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Sample records for potentiokinetic reactivation method

  1. NDE evaluation of the intergranular corrosion susceptibility of a 2205 duplex stainless steel using thermoelectric power and double loop electrochemical potentiokinetic reactivation methods

    NASA Astrophysics Data System (ADS)

    Ortiz, N.; Carreón, H.; Ruiz, A.

    2013-01-01

    There is a need for a nondestructive technique to assess rapidly and with confidence the degree of sensitization (DOS) in duplex stainless steel (DSS). In this investigation, we present the use of thermoelectric power (TEP) measurements as nondestructive method for the determination of DOS in isothermally aged 2205 DSS at 700°C for different aging times. The DOS of the aged samples was first established by performing the double loop electrochemical potentiokinetic reactivation (DL-EPR) test. The microstructural evolution was evaluated by scanning electron microscopy (SEM). Experimental results indicate that TEP coefficient is sensitive to gradual microstructural changes produced by thermal aging and can be used to monitor IGC sensitization of 2205 duplex stainless steel.

  2. Corrosion resistance and electrochemical potentiokinetic reactivation testing of some iron-base hardfacing alloys

    SciTech Connect

    Cockeram, B.V.

    1999-11-01

    Hardfacing alloys are weld deposited on a base material to provide a wear resistant surface. Commercially available iron-base hardfacing alloys are being evaluated for replacement of cobalt-base alloys to reduce nuclear plant activation levels. Corrosion testing was used to evaluate the corrosion resistance of several iron-base hardfacing alloys in highly oxygenated environments. The corrosion test results indicate that iron-base hardfacing alloys in the as-deposited condition have acceptable corrosion resistance when the chromium to carbon ratio is greater than 4. Tristelle 5183, with a high niobium (stabilizer) content, did not follow this trend due to precipitation of niobium-rich carbides instead of chromium-rich carbides. This result indicates that iron-base hardfacing alloys containing high stabilizer contents may possess good corrosion resistance with Cr:C < 4. NOREM 02, NOREM 01, and NoCo-M2 hardfacing alloys had acceptable corrosion resistance in the as-deposited and 885 C/4 hour heat treated condition, but rusting from sensitization was observed in the 621 C/6 hour heat treated condition. The feasibility of using an Electrochemical Potentiokinetic Reactivation (EPR) test method, such as used for stainless steel, to detect sensitization in iron-base hardfacing alloys was evaluated. A single loop-EPR method was found to provide a more consistent measurement of sensitization than a double loop-EPR method. The high carbon content that is needed for a wear resistant hardfacing alloy produces a high volume fraction of chromium-rich carbides that are attacked during EPR testing. This results in inherently lower sensitivity for detection of a sensitized iron-base hardfacing alloy than stainless steel using conventional EPR test methods.

  3. Assessment of electrochemical potentiokinetic reactivation tests to qualify stainless steel for nitric acid service

    SciTech Connect

    Olsen, A.R.; Dillon, J.J.; Peters, A.H.; Clift, T.L.

    1986-12-31

    To minimize the costs and delivery time delays associated with purchasing type 304L stainless steel materials for service in nitric-acid-containing media, an alternative to the current Oak Ridge Y-12 Plant requirement of testing in accordance with American Society for Testing and Materials (ASTM) A 262, Practice C (the boiling nitric acid test), is being sought. A possible candidate is the electrochemical potentiokinetic reactivation (EPR) test being developed for the nuclear industry and under consideration for acceptance as an ASTM standard. Based on a review of the literature and some limited screening tests, this test, as currently proposed, is not a suitable substitute for the nitric acid test. However, with additional development the EPR test is a likely candidate for providing a quantitative substitute for the current qualitative oxalic acid etching (ASTM A 282, Practice A) often used to accept, but not reject, materials for use in a nitric acid medium.

  4. Evaluation by the Double Loop Electrochemical Potentiokinetic Reactivation Test of Aged Ferritic Stainless Steel Intergranular Corrosion Susceptibility

    NASA Astrophysics Data System (ADS)

    Sidhom, H.; Amadou, T.; Braham, C.

    2010-12-01

    An experimental design method was used to determine the effect of factors that significantly affect the response of the double loop-electrochemical potentiokinetic reactivation (DL-EPR) test in controlling the susceptibility to intergranular corrosion (IGC) of UNS S43000 (AISI 430) ferritic stainless steel. The test response is expressed in terms of the reactivation/activation current ratio ( I r / I a pct). Test results analysed by the analysis of variance (ANOVA) method show that the molarity of the H2SO4 electrolyte and the potential scanning rate have a more significant effect on the DL-EPR test response than the temperature and the depassivator agent concentration. On the basis of these results, a study was conducted in order to determine the optimal operating conditions of the test as a nondestructive technique for evaluating IGC resistance of ferritic stainless steel components. Three different heat treatments are considered in this study: solution annealing (nonsensitized), aging during 3 hours at 773 K (500 °C) (slightly sensitized), and aging during 2 hours at 873 K (600 °C) (highly sensitized). The aim is to find the operating conditions that simultaneously ensure the selectivity of the attack (intergranular and chromium depleted zone) and are able to detect the effect of low dechromization. It is found that a potential scanning rate of 2.5 mV/s in an electrolyte composed of H2SO4 3 M solution without depassivator, at a temperature around 293 K (20 °C), is the optimal operating condition for the DL-EPR test. Using this condition, it is possible to assess the degree of sensitization (DOS) to the IGC of products manufactured in ferritic stainless steels rapidly, reliably, and quantitatively. A time-temperature-start of sensitization (TTS) diagram for the UNS S43000 (France Inox, Villepinte, France) stainless steel was obtained with acceptable accuracy by this method when the IGC sensitization criterion was set to I r / I a > 1 pct. This diagram is in

  5. Sensitization phenomena on aged SAF 2205 duplex stainless steel and their control using the electrochemical potentiokinetic reactivation test

    SciTech Connect

    Angelini, E.; Benedetti, B. de; Maizza, G.; Rosalbino, F. . Dept. of Materials Science and Chemical Engineering)

    1999-06-01

    Microstructural changes and resulting properties were studied for SAF 2205 (UNS S31803) austeno-ferritic stainless steel (SS) aged between 700 C and 900 C for up to 2 weeks and then water-quenched. Quantitative metallography coupled with x-ray diffraction techniques were adopted to follow ferrite ([alpha]) transformation with subsequent formation of secondary austenite ([gamma][sub 2]) and sigma ([sigma]) phase. The kinetic model of a transformation was interpreted in the form of an Avrami-type expression. The electrochemical potentiokinetic reactivation (EPR) test was used to evaluate the degree of sensitization of the aged specimens. Results were compared with results from the corrosion test in boiling nitric acid (HNO[sub 3]). Influences of the transformation of ferrite into austenite, sigma phase, and of other microstructural variations such as chromium nitride (Cr[sub 2]N) precipitation on stability of the passive film were shown. The susceptibility to intergranular corrosion phenomena was caused by chromium depletion caused by sigma phase precipitation, while chromium nitrides appeared less harmful. Results were expressed as an isocharge line diagram that allowed concise identification of sensitization and desensitization ranges.

  6. Method for reactivating catalysts and a method for recycling supercritical fluids used to reactivate the catalysts

    DOEpatents

    Ginosar, Daniel M.; Thompson, David N.; Anderson, Raymond P.

    2008-08-05

    A method of reactivating a catalyst, such as a solid catalyst or a liquid catalyst. The method comprises providing a catalyst that is at least partially deactivated by fouling agents. The catalyst is contacted with a fluid reactivating agent that is at or above a critical point of the fluid reactivating agent and is of sufficient density to dissolve impurities. The fluid reactivating agent reacts with at least one fouling agent, releasing the at least one fouling agent from the catalyst. The at least one fouling agent becomes dissolved in the fluid reactivating agent and is subsequently separated or removed from the fluid reactivating agent so that the fluid reactivating agent may be reused. A system for reactivating a catalyst is also disclosed.

  7. Method for reactivating solid catalysts used in alkylation reactions

    DOEpatents

    Ginosar, Daniel M.; Thompson, David N.; Coates, Kyle; Zalewski, David J.; Fox, Robert V.

    2003-06-17

    A method for reactivating a solid alkylation catalyst is provided which can be performed within a reactor that contains the alkylation catalyst or outside the reactor. Effective catalyst reactivation is achieved whether the catalyst is completely deactivated or partially deactivated. A fluid reactivating agent is employed to dissolve catalyst fouling agents and also to react with such agents and carry away the reaction products. The deactivated catalyst is contacted with the fluid reactivating agent under pressure and temperature conditions such that the fluid reactivating agent is dense enough to effectively dissolve the fouling agents and any reaction products of the fouling agents and the reactivating agent. Useful pressures and temperatures for reactivation include near-critical, critical, and supercritical pressures and temperatures for the reactivating agent. The fluid reactivating agent can include, for example, a branched paraffin containing at least one tertiary carbon atom, or a compound that can be isomerized to a molecule containing at least one tertiary carbon atom.

  8. Method For Reactivating Solid Catalysts Used For Alklation Reactions

    DOEpatents

    Ginosar, Daniel M.; Thompson, David N.; Coates, Kyle; Zalewski, David J.; Fox, Robert V.

    2005-05-03

    A method for reactivating a solid alkylation catalyst is provided which can be performed within a reactor that contains the alkylation catalyst or outside the reactor. Effective catalyst reactivation is achieved whether the catalyst is completely deactivated or partially deactivated. A fluid reactivating agent is employed to dissolve catalyst fouling agents and also to react with such agents and carry away the reaction products. The deactivated catalyst is contacted with the fluid reactivating agent under pressure and temperature conditions such that the fluid reactivating agent is dense enough to effectively dissolve the fouling agents and any reaction products of the fouling agents and the reactivating agent. Useful pressures and temperatures for reactivation include near-critical, critical, and supercritical pressures and temperatures for the reactivating agent. The fluid reactivating agent can include, for example, a branched paraffin containing at least one tertiary carbon atom, or a compound that can be isomerized to a molecule containing at least one tertiary carbon atom.

  9. PDF methods for turbulent reactive flows

    NASA Technical Reports Server (NTRS)

    Hsu, Andrew T.

    1995-01-01

    Viewgraphs are presented on computation of turbulent combustion, governing equations, closure problem, PDF modeling of turbulent reactive flows, validation cases, current projects, and collaboration with industry and technology transfer.

  10. A heuristic method for reactive power planning

    SciTech Connect

    Mantovani, J.R.S.

    1996-02-01

    An approach for solving reactive power planning problems is presented, which is based on binary search techniques and the use of a special heuristic to obtain a discrete solution. Two versions were developed, one to run on conventional (sequential) computers and the other to run on a distributed memory (hypercube) machine. This latter parallel processing version employs an asynchronous programming model. Once the set of candidate bases has been defined, the program gives the location and size of the reactive sources needed (if any) in keeping with operating and security constraints.

  11. Reactive ion etched substrates and methods of making and using

    SciTech Connect

    Rucker, Victor C.; Shediac, Rene; Simmons, Blake A.; Havenstrite, Karen L.

    2007-08-07

    Disclosed herein are substrates comprising reactive ion etched surfaces and specific binding agents immobilized thereon. The substrates may be used in methods and devices for assaying or isolating analytes in a sample. Also disclosed are methods of making the reactive ion etched surfaces.

  12. Method for generating a highly reactive plasma for exhaust gas after treatment and enhanced catalyst reactivity

    SciTech Connect

    Whealton, John H.; Hanson, Gregory R.; Storey, John M.; Raridon, Richard J.; Armfield, Jeffrey S.; Bigelow, Timothy S.; Graves, Ronald L.

    2000-07-01

    This patent application describes a method and apparatus of exhaust gas remediation that enhance the reactivity of the material catalysts found within catalytic converters of cars, trucks, and power stations.

  13. Development and first applications of an OH reactivity instrument based on the Comparative Reactivity Method

    NASA Astrophysics Data System (ADS)

    Dusanter, S.; Michoud, V.; Hansen, R. F.; Leonardis, T.; Locoge, N.; Stevens, P. S.; Blocquet, M.; Schoemaecker, C.; Fittschen, C. M.; Zannoni, N.; Gros, V.; Sarda Esteve, R.; Sinha, V.

    2015-12-01

    Assessing the oxidative capacity of the atmosphere is important to address fundamental issues related to both air quality and climate change. However, recent measurements of total OH reactivity have highlighted an incomplete understanding of the hydroxyl radical (OH) budget, the main oxidizing agent in the atmosphere. This context has led to the development of several techniques for measuring total OH reactivity to better constrain atmospheric chemistry. This presentation will review the development of an OH reactivity instrument developed at Mines Douai, France. This instrument, based on the Comparative Reactivity Method (CRM), has been carefully characterized in the laboratory and has been compared to other OH reactivity instruments during two different field campaigns. These studies will be summarized to show that CRM instruments can perform reliable measurements in urban and remote areas providing that a few measurement artefacts are well characterized and accounted for during field campaigns.

  14. A Multi-domain Spectral Method for Supersonic Reactive Flows

    NASA Technical Reports Server (NTRS)

    Don, Wai-Sun; Gottlieb, David; Jung, Jae-Hun; Bushnell, Dennis M. (Technical Monitor)

    2002-01-01

    This paper has a dual purpose: it presents a multidomain Chebyshev method for the solution of the two-dimensional reactive compressible Navier-Stokes equations, and it reports the results of the application of this code to the numerical simulations of high Mach number reactive flows in recessed cavity. The computational method utilizes newly derived interface boundary conditions as well as an adaptive filtering technique to stabilize the computations. The results of the simulations are relevant to recessed cavity flameholders.

  15. Evaluation of Methods to Predict Reactivity of Gold Nanoparticles

    SciTech Connect

    Allison, Thomas C.; Tong, Yu ye J.

    2011-06-20

    Several methods have appeared in the literature for predicting reactivity on metallic surfaces and on the surface of metallic nanoparticles. All of these methods have some relationship to the concept of frontier molecular orbital theory. The d-band theory of Hammer and Nørskov is perhaps the most widely used predictor of reactivity on metallic surfaces, and it has been successfully applied in many cases. Use of the Fukui function and the condensed Fukui function is well established in organic chemistry, but has not been so widely applied in predicting the reactivity of metallic nanoclusters. In this article, we will evaluate the usefulness of the condensed Fukui function in predicting the reactivity of a family of cubo-octahedral gold nanoparticles and make comparison with the d-band method.

  16. Method for preparing hydride configurations and reactive metal surfaces

    DOEpatents

    Silver, G.L.

    1984-05-18

    A method for preparing reactive metal surfaces, particularly uranium surfaces is disclosed, whereby the metal is immediately reactive to hydrogen gas at room temperature and low pressure. The metal surfaces are first pretreated by exposure to an acid which forms an adherent hydride-bearing composition on the metal surface. Subsequent heating of the pretreated metal at a temperature sufficient to decompose the hydride coating in vacuum or inert gas renders the metal surface instantaneously reactive to hydrogen gas at room temperature and low pressure.

  17. Quantification of Hydroxyl Radical reactivity in the urban environment using the Comparative Reactivity Method (CRM)

    NASA Astrophysics Data System (ADS)

    Panchal, Rikesh; Monks, Paul

    2015-04-01

    Hydroxyl (OH) radicals play an important role in 'cleansing' the atmosphere of many pollutants such as, NOx, CH4 and various VOCs, through oxidation. To measure the reactivity of OH, both the sinks and sources of OH need to be quantified, and currently the overall sinks of OH seem not to be fully constrained. In order to measure the total rate loss of OH in an ambient air sample, all OH reactive species must be considered and their concentrations and reaction rate coefficients with OH known. Using the method pioneered by Sinha and Williams at the Max Plank Institute Mainz, the Comparative Reactivity Method (CRM) which directly quantifies total OH reactivity in ambient air without the need to consider the concentrations of individual species within the sample that can react with OH, has been developed and applied in a urban setting. The CRM measures the concentration of a reactive species that is present only in low concentrations in ambient air, in this case pyrrole, flowing through a reaction vessel and detected using Proton Transfer Reaction - Mass Spectrometry (PTR-MS). The poster will show a newly developed and tested PTR-TOF-MS system for CRM. The correction regime will be detailed to account for the influence of the varying humidity between ambient air and clean air on the pyrrole signal. Further, examination of the sensitivity dependence of the PTR-MS as a function of relative humidity and H3O+(H2O) (m/z=37) cluster ion allows the correction for the humidity variation, between the clean humid air entering the reaction vessel and ambient air will be shown. NO, present within ambient air, is also a potential interference and can cause recycling of OH, resulting in an overestimation of OH reactivity. Tests have been conducted on the effects of varying NO concentrations on OH reactivity and a correction factor determined for application to data when sampling ambient air. Finally, field tests in the urban environment at the University of Leicester will be shown

  18. Method and apparatus for measuring reactivity of fissile material

    DOEpatents

    Lee, D.M.; Lindquist, L.O.

    1982-09-07

    Given are a method and apparatus for measuring nondestructively and noninvasively (i.e., using no internal probing) the burnup, reactivity, or fissile content of any material which emits neutrons and which has fissionable components. The assay is accomplished by altering the return flux of neutrons into the fuel assembly by means of changing the reflecting material. The existing passive neutron emissions in the material being assayed are used as the source of interrogating neutrons. Two measurements of either emitted neutron or emitted gamma-ray count rates are made and are then correlated to either reactivity, burnup, or fissionable content of the material being assayed, thus providing a measurement of either reactivity, burnup, or fissionable content of the material being assayed. Spent fuel which has been freshly discharged from a reactor can be assayed using this method and apparatus. Precisions of 1000 MWd/tU appear to be feasible.

  19. Environmentally stable reactive alloy powders and method of making same

    DOEpatents

    Anderson, Iver E.; Lograsso, Barbara K.; Terpstra, Robert L.

    1998-09-22

    Apparatus and method for making powder from a metallic melt by atomizing the melt to form droplets and reacting the droplets downstream of the atomizing location with a reactive gas. The droplets are reacted with the gas at a temperature where a solidified exterior surface is formed thereon and where a protective refractory barrier layer (reaction layer) is formed whose penetration into the droplets is limited by the presence of the solidified surface so as to avoid selective reduction of key reactive alloyants needed to achieve desired powder end use properties. The barrier layer protects the reactive powder particles from environmental constituents such as air and water in the liquid or vapor form during subsequent fabrication of the powder to end-use shapes and during use in the intended service environment.

  20. Environmentally stable reactive alloy powders and method of making same

    DOEpatents

    Anderson, I.E.; Lograsso, B.K.; Terpstra, R.L.

    1998-09-22

    Apparatus and method are disclosed for making powder from a metallic melt by atomizing the melt to form droplets and reacting the droplets downstream of the atomizing location with a reactive gas. The droplets are reacted with the gas at a temperature where a solidified exterior surface is formed thereon and where a protective refractory barrier layer (reaction layer) is formed whose penetration into the droplets is limited by the presence of the solidified surface so as to avoid selective reduction of key reactive alloys needed to achieve desired powder end use properties. The barrier layer protects the reactive powder particles from environmental constituents such as air and water in the liquid or vapor form during subsequent fabrication of the powder to end-use shapes and during use in the intended service environment. 7 figs.

  1. Method and apparatus for measuring reactivity of fissile material

    DOEpatents

    Lee, David M.; Lindquist, Lloyd O.

    1985-01-01

    Given are a method and apparatus for measuring nondestructively and non-invasively (i.e., using no internal probing) the burnup, reactivity, or fissile content of any material which emits neutrons and which has fissionable components. No external neutron-emitting interrogation source or fissile material is used and no scanning is required, although if a profile is desired scanning can be used. As in active assays, here both reactivity and content of fissionable material can be measured. The assay is accomplished by altering the return flux of neutrons into the fuel assembly. The return flux is altered by changing the reflecting material. The existing passive neutron emissions in the material being assayed are used as the source of interrogating neutrons. Two measurements of either emitted neutron or emitted gamma-ray count rates are made and are then correlated to either reactivity, burnup, or fissionable content of the material being assayed, thus providing a measurement of either reactivity, burnup, or fissionable content of the material being assayed. Spent fuel which has been freshly discharged from a reactor can be assayed using this method and apparatus. Precisions of 1000 MWd/tU appear to be feasible.

  2. Method for generating a highly reactive plasma for exhaust gas aftertreatment and enhanced catalyst reactivity

    DOEpatents

    Whealton, John H.; Hanson, Gregory R.; Storey, John M.; Raridon, Richard J.; Armfield, Jeffrey S.; Bigelow, Timothy S.; Graves, Ronald L.

    2002-01-01

    A method for non-thermal plasma aftertreatment of exhaust gases the method comprising the steps of providing short risetime, high frequency, high power bursts of low-duty factor microwaves sufficient to generate a plasma discharge and passing a gas to be treated through the discharge so as to cause dissociative reduction of the exhaust gases and enhanced catalyst reactivity through application of the pulsed microwave fields directly to the catalyst material sufficient to cause a polarizability catastrophe and enhanced heating of the metal crystallite particles of the catalyst, and in the presence or absence of the plasma. The invention also includes a reactor for aftertreatment of exhaust gases.

  3. Parallel computation of multigroup reactivity coefficient using iterative method

    SciTech Connect

    Susmikanti, Mike; Dewayatna, Winter

    2013-09-09

    One of the research activities to support the commercial radioisotope production program is a safety research target irradiation FPM (Fission Product Molybdenum). FPM targets form a tube made of stainless steel in which the nuclear degrees of superimposed high-enriched uranium. FPM irradiation tube is intended to obtain fission. The fission material widely used in the form of kits in the world of nuclear medicine. Irradiation FPM tube reactor core would interfere with performance. One of the disorders comes from changes in flux or reactivity. It is necessary to study a method for calculating safety terrace ongoing configuration changes during the life of the reactor, making the code faster became an absolute necessity. Neutron safety margin for the research reactor can be reused without modification to the calculation of the reactivity of the reactor, so that is an advantage of using perturbation method. The criticality and flux in multigroup diffusion model was calculate at various irradiation positions in some uranium content. This model has a complex computation. Several parallel algorithms with iterative method have been developed for the sparse and big matrix solution. The Black-Red Gauss Seidel Iteration and the power iteration parallel method can be used to solve multigroup diffusion equation system and calculated the criticality and reactivity coeficient. This research was developed code for reactivity calculation which used one of safety analysis with parallel processing. It can be done more quickly and efficiently by utilizing the parallel processing in the multicore computer. This code was applied for the safety limits calculation of irradiated targets FPM with increment Uranium.

  4. Parallel computation of multigroup reactivity coefficient using iterative method

    NASA Astrophysics Data System (ADS)

    Susmikanti, Mike; Dewayatna, Winter

    2013-09-01

    One of the research activities to support the commercial radioisotope production program is a safety research target irradiation FPM (Fission Product Molybdenum). FPM targets form a tube made of stainless steel in which the nuclear degrees of superimposed high-enriched uranium. FPM irradiation tube is intended to obtain fission. The fission material widely used in the form of kits in the world of nuclear medicine. Irradiation FPM tube reactor core would interfere with performance. One of the disorders comes from changes in flux or reactivity. It is necessary to study a method for calculating safety terrace ongoing configuration changes during the life of the reactor, making the code faster became an absolute necessity. Neutron safety margin for the research reactor can be reused without modification to the calculation of the reactivity of the reactor, so that is an advantage of using perturbation method. The criticality and flux in multigroup diffusion model was calculate at various irradiation positions in some uranium content. This model has a complex computation. Several parallel algorithms with iterative method have been developed for the sparse and big matrix solution. The Black-Red Gauss Seidel Iteration and the power iteration parallel method can be used to solve multigroup diffusion equation system and calculated the criticality and reactivity coeficient. This research was developed code for reactivity calculation which used one of safety analysis with parallel processing. It can be done more quickly and efficiently by utilizing the parallel processing in the multicore computer. This code was applied for the safety limits calculation of irradiated targets FPM with increment Uranium.

  5. Method for treating reactive metals in a vacuum furnace

    DOEpatents

    Hulsey, W.J.

    1975-10-28

    The invention is directed to a method for reducing the contamination of reactive metal melts in vacuum furnaces due to the presence of residual gaseous contaminants in the furnace atmosphere. This reduction is achieved by injecting a stream of inert gas directly over the metal confined in a substantially closed crucible with the flow of the gas being sufficient to establish a pressure differential between the interior of the crucible and the furnace atmosphere.

  6. Treatment of reactive interfaces in pore-scale reactive transport with the phase-field method

    NASA Astrophysics Data System (ADS)

    Huber, C.; Di Palma, P. R.

    2014-12-01

    The two major challenges for continuum reactive transport models are the treatment of interfaces between different phases (multi-fluids like DNAPL-water, or solid-fluid) and the ability to model transient chemical gradients at the pore-scale. Pore-scale models allow us to deal naturally with chemical gradients at the discrete scale and they generally consider interfaces as boundary conditions that satisfy a local, but modified, mass balance equation. In other word grains do not take part in the mass balance of chemical species besides providing a boundary condition for the fluid. For instance, heterogeneous reactions at solid-fluid boundaries are framed as a balance between incoming chemical flux and reactions. Due to complex topology of interfaces in natural porous media, the treatment of heterogeneous reactions depends on the orientation of the interface and therefore requires a special care. It can become complicated and tedious especially when interfaces are allowed to evolve with time. Approaches such as the enthalpy method, which was developed for solving moving interfaces during melting processes, offer the advantage of a treatment that is independent of the shape of the moving interface. Similar methods have been used for modeling multiphase flows with diffuse interface successfully. Here, we expand on these approaches and introduce a phase-field approach to introduce heterogeneous reactions in single and multiphase reactive flows at the pore-scale. Mass conservation is solved in each phase and we introduce interface conditions as a source/sink term in the conservation equation rather than a boundary condition. The advantages are that the method becomes independent of the (time-dependent) topology of the interface and automatically enforces local mass conservation between the different constituents of the domain. We show validations of the model and applications to multispecies reactive transport, isotope fractionation during calcite growth and finally

  7. Layered reactive particles with controlled geometries, energies, and reactivities, and methods for making the same

    DOEpatents

    Fritz, Gregory M; Knepper, Robert Allen; Weihs, Timothy P; Gash, Alexander E; Sze, John S

    2013-04-30

    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.

  8. Layered reactive particles with controlled geometries, energies, and reactivities, and methods for making the same

    DOEpatents

    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.

  9. Method for preparing hydride configurations and reactive metal surfaces

    DOEpatents

    Silver, Gary L.

    1988-08-16

    A method for preparing highly hydrogen-reactive surfaces on metals which normally require substantial heating, high pressures, or an extended induction period, which involves pretreatment of said surfaces with either a non-oxidizing acid or hydrogen gas to form a hydrogen-bearing coating on said surfaces, and subsequently heating said coated metal in the absence of moisture and oxygen for a period sufficient to decompose said coating and cooling said metal to room temperature. Surfaces so treated will react almost instantaneously with hydrogen gas at room temperature and low pressure. The method is particularly applicable to uranium, thorium, and lanthanide metals.

  10. Quadrature Moments Method for the Simulation of Turbulent Reactive Flows

    NASA Technical Reports Server (NTRS)

    Raman, Venkatramanan; Pitsch, Heinz; Fox, Rodney O.

    2003-01-01

    A sub-filter model for reactive flows, namely the DQMOM model, was formulated for Large Eddy Simulation (LES) using the filtered mass density function. Transport equations required to determine the location and size of the delta-peaks were then formulated for a 2-peak decomposition of the FDF. The DQMOM scheme was implemented in an existing structured-grid LES solver. Simulations of scalar shear layer using an experimental configuration showed that the first and second moments of both reactive and inert scalars are in good agreement with a conventional Lagrangian scheme that evolves the same FDF. Comparisons with LES simulations performed using laminar chemistry assumption for the reactive scalar show that the new method provides vast improvements at minimal computational cost. Currently, the DQMOM model is being implemented for use with the progress variable/mixture fraction model of Pierce. Comparisons with experimental results and LES simulations using a single-environment for the progress-variable are planned. Future studies will aim at understanding the effect of increase in environments on predictions.

  11. Advanced hydraulic fracturing methods to create in situ reactive barriers

    SciTech Connect

    Murdoch, L. |; Siegrist, B.; Vesper, S.

    1997-12-31

    Many contaminated areas consist of a source area and a plume. In the source area, the contaminant moves vertically downward from a release point through the vadose zone to an underlying saturated region. Where contaminants are organic liquids, NAPL may accumulate on the water table, or it may continue to migrate downward through the saturated region. Early developments of permeable barrier technology have focused on intercepting horizontally moving plumes with vertical structures, such as trenches, filled with reactive material capable of immobilizing or degrading dissolved contaminants. This focus resulted in part from a need to economically treat the potentially large volumes of contaminated water in a plume, and in part from the availability of construction technology to create the vertical structures that could house reactive compounds. Contaminant source areas, however, have thus far remained largely excluded from the application of permeable barrier technology. One reason for this is the lack of conventional construction methods for creating suitable horizontal structures that would place reactive materials in the path of downward-moving contaminants. Methods of hydraulic fracturing have been widely used to create flat-lying to gently dipping layers of granular material in unconsolidated sediments. Most applications thus far have involved filling fractures with coarse-grained sand to create permeable layers that will increase the discharge of wells recovering contaminated water or vapor. However, it is possible to fill fractures with other compounds that alter the chemical composition of the subsurface. One early application involved development and field testing micro-encapsulated sodium percarbonate, a solid compound that releases oxygen and can create aerobic conditions suitable for biodegradation in the subsurface for several months.

  12. Advanced hydraulic fracturing methods to create in situ reactive barriers

    SciTech Connect

    Murdoch, L. |; Siegrist, B.; Meiggs, T.

    1997-12-31

    This article describes the use of hydraulic fracturing to increase permeability in geologic formations where in-situ remedial action of contaminant plumes will be performed. Several in-situ treatment strategies are discussed including the use of hydraulic fracturing to create in situ redox zones for treatment of organics and inorganics. Hydraulic fracturing methods offer a mechanism for the in-situ treatment of gently dipping layers of reactive compounds. Specialized methods using real-time monitoring and a high-energy jet during fracturing allow the form of the fracture to be influenced, such as creation of assymmetric fractures beneath potential sources (i.e. tanks, pits, buildings) that should not be penetrated by boring. Some examples of field applications of this technique such as creating fractures filled with zero-valent iron to reductively dechlorinate halogenated hydrocarbons, and the use of granular activated carbon to adsorb compounds are discussed.

  13. Method of measuring reactive acoustic power density in a fluid

    DOEpatents

    Wheatley, John C.; Swift, Gregory W.; Migliori, Albert

    1985-01-01

    A method for determining reactive acoustic power density level and its direction in a fluid using a single sensor is disclosed. In the preferred embodiment, an apparatus for conducting the method, which is termed a thermoacoustic couple, consists of a stack of thin, spaced apart polymeric plates, selected ones of which include multiple bimetallic thermocouple junctions positioned along opposite end edges thereof. The thermocouple junctions are connected in series in the nature of a thermopile, and are arranged so as to be responsive to small temperature differences between the opposite edges of the plates. The magnitude of the temperature difference, as represented by the magnitude of the electrical potential difference generated by the thermopile, is found to be directly related to the level of acoustic power density in the gas.

  14. Method of measuring reactive acoustic power density in a fluid

    DOEpatents

    Wheatley, J.C.; Swift, G.W.; Migliori, A.

    1985-09-03

    A method for determining reactive acoustic power density level and its direction in a fluid using a single sensor is disclosed. In the preferred embodiment, an apparatus for conducting the method, which is termed a thermoacoustic couple, consists of a stack of thin, spaced apart polymeric plates, selected ones of which include multiple bimetallic thermocouple junctions positioned along opposite end edges thereof. The thermocouple junctions are connected in series in the nature of a thermopile, and are arranged so as to be responsive to small temperature differences between the opposite edges of the plates. The magnitude of the temperature difference, as represented by the magnitude of the electrical potential difference generated by the thermopile, is found to be directly related to the level of acoustic power density in the gas. 5 figs.

  15. A new three-dimensional method of fault reactivation analysis

    NASA Astrophysics Data System (ADS)

    Leclere, H.; Fabbri, O.

    2012-12-01

    A 3-D method to evaluate the reactivation potential of fault planes is proposed. The method can be applied to cohesive or non cohesive faults whatever their orientation and without any condition on the regional stress field. It allows to compute the effective stress ratio σ3'/σ1' required to reactivate any fault plane and to determine whether the plane is favorably oriented, unfavorably oriented or severely misoriented with respect to the ambient stress field. The method also includes a graphical sorting tool which consists in plotting poles of fault planes on stereoplots on which the boundaries separating the three domains corresponding to favorable orientations, unfavorable orientations and severe misorientations cases are drawn. The delineation of these domains is based on the value of the σ3'/σ1' ratio which itself depends on the orientation of the fault plane with respect to the principal stress axis orientations, the stress shape ratio (Φ = (σ2 - σ3)/(σ1- σ3)), the coefficient of static friction μs of the fault, and the fault cohesion C0. The method is applied on 145 focal mechanisms of the 2011 March 11th Tohoku-Oki (Japan) earthquake sequence. This application allows to delineate, along or in the vicinity of the plate interface, three types of domains characterized by favorable orientations, unfavorable orientations or severe misorientations of mainshock/aftershock fault planes. The 'severe misorientation' domains likely correspond to parts of the plate interface characterized by pore fluid pressures exceeding the magnitude of the regional least principal stress component. Stereoplots for application of the 3-D fault reactivation analysis. The stereoplots at the summits of the central triangle correspond to the three possible Andersonian stress tensors (one vertical principal stress axis, successively σ1 ,σ2 and σ3). The three other triangles shearing two tops with the central triangle are characterized by non-Andersonian stress tensors with

  16. Methods for Detection of Mitochondrial and Cellular Reactive Oxygen Species

    PubMed Central

    Harrison, David G.

    2014-01-01

    Abstract Significance: Mitochondrial and cellular reactive oxygen species (ROS) play important roles in both physiological and pathological processes. Different ROS, such as superoxide (O2•−), hydrogen peroxide, and peroxynitrite (ONOO•−), stimulate distinct cell-signaling pathways and lead to diverse outcomes depending on their amount and subcellular localization. A variety of methods have been developed for ROS detection; however, many of these methods are not specific, do not allow subcellular localization, and can produce artifacts. In this review, we will critically analyze ROS detection and present advantages and the shortcomings of several available methods. Recent Advances: In the past decade, a number of new fluorescent probes, electron-spin resonance approaches, and immunoassays have been developed. These new state-of-the-art methods provide improved selectivity and subcellular resolution for ROS detection. Critical Issues: Although new methods for HPLC superoxide detection, application of fluorescent boronate-containing probes, use of cell-targeted hydroxylamine spin probes, and immunospin trapping have been available for several years, there has been lack of translation of these into biomedical research, limiting their widespread use. Future Directions: Additional studies to translate these new technologies from the test tube to physiological applications are needed and could lead to a wider application of these approaches to study mitochondrial and cellular ROS. Antioxid. Redox Signal. 20, 372–382. PMID:22978713

  17. Comparison of Total OH Reactivity Measurement Methods in Ambient Air between a Comparative Reactivity Method using PTR-MS and a LASER Technique

    NASA Astrophysics Data System (ADS)

    Okazaki, H.; Osada, T.; Nakashima, Y.; Kato, S.; Kajii, Y.

    2008-12-01

    OH radical plays an important role in atmospheric chemistry. OH reactivity measurement is essential to understand atmospheric chemical reaction processes. We have developed LASER technique to measure OH reactivity. This system requires both pump and probe lasers and high vacuum system. We have to pay a lot of efforts to bring the instrument in the field for ambient observation. Therefore we have developed a comparative reactivity method for measuring total OH reactivity recently. Since this method does not need a large space and complicated devices, it makes relatively easy to measure OH reactivity anywhere. The result of this non-laser OH reactivity measurement was compared with that of laser pump and probe technique as conducted an intensive field measurement of sub-urban air in Tokyo, July 2008. In comparative reactivity method, a regent species (X), which is ideally not present in ambient air, is introduced into the flow tube reactor and its concentration (C1) is monitored by a suitable detector under nitrogen atmospheric condition. A constant amount of OH radicals is then introduced into the flow tube to react with X under either nitrogen atmosphere (the concentration of X became C2) or ambient air (the concentration of X became C3). Total OH reactivity can be calculated by comparing C1, C2 and C3. OH radicals were produced in the photolysis of water vapor by a UV lamp. In our experiment, Pyrrole is selected as X and PTR-MS is used as a detector. The concentrations of NO, NO2, CO, SO2 were also measured. In some case, the two methods indicated some differences, for example, OH reactivity of 10 to 30 s-1 measured by LASER technique while the comparative reactivity method showed the value of only 5 to 12 s-1.This reason appears to be humidity dependence of PTR-MS sensitivity. Good agreements, for trends and absolute values, were found for comparison between the two methods during another day of experiment where both methods reveal OH reactivity ranging between

  18. Atmospheric measurements of total OH reactivity: Intercomparison of the pump-probe technique and the comparative reactivity method

    NASA Astrophysics Data System (ADS)

    Dusanter, Sebastien; Hansen, Robert; Leonardis, Thierry; Schoemaecker, Coralie; Blocquet, Marion; Fittschen, Christa; Hanoune, Benjamin; Sinha, Vinayak; Stevens, Philip; Locoge, Nadine

    2013-04-01

    The hydroxyl radical (OH) drives the oxidation of organic trace gases that can lead to the production of ozone and secondary organic aerosols in the atmosphere. A complete understanding of the sources and sinks of OH is therefore important to address issues related to both air quality and climate change. However, recent measurements of total OH reactivity [1-2], which is the inverse of the OH lifetime, have pointed out that our understanding of OH sinks is still incomplete and important reactive trace gases have not yet been identified. These measurements of total OH reactivity are of particular interest since they provide a critical test of our understanding of the OH budget. Three techniques are available to measure the total OH reactivity, including the total OH loss rate method [3], the pump-probe method [4], and the comparative reactivity method (CRM) [5]. While the first two methods are based on direct measurements of OH decays using laser-induced fluorescence instruments, the CRM is based on a different approach in which a tracer molecule is detected instead of OH to determine the ambient OH loss rate. As these instruments were deployed in different field campaigns, intercomparison exercises would be useful to ensure the accuracy of the measurements. However, such intercomparisons have not yet been published. An informal intercomparison involving a CRM instrument from the Ecole des Mines de Douai (EMD) and a pump-probe instrument from the laboratory Physicochimie des Processus de Combustion et de l'Atmosphere (PC2A) took place in an urban environment at the university of Lille (France). The two OH reactivity instruments measured continuously side by side for a duration of two weeks. Collocated measurements of trace gases were also performed using O3, NOx and SO2 monitors, as well as two automated chromatographic instruments capable of measuring more than 50 volatile organic compounds (VOC). We will present cross calibrations of the two OH reactivity

  19. Grinding methods to enhance the reactivity of olivine

    SciTech Connect

    Summers, Cathy A.; Dahlin, David C.; Rush, Gilbert E.; O'Connor, William K.; Gerdemann, Stephen J.

    2005-08-01

    The Albany Research Center (ARC) conducted studies of mechanical activation by conventional and ultrafine grinding techniques to enhance olivine reactivity in mineral carbonation reactions. Activated olivine is one of several solid feed materials used at ARC in reactions with carbon dioxide to form carbonate minerals. This paper compares grinding techniques via energy demand data and product characteristics, including particle size distributions, surface areas, full-width-at-half-maximum (FWHM) XRD analyses, and particle morphology by SEM analyses. Reactivity was calculated by percent conversion to carbonate in subsequent carbonation tests. Particle size reduction has the greatest impact on reactivity, and wet grinding is more energy efficient than dry grinding. Large additional inputs of energy to increase surface area or reduce crystallinity do not result in proportional improvements in reactivity.

  20. METHOD OF ALLOYING REACTIVE METALS WITH ALUMINUM OR BERYLLIUM

    DOEpatents

    Runnalls, O.J.C.

    1957-10-15

    A halide of one or more of the reactive metals, neptunium, cerium and americium, is mixed with aluminum or beryllium. The mass is heated at 700 to 1200 deg C, while maintaining a substantial vacuum of above 10/sup -3/ mm of mercury or better, until the halide of the reactive metal is reduced and the metal itself alloys with the reducing metal. The reaction proceeds efficiently due to the volatilization of the halides of the reducing metal, aluminum or beryllium.

  1. Grinding methods to enhance the reactivity of olivine

    SciTech Connect

    Summers, Cathy A.; Dahlin, David C.; Rush, Gilbert E.; O'Connor, William K.; Gerdemann, Stephen J.

    2004-01-01

    The Albany Research Center (ARC) conducted studies of mechanical activation by conventional and ultra-fine grinding techniques to enhance olivine reactivity in mineral carbonation reactions. Activated olivine is one of several solid feed materials used at ARC in reactions with carbon dioxide to form carbonate minerals. This paper compares grinding techniques via energy demand data and product characteristics, including particle size distributions, surface areas, full width at half maximum (FWHM) XRD analyses, and particle morphology by SEM analyses. Reactivity was gauged by percent conversion to carbonate in subsequent carbonation tests.

  2. Solution of Reactive Compressible Flows Using an Adaptive Wavelet Method

    NASA Astrophysics Data System (ADS)

    Zikoski, Zachary; Paolucci, Samuel; Powers, Joseph

    2008-11-01

    This work presents numerical simulations of reactive compressible flow, including detailed multicomponent transport, using an adaptive wavelet algorithm. The algorithm allows for dynamic grid adaptation which enhances our ability to fully resolve all physically relevant scales. The thermodynamic properties, equation of state, and multicomponent transport properties are provided by CHEMKIN and TRANSPORT libraries. Results for viscous detonation in a H2:O2:Ar mixture, and other problems in multiple dimensions, are included.

  3. Method for generating a highly reactive plasma for exhaust gas aftertreatment and enhanced catalyst reactivity

    DOEpatents

    Whealton, John H.; Hanson, Gregory R.; Storey, John M.; Raridon, Richard J.; Armfield, Jeffrey S.; Bigelow, Timothy S.; Graves, Ronald L.

    2001-01-01

    A method for non-thermal plasma aftertreatment of exhaust gases the method comprising the steps of providing short risetime (about 40 ps), high frequency (about 5G hz), high power bursts of low-duty factor microwaves sufficient to generate a dielectric barrier discharge and passing a gas to treated through the discharge so as to cause dissociative reduction of the exhaust gases. The invention also includes a reactor for generating the non-thermal plasma.

  4. Detailed characterization of a Comparative Reactivity Method (CRM) instrument for ambient OH reactivity measurements: experiments vs. modeling

    NASA Astrophysics Data System (ADS)

    Michoud, Vincent; Locoge, Nadine; Dusanter, Sébastien

    2015-04-01

    The Hydroxyl radical (OH) is the main daytime oxidant in the troposphere, leading to the oxidation of Volatile Organic Compounds (VOCs) and the formation of harmful pollutants such as ozone (O3) and Secondary Organic Aerosols (SOA). While OH plays a key role in tropospheric chemistry, recent studies have highlighted that there are still uncertainties associated with the OH budget, i.e the identification of sources and sinks and the quantification of production and loss rates of this radical. It has been demonstrated that ambient measurements of the total OH loss rate (also called total OH reactivity) can be used to identify and reduce these uncertainties. In this context, the Comparative Reactivity Method (CRM), developed by Sinha et al. (ACP, 2008), is a promising technique to measure total OH reactivity in ambient air and has already been used during several field campaigns. This technique relies on monitoring competitive reactions of OH with ambient trace gases and a reference compound (pyrrole) in a sampling reactor to derive ambient OH reactivity. However, this technique requires a complex data processing chain that has yet to be carefully investigated in the laboratory. In this study, we present a detailed characterization of a CRM instrument developed at Mines Douai, France. Experiments have been performed to investigate the dependence of the CRM response on humidity, ambient NOx levels, and the pyrrole-to-OH ratio inside the sampling reactor. Box modelling of the chemistry occurring in the reactor has also been performed to assess our theoretical understanding of the CRM measurement. This work shows that the CRM response is sensitive to both humidity and NOx, which can be accounted for during data processing using parameterizations depending on the pyrrole-to-OH ratio. The agreement observed between laboratory studies and model results suggests a good understanding of the chemistry occurring in the sampling reactor and gives confidence in the CRM

  5. Method of making a ceramic with preferential oxygen reactive layer

    NASA Technical Reports Server (NTRS)

    Wang, Hongyu (Inventor); Luthra, Krishan Lal (Inventor)

    2003-01-01

    A method of forming an article. The method comprises forming a silicon-based substrate that is oxidizable by reaction with an oxidant to form at least one gaseous product and applying an intermediate layer/coating onto the substrate, wherein the intermediate layer/coating is oxidizable to a nongaseous product by reaction with the oxidant in preference to reaction of the silicon-containing substrate with the oxidant.

  6. Cold Pad-Batch dyeing method for cotton fabric dyeing with reactive dyes using ultrasonic energy.

    PubMed

    Khatri, Zeeshan; Memon, Muhammad Hanif; Khatri, Awais; Tanwari, Anwaruddin

    2011-11-01

    Reactive dyes are vastly used in dyeing and printing of cotton fibre. These dyes have a distinctive reactive nature due to active groups which form covalent bonds with -OH groups of cotton through substitution and/or addition mechanism. Among many methods used for dyeing cotton with reactive dyes, the Cold Pad Batch (CPB) method is relatively more environment friendly due to high dye fixation and non requirement of thermal energy. The dyed fabric production rate is low due to requirement of at least twelve hours batching time for dye fixation. The proposed CPB method for dyeing cotton involves ultrasonic energy resulting into a one third decrease in batching time. The dyeing of cotton fibre was carried out with CI reactive red 195 and CI reactive black 5 by conventional and ultrasonic (US) method. The study showed that the use of ultrasonic energy not only shortens the batching time but the alkalis concentrations can considerably be reduced. In this case, the colour strength (K/S) and dye fixation (%F) also enhances without any adverse effect on colour fastness of the dyed fabric. The appearance of dyed fibre surface using scanning electron microscope (SEM) showed relative straightening of fibre convolutions and significant swelling of the fibre upon ultrasonic application. The total colour difference values ΔE (CMC) for the proposed method, were found within close proximity to the conventionally dyed sample. PMID:21550289

  7. Molecular simulation of shocked materials using the reactive Monte Carlo method.

    PubMed

    Brennan, John K; Rice, Betsy M

    2002-08-01

    We demonstrate the applicability of the reactive Monte Carlo (RxMC) simulation method [J. K. Johnson, A. Z. Panagiotopoulos, and K. E. Gubbins, Mol. Phys. 81, 717 (1994); W. R. Smith and B. Tríska, J. Chem. Phys. 100, 3019 (1994)] for calculating the shock Hugoniot properties of a material. The method does not require interaction potentials that simulate bond breaking or bond formation; it requires only the intermolecular potentials and the ideal-gas partition functions for the reactive species that are present. By performing Monte Carlo sampling of forward and reverse reaction steps, the RxMC method provides information on the chemical equilibria states of the shocked material, including the density of the reactive mixture and the mole fractions of the reactive species. We illustrate the methodology for two simple systems (shocked liquid NO and shocked liquid N2), where we find excellent agreement with experimental measurements. The results show that the RxMC methodology provides an important simulation tool capable of testing models used in current detonation theory predictions. Further applications and extensions of the reactive Monte Carlo method are discussed. PMID:12241148

  8. ADVANCING REACTIVE TRACER METHODS FOR MONITORING THERMAL DRAWDOWN IN GEOTHERMAL ENHANCED GEOTHERMAL RESERVOIRS

    SciTech Connect

    Mitchell A. Plummer; Carl D. Palmer; Earl D. Mattson; George D. Redden; Laurence C. Hull

    2010-10-01

    Reactive tracers have long been considered a possible means of measuring thermal drawdown in a geothermal system, before significant cooling occurs at the extraction well. Here, we examine the sensitivity of the proposed method to evaluate reservoir cooling and demonstrate that while the sensitivity of the method as generally proposed is low, it may be practical under certain conditions.

  9. Methods and apparatuses for reagent delivery, reactive barrier formation, and pest control

    DOEpatents

    Gilmore, Tyler [Pasco, WA; Kaplan, Daniel I [Aiken, SC; Last, George [Richland, WA

    2002-07-09

    A reagent delivery method includes positioning reagent delivery tubes in contact with soil. The tubes can include a wall that is permeable to a soil-modifying reagent. The method further includes supplying the reagent in the tubes, diffusing the reagent through the permeable wall and into the soil, and chemically modifying a selected component of the soil using the reagent. The tubes can be in subsurface contact with soil, including groundwater, and can be placed with directional drilling equipment independent of groundwater well casings. The soil-modifying reagent includes a variety of gases, liquids, colloids, and adsorbents that may be reactive or non-reactive with soil components. The method may be used inter alia to form reactive barriers, control pests, and enhance soil nutrients for microbes and plants.

  10. Intercomparison of two comparative reactivity method instruments inf the Mediterranean basin during summer 2013

    NASA Astrophysics Data System (ADS)

    Zannoni, N.; Dusanter, S.; Gros, V.; Sarda Esteve, R.; Michoud, V.; Sinha, V.; Locoge, N.; Bonsang, B.

    2015-09-01

    The hydroxyl radical (OH) plays a key role in the atmosphere, as it initiates most of the oxidation processes of volatile organic compounds (VOCs), and can ultimately lead to the formation of ozone and secondary organic aerosols (SOAs). There are still uncertainties associated with the OH budget assessed using current models of atmospheric chemistry and direct measurements of OH sources and sinks have proved to be valuable tools to improve our understanding of the OH chemistry. The total first order loss rate of OH, or total OH reactivity, can be directly measured using three different methods, such as the following: total OH loss rate measurement, laser-induced pump and probe technique and comparative reactivity method. Observations of total OH reactivity are usually coupled to individual measurements of reactive compounds in the gas phase, which are used to calculate the OH reactivity. Studies using the three methods have highlighted that a significant fraction of OH reactivity is often not explained by individually measured reactive compounds and could be associated to unmeasured or unknown chemical species. Therefore accurate and reproducible measurements of OH reactivity are required. The comparative reactivity method (CRM) has demonstrated to be an advantageous technique with an extensive range of applications, and for this reason it has been adopted by several research groups since its development. However, this method also requires careful corrections to derive ambient OH reactivity. Herein we present an intercomparison exercise of two CRM instruments, CRM-LSCE (Laboratoire des Sciences du Climat et de l'Environnement) and CRM-MD (Mines Douai), conducted during July 2013 at the Mediterranean site of Ersa, Cape Corsica, France. The intercomparison exercise included tests to assess the corrections needed by the two instruments to process the raw data sets as well as OH reactivity observations. The observation was divided in three parts: 2 days of plant

  11. Quantum mechanical algebraic variational methods for inelastic and reactive molecular collisions

    NASA Technical Reports Server (NTRS)

    Schwenke, David W.; Haug, Kenneth; Zhao, Meishan; Truhlar, Donald G.; Sun, Yan

    1988-01-01

    The quantum mechanical problem of reactive or nonreactive scattering of atoms and molecules is formulated in terms of square-integrable basis sets with variational expressions for the reactance matrix. Several formulations involving expansions of the wave function (the Schwinger variational principle) or amplitude density (a generalization of the Newton variational principle), single-channel or multichannel distortion potentials, and primitive or contracted basis functions are presented and tested. The test results, for inelastic and reactive atom-diatom collisions, suggest that the methods may be useful for a variety of collision calculations and may allow the accurate quantal treatment of systems for which other available methods would be prohibitively expensive.

  12. Modeling two-dimensional reactive transport using a Godunov-mixed finite element method

    NASA Astrophysics Data System (ADS)

    James, Andrew I.; Jawitz, James W.

    2007-05-01

    SummaryThe development of a model to simulate transport of materials in variable-depth flows is discussed. The model numerically approximates solutions to the advection-dispersion-reaction equation using a time-splitting technique where the advective, dispersive, and reactive parts of the equation are solved separately. An explicit finite-volume Godunov method is used to approximate the advective part while a hybridized mixed finite element method is used to solve for the dispersive step. A backward Euler method is used to solve the reactive component. Rather than solving each component once at each time step, the advective and reactive steps are fractionally and symmetrically split around the dispersive step, so that half of a reactive and advective step are solved before and after each dispersive step. Since the dispersive step is implicit, but computationally expensive, while the advective step is explicit but has time step constraints, this allows stable and more efficient schemes to be implemented in contrast to non-split or simple time-split algorithms. This technique allows problems with high grid Peclet numbers, such as transport problems with sharp solute fronts, to be solved without oscillations in the solution and with virtually no artificial diffusion. By applying the technique to variable depth flows, a variety of applications to transport and reaction problems in surface water and unconfined aquifers can be undertaken. Numerical results for several non-reactive and reactive transport problems in one- and two-dimensions are presented. Observed convergence rates are up to second-order for these simulations.

  13. Interest of the non linear fitting method for reactivity assessment using flux transient experiments

    SciTech Connect

    Geslot, B.; Jammes, C.

    2006-07-01

    Flux transient measurements, meaning rod drop or source jerk experiments, are useful to estimate subcritical core reactivity or control rod worth. Among numerous analysis methods, the most widely used is the so called 'inverse kinetics' method (IK). Based on the inversion of the counting rates, this method gives very good results when counting rates are high. When assessing far subcritical levels with low counting rates, it appears that results are biased and very imprecise. In order to overcome those problems in the case of measurements performed in the framework of the first phase of the RACE-T program, we used a non linear fitting method (NF) to analyse transient experiments. In this paper, we present the NF method reactivity estimator and study its behaviour, in terms of bias and uncertainties, on simulated transients. Then, RACE-T results on experimental source jerk measurements, obtained using IK and NF, are compared and discussed. (authors)

  14. Catalytic and reactive polypeptides and methods for their preparation and use

    DOEpatents

    Schultz, Peter

    1994-01-01

    Catalytic and reactive polypeptides include a binding site specific for a reactant or reactive intermediate involved in a chemical reaction of interest. The polypeptides further include at least one active functionality proximate the binding site, where the active functionality is capable of catalyzing or chemically participating in the chemical reaction in such a way that the reaction rate is enhanced. Methods for preparing the catalytic peptides include chemical synthesis, site-directed mutagenesis of antibody and enzyme genes, covalent attachment of the functionalities through particular amino acid side chains, and the like.

  15. Intercomparison of the comparative reactivity method (CRM) and pump-probe technique for measuring total OH reactivity in an urban environment

    NASA Astrophysics Data System (ADS)

    Hansen, R. F.; Blocquet, M.; Schoemaecker, C.; Léonardis, T.; Locoge, N.; Fittschen, C.; Hanoune, B.; Stevens, P. S.; Sinha, V.; Dusanter, S.

    2015-10-01

    The investigation of hydroxyl radical (OH) chemistry during intensive field campaigns has led to the development of several techniques dedicated to ambient measurements of total OH reactivity, which is the inverse of the OH lifetime. Three techniques are currently used during field campaigns, including the total OH loss rate method, the pump-probe method, and the comparative reactivity method. However, no formal intercomparison of these techniques has been published so far, and there is a need to ensure that measurements of total OH reactivity are consistent among the different techniques. An intercomparison of two OH reactivity instruments, one based on the comparative reactivity method (CRM) and the other based on the pump-probe method, was performed in October 2012 in a NOx-rich environment, which is known to be challenging for the CRM technique. This study presents an extensive description of the two instruments, the CRM instrument from Mines Douai (MD-CRM) and the pump-probe instrument from the University of Lille (UL-FAGE), and highlights instrumental issues associated with the two techniques. It was found that the CRM instrument used in this study underestimates ambient OH reactivity by approximately 20 % due to the photolysis of volatile organic compounds (VOCs) inside the sampling reactor; this value is dependent on the position of the lamp within the reactor. However, this issue can easily be fixed, and the photolysis of VOCs was successfully reduced to a negligible level after this intercomparison campaign. The UL-FAGE instrument may also underestimate ambient OH reactivity due to the difficulty to accurately measure the instrumental zero. It was found that the measurements are likely biased by approximately 2 s-1, due to impurities in humid zero air. Two weeks of ambient sampling indicate that the measurements performed by the two OH reactivity instruments are in agreement, within the measurement uncertainties for each instrument, for NOx mixing ratios

  16. Intercomparison of the comparative reactivity method (CRM) and pump-probe technique for measuring total OH reactivity in an urban environment

    NASA Astrophysics Data System (ADS)

    Hansen, R. F.; Blocquet, M.; Schoemaecker, C.; Léonardis, T.; Locoge, N.; Fittschen, C.; Hanoune, B.; Stevens, P. S.; Sinha, V.; Dusanter, S.

    2015-06-01

    The investigation of hydroxyl radical (OH) chemistry during intensive field campaigns has led to the development of several techniques dedicated to ambient measurements of total OH reactivity, which is the inverse of the OH lifetime. Three techniques are currently used during field campaigns, including the total OH loss rate method, the pump-probe method, and the comparative reactivity method. However, no formal intercomparison of these techniques has been published so far, and there is a need to ensure that measurements of total OH reactivity are consistent among the different techniques. An intercomparison of two OH reactivity instruments, one based on the Comparative Reactivity Method (CRM) and the other based on the pump-probe method, was performed in October 2012 in a NOx-rich environment, which is known to be challenging for the CRM technique. This study presents an extensive description of the two instruments, the CRM instrument from Mines Douai (MD-CRM) and the pump-probe instrument from the University of Lille (UL-FAGE), and highlights instrumental issues associated with the two techniques. It was found that the CRM instrument used in this study underestimates ambient OH reactivity by approximately 20 % due to the photolysis of Volatile Organic Compounds (VOCs) inside the sampling reactor; this value is dependent on the position of the lamp within the reactor. However, this issue can easily be fixed, and the photolysis of VOCs was successfully reduced to a negligible level after this intercomparison campaign. The UL-FAGE instrument may also underestimate ambient OH reactivity due to the difficulty to accurately measure the instrumental zero. It was found that the measurements are likely biased by approximately 2 s-1, due to impurities in humid zero air. Two weeks of ambient sampling indicate that the measurements performed by the two OH reactivity instruments are in agreement, within the measurement uncertainties for each instrument, for NOx mixing ratios

  17. Application of a data assimilation method via an ensemble Kalman filter to reactive urea hydrolysis transport modeling

    SciTech Connect

    Juxiu Tong; Bill X. Hu; Hai Huang; Luanjin Guo; Jinzhong Yang

    2014-03-01

    With growing importance of water resources in the world, remediations of anthropogenic contaminations due to reactive solute transport become even more important. A good understanding of reactive rate parameters such as kinetic parameters is the key to accurately predicting reactive solute transport processes and designing corresponding remediation schemes. For modeling reactive solute transport, it is very difficult to estimate chemical reaction rate parameters due to complex processes of chemical reactions and limited available data. To find a method to get the reactive rate parameters for the reactive urea hydrolysis transport modeling and obtain more accurate prediction for the chemical concentrations, we developed a data assimilation method based on an ensemble Kalman filter (EnKF) method to calibrate reactive rate parameters for modeling urea hydrolysis transport in a synthetic one-dimensional column at laboratory scale and to update modeling prediction. We applied a constrained EnKF method to pose constraints to the updated reactive rate parameters and the predicted solute concentrations based on their physical meanings after the data assimilation calibration. From the study results we concluded that we could efficiently improve the chemical reactive rate parameters with the data assimilation method via the EnKF, and at the same time we could improve solute concentration prediction. The more data we assimilated, the more accurate the reactive rate parameters and concentration prediction. The filter divergence problem was also solved in this study.

  18. Method of extruding and packaging a thin sample of reactive material including forming the extrusion die

    DOEpatents

    Lewandowski, Edward F.; Peterson, Leroy L.

    1985-01-01

    This invention teaches a method of cutting a narrow slot in an extrusion die with an electrical discharge machine by first drilling spaced holes at the ends of where the slot will be, whereby the oil can flow through the holes and slot to flush the material eroded away as the slot is being cut. The invention further teaches a method of extruding a very thin ribbon of solid highly reactive material such as lithium or sodium through the die in an inert atmosphere of nitrogen, argon or the like as in a glovebox. The invention further teaches a method of stamping out sample discs from the ribbon and of packaging each disc by sandwiching it between two aluminum sheets and cold welding the sheets together along an annular seam beyond the outer periphery of the disc. This provides a sample of high purity reactive material that can have a long shelf life.

  19. Method of extruding and packaging a thin sample of reactive material, including forming the extrusion die

    DOEpatents

    Lewandowski, E.F.; Peterson, L.L.

    1981-11-30

    This invention teaches a method of cutting a narrow slot in an extrusion die with an electrical discharge machine by first drilling spaced holes at the ends of where the slot will be, whereby the oil can flow through the holes and slot to flush the material eroded away as the slot is being cut. The invention further teaches a method of extruding a very thin ribbon of solid highly reactive material such as lithium or sodium through the die in an inert atmosphere of nitrogen, argon, or the like as in a glovebox. The invention further teaches a method of stamping out sample discs from the ribbon and of packaging each disc by sandwiching it between two aluminum sheets and cold welding the sheets together along an annular seam beyond the outer periphery of the disc. This provides a sample of high purity reactive material that can have a long shelf life.

  20. Computational methods for multiphase equilibrium and kinetics calculations for geochemical and reactive transport applications

    NASA Astrophysics Data System (ADS)

    Leal, Allan; Saar, Martin

    2016-04-01

    Computational methods for geochemical and reactive transport modeling are essential for the understanding of many natural and industrial processes. Most of these processes involve several phases and components, and quite often requires chemical equilibrium and kinetics calculations. We present an overview of novel methods for multiphase equilibrium calculations, based on both the Gibbs energy minimization (GEM) approach and on the solution of the law of mass-action (LMA) equations. We also employ kinetics calculations, assuming partial equilibrium (e.g., fluid species in equilibrium while minerals are in disequilibrium) using automatic time stepping to improve simulation efficiency and robustness. These methods are developed specifically for applications that are computationally expensive, such as reactive transport simulations. We show how efficient the new methods are, compared to other algorithms, and how easy it is to use them for geochemical modeling via a simple script language. All methods are available in Reaktoro, a unified open-source framework for modeling chemically reactive systems, which we also briefly describe.

  1. A new method for analysis of reactive adsorbed intermediates: Bismuth postdosing in thermal desorption mass spectroscopy

    NASA Astrophysics Data System (ADS)

    Campbell, Charles T.; Rodriguez, J. A.; Henn, F. C.; Campbell, J. M.; Dalton, P. J.; Seimanides, S. G.

    1988-05-01

    A new method which should have relatively general applicability for the identification and quantitative analysis of reactive adsorbed molecular intermediates in surface reactions will be described, and the first examples of its application will be presented. When a reactive intermediate is generated on a surface, it often has a tendency to dissociate before desorbing. Since dissociation generally requires additional free sites on the surface, dissociation can be suppressed and desorption correspondingly enhanced if the free sites on the surface can be properly poisoned. We have found that bismuth adatoms are very good inert site blockers, which can be postdosed to the surface of a transition metal containing a reactive adsorbed hydrocarbon without destroying the hydrocarbon. Whereas in the absence of bismuth, the hydrocarbon would completely dehydrogenate during thermal desorption spectroscopy (TDS) and liberate only H2 into the gas phase, after bismuth postdosing the reactive hydrocarbon desorbs intact for mass spectral identification and quantitative analysis. This method has been used to prove that adsorbed benzene is the initial product of the dehydrogenation of cyclohexane on Pt(111) at ˜235 K. In the absence of bismuth, this benzene all dissociates during TDS to liberate only H2, leaving graphitic carbon residue on the surface. When one-third monolayer of Bi is postdosed at 110 K, the dehydrogenation pathway is sterically poisoned and the adsorbed benzene quantitatively desorbs during TDS, where it is unambiguously identified by mass spectroscopy. By briefly heating the reactive adsorbed intermediate to increasing temperatures prior to Bi deposition, the thermal stability limits of the intermediate and the kinetic parameters for its dissociation can be established. This is demonstrated for the dehydrogenation reaction of adsorbed cyclopentene on Pt(111). Bismuth postdosing in thermal desorption mass spectroscopy (BPTDS) should be a very useful but

  2. Computational methods for reactive transport modeling: A Gibbs energy minimization approach for multiphase equilibrium calculations

    NASA Astrophysics Data System (ADS)

    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.

  3. Evaluation of an offline method for the analysis of atmospheric reactive gaseous mercury and particulate mercury

    USGS Publications Warehouse

    Rutter, A.P.; Hanford, K.L.; Zwers, J.T.; Perillo-Nicholas, A. L.; Schauer, J.J.; Olson, M.L.

    2008-01-01

    Reactive gaseous mercury (RGM) and particulate mercury (PHg) were collected in Milwaukee, WI, between April 2004 and May 2005, and in Riverside, CA, between July 25 and August 7, 2005 using sorbent and filter substrates. The substrates were analyzed for mercury by thermal desorption analysis (TDA) using a purpose-built instrument. Results from this offline-TDA method were compared with measurements using a real-time atmospheric mercury analyzer. RGM measurements made with the offline-TDA agreed well with a commercial real-time method. However, the offline TDA reported PHg concentrations 2.7 times higher than the real-time method, indicating evaporative losses might be occurring from the real-time instrument during sample collection. TDA combined with reactive mercury collection on filter and absorbent substrates was cheap, relatively easy to use, did not introduce biases due to a semicontinuous sample collection strategy, and had a dynamic range appropriate for use in rural and urban locations. The results of this study demonstrate that offline-TDA is a feasible method for collecting reactive mercury concentrations in a large network of filter-based samplers. Copyright 2008 Air & Waste Management Association.

  4. Shock compression of condensed matter using multimaterial reactive ghost fluid method

    NASA Astrophysics Data System (ADS)

    Kim, Ki-hong; Yoh, Jack J.

    2008-04-01

    For the flow analysis of reactive compressible media involving energetic materials and deforming metallic boundaries, a HYDRO-SCCM (shock compression of condensed matter) tool is developed for handling multiphysics shock analysis of energetic and inert matters. The highly energetic flows give rise to the strong nonlinear shock waves and the high strain rate deformation of solid boundaries at high pressure and temperature. For handling the large gradients associated with these complex flows in the condensed phase as well as in the reactive gaseous phase, a new Eulerian multifluid method is formulated. The numerical methodology is described in this paper, while the extended applications and the capacity of the tool are discussed in a separate paper [J. J. Yoh and K. H. Kim, "Shock Compression of Condensed Matter using Eulerian Multimaterial Method: Applications to multi-dimensional shocks, deflagration, detonation, and laser ablation," J. Appl. Phys. (accepted)].

  5. Apparatus and method for atmospheric pressure reactive atom plasma processing for shaping of damage free surfaces

    DOEpatents

    Carr; Jeffrey W.

    2009-03-31

    Fabrication apparatus and methods are disclosed for shaping and finishing difficult materials with no subsurface damage. The apparatus and methods use an atmospheric pressure mixed gas plasma discharge as a sub-aperture polisher of, for example, fused silica and single crystal silicon, silicon carbide and other materials. In one example, workpiece material is removed at the atomic level through reaction with fluorine atoms. In this example, these reactive species are produced by a noble gas plasma from trace constituent fluorocarbons or other fluorine containing gases added to the host argon matrix. The products of the reaction are gas phase compounds that flow from the surface of the workpiece, exposing fresh material to the etchant without condensation and redeposition on the newly created surface. The discharge provides a stable and predictable distribution of reactive species permitting the generation of a predetermined surface by translating the plasma across the workpiece along a calculated path.

  6. Reaction sampling and reactivity prediction using the stochastic surface walking method.

    PubMed

    Zhang, Xiao-Jie; Liu, Zhi-Pan

    2015-01-28

    The prediction of chemical reactivity and thus the design of new reaction systems are the key challenges in chemistry. Here, we develop an unbiased general-purpose reaction sampling method, the stochastic surface walking based reaction sampling (SSW-RS) method, and show that the new method is a promising solution for reactivity prediction of complex reaction systems. The SSW-RS method is capable of sampling both the configuration space of the reactant and the reaction space of pathways, owing to the combination of two recently developed theoretical methods, namely, the stochastic surface walking (SSW) method for potential energy surface (PES) exploration and the double-ended surface walking (DESW) method for building pathways. By integrating with first principles calculations, we show that the SSW-RS method can be applied to investigate the kinetics of complex organic reactions featuring many possible reaction channels and complex hydrogen-bonding networks, as demonstrated here using two examples, epoxypropane hydrolysis in aqueous solution and β-d-glucopyranose decomposition. Our results show that simultaneous sampling of the soft hydrogen-bonding conformations and the chemical reactions involving hard bond making/breaking can be achieved in the SSW-RS simulation, and the mechanism and kinetics can be predicted without a priori information on the system. Unexpected new chemistry for these reactions is revealed and discussed. In particular, despite many possible pathways for β-d-glucopyranose decomposition, the SSW-RS shows that only β-d-glucose and levoglucosan are kinetically preferred direct products and the 5- or 7-member ring products should be secondary products derived from β-d-glucose or levoglucosan. As a general tool for reactivity prediction, the SSW-RS opens a new route for the design of rational reactions. PMID:25503262

  7. Advancing Reactive Tracer Methods for Measurement of Thermal Evolution in Geothermal Reservoirs: Final Report

    SciTech Connect

    Mitchell A. Plummer; Carl D. Palmer; Earl D. Mattson; Laurence C. Hull; George D. Redden

    2011-07-01

    The injection of cold fluids into engineered geothermal system (EGS) and conventional geothermal reservoirs may be done to help extract heat from the subsurface or to maintain pressures within the reservoir (e.g., Rose et al., 2001). As these injected fluids move along fractures, they acquire heat from the rock matrix and remove it from the reservoir as they are extracted to the surface. A consequence of such injection is the migration of a cold-fluid front through the reservoir (Figure 1) that could eventually reach the production well and result in the lowering of the temperature of the produced fluids (thermal breakthrough). Efficient operation of an EGS as well as conventional geothermal systems involving cold-fluid injection requires accurate and timely information about thermal depletion of the reservoir in response to operation. In particular, accurate predictions of the time to thermal breakthrough and subsequent rate of thermal drawdown are necessary for reservoir management, design of fracture stimulation and well drilling programs, and forecasting of economic return. A potential method for estimating migration of a cold front between an injection well and a production well is through application of reactive tracer tests, using chemical whose rate of degradation is dependent on the reservoir temperature between the two wells (e.g., Robinson 1985). With repeated tests, the rate of migration of the thermal front can be determined, and the time to thermal breakthrough calculated. While the basic theory behind the concept of thermal tracers has been understood for some time, effective application of the method has yet to be demonstrated. This report describes results of a study that used several methods to investigate application of reactive tracers to monitoring the thermal evolution of a geothermal reservoir. These methods included (1) mathematical investigation of the sensitivity of known and hypothetical reactive tracers, (2) laboratory testing of novel

  8. Novel dual-mode immunomagnetic method for studying reactivation of nerve agent-inhibited butyrylcholinesterase.

    PubMed

    Abney, Carter W; Knaack, Jennifer L S; Ali, Ahmed A I; Johnson, Rudolph C

    2013-05-20

    A novel immunomagnetic method has been developed for the simultaneous measurement of organophosphorus nerve agent (OPNA) adducts to butyrylcholinesterase (BuChE) and free OPNAs in serum. This new approach, deemed dual-mode immunomagnetic analysis (Dual-Mode IMA), combines immunomagnetic separation (IMS) and immunomagnetic scavenging (IMSc) and has been used to measure the effectiveness of cholinesterase reactivators on OPNA-inhibited BuChE in serum. BuChE inhibited by the nerve agent VX, uninhibited BuChE, and unbound VX were measured up to 1 h after the addition of oxime reactivators pralidoxime (2-PAM) and obidoxime. IMS experiments consisted of extracting BuChE and VX-BuChE serum adducts using antibutyrylcholinesterase monoclonal antibodies conjugated to protein-G ferromagnetic particles. In a parallel set of experiments using IMSc, BuChE-coated magnetic beads were used to extract free VX from protein-depleted serum. Adducts from both IMS and IMSc were analyzed using a published IMS liquid chromatography tandem mass spectrometry (IMS-LC-MS/MS) protocol, which has also been demonstrated with other OPNAs. By applying this Dual-Mode IMA approach, 2-PAM was observed to be more potent than obidoxime in reactivating VX-adducted BuChE. VX-BuChE peptide concentrations initially measured at 19.7 ± 0.7 ng/mL decreased over 1 h to 10.6 ± 0.6 ng/mL when reactivated with 2-PAM and 14.4 ± 1.2 ng/mL when reactivated with obidoxime. These experiments also show that previously published IMS-LC-MS/MS analyses are compatible with serum treated with oximes. Dual-Mode IMA is the first immunoaffinity method developed for the simultaneous measurement of OPNA adducted BuChE, unadducted BuChE, and free nerve agent in serum and is a promising new tool for studying reactivator effectiveness on cholinesterases inhibited by nerve agents. PMID:23656164

  9. Catalytic and reactive polypeptides and methods for their preparation and use

    DOEpatents

    Schultz, Peter

    1994-01-01

    Catalytic and reactive polypeptides include a binding site specific for a reactant or reactive intermediate involved in a chemical reaction of interest. The polypeptides further include at least one active functionality proximate the binding site, where the active functionality is capable of catalyzing or chemically participating in the chemical reaction in such a way that the reaction rate is enhanced. Methods for preparing the catalytic peptides include chemical synthesis, site-directed mutagenesis of antibody and enzyme genes, covalent attachment of the functionalities through particular amino acid side chains, and the like. This invention was made with Government support under Grant Contract No. AI-24695, awarded by the Department of health and Human Services, and under Grant Contract No. N 00014-87-K-0256, awarded by the Office of Naval Research. The Government has certain rights in this invention.

  10. A Simple Spectrophotometric Method for the Determination of Thiobarbituric Acid Reactive Substances in Fried Fast Foods.

    PubMed

    Zeb, Alam; Ullah, Fareed

    2016-01-01

    A simple and highly sensitive spectrophotometric method was developed for the determination of thiobarbituric acid reactive substances (TBARS) as a marker for lipid peroxidation in fried fast foods. The method uses the reaction of malondialdehyde (MDA) and TBA in the glacial acetic acid medium. The method was precise, sensitive, and highly reproducible for quantitative determination of TBARS. The precision of extractions and analytical procedure was very high as compared to the reported methods. The method was used to determine the TBARS contents in the fried fast foods such as Shami kebab, samosa, fried bread, and potato chips. Shami kebab, samosa, and potato chips have higher amount of TBARS in glacial acetic acid-water extraction system than their corresponding pure glacial acetic acid and vice versa in fried bread samples. The method can successfully be used for the determination of TBARS in other food matrices, especially in quality control of food industries. PMID:27123360

  11. A Simple Spectrophotometric Method for the Determination of Thiobarbituric Acid Reactive Substances in Fried Fast Foods

    PubMed Central

    Zeb, Alam; Ullah, Fareed

    2016-01-01

    A simple and highly sensitive spectrophotometric method was developed for the determination of thiobarbituric acid reactive substances (TBARS) as a marker for lipid peroxidation in fried fast foods. The method uses the reaction of malondialdehyde (MDA) and TBA in the glacial acetic acid medium. The method was precise, sensitive, and highly reproducible for quantitative determination of TBARS. The precision of extractions and analytical procedure was very high as compared to the reported methods. The method was used to determine the TBARS contents in the fried fast foods such as Shami kebab, samosa, fried bread, and potato chips. Shami kebab, samosa, and potato chips have higher amount of TBARS in glacial acetic acid-water extraction system than their corresponding pure glacial acetic acid and vice versa in fried bread samples. The method can successfully be used for the determination of TBARS in other food matrices, especially in quality control of food industries. PMID:27123360

  12. Preparation of superconducting Y-Ba-Cu-O films by a reactive plasma evaporation method

    NASA Astrophysics Data System (ADS)

    Terashima, Kazuo; Eguchi, Keisuke; Yoshida, Toyonobu; Akashi, Kazuo

    1988-04-01

    Y-Ba-Cu-O superconducting films were prepared by a reactive plasma evaporation method, in which mixed powders were coevaporated in a thermal RF Ar + O2 plasma, and the ternary-composition controlled high-temperature metallic vapors were codeposited onto a substrate. The deposition rate was much more than 10 micron/min, which is several orders of magnitude higher than those reported for other methods. The structure of the prepared films was identified as an orthorhombic oxygen-deficient perovskite phase, and some films showed the preferred orientation of (001). The as-deposited film without postannealing showed a superconducting transition temperature Tcm (midpoint) of 94 K.

  13. Systems and methods for reactive distillation with recirculation of light components

    DOEpatents

    Stickney, Michael J.; Jones, Jr., Edward M.

    2011-07-26

    Systems and methods for producing gas-to-liquids products using reactive distillation are provided. The method for producing gas-to-liquids products can include reacting a feedstock in a column having a distillation zone and a reaction zone to provide a bottoms stream and an overhead stream. A first portion of the overhead stream can be recycled to the column at the top of the reaction zone and second portion of the overhead stream can be recycled to the column at the bottom of the reaction zone.

  14. A simplified method for determining reactive rate parameters for reaction ignition and growth in explosives

    SciTech Connect

    Miller, P.J.

    1996-07-01

    A simplified method for determining the reactive rate parameters for the ignition and growth model is presented. This simplified ignition and growth (SIG) method consists of only two adjustable parameters, the ignition (I) and growth (G) rate constants. The parameters are determined by iterating these variables in DYNA2D hydrocode simulations of the failure diameter and the gap test sensitivity until the experimental values are reproduced. Examples of four widely different explosives were evaluated using the SIG model. The observed embedded gauge stress-time profiles for these explosives are compared to those calculated by the SIG equation and the results are described.

  15. GUINEVERE experiment: Kinetic analysis of some reactivity measurement methods by deterministic and Monte Carlo codes

    SciTech Connect

    Bianchini, G.; Burgio, N.; Carta, M.; Peluso, V.; Fabrizio, V.; Ricci, L.

    2012-07-01

    The GUINEVERE experiment (Generation of Uninterrupted Intense Neutrons at the lead Venus Reactor) is an experimental program in support of the ADS technology presently carried out at SCK-CEN in Mol (Belgium). In the experiment a modified lay-out of the original thermal VENUS critical facility is coupled to an accelerator, built by the French body CNRS in Grenoble, working in both continuous and pulsed mode and delivering 14 MeV neutrons by bombardment of deuterons on a tritium-target. The modified lay-out of the facility consists of a fast subcritical core made of 30% U-235 enriched metallic Uranium in a lead matrix. Several off-line and on-line reactivity measurement techniques will be investigated during the experimental campaign. This report is focused on the simulation by deterministic (ERANOS French code) and Monte Carlo (MCNPX US code) calculations of three reactivity measurement techniques, Slope ({alpha}-fitting), Area-ratio and Source-jerk, applied to a GUINEVERE subcritical configuration (namely SC1). The inferred reactivity, in dollar units, by the Area-ratio method shows an overall agreement between the two deterministic and Monte Carlo computational approaches, whereas the MCNPX Source-jerk results are affected by large uncertainties and allow only partial conclusions about the comparison. Finally, no particular spatial dependence of the results is observed in the case of the GUINEVERE SC1 subcritical configuration. (authors)

  16. Evaluation of toughness deterioration by an electrochemical method in an isothermally-aged N-containing austenitic stainless steel

    SciTech Connect

    Saucedo-Munoz, Maribel L. Lopez-Hirata, Victor M.; Avila-Davila, Erika O.; Melo-Maximo, Dulce V.

    2009-02-15

    This work presents the results of an evaluation of the deterioration of cryogenic toughness by means of an electrochemical method in a N-containing austenitic stainless steel (JK2) aged at temperatures of 700, 800 and 900 deg. C for times from 10 to 1000 min. The aging process at 700 and 800 deg. C caused the decrease in the Charpy V-Notch impact energy at - 196 deg. C because of the intergranular precipitation of carbides. Scanning electron micrographs of the Charpy V-Notch test specimens showed the presence of intergranular brittle fracture. The degree of sensitization was determined by the ratio of the maximum current density generated by the reactivation scan to that of the anodic scan, I{sub r}/I{sub a}, using the double-loop electrochemical potentiokinetic reactivation test. The Charpy V-Notch impact energy decreased with increase in the I{sub r}/I{sub a} ratio. This relation permits an estimate of the deterioration of cryogenic toughness due to thermal aging in this type of steel.

  17. A new method for total OH reactivity measurements using a fast Gas Chromatographic Photo-Ionization Detector (GC-PID)

    NASA Astrophysics Data System (ADS)

    Nölscher, A. C.; Sinha, V.; Bockisch, S.; Klüpfel, T.; Williams, J.

    2012-05-01

    The primary and most important oxidant in the atmosphere is the hydroxyl radical (OH). Currently OH sinks, particularly gas phase reactions, are poorly constrained. One way to characterize the overall sink of OH is to measure directly the ambient loss rate of OH, the total OH reactivity. To date direct measurements of total OH reactivity have been either performed using a Laser Induced Fluorescence (LIF) system ("pump-and-probe" or "flow reactor") or the Comparative Reactivity Method (CRM) with a Proton Transfer Reaction Mass Spectrometer (PTR-MS). Both techniques require large, complex and expensive detection systems. This study presents a feasibility assessment for CRM total OH reactivity measurements using a new detector, a Gas Chromatographic Photo-Ionization Detector (GC-PID). Such a system is smaller, more portable, less power consuming and less expensive than other total OH reactivity measurement techniques. Total OH reactivity is measured by the CRM using a competitive reaction between a reagent (here pyrrole) with OH alone and in the presence of atmospheric reactive molecules. The new CRM method for total OH reactivity has been tested with parallel measurements of the GC-PID and the previously validated PTR-MS as detector for the reagent pyrrole during laboratory experiments, plant chamber and boreal field studies. Excellent agreement of both detectors was found when the GC-PID was operated under optimum conditions. Time resolution (60-70 s), sensitivity (LOD 3-6 s-1) and overall uncertainty (25% in optimum conditions) for total OH reactivity were equivalent to PTR-MS based total OH reactivity measurements. One drawback of the GC-PID system was the steady loss of sensitivity and accuracy during intensive measurements lasting several weeks, and a possible toluene interference. Generally, the GC-PID system has been shown to produce closely comparable results to the PTR-MS and thus in suitable environments (e.g. forests) it presents a viably economical

  18. Tableau method for reactive path planning in an obstacle avoidance system

    NASA Astrophysics Data System (ADS)

    Beeson, Bradley K.; Kurtz, John J.; Bonner, Kevin G.

    1999-07-01

    Autonomous off-road vehicles face the daunting challenge of successfully navigating through terrain in which unmapped obstacles present hazards to safe vehicle operation. These obstacles can be sparsely scattered or densely clustered. The obstacle avoidance (OA) system on-board the autonomous vehicle must be capable of detecting all non-negotiable obstacles and planning paths around them in a sufficient computing interval to permit effective operation of the platform. To date, the reactive path planning function performed by OA systems has been essentially an exhaustive search through a set of preprogrammed swaths (linear trajectories projected through the on-board local obstacle map) to determine the best path for the vehicle to travel toward achieving a goal state. Historically, this function is a large consumer of computational resources in an OA system. A novel reactive path planner is described that minimizes processing time through the use of pre-computed indices into an n over n + 1 tableau structure with the lowest level in the tableau representing the traditional 'histogram' result. The tableau method differs significantly from other reactive planners in three ways: (1) the entire tableau is computed off-line and loaded on system startup, minimizing computational load; (2) the real-time computational load is directly proportional to the number of grid points searched and proportional to the square of the number of paths; and (3) the tableau is independent of grid resolution. Analytical and experimental comparisons of the tableau and histogram methods are presented along with generalization into an autonomous mobility system incorporating multiple feature planes and path cost evaluation.

  19. Surface treatment method for 1/f noise suppression in reactively sputtered nickel oxide film

    NASA Astrophysics Data System (ADS)

    Kim, Dong Soo; Park, Seung-Man; Lee, Hee Chul

    2012-07-01

    A surface treatment method combined with O2 plasma treatment and Ar+ bombardment is proposed for 1/f noise suppression in a reactively sputtered NiO film as a micro-bolometer sensing material. The 1/f noise power spectral density on a sample prepared by the proposed surface treatment method prior to the contact formation is suppressed to a level roughly 18 times lower than that on an untreated sample. The improved noise characteristic can be ascribed to the cooperative effects of the two steps in the proposed surface treatment method. In its effects, the oxygen plasma treatment is supposed to increase the Ni3+ component on the surface of the NiO film, which in turn increases the hole concentration on the surface. Additional Ar+ bombardment is expected to remove contaminants on the surface of the NiO film, leading to a low contact resistance.

  20. A fluorescence high throughput screening method for the detection of reactive electrophiles as potential skin sensitizers.

    PubMed

    Avonto, Cristina; Chittiboyina, Amar G; Rua, Diego; Khan, Ikhlas A

    2015-12-01

    Skin sensitization is an important toxicological end-point in the risk assessment of chemical allergens. Because of the complexity of the biological mechanisms associated with skin sensitization, integrated approaches combining different chemical, biological and in silico methods are recommended to replace conventional animal tests. Chemical methods are intended to characterize the potential of a sensitizer to induce earlier molecular initiating events. The presence of an electrophilic mechanistic domain is considered one of the essential chemical features to covalently bind to the biological target and induce further haptenation processes. Current in chemico assays rely on the quantification of unreacted model nucleophiles after incubation with the candidate sensitizer. In the current study, a new fluorescence-based method, 'HTS-DCYA assay', is proposed. The assay aims at the identification of reactive electrophiles based on their chemical reactivity toward a model fluorescent thiol. The reaction workflow enabled the development of a High Throughput Screening (HTS) method to directly quantify the reaction adducts. The reaction conditions have been optimized to minimize solubility issues, oxidative side reactions and increase the throughput of the assay while minimizing the reaction time, which are common issues with existing methods. Thirty-six chemicals previously classified with LLNA, DPRA or KeratinoSens™ were tested as a proof of concept. Preliminary results gave an estimated 82% accuracy, 78% sensitivity, 90% specificity, comparable to other in chemico methods such as Cys-DPRA. In addition to validated chemicals, six natural products were analyzed and a prediction of their sensitization potential is presented for the first time. PMID:26455772

  1. Catalytic and reactive polypeptides and methods for their preparation and use

    DOEpatents

    Schultz, Peter

    1993-01-01

    Catalytic and reactive polypeptides include a binding site specific for a reactant or reactive intermediate involved in a chemical reaction of interest. The polypeptides further include at least one active functionality proximate the bi.

  2. Organic/inorganic nanocomposites, methods of making, and uses as a permeable reactive barrier

    DOEpatents

    Harrup, Mason K.; Stewart, Frederick F.

    2007-05-15

    Nanocomposite materials having a composition including an inorganic constituent, a preformed organic polymer constituent, and a metal ion sequestration constituent are disclosed. The nanocomposites are characterized by being single phase, substantially homogeneous materials wherein the preformed polymer constituent and the inorganic constituent form an interpenetrating network with each other. The inorganic constituent may be an inorganic oxide, such as silicon dioxide, formed by the in situ catalyzed condensation of an inorganic precursor in the presence of the solvated polymer and metal ion sequestration constituent. The polymer constituent may be any hydrophilic polymer capable of forming a type I nanocomposite such as, polyacrylonitrile (PAN), polyethyleneoxide (PEO), polyethylene glycol (PEG), polyvinyl acetate (PVAc), polyvinyl alcohol (PVA), and combinations thereof. Nanocomposite materials of the present invention may be used as permeable reactive barriers (PRBs) to remediate contaminated groundwater. Methods for making nanocomposite materials, PRB systems, and methods of treating groundwater are also disclosed.

  3. COD and color removal of reactive orange 16 dye solution by electrochemical oxidation and adsorption method

    NASA Astrophysics Data System (ADS)

    Zakaria, Zuhailie; Ahmad, Wan Yaacob Wan; Yusop, Muhammad Rahimi; Othman, Mohamed Rozali

    2015-09-01

    Degradation of Reactive Orange 16 (RO16) dye was investigated using electrochemical oxidation and adsorption (batch method) using mixture of coconut trunk charcoal-graphite-tin-polyvinyl chloride(PVC). In batch studies for adsorbents pellet and powder form of the charcoal mixture were used. RO16 was chosen as the model dye because of its high resistance towards conventional treatment methods. NaCl and RO16 concentration, treatment duration, weight of electrode and adsorbent and volume of solution were kept constant for both methods. The effectiveness of the treatments were compared and evaluated by percentage of RO16 decolorization and chemical oxygen demand (COD) removal and results indicated that electrochemical oxidation method ables to decolorized RO16 dye up to 98.5% after 20 minutes electrolysis time while pellet and powder in batch method only removed 17.1 and 33.6% of RO16 color respectively. However, only 45.6% of COD can be removed using electrochemical oxidation method while pellet and powder in batch method removed 47.8 and 49.6% of COD respectively. The decolorization and COD removal of RO16 was determined using UV-Vis spectrophotometer (by the changes of absorption spectrum intensity of azo chromophore (-N=N-) at λ=388 and 492.50 nm and Hach spectrophotometer respectively. FTIR was used to determine functional groups present in the coconut trunk charcoal.

  4. SPATIAL DISTRIBUTION OF CARBON AND SULFUR PRECIPITATING WITHIN PERMEABLE REACTIVE BARRIERS: DEVELOPMENT OF ANALYTICAL METHODS

    EPA Science Inventory

    A permeable reactive barrier (PRB) is a wall of porous reactive material placed in the path of a dissolved contaminant plume for the purpose of removing contaminants from ground water. Chemical processes within these reactive materials remove both inorganic and organic contamina...

  5. Identification of Mesenchymal Stem Cell Marker STRO-1 in Oral Reactive Lesions by Immunofluorescence Method

    PubMed Central

    Dehghani Nazhvani, Ali; Hosseini, Seyed-Mojtaba; Tahoori, Bita; Tavangar, Maryam-Sadat; Attar, Armin

    2015-01-01

    Statement of the Problem Stem cells are considered as new implement for tissue regeneration. Several niches in adult human body are colonized by multipotent stem cells but access to these potential reservoirs is often limited. Although human dental pulp stem cells isolated from healthy teeth have been extensively characterized, it is still unknown whether stem cells also exist in reactive lesions of oral cavity such as pyogenic granuloma and peripheral ossifying fibroma which are deliberated as inflammatory proliferation of different cell families. Purpose The aim of this study was to explore for clues to see whether pyogenic granuloma or peripheral ossifying fibroma contain dental mesenchymal stem cell (DMSC). Materials and Method Four pyogenic granuloma and four peripheral ossifying fibroma specimens were collected by excisional biopsy and preserved in PBS-EDTA at -86 °C. Then we cut them in 5µm diameter using Cryostat. Having been rinsed with PBS, the samples were stained with a primary mouse anti-human STRO-1 monoclonal IgM antibody. Afterward, a secondary goat anti-mouse IgM-FITC antibody was applied to detect STRO-1+ cells as probable stem cells by immunofluorescence technique. Results Immunofluorescence microscopy revealed presence of STRO-1+ cells in these lesions, particularly localized on perivascular zone. The negative control group was not glowing. Conclusion Based on these results, it was found that reactive lesions of pyogenic granuloma and peripheral ossifying fibroma have STRO-1 positive cells, which raises the possibility that these cells may be DMSCs. PMID:26535404

  6. Method for atmospheric pressure reactive atom plasma processing for surface modification

    DOEpatents

    Carr, Jeffrey W.

    2009-09-22

    Reactive atom plasma processing can be used to shape, polish, planarize and clean the surfaces of difficult materials with minimal subsurface damage. The apparatus and methods use a plasma torch, such as a conventional ICP torch. The workpiece and plasma torch are moved with respect to each other, whether by translating and/or rotating the workpiece, the plasma, or both. The plasma discharge from the torch can be used to shape, planarize, polish, and/or clean the surface of the workpiece, as well as to thin the workpiece. The processing may cause minimal or no damage to the workpiece underneath the surface, and may involve removing material from the surface of the workpiece.

  7. Nuclear spin selection rules for reactive collision systems by the spin-modification probability method.

    PubMed

    Park, Kisam; Light, John C

    2007-12-14

    The spin-modification probability (SMP) method, which provides fundamental and detailed quantitative information on the nuclear spin selection rules, is discussed more systematically and generalized for reactive collision systems involving more than one configuration of reactant and product molecules, explicitly taking account of the conservation of the overall nuclear spin symmetry as well as the conservation of the total nuclear spin angular momentum, under the assumption of no nuclear hyperfine interaction. The values of SMP once calculated can be used for any system of identical nuclei of any spin as long as the system has the corresponding nuclear spin symmetry. The values of SMP calculated for simple systems can also be used for more complex systems containing several kinds of identical nuclei or various isotopomers. The generalized formulation of statistical scattering theory which can easily represent various rearrangement mechanisms is also presented. PMID:18081384

  8. Method for cracking hydrocarbon compositions using a submerged reactive plasma system

    DOEpatents

    Kong, P.C.

    1997-05-06

    A method is described for cracking a liquid hydrocarbon composition (e.g. crude oil) to produce a cracked hydrocarbon product. A liquid hydrocarbon composition is initially provided. An electrical arc is generated directly within the hydrocarbon composition so that the arc is entirely submerged in the composition. Arc generation is preferably accomplished using a primary and secondary electrode each having a first end submerged in the composition. The first ends of the electrodes are separated from each other to form a gap there between. An electrical potential is then applied to the electrodes to generate the arc within the gap. A reactive gas is thereafter delivered to the arc which forms a bubble around the arc. Gas delivery may be accomplished by providing a passageway through each electrode and delivering the gas through the passageways. The arc and gas cooperate to produce a plasma which efficiently cracks the hydrocarbon composition. 6 figs.

  9. Method for cracking hydrocarbon compositions using a submerged reactive plasma system

    DOEpatents

    Kong, Peter C.

    1997-01-01

    A method for cracking a liquid hydrocarbon composition (e.g. crude oil) to produce a cracked hydrocarbon product. A liquid hydrocarbon composition is initially provided. An electrical arc is generated directly within the hydrocarbon composition so that the arc is entirely submerged in the composition. Arc generation is preferably accomplished using a primary and secondary electrode each having a first end submerged in the composition. The first ends of the electrodes are separated from each other to form a gap therebetween. An electrical potential is then applied to the electrodes to generate the arc within the gap. A reactive gas is thereafter delivered to the arc which forms a bubble around the arc. Gas delivery may be accomplished by providing a passageway through each electrode and delivering the gas through the passageways. The arc and gas cooperate to produce a plasma which efficiently cracks the hydrocarbon composition.

  10. Detailed characterizations of the new Mines Douai comparative reactivity method instrument via laboratory experiments and modeling

    NASA Astrophysics Data System (ADS)

    Michoud, V.; Hansen, R. F.; Locoge, N.; Stevens, P. S.; Dusanter, S.

    2015-08-01

    The hydroxyl (OH) radical is an important oxidant in the troposphere, which controls the lifetime of most air quality- and climate-related trace gases. However, there are still uncertainties concerning its atmospheric budget, and integrated measurements of OH sinks have been valuable to improve this aspect. Among the analytical tools used for measuring total OH reactivity in ambient air, the comparative reactivity method (CRM) is spreading rapidly in the atmospheric community. However, measurement artifacts have been highlighted for this technique, and additional work is needed to fully characterize them. In this study, we present the new Mines Douai CRM instrument, with an emphasis on the corrections that need to be applied to ambient measurements of total OH reactivity. Measurement artifacts identified in the literature have been investigated, including (1) a correction for a change in relative humidity between the measurement steps leading to different OH levels, (2) the formation of spurious OH in the sampling reactor when hydroperoxy radicals (HO2) react with nitrogen monoxide (NO), (3) not operating the CRM under pseudo-first-order kinetics, and (4) the dilution of ambient air inside the reactor. The dependences of these artifacts on various measurable parameters, such as the pyrrole-to-OH ratio and the bimolecular reaction rate constants of ambient trace gases with OH, have also been studied. Based on these observations, parameterizations are proposed to correct ambient OH reactivity measurements. On average, corrections of 5.2 ± 3.2, 9.2 ± 15.7, and 8.5 ± 5.8 s-1 were respectively observed for (1), (2) and (3) during a field campaign performed in Dunkirk, France (summer 2014). Numerical simulations have been performed using a box model to check whether experimental observations mentioned above are consistent with our understanding of the chemistry occurring in the CRM reactor. Two different chemical mechanisms have been shown to reproduce the magnitude

  11. Surface chemistry, reactivity, and pore structure of porous silicon oxidized by various methods.

    PubMed

    Riikonen, Joakim; Salomäki, Mikko; van Wonderen, Jessica; Kemell, Marianna; Xu, Wujun; Korhonen, Ossi; Ritala, Mikko; MacMillan, Fraser; Salonen, Jarno; Lehto, Vesa-Pekka

    2012-07-17

    Oxidation is the most commonly used method of passivating porous silicon (PSi) surfaces against unwanted reactions with guest molecules and temporal changes during storage or use. In the present study, several oxidation methods were compared in order to find optimal methods able to generate inert surfaces free of reactive hydrides but would cause minimal changes in the pore structure of PSi. The studied methods included thermal oxidations, liquid-phase oxidations, annealings, and their combinations. The surface-oxidized samples were studied by Fourier transform infrared spectroscopy, isothermal titration microcalorimetry, nitrogen sorption, ellipsometry, X-ray diffraction, electron paramagnetic resonance spectroscopy, and scanning electron microscopy imaging. Treatment at high temperature was found to have two advantages. First, it enables the generation of surfaces free of hydrides, which is not possible at low temperatures in a liquid or a gas phase. Second, it allows the silicon framework to partially accommodate a volume expansion because of oxidation, whereas at low temperature the volume expansion significantly consumes the free pore volume. The most promising methods were further optimized to minimize the negative effects on the pore structure. Simple thermal oxidation at 700 °C was found to be an effective oxidation method although it causes a large decrease in the pore volume. A novel combination of thermal oxidation, annealing, and liquid-phase oxidation was also effective and caused a smaller decrease in the pore volume with no significant change in the pore diameter but was more complicated to perform. Both methods produced surfaces that were not found to react with a model drug cinnarizine in isothermal titration microcalorimetry experiments. The study enables a reasonable choice of oxidation method for PSi applications. PMID:22671967

  12. Detailed characterizations of a Comparative Reactivity Method (CRM) instrument: experiments vs. modelling

    NASA Astrophysics Data System (ADS)

    Michoud, V.; Hansen, R. F.; Locoge, N.; Stevens, P. S.; Dusanter, S.

    2015-04-01

    The Hydroxyl radical (OH) is an important oxidant in the daytime troposphere that controls the lifetime of most trace gases, whose oxidation leads to the formation of harmful secondary pollutants such as ozone (O3) and Secondary Organic Aerosols (SOA). In spite of the importance of OH, uncertainties remain concerning its atmospheric budget and integrated measurements of the total sink of OH can help reducing these uncertainties. In this context, several methods have been developed to measure the first-order loss rate of ambient OH, called total OH reactivity. Among these techniques, the Comparative Reactivity Method (CRM) is promising and has already been widely used in the field and in atmospheric simulation chambers. This technique relies on monitoring competitive OH reactions between a reference molecule (pyrrole) and compounds present in ambient air inside a sampling reactor. However, artefacts and interferences exist for this method and a thorough characterization of the CRM technique is needed. In this study, we present a detailed characterization of a CRM instrument, assessing the corrections that need to be applied on ambient measurements. The main corrections are, in the order of their integration in the data processing: (1) a correction for a change in relative humidity between zero air and ambient air, (2) a correction for the formation of spurious OH when artificially produced HO2 react with NO in the sampling reactor, and (3) a correction for a deviation from pseudo first-order kinetics. The dependences of these artefacts to various measurable parameters, such as the pyrrole-to-OH ratio or the bimolecular reaction rate constants of ambient trace gases with OH are also studied. From these dependences, parameterizations are proposed to correct the OH reactivity measurements from the abovementioned artefacts. A comparison of experimental and simulation results is then discussed. The simulations were performed using a 0-D box model including either (1) a

  13. Method for estimating S(N)1 rate constants: solvolytic reactivity of benzoates.

    PubMed

    Matić, Mirela; Denegri, Bernard; Kronja, Olga

    2012-10-19

    Nucleofugalities of pentafluorobenzoate (PFB) and 2,4,6-trifluorobenzoate (TFB) leaving groups have been derived from the solvolysis rate constants of X,Y-substituted benzhydryl PFBs and TFBs measured in a series of aqueous solvents, by applying the LFER equation: log k = s(f)(E(f) + N(f)). The heterolysis rate constants of dianisylmethyl PFB and TFB, and those determined for 10 more dianisylmethyl benzoates in aqueous ethanol, constitute a set of reference benzoates whose experimental ΔG(‡) have been correlated with the ΔH(‡) (calculated by PCM quantum-chemical method) of the model epoxy ring formation. Because of the excellent correlation (r = 0.997), the method for calculating the nucleofugalities of substituted benzoate LGs have been established, ultimately providing a method for determination of the S(N)1 reactivity for any benzoate in a given solvent. Using the ΔG(‡) vs ΔH(‡) correlation, and taking s(f) based on similarity, the nucleofugality parameters for about 70 benzoates have been determined in 90%, 80%, and 70% aqueous ethanol. The calculated intrinsic barriers for substituted benzoate leaving groups show that substrates producing more stabilized LGs proceed over lower intrinsic barriers. Substituents on the phenyl ring affect the solvolysis rate of benzhydryl benzoates by both field and inductive effects. PMID:22973993

  14. Hybrid finite-volume/transported PDF method for the simulation of turbulent reactive flows

    NASA Astrophysics Data System (ADS)

    Raman, Venkatramanan

    A novel computational scheme is formulated for simulating turbulent reactive flows in complex geometries with detailed chemical kinetics. A Probability Density Function (PDF) based method that handles the scalar transport equation is coupled with an existing Finite Volume (FV) Reynolds-Averaged Navier-Stokes (RANS) flow solver. The PDF formulation leads to closed chemical source terms and facilitates the use of detailed chemical mechanisms without approximations. The particle-based PDF scheme is modified to handle complex geometries and grid structures. Grid-independent particle evolution schemes that scale linearly with the problem size are implemented in the Monte-Carlo PDF solver. A novel algorithm, in situ adaptive tabulation (ISAT) is employed to ensure tractability of complex chemistry involving a multitude of species. Several non-reacting test cases are performed to ascertain the efficiency and accuracy of the method. Simulation results from a turbulent jet-diffusion flame case are compared against experimental data. The effect of micromixing model, turbulence model and reaction scheme on flame predictions are discussed extensively. Finally, the method is used to analyze the Dow Chlorination Reactor. Detailed kinetics involving 37 species and 158 reactions as well as a reduced form with 16 species and 21 reactions are used. The effect of inlet configuration on reactor behavior and product distribution is analyzed. Plant-scale reactors exhibit quenching phenomena that cannot be reproduced by conventional simulation methods. The FV-PDF method predicts quenching accurately and provides insight into the dynamics of the reactor near extinction. The accuracy of the fractional time-stepping technique in discussed in the context of apparent multiple-steady states observed in a non-premixed feed configuration of the chlorination reactor.

  15. A High Precision Method for Quantitative Measurements of Reactive Oxygen Species in Frozen Biopsies

    PubMed Central

    Lindgren, Mikael; Gustafsson, Håkan

    2014-01-01

    Objective An electron paramagnetic resonance (EPR) technique using the spin probe cyclic hydroxylamine 1-hydroxy-3-methoxycarbonyl-2,2,5,5-tetramethylpyrrolidine (CMH) was introduced as a versatile method for high precision quantification of reactive oxygen species, including the superoxide radical in frozen biological samples such as cell suspensions, blood or biopsies. Materials and Methods Loss of measurement precision and accuracy due to variations in sample size and shape were minimized by assembling the sample in a well-defined volume. Measurement was carried out at low temperature (150 K) using a nitrogen flow Dewar. The signal intensity was measured from the EPR 1st derivative amplitude, and related to a sample, 3-carboxy-proxyl (CP•) with known spin concentration. Results The absolute spin concentration could be quantified with a precision and accuracy better than ±10 µM (k = 1). The spin concentration of samples stored at −80°C could be reproduced after 6 months of storage well within the same error estimate. Conclusion The absolute spin concentration in wet biological samples such as biopsies, water solutions and cell cultures could be quantified with higher precision and accuracy than normally achievable using common techniques such as flat cells, tissue cells and various capillary tubes. In addition; biological samples could be collected and stored for future incubation with spin probe, and also further stored up to at least six months before EPR analysis, without loss of signal intensity. This opens for the possibility to store and transport incubated biological samples with known accuracy of the spin concentration over time. PMID:24603936

  16. Implementation of an original approach on the Mines-Douai Comparative Reactivity Method (MD-CRM) instrument to identify part of the missing OH reactivity at an urban site

    NASA Astrophysics Data System (ADS)

    Dusanter, S.; Michoud, V.; Leonardis, T.; Riffault, V.; Zhang, S.; Locoge, N.

    2015-12-01

    Due to the large number of Volatile Organic Compounds (VOCs) expected in the atmosphere (104-105) (Goldstein and Galbally, ES&T, 2007), exhaustive measurements of VOCs appear to be currently unfeasible using common analytical techniques. In this context, measurements of the total sink of OH, referred as total OH reactivity, can provide a critical test to assess the completeness of trace gas measurements during field campaigns. This can be done by comparing the measured total OH reactivity to values calculated from trace gas measurements. Indeed, large discrepancies are usually found between measured and calculated OH reactivity values revealing the presence of important unmeasured reactive species, which have yet to be identified. A Comparative Reactivity Method (CRM) instrument has been setup at Mines Douai to allow sequential measurements of VOCs and OH reactivity using the same Proton Transfer Reaction-Time of Flight Mass Spectrometer. This approach aims at identifying unmeasured reactive VOCs based on a method proposed by Kato et al. (Atmos. Environ., 2011), taking advantage of VOC oxidations occurring in the CRM sampling reactor. MD-CRM has been deployed at an urban site in Dunkirk (France) during July 2014 to test this new approach. During this campaign, a large fraction of the OH reactivity was not explained by collocated measurements of trace gases (67% on average). In this presentation, we will first describe the approach that was implemented in the CRM instrument to identify part of the observed missing OH reactivity and we will then discuss the OH reactivity budget regarding the origin of air masses reaching the measurement site.

  17. Method and apparatus for continuously referenced analysis of reactive components in solution

    DOEpatents

    Bostick, W.D.; Denton, M.S.; Dinsmore, S.R.

    1979-07-31

    A continuously referenced apparatus for measuring the concentration of a reactive chemical species in solution comprises in combination conduit means for introducing a sample solution, means for introducing one or more reactants into a sample solution, and a stream separator disposed within the conduit means for separating the sample solution into a first sample stream and a second sample stream. A reactor is disposed in fluid communication with the first sample stream. A reaction takes place between the reactants introduced and the reactive chemical species of interest, causing the consumption or production of an indicator species in the first sample stream. Measurement means such as a photometric system are disposed in communication with the first and second sample streams, and the outputs of the measurement means are compared to provide a blanked measurement of the concentration of indicator species. The apparatus is particularly suitable for measurement of isoenzymes in body tissues or fluids.

  18. Method to Prepare Processable Polymides with Reactive Endgroups using 1,3-Bis (3-Aminophenoxy) Benzene

    NASA Technical Reports Server (NTRS)

    Jensen, Brian J. (Inventor)

    2000-01-01

    Polyimide copolymers were obtained containing 1,3-bis(3-aminophenoxy)benzene (APB) and other diamines and dianhydrides and terminating with the appropriate amount of reactive endcapper. The reactive endcappers studied include but should not be limited to 4-phenylethynyl phthalic anhydride (PEPA ), 3-aminophenoxy- 4'-phenylethynylbenzophenone (3-APEB), maleic anhydride (MA) and nadic anhydride (5-norbomene-2,3-dicarboxylic anhydride, NA). Homopolymers containing only other diamines and dianhydrides which are not processable under conditions described previously can be made processable by incorporating various amounts of APB, depending on the chemical structures of the diamines and dianhydrides used. By simply changing the ratio of APB to the other diamine in the polyimide backbone, a material with a unique combination of solubility, Tg, Tm, melt viscosity, toughness and elevated temperature mechanical properties can be prepared. The copolymers that result from using APB to enhance processability have a unique combination of properties that include low pressure processing (200 psi and below), long term melt stability (several hours at 300 C. for the phenylethynyl terminated polymers), high toughness, improved solvent resistance, improved adhesive properties, and improved composite mechanical properties. These copolyimides are eminently suitable as adhesives, composite matrices, moldings, films and coatings.

  19. Method of recovering elemental sulfur from reactive gases containing sulfur dioxide and hydrogen sulfide

    SciTech Connect

    Thomsen, A.

    1981-12-01

    Reactive gases containing sulfur dioxide and hydrogen sulfide, e.g. reaction gases of the claus process, are passed through a catalyst stage having an inlet side and an outlet side for the gas mixture to produce elemental sulfur and water. According to the invention the gases are cooled between the inlet and discharge sides by heat-exchanger means to a temperature not less than the activation temperature for the reaction and preferably not less than the temperature at which the gases are initially introduced into the catalyst body. The heat exchanger means can be provided in gaps between catalyst beds and/or within the catalyst beds of the body of catalyst.

  20. Methods for modeling impact-induced reactivity changes in small reactors.

    SciTech Connect

    Tallman, Tyler N.; Radel, Tracy E.; Smith, Jeffrey A.; Villa, Daniel L.; Smith, Brandon M.; Radel, Ross F.; Lipinski, Ronald J.; Wilson, Paul Philip Hood

    2010-10-01

    This paper describes techniques for determining impact deformation and the subsequent reactivity change for a space reactor impacting the ground following a potential launch accident or for large fuel bundles in a shipping container following an accident. This technique could be used to determine the margin of subcriticality for such potential accidents. Specifically, the approach couples a finite element continuum mechanics model (Pronto3D or Presto) with a neutronics code (MCNP). DAGMC, developed at the University of Wisconsin-Madison, is used to enable MCNP geometric queries to be performed using Pronto3D output. This paper summarizes what has been done historically for reactor launch analysis, describes the impact criticality analysis methodology, and presents preliminary results using representative reactor designs.

  1. Shock Simulations of Single-Site Coarse-Grain RDX using the Dissipative Particle Dynamics Method with Reactivity

    NASA Astrophysics Data System (ADS)

    Sellers, Michael; Lisal, Martin; Schweigert, Igor; Larentzos, James; Brennan, John

    2015-06-01

    In discrete particle simulations, when an atomistic model is coarse-grained, a trade-off is made: a boost in computational speed for a reduction in accuracy. Dissipative Particle Dynamics (DPD) methods help to recover accuracy in viscous and thermal properties, while giving back a small amount of computational speed. One of the most notable extensions of DPD has been the introduction of chemical reactivity, called DPD-RX. Today, pairing the current evolution of DPD-RX with a coarse-grained potential and its chemical decomposition reactions allows for the simulation of the shock behavior of energetic materials at a timescale faster than an atomistic counterpart. In 2007, Maillet et al. introduced implicit chemical reactivity in DPD through the concept of particle reactors and simulated the decomposition of liquid nitromethane. We have recently extended the DPD-RX method and have applied it to solid hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) under shock conditions using a recently developed single-site coarse-grain model and a reduced RDX decomposition mechanism. A description of the methods used to simulate RDX and its tranition to hot product gases within DPD-RX will be presented. Additionally, examples of the effect of microstructure on shock behavior will be shown. Approved for public release. Distribution is unlimited.

  2. System for reactivating catalysts

    SciTech Connect

    Ginosar, Daniel M.; Thompson, David N.; Anderson, Raymond P.

    2010-03-02

    A method of reactivating a catalyst, such as a solid catalyst or a liquid catalyst is provided. The method comprises providing a catalyst that is at least partially deactivated by fouling agents. The catalyst is contacted with a fluid reactivating agent that is at or above a critical point of the fluid reactivating agent and is of sufficient density to dissolve impurities. The fluid reactivating agent reacts with at least one fouling agent, releasing the at least one fouling agent from the catalyst. The at least one fouling agent becomes dissolved in the fluid reactivating agent and is subsequently separated or removed from the fluid reactivating agent so that the fluid reactivating agent may be reused. A system for reactivating a catalyst is also disclosed.

  3. Development of Modeling Methods and Tools for Predicting Coupled Reactive Transport Processes in Porous Media at Multiple Scales

    SciTech Connect

    Clement, T Prabhakar; Barnett, Mark O; Zheng, Chunmiao; Jones, Norman L

    2010-05-05

    DE-FG02-06ER64213: Development of Modeling Methods and Tools for Predicting Coupled Reactive Transport Processes in Porous Media at Multiple Scales Investigators: T. Prabhakar Clement (PD/PI) and Mark O. Barnett (Auburn), Chunmiao Zheng (Univ. of Alabama), and Norman L. Jones (BYU). The objective of this project was to develop scalable modeling approaches for predicting the reactive transport of metal contaminants. We studied two contaminants, a radioactive cation [U(VI)] and a metal(loid) oxyanion system [As(III/V)], and investigated their interactions with two types of subsurface materials, iron and manganese oxyhydroxides. We also developed modeling methods for describing the experimental results. Overall, the project supported 25 researchers at three universities. Produced 15 journal articles, 3 book chapters, 6 PhD dissertations and 6 MS theses. Three key journal articles are: 1) Jeppu et al., A scalable surface complexation modeling framework for predicting arsenate adsorption on goethite-coated sands, Environ. Eng. Sci., 27(2): 147-158, 2010. 2) Loganathan et al., Scaling of adsorption reactions: U(VI) experiments and modeling, Applied Geochemistry, 24 (11), 2051-2060, 2009. 3) Phillippi, et al., Theoretical solid/solution ratio effects on adsorption and transport: uranium (VI) and carbonate, Soil Sci. Soci. of America, 71:329-335, 2007

  4. Illuminating reactive microbial transport in saturated porous media: Demonstration of a visualization method and conceptual transport model

    NASA Astrophysics Data System (ADS)

    Oates, Peter M.; Castenson, Catherine; Harvey, Charles F.; Polz, Martin; Culligan, Patricia

    2005-05-01

    We demonstrate a method to study reactive microbial transport in saturated translucent porous media using the bacteria Pseudomonas fluorescens 5RL genetically engineered to carry a plasmid with bioluminescence genes inducible by salicylate. Induced bacteria were injected into a cryolite grain filled chamber saturated with a sterile non-growth-promoting (phosphorus limited) chemical mixture containing salicylate as an aromatic hydrocarbon analogue. The amount of light produced by the bacteria serves as an estimator of the relative efficiency of aerobic biodegradation since bioluminescence is dependent on both salicylate and oxygen but only consumes oxygen. Bioluminescence was captured with a digital camera and analyzed to study the evolving spatial pattern of the bulk oxygen consuming reactions. As fluid flow transported the bacteria through the chamber, bioluminescence was observed to initially increase until an oxygen depletion zone developed behind the advective front. Bacterial transport was modeled with the advection dispersion equation and oxygen concentration was modeled assuming bacterial consumption via Monod kinetics with consideration of additional effects of rate-limited mass transfer from residual gas bubbles. Consistent with previous measurements, bioluminescence was considered proportional to oxygen consumed. Using the observed bioluminescence, model parameters were fit that were consistent with literature values and produced results in good agreement with the experimental data. These findings demonstrate potential for using this method to investigate the complex spatial and temporal dynamics of reactive microbial transport in saturated porous media.

  5. Illuminating reactive microbial transport in saturated porous media: demonstration of a visualization method and conceptual transport model.

    PubMed

    Oates, Peter M; Castenson, Catherine; Harvey, Charles F; Polz, Martin; Culligan, Patricia

    2005-05-01

    We demonstrate a method to study reactive microbial transport in saturated translucent porous media using the bacteria Pseudomonas fluorescens 5RL genetically engineered to carry a plasmid with bioluminescence genes inducible by salicylate. Induced bacteria were injected into a cryolite grain filled chamber saturated with a sterile non-growth-promoting (phosphorus limited) chemical mixture containing salicylate as an aromatic hydrocarbon analogue. The amount of light produced by the bacteria serves as an estimator of the relative efficiency of aerobic biodegradation since bioluminescence is dependent on both salicylate and oxygen but only consumes oxygen. Bioluminescence was captured with a digital camera and analyzed to study the evolving spatial pattern of the bulk oxygen consuming reactions. As fluid flow transported the bacteria through the chamber, bioluminescence was observed to initially increase until an oxygen depletion zone developed behind the advective front. Bacterial transport was modeled with the advection dispersion equation and oxygen concentration was modeled assuming bacterial consumption via Monod kinetics with consideration of additional effects of rate-limited mass transfer from residual gas bubbles. Consistent with previous measurements, bioluminescence was considered proportional to oxygen consumed. Using the observed bioluminescence, model parameters were fit that were consistent with literature values and produced results in good agreement with the experimental data. These findings demonstrate potential for using this method to investigate the complex spatial and temporal dynamics of reactive microbial transport in saturated porous media. PMID:15854718

  6. Multidimensional Mapping Method Using an Arrayed Sensing System for Cross-Reactivity Screening

    PubMed Central

    Chocron, Sheryl E.; Weisberger, Bryce M.; Ben-Yoav, Hadar; Winkler, Thomas E.; Kim, Eunkyoung; Kelly, Deanna L.; Payne, Gregory F.; Ghodssi, Reza

    2015-01-01

    When measuring chemical information in biological fluids, challenges of cross-reactivity arise, especially in sensing applications where no biological recognition elements exist. An understanding of the cross-reactions involved in these complex matrices is necessary to guide the design of appropriate sensing systems. This work presents a methodology for investigating cross-reactions in complex fluids. First, a systematic screening of matrix components is demonstrated in buffer-based solutions. Second, to account for the effect of the simultaneous presence of these species in complex samples, the responses of buffer-based simulated mixtures of these species were characterized using an arrayed sensing system. We demonstrate that the sensor array, consisting of electrochemical sensors with varying input parameters, generated differential responses that provide synergistic information of sample. By mapping the sensing array response onto multidimensional heat maps, characteristic signatures were compared across sensors in the array and across different matrices. Lastly, the arrayed sensing system was applied to complex biological samples to discern and match characteristic signatures between the simulated mixtures and the complex sample responses. As an example, this methodology was applied to screen interfering species relevant to the application of schizophrenia management. Specifically, blood serum measurement of antipsychotic clozapine and antioxidant species can provide useful information regarding therapeutic efficacy and psychiatric symptoms. This work proposes an investigational tool that can guide multi-analyte sensor design, chemometric modeling and biomarker discovery. PMID:25789880

  7. New Method for Production of High-Energy Neutral Molecules of Reactive Gases

    NASA Astrophysics Data System (ADS)

    Metel, Alexander; Bolbukov, Vasily; Volosova, Marina; Grigoriev, Sergei; Melnik, Yury

    2015-09-01

    For the surface modification of dielectric substrates by reactive gas molecules with energy of 100 keV they are usually produced due to charge exchange collisions of ions extracted from a plasma emitter and accelerated by high-voltage pulses. As generation of the ion plasma emitter at a 100-kV potential is quite difficult, it was proposed to extract the ions from a ground potential emitter, accelerate them by high voltage between the emitter and a negatively biased high-transparency grid and transform them into fast neutral molecules in the positive space charge sheaths of the grid. As the energy of fast molecules is defined by potentials of charge exchange collision points inside the sheath their spectrum ranges from zero to a value corresponding to the pulse amplitude. A reverse beam is always generated due to acceleration of ions from the plasma on the other side of the grid. The lower the latter density, the higher the ratio of the primary to the reverse beam currents. When the grid is composed of parallel flat plates, the charge exchange due to reflections from the plates substantially contributes at low gas pressure to production of molecules with the energy corresponding to the pulse amplitude. The work was supported by the Grant No. 14-29-00297 of the Russian Science Foundation.

  8. Numerical solution of multi-dimensional compressible reactive flow using a parallel wavelet adaptive multi-resolution method

    NASA Astrophysics Data System (ADS)

    Grenga, Temistocle

    The aim of this research is to further develop a dynamically adaptive algorithm based on wavelets that is able to solve efficiently multi-dimensional compressible reactive flow problems. This work demonstrates the great potential for the method to perform direct numerical simulation (DNS) of combustion with detailed chemistry and multi-component diffusion. In particular, it addresses the performance obtained using a massive parallel implementation and demonstrates important savings in memory storage and computational time over conventional methods. In addition, fully-resolved simulations of challenging three dimensional problems involving mixing and combustion processes are performed. These problems are particularly challenging due to their strong multiscale characteristics. For these solutions, it is necessary to combine the advanced numerical techniques applied to modern computational resources.

  9. [Sensitive determination of reactive oxygen species by chemiluminescence methods and their application to biological samples and health foods].

    PubMed

    Wada, Mitsuhiro

    2008-07-01

    Sensitive and selective methods, based on chemiluminescence reactions, were introduced for determination of reactive oxygen species (ROS) and their applications to biological samples and health foods. First, a sensitive method for determination of H(2)O(2) by peroxyoxalate chemiluminescence (PO-CL) was developed. This method could be applied to determine small amounts of H(2)O(2) in cola drinks and bacterial contamination of food items. Secondly, the combination of immobilized enzyme column reactor, or ultraviolet irradiation system, with the PO-CL detection method was able to determine clinical substrates (i.e. choline-containing phospholipids, polyamines and D-amino acids) and organic peroxides. Also, an evaluation method of the quenching effect of luminol chemiluminescence against ROS was developed. The sensitive, rapid and precise measurement of the quenching effect against ROS such as superoxide, singlet oxygen, hydroxyl radical, peroxynitrite and hypochlorous ion was achieved. The proposed method could be applied to rosemary extracts, natural colorants and grape seed extracts. PMID:18591871

  10. Improved quasiclassical trajectory method for state to state reactive scattering cross sections and rate constants

    SciTech Connect

    Ashton, C.J.; Muckerman, J.T.; Schubert, F.E.

    1984-12-15

    A systematic scheme is developed for the incorporation into quasiclassical trajectory (QCT) methodology of recent advances in the understanding of vibrationally adiabatic barriers in collinear atom + diatom reactions. The resulting hybrid QCT method centers on a definite set of rules for optimally combining the results of forward and reverse trajectory calculations. It is argued, and demonstrated by practical examples, that the hybrid method will give a more consistently reliable account of the threshold behavior of collinear reaction cross sections than the conventional QCT method. Extension of the method to the three dimensional F+H/sub 2/ reaction gives similarly encouraging results, both for state to state reaction cross sections and for rate constants.

  11. Improved quasiclassical trajectory method for state to state reactive scattering cross sections and rate constants

    SciTech Connect

    Ashton, C.J.; Muckerman, J.T.; Schubert, F.E.

    1984-12-15

    A systematic scheme is developed for the incorporation into quasiclassical trajectory (QCT) methodology of recent advances in the understanding of vibrationally adiabatic barriers in collinear atom + diatom reactions. The resulting hybrid QCT method centers on a definite set of rules for optimally combining the results of forward and reverse trajectory calculations. It is argued, and demonstrated by practical examples, that the hybrid method will give a more consistently reliable account of the threshold behavior of collinear reaction cross sections than the conventional QCT method. Extension of the method to the three dimensional F + H/sub 2/ reaction gives similarly encouraging results, both for state to state reaction cross sections and for rate constants. 43 references, 15 figures, 4 tables.

  12. Conformational and reactivity study of dithiophenyl-fucosyl ketals with theoretical chemical methods.

    PubMed

    Bañuelos-Hernandez, Angel E; García-Gutiérrez, Hugo A; Fragoso-Serrano, Mabel; Mendoza-Espinoza, José Alberto

    2016-09-01

    Carbohydrates can be used as substrates to synthesize new complex molecules; these molecules contain several chiral centers that can be used in organic synthesis. D-Fucose diphenyl thioacetal reacts differentially with acetone, and this paper describes a study of the mechanism of this reaction using theoretical chemistry methods. The conformer distribution was studied using a Monte Carlo method for the reaction products, and the obtained conformers were validated by calculating the hydrogen spin-spin coupling constants with the DFT/B3LYP/DGDZVP method. Results agreed with the experimental coupling constants with an adequate root mean squared deviation. The free energies and enthalpies of formation of the resulting global minimum conformers were calculated with the same method and with the thermochemical compound method CBS-4 M. This technique, combined with the conformational analysis, allowed comparison of the formation enthalpies of the compounds involved in this reaction, and, with this information, we can postulate the correct reaction pathway. Graphical abstract Reaction pathway. PMID:27542798

  13. Eulerian-Lagrangian localized adjoint methods for reactive transport in groundwater

    SciTech Connect

    Ewing, R.E.; Wang, Hong

    1996-12-31

    In this paper, we present Eulerian-Lagrangian localized adjoint methods (ELLAM) to solve convection-diffusion-reaction equations governing contaminant transport in groundwater flowing through an adsorbing porous medium. These ELLAM schemes can treat various combinations of boundary conditions and conserve mass. Numerical results are presented to demonstrate the strong potential of ELLAM schemes.

  14. A fluorescence high throughput screening method for the detection of reactive electrophiles as potential skin sensitizers

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Skin sensitization is an important toxicological end-point in the risk assessment of chemical allergens. Because of the complexity of the biological mechanisms associated with skin sensitization integrated approaches combining different chemical, biological and in silico methods are recommended to r...

  15. COMPARISON OF QUANTUM MECHANICAL METHODS TO COMPUTE THE BIOLOGICALLY RELEVANT REACTIVITIES OF CYCLOPENTA POLYCYCLIC AROMATIC HYDROCARBONS

    EPA Science Inventory

    In computational studies to understand the interaction of polycyclic aromatic hydrocarbons (PAHS) with biomolecular systems, the semi-empirical method AM1 has been used to determine the geometry of the PAH, its metabolites and relevant intermediates. umber of studies have shown t...

  16. Applications of the Method of Space-Time Conservation Element and the Solution Element to Unsteady Chemically Reactive Flows

    NASA Technical Reports Server (NTRS)

    Yu, Sheng-Tao

    2001-01-01

    This document reports the conclusion and findings of our research activities for this grant. The goal of the project is the development and application of the method of Space-Time Conservation Element and Solution Element, or the CE/SE method, to simulate chemically reacting flows. The product of this project will be a high-fidelity, time-accurate flow solver analyzing unsteady flow fields advanced propulsion concepts, including the low-emission turbojet engine combustion and flow fields of the Pulse Detonation Engines (PDE). Based on the documents and computer software of the CE/SE method that we have received from the CE/SE working group at NASA Lewis, we have focused our research effort on addressing outstanding technical issues related to the extension of the CE/SE method for unsteady, chemically reactive flows. In particular, we have made progresses in the following three aspects: (1) Derivation of the governing equations for reacting flows; (2) Numerical treatments of stiff source terms; and (3) Detailed simulations of ZND detonation waves.

  17. A nonlinear wave mixing method for detecting Alkali-Silica reactivity of aggregates

    NASA Astrophysics Data System (ADS)

    Liu, M.; Tang, G.; Jacobs, L. J.; Qu, J.

    2012-05-01

    Alkali-silica reaction (ASR) is a deleterious reaction in concrete. Significant ASR damage could undermine the durability of concrete structures and may result in reduced service life. Several nondestructive techniques based on ultrasound have been used to assess ASR damage. It has been shown that nonlinear ultrasound is more sensitive to internal stresses as well as to micro-cracks induced by ASR damage. In this investigation, we developed a co-linear wave mixing method for assessing ASR damage in concrete. By mixing two longitudinal waves, a new longitudinal wave with a lower frequency is generated. The amplitude of this new wave is proportional to the acoustic nonlinear parameter β which can then be obtained from the frequency spectrum of the newly generated longitudinal wave. Our experimental results show that (i) the acoustic nonlinearity parameter is closely correlated to ASR damage in concrete, (ii) the nonlinear wave mixing technique developed here is capable of measuring the changes in the acoustic nonlinearity parameter caused by ASR damage, even in its early stages, and (iii) the nonlinear wave mixing method has the potential to identify the different stages of ASR damage and to track the intrinsic characteristics of the ASR damage.

  18. A quantitative method to monitor reactive oxygen species production by electron paramagnetic resonance in physiological and pathological conditions.

    PubMed

    Mrakic-Sposta, Simona; Gussoni, Maristella; Montorsi, Michela; Porcelli, Simone; Vezzoli, Alessandra

    2014-01-01

    The growing interest in the role of Reactive Oxygen Species (ROS) and in the assessment of oxidative stress in health and disease clashes with the lack of consensus on reliable quantitative noninvasive methods applicable. The study aimed at demonstrating that a recently developed Electron Paramagnetic Resonance microinvasive method provides direct evidence of the "instantaneous" presence of ROS returning absolute concentration levels that correlate with "a posteriori" assays of ROS-induced damage by means of biomarkers. The reliability of the choice to measure ROS production rate in human capillary blood rather than in plasma was tested (step I). A significant (P < 0.01) linear relationship between EPR data collected on capillary blood versus venous blood (R (2) = 0.95), plasma (R (2) = 0.82), and erythrocytes (R (2) = 0.73) was found. Then (step II) ROS production changes of various subjects' categories, young versus old and healthy versus pathological at rest condition, were found significantly different (range 0.0001-0.05 P level). The comparison of the results with antioxidant capacity and oxidative damage biomarkers concentrations showed that all changes indicating increased oxidative stress are directly related to ROS production increase. Therefore, the adopted method may be an automated technique for a lot of routine in clinical trials. PMID:25374651

  19. Simultaneous 2D imaging of dissolved iron and reactive phosphorus in sediment porewaters by thin-film and hyperspectral methods.

    PubMed

    Cesbron, Florian; Metzger, Edouard; Launeau, Patrick; Deflandre, Bruno; Delgard, Marie-Lise; Thibault de Chanvalon, Aubin; Geslin, Emmanuelle; Anschutz, Pierre; Jézéquel, Didier

    2014-01-01

    This study presents a new approach combining diffusive equilibrium in thin-film (DET) and spectrophotometric methods to determine the spatial variability of dissolved iron and dissolved reactive phosphorus (DRP) with a single gel probe. Its originality is (1) to postpone up to three months the colorimetric reaction of DET by freezing and (2) to measure simultaneously dissolved iron and DRP by hyperspectral imaging at a submillimeter resolution. After a few minutes at room temperature, the thawed gel is sandwiched between two monospecific reagent DET gels, leading to magenta and blue coloration for iron and phosphate, respectively. Spatial distribution of the resulting colors is obtained using a hyperspectral camera. Reflectance spectra analysis enables deconvolution of specific colorations by the unmixing method applied to the logarithmic reflectance, leading to an accurate quantification of iron and DRP. This method was applied in the Arcachon lagoon (France) on muddy sediments colonized by eelgrass (Zostera noltei) meadows. The 2D gel probes highlighted microstructures in the spatial distribution of dissolved iron and phosphorus, which are most likely associated with the occurrence of benthic fauna burrows and seagrass roots. PMID:24502458

  20. Positivity-preserving, flux-limited finite-difference and finite-element methods for reactive transport

    NASA Astrophysics Data System (ADS)

    MacKinnon, Robert J.; Carey, Graham F.

    2003-01-01

    A new class of positivity-preserving, flux-limited finite-difference and Petrov-Galerkin (PG) finite-element methods are devised for reactive transport problems.The methods are similar to classical TVD flux-limited schemes with the main difference being that the flux-limiter constraint is designed to preserve positivity for problems involving diffusion and reaction. In the finite-element formulation, we also consider the effect of numerical quadrature in the lumped and consistent mass matrix forms on the positivity-preserving property. Analysis of the latter scheme shows that positivity-preserving solutions of the resulting difference equations can only be guaranteed if the flux-limited scheme is both implicit and satisfies an additional lower-bound condition on time-step size. We show that this condition also applies to standard Galerkin linear finite-element approximations to the linear diffusion equation. Numerical experiments are provided to demonstrate the behavior of the methods and confirm the theoretical conditions on time-step size, mesh spacing, and flux limiting for transport problems with and without nonlinear reaction.

  1. A fully-implicit finite-volume method for multi-fluid reactive and collisional magnetized plasmas on unstructured meshes

    NASA Astrophysics Data System (ADS)

    Alvarez Laguna, A.; Lani, A.; Deconinck, H.; Mansour, N. N.; Poedts, S.

    2016-08-01

    We present a Finite Volume scheme for solving Maxwell's equations coupled to magnetized multi-fluid plasma equations for reactive and collisional partially ionized flows on unstructured meshes. The inclusion of the displacement current allows for studying electromagnetic wave propagation in a plasma as well as charge separation effects beyond the standard magnetohydrodynamics (MHD) description, however, it leads to a very stiff system with characteristic velocities ranging from the speed of sound of the fluids up to the speed of light. In order to control the fulfillment of the elliptical constraints of the Maxwell's equations, we use the hyperbolic divergence cleaning method. In this paper, we extend the latter method applying the CIR scheme with scaled numerical diffusion in order to balance those terms with the Maxwell flux vectors. For the fluids, we generalize the AUSM+-up to multiple fluids of different species within the plasma. The fully implicit second-order method is first verified on the Hartmann flow (including comparison with its analytical solution), two ideal MHD cases with strong shocks, namely, Orszag-Tang and the MHD rotor, then validated on a much more challenging case, representing a two-fluid magnetic reconnection under solar chromospheric conditions. For the latter case, a comparison with pioneering results available in literature is provided.

  2. A Quantitative Method to Monitor Reactive Oxygen Species Production by Electron Paramagnetic Resonance in Physiological and Pathological Conditions

    PubMed Central

    Mrakic-Sposta, Simona; Gussoni, Maristella; Montorsi, Michela; Porcelli, Simone; Vezzoli, Alessandra

    2014-01-01

    The growing interest in the role of Reactive Oxygen Species (ROS) and in the assessment of oxidative stress in health and disease clashes with the lack of consensus on reliable quantitative noninvasive methods applicable. The study aimed at demonstrating that a recently developed Electron Paramagnetic Resonance microinvasive method provides direct evidence of the “instantaneous” presence of ROS returning absolute concentration levels that correlate with “a posteriori” assays of ROS-induced damage by means of biomarkers. The reliability of the choice to measure ROS production rate in human capillary blood rather than in plasma was tested (step I). A significant (P < 0.01) linear relationship between EPR data collected on capillary blood versus venous blood (R2 = 0.95), plasma (R2 = 0.82), and erythrocytes (R2 = 0.73) was found. Then (step II) ROS production changes of various subjects' categories, young versus old and healthy versus pathological at rest condition, were found significantly different (range 0.0001–0.05 P level). The comparison of the results with antioxidant capacity and oxidative damage biomarkers concentrations showed that all changes indicating increased oxidative stress are directly related to ROS production increase. Therefore, the adopted method may be an automated technique for a lot of routine in clinical trials. PMID:25374651

  3. Isochoric Burn, an Internally Consistent Method for the Reactant to Product Transformation in Reactive Flow

    SciTech Connect

    Reaugh, J E; Lee, E L

    2002-07-01

    Mixture rules for partially reacted explosives differ amongst various models. For instance, JWL++ uses a partial pressure addition to compute an average zonal pressure, Ignition and Growth requires pressure equilibration and thermal equilibration of temperature dependent JWL EOSs, CHEETAH In Line RF also assumes temperature and pressure equilibration. It has been suggested in the past that a more realistic equilibration scheme should comprise isentropic pressure equilibration of the separate reacted and unreacted phases. This turns out not to be a proper path for equilibration. Rather, we find that the only internally consistent method is the evaluation of the equilibrium pressure that satisfies the particular conditions of reactant and product resulting from deflagration in a fixed volume.

  4. Enforcing positivity in intrusive PC-UQ methods for reactive ODE systems

    DOE PAGESBeta

    Najm, Habib N.; Valorani, Mauro

    2014-04-12

    We explore the relation between the development of a non-negligible probability of negative states and the instability of numerical integration of the intrusive Galerkin ordinary differential equation system describing uncertain chemical ignition. To prevent this instability without resorting to either multi-element local polynomial chaos (PC) methods or increasing the order of the PC representation in time, we propose a procedure aimed at modifying the amplitude of the PC modes to bring the probability of negative state values below a user-defined threshold. This modification can be effectively described as a filtering procedure of the spectral PC coefficients, which is applied on-the-flymore » during the numerical integration when the current value of the probability of negative states exceeds the prescribed threshold. We demonstrate the filtering procedure using a simple model of an ignition process in a batch reactor. This is carried out by comparing different observables and error measures as obtained by non-intrusive Monte Carlo and Gauss-quadrature integration and the filtered intrusive procedure. Lastly, the filtering procedure has been shown to effectively stabilize divergent intrusive solutions, and also to improve the accuracy of stable intrusive solutions which are close to the stability limits.« less

  5. Enforcing positivity in intrusive PC-UQ methods for reactive ODE systems

    SciTech Connect

    Najm, Habib N.; Valorani, Mauro

    2014-04-12

    We explore the relation between the development of a non-negligible probability of negative states and the instability of numerical integration of the intrusive Galerkin ordinary differential equation system describing uncertain chemical ignition. To prevent this instability without resorting to either multi-element local polynomial chaos (PC) methods or increasing the order of the PC representation in time, we propose a procedure aimed at modifying the amplitude of the PC modes to bring the probability of negative state values below a user-defined threshold. This modification can be effectively described as a filtering procedure of the spectral PC coefficients, which is applied on-the-fly during the numerical integration when the current value of the probability of negative states exceeds the prescribed threshold. We demonstrate the filtering procedure using a simple model of an ignition process in a batch reactor. This is carried out by comparing different observables and error measures as obtained by non-intrusive Monte Carlo and Gauss-quadrature integration and the filtered intrusive procedure. Lastly, the filtering procedure has been shown to effectively stabilize divergent intrusive solutions, and also to improve the accuracy of stable intrusive solutions which are close to the stability limits.

  6. Enforcing positivity in intrusive PC-UQ methods for reactive ODE systems

    SciTech Connect

    Najm, Habib N.; Valorani, Mauro

    2014-08-01

    We explore the relation between the development of a non-negligible probability of negative states and the instability of numerical integration of the intrusive Galerkin ordinary differential equation system describing uncertain chemical ignition. To prevent this instability without resorting to either multi-element local polynomial chaos (PC) methods or increasing the order of the PC representation in time, we propose a procedure aimed at modifying the amplitude of the PC modes to bring the probability of negative state values below a user-defined threshold. This modification can be effectively described as a filtering procedure of the spectral PC coefficients, which is applied on-the-fly during the numerical integration when the current value of the probability of negative states exceeds the prescribed threshold. We demonstrate the filtering procedure using a simple model of an ignition process in a batch reactor. This is carried out by comparing different observables and error measures as obtained by non-intrusive Monte Carlo and Gauss-quadrature integration and the filtered intrusive procedure. The filtering procedure has been shown to effectively stabilize divergent intrusive solutions, and also to improve the accuracy of stable intrusive solutions which are close to the stability limits.

  7. A new and reliable method for live imaging and quantification of reactive oxygen species in Botrytis cinerea: technological advancement.

    PubMed

    Marschall, Robert; Tudzynski, Paul

    2014-10-01

    Reactive oxygen species (ROS) are produced in conserved cellular processes either as by-products of the cellular respiration in mitochondria, or purposefully for defense mechanisms, signaling cascades or cell homeostasis. ROS have two diametrically opposed attributes due to their highly damaging potential for DNA, lipids and other molecules and due to their indispensability for signaling and developmental processes. In filamentous fungi, the role of ROS in growth and development has been studied in detail, but these analyses were often hampered by the lack of reliable and specific techniques to monitor different activities of ROS in living cells. Here, we present a new method for live cell imaging of ROS in filamentous fungi. We demonstrate that by use of a mixture of two fluorescent dyes it is possible to monitor H2O2 and superoxide specifically and simultaneously in distinct cellular structures during various hyphal differentiation processes. In addition, the method allows for reliable fluorometric quantification of ROS. We demonstrate that this can be used to characterize different mutants with respect to their ROS production/scavenging potential. PMID:25220147

  8. Heterogeneous reactive transport under unsaturated transient conditions characterized by 3D electrical resistivity tomography and advanced lysimeter methods

    NASA Astrophysics Data System (ADS)

    Wehrer, Markus; Slater, Lee

    2015-04-01

    Our ability to predict flow and transport processes in the unsaturated critical zone is considerably limited by two characteristics: heterogeneity of flow and transience of boundary conditions. The causes of heterogeneous flow and transport are fairly well understood, yet the characterization and quantification of such processes in natural profiles remains challenging. This is due to current methods of observation, such as staining and isotope tracers, being unable to observe multiple events on the same profile and offering limited spatial information. In our study we demonstrate an approach to characterize preferential flow and transport processes applying a combination of geoelectrical methods and advanced lysimeter techniques. On an agricultural soil profile, which was transferred undisturbed into a lysimeter container, we systematically applied a variety of input flow boundary conditions, resembling natural precipitation events. We measured breakthroughs of a conservative tracer and of nitrate, originating from the application of a slow release fertilizer and serving as a reactive tracer. Flow and transport in the soil column were observed using electrical resistivity tomography (ERT), tensiometers, water content probes and a multicompartment suction plate (MSP). These techniques allowed a direct validation of water content dynamics and tracer breakthrough under transient boundary conditions characterized noninvasively by ERT. We were able to image the advancing infiltration front and the advancing front of tracer and nitrate using time lapse ERT. Water content changes associated with the advancing infiltration front dominated over pore fluid conductivity changes during short term precipitation events. Conversely, long-term displacement of the solute fronts was monitored during periods of constant water content in between infiltration events. We observed preferential flow phenomena through ERT and through the MSP, which agreed in general terms. The preferential

  9. One-Step Conjugation Method for Site-Specific Antibody-Drug Conjugates through Reactive Cysteine-Engineered Antibodies.

    PubMed

    Shinmi, Daisuke; Taguchi, Eri; Iwano, Junko; Yamaguchi, Tsuyoshi; Masuda, Kazuhiro; Enokizono, Junichi; Shiraishi, Yasuhisa

    2016-05-18

    Engineered cysteine residues are particularly convenient for site-specific conjugation of antibody-drug conjugates (ADC), because no cell engineering and additives are required. Usually, unpaired cysteine residues form mixed disulfides during fermentation in Chinese hamster ovarian (CHO) cells; therefore, additional reduction and oxidization steps are required prior to conjugation. In this study, we prepared light chain (Lc)-Q124C variants in IgG and examined the conjugation efficiency. Intriguingly, Lc-Q124C exhibited high thiol reactivity and directly generated site-specific ADC without any pretreatment (named active thiol antibody: Actibody). Most of the cysteine-maleimide conjugates including Lc-Q124C showed retro-Michael reaction with cysteine 34 in albumin and were decomposed over time. In order to acquire resistance to a maleimide exchange reaction, the facile procedure for succinimide hydrolysis on anion exchange resin was employed. Hydrolyzed Lc-Q124C conjugate prepared with anion exchange procedure retained high stability in plasma. Recently, various stable linkage schemes for cysteine conjugation have been reported. The combination with direct conjugation by the use of Actibody and stable linker technology could enable the generation of stable site-specific ADC through a simple method. Actibody technology with Lc-Q124C at a less exposed position opens a new path for cysteine-based conjugation, and contributes to reducing entry barriers to the preparation and evaluation of ADC. PMID:27074832

  10. Study of ice cluster impacts on amorphous silica using the ReaxFF reactive force field molecular dynamics simulation method

    NASA Astrophysics Data System (ADS)

    Rahnamoun, A.; van Duin, A. C. T.

    2016-03-01

    We study the dynamics of the collisions between amorphous silica structures and amorphous and crystal ice clusters with impact velocities of 1 km/s, 4 km/s, and 7 km/s using the ReaxFF reactive molecular dynamics simulation method. The initial ice clusters consist of 150 water molecules for the amorphous ice cluster and 128 water molecules for the crystal ice cluster. The ice clusters are collided on the surface of amorphous fully oxidized and suboxide silica. These simulations show that at 1 km/s impact velocities, all the ice clusters accumulate on the surface and at 4 km/s and 7 km/s impact velocities, some of the ice cluster molecules bounce back from the surface. At 4 km/s and 7 km/s impact velocities, few of the water molecules dissociations are observed. The effect of the second ice cluster impacts on the surfaces which are fully covered with ice, on the mass loss/accumulation is studied. These studies show that at 1 km/s impacts, the entire ice cluster accumulates on the surface at both first and second ice impacts. At higher impact velocities, some ice molecules which after the first ice impacts have been attached to the surface will separate from the surface after the second ice impacts at 7 km/s impact velocity. For the 4 km/s ice cluster impact, ice accumulation is observed for the crystal ice cluster impacts and ice separation is observed for the amorphous ice impacts. Observing the temperatures of the ice clusters during the collisions indicates that the possibility of electron excitement at impact velocities less than 10 km/s is minimal and ReaxFF reactive molecular dynamics simulation can predict the chemistry of these hypervelocity impacts. However, at impact velocities close to 10 km/s the average temperature of the impacting ice clusters increase to about 2000 K, with individual molecules occasionally reaching temperatures of over 8000 K and thus it will be prudent to consider the concept of electron excitation at these higher impact velocities

  11. A new method for direct total OH reactivity measurements using a fast Gas Chromatographic Photo-Ionization Detector (GC-PID)

    NASA Astrophysics Data System (ADS)

    Nölscher, A. C.; Sinha, V.; Bockisch, S.; Klüpfel, T.; Williams, J.

    2012-04-01

    The primary and most important oxidant in the troposphere is the hydroxyl radical (OH). Currently the atmospheric sinks of OH are poorly constrained. One way to characterize the overall sink term of OH is to measure directly the ambient loss rate of OH, the total OH reactivity. The first direct measurements of total OH reactivity were performed using laser induced fluorescence (LIF) [1], [2]. Recently a new method for determining OH reactivity was developed called the comparative reactivity method (CRM) [3]. The measurement principle is based on a competitive reaction between a reactive molecule not normally present in air with OH, and atmospheric OH reactive molecules with OH. The reactive molecule (X), is passed through a Teflon coated glass reactor and its concentration is monitored with a suitable detector. OH radicals are then introduced into the reactor at a constant rate to react with X, first in the presence of zero air and then in the presence of ambient air containing OH reactive species. Comparing the amount of X exiting the reactor with and without the competing ambient air molecules directly provides the atmospheric total OH reactivity. In the first version of this set up, molecule X is pyrrole (C5H4N) and the detector used is a proton transfer reaction mass spectrometer (PTR-MS). In comparison to the original LIF based system, the PTR-MS has the advantage of being smaller, less expensive, and commercially available. However, using the PTR-MS for total OH reactivity measurements prevents it from probing the broad variety of volatile organic compounds in ambient air. Moreover, even smaller, less expensive and more portable detectors are available. This work examines the potential for a GC-PID in order to make the total OH reactivity measurement accessible to more practitioners. This study presents measurements of total OH reactivity with a custom built GC-PID (VOC-Analyzer from IUT-Berlin, now ENIT (Environics-IUT GmbH))[4]. The GC-PID is small (260

  12. An adaptive sparse-grid high-order stochastic collocation method for Bayesian inference in groundwater reactive transport modeling

    SciTech Connect

    Zhang, Guannan; Webster, Clayton G; Gunzburger, Max D

    2012-09-01

    Although Bayesian analysis has become vital to the quantification of prediction uncertainty in groundwater modeling, its application has been hindered due to the computational cost associated with numerous model executions needed for exploring the posterior probability density function (PPDF) of model parameters. This is particularly the case when the PPDF is estimated using Markov Chain Monte Carlo (MCMC) sampling. In this study, we develop a new approach that improves computational efficiency of Bayesian inference by constructing a surrogate system based on an adaptive sparse-grid high-order stochastic collocation (aSG-hSC) method. Unlike previous works using first-order hierarchical basis, we utilize a compactly supported higher-order hierar- chical basis to construct the surrogate system, resulting in a significant reduction in the number of computational simulations required. In addition, we use hierarchical surplus as an error indi- cator to determine adaptive sparse grids. This allows local refinement in the uncertain domain and/or anisotropic detection with respect to the random model parameters, which further improves computational efficiency. Finally, we incorporate a global optimization technique and propose an iterative algorithm for building the surrogate system for the PPDF with multiple significant modes. Once the surrogate system is determined, the PPDF can be evaluated by sampling the surrogate system directly with very little computational cost. The developed method is evaluated first using a simple analytical density function with multiple modes and then using two synthetic groundwater reactive transport models. The groundwater models represent different levels of complexity; the first example involves coupled linear reactions and the second example simulates nonlinear ura- nium surface complexation. The results show that the aSG-hSC is an effective and efficient tool for Bayesian inference in groundwater modeling in comparison with conventional

  13. Quantitative assessment of alkali-reactive aggregate mineral content through XRD using polished sections as a supplementary tool to RILEM AAR-1 (petrographic method)

    SciTech Connect

    Castro, Nelia; Sorensen, Bjorn E.; Broekmans, Maarten A.T.M.

    2012-11-15

    The mineral content of 5 aggregate samples from 4 different countries, including reactive and non-reactive aggregate types, was assessed quantitatively by X-ray diffraction (XRD) using polished sections. Additionally, electron probe microanalyzer (EPMA) mapping and cathodoluminescence (CL) were used to characterize the opal-CT identified in one of the aggregate samples. Critical review of results from polished sections against traditionally powdered specimen has demonstrated that for fine-grained rocks without preferred orientation the assessment of mineral content by XRD using polished sections may represent an advantage over traditional powder specimens. Comparison of data on mineral content and silica speciation with expansion data from PARTNER project confirmed that the presence of opal-CT plays an important role in the reactivity of one of the studied aggregates. Used as a complementary tool to RILEM AAR-1, the methodology suggested in this paper has the potential to improve the strength of the petrographic method.

  14. Time-dependent wave-packet method for the complete determination of S-matrix elements for reactive molecular collisions in three dimensions

    NASA Technical Reports Server (NTRS)

    Judson, Richard S.; Kouri, Donald J.; Neuhauser, Daniel; Baer, Michael

    1990-01-01

    An alternative time-dependent wave-packet method for treating three-dimensional gas phase reactive atom-diatom collisions is presented. The method employs a nonreactive body-frame wave packet propagation procedure, made possible by judicious use of absorbing optical potentials, a novel scheme for interpolating the wave function from coordinates in one arrangement to those in another and the fact that the time-dependent Schroedinger equation is an initial-value problem. The last feature makes possible a computationally viable and accurate procedure for changing from one arrangement's coordinates to another. In addition, the method allows the determination of S-matrix elements over a wide range of energies from a single wave-packet propagation. The method is illustrated by carrying out detailed calculations of inelastic and reactive scattering in the H + H2 system using the Liu-Siegbahn-Truhlar-Horowitz potential surface.

  15. Do we really need a large number of particles to simulate bimolecular reactive transport with random walk methods? A kernel density estimation approach

    NASA Astrophysics Data System (ADS)

    Rahbaralam, Maryam; Fernàndez-Garcia, Daniel; Sanchez-Vila, Xavier

    2015-12-01

    Random walk particle tracking methods are a computationally efficient family of methods to solve reactive transport problems. While the number of particles in most realistic applications is in the order of 106-109, the number of reactive molecules even in diluted systems might be in the order of fractions of the Avogadro number. Thus, each particle actually represents a group of potentially reactive molecules. The use of a low number of particles may result not only in loss of accuracy, but also may lead to an improper reproduction of the mixing process, limited by diffusion. Recent works have used this effect as a proxy to model incomplete mixing in porous media. In this work, we propose using a Kernel Density Estimation (KDE) of the concentrations that allows getting the expected results for a well-mixed solution with a limited number of particles. The idea consists of treating each particle as a sample drawn from the pool of molecules that it represents; this way, the actual location of a tracked particle is seen as a sample drawn from the density function of the location of molecules represented by that given particle, rigorously represented by a kernel density function. The probability of reaction can be obtained by combining the kernels associated to two potentially reactive particles. We demonstrate that the observed deviation in the reaction vs time curves in numerical experiments reported in the literature could be attributed to the statistical method used to reconstruct concentrations (fixed particle support) from discrete particle distributions, and not to the occurrence of true incomplete mixing. We further explore the evolution of the kernel size with time, linking it to the diffusion process. Our results show that KDEs are powerful tools to improve computational efficiency and robustness in reactive transport simulations, and indicates that incomplete mixing in diluted systems should be modeled based on alternative mechanistic models and not on a

  16. Reactive arthritis

    MedlinePlus

    Reactive arthritis is a group of conditions that may involve the joints, eyes, and urinary and genital systems. ... The exact cause of reactive arthritis is unknown. It occurs most often in men younger than age 40. It may follow an infection in the urethra ...

  17. A liquid chromatography tandem mass spectrometric method on in vitro nerve agents poisoning characterization and reactivator efficacy evaluation by determination of specific peptide adducts in acetylcholinesterase.

    PubMed

    Yan, Long; Chen, Jia; Xu, Bin; Guo, Lei; Xie, Yan; Tang, Jijun; Xie, Jianwei

    2016-06-10

    The terroristic availability of highly toxic nerve agents (NAs) highlights the necessity for a deep understanding of their toxicities and effective medical treatments. A liquid chromatography tandem mass spectrometry (LC-MS/MS) method for a characterization of the NAs poisoning and an evaluation on the efficacy of reactivators in in vitro was developed for the first time. After exposure to sarin or VX and pepsin digestion, the specific peptides of acetylcholinesterase (AChE) in a purified status, i.e. undecapeptide "GESAGAASVGM" in free, unaged, or aged status was identified and quantified. A key termination procedure is focused to make the reaction system "frozen" and precisely "capture" the poisoning, aging and spontaneous reactivation status of AChE, and the abundance of such specific peptides can thus be simultaneously measured. In our established method, as low as 0.72% and 0.84% inhibition level of AChE induced by 0.5nM sarin and VX can be detected from the measurement of peptide adducts, which benefits a confirmation of NAs exposure, especially at extremely low levels. Comparing with conventional colorimetric Ellman assays, our method provides not only enzyme activity and inhibition rate, but also the precise poisoning status of NAs exposed AChE. Based on the full information provided by this method, the efficacy of reactivators, such as HI-6, obidoxime and pralidoxime, in the typical treatment of NAs poisoned AChE in in vitro was further evaluated. Our results showed that this method is a promising tool for the characterization of NAs poisoning and the evaluation of reactivator efficacy. PMID:27179675

  18. UV-Vis microspectrophotometry as a method of differentiation between cotton fibre evidence coloured with reactive dyes

    NASA Astrophysics Data System (ADS)

    Was-Gubala, Jolanta; Starczak, Roza

    2015-05-01

    The main purposes of this study was to assess the usefulness of microspectrophotometry (MSP), both in the ultraviolet (UV) and visible (Vis) range for discriminating single cotton fibres dyed with reactive dyes coming from the same manufacturer, as well as the possibility of evaluation of the concentration of dye in an examine fibre. This study utilised woven cotton fabrics dyed with different concentrations of one-compound reactive dyes with the commercial name Cibacron® (at present Novacron®) as the focus of the MSP analysis. The spectra were recorded in the UV-Vis range between 200 and 800 nm, in transmission mode. The results from this study illustrated that all of the analysed cotton samples dyed with reactive dyes were distinguishable between each other with the use of MSP, mostly in the visible, and also in ultraviolet range. The limit for applied MSP techniques was 0.18% of the concentration of a dye in the textile sample. The results indicate that based on the absorbance measurements for fibres constituting e.g. forensic traces it was not possible to estimate the concentration of the dye in the fibre because Beer's law did not obey. The intra-sample, and inter- sample variation, as well as dichroism effect in a case of a cotton fibres dyed with reactive dye were observed. On the basis of the results obtained for each analysed cotton sample, it was concluded that there was no correlation between colour uniformity in cotton fabric (changes in lightness, red/green and yellow/blue colour) and concentration of the reactive dye.

  19. UV-Vis microspectrophotometry as a method of differentiation between cotton fibre evidence coloured with reactive dyes.

    PubMed

    Was-Gubala, Jolanta; Starczak, Roza

    2015-05-01

    The main purposes of this study was to assess the usefulness of microspectrophotometry (MSP), both in the ultraviolet (UV) and visible (Vis) range for discriminating single cotton fibres dyed with reactive dyes coming from the same manufacturer, as well as the possibility of evaluation of the concentration of dye in an examine fibre. This study utilised woven cotton fabrics dyed with different concentrations of one-compound reactive dyes with the commercial name Cibacron® (at present Novacron®) as the focus of the MSP analysis. The spectra were recorded in the UV-Vis range between 200 and 800nm, in transmission mode. The results from this study illustrated that all of the analysed cotton samples dyed with reactive dyes were distinguishable between each other with the use of MSP, mostly in the visible, and also in ultraviolet range. The limit for applied MSP techniques was 0.18% of the concentration of a dye in the textile sample. The results indicate that based on the absorbance measurements for fibres constituting e.g. forensic traces it was not possible to estimate the concentration of the dye in the fibre because Beer's law did not obey. The intra-sample, and inter- sample variation, as well as dichroism effect in a case of a cotton fibres dyed with reactive dye were observed. On the basis of the results obtained for each analysed cotton sample, it was concluded that there was no correlation between colour uniformity in cotton fabric (changes in lightness, red/green and yellow/blue colour) and concentration of the reactive dye. PMID:25699701

  20. Detection of Virus-Specific CD8+ T Cells With Cross-Reactivity Against Alloantigens: Potency and Flaws of Present Experimental Methods

    PubMed Central

    van den Heuvel, Heleen; Heutinck, Kirstin M.; van der Meer-Prins, Ellen P.M.W.; Yong, Si La; Claas, Frans H.J.; ten Berge, Ineke J.M.

    2015-01-01

    Background Virus-specific T cells have the intrinsic capacity to cross-react against allogeneic HLA antigens, a phenomenon known as heterologous immunity. In transplantation, these cells may contribute to the alloimmune response and negatively impact graft outcome. This study describes the various techniques that can be used to detect heterologous immune responses of virus-specific CD8+ T cells against allogeneic HLA antigens. The strengths and weaknesses of the different approaches are discussed and illustrated by experimental data. Methods Mixed-lymphocyte reactions (MLRs) were performed to detect allo-HLA cross-reactivity of virus-specific CD8+ T cells in total peripheral blood mononuclear cells. T-cell lines and clones were generated to confirm allo-HLA cross-reactivity by IFNγ production and cytotoxicity. In addition, the conventional MLR protocol was adjusted by introducing a 3-day resting phase and subsequent short restimulation with alloantigen or viral peptide, whereupon the expression of IFNγ, IL-2, CD107a, and CD137 was determined. Results The accuracy of conventional MLR is challenged by potential bystander activation. T-cell lines and clones can circumvent this issue, yet their generation is laborious and time-consuming. Using the adjusted MLR and restimulation protocol, we found that only truly cross-reactive T cells responded to re-encounter of alloantigen and viral peptide, whereas bystander-activated cells did not. Conclusions The introduction of a restimulation phase improved the accuracy of the MLR as a screening tool for the detection of allo-HLA cross-reactivity by virus-specific CD8+ T cells at bulk level. For detailed characterization of cross-reactive cells, T-cell lines and clones remain the golden standard.

  1. Combining field methods and numerical modeling to characterize the flow of a Sr-90 plume through a permeable reactive barrier

    NASA Astrophysics Data System (ADS)

    Hoppe, J.; Bain, J.; Lee, D. R.; Jeen, S.; Blowes, D.

    2012-12-01

    In 1998, a passive remediation system known as the Wall-and-Curtain was installed at the Chalk River Laboratories in Ontario, Canada, to prevent a Sr-90 plume present in the lower part of a 12 m thick aquifer from discharging into a nearby swamp. To improve knowledge of the variability of aquifer hydraulic conductivities and groundwater velocities, slug tests and borehole dilution tests were conducted in isolated intervals upgradient of the Wall-and-Curtain using stainless steel drive point piezometers. The measurements from the field study were combined with previous characterization of the hydrogeology of the site to develop a three dimensional physical flow model. The numerical computer code HydroGeoSphere was used to provide an approximate representation of groundwater flow in the aquifer and through the Wall-and-Curtain. Developing a quantitative description of the groundwater flow system is an essential step in understanding the fate of the Sr-90 plume in the Wall-and-Curtain and for conducting meaningful geochemical reactive transport simulations. The model was calibrated by comparing simulated and observed hydraulic heads across the site. The results from the field tests were compared with groundwater velocities simulated by the numerical model. The model shows good agreement with the observed heads and acceptable agreement with the field estimates of groundwater velocities, while also showing the deficiencies of the model in accurately simulating flow in the boundary regions of the domain. Ongoing work focuses on the detailed geochemical characterization of the aquifer and the reactive material (i.e., clinoptilolite), which will be used to construct a geochemical reactive transport model to evaluate the potential longevity of the reactive zone in the Wall-and-Curtain.

  2. Reactive Arthritis

    MedlinePlus

    ... with treatment and may cause joint damage. What Research Is Being Conducted on Reactive Arthritis? Researchers continue ... such as methotrexate and sulfasalazine. More information on research is available from the following websites: National Institutes ...

  3. Non-invasive in situ plasma monitoring of reactive gases using the floating harmonic method for inductively coupled plasma etching application

    SciTech Connect

    Lee, J. H.; Kim, M. J.; Yoon, Y. S.

    2013-04-15

    The floating harmonic method was developed for in situ plasma diagnostics of allowing real time measurement of electron temperature (T{sub e}) and ion flux (J{sub ion}) without contamination of the probe from surface modification by reactive species. In this study, this novel non-invasive diagnostic system was studied to characterize inductively coupled plasma of reactive gases monitoring T{sub e} and J{sub ion} for investigating the optimum plasma etching conditions and controlling of the real-time plasma surface reaction in the range of 200-900 W source power, 10-100 W bias power, and 3-15 mTorr chamber pressure, respectively.

  4. The role of serum C-reactive protein measured by high-sensitive method in thyroid disease.

    PubMed

    Czarnywojtek, Agata; Owecki, Maciej; Zgorzalewicz-Stachowiak, Małgorzata; Woliński, Kosma; Szczepanek-Parulska, Ewelina; Budny, Bartłomiej; Florek, Ewa; Waligórska-Stachura, Joanna; Miechowicz, Izabela; Bączyk, Maciej; Sawicka, Nadia; Dhir, Sumit; Ruchała, Marek

    2014-12-01

    The aim of this study was the evaluation of serum C-reactive protein (CRP) concentration as a marker of the inflammatory state in many different thyroid diseases and its dependence on the stage and duration of disease. We conducted a retrospective analysis of 444 randomly selected patients with different kinds of thyroid disease (106 men and 338 women, ranging 18-72 years of age; mean 56.2 ± 5.0 years; median 52 years). Group 1 (G1) comprised 250 patients with hyperthyroidism. Group 2 (G2) consisted of 72 euthyroid patients. Group 3 (G3) consisted of 122 patients with hypothyroidism. Free T4, free T3, and thyrotropin (TSH) levels were measured using the electrochemiluminescent method. Human serum thyroglobulin autoantibodies (Tg-Abs), thyroperoxidase autoantibodies (TPO-Abs), and autoantibodies against the thyrotropin receptor (TSHR-Abs) levels were measured by radioimmunoassay. The high-sensitive CRP (Hs-CRP) level (reference range <3 mg/L) was determined with a highly sensitive latex-based immunoassay. The mean value of Hs-CRP in G1 was 3.6 ± 2.8 mg/L, in G2 2.5 ± 1.5 mg/L and in G3 5.9 ± 5.8 mg/L. Hs-CRP (in mg/L) medians, interquartile and the total ranges in G1 were 3.0 (2.0 [0.1-21.0] 4.0); in G2: 2.3 [1.8 (0.2-9.2) 3.2]; and in G3: 4.3 [2.2 (0.3-31.5) 7.8]. We found statistically significant differences (Kruskal-Wallis test) in serum Hs-CRP values between G1 and G2 (P = 0.007), G1 and G3 (P = 0.001), G2 and G3 (P < 0.001). In G1, statistically significant correlation was confirmed between Hs-CRP and Tg-Abs (r = -0.22, P = 0.0016), CRP and TPO-Abs (r = -0.26, P < 0.001), and also between Hs-CRP and TSHR-Abs (r = -0.18, P = 0.02). In the remaining cases, differences between Hs-CRP and TSH levels (r = -0.09, P = 0.16) were not statistically significant. In G2, no statistically significant correlation was observed: Hs-CRP and Tg-Abs (r = -0.18, P = 0.13), Hs-CRP and TPO-Abs (r = -0.17, P = 0.15), Hs-CRP and TSH (r = 0.01, P = 0.91), Hs-CRP and TSHR-Abs (r

  5. A GPU accelerated, discrete time random walk model for simulating reactive transport in porous media using colocation probability function based reaction methods

    NASA Astrophysics Data System (ADS)

    Barnard, J. M.; Augarde, C. E.

    2012-12-01

    The simulation of reactions in flow through unsaturated porous media is a more complicated process when using particle tracking based models than in continuum based models. In the fomer particles are reacted on an individual particle-to-particle basis using either deterministic or probabilistic methods. This means that particle tracking methods, especially when simulations of reactions are included, are computationally intensive as the reaction simulations require tens of thousands of nearest neighbour searches per time step. Despite this, particle tracking methods merit further study due to their ability to eliminate numerical dispersion, to simulate anomalous transport and incomplete mixing of reactive solutes. A new model has been developed using discrete time random walk particle tracking methods to simulate reactive mass transport in porous media which includes a variation of colocation probability function based methods of reaction simulation from those presented by Benson & Meerschaert (2008). Model development has also included code acceleration via graphics processing units (GPUs). The nature of particle tracking methods means that they are well suited to parallelization using GPUs. The architecture of GPUs is single instruction - multiple data (SIMD). This means that only one operation can be performed at any one time but can be performed on multiple data simultaneously. This allows for significant speed gains where long loops of independent operations are performed. Computationally expensive code elements, such the nearest neighbour searches required by the reaction simulation, are therefore prime targets for GPU acceleration.

  6. Forebody and base region real gas flow in severe planetary entry by a factored implicit numerical method. II - Equilibrium reactive gas

    NASA Technical Reports Server (NTRS)

    Davy, W. C.; Green, M. J.; Lombard, C. K.

    1981-01-01

    The factored-implicit, gas-dynamic algorithm has been adapted to the numerical simulation of equilibrium reactive flows. Changes required in the perfect gas version of the algorithm are developed, and the method of coupling gas-dynamic and chemistry variables is discussed. A flow-field solution that approximates a Jovian entry case was obtained by this method and compared with the same solution obtained by HYVIS, a computer program much used for the study of planetary entry. Comparison of surface pressure distribution and stagnation line shock-layer profiles indicates that the two solutions agree well.

  7. Testing single extraction methods and in vitro tests to assess the geochemical reactivity and human bioaccessibility of silver in urban soils amended with silver nanoparticles.

    PubMed

    Cruz, N; Rodrigues, S M; Tavares, D; Monteiro, R J R; Carvalho, L; Trindade, T; Duarte, A C; Pereira, E; Römkens, Paul F A M

    2015-09-01

    To assess if the geochemical reactivity and human bioaccessibility of silver nanoparticles (AgNPs) in soils can be determined by routine soil tests commonly applied to other metals in soil, colloidal Ag was introduced to five pots containing urban soils (equivalent to 6.8 mg Ag kg(-1) soil). Following a 45 days stabilization period, the geochemical reactivity was determined by extraction using 0.43 M and 2 M HNO3. The bioaccessibility of AgNPs was evaluated using the Simplified Bioaccessibility Extraction Test (SBET) the "Unified BARGE Method" (UBM), and two simulated lung fluids (modified Gamble's solution (MGS) and artificial lysosomal fluid (ALF)). The amount of Ag extracted by 0.43 M and 2 M HNO3 soil tests was <8% and <50%, respectively of the total amount of Ag added to soils suggesting that the reactivity of Ag present in the soil can be relatively low. The bioaccessibility of Ag as determined by the four in vitro tests ranged from 17% (ALF extraction) to 99% (SBET) indicating that almost all Ag can be released from soil due to specific interactions with the organic ligands present in the simulated body fluids. This study shows that to develop sound soil risk evaluations regarding soil contamination with AgNPs, aspects of Ag biochemistry need to be considered, particularly when linking commonly applied soil tests to human risk assessment. PMID:25966049

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

    NASA Astrophysics Data System (ADS)

    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.

  9. Selective complexation and reactivity of metallic nitride and oxometallic fullerenes with Lewis acids and use as an effective purification method.

    PubMed

    Stevenson, Steven; Mackey, Mary A; Pickens, Jane E; Stuart, Melissa A; Confait, Bridget S; Phillips, J Paige

    2009-12-21

    Metallic nitride fullerenes (MNFs) and oxometallic fullerenes (OMFs) react quickly with an array of Lewis acids. Empty-cage fullerenes are largely unreactive under conditions used in this study. The reactivity order is Sc(4)O(2)@I(h)-C(80) > Sc(3)N@C(78) > Sc(3)N@C(68) > Sc(3)N@D(5h)-C(80) > Sc(3)N@I(h)-C(80). Manipulations of Lewis acids, molar ratios, and kinetic differences within the family of OMF and MNF metallofullerenes are demonstrated in a selective precipitation scheme, which can be used either alone for purifying Sc(3)N@I(h)-C(80) or combined with a final high-performance liquid chromatography pass for Sc(4)O(2)@I(h)-C(80), Sc(3)N@D(5h)-C(80), Sc(3)N@C(68), or Sc(3)N@C(78). The purification process is scalable. Analysis of the experimental rate constants versus electrochemical band gap explains the order of reactivity among the OMFs and MNFs. PMID:19911812

  10. Reactive arthritis.

    PubMed

    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

  11. Method To Prepare Processable Polyimides With Reactive Endogroups Using 1,3-bis(3-aminophenoxy)benzene

    NASA Technical Reports Server (NTRS)

    Jensen, Brian J. (Inventor)

    2001-01-01

    Polyimide copolymers were obtained containing 1,3-bis(3-aminophenoxy)benzene (APB) and other diamines and dianhydrides and terminating with the appropriate amount of a non-reactive endcapper, such as phthalic anhydride. Homopolymers containing only other diamines and dianhydrides which are not processable under conditions described previously can be made processable by incorporating various amounts of APB, depending on the chemical structures of the diamines and dianhydrides used. Polyimides that are more rigid in nature require more APB to impart processability than polyimides that are less rigid in nature. The copolymers that result from using APB to enhance processability have a unique combination of properties including excellent thin film properties, low pressure processing (200 psi and below), improved toughness, improved solvent resistance, improved adhesive properties, improved composite mechanical properties, long term melt stability (several hours at 390 C), and lower melt viscosities.

  12. Method to Prepare Processable Polyimides with Non-Reactive Endgroups Using 1,3-bis(3-Aminophenoxy) Benzene

    NASA Technical Reports Server (NTRS)

    Jensen, Brian J. (Inventor)

    2000-01-01

    Polyimide copolymers were obtained containing 1,3-bis(3-aminophenoxy)benzene (APB) and other diamines and dianhydrides and terminating with the appropriate amount of a non-reactive endcapper, such as phthalic anhydride. Homopolymers containing only other diamines and dianhydrides which are not processable under conditions described previously can be made processable by incorporating various amounts of APB, depending on the chemical structures of the diamines and dianhydrides used. Polyimides that are more rigid in nature require more APB to impart processability than polyimides that are less rigid in nature. The copolymers that result from using APB to enhance processability have a unique combination of properties including excellent thin film properties, low pressure processing (200 psi and below), improved toughness, improved solvent resistance, improved adhesive properties, improved composite mechanical properties, long term melt stability (several hours at 390 C), and lower melt viscosities.

  13. A Method for Compensating Customer Voltage Drops due to Nighttime Simultaneous Charging of EVs Utilizing Reactive Power Injection from Battery Chargers

    NASA Astrophysics Data System (ADS)

    Noda, Taku; Kabasawa, Yuichiro; Fukushima, Kentaro; Nemoto, Koshichi; Uemura, Satoshi

    When we consider the global warming, the reduction of CO2 emission is one of the most important problems which require urgent solutions. One option is to integrate low-CO2-emission generators to the grid as much as possible. Another option is to replace inefficient vehicles based on internal-combustion engines with electric ones (EVs). Due to the latter, we can easily estimate that most consumers will charge EVs' batteries at nighttime. Thus, excessive voltage drops due to the nighttime simultaneous charging are supposed to be a possible future problem. This paper proposes a method for compensating the voltage drops by injecting reactive power from EV battery chargers.

  14. A Chebyshev method for state-to-state reactive scattering using reactant-product decoupling: OH + H2 → H2O + H

    NASA Astrophysics Data System (ADS)

    Cvitaš, Marko T.; Althorpe, Stuart C.

    2013-08-01

    We extend a recently developed wave packet method for computing the state-to-state quantum dynamics of AB + CD → ABC + D reactions [M. T. Cvitaš and S. C. Althorpe, J. Phys. Chem. A 113, 4557 (2009)], 10.1021/jp8111974 to include the Chebyshev propagator. The method uses the further partitioned approach to reactant-product decoupling, which uses artificial decoupling potentials to partition the coordinate space of the reaction into separate reactant, product, and transition-state regions. Separate coordinates and basis sets can then be used that are best adapted to each region. We derive improved Chebyshev partitioning formulas which include Mandelshtam-and-Taylor-type decoupling potentials, and which are essential for the non-unitary discrete variable representations that must be used in 4-atom reactive scattering calculations. Numerical tests on the fully dimensional OH + H2 → H2O + H reaction for J = 0 show that the new version of the method is as efficient as the previously developed split-operator version. The advantages of the Chebyshev propagator (most notably the ease of parallelization for J > 0) can now be fully exploited in state-to-state reactive scattering calculations on 4-atom reactions.

  15. A new method of wound treatment: targeted therapy of skin wounds with reactive oxygen species-responsive nanoparticles containing SDF-1α

    PubMed Central

    Tang, Tao; Jiang, Hao; Yu, Yuan; He, Fang; Ji, Shi-zhao; Liu, Ying-ying; Wang, Zhong-shan; Xiao, Shi-chu; Tang, Cui; Wang, Guang-Yi; Xia, Zhao-Fan

    2015-01-01

    Objective To accelerate wound healing through promoting vascularization by using reactive oxygen species (ROS)-responsive nanoparticles loaded with stromal cell-derived factor-1α(SDF-1α). Methods The ROS-reactive nanomaterial poly-(1,4-phenyleneacetone dimethylene thioketal) was synthesized, and its physical and chemical properties were characterized. ROS-responsive nanoparticles containing SDF-1α were prepared through a multiple emulsion solvent evaporation method. The loading capacity, stability, activity of the encapsulated protein, toxicity, and in vivo distribution of these nanoparticles were determined. These nanoparticles were administered by intravenous infusion to mice with full-thickness skin defects to study their effects on the directed chemotaxis of bone marrow mesenchymal stem cells, wound vascularization, and wound healing. Results The synthesized ROS-reactive organic polymer poly-(1,4-phenyleneacetone dimethylene thioketal) possessed a molecular weight of approximately 11.5 kDa with a dispersity of 1.97. ROS-responsive nanoparticles containing SDF-1α were prepared with an average diameter of 110 nm and a drug loading capacity of 1.8%. The encapsulation process showed minimal effects on the activity of SDF-1α, and it could be effectively released from the nanoparticles in the presence of ROS. Encapsulated SDF-1α could exist for a long time in blood. In mice with full-thickness skin defects, SDF-1α was effectively released and targeted to the wounds, thus promoting the chemotaxis of bone marrow mesenchymal stem cells toward the wound and its periphery, inducing wound vascularization, and accelerating wound healing. PMID:26527874

  16. A Parallel, Fully Coupled, Fully Implicit Solution to Reactive Transport in Porous Media Using the Preconditioned Jacobian-Free Newton-Krylov Method

    SciTech Connect

    Luanjing Guo; Hai Huang; Derek Gaston; Cody Permann; David Andrs; George Redden; Chuan Lu; Don Fox; Yoshiko Fujita

    2013-03-01

    Modeling large multicomponent reactive transport systems in porous media is particularly challenging when the governing partial differential algebraic equations (PDAEs) are highly nonlinear and tightly coupled due to complex nonlinear reactions and strong solution-media interactions. Here we present a preconditioned Jacobian-Free Newton-Krylov (JFNK) solution approach to solve the governing PDAEs in a fully coupled and fully implicit manner. A well-known advantage of the JFNK method is that it does not require explicitly computing and storing the Jacobian matrix during Newton nonlinear iterations. Our approach further enhances the JFNK method by utilizing physics-based, block preconditioning and a multigrid algorithm for efficient inversion of the preconditioner. This preconditioning strategy accounts for self- and optionally, cross-coupling between primary variables using diagonal and off-diagonal blocks of an approximate Jacobian, respectively. Numerical results are presented demonstrating the efficiency and massive scalability of the solution strategy for reactive transport problems involving strong solution-mineral interactions and fast kinetics. We found that the physics-based, block preconditioner significantly decreases the number of linear iterations, directly reducing computational cost; and the strongly scalable algebraic multigrid algorithm for approximate inversion of the preconditioner leads to excellent parallel scaling performance.

  17. Numerical methods for improving sensitivity analysis and parameter estimation of virus transport simulated using sorptive-reactive processes

    USGS Publications Warehouse

    Barth, G.; Hill, M.C.

    2005-01-01

    Using one- and two-dimensional homogeneous simulations, this paper addresses challenges associated with sensitivity analysis and parameter estimation for virus transport simulated using sorptive-reactive processes. Head, flow, and conservative- and virus-transport observations are considered. The paper examines the use of (1) observed-value weighting, (2) breakthrough-curve temporal moment observations, and (3) the significance of changes in the transport time-step size. The results suggest that (1) sensitivities using observed-value weighting are more susceptible to numerical solution variability, (2) temporal moments of the breakthrough curve are a more robust measure of sensitivity than individual conservative-transport observations, and (3) the transport-simulation time step size is more important than the inactivation rate in solution and about as important as at least two other parameters, reflecting the ease with which results can be influenced by numerical issues. The approach presented allows more accurate evaluation of the information provided by observations for estimation of parameters and generally improves the potential for reasonable parameter-estimation results. ?? 2004 Elsevier B.V. All rights reserved.

  18. Controlling Material Reactivity Using Architecture.

    PubMed

    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

  19. Most anti-BrdU antibodies react with 2'-deoxy-5-ethynyluridine -- the method for the effective suppression of this cross-reactivity.

    PubMed

    Liboska, Radek; Ligasová, Anna; Strunin, Dmytro; Rosenberg, Ivan; Koberna, Karel

    2012-01-01

    5-Bromo-2'-deoxyuridine (BrdU) and 2'-deoxy-5-ethynyluridine (EdU) are widely used as markers of replicated DNA. While BrdU is detected using antibodies, the click reaction typically with fluorescent azido-dyes is used for EdU localisation. We have performed an analysis of ten samples of antibodies against BrdU with respect to their reactivity with EdU. Except for one sample all the others evinced reactivity with EdU. A high level of EdU persists in nuclear DNA even after the reaction of EdU with fluorescent azido-dyes if the common concentration of dye is used. Although a ten-time increase of azido-dye concentration resulted in a decrease of the signal provided by anti-BrdU antibodies, it also resulted in a substantial increase of the non-specific signal. We have shown that this unwanted reactivity is effectively suppressed by non-fluorescent azido molecules. In this respect, we have tested two protocols of the simultaneous localisation of incorporated BrdU and EdU. They differ in the mechanism of the revelation of incorporated BrdU for the reaction with antibodies. The first one was based on the use of hydrochloric acid, the second one on the incubation of samples with copper(I) ions. The use of hydrochloric acid resulted in a significant increase of the non-specific signal. In the case of the second method, no such effect was observed. PMID:23272138

  20. Most Anti-BrdU Antibodies React with 2′-Deoxy-5-Ethynyluridine — The Method for the Effective Suppression of This Cross-Reactivity

    PubMed Central

    Strunin, Dmytro; Rosenberg, Ivan; Koberna, Karel

    2012-01-01

    5-Bromo-2′-deoxyuridine (BrdU) and 2′-deoxy-5-ethynyluridine (EdU) are widely used as markers of replicated DNA. While BrdU is detected using antibodies, the click reaction typically with fluorescent azido-dyes is used for EdU localisation. We have performed an analysis of ten samples of antibodies against BrdU with respect to their reactivity with EdU. Except for one sample all the others evinced reactivity with EdU. A high level of EdU persists in nuclear DNA even after the reaction of EdU with fluorescent azido-dyes if the common concentration of dye is used. Although a ten-time increase of azido-dye concentration resulted in a decrease of the signal provided by anti-BrdU antibodies, it also resulted in a substantial increase of the non-specific signal. We have shown that this unwanted reactivity is effectively suppressed by non-fluorescent azido molecules. In this respect, we have tested two protocols of the simultaneous localisation of incorporated BrdU and EdU. They differ in the mechanism of the revelation of incorporated BrdU for the reaction with antibodies. The first one was based on the use of hydrochloric acid, the second one on the incubation of samples with copper(I) ions. The use of hydrochloric acid resulted in a significant increase of the non-specific signal. In the case of the second method, no such effect was observed. PMID:23272138

  1. Reactive Power Compensator.

    DOEpatents

    El-Sharkawi, M.A.; Venkata, S.S.; Chen, M.; Andexler, G.; Huang, T.

    1992-07-28

    A system and method for determining and providing reactive power compensation for an inductive load. A reactive power compensator (50,50') monitors the voltage and current flowing through each of three distribution lines (52a, 52b, 52c), which are supplying three-phase power to one or more inductive loads. Using signals indicative of the current on each of these lines when the voltage waveform on the line crosses zero, the reactive power compensator determines a reactive power compensator capacitance that must be connected to the lines to maintain a desired VAR level, power factor, or line voltage. Alternatively, an operator can manually select a specific capacitance for connection to each line, or the capacitance can be selected based on a time schedule. The reactive power compensator produces control signals, which are coupled through optical fibers (102/106) to a switch driver (110, 110') to select specific compensation capacitors (112) for connections to each line. The switch driver develops triggering signals that are supplied to a plurality of series-connected solid state switches (350), which control charge current in one direction in respect to ground for each compensation capacitor. During each cycle, current flows from ground to charge the capacitors as the voltage on the line begins to go negative from its positive peak value. The triggering signals are applied to gate the solid state switches into a conducting state when the potential on the lines and on the capacitors reaches a negative peak value, thereby minimizing both the potential difference and across the charge current through the switches when they begin to conduct. Any harmonic distortion on the potential and current carried by the lines is filtered out from the current and potential signals used by the reactive power compensator so that it does not affect the determination of the required reactive compensation. 26 figs.

  2. Reactive power compensator

    DOEpatents

    El-Sharkawi, Mohamed A.; Venkata, Subrahmanyam S.; Chen, Mingliang; Andexler, George; Huang, Tony

    1992-01-01

    A system and method for determining and providing reactive power compensation for an inductive load. A reactive power compensator (50,50') monitors the voltage and current flowing through each of three distribution lines (52a, 52b, 52c), which are supplying three-phase power to one or more inductive loads. Using signals indicative of the current on each of these lines when the voltage waveform on the line crosses zero, the reactive power compensator determines a reactive power compensator capacitance that must be connected to the lines to maintain a desired VAR level, power factor, or line voltage. Alternatively, an operator can manually select a specific capacitance for connection to each line, or the capacitance can be selected based on a time schedule. The reactive power compensator produces control signals, which are coupled through optical fibers (102/106) to a switch driver (110, 110') to select specific compensation capacitors (112) for connections to each line. The switch driver develops triggering signals that are supplied to a plurality of series-connected solid state switches (350), which control charge current in one direction in respect to ground for each compensation capacitor. During each cycle, current flows from ground to charge the capacitors as the voltage on the line begins to go negative from its positive peak value. The triggering signals are applied to gate the solid state switches into a conducting state when the potential on the lines and on the capacitors reaches a negative peak value, thereby minimizing both the potential difference and across the charge current through the switches when they begin to conduct. Any harmonic distortion on the potential and current carried by the lines is filtered out from the current and potential signals used by the reactive power compensator so that it does not affect the determination of the required reactive compensation.

  3. Pore-scale simulation of coupled reactive transport and dissolution in fractures and porous media using the level set interface tracking method

    SciTech Connect

    Hai Huang; Xiaoyi Li

    2011-01-01

    A level set simulation methodology developed for modeling coupled reactive transport and structure evolution has been applied to dissolution in fracture apertures and porous media. The coupled processes such as fluid flow, reactant transport and dissolution at the solid-liquid interfaces are handled simultaneously. The reaction-induced evolution of solid-liquid interfaces is captured using the level set method, with the advantage of representing the interface with sub-grid scale resolution. The coupled processes are simulated for several geometric models of fractures and porous media under various flow conditions and reaction rates. Quantitative relationships between permeability and porosity are obtained from some of the simulation results and compared with analytical constitutive relations (i.e., the conventional cubic law and the Carman-Kozeny law) based on simplified pore space geometries and reaction induced geometric evolutions. The drastic deviation of the simulation results from these analytical theories is explained by the development of large local concentration gradients of reactants within fracture apertures and individual pores observed in the simulation results and consequently the complex geometric evolution patterns of fracture apertures and pores due to mineral dissolution. The simulation results support the argument that traditional constitutive relations based on simplified geometries and conditions have limited applicability in predicting field scale reactive transport and that incorporation of micro-scale physics is necessary.

  4. A Method for Capturing Sub-Gridscale Interactions in Numerical Simulation of Flow and Reactive Transport in Power-Law Media

    NASA Astrophysics Data System (ADS)

    Travis, B. J.

    2013-12-01

    For nonlinear, coupled flow and reactive transport in heterogeneous systems, capturing sub-gridscale dynamics is a serious challenge for coarse-grained numerical simulation. Even simply for linear, uncomplicated flow systems, accurate estimation of sub-gridscale effects may require averaging over a possibly tensor, multi-scale permeability distribution. Stochastic process modeling and statistical analysis methods are available and are being improved for calculating average and variance properties of flow and transport systems. Frequently, in addition to the average dynamics, a solution for an individual realization, or for many realizations, is desired or required. For media whose smaller-scale heterogeneity can be approximated by a power law (fractal) model (and this is approximately true for many soils), fractal interpolating functions, constrained by measured properties and distributions, provide an efficient way to capture sub-gridscale dynamics for individual realizations. An advantage of this approach is that it can be incorporated readily into conventional finite difference or finite element flow and transport codes, providing a multi-resolution solution for less cost than a finely-grained one. Several examples illustrate the potential usefulness of this approach for numerical simulation of flow and reactive transport in heterogeneous media. Comparisons are made to finely gridded traditional numerical solutions. Limitations and conditions of use are discussed.

  5. Interactive chemical reactivity exploration.

    PubMed

    Haag, Moritz P; Vaucher, Alain C; Bosson, Maël; Redon, Stéphane; Reiher, Markus

    2014-10-20

    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. PMID:25205397

  6. What Is Reactive Arthritis?

    MedlinePlus

    ... 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 ...

  7. RADMAP: Simple probes for rapid assessment of complex reactivity: A method and case studies on the reaction of hydrogen atoms with unsaturated organic molecules.

    PubMed

    Long, Andrew K; Fawcett, Jason A; Clyburne, Jason A C; Pye, Cory C

    2016-03-01

    RADMAP, an open source program, allows for rapid analysis and visualization of the earliest stages of reactions between any molecule and a monoatomic probe (i.e., H*, H(+), H(-), Br*, or any other monoatomic species) using ab initio methods. This program creates non-planar potential energy surfaces of the initial interaction between a molecule of interest and the monoatomic probe. These surfaces can be used to both predict the site of addition as well as provide a qualitative estimate for the relative proportion of the formation of adducts; therefore, it gives insight into both the reactivity and the kinetic stability of a molecule. The program presents a way to quickly predict the number of signals anticipated in transverse field muon spin resonance spectra as well as their relative intensities. PMID:26851865

  8. Fuel Temperature Coefficient of Reactivity

    SciTech Connect

    Loewe, W.E.

    2001-07-31

    A method for measuring the fuel temperature coefficient of reactivity in a heterogeneous nuclear reactor is presented. The method, which is used during normal operation, requires that calibrated control rods be oscillated in a special way at a high reactor power level. The value of the fuel temperature coefficient of reactivity is found from the measured flux responses to these oscillations. Application of the method in a Savannah River reactor charged with natural uranium is discussed.

  9. Quantum wave packet method for state-to-state reactive scattering calculations on AB + CD --> ABC + D reactions.

    PubMed

    Cvitas, Marko T; Althorpe, Stuart C

    2009-04-23

    We describe a quantum wave packet method for computing the state-to-state quantum dynamics of 4-atom AB + CD --> ABC + D reactions. The approach is an extension to 4-atom reactions of a version of the reactant-product decoupling (RPD) approach, applied previously to 3-atom reactions ( J. Chem. Phys. 2001, 114 , 1601 ). The approach partitions the coordinate space of the reaction into separate reagent, strong-interaction, and product regions, using a system of artificial absorbing and reflecting potentials. It employs a partitioned version of the split-operator propagator, which is more efficient than partitioning the (exact) time-dependent Schrodinger equation. The wave packet bounces off a reflecting potential in the entrance channel, which generates a source term; this is transformed efficiently from reagent to product Jacobi coordinates by exploiting some simple angular momentum properties. The efficiency and accuracy of the method is demonstrated by numerical tests on the benchmark OH + H(2) --> H(2)O + H reaction. PMID:19298045

  10. Preparation of nitrogen-substituted TiO2 thin film photocatalysts by the radio frequency magnetron sputtering deposition method and their photocatalytic reactivity under visible light irradiation.

    PubMed

    Kitano, Masaaki; Funatsu, Keisho; Matsuoka, Masaya; Ueshima, Michio; Anpo, Masakazu

    2006-12-21

    Nitrogen-substituted TiO2 (N-TiO2) thin film photocatalysts have been prepared by a radio frequency magnetron sputtering (RF-MS) deposition method using a N2/Ar mixture sputtering gas. The effect of the concentration of substituted nitrogen on the characteristics of the N-TiO2 thin films was investigated by UV-vis absorption spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and scanning electron microscopy (SEM) analyses. The absorption band of the N-TiO2 thin film was found to shift smoothly to visible light regions up to 550 nm, its extent depending on the concentration of nitrogen substituted within the TiO2 lattice in a range of 2.0-16.5%. The N-TiO2 thin film photocatalyst with a nitrogen concentration of 6.0% exhibited the highest reactivity for the photocatalytic oxidation of 2-propanol diluted in water even under visible (lambda > or = 450 nm) or solar light irradiation. Moreover, N-TiO2 thin film photocatalysts prepared on conducting glass electrodes showed anodic photocurrents attributed to the photooxidation of water under visible light, its extent depending on wavelengths up to 550 nm. The absorbed photon to current conversion efficiencies reached 25.2% and 22.4% under UV (lambda = 360 nm) and visible light (lambda = 420 nm), respectively. UV-vis and photoelectrochemical investigations also confirmed that these thin films remain thermodynamically and mechanically stable even under heat treatment at 673 K. In addition, XPS and XRD studies revealed that a significantly high substitution of the lattice O atoms of the TiO2 with the N atoms plays a crucial role in the band gap narrowing of the TiO2 thin films, enabling them to absorb and operate under visible light irradiation as a highly reactive, effective photocatalyst. PMID:17165971

  11. Multiscale reactive molecular dynamics

    NASA Astrophysics Data System (ADS)

    Knight, Chris; Lindberg, Gerrick E.; Voth, Gregory A.

    2012-12-01

    Many processes important to chemistry, materials science, and biology cannot be described without considering electronic and nuclear-level dynamics and their coupling to slower, cooperative motions of the system. These inherently multiscale problems require computationally efficient and accurate methods to converge statistical properties. In this paper, a method is presented that uses data directly from condensed phase ab initio simulations to develop reactive molecular dynamics models that do not require predefined empirical functions. Instead, the interactions used in the reactive model are expressed as linear combinations of interpolating functions that are optimized by using a linear least-squares algorithm. One notable benefit of the procedure outlined here is the capability to minimize the number of parameters requiring nonlinear optimization. The method presented can be generally applied to multiscale problems and is demonstrated by generating reactive models for the hydrated excess proton and hydroxide ion based directly on condensed phase ab initio molecular dynamics simulations. The resulting models faithfully reproduce the water-ion structural properties and diffusion constants from the ab initio simulations. Additionally, the free energy profiles for proton transfer, which is sensitive to the structural diffusion of both ions in water, are reproduced. The high fidelity of these models to ab initio simulations will permit accurate modeling of general chemical reactions in condensed phase systems with computational efficiency orders of magnitudes greater than currently possible with ab initio simulation methods, thus facilitating a proper statistical sampling of the coupling to slow, large-scale motions of the system.

  12. Multiscale reactive molecular dynamics

    PubMed Central

    Knight, Chris; Lindberg, Gerrick E.; Voth, Gregory A.

    2012-01-01

    Many processes important to chemistry, materials science, and biology cannot be described without considering electronic and nuclear-level dynamics and their coupling to slower, cooperative motions of the system. These inherently multiscale problems require computationally efficient and accurate methods to converge statistical properties. In this paper, a method is presented that uses data directly from condensed phase ab initio simulations to develop reactive molecular dynamics models that do not require predefined empirical functions. Instead, the interactions used in the reactive model are expressed as linear combinations of interpolating functions that are optimized by using a linear least-squares algorithm. One notable benefit of the procedure outlined here is the capability to minimize the number of parameters requiring nonlinear optimization. The method presented can be generally applied to multiscale problems and is demonstrated by generating reactive models for the hydrated excess proton and hydroxide ion based directly on condensed phase ab initio molecular dynamics simulations. The resulting models faithfully reproduce the water-ion structural properties and diffusion constants from the ab initio simulations. Additionally, the free energy profiles for proton transfer, which is sensitive to the structural diffusion of both ions in water, are reproduced. The high fidelity of these models to ab initio simulations will permit accurate modeling of general chemical reactions in condensed phase systems with computational efficiency orders of magnitudes greater than currently possible with ab initio simulation methods, thus facilitating a proper statistical sampling of the coupling to slow, large-scale motions of the system. PMID:23249062

  13. Modelling of Thermal Advective Reactive Flow in Hydrothermal Mineral Systems Using an Implicit Time-stepped Finite Element Method.

    NASA Astrophysics Data System (ADS)

    Hornby, P. G.

    2005-12-01

    Understanding chemical and thermal processes taking place in hydrothermal mineral deposition systems could well be a key to unlocking new mineral reserves through improved targeting of exploration efforts. To aid in this understanding it is very helpful to be able to model such processes with sufficient fidelity to test process hypotheses. To gain understanding, it is often sufficient to obtain semi-quantitative results that model the broad aspects of the complex set of thermal and chemical effects taking place in hydrothermal systems. For example, it is often sufficient to gain an understanding of where thermal, geometric and chemical factors converge to precipitate gold (say) without being perfectly precise about how much gold is precipitated. The traditional approach is to use incompressible Darcy flow together with the Boussinesq approximation. From the flow field, the heat equation is used to advect-conduct the heat. The flow field is also used to transport solutes by solving an advection-dispersion-diffusion equation. The reactions in the fluid and between fluid and rock act as source terms for these advection-dispersion equations. Many existing modelling systems that are used for simulating such systems use explicit time marching schemes and finite differences. The disadvantage of this approach is the need to work on rectilinear grids and the number of time steps required by the Courant condition in the solute transport step. The second factor can be particularly significant if the chemical system is complex, requiring (at a minimum) an equilibrium calculation at each grid point at each time step. In the approach we describe, we use finite elements rather than finite differences, and the pressure, heat and advection-dispersion equations are solved implicitly. The general idea is to put unconditional numerical stability of the time integration first, and let accuracy assume a secondary role. It is in this sense that the method is semi-quantiative. However

  14. The 'reactive

    NASA Astrophysics Data System (ADS)

    Battista Piccardo, Giovanni; Guarnieri, Luisa

    2010-05-01

    The Ligurian ophiolitic peridotites [South Lanzo, Erro-Tobbio, Internal Ligurides and Corsica] are characterized by the abundance of spinel(Sp) peridotites showing depleted compositions and ranging from Cpx-poor Sp lherzolites to Sp harzburgites. They were recognized in the last decades as refractory residua by MORB-forming partial melting of the asthenosphere, and were similar to abyssal peridotites. Recent structural and compositional studies promoted a better understanding of their structural and compositional features and their genetic processes. In the field these depleted peridotites replace with primary contacts pyroxenite-bearing fertile Sp lherzolites that have been recognized as sub-continental lithospheric mantle. Field relationships evidence that decametric-hectometric bodies of pristine pyroxenite-veined lithospheric Sp lherzolites are preserved as structural remnants within the km-scale masses of depleted peridotites. The depleted peridotites show coarse-grained recrystallized textures and reaction micro-structures indicating pyroxene dissolution and olivine precipitation that have been considered as records of melt/peridotite interaction during reactive diffuse porous flow of undersaturated melts. They show, moreover, contrasting bulk and mineral chemistries that cannot be produced by simple partial melting and melt extraction. In particular, their bulk compositions are depleted in SiO2 and enriched in FeO with respect to refractory residua after any kind of partial melting, as calculated by Niu (1997), indicating that they cannot be formed by simple partial melting and melt extraction processes. Moreover, TiO2 content in Sp is usually significantly higher (up to 0.8-1.0 wt%) than typical TiO2 contents of spinels (usually < 0.1-0.2 wt %) in fertile mantle peridotites and melting refractory residua, indicating that spinel attained element equilibration with a Ti-bearing basaltic melt. The depleted peridotites usually show strongly variable Cpx modal

  15. Effect of cooking method on carnosine and its homologues, pentosidine and thiobarbituric acid-reactive substance contents in beef and turkey meat.

    PubMed

    Peiretti, Pier Giorgio; Medana, Claudio; Visentin, Sonja; Dal Bello, Federica; Meineri, Giorgia

    2012-05-01

    Commercial samples of beef and turkey meat were prepared by commonly used cooking methods with standard cooking times: (1) broiled at 200°C for 10min, (2) broiled at a medium temperature (140°C) for 10min, (3) cooked by microwave (MW) for 3min and then grilled (MW/grill) for 7min, (4) cooked in a domestic microwave oven for 10min, and (5) boiled in water for 10min. The raw and cooked meats were then analysed to determine the carnosine, anserine, homocarnosine, pentosidine, and thiobarbituric acid-reactive substance (TBARS) contents. It was observed that boiling beef caused a loss of approximately 50% of the carnosine, probably because of the high water solubility of carnosine and its homologues; cooking by microwave caused a medium loss of the anti-oxidants of approximately 20%; cooking by MW/grill led to a reduction in carnosine of approximately 10%. As far as the anserine and homocarnosine contents were concerned, a greater loss was observed for the boiling method (approximately 70%) while, for the other cooking methods, the value ranged from 30% to 70%. The data oscillate more for the turkey meat: the minimum carnosine decrease was observed in the cases of MW/grill and broiling at high temperature (25%). Analogously, the anserine and homocarnosine contents decreased slightly in the case of MW/grill and broiling at a high temperature (2-7%) and by 10-30% in the other cases. No analysed meat sample showed any traces of pentosidine above the instrumental determination limits. The cooked beef showed an increased TBARS value compared to the raw meat, and the highest values were found when the beef was broiled at a high temperature, cooked by microwave or boiled in water. The TBARS value of the turkey meat decreased for all the cooking methods in comparison to the TBARS value of the fresh meat. PMID:26434266

  16. Roles of reactive oxygen species in UVA-induced oxidation of 5,6-dihydroxyindole-2-carboxylic acid-melanin as studied by differential spectrophotometric method.

    PubMed

    Ito, Shosuke; Kikuta, Marina; Koike, Shota; Szewczyk, Grzegorz; Sarna, Michal; Zadlo, Andrzej; Sarna, Tadeusz; Wakamatsu, Kazumasa

    2016-05-01

    Eumelanin photoprotects pigmented tissues from ultraviolet (UV) damage. However, UVA-induced tanning seems to result from the photooxidation of preexisting melanin and does not contribute to photoprotection. We investigated the mechanism of UVA-induced degradation of 5,6-dihydroxyindole-2-carboxylic acid (DHICA)-melanin taking advantage of its solubility in a neutral buffer and using a differential spectrophotometric method to detect subtle changes in its structure. Our methodology is suitable for examining the effects of various agents that interact with reactive oxygen species (ROS) to determine how ROS is involved in the UVA-induced oxidative modifications. The results show that UVA radiation induces the oxidation of DHICA to indole-5,6-quinone-2-carboxylic acid in eumelanin, which is then cleaved to form a photodegraded, pyrrolic moiety and finally to form free pyrrole-2,3,5-tricarboxylic acid. The possible involvement of superoxide radical and singlet oxygen in the oxidation was suggested. The generation and quenching of singlet oxygen by DHICA-melanin was confirmed by direct measurements of singlet oxygen phosphorescence. PMID:26920809

  17. Injection of colloidal size particles of Fe{sup 0} in porous media with shearthinning fluids as a method to emplace a permeable reactive zone

    SciTech Connect

    Cantrell, K.J.; Kaplan, D.I.; Gilmore, T.J.

    1997-12-31

    Previous work has demonstrated the feasibility of injecting suspensions of micron-size zero-valent (FeO) particles into porous media as a method to emplace a permeable reactive zone. Further studies were conducted to evaluate the effects of several shearthinning fluids on enhancing the injectability of micron-size FeO particles into porous media. In contrast to Newtonian fluids, whose viscosities are constant with shear rate, certain non-Newtonian fluids are shearthinning, that is, the viscosity of these fluids decreases with increasing shear rate. The primary benefit of using these fluids for this application is that they increase the viscosity of the aqueous phase without adversely decreasing the hydraulic conductivity. A suspension formulated with a shearthinning fluid will maintain a relatively high viscosity in solution near the FeO particles (where the shear stress is low) relative to locations near the surfaces of the porous media, where the shear stress is high. The increased viscosity decreases the rate of gravitational settling of the dense FeO colloids (7.6 9/cm3) while maintaining a relatively high hydraulic conductivity that permits pumping the colloid suspensions into porous media at greater flowrates and distances. Aqueous solutions of three polymers at different concentrations were investigated. It was determined that, the use of shear thinning fluids greatly increases the injectability of the colloidal FeO suspensions in porous media.

  18. Effect of titanium incorporation on the structural, mechanical and biocompatible properties of DLC thin films prepared by reactive-biased target ion beam deposition method

    NASA Astrophysics Data System (ADS)

    Bharathy, P. Vijai; Nataraj, D.; Chu, Paul K.; Wang, Huaiyu; Yang, Q.; Kiran, M. S. R. N.; Silvestre-Albero, J.; Mangalaraj, D.

    2010-10-01

    Amorphous diamond like carbon (DLC) and titanium incorporated diamond like carbon (Ti-DLC) thin films were deposited by using reactive-biased target ion beam deposition method. The effects of Ti incorporation and target bias voltage on the microstructure and mechanical properties of the as-deposited films were investigated by means of X-ray photoelectron spectroscopy, Raman spectroscopy, transmission electron microscopy and nano-indentation. It was found that the Ti content in Ti-DLC films gets increased with increasing target bias voltage. At about 4.2 at.% of Ti, uniform sized well dispersed nanocrystals were seen in the DLC matrix. Using FFT analysis, a facility available in the TEM, it was found that the nanocrystals are in cubic TiC phase. Though at the core, the incorporated Ti atoms react with carbon to form cubic TiC; most of the surface exposed Ti atoms were found to react with the atmospheric oxygen to form weakly bonded Ti-O. The presence of TiC nanocrystals greatly modified the sp 3/sp 2 hybridized bonding ratio and is reflected in mechanical hardness of Ti-DLC films. These films were then tested for their biocompatibility by an invitro cell culturing test. Morphological observation and the cell proliferation test have demonstrated that the human osteoblast cells well attach and proliferate on the surface of Ti incorporated DLC films, suggesting possible applications in bone related implant coatings.

  19. A new multi-species pore-scale reactive transport modeling of arsenic sorption in dissolving porous media using lattice Boltzmann method

    NASA Astrophysics Data System (ADS)

    Shafei, B.; Huber, C.; Parmigiani, A.; Taillefert, M.

    2012-12-01

    Physical and chemical heterogeneities associated with biogeochemical processes influence the fate and transport of contaminants in subsurface environments. We develop a new multi-species pore-scale reactive transport model based on the lattice Boltzmann method (LBM) to examine the temporal and spatial evolution of chemical species during the sorption of Arsenic. This model couples a fluid flow solver to an optimal advection-diffusion transport model where transport and reactions between chemical species are solved iteratively yielding a better stability and accuracy over a wide range of peclet numbers. It has already been applied to study 1) the permeability change of a porous medium during dissolution and precipitation and 2) the effect of spatial and chemical heterogeneities on the uptake of arsenic from the aqueous solution. By combining these two scenarios, we extend the model to incorporate arsenic speciation (i.e. As(III) and As(V)) and solid iron phase transformation, explore the distribution of iron, arsenic and partitioning of arsenic on various iron bearing solid phases. We investigate how the multitude of pore-domains affects the formation of redox gradients. As(III) and magnetite concentrations increase toward the anoxic zones while ferrihydrite and As(V) remains the dominant species in oxic conditions. The proposed reaction network includes: biotic reduction of ferrihydrite and magnetite to Fe2+(aq), of ferrihydrite to magnetite, biologically-mediated organic matter oxidation coupled with reduction of O2(aq) and As(V) , abiotic oxidation of Fe(II) by O2(aq) and sorption of As(V) and As(III) on Fe (hydr)oxide(s). All of these reactions are treated as kinetically controlled except As(V) and As(III) adsorption/desorption reactions which are expressed by equilibrium mass action laws. Similar set of reactions has been applied to simulate the distribution of As within constructed soil aggregates using continuum-scale model MIN3P (Masue-Slowey et al., 2010

  20. Reactive Air Aluminization

    SciTech Connect

    Choi, Jung-Pyung; Chou, Y. S.; Stevenson, Jeffry W.

    2011-10-28

    Ferritic stainless steels and other alloys are of great interest to SOFC developers for applications such as interconnects, cell frames, and balance of plant components. While these alloys offer significant advantages (e.g., low material and manufacturing cost, high thermal conductivity, and high temperature oxidation resistance), there are challenges which can hinder their utilization in SOFC systems; these challenges include Cr volatility and reactivity with glass seals. To overcome these challenges, protective coatings and surface treatments for the alloys are under development. In particular, aluminization of alloy surfaces offers the potential for mitigating both evaporation of Cr from the alloy surface and reaction of alloy constituents with glass seals. Commercial aluminization processes are available to SOFC developers, but they tend to be costly due to their use of exotic raw materials and/or processing conditions. As an alternative, PNNL has developed Reactive Air Aluminization (RAA), which offers a low-cost, simpler alternative to conventional aluminization methods.

  1. Methods for the in vitro determination of an individual disposition towards TH1- or TH2-reactivity by the application of appropriate stimulatory antigens

    PubMed Central

    BARTH, H; BERG, P A; KLEIN, R

    2003-01-01

    In this study we performed several methods for the determination of cytokines (RT-PCR for the demonstration of cytokine mRNA and flow cytometry for the analysis of intracellular cytokines) and compared them with a recently established test system stimulating peripheral blood mononuclear cells (PBMC) with TH1- and TH2-relevant recall antigens and analysing type 1 and type 2 cytokines by ELISA. Aim of the study was therefore to evaluate the reliability of TH1/TH2 cytokine profiles in two individuals with different types of an allergic/atopic disposition: one of them showed a strong TH1/type 1-mediated tuberculin-reaction (subject A), the other (subject B) revealed elevated IgE-levels and eosinophil counts (TH2/type 2-mediated). PBMC were incubated with the type 1-antigen purified protein derivative (PPD) and the type 2-antigen tetanus-toxoid (TT) for seven days. From the comparison of ELISA with RT-PCR and flow cytometry-analysis it became evident that all three methods allowed the definition of subject A as a ‘type 1-responder’. Subject B showed a pure type 2-response in the ELISA method; PCR and flow cytometry analysis revealed the simultaneous production of type 1- and type 2-cytokines resulting in a mixed type 1/type 2-profile. Active immunization of subject A with TT at the end of the observation period of 12 months resulted in a transient shift from type 1- to a mixed type 1/type 2-profile (simultaneous PPD-induced IFN-γ- and TT-induced IL-5 production). From this pilot study based on clear cut clinical criteria concerning either a humoral or cellular immunological reactivity towards allergens/antigens it is suggested that the determination of type 1/type 2-cytokines by ELISA in supernatants of PBMC stimulated with type 1/type 2-relevant antigens is a useful approach for a better classification of ‘type1-’ or ‘type 2-responder’. PMID:12974758

  2. Multifunctional reactive nanocomposite materials

    NASA Astrophysics Data System (ADS)

    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

  3. The First Crystal Structure of a Reactive Dirhodium Carbene Complex and a Versatile Method for the Preparation of Gold Carbenes by Rhodium‐to‐Gold Transmetalation

    PubMed Central

    Werlé, Christophe; Goddard, Richard

    2015-01-01

    Abstract The dirhodium carbene derived from bis(4‐methoxyphenyl)diazomethane and [Rh(tpa)4]⋅CH2Cl2 (tpa=triphenylacetate) was characterized by UV, IR, and NMR spectroscopy, HRMS, as well as by X‐ray diffraction. The isolated complex exhibits prototypical rhodium carbene reactivity in that it cyclopropanates 4‐methoxystyrene at low temperature. Experimental structural information on this important type of reactive intermediate is extremely scarce and thus serves as a reference point for mechanistic discussions of rhodium catalysis in general. Moreover, dirhodium carbenes are shown to undergo remarkably facile carbene transfer on treatment with [LAuNTf2] (L=phosphine). This formal transmetalation opens a valuable new entry into gold carbene complexes that cannot easily be made otherwise; three fully characterized representatives illustrate this aspect. PMID:26534892

  4. The First Crystal Structure of a Reactive Dirhodium Carbene Complex and a Versatile Method for the Preparation of Gold Carbenes by Rhodium-to-Gold Transmetalation.

    PubMed

    Werlé, Christophe; Goddard, Richard; Fürstner, Alois

    2015-12-14

    The dirhodium carbene derived from bis(4-methoxyphenyl)diazomethane and [Rh(tpa)4 ]⋅CH2 Cl2 (tpa=triphenylacetate) was characterized by UV, IR, and NMR spectroscopy, HRMS, as well as by X-ray diffraction. The isolated complex exhibits prototypical rhodium carbene reactivity in that it cyclopropanates 4-methoxystyrene at low temperature. Experimental structural information on this important type of reactive intermediate is extremely scarce and thus serves as a reference point for mechanistic discussions of rhodium catalysis in general. Moreover, dirhodium carbenes are shown to undergo remarkably facile carbene transfer on treatment with [LAuNTf2 ] (L=phosphine). This formal transmetalation opens a valuable new entry into gold carbene complexes that cannot easily be made otherwise; three fully characterized representatives illustrate this aspect. PMID:26534892

  5. Reactive molecular dynamics simulation on the disintegration of Kapton, POSS polyimide, amorphous silica, and teflon during atomic oxygen impact using the ReaxFF reactive force-field method.

    PubMed

    Rahnamoun, A; van Duin, A C T

    2014-04-17

    Atomic oxygen (AO) is the most abundant element in the low Earth orbit (LEO). It is the result of the dissociation of molecular oxygen by ultraviolet radiation from the sun. In the LEO, it collides with the materials used on spacecraft surfaces and causes degradation of these materials. The degradation of the materials on the surface of spacecrafts at LEO has been a significant problem for a long time. Kapton polyimide, polyhedral oligomeric silsesquioxane (POSS), silica, and Teflon are the materials extensively used in spacecraft industry, and like many other materials used in spacecraft industry, AO collision degradation is an important issue in their applications on spacecrafts. To investigate the surface chemistry of these materials in exposure to space AO, a computational chemical evaluation of the Kapton polyimide, POSS, amorphous silica, and Teflon was performed in separate simulations under similar conditions. For performing these simulations, the ReaxFF reactive force-field program was used, which provides the computational speed required to perform molecular dynamics (MD) simulations on system sizes sufficiently large to describe the full chemistry of the reactions. Using these simulations, the effects of AO impact on different materials and the role of impact energies, the content of material, and temperature of material on the behavior of the materials are studied. The ReaxFF results indicate that Kapton is less resistant than Teflon toward AO damage. These results are in good agreement with experiment. These simulations indicate that the amorphous silica shows the highest stability among these materials before the start of the highly exothermic silicon oxidation. We have verified that adding silicon to the bulk of the Kapton structure enhances the stability of the Kapton against AO impact. Our canonical MD simulations demonstrate that an increase in the heat transfer in materials during AO impact can provide a considerable decrease in the

  6. Fracture Reactivation in Chemically Reactive Rock Systems

    NASA Astrophysics Data System (ADS)

    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

  7. DETERMINATION OF SPECIFIC NEUTRONIC REACTIVITY

    DOEpatents

    Dessauer, G.

    1960-05-10

    A method is given for production-line determination of the specific neutronic reactivity of such objects as individual nuclear fuel or neutron absorber elements and is notable for rapidity and apparatus simplicity. The object is incorporated in a slightly sub-critical chain fission reactive assembly having a discrete neutron source, thereby establishing a K/sub eff/ within the crucial range of 0.95 to 0.995. The range was found to afford, uniquely, flux- transient damped response in a niatter of seconds simultaneously with acceptable analytical sensitivity. The resulting neutron flux measured at a situs spaced from both object and source within the assembly serves as a calibrable indication of said reactivity.

  8. Comparison of Reactive Inkjet Printing and Reactive Sintering to Fabricate Metal Conductive Patterns

    NASA Astrophysics Data System (ADS)

    Kheawhom, Soorathep; Foithong, Kamolrat

    2013-05-01

    Two methods to fabricate metal conductive patterns including reactive inkjet printing and reactive sintering were investigated. The silver printed lines were prepared from reactive inkjet printing of silver nitrate and L-ascorbic acid. Alternatively, the silver lines were prepared by the reactive sintering process of ethylene glycol vapor at 250 °C and formic acid vapor at 150 °C. In reactive printing, we investigated the effect of the number of printing cycles and the effect of silver nitrate concentration on the properties of the conductive patterns obtained. In reactive sintering, we investigated the usage of formic acid and ethylene glycol as reducing agents. The effect of reactive sintering time on the properties of the conductive patterns obtained was studied. As compared to reactive inkjet printing, the reactive sintering process gives more smooth and contiguous pattern resulting in lower resistivity. The resistivity of the silver line obtained by ethylene glycol vapor reduction at 250 °C for 30 min was 12 µΩ cm, which is about eight times higher than that of bulk silver. In contrast, the copper lines were fabricated by reactive inkjet printing and reactive sintering using various conditions of formic acid, ethylene glycol and hydrogen atmosphere, the copper lines printed have no conductivity due to the formation of copper oxide.

  9. Phenylethynyl reactive diluents

    NASA Technical Reports Server (NTRS)

    Bryant, Robert G. (Inventor); Jensen, Brian J. (Inventor); Hergenrother, Paul M. (Inventor)

    1995-01-01

    A composition of matter having a specified general structure is employed to terminate a nucleophilic reagent, resulting in the exclusive production of phenylethynyl terminated reactive oligomers which display unique thermal characteristics. A reactive diluent having a specified general structure is employed to decrease the melt viscosity of a phenylethynyl terminated reactive oligomer and to subsequently react with to provide a thermosetting material of enhanced density. These materials have features which make them attractive candidates for use as composite matrices and adhesives.

  10. [Present situation and question and prospect of study on kidney-supplementing and blood-activating method in treating ovaries functional disorders (infertility with dysfunctional ovulation) for stimulating ovaries reactive mechanism to gonadotropic hormones].

    PubMed

    Ma, Kun

    2011-09-01

    To summarize present situation of a study on kidney-supplementing and blood-activating method in treating ovaries functional disorders (infertility with dysfunctional ovulation) for stimulating ovaries reactive mechanism to gonadotropic hormones. Refer to correlative articles and combine clinical experience to report. Kidney-supplementing and blood-activating method have obvious therapeutic effect and no side effect and no adverse reaction. More attention are paid on influence factors and contribution about kidney-supplementing and blood-activating method in treating ovaries functional disorders especially on sex hormones, ovulating, corpora luteuman and implantation factors. Indicate the necessarity to develop polycentric kidney-supplementing and blood-activating method in treating ovaries functional disorders (infertility with dysfunctional ovulation) evaluation research. PMID:22121820

  11. Reactive Arthritis Diagnosis

    MedlinePlus

    ... Of Spondylitis The Heart In Spondyloarthritis Inflammatory vs. Mechanical Back ... Arthritis Symptoms Because there is no specific laboratory test for reactive arthritis, doctors sometimes find it difficult ...

  12. First OH reactivity measurements in Harvard Forest

    NASA Astrophysics Data System (ADS)

    Herdlinger-Blatt, I. S.; Martin, S. T.; Hansel, A.; McKinney, K. A.

    2013-12-01

    The OH reactivity provides critical insight into the HOx budget under actual atmospheric conditions, and has implications for the production of ozone and the formation of secondary organic material. Previous studies have indicated that the OH reactivity measured at field sites often exceeds model estimations, but current experiments remain inconclusive about the origin of the discrepancy between the modeled and measured OH reactivity (Lou et al., 2010). As of now there are only a limited number of atmospheric studies of total OH reactivity available, so to improve understanding of the OH reactivity more studies are needed. The first OH reactivity measurements in the northeastern United States are being performed during the summer of 2013 at Harvard Forest. Harvard forest, is located about 100 km west of the Boston metropolitan area, is one of the most intensively studied forests in North America. The main biogenic VOC emitted from Harvard Forest is isoprene followed by monoterpenes and methanol. Sampling for the OH reactivity measurements will be conducted from a 30m tall meteorological tower at the Harvard Forest site. The air is drawn into a reaction cell where the OH reactivity is determined using the Comparative Reactivity Method (Sinha et al., 2008) employing a High-Sensitivity Proton Transfer Reaction Mass Spectrometer (Lindinger et al., 1998, Hansel et al., 1998). In addition to the OH reactivity measurements, the most abundant compounds present in the air sample will be quantified using PTR-MS. The quantification of these compounds is needed to compare the theoretical calculated OH reactivity with the measured OH reactivity data. The measurements will be used to evaluate our understanding of the OH budget at Harvard Forest. References: A. Hansel, A. Jordan, C. Warneke, R. Holzinger, and W. Lindinger.: Improved Detection Limit of the Proton-transfer Reaction Mass Spectrometer: On-line Monitoring of Volatile Organic Compounds at Mixing Ratios of a Few PPTV

  13. The design of reactive shielded magnet clutches

    NASA Technical Reports Server (NTRS)

    Gertsov, S. M.

    1978-01-01

    The design of reactive shielded magnet clutches is considered along with their schematics, design formulas and characteristics of clutches in general. The design method suggested makes it possible to reduce calculation errors to 10%.

  14. Groundwater well with reactive filter pack

    DOEpatents

    Gilmore, T.J.; Holdren, G.R. Jr.; Kaplan, D.I.

    1998-09-08

    A method and apparatus are disclosed for the remediation of contaminated soil and ground water wherein a reactive pack material is added to the annular fill material utilized in standard well construction techniques. 3 figs.

  15. Groundwater well with reactive filter pack

    DOEpatents

    Gilmore, Tyler J.; Holdren, Jr., George R.; Kaplan, Daniel I.

    1998-01-01

    A method and apparatus for the remediation of contaminated soil and ground water wherein a reactive pack material is added to the annular fill material utilized in standard well construction techniques.

  16. Acquired reactive perforating collagenosis.

    PubMed

    Basak, P Y; Turkmen, C

    2001-01-01

    Acquired perforating disorder has been recognized as an uncommon distinct dermatosis in which altered collagen is eliminated through the epidermis. Several disorders accompanied by itching and scratching were reported to be associated with reactive perforating collagenosis. A 67-year-old white woman diagnosed as acquired reactive perforating collagenosis with poorly controlled diabetes mellitus and congestive cardiac failure is presented. PMID:11525959

  17. Method of uranium reclamation from aqueous systems by reactive ion exchange. [US DOE patent application; anion exchange resin of copolymerized divinyl-benzene and styrene having quarternary ammonium groups and bicarbonate ligands

    DOEpatents

    Maya, L.

    1981-11-05

    A reactive ion exchange method for separation and recovery of values of uranium, neptunium, plutonium, or americium from substantially neutral aqueous systems of said metals comprises contacting said system with an effective amount of a basic anion exchange resin of copolymerized divinyl-benzene and styrene having quarternary ammonium groups and bicarbonate ligands to achieve nearly 100% sorption of said actinyl ion onto said resin and an aqueous system practically free of said actinyl ions. The method is operational over an extensive range of concentrations from about 10/sup -6/ M to 1.0 M actinyl ion and a pH range of about 4 to 7. The method has particulr application to treatment of waste streams from Purex-type nuclear fuel reprocessing facilities and hydrometallurgical processes involving U, Np, P, or Am.

  18. Reactivity analysis of core distortion effects in the FFTF

    SciTech Connect

    Knutson, B.J.

    1982-01-01

    An improved technique for evaluating core distortion reactivity effects was developed using reactivity analyses of two core geometry models (R-Z and HEX). This technique is incorporated into a new processor code called CORDIS. The advantages of this technique over existing reactivity models are that is preserves core heterogeneity, provides a control rod insertion effect model, uses row-dependent axial shape functions, and provides a flexible and cost efficient core distortion reactivity analysis method.

  19. Theoretical Investigation of Hydrogen Adsorption and Dissociation on Iron and Iron Carbide Surfaces Using the ReaxFF Reactive Force Field Method

    SciTech Connect

    Zou, Chenyu; van Duin, Adri C.T.; Sorescu, Dan C.

    2012-06-01

    We have developed a ReaxFF reactive force field to describe hydrogen adsorption and dissociation on iron and iron carbide surfaces relevant for simulation of Fischer–Tropsch (FT) synthesis on iron catalysts. This force field enables large system (>>1000 atoms) simulations of hydrogen related reactions with iron. The ReaxFF force field parameters are trained against a substantial amount of structural and energetic data including the equations of state and heats of formation of iron and iron carbide related materials, as well as hydrogen interaction with iron surfaces and different phases of bulk iron. We have validated the accuracy and applicability of ReaxFF force field by carrying out molecular dynamics simulations of hydrogen adsorption, dissociation and recombination on iron and iron carbide surfaces. The barriers and reaction energies for molecular dissociation on these two types of surfaces have been compared and the effect of subsurface carbon on hydrogen interaction with iron surface is evaluated. We found that existence of carbon atoms at subsurface iron sites tends to increase the hydrogen dissociation energy barrier on the surface, and also makes the corresponding hydrogen dissociative state relatively more stable compared to that on bare iron. These properties of iron carbide will affect the dissociation rate of H{sub 2} and will retain more surface hydride species, thus influencing the dynamics of the FT synthesis process.

  20. Reactive metabolites and agranulocytosis.

    PubMed

    Uetrecht, J P

    1996-01-01

    Central to most hypotheses of the mechanism of idiosyncratic drug-induced blood dyscrasias is the involvement of reactive metabolites. In view of the reactive nature of the majority of such metabolites, it is likely that they are formed by, or in close proximity to the blood cells affected. The major oxidative system of neutrophils generates hypochlorous acid. We have demonstrated that the drugs associated with the highest incidence of agranulocytosis are oxidized to reactive metabolites by hypochlorous acid and/or activated neutrophils. There are many mechanisms by which such reactive metabolites could induce agranulocytosis. In the case of aminopyrine-induced agranulocytosis, most cases appear to involve drug-dependent anti-neutrophil antibodies, and these are likely to be induced by cell membrane antigens modified by the reactive metabolite of aminopyrine. The target of agranulocytosis associated with many other drugs is usually neutrophil precursors and may involve cytotoxicity or a cell-mediated immune reaction induced by a reactive metabolite. In the case of aplastic anaemia, there is evidence in some cases for involvement of cytotoxic T cells, which could either be induced by metabolites generated by neutrophils, or more likely, by reactive metabolites generated by stem cells. PMID:8987247

  1. Reactive Leidenfrost droplets

    NASA Astrophysics Data System (ADS)

    Raufaste, C.; Bouret, Y.; Celestini, F.

    2016-05-01

    We experimentally investigate the reactivity of Leidenfrost droplets with their supporting substrates. Several organic liquids are put into contact with a copper substrate heated above their Leidenfrost temperature. As the liquid evaporates, the gaseous flow cleans the superficial copper oxide formed at the substrate surface and the reaction maintains a native copper spot below the evaporating droplet. The copper spot can reach several times the droplet size for the most reactive organic compounds. This study shows an interesting coupling between the physics of the Leidenfrost effect and the mechanics of reactive flows. Different applications are proposed such as drop motion tracking and vapor flow monitoring.

  2. Mechanical, tribological, and electrochemical behavior of Cr 1- xAl xN coatings deposited by r.f. reactive magnetron co-sputtering method

    NASA Astrophysics Data System (ADS)

    Sanchéz, J. E.; Sanchéz, O. M.; Ipaz, L.; Aperador, W.; Caicedo, J. C.; Amaya, C.; Landaverde, M. A. Hernández; Beltran, F. Espinoza; Muñoz-Saldaña, J.; Zambrano, G.

    2010-02-01

    Chromium aluminum nitride (Cr 1- xAl xN) coatings were deposited onto AISI H13 steel and silicon substrates by r.f. reactive magnetron co-sputtering in (Ar/N 2) gas mixture from chromium and aluminum targets. Properties of deposited Cr 1- xAl xN coatings such as compositional, structural, morphological, electrochemical, mechanical and tribological, were investigated as functions of aluminum content. X-ray diffraction patterns of Cr 1- xAl xN coatings with different atomic concentrations of aluminum (0.51 < x < 0.69) showed the presence and evolution of (1 1 1), (2 0 0), and (1 0 2) crystallographic orientations associated to the Cr 1- xAl xN cubic and w-AlN phases, respectively. The rate of corrosion of the steel coated with Cr 1- xAl xN varied with the applied power; however, always being clearly lower when compared to the uncoated substrate. The behavior of the protective effect of the Cr 1- xAl xN coatings is based on the substitution of Cr for Al, when the power applied to the aluminum target increases. The mechanical properties were also sensitive to the power applied, leading to a maximum in hardness and a reduced elastic modulus of 30 and 303 GPa at 350 W and a monotonic decrease to 11 and 212 GPa at 450 W, respectively. Finally, the friction coefficient measured by pin-on disk revealed values between 0.45 and 0.70 in humid atmosphere.

  3. When is arthritis reactive?

    PubMed

    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

  4. When is arthritis reactive?

    PubMed Central

    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 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

  5. Stress Reactivity in Insomnia.

    PubMed

    Gehrman, Philip R; Hall, Martica; Barilla, Holly; Buysse, Daniel; Perlis, Michael; Gooneratne, Nalaka; Ross, Richard J

    2016-01-01

    This study examined whether individuals with primary insomnia (PI) are more reactive to stress than good sleepers (GS). PI and GS (n = 20 per group), matched on gender and age, completed three nights of polysomnography. On the stress night, participants received a mild electric shock and were told they could receive additional shocks during the night. Saliva samples were obtained for analysis of cortisol and alpha amylase along with self-report and visual analog scales (VAS). There was very little evidence of increased stress on the stress night, compared to the baseline night. There was also no evidence of greater stress reactivity in the PI group for any sleep or for salivary measures. In the GS group, stress reactivity measured by VAS scales was positively associated with an increase in sleep latency in the experimental night on exploratory analyses. Individuals with PI did not show greater stress reactivity compared to GS. PMID:25126695

  6. OH reactivity measurements within a boreal forest: evidence for unknown reactive emissions.

    PubMed

    Sinha, Vinayak; Williams, J; Lelieveld, J; Ruuskanen, T M; Kajos, M K; Patokoski, J; Hellen, H; Hakola, H; Mogensen, D; Boy, M; Rinne, J; Kulmala, M

    2010-09-01

    Boreal forests emit large amounts of volatile organic compounds (VOCs) which react with the hydroxyl radical (OH) to influence regional ozone levels and form secondary organic aerosol. Using OH reactivity measurements within a boreal forest in Finland, we investigated the budget of reactive VOCs. OH reactivity was measured using the comparative reactivity method, whereas 30 individual VOCs were measured using proton transfer reaction mass spectrometry, thermal-desorption gas chromatography mass spectrometry, and liquid chromatography mass spectrometry, in August 2008. The measured OH reactivity ranged from below detection limit (3.5 s(-1)), to approximately 60 s(-1) in a single pollution event. The average OH reactivity was approximately 9 s(-1) and no diel variation was observed in the profiles. The measured OH sinks (approximately 30 species) accounted for only 50% of the total measured OH reactivity, implying unknown reactive VOCs within the forest. The five highest measured OH sinks were: monoterpenes (1 s(-1)), CO (0.7 s(-1)), isoprene (0.5 s(-1)), propanal and acetone (0.3 s(-1)), and methane (0.3 s(-1)). We suggest that models be constrained by direct OH reactivity measurements to accurately assess the impact of boreal forest emissions on regional atmospheric chemistry and climate. PMID:20687598

  7. Reactive Magnetospinning of Nano- and Microfibers.

    PubMed

    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

  8. Synthesis of Ag{sub 9}(SiO{sub 4}){sub 2}NO{sub 3} through a reactive flux method and its visible-light photocatalytic performances

    SciTech Connect

    Zhu, Xianglin; Wang, Zeyan E-mail: bbhuang@sdu.edu.cn; Huang, Baibiao E-mail: bbhuang@sdu.edu.cn; Zhang, Xiaoyang; Qin, Xiaoyan; Wei, Wei; Dai, Ying

    2015-10-01

    Ag{sub 9}(SiO{sub 4}){sub 2}NO{sub 3} was prepared by a reactive flux method. The structures, morphologies, and light absorption properties were investigated. Owing to the polar crystal structure, an internal electric field can be formed inside the material, which can facilitate the photogenerated charge separation during the photocatalytic process. Based on both the wide light absorption spectra and high charge separation efficiency originated from the polarized internal electric field, Ag{sub 9}(SiO{sub 4}){sub 2}NO{sub 3} exhibit higher efficiency over Ag{sub 3}PO{sub 4} during the degradation of organic dyes under visible light irradiation, which is expected to be a potential material for solar energy harvest and conversion.

  9. Do Procedures for Verbal Reporting of Thinking Have to Be Reactive? A Meta-Analysis and Recommendations for Best Reporting Methods

    ERIC Educational Resources Information Center

    Fox, Mark C.; Ericsson, K. Anders; Best, Ryan

    2011-01-01

    Since its establishment, psychology has struggled to find valid methods for studying thoughts and subjective experiences. Thirty years ago, Ericsson and Simon (1980) proposed that participants can give concurrent verbal expression to their thoughts (think aloud) while completing tasks without changing objectively measurable performance (accuracy).…

  10. Integrating planning and reactive control

    NASA Technical Reports Server (NTRS)

    Rosenschein, Stanley J.; Kaelbling, Leslie Pack

    1989-01-01

    Artificial intelligence research on planning is concerned with designing control systems that choose actions by manipulating explicit descriptions of the world state, the goal to be achieved, and the effects of elementary operations available to the system. Because planning shifts much of the burden of reasoning to the machine, it holds great appeal as a high-level programming method. Experience shows, however, that it cannot be used indiscriminately because even moderately rich languages for describing goals, states, and the elementary operators lead to computational inefficiencies that render the approach unsuitable for realistic applications. This inadequacy has spawned a recent wave of research on reactive control or situated activity in which control systems are modeled as reacting directly to the current situation rather than as reasoning about the future effects of alternative action sequences. While this research has confronted the issue of run-time tractability head on, in many cases it has done so by sacrificing the advantages of declarative planning techniques. Ways in which the two approaches can be unified are discussed. The authors begin by modeling reactive control systems as state machines that map a stream of sensory inputs to a stream of control outputs. These machines can be decomposed into two continuously active subsystems: the planner and the execution module. The planner computes a plan, which can be seen as a set of bits that control the behavior of the execution module. An important element of this work is the formulation of a precise semantic interpretation for the inputs and outputs of the planning system. They show that the distinction between planned and reactive behavior is largely in the eye of the beholder: systems that seem to compute explicit plans can be redescribed in situation-action terms and vice versa. They also discuss practical programming techniques that allow the advantages of declarative programming and guaranteed

  11. Haptenation: Chemical Reactivity and Protein Binding

    PubMed Central

    Chipinda, Itai; Hettick, Justin M.; Siegel, Paul D.

    2011-01-01

    Low molecular weight chemical (LMW) allergens are commonly referred to as haptens. Haptens must complex with proteins to be recognized by the immune system. The majority of occupationally related haptens are reactive, electrophilic chemicals, or are metabolized to reactive metabolites that form covalent bonds with nucleophilic centers on proteins. Nonelectrophilic protein binding may occur through disulfide exchange, coordinate covalent binding onto metal ions on metalloproteins or of metal allergens, themselves, to the major histocompatibility complex. Recent chemical reactivity kinetic studies suggest that the rate of protein binding is a major determinant of allergenic potency; however, electrophilic strength does not seem to predict the ability of a hapten to skew the response between Th1 and Th2. Modern proteomic mass spectrometry methods that allow detailed delineation of potential differences in protein binding sites may be valuable in predicting if a chemical will stimulate an immediate or delayed hypersensitivity. Chemical aspects related to both reactivity and protein-specific binding are discussed. PMID:21785613

  12. Phenylethynyl terminated reactive oligomer

    NASA Technical Reports Server (NTRS)

    Bryant, Robert G. (Inventor); Jensen, Brian J. (Inventor); Hergenrother, Paul M. (Inventor)

    1995-01-01

    A composition of matter having the general structure: ##STR1## (wherein X is F, Cl, or NO.sub.2, and Y is CO, SO.sub.2 or C(CF.sub.3).sub.2) is employed to terminate a nucleophilic reagent, resulting in the exclusive production of phenylethynyl terminated reactive oligomers which display unique thermal characteristics. A reactive diluent having the general structure: ##STR2## (wherein R is any aliphatic or aromatic moiety) is employed to decrease the melt viscosity of a phenylethynyl terminated reactive oligomer and to subsequently react therewith to provide a thermosetting material of enhanced density. These materials have features which make them attractive candidates for use as composite matrices and adhesives.

  13. A semi-experimental nodal synthesis method for the on-line reconstruction of three-dimensional neutron flux-shapes and reactivity

    SciTech Connect

    Jacqmin, R.P.

    1991-12-10

    The safety and optimal performance of large, commercial, light-water reactors require the knowledge at all time of the neutron-flux distribution in the core. In principle, this information can be obtained by solving the time-dependent neutron diffusion equations. However, this approach is complicated and very expensive. Sufficiently accurate, real-time calculations (time scale of approximately one second) are not yet possible on desktop computers, even with fast-running, nodal kinetics codes. A semi-experimental, nodal synthesis method which avoids the solution of the time-dependent, neutron diffusion equations is described. The essential idea of this method is to approximate instantaneous nodal group-fluxes by a linear combination of K, precomputed, three-dimensional, static expansion-functions. The time-dependent coefficients of the combination are found from the requirement that the reconstructed flux-distribution agree in a least-squares sense with the readings of J ({ge}K) fixed, prompt-responding neutron-detectors. Possible numerical difficulties with the least-squares solution of the ill-conditioned, J-by-K system of equations are brought under complete control by the use of a singular-value-decomposition technique. This procedure amounts to the rearrangement of the original, linear combination of K expansion functions into an equivalent more convenient, linear combination of R ({le}K) orthogonalized modes'' of decreasing magnitude. Exceedingly small modes are zeroed to eliminate any risk of roundoff-error amplification, and to assure consistency with the limited accuracy of the data. Additional modes are zeroed when it is desirable to limit the sensitivity of the results to measurement noise.

  14. A semi-experimental nodal synthesis method for the on-line reconstruction of three-dimensional neutron flux-shapes and reactivity. Final report

    SciTech Connect

    Jacqmin, R.P.

    1991-12-10

    The safety and optimal performance of large, commercial, light-water reactors require the knowledge at all time of the neutron-flux distribution in the core. In principle, this information can be obtained by solving the time-dependent neutron diffusion equations. However, this approach is complicated and very expensive. Sufficiently accurate, real-time calculations (time scale of approximately one second) are not yet possible on desktop computers, even with fast-running, nodal kinetics codes. A semi-experimental, nodal synthesis method which avoids the solution of the time-dependent, neutron diffusion equations is described. The essential idea of this method is to approximate instantaneous nodal group-fluxes by a linear combination of K, precomputed, three-dimensional, static expansion-functions. The time-dependent coefficients of the combination are found from the requirement that the reconstructed flux-distribution agree in a least-squares sense with the readings of J ({ge}K) fixed, prompt-responding neutron-detectors. Possible numerical difficulties with the least-squares solution of the ill-conditioned, J-by-K system of equations are brought under complete control by the use of a singular-value-decomposition technique. This procedure amounts to the rearrangement of the original, linear combination of K expansion functions into an equivalent more convenient, linear combination of R ({le}K) orthogonalized ``modes`` of decreasing magnitude. Exceedingly small modes are zeroed to eliminate any risk of roundoff-error amplification, and to assure consistency with the limited accuracy of the data. Additional modes are zeroed when it is desirable to limit the sensitivity of the results to measurement noise.

  15. Modeling Atmospheric Reactive Nitrogen

    EPA Science Inventory

    Nitrogen is an essential building block of all proteins and thus an essential nutrient for all life. Reactive nitrogen, which is naturally produced via enzymatic reactions, forest fires and lightning, is continually recycled and cascades through air, water, and soil media. Human ...

  16. Reactive power compensating system

    DOEpatents

    Williams, Timothy J.; El-Sharkawi, Mohamed A.; Venkata, Subrahmanyam S.

    1987-01-01

    The reactive power of an induction machine is compensated by providing fixed capacitors on each phase line for the minimum compensation required, sensing the current on one line at the time its voltage crosses zero to determine the actual compensation required for each phase, and selecting switched capacitors on each line to provide the balance of the compensation required.

  17. Reactive Power Compensating System.

    DOEpatents

    Williams, Timothy J.; El-Sharkawi, Mohamed A.; Venkata, Subrahmanyam S.

    1985-01-04

    The circuit was designed for the specific application of wind-driven induction generators. It has great potential for application in any situation where a varying reactive power load is present, such as with induction motors or generators, or for transmission network compensation.

  18. Working Memory and Reactivity

    ERIC Educational Resources Information Center

    Goo, Jaemyung

    2010-01-01

    The present study explores the relationship between working memory capacity (WMC) and think-alouds, focusing on the issue of reactivity. Two WM span tasks (listening span and operation span) were administered to 42 English-speaking learners of Spanish. Learner performance on reading comprehension and written production was measured under two…

  19. Optimal reactive planning with security constraints

    SciTech Connect

    Thomas, W.R.; Cheng, D.T.Y.; Dixon, A.M.; Thorp, J.D.; Dunnett, R.M.; Schaff, G.

    1995-12-31

    The National Grid Company (NGC) of England and Wales has developed a computer program, SCORPION, to help system planners optimize the location and size of new reactive compensation plant on the transmission system. The reactive power requirements of the NGC system have risen as a result of increased power flows and the shorter timescale on which power stations are commissioned and withdrawn from service. In view of the high costs involved, it is important that reactive compensation be installed as economically as possible, without compromising security. Traditional methods based on iterative use of a load flow program are labor intensive and subjective. SCORPION determines a near-optimal pattern of new reactive sources which are required to satisfy voltage constraints for normal and contingent states of operation of the transmission system. The algorithm processes the system states sequentially, instead of optimizing all of them simultaneously. This allows a large number of system states to be considered with an acceptable run time and computer memory requirement. Installed reactive sources are treated as continuous, rather than discrete, variables. However, the program has a restart facility which enables the user to add realistically sized reactive sources explicitly and thereby work towards a realizable solution to the planning problem.

  20. Total OH reactivity emissions from Norway spruce

    NASA Astrophysics Data System (ADS)

    Nölscher, Anke; Bourtsoukidis, Efstratios; Bonn, Boris; Kesselmeier, Jürgen; Lelieveld, Jos; Williams, Jonathan

    2013-04-01

    Forest emissions represent a strong potential sink for the main tropospheric oxidant, the hydroxyl radical (OH). In forested environments, the comparison of the directly determined overall sink of OH radicals, the total OH reactivity, and the individually measured OH sink compounds often exposes a significant gap. This "missing" OH reactivity can be high and influenced by both direct biogenic emissions and secondary photo-oxidation products. To investigate the source of the missing OH sinks in forests, total OH reactivity emission rates were determined for the first time from a Norway spruce (Picea abies) throughout spring, summer and autumn 2011. The total OH reactivity was measured inside a branch enclosure using the Comparative Reactivity Method (CRM) with a Proton Transfer Reaction-Mass Spectrometer (PTR-MS) as the detector. In parallel, separate volatile organic compounds (VOC) emission rates were monitored by a second PTR-MS, including the signal of isoprene, acetaldehyde, total monoterpenes and total sesquiterpenes. The comparison of known and PTR-MS detected OH sink compounds and the directly measured total OH reactivity emitted from Norway spruce revealed unmeasured and possibly unknown primary biogenic emissions. These were found to be highest in late summer during daytime coincident with highest temperatures and ozone levels.

  1. Studying chemical reactivity in a virtual environment.

    PubMed

    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

  2. Measurement of reactive species for plasma medicine

    NASA Astrophysics Data System (ADS)

    Ono, Ryo

    2015-09-01

    Plasma medicine has been intensively studied over the last decade. Reactive oxygen and nitrogen species are responsible for the therapeutic effects in plasma medicine. To examine the therapeutic effects of reactive species, the densities of OH, O, and NO were measured using laser-induced fluorescence (LIF). A helium atmospheric-pressure plasma jet (10 kV, 10 kHz of 40 μs pulses) and a nanosecond streamer discharge (24 kV, 8 ns, 30 Hz) were utilized to treat mouse melanoma cells in a culture medium. Correlation between the dose of reactive species and deactivation rate of melanoma cells was measured with the aid of LIF. The results showed that the rate of cell death correlates with OH density, but not with O and NO densities. Next, a method to supply a specific reactive species to living organisms was developed. It utilizes photolysis of helium-buffered H2O and O2 by vacuum ultraviolet (VUV) light to produce reactive species. The VUV method was utilized to sterilize Bacillus atrophaeus on agar plate. With the VUV method, it was succeeded to show sterilization only by OH radicals. A 30 s treatment with approximately 0.1 ppm OH radicals caused visible sterilization.

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

    ERIC Educational Resources Information Center

    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)

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

    NASA Astrophysics Data System (ADS)

    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.

  5. PREDICTING CHEMICAL REACTIVITY BY COMPUTER

    EPA Science Inventory

    Mathematical models for predicting the fate of pollutants in the environment require reactivity parameter values--that it, the physical and chemical constants that govern reactivity. lthough empirical structure-activity relationships have been developed that allow estimation of s...

  6. An advanced approach to reactivity rating.

    PubMed

    Kossoy, A; Benin, A; Akhmetshin, Yu

    2005-02-14

    Reactive hazards remain a significant safety challenge in the chemical industry despite continual attention devoted to this problem. The application of various criteria, which are recommended by the guidelines for assessment of reactive hazards, often causes unsafe results to be obtained. The main origins of such failures are as follows: (a) reactivity of a compound is considered as an inherent property of a compound; (b) some appropriate criteria are determined by using too simple methods that cannot reveal potential hazards properly. Four well-known hazard indicators--time to certain conversion limit, TCL; adiabatic time to maximum rate, TMR; adiabatic temperature rise; and NFPA reactivity rating number, Nr--are analyzed in the paper. It was ascertained that they could be safely used for preliminary assessment of reactive hazards provided that: (a) the selected indicator is appropriate for the specific conditions of a process; (b) the indicators have been determined by using the pertinent methods. The applicability limits for every indicator were determined and the advanced kinetics-based simulation approach, which allows reliable determination of the indicators, is proposed. The technique of applying this approach is illustrated by two practical examples. PMID:15721524

  7. Advances in reactive surfactants.

    PubMed

    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

  8. Phenylethynyl Containing Reactive Additives

    NASA Technical Reports Server (NTRS)

    Connell, John W. (Inventor); Smith, Joseph G., Jr. (Inventor); Hergenrother, Paul M. (Inventor)

    2002-01-01

    Phenylethynyl containing reactive additives were prepared from aromatic diamine, containing phenylethvnvl groups and various ratios of phthalic anhydride and 4-phenylethynviphthalic anhydride in glacial acetic acid to form the imide in one step or in N-methyl-2-pvrrolidinone to form the amide acid intermediate. The reactive additives were mixed in various amounts (10% to 90%) with oligomers containing either terminal or pendent phenylethynyl groups (or both) to reduce the melt viscosity and thereby enhance processability. Upon thermal cure, the additives react and become chemically incorporated into the matrix and effect an increase in crosslink density relative to that of the host resin. This resultant increase in crosslink density has advantageous consequences on the cured resin properties such as higher glass transition temperature and higher modulus as compared to that of the host resin.

  9. Skylab reactivation mission report

    NASA Technical Reports Server (NTRS)

    Chubb, W. B.

    1980-01-01

    On July 11, 1979, Skylab impacted the Earth's surface. The debris dispersion area stretched from the South Eastern Indian Ocean across a sparsely populated section of Western Australia. The events leading to the reentry of Skylab are discussed and a final assessment of the Skylab debris impact footprint is presented. Also included are detailed evaluations of the various Skylab systems that were reactivated when control of Skylab was regained in mid-1978 after having been powered down since February 4, 1974.

  10. Becoming Reactive by Concretization

    NASA Technical Reports Server (NTRS)

    Prieditis, Armand; Janakiraman, Bhaskar

    1992-01-01

    One way to build a reactive system is to construct an action table indexed by the current situation or stimulus. The action table describes what course of action to pursue for each situation or stimulus. This paper describes an incremental approach to constructing the action table through achieving goals with a hierarchical search system. These hierarchies are generated with transformations called concretizations, which add constraints to a problem and which can reduce the search space. The basic idea is that an action for a state is looked up in the action table and executed whenever the action table has an entry for that state; otherwise, a path is found to the nearest (cost-wise in a graph with costweighted arcs) state that has a mappring from a state in the next highest hierarchy. For each state along the solution path, the successor state in the path is cached in the action table entry for that state. Without caching, the hierarchical search system can logarithmically reduce search. When the table is complete the system no longer searches: it simply reacts by proceeding to the state listed in the table for each state. Since the cached information is specific only to the nearest state in the next highest hierarchy and not the goal, inter-goal transfer of reactivity is possible. To illustrate our approach, we show how an implemented hierarchical search system can completely reactive.

  11. Photocatalytic degradation of an azo textile dye (C.I. Reactive Red 195 (3BF)) in aqueous solution over copper cobaltite nanocomposite coated on glass by Doctor Blade method

    NASA Astrophysics Data System (ADS)

    Habibi, Mohammad Hossein; Rezvani, Zoya

    2015-08-01

    The degradation of C.I. Reactive Red 195 (3BF) in aqueous solution using copper cobaltite nanocomposite coated on glass by Doctor Blade method was studied. Structural, optical and morphological properties of nanocomposite coatings were characterized by X-ray powder diffractometry (XRD), diffuse reflectance spectroscopy (DRS) and field emission scanning electron microscopy (FESEM). The nanoparticles exhibit a particle size of 31 nm, showing a good nanoscale crystalline morphology. The photocatalytic activity of copper cobaltite nanocomposite coated on glass was studied by performing the photocatalytic degradation of 3BF at different irradiation time. The effect of irradiation time on the degradation of 3BF was studied and the results showed that more than 85% of the 3BF was degraded in 45 min of irradiation. The pseudo-first-order kinetic models were used and the rate constants were evaluated with pseudo first order rate constants of 4.10 × 10-2 min-1. The main advantage of the photocatalyst coated on glass overcomes the difficulties in separation and recycle of photocatalyst suspensions.

  12. Cobalt ferrite nano-composite coated on glass by Doctor Blade method for photo-catalytic degradation of an azo textile dye Reactive Red 4: XRD, FESEM and DRS investigations.

    PubMed

    Habibi, Mohammad Hossein; Parhizkar, Janan

    2015-11-01

    Cobalt ferrite nano-composite was prepared by hydrothermal route using cobalt nitrate, iron nitrate and ethylene glycol as chelating agent. The nano-composite was coated on glass by Doctor Blade method and annealed at 300 °C. The structural, optical, and photocatalytic properties have been studied by powder X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and UV-visible spectroscopy (UV-Vis DRS). Powder XRD analysis confirmed formation of CoFe2O4 spinel phase. The estimated particle size from FESEM data was 50 nm. The calculated energy band gaps, obtained by Tauc relation from UV-Vis absorption spectra was 1.3 eV. Photocatalytic degradation of Reactive Red 4 as an azo textile was investigated in aqueous solution under irradiation showed 68.0% degradation of the dye within 100 min. The experimental enhanced activity compare to pure Fe2O3 can be ascribed to the formation of composite, which was mainly attributable to the transfer of electron and hole to the surface of composite and hinder the electron hole recombination. PMID:26116997

  13. Photocatalytic degradation of an azo textile dye (C.I. Reactive Red 195 (3BF)) in aqueous solution over copper cobaltite nanocomposite coated on glass by Doctor Blade method.

    PubMed

    Habibi, Mohammad Hossein; Rezvani, Zoya

    2015-08-01

    The degradation of C.I. Reactive Red 195 (3BF) in aqueous solution using copper cobaltite nanocomposite coated on glass by Doctor Blade method was studied. Structural, optical and morphological properties of nanocomposite coatings were characterized by X-ray powder diffractometry (XRD), diffuse reflectance spectroscopy (DRS) and field emission scanning electron microscopy (FESEM). The nanoparticles exhibit a particle size of 31 nm, showing a good nanoscale crystalline morphology. The photocatalytic activity of copper cobaltite nanocomposite coated on glass was studied by performing the photocatalytic degradation of 3BF at different irradiation time. The effect of irradiation time on the degradation of 3BF was studied and the results showed that more than 85% of the 3BF was degraded in 45 min of irradiation. The pseudo-first-order kinetic models were used and the rate constants were evaluated with pseudo first order rate constants of 4.10 × 10(-2) min(-1). The main advantage of the photocatalyst coated on glass overcomes the difficulties in separation and recycle of photocatalyst suspensions. PMID:25840025

  14. Water reactive hydrogen fuel cell power system

    DOEpatents

    Wallace, Andrew P; Melack, John M; Lefenfeld, Michael

    2014-11-25

    A water reactive hydrogen fueled power system includes devices and methods to combine reactant fuel materials and aqueous solutions to generate hydrogen. The generated hydrogen is converted in a fuel cell to provide electricity. The water reactive hydrogen fueled power system includes a fuel cell, a water feed tray, and a fuel cartridge to generate power for portable power electronics. The removable fuel cartridge is encompassed by the water feed tray and fuel cell. The water feed tray is refillable with water by a user. The water is then transferred from the water feed tray into the fuel cartridge to generate hydrogen for the fuel cell which then produces power for the user.

  15. Water reactive hydrogen fuel cell power system

    DOEpatents

    Wallace, Andrew P; Melack, John M; Lefenfeld, Michael

    2014-01-21

    A water reactive hydrogen fueled power system includes devices and methods to combine reactant fuel materials and aqueous solutions to generate hydrogen. The generated hydrogen is converted in a fuel cell to provide electricity. The water reactive hydrogen fueled power system includes a fuel cell, a water feed tray, and a fuel cartridge to generate power for portable power electronics. The removable fuel cartridge is encompassed by the water feed tray and fuel cell. The water feed tray is refillable with water by a user. The water is then transferred from the water feed tray into a fuel cartridge to generate hydrogen for the fuel cell which then produces power for the user.

  16. Design and synthesis of reactive separation systems

    SciTech Connect

    Doherty, M.F.

    1992-01-01

    During the last decade there has been a rapid upturn in interest in reactive distillation. The chemical process industry recognizes the favorable economics of carrying out reaction simultaneously with distillation for certain classes of reacting systems, and many new processes have been built based on this technology. Interest is also increasing by academics and software vendors. Systematic design methods for reactive distillation systems have only recently begun to emerge. In this report we survey the available design techniques and point out the contributions made by our group at the University of Massachusetts.

  17. Using qualitative maps to direct reactive robots

    NASA Technical Reports Server (NTRS)

    Bertin, Randolph; Pendleton, Tom

    1992-01-01

    The principal advantage of mobile robots is that they are able to go to specific locations to perform useful tasks rather than have the tasks brought to them. It is important therefore that the robot be used to reach desired locations efficiently and reliably. A mobile robot whose environment extends significantly beyond its sensory horizon must maintain a representation of the environment, a map, in order to attain these efficiency and reliability requirements. We believe that qualitative mapping methods provide useful and robust representation schemes and that such maps may be used to direct the actions of a reactively controlled robot. In this paper we describe our experience in employing qualitative maps to direct, through the selection of desired control strategies, a reactive-behavior based robot. This mapping capability represents the development of one aspect of a successful deliberative/reactive hybrid control architecture.

  18. Sensitivity and uncertainty analysis of reactivities for UO2 and MOX fueled PWR cells

    SciTech Connect

    Foad, Basma; Takeda, Toshikazu

    2015-12-31

    The purpose of this paper is to apply our improved method for calculating sensitivities and uncertainties of reactivity responses for UO{sub 2} and MOX fueled pressurized water reactor cells. The improved method has been used to calculate sensitivity coefficients relative to infinite dilution cross-sections, where the self-shielding effect is taken into account. Two types of reactivities are considered: Doppler reactivity and coolant void reactivity, for each type of reactivity, the sensitivities are calculated for small and large perturbations. The results have demonstrated that the reactivity responses have larger relative uncertainty than eigenvalue responses. In addition, the uncertainty of coolant void reactivity is much greater than Doppler reactivity especially for large perturbations. The sensitivity coefficients and uncertainties of both reactivities were verified by comparing with SCALE code results using ENDF/B-VII library and good agreements have been found.

  19. Comparison of simian and human cytomegalovirus reactivities in an enzyme-linked immunospecific assay: effect of antigen preparation on cross-reactive antigens.

    PubMed Central

    Tinghitella, T J; Swack, N; Baumgarten, A; Hsiung, G D

    1982-01-01

    Simian cytomegalovirus was substituted for human cytomegalovirus in an enzyme-linked immunoassay. Unlike the indirect immunofluorescence assay which demonstrates a two-way cross-reactivity, only one-way cross-reactivity was observed. Altering the method of simian antigen preparation gave some insight other this different reactivity. PMID:6288573

  20. Genomic Analysis of Reactive Astrogliosis

    PubMed Central

    Zamanian, JL; Xu, L; Foo, LC; Nouri, N; Zhou, L; Giffard, RG; Barres, BA

    2012-01-01

    Reactive astrogliosis is characterized by a profound change in astrocyte phenotype in response to all CNS injuries and diseases. To better understand the reactive astrocyte state, we used Affymetrix GeneChip arrays to profile gene expression in populations of reactive astrocytes isolated at various time points after induction using two mouse injury models, ischemic stroke and neuroinflammation. We find reactive gliosis consists of a rapid, but quickly attenuated induction of gene expression after insult and identify two induced genes, Lcn2 and Serpina3n, as strong markers of reactive astrocytes. Strikingly, reactive astrocyte phenotype strongly depended on the type of inducing injury. Although there is a core set of genes that is up-regulated in reactive astrocytes from both injury models, at least 50% of the altered gene expression is specific to a given injury type. Reactive astrocytes in ischemia exhibited a molecular phenotype that suggests that they may be beneficial or protective, whereas reactive astrocytes induced by LPS exhibited a phenotype that suggests that they may be detrimental. These findings demonstrate that, despite well established commonalities, astrocyte reactive gliosis is a highly heterogeneous state in which astrocyte activities are altered to respond to the specific injury. This raises the question of how many subtypes of reactive astrocytes exist. Our findings provide transcriptome databases for two subtypes of reactive astrocytes that will be highly useful in generating new and testable hypotheses of their function, as well as for providing new markers to detect different types of reactive astrocytes in human neurological diseases. PMID:22553043

  1. Tetrabromobisphenol A (TBBPA)-stimulated reactive oxygen species (ROS) production in cell-free model using the 2',7'-dichlorodihydrofluorescein diacetate (H2DCFDA) assay-limitations of method.

    PubMed

    Szychowski, Konrad A; Rybczyńska-Tkaczyk, Kamila; Leja, Marcin L; Wójtowicz, Anna K; Gmiński, Jan

    2016-06-01

    Tetrabromobisphenol A (TBBPA) is a widely used brominated flame retardant, applied in a variety of commercial and household products, mainly electronic ones. Since the production of reactive oxygen species (ROS) is considered one of the principal cytotoxicity mechanisms, numerous studies undertake that aspect of TBBPA's mechanism of action. The present study verifies if the fluorogenic substrate 2',7'-dichlorodihydrofluorescein diacetate (H2DCFDA) should be used to detect ROS production induced by TBBPA. To determine the ability of TBBPA alone to stimulate the conversion of H2DCFDA to its fluorescent product 2',7'-dichlorofluorescein (DCF), we used a cell-free model. In the experiments we check different cultured media also in combination with free radical scavenger N-acetyl-l-cysteine (NAC). Additionally, experiments with stable free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH·) have been made. The presented data showed that TBBPA in all tested concentrations interacts with H2DCFDA in phosphate-buffered saline (PBS) buffer while in micromolar concentrations in the DMEM/F12 medium with and without serum. The addition of NAC inhibited the interaction of TBBPA with H2DCFDA. Experiments with DPPH· showed that, in the presence of NAC, TBBPA acts like a free radical. TBBPA has similar properties to free radical and is susceptible to free radical scavenging properties of NAC. Our results indicated that H2DCFDA assay cannot be used to evaluate cellular ROS production in TBBPA studies. The study connected with TBBPA-stimulated ROS production in cell culture models using the H2DCFDA assay should be revised using a different method. However, due to the free radical-like nature of TBBPA, it can be very difficult. Therefore, further investigation of the nature of TBBPA as a compound with similar properties to free radical is required. PMID:26976009

  2. Latent Herpes Viral Reactivation in Astronauts

    NASA Technical Reports Server (NTRS)

    Pierson, D. L.; Mehta, S. K.; Stowe, R.

    2008-01-01

    Latent viruses are ubiquitous and reactivate during stressful periods with and without symptoms. Latent herpes virus reactivation is used as a tool to predict changes in the immune status in astronauts and to evaluate associated health risks. Methods: Viral DNA was detected by real time polymerase chain reaction in saliva and urine from astronauts before, during and after short and long-duration space flights. Results and Discussion: EpsteinBarr virus (EBV), cytomegalovirus (CMV), and varicella zoster virus (VZV) reactivated, and viral DNA was shed in saliva (EBV and VZV) or urine (CMV). EBV levels in saliva during flight were 10fold higher than baseline levels. Elevations in EBV specific CD8+ T-cells, viral antibody titers, and specific cytokines were consistent with viral reactivation. Intracellular levels of cytokines were reduced in EBVspecific Tcells. CMV, rarely present in urine of healthy individuals, was shed in urine of 27% of astronauts during all phases of spaceflight. VZV, not found in saliva of asymptomatic individuals, was found in saliva of 50% of astronauts during spaceflight and 35 days after flight. VZV recovered from astronaut saliva was found to be live, infectious virus. DNA sequencing demonstrated that the VZV recovered from astronauts was from the common European strain of VZV. Elevation of stress hormones accompanied viral reactivation indicating involvement of the hypothalmic-pituitary-adrenal and sympathetic adrenal-medullary axes in the mechanism of viral reactivation in astronauts. A study of 53 shingles patients found that all shingles patients shed VZV DNA in their saliva and the VZV levels correlated with the severity of the disease. Lower VZV levels in shingles patients were similar to those observed in astronauts. We proposed a rapid, simple, and cost-effective assay to detect VZV in saliva of patients with suspected shingles. Early detection of VZV infection allows early medical intervention.

  3. 40 CFR Appendix A to Subpart Pppp... - Determination of Weight Volatile Matter Content and Weight Solids Content of Reactive Adhesives

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... Content and Weight Solids Content of Reactive Adhesives A Appendix A to Subpart PPPP of Part 63 Protection... Reactive Adhesives 1.0Applicability and Principle 1.1Applicability: This method applies to the... reactive adhesives. Reactive adhesives are composed, in large part, of monomers that react during...

  4. 40 CFR Appendix A to Subpart Pppp... - Determination of Weight Volatile Matter Content and Weight Solids Content of Reactive Adhesives

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... Content and Weight Solids Content of Reactive Adhesives A Appendix A to Subpart PPPP of Part 63 Protection... Reactive Adhesives 1.0Applicability and Principle 1.1Applicability: This method applies to the... reactive adhesives. Reactive adhesives are composed, in large part, of monomers that react during...

  5. [Reactive airways dysfunction syndrome].

    PubMed

    Costa, R; Orriols, R

    2005-01-01

    Reactive airways dysfunction syndrome, better known as RADS, was described as a clinical entity consisting in the appearance of bronchial asthma due to massive toxic inhalation. The term was coined and recognised for the first time in 1985. Since then different publications have verified new cases as well as different causal agents. It usually arises from an accident at the work place and in closed or poorly ventilated spaces, where high concentrations of irritant products are inhaled in the form of gas, smoke or vapour. In the following minutes or hours symptoms of bronchial obstruction appear in an acute form, with bronchial hyperresponsiveness persisting for months or years. The affected patients do not show a recurrence of symptoms following exposure to non-toxic doses of the same agent that started the symptoms. This is why diagnosis is based on clinical manifestations as it is not reproducible through a provocation test. PMID:15915173

  6. On 'reactivity' versus 'tolerance'.

    PubMed

    Zinkernagel, Rolf M

    2004-08-01

    In Burnet's review on 'The impact of ideas on immunology' he considers himself an observer of nature using biochemical and molecular analysis for more detailed understanding, a description that applies also to me. I use three examples--repertoire selection of T cells, rules of immune reactivity versus non-reactivity and immunological memory--to illustrate the difficulties we all have in probing nature's immunological secrets and in critically testing immunologists' ideas. At one end of the spectrum of biological research one may argue everything is possible and therefore all results are correct, if correctly measured. But perhaps it is more important to always ask again and again what is frequent and enhances survival versus what is rare and an exception. At the same time one must keep in mind that special situations and special tricks may well be applied for medical benefits, although they may have little impact on physiology and species survival. I will attempt to use disease in virus-infected mice to obtain some answers to what I consider to be important immunological questions with the hope of improving the ratio of answers that are right for the right experimental reasons versus those that are right for the wrong reasons. Some of these experiments falsify hypotheses, previous experiments and interpretations and therefore are particularly important in correcting misleading concepts. They should help to find out which half of immunological ideas and truths in immunological text books written today are likely to be wrong. Ideas are important in immunology, but are often rather demagogically handled and therefore may cost us very dearly indeed. Evaluating immunity to infections and tumours in vivo should help prevent us from getting lost in immunology. PMID:15283843

  7. Differentiating challenge reactivity from psychomotor activity in studies of children's psychophysiology: considerations for theory and measurement.

    PubMed

    Bush, Nicole R; Alkon, Abbey; Obradović, Jelena; Stamperdahl, Juliet; Boyce, W Thomas

    2011-09-01

    Current methods of assessing children's physiological "stress reactivity" may be confounded by psychomotor activity, biasing estimates of the relation between reactivity and health. We examined the joint and independent contributions of psychomotor activity and challenge reactivity during a protocol for 5- and 6-year-old children (N = 338). Measures of parasympathetic reactivity (respiratory sinus arrhythmia [RSA]) and sympathetic reactivity (preejection period [PEP]) were calculated for social, cognitive, sensory, and emotional challenge tasks. Reactivity was calculated relative to both resting and a paired comparison task that accounted for psychomotor activity effects during each challenge. Results indicated that comparison tasks themselves elicited RSA and PEP responses, and reactivity adjusted for psychomotor activity was incongruent with reactivity calculated using rest. Findings demonstrate the importance of accounting for confounding psychomotor activity effects on physiological reactivity. PMID:21524757

  8. Latent Virus Reactivation: From Space to Earth

    NASA Technical Reports Server (NTRS)

    Mehta, Satish K.; Cohrs, Randall J.; Gilden, Donald H.; Tyring, Stephen K.; Castro, Victoria A.; Ott, C. Mark; Pierson, Duane L.

    2010-01-01

    Reactivation of latent viruses is a recognized consequence of decreased immunity. More recently viral reactivation has been identified as an important in vivo indicator of clinically relevant immune changes. Viral reactivation can be determined quickly and easily by the presence of virus in saliva and other body fluids. Real-time polymerase chain reaction (PCR) is a highly sensitive and specific molecular method to detect the presence of specific viral DNA. Studies in astronauts demonstrated that herpes simplex virus type 1(HSV-1), Epstein-Barr Virus (EBV), cytomegalovirus (CMV), and varicella zoster virus (VZV) reactivate at rates above normal during and after spaceflight in response to moderately decreased T-cell immunity. This technology was expanded to patients on Earth beginning with human immune deficiency virus (HIV) immuno-compromised patients. The HIV patients shed EBV in saliva at rates 9-fold higher than observed in astronauts demonstrating that the level of EBV shedding reflects the severity of impaired immunity. Whereas EBV reactivation is not expected to produce serious effects in astronauts on missions of 6 months or less, VZV reactivation in astronauts could produce shingles. Reactivation of live, infectious VZV in astronauts with no symptoms was demonstrated in astronauts during and after spaceflight. We applied our technology to study VZV-induced shingles in patients. In a study of 54 shingles patients, we showed salivary VZV was present in every patient on the day antiviral (acyclovir) treatment was initiated. Pain and skin lesions decreased with antiviral treatment. Corresponding decreases in levels of VZV were also observed and accompanied recovery. Although the level of VZV in shingles patients before the treatment was generally higher than those found in astronauts, lower range of VZV numbers in shingles patients overlapped with astronaut s levels. This suggests a potential risk of shingles to astronauts resulting from reactivation of VZV. In

  9. Initiator Effects in Reactive Extrusion of Starch Graft Copolymers

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Graft copolymers of starch with water-soluble polymers such as polyacrylamide have potential applications including hydrogels, superabsorbents, and thickening agents. Reactive extrusion is a rapid, continuous method for production of starch graft copolymers with high reaction and grafting efficienc...

  10. A reactive torque control law for gyroscopically controlled space vehicles

    NASA Technical Reports Server (NTRS)

    Farmer, J. E.

    1973-01-01

    A method of control is developed based on the reactive torques as seen by the individual CMG gimbals. The application of a torque to the gimbal of a CMG rotates the momentum vector and applies a torque to the spacecraft according to well-known laws. The response (rotation) of the vehicle produces a reverse or reaction torque opposing the torque producing the gimbal movement. The reactive torque and the pseudoinverse control schemes are contrasted in order to point out the simplicity of the first method. Simulation was performed only to the extent necessary to prove that reactive torque stabilization and control is feasible.

  11. Differentiating Challenge Reactivity from Psychomotor Activity in Studies of Children's Psychophysiology: Considerations for Theory and Measurement

    ERIC Educational Resources Information Center

    Bush, Nicole R.; Alkon, Abbey; Obradovic, Jelena; Stamperdahl, Juliet; Boyce, W. Thomas

    2011-01-01

    Current methods of assessing children's physiological "stress reactivity" may be confounded by psychomotor activity, biasing estimates of the relation between reactivity and health. We examined the joint and independent contributions of psychomotor activity and challenge reactivity during a protocol for 5- and 6-year-old children (N = 338).…

  12. Quantitative reactivity profiling predicts functional cysteines in proteomes.

    PubMed

    Weerapana, Eranthie; Wang, Chu; Simon, Gabriel M; Richter, Florian; Khare, Sagar; Dillon, Myles B D; Bachovchin, Daniel A; Mowen, Kerri; Baker, David; Cravatt, Benjamin F

    2010-12-01

    Cysteine is the most intrinsically nucleophilic amino acid in proteins, where its reactivity is tuned to perform diverse biochemical functions. The absence of a consensus sequence that defines functional cysteines in proteins has hindered their discovery and characterization. Here we describe a proteomics method to profile quantitatively the intrinsic reactivity of cysteine residues en masse directly in native biological systems. Hyper-reactivity was a rare feature among cysteines and it was found to specify a wide range of activities, including nucleophilic and reductive catalysis and sites of oxidative modification. Hyper-reactive cysteines were identified in several proteins of uncharacterized function, including a residue conserved across eukaryotic phylogeny that we show is required for yeast viability and is involved in iron-sulphur protein biogenesis. We also demonstrate that quantitative reactivity profiling can form the basis for screening and functional assignment of cysteines in computationally designed proteins, where it discriminated catalytically active from inactive cysteine hydrolase designs. PMID:21085121

  13. A Tariff for Reactive Power

    SciTech Connect

    Kueck, John D; Kirby, Brendan J; Li, Fangxing; Tufon, Christopher; Isemonger, Alan

    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 reduce

  14. Multisurface Adiabatic Reactive Molecular Dynamics.

    PubMed

    Nagy, Tibor; Yosa Reyes, Juvenal; Meuwly, Markus

    2014-04-01

    Adiabatic reactive molecular dynamics (ARMD) simulation method is a surface-crossing algorithm for modeling chemical reactions in classical molecular dynamics simulations using empirical force fields. As the ARMD Hamiltonian is time dependent during crossing, it allows only approximate energy conservation. In the current work, the range of applicability of conventional ARMD is explored, and a new multisurface ARMD (MS-ARMD) method is presented, implemented in CHARMM and applied to the vibrationally induced photodissociation of sulfuric acid (H2SO4) in the gas phase. For this, an accurate global potential energy surface (PES) involving 12 H2SO4 and 4 H2O + SO3 force fields fitted to MP2/6-311G++(2d,2p) reference energies is employed. The MS-ARMD simulations conserve total energy and feature both intramolecular H-transfer reactions and water elimination. An analytical treatment of the dynamics in the crossing region finds that conventional ARMD can approximately conserve total energy for limiting cases. In one of them, the reduced mass of the system is large, which often occurs for simulations of solvated biomolecular systems. On the other hand, MS-ARMD is a general approach for modeling chemical reactions including gas-phase, homogeneous, heterogeneous, and enzymatic catalytic reactions while conserving total energy in atomistic simulations. PMID:26580356

  15. Measuring and monitoring KIPT Neutron Source Facility Reactivity

    SciTech Connect

    Cao, Yan; Gohar, Yousry; Zhong, Zhaopeng

    2015-08-01

    Argonne National Laboratory (ANL) of USA and Kharkov Institute of Physics and Technology (KIPT) of Ukraine have been collaborating on developing and constructing a neutron source facility at Kharkov, Ukraine. The facility consists of an accelerator-driven subcritical system. The accelerator has a 100 kW electron beam using 100 MeV electrons. The subcritical assembly has keff less than 0.98. To ensure the safe operation of this neutron source facility, the reactivity of the subcritical core has to be accurately determined and continuously monitored. A technique which combines the area-ratio method and the flux-to-current ratio method is purposed to determine the reactivity of the KIPT subcritical assembly at various conditions. In particular, the area-ratio method can determine the absolute reactivity of the subcritical assembly in units of dollars by performing pulsed-neutron experiments. It provides reference reactivities for the flux-to-current ratio method to track and monitor the reactivity deviations from the reference state while the facility is at other operation modes. Monte Carlo simulations are performed to simulate both methods using the numerical model of the KIPT subcritical assembly. It is found that the reactivities obtained from both the area-ratio method and the flux-to-current ratio method are spatially dependent on the neutron detector locations and types. Numerical simulations also suggest optimal neutron detector locations to minimize the spatial effects in the flux-to-current ratio method. The spatial correction factors are calculated using Monte Carlo methods for both measuring methods at the selected neutron detector locations. Monte Carlo simulations are also performed to verify the accuracy of the flux-to-current ratio method in monitoring the reactivity swing during a fuel burnup cycle.

  16. High missing OH reactivity in summertime boreal forest environment

    NASA Astrophysics Data System (ADS)

    Nölscher, A. C.; Williams, J.; Sinha, V.; Song, W.; Johnson, A.; Yassaa, N.; Phillips, G.; Crowley, J.; Axinte, R.; Fischer, H.; Gonzales, D.; Valverde-Canossa, J.; Vogel, A.; Hoffmann, T.; Rantala, P.; Rinne, J.; Kulmala, M.; Ouwersloot, H.; Vila, J.; Lelieveld, J.

    2012-04-01

    Forest emissions represent a strong potential sink for the main tropospheric oxidant, the hydroxyl radical (OH). Resulting photochemical products can influence ambient ozone, contribute to particle formation and growth processes, and therefore impact climate and air quality. Direct measurements of total OH reactivity in ambient air can reveal gaps in the general understanding of reactive gaseous emissions from the biosphere to the atmosphere. By comparing the contribution from individually measured compounds to the overall OH sink and the directly measured total OH reactivity, the size of any unaccounted for, or "missing" sink can be deduced. In July and August 2010 an intensive field measurement campaign (HUMPPA-COPEC 2010) was performed at the Finnish boreal forest station SMEAR II in Hyytiälä (Latitude 61° 51' N; Longitude 24° 17' E) to investigate the summertime emissions and photochemistry of volatile organic compounds (VOCs) [1]. Speciated VOCs, the key oxidants OH, O3 and NO3, as well as aerosol, ions and other trace gases were quantified. Total OH reactivity was measured directly using the Comparative Reactivity Method (CRM) [2]. This total OH reactivity method is an in-situ determination of the total loss rate of OH radicals caused by all reactive species in ambient air. During HUMPPA-COPEC 2010, total OH reactivity was monitored both inside and directly above the canopy. The impact of various parameters such as temperature and light dependent biogenic emissions and reaction products in "normal" and "stressed" conditions, the long-range transport of pollution and the boundary layer height development were characterized. For "normal" boreal conditions a missing reactivity of 58% was determined, whereas for "stressed" boreal conditions this increased to 89 %. Possible explanations are proposed to explain the high missing OH reactivity in summertime boreal forest environment. [1] J. Williams et al, 2011, Atmos. Chem. Phys., 11, 10599-10618 [2] V. Sinha et

  17. Hydrothermal reactivity of saponite.

    USGS Publications Warehouse

    Whitney, G.

    1983-01-01

    The nature and extent of the reactions of synthetic Fe-free saponite have been investigated under experimental hydrothermal conditions as a first step towards understanding saponite reactivity under relatively simple conditions. Saponite crystallizes from amorphous gel of ideal saponite composition within 7 days at 300o-550oC under P = 1 kbar. Reactions subsequent to this initial crystallization depend on reaction T and interlayer cations. Saponite is found to react hydrothermally, over a period of 200 days, at T down to 400oC, at least 150oC lower than previously reported, but showed no signs of reaction below 400oC. At 450oC, a mixture of talc/saponite and saponite/phlogopite clays forms from K-saponite via intracrystalline layer transformations, while above 450oC the initial K-saponite dissolves, with talc and phlogopite forming as discrete phases. After 200 days reactions at 400-450oC were not complete, so that given sufficient time to reach equilibrium, a lower hydrothermal stability limit for saponite is possible. Further study of the Fe-bearing saponite system will be required before experimental results can be applied to natural systems.-D.F.B.

  18. One-step purification of phosphinothricin acetyltransferase using reactive dye-affinity chromatography.

    PubMed

    Wang, Cunxi; Lee, Thomas C; Crowley, Kathleen S; Bell, Erin

    2015-01-01

    Reactive dye purification is an affinity purification technique offering unique selectivity and high purification potential. Historically, purification of phosphinothricin acetyltransferase (PAT) has involved several steps of precipitation and column chromatography. Here, we describe a novel purification method that is simple, time-saving, inexpensive, and reproducible. The novel method employs a single chromatography step using a reactive dye resin, Reactive brown 10-agarose. Reactive brown 10 preferentially binds the PAT protein, which can then be specifically released by one of its substrates, acetyl-CoA. Using Reactive brown 10-agarose, PAT protein can be purified to homogeneity from E. coli or plant tissue with high recovery efficiency. PMID:25749943

  19. Sexual Orientation Modulates Endocrine Stress Reactivity

    PubMed Central

    Juster, Robert-Paul; Hatzenbuehler, Mark L.; Mendrek, Adrianna; Pfaus, James G.; Smith, Nathan Grant; Johnson, Philip Jai; Lefebvre-Louis, Jean-Philippe; Raymond, Catherine; Marin, Marie-France; Sindi, Shireen; Lupien, Sonia J.; Pruessner, Jens C.

    2015-01-01

    BACKGROUND Biological sex differences and sociocultural gender diversity influence endocrine stress reactivity. Although numerous studies have shown that men typically activate stronger stress responses than women when exposed to laboratory-based psychosocial stressors, it is unclear whether sexual orientation further modulates stress reactivity. Given that lesbian, gay, and bisexual (LGB) individuals frequently report heightened distress secondary to stigma-related stressors, we investigated whether cortisol stress reactivity differs between LGB individuals and heterosexual individuals in response to a well-validated psychosocial stressor. METHODS The study population comprised 87 healthy adults (mean age, 25 years) who were grouped according to their biological sex and their gendered sexual orientation: lesbian/bisexual women (n = 20), heterosexual women (n = 21), gay/bisexual men (n = 26), and heterosexual men (n = 20). Investigators collected 10 salivary cortisol samples throughout a 2-hour afternoon visit involving exposure to the Trier Social Stress Test modified to maximize between-sex differences. RESULTS Relative to heterosexual women, lesbian/bisexual women showed higher cortisol stress reactivity 40 min after exposure to the stressor. In contrast, gay/bisexual men displayed lower overall cortisol concentrations throughout testing compared with heterosexual men. Main findings were significant while adjusting for sex hormones (estradiol-to-progesterone ratio in women and testosterone in men), age, self-esteem, and disclosure status (whether LGB participants had completed their “coming out”). CONCLUSIONS Our results provide novel evidence for gender-based modulation of cortisol stress reactivity based on sexual orientation that goes beyond well-established between-sex differences. This study raises several important avenues for future research related to the physiologic functioning of LGB populations and gender diversity more broadly. PMID:25444167

  20. Kinetics of reactive wetting

    SciTech Connect

    Yost, F.G.

    2000-04-14

    The importance of interfacial processes in materials joining has a long history. A significant amount of work has suggested that processes collateral to wetting can affect the extent of wetting and moderate or retard wetting rate. Even very small additions of a constituent, known to react with the substrate, cause pronounced improvement in wetting and are exploited in braze alloys, especially those used for joining to ceramics. In the following a model will be constructed for the wetting kinetics of a small droplet of metal containing a constituent that diffuses to the wetting line and chemically reacts with a flat, smooth substrate. The model is similar to that of Voitovitch et al. and Mortensen et al. but incorporates chemical reaction kinetics such that the result contains both diffusion and reaction kinetics. The model is constructed in the circular cylinder coordinate system, satisfies the diffusion equation under conditions of slow flow, and considers diffusion and reaction at the wetting line to be processes in series. This is done by solving the diffusion equation with proper initial and boundary conditions, computing the diffusive flux at the wetting line, and equating this to both the convective flux and reaction flux. This procedure is similar to equating the current flowing in components of a series circuit. The wetting rate will be computed versus time for a variety of diffusion and reaction conditions. A transition is observed from nonlinear (diffusive) to linear (reactive) behavior as the control parameters (such as the diffusion coefficient) are modified. This is in agreement with experimental observations. The adequacy of the slow flow condition, used in this type of analysis, is discussed and an amended procedure is suggested.

  1. Shear-Induced Reactive Gelation.

    PubMed

    Brand, Bastian; Morbidelli, Massimo; Soos, Miroslav

    2015-11-24

    In this work, we describe a method for the production of porous polymer materials in the form of particles characterized by narrow pore size distribution using the principle of shear-induced reactive gelation. Poly(styrene-co-divinylbenzene) primary particles with diameter ranging from 80 to 200 nm are used as building blocks, which are assembled into fractal-like clusters when exposed to high shear rates generated in a microchannel. It was found that independent of the primary particle size, it is possible to modulate the internal structure of formed fractal-like aggregates having fractal dimension ranging from 2.4 to 2.7 by varying the residence time in the microchannel. Thermally induced postpolymerization was used to increase the mechanical resilience of such formed clusters. Primary particle interpenetration was observed by SEM and confirmed by light scattering resulting in an increase of fractal dimension. Nitrogen sorption measurements and mercury porosimetry confirmed formation of a porous material with surface area ranging from 20 to 40 m(2)/g characterized by porosity of 70% and narrow pore size distribution with an average diameter around 700 nm without the presence of any micropores. The strong perfusive character of the synthesized material was confirmed by the existence of a plateau of the height equivalent to a theoretical plate measured at high reduced velocities using a chromatographic column packed with the synthesized microclusters. PMID:26488233

  2. Reactive Simulations for Biochemical Processes

    NASA Astrophysics Data System (ADS)

    Boero, M.

    After a brief review of the hybrid QM/MM molecular dynamics scheme and its coupling to the metadynamics method, I will show how such a combination of computational tools can be used to study chemical reactions of general biological interest. Specifically, by using such a reactive hybrid paradigm, where the QM driver is a Car-Parrinello Lagrangian dynamics, we have inspected the ATP hydrolysis reaction in the anti-freezing protein known as heat shock cognate protein (Hsc70) and the unconventional propagation of protons across peptide groups in the H-path of the bovine cytochrome c oxidase. While the former represents a fundamental reaction operated by all living beings in a wealth of processes and functions, the second one is involved in cell respiration. For both systems accurate X-ray data are available, yet the actual reaction mechanism escapes experimental probes. The simulations presented here provide the complementary information missing in experiments, offer a direct insight into the reaction mechanisms at a molecular level, and allow to understand which pathways nature can follow to realize these processes fundamental to living organisms.

  3. Peer victimization (and harsh parenting) as developmental correlates of cognitive reactivity, a diathesis for depression.

    PubMed

    Cole, David A; Martin, Nina C; Sterba, Sonya K; Sinclair-McBride, Keneisha; Roeder, Kathryn M; Zelkowitz, Rachel; Bilsky, Sarah A

    2014-05-01

    Prior research has shown cognitive reactivity to be a diathesis for depression. Seeking evidence for the developmental origins of such diatheses, the current study examined peer victimization and harsh parenting as developmental correlates of cognitive reactivity in 571 children and adolescents (ages 8-13 years). Four major findings emerged. First, a new method for assessing cognitive reactivity in children and adolescents showed significant reliability and demonstrated construct validity vis-à-vis its relation to depression. Second, history of more severe peer victimization was significantly related to cognitive reactivity, with verbal victimization being more strongly tied to cognitive reactivity than other subtypes of peer victimization. Third, harsh parenting was also significantly related to cognitive reactivity. Fourth, both peer victimization and harsh parenting made unique statistical contributions to cognitive reactivity, after controlling for the effects of the other. Taken together, these findings provide preliminary support for a developmental model pertaining to origins of cognitive reactivity in children and adolescents. PMID:24886008

  4. Adolescents’ Emotional Reactivity across Relationship Contexts

    PubMed Central

    Cook, Emily C.; Buehler, Cheryl; Blair, Bethany L.

    2012-01-01

    Adolescents’ emotional reactivity in family, close friendships, and romantic relationships was examined in a community-based sample of 416 two-parent families. Six waves of annual data were analyzed using structural equation modeling. Emotional reactivity to interparental conflict during early adolescence was associated prospectively with adolescents’ reactivity to conflict in friendships and romantic relationships during middle adolescence. Close friendship reactivity partially explained the prospective association between reactivity to interparental conflict and romantic relationship reactivity. The association between perceived emotional reactivity and relationship conflict was stronger for girls than boys. Results have important developmental implications regarding adolescents’ emotional reactivity across salient interpersonal contexts during adolescence. PMID:22545839

  5. Reactive Collision Avoidance Algorithm

    NASA Technical Reports Server (NTRS)

    Scharf, Daniel; Acikmese, Behcet; Ploen, Scott; Hadaegh, Fred

    2010-01-01

    The reactive collision avoidance (RCA) algorithm allows a spacecraft to find a fuel-optimal trajectory for avoiding an arbitrary number of colliding spacecraft in real time while accounting for acceleration limits. In addition to spacecraft, the technology can be used for vehicles that can accelerate in any direction, such as helicopters and submersibles. In contrast to existing, passive algorithms that simultaneously design trajectories for a cluster of vehicles working to achieve a common goal, RCA is implemented onboard spacecraft only when an imminent collision is detected, and then plans a collision avoidance maneuver for only that host vehicle, thus preventing a collision in an off-nominal situation for which passive algorithms cannot. An example scenario for such a situation might be when a spacecraft in the cluster is approaching another one, but enters safe mode and begins to drift. Functionally, the RCA detects colliding spacecraft, plans an evasion trajectory by solving the Evasion Trajectory Problem (ETP), and then recovers after the collision is avoided. A direct optimization approach was used to develop the algorithm so it can run in real time. In this innovation, a parameterized class of avoidance trajectories is specified, and then the optimal trajectory is found by searching over the parameters. The class of trajectories is selected as bang-off-bang as motivated by optimal control theory. That is, an avoiding spacecraft first applies full acceleration in a constant direction, then coasts, and finally applies full acceleration to stop. The parameter optimization problem can be solved offline and stored as a look-up table of values. Using a look-up table allows the algorithm to run in real time. Given a colliding spacecraft, the properties of the collision geometry serve as indices of the look-up table that gives the optimal trajectory. For multiple colliding spacecraft, the set of trajectories that avoid all spacecraft is rapidly searched on

  6. Kinetics of Reactive Wetting

    SciTech Connect

    YOST, FREDERICK G.

    1999-09-09

    for a variety of diffusion and reaction conditions. A transition is observed from nonlinear (diffusive) to linear (reactive) behavior as the control parameters (such as the diffusion coefficient) are modified. This is in agreement with experimental observations. The adequacy of the slow flow condition, used in this type of analysis, is discussed and an amended procedure is suggested.

  7. Tropospheric budget of reactive chlorine

    NASA Astrophysics Data System (ADS)

    Graedel, T. E.; Keene, W. C.

    1995-03-01

    Reactive chlorine in the lower atmosphere (as distinguished from chlorofluorocarbon-derived chlorine in the stratosphere) is important to considerations of precipitation acidity, corrosion, foliar damage, and chemistry of the marine boundary layer. Many of the chlorine-containing gases are difficult to measure, and natural sources appear to dominate anthropogenic sources for some chemical species. As a consequence, no satisfactory budget for reactive chlorine in the lower atmosphere is available. We have reviewed information on sources; source strengths; measurements in gas, aqueous, and aerosol phases; and chemical processes and from those data derive global budgets for nine reactive chlorine species and for reactive chlorine as a whole. The typical background abundance of reactive chlorine in the lower tropospheric is about 1.5 ppbv. The nine species, CH3 Cl, CH3 CCl3, HCl, CHClF2, Cl2* (thought to be HOCl and/or Cl2), CCl2 = CCl2, CH2 Cl2 , COCl2 , and CHCl3, each contribute at least a few percent to that total. The tropospheric reactive chlorine burden of approximately 8.3 Tg Cl is dominated by CH3 Cl (≈45 %) and CH3 CCl3 (≈25 %) and appears to be increasing by several percent per year. By far the most vigorous chlorine cycling appears to occur among seasalt aerosol, HCl, and Cl2*. The principal sources of reactive chlorine are volatilization from seasalt (enhanced by anthropogenically generated reactants), marine algae, volcanoes, and coal combustion (natural sources being thus quite important to the budget). It is anticipated that the concentrations of tropospheric reactive chlorine will continue to increase in the next several decades, particularly near urban areas in the rapidly developing countries.

  8. [Hyper-reactive malarial splenomegaly].

    PubMed

    Maazoun, F; Deschamps, O; Barros-Kogel, E; Ngwem, E; Fauchet, N; Buffet, P; Froissart, A

    2015-11-01

    Hyper-reactive malarial splenomegaly is a rare and severe form of chronic malaria. This condition is a common cause of splenomegaly in endemic areas. The pathophysiology of hyper-reactive malarial splenomegaly involves an intense immune reaction (predominantly B cell-driven) to repeated/chronic infections with Plasmodium sp. The diagnosis may be difficult, due to a poorly specific clinical presentation (splenomegaly, fatigue, cytopenias), a long delay between residence in a malaria-endemic area and onset of symptoms, and a frequent absence of parasites on conventional thin and thick blood smears. A strongly contributive laboratory parameter is the presence of high levels of total immunoglobulin M. When the diagnostic of hyper-reactive malarial splenomegaly is considered, search for anti-Plasmodium antibodies and Plasmodium nucleic acids (genus and species) by PCR is useful. Diagnosis of hyper-reactive malarial splenomegaly relies on the simultaneous presence of epidemiological, clinical, biological and follow-up findings. Regression of both splenomegaly and hypersplenism following antimalarial therapy allows the differential diagnosis with splenic lymphoma, a common complication of hyper-reactive malarial splenomegaly. Although rare in Western countries, hyper-reactive malarial splenomegaly deserves increased medical awareness to reduce the incidence of incorrect diagnosis, to prevent progression to splenic lymphoma and to avoid splenectomy. PMID:26119345

  9. Synchronous reactive programming in Ptolemy

    SciTech Connect

    Boulanger, F.; Vidal-Naquet, G.

    1996-12-31

    Synchronous reactive languages allow a high level deterministic description of reactive systems such as control-command systems. Their well defined mathematical semantics makes it possible to check formal properties on the control of a system. In previous work, we developed an object-oriented execution model for synchronous reactive modules. This model is implemented as a set of tools and a C++ class library, and allows us to use object-oriented methodologies and tools for the design of complex applications with both transformational and reactive parts. Among these design tools, the Ptolemy system stands as an object-oriented framework that supports various execution models, or {open_quotes}domains{close_quotes}. We are currently working on a translator from the output format of the Lustre and Esterel compilers to the Ptolemy language. Since no existing domain matches the reactive synchronous execution model, we also plan to develop a SEC (Synchronous Execution and Communication) domain. Such a domain will provide support for the execution of synchronous modules in Ptolemy. One of the most interesting features of Ptolemy is the communication between domains. Therefore we discuss the interface of the SEC domain to other domains to determine the meaning of communications between them. The main goal is to allow the use of synchronous reactive modules for the control of the behavior of data-flow or discrete event processes.

  10. Design and minimum reflux calculations for multicomponent reactive distillation columns

    SciTech Connect

    Barbosa, D.; Doherty, M.F.

    1987-01-01

    A new set of transformed composition variables is introduced to simplify the design equations for single-feed, multicomponent reactive distillation columns. Based on these equations, a general method of calculating minimum reflux ratios for reactive distillation columns is presented. The new composition variables are also used to derive simple relationships between the dependent design variables, which are not evident when the design equations are written in terms of mole fractions.

  11. Brachial artery reactivity and vascular reactive hyperemia for preoperative anaesthesia risk assessment – an observational study

    PubMed Central

    2014-01-01

    Background Non-invasive measures of vascular reactivity have emerged to refine cardiovascular risk. However, limited data exists investigating vascular reactivity as a preoperative diagnostic tool for anesthesiologists. In this study, we compare the utility of two non-invasive techniques, Brachial Artery Reactivity Testing (BART) and Digital Thermal Monitoring (DTM), as surrogates for measuring vascular reactivity. Methods Following IRB approval, 26 patients scheduled for major thoracic surgery (e.g. esophagectomy and pneumonectomy) were studied prospectively. BART [Flow mediated dilation (FMD) and Peak flow velocity (PFV)] and DTM [Temperature rebound (TR%)] were performed preoperatively at baseline using 5 minute blood pressure cuff occlusion of the upper arm. Statistical summaries were provided for the comparison of BART and DTM with select patient characteristics, and correlations were used to investigate the strength of the relationship between BART and DTM measurements. Results Patients preoperatively diagnosed with hyperlipidemia were associated with lower FMD% values {Median (Range): 14.8 (2.3, 38.1) vs. 6.2 (0.0, 14.3); p = 0.006}. There were no significant associations between BART and DTM techniques in relation to cardiovascular risk factors or postoperative complications. Conclusion Our study suggests that impaired vascular reactivity as measured by BART is associated with the incidence of hyperlipidemia. Also, using a novel technique such as DTM may provide a simpler and more accessible point of care testing for vascular reactivity in a perioperative setting. Both non-invasive techniques assessing vascular function warrant further refinement to better assist preoperative optimization strategies aimed at improving perioperative vascular function. PMID:24971042

  12. Evaluation of mineral reactive surface area estimates for prediction of reactivity of a multi-mineral sediment

    NASA Astrophysics Data System (ADS)

    Beckingham, Lauren E.; Mitnick, Elizabeth H.; Steefel, Carl I.; Zhang, Shuo; Voltolini, Marco; Swift, Alexander M.; Yang, Li; Cole, David R.; Sheets, Julia M.; Ajo-Franklin, Jonathan B.; DePaolo, Donald J.; Mito, Saeko; Xue, Ziqiu

    2016-09-01

    Our limited understanding of mineral reactive surface area contributes to significant uncertainties in quantitative simulations of reactive chemical transport in subsurface processes. Continuum formulations for reactive transport typically use a number of different approximations for reactive surface area, including geometric, specific, and effective surface area. In this study, reactive surface area estimates are developed and evaluated for their ability to predict dissolution rates in a well-stirred flow-through reactor experiment using disaggregated samples from the Nagaoka pilot CO2 injection site (Japan). The disaggregated samples are reacted with CO2 acidified synthetic brine under conditions approximating the field conditions and the evolution of solute concentrations in the reactor effluent is tracked over time. The experiments, carried out in fluid-dominated conditions at a pH of 3.2 for 650 h, resulted in substantial dissolution of the sample and release of a disproportionately large fraction of the divalent cations. Traditional reactive surface area estimation methods, including an adjusted geometric surface area and a BET-based surface area, are compared to a newly developed image-based method. Continuum reactive transport modeling is used to determine which of the reactive surface area models provides the best match with the effluent chemistry from the well-stirred reactor. The modeling incorporates laboratory derived mineral dissolution rates reported in the literature and the initial modal mineralogy of the Nagaoka sediment was determined from scanning electron microscopy (SEM) characterization. The closest match with the observed steady-state effluent concentrations was obtained using specific surface area estimates from the image-based approach supplemented by literature-derived BET measurements. To capture the evolving effluent chemistry, particularly over the first 300 h of the experiment, it was also necessary to account for the grain size

  13. Personality may influence reactivity to stress

    PubMed Central

    Flaa, Arnljot; Ekeberg, Øivind; Kjeldsen, Sverre Erik; Rostrup, Morten

    2007-01-01

    Background Possible mechanisms behind psychophysiological hyperreactivity may be located at a cognitive-emotional level. Several personality traits have been associated with increased cardiovascular reactivity. Subjects with white coat hypertension, which may constitute a kind of hyperreactivity, are found to suppress their emotions and adapt to the surroundings to a larger extent than controls. We hypothesized in this study that a) stress reactivity is related to personality, and that b) responses to cold pressor test (CPT) and mental stress test (MST) are associated with different personality traits. Methods 87 men were selected from the 1st, 50th and 99th percentile of a blood pressure screening. Cardiovascular and catecholamine responses to MST and CPT were recorded. Fifteen personality traits were assessed using the Karolinska Scale of Personality. Possible independent explanatory predictors for cardiovascular and catecholamine variables at baseline and during stress were analyzed in multiple linear regression analyses using a stepwise forward procedure. Results Multiple regression analyses showed that muscular tension (β = 0.298, p = 0.004), irritability (β = 0.282, p = 0.016), detachment (β = 0.272, p = 0.017), psychasthenia (β = 0.234, p = 0.031) and somatic anxiety (β = 0.225, p = 0.046) were significant explanatory variables of reactivity to CPT. During MST, verbal aggression (β = -0.252, 0.031) and detachment (β = 0.253, p = 0.044) were significant predictors of norepinephrine and diastolic blood pressure response, respectively. Based on KSP-trait quartiles, delta (Δ) systolic (p = 0.025) and Δ diastolic blood pressure (p = 0.003) during MST were related to detachment score, with the highest reactivity in the 4th quartile, while Δ norepinephrine was significantly related to muscular tension (p = 0.033). Δ systolic and Δ diastolic blood pressure responses to CPT were dependent on detachment (p = 0.049 and p = 0.011, respectively) and

  14. Reactive decontamination formulation

    DOEpatents

    Giletto, Anthony; White, William; Cisar, Alan J.; Hitchens, G. Duncan; Fyffe, James

    2003-05-27

    The present invention provides a universal decontamination formulation and method for detoxifying chemical warfare agents (CWA's) and biological warfare agents (BWA's) without producing any toxic by-products, as well as, decontaminating surfaces that have come into contact with these agents. The formulation includes a sorbent material or gel, a peroxide source, a peroxide activator, and a compound containing a mixture of KHSO.sub.5, KHSO.sub.4 and K.sub.2 SO.sub.4. The formulation is self-decontaminating and once dried can easily be wiped from the surface being decontaminated. A method for decontaminating a surface exposed to chemical or biological agents is also disclosed.

  15. Geotechnical techniques for the construction of reactive barriers

    PubMed

    Day; O'Hannesin; Marsden

    1999-06-30

    One of the newest and most promising remediation techniques for the treatment of contaminated groundwater and soil is the reactive barrier wall (commonly known as PRB for permeable reactive barrier or reactive barrier). Although a variety of treatment media and strategies are available, the most common technique is to bury granular iron in a trench so that contaminated groundwater passes through the reactive materials, the contaminants are removed and the water becomes 'clean'. The principal advantages of the technique are the elimination of pumping, mass excavation, off-site disposal, and a very significant reduction in costs. The use of this technology is now becoming better known and implemented. Special construction considerations need to be made when planning the installation of reactive barriers or PRBs to ensure the design life of the installation and to be cost-effective. Geotechnical techniques such as slurry trenching, deep soil mixing, and grouting can be used to simplify and improve the installation of reactive materials relative to conventional trench and fill methods. These techniques make it possible to reduce the hazards to workers during installation, reduce waste and reduce costs for most installations. To date, most PRBs have been installed to shallow depths using construction methods such as open trenching and/or shored excavations. While these methods are usable, they are limited to shallow depths and more disruptive to the site's normal use. Geotechnical techniques are more quickly installed and less disruptive to site activities and thus more effective. Recently, laboratory studies and pilot projects have demonstrated that geotechnical techniques can be used successfully to install reactive barriers. This paper describes the factors that are important in designing a reactive barrier or PRB installation and discusses some of the potential problems and pitfalls that can be avoided with careful planning and the use of geotechnical techniques

  16. Reactivity to nicotine cues over repeated cue reactivity sessions.

    PubMed

    LaRowe, Steven D; Saladin, Michael E; Carpenter, Matthew J; Upadhyaya, Himanshu P

    2007-12-01

    The present study investigated whether reactivity to nicotine-related cues would attenuate across four experimental sessions held 1 week apart. Participants were nineteen non-treatment seeking, nicotine-dependent males. Cue reactivity sessions were performed in an outpatient research center using in vivo cues consisting of standardized smoking-related paraphernalia (e.g., cigarettes) and neutral comparison paraphernalia (e.g., pencils). Craving ratings were collected before and after both cue presentations while physiological measures (heart rate, skin conductance) were collected before and during the cue presentations. Although craving levels decreased across sessions, smoking-related cues consistently evoked significantly greater increases in craving relative to neutral cues over all four experimental sessions. Skin conductance was higher in response to smoking cues, though this effect was not as robust as that observed for craving. Results suggest that, under the described experimental parameters, craving can be reliably elicited over repeated cue reactivity sessions. PMID:17537583

  17. Campylobacter Reactive Arthritis: A Systematic Review

    PubMed Central

    Pope, Janet E.; Krizova, Adriana; Garg, Amit X.; Thiessen-Philbrook, Heather; Ouimet, Janine M.

    2010-01-01

    Objective To review the literature on the epidemiology of Campylobacter associated ReA. Methods A Medline (PubMed) search identified studies from 1966–2006 that investigated the epidemiology of Campylobacter associated ReA. Search terms included: “reactive arthritis”, “spondyloarthropathy”, “Reiter’s syndrome”, “gastroenteritis”, “diarrhea”, “epidemiology”, “incidence”, “prevalence”, and “Campylobacter”. Results The literature available to date suggests that the incidence of Campylobacter reactive arthritis may occur in 1 to 5% of those infected. The annual incidence of ReA after Campylobacter or Shigella may be 4.3 and 1.3 respectively per 100,000. The duration of acute ReA varies considerably between reports, and the incidence and impact of chronic reactive arthritis from Campylobacter infection is virtually unknown. Conclusions Campylobacter associated ReA incidence and prevalence varies widely from reviews such as: case ascertainment differences, exposure differences, lack of diagnostic criteria for ReA and perhaps genetics and ages of exposed individuals. At the population level it may not be associated with HLA-B27 and inflammatory back involvement is uncommon. Follow up for long-term sequelae is largely unknown. Five percent of Campylobacter ReA may be chronic or relapsing (with respect to musculoskeletal symptoms). PMID:17360026

  18. Impact of Particle Aggregation on Nanoparticle Reactivity

    NASA Astrophysics Data System (ADS)

    Jassby, David

    2011-12-01

    nanoparticle that photoluminesces after exposure to UV; TiO2 and ZnO nanoparticles---photocatalytic nanoparticles that generate reactive oxygen species upon UV irradition; and, fullerene nanoparticles used in the filtration experiments, selected for their potential use, small size, and surface chemistry. Our primary methods used to characterize particle and aggregate characteristics include dynamic light scattering used to describe particle size, static light scattering used to characterize aggregate structure (fractal dimension), transmission electron microscopy used to verify primary particle sizes, and electrophoretic mobility measurements to evaluate suspension stability. The reactive property of ZnS that was measured as a function of aggregation was photoluminescence, which was measured using a spectrofluorometer. The reactive property of TiO2 and ZnO that was studied was their ability to generate hydroxyl radicals; these were measured by employing a fluorescent probe that becomes luminescent upon interaction with the hydroxyl radical. To detect the presence of fullerene nanoparticles and calculate removal efficiencies, we used total organic carbon measurements. Additionally, we used UV-vis spectroscopy to approximate the impact of particle shadowing in TiO2 and ZnO aggregates, and Fourier transformed infrared spectroscopy to determine how different electrolytes interact with fullerene surface groups. Our findings indicate that the impact of aggregation on nanoparticle reactivity is material specific. ZnS nanoparticles exhibit a 2-fold increase in band-edge photoluminescence alongside a significant decrease in defect-site photoluminescence. This is attributed to aggregate size-dependent surface tension. Additionally, we used photoluminescence measurements to develop a new method for calculating the critical coagulation concentration of a nanoparticle suspension. The ability of both TiO2 and ZnO to generate hydroxyl radicals was significantly hampered by aggregation. The

  19. Clamshell excavation of a permeable reactive barrier

    NASA Astrophysics Data System (ADS)

    Molfetta, Antonio Di; Sethi, Rajandrea

    2006-06-01

    Nowadays, permeable reactive barriers (PRB) are one of the most widespread techniques for the remediation of contaminated aquifers. Over the past 10 years, the use of iron-based PRBs has evolved from innovative to accepted standard practice for the treatment of a variety of groundwater contaminants (ITRC in: Permeable reactive barriers: lessons learned/new directions. The Interstate Technology and Regulatory Council, Permeable Reactive Barriers Team 2005). Although, a variety of excavation methods have been developed, backhoe excavators are often used for the construction of PRBs. The aim of this study is to describe the emplacement of a full-scale PRB and the benefits deriving from the use of a crawler crane equipped with a hydraulic grab (also known as clamshell excavator) in the excavation phases. The studied PRB was designed to remediate a chlorinated hydrocarbons plume at an old industrial landfill site, in Avigliana, near the city of Torino, in Italy. The continuous reactive barrier was designed to be 120 m long, 13 m deep, and 0.6 m thick. The installation of the barrier was accomplished using a clamshell for the excavation of the trench and a guar-gum slurry to support the walls. The performance of this technique was outstanding and allowed the installation of the PRB in 7 days. The degree of precision of the excavation was very high because of the intrinsic characteristics of this excavation tool and of the use of a concrete curb to guide the hydraulic grab. Moreover, the adopted technique permitted a saving of bioslurry thus minimizing the amount of biocide required.

  20. Deleterious effects of reactive metabolites

    PubMed Central

    2010-01-01

    A number of drugs have been withdrawn from the market or severely restricted in their use because of unexpected toxicities that become apparent only after the launch of new drug entities. Circumstantial evidence suggests that, in most cases, reactive metabolites are responsible for these unexpected toxicities. In this review, a general overview of the types of reactive metabolites and the consequences of their formation are presented. The current approaches to evaluate bioactivation potential of new compounds with particular emphasis on the advantages and limitation of these procedures will be discussed. Reasonable reasons for the excellent safety record of certain drugs susceptible to bioactivation will also be explored and should provide valuable guidance in the use of reactive-metabolite assessments when nominating drug candidates for development. This will, in turn, help us to design and bring safer drugs to the market. PMID:20972370

  1. Reactive power optimization by genetic algorithm

    SciTech Connect

    Iba, Kenji )

    1994-05-01

    This paper presents a new approach to optimal reactive power planning based on a genetic algorithm. Many outstanding methods to this problem have been proposed in the past. However, most of these approaches have the common defect of being caught to a local minimum solution. The integer problem which yields integer value solutions for discrete controllers/banks still remains as a difficult one. The genetic algorithm is a kind of search algorithm based on the mechanics of natural selection and genetics. This algorithm can search for a global solution using multiple paths and treat integer problems naturally. The proposed method was applied to practical 51-bus and 224-bus systems to show its feasibility and capabilities. Although this method is not as fast as sophisticated traditional methods, the concept is quite promising and useful.

  2. Modeling Reactivity to Biological Macromolecules with a Deep Multitask Network

    PubMed Central

    2016-01-01

    Most small-molecule drug candidates fail before entering the market, frequently because of unexpected toxicity. Often, toxicity is detected only late in drug development, because many types of toxicities, especially idiosyncratic adverse drug reactions (IADRs), are particularly hard to predict and detect. Moreover, drug-induced liver injury (DILI) is the most frequent reason drugs are withdrawn from the market and causes 50% of acute liver failure cases in the United States. A common mechanism often underlies many types of drug toxicities, including both DILI and IADRs. Drugs are bioactivated by drug-metabolizing enzymes into reactive metabolites, which then conjugate to sites in proteins or DNA to form adducts. DNA adducts are often mutagenic and may alter the reading and copying of genes and their regulatory elements, causing gene dysregulation and even triggering cancer. Similarly, protein adducts can disrupt their normal biological functions and induce harmful immune responses. Unfortunately, reactive metabolites are not reliably detected by experiments, and it is also expensive to test drug candidates for potential to form DNA or protein adducts during the early stages of drug development. In contrast, computational methods have the potential to quickly screen for covalent binding potential, thereby flagging problematic molecules and reducing the total number of necessary experiments. Here, we train a deep convolution neural network—the XenoSite reactivity model—using literature data to accurately predict both sites and probability of reactivity for molecules with glutathione, cyanide, protein, and DNA. On the site level, cross-validated predictions had area under the curve (AUC) performances of 89.8% for DNA and 94.4% for protein. Furthermore, the model separated molecules electrophilically reactive with DNA and protein from nonreactive molecules with cross-validated AUC performances of 78.7% and 79.8%, respectively. On both the site- and molecule

  3. Modeling Reactivity to Biological Macromolecules with a Deep Multitask Network.

    PubMed

    Hughes, Tyler B; Dang, Na Le; Miller, Grover P; Swamidass, S Joshua

    2016-08-24

    Most small-molecule drug candidates fail before entering the market, frequently because of unexpected toxicity. Often, toxicity is detected only late in drug development, because many types of toxicities, especially idiosyncratic adverse drug reactions (IADRs), are particularly hard to predict and detect. Moreover, drug-induced liver injury (DILI) is the most frequent reason drugs are withdrawn from the market and causes 50% of acute liver failure cases in the United States. A common mechanism often underlies many types of drug toxicities, including both DILI and IADRs. Drugs are bioactivated by drug-metabolizing enzymes into reactive metabolites, which then conjugate to sites in proteins or DNA to form adducts. DNA adducts are often mutagenic and may alter the reading and copying of genes and their regulatory elements, causing gene dysregulation and even triggering cancer. Similarly, protein adducts can disrupt their normal biological functions and induce harmful immune responses. Unfortunately, reactive metabolites are not reliably detected by experiments, and it is also expensive to test drug candidates for potential to form DNA or protein adducts during the early stages of drug development. In contrast, computational methods have the potential to quickly screen for covalent binding potential, thereby flagging problematic molecules and reducing the total number of necessary experiments. Here, we train a deep convolution neural network-the XenoSite reactivity model-using literature data to accurately predict both sites and probability of reactivity for molecules with glutathione, cyanide, protein, and DNA. On the site level, cross-validated predictions had area under the curve (AUC) performances of 89.8% for DNA and 94.4% for protein. Furthermore, the model separated molecules electrophilically reactive with DNA and protein from nonreactive molecules with cross-validated AUC performances of 78.7% and 79.8%, respectively. On both the site- and molecule-level, the

  4. The triple line in reactive wetting

    SciTech Connect

    Yost, F.G.

    1998-03-13

    The classical method for specifying the conditions of capillary equilibrium has been used to describe the wetting line in a simple reactive system. The results, being Young-Neumann equations for the contact angles, are compared to suggestions made by Landry et al. It was shown that under specific circumstances the suggestions made by Landry et al. agree with the classical approach. A discussion was also presented regarding the complexity of real capillary microstructures and their very simplistic theoretical description. An approach that considers microstructural defects and can distinguish metastable and true equilibrium states in complex systems is needed.

  5. Etching Semiconductors With Beams Of Reactive Atoms

    NASA Technical Reports Server (NTRS)

    Minton, Timothy K.; Giapis, Konstantinos P.; Moore, Teresa A.

    1995-01-01

    Method of etching semiconductors with energetic beams of electrically neutral, but chemically reactive, species undergoing development. Enables etching of straight walls into semiconductor substrates at edges of masks without damage to underlying semiconductor material. In addition to elimination of charge damage, technique reduces substrate bombardment damage because translational energy of neutral species in range 2-12 eV, below damage threshold of many semiconductor materials. Furthermore, low-energy neutrals cause no mask erosion allowing for etching features with very high aspect ratios.

  6. Silica fractionation and reactivity in soils

    NASA Astrophysics Data System (ADS)

    Unzué Belmonte, Dácil; Barão, Lúcia; Vandevenne, Floor; Schoelynck, Jonas; Struyf, Eric; Meire, Patrick

    2014-05-01

    The Si cycle is a globally important biogeochemical cycle, with strong connections to other biogeochemical cycles, including C. Silica is taken up by plants to form protective structures called phytoliths, which become a part of the soil and contribute strongly to soil Si cycling upon litter burial. Different silica fractions are found in soils, with phytoliths among the most easily soluble, especially compared to silicate minerals. A whole set of secondary non-biogenic fractions exist, that also have a high reactivity (adsorbed Si, reactive secondary minerals…). A good characterization of the different fractions of reactive silica is crucial to move forward knowledge on ecosystem Si cycling, which has been recognized in the last decade as crucial for terrestrial Si fluxes. A new method to analyze the different fractions of silica in soils has been described by Koning et al. (2002) and adapted by our research team (Barão et al. 2013). Using a continuous extraction of Si and aluminum in 0.5M NaOH, biogenic and non-biogenic reactive fractions are separated based on their Si/Al ratios and their reactivity in NaOH. Applying this new method I will investigate three emerging ideas on how humans can affect directly terrestrial Si fluxes. -Land use. I expect strong silica fractionation and reactivity differences in different land uses. These effects due to agricultural and forestry management have already been shown earlier in temperate soils (Vandevenne et al. 2012). Now we will test this hypothesis in recently deforested soils, in the south of Brazil. 'Pristine' forest, managed forest and tobacco field soils (with and without rotation crops) will be studied. This research belongs to an interdisciplinary project on soils and global change. -Fire. According to the IPCC report, extreme events such as fires (number and intensity) would increase due to climate change. We analyzed litter from spruce forest, beech forest and peat soils at two burning levels, after 350°C and

  7. PROCEEDINGS: MULTIPOLLUTANT SORBENT REACTIVITY WORKSHOP

    EPA Science Inventory

    The report is a compilation of technical papers and visual aids presented by representatives of industry, academia, and government agencies at a workshop on multipollutant sorbent reactivity that was held at EPA's Environmental Research Center in Research Triangle Park, NC, on Ju...

  8. Neurological Complications of VZV Reactivation

    PubMed Central

    Nagel, Maria A.

    2014-01-01

    Purpose of the review Varicella zoster virus (VZV) reactivation results in zoster, which may be complicated by postherpetic neuralgia, myelitis, meningoencephalitis and VZV vasculopathy. This review highlights the clinical features, laboratory abnormalities, imaging changes and optimal treatment of each of those conditions. Because all of these neurological disorders produced by VZV reactivation can occur in the absence of rash, the virological tests proving that VZV caused disease are discussed. Recent findings After primary infection, VZV becomes latent in ganglionic neurons along the entire neuraxis. With a decline in VZV-specific cell-mediated immunity, VZV reactivates from ganglia and travels anterograde to the skin to cause zoster, which is often complicated by postherpetic neuralgia. VZV can also travel retrograde to produce meningoencephaltis, myelitis and stroke. When these complications occur without rash, VZV-induced disease can be diagnosed by detection of VZV DNA or anti-VZV antibody in CSF and treated with intravenous acyclovir. Summary Awareness of the expanding spectrum of neurological complications caused by VZV reactivation with and without rash will improve diagnosis and treatment. PMID:24792344

  9. Emotional Reactivity and Psychological Distress.

    ERIC Educational Resources Information Center

    Bartle-Haring, Suzanne; Rosen, Karen H.; Stith, Sandra M.

    2002-01-01

    This article reports on an empirical test of Bowen's hypothesized relationships between differentiation of self and psychological symptoms, and examines further evidence for the construct validity of a newly developed instrument, the Behavioral and Emotional Reactivity Index (BERI). Finds an indirect relationship between emotional reactivity…

  10. Persistent Latent Tuberculosis Reactivation Risk in United States Immigrants

    PubMed Central

    Painter, John; Parker, Matthew; Lowenthal, Phillip; Flood, Jennifer; Fu, Yunxin; Asis, Redentor; Reves, Randall

    2014-01-01

    Rationale: Current guidelines limit latent tuberculosis infection (LTBI) evaluation to persons in the United States less than or equal to 5 years based on the assumption that high TB rates among recent entrants are attributable to high LTBI reactivation risk, which declines over time. We hypothesized that high postarrival TB rates may instead be caused by imported active TB. Objectives: Estimate reactivation and imported TB in an immigrant cohort. Methods: We linked preimmigration records from a cohort of California-bound Filipino immigrants during 2001–2010 with subsequent TB reports. TB was likely LTBI reactivation if the immigrant had no evidence of active TB at preimmigration examination, likely imported if preimmigration radiograph was abnormal and TB was reported less than or equal to 6 months after arrival, and likely reactivation of inactive TB if radiograph was abnormal but TB was reported more than 6 months after arrival. Measurements and Main Results: Among 123,114 immigrants, 793 TB cases were reported. Within 1 year of preimmigration examination, 85% of TB was imported; 6 and 9% were reactivation of LTBI and inactive TB, respectively. Conversely, during Years 2–9 after U.S. entry, 76 and 24% were reactivation of LTBI and inactive TB, respectively. The rate of LTBI reactivation (32 per 100,000) did not decline during Years 1–9. Conclusions: High postarrival TB rates were caused by detection of imported TB through active postarrival surveillance. Among immigrants without active TB at baseline, reported TB did not decline over 9 years, indicating sustained high risk of LTBI reactivation. Revised guidelines should support LTBI screening and treatment more than 5 years after U.S. arrival. PMID:24308495

  11. Titanium-Oxygen Reactivity Study

    NASA Technical Reports Server (NTRS)

    Chafey, J. E.; Scheck, W. G.; Witzell, W. E.

    1962-01-01

    A program has been conducted at Astronautics to investigate the likelihood of occurrence of the catastrophic oxidation of titanium alloy sheet under conditions which simulate certain cases of accidental failure of the metal while it is in contact with liquid or gaseous oxygen. Three methods of fracturing the metal were used; they consisted of mechanical puncture, tensile fracture of welded joints, and perforation by very high velocity particles. The results of the tests which have been conducted provide further evidence of the reactivity of titanium with liquid and gaseous oxygen. The evidence indicates that the rapid fracturing of titanium sheet while it is in contact with oxygen initiates the catastrophic oxidation reaction. Initiation occurred when the speed of the fracture was some few feet per second, as in both the drop-weight puncture tests and the static tensile fracture tests of welded joints, as well as when the speed was several thousand feet per second, as in the simulated micrometeoroid penetration tests. The slow propagation of a crack, however, did not initiate the reaction. It may logically be concluded that the localized frictional heat of rapid fracture and/or spontaneous oxidation (exothermic) of minute particles emanating from the fracture cause initiation of the reaction. Under conditions of slow fracture, however, the small heat generated may be adequately dissipated and the reaction is not initiated. A portion of the study conducted consisted of investigating various means by which the reaction might be retarded or prevented. Providing a "barrier" at the titanium-oxygen interface consisting of either aluminum metal or a coating of a petroleum base corrosion inhibitor appeared to be only partially effective in retarding the reaction. The accidental puncturing or similar rupturing of thin-walled pressurized oxygen tanks on missiles and space vehicle will usually constitute loss of function, and may sometimes cause their catastrophic destruction

  12. On Spurious Numerics in Solving Reactive Equations

    NASA Technical Reports Server (NTRS)

    Kotov, D. V; Yee, H. C.; Wang, W.; Shu, C.-W.

    2013-01-01

    The objective of this study is to gain a deeper understanding of the behavior of high order shock-capturing schemes for problems with stiff source terms and discontinuities and on corresponding numerical prediction strategies. The studies by Yee et al. (2012) and Wang et al. (2012) focus only on solving the reactive system by the fractional step method using the Strang splitting (Strang 1968). It is a common practice by developers in computational physics and engineering simulations to include a cut off safeguard if densities are outside the permissible range. Here we compare the spurious behavior of the same schemes by solving the fully coupled reactive system without the Strang splitting vs. using the Strang splitting. Comparison between the two procedures and the effects of a cut off safeguard is the focus the present study. The comparison of the performance of these schemes is largely based on the degree to which each method captures the correct location of the reaction front for coarse grids. Here "coarse grids" means standard mesh density requirement for accurate simulation of typical non-reacting flows of similar problem setup. It is remarked that, in order to resolve the sharp reaction front, local refinement beyond standard mesh density is still needed.

  13. Astrocyte reactivity and reactive astrogliosis: costs and benefits.

    PubMed

    Pekny, Milos; Pekna, Marcela

    2014-10-01

    Astrocytes are the most abundant cells in the central nervous system (CNS) that provide nutrients, recycle neurotransmitters, as well as fulfill a wide range of other homeostasis maintaining functions. During the past two decades, astrocytes emerged also as increasingly important regulators of neuronal functions including the generation of new nerve cells and structural as well as functional synapse remodeling. Reactive gliosis or reactive astrogliosis is a term coined for the morphological and functional changes seen in astroglial cells/astrocytes responding to CNS injury and other neurological diseases. Whereas this defensive reaction of astrocytes is conceivably aimed at handling the acute stress, limiting tissue damage, and restoring homeostasis, it may also inhibit adaptive neural plasticity mechanisms underlying recovery of function. Understanding the multifaceted roles of astrocytes in the healthy and diseased CNS will undoubtedly contribute to the development of treatment strategies that will, in a context-dependent manner and at appropriate time points, modulate reactive astrogliosis to promote brain repair and reduce the neurological impairment. PMID:25287860

  14. Synthesis and analysis of reactive nanocomposites prepared arrested reactive milling

    NASA Astrophysics Data System (ADS)

    Umbrajkar, Swati M.

    Different types of reactive nanocomposites have been synthesized by Arrested Reactive Milling (ARM). The technical approach was to increase the interface area available for heterogeneous reaction between solid fuel and oxidizer components. Using aluminum as the main fuel and different metal oxides as oxidizers, highly energetic reactive nanocomposites with different degrees of structural refinement were synthesized. Specifically, stoichiometric Al-MoO 3, Al-CuO, and Al-NaNO3 material systems were studied in detail. The correlation of heterogeneous exothermic reactions occurring in the nanocomposite powders upon their heating at low rates and ignition events observed for the same powders heated rapidly was of interest. Differential scanning calorimetry (DSC), X-ray diffraction (XRD) and heated filament ignition experiments were used to quantify the ignition kinetics and related reaction mechanisms. Fuel rich Al-MoO3 nanocomposites were also synthesized using ARM. Optimum composition and milling parameters were identified for fuel-rich compositions. Analysis of exothermic reactions in Al-MoO3 system showed that kinetics of such reactions could not be determined by isoconversion processing and respective activation energies could not be meaningfully found as functions of reaction progress. Instead, detailed DSC measurements at different heating rates are required to enable one in developing a multi-step kinetic model to describe such reactions adequately.

  15. Reactive biomolecular divergence in genetically altered yeast cells and isolated mitochondria as measured by biocavity laser spectroscopy : a rapid diagnostic method for studying cellular responses to stress and disease.

    SciTech Connect

    Yaffe, Michael P.; Gourley, Paul Lee; Copeland, Robert Guild; McDonald, Anthony Eugene; Hendricks, Judy K.; Naviaux, Robert K.

    2006-12-01

    We report an analysis of four strains of baker's yeast (Saccharomyces cerevisiae) using biocavity laser spectroscopy. The four strains are grouped in two pairs (wild type and altered), in which one strain differs genetically at a single locus, affecting mitochondrial function. In one pair, the wild-type rho+ and a rho0 strain differ by complete removal of mitochondrial DNA (mtDNA). In the second pair, the wild-type rho+ and a rho- strain differ by knock-out of the nuclear gene encoding Cox4, an essential subunit of cytochrome c oxidase. The biocavity laser is used to measure the biophysical optic parameter Deltalambda, a laser wavelength shift relating to the optical density of cell or mitochondria that uniquely reflects its size and biomolecular composition. As such, Deltalambda is a powerful parameter that rapidly interrogates the biomolecular state of single cells and mitochondria. Wild-type cells and mitochondria produce Gaussian-like distributions with a single peak. In contrast, mutant cells and mitochondria produce leptokurtotic distributions that are asymmetric and highly skewed to the right. These distribution changes could be self-consistently modeled with a single, log-normal distribution undergoing a thousand-fold increase in variance of biomolecular composition. These features reflect a new state of stressed or diseased cells that we call a reactive biomolecular divergence (RBD) that reflects the vital interdependence of mitochondria and the nucleus.

  16. Prediction of reactive hazards based on molecular structure.

    PubMed

    Saraf, S R; Rogers, W J; Mannan, M S

    2003-03-17

    There is considerable interest in prediction of reactive hazards based on chemical structure. Calorimetric measurements to determine reactivity can be resource consuming, so computational methods to predict reactivity hazards present an attractive option. This paper reviews some of the commonly employed theoretical hazard evaluation techniques, including the oxygen-balance method, ASTM CHETAH, and calculated adiabatic reaction temperature (CART). It also discusses the development of a study table to correlate and predict calorimetric properties of pure compounds. Quantitative structure-property relationships (QSPR) based on quantum mechanical calculations can be employed to correlate calorimetrically measured onset temperatures, T(o), and energies of reaction, -deltaH, with molecular properties. To test the feasibility of this approach, the QSPR technique is used to correlate differential scanning calorimeter (DSC) data, T(o) and -deltaH, with molecular properties for 19 nitro compounds. PMID:12628775

  17. Characterizing Reactive Flow Paths in Fractured Cement

    NASA Astrophysics Data System (ADS)

    Wenning, Q. C.; Huerta, N. J.; Hesse, M. A.; Bryant, S. L.

    2011-12-01

    Geologic carbon sequestration can be a viable method for reducing anthropogenic CO2 flux into the atmosphere. However, the technology must be economically feasible and pose acceptable risk to stakeholders. One key risk is CO2 leakage out of the storage reservoir. Potential driving forces for leakage are the overpressure due to CO2 injection and the buoyancy of free phase CO2. Potential hazards of leakage are contamination of Underground Sources of Drinking Water or the atmosphere and would be deemed an unacceptable risk. Wells potentially provide a fast path for leakage from the reservoir. While the well's cement casing is reactive with CO2 and CO2-saturated brine, the low cement matrix permeability and slow diffusion rate make it unlikely that CO2 will escape through a properly constructed wellbore. However, highly permeable fractures with micrometer scale apertures can occur in cement casings. Reactions that occur in the flow in these fractures can either be self-limiting or self-enhancing. Therefore, understanding the reactive flow is critical to understanding of leakage evolution through these fractures. The goal of our work is to characterize the modification of the flow paths in the fracture due to reaction with acidic brine. With this aim we have characterized both the initial flow path of un-reactive flow and the final flow path after introduction of low-pH acid along the same fracture. Class H cement cores 3-6 cm in length and 2.5 cm diameter are created and a single natural and unique fracture is produced in each core using the Brazilian method. Our experimental fluid is injected at a constant rate into the cement core housed in a Hassler Cell under confining pressure. A solution of red dye and deionized water is pumped through the fracture to stain the un-reactive flow paths. Deionized water is then pumped through the core to limit diffusion of the dye into non-flowing portions of the fracture. After staining the initial flow path, low pH water due to

  18. Assessment of parametric uncertainty for groundwater reactive transport modeling,

    USGS Publications Warehouse

    Shi, Xiaoqing; Ye, Ming; Curtis, Gary P.; Miller, Geoffery L.; Meyer, Philip D.; Kohler, Matthias; Yabusaki, Steve; Wu, Jichun

    2014-01-01

    The validity of using Gaussian assumptions for model residuals in uncertainty quantification of a groundwater reactive transport model was evaluated in this study. Least squares regression methods explicitly assume Gaussian residuals, and the assumption leads to Gaussian likelihood functions, model parameters, and model predictions. While the Bayesian methods do not explicitly require the Gaussian assumption, Gaussian residuals are widely used. This paper shows that the residuals of the reactive transport model are non-Gaussian, heteroscedastic, and correlated in time; characterizing them requires using a generalized likelihood function such as the formal generalized likelihood function developed by Schoups and Vrugt (2010). For the surface complexation model considered in this study for simulating uranium reactive transport in groundwater, parametric uncertainty is quantified using the least squares regression methods and Bayesian methods with both Gaussian and formal generalized likelihood functions. While the least squares methods and Bayesian methods with Gaussian likelihood function produce similar Gaussian parameter distributions, the parameter distributions of Bayesian uncertainty quantification using the formal generalized likelihood function are non-Gaussian. In addition, predictive performance of formal generalized likelihood function is superior to that of least squares regression and Bayesian methods with Gaussian likelihood function. The Bayesian uncertainty quantification is conducted using the differential evolution adaptive metropolis (DREAM(zs)) algorithm; as a Markov chain Monte Carlo (MCMC) method, it is a robust tool for quantifying uncertainty in groundwater reactive transport models. For the surface complexation model, the regression-based local sensitivity analysis and Morris- and DREAM(ZS)-based global sensitivity analysis yield almost identical ranking of parameter importance. The uncertainty analysis may help select appropriate likelihood

  19. C-Reactive Protein (CRP) Test

    MedlinePlus

    ... 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 ...

  20. Engine combustion control via fuel reactivity stratification

    SciTech Connect

    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).

  1. Engine combustion control via fuel reactivity stratification

    SciTech Connect

    Reitz, Rolf Deneys; Hanson, Reed M; Splitter, Derek A; Kokjohn, Sage L

    2013-12-31

    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 choose 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).

  2. Engine combustion control via fuel reactivity stratification

    DOEpatents

    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).

  3. Perceptual basis for reactive teleoperation.

    SciTech Connect

    Park, Y. S.; Ewing, T. F.; Boyle, J. M.; Yule, T. J.

    2001-08-28

    To enhance task performance in partially structured environment, enhancement of teleoperation was proposed by introducing autonomous behaviors. Such autonomy is implemented based on reactive robotic architecture, where reactive motor agents that directly couples sensory inputs and motor actions become the building blocks. To this end, presented in this paper is a perceptual basis for the motor agents. The perceptual basis consists of perceptual agents that extracts environmental information from a structured light vision system and provide action oriented perception for the corresponding motor agents. Rather than performing general scene reconstruction, a perceptual agent directly provides the motion reference for the motor behavior. Various sensory mechanisms--sensor fission, fusion, and fashion--becomes basic building blocks of the perception process. Since perception is a process deeply intertwined with the motor actions, active perception may also incorporate motor behaviors as an integral perceptual process.

  4. Reactive behavior, learning, and anticipation

    NASA Technical Reports Server (NTRS)

    Whitehead, Steven D.; Ballard, Dana H.

    1989-01-01

    Reactive systems always act, thinking only long enough to 'look up' the action to execute. Traditional planning systems think a lot, and act only after generating fairly precise plans. Each represents an endpoint on a spectrum. It is argued that primitive forms of reasoning, like anticipation, play an important role in reducing the cost of learning and that the decision to act or think should be based on the uncertainty associated with the utility of executing an action in a particular situation. An architecture for an adaptable reactive system is presented and it is shown how it can be augmented with a simple anticipation mechanism that can substantially reduce the cost and time of learning.

  5. Melioidosis: reactivation during radiation therapy

    SciTech Connect

    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.

  6. Functional Reactive Polymer Electrospun Matrix.

    PubMed

    Agarwal, Vipul; Ho, Dominic; Ho, Diwei; Galabura, Yuriy; Yasin, Faizah; Gong, Peijun; Ye, Weike; Singh, Ruhani; Munshi, Alaa; Saunders, Martin; Woodward, Robert C; St Pierre, Timothy; Wood, Fiona M; Fear, Mark; Lorenser, Dirk; Sampson, David D; Zdyrko, Bogdan; Luzinov, Igor; Smith, Nicole M; Iyer, K Swaminathan

    2016-02-01

    Synthetic multifunctional electrospun composites are a new class of hybrid materials with many potential applications. However, the lack of an efficient, reactive large-area substrate has been one of the major limitations in the development of these materials as advanced functional platforms. Herein, we demonstrate the utility of electrospun poly(glycidyl methacrylate) films as a highly versatile platform for the development of functional nanostructured materials anchored to a surface. The utility of this platform as a reactive substrate is demonstrated by grafting poly(N-isopropylacrylamide) to incorporate stimuli-responsive properties. Additionally, we demonstrate that functional nanocomposites can be fabricated using this platform with properties for sensing, fluorescence imaging, and magneto-responsiveness. PMID:26780245

  7. OH Reactivity Observations during the MAPS-Seoul Campaign: Contrasts between Urban and Suburban Environments

    NASA Astrophysics Data System (ADS)

    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?

  8. Reactive Nitrogen Species Reactivities with Nitrones: Theoretical and Experimental Studies

    PubMed Central

    Nash, Kevin M.; Rockenbauer, Antal; Villamena, Frederick A.

    2012-01-01

    Reactive nitrogen species (RNS) such as nitrogen dioxide (•NO2), peroxynitrite (ONOO–), and nitrosoperoxycarbonate (ONOOCO2–) are among the most damaging species present in biological systems due to their ability to cause modification of key biomolecular systems through oxidation, nitrosylation and nitration. Nitrone spin traps are known to react with free radicals and non-radicals via electrophilic and nucleophilic addition reactions, and have been employed as reagents to detect radicals using electron paramagnetic resonance (EPR) spectroscopy, and as pharmacological agents against oxidative stress-mediated injury. This study examines the reactivity of cyclic nitrones such as 5,5-dimethylpyrroline N-oxide (DMPO) with, •NO2, ONOO–, ONOOCO2–, SNAP and SIN-1 using EPR. The thermochemistries of nitrone reactivity with RNS, and isotropic hfsc's of the addition products were also calculated at the PCM(water)/B3LYP/6-31+G**//B3LYP/6-31G* level of theory with and without explicit water molecules in order to rationalize the nature of the observed EPR spectra. Spin trapping of other RNS such as azide (•N3), nitrogen trioxide (•NO3), amino (•NH2) radicals, and nitroxyl (HNO) were also theoretically and experimentally investigated by EPR spin trapping and mass spectrometry. This study also shows other spin traps such as AMPO, EMPO and DEPMPO can react with radical and non-radical RNS, thus, making spin traps suitable probes as well as antioxidants against RNS mediated oxidative damage. PMID:22775566

  9. Tropomyosin lysine reactivities and relationship to coiled-coil structure.

    PubMed

    Hitchcock-DeGregori, S E; Lewis, S F; Chou, T M

    1985-06-18

    We have carried out a detailed analysis of tropomyosin structure using lysines as specific probes for the protein surface in regions of the molecule that have not been investigated by other methods. We have measured the relative reactivities of lysines in rabbit skeletal muscle alpha, alpha-tropomyosin with acetic anhydride using a competitive labeling procedure. We have identified 37 of 39 lysines and find that they range 20-fold in reactivity. The observed reactivities are related to the coiled-coil model of the tropomyosin molecule [Crick, F.H.C. (1953) Acta Crystallogr. 6, 689-697; McLachlan, A.D., Stewart, M., & Smillie, L.B. (1975) J. Mol. Biol. 98, 281-291] and other available chemical and physical information about the structure. In most cases, the observed lysine reactivities can be explained by allowable interactions with neighboring amino acid side chains on the same or facing alpha-helix. However, we found no correlation between reactivity and helical position of a given lysine. For example, lysines in the outer helical positions included lysines of low as well as high reactivity, indicating that they vary widely in their accessibility to solvent and that the coiled coil is heterogeneous along its length. Furthermore, the middle of the molecule (residues 126-182) that is susceptible to proteolysis and known to be the least stable region of the protein also contains some of the least and most reactive lysines. We have discussed the implications of our results on our understanding the structures of tropomyosin and other coiled-coil proteins as well as globular proteins containing helical regions. PMID:3927977

  10. Fuel temperature reactivity coefficient calculation by Monte Carlo perturbation techniques

    SciTech Connect

    Shim, H. J.; Kim, C. H.

    2013-07-01

    We present an efficient method to estimate the fuel temperature reactivity coefficient (FTC) by the Monte Carlo adjoint-weighted correlated sampling method. In this method, a fuel temperature change is regarded as variations of the microscopic cross sections and the temperature in the free gas model which is adopted to correct the asymptotic double differential scattering kernel. The effectiveness of the new method is examined through the continuous energy MC neutronics calculations for PWR pin cell problems. The isotope-wise and reaction-type-wise contributions to the FTCs are investigated for two free gas models - the constant scattering cross section model and the exact model. It is shown that the proposed method can efficiently predict the reactivity change due to the fuel temperature variation. (authors)

  11. Reactive composite compositions and mat barriers

    DOEpatents

    Langton, Christine A.; Narasimhan, Rajendran; Karraker, David G.

    2001-01-01

    A hazardous material storage area has a reactive multi-layer composite mat which lines an opening into which a reactive backfill and hazardous material are placed. A water-inhibiting cap may cover the hazardous material storage area. The reactive multi-layer composite mat has a backing onto which is placed an active layer which will neutralize or stabilize hazardous waste and a fronting layer so that the active layer is between the fronting and backing layers. The reactive backfill has a reactive agent which can stabilize or neutralize hazardous material and inhibit the movement of the hazardous material through the hazardous material storage area.

  12. Study on Reactive Automatic Compensation System Design

    NASA Astrophysics Data System (ADS)

    Zhe, Sun; Qingyang, Liang; Peiqing, Luo; Chenfei, Zhang

    At present, low-voltage side of transformer is public in urban distribution network, as inductive load of household appliances is increasing, the power factor decreased, this lead to a large loss of public transformer low voltage side, the supply voltage indicators can not meet user's requirements. Therefore, the design of reactive power compensation system has become another popular research. This paper introduces the principle of reactive power compensation, analyzes key technologies of reactive power compensation, design an overall program of reactive power automatic compensation system to conquer various deficiencies of reactive power automatic compensation equipment.

  13. COYOTE: A computer program for 2-D reactive flow simulations

    SciTech Connect

    Cloutman, L.D.

    1990-04-01

    We describe the numerical algorithm used in the COYOTE two- dimensional, transient, Eulerian hydrodynamics program for reactive flows. The program has a variety of options that provide capabilities for a wide range of applications, and it is designed to be robust and relatively easy to use while maintaining adequate accuracy and efficiency to solve realistic problems. It is based on the ICE method, and it includes a general species and chemical reaction network for simulating reactive flows. It also includes swirl, turbulence transport models, and a nonuniform mesh capability. We describe several applications of the program. 33 refs., 4 figs.

  14. Enhanced durability and reactivity for zinc ferrite desulfurization sorbent

    SciTech Connect

    Jha, M.C.; Berggren, M.H.

    1988-11-14

    AMAX Research Development Center (AMAX R D) has been investigating methods for enhancing the reactivity and durability of the zinc ferrite desulfurization sorbent. Zinc ferrite sorbents are intended for use in desulfurization of hot coal gas in integrated gasification combined cycle (IGCC) or molten carbonate fuel cell (MCFC) applications. For the present program, the reactivity of the sorbent may be defined as its sulfur sorption capacity at the breakthrough point and at saturation in a bench-scale, fixed-bed reactor. Durability may be defined as the ability of the sorbent to maintain important physical characteristics such As size, strength, and specific surface area during 10 cycles of sulfidation and oxidation.

  15. Enhanced durability and reactivity for zinc ferrite desulfurization sorbent

    SciTech Connect

    Jha, M.C.; Berggren, M.H.

    1989-05-02

    AMAX Research Development Center (AMAX R D) has been investigating methods for enhancing the reactivity and durability of the zinc ferrite desulfurization sorbent. Zinc ferrite sorbents are intended for use in desulfurization of hot coal gas in integrated gasification combined cycle (IGCC) or molten carbonate fuel cell (MCFC) applications. For the present program, the reactivity of the sorbent may be defined as its sulfur sorption capacity at the breakthrough point and at saturation in a bench-scale, fixed-bed reactor. Durability may be defined as the ability of the sorbent to maintain important physical characteristics such As size, strength, and specific surface area during 10 cycles of sulfidation and oxidation.

  16. Design and synthesis of reactive separation systems. Final report

    SciTech Connect

    Doherty, M.F.

    1992-12-31

    During the last decade there has been a rapid upturn in interest in reactive distillation. The chemical process industry recognizes the favorable economics of carrying out reaction simultaneously with distillation for certain classes of reacting systems, and many new processes have been built based on this technology. Interest is also increasing by academics and software vendors. Systematic design methods for reactive distillation systems have only recently begun to emerge. In this report we survey the available design techniques and point out the contributions made by our group at the University of Massachusetts.

  17. Transport equations for partially ionized reactive plasma in magnetic field

    NASA Astrophysics Data System (ADS)

    Zhdanov, V. M.; Stepanenko, A. A.

    2016-06-01

    Transport equations for partially ionized reactive plasma in magnetic field taking into account the internal degrees of freedom and electronic excitation of plasma particles are derived. As a starting point of analysis the kinetic equation with a binary collision operator written in the Wang-Chang and Uhlenbeck form and with a reactive collision integral allowing for arbitrary chemical reactions is used. The linearized variant of Grad's moment method is applied to deduce the systems of moment equations for plasma and also full and reduced transport equations for plasma species nonequilibrium parameters.

  18. Enhanced durability and reactivity for zinc ferrite desulfurization sorbent

    SciTech Connect

    Jha, M.C.; Berggren, M.H.

    1988-08-19

    AMAX Research Development Center (AMAX R D) has been investigating methods for enhancing the reactivity and durability of the zinc ferrite desulfurization sorbent. Zinc ferrite sorbents are intended for use in desulfurization of hot coal gas in integrated gasification combined cycle (IGCC) or molten carbonate fuel cell (MCFC) applications. For the present program, the reactivity of the sorbent may be defined as its sulfur sorption capacity at the breakthrough point and at saturation in a bench-scale, fixed-bed reactor. Durability may be defined as the ability of the sorbent to maintain important physical characteristics such As size, strength, and specific surface area during 10 cycles of sulfidation and oxidation.

  19. A Gas-Kinetic Scheme for Reactive Flows

    NASA Technical Reports Server (NTRS)

    Lian,Youg-Sheng; Xu, Kun

    1998-01-01

    In this paper, the gas-kinetic BGK scheme for the compressible flow equations is extended to chemical reactive flow. The mass fraction of the unburnt gas is implemented into the gas kinetic equation by assigning a new internal degree of freedom to the particle distribution function. The new variable can be also used to describe fluid trajectory for the nonreactive flows. Due to the gas-kinetic BGK model, the current scheme basically solves the Navier-Stokes chemical reactive flow equations. Numerical tests validate the accuracy and robustness of the current kinetic method.

  20. Plasma & reactive ion etching to prepare ohmic contacts

    SciTech Connect

    Gessert, Timothy A.

    2002-01-01

    A method of making a low-resistance electrical contact between a metal and a layer of p-type CdTe surface by plasma etching and reactive ion etching comprising: a) placing a CdS/CdTe layer into a chamber and evacuating said chamber; b) backfilling the chamber with Argon or a reactive gas to a pressure sufficient for plasma ignition; and c) generating plasma ignition by energizing a cathode which is connected to a power supply to enable the plasma to interact argon ions alone or in the presence of a radio-frequency DC self-bias voltage with the p-CdTe surface.

  1. Enhanced durability and reactivity for zinc ferrite desulfurization sorbent

    SciTech Connect

    Jha, M.C.; Berggren, M.H.

    1989-03-06

    AMAX Research Development Center (AMAX R D) has been investigating methods for enhancing the reactivity and durability of the zinc ferrite desulfurization sorbent. Zinc ferrite sorbents are intended for use in desulfurization of hot coal gas in integrated gasification combined cycle (IGCC) or molten carbonate fuel cell (MCFC) applications. For the present program, the reactivity of the sorbent may be defined as its sulfur sorption capacity at the breakthrough point and at saturation in a bench-scale, fixed-bed reactor. Durability may be defined as the ability of the sorbent to maintain important physical characteristics such As size, strength, and specific surface area during 10 cycles of sulfidation and oxidation.

  2. Predictors of Restrictive Reactive Strategy Use in People with Challenging Behaviour

    ERIC Educational Resources Information Center

    Allen, David; Lowe, Kathy; Brophy, Sam; Moore, Kate

    2009-01-01

    Background: Intrusive reactive strategies (physical restraint, emergency medication and seclusion) are frequently used procedures in the management of challenging behaviour. The present study identifies predictors for reactive strategy use in an attempt to more clearly delineate at risk service users. Method: Eight hundred and thirty-nine agencies…

  3. An Experiment with Manifold Purposes: The Chemical Reactivity of Crystal Defects upon Crystal Dissolution.

    ERIC Educational Resources Information Center

    Lazzarini, Annaluisa Fantola; Lazzarini, Ennio

    1983-01-01

    Background information and procedures are provided for an experiment designed to introduce (1) crystal defects and their reactivity upon crystal dissolution; (2) hydrates electron and its reactivity; (3) application of radiochemical method of analysis; and (4) the technique of competitive kinetics. Suggested readings and additional experiments are…

  4. Oscillations and Synchronization in a System of Three Reactively Coupled Oscillators

    NASA Astrophysics Data System (ADS)

    Kuznetsov, Alexander P.; Turukina, Ludmila V.; Chernyshov, Nikolai Yu.; Sedova, Yuliya V.

    We consider a system of three interacting van der Pol oscillators with reactive coupling. Phase equations are derived, using proper order of expansion over the coupling parameter. The dynamics of the system is studied by means of the bifurcation analysis and with the method of Lyapunov exponent charts. Essential and physically meaningful features of the reactive coupling are discussed.

  5. Quick monitoring of pozzolanic reactivity of waste ashes.

    PubMed

    Sinthaworn, Suppachai; Nimityongskul, Pichai

    2009-05-01

    This article proposes a quick method of monitoring for pozzolanic reactivity of waste ashes by investigating the electrical conductivity of the suspension at an elevated temperature. This suspension is obtained by mixing tested pozzolan with an ordinary Portland cement (OPC) solution produced by mixing ordinary Portland cement with water. For comparison, silica fume, metakaolin, rice husk ash and river sand - whose pozzolanic reactivities range from reactive to inert - were used in the experimental investigation. The electrical conductivity of the suspension was continually recorded by using an electrical conductivity meter and stored by using a personal computer for a period of slightly over 1day. The indicative parameters that can be related to pozzolanic reactivity were discussed and analyzed in detail. It was found that it is possible to determine the pozzolanic reactivity of fly ash within 28h by using the proposed technique, as compared to 7 or 28 days for the determination of strength activity index according to ASTM. This technique would help concrete technologists to speedily investigate the quality of fly ash for use as a cement replacement in order to alleviate pollution caused by cement production and solve disposal problems of waste ashes. PMID:19131237

  6. Quantitative reactivity profiling predicts functional cysteines in proteomes

    PubMed Central

    Weerapana, Eranthie; Wang, Chu; Simon, Gabriel M.; Richter, Florian; Khare, Sagar; Dillon, Myles B.D.; Bachovchin, Daniel A.; Mowen, Kerri; Baker, David; Cravatt, Benjamin F.

    2010-01-01

    Cysteine is the most intrinsically nucleophilic amino acid in proteins, where its reactivity is tuned to perform diverse biochemical functions. The absence of a consensus sequence that defines functional cysteines in proteins has hindered their discovery and characterization. Here, we describe a proteomics method to quantitatively profile the intrinsic reactivity of cysteine residues en masse directly in native biological systems. Hyperreactivity was a rare feature among cysteines and found to specify a wide range of activities, including nucleophilic and reductive catalysis and sites of oxidative modification. Hyperreactive cysteines were identified in several proteins of uncharacterized function, including a residue conserved across eukaryotic phylogeny that we show is required for yeast viability and involved in iron-sulfur protein biogenesis. Finally, we demonstrate that quantitative reactivity profiling can also form the basis for screening and functional assignment of cysteines in computationally designed proteins, where it discriminated catalytically active from inactive cysteine hydrolase designs. PMID:21085121

  7. Selective Catalytic Combustion Sensors for Reactive Organic Analysis

    NASA Technical Reports Server (NTRS)

    Innes, W. B.

    1971-01-01

    Sensors involving a vanadia-alumina catalyst bed-thermocouple assembly satisfy requirements for simple, reproducible and rapid continuous analysis or reactive organics. Responses generally increase with temperature to 400 C and increase to a maximum with flow rate/catalyst volume. Selectivity decreases with temperature. Response time decreases with flow rate and increases with catalyst volume. At chosen optimum conditions calculated response which is additive and linear agrees better with photochemical reactivity than other methods for various automotive sources, and response to vehicle exhaust is insensitive to flow rate. Application to measurement of total reactive organics in vehicle exhaust as well as for gas chromatography detection illustrate utility. The approach appears generally applicable to high thermal effect reactions involving first order kinetics.

  8. Apparatus for making environmentally stable reactive alloy powders

    DOEpatents

    Anderson, Iver E.; Lograsso, Barbara K.; Terpstra, Robert L.

    1996-12-31

    Apparatus and method for making powder from a metallic melt by atomizing the melt to form droplets and reacting the droplets downstream of the atomizing location with a reactive gas. The droplets are reacted with the gas at a temperature where a solidified exterior surface is formed thereon and where a protective refractory barrier layer (reaction layer) is formed whose penetration into the droplets is limited by the presence of the solidified surface so as to avoid selective reduction of key reactive alloyants needed to achieve desired powder end use properties. The barrier layer protects the reactive powder particles from environmental constituents such as air and water in the liquid or vapor form during subsequent fabrication of the powder to end-use shapes and during use in the intended service environment.

  9. Apparatus for making environmentally stable reactive alloy powders

    DOEpatents

    Anderson, I.E.; Lograsso, B.K.; Terpstra, R.L.

    1996-12-31

    Apparatus and method are disclosed for making powder from a metallic melt by atomizing the melt to form droplets and reacting the droplets downstream of the atomizing location with a reactive gas. The droplets are reacted with the gas at a temperature where a solidified exterior surface is formed thereon and where a protective refractory barrier layer (reaction layer) is formed whose penetration into the droplets is limited by the presence of the solidified surface so as to avoid selective reduction of key reactive alloyants needed to achieve desired powder end use properties. The barrier layer protects the reactive powder particles from environmental constituents such as air and water in the liquid or vapor form during subsequent fabrication of the powder to end-use shapes and during use in the intended service environment. 7 figs.

  10. Integrating planning and reactive control

    NASA Astrophysics Data System (ADS)

    Wilkins, David E.; Myers, Karen L.

    1994-10-01

    Our research is developing persistent agents that can achieve complex tasks in dynamic and uncertain environments. We refer to such agents as taskable, reactive agents. An agent of this type requires a number of capabilities. The ability to execute complex tasks necessitates the use of strategic plans for accomplishing tasks; hence, the agent must be able to synthesize new plans at run time. The dynamic nature of the environment requires that the agent be able to deal with unpredictable changes in its world. As such, agents must be able to react to unanticipated events by taking appropriate actions in a timely manner, while continuing activities that support current goals. The unpredictability of the world could lead to failure of plans generated for individual tasks. Agents must have the ability to recover from failures by adapting their activities to the new situation, or replanning if the world changes sufficiently. Finally, the agent should be able to perform in the face of uncertainty. The Cypress system, described here, provides a framework for creating taskable, reactive agents. Several features distinguish our approach: (1) the generation and execution of complex plans with parallel actions; (2) the integration of goal-driven and event driven activities during execution; (3) the use of evidential reasoning for dealing with uncertainty; and (4) the use of replanning to handle run-time execution problems. Our model for a taskable, reactive agent has two main intelligent components, an executor and a planner. The two components share a library of possible actions that the system can take. The library encompasses a full range of action representations, including plans, planning operators, and executable procedures such as predefined standard operating procedures (SOP's). These three classes of actions span multiple levels of abstraction.

  11. Integrating planning and reactive control

    NASA Technical Reports Server (NTRS)

    Wilkins, David E.; Myers, Karen L.

    1994-01-01

    Our research is developing persistent agents that can achieve complex tasks in dynamic and uncertain environments. We refer to such agents as taskable, reactive agents. An agent of this type requires a number of capabilities. The ability to execute complex tasks necessitates the use of strategic plans for accomplishing tasks; hence, the agent must be able to synthesize new plans at run time. The dynamic nature of the environment requires that the agent be able to deal with unpredictable changes in its world. As such, agents must be able to react to unanticipated events by taking appropriate actions in a timely manner, while continuing activities that support current goals. The unpredictability of the world could lead to failure of plans generated for individual tasks. Agents must have the ability to recover from failures by adapting their activities to the new situation, or replanning if the world changes sufficiently. Finally, the agent should be able to perform in the face of uncertainty. The Cypress system, described here, provides a framework for creating taskable, reactive agents. Several features distinguish our approach: (1) the generation and execution of complex plans with parallel actions; (2) the integration of goal-driven and event driven activities during execution; (3) the use of evidential reasoning for dealing with uncertainty; and (4) the use of replanning to handle run-time execution problems. Our model for a taskable, reactive agent has two main intelligent components, an executor and a planner. The two components share a library of possible actions that the system can take. The library encompasses a full range of action representations, including plans, planning operators, and executable procedures such as predefined standard operating procedures (SOP's). These three classes of actions span multiple levels of abstraction.

  12. Derivatization of isothiocyanates and their reactive adducts for chromatographic analysis.

    PubMed

    Agerbirk, Niels; De Nicola, Gina Rosalinda; Olsen, Carl Erik; Müller, Caroline; Iori, Renato

    2015-10-01

    Isothiocyanates form adducts with a multitude of biomolecules, and these adducts need analytical methods. Likewise, analytical methods for hydrophilic isothiocyanates are needed. We considered reaction with ammonia to form thiourea derivatives. The hydrophilic, glycosylated isothiocyanate moringin, 4-(α-L-rhamnopyranosyloxy)benzyl isothiocyanate, was efficiently derivatized to the thiourea derivative by incubation with ammonia. The hydrophobic benzyl isothiocyanate was also efficiently derivatized to the thiourea derivative. The thiourea group provided a UV absorbing chromophore, and the derivatives showed expectable sodium and hydrogen adducts in ion trap mass spectrometry and were suitable for liquid chromatography analysis. Reactive dithiocarbamate adducts constitute the major type of reactive ITC adduct expected in biological matrices. Incubation of a model dithiocarbamate with ammonia likewise resulted in conversion to the corresponding thiourea derivative, suggesting that a variety of matrix-bound reactive isothiocyanate adducts can be determined using this strategy. As an example of the application of the method, recovery of moringin and benzyl isothiocyanate applied to cabbage leaf discs was studied in simulated insect feeding assays. The majority of moringin was recovered as native isothiocyanate, but a major part of benzyl isothiocyanate was converted to reactive adducts. PMID:26342619

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

    NASA Astrophysics Data System (ADS)

    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.

  14. Enhanced reactivity of mechanically-activated nano-scale gasless reactive materials consolidated via the cold-spray technique

    NASA Astrophysics Data System (ADS)

    Bacciochini, Antoine; Radulescu, Matei; Meydanoglu, Onur; Charron-Tousignant, Yannick; van Dyke, Jason; Jodoin, Bertrand; Nganbe, Michel; Yandouzi, Mohamed; Lee, Julian J.

    2011-06-01

    It has been speculated that gasless reactive systems can sustain supersonic detonations waves, provided the local decomposition rate is sufficiently fast and the initial density is sufficiently close to the theoretical maximal density. The present study presents a novel method to prepare nano-scale energetic materials with high reactivity, vanishing porosity, structural integrity and arbitrary shape. The experiments have focused on the Ni-Al system. To increase the reactivity, an initial mechanical activation was achieved by the technique of ball milling. The consolidation of the materials used the supersonic cold gas spray technique, where the particles are accelerated to high speeds and consolidated via plastic deformation upon impact, forming activated nano-composites in arbitrary shapes with close to zero porosity. This technique permits to retain the micro-structures in the powders and prevents any reactions during the consolidation phase. Deflagration tests of the obtained samples showed an increase in the deflagration rate by up to two orders of magnitude.

  15. Fluoropolymer and aluminum piezoelectric reactives

    NASA Astrophysics Data System (ADS)

    Janesheski, Robert S.; Groven, Lori J.; Son, Steven

    2012-03-01

    The ability to sensitize a nanoaluminum/piezoelectric polymer composite has been studied using two fluoropolymer systems (THV220A and FC-2175). Reactive composite samples of the nanoaluminum/polymer were made into thin sheets and their ability to store energy and exhibit piezoelectric properties was measured. Also, initial drop weight impact tests were performed on the samples and results showed the piezoelectric energetic composites failed to ignite at a given impact energy unless sensitized. When a DC voltage was applied to the sample, the materials ignited at the same impact energy where previous ignition failed. Results indicate that the reactive composites may have been sensitized by storing the applied charge. The application of a DC voltage may also have an effect on the piezoelectric properties of the energetic composites similar to the way poling techniques work. Further work is planned to investigate what parameters are inducing the sensitization of the material. A better understanding could lead to applications where switching or tuning the sensitization of an energetic material is beneficial.

  16. Relationship Between Reactive Agility and Change of Direction Speed in Amateur Soccer Players.

    PubMed

    Matlák, János; Tihanyi, József; Rácz, Levente

    2016-06-01

    Matlák, J, Tihanyi, J, and Rácz, L. Relationship between reactive agility and change of direction speed in amateur soccer players. J Strength Cond Res 30(6): 1547-1552, 2016-The aim of the study was to assess the relationship between reactive agility and change of direction speed (CODS) among amateur soccer players using running tests with four directional changes. Sixteen amateur soccer players (24.1 ± 3.3 years; 72.4 ± 7.3 kg; 178.7 ± 6 cm) completed CODS and reactive agility tests with four changes of direction using the SpeedCourt™ system (Globalspeed GmbH, Hemsbach, Germany). Countermovement jump (CMJ) height and maximal foot tapping count (completed in 3 seconds) were also measured with the same device. In the reactive agility test, participants had to react to a series of light stimuli projected onto a screen. Total time was shorter in the CODS test than in the reactive agility test (p < 0.001). Nonsignificant correlations were found among variables measured in the CODS, reactive agility, and CMJ tests. Low common variance (r = 0.03-0.18) was found between CODS and reactive agility test variables. The results of this study underscore the importance of cognitive factors in reactive agility performance and suggest that specific methods may be required for training and testing reactive agility and CODS. PMID:26562713

  17. Phenylethynyl endcapping reagents and reactive diluents

    NASA Technical Reports Server (NTRS)

    Jensen, Brian J. (Inventor); Bryant, Robert G. (Inventor); Hergenrother, Paul M. (Inventor)

    1994-01-01

    A phenylethynyl composition which can be used to endcap nucleophilic species is employed in the production of phenylethynyl terminated reactive oligomers exclusively. These phenylethynyl terminated reactive oligomers display unique thermal characteristics, as exemplified by the model compound, 4-phenoxy 4'-phenylethynylbenzophenone, which is relatively stable at 200 C, but reacts at 350 C. In addition, a reactive diluent was prepared which decreases the melt viscosity of the phenylethynyl terminated oligomers and subsequently reacts therewith to increase density of the resulting thermoset. The novelty of this invention resides in the phenylethynyl composition used to terminate a nucleophilic reagent, resulting in the exclusive production of phenylethynyl terminated reactive oligomers which display unique thermal characteristics. A reactive diluent was also employed to decrease the melt viscosity of a phenylethynyl terminated reactive oligomer and to subsequently react therewith to increase the crosslink density of the resulting thermoset. These materials have features which make them attractive candidates for use as composite matrices and adhesives.

  18. Determination of Reactive Surface Area of Melt Glass

    SciTech Connect

    Bourcier,W.L.; Roberts, S.; Smith, D.K.; Hulsey, S.; Newton,L.; Sawvel, A.; Bruton, C.; Papelis, C.; Um, W.; Russell, C. E.; Chapman,J.

    2000-10-01

    A comprehensive investigation of natural and manmade silicate glasses, and nuclear melt glass was undertaken in order to derive an estimate of glass reactive surface area. Reactive surface area is needed to model release rates of radionuclides from nuclear melt glass in the subsurface. Because of the limited availability of nuclear melt glasses, natural volcanic glass samples were collected which had similar textures and compositions as those of melt glass. A flow-through reactor was used to measure the reactive surface area of the analog glasses in the presence of simplified NTS site ground waters. A measure of the physical surface area of these glasses was obtained using the BET gas-adsorption method. The studies on analog glasses were supplemented by measurement of the surface areas of pieces of actual melt glass using the BET method. The variability of the results reflect the sample preparation and measurement techniques used, as well as textural heterogeneity inherent to these samples. Based on measurements of analog and actual samples, it is recommended that the hydraulic source term calculations employ a range of 0.001 to 0.01 m{sup 2}/g for the reactive surface area of nuclear melt glass.

  19. Modeling Fe0 permeable reactive barriers for groundwater remediation

    NASA Astrophysics Data System (ADS)

    Carniato, Luca; Schoups, Gerrit; Seuntjens, Piet; Bastiaens, Leen

    2010-05-01

    Remediation of groundwater pollution has traditionally been achieved by energy-intensive and drastic methods such as pump and treat (P&T) systems. Recently, more economically viable and less invasive methods such as permeable reactive barriers have been used to clean up a wide variety of groundwater pollutants (volatile organic compounds, VOCl). Permeable reactive barriers are installed in the subsurface and the naturally present hydraulic gradient makes the groundwater flow through the barrier where the contaminants are removed by different removal processes (biodegradation, sorption, precipitation, chemical destruction). Effective application of these techniques requires a solid understanding of the site-specific hydrogeological and biochemical conditions, as well as a predictive assessment of long-term remediation efficiency. For example, secondary mineral precipitation has been shown to reduce reactivity and efficiency of permeable reactive barriers and the interactions between biological and chemical processes may also influence the long-term efficiency of such systems. In this study a multi-component transport model based on PHAST USGS has been developed to simulate the removal processes in the barrier and to make quantitative predictions about the long-term efficiency of the system. In particular the modelling approach will be presented together with the model application in lab-scale experiments and in field.

  20. Attributional bias and reactive aggression.

    PubMed

    Hudley, C; Friday, J

    1996-01-01

    This article looks at a cognitive behavioral intervention designed to reduce minority youths' (Latino and African-American boys) levels of reactive peer-directed aggression. The BrainPower Program trains aggressive boys to recognize accidental causation in ambiguous interactions with peers. The objective of this research is to evaluate the effectiveness of this attribution retraining program in reducing levels of reactive, peer-directed aggression. This research hypothesizes that aggressive young boys' tendency to attribute hostile intentions to others in ambiguous social interactions causes display of inappropriate, peer-directed aggression. A reduction in attributional bias should produce a decrease in reactive physical and verbal aggression directed toward peers. A 12-session, attributional intervention has been designed to reduce aggressive students' tendency to infer hostile intentions in peers following ambiguous peer provocations. The program trains boys to (1) accurately perceive and categorize the available social cues in interactions with peers, (2) attribute negative outcomes of ambiguous causality to accidental or uncontrollable causes, and (3) generate behaviors appropriate to these retrained attributions. African-American and Latino male elementary-school students (N = 384), in grades four-six, served as subjects in one of three groups: experimental attribution retraining program, attention training, and no-attention control group. Three broad categories of outcome data were collected: teacher and administrator reports of behavior, independent observations of behavior, and self-reports from participating students. Process measures to assess implementation fidelity include videotaped training sessions, observations of intervention sessions, student attendance records, and weekly team meetings. The baseline data indicated that students who were evenly distributed across the four sites were not significantly different on the baseline indicators: student

  1. Evaluation of incremental reactivity and its uncertainty in Southern California.

    PubMed

    Martien, Philip T; Harley, Robert A; Milford, Jana B; Russell, Armistead G

    2003-04-15

    The incremental reactivity (IR) and relative incremental reactivity (RIR) of carbon monoxide and 30 individual volatile organic compounds (VOC) were estimated for the South Coast Air Basin using two photochemical air quality models: a 3-D, grid-based model and a vertically resolved trajectory model. Both models include an extended version of the SAPRC99 chemical mechanism. For the 3-D modeling, the decoupled direct method (DDM-3D) was used to assess reactivities. The trajectory model was applied to estimate uncertainties in reactivities due to uncertainties in chemical rate parameters, deposition parameters, and emission rates using Monte Carlo analysis with Latin hypercube sampling. For most VOC, RIRs were found to be consistent in rankings with those produced by Carter using a box model. However, 3-D simulations show that coastal regions, upwind of most of the emissions, have comparatively low IR but higher RIR than predicted by box models for C4-C5 alkenes and carbonyls that initiate the production of HOx radicals. Biogenic VOC emissions were found to have a lower RIR than predicted by box model estimates, because emissions of these VOC were mostly downwind of the areas of primary ozone production. Uncertainties in RIR of individual VOC were found to be dominated by uncertainties in the rate parameters of their primary oxidation reactions. The coefficient of variation (COV) of most RIR values ranged from 20% to 30%, whereas the COV of absolute incremental reactivity ranged from about 30% to 40%. In general, uncertainty and variability both decreased when relative rather than absolute reactivity metrics were used. PMID:12731843

  2. Monitoring microvascular reactivity in dental subjects.

    PubMed

    Roth, G I; Matheny, J L; Gonty, A A; Paterson, R L

    1980-01-01

    In this section of a larger study, a system for monitoring changes in the microcirculation, in humans in the dental setting, is described. The technique involves clinical nailfold capillary photomicroscopy and electronic image-scan measurements. The system was tested using reactive hyperemia after vascular occlusion; it proved reliable and sufficiently sensitive for measuring vascular reactivity in humans. (In a subsequent paper, clinical findings relative to the use of this technique with patients undergoing nitrous oxide/oxygen anesthesia will be presented).The importance of the microcirculation for the integrity of the tissues cannot be overemphasized. Since the term "microcirculation" can be defined as the microscopic subdivisions of the vascular system that lie within the tissue proper and are exposed to its immediate environment,(1) it is evident that most of the exchange of nutrients and waste products occuring in the tissue will occur at this level. Furthermore, the adequacy of tissue perfusion during drug administration, or during and after anesthesia, is dependent on the adequacy and reactivity of this subdivision of the vascular system.(2)A basic prerequisite to the understanding of microcirculatory function in a given vascular bed is the precise quantitation of dimensional changes in those vessels(3). Dynamic measurements in vivo are required, since it is difficult, if not impossible, to ensure that the dimensions obtained from fixed tissue specimens are accurate measures of those occurring in the living state. This is especially true where vessel dimensions are rapidly changing in response to endogenous or exogenous influences. Unfortunately the task of in vivo measurement of microvascular dimensions is difficult in most microcirculatory beds. Since the vessels are an integral part of a threedimensional structure,(4) the tasks of visualizing, isolating and measuring the vessels are formidable. These difficulties are compounded if the particular vessels

  3. Surface Sites in Cu-Nanoparticles: Chemical Reactivity or Microscopy?

    PubMed

    Larmier, Kim; Tada, Shohei; Comas-Vives, Aleix; Copéret, Christophe

    2016-08-18

    Copper nanoparticles are widely used in catalysis and electrocatalysis, and the fundamental understanding of their activity requires reliable methods to assess the number of potentially reactive atoms exposed on the surface. Herein, we provide a molecular understanding of the difference observed in addressing surface site titration using prototypical methods: transmission electron micrscopy (TEM), H2 chemisorption, and N2O titration by a combination of experimental and theoretical study. We show in particular that microscopy does not allow assessing the amount of reactive surface sites, while H2 and N2O chemisorptions can, albeit with slightly different stoichiometries (1 O/2CuS and 1 H2/2.2CuS), which can be rationalized by density functional theory calculations. High-resolution TEM shows that the origin of the observed difference between microscopy and titration methods is due to the strong metal support interaction experienced by small copper nanoparticles with the silica surface. PMID:27490121

  4. Automatic Processing of Reactive Polymers

    NASA Technical Reports Server (NTRS)

    Roylance, D.

    1985-01-01

    A series of process modeling computer codes were examined. The codes use finite element techniques to determine the time-dependent process parameters operative during nonisothermal reactive flows such as can occur in reaction injection molding or composites fabrication. The use of these analytical codes to perform experimental control functions is examined; since the models can determine the state of all variables everywhere in the system, they can be used in a manner similar to currently available experimental probes. A small but well instrumented reaction vessel in which fiber-reinforced plaques are cured using computer control and data acquisition was used. The finite element codes were also extended to treat this particular process.

  5. Reactivity Studies on a Diazadiphosphapentalene.

    PubMed

    Cui, Jingjing; Li, Yongxin; Ganguly, Rakesh; Kinjo, Rei

    2016-07-11

    The reactivity of diazadiphosphapentalene 1 towards various substrates was investigated. Reaction of 1 with ammonia-borane resulted in transfer hydrogenolysis concomitantly with the cleavage of a P-N bond. By treatment of 1 with 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO), oxidation took place at one of the phosphorus atoms of 1, and a P(V) /P(III) mixed-valence derivative was isolated. At the same time, it was demonstrated that only one of the phosphorus atoms in 1 behaves as an electron donor for electrophiles and Lewis acids. The former afforded an intramolecularly coordinated phosphine-phosphenium species, whereas the latter demonstrates the ligand property of 1. UV irradiation induced rearrangement of 1 into another example of another diazadiphosphapentalene. PMID:27283866

  6. Reactivation tuberculosis: role of surveillance.

    PubMed

    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

  7. Regulatory Analysis of Reactivity Transients

    SciTech Connect

    Beyer, Carl E.; Clifford, Paul M.; Geelhood, Kenneth J.; Voglewede, John C.

    2009-08-01

    This paper will describe modifications made to the FRAPCON-3 and FRAPTRAN fuel performance codes and models that impact reactivity initiated accident (RIA) analyses. The modified models include an upper bound empirical and best estimate release models for fast transients, and a revised fuel failure model that accounts for ductile and brittle failure. Because experimental data exists for discrete test conditions, the codes and models are used to interpolate and to some extent, to extrapolate these test conditions. An upper bound empirical model for release is used to establish new recommended release fractions for long-lived and short lived (radioactive) isotopes for RIA events in Regulatory Guide 1.183. A best estimate release model is used in FRAPTRAN 1.4 based on grain boundary gas concentrations from FRAPCON-3.4 to predict release for RIA events. Code and model predictions will be compared to failure and release data from RIA tests to demonstrate accuracy.

  8. Buckybomb: Reactive Molecular Dynamics Simulation.

    PubMed

    Chaban, Vitaly V; Fileti, Eudes Eterno; Prezhdo, Oleg V

    2015-03-01

    Energetic materials, such as explosives, propellants, and pyrotechnics, are widely used in civilian and military applications. Nanoscale explosives represent a special group because of the high density of energetic covalent bonds. The reactive molecular dynamics (ReaxFF) study of nitrofullerene decomposition reported here provides a detailed chemical mechanism of explosion of a nanoscale carbon material. Upon initial heating, C60(NO2)12 disintegrates, increasing temperature and pressure by thousands of Kelvins and bars within tens of picoseconds. The explosion starts with NO2 group isomerization into C-O-N-O, followed by emission of NO molecules and formation of CO groups on the buckyball surface. NO oxidizes into NO2, and C60 falls apart, liberating CO2. At the highest temperatures, CO2 gives rise to diatomic carbon. The study shows that the initiation temperature and released energy depend strongly on the chemical composition and density of the material. PMID:26262672

  9. Immune reactivity to food coloring.

    PubMed

    Vojdani, Aristo; Vojdani, Charlene

    2015-01-01

    Artificial food dyes are made from petroleum and have been approved by the US Food and Drug Administration (FDA) for the enhancement of the color of processed foods. They are widely used in the food and pharmaceutical industries to increase the appeal and acceptability of their products. Synthetic food colorants can achieve hues not possible for natural colorants and are cheaper, more easily available, and last longer. However, since the use of artificial food coloring has become widespread, many allergic and other immune reactive disorders have increasingly been reported. During the past 50 y, the amount of synthetic dye used in foods has increased by 500%. Simultaneously, an alarming rise has occurred in behavioral problems in children, such as aggression, attention deficit disorder (ADD), and attention-deficit/hyperactivity disorder (ADHD). The ingestion of food delivers the greatest foreign antigenic load that challenges the immune system. Artificial colors can also be absorbed via the skin through cosmetic and pharmaceutical products. The molecules of synthetic colorants are small, and the immune system finds it difficult to defend the body against them. They can also bond to food or body proteins and, thus, are able to act in stealth mode to circumvent and disrupt the immune system. The consumption of synthetic food colors, and their ability to bind with body proteins, can have significant immunological consequences. This consumption can activate the inflammatory cascade, can result in the induction of intestinal permeability to large antigenic molecules, and could lead to cross-reactivities, autoimmunities, and even neurobehavioral disorders. The Centers for Disease Control (CDC) recently found a 41% increase in diagnoses of ADHD in boys of high-school age during the past decade. More shocking is the legal amount of artificial colorants allowed by the FDA in the foods, drugs, and cosmetics that we consume and use every day. The consuming public is largely

  10. Sodium doping and reactivity in pure and mixed ice nanoparticles*

    NASA Astrophysics Data System (ADS)

    Lengyel, Jozef; Pysanenko, Andriy; Rubovič, Peter; Fárník, Michal

    2015-12-01

    Doping of clusters by sodium atoms and subsequent photoionization (NaPI) is used as a fragmentation-free cluster ionization method. Here we investigate different clusters using NaPI and electron ionization (EI) with a reflectron time-of-flight mass spectrometer (RTOF). The mass spectra of the same clusters ionized by NaPI and EI reveal significant differences which point to Na reactivity in the clusters. First, we discuss mixed X M ·(H2O) N (X = HNO3, N2O) clusters where reactions between Na and molecules X leads to the "cluster invisibility" for the NaPI method. Second, mixed (NH3) M ·(H2O) N clusters are observed by both methods, but they reveal different cluster compositions, and the mass spectra suggest that neither the EI nor the NaPI spectrum corresponds exactly to the neutral cluster distribution. Finally, we discuss the reactions of Na in pure water clusters as a function of the number of Na atoms doped into the clusters. In summary, we present experimental evidence that the NaPI method in the present cases does not reveal the size and composition of the neutral clusters. A detailed understanding of Na reactivity in the clusters is needed for its application as a fragmentation-free cluster ionization method. Besides, we introduce the combination of NaPI and EI as a new tool to investigate the sodium reactivity in clusters and aerosol particles.

  11. Capturing a Reactive State of Amyloid Aggregates

    PubMed Central

    Parthasarathy, Sudhakar; Yoo, Brian; McElheny, Dan; Tay, William; Ishii, Yoshitaka

    2014-01-01

    The interaction of redox-active copper ions with misfolded amyloid β (Aβ) is linked to production of reactive oxygen species (ROS), which has been associated with oxidative stress and neuronal damages in Alzheimer disease. Despite intensive studies, it is still not conclusive how the interaction of Cu+/Cu2+ with Aβ aggregates leads to ROS production even at the in vitro level. In this study, we examined the interaction between Cu+/Cu2+ and Aβ fibrils by solid-state NMR (SSNMR) and other spectroscopic methods. Our photometric studies confirmed the production of ∼60 μm hydrogen peroxide (H2O2) from a solution of 20 μm Cu2+ ions in complex with Aβ(1–40) in fibrils ([Cu2+]/[Aβ] = 0.4) within 2 h of incubation after addition of biological reducing agent ascorbate at the physiological concentration (∼1 mm). Furthermore, SSNMR 1H T1 measurements demonstrated that during ROS production the conversion of paramagnetic Cu2+ into diamagnetic Cu+ occurs while the reactive Cu+ ions remain bound to the amyloid fibrils. The results also suggest that O2 is required for rapid recycling of Cu+ bound to Aβ back to Cu2+, which allows for continuous production of H2O2. Both 13C and 15N SSNMR results show that Cu+ coordinates to Aβ(1–40) fibrils primarily through the side chain Nδ of both His-13 and His-14, suggesting major rearrangements from the Cu2+ coordination via Nϵ in the redox cycle. 13C SSNMR chemical shift analysis suggests that the overall Aβ conformations are largely unaffected by Cu+ binding. These results present crucial site-specific evidence of how the full-length Aβ in amyloid fibrils offers catalytic Cu+ centers. PMID:24523414

  12. Investigation of ambient OH reactivity at a receptor site impacted by industrial, urban and marine emissions: Identification of missing OH reactivity

    NASA Astrophysics Data System (ADS)

    Dusanter, Sébastien; Michoud, Vincent; Léonardis, Thierry; Locoge, Nadine; Riffault, Véronique; Zhang, Shouwen

    2015-04-01

    The hydroxyl radical (OH), the main daytime oxidant in the troposphere, plays a key role in atmospheric chemistry. OH initiates the oxidation of most of the trace gases, including Volatile Organic Compounds (VOC), leading to the formation of harmful secondary pollutants such as ozone and secondary organic aerosols. VOCs are directly emitted by a large number of natural and anthropogenic sources and can be formed photochemically. It is expected that several thousand VOCs could be present in the troposphere at ppt-ppb levels (Goldstein and Galbally, ES&T, 2007), making exhaustive measurements of VOCs currently unfeasible with common analytical techniques. In this context, measuring the total sink of OH, so called total OH reactivity, can provide insights into the reactivity of unmeasured trace gases to test the completeness of VOC measurements during field campaigns. A Comparative Reactivity Method (CRM) instrument was deployed in Dunkirk (France) to measure ambient OH reactivity during July 2014. An objective of this field campaign was to investigate the OH reactivity budget in different types of air masses, characterized by industrial, urban, and marine emissions, as well as different photochemical ages. Collocated measurements of non-methane hydrocarbons, oxygenated VOCs, and inorganic gases were also performed. OH reactivity measurements ranged from the detection limit of 3 s-1 up to 90 s-1, with a campaign average of approximately 14 s-1. Large discrepancies were observed between OH reactivity measurements and values calculated from measured trace gases, highlighting the presence of unmeasured reactive compounds. In this presentation, the measured and missing OH reactivity will be discussed regarding air mass origins and compositions. We will also present a novel approach that was implemented on the CRM instrument to identify part of the observed missing OH reactivity.

  13. Differentiating Challenge Reactivity from Psychomotor Activity in Studies of Children’s Psychophysiology: Considerations for Theory and Measurement

    PubMed Central

    Bush, Nicole R.; Alkon, Abbey; Obradović, Jelena; Stamperdahl, Juliet; Boyce, W. Thomas

    2014-01-01

    Current methods of assessing children’s physiologic “stress reactivity” may be confounded by psychomotor activity, biasing estimates of the relation between reactivity and health. We examine the joint and independent contributions of psychomotor activity and challenge reactivity during a protocol for children ages 5–6 (N=338). Measures of parasympathetic (RSA) and sympathetic (PEP) reactivity were calculated for social, cognitive, sensory, and emotional challenge tasks. Reactivity was calculated relative to both resting and a paired comparison task that accounted for psychomotor activity effects during each challenge. Results indicated that comparison tasks themselves elicited RSA and PEP responses, and reactivity adjusted for psychomotor activity was incongruent with reactivity calculated using rest. Findings demonstrate the importance of accounting for confounding psychomotor activity effects on physiologic reactivity. PMID:21524757

  14. Systems and methods for forming defects on graphitic materials and curing radiation-damaged graphitic materials

    DOEpatents

    Ryu, Sunmin; Brus, Louis E.; Steigerwald, Michael L.; Liu, Haitao

    2012-09-25

    Systems and methods are disclosed herein for forming defects on graphitic materials. The methods for forming defects include applying a radiation reactive material on a graphitic material, irradiating the applied radiation reactive material to produce a reactive species, and permitting the reactive species to react with the graphitic material to form defects. Additionally, disclosed are methods for removing defects on graphitic materials.

  15. Microstructure-reactivity relationship of Ti + C reactive nanomaterials

    NASA Astrophysics Data System (ADS)

    Manukyan, Khachatur V.; Lin, Ya-Cheng; Rouvimov, Sergei; McGinn, Paul J.; Mukasyan, Alexander S.

    2013-01-01

    The influence of short-term (≤10 min) high energy ball milling (HEBM) on the microstructure and reactivity of a titanium-carbon powder mixture is reported. It is proved that the mechanism of microstructural transformation in a Ti-C mixture during HEBM defines the reaction mechanism in the produced Ti/C structural energetic materials. More specifically, it is shown that after the first two minutes of dry milling (DM) in an inert (argon) atmosphere the initially crystalline graphite flakes were almost completely amorphized and uniformly distributed on the surface of the deformed titanium particles. A subsequent "cold-welding" leads to formation of Ti-(C-rich/Ti)-Ti agglomerates. TEM studies reveal that the (C-rich/Ti) composite layers consist of nano-size (20 nm) Ti particles distributed in the matrix of the amorphous carbon and thus are characterized by extremely high surface area contacts between the reagents. A rapid self-ignition of the material during DM occurs just after 9.5 min of mechanical treatment, resulting in formation of pure cubic TiC. Wet grinding (WG) of a Ti-C mixture in hexane, under otherwise identical parameters, provides more "soft" conditions, which do not allow the rapid amorphization of carbon during the first stage of grinding. As a result graphite and titanium form sandwich-like Ti/C composite particles, in which the reagents contact primarily along the boundaries of the layers. Such particles gradually transform to the TiC phase without a spontaneous reaction during the HEBM process. The reactivity, i.e., self-ignition temperature and ignition delay time, of different milling-induced microstructures, were also studied. It was found that the ignition temperature in Ti-C structural energetic material prepared under optimized HEBM conditions is ˜600 K, which is more than three times lower than that of the initial reaction mixture (Tig ˜ 1900 K). A significant decrease of the effective activation energy for interaction in the Ti-C system

  16. Seasonal measurements of total OH reactivity emission rates from Norway spruce in 2011

    NASA Astrophysics Data System (ADS)

    Nölscher, A. C.; Bourtsoukidis, E.; Bonn, B.; Kesselmeier, J.; Lelieveld, J.; Williams, J.

    2013-06-01

    Numerous reactive volatile organic compounds (VOCs) are emitted into the atmosphere by vegetation. Most biogenic VOCs are highly reactive towards the atmosphere's most important oxidant, the hydroxyl (OH) radical. One way to investigate the chemical interplay between biosphere and atmosphere is through the measurement of total OH reactivity, the total loss rate of OH radicals. This study presents the first determination of total OH reactivity emission rates (measurements via the comparative reactivity method) based on a branch cuvette enclosure system mounted on a Norway spruce (Picea abies) throughout spring, summer and autumn 2011. In parallel VOC emission rates were monitored by a second proton-transfer-reaction mass spectrometer (PTR-MS), and total ozone (O3) loss rates were obtained inside the cuvette. Total OH reactivity emission rates were in general temperature and light dependent, showing strong diel cycles with highest values during daytime. Monoterpene emissions contributed most, accounting for 56-69% of the measured total OH reactivity flux in spring and early summer. However, during late summer and autumn the monoterpene contribution decreased to 11-16%. At this time, a large missing fraction of the total OH reactivity emission rate (70-84%) was found when compared to the VOC budget measured by PTR-MS. Total OH reactivity and missing total OH reactivity emission rates reached maximum values in late summer corresponding to the period of highest temperature. Total O3 loss rates within the closed cuvette showed similar diel profiles and comparable seasonality to the total OH reactivity fluxes. Total OH reactivity fluxes were also compared to emissions from needle storage pools predicted by a temperature-only-dependent algorithm. Deviations of total OH reactivity fluxes from the temperature-only-dependent emission algorithm were observed for occasions of mechanical and heat stress. While for mechanical stress, induced by strong wind, measured VOCs could

  17. PERFORMANCE OF PERMEABLE REACTIVE BARRIER AT U.S. COAST GUARD SITE, ELIZABETH CITY, NC

    EPA Science Inventory

    Permeable reactive barriers are innovative and cost-effective remedial technologies and are becoming more desirable methods for in-situ passive remediation of ground water contaminated with chlorinated hydrocarbons and redox-sensitive metals. As contaminated water passes through ...

  18. Geophysical Characterization and Reactive Transport Modeling to Quantify Plume Behavior

    NASA Astrophysics Data System (ADS)

    Hubbard, S. S.; Wainwright, H.; Bea, S. A.; Spycher, N.; Li, L.; Sassen, D.; Chen, J.

    2012-12-01

    Predictions of subsurface contaminant plume mobility and remediation often fail due to the inability to tractably characterize heterogeneous flow-and-transport properties and monitor critical geochemical transitions over plume-relevant scales. This study presents two recently developed strategies to quantify and predict states and processes across scales that govern plume behavior. Development of both strategies takes advantage of multi-scale and disparate datasets and has involved the use of reactive transport models, geophysical methods, and stochastic integration approaches. The first approach, called reactive facies, exploits coupled physiochemical heterogeneity to characterize subsurface flow and transport properties that impact plume sorption and thus mobility. We develop and test the reactive facies concept within uranium contaminated Atlantic Coastal Plain sediments that underlie the U.S. Department of Energy Savannah River Site, F-Area, South Carolina. Through analysis of field data (core samples, geophysical well logs, and cross-hole ground penetrating radar and seismic datasets) coupled with laboratory sorption studies, we have identified two reactive facies that have unique distributions of mineralogy, texture, porosity, hydraulic conductivity and geophysical attributes. We develop and use facies-based relationships with geophysical data in a Bayesian framework to spatially distribute reactive facies and their associated transport properties and uncertainties along local and plume-scale geophysical transects. To illustrate the value of reactive facies, we used the geophysically-obtained reactive facies properties to parameterize reactive transport models and simulate the migration of an acidic-U(VI) plume through the 2D domains. Modeling results suggest that each identified reactive facies exerts control on plume evolution, highlighting the usefulness of the reactive facies concept and approach for spatially distributing properties that control flow and

  19. Effects of Processing Parameters on the Synthesis of (K0.5Na0.5)NbO3 Nanopowders by Reactive High-Energy Ball Milling Method

    PubMed Central

    Duc Van, Nguyen

    2014-01-01

    The effects of ball milling parameters, namely, the ball-to-powder mass ratio and milling speed, on the synthesis of (K0.5Na0.5)NbO3 nanopowders by high-energy ball milling method from a stoichiometric mixture containing Na2CO3, K2CO3, and Nb2O5 were investigated in this paper. The results indicated that the single crystalline phase of (K0.5Na0.5)NbO3 was received in as-milled samples synthesized using optimized ball-to-powder mass ratio of 35 : 1 and at a milling speed of 600 rpm for 5 h. In the optimized as-milled samples, no remaining alkali carbonates that can provide the volatilizable potassium-containing species were found and (K0.5Na0.5)NbO3 nanopowders were readily obtained via the formation of an intermediate carbonato complex. This complex was mostly transformed into (K0.5Na0.5)NbO3 at temperature as low as 350°C and its existence was no longer detected at spectroscopic level when calcination temperature crossed over 700°C. PMID:24592146

  20. Experimental and Numerical Investigation of Reactive and Dissipative Mufflers

    NASA Astrophysics Data System (ADS)

    Mohanty, Amiya Ranjan

    In this research both experimental and numerical investigations are carried out for passive mufflers. These mufflers, both reactive and dissipative, can be used in automotive applications. The reactive mufflers have perforates, baffles, flow plugs and extended inlet/outlet tubes, whereas the dissipative mufflers have sound absorbing materials. A multi-domain boundary element method is used as a numerical technique for modeling such mufflers and predicting their transmission loss. In reactive mufflers, like the concentric resonators and plug flow mufflers, the transfer impedance across the perforate is incorporated in the multi-domain boundary element model. In dissipative mufflers, the sound absorbing material lining is treated both as bulk as well as locally reacting. To successfully incorporate perforates and sound absorbing materials in the boundary element models, experiments are conducted to determine the perforate transfer impedance and the propagation constant, characteristic impedance and surface impedance of the sound absorbing material. To validate the boundary element solution, an analytical one-dimensional solution for a duct with a perforated partition and the transmission loss of a family of reactive and dissipative mufflers are obtained. Various techniques to determine the transmission loss are investigated. One of the techniques, the transfer function method requires the design and fabrication of a perfect anechoic termination of the system, and it is a difficult task. Alternate methods are then investigated, where the transmission loss is computed from the experimentally determined four-pole parameters of the muffler in question. The two-load and the two-source location methods are used to determine the four-pole parameters and then the transmission loss, without the use of an anechoic termination. Excellent agreement is found between the results of the experimental investigation and the boundary element method for the various mufflers.

  1. Reactivity of pyrites and dislocation density

    SciTech Connect

    Pollack, S.S.; Martello, D.V.; Diehl, J.R.; Tamilia, J.V. ); Graham, R.A. )

    1991-01-01

    Highly reactive coal pyrites and unstable museum specimens are easily distinguished from the stable pyrites by the growth of white crystals that cover samples exposed to room atmosphere for short periods of time. Continued exposure to the atmosphere will eventually cause the specimens to fall apart. The term rotten pyrite has been applied to museum specimens that fall apart in this way. SEM studies show that reactive (rotten) pyrites contain between 100 and 10,000 times more dislocations than stable pyrites. Shock-loading of a stable pyrite to 7.5 GPa and 17 GPa increased its reactivity by a factor of two, probably caused by an increase in the number of imperfections. However, shock-loading at 22 GPa decreased the reactivity of pyrite because the imperfections produced at the higher pressure were removed during annealing the sample received at the higher temperature. Although there was a factor of six difference between the most and least reactive shocked MCB (commercial pyrite) samples, shock-loading did not increase the reactivity of the MCB pyrite to that of the Queensland coal pyrite. The results in hand show that while shock-loading produces sufficient imperfections to increase the reactivity of pyrites, there is insufficient data to show that imperfections are the main reason why some coal pyrites are highly reactive. 9 refs., 1 fig., 1 tab.

  2. Making real-time reactive systems reliable

    NASA Technical Reports Server (NTRS)

    Marzullo, Keith; Wood, Mark

    1990-01-01

    A reactive system is characterized by a control program that interacts with an environment (or controlled program). The control program monitors the environment and reacts to significant events by sending commands to the environment. This structure is quite general. Not only are most embedded real time systems reactive systems, but so are monitoring and debugging systems and distributed application management systems. Since reactive systems are usually long running and may control physical equipment, fault tolerance is vital. The research tries to understand the principal issues of fault tolerance in real time reactive systems and to build tools that allow a programmer to design reliable, real time reactive systems. In order to make real time reactive systems reliable, several issues must be addressed: (1) How can a control program be built to tolerate failures of sensors and actuators. To achieve this, a methodology was developed for transforming a control program that references physical value into one that tolerates sensors that can fail and can return inaccurate values; (2) How can the real time reactive system be built to tolerate failures of the control program. Towards this goal, whether the techniques presented can be extended to real time reactive systems is investigated; and (3) How can the environment be specified in a way that is useful for writing a control program. Towards this goal, whether a system with real time constraints can be expressed as an equivalent system without such constraints is also investigated.

  3. Reactivity of pyrylium salts toward basic reactants

    NASA Technical Reports Server (NTRS)

    Neidlein, R.; Witerzens, P.

    1981-01-01

    The reactivity of some N-acyl and N-sulfonyl-hydrazines 2-4, 10a-10g, 12, 13, 16a, 16b and of hydrazones 18, benzyldihydrazone 21 towards pyrylium salts 1 was examined. By reaction of 2,4,6-trimethyl-pyrylium salt 1 with substituted hydrazines some pyridinium salts were obtained. Relationships between basicity and reactivity were discussed.

  4. Understanding the chemically-reactive proteome.

    PubMed

    Jones, Lyn H

    2016-05-24

    The reactivity of amino acid residues in proteins is context-dependent and difficult to predict. Chemical biology can be used to understand the chemical modifications of proteins to help elucidate the nature of the reactive proteome. The resulting insights can be applied to pharmacoproteomics, target identification and molecular pathology. PMID:26726011

  5. Adolescents' Emotional Reactivity across Relationship Contexts

    ERIC Educational Resources Information Center

    Cook, Emily C.; Buehler, Cheryl; Blair, Bethany L.

    2013-01-01

    Adolescents' emotional reactivity in family, close friendships, and romantic relationships was examined in a community-based sample of 416 two-parent families. Six waves of annual data were analyzed using structural equation modeling. Emotional reactivity to interparental conflict during early adolescence was associated prospectively with…

  6. Sensitivity-Based VOC Reactivity Calculation

    EPA Science Inventory

    Volatile Organic Compound (VOC) reactivity scales are used to compare the ozone-forming potentials of various compounds. The comparison allows for substitution of compounds to lessen formation of ozone from paints, solvents, and other products. Current reactivity scales for VOC c...

  7. Reactive nitrogen emissions from agricultural operations

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Reactive nitrogen is essential to the growth of plants and animals and is typically the most limiting nutrient in agricultural production. While reactive nitrogen in fertilizer has enabled the growing global population to maintain food production, the inefficient and sometimes excessive use of nitro...

  8. Dietary restraint and heightened reactivity to food.

    PubMed

    Brunstrom, Jeffrey M; Yates, Heather M; Witcomb, Gemma L

    2004-03-01

    Previously, studies have explored the relationship between dietary behavior and salivary reactivity to food. Despite this, it remains unclear which behaviors are associated with enhanced reactivity. One problem is that measures of behavior have not been compared directly. In particular, it is unclear whether elevated reactivity is associated with measures of dietary restraint or with measures of failed dietary control and a tendency to overeat. To address this problem, we compared the association between salivary reactivity and scores on the subscales of the Three-Factor Eating Questionnaire (restraint, disinhibition, and hunger). Estimates of reactivity were derived from the difference between a baseline saliva measure and a similar measure taken in close proximity to hot pizza. Our second aim was to explore how salivary reactivity changes after a meal. Female participants (N=40) were tested before and after a lunch (cheese sandwiches). All tended to show reactivity to pizza before but not after lunch. No significant differences were associated with the disinhibition or hunger subscales. However, prelunch reactivity was significantly greater in those participants with high scores on the restraint scale. This does not appear to be related to reported levels of hunger before lunch. Rather, it may reveal an intrinsic difference between the reaction of restrained and unrestrained eaters to food. PMID:15059687

  9. Reactive intermediates: Radicals with multiple personalities

    NASA Astrophysics Data System (ADS)

    Forbes, Malcolm D. E.

    2013-06-01

    A combined theoretical and experimental approach has revealed that radicals can be significantly stabilized by the presence of a remote anionic site in the same molecule. This finding has implications for understanding and potentially controlling the reactivity of these important reactive intermediates.

  10. Biochemical reactivity of melatonin with reactive oxygen and nitrogen species: a review of the evidence.

    PubMed

    Reiter, R J; Tan, D X; Manchester, L C; Qi, W

    2001-01-01

    Melatonin (N-acetyl-5-methoxytryptamine), an endogenously produced indole found throughout the animal kingdom, was recently reported, using a variety of techniques, to be a scavenger of a number of reactive oxygen and reactive nitrogen species both in vitro and in vivo. Initially, melatonin was discovered to directly scavenge the high toxic hydroxyl radical (*OH). The methods used to prove the interaction of melatonin with the *OH included the generation of the radical using Fenton reagents or the ultraviolet photolysis of hydrogen peroxide (H202) with the use of spin-trapping agents, followed by electron spin resonance (ESR) spectroscopy, pulse radiolysis followed by ESR, and several spectrofluorometric and chemical (salicylate trapping in vivo) methodologies. One product of the reaction of melatonin with the *OH was identified as cyclic 3-hydroxymelatonin (3-OHM) using high-performance liquid chromatography with electrochemical (HPLC-EC) detection, electron ionization mass spectrometry (EIMS), proton nuclear magnetic resonance (1H NMR) and COSY 1H NMR. Cyclic 3-OHM appears in the urine of humans and other mammals and in rat urine its concentration increases when melatonin is given exogenously or after an imposed oxidative stress (exposure to ionizing radiation). Urinary cyclic 3-OHM levels are believed to be a biomarker (footprint molecule) of in vivo *OH production and its scavenging by melatonin. Although the data are less complete, besides the *OH, melatonin in cell-free systems has been shown to directly scavenge H2O2, singlet oxygen (1O2) and nitric oxide (NO*), with little or no ability to scavenge the superoxide anion radical (O2*-) In vitro, melatonin also directly detoxifies the peroxynitrite anion (ONOO-) and/or peroxynitrous acid (ONOOH), or the activated form of this molecule, ONOOH*; the product of the latter interaction is proposed to be 6-OHM. How these in vitro findings relate to the in vivo antioxidant actions of melatonin remains to be

  11. Probabilistic models for reactive behaviour in heterogeneous condensed phase media

    NASA Astrophysics Data System (ADS)

    Baer, M. R.; Gartling, D. K.; DesJardin, P. E.

    2012-02-01

    This work presents statistically-based models to describe reactive behaviour in heterogeneous energetic materials. Mesoscale effects are incorporated in continuum-level reactive flow descriptions using probability density functions (pdfs) that are associated with thermodynamic and mechanical states. A generalised approach is presented that includes multimaterial behaviour by treating the volume fraction as a random kinematic variable. Model simplifications are then sought to reduce the complexity of the description without compromising the statistical approach. Reactive behaviour is first considered for non-deformable media having a random temperature field as an initial state. A pdf transport relationship is derived and an approximate moment approach is incorporated in finite element analysis to model an example application whereby a heated fragment impacts a reactive heterogeneous material which leads to a delayed cook-off event. Modelling is then extended to include deformation effects associated with shock loading of a heterogeneous medium whereby random variables of strain, strain-rate and temperature are considered. A demonstrative mesoscale simulation of a non-ideal explosive is discussed that illustrates the joint statistical nature of the strain and temperature fields during shock loading to motivate the probabilistic approach. This modelling is derived in a Lagrangian framework that can be incorporated in continuum-level shock physics analysis. Future work will consider particle-based methods for a numerical implementation of this modelling approach.

  12. Chemical reactivity in solid-state pharmaceuticals: formulation implications.

    PubMed

    Byrn, S R; Xu, W; Newman, A W

    2001-05-16

    Solid-state reactions that occur in drug substances and formulations include solid-state phase transformations, dehydration/desolvation, and chemical reactions. Chemical reactivity is the focus of this chapter. Of particular interest are cases where the drug-substance may be unstable or react with excipients in the formulation. Water absorption can enhance molecular mobility of solids and lead to solid-state reactivity. Mobility can be measured using various methods including glass transition (T(g)) measurements, solid-state NMR, and X-ray crystallography. Solid-state reactions of drug substances can include oxidation, cyclization, hydrolysis, and deamidation. Oxidation studies of vitamin A, peptides (DL-Ala-DL-Met, N-formyl-Met-Leu-Phe methyl ester, and Met-enkaphalin acetate salt), and steroids (hydrocortisone and prednisolone derivatives) are discussed. Cyclization reactions of crystalline and amorphous angiotensin-converting enzyme (ACE) inhibitors (spirapril hydrochloride, quinapril hydrochloride, and moexipril) are presented which investigate mobility and chemical reactivity. Examples of drug-excipient interactions, such as transacylation, the Maillard browning reaction, and acid base reactions are discussed for a variety of compounds including aspirin, fluoxitine, and ibuprofen. Once solid-state reactions are understood in a pharmaceutical system, the necessary steps can be taken to prevent reactivity and improve the stability of drug substances and products. PMID:11325479

  13. Fluctuating hydrodynamics of multi-species reactive mixtures

    SciTech Connect

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

    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.

  14. Performance analysis of reactive congestion control for ATM networks

    NASA Astrophysics Data System (ADS)

    Kawahara, Kenji; Oie, Yuji; Murata, Masayuki; Miyahara, Hideo

    1995-05-01

    In ATM networks, preventive congestion control is widely recognized for efficiently avoiding congestion, and it is implemented by a conjunction of connection admission control and usage parameter control. However, congestion may still occur because of unpredictable statistical fluctuation of traffic sources even when preventive control is performed in the network. In this paper, we study another kind of congestion control, i.e., reactive congestion control, in which each source changes its cell emitting rate adaptively to the traffic load at the switching node (or at the multiplexer). Our intention is that, by incorporating such a congestion control method in ATM networks, more efficient congestion control is established. We develop an analytical model, and carry out an approximate analysis of reactive congestion control algorithm. Numerical results show that the reactive congestion control algorithms are very effective in avoiding congestion and in achieving the statistical gain. Furthermore, the binary congestion control algorithm with pushout mechanism is shown to provide the best performance among the reactive congestion control algorithms treated here.

  15. Fluctuating hydrodynamics of multi-species reactive mixtures

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

    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.

  16. Reactive Evaporation And Plasma Processes For Thin Film Optical Coatings

    NASA Astrophysics Data System (ADS)

    Ebert, Johannes

    1989-02-01

    Bombardment of growing films with reactive particles has developed into a powerful technology over the last 3o years. Compared to normal evaporation methods, important improvements are: better adhesion between film and substrate, high film density, fast coating rate and stoichiometric layers with low optical losses. Although the techniques used to achieve the desired properties vary quite dramatically from high pressure plasma processing to bombardment with monoenergetic ion beams in ultra high vacuum environment, from particles with nearly thermal to some keV energy and from discharge currents of some μA to more than 1oo A in industrial applications, the ion-surface interaction, which causes the modification of the films, is the basic of all reactive deposition processes. The purpose of this paper is to review plasma processes for the production of optical coatings including ion assisted deposition, ion plating and ion cluster beam deposition, comparing the structural and optical properties of the films. Some applications of reactive evaporation presented in the following papers demonstrate the potential use of reactive evaporation and plasma processes for solving optical problems.

  17. Design guidelines for solid-catalyzed reactive distillation systems

    SciTech Connect

    Subawalla, H.; Fair, J.R.

    1999-10-01

    In this paper the authors discuss design guidelines for solid-catalyzed reactive distillation systems. The guidelines are used to generate initial estimates for column pressure, reactive zone location, catalyst mass, reactant feed location, reactant ratio, reflux ratio, column diameter, number of equilibrium stages, and packed height. They form a part of a methodical design procedure that makes extensive use of both nonequilibrium (rate-based) and equilibrium-stage simulation models. Important choices prior to design include selection of reliable thermodynamic and reaction kinetic models. The authors tested the guidelines for two etherification systems and validated them experimentally for a hydration reaction. The results from a case study, the manufacture of tert-amyl methyl ether, are shown here. Superimposing reaction on separation leads to unique design trade-offs. Thus, column diameter depends both on maximum vapor velocity and on packing catalyst density, reactant ratios are a function of conversion and azeotrope formation, the operating pressure affects the relative volatility, chemical equilibrium, and reaction rate (reactive zone temperature), and the reflux ratio impacts both separation and conversion. The guidelines and procedures presented here simplify the detailed reactive column design considerably.

  18. Synthesis and processing of composites by reactive metal penetration

    SciTech Connect

    Loehman, R.E.; Ewsuk, K.G.; Tomsia, A.P.

    1995-05-01

    Ceramic-metal composites are being developed because their high stiffness-to weight ratios, good fracture toughness, and variable electrical and thermal properties give them advantages over more conventional materials. However, because ceramic-metal composite components presently are more expensive than monolithic materials, improvements in processing are required to reduce manufacturing costs. Reactive metal penetration is a promising new method for making ceramic- and metal-matrix composites that has the advantage of being inherently a net-shape process. This technique, once fully developed, will provide another capability for manufacturing the advanced ceramic composites that are needed for many light-weight structural and wear applications. The lower densities of these composites lead directly to energy savings in use. Near-net-shape fabrication of composite parts should lead to additional savings because costly and energy intensive grinding and machining operations are significantly reduced, and the waste generated from such finishing operations is minimized. The goals of this research program are: (1) to identify feasible compositional systems for making composites by reactive metal penetration; (2) to understand the mechanism(s) of composite formation by reactive metal penetration; and (3) to learn how to control and optimize reactive metal penetration for economical production of composites and composite coatings.

  19. Reactivity of young chars via energetic distribution measurements

    SciTech Connect

    Calo, J.M.; Zhang, L.H.; Lu, W.; Lilly, W.D.

    1992-06-10

    We have developed what we believe to be the very first a priori prediction technique for the gasification reactivity of coal char. With this method the gasification reactivity of a coal char as function of temperature can be predicted from a single temperature programmed desorption (TPD) experiment following mild gasification at a single temperature (Calo et al., 1989; Hall and Calo, 1990a). This approach has been demonstrated for C0{sub 2} gasification of coal chars where the gasification reactivity is controlled by the thermal desorption of oxygen surface complexes formed during gasification. This approach may be extended to other oxidant species, such as steam, and carbon-hydrogen complexes for hydrogen gasification as well. In the current report, we present a summary of the work that has been conducted to date in constructing a new TGA/TPD-MS experimental system which provides us with the capability of simultaneous monitoring of transient sample mass data, as well as gas phase composition during thermal desorption experiments. In addition, we present some steam reactivity data obtained with another TGA (Cahn 113 system) which has been modified for steam gasification experiments.

  20. Oxidation of trichloroethylene, toluene, and ethanol vapors by a partially saturated permeable reactive barrier

    NASA Astrophysics Data System (ADS)

    Mahmoodlu, Mojtaba G.; Hassanizadeh, S. Majid; Hartog, Niels; Raoof, Amir

    2014-08-01

    The mitigation of volatile organic compound (VOC) vapors in the unsaturated zone largely relies on the active removal of vapor by ventilation. In this study we considered an alternative method involving the use of solid potassium permanganate to create a horizontal permeable reactive barrier for oxidizing VOC vapors. Column experiments were carried out to investigate the oxidation of trichloroethylene (TCE), toluene, and ethanol vapors using a partially saturated mixture of potassium permanganate and sand grains. Results showed a significant removal of VOC vapors due to the oxidation. We found that water saturation has a major effect on the removal capacity of the permeable reactive layer. We observed a high removal efficiency and reactivity of potassium permanganate for all target compounds at the highest water saturation (Sw = 0.6). A change in pH within the reactive layer reduced oxidation rate of VOCs. The use of carbonate minerals increased the reactivity of potassium permanganate during the oxidation of TCE vapor by buffering the pH. Reactive transport of VOC vapors diffusing through the permeable reactive layer was modeled, including the pH effect on the oxidation rates. The model accurately described the observed breakthrough curve of TCE and toluene vapors in the headspace of the column. However, miscibility of ethanol in water in combination with produced water during oxidation made the modeling results less accurate for ethanol. A linear relationship was found between total oxidized mass of VOC vapors per unit volume of permeable reactive layer and initial water saturation. This behavior indicates that pH changes control the overall reactivity and longevity of the permeable reactive layer during oxidation of VOCs. The results suggest that field application of a horizontal permeable reactive barrier can be a viable technology against upward migration of VOC vapors through the unsaturated zone.

  1. Design Principles of Inert Substrates for Exploiting Gold Clusters’ Intrinsic Catalytic Reactivity

    PubMed Central

    Gao, Wang; Ting Cui, Ting; Fu Zhu, Yong; Wen, Zi; Zhao, Ming; Chen Li, Jian; Jiang, Qing

    2015-01-01

    Ultralow stability of gold clusters prohibits the understanding of their intrinsic reactivity (that is vital for revealing the origin of gold’s catalytic properties). Using density functional theory including many-body dispersion method, we aim to ascertain effective ways in exploiting gold clusters’ intrinsic reactivity on carbon nanotubes (CNTs). We find that the many body van der Waals interactions are essential for gold clusters’ reactivity on CNTs and even for O2 activation on these supported clusters. Furthermore, curvature and dopant of CNTs are found to qualitatively change the balance between physisorption and chemisorption for gold clusters on CNTs, determining the clusters’ morphology, charge states, stability, and reactivity, which rationalize the experimental findings. Remarkably, N doped small curvature CNTs, which effectively stabilize gold clusters and retain their inherent geometric/electronic structures, can be promising candidates for exploiting gold clusters’ intrinsic reactivity. PMID:26459871

  2. Ambident reactivities of pyridone anions.

    PubMed

    Breugst, Martin; Mayr, Herbert

    2010-11-01

    The kinetics of the reactions of the ambident 2- and 4-pyridone anions with benzhydrylium ions (diarylcarbenium ions) and structurally related Michael acceptors have been studied in DMSO, CH(3)CN, and water. No significant changes of the rate constants were found when the counterion was varied (Li(+), K(+), NBu(4)(+)) or the solvent was changed from DMSO to CH(3)CN, whereas a large decrease of nucleophilicity was observed in aqueous solution. The second-order rate constants (log k(2)) correlated linearly with the electrophilicity parameters E of the electrophiles according to the correlation log k(2) = s(N + E) (Angew. Chem., Int. Ed. Engl. 1994, 33, 938-957), allowing us to determine the nucleophilicity parameters N and s for the pyridone anions. The reactions of the 2- and 4-pyridone anions with stabilized amino-substituted benzhydrylium ions and Michael acceptors are reversible and yield the thermodynamically more stable N-substituted pyridones exclusively. In contrast, highly reactive benzhydrylium ions (4,4'-dimethylbenzhydrylium ion), which react with diffusion control, give mixtures arising from N- and O-attack with the 2-pyridone anion and only O-substituted products with the 4-pyridone anion. For some reactions, rate and equilibrium constants were determined in DMSO, which showed that the 2-pyridone anion is a 2-4 times stronger nucleophile, but a 100 times stronger Lewis base than the 4-pyridone anion. Quantum chemical calculations at MP2/6-311+G(2d,p) level of theory showed that N-attack is thermodynamically favored over O-attack, but the attack at oxygen is intrinsically favored. Marcus theory was employed to develop a consistent scheme which rationalizes the manifold of regioselectivities previously reported for the reactions of these anions with electrophiles. In particular, Kornblum's rationalization of the silver ion effect, one of the main pillars of the hard and soft acid/base concept of ambident reactivity, has been revised. Ag(+) does not

  3. On the reactivity of methylbenzenes

    SciTech Connect

    Silva, Gabriel da; Bozzelli, Joseph W.

    2010-11-15

    Alkylated aromatic hydrocarbons, including the methylbenzenes, are a major and growing component of liquid transportation fuels. Reactivity (or lack thereof) for the methylbenzenes in combustion systems, measured by octane rating, ignition delay, and laminar flame speed, varies widely with the number and position of methyl substituents. At present this behaviour is not fully understood. This study demonstrates how the low temperature and ignition reactivity of methylbenzenes is controlled by the presence of isolated methyl groups and adjacent methyl pairs (the ortho effect); this allows for the development of octane number correlations. Introduction of an isolated methyl group, adjacent only to CH ring sites, consistently increases the research octane number (RON) by around 26. This phenomenon is explained by the formation of relatively unreactive benzyl free radicals. When an adjacent pair of methyl substituents is present the RON consistently decreases by between 8 and 26, compared to the case when these methyl groups are isolated from each other (this effect generally diminishes with increasing degree of substitution). Research octane numbers for all aromatics with zero to three methyl substituents are accurately described by the empirical relationship RON = 98 + 24.2n{sub m} - 25.8n{sub p}, where n{sub m} is the total number of methyl groups and n{sub p} is the number of contiguous adjacent methyl pairs. The ortho effect is attributed to the unique oxidation chemistry of o-methylbenzyl, o-methylbenzoxyl, and o-methylphenyl type radicals here we provide a preliminary exploration of this chemistry and highlight areas requiring further research. It is shown that the o-methylbenzyl radical can react with two oxygen molecules to form 1,2-diformylbenzene + 2OH + H, a highly chain-branching process. This chemistry is expected to largely explain the two-stage ignition and negative temperature coefficient (NTC) behavior witnessed for polymethylbenzenes with adjacent

  4. Alkylating reactivity and herbicidal activity of chloroacetamides.

    PubMed

    Jablonkai, Istvan

    2003-04-01

    The relationship between S- and N-alkylating reactivity and herbicidal activity within a series of chloroacetamides, including several commercial herbicides and newly synthesised analogues was studied. The S-alkylating reactivity of selected chloroacetamides, as well as those of atrazine and chlorfenprop-methyl, was determined by in vitro GSH conjugation at a ratio of GSH to alkylating agent of 25:1. A spectrophotometric reaction using 4-(4-nitrobenzyl)pyridine was used to characterise the N-alkylating reactivity of the chemicals. Our results indicate that a reduced level of N-alkylating reactivity correlates with an improved herbicidal efficacy at a practical rate. However, the phytoxicity of the molecules is not simply dependent on chemical reactivities, but strictly related to the molecular structure, indicating that lipophilicity, uptake, mobility and induction of detoxifying enzymes may also be decisive factors in the mode of action. PMID:12701706

  5. Reversible reactivity by optic nerve astrocytes

    PubMed Central

    Sun, Daniel; Qu, Juan; Jakobs, Tatjana C.

    2013-01-01

    Reactive astrocytes are typically studied in models that cause irreversible mechanical damage to axons, neuronal cell bodies, and glia. Here, we evaluated the response of astrocytes in the optic nerve head to a subtle injury induced by a brief, mild elevation of the intraocular pressure. Astrocytes demonstrated reactive remodeling that peaked at three days, showing hypertrophy, process retraction and simplification of their shape. This was not accompanied by any significant changes in the gene expression profile. At no time was there discernible damage to the optic axons, as evidenced by electron microscopy and normal anterograde and retrograde transport. Remarkably, the morphological remodeling was reversible. These findings underscore the plastic nature of reactivity. They show that reactivity can resolve fully if the insult is removed, and suggest that reactivity per se is not necessarily deleterious to axons. This reaction may represent very early events in the sequence that eventually leads to glial scarring. PMID:23650091

  6. AI approach to optimal var control with fuzzy reactive loads

    SciTech Connect

    Abdul-Rahman, K.H.; Shahidehpour, S.M.; Daneshdoost, M.

    1995-02-01

    This paper presents an artificial intelligence (AI) approach to the optimal reactive power (var) control problem. The method incorporates the reactive load uncertainty in optimizing the overall system performance. The artificial neural network (ANN) enhanced by fuzzy sets is used to determine the memberships of control variables corresponding to the given load values. A power flow solution will determine the corresponding state of the system. Since the resulting system state may not be feasible in real-time, a heuristic method based on the application of sensitivities in expert system is employed to refine the solution with minimum adjustments of control variables. Test cases and numerical results demonstrate the applicability of the proposed approach. Simplicity, processing speed and ability to model load uncertainties make this approach a viable option for on-line var control.

  7. Modeling the reactivities of hydroxyl radical and ozone towards atmospheric organic chemicals using quantitative structure-reactivity relationship approaches.

    PubMed

    Gupta, Shikha; Basant, Nikita; Mohan, Dinesh; Singh, Kunwar P

    2016-07-01

    The persistence and the removal of organic chemicals from the atmosphere are largely determined by their reactions with the OH radical and O3. Experimental determinations of the kinetic rate constants of OH and O3 with a large number of chemicals are tedious and resource intensive and development of computational approaches has widely been advocated. Recently, ensemble machine learning (EML) methods have emerged as unbiased tools to establish relationship between independent and dependent variables having a nonlinear dependence. In this study, EML-based, temperature-dependent quantitative structure-reactivity relationship (QSRR) models have been developed for predicting the kinetic rate constants for OH (kOH) and O3 (kO3) reactions with diverse chemicals. Structural diversity of chemicals was evaluated using a Tanimoto similarity index. The generalization and prediction abilities of the constructed models were established through rigorous internal and external validation performed employing statistical checks. In test data, the EML QSRR models yielded correlation (R (2)) of ≥0.91 between the measured and the predicted reactivities. The applicability domains of the constructed models were determined using methods based on descriptors range, Euclidean distance, leverage, and standardization approaches. The prediction accuracies for the higher reactivity compounds were relatively better than those of the low reactivity compounds. Proposed EML QSRR models performed well and outperformed the previous reports. The proposed QSRR models can make predictions of rate constants at different temperatures. The proposed models can be useful tools in predicting the reactivities of chemicals towards OH radical and O3 in the atmosphere. PMID:27040550

  8. Voltage and Reactive Power Control by Integration of Genetic Algorithm and Tabu Search

    NASA Astrophysics Data System (ADS)

    Aoki, Hidenori; Yamamoto, Kensei; Mizutani, Yoshibumi

    This paper presents on the result of voltage and reactive power control by use of the proposed method. The feature of proposed method is integration of genetic algorithm (GA) and tabu search (TS). This method obtains an excellent fitness at shorter calculation time than GA considering conventional control process. The effectiveness of this method is shown by a practicable 15-bus system.

  9. Serial follow-up of repeat voluntary blood donors reactive for anti-HCV ELISA

    PubMed Central

    Choudhury, N.; Tulsiani, Sunita; Desai, Priti; Shah, Ripal; Mathur, Ankit; Harimoorthy, V.

    2011-01-01

    Background: Voluntary non-remunerated repeat blood donors are perceived to be safer than the first time blood donors. This study was planned for follow-up of previous hepatitis C virus (HCV) test results of anti-HCV enzyme-linked immunosorbent assay (ELISA) reactive repeat blood donors. The aim was to suggest a protocol for re-entry of the blood donors who are confirmed HCV negative by nucleic acid test (NAT) and recombinant immunoblot assay (RIBA). A group of repeat voluntary donors were followed retrospectively who became reactive on a cross sectional study and showed HCV reactivity while donating blood regularly. Material and Methods: A total of 51,023 voluntary non remunerated blood donors were screened for anti-HCV ELISA routinely. If anybody showed positivity, they were tested by two ELISA kits (screening and confirmatory) and then confirmed infection status by NAT and or RIBA. The previous HCV test results of repeat donors reactive by anti-HCV ELISA were looked back from the records. Data of donors who were repeat reactive with single ELISA kit (in the present study) were analyzed separately from those reactive with two ELISA kits (in the present study). Results: In this study, 140 (0.27%) donors who were reactive by anti HCV ELISA were included. Out of them, 35 were repeat voluntary donors and 16 (11.43%) were reactive with single ELISA kit. All 16 donors were reactive by single ELISA kit occasionally in previous donations. Their present ELISA positive donations were negative for HCV NAT and RIBA. A total of 19 (13.57%) donors were reactive with two ELISA kits. In their previous donations, the donors who were reactive even once with two ELISA kits were consistently reactive by the same two ELISA kits in their next donations also. Conclusion: Donor sample reactive by only single ELISA kit may not be considered as infectious for disposal as they were negative by NAT and or RIBA. One time ELISA positivity was found probably due to ELISA kit specificity and

  10. [Reiter disease or reactive arthritis?].

    PubMed

    Eppinger, S; Schmitt, J; Meurer, M

    2006-04-01

    There is an ongoing international discussion on whether the condition reactive arthritis should be named after a former Nazi functionary. The German dermatological community should participate in this debate. In 1916, Hans Reiter described a disease with the symptoms urethritis, conjunctivitis, and arthritis, which was later named after him. After becoming titular professor in May 1918, Reiter was appointed director of the regional public health department Mecklenburg-Schwerin in 1926. At the same time he taught social hygiene at the University of Rostock, where he was appointed full professor in 1928. In 1931, Hans Reiter became a member of the National Socialist German Workers Party (NSDAP). In July 1932 he was elected representative of the NSDAP to the seventh assembly of Mecklenburg-Schwerin. After becoming its acting director in July 1933, Reiter was appointed president of the Reich public health department in Berlin on October 1, 1933. Both his excellent professional qualifications, as well as his National Socialist attitudes, were considered key criteria for taking over this important position. As the president of the Reich public health department, Reiter was said to have known about the conduct of experiments with typhus-fever at the concentration camp Buchenwald in which 250 humans died. From the end of the Second World War until 1947, Reiter was imprisoned in the Nuremberg Prison for War Criminals, but never convicted of a crime. PMID:17419129

  11. General Reactive Atomistic Simulation Program

    Energy Science and Technology Software Center (ESTSC)

    2004-09-22

    GRASP (General Reactive Atomistic Simulation Program) is primarily intended as a molecular dynamics package for complex force fields, The code is designed to provide good performance for large systems, either in parallel or serial execution mode, The primary purpose of the code is to realistically represent the structural and dynamic properties of large number of atoms on timescales ranging from picoseconds up to a microsecond. Typically the atoms form a representative sample of some material,more » such as an interface between polycrystalline silicon and amorphous silica. GRASP differs from other parallel molecular dynamics codes primarily due to it’s ability to handle relatively complicated interaction potentials and it’s ability to use more than one interaction potential in a single simulation. Most of the computational effort goes into the calculation of interatomic forces, which depend in a complicated way on the positions of all the atoms. The forces are used to integrate the equations of motion forward in time using the so-called velocity Verlet integration scheme. Alternatively, the forces can be used to find a minimum energy configuration, in which case a modified steepest descent algorithm is used.« less

  12. Impulsive model for reactive collisions

    NASA Technical Reports Server (NTRS)

    Marron, M. T.; Bernstein, R. B.

    1972-01-01

    A simple classical mechanical model of the reactive scattering of a structureless atom A and a quasi-diatomic BC is developed which takes full advantage of energy, linear and angular momentum conservation relations but introduces a minimum of further assumptions. These are as follows: (1) the vibrational degree of freedom of the reactant (BC) and product (AB) molecules is suppressed, so the change in vibrational energy is simply a parameter; (2) straight-line trajectories are assumed outside of a reaction shell; (3) within this zone, momentum transfer occurs impulsively (essentially instantaneously) following mass transfer; (4) the impulse, which may be either positive or negative, is directed along the BC axis, which may, however, assume all orientations with respect to the incident relative velocity. The model yields differential and total cross sections and product rotational energy distributions for a given collision exoergicity Q, or for any known distribution over Q. Numerical results are presented for several prototype reactions whose dynamics have been well-studied.

  13. Voltage and Reactive Power Control by Parallel Calculation Processing

    NASA Astrophysics Data System (ADS)

    Michihata, Masashi; Aoki, Hidenori; Mizutani, Yoshibumi

    This paper presents a new approach to optimal voltage and reactive power control based on a genetic algorithm (GA) and a tabu search (TS). To reduce time to calculate the control procedure, the parallel computation using Linux is executed. In addition, TS and GA are calculated by the master and each slave based on the parallel program language. The effectiveness of the proposed method is demonstrated by practical 118-bus system.

  14. Properties Of Electrochromic Nickel Oxide Coatings Produced By Reactive Evaporation

    NASA Astrophysics Data System (ADS)

    Bange, Klaus; Baucke, Friedrich G.; Metz, Bernard

    1989-03-01

    Single films of nickel oxide deposited by reactive evaporation and all-solid-state devices (ASSDs) containing such films have been investigated. The as-deposited nickel oxide films were analysed by standard surface and thin film-sensitive methods (AES, ESCA, RBS, NRA), and the findings were correlated with deposition parameters. The electrochromism of single layers was characterized by cyclic voltammetry and photospectrometry and compared with optical and electrical data of electrochromic all-solid-state devices.

  15. Determinants of Physiological and Perceived Physiological Stress Reactivity in Children and Adolescents

    PubMed Central

    Evans, Brittany E.; Greaves-Lord, Kirstin; Euser, Anja S.; Tulen, Joke H. M.; Franken, Ingmar H. A.; Huizink, Anja C.

    2013-01-01

    Aims Abnormal physiological stress reactivity is increasingly investigated as a vulnerability marker for various physical and psychological health problems. However, studies are inconsistent in taking into account potential covariates that may influence the developing stress system. We systematically tested determinants (individual, developmental, environmental and substance use-related) of physiological and perceived physiological stress reactivity. We also examined the relation between physiological and perceived physiological stress reactivity. Method In a stratified sample of 363 children (7–12 years) and 344 adolescents (13–20 years) from the general population, we examined cortisol, heart rate, respiratory sinus arrhythmia and perceived physiological stress reactivity to a psychosocial stress procedure. Results Using multivariate linear regression models, we found that individual, developmental, environmental and substance use-related factors were related to each of the stress response indices. These determinant factors were different for each of the stress reactivity indices, and different in children versus adolescents. Perceived physiological stress reactivity predicted cortisol reactivity in adolescents only. All other relations between perceived physiological and physiological stress reactivity were not significant. Conclusions As physiological stress variables are often examined as vulnerability markers for the development of health problems, we maintain that it is essential that future studies take into consideration factors that may account for found relations. Our study provides an overview and indication of which variables should be considered in the investigation of the relation between physiological stress indices and illness. PMID:23620785

  16. A transport based one-dimensional perturbation code for reactivity calculations in metal systems

    SciTech Connect

    Wenz, T.R.

    1995-02-01

    A one-dimensional reactivity calculation code is developed using first order perturbation theory. The reactivity equation is based on the multi-group transport equation using the discrete ordinates method for angular dependence. In addition to the first order perturbation approximations, the reactivity code uses only the isotropic scattering data, but cross section libraries with higher order scattering data can still be used with this code. The reactivity code obtains all the flux, cross section, and geometry data from the standard interface files created by ONEDANT, a discrete ordinates transport code. Comparisons between calculated and experimental reactivities were done with the central reactivity worth data for Lady Godiva, a bare uranium metal assembly. Good agreement is found for isotopes that do not violate the assumptions in the first order approximation. In general for cases where there are large discrepancies, the discretized cross section data is not accurately representing certain resonance regions that coincide with dominant flux groups in the Godiva assembly. Comparing reactivities calculated with first order perturbation theory and a straight {Delta}k/k calculation shows agreement within 10% indicating the perturbation of the calculated fluxes is small enough for first order perturbation theory to be applicable in the modeled system. Computation time comparisons between reactivities calculated with first order perturbation theory and straight {Delta}k/k calculations indicate considerable time can be saved performing a calculation with a perturbation code particularly as the complexity of the modeled problems increase.

  17. Reactivation-dependent amnesia for appetitive memories is determined by the contingency of stimulus presentation.

    PubMed

    Lee, Jonathan L C; Everitt, Barry J

    2008-06-01

    Previously acquired aversive and appetitive memories are not stable and permanent. The reactivation of such memories by re-exposure to training stimuli renders them vulnerable to disruption by amnestic agents such as the noncompetitive N-methyl-D-aspartate receptor antagonist (+)-5-methyl-10,11-dihydro-SH-dibenzo{a,d}cyclohepten-5,10-imine maleate (MK-801). However, relatively little is known about the parameters that influence the reactivation process. Here, we show that the method of stimulus presentation during memory reactivation is of great importance. Male Lister Hooded rats were trained to acquire a lever press response that delivered a sucrose reward paired with a light conditioned stimulus (CS). The CS-sucrose association was then reactivated through re-exposure to the CS, either contingently upon the lever press response, or noncontingently in the absence of instrumental responding. Systemic administration of MK-801 (0.1 mg/kg) at the time of memory reactivation resulted in amnesia, and hence a reduction in subsequent sucrose seeking induced by, and dependent upon, presentation of the CS, only when the memory was reactivated contingently. Therefore, stimuli may have to be presented in the same manner at memory reactivation as during learning in order to render a previously acquired memory vulnerable to disruption. These results have important implications for the potential translational use of glutamatergic treatments in conjunction with targeted memory reactivation. PMID:18509112

  18. Flaxseed oil increases aortic reactivity to phenylephrine through reactive oxygen species and the cyclooxygenase-2 pathway in rats

    PubMed Central

    2014-01-01

    Background Flaxseed oil has the highest concentration of omega-3 α-linolenic acid, which has been associated with cardiovascular benefit. However, the mechanism underlying the vascular effects induced through flaxseed oil is not well known. Thus, in the present study, we investigated the effects of flaxseed oil on vascular function in isolated rat aortic rings. Methods Wistar rats were treated daily with flaxseed oil or a control (mineral oil) intramuscular (i.m.) for fifteen days. Isolated aortic segments were used to evaluate cyclooxygenase-2 (COX-2) protein expression, superoxide anion levels and vascular reactivity experiments. Results Flaxseed oil treatment increased the vasoconstrictor response of aortic rings to phenylephrine. Endothelium removal increased the response to phenylephrine in aortic segments isolated from both groups, but the effect was smaller in the treated group. L-NAME incubation similarly increased the phenylephrine response in segments from both groups. The TXA2 synthase inhibitor furegrelate, the selective COX-2 inhibitor NS 398, the TP receptor antagonist SQ 29.548, the reactive oxygen species (ROS) scavenger apocynin, the superoxide anion scavengers tiron and the phospholipase A2 inhibitor dexamethasone partially reversed the flaxseed oil-induced increase in reactivity to phenylephrine. Conclusions These findings suggest that flaxseed oil treatment increased vascular reactivity to phenylephrine through an increase in ROS production and COX-2-derived TXA2 production. The results obtained in the present study provide new insight into the effects of flaxseed oil treatment (i.m.) on vascular function. PMID:24993607

  19. Two-Dimensional Diffusion Theory Analysis of Reactivity Effects of a Fuel-Plate-Removal Experiment

    NASA Technical Reports Server (NTRS)

    Gotsky, Edward R.; Cusick, James P.; Bogart, Donald

    1959-01-01

    Two-dimensional two-group diffusion calculations were performed on the NASA reactor simulator in order to evaluate the reactivity effects of fuel plates removed successively from the center experimental fuel element of a seven- by three-element core loading at the Oak Ridge Bulk Shielding Facility. The reactivity calculations were performed by two methods: In the first, the slowing-down properties of the experimental fuel element were represented by its infinite media parameters; and, in the second, the finite size of the experimental fuel element was recognized, and the slowing-down properties of the surrounding core were attributed to this small region. The latter calculation method agreed very well with the experimented reactivity effects; the former method underestimated the experimental reactivity effects.

  20. A case of mistaken identity: are reactive oxygen species actually reactive sulfide species?

    PubMed

    DeLeon, Eric R; Gao, Yan; Huang, Evelyn; Arif, Maaz; Arora, Nitin; Divietro, Alexander; Patel, Shivali; Olson, Kenneth R

    2016-04-01

    Stepwise one-electron reduction of oxygen to water produces reactive oxygen species (ROS) that are chemically and biochemically similar to reactive sulfide species (RSS) derived from one-electron oxidations of hydrogen sulfide to elemental sulfur. Both ROS and RSS are endogenously generated and signal via protein thiols. Given the similarities between ROS and RSS, we wondered whether extant methods for measuring the former would also detect the latter. Here, we compared ROS to RSS sensitivity of five common ROS methods: redox-sensitive green fluorescent protein (roGFP), 2', 7'-dihydrodichlorofluorescein, MitoSox Red, Amplex Red, and amperometric electrodes. All methods detected RSS and were as, or more, sensitive to RSS than to ROS. roGFP, arguably the "gold standard" for ROS measurement, was more than 200-fold more sensitive to the mixed polysulfide H2Sn(n = 1-8) than to H2O2 These findings suggest that RSS may be far more prevalent in intracellular signaling than previously appreciated and that the contribution of ROS may be overestimated. This conclusion is further supported by the observation that estimated daily sulfur metabolism and ROS production are approximately equal and the fact that both RSS and antioxidant mechanisms have been present since the origin of life, nearly 4 billion years ago, long before the rise in environmental oxygen 600 million years ago. Although ROS are assumed to be the most biologically relevant oxidants, our results question this paradigm. We also anticipate our findings will direct attention toward development of novel and clinically relevant anti-(RSS)-oxidants. PMID:26764057

  1. Enhanced durability and reactivity for zinc ferrite desulfurization sorbent

    SciTech Connect

    Berggren, M.H.; Jha, M.C.

    1989-10-01

    AMAX Research Development Center (AMAX R D) investigated methods for enhancing the reactivity and durability of zinc ferrite desulfurization sorbents. Zinc ferrite sorbents are intended for use in desulfurization of hot coal gas in integrated gasification combined cycle (IGCC) or molten carbonate fuel cell (MCFC) applications. For this program, the reactivity of the sorbent may be defined as its sulfur sorption capacity at the breakthrough point and at saturation in a bench-scale, fixed-bed reactor. Durability may be defined as the ability of the sorbent to maintain important physical characteristics such as size, strength, and specific surface area during 10 cycles of sulfidation and oxidation. Two base case sorbents, a spherical pellet and a cylindrical extrude used in related METC-sponsored projects, were used to provide a basis for the aimed enhancement in durability and reactivity. Sorbent performance was judged on the basis of physical properties, single particle kinetic studies based on thermogravimetric (TGA) techniques, and multicycle bench-scale testing of sorbents. A sorbent grading system was utilized to quantify the characteristics of the new sorbents prepared during the program. Significant enhancements in both reactivity and durability were achieved for the spherical pellet shape over the base case formulation. Overall improvements to reactivity and durability were also made to the cylindrical extrude shape. The primary variables which were investigated during the program included iron oxide type, zinc oxide:iron oxide ratio, inorganic binder concentration, organic binder concentration, and induration conditions. The effects of some variables were small or inconclusive. Based on TGA studies and bench-scale tests, induration conditions were found to be very significant.

  2. Viral Reactivation in Astronauts and Technology Transfer to Clinics

    NASA Technical Reports Server (NTRS)

    Pierson, Duane L.; Renner, Ashley N.; Rooney, Bridgett; Mehta, Satish K.

    2016-01-01

    Dysfunction of immunity in astronauts has been known for several decades. Advances were hampered due to lack of sophisticated equipment to measure immune status during space flight. We developed the use of latent herpes viruses as biomarkers for immune status in astronauts. There are eight known human-specific herpes viruses, and virtually everyone is infected by one or more of these viruses. Herpes viruses are important human infectious pathogens with oncogenic potential. They cause disease following primary infection and then become latent in human tissues. Latency is maintained by a robust immune system. Diminished immunity allows for the reactivation of these viruses. Reactivation can result in a plethora of diseases. We have shown that Epstein-Barr virus (EBV), varicella zoster virus (VZV), herpes simplex-1 (HSV-1) and cytomegalovirus (CMV) reactivate during spaceflight and are shed in body fluids. These viruses have caused disease during spaceflight. Detection of viruses in saliva or urine by polymerase chain reaction (PCR) is a rapid, non-invasive, very sensitive, and a highly specific method to detect, identify, and quantitate the viruses present in body fluids. These viruses reactivate and are shed independently of each other. Recently we have shown that reactivation and shedding increases with longer stays in space, contrary to earlier speculation. Astronaut studies demonstrated that the reactivated herpes viruses are cell-associated, live, infectious, and serve as excellent biomarkers for immune status. Virus reactivation coincides with diminished T-cell function. Vaccine and antivirals are potential countermeasures for VZV diseases. This NASA-derived technology for astronauts has been successfully transferred to neurologists, infectious disease specialists, dermatologists, and ophthalmologists for patient diagnostics. Viruses in body fluids of patients can be analyzed for virus identity and copy number with results available in 1-hour. Technology is

  3. Comparison of biomass and coal char reactivities

    SciTech Connect

    Huey, S.P.; Davis, K.A.; Hurt, R.H.

    1995-08-01

    Char combustion is typically the rate limiting step during the combustion of solid fuels. The magnitude and variation of char reactivity during combustion are, therefore, of primary concern when comparing solid fuels such as coal and biomass. In an effort to evaluate biomass` potential as a sustainable and renewable energy source, the reactivities of both biomass and coal chars were compared using Sandia`s Captive Particle Imaging (CPI) apparatus. This paper summarizes the experimental approach used to determine biomass and coal reactivities and presents results from CPT experiments. The reactivity of six types of char particles, two high-rank coal chars, two low-rank coal chars, and two biomass chars, were investigated using the CPT apparatus. Results indicate that both of the high-rank coal chars have relatively low reactivities when compared with the higher reactivities measured for the low-rank coal and the biomass chars. In addition, extinction behavior of the chars support related investigations that suggest carbonaceous structural ordering is an important consideration in understanding particle reactivity as a function of extent of burnout. High-rank coal chars were found to have highly ordered carbon structures, where as, both low-rank coal and biomass chars were found to have highly disordered carbon structures.

  4. COAL SLAGGING AND REACTIVITY TESTING

    SciTech Connect

    Donald P. McCollor; Kurt E. Eylands; Jason D. Laumb

    2003-10-01

    carbon as well as slagging. A second phase of the project involved advanced analysis of the baseline coal along with an Australian coal fired at the plant. These analysis results were used in equilibrium thermodynamic modeling along with a coal quality model developed by the EERC to assess slagging, fouling, and opacity for the coals. Bench-scale carbon conversion testing was performed in a drop-tube furnace to assess the reactivity of the coals. The Australian coal had a higher mineral content with significantly more clay minerals present than the baseline coal. The presence of these clay minerals, which tend to melt at relatively low temperatures, indicated a higher potential for problematic slagging than the baseline coal. However, the pyritic minerals, comprising over 25% of the baseline mineral content, may form sticky iron sulfides, leading to severe slagging in the burner region if local areas with reducing conditions exist. Modeling results indicated that neither would present significant fouling problems. The Australian coal was expected to show slagging behavior much more severe than the baseline coal except at very high furnace temperatures. However, the baseline coal was predicted to exhibit opacity problems, as well as have a higher potential for problematic calcium sulfate-based low-temperature fouling. The baseline coal had a somewhat higher reactivity than the Australian coal, which was consistent with both the lower average activation energy for the baseline coal and the greater carbon conversion at a given temperature and residence time. The activation energy of the baseline coal showed some effect of oxygen on the activation energy, with E{sub a} increasing at the lower oxygen concentration, but may be due to the scatter in the baseline coal kinetic values at the higher oxygen level tested.

  5. Comparative study: sensitization development in hot-isostatic-pressed cast and wrought structures type 316L(N)-IG stainless steel under isothermal heat treatment

    NASA Astrophysics Data System (ADS)

    Shutko, K. I.; Belous, V. N.

    2002-12-01

    This work focuses on the relative sensitization resistance of type 316L(N)-IG stainless steel (SS). Cast and wrought structures SS after solid hot-isostatic pressing (solid-HIP) operation are investigated under isothermal heat treatment. Wrought SS/SS solid-HIP joint sensitization is taken also into consideration. These experiments employed the quantitative double-loop electrochemical potentiokinetic reactivation (DL-EPR) and oxalic acid etch screening tests. A copper-copper sulfate-16% sulfuric acid test applied for strongly sensitized cast SS to reinforce the results were received by the methods mentioned above. Results from all employed methods correlate well. Sensitization was detected neither in cast nor in wrought SS in as-HIPed condition excluding wrought SS/SS solid-HIP joints. Significant difference between sensitization development rates was determined in cast and wrought SS structures when annealing at 675 °C for a duration up to 50 h.

  6. Adaptive Reactive Rich Internet Applications

    NASA Astrophysics Data System (ADS)

    Schmidt, Kay-Uwe; Stühmer, Roland; Dörflinger, Jörg; Rahmani, Tirdad; Thomas, Susan; Stojanovic, Ljiljana

    Rich Internet Applications significantly raise the user experience compared with legacy page-based Web applications because of their highly responsive user interfaces. Although this is a tremendous advance, it does not solve the problem of the one-size-fits-all approach1 of current Web applications. So although Rich Internet Applications put the user in a position to interact seamlessly with the Web application, they do not adapt to the context in which the user is currently working. In this paper we address the on-the-fly personalization of Rich Internet Applications. We introduce the concept of ARRIAs: Adaptive Reactive Rich Internet Applications and elaborate on how they are able to adapt to the current working context the user is engaged in. An architecture for the ad hoc adaptation of Rich Internet Applications is presented as well as a holistic framework and tools for the realization of our on-the-fly personalization approach. We divided both the architecture and the framework into two levels: offline/design-time and online/run-time. For design-time we explain how to use ontologies in order to annotate Rich Internet Applications and how to use these annotations for conceptual Web usage mining. Furthermore, we describe how to create client-side executable rules from the semantic data mining results. We present our declarative lightweight rule language tailored to the needs of being executed directly on the client. Because of the event-driven nature of the user interfaces of Rich Internet Applications, we designed a lightweight rule language based on the event-condition-action paradigm.2 At run-time the interactions of a user are tracked directly on the client and in real-time a user model is built up. The user model then acts as input to and is evaluated by our client-side complex event processing and rule engine.

  7. Myochrysine Solution Structure and Reactivity

    PubMed Central

    Jones, William B.; Zhao, Zheng; Dorsey, John G.; Tepperman, Katherine

    1994-01-01

    We have determined the framework structure of Myochrysine (disodium gold(I)thiomalate) in the solid state and extremely concentrated aqueous solution, previously. It consists of an open chain polymer with linear gold coordination to two thiolates from the thiomalic acid moieties which bridge between pairs of gold atoms providing an Au-S-Au angle of 95°. The question remained: was this structure relevant to the dilute solutions of drugs administered and the still lower concentrations of gold found in the bodies of patients (typically 1 ppm Au in blood and urine or 5 μM in Au). We have provided an answer to that question using extended X-ray absorption spectroscopy (EXAFS) and capillary zone electrophoresis (CZE). EXAFS studies confirm that the polymeric structure with two sulfur atoms per gold atom persists from molar concentrations down to millimolar concentrations. CZE is able to separate and detect Myochrysine at millimolar levels. More importantly, at micromolar levels Myochrysine solutions exhibit identical CZE behavior to that measured at millimolar levels. Thus, aqueous solutions of the drug remain oligomeric at concentrations commensurate with those found in patient blood and urine. The reactivity of Myochrysine with cyanide, a species especially prevalent in smoking patients, was explored using CZE. Cyanide freely replaces thiomalic acid to form [Au(CN)2]- and thiomalic acid via a mixed ligand intermediate. The overall apparent equilibrium constant (Kapp) for the reaction is 6×10-4M-1. Further reaction of [Au(CN)2]- with a large excess of L, where L is cysteine, N-acetylcysteine, or glutathione, shows that these amino acids readily replace cyanide to form [AuL2]-. These species are thus potential metabolites and could possibly be active forms of gold in vivo. That all of these species are readily separated and quantified using CZE demonstrates that capillary electrophoresis is an accessible and powerful tool to add to those used for the study of gold

  8. Matrix deactivation: A general approach to improve stability of unstable and reactive pharmaceutical genotoxic impurities for trace analysis.

    PubMed

    Sun, Mingjiang; Bai, Lin; Terfloth, Gerald J; Liu, David Q; Kord, Alireza S

    2010-05-01

    Trace analysis of unstable and reactive pharmaceutical genotoxic impurities (GTIs) is a challenging task in pharmaceutical analysis. Many method issues such as insufficient sensitivity, poor precision, and unusual (too high/low) spiking recovery are often directly related to analytes' instability. We report herein a matrix deactivation approach that chemically stabilizes these analytes for analytical method development. In contrast to the conventional chemical derivatization approach where the analytes are transformed into stable detectable species, the matrix deactivation approach chemically deactivates the hypothetical reactive species in the sample matrix. The matrix deactivation approach was developed on the premise that the instability of certain analytes at trace level is caused by reactions between the analytes and low level reactive species in the sample matrix. Thus, quenching the reactivity of the reactive species would be a key to stabilizing the unstable and reactive analytes. For example, electrophilic alkylators could be destabilized by nucleophiles or bases through either nucleophilic substitution or elimination reactions. One way to mask those reactive species is via protonation by adding acids to the diluent. Alternatively, one can use nucleophile scavengers to deplete reactive unknown species in the sample matrix completely, in analogy to the use of antioxidants and metal chelators to prevent oxidation in the analysis of compounds liable to oxidation. This paper reports the application of the matrix deactivation to the analyses of unstable and reactive pharmaceutical genotoxic impurities. Some of the methods have been used to support development of manufacturing processes for drug substances and a recent regulatory filing. PMID:20036478

  9. [Reactive arthritis: inflammation or true infection?].

    PubMed

    Finckh, Axel

    2016-03-01

    Reactive arthritis has been classically defined as an aseptic arthritis induced by a bacterial infection in another organ. If the classical form of reactive arthritis is in fact a spondyloarthritis triggered by a urogenital or intestinal bacterial infection, it is not necessarily sterile, and in some cases it may be worthwhile to treat a chronic infection with long-term antibiotherapy. In a broader definition, the concept of reactive arthritis is widened to other post-infectious rheumatism, such as post-streptococcal arthritis or post-viral arthritis. PMID:27089639

  10. Quantum reactive scattering on innovative computing platforms

    NASA Astrophysics Data System (ADS)

    Pacifici, Leonardo; Nalli, Danilo; Laganà, Antonio

    2013-05-01

    The possibility of implementing quantum reactive scattering programs on cheap platforms, originally used for graphic purposes only, has been investigated using a NVIDIA GPU. After a conversion of the code considered from Fortran to C and its deep restructuring for exploiting the GPU key features, significant speedups have been obtained for RWAVEPR, a time dependent quantum reactive scattering code propagating in time a complex wavepacket. As benchmark calculations those concerned with the evaluation of the reactive probabilities of the Cl+H2 and the N+N2 reactions have been considered.

  11. Reactive multiphase flow simulation workshop summary

    SciTech Connect

    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.

  12. 77 FR 11109 - Reactive Power Resources; Notice of Technical Conference

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-02-24

    ... Energy Regulatory Commission Reactive Power Resources; Notice of Technical Conference The Federal Energy... docket highlights potential issues regarding the need for reactive power capability among newly... technical conference to examine whether the Commission should reconsider or modify the reactive...

  13. Moving Overlapping Grids with Adaptive Mesh Refinement for High-Speed Reactive and Non-reactive Flow

    SciTech Connect

    Henshaw, W D; Schwendeman, D W

    2005-08-30

    We consider the solution of the reactive and non-reactive Euler equations on two-dimensional domains that evolve in time. The domains are discretized using moving overlapping grids. In a typical grid construction, boundary-fitted grids are used to represent moving boundaries, and these grids overlap with stationary background Cartesian grids. Block-structured adaptive mesh refinement (AMR) is used to resolve fine-scale features in the flow such as shocks and detonations. Refinement grids are added to base-level grids according to an estimate of the error, and these refinement grids move with their corresponding base-level grids. The numerical approximation of the governing equations takes place in the parameter space of each component grid which is defined by a mapping from (fixed) parameter space to (moving) physical space. The mapped equations are solved numerically using a second-order extension of Godunov's method. The stiff source term in the reactive case is handled using a Runge-Kutta error-control scheme. We consider cases when the boundaries move according to a prescribed function of time and when the boundaries of embedded bodies move according to the surface stress exerted by the fluid. In the latter case, the Newton-Euler equations describe the motion of the center of mass of the each body and the rotation about it, and these equations are integrated numerically using a second-order predictor-corrector scheme. Numerical boundary conditions at slip walls are described, and numerical results are presented for both reactive and non-reactive flows in order to demonstrate the use and accuracy of the numerical approach.

  14. Senescence, Stress, and Reactive Oxygen Species

    PubMed Central

    Jajic, Ivan; Sarna, Tadeusz; Strzalka, Kazimierz

    2015-01-01

    Generation of reactive oxygen species (ROS) is one of the earliest responses of plant cells to various biotic and abiotic stresses. ROS are capable of inducing cellular damage by oxidation of proteins, inactivation of enzymes, alterations in the gene expression, and decomposition of biomembranes. On the other hand, they also have a signaling role and changes in production of ROS can act as signals that change the transcription of genes that favor the acclimation of plants to abiotic stresses. Among the ROS, it is believed that H2O2 causes the largest changes in the levels of gene expression in plants. A wide range of plant responses has been found to be triggered by H2O2 such as acclimation to drought, photooxidative stress, and induction of senescence. Our knowledge on signaling roles of singlet oxygen (1O2) has been limited by its short lifetime, but recent experiments with a flu mutant demonstrated that singlet oxygen does not act primarily as a toxin but rather as a signal that activates several stress-response pathways. In this review we summarize the latest progress on the signaling roles of ROS during senescence and abiotic stresses and we give a short overview of the methods that can be used for their assessment. PMID:27135335

  15. Reactive Oxygen Species and Cellular Oxygen Sensing

    PubMed Central

    Cash, Timothy P; Pan, Yi; Simon, M. Celeste

    2008-01-01

    Many organisms activate adaptive transcriptional programs to help them cope with decreased oxygen levels, or hypoxia, in their environment. These responses are triggered by various oxygen sensing systems in bacteria, yeast and metazoans. In metazoans, the hypoxia inducible factors (HIFs) mediate the adaptive transcriptional response to hypoxia by upregulating genes involved in maintaining bioenergetic homeostasis. The HIFs in turn are regulated by HIF-specific prolyl hydroxlase activity, which is sensitive to cellular oxygen levels and other factors such as tricarboxylic acid cycle metabolites and reactive oxygen species (ROS). Establishing a role for ROS in cellular oxygen sensing has been challenging since ROS are intrinsically unstable and difficult to measure. However, recent advances in fluorescence energy transfer resonance (FRET)-based methods for measuring ROS are alleviating some of the previous difficulties associated with dyes and luminescent chemicals. In addition, new genetic models have demonstrated that functional mitochondrial electron transport and associated ROS production during hypoxia are required for HIF stabilization in mammalian cells. Current efforts are directed at how ROS mediate prolyl hydroxylase activity and hypoxic HIF stabilization. Progress in understanding this process has been enhanced by the development of the FRET-based ROS probe, an vivo prolyl hydroxylase reporter and various genetic models harboring mutations in components of the mitochondrial electron transport chain. PMID:17893032

  16. Nondestructive Evaluation of Reactive Powder Concrete

    NASA Astrophysics Data System (ADS)

    Washer, Glenn; Fuchs, Paul; Graybeal, Benjamin; Rezaizadeh, Ali

    2004-02-01

    Reactive powder concrete (RPC) has been introduced as a structural material for civil engineering applications. The material consists of a finely graded combination of cement, sand, ground quartz and silica fume which combined with water form a cement paste. Small steel fibers measuring approximately 0.2 mm in diameter and 12 mm in length are distributed throughout the cement matrix and the combined material has very high compressive strength and toughness. The material is proposed for use in the primary load bearing members in bridges, and as such nondestructive evaluation technologies are needed to evaluate material quality and monitor in-service condition. This paper reports on research to determine the effectiveness of ultrasonic testing for determining the elastic properties of RPC. Comparison between static modulus of elasticity and ultrasonic modulus measurements is presented. A system for determining elastic moduli as a quality control tool is discussed. The effect of curing conditions on ultrasonic velocities and resulting calculated moduli values is presented and compared with traditional measurement methods.

  17. Fetal and postnatal ovine mesenteric vascular reactivity

    PubMed Central

    Nair, Jayasree; Gugino, Sylvia F.; Nielsen, Lori C.; Caty, Michael G.; Lakshminrusimha, Satyan

    2016-01-01

    BACKGROUND Intestinal circulation and mesenteric arterial (MA) reactivity may play a role in preparing the fetus for enteral nutrition. We hypothesized that MA vasoreactivity changes with gestation and vasodilator pathways predominate in the postnatal period. METHODS Small distal MA rings (0.5-mm diameter) were isolated from fetal (116-d, 128-d, 134-d, and 141-d gestation, term ~ 147 d) and postnatal lambs. Vasoreactivity was evaluated using vasoconstrictors (norepinephrine (NE) after pretreatment with propranolol and endothelin-1(ET-1)) and vasodilators (NO donors A23187 and s-nitrosopenicillamine (SNAP)). Protein and mRNA assays for receptors and enzymes (endothelin receptor A, alpha-adrenergic receptor 1A (ADRA1A), endothelial NO synthase (eNOS), soluble guanylyl cyclase (sGC), and phosphodiesterase5 (PDE5)) were performed in mesenteric arteries. RESULTS MA constriction to NE and ET-1 peaked at 134 d. Relaxation to A23187 and SNAP was maximal after birth. Basal eNOS activity was low at 134 d. ADRA1A mRNA and protein increasedsignificantlyat134danddecreasedpostnatally.sGC and PDE5 protein increased from 134 to 141 d. CONCLUSION Mesenteric vasoconstriction predominates in late-preterm gestation (134 d; the postconceptional age with the highest incidence of necrotizing enterocolitis (NEC)) followed by a conversion to vasodilatory influences near the time of full-term birth. Perturbations in this ontogenic mechanism, including preterm birth, may be a risk factor for NEC. PMID:26672733

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

    NASA Astrophysics Data System (ADS)

    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.

  19. Cytomegalovirus Reactivation in Adult Recipients of Autologous Stem Cell Transplantation: a Single Center Experience

    PubMed Central

    Al-Rawi, Omar; Abdel-Rahman, Fawzi; Al-Najjar, Rula; Abu-Jazar, Husam; Salam, Mourad; Saad, Mustafa

    2015-01-01

    Introduction Cytomegalovirus (CMV) reactivation and infection are well-recognized complications after allogeneic stem cell transplantation (SCT). Only a few studies have addressed CMV reactivation after autologous SCT (ASCT). Methods We retrospectively reviewed medical records of 210 adult patients who underwent ASCT for lymphoma or multiple myeloma (MM) at a single center from January 1st, 2007 until December 31st, 2012. All patients were monitored weekly with CMV antigenemia test till day 42 after transplantation, and for 2 months after last positive test in those who had any positive CMV antigenemia test before day 42. Results Thirty-seven (17.6%) patients had CMV reactivation; 23 patients had lymphoma while 14 had MM as the underlying disease. There was no difference in the rate of CMV reactivation between lymphoma and MM patients (20% versus 14.7%, P = 0.32). The majority of the patients were treated with ganciclovir/valganciclovir, all patients had their reactivation resolved with therapy, and none developed symptomatic CMV infection. None of the patients who died within 100 days of transplantation had CMV reactivation. Log-rank test showed that CMV reactivation had no effect on the overall survival of patients (P values, 0.29). Conclusion In our cohort, CMV reactivation rate after ASCT was 17.6%. There was no difference in reactivation rates between lymphoma and MM patients. With the use of preemptive therapy, symptomatic CMV infection was not documented in any patient in our cohort. CMV reactivation had no impact on patients’ survival post ASCT. PMID:26401238

  20. Evaluation of Airway Reactivity and Immune Characteristics as Risk Factors for Wheezing Early in Life

    PubMed Central

    Yao, Weiguo; Barbé-Tuana, Florencia M.; Llapur, Conrado J.; Jones, Marcus H.; Tiller, Christina; Kimmel, Risa; Kisling, Jeffrey; Nguyen, Evelyn T.; Nguyen, James; Yu, Zhangsheng; Kaplan, Mark H.; Tepper, Robert S.

    2010-01-01

    Background Childhood asthma is most often characterized by recurrent wheezing, airway hyper-reactivity, and atopy; however, our understanding of these relationships from early in life remains unclear. Respiratory illnesses and atopic sensitization early in life may produce an interaction between innate and acquired immune responses leading to airway inflammation and heightened airway reactivity. Objective We hypothesized that pre-morbid airway reactivity and immunologic characteristics of infants without prior episodes of wheezing would be associated with subsequent wheezing during 1-year follow-up. Methods 116 infants with chronic dermatitis were enrolled prior to episodes of wheezing. Airway reactivity, allergen-specific IgE, cytokine production by stimulated peripheral blood mononuclear cells (PBMCs), and percentages of dendritic cells were measured upon entry and airway reactivity was reassessed at 1-year follow-up. Linear regression models were used to evaluate predictor’s effect on continuous outcomes. Results milk and/or egg sensitization was associated with heightened airway reactivity prior to wheezing and after the onset of wheezing; however, these factors were not associated with an increased risk of wheezing. There was an interaction between initial airway reactivity and wheezing as a determinant of airway reactivity at follow-up. In addition, cytokine production by stimulated PBMCs was a risk factor for wheezing, while increased percentages of conventional dendritic cells were protective for wheezing. Conclusion Our data in a selected cohort of infants support a model with multiple risk factors for subsequent wheezing that are independent of initial airway reactivity; however, the etiologic factors that produce wheezing very early in life may contribute to heightened airway reactivity. PMID:20816184

  1. Interface-Tracking Simulations of Vaporization and Burning of Reactive Droplet

    NASA Astrophysics Data System (ADS)

    Tani, Hiroumi; Kanno, Nozomu; Umemura, Yutaka; Terashima, Hiroshi; Koshi, Mitsuo

    2015-11-01

    Liquid fuel and oxidizer of space propulsion often have highly reactive characteristics which mean fuel and oxidizer spontaneously auto-ignite when they come into contact with each other in combustors. To control the timing of the ignition and consumption rate of such reactive liquids, the phase change and chemical reactions near the liquid-liquid and liquid-gas interfaces should be understood. Lagrangian droplet-tracking method, which is often employed for spray combustion of industrial fuels, cannot accurately predict the vaporization and auto-ignition of reactive droplets. Thus, the present study developed a CFD method, by coupling an interface tracking method with a phase change model and chemical reaction model, to explore the reactive flows near the liquid-gas interface of reactive droplets. The auto-ignition processes and the interaction between chemical reactions and evaporation of reactive droplets will be discussed. Furthermore, the effects of the droplet size and ambient pressure upon the ignition delay time and burning rate will be presented to develop or modify the droplet evaporation models of lagrangian droplet-tracking methods.

  2. Determination of OH reactivity of unidentified VOCs detected by GC-FID analysis

    NASA Astrophysics Data System (ADS)

    Kato, S.; Sato, T.; Kajii, Y.

    2009-12-01

    OH reactivity which is defined as a sum of reaction rates of each reactive chemical species with OH radicals provides quite useful information about air quality as index of photochemical activity in the atmosphere. To determine OH reactivity of the air abundances of each VOCs existing in the air are essential. A lot of efforts to characterize VOC concentrations have been carried out by GC-FID analysis. There are considerable numbers of unidentified peaks of volatile organic compounds (VOCs) generally detected when urban air samples were analyzed by a GC-FID technique. A new method to determine the contribution of OH reactivity of such unidentified VOCs using relative rate analysis of OH radicals is proposed. Sampled air was analyzed by 2 different modes. One is analyzed as usual by a GC-FID method. The other sample was at first exposed by OH radicals that were generated in the photolysis of water vapor by a pen ray mercury lamp for a certain period and was analyzed by the same method. The difference of peak area of each species with and without of OH exposure should depend on OH reactivity of the species of interest. Standard gas sample which included 56 kinds of VOCs was tested by this method and the validity and utility of the system developed by this study was confirmed. An ambient air sample obtained in suburban of Tokyo was then examined. Using known species OH reactivity of each unidentified species was successfully applied and the result will be presented.

  3. Detection of Pesticides and Pesticide Metabolites Using the Cross Reactivity of Enzyme Immunoassays

    USGS Publications Warehouse

    Thurman, E.M.; Aga, D.S.

    2001-01-01

    Enzyme immunoassay is an important environmental analysis method that may be used to identify many pesticide analytes in water samples. Because of similarities in chemical structure between various members of a pesticide class, there often may be an unwanted response that is characterized by a percentage of cross reactivity. Also, there may be cross reactivity caused by degradation products of the target analyte that may be present in the sample. In this paper, the concept of cross reactivity caused by degradation products or by nontarget analytes is explored as a tool for identification of metabolites or structurally similar compounds not previously known to be present in water samples. Two examples are examined in this paper from various water quality studies. They are alachlor and its metabolite, alachlor ethane sulfonic acid, and atrazine and its class members, prometryn and propazine. A method for using cross reactivity for the detection of these compounds is explained in this paper.

  4. Reactive Nitrogen in Atmospheric Emission Inventories

    EPA Science Inventory

    Excess reactive Nitrogen (NT) has become one of the most pressing environmental problems leading to air pollution, acidification and eutrophication of ecosystems, biodiversity impacts, leaching of nitrates into groundwater and global warming. This paper investigates how current i...

  5. A Tariff for Reactive Power - IEEE

    SciTech Connect

    Kueck, John D; Tufon, Christopher; Isemonger, Alan; Kirby, Brendan J

    2008-11-01

    This paper describes a suggested tariff or payment for the local supply of reactive power from distributed energy resources. The authors consider four sample customers, and estimate the cost of supply of reactive power for each customer. The power system savings from the local supply of reactive power are also estimated for a hypothetical circuit. It is found that reactive power for local voltage regulation could be supplied to the distribution system economically by customers when new inverters are installed. The inverter would be supplied with a power factor of 0.8, and would be capable of local voltage regulation to a schedule supplied by the utility. Inverters are now installed with photovoltaic systems, fuel cells and microturbines, and adjustable-speed motor drives.

  6. Reactive navigational controller for autonomous mobile robots

    NASA Astrophysics Data System (ADS)

    Hawkins, Scott

    1993-12-01

    Autonomous mobile robots must respond to external challenges and threats in real time. One way to satisfy this requirement is to use a fast low level intelligence to react to local environment changes. A fast reactive controller has been implemented which performs the task of real time local navigation by integrating primitive elements of perception, planning, and control. Competing achievement and constraint behaviors are used to allow abstract qualitative specification of navigation goals. An interface is provided to allow a higher level deliberative intelligence with a more global perspective to set local goals for the reactive controller. The reactive controller's simplistic strategies may not always succeed, so a means to monitor and redirect the reactive controller is provided.

  7. Dynamic reactive astrocytes after focal ischemia

    PubMed Central

    Ding, Shinghua

    2014-01-01

    Astrocytes are specialized and most numerous glial cell type in the central nervous system and play important roles in physiology. Astrocytes are also critically involved in many neural disorders including focal ischemic stroke, a leading cause of brain injury and human death. One of the prominent pathological features of focal ischemic stroke is reactive astrogliosis and glial scar formation associated with morphological changes and proliferation. This review paper discusses the recent advances in spatial and temporal dynamics of morphology and proliferation of reactive astrocytes after ischemic stroke based on results from experimental animal studies. As reactive astrocytes exhibit stem cell-like properties, knowledge of dynamics of reactive astrocytes and glial scar formation will provide important insights for astrocyte-based cell therapy in stroke. PMID:25657720

  8. Language reactivity and work functioning in schizophrenia.

    PubMed

    St-Hilaire, Annie; Docherty, Nancy M

    2005-06-15

    Some studies have found that the speech of certain schizophrenia patients becomes more disordered in stressful laboratory situations. It is unknown, however, whether affective reactivity of speech is associated with stress responsiveness of symptoms in the real world. This study examines whether language-reactive patients report more stress-related impairments in work functioning than language-nonreactive patients. Forty-six patients provided speech samples and completed a work history interview. It was found that the language-reactive patients were more likely than the language-nonreactive patients to endorse items pertaining to social anxiety and difficulty relating to others as reasons for their work difficulties. This suggests that language-reactive patients are more sensitive to social stressors than language-nonreactive patients. PMID:15885516

  9. REGIONAL DEPOSITION OF INHALED REACTIVE GASES

    EPA Science Inventory

    A critical concept in inhalation toxicology involves the determination of dose as the first component for providing a perspective to judge the applicability of various toxicological results to human exposure conditions. Available experimental data for reactive gases were reviewed...

  10. Simian varicella virus reactivation in cynomolgus monkeys

    SciTech Connect

    Mahalingam, Ravi Traina-Dorge, Vicki Wellish, Mary Lorino, Rebecca Sanford, Robert Ribka, Erin P. Alleman, Scott J. Brazeau, Elizabeth Gilden, Donald H.

    2007-11-10

    SVV infection of primates closely resembles VZV infection of humans. Like VZV, SVV becomes latent in ganglionic neurons. We used this model to study the effect of immunosuppression on varicella reactivation. Cynomolgus monkeys latently infected with SVV were irradiated and treated with tacrolimus and prednisone. Of four latently infected monkeys that were immunosuppressed and subjected to the stress of transportation and isolation, one developed zoster, and three others developed features of subclinical reactivation. Another non-immunosuppressed latently infected monkey that was subjected to the same stress of travel and isolation showed features of subclinical reactivation. Virus reactivation was confirmed not only by the occurrence of zoster in one monkey, but also by the presence of late SVV RNA in ganglia, and the detection of SVV DNA in non-ganglionic tissue, and SVV antigens in skin, ganglia and lung.

  11. REACTIVE AND PROACTIVE AGGRESSION IN ADOLESCENT MALES

    PubMed Central

    Fite, Paula J.; Raine, Adrian; Stouthamer-Loeber, Magda; Loeber, Rolf; Pardini, Dustin A.

    2010-01-01

    There is limited knowledge about the unique relations between adolescent reactive and proactive aggression and later psychosocial adjustment in early adulthood. Accordingly, this study prospectively examined associations between adolescent (mean age = 16) reactive and proactive aggression and psychopathic features, antisocial behavior, negative emotionality, and substance use measured 10 years later in early adulthood (mean age = 26). Study questions were examined in a longitudinal sample of 335 adolescent males. Path analyses indicate that after controlling for the stability of the outcome and the overlap between the two subtypes of aggression, reactive aggression is uniquely associated with negative emotionality, specifically anxiety, in adulthood. In contrast, proactive aggression is uniquely associated with measures of adult psychopathic features and antisocial behavior in adulthood. Both reactive and proactive aggression uniquely predicted substance use in adulthood, but the substances varied by subtype of aggression. Implications for findings are discussed. PMID:20589225

  12. Reactivity control assembly for nuclear reactor

    DOEpatents

    Bollinger, Lawrence R.

    1984-01-01

    Reactivity control assembly for nuclear reactor comprises supports stacked above reactor core for holding control rods. Couplers associated with the supports and a vertically movable drive shaft have lugs at their lower ends for engagement with the supports.

  13. Evaluation the pozzolanic reactivity of sonochemically fabricated nano natural pozzolan.

    PubMed

    Askarinejad, Azadeh; Pourkhorshidi, Ali Reza; Parhizkar, Tayebeh

    2012-01-01

    Natural pozzolans are appropriate supplementary cementitious materials in cement and concrete industry. A simple sonochemical method was developed to synthesize nanostructures of natural pozzolan. Chemical composition, crystallinity, morphology and reactivity of the natural pozzolan samples were compared before and after the sonochemical process, by using powder X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Thermal Gravimetry and Differential Thermal Analysis (TG/DTA). Compressive strength tests were performed to evaluate the properties of blended cements incorporating nano natural pozzolan. Under optimized conditions, the nano natural pozzolans showed a superior reactivity as compared with the bulk natural pozzolan. Also higher compressive strength was obtained for the cement specimen incorporating nano natural pozzolan. PMID:21636307

  14. Introducing "UCA-FUKUI" software: reactivity-index calculations.

    PubMed

    Sánchez-Márquez, Jesús; Zorrilla, David; Sánchez-Coronilla, Antonio; de los Santos, Desireé M; Navas, Javier; Fernández-Lorenzo, Concha; Alcántara, Rodrigo; Martín-Calleja, Joaquín

    2014-11-01

    A new software (UCA-FUKUI) has been developed to facilitate the theoretical study of chemical reactivity. This program can calculate global parameters like hardness, softness, philicities, and Fukui condensed functions, and also local parameters from the condensed functions. To facilitate access to the program we have developed a very easy-to-use interface. We have tested the performance of the software by calculating the global and local reactivity indexes of a group of representative molecules. Finite difference and frontier molecular orbital methods were compared and their correlation tested. Finally, we have extended the analysis to a set of ligands of importance in coordination chemistry, and the results are compared with the exact calculation. As a general trend, our study shows the existence of a high correlation between global parameters, but a weaker correlation between local parameters. PMID:25338819

  15. Microsphere coated substrate containing reactive aldehyde groups

    NASA Technical Reports Server (NTRS)

    Rembaum, Alan (Inventor); Yen, Richard C. K. (Inventor)

    1984-01-01

    A synthetic organic resin is coated with a continuous layer of contiguous, tangential, individual microspheres having a uniform diameter preferably between 100 Angstroms and 2000 Angstroms. The microspheres are an addition polymerized polymer of an unsaturated aldehyde containing 4 to 20 carbon atoms and are covalently bonded to the substrate by means of high energy radiation grafting. The microspheres contain reactive aldehyde groups and can form conjugates with proteins such as enzymes or other aldehyde reactive materials.

  16. High throughput assay for evaluation of reactive carbonyl scavenging capacity☆

    PubMed Central

    Vidal, N.; Cavaille, J.P.; Graziani, F.; Robin, M.; Ouari, O.; Pietri, S.; Stocker, P.

    2014-01-01

    Many carbonyl species from either lipid peroxidation or glycoxidation are extremely reactive and can disrupt the function of proteins and enzymes. 4-hydroxynonenal and methylglyoxal are the most abundant and toxic lipid-derived reactive carbonyl species. The presence of these toxics leads to carbonyl stress and cause a significant amount of macromolecular damages in several diseases. Much evidence indicates trapping of reactive carbonyl intermediates may be a useful strategy for inhibiting or decreasing carbonyl stress-associated pathologies. There is no rapid and convenient analytical method available for the assessment of direct carbonyl scavenging capacity, and a very limited number of carbonyl scavengers have been identified to date, their therapeutic potential being highlighted only recently. In this context, we have developed a new and rapid sensitive fluorimetric method for the assessment of reactive carbonyl scavengers without involvement glycoxidation systems. Efficacy of various thiol- and non-thiol-carbonyl scavenger pharmacophores was tested both using this screening assay adapted to 96-well microplates and in cultured cells. The scavenging effects on the formation of Advanced Glycation End-product of Bovine Serum Albumin formed with methylglyoxal, 4-hydroxynonenal and glucose-glycated as molecular models were also examined. Low molecular mass thiols with an α-amino-β-mercaptoethane structure showed the highest degree of inhibitory activity toward both α,β-unsaturated aldehydes and dicarbonyls. Cysteine and cysteamine have the best scavenging ability toward methylglyoxal. WR-1065 which is currently approved for clinical use as a protective agent against radiation and renal toxicity was identified as the best inhibitor of 4-hydroxynonenal. PMID:24688895

  17. A roadmap for OH reactivity research

    NASA Astrophysics Data System (ADS)

    Williams, Jonathan; Brune, William

    2015-04-01

    A fundamental property of the atmosphere is the frequency of gas-phase reactions with the OH radical, the atmosphere's primary oxidizing agent. This reaction frequency is called the OH reactivity and is the inverse the lifetime of the OH radical itself, which varies from a few seconds in the clean upper troposphere to below 10 ms in forests and polluted city environments. Ever since the discovery of the OH radical's importance to tropospheric chemistry, the characterization of its overall loss rate (OH reactivity) has remained a key question. At first, this property was assessed by summing the reactivity contributions of individually measured compounds; however, as improving analytical technology revealed ever more reactive species in ambient air, it became clear that this approach could provide only a lower limit. Approximately 15 years ago, the direct measurement of total OH reactivity was conceived independently by two groups. The first publications demonstrated direct OH reactivity measurements in the laboratory (Calpini et al., 1999) based on LIDAR and in the ambient air (Kovacs and Brune, 2001) based on in situ laser induced fluorescence detection of OH.

  18. Neighborhood disadvantage and adolescent stress reactivity

    PubMed Central

    Hackman, Daniel A.; Betancourt, Laura M.; Brodsky, Nancy L.; Hurt, Hallam; Farah, Martha J.

    2012-01-01

    Lower socioeconomic status (SES) is associated with higher levels of life stress, which in turn affect stress physiology. SES is related to basal cortisol and diurnal change, but it is not clear if SES is associated with cortisol reactivity to stress. To address this question, we examined the relationship between two indices of SES, parental education and concentrated neighborhood disadvantage, and the cortisol reactivity of African–American adolescents to a modified version of the Trier Social Stress Test (TSST). We found that concentrated disadvantage was associated with cortisol reactivity and this relationship was moderated by gender, such that higher concentrated disadvantage predicted higher cortisol reactivity and steeper recovery in boys but not in girls. Parental education, alone or as moderated by gender, did not predict reactivity or recovery, while neither education nor concentrated disadvantage predicted estimates of baseline cortisol. This finding is consistent with animal literature showing differential vulnerability, by gender, to the effects of adverse early experience on stress regulation and the differential effects of neighborhood disadvantage in adolescent males and females. This suggests that the mechanisms underlying SES differences in brain development and particularly reactivity to environmental stressors may vary across genders. PMID:23091454

  19. On reactive high power impulse magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Gudmundsson, J. T.

    2016-01-01

    High power impulse magnetron sputtering (HiPIMS) is an ionized physical vapor deposition (IPVD) technique that is particularly promising for reactive sputtering applications. However, there are few issues that have to be resolved before the full potential of this technique can be realized. Here we give an overview of the key experimental findings for the reactive HiPIMS discharge. An increase in the discharge current is commonly observed with increased partial pressure of the reactive gas or decreased repetition pulse frequency. There are somewhat conflicting claims regarding the hysteresis effect in the reactive HiPIMS discharge as some report reduction or elimination of the hysteresis effect while others claim a feedback control is essential. The ion energy distribution of the metal ion and the atomic ion of the reactive gas are similar and extend to very high energies while the ion energy distribution of the working gas and the molecular ion of the reactive gas are similar and are much less energetic.

  20. The use of density functional theory-based reactivity descriptors in molecular similarity calculations

    NASA Astrophysics Data System (ADS)

    Boon, Greet; De Proft, Frank; Langenaeker, Wilfried; Geerlings, Paul

    1998-10-01

    Molecular similarity is studied via density functional theory-based similarity indices using a numerical integration method. Complementary to the existing similarity indices, we introduce a reactivity-related similarity index based on the local softness. After a study of some test systems, a series of peptide isosteres is studied in view of their importance in pharmacology. The whole of the present work illustrates the importance of the study of molecular similarity based on both shape and reactivity.

  1. Reactive multilayer synthesis of hard ceramic foils and films

    DOEpatents

    Makowiecki, D.M.; Holt, J.B.

    1996-02-13

    A method is disclosed for synthesizing hard ceramic materials such as carbides, borides and aluminides, particularly in the form of coatings provided on another material so as to improve the wear and abrasion performance of machine tools, for example. The method involves the sputter deposition of alternating layers of reactive metals with layers of carbon, boron, or aluminum and the subsequent reaction of the multilayered structure to produce a dense crystalline ceramic. The material can be coated on a substrate or formed as a foil which can be coiled as a tape for later use.

  2. Reactive multilayer synthesis of hard ceramic foils and films

    DOEpatents

    Makowiecki, Daniel M.; Holt, Joseph B.

    1996-01-01

    A method for synthesizing hard ceramic materials such as carbides, borides nd aluminides, particularly in the form of coatings provided on another material so as to improve the wear and abrasion performance of machine tools, for example. The method involves the sputter deposition of alternating layers of reactive metals with layers of carbon, boron, or aluminum and the subsequent reaction of the multilayered structure to produce a dense crystalline ceramic. The material can be coated on a substrate or formed as a foil which can be coild as a tape for later use.

  3. Reactive multilayer synthesis of hard ceramic foils and films

    SciTech Connect

    Makowiecki, D.M.; Holt, J.B.

    1993-12-31

    Disclosed is method for synthesizing hard ceramic materials such as carbides, borides and aluminides, particularly in the form of coatings provided on another material so as to improve the wear and abrasion performance of machine tools, for example. Method involves the sputter deposition of alternating layers of reactive metals with layers of carbon, boron, or aluminum and the subsequent reaction of the multilayered structure to produce a dense crystalline ceramic. The material can be coated on a substrate or formed as a foil which can be coiled as a tape for later use.

  4. Smell differential reactivity, but not taste differential reactivity, is related to food neophobia in toddlers.

    PubMed

    Monnery-Patris, Sandrine; Wagner, Sandra; Rigal, Natalie; Schwartz, Camille; Chabanet, Claire; Issanchou, Sylvie; Nicklaus, Sophie

    2015-12-01

    Previous research has identified relationships between chemosensory reactivity and food neophobia in children. However, most studies have investigated this relationship using declarative data and without separately analysing smell and taste reactivity. Our first objective was to assess the relationships between smell and taste differential reactivity in toddlers (i.e. reactivity towards several stimuli), using experimental behavioural measurements. The second objective was to determine the relationships between smell (or taste) differential reactivity and food neophobia in toddlers, with the hypothesis that the more responsive a toddler was across food odours or tastes, the more neophobic s/he would be. An additional objective was to determine whether the potential relationships between smell (or taste) differential reactivity and food neophobia differ according to gender. One hundred and twenty-three toddlers aged from 20 to 22 months from the Opaline birth cohort (Observatory of Food Preferences in Infants and Children) were involved. A questionnaire was used to assess child's food neophobia. Toddlers' differential reactivity for smell (and for taste) was defined as the variability of behavioural responses over 8 odorants, and over the five basic tastes. Smell and taste differential reactivities were not correlated. Food neophobia scores were modestly but significantly positively correlated with smell differential reactivity but not with taste differential reactivity. When gender was considered, smell reactivity and neophobia were correlated only among boys. This indicates the need to study smell and taste reactivity separately to determine their associations with eating behaviours. This suggests that the rejection of novel foods in neophobic boys could be partly due to food odour. This finding is new and clearly requires further investigation. PMID:26208908

  5. Effects of thermomechanical processing on strength and toughness of iron - 12-percent-nickel - reactive metal alloys at -196 C

    NASA Technical Reports Server (NTRS)

    Stephens, J. R.; Witzke, W. R.

    1978-01-01

    Thermomechanical processing (TMP) was evaluated as a method of strengthening normally tough iron-12-nickel-reactive metal alloys at cryogenic temperatures. Five iron-12 nickel alloys with reactive metal additions of aluminum, niobium, titanium, vanadium, and aluminum plus niobium were investigated. Primary evaluation was based on the yield strength and fracture toughness of the thermomechanically processed alloys at -196 C.

  6. Experimental and Theoretical Investigations of Hot Isostatically Pressed-Produced Stainless Steel/High Alloy Tool Steel Compound Materials

    NASA Astrophysics Data System (ADS)

    Lindwall, Greta; Flyg, Jesper; Frisk, Karin; Sandberg, Odd

    2011-05-01

    Consolidation of tool steel powders and simultaneous joining to a stainless 316L steel are performed by hot isostatic pressing (HIP). Two tool steel grades are considered: a high vanadium alloyed carbon tool steel, and a high vanadium and chromium alloyed nitrogen tool steel. The boundary layer arising during diffusion bonding is in focus and, in particular, the diffusion of carbon and nitrogen over the joint. Measurements of the elemental concentration profiles and corrosion tests by the double loop-electrochemical potentiokinetic reactivation (DL-EPR) method are performed. Comparative calculations with the DICTRA software are performed and are found to be in agreement with the experimental results. It is found that the carbon tool steel grade has a more critical influence on the corrosion resistance of the stainless 316L steel in comparison to the nitrogen tool steel grade.

  7. EPA/ITRC-RTDF permeable reactive barrier short course. Permeable reactive barriers: Application and deployment

    SciTech Connect

    Not Available

    1999-01-01

    This report focuses on the following: Permeable Reactive Barriers: Application and Deployment; Introduction to Permeable Reactive Barriers (PRBs) for Remediating and Managing Contaminated Groundwater in Situ; Collection and Interpretation of Design Data 1: Site Characterization for PRBs; Reactive Materials: Zero-Valent Iron; Collection and Interpretation of Design Data 2: Laboratory and Pilot Scale Tests; Design Calculations; Compliance Monitoring, Performance Monitoring and Long-Term Maintenance for PRBs; PRB Emplacement Techniques; PRB Permitting and Implementation; Treatment of Metals; Non-Metallic Reactive Materials; Economic Considerations for PRB Deployment; and Bibliography.

  8. EPA/ITRC-RTDF permeable reactive barrier short course. Permeable reactive barriers: Application and deployment

    SciTech Connect

    1999-11-01

    This report focuses on the following: Permeable Reactive Barriers: Application and Deployment; Introduction to Permeable Reactive Barriers (PRBs) for Remediating and Managing Contaminated Groundwater in Situ; Collection and Interpretation of Design Data 1: Site Characterization for PRBs; Reactive Materials: Zero-Valent Iron; Collection and Interpretation of Design Data 2: Laboratory and Pilot Scale Tests; Design Calculations; Compliance Monitoring, Performance Monitoring and Long-Term Maintenance for PRBs; PRB Emplacement Techniques; PRB Permitting and Implementation; Treatment of Metals; Non-Metallic Reactive Materials; Economic Considerations for PRB Deployment; and Bibliography.

  9. Reactive modification of polyesters and their blends

    NASA Astrophysics Data System (ADS)

    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. Serum peptide reactivities may distinguish neuromyelitis optica subgroups and multiple sclerosis

    PubMed Central

    Metz, Imke; Beißbarth, Tim; Ellenberger, David; Pache, Florence; Stork, Lidia; Ringelstein, Marius; Aktas, Orhan; Jarius, Sven; Wildemann, Brigitte; Dihazi, Hassan; Friede, Tim; Ruprecht, Klemens; Paul, Friedemann

    2016-01-01

    Objective: To assess in an observational study whether serum peptide antibody reactivities may distinguish aquaporin-4 (AQP4) antibody (Ab)–positive and -negative neuromyelitis optica spectrum disorders (NMOSD) and relapsing-remitting multiple sclerosis (RRMS). Methods: We screened 8,700 peptides that included human and viral antigens of potential relevance for inflammatory demyelinating diseases and random peptides with pooled sera from different patient groups and healthy controls to set up a customized microarray with 700 peptides. With this microarray, we tested sera from 66 patients with AQP4-Ab-positive (n = 16) and AQP4-Ab-negative (n = 19) NMOSD, RRMS (n = 11), and healthy controls (n = 20). Results: Differential peptide reactivities distinguished NMOSD subgroups from RRMS in 80% of patients. However, the 2 NMOSD subgroups were not well-discriminated, although those patients are clearly separated by their antibody reactivities against AQP4 in cell-based assays. Elevated reactivities to myelin and Epstein-Barr virus peptides were present in RRMS and to AQP4 and AQP1 peptides in AQP4-Ab-positive NMOSD. Conclusions: While AQP4-Ab-positive and -negative NMOSD subgroups are not well-discriminated by peptide antibody reactivities, our findings suggest that peptide antibody reactivities may have the potential to distinguish between both NMOSD subgroups and MS. Future studies should thus concentrate on evaluating peptide antibody reactivities for the differentiation of AQP4-Ab-negative NMOSD and MS. PMID:26894206

  11. Memories reactivated under ketamine are subsequently stronger: A potential pre-clinical behavioral model of psychosis

    PubMed Central

    Honsberger, Michael J.; Taylor, Jane R.; Corlett, Philip R.

    2015-01-01

    Background Sub-anesthetic doses of the NMDA antagonist ketamine have been shown to model the formation and stability of delusion in human subjects. The later has been predicted to be due to aberrant prediction error resulting in enhanced destabilization of beliefs. To extend the scope of this model, we investigated the effect of administration of low dose systemic ketamine on memory in a rodent model of memory reconsolidation. Methods Systemic ketamine was administered either prior to or immediately following auditory fear memory reactivation in rats. Memory strength was assessed by measuring freezing behavior 24 hours later. Follow up experiments were designed to investigate an effect of pre-reactivation ketamine on short-term memory (STM), closely related memories, and basolateral amygdala (BLA) specific destabilization mechanisms. Results Rats given pre-reactivation, but not post-reactivation, ketamine showed larger freezing responses 24 hours later compared to vehicle. This enhancement was not observed 3 hours after the memory reactivation, nor was it seen in a closely related contextual memory. Prior inhibition of a known destabilization mechanism in the BLA blocked the effect of pre-reactivation ketamine. Conclusions Pre- but not post-reactivation ketamine enhances fear memory. These data together with recent data in human subjects supports a model of delusion fixity that proposes that aberrant prediction errors result in enhanced destabilization and strengthening of delusional belief. PMID:25728834

  12. Crossing the dividing surface of transition state theory. III. Once and only once. Selecting reactive trajectories

    SciTech Connect

    Lorquet, J. C.

    2015-09-14

    The purpose of the present work is to determine initial conditions that generate reacting, recrossing-free trajectories that cross the conventional dividing surface of transition state theory (i.e., the plane in configuration space passing through a saddle point of the potential energy surface and perpendicular to the reaction coordinate) without ever returning to it. Local analytical equations of motion valid in the neighborhood of this planar surface have been derived as an expansion in Poisson brackets. We show that the mere presence of a saddle point implies that reactivity criteria can be quite simply formulated in terms of elements of this series, irrespective of the shape of the potential energy function. Some of these elements are demonstrated to be equal to a sum of squares and thus to be necessarily positive, which has a profound impact on the dynamics. The method is then applied to a three-dimensional model describing an atom-diatom interaction. A particular relation between initial conditions is shown to generate a bundle of reactive trajectories that form reactive cylinders (or conduits) in phase space. This relation considerably reduces the phase space volume of initial conditions that generate recrossing-free trajectories. Loci in phase space of reactive initial conditions are presented. Reactivity is influenced by symmetry, as shown by a comparative study of collinear and bent transition states. Finally, it is argued that the rules that have been derived to generate reactive trajectories in classical mechanics are also useful to build up a reactive wave packet.

  13. Baseline Platelet Activation and Reactivity in Patients with Critical Limb Ischemia

    PubMed Central

    de Borst, Gert Jan; Verhaar, Marianne C.; Roest, Mark; Moll, Frans L.

    2015-01-01

    Background Patients with critical limb ischemia (CLI) have a high risk to develop cardiovascular events (CVE). We hypothesized that in CLI patients platelets would display increased baseline activation and reactivity. Objectives We investigated baseline platelet activation and platelet reactivity in patients with CLI. Patients/Methods In this study baseline platelet activation and platelet reactivity in response to stimulation of all major platelet activation pathways were determined in 20 CLI patients (11 using aspirin and 9 using vitamin K-antagonists) included in the Juventas-trial (clinicaltrials.gov NCT00371371) and in 17 healthy controls. Platelet activation was quantified with flow cytometric measurement of platelet P-selectin expression and fibrinogen binding. Results CLI patients not using aspirin showed higher baseline platelet activation compared to healthy controls. Maximal reactivity to stimulation of the collagen and thrombin activation pathway was decreased in CLI patients compared to healthy controls. In line, attenuated platelet reactivity to stimulation of multiple activation pathways was associated with several traditional risk factors for cardiovascular disease. Conclusions Baseline platelet activation was increased in CLI patients, whereas the reactivity of circulating platelets to several stimulatory agents is decreased. Reactivity of platelets was inversely correlated with cardiovascular risk factors. PMID:26148006

  14. Biodegradable hollow zein nanoparticles for removal of reactive dyes from wastewater.

    PubMed

    Xu, Helan; Zhang, Yue; Jiang, Qiuran; Reddy, Narendra; Yang, Yiqi

    2013-08-15

    In this study, biodegradable hollow zein nanoparticles with diameters less than 100 nm were developed to remove reactive dyes from simulated post-dyeing wastewater with remarkably high efficiency. Reactive dyes are widely used to color cellulosic materials, such as cotton and rayon. Wastewater from reactive dyeing process contains up to 50% dye and electrolytes with concentrations up to 100 g L(-1). Current methods to remove reactive dyes from wastewater are suffering from low adsorption capacities or low biodegradability of the sorbents. In this research, biodegradable zein nanoparticles showed high adsorption capacities for dyes. Hollow zein nanoparticles showed higher adsorption for Reactive Blue 19 than solid structures, and the adsorption amount increased as temperature decreased, pH decreased or initial dye concentration increased. At pH 6.5 and pH 9.0, increasing electrolyte concentration could improve dye adsorption significantly. Under simulated post-dyeing condition with 50.0 g L(-1) salt and pH 9.0, maximum adsorption of 1016.0 mg dye per gram zein nanoparticles could be obtained. The adsorption capacity was much higher than that of various biodegradable adsorbents developed to remove reactive dye. It is suggested that the hollow zein nanoparticles are good candidates to remove reactive dye immediately after dyeing process. PMID:23643969

  15. Characteristics of high quality sorbent for fluidized bed combustion and problems of maintaining uniform reactivity

    SciTech Connect

    Bain, R.J. . Dept. of Geology)

    1993-03-01

    Fluidized bed combustion of coal is considered one of the more promising clean coal technologies for the future. While much research has gone into the design and operation of FBC units, there is little concern for what characterizes a high quality sorbent and the source of such a sorbent. Carbonate rocks, limestone and dolomite, have been tested extensively as sorbents and primarily two rock characteristics appear to significantly control reactivity: composition and texture. Calcium carbonate is more reactive than magnesium carbonate where all other rock characteristics are the same. In considering texture, highest reactivity is measured for carbonate rocks which consist of homogeneous, euhedral crystals ranging in size from .05 to .2 mm and which possess uniform intercrystalline porosity. The most reactive material possesses both high calcium content, uniform microcrystalline texture and intercrystalline porosity, however, such material is not very abundant in nature and is not locally available to midcontinent facilities. Sucrosic dolomite, which possesses uniform microcrystalline texture and intercrystalline porosity has high rank reactivity. While this rock is quite common, it occurs as beds, generally less than twenty feet thick, interlayered with less reactive dolomite types. Therefore, without selective quarrying methods, production of sorbent with uniformly high reactivity will be impossible.

  16. KSHV Rta Promoter Specification and Viral Reactivation.

    PubMed

    Guito, Jonathan; Lukac, David M

    2012-01-01

    Viruses are obligate intracellular pathogens whose biological success depends upon replication and packaging of viral genomes, and transmission of progeny viruses to new hosts. The biological success of herpesviruses is enhanced by their ability to reproduce their genomes without producing progeny viruses or killing the host cells, a process called latency. Latency permits a herpesvirus to remain undetected in its animal host for decades while maintaining the potential to reactivate, or switch, to a productive life cycle when host conditions are conducive to generating viral progeny. Direct interactions between many host and viral molecules are implicated in controlling herpesviral reactivation, suggesting complex biological networks that control the decision. One viral protein that is necessary and sufficient to switch latent Kaposi's sarcoma-associated herpesvirus (KSHV) into the lytic infection cycle is called K-Rta. K-Rta is a transcriptional activator that specifies promoters by binding DNA directly and interacting with cellular proteins. Among these cellular proteins, binding of K-Rta to RBP-Jk is essential for viral reactivation. In contrast to the canonical model for Notch signaling, RBP-Jk is not uniformly and constitutively bound to the latent KSHV genome, but rather is recruited to DNA by interactions with K-Rta. Stimulation of RBP-Jk DNA binding requires high affinity binding of Rta to repetitive and palindromic "CANT DNA repeats" in promoters, and formation of ternary complexes with RBP-Jk. However, while K-Rta expression is necessary for initiating KSHV reactivation, K-Rta's role as the switch is inefficient. Many factors modulate K-Rta's function, suggesting that KSHV reactivation can be significantly regulated post-Rta expression and challenging the notion that herpesviral reactivation is bistable. This review analyzes rapidly evolving research on KSHV K-Rta to consider the role of K-Rta promoter specification in regulating the progression of KSHV

  17. Bayesian hierarchical approach and geophysical data sets for estimation of reactive facies over plume scales

    NASA Astrophysics Data System (ADS)

    Wainwright, Haruko M.; Chen, Jinsong; Sassen, Douglas S.; Hubbard, Susan S.

    2014-06-01

    A stochastic model is developed to integrate multiscale geophysical and point data sets for characterizing coupled subsurface physiochemical properties over plume-relevant scales, which is desired for parameterizing reactive transport models. We utilize the concept of reactive facies, which is based on the hypothesis that subsurface units can be identified that have distinct reactive-transport-property distributions. To estimate and spatially distribute reactive facies and their associated properties over plume-relevant scales, we need to (1) document the physiochemical controls on plume behavior and the correspondence between geochemical, hydrogeological, and geophysical measurements; and (2) integrate multisource, multiscale data sets in a consistent manner. To tackle these cross-scale challenges, we develop a hierarchical Bayesian model to jointly invert various wellbore and geophysical data sets that have different resolutions and spatial coverage. We use Markov-chain Monte-Carlo sampling methods to draw many samples from the joint posterior distribution and subsequently estimate the marginal posterior distribution of reactive-facies field and their associated reactive transport properties. Synthetic studies demonstrate that our method can successfully integrate different types of data sets. We tested the framework using the data sets collected at the uranium-contaminated Savannah River Site F-Area, including wellbore lithology, cone penetrometer testing, and crosshole and surface seismic data. Results show that the method can estimate the spatial distribution of reactive facies and their associated reactive-transport properties along a 300 m plume centerline traverse with high resolution (1.2 m by 0.305 m).

  18. Reactivation of landslides by surface subsidence from longwall mining

    SciTech Connect

    Iannacchione, A.T.; Ackman, T.E.

    1984-12-01

    Subsidence research by the US Bureau of Mines has identified and documented the occurrence of landslides over a longwall mining area in the Dunkard basin. Mining by longwall methods has been observed or produce a gradual surface subsidence profile of up to 60% of the thickness of the mined coal bed. The gradual subsidence of panels averaging 600 x 5000 ft (180 x 1525 m) can cause reactivation of older landslide deposits by decreasing the support to the landslide toe area. Examination of surficial features over a longwall mining area comprised of nine panels has led to the identification of several reactivated landslides. The two largest landslides occurred above a thin sandstone member with several associated springs. The largest landslides ranged from 100 to 300 ft (30 to 90 m) in length and from 100 to 200 ft (30 to 60 m) in width. Maximum scarp-slope displacements were approximately 7 ft (2 m). Less significant mass wasting was also observed over the longwall panels. Identification of landslides was accomplished through examination of premining aerial photographs and geologic field investigation. Characterization of reactivated zones was achieved through evaluation of current aerial 2-ft (0.6-m) surface contour map and field surveys. Recognition of problem areas will make civic and mining personnel aware of the landslide potential so that damage in such areas can be minimized.

  19. Profiling Reactive Metabolites via Chemical Trapping and Targeted Mass Spectrometry.

    PubMed

    Chang, Jae Won; Lee, Gihoon; Coukos, John S; Moellering, Raymond E

    2016-07-01

    Metabolomic profiling studies aim to provide a comprehensive, quantitative, and dynamic portrait of the endogenous metabolites in a biological system. While contemporary technologies permit routine profiling of many metabolites, intrinsically labile metabolites are often improperly measured or omitted from studies due to unwanted chemical transformations that occur during sample preparation or mass spectrometric analysis. The primary glycolytic metabolite 1,3-bisphosphoglyceric acid (1,3-BPG) typifies this class of metabolites, and, despite its central position in metabolism, has largely eluded analysis in profiling studies. Here we take advantage of the reactive acylphosphate group in 1,3-BPG to chemically trap the metabolite with hydroxylamine during metabolite isolation, enabling quantitative analysis by targeted LC-MS/MS. This approach is compatible with complex cellular metabolome, permits specific detection of the reactive (1,3-) instead of nonreactive (2,3-) BPG isomer, and has enabled direct analysis of dynamic 1,3-BPG levels resulting from perturbations to glucose processing. These studies confirmed that standard metabolomic methods misrepresent cellular 1,3-BPG levels in response to altered glucose metabolism and underscore the potential for chemical trapping to be used for other classes of reactive metabolites. PMID:27314642

  20. Colorimetric detection of catalytic reactivity of nanoparticles in complex matrices.

    PubMed

    Corredor, Charlie; Borysiak, Mark D; Wolfer, Jay; Westerhoff, Paul; Posner, Jonathan D

    2015-03-17

    There is a need for new methodologies to quickly assess the presence and reactivity of nanoparticles (NPs) in commercial, environmental, and biological samples since current detection techniques require expensive and complex analytical instrumentation. Here, we investigate a simple and portable colorimetric detection assay that assesses the surface reactivity of NPs, which can be used to detect the presence of NPs, in complex matrices (e.g., environmental waters, serum, urine, and in dissolved organic matter) at as low as part per billion (ppb) or ng/mL concentration levels. Surface redox reactivity is a key emerging property related to potential toxicity of NPs with living cells, and is used in our assays as a key surrogate for the presence of NPs and a first tier analytical strategy toward assessing NP exposures. We detect a wide range of metal (e.g., Ag and Au) and oxide (e.g., CeO2, SiO2, VO2) NPs with a diameter range of 5 to 400 nm and multiple capping agents (tannic acid (TA), polyvinylpyrrolidone (PVP), branched polyethylenimine (BPEI), polyethylene glycol (PEG)). This method is sufficiently sensitive (ppb levels) to measure concentrations typically used in toxicological studies, and uses inexpensive, commercially available reagents. PMID:25635807

  1. Interactive effects of early and recent exposure to stressful contexts on cortisol reactivity in middle childhood

    PubMed Central

    Jaffee, Sara R; McFarquhar, Tara; Stevens, Suzanne; Ouellet-Morin, Isabelle; Melhuish, Edward; Belsky, Jay

    2015-01-01

    Background Given mixed findings as to whether stressful experiences and relationships are associated with increases or decreases in children's cortisol reactivity, we tested whether a child's developmental history of risk exposure explained variation in cortisol reactivity to an experimentally induced task. We also tested whether the relationship between cortisol reactivity and children's internalizing and externalizing problems varied as a function of their developmental history of stressful experiences and relationships. Method Participants included 400 children (M = 9.99 years, SD = 0.74 years) from the Children's Experiences and Development Study. Early risk exposure was measured by children's experiences of harsh, nonresponsive parenting at 3 years. Recent risk exposure was measured by children's exposure to traumatic events in the past year. Children's cortisol reactivity was measured in response to a social provocation task and parents and teachers described children's internalizing and externalizing problems. Results The effect of recent exposure to traumatic events was partially dependent upon a child's early experiences of harsh, nonresponsive parenting: the more traumatic events children had recently experienced, the greater their cortisol reactivity if they had experienced lower (but not higher) levels of harsh, nonresponsive parenting at age 3. The lowest levels of cortisol reactivity were observed among children who had experienced the most traumatic events in the past year and higher (vs. lower) levels of harsh, nonresponsive parenting in early childhood. Among youth who experienced harsh, nonresponsive parent–child relationships in early childhood and later traumatic events, lower levels of cortisol reactivity were associated with higher levels of internalizing and externalizing problems. Conclusions Hypothalamic–pituitary–adrenal (HPA) axis reactivity to psychological stressors and the relationship between HPA axis reactivity and children

  2. Reactive Distillation for Esterification of Bio-based Organic Acids

    SciTech Connect

    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

  3. Control of Mixing and Reactive Flow Processes

    NASA Technical Reports Server (NTRS)

    Karagozian, A. R.

    1999-01-01

    The interdisciplinary field of reactive flow control is one that holds a great deal of promise for the optimization of complex phenomena occurring in many practical systems, ranging from automobile and gas turbine engines to environmental thermal destruction systems. The fundamental underpinnings of combustion control, however, require a detailed level of understanding of complex reactive flow phenomena, and, in the case of closed-loop active control, require the ability to sense (monitor) and actuate (manipulate) flow processes in a spatially distributed manner in "near real time". Hence the ultimate growth and success of the field of reactive flow control is intimately linked: 1) to advances in the understanding, simulation, and model reduction for complex reactive flows, 2) to the development of experimental diagnostic techniques, in particular, to the development of physically robust sensors, and 3) to the development of a framework or frameworks for generation of closed loop control algorithms suitable for unsteady, nonlinear reactive flow systems. The present paper seeks to outline the potential benefits and technical challenges that exist for mixing and combustion control in fundamental as well as practical systems and to identify promising research directions that could help meet these challenges.

  4. Reactive spraying of nickel-aluminide coatings

    NASA Astrophysics Data System (ADS)

    Deevi, S. C.; Sikka, V. K.; Swindeman, C. J.; Seals, R. D.

    1997-09-01

    Reactive spraying of nickel aluminides was accomplished via reaction synthesis techniques in which nickel and aluminum powders were fed through a direct- current plasma torch onto carbon steel substrates. The as- sprayed coatings obtained by reactive spraying were characterized by x- ray diffraction and microscopic techniques. Reactive spraying of nickel and aluminum resulted in coatings consisting of Ni, Al, Ni 3Al, NiAl3, Ni5Al3, NiAl, and Al2O3, depending on the experimental conditions. Nickel aluminide phases observed in plasma spray depositions were compared with the phases obtained by combustion synthesis techniques, and the formation of phases in reactive spraying was attributed to the exothermic reaction between splats of aluminum and nickel. Primary and secondary reactions leading to the formation of nickel aluminides were also examined. The splat thickness and the reaction layer suppressed the formation of desired equilibrium phases such as Ni3Al and NiAl. As- sprayed coatings were annealed to enhance the diffusional reactions between the product phases and aluminum and nickel. Coatings obtained by reactive spraying of elemental powders were compared with as- sprayed and annealed coatings obtained with a bond coat material in which nickel was deposited onto aluminum particles.

  5. Seronegative reactive spondyloarthritis and the skin.

    PubMed

    Generali, Elena; Ceribelli, Angela; Massarotti, Marco; Cantarini, Luca; Selmi, Carlo

    2015-01-01

    Spondyloarthritidies represent a group of conditions affecting the axial and peripheral muscoloskeletal apparatus and are often associated with psoriasis, infections, and inflammatory bowel diseases. Other diseases included in this category are psoriatic arthritis, ankylosing spondylitis, and enteropathic arthritis. Reactive arthritis is an elusive spondyloarthritis, commonly occurring 1 to 3 weeks after a digestive or a genitourinary tract infection, in which microorganisms do not infect the joint directly. Reactive arthritis is classically characterized by large-joint arthritis, urethritis in men and cervicitis in women, and eye inflammation (usually conjunctivitis or uveitis) but encompasses numerous other symptoms and signs, including manifestations of dermatologic interest such as keratoderma blenorrhagicum and circinate balanitis. The diagnosis of reactive arthritis is clinical, and the infectious agent cannot always be identified due to disease latency after the infection. Most cases are self-limiting, but reactive arthritis may become chronic in 30% of cases. Treatment options include anti-inflammatory drugs, steroids, and sulfasalazine; biologic agents, such as tumor necrosis factor α (TNF-α) blockers, have been recently used, but there are only a few randomized clinical trials on the treatment of reactive arthritis. The effectiveness of antimicrobials needs further evaluation. PMID:26321399

  6. Reward disrupts reactivated human skill memory.

    PubMed

    Dayan, Eran; Laor-Maayany, Rony; Censor, Nitzan

    2016-01-01

    Accumulating evidence across species and memory domains shows that when an existing memory is reactivated, it becomes susceptible to modifications. However, the potential role of reward signals in these mechanisms underlying human memory dynamics is unknown. Leaning on a wealth of findings on the role of reward in reinforcing memory, we tested the impact of reinforcing a skill memory trace with monetary reward following memory reactivation, on strengthening of the memory trace. Reinforcing reactivated memories did not strengthen the memory, but rather led to disruption of the memory trace, breaking down the link between memory reactivation and subsequent memory strength. Statistical modeling further revealed a strong mediating role for memory reactivation in linking between memory encoding and subsequent memory strength only when the memory was replayed without reinforcement. We suggest that, rather than reinforcing the existing memory trace, reward creates a competing memory trace, impairing expression of the original reward-free memory. This mechanism sheds light on the processes underlying skill acquisition, having wide translational implications. PMID:27306380

  7. Reward disrupts reactivated human skill memory

    PubMed Central

    Dayan, Eran; Laor-Maayany, Rony; Censor, Nitzan

    2016-01-01

    Accumulating evidence across species and memory domains shows that when an existing memory is reactivated, it becomes susceptible to modifications. However, the potential role of reward signals in these mechanisms underlying human memory dynamics is unknown. Leaning on a wealth of findings on the role of reward in reinforcing memory, we tested the impact of reinforcing a skill memory trace with monetary reward following memory reactivation, on strengthening of the memory trace. Reinforcing reactivated memories did not strengthen the memory, but rather led to disruption of the memory trace, breaking down the link between memory reactivation and subsequent memory strength. Statistical modeling further revealed a strong mediating role for memory reactivation in linking between memory encoding and subsequent memory strength only when the memory was replayed without reinforcement. We suggest that, rather than reinforcing the existing memory trace, reward creates a competing memory trace, impairing expression of the original reward-free memory. This mechanism sheds light on the processes underlying skill acquisition, having wide translational implications. PMID:27306380

  8. Perinatal Factors, Parenting Behavior, and Reactive Aggression: Does Cortisol Reactivity Mediate This Developmental Risk Process?

    ERIC Educational Resources Information Center

    Ryan, Stacy R.; Schechter, Julia C.; Brennan, Patricia A.

    2012-01-01

    Little is known about the mechanisms of action that link perinatal risk and the development of aggressive behavior. The aim of this study was to examine whether perinatal risk and parenting interacted to specifically predict reactive aggression, as opposed to general aggressive behavior, and to examine cortisol reactivity as a mediator of this…

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

    ERIC Educational Resources Information Center

    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)

  10. Study on CO2 gasification reactivity and physical characteristics of biomass, petroleum coke and coal chars.

    PubMed

    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. Molten salt extraction of transuranic and reactive fission products from used uranium oxide fuel

    SciTech Connect

    Herrmann, Steven Douglas

    2014-05-27

    Used uranium oxide fuel is detoxified by extracting transuranic and reactive fission products into molten salt. By contacting declad and crushed used uranium oxide fuel with a molten halide salt containing a minor fraction of the respective uranium trihalide, transuranic and reactive fission products partition from the fuel to the molten salt phase, while uranium oxide and non-reactive, or noble metal, fission products remain in an insoluble solid phase. The salt is then separated from the fuel via draining and distillation. By this method, the bulk of the decay heat, fission poisoning capacity, and radiotoxicity are removed from the used fuel. The remaining radioactivity from the noble metal fission products in the detoxified fuel is primarily limited to soft beta emitters. The extracted transuranic and reactive fission products are amenable to existing technologies for group uranium/transuranic product recovery and fission product immobilization in engineered waste forms.

  12. Unifying Model-Based and Reactive Programming within a Model-Based Executive

    NASA Technical Reports Server (NTRS)

    Williams, Brian C.; Gupta, Vineet; Norvig, Peter (Technical Monitor)

    1999-01-01

    Real-time, model-based, deduction has recently emerged as a vital component in AI's tool box for developing highly autonomous reactive systems. Yet one of the current hurdles towards developing model-based reactive systems is the number of methods simultaneously employed, and their corresponding melange of programming and modeling languages. This paper offers an important step towards unification. We introduce RMPL, a rich modeling language that combines probabilistic, constraint-based modeling with reactive programming constructs, while offering a simple semantics in terms of hidden state Markov processes. We introduce probabilistic, hierarchical constraint automata (PHCA), which allow Markov processes to be expressed in a compact representation that preserves the modularity of RMPL programs. Finally, a model-based executive, called Reactive Burton is described that exploits this compact encoding to perform efficIent simulation, belief state update and control sequence generation.

  13. Birth Weight, Current Anthropometric Markers, and High Sensitivity C-Reactive Protein in Brazilian School Children

    PubMed Central

    Pellanda, Lucia Campos

    2015-01-01

    Studies have shown associations of birth weight with increased concentrations of high sensitivity C-reactive protein. This study assessed the relationship between birth weight, anthropometric and metabolic parameters during childhood, and high sensitivity C-reactive protein. A total of 612 Brazilian school children aged 5–13 years were included in the study. High sensitivity C-reactive protein was measured by particle-enhanced immunonephelometry. Nutritional status was assessed by body mass index, waist circumference, and skinfolds. Total cholesterol and fractions, triglycerides, and glucose were measured by enzymatic methods. Insulin sensitivity was determined by the homeostasis model assessment method. Statistical analysis included chi-square test, General Linear Model, and General Linear Model for Gamma Distribution. Body mass index, waist circumference, and skinfolds were directly associated with birth weight (P < 0.001, P = 0.001, and P = 0.015, resp.). Large for gestational age children showed higher high sensitivity C-reactive protein levels (P < 0.001) than small for gestational age. High birth weight is associated with higher levels of high sensitivity C-reactive protein, body mass index, waist circumference, and skinfolds. Large for gestational age altered high sensitivity C-reactive protein and promoted additional risk factor for atherosclerosis in these school children, independent of current nutritional status. PMID:25874126

  14. Application of the Firefly and Luus-Jaakola algorithms in the calculation of a double reactive azeotrope

    NASA Astrophysics Data System (ADS)

    Mendes Platt, Gustavo; Pinheiro Domingos, Roberto; Oliveira de Andrade, Matheus

    2014-01-01

    The calculation of reactive azeotropes is an important task in the preliminary design and simulation of reactive distillation columns. Classically, homogeneous nonreactive azeotropes are vapor-liquid coexistence conditions where phase compositions are equal. For homogeneous reactive azeotropes, simultaneous phase and chemical equilibria occur concomitantly with equality of compositions (in the Ung-Doherty transformed space). The modeling of reactive azeotrope calculation is represented by a nonlinear algebraic system with phase equilibrium, chemical equilibrium and azeotropy equations. This nonlinear system can exhibit more than one solution, corresponding to a double reactive azeotrope. In a previous paper (Platt et al 2013 J. Phys.: Conf. Ser. 410 012020), we investigated some numerical aspects of the calculation of reactive azeotropes in the isobutene + methanol + methyl-tert-butyl-ether (with two reactive azeotropes) system using two metaheuristics: the Luus-Jaakola adaptive random search and the Firefly algorithm. Here, we use a hybrid structure (stochastic + deterministic) in order to produce accurate results for both azeotropes. After identifying the neighborhood of the reactive azeotrope, the nonlinear algebraic system is solved using Newton's method. The results indicate that using metaheuristics and some techniques devoted to the calculation of multiple minima allows both azeotropic coordinates in this reactive system to be obtains. In this sense, we provide a comprehensive analysis of a useful framework devoted to solving nonlinear systems, particularly in phase equilibrium problems.

  15. Greater sadness reactivity in late life

    PubMed Central

    Seider, Benjamin H.; Shiota, Michelle N.; Whalen, Patrick

    2011-01-01

    Although previous research suggests that overall emotional reactivity does not change with normal aging, it is possible that different emotions follow different developmental courses. We examined emotional reactivity to films selected to elicit sadness, disgust, and a neutral state in young, middle-aged and older adults (total N = 222). Physiology and expressive behavior were measured continuously and reports of subjective emotional experience were obtained following each film. Results indicated that older adults reported greater sadness in response to all films and greater physiological responses to the sadness film than did the younger age groups. There were no age differences found in self-reported disgust or in behavioral expressions of sadness or disgust in response to any film. The age differences that were found were maintained even after controlling for pre-film self-reported sadness and for personal experiences of loss. These findings support the notion that sadness reactivity is heightened with age. PMID:20650943

  16. Environmental stress, reactivity and ischaemic heart disease.

    PubMed

    Krantz, D S; Raisen, S E

    1988-03-01

    This article provides an overview of work in two areas of biobehavioural research: the effects of environmental stress and the role of psychophysiologic reactivity in the development of ischaemic heart disease. Attention is given first to evidence that low socio-economic status, low social support, and occupational settings characterized by high demands and low levels of control over the job are associated with increased coronary risk. Also discussed is a promising animal primate model of social stress and its role in development of coronary atherosclerosis. Next, we discuss physiological responsiveness (reactivity) to emotional stress, which is being studied as a marker of processes involved in the development of cardiovascular disease. Stress and psychophysiological reactivity constitute promising targets for research on biobehavioural antecedents of coronary disease and for clinical intervention studies. However, further evidence is needed before these variables can be regarded as proven coronary risk factors. PMID:3129010

  17. Indirect Ultraviolet-Reactivation of Phage λ

    PubMed Central

    George, Jacqueline; Devoret, Raymond; Radman, Miroslav

    1974-01-01

    When an F- recipient Escherichia coli K12 bacterium receives Hfr or F-lac+ DNA from an ultraviolet-irradiated donor, its capacity to promote DNA repair and mutagenesis of ultraviolet-damaged phage λ is substantially increased. We call this phenomenon indirect ultraviolet-reactivation, since its features are essentially the same as those of ultraviolet-reactivation; this repair process occurs in pyrimidine dimer excision-deficient strains and produces clear plaque mutations of the restored phage. Moreover, this process is similar to indirect ultraviolet-induction of prophage λ, since it is promoted by conjugation. However, contrarily to indirect induction, it is produced by Hfr donors and occurs in recipients restricting the incoming ultraviolet-damaged donor DNA. The occurrence of indirect ultraviolet-reactivation provides evidence for the existence in E. coli of an inducible error-prone mechanism for the repair of DNA. PMID:4589889

  18. Total OH reactivity measurements using a new fast Gas Chromatographic Photo-Ionization Detector (GC-PID)

    NASA Astrophysics Data System (ADS)

    Nölscher, A. C.; Sinha, V.; Bockisch, S.; Klüpfel, T.; Williams, J.

    2012-12-01

    The primary and most important oxidant in the atmosphere is the hydroxyl radical (OH). Currently OH sinks, particularly gas phase reactions, are poorly constrained. One way to characterize the overall sink of OH is to measure directly the ambient loss rate of OH, the total OH reactivity. To date, direct measurements of total OH reactivity have been either performed using a Laser-Induced Fluorescence (LIF) system ("pump-and-probe" or "flow reactor") or the Comparative Reactivity Method (CRM) with a Proton-Transfer-Reaction Mass Spectrometer (PTR-MS). Both techniques require large, complex and expensive detection systems. This study presents a feasibility assessment for CRM total OH reactivity measurements using a new detector, a Gas Chromatographic Photoionization Detector (GC-PID). Such a system is smaller, more portable, less power consuming and less expensive than other total OH reactivity measurement techniques. Total OH reactivity is measured by the CRM using a competitive reaction between a reagent (here pyrrole) with OH alone and in the presence of atmospheric reactive molecules. The new CRM method for total OH reactivity has been tested with parallel measurements of the GC-PID and the previously validated PTR-MS as detector for the reagent pyrrole during laboratory experiments, plant chamber and boreal field studies. Excellent agreement of both detectors was found when the GC-PID was operated under optimum conditions. Time resolution (60-70 s), sensitivity (LOD 3-6 s-1) and overall uncertainty (25% in optimum conditions) for total OH reactivity were similar to PTR-MS based total OH reactivity measurements. One drawback of the GC-PID system was the steady loss of sensitivity and accuracy during intensive measurements lasting several weeks, and a possible toluene interference. Generally, the GC-PID system has been shown to produce closely comparable results to the PTR-MS and thus in suitable environments (e.g. forests) it presents a viably economical

  19. Cardiovascular reactivity and proactive and reactive relational aggression among women with and without a history of sexual abuse.

    PubMed

    Murray-Close, Dianna; Rellini, Alessandra H

    2012-01-01

    This study examined the association between cardiovascular reactivity and proactive and reactive functions of relational aggression among women with and without a history of sexual abuse. Heart rate reactivity, blood pressure reactivity, and respiratory sinus arrhythmia reactivity while recounting a relational stressor (e.g., being left out) were assessed. Participants provided self-reports of relational aggression and a history of sexual abuse prior to age 16. Results indicated that cardiovascular reactivity was only associated with relational aggression among women with a history of sexual abuse. In addition, whereas blunted reactivity was associated with proactive relational aggression, exaggerated reactivity was associated with reactive relational aggression. These findings highlight the importance of considering contextual moderators of the association between cardiovascular reactivity and aggression; moreover, results highlight distinct cardiovascular correlates of different functions of aggression. Finally, the findings underscore the need for additional research examining the physiological correlates of aggressive behavior among women. PMID:21963609

  20. Mechanisms Governing Metastatic Dormancy and Reactivation

    PubMed Central

    Giancotti, Filippo G.

    2015-01-01

    Summary Many cancer patients suffer from metastatic relapse several years after they have undergone radical surgery. Early cancer cell dissemination followed by a protracted period of dormancy potentially explains this prevalent clinical behavior. Increasing evidence suggests that the metastasis-initiating cells are cancer stem cells or functionally equivalent to cancer stem cells. Here, I discuss newly uncovered mechanisms governing metastatic dormancy and reactivation, placing emphasis on tumor evolution, stem cell signaling, and micro-environmental niches. In spite of significant remaining uncertainties, these findings provide a framework to understand the logic of metastatic dormancy and reactivation and open new avenues for therapeutic intervention. PMID:24209616

  1. Rosacea, Reactive Oxygen Species, and Azelaic Acid

    PubMed Central

    2009-01-01

    Rosacea is a common skin condition thought to be primarily an inflammatory disorder. Neutrophils, in particular, have been implicated in the inflammation associated with rosacea and mediate many of their effects through the release of reactive oxygen species. Recently, the role of reactive oxygen species in the pathophysiology of rosacea has been recognized. Many effective agents for rosacea, including topical azelaic acid and topical metronidazole, have anti-inflammatory properties. in-vitro models have demonstrated the potent antioxidant effects of azelaic acid, providing a potential mechanistic explanation for its efficacy in the treatment of rosacea. PMID:20967185

  2. Nuclear engine flow reactivity shim control

    DOEpatents

    Walsh, J.M.

    1973-12-11

    A nuclear engine control system is provided which automatically compensates for reactor reactivity uncertainties at the start of life and reactivity losses due to core corrosion during the reactor life in gas-cooled reactors. The coolant gas flow is varied automatically by means of specially provided control apparatus so that the reactor control drums maintain a predetermined steady state position throughout the reactor life. This permits the reactor to be designed for a constant drum position and results in a desirable, relatively flat temperature profile across the core. (Official Gazette)

  3. Comparison of Global Reactivity Descriptors Calculated Using Various Density Functionals: A QSAR Perspective.

    PubMed

    Vijayaraj, R; Subramanian, V; Chattaraj, P K

    2009-10-13

    Conceptual density functional theory (DFT) based global reactivity descriptors are used to understand the relationship between structure, stability, and global chemical reactivity. Furthermore, these descriptors are employed in the development of quantitative structure-activity (QSAR), structure-property (QSPR), and structure-toxicity (QSTR) relationships. However, the predictive power of various relationships depends on the reliable estimates of these descriptors. The basic working equations used to calculate these descriptors contain both the ionization potential and the electron affinity of chosen molecules. Therefore, efficiency of different density functionals (DFs) in predicting the ionization potential and the electron affinity has to be systematically evaluated. With a view to benchmark the method of calculation of global reactivity descriptors, comprehensive calculations have been carried out on a series of chlorinated benzenes using a variety of density functionals employing different basis sets. In addition, to assess the utility of global reactivity descriptors, the relationships between the reactivity-electrophilicity and the structure-toxicity have been developed. The ionization potential and the electron affinity values obtained from M05-2X method using the ΔSCF approach are closer to the corresponding experimental values. This method reliably predicts these electronic properties when compared to the other DFT methods. The analysis of a series of QSTR equations reveals that computationally economic DFT functionals can be effectively and routinely applied in the development of QSAR/QSPR/QSTR. PMID:26631787

  4. Gas sampling system for reactive gas-solid mixtures

    DOEpatents

    Daum, Edward D.; Downs, William; Jankura, Bryan J.; McCoury, Jr., John M.

    1990-01-01

    An apparatus and method for sampling gas containing a reactive particulate solid phase flowing through a duct and for communicating a representative sample to a gas analyzer. A sample probe sheath 32 with an angular opening 34 extends vertically into a sample gas duct 30. The angular opening 34 is opposite the gas flow. A gas sampling probe 36 concentrically located within sheath 32 along with calibration probe 40 partly extends in the sheath 32. Calibration probe 40 extends further in the sheath 32 than gas sampling probe 36 for purging the probe sheath area with a calibration gas during calibration.

  5. Gas sampling system for reactive gas-solid mixtures

    DOEpatents

    Daum, Edward D.; Downs, William; Jankura, Bryan J.; McCoury, Jr., John M.

    1989-01-01

    An apparatus and method for sampling a gas containing a reactive particulate solid phase flowing through a duct and for communicating a representative sample to a gas analyzer. A sample probe sheath 32 with an angular opening 34 extends vertically into a sample gas duct 30. The angular opening 34 is opposite the gas flow. A gas sampling probe 36 concentrically located within sheath 32 along with calibration probe 40 partly extend in the sheath 32. Calibration probe 40 extends further in the sheath 32 than gas sampling probe 36 for purging the probe sheath area with a calibration gas during calibration.

  6. Perspective on fossil power plant layup and reactivation

    SciTech Connect

    Tsou, J.L.

    1996-12-31

    In recent years, many utilities have developed excess generation capacity problems during period of low system load growth, particularly with new generation units coming on-line. System load studies may indicate that the situation is temporary and higher generation capacity will be needed in the near future. The objective of layup is to prevent component deterioration during the long shut down periods. This paper discusses equipment preservation practices in use by the electric utility industry and the advantages/disadvantages of various layup methods. Other issues related to plant layup and reactivation are also presented.

  7. Reactivation of a tin oxide-containing catalyst

    NASA Technical Reports Server (NTRS)

    Upchurch, Billy T. (Inventor); Miller, Irvin M. (Inventor); Brown, Kenneth G. (Inventor); Hess, Robert V. (Inventor); Schryer, David R. (Inventor); Sidney, Barry D. (Inventor); Wood, George M. (Inventor); Paulin, Patricia A. (Inventor)

    1989-01-01

    A method for the reactivation of a tin oxide-containing catalyst of a CO.sub.2 laser is provided. First, the catalyst is pretreated by a standard procedure. When the catalyst experiences diminished activity during usage, the heated zone surrounding the catalyst is raised to a temperature which is the operating temperature of the laser and 400.degree. C. for approximately one hour. The catalyst is exposed to the same laser gas mixture during this period. The temperature of the heated zone is then lowered to the operating temperature of the CO.sub.2 laser.

  8. Electronic Structure Contributions to Reactivity in Xanthine Oxidase Family Enzymes

    PubMed Central

    Stein, Benjamin W.; Kirk, Martin L.

    2016-01-01

    We review the xanthine oxidase (XO) family of pyranopterin molybdenum enzymes with a specific emphasis on electronic structure contributions to reactivity. In addition to xanthine and aldehyde oxidoreductases, which catalyze the 2-electron oxidation of aromatic heterocycles and aldehyde substrates, this mini-review highlights recent work on the closely related carbon monoxide dehydrogenase (CODH) that catalyzes the oxidation of CO using a unique Mo-Cu heterobimetallic active site. A primary focus of this mini-review relates to how spectroscopy and computational methods have been used to develop an understanding of critical relationships between geometric structure, electronic structure, and catalytic function. PMID:25425163

  9. Thiol Reactive Probes and Chemosensors

    PubMed Central

    Peng, Hanjing; Chen, Weixuan; Cheng, Yunfeng; Hakuna, Lovemore; Strongin, Robert; Wang, Binghe

    2012-01-01

    Thiols are important molecules in the environment and in biological processes. Cysteine (Cys), homocysteine (Hcy), glutathione (GSH) and hydrogen sulfide (H2S) play critical roles in a variety of physiological and pathological processes. The selective detection of thiols using reaction-based probes and sensors is very important in basic research and in disease diagnosis. This review focuses on the design of fluorescent and colorimetric probes and sensors for thiol detection. Thiol detection methods include probes and labeling agents based on nucleophilic addition and substitution, Michael addition, disulfide bond or Se-N bond cleavage, metal-sulfur interactions and more. Probes for H2S are based on nucleophilic cyclization, reduction and metal sulfide formation. Thiol probe and chemosensor design strategies and mechanism of action are discussed in this review. PMID:23202239

  10. [Buccal epithelium reactivity in children].

    PubMed

    Kurkin, A V; Rybalkina, D Kh

    2011-01-01

    The purpose of this study was the analysis of the buccal smears from 200 healthy children and children with chronic tonsillitis and chicken pox. The smears were stained using Pappenheim's method. The peculiarity of buccal mucosa cytograms of children of different ages was the significant increase in mature forms of the cells (presence of differentiation stage 5 and 6 cells) in adolescents. They also had a lower area of epitheliocytes at all the stages of differentiation and of their nuclei. In chronic tonsillitis and chicken pox, the complex of cytological changes was detected, that included the increase of the leukocyte number, changes in the proportions of epitheliocytes in cell population, augmentation of inflammation-destruction and destruction indexes. PMID:21539088

  11. 2 minute non-invasive screening for cardio-vascular diseases: relative limitation of C-Reactive Protein compared with more sensitive L-Homocystine as cardio-vascular risk factors; safe and effective treatment using the selective drug uptake enhancement method.

    PubMed

    Omura, Yoshiaki; Shimotsuura, Yasuhiro; Ohki, Motomu

    2003-01-01

    Contrary to the present practice of measurement of cardio-vascular risk factors or inflammatory risk factors such as C-Reactive Protein (CRP) from a blood sample from the vein of one arm, by using the Bi-Digital O-Ring Test Resonance Phenomena between 2 identical substances, one can non-invasively detect the approximate location on the body of abnormally increased risk factors in just 2 minutes, by detecting the resonance with L-Homocystine, even when blood CRP failed to detect any abnormality. This is performed by projecting a 0.5 to approximately 5mW red spectral laser beam with 560-670nm wavelength, to at least 6 standard parts of the body, when one of the control risk markers placed next to the laser beam also exists in the part of the body tested. It is generally believed that CRP is increased in the presence of acute myocardial infarct, chronic rheumatoid arthritis, ulcerative colitis, metabolic abnormalities such as often detected in diabetes, inflammation and underlying infection of the cardio-vascular system, and in some cancers. However, in our study, when the clinical significance of CRP and L-Homocystine was compared, we found that CRP often was not increased when there was extensive infection of Mycobacterium Tuberculosis as well as asymptomatic infection by Cytomegalovirus, Herpes Simplex Virus Type I, Human Herpes Virus Type 6, Borrelia Burgdorferi, or Chlamydia Trachomatis in the heart (and other parts of the body), particularly when there was liver cell dysfunction such as an increase in ALT. In contrast, L-Homocystine was often increased in the presence of localized infections of the heart and other parts of the body. For screening of Cardio-Vascular diseases by this method, 0.5mg of L-Homocystine as a control marker was found to be the most sensitive and reliable, compared with most effective amount of CRP, 0.5ng, for detecting early Cardio-Vascular problems due to various localized infections. About 0.5ng of cardiac Troponin T and cardiac

  12. OH reactivity and concentrations of Biogenic Volatile Organic Compounds in a Mediterranean forest of downy oak trees

    NASA Astrophysics Data System (ADS)

    Zannoni, N.; Gros, V.; Lanza, M.; Sarda, R.; Bonsang, B.; Kalogridis, C.; Preunkert, S.; Legrand, M.; Jambert, C.; Boissard, C.; Lathiere, J.

    2015-08-01

    Understanding the processes between the biosphere and the atmosphere is challenged by the difficulty to determine with enough accuracy the composition of the atmosphere. Total OH reactivity, which is defined as the total loss of the hydroxyl radical in the atmosphere, has proved to be an excellent tool to identify indirectly the important reactive species in ambient air. High levels of unknown reactivity were found in several forests worldwide and were often higher than at urban sites. Such results demonstrated the importance of OH reactivity for characterizing two of the major unknowns currently present associated to forests: the set of primary emissions from the canopy to the atmosphere and biogenic compounds oxidation pathways. Previous studies also highlighted the need to quantify OH reactivity and missing OH reactivity at more forested sites. Our study presents results of a field experiment conducted during late spring 2014 at the forest site at the Observatoire de Haute Provence, OHP, France. The forest is mainly composed of downy oak trees, a deciduous tree species characteristic of the Mediterranean region. We deployed the Comparative Reactivity Method and a set of state-of-the-art techniques such as Proton Transfer Reaction-Mass Spectrometry and Gas Chromatography to measure the total OH reactivity, the concentration of volatile organic compounds and main atmospheric constituents at the site. We sampled the air masses at two heights: 2 m, i.e. inside the canopy, and 10 m, i.e. above the canopy, where the mean canopy height is 5 m. We found that the OH reactivity at the site mainly depended on the main primary biogenic species emitted by the forest, which was isoprene and to a lesser extent by its degradation products and long lived atmospheric compounds (up to 26 % during daytime). We determined that the daytime total measured reactivity equaled the calculated reactivity obtained from the concentrations of the compounds measured at the site. Hence, no

  13. Cue reactivity in virtual reality: the role of context.

    PubMed

    Paris, Megan M; Carter, Brian L; Traylor, Amy C; Bordnick, Patrick S; Day, Susan X; Armsworth, Mary W; Cinciripini, Paul M

    2011-07-01

    Cigarette smokers in laboratory experiments readily respond to smoking stimuli with increased craving. An alternative to traditional cue-reactivity methods (e.g., exposure to cigarette photos), virtual reality (VR) has been shown to be a viable cue presentation method to elicit and assess cigarette craving within complex virtual environments. However, it remains poorly understood whether contextual cues from the environment contribute to craving increases in addition to specific cues, like cigarettes. This study examined the role of contextual cues in a VR environment to evoke craving. Smokers were exposed to a virtual convenience store devoid of any specific cigarette cues followed by exposure to the same convenience store with specific cigarette cues added. Smokers reported increased craving following exposure to the virtual convenience store without specific cues, and significantly greater craving following the convenience store with cigarette cues added. However, increased craving recorded after the second convenience store may have been due to the pre-exposure to the first convenience store. This study offers evidence that an environmental context where cigarette cues are normally present (but are not), elicits significant craving in the absence of specific cigarette cues. This finding suggests that VR may have stronger ecological validity over traditional cue reactivity exposure methods by exposing smokers to the full range of cigarette-related environmental stimuli, in addition to specific cigarette cues, that smokers typically experience in their daily lives. PMID:21349649

  14. Shape-programmed nanofabrication: understanding the reactivity of dichalcogenide precursors.

    PubMed

    Guo, Yijun; Alvarado, Samuel R; Barclay, Joshua D; Vela, Javier

    2013-04-23

    characterized using structural and spectroscopic methods. An intimate understanding of how molecular structure affects the chemical reactivity of molecular precursors enables highly predictable and reproducible synthesis of colloidal nanocrystals with specific sizes, shapes, and optoelectronic properties for customized applications. PMID:23517277

  15. Biologic nanoparticles and platelet reactivity

    PubMed Central

    Miller, Virginia M; Hunter, Larry W; Chu, Kevin; Kaul, Vivasvat; Squillace, Phillip D; Lieske, John C; Jayachandran, Muthuvel

    2009-01-01

    Aim Nanosized particles (NPs) enriched in hydroxyapatite and protein isolated from calcified human tissue accelerate occlusion of endothelium-denuded arteries when injected intravenously into rabbits. Since platelet aggregation and secretory processes participate in normal hemostasis, thrombosis and vascular remodeling, experiments were designed to determine if these biologic NPs alter specific platelet functions in vitro. Methods Platelet-rich plasma was prepared from citrate anticoagulated human blood. Platelet aggregation and ATP secretion were monitored in response to thrombin receptor agonists peptide (10 μM) or convulxin (50 μg/ml) prior to and following 15 min incubation with either control solution, human-derived NPs, bovine-derived NPs or crystals of hydroxyapatite at concentrations of 50 and 150 nephelometric turbidity units. Results Incubation of platelets for 15 min with either human- or bovine-derived NPs reduced aggregation induced by thrombin receptor activator peptide and convulxin in a concentration-dependent manner. Hydroxyapatite caused a greater inhibition than either of the biologically derived NPs. Human-derived NPs increased ATP secretion by unstimulated platelets during the 15 min incubation period. Conclusion Effects of bovine-derived and hydroxyapatite NPs on basal release of ATP were both time and concentration dependent. These results suggest that biologic NPs modulate both platelet aggregation and secretion. Biologically derived NPs could modify platelet responses within the vasculature, thereby reducing blood coagulability and the vascular response to injury. PMID:19839809

  16. Test Pile Reactivity Loss Due to Trichloroethylene

    SciTech Connect

    Plumlee, K.E.

    2001-03-09

    The presence of trichloroethylene in the test pile caused a continual decrease in pile reactivity. A system which removed, purified, and returned 12,000 cfh helium to the pile has held contamination to a negligible level and has permitted normal pile operation.

  17. Production of reactive sintered nickel aluminide

    SciTech Connect

    1995-10-01

    This is the final report pertaining to the development of aluminides by reactive synthesis. Included in this report is an overview of results during the scope of this effort, details on specific task accomplishments, and a summary of customer evaluations. Opportunities for future work are also included at the end of this report.

  18. Prenatal Cocaine Exposure and Infant Cortisol Reactivity

    ERIC Educational Resources Information Center

    Eiden, Rina D.; Veira, Yvette; Granger, Douglas A.

    2009-01-01

    This study examined the effects of prenatal cocaine exposure on infant hypothalamic-pituitary-adrenal axis activity and reactivity at 7 months of infant age. Participants were 168 caregiver-infant dyads (87 cocaine exposed, 81 not cocaine exposed; 47% boys). Maternal behavior, caregiving instability, and infant growth and behavior were assessed,…

  19. Zeroing in on Tumor-Reactive TILs.

    PubMed

    Ohashi, Pamela S

    2016-09-01

    Adoptive cell transfer of tumor-specific T cells provides an effective strategy for cancer immunotherapy. An article in this issue provides a novel approach to refine this technology by identifying tumor-reactive T cells based on frequency and PD-1 expression. Cancer Immunol Res; 4(9); 719. ©2016 AACRSee article by Ascierto et al., p. 726. PMID:27590279

  20. Cross-reactivity of peanut allergens.

    PubMed

    Bublin, Merima; Breiteneder, Heimo

    2014-04-01

    Peanut seeds are currently widely used as source of human food ingredients in the United States of America and in European countries due to their high quality protein and oil content. This article describes the classification and molecular biology of peanut seed allergens with particular reference to their cross-reactivities. Currently, the IUIS allergen nomenclature subcommittee accepts 12 peanut allergens. Two allergens belong to the cupin and four to the prolamin superfamily, and six are distributed among profilins, Bet v 1-like proteins, oleosins, and defensins. Clinical observations frequently report an association of peanut allergy with allergies to legumes, tree nuts, seeds, fruits and pollen. Molecular cross-reactivity has been described between members of the Bet v 1-like proteins, the non-specific lipid transfer proteins, and the profilins. This review also addresses the less well-studied cross-reactivity between cupin and prolamin allergens of peanuts and of other plant food sources and the recently discovered cross-reactivity between peanut allergens of unrelated protein families. PMID:24554241