical modifications around the P-N linkage should change the reactivity by altering the microenvironment. We synthesized 5'-aminomethyl type nucleic acids, and incorporated them into TFOs instead of 5'-amino-2',4'-BNA to investigate the effect of 5'-elongation. In addition, 2',4'-BNA/LNA or 2',5'-linked DNA were introduced at the 3'- and/or 5'-neighboring residues of 5'-amino-2',4'-BNA to reveal neighboring residual effects. We evaluated the triplex stability and reaction properties of these TFOs, and found out that chemical modifications around the P-N linkage greatly affected their reaction properties. Notably, 2',5'-linked DNA at the 3' position flanking 5'-amino-2',4'-BNA brought significantly higher reactivity, and we succeeded in indicating that a TFO with this modification is promising as a DNA analysis tool. PMID:20615902

  3. Quantum mechanical calculations of vibrational population inversion in chemical reactions - Numerically exact L-squared-amplitude-density study of the H2Br reactive system

    Science.gov (United States)

    Zhang, Y. C.; Zhang, J. Z. H.; Kouri, D. J.; Haug, K.; Schwenke, D. W.

    1988-01-01

    Numerically exact, fully three-dimensional quantum mechanicl reactive scattering calculations are reported for the H2Br system. Both the exchange (H + H-prime Br to H-prime + HBr) and abstraction (H + HBR to H2 + Br) reaction channels are included in the calculations. The present results are the first completely converged three-dimensional quantum calculations for a system involving a highly exoergic reaction channel (the abstraction process). It is found that the production of vibrationally hot H2 in the abstraction reaction, and hence the extent of population inversion in the products, is a sensitive function of initial HBr rotational state and collision energy.

  4. Structure and reactivity of TNT and related species: Application of spectroscopic approaches and quantum-chemical approximations toward understanding transformation mechanisms

    International Nuclear Information System (INIS)

    This paper presents our latest findings regarding the structure and reactivity of the nitroaromatics, TNT and selected derivatives, within their environmental context. We also demonstrate the useful and proactive role of combined computational chemistry and spectroscopy tools in studying competing transformation mechanisms, particularly those with toxic potential. TNT and selected derivatives were reacted via alkaline hydrolysis as well as via free radical initiators through monochromatic irradiation and through Fenton reactions in complex competing transformation mechanisms. Only alkaline hydrolysis produced consistent and effective transformation intermediate and final products in this research. However, irradiation of the product generated by alkaline hydrolysis at 450 nm (wavelength of maximum absorption) caused complete disappearance of the spectra.

  5. Reactive Systems

    DEFF Research Database (Denmark)

    Aceto, Luca; Ingolfsdottir, Anna; Larsen, Kim Guldstrand;

    A reactive system comprises networks of computing components, achieving their goals through interaction among themselves and their environment. Thus even relatively small systems may exhibit unexpectedly complex behaviours. As moreover reactive systems are often used in safety critical systems......, the need for mathematically based formal methodology is increasingly important. There are many books that look at particular methodologies for such systems. This book offers a more balanced introduction for graduate students and describes the various approaches, their strengths and weaknesses, and when...... they are best used. Milner's CCS and its operational semantics are introduced, together with the notions of behavioural equivalences based on bisimulation techniques and with recursive extensions of Hennessy-Milner logic. In the second part of the book, the presented theories are extended to take timing issues...

  6. 1D Thermal-Hydraulic-Chemical (THC) Reactive transport modeling for deep geothermal systems: A case study of Groß Schönebeck reservoir, Germany

    Science.gov (United States)

    Driba, D. L.; De Lucia, M.; Peiffer, S.

    2014-12-01

    Fluid-rock interactions in geothermal reservoirs are driven by the state of disequilibrium that persists among solid and solutes due to changing temperature and pressure. During operation of enhanced geothermal systems, injection of cooled water back into the reservoir disturbs the initial thermodynamic equilibrium between the reservoir and its geothermal fluid, which may induce modifications in permeability through changes in porosity and pore space geometry, consequently bringing about several impairments to the overall system.Modeling of fluid-rock interactions induced by injection of cold brine into Groß Schönebeck geothermal reservoir system situated in the Rotliegend sandstone at 4200m depth have been done by coupling geochemical modeling Code Phreeqc with OpenGeoSys. Through batch modeling the re-evaluation of the measured hydrochemical composition of the brine has been done using Quintessa databases, the results from the calculation indicate that a mineral phases comprising of K-feldspar, hematite, Barite, Calcite and Dolomite was found to match the hypothesis of equilibrium with the formation fluid, Reducing conditions are presumed in the model (pe = -3.5) in order to match the amount of observed dissolved Fe and thus considered as initial state for the reactive transport modeling. based on a measured composition of formation fluids and the predominant mineralogical assemblage of the host rock, a preliminary 1D Reactive transport modeling (RTM) was run with total time set to 30 years; results obtained for the initial simulation revealed that during this period, no significant change is evident for K-feldspar. Furthermore, the precipitation of calcite along the flow path in the brine results in a drop of pH from 6.2 to a value of 5.2 noticed over the simulated period. The circulation of cooled fluid in the reservoir is predicted to affect the temperature of the reservoir within the first 100 -150m from the injection well. Examination of porosity change in

  7. What Is Reactive Arthritis?

    Science.gov (United States)

    ... Arthritis PDF Version Size: 69 KB November 2014 What is Reactive Arthritis? Fast Facts: An Easy-to- ... Information About Reactive Arthritis and Other Related Conditions What Causes Reactive Arthritis? Sometimes, reactive arthritis is set ...

  8. The reactivity meter and core reactivity

    International Nuclear Information System (INIS)

    The point kinetic equations and the characteristics of the point kinetic reactivity meter are discussed, particularly for large negative reactivities. From a given input signal representing the neutron flux seen by a detector, the meter computes a value of reactivity in dollars (ρ/β), based on inverse point kinetics. The prompt jump point of view is emphasised. A simple point model of the reactor and a local flux distortion factor are used to generate input signals into a simulated reactivity meter. The obtained results show how the reading of the reactivity meter will approach the reactivity of the core model, if the reactivity is lower than -1 dollars. However, for reactivity values higher than -1 dollars, the influence of the flux distortion on the reading of the reactivity meter persists. Reactivity meter measurements taken during typical rod drop experiments in VVER-440 reactors do not produce accurate indications of the (static) core reactivity. (author)

  9. Double-stranded DNA-templated cleavage of oligonucleotides containing a P3′→N5′ linkage triggered by triplex formation: the effects of chemical modifications and remarkable enhancement in reactivity

    Science.gov (United States)

    Ito, Kosuke Ramon; Kodama, Tetsuya; Tomizu, Masaharu; Negoro, Yoshinori; Orita, Ayako; Osaki, Tomohisa; Hosoki, Noritsugu; Tanaka, Takaya; Imanishi, Takeshi; Obika, Satoshi

    2010-01-01

    We recently reported double-stranded DNA-templated cleavage of oligonucleotides as a sequence-specific DNA-detecting method. In this method, triplex-forming oligonucleotides (TFOs) modified with 5′-amino-2′,4′-BNA were used as a DNA-detecting probe. This modification introduced a P3′→N5′ linkage (P–N linkage) in the backbone of the TFO, which was quickly cleaved under acidic conditions when it formed a triplex. The prompt fission of the P–N linkage was assumed to be driven by a conformational strain placed on the linkage upon triplex formation. Therefore, chemical modifications around the P–N linkage should change the reactivity by altering the microenvironment. We synthesized 5′-aminomethyl type nucleic acids, and incorporated them into TFOs instead of 5′-amino-2′,4′-BNA to investigate the effect of 5′-elongation. In addition, 2′,4′-BNA/LNA or 2′,5′-linked DNA were introduced at the 3′- and/or 5′-neighboring residues of 5′-amino-2′,4′-BNA to reveal neighboring residual effects. We evaluated the triplex stability and reaction properties of these TFOs, and found out that chemical modifications around the P–N linkage greatly affected their reaction properties. Notably, 2′,5′-linked DNA at the 3′ position flanking 5′-amino-2′,4′-BNA brought significantly higher reactivity, and we succeeded in indicating that a TFO with this modification is promising as a DNA analysis tool. PMID:20615902

  10. The synthesis and coupling of photoreactive collagen-based peptides to restore integrin reactivity to an inert substrate, chemically-crosslinked collagen.

    Science.gov (United States)

    Malcor, Jean-Daniel; Bax, Daniel; Hamaia, Samir W; Davidenko, Natalia; Best, Serena M; Cameron, Ruth E; Farndale, Richard W; Bihan, Dominique

    2016-04-01

    Collagen is frequently advocated as a scaffold for use in regenerative medicine. Increasing the mechanical stability of a collagen scaffold is widely achieved by cross-linking using 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) and N-hydroxysuccinimide (NHS). However, this treatment consumes the carboxylate-containing amino acid sidechains that are crucial for recognition by the cell-surface integrins, abolishing cell adhesion. Here, we restore cell reactivity to a cross-linked type I collagen film by covalently linking synthetic triple-helical peptides (THPs), mimicking the structure of collagen. These THPs are ligands containing an active cell-recognition motif, GFOGER, a high-affinity binding site for the collagen-binding integrins. We end-stapled peptide strands containing GFOGER by coupling a short diglutamate-containing peptide to their N-terminus, improving the thermal stability of the resulting THP. A photoreactive Diazirine group was grafted onto the end-stapled THP to allow covalent linkage to the collagen film upon UV activation. Such GFOGER-derivatized collagen films showed restored affinity for the ligand-binding I domain of integrin α2β1, and increased integrin-dependent cell attachment and spreading of HT1080 and Rugli cell lines, expressing integrins α2β1 and α1β1, respectively. The method we describe has wide application, beyond collagen films or scaffolds, since the photoreactive diazirine will react with many organic carbon skeletons. PMID:26854392

  11. Production of chemically reactive radioactive ion beams through on-line separation; Production de faisceaux d'ions radioactifs chimiquement reactifs par separation en ligne

    Energy Technology Data Exchange (ETDEWEB)

    Joinet, A

    2003-10-01

    The ISOL (isotope separation on line) allows the production of secondary radioactive ion beams through spallation or fragmentation or fission reactions that take place in a thick target bombarded by a high intensity primary beam. The challenge is to increase the intensity and purity of the radioactive beam. The optimization of the system target/source requires the right choice of material for the target by taking into account the stability of the material, its reactivity and the ionization method used. The target is an essential part of the system because radioactive elements are generated in it and are released more or less quickly. Tests have been made in order to select the best fitted material for the release of S, Se, Te, Ge and Sn. Materials tested as target filling are: ZrO{sub 2}, Nb, Ti, V,TiO{sub 2}, CeO{sub x}, ThO{sub 2}, C, ZrC{sub 4} and VC). Other molecules such as: COSe, COS, SeS, COTe, GeS, SiS, SnS have been studied to ease the extraction of recoil nuclei (Se, S, Te, Ge and Sn) produced inside the target.

  12. Electrochemical investigations of the interaction of C-reactive protein (CRP) with a CRP antibody chemically immobilized on a gold surface

    International Nuclear Information System (INIS)

    A possibility of using a range of dc and ac electrochemical techniques to probe associative interactions of C-reactive protein (CRP) with CRP antibody (aCRP) immobilized on a gold electrode surface was investigated. It was demonstrated that the investigated electrochemical techniques can be used efficiently to probe these interactions over a wide CRP concentration range, from 1.15 x 10-5 to 1.15 mg L-1. The measured sensitivity of the techniques is in the following decreasing order: differential pulse voltammetry, charge-transfer resistance obtained from electrochemical impedance spectroscopy (EIS), cyclic voltammetry, chronoamperometry, and double-layer capacitance deduced from EIS measurements which gave the poorest sensitivity. Measurements of kinetic parameters demonstrated that the associative interactions of CRP with the immobilized aCRP reached quasi-equilibrium after 20-30 min. The kinetics of these interactions was modeled successfully using a two-step kinetic model. In this model, the first step represents reversible CRP-aCRP associative-dissociative interactions, while the second step represents the irreversible transformation of the bound CRP into a thermodynamically stable configuration. It was demonstrated that the thermodynamically stable configuration of CRP starts prevailing after 7 min of interaction of CRP with the immobilized aCRP.

  13. Analysis Of Convective Plane Stagnation Point Chemically Reactive Mhd Flow Past A Vertical Porous Plate With A Convective Boundary Condition In The Presence Of A Uniform Magnetic Field.

    Directory of Open Access Journals (Sweden)

    Adeniyan, A.,

    2013-09-01

    Full Text Available The numerical investigation of a stagnation point boundary layer flow , mass and heat transfer of a steady two dimensional , incompressible , viscous electrically conducting, chemically reacting laminar fluid over a vertical convectively heated , electrically neutral flat plate exposed to a transverse uniform magnetic field has been carried out to examine the influence of the simultaneous presence of the effects of a convective boundary condition, chemical reaction, heat transfer and suction or injection. The governing coupled partial differential equations have been reduced to a set of coupled nonlinear ordinary differential equations by means of the similarity transformation , which has been solved using the classical fourth order Runge-Kutta method alongside with a shooting technique. The computational results have been presented by means of the table and discussed graphically. It has been observed that pertinent and invaluable engineering parameters such as the Skin-friction coefficient, the plate temperature distribution, the velocity , temperature and concentration profiles are appreciably influenced by flow parameters such as the magnetic field, convective heat parameters , Prandtl number, Sherwood number, Nusselt number, etc .

  14. Comparison of boranol and silanol reactivities in boron-doped SiO2 chemical vapor deposition from trimethyl borate and tetraethyl orthosilicate

    International Nuclear Information System (INIS)

    For the first time, the relative rates of consumption of surface boranols and silanols reacting with tetraethyl orthosilicate [TEOS, Si(OCH2CH3)4] have been measured. This comparison has direct bearing on understanding the growth of doped SiO2 films from TEOS and trimethyl borate [TMB, B(OCH3)3] sources since surface boranols and silanols are expected to be present during the thermal chemical vapor deposition process. The measurements were accomplished by first derivatizing a porous silica substrate with boranols and silanols via hydrolysis of the products from an initial trimethyl borate (TMB) chemisorption step. TEOS exposures in the mTorr pressure regime were then carried out in a cold-wall reactor. Reaction products on the surface were identified with Fourier transform infrared spectroscopy and x-ray photoelectron spectroscopy in analysis chambers adjoining the reactor. Although TEOS does not react with SiOH at 300 K, it does react with BOH at this temperature. Using the deuterated species (SiOD and BOD) to measure the relative rates of hydroxyl consumption without interference from concurrent hydroxyl formation, the reaction rate constant for boranols with TEOS at 1000 K was determined to be twice that of silanols. At 1000 K, subsequent decomposition of the TEOS chemisorption products regenerates both BOH and SiOH

  15. Reactive transport modeling of chemical and isotope data to identify degradation processes of chlorinated ethenes in a diffusion-dominated media

    DEFF Research Database (Denmark)

    Chambon, Julie Claire Claudia; Damgaard, Ida; Jeannottat, Simon;

    Chlorinated ethenes are among the most widespread contaminants in the subsurface and a major threat to groundwater quality at numerous contaminated sites. Many of these contaminated sites are found in low-permeability media, such as clay tills, where contaminant transport is controlled by diffusi...... important finding, that is further supported by microbial and chemical data. Improved understanding of degradation processes in clay tills is useful for improving the reliability of risk assessment and the design of remediation schemes for chlorinated solvents....... modeling has been used to identify the degradation processes occurring at the core scale. The field data was from a site located at Vadsby, Denmark, where chlorinated solvents were spilled during the 1960-70’s, resulting in contamination of the clay till and the underlying sandy layer (15 meters below...... source zone (between 6 and 12 mbs). Concentrations and stable isotope ratios of the mother compounds and their daughter products, as well as redox parameters, fatty acids and microbial data, were analyzed with discrete sub-sampling along the cores. More samples (each 5 mm) were collected around the...

  16. Experimental study of chemical-mechanical coupling during percolation of reactive fluid through rocks under stress, in the context of the CO2 geological sequestration

    International Nuclear Information System (INIS)

    CO2 injection into geological repositories will induce chemical and mechanical instabilities. The study of these instabilities is based on experimental deformation of natural rock samples under stress, in the presence of fluids containing, or not, dissolved CO2. Triaxial cells used for the experiments permitted an independent control and measurement of stress, temperature, fluid pressure and composition. Vertical strains were measured during several months, with a resolution of 1.10-12 s-1 on the strain rate. Simultaneously, fluids were analysed in order to quantify fluid-rock interactions. For limestone samples, percolation of CO2-rich fluids increases strain rate by a factor 1.7 up to 5; on the other hand, sandstone deformation remained almost the same. Increase in strain rate with limestone samples was explained by injected water acidification by the CO2 which increases rock solubility and reaction kinetics. On the opposite, small effect of CO2 on quartz explains the absence of deformation. X-ray observations confirmed the importance of rock composition and structure on the porosity evolution. Numerical simulations of rock elastic properties showed increasing shear stress into the sample. Measured deformation showed an evolution of reservoir rocks mechanical properties. It was interpreted as the consequence of pressure solution mechanisms both at grains contacts and on grain free surfaces. (author)

  17. Structural, chemical and nanomechanical investigations of SiC/polymeric a-C:H films deposited by reactive RF unbalanced magnetron sputtering

    Science.gov (United States)

    Tomastik, C.; Lackner, J. M.; Pauschitz, A.; Roy, M.

    2016-03-01

    Amorphous carbon (or diamond-like carbon, DLC) films have shown a number of important properties usable for a wide range of applications for very thin coatings with low friction and good wear resistance. DLC films alloyed with (semi-)metals show some improved properties and can be deposited by various methods. Among those, the widely used magnetron sputtering of carbon targets is known to increase the number of defects in the films. Therefore, in this paper an alternative approach of depositing silicon-carbide-containing polymeric hydrogenated DLC films using unbalanced magnetron sputtering was investigated. The influence of the C2H2 precursor concentration in the deposition chamber on the chemical and structural properties of the deposited films was investigated by Raman spectroscopy, X-ray photoelectron spectroscopy and elastic recoil detection analysis. Roughness, mechanical properties and scratch response of the films were evaluated with the help of atomic force microscopy and nanoindentation. The Raman spectra revealed a strong correlation of the film structure with the C2H2 concentration during deposition. A higher C2H2 flow rate results in an increase in SiC content and decrease in hydrogen content in the film. This in turn increases hardness and elastic modulus and decreases the ratio H/E and H3/E2. The highest scratch resistance is exhibited by the film with the highest hardness, and the film having the highest overall sp3 bond content shows the highest elastic recovery during scratching.

  18. High temperature chemical reactivity in the system (U, Zr,Fe, O). A contribution to the study of zirconia as a ''core catcher''

    International Nuclear Information System (INIS)

    Within the framework of the improvement of nuclear reactor safety, a device to recover corium is proposed to be installed under the reactor vessel to limit the consequences of a core melting. According to our bibliographic study, stabilised zirconia seems to be the best refractory material to play this role and to support the physicochemical, mechanical and thermal requirements imposed to the corium catcher. The nature of the chemical interactions between zirconia and iron of high temperature were established and experimental data on the (U, Fe, Zr, O) quaternary system which stands for the corium were determined. First of all, the Knudsen effusion mass-spectrometric method was used to establish the liquidus position for a (U, Zr, O) alloy representative of the corium (U/Zr = 1,5) at 2000 deg C. The oxygen solubility limit in a (U, Zr, O) liquid alloy is about 7 atomic %. In oxidising conditions, the reaction between zirconia and iron leads to the formation of a stabilised zirconia-iron oxide solid solution. Up to 10 atomic % of iron can be incorporated in the structure, leading to the stabilisation of cubic zirconia and a modification of lattice constants. The valence and localisation of those iron measured as a function of time and temperature from 1500 to 2400 deg C, after high frequency inductive heating, both on laboratory materials are commercial bricks. The reaction rate is governed by an activation energy of about 80 kJ/mol. Our results demonstrate that stabilised zirconia is able to efficiently absorb oxidised iron. (author)

  19. Numerical simulation of in-situ chemical oxidation (ISCO) and biodegradation of petroleum hydrocarbons using a coupled model for bio-geochemical reactive transport

    Science.gov (United States)

    Marin, I. S.; Molson, J. W.

    2013-05-01

    Petroleum hydrocarbons (PHCs) are a major source of groundwater contamination, being a worldwide and well-known problem. Formed by a complex mixture of hundreds of organic compounds (including BTEX - benzene, toluene, ethylbenzene and xylenes), many of which are toxic and persistent in the subsurface and are capable of creating a serious risk to human health. Several remediation technologies can be used to clean-up PHC contamination. In-situ chemical oxidation (ISCO) and intrinsic bioremediation (IBR) are two promising techniques that can be applied in this case. However, the interaction of these processes with the background aquifer geochemistry and the design of an efficient treatment presents a challenge. Here we show the development and application of BIONAPL/Phreeqc, a modeling tool capable of simulating groundwater flow, contaminant transport with coupled biological and geochemical processes in porous or fractured porous media. BIONAPL/Phreeqc is based on the well-tested BIONAPL/3D model, using a powerful finite element simulation engine, capable of simulating non-aqueous phase liquid (NAPL) dissolution, density-dependent advective-dispersive transport, and solving the geochemical and kinetic processes with the library Phreeqc. To validate the model, we compared BIONAPL/Phreeqc with results from the literature for different biodegradation processes and different geometries, with good agreement. We then used the model to simulate the behavior of sodium persulfate (NaS2O8) as an oxidant for BTEX degradation, coupled with sequential biodegradation in a 2D case and to evaluate the effect of inorganic geochemistry reactions. The results show the advantages of a treatment train remediation scheme based on ISCO and IBR. The numerical performance and stability of the integrated BIONAPL/Phreeqc model was also verified.

  20. Label-Free Proteomics Assisted by Affinity Enrichment for Elucidating the Chemical Reactivity of the Liver Mitochondrial Proteome toward Adduction by the Lipid Electrophile 4-hydroxy-2-nonenal (HNE)

    Science.gov (United States)

    Tzeng, Shin-Cheng; Maier, Claudia S.

    2016-01-01

    The analysis of oxidative stress-induced post-translational modifications remains challenging due to the chemical diversity of these modifications, the possibility of the presence of positional isomers and the low stoichiometry of the modified proteins present in a cell or tissue proteome. Alcoholic liver disease (ALD) is a multifactorial disease in which mitochondrial dysfunction and oxidative stress have been identified as being critically involved in the progression of the disease from steatosis to cirrhosis. Ethanol metabolism leads to increased levels of reactive oxygen species (ROS), glutathione depletion and lipid peroxidation. Posttranslational modification of proteins by electrophilic products of lipid peroxidation has been associated with governing redox-associated signaling mechanisms, but also as contributing to protein dysfunction leading to organelle and liver injury. In particular the prototypical α,β-unsaturated aldehyde, 4-hydroxy-2-nonenal (HNE), has been extensively studied as marker of increased oxidative stress in hepatocytes. In this study, we combined a LC-MS label-free quantification method and affinity enrichment to assess the dose-dependent insult by HNE on the proteome of rat liver mitochondria. We used a carbonyl-selective probe, the ARP probe, to label HNE-protein adducts and to perform affinity capture at the protein level. Using LC-MS to obtain protein abundance estimates, a list of protein targets was obtained with increasing concentration of HNE used in the exposure studies. In parallel, we performed affinity capture at the peptide level to acquire site-specific information. Examining the concentration-dependence of the protein modifications, we observed distinct reactivity profiles for HNE-protein adduction. Pathway analysis indicated that proteins associated with metabolic processes, including amino acid, fatty acid, and glyoxylate and dicarboxylate metabolism, bile acid synthesis and TCA cycle, showed enhanced reactivity to HNE

  1. Label-free proteomics assisted by affinity enrichment for elucidating the chemical reactivity of the liver mitochondrial proteome toward adduction by the lipid electrophile 4-hydroxy-2-nonenal (HNE)

    Science.gov (United States)

    Maier, Claudia

    2016-03-01

    The analysis of oxidative stress-induced post-translational modifications remains challenging due to the chemical diversity of these modifications, the possibility of the presence of positional isomers and the low stoichiometry of the modified proteins present in a cell or tissue proteome. Alcoholic liver disease (ALD) is a multifactorial disease in which mitochondrial dysfunction and oxidative stress have been identified as being critically involved in the progression of the disease from steatosis to cirrhosis. Ethanol metabolism leads to increased levels of reactive oxygen species (ROS), glutathione depletion and lipid peroxidation. Posttranslational modification of proteins by electrophilic products of lipid peroxidation has been associated with governing redox-associated signaling mechanisms, but also as contributing to protein dysfunction leading to organelle and liver injury. In particular the prototypical α,β-unsaturated aldehyde, 4-hydroxy-2-nonenal (HNE), has been extensively studied as marker of increased oxidative stress in hepatocytes. In this study, we combined a LC-MS label-free quantification method and affinity enrichment to assess the dose-dependent insult by HNE on the proteome of rat liver mitochondria. We used a carbonyl-selective probe, the ARP probe, to label HNE-protein adducts and to perform affinity capture at the protein level. Using LC-MS to obtain protein abundance estimates, a list of protein targets was obtained with increasing concentration of HNE used in the exposure studies. In parallel, we performed affinity capture at the peptide level to acquire site-specific information. Examining the concentration-dependence of the protein modifications, we observed distinct reactivity profiles for HNE-protein adduction. Pathway analysis indicated that proteins associated with metabolic processes, including amino acid, fatty acid and glyoxylate and dicarboxylate metabolism, bile acid synthesis and TCA cycle, showed enhanced reactivity to HNE

  2. Aspects of Antonio Ventura Pinto Scientific Work: A Life Dedicated to the Chemical Reactivity of Natural and Synthetic Quinones [Aspectos da Obra Científica de Antonio Ventura Pinto: Uma Vida Dedicada ao Estudo da Reatividade Química de Quinonas Naturais e Sintéticas

    Directory of Open Access Journals (Sweden)

    Vitor F. Ferreira

    2013-10-01

    Full Text Available The objective of the present paper, is to accomplish a digression of thescientific work and formation of human resources of the Professor Antonio Ventura Pinto, focusing mainly his contribution to the study of the chemical reactivity of naphthoquinoidal substances, besides his continues search for bioactive substances.

  3. Development of Prediction Models for the Reactivity of Organic Compounds with Ozone in Aqueous Solution by Quantum Chemical Calculations: The Role of Delocalized and Localized Molecular Orbitals.

    Science.gov (United States)

    Lee, Minju; Zimmermann-Steffens, Saskia G; Arey, J Samuel; Fenner, Kathrin; von Gunten, Urs

    2015-08-18

    Second-order rate constants (kO3) for the reaction of ozone with micropollutants are essential parameters for the assessment of micropollutant elimination efficiency during ozonation in water and wastewater treatment. Prediction models for kO3 were developed for aromatic compounds, olefins, and amines by quantum chemical molecular orbital calculations employing ab initio Hartree-Fock (HF) and density functional theory (B3LYP) methods. The kO3 values for aromatic compounds correlated well with the energy of a delocalized molecular orbital first appearing on an aromatic ring (i.e., the highest occupied molecular orbital (HOMO) or HOMO-n (n ≥ 0) when the HOMO is not located on the aromatic ring); the number of compounds tested (N) was 112, and the correlation coefficient (R(2)) values were 0.82-1.00. The kO3 values for olefins and amines correlated well with the energy of a localized molecular orbital (i.e., the natural bond orbital (NBO)) energy of the carbon-carbon π bond of olefins (N = 45, R(2) values of 0.82-0.85) and the NBO energy of the nitrogen lone-pair electrons of amines (N = 59, R(2) values of 0.81-0.83), respectively. Considering the performance of the kO3 prediction model and the computational costs, the HF/6-31G method is recommended for all aromatic groups and olefins investigated herein, whereas the HF/MIDI!, HF/6-31G*, or HF/6-311++G** methods are recommended for amines. Based on their mean absolute errors, the above models could predict kO3 within a factor of 4, on average, relative to the experimentally determined values. Overall, good correlations were also observed (R(2) values of 0.77-0.96) between kO3 predictions by quantum molecular orbital descriptors in this study and by the Hammett (σ) and Taft (σ*) constants from previously developed quantitative structure-activity relationship (QSAR) models. Hence, the quantum molecular orbital descriptors are an alternative to σ and σ*-values in QSAR applications and can also be utilized to

  4. The translational, rotational, and vibrational energy effects on the chemical reactivity of water cation H2O+(X 2B1) in the collision with deuterium molecule D2.

    Science.gov (United States)

    Xu, Yuntao; Xiong, Bo; Chang, Yih Chung; Ng, C Y

    2013-07-14

    By employing the newly established vacuum ultraviolet (VUV) laser pulsed field ionization-photoion (PFI-PI) double quadrupole-double octopole ion guide apparatus, we have examined the translational, rotational, and vibrational energy effects on the chemical reactivity of water cation H2O(+)(X(2)B1) in the collision with deuterium molecule D2. The application of a novel electric-field pulsing scheme to the VUV laser PFI-PI ion source has enabled the preparation of a rovibrationally selected H2O(+)(X(2)B1; v1 (+)v2 (+)v3 (+); N(+) K a+Kc+) ion beam with not only high internal-state selectivity and high intensity but also high translational energy resolution. Despite the unfavorable Franck-Condon factors, we are able to prepare the excited vibrational states (v1 (+)v2 (+)v3 (+))=(100) and (020) along with the (000) ground vibrational state, for collisional studies, where v1 (+), v2 (+), and v3 (+) represent the symmetric stretching, bending, and asymmetric stretching modes of H2O(+)(X(2)B1). We show that a range of rotational levels from N(+) K a+Kc+ = 000 to 322, covering a rotational energy range of 0-200 cm(-1) of these vibrational states, can also be generated for absolute integral cross section (σ) measurements at center-of-mass collision energies (Ecms) from thermal energies to 10.00 eV. The Ecm dependences of the σ values are consistent with the prediction of the orbiting model, indicating that translational energy significantly hinders the chemical reactivity of H2O(+)(X(2)B1). Rotational enhancements are observed at Ecm < 0.30 eV for all the three vibrational states, (000), (100), and (020). While the σ values for (100) are found to be only slightly below those for (000), the σ values for (020) are lower than those for (000) and (100) by up to 20% at Ecm ≤ 0.20 eV, indicative of vibrational inhibition at low Ecm by excitation of the (020) mode. Rationalizations are proposed for the observed rotational enhancements and the bending vibrational

  5. Heat and Mass Transfer Effects on Unsteady MHD Natural Convection Flow of a Chemically Reactive and Radiating Fluid through a Porous Medium Past a Moving Vertical Plate with Arbitrary Ramped Temperature

    Directory of Open Access Journals (Sweden)

    Gauri Shanker Seth

    2016-01-01

    Full Text Available Investigation of unsteady hydromagnetic natural convection flow with heat and mass transfer of a viscous, incompressible, electrically conducting, chemically reactive and optically thin radiating fluid past an exponentially accelerated moving vertical plate with arbitrary ramped temperature embedded in a fluid saturated porous medium is carried out. Exact solutions of momentum, energy and concentration equations are obtained in closed form by Laplace transform technique. The expressions for the shear stress, rate of heat transfer and rate of mass transfer at the plate for both ramped temperature and isothermal plates are derived. The numerical values of fluid velocity, fluid temperature and species concentration are displayed graphically whereas those of shear stress, rate of heat transfer and rate of mass transfer at the plate are presented in tabular form for various values of pertinent flow parameters. It is found that, for isothermal plate, the fluid temperature approaches steady state when t  1.5 . Consequently, the rate of heat transfer at isothermal plate approaches steady state when t  1.5 .

  6. MOLMAP指数生成及其在化学反应分类和反应性预测中的应用%Generation of MOLMAP descriptors and its application to classification of chemical reactions and prediction of chemical reactivity

    Institute of Scientific and Technical Information of China (English)

    龙海林; 冯秀林; 索净洁; 张丹丹; 李静亚; 张庆友; 许禄

    2012-01-01

    to chemical reactions without explicit informatics of chemical bonds involved in these reactions, thus, they could be widely used. Three kinds of applications of the MOLMAP descriptors were reviewed in this article: (1) prediction of the classification of chemical reactions, such as the classification prediction of metabolic reactions; (2) prediction of chemical reactivity, which was the property related to chemical reaction, e.g. the prediction of mutagenicity and antioxidation; and (3) the application to the 3-D data processing, which was extension of the algorithm of the MOLMAP descriptors, such as the prediction of the toxicity of a set of chlorophenols.

  7. The chemical reactivity of REFEL silicon carbide

    International Nuclear Information System (INIS)

    There was no general or localised attack of REFEL SiC during 700 h immersion in up to 80% H2SO4 or HCl solutions at 1000C. In water at =0C and NaOH solutions at =0C the free silicon was leached from the ceramic, being controlled by silica dissolution, whose rate increased with solution pH. Silicon removal also predominated in steam at 5000C, through volatile product formation. Solid-solid interaction was measurable during 100 h contact with representative Ni based alloys at >= 8000C and with Fe and Co based alloys at >= 9000C, with the formation of metallic silicides. Carbon and silicon were picked up by the alloys. (author)

  8. Reactive Magnetospinning of Nano- and Microfibers.

    Science.gov (United States)

    Tokarev, Alexander; Trotsenko, Oleksandr; Asheghali, Darya; Griffiths, Ian M; Stone, Howard A; Minko, Sergiy

    2015-11-01

    Reactive spinning of nano- and microfibers that involves very fast chemical reactions and ion exchange is a challenge for the common methods for nanofiber formation. Herein, we introduce the reactive magnetospinning method. This procedure is based on the magnetic-field-directed collision of ferrofluid droplets with liquid droplets that contain complementary reactants. The collision, start of the chemical reaction, and the fiber drawing are self-synchronized. The method is used to synthesize, cross-link, and chemically modify fiber-forming polymers in the stage of fiber formation. The method provides new opportunities for the fabrication of nanofibers for biomedical applications. PMID:26403723

  9. 40 CFR 721.9717 - Azo monochloro triazine reactive dye.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Azo monochloro triazine reactive dye... Substances § 721.9717 Azo monochloro triazine reactive dye. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as an azo monochloro...

  10. Designing reactive distillation columns under explicit sustainability considerations

    OpenAIRE

    Puigjaner Corbella, Lluís; Bojarski, Aarón David

    2011-01-01

    Homenatge al prf. Pierucci Reactive distillation is one of the most attractive reactive separations, combining chemical reaction with the separation of chemicals, leading to new processes providing higher economy. This work investigates the sustainability of those process systems, which incorporate reactive distillation, through the use of Life Cycle Thinking via Life Cycle Assessment. Moreover we use economic and environmental metrics. The proposed decision support strategy is exemplified...

  11. Introduction to Reactive Gas Dynamics

    CERN Document Server

    Brun, Raymond

    2009-01-01

    In high energy gas flows, at high velocities and high temperatures, physical and chemical processes such as molecular vibrational excitation, dissociation, ionisation or various reactions take place and deeply influence the structure of the flows. The characteristic times of these processes have the same order of magnitude as aerodynamic characteristic times, so that these reactive media are generally in thermodynamic and chemical non-equilibrium. This book presents a generalintroductory study of these media. In the first part their fundamental statistical aspects are described, starting from

  12. Framework for reactive mass transport

    DEFF Research Database (Denmark)

    Jensen, Mads Mønster; Johannesson, Björn; Geiker, Mette Rica

    2014-01-01

    description is coupled to the system. The mass transport is solved by using the finite element method where the chemical equilibrium is solved explicitly by an operator splitting method. The IPHREEQC library is used as chemical equilibrium solver. The equation system, solved by IPHREEQC, is explained...... simulation, showing multi-species ingress with formation of new solid phases in the domain is described and calculated. It is shown that the numerical solution method is capable of solving the reactive mass transport system for the examples considered. (C) 2014 Elsevier B.V. All rights reserved....

  13. Reactive Kripke semantics

    CERN Document Server

    Gabbay, Dov M

    2013-01-01

    This text offers an extension to the traditional Kripke semantics for non-classical logics by adding the notion of reactivity. Reactive Kripke models change their accessibility relation as we progress in the evaluation process of formulas in the model. This feature makes the reactive Kripke semantics strictly stronger and more applicable than the traditional one. Here we investigate the properties and axiomatisations of this new and most effective semantics, and we offer a wide landscape of applications of the idea of reactivity. Applied topics include reactive automata, reactive grammars, rea

  14. Reactive dispersive contaminant transport in coastal aquifers: Numerical simulation of a reactive Henry problem

    KAUST Repository

    Nick, H.M.

    2013-02-01

    The reactive mixing between seawater and terrestrial water in coastal aquifers influences the water quality of submarine groundwater discharge. While these waters come into contact at the seawater groundwater interface by density driven flow, their chemical components dilute and react through dispersion. A larger interface and wider mixing zone may provide favorable conditions for the natural attenuation of contaminant plumes. It has been claimed that the extent of this mixing is controlled by both, porous media properties and flow conditions. In this study, the interplay between dispersion and reactive processes in coastal aquifers is investigated by means of numerical experiments. Particularly, the impact of dispersion coefficients, the velocity field induced by density driven flow and chemical component reactivities on reactive transport in such aquifers is studied. To do this, a hybrid finite-element finite-volume method and a reactive simulator are coupled, and model accuracy and applicability are assessed. A simple redox reaction is considered to describe the degradation of a contaminant which requires mixing of the contaminated groundwater and the seawater containing the terminal electron acceptor. The resulting degradation is observed for different scenarios considering different magnitudes of dispersion and chemical reactivity. Three reactive transport regimes are found: reaction controlled, reaction-dispersion controlled and dispersion controlled. Computational results suggest that the chemical components\\' reactivity as well as dispersion coefficients play a significant role on controlling reactive mixing zones and extent of contaminant removal in coastal aquifers. Further, our results confirm that the dilution index is a better alternative to the second central spatial moment of a plume to describe the mixing of reactive solutes in coastal aquifers. © 2012 Elsevier B.V.

  15. Modeling and simulation of reactive flows

    CERN Document Server

    Bortoli, De AL; Pereira, Felipe

    2015-01-01

    Modelling and Simulation of Reactive Flows presents information on modeling and how to numerically solve reactive flows. The book offers a distinctive approach that combines diffusion flames and geochemical flow problems, providing users with a comprehensive resource that bridges the gap for scientists, engineers, and the industry. Specifically, the book looks at the basic concepts related to reaction rates, chemical kinetics, and the development of reduced kinetic mechanisms. It considers the most common methods used in practical situations, along with equations for reactive flows, and va

  16. Reactive multiphase flow simulation workshop summary

    Energy Technology Data Exchange (ETDEWEB)

    VanderHeyden, W.B.

    1995-09-01

    A workshop on computer simulation of reactive multiphase flow was held on May 18 and 19, 1995 in the Computational Testbed for Industry at Los Alamos National Laboratory (LANL), Los Alamos, New Mexico. Approximately 35 to 40 people attended the workshop. This included 21 participants from 12 companies representing the petroleum, chemical, environmental and consumer products industries, two representatives from the DOE Office of Industrial Technologies and several from Los Alamos. The dialog at the meeting suggested that reactive multiphase flow simulation represents an excellent candidate for government/industry/academia collaborative research. A white paper on a potential consortium for reactive multiphase flow with input from workshop participants will be issued separately.

  17. Reactive perforating collagenosis

    Directory of Open Access Journals (Sweden)

    Yadav Mukesh

    2009-01-01

    Full Text Available Reactive perforating collagenosis is a rare cutaneous disorder of unknown etiology. We hereby describe a case of acquired reactive perforating collagenosis in a patient of diabetes and chronic renal failure.

  18. Reactive perforating collagenosis

    OpenAIRE

    Yadav Mukesh; Sangal B; Bhargav Puneet; Jai P; Goyal Mukul

    2009-01-01

    Reactive perforating collagenosis is a rare cutaneous disorder of unknown etiology. We hereby describe a case of acquired reactive perforating collagenosis in a patient of diabetes and chronic renal failure.

  19. Reactivity and neutron dynamics

    International Nuclear Information System (INIS)

    Basing on the results of experiments mad with the full-scale WWER-1000 reactor core the problems of simulating neutron distributed transients, reactivity role in their description and uncertainties connected with reactivity value determination are discussed. Adiabatic approximation application and reactivity insertions lead to multiplicative representation of the solution kinetics equation including amplitude multiplier and form function

  20. Kinetics of Hydrolysis of Cationic Reactive Disperse Dyes Containing Quaternary Group

    Institute of Scientific and Technical Information of China (English)

    XIE Kong-liang; HOU Ai-qin

    2006-01-01

    The kinetics of hydrolysis of cationic reactive disperse dyes containing quaternary group and chemical shift(13CNMR) of the adjacent carbon atoms with pyridine-acetylamino were discussed. The results show pyridine-acetylamino reactive group had higher reactivity than chloroacetylamino and chemical shift(13CNMR) of the adjacent carbon atoms with pyridine-acetylamino moved 18.77 ppm.

  1. Structure, reactivity, and biological properties of hidantoines

    International Nuclear Information System (INIS)

    Hydantoin (imidazolidine-2,4-dione) is a 2,4-diketotetrahydroimidazole discovered by Baeyer in 1861. Thiohydantoins and derivatives were prepared, having chemical properties similar to the corresponding carbonyl compounds. Some biological activities (antimicrobial, anticonvulsant, schistosomicidal) are attributed to the chemical reactivity and consequent affinity of hydantoinic rings towards biomacromolecules. Therefore, knowledge about the chemistry of hydantoins has increased enormously. In this review, we present important aspects such as reactivity of hydantoins, acidity of hydantoins, spectroscopy and crystallographic properties, and biological activities of hydantoin and its derivatives. (author)

  2. Towards a quantitative understanding of total OH reactivity: A review

    Science.gov (United States)

    Yang, Yudong; Shao, Min; Wang, Xuemei; Nölscher, Anke C.; Kessel, Stephan; Guenther, Alex; Williams, Jonathan

    2016-06-01

    Over the past fifty years, considerable efforts have been devoted to measuring the concentration and chemical speciation of volatile organic compounds (VOCs) in ambient air and emissions. Recently, it has become possible to directly determine the overall effect of atmospheric trace gases on the oxidant hydroxyl radicals (OH), by measuring OH reactivity (OH loss frequency). Quantifying total OH reactivity is one way to characterize the roles of VOCs in formation of ground-level ozone and secondary organic aerosols (SOA). Approaches for measuring total OH reactivity in both emissions and ambient air have been progressing and have been applied in a wide range of studies. Here we evaluate the main techniques used to measure OH reactivity, including two methods directly measuring OH decay and one comparative reactivity method (CRM), and summarize the existing experimental and modeling studies. Total OH reactivity varies significantly on spatial, diurnal, seasonal and vertical bases. Comparison with individually detected OH sinks often reveals a significant missing reactivity, ranging from 20% to over 80% in some environments. Missing reactivity has also been determined in most source emission studies. These source measurements, as well as numerical models, have indicated that both undetected primary emissions and unmeasured secondary products could contribute to missing reactivity. A quantitative understanding of total OH reactivity of various sources and ambient environments will enhance our understanding of the suite of compounds found in emissions as well as chemical processes, and will also provide an opportunity for the improvement of atmospheric chemical mechanisms.

  3. Quantum-chemical insight into structure-reactivity relationship in 4,5,6,7-tetrahalogeno-1H-benzimidazoles: a combined X-ray, DSC, DFT/QTAIM, Hirshfeld surface-based, and molecular docking approach.

    Science.gov (United States)

    Latosińska, Jolanta Natalia; Latosińska, Magdalena; Maurin, Jan Krzysztof; Orzeszko, Andrzej; Kazimierczuk, Zygmunt

    2014-03-20

    The weak interaction patterns in 4,5,6,7-tetrahalogeno-1H-benzimidazoles, protein kinase CK2 inhibitors, in solid state are studied by the X-ray method and quantum chemistry calculations. The crystal structures of 4,5,6,7-tetrachloro- and 4,5,6,7-tetrabromo-1H-benzimidazole are determined by X-ray diffraction and refined to a final R-factor of 3.07 and 3.03%, respectively, at room temperature. The compound 4,5,6,7-tetrabromo-1H-benzimidazole, which crystallizes in the I41/a space group, is found to be isostructural with previously studied 4,5,6,7-tetraiodo-1H-benzimidazole in contrast to 4,5,6,7-tetrachloro-1H-benzimidazole, which crystallizes as triclinic P1̅ with 4 molecules in elementary unit. For 4,5,6,7-tetrachloro-1H-benzimidazole, differential scanning calorimetry (DSC) revealed a second order glassy phase transition at Tg = 95°/106° (heating/cooling), an indication of frozen disorder. The lack of 3D isostructurality found in all 4,5,6,7-tetrahalogeno-1H-benzimidazoles is elucidated on the basis of the intra- and intermolecular interactions (hydrogen bonding, van der Waals contacts, and C-H···π interactions). The topological Bader's Quantum Theory of Atoms in Molecules (QTAIM) and Spackman's Hirshfeld surface-based approaches reveal equilibration of electrostatic matching and dispersion van der Waals interactions between molecules consistent with the crystal site-symmetry. The weakening of van der Waals forces accompanied by increasing strength of the hydrogen bond (N-H···N) result in a decrease in the crystal site-symmetry and a change in molecular packing in the crystalline state. Crystal packing motifs were investigated with the aid of Hirshfeld surface fingerprint plots. The ordering 4,5,6,7-tetraiodo > 4,5,6,7-tetrabromo > 4,5,6,7-tetrachloro > 4,5,6,7-tetrafluoro reflects not only a decrease in crystal symmetry but also increase in chemical reactivity (electronic activation), which could explain some changes in biological activity of

  4. Airborne measurement of OH reactivity during INTEX-B

    OpenAIRE

    J. Mao; Ren, X.; Brune, W. H.; J. R. Olson; Crawford, J. H.; A. Fried; Huey, L.G.; Cohen, R. C.; B. Heikes; Singh, H. B.; Blake, D. R.; Sachse, G. W.; Diskin, G. S.; S. R. Hall; Shetter, R. E.

    2009-01-01

    The measurement of OH reactivity, the inverse of the OH lifetime, provides a powerful tool to investigate atmospheric photochemistry. A new airborne OH reactivity instrument was designed and deployed for the first time on the NASA DC-8 aircraft during the second phase of Intercontinental Chemical Transport Experiment-B (INTEX-B) campaign, which was focused on the Asian pollution outflow over Pacific Ocean and was based in Hawaii and Alaska. The OH reactivity was measured by adding OH, generat...

  5. Coupled Flow and Reactivity in the Variably Saturated Porous Media

    Energy Technology Data Exchange (ETDEWEB)

    Palmer, Carl; Smith Bob W.

    2003-06-01

    This Environmental Management Science Program project (86598) is a collaborative effort between the University of Idaho (UI) and the Idaho National Engineering and Environmental Laboratory (INEEL) with the goal of developing a better understanding of the relationships between chemical reactivity, moisture content, and reactive transport for vadose zone porous media.

  6. Chemical reagent and process for refuse disposal

    International Nuclear Information System (INIS)

    A process for treating refuse by mixing them with a reactive chemical and a puzzolana-type material. Said chemical includes a retarding agent which modifies the viscosity and an accelerating agent. (author)

  7. Production and Consumption of Reactive Oxygen Species by Fullerenes

    Science.gov (United States)

    Reactive oxygen species (ROS) are one of the most important intermediates in chemical, photochemical, and biological processes. To understand the environmental exposure and toxicity of fullerenes better, the production and consumption of ROS (singlet oxygen, superoxide, hydrogen ...

  8. Reactive transport models and simulation with ALLIANCES

    International Nuclear Information System (INIS)

    Many chemical processes influence the evolution of nuclear waste storage. As a result, simulations based only upon transport and hydraulic processes fail to describe adequately some industrial scenarios. We need to take into account complex chemical models (mass action laws, kinetics...) which are highly non-linear. In order to simulate the coupling of these chemical reactions with transport, we use a classical Sequential Iterative Approach (SIA), with a fixed point algorithm, within the mainframe of the ALLIANCES platform. This approach allows us to use the various transport and chemical modules available in ALLIANCES, via an operator-splitting method based upon the structure of the chemical system. We present five different applications of reactive transport simulations in the context of nuclear waste storage: 1. A 2D simulation of the lixiviation by rain water of an underground polluted zone high in uranium oxide; 2. The degradation of the steel envelope of a package in contact with clay. Corrosion of the steel creates corrosion products and the altered package becomes a porous medium. We follow the degradation front through kinetic reactions and the coupling with transport; 3. The degradation of a cement-based material by the injection of an aqueous solution of zinc and sulphate ions. In addition to the reactive transport coupling, we take into account in this case the hydraulic retroaction of the porosity variation on the Darcy velocity; 4. The decalcification of a concrete beam in an underground storage structure. In this case, in addition to the reactive transport simulation, we take into account the interaction between chemical degradation and the mechanical forces (cracks...), and the retroactive influence on the structure changes on transport; 5. The degradation of the steel envelope of a package in contact with a clay material under a temperature gradient. In this case the reactive transport simulation is entirely directed by the temperature changes and

  9. Reactive modification of polyesters and their blends

    Science.gov (United States)

    Wan, Chen

    2004-12-01

    As part of a broader research effort to investigate the chemical modification of polyesters by reactive processing a low molecular weight (MW) unsaturated polyester (UP) and a higher MW saturated polyester, polyethylene terephthalate (PET), alone or blended with polypropylene (PP) were melt processed in a batch mixer and continuous twin screw extruders. Modification was monitored by on-line rheology and the products were characterized primarily by off-line rheology, morphology and thermal analysis. Efforts were made to establish processing/property relationships and provide an insight of the accompanying structural changes. The overall response of the reactively modified systems was found to be strongly dependent on the component characteristics, blend composition, type and concentrations of reactive additives and processing conditions. The work concluded that UP can be effectively modified through reactive melt processing. Its melt viscosity and MW can be increased through chemical reactions between organic peroxides (POX) and chain unsaturation or between MgO and carboxyl/hydroxyl end groups. Reactive blending of PP/UP blends through peroxide modification gave finer and more uniform morphology than unreacted blends and at a given PP/UP weight ratio more thermoplastic elastomers-like rheological behavior. This is due to the continuously decreasing viscosity ratio of PP/UP towards unity by the competing reactions between POX and the blend components and formation of PP-UP copolymers which serve as in-situ compatibilizers to promote better interfacial adhesion. Kinetics of the competing reactions were analyzed through a developed model. In addition to POX concentration and mixing efficiency, rheology and morphology of UP/PP bends were significantly affected by the addition of inorganic and organic coagents. Addition of coagents such as a difunctional maleimide, MgO and/or an anhydride functionalized PP during reactive blending offers effective means for tailoring

  10. Chemical effects of radiation

    International Nuclear Information System (INIS)

    Ionizing radiations initiate chemical changes in materials because of the high energy of their quanta. In water, highly reactive free radicals are produced which can initiate secondary changes of solutes, and in chemical of biological molecules in contact with the water. Free radicals can also be directly produced in irradiated medical products. Their fate can be identified and the molecular basis of radiation inactivation clarified. Methods have now been developed to protect and minimise such radiation damage. (author)

  11. When is arthritis reactive?

    Science.gov (United States)

    Hamdulay, S S; Glynne, S J; Keat, A

    2006-07-01

    Reactive arthritis is an important cause of lower limb oligoarthritis, mainly in young adults. It is one of the spondyloarthropathy family; it is distinguishable from other forms of inflammatory arthritis by virtue of the distribution of affected sites and the high prevalence of characteristic extra-articular lesions. Many terms have been used to refer to this and related forms of arthritis leading to some confusion. Reactive arthritis is precipitated by an infection at a distant site and genetic susceptibility is marked by possession of the HLA-B27 gene, although the mechanism remains uncertain. Diagnosis is a two stage process and requires demonstration of a temporal link with a recognised "trigger" infection. The identification and management of "sexually acquired" and "enteric" forms of reactive arthritis are considered. Putative links with HIV infection are also discussed. The clinical features, approach to investigation, diagnosis, and management of reactive arthritis are reviewed. PMID:16822921

  12. Reactive sputter deposition

    CERN Document Server

    Mahieu, Stijn

    2008-01-01

    In this valuable work, all aspects of the reactive magnetron sputtering process, from the discharge up to the resulting thin film growth, are described in detail, allowing the reader to understand the complete process. Hence, this book gives necessary information for those who want to start with reactive magnetron sputtering, understand and investigate the technique, control their sputtering process and tune their existing process, obtaining the desired thin films.

  13. Reactive plasma spraying

    OpenAIRE

    Al-Sabouni, Omar

    1999-01-01

    Reactive Plasma Spraying (RPS) with a hydrocarbon gas has been studied as a method to improve the mechanical properties of a commercially available 80: 20 nickel-chromium alloy, and subsequently as a method to reduce the oxygen content of sprayed MCrAlY coatings. A conventional d. c. plasma torch has been modified by attaching a conical graphite tube (reactor) onto the end of the gun. The powder is then sprayed through the reactor with injected reactive hydrocarbon gas. The ...

  14. When is arthritis reactive?

    OpenAIRE

    Hamdulay, S. S.; Glynne, S J; Keat, A

    2006-01-01

    Reactive arthritis is an important cause of lower limb oligoarthritis, mainly in young adults. It is one of the spondyloarthropathy family; it is distinguishable from other forms of inflammatory arthritis by virtue of the distribution of affected sites and the high prevalence of characteristic extra‐articular lesions. Many terms have been used to refer to this and related forms of arthritis leading to some confusion. Reactive arthritis is precipitated by an infection at a distant site and gen...

  15. Reactivity of polychlorinated biphenyls in nucleophilic and electrophilic substitutions

    Energy Technology Data Exchange (ETDEWEB)

    Gorbunova, Tatyana I., E-mail: gorbunova@ios.uran.ru [I. Ya. Postovskii Institute of Organic Synthesis, Ural Branch, Russian Academy of Sciences, Kovalevskoy St., 22, Ekaterinburg 620990 (Russian Federation); Subbotina, Julia O. [Ural Federal University named after the first President of Russia B.N. Yeltsin, Mira St., 19, Ekaterinburg 620002 (Russian Federation); Saloutin, Viktor I.; Chupakhin, Oleg N. [I. Ya. Postovskii Institute of Organic Synthesis, Ural Branch, Russian Academy of Sciences, Kovalevskoy St., 22, Ekaterinburg 620990 (Russian Federation)

    2014-08-15

    Graphical abstract: - Highlights: • Quantum chemical calculations were carried out for PCBs congeners. • Calculated descriptors were used to explain the PCBs reactivity in S{sub N} and S{sub E} substitutions. • Obtained data were used to estimate the PCBs reactivity in the S{sub N} reactions. • Calculated descriptors were insufficient to explain the PCBs reactivity in the S{sub E} reactions. • New neutralization methods of the large-capacity PCBs were discussed. - Abstract: To explain the chemical reactivity of polychlorinated biphenyls in nucleophilic (S{sub N}) and electrophilic (S{sub E}) substitutions, quantum chemical calculations were carried out at the B3LYP/6-31G(d) level of the Density Functional Theory in gas phase. Carbon atomic charges in biphenyl structure were calculated by the Atoms-in-Molecules method. Chemical hardness and global electrophilicity index parameters were determined for congeners. A comparison of calculated descriptors and experimental data for congener reactivity in the S{sub N} and S{sub E} reactions was made. It is shown that interactions in the S{sub N} mechanism are reactions of the hard acid–hard base type, these are the most effective in case of highly chlorinated substrates. To explain the congener reactivity in the S{sub E} reactions, correct descriptors were not established. The obtained results can be used to carry out chemical transformations of the polychlorinated biphenyls in order to prepare them for microbiological destruction or preservation.

  16. Digital reactivity meter

    International Nuclear Information System (INIS)

    Digital reactivity meters (DRM) are mostly used as measuring instruments, e.g. for calibration of control rods, and there are only a few cases of their incorporation into the control systems of the reactors. To move in this direction there is more development work needed. First of all, fast algorithms are needed for inverse kinetics equations to relieve the computer for more important tasks of reactor model solving in real time. The next problem, currently under investigation, is the incorporation of the reactor thermal-hydraulic model into the DRM so that it can be used in the power range. Such an extension of DHM allows presentation not only of the instantaneous reactivity of the system, but also the inserted reactivity can be estimated from the temperature reactivity feed-backs. One of the applications of this concept is the anomalous digital reactivity monitor (ADRN) as part of the reactor protection system. As a solution of the first problem, a fast algorithm for solving the inverse kinetics equations has been implemented in the off-line program RODCAL on CDC 1700 computer and tested for its accuracy by performing different control rod calibrations on the reactor TRIGA

  17. Chemical sputtering

    International Nuclear Information System (INIS)

    In this thesis, the author focuses on chemical sputtering by keV ions, treating two specific examples: the chemical effects occurring when bombarding simple condensed gases and the mechanisms of the ion-assisted etching process. First, however, the mechanism of sputtering of condensed gases in general is discussed. These mechanisms have been investigated using condensed noble gases as target material. The thesis is a compilation of articles published elsewhere. Contents: sputtering of condensed noble gases by keV heavy ions; surface distribution as an observable factor in the energy distribution of sputtered particles; reactive sputtering of simple condensed gases by keV heavy ion bombardment; mass spectra of nozzle-produced small molecular clusters of H2O, NH3, CO and CH4; mass and energy distribution of particles sputter-etched from Si in a XeF2 environment; argon-ion assisted etching of silicon by molecular chlorine; energy distribution of sputtered poly-atomic molecules. (Auth.)

  18. Sunlight induced photo reactivity of drugs

    Energy Technology Data Exchange (ETDEWEB)

    Dallera, R.; Dondi, D.; Ricci, A.; Fasani, E.; Albini, A.

    2003-07-01

    The reactivity under natural light of some UVA-UVB photol able drugs belonging to the classes of fluoroquinolones, glucocortocosteroids, sunscreens and nitrophenyldihydropyridines has been investigated. The data suggest that exposition to sunlight for times ranging from some minutes to few hours at PSA is sufficient for promoting a high degradation in the drugs investigated. the chemical reactions are the same as observed under artificial UV light. (Author) 28 refs.

  19. Mixed Solvent Reactive Recrystallization of Sodium Carbonate

    OpenAIRE

    Gaertner, R.S.

    2005-01-01

    Investigation of the reactive recrystallization of trona (sodium sesquicarbonate) and sodium bicarbonate to sodium carbonate (soda) in a mixed solvent led to the design of several alternative, less energy consumptive, economically very attractive process routes for the production of soda from all principal sodium carbonate sources. The kinetics of the recrystallization as well as of the superimposed chemical reaction, the decomposition of the bicarbonate ion, have been measured, a thermodynam...

  20. Distinct reactivities on segmented selenium nanorods.

    Science.gov (United States)

    Liu, Ming-Han; Chen, Yun-Wen; Kuo, Jer-Lai; Wang, C R Chris

    2015-09-18

    We demonstrate a new approach to synthesize several unique nanostructures by tuning the selective reactivities on individual symmetry-breaking segmented selenium nanorods (SBS-SeNRs). The segment-selective reactions from thiolated silane endowed the formation of float-like SBS-SeNR@SiO2 with a silica coating on the t-Se segment. Several other unique nanostructures were further synthesized by applying other selective reactions, such as Se chemical removal and nanogold deposition. Such a segmented nanomaterial of SBS-SeNRs acts as a new chemical template for preparing various segmented nanocomposites. PMID:26236788

  1. Hydroxyquinones: Synthesis and Reactivity

    Directory of Open Access Journals (Sweden)

    Spyros Spyroudis

    2000-12-01

    Full Text Available Quinones having hydroxy groups directly attached to the quinone ring constitute a very interesting class of quinoid compounds. A great number of hydroxyquinones are found in nature and the majority of them exhibit unique biological activity. Their syntheses and their main reactivity patterns are reviewed in this paper.

  2. C-reactive protein

    Science.gov (United States)

    C-reactive protein (CRP) is produced by the liver. The level of CRP rises when there is inflammation throughout the body. It is one of a group of proteins called "acute phase reactants" that go up in response to inflammation. ...

  3. Clojure reactive programming

    CERN Document Server

    Borges, Leonardo

    2015-01-01

    If you are a Clojure developer who is interested in using Reactive Programming to build asynchronous and concurrent applications, this book is for you. Knowledge of Clojure and Leiningen is required. Basic understanding of ClojureScript will be helpful for the web chapters, although it is not strictly necessary.

  4. Modelling reactive distillation

    NARCIS (Netherlands)

    Taylor, R.; Krishna, R.

    2000-01-01

    The design and operation issues for reactive distillation systems are considerably more complex than those involved for either conventional reactors or conventional distillation columns. The introduction of an in situ separation function within the reaction zone leads to complex interactions between

  5. Reactivity Network: Secondary Sources for Inorganic Reactivity Information.

    Science.gov (United States)

    Mellon, E. K.

    1989-01-01

    Provides an eclectic annotated bibliography of secondary sources for inorganic reactivity information of interest to reactivity network review authors and to anyone seeking information about simple inorganic reactions in order to develop experiments and demonstrations. Gives 119 sources. (MVL)

  6. Permeable reactive barriers for pollutant removal from groundwater

    International Nuclear Information System (INIS)

    The removal of pollutants from the groundwater using permeable reactive barriers is a novel in-situ groundwater remediation technology. The most relevant decontamination processes used are chemical reduction, oxidation, precipitation and sorption, for which examples are given. Some common organic pollutants are halogenated hydrocarbons, aromatic and nitroaromatic compounds which can be treated in reactive barriers successfully. Lead, chromium and, in particular, uranium are dealt with in great detail among inorganic pollutants because of their occurrence in many European countries. Construction methods for cut-off walls and reactive barriers exhibit similar features. Apart from conventional methods, drilling, deep soil mixing, jet technology, arrays of wells, injected systems and biobarriers are applied to construct permeable reactive barriers. Permeable reactive barriers bear great potential for the future in remediation engineering. (orig.)

  7. Relations among several nuclear and electronic density functional reactivity indexes

    OpenAIRE

    Torrent Sucarrat, Miquel; Luis Luis, Josep Maria; Duran i Portas, Miquel; Toro-Labbé, Alejandro; Solà i Puig, Miquel

    2003-01-01

    A set of connections among several nuclear and electronic indexes of reactivity in the framework of the conceptual Density Functional Theory by using an expansion ofthe energy functional in terms of the total number of electrons and the normal coordinates within a canonical ensemble was derived. The relations obtained provided explicit links between important quantities related to the chemical reactivity of a system. This paper particularly demonstrates that the derivative of the electronic e...

  8. Contribution of different granulometric populations to powder reactivity

    Institute of Scientific and Technical Information of China (English)

    Jean-Charles Benezet; Ali Benhassaine

    2009-01-01

    In this article, different population contributions of quartz powders to chemical reactivity in pozzolanic reaction were studied. Deconvolution software was used to show the different particle populations of each product. Reaction of quartz powder with lime in the pozzolanic reaction at 20 ℃ shows that reactivity of each powder population depends on its particle size. Adsorbed fine particles on coarse particle surfaces have a significant role in the first term of the reaction. In a second term, the micropowders react. The mesopowders react only in the last reaction terms. Until now, the reactivity of adsorbed powder has been attributed to amorphization of the particle surface.

  9. Detonation wave solutions and linear stability in a four component gas with bimolecular chemical reaction

    OpenAIRE

    Carvalho, Filipe; De Silva, A.W.; Soares, A. J.

    2015-01-01

    We consider a four component gas undergoing a bimolecular chemical reaction of type A1 + A2 = A3 + A4, described by the Boltzmann equation (BE) for chemically reactive mixtures. We adopt hard-spheres elastic cross sections and modified line-of-centers reactive cross sections depending on both the activation energy and geometry of the reactive collisions. Then we consider the hydrodynamic limit specified by the reactive Euler equations, in an earlier stage of the chemical reaction, when the ga...

  10. Multifunctional reactive nanocomposite materials

    Science.gov (United States)

    Stamatis, Demitrios

    Many multifunctional nanocomposite materials have been developed for use in propellants, explosives, pyrotechnics, and reactive structures. These materials exhibit high reaction rates due to their developed reaction interfacial area. Two applications addressed in this work include nanocomposite powders prepared by arrested reactive milling (ARM) for burn rate modifiers and reactive structures. In burn rate modifiers, addition of reactive nanocomposite powders to aluminized propellants increases the burn rate of aluminum and thus the overall reaction rate of an energetic formulation. Replacing only a small fraction of aluminum by 8Al·MoO3 and 2B·Ti nanocomposite powders enhances the reaction rate with little change to the thermodynamic performance of the formulation; both the rate of pressure rise and maximum pressure measured in the constant volume explosion test increase. For reactive structures, nanocomposite powders with bulk compositions of 8Al·MoO3, 12Al·MoO3, and 8Al·3CuO were prepared by ARM and consolidated using a uniaxial die. Consolidated samples had densities greater than 90% of theoretical maximum density while maintaining their high reactivity. Pellets prepared using 8Al·MoO3 powders were ignited by a CO2 laser. Ignition delays increased at lower laser powers and greater pellet densities. A simplified numerical model describing heating and thermal initiation of the reactive pellets predicted adequately the observed effects of both laser power and pellet density on the measured ignition delays. To investigate the reaction mechanisms in nanocomposite thermites, two types of nanocomposite reactive materials with the same bulk compositions 8Al·MoO3 were prepared by different methods. One of the materials was manufactured by ARM and the other, so called metastable interstitial composite (MIC), by mixing of nano-scaled individual powders. Clear differences in the low-temperature redox reactions, welldetectable by differential scanning calorimetry

  11. Advances in reactive surfactants.

    Science.gov (United States)

    Guyot, A

    2004-05-20

    The study of reactive surfactants and their applications in the synthesis of latexes for waterborne coatings has been recently boosted by two successive European programmes, involving all together eight academic and five industrial laboratories. The most significant results were obtained using surfactants derived from maleic and related anhydrides, or both nonionic and anionic reactive polymeric surfactants. Such surfactants are able to improve the stability of styrenic and acrylic latexes vs. various constraints, such as electrolyte addition, freeze-thawing tests or extraction with alcohol or acetone. The properties of films used in waterborne coatings are also improved in case of water exposure (less water uptake, dimensional stability), as well as improved weatherability, and blocking properties. Formulations for woodstain varnishes, metal coating of printing inks, based on the use of simple polymerizable surfactants, are now in the market. PMID:15072924

  12. Alkylidynephosphines : syntheses and reactivity

    OpenAIRE

    Becker, Gerd; Becker, Winfried; Knebl, Robert; Schmidt, Helmut; Hildenbrand, Ute; Westerhausen, Matthias

    1987-01-01

    In the past, different methods have been utilized for the preparation of alkylidynephosphines. Whereas, however, small amounts of thermally instable derivatives might be obtained from reactions in the gas phase, the synthesis of phosphines which are stable under an inert atmosphere, as for instance those with a tert-butyl or a 1-adamantyl substituent at the carbon atom of the PEC group, is best started with tris (trimethylsilyl) phosphine itself or with the more reactive lithium bis (trimethy...

  13. Reactive Turing Machines

    OpenAIRE

    Baeten, J.C.M.; Luttik, B.; Tilburg, van, T.G.

    2011-01-01

    We propose reactive Turing machines (RTMs), extending classical Turing machines with a process-theoretical notion of interaction, and use it to define a notion of executable transition system. We show that every computable transition system with a bounded branching degree is simulated modulo divergence-preserving branching bisimilarity by an RTM, and that every effective transition system is simulated modulo the variant of branching bisimilarity that does not require divergence preservation. ...

  14. Reactivity of nitrosyl group

    International Nuclear Information System (INIS)

    Reactivity of ruthenium nitrosyl complexes is considered. According to X-ray structure analysis data nitrogen oxide interaction with metals results in formation of two complexes. The first ones contain linear nitrosyls (valence bond angle 180 deg in M-NO grouping), the second ones - bend nitrosyls (the bond angle in M-N-O grouping 120-130 deg). The first type complexes react primarily with nucleophilic reagents (OH-, N3-), the second ones - with electrophilic reagents

  15. Therapeutic reactive oxygen generation.

    Science.gov (United States)

    Scharff, Peter; Ritter, Uwe; Matyshevska, Olga P; Prylutska, Svitlana V; Grynyuk, Iryna I; Golub, Alexandr A; Prylutskyy, Yuriy I; Burlaka, Anatoliy P

    2008-01-01

    An increase of the intracellular reactive oxygen species (ROS) concentration leads to the development of oxidative stress and, thus, to the damage of cell components. The cause-and-effect relations between these processes have not been fully established yet. The ability of photo excited supramolecular composites containing fullerenes C60 immobilized at nanosilica particles to generate reactive oxygen species (ROS) in cells of two types (rat thymocytes, and transformed cells of ascite Erlich carcinoma, EAC, and leucosis L1210) is demonstrated. The damaging effect of photo excited C60-composites are shown, which appeared to be selective and manifested in transformed cells, but not in thymocytes. It has been shown that after the irradiation of aqueous solutions or cell suspensions in the presence of fullerene C60, the generation of reactive oxygen species is observed. It has been shown that the influence of photo excited fullerene C60 on metabolic processes depends on the composition of C60-containing complex and on the type of the cells. The damaging effects of photo excited fullerene C60-containing composites were demonstrated to be selective. The data presented suggest that the application of fullerene C60-containing composites for the selective activation of ROS-dependent death program in certain types of tumor cells is very promising. PMID:18564617

  16. Infiltration processing of boron carbide-, boron-, and boride-reactive metal cermets

    International Nuclear Information System (INIS)

    This patent describes a method of fabricating metal-ceramic composites from previously formed ceramic precursor starting constituents selected from boron-carbide, boron and borides and metals reactive therewith selected from reactive metals, alloys thereof, and compounds thereof which reduce to reactive metals or alloys thereof. It comprises: chemically pretreating the previously formed starting constituents of a ceramic precursor; consolidating the chemically pretreated starting constituents into a porous ceramic precursor; infiltrating molten reactive metal into the chemically pretreated ceramic precursor; wherein the step of chemically pretreating the starting constituents of the ceramic precursor alters the surface chemistry to enhance infiltration of the precursor by the molten reactive metal by slowing the kinetics of reaction relative to the kinetics of densification

  17. Global Reactive Gases in the MACC project

    Science.gov (United States)

    Schultz, M. G.

    2012-04-01

    In preparation for the planned atmospheric service component of the European Global Monitoring for Environment and Security (GMES) initiative, the EU FP7 project Monitoring of Atmospheric Composition and Climate (MACC) developed a preoperational data assimilation and modelling system for monitoring and forecasting of reactive gases, greenhouse gases and aerosols. The project is coordinated by the European Centre for Medium-Range Weather Forecast (ECMWF) and the system is built on ECMWF's Integrated Forecasting System (IFS) which has been coupled to the chemistry transport models MOZART-3 and TM5. In order to provide daily forecasts of up to 96 hours for global reactive gases, various satellite retrieval products for ozone (total column and profile data), CO, NO2, CH2O and SO2 are either actively assimilated or passively monitored. The MACC system is routinely evaluated with in-situ data from ground-based stations, ozone sondes and aircraft measurements, and with independent satellite retrievals. Global MACC reactive gases forecasts are used in the planning and analysis of large international field campaigns and to provide dynamical chemical boundary conditions to regional air quality models worldwide. Several case studies of outstanding air pollution events have been performed, and they demonstrate the strengths and weaknesses of chemical data assimilation based on current satellite data products. Besides the regular analyses and forecasts of the tropospheric chemical composition, the MACC system is also used to monitor the evolution of stratospheric ozone. A comprehensive reanalysis simulation from 2003 to 2010 provides new insights into the interannual variability of the atmospheric chemical composition.

  18. A Novel Permeable Reactive Barrier (PRB) for Simultaneous and Rapid Removal of Heavy Metal and Organic Matter - A Systematic Chemical Speciation Approach on Sustainable Technique for Pallikarani Marshland Remediation

    Science.gov (United States)

    Selvaraj, A.; Nambi, I. M.

    2014-12-01

    In this study, an innovative technique of ZVI mediated 'coupling of Fenton like oxidation of phenol and Cr(VI) reduction technique' was attempted. The hypothesis is that Fe3+ generated from Cr(VI) reduction process acts as electron acceptor and catalyst for Fenton's Phenol oxidation process. The Fe2+ formed from Fenton reactions can be reused for Cr(VI) reduction. Thus iron can be made to recycle between two reactions, changing back and forth between Fe2+ and Fe3+ forms, makes treatment sustainable.(Fig 1) This approach advances current Fenton like oxidation process by (i)single system removal of heavy metal and organic matter (ii)recycling of iron species; hence no additional iron required (iii)more contaminant removal to ZVI ratio (iv)eliminating sludge related issues. Preliminary batch studies were conducted at different modes i) concurrent removal ii) sequential removal. The sequential removal was found better for in-situ PRB applications. PRB was designed based on kinetic rate slope and half-life time, obtained from primary column study. This PRB has two segments (i)ZVI segment[Cr(VI)] (ii)iron species segment[phenol]. This makes treatment sustainable by (i) having no iron ions in outlet stream (ii)meeting hypothesis and elongates the life span of PRB. Sequential removal of contaminates were tested in pilot scale PRB(Fig 2) and its life span was calculated based on the exhaustion of filling material. Aqueous, sand and iron aliquots were collected at various segments of PRB and analyzed for precipitation and chemical speciation thoroughly (UV spectrometer, XRD, FTIR, electron microscope). Chemical speciation profile eliminates the uncertainties over in-situ PRB's long term performance. Based on the pilot scale PRB study, 'field level PRB wall construction' was suggested to remove heavy metal and organic compounds from Pallikaranai marshland(Fig 3)., which is contaminated with leachate coming from nearby Perungudi dumpsite. This research provides (i

  19. Reactive geochemical transport problems in nuclear waste analyses

    International Nuclear Information System (INIS)

    This paper reviews the generic formulation of reactive geochemical transport problems that may be associated with the design or characterization of a nuclear waste repository. A summary of the relevant physical and chemical transport phenomena is provided as a basis for developing suitable numerical models of these processes. Particular emphasis is devoted to numerical and computational aspects of simulating the movement of several reactive chemical components within a porous medium using a particle method. In addition, avenues for future theoretical and applied research are discussed in light of the various uncertainties that presently exist in solving these problems

  20. Programming Reactive Extensions and LINQ

    CERN Document Server

    Liberty, Jesse

    2011-01-01

    Pro Reactive Extensions and LINQ is a deep dive into the next important technology for .NET developers: Reactive Extensions. This in-depth tutorial goes beyond what is available anywhere else to teach how to write WPF, Silverlight, and Windows Phone applications using the Reactive Extensions (Rx) to handle events and asynchronous method calls. Reactive programming allows you to turn those aspects of your code that are currently imperative into something much more event-driven and flexible. For this reason, it's sometimes referred to as LINQ for Events. Reactive programming hinges on the concep

  1. Intercomparison 9711. pH, conductivity, alkalinity, nitrate + nitrite, chloride, sulfate, calcium, magnesium, sodium, potassium, total aluminium, reactive and non-labile aluminium, dissolved organic carbon, and chemical oxygen demand

    Energy Technology Data Exchange (ETDEWEB)

    Hovind, Haavard

    1997-09-22

    The work described in this report was a part of an international cooperative programme for assessment and monitoring of acidification of rivers and lakes. Two sample sets were prepared for intercomparison, one for determination of the major ions, the other for determination of aluminium fractions and unspecified organic matter. The samples were sent to 50 laboratories and 47 laboratories from 22 countries submitted results. Good agreement was found for chloride, sulfate, calcium, magnesium, sodium and the unspecific organic compounds, dissolved organic carbon and chemical oxygen demand, more than 80% being evaluated as acceptable for these analytic variables. The results for nitrate + nitrite and aluminium species did not agree well, probably because different methods were used to determine the aluminium species. On the whole, 78% of the results were within the general target accuracy of plus or minus 20%. Laboratories with results outside this accuracy should improve their methods if they want to analyse low-concentration samples. To improve the compatibility of the analytical results for aluminium fractions, it seems necessary to normalize the analytical methods and determination techniques used for these determinations. A total error of plus minus 0.2 pH units seems to be a reasonable assessment of the accuracy for pH measurements when weakly acid or neutral water samples not in CO{sub 2} equilibrium are analyzed. 7 refs., 1 fig., 34 tabs.

  2. Frustrated Lewis pairs: Design and reactivity

    Indian Academy of Sciences (India)

    Sanjoy Mukherjee; Pakkirisamy Thilagar

    2015-02-01

    The interaction of a Lewis acid with a Lewis base results in the formation of a Lewis acid–base adduct. Understanding Lewis acids and bases is central to conceptualizing chemical interactions and constitutes a major portion of metal–ligand chemistry. Sterically encumbered/constrained Lewis pairs cannot form acid–base adducts, but such ‘Frustrated Lewis Pairs’ (FLPs), with their unquenched electronic demands can be elegantly used to simultaneously react with a third species, resulting in unusual reactivity of small molecules. Such unusual reactions, explored only in the last few years, have found several applications, e.g., heterolytic splitting of H2, activation of small molecules (CO2, N2O, etc.). FLPs have opened new opportunities in synthetic chemistry, covering organic, main group as well as transition metal chemistry. The design strategies adopted for FLP systems and their unique reactivity are discussed here.

  3. Principles and practice of reactive transport modeling

    International Nuclear Information System (INIS)

    This paper presents a review of the principles underlying a continuum formulation of reactive transport in a porous medium. Partial differential equations representing conservation of mass are derived for transport by advection, diffusion, and electrochemical migration combined with chemical reaction of aqueous species and solids. Several examples are presented to illustrate the general theory. These include weathering along a narrow crevice, electrochemical migration in a dilute NaCl solution, secondary pyrite formation mediated through intermediate sulfur oxidation states, and a description of a uranium roll-front deposit. Numerical techniques which take advantage of the quasi-stationary state approximation, based on the much longer time scale involved in mineral alteration compared to that characterizing changes in the aqueous phase, permit solving the reactive transport equations over geologic time scales

  4. Chemical Emergencies

    Science.gov (United States)

    When a hazardous chemical has been released, it may harm people's health. Chemical releases can be unintentional, as in the case of an ... the case of a terrorist attack with a chemical weapon. Some hazardous chemicals have been developed by ...

  5. A finite-element simulation model for saturated-unsaturated, fluid-density-dependent ground-water flow with energy transport or chemically- reactive single-species solute transport

    Science.gov (United States)

    Voss, C.I.

    1984-01-01

    SUTRA (Saturated-Unsaturated Transport) is a computer program which can be used to simulate the movement of fluid and the transport of either energy or dissolved substances in a subsurface environment. The model employs a two-dimensional hybrid finite-element and integrated-finite-difference method to approximate the governing equations that describe the two interdependent processes that are simulated by SUTRA: (1) fluid density-dependent saturated or unsaturated groundwater flow, and either (2a) transport of a solute in the groundwater, in which the solute may be subject to: equilibrium adsorption on the porous matrix, and both first-order and zero-order production or decay, or, (2b) transport of thermal energy in the groundwater and solid matrix of the aquifer. SUTRA provides, as the primary calculated results, fluid pressures and either solute concentrations or temperatures, as they vary with time, everywhere in the simulated subsurface system. SUTRA may also be used to simulate simpler subsets of the above process. SUTRA may be employed for areal and cross-sectional models of saturated groundwater flow systems, and for cross-sectional models of unsaturated zone flow. Solute transport simulation using SUTRA may be used to simulate natural or man-induced chemical transport, solute sorption, production and decay. SUTRA may be used for simulation of variable density leachate movement, and for cross-sectional simulation of salt-water intrusion in aquifers at near-well or regional scales, with either dispersed or relatively sharp transition zones between fresh water and salt water. SUTRA energy transport simulation may be employed to model thermal regimes in aquifers, subsurface heat conduction, aquifer thermal energy storage systems, geothermal reservoirs, thermal pollution of aquifers, and natural hydrogeologic convection systems. (USGS)

  6. Fiber optic chemical sensors on Mars

    Energy Technology Data Exchange (ETDEWEB)

    Butler, M.A.; Ricco, A.J. [Sandia National Labs., Albuquerque, NM (United States); Grunthaner, F.J.; Lane, A.L. [Jet Propulsion Lab., Pasadena, CA (United States)

    1993-12-31

    A fiber optic chemical sensing instrument is described that will measure the reactivity of the martian soil and atmosphere. The self- contained instrument monitors reflectivity changes in reactive thin films caused by chemical reactions with the martian soil or atmosphere. Data from over 200 separate thin-film-coated optical fibers are recorded simultaneously. This fiber optic sensing technology has many advantages for planetary exploration and monitoring applications on manned spacecraft, in addition to many practical terrestrial uses.

  7. A Universal Reactive Machine

    DEFF Research Database (Denmark)

    Andersen, Henrik Reif; Mørk, Simon; Sørensen, Morten U.

    1997-01-01

    Turing showed the existence of a model universal for the set of Turing machines in the sense that given an encoding of any Turing machine asinput the universal Turing machine simulates it. We introduce the concept of universality for reactive systems and construct a CCS processuniversal in the...... sense that, given an encoding of any CCS process, it behaves like this process up to weak bisimulation. This construction has arather non-constructive use of silent actions and we argue that this would be the case for any universal CCS process....

  8. Relationship between Structural Characteristics of Fly Ash and Reactivity under Autoclave Curing

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The reactivity of autoclaved materials is conventionally estimated by their chemical composition. In this paper, after determining the chemical composition of various types of fly ash, a series of new tests which included X-ray Diffraction (XRD), infrared spectral analysis (IR) and bound water testing, were applied to investigate the performance of autoclaved fly ash products. The relationship between the infrared spectral analysis of Si-O wavenumber (about 1 100 cm-1) and its autoclaved chemical reactivity, and compressive strength of its autoclaved samples, is analyzed. The results show that fly ash with a lower wavenumber will have stronger autoclaved chemical reactivity and higher compressive strength for its autoclaved sample. Thus, the Si-O stretching vibration wavelength can be used to estimate autoclaved chemical reactivity of fly ash, so as to control the quality of fly ash to be autoclaved, and to predict the compressive strength of autoclaved fly ash products.

  9. Iron topochemistry and surface reactivity of amphibole asbestos: relations with in vitro toxicity

    Energy Technology Data Exchange (ETDEWEB)

    Pacella, Alessandro; Andreozzi, Giovanni B. [Sapienza Universita di Roma, Dipartimento di Scienze della Terra, Rome (Italy); Fournier, Jeanine [UPMC Paris VI, UMR 7197, Laboratoire de Reactivite de Surface, Paris (France); Stievano, Lorenzo [UPMC Paris VI, UMR 7197, Laboratoire de Reactivite de Surface, Paris (France); Institut Charles Gerhardt-AIME, UMR CNRS 5253, Universite Montpellier 2, Montpellier (France); Giantomassi, Federica; Lucarini, Guendalina; Rippo, Maria Rita; Pugnaloni, Armanda [Universita' Politecnica delle Marche, Dipartimento di Scienze Cliniche e Molecolari, Torrette (Ancona) (Italy)

    2012-01-15

    Chemical reactivity of asbestos tremolite from Italy and USA localities and Union Internationale Contre le Cancer (UICC) crocidolite was studied in relation to Fe content, oxidation state, and structural coordination. Direct correlation between amount of Fe{sup 2+} at the exposed M(1) and M(2) sites of the amphibole structure and fiber chemical reactivity was established. The in vitro toxicity of the same samples was investigated on human alveolar A549 cell line. Relationship between crystal-chemical features and cell toxicity is not straightforward. UICC crocidolite has Fe content and chemical reactivity largely higher than that of tremolite samples, but all show comparable in vitro toxic potential. Results obtained evidenced that Fe topochemistry is not a primary factor for induced cell toxicity, though it accounts for asbestos chemical reactivity (and possibly genotoxicity). (orig.)

  10. Reactive sputter deposition of boron nitride

    International Nuclear Information System (INIS)

    The preparation of fully dense, boron targets for use in planar magnetron sources has lead to the synthesis of Boron Nitride (BN) films by reactive rf sputtering. The deposition parameters of gas pressure, flow and composition are varied along with substrate temperature and applied bias. The films are characterized for composition using Auger electron spectroscopy, for chemical bonding using Raman spectroscopy and for crystalline structure using transmission electron microscopy. The deposition conditions are established which lead to the growth of crystalline BN phases. In particular, the growth of an adherent cubic BN coating requires 400--500 C substrate heating and an applied -300 V dc bias

  11. Leaching of Pyrites of Various Reactivities by Thiobacillus ferrooxidans

    OpenAIRE

    Baldi, Franco; Clark, Thomas; Pollack, S. S.; Olson, Gregory J.

    1992-01-01

    Wide variations were found in the rate of chemical and microbiological leaching of iron from pyritic materials from various sources. Thiobacillus ferrooxidans accelerated leaching of iron from all of the pyritic materials tested in shake flask suspensions at loadings of 0.4% (wt/vol) pulp density. The most chemically reactive pyrites exhibited the fastest bioleaching rates. However, at 2.0% pulp density, a delay in onset of bioleaching occurred with two of the pyrites derived from coal source...

  12. Unusual reactivity of MoS2 nanosheets

    Science.gov (United States)

    Mondal, Biswajit; Som, Anirban; Chakraborty, Indranath; Baksi, Ananya; Sarkar, Depanjan; Pradeep, Thalappil

    2016-05-01

    The reactivity of the 2D nanosheets of MoS2 with silver ions in solution, leading to their spontaneous morphological and chemical transformations, is reported. This unique reactivity of the nanoscale form of MoS2 was in stark contrast to its bulk counterpart. While the gradual morphological transformation involving several steps has been captured with an electron microscope, precise chemical identification of the species involved was achieved by electron spectroscopy and mass spectrometry. The energetics of the system investigated supports the observed chemical transformation. The reaction with mercury and gold ions shows similar and dissimilar reaction products, respectively and points to the stability of the metal-sulphur bond in determining the chemical compositions of the final products.The reactivity of the 2D nanosheets of MoS2 with silver ions in solution, leading to their spontaneous morphological and chemical transformations, is reported. This unique reactivity of the nanoscale form of MoS2 was in stark contrast to its bulk counterpart. While the gradual morphological transformation involving several steps has been captured with an electron microscope, precise chemical identification of the species involved was achieved by electron spectroscopy and mass spectrometry. The energetics of the system investigated supports the observed chemical transformation. The reaction with mercury and gold ions shows similar and dissimilar reaction products, respectively and points to the stability of the metal-sulphur bond in determining the chemical compositions of the final products. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr00878j

  13. Removal of reactive dyes from wastewater by shale

    OpenAIRE

    Jareeya Yimrattanabovorn; Somchai Dararat; Sairoong Nopkhuntod

    2012-01-01

    Colored textile effluents represent severe environmental problems as they contain mixture of chemicals, auxiliariesand dyestuffs of different classes and chemical constitutions. Elimination of dyes in the textile wastewater by conventionalwastewater treatment methods is very difficult. At present, there is a growing interest in using inexpensive and potentialmaterials for the adsorption of reactive dyes. Shale has been reported to be a potential media to remove color from wastewaterbecause of...

  14. Controlling Material Reactivity Using Architecture.

    Science.gov (United States)

    Sullivan, Kyle T; Zhu, Cheng; Duoss, Eric B; Gash, Alexander E; Kolesky, David B; Kuntz, Joshua D; Lewis, Jennifer A; Spadaccini, Christopher M

    2016-03-01

    3D-printing methods are used to generate reactive material architectures. Several geometric parameters are observed to influence the resultant flame propagation velocity, indicating that the architecture can be utilized to control reactivity. Two different architectures, channels and hurdles, are generated, and thin films of thermite are deposited onto the surface. The architecture offers an additional route to control, at will, the energy release rate in reactive composite materials. PMID:26669517

  15. Does oligomerization in fused thiophene affect reactivity and aromaticity?

    Indian Academy of Sciences (India)

    Siddhartha Kr Purkayastha; Pradip Kr Bhattacharyya

    2016-02-01

    Reactivity and aromaticity of a few fused thiophene oligomers and their conformers are discussed in the light of density functional theory (DFT) and conceptual density functional theory. Reactivity parameters, such as hardness () and electrophilicity (), chemical potential () and energy of the HOMO (highest occupied molecular orbital) have been studied. Oligomerization raises the HOMO of the species, which in turn increases the reactivity of the oligomers. The absorption spectra of the species are analysed using TDDFT (time dependent density functional theory). The absorption peaks show red shift with increasing size of the oligomers. Aromaticity of the species is gauged by nucleus independent chemical shift (NICS). The out-of-plane component, (NICSzz) values advocate higher aromatic character at longer distance whereas, NICS supports the reverse.

  16. Development and applications of reactive transport models in the framework of the reactive transport consortium (PGT)

    International Nuclear Information System (INIS)

    Full text of publication follows: Reactive transport models permit the simulation of hydrodynamic migration of reactive chemicals through different types of media. They have proven to be highly effective tools to better understand and predict the long-term evolution of geo-materials and the fate of hazardous substances in hydrodynamic systems via a wide variety of applications in different domains and at different scales. In an attempt to correctly represent a large number of simultaneously occurring processes, instances of these models tend to become increasingly complex. Accordingly, the efforts to develop, test and validate the model largely exceed the scope of a single laboratory and the timescale of a Ph.D. thesis. The Reactive Transport Consortium (PGT or 'Pole Geochimie-Transport') is a national research project with the objective of creating a long-term framework for the development of reactive transport models, reference studies and new application domains. Already operational for several years, the collaborative efforts within the PGT have allowed considerable progress to be made in the domain of reactive transport modelling, including generalized kinetics, reactive processes in unsaturated medium, complex boundary conditions, code parallelization and strong coupling between geochemistry, porosity and hydrodynamic parameters. The resulting code is applied to a wide variety of domains at different scales. This paper outlines the objectives, structure, operation mode and main results of the PGT. Model performance will be illustrated by simulations with a focus on subsystems of a radioactive waste repository, i.e. the waste glass, clay-concrete interface and excavation damaged zone (EDZ). (authors)

  17. Reclamation of reactive metal oxides from complex minerals using alkali roasting and leaching- an improved approach to process engineering

    OpenAIRE

    Sanchez Segado, S; Makanyire, T; Escudero-Castejon, L; Hara, Y.; Jha, A.

    2015-01-01

    In nature, the commonly occurring reactive metal oxides of titanium, chromium, aluminium, and vanadium often chemically combine with the transition metal oxides such as iron oxides and form complex minerals. Physico-chemical separation of transition metal oxides from the remaining reactive metal oxides is therefore an important step in the purification of reactive oxide constituents. Each purification step has quite a high energy requirement at present. Current practice in industry yields sul...

  18. 杭州市道路空气中挥发性有机物及其大气化学反应活性研究%Analysis of volatile organic compounds (VOCs) and their atmospheric chemical reactivity in ambient air around urban traffic roads in Hangzhou

    Institute of Scientific and Technical Information of China (English)

    应方; 包贞; 杨成军; 姚琳; 朱利中; 焦荔; 洪盛茂

    2012-01-01

    Volatile organic compounds(VOCs) in the ambient air were measured around main types of urban traffic roads (tunnel,expressway,trunk road and brach) from October 2010 to July 2011 in Hangzhou,China.The results showed that VOC concentration around the traffic roads was much higher than that in scenic spot,and the concentration decreased with the decrease of vehicle flow rate.Source apportionment results indicated that the VOCs in Hangzhou mainly came from anthropogenic sources,including vehicle emission,solvent evaporation,biomass fuel and coal burning.The VOCs around the traffic roads were mainly influenced by vehicle emissions,while the VOCs in scenic spot were more readily impacted by biomass fuel or coal burning.The concentration and chemical reactivity of VOCs around expressway was the highest in summer and lowest in spring,which was influenced by vehicle emissions,temperature,biogenic VOC and topographic conditions.Alkenes and aromatic compounds from the vehicle emissions contributed more than 80% of the VOCs reactivity in the air around all kinds of the traffic roads,suggesting that the VOCs reactivity in ambient air in Hangzhou was determined mainly by vehicle emissions.In summer and autumn,the emission of isoprene from plants increased the VOCs reactivity in the air around roads remarkably.%研究了夏季杭州市主要类型道路(隧道、快速道路、主干道和支路)空气中挥发性有机物的污染特征,以及2010年11月—2011年7月间快速道路空气中VOC的季节变化规律.分析结果表明,杭州市道路空气中VOC浓度显著大于风景区内VOC浓度,隧道浓度最高(828.4μg·m-3),其它道路空气中VOC浓度随着车流量减少而降低.源解析结果发现道路空气中VOC的主要贡献者为机动车排放,但同时也受到溶剂挥发、煤或生物质燃烧的影响,风景区内VOC则受煤或生物质燃料燃烧的影响更大.快速道路空气中VOC浓度和反应活性由机动车排放、植物排

  19. Bonding, aromaticity and reactivity patterns in some all-metal and non-metal clusters

    Indian Academy of Sciences (India)

    S Duley; S Giri; A Chakraborty; P K Chattaraj

    2009-09-01

    Several sandwich-like metal clusters have been studied at the B3LYP/6-311 + G∗ level of theory. Bonding and reactivity have been analysed through various geometrical parameters and conceptual density functional theory based global reactivity descriptors. Aromaticity patterns have been understood in terms of the associated nucleus independent chemical shift values. Possibility of bond-stretch isomerism in some doped clusters is explored. Preferable sites for electrophilic and nucleophilic attacks have been identified using different local reactivity descriptors.

  20. Reactive multilayers fabricated by vapor deposition: A critical review

    International Nuclear Information System (INIS)

    Reactive multilayer thin films are a class of energetic materials that continue to attract attention for use in joining applications and as igniters. Generally composed of two reactants, these heterogeneous solids can be stimulated by an external source to promptly release stored chemical energy in a sudden emission of light and heat. In this critical review article, results from recent investigations of these materials are discussed. Discussion begins with a brief description of the vapor deposition techniques that provide accurate control of layer thickness and film composition. More than 50 reactive film compositions have been reported to date, with most multilayers fabricated by magnetron sputter deposition or electron-beam evaporation. In subsequent sections, we review how multilayer ignition threshold, reaction rate, and total heat are tailored via thin film design. For example, planar multilayers with nanometer-scale periodicity exhibit rapid, self-sustained reactions with wavefront velocities up to 100 m/s. Numeric and analytical models have elucidated many of the fundamental processes that underlie propagating exothermic reactions while demonstrating how reaction rates vary with multilayer design. Recent, time-resolved diffraction and imaging studies have further revealed the phase transformations and the wavefront dynamics associated with propagating chemical reactions. Many reactive multilayers (e.g., Co/Al) form product phases that are consistent with published equilibrium phase diagrams, yet a few systems, such as Pt/Al, develop metastable products. The final section highlights current and emerging applications of reactive multilayers. Examples include reactive Ni(V)/Al and Pd/Al multilayers which have been developed for localized soldering of heat-sensitive components. - Highlights: • Vapor-deposited, reactive multilayers and their properties are reviewed. • This article includes discussion of various structure-property relationships.

  1. Massive florid reactive periostitis

    International Nuclear Information System (INIS)

    Florid reactive periostitis is a rare, benign process usually occurring in the small, tubular bones of the hands and feet. Typically the lesion occurs in an adolescent or young adult and presents as a small area of pain and erythema over the affected bone. Although the histologic features may suggest malignancy, there is usually little radiographic evidence to support such a diagnosis. In the following report an unusual example of this entity is described whose large size and relentless local progression led to initial diagnostic uncertainty and eventual aggressive management. This case suggests that a wide spectrum of radiologic and morphologic changes may be seen in this entity and that a seemingly unrelated genetic disease may alter the typical clinical course. (orig.)

  2. New extraction techniques on bioseparations: 1. Reactive extraction

    OpenAIRE

    Cascaval Dan; Galaction Anca-Irina

    2004-01-01

    The complexity of downstream processes for biosynthetic products constitutes a particularity of industrial biotechnologies, especially because of the biosynthetic product high dilution in fermentation broth, their chemical and thermal liability and the presence of secondary products. For these reasons, new separation techniques have been developed and applied to bioseparations. Among them, reactive extraction, pertraction (extraction and transport through liquid membranes) and direct extracti...

  3. Fluctuating hydrodynamics of multi-species reactive mixtures.

    Science.gov (United States)

    Bhattacharjee, Amit Kumar; Balakrishnan, Kaushik; Garcia, Alejandro L; Bell, John B; Donev, Aleksandar

    2015-06-14

    We formulate and study computationally the fluctuating compressible Navier-Stokes equations for reactive multi-species fluid mixtures. We contrast two different expressions for the covariance of the stochastic chemical production rate in the Langevin formulation of stochastic chemistry, and compare both of them to predictions of the chemical master equation for homogeneous well-mixed systems close to and far from thermodynamic equilibrium. We develop a numerical scheme for inhomogeneous reactive flows, based on our previous methods for non-reactive mixtures [Balakrishnan , Phys. Rev. E 89, 013017 (2014)]. We study the suppression of non-equilibrium long-ranged correlations of concentration fluctuations by chemical reactions, as well as the enhancement of pattern formation by spontaneous fluctuations. Good agreement with available theory demonstrates that the formulation is robust and a useful tool in the study of fluctuations in reactive multi-species fluids. At the same time, several problems with Langevin formulations of stochastic chemistry are identified, suggesting that future work should examine combining Langevin and master equation descriptions of hydrodynamic and chemical fluctuations. PMID:26071701

  4. Fluctuating hydrodynamics of multi-species reactive mixtures

    Energy Technology Data Exchange (ETDEWEB)

    Bhattacharjee, Amit Kumar; Donev, Aleksandar [Courant Institute of Mathematical Sciences, New York University, 251 Mercer Street, New York, New York 10012 (United States); Balakrishnan, Kaushik [Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, California 91109 (United States); Garcia, Alejandro L. [Department of Physics and Astronomy, San Jose State University, 1 Washington Square, San Jose, California 95192 (United States); Bell, John B. [Computational Research Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720 (United States)

    2015-06-14

    We formulate and study computationally the fluctuating compressible Navier-Stokes equations for reactive multi-species fluid mixtures. We contrast two different expressions for the covariance of the stochastic chemical production rate in the Langevin formulation of stochastic chemistry, and compare both of them to predictions of the chemical master equation for homogeneous well-mixed systems close to and far from thermodynamic equilibrium. We develop a numerical scheme for inhomogeneous reactive flows, based on our previous methods for non-reactive mixtures [Balakrishnan , Phys. Rev. E 89, 013017 (2014)]. We study the suppression of non-equilibrium long-ranged correlations of concentration fluctuations by chemical reactions, as well as the enhancement of pattern formation by spontaneous fluctuations. Good agreement with available theory demonstrates that the formulation is robust and a useful tool in the study of fluctuations in reactive multi-species fluids. At the same time, several problems with Langevin formulations of stochastic chemistry are identified, suggesting that future work should examine combining Langevin and master equation descriptions of hydrodynamic and chemical fluctuations.

  5. Reactivity of surface carbonaceous intermediates. Doctoral thesis

    Energy Technology Data Exchange (ETDEWEB)

    Koerts, T.

    1992-06-19

    The study has concentrated on two reactions both related with carbon-carbon bond formation on transition metal catalysts. The first concerns the influences of a vanadium promoter on the kinetics of elementary reaction steps upon synthesis gas conversion on a rhodium catalyst. The second is related to the general problem of initiating a carbon-carbon bond between two methane molecules. Both reactions occur via reactive C1 surface intermediates. These surface species were created from CO and CH4 respectively. Mainly transient kinetic techniques were used which were combined with some quantum chemical calculations. The influence of a vanadium promoter on the formation and intrinsic reactivity of CHx species adsorbed on rhodium catalysts, for hydrogenation, chaingrowth and CO insertion, has also been investigated. On rhodium catalysts a very reactive C1 intermediate was found to be formed from dissociative CO adsorption. The formation of the surface species was found to be enhanced by vanadium promotion, which lowers the activation energy for CO dissociation.

  6. Advanced oxidation of acid and reactive dyes

    DEFF Research Database (Denmark)

    Arslan-Alaton, I.; Gursoy, B.H.; Schmidt, Jens Ejbye

    2008-01-01

    The effect of untreated and Fenton-treated acid dyes (C.I. Acid Red 183 and C.I. Acid Orange 51) and a reactive dye (C.I. Reactive Blue 4) on aerobic, anoxic and anaerobic processes was investigated. The optimum Fe2+:H2O2 molar ratio was selected as 1:5 (4:hsp sp="0.25" mM:20:hsp sp="0.25"mM) for...... 10:hsp sp="0.25" min Fenton treatment at pH 3, resulting in reduced chemical oxygen demand and dissolved organic carbon removal efficiencies; only acetate was detected as a stable dye oxidation end product. During anaerobic digestion, 100, 29% and no inhibition in methane production was observed for...... the untreated blue, red and orange dyes, respectively. The inhibitory effect of the blue reactive dye on methane production was ∼21% after Fenton treatment. Neither untreated nor treated dyes exhibited an inhibitory effect on denitrification. Aerobic glucose degradation was inhibited by 23-29% by...

  7. Simulation of reactive processes related to biodegradation in aquifers. 1. Structure of the three-dimensional reactive transport model

    Science.gov (United States)

    Schäfer, Dirk; Schäfer, Wolfgang; Kinzelbach, Wolfgang

    1998-05-01

    The reactive transport model TBC (transport, biochemistry, and chemistry) numerically solves the equations for reactive transport in three-dimensional saturated groundwater flow. A finite element approximation and a standard Galerkin method are used. Solute transport is coupled to microbially mediated organic carbon degradation. Microbial growth is assumed to follow Monod-type kinetics. Substrate consumption and release of metabolic products is coupled to microbial growth via yield coefficients and stoichiometric relations. Additionally, the effects of microbial activity on selected inorganic chemical species in the aquifer can be considered. TBC allows the user to specify a wide range of possible biochemical and chemical reactions in the input file. This makes TBC a powerful and flexible simulation tool. It was developed to simulate reactive processes related to in situ bioremediation, but further fields of application are laboratory column studies on redox processes coupled to organic carbon degradation, field cases of intrinsic biodegradation, and early diagenetic processes in sediments.

  8. Concurrent transport of reactive and non-reactive ions in undisturbed soil columns

    Directory of Open Access Journals (Sweden)

    Pachepsky Y.A.

    2004-06-01

    Full Text Available Advective-dispersive contaminant transport in soils continues to be a subject of extensive studies. Transport of conservative tracers, ie non-reactive ions, is mostly affected by soil physical heterogeneity that causes differences in mobility of different parts of soil solution. Transport of reactive contaminants is affected by both physical and chemical heterogeneity. The objective of this study was to observe the effects of soil structure and flow velocity on the transport of reactive calcium and sodium ions. Undisturbed southern chernozem and chestnut soil columns were used to monitor the concurrent chloride, calcium and sodium transport in slow-flow and fast-flow breakthrough experiments. Parameters of the advective-dispersive transport were estimated by fitting the advective-dispersive equation to the reduced break-through data. At low velocities, transport seemed to occur in pores having a wide range of effective diameters. Diffusion and slow transport in fine pores caused slow effluent concentration changes at the late stages of the transport. Creating fast flow resulted in a decrease in the proportion of pore space providing the initial breakthrough and in an increase in the proportion of pore space participating in the diffusion-driven mass exchange as compared with the slow-flow transport. Transport of reactive ions was affected by the flow rates in the same way as the transport of the conservative tracers. Flow rate effects on the transport were more pronounced in the chestnut soil that had poorer structure as compared with the chernozem soil.

  9. Solar light-induced production of reactive oxygen species by single walled carbon nanotubes in water

    Science.gov (United States)

    Photosensitizing processes of engineered nanomaterials (ENMs) which include photo-induced production of reactive oxygen species (ROS) convert light energy into oxidizing chemical energy that mediates transformations of nanomaterials. The oxidative stress associated with ROS may p...

  10. Weigle Reactivation in Acinetobacter Calcoaceticus

    DEFF Research Database (Denmark)

    Berenstein, Dvora

    1982-01-01

    Weigle (W)-reactivation was demonstrated in Acinetobacter calcoaceticus for the UV-irra-diated lysogenic phage P78. The reactivation factor (survival of irradiated phage on irradiated bacteria/ survival on unirradiated bacteria) reached a maximum value of 20. This was obtained at UV-doses giving ...

  11. Weigle Reactivation in Acinetobacter Calcoaceticus

    DEFF Research Database (Denmark)

    Berenstein, Dvora

    1982-01-01

    Weigle (W)-reactivation was demonstrated in Acinetobacter calcoaceticus for the UV-irra-diated lysogenic phage P78. The reactivation factor (survival of irradiated phage on irradiated bacteria/ survival on unirradiated bacteria) reached a maximum value of 20. This was obtained at UV-doses giving...

  12. Regarding KUR Reactivity Measurement System

    International Nuclear Information System (INIS)

    This article reported: (1) the outline of the reactivity measurement system of Kyoto University Research Reactor (KUR), (2) the calibration data of control rod, (3) the problems and the countermeasures for range switching of linear output meter. For the laptop PC for the reactivity measurement system, there are four input signals: (1) linear output meter, (2) logarithmic output meter, (3) core temperature gauge, and (4) control rod position. The hardware of reactivity measurement system is controlled with Labview installed on the laptop. Output, reactivity, reactor period, and the change in reactivity due to temperature effect or Xenon effect are internally calculated and displayed in real-time with Labview based on the four signals above. Calculation results are recorded in the form of a spreadsheet. At KUR, the reactor core arrangement was changed, so the control rod was re-calibrated. At this time, calculated and experimental values of reactivity based on the reactivity measurement system were compared, and it was confirmed that the reactivity calculation by Labview was accurate. The range switching of linear output meter in the nuclear instrumentation should automatically change within the laptop, however sometimes this did not function properly in the early stage. It was speculated that undefined percent values during the transition of percent value were included in the calculation and caused calculation errors. The range switching started working properly after fixing this issue. (S.K.)

  13. Development of numerical methods for reactive transport

    International Nuclear Information System (INIS)

    When a radioactive waste is stored in deep geological disposals, it is expected that the waste package will be damaged under water action (concrete leaching, iron corrosion). Then, to understand these damaging processes, chemical reactions and solutes transport are modelled. Numerical simulations of reactive transport can be done sequentially by the coupling of several codes. This is the case of the software platform ALLIANCES which is developed jointly with CEA, ANDRA and EDF. Stiff reactions like precipitation-dissolution are crucial for the radioactive waste storage applications, but standard sequential iterative approaches like Picard's fail in solving rapidly reactive transport simulations with such stiff reactions. In the first part of this work, we focus on a simplified precipitation and dissolution process: a system made up with one solid species and two aqueous species moving by diffusion is studied mathematically. It is assumed that a precipitation dissolution reaction occurs in between them, and it is modelled by a discontinuous kinetics law of unknown sign. By using monotonicity properties, the convergence of a finite volume scheme on admissible mesh is proved. Existence of a weak solution is obtained as a by-product of the convergence of the scheme. The second part is dedicated to coupling algorithms which improve Picard's method and can be easily used in an existing coupling code. By extending previous works, we propose a general and adaptable framework to solve nonlinear systems. Indeed by selecting special options, we can either recover well known methods, like nonlinear conjugate gradient methods, or design specific method. This algorithm has two main steps, a preconditioning one and an acceleration one. This algorithm is tested on several examples, some of them being rather academical and others being more realistic. We test it on the 'three species model'' example. Other reactive transport simulations use an external chemical code CHESS. For a

  14. A Tariff for Reactive Power

    Energy Technology Data Exchange (ETDEWEB)

    Kueck, John D [ORNL; Kirby, Brendan J [ORNL; Li, Fangxing [ORNL; Tufon, Christopher [Pacific Gas and Electric Company; Isemonger, Alan [California Independent System Operator

    2008-07-01

    Two kinds of power are required to operate an electric power system: real power, measured in watts, and reactive power, measured in volt-amperes reactive or VARs. Reactive power supply is one of a class of power system reliability services collectively known as ancillary services, and is essential for the reliable operation of the bulk power system. Reactive power flows when current leads or lags behind voltage. Typically, the current in a distribution system lags behind voltage because of inductive loads such as motors. Reactive power flow wastes energy and capacity and causes voltage droop. To correct lagging power flow, leading reactive power (current leading voltage) is supplied to bring the current into phase with voltage. When the current is in phase with voltage, there is a reduction in system losses, an increase in system capacity, and a rise in voltage. Reactive power can be supplied from either static or dynamic VAR sources. Static sources are typically transmission and distribution equipment, such as capacitors at substations, and their cost has historically been included in the revenue requirement of the transmission operator (TO), and recovered through cost-of-service rates. By contrast, dynamic sources are typically generators capable of producing variable levels of reactive power by automatically controlling the generator to regulate voltage. Transmission system devices such as synchronous condensers can also provide dynamic reactive power. A class of solid state devices (called flexible AC transmission system devices or FACTs) can provide dynamic reactive power. One specific device has the unfortunate name of static VAR compensator (SVC), where 'static' refers to the solid state nature of the device (it does not include rotating equipment) and not to the production of static reactive power. Dynamic sources at the distribution level, while more costly would be very useful in helping to regulate local voltage. Local voltage regulation would

  15. Chemical labeling of electrochemically cleaved peptides

    NARCIS (Netherlands)

    Roeser, Julien; Alting, Niels F. A.; Permentier, Hjalmar P.; Bruins, Andries P.; Bischoff, Rainer P. H.

    2013-01-01

    RATIONALE Cleavage of peptide bonds C-terminal to tyrosine and tryptophan after electrochemical oxidation may become a complementary approach to chemical and enzymatic cleavage. A chemical labeling approach specifically targeting reactive cleavage products is presented here and constitutes a promisi

  16. Generalized Reactive Manufacturing System

    Institute of Scientific and Technical Information of China (English)

    李蓓智

    2001-01-01

    Generalized reactive manufacturing system named GRMS is introduced. GRMS is a human-centered system based on Multi-agent. Its management and control organization is made up of three types of agents named device agent,task agent and shop-floor agent. GRMS adopts a top down and bottom- up competition and cooperation strategy based on the dynamic sifter and funnel To constrain the behavior of agents, a reward and penaity policy is introduced into the system and the closed-loop adjustment of GRMS is realized through such policy.Agents for the same task should be cooperated with each other and agents for different tasks should compete for survival in the dynamic changing environment. A distributed-hierarchical architecture with three levels of master-slave relationships among agents are proposed.Self-propelled process planning is also discussed. In order to evaluate GRMS, a time-driven simulation system-GRMOSS is developed to check the physical consistency of GRMS.

  17. Reactivation with productivity

    International Nuclear Information System (INIS)

    A market to five years that it will move near $63.000 millions, starting from the production of 254.000 reserves that Ecopetrol requires for its maintenance and operation, it was projected with base in the offer study and it demands that they carried out the universities Javeriana and Industrial of Santander for the Colombian Company of Petroleum around the metal mechanic sector. In accordance with the figures of the report, Ecopetrol, like one of the state entities selected by the national government to design pilot programs, guided to reactivate the Colombian industry; it is projecting a good perspective for the Colombian economy and the invigoration of the national productive sector. In practical terms, the report points out that Ecopetrol, in its different operative centers, will require in next five years the quantity of had restored before mentioned in the lines of mechanical stamps, centrifugal bombs, inter chambers of heat, compressors and valves of security; pieces that are elaborated by international makers in 99%. To produce them nationally would represent to the company an economy of 52% of the total value of the purchases in next five years and a reduction of time of delivery of 17 weeks to one week

  18. Reactivity measurement in estimation of benzoquinone and benzoquinone derivatives' allergenicity.

    Science.gov (United States)

    Mbiya, Wilbes; Chipinda, Itai; Simoyi, Reuben H; Siegel, Paul D

    2016-01-01

    Benzoquinone (BQ) and benzoquinone derivatives (BQD) are used in the production of dyes and cosmetics. While BQ, an extreme skin sensitizer, is an electrophile known to covalently modify proteins via Michael Addition (MA) reaction whilst halogen substituted BQD undergo nucleophilic vinylic substitution (SNV) mechanism onto amine and thiol moieties on proteins, the allergenic effects of adding substituents on BQ have not been reported. The effects of inserting substituents on the BQ ring has not been studied in animal assays. However, mandated reduction/elimination of animals used in cosmetics testing in Europe has led to an increased need for alternatives for the prediction of skin sensitization potential. Electron withdrawing and electron donating substituents on BQ were assessed for effects on BQ reactivity toward nitrobenzene thiol (NBT). The NBT binding studies demonstrated that addition of EWG to BQ as exemplified by the chlorine substituted BQDs increased reactivity while addition of EDG as in the methyl substituted BQDs reduced reactivity. BQ and BQD skin allerginicity was evaluated in the murine local lymph node assay (LLNA). BQD with electron withdrawing groups had the highest chemical potency followed by unsubstituted BQ and the least potent were the BQD with electron donating groups. The BQD results demonstrate the impact of inductive effects on both BQ reactivity and allergenicity, and suggest the potential utility of chemical reactivity data for electrophilic allergen identification and potency ranking. PMID:26612505

  19. A Hydrazine Leak Sensor Based on Chemically Reactive Thermistors

    Science.gov (United States)

    Davis, Dennis D.; Mast, Dion J.; Baker, David L.

    1999-01-01

    Leaks in the hydrazine supply system of the Shuttle APU can result in hydrazine ignition and fire in the aft compartment of the Shuttle. Indication of the location of a leak could provide valuable information required for operational decisions. WSTF has developed a small, single use sensor for detection of hydrazine leaks. The sensor is composed of a thermistor bead coated with copper(II) oxide (CuO) dispersed in a clay or alumina binder. The CuO-coated thermistor is one of a pair of closely located thermistors, the other being a reference. On exposure to hydrazine the CuO reacts exothermically with the hydrazine and increases the temperature of the coated-thermistor by several degrees. The temperature rise is sensed by a resistive bridge circuit and an alarm registered by data acquisition software. Responses of this sensor to humidity changes, hydrazine concentration, binder characteristics, distance from a liquid leak, and ambient pressure levels as well as application of this sensor concept to other fluids are presented.

  20. A soluble, low-temperature thermochromic and chemically reactive polydiacetylene.

    Science.gov (United States)

    Park, In Sung; Park, Hye Jin; Kim, Jong-Man

    2013-09-11

    The majority of polydiacetylenes (PDAs) described to date display thermochromic transitions above room temperature. By following a strategy that employs headgroups that do not participate in strong interactions, we have designed and prepared a liquid diacetylene (DA) monomer that solidifies at a temperature near 0 °C. The isocyanate-containing DA monomer, DA-NCO, having this property does not undergo polymerization in its liquid state at room temperature. However, UV irradiation of frozen DA-NCO at 0 °C causes the instantaneous formation of a blue PDA (PDA-NCO). Interestingly, PDA-NCO was found to display a sharp blue-to-red color transition at a temperature near 11 °C. By taking advantage of its room temperature liquid-phase property, we were able to readily transfer the DA monomer to solid substrates by using common stamping and writing methods used for creating patterned PDA images. In addition, PDA-NCO dissolves in chloroform, giving a yellow solution that becomes red and simultaneously generates polymer aggregates when hexane is added. Finally, the isocyanate moieties present in PDA-NCO have been utilized to differentiate 1° from 2° and 3° amines owing to the fact that a chloroform solution of PDA-NCO undergoes a rapid yellow-to-red color change associated with an insoluble urea-forming reaction with primary amines. PMID:23964929

  1. Physico-chemical modification of asphalt bitumens by reactive agents

    OpenAIRE

    Cuadri Vega, Antonio Abad

    2013-01-01

    Bitumen, a by-product from crude oil distillation, has long been used in numerous engineering applications that range from the construction of road pavements to waterproof membranes for the roofing industry. On account of its properties (impermeability, adhesiveness, elasticity, ductility, etc.), bitumen is the most suitable material to be used as a binder of mineral aggregates for paving industry, and consequently, roads are mainly constructed using a composite mixture of bitumen (~ 5 wt.%) ...

  2. EFFECTS OF THERMAL TREATMENTS ON THE CHEMICAL REACTIVITY OF TRICHLOROETHYLENE

    Science.gov (United States)

    A series of experiments was completed to investigate abiotic degradation and reaction product formation of trichloroethylene (TCE) when heated. A quartz-tube apparatus was used to study short residence time and high temperature conditions that are thought to occur during thermal ...

  3. Reduce Plasticizer Migration by Modification of PVC during Reactive Processing

    Institute of Scientific and Technical Information of China (English)

    XINGXS; SCOTTG

    2003-01-01

    Plasticizers in plasticized polyvinyl chloride (PVC) are generally physically added into PVC by compounding so that they can be rapidly leached from PVC articles during service. This results in their migration into the human environment with potentially serious consequences and lower effectiveness of the additives in PVC. Potentially the chemical modification of PVC during processing via reactive processing procedure is one of the most attractive solutions to these problems. In this paper, we will report our work in exploring an environmentally friendly and cost-effective reactive processing approach for chemically binding plasticizer into PVC chains. Our research results indicate that it is possible to reduce the plasticizer migration from a plasticized PVC by chemically binding of a certain plasticizer into PVC chains via reactive processing. Thus, high levels of binding of DBM,a maleate plasticizer, to PVC may be reached in less than 10 min under prevailing reactive processing conditions. The extent of binding of DBM as a function of the loading shows two peaks: one at a relatively low loading (less than 0.12 mol·kg-1 PVC) tends to 100%, the other in the high loading region (more than 1.5 mol·kg-1 PVC) approaches around 50%. The DBM modified PVC polymer exhibits behaviours as a plasticized PVC but its bound plasticising groups would not be leached by solvent extraction.

  4. Reduce Plasticizer Migration by Modification of PVC during Reactive Processing

    Institute of Scientific and Technical Information of China (English)

    XING X S; SCOTT G

    2003-01-01

    Plasticizers in plasticized polyvinyl chloride (PVC) are generally physically added into PVC by compounding so that they can be rapidly leached from PVC articles during service. This results in their migration into the human environment with potentially serious consequences and lower effectiveness of the additives in PVC. Potentially the chemical modification of PVC during processing via reactive processing procedure is one of the most attractive solutions to these problems.In this paper, we will report our work in exploring an environmentally friendly and cost-effective reactive processing approach for chemically binding plasticizer into PVC chains.Our research results indicate that it is possible to reduce the plasticizer migration from a plasticized PVC by chemically binding of a certain plasticizer into PVC chains via reactive processing. Thus, high levels of binding of DBM, a maleate plasticizer, to PVC may be reached in less than 10 min under prevailing reactive processing conditions. The extent of binding of DBM as a function of the loading shows two peaks: one at a relatively low loading (less than 0.12 mol*kg-1 PVC) tends to 100%, the other in the high loading region (more than 1.5 mol*kg-1 PVC) approaches around 50%. The DBM modified PVC polymer exhibits behaviours as a plasticized PVC but its bound plasticising groups would not be leached by solvent extraction.

  5. Laboratory Research into Permeable Reactive Barriers for Groundwater Remediation

    Institute of Scientific and Technical Information of China (English)

    Anthony Adzomani; Jun Dong; Yan Jin

    2003-01-01

    Permeable Reactive Barriers (PRB) is a new technology for groundwater pollution remediation. Contaminants are converted into harmless by products in situ as the polluted water passes through a reactive wall. Experimental results demonstrate how reactive media can be used to remove contaminants from polluted water by laying the reactive wall across the flow direction of the water. The most comprehensively studied and applied reactive barrier type uses granulated Zero Valent Iron (ZVI) particles. In this process elemental iron provides a reducing environment which makes reductive dechlorination of chlorinated organic compounds feasible or changes redox sensitive metals, so that they are immobilized by a precipitation reaction. A reactive wall column which is made up of ZVI, sand and zeolite has shown the highest contaminant removal capacity compared to the other two which have different components. The potentials of ZVI, zeolite and Powdered Activated Carbon (PAC) to remove contaminants are due to their different physico-chemical proper-ties which make them to "sorb"metal contaminants. The results of this experiment show that PRB technology is an efficient method for the treatment of leachate-contaminated groundwater.

  6. Direct numerical simulations of high speed reactive mixing layers

    International Nuclear Information System (INIS)

    The present work is devoted to the analysis of ignition phenomena in high speed turbulent reactive flows. From the computational modelling point of view, this requires to account accurately for the competition between molecular diffusion effects and chemical kinetics as well as complex flowfield structures that may feature shock and expansion waves. Some results of direct numerical simulations of the multicomponent, compressible, reactive Navier-Stokes equations are reported here for the particular case of a two-dimensional mixing layer. Special emphasis is placed on the effects associated with heat release.

  7. Reactivity of carborane-4 in the water vapor medium

    International Nuclear Information System (INIS)

    Reactivity of carborane-4 with respect to water vapor was investigated with the use of shock tubes and fast compression plant. Reculiarities of interaction of mentioned components in the mixture 0.056C-2B4H6+0.444H2O+0.5Ar were determined. It was established that carborane reacted intensively with water vapor at temperatures above 1300 K, its reactivity at that exceeded one of hydrogen in the air. Chemical activity of carborane in water vapor medium decreased almost by two orders with decrease of temperature from 1000 to 900 K

  8. Quantitative assessment of reactive oxygen species generation by cavitation incepted efficiently using nonlinear propagation effect

    Science.gov (United States)

    Yasuda, Jun; Yoshizawa, Shin; Umemura, Shin-ichiro

    2015-10-01

    Sonodynamic treatment is a treatment method that uses chemical bio-effect of cavitation bubbles. Reactive oxygen species that can kill cancerous tissue is induced by such chemical effect of cavitation bubbles and it is important to generate them efficiently for effective sonodynamic treatment. Cavitation cloud can be formed by an effect of nonlinear propagation and focus and in this study, it was experimentally investigated if cavitation cloud was useful for efficient generation of reactive oxygen species. As a result, it was demonstrated that cavitation cloud would be useful for efficient generation of reactive oxygen species.

  9. Conservation of reactive electromagnetic energy in reactive time

    CERN Document Server

    Kaiser, Gerald

    2015-01-01

    The complex Poynting theorem (CPT) is extended to a canonical time-scale domain $(t,s)$. Time-harmonic phasors are replaced by the positive-frequency parts of general fields, which extend analytically to complex time $t+is$, with $s>0$ interpreted as a time resolution scale. The real part of the extended CPT gives conservation in $t$ of a time-averaged field energy, and its imaginary part gives conservation in $s$ of a time-averaged reactive energy. In both cases, the averaging windows are determined by a Cauchy kernel of width $\\Delta t\\sim \\pm s$. This completes the time-harmonic CPT, whose imaginary part is generally supposed to be vaguely `related to' reactive energy without giving a conservation law, or even an expression, for the latter. The interpretation of $s$ as reactive time, tracking the leads and lags associated with stored capacitative and inductive energy, gives a simple explanation of the volt-ampere reactive (var) unit measuring reactive power: a var is simply one Joule per reactive second. T...

  10. Modification of Bitumen with Desulfurized Crumb Rubber in the Present of Reactive Additives

    Institute of Scientific and Technical Information of China (English)

    YE Zhigang; ZHANG Yuzhen; KONG Xianming

    2005-01-01

    Bitumen was modified with desulfurized crumb rubber (DCR) in the present of reactive additives. The effect of the kinds and content of the reactive additive on properties of DCR modified bitumen (DCRMB) was investigated. The morphology of DCRMB was characterized by SEM and the changes of the chemical structure of DCRMB without and with the addition of the reactive additive were analyzed by FTIR. The experimented results show that the softening point,the elasticity recovery and the storage stability of DCRMB were improved significantly by the addition of the reactive additive. This is because that a network structure of rubber in DCRMB was formed and the chemical reaction between C=C double bonds in bitumen and DCR has happened after the reactive additive was added into DCRMB.

  11. Functional reactive paradigm advantages for Android development

    OpenAIRE

    SUTULA ALEXANDER

    2015-01-01

    This article describes conceptual difference between imperative, reactive paradigms and functional reactive style advantages in Android development. Solutions of imperative paradigm main problems are described.

  12. Major reactive species of ambient volatile organic compounds (VOCs) and their sources in Beijing

    Institute of Scientific and Technical Information of China (English)

    SHAO Min; FU Linlin; LIU Ying; LU Sihua; ZHANG Yuanhang; TANG Xiaoyan

    2005-01-01

    Volatile organic compounds (VOCs) are important precursors of atmospheric chemical processes. As a whole mixture, the ambient VOCs show very strong chemical reactivity. Based on OH radical loss rates in the air, the chemical reactivity of VOCs in Beijing was calculated. The results revealed that alkenes, accounting for only about 15% in the mixing ratio of VOCs, provide nearly 75% of the reactivity of ambient VOCs and the C4 to C5 alkenes were the major reactive species among the alkenes. The study of emission characteristics of various VOCs sources indicated that these alkenes are mainly from vehicle exhaust and gasoline evaporation. The reduction of alkene species in these two sources will be effective in photochemical pollution control in Beijing.

  13. Chemical use

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This is a summary of research and activities related to chemical use on Neal Smith National Wildlife Refuge between 1992 and 2009. The chemicals used on the Refuge...

  14. TOUGH2, Unsaturated Ground Water and Heat Transfer - T2VOC, H2O, Air, VOC Flow Simulation in Porous Multidimensional Media - iTOUGH2, Inverse Modeling for TOUGH2 Multiphase Flow Simulators - TOUGHREACT, Chemically reactive non-isothermal flows of multiphase fluids in porous and fractured media - TMVOCV1.0, Multicomponent, multiphase, nonisothermal flows of water, soil gas, volatile organic chemicals (VOCs) - ECO2N, a TOUGH2 fluid property module for mixtures of water-NaCl-CO2

    International Nuclear Information System (INIS)

    multiphase, multicomponent, non-isothermal flows in fractured-porous media. TOUGHREACT is a numerical simulation program for chemically reactive non-isothermal flows of multiphase fluids in porous and fractured media. TMVOC is a simulator for multicomponent, multiphase, nonisothermal flows of water, soil gas, and several volatile organic chemicals (VOCs). TMVOC is designed for applications to contamination problems that involve hydrocarbon fuel or organic solvent spills in saturated and unsaturated zones. ECO2N is a fluid property module for the TOUGH2 simulator (Version 2.0) that was designed for applications to geologic sequestration of CO2 in saline aquifers. 2 - Method of solution: TOUGH2V2.0 performs a fully-coupled, simultaneous solution of mass and energy balance for multi-component, multi-phase fluids in permeable media coupled with a multiphase extension of Darcy's Law, and Fickian diffusion and dispersion. iTOUGH2 solves the inverse problem by automatically calibrating a TOUGH2 model against observed data. Any TOUGH2 input parameter can be estimated based on any observation for which a corresponding TOUGH2 output can be calculated. iTOUGH2 runs in three application modes: - Sensitivity Analysis; - Parameter Estimation; - Uncertainty Propagation Analysis. TMVOC input files are very similar to T2VOC input files. Slight revisions in T2VOC input files are required in data blocks CHEMP for VOC parameters. ECO2N: The partitioning of H2O and CO2 between liquid and gas phases is modeled as a function of temperature, pressure, and salinity, using the recently developed correlations of Spycher and Pruess (2005). Dissolution and precipitation of salt is treated by means of local equilibrium solubility. 3 - Restrictions on the complexity of the problem: Storage requirements increase with number of grid blocks (mesh size). Maximum problem dimensions can be specified through parameter statements in the main program, or through an include file

  15. Reactive, anomalous compression in shocked polyurethane foams

    Science.gov (United States)

    Dattelbaum, Dana M.; Coe, Joshua D.; Kiyanda, Charles B.; Gustavsen, Richard L.; Patterson, Brian M.

    2014-05-01

    We present the results of plate impact experiments performed on 30%-75% porous, polymeric methylene diphenyl diisocyanate polyurethane foams. The combination of new data with those previously obtained on full-density material was used to calibrate complete equations-of-state under both inert and chemically reactive frameworks. Description of unreacted polyurethane was based on a combination of Hayes and P-α models, whereas its decomposition products were predicted via free energy minimization under the assumption of chemical and thermodynamic equilibrium. Correspondence of experiment and theory suggests that polyurethane at all densities decomposes when shocked above some threshold pressure, and that this threshold falls dramatically as a function of initial porosity. The shock locus of foams at 50% or less of theoretical maximum density was found "anomalous" in the sense that final volumes increased with pressure. We attribute this anomaly to chemical decomposition of the initial matrix to a mixture of small-molecule fluids and bulk carbon (graphite or diamond, depending on the initial density).

  16. Reactive, anomalous compression in shocked polyurethane foams

    International Nuclear Information System (INIS)

    We present the results of plate impact experiments performed on 30%–75% porous, polymeric methylene diphenyl diisocyanate polyurethane foams. The combination of new data with those previously obtained on full-density material was used to calibrate complete equations-of-state under both inert and chemically reactive frameworks. Description of unreacted polyurethane was based on a combination of Hayes and P-α models, whereas its decomposition products were predicted via free energy minimization under the assumption of chemical and thermodynamic equilibrium. Correspondence of experiment and theory suggests that polyurethane at all densities decomposes when shocked above some threshold pressure, and that this threshold falls dramatically as a function of initial porosity. The shock locus of foams at 50% or less of theoretical maximum density was found “anomalous” in the sense that final volumes increased with pressure. We attribute this anomaly to chemical decomposition of the initial matrix to a mixture of small-molecule fluids and bulk carbon (graphite or diamond, depending on the initial density)

  17. The ionising radiation effect on reactivation of antibiotics

    International Nuclear Information System (INIS)

    The effect of gamma-radiation on the molecular structure of antibiotics was studied with a view to extending their useful life beyond the current expiration period. The following antibiotics were examined: penicillin, bicillin-3,5, streptomycine, and ampioxe. The samples were irradiated by Co-60 gamma-radiation from a research irradiator. Doses of 0.1, 1, 5, 7, and 10 Gy were applied. The processes were elucidated using the classical method of 2-divisible serial dilutions and IR-spectroscopy. All the measurements were carried out at 300 K. The IR-spectra revealed that the chemical structure of new and old antibiotics is identical; the change in the antibiotic activity is generally a result of deformation of the molecule or change in its conformation; the reactivation process returns the molecule to its previous state and the activity of antibiotic after reactivation meets established standards. Hence, this method can be used for the reactivation of expired antibiotics

  18. Chemical sensor

    Science.gov (United States)

    Rauh, R. David (Inventor)

    1990-01-01

    A sensor for detecting a chemical substance includes an insertion element having a structure which enables insertion of the chemical substance with a resulting change in the bulk electrical characteristics of the insertion element under conditions sufficient to permit effective insertion; the change in the bulk electrical characteristics of the insertion element is detected as an indication of the presence of the chemical substance.

  19. Complex Chemical Reaction Networks from Heuristics-Aided Quantum Chemistry

    OpenAIRE

    Rappoport, Dmitrij; Galvin, Cooper J.; Zubarev, Dmitry; Aspuru-Guzik, Alan

    2014-01-01

    While structures and reactivities of many small molecules can be computed efficiently and accurately using quantum chemical methods, heuristic approaches remain essential for modeling complex structures and large-scale chemical systems. Here, we present a heuristics-aided quantum chemical methodology applicable to complex chemical reaction networks such as those arising in cell metabolism and prebiotic chemistry. Chemical heuristics offer an expedient way of traversing high-dimensional reacti...

  20. Utilization of chemical looping strategy in coal gasification processes

    Institute of Scientific and Technical Information of China (English)

    Liangshih Fan; Fanxing Li; Shwetha Ramkumar

    2008-01-01

    Three chemical looping gasification processes, i. e. Syngas Chemical Looping (SCL) process, Coal Direct Chemical Looping (CDCL) process, and Calcium Looping process (CLP), are being developed at the Ohio State University (OSU). These processes utilize simple reaction schemes to convert carbonaceous fuels into products such as hydrogen, electricity, and synthetic fuels through the transformation of a highly reactive, highly recyclable chemical intermediate. In this paper, these novel chemical looping gasification processes are described and their advantages and potential challenges for commercialization are discussed.

  1. OH Reactivity Observations during the MAPS-Seoul Campaign: Contrasts between Urban and Suburban Environments

    Science.gov (United States)

    Sanchez, D.; Jeong, D.; Blake, D. R.; Wang, M. D.; Kim, D. S.; Lee, G.; Lee, M.; Jung, J.; Ahn, J.; Cho, G.; Guenther, A. B.; Kim, S.

    2015-12-01

    Direct total OH reactivity was observed in the urban and suburban environments of Seoul, South Korea using a comparative reactivity method (CRM) during the MAPS-Seoul field campaign. In addition, CO, NOx, SO2, ozone, VOCs, aerosol, physical, and chemical parameters were also deployed. By comparing the observed total OH reactivity results with calculated OH reactivity from the trace gas observational datasets, we will evaluate our current status in constraining reactive gases in the urban and suburban environments in the East Asian megacity. Observed urban OH reactivity will be presented in the context of the ability to constrain anthropogenic reactive trace gas emissions. It will then be compared to the observed suburban results from Taehwa Research Forest (located ~ 50 km from the Seoul City Center). Our understanding of reactive trace gases in an environment of high BVOC emissions in a mildly aged anthropogenic influences will be evaluated. Using an observational constrained box model with detailed VOC oxidation schemes (e.g. MCM), we will discuss: 1) what is the amount of missing OH reactivity 2) what are the potential sources of the missing OH reactivity, and 3) what are the implications on regional air quality?

  2. Reactivity monitoring in ADS systems

    International Nuclear Information System (INIS)

    Monitoring reactivity in an ADS should be performed on-line with a simple, accurate and robust technique. Within the range of experimental reactor techniques, no single technique can be selected which meet these requirements. Therefore a combination of different techniques has to be chosen in a way that various off-line techniques serve as a calibration for the on-line measurement technique. As an on-line measurement technique, the current/flux reactivity indicator is the most simple and robust solution. It is based on the fact that in a subcritical multiplying medium with a driving source the flux level is proportional to the driving source intensity, hence the beam current, and the reactivity level. However, since the proportionality constant depends on a number of core dependent parameters and detector characteristics, this current-to-flux indicator has to be calibrated on a regular basis. For this calibration, one could benefit from the occurrence of accelerator beam trips to determine the reactivity level in dollars by means of a prompt jump analysis of the flux level change. Hence, the prompt jump reactivity indicator could act as a first calibration tool of the current-to-flux indicator. Since the prompt jump indicator still relies on the value for the effective delayed neutron fraction to determine reactivity level, complementary techniques have to be used to obtain a more accurate determination of the reactivity. Techniques based on reactor noise methods such as RAPJA technique which is combination of the Rossi-alpha method and Prompt jump analysis can be used in this respect. In the future the bi-spectral ratio from the Cf - source driven noise analysis could be used for this purpose. (author)

  3. Thiol-reactivity of the fungicide maneb

    Directory of Open Access Journals (Sweden)

    James R. Roede

    2014-01-01

    Full Text Available Maneb (MB is a manganese-containing ethylene bis-dithiocarbamate fungicide that is implicated as an environmental risk factor for Parkinson's disease, especially in combination with paraquat (PQ. Dithiocarbamates inhibit aldehyde dehydrogenases, but the relationship of this to the combined toxicity of MB + PQ is unclear because PQ is an oxidant and MB activates Nrf2 and increases cellular GSH without apparent oxidative stress. The present research investigated the direct reactivity of MB with protein thiols using recombinant thioredoxin-1 (Trx1 as a model protein. The results show that MB causes stoichiometric loss of protein thiols, reversibly dimerizes the protein and inhibits its enzymatic activity. MB reacted at similar rates with low-molecular weight, thiol-containing chemicals. Together, the data suggest that MB can potentiate neurotoxicity of multiple agents by disrupting protein thiol functions in a manner analogous to that caused by oxidative stress, but without GSH depletion.

  4. Thiol-reactivity of the fungicide maneb.

    Science.gov (United States)

    Roede, James R; Jones, Dean P

    2014-01-01

    Maneb (MB) is a manganese-containing ethylene bis-dithiocarbamate fungicide that is implicated as an environmental risk factor for Parkinson's disease, especially in combination with paraquat (PQ). Dithiocarbamates inhibit aldehyde dehydrogenases, but the relationship of this to the combined toxicity of MB + PQ is unclear because PQ is an oxidant and MB activates Nrf2 and increases cellular GSH without apparent oxidative stress. The present research investigated the direct reactivity of MB with protein thiols using recombinant thioredoxin-1 (Trx1) as a model protein. The results show that MB causes stoichiometric loss of protein thiols, reversibly dimerizes the protein and inhibits its enzymatic activity. MB reacted at similar rates with low-molecular weight, thiol-containing chemicals. Together, the data suggest that MB can potentiate neurotoxicity of multiple agents by disrupting protein thiol functions in a manner analogous to that caused by oxidative stress, but without GSH depletion. PMID:24936438

  5. Chemical machining

    Directory of Open Access Journals (Sweden)

    A. Yardimeden

    2007-08-01

    Full Text Available Purpose: Nontraditional machining processes are widely used to manufacture geometrically complex and precision parts for aerospace, electronics and automotive industries. There are different geometrically designed parts, such as deep internal cavities, miniaturized microelectronics and fine quality components may only be produced by nontraditional machining processes. This paper is aiming to give details of chemical machining process, industrial applications, applied chemical etchants and machined materials. Advantages and disadvantages of the chemical machining are mentioned.Design/methodology/approach: In this study, chemical machining process was described its importance as nontraditional machining process. The steps of process were discussed in detail. The tolerances of machined parts were examined.Findings: Paper describes the chemical machining process, industrial applications, applied chemical etchants and machined materials.Practical implications: The machining operation should be carried out carefully to produce a desired geometry. Environmental laws have important effects when chemical machining is used.Originality/value: The importance of nontraditional machining processes is very high.

  6. Chemical Leukoderma.

    Science.gov (United States)

    Bonamonte, Domenico; Vestita, Michelangelo; Romita, Paolo; Filoni, Angela; Foti, Caterina; Angelini, Gianni

    2016-01-01

    Chemical leukoderma, often clinically mimicking idiopathic vitiligo and other congenital and acquired hypopigmentation, is an acquired form of cutaneous pigment loss caused by exposure to a variety of chemicals that act through selective melanocytotoxicity. Most of these chemicals are phenols and aromatic or aliphatic catechols derivatives. These chemicals, however, are harmful for melanocytes in individuals with an individual susceptibility. Nowadays, chemical leukoderma is fairly common, caused by common domestic products. The presence of numerous acquired confetti- or pea-sized macules is clinically characteristic of chemical leukoderma, albeit not diagnostic. Other relevant diagnostic elements are a history of repeated exposure to a known or suspected depigmenting agent at the sites of onset and a macules distribution corresponding to sites of chemical exposure. Spontaneous repigmentation has been reported when the causative agent is avoided; the repigmentation process is perifollicular and gradual, taking place for a variable period of weeks to months. PMID:27172302

  7. Preparation of reactive fibre interfaces using multifunctional cellulose derivatives.

    Science.gov (United States)

    Vega, Beatriz; Wondraczek, Holger; Bretschneider, Leonore; Näreoja, Tuomas; Fardim, Pedro; Heinze, Thomas

    2015-11-01

    Cellulose fibres have poor reactivity and limited potential for surface engineering with advanced chemical functionalization in water. In this work, cellulose fibres were decorated with azide functions by charge-directed self-assembly of a novel water-soluble multifunctional cellulose derivative yielding reactive fibres. Propargylamine and 1-ethynylpyrene were utilized as a proof of concept that alkyne molecules may react with the azide functions of the reactive fibres via copper(I)-catalyzed azide-alkyne Huisgen cycloaddition (CuAAc) reaction in mild conditions. Chemical characterization of the fibres was carried out using classical techniques such as Raman-, fluorescence-, and UV-vis spectroscopy. Among other techniques, time-of-flight secondary ion mass spectrometry (ToF-SIMS), X-ray spectroscopy (XPS), two-photon microscopy (TPM), and inductively coupled plasma mass spectrometry (ICP-MS) were useful tools for additional characterization of the fibres decorated with amino- or photoactive groups. The information gathered in this work might contribute to the basis for the preparation of reactive cellulose-based interfaces with potential application in CuAAc reactions. PMID:26256349

  8. Simulations of reactive transport and precipitation with smoothed particle hydrodynamics

    Science.gov (United States)

    Tartakovsky, Alexandre M.; Meakin, Paul; Scheibe, Timothy D.; Eichler West, Rogene M.

    2007-03-01

    A numerical model based on smoothed particle hydrodynamics (SPH) was developed for reactive transport and mineral precipitation in fractured and porous materials. Because of its Lagrangian particle nature, SPH has several advantages for modeling Navier-Stokes flow and reactive transport including: (1) in a Lagrangian framework there is no non-linear term in the momentum conservation equation, so that accurate solutions can be obtained for momentum dominated flows and; (2) complicated physical and chemical processes such as surface growth due to precipitation/dissolution and chemical reactions are easy to implement. In addition, SPH simulations explicitly conserve mass and linear momentum. The SPH solution of the diffusion equation with fixed and moving reactive solid-fluid boundaries was compared with analytical solutions, Lattice Boltzmann [Q. Kang, D. Zhang, P. Lichtner, I. Tsimpanogiannis, Lattice Boltzmann model for crystal growth from supersaturated solution, Geophysical Research Letters, 31 (2004) L21604] simulations and diffusion limited aggregation (DLA) [P. Meakin, Fractals, scaling and far from equilibrium. Cambridge University Press, Cambridge, UK, 1998] model simulations. To illustrate the capabilities of the model, coupled three-dimensional flow, reactive transport and precipitation in a fracture aperture with a complex geometry were simulated.

  9. Coupled reactive flow modeling with declining reactivity in fractured geothermal systems

    Science.gov (United States)

    Palguta, J.; Williams, C. F.; Ingebritsen, S.; Hickman, S.; Sonnenthal, E. L.

    2011-12-01

    Changes in permeability and fluid flow within geothermal systems are driven by geochemical reactions, advective and diffusive transport of heat and solute mass, and evolving thermal and mechanical environments. Representation of these simultaneous processes in numerical models is required for the characterization and simulation of natural geothermal systems. However, identifying and developing mathematical representations for all of the relevant mechanisms that control system behavior presents a major challenge. We have developed two-dimensional simulations of physical and chemical evolution in fractured granite under geothermal conditions with temperatures ranging from 150-300 °C. The goal of this study is to help identify possible sources for existing discrepancies between model results and laboratory-based measurements by adding a new mathematical formulation to the code TOUGHREACT. The revised code is designed to further quantify the link between the progressive evolution of reaction rates and alteration mineralogy. We explicitly couple reaction rates to mineral precipitation/dissolution effects by using an exponential function that defines evolving reactive surface areas in terms of each of the following (i) the accumulated total secondary mineral volume fraction, (ii) the accumulated clay (smectite) portion of the secondary mineral volume fraction, and (iii) the net change in mineral volume fraction (combined effects of dissolution and precipitation). We evaluate the performance of these three modified approaches by comparing simulation results to detailed laboratory measurements of fluid compositions, mineral abundances, and permeability changes in fractured Westerly granite and to previous one-dimensional simulations in which reactive surface areas were adjusted with time to match the observed fracture permeability history. The simulation results offer a potentially useful means of quantifying reactivity loss and of examining the extent to which secondary

  10. Neurobehavioral foundation of environmental reactivity.

    Science.gov (United States)

    Moore, Sarah R; Depue, Richard A

    2016-02-01

    Sensitivity to environmental context has been of interest for many years, but the nature of individual differences in environmental sensitivity has become of particular focus over the past 2 decades. What is particularly uncertain are the neural variables and processes that mediate the effects of environment on developmental outcomes. Accordingly, we provide a neurobehavioral foundation of reactivity to the environment in several steps. First, the different patterns of environmental sensitivity are defined to identify the significant factors involved in the manifestation of these patterns. Second, we focus on neurobiological reactivity as the construct underlying variation in sensitivity to the environment by (a) providing an organizing threshold model of elicitation of neurobiology by environmental context; and (b) integrating the literature on 2 sets of neuromodulators in terms of each modulator's (a) contribution to neural and behavioral reactivity to stimulation, and (b) relation to emotional-motivational systems (dopamine, opiates and oxytocin, corticotropin-releasing hormone) or the general modulation of those systems (serotonin, norepinephrine, and GABA). Discussion concludes with (a) a comprehensive neurobehavioral framework of environmental reactivity based on a combinatorial model of a supertrait, (b) methodological implications of the model, and (c) a developmental perspective on environmental reactivity. PMID:26479069

  11. Synthesis of functional nanocrystallites through reactive thermal plasma processing

    Directory of Open Access Journals (Sweden)

    Takamasa Ishigaki and Ji-Guang Li

    2007-01-01

    Full Text Available A method of synthesizing functional nanostructured powders through reactive thermal plasma processing has been developed. The synthesis of nanosized titanium oxide powders was performed by the oxidation of solid and liquid precursors. Quench gases, either injected from the shoulder of the reactor or injected counter to the plasma plume from the bottom of the reactor, were used to vary the quench rate, and therefore the particle size, of the resultant powders. The experimental results are well supported by numerical analysis on the effects of the quench gas on the flow pattern and temperature field of the thermal plasma as well as on the trajectory and temperature history of the particles. The plasma-synthesized TiO2 nanoparticles showed phase preferences different from those synthesized by conventional wet-chemical processes. Nanosized particles of high crystallinity and nonequilibrium chemical composition were formed in one step via reactive thermal plasma processing.

  12. Interaction of reactive oily bubble in flotation of bastnaesite

    Institute of Scientific and Technical Information of China (English)

    周芳; 王娄翔; 徐政和; 刘青侠; 池汝安

    2014-01-01

    To understand the flotation mechanism of bastnaesite using reactive oily bubble, the interaction between bastnaesite parti-cles and reactive oily bubbles was investigated by electro-kinetic studies, induction time measurements and small-scale flotation ex-periments. The bastnaesite flotation could be seen as a hetero-coagulation between bastnaesite particles and reactive oily bubbles which was confirmed by the zeta potential distribution and induction time measurements from pH 4.8 to pH 9.0. The small-scale flo-tation tests were consistent with the hetero-coagulation results, and showed a better flotation of reactive oily bubble than air bubble among all pH range. The interaction force between bastnaesite particles and reactive oily bubbles was evaluated by the classical DLVO theory. It indicated that the attachment could be predicted well by the DLVO theory only in a restricted pH range due to the absence of hydrophilic interaction repulsion force and chemical interaction force.

  13. Reactive Nitrogen Emissions from Crop and Livestock Farming in India

    International Nuclear Information System (INIS)

    Recent studies suggest that human activities have accelerated the production and emissions of reactive nitrogen on a global scale. Increased nitrogen emissions may lead to environmental impacts including photochemical air pollution, reduced visibility, changes in biodiversity, and stratospheric ozone depletion. Emissions from agricultural activities, both crop and animal, are known to contain reactive nitrogen compounds. Emissions of reactive nitrogen for India (for the base year 2003 as a case study) from animal and crop farming are analyzed. These emissions are compared and contrasted with global, US, and European reactive nitrogen emissions. Ammonia and nitrous oxide from animal farming in India were estimated at about 1392 Gg NH3-N and 136 Gg N2O-N from livestock; and 2221 Gg NH3-N and 126 Gg N2O-N from fertilizer application. The activity data for all livestock in all the districts were collected from the website of the Department of Animal Husbandry, Dairying and Fisheries; and for fertilizers consumption, the activity data were collected from the Ministry of Chemicals and Fertilizers, Govt. of India. Emission factor suitable for region specific for all sources were utilized. Overall, the Indo-Gangetic basin in the North India had considerably high emissions of all reactive nitrogen components.

  14. First principles study of CO reactivity on metallic nano particles

    OpenAIRE

    Lindberg, Vanja

    2007-01-01

    The activity of a surface is determined by the local electronic structure. When nano particles are adsorbed, the catalytic properties will change. Surfaces with adsorbed nano particles often show a significantly higher chemical reactivity than the clean counterpart. Gold, for instance, shows an extra high activity towards many reactions, such as low-temperature catalytic combustion, partial oxidation of hydrocarbons and CO oxidation when dispersed as ultra-fine particles on metal oxide surfac...

  15. Reactive Distillation for Esterification of Bio-based Organic Acids

    Energy Technology Data Exchange (ETDEWEB)

    Fields, Nathan; Miller, Dennis J.; Asthana, Navinchandra S.; Kolah, Aspi K.; Vu, Dung; Lira, Carl T.

    2008-09-23

    The following is the final report of the three year research program to convert organic acids to their ethyl esters using reactive distillation. This report details the complete technical activities of research completed at Michigan State University for the period of October 1, 2003 to September 30, 2006, covering both reactive distillation research and development and the underlying thermodynamic and kinetic data required for successful and rigorous design of reactive distillation esterification processes. Specifically, this project has led to the development of economical, technically viable processes for ethyl lactate, triethyl citrate and diethyl succinate production, and on a larger scale has added to the overall body of knowledge on applying fermentation based organic acids as platform chemicals in the emerging biorefinery. Organic acid esters constitute an attractive class of biorenewable chemicals that are made from corn or other renewable biomass carbohydrate feedstocks and replace analogous petroleum-based compounds, thus lessening U.S. dependence on foreign petroleum and enhancing overall biorefinery viability through production of value-added chemicals in parallel with biofuels production. Further, many of these ester products are candidates for fuel (particularly biodiesel) components, and thus will serve dual roles as both industrial chemicals and fuel enhancers in the emerging bioeconomy. The technical report from MSU is organized around the ethyl esters of four important biorenewables-based acids: lactic acid, citric acid, succinic acid, and propionic acid. Literature background on esterification and reactive distillation has been provided in Section One. Work on lactic acid is covered in Sections Two through Five, citric acid esterification in Sections Six and Seven, succinic acid in Section Eight, and propionic acid in Section Nine. Section Ten covers modeling of ester and organic acid vapor pressure properties using the SPEAD (Step Potential

  16. Global modeling of organic aerosol: the importance of reactive nitrogen

    OpenAIRE

    H. O. T. Pye; A. W. H. Chan; Barkley, M. P.; Seinfeld, J. H.

    2010-01-01

    Reactive nitrogen compounds, specifically NOx and NO3, likely influence global organic aerosol levels. To assess these interactions, GEOS-Chem, a chemical transport model, is updated to include improved biogenic emissions (following MEGAN v2.1/2.04), a new organic aerosol tracer lumping scheme, aerosol from nitrate radical (NO3) oxidation of isoprene, and NOx-dependent terpene aerosol yields. As a resu...

  17. The reactivity of natural phenols

    Energy Technology Data Exchange (ETDEWEB)

    Denisov, Evgenii T; Denisova, Taisa G [Institute of Problems of Chemical Physics, Russian Academy of Sciences, Chernogolovka, Moscow Region (Russian Federation)

    2009-11-30

    This review surveys physicochemical data of natural phenols published in recent years. The structures of some compounds of this class are given. A complete set of the dissociation energies of the O-H bonds for 71 natural phenols is presented. Kinetic characteristics of the reactions of peroxyl, alkyl and thiyl radicals with natural phenols, exchange reactions of phenoxyl radicals with phenols and reactions of phenoxyl radicals with lipids, hydroperoxides, cysteine and ascorbic acid are compiled and described systematically. The reactivity of phenols in radical reactions and the factors that determine the reactivity (the enthalpy of reaction, triplet repulsion, the electronegativities of atoms at the reaction centre, the presence of pi-electrons adjacent to the reaction centre, the radii of atoms at the reaction centre, steric hindrance, the force constants of the reacting bonds) are discussed. An important role of hydrogen bonding between surrounding molecules and the OH groups of natural phenols in decreasing their reactivities is noted.

  18. Chemical equilibrium modeling of detonation

    Energy Technology Data Exchange (ETDEWEB)

    Fried, Laurence E. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Bastea, Sorin [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2010-05-19

    Energetic materials are unique for having a strong exothermic reactivity, which has made them desirable for both military and commercial applications. Energetic materials are commonly divided into high explosives, propellants, and pyrotechnics. We will focus on high explosive (HE) materials here, although there is a great deal of commonality between the classes of energetic materials. Furthermore the history of HE materials is long, their condensed-phase chemical properties are poorly understood.

  19. Chlorpyrifos Induces the Expression of the Epstein-Barr Virus Lytic Cycle Activator BZLF-1 via Reactive Oxygen Species

    OpenAIRE

    Ling Zhao; Fei Xie; Ting-ting Wang; Meng-yu Liu; Jia-la Li; Lei Shang; Zi-xuan Deng; Peng-xiang Zhao; Xue-mei Ma

    2015-01-01

    Organophosphate pesticides (OPs) are among the most widely used synthetic chemicals for the control of a wide variety of pests, and reactive oxygen species (ROS) caused by OPs may be involved in the toxicity of various pesticides. Previous studies have demonstrated that a reactivation of latent Epstein-Barr virus (EBV) could be induced by oxidative stress. In this study, we investigated whether OPs could reactivate EBV through ROS accumulation. The Raji cells were treated with chlorpyrifos (C...

  20. Modeling the Geochemical Impact of an Injection of CO2 and Associated Reactive Impurities into a Saline Reservoir

    OpenAIRE

    Andre, Laurent; Azaroual, Mohamed; Bernstone, Christian; Wittek, Andrea

    2012-01-01

    Numerical simulations performed with the TOUGHREACT code focus on the chemical reactivity of deep reservoir rock impacted by an injection of CO2 and associated reactive impurities (mainly SO2 and O2). A simplified two-dimensional radial geo-model representing the near wellbore domain of a saline reservoir enabled us to capture the global geochemical behaviour of this underground zone. Two ratios CO2/SO2 are investigated. The results of the numerical simulations highlight the high reactivity o...

  1. Two forms of reactive arthritis?

    OpenAIRE

    Toivanen, P; Toivanen, A

    1999-01-01

    Inflammatory arthritides developing after a distant infection have so far been called reactive or postinfectious, quite often depending on the microbial trigger and/or HLA-B27 status of the patient. For clarity, it is proposed that they all should be called reactive arthritis, which, according to the trigger, occurs as an HLA-B27 associated or non-associated form. In addition to the causative agents and HLA-B27, these two categories are also distinguished by other characteristics. Most import...

  2. Paraneoplastic importance of reactive dermatoses

    Directory of Open Access Journals (Sweden)

    Algün Polat Ekinci

    2013-12-01

    Full Text Available Reactive dermatoses may occur related to many underlying causes including infections, inflammatory diseases, medications and malignancies. In the management of these dermatoses the investigation of underlying cause is crucial besides the therapy of dermatosis. In this review, mainly the paraneoplastic potentials of reactive dermatoses have been evaluated and additionally the etiology, follow-up and treatment have been discussed. Recent literature about figurated erythemas (erythema annulare centrifugum, erythema gyratum repens, necrolytic migratory erythema, neutrophilic dermatoses (Sweet’s syndrome, pyoderma gangrenosum, subcorneal pustular dermatosis and erythema nodosum have been scrutinized.

  3. Chemical networks*

    OpenAIRE

    Thi Wing-Fai

    2015-01-01

    This chapter discusses the fundamental ideas of how chemical networks are build, their strengths and limitations. The chemical reactions that occur in disks combine the cold phase reactions used to model cold molecular clouds with the hot chemistry applied to planetary atmosphere models. With a general understanding of the different types of reactions that can occur, one can proceed in building a network of chemical reactions and use it to explain the abundance of species seen in disks. One o...

  4. Use of Reactive Distillation for Biodiesel Production: A Literature Survey

    Directory of Open Access Journals (Sweden)

    Muhammad Dani Supardan

    2006-06-01

    Full Text Available Biodiesel has been shown to be the best substitute for fossil-based fuels to its environmental advantages and renewable resource availability. There is a great demand for the commercialization of biodiesel production, which in turn calls for a technically and economically reactor technology. The production of biodiesel in existing batch and continuous-flow processes requires excess alcohol, typically 100%, over the stoichiometric molar requirement in order to drive the chemical reaction to completion. In this study, a novel reactor system using a reactive distillation (RD technique was discussed for biodiesel production. RD is a chemical unit operation in which chemical reactions and separations occur simultaneously in one unit. It is an effective alternative to the classical combination of reactor and separation units especially when involving reversible or consecutive chemical reactions such as transesterication process in biodiesel production.

  5. Separability of local reactivity descriptors

    Indian Academy of Sciences (India)

    Akhilesh Tanwar; Sourav Pal

    2005-09-01

    The size-dependence of different local reactivity descriptors of dimer A2 and AB type of systems is discussed. We derive analytic results of these descriptors calculated using finite difference approximation. In particular, we studied Fukui functions, relative electrophilicity and relative nucleophilicity, local softness and local philicity. The results are explained using the example of the dimer of BH3NH3.

  6. Treating water-reactive wastes

    International Nuclear Information System (INIS)

    Some compounds and elements, such as lithium hydride, magnesium, sodium, and calcium react violently with water to generate much heat and produce hydrogen. The hydrogen can ignite or even form an explosive mixture with air. Other metals may react rapidly only if they are finely divided. Some of the waste produced at Los Alamos National Lab. includes these metals that are contaminated with radioactivity. By far the greatest volume of water-reactive waste is lithium hydride contaminated with depleted uranium. Reactivity of the water-reactive wastes is neutralized with an atmosphere of humid nitrogen, which prevents the formation of an explosive mixture of hydrogen and air. When we adjust the temperature of the nitrogen and the humidifier, the nitrogen can be more or less humid, and the rate of reaction can be adjusted and controlled. Los Alamos has investigated the rates of reaction of lithium hydride as a function of the temperature and humidity. Los Alamos will investigate other variables. For example, the nitrogen flow will be optimized to conserve nitrogen and yet keep the reaction rates high. Reaction rates will be determined for various forms of lithium waste, from small chips to powder. Bench work will lead to the design of a skid-mounted process for treating wastes. Other water-reactive wastes will also be investigated

  7. Chemical machining

    OpenAIRE

    A. Yardimeden; T. Ozben; O. Cakir

    2007-01-01

    Purpose: Nontraditional machining processes are widely used to manufacture geometrically complex and precision parts for aerospace, electronics and automotive industries. There are different geometrically designed parts, such as deep internal cavities, miniaturized microelectronics and fine quality components may only be produced by nontraditional machining processes. This paper is aiming to give details of chemical machining process, industrial applications, applied chemical etchants and mac...

  8. Chemical Radioprotectors

    Directory of Open Access Journals (Sweden)

    S. N. Upadhyay

    2005-10-01

    Full Text Available Protection of biological systems against radiation damage is of paramount importance during accidental and unavoidable exposure to radiation. Several physico-chemical and biological factors collectively contribute to the damage caused by radiation and are, therefore, targets for developing radioprotectors. Work on the development of chemicals capable of protecting biological systemsfrom radiation damage was initiated nearly six decades ago with cysteine being the first molecule to be reported. Chemicals capable of scavenging free radicals, inducing oxygen depletion,antioxidants and modulators of immune response have been some of the radioprotectors extensively investigated with limited success. Mechanism of action of some chemical radioprotectors and their combinations have been elucidated, while further understanding is required in many instances. The present review elaborates on structure-activity relationship of some of the chemical radioprotectors, their evaluation, and assessment, limitation, and future prospects.

  9. Airborne measurement of OH reactivity during INTEX-B

    Directory of Open Access Journals (Sweden)

    J. Mao

    2009-01-01

    Full Text Available The measurement of OH reactivity, the inverse of the OH lifetime, provides a powerful tool to investigate atmospheric photochemistry. A new airborne OH reactivity instrument was designed and deployed for the first time on the NASA DC-8 aircraft during the second phase of Intercontinental Chemical Transport Experiment-B (INTEX-B campaign, which was focused on the Asian pollution outflow over Pacific Ocean and was based in Hawaii and Alaska. The OH reactivity was measured by adding OH, generated by photolyzing water vapor with 185 nm UV light in a moveable wand, to the flow of ambient air in a flow tube and measuring the OH signal with laser induced fluorescence. As the wand was pulled back away from the OH detector, the OH signal decay was recorded; the slope of −Δln(signal/Δ time was the OH reactivity. The overall absolute uncertainty at the 2σ confidence levels is about 1 s−1 at low altitudes (for decay about 6 s−1, and 0.7 s−1 at high altitudes (for decay about 2 s−1. From the median vertical profile obtained in the second phase of INTEX-B, the measured OH reactivity (4.0±1.0 s−1 is higher than the OH reactivity calculated from assuming that OH was in steady state (3.3±0.8 s−1, and even higher than the OH reactivity that was calculated from the total measurements of all OH reactants (1.6±0.4 s−1. Model calculations show that the missing OH reactivity is consistent with the over-predicted OH and under-predicted HCHO in the boundary layer and lower troposphere. The over-predicted OH and under-predicted HCHO suggest that the missing OH sinks are most likely related to some highly reactive VOCs that have HCHO as an oxidation product.

  10. Reactive Oxygen Species (ROS) generation by lunar simulants

    Science.gov (United States)

    Kaur, Jasmeet; Rickman, Douglas; Schoonen, Martin A.

    2016-05-01

    The current interest in human exploration of the Moon and past experiences of Apollo astronauts has rekindled interest into the possible harmful effects of lunar dust on human health. In comparison to the Apollo-era explorations, human explorers may be weeks on the Moon, which will raise the risk of inhalation exposure. The mineralogical composition of lunar dust is well documented, but its effects on human health are not fully understood. With the aim of understanding the reactivity of dusts that may be encountered on geologically different lunar terrains, we have studied Reactive Oxygen Species (ROS) generation by a suite of lunar simulants of different mineralogical-chemical composition dispersed in water and Simulated Lung Fluid (SLF). To further explore the reactivity of simulants under lunar environmental conditions, we compared the reactivity of simulants both in air and inert atmosphere. As the impact of micrometeorites with consequent shock-induced stresses is a major environmental factor on the Moon, we also studied the effect of mechanical stress on samples. Mechanical stress was induced by hand crushing the samples both in air and inert atmosphere. The reactivity of samples after crushing was analyzed for a period of up to nine days. Hydrogen peroxide (H2O2) in water and SLF was analyzed by an in situ electrochemical probe and hydroxyl radical (•OH) by Electron Spin Resonance (ESR) spectroscopy and Adenine probe. Out of all simulants, CSM-CL-S was found to be the most reactive simulant followed by OB-1 and then JSC-1A simulant. The overall reactivity of samples in the inert atmosphere was higher than in air. Fresh crushed samples showed a higher level of reactivity than uncrushed samples. Simulant samples treated to create agglutination, including the formation of zero-valent iron, showed less reactivity than untreated simulants. ROS generation in SLF is initially slower than in deionized water (DI), but the ROS formation is sustained for as long as 7

  11. DFT study on structure, electronic properties, and reactivity of cis-isomers of [(NC5H4-S)2Fe(CO)2

    Indian Academy of Sciences (India)

    Charles A Mebi

    2011-09-01

    Three cis-isomers of [(NC5H4-S)2Fe(CO)2], models for the active site of [Fe] hydrogenase, have been examined by computational method at DFT B3LYP/6-311+G(d,p) level. The computed geometric parameters are remarkably close to experimental values. DFT global chemical reactivity descriptors (chemical hardness, total energy, electronic chemical potential, and electrophilicity) are calculated for the isomers and used to predict their relative stability and reactivity. The chemical reactivity indices are found to be related to the bond angle defined by the cis carbonyls and the iron center.

  12. Relationships of coal characteristics to coal reactivity for direct hydrogenation liquefaction

    Energy Technology Data Exchange (ETDEWEB)

    Baldwin, R.M.; Voorhees, K.J.; Durfee, S.L.

    1987-01-01

    Two suites of coals from the US have been liquefied in a batch stirred autoclave reactor under a set of standard conditions. Data from the reactor have permitted both the rate and extent of conversion to be measured. Rate of reaction and extent of conversion of coal have then been used as dependent variables for development of correlations for reactivity with basic coal chemical, geochemical, and structural properties. In general, use of a kinetic definition for reactivity has been shown to be superior in ranking relative reactivities among closely related coals, and for developing correlations with compositional parameters such as volatile matter, reactive macerals, and vitrinite reflectance. Carbon aromaticity as determined by /sup 13/C-NMR and structural parameters as determined by pyrolysis/mass spectrometry have also been found to be useful in providing insight into the relationship between coal structure and coal reactivity. 17 references.

  13. TOURGHREACT: A Simulation Program for Non-isothermal Multiphase Reactive Geochemical Transport in Variably Saturated Geologic Media

    OpenAIRE

    Xu, Tianfu; Sonnenthal, Eric; Spycher, Nicolas; Pruess, Karsten

    2004-01-01

    TOUGHREACT is a numerical simulation program for chemically reactive non-isothermal flows of multiphase fluids in porous and fractured media. The program was written in Fortran 77 and developed by introducing reactive geochemistry into the multiphase fluid and heat flow simulator TOUGH2. A variety of subsurface thermo-physical-chemical processes are considered under a wide range of conditions of pressure, temperature, water saturation, ionic strength, and pH and Eh. Interactions between ...

  14. RETRASO, a code for modeling reactive transport in saturated and unsaturated porous media

    OpenAIRE

    Saaltink, M. W.; Batlle, F.; Ayora, Carlos; Carrera, Jesús; S. Olivella

    2004-01-01

    The code RETRASO (REactive TRAnsport of SOlutes) simulates reactive transport of dissolved and gaseous species in non-isothermal saturated or unsaturated problems. Possible chemical reactions include aqueous complexation (including redox reactions), sorption, precipitation-dissolution of minerals and gas dissolution. Various models for sorption of solutes on solids are available, from experimental relationships (linear KD, Freundlich and Langmuir isotherms) to cation exchange and surface comp...

  15. Numerical Simulation of Reactive Transport Problems in Porous Media Using Global Implicit Approach

    OpenAIRE

    Zolfaghari, Reza

    2016-01-01

    This thesis focuses on solutions of reactive transport problems in porous media. The principle mechanisms of flow and reactive mass transport in porous media are investigated. Global implicit approach (GIA), where transport and reaction are fully coupled, and sequential noniterative approach (SNIA) are implemented into the software OpenGeoSys (OGS6) to couple chemical reaction and mass transport. The reduction scheme proposed by Kräutle is used in GIA to reduce the number of coupled nonlinear...

  16. Do Spin State and Spin Density Affect Hydrogen Atom Transfer Reactivity?

    OpenAIRE

    Saouma, Caroline T.; Mayer, James M.

    2013-01-01

    The prevalence of hydrogen atom transfer (HAT) reactions in chemical and biological systems has prompted much interest in establishing and understanding the underlying factors that enable this reactivity. Arguments have been advanced that the electronic spin state of the abstractor and/or the spin-density at the abstracting atom are critical for HAT reactivity. This is consistent with the intuition derived from introductory organic chemistry courses. Herein we present an alternative view on t...

  17. Non-Natural and Photo-Reactive Amino Acids as Biochemical Probes of Immune Function

    OpenAIRE

    Marta Gómez-Nuñez; Haro, Kurtis J.; Tao Dao; Deming Chau; Annie Won; Sindy Escobar-Alvarez; Victoriya Zakhaleva; Tatyana Korontsvit; Gin, David Y.; Scheinberg, David A.

    2008-01-01

    Wilms tumor protein (WT1) is a transcription factor selectively overexpressed in leukemias and cancers; clinical trials are underway that use altered WT1 peptide sequences as vaccines. Here we report a strategy to study peptide-MHC interactions by incorporating non-natural and photo-reactive amino acids into the sequence of WT1 peptides. Thirteen WT1 peptides sequences were synthesized with chemically modified amino acids (via fluorination and photo-reactive group additions) at MHC and T cell...

  18. Validation of MARTHE-REACT coupled surface and groundwater reactive transport code for modeling hydro systems.

    OpenAIRE

    Thiéry, Dominique; Jacquemet, Nicolas; Picot-Colbeaux, Géraldine; Kervévan, Christophe; André, Laurent; Azaroual, Mohamed

    2009-01-01

    This paper presents the validation of the computer code MARTHE-REACT enabling the simulation of reactive transport in hydrosystems. MARTHE-REACT results from coupling the MARTHE code (flow and transport in porous media) with the chemical simulator TOUGHREACT. The resulting coupled model takes advantage of the functionalities already available in each of the two codes. In particular, it is now possible to simulate flow, reactive mass, and energy transfer in both saturated and unsaturated media...

  19. Types of oil shale ash and methods for increasing their reactivity

    International Nuclear Information System (INIS)

    Ash from the combustion of powdered Estonian oil shale in power plants has a high chemical reactivity and ability to bind hazardous components in the waste from the Sillamaee plant. This characteristic suggests that the ash should be considered as a component of a barrier system for remediation of the tailings pond. Different types of ash, collected in different parts of a power plant, show different reactivities

  20. Synthesis, characterization, and reactivity of pentamethylcyclopentadienyl complexes of divalent cobalt and nickel

    Energy Technology Data Exchange (ETDEWEB)

    Smith, M.E.

    1993-10-01

    The thesis is divided into the following 4 chapters: synthesis, characterization, and reactivity of trinuclear pentamethylcyclopentadienyl cobalt and nickel clusters with triply-bridging methylidyne groups; chemical and physical properties of pentamethylcyclopentadienyl acetylacetonate complexes of Co(II) and Ni(II); synthesis, characterization, and reactivity of pentamethylcyclopentadienyl halide complexes of Co and Ni; and crystallographic studies of distortions in metallocenes with C{sub 5}-symmetrical cyclopentadienyl rings.

  1. Decolorization of reactive violet 5 dye in textile wastewater by electrocoagulation

    OpenAIRE

    Borislav N. Malinovic; MIOMIR G. PAVLOVIC

    2016-01-01

    The textile dyeing industry consumes large quantities of water and produces large volumes of wastewater from different steps in the dyeing and finishing processes. Wastewater from printing and dyeing units is often rich in color, containing residues of reactive dyes and chemicals, such as complex components. This study investigates the decolorization of synthetic dye wastewater containing textile dye Reactive Violet 5 (RV5) by electrocoagulation. A laboratory batch reactor was used to investi...

  2. Chemical mechanisms of the interaction between radiation and chemical carcinogens

    International Nuclear Information System (INIS)

    There is evidence to suggest that ionizing radiation and chemical carcinogens can act synergistically to produce deleterious biological effects. In addition, many carcinogens undergo metabolic activation in vivo. This activation, initiated by biochemical redox reactions, can be simulated chemically, electrochemically, photochemically and radiation chemically. The principal reactive species formed by the action of ionizing radiation on aqueous solutions of macromolecules and mammalian cells, are hydroxyl radicals and superoxide anions. Pulse and steady-state radiolysis studies of model chemical systems have established that these species can 'activate' chemical carcinogens by a radical oxidation process, and that the resulting activated carcinogens can subsequently react with nucleophilic sites on DNA and other potential target macromolecules. Rate constants for some of the fast reactions involved in the radiation activation of carcinogens and in the subsequent carcinogen-DNA interactions have been determined, together with the yields of radiation-induced covalent DNA-carcinogen binding. A redox models for radiation-induced chemical carcinogenesis is proposed which describes a possible mechanism of action involving free radical species generated in the aqueous cellular milieu, which diffuse to and react with carcinogens located within the micro-environment of the cell. Preliminary experiments suggest that protection against radiation and chemical carcinogenesis can be achieved by radical scavenging or by competitive free radical inhibition

  3. Hazardous Chemicals

    Centers for Disease Control (CDC) Podcasts

    2007-04-10

    Chemicals are a part of our daily lives, providing many products and modern conveniences. With more than three decades of experience, The Centers for Disease Control and Prevention (CDC) has been in the forefront of efforts to protect and assess people's exposure to environmental and hazardous chemicals. This report provides information about hazardous chemicals and useful tips on how to protect you and your family from harmful exposure.  Created: 4/10/2007 by CDC National Center for Environmental Health.   Date Released: 4/13/2007.

  4. Fatty acid methyl esters as reactive diluents in solvent-borne thermally cured coil-coatings

    OpenAIRE

    Johansson, Katarina

    2006-01-01

    This work describes how a fatty acid methyl ester (FAME) derived from a vegetable oil can be introduced as reactive diluent in a solvent-borne thermally cured coil-coating system. The evaluated reactive diluent, rape seed methyl ester (RME), has been evaluated both in a fully formulated clear coat system and via model studies. A reactive diluent is a compound that acts as a solvent in the liquid paint, lowering the viscosity, and chemically reacts into the final film during cure. Introduction...

  5. Concepts and methods in modern theoretical chemistry electronic structure and reactivity

    CERN Document Server

    Ghosh, Swapan Kumar

    2013-01-01

    Concepts and Methods in Modern Theoretical Chemistry: Electronic Structure and Reactivity, the first book in a two-volume set, focuses on the structure and reactivity of systems and phenomena. A new addition to the series Atoms, Molecules, and Clusters, this book offers chapters written by experts in their fields. It enables readers to learn how concepts from ab initio quantum chemistry and density functional theory (DFT) can be used to describe, understand, and predict electronic structure and chemical reactivity. This book covers a wide range of subjects, including discussions on the followi

  6. The Reactivity of Energetic Materials At Extreme Conditions

    Energy Technology Data Exchange (ETDEWEB)

    Fried, L E

    2006-10-23

    Energetic materials are unique for having a strong exothermic reactivity, which has made them desirable for both military and commercial applications. Energetic materials are commonly divided into high explosives, propellants, and pyrotechnics. We will focus on high explosive (HE) materials here, although there is a great deal of commonality between the classes of energetic materials. Although the history of HE materials is long, their condensed-phase properties are poorly understood. Understanding the condensed-phase properties of HE materials is important for determining stability and performance. Information regarding HE material properties (for example, the physical, chemical, and mechanical behaviors of the constituents in plastic-bonded explosive, or PBX, formulations) is necessary for efficiently building the next generation of explosives as the quest for more powerful energetic materials (in terms of energy per volume) moves forward. In modeling HE materials there is a need to better understand the physical, chemical, and mechanical behaviors from fundamental theoretical principles. Among the quantities of interest in plastic-bonded explosives (PBXs), for example, are thermodynamic stabilities, reaction kinetics, equilibrium transport coefficients, mechanical moduli, and interfacial properties between HE materials and the polymeric binders. These properties are needed (as functions of stress state and temperature) for the development of improved micro-mechanical models, which represent the composite at the level of grains and binder. Improved micro-mechanical models are needed to describe the responses of PBXs to dynamic stress or thermal loading, thus yielding information for use in developing continuum models. Detailed descriptions of the chemical reaction mechanisms of condensed energetic materials at high densities and temperatures are essential for understanding events that occur at the reactive front under combustion or detonation conditions. Under

  7. Engine combustion control via fuel reactivity stratification

    Energy Technology Data Exchange (ETDEWEB)

    Reitz, Rolf Deneys; Hanson, Reed M.; Splitter, Derek A.; Kokjohn, Sage L.

    2016-06-28

    A compression ignition engine uses two or more fuel charges having two or more reactivities to control the timing and duration of combustion. In a preferred implementation, a lower-reactivity fuel charge is injected or otherwise introduced into the combustion chamber, preferably sufficiently early that it becomes at least substantially homogeneously dispersed within the chamber before a subsequent injection is made. One or more subsequent injections of higher-reactivity fuel charges are then made, and these preferably distribute the higher-reactivity matter within the lower-reactivity chamber space such that combustion begins in the higher-reactivity regions, and with the lower-reactivity regions following thereafter. By appropriately choosing the reactivities of the charges, their relative amounts, and their timing, combustion can be tailored to achieve optimal power output (and thus fuel efficiency), at controlled temperatures (and thus controlled NOx), and with controlled equivalence ratios (and thus controlled soot).

  8. Research Works on Reactivity Measurement in Japan

    International Nuclear Information System (INIS)

    In Japan, many research works have been performed for the wide range of the field on the reactivity measurement from the basic discussion to the application of on-line computers. The works on the reactivity measurement may be classified into the following categories. 1. The theoretical work - on the definition or the meaning of the reactivity and its application to the experiment. 2. The improvement of the principle of the reactivity measurement and its application to the experiment. 3. The works whose interests are in the values of the' reactivity to be measured. 4. Reactivity measurement on the on-power reactor. 5. On-line reactivity measurement. The works on the reactivity measurement in Japan will be briefly reviewed following the above classification

  9. Engine combustion control via fuel reactivity stratification

    Energy Technology Data Exchange (ETDEWEB)

    Reitz, Rolf Deneys; Hanson, Reed M.; Splitter, Derek A.; Kokjohn, Sage L.

    2015-07-14

    A compression ignition engine uses two or more fuel charges having two or more reactivities to control the timing and duration of combustion. In a preferred implementation, a lower-reactivity fuel charge is injected or otherwise introduced into the combustion chamber, preferably sufficiently early that it becomes at least substantially homogeneously dispersed within the chamber before a subsequent injection is made. One or more subsequent injections of higher-reactivity fuel charges are then made, and these preferably distribute the higher-reactivity matter within the lower-reactivity chamber space such that combustion begins in the higher-reactivity regions, and with the lower-reactivity regions following thereafter. By appropriately choosing the reactivities of the charges, their relative amounts, and their timing, combustion can be tailored to achieve optimal power output (and thus fuel efficiency), at controlled temperatures (and thus controlled NOx), and with controlled equivalence ratios (and thus controlled soot).

  10. the Study of Hepatitis B Virus Reactivation

    Institute of Scientific and Technical Information of China (English)

    Zhao-chun Chi

    2014-01-01

    Hepatitis B virus (HBV) reactivation after chemotherapy or immunosuppressive therapy is a cause of liver-related morbidity and mortality. Not all chronic hepatitis B patients will lead to HBV reactivation. The incidence is 0.3%-30.2%according to the reports. The mechanism of HBV reactivation is still unclear, but it is believed that the viral load is increasing due to the suppression of immune response. No uniform diagnostic criteria are available. HBV reactivation can be confirmed by an increase of serum HBV DNA level. Recently, awareness of reactivation of occult HBV has been improved, especially in HBV endemic area. Preemptive antiviral therapy was the best approach to prevent the HBV reactivation. HBV reactivation can lead to acute hepatitis, severe hepatitis and acute liver failure. Therefore, it is worthy of great attention and further study. Antiviral therapy is safe and effective to prevent HBV reactivation.

  11. C-Reactive Protein (CRP) Test

    Science.gov (United States)

    ... Home Visit Global Sites Search Help? C-Reactive Protein Share this page: Was this page helpful? Also known as: CRP Formal name: C-Reactive Protein Related tests: ESR , Complement , Procalcitonin , ANA , Rheumatoid Factor ...

  12. Unnecessary Chemicals

    Science.gov (United States)

    Johnson, Anita

    1978-01-01

    Discusses the health hazards resulting from chemical additions of many common products such as cough syrups, food dyes, and cosmetics. Steps being taken to protect consumers from these health hazards are included. (MDR)

  13. [Acute and subacute chemical pneumonitis].

    Science.gov (United States)

    Andujar, P; Nemery, B

    2009-10-01

    Acute or subacute chemical-induced lung injury is rarely compound specific and is most often caused by an accidental occupational, domestic or environmental exposure to an inhaled chemical agent. The industrial disaster that happened in Bhopal in 1984, accidental poisoning with chlorine and petroleum hydrocarbons and also vesicant gases used during conflicts, are specific examples. Rarely, a chemical agent can cause lung damage by being ingested and reaching the lung through the systemic circulation (for example accidental or deliberate paraquat ingestion). Household accidents should not be underestimated. An important cause of household accidents is chlorine inhalation resulting from mixing bleach with acids such as the scale removers used to clean toilets. Chemical agents can provoke direct and/or indirect damage to the respiratory tract. The acute or subacute clinical manifestations resulting from inhalation of chemical agents are very varied and include inhalation fevers, acute non-cardiogenic pulmonary oedema, adult respiratory distress syndrome, reactive airways dysfunction syndrome and acute or subacute pneumonitis. The site and the severity of chemical-induced respiratory damage caused by inhaled chemical agents depend mainly on the nature and the amount of the agent inhaled. The immediate and long-term prognosis and possible sequelae are also variable. This review excludes infectious or immunologically induced acute respiratory diseases. PMID:19953031

  14. Melioidosis: reactivation during radiation therapy

    International Nuclear Information System (INIS)

    Melioidosis is caused by Pseudomonas pseudomallei, a gram-negative, motile bacillus which is a naturally occurring soil saprophyte. The organism is endemic in Southeast Asia, the Philippines, Australia, and parts of Central and South America. Most human disease occurs from infection acquired in these countries. Infection with P pseudomallei may produce no apparent clinical disease. Acute pneumonitis or septicemia may result from inhalation of the organism, and inoculation into sites of trauma may cause localized skin abscesses, or the disease may remain latent and be reactivated months or years later by trauma, burns, or pneumococcal pneumonia, diabetic ketoacidosis, influenza, or bronchogenic carcinoma. The last is probably the commonest form of melioidosis seen in the United States. We present the first case of reactivation of melioidosis after radiation therapy for carcinoma of the lung, again emphasizing the need to consider melioidosis in a septic patient with a history of travel, especially to Southeast Asia

  15. Melioidosis: reactivation during radiation therapy

    Energy Technology Data Exchange (ETDEWEB)

    Jegasothy, B.V.; Goslen, J.B.; Salvatore, M.A.

    1980-05-01

    Melioidosis is caused by Pseudomonas pseudomallei, a gram-negative, motile bacillus which is a naturally occurring soil saprophyte. The organism is endemic in Southeast Asia, the Philippines, Australia, and parts of Central and South America. Most human disease occurs from infection acquired in these countries. Infection with P pseudomallei may produce no apparent clinical disease. Acute pneumonitis or septicemia may result from inhalation of the organism, and inoculation into sites of trauma may cause localized skin abscesses, or the disease may remain latent and be reactivated months or years later by trauma, burns, or pneumococcal pneumonia, diabetic ketoacidosis, influenza, or bronchogenic carcinoma. The last is probably the commonest form of melioidosis seen in the United States. We present the first case of reactivation of melioidosis after radiation therapy for carcinoma of the lung, again emphasizing the need to consider melioidosis in a septic patient with a history of travel, especially to Southeast Asia.

  16. Chemical kinetics

    International Nuclear Information System (INIS)

    This book gives descriptions of chemical kinetics. It starts summary of chemical kinetics and reaction mechanism, and explains basic velocity law, experiment method for determination of reaction velocity, temperature dependence of reaction velocity, theory of reaction velocity, theory on reaction of unimolecular, process of atom and free radical, reaction in solution, catalysis, photochemical reaction, such as experiment and photochemical law and rapid reaction like flame, beam of molecule and shock tube.

  17. Reactivity of Alkyldibenzothiophenes Using Theoretical Descriptors

    OpenAIRE

    Jose Luis Rivera; Pedro Navarro-Santos; Luis Hernandez-Gonzalez; Roberto Guerra-Gonzalez

    2014-01-01

    Theoretical calculations of the reactivity of dibenzothiophene and its methyl, dimethyl, and trimethyl derivatives show that local reactivity descriptors reproduce their experimental desulfurization reactivity trend if the first desulfurization step involves directly the sulfur atom, which only occurs if the sulfur atom is blocked at most by one methyl group. In the series of molecules {4,7-dimethyldibenzothiophene, x,4,7-trimethyldibenzothiophene (x=1,2,3)}, the most reactive molecule is 2,4...

  18. The iodine reactivity; La reactivite de l'iode

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2003-07-01

    The iodine is an important element because it has long life isotopes (such as iodine 129) and a great mobility in natural media. Iodine presents a complex chemistry because of its volatility and its strong redox reactivity. The S.E.C.R. works to better understand the reactivity of this element in different natural, industrial or biological environments. It plays a part in thermochemical sites as a possible way of hydrogen formation. This seminar gives some aspects relative to the chemical reactivity of iodine, since its thermochemistry in the I/S cycles to produce hydrogen to its reactivity in the natural medium and its potential radiological impact. This document includes 4 presentations transparencies dealing with: the {sup 129}I cycle rejected in the low radioactive gaseous and liquid effluents of the La Hague reprocessing plant (C. Frechou); a bibliographic review of iodine retention in soils (F. Bazer-Bachi); the hydrogen production and the iodine/sulfur thermochemical cycle (role of iodine in the process); and the direct characterization by electro-spray ionization mass spectroscopy of iodine fixation by fulvic acids (P. Reiller, B. Amekraz, C. Moulin, V. Moulin)

  19. Charge inhomogeneity determines oxidative reactivity of graphene on substrates.

    Science.gov (United States)

    Yamamoto, Mahito; Einstein, Theodore L; Fuhrer, Michael S; Cullen, William G

    2012-09-25

    Single-layer graphene (SLG) supported on SiO(2) shows anomalously large chemical reactivity compared to thicker graphene, with charge inhomogeneity-induced potential fluctuations or topographic corrugations proposed as the cause. Here we systematically probe the oxidative reactivity of graphene supported on substrates with different surface roughnesses and charged impurity densities: hexagonal boron nitride (hBN), mica, thermally grown SiO(2) on Si, and SiO(2) nanoparticle thin films. SLG on low charge trap density hBN is not etched and shows little doping after oxygen treatment at temperatures up to 550 °C, in sharp contrast with oxidative etching under similar conditions of graphene on high charge trap density SiO(2) and mica. Furthermore, bilayer graphene shows reduced reactivity compared to SLG regardless of its substrate-induced roughness. Together the observations indicate that graphene's reactivity is predominantly controlled by charge inhomogeneity-induced potential fluctuations rather than surface roughness. PMID:22917254

  20. Sea sand for reactive barriers

    International Nuclear Information System (INIS)

    Some phosphates have the property to suck in radioactive metals in solution, what it is taken in advance to make reactive barriers which are placed in the nuclear waste repositories. In an effort for contributing to the study of this type of materials, it has been obtained the zirconium silicate (ZrSiO4) and the alpha zirconium hydrogen phosphate (Zr(HPO4) 2H2O) starting from sea sand in an easy and economic way. (Author)

  1. Staphylococcus aureus triggered reactive arthritis.

    OpenAIRE

    Siam, A R; M. Hammoudeh

    1995-01-01

    OBJECTIVES--To report two patients who developed reactive arthritis in association with Staphylococcus aureus infection. METHODS--A review of the case notes of two patients. RESULTS--Two adult female patients have developed sterile arthritis in association with Staph aureus infection. The first patient has had two episodes of arthritis; the first followed olecranon bursitis, the second followed infection of a central venous catheter used for dialysis. The second patient developed sterile arth...

  2. Modelling of reactive gas transport

    OpenAIRE

    Sundelöf, Erik

    2003-01-01

    A rather general microscopic model for reactive gastransport in porous media is developed and applied to twodifferent processes in powder metal technology: carburization,and reduction of surface oxides. The carburization model is developed from the kinetic modelproposed by Grabke and applied to a 2-D porous geometryobtained from images. The effect of pore geometry on convectiveand diffusive transport is discussed by model problems andaveraging. The exercise demonstrates the capacity of theFEM...

  3. Reactive thrombocytosis in pulmonary tuberculosis.

    OpenAIRE

    Baynes, R D; Bothwell, T H; Flax, H.; McDonald, T P; Atkinson, P.; Chetty, N.; Bezwoda, W. R.; Mendelow, B V

    1987-01-01

    The incidence of reactive thrombocytosis in active pulmonary tuberculosis was studied in 122 patients. Thrombocytosis was common, platelet counts often exceeding 1 X 10(12)/1. A significant inverse correlation was noted between the mean platelet volume and the platelet count (r = -0.54, p less than 0.0001). Interval estimation suggested that this relation was non-linear. Further studies were done in a small group of six patients. Platelet survival was considerably shortened, the platelets agg...

  4. Oilseed rape and bronchial reactivity.

    OpenAIRE

    Soutar, A; Harker, C; Seaton, A.; Packe, G

    1995-01-01

    OBJECTIVES--To investigate atopy and changes in symptoms, peak flow rate, and bronchial reactivity in people complaining of symptoms during the oilseed rape flowering season. METHODS--37 people who had given positive answers to questions about the presence of symptoms in relation to the flowering season of oilseed rape and 24 controls with no such symptoms were studied, although not all took part in all parts of the study. All had been previously identified in a cross sectional survey of a ra...

  5. SPATIAL DEPENDENCE OF REACTIVITY COEFFICIENTS

    OpenAIRE

    Salah, Sideeg

    2011-01-01

    The objective of this thesis is to study and understand the behavior of the reactivity coefficients (RCs) in a boiling water reactor (BWR) partially within 25 different segments with different void fractions, with enriched oxide fuel (UOX) core, as well as to evaluate the methodologies exposed in [10]. These two normalization  methods (described in chapter 3) are used to analyse the contribution of each segment of the core having different regions (fuel, clad, coolant, moderator and channel b...

  6. Potential energy surfaces for chemical reactions

    International Nuclear Information System (INIS)

    Research into potential energy surfaces for chemical reactions at Lawrence Berkeley Laboratory during 1976 is described. Topics covered include: the fuzzy interface between surface chemistry catalysis and organometallic chemistry; potential energy surfaces for elementary fluorine hydrogen reactions; structure, energetics, and reactivity of carbenes; and the theory of self-consistent electron pairs

  7. Chemical sciences, annual report 1993

    Energy Technology Data Exchange (ETDEWEB)

    1994-10-01

    The Chemical Sciences Division (CSD) is one of eleven research Divisions of the Lawrence Berkeley Laboratory, a DOE National Laboratory. In FY 1993, the Division made considerable progress on developing two end-stations and a beamline to advance combustion dynamics at the Advanced Light Source (ALS). In support of DOE`s national role in combustion research and chemical science, the beamline effort will enable researchers from around the world to make fundamental advances in understanding the structure and reactivity of critical reaction intermediates and transients, and in understanding the dynamics of elementary chemical reactions. The Division has continued to place a strong emphasis on full compliance with environmental health and safety guidelines and regulations and has made progress in technology transfer to industry. Finally, the Division has begun a new program in advanced battery research and development that should help strengthen industrial competitiveness both at home and abroad.

  8. Chemical sciences, annual report 1993

    International Nuclear Information System (INIS)

    The Chemical Sciences Division (CSD) is one of eleven research Divisions of the Lawrence Berkeley Laboratory, a DOE National Laboratory. In FY 1993, the Division made considerable progress on developing two end-stations and a beamline to advance combustion dynamics at the Advanced Light Source (ALS). In support of DOE's national role in combustion research and chemical science, the beamline effort will enable researchers from around the world to make fundamental advances in understanding the structure and reactivity of critical reaction intermediates and transients, and in understanding the dynamics of elementary chemical reactions. The Division has continued to place a strong emphasis on full compliance with environmental health and safety guidelines and regulations and has made progress in technology transfer to industry. Finally, the Division has begun a new program in advanced battery research and development that should help strengthen industrial competitiveness both at home and abroad

  9. Incremental Reactivity Effects of Anthropogenic and Biogenic Volatile Organic Compounds on Secondary Organic Aerosol Formation

    Science.gov (United States)

    Kacarab, M.; Li, L.; Carter, W. P. L.; Cocker, D. R., III

    2015-12-01

    Two surrogate reactive organic gas (ROG) mixtures were developed to create a controlled reactivity environment simulating different urban atmospheres with varying levels of anthropogenic (e.g. Los Angeles reactivity) and biogenic (e.g. Atlanta reactivity) influences. Traditional chamber experiments focus on the oxidation of one or two volatile organic compound (VOC) precursors, allowing the reactivity of the system to be dictated by those compounds. Surrogate ROG mixtures control the overall reactivity of the system, allowing for the incremental aerosol formation from an added VOC to be observed. The surrogate ROG mixtures were developed based on that used to determine maximum incremental reactivity (MIR) scales for O3 formation from VOC precursors in a Los Angeles smog environment. Environmental chamber experiments were designed to highlight the incremental aerosol formation in the simulated environment due to the addition of an added anthropogenic (aromatic) or biogenic (terpene) VOC. All experiments were conducted in the UC Riverside/CE-CERT dual 90m3 environmental chambers. It was found that the aerosol precursors behaved differently under the two altered reactivity conditions, with more incremental aerosol being formed in the anthropogenic ROG system than in the biogenic ROG system. Further, the biogenic reactivity condition inhibited the oxidation of added anthropogenic aerosol precursors, such as m-xylene. Data will be presented on aerosol properties (density, volatility, hygroscopicity) and bulk chemical composition in the gas and particle phases (from a SYFT Technologies selected ion flow tube mass spectrometer, SIFT-MS, and Aerodyne high resolution time of flight aerosol mass spectrometer, HR-ToF-AMS, respectively) comparing the two controlled reactivity systems and single precursor VOC/NOx studies. Incremental aerosol yield data at different controlled reactivities provide a novel and valuable insight in the attempt to extrapolate environmental chamber

  10. Investigation of the role of the C-PCM solvent effect in reactivity indices

    Indian Academy of Sciences (India)

    Piotr Ordona; Akitomo Tachibana

    2005-09-01

    It has been shown recently, how the coupling between electronic degrees of freedom and vibrational modes is reflected in the properties of molecules. The necessary derivatives have been analyzed and their thermodynamic relations were demonstrated. This present work is focused on the analysis of a molecular system, under the influence of C-PCM induced solvent effect. The analysis is based on reactivity indices derived from DFT. The shift of frequency for diatomic molecules has been obtained. It has been identified as chemical force effect. The role of nuclear reactivity indices has been emphasized. This concept has been extended to obtain regional chemical potential values within C-PCM model for polyatomic molecules

  11. Separation of C6-Olefin Isomers in Reactive Extractants

    Institute of Scientific and Technical Information of China (English)

    SONG Fengxia; YU Yanmei; CHEN Jian

    2008-01-01

    Chemical complexation,in which certain metal ions (especially Ag+ and Cu+) reversibly and selectively complex olefin isomers,was used to separate 1-hexene from a mixture of intemal hexenes as an attractive alternative to traditional distillation.Several potential reactive extractants were investigated for their selectivity of both 1-hexene to 2-hexene and 1-hexene to 3-hexene.With 3 mol/L AgNO3-N-methyl-pyrrolidone (NMP) solution as extractant,the selectivity of 1-hexene to 3-hexane was increased to about 2.0 and the selectivity of 1-hexene to 2-hexene reached 1.5.Both the raffinate phase and the extracted phase were analyzed using a gas chromatograph equipped with a flame ionization detector and a 50-m capillary column.The experimental results show that the silver nitrate NMP solution has the better selectivity than other reactive extractions.

  12. Reactivity of ceramic coating materials with uranium and uranium trichlorid

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Sung Ho; Cho, Choon Ho; Lee, Yoon Sang; Lee, Han Soo; Kim, Jeong Guk [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2010-05-15

    Uranium and uranium alloys are typically induction melted in graphite crucibles under a vacuum. The graphite crucible is used for the manufacturing of uranium ingots in the casting equipment. But, due to the chemical reactivity of uranium and most alloying elements with carbon, a protective ceramic coating is generally applied to the crucibles. In this study, to investigate the most suitable ceramic coating material applied to graphite melting crucibles and ingot moldsused in the melting and casting of uranium in the casting equipment, firstly, the thermodynamic analysis was performed by using HSC software to investigate the reactivity between uranium and several ceramic materials and the experiments on the reaction of ceramic coated crucibles in molten uranium were carried out at 1300 .deg. C

  13. Reactivity of ceramic coating materials with uranium and uranium trichlorid

    International Nuclear Information System (INIS)

    Uranium and uranium alloys are typically induction melted in graphite crucibles under a vacuum. The graphite crucible is used for the manufacturing of uranium ingots in the casting equipment. But, due to the chemical reactivity of uranium and most alloying elements with carbon, a protective ceramic coating is generally applied to the crucibles. In this study, to investigate the most suitable ceramic coating material applied to graphite melting crucibles and ingot moldsused in the melting and casting of uranium in the casting equipment, firstly, the thermodynamic analysis was performed by using HSC software to investigate the reactivity between uranium and several ceramic materials and the experiments on the reaction of ceramic coated crucibles in molten uranium were carried out at 1300 .deg. C

  14. Molecular propensity as a driver for explorative reactivity studies

    CERN Document Server

    Vaucher, Alain C

    2016-01-01

    Quantum chemical studies of reactivity involve calculations on a large number of molecular structures and comparison of their energies. Already the set-up of these calculations limits the scope of the results that one will obtain, because several system-specific variables such as the charge and spin need to be set prior to the calculation. For a reliable exploration of reaction mechanisms, a considerable number of calculations with varying global parameters must be taken into account, or important facts about the reactivity of the system under consideration can go undetected. For example, one could miss crossings of potential energy surfaces for different spin states or might not note that a molecule is prone to oxidation. Here, we introduce the concept of molecular propensity to account for the predisposition of a molecular system to react across different electronic states in certain nuclear configurations. Within our real-time quantum chemistry framework, we developed an algorithm that allows us to be aler...

  15. Functionalization of whey proteins by reactive supercritical fluid extrusion

    Directory of Open Access Journals (Sweden)

    Khanitta Ruttarattanamongkol

    2012-09-01

    Full Text Available Whey protein, a by-product from cheese-making, is often used in a variety of food formulations due to its unsurpassednutritional quality and inherent functional properties. However, the possibilities for the improvement and upgrading of wheyprotein utilization still need to be explored. Reactive supercritical fluid extrusion (SCFX is a novel technique that has beenrecently reported to successfully functionalize commercially available whey proteins into a product with enhanced functionalproperties. The specific goal of this review is to provide fundamental understanding of the reinforcement mechanism andprocessing of protein functionalization by reactive SCFX process. The superimposed extrusion variables and their interactionmechanism affect the physico-chemical properties of whey proteins. By understanding the structure, functional properties andprocessing relationships of such materials, the rational design criteria for novel functionalized proteins could be developedand effectively utilized in food systems.

  16. The Reactive-Diffusive Length of OH Radical in Squalane

    Science.gov (United States)

    Lee, L.; Wilson, K. R.

    2015-12-01

    With the technique of core-shell particle configuration, we have measured the radical penetration length in a reactive matrix by observing the transmission efficiency of OH radical through squalane shell of various thickness ranging from 0 nm (without coating) to 16 nm. The result indicates a penetration depth of 2.2 nm. Our data suggest that the OH concentration profile in squalane as a function of the distance from the squalane/air interface can be satisfactorily described by the analytical solution to diffusion equation with an added chemical loss term experienced by the OH radical. This allowed an almost unambiguous determination of either OH diffusivity or OH reactivity given that one of the value is known in systems where radical chain propagation is not a significant factor and can shed new lights on the lifetime alteration of particulate matters in the atmosphere where possible coating processes are abundant.

  17. Extension of a reactive distillation process design methodology: application to the hydrogen production through the Iodine-Sulfur thermochemical cycle

    International Nuclear Information System (INIS)

    Reactive distillation is a promising way to improve classical processes. This interest has been comforted by numerous successful applications involving reactive systems in liquid phase but never in vapour phase. In this context, general design tools have been developed for the analysis of reactive distillation processes whatever the reactive phase. A general model for open condensation and evaporation of vapour or liquid reactive systems in chemical equilibrium has been written and applied to extend the feasibility analysis, synthesis and design methods of the sequential design methodology of R. Thery (2002). The extended design methodology is applied to the industrial production of hydrogen through the iodine-sulphur thermochemical cycle by vapour phase reactive distillation. A column configuration is proposed with better performance formerly published configuration. (author)

  18. Chemical networks

    Science.gov (United States)

    Thi, Wing-Fai

    2015-09-01

    This chapter discusses the fundamental ideas of how chemical networks are build, their strengths and limitations. The chemical reactions that occur in disks combine the cold phase reactions used to model cold molecular clouds with the hot chemistry applied to planetary atmosphere models. With a general understanding of the different types of reactions that can occur, one can proceed in building a network of chemical reactions and use it to explain the abundance of species seen in disks. One on-going research subject is finding new paths to synthesize species either in the gas-phase or on grain surfaces. Specific formation routes for water or carbon monoxide are discussed in more details. 13th Lecture of the Summer School "Protoplanetary Disks: Theory and Modelling Meet Observations"

  19. Reactivity Measurements. Proceedings of a Panel

    International Nuclear Information System (INIS)

    The general idea of this Panel was to make an evaluation of the concept of reactivity from the standpoint both of theory and experiment. Sixteen papers were presented describing different types of reactivity measurement for different types of reactor systems. The scope of the Panel was divided into four sections: a) Theory of Reactivity Measurement; b) Measurement of Reactivity in the Time Domain; c) Measurement of Reactivity by Statistical Methods; d) Reactivity Measurement in Large Power Reactors. Certain types of reactivity measurements were discussed and considered in sufficient detail. On the basis of the presentations and discussions, the Conclusions and General. Recommendations have been prepared. This part of the report does not pretend to give a full and complete picture of the problem but should be regarded as a first step to approach it as a whole

  20. Mechanism of flue gas simultaneous desulfurization and denitrification using the highly reactive absorbent

    Institute of Scientific and Technical Information of China (English)

    ZHAO; Yi; SUN; Xiaojun; XU; Peiyao; MA; Shuangchen; WANG; L

    2005-01-01

    Fly ash, industry-grade lime and a few oxidizing manganese compound additive were used to prepare the "Oxygen-riched" highly reactive absorbent for simultaneous desulfurization and denitrification. Experiments of simultaneous desulfurization and denitrification were carried out using the highly reactive absorbent in the flue gas circulating fluidized bed (CFB) system. Removal efficiencies of 94.5% for SO2 and 64.2% for NO were obtained respectively. The scanning electron microscope (SEM) and accessory X-ray energy spectrometer were used to observe micro-properties of the samples, including fly ash, common highly reactive absorbent, "Oxygen-riched" highly reactive absorbent and spent absorbent. The white flake layers were observed in the SEM images about surfaces of the common highly reactive absorbent and "Oxygen- riched" one, and the particle surfaces of the spent absorbent were porous. The content of calcium on surface was higher than that of the average in the highly reactive absorbent. The manganese compound additive dispersed uniformly on the surfaces of the "Oxygen- riched" highly reactive absorbent. There was a sulfur peak in the energy spectra pictures of the spent absorbent. The component of the spent absorbent was analyzed with chemical analysis methods, and the results indicated that more nitrogen species appeared in the absorbent except sulfur species, and SO2 and NO were removed by chemical absorption according to the experimental results of X-ray energy spectrometer and the chemical analysis. Sulfate being the main desulfurization products, nitrite was the main denitrification ones during the process, in which NO was oxidized rapidly to NO2 and absorbed by the chemical reaction.

  1. Effect of environment on iodine oxidation state and reactivity with aluminum.

    Science.gov (United States)

    Smith, Dylan K; McCollum, Jena; Pantoya, Michelle L

    2016-04-20

    Iodine oxide is a highly reactive solid oxidizer and with its abundant generation of iodine gas during reaction, this oxidizer also shows great potential as a biocidal agent. A problem with using I2O5 in an energetic mixture is its highly variable reactive behavior. This study isolates the variable reactivity associated with I2O5 as a function of its chemical reaction in various environments. Specifically, aluminum fuel and iodine oxide powder are combined using a carrier fluid to aid intermixing. The carrier fluid is shown to significantly affect the oxidation state of iodine oxide, thereby affecting the reactivity of the mixture. Four carrier fluids were investigated ranging in polarity and water miscibility in increasing order from hexane water as well as untreated, dry-mixed reactants. Oxidation state and reactivity were examined with experimental techniques including X-ray photoelectric spectroscopy (XPS) and differential scanning calorimetry (DSC). Results are compared with thermal equilibrium simulations. Flame speeds increased with polarity of the fluid used to intermix the powder and ranged from 180 to 1202 m s(-1). The I2O5 processed in the polar fluids formed hydrated states of iodine oxide: HIO3 and HI3O8; and, the nonpolar and dry-mixed samples formed: I2O4 and I4O9. During combustion, the hydrated iodine oxides rapidly dehydrated from HIO3 to HI3O8 and from HI3O8 to I2O5. Both steps release 25% of their mass as vapor during combustion. Increased gas generation enhances convective energy transport and accounts for the increase in reactivity seen in the mixtures processed in polar fluids. These results explain the chemical mechanisms underlying the variable reactivity of I2O5 that are a function of the oxide's highly reactive nature with its surrounding environment. These results will significantly impact the selection of carrier fluid in the synthesis approach for iodine containing reactive mixtures. PMID:27052472

  2. Characterization and reactivity of sodium aluminoborosilicate glass fiber surfaces

    Science.gov (United States)

    Ortiz Rivera, Lymaris; Bakaev, Victor A.; Banerjee, Joy; Mueller, Karl T.; Pantano, Carlo G.

    2016-05-01

    Multicomponent complex oxides, such as sodium aluminoborosilicate glass fibers, are important materials used for thermal insulation in buildings and homes. Although the surface properties of single oxides, such as silica, have been extensively studied, less is known about the distribution of reactive sites at the surface of multicomponent oxides. Here, we investigated the reactivity of sodium aluminoborosilicate glass fiber surfaces for better understanding of their interface chemistry and bonding with acrylic polymers. Acetic acid (with and without a 13C enrichment) was used as a probe representative of the carboxylic functional groups in many acrylic polymers and adhesives. Inverse gas chromatography coupled to a mass spectrometer (IGC-MS), and solid state nuclear magnetic resonance (NMR), were used to characterize the fiber surface reactions and surface chemical structure. In this way, we discovered that both sodium ions in the glass surface, as well as sodium carbonate salts that formed on the surface due to the intrinsic reactivity of this glass in humid air, are primary sites of interaction with the carboxylic acid. Surface analysis by X-ray photoelectron spectroscopy (XPS) confirmed the presence of sodium carbonates on these surfaces. Computer simulations of the interactions between the reactive sites on the glass fiber surface with acetic acid were performed to evaluate energetically favorable reactions. The adsorption reactions with sodium in the glass structure provide adhesive bonding sites, whereas the reaction with the sodium carbonate consumes the acid to form sodium-carboxylate, H2O and CO2 without any contribution to chemical bonding at the interface.

  3. Reactive scattering of halogen molecules

    International Nuclear Information System (INIS)

    A study of the endoergic, bimolecular reactions of F2 with I2, ICl, and HI in a crossed molecular beam experiment is described. The trihalogens IIF, ClIF, and HIF were directly observed as the products of these reactions. At high collision energies a second reactive channel producing IF becomes important. Product angular and velocity distributions show that this IF does not result from a four-center exchange reaction. Measured threshold energies for the formation of IIF, ClIF, and HIF yield lower bounds to the stabilities of these molecules, with respect to the separated atoms, of 69, 81, and 96 kcal/mole, respectively. Analysis of product center-of-mass angular distributions indicates that a slightly nonlinear approach is most effective in bringing about reaction to form the stable triatomic radical. Also described is a crossed molecular beam study of the Cl + Br2 → BrCl + Br reaction at collision energies from 6.8 to 17.7 kcal/mole. The results indicate that this reaction has the characteristics of an exoergic reaction on an attractive potential energy surface with early energy release. Reagent translational energy is very efficiently channeled into product internal energy. At high collision energy the reaction appears to approach the spectator stripping limit. Finally, a series of computer programs which can be used to carry out the requisite data analysis for crossed molecular beam reactive scattering experiments are described. These programs recover the reactive scattering center-of-mass flux distribution from the measured angular and velocity distributions of the products

  4. Atmospheric OH reactivity in central London: observations, model predictions and estimates of in situ ozone production

    Science.gov (United States)

    Whalley, Lisa K.; Stone, Daniel; Bandy, Brian; Dunmore, Rachel; Hamilton, Jacqueline F.; Hopkins, James; Lee, James D.; Lewis, Alastair C.; Heard, Dwayne E.

    2016-02-01

    Near-continuous measurements of hydroxyl radical (OH) reactivity in the urban background atmosphere of central London during the summer of 2012 are presented. OH reactivity behaviour is seen to be broadly dependent on air mass origin, with the highest reactivity and the most pronounced diurnal profile observed when air had passed over central London to the east, prior to measurement. Averaged over the entire observation period of 26 days, OH reactivity peaked at ˜ 27 s-1 in the morning, with a minimum of ˜ 15 s-1 during the afternoon. A maximum OH reactivity of 116 s-1 was recorded on one day during morning rush hour. A detailed box model using the Master Chemical Mechanism was used to calculate OH reactivity, and was constrained with an extended measurement data set of volatile organic compounds (VOCs) derived from a gas chromatography flame ionisation detector (GC-FID) and a two-dimensional GC instrument which included heavier molecular weight (up to C12) aliphatic VOCs, oxygenated VOCs and the biogenic VOCs α-pinene and limonene. Comparison was made between observed OH reactivity and modelled OH reactivity using (i) a standard suite of VOC measurements (C2-C8 hydrocarbons and a small selection of oxygenated VOCs) and (ii) a more comprehensive inventory including species up to C12. Modelled reactivities were lower than those measured (by 33 %) when only the reactivity of the standard VOC suite was considered. The difference between measured and modelled reactivity was improved, to within 15 %, if the reactivity of the higher VOCs (⩾ C9) was also considered, with the reactivity of the biogenic compounds of α-pinene and limonene and their oxidation products almost entirely responsible for this improvement. Further improvements in the model's ability to reproduce OH reactivity (to within 6 %) could be achieved if the reactivity and degradation mechanism of unassigned two-dimensional GC peaks were estimated. Neglecting the contribution of the higher VOCs (⩾ C

  5. Protein Structure Is Related to RNA Structural Reactivity In Vivo.

    Science.gov (United States)

    Tang, Yin; Assmann, Sarah M; Bevilacqua, Philip C

    2016-02-27

    We assessed whether in vivo mRNA structural reactivity and the structure of the encoded protein are related. This is the first investigation of such a relationship that utilizes information on RNA structure obtained in living cells. Based on our recent genome-wide Structure-seq analysis in Arabidopsis thaliana, we report that, as a meta property, regions of individual mRNAs that code for protein domains generally have higher reactivity to DMS (dimethyl sulfate), a chemical that covalently modifies accessible As and Cs, than regions that encode protein domain junctions. This relationship is prominent for proteins annotated for catalytic activity and reversed in proteins annotated for binding and transcription regulatory activity. Upon analyzing intrinsically disordered proteins, we found a similar pattern for disordered regions as compared to ordered regions: regions of individual mRNAs that code for ordered regions have significantly higher DMS reactivity than regions that code for intrinsically disordered regions. Based on these effects, we hypothesize that the decreased DMS reactivity of RNA regions that encode protein domain junctions or intrinsically disordered regions may reflect increased RNA structure that may slow translation, allowing time for the nascent protein domain or ordered region of the protein to fold, thereby reducing protein misfolding. In addition, a drop in DMS reactivity was observed on portions of mRNA sequences that correspond to the C-termini of protein domains, suggesting ribosome protection at these mRNA regions. Structural relationships between mRNAs and their encoded proteins may have evolved to allow efficient and accurate protein folding. PMID:26598238

  6. Stereodynamics: From elementary processes to macroscopic chemical reactions

    Energy Technology Data Exchange (ETDEWEB)

    Kasai, Toshio [Department of Chemistry, National Taiwan University, Taipei 106, Taiwan (China); Graduate School of Science, Department of Chemistry, Osaka University, Toyonaka, 560-0043 Osaka (Japan); Che, Dock-Chil [Graduate School of Science, Department of Chemistry, Osaka University, Toyonaka, 560-0043 Osaka (Japan); Tsai, Po-Yu [Department of Chemistry, National Taiwan University, Taipei 106, Taiwan (China); Department of Chemistry, National Chung Hsing University, Taichung 402, Taiwan (China); Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 106, Taiwan (China); Lin, King-Chuen [Department of Chemistry, National Taiwan University, Taipei 106, Taiwan (China); Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 106, Taiwan (China); Palazzetti, Federico [Scuola Normale Superiore, Pisa (Italy); Dipartimento di Chimica Biologia e Biotecnologie, Università di Perugia, 06123 Perugia (Italy); Aquilanti, Vincenzo [Dipartimento di Chimica Biologia e Biotecnologie, Università di Perugia, 06123 Perugia (Italy); Istituto di Struttura della Materia, Consiglio Nazionale delle Ricerche, Roma (Italy); Instituto de Fisica, Universidade Federal da Bahia, Salvador (Brazil)

    2015-12-31

    This paper aims at discussing new facets on stereodynamical behaviors in chemical reactions, i.e. the effects of molecular orientation and alignment on reactive processes. Further topics on macroscopic processes involving deviations from Arrhenius behavior in the temperature dependence of chemical reactions and chirality effects in collisions are also discussed.

  7. Stereodynamics: From elementary processes to macroscopic chemical reactions

    International Nuclear Information System (INIS)

    This paper aims at discussing new facets on stereodynamical behaviors in chemical reactions, i.e. the effects of molecular orientation and alignment on reactive processes. Further topics on macroscopic processes involving deviations from Arrhenius behavior in the temperature dependence of chemical reactions and chirality effects in collisions are also discussed

  8. Trends in reactivity of oxides

    DEFF Research Database (Denmark)

    Toftelund, Anja

    linearly with the adsorption energy of their central N, O and S atoms. It is also found that they follow the same trend as in the case of adsorption of the same molecules on transition metals. The same type of scaling relations are also established between the adsorption energies of the halides (Cl, Br...... chemisorption energies. It turns out that the BEP relation for rutile oxides is almost coinciding with the dissociation line, i.e. no barrier exists for the reactive surfaces. The heterogeneous catalytic oxidation of hydrogen halides (HCl, HBr, and HI) is investigated. A micro-kinetic model is solved and the...

  9. Method for reactively joining materials

    OpenAIRE

    Brinkman, H J; Duszczyk, J.; Katgerman, L

    2000-01-01

    Method for reactively joining materials in solid form, such as intermetallic compounds and technical ceramics, wherein: a) a mixed powder is provided in solid form between the materials to be joined; b) at least the powder mixture is locally heated, causing exothermic reactions to take place, whereby the heat is released at the contact surfaces of the materials to be joined, where it causes a local melting; and c) subsequently cools down. At least one of the materials to be joined has a melti...

  10. Self-reactive T cells

    DEFF Research Database (Denmark)

    Becker, Jürgen C; thor Straten, Per; Andersen, Mads Hald

    2014-01-01

    The immune system is a tightly regulated and complex system. An important part of this immune regulation is the assurance of tolerance toward self-antigens to maintain immune homeostasis. However, in recent years, antigen-specific cellular immune responses toward several normal self......-proteins expressed in regulatory immune cells have been reported, especially in patients with cancer. The seemingly lack of tolerance toward such proteins is interesting, as it suggests a regulatory function of self-reactive T (srT) cells, which may be important for the fine tuning of the immune system. In...

  11. Ultrasound assisted reactive crystallization of strontium sulfate

    Science.gov (United States)

    Sheikh, Abdul Rahim; Patel, Sanjaykumar R.

    2014-03-01

    SrSO4 is the main source of strontium element and widely used by industries as a raw material with narrow crystal size distribution (CSD) to meet excellent physical and chemical properties. An effort has been made to study the effects of various operating parameters such as concentration, temperature, additive (i.e. ethylene disodium salt dihydrate (EDTA)), and power of ultrasound on induction time, CSD and morphology during the reactive crystallization of strontium sulfate. The results showed that the induction time was decreased with an increase in the concentration of the reactant, temperature, and power of ultrasound, while an increasing trend observed with an increase in the concentration of EDTA. CSD was observed to be narrower with an increase in the concentration of EDTA and power of ultrasound while broader CSD observed with the initial concentration of the reactants. The temperature did not show the significant effect on CSD. The morphologies observed were the mixture of cuboids and hexagonal plate structures in the presence of ultrasound.

  12. Ionic Liquids: Radiation Chemistry, Solvation Dynamics and Reactivity Patterns

    Energy Technology Data Exchange (ETDEWEB)

    Wishart, J.F.

    2011-06-12

    Ionic liquids (ILs) are a rapidly expanding family of condensed-phase media with important applications in energy production, nuclear fuel and waste processing, improving the efficiency and safety of industrial chemical processes, and pollution prevention. ILs generally have low volatilities and are combustion-resistant, highly conductive, recyclable and capable of dissolving a wide variety of materials. They are finding new uses in chemical synthesis, catalysis, separations chemistry, electrochemistry and other areas. Ionic liquids have dramatically different properties compared to conventional molecular solvents, and they provide a new and unusual environment to test our theoretical understanding of primary radiation chemistry, charge transfer and other reactions. We are interested in how IL properties influence physical and dynamical processes that determine the stability and lifetimes of reactive intermediates and thereby affect the courses of reactions and product distributions. We study these issues by characterization of primary radiolysis products and measurements of their yields and reactivity, quantification of electron solvation dynamics and scavenging of electrons in different states of solvation. From this knowledge we wish to learn how to predict radiolytic mechanisms and control them or mitigate their effects on the properties of materials used in nuclear fuel processing, for example, and to apply IL radiation chemistry to answer questions about general chemical reactivity in ionic liquids that will aid in the development of applications listed above. Very early in our radiolysis studies it became evident that the slow solvation dynamics of the excess electron in ILs (which vary over a wide viscosity range) increase the importance of pre-solvated electron reactivity and consequently alter product distributions and subsequent chemistry. This difference from conventional solvents has profound effects on predicting and controlling radiolytic yields

  13. High fluence implantation in glasses: chemical interactions

    International Nuclear Information System (INIS)

    Results will be given on chemical interactions in amorphous SiO2 implanted with reactive and non-reactive species. Samples were implanted with nitrogen, silicon, titanium and silver; a set of samples already implanted with these elements (excluding those implanted with nitrogen) has been subjected to a second implant with nitrogen ions, at the dose of 2x1017 ions cm-2, at different energies. Samples have been characterized by secondary ion mass spectrometry, X-ray photoelectron spectroscopy, nuclear techniques and optical absorption measurements. Radiation damage and chemical effects have been discriminated; precipitation of the implanted species, as well as chemical compound formation in the interaction both between the implanted species and the host matrix and between the implanted species themselves have been detected. (orig.)

  14. Chemical Sciences Division annual report 1994

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1995-06-01

    The division is one of ten LBL research divisions. It is composed of individual research groups organized into 5 scientific areas: chemical physics, inorganic/organometallic chemistry, actinide chemistry, atomic physics, and chemical engineering. Studies include structure and reactivity of critical reaction intermediates, transients and dynamics of elementary chemical reactions, and heterogeneous and homogeneous catalysis. Work for others included studies of superconducting properties of high-{Tc} oxides. In FY 1994, the division neared completion of two end-stations and a beamline for the Advanced Light Source, which will be used for combustion and other studies. This document presents summaries of the studies.

  15. Chemical pressure

    OpenAIRE

    Hauser, Andreas; Amstutz, Nahid; Delahaye, Sandra; Sadki, Asmaâ; Schenker, Sabine; Sieber, Regula; Zerara, Mohamed

    2002-01-01

    The physical and photophysical properties of three classic transition metal complexes, namely [Fe(bpy)3]2+, [Ru(bpy)3]2+, and [Co(bpy)3]2+, can be tuned by doping them into a variety of inert crystalline host lattices. The underlying guest-host interactions are discussed in terms of a chemical pressure.

  16. Chemical Peels

    Science.gov (United States)

    ... resources Meet our partners Español Donate Diseases and treatments Acne and rosacea Bumps and growths Color problems Contagious skin diseases ... Chemical peels public SPOT Skin Cancer™ Diseases and treatments Acne and rosacea Bumps and growths Color problems Contagious skin diseases ...

  17. Chemical Mahjong

    Science.gov (United States)

    Cossairt, Travis J.; Grubbs, W. Tandy

    2011-01-01

    An open-access, Web-based mnemonic game is described whereby introductory chemistry knowledge is tested using mahjong solitaire game play. Several tile sets and board layouts are included that are themed upon different chemical topics. Introductory tile sets can be selected that prompt the player to match element names to symbols and metric…

  18. Chemical dispersants

    NARCIS (Netherlands)

    Rahsepar, Shokouhalsadat; Smit, Martijn P.J.; Murk, Albertinka J.; Rijnaarts, Huub H.M.; Langenhoff, Alette A.M.

    2016-01-01

    Chemical dispersants were used in response to the Deepwater Horizon oil spill in the Gulf of Mexico, both at the sea surface and the wellhead. Their effect on oil biodegradation is unclear, as studies showed both inhibition and enhancement. This study addresses the effect of Corexit on oil biodeg

  19. Reactivity coefficients by perturbation theory

    International Nuclear Information System (INIS)

    The development of the formulae of perturbation theory provides a good opportunity to use one of the principal devices of mathematical heuristics, i.e. proceeding by analogy from something that is simple to something that is more complicated. This paper: (a) Reviews the formulation of perturbation theory as a method of calculating reactivity coefficients; this consists mainly of developing the differential equation for the adjoint flux, as a continuous function of position and lethargy, by proceeding by analogy from the one-group differential equation for adjoint flux. (b) Presents an application of the two-group form of perturbation theory to a boiling-mercury-cooled fast-breeder reactor (MCBR). It is seen that the net Hg density coefficient of reactivity for the first-design-try for the MCBR is negative for some regions and positive for others. However, it is negative for regions of highest statistical weight and where the density change for a power change would be the greatest. The overall Hg density coefficient is thus negative, i.e. the void coefficient is positive-an unsafe condition. It can be easily seen from the two-group formulation what design changes had to be made to obtain a design which would have a negative void coefficient. It developed in subsequent investigations that there were such design changes that could be made and a design of the MCBR with a negative void coefficient was eventually achieved. (author)

  20. Measurement of OH reactivity by laser flash photolysis coupled with laser-induced fluorescence spectroscopy

    Science.gov (United States)

    Stone, Daniel; Whalley, Lisa K.; Ingham, Trevor; Edwards, Peter M.; Cryer, Danny R.; Brumby, Charlotte A.; Seakins, Paul W.; Heard, Dwayne E.

    2016-07-01

    OH reactivity (k'OH) is the total pseudo-first-order loss rate coefficient describing the removal of OH radicals to all sinks in the atmosphere, and is the inverse of the chemical lifetime of OH. Measurements of ambient OH reactivity can be used to discover the extent to which measured OH sinks contribute to the total OH loss rate. Thus, OH reactivity measurements enable determination of the comprehensiveness of measurements used in models to predict air quality and ozone production, and, in conjunction with measurements of OH radical concentrations, to assess our understanding of OH production rates. In this work, we describe the design and characterisation of an instrument to measure OH reactivity using laser flash photolysis coupled to laser-induced fluorescence (LFP-LIF) spectroscopy. The LFP-LIF technique produces OH radicals in isolation, and thus minimises potential interferences in OH reactivity measurements owing to the reaction of HO2 with NO which can occur if HO2 is co-produced with OH in the instrument. Capabilities of the instrument for ambient OH reactivity measurements are illustrated by data collected during field campaigns in London, UK, and York, UK. The instrumental limit of detection for k'OH was determined to be 1.0 s-1 for the campaign in London and 0.4 s-1 for the campaign in York. The precision, determined by laboratory experiment, is typically < 1 s-1 for most ambient measurements of OH reactivity. Total uncertainty in ambient measurements of OH reactivity is ˜ 6 %. We also present the coupling and characterisation of the LFP-LIF instrument to an atmospheric chamber for measurements of OH reactivity during simulated experiments, and provide suggestions for future improvements to OH reactivity LFP-LIF instruments.

  1. User Friendly Explosives Reactive Armour a Long term Reality

    Directory of Open Access Journals (Sweden)

    S. N. Dikshit

    1997-04-01

    Full Text Available Abstract : There is a strong need to develop explosive reactive armour (ERA for protecting battle tanks against an emerging threat of kinetic and chemical energy missiles. In this context, global trends, principle and limitations of ERA and threat perception-based types of ERA have been dwelt upon. User-friendly ERA is a long-term reality. User-friendly ERA system is thus defined to be an efficient and protective system that not only provide full protection to the tank crew, but is also harmless to the supporting infantory. The indigenously-developed ERA system is close to be termed as a user-friendly ERA.

  2. New NIR Calibration Models Speed Biomass Composition and Reactivity Characterization

    Energy Technology Data Exchange (ETDEWEB)

    2015-09-01

    Obtaining accurate chemical composition and reactivity (measures of carbohydrate release and yield) information for biomass feedstocks in a timely manner is necessary for the commercialization of biofuels. This highlight describes NREL's work to use near-infrared (NIR) spectroscopy and partial least squares multivariate analysis to develop calibration models to predict the feedstock composition and the release and yield of soluble carbohydrates generated by a bench-scale dilute acid pretreatment and enzymatic hydrolysis assay. This highlight is being developed for the September 2015 Alliance S&T Board meeting.

  3. Governing processes for reactive nitrogen compounds in the European atmosphere

    DEFF Research Database (Denmark)

    Hertel, Ole; Skjøth, Carsten Ambelas; Reis, S.;

    2012-01-01

    Reactive nitrogen (N-r) compounds have different fates in the atmosphere due to differences in the governing processes of physical transport, deposition and chemical transformation. N-r compounds addressed here include reduced nitrogen (NHx: ammonia (NH3) and its reaction product ammonium (NH4.......5 and PM10 (mass of aerosols with an aerodynamic diameter of less than 2.5 and 10 mu m, respectively) with an impact on radiation balance as well as potentially on human health. Little is known quantitatively and qualitatively about organic N in the atmosphere, other than that it contributes a significant...

  4. KIVA reactive hydrodynamics code applied to detonations in high vacuum

    Science.gov (United States)

    Greiner, N. Roy

    1989-08-01

    The KIVA reactive hydrodynamics code was adapted for modeling detonation hydrodynamics in a high vacuum. Adiabatic cooling rapidly freezes detonation reactions as a result of free expansion into the vacuum. After further expansion, a molecular beam of the products is admitted without disturbance into a drift tube, where the products are analyzed with a mass spectrometer. How the model is used for interpretation and design of experiments for detonation chemistry is explained. Modeling of experimental hydrodynamic characterization by laser-schlieren imaging and model-aided mapping that will link chemical composition data to particular volume elements in the explosive charge are also discussed.

  5. Layered reactive particles with controlled geometries, energies, and reactivities, and methods for making the same

    Energy Technology Data Exchange (ETDEWEB)

    Fritz, Gregory M.; Weihs, Timothy P.; Grzyb, Justin A.

    2016-07-05

    An energetic composite having a plurality of reactive particles each having a reactive multilayer construction formed by successively depositing reactive layers on a rod-shaped substrate having a longitudinal axis, dividing the reactive-layer-deposited rod-shaped substrate into a plurality of substantially uniform longitudinal segments, and removing the rod-shaped substrate from the longitudinal segments, so that the reactive particles have a controlled, substantially uniform, cylindrically curved or otherwise rod-contoured geometry which facilitates handling and improves its packing fraction, while the reactant multilayer construction controls the stability, reactivity and energy density of the energetic composite.

  6. Reduction Chemistry of Rare-Earth Metal Complexes: Toward New Reactivity and Properties

    OpenAIRE

    Huang, Wenliang

    2013-01-01

    Rare-earths are a group of metals with fascinating physical properties and intriguing chemical reactivity. Organometallic rare-earth chemistry is of particular interest because of the increasing number of their applications in industry and consumer goods as well as the importance of understanding their physical and chemical properties. Despite the dominance of the trivalent oxidation state, recently, low-valent organometallic rare-earth compounds were characterized and showed interesting reac...

  7. DECOLORIZATION AND BIOLOGICAL DEGRADATION OF AZO DYE REACTIVE RED2 BY ANAEROBIC/AEROBIC SEQUENTIAL PROCESS

    OpenAIRE

    A. Naimabadi ، H. Movahedian Attar ، A. Shahsavani

    2009-01-01

    This study investigates the anaerobic treatability of reactive Red2 in an anaerobic/aerobic sequential process. Laboratory scale anaerobic baffled reactor and fixed activated sludge reactor were operated at different organic loadings and hydraulic retention times. The effects of shock dye concentration on the chemical oxygen demand and color removal efficiencies were investigated in the anaerobic baffled reactor. The effect of hydraulic retention time on the color and chemical oxygen demand r...

  8. Reactivity and burnout of wood fuels

    Energy Technology Data Exchange (ETDEWEB)

    Dall' Ora, M.

    2011-07-01

    pyrolysis temperature increased. During fast pyrolysis wood particles underwent melting, yet to different extents for the two investigated fuels: pine wood produced chars of porous spherical particles, whereas beech sawdust chars showed a somewhat less drastic change of morphology with respect to the parent fuel. Char produced by low heating rate pyrolysis fully retained the original fibrous structure of wood. Fast pyrolysis chars were significantly more reactive than slow pyrolysis chars (for the same activation energy, the pre-exponential factor was up to 2 orders of magnitude greater for chars increased). The amount and composition of the ash forming matter of the wood fuels is believed to play an important role in determining the differences in char yield, morphology and reactivity. The modelling of wood char combustion is the subject of Chapter 5. The lowest and the highest reactivities obtained for the chars produced in the EFR are used in a simple single particle combustion model in combination with a description of Avedoerevaerket's boiler. In the model the char particle is assumed to burn in a gas with constant temperature and constant oxygen fraction. The particle temperature is on the other hand determined taking reaction heat, convection through boundary gas layer and radiation into account. The model accounts for external diffusion of oxygen to the particle outer surface, internal diffusion in the pores and heterogeneous chemical reaction (CO is considered the only product). The model calculates an overall efficiency factor for combustion, yet assumes that all the reacting carbon is consumed at the outer surface of the char. The model predicts that at an average furnace temperature of 1200 K the conversion of char particles with radius 20-350 {micro}m is very much affected by the reactivity of the char. The influence of the particle's reactivity is lower at higher temperatures: at furnace temperatures of 1500 K and 1700 K the combustion of the char is

  9. Chemical flashlamps

    International Nuclear Information System (INIS)

    The authors have characterized the optical output and Nd:glass pumping performance of large-scale (120-cm-long, 1.2-cm-inner-diam), metal-oxidizer chemical flashlamps supplied to us by G.T.E. Sylvania. The experimental results were obtained on the same test bed that was used to study xenon electrical flashlamps, as described in Dependence of Flashlamp Performance on Gas Fill and Bore Size, earlier in this section. The peak Nd inversion levels produced by the chemical lamps were less than or equal to 10% of those generated by a xenon lamp of similar size and energy loading. The Peak Nd levels are in good agreement with predictions for the pumping rates in Nd:glass by a blackbody at the color temperatures of 30000 to 50000C, which they have measured during the burn of the pyrotechnic lamp

  10. Study on CO2 gasification reactivity and physical characteristics of biomass, petroleum coke and coal chars.

    Science.gov (United States)

    Huo, Wei; Zhou, Zhijie; Chen, Xueli; Dai, Zhenghua; Yu, Guangsuo

    2014-05-01

    Gasification reactivities of six different carbonaceous material chars with CO2 were determined by a Thermogravimetric Analyzer (TGA). Gasification reactivities of biomass chars are higher than those of coke and coal chars. In addition, physical structures and chemical components of these chars were systematically tested. It is found that the crystalline structure is an important factor to evaluate gasification reactivities of different chars and the crystalline structures of biomass chars are less order than those of coke and coal chars. Moreover, initial gasification rates of these chars were measured at high temperatures and with relatively large particle sizes. The method of calculating the effectiveness factor η was used to quantify the effect of pore diffusion on gasification. The results show that differences in pore diffusion effects among gasification with various chars are prominent and can be attributed to different intrinsic gasification reactivities and physical characteristics of different chars. PMID:24642484

  11. Analysis of burnup credit on spent fuel transport / storage casks - estimation of reactivity bias

    International Nuclear Information System (INIS)

    Chemical analyses of high burnup UO2 (65 GWd/t) and MOX (45 GWd/t) spent fuel pins were carried out. Measured data of nuclides' composition from U234 to P 242 were used for evaluation of ORIGEN-2/82 code and a nuclear fuel design code (NULIF). Critically calculations were executed for transport and storage casks for 52 BWR or 21 PWR spent fuel assemblies. The reactivity biases were evaluated for axial and horizontal profiles of burnup, and historical void fraction (BWR), operational histories such as control rod insertion history, BPR insertion history and others, and calculational accuracy of ORIGEN-2/82 on nuclides' composition. This study shows that introduction of burnup credit has a large merit in criticality safety analysis of casks, even if these reactivity biases are considered. The concept of equivalent uniform burnup was adapted for the present reactivity bias evaluation and showed the possibility of simplifying the reactivity bias evaluation in burnup credit. (authors)

  12. The reactive extrusion of thermoplastic polyurethane

    OpenAIRE

    Verhoeven, Vincent Wilhelmus Andreas

    2006-01-01

    The objective of this thesis was to increase the understanding of the reactive extrusion of thermoplastic polyurethane. Overall, several issues were identified: • Using a relative simple extrusion model, the reactive extrusion process can be described. This model can be used to further investigate and optimize the reactive extrusion of thermoplastic polyurethane. • Premixing has a small beneficiary effect on the efficiency of the extrusion process and the quality of the product formed. • The ...

  13. Reactive power compensation a practical guide

    CERN Document Server

    Hofmann, Wolfgang; Just, Wolfgang

    2012-01-01

    The comprehensive resource on reactive power compensation, presenting the design, application and operation of reactive power equipment and installations The area of reactive power compensation is gaining increasing importance worldwide. If suitably designed, it is capable of improving voltage quality significantly, meaning that losses in equipment and power systems are reduced, the permissible loading of equipment can be increased, and the over-all stability of system operation improved. Ultimately, energy use and CO2 emisson are reduced. This unique guide discusses the

  14. Implementing a teleo-reactive programming system

    OpenAIRE

    Webb, Robert

    2015-01-01

    This thesis explores the teleo-reactive programming paradigm for controlling autonomous agents, such as robots. Teleo-reactive programming provides a robust, opportunistic method for goal-directed programming that continuously reacts to the sensed environment. In particular, the TR and TeleoR systems are investigated. They influence the design of a teleo-reactive system programming in Python, for controlling autonomous agents via the Pedro communications architecture. To demonstrate the syste...

  15. Sex moderates stress reactivity in heavy drinkers

    OpenAIRE

    Hartwell, EE; Ray, LA

    2013-01-01

    Psychological stress and alcohol use disorders have a well-known connection. Individual differences in stress reactivity have been an area of interest in alcohol research, particularly given the relationship between craving and stress reactivity to later relapse. The present study examines the role of sex on stress-induced alcohol craving and emotional reactivity using a guided imagery stress paradigm. Participants were 64 non-treatment seeking heavy drinkers from the community who completed ...

  16. A Gibbs Formulation for Reactive Materials with Phase Change

    Science.gov (United States)

    Stewart, D. Scott

    2015-11-01

    A large class of applications have pure, condensed phase constituents that come into contact, chemically react and simultaneously undergo phase change. Phase change in a given molecular material has often been considered to be separate from chemical reaction. Continuum modelers of phase change often use a phase field model whereby an indicator function is allowed to change from one value to another in regions of phase change, governed by evolutionary (Ginzburg-Landau) equations, whereas classic chemical kinetics literally count species concentrations and derive kinetics evolution equations based on species mass transport. We argue the latter is fundamental and is the same as the former, if all species, phase or chemical are treated as distinct chemical species. We pose a self-consistent continuum, thermo-mechanical model to account for significant energetic quantities with correct molecular and continuum limits in the mixture. A single stress tensor, and a single temperature is assumed for the mixture with specified Gibbs potentials for all relevant species, and interaction energies. We discuss recent examples of complex reactive material modeling, drawn from thermitic and propellant combustion that use this new model. DSS supported by DTRA, ONR and AFOSR.

  17. Computational methods for reactive transport modeling: A Gibbs energy minimization approach for multiphase equilibrium calculations

    Science.gov (United States)

    Leal, Allan M. M.; Kulik, Dmitrii A.; Kosakowski, Georg

    2016-02-01

    We present a numerical method for multiphase chemical equilibrium calculations based on a Gibbs energy minimization approach. The method can accurately and efficiently determine the stable phase assemblage at equilibrium independently of the type of phases and species that constitute the chemical system. We have successfully applied our chemical equilibrium algorithm in reactive transport simulations to demonstrate its effective use in computationally intensive applications. We used FEniCS to solve the governing partial differential equations of mass transport in porous media using finite element methods in unstructured meshes. Our equilibrium calculations were benchmarked with GEMS3K, the numerical kernel of the geochemical package GEMS. This allowed us to compare our results with a well-established Gibbs energy minimization algorithm, as well as their performance on every mesh node, at every time step of the transport simulation. The benchmark shows that our novel chemical equilibrium algorithm is accurate, robust, and efficient for reactive transport applications, and it is an improvement over the Gibbs energy minimization algorithm used in GEMS3K. The proposed chemical equilibrium method has been implemented in Reaktoro, a unified framework for modeling chemically reactive systems, which is now used as an alternative numerical kernel of GEMS.

  18. Reactive Rayleigh-Taylor Turbulence

    CERN Document Server

    Chertkov, M; Vladimirova, N

    2008-01-01

    The Rayleigh-Taylor (RT) instability develops and leads to turbulence when a heavy fluid falls under the action of gravity through a light one. We consider this phenomenon accompanied by a reactive transformation between the fluids, and study with Direct Numerical Simulations (DNS) how the reaction (flame) affects the turbulent mixing in the Boussinesq approximation. We discuss "slow" reactions where the characteristic reaction time exceeds the temporal scale of the RT instability. In the early turbulent stage, effects of the flame are distributed over a maturing mixing zone, whose development is weakly influenced by the reaction. At later times, the fully mixed zone transforms into a conglomerate of pure-fluid patches of sizes proportional to the mixing zone width. In this "stirred flame'' regime, temperature fluctuations are consumed by reactions in the regions separating the pure-fluid patches. This DNS-based qualitative description is followed by a phenomenology suggesting that thin turbulent flame is of ...

  19. Reactivation tuberculosis: role of surveillance.

    Science.gov (United States)

    DiNardo, Andrew R; Guy, Elizabeth

    2016-05-01

    The incidence and death rates from tuberculosis (TB) have declined through concerted efforts in the diagnosis and treatment of active disease. Despite this, 9.6 million new cases and 1.1 million deaths in 2014 are unacceptably high. To decrease the rates of TB further, the huge number of persons with latent TB infection (LTBI) from whom new cases will arise has to be addressed with a sense of priority. Identifying the highest risk groups and providing effective treatment has been shown to decrease active TB. Further research to refine the predictors of reactivation and shorter effective treatments are urgently needed. Implementing intensified case finding, testing and treatment for LTBI will require continued investment in health care capacity at multiple levels. PMID:27042967

  20. Pattern transfer on large samples using a sub-aperture reactive ion beam

    International Nuclear Information System (INIS)

    In comparison to sole Ar ion beam sputtering Reactive Ion Beam Etching (RIBE) reveals the main advantage of increasing the selectivity for different kind of materials due to chemical contributions during the material removal. Therefore RIBE is qualified to be an excellent candidate for pattern transfer applications. The goal of the present study is to apply a sub-aperture reactive ion beam for pattern transfer on large fused silica samples. Concerning this matter, the etching behavior in the ion beam periphery plays a decisive role. Using CF4 as reactive gas, XPS measurements of the modified surface exposes impurities like Ni, Fe and Cr, which belongs to chemically eroded material of the plasma pot as well as an accumulation of carbon (up to 40 atomic percent) in the beam periphery, respectively. The substitution of CF4 by NF3 as reactive gas reveals a lot of benefits: more stable ion beam conditions in combination with a reduction of the beam size down to a diameter of 5 mm and a reduced amount of the Ni, Fe and Cr contaminations. However, a layer formation of silicon nitride handicaps the chemical contribution of the etching process. These negative side effects influence the transfer of trench structures on quartz by changing the selectivity due to altered chemical reaction of the modified resist layer. Concerning this we investigate the pattern transfer on large fused silica plates using NF3-sub-aperture RIBE.